NZ721985B2

NZ721985B2 - Methods and compositions for the targeted modification of a genome

Info

Publication number: NZ721985B2
Application number: NZ721985A
Authority: NZ
Inventors: Wojtek Auerbach; David Frendewey; Junko Kuno; KaMan Venus LAI; David M Valenzuela; George D Yancopoulos; Ka Man Venus Lai
Original assignee: Regeneron Pharmaceuticals Inc
Priority date: 2013-12-11
Filing date: 2014-10-15
Publication date: 2021-02-02

Abstract

Currently the use of rats in modelling human diseases has been limited compared to mice, due in part to unavailability of genomic transmittable pluripotent rat cells, which can sustain their pluripotency following a series of genetic modifications in vitro. This limitation is also due in part to the lack of efficient targeting technologies that allow introduction or deletion of large genomic sequences, or replacement of large genomic DNA sequences with exogenous nucleic acid sequences in pluripotent rat cells. The present invention seeks to solve this problem by providing compositions and methods for modifying a genomic locus of interest in a eukaryotic cell, a mammalian cell, a human cell or a non-human mammalian cell using a large targeting vector (LTVEC) comprising various endogenous or exogenous nucleic acid sequences as described herein. Further methods combine the use of the LTVEC with a CRISPR/Cas system. Compositions and methods for generating a genetically modified non-human animal comprising one or more targeted genetic modifications in their germline are also provided. lack of efficient targeting technologies that allow introduction or deletion of large genomic sequences, or replacement of large genomic DNA sequences with exogenous nucleic acid sequences in pluripotent rat cells. The present invention seeks to solve this problem by providing compositions and methods for modifying a genomic locus of interest in a eukaryotic cell, a mammalian cell, a human cell or a non-human mammalian cell using a large targeting vector (LTVEC) comprising various endogenous or exogenous nucleic acid sequences as described herein. Further methods combine the use of the LTVEC with a CRISPR/Cas system. Compositions and methods for generating a genetically modified non-human animal comprising one or more targeted genetic modifications in their germline are also provided.

Description

METHODS AND COMPOSITIONS FOR THE TARGETED MODIFICATION OF A GENOME CROSS REFERENCE TO RELATED APPLICATIONS This ation claims the beneﬁt of US. Provisional Patent Application No. 61/914,768, ﬁled December 11, 2013, US. Provisional Patent ation No. 62/017,416, ﬁled June 26, 2014, US. Provisional Patent Application No. ,261, ﬁled July 25, 2014, US. Provisional Patent Application No. 62/052,906, ﬁled September 19, 2014, US. Provisional Patent Application No. 62/059,527, ﬁled October 03, 2014, and US. Provisional Patent Application No. 62/064,3 84, ﬁled October 15, 2014, each of which is incorporated by reference in its entirety for all purposes.

REFERENCE TO A SEQUENCE LISTING SUBMITTED AS A TEXT FILE VIA EFS WEB The ofﬁcial copy of the sequence g is submitted electronically via b as an ASCII ted sequence listing with a ﬁle named 453460SEQLIST.TXT, created on October 15, 2014, and having a size of 27.5 kilobytes, and is ﬁled concurrently with the speciﬁcation. The sequence listing contained in this ASCII formatted nt is part of the speciﬁcation and is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION While rats have been regarded as an important animal model system that can recapitulate the pathology of various human diseases, including, but not limited to, cardiovascular (e.g., hypertension), metabolic (e.g., obesity, diabetes), ogical (e.g., pain pathologies), and a variety of cancers, the use of rats in modeling human diseases has been limited as compared to mice, due in part to unavailability of germline- transmittable pluripotent rat cells, which can sustain their pluripotency following a series of genetic modiﬁcations in vitro, e.g., one or more serial electroporations, and due in part 2014/060788 to lack of efﬁcient targeting technologies that allow introduction or deletion of large genomic DNA sequences, or replacement of large endogenous c DNA sequences with exogenous nucleic acid sequences in pluripotent rat cells.

There is a need in the art for compositions and methods that allow precise targeted changes in the genome of an organism, which can open or expand t areas of target discovery and validate therapeutic agents more quickly and easily.

SUMMARY Methods are provided for modifying a c locus of interest in a eukaryotic cell via targeted genetic modiﬁcation. Such a method comprises (a) introducing into the eukaryotic cell: (i) a large targeting vector (LTVEC) comprising ’ homology ’ homology a ﬁrst nucleic acid ﬂanked with a 5 arm and a 3 arm, wherein the LTVEC is at least 10 kb; (ii) a ﬁrst expression construct comprising a ﬁrst promoter operably linked to a second c acid encoding a Cas protein, (iii) a second expression construct comprising a second promoter operably linked to a third nucleic acid encoding a guide RNA (gRNA) comprising a nucleotide ce that hybridizes to a target sequence and a trans-activating CRISPR RNA (trachNA), wherein the ﬁrst and the second promoters are active in the eukaryotic cell; and (b) identifying a modiﬁed eukaryotic cell comprising a targeted genetic modiﬁcation at the genomic locus of interest.

In one ment, the targeted genetic modiﬁcation is a biallelic c modiﬁcation.

In one embodiment, the LTVEC is at least 15 kb, at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, or at least 90 kb. In another embodiment, the LTVEC is at least 100 kb, at least 150 kb, or at least 200 In one embodiment, the eukaryotic cell is a mammalian cell. In one embodiment, the mammalian cell is a ﬁbroblast.

In one embodiment, the eukaryotic cell is a pluripotent cell. In one ment, the pluripotent cell is a human pluripotent cell. In one ment the human pluripotent cell is a human embryonic stem (ES) cell or a human adult stem cell.

In another embodiment, the human pluripotent cell is a developmentally restricted human progenitor cell. In another embodiment, the human pluripotent cell is a human induced pluripotent stem (iPS) cell.

In one embodiment, the Cas protein is Cas9.

In one ment, the target sequence is ﬂanked by a Protospacer Adjacent Motif (PAM) sequence. In one embodiment, the target sequence is immediately ﬂanked on the 3’ end by a Protospacer Adjacent Motif (PAM) sequence.

In some embodiments, the sum total of the 5’ and the 3’ homology arms is from about 10 kb to about 150 kb. In some embodiments, the sum total of the 5’ and the 3’ homology arms of the LTVEC is from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 120 kb, or from about 120 kb to 150 kb.

The methods ﬁarther provide that the targeted c modiﬁcation comprises: (a) a ement of an endogenous nucleic acid sequence with a homologous or an orthologous nucleic acid sequence; (b) a deletion of an endogenous nucleic acid sequence; (c) a deletion of an endogenous nucleic acid sequence, n the deletion ranges from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, or from about 150 kb to about 200 kb, from about 200 kb to about 300 kb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to about 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, or from about 2.5 Mb to about 3 Mb; (d) insertion of an exogenous nucleic acid sequence; (e) insertion of an exogenous nucleic acid sequence g from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb; (1) ion of an exogenous nucleic acid sequence comprising a homologous or an orthologous c acid sequence; (g) insertion of a chimeric nucleic acid sequence comprising a human and a non-human nucleic acid sequence; (h) insertion of a conditional allele ﬂanked with site-speciﬁc recombinase target sequences; (i) insertion of a selectable marker or a reporter gene ly linked to a third promoter active in the pluripotent cell; or (j ) a combination thereof.

In one embodiment, the genomic locus of interest comprises (i) a 5’ target ce that is homologous to the 5’ homology arm; and (ii) a 3’ target sequence that is homologous to the 3’ homology arm.

In some embodiments, the 5’ target sequence and the 3’ target sequence is separated by at least 5 kb but less than 3 Mb. In some ments, the 5’ target sequence and the 3’ target sequence is separated by at least 5 kb but less than 10 kb, at least 10 kb but less than 20 kb, at least 20 kb but less than 40 kb, at least 40 kb but less than 60 kb, at least 60 kb but less than 80 kb, at least about 80 kb but less than 100 kb, at least 100 kb but less than 150 kb, or at least 150 kb but less than 200 kb, at least about 200 kb but less than about 300 kb, at least about 300 kb but less than about 400 kb, at least about 400 kb but less than about 500 kb, at least about 500 kb but less than about 1 Mb, at least about 1 Mb but less than about 1.5 Mb, at least about 1.5 Mb but less than about 2 Mb, at least about 2 Mb but less than about 2.5 Mb, or at least about 2.5 Mb but less than about 3 Mb.

In one embodiment, the genomic locus of interest comprises the eukin-2 or gamma locus, the ApoE locus, the Rag] locus, the Rag2 locus, or both ofthe Rag] and the Rag2 loci.

In one embodiment, the ﬁrst and the second expression constructs are on a single nucleic acid molecule. r provided is a method for modifying a genome, comprising ng the genome to a Cas protein and a CRISPR RNA in the presence of a large targeting vector (LTVEC) comprising a nucleic acid sequence of at least 10 kb, Wherein following exposure to the Cas protein, the CRISPR RNA, and the LTVEC, the genome is modiﬁed to contain at least 10 kb nucleic acid sequence.

In some such methods, the LTVEC comprises a nucleic acid sequence of at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, or at least 90 kb. In some such methods, the LTVEC comprises a nucleic acid sequence of at least 100 kb, at least 150 kb, or at least 200 kb.

Further provided is a method for modifying a genome, sing contacting the genome with a Cas protein, a CRISPR RNA that hybridizes to a target ce, and a trachNA in the presence of a large targeting vector (LTVEC), wherein the LTVEC is at least 10 kb and comprises a ﬁrst nucleic acid ﬂanked with a 5’ homology arm and a 3 ’ homology arm, n following contacting with the Cas protein, CRISPR RNA, and A in the presence of the LTVEC, the genome is modiﬁed at a genomic locus of interest to contain the ﬁrst nucleic acid. The target sequence can be at or near the genomic locus of interest.

In some such methods, the genome is in a otic cell, and the Cas protein, the CRISPR RNA, the trachNA, and the LTVEC are introduced into the eukaryotic cell. Some such s r comprise identifying a modiﬁed otic cell comprising a targeted genetic modiﬁcation at the genomic locus of interest.

In some such methods, the CRISPR RNA and the trachNA are introduced together in the form of a single guide RNA (gRNA). In other methods, the CRISPR RNA and the trachNA are introduced separately.

In some such methods (a) the Cas protein is introduced into the eukaryotic cell in the form of a protein, a messenger RNA (mRNA) encoding the Cas protein, or a DNA encoding the Cas protein; (b) the CRISPR RNA is introduced into the eukaryotic cell in the form of an RNA or a DNA encoding the CRISPR RNA; and (c) the trachNA is introduced into the eukaryotic cell in the form of an RNA or a DNA encoding the trachNA.

In some methods (a) the DNA encoding the Cas protein is in the form of a ﬁrst expression construct sing a ﬁrst promoter operably linked to a second c acid encoding the Cas protein; (b) the DNA encoding the CRISPR RNA is in the form of a second expression uct comprising a second promoter operably linked to a third nucleic acid encoding the CRISPR RNA; and (c) the DNA encoding the trachNA is in the form of a third expression construct comprising a third promoter operably linked to a fourth nucleic acid encoding the trachNA, wherein the ﬁrst, second, and third promoters are active in the eukaryotic cell. Optionally, the ﬁrst, second, and/or third expression constructs are on a single nucleic acid molecule.

In some methods (a) the DNA encoding the Cas protein is in the form of a ﬁrst expression construct comprising a ﬁrst er operably linked to a second nucleic acid encoding the Cas protein; and (b) the DNA encoding the CRISPR RNA and the DNA encoding the trachNA are in the form of a second expression construct comprising a second promoter operably linked to a third nucleic acid encoding a gRNA comprising the CRISPR RNA and the trachNA; wherein the ﬁrst and second promoters are active in the eukaryotic cell. Optionally, the ﬁrst and the second expression constructs are on a single nucleic acid molecule.

In some methods, the Cas protein, the CRISPR RNA, and the trachNA are uced into the eukaryotic cell as a protein-RNA complex.

In some methods, the targeted genetic modiﬁcation comprises simultaneous deletion of an endogenous c acid sequence at the genomic locus of interest and insertion of the ﬁrst nucleic acid at the genomic locus of interest. In some methods, the deleted endogenous c acid ce is about 30 kb to about 1 10 kb, and the inserted ﬁrst nucleic acid is about 40 kb to about 140 kb. In some methods, the deleted endogenous nucleic acid sequence is about 38 kb to about 1 10 kb, and the inserted ﬁrst nucleic acid is about 43 kb to about 134 kb.

In some s, the targeted c modiﬁcation is a biallelic genetic ation. Optionally, the biallelic genetic modiﬁcation comprises deletion of an endogenous nucleic acid sequence and insertion of the ﬁrst nucleic acid at the genomic locus of interest in two homologous chromosomes.

In some methods, the modiﬁed eukaryotic cell is nd heterozygous at the genomic locus of interest. In some methods, the modiﬁed eukaryotic cell is hemizygous at the c locus of interest. Optionally, the targeted genetic modiﬁcation at the genomic locus of st in one chromosome comprises deletion of an endogenous c acid sequence and ion of the ﬁrst nucleic acid. Optionally, the targeted c modiﬁcation comprises: (1) deletion of an endogenous nucleic acid sequence at the genomic locus of interest in two homologous chromosomes; and (2) insertion of the ﬁrst nucleic acid into the genomic locus of interest in a ﬁrst chromosome and disruption of the genomic locus of st in a second chromosome. The ﬁrst chromosome can be one of the two homologous somes, and the second chromosome can be the other homologous chromosome.

In some s, the LTVEC is at least 15 kb, at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, or at least 90 kb. Optionally, the LTVEC is at least 100 kb, at least 150 kb, or at least 200 kb.

In some s, the ﬁrst nucleic acid is at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, at least 90 kb, at least 100 kb, at least 150 kb, at least 200 kb, at least 250 kb, or at least 300 kb. In some methods, the ﬁrst nucleic acid is about 40 kb to about 140 kb. In some methods, the ﬁrst nucleic acid is about 43 kb to about 134 kb.

In some methods, the eukaryotic cell is a mammalian cell, a ﬁbroblast, a pluripotent cell, a non-human pluripotent cell, a rodent pluripotent cell, a mouse or rat embryonic stem (ES) cell, a human pluripotent cell, a human nic stem (ES) cell, a human adult stem cell, a developmentally restricted human itor cell, or a human induced pluripotent stem (iPS) cell.

In some methods, the Cas protein is Cas9. In some methods, the target sequence is immediately ﬂanked by a Protospacer Adjacent Motif (PAM) sequence.

In some methods, the sum total of the 5’ and the 3’ homology arms of the LTVEC is from about 10 kb to about 150 kb. Optionally, the sum total of the 5’ and the 3’ homology arms of the LTVEC is from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 120 kb, or from about 120 kb to 150 kb.

In some methods, the targeted genetic modiﬁcation comprises: (a) a replacement of an endogenous nucleic acid sequence with a homologous or an orthologous nucleic acid sequence; (b) a on of an endogenous nucleic acid sequence; (c) a deletion of an endogenous nucleic acid sequence, wherein the deletion ranges from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, or from about 150 kb to about 200 kb, from about 200 kb to about 300 kb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to about 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, or from about 2.5 Mb to about 3 Mb; (d) insertion of an exogenous nucleic acid sequence; (e) insertion of an exogenous nucleic acid sequence ranging from about 5kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb; (l) insertion of an exogenous c acid sequence comprising a homologous or an orthologous nucleic acid ce; (g) insertion of a chimeric nucleic acid sequence comprising a human and a man nucleic acid sequence; (h) insertion of a conditional allele ﬂanked with site-speciﬁc recombinase target sequences; (i) ion of a selectable marker or a er gene operably linked to a third promoter active in the pluripotent cell; or (j ) a combination thereof.

In some methods, the genomic locus of interest comprises (i) a 5’ target sequence that is homologous to the 5’ homology arm; and (ii) a 3’ target sequence that is homologous to the 3’ homology arm. Optionally, the 5’ target sequence and the 3’ target sequence are separated by at least 5 kb but less than 3 Mb. Optionally, the 5’ target sequence and the 3’ target sequence are separated by at least 5 kb but less than 10 kb, at least 10 kb but less than 20 kb, at least 20 kb but less than 40 kb, at least 40 kb but less than 60 kb, at least 60 kb but less than 80 kb, at least about 80 kb but less than 100 kb, at least 100 kb but less than 150 kb, or at least 150 kb but less than 200 kb, at least about 200 kb but less than about 300 kb, at least about 300 kb but less than about 400 kb, at least about 400 kb but less than about 500 kb, at least about 500 kb but less than about le, at least about 1 Mb but less than about 1.5 Mb, at least about 1.5 Mb but less than about 2 Mb, at least about 2 Mb but less than about 2.5 Mb, or at least about 2.5 Mb but less than about 3 Mb. Optionally, the 5’ target ce and the 3’ target sequence are separated by at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, at least 90 kb, at least 100 kb, at least 110 kb, at least 120 kb, at least 130 kb, at least 140 kb, at least 150 kb, at least 160 kb, at least 170 kb, at least 180 kb, at least 190 kb, or at least 200 kb. In some methods, the 5’ and 3’ target sequences are ted by about 30 kb to about 1 10 kb. In some methods, the 5’ and 3’ target sequences are separated by about 38 kb to about 110 kb.

In some methods, the genomic locus of interest comprises the Interleukin- 2 receptor gamma locus, the ApoE locus, the Rag] locus, the Rag2 locus, or both of the Rag] and the Rag2 loci. In other methods, the genomic locus of interest comprises the Adamts5 locus, the Trpal locus, the Folk] locus, or the Erbb4 locus. In yet other s, the genomic locus of interest comprises the Lrp5 locus. In yet other methods, the genomic locus of interest comprises the C5 (Hc) locus, the RorI locus, or the Dpp4 locus.

Further provided is a method for producing an F0 tion non-human animal that ses a targeted genetic modiﬁcation at a genomic locus of interest, the method comprising: (a) contacting the genome in a non-human ES cell with a Cas protein, a CRISPR RNA, and a trachNA in the presence of a large targeting vector (LTVEC) to form a modiﬁed non-human ES cell, wherein the LTVEC is at least 10 kb and comprises a ﬁrst nucleic acid ﬂanked with a 5 ’ homology arm and a 3’ homology arm; (b) identifying the modiﬁed non-human ES cell comprising the targeted genetic modiﬁcation at the genomic locus of interest; (c) introducing the modiﬁed non-human ES cell into a non-human host embryo; and (d) gestating the non-human host embryo in a surrogate mother, wherein the surrogate mother produces the F0 generation non-human animal comprising the targeted genetic modiﬁcation at the genomic locus of interest.

In some such methods, the CRISPR RNA and the trachNA are introduced together in the form of a single guide RNA (gRNA). In other such s, the CRISPR RNA and the trachNA are uced separately.

In some such methods, (a) the Cas protein is introduced into the non- human ES cell in the form of a protein, a messenger RNA (mRNA) ng the Cas protein, or a DNA encoding the Cas protein; (b) the CRISPR RNA is introduced into the non-human ES cell in the form of an RNA or a DNA ng the CRISPR RNA; and (c) the trachNA is introduced into the non-human ES cell in the form of an RNA or a DNA encoding the trachNA.

WO 88643 In some such methods, (a) the DNA encoding the Cas n is in the form of a ﬁrst expression construct comprising a ﬁrst promoter operably linked to a second nucleic acid encoding the Cas protein; (b) the DNA encoding the CRISPR RNA is in the form of a second expression construct comprising a second promoter operably linked to a third nucleic acid encoding the CRISPR RNA; and (c) the DNA encoding the trachNA is in the form of a third expression construct sing a third promoter operably linked to a fourth nucleic acid encoding the trachNA, wherein the ﬁrst, second, and third promoters are active in the non-human ES cell. Optionally, the ﬁrst, second, and third expression constructs are on a single nucleic acid le.

In some such methods, (a) the DNA encoding the Cas protein is in the form of a ﬁrst expression construct comprising a ﬁrst promoter operably linked to a second nucleic acid encoding the Cas n; and (b) the DNA encoding the CRISPR RNA and the DNA encoding the trachNA are in the form of a second expression construct comprising a second promoter operably linked to a third c acid encoding a gRNA comprising the CRISPR RNA and the trachNA; wherein the ﬁrst and second promoters are active in the non-human ES cell. ally, the ﬁrst and the second expression constructs are on a single c acid molecule.

In some such methods, the Cas protein, the CRISPR RNA, and the trachNA are introduced into the non-human ES cell as a protein-RNA x.

In some such methods, the targeted genetic modiﬁcation comprises simultaneous deletion of an endogenous nucleic acid sequence at the c locus of interest and insertion of the ﬁrst nucleic acid at the genomic locus of interest.

In some such methods, the targeted genetic modiﬁcation is a lic genetic modiﬁcation. Optionally, the biallelic genetic modiﬁcation ses on of an endogenous nucleic acid sequence and insertion of the ﬁrst nucleic acid at the genomic locus of interest in two homologous chromosomes.

In some such methods, the modiﬁed non-human ES cell is compound heterozygous at the genomic locus of interest. In some such methods, the modiﬁed non- human ES cell is hemizygous at the genomic locus of interest. Optionally, the targeted genetic modiﬁcation at the genomic locus of interest in one chromosome comprises deletion of an endogenous nucleic acid sequence and insertion of the ﬁrst nucleic acid. 2014/060788 Optionally, the ed genetic modiﬁcation ses: (1) deletion of an nous nucleic acid sequence at the genomic locus of st in two homologous chromosomes; and (2) ion of the ﬁrst nucleic acid into the genomic locus of interest in a ﬁrst chromosome and disruption of the genomic locus of interest in a second chromosome.

The ﬁrst chromosome can be one of the two homologous chromosomes, and the second chromosome can be the other homologous chromosome.

In some such methods, the Cas n is Cas9.

Further provided are methods for modifying a genome at a genomic locus of interest in a eukaryotic cell, a mouse cell, or a human cell, comprising contacting the genome with a Cas protein, a CRISPR RNA that hybridizes to a target sequence at the genomic locus of interest, and a trachNA in the presence of a large targeting vector (LTVEC), wherein the LTVEC is at least 10 kb and comprises a ﬁrst nucleic acid ﬂanked with a 5’ gy arm that is homologous to a 5’ target sequence at the genomic locus of interest and a 3 ’ homology ’ target arm that is homologous to a 3 sequence at the genomic locus of interest, wherein the ﬁrst nucleic acid is at least 30 kb and/or the 5’ target sequence and the 3’ target sequence are separated by at least 30 kb, n following contacting with the Cas protein, the CRISPR RNA, and the trachNA in the presence of the LTVEC, the genome is modiﬁed to comprise a targeted genetic modiﬁcation comprising insertion of the ﬁrst nucleic acid at the genomic locus of interest.

Any of the above methods can further comprise introducing the Cas protein, the CRISPR RNA, the A, and the LTVEC into the eukaryotic cell, the mouse cell, or the human cell. Any of the above methods can ﬁthher comprise identifying the modiﬁed eukaryotic cell, the modiﬁed mouse cell, or the modiﬁed human cell comprising the ed genetic modiﬁcation at the genomic locus of interest.

In some of the above methods, the CRISPR RNA and the trachNA are introduced together in the form of a single transcript. In some of the above methods, the CRISPR RNA and the trachNA are introduced separately.

In some of the above methods, (a) the Cas protein is introduced into the eukaryotic cell, the mouse cell, or the human cell in the form of a protein, a ger RNA (mRNA) encoding the Cas protein, or a DNA encoding the Cas protein; (b) the CRISPR RNA is introduced into the eukaryotic cell, the mouse cell, or the human cell in the form of an RNA or a DNA encoding the CRISPR RNA; and (c) the trachNA is introduced into the eukaryotic cell, the mouse cell, or the human cell in the form of an RNA or a DNA encoding the trachNA. In some of the above methods, the Cas n, the CRISPR RNA, and the A are introduced into the eukaryotic cell, the mouse cell, or the human cell as a protein-RNA complex.

In some of the above methods, (a) the DNA encoding the Cas protein is in the form of a ﬁrst expression construct comprising a ﬁrst promoter operably linked to a second nucleic acid ng the Cas protein; (b) the DNA ng the CRISPR RNA is in the form of a second expression construct comprising a second promoter operably linked to a third nucleic acid ng the CRISPR RNA; and (c) the DNA encoding the trachNA is in the form of a third expression construct comprising a third promoter operably linked to a fourth nucleic acid encoding the trachNA; wherein the ﬁrst, second, and third promoters are active in the eukaryotic cell, the mouse cell, or the human cell. In some of the above methods, the ﬁrst, second, and/or third expression constructs are on a single nucleic acid molecule.

In some of the above methods, (a) the DNA encoding the Cas protein is in the form of a ﬁrst expression construct comprising a ﬁrst promoter operably linked to a second nucleic acid ng the Cas protein; and (b) the DNA encoding the CRISPR RNA and the DNA encoding the trachNA are in the form of a second sion construct comprising a second promoter operably linked to a third nucleic acid encoding a gRNA comprising the CRISPR RNA and the trachNA in a single transcript; wherein the ﬁrst and second promoters are active in the eukaryotic cell, the mouse cell, or the human cell. In some of the above methods, the ﬁrst and the second expression constructs are on a single c acid molecule.

In some of the above methods, the LTVEC is at least 15 kb, at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, or at least 90 kb. In some of the above methods, the LTVEC is at least 100 kb, at least 150 kb, or at least 200 kb.

In some of the above methods, the ﬁrst nucleic acid is at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, at least 90 kb, at least 100 kb, at least 150 kb, at least 200 kb, at least 250 kb, or at least 300 kb. In some of the above methods, the ﬁrst nucleic acid is about 40 kb to about 140 kb.

In some of the above methods, the sum total of the 5’ and the 3’ gy arms of the LTVEC is from about 10 kb to about 150 kb. In some of the above methods, the sum total of the 5’ and the 3’ homology arms of the LTVEC is from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 120 kb, or from about 120 kb to 150 kb.

In some of the above methods, the 5’ target sequence and the 3’ target sequence are separated by at least 5 kb but less than 3 Mb. In some of the above methods, the 5’ target sequence and the 3’ target sequence are ted by at least 5 kb but less than 10 kb, at least 10 kb but less than 20 kb, at least 20 kb but less than 40 kb, at least 40 kb but less than 60 kb, at least 60 kb but less than 80 kb, at least about 80 kb but less than 100 kb, at least 100 kb but less than 150 kb, or at least 150 kb but less than 200 kb, at least about 200 kb but less than about 300 kb, at least about 300 kb but less than about 400 kb, at least about 400 kb but less than about 500 kb, at least about 500 kb but less than about le, at least about 1 Mb but less than about 1.5 Mb, at least about 1.5 Mb but less than about 2 Mb, at least about 2 Mb but less than about 2.5 Mb, or at least about 2.5 Mb but less than about 3 Mb. In some of the above methods, the 5’ target sequence and the 3’ target sequence are separated by at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, at least 90 kb, at least 100 kb, at least 110 kb, at least 120 kb, at least 130 kb, at least 140 kb, at least 150 kb, at least 160 kb, at least 170 kb, at least 180 kb, at least 190 kb, or at least 200 kb. In some of the above methods, the 5’ target sequence and the 3’ target sequence are separated by from about 30 kb to about 110 kb.

In some of the above methods, the eukaryotic cell is not a rat cell. In some of the above methods, the eukaryotic cell is a pluripotent cell, a non-pluripotent cell, a mammalian cell, a human cell, a non-human mammalian cell, a rodent cell, a mouse cell, a hamster cell, a non-human otent cell, a human pluripotent cell, a rodent pluripotent cell, or a ﬁbroblast. In some of the above s, the eukaryotic cell is a primary cell or an immortalized cell. In some of the above methods, the rodent pluripotent cell is a mouse or rat embryonic stem (ES) cell.

In some of the above methods, the mouse cell, or the human cell is a primary cell or an immortalized cell. In some of the above methods, the mouse cell, or the human cell is a pluripotent cell. In some of the above methods, the mouse pluripotent cell is a mouse embryonic stem (ES) cell. In some of the above methods, the human pluripotent cell is a human embryonic stem (ES) cell, a human adult stem cell, a developmentally restricted human progenitor cell, or a human induced pluripotent stem (iPS) cell. In some of the above methods, the human iPS cells is being maintained in a medium sing a base medium and supplements, wherein the medium comprises: (a) a leukemia inhibitory factor (LIF) polypeptide; (b) a glycogen synthase kinase (GSK3) inhibitor; and (c) a MEK tor; wherein the medium has an osmolality of about 175 g to about 280 mOsm/kg.

In some of the above methods, the Cas protein is Cas9. In some of the above methods, the target sequence is immediately ﬂanked by a Protospacer Adjacent Motif (PAM) sequence.

In some of the above methods, the targeted genetic modiﬁcation comprises simultaneous deletion of an endogenous nucleic acid sequence at the genomic locus of interest and insertion of the ﬁrst nucleic acid at the genomic locus of interest in a single step. In some of the above methods, the deleted endogenous nucleic acid sequence is from about 30 kb to about 110 kb, and the inserted ﬁrst nucleic acid is from about 40 kb to about 140 kb.

In some of the above methods, the targeted genetic modiﬁcation is a biallelic genetic modiﬁcation. In some of the above methods, the biallelic genetic modiﬁcation ses deletion of an endogenous nucleic acid sequence and insertion of the ﬁrst nucleic acid at the genomic locus of st in two homologous somes.

In some of the above methods, the modiﬁed eukaryotic cell, the modiﬁed mouse cell, or the modiﬁed human cell is compound zygous at the c locus of st. In some of the above methods, the d eukaryotic cell, the modiﬁed mouse cell, or the d human cell is hemizygous at the genomic locus of interest. In some of the above methods, the targeted genetic modiﬁcation at the genomic locus of interest in one chromosome comprises deletion of an endogenous nucleic acid sequence and insertion of the ﬁrst nucleic acid. In some of the above methods, the targeted c modiﬁcation comprises: (1) deletion of an endogenous nucleic acid sequence at the genomic locus of interest in ﬁrst and second homologous chromosomes; and (2) insertion of the ﬁrst nucleic acid into the genomic locus of interest in the ﬁrst homologous chromosome and disruption of the genomic locus of interest in the second homologous chromosome.

In some of the above s, the targeted genetic modiﬁcation comprises: (a) a replacement of an endogenous nucleic acid sequence with a gous or an orthologous nucleic acid sequence; (b) a on of an endogenous nucleic acid sequence; (c) a on of an nous nucleic acid sequence, n the deletion ranges from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, or from about 150 kb to about 200 kb, from about 200 kb to about 300 kb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to about 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, or from about 2.5 Mb to about 3 Mb; (d) insertion of an exogenous c acid sequence; (e) insertion of an exogenous nucleic acid sequence ranging from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb; (l) insertion of an exogenous nucleic acid sequence comprising a gous or an orthologous nucleic acid sequence; (g) insertion of a chimeric nucleic acid sequence comprising a human and a non-human nucleic acid sequence; (h) insertion of a conditional allele ﬂanked with site-speciﬁc recombinase target sequences; (i) insertion of a selectable marker or a reporter gene operably linked to a promoter active in the pluripotent cell; or (j ) a combination thereof.

In some of the above methods, the genomic locus of interest comprises the Interleukin-2 or gamma locus, the ApoE locus, the Rag] locus, the Rag2 locus, both ofthe Rag] and the Rag2 loci, the Adamts5 locus, the Trpal locus, the Folk] locus, the Erbb4 locus, the Lrp5 locus, the C5 (Hc) locus, the RorI locus, or the Dpp4 locus. In some of the above methods, the genomic locus of interest comprises extrachromosomal DNA.

Also provided are methods for producing an F0 generation non-human animal or mouse that comprises a targeted genetic modiﬁcation at a genomic locus of interest, comprising: (a) modifying a non-human or mouse ES cell using any of the above methods; (b) identifying the modiﬁed non-human or mouse ES cell comprising the targeted genetic modiﬁcation at the genomic locus of interest; (c) ucing the modiﬁed non-human or mouse ES cell into a non-human or mouse host embryo; and (d) gestating the non-human or mouse host embryo in a surrogate mother, wherein the surrogate mother produces the F0 generation non-human animal or mouse comprising the targeted genetic ation at the genomic locus of interest.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 depicts rat ESCs, which grow as compact cal colonies that routinely detach and ﬂoat in the dish.

Figure 2A through D depict various pluripotency markers expressed by rat ESCs: A depicts Oct-4 (green); B depicts Sox-2 (red); C s DAPI (blue); D depicts an overlay of pluripotency markers expressed by rESCs.

Figure 3 depicts that the rat ESCs express light levels of alkaline phosphatase (a otency marker).

Figure 4 depicts the karyotype for line DA.2B, which is 42X,Y.

Karyotyping was done e rat ESCs often become tetraploid; lines were thus pre- screened by counting ase chromosome spreads, and lines with mostly normal counts were then formally karyotyped.

Figure 5A-B provides photographs g the analysis of the chromosome number of the ACI.Gl rat ES cell line.

Figure 6A-B provides photographs g the analysis of the chromosome number of the DA.2B rat ES cell line.

Figure 7A-B provides raphs showing the analysis of the chromosome number of the DA.2C rat ES cell line.

Figure 8 depicts a closer view of a rat ESC of Figure l.

Figure 9 depicts production of chimeras by blastocyst injection and transmission of the rat ESC genome through the germline. Chimeras were produced by blastocyst ion using parental ACI.Gl rat ESCs. High tage chimeras y have albino snouts.

Figure 10 depicts Fl agouti pups with albino littermates, sired by ACI/SD chimera labeled with an asterisk (*) in Figure 9.

Figure 11 provides a schematic of the rat ApoE locus and denotes with grey bars the cutting site for zinc ﬁnger nucleases (ZFNl and ZFN2). The c regions corresponding to the 5’ and 3’ homology arms (5 kb and 5.4 kb, respectively) are d by the dark grey boxes. Exon 1 of the ApoE gene is non-coding and is shown as an open box closest to the 5’ homology arm. The three introns of the ApoE gene are denoted as lines. Exons 2 and 3 comprise coding regions and are shown as stippled grey boxes. Exon 4 contains both coding and non-coding sequences as denoted by the stippled grey shading and the open box.

Figure 12 depicts targeting of the rat R0sa26 locus, which lies between the Setd5 and Thumpd3 genes as in mouse, with the same spacing. Panel A shows the structure of the mouse R0sa26 locus. Mouse R0sa26 transcripts consist of 2 or 3 exons.

Panel B depicts the structure of the rat R0sa26 locus; the rat locus contains a second exon 1 (Exlb) in addition to the homologous exon to mouse exonl (Exla); no third exon has been ﬁed in rat. Panel C depicts a targeted rat R0sa26 allele; homology arms of 5 kb each were cloned by PCR using genomic DNA from DA rESC; the targeted allele contains a Splicing Acceptor (SA)—lacZ-hUB-neo cassette replacing a 117 bp deletion in the rat R0sa26 .

Figure 13A depicts a control brain of a l4-week-old wild type rat, which was d with X-gal. The control brain showed a low level of background staining for LacZ (dorsal view).

Figure 13B depicts LacZ expression in the brain of an rRosa26 heterozygous rat (14-week old). The lacZ reporter was expressed ubiquitously throughout the brain of the rRosa26 heterozygote.

Figure 13C depicts a control heart and thymus (inset) of a k-old wild type rat, which were treated with X-gal. The control heart and thymus showed a low level of background staining for LacZ.

Figure 13D depicts LacZ expression in the heart and thymus (inset) of a l4-week-old rRosa26 heterozygous rat. The lacZ reporter was expressed ubiquitously throughout the heart and thymus of the rROSA26 heterozygote.

Figure 13E depicts a control lung of a l4-week-old wild type rat, which was treated with X-gal. The control lung showed a low level of background staining for LacZ.

Figure l3F depicts LacZ expression in the lung of a l4-week-old rRosa26 heterozygote rat. The lacZ reporter was expressed ubiquitously throughout the lung of the 6 heterozygote.

Figure 13G and H depict LacZ expression in E125 rat embryos. In contrast to the ype control embryo (H), which shows a low level of background LacZ staining, the 6 heterozygous embryo exhibited ubiquitous expression of the LacZ reporter throughout the embryo.

Figure 131 and J depict LacZ expression in El4.5 rat embryos. In contrast to the wild-type l embryo (J), which shows a low level of background LacZ ng, the rRosa26 heterozygous rat embryo exhibited ubiquitous expression of the LacZ reporter throughout the embryo.

Figure 14 illustrates a homologous or non-homologous recombination event that occurs inside a rat ES cell following an electroporation of a ing vector comprising a ion cassette neo cassette).

Figure 15 illustrates the mechanism by which genome-editing endonucleases (e. g., ZFNs and TALENs) introduce a double strand break (DSB) in a target genomic sequence and activate non-homologous end-joining (NHEJ) in an ES cell.

Figure 16 illustrates a gene targeting technique that utilizes ZFN/TALENs to improve the efﬁciency of homologous recombination of a ing vector. DSB represents double strand break. 2014/060788 Figure 17 shows ApoE-ZFN-ABS chimeras produced by chimera production and germline transmission of the modiﬁed rat ApoE locus. The targeted modiﬁcation was assisted by zinc ﬁnger nucleases.

Figure 18 provides a schematic of the IL2r-y targeting event in combination with zinc ﬁnger nucleases that target ZFN U and ZFN D. The region of the rat IL2r-y locus targeted by ZFN U and ZFN D is shown (SEQ ID NO: 93). ZFN cut sites are noted in the ﬁgure.

Figure 19 provides a tic of the IL2r-y targeting event in combination with zinc ﬁnger nucleases that target ZFN U and ZFN D or in combination with gRNAs , gRNAZ, gRNA3, gRNA4). The regions of the rat IL2r-y locus targeted by ZFN U and ZFN D or -4 are shown, and ZFN cut sites are noted.

Figure 20 provides a schematic of the rat ApoE locus and a targeting plasmid. The upper schematic shows the genomic structure of the rat ApoE locus and the c s corresponding to the 5’ and 3’ homology arms (5 kb and 5.4 kb respectively; dark grey boxes). Exon 1 of the ApoE gene is non-coding and is shown as an open box closest to the 5’ homology arm. The three introns of the ApoE gene are denoted as lines. Exons 2 and 3 se coding regions and are shown as stippled grey boxes. Exon 4 contains both coding and non-coding sequences as d by the stippled ’ and grey shading and the open box. The lower panel shows the targeting plasmid. The 5 3’ homology arms (5 kb and 5.4 kb, respectively) are denoted by the dark grey boxes.

The ing vector comprises a reporter gene (lacZ) and a self-deleting cassette ﬂanked by loxP sites (open arrows). The self-deleting cassette comprises a mouse PrmI promoter operably linked to the Crei gene and a drug selection cassette comprising a human ubiquitin promoter operably linked to a neomycin resistance gene.

Figure 21A provides a schematic for ing the ApoE locus in rat ES cells using zinc-ﬁnger nucleases and a targeting vector comprising a reporter gene (LacZ) and a self-deleting cassette comprising a mouse PrmI promoter operably linked to the Crei gene and a drug selection cassette comprising a human ubiquitin promoter operably linked to a neomycin resistance gene. Figure 21B depicts a homozygous targeted ApoE locus.

Figure 22 provides a schematic of the rat ApoE locus and a large targeting vector (LTVEC). The upper panel shows the genomic organization of the rat ApoE locus and the c regions corresponding to the 5’ and 3’ gy arms (45 kb and 23 kb, respectively; the dark grey boxes). Exon 1 ofApoE is non-coding and is shown as an open box closest to the 5’ homology arm. The three introns of the ApoE gene are denoted as lines and exons 2 and 3 comprise coding regions and are shown as stippled grey boxes.

Exon 4 contains both coding and ding sequences as denoted by the stippled grey shading and the open box. The lower panel shows the LTVEC for modifying the rat ApoE locus. The 5’ and 3’ homology arms (45 kb and 23 kb, respectively) are denoted by the dark grey boxes. The LTVEC comprises a reporter gene (lacZ) and a self-deleting cassette ﬂanked by loxP sites (open arrows), which comprises a mouse PrmI promoter ly linked to the Crei gene and a drug selection cassette sing a human ubiquitin promoter operably linked to a neomycin resistance gene.

Figure 23 provides a schematic of the rat ApoE locus and denotes with grey bars the cutting sites for zinc ﬁnger nucleases (ZFNl and ZFN2) used together with the large targeting vector (LTVEC) to enhance homologous recombination between the targeting vector and the target cognate somal region.

Figure 24 depicts the rat IL2r—y locus that has been disrupted by a 3.2 kb deletion and the insertion of a reporter gene (eGFP) and a self-deleting cassette comprising a drug selection cassette (hUb-neo) and the Crei gene operably linked to a mouse PrmI promoter.

Figure 25 provides another depiction of the rat IL2r—y locus that has been disrupted by a 3.2 kb deletion and the ion of a reporter gene (eGFP) and a selfdeleting cassette comprising the Crei gene ly linked to a mouse PrmI promoter and a drug selection cassette (hUb-Neo).

Figure 26 provides a schematic of the rat Rag2 locus and a large ing vector ) for modifying the rat Rag2 locus. The upper panel shows the c organization of the rat Rag2 locus and the cognate genomic regions corresponding to the ’ and 3’ homology arms (48 kb and 84 kb, respectively; dark grey boxes). Rag2 comprises single exon denoted by the stippled grey shading. The lower panel is the LTVEC. The 5’ and 3’ homology arms (48 kb and 84 kb, respectively) are denoted by the dark grey boxes. The LTVEC comprises a reporter gene (lacZ) and a self-deleting cassette ﬂanked by loxP sites (open arrows) that contains a rat PrmI promoter operably linked to the Crei gene and a drug selection te containing a human ubiquitin er operably linked to a neomycin resistance gene.

Figure 27 provides the genomic structure of the rat RagI/Rag2 locus and the genomic regions deleted by either Rag2 targeting (Rag2 deletion) or Rag2/Rag1 double targeting (Rag2/Rag1 deletion).

Figure 28 provides a schematic of the rat Rag2 and Rag] loci and a large targeting vector (LTVEC) used for modifying the loci. The upper panel shows the genomic organization of the Rag] and Rag2 loci and the cognate genomic s corresponding to the 5’ and 3’ homology arms (48 kb and 15 kb, respectively; dark grey boxes). Rag2 and Rag] each comprise a single exon denoted by the ed grey shading. The lower panel is the LTVEC. The 5’ and 3’ homology arms (48 kb and 15 kb, respectively) are denoted by the dark grey boxes. The LTVEC comprises a reporter gene (lacZ) and a self-deleting cassette ﬂanked by loxP sites (open arrows), which comprises a rat PrmI promoter operably linked to the Crei gene and a drug selection cassette comprising a human tin promoter operably linked to a neomycin resistance gene.

Figure 29 shows ﬂow cytometry analysis for GFP expression and for T- cell marker CD3 (panels A and D), B-cell marker B220 s B and E), and NK cell marker CDl6la (panels C and F) in peripheral blood mononuclear cells (PBMCs) from an II2rg-/y chimeric rat (panels A-C) and a WT DA rat (panels D-F). Double-positive cells are showin in nt R8. Figure 29 shows that II2rg-/y PBMC do not express mature lymphocyte markers.

Figure 30 shows that GFP-positive lymphocytes were detected in eral blood in 2 of the 3 /y chimeras.

Figure 31 provides a schematic of the rat Il2rg locus and a targeting plasmid for the ﬁlll humanization of the rat Il2rg locus. The upper panel shows the c organization of the rat Il2rg locus and the e genomic regions corresponding to the 5’ and 3’ homology arms (4.3 kb and 4.0 kb, respectively; grey boxes). The lower panel is the targeting plasmid. The 5’ and 3’ homology arms (4.3 kb and 4.0 kb, respectively) are d by the grey boxes. The targeting plasmid ses the human IL-2rg genomic region and a deletion cassette ﬂanked by loxP sites (open arrows) that contains a drug selection cassette containing a human tin promoter operably linked to a neomycin resistance gene.

Figure 32 provides a schematic of the rat Il2rg locus and a targeting plasmid for the ecto-domain humanization of the rat Il2rg locus. The upper panel shows the c organization of the rat Il2rg locus and the cognate genomic regions corresponding to the 5’ and 3’ homology arms (4.3 kb and 4.0 kb, respectively; grey boxes). The lower panel is the targeting plasmid. The 5’ and 3’ homology arms (4.3 kb and 4.0 kb, respectively) are denoted by the grey boxes. The targeting plasmid comprises the human ecto-domain of the IL-2Rg genomic region and a self-deleting cassette ﬂanked by loxP sites (open arrows) that contains a rat PrmI promoter operably linked to the Crei gene and a drug selection cassette ning a human ubiquitin er operably linked to a neomycin resistance gene.

] Figure 33 provides a sequence alignment of the human IL-2rg protein (SEQ ID NO: 20; NP_000197.l); the rat IL-2rg protein (SEQ ID NO: 21; NP_543 165. l); and the chimeric IL-2rg protein (SEQ ID NO: 22) comprising the human ecto-domain of IL-2rg fused to the remainder of the rat IL-2rg protein. The junction between the human and rat IL-2rg is noted by the al line.

Figure 34 es a schematic of CRISPIVCas9-assisted humanization of the mouse Lrp5 gene; the LTVEC is shown the top panel and the mouse Lrp5 locus is shown in the bottom panel. The region humanized is the ectodomain. The arrows indicate target sites for each gRNA (gA, gB, gB2, gC, gD, gE2, gE, gF) and ZFN (a-d).

Figure 35 depicts the percent targeting efﬁciency of LTVECs targeting genes of increasing size for deletion e 35A) and LTVECs with human gene insertions of increasing size (Figure 35B). The LTVECs were used alone (gray squares or triangles) or in combination with ZFNs (black squares or triangles).

Figure 36 provides a schematic of CRISPIVCas9-assisted humanization of the entire coding region of the mouse Trpal gene; the LTVEC is shown the top panel and the mouse Trpal locus is shown in the bottom panel. The arrows indicate target sites for each gRNA (gA, gA2, gB, gC, gD, gE2, gE, gF)- 2014/060788 Figure 37 provides a schematic of CRISPlVCas9-assisted humanization of the ectodomain (exon 2 to stop codon) of the mouse Folk] gene; the LTVEC is shown the top panel and the mouse F01h] locus is shown in the bottom panel. The arrows indicate target sites for each gRNA (gA, gA2, gB, gC, gD, gE, gE2, gF).

Figure 38 es a schematic of CRISPlVCas9-assisted humanization of the region from exon 2 to the stop codon of the mouse C5 (H6) gene; the LTVEC is shown the top panel and the mouse C5 (Hc) locus is shown in the bottom panel. The arrows indicate target sites for each gRNA (gA, gB, gB2, gC, gD, gE2, gE, gF).

Figure 39 provides a schematic of CRISPlVCas9-assisted humanization of the entire coding region of the mouse Adamts5 gene; the LTVEC is shown the top panel and the mouse Adamts5 locus is shown in the bottom panel. The arrows indicate target sites for each gRNA (gA, gA2, gB, gC, gD, gE2, gE, gF).

Figure 40 provides a schematic of VCas9-assisted humanization of exons 4-15 of the mouse Erbb4 gene; the LTVEC is shown the top panel and the mouse Erbb4 locus is shown in the bottom panel. The arrows indicate target sites for each gRNA (gA, gB, gB2, gC, gD, gE2, gE, gF).

Figure 41 provides a schematic of CRISPlVCas9-assisted humanization of exons 2-7 of the mouse R0r1 gene; the LTVEC is shown the top panel and the mouse R0r1 locus is shown in the bottom panel. The arrows indicate target sites for each gRNA (gA, gB, gC, gD, gE, gF)- Figure 42 provides a schematic of CRISPlVCas9-assisted humanization of the region from exon 2 to the stop codon of the mouse Dpp4 gene; the LTVEC is shown the top panel and the mouse Dpp4 locus is shown in the bottom panel. The arrows indicate target sites for each gRNA (gA, gB, gB2, gC, gD, gE2, gE, gF).

Figure 43 shows l2-week-old female rat brains stained with X-gal. Figure 43A-C show a brain from a wild type rat, and Figure 43D-F show a brain from an ApoE rat. Figure 43A and D show dorsal views, Figure 43B and E show ventral views, and Figure 43C and F show close-up views.

Figure 44 shows l2-week-old female rat hearts (A and C) and corresponding close-ups of blood vessels (B and D) stained with X-gal. Figure 44A and B show a heart and blood vessels, respectively, from a wild type rat, and Figure 44C and D show a heart and blood vessels, respectively, from an ApoE rat. Staining was present in the atria of the heart and in some vessels (e. g., vena cava).

Figure 45 shows l2-week-old female rat livers stained with X-gal. Figure 45A and B show a liver from a wild type rat, and Figure 45C and D show a liver from an ApoE rat. Figure 45B and D are close-ups of the livers.

Figure 46 shows detection of cholesterol, LDL, HDL, and triglyceride levels (Figure 46A-D, respectively) in homozygous ApoE—targeted rats, heterozygous ApoE—targeted rats, and wild type rats at 6 weeks, 9 weeks, 12 weeks, and 15 weeks.

] Figure 47 shows a schematic of the rat ApoE locus (upper panel) and a large targeting vector (LTVEC) that targets the rat ApoE locus (lower panel). The upper panel shows the genomic organization of the rat ApoE locus and the genomic regions corresponding to the 5’ and 3’ gy arms (45 kb and 23 kb, respectively; the dark grey boxes). Exon 1 ofApoE is non-coding and is shown as an open box closest to the 5’ homology arm. The three introns of the ApoE gene are denoted as lines and exons 2 and 3 comprise coding regions and are shown as stippled grey boxes. Exon 4 ns both coding and non-coding sequences as denoted by the stippled grey shading and the open box. Target sites for ApoE gRNA2 (SEQ ID NO: 87) and gRNA3 (SEQ ID NO: 88) are indicated. The lower panel shows the LTVEC for modifying the rat ApoE locus. The 5 ’ and 3’ homology arms (45 kb and 23 kb, respectively) are denoted by the dark grey boxes. The LTVEC comprises a reporter gene (lacZ) and a self-deleting cassette ﬂanked by loxP sites (open arrows), which comprises a mouse PrmI promoter operably linked to the Crei gene and a drug selection cassette comprising a human ubiquitin promoter operably linked to a neomycin resistance gene.

Figure 48 shows a tic of the rat Rag2 locus (upper panel) and a large targeting vector (LTVEC) that targets the rat Rag2 locus (lower panel). The upper panel shows the genomic organization of the rat Rag2 locus and the cognate c regions ponding to the 5’ and 3’ homology arms (48 kb and 84 kb, respectively; dark grey boxes). Rag2 comprises a single exon d by the stippled grey g.

Target sites for Rag2 gRNAl (SEQ ID NO: 89) and gRNA4 (SEQ ID NO: 90) are indicated. The lower panel is the LTVEC. The 5’ and 3’ homology arms (48 kb and 84 kb, respectively) are denoted by the dark grey boxes. The LTVEC comprises a reporter gene (lacZ) and a self-deleting cassette ﬂanked by loxP sites (open arrows) that contains a rat PrmI promoter ly linked to the Crei gene and a drug ion cassette containing a human ubiquitin promoter operably linked to a hygromycin resistance gene.

Figure 49 shows a schematic of the rat Il2rg locus (upper panel) and a targeting plasmid for ectodomain humanization of the rat Il2rg locus (lower panel). The upper panel shows the genomic organization of the rat Il2rg locus and the cognate genomic regions corresponding to the 5’ and 3’ homology arms (4.3 kb and 4.0 kb, respectively; grey . Target sites for Il2rg gRNA2 (SEQ ID NO: 91) and gRNA4 (SEQ ID NO: 92) are indicated. The lower panel is the targeting plasmid. The 5’ and 3’ homology arms (4.3 kb and 4.0 kb, respectively) are denoted by the grey boxes. The targeting plasmid ses the human ecto-domain of the IL-2Rg genomic region and a eleting cassette ﬂanked by loxP sites (open arrows) that contains a rat PrmI promoter operably linked to the Crei gene and a drug selection cassette containing a human ubiquitin promoter operably linked to a neomycin resistance gene.

Figure 50 shows a schematic of the rat Rag2 and Rag] loci and a large targeting vector ) used for modifying the loci in Il2rg—targeted rat ES cells (clone Il2rg—CGl2). The upper panel shows the genomic organization of the Rag] and Rag2 loci and the cognate genomic regions corresponding to the 5’ and 3’ homology arms (48 kb and 15 kb, tively; grey boxes). Rag2 and Rag] each comprise a single exon denoted by the unshaded . The lower panel is the LTVEC. The 5’ and 3’ homology arms (48 kb and 15 kb, respectively) are denoted by the grey boxes. The LTVEC comprises a reporter gene (eGFP) and a puromycin resistance gene separated by an internal ribosome entry site (IRES) and operably linked to an actin promoter. The LTVEC further comprises a self-deleting cassette ﬂanked by loxP sites (open arrows), which ses a rat PrmI promoter ly linked to the Crei gene and a drug selection cassette sing a human ubiquitin promoter operably linked to a neomycin resistance gene.

Figure 51 depicts a schematic for replacement of a portion of the human ADAM6 locus with a nucleic acid comprising the mouse Adam6a and mouse Adam6b loci using an LTVEC and a guide RNA in human iPS cells. The target site for the guide RNA is indicated by the arrow.

] Figure 52A depicts the morphology displayed by human iPS cells cultured for 8 days in 2i medium. Figure 52B depicts the morphology displayed by human iPS cells cultured for 12 days in 2i medium.

Figures 53A-53D depict the morphology of human iPS cells cultured in mTeSR™ -hLIF medium or low lity VG2i medium for 6 days. s 53A and 53B depict the morphology of human iPS cells cultured in mTeSR™ -hLIF medium (Figure 53A) or VG2i medium (Figure 53B) for 6 days. Figures 53C and 53D depict the morphology of human iPS cells ed on newborn human in fibroblast (NuFF) feeder cells in mTeSR™ -hLIF medium (Figure 53C) or VG2i medium (Figure 53D) for 6 days.

Figure 54A depicts reprogrammed human iPS cells cultured in VG2i medium that have been stained for alkaline phosphatase. Figures 54B and 54C depict reprogrammed human iPS cells cultured in VG2i medium that have been immunostained for the sion of NANOG.

Figures 55A-55C illustrate enzymatic dissociation and subculture of reprogrammed human iPS cells cultured in VG2i medium. Figure 55A depicts reprogrammed human iPS cells ed in VG2i medium prior to enzymatic dissociation with trypsin in the absence of a ROCK inhibitor. Figure 55B depicts human iPS cells ed in VG2i medium for 1 day after subculture. Figure 55C s human iPS cells cultured in VG2i medium for 4 days after subculture.

DETAILED DESCRIPTION OF THE INVENTION Compositions and s are provided for modifying a rat, eukaryotic, nonrat eukaryotic, mammalian, man mammalian, human, rodent, non-rat rodent, mouse, or hamster genomic locus of interest via bacterial homologous recombination (BHR) in a prokaryotic cell. Compositions and methods are also provided for genetically modifying a genomic locus of interest, for example, rat, eukaryotic, non-rat eukaryotic, mammalian, nonhuman mammalian, human, rodent, non-rat rodent, or mouse genomic locus of st using a large targeting vector (LTVEC) in combination with endonucleases. Compositions and methods are also provided for producing a genetically modified non-human animal, for example, a rat, mouse, rodent, or non-rat rodent, comprising one or more targeted genetic modiﬁcations. Also ed are isolated human and non-human totipotent or pluripotent stem cells, in ular rat embryonic stem cells, that are capable of sustaining pluripotency following one or more serial genetic modiﬁcations in vitro, and that are capable of transmitting the ed c modiﬁcations to uent generations through germline.

Glossary ] The term "embryonic stem cell" or "ES cell" as used herein includes an embryo-derived totipotent or pluripotent cell that is capable of contributing to any tissue of the developing embryo upon introduction into an embryo. The term "pluripotent cell" as used herein includes an undifferentiated cell that possesses the ability to develop into more than one differentiated cell types. The term "non-pluripotent cell" includes cells that are not pluripotent cells.

The term "homologous nucleic acid" as used herein includes a nucleic acid sequence that is either cal or substantially similar to a known reference sequence. In one embodiment, the term "homologous nucleic acid" is used to characterize a sequence having amino acid sequence that is at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or even 100% identical to a known reference sequence.

The term "orthologous c acid" as used herein includes a nucleic acid sequence from one species that is functionally equivalent to a known reference sequence in another species.

The term "large targeting vector" or "LTVEC" as used herein includes large targeting vectors for eukaryotic cells that are derived from fragments of cloned genomic DNA larger than those typically used by other approaches intended to perform homologous gene targeting in otic cells. Examples of LTVEC, include, but are not limited to, bacterial homologous chromosome (BAC) and yeast artiﬁcial chromosome (YAC).

] The term "modiﬁcation of allele" (MOA) as used herein includes the modiﬁcation of the exact DNA sequence of one allele of a gene(s) or chromosomal locus (loci) in a genome. Examples of "modiﬁcation of allele (MOA)" as described herein includes, but is not limited to, ons, substitutions, or insertions of as little as a single nucleotide or deletions of many kilobases spanning a gene(s) or chromosomal locus (loci) of interest, as well as any and all le modiﬁcations between these two extremes.

] The term "recombination site" as used herein includes a nucleotide sequence that is recognized by a site-speciﬁc recombinase and that can serve as a substrate for a recombination event. l" genetic modiﬁcations include two or more modiﬁcations ted independently to a cell (e.g., a eukaryotic cell, a t eukaryotic cell, a mammalian cell, a human cell, a non-human mammalian cell, a pluripotent cell, a non- pluripotent cell, a non-human pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a developmentally-restricted human progenitor cell, a human iPS cell, a human cell, a rodent cell, a non-rat rodent cell, a rat cell, a mouse cell, a hamster cell, a ast, or a Chinese hamster ovary (CHO) cell). The ﬁrst modiﬁcation may be achieved by oporation, or any other method known in the art. Then a second modiﬁcation is made to the same cell genome employing a le second nucleic acid construct. The second modiﬁcation may be achieved by a second electroporation, or any other method known in the art. In various embodiments, following the ﬁrst and the second genetic modiﬁcations of the same cell, a third, a fourth, a ﬁfth, a sixth, and so on, serial genetic modiﬁcations (one following another) may be achieved using, e.g., serial electroporation or any other suitable method (serially) known in the art.

The term "site-speciﬁc recombinase" as used herein es a group of enzymes that can facilitate recombination between "recombination sites" where the two recombination sites are physically separated within a single nucleic acid molecule or on separate nucleic acid molecules. Examples of "site-speciﬁc recombinase" include, but are not limited to, Cre, Flp, and Dre recombinases.

The term ine" in reference to a nucleic acid sequence includes a nucleic acid sequence that can be passed to progeny.

The phrase "heavy chain," or "immunoglobulin heavy chain" includes an immunoglobulin heavy chain sequence, including immunoglobulin heavy chain constant region sequence, from any organism. Heavy chain variable domains include three heavy chain CDRs and four FR regions, unless otherwise ed. Fragments of heavy chains include CDRs, CDRs and FRs, and combinations thereof. A typical heavy chain has, following the variable domain (from N—terminal to C-terminal), a CH1 domain, a hinge, a CH2 domain, and a CH3 domain. A functional fragment of a heavy chain es a fragment that is capable of speciﬁcally recognizing an epitope (e.g., recognizing the epitope with a KD in the micromolar, nanomolar, or picomolar range), that is e of expressing and secreting from a cell, and that comprises at least one CDR. Heavy chain variable s are encoded by variable region nucleotide sequence, which lly comprises VH, DH, and JH segments derived from a repertoire of VH, DH, and JH segments present in the ne. Sequences, locations and nomenclature for V, D, and J heavy chain segments for various organisms can be found in IMGT database, which is accessible Via the intemet on the world wide web (www) at the URL "imgt.org." The phrase "light chain" includes an immunoglobulin light chain sequence from any organism, and unless otherwise speciﬁed includes human kappa (K) and lambda (7») light chains and a VpreB, as well as surrogate light chains. Light chain variable domains typically include three light chain CDRs and four framework (FR) regions, unless ise speciﬁed. Generally, a full-length light chain includes, from amino terminus to carboxyl terminus, a variable domain that includes FRl-CDRl-FRZ-CDRZ- FR3-CDR3-FR4, and a light chain constant region amino acid sequence. Light chain variable s are encoded by the light chain variable region tide sequence, which generally comprises light chain VL and light chain JL gene segments, d from a repertoire of light chain V and J gene ts present in the germline. Sequences, locations and nomenclature for light chain V and J gene segments for various organisms can be found in IMGT database, which is accessible Via the intemet on the world wide web (www) at the URL "imgt.org." Light chains e those, e.g., that do not selectively bind either a ﬁrst or a second epitope selectively bound by the epitope-binding protein in which they appear. Light chains also include those that bind and recognize, or assist the heavy chain with g and recognizing, one or more epitopes selectively bound by the epitope-binding protein in which they appear.

