WO2002074905A9 - Leptin induced genes - Google Patents

Abstract

LIG 46, a gene whose expression is induced by leptin is disclosed. LIG46 represents a target for the development of therapeutic agents for use in modulating body weight. For example, agents that alter the expression or activity of LIG46 can be used to modulate body weight. Such agents can be identified using cellular, in vitro, or in vivo assays which monitor the expression or activity of LIG46. LIG46 nucleic acid molecules and polypeptides are potentially useful therapeutically and diagnostically.

Description

LEPTIN INDUCED GENES

RELATED APPLICATION INFORMATION

This application is a continuation-in-part of application serial no. 09/292,228, filed April 15, 1999, which is a continuation-in-part of application serial no. 09/195,896, filed November 19, 1998, which is a continuation-in-part of application serial no. 09/150,857, filed September 10, 1998.

BACKGROUND

The oh gene product, leptin, is an important circulating regulator of body weight. Leptin binds to and activates the long form of ObR, the leptin receptor (Tartaglia et al. (1995) Cell 83 : 1263 -71 ). Leptin is thought to modulate body weight by influencing appetite and other factors. Compounds other than leptin, e.g., neuropeptide Y, melanocortins, CART, and orexins are also thought to play a role in modulation of body weight by influencing factors such as appetite and satiety, fat storage, and energy output.

SUMMARY The present invention is based, at least in part, on the identification of a gene, LIG46, whose expression is induced by leptin.

LIG46 represents a target for the development of therapeutic agents for use in modulating body weight. For example, agents that alter the expression or activity of LIG46 can be used to modulate body weight. Such agents can be identified using cellular, in vitro, or in vivo assays which monitor the expression or activity of LIG46. Potentially useful therapeutic agents can also be identified through the use of assays designed to identify agents that bind to LIG46. The LIG46 gene and LIG46 protein may themselves may be useful therapeutically and diagnostically.

The murine LIG46 cDNA described below (SEQ ID NO:l) has a 1191 nucleotide open reading frame (nucleotides 3 - 1193 of SEQ ID NO:l ; SEQ ID NO:5) which encodes a

397 amino acid protein (SEQ ID NO:2). This protein includes a predicted signal sequence of about 32 amino acids (from amino acid 1 to about amino acid 32 of SEQ ID NO:2) and a predicted mature protein of about 365 amino acids (from about amino acid 33 to amino acid 397 of SEQ ID NO:2). The extracellular domain of LIG46 extends from about amino acid 33 to about amino acid 302. LIG46 possesses one predicted transmembrane domain which extends from about amino acid 303 (extracellular end) to about 320 (intracellular end) of SEQ ID NO:2. The cytoplasmic domain of LIG46 extends from about amino acid 321 to about amino acid 397.

The human LIG46 cDNA described below (SEQ ID NO:3) has a 1191 nucleotide open reading frame (nucleotides _ - _ of SEQ ID NO:3; SEQ ID NO:6) which encodes a 397 amino acid protein (SEQ ID NO:4). This protein includes a predicted signal sequence of about 32 amino acids (from amino acid 1 to about amino acid 32 of SEQ ID NO:4) and a predicted mature protein of about 365 amino acids (from about amino acid 33 to amino acid 397 of SEQ ID NO:4).

LIG46 protein has some sequence similarity to a number of galactosyltransferases. Galactosyltransferases have been implicated in developmental processes. In addition, galactosyltransferases may play a role in cell-to-cell signaling by modifying the carbohydrate repertoire on cell surface receptors to activate, inhibit or otherwise modify (e.g., by altering receptor affinity for a ligand) receptor activity. Thus, LIG46 may play a role body weight regulation by influencing cell-to-cell signaling mediated by molecules involved in body weight regulation, e.g., leptin.

The LIG46 polypeptide sequence of SEQ ID NO:2 includes potential N-glycosylation sites at amino acids 30-33, 79-82, 89-92, 127-173, and 219-222; potential protein kinase C phosphorylation sites at amino acids 54-56, 202-204, 221-223, 323-325, and 377-379; potential casein kinase II phosphorylation sites at amino acids 31-34, 94-97, 185-188, 221- 224, 234-237, and 368-371 ; a potential tyrosine kinase phosphorylation site at amino acids 115-122; and a potential amidation site at amino acids 3-6.

In one aspect, the invention provides isolated nucleic acid molecules encoding LIG46 proteins or biologically active portions thereof, as well as nucleic acid molecules suitable for use as primers or hybridization probes for the detection of LIG46-encoding nucleic acid molecules. The invention further provides nucleic acid molecules that are at least 45% (or 55%, 65%, 75%, 85%, 95%, or 98%) identical to the nucleotide sequence shown in SEQ ID NO:l, or SEQ ID NO:3, or a complement thereof.

The invention provides a nucleic acid molecule which includes a fragment of at least 300 (325, 350, 375, 400, 425, 450, 500, 550, 600, 650, 700, 800, 900, 1000, 1200, 1300, or ,

1400) nucleotides of the nucleotide sequence shown in SEQ ID NO.l, or SEQ ID NO:3, or a complement thereof.

The invention also features a nucleic acid molecule which includes a nucleotide sequence encoding a protein having an amino acid sequence that is at least 45% (or 55%, 65%, 75%, 85%, 95%, or 98% identical to the amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4.

In a preferred embodiment, a LIG46 nucleic acid molecule has the nucleotide sequence shown SEQ ID NO:l or SEQ ID NO:3.

Also within the invention is a nucleic acid molecule which encodes a fragment of a polypeptide having the amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4, the fragment including at least 15 (25, 30, 50, 100, 150, 300, or 390) contiguous amino acids of SEQ ID NO:2 or SEQ ID NO:4.

The invention includes a nucleic acid molecule which encodes a naturally occurring allelic variant of a polypeptide comprising the amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4, wherein the nucleic acid molecule hybridizes to a nucleic acid molecule comprising SEQ ID NO:l or SEQ ID NO:3 under stringent conditions.

Also within the invention are: an isolated LIG46 protein having an amino acid sequence that is at least about 65%, preferably 75%, 85%, 95%, or 98% identical to amino acids 33-397 of SEQ ID NO:2 (mature murine LIG46) or amino