The phrase bly linked" comprises a relationship wherein the ents operably linked ﬁanction in their intended manner. In one instance, a nucleic acid sequence encoding a protein may be operably linked to regulatory sequences (e.g., promoter, er, silencer sequence, etc.) so as to retain proper transcriptional regulation. In one instance, a c acid sequence of an immunoglobulin le region (or V(D)J ts) may be operably linked to a nucleic acid sequence of an immunoglobulin constant region so as to allow proper recombination between the sequences into an immunoglobulin heavy or light chain sequence. 1. Target Locus sing a Nucleic Acid Various methods and compositions are provided, which allow for the integration of at least one insert nucleic acid at a target locus. As used herein, a "genomic locus of interest" comprises any segment or region ofDNA within the genome that one desires to integrate an insert nucleic acid. The terms "genomic locus of interest" and "target genomic locus of interest" can be used interchangeable. The genomic locus of interest can be native to the cell, or alternatively can comprise a heterologous or exogenous segment ofDNA that was integrated into the genome of the cell. Such heterologous or exogenous segments of DNA can include transgenes, expression cassettes, polynucleotide encoding selection makers, or heterologous or exogenous regions of genomic DNA. The term "locus" is a deﬁned herein as a segment ofDNA within the genomic DNA. Genetic modiﬁcations as bed herein can include one or more deletions from a locus of interest, additions to a locus of interest, ement of a locus of interest, and/or any combination f. The locus of interest can comprise coding regions or non-coding regulatory regions.

The c locus of interest can further se any component of a targeted integration system including, for example, a recognition site, a selection marker, a previously integrated insert nucleic acid, polynucleotides encoding nuclease agents, promoters, etc. Alternatively, the genomic locus of interest can be located within an extrachromosomal DNA within the cell, such as a yeast artiﬁcial chromosome (YAC), a bacterial artiﬁcial chromosome (BAC), a human artiﬁcial chromosome, or any other engineered genomic region ned in an appropriate host cell. In various embodiments, the targeted locus can comprise native, heterologous, or exogenous c acid sequence from a prokaryote, a eukaryote, a t ote, yeast, bacteria, a non- human mammal, a non-human cell, a rodent, a non-rat rodent, a human, a rat, a mouse, a hamster, a rabbit, a pig, a bovine, a deer, a sheep, a goat, a chicken, a cat, a dog, a ferret, a primate (e.g., marmoset, rhesus monkey), domesticated mammal or an agricultural mammal or any other organism of st or a combination thereof. In some embodiments, the genomic locus of interest comprises a nucleic acid sequence from a human, a mouse, or a combination thereof.

In speciﬁc ments, the target locus is from, for example, a eukaryotic cell, a non-rat otic cell, a mammalian cell, human cell, a non-human mammalian cell, a pluripotent cell, a non-pluripotent cell, a non-human pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a developmentally- cted human progenitor cell, a human iPS cell, a human cell, a rodent cell, a t rodent cell, a rat cell, a mouse cell, a hamster cell, a ﬁbroblast, or a CHO cell.

In c embodiments, the genomic locus of interest comprises a target locus of a "rat nucleic acid." Such a region comprises a nucleic acid from a rat that is integrated Within the genome of a cell. miting examples of the target locus include a genomic locus that encodes a protein expressed in a B cell, a genomic locus that expresses a polypeptide in an immature B cell, a genomic locus that expresses a polypeptide in a mature B cell, an immunoglobulin (Ig) loci, or a T cell receptor loci, including, for example, a T cell receptor alpha locus. Additional examples of target genomic locus include an FcerIa locus, a T[M locus, a Prlr locus, a 4 locus, an Accn2 locus, an Adamts5 locus, a TrpaI locus, Folk] locus, an Lrp5 locus, an IL2 receptor locus, including, for example, an IL2 or gamma (Il2rg) locus, an ApoE locus, a Rag] locus, a Rag2 locus, a RagI/Rag2 locus, and an Erbb4 locus. Any such target locus can be from a rat or can be from a eukaryotic cell, a non-rat eukaryotic cell, a mammalian cell, a human cell, or a non-human mammalian cell.

In one embodiment, the target locus encodes a mammalian immunoglobulin heavy chain variable region amino acid sequence. In one embodiment, the target locus encodes a rat immunoglobulin heavy chain variable region amino acid sequence. In one embodiment, the target locus comprises a c DNA sequence comprising an unrearranged rat, mouse, or human immunoglobulin heavy chain variable region nucleic acid sequence operably linked to an immunoglobulin heavy chain constant region nucleic acid sequence. In one ment, the immunoglobulin heavy chain constant region nucleic acid sequence is a rat, mouse, or human immunoglobulin heavy chain constant region nucleic acid sequence selected from a CHl, a hinge, a CH2, a CH3, and a combination thereof. In one embodiment, the heavy chain constant region nucleic acid sequence comprises a CHl-hinge-CH2-CH3. In one embodiment, the target locus comprises a rearranged rat, mouse, or human immunoglobulin heavy chain variable region nucleic acid ce ly linked to an immunoglobulin heavy chain constant region nucleic acid sequence. In one ment, the immunoglobulin heavy chain constant region nucleic acid sequence is a rat, mouse, or human immunoglobulin heavy chain constant region nucleic acid sequence selected from a CHl, a hinge, a CH2, a CH3, and a combination thereof. In one ment, the heavy chain constant region nucleic acid sequence comprises a CHl-hinge-CH2-CH3.

In one embodiment, the target locus comprises a genomic DNA ce that encodes a mammalian immunoglobulin light chain variable region amino acid sequence. In one embodiment, the genomic DNA sequence comprises an unrearranged mammalian 7» and/or K light chain variable region nucleic acid ce.

] In one ment, the genomic DNA sequence comprises a rearranged mammalian 7» and/or K light chain variable region nucleic acid sequence. In one embodiment, the unrearranged 7» or K light chain variable region nucleic acid sequence is ly linked to a mammalian immunoglobulin light chain constant region nucleic acid sequence selected from a 9» light chain constant region nucleic acid sequence and a K light chain constant region nucleic acid sequence. In one embodiment, the mammalian immunoglobulin light chain constant region nucleic acid sequence is a rat immunoglobulin light chain constant region c acid sequence. In one embodiment, the mammalian immunoglobulin light chain constant region nucleic acid sequence is a mouse immunoglobulin light chain constant region nucleic acid sequence. In one embodiment, the mammalian immunoglobulin light chain constant region nucleic acid ce is a human immunoglobulin light chain constant region c acid sequence.

As used herein, an ApoE locus, an interleukin-2 receptor gamma (Il2rg) locus, a Rag2 locus, a Rag] locus and/or a ag1 locus comprise the respective regions of the genome (i.e., a mammalian , a human genome or a non-human mammalian genome) in which each of these genes or gene combinations are located.

Modifying any one of the ApoE locus, interleukin-2 receptor gamma ) locus, Rag2 locus, Ragl locus and/or Rag2/Ragl locus (i.e., a mammalian, a human, or a man mammalian ApoE locus, the interleukin-2 receptor gamma locus, the Rag2 locus, the Ragl locus and/or the combined Rag2/Ragl locus) can se any desired alteration to the given locus. Non-limiting examples of modiﬁcation to the given locus (i.e., a mammalian, a human, or a non-human mammalian locus) are discussed in further detail herein.

For example, in speciﬁc embodiments, one or more of the ApoE locus, interleukin-2 receptor gamma (Il2rg) locus, Rag2 locus, Ragl locus and/or Rag2/Ragl locus (i.e., a mammalian, a human, or a non-human ian ApoE locus, a mammalian, a human, or a non-human mammalian eukin-2 receptor gamma locus, a mammalian, a human, or a non-human mammalian Rag2 locus, and/or the Rag2/Ragl locus) is modiﬁed such that the activity and/or level of the d ApoE protein or the interleukin-2 receptor gamma protein or the Ragl protein or the Rag2 protein or a combination of the Ragl and Rag2 proteins are decreased. In other embodiments, the activity of the ApoE protein, the interleukin-2 receptor gamma protein, the Ragl protein, or the Rag2 protein, or a combination of the Ragl and Rag2 proteins is absent.

By "decreased" is intended any decrease in the level or activity of the rotein encoded at the locus of interest. For example, a decrease in activity can comprise either (1) a statistically signiﬁcant decrease in the overall level or activity of a given protein (i.e., ApoE, interleukin-2 receptor gamma, Rag2, Rag2 or a combination of Rag1 and Rag2) including, for example, a decreased level or activity of 0.5%, 1%, 5%, %, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 120% or greater when compared to an appropriate l. Methods to assay for a decrease in the concentration and/or the activity of anyone of ApoE, interleukin-2 receptor gamma, Ragl and Rag2 are known in the art.

In other embodiments, one or more of the a mammalian, a human, or a non-human mammalian ApoE locus, the a mammalian, a human, or a non-human ian interleukin-2 receptor gamma locus, a ian, a human, or a non- human ian Rag2 locus, a mammalian, a human, or a non-human mammalian Ragl locus and/or a mammalian, a human, or a non-human mammalian Rag2/Ragl locus comprise a modiﬁcation such that the activity and/or level of the d ApoE polypeptide, the interleukin-2 receptor gamma polypeptide, the Rag2 polypeptide, the Ragl polypeptide, or both the Ragl and Rag2 polypeptide is increased. By "increased" is intended any increase in the level or activity of the gene/polypeptide encoded at the locus of interest. For example, an increase in actiVity can comprise either (1) a statistically signiﬁcant increase in the overall level or actiVity of a given protein (i.e., ApoE, interleukin-2 receptor gamma, Ragl, Rag2 or Ragl and Rag2) including, for example, an increased level or activity of 0.5%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 120% or greater when compared to an appropriate control. Methods to assay for an increase in the concentration and/or the actiVity of anyone of the ApoE, Ragl , Rag2 and interleukin-2 receptor gamma ns are known in the art.

The genetic modiﬁcation to the a mammalian, a human, or a non-human mammalian ApoE locus, a mammalian, a human, or a non-human mammalian interleukin-2 receptor gamma locus, a mammalian, a human, or a non-human ian Rag2 locus, a mammalian, a human, or a man mammalian Ragl locus and/or a ian, a human, or a non-human mammalian Rag2/Ragl locus can comprise a deletion of an endogenous nucleic acid sequence at the genomic locus, an insertion of an exogenous nucleic acid at the genomic locus, or a combination thereof. The deletion and/or insertion can occur anywhere within the given locus as discussed elsewhere herein.

Further ments provided herein comprise the modiﬁcation of one or more of the mammalian, human, or non-human mammalian ApoE locus, interleukin-2 receptor gamma locus, Rag2 locus, Ragl locus and/or agl locus through the replacement of a portion of the ApoE locus, interleukin-2 receptor gamma (Il2rg) locus, Rag2 locus, Ragl locus and/or agl locus with the corresponding homologous or orthologous portion of an ApoE locus, an interleukin-2 receptor gamma locus, a Rag2 locus, a Ragl locus and/or a Rag2/Rag] locus from another organism.

In still other embodiments, the ation of one or more of the ian, human, or non-human mammalian ApoE locus, the interleukin-2 receptor gamma locus, Rag2 locus, Ragl locus, and/or Rag2/Ragl locus is carried out through the replacement of a portion of the ApoE locus, interleukin-2 receptor gamma (Il2rg) locus, Rag2 locus, Rag] locus and/or ag1 locus with an insert polynucleotide sharing across its full length least 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% to a portion of an ApoE locus, an interleukin-2 receptor gamma locus, a Rag2 locus, a Rag] locus and/or a Rag2/Rag1 locus it is replacing.

The given insert polynucleotide and/or the corresponding region of the locus being deleted can be a coding region, an , an exon, an untranslated region, a regulatory region, a promoter, or an enhancer or any combination thereof or any portion thereof. Moreover, the given insert polynucleotide and/or the region of the locus, for example, being deleted can be of any desired length, including for example, between 10- 100 nucleotides in length, 100-500 tides in length, 500-1 kb nucleotide in length, 1 Kb to 1.5 kb nucleotide in length, 1.5 kb to 2 kb nucleotides in length, 2 kb to 2.5 kb nucleotides in length, 2.5 kb to 3 kb tides in length, 3 kb to 5 kb nucleotides in , 5 kb to 8 kb tides in length, 8 kb to 10 kb nucleotides in length or more. In other instances, the size of the insertion or replacement is from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, from about 350 kb to about 400 kb, from about 400 kb to about 800 kb, from about 800 kb to 1 Mb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, from about 2.5 Mb to about 2.8 Mb, from about 2.8 Mb to about 3 Mb. In other embodiments, the given insert polynucleotide and/or the region ofthe locus being deleted is at least 100, 200, 300, 400, 500, 600, 700, 800, or 900 nucleotides or at least 1 kb, 2 kb, 3 kb, 4 kb, 5 kb, 6 kb, 7 kb, 8 kb, 9 kb, 10 kb, 11 kb, 12 kb, 13 kb, 14 kb, 15 kb, 16 kb or greater. In other embodiments, the given insert polynucleotide and/or the region of the locus being deleted is at least 10 kb, at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, at least 90 kb, at least 100 kb, at least 150 kb, at least 200 kb, at least 250 kb, or at least 300 kb or greater.

The given insert polynucleotide can be from any organism, including, for example, a rodent, a t rodent, a rat, a mouse, a hamster, a mammal, a non-human mammal, a eukaryote, a non-rat ote, a human, an agricultural animal or a domestic animal.

As discussed in further detail herein, various methods are ed to generate targeted modiﬁcations of any locus of interest, including for example, ed modiﬁcations in the ApoE locus, interleukin-2 or gamma (Il2rg) locus, Rag2 locus, Rag] locus and/or Rag2/Rag1 locus. Further provided are genetically modiﬁed non- human animals, genetically modiﬁed non-human mammals, genetically modiﬁed non-rat eukaryotes, cally modiﬁed non-pluripotent cells, or genetically modiﬁed pluripotent cells (e.g., a pluripotent cell, a man pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a developmentally-restricted human progenitor cell, or a human iPS cell), which comprise a deletion, an insertion, a replacement and/or any combination thereof at the interleukin-2 receptor gamma locus, at the ApoE locus, at the Rag2 locus, at the Rag] locus, and/or at the Rag2/Rag1 locus.

Such genetic modiﬁcations (including those that result in an e, a decrease, an increase or a modulation in activity of the target locus) and are also capable of being transmitted through the germline. In speciﬁc embodiments, the genetic modiﬁcations result in a knockout of the d target locus. Such man animals, for e, ﬁnd use in in a variety of experimental systems as discussed elsewhere herein.

For example, ApoE (Apolipoprotein E) knockouts offer an animal model to study endothelial function, including, but not limited to, plaque formation, transcriptional changes (Whole Transcriptome Shotgun Sequencing (RNA-Seq), and ex vivo ﬁlnction. ApoE is an important transport molecule and can transport lipids, such as cholesterol, through the bloodstream. ApoE can also ﬁlnction in the nervous system, for example, to clear loid from the brain. Modiﬁcations in ApoE have been implicated in various conditions, including, for example, atherosclerosis, hyperlipidemia, and mer’s disease. ApoE knockout animals y impaired clearing of lipoproteins from the blood and develop atherosclerosis. Thus, ApoE knockout animals provide a model to study conditions and/or processes such as, for example, endothelia on, plaque formation, transcriptional changes (RNA-Seq), hyperlipidemia, atherosclerosis and Alzheimer’s disease. Assays to measure ApoE activity are known in the art. For example, a decrease in ApoE activity can be measured by assaying for a se in the ApoE levels in a blood sample obtained from a subject by immunoassays, such as by ELISA or by Immunoblotting techniques. Moreover, the large size of rats facilitates all these assays and improves the quality of the data.

RAGl (Recombination-Activating Gene 1) and RAGZ (Recombination- Activating Gene 2) are enzymes that are part of a multi-subunit complex haVing VDJ recombination actiVity and play an important role in the rearrangement and recombination of immunoglobulin and T-cell or genes in cytes. RAGl and RAGZ induce a double stranded DNA cleavage to facilitate recombination and join of segments of the T cell receptor and B cell receptor (i.e., immunoglobulin) genes.

Knockout of RAGl and/or RAGZ causes a loss of B cells and T cells in the animal resulting in severe immunodeﬁciency. RAGl and/or RAG2 knockout animals ﬁnd use, for example, in studies of xenografts (i.e., human cell xenografts in rats), cancer, vaccine development, autoimmune disease, infectious e and graft versus host disease (GVHD). Various assays to measure RAGl and/or RAGZ ty are known in the art and include, for example, measuring recombination efﬁciency or assaying for the presence or absence of B cells and/or T cells in a subject.

The IL-2 receptor (IL-2R) is expressed on the surface of certain immune cells and binds to the cytokine interleukin-2 (IL-2). The IL-2R is an integral membrane n comprising at least three separate subunit chains, including, an alpha chain (IL- 2Ra, CD25), a beta chain b, CD122) and a gamma chain (IL2-Rg, CD132). The IL-2 receptor gamma (also referred to as IL2r-y or IL2Rg) chain is a common gamma chain that is shared by various cytokine receptors, including, for example, the receptors for IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21. IL-2Rg comprises an ectodomain on the extracellular e of the cell, which contributes to the binding of the ligand, a embrane domain, and an intracellular domain, which can ct with various molecules to induce intracellular signal transduction pathways. The Il2rg gene is found on the X-chromosome in s and n mutations in the gamma chain gene in humans can cause human X-linked severe combined immunodeﬁciency ) characterized by a profound T-cell defect. In addition, the gamma chain ecto-domain can WO 88643 be shed off of the transmembrane receptor and released as a soluble gamma chain receptor. The soluble gamma chain receptor can be detected in the blood of a t and can ﬁlnction to regulate cytokine signaling.

In some embodiments, the non-human IL-2Rg chain is replaced with the human IL2-Rg chain such that the genetically modiﬁed animal expresses a fully human IL-2Rg chain. In other ces, it may be useful to replace only the ectodomain of a non-human IL-2Rg chain with the ectodomain of the human IL-2Rg chain. In such cases, the resulting humanized IL-2Rg chain expressed in a non-human comprises a human ectodomain, with the remainder of the molecule being from the native organism.

] The full-length humanization of IL-2Rg is useful because man mammals having this modiﬁed locus will produce human IL-2Rg. This will allow for the detection of human IL-2Rg in non-human mammals with antibodies speciﬁc to human . The ecto-humanization (i.e., replacing the ecto-domain of IL-2Rg a non-human mammal with the human ecto-domain of IL-2Rg) will result in an IL-2Rg ptide that will bind the human ligands for IL2—Rg, but because the cytoplasmic domain is still from the non-human mammal, the ecto-humanized form of IL-2Rg will also interact with the man mammal signaling machinery. 2. Modifying a Target Locus A. ing Vectors and Insert Nucleic Acids i. Insert Nucleic Acid As used herein, the "insert nucleic acid" comprises a segment ofDNA that one desires to integrate at the target locus. In one embodiment, the insert nucleic acid comprises one or more polynucleotides of interest. In other embodiments, the insert nucleic acid can comprise one or more expression cassettes. A given expression cassette can comprise a polynucleotide of interest, a polynucleotide ng a selection marker and/or a reporter gene along with the various regulatory components that inﬂuence expression. Non-limiting examples of polynucleotides of interest, selection markers, and reporter genes that can be included within the insert nucleic acid are sed in detail elsewhere herein.

In speciﬁc embodiments, the insert nucleic acid can comprise a nucleic acid from rat, which can include a segment of genomic DNA, a cDNA, a regulatory region, or any portion or combination thereof. In other embodiments, the insert nucleic acid can comprise a nucleic acid from a eukaryote, a non-rat eukaryote, a mammal, a human, a man mammal, a rodent, a non-rat rodent, a human, a rat, a mouse, a r, a rabbit, a pig, a bovine, a deer, a sheep, a goat, a chicken, a cat, a dog, a ferret, a primate (e.g., marmoset, rhesus ), a domesticated mammal, or an agricultural mammal or any other organism of interest. As outlined in further detail herein, the insert nucleic acid employed in the various methods and compositions can result in the "humanization" of the a target locus of interest.

In one embodiment, the insert nucleic acid comprises a knock-in allele of at least one exon of an endogenous gene. In one embodiment, the insert c acid comprises a knock-in allele of the entire endogenous gene (i.e., "gene-swap in").

In one embodiment, the insert nucleic acid comprises a regulatory element, including for example, a promoter, an enhancer, or a riptional repressor- binding element.

In further ments, the insert nucleic acid comprises a conditional allele. In one embodiment, the conditional allele is a multiﬁlnctional allele, as described in US 2011/0104799, which is incorporated by reference in its entirety. In speciﬁc embodiments, the ional allele comprises: (a) an actuating sequence in sense orientation with respect to transcription of a target gene, and a drug selection cassette in sense or antisense orientation; (b) in antisense ation a nucleotide sequence of interest (NSI) and a conditional by inversion module (COIN, which utilizes an exon- splitting intron and an invertible genetrap-like module; see, for example, US 201 1/0104799, which is orated by reference in its ty); and (c) recombinable units that recombine upon re to a f1rstrecombinase to form a conditional allele that (i) lacks the actuating sequence and the DSC, and (ii) contains the NSI in sense ation and the COIN in antisense orientation.

The insert nucleic acid ranges from about 5 kb to about 10 kb, from about kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to 2014/060788 about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb.

In one embodiment, the insert c acid comprises a deletion of, for e, a eukaryotic cell, a non-rat eukaryotic cell, a mammalian cell, a human cell or a non-human mammalian cell genomic DNA ce ranging from about 1 kb to about 200 kb, from about 2 kb to about 20 kb, or from about 0.5 kb to about 3 Mb. In one embodiment, the extent of the deletion of the genomic DNA sequence is greater than a total length of the 5’ homology arm and the 3’ homology arm. In one embodiment, the extent of the deletion of the genomic DNA sequence ranges from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 20 kb to about 30 kb, from about 30 kb to about 40 kb, from about 40 kb to about 50 kb, from about 50 kb to about 60 kb, from about 60 kb to about 70 kb, from about 70 kb to about 80 kb, from about 80 kb to about 90 kb, from about 90 kb to about 100 kb, from about 100 kb to about 110 kb, from about 110 kb to about 120 kb, from about 120 kb to about 130 kb, from about 130 kb to about 140 kb, from about 140 kb to about 150 kb, from about 150 kb to about 160 kb, from about 160 kb to about 170 kb, from about 170 kb to about 180 kb, from about 180 kb to about 190 kb, from about 190 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, from about 350 kb to about 400 kb, from about 400 kb to about 800 kb, from about 800 kb to 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb, to about 2.5 Mb, from about 2.5 Mb to about 2.8 Mb, from about 2.8 Mb to about 3 Mb, from about 200 kb to about 300 kb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to about 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, or from about 2.5 Mb to about 3 Mb.

In one embodiment, the insert nucleic acid comprises an insertion or a replacement of a eukaryotic, a non-rat eukaryotic, a mammalian, a human or a non- human mammalian nucleic acid sequence with a homologous or orthologous human nucleic acid sequence. In one embodiment, the insert nucleic acid comprises an ion or replacement of a DNA sequence with a homologous or ogous human c acid sequence at an endogenous locus that comprises the corresponding DNA sequence.

In one embodiment, the genetic modiﬁcation is an addition of a nucleic acid sequence. In one embodiment, the added nucleotide sequence ranges from 5 kb to 200 kb.

In one embodiment, the insert nucleic acid comprises a c modiﬁcation in a coding sequence. In one embodiment, the genetic modiﬁcation comprises a deletion mutation of a coding sequence. In one ment, the genetic modiﬁcation comprises a fusion of two endogenous coding sequences.

In one embodiment, the insert nucleic acid comprises an insertion or a replacement of a otic, a non-rat eukaryotic, a mammalian, a human, or a man mammalian, nucleic acid sequence with a homologous or orthologous human nucleic acid sequence.

In one embodiment, the insert nucleic acid comprises an insertion or replacement of a rat DNA sequence with a gous or orthologous human nucleic acid sequence at an endogenous rat locus that comprises the corresponding rat DNA sequence.

In one embodiment, the genetic modiﬁcation comprises a deletion of a non-protein-coding sequence, but does not comprise a deletion of a n-coding sequence. In one embodiment, the deletion of the non-protein-coding sequence ses a deletion of a regulatory element. In one embodiment, the genetic ation comprises a deletion of a promoter. In one embodiment, the genetic modiﬁcation comprises an on of a promoter or a regulatory element. In one embodiment, the genetic modiﬁcation comprises a replacement of a promoter or a regulatory element.

In one embodiment, the nucleic acid ce of the targeting vector can comprise a polynucleotide that when ated into the genome will produce a genetic modiﬁcation of a region of the mammalian, human, or a non-human mammalian ApoE locus, wherein the genetic modiﬁcation at the ApoE locus results in a decrease in ApoE actiVity, increase in ApoE actiVity, or a modulation ofApoE actiVity. In one embodiment, an ApoE knockout ("null allele) is generated.

In one embodiment, the c acid sequence of the targeting vector can comprise a polynucleotide that when integrated into the genome will produce a genetic modiﬁcation of a region of the mammalian, human cell, or non-human mammalian interleukin-2 receptor locus, wherein the genetic modiﬁcation at the interleukin-2 receptor locus results in a se in interleukin-2 receptor activity. In one embodiment, an interleukin-2 or knockout ("null allele") is generated.

In further ments, the insert nucleic acid results in the replacement of a n of the mammalian, human cell, or non-human mammalian ApoE locus, the interleukin-2 receptor gamma locus and/or Rag2 locus, and/or Rag] locus and/or ag1 locus with the corresponding homologous or orthologous portion of an ApoE locus, an interleukin-2 receptor gamma locus, a Rag2 locus, a Rag] locus and/or a Rag2/Rag1 locus from another organism.

Still other ments, the insert nucleic acid comprises a polynucleotide sharing across its full length least 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% to a portion of an ApoE locus, an eukin-2 receptor gamma locus, a Rag2 locus, a Rag] locus and/or a Rag2/Rag1 locus it is replacing.

The given insert polynucleotide and the corresponding region of the mammalian, human cell, or non-human mammalian locus being replaced can be a coding region, an intron, an exon, an untranslated region, a regulatory region, a promoter, or an enhancer or any combination thereof. Moreover, the given insert polynucleotide and/or the region of the mammalian, human cell, or non-human mammalian locus being d can be of any desired length, including for example, between 10-100 nucleotides in length, 100-500 nucleotides in length, 500-1 kb nucleotide in length, 1 Kb to 1.5 kb tide in length, 1.5 kb to 2 kb nucleotides in length, 2 kb to 2.5 kb nucleotides in length, 2.5 kb to 3 kb nucleotides in length, 3 kb to 5 kb nucleotides in length, 5 kb to 8 kb nucleotides in length, 8 kb to 10 kb nucleotides in length or more. In other ces, the size of the insertion or replacement is from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, from about 350 kb to about 400 kb, from about 400 kb to about 800 kb, from about 800 kb to 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb, to about 2.5 Mb, from about 2.5 Mb to about 2.8 Mb, from about 2.8 Mb to about 3 Mb. In other embodiments, the given insert cleotide and/or the region of the mammalian, human cell, or non-human mammalian locus being deleted is at least 100, 200, 300, 400, 500, 600, 700, 800, or 900 nucleotides or at least 1 kb, 2 kb, 3 kb, 4 kb, 5 kb, 6 kb, 7 kb, 8 kb, 9 kb, 10 kb,11kb,12 kb, 13 kb, 14 kb, 15 kb, 16 kb or greater.

In one embodiment, the promoter is constitutively active promoter.

In one embodiment, the promoter is an inducible promoter. In one embodiment, the ble promoter is a chemically-regulated promoter. In one embodiment, the chemically-regulated er is an alcohol-regulated promoter. In one embodiment, the alcohol-regulated promoter is an alcohol dehydrogenase (ach) gene er. In one embodiment, the chemically-regulated promoter is a tetracycline- regulated promoter. In one embodiment, the tetracycline-regulated promoter is a ycline-responsive promoter. In one embodiment, the tetracycline-regulated promoter is a tetracycline operator sequence (tetO). In one ment, the tetracycline- regulated promoter is a tet-On er. In one embodiment, the tetracycline-regulated promoter a tet-Off promoter. In one embodiment, the chemically-regulated promoter is a steroid regulated promoter. In one embodiment, the steroid regulated promoter is a promoter of a rat glucocorticoid receptor. In one embodiment, the steroid regulated promoter is a promoter of an estrogen receptor. In one embodiment, the d-regulated promoter is a promoter of an ecdysone receptor. In one embodiment, the ally- regulated promoter is a metal-regulated promoter. In one embodiment, the metalregulated er is a metalloprotein er. In one embodiment, the inducible promoter is a ally-regulated promoter. In one embodiment, the physically- regulated promoter is a temperature-regulated promoter. In one embodiment, the ature-regulated promoter is a heat shock promoter. In one embodiment, the physically-regulated promoter is a light-regulated promoter. In one embodiment, the light-regulated promoter is a light-inducible promoter. In one embodiment, the lightregulated promoter is a light-repressible promoter.

In one embodiment, the promoter is a tissue-speciﬁc promoter. In one embodiment, the promoter is a neuron-speciﬁc er. In one embodiment, the promoter is a peciﬁc promoter. In one embodiment, the promoter is a muscle cell- speciﬁc promoter. In one embodiment, the promoter is a heart cell-speciﬁc promoter. In one ment, the promoter is a kidney cell-speciﬁc promoter. In one embodiment, the promoter is a bone cell-speciﬁc er. In one embodiment, the er is an elial cell-speciﬁc promoter. In one ment, the promoter is an immune cell- speciﬁc promoter. In one embodiment, the immune cell promoter is a B cell promoter. In one embodiment, the immune cell promoter is a T cell promoter.

In one embodiment, the promoter is a deVelopmentally-regulated promoter. In one ment, the deVelopmentally-regulated promoter is active only during an embryonic stage of development. In one embodiment, the developmentally- ted promoter is active only in an adult cell.

In speciﬁc embodiments, the promoter may be selected based on the cell type. Thus the various promoters ﬁnd use in a eukaryotic cell, a non-rat eukaryotic cell, a mammalian cell, a non-human mammalian cell, a pluripotent cell, a non-pluripotent cell, a man pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a deVelopmentally-restricted human progenitor cell, a human iPS cell, a human cell, a rodent cell, a non-rat rodent cell, a rat cell, a mouse cell, a hamster cell, a ﬁbroblast or a CHO cell.

In some embodiments, the insert c acid comprises a nucleic acid ﬂanked with site-speciﬁc recombination target sequences. It is recognized the while the entire insert nucleic acid can be ﬂanked by such site-speciﬁc ination target sequences, any region or individual polynucleotide of interest within the insert nucleic acid can also be ﬂanked by such sites. The site-speciﬁc recombinase can be introduced into the cell by any means, including by introducing the recombinase polypeptide into the cell or by introducing a polynucleotide encoding the site-speciﬁc recombinase into the host cell. The cleotide encoding the site-speciﬁc recombinase can be located within the insert nucleic acid or within a separate polynucleotide. The site-speciﬁc recombinase can be operably linked to a promoter active in the cell including, for example, an inducible promoter, a promoter that is endogenous to the cell, a promoter that is heterologous to the cell, a cell-specif1c promoter, atissue-specif1c promoter, or a developmental stage-speciﬁc promoter. Site-specif1c recombination target sequences, which can ﬂank the insert nucleic acid or any polynucleotide of interest in the insert nucleic acid can include, but are not limited to, loxP, lox511, lox2272, lox66, lox7l, loxM2, lox517l, FRT, FRTl l, FRT7l, attp, att, FRT, rox, and a ation f.

In some embodiments, the site-specific recombination sites ﬂank a cleotide encoding a ion marker and/or a er gene contained within the insert nucleic acid. In such instances following integration of the insert c acid at the targeted locus the sequences between the site-specif1c recombination sites can be removed.

In one embodiment, the insert nucleic acid comprises a polynucleotide encoding a selection marker. The selection marker can be ned in a selection cassette. Such selection markers include, but are not limited, to neomycin phosphotransferase (neor), hygromycin B phosphotransferase (hygr), cin-N- acetyltransferase (puror), blasticidin S deaminase (bsrr), xanthine/guanine phosphoribosyl transferase (gpt), or herpes simplex virus thymidine kinase (HSV-k), or a combination thereof. In one embodiment, the polynucleotide encoding the selection marker is operably linked to a promoter active in the cell, rat cell, pluripotent rat cell, the ES rat cell, a eukaryotic cell, a non-rat eukaryotic cell, a pluripotent cell, a non-pluripotent cell, a non-human pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a developmentally-restricted human progenitor cell, a human iPS cell, a mammalian cell, a non-human mammalian cell, a human cell, a rodent cell, a non-rat rodent cell, a mouse cell, a hamster cell, a f1broblast, or a CHO cell. When serially tiling polynucleotides of interest into a targeted locus, the selection marker can comprise a ition site for a nuclease agent, as outlined above. In one ment, the polynucleotide encoding the selection marker is ﬂanked with a site-speciﬁc recombination target sequences.

The insert nucleic acid can further comprise a er gene operably linked to a promoter, wherein the reporter gene encodes a reporter protein selected from the group consisting of or sing LacZ, mPlum, mCherry, thomato, mStrawberry, J-Red, DsRed, mOrange, mKO, mCitrine, Venus, YPet, enhanced yellow ﬂuorescent protein (eYFP), Emerald, ed green ﬂuorescent protein (EGFP), CyPet, cyan ﬂuorescent protein (CFP), an, T-Sapphire, luciferase, alkaline phosphatase, and/or a combination thereof. Such er genes can be operably linked to a promoter active in the cell. Such promoters can be an inducible er, a promoter that is endogenous to the reporter gene or the cell, a er that is logous to the reporter gene or to the cell, a cell-speciﬁc er, atissue-specif1c promoter, or a developmental stage- specif1c er.

In one embodiment, nucleic acid insert can comprise a ian nucleic acid comprises a genomic locus that encodes a protein expressed in the nervous system, the skeletal system, the ive system, the atory system, the muscular system, the respiratory system, the cardiovascular system, the lymphatic system, the endocrine system, the urinary system, the reproductive system, or a combination thereof. In one embodiment, the mammalian nucleic acid comprises a genomic locus that encodes a protein expressed in a bone marrow or a bone marrow-derived cell. In one embodiment, the nucleic acid comprises a genomic locus that encodes a protein expressed in a spleen cell.

In one embodiment, the mammalian nucleic acid comprises a genomic locus that encodes a n expressed in the nervous system, the skeletal system, the digestive system, the circulatory system, the muscular system, the respiratory system, the vascular system, the lymphatic system, the endocrine , the urinary system, the reproductive system, or a combination thereof. In one embodiment, the mammalian nucleic acid comprises a genomic locus that encodes a protein expressed in a bone marrow or a bone marrow-derived cell. In one embodiment, the nucleic acid comprises a genomic locus that encodes a n expressed in a spleen cell. In one embodiment, the genomic locus comprises a mouse genomic DNA sequence, a rat genomic DNA sequence, eukaryotic genomic DNA sequence, a non-rat eukaryotic genomic DNA sequence, a mammalian genomic DNA sequence, a human genomic DNA sequence, or non-human DNA sequence mammalian, or a combination thereof In one embodiment, the genomic locus ses, in any order, rat and human genomic DNA sequences. In one embodiment, the genomic locus comprises, in any order, mouse and human genomic DNA sequences. In one embodiment, the genomic locus comprises, in any order, mouse and rat genomic DNA sequences. In one embodiment, the genomic locus comprises, in any order, rat, mouse, and human genomic DNA sequences.

In one embodiment, the genomic locus comprises a mouse genomic DNA sequence, a rat genomic DNA sequence, a hamster genomic DNA sequence, a human genomic DNA sequence, otic genomic DNA sequence, a non-rat otic genomic DNA sequence, a mammalian c DNA sequence, or man DNA sequence mammalian, or a combination thereof. In one embodiment, the genomic locus comprises, in any order, rat and human genomic DNA sequences. In one embodiment, the genomic locus comprises, in any order, mouse and human genomic DNA sequences.

In one embodiment, the genomic locus comprises, in any order, mouse and rat genomic DNA sequences. In one embodiment, the genomic locus comprises, in any order, rat, mouse, and human genomic DNA sequences.

In one embodiment, the genetic modiﬁcation comprises at least one human disease allele of a human gene. In one embodiment, the human e is a neurological disease. In one embodiment, the human disease is a cardiovascular disease.

In one embodiment, the human disease is a kidney disease. In one embodiment, the human disease is a muscle disease. In one ment, the human disease is a blood disease. In one ment, the human disease is a cancer. In one embodiment, the human disease is an immune system disease.

In one embodiment, the human disease allele is a dominant allele. In one embodiment, the human disease allele is a recessive allele. In one embodiment, the human disease allele comprises a single nucleotide rphism (SNP) allele.

In one embodiment, the genetic modiﬁcation produces a mutant form of a protein with an altered binding characteristic, altered localization, altered expression, and/or altered expression pattern.

In one embodiment, the insert nucleic acid ses a selection cassette.

In one embodiment, the selection cassette comprises a nucleic acid sequence encoding a ive marker, wherein the nucleic acid sequence is operably linked to a promoter active in rat ES cells. In one embodiment, the selective marker is ed from or ses a hygromycin resistance gene or a in resistance gene.

In one embodiment, the nucleic acid comprises a genomic locus that encodes a protein expressed in a B cell. In one ment, the nucleic acid ses a genomic locus that encodes a protein expressed in an immature B cell. In one embodiment, the nucleic acid comprises a genomic locus that encodes a protein expressed in a mature B cell.

] In one embodiment, the insert nucleic acid comprises a regulatory element. In one embodiment, the regulatory element is a promoter. In one ment, the regulatory element is an enhancer. In one ment, the regulatory element is a transcriptional repressor-binding element.

In one embodiment, the genetic modiﬁcation comprises a deletion of a non-protein-coding sequence, but does not comprise a deletion of a protein-coding sequence. In one embodiment, the deletion of the non-protein-coding sequence comprises a deletion of a regulatory element. In one embodiment, the genetic ation comprises a deletion of a regulatory element. In one embodiment, the genetic modiﬁcation comprises an addition of a promoter or a regulatory element. In one ment, the genetic modiﬁcation ses a replacement of a promoter or a regulatory element. ii. Expression tes ed herein are polynucleotides or nucleic acid molecules sing the various components employed in a targeted genomic integration system provided herein (z'.e., any one of or any combination of nuclease agents, recognition sites, insert nucleic acids, polynucleotides of interest, targeting vectors, selection markers, and other components).

The terms "polynucleotide," "polynucleotide sequence, 3, (Cnucleic acid sequence," and ic acid fragment" are used interchangeably herein. These terms encompass nucleotide sequences and the like. A polynucleotide may be a polymer of RNA or DNA that is single- or double-stranded, that optionally contains synthetic, non- natural or altered nucleotide bases. A cleotide in the form of a polymer ofDNA may be comprised of one or more ts of cDNA, genomic DNA, tic DNA, or mixtures thereof. Polynucleotides can comprise deoxyribonucleotides and ribonucleotides include both naturally occurring molecules and synthetic analogues, and any combination these. The polynucleotides provided herein also ass all forms of ces ing, but not limited to, -stranded forms, double-stranded forms, hairpins, stem-and-loop structures, and the like.

] Further provided are recombinant polynucleotides comprising the various components of the targeted genomic integration system. The terms binant polynucleotide" and "recombinant DNA construct" are used interchangeably . A recombinant construct comprises an artiﬁcial or heterologous combination of nucleic acid sequences, e.g., regulatory and coding ces that are not found together in nature. In other embodiments, a recombinant construct may comprise regulatory sequences and coding sequences that are derived from different sources, or regulatory sequences and coding sequences derived from the same source, but arranged in a manner different than that found in nature. Such a construct may be used by itself or may be used in conjunction with a vector. If a vector is used, then the choice of vector is dependent upon the method that is used to transform the host cells as is well known to those skilled in the art. For example, a plasmid vector can be used. Genetic elements required to successfully transform, select, and propagate host cells comprising any of the isolated nucleic acid fragments provided herein are also provided. Screening may be accomplished by Southern analysis of DNA, rn analysis ofmRNA expression, immunoblotting analysis of protein expression, or phenotypic analysis, among others.

In specific embodiments, one or more of the components of the targeted genomic integration system described herein can be ed in an expression cassette for expression in a prokaryotic cell, a eukaryotic cell, a non-rat eukaryotic cell, a bacterial, a yeast cell, or a ian cell or other organism or cell type of interest. The cassette can include 5' and 3' regulatory sequences operably linked to a polynucleotide provided herein. "Operably linked" comprises a relationship wherein the components operably linked function in their intended manner. For example, an operable linkage between a polynucleotide of interest and a tory sequence (i.e., a promoter) is a onal link that allows for expression of the polynucleotide of interest. Operably linked elements may be contiguous or ntiguous. When used to refer to the joining of two protein coding regions, ly linked means that the coding regions are in the 2014/060788 same reading frame. In another ce, a nucleic acid sequence encoding a protein may be operably linked to regulatory sequences (e.g., promoter, enhancer, silencer sequence, etc.) so as to retain proper transcriptional regulation. In one instance, a nucleic acid sequence of an immunoglobulin variable region (or V(D)J ts) may be operably linked to a nucleic acid sequence of an immunoglobulin constant region so as to allow proper recombination between the sequences into an immunoglobulin heavy or light chain sequence.

The cassette may additionally contain at least one additional polynucleotide of interest to be co-introduced into the organism. Alternatively, the additional polynucleotide of interest can be provided on multiple expression cassettes.

Such an expression cassette is provided with a plurality of restriction sites and/or recombination sites for insertion of a recombinant cleotide to be under the transcriptional regulation of the regulatory s. The expression cassette may additionally contain selection marker genes.

The expression cassette can include in the 5'-3' direction of transcription, a transcriptional and translational initiation region (i.e., a promoter), a recombinant polynucleotide provided herein, and a transcriptional and ational termination region (i.e., termination region) functional in mammalian cell or a host cell of interest. The regulatory regions (i.e., promoters, transcriptional regulatory regions, and translational termination regions) and/or a polynucleotide provided herein may be native/analogous to the host cell or to each other. Alternatively, the regulatory regions and/or a cleotide provided herein may be logous to the host cell or to each other. For example, a er operably linked to a heterologous polynucleotide is from a species different from the species from which the polynucleotide was derived, or, if from the same/analogous species, one or both are ntially modified from their original form and/or genomic locus, or the promoter is not the native promoter for the operably linked polynucleotide. Alternatively, the regulatory regions and/or a recombinant polynucleotide provided herein may be ly tic.

The ation region may be native with the transcriptional initiation region, may be native with the operably linked recombinant polynucleotide, may be native with the host cell, or may be derived from another source (i.e., foreign or logous) to the promoter, the recombinant polynucleotide, the host cell, or any combination thereof.

In preparing the expression te, the various DNA fragments may be manipulated, so as to provide for the DNA sequences in the proper orientation. Toward this end, adapters or linkers may be employed to join the DNA nts or other manipulations may be involved to provide for convenient restriction sites, removal of superﬂuous DNA, removal of restriction sites, or the like. For this e, in vitro mutagenesis, primer repair, restriction, annealing, resubstitutions, e. g., transitions and transversions, may be ed.

A number of promoters can be used in the expression cassettes provided herein. The promoters can be selected based on the desired outcome. It is recognized that different applications can be enhanced by the use of different promoters in the expression cassettes to modulate the timing, location and/or level of expression of the polynucleotide of interest. Such expression ucts may also contain, if desired, a promoter tory region (e.g., one conferring inducible, constitutive, environmentally- or developmentally-regulated, or cell- or tissue-specific/selective expression), a transcription initiation start site, a ribosome binding site, an RNA processing signal, a transcription ation site, and/or a enylation signal.

The expression cassette containing the polynucleotides provided herein can also comprise a selection marker gene for the selection of transformed cells.

Selectable marker genes are utilized for the selection of transformed cells or tissues.

Where appropriate, the sequences employed in the methods and compositions (i.e., the polynucleotide of st, the nuclease agent, etc.) may be optimized for increased expression in the cell. That is, the genes can be synthesized using codons preferred in a given cell of interest including, for example, mammalian- preferred , human-preferred codons, rodent-preferred codons, non-rat-rodentpreferred codons, mouse-preferred codons, rat-preferred , hamster-preferred codons, etc. for improved expression.

The various methods and compositions provided herein can employ selection markers. Various selection markers can be used in the s and compositions disclosed herein. Such selection markers can, for example, impart resistance to an antibiotic such as G418, hygromycin, blasticidin, neomycin, or puromycin. Such selection markers include neomycin phosphotransferase , hygromycin B phosphotransferase (hygr), puromycin-N-acetyltransferase (puror), and blasticidin S deaminase (bsrr). In still other embodiments, the selection marker is operably linked to an inducible promoter and the expression of the selection marker is toxic to the cell. Non-limiting examples of such selection markers include xanthine/guanine phosphoribosyl erase (gpt), hypoxanthine-guanine phosphoribosyltransferase (HGPRT) or herpes simplex Virus thymidine kinase (HSV- TK). The polynucleotide encoding the selection markers are operably linked to a promoter active in the cell. iii. Targeting Vectors Targeting vectors are employed to introduce the insert nucleic acid into the target locus of the rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat , mouse or hamster nucleic acid. The targeting vector ses the insert nucleic acid and further ses a 5' and a 3' gy arm, which ﬂank the insert c acid. The gy arms, which ﬂank the insert nucleic acid, correspond to regions within the target locus of the rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster nucleic acid. For ease of reference, the corresponding cognate genomic regions within the targeted genomic locus are referred to herein as "target sites". For example, a targeting vector can comprise a ﬁrst insert nucleic acid ﬂanked by a ﬁrst and a second homology arm complementary to a ﬁrst and a second target site. As such, the targeting vector y aids in the integration of the insert c acid into the target locus of the rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster nucleic acid through a homologous recombination event that occurs n the homology arms and the mentary target sites within the genome of the cell.

In one embodiment, the target locus of the rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster nucleic acid comprises a ﬁrst nucleic acid sequence that is complementary to the 5’ homology arm and a second nucleic acid sequence that is complementary to the 3’ homology arm. In one embodiment, the ﬁrst and the second nucleic acid sequences are separated by at least 5 kb. In another embodiment, the ﬁrst and the second c acid sequences are separated by at least 5 kb but less than 200 kb. In one embodiment, the ﬁrst and the second nucleic acid sequences are separated by at least 10 kb. In one embodiment, the ﬁrst and the second nucleic acid sequences are ted by at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, at least 90 kb, at least 100 kb, at least 110 kb, at least 120 kb, at least 130 kb, at least 140 kb, at least 150 kb, at least 160 kb, at least 170 kb, at least 180 kb, at least 190 kb, or at least 200 kb. In still further embodiments, the ﬁrst and the second nucleic acid sequence is separated by at least 5 kb but less than 10 kb, at least 5 kb but less than 3 Mb, at least 10 kb but less than 20 kb, at least 20 kb but less than 40 kb, at least 40 kb but less than 60 kb, at least 60 kb but less than 80 kb, at least about 80 kb but less than 100 kb, at least 100 kb but less than 150 kb, or at least 150 kb but less than 200 kb, at least about 200 kb but less than about 300 kb, at least about 300 kb but less than about 400 kb, at least about 400 kb but less than about 500 kb, at least about 500 kb but less than about 1 Mb, at least about 1.5 Mb but less than about 2 Mb, at least about 1 Mb but less than about 1.5 Mb, at least about 2 Mb but less than 2.5 Mb, at least about 2.5 Mb but less than 3 Mb, or at least about 2 Mb but less than about 3 Mb.

A homology arm of the targeting vector can be of any length that is sufﬁcient to promote a homologous ination event with a corresponding target site, including for example, at least 5-10 kb, 5-l5 kb, 10-20 kb, 20-30 kb, 30-40 kb, 40-50 kb, 50-60 kb, 60-70 kb, 70-80 kb, 80-90 kb, 90-100 kb, 100-1 10 kb, llO-l20 kb, l20-l30 kb, l30-l40 kb, l40-l50 kb, l50-l60 kb, 160-170 kb, 170-180 kb, 180-190 kb, 190-200 kb in length or greater. As outlined in r detail below, large ing s can employ targeting arms of greater length. In a speciﬁc embodiment, the sum total of the 5' homology arm and the 3' homology arm is at least 10 kb or the sum total of the 5' homology arm and the 3' homology arm is at least about 16 kb to about 100 kb or about kb to about 100 kb. In other embodiments, the size of the sum total of the total of the ' and 3' homology arms of the LTVEC is about 10 kb to about 150 kb, about 10 kb to about 100 kb, about 10 kb to about 75 kb, about 20 kb to about 150 kb, about 20 kb to about 100 kb, about 20 kb to about 75 kb, about 30 kb to about 150 kb, about 30 kb to about 100 kb, about 30 kb to about 75 kb, about 40 kb to about 150 kb, about 40 kb to about 100 kb, about 40 kb to about 75 kb, about 50 kb to about 150 kb, about 50 kb to about 100 kb, or about 50 kb to about 75 kb, about 10 kb to about 30 kb, about 20 kb to about 40 kb, about 40 kb to about 60 kb, about 60 kb to about 80 kb, about 80 kb to about 100 kb, about 100 kb to about 120 kb, or from about 120 kb to about 150 kb. In one embodiment, the size of the on is the same or similar to the size of the sum total of the 5' and 3' homology arms of the LTVEC.

In one embodiment, the genomic locus of interest comprises (i) a 5’ target sequence that is homologous to the 5’ gy arm; and (ii) a 3’ target sequence that is gous to the 3’ homology arm. In one embodiment, the 5’ target sequence and the 3’ target sequence are separated by at least 5 kb but less than 3 Mb. In still further embodiments, the 5’ target sequence and the 3’ target sequence are separated by at least 5 kb but less than 10 kb, at least 5 kb but less than 3 Mb, at least 10 kb but less than 20 kb, at least 20 kb but less than 40 kb, at least 40 kb but less than 60 kb, at least 60 kb but less than 80 kb, at least about 80 kb but less than 100 kb, at least 100 kb but less than 150 kb, or at least 150 kb but less than 200 kb, at least about 200 kb but less than about 300 kb, at least about 300 kb but less than about 400 kb, at least about 400 kb but less than about 500 kb, at least about 500 kb but less than about 1 Mb, at least about 1.5 Mb but less than about 2 Mb, at least about 1 Mb but less than about 1.5 Mb, at least about 2 Mb but less than 2.5 Mb, at least about 2.5 Mb but less than about 3 Mb, or at least about 2 Mb but less than about 3 Mb.

] When nuclease agents are employed, the cognate genomic regions corresponding to the 5' and 3' homology arms of a targeting vector are "located in sufﬁcient proximity" to nuclease target sites so as to promote the ence of a homologous recombination event between the cognate genomic regions and the homology arms upon a nick or double-strand break at the ition site. For example, the nuclease target sites can be located anywhere between the cognate genomic regions corresponding to the 5’ and 3’ homology arms. In speciﬁc embodiments, the recognition site is immediately adjacent to at least one or both of the cognate genomic regions.

] As used herein, a homology arm and a target site (i.e., cognate genomic region) "complement" or are "complementary" to one another when the two regions share a sufficient level of sequence ty to one another to act as ates for a homologous ination reaction. By "homology" is meant DNA sequences that are either identical or share sequence ty to a corresponding or "complementary" sequence. The ce identity between a given target site and the corresponding gy arm found on the targeting vector can be any degree of sequence identity that allows for homologous recombination to occur. For example, the amount of sequence identity shared by the homology arm of the targeting vector (or a fragment thereof) and the target site (or a fragment thereof) can be at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence ty, such that the sequences undergo homologous recombination. Moreover, a complementary region of homology between the homology arm and the mentary target site can be of any length that is ient to promote homologous recombination at the cleaved recognition site. For example, a given homology arm and/or mentary target site can comprise complementary regions of homology that are at least 5-10 kb, 5-15 kb, 10-20 kb, 20-30 kb, 30-40 kb, 40-50 kb, 50-60 kb, 60-70 kb, 70-80 kb, 80-90 kb, 90-100 kb, 100-110 kb, 110-120 -130 kb, 130-140 kb,140-150 kb,150-160 kb,160-170 kb, 170-180 kb, 180-190 kb, 190-200 kb, 200 kb to 300 kb in length or greater (such as described in the LTVEC vectors described elsewhere herein) such that the homology arm has sufﬁcient homology to undergo homologous recombination with the corresponding target sites within the genome of the cell. For ease of reference the homology arms are referred to herein as a 5' and a 3' homology arm. This terminology relates to the ve position of the homology arms to the insert nucleic acid within the targeting vector.

The homology arms of the targeting vector are therefore designed to be complementary to a target site with the targeted locus. Thus, the homology arms can be complementary to a locus that is native to the cell, or alternatively they can be complementary to a region of a heterologous or exogenous segment ofDNA that was integrated into the genome of the cell, including, but not limited to, transgenes, expression cassettes, or heterologous or exogenous regions of genomic DNA.

Alternatively, the homology arms of the targeting vector can be complementary to a region of a human ial chromosome or any other ered genomic region ned in an appropriate host cell. Still ﬁlrther, the homology arms of the targeting vector can be complementary to or be derived from a region of a BAC library, a cosmid y, or a P1 phage library. Thus, in speciﬁc embodiments, the homology arms of the ing vector are complementary to a rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster genomic locus that is native, heterologous or exogenous to a given cell. In ﬁlrther embodiments, the homology arms are complementary to a rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster genomic locus that is not targetable using a conventional method or can be targeted only incorrectly or only with signiﬁcantly low efﬁciency, in the absence of a nick or double-strand break induced by a se agent. In one embodiment, the homology arms are derived from a synthetic DNA.

In still other embodiments, the 5' and 3' homology arms are complementary to the same genome as the targeted genome. In one embodiment, the homology arms are from a related genome, e. g., the targeted genome is a rat genome of a ﬁrst strain, and the targeting arms are from a rat genome of a second strain, n the ﬁrst strain and the second strain are different. In other embodiments, the homology arms are from the genome of the same animal or are from the genome of the same strain, e. g., the targeted genome is a rat genome of a ﬁrst strain, and the targeting arms are from a rat genome from the same rat or from the same .

The ing vector (such as a large targeting vector) can also comprise a selection cassette or a er gene as discussed elsewhere herein. The selection te can comprise a nucleic acid sequence encoding a selection marker, wherein the nucleic acid sequence is operably linked to a promoter. The promoter can be active in a prokaryotic cell of interest and/or active in a otic cell of st. Such promoters can be an inducible promoter, a promoter that is endogenous to the reporter gene or the cell, a promoter that is heterologous to the reporter gene or to the cell, a cell-speciﬁc promoter, a tissue-speciﬁc promoter or a developmental stage-speciﬁc promoter. In one embodiment, the selection marker is selected from or comprises neomycin WO 88643 phosphotransferase (neor), hygromycin B phosphotransferase (hygr), puromycin-N- acetyltransferase ), blasticidin S deaminase (bsrr), xanthine/guanine phosphoribosyl transferase (gpt), and herpes simplex virus thymidine kinase (HSV-k), and/or a combination thereof. The selection marker of the targeting vector can be ﬂanked by the ' and 3' homology arms or found either 5’ or 3’ to the homology arms.

In one embodiment, the targeting vector (such as a large targeting vector) comprises a reporter gene operably linked to a promoter, wherein the reporter gene encodes a reporter protein selected from the group consisting of or comprises LacZ, mPlum, mCherry, thomato, mStrawberry, J-Red, DsRed, mOrange, mKO, mCitrine, Venus, YPet, enhanced yellow ﬂuorescent protein (EYFP), d, enhanced green ﬂuorescent protein (EGFP), CyPet, cyan ﬂuorescent protein (CFP), an, T- Sapphire, luciferase, alkaline phosphatase, and/or a ation thereof. Such reporter genes can be operably linked to a promoter active in the cell. Such promoters can be an inducible promoter, a promoter that is endogenous to the report gene or the cell, a promoter that is heterologous to the reporter gene or to the cell, a cell-speciﬁc promoter, a tissue-speciﬁc promoter or a pmental stage-speciﬁc promoter.

In one embodiment, combined use of the ing vector (including, for example, a large targeting vector) with the nuclease agent results in an sed targeting efﬁciency compared to use of the ing vector alone. In one embodiment, when the targeting vector is used in conjunction with the nuclease agent, targeting efficiency of the targeting vector is increased at least by two-fold, at least three-fold, or at least 4-fold when compared to when the ing vector is used alone.

When employing a ing vector, the vector design can be such as to allow for the ion of a given sequence that is from about 5 kb to about 200 kb as described herein. In one embodiment, the insertion is from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 30 kb, from about 30 kb to about 40 kb, from about 40 kb to about 50 kb, from about 50 kb to about 60 kb, from about 60 kb to about 70 kb, from about 80 kb to about 90 kb, from about 90 kb to about 100 kb, from about 100 kb to about 110 kb, from about 110 kb to about 120 kb, from about 120 kb to about 130 kb, from about 130 kb to about 140 kb, from about 140 kb to about 150 kb, from about 150 kb to about 160 kb, from about 160 kb to about 170 kb, from about 170 kb to about 180 kb, from about 180 kb to about 190 kb, or from about 190 kb to about 200 kb, from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb.

When employing a targeting vector, the vector design can be such as to allow for the ement of a given sequence that is from about 5 kb to about 200 kb or from about 5 kb to about 3.0 Mb as described herein. In one embodiment, the replacement is from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 30 kb, from about 30 kb to about 40 kb, from about 40 kb to about 50 kb, from about 50 kb to about 60 kb, from about 60 kb to about 70 kb, from about 80 kb to about 90 kb, from about 90 kb to about 100 kb, from about 100 kb to about 110 kb, from about 110 kb to about 120 kb, from about 120 kb to about 130 kb, from about 130 kb to about 140 kb, from about 140 kb to about 150 kb, from about 150 kb to about 160 kb, from about 160 kb to about 170 kb, from about 170 kb to about 180 kb, from about 180 kb to about 190 kb, from about 190 kb to about 200 kb, from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, or from about 150 kb to about 200 kb, from about 200 kb to about 300 kb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to about 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, or from about 2.5 Mb to about 3 Mb.

In one embodiment, the targeting vector comprises a site-speciﬁc recombinase gene. In one embodiment, the peciﬁc recombinase gene encodes a Cre recombinase. In one embodiment, the Cre recombinase gene is Crei, n two exons encoding the Cre recombinase are separated by an intron to prevent its expression in a prokaryotic cell.

In one embodiment, the Cre recombinase gene ﬁarther comprises a nuclear localization signal to facilitate localization of Cre (or any inase or nuclease agent) to the nucleus (e. g., the gene is an NL-Cre gene). In a speciﬁc embodiment, the Cre recombinase gene further comprises a nuclear localization signal and an intron (e.g., NL- Crei).

In various embodiments, a le promoter for expression of the nuclease agent (including the Cre or Crei recombinase discussed above) is selected from or comprises a PrmI and/or Pax3. In a speciﬁc , Blimp] , Gata6, Gata4, Ing, th2, th5, embodiment, the promoter is the Gata6 or Gata4 promoter. The various promoters can be from any organism, including for example, a rodent such as a mouse or a rat, a t rodent, a eukaryote, a non-rat eukaryote, a non-human mammal, a mammal, a human or a r. In another speciﬁc embodiment, the promoter is a PrmI promoter. In another speciﬁc embodiment, the promoter is a rat PrmI promoter. In another speciﬁc embodiment, the promoter is a mouse PrmI promoter. In another speciﬁc embodiment, the promoter is a Blimp] promoter or a fragment f, e.g., a 1 kb or 2 kb fragment of a Blimp] promoter. See, for example, US. Patent 851 and US. Application Publication 2013-0312129, both of which are herein incorporated by reference in their iv. Large Targeting Vectors The term "large targeting vector" or "LTVEC" as used herein comprises large targeting vectors that comprise gy arms that correspond to and are derived from c acid sequences larger than those typically used by other approaches intended to perform homologous targeting in cells and/or sing insert nucleic acids comprising nucleic acid sequences larger than those typically used by other approaches intended to perform homologous recombination targeting in cells. For example, the LTVEC make possible the modiﬁcation of large loci that cannot be accommodated by traditional plasmid-based targeting vectors e of their size tions. In speciﬁc embodiments, the homology arms and/or the insert nucleic acid of the LTVEC comprises genomic sequence of a otic cell or a t eukaryotic cell. The size of the LTVEC is too large to enable screening of targeting events by tional assays, e.g., southern blotting and long-range (e.g., 1 kb-5 kb) PCR. Examples of the LTVEC, include, but are not limited to, vectors derived from a bacterial artiﬁcial chromosome (BAC), a human artiﬁcial chromosome or a yeast artiﬁcial chromosome (YAC). Non- limiting examples of LTVECs and methods for making them are described, e.g., in US Pat. No. 6,586,251, 6,596,541, 7,105,348, and (PCT/USOl/45375), and US 2013/0137101, each of which is herein incorporated by reference.

The LTVEC can be of any , including, but not d to, from about kb to about 400 kb, from about 20 kb to about 30 kb, from about 30 kb to 40 kb, from about 40 kb to about 50 kb, from about 50 kb to about 75 kb, from about 75 kb to about 100 kb, from about 100 kb to 125 kb, from about 125 kb to about 150 kb, from about 150 kb to about 175 kb, about 175 kb to about 200 kb, from about 200 kb to about 225 kb, from about 225 kb to about 250 kb, from about 250 kb to about 275 kb or from about 275 kb to about 300 kb, from about 200 kb to about 300 kb, from about 300 kb to about 350 kb, from about 350 kb to about 400 kb, from about 350 kb to about 550 kb. In one embodiment, the LTVEC is about 100 kb.

In some embodiments, the LTVEC is at least 10 kb, at least 15 kb, at least kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, at least 90 kb, at least 100 kb, at least 150 kb or at least 200 kb.

In some embodiments, the LTVEC comprises a nucleic acid sequence of at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, at least 90 kb, at least 100 kb, at least 150 kb or at least 200 kb.

In one embodiment, the LTVEC comprises an insert nucleic acid ranging from about 5 kb to about 200 kb, from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 30 kb, from about 0.5 kb to about 30 kb, from about 0.5 kb to about 40 kb, from about 30 kb to about 150 kb, from about 0.5 kb to about 150 kb, from about 30 kb to about 40 kb, from about 40 kb to about 50 kb, from about 60 kb to about 70 kb, from about 80 kb to about 90 kb, from about 90 kb to about 100 kb, from about 100 kb to about 110 kb, from about 120 kb to about 130 kb, from about 130 kb to about 140 kb, from about 140 kb to about 150 kb, from about 150 kb to about 160 kb, from about 160 kb to about 170 kb, from about 170 kb to about 180 kb, from about 180 kb to about 190 kb, or from about 190 kb to about 200 kb, from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb.

In one embodiment, the LTVEC ses a nucleic acid sequence of at least 100 kb, at least 150 kb, or at least 200 kb.

When employing a LTVEC, the vector design can be such as to allow for the replacement of a given sequence that is from about 5 kb to about 200 kb or from about 5 kb to about 3 Mb as described herein. In one embodiment, the ement is from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 30 kb, from about 30 kb to about 40 kb, from about 40 kb to about 50 kb, from about 50 kb to about 60 kb, from about 60 kb to about 70 kb, from about 80 kb to about 90 kb, from about 90 kb to about 100 kb, from about 100 kb to about 110 kb, from about 110 kb to about 120 kb, from about 120 kb to about 130 kb, from about 130 kb to about 140 kb, from about 140 kb to about 150 kb, from about 150 kb to about 160 kb, from about 160 kb to about 170 kb, from about 170 kb to about 180 kb, from about 180 kb to about 190 kb, from about 190 kb to about 200 kb, from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, or from about 150 kb to about 200 kb, from about 200 kb to about 300 kb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to about 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, or from about 2.5 Mb to about 3 Mb.

In one embodiment, the homology arms of the LTVEC are derived from a BAC y, a cosmid library, or a Pl phage library. In other embodiments, the homology arms are derived from the targeted genomic locus of the cell and in some instances the target c locus, which the LTVEC is designed to target is not targetable using a conventional method. In still other embodiments, the homology arms are derived from a synthetic DNA.

In one embodiment, a sum total of the 5' homology arm and the 3' homology arm in the LTVEC is at least 10 kb. In other embodiments, the sum total of the 5’ and the 3’ homology arms of the LTVEC is from about 10 kb to about 30 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 2014/060788 80 kb, from about 80 kb to about 100 kb, from 100 kb to about 120 kb, from about 120 kb to about 140 kb, from about 140 kb to about 160 kb, from about 160 kb to about 180 kb, from about 180 kb to about 200 kb. In one embodiment the sum total of the 5’ and the 3’ homology arms of the LTVEC is from about 30 kb to about 100 kb. In other embodiments, the size of the sum total of the total of the 5' and 3' homology arms of the LTVEC is about 10 kb to about 150 kb, about 10 kb to about 100 kb, about 10 kb to about 75 kb, about 20 kb to about 150 kb, about 20 kb to about 100 kb, about 20 kb to about 75 kb, about 30 kb to about 150 kb, about 30 kb to about 100 kb, about 30 kb to about 75 kb, about 40 kb to about 150 kb, about 40 kb to about 100 kb, about 40 kb to about 75 kb, about 50 kb to about 150 kb, about 50 kb to about 100 kb, or about 50 kb to about 75 kb, about 10 kb to about 30 kb, about 20 kb to about 40 kb, about 40 kb to about 60 kb, about 60 kb to about 80 kb, about 80 kb to about 100 kb, about 100 kb to about 120 kb, or from about 120 kb to about 150 kb. In one embodiment, the size of the deletion is the same or similar to the size of the sum total of the 5' and 3' homology arms of the LTVEC.

In other embodiments, the 5' homology arm ranges from about 5 kb to about 100 kb. In one embodiment, the 3' homology arm ranges from about 5 kb to about 100 kb. In other embodiments, the sum total of the 5' and 3' homology arms are from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 30 kb, from about 30 kb to about 40 kb, from about 40 kb to about 50 kb, from about 50 kb to about 60 kb, from about 60 kb to about 70 kb, from about 70 kb to about 80 kb, from about 80 kb to about 90 kb, from about 90 kb to about 100 kb, from about 100 kb to about 110 kb, from about 110 kb to about 120 kb, from about 120 kb to about 130 kb, from about 130 kb to about 140 kb, from about 140 kb to about 150 kb, from about 150 kb to about 160 kb, from about 160 kb to about 170 kb, from about 170 kb to about 180 kb, from about 180 kb to about 190 kb, from about 190 kb to about 200 kb, or from about kb to about 100 kb, about 10 kb to about 30 kb, about 20 kb to about 40 kb, about 40 kb to about 60 kb, about 60 kb to about 80 kb, about 80 kb to about 100 kb, about 100 kb to about 120 kb, or from about 120 kb to about 150 kb.

] In one embodiment, the LTVEC comprises an insert nucleic acid that is homologous or orthologous to a rat nucleic acid sequence ﬂanked by the LTVEC homology arms. In one embodiment, the insert nucleic acid sequence is from a species other than a rat. In one embodiment, the insert c acid sequence is from a eukaryote.

In one embodiment, the insert nucleic acid that is homologous or orthologous to the rat c acid sequence is a mammalian nucleic acid. In one embodiment, the insert nucleic acid that is homologous or orthologous to the rat nucleic acid sequence is a non-human mammalian nucleic acid. In one embodiment, the mammalian c acid is a mouse nucleic acid. In one embodiment, the mammalian nucleic acid is a human nucleic acid. In one embodiment, the ian nucleic acid is a hamster nucleic acid. In one embodiment, the insert nucleic acid is a genomic DNA. In one embodiment, the insert is from 5 kb to 200 kb as described above.

In one embodiment, the LTVEC ses a selection cassette or a reporter gene. Various forms of the selection cassette and reporter gene that can be employed are discussed elsewhere herein.

As described elsewhere herein, the LTVEC can also be used in the methods provided herein in combination with a nuclease agent that promotes a homologous recombination n the targeting vector and the target locus of a rat, otic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster nucleic acid in a pluripotent or non-pluripotent rat, eukaryotic, non-rat otic, ian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster cell.

In one embodiment, the large targeting vector (LTVEC) comprises a site- speciﬁc recombinase gene. In one embodiment, the site-speciﬁc recombinase gene encodes a Cre recombinase. In one embodiment, the Cre inase gene is Crei, wherein two exons encoding the Cre recombinase are separated by an intron to prevent its expression in a prokaryotic cell. In one embodiment, the Cre recombinase gene further comprises a nuclear localization signal to facilitate localization of Cre (or any recombinase or se agent) to the nucleus (e. g., the gene is an NL-Cre gene). In a speciﬁc embodiment, the Cre inase gene ﬁarther comprises a nuclear localization signal and an intron (e. g., i) In various embodiments, a suitable promoter for expression of the nuclease agent ding the Cre or Crei recombinase discussed above) is selected from or comprises a PrmI and/or Pax3. In a speciﬁc , Blimp] , Gata6, Gata4, Ing, th2, th5, embodiment, the promoter is the Gata6 or Gata4 promoter. The s promoters can be from any organism, including for example, a rodent such as a mouse or a rat, a non-rat rodent, a eukaryote, a non-rat eukaryote, a non-human mammal, a mammal, a human or a hamster. In another speciﬁc embodiment, the promoter is a PrmI promoter. In another speciﬁc embodiment, the promoter is a rat PrmI promoter. In another speciﬁc embodiment, the promoter is a mouse PrmI promoter. In r speciﬁc embodiment, the er is a Blimp] promoter or a fragment thereof, e.g., a 1 kb or 2 kb fragment of a Blimp] promoter. See, for example, US. Patent 8,697,851 and US. Application ation 2013-0312129, both of which are herein incorporated by reference in their entirety.

In one embodiment, the LTVEC comprises an insert nucleic acid that can produce a deletion, addition, replacement or a combination thereof of a region of the rat, a eukaryotic, a non-rat otic, a mammalian, non-human mammalian, a human, a , a non-rat rodent, a mouse or a hamster ApoE locus, the Il2rg locus, the Rag2 locus, the Rag] locus and/or the Rag2/Rag] locus as discussed in detail elsewhere herein.

In speciﬁc embodiments, the genetic modiﬁcation at the ApoE locus results in a se, an se or a modulation in ApoE actiVity, IL-2Rg actiVity, Rag2 actiVity, Ragl actiVity and/or Rag2 and Ragl ty. In one embodiment, an ApoE knockout, and Il2rg knockout, a Rag2 knockout, a Rag] ut, a Rag2/Rag] knockout is generated.

As discussed below, nuclease agents can be employed with any of the LTVEC targeting systems to target any genomic locus of interest.

In another ment, the genome is exposed to a Cas protein and a CRISPR RNA in the presence of a large targeting vector (LTVEC) comprising a nucleic acid sequence of at least 10 kb. In such cases, following re to the Cas protein, the CRISPR RNA, and the LTVEC, the genome is modiﬁed to contain at least 10 kb of nucleic acid sequence. In speciﬁc embodiments, the LTVEC comprises a nucleic acid sequence of at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, at least 90 kb, at least 100 kb, at least 150 kb or at least 200 kb.

V. Nuclease Agents and Recognition Sites for se Agents As outlined in detail above, nuclease agents may be utilized in the methods and compositions disclosed herein to aid in the modiﬁcation of the target locus both in a yotic cell or within a pluripotent or non-pluripotent rat, eukaryotic, non- rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent ,mouse or hamster cell. Such a nuclease agent may promote homologous recombination n the targeting vector and the target locus. In one embodiment, the nuclease agent comprises an clease agent.

As used herein, the term "recognition site for a nuclease agent" comprises a DNA sequence at which a nick or double-strand break is induced by a nuclease agent.

The recognition site for a nuclease agent can be endogenous (or native) to the cell or the recognition site can be exogenous to the cell. In speciﬁc embodiments, the recognition site is exogenous to the cell and thereby is not lly occurring in the genome of the cell. In still further embodiments, the recognition site is exogenous to the cell and to the polynucleotides of interest that one desired to be positioned at the target genomic locus.

In further embodiments, the exogenous or nous recognition site is t only once in the genome of the host cell. In speciﬁc embodiments, an endogenous or native site that occurs only once within the genome is ﬁed. Such a site can then be used to design nuclease agents that will produce a nick or double-strand break at the endogenous recognition site.

The length of the recognition site can vary, and includes, for example, recognition sites that are at least 4, 6, 8, 10, l2, l4, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70 or more nucleotides in length. In one embodiment, each monomer of the se agent recognizes a recognition site of at least 9 nucleotides. In other embodiments, the recognition site is from about 9 to about 12 nucleotides in length, from about 12 to about nucleotides in length, from about 15 to about 18 nucleotides in length, or from about 18 to about 21 nucleotides in length, and any combination of such subranges (e. g., 9-l8 nucleotides). The recognition site could be romic, that is, the sequence on one 2014/060788 strand reads the same in the opposite direction on the complementary strand. It is recognized that a given nuclease agent can bind the ition site and cleave that binding site or atively, the nuclease agent can bind to a sequence that is the different from the recognition site. Moreover, the term recognition site ses both the nuclease agent binding site and the nick/cleavage site ective whether the nick/cleavage site is within or e the se agent binding site. In another variation, the cleavage by the nuclease agent can occur at tide positions immediately opposite each other to produce a blunt end cut or, in other cases, the incisions can be staggered to produce single-stranded overhangs, also called "sticky ends", which can be either 5' overhangs, or 3' overhangs.

Any nuclease agent that induces a nick or double-strand break into a desired recognition site can be used in the methods and compositions disclosed herein. A naturally-occurring or native nuclease agent can be employed so long as the nuclease agent induces a nick or double-strand break in a desired ition site. Alternatively, a modiﬁed or engineered nuclease agent can be employed. An "engineered nuclease agent" comprises a se that is engineered (modiﬁed or derived) from its native form to speciﬁcally recognize and induce a nick or double-strand break in the desired recognition site. Thus, an engineered nuclease agent can be derived from a native, naturally-occurring nuclease agent or it can be artiﬁcially created or synthesized. The modiﬁcation of the nuclease agent can be as little as one amino acid in a protein cleavage agent or one nucleotide in a nucleic acid cleavage agent. In some embodiments, the ered nuclease induces a nick or double-strand break in a recognition site, wherein the recognition site was not a sequence that would have been recognized by a native (non-engineered or non-modiﬁed) nuclease agent. Producing a nick or double-strand break in a recognition site or other DNA can be referred to herein as "cutting" or "cleaving" the recognition site or other DNA.

Active variants and fragments of the exempliﬁed recognition sites are also provided. Such active variants can comprise at least 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity to the given recognition site, wherein the active variants retain biological actiVity and hence are capable of being ized and cleaved by a nuclease agent in a sequence-speciﬁc manner. Assays to measure the double-strand break of a recognition site by a se agent are known in the art and generally e the ability of a nuclease to cut the recognition site.

The recognition site of the nuclease agent can be positioned anywhere in or near the target locus. The recognition site can be located within a coding region of a gene, or within regulatory regions, which ce expression of the gene. Thus, a recognition site of the nuclease agent can be located in an intron, an exon, a promoter, an enhancer, a regulatory region, or any non-protein coding region.

In one embodiment, the nuclease agent is a Transcription tor-Like Effector Nuclease (TALEN). TAL effector nucleases are a class of sequence-speciﬁc nucleases that can be used to make double-strand breaks at speciﬁc target sequences in the genome of a prokaryotic or otic organism. TAL effector nucleases are created by fusing a native or engineered transcription activator-like (TAL) effector, or ﬁanctional part f, to the catalytic domain of an endonuclease, such as, for example, FokI. The unique, modular TAL effector DNA binding domain allows for the design of proteins with potentially any given DNA recognition speciﬁcity. Thus, the DNA binding domains of the TAL effector nucleases can be engineered to recognize specific DNA target sites and thus, used to make double-strand breaks at desired target sequences. See, WO 2010/079430; Morbitzer et al. (2010) PNAS 10.1073/pnas.1013133107; Scholze & Boch (2010) Virulence 1:428-432; Christian et al. Genetics (2010) 7-761; Li et al. (2010) Nuc. Acids Res. (2010) doi:10.1093/nar/gkq704; and Miller et al. (2011) Nature Biotechnology 29: 8; all of which are herein incorporated by reference.

] Examples of suitable TAL nucleases, and methods for preparing le TAL nucleases, are disclosed, e. g., in US Patent Application No. 2011/0239315 A1, 2011/0269234 A1, 2011/0145940 A1, 2003/0232410 A1, 2005/0208489 A1, 2005/0026157 A1, 2005/0064474 A1, 2006/0188987 A1, and 2006/0063231 A1 (each hereby incorporated by reference). In various embodiments, TAL or ses are engineered that cut in or near a target nucleic acid sequence in, e. g., a genomic locus of interest, wherein the target nucleic acid sequence is at or near a sequence to be modified by a targeting vector. The TAL nucleases suitable for use with the various methods and compositions provided herein include those that are cally designed to bind at or near target nucleic acid ces to be modiﬁed by targeting vectors as described herein.

In one embodiment, each monomer of the TALEN ses 12-25 TAL repeats, wherein each TAL repeat binds a 1 bp subsite. In one embodiment, the nuclease agent is a chimeric protein comprising a TAL repeat-based DNA binding domain operably linked to an independent nuclease. In one embodiment, the independent nuclease is a FokI endonuclease. In one embodiment, the nuclease agent comprises a ﬁrst TAL-repeat-based DNA binding domain and a second TAL-repeat-based DNA binding domain, wherein each of the ﬁrst and the second TAL-repeat-based DNA binding domain is operably linked to a FokI se, wherein the ﬁrst and the second TAL-repeat-based DNA binding domain recognize two contiguous target DNA sequences in each strand of the target DNA sequence separated by about 6 bp to about 40 bp cleavage site, and wherein the FokI nucleases dimerize and make a double strand break at a target sequence.

In one ment, the nuclease agent comprises a ﬁrst TAL-repeat- based DNA binding domain and a second TAL-repeat-based DNA binding , wherein each of the ﬁrst and the second TAL-repeat-based DNA binding domain is operably linked to a FokI nuclease, wherein the ﬁrst and the second TAL-repeat-based DNA binding domain recognize two contiguous target DNA sequences in each strand of the target DNA sequence ted by a 5 bp or 6 bp ge site, and wherein the FokI nucleases ze and make a double strand break.

The nuclease agent employed in the various methods and compositions sed herein can further comprise a zinc-ﬁnger nuclease (ZFN). In one embodiment, each monomer of the ZFN comprises 3 or more zinc ﬁnger-based DNA binding domains, wherein each zinc ﬁnger-based DNA binding domain binds to a 3 bp subsite. In other embodiments, the ZFN is a chimeric protein comprising a zinc ﬁnger-based DNA g domain operably linked to an ndent nuclease. In one embodiment, the ndent endonuclease is a FokI endonuclease. In one embodiment, the nuclease agent comprises a ﬁrst ZFN and a second ZFN, wherein each of the ﬁrst ZFN and the second ZFN is operably linked to a FokI nuclease, wherein the ﬁrst and the second ZFN recognize two contiguous target DNA sequences in each strand of the target DNA sequence separated by about 6 bp to about 40 bp cleavage site or about a 5 bp to about 6 bp cleavage site, and wherein the FokI nucleases dimerize and make a double strand break. See, for example, US20060246567; US20080182332; 0081614; US20030021776; WO/2002/057308A2; US20130123484; US20100291048; and, WO/201 1/017293A2, each of which is herein incorporated by reference.

In one embodiment of the methods ed , the nuclease agent ses (a) a chimeric protein comprising a zinc finger-based DNA binding domain fused to a FokI endonuclease; or (b) a chimeric protein comprising a Transcription Activator-Like Effector Nuclease (TALEN) fused to a FokI endonuclease.

In still another embodiment, the nuclease agent is a meganuclease.

Meganucleases have been ﬁed into four families based on conserved sequence motifs, the families are the LAGLIDADG (SEQ ID NO: 16), GIY-YIG, H-N-H, and His- Cys box families. These motifs participate in the coordination of metal ions and hydrolysis of phosphodiester bonds. HEases are e for their long recognition sites, and for tolerating some sequence polymorphisms in their DNA substrates. Meganuclease domains, structure and ﬁanction are known, see for example, Guhan and Muniyappa (2003) Crit Rev Biachem Mal Biol 38: 199-248; Lucas et al. , (2001) Nucleic Acids Res -9; Jurica and Stoddard, (1999) Cell Mal Life Sci 55:1304-26; Stoddard, (2006) Q Rev Biaphys 38:49-95; and Moure et al., (2002) Nat Struct Biol 9:764. In some examples a naturally occurring variant, and/or engineered derivative meganuclease is used.

Methods for modifying the kinetics, cofactor interactions, expression, l conditions, and/or recognition site speciﬁcity, and screening for activity are known, see for example, Epinat et al., (2003) Nucleic Acids Res 31 62; Chevalier et al., (2002) Mal Cell :895-905; Gimble et al, (2003) Mal Bial 334:993-1008; Seligman et al, (2002) Nucleic Acids Res 30:3870-9; Sussman et al., (2004) JMal Bial 342:31-41; Rosen et al., (2006) c Acids Res 34:4791-800; Chames et al., (2005) Nucleic Acids Res 33 :el78; Smith et al., (2006) Nucleic Acids Res 34:el49; Gruen et al., (2002) Nucleic Acids Res :e29; Chen and Zhao, (2005) Nucleic Acids Res 33:e154; W02005105989; 0786l9; W02006097854; W02006097853; W02006097784; and W0200403 1346.

Any meganuclease can be used herein, including, but not limited to, I- SceI, I-SceII, I-SceIII, I-SceIV, I-SceV, I, I-SceVII, , I-CeuAIIP, I-CreI, I- CrepsbIP, I-CrepsbIIP, I-CrepsbIIIP, sbIVP, , I-PpoI, PI-PspI, F-SceI, F- SceII, F-SuvI, F-TevI, F-TevII, I-AmaI, I-AniI, , I-CmoeI, I-CpaI, I-CpaII, I-CsmI, I-CvuI, I-CvuAIP, I-DdiI, I-DdiII, I-DirI, , I-HmuI, I-HmuII, P, , I- MsoI, I-NaaI, I-NanI, I-NcIIP, I-NngP, I-NitI, I-NjaI, I-Nsp236IP, I-PakI, I-PboIP, I- PcuIP, I-PcuAI, I, I-PngP, I-PobIP, I-PorI, I-PorIIP, I-PprP, I-SpBetaIP, I-ScaI, I-SeXIP, P, I-SpomI, I-SpomCP, I-SpomIP, I-SpomIIP, I-SquIP, I-Ssp6803I, I- SthPhiJP, I-SthPhiST3P, I-SthPhiSTe3bP, I-TdeIP, I-TevI, I-TevII, I-TevIII, I-UarAP, I- UarHGPAIP, I-UarHGPAl3P, I-VinIP, I-ZbiIP, PI-MtuI, PI-MtuHIP HIIP, PI- PfuI, PI-PfuII, PI-PkoI, PI-PkoII, PI-Rma438lZIP, PI-SpBetaIP, PI-SceI, PI-TfuI, PI- TﬁlH, PI—ThyI, PI-TliI, PI-TliII, or any active variants or fragments f.

In one embodiment, the meganuclease recognizes double-stranded DNA sequences of 12 to 40 base pairs. In one embodiment, the meganuclease recognizes one perfectly matched target sequence in the genome. In one embodiment, the meganuclease is a homing se. In one embodiment, the homing nuclease is a LAGLIDADG (SEQ ID NO: 16) family of homing nuclease. In one embodiment, the LAGLIDADG (SEQ ID NO: 16) family of homing nuclease is selected from I-SceI, I-CreI, and .

Nuclease agents can further comprise restriction endonucleases, which include Type I, Type II, Type III, and Type IV endonucleases. Type I and Type III ction endonucleases recognize specific recognition sites, but typically cleave at a variable position from the nuclease binding site, which can be hundreds of base pairs away from the cleavage site (recognition site). In Type II systems the restriction activity is ndent of any methylase activity, and ge typically occurs at speciﬁc sites within or near to the binding site. Most Type II enzymes cut palindromic sequences, r Type IIa enzymes recognize non-palindromic recognition sites and cleave outside of the recognition site, Type IIb enzymes cut sequences twice with both sites outside of the recognition site, and Type IIs enzymes recognize an asymmetric recognition site and cleave on one side and at a deﬁned distance of about 1-20 nucleotides from the recognition site. Type IV restriction enzymes target methylated DNA. Restriction enzymes are ﬁarther bed and classified, for example in the REBASE database (webpage at rebase.neb.com; Roberts et al., (2003) Nucleic Acids Res 31 :418-20), Roberts et al., (2003) Nucleic Acids Res 31 :1805-12, and Belfort et al., (2002) in Mobile DNA II, pp. 761-783, Eds. Craigie et al., (ASM Press, Washington, DC).

The nuclease agent employed in the various methods and itions can also comprise a CRISPIVCas system. Such s can employ, for example, a Cas9 se, which in some instances, is codon-optimized for the desired cell type in which it is to be expressed. Such systems can also employ a guide RNA (gRNA) that comprises two separate molecules. An exemplary two-molecule gRNA comprises a chNA-like ("CRISPR RNA" or "targeter-RNA" or "chNA" or "chNA repeat") molecule and a corresponding trachNA-like ("trans-acting CRISPR RNA" or "activator-RNA" or "trachNA" or "scaffold") molecule. A chNA comprises both the rgeting segment (single stranded) of the gRNA and a stretch of nucleotides that forms one half of a double ed RNA (dsRNA) duplex of the protein-binding segment of the gRNA. A corresponding trachNA ator-RNA) comprises a stretch of nucleotides that forms the other half of the dsRNA duplex of the protein-binding segment of the gRNA. Thus, a stretch of nucleotides of a chNA are complementary to and hybridize with a stretch of nucleotides of a trachNA to form the dsRNA duplex of the protein-binding domain of the gRNA. As such, each chNA can be said to have a corresponding trachNA. The chNA additionally provides the single stranded DNA-targeting segment. Accordingly, a gRNA comprises a ce that hybridizes to a target sequence, and a trachNA. Thus, a chNA and a trachNA (as a corresponding pair) hybridize to form a gRNA. If used for modiﬁcation within a cell, the exact sequence and/or length of a given chNA or trachNA molecule can be designed to be speciﬁc to the species in which the RNA molecules will be used.

] Naturally occurring genes encoding the three elements (Cas9, trachNA and chNA) are typically organized in operon(s). Naturally occurring CRISPR RNAs differ ing on the Cas9 system and organism but often contain a targeting segment of between 21 to 72 nucleotides length, ﬂanked by two direct repeats (DR) of a length of between 21 to 46 nucleotides (see, e.g., WO2014/131833). In the case of S. pyogenes, the DRs are 36 nucleotides long and the targeting segment is 30 tides long. The 3’ located DR is mentary to and izes with the corresponding trachNA, which in turn binds to the Cas9 protein.

Alternatively, the system ﬁarther employs a ﬁased chNA-trachNA construct (i.e., a single transcript) that ﬁanctions with the codon-optimized Cas9. This single RNA is often referred to as a guide RNA or gRNA. Within a gRNA, the chNA portion is identiﬁed as the ‘target sequence’ for the given recognition site and the trachNA is often referred to as the ‘scaffold.’ Brieﬂy, a short DNA fragment containing the target ce is inserted into a guide RNA expression plasmid. The gRNA expression d comprises the target sequence (in some embodiments around 20 nucleotides), a form of the trachNA sequence (the scaffold) as well as a le promoter that is active in the cell and necessary elements for proper processing in eukaryotic cells. Many of the systems rely on custom, complementary oligos that are annealed to form a double ed DNA and then cloned into the gRNA expression plasmid. The gRNA expression cassette and the Cas9 sion cassette are then uced into the cell. See, for example, Mali P et al. (2013) Science 2013 Feb ;339(6121):823-6; Jinek M et al. Science 2012 Aug 17;337(6096):816-21; Hwang WY et al. Nat Biotechnol 2013 Mar;31(3):227-9; Jiang W et al. Nat Biotechnol 2013 Mar;31(3):233-9; and Cong L et al. Science 2013 Feb 15;339(6121):819-23, each of which is herein incorporated by reference. See also, for example, WO/2013/176772A1, WO/2014/065596A1, WO/2014/089290A1, WO/2014/093622A2, WO/2014/099750A2, and WO/2013142578A1, each of which is herein incorporated by reference.

In some embodiments, the Cas9 se can be provided in the form of a protein. In some embodiments, the Cas9 protein can be provided in the form of a complex with the gRNA. In other embodiments, the Cas9 nuclease can be provided in the form of a nucleic acid encoding the protein. The nucleic acid encoding the Cas9 nuclease can be RNA (e. g., messenger RNA (mRNA)) or DNA.

In some embodiments, the gRNA can be provided in the form of RNA. In other embodiments, the gRNA can be ed in the form ofDNA encoding the RNA.

In some embodiments, the gRNA can be ed in the form of separate chNA and A molecules, or separate DNA molecules encoding the chNA and trachNA, respectively.

] In one ment, the method for modifying a genomic locus of interest in a cell further comprises introducing into the cell: (a) a first expression construct comprising a ﬁrst promoter operably linked to a ﬁrst nucleic acid sequence encoding a Clustered Regularly Interspaced Short Palindromic Repeats R)-associated (Cas) protein; (b) a second expression construct comprising a second promoter operably linked to a genomic target sequence linked to a guide RNA (gRNA), wherein the genomic target sequence is ﬂanked by a Protospacer Adjacent Motif. Optionally, the genomic target sequence is ﬂanked on the 3 ’end by a pacer Adjacent Motif (PAM) sequence. In one embodiment, the cell comprises a otic cell, a non-rat otic cell, a mammalian cell, a human cell, a non-human mammalian cell, a pluripotent cell, a non- pluripotent cell, a non-human pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a deVelopmentally-restricted human progenitor cell, a human iPS cell, a human cell, a rodent cell, a non-rat rodent cell, a rat cell, a mouse cell, a hamster cell, a ﬁbroblast, or a CHO cell.

In one embodiment, the genomic target sequence comprises the nucleotide sequence of GNNNNNNNNNNNNNNNNNNNNGG (GN1_20 GG; SEQ ID NO: 1). In one embodiment, the genomic target sequence comprises SEQ ID NO: 23, wherein N is between 1 and 20 tides in length. In another embodiment, the genomic target sequence ses n 14 and 20 nucleotides in length of SEQ ID NO: 1.

In one embodiment, the gRNA comprises a third nucleic acid sequence encoding a Clustered rly Interspaced Short Palindromic Repeats (CRISPR) RNA (chNA) and a trans-activating CRISPR RNA (trachNA). In speciﬁc embodiments, the Cas n is Cas9.

In some embodiments, the gRNA comprises (a) the chimeric RNA of the nucleic acid sequence 5’-GUUUUAGAGCUAGAAAUAGCAAGUUAAAAU AAGGCUAGUCCGUUAUCAACUUGAAAAAGUGGCACCGAGUCGGUGCUUUU- 3’ (SEQ ID NO: 2); or (b) the ic RNA of the nucleic acid ce 5 ’- GUUUUAGAGCUAGAAAUAGCAAGUUAAAAUAAGGCUAGUCCG-3’ (SEQ ID NO: 3).

In another embodiment, the chNA comprises 5’- GUUUUAGAGCUAGAAAUAGCAAGUUAAAAU-3’ (SEQ ID NO: 4); 5’- GUUUUAGAGCUAGAAAUAGCAAGUUAAAAUAAG (SEQ ID NO: 5); or 5’- GAGUCCGAGCAGAAGAAGAAGUUUUA-3’ (SEQ ID NO: 6).

In yet other embodiments, the A comprises, 5 ’- AAGGCUAGUCCG-3’ (SEQ ID NO: 7) or 5’-AAGGCUAGUCCGU UAUCAACUUGAAAAAGUGGCACCGAGUCGGUGCUUUU-3’ (SEQ ID NO: 8).

In one embodiment, the Cas protein is a type I Cas protein. In one ment, the Cas protein is a type II Cas protein. In one embodiment, the type II Cas n is Cas9. In one ment, the ﬁrst nucleic acid ce encodes a human codon-optimized Cas protein.

In certain embodiments, the Cas protein is a "nickase" that can create single strand breaks (i.e., "nicks") at the target site without cutting both strands of double stranded DNA (dsDNA). Cas9, for example, comprises two nuclease domains—a Rqu- like nuclease domain and an HNH-like nuclease domain—which are responsible for cleavage of opposite DNA strands. Mutation in either of these domains can create a nickase. Examples of mutations creating nickases can be found, for example, WO/2013/l76772Al and WO/2013/l42578Al each of which is herein incorporated by reference.

In certain embodiments, two separate Cas ns (e. g., nickases) speciﬁc for a target site on each strand of dsDNA can create overhanging sequences complementary to overhanging sequences on another nucleic acid, or a separate region on the same nucleic acid. The overhanging ends created by contacting a nucleic acid with two es speciﬁc for target sites on both strands of dsDNA can be either 5' or 3' overhanging ends. For example, a ﬁrst nickase can create a single strand break on the ﬁrst strand of dsDNA, while a second nickase can create a single strand break on the second strand of dsDNA such that overhanging sequences are created. The target sites of each nickase creating the single strand break can be selected such that the overhanging end ces created are mentary to overhanging end ces on a different nucleic acid molecule. The complementary overhanging ends of the two different nucleic acid molecules can be annealed by the methods disclosed herein. In some embodiments, the target site of the nickase on the ﬁrst strand is different from the target site of the nickase on the second strand.

In one embodiment, the ﬁrst nucleic acid comprises a mutation that disrupts at least one amino acid residue of nuclease active sites in the Cas protein, wherein the mutant Cas protein generates a break in only one strand of the target DNA region, and n the mutation diminishes nonhomologous recombination in the target DNA region.

] In one embodiment, the ﬁrst nucleic acid that encodes the Cas protein further comprises a nuclear localization signal (NLS). In one embodiment, the nuclear zation signal is a SV40 nuclear localization signal.

In one embodiment, the second promoter that drives the expression of the genomic target sequence and the guide RNA (gRNA) is an RNA rase III promoter. In one embodiment, the RNA rase III promoter is a human U6 promoter. In one embodiment, the RNA polymerase III er is a rat U6 polymerase III promoter. In one embodiment, the RNA polymerase III promoter is a mouse U6 polymerase III promoter.

In one embodiment, the nucleic acid sequences encoding chNA and the trachNA are linked via a synthetic loop, wherein, upon expression, the chNA and the trachNA forms a chNA:trachNA duplex.

The CRISPIVCas system as described above can be used in combination with large targeting vectors with any of the following cell types: a eukaryotic cell, a non- rat eukaryotic cell, a mammalian cell, a non-human mammalian cell, a pluripotent cell, a non-pluripotent cell, a man pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a developmentally-restricted human progenitor cell, a human iPS cell, a human cell, a rodent cell, a t rodent cell, a rat cell, a mouse cell, a hamster cell, a ﬁbroblast or a CHO cell.

In one ment, the ﬁrst expression construct and the second expression uct are expressed from a same plasmid.

In one embodiment, the ﬁrst and the second expression constructs are introduced together with the LTVEC. In one embodiment, the ﬁrst and the second expression constructs are introduced separately from the LTVEC over a period of time.

In one embodiment, the method comprises ucing a plurality of the second construct and a plurality of the LTVEC for multiplex editing of distinct target loci as described herein.

Active variants and fragments of nuclease agents (i.e., an ered nuclease agent) are also provided. Such active variants can se at least 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity to the native nuclease agent, wherein the active variants retain the ability to cut at a desired recognition site and hence retain nick or double-strand-break- inducing ty. For example, any of the nuclease agents described herein can be modiﬁed from a native endonuclease sequence and designed to recognize and induce a nick or double-strand break at a recognition site that was not recognized by the native nuclease agent. Thus in some embodiments, the ered se has a speciﬁcity to induce a nick or double-strand break at a recognition site that is different from the corresponding native nuclease agent recognition site. Assays for nick or double-strandbreak-inducing activity are known and generally measure the overall activity and speciﬁcity of the endonuclease on DNA ates containing the recognition site.

The nuclease agent may be introduced into the cell by any means known in the art. The polypeptide encoding the nuclease agent may be directly introduced into the cell. Alternatively, a polynucleotide encoding the se agent can be introduced into the cell. When a polynucleotide encoding the nuclease agent is introduced into the cell, the nuclease agent can be transiently, ionally or constitutively expressed within the cell. Thus, the polynucleotide encoding the nuclease agent can be contained in an sion cassette and be operably linked to a conditional promoter, an inducible promoter, a constitutive promoter, or a tissue-speciﬁc promoter. Such promoters of interest are discussed in further detail elsewhere herein. Alternatively, the nuclease agent is introduced into the cell as an mRNA encoding or comprising a nuclease agent.

In one embodiment, the chNA and the trachNA are expressed as separate RNA transcripts.

In speciﬁc embodiments, the polynucleotide encoding the nuclease agent is stably integrated in the genome of the cell and operably linked to a promoter active in the cell. In other ments, the polynucleotide encoding the nuclease agent is in the same targeting vector comprising the insert nucleic acid, while in other instances the polynucleotide encoding the nuclease agent is in a vector or a d that is separate from the ing vector comprising the insert nucleic acid.

When the nuclease agent is provided to the cell through the introduction of a polynucleotide encoding the nuclease agent, such a polynucleotide encoding a nuclease agent can be d to substitute codons having a higher frequency of usage in the cell of interest, as compared to the naturally occurring polynucleotide sequence encoding the nuclease agent. For example the polynucleotide encoding the nuclease agent can be modiﬁed to tute codons having a higher frequency of usage in a given prokaryotic or eukaryotic cell of interest, including a bacterial cell, a yeast cell, a human cell, a non- human cell, a non-rat eukaryotic cell, a ian cell, a rodent cell, a non-rat rodent cell, a mouse cell, a rat cell, a hamster cell or any other host cell of interest, as compared to the naturally occurring cleotide sequence.

In one embodiment, the endonuclease agent is introduced together with the LTVEC. In one ment, the endonuclease agent is introduced separately from the LTVEC over a period of time. In one embodiment, the clease agent is introduced prior to the introduction of the LTVEC. In one embodiment, the endonuclease agent is introduced into the rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster ES cell following introduction of the LTVEC.

] In one embodiment, the endonuclease agent is an expression construct comprising a nucleic acid sequence encoding an endonuclease, n the nucleic acid ce is operably linked to a promoter. In one embodiment, the promoter is a constitutively active promoter. In one embodiment, the promoter is an inducible promoter. In one embodiment, the promoter is active in the pluripotent or non-pluripotent rat, otic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster cell. In one embodiment, the endonuclease agent is an mRNA ng an endonuclease.

B. Methods for ating a Polynucleotide of st Into a Target Locus Methods for modifying a target locus of interest are provided. In one embodiment, a target locus in a pluripotent or non-pluripotent rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster cell is targeted for genetic modiﬁcation. Such a method comprises: (a) introducing into the pluripotent or non-pluripotent rat, eukaryotic, non-rat eukaryotic, mammalian, man mammalian, human, rodent, non-rat rodent, mouse or hamster cell a targeting vector comprising an insert nucleic acid ﬂanked with a 5 ’ rat, otic, non-rat otic, mammalian, non-human mammalian, human, rodent, non-rat rodent, ’ rat, eukaryotic, non-rat eukaryotic, mouse or hamster homology arm and a 3 mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster homology arm; and (b) identifying a genetically modiﬁed pluripotent or non-pluripotent rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammalian, human, rodent, non-rat rodent, mouse or hamster cell comprising the targeted genetic modiﬁcation at the target locus, wherein the targeted genetic modiﬁcation is capable of being itted h the ne. In c embodiments, the sum total of the 5’ gy arm and the 3’ homology arm is at least 10 kb and/or a large targeting vector is employed.

In other embodiments, the size of the sum total of the total of the 5' and 3' homology arms of the LTVEC is about 10 kb to about 150 kb, about 10 kb to about 100 kb, about 10 kb to about 75 kb, about 20 kb to about 150 kb, about 20 kb to about 100 kb, about 20 kb to about 75 kb, about 30 kb to about 150 kb, about 30 kb to about 100 kb, about 30 kb to about 75 kb, about 40 kb to about 150 kb, about 40 kb to about 100 kb, about 40 kb to about 75 kb, about 50 kb to about 150 kb, about 50 kb to about 100 kb, or about 50 kb to about 75 kb, about 10 kb to about 30 kb, about 20 kb to about 40 kb, about 40 kb to about 60 kb, about 60 kb to about 80 kb, about 80 kb to about 100 kb, about 100 kb to about 120 kb, or from about 120 kb to about 150 kb. In one embodiment, the size of the deletion is the same or similar to the size of the sum total of the 5' and 3' homology arms of the LTVEC.

The pluripotent cell, for example, a rat cell, can be an embryonic stem cell, for example, a rat embryonic stem cell. In a speciﬁc embodiment, (a) the rat ES cell is derived from a DA strain or an ACI strain; or (b) the rat ES cell is terized by expression of a pluripotency marker comprising Oct-4, Sox-2, alkaline phosphatase, or a combination thereof. In other instances, the rat embryonic stem cell employed comprises a rat ES cell as described in US. Patent Application No. 14/185,103, ﬁled on February , 2014, herein incorporated by reference in its entirety.

WO 88643 Any pluripotent or non-pluripotent cell can be used in the methods provided herein. For example, the pluripotent or non-pluripotent cell can be from a eukaryote, a non-rat eukaryote, a non-human , a mammal, a rodent, a non-rat rodent, a rat, a mouse, a human or a hamster.

As described elsewhere herein, the insert nucleic acid can be any nucleic acid sequence. In non-limiting ments, (a) the insert nucleic acid comprises a replacement of an nous rat, eukaryotic, non-rat eukaryotic, mammalian, human, rodent, non-rat rodent, mouse or hamster c acid sequence with a homologous or a orthologous mammalian nucleic acid sequence; (b) the insert nucleic acid comprises a on of an endogenous rat, eukaryotic, non-rat eukaryotic, mammalian, human, rodent, non-rat rodent, mouse or hamster nucleic acid sequence; (c) the insert nucleic acid comprises a deletion of an endogenous rat, eukaryotic, non-rat eukaryotic, ian, non-human ian, human, rodent, non-rat rodent, mouse or hamster nucleic acid sequence, wherein the on ranges from 5 kb to 200 kb or from 5 kb to 3 Mb (as discussed in detail elsewhere herein); (d) the insert nucleic acid comprises an addition of an exogenous nucleic acid ce (including for example an exogenous nucleic acid sequence ranging from about 5 kb to about 10 kb, from about 10 kb to about kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb); (e) the insert nucleic acid comprises an exogenous nucleic acid sequence comprising a homologous or an ogous c acid sequence; (f) the homologous or the orthologous nucleic acid sequence of (a) wherein the nucleic acid sequence is a human nucleic acid ce; (g) the insert nucleic acid comprises the homologous or the orthologous nucleic acid sequence of (a) wherein the nucleic acid ce is a chimeric nucleic acid sequence comprising a human and a rat nucleic acid sequence; (h) the insert nucleic acid comprises the exogenous nucleic acid sequence of (e), wherein the insert nucleic acid ranges from about 5 kb to about 200 kb; (i) the insert nucleic acid comprises a conditional allele ﬂanked with site-speciﬁc recombinase target sequences; (j) the insert nucleic acid comprises a reporter gene operably linked to a promoter; (k) the insert c acid comprises one or more unrearranged human globulin heavy chain VH gene segments, one or more unrearranged human immunoglobulin heavy chain D gene segments, and one or more ranged human immunoglobulin heavy chain JH gene segments, which are operably linked to a rodent heavy chain constant region nucleic acid sequence; (1) the insert nucleic acid ses a rearranged human immunoglobulin heavy chain variable region nucleic acid sequence operably linked to a rodent heavy chain constant region nucleic acid sequence; (m) the insert nucleic acid comprises one or more unrearranged human immunoglobulin VK or Vk gene ts and one or more unrearranged human immunoglobulin JK or Jk gene segments, which are operably linked to a mammalian immunoglobulin 9» or K light chain light chain constant region nucleic acid sequence; (11) the insert nucleic acid comprises a rearranged human immunoglobulin 9» or K light chain variable region nucleic acid sequence ly linked to a mammalian immunoglobulin 7» or K light chain light chain constant region nucleic acid sequence; (0) the mammalian heavy chain constant region c acid sequence of (k) and/or (1) comprises a rat constant region c acid sequence, a human constant region c acid sequence, or a combination thereof; or (p) the mammalian immunoglobulin 9» or K light chain constant region nucleic acid of (m) and/or (11) comprises a rat constant region nucleic acid sequence, a human constant region nucleic acid sequence, or a combination thereof.

In one embodiment, the insert nucleic acid comprises one or more functional human VH gene segments comprising VHl-2, VHl-3, VHl-8, VHl-18, VHl-24, VHl-45, VHl-46, VHl-58, VHl-69, VH2-5, VH2-26, VH2-70, VH3-7, VH3-9, VH3-l l, VH3- 13, , VH3-l6, VH3-20, VH3-21, VH3-23, VH3-30, VH33, VH , VH3-33, VH3-35, VH3-38, VH3-43, VH3-48, VH3-49, VH3-53, VH3-64, VH3-66, VH3-72, VH3-73, VH3-74, VH4-4, VH4-28, VH4l, VH42, VH44, VH4-31, VH4-34, VH4-39, VH4- 59, VH4-6l, VHS-51, VH6-l, VH7l, VH7-81, or a combination thereof In one embodiment, the insert nucleic acid ses one or more functional human D gene segments comprising D l -l D l -7, D 1 -l4, D l -20, D l -26, D2-2, 2-15,D2-21,D3-3,D3-9,D3-10,D3-l6,D3-22,D4-4,D4-11,D4-17,D4-23, D5-l2, D5-5, D5-18, D5-24, D6-6, D6-l3, D6-l9, D6-25, D7-27, or a combination thereof In one embodiment, the insert nucleic acid comprises one or more functional JH gene segments comprising JHl JH2, JH3, JH4, JHS, JH6, or a combination thereof. In one embodiment, the insert nucleic acid comprises one or more human VK gene segments sing VK4-l, VK5-2, VK 7-3, VK 2-4, VKl-S, VKl-6, VK3-7, VKl-8, VKl-9,VKZ-lo,VK3-ll,VKl-lz,VKl-l3,VK2-14,VK3-15,VKl-l6,VKl-l7,VK2-18, VK2-l9, VK3-20, VK6-21, VKl-22, VKl-23, VK2-24, VK3-25, VK2-26, VKl-27, VK2-28, VK2-29, VK2-30, VK3-3l, VKl-32, , VK3-34, , VK2-36, VKl-37, VK2-38, VKl-39, VK2-40, or a combination thereof.

In one embodiment, the insert nucleic acid comprises one or more human V?» gene segments comprising Vk3-l, Vk4-3, VkZ-S, Vk3-9, Vk3-10, VXZ-l l, Vk3-12, V2244, Vk3-16, V2248, Vk3-l9, Vk3-21, Vk3-22, V22-23, Vk3-25, Vk3-27, or a combination thereof In one embodiment, the insert nucleic acid comprises one or more human JK gene segments comprising JKl, JK2, JK3, JK4, JKS, or a combination thereof.

In speciﬁc embodiments, upon modiﬁcation of the target locus in a pluripotent or non-pluripotent rat, eukaryotic, non-rat eukaryotic, mammalian, non- human mammal, human, rodent, non-rat , mouse or hamster cell, the genetic modiﬁcation is transmitted through the germline.

In one embodiment, the insert c acid ce comprises a cleotide that when integrated into the genome will produce a genetic modiﬁcation of a region of the rat, eukaryotic, non-rat eukaryotic, mammalian, man , human, rodent, non-rat rodent, mouse or r ApoE locus, wherein the genetic modiﬁcation at the ApoE locus results in a decrease in ApoE actiVity, an increase in ApoE actiVity or a modulation ofApoE activity. In one embodiment, an ApoE knockout is generated.

In one embodiment, the insert nucleic acid sequence comprises a polynucleotide that when integrated into the genome will produce a genetic ation of a region of the rat, eukaryotic, non-rat eukaryotic, mammal, human, non-human mammal, rodent, non-rat rodent, mouse or hamster interleukin-2 receptor gamma locus, wherein the genetic modiﬁcation at the eukin-2 receptor gamma locus results in a se in interleukin-2 receptor actiVity, an se in interleukin-2 receptor gamma activity, or a tion of interleukin-2 receptor activity. In one embodiment, an eukin-2 receptor knockout is generated.

In still another embodiment, the insert nucleic acid sequence comprises a polynucleotide that when integrated into the genome will e a genetic ation of a region of the rat, otic, non-rat eukaryotic, mammal, non-human mammal, human, rodent, non-rat rodent, mouse or r Ragl locus, the rat, otic, non-rat eukaryotic, man mammal, ian, human, rodent, non-rat rodent, mouse or hamster Rag2 locus and/or the rat, eukaryotic, non-rat eukaryotic, mammalian, non- human mammal, human, rodent, non-rat rodent, mouse or hamster Rag2/Ragl locus, wherein the genetic modiﬁcation at the rat, eukaryotic, non-rat eukaryotic, mammalian, non-human mammal, human, rodent, non-rat rodent, mouse or hamster Ragl , Rag2 and/or Rag2/Ragl locus results in a decrease in in Ragl, Rag2 or Ragl and Rag2 protein actiVity, an increase in Ragl , Rag2 or Ragl and Rag2 protein activity, or a modulation in Ragl, Rag2 or Rag l and Rag2 protein actiVity. In one embodiment, a Ragl or , Rag2 Rag2/Rag] knockout is generated.

In further embodiments, the insert nucleic acid results in the replacement of a portion of the rat, eukaryotic, non-rat eukaryotic, mammalian, non-human , human, rodent, non-rat rodent, mouse or hamster ApoE locus, the interleukin-2 receptor gamma locus and/or Rag2 locus, and/or Ragl locus and/or Rag2/Ragl locus with the corresponding ogous portion of an ApoE locus, an interleukin-2 receptor gamma locus, a Rag2 locus, a Ragl locus and/or a Rag2/Rag] locus from another organism.

In still other embodiments, the insert nucleic acid comprises a polynucleotide sharing across its full length least 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% to a portion of an ApoE locus, an interleukin-2 receptor gamma locus, a Rag2 locus, a Ragl locus and/or a Rag2/Ragl locus it is replacing.

] The given insert polynucleotide and the corresponding region of the rat, eukaryotic, non-rat eukaryotic, mammal, non-human mammal, human, rodent, non-rat , mouse or hamster locus being replaced can be a coding region, an intron, an exon, an untranslated region, a regulatory region, a promoter, or an enhancer or any combination thereof. Moreover, the given insert polynucleotide and/or the region of the rat, eukaryotic, t otic, mammalian, human, non-human mammal, rodent, non-rat , mouse or hamster locus being replaced can be of any desired length, ing for example, between 10-100 nucleotides in length, 0 nucleotides in length, 500-1 kb tide in length, 1 kb to 1.5 kb nucleotide in length, 1.5 kb to 2 kb tides in length, 2 kb to 2.5 kb nucleotides in length, 2.5 kb to 3 kb nucleotides in length, 3 kb to 5 kb nucleotides in length, 5 kb to 8 kb nucleotides in length, 8 kb to 10 kb nucleotides in length or more. In other instances, the size of the insertion or replacement is from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, from about 350 kb to about 400 kb, from about 400 kb to about 800 kb, from about 800 kb to 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb, to about 2.5 Mb, from about 2.5 Mb to about 2.8 Mb, from about 2.8 Mb to about 3 Mb. In other embodiments, the given insert polynucleotide and/or the region of the rat, eukaryotic, non-rat eukaryotic, non-human mammal, mammal, human, rodent, non-rat rodent, mouse or hamster locus being replaced is at least 100, 200, 300, 400, 500, 600, 700, 800, or 900 nucleotides or at least 1 kb, 2 kb, 3 kb, 4 kb, 5 kb, 6 kb, 7 kb, 8 kb, 9 kb, 10 kb, 11kb, 12 kb, 13 kb, 14 kb, 15 kb, 16 kb or greater. i. Methods for Modifying a Target Locus of a Nucleic Acid via Bacterial Homologous Recombination (BHR) s and compositions are provided for modifying a target locus of a otic, non-rat eukaryotic, a ian, a human or a non-human mammalian nucleic acid, via bacterial homologous recombination (BHR) in a prokaryotic cell. Such s ﬁnd use in utilizing bacterial homologous ination in a prokaryotic cell to genetically modify a target locus of a eukaryotic, non-rat eukaryotic, a mammalian, a human or a non-human mammalian nucleic acid in order to create a targeting vector.

Such a targeting vector comprising the genetically modified target locus can be introduced into a eukaryotic cell, for example, a eukaryotic cell, non-rat eukaryotic cell, a mammalian cell, a human cell, a non-human mammalian cell, a pluripotent cell, a non- pluripotent cell, a non-human pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a deVelopmentally-restricted human progenitor cell, a human iPS cell, a human cell, a rodent cell, a non-rat rodent cell, a rat cell, a mouse cell, a hamster cell, a ﬁbroblast, or a CHO cell. "Homologous recombination" includes the exchange ofDNA fragments between two DNA molecules at cross-over sites within regions of homology. Thus, rial gous recombination" or "BHR" includes homologous recombination that occurs in bacteria. s for modifying a target locus of a c acid from a eukaryotic cell, non-rat eukaryotic cell, a mammalian cell, a human cell, a non-human mammalian cell, a pluripotent cell, a non-pluripotent cell, a non-human pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a deVelopmentally-restricted human progenitor cell, a human iPS cell, a human cell, a rodent cell, a non-rat rodent cell, a rat cell, a mouse cell, a r cell, a ﬁbroblast, or a CHO cell Via bacterial homologous recombination (BHR) are provided. The s comprise introducing into a prokaryotic cell a targeting vector comprising an insert c acid ﬂanked with a 5 gy arm and a 3 ’ homology arm, wherein the prokaryotic cell comprises a target locus of a nucleic acid and is capable of sing a recombinase that mediates the BHR at the target locus. Such ing vectors can include any of the large targeting vectors described herein.

In one embodiment, the method comprises introducing into a prokaryotic cell: (i) a ﬁrst construct sing a nucleic acid haVing a DNA sequence of interest; (ii) a second targeting construct comprising an insert nucleic acid ﬂanked with a 5 homology arm and a 3 ’ homology arm, and (iii) a third construct encoding a recombinase that mediates bacterial homologous recombination. In one embodiment, the ﬁrst, the second, and the third construct are introduced into the prokaryotic cell separately over a period of time. In one embodiment, the yotic cell comprises a nucleic acid that encodes the recombinase, and the method does not require introduction of the third construct. In one embodiment, the recombinase is expressed under the control of an inducible promoter.

In one embodiment the ﬁrst construct comprising the nucleic acid, is d from a bacterial artiﬁcial chromosome (BAC) or yeast artiﬁcial chromosome (YAC). A prokaryotic cell sing the insert nucleic acid at the target genomic locus can be selected. This method can be serially repeated as disclosed herein to allow the introduction of le insert nucleic acids at the targeted locus in the prokaryotic cell.

Once the target nucleic acid locus is "built" within the yotic cell, a targeting vector comprising the modiﬁed target locus can be isolated from the prokaryotic cell and introduced into a target genomic locus within a eukaryotic cell, t eukaryotic cell, a mammalian cell, a human cell, a man mammalian cell, a pluripotent cell, a non- pluripotent cell, a non-human pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a developmentally-restricted human progenitor cell, a human iPS cell, a human cell, a rodent cell, a non-rat rodent cell, a rat cell, a mouse cell, a hamster cell, a ﬁbroblast, or a CHO cell.

Preferred rat cells for receiving ing vectors are described in US.

Application 14/185,703, ﬁled February 20, 2014, the contents of which are summarized herein. These rat cells are pluripotent rat cells capable of sustaining their pluripotency following one or more ed genetic modiﬁcations in vitro, and are capable of transmitting the targeted genetic ations through the germline.

Electroporated pluripotent cells, for example, are plated at a high density for the selection of drug-resistant cells comprising the targeting vector. The drug selection process removes the majority of the plated cells (~99%), leaving behind individual colonies, each of which is a clone derived from a single cell. Of the ing cells, most cells (~ 80-100%) contain the targeting vector (comprising a drug selection cassette) integrated at a random location in the genome. Therefore, the colonies are picked individually and genotyped to identify ES cells harboring the targeting vector at the correct genomic location (e. g., using the modiﬁcation of allele assay described below).

A high-throughput quantitative assay, namely, modiﬁcation of allele (MOA) assay, can be used for genotyping. Such an assay allows a large-scale screening of a d allele(s) in a parental chromosome following a c modiﬁcation. The MOA assay can be carried out via various analytical techniques, including, but not limited to, a quantitative PCR, e.g., a real-time PCR (qPCR). For e, the real-time PCR comprises a ﬁrst primer set that recognizes the target locus and a second primer set that recognizes a non-targeted reference locus. In addition, the primer set comprises a ﬂuorescent probe that recognizes the ampliﬁed sequence. In one embodiment, the tative assay is carried out via Invader Probes®. In one embodiment, the quantitative assay is carried out via MMP assays®. In one ment, the quantitative assay is carried out via TaqMan® Molecular Beacon. In one embodiment, the quantitative assay is carried out via EclipseTM probe technology. (See, for example, US2005/0144655, which is incorporated by reference herein in its entirety).

The selected pluripotent cell (i.e., a non-human pluripotent cell, a non- human ES cell) comprising the targeted genetic modiﬁcation can then be introduced into a host , for example, a pre-morula stage or blastocyst stage embryo and implanted in the uterus of a surrogate mother to generate a founder non-human animal (F0 animal). uently, the founder animal, for example, can be bred to a wild-type animal to create Fl progeny heterozygous for the genetic modiﬁcation. Mating of the heterozygous Fl animal can produce progeny homozygous for the genetic modiﬁcation. Mating of the heterozygous Fl animal can produce progeny homozygous for the genetic modiﬁcation.

In some embodiments, various genetic modiﬁcations of the target loci described herein can be d out using a large ing vector (LTVEC) as described in detail ere herein. For example, an LTVEC can be derived from Bacterial Artiﬁcial Chromosome (BAC) DNA using VELOCIGENE® genetic engineering technology (see, e.g., US Pat. No. 6,586,251 and Valenzuela, D. M. et al. (2003), High-throughput ering of the mouse genome d with high-resolution expression analysis, Nature Biotechnology 21(6): 652-659, which is incorporated herein by reference in their entireties).

Use of ial homologous ination (BHR) to generate a large targeting vector (LTVEC) circumvents the limitations of plasmids in accommodating a large genomic DNA fragment and consequent low efﬁciency of introducing a targeted modiﬁcation into an endogenous locus in pluripotent or non-pluripotent cells. One or more targeted genetic modiﬁcations can be performed in generating a LTVEC. An exemplary LTVEC produced in the yotic cell can comprises an insert nucleic acid that carries a c sequence with one or more genetic modiﬁcations or an exogenous nucleic acid (e. g., a homolog or og of a rat nucleic acid), which is ﬂanked by homologous arms, complementary to speciﬁc genomic regions.

] Host prokaryotic cells comprising the various targeting vectors described herein are also provided. Such prokaryotic cells include, but are not limited to, bacteria such as E. 6012'. In one ment, a host prokaryotic cell comprises a targeting vector comprising an insert nucleic acid ﬂanked with a 5' homology arm and a 3' homology arm, wherein the insert nucleic acid ranges from about 5 kb to about 200 kb.

The host prokaryotic cell can further comprise a nucleic acid that encodes a recombinase polypeptide or the nucleic acid that encodes the recombinase polypeptide is operably linked to an inducible promoter.

Further provided are various methods and compositions, which employ the LTVEC as described herein in combination with a prokaryotic cell in order to produce targeted genetic modiﬁcations. Such compositions and methods are discussed elsewhere herein.

] Methods for modifying a target locus of a nucleic acid via bacterial homologous ination (BHR) are provided that se introducing into a prokaryotic cell a targeting vector comprising an insert nucleic acid ﬂanked with a 5 ’ homology arm and a 3 ’ homology arm, wherein the prokaryotic cell comprises nucleic acids corresponding to the 5’ and 3’ homology arms and the prokaryotic cell is capable of expressing a recombinase that mediates the BHR at the target locus. Such targeting vectors can include any of the large targeting vectors described herein. Such s can employ a LTVEC as discussed in detail herein and ﬁarther employ the CRISPIVCas system as discussed elsewhere herein.

In one embodiment, the VCas system can be controlled by a promoter active in a prokaryotic cell, such as, for example, . ii. Methods for Modifying a Target Locus of Interest in a Pluripotent Cell or Non-Pluripotent Cell.

Further provided is a method for modifying a target locus of interest in a pluripotent cell or non-pluripotent cell via targeted c ation, sing (a) introducing into the pluripotent cell or non-pluripotent cell a targeting vector comprising ’ homology ’ homology an insert c acid ﬂanked with a 5 arm and a 3 arm, n the sum total of the 5’ homology arm and the 3’ gy arm is at least 10 kb; and (b) identifying a genetically modiﬁed pluripotent or non-pluripotent cell comprising the targeted genetic modiﬁcation at the target locus of interest. In one embodiment, the sum total of the 5’ homology arm and the 3’ homology arm is at least about 16 kb to about 30 kb. In speciﬁc embodiments, the targeted genetic modiﬁcation is capable of being transmitted through the germline. Such targeting vectors can include any of the large targeting vectors described herein.

Various cells can also be used in the methods for modifying a target locus of interest provided herein. In speciﬁc embodiments, the cell is a eukaryotic cell, non-rat eukaryotic cell, a otent cell, a non-pluripotent cell, a non-human pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a developmentally restricted human progenitor cell, a human induced pluripotent cell (iPS) cell, a ian cell, a human cell, a ﬁbroblast, a rodent cell, a non-rat rodent cell, a mouse cell, a r cell or a CHO cell.

In one aspect, a method for modifying a genomic locus of interest in a pluripotent cell via targeted genetic modiﬁcation is ed, comprising: (a) providing a pluripotent cell that is able to sustain its pluripotency following at least one ed genetic modiﬁcation of its genome and is able to it the targeted modiﬁcation to a germline of an Fl generation; (b) introducing a large targeting vector (LTVEC) into the pluripotent cell, wherein the LTVEC comprises an insert nucleic acid ﬂanked with a 5 ’ homology arm and a 3 ’ homology arm, wherein the 5 ’ homology arm and the 3 ’ homology arm comprise a genomic DNA fragment; and (c) identifying a genetically modiﬁed pluripotent cell comprising the targeted genetic modiﬁcation.

Various methods can be used to identify cells having the insert nucleic acid ated at the target locus of interest. Insertion of the insert nucleic acid at the target locus of interest results in a "modiﬁcation of allele". The term cation of allele" and methods for the detection of the modiﬁed allele are sed in further detail ere herein.

In one aspect, a method for ing a genomic locus of interest in a non-pluripotent cell or a pluripotent cell via endonuclease-mediated gene targeting is provided, the method comprising: (a) providing an isolated non-pluripotent cell or an isolated pluripotent cell that is able to transmit the genetically modiﬁed genome to a germline of an Fl generation; (b) introducing into the non-pluripotent cell or the pluripotent cell an endonuclease agent; wherein the clease agent makes a nick or a double strand break at a target DNA sequence located in the genomic locus of interest, and wherein the nick or the double strand break at the target DNA sequence in the non- pluripotent cell or the pluripotent cell induces: (i) non-homologous end joining — mediated DNA repair of the nick or the double strand break, wherein the NHEJ- mediated DNA repair generates a mutant allele comprising an insertion or a deletion of a nucleic acid sequence at the target DNA sequence; or (ii) gous recombination- mediated DNA repair that results in restoration of a wild-type nucleic acid sequence; and (c) identifying the d genomic locus of interest.

In one aspect, a method for modifying a genomic locus of interest in an isolated embryonic stem cell (ES) Via a nuclease agent is ed, comprising: (a) providing an isolated ES cell that is able to it the targeted genetic ation to a germline of an F1 generation; (b) introducing into the ES cell: (i) a large targeting vector (LTVEC) comprising an insert nucleic acid ﬂanked with a 5 ’ gy arm and a 3’ homology arm, wherein the insert is a nucleic acid sequence that is at least 5 kb; and (ii) an clease agent, wherein the endonuclease agent makes a nick or a double strand break at a target DNA sequence located in the genomic locus of interest, and wherein the target sequence is not present in the insert c acid; and (c) identifying the targeted c modiﬁcation in the embryonic stem (ES) cell.

In one aspect, a method for ing a genomic locus of interest in a non-pluripotent cell or a pluripotent cell via RNA-guided genome engineering is provided, the method comprising: (a) providing a non-pluripotent cell or a pluripotent cell that is able to transmit the genetically modiﬁed genome to a germline of an El generation; (b) introducing into the non-pluripotent cell or the pluripotent cell: (i) a ﬁrst expression uct comprising a ﬁrst er operably linked to a ﬁrst nucleic acid sequence encoding a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)—associated (Cas) protein, (ii) a second expression construct comprising a second promoter operably linked to a genomic target sequence linked to a guide RNA (gRNA), wherein the genomic target sequence is ﬂanked by a Protospacer Adjacent Motif (PAM) sequence. Optionally the genomic target ce is ﬂanked on the 3’end by a Protospacer nt Motif (PAM) sequence. In one ment, the Cas protein and the CRISPR RNA and/or trachNA do not naturally occur together (e.g., the Cas protein and CRISPR RNA do not naturally occur together). In one embodiment, the genomic target sequence comprises the nucleotide sequence of GNNNNNNNNNNNNNNNNNNNNGG (GN1_20GG; SEQ ID NO: 1). In one ment, the genomic target sequence comprises SEQ ID NO: 1, wherein N is between 14 and 20 nucleotides in length. In one embodiment, the gRNA comprises a third nucleic acid sequence encoding a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) RNA (chNA) and a fourth nucleic acid sequence ng a trans-activating CRISPR RNA (trachNA). In one embodiment, upon expression, the Cas protein forms a CRISPR-Cas x comprising the chNA and the trachNA, and the CRISPR-Cas complex makes a nick or a double strand break at a target DNA sequence located in the c locus of interest, and wherein the nick or the double strand break at the target DNA sequence in the non-pluripotent cell or the pluripotent cell induces: (i) mologous end joining (NHEJ)-mediated DNA repair of the nick or the double strand break created by the CRISPR-Cas complex, wherein the NHEJ tes a mutant allele comprising an insertion or a deletion of a c acid sequence at the target DNA sequence; or (ii) homologous recombination-mediated DNA repair that results in restoration of a ype nucleic acid sequence; and (c) identifying the modified the genomic locus of interest.

In one aspect, a method for modifying a genomic locus of interest in a non-pluripotent cell or a pluripotent cell Via RNA-guided genome engineering is provided, the method sing introducing into the non-pluripotent cell or the pluripotent cell that is able to it the modiﬁed genome h the germline: (i) a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)—associated (Cas) protein or a nucleic acid encoding the Cas protein; and (ii) a gRNA or a DNA encoding the gRNA, wherein the gRNA comprises a nucleotide sequence that hybridizes to a genomic target sequence and a trans-activating CRISPR RNA (trachNA); wherein the genomic target sequence is ﬂanked by a Protospacer Adjacent Motif (PAM) sequence.

In some embodiments, the Cas protein can be introduced into the non- pluripotent cell or the pluripotent cell as an isolated n. In some embodiments, the Cas protein can ﬁarther comprise a cell-penetrating domain that facilitates cellular uptake of the protein. In other embodiments, the Cas protein can be introduced into the cell as a messenger RNA (mRNA) molecule encoding the Cas protein. In other embodiments, the Cas protein can be introduced into the cell as a DNA le encoding the Cas protein. For example, the DNA molecule encoding the Cas protein can be provided in a construct and be operably linked to a promoter capable of expressing in the non- pluripotent cell or the pluripotent cell. In certain embodiments, the nucleic acid encoding the Cas protein is codon-optimized for expression in the non-pluripotent cell or the otent cell.

In some embodiments, the gRNA can be introduced into the non- pluripotent cell or the pluripotent cell as a RNA molecule. For example, the gRNA le can be transcribed in vitro. In other ments, the gRNA can be introduced into the non-pluripotent cell or the pluripotent cell as a DNA molecule ng the gRNA. For example, the DNA molecule encoding the gRNA can be in a construct and be operably linked to a promoter capable of expressing the gRNA in the non-pluripotent cell or the otent cell. In other embodiments, the gRNA can be chemically sized.

] In some embodiments, the gRNA can be introduced into the non- otent cell or the pluripotent cell as a fused chNA-trachNA molecule (i.e., a single transcript). In other ments, the gRNA can be introduced into the non- pluripotent cell or the pluripotent cell as separate chNA and A molecules (i.e., separate transcripts). In other embodiments, the gRNA can be introduced into the non- pluripotent cell or the pluripotent cell as separate DNA molecules encoding the chNA and trachNA, respectively. For example, the separate DNA molecules encoding the chNA and trachNA can be in separate constructs and be operably linked to promoters capable of expressing in the non-pluripotent cell or the pluripotent cell. In any of the above embodiments, any combination of the constructs can be in separate nucleic acid molecules or together in a single nucleic acid molecule In some embodiments, the Cas protein and the gRNA can be introduced into the non-pluripotent cell or the pluripotent cell simultaneously or sequentially.

Likewise, the chNA and the trachNA of the gRNA can be introduced into the non- otent cell or the pluripotent cell aneously or sequentially. The ratio of the Cas protein (or encoding nucleic acid) to the gRNA (or encoding DNA) and/or the ratio of the chA to the trachNA can be about stoichiometric such that they can form an RNA-protein complex.

In certain ments, the Cas protein can be introduced into the non- pluripotent cell or the otent cell in the form of a complex with the gRNA.

In one embodiment, the otent cell is an induced pluripotent stem cell (iPS). In one embodiment, the pluripotent cell is a developmentally restricted progenitor cell.

The presence of a nick or a double-strand break in the recognition site within the selection marker, in various embodiments, increases the efﬁciency and/or frequency of ination between a targeting vector (such as a LTVEC) and the targeted locus of interest. In one embodiment, the recombination is homologous recombination. In another embodiment, the recombination is an insertion by non- homologous end joining. In various embodiments, in the presence of the nick or double strand break, ing efﬁciency of a targeting vector (such as a LTVEC) at the target genomic locus is at least about 2-fold higher, at least about 3-fold higher, at least about 4-fold higher than in the absence of the nick or double-strand break (using, e. g., the same targeting vector and the same gy arms and ponding target sites at the genomic locus of interest but in the absence of an added nuclease agent that makes the nick or double strand break).

In one embodiment, the targeted genetic modiﬁcation at the target locus is biallelic. By "biallelic" is meant that both alleles of a gene comprise the targeted genetic modiﬁcation. The targeted genetic modiﬁcation can be the same or different in each allele. For e, a biallelic modiﬁcation can result from the same ation being made to corresponding alleles on corresponding homologous chromosomes, or from different ations being made to corresponding alleles on corresponding homologous chromosomes. Thus, a biallelic modiﬁcation can result, for example, in homozygosity for a speciﬁc modiﬁcation at a c locus of interest (i.e., the speciﬁc modiﬁcation in both alleles), compound heterozygosity at a genomic locus of interest (e.g., the speciﬁc modiﬁcation in one allele and inactivation or disruption of the other allele), or hemizyogosity at a genomic locus of interest (e. g., the speciﬁc modiﬁcation in one allele and loss of the other allele). In certain embodiments, the combined use of a targeting vector ding, for example, an LTVEC) with a nuclease agent results in biallelic targeted genetic ation of the genomic locus of interest in a cell as compared to use of the targeting vector alone. When the ing vector is used in conjunction with a nuclease agent, biallelic targeting efﬁciency is increased at least by two-fold, at least three-fold, at least 4-fold or more as compared to when the targeting vector is used alone. In further ments, the biallelic targeting efﬁciency is at least 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, l%, 2%, 3%, 4% or 5% or higher.

The biallelic targeted genetic ation at the target locus can result in a homozygous genetically modiﬁed cell. By "homozygous" is meant that both alleles of the target locus (i.e., the alleles on both homologous chromosomes) have been modiﬁed in the same way. In certain embodiments, the combined use of a targeting vector (including, for example, an LTVEC) with a se agent results in biallelic homozygous targeted genetic modiﬁcation of the genomic locus of interest in a cell. In one embodiment, the biallelic genetic modiﬁcation comprises deletion of an endogenous nucleic acid sequence at the genomic locus of st in two homologous chromosomes (i.e., a pair of ﬁrst and second homologous chromosomes) and insertion of the insert nucleic acid at the genomic locus of interest in two homologous chromosomes (i.e., the pair of ﬁrst and second homologous chromosomes). In some ments, the insert nucleic acid replaces the endogenous nucleic acid sequence at the genomic locus of interest in both gous chromosomes. In one embodiment, the insert nucleic acid is homologous or orthologous to the deleted endogenous nucleic acid sequence.

In one embodiment, the targeted genetic modiﬁcation at the target locus results in a hemizygous cally d cell. By "hemizygous" is meant that only one allele (i.e., the allele on one of two homologous chromosomes) of the target locus is present or only one allele is capable of being expressed and functional. In other embodiments, the ed genetic modiﬁcation results more generally in compound heterozygosity. Compound heterozygosity includes situations in which both alleles of the target locus (i.e., the alleles on both homologous chromosomes) have been modiﬁed, but they have been modiﬁed in ent ways (e.g., an insertion in one allele and inactivation or tion of the other allele). In certain ments, the combined use of a targeting vector (including, for example, an LTVEC) with a nuclease agent results in hemizygous targeted genetic modiﬁcation of the genomic locus of interest in a cell. In certain embodiments, the combined use of a targeting vector ding, for example, an LTVEC) with a se agent results in targeted genetic modiﬁcations that create compound heterozygosity at a c locus of interest in a cell. In one embodiment, the targeted genetic ation at the genomic locus of interest in one chromosome comprises deletion of an nous nucleic acid sequence and insertion of the insert nucleic acid. In other ments, the targeted genetic modiﬁcation comprises: (1) deletion of an endogenous nucleic acid sequence at the genomic locus of interest in two homologous chromosomes; and (2) insertion of the insert nucleic acid into the genomic locus of interest in a ﬁrst chromosome and disruption of the genomic locus of interest in a second chromosome. The ﬁrst chromosome can be the ﬁrst of the two gous chromosomes, and the second chromosome can be the second of the two homologous chromosomes. In other embodiments, the targeted modiﬁcation ses: (1) deletion of an endogenous nucleic acid sequence at the genomic locus of interest and insertion of the insert nucleic acid into the c locus of interest in the ﬁrst homologous chromosome; and (2) disruption of the genomic locus of st in the second homologous chromosome. Disruption of the endogenous nucleic acid sequence can result, for example, when a -strand break at the genomic locus of interest created by the nuclease agent is repaired by non-homologous end joining (NHEJ)—mediated DNA repair, which generates a mutant allele comprising an insertion or a deletion of a nucleic acid sequence at the genomic locus of interest and thereby causes disruption of the c locus of interest. Examples of disruption include alteration of a tory element (e.g., promoter or enhancer) at the genomic locus of interest, a missense mutation, a truncation mutation, a null mutation, or an insertion or deletion of small number of nucleotides (e.g., causing a frameshift mutation). Another example of tion is a nonsense mutation. Disruption can result in vation (i.e., loss of function) or loss of the allele.

] Homozygous and gous targeted genetic modiﬁcations are advantageous because when genetically modiﬁed cells containing these mutations are used to generate genetically modiﬁed animals as discussed below, the process for generating genetically modiﬁed animals that are non-heterozygous (i.e., homozygous or hemizygous) for the intended ed genetic modiﬁcation is more efﬁcient and less- time consuming because fewer breeding steps are required. Targeted genetic modiﬁcations resulting in compound heterozygosity or hemizygosity (e.g., an insertion in one allele and vation, disruption, or loss of the other allele) can be advantageous for the same reason.

Various cell types can also be used in any of the various methods described herein above for modifying a genomic locus via a nuclease agent. In speciﬁc embodiments, the cell is a eukaryotic cell, non-rat eukaryotic cell, a pluripotent cell, a non-pluripotent cell, a non-human pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a developmentally cted human progenitor cell, a human induced pluripotent cell (iPS) cell, a mammalian cell, a human cell, a ﬁbroblast, a rodent cell, a non-rat rodent cell, a mouse cell, a hamster cell or a CHO cell.

] Compositions are provided which comprise a genetically modiﬁed non- human animal, having a targeted genetic modiﬁcation in the interleukin-2 receptor gamma locus or in the ApoE locus. The various methods and compositions provided herein allows for these modiﬁed loci to be itted through the germline.

In speciﬁc embodiments, a genetically modiﬁed non-human animal, or a genetically modiﬁed pluripotent or non-pluripotent cell comprises a genomic locus having a targeted genetic ation in the eukin-2 gamma receptor locus or having a targeted genetic modiﬁcation in the ApoE locus, wherein the interleukin-2 gamma receptor genomic locus or the ApoE locus comprise: (i) a deletion of at least a portion of the interleukin-2 gamma receptor locus or at least a portion of the ApoE locus; (ii) an ion of a heterologous nucleic acid sequence into the ApoE locus or into the eukin-2 gamma receptor locus; or (iii) a combination thereof, wherein the genetically modiﬁed genomic locus is capable of being transmitted through the germline.

Methods are further provided that allow for such genetically modiﬁed man s, and for such genetically modiﬁed otent cells to be made. Such methods include a method for modifying an ApoE genomic locus or an interleukin-2 gamma receptor locus in a pluripotent cell via targeted genetic modiﬁcation. The method comprises (a) introducing into the pluripotent cell a targeting vector comprising an insert nucleic acid ﬂanked with a 5’ homology arm, to the ApoE locus and a 3 ’ homology arm, to the ApoE locus, (b) identifying a genetically modiﬁed pluripotent cell comprising the targeted genetic modiﬁcation at the ApoE genomic locus of interest, wherein the targeted genetic ation is capable of being transmitted through ne.

Additional methods e (a) ucing into the pluripotent cell a targeting vector comprising an insert nucleic acid ﬂanked with a 5 ’ homology arm to the interleukin-2 receptor gamma locus and a 3 ’ homology arm to the interleukin-2 receptor gamma locus, (b) identifying a genetically modiﬁed pluripotent cell comprising the targeted genetic modiﬁcation at the eukin-2 receptor gamma locus, wherein the targeted genetic modiﬁcation is capable of being itted through germline. iii. Methods of Integrating Multiple cleotides of Interest at the Targeted Locus The various methods and compositions provided herein allow for the targeted integration of multiple polynucleotides of interest with a given target locus. The s methods set forth above can be tially repeated to allow for the ed integration of any number of insert nucleic acids into a given targeted locus. Thus, the various methods provide for the insertion of at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, l6, 17, 18, 19, 20 or more insert nucleic acids into the target locus. In ular embodiments, such sequential tiling methods allow for the reconstruction of large genomic regions from a eukaryotic cell, for example, non-rat eukaryotic cell, a mammalian cell (i.e., a human, a non-human, a rodent, a non-rat rodent, a mouse, a monkey, a rat, a hamster, a domesticated mammal or an agricultural animal) into a targeted locus. In such instances, the transfer and reconstruction of genomic regions that include both coding and non-coding regions allow for the complexity of a given region to be preserved by retaining, at least in part, the coding regions, the non-coding regions and the copy number variations found Within the native genomic region. Thus, the various methods provide, for example, methods to generate "heterologous" or "exogenous" genomic regions Within any otic cell, any non-rat eukaryotic cell, any mammalian cell or animal of interest, particularly Within a prokaryotic host cell or within a non- pluripotent cell, a pluripotent cell or an ES cell. In one non-limiting example, a "humanized" genomic region Within a non-human animal (i.e., Within a rat) is generated.

Methods to generate genomic regions Within any cell are provided herein. In c embodiments, the cell is a eukaryotic cell, a non-rat eukaryotic cell, a pluripotent cell, a non-pluripotent cell, a non-human pluripotent cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a pmentally cted human progenitor cell, a human induced pluripotent cell (iPS) cell, a mammalian cell, a human cell, a ﬁbroblast, a rodent cell, a non-rat rodent cell, a mouse cell, a hamster cell or a CHO cell. 3. A Humanized Genomic Locus Provided herein are various methods and compositions comprising a humanized c locus. As used , by "humanized" genomic locus is meant a region of a non-human genome comprising at least one human nucleic acid sequence.

The humanized genomic locus can comprise a region ofDNA from any organism that has a human DNA sequence inserted therein. In speciﬁc embodiments, the sm is a ote, a non-rat eukaryote, a non-human mammal, a mammal, a human, a rodent, a non-rat rodent, a rat, a mouse or a hamster. For e, a "humanized rat locus" comprises a region of rat DNA that has a human DNA sequence inserted therein.

The human DNA sequence can be a naturally occurring human DNA sequence or it can be modiﬁed from its native form. In speciﬁc embodiments, the human DNA shares at least 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity to a native human sequence. If a human sequence is not a native human ce it at least has greater sequence identity to a native human sequence than it does to an ogous non-human ce. Moreover, the human DNA sequence can comprise a cDNA, a region of human genomic DNA, a non-coding tory region, or any portion of a coding, genomic, or regulatory region of the human DNA. The human DNA sequence inserted into the non-human locus can comprise any of the insert polynucleotides as described ere herein. In speciﬁc ments, the human DNA sequence is orthologous to the non-human target locus, while in other instances, the human DNA sequence is homologous to the non-human target locus.

In one embodiment, the targeted genetic modiﬁcation is an insertion or a replacement of an endogenous nucleic acid sequence, with a homologous or orthologous human nucleic acid sequence. In one embodiment, the targeted c modiﬁcation comprises an insertion or replacement of an endogenous nucleic acid sequence with a homologous or orthologous human nucleic acid sequence at an nous locus that comprises the corresponding non-human nucleic acid sequence.

Methods for making a humanized locus comprise introducing into the target locus comprising a nucleic acid a human c acid sequence. In one embodiment, a method of making a humanized non-human animal provided. Such a method comprises (a) modifying a genome of a non-human pluripotent cell or non- pluripotent cell with a targeting vector comprising an insert nucleic acid that comprises a human nucleic acid sequence to form a donor cell; (b) introducing the donor cell into a host embryo; and (c) ing the host embryo in a surrogate ; wherein the surrogate mother produces a progeny that comprises the human nucleic acid sequence. In speciﬁc embodiments, the humanized locus is capable of being transmitted through the ne. In a further embodiment, the targeting vector comprises a large targeting vector (LTVEC) and the insert nucleic acid that comprises a human nucleic acid sequence is at least 5 kb.

In other s, the humanized genomic locus is made by modifying a target locus of a nucleic acid via bacterial homologous recombination (BHR). The method comprises ucing into a prokaryotic cell a targeting vector sing an insert nucleic acid ﬂanked with a 5 ’ homology arm and a 3 ’ homology arm, wherein the insert nucleic acid comprises a human nucleic acid sequence, and wherein the prokaryotic cell comprises a nucleic acid and is capable of expressing a recombinase that mediates the BHR at the target locus.

The humanized genomic locus can comprise (a) an insertion of a homologous or orthologous human c acid sequence; (b) a replacement of an endogenous nucleic acid ce with a homologous or orthologous human nucleic acid sequence; or (c) a combination thereof. In speciﬁc embodiments, the humanized c locus is capable of being transmitted through the germline. In still other embodiments, the human orthologous sequence replaces the corresponding sequence found in the non-human locus.

Any human nucleic acid sequence can be used in the methods and compositions provided herein. Non-limiting examples of human nucleic acid ces that can be used in the methods and compositions are discussed in detail elsewhere ] The human nucleic acid sequence for insertion into a locus of interest can be any size. In one embodiment, the human nucleic acid sequence can be from about 500 nucleotides to about 200 kb, from about 500 nucleotides to about 5 kb, from about 5 kb to about 200 kb, from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 30 kb, from about 30 kb to about 40 kb, from about 40 kb to about 50 kb, from about 60 kb to about 70 kb, from about 80 kb to about 90 kb, from about 90 kb to about 100 kb, from about 100 kb to about 110 kb, from about 120 kb to about 130 kb, from about 130 kb to about 140 kb, from about 140 kb to about 150 kb, from about 150 kb to about 160 kb, from about 160 kb to about 170 kb, from about 170 kb to about 180 kb, from about 180 kb to about 190 kb, or from about 190 kb to about 200 kb. In a speciﬁc embodiment, the human nucleic acid sequence is at least 5 kb.

] In one embodiment, a genomic locus is provided wherein the gous or orthologous human nucleic acid sequence ses (a) one or more unrearranged human immunoglobulin heavy chain VH gene segments, one or more unrearranged human immunoglobulin heavy chain D gene segments, and one or more unrearranged human globulin heavy chain JH gene segments, which are operably linked to a mammalian heavy chain constant region nucleic acid sequence; (b) a rearranged human immunoglobulin heavy chain variable region nucleic acid sequence operably linked to a ian immunoglobulin heavy chain constant region nucleic acid sequence; (c) one or more unrearranged human immunoglobulin VK or V] gene segments and one or more unrearranged human immunoglobulin JK or I] gene segments, which are operably linked to a mammalian, immunoglobulin 9» or K light chain light chain constant region nucleic acid ce; or (d) a rearranged human immunoglobulin 7» or K light chain variable region c acid sequence operably linked to a mammalian immunoglobulin 7» or K light chain light chain constant region nucleic acid sequence.

In another embodiment, a genomic locus is provided n (a) the mammalian immunoglobulin heavy chain constant region nucleic acid sequence is a constant region nucleic acid sequence, a human constant region nucleic acid sequence, or a combination thereof; or (b) the mammalian immunoglobulin 9» or K light chain light chain constant region nucleic acid sequence is a rat nt region nucleic acid sequence, a human constant region nucleic acid sequence, or a combination f.

In a speciﬁc embodiment, a genomic locus is provided wherein the immunoglobulin heavy chain nt region nucleic acid sequence is selected from or ses a CHl, a hinge, a CH2, a CH3, and/or a combination thereof.

In one embodiment, the genomic locus ses one or more functional human VH gene segments comprising VH1 -2, VH1 -3, VHl-8, VHl-18, VHl-24, VHl-45, VHl-46, VHl-58, VHl-69, VH2-5, VH2-26, VH2-70, VH3-7, VH3-9, VH3-l l, VH3-l3, VH3- , VH3-l6, VH3-20, VH3-21, VH3-23, VH3-30, VH33, VH 35, VH3-33, VH3-35, VH3-38, VH3-43, VH3-48, VH3-49, VH3-53, VH3-64, , VH3-72, VH3-73, VH3-74, VH4-4, VH4-28, VH4l, VH42, VH44, VH4-31, VH4-34, VH4-39, VH4-59, VH4- 61, VHS-51, VH6-l, VH7l, VH7-81, or a combination thereof In one embodiment, the genomic locus comprises one or more functional human D gene segments comprisingD l - l D l -7, D 1 -l4, D l -20, D l -26, D2-2, D2-8, D2- , D2-21, D3-3, D3-9, D3-10, D3-l6, D3-22, D4-4, D4-l l, D4-l7, D4-23, D5-12, D5-5, D5-18, D5-24, D6-6, D6-l3, D6-l9, D6-25, D7-27, or a combination thereof.

] In one embodiment, the genomic locus comprises one or more onal JH gene segments comprising JHl, JH2, JH3, JH4, JHS, JH6, and/or a combination thereof In one embodiment, the insert nucleic acid comprises one or more human VK gene segments comprisesVK4-l, VK5-2, VK 7-3, VK 2-4, VKl-S, VKl-6, VK3 -7, VKl-8, VKl-9, , VK3-l l, VKl-lZ, , , VK3-15, VKl-l6, VKl-l7, VK2-18, VK2-19, VK3-20, VK6-21, VKl-22, VKl-23, , VK3-25, VK2-26, VKl-27, VK2-28, VK2-29, VK2-30, VK3-3l, VKl-32, VKl-33, VK3-34, , VK2-36, VKl-37, VK2-38, VKl-39, VK2-40, or a combination thereof.

In one embodiment, the genomic locus comprises one or more human V?» gene segments comprising Vk3-l, Vk4-3, Vk2-8, Vk3-9, Vk3-10, VXZ-l l, Vk3-12, VX2- l4, Vk3-l6, VX2-l8, Vk3-l9, Vk3-21, Vk3-22, Vk2-23, Vk3-25, Vk3-27, or a combination f.

In one embodiment, the c locus comprises one or more human JK gene segments comprising JKl, JK2, JK3, JK4, JKS, or a combination thereof.

] In yet another embodiment, the genomic locus, ses a humanized genomic locus comprising a human interleukin-2 receptor (IL2R) nucleic acid sequence or a variant or a fragment thereof is provided. In ic embodiments, the IL2R nucleic acid sequence comprises an interleukin-2 receptor alpha, an interleukin-2 receptor beta, or an interleukin-2 receptor gamma nucleic acid sequence or variants or fragments thereof.

In further embodiments, a genomic locus, ses a humanized genomic locus comprising of a portion of the human ApoE locus, the human interleukin-2 receptor gamma locus, the human Rag2 locus, the human Rag] locus and/or the human Rag2/Rag1 locus replacing the corresponding homologous or orthologous portion of the non-human ApoE locus, interleukin-2 receptor gamma locus, Rag2 locus, Rag] locus and/or Rag2/Rag1 locus. In one embodiment, the non-human ecto-domain of IL-2Rg is replaced with the ecto-domain of human IL-2Rg, with the remainder of the molecule being from the non-human.

In another ment, a cally modified non-human animal, comprising a humanized genomic locus is provided. Such genetically modiﬁed non- human animals comprise (a) an insertion of a homologous or orthologous human nucleic acid sequence; (b) a replacement of nucleic acid sequence with a gous or orthologous human nucleic acid sequence at an nous genomic locus; or (c) a combination f, wherein the humanized genomic locus is capable of being transmitted through the ne.

Genetically modified animals, ing non-human s) comprising any ofthe various humanized genomic loci provided herein and described above are also provided. 4. Polynucleotides of Interest Any cleotide of interest may be contained in the various insert nucleic acids and thereby integrated at the target locus. The methods disclosed herein, e for at least 1, 2, 3, 4, 5, 6 or more polynucleotides of interest to be integrated into the targeted genomic locus.

] The polynucleotide of interest within the insert nucleic acid when integrated at the target genomic locus can introduce one or more genetic modiﬁcations into the cell. The genetic modiﬁcation can comprise a deletion of an endogenous nucleic acid sequence and/or the addition of an exogenous or heterologous or orthologous polynucleotide into the target genomic locus. In one embodiment, the genetic modiﬁcation comprises a replacement of an endogenous nucleic acid sequence with an exogenous polynucleotide of interest at the target genomic locus. Thus, methods provided herein allow for the generation of a genetic modiﬁcation sing a ut, a deletion, an insertion, a replacement k-in"), a point mutation, a domain swap, an exon swap, an intron swap, a regulatory sequence swap, a gene swap, or a combination thereof. Such modiﬁcations may occur upon integration of the ﬁrst, second, third, , ﬁfth, six, seventh, or any subsequent insert nucleic acids into the target genomic locus.

The polynucleotide of interest within the insert nucleic acid and/or integrated at the target locus can se a sequence that is native to the cell it is introduced into; the polynucleotide of interest can be heterologous to the cell it is introduced to; the cleotide of interest can be ous to the cell it is introduced into; the polynucleotide of interest can be orthologous to the cell it is introduced into; or the polynucleotide of interest can be from a different species than the cell it is introduced into. As used herein "native" in nce to a sequence inserted at the target locus is a sequence that is native to the cell having the target locus or native to the cell from which the target locus was derived (i.e., from a rat). As used herein, "heterologous" in reference to a sequence includes a sequence that originates from a foreign species, or, if from the same species, is substantially ent or modiﬁed from its native form in composition and/or genomic locus by deliberate human intervention. As used herein, "exogenous" in reference to a sequence is a sequence that originates from a foreign species. The polynucleotide of interest can be from any sm of interest including, but not limited to, non-human, a rodent, a non-rat , a hamster, a mouse, a rat, a human, a monkey, an agricultural mammal or a non-agricultural mammal. The polynucleotide of interest can ﬁarther comprise a coding region, a non-coding , a regulatory region, or a genomic DNA. Thus, the lst, 2nd, 3rd, 4th, 5th, 6th, 7th, and/or any of the subsequent insert nucleic acids can comprise such sequences.

In one embodiment, the polynucleotide of interest within the insert nucleic acid and/or integrated at the target locus is native to a mouse nucleic acid sequence, a human c acid, a non-human c acid, a eukaryotic c acid, a non-rat eukaryotic nucleic acid, a non-human mammalian nucleic acid, a mammalian nucleic acid, a rodent nucleic acid, a non-rat rodent nucleic acid, a rat nucleic acid, a hamster c acid, a monkey nucleic acid, an agricultural mammal nucleic acid, or a non- agricultural mammal nucleic acid. In still further embodiments, the polynucleotide of st integrated at the target locus is a fragment of a genomic nucleic acid. In one embodiment, the genomic nucleic acid is a mouse genomic nucleic acid, a human genomic nucleic acid, a non-human nucleic acid, a eukaryotic c acid, a non-rat eukaryotic nucleic acid, a non-human mammalian nucleic acid, a mammalian nucleic acid, a rodent nucleic acid, a non-rat rodent c acid, a rat c acid, a hamster nucleic acid, a monkey nucleic acid, an agricultural mammal nucleic acid or a non- agricultural mammal nucleic acid or a combination thereof.

In one embodiment, the polynucleotide of interest can range from about 500 nucleotides to about 200 kb as described above. The polynucleotide of interest can be from about 500 nucleotides to about 5 kb, from about 5 kb to about 200 kb, from about kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 30 kb, from about 30 kb to about 40 kb, from about 40 kb to about 50 kb, from about 60 kb to about 70 kb, from about 80 kb to about 90 kb, from about 90 kb to about 100 kb, from about 100 kb to about 110 kb, from about 120 kb to about 130 kb, from about 130 kb to about 140 kb, from about 140 kb to about 150 kb, from about 150 kb to about 160 kb, from about 160 kb to about 170 kb, from about 170 kb to about 180 kb, from about 180 kb to about 190 kb, or from about 190 kb to about 200 kb, from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb.

The cleotide of interest within the insert nucleic acid and/or inserted at the target genomic locus can encode a ptide, can encode an miRNA, or it can comprise any regulatory regions or non-coding regions of interest including, for example, a regulatory sequence, a promoter sequence, an enhancer sequence, a riptional repressor-binding sequence, or a deletion of a non-protein-coding sequence, but does not comprise a deletion of a protein-coding sequence. In addition, the polynucleotide of interest within the insert c acid and/or inserted at the target c locus can encode a n expressed in the s system, the skeletal system, the digestive system, the atory system, the muscular system, the respiratory system, the cardiovascular system, the tic system, the endocrine system, the urinary system, the reproductive system, or a combination thereof. In one embodiment, the polynucleotide of interest within the insert nucleic acid and/or inserted at the target genomic locus encodes a protein sed in a bone marrow or a bone marrow-derived cell. In one embodiment, the polynucleotide of interest within the insert nucleic acid and/or integrated at the target locus encodes a protein expressed in a spleen cell. In still further embodiments, the polynucleotide of interest within the insert nucleic acid and/or inserted at the target locus encodes a protein expressed in a B cell, encodes a protein expressed in an immature B cell or encodes a protein expressed in a mature B cell.

The polynucleotide of interest within the insert polynucleotide can comprise a portion of an ApoE locus, an Il2rg locus, a Rag] locus, a Rag2 locus and/or a Rag2/Rag1 locus. Such portions of these given loci are discussed elsewhere herein, as are the various homologous and orthologous regions from any organism of interest that can be employed.

In one embodiment, polynucleotide of interest within the insert c acid and/or inserted at the target locus comprises a genomic nucleic acid ce that encodes an immunoglobulin heavy chain variable region amino acid ce. The phrase "heavy chain," or "immunoglobulin heavy chain" are described elsewhere herein.

In one embodiment, the polynucleotide of interest within the insert nucleic acid and/or integrated at the target locus comprises a c nucleic acid sequence that encodes a human immunoglobulin heavy chain variable region amino acid sequence.

In one embodiment, the genomic nucleic acid sequence comprises one or more unrearranged human globulin heavy chain VH gene segments, one or more unrearranged human immunoglobulin heavy chain D gene segments, and one or more unrearranged human immunoglobulin heavy chain JH gene segments, which are operably linked to a mammalian heavy chain constant region nucleic acid ce. In one embodiment, the genomic nucleic acid sequence comprises a rearranged human immunoglobulin heavy chain variable region nucleic acid sequence operably linked to a mammalian heavy chain nt region nucleic acid sequence. In one embodiment, the genomic nucleic acid ce comprises one or more unrearranged human immunoglobulin VK or V] gene segments and one or more unrearranged human immunoglobulin JK or I] gene segments, which are operably linked to a mammalian immunoglobulin 9» or K light chain light chain nt region nucleic acid sequence. In one embodiment, the genomic nucleic acid sequence comprises a rearranged human immunoglobulin 7» or K light chain variable region nucleic acid sequence operably linked to a mammalian globulin 9» or K light chain light chain constant region nucleic acid sequence. In one ment, the heavy chain constant region nucleic acid sequence comprises a rat nt region nucleic acid sequence, a human constant region nucleic acid sequence, or a ation f. In one embodiment, the immunoglobulin 9» or K light chain constant region nucleic acid comprises a rat constant region nucleic acid sequence, a human constant region nucleic acid sequence, or a combination thereof.

In one embodiment, the immunoglobulin heavy chain constant region nucleic acid sequence is selected from or comprises a CHl, a hinge, a CH2, a CH3, and/or a combination thereof. In one embodiment, the heavy chain constant region nucleic acid sequence comprises a CHl-hinge-CH2-CH3.

In one ment, the polynucleotide of interest within the insert nucleic acid and/or integrated at the target locus comprises a genomic nucleic acid sequence that s an immunoglobulin light chain le region amino acid sequence. The phrase "light chain" includes an immunoglobulin light chain sequence from any organism, and is described elsewhere herein.

In one embodiment, the polynucleotide of interest within the insert c acid and/or integrated at the target genomic locus comprises a genomic nucleic acid sequence that encodes a human immunoglobulin light chain variable region amino acid sequence.

In one embodiment, the c nucleic acid ce comprises one or more unrearranged human immunoglobulin VK or V] gene segments and one or more unrearranged human globulin JK or I] gene segments, which are operably linked to a rodent immunoglobulin 9» or K light chain light chain constant region nucleic acid sequence. In one embodiment, the c nucleic acid sequence comprises a rearranged human immunoglobulin 7» or K light chain variable region c acid sequence operably linked to a rodent immunoglobulin 9» or K light chain light chain constant region nucleic acid sequence. In one embodiment, the light chain constant region nucleic acid sequence comprises a rat constant region nucleic acid sequence, a human constant region nucleic acid sequence, or a combination thereof. In one embodiment, the immunoglobulin 7» or K light chain constant region nucleic acid comprises a rat constant region nucleic acid sequence, a human nt region nucleic acid sequence, or a combination thereof.

The polynucleotide of interest within the insert nucleic acid and/or integrated at the target locus can encode an extracellular protein or a ligand for a receptor.

In speciﬁc embodiments, the encoded ligand is a cytokine. nes of interest includes a chemokine selected from or sing CCL, CXCL, CX3CL, and/or XCL. The ne can also comprise a tumor necrosis factor (TNF). In still other embodiments, the cytokine is an interleukin (IL). In one embodiment, the interleukin is selected from or comprises IL-1, IL-2, IL-3, IL-4, IL-5, IL—6, IL-7, IL-8, IL-9, IL-10, IL-1 1, IL-12, IL-l3, IL-l4, IL-lS, IL-l6, IL-l7, IL-18, IL-l9, IL-20, IL-21, IL-22, IL-23, IL-24, IL-25, IL-26, IL-27, IL-28, IL-29, IL-30, IL-31, IL-32, IL-33, IL-34, IL-35, and/or IL-36. In one embodiment, the eukin is IL-2. In speciﬁc embodiments, such polynucleotides of interest within the insert nucleic acid and/or integrated at the target genomic locus are from a human and, in more specific embodiments, can comprise human genomic sequence.

The polynucleotide of interest within the insert nucleic acid and/or integrated at the target genomic locus can encode Apolipoprotein E .

The polynucleotide of interest within the insert nucleic acid and/or integrated at the target locus can encode a cytoplasmic protein or a membrane protein. In one embodiment, the ne protein is a or, such as, a cytokine receptor, an interleukin receptor, an interleukin 2 receptor-alpha, an interleukin-2 receptor beta, an eukin-2 receptor gamma or receptor tyrosine kinase. In other ces, the polynucleotide of interest within the insert nucleic acid and/or integrated at the target locus can comprise an orthologous or homologous region of the target locus.

The polynucleotide of interest within the insert nucleic acid and/or integrated at the target locus can comprise a polynucleotide encoding at least a region of a T cell receptor, ing the T cell receptor alpha. In speciﬁc methods each of the insert nucleic acids comprise a genomic region of the T cell receptor locus (i.e., the T cell receptor alpha locus) such that upon completion of the serial integration, a portion or the entirety of the genomic T cell receptor locus has been integrated at the target locus. Such insert nucleic acids can comprise at least one or more of a variable segment or a joining segment of a T cell receptor locus (i.e., of the T cell receptor alpha locus). In still further embodiments, the cleotide of interest encoding the region of the T cell receptor can be from, for example, a eukaryote, a non-rat eukaryote, a mammal, a non-human , rodent, non-rat rodent, mouse, rat, a human, a monkey, a hamster, an agricultural mammal or a domestic mammal polynucleotide encoding a mutant protein.

In other embodiments, the polynucleotide of interest integrated at the target locus encodes a nuclear protein. In one embodiment, the nuclear protein is a nuclear receptor. In speciﬁc ments, such polynucleotides of interest within the insert nucleic acid and/or integrated at the target locus are from a human and, in more speciﬁc embodiments, can comprise human c sequence.

The polynucleotide of interest within the insert nucleic acid and/or integrated at the target genomic locus can comprise a genetic modiﬁcation in a coding sequence. Such c ations include, but are not limited to, a deletion on of a coding sequence or the fusion of two coding sequences.

WO 88643 The polynucleotide of interest within the insert c acid and/or integrated at the target locus can comprise a polynucleotide encoding a mutant protein, including, for example, a human mutant protein. In one embodiment, the mutant protein is characterized by an altered binding characteristic, altered localization, altered expression, and/or altered sion pattern. In one embodiment, the polynucleotide of interest within the insert nucleic acid and/or integrated at the target locus ses at least one disease allele, including for example, an allele of a neurological e, an allele of a cardiovascular disease, an allele of a kidney disease, an allele of a muscle disease, an allele of a blood disease, an allele of a cancer-causing gene, or an allele of an immune system disease. In such instances, the disease allele can be a dominant allele or the disease allele is a recessive allele. Moreover, the disease allele can comprises a single nucleotide polymorphism (SNP) allele. The polynucleotide of interest encoding the mutant protein can be from any organism, including, but not d to, a eukaryote, a non-rat eukaryote, a mammal, a non-human , , non-rat rodent, mouse, rat, a human, a hamster, a monkey, an agricultural mammal or a domestic mammal polynucleotide encoding a mutant protein.

In one embodiment, the genetic modiﬁcation produces a mutant form of a protein with an altered binding teristic, altered localization, altered expression, and/or altered expression n.

] In one embodiment, the genetic modiﬁcation es a deletion, addition, replacement or a combination thereof of a region of the ApoE locus, for example, the rat ApoE locus, wherein the c modiﬁcation at the ApoE locus results in a decrease in ApoE activity. In one embodiment, an ApoE knockout is generated.

In one embodiment, the c modiﬁcation produces a deletion, addition, replacement or a combination thereof of a region of the Ragl locus, for example, the rat Ragl locus, wherein the genetic modiﬁcation at the Ragl locus results in a decrease in Ragl activity. In one embodiment, a Ragl knockout is generated. In one embodiment, the genetic modiﬁcation produces a deletion, addition, replacement or a combination thereof of a region of the Rag2 locus, for example, the rat Rag2 locus, wherein the genetic modiﬁcation at the Rag2 locus results in a decrease in Rag2 activity.

In one embodiment, a Rag2 knockout is generated. In one embodiment, the genetic modiﬁcation produces a deletion, addition, replacement or a combination thereof of a region of the RagI/Rag2 locus, for example, the rat RagI/Rag2 locus, wherein the genetic modiﬁcation at the RagI/Rag2 locus results in a decrease in Ragl ty and a decrease in Rag2 activity. In one embodiment, a RagI/Rag2 knockout is generated.

In one embodiment, the genetic modiﬁcation produces a deletion, on, replacement or a combination thereof of a region of the eukin-2 receptor gamma locus, for example, the rat interleukin-2 receptor gamma locus, n the genetic modiﬁcation at the interleukin-2 or gamma locus results in a decrease in interleukin-2 receptor gamma. In one embodiment, an eukin-2 receptor gamma knockout is generated.

As discussed elsewhere herein, ﬁarther embodiments provided herein comprises one or more of the ApoE locus, the interleukin-2 receptor gamma locus, the Rag2 locus, the Rag] locus and/or the Rag2/Rag] locus, for example, the rat ApoE locus, the rat interleukin-2 receptor gamma locus the Rag2 locus, the Rag] locus and/or the Rag2/Rag] locus, is modiﬁed through the replacement of a portion of the rat ApoE locus, the interleukin-2 receptor gamma locus the Rag2 locus, the Rag] locus and/or Rag2/Rag] locus with the corresponding orthologous portion of an ApoE locus, an eukin-2 receptor gamma locus, a Rag2 locus, a Rag] locus and/or a Rag2/Rag] locus from another organism.

] In one embodiment, multiple genetic modiﬁcations are generated. In one embodiment, a genetic modiﬁcation es a deletion, addition, replacement or a combination f of a region of interleukin-2 receptor gamma locus, for example, the rat interleukin-2 receptor gamma locus, wherein the genetic modiﬁcation at the interleukin-2 receptor gamma locus results in a decrease in interleukin-2 receptor gamma and a second genetic ation produces a deletion, addition, replacement or a ation f of a region of the rat Rag2 locus, wherein the genetic modiﬁcation at the Rag2 locus results in a decrease in Rag2 activity. In one embodiment, an interleukin- 2 receptor gamma/Rag2 knockout is generated. Such a rat has a SCID ype.

In one embodiment, the mammalian nucleic acid comprises a genomic locus that encodes a protein expressed in the nervous system, the skeletal , the digestive system, the circulatory system, the muscular system, the respiratory system, the cardiovascular system, the lymphatic system, the endocrine system, the urinary , the uctive , or a combination thereof. In one embodiment, the mammalian nucleic acid comprises a genomic locus that encodes a protein expressed in a bone marrow or a bone marrow-derived cell. In one embodiment, the nucleic acid comprises a genomic locus that encodes a n expressed in a spleen cell. In one embodiment, the genomic locus comprises a mouse genomic DNA sequence, a rat c DNA sequence, a human genomic DNA sequence, or a combination thereof. In one ment, the genomic locus ses, in any order, rat and human genomic DNA sequences. In one embodiment, the genomic locus comprises, in any order, mouse and human genomic DNA sequences. In one embodiment, the genomic locus comprises, in any order, mouse and rat genomic DNA sequences. In one embodiment, the genomic locus ses, in any order, rat, mouse, and human genomic DNA ces.

In one embodiment, the insert nucleic acid comprises a genetic modiﬁcation in a coding sequence of a gene. In one embodiment, the genetic modiﬁcation comprises a deletion mutation in the coding ce. In one embodiment, the genetic modiﬁcation comprises a fusion of two endogenous coding sequences.

] In one embodiment, the genetic modiﬁcation comprises a deletion of a non-protein-coding sequence, but does not comprise a deletion of a protein-coding sequence. In one embodiment, the deletion of the non-protein-coding sequence comprises a deletion of a regulatory element. In one embodiment, the genetic modiﬁcation comprises an addition of a promoter. In one embodiment, the genetic modiﬁcation comprises a ement of a promoter or regulatory element. In one embodiment, the regulatory element is an enhancer. In one embodiment, the regulatory element is a transcriptional repressor-binding element.

In one embodiment, the genetic modiﬁcation comprises placement of a human nucleic acid sequence encoding a mutant human protein. In one embodiment, the c ation comprises at least one human disease allele of a human gene. In one embodiment, the human disease is a neurological disease. In one embodiment, the human disease is a cardiovascular disease. In one embodiment, the human disease is a kidney disease. In one embodiment, the human disease is a muscle disease. In one ment, the human disease is a blood disease. In one embodiment, the human disease is a cancer.

In one embodiment, the human e is an immune system disease. In one embodiment, the human disease allele is a dominant allele. In one embodiment, the human disease allele is a recessive allele. In one embodiment, the human disease allele comprises a single nucleotide polymorphism (SNP) allele.

The polynucleotide of st within the insert nucleic acid and/or integrated at the target locus can also comprise a regulatory sequence, including for example, a promoter sequence, an enhancer sequence, or a transcriptional sor- g sequence. In speciﬁc embodiments, the polynucleotide of interest within the insert nucleic acid and/or ated at the target genomic locus ses a polynucleotide having a deletion of a non-protein-coding sequence, but does not comprise a deletion of a protein-coding sequence. In one embodiment, the deletion of the non-protein-coding sequence comprises a deletion of a regulatory ce. In another embodiment, the on of the tory t comprises a deletion of a promoter sequence. In one embodiment, the deletion of the regulatory element comprises a deletion of an enhancer sequence. Such a polynucleotide of interest can be from any organism, including, but not limited to, a eukaryote, a non-rat eukaryote, a mammal, a non-human mammal, , non-rat rodent, mouse, rat, a human, a , an agricultural mammal or a domestic mammal polynucleotide encoding a mutant protein.

. Methods of Introducing Sequences and Generation of Transgenic Animals As outlined above, methods and compositions are provided herein to allow for the targeted integration of one or more polynucleotides of interest into a target locus.

Such systems employ a variety of components and for ease of reference, herein the term "targeted integration system" generically comprises all the components required for an integration event (i.e., in non-limiting examples, the various nuclease , recognition sites, insert DNA polynucleotides, targeting vectors, target genomic locus, and/or polynucleotides of interest).

The methods ed herein se introducing into a cell one or more polynucleotides or polypeptide constructs comprising the various components of the targeted genomic integration system. "Introducing" means presenting to the cell the sequence (polypeptide or polynucleotide) in such a manner that the sequence gains access to the interior of the cell. The methods provided herein do not depend on a particular method for introducing any component of the targeted genomic integration system into the cell, only that the polynucleotide gains access to the interior of a least one cell.

Methods for introducing cleotides into various cell types are known in the art and include, but are not limited to, stable transfection methods, transient transfection methods, and virus-mediated methods.

Any cells from any organism can be used in the methods provided herein.

In speciﬁc embodiments the cells are from a ote, a non-rat eukaryote, a mammal, a man mammal, a human, a rodent, a non-rat rodent, a rat, a mouse or a hamster. In speciﬁc embodiments, the cells are a otic cell, a non-rat eukaryotic cell, a pluripotent cell, a non-pluripotent cell, a non-human pluripotent cell, a man mammalian cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a developmentally restricted human progenitor cell, a human induced pluripotent cell (iPS) cell, a mammalian cell, a human cell, a ﬁbroblast, a rodent cell, a non-rat rodent cell, a rat cell, a mouse cell, a hamster cell or a CHO cell.

In some embodiments, the cells employed in the methods and compositions have a DNA uct stably incorporated into their genome. "Stably incorporated" or "stably introduced" means the introduction of a polynucleotide into the cell such that the nucleotide ce integrates into the genome of the cell and is capable of being inherited by progeny thereof. Any protocol may be used for the stable incorporation of the DNA constructs or the various components of the targeted genomic integration system.

Transfection protocols as well as protocols for introducing polypeptides or polynucleotide sequences into cells may vary. Non-limiting transfection methods include chemical-based transfection methods include the use of mes; nanoparticles; calcium phosphate (Graham et al. (1973). Virology 52 (2): 456—67, Bacchetti et al. (1977) Proc Natl Acad Sci USA 74 (4): 1590—4 and, Kriegler, M . Transfer and Expression: A tory Manual. New York: W. H. Freeman and Company. pp. 96— 97); dendrimers; or cationic polymers such as DEAE-dextran or polyethylenimine. Non chemical s include oporation; Sono-poration; and l transfection .

Particle-based transfection include the use of a gene gun, magnet assisted transfection am, J. (2006) Current Pharmaceutical Biotechnology 7, 277—28). Viral methods can also be used for ection.

In one embodiment, the introducing one or more of the cleotides into a cell is mediated by oporation, by intracytoplasmic injection, by a viral infection, by an adenovirus, by lentivirus, by retrovirus, by transfection, by lipid- mediated transfection or is mediated via NucleofectionTM.

In one embodiment, introduction one or more of the polynucleotides into a cell further comprises: introducing an expression construct comprising a nucleic acid sequence of interest operably linked to a promoter. In one embodiment, the promoter is a constitutively-active promoter. In one embodiment, the promoter is an inducible promoter. In one ment, the promoter is active in a stem cell, for example, an embryonic stem cell.

In one embodiment, the expression construct is introduced together with the LTVEC. In one embodiment, the expression uct is introduced separately from the LTVEC over a period of time.

] In one embodiment, the introduction of the one or more polynucleotides into the cell can be performed multiple times over a period of time. In one embodiment, the introduction of the one or more polynucleotides into the cell are performed at least two times over a period of time, at least three times over a period of time, at least four times over a period of time, at least ﬁve times over a period of time, at least six times over a period of time, at least seven times over a period of time, at least eight times over a period of time, at least nine times over a period of times, at least ten times over a period of time, at least eleven times, at least twelve times over a period of time, at least thirteen times over a period of time, at least fourteen times over a period of time, at least ﬁfteen times over a period of time, at least sixteen times over a period of time, at least seventeen times over a period of time, at least eighteen times over a period of time, at least nineteen times over a period of time, or at least twenty times over a period of time.

In one embodiment, the nuclease agent is introduced into the cell simultaneously with the targeting vector or the large targeting vector (LTVEC).

Alternatively, the nuclease agent is introduced separately from the targeting vector or the LTVEC over a period of time. In one embodiment, the nuclease agent is introduced prior to the introduction of the targeting vector or the LTVEC, while in other embodiments, the nuclease agent is uced following introduction of the targeting vector or the LTVEC.

In one embodiment, screening step comprises a quantitative assay for assessing modiﬁcation of allele (MOA) of a parental chromosome. In one embodiment, the quantitative assay is carried out via a quantitative PCR. In one embodiment, the quantitative PCR is a real-time PCR (qPCR). In one embodiment, the real-time PCR comprises a ﬁrst primer set that recognizes the target locus and a second primer set that recognizes a rgeted reference locus. In one embodiment, the primer set comprises a ﬂuorescent probe that recognizes the ampliﬁed ce. In one embodiment, the quantitative assay is carried out via ﬂuorescence-mediated in situ hybridization (FISH).

In one embodiment, the quantitative assay is carried out via comparative genomic hybridization. In one embodiment, the quantitative assay is carried out via isothermic DNA ampliﬁcation. In one embodiment, the tative assay is carried out via isothermic DNA ampliﬁcation. In one embodiment, the quantitative assay is carried out via tative hybridization to an immobilized probe(s). In one embodiment, the quantitative assay is carried out via Invader Probes®. In one embodiment, the quantitative assay is carried out via MMP assays®. In one embodiment, the quantitative assay is d out via TaqMan® Molecular Beacon. In one embodiment, the quantitative assay is carried out via EclipseTM probe technology. (See, for example, USZOOS/0144655, which is incorporated by reference herein in its entirety).

Further provided is a method for making a humanized non-human animal, comprising: (a) modifying a genome of a pluripotent cell with a targeting vector sing an insert nucleic acid that comprises a human c acid sequence to form a donor cell; (b) introducing the donor cell into a host embryo; and (c) gestating the host embryo in a surrogate ; wherein the surrogate mother produces a progeny that comprises the human nucleic acid sequence. In one ment, the donor cell is introduced into a host embryo that is at the blastocyst stage or at a pre-morula stage (i.e., a 4 cell stage or an 8 cell stage). Moreover, step (a) can also be performed with a large targeting vector (LTVEC) and/or a human nucleic acid sequence at least 5 kb in .

In still further embodiments, the genetic modiﬁcation is capable of being transmitted through the germline. cally modiﬁed non-human animals can be generated employing the various methods disclosed herein. Such methods comprise (1) integrating one or more polynucleotide of interest at the target locus of a pluripotent cell to generate a genetically modiﬁed pluripotent cell comprising the insert nucleic acid in the targeted c locus employing the methods disclosed herein; (2) selecting the genetically modiﬁed pluripotent cell having the one or more polynucleotides of interest at the target genomic locus; (3) introducing the cally modiﬁed pluripotent cell into a host embryo; and (4) implanting the host embryo comprising the cally modiﬁed pluripotent cell into a surrogate mother. A progeny from the cally d pluripotent cell is generated.

In one embodiment, the donor cell is introduced into a host embryo at the blastocyst stage or at the pre-morula stage (i.e., the 4 cell stage or the 8 cell stage). Progeny that are capable of itting the genetic modiﬁcation though the germline are generated. The pluripotent cell can be an ES cell as discussed elsewhere herein.

Nuclear transfer techniques can also be used to generate the cally modiﬁed non-human animals. Brieﬂy, methods for nuclear transfer include the steps of: (l) ating an oocyte; (2) isolating a donor cell or s to be combined with the enucleated oocyte; (3) inserting the cell or nucleus into the ated oocyte to form a reconstituted cell; (4) implanting the reconstituted cell into the womb of an animal to form an embryo; and (5) allowing the embryo to develop. In such methods oocytes are generally retrieved from ed animals, although they may be isolated also from either oviducts and/or ovaries of live animals. Oocytes can be matured in a variety of medium known to those of ordinary skill in the art prior to enucleation. Enucleation of the oocyte can be performed in a number of manners well known to those of ordinary skill in the art. Insertion of the donor cell or nucleus into the enucleated oocyte to form a reconstituted cell is usually by microinj ection of a donor cell under the zona pellucida prior to fusion. Fusion may be induced by ation of a DC electrical pulse across the contact/fusion plane (electrofusion), by exposure of the cells to fusion-promoting chemicals, such as polyethylene glycol, or by way of an vated virus, such as the Sendai virus. A reconstituted cell is typically activated by electrical and/or non-electrical means before, during, and/or after fusion of the nuclear donor and recipient oocyte.

Activation methods include electric pulses, chemically induced shock, penetration by sperm, sing levels of divalent cations in the oocyte, and reducing phosphorylation of cellular proteins (as by way of kinase inhibitors) in the oocyte. The activated reconstituted cells, or embryos, are typically cultured in medium well known to those of ordinary skill in the art and then transferred to the womb of an animal. See, for example, U820080092249, WO/l999/005266A2, 0177390, WO/2008/017234Al, and US Patent No. 7,612,250, each of which is herein incorporated by reference.

In one aspect, a method for making a genetically modiﬁed non-human animal is provided, comprising modifying a genomic locus of interest in a pluripotent cell employing endonuclease-mediated gene targeting to introduce a modiﬁcation at a genomic locus of interest to form a modiﬁed pluripotent cell, ining the modiﬁed pluripotent cell under conditions sufﬁcient to maintain pluripotency, employing the modiﬁed pluripotent cell as a donor cell in a host embryo, and ing the host embryo comprising the modiﬁed pluripotent cell in a surrogate mother, n the host embryo is gestated by the surrogate mother and a genetically modiﬁed progeny is born.

In one embodiment, the target sequence is located in an . In one embodiment, the target ce is d in an exon. In one embodiment, the target sequence is located in a promoter. In one embodiment, the target sequence is located in a promoter regulatory region. In one embodiment, the target ce is located in an enhancer region.

In one embodiment, introducing step is performed multiple times over a period of time using a plurality of endonucleases that recognize ct target sequences.

In one embodiment, step is performed at least two times over a period of time using a plurality of endonucleases that recognize distinct target ces, at least three times over a period of time using a plurality of endonucleases that recognize distinct target ces, at least four times over a period of time using a plurality of cleases that recognize distinct target sequences, at least ﬁve times over a period of time using a plurality of endonucleases that recognize distinct target sequences, at least six times over a period of time using a plurality of endonucleases that recognize distinct target sequences, at least seven times over a period of time using a plurality of endonucleases that ize distinct target sequences, at least eight times over a period of time using a plurality of endonucleases that recognize distinct target sequences, at least nine times over a period of time using a ity of endonucleases that recognize distinct target sequences, at least ten times over a period of time using a plurality of cleases that recognize distinct target sequences, at least eleven times over a period of time using a plurality of endonucleases that ize ct target sequences, at least twelve times over a period of time using a plurality of endonucleases that recognize ct target sequences, at least thirteen times over a period of time using a plurality of endonucleases that recognize distinct target sequences, at least fourteen times over a period of time using a plurality of endonucleases that recognize distinct target sequences, at least ﬁfteen times over a period of time using a plurality of endonucleases that recognize distinct target sequences, at least sixteen times over a period of time using a plurality of cleases that recognize distinct target sequences, at least seventeen times over a period of time using a plurality of endonucleases that recognize distinct target sequences, at least en times over a period of time using a ity of cleases that recognize distinct target sequences, at least en times over a period of time using a ity of endonucleases that recognize distinct target sequences, or at least twenty times over a period of time using a plurality of endonucleases that recognize distinct target sequences.

In one embodiment, introducing step is mediated by electroporation, by intracytoplasmic injection, by an adenovirus, by lentivirus, by retrovirus, by transfection, by mediated transfection or is mediated via NucleofectionTM.

In one embodiment, the method ﬁlrther comprises introducing an exogenous nucleic acid into the genetically modiﬁed pluripotent cell. In one embodiment, the exogenous nucleic acid is a transgene. In one embodiment, the exogenous nucleic acid is introduced into an endogenous locus. In one embodiment, the exogenous nucleic acid is introduced ectopically (e.g., at a locus different from its endogenous locus).

In one aspect, a method for making a genetically modiﬁed non-human animal is provided, comprising modifying a genomic locus of interest in a pluripotent cell employing RNA-guided genome engineering to introduce a modiﬁcation at a genomic locus of interest to form a modiﬁed pluripotent cell, maintaining the modiﬁed pluripotent cell under conditions ent to maintain pluripotency, employing the modiﬁed pluripotent cell as a donor cell in a host embryo and gestating the host embryo comprising the modiﬁed pluripotent cell in a surrogate mother, n the host embryo is gestated by the surrogate mother and a cally modiﬁed progeny is born.

In one embodiment, the method has a targeting rate ranging from about 2% to about 80%.

In one ment, the method comprises roducing a plurality of the second expression construct comprising distinct genomic target sequences for multiplex editing of distinct c loci. In one embodiment, the method comprises introducing a plurality of the second expression construct comprising distinct genomic target sequences for multiplex g of distinct genomic loci over a period of time.

In one embodiment, introducing step is performed multiple times over a period of time. In one embodiment, introducing step (b) is performed at least two times over a period of time, at least three times over a period of time, at least four times over a period of time, at least ﬁve times over a period of time, at least six times over a period of time, at least seven times over a period of time, at least eight times over a period of time, at least nine times over a period of time, at least ten times over a period of time, at least eleven times over a period of time, at least twelve times over a period of time, at least thirteen times over a period of time, at least fourteen times over a period of time, at least ﬁfteen times over a period of time, at least sixteen times over a period of time, at least seventeen times over a period of time, at least eighteen times over a period of time, at least nineteen times over a period of time, at least twenty times over a period of time.

] In one embodiment, the ﬁrst expression construct and the second expression construct are sed from a same plasmid.

In one embodiment, introducing step is mediated by oporation, by intracytoplasmic injection, by an irus, by lentivirus, by retrovirus, by transfection, by lipid-mediated transfection or is mediated via NucleofectionTM.

In one embodiment, the method ﬁlrther comprises introducing an exogenous nucleic acid into the pluripotent cell comprising the mutant allele.

In one embodiment, the exogenous nucleic acid is a transgene. In one embodiment, the exogenous nucleic acid is introduced into an endogenous locus. In one 2014/060788 embodiment, the exogenous nucleic acid is placed ectopically (e. g., at a locus different from its endogenous locus).

In one embodiment, the method ﬁlrther comprises introducing an exogenous nucleic acid into the genetically d pluripotent cell. In one embodiment, the exogenous nucleic acid is a transgene. In one embodiment, the exogenous c acid is introduced into an endogenous locus. In one embodiment, the exogenous nucleic acid is introduced ectopically (e. g., at a locus different from its endogenous locus).

In one aspect, a method for making a humanized non-human animal is ed, comprising modifying a genome of a pluripotent cell with an LTVEC comprising an insert that comprises a human sequence of at least 5 kb, and employing the pluripotent cell as a donor cell, introducing the donor cell into a host embryo, and gestating the host embryo in a surrogate mother, wherein the surrogate mother births a progeny that comprises the humanization.

Other methods for making a genetically modiﬁed non-human animal comprising in its germline one or more genetic modiﬁcations as described herein is provided, comprising: (a) modifying a targeted locus contained in a prokaryotic cell employing the various methods described herein; (b) selecting a d prokaryotic cell comprising the genetic modiﬁcation at the targeted locus; (c) isolating the genetically modiﬁed targeting vector from the genome of the modiﬁed prokaryotic cell; (d) ucing the cally modiﬁed targeting vector into a pluripotent cell to generate a genetically d pluripotent cell comprising the insert c acid at the targeted c locus; (e) selecting the genetically modiﬁed otent cell; (f) introducing the genetically modiﬁed pluripotent cell into a host embryo at a pre-morula stage; and (g) implanting the host embryo comprising the genetically modiﬁed otent cell into a surrogate mother to generate an F0 generation derived from the genetically modiﬁed otent cell. In such s the targeting vector can comprise a large targeting vector. The pluripotent cell can be an ES cell. In further methods, the isolating step (c) further ses (cl) linearizing the genetically modiﬁed targeting vector (i.e., the genetically modiﬁed LTVEC). In still ﬁlrther embodiments, the introducing step (d) further comprises (dl) introducing a nuclease agent as described herein into the pluripotent cell. In one embodiment, selecting steps (b) and/or (e) are carried out by applying a selectable agent as described herein to the prokaryotic cell or the pluripotent cell. In one embodiment, selecting steps (b) and/or (e) are carried out via a modiﬁcation of allele (MOA) assay as described herein.

Further methods for modifying a target c locus of a mammalian cell Via bacterial homologous recombination (BHR) in a prokaryotic cell are provided and comprise: (a) providing a prokaryotic cell sing a target locus comprising a nucleic acid, (b) introducing into the prokaryotic cell a targeting vector comprising an insert nucleic acid ﬂanked with a 5' homology arm and a 3' gy arm, wherein the insert nucleic acid comprises a mammalian region (including, for example, a DNA insert from a human), and (c) selecting a targeted prokaryotic cell comprising the insert nucleic acid at the target locus wherein the yotic cell is e of expressing a recombinase that es the BHR. Step (al) can comprise providing a prokaryotic cell comprising a target locus comprising a nucleic acid comprising a ﬁrst polynucleotide comprising a ﬁrst recognition site for a ﬁrst nuclease agent, and step (bl) can further comprise expressing in the prokaryotic cell a nuclease agent that makes a nick or double- strand break at or near the ﬁrst recognition site. Steps (a)-(c) can be serially repeated as disclosed herein to allow the introduction of multiple insert nucleic acids at the targeted locus in the prokaryotic cell. Once the targeted genomic locus is "built" with the prokaryotic cell, a targeting vector comprising the d target locus can be isolated from the prokaryotic cell and introduced into a target genomic locus within a pluripotent cell. Pluripotent cells (i.e., ES cells) comprising the modiﬁed genomic locus can then be made into genetically modiﬁed non-human animals.

In some embodiments, various c modiﬁcations of the target genomic loci described herein can be d out by a series of homologous recombination reactions (BHR) in bacterial cells using an LTVEC d from Bacterial Artiﬁcial Chromosome (BAC) DNA using VELOCIGENE® genetic engineering technology (see, e.g., US Pat. No. 6,586,251 and Valenzuela, D. M. et al. , High-throughput ering of the mouse genome d with high-resolution expression analysis, Nature Biotechnology 21 (6): 652-659, which is incorporated herein by reference in their entireties).

In some embodiments, targeted ES cells comprising various genetic modiﬁcations as described herein are used as insert ES cells and introduced into a pre- morula stage embryo from a corresponding organism, e.g., an 8-cell stage mouse embryo, via the VELOCIMOUSE® method (see, e.g., US 7,576,259, US 7,659,442, US 7,294,754, and US 2008-0078000 Al, all of which are incorporated by nce herein in their entireties). The embryo comprising the genetically modiﬁed ES cells is incubated until the blastocyst stage and then implanted into a surrogate mother to produce an F0.

Animals bearing the genetically modiﬁed genomic locus can be ﬁed via modiﬁcation of allele (MOA) assay as described herein. The resulting F0 generation non- human animal derived from the genetically modiﬁed ES cells is crossed to a wild-type non-human animal to obtain Fl generation offspring. Following genotyping with speciﬁc primers and/or probes, Fl non-human animals that are heterozygous for the genetically modiﬁed genomic locus are crossed to each other to produce animals that are gous for the genetically modiﬁed genomic locus. atively, an F0 female non-human animal and an F0 male non-human animal each having the c modiﬁcation can be d to obtain an Fl non-human animal homozygous for the genetic modiﬁcation.

In one aspect, a genetically modiﬁed rat genome, for example, is provided, comprising a targeted ation of an endogenous nucleic acid sequence with a gous or orthologous nucleic acid sequence from another organism.

In one embodiment, the homologous or orthologous nucleic acid sequence is of a length from about 5 kb to about 200 kb. In one embodiment, the homologous or orthologous non-rat nucleic acid ce ranges from about 5 kb to about 10 kb. In one embodiment, the homologous or orthologous t nucleic acid sequence ranges from about 10 kb to about 20 kb. In one embodiment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 20 kb to about 30 kb. In one embodiment, the homologous or orthologous non-rat c acid sequence ranges from about 30 kb to about 40 kb. In one embodiment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 40 kb to about 50 kb. In one embodiment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 50 kb to about 60 kb. In one embodiment, the homologous or orthologous non-rat c acid sequence ranges from about 60 kb to about 70 kb. In one embodiment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 70 kb to about 80 kb. In one embodiment, the gous or orthologous non-rat nucleic acid sequence ranges from about 80 kb to about 90 kb. In one embodiment, the homologous or ogous non-rat nucleic acid sequence ranges from about 90 kb to about 100 kb. In one embodiment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 100 kb to about 110 kb.

In one embodiment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 110 kb to about 120 kb. In one embodiment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 120 kb to about 130 kb. In one ment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 140 kb to about 150 kb. In one embodiment, the homologous or orthologous non- rat nucleic acid sequence ranges from about 150 kb to about 160 kb. In one embodiment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 160 kb to about 170 kb. In one embodiment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 170 kb to about 180 kb. In one embodiment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 180 kb to about 190 kb.

In one embodiment, the homologous or orthologous non-rat nucleic acid sequence ranges from about 190 kb to about 200 kb. Various polynucleotides of interest that can be employed in the insert nucleic acid are described elsewhere herein. r methods for targeted genome modiﬁcation of a man animal are provided. Such methods can comprise (a) modifying a genomic locus of interest in a non-human pluripotent cell ing to any of the various methods provided herein for modifying a genomic locus of interest, thereby ing a genetically modiﬁed non- human pluripotent cell comprising a targeted genome modiﬁcation; (b) introducing the modiﬁed non-human pluripotent cell of step (a) into a non-human host embryo; and (c) gestating the non-human host embryo comprising the d otent cell in a surrogate mother, wherein the surrogate mother produces F0 progeny sing the targeted genome modiﬁcation, and n the targeted genome modiﬁcation is capable of being transmitted through the germline.

] In some embodiments, the targeted genome ation comprises simultaneous deletion of an endogenous nucleic acid ce at the genomic locus of interest and insertion of an exogenous nucleic acid at the genomic locus of interest (i.e., deletion and insertion in a single step). In some ments, the targeted genome modiﬁcation comprises a lic genetic modiﬁcation. The lic genetic modiﬁcation can comprise deletion of an endogenous nucleic acid sequence and insertion of an exogenous nucleic acid at the genomic locus of interest in two homologous chromosomes (i.e., a pair of ﬁrst and second homologous chromosomes).

In other ments, the targeted genome modiﬁcation creates a modiﬁed pluripotent cell that is compound heterozygous at the genomic locus of interest.

In other embodiments, the ed genome modiﬁcation creates a modiﬁed pluripotent cell that is hemizygous at the genomic locus of interest. In some embodiments, the targeted genetic modiﬁcation at the genomic locus of interest in one chromosome comprises deletion of an endogenous c acid sequence and insertion of an exogenous nucleic acid. For example, the targeted genetic modiﬁcation can comprise: (l) deletion of an endogenous nucleic acid sequence at the genomic locus of interest in two homologous chromosomes; and (2) insertion of an exogenous nucleic acid into the genomic locus of interest in a ﬁrst chromosome and disruption of the genomic locus of interest in a second chromosome. The ﬁrst chromosome can be the ﬁrst of the two gous chromosomes, and the second some can be the second of the two homologous chromosomes. 6. Cells The various s and compositions described herein employ a genomic locus targeting system in a cell. In one embodiment, the cell is a pluripotent cell. In one embodiment, the cell is a non-pluripotent cell. In one embodiment, the pluripotent cell is a non-human pluripotent cell. In one ment, the non-human pluripotent cell is a mammalian pluripotent cell. In one embodiment, the pluripotent cell is a human induced otent stem (iPS) cell.

In other embodiments, the cell is a eukaryotic cell, a non-rat eukaryotic cell, a human pluripotent cell, a human ES cell, a human adult stem cell, a pmentally restricted human progenitor cell, a non-human mammalian cell, a mammalian cell, a human cell, a ﬁbroblast, a rodent cell, a non-rat rodent cell, a rat cell, a mouse cell, a hamster cell or a CHO cell.

In one embodiment, a otic cell is a primary cell. Primary cells e cells or cultures of cells that have been isolated directly from an organism, organ, or tissue. Primary cells include cells that are neither transformed nor al.

They include any cell obtained from an organism, organ, or tissue which was not previously passed in tissue culture or has been previously passed in tissue culture but is incapable of being indeﬁnitely passed in tissue e. Such cells can be isolated by conventional techniques and include, for example, hematopoietic cells, endothelial cells, epithelial cells, ﬁbroblasts, mesenchymal cells, keratinocytes, melanocytes, monocytes, mononuclear cells, adipocytes, preadipocytes, neurons, glial cells, hepatocytes, skeletal myoblasts, and smooth muscle cells. In some embodiments, primary cells are derived from connective tissues, muscle tissues, nervous system tissues, or epithelial tissues.

In another embodiment, a eukaryotic cell is an immortalized cell.

Immortalized cells e cells from a multicellular organism that would normally not erate indeﬁnitely but, due to mutation or alteration, have evaded normal cellular senescence and instead can keep undergoing division. Such mutations or alterations can occur naturally or be intentionally induced. Examples of immortalized cells include Chinese hamster ovary (CHO) cells, human embryonic kidney cells (e. g., HEK 293 cells), and mouse embryonic ast cells (e. g., 3T3 . Numerous types of immortalized cells are well known in the art.

In some embodiments, immortalized cells are derived from cancer cells. In another embodiment, a primary or immortalized cell is one that is lly used for culturing or for expressing inant genes or proteins.

In other embodiments, the pluripotent cell is able to sustain its otency following at least one ed genetic modiﬁcation of its genome and is able to transmit the targeted modiﬁcation to a ne of an F1 generation.

In one embodiment, the pluripotent cell is a non-human fertilized egg at the single cell stage. In one embodiment, the non-human fertilized egg is a mammalian fertilized egg. In one embodiment, the mammalian fertilized egg is a rodent fertilized egg at the single cell stage. In one embodiment, the mammalian fertilized egg is a rat or mouse ized egg at the single cell stage.

The various cells employed in the method and compositions disclosed herein can also se prokaryotic cells, such as a bacterial cell, including E. 0012'. In speciﬁc embodiments, the prokaryotic cell is a recombination-competent strain of E. 6012'. In one ment, the prokaryotic cell comprises a nucleic acid that encodes the recombinase, while in other instances, the prokaryotic cell does not comprise the nucleic acid that s the recombinase, and the nucleic acid ng the recombinase is introduced into the prokaryotic cell. In one embodiment, the nucleic acid encoding the recombinase comprises a DNA or an mRNA. In some embodiments, the nucleic acid encoding the recombinase is pABG. In one embodiment, the recombinase is expressed under the control of an inducible promoter. In one embodiment, expression of the recombinase is controlled by arabinose.

A. Low Osmolality Medium for Making and Maintaining Human Induced Pluripotent Stem Cells A cell culture medium is provided for use in the methods and compositions of the invention. In one embodiment, the medium is suitable for making a population of human iPS cells. In another ment, the medium is suitable for maintaining human iPS cells in culture. In some embodiments, the human iPS cells are na'ive or na'ive-looking.

The medium provided herein comprises at least a base medium, supplements, a leukemia inhibitory factor (LIF) polypeptide, a glycogen synthase kinase 3 (GSK3) inhibitor, and a MEK inhibitor.

The present medium is a low lity medium. In one example, the osmolality is between about 175-280 mOsm/kg. In further examples, the osmolality of the medium is about 180-270 mOsm/kg, about 200-250 mOsm/kg, about 220-240 mOsm/kg, or about 225-235 mOsm. In a particular embodiment, the osmolality of the medium is about 233 mOsm/kg.

The base medium provided for the invention is a low lity base medium to which supplements are added. The present base medium differs from base media lly used to in human iPS cells in e, which include Dulbecco’s d Eagle’s Medium (DMEM), in various forms (e.g., ogen DMEM, Cat. No. l 1971 -025), and a low salt DMEM available commercially as KO-DMEMTM (Invitrogen Cat. No. 10829-018).

The base medium provided herein is a low osmolality medium but exhibits characteristics that are not limited to low osmolality. For example, the DMEM formulation shown in Table A can be made suitable for the purposes of the invention by altering the sodium chloride and/or sodium bicarbonate concentrations as provided herein, which will result in a ent osmolality as compared with the standard DMEM base medium or low-salt DMEM base medium (KO-DMEM) shown in Table A.

] Table A: DMEM base medium formulation.

D-Calcium pantothenate 4 8.39 X 10'3 Folic Acid 4 9.07 x 10-3 4 0.0328 Pyridoxine-HCI 4 0.0196 Thiamine°HCI 4 0.01 19 i-Inositol 7.2 0.04 Calcium Chloride (CaClz) (anhydrous) 200 Ferric Nitrate (Fe(N03)3.9H20) 0.1 Magnesium Sulfate (MgSO4) (anhyd.) 97.67 Potassium Chloride (KCI) 400 D-Glucose (Dextrose) 4500 Phenol Red 15 NaCL/NaHCO3 Content of DMEM Sodium Bicarbonate (NaHCOg) 3700 Sodium Chloride (NaCl) 6400 NaCl/NaHC03 Content of Low salt DMEM (KO-DMEM) Sodium Bicarbonate g) 2200 Sodium de (NaCl) 5100 NaCl/NaHC03 Content of Low li DMEM Sodium onate (NaHC03 2200 Sodium Chloride (NaCl 3000 The present base medium can include a salt of an alkaline metal and a halide, such as sodium chloride (NaCl). Exemplary concentrations ofNaCl in the base medium include 50 :: 5 mM or about 3 mg/mL.

In another embodiment, the base medium exhibits a concentration of a salt of carbonic acid. The salt of carbonic acid can be a sodium salt. In such an example, the sodium salt can be sodium bicarbonate. In a particular embodiment, sodium bicarbonate is present in the base medium at a concentration of about 26 :: 5 mM or about 2.2 mg/mL.

In yet another embodiment, the base medium is a low osmolality base medium. The osmolality of the base medium can be Within a range of about 175-280 mOsm/kg, about 180-250 mOsm/kg, about 190-225 mOsm/kg, or about 195-205 mOsm/kg. An ary osmolality of the base medium can be 200, 214, 216, or 218 mOsm/kg. In a particular example, the lity of the base medium is 200 mOsm/kg.

The lity can be determined when cells are cultured in different concentrations of C02. In some examples, cells are cultured at 3% C02 or 5% C02.

In a preferred embodiment, the base medium comprises NaCl at a concentration of 3.0 mg/mL, sodium bicarbonate at a concentration of about 2.2 mg/mL, and has an osmolality of 200 mOsm/kg.

Supplements formulated with the base medium of the invention are le for making, maintaining, or ing populations of human iPS cells disclosed herein. Such supplements are indicated as "supplements" or "+ supplements" in this disclosure. The term "supplements" or the phrase "+ ments," includes one or more onal elements added to the components of the base medium described in Table A. For example, supplements can e, Without limitation, F-l2® medium (Gibco), N2® supplement ; lOOX solution), NEUROBASAL® medium ), B-27® supplement (Gibco; 50X solution), L-glutamine, glucose, 2-mercaptoethanol, a Leukemia Inhibitory Factor (LIF) polypeptide, a glycogen synthase kinase 3 inhibitor, a MEK inhibitor, or any combination thereof.

In a particular embodiment, the LIF polypeptide is a human LIF (hLIF) polypeptide. In some examples, a hLIF polypeptide is used at a concentration of about 1-1000 units/mL, about 20-800 units/mL, about 50-500 units/mL, about 75-250 units/mL, or about 100 units/mL.

In another particular embodiment, the GSK3 inhibitor comprises 021. In some examples, CHIR99021 is used at a concentration of about 0.1 to uM, about 1-5 uM, about 2-4 uM, or about 3 uM.

In another particular embodiment, the MEK inhibitor comprises PD0325901. In some examples, PD032590l is used at a concentration of about 0.1-5 uM, about 0.2-1 uM, about 7 uM, or about 0.5 uM.

An exemplary medium comprises a low lity base medium described herein at about 24.75% (V/V), F-12 medium at about 24.75% (V/V), N2 supplement at about 0.5% (V/V), NEUROBASAL medium at about 49% (V/V), B-27 supplement at about 1% (V/V), L-glutamine at about 2 mM, 2-mercaptoethanol at about 0.1 mM, hLIF at about 100 units/mL, CHIR99021 at about 3 uM, and PD0325901 at about 0.5 uM.

] In another particular embodiment, the medium may or may not comprise basic fibroblast growth factor (bFGF, also known as FGF2 or FGF-B). Preferably the present medium does not comprise bFGF.

B. Human Induced Pluripotent Stem Cells Methods and compositions are provided herein for making a tion of human iPS cells. Methods and compositions are further provided for maintaining human iPS cells in culture. Human iPS cells that are produced or ined in culture are also provided.

The term "pluripotent cell" or "pluripotent stem cell" es an undifferentiated cell that possesses the ability to develop into more than one entiated cell type. Such pluripotent cells can be, for example, a mammalian embryonic stem (ES cell) cell or a mammalian induced pluripotent stem cell (iPS cell).

Examples of pluripotent cells include human iPS cells.

The term "embryonic stem cell" or "ES cell" means an embryo-derived totipotent or pluripotent stem cell, derived from the inner cell mass of a blastocyst, that can be maintained in an in vitro culture under suitable conditions. ES cells are capable of entiating into cells of any of the three vertebrate germ layers, e. g., the endoderm, the ectoderm, or the mesoderm. ES cells are also characterized by their ability propagate nitely under suitable in vitro e conditions. See, for example, n et al. (Science (1998) Vol. 282(5391), pp. 1145-1147).

The term "induced pluripotent stem cell" or "iPS cell" includes a pluripotent stem cell that can be derived directly from a differentiated adult cell. Human iPS cells can be generated by introducing ic sets of reprogramming factors into a non-pluripotent cell which can include, for example, Oct3/4, Sox family transcription factors (e.g., Soxl, Sox2, Sox3, SoxlS), Myc family transcription factors (e.g., c-Myc, l- Myc, n-Myc), Kriippel-like family (KLF) transcription factors (e. g., KLFl, KLFZ, KLF4, KLFS), and/or related transcription factors, such as NANOG, LIN28, and/or Glisl. Human iPS cells can also be generated, for example, by the use of miRNAs, small molecules that mimic the actions of transcription factors, or e specifiers.

Human iPS cells are characterized by their ability to differentiate into any cell of the three vertebrate germ layers, e.g., the endoderm, the ectoderm, or the mesoderm.

Human iPS cells are also characterized by their ability propagate indeﬁnitely under suitable in vitro culture conditions. See, for example, Takahashi and Yamanaka (Cell (2006) Vol. , pp. 6).

The terms "naive" and "primed" identify different pluripotency states of human iPS cells. The term "naive-looking" identiﬁes a cell expressing a pluripotent state that exhibits one or more characteristics of a naive pluripotent cell. Naive-looking human iPS cells can also be referred to as "naive-like" human iPS cells. In some embodiments, naive-looking human iPS cells exhibit one or more logical characteristics of naive human iPS cells, such as a morphology characterized by compact dome-shaped colonies. In some embodiments, naive-looking human iPS cells express one or more of the pluripotency markers described herein. In some embodiments, na'ive or naive-looking human iPS cells are na'ive human iPS cells. In other embodiments, na'ive or naive-looking human iPS cells are naive-looking iPS cells.

Characteristics of naive and primed iPS cells are described in the art. See, for example, Nichols and Smith (Cell Stem Cell (2009) Vol. 4(6), pp. 487-492). Na'ive human iPS cells exhibit a pluripotency state r to that of ES cells of the inner cell mass of a pre-implantation embryo. Such na'ive cells are not primed for lineage specification and commitment. Female na'ive iPS cells are characterized by two active X chromosomes. In e, self-renewal of naive human iPS cells is ent on leukemia inhibitory factor (LIF) and other inhibitors. Cultured na'ive human iPS cells y a clonal morphology characterized by rounded dome-shaped colonies and a lack of apico-basal polarity. Cultured na'ive cells can r display one or more pluripotency makers as described elsewhere herein. Under appropriate conditions, the doubling time of naive human iPS cells in culture can be between 16 and 24 hours.

Primed human iPS cells express a pluripotency state similar to that of post-implantation epiblast cells. Such cells are primed for lineage specification and ment. Female primed iPS cells are characterized by one active X chromosome and one inactive X some. In culture, self-renewal of primed human iPS cells is dependent on fibroblast growth factor (FGF) and activin. Cultured primed human iPS cells display a clonal morphology characterized by an epithelial yer and display apico-basal polarity. Under appropriate conditions, the doubling time of primed human iPS cells in culture can be 24 hours or more.

In one embodiment, human iPS cells can be d from non-pluripotent cells transformed to express a pluripotent state. Such transformed cells include, for example, cells that have been transformed to express reprogramming genes that induce pluripotency. A pluripotent state can include, for example, expression of one or more of the pluripotency markers described herein. Such cells (such as human foreskin f1broblasts) can be transformed to express reprogramming genes, or any additional genes of interest, by any means known in the art. See, for example, Takahashi and ka (Cell (2006) Vol. 126(4), pp. 663-676). For example, they can be introduced into the cells using one or more plasmids, ral vectors, or retroviral vectors. In some cases, the vectors integrate into the genome and can be removed after reprogramming is complete. In particular embodiments, the non-pluripotent cells are transformed with reprogramming genes comprising Oct4, Sox2, Klf4, Myc, or any combination f.

In some examples, the transformed cells comprise primed human iPS cells.

] In some embodiments, the human iPS cells cultured in the low osmolality medium described herein express one or more phenotypes, gene expression proﬁles, or markers characteristic of a naive state. In one e, the human iPS cells express one or more pluripotency markers Whose expression is indicative of a naive state. Such pluripotency markers can include alkaline atase, NANOG, 5T4, ABCGZ, Activin RIB/ALK-4, n RIIB, E-Cadherin, Cbx2, CD9, CD30/TNFRSF8, CDl l7/c-kit, CDX2, CHDl, Cripto, DNMT3B, DPPAZ, DPPA4, DPPAS/ESGl, EpCAM/TROPl, ERR beta/NR3B2, ESGP, F-box protein lS/FBXOlS, FGF-4, FGF-S, FoxD3, GBXZ, GCNF/NR6Al, GDP-3, Gi24/VISTA/B7-H5, integrin alpha f, integrin alpha 6 beta 1, integrin alpha 6 beta 4, integrin beta l/CD29, KLF4, KLFS, LlTDl, Lefty, Lefty-l, Lefty-A, LIN-28A, LIN-28B, LIN-41, cMaf, cMyc, Oct-3/4, Oct-4A, lyxin, Rex-l/ZFP42, Smad2, Smad2/3, SOX2, SSEA-l, SSEA-3, SSEA-4, STAT3, Stella/Dppa3, SUZlZ, TBXZ, TBX3, TBXS, TERT, TEXl9, TEXl9. l, THAPl l, 60(R), TROP-Z, UTFl, and/or ZIC3. In a speciﬁc example, the expressed pluripotency marker is alkaline phosphatase, NANOG, or both.

In r embodiment, human iPS cells cultured in the low osmolality medium described herein display morphological characteristics indicative of a naive state. An exemplary morphology is terized by cells having compact haped colonies in culture.

In another embodiment, human iPS cells cultured in the low osmolality medium described herein can be mechanically or enzymatically dissociated into a single-cell suspension, passaged, and/or subcultured. In one example, enzymatic dissociation can be performed using trypsin. When cultured in the t low osmolality , human iPS cells can provide greater transformation efficiency due to enhanced dissociation into a single-cell suspension. With other types of medium (e. g., mTeSRTM medium or 2i medium) typically used to maintain human iPS cells in e, dissociation of human iPS cells must be performed mechanically or with enzymes such as collagenase that are less harsh than trypsin. Consequently, the cells are not dissociated as effectively or as completely. In contrast, with the present low osmolality , trypsin can be used to dissociate the cells, and the enhanced dissociation results in increased transformation ency. Furthermore, unlike with other types of medium typically used to maintain human iPS cells in e (e. g., mTeSRTM medium or 2i medium), enzymatic dissociation of human iPS cells cultured with the present low osmolality medium (preferably a low osmolality medium not comprising bFGF) can be performed in the absence of one or more inhibitors that are generally necessary for the e of such cells. An exemplary inhibitor that can be omitted is a Rho-associated protein kinase (ROCK) inhibitor. A ROCK inhibitor is generally necessary when passaging human iPS cells to inhibit the activation of proapoptotic pathways.

In a further embodiment, subcultured human iPS cells cultured in the low osmolality medium bed herein can maintain a naive or naive-looking state following enzymatic iation and subculture. In some examples, subcultured human iPS cells can ue to display a morphology characterized by compact dome-shaped colonies. Subcultured human iPS cells can also continue to express one or pluripotency markers as described herein.

C. Methods for Making and ining a Population of Human Induced Pluripotent Stem Cells Methods and compositions are provided for making human iPS cells in an in vitro culture. Methods and compositions are r provided for ining human iPS cells in an in vitro culture.

The term "making" includes culturing non-pluripotent cells transformed to s one or more reprogramming factors as described herein, under suitable conditions to induce a change in cell phenotype, gene expression, or both, such that the cells display a naive or na'ive-looking state, i.e., express one or more characteristics of naive human iPS cells. A na'1've or naive-looking state can be expressed in response to ular culture conditions, e.g., e in a low lity medium as described herein. In some examples, the proportion of cells expressing a naive or na'ive-looking state is at least about 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, and up to 100% of the cells in culture.

In one embodiment, the method enriches an in vitro culture for a population of naive or na'ive-looking human iPS cells. In such an embodiment, na'ive or na'ive-looking human iPS cells can be propagated in culture preferentially over cells that do not express a naive or na'ive-looking state. In another embodiment, na'ive or na'ive- looking human iPS cells can be selected from a culture, be enzymatically dissociated, and subcultured to produce an enriched population of naive or naive-looking human iPS cells.

In one embodiment, non-pluripotent cells transformed to express a pluripotent state, are cultured in vitro in a medium provided herein that is suitable for inducing expression of a naive or na'ive-looking state for a period of at least 1, 2, 5, 7, , 14, 21, or 28 days, or any period of time sufﬁcient to induce expression of a naive or -looking state in culture. Transformed cells can be cultured in the present medium for at least 1, 2, 3, or 4 weeks. Sometimes ormed cells are ed for 1-4 weeks. sion of a naive or na'1've-looking state can be determined by observing morphological characteristics or the expression of pluripotency markers, characteristic of a naive or na'1've-looking state, that are described elsewhere herein.

In one ment, uripotent cells transformed to s a pluripotent state, are cultured in the present low osmolality medium until they express characteristics of a naive or naive-looking state. Cells can then be cultured in the present medium to maintain a naive or naive-looking state. In another embodiment, non-pluripotent cells transformed to s a pluripotent state, are ﬁrst cultured in a high osmolality medium prior to culturing in the present low osmolality . Such high lity medium exhibits an osmolality higher than the present low osmolality medium and can comprise bFGF. Some high osmolality medium comprises one or more of bovine serum albumin, bFGF, transforming growth factor B , lithium chloride, pipecolic acid, and gamma-aminobutyric acid (GABA). Examples of a high osmolality medium include mTeSRTM medium (Stemcell logies).

In some embodiments, non-pluripotent cells transformed to express a pluripotent state, can ﬁrst be cultured in high osmolality medium comprising bFGF until they begin to express characteristics of a naive or naive-looking state, at which time the cells are cultured in the present low osmolality medium. In one example, cells can be cultured in high osmolality medium comprising bFGF for a period of at least 1, 2, 5, 10, , 60, or 90 days, a period of l, 2, 4, 8, or 12 weeks, or a period between 1 day to 3 months. An exemplary time period for culture in a high osmolality medium comprising bFGF is 2 months.

In other embodiments, non-pluripotent cells transformed to express a pluripotent state, can ﬁrst be cultured in high osmolality medium comprising bFGF until they begin to display a morphology characterized by dimensional cell clumps, at which time cells are ed in the present low osmolality medium. In such embodiments, cells displaying dimensional clumps can be selected, dissociated (e.g., with trypsin), and transferred to a new culture in the low osmolality medium described herein.

] The terms "maintain," "maintaining," and "maintenance" include the preservation of at least one or more of the characteristics or phenotypes of the human iPS cells described . Such characteristics can include maintaining pluripotency, cell morphology, gene expression proﬁles, and/or other ﬁanctional characteristics of na'1've cells. The terms "maintain,3, "maintaining," and "maintenance" can also encompass the propagation of cells and/or an increase in the number of naive cells being cultured. The terms include culture ions that t cells from converting to a primed or non-pluripotent state. The terms further include culture conditions that permit the cells to remain pluripotent and/or naive, while the cells may or may not continue to divide and increase in number.

In one embodiment, human iPS cells are cultured in vitro in a medium provided herein that is suitable for maintaining such cells in a naive or na'ive-looking state. In a particular e, human iPS cells can be cultured in a suitable medium for a period of l, 2, 5, 7, 10, 14, 21, or 28 days, or for a period of about 2 weeks, about 3 weeks, about 4 weeks, or more, so long as the cultured cells are maintained in a naive or looking state. Cells can be cultured for at least 1, 2, 3 or 4 weeks. Sometimes cells are cultured for 1-4 weeks. Human iPS cells can be maintained, for example, for any period of time sufficient for propagation of the cells in culture, genetic modiﬁcation of the cells, and/or subculture of the cells.

In another embodiment, human iPS cells or non-pluripotent cells ormed to express a pluripotent state, can be cultured on a substrate or feeder cell layer le for in vitro culture. In a particular example, cells are cultured on MATRIGELTM (BD Biosciences). In r example, cells are cultured on newborn human foreskin last (NuFF) feeder cells. In another example, cells are cultured on GELTREXTM (Life Technologies).

In a further embodiment, the doubling time of human iPS cells cultured in the t low osmolality medium is d as compared to primed human iPS cells or non-pluripotent cells transformed to express a pluripotent state. In a particular example, the doubling time of the present human iPS cells is between about 16-24 hours. 7. Sequence Identity The methods and itions provided herein employ a variety of different components of the targeted genomic integration system (i.e., se agents, recognition sites, insert nucleic acids, polynucleotides of interest, targeting vectors, selection markers and other components). It is recognized throughout the description that some components of the targeted genomic integration system can have active variants and fragments. Such components include, for e, se agents (i.e., engineered nuclease agents), nuclease agent ition sites, polynucleotides of interest, target sites and corresponding homology arms of the targeting vector. Biological activity for each of these components is described elsewhere herein.

As used herein, "sequence identity" or "identity" in the context of two polynucleotides or polypeptide sequences makes reference to the residues in the two sequences that are the same when aligned for maximum correspondence over a ed comparison window. When percentage of ce identity is used in reference to proteins it is recognized that residue positions which are not identical often differ by conservative amino acid substitutions, where amino acid residues are substituted for other amino acid residues with similar chemical properties (e.g., charge or hydrophobicity) and therefore do not change the functional properties of the molecule. When sequences differ in conservative substitutions, the percent sequence identity may be adjusted s to correct for the conservative nature of the substitution. Sequences that differ by such conservative substitutions are said to have nce similarity" or "similarity". Means for making this ment are well known to those of skill in the art. Typically this involves scoring a vative substitution as a partial rather than a full mismatch, thereby increasing the percentage sequence identity. Thus, for example, where an identical amino acid is given a score of l and a non-conservative substitution is given a score of zero, a conservative substitution is given a score n zero and l. The scoring of conservative substitutions is calculated, e.g., as implemented in the program E (Intelligenetics, Mountain View, rnia).

As used herein, "percentage of sequence identity" means the value determined by comparing two lly d sequences over a comparison window, wherein the portion of the polynucleotide sequence in the comparison window may comprise additions or ons (i.e., gaps) as compared to the reference sequence (which does not comprise additions or deletions) for optimal alignment of the two sequences.

The percentage is calculated by determining the number of positions at which the identical nucleic acid base or amino acid residue occurs in both sequences to yield the number ofmatched positions, dividing the number of matched positions by the total number of positions in the window of comparison, and lying the result by 100 to yield the percentage of sequence identity.

Unless otherwise stated, sequence ty/similarity values provided herein refer to the value obtained using GAP Version 10 using the following parameters: % identity and % similarity for a nucleotide sequence using GAP Weight of 50 and Length Weight of 3, and the dna.cmp scoring matrix; % identity and % similarity for an amino acid sequence using GAP Weight of 8 and Length Weight of 2, and the BLOSUM62 scoring matrix; or any equivalent program thereof. "Equivalent program" means any sequence comparison program that, for any two sequences in question, generates an alignment having cal nucleotide or amino acid residue matches and an identical t sequence identity when compared to the corresponding alignment generated by GAP Version 10.

Unless deﬁned otherwise, all technical and scientiﬁc terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein also can be used in the practice or testing of the bed invention, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited.

] It must be noted that as used herein and in the appended , the singular forms "a", "and", and "the" e plural references unless the context clearly dictates otherwise. All technical and scientiﬁc terms used herein have the same meaning.

The ations discussed herein are ed solely for their disclosure prior to the ﬁling date of the present application. Nothing herein is to be construed as an admission that the described invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication ed may be different from the actual publication dates, which may need to be independently conﬁrmed.

] The described invention may be embodied in other speciﬁc forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing cation, as indicating the scope of the invention.

] Non-limiting embodiments include: 1. A method for targeted modiﬁcation of a c locus of interest in a pluripotent rat cell, comprising (a) introducing into the pluripotent rat cell a large targeting vector (LTVEC) comprising an insert nucleic acid ﬂanked with a 5 ’ rat homology arm and a 3 ’ rat homology arm, wherein the sum total of the 5 ’ and the 3 ’ homology arms is at least 10 kb but less than 150 kb; and (b) identifying a genetically modiﬁed otent rat cell sing the targeted c ation at the genomic locus of interest, wherein the ed genetic modiﬁcation is capable of being transmitted through the germline. 2. The method of embodiment 1, wherein the targeted genetic modiﬁcation is biallelic. 3. The method of embodiment l or 2, wherein the pluripotent rat cell is a rat embryonic stem (ES) cell. 4. The method of embodiment l, 2 or 3, wherein the pluripotent rat cell is derived from a DA strain or an AC1 strain. 5. The method of any one of embodiments 1-4, wherein the pluripotent rat cell is characterized by expression of at least one pluripotency marker comprising Dnmt3L, Eras, Err-beta, FbxolS, Fgf4, Gdf3, Klf4, Lefl, LIF receptor, Lin28, Nanog, Oct4, SoxlS, Sox2, Utfl, or a combination thereof. 6. The method of any one of embodiments 1-4 wherein the pluripotent rat cell is characterized by one of more of the following characteristics: (a) lack of expression of one or more pluripotency markers comprising c-Myc, Ecatl and/or Rexol; (b) lack of expression of rmal markers comprising Brachyury and/or Bmpr2; (c) lack of expression of one or more endodermal markers comprising Gata6, Soxl7 and/or Sox7; or (d) lack of expression of one or more neural markers sing Nestin and/or Pax6. 7. The method of any one of embodiments 1-6, n the sum total of the 5’ and the 3’ homology arms of the LTVEC is from about 10 kb to about 30 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 120 kb, or from about 120 kb to 150 kb. 8. The method of any one of embodiments 1-6, wherein the sum total of the 5’ and the 3’ homology arms of the LTVEC is from about 16 kb to about 150 kb. 9. The method of any one of embodiments 1-8, wherein the targeted genetic modiﬁcation comprises: (a) a replacement of an endogenous rat nucleic acid sequence with a homologous or an ogous nucleic acid sequence; (b) a deletion of an endogenous rat nucleic acid sequence; (c) a deletion of an endogenous rat nucleic acid sequence, wherein the deletion ranges from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, or from about 150 kb to about 200 kb, from about 200 kb to about 300 kb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to about 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, or from about 2.5 Mb to about 3 Mb; ((1) an exogenous nucleic acid sequence ranging from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb; ( e) an exogenous nucleic acid sequence comprising a gous or an orthologous nucleic acid sequence; (1) a ic nucleic acid sequence comprising a human and a rat c acid sequence; (g) a conditional allele ﬂanked with peciﬁc inase target sequences; or (h) a reporter gene operably linked to a promoter active in a rat cell. ] 10. The method of any one of embodiments 1-9, wherein the genomic locus of interest comprises (i) a ﬁrst nucleic acid sequence that is complementary to the ’ rat homology arm; and (ii) a second nucleic acid sequence that is complementary to the 3 ’ rat homology arm. 1 1. The method of embodiment 10, wherein the ﬁrst and the second nucleic acid sequence is separated by at least 5 kb but less than 3 Mb. 12. The method of embodiment 10, n the ﬁrst and the second nucleic acid sequence is separated by at least 5 kb but less than 10 kb, at least 10 kb but less than 20 kb, at least 20 kb but less than 40 kb, at least 40 kb but less than 60 kb, at least 60 kb but less than 80 kb, at least about 80 kb but less than 100 kb, at least 100 kb but less than 150 kb, or at least 150 kb but less than 200 kb, at least about 200 kb but less than about 300 kb, at least about 300 kb but less than about 400 kb, at least about 400 kb but less than about 500 kb, at least about 500 kb but less than about 1 Mb, at least about 1 Mb but less than about 1.5 Mb, at least about 1.5 Mb but less than about 2 Mb, at least about 2 Mb but less than about 2.5 Mb, or at least about 2.5 Mb but less than about 3 Mb. 13. The method of any one of embodiment 1-12, n ucing step (a) further comprises introducing a second nucleic acid encoding a nuclease agent that promotes a homologous recombination between the targeting construct and the genomic locus of interest in the pluripotent rat cell. 14. The method of embodiment 13, wherein the nuclease agent comprises (a) a chimeric protein sing a zinc finger-based DNA binding domain fused to a FokI endonuclease; or (b) a chimeric protein comprising a ription Activator-Like Effector Nuclease (TALEN) fused to a FokI endonuclease. 15. The method of any one of embodiments 1-12, wherein introducing step (a) further comprises ucing into the pluripotent rat cell: (i) a ﬁrst expression construct comprising a first promoter operably linked to a ﬁrst c acid sequence encoding a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)- associated (Cas) protein, (ii) a second expression construct comprising a second promoter operably linked to a genomic target sequence linked to a guide RNA (gRNA), wherein the genomic target sequence is immediately ﬂanked on the 3’ end by a Protospacer Adjacent Motif (PAM) sequence. 16. The method of embodiment 15, wherein the c locus of interest comprises the nucleotide sequence of SEQ ID NO: 1. 17. The method of ment 15 or 16, wherein the gRNA comprises a third nucleic acid sequence ng a Clustered Regularly Interspaced Short Palindromic s (CRISPR) RNA (chNA) and a trans-activating CRISPR RNA (trachNA). 18. The method of embodiment 15, 16 or 17, wherein the Cas protein is Cas9. 19. The method of embodiment 15, l6, 17, or 18, wherein the gRNA comprises: (a) the chimeric RNA of the nucleic acid sequence of SEQ ID NO: 2; or (b) the chimeric RNA of the nucleic acid sequence of SEQ ID NO: 3. 20. The method of embodiment 17, wherein the chNA comprises SEQ ID NO: 4; SEQ ID NO: 5; or SEQ ID NO: 6. 21. The method of embodiment 17, wherein the A comprises SEQ ID NO: 7 or SEQ ID NO: 8. 22. A modiﬁed rat genomic locus comprising: (i) an insertion of a homologous or orthologous human nucleic acid sequence; (ii) a replacement of an endogenous rat nucleic acid sequence with the homologous or orthologous human c acid sequence; or (iii) a combination thereof, wherein the modiﬁed rat genomic locus is capable of being transmitted through the germline. 23. The modiﬁed rat genomic locus of embodiment 22, wherein the size of the insertion or replacement is from about 5 kb to about 400 kb. 24. The rat genomic locus of embodiment 22, n the size of the ion or replacement is from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb. 25. A method for making a zed rat, comprising: (a) targeting a genomic locus of interest in a pluripotent rat cell with a targeting uct comprising a human nucleic acid to form a genetically modiﬁed pluripotent rat cell; (b) introducing the genetically modiﬁed pluripotent rat cell into a host rat embryo; and (c) gestating the host rat embryo in a surrogate mother; n the ate mother es rat progeny comprising a modiﬁed genomic locus that comprises: (i) an insertion of a human nucleic acid sequence; (ii) a replacement of the rat nucleic acid sequence at the genomic locus of interest with a homologous or orthologous human nucleic acid sequence; (iii) a chimeric nucleic acid sequence comprising a human and a rat nucleic acid sequence; or (iv) a combination thereof, wherein the modiﬁed genomic locus is e of being transmitted through the germline. 26. The method of embodiment 25, wherein the targeting construct is a large targeting vector (LTVEC), and the sum total of the 5 ’ and the 3 ’ homology arms of the LTVEC is at least 10 kb but less than 150 kb. 27. The method of embodiment 26, wherein the sum total of the 5’ and the 3’ homology arms of the targeting uct is from about 10 kb to about 30 kb, from about 20 kb to 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, or from about 80 kb to about 100 kb, from about 100 kb to about 120 kb, or from about 120 kb to 150 kb. ] 28. The method of embodiment 25, 26 or 27, wherein the human nucleic acid sequence is at least 5 kb but less than 400 kb. 29. The method of embodiment 25, 26, or 27, wherein the human nucleic acid sequence is at least 5 kb but less than 10 kb, at least 10 kb but less than 20 kb, at least 20 kb but less than 40 kb, at least 40 kb but less than 60 kb, at least 60 kb but less than 80 kb, at least about 80 kb but less than 100 kb, at least 100 kb but less than 150 kb, at least 150 kb but less than 200 kb, at least 200 kb but less than 250 kb, at least 250 kb but less than 300 kb, at least 300 kb but less than 350 kb, or at least 350 kb but less than 400 kb. 30. The method of any one of embodiments 25-29, wherein the pluripotent rat cell is a rat nic stem (ES) cell. 3 l. The method of any one of embodiments 25-30, wherein the pluripotent rat cell is derived from a DA strain or an AC1 . 32. The method of any one of embodiments 25-31, wherein the pluripotent rat cell is characterized by expression of at least one pluripotency marker comprising Dnmt3L, Eras, Err-beta, Fbxol5, Fgf4, Gdf3, Klf4, Lefl, LIF receptor, Lin28, Nanog, Oct4, Soxl5, Sox2, Utfl, or a combination thereof. 33. The method of any one of embodiment 25-31, wherein the pluripotent rat cell is characterized by one or more of the ing es: (a) lack of expression of one or more pluripotency markers comprising c-Myc, Ecatl and/or Rexol; (b) lack of expression of one or more mesodermal markers comprising Brachyury and/or Bmpr2; (c) lack of expression of one or more endodermal markers comprising Gata6, Soxl7, and/or Sox7; or (d) lack of expression of one or more neural markers sing Nestin and/or Pax6. 34. A modiﬁed rat comprising a humanized genomic locus, wherein the humanized genomic locus comprises: (i) an insertion of a homologous or orthologous human nucleic acid sequence; (ii) a replacement of a rat nucleic acid sequence at an endogenous genomic locus with a homologous or orthologous human nucleic acid sequence; (iii) a chimeric nucleic acid sequence comprising a human and a rat nucleic acid sequence or (iV) a combination thereof, wherein the zed genomic locus is capable of being transmitted through the germline. 35. A rat or rat cell comprising a targeted genetic modiﬁcation in its genomic locus, wherein the genomic locus is an eukin-2 receptor gamma locus, an ApoE locus, a Rag] locus, a Rag2 locus, or a Rag2/Rag1 locus, wherein the targeted genetic modiﬁcation comprises: (a) a deletion of an endogenous rat nucleic acid sequence at the genomic locus; (b) an insertion of a homologous nucleic acid, an orthologous nucleic acid, or a chimeric c acid sing a human and a rat nucleic acid sequence, or (c) a combination thereof, wherein the targeted genetic modiﬁcation is transmissible through the germline of the rat or a rat propagated from the rat cell. 36. The rat or rat cell of embodiment 35, n (a) the deletion of the endogenous rat nucleic acid at the genomic locus is at least about 10 kb; or (b) the deletion of the endogenous rat nucleic acid at the genomic locus is from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, or from about 150 kb to about 200 kb, from about 200 kb to about 300 kb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to about 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, or from about 2.5 Mb to about 3 Mb; (c) the insertion of the ous nucleic acid ce at the genomic locus is at least about 5 kb; or (d) the insertion of the exogenous nucleic acid sequence at the genomic locus is from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb. 37. The rat or rat cell of embodiment 35 or 36, wherein (a) the targeted genetic modiﬁcation at the Interleukin-2 receptor gamma locus results in a decrease in or absence of Interleukin-2 receptor gamma protein activity; (b) the targeted genetic modiﬁcation at the ApoE locus results in a decrease in or absence of ApoE protein activity; (c) the targeted genetic modiﬁcation at the Rag] locus results in a decrease in or absence of Ragl protein ty; (d) the targeted genetic modiﬁcation at the Rag2 locus results in a decrease in or absence of Rag2 protein actiVity; or (e) the targeted genetic modiﬁcation at the Rag2/Ragl locus results in a se in or absence of Rag2 protein actiVity and Ragl actiVity. ] 38. The rat or rat cell of embodiment 35, 36, or 37, wherein the targeted genetic modiﬁcation of the Interleukin-2 receptor gamma locus comprises: (a) a deletion of the entire rat Interleukin-2 receptor gamma coding region or a portion thereof; (b) a replacement of the entire rat Interleukin-2 or gamma coding region or a portion thereof with a human Interleukin-2 receptor gamma coding region or a portion thereof; (c) a replacement of an omain of the rat eukin-2 receptor gamma coding region with the ecto-domain of a human eukin-2 receptor gamma; or (d) at least a 3 kb deletion of the Interleukin-2 receptor gamma locus. 39. The rat or rat cell of any one of embodiments 35-37, wherein the targeted c modiﬁcation of the ApoE locus comprises: (a) a deletion of the entire ApoE coding region or a portion thereof; or (b) at least a 1.8 kb deletion of the ApoE locus comprising the ApoE coding region. 40. The rat or rat cell of any one of embodiments 35-37, wherein the targeted genetic modiﬁcation of the Rag2 locus comprises: (a) a deletion of the entire Rag2 coding region or a portion thereof; (b) at least a 5.7 kb deletion of the Rag2 locus comprising the Rag2 coding region. 41. The rat or rat cell of any one of ments 35-37, wherein the ed genetic modiﬁcation of the Rag2/Rag] locus comprises: (a) a on of the entire Rag2 coding region or a n thereof and a deletion of the entire Ragl coding region or portion thereof; or (b) a deletion of at least 16 kb of the Rag2/Rag1 locus comprising the Rag2 coding region. 42. The rat or rat cell of any one of ment 35-41, wherein the targeted genetic modiﬁcation ses an insertion of an expression cassette comprising a selective marker at the Interleukin-2 receptor gamma locus, the ApoE locus, the Rag] locus, the Rag2 locus, or the Rag2/Rag1 locus. ] 43. The rat or rat cell of any one of embodiments 42, wherein the expression cassette comprises a lacZ gene ly linked to the endogenous promoter at the genomic locus and a human ubiquitin promoter operably linked to a selective marker. 44. The rat or rat cell of any one of embodiments 35-43, n the targeted genetic modiﬁcation in the Interleukin-2 receptor gamma locus, the ApoE locus, the Rag] locus, the Rag2 locus or the Rag2/Rag1 locus ses the insertion of a self- deleting ion cassette. 45. The rat or rat cell of ment 44, wherein the self-deleting selection cassette ses a selective marker gene operably linked to a er active in the rat cell and a recombinase gene operably linked to a male germ cell-speciﬁc promoter, wherein the self-deleting cassette is ﬂanked by recombination recognition sites recognized by the recombinase. 46. The rat or rat cell of embodiment 45, wherein (a) the male germ cell- speciﬁc promoter is a Protamine-l promoter; or (b) the recombinase gene encodes Cre, and the recombination recognition sites are loxP sites. 47. The rat or rat cell of any one of embodiments 35-46, wherein the insertion of the exogenous nucleic acid sequence at the genomic locus comprises a reporter nucleic acid operably linked to an endogenous Interleukin-2 receptor gamma promoter, an endogenous ApoE er, an endogenous Rag] promoter, or an endogenous Rag2 promoter. 48. The rat or rat cell of embodiment 47, wherein the reporter nucleic acid encodes a reporter sing B-galactosidase, mPlum, mCherry, thomato, mStrawberry, J-Red, DsRed, mOrange, mKO, mCitrine, Venus, YPet, enhanced yellow ﬂuorescent protein (EYFP), Emerald, enhanced green ﬂuorescent protein (EGFP), CyPet, cyan ﬂuorescent protein (CFP), Cerulean, T-Sapphire, rase, alkaline phosphatase, or a combination thereof. 49. The rat cell of any one of embodiments 35-48, wherein the rat cell is a pluripotent rat cell or a rat embryonic stem (ES) cell. ] 5 0. The rat cell of embodiment 49, wherein the pluripotent rat cell or the rat embryonic stem (ES) cell (a) is derived from a DA strain or an AC1 strain; (b) is characterized by expression of at least one pluripotency marker sing Dnmt3 L, Eras, Err-beta, FbxolS, Fgf4, Gdf3, Klf4, Lefl, LIF receptor, Lin28, Nanog, Oct4, SoxlS, Sox2, Utfl, or a combination thereof; or (c) is characterized by one or more of the following characteristics: (i) lack of expression of one or more pluripotency markers comprising c-Myc, Ecatl and/or Rexol; (ii) lack of expression of rmal markers comprising ury and/or Bmpr2; (iii) lack of expression of one or more rmal markers comprising Gata6, Soxl7 and/or Sox7; or (iv) lack of expression of one or more neural markers comprising Nestin and/or Pax6. 51. A method for modifying a target genomic locus in an Interleukin-2 receptor gamma locus, an ApoE locus, a Rag] locus, a Rag2 locus or a Rag2/Rag1 locus in a pluripotent rat cell, the method comprising: (a) introducing into the pluripotent rat cell a targeting vector comprising an insert nucleic acid ﬂanked with 5’ and 3’ rat homology arms homologous to the target genomic locus, (b) identifying a genetically modiﬁed pluripotent rat cell comprising a targeted genetic modiﬁcation at the target genomic locus, wherein the targeted genetic modification is capable of being itted through the germline of a rat ated from the pluripotent rat cell. 52. The method of embodiment 51, n the targeting vector is a large targeting vector (LTVEC) wherein the sum total of the 5 ’ and the 3 ’ rat homology arms is at least about 10 kb but less than about 150 kb. 53. The method of embodiment 51 or 52, wherein introducing the targeting vector into the pluripotent rat cell leads to: (i) a on of an endogenous rat nucleic acid sequence at the target genomic locus; (ii) an insertion of an exogenous nucleic acid sequence at the target genomic locus; or (iii) a combination f 54. The method of embodiment 53, wherein (a) the deletion of the endogenous rat nucleic acid at the genomic locus is at least about 10 kb; or (b) the deletion of the endogenous rat nucleic acid at the genomic locus is from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, or from about 150 kb to about 200 kb, from about 200 kb to about 300 kb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to about 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, or from about 2.5 Mb to about 3 Mb; (c) the insertion of the exogenous nucleic acid ce at the genomic locus is at least about 5 kb; or. (d) the insertion of the exogenous nucleic acid sequence at the genomic locus is from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb. 55. The method of any one of embodiment 5 1-54, wherein (a) the targeted genetic modiﬁcation at the Interleukin-2 or gamma locus results in a decrease in or absence of eukin-2 receptor gamma protein activity; (b) the targeted genetic modiﬁcation at the ApoE locus results in a decrease in or absence of ApoE protein activity; (c) the targeted genetic modiﬁcation at the Rag] locus results in a decrease in or absence of Ragl protein ty; (d) the targeted genetic modiﬁcation at the Rag2 locus results in a decrease in or absence of Rag2 protein actiVity; or (e) the targeted genetic modiﬁcation at the Rag2/Ragl locus results in a decrease in or absence of Rag2 protein actiVity and i Ragl protein actiVity. 56. The method of any one of embodiment 5 1-54, wherein the targeted genetic modiﬁcation of the eukin-2 or gamma locus comprises (a) a deletion of the entire rat Interleukin-2 receptor gamma coding region or a portion f; (b) a replacement of the entire rat eukin-2 receptor gamma coding region or a portion thereof with a human eukin-2 receptor gamma coding region or a portion thereof; (c) a replacement of an ecto-domain of the rat Interleukin-2 receptor gamma coding region with the ecto-domain of a human Interleukin-2 receptor gamma; or (d) at least a 3 kb deletion of the eukin-2 receptor gamma locus comprising the Interleukin-2 receptor gamma coding . 57. The method of any one of embodiment 51-55, wherein the targeted genetic modiﬁcation of the ApoE locus comprises: (a) a deletion of the entire ApoE coding region or a portion thereof; or (b) at least a 1.8 kb deletion of the ApoE locus comprising the ApoE coding region. 58. The method of any one of embodiment 51-55, wherein the targeted genetic modiﬁcation of the Rag2 locus ses: (a) a deletion of the entire Rag2 coding region or a portion thereof; or (b) at least a 5.7 kb deletion of the Rag2 locus comprising the Rag2 coding region. 59. The method of any one of ment 51-55, n the targeted genetic modiﬁcation of the Ragl/Rag2 locus comprises: (a) a deletion of the entire Rag2 coding region or a portion thereof and a deletion of the entire Rag] coding region or portion thereof; or (b) a deletion of at least 16 kb of the Rag2/Rag1 locus comprising the Rag2 and Rag] coding regions. 60. The method of any one of embodiment 51-59, n the insert nucleic acid comprises an expression cassette comprising a polynucleotide encoding a selective marker. 61. The method embodiment 60, n the expression cassette comprises a lacZ gene operably linked to an endogenous promoter at the genomic locus and a human ubiquitin promoter operably linked to a selective marker gene. 62. The method of any one of embodiments 51-60, wherein the insert nucleic acid comprises a eleting selection te. 63. The method of embodiment 62, wherein the self-deleting selection cassette comprises a selective marker operably linked to a er active in the rat pluripotent cell and a polynucleotide encoding a recombinase operably linked to a male germ cell-speciﬁc promoter, wherein the self-deleting cassette is ﬂanked by recombination recognition sites recognized by the recombinase. 64. The method of embodiment 63, wherein (a) the male germ cell- speciﬁc promoter is a ine-l promoter; or (b) the inase gene encodes Cre and the recombination recognition sites are loxP sites. 65. The method of embodiment 53, wherein the insertion of the exogenous nucleic acid sequence at the genomic locus comprises a reporter nucleic acid ce operably linked to an endogenous Interleukin-2 receptor gamma promoter, an endogenous ApoE promoter, an endogenous Rag] promoter, or an nous Rag2 promoter. 66. The method of embodiment 65, wherein the reporter nucleic acid sequence encodes a reporter comprising B-galactosidase, mPlum, mCherry, thomato, mStrawberry, J-Red, DsRed, mOrange, mKO, mCitrine, Venus, YPet, enhanced yellow ﬂuorescent protein (EYFP), Emerald, enhanced green cent protein (EGFP), CyPet, cyan ﬂuorescent protein (CFP), Cerulean, T-Sapphire, luciferase, alkaline phosphatase, or a combination thereof. ] 67. The method of any one of embodiment 51-66, wherein the pluripotent rat cell is a rat embryonic stem (ES) cell. ] 68. The method of any one of embodiment 51-67, n the pluripotent rat cell (a) is derived from a DA strain or an AC1 strain; or (b) is terized by expression of a pluripotency marker comprising Oct-4, Sox-2, alkaline phosphatase, or a ation thereof; or (c) is characterized by one or more of the ing characteristics: (i) lack of expression of one or more pluripotency markers comprising c- Myc, Ecatl , and/or Rexol; (ii) lack of expression of mesodermal markers comprising Brachyury and/or Bmpr2; (iii) lack of expression of one or more endodermal markers comprising Gata6, Soxl7 and/or Sox7; or (iv) lack of expression of one or more neural markers comprising Nestin and/or Pax6. 69. The method of any one of embodiment 51-68, ﬁarther comprising fying the targeted genetic modification at the target c locus, wherein the identiﬁcation step employs a quantitative assay for assessing a modification of allele (MOA) at the target genomic locus. 70. The method of any one of embodiment 51-69, wherein introducing step (a) further comprises introducing a second nucleic acid encoding a nuclease agent that promotes a homologous recombination between the targeting vector and the target c locus in the pluripotent rat cell. ] 71. The method of embodiment 70, wherein the nuclease agent ses a ic protein comprising a zinc ﬁnger-based DNA binding domain ﬁlsed to a FokI endonuclease. 72. The method of ment 71, wherein the method results in bi- allelic modiﬁcation of the target c locus. 73. The method of any one of embodiment 51-70, wherein introducing step (a) further comprises introducing into the pluripotent rat cell: (i) a ﬁrst expression construct comprising a ﬁrst promoter operably linked to a ﬁrst nucleic acid sequence encoding a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)- associated (Cas) protein, (ii) a second expression construct comprising a second promoter operably linked to a genomic target sequence linked to a guide RNA (gRNA), wherein the c target sequence is ately ﬂanked on the 3 ’ end by a Protospacer Adjacent Motif (PAM) sequence. 74. The method of embodiment 73, wherein the genomic locus of st comprises the nucleotide sequence of SEQ ID NO: 1. 75. The method of embodiment 73 or 74, wherein the gRNA comprises a third nucleic acid sequence encoding a Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) RNA (chNA) and a trans-activating CRISPR RNA (trachNA). 76. The method of embodiment 73, wherein the Cas protein is Cas9. ] 77. The method of embodiment 73, 74, or 75, wherein the gRNA comprises: (a) the chimeric RNA of the nucleic acid ce of SEQ ID NO: 2; or (b) the chimeric RNA of the nucleic acid sequence of SEQ ID NO: 3. 78. The method of embodiment 75, wherein the chNA comprises SEQ ID NO: 4; SEQ ID NO: 5; or SEQ ID NO: 6. 79. The method of embodiment 75, wherein the trachNA comprises SEQ ID NO: 7 or SEQ ID NO: 8. 80. The rat or rat cell of any one of embodiments 35-50, wherein the rat or rat cell comprises ed genetic modiﬁcations at the Interleukin-2 receptor gamma locus, the ApoE locus, the Rag] locus, the Rag2 locus, and/or the Rag2/Rag1 locus. 2014/060788 81. The rat or rat cell of embodiment 80, wherein the rat or rat cell comprises targeted c modiﬁcations at the Interleukin-2 receptor gamma locus and the Rag2/Rag1 locus.

] Additional non-limiting embodiments include: 1. A method for modifying a genomic locus of interest in a eukaryotic cell, comprising: (a) introducing into the eukaryotic cell: (i) a large ing vector (LTVEC) comprising a ﬁrst nucleic acid ﬂanked with a 5’ homology arm and a 3’ homology arm, wherein the LTVEC is at least 10 kb; (ii) a ﬁrst expression construct sing a ﬁrst promoter operably linked to a second nucleic acid encoding a Cas protein, (iii) a second sion construct comprising a second er operably linked to a third nucleic acid encoding a guide RNA (gRNA) comprising a nucleotide sequence that hybridizes to a target sequence and a trans-activating CRISPR RNA (trachNA), wherein the ﬁrst and the second promoters are active in the eukaryotic cell; and (b) identifying a modiﬁed otic cell comprising a targeted genetic modiﬁcation at the genomic locus of interest. 2. The method of embodiment 1, n the targeted genetic modiﬁcation is a biallelic genetic modiﬁcation. 3. The method of embodiment 1, wherein the LTVEC is at least 15 kb, at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, or at least 90 kb. 4. The method of embodiment 1, wherein the LTVEC is at least 100 kb, at least 150 kb, or at least 200 kb. 5. The method of embodiment 1, wherein the eukaryotic cell is a mammalian cell. 6. The method of embodiment 5, wherein the mammalian cell is a ﬁbroblast. 7. The method of embodiment 1, wherein the eukaryotic cell is a pluripotent cell. 8. The method of ment 7, wherein the pluripotent cell is a human pluripotent cell. 9. The method of embodiment 8, wherein the human pluripotent cell is a human embryonic stem (ES) cell or a human adult stem cell. 10. The method of embodiment 8, wherein the human pluripotent cell is a pmentally restricted human progenitor cell. ll. The method of embodiment 8, wherein the human pluripotent cell is a human induced pluripotent stem (iPS) cell. 12. The method of embodiment 1, wherein the Cas protein is Cas9. 13. The method of embodiment 1, wherein the target sequence is immediately ﬂanked on the 3’ end by a Protospacer Adjacent Motif (PAM) sequence. 14. The method of embodiment 1, wherein the sum total of the 5’ and the 3’ homology arms is from about 10 kb to about 150 kb. 15. The method of embodiment 1, wherein the sum total of the 5’ and the 3’ homology arms of the LTVEC is from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 120 kb, or from about 120 kb to 150 kb. 16. The method of embodiment 1, wherein the targeted genetic modiﬁcation comprises:(a) a ement of an endogenous nucleic acid sequence with a homologous or an orthologous nucleic acid ce; (b) a on of an endogenous nucleic acid sequence; (c) a deletion of an endogenous nucleic acid sequence, n the deletion ranges from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, or from about 150 kb to about 200 kb, from about 200 kb to about 300 kb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to about 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, or from about 2.5 Mb to about 3 Mb; (d) insertion of an ous c acid sequence; (e) insertion of an exogenous nucleic acid sequence ranging from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb; (f) insertion of an exogenous nucleic acid sequence comprising a homologous or an orthologous nucleic acid sequence; (g) insertion of a chimeric nucleic acid sequence comprising a human and a non-human nucleic acid sequence; (h) insertion of a conditional allele ﬂanked with site-speciﬁc recombinase target ces; (i) insertion of a selectable marker or a reporter gene operably linked to a third promoter active in the pluripotent cell; or (j ) a combination 17. The method of embodiment 1, wherein the genomic locus of st ses (i) a 5’ target sequence that is homologous to the 5’ homology arm; and (ii) a 3’ target sequence that is homologous to the 3’ homology arm. 18. The method of embodiment 17, wherein the 5’ target sequence and the 3’ target sequence is ted by at least 5 kb but less than 3 Mb. 19. The method of embodiment 17, wherein the 5’ target sequence and the 3’ target sequence is separated by at least 5 kb but less than 10 kb, at least 10 kb but less than 20 kb, at least 20 kb but less than 40 kb, at least 40 kb but less than 60 kb, at least 60 kb but less than 80 kb, at least about 80 kb but less than 100 kb, at least 100 kb but less than 150 kb, or at least 150 kb but less than 200 kb, at least about 200 kb but less than about 300 kb, at least about 300 kb but less than about 400 kb, at least about 400 kb but less than about 500 kb, at least about 500 kb but less than about 1 Mb, at least about 1 Mb but less than about 1.5 Mb, at least about 1.5 Mb but less than about 2 Mb, at least about 2 Mb but less than about 2.5 Mb, or at least about 2.5 Mb but less than about 3 Mb. 20. The method of embodiment 1, wherein the genomic locus of st comprises the Interleukin-2 receptor gamma locus, the ApoE locus, the Rag] locus, the Rag2 locus, or both of the Rag] and the Rag2 loci. 21. The method of embodiment 1, wherein the first and the second expression constructs are on a single nucleic acid molecule. 22. A method for modifying a genome, comprising ng the genome to a Cas protein and a CRISPR RNA in the presence of a large targeting vector ) comprising a nucleic acid sequence of at least 10 kb, wherein following exposure to the WO 88643 Cas n, the CRISPR RNA, and the LTVEC, the genome is modiﬁed to contain at least 10 kb nucleic acid sequence. 23. The method of embodiment 22, n the LTVEC comprises a nucleic acid sequence of at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, or at least 90 kb. 24. The method of embodiment 22, wherein the LTVEC comprises a nucleic acid sequence of at least 100 kb, at least 150 kb, or at least 200 kb. 25. A method for modifying a genome, comprising contacting the genome with a Cas protein, a CRISPR RNA that hybridizes to a target sequence, and a trachNA in the presence of a large targeting vector (LTVEC), wherein the LTVEC is at least 10 kb and comprises a ﬁrst nucleic acid ﬂanked with a 5 ’ homology arm and a 3’ homology arm, wherein following contacting with the Cas protein, CRISPR RNA, and trachNA in the presence of the LTVEC, the genome is modiﬁed at a genomic locus of interest to contain the ﬁrst nucleic acid. 26. The method of embodiment 25, wherein the genome is in a eukaryotic cell, and the Cas protein, the CRISPR RNA, the trachNA, and the LTVEC are uced into the eukaryotic cell 27. The method of embodiment 26, further comprising identifying a modiﬁed otic cell comprising a targeted genetic ation at the genomic locus of st. 28. The method of ment 26 or 27, wherein the CRISPR RNA and the trachNA are introduced together in the form of a single guide RNA . 29. The method of embodiment 26 or 27, wherein the CRISPR RNA and the trachNA are uced separately. 30. The method of any one of embodiments 26-29, wherein: (a) the Cas protein is introduced into the eukaryotic cell in the form of a protein, a messenger RNA (mRNA) encoding the Cas protein, or a DNA encoding the Cas protein; (b) the CRISPR RNA is introduced into the eukaryotic cell in the form of an RNA or a DNA encoding the CRISPR RNA; and (c) the trachNA is introduced into the eukaryotic cell in the form of an RNA or a DNA encoding the trachNA. 3 l. The method of embodiment 30, wherein the Cas protein, the CRISPR RNA, and the trachNA are uced into the eukaryotic cell as a protein-RNA complex. 32. The method of embodiment 30, wherein: (a) the DNA encoding the Cas protein is in the form of a ﬁrst expression uct comprising a ﬁrst promoter operably linked to a second nucleic acid ng the Cas protein; (b) the DNA encoding the CRISPR RNA is in the form of a second expression construct comprising a second promoter operably linked to a third nucleic acid ng the CRISPR RNA; and (c) the DNA encoding the trachNA is in the form of a third expression construct comprising a third promoter operably linked to a fourth nucleic acid encoding the trachNA, wherein the ﬁrst, second, and third promoters are active in the eukaryotic cell. 33. The method of embodiment 32, wherein the ﬁrst, second, and/or third sion constructs are on a single nucleic acid molecule. 34. The method of embodiment 30, wherein: (a) the DNA ng the Cas protein is in the form of a ﬁrst expression construct comprising a ﬁrst promoter operably linked to a second nucleic acid encoding the Cas protein; and (b) the DNA encoding the CRISPR RNA and the DNA encoding the trachNA are in the form of a second expression construct comprising a second promoter operably linked to a third nucleic acid ng a gRNA comprising the CRISPR RNA and the trachNA; wherein the ﬁrst and second promoters are active in the eukaryotic cell. 35. The method of embodiment 34, wherein the ﬁrst and the second expression constructs are on a single nucleic acid molecule. 36. The method of any one of embodiments 27-35, wherein the targeted c ation comprises simultaneous deletion of an endogenous nucleic acid ce at the genomic locus of st and insertion of the ﬁrst nucleic acid at the genomic locus of interest. 37. The method of any one of embodiments 27-36, wherein the targeted genetic modiﬁcation is a biallelic genetic modiﬁcation. 38. The method of embodiment 37, wherein the biallelic genetic ation comprises deletion of an endogenous nucleic acid sequence and insertion of the ﬁrst c acid at the genomic locus of interest in two homologous chromosomes. 2014/060788 39. The method of any one of embodiments 27-36, wherein the modiﬁed eukaryotic cell is hemizygous at the genomic locus of interest. 40. The method of embodiment 39, wherein the targeted genetic modiﬁcation at the genomic locus of interest in one chromosome comprises deletion of an nous nucleic acid ce and insertion of the ﬁrst nucleic acid. 41. The method of embodiment 39, wherein the ed genetic modiﬁcation comprises: (1) deletion of an endogenous nucleic acid sequence at the genomic locus of interest in two homologous chromosomes; and (2) insertion of the ﬁrst nucleic acid into the genomic locus of interest in a ﬁrst chromosome and disruption of the genomic locus of interest in a second chromosome. 42. The method of any one of embodiments 25-41, wherein the LTVEC is at least 15 kb, at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, or at least 90 kb. 43. The method of any one of embodiments 25-42, wherein the LTVEC is at least 100 kb, at least 150 kb, or at least 200 kb. 44. The method of any one of embodiments 25-43, wherein the ﬁrst nucleic acid is at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, at least 90 kb, at least 100 kb, at least 150 kb, at least 200 kb, at least 250 kb, or at least 300 kb. 45. The method of any one of embodiments 26-44, wherein the eukaryotic cell is a mammalian cell. 46. The method of embodiment 45, wherein the ian cell is a ﬁbroblast. 47. The method of any one of embodiments 26-43, wherein the eukaryotic cell is a pluripotent cell. 48. The method of embodiment 47, wherein the pluripotent cell is a non- human otent cell. 49. The method of ment 48, wherein the non-human pluripotent cell is a rodent pluripotent cell. 50. The method of embodiment 49, wherein the rodent pluripotent cell is a mouse or rat embryonic stem (ES) cell. 5 l. The method of embodiment 47, wherein the pluripotent cell is a human pluripotent cell. 52. The method of embodiment 51, wherein the human pluripotent cell is a human embryonic stem (ES) cell or a human adult stem cell. 53. The method of embodiment 51, wherein the human pluripotent cell is a developmentally restricted human progenitor cell. 54. The method of embodiment 51, wherein the human pluripotent cell is a human induced pluripotent stem (iPS) cell. 55. The method of any one of embodiments 25-54, wherein the Cas protein is Cas9. 56. The method of any one of embodiments 25-55, wherein the target sequence is immediately ﬂanked by a Protospacer nt Motif (PAM) sequence. 57. The method of any one of ments 25-56, wherein the sum total of the 5’ and the 3’ homology arms of the LTVEC is from about 10 kb to about 150 kb. 58. The method of any one of ments 25-57, wherein the sum total of the 5’ and the 3 ’ homology arms of the LTVEC is from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 120 kb, or from about 120 kb to 150 kb. ] 59. The method of any one of embodiments 27-58, wherein the targeted genetic modiﬁcation ses: (a) a replacement of an endogenous nucleic acid sequence with a homologous or an orthologous nucleic acid ce; (b) a deletion of an endogenous nucleic acid sequence; (c) a deletion of an endogenous nucleic acid sequence, wherein the deletion ranges from about 5 kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, or from about 150 kb to about 200 kb, from about 200 kb to about 300 kb, from about 300 kb to about 400 kb, from about 400 kb to about 500 kb, from about 500 kb to about 1 Mb, from about 1 Mb to about 1.5 Mb, from about 1.5 Mb to about 2 Mb, from about 2 Mb to about 2.5 Mb, or from about 2.5 Mb to about 3 Mb; (d) insertion of an ous nucleic acid sequence; (e) insertion of an exogenous nucleic acid sequence ranging from about 5kb to about 10 kb, from about 10 kb to about 20 kb, from about 20 kb to about 40 kb, from about 40 kb to about 60 kb, from about 60 kb to about 80 kb, from about 80 kb to about 100 kb, from about 100 kb to about 150 kb, from about 150 kb to about 200 kb, from about 200 kb to about 250 kb, from about 250 kb to about 300 kb, from about 300 kb to about 350 kb, or from about 350 kb to about 400 kb; (l) insertion of an exogenous nucleic acid sequence comprising a homologous or an orthologous nucleic acid sequence; (g) insertion of a chimeric nucleic acid sequence comprising a human and a non-human nucleic acid sequence; (h) insertion of a conditional allele ﬂanked with site- speciﬁc inase target sequences; (i) insertion of a selectable marker or a reporter gene ly linked to a third promoter active in the pluripotent cell; or (j ) a combination thereof. 60. The method of any one of embodiments 25-59, wherein the genomic locus of interest ses (i) a 5’ target sequence that is gous to the 5’ homology arm; and (ii) a 3’ target sequence that is gous to the 3’ homology arm. 61. The method of embodiment 60, wherein the 5’ target sequence and the 3’ target sequence are separated by at least 5 kb but less than 3 Mb. 62. The method of embodiment 60, wherein the 5’ target sequence and the 3’ target sequence are separated by at least 5 kb but less than 10 kb, at least 10 kb but less than 20 kb, at least 20 kb but less than 40 kb, at least 40 kb but less than 60 kb, at least 60 kb but less than 80 kb, at least about 80 kb but less than 100 kb, at least 100 kb but less than 150 kb, or at least 150 kb but less than 200 kb, at least about 200 kb but less than about 300 kb, at least about 300 kb but less than about 400 kb, at least about 400 kb but less than about 500 kb, at least about 500 kb but less than about le, at least about 1 Mb but less than about 1.5 Mb, at least about 1.5 Mb but less than about 2 Mb, at least about 2 Mb but less than about 2.5 Mb, or at least about 2.5 Mb but less than about 3 Mb. 63. The method of embodiment 60, wherein the 5’ target sequence and the 3’ target sequence are separated by at least 20 kb, at least 30 kb, at least 40 kb, at least 50 kb, at least 60 kb, at least 70 kb, at least 80 kb, at least 90 kb, at least 100 kb, at least 110 kb, at least 120 kb, at least 130 kb, at least 140 kb, at least 150 kb, at least 160 kb, at least 170 kb, at least 180 kb, at least 190 kb, or at least 200 kb. 64. The method of any one of ments 25-63, wherein the genomic locus of interest comprises the Interleukin-2 receptor gamma locus, the ApoE locus, the Rag] locus, the Rag2 locus, or both of the Rag] and the Rag2 loci. 65. The method of any one of embodiments 25-63, wherein the genomic locus of interest comprises the Adamts5 locus, the Trpal locus, the Folk] locus, or the Erbb4 locus. 66. The method of any one of ments 25-63, wherein the genomic locus of interest comprises the Lrp5 locus. 67. A method for producing an F0 generation non-human animal that comprises a targeted genetic ation at a genomic locus of interest, the method comprising: (a) contacting the genome in a non-human ES cell with a Cas protein, a CRISPR RNA, and a trachNA in the presence of a large targeting vector (LTVEC) to form a d non-human ES cell, wherein the LTVEC is at least 10 kb and comprises a ﬁrst nucleic acid ﬂanked with a 5’ homology arm and a 3’ homology arm; (b) identifying the modiﬁed man ES cell comprising the targeted genetic modiﬁcation at the genomic locus of interest; (c) introducing the modiﬁed non-human ES cell into a non-human host embryo; and (d) gestating the non-human host embryo in a ate , wherein the surrogate mother produces the F0 generation non-human animal comprising the targeted genetic modiﬁcation at the genomic locus of interest. 68. The method of embodiment 67, wherein the CRISPR RNA and the trachNA are introduced together in the form of a single guide RNA (gRNA). 69. The method of embodiment 67, wherein the CRISPR RNA and the trachNA are introduced separately. 70. The method of any one of embodiments 67-69, wherein: (a) the Cas protein is uced into the non-human ES cell in the form of a n, a messenger RNA (mRNA) encoding the Cas protein, or a DNA encoding the Cas protein; (b) the CRISPR RNA is introduced into the non-human ES cell in the form of an RNA or a DNA encoding the CRISPR RNA; and (c) the trachNA is introduced into the man ES cell in the form of an RNA or a DNA encoding the trachNA. 2014/060788 71. The method of embodiment 70, n the Cas protein, the CRISPR RNA, and the trachNA are introduced into the man ES cell as a protein-RNA complex. 72. The method of embodiment 70, wherein: (a) the DNA encoding the Cas protein is in the form of a ﬁrst expression construct comprising a ﬁrst promoter operably linked to a second nucleic acid encoding the Cas protein; (b) the DNA encoding the CRISPR RNA is in the form of a second expression construct comprising a second promoter operably linked to a third nucleic acid encoding the CRISPR RNA; and (c) the DNA encoding the trachNA is in the form of a third expression construct comprising a third promoter operably linked to a fourth nucleic acid encoding the trachNA, wherein the ﬁrst, second, and third promoters are active in the non-human ES cell. 73. The method of embodiment 72, wherein the ﬁrst, second, and third expression ucts are on a single nucleic acid molecule. 74. The method of embodiment 70, wherein: (a) the DNA encoding the Cas protein is in the form of a ﬁrst expression construct comprising a ﬁrst promoter operably linked to a second nucleic acid encoding the Cas protein; and (b) the DNA encoding the CRISPR RNA and the DNA encoding the trachNA are in the form of a second expression uct sing a second promoter ly linked to a third nucleic acid encoding a gRNA comprising the CRISPR RNA and the trachNA; wherein the ﬁrst and second ers are active in the non-human ES cell. 75. The method of embodiment 74, wherein the ﬁrst and the second expression constructs are on a single nucleic acid molecule. 76. The method of any one of embodiments 67-75, wherein the targeted genetic modiﬁcation comprises simultaneous deletion of an endogenous c acid sequence at the genomic locus of interest and insertion of the ﬁrst nucleic acid at the genomic locus of interest. ] 77. The method of any one of embodiments 67-76, wherein the targeted genetic modiﬁcation is a lic genetic modiﬁcation. 78. The method of ment 77, wherein the biallelic genetic modiﬁcation comprises deletion of an endogenous nucleic acid sequence and insertion of the ﬁrst nucleic acid at the genomic locus of interest in two homologous chromosomes. 79. The method of any one of embodiments 67-76, wherein the modiﬁed non-human ES cell is hemizygous at the genomic locus of interest. 80. The method of embodiment 79, wherein the targeted c modiﬁcation at the genomic locus of interest in one chromosome comprises deletion of an endogenous nucleic acid sequence and insertion of the ﬁrst nucleic acid. 81. The method of embodiment 79, wherein the targeted c modiﬁcation comprises: (1) deletion of an endogenous nucleic acid sequence at the genomic locus of interest in two gous chromosomes; and (2) insertion of the ﬁrst nucleic acid into the genomic locus of interest in a ﬁrst chromosome and disruption of the genomic locus of interest in a second some. 82. The method of any one of embodiments 67-81, wherein the Cas protein is Cas9.

EXAMPLES The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the present invention, and are not ed to limit the scope of what the inventors regard as their invention nor are they intended to represent that the experiments below are all or the only experiments performed. Efforts have been made to ensure accuracy with respect to s used (e.g. amounts, temperature, etc.) but some experimental errors and deviations should be ted for. Unless ted otherwise, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Centigrade, and pressure is at or near heric.

Example 1. Rat ES Cell Derivation and Characterization 1.1. Rat ES Cell Characterization As shown in Figure l, rat ESCs grow as compact spherical colonies, which ely detach and ﬂoat in the dish (close-up, Figure 8). Rat ESCs express pluripotency markers including Oct-4 (Figure 2A) and Sox2 (Figure 2B), and express high levels of alkaline phosphatase (Figure 3). Karyotype for line DA.2B is 42X,Y (Figure 4). Rat ESCs often become tetraploid; thus, lines were pre-screened by counting metaphase chromosome spreads; lines with mostly normal counts were then formally karyotyped.

] ACI blastocysts were collected from super-ovulated females obtained commercially. DA blastocysts were cultured from frozen 8-cell embryos obtained cially. Zona pellucidae were d with Acid Tyrodes; and blastocysts were plated onto mitotically inactivated MEFs. wths were picked and ed using standard methods. All blastocysts were plated, cultured and expanded using 2i media (Li et al. (2008) Germline ent embryonic stem cells derived from rat blastocysts, Cell 135 : 1299- l 3 10; incorporated herein by reference in its entirety).

Table 1. Rat ES Cell Derivation Embryo source Blastocysts Frozen 8-cell embryos cultured to (Superovulation) blastocyst Outgrowths: 32 (30% of blasts) 10 (45% of blasts) Lines: 16 (50% of 9 (90% of outgrowths) outgrowths) Karyotyped: 3; all 42X,Y 6: 3 42X,X 3 42X,Y GLT validated: 1 (ACI.G1) 1 42X,X (DA.2C) 1 42X,Y (DA.2B) 1.2. : Rat Production Chimeric rats were produced by blastocyst injection and transmission of the rat ESC . Chimeras produced by blastocyst microinjection using parental ACI.Gl rat ESCs are shown in Figure 9. Fl agouti pups with albino littermates, sired by the ACI/SD chimera labeled with an asterisk (*) in Figure 9 are shown in Figure 10.

Germline transmission of parental rat ESC.

Three euploid rat ESC lines were evaluated for pluripotency by microinj ection into albino SD blastocysts. Chimeras were identiﬁed by agouti coat color, which indicates rat ESC contribution (see Figure 10). For each line, a majority of as transmitted the rESC genome to Fl offspring (Table 2).

Table 2. Germline Transmission of Parental rESC Total pups Line Chimeras Germline rE5C- GPT from GLT derlved efﬁCIency (Karyotype) bred transmitters chimeras pups (%) ACLGI 3 (60 A.)0 103 11 (XY) DA.ZB 4 ‘8")0 129 9 ‘XY’ DA.2C 3 2 (66 A.)0 45 7 16 1.3. : Derivation 0fRat nic Stem Cells.

] Superovulation ol, rats Day 0: injected with pregnant mare serum: IP, 20 U (0.4 ml).

Day 1: no action Day 2: (46 hr. : injected with hCG, IP, 50 U (1 ml). - set up single female matings.

Day 3: checked plugs. Females were plugged. This is day 0.5.

Day 6 (e3.5): Euthanized females and ﬂushed embryos.

ES Cell derivation protocol (superovulation) Day 0: 1) Euthanized female rat with C02. 2) Swabbed ventral abdomen with 70% l; using scissors, opened the l body wall to expose the viscera. 3) Dissected out the oviducts and uterine horns and placed them into a tissue culture dish containing warm N2B27 media. Washed out as much blood as possible and transferred to a new dish with N2B27. 4) Using a 1 ml syringe and a blunt 27g needle, flushed media h the uterine horns and oviducts to eject blastocysts into the media. 5) Collected the blastocysts with a mouth pipet and transfer to embryo culture dish containing KSOM + 2i (1 uMPD0325901, 3 uM CHIR99021). KSOM is a culture medium produced by Millipore. Catalog number is MR- lO6-D. 6) Cultured ght at 37°; 7.5% C02.

ES Cell derivation protocol n embryos) Day 0: 1) Thawed frozen 8-cell embryos (commercially obtained) into M2 medium. Cultured 10 minutes at room temperature. 2) Transferred to KSOM + 2i and culture overnight.

ES Cell derivation protocol (same for both) Day 1: 1) Transferred cavitated embryos to 2i medium & culture overnight. ] 2) ued culturing un-cavitated embryos in KSOM +2i Day 2: 1) Transferred all remaining embryos to 2i medium er or not e ted). 2) Cultured overnight; continued culturing earlier embryos in 2i medium.

Day 3: 1) Transferred embryos for 30 — 60 seconds with Acid Tyrodes to remove the zona pellucida. 2) Washed embryos 3x in 2i medium to remove Acid Tyrodes. 3) Deposited each embryo into a separate well of a 96-well feeder plate (the well contains a monolayer of mitotically inactivated mouse nic ﬁbroblasts (MEFs). 4) Cultured overnight in 2i medium.

Day 4 — 5: l) Monitored plated embryos for the presence of an outgrowth (an amorphous undifferentiated mass of cells). Outgrowths are ready for transfer when they are approximately twice the size of the plated embryo. 2) Each day: remove spent media with a mircropipet and replace with fresh 2i media. ] 3) Transferred outgrowths to new feeder wells: a. Removed spent media and gently wash well with PBS. b. Removed PBS and add 30 ul 0.05% trypsin; incubate for 10 minutes. c. Stopped trypsin reaction by adding 30 ul 2i + 10% FBS. d. Gently dissociated the cells with a micropipettor and erred entire contents of the well to a new well in a 24-well feeder plate. This was Passage 1 (P l ). e. Cultured overnight in 2i .

Day 5 — 8: (timing depends on how fast each line expands) 1) Changed media each day (2i media) and monitored for the presence of es with an ESC morphology. 2) When colonies appear, ued culturing until colonies expand to ~ 50% conﬂuency. 3) Trypsinized and passaged colonies as before; plated on feeders, 1 well per line, in a 6-well dish. This was Passage 2 (P2).

Ongoing: 1) Continued feeding and monitoring each line until approximately 50% conﬂuent. 2) Trypsinized cells as usual. 3) stopped trypsin with 2i + 10% FBS; pelleted the cells by centriﬁJgation (5 ’, 1200 rpm in Beckman-Coulter tabletop centrifuge). 4) Aspirated the atant and gently resuspend the cells in 400 ul ng Medium (70% 2i, 20% FBS, 10% DMSO). 5) buted the cells into 2 Vials and freeze at -80°. This was Passage 3 (P3). 6) For long-term storage, erred the Vials to liquid N2 The 2i media was prepared as follows in Table 3.

Reagent Vendor Concentration DMEM/F l2 basal media InVitrogen/Life lx Technologies Neurobasal media InVitrogen/Life lx Technologies Penicillin/streptomycin InVitrogen/Life Technologies L-Glutamine InVitrogen/Life Technologies 2-Mercaptoethanol InVitrogen/Life Technologies N2 supplement InVitrogen/Life lx Technologies B27 supplement InVitrogen/Life lx logies LIF Millipore 100 U/ml PD032590l (MEK Stemgent 1 uM tor).

CHIR9902l (GSK Stemgent 3 uM inhibitor).

Materials: Pregnant Mare’s Serum Gonadotropin (PMSG) Human Pregnancy Urine Chorionic Gonadotropin (HCG) Female Rats (5-12 weeks old) Male rats (12 wks. to 8 mos. old), one per cage Syringes/needles Animal room with lights on 6:00-18:00 ] Procedure: Day 1: 8:00-10:00 AM Inject females with 20 IU PMSG (0.4 ml), IP Discard unused PMSG.

Day 3: 8:00-10:00 AM (48 hours after PMSG injection) Inject females with 50 IU HCG (1 ml), IP Place one female per male in mating cage.

] Discard unused HCG.

Day 4: 8:00-10:00 AM (24 hrs. after HCG injection) Check females for plugs.

Hormone suppliers PMSG: Sigma #G-4877 (1000 IU). Resuspend in PBS to a ﬁnal [ ] of 50 IU/ml. Store at -20° in 1 ml aliquots.

HCG: Sigma #CG-S (5000 IU). Resuspend in PBS to a ﬁnal [ ] of 50 IU/ml. Store at -20° in 1 ml aliquots. 1.4.: Karyotyping 0fRat Embryonic Stem Cell Lines The rat ES cell lines generated herein were yped, and the results are summarized in Tables 4-7.

Table 4 ACI.G1 Kar o in_ s Number of cells Number of cells karyotyped Number of cells analyzed 20 Number of 42, XY cells 18 Number of abnormal cells 2 Other notes: Two analyzed cells were missing different autosomes, which may be a sporadic occurrence due to technical artifact. 90% of analyzed cells had a normal male 42, XY karyotype.

Figure 5 provides a photograph showing the is of the chromosome number of the ACI.Gl rat ES cell line.

Table 5 Number of cells Number of abnormal cells 0 42, XY 20 Other notes: All ed cells had a normal diploid 42, XY karyotype.

Figure 6 provides a photograph showing the analysis of the chromosome number of the DA.2B rat ES cell line.

] Table 6 DA.2C Kar 0t in_ Results Number of cells Number of cells karyotyped Number of cells analyzed Number of 42, XX cells Number of abnormal cells 42, XX Other notes: 100% of analyzed cells had normal female XX rat karyotype.

Figure 7 provides a photograph showing the is of the chromosome number of the DA.2C rat ES cell line.

Table 7.

Blastocysts Lines Lines strain olated established Ka ot oed Kar ot oes all lines were high % complex 8 (20%) polyploid G1: 90% 42 XY; others were 16 60% 70-85% euoloid 2B: 100% 42 XY; 2C: 100% 42 XX; others were 95-100% 9 45% eunloid F344 1 (25% — Totals 34 (37%) 1.5.: Electroporation of Vector into Rat Embryonic Stem Cell 1. ed rat ES cells 24-48 hrs prior to electroporation. 2. Changed media to RVG2i + ROCKi (10uM Y-27632) 24 hr. prior to electroporation 3. Changed media 30’ prior to trypsinization. 4. Aliquoted DNA to be electroporated. ] 5. Allowed DNA to warm at RT for >10 min. 6. Heated DNA for 5’ @ 62°C. Place DNA on ice. 7. nized cells: a. ted ﬂoating colonies. Washed plate to collect as many ﬂoaters as possible. b. Pelleted colonies: 3’ @ 750 rpm. c. Washed pellet 1X with 5-10ml PBS and re-spin/pellet d. Aspirated supernatant; add 500% trypsin, 0.05% + 1% chicken serum. i. Did not pool more than 1 10 cm plate of colonies per tube. If there are too many colonies packed into the bottom of the tube during trypsinization they will clump and most of the cells will be lost. e. 4’ @ 37°. Pipeted colonies several times to minimize f. Repeated steps 1-2 X: 4’ @ 37°. g. Stopped trypsin with 500k RVG2i + 10% FBS. 8. Pelleted cells: 5’ @ 1200 rpm. 9. Resuspend cells in 10 ml PBS. Count two 20% aliquots to determine total cell . 10. Pelleted cells (5’/l200rpm); calculate total cell number and total resuspension volume to e correct cell concentration (target #/75 ul EP buffer). 11. Resuspend in a minimal volume of EP buffer; measure total volume and adjust to target volume with EP . Electroporation buffer is sold by Millipore.

The g # is ESD. See, Valenzuela et al. (2003) Nature Biotechnology 21 :652- 659, which is herein incorporated by reference. 12. Add 75k cells to 50k DNA; transfer the 125k cells/DNA solution to one well of a BTX 48-well cuvette. ] a. Filled the empty wells in the same column with 125k EP buffer. 13. Pulsed the cuvette once in the BTX electroporator: a. gs: 400V; 9; 100 uF (settings may vary) 14. Placed cuvette on ice for 15’ to recover. 15. Removed cells into 5 ml RVG2i + 10 uM ROCKi. 16. Added to 15 cm plate with 20 ml RVG2i + 10uM ROCKi. Plate has 2X neoR MEFs (or other MEFs depending on project). The neoR selectable marker is the neomycin phosphotransferase (neo) gene of Beck et al. (1982) Gene, 19:327-36 or in US Patent No, 7,205,148 or 6,596,541, each of which are herein incorporated by reference. 17. Incubated @ 37°. Begin selection 48hrs later.

] ROCK tor used was Y-27632.

I. 6: Selecting a Targeted Genetic Modiﬁcation in a Rat Embryonic Stem Cell. 1. Passaged cells for 24-48 hrs prior to electroporation. 2. Changed media to RVG2i + ROCKi (10uM Y-27632) 24 hr. prior to electroporation 3. Changed media 30’ prior to trypsinization. ] 4. Aliquoted DNA to be electroporated. 5. Allowed DNA warm at RT for >10 min. 6. Heated DNA for 5’ @ 62°C. Place DNA on ice. 7. Trypsinized cells: ] a. Collected ﬂoating colonies. Washed plate to collect as many ﬂoaters as possible.

Pelleted es: 3’ @ 750 rpm.

Washed pellet 1X with 5-10ml PBS and re-spin/pellet Aspirated supernatant; add 500% trypsin, 0.05% + 1% chicken serum. i. Did not pool more than 1 10 cm plate of colonies per tube. If there are too many colonies packed into the bottom of the tube during trypsinization they will clump and most of the cells will be lost. 4’ @ 37°. Pipeted es several times to minimize clumping f. Repeated l-2 X: 4’ @ 37°. ] g. d trypsin with 500% RVG2i + 10% PBS. 8. Pelleted cells: 5’ @ 1200 rpm. 9. Resuspended cells in 10 ml PBS. Count two 20% aliquots to determine total cell number. 10. Pelleted cells 00rpm); calculate total cell number and total resuspension volume to achieve correct cell concentration (target #/75 ul EP ). 11. Resuspend in a minimal volume of EP buffer; measured total volume and adjusted to target volume with EP buffer. 12. Added 75% cells to 50% DNA; transfer the 125k cells/DNA solution to one well of a BTX 48-well cuvette. a. Filled the empty wells in the same column with 1252 EP buffer. 13. Pulsed the cuvette once in the BTX electroporator: a. Settings: 400V; 100 uF (settings may vary) 14. Placed cuvette on ice for 15’ to recover. 15. d cells into 5 ml RVG2i + 10uM ROCKi. 16. Added to 15 cm plate with 20 ml RVG2i + 10uM ROCKi. Plate had 2x neoR MEFs (or other MEFs depending on project). 17. Incubated @ 37°. Began ion 48hrs later. 18. G418 selection protocol was as follows: a. Day 2 (211d day after EP): incubated cells in 2i media + G418, 75 ug/ml.

F7 Day 3: incubated cells in 2i media without G418 .0 Day 4: incubated cells in 2i media + G418, 75 ug/ml. .9— Day 5: incubated cells in 2i media without G418 Day 6: incubated cells in 2i media + G418, 75 ug/ml.

Day 7: incubated cells in 2i media without G418 Day 8: incubated cells in 2i media + G418, 75 ug/ml. .rqorbo Day 9: incubated cells in 2i media without G418 H- Day 10: incubated cells in 2i media + G418, 75 ug/ml.

Day 11: incubated cells in 2i media without G418 Day 12: picked colonies to expand for screening. Each colony was dissociated in 0.05% trypsin + 1% n serum for 10 s and then plated into 1 well of a 96- well feeder plate. 19. Expanded colonies for 3 days in 2i media. 20. Passaged clones 1:1 to new 96-well feeder plates. 21. Expanded clones for 3 days in 2i media. 22. For each clone, dissociated es in trypsin. Froze 2/3 of each clone and store at -80°; plated the remaining 1/3 onto laminin plates (96-well plates coated with 10 ug/ml laminin). ] 23. When the laminin plates were conﬂuent, passed off to the ing lab for genotyping of the clones. 1.7. Molecular Signature of the Rat Embryonic Stem Cells The genes listed in Table 8 were expressed at d lower in rat ES cells than the corresponding genes in mouse ES cells. The genes listed in Table 9 were expressed at levels 20-fold higher in rat ES cells than the corresponding genes in mouse ES cells.

The microarray data in Tables 8 and 9 were generated as s. Rat ES cells (ACI.G2 and DA.2B) and mouse ES cells (FlH4) were cultured in 2i media for 3 passages until conﬂuent. FlH4 cells were cultured on gelatin-coated plates in the absence of feeders. FlH4 mouse ES cells were d from 129S6/SvaTac and C57BL/6NTac heterozygous s (see, e.g., US Pat. No. 7,294,754 and Poueymirou, W.T., Auerbach, W., Frendewey, D., Hickey, J.F., Escaravage, J.M., Esau, L., Dore, A.T., Stevens, 8., Adams, N.C., Dominguez, M.G., Gale, N.W., Yancopoulos, G.D., DeChiara, T.M., Valenzuela,D.M. , incorporated by reference herein in its entirety).

The following protocol was used for sample prep: The 1.5mL Eppendorf tubes were labeled with the Sample ID. Cells grown on a plate were rinsed in 37°C Phosphate-Buffered Saline (PBS). PBS was removed and 300 111 of Trizol® was added. A scraper was used to break the cells in Trizol® (Life Technology). The lysed cells were collected in Trizol® in a 1.5mL orf tube. For cells grown on suspension, the cells were rinsed in 37°C PBS and collected in a l.5mL tube. The cells were spun down; PBS was removed; and 300 111 of Trizol® was added to the cells. The cell membranes were broken by pipetting. Samples were sorted for FACS with 10 to 105 cells, the volume was concentrated to less than lOOuL. 4 volumes ofRNA Lysis buffer were added and mixed by pipetting. For , 320uL RNA Lysis buffer was added to 80uL sample. Samples were stored at —20°C.

RNA-Seq was used to e the expression level of mouse and rat genes. Sequencing reads were mapped to mouse and rat reference genome by Tophat, and RPKM (fragments per kilobase of exon per million fragments mapped) were calculated for mouse and rat genes. Homology genes based on gene symbol were selected, and then used t—test to compare the expression level of each gene between mouse and rat. miR-32 was in the top 10 highest expressed in rat ESCs but was not expressed in mouse ES cells.

Although no ative data exist from miR-632, based on the level of its expression compared to other genes expressed in rat ESCs and their known function in embryonic pment, miR-632 was selected as a marker for rat ES cells.

] Table 8. The genes listed were expressed at levels 20-fold lower in rat ES cells than the corresponding genes in mouse ES cells.

ID S mbol Entrez Gene Name Location T ne(s) ATP-binding cassette, sub-family B (MDR/TAP), member Plasma Abcb lb Abcb lb 1 B Membrane transporter Acta2 ACTAZ muscle, aorta Cytoplasm other Actg2 ACTGZ muscle, enteric Cytoplasm other Aebpl AEBPl AE binding protein 1 Nucleus peptidase Extracellular AngptlZ ANGPTLZ angiopoietin-like 2 Space other Ankrdl ANKRDl 1 (cardiac muscle) asm regulator Anxal ANXAl _"as"annexin Al Membrane other Anxa6 ANXA6 _"as"annexin A6 Membrane other Plasma Anxa8 ANXA8L2 annexin A8-like 2 Membrane other Rho guanine nucleotide ARHGEFZ ge factor (GEF) ArhgefZS 5 25 Cytoplasm other AXL receptor tyrosine Plasma Axl AXL kinase Membrane kinase brain nt, membrane ed transcription Baspl BASPl signal protein 1 Nucleus regulator _Extracellular Bgn BGN biglycan Space other bone marrow stromal Plasma Bst2 BSTZ cell antigen 2 Vlembrane other basic transcription transcription Btf3 BTF3 factor 3 \Iucleus regulator Btg2 BTGZ BTG family, member 2 \Iucleus regulator Capsl CAPSL Other other Plasma transmembrane Cavl CAVl n, 22kDa Vlembrane receptor coiled-coil domain Ccdc80 CCDC80 containing 80 \Iucleus other Ccnd2 CCNDZ cyclin D2 \Iucleus other PCT/USZOl4/060788 ID S mbol Entrez Gene Name Location T ne(s) "as" Cd248 CD248 alin Membrane other "as" Cd44 CD44 blood group) Membrane enzyme Plasma G-protein coupled Cd97 CD97 _ CD97 molecule Membrane or CDC42 effector protein (Rho GTPase binding) Cdc42ep5 CDC42EP5 5 Cytoplasm other cadherin 11, type 2, OB-cadherin Plasma thl l CDHl l (osteoblast) ne other cyclin—dependent kinase transcription Cdkn2a CDKNZA inhibitor 2A Nucleus tor Cdol CDOl type 1 Cytoplasm enzyme Y domain containing linker Clip3 CLIP3 protein 3 Cytoplasm other Cln5 CLN5 neuronal 5 Cytoplasm other Cnnl CNNl smooth muscle Cytoplasm other _Extracellular Collal COLlAl collagen, type 1, alpha 1 Space other Extracellular Colla2 COLlAZ m collaen, t .e I, alnha 2 Snace other Extracellular Col3al COL3Al 1 Space other Extracellular ColSaZ COLSAZ 2 Space other Extracellular Col6a2 COL6A2 2 Space other Cryab CRYAB Nucleus other Extracellular Csfl CSFl factor 1 (macrophage) Space cytokine cystathionase (cystathionine gamma- Cth CTH lyase) Cytoplasm enzyme Extracellular Cthrcl CTHRCl repeat containing 1 Space other Ctsc CTSC asm peptidase Extracellular Cyr6l CYR6l angiogenic inducer, 61 Space other DEAD (Asp-Glu-Ala- Asp) box polypeptide Ddx5 8 DDXS8 5 8 Cytoplasm enzyme dickkopfWNT signaling pathway Extracellular Dkk3 DKK3 inhibitor 3 Space cytokine Dmcl DMCl recombinase l Nucleus enzyme 17U1 ID S mbol Entrez Gene Name Location T ne(s) Dpysl3 DPYSL3 like 3 Cytoplasm enzyme Dse DSE ase Cytoplasm enzyme dual specificity Dusp l DUSP l phosphatase 1 Nucleus phosphatase dual specificity phosphatase 27 Dusp27 DUSP27 (putative) Other phosphatase Dusp9 DUSP9 phosphatase 9 Nucleus phosphatase "as" Ece2 ECEZ enzyme 2 Membrane peptidase Extracellular Ecml ECMl protein 1 Space transporter Egrl EGRl early growth response 1 Nucleus regulator "as" Empl EMF 1 protein 1 ne other "as" Emp3 EMP3 protein 3 Membrane other Ephx2 EPHXZ cytoplasmic Cytoplasm enzyme coagulation factor 111 (thromboplastin, tissue Plasma transmembrane F3 F3 factor) Membrane receptor -Biskis-Reilly murine sarcoma Virus uSV) Fau FAU ubiquitously expressed Cytoplasm other Extracellular anl FBNl _ f1brillin 1 Space other Fbxo l 5 FBXO l 5 F-box protein 15 Other regulator FhlZ FHLZ domains 2 Nucleus tor Flnc FLNC Cytoplasm other FBJ murine osteosarcoma Viral transcription Fos FOS oncogene homolog Nucleus regulator Funch FUNDCZ containing 2 Cytoplasm other "as" Gjb3 GJB3 beta 3, 3 lkDa Membrane transporter glycoprotein A3 3 Plasma Gpa3 3 GPA3 3 (transmembrane) Membrane other GC-rich promoter prp1 ll GPBP lL 1 g protein 1 -like 1 Other other G 0 c3 GPC3 _"as"l0 ican 3 Membrane other growth factor receptor- Grb l 0 GRB 10 Cytoplasm other Gstml GSTMS Cytoplasm enzyme ID S mbol Entrez Gene Name Location T ne(s) huntingtin-associated Hapl HAPl protein 1 Cytoplasm other HISTZHZB E (includes 2bc others) e r 2, H2be Nucleus other nga2 HMGAZ AT-hook 2 s enzyme high mobility group nucleosomal binding ngn3 ngn3 domain 3 Nucleus other l containing 1 Nucleus other Hsdl 7bl4 HSDl7Bl4 beta) dehydrogenase l4 Cytoplasm enzyme Hspbl HSPBl protein 1 Cytoplasm other Hspb8 HSPB8 protein 8 Cytoplasm kinase Extracellular Htral HTRAl _HtrA serine peptidase1 Space peptidase If1204 (includes interferon activated transcription If1204 others) gene 204 Nucleus regulator interferon-induced If144 IFI44 protein 44 Cytoplasm other eron-induced protein with tetratricopeptide repeats If1tl IFIT l B l B Cytoplasm other interferon induced embrane protein If1tm3 IFITMZ 2 Cytoplasm other insulin-like growth factor 2 (somatomedin Extracellular Igf2 IGFZ Space growth factor Extracellular Igfbp7 IGFBP7 factor binding protein 7 Space transporter Plasma transmembrane Illrll ILlRLl like 1 Membrane receptor Extracellular Inhba INHBA _inhibin, beta A Space grth factor Extracellular Inhbb INHBB inhibin, beta B Space grth factor interferon regulatory transcription Irf7 IRF7 factor 7 Nucleus regulator ISG l 5 ubiquitin—like Extracellular Is;15 ISG l 5 modif1er S 0 ace other integrin, alpha 5 (f1bronectin receptor Plasma transmembrane Itga5 ITGAS alpha polypeptide) Membrane receptor Jun JUN jun proto-oncogene Nucleus regulator PCT/USZOl4/060788 ID S mbol Entrez Gene Name Location T e(s) Junb JUNB jun B proto-oncogene Nucleus regulator lectin, galactoside- LGALS3B binding, soluble, 3 Plasma embrane Lgals3bp P binding protein Membrane receptor Extracellular L,als9 LGALS9 bindin, soluble, 9 S u ace other Lmna LMNA Nucleus other _Extracellular Lox LOX l s l oxidase S ace enz me _Extracellular Lole LOXLZ lysyl oxidase-like 2 Space enzyme _Extracellular Loxl3 LOXL3 lysyl e-like 3 Space enzyme low density lipoprotein receptor-related protein Plasma embrane Lrpl LRP l l Membrane receptor Mageb l 6 MAGEB l 6 family B, 16 Other other "as" Mcam MCAM molecule Membrane other _Extracellular Mgp MGP matrix Gla protein Space other matrix metallopeptidase 2 (gelatinase A, 72kDa gelatinase, 72kDa type Extracellular VImpZ MMPZ IV collagenase) Space peptidase VIxra8 MXRA8 associated 8 Other other \/Iyl9 MYL9 regulatory Cytoplasm other myosin light chain, phosphorylatable, fast VIylpf MYLPF skeletal muscle Cytoplasm other NGFI-A binding n 2 (EGRl transcription \Iab2 NABZ binding protein 2) Nucleus regulator NADH dehydrogenase (ubiquinone) 1 beta \Idufb4 NDUFB4 subcomplex, 4, lSkDa Cytoplasm transporter nucleophosmin olar oprotein B23, transcription Npml NPMl numatrin) Nucleus regulator nuclear receptor subfamily 0, group B, ligand-dependent Nr0bl NROBl member 1 Nucleus nuclear or nuclear receptor subfamily 4, group A, ligand-dependent Nr4al NR4Al member 1 s nuclear receptor Nrp2 NRPZ _"as"neuropilin 2 Membrane kinase Oas l a OAS l Cytoplasm enzyme ID S mbol Entrez Gene Name Location T e(s) 2'-5' denylate Oale Oale synthetase-like 2 Other enzyme prolyl oxylase, P4ha2 P4HA2 alpha polypeptide 11 Cytoplasm enzyme poly (ADP-ribose) polymerase family, Parp3 PARP3 member 3 Nucleus enzyme Extracellular Pcolce PCOLCE endo unetidase enhancer S ace other phosphate cytidylyltransferase l, Pcytlb PCYT 1B choline, beta Cytoplasm enzyme Extracellular Pdgfc PDGFC factor C Space growth factor pleckstrin homology- like domain, family A, Phldal PHLDAl member 1 Cytoplasm other pleckstrin homology- like domain, family A, Phlda2 PHLDAZ member 2 Cytoplasm other phospholipase A2, Extracellular Pla2glb PLAZGlB group IB (pancreas) Space enzyme phospholipase A2, group IVA (cytosolic, Pla2g4a PLA2G4A calcium-dependent) Cytoplasm enzyme Porcn PORCN Drosmhz‘la C o.lasm other ellular Postn POSTN specific factor Space other Prrxl PRRXl homeobox l Nucleus regulator Extracellular Prss23 PRSS23 _ protease, serine, 23 Space peptidase proteasome (prosome, macropain) subunit, Psmb8 PSMB8 beta type, 8 Cytoplasm peptidase prostaglandin— endoperoxide synthase 2 (prostaglandin G/H synthase and Ptgs2 PTGSZ cyclooxygenase) Cytoplasm enzyme Extracellular Ptn PTN pleiotrophin Space grth factor Ptrf PTRF transcri .t release factor Nucleus or ligand-dependent Rarg RARG gamma Nucleus nuclear or regulator of ein Rgs l 6 RGS l 6 ing 16 Cytoplasm other 45S pre-ribosomal Rn45s Rn45s RNA Other other RpllOa RPLlOA Other other WO 88643 ID S mbol Entrez Gene Name Location T ne(s) Rpl3l RPL3 1 Other other Rpl37a RPL37A Cytoplasm other "810' Rps l 0 NUDT3 readthrough Cytoplasm other Rps l 4 RPS l 4 ribosomal protein S l 4 Cytoplasm regulator Rps20 Rps20 Cytoplasm other Rps26 RPS26 Cytoplasm other Rps9 RPS9 ribosomal n S9 Cytoplasm regulator S100a4 S 100A4 protein A4 Cytoplasm other S 100 calcium binding S100a6 S 100A6 protein A6 Cytoplasm transporter schwannomin Schipl SCHIPl interacting n 1 asm other Plasma Sch SDCZ syndecan 2 Membrane other serpin peptidase inhibitor, clade E (nexin, plasminogen activator inhibitor type Extracellular Serpinel SERPINEl 1), member 1 Space other serpin peptidase inhibitor, clade E (nexin, plasminogen activator inhibitor type Extracellular Serpine2 SERPINEZ 1), member 2 Space other serpin peptidase inhibitor, clade F (alpha-2 asmin, pigment epithelium derived factor), member Extracellular Serpinfl SERPINFl 1 Space other SH3-domain GRBZ- Plasma Sh3ng SH3GL2 like 2 Membrane enzyme solute carrier family 19 (thiamine transporter), Plasma Slc l 9a2 SLC l 9A2 member 2 ne transporter solute carrier family 25 (mitochondrial r; adenine nucleotide SchSaS SLC25A5 translocator), member 5 Cytoplasm transporter solute carrier family 29 (equilibrative nucleoside transporter), Plasma Sch9al SLC29A1 member 1 Membrane transporter solute carrier family 35, Slc35f2 SLC35F2 member F2 Other other small nuclear ribonucleoprotein Snrpn SNRPN ptide N Nucleus other PCT/USZOl4/060788 ID S mbol Entrez Gene Name Location T ne(s) Snx22 SNX22 Other transporter ed protein, acidic, cysteine-rich Extracellular Sparc SPARC (osteonectin) Space other Extracellular Sppl SPP l phosphoprotein 1 Space cytokine sulfotransferase family l SULT4Al 4A, member 1 Cytoplasm enzyme Tagln TAGLN Cytoplasm other transcription elongation transcription Tcea3 TCEA3 factor A (SH), 3 Nucleus regulator transforming growth Extracellular Tfb3 TGFB3 factor, beta 3 S ace 3 owth factor _Extracellular Thbsl THES l thrombospondin 1 Space other _Extracellular Thbs2 THBSZ thrombospondin 2 Space other "as" Tm4sfl TM4SFl family member 1 Membrane other transmembrane BAX inhibitor motif Tmbiml TMBIMl ning 1 Cytoplasm other Tmeml 76b B 176B Other other _Extracellular Tnc TNC tenascin C Space other TpdSle TPDSZLl l Cytoplasm other Tme TPMZ Cytoplasm other Uspl 8 USPl 8 peptidase l 8 Cytoplasm peptidase Vim VIM asm other Extracellular Wfdc2 WFDCZ core domain 2 Space other WNTl inducible signaling pathway Extracellular Wisp2 WISPZ protein 2 Space grth factor transcription be1 YBXl Y box g protein 1 Nucleus regulator Table 9. The genes listed were expressed at levels 20-fold higher in rat ES cells than the corresponding genes in mouse ES cells.

ID S mbol Entrez Gene Name Location T ne(s) adherens on associated Aj apl Aj apl n 1 Other other adenosylmethionine Amdl AMDl decarboxylase l Cytoplasm enzyme ANKRD ankyrin repeat domain 2 transcription AnkrdZ 2 (stretch responsive muscle) Nucleus tor ARHGE Cdc42 guanine nucleotide Arhgef9 F9 exchange factor (GEF) 9 Cytoplasm other ATP synthase, H+ transporting, mitochondrial F0 Atp5h AtpSh complex, subunit d Cytoplasm enzyme Btg3 BTG3 BTG family, member 3 Nucleus other Extracellular Car6 CA6 carbonic anhydrase VI Space enzyme calcium/calmodulin-dependent Camk4 CAMK4 protein kinase IV Nucleus kinase Capan CAPNlZ calpain 12 Other peptidase onin containing TCP l , Cct6b CCT6B subunit 6B (zeta 2) Cytoplasm transporter transcription Cdx2 CDXZ caudal type ox 2 Nucleus regulator Plasma CldnS CLDNS claudin 5 Membrane other C-type lectin domain family 3, Clec3a CLEC3A member A Other other chloride intracellular channel Plasma Clic6 CLIC6 6 Membrane ion channel dehydrogenase/reductase Dhrsx DHRSX (SDR family) X-linked Other enzyme Dpyle DPYSLZ dihydropyrimidinase-like 2 Cytoplasm enzyme dual specificity phosphatase Dusp26 DUSP26 26 (putative) asm enzyme enoyl-Coenzyme A delta Eci3 Eci3 isomerase 3 Other enzyme eukaryotic elongation factor-2 Eeka EEFZK kinase Cytoplasm kinase Plasma Efnal EFNAl ephrin-Al Membrane other Plasma Epha4 EPHA4 EPH receptor A4 Membrane kinase fibronectin type III and transcription Fankl FANKl ankyrin repeat domains 1 Nucleus regulator Fhit FHIT fragile ine triad asm enzyme Filipl FILIPl filamin A interacting protein 1 Cytoplasm other Extracellular Fmod FMOD fibromodulin Space other forkhead box El (thyroid transcription Foxel FOXEl transcription factor 2) Nucleus regulator PCT/USZOl4/060788 ID S mbol Entrez Gene Name on T ne(s) Extracellular Fry FRY furry homolog (Drosophila) Space other gap junction protein, beta 5, Plasma Gjb5 GJBS 3 l . lkDa Membrane transporter glutathione peroxidase 2 pr2 GPXZ (gastrointestinal) Cytoplasm enzyme GRXCR ercr2 2 lutaredoxin, c steine rich 2 Other other HECT, C2 and WW domain containing E3 ubiquitin ellular Hecw2 HECWZ protein ligase 2 Space enzyme hairy/enhancer-of-split related transcription Hey2 HEYZ with YRPW motif 2 Nucleus regulator Plasma Icos Icos inducible T-cell co-stimulator ne other interferon induced Plasma transmembrane Ifitml IFITMl transmembrane protein 1 Membrane receptor 11le Interleukin-l family member ILlF8 (Interleukin 36 beta) (IL3 6B) Extracellular space cytokine IlZSra IL-28RA Interleukin 28 receptor, alpha Plasma membrane Cytokine receptor IGFBPL insulin-like growth factor Igfbpll 1 binding protein-like 1 Other other interaction n for Incefl IPCEFl c ohesin exchane factors 1 C o.lasm enz me Lctl Lctl lactase-like asm other thd LDHD lactate dehydrogenase D Cytoplasm enzyme id enhancer-binding transcription Lefl LEFl factor 1 Nucleus regulator left-right determination factor Extracellular Left 1 LEFTYl l Sace y owth factor leukemia inhibitory factor Plasma transmembrane Lifr LIFR or alpha Membrane receptor lysophosphatidic acid receptor Plasma G-protein d Lpar2 LPARZ 2 Membrane receptor myelin oligodendrocyte Extracellular Mog MOG glycoprotein Space other Morn5 MORNS MORN repeat containing 5 Other other nuclear cap binding protein Pigz NCBPZ subunit 2, 20kDa \Iucleus other Plasma transmembrane Nptxr NPTXR neuronal pentraxin receptor VIembrane receptor Plasma Ntm NTM neurotrimin VIembrane other Nutf2 NUTFZ nuclear ort factor 2 \Iucleus orter Plasma Ocln OCLN occludin VIembrane enzyme oxidized low density lipoprotein (lectin-like) Plasma transmembrane Olrl OLRl receptor 1 VIembrane receptor ID S mbol Entrez Gene Name Location T ne(s) p01y(A) binding protein, translation Pabpc4 PABPC4 cytoplasmic 4 ible form) Cytoplasm tor Pdel la PDEl 1A phosphodiesterase 1 1A Cytoplasm enzyme Extracellular den PDYN prodynorphin Space transporter Per3 PER3 period circadian clock 3 Nucleus other Plasma Pllp PLLP plasmolipin Membrane orter protein phosphatase 1, PPPlRl4 regulatory (inhibitor) subunit Ppplrl4c C 14C Cytoplasm other entially expressed Pramel6 Pramel6 antien in melanoma like 6 Other other protein tyrosine phosphatase, ceptor type 18 (brain- Ptpnl 8 PTPNl 8 derived) Nucleus phosphatase pyrroline-5 xylate Pycrl PYCRl reductase l Cytoplasm enzyme RAB26, member RAS Plasma Rab26 RAB26 oncogene family Membrane enzyme receptor (G protein-coupled) Plasma Ramp2 RAMPZ activity modifying protein 2 ne transporter Rbm24 RBM24 RNA binding motif protein 24 Other other Plasma Rhag RHAG Rh-associated glycoprotein Membrane peptidase Rpl3 RPL3 ribosomal protein L3 Cytoplasm other Sall3 SALL3 sal-like 3 (Drosophila) Nucleus other transcription Satbl SATBl SATB homeobox l Nucleus regulator Extracellular ch2 SCGZ secretogranin 11 Space cytokine solute carrier family 15 SLC 1 5A (oligopeptide transporter), Plasma SlclSal 1 member 1 Membrane transporter solute carrier family 1 (neuronal/epithelial high affinity glutamate transporter, Plasma Slclal SLC lAl system Xag), member 1 Membrane transporter solute carrier family 24 m/potassium/calcium Sch4a5 Sch4a5 exchanger), member 5 Other other solute carrier family 37 SLC37A (glucosephosphate 2 2 transporter), member 2 Other transporter syntrophin, beta 1 (dystrophin- associated n Al, 59kDa, Plasma 40424 SNTBl basic component 1) Membrane other ST6 (alpha-N-acetyl- neuraminyl-Z, 3 -betagalactosyl- l ,3)-N- ST6GAL acetylgalactosaminide alpha- St6galnac3 NAC3 2,6-sialyltransferase 3 Cytoplasm enzyme ID S mbol Entrez Gene Name Location T ne(s) Tex12 TEX12 testis expressed 12 Nucleus other Extracellular Tex15 TEX 1 5 testis expressed 15 Space other transcription factor AP-Z alpha (activating enhancer binding ription Tfap2a TFAPZA protein 2 alpha) Nucleus regulator Plasma Tmc1 TMCl transmembrane channel-like 1 Membrane other TMEMl Tmem130 30 transmembrane nrotein 130 Other other TMEM3 Tmem30b 0B transmembrane protein 30B Other other translocase of outer TOMMZ mitochondrial membrane 20 Tomm20 0 homolog (yeast) Cytoplasm transporter TOX high mobility group box Tox3 TOX3 family member 3 Other other tetratricopeptide repeat th25 TTC25 domain 25 Cytoplasm other Extracellular Tymp TYMP thymidine phosphorylase Space grth factor Ubb Ubb ubiquitin B Cytoplasm other vesicle-associated ne Vamp7 VAMP7 protein 7 Cytoplasm transporter WAP four-disulfrde core Extracellular Wfdc12 Wfdc12 domain 12 Space other WAP four-disulfrde core a a domain 15A Other other WAP four-disulfrde core Wfdc6a Wfdc6a domain 6A Other other ] Table 10. A subset of genes from Table 9, which are expressed at levels -fold higher in rat ES cells than the corresponding genes in mouse ES cells. _Entrez Gene Name Adherens Iunctions Associate Protein Cldn5 Arh _ef9 Camk4 Efnal tha4 G'b5 Igfbpll 111f8 Interleukin 36 beta IlZ8ra Lef 1 Lifr LoarZ n rosine oohoshatase non-receotor oe 18 Cdx2 Caudal oe homeobox 2 ID Entrez Gene Name Fibronectin oe III and ank rin reoeat domains 1 Forkhead box E1 th roid transcri otion factor 2 Hair enhancer-of—s olit related with YRPW motif 2 L mohoid enhancer-bindin_ factor 1 Sa113 Sal-like 3 Drosoohila SATB homeobox 1 An additional lar signature employing the pluripotency markers/genes for the rat ES cells has also been developed. Table 11 provides a gene list and their expression ranks from the RNA proﬁling data. mRNA was isolated from rat ES cells and the expression levels of various markers were compared relative to each other.

The term "rank" means the comparative expression levels of individual genes: the higher the rank (1 is highest), the higher the expression. For example, Oct4's rank of 13 means that, of all the genes assayed, it was sed higher than all but 12 genes. Background in this experiment was any expression value below 30; 6107 genes had expression values of 30 or higher.

Table ll. Rat ES cell molecular signature employing various pluripotency, mesodermal, rmal, neural and trophectoderm s/genes.

Endoderm aIRank c—hﬂyc Brachyury 7542 Gam6 Dnmt3L Hkl tested 50x17 Pax6 13570 DppaZ Nottested Nodm 3050 50x2 681 DppaS ted Bmp4 3072 Ecatl 9714 Bmpr2 6382 Eras 2541 Err—beta 1368 FbxolS 1369 Fgf4 3440 Fth|17 Nottested Gdf3 2771 Rank > 6107 = bkg sion KH4 836 Lefl 1313 UFreceptor 724 Un28 828 Nanog 774 Not tested Not tested Not tested Not tested 1501 Example 2: Inactivation of Genomic Loci in Rats 2.1: Inactivation ofEndogenous Genomic Loci Using an Endonuclease Agent In order to introduce a mutant allele at an endogenous rat genomic locus, the rat ES cells described herein are electroporated with expression vectors (or mRNA) that express ZFNs l and 2 (or TALENs l and 2). These proteins bind their target sequences on opposite strands, separated by about 6 bp to about 40 bp. A double- stranded break is formed Within the target locus, which the cell ts to repair by Non- Homologous ining . In many cases, NHEJ results in creation of a deletion, Which often disrupts the function of the gene (most often by producing a frameshift mutation). In order to identify a positive clone comprising a mutant allele, the electroporated cells are plated at low density, e no drug selection is done. Colonies are picked and assayed at the target site to see if a mutation was produced (e.g., using a modiﬁcation of allele (MOA) assay described above). The selected ES cells comprising the mutant allele are then introduced into a host rat embryo, for example, a pre-morula stage or cyst stage rat embryo, and implanted in the uterus of a surrogate mother to generate a founder rat (F0 rat). Subsequently, the founder rat is bred to a wild-type rat to create Fl progeny heterozygous for the mutant allele. Mating of the heterozygous Fl rat can produce progeny homozygous for the mutant allele. 2.2.: Rat ESC Targetingfor the vation ofthe Rat oprotein E (ApoE) gene Using Zinc Finger Nucleases Zinc ﬁnger nucleases use sequence speciﬁc modular DNA binding domains to direct endonuclease activity to unique target sequence in the genome. ZFNs are engineered as a pair of monomers. Each r contains nonspeciﬁc cleavage domain from F0k] endonuclease fused to 3 or more zinc ﬁnger DNA-binding domains.

Each zinc ﬁnger binds a 3 bp subsite and speciﬁcity is achieved by the combined target sites of both monomers. ZFNs e double-stranded breaks (DSBs) in DNA, and mutations (insertions or deletions) frequently occur during non-homologous end joining (NHEJ). Figure 15 illustrates the mechanism by which genome-editing endonucleases such as ZFNs and TALENs introduce double strand breaks in a target genomic sequence and activate NHEJ in a cell. DSBs also stimulate homology-directed repair (HDR) by homologous recombination if a donor ce is provided with ZFN.

Such ZFNs were employed in combination with the various methods and compositions described herein to improve targeting efﬁciency. The rat Apolipoprotein E (ApoE) locus was ed as described in Example 3.2(a)(i), except expression vectors that express ZFNs l and 2 were also introduced into the rat ES cells. See Figure ll, which provides a schematic of the ApoE targeting event in combination with rTZFNlP and rTZFN2P. The targeting efﬁciency was determined as discussed below in Example 5 and s are shown in Table 12. To screen for zygous targeting, homozygous targeting, and "mixed" doubles (e.g., compound heterozygous targeting), speciﬁc primers and probes were used to determine genotype. Surprisingly, the targeting efﬁciency went up 8-10 fold.

Table 12. Rat ApoE ZFNs: Improved Targeting Efﬁciency. 8.2% -_-_— W<> W 189% "(8.9%) vector-- W> W W 180.4%) A plasmid ing vector was built with a self-deleting drug selection te and a lacZ gene as a er gene (see Figure 14 for an illustration of the homologous and non-homologous recombination events that can occur upon electroporation of a targeting vector comprising a selection cassette). Good targeting ncy was achieved and high % as were produced. Zinc ﬁnger nucleases (ZFNs) were also tested in combination with targeting vectors to examine its effect on improving targeting efﬁciency (see Figure 16 for an illustration of the gene targeting technique utilizing ZFNs or TALENs to improve the efﬁciency of homologous ination of a targeting vector). The targeting vector was co-expressed with the expression vectors for 2 ZFN pairs that cut the ApoE locus. The rat ESC clones oporated with both the targeting vector and a set of the ZFNs showed a targeting efﬁciency of 8-10 fold higher than that of rat ESC clones electroporated with a targeting vector alone. Moreover, bi-allelic homozygous targeting in about 2% of our clones was detected. High % chimeras from two of these targeted clones were obtained.

The argeted (with ZFN assistance) rat ESC clones were microinjected into SD blastocysts, which were then transferred to pseudopregnant SD recipient females, using standard techniques. Chimeras were identiﬁed by coat color (see Figure 17, showing ApoE-ZFN—ABS chimeras (i.e., ApoE'/' chimeras); male F0 chimeras were bred to SD females. ne Fl pups were genotyped for the presence of the targeted ApoE allele (Table 13). High % chimeras were obtained from two of these targeted clones.

Table 13. Microinjection s. (% of a) ApoE-ZFNl -AB5 ApoE-ZFNl-AES An ApoE knockout rat provides a means to study s types of disorders and diseases. In humans, oprotein is found in chylomicron, HDL, LDL and VLDL. ApoE is essential for the normal catabolism of triglyceride-rich lipoprotein constituents. Defects in APOE result in numerous disease states ing, for example, familial hypercholesterolemia, hyperlipidemia, betalipoproteinemia, familial dysbetalipoproteinemia, type III hyperlipoproteinemia (HLP III), risk of coronary artery disease. One isoform (ApoE4) is associated with late-onset familial and sporadic Alzheimer’s disease, possibly with MS as well.

In mice, ApoE is primarily found in HDL; transports cholesterol, as in humans. eficient mice (2 independent KOs) have 5 times normal plasma cholesterol; developed foam cell-rich depositions in their proximal aortas by age 3 months (comparable to human syndrome).

ApoE knockouts in rats offer an animal model to study endothelial function, including, but not d to, plaque formation, transcriptional changes (RNA- Seq), ex vivo function. Moreover, larger size of rats would facilitate all these assays and potentially improve the quality of the RNA-Seq data. 2.3. Inactivation of The Rat Interleukin-2 Receptor Gamma (IL2r-y) Locus Using Zinc Finger Nucleases The rat eukin-2 receptor gamma (IL2r—y or Il2rg) locus was targeted as described in Example 3.3(a), except that expression vectors that express ZFN U (ZFN upstream) and ZFN D (ZFN downstream) were also introduced into the rat ES cells.

Figure 18 provides a schematic of the IL2r-y targeting event in combination with ZFN U and ZFN D. The sequence of the IL2r-y locus which these zinc fingers bind is denoted in Figure 18 within SEQ ID NO: 93. The ing efficiency was determined as sed below in Example 3.3(a) and the results are shown in Table 14. Brieﬂy, homozygously targeted clones were confirmed by PCR. For the ZFNl pair: 173 mutant clones out of 192 ed (90%) and for the ZFN2 pair: 162 clones out of 192 (84%) screened.

Table 14. Targeting of Rat IL2r-y Locus. 7/18:Vector alone"—— 7/18:Vector+ZFN"—— ] The IL2r-y -targeted (with ZFN assistance) rat ESC clones were microinjected into SD cysts, which were then transferred to pseudopregnant SD recipient s, using standard techniques. Chimeras were identiﬁed by coat color; male F0 chimeras were bred to SD females. Germline F1 pups were genotyped for the presence of the targeted IL2r-y allele. 2014/060788 2.4.: Inactivation of The Rat Interleukin-2 Receptor Gamma (IL2r-y) using CRISPR/Cas9 The rat IL2r—y locus was targeted as bed in Example 3.3(a), except that the VCas9 system was also introduced into the rat ES cells to aid in targeting efﬁciency. SBI: System Biosciences Cas9 "SmartNuclease" all-in-one vectors were ed and Cas9 expression was driven by CAG, EFla, PGK, or CMV promoter.

Custom gRNA was ligated into a vector and sed by Hl promoter. 4 gRNAs against Il2rg were designed. The regions of the rat IL2r-y locus targeted by gRNAsl-4 are shown in Figure 19. To screen for targeting (e. g., heterozygous targeting, homozygous targeting, and compound heterozygous targeting), speciﬁc primers and probes were used to determine genotype. Targeting results when ing the various guide RNAs is shown in Table 15. "Strong" and "weak" refer to the strength of the evidence based on screening that the colony has a targeted modiﬁcation.

Table 15. Targeting of Rat Il2rg Locus with Guide RNAs.

Candidates Construct(s) Colonies (Potentially Targeted) Ierg plasmid vector g 30 3 weak 1 strong, 1 weak 2 strong, 1 weak 1 strong, 2 weak 2.5.: Inactivation ofthe Mouse Hypoxanthine Guanine Phosphoribosyl Transferase (Hprt) gene using CRISPR/Cas9 The mouse Hprt locus was targeted in mouse ES cells using LTVECs alone or in combination with CRISPlVCas9. The 32.9 kb complete Hprt coding sequence was targeted for deletion and replacement with the pCAGG-Puro puromycin ance selection cassette, which also sed eGFP. The deletion end points were the start and stop codons. The guide RNA sequence used was 5’- 2014/060788 GACCCGCAGUCCCAGCGUCG-3' (SEQ ID NO: 84), which targeted exon 1 of the mouse Hprt gene. The predicted target site cleavage position was 22 base pairs from the ’ end of the deletion. The RNA on-target cleavage efﬁciency observed in the ES cells was 2 93%. A summary is shown in Table 16. Use of CRISPlVCas9 to assist in targeting of the complete 32.9 kb Hprt locus resulted in a five-fold enhancement of targeting over use of LTVEC alone.

Table 16. Summary of CRISPR—Assisted Deletion ofHprt Gene Summary of CRISPR-Assisted Deletion of the Hprt Gene Targeting Efﬁciency (%) Target Deletion 5 'Homology 3 'Homology LTVEC LTVEC + Fold Gene (kb) Arm (kb) Arm (kb) Alone CRISPR/Cas9 ement Hprt 32.9 88 66 5.0 25.4 5.1 e 3: Targeted Modiﬁcation of Rat c Loci 3.1: Rat ESC Targeting: The Rat R0sa26 Locus.

The rat R0sa26 locus lies n the Setd5 and Thumpd3 genes as in mouse, with the same spacing. The rat R0sa26 locus (Figure 12, Panel B) differs from the mouse R0sa26 locus (Figure 12, Panel A). The mouse R0sa26 transcripts consist of 2 or 3 exons. The rat locus contains a 2nd exon 1 (Exlb) in addition to the homologous exon to mouse exonl (EXla). No 3rd exon has been identified in rat. ing of a rat R0sa26 allele is depicted in Figure 12C, where homology arms of 5 kb each were cloned by PCR using genomic DNA from DA rat ESC. The targeted allele contains a SA (splicing acceptor)—lacZ-hUb-neo cassette replacing a 117 bp deletion in the rat R0sa26 intron.

Targeting efficiency at the rat R0sa26 locus was determined (Table 17).

Linearized vector was electroporated into DA or AC1 rat ESCs, and transfected colonies were cultured in 2i media + G418, using standard techniques. Individual colonies were picked and ed using a Loss of Allele (LOA) assay (Valenzuela, D. et al. (2003) High-throughput engineering of the mouse genome coupled with high-resolution expression analysis, Nature Biotech. 21 :652-660, incorporated herein by reference).

Table 17. rat Rosa26 ing Efﬁciency Colonies Reconﬁrmed Targeting efﬁciency Cell line picked positives (%) DA.2B 192 Chimera production and germline transmission using Rosa26- targeted rat ESC clones. rmed R0sa26-targeted rat ESC clones were microinjected into SD blastocysts, which were then transferred to pseudopregnant SD recipient females, using rd ques. Chimeras were identiﬁed by coat color; male F0 chimeras were bred to SD females. Germline (agouti) Fl pups were genotyped for the ce of the targeted R0sa26 allele; nine of 22 agouti pups genotyped as heterozygous at the R0sa26 locus (Table 18).

Table 18. Germline Transmission Using Targeted Rosa26 rESC R26 Clones Germline ESC-derived clones producing Transmitting pups injected Chimeras Clones (%) AH7: 64 AE3: 112 To conﬁrm that the genetically d allele at the R0sa26 locus was transmitted through the germline, lacZ sion was conﬁrmed by X-gal staining in heterozygous R0sa26-targeted rats. X-gal staining of the brain, heart and thymus, and a lung from a 14-week-old heterozygous R0sa26-targeted rat showed expression of lacZ (Figure 13B, D, and F, respectively), whereas age-matched wild type controls showed a low level of background X-gal staining (Figure 13A, C, and E, respectively). X-gal staining in E125 and E 14.5 heterozygous R0sa26-targeted rat embryos showed ubiquitous expression of lacZ (Figure 13G and 1, respectively), whereas control rat embryos showed low levels of background X-gal staining (Figure 13H and J, respectively). 3.2. (a)(i) : Targeting ofthe Rat oprotein E (ApoE) Locus.

The rat Apolipoprotein E (ApoE) locus was targeted to disrupt ApoE function. Targeting of the ApoE locus was done using a targeting vector comprising a Ub-neo cassette ﬂanked with a 5’ and 3’ homology arms homologous to the ApoE locus. Figure 20 depicts a cally modiﬁed rat ApoE locus that has been disrupted by a 1.8 kb deletion and the insertion of a lacZ-hUb-neo cassette, which r es a self-deleting Cre cassette comprising a Crei gene driven by a protamine promoter. The electroporation conditions were as follows: 6 ug DNA; 2.05 X 106 cells; 400V; 200 uF: 342 V, 593 usec; plate on 15 cm 2X dense neoR MEFs in 2i + 10 uM ROCKi.

Targeting efficiency at the ApoE locus was determined and is shown in Table 19. Linearized vector was electroporated into DA.2B rat ESCs derived from the DA strain, and transfected colonies were cultured using standard techniques. Individual colonies were picked and screened using a Loss of Allele (LOA) assay.

- Table 19. rat ApoE Targeting Efﬁciency . Colonies Targeting efﬁciency Chimera production and germline transmission using ApoE-targeted rat ESC clones was performed. ApoE-targeted rat ESC clones were microinjected into SD blastocysts, which were then transferred to pseudopregnant SD recipient females, using standard techniques. Chimeras were identiﬁed by coat color; male F0 as were bred to SD females. Germline transmission was achieved. F1 pups were ped for the presence of the ed ApoE allele (Table 20).

Table 20 njection Results E—ApoE-AFS _Clone Pups Chimeras (% of chimera) 3 (90 90 90) _ApoE--BC4__ LacZ expression driven by the endogenous ApoE promoter was ed by X-gal staining in 12-week-old ApoE H" female rats in the brain, blood vessels, and liver (Figures 43-45, respectively). Figures 43-45 show an expression pattern for lacZ that mirrors the expression pattern of endogenous ApoE. Age-matched wild type controls showed a low level of background X-gal staining.

The phenotypes —deleted rats were ﬁarther studied. Longitudinal serum chemistry studies were performed to measure cholesterol, LDL, HDL, and ceride levels at three-week intervals. Figure 46A-D show serum cholesterol, LDL, HDL, and triglyceride levels in homozygous targeted, heterozygous targeted, and wild type rats at 6 weeks, 9 weeks, 12 weeks, and 15 weeks of age. Eye bleeds were performed on an age-matched cohort consisting of 2 wild type, 7 heterozygous, and 8 homozygous rats. No signiﬁcant differences were seen between males and females. gous ApoE-deleted rats showed elevated cholesterol and LDL levels and decreased HDL levels. Unlike ApoE '/' mice, no significant increase in triglycerides was observed in eleted rats.

Additional phenotypic analysis that is performed includes histology/ex vivo imaging for aortic arch plaque formation, in viva imaging for aortic arch plaque formation, and transcriptional changes (Whole Transcriptome Shotgun Sequencing (RNA-Seq» for aortic arch elium. The timing of these assays s on the timeline of plaque formation. Plaques are detectable in ApoE '/' mice at 24 weeks.

Additional targeting data for ApoE is also provided in Table 22. 3.2. (a)(ii). Targeting ApoE in Rats with a Targeting Vector Figure 20 provides a schematic of the rat ApoE locus and a targeting d. The upper tic of Figure 20 shows the c structure of the rat ApoE locus and the genomic regions ponding to 5’ and 3’ homology arms (5 kb and 5.4 kb, respectively; dark grey boxes). Exon 1 ofApoE is non-coding and is shown as an open box closest to the 5’ homology arm. The 3 introns ofApoE are denoted as lines and exons 2 and 3 comprise coding regions and are shown as stippled grey boxes. Exon 4 contains both coding and non-coding sequences as denoted by the stippled grey shading and the open box.

The lower schematic in Figure 20 is the targeting . The 5 ’ and 3’ homology arms (5 kb and 5.4 kb respectively) are denoted by the dark grey boxes. The targeting vector comprises a er gene (lacZ) and a self-deleting cassette ﬂanked by loxP sites (open arrows). The self-deleting cassette comprises the Crei gene operably linked to a mouse PrmI promoter and a selection cassette comprising a neomycin resistance gene operably linked to a human ubiquitin promoter.

The Crei gene comprises two exons ng a Cre inase, which are separated by an intron (Crei) to prevent its expression in a prokaryotic cell. See, for example, US. Patent 8,697,851 and US. Application Publication 2013-0312129, which describe the self-deleting te in detail and are hereby incorporated by reference in their entirety. By employing the PrmI promoter, the eleting cassette can be deleted speciﬁcally in male germ cells of F0 rats. The targeting vector was electroporated into the rat ES cells obtained in Example 1 and the cells were plated on 15 cm 2x dense neomycin-resistant MEFs in 2i + 10 uM ROCKi. The transformed rat ES cells were cultured, selected, and maintained as described in Example 1.

As shown in Table 44, 384 colonies were screened and 23 targeted clones were obtained. The targeting efﬁciency was 5.99%. 3 clones were injected into blastocysts as bed herein in Example 1. 3 clones producing chimeras were obtained and 1 of the clones transmitted the ed modiﬁcation h the ne. 3.2.(a)(iii). Targeting ApoE in Rats with a Targeting Vector in Combination with Zinc Finger Nucleases The ing vector employed in Example 3.2(a)(ii) was used in combination with zinc ﬁnger nucleases to target the rat ApoE locus. Table 21 provides a summary of the genomic organization of the rat ApoE locus. The positions shown in the Table 21 were taken from build 5.0 of the Reference Sequence of the rat genome (ENSMBL). ApoE is on chromosome 1 on the (-) strand.

Table 21. Summary of the rat ApoE locus and the positions of the zinc ﬁnger nuclease binding sites and cutting sites.

Feature Notes Exon 1 5' non-codin Exon2 contains ATG ATG start codon Exon3 ZFNla bindin Site CAGGCCCTGAACCGC SEQ ID NO: 10 ZFN] cuttin Site TTCTGG SEQ ID NO: 11 ZFNlb binding site GATTACCTGCGCTGGG (SEQ ID NO: 12) Intron 3—4 ZF21a g site TTCACCCTCCGCACC (SEQ ID NO: 13) ZFN2 cutting site G (SEQ ID NO: 14) TATCCAGATCCAGGGGTT (SEQ ID NO: ZF21b binding Site 69 81879552 18 15) Exon 4 81878371 81879208 838 contains TGA TGA 82 84 3 ApoE deletion 81878482 81880311 1830 Figure 11 provides a schematic of the rat ApoE locus and denotes with grey bars the cutting site for ZFNl and ZFN2. The cutting site for ZFNl is in exon 3 and the cutting site for ZNF2 is in intron 3. The exact position of the both ZFN sites is set forth in Table 21. The genomic regions ponding to the 5’ and 3’ homology arms (5 kb and 5.4 kb, respectively) are denoted by the dark grey boxes. Exon 1 ofApoE is non- coding and is shown as an open box closest to the 5’ homology arm. The three introns of the ApoE gene are denoted as lines and exons 2 and 3 comprise coding regions and are shown as stippled grey boxes. Exon 4 contains both coding and non-coding sequences as denoted by the stippled grey shading and the open box.

The employed targeting vector was the same as that in Example 3.2(a)(ii) and shown in Figure 20, and Figure 21A provides a schematic for targeting the ApoE locus in rat ES cells using zinc-ﬁnger nucleases and the targeting vector depicted in Figure 20. The ZFNs were introduced as two expression plasmids, one for each half of the ZFN pair. 20 ug of the plasmid for ZFNl and 20 ug of the plasmid for ZFN2 was used. ZFNs were purchased from Sigma. The expression of each ZFN was driven by the CMV promoter.

The targeting vector were electroporated into the rat ES cells obtained in Example 1 and the cells were plated on 15 cm 2x dense neoR MEFs in 2i + 10 uM ROCKi. The ormed rat ES cells were cultured, selected and maintained as described in Example 1.

As shown in Table 22 and Table 44, 384 colonies were screened and 290 targeted clones were obtained. The ing efﬁciency was 75.52%. 2 clones were ed into blastocysts as described herein in Example 1. Two clones producing chimeras were obtained and one of the clones transmitted the targeted modiﬁcation through the germline.

Moreover, employing ZFNl and ZFN2 produced 8 biallelic targeted clones with an efﬁciency of 2.08%.

Table 22. Targeting ofApoE Locus.

Heterozygous Homozygous . .. Chimeras . /192 (8%) -_——— 3.2.(b)(i): Targeted Modiﬁcation ofthe Rat Apolipoprotein E (ApoE) Locus Using a Large Targeting Vector (L TC).

Targeting of the ApoE locus is done using a large targeting vector (LTVEC) comprising a lacZ-mouse rei cassette ﬂanked with a 5 ’ homology arm to the ApoE locus of about 45 kb and a 3’ homology arm to the ApoE locus of about 23 Kb. Figure 22 s the rat ApoE locus in which the ApoE locus has been disrupted by a 1.83 kb on and the insertion of the lacZ gene and a self-deleting cassette comprising mPrmI-Crei te and a hUb-neo selection cassette. Methods employed in example 3.2(a)(i) can be used to introduce this vector into rat ES cells.

Example 3.2. (b) (ii). Targeting ofthe Rat ApoE locus with a Large Targeting Vector (LTVEC) Figure 22 provides a schematic of the rat ApoE locus and a large targeting vector (LTVEC). The upper schematic of Figure 22 shows the genomic zation of the rat ApoE locus and the c regions corresponding to the 5’ and 3’ gy arms (45 kb and 23 kb, respectively; dark grey boxes). Exon 1 ofApoE is non-coding and is shown as an open box closest to the 5’ homology arm. The 3 introns ofApoE are denoted as lines and exons 2 and 3 comprise coding regions and are shown as ed grey boxes. Exon 4 contains both coding and non-coding sequences as denoted by the ed grey shading and the open box.

The lower schematic in Figure 22 is the LTVEC. The 5’ and 3’ homology arms (45 kb and 23 kb, respectively) are denoted by the dark grey boxes. The targeting vector comprises a reporter gene (lacZ) and a self-deleting cassette ﬂanked by loxP sites (open arrows), which ses the Crei gene operably linked to a mouse PrmI promoter and a drug selection cassette comprising a neomycin ance gene operably linked to a human ubiquitin promoter. The Crei comprises two exons encoding the Cre recombinase which are separated by an intron (Crei) to prevent its expression in a prokaryotic cell. See, for example, US. Patent 8,697,851 and US. Application Publication 2013- 03 12129, which describes the self-deleting cassette in detail and is hereby incorporated by reference in their entirety. By employing a mouse PrmI er, the self-deleting te can be deleted speciﬁcally in male germ cells of F0 rat.

The LTVEC was electroporated into the rat ES cells obtained in Example 1 and the cells were plated on 15 cm 2x dense neoR MEFs in 2i + 10 uM ROCKi. The transformed rat ES cells were cultured, selected, and maintained as described in Example ] As shown in Table 44, 288 colonies were screened and 8 targeted clones were obtained. The targeting efﬁciency was 2.78%. 3 clones were injected into a host embryo at a blastocyst stage as described herein in Example 2 to produce chimeric rats (F0). Moreover, one biallelic targeted clone was produced providing a biallelic efﬁciency of0.35%. 3.2. (b)(iii). Targeting ApoE in Rats with a Large Targeting Vector (LTVEC) In Combination with Zinc Finger Nacleases The LTVEC employed in Example 3.2.(b)(ii) was used in combination with zinc ﬁnger ses to target the rat ApoE locus. Table 21 provides a summary of the genomic organization of the rat ApoE locus and the positions shown were taken from build 5.0 of the Reference Sequence of the rat genome (ENSMBL).

Figure 23 provides a schematic of the rat ApoE locus and s with grey bars the cutting site for ZFNl and ZFN2. The cutting site for ZFNl is in t exon 3 and the cutting site for ZNF2 is in intron 3. The exact position of the both ZFN sites is set forth in Table 21. The 5’ and 3’ homology arms (45 kb and 23 kb, respectively) are denoted by the dark grey boxes. Exon 1 of the ApoE gene is non-coding and is shown as an open box t to the 5’ homology arm. The three introns of the ApoE gene are denoted as lines. Exons 2 and 3 comprise coding regions and are shown as stippled grey boxes. Exon 4 contains both coding and non-coding sequences as denoted by the stippled grey shading and the open box.

] The LTVEC employed was the same as that in Example 3.2(b)(ii) and shown in Figure 22. The ZFNs were introduced as two expression plasmids, one for each half of the ZFN pair. 20 ug of the plasmid for ZFN l and 20 ug of the plasmid for ZFN2 was used. ZFNs were purchased from Sigma. The expression of each ZFN was driven by the CMV promoter.

The targeting vector was electroporated into the rat ES cells obtained in e 1 and the cells were plated on 15 cm 2x dense neoR MEFs in 2i + 10 uM ROCKi. The transformed rat ES cells were cultured, selected, and maintained as described in Example 1.

As shown in Table 44, 288 colonies were screened and 16 targeted clones were obtained. The targeting efﬁciency was 5.56%. One clone was injected into blastocysts as described herein in Example 2.

] Moreover, the ment of ZFNl and ZFN2 produced one biallelic targeted clone, with an efﬁciency of 0.35%. 3. 2. (b)(iv). Targeting ApoE in Rats with a Large Targeting Vector (LTVEC) in Combination with CRISPR/Cas9 The LTVEC employed in Example 3.2.(b)(ii) was used in ation with CRISPIVCas9 to target the rat ApoE locus. Table 23 shows a comparison of the results of experiments in which the ApoE LTVEC was used alone to target the rat ApoE locus or was used in combination with a CRISPIVCas9 nuclease to target the rat ApoE locus. In each experiment, electroporated cells were plated at a high density and ted to drug selection to ﬁnd colonies that were drug-resistant. Drug-resistant colonies were picked and screened for the targeted modiﬁcation using the modiﬁcation of allele (MOA) assay as described herein. Speciﬁcally, 4 x 106 cells were oporated with 2 ug ofApoE LTVEC at a voltage of 400V, a tance of 100 uF, and a resistance of 0. In the latter experiment, 6 ug of Cas9 expression plasmid and 3 ug ofApoE gRNA2 or 3 ug ofApoE gRNA3 were also electroporated. Selection was done using 75 ug/mL of G418. ApoE gRNA2 has a sequence of GCAGGCCCTGAACCGCTTCTTGG (SEQ ID NO: 87) and targets a region 67 bp 3’ of the start of rat ApoE exon 3. ApoE gRNA3 has a sequence of CCTGCGCTGGGTGCAGACGCTTT (SEQ ID NO: 88) and targets a region 97 bp 3’ of the start of rat ApoE exon 3 (see Figure 47). As shown in Table 23, when Cas9 and either of the gRNAs were introduced into the cells together with the ApoE LTVEC, targeting efﬁciency sed (from 43% to 53% or 47%). Biallelic targeting was observed in ﬁve colonies targeted with the ApoE LTVEC in combination with ApoE gRNA2 or 3, but no biallelic targeting was observed with ApoE LTVEC alone.

Table 23. Comparison of Rag2 LTVEC Targeting with and without CRISPIVCas9 Colonies Targeted Biallelic ing ApoE 0 ApoE ApoE 0 LTVEC gRVA2 "-- ApoE ApoE 0 LTVEC gRVA3"- 3.3(a): Targeting ofthe Rat Interleukin-2 Receptor Gamma (IL2r-y) Locus The rat Interleukin-2 receptor gamma (IL2r—y or Il2rg) locus was targeted to disrupt IL2r-y ﬁlnction. IL2r-y plays an important role for signaling by IL-2, IL-4, IL- 7, IL-9, IL-l5, IL-2l and mutations in IL2r-y are associated with severe defects in T, B and NK cell development.

Targeting of the IL2r—y locus was done using a targeting vector comprising an eGFP-hUb-neo cassette ﬂanked with a 5’ and 3’ homology arms gous to the IL2r—y locus, as depicted in Figure 24. Figure 25 depicts the genomic structure of the rat IL2r—y locus in which the IL2r-y locus has been disrupted by a 3.2 kb deletion. The targeted IL2r—y locus also comprised an eGFP gene and a self-deleting cassette containing Crei operably linked to a mouse Protaminel promoter and a drug selection te comprising a hUb promoter operably linked to a neomycin resistance gene.

Targeting efﬁciency at the IL2r-y locus was determined and shown in Table 24. Linearized vector was electroporated into DA.2B rat ESCs, and transfected colonies were cultured using standard techniques. dual colonies were picked and screened using a Loss of Allele (LOA) assay.

Table 24. rat IL2r-y Targeting Efﬁciency Targeting as . Colonies Cell llne Targeted efﬁ(c0;e;1cy. (A) Chlmerlsm)0 . . picked II2rg-ﬂoxed (70-90%) II2rg-mSDC Chimera tion and germline ission using IL2r-y-targeted rat ESC clones was performed. IL2r-y-targeted rat ESC clones were microinj ected into SD cysts, which were then transferred to pseudopregnant SD recipient females, using standard techniques. Chimeras were identiﬁed by coat color; male F0 as were bred to SD females. Germline Fl pups were genotyped for the presence of the targeted IL2r-y allele (Table 25). In another microinjection experiment with clone Il2rg—CGl2, germline transmission was also conﬁrmed by coat colors and genotyping.

Table 25. Microinjection Results Chimeras (% of chimera) _—5—Il2rg-AAl 2 (90, 70) 3 (90 90 80) _Il2rg-coiz 7(95, 90, 90, 90, 80, 80, 80) The phenotype of Il2rg chimera #3 was further studied. The peripheral blood mononuclear cells (PBMCs) were stained with antibodies that recognize antigens in several lymphoid es. GFP-positive PBMCs were detected from 2 of the chimeras, as shown in Figure 30. Moreover, the GFP+ cells were negative for the T-cell marker CD3 (Figure 29A), and were mostly negative for the B-cell marker B220 and the NK cell marker CDl6la (Figure 29B and C, respectively). PBMCs from a wild type rat were used as negative controls for GFP expression. See Figure 29D-F. The small double-positive populations are consistent with the published Il2rg knockout phenotype in mice. These data were obtained from a chimeric rat, which contains 1L2 receptor gamma-positive cells, and this may cate the analysis of the phenotype. Flow cytometry analysis can also be performed on cell populations from bone marrow and spleen to reveal ponding decreases in the number of lymphocytes. See Mashimo et al. (2010) PLoS One 5(l):e8870. 3.3(b): Targeted Modiﬁcation of The Rat Interleukin-2 Receptor Gamma (IL2r- y) Locus The rat Interleukin-2 receptor gamma (IL2r—y) locus was targeted to disrupt the IL2r-y ﬁlnction in rats. Figure 25 shows the genomic structure of the rat Il2rg locus (upper panel of Figure 25) and the ing vector introduced into the locus (lower panel of Figure 25). eGFP was chosen as a reporter so that the immunophenotype of the genetically modiﬁed rats could be examined using FACS. The self-deleting te (hUb-Neo; PrmI-Cre) was used to delete the drug section te and the Cre gene speciﬁcally in male germ cells of the F0 rat. Additionally, the targeting vector was designed to delete the entire coding region (about 3.2 kb) of the rat Il2rg gene.

] The size of the deletion in rat ESCs was conﬁrmed by PCR using primers speciﬁc to the rat Il2rg locus. Upon microinj ection of the targeted clones into host s at a blastocyst stage, high percentage chimeras were obtained. Those chimeras have been set up for breeding. To determine if the ing worked as expected, the peripheral blood from the chimeras were collected prior to breeding, and the phenotype of the immune cells in the peripheral blood was analyzed Via FACS. As shown in Figure , GFP-positive cells were detected in the peripheral blood in 2 of the 3 chimeras examined, and the chimeric rats contained less than 1% of T cells, less than 1% of B cells, and less than 1% ofNK-cells, which are positive for GFP (i.e., Il2rg KO cells) (Figure . 3.4(a) (i). ing the Rag2 Locus in Rats with a Large ing Vector (LTVEC) Table 26 provides a summary of the genomic organization of the rat Rag2 locus and the positions shown were taken from build 5.0 of the Reference Sequence of the rat genome (ENSMBL). Rag2 is on chromosome 3 on the (+) strand.

Table 26. Genomic organization summary of the rat Rag2 locus.

Feature Start End Length Notes Exon 1 97,851,317 97,851,448 132 Exon 2 97,854,635 97,854,693 59 Exon 3 97,858,260 97,859,615 1,356 contains entire coding sequence ATG 97,856,286 97,856,288 3 start codon TGA 97,857,867 97,857,869 3 stop codon Rag2 deletion 97,856,289 ,784 3,496 Figure 26 es a tic of the rat Rag2 locus and a large targeting vector (LTVEC). The LTVEC is 140 kb and targets an approximately 5.7 kb portion of the rat Rag2 locus for deletion. The upper schematic of Figure 26 shows the genomic organization of the rat ApoE locus and the genomic regions corresponding to the 5’ and 3’ homology arms (48 kb and 84 kb, respectively; dark grey boxes). Rag2 comprises a single exon denoted by the stippled grey g.

The lower schematic in Figure 26 is the LTVEC. The 5’ and 3’ homology arms (48 kb and 84 kb, respectively) are denoted by the dark grey boxes. The LTVEC comprises a reporter gene (lacZ) and a self-deleting cassette ﬂanked by loxP sites (open arrows). The self-deleting cassette comprises a mouse PrmI promoter operably linked to the Crei gene and a drug selection cassette comprising a human ubiquitin promoter operably linked to a neomycin resistance gene. Another version of the LTVEC was ted in which the neomycin resistance gene was ed with a hygromycin resistance gene to enable retargeting of Il2rg—targeted rat ES cells. The Crei comprises two exons encoding the Cre recombinase that are separated by an intron (Crei) to prevent its expression in a yotic cell. See, for example, US. Patent 851 and US.

Application Publication 2013-0312129, which describe the self-deleting cassette in detail and are hereby incorporated by reference in their entirety. By ing a mouse PrmI promoter, the self-deleting cassette can be deleted speciﬁcally in male germ cells of F0 rats.

The LTVEC was oporated into the rat ES cells obtained in Example 1 and the cells were plated on 15 cm 2x dense neoR MEFs in 2i + 10 uM ROCKi. The transformed rat ES cells were cultured and maintained as described in Example 1.

Colonies are screened as described elsewhere herein and targeted clones are ed. The targeted clones are then injected into a host embryo as described elsewhere herein to produce an F0 rat. 3.4(a) (ii). Targeting the Rag2 Locus in Rats with a Large Targeting Vector ) and CRISPR/Cas9 Table 27 shows a comparison of the s of experiments in which a version of the Rag2 LTVEC having a hygromycin resistance gene (see Figure 48) was used alone to target the rat Rag2 locus or was used in combination with a CRISPlVCas9 nuclease to target the rat Rag2 locus. In each experiment, electroporated cells were plated at a high density and subjected to drug selection to ﬁnd colonies that were drug- resistant. Drug-resistant colonies were picked and screened for the targeted modiﬁcation using the modiﬁcation of allele (MOA) assay as described . Speciﬁcally, 4 x 106 cells were electroporated with 2 ug ofRag2 LTVEC at a voltage of 400V, a capacitance of 100 uF, and a resistance of 0. In the latter experiment, 6 ug of Cas9 expression plasmid and 3 ug ofRag2 gRNAl or 3 ug ofRag2 gRNA4 were also oporated.

Selection was done using 75 ug/mL of G418. Rag2 gRNAl has a sequence of WO 88643 CCAGCTACTTGCTCGTACAA (SEQ ID NO: 89) and targets a region 219 bp 3’ of the rat Rag2 start codon (ATG). Rag2 gRNA4 has a sequence of CCCCTCAGATTCACGTGCGT (SEQ ID NO: 90) and targets a region 12 bp 3’ of the rat Rag2 stop codon (TAG) (see Figure 48). As shown in Table 27, when Cas9 and either of the gRNAs were introduced into the cells er with the Rag2 LTVEC, targeting eff1ciency increased (from 0 to 10% or 38%). Biallelic targeting was ed in one colony.

Table 27. Comparison of Rag2 LTVEC Targeting with and without CRISPlVCas9 Colonies Targeted Biallelic Targeting Rag2 Rag2 Rag2 0 LTVEC gRVAl Rag2 Rag2 0 LTVEC gRVA4 ---— 3. 4. (b)(i): Targeting the Rag] and the Rug 2 Locus in Rats Figure 27 provides the genomic ure of the rat ag2 locus.

CDS denotes the coding sequence and grey boxes represent exons. Rag2 is on the "plus" strand with transcription to the right. Rag] is on the "minus" strand with transcription to the left. Mbp = million base pairs.

Table 28 provides a summary of the genomic organization of the rat Rag2 and Rag] locus and the positions shown were taken from build 5.0 of the Reference Sequence of the rat genome (ENSMBL). Rag] is on chromosome 3 on the (-) strand.

Table 28. Genomic organization summary of the rat Rag] locus.

Feeeeee see me Exeee —-a_— Exeez Rag" deletion 97,856,289 97,872,486 16,198— Figure 28 provides a schematic of the rat Rag2 and Rag] locus and a large targeting vector (LTVEC). The LTVEC is about 70 kb and targets an approximately 16.6 kb rat genomic locus comprising the Rag] and Rag2 loci for deletion. The upper schematic of Figure 28 shows the c organization of the Rag] and Rag2 loci and the genomic regions corresponding to the 5’ and 3’ homology arms (48 kb and 15 kb, respectively; dark grey boxes). Rag2 and Rag 1 each comprises a single exon denoted by the ed grey shading. The lower schematic in Figure 28 is the LTVEC. The 5’ and 3’ homology arms (48 kb and 15 kb, respectively) are d by the dark grey boxes.

The LTVEC comprises a reporter gene (lacZ) and a eleting cassette ﬂanked by loxP sites (open arrows). The self-deleting cassette comprises a rat PrmI promoter operably linked to the Crei gene and a drug selection te comprising a human tin promoter operably linked to a neomycin resistance gene. Another version of the LTVEC was generated in which the neomycin resistance gene was replaced with a hygromycin resistance gene to enable retargeting of Il2rg—targeted rat ES cells. The Crei comprises two exons ng the Cre recombinase are separated by an intron (Crei) to prevent its expression in a prokaryotic cell. See, for example, US. Patent 851 and US.

Application Publication 2013-0312129, which describe the self-deleting cassette in detail and is hereby incorporated by reference in their entirety. By employing a rat PrmI promoter that drives expression of Crei speciﬁcally in male germ cells, the self-deleting cassette can be deleted from the male germ cells of F0 rats.

The LTVEC was electroporated into the rat ES cells obtained in Example 1 and the cells were plated on 15 cm 2x dense neoR MEFs in 2i + 10 uM ROCKi. The transformed rat ES cells were ed and maintained as described in Example 1.

Colonies are screened as described elsewhere herein and targeted clones are obtained. The targeted clones are then injected into a host embryo as described ere herein to produce an F0 rat. 3. 4. (b)(ii): Retargeting the Rag] and the Rag2 Locus in Rats ES Cells in which the Il2rg Locus Has Already Been Targeted An LTVEC as in Figure 50 was prepared to target the Rag] and Rag2 loci for deletion. The total length of the LTVEC was 72 kb. The LTVEC was oporated into rat ES cells that had already been ed for deletion of the Il2rg locus as in e 3.3. Speciﬁcally, the rat ES cells were from clone Il2rg—CG12, for which germline transmission was conﬁrmed in Example 3.3(a). The transformed rat ES cells were cultured and maintained as described in Example 1. Double targeted clones were screened as described elsewhere herein, and targeted clones were obtained. Il2rg—CG12 cells were retargeted at an efﬁciency of 85%, and Il2rg mutations were still present in the targeted clones. Electroporation was carried out as described elsewhere herein, and antibiotic ion was carried out using 1.5 ug/ml of puromycin. The targeted clones will then be injected into a host embryo as described elsewhere herein to produce an F0 rat. eting is advantageous because it is faster than interbreeding RagI/Rag2- targeted rats with Il2rg-targeted rats.

Example 4. Humanization 4.1. Humanization ofRat Genomic Loci zation of rat genomic loci is carried out employing the rat ES cells described herein, which are capable of sustaining their pluripotency following one or more electroporations in vitro, and are capable of transmitting the targeted genetic modiﬁcations to subsequent generations. In addition, in order to circumvent the limitations of plasmids in accommodating a large genomic DNA fragment, and to overcome the low efﬁciency of introducing a targeted genetic modiﬁcation into an endogenous locus in rat ES cells, one or more targeted genetic modiﬁcations are carried out in bacteria, e.g., E. coli, by ing bacterial homologous recombination (BHR) and employing a large ing vector (LTVEC). The LTVEC described herein, for e, includes a large fragment of an endogenous rat c sequence with one or more modiﬁcations or comprises an exogenous nucleic acid (e.g., a gous or orthologous human nucleic acid) ﬂanked with rat homology arms complementary to speciﬁc genomic regions. 4.2. Humanization ofRat Immunoglobulin Loci Humanization of an nous rat immunoglobulin heavy chain locus is carried out by removing one or more endogenous rat immunoglobulin heavy chain nucleic acid sequences (e.g., one or more endogenous VH gene segments, one or more human D gene segments, and one or more human JH gene segments); and introducing into the modiﬁed immunoglobulin locus a targeting vector, e.g., a large ing vector (LTVEC) comprising: (i) one or more unrearranged human variable region nucleic acid sequences (e.g., one or more human VH gene segments, one or more human D gene segments, and one or more human JH gene segments), or one or more nged human variable region c acid sequences (e.g., one or more human rearranged V-D-J gene segments); (ii) a ion cassette (e. g., neomycin resistance gene ﬂanked with loxP sites); and (iii) 5 ’ and 3 ’ rat homology arms.

Brieﬂy, one or more nous rat immunoglobulin heavy chain variable region gene segments (z'.e., one or more VH gene segments, one or more human D gene segments, and one or more human JH gene segments) in a rat BAC clone are removed or inactivated by targeting the endogenous rat immunoglobulin heavy chain locus with a selection cassette ﬂanked by rat homology arms. More speciﬁcally, a targeting vector is ucted to contain a selection cassette (e.g., a neomycin resistance gene ﬂanked with loxP sites) ﬂanked with 5 ’ and 3 ’ rat homology arms that are complementary to target rat genomic sequences (e. g., upstream and downstream rat genomic DNA sequences encompassing one or more rat VH gene segments, one or more human D gene segments, and one or more human JH gene segments).

Next, bacterial cells containing a large rat genomic DNA fragment encompassing a rat globulin heavy chain locus are selected and introduced with a d (e.g., pABG) encoding a recombinase operably linked to a transiently inducible promoter. The targeting vector constructed above is then introduced into the ination-competent bacterial cells. Following electroporation, the bacterial cells are treated with an inducer (e.g., arabinoside) to initiate homologous ination between the targeting vector and the target rat genomic sequence in the BAC clone. Transformed cells are plated at a high density and ted to drug selection to ﬁnd colonies that are drug-resistant. Drug-resistant colonies are picked and screened for the targeted modiﬁcation.

In order to facilitate identiﬁcation of the targeted genetic modiﬁcation, a high-throughput quantitative assay, namely, modiﬁcation of allele (MOA) assay, is employed, which allows a scale screening of a modiﬁed allele(s) in a parental chromosome following a genetic ation. The MOA assay can be carried out via various analytical techniques, including, but not limited to, a quantitative PCR, e.g., a real-time PCR (qPCR). For example, the real-time PCR comprises a ﬁrst primer set that recognizes the target locus and a second primer set that recognizes a non-targeted reference locus. In addition, the primer set can comprise a ﬂuorescent probe that recognizes the ampliﬁed sequence. Alternatively, the tative assay can be carried out via a variety of analytical techniques, including, but not d to, ﬂuorescence- mediated in situ hybridization (FISH), comparative genomic hybridization, isothermic DNA ampliﬁcation, quantitative hybridization to an immobilized probe(s), Invader Probes®, MMP assays®, TaqMan® Molecular Beacon, and EclipseTM probe technology.

(See, for example, /0144655, incorporated by reference herein in its entirety).

The bacterial cells comprising the modiﬁed rat BAC clone, i.e., a BAC clone containing a rat genomic DNA sequence wherein one or more nous heavy chain variable region gene segments (VH, D, and/or JH gene segments) have been deleted or inactivated, are then electroporated with a large ing vector (LTVEC) sing: (i) one or more unrearranged human variable region nucleic acid sequences (e. g., one or more ranged human VH gene segments, one or more human D gene segments, and one or more human IH gene segments), or one or more rearranged human variable region nucleic acid sequences (e. g., one or more rearranged human V-D-J gene segments).

Initiation of homologous recombination in the bacterial cells and the selection of positive clones are performed as bed above. The unrearranged or nged human immunoglobulin heavy chain variable region nucleic acid sequences, when targeted into the endogenous immunoglobulin heavy chain locus, become operably linked to an endogenous rat immunoglobulin heavy chain nt region nucleic acid sequence. Alternatively, endogenous rat heavy chain constant region locus can be inactivated, for example, by deleting one or more rat heavy chain constant region gene ts (CH) from the endogenous heavy chain constant region locus, and can be replaced with a human heavy chain constant region nucleic acid sequence.

Likewise, humanization of an endogenous rat globulin K or 9» light chain locus is carried out by removing one or more endogenous rat immunoglobulin K and/or 7» light chain variable region nucleic acid sequences (e.g., one or more endogenous rat VK gene segments and one or more endogenous rat JK gene ts); and targeting the modiﬁed immunoglobulin light chain locus with a targeting vector, e.g., a large targeting vector (LTVEC), comprising: (i) one or more unrearranged human immunoglobulin light chain variable region nucleic acid sequences (e.g., one or more human VK gene segments and one or more human JK gene segments), or one or more rearranged human variable region nucleic acid sequences (e.g., one or more human nged VK-JK gene segments); (ii) a selection te (e. g., neomycin resistance gene ﬂanked with loxP sites); and (iii) 5 ’ and 3 ’ rat homology arms.

The unrearranged or rearranged human immunoglobulin light chain variable region nucleic acid ces, when targeted into the endogenous immunoglobulin light chain locus, become operably linked to the endogenous rat immunoglobulin light chain constant region nucleic acid sequence.

The LTVEC so produced in the bacterial cells comprises, for example, an insert c acid that contains a humanized rat immunoglobulin heavy chain or light chain locus in which one or more endogenous rat heavy or light chain le region gene segments have been replaced with one or more human heavy or light chain variable region gene segments; and rat homologous arms (e.g., ranging from 5 kb to 150 kb) complementary to speciﬁc genomic target ces. The LTVEC comprising the genetic modiﬁcation described above is then linearized and electroporated into the rat ES cells. Electroporated rat ES cells are plated at a high density to select drug-resistant ES cells comprising the targeting vector. The drug selection s removes the majority of the plated cells (~99%), leaving behind individual colonies, each of which is a clone d from a single cell. Of the remaining cells, most cells (~ 80-100%) contain the targeting vector integrated at a random location in the . Therefore, the colonies are picked and genotyped individually in order to identify rat ES cells comprising the targeting vector at the correct genomic location (e.g., using the modiﬁcation of allele (MOA) assay described above).

In order to increase the efﬁciency of the targeted genetic modiﬁcation, the rat ES cells are oporated with sion vectors (or mRNA) that express ZFNs l and 2 (or TALENs l and 2) together with the LTVEC. The targeting vector’s homology arms lie e the ZFN target site, therefore, the targeting vector is not cleaved by the ZFNs. The double strand break produced by the ZFNs stimulates homology-directed repair (HDR), which otherwise accounts for a very small percentage of repairs occurred normally in mammalian cells (compared to mologous end-joining; NHEJ).

] Alternatively, expression vectors containing a type II -associated nuclease (e. g., Cas9), a guide RNA (including CRISPR-RNA (cr-RNA) and trans- activating CRISPR RNA (trachNA)), as bed herein, can be introduced into the bacterial cells together with the LTVEC to increase the efﬁciency of homologous recombination at the target genomic locus. Electroporated cells are plated at a high density and subjected to drug selection to ﬁnd colonies that are drug-resistant. Drug- resistant colonies are picked and screened for the targeted modiﬁcation using the modiﬁcation of allele (MOA) assay as described herein. ing these procedures, improvement in the targeting efﬁciency can be achieved. For e, the amount of improvement can be small (e. g., improve from 10% to 15%) or large (e. g., improve from % to 80%).

The selected rat ES cells comprising the targeted c modiﬁcation are then introduced into a host rat embryo, for example, a pre-morula stage or blastocyst stage rat embryo, and implanted in the uterus of a ate mother to generate a founder rat (F0 rat). Subsequently, the founder rat is bred to a ype rat to create Fl progeny heterozygous for the genetic modiﬁcation. Mating of the heterozygous Fl rat can produce progeny homozygous for the genetic modiﬁcation. 4.3(a). Replacing Rat IL2rg with Human 1L2 Receptor Gamma Table 29 provides a summary of the genomic organization of the rat Interleukin 2 receptor gamma locus and the positions shown were taken from build 5.0 of the Reference Sequence of the rat genome (ENSMBL). Il2rg is on chromosome X on the (-) strand.

Table 29. Summary of the genomic organization of the rat Il2rg locus Feature Start End lenth Notes Exon 1 129 contains ATG Am stancodon mm 154 ZFNla binding site CAGGCCCTGAACCGC (SEQ ID NO: 17) ZFNl cutting site —n TTCTGG (SEQ ID NO: 18) ZFN1b binding site GATTACCTGCGCTGGG (SEQ ID NO: 20) ms 185 Exon4 14o Exons 163 Exon7 72,018,844 72,018,910 67 Exon8 72,017,856 72,018,506 651 contains TGA TGA ,321 ,323 sto-codon Il2rgdeletion 72,018,323 72,021,502 3,180 The lower schematic in Figure 25 is the targeting vector for the Il2rg 3.2 kb deletion. The targeting vector comprises a reporter gene (eGFP) operably linked to the endogenous promoter and a self-deleting cassette ﬂanked by loxP sites (open arrows).

The eleting cassette ses the Crei gene operably linked to a mouse PrmI promoter and a selection cassette comprising a neomycin resistance gene operably linked to a human tin promoter.

] The Crei gene comprises two exons encoding a Cre recombinase, which are separated by an intron (Crei) to prevent its expression in a prokaryotic cell. See, for example, US. Patent 8,697,851 and US. Application Publication 2013-0312129, which describe the self-deleting cassette in detail and are hereby incorporated by reference in their entirety. By employing the mouse PrmI er the Cre expression cassette and the drug selection te can be deleted speciﬁcally in male germ cells of F0 rats. The targeting vector was electroporated into the rat ES cells obtained in Example 1 and the cells were plated on 15 cm 2x dense neomycin-resistant MEFs in 2i + 10 uM ROCKi.

The transformed rat ES cells were cultured, selected, and ined as described in Example 1.

A plasmid targeting vector was constructed to replace the ﬁJll-length rat interleukin 2 receptor gamma coding region with the ﬁJll-length human interleukin 2 receptor gamma coding region as shown in Figure 3 l. The targeting vector was electroporated into the rat ES cells obtained in Example 1, and the cells were plated on 15 cm 2x dense neomycin-resistant MEFs in 2i + 10 uM ROCKi. Speciﬁcally, 4 x 106 cells were electroporated with 2 ug of Il2rg full-length humanization vector at a voltage of 400V, a capacitance of 100 uF, and a resistance of 0. Selection was done using 75 ug/mL of G418. The transformed rat ES cells were ed, ed, and ined as described in Example 1.

As shown in Table 44, 168 colonies were ed and 6 targeted clones were obtained. The targeting efﬁciency was 3.57%. One clone was injected into blastocysts as described in Example 1, and one clone producing chimeras was obtained.

Clones were ed into blastocysts as described herein in Example 1.

Clones producing F0 chimeric rats were obtained. The blastocysts were transferred to pseudopregnant recipient females using standard techniques, and chimeric F0 rats were obtained. F0 rats that transmit the targeted modiﬁcation through the germline are obtained. 4.3(b) (i). Replacing Rat IL2rg Ecto-Domain with Human ILng Ecto-Domain ] The full-length humanization of IL 2 receptor gamma is useful because rats having this modiﬁed locus will produce human Il2rg; and this would allow for the ion of human Il2rg in rats with antibodies speciﬁc to human Il2rg.

The ecto-humanization (i.e., replacing the rat ecto-domain of Il2rg with the human ecto-domain of Il2rg) will result in an Il2rg polypeptide that will bind the human ligands for Il2rg, but because the cytoplasmic domain is still rat, it ecto- humanized form of Il2rg will also interact with the rat ing machinery. Figure 33 provides a sequence alignment of the human IL-2rg protein (SEQ ID NO: 20; NP_000197.1); the rat IL-2rg protein (SEQ ID NO: 21; NP_543 165. l); and the chimeric IL-2rg protein (SEQ ID NO: 22) comprising the human ecto-domain of IL-2rg ﬁlsed to the remainder of the rat IL-2rg protein. The junction between the human and rat IL-2rg is noted by the al line.

] Table 30 provides a summary of the genomic organization of the rat Interleukin 2 receptor gamma locus and the positions shown were taken from build 5.0 of the Reference Sequence of the rat genome (ENSMBL). Il2rg is on chromosome X on the (-) strand. Further noted is the position of the ecto-domain of Il2rg.

Table 30. Summary of the genomic organization of the rat Il2rg locus e Start End Notes Exon 1 71,111,444 71,111,543 contains ATG ATG 71,111,537 71,111,539 U) start codon Exon2 71,110,897 ,050 Exon3 71,110,504 71,110,688 Exon4 71,110,156 71,110,295 Exon5 71,109,228 71,109,390 contains transmembrane Exon6 ,599 71,108,645 domain Exon7 71,108,277 71,108,346 \10 Exon8 71,107,404 71,107,921 contains TGA ||TGA 71,108,736 71,108,738 stop codon full-length (ATG to TGA plus 3' humanization: 71,107,404 71,111,539 4,136 poly-A) ecto- (ATG to ing of humanization 71,108,679 71,111,539 2,861 transmembrane domain) A plasmid targeting vector was constructed to replace the rat ecto-domain of the interleukin 2 receptor gamma coding region with the human ecto domain as shown in Figure 32. The targeting vector was electroporated into the rat ES cells ed in Example 1 and the cells were plated on 15 cm 2x dense neomycin-resistant MEFs in 2i + uM ROCKi. The transformed rat ES cells were cultured, selected, and ined as described in Example 1.

As shown in Table 44, 192 colonies were screened and 13 targeted clones were obtained. The targeting efﬁciency was 6.77%.

Two clones were injected into blastocysts as described herein in Example 1, and two clones producing as were ed. Clones producing F0 rats were obtained. F0 rats that transmit the targeted modification through the ne are obtained. 4.3(b) (ii). Replacing Rat IL2rg Ecto-Domain with Human IL2rg Ecto-Domain Using Plasmid in Combination with CRISPR/Cas9 Table 31 shows a comparison of the results of experiments in which a version of the Il2rg ecto-domain humanization vector shown in Figure 32 was used alone to target the rat Il2rg locus or was used in combination with a CRISPlVCas9 nuclease to target the rat Il2rg locus. In each experiment, electroporated cells were plated at a high density and subjected to drug selection to ﬁnd colonies that were esistant. Drug- resistant colonies were picked and screened for the targeted modiﬁcation using the modiﬁcation of allele (MOA) assay as described . Speciﬁcally, 4 x 106 cells were electroporated with 2 ug of Il2rg ecto-domain zation vector at a voltage of 400V, a capacitance of 100 uF, and a resistance of 0. In the latter ment, 6 ug of Cas9 expression plasmid and 3 ug of Il2rg gRNA2 or 3 ug ofIl2rg gRNA4 were also electroporated. Selection was done using 75 ug/mL of G418. Il2rg gRNA2 has a sequence of GAAGCTCTTTCTATACAATCTGG (SEQ ID NO: 91) and targets a region 190 bp 3’ of the rat Il2rg exon 1. Il2rg gRNA4 has a sequence of CCCCCGAAAGGAGGAGCCCTAGG (SEQ ID NO: 92) and targets a region 80 bp 5’ of the rat Il2rg stop codon (TGA) (see Figure 49).

Table 3 1. Comparison of Il2rg Ecto-Domain Humanization Vector ing with and without CRISPlVCas9 Colonies Targeted Targeting ed Clones Efﬁcienc Il2rg plasm1d vector Il2rg plasm1d vector Il2rg plasmid Il2rg Yes 88 50 57 A)0 vector gRNA4 4.4(a). Enhanced Targeting by CRISPR/Cas9 Endonucleases ofLarge Non- Human Animal Gene ons with Simultaneous Human Gene Replacements Newly developed drugs for human disease conditions, such as ﬁally human antibodies, are often highly speciﬁc for their targets in human cells and tissues and do not recognize the homologous targets in rodents. This high level of selectivity makes it impossible to test the efﬁcacy and mechanism of action of the drugs in rodents prior to their ﬁrst use in humans.

A very effective solution to this problem is to create a genetically modiﬁed mouse or rat in which the human gene encoding the drug target replaces the rodent homolog. One way to create such a humanized allele in a rodent is to ﬁrst delete the rodent gene in an embryonic stem (ES) cell and then, in a second gene modiﬁcation event, to insert the human gene ely at the deleted locus. The ES cells are then injected into a rodent embryo and implanted in the uterus of a ate mother rodent, which subsequently gives birth to genetically modiﬁed pups that carry the humanized allele.

A more efﬁcient method of creating the humanized gene modiﬁcation is to use a large targeting vector (LTVEC) that directs the simultaneous deletion of the rodent gene and replacement with its human counterpart. By employing VELOCIGENE® genetic ering methods, such single-step humanizations can be achieved with vely high efﬁciency when the rodent gene deletion and human gene insertion are smaller than about 20 kilobase pairs (kb). Larger single-step humanizations entailing deletions and replacements of greater than 100 kb are possible with LTVECs and genetic ering methods such as VELOCIGENE® genetic engineering s, but because of reduced targeting efﬁciencies sometimes encountered with very large modiﬁcations, success often requires the ing or hundreds to nds of ES cell clones to ﬁnd one that carries the desired gene modiﬁcation.

To improve the efﬁciency of large humanizations we have ped methods that combine LTVEC gene targeting with clustered regularly interspaced short palindromic repeat RNA-guided Cas9 endonucleases (CRISPlVCas9). CRISPlVCas9 nucleases are ribonucleoprotein enzymes comprised of a bacterial Cas9 DNA endonuclease bound to a CRISPR RNA that guides Cas9 to cleave at a c DNA sequence by Watson-Crick base pairing between the guide RNA and one strand of the target DNA. Because of the simplicity of the targeting ism, it is easy to design CRISPlVCas9 endonucleases that direct a double strand break at nearly any genomic locus. Double strand breaks induce ar genomic repair by the non-homologous end joining (NHEJ) pathways, which are error prone and often result in deletions or insertions at the site of the double strand break. An alternative ism of repairing the double strand break is homology-directed repair (HDR) in which an nous or exogenous piece ofDNA that shares sequence ty or similarity with the broken site seamlessly repairs the broken ends by the action of the cellular homologous recombination machinery. HDR can result in a perfect repair that restores the al sequence at the broken site, or it can be used to direct a designed modiﬁcation, such as a deletion, ion, or replacement of the sequence at the site of the double strand break.

CRISPlVCas9 nucleases can greatly enhance the rate of engineered HDR events by directing e double strand cleavages at the sites of the intended gene modiﬁcations.

To effect a precise, single-step deletion of all or part of a rodent gene and simultaneous replacement with all or part of its human homolog, we uced by electroporation into rodent ES cells three nucleic acid les: (1) an LTVEC; (2) a plasmid or mRNA encoding a Cas9 endonuclease; and (3) a plasmid encoding a CRISPR single guide RNA (ngNA) or the ngNA itself. The LTVEC comprised all or part of a human gene that encodes the gene product (protein or RNA) ﬂanked by homology arms of rodent DNA ed to direct an HR event that deletes the rodent gene and inserts the human gene. The humanizing LTVEC also carried a drug ion cassette that directs the expression of an enzyme (e.g., neomycin phosphotransferase) that imparts resistance to an antibiotic drug (for example, G418). ES cells that took up the LTVEC and incorporated it into their genomes were able to grow and form colonies on a Petri dish in a growth medium containing the antibiotic drug. Because we introduced 500 to 1,000 times more CRISPlVCas9-encoding nucleic molecules than LTVEC molecules, most of the LTVEC-containing drug resistant colonies also contained, at least transiently, the CRISPlVCas9 ents. We picked drug resistant colonies and screened them by the loss-of-allele method (Valenzuela, D. et a]. (2003) High-throughput engineering of the mouse genome coupled with high-resolution expression analysis, Nature Biotech. 21 :652-660; Frendewey, D. et al. (2010) The loss-of—allele assay for ES cell screening and mouse genotyping, Methods Enzymol. 476:295-307; incorporated herein by reference in their entireties) to fy clones that had the correctly targeted humanized allele.

In one particular experiment the LTVEC was ed to create a 68 kb deletion of the mouse Lrp5 ensity lipoprotein receptor-related protein 5) gene and a simultaneous replacement with a 91 kb fragment of the homologous human LRP5 gene (Figure 34). The LTVEC comprised the 91-kb fragment of the human LRP5 gene ﬂanked by homology arms containing 7 kb and 33 kb of genomic DNA derived from parts of the mouse Lrp5 locus that ﬂank the 68 kb sequence of the mouse Lrp5 gene ed for deletion. In separate ments, we combined the Lrp5 humanizing LTVEC with a plasmid ng Cas9 and a second plasmid encoding one of eight ngNAs (gA, gB, gB2, gC, gD, gE2, gE, gF) designed to create double strand breaks within the region of the mouse Lrp5 gene that was targeted for deletion. The ngNAs were designed to avoid recognition of any sequence in the inserted portion of the human LRP5 gene.

The results of the CRISPIVCas9-assisted humanization of the Lrp5 gene are shown in Table 32. When the LTVEC alone was introduced into ES cells, we found that 1.0% of the screened drug resistant clones d a tly targeted mono-allelic heterozygous humanized allele. In contrast, combining the LTVEC with Cas9 endonucleases guided by seven of the eight tested ngNAs (ngNA-S 'A, ngNA-S 'B, ngNA-S 'B2, ngNA-C, ngNA-D, ngNA-3 'E2, and ngA-3 'F; sequences provided in Table 33) ed correctly targeted monoallelic heterozygous mutations at efﬁciencies that ranged from 2.1 to 7.3%, representing a 2- to 9-fold enhancement of single-step humanized gene targeting compared with the unaided LTVEC. For Cas9- guided cleavage by ngNA-S 'B2, in addition to monoallelic targeting, we detected biallelic homozygous humanization at a frequency of 1%. The homozygous Lrp5 humanized ES cells can be converted by the VELOCIMOUSE® c engineering method (Poueymirou, W. T. et al. (2007) F0 generation mice ﬁJlly derived from gene- targeted embryonic stem cells allowing ate phenotypic analyses, Nature Biotech. :91-99, incorporated herein by reference in its entirety) directly into completely ES cell-derived mice ready for ypic and drug eff1cacy studies.

Table 32. Screening Results for CRISPIVCas9-Assisted Humanization of the Lrp5 Gene.

Clones CRISPR Monoallelic Biallelic Biallelic Experiment Screened Activi z _ous Comound Homoz _ous (%) Mutation Heterozygous on Frequency (%) Mutation Frequency (%) Fre u uenc (%) LTVEC alone 96 0 LTVEC -- Cas9 7 3 96 75.6 0 -- ngNA-5 ’A - LTVEC -- Cas9 96 79.5 0 -- ngNA-5 ’B -— LTVEC -- Cas9 - 6.2 1.0 96 60.5 0 + ngNA-5 'B2 (6/96) (1/96) LTVEC -- Cas9 4.2 96 no assay 0 -- ngI\A-C - (4/96) LTVEC -- Cas9 7. 3 96 0 -- ngI\A-D LTVEC -- Cas9 2. l 96 84.5 0 + ngNA-3 'E2 LTVEC -- Cas9 96 52.4 -- ngNA-3 ’E LTVEC -- Cas9 -—6.2 96 79.8 —— ngNA-3 ’F Table 33. Sequences of the Guide Portions of Six ngNAs Targeting the Mouse Lrp5 Gene. imate Distance from ngNA Guide Sequence (5'to 3') Deletion End n oint (b) ng\ ' - GGGAACCCACAGCATACTCC (SEQ ID NO: 24) ng\A 5 B GAATCATGCACGGCTACCCC (SEQ ID NO 25) ngNA-S 'B2 1000 TATGGGGAGGCGCG (SEQ ID NO: 26) ngVA-C 29900/ 38430 ACTGAGATCAATGACCCCGA (SEQ ID NO: 85) ngVA-D 29950/ 38380 GGGTCGCCCGGAACCTCTAC (SEQ ID NO: 86) ngNA 3 E2 1000 CTTGGATAACATTGATACCC (SEQ ID NO 27) ngV\IA 3 E'- GGGGCAGAGCCCTTATATCA (SEQ ID NO: 28) ngNA 3 F TCGCTCACATTAATCCCTAG (SEQ ID NO. 29) The enhanced targeting of the large Lrp5 humanization by CRISPlVCas9 endonucleases is remarkable when compared with lent experiments performed with zinc ﬁnger nucleases (ZENS). We obtained four ZENS designed to make double strand breaks at sites within the region of the mouse Lrp5 gene targeted for deletion (Figure 34). One ZEN targeted a sequence near the 5 'end of the on (a), one targeted a sequence in the middle of the deletion (b), and two targeted sequences near the 3 'end of the deletion (c, d). In separate experiments, we combined the Lrp5 humanizing LTVEC with a plasmid encoding one of the four ZFNs (a-d) designed to create double strand breaks within the region of the mouse Lrp5 gene that were targeted for deletion. We determined that all of the ZFNs were active and able to induce NHEJ mutations in the Lrp5 gene (data not shown), but when combined with the LTVEC, none enhanced HDR- mediated gene targeting compared with the LTVEC alone.

The enhanced targeting efﬁciency of the large Lrp5 humanization by CRISPIVCas9 cleases is also remarkable when compared with a series of ZFN- assisted humanization experiments. In these experiments, a series of ZFN-assisted humanizations were performed in which the mouse target gene deletions and the human gene insertions were generally of increasing size (Table 34; Figure 35). Figure 35A depicts the percent targeting efﬁciency of LTVECs targeting genes of increasing size for deletion. The LTVECs were used alone (gray squares) or in combination with ZFNs (black squares). Figure 35B depicts the percent targeting efﬁciency of LTVECs with human gene insertions of sing size. Again, the LTVECs were used alone (gray triangles) or in combination with ZFNs (black triangles). As shown in Table 34 and Figure 35, the ability of ZFN-mediated DNA cleavage to enhance LTVEC targeting efﬁciency disappeared when the size of the mouse target gene deletion was r than 24.7 kb and when the size of the human gene insertion was r than 22.2 kb (Table 34; Figure 35A). In contrast, CRISPIVCas9 was capable of enhancing LTVEC targeting efﬁciency of the Lrp5 gene, which involved a mouse gene on of 68.3 kb and a human gene insertion of 91.0 kb (Table 32; Figure 34). This indicates that VCas9 endonucleases are able to enhance LTVEC targeting efﬁciency in situations where other nucleases (e. g., zinc ﬁnger ses) cannot.

Table 34. y of ZFN-Assisted Humanizations.

Targeting Efﬁcienc (%) Mouse Human ZFN Target Gene Gene 5'Homology 3 'Homology Cleavage LTVEC LTVEC Fold Gene Deletion Insertion Arm (kb) Arm (kb) Efﬁciency Alone + ZFN Enhancement kb kb % Fcerla 4.1 10.9 76.8 22.9 5.20 32.81 6.3 67.6 85.5 12.5 5.20 22.39 4.3 49.6 112.9 30.7 1.56 24.48 15.7 50.1 34.9 27.1 10.41 12.50 1.2 57.8 60.1 20.8 4.17 8.33 2.0 83.3 61.5 4.2 0.00 0.00 n.a. 41.3 57.8 8.8 0.52 0.00 18.4 114.7 8.8 1.04 0.00 Lrp5 683 910 334 (0 5) n.d.—— not determined n.a. = not applicable ( ) = targeting efﬁciency lower with ZFN than without Comparable ments were performed for humanization of other mouse genes. In one experiment, the LTVEC was ed to create a 45 kb deletion of the mouse Trpal (transient receptor potential cation channel subfamily A member 1) gene and a simultaneous replacement with a 55 kb fragment of the gous human TRPAI gene (Figure 36). The LTVEC comprised the 55 kb fragment of the human TRPAI gene ﬂanked by homology arms containing 41 kb and 58 kb of genomic DNA d from parts of the mouse TrpaI locus that ﬂank the 45 kb sequence of the mouse Trpal gene intended for deletion. In separate experiments, we combined the Trpal humanizing LTVEC with a plasmid encoding Cas9 and a second plasmid encoding one of eight ngNAs (gA, gA2, gB, gC, gD, gE, gE2, and gF) designed to create double strand breaks within the region of the mouse Trpal gene that was targeted for on. The ngNAs were designed to avoid recognition of any sequence in the inserted portion of the human TRPAI gene.

The results of the CRISPIVCas9-assisted humanization of the Trpal gene are shown in Table 35. When the LTVEC alone was uced into ES cells, we found that 1.0% of the screened drug resistant clones carried a correctly targeted monoallelic heterozygous humanized allele. In contrast, ing the LTVEC with Cas9 endonuclease guided by six of eight tested ngNAs (A, A2, B, C, D, and F; sequences provided in Table 43) produced correctly targeted monoallelic heterozygous mutations or biallelic compound zygous or homozygous mutations at efficiencies that ranged from 1.0 to 3.1%. For Cas9-guided cleavage by gRNA A and gRNA F, we detected compound heterozygous mutations at a frequency of 1.0%.

Table 35. Screening s for CRISPIVCas9-Assisted Humanization of the Trpal Gene.

Approx1mate CRISPR ngNA Distance from Clones Heterozygous Compound Homozygous gRNA ty Position Deletion Screened Targeted Heterozygous Targeted End 1 oint (b) Approximate CRISPR ngNA Distance from Clones Heterozygous Compound Homozygous gRVA Activity Position on Screened ed Heterozygous Targeted "7%B/> "7%/a> 25600/19740 g:C no assay 18370 gRD gR\A 1000 no assay 0 g1?\A -— 28.6 1 N/ _none_: In another experiment, the LTVEC was designed to create a 55 kb deletion of the mouse F01h] (glutamate carboxypeptidase 2) gene and a simultaneous replacement with a 61 kb fragment of the gous human FOLHI gene (Figure 37). The LTVEC comprised the 61 kb fragment of the human FOLHI gene ﬂanked by homology arms containing 22 kb and 46 kb of genomic DNA derived from parts of the mouse F01h] locus that ﬂank the 55 kb sequence of the mouse F01h] gene intended for deletion. In separate experiments, we combined the F01h] zing LTVEC with a plasmid encoding Cas9 and a second plasmid ng one of six ngNAs (gA, gA2, gC, gD, gE, and gE2) designed to create double strand breaks within the region of the mouse F01h] gene that was targeted for deletion. The ngNAs were designed to avoid ition of any sequence in the inserted portion of the human FOLHI gene.

The results of the CRISPlVCas9-assisted humanization of the F01h] gene are shown in Table 36. When the LTVEC alone was introduced into ES cells, we found that none of the 96 screened drug resistant clones carried a correctly targeted monoallelic heterozygous humanized allele. In contrast, combining the LTVEC with Cas9 endonuclease guided by three of six tested ngNAs (A, D, and E2; sequences provided in Table 43) produced tly targeted monoallelic heterozygous mutations at efﬁciencies that ranged from 1.0 to 3.1%.

Table 36. Screening Results for CRISPlVCas9-Assisted Humanization of the Folk] Gene.

CRISPR Position Distance Activity Screened Targeted Heterozygous ed from Deletion (%) Endpoint middle 31290/23810 :RNAD 392 500 :RNA E2 no assa 3' 100 gRNA E 1 2 N/A N/A none N/A 96 0 0 0 ] In another experiment, the LTVEC was designed to create a 76 kb deletion of the mouse gene for complement component 5 (C5 or H0) and a simultaneous replacement with a 97 kb fragment of the gous human C5 gene (Figure 38). The LTVEC comprised the 97 kb fragment of the human C5 gene ﬂanked by homology arms containing 34.1 kb and 31.2 kb of genomic DNA derived from parts of the mouse C5 (Hc) locus that ﬂank the 76 kb sequence of the mouse C5 (H6) gene intended for deletion. In separate experiments, we combined the C5 (Hc) humanizing LTVEC with a plasmid encoding Cas9 and a second plasmid encoding one of six ngNAs (gA, gB, gC, gD, gE, and gE2) designed to create double strand breaks within the region of the mouse C5 (H6) gene that was ed for deletion. The ngNAs were designed to avoid recognition of any sequence in the inserted portion of the human C5 gene.

The results of the VCas9-assisted humanization of the C5 (H6) gene are shown in Table 37. When the LTVEC alone was uced into ES cells, we found that 1.0% of the screened drug resistant clones carried a tly ed monoallelic heterozygous humanized allele. In st, combining the LTVEC with Cas9 endonuclease guided by all six tested ngNAs (A, B, C, D, E, and E2; sequences ed in Table 43) produced correctly targeted monoallelic heterozygous mutations or biallelic compound heterozygous or homozygous mutations at efﬁciencies that ranged from 4.2 to 16.7%. For Cas9-guided cleavage by gRNAs A and E, we detected compound heterozygous mutations at frequencies of 5.2% and 4.2%, respectively.

Table 37. Screening Results for CRISPlVCas9-Assisted Humanization of the C5 (Hc) Gene.

Approximate Distance ngNA CRESFR Clones Heterozygous Compound Homozygous from Act1v1ty Position Screened Targeted Heterozygous Targeted Deletion (%) End n oint -RNAA _——"-_ -RNAB _ 38200/37500 gRNAC _ middle —"—-_-_ mn—n n-_-_ m—"n In another experiment, the LTVEC was designed to create a 38 kb deletion of the mouse Adamts5 (a disintegrin and metalloproteinase with thrombospondin motifs ) gene and a simultaneous replacement with a 43 kb fragment of the homologous human ADAMTS5 gene (Figure 39). The LTVEC comprised the 43 kb fragment of the human ADAMTS5 gene ﬂanked by homology arms containing 22 kb and 46 kb of genomic DNA derived from parts of the mouse Adamts5 locus that ﬂank the 38 kb sequence of the mouse Adamts5 gene intended for deletion. In separate experiments, we ed the Adamts5 humanizing LTVEC with a plasmid encoding Cas9 and a second plasmid encoding one of eight ngNAs (gA, gA2, gB, gC, gD, gE, gE2, and gF) designed to create double strand breaks within the region of the mouse 5 gene that was targeted for deletion. The ngNAs were designed to avoid recognition of any sequence in the inserted portion of the human 5 gene.

The results of the CRISPIVCas9-assisted zation of the Adamts5 gene are shown in Table 38. When the LTVEC alone was introduced into ES cells, we found that none of the 96 screened drug resistant clones carried a correctly targeted monoallelic heterozygous humanized allele. In contrast, combining the LTVEC with Cas9 endonuclease guided by two of eight tested ngNAs (B and F; sequences provided in Table 43) ed correctly targeted monoallelic heterozygous mutations or biallelic compound zygous mutations at an efﬁciency of 1.0%. For Cas9-guided cleavage by gRNA E2, we detected compound heterozygous mutations at a frequency of 1.0%.

Table 38. Screening s for CRISPIVCas9-Assisted Humanization of the Adamts5 Gene.

Approximate CRISPR ngNA Distance from Clones Heterozygous Compound Homozygous gRNA Position Deletion 18:27)"), Screened Targeted Heterozygous Targeted End . oint (b ) , gRNA mun" 1000 96 18700/ 18950 96 18800/ 18850 96 1000 96 ] In another experiment, the LTVEC was designed to create a 102 kb deletion of the mouse Erbb4 (receptor tyrosine-protein kinase erbB-4) gene and a simultaneous replacement with a 127 kb nt of the homologous human ERBB4 gene (Figure 40). The LTVEC sed the 127 kb fragment of the human ERBB4 gene ﬂanked by homology arms containing 48 kb and 26 kb of c DNA derived from parts of the mouse Erbb4 locus that ﬂank the 102 kb sequence of the mouse Erbb4 gene intended for deletion. In te experiments, we combined the Erbb4 humanizing LTVEC with a plasmid encoding Cas9 and a second plasmid encoding one of eight ngNAs (gA, gB, gB2, gC, gD, gE, gE2, and gF) designed to create double strand breaks within the region of the mouse Erbb4 gene that was targeted for deletion. The ngNAs were designed to avoid recognition of any sequence in the inserted portion of the human ERBB4 gene.

The results of the CRISPlVCas9-assisted humanization of the Erbb4 gene are shown in Table 39. When the LTVEC alone was introduced into ES cells, we found that none of the 96 screened drug resistant clones carried a correctly targeted monoallelic heterozygous humanized allele. In contrast, combining the LTVEC with Cas9 endonuclease guided by one of eight tested ngNAs (D; sequence provided in Table 43) produced correctly targeted monoallelic heterozygous ons or biallelic compound heterozygous mutations at an efﬁciency of 1.0%. For Cas9-guided ge by gRNA D, we detected compound heterozygous mutations at a frequency of 1%.

Table 39. Screening s for CRISPlVCas9-Assisted Humanization of the Erbb4 Gene. ngNA Approximate CRISPR Clones Heterozygous Compound Homozygous gRNA Position Distance from t Screened Tar_eted Hetero o_us Tar_eted Deletion (%) End n ointbn gAR\A gBR\A - g gR\A middle 50200 / 51350 :DR\A 50230/51320 . m/m/A> gRE\> In another experiment, the LTVEC was designed to create a 110 kb on of the mouse R0r1 ine-protein kinase transmembrane receptor RORl) gene and a simultaneous replacement with a 134 kb nt of the homologous human RORI gene (Figure 41). The LTVEC comprised the 134 kb fragment of the human RORI gene ﬂanked by homology arms containing 41.8 kb and 96.4 kb of genomic DNA derived from parts of the mouse RorI locus that ﬂank the 110 kb sequence of the mouse RorI gene intended for deletion. In separate experiments, we combined the Rorl humanizing LTVEC with a plasmid encoding Cas9 and a second d encoding one of six ngNAs (gA, gB, gC, gD, gE, and gF) designed to create double strand breaks within the region of the mouse RorI gene that was targeted for deletion. The ngNAs were designed to avoid recognition of any sequence in the inserted portion of the human RORI gene.

The results of the CRISPlVCas9-assisted humanization of the R0r1 gene are shown in Table 40. When the LTVEC alone was introduced into ES cells, we found that none of the 96 screened drug resistant clones carried a tly targeted monoallelic heterozygous humanized allele. In st, combining the LTVEC with Cas9 endonuclease guided by two of six tested ngNAs (D and F; sequences provided in Table 43) produced correctly targeted monoallelic heterozygous or biallelic mutations at efﬁciencies of 1.0%. For Cas9-guided cleavage by gRNA F, we also detected compound zygous mutations at a frequency of 1%.

Table 40. Screening Results for CRISPlVCas9-Assisted zation of the RorI Gene.

Approximate CRISPR ngNA ce from Clones Heterozygous Compound Homozygous Position Deletion Aiil/ny Screened Targeted Heterozygous Targeted no assay—- no assay—- N/A N/A —-_ In another experiment, the LTVEC was designed to create a 79 kb deletion of the mouse Dpp4 (dipeptidyl peptidase 4) gene and a simultaneous replacement with an 82 kb fragment of the homologous human DPP4 gene (Figure 42). The LTVEC sed the 82 kb fragment of the human DPP4 gene ﬂanked by 5 ’ and 3 ’ homology arms, each containing 46 kb of genomic DNA derived from parts of the mouse Dpp4 locus that ﬂank the 79 kb ce of the mouse Dpp4 gene intended for deletion. In separate ments, we combined the Dpp4 humanizing LTVEC with a plasmid ng Cas9 and a second plasmid encoding one of eight ngNAs (gA, gB, gB2, gC, gD, gE, gE2, and gF) designed to create double strand breaks within the region of the mouse Dpp4 gene that was targeted for deletion. The ngNAs were designed to avoid recognition of any sequence in the inserted portion of the human DPP4 gene.

The results of the CRISPlVCas9-assisted humanization of the Dpp4 gene are shown in Table 41. When the LTVEC alone was introduced into ES cells, we found that 2.1% of the screened drug resistant clones carried a correctly targeted monoallelic heterozygous humanized allele. In contrast, combining the LTVEC with Cas9 clease guided by any one of eight tested ngNAs (A, B, B2, C, D, E, E2, and F; sequences provided in Table 43) produced correctly ed monoallelic heterozygous mutations at efﬁciencies that ranged from 2.1 to 7.3%.

Table 41. Screening Results for CRISPlVCas9-Assisted Humanization of the Dpp4 Gene.

Approx1mate CRISPR ngNA Distance from Clones Heterozygous Compound Homozygous Position Deletion A???" Screened Targeted Heterozygous Targeted End . oint (b ) -«"7%/w/>/> no assay 0/3> "7%E/> no assay no assay A table summarizing the results for CRISPlVCas9-assisted humanization of the various mouse genes is ed in Table 42. The ﬁrst row indicates the gene locus being targeted. The second row indicates the deletion size (Del) of the nous mouse locus and the ion size (Ins) of the corresponding human locus. The remaining rows show the number of colonies (out of 96) for each condition that had tly targeted monoallelic heterozygous ons, biallelic compound heterozygous mutations, or biallelic homozygous mutations. "No gRNA" represents LTVEC alone, Whereas the other rows represent LTVEC plus corresponding gRNAs (indicated by relative position within the deletion locus).

Table 42. Summary of CRISPlVCas9-Assisted Humanization of Mouse Genes. "____-_-_-_-_ "_______-_ ______-_-_-_ _-_-_ _______-_-_ 3’ 0 1 4 0 0 6 Most 3' 6 6 0 0 5 1 0 1 0 0 2 gRNA Table 43. Guide RNA Sequences Used for CRISPIVCas9-Assisted Humanization of Mouse Genes. i>Guide Se uence (5't0 3') SEQ ID NO Trpa gRVA A GTACTGGGGAATCGGTGGTC Trpal gRNA A2 CACGCACTCCAAATTTATCC Trpal gR Trpal gRAZ>> 003 CTAAGTGTGTATCAGTACAT TGCCCTGCACAATAAGCGCA 93939393 WNHO Trpal gRVA D ACTCATTGAAACGTTATGGC DJ L Trpal gRNA E2 AGTAAGGGTGGATTAAATTC Trpal gRVA E GCCATCTAGATTCATGTAAC Trpal gRVA F AAATGTTCTGCACC WWW \]O\U1 Folk] gRVAA TGAACCAATTGTGTAGCCTT Folk] gRNA A2 AATAGTGGTAAAGCACCATG WU) COO Folk] gRAZ>> 003 TAAGGATCGAAGTC Folk] gR, CACCGAGATGCTTGGGTATT A4; #0 Folk] gRVAD TGTAACCGCCCTGAATGACC LN Folk] gRVAE AAAAGGGCATCATAAATCCC Folk] gRNA E2 TCAAAAATAGTCATACACCT Folk] gRVA F GGTCTCTAGTACATTGTAGA C5 (Hc) gR\ ATCACAAACCAGTTAACCGG C5 (Hc) gR\A B TTTCAGACGAGCCGACCCGG C5 (Hc) gRN CTGTCAACAGTGCCGCGTTT C5 (Hc) gR\ TGTGTGTCATAGCGATGTCG C5 (Hc) gR\ >> GO AACAGGTACCCTATCCTCAC C5 (Hc) gRNA E2 TTGCATGCGCACTG MML How: C5 (Hc) gR\A E GGCCCGGACCTAGTCTCTCT C5 (Hc) gR\A F AGTCTGTAAAGTTAGCAGTC U101 LAN Adamts5 gR\A A GGTGGTGGTGCTGACGGACA £11 L l>NAdamts5 gRN TATGAGATCAACACTCGCTA U1 U1 Adamts5 gR\A B CCAAGGACTTCCCCACGTTA gR\A C TGCTTCCCTTATGCAAGATT Adamts5 gR\A D TTAGGTACCCTATTTGAATA Adamts5 gRNA E2 TGCAGTGGGTGACAGGTCCA Adamts5 gR\A E AGGGTTATACTGACGTTGTG O\U‘IU‘IU‘IU‘I O©OO\]O\ gR\A F TGTCTTTCAAGGAGGGCTAC O\ )—A Erbb4 gRNA A TGATGTGCAGTCAGACAAAG 62 Erbb4 gRNA B TGCACTATGGTTGACTATGA 0DJ |Erbb4 gRNA B2 GGAATATTCTAATAGGAAGT 0\ Erbb4 gRVA C AAGTGCTGTACCATTCTAGC Erbb4 gRNA D TAATCAATAGACAACCTCGT Erbb4 gRNA E2 TCATTCCTAATGGTATTATA O\O\O\ \]O\U1 |00Erbb4 gRVA E AGGGTACATAGATGGCATCG Erbb4 gRNA F CTCTTTAACAATTACCACTT O\O Rorl gR\> > TGTGGGCCTTTGCTGATCAC \lO |)—ARorl gR\A B TGATCCTATGGCCT Rorl gR\ TGCCAATAGCAGTGACTTGA \1N Rorl gR\>> GO GGGAAGAATGGGCTATTGTC \l DJ Rorl gR\A E GGTTGTTTGTGCTGATGACG Rorl gR\A F CCGTCCTAGGCCTTCTACGT \l\l Ui-h Dpp4 gR\A A ACTAGTAGACCTGAGGGGTT \l O\ Dpp4 gR\A B GCTCCAGTGTTTAGGCCTTG Dpp4 gRNA 132 GGCAAGCTGAAAACGCATGC \l\l OO\l Dpp4 gR\A c GTAGATCGCTTTCCACTACC Dpp4 gR\A D GAACTCCACTGCTCGTGAGC OO\l OO Dpp4 gRNA E2 GGGCACTATTGAAG 00 )—A Dpp4 gR\A E ATGGGAAGGTTTATACCAGC Dpp4 gR\A F CGGTGTAAAAACAACGGGAA 0000 DJN Example 5. Summary of Targeted ation of Rat Genomic Loci Table 44. Summary of rat targeting with various vector types and nuclease agents discussed in Examples 3 and 4. 2014/060788 can 36sz was -98 835: -98 863.3 :2 835: mg ﬂ £3 93 age mono? ﬂ 05:0 gas: mum: 5m mum: NE m 0:20 @8353 HS ﬁg Emﬁouépoo 3235 8338 HS HEB Emﬁouépoo :oﬂoﬁou :oﬂoﬁou 855 Awﬁpowuﬁob 82? :23 mi? Emﬁou EN: was 8338 8338 £386 EN: 88%on 38%on imam Uopﬁomobooﬁo 900-3% 0:20 3:20 "Eta—mash @585 05:53 meg—U "£2695 £2255 meg—U 638?: oany—Em— 5535"" «$2 m— F5333 «$2 "£33.; 5:23am Axvncdv $55.0 . "with 3335; meg—U vw c x: humanism @2528 wf I!I 5:539 m2 m: Ell wﬁBwEH 339/ Exam Em Umgq Exam Q Q 3853 E IIIEHHE E .3" + H m m m 2an Um>Hq mm . .

ZmN mum: . mom< mmmUEmmHmo nozmﬁqmﬁsﬂ .nozmﬁqmﬁsﬂ :oﬂmﬁqmﬁdﬂ was Engages: ammobamao mwmm BEE 52.2 29:an "a 253% 253$ 83$ @200 .omnOEmmEO :n 08 8083 $8 88850 msowNANQHBoa mm 8 UBBQQ A 85m £3 m§> 88m 885 8088588 .62 88> @3830 8088588 ommUEmmEU 8 $82880 88oqow 83 @9829 034 685 .53. msomNANQBBE 88 A258V 88on 8 mo m§> as, >X >880me oanEmmEU 52.2.3 mo 8: God momiq souésaoo 5 ! 338% 888-8 8838,8808 88> mo o o <2 <2 Axbm 80 280qu msomNANQBBE || @200 $8888 089620 8085 mm gm a mo H8 >85 8H @8098 2:5 $3 586 .MKNE 38890 68/8 83 385880885 80m ESE £28: 9E 885 8 .38 888800 68» m§> 8% 888% 8588,8802 mm «mg? ﬁ 2858 8: .858 "NMSN 88888888 :8 as, 229% UBomaEfMgmb 8 m anowEH mo m8>oEo< 80m 8:083 "802 86:89 8:088 ll ! 50 83 bwoa as. $8 gm 828% 859888 888800 85 80$8888E 38808 5 x"? - I $820 - £8 S o S 08 @8088 :8 ! mo @200 mo mm 68» 9886 ~n§885m UBQQEQQQV mm 83883 some 8 8388 88888889 8.8 8o @3098 EB $820 a m803u8m E80880 a >880me 9%? + 88 83 86% boEEQ—om 888% 88880 m>>oam 8: Q ﬁ dog/HA .3 9885 9:86 2553 2853 ow 58> 20:5 .3 688 68» 388,88 Bash 62mg 38808 038 oEmH 88:8 2an 8820 88> $8888 + 98> .8882 mag/Em "88883 8: Ill .62 68% +088 amid 83d soggesm Suﬁemasm Emmi: wsuowhﬁ Emacs NE m2? mo? 63098 >88 mug 892:: 88388888 850 mo? $8 95H 088 9N: $8 3% :32: @30wa Example 6. Generating, Maintaining, and Targeting Human Induced otent Stem Cells 6.1. Generation ofHuman iPS Cells This example describes the generation of human iPS cells from non- pluripotent human cells. ac (System Biosciences) vectors (PB-600A_CAGGS Bst XI (0.64 ug/uL) and PB-200 (0.99 ug/uL) comprising the genes that encode four reprogramming factors (hOct4, hSox2, hKLF-4, hMYC) operably linked to a CM7 promoter were introduced into neonatal human foreskin ﬁbroblasts using RED and BLUE GenelnTM transfection reagents (GlobalStem). The ected cells were incubated on NuFFl feeder cells in E7 medium to allow for incorporation of the vectors and expression of the reprogramming factors. E7 medium comprised DMEM/F-l2, , L-ascorbic acid, insulin, transferrin, selenium, and FGF-2.

Puromycin selection began 10 days after transfection using 2 ug/mL puromycin in E7 . At day 21, colonies were selected and cultured in mTeSRTM medium, which comprised DMEM/F-l2, NaHCOg, L-ascorbic acid, insulin, transferrin, selenium, FGF-2, TGF-Bl, glutathione, L-glutamine, defined lipids, thiamine, trace elements B and C, B-mercaptoethanol, bovine serum albumin, pipecolic acid, lithium chloride, and GABA. At days 29 to 57, cells were propagated and ed in mTeSRTM medium until reaching ~50% conﬂuent in 6 well plates. At days 65 to 73, propagation and e ued using mTeSRTM medium and Gentle Cell Dissociation t (Stem Cell Technologies). At day 76, medium was changed to low osmolality VG2i medium for ﬁarther propagation, passage, and maintenance of the cells sing naive or naive-looking hiPSCs. 6.2. LTVEC Targeting in Human iPS Cells This example describes the use of LTVEC targeting in human iPS cells.

As shown in Figure 51, we introduced by oporation into human iPS cells propagated in VG2i medium the following nucleic acid les: (1) an LTVEC (0.67 pg); (2) a plasmid encoding a Cas9 endonuclease (5 ug); and (3) a plasmid encoding a CRISPR single guide RNA (gRNA) (10 ug). In one set of samples, the Cas9 and gRNA were excluded. Speciﬁcally, 3 x 106 cells were electroporated at a voltage of 700V, a capacitance of 25 uF, and a resistance of 400 ohms. The LTVEC comprised a 16.7 kb nucleic acid sing mouse Adam6a and Adam6b genes ﬂanked by homology arms containing 34 kb and 105 kb of genomic DNA derived from genomic regions that ﬂank the 4.1 kb sequence of the human ADAM6 locus intended for deletion. The LTVEC also carried a drug selection cassette that directs the expression of an enzyme that imparts resistance to an otic drug (hygromycin). The human ADAM6 gRNA used had the following sequence: GTATAGCCCTGTTACACATT (SEQ ID NO: 94).

Cells that took up the LTVEC and incorporated it into their genomes were able to grow and form colonies on a GELTREXTM-coated tissue culture dish in a grth medium containing the antibiotic drug. Because we introduced 500 to 1,000 times more CRISPlVCas9-encoding nucleic molecules than LTVEC molecules, most of the LTVEC- ning drug resistant colonies also ned, at least transiently, the CRISPlVCas9 components. We picked drug resistant colonies and screened them by the loss-of-allele method (Valenzuela et al. (2003) Nat. Biotech. 21 :652-660; Frendewey et al. (2010) Methods Enzymol. 476:295-307; incorporated herein by reference in their entireties) to identify clones that had the correctly ed allele.

The s of the VCas9-assisted LTVEC targeting of the ADAM6 locus are shown in Table 47.

Table 47. VCas9-assisted LTVEC targeting When the LTVEC alone was introduced into human iPS cells, a targeting efﬁciency of 3. 1% was observed. In contrast, combining the LTVEC with Cas9 guided by the ADAM6 gRNA resulted in a targeting efficiency of 7.3%. 6.3. Eﬂect ofLow Osmolality Medium on Human iPS Cell Morphology This example describes the effect of salt concentration, ionic strength, and/or osmolality on the pluripotency state of human iPS cells in culture. Human iPS cells were cultured on a MATRIGELTM or XTM substrate in a medium described in Table 48 or in mTeSRTM -hLIF medium.

WO 88643 Table 48. Medium for iPS cell culture.

Base Medium 24.75 24-75 Neurobasal® Medium 49 B-27® Supplement Penicillin/Streptomycin amine (200 mM) 1 2-Mercaptoethanol (55 mM) 0. l 836 hLIF (1 x 104 units/mL) 0.001 CHIR99021 (10 mM) 0.03 —PD0325901 (10 mM) 0.005 When the base medium used was DMEM, this medium was referred to as 2i medium. When the base medium used was VG-DMEM, this low osmolality medium was referred to as VG2i medium. The osmolality ofVG2i medium (233 mOsm/kg) is lower than the osmolality of traditional 2i medium (261 mOsm/kg).

As shown in Figure 52, human iPS cells cultured on MATRIGELTM in 2i medium for a period of 8 days (Figure 52A) or 12 days (Figure 52B) displayed a morphology characteristic of iPS cells in a primed state, particularly growth in an epithelial monolayer and the appearance of apico-basal polarity. hLIF medium and VG2i medium were further evaluated for their effects on the morphology and pluripotency state of human iPS cells. In this study, human iPS cells were ed on MATRIGELTM or NuFF feeder cells in mTeSRTM - hLIF medium (Figures 53A and 53C) or in VG2i medium (Figures 53B and 53D) for a period of 6 days. When cultured in mTeSRTM -hLIF medium on ELTM or NuFF feeder cells, human iPS cells yed a morphology characteristic of a primed pluripotency state, particularly growth in an epithelial monolayer and the appearance of apico-basal polarity. Some cells cultured in M -hLIF medium began to display a morphology characterized by three-dimensional clumping. By contrast, when cultured in VG2i medium on MATRIGELTM or NuFF feeder cells, the human iPS cells displayed a logy characteristic of a naive pluripotency state, particularly growth in round, dome-shaped colonies and a lack of apico-basal polarity. 6.4. Eﬂect ofLow Osmolality Medium 0n the Expression of Pluripotency Markers in Human iPS Cells This example describes the effect of salt concentration, ionic strength, and/or osmolality on the expression of pluripotency markers in human iPS cells that have been rammed from a primed state to a naive state. Following 24 days of culture in VG2i medium on a MATRIGELTM ate, reprogrammed naive human iPS cells were d for the expression of alkaline phosphatase or NANOG. It was observed that the reprogrammed cells strongly expressed both alkaline phosphatase (Figure 54A) and NANOG (Figures 54B and 54C), which are indicative of a naive pluripotency state. 6.5. Eﬂect ofLow Osmolality Medium 0n tic Dissociation and Subculture 0fHuman iPS Cells In this example, human iPS cells that were reprogrammed to a naive state using low osmolality VG2i medium were enzymatically dissociated using trypsin to create a single cell suspension (Figure 55A). The cell suspension was ed onto new GELTREXTM-coated plates for subculture in VG2i medium. It was observed after 1 day (Figure 55B) and 4 days (Figure 55C) that the subcultured cells continued to display a morphology characteristic of cells in a naive pluripotency state. Particularly, the cells grew as rounded dome-shaped colonies and did not exhibit an basal polarity. It was notable that enzymatic dissociation could be performed in the absence of a ROCK inhibitor, which is lly necessary to prevent activation of pro-apoptotic pathways.

This suggests that pro-apoptotic pathways are not as strongly activated during tic dissociation and subculture in naive human iPS cells cultured under the conditions fied herein.

All publications and patent applications mentioned in the specification are indicative of the level of those skilled in the art to which this invention ns. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. Unless otherwise apparent from the context of any embodiment, aspect, step or feature of the invention can be used in ation with any other. Reference to a range includes any integers Within the range, any subrange within the range. Reference to multiple ranges includes composites of such ranges.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. An in vitro method for modifying a genome at a genomic locus of st in a pluripotent cell, comprising: introducing into the pluripotent cell a Cas9 protein or a nucleic acid ng the Cas9 protein, a CRISPR RNA that hybridizes to a CRISPR target sequence ately flanked by a Protospacer Adjacent Motif (PAM) sequence at the genomic locus of interest or a DNA encoding the CRISPR RNA, a tracrRNA or a DNA encoding the tracrRNA, and a large targeting vector (LTVEC) that is at least 10 kb in size and comprises an insert nucleic acid flanked by: (i) a 5’ homology arm that is homologous to a 5’ target sequence at the genomic locus of interest; and (ii) a 3’ homology arm that is homologous to a 3’ target ce at the genomic locus of interest, wherein the pluripotent cell is a non-human mammalian pluripotent cell or a human induced pluripotent stem cell, and wherein following introducing into the pluripotent cell the Cas9 protein or the nucleic acid encoding the Cas9 protein, the CRISPR RNA or the DNA encoding the CRISPR RNA, the tracrRNA or the DNA encoding the tracrRNA, and the LTVEC: (i) the genome of the pluripotent cell is modified to comprise a targeted genetic modification comprising deletion of a region of the genomic locus of st and insertion of the insert nucleic acid at the genomic locus of interest, n the deletion is at least 30 kb, the insertion is at least 30 kb, or both the on and the ion are at least 30 kb; or (ii) the genome of the pluripotent cell is modified to comprise a targeted genetic modification comprising insertion of the insert nucleic acid at the genomic locus of interest, wherein the insertion is at least 30 kb, wherein the combined use of the LTVEC with the Cas9 protein or the nucleic acid encoding the Cas9 protein, the CRISPR RNA or the DNA encoding the CRISPR RNA, and the tracrRNA or the DNA encoding the tracrRNA results in an increased targeting ency compared to use of the LTVEC alone.

2. The method of claim 1, n the CRISPR RNA and the tracrRNA are introduced as a single nucleic acid molecule comprising the CRISPR RNA and the tracrRNA.

3. The method of claim 2, wherein the single nucleic acid le comprises the CRISPR RNA and the tracrRNA fused together in the form of a single guide RNA (sgRNA).

4. The method of claim 1, wherein the CRISPR RNA and the NA are introduced separately.

5. The method of any one of claims 1 to 4, n: (a) the Cas9 protein is introduced in the form of a protein, the CRISPR RNA is introduced in the form of an RNA, and the tracrRNA is introduced in the form of an RNA; (b) the Cas9 protein is introduced in the form of a messenger RNA (mRNA) encoding the Cas9 protein, the CRISPR RNA is introduced in the form of an RNA, and the tracrRNA is introduced in the form of an RNA; or (c) the Cas9 protein is introduced in the form of a DNA encoding the Cas9 protein, the CRISPR RNA is introduced in the form of a DNA encoding the CRISPR RNA, and the tracrRNA is introduced in the form of a DNA encoding the tracrRNA.

6. The method of claim 5, wherein the Cas9 protein, the CRISPR RNA, and the tracrRNA are introduced as a protein-RNA complex.

7. The method of claim 5, wherein: (a) the DNA encoding the Cas9 protein is in the form of a first expression construct comprising a first promoter ly linked to a first nucleic acid encoding the Cas9 (b) the DNA encoding the CRISPR RNA is in the form of a second expression construct comprising a second promoter operably linked to a second nucleic acid encoding the CRISPR RNA; and (c) the DNA encoding the NA is in the form of a third expression uct comprising a third promoter operably linked to a third nucleic acid encoding the tracrRNA; wherein the first, second, and third promoters are active in the pluripotent cell, wherein the first, , and third expression constructs are on a single nucleic acid molecule or on multiple nucleic acid molecules.

8. The method of claim 5, wherein: (a) the DNA encoding the Cas9 protein is in the form of a first expression construct comprising a first er operably linked to a first nucleic acid encoding the Cas9 protein; and (b) the DNA encoding the CRISPR RNA and the DNA encoding the tracrRNA are in the form of a second sion construct comprising a second promoter operably linked to a second nucleic acid encoding a gRNA comprising the CRISPR RNA and the tracrRNA; wherein the first and second promoters are active in the pluripotent cell, and wherein the first and second expression constructs are on a single nucleic acid molecule or on separate c acid molecules.

9. The method of any one of claims 1 to 8, wherein the targeted genetic modification comprises simultaneous deletion of an endogenous nucleic acid sequence at the c locus of interest and insertion of the insert nucleic acid at the genomic locus of st.

10. The method of claim 9, n the deleted endogenous nucleic acid sequence is from 30 kb to about 110 kb, and the insert nucleic acid is from about 40 kb to about 140 kb.

11. The method of any one of claims 1 to 10, wherein the targeted genetic modification is a biallelic genetic modification.

12. The method of claim 11, wherein the biallelic genetic modification ses deletion of an endogenous nucleic acid sequence and insertion of the insert nucleic acid at the genomic locus of st in two homologous chromosomes.

13. The method of claim 11, wherein the modified pluripotent cell is compound heterozygous or hemizygous at the genomic locus of st.

14. The method of claim 13, wherein the targeted genetic modification at the genomic locus of interest in one chromosome comprises deletion of an nous nucleic acid sequence and insertion of the insert nucleic acid.

15. The method of claim 14, wherein the targeted genetic modification comprises: (1) deletion of an endogenous nucleic acid ce at the genomic locus of interest in first and second homologous chromosomes; and (2) insertion of the insert nucleic acid into the genomic locus of interest in the first homologous chromosome and disruption of the c locus of st in the second homologous chromosome.

16. The method of any one of claims 1 to 15, wherein the LTVEC is at least 40 kb; or wherein the targeted genetic modification comprises deletion of a region of the genomic locus of interest wherein the deletion is at least 30 kb, and the LTVEC is at least 15 kb.

17. The method of any one of claims 1 to 16, wherein targeted genetic modification comprises ion of the insert nucleic acid, wherein the insert nucleic acid is at least 40 kb; or n the targeted genetic modification comprises deletion of a region of the c locus of interest wherein the deletion is at least 30 kb and insertion of the insert nucleic acid wherein the insert nucleic acid is at least 10 kb.

18. The method of any one of claims 1 to 17, wherein the insert nucleic acid is from about 40 kb to about 140 kb.

19. The method of any one of claims 1 to 18, wherein the sum total of the 5’ and the 3’ homology arms of the LTVEC is from 10 kb to 150 kb.

20. The method of claim 19, wherein the sum total of the 5’ and the 3’ homology arms of the LTVEC is from 30 kb to 150 kb.

21. The method of any one of claims 1 to 20, wherein the LTVEC is from 100 kb to 300 kb in length.

22. The method of any one of claims 1 to 21, wherein the targeted genetic modification comprises: (a) replacement of an endogenous c acid sequence with a homologous or an orthologous nucleic acid sequence; (b) deletion of an endogenous nucleic acid ce; (c) deletion of an endogenous nucleic acid sequence, wherein the deletion ranges from at least 30 kb to about 400 kb; (d) ion of an exogenous nucleic acid sequence; (e) insertion of an exogenous nucleic acid sequence ranging from at least 30 kb to about 400 kb; (f) insertion of an exogenous nucleic acid sequence sing a gous or an orthologous nucleic acid sequence; (g) ion of a chimeric nucleic acid sequence comprising a human and a non-human nucleic acid sequence; (h) insertion of a conditional allele flanked by site-specific inase target sequences; (i) insertion of a selectable marker or a reporter gene operably linked to a promoter active in the otent cell; or (j) a combination thereof.

23. The method of any one of claims 1 to 22, wherein the targeted genetic modification comprises deletion of a region of the genomic locus of interest, wherein the deletion is at least 40 kb; or wherein the targeted genetic modification further comprises insertion of the insert nucleic acid at the genomic locus of interest wherein the ion is at least 30 kb and deletion of a region of the genomic locus of interest wherein the deletion is at least 10 kb.

24. The method of any one of claims 1 to 23, wherein the region of the genomic locus being d is from about 30 kb to about 110 kb.

25. The method of any one of claims 1 to 24, wherein the targeted genetic modification comprises deletion of a region of the genomic locus of interest wherein the deletion is at least 30 kb and insertion of the insert nucleic acid at the genomic locus of interest wherein the insertion is at least 30 kb.

26. The method of any one of claims 1 to 25, wherein the LTVEC is from 100 kb to 300 kb, the sum total of the 5’ and 3’ homology arms is from 30 kb to 150 kb, and the targeted genetic modification comprises deletion of a region of the genomic locus of interest wherein the deletion is from 30 kb to 110 kb and insertion of the insert nucleic acid at the genomic locus of interest wherein the insertion is from 40 kb to 140 kb.

27. The method of any one of claims 1 to 26, wherein the genomic locus of interest is endogenous to the pluripotent cell.

28. The method of any one of claims 1 to 26, wherein the genomic locus of interest ses a logous or ous segment of DNA that was integrated into the genome of the pluripotent cell.

29. The method of any one of claims 1 to 28, wherein the genomic locus of interest is an globulin locus.

30. The method of claim 29, wherein the immunoglobulin locus encodes a mammalian immunoglobulin heavy chain variable region amino acid sequence.

31. The method of claim 29, wherein the immunoglobulin locus encodes a mammalian immunoglobulin light chain variable region amino acid sequence.

32. The method of claim 31, wherein the immunoglobulin locus comprises an unrearranged mammalian λ and/or κ light chain variable region nucleic acid sequence.

33. The method of claim 31, wherein the immunoglobulin locus comprises a nged mammalian λ and/or κ light chain le region nucleic acid sequence.

34. The method of any one of claims 1 to 28, wherein the genomic locus of interest is a T cell receptor locus.

35. The method of claim 34, wherein the T cell receptor locus is a T cell or alpha locus.

36. The method of any one of claims 1 to 28, wherein the genomic locus of interest comprises an interleukin-2 receptor gamma locus, an ApoE locus, a Rag1 locus, a Rag2 locus, both of the Rag1 and the Rag2 loci, an Adamts5 locus, a Trpa1 locus, a Folh1 locus, an Erbb4 locus, a Lrp5 locus, a C5 (Hc) locus, a Ror1 locus, or a Dpp4 locus.

37. The method of any one of claims 1 to 36, wherein the insert nucleic acid comprises a genomic nucleic acid sequence that encodes a human globulin heavy chain variable region amino acid sequence.

38. The method of claim 37, wherein the insert nucleic acid comprises one or more functional human VH gene segments comprising VH1-2, VH1-3, VH1-8, VH1-18, , VH1-45, VH1-46, , VH1-69, VH2-5, VH2-26, VH2-70, VH3-7, VH3-9, VH3-11, , VH3-15, VH3-16, VH3-20, VH3-21, VH3-23, VH3-30, VH33, VH35, VH3-33, , VH3-38, VH3-43, VH3-48, VH3-49, VH3-53, VH3-64, VH3-66, VH3-72, VH3-73, VH3-74, VH4-4, VH4-28, VH41, VH42, VH44, VH4-31, VH4-34, VH4-39, VH4-59, VH4-61, VH5-51, VH6-1, VH71, VH7-81, or a combination thereof.

39. The method of claim 37 or 38, wherein the insert nucleic acid ses one or more functional human D gene segments sing D1-1, D1-7, D1-14, D1-20, D1-26, D2-2, D2-8, D2-15, D2-21, D3-3, D3-9, D3-10, D3-16, D3-22, D4-4, D4-11, D4-17, D4-23, D5- 12, D5-5, D5-18, D5-24, D6-6, D6-13, D6-19, D6-25, D7-27, or a combination thereof.

40. The method of any one of claims 37 to 39, wherein the insert nucleic acid comprises one or more onal JH gene segments comprising JH1, JH2, JH3, JH4, JH5, JH6, or a ation thereof.

41. The method of any one of claims 1 to 36, wherein the insert nucleic acid comprises a genomic nucleic acid sequence that encodes a human immunoglobulin light chain variable region amino acid sequence.

42. The method of claim 41, wherein the insert nucleic acid comprises one or more human Vκ gene segments comprising Vκ4-1, Vκ5-2, Vκ 7-3, Vκ 2-4, Vκ1-5, Vκ1-6, Vκ3- 7, Vκ1-8, Vκ1-9, Vκ2-10, Vκ3-11, Vκ1-12, Vκ1-13, Vκ2-14, Vκ3-15, Vκ1-16, Vκ1-17, Vκ2-18, Vκ2-19, Vκ3-20, Vκ6-21, , Vκ1-23, Vκ2-24, , Vκ2-26, Vκ1-27, Vκ2-28, Vκ2-29, Vκ2-30, Vκ3-31, Vκ1-32, Vκ1-33, Vκ3-34, Vκ1-35, , Vκ1-37, Vκ2-38, Vκ1-39, Vκ2-40, or a combination thereof.

43. The method of claim 41 or 42, wherein the insert nucleic acid comprises one or more human Vλ gene segments comprising Vλ3-1, Vλ4-3, Vλ2-8, Vλ3-9, Vλ3-10, Vλ2-11, Vλ3-12, Vλ2-14, Vλ3-16, Vλ2-18, Vλ3-19, Vλ3-21, , , Vλ3-25, Vλ3-27, or a combination thereof.

44. The method of any one of claims 41 to 43, wherein the insert c acid comprises one or more human Jκ gene segments comprising Jκ1, Jκ2, Jκ3, Jκ4, Jκ5, or a combination thereof.

45. The method of any one of claims 1 to 36, wherein the insert nucleic acid comprises a polynucleotide ng at least a region of a human T cell receptor.

46. The method of claim 45, wherein the T cell receptor is a T cell receptor alpha.

47. The method of any one of claims 1 to 36, wherein the insert nucleic acid comprises at least one disease allele.

48. The method of claim 47, wherein the insert nucleic acid comprises at least one human disease allele of a human gene.

49. The method of any one of claims 1 to 48, wherein the pluripotent cell is the non-human mammalian pluripotent cell, and wherein the targeted c modification results in a humanized genomic locus comprising: (a) an insertion of a homologous or orthologous human nucleic acid sequence; (b) a replacement of an nous nucleic acid sequence with a homologous or orthologous c acid sequence; or (c) a combination thereof.

50. The method of claim 49, wherein the otent cell is the non-human mammalian pluripotent cell, and n the targeted genetic modification comprises a replacement of an endogenous nucleic acid sequence with a homologous or orthologous human nucleic acid sequence.

51. The method of any one of claims 1 to 50, wherein the CRISPR target sequence is not present in the insert nucleic acid.

52. The method of any one of claims 1 to 51, n the CRISPR target sequence is located anywhere between the 5’ target sequence and the 3’ target sequence at the genomic locus of interest.

53. The method of any one of claims 1 to 52, wherein the CRISPR target sequence is immediately adjacent to the 5’ target sequence or the 3’ target sequence at the genomic locus of interest.

54. The method of any one of claims 1 to 53, wherein the CRISPR target sequence is within the 5’ end of the region of the genomic locus of interest ed for deletion.

55. The method of claim 54, wherein the CRISPR target sequence is 50 to 1000 base pairs from the deletion endpoint.

56. The method of any one of claims 1 to 55, n the CRISPR target sequence is within the 3’ end of the region of the genomic locus of interest targeted for deletion.

57. The method of claim 56, n the CRISPR target sequence is 50 to 1000 base pairs from the deletion endpoint.

58. The method of any one of claims 1 to 57, wherein the CRISPR target sequence is located in an intron, an exon, a promoter, an enhancer, a regulatory region, or any non-protein coding .

59. The method of any one of claims 1 to 58, wherein the CRISPR target sequence is located within a coding region of a gene or within a regulatory region that nces expression of the gene.

60. The method of any one of claims 1 to 59, wherein the guide RNA comprises SEQ ID NO: 2, 3, 4, 5, 6, 7, or 8.

61. The method of any one of claims 1 to 60, wherein the mammalian pluripotent cell is a human induced pluripotent stem cell.

62. The method of claim 61, wherein the human induced pluripotent stem cell is being maintained in a medium comprising a base medium and supplements, wherein the medium comprises: (a) a leukemia inhibitory factor (LIF) polypeptide; (b) a glycogen synthase kinase (GSK3) inhibitor; and (c) a MEK inhibitor; wherein the base medium has an lity of about 180 mOsm/kg to about 250 mOsm/kg.

63. The method of any one of claims 1 to 60, wherein the pluripotent cell is a non-rat eukaryotic cell.

64. The method of any one of claims 1 to 60, wherein the mammalian otent cell is a rodent pluripotent cell.

65. The method of claim 64, wherein the rodent pluripotent cell is a rat embryonic stem (ES) cell or a mouse ES cell.

66. The method of claim 65, wherein the rodent pluripotent cell is a mouse ES cell.

67. The method of claim 65, wherein the rodent pluripotent cell is a rat ES cell.

68. The method of claim 67, wherein the rat ES cell is obtainable by culturing cyst outgrowths on a feeder cell layer of mitotically inactivated mouse embryonic fibroblasts with the 2i medium set forth in Table 3, wherein the targeted genetic cation is capable of being transmitted through the ne.

69. The method of claim 67 or 68, further comprising: (a) identifying the ed rat ES cell comprising the targeted genetic modification at the genomic locus of interest; (b) ucing the modified rat ES cell into a rat host embryo; and (c) gestating the rat host embryo in a surrogate , wherein the surrogate mother produces an F0 generation rat comprising the targeted genetic cation at the genomic locus of interest.

70. The method of claim 66, further comprising: (a) identifying the modified mouse ES cell comprising the targeted genetic modification at the genomic locus of interest; (b) introducing the modified mouse ES cell into a mouse host embryo; and (c) gestating the mouse host embryo in a surrogate mother, n the surrogate mother produces an F0 tion mouse comprising the targeted genetic modification at the genomic locus of interest.

71. The method of any one of claims 1 to 70, wherein the Cas9 protein comprises a nuclear localization signal.

72. The method of any one of claims 1 to 71, wherein the sum total of the 5’ and the 3’ homology arms of the LTVEC is at least 10 kb.

73. The method of any one of claims 1 to 72, wherein the CRISPR target sequence is a native sequence that is endogenous to the cell.

74. The method of any one of claims 1 to 73, wherein the genomic locus of interest is native to the cell.

75. The method of any one of claims 1 to 74, wherein the Cas9 protein comprises a nuclear localization signal, and wherein the CRISPR target sequence is located re n the 5’ target sequence and the 3’ target sequence or the CRISPR target sequence is immediately adjacent to the 5’ target sequence or the 3’ target sequence.

76. The method of any one of claims 1 to 75, wherein the CRISPR target ce is a native sequence that is endogenous to the cell, and wherein the sum total of the 5’ and the 3’ homology arms of the LTVEC is from 10 kb to 150 kb.

77. The method of claim 76, n the CRISPR target sequence is a native sequence that is nous to the cell, and wherein the CRISPR target sequence is located anywhere between the 5’ target sequence and the 3’ target sequence or the CRISPR target sequence is immediately adjacent to the 5’ target sequence or the 3’ target sequence.

78. The method of any one of claims 1 to 77, n the sum total of the 5’ and the 3’ homology arms of the LTVEC is at least 10 kb, wherein the genomic locus of interest is native to the cell, and wherein the CRISPR target sequence is located anywhere between the 5’ target sequence and the 3’ target sequence or the CRISPR target sequence is immediately adjacent to the 5’ target sequence or the 3’ target sequence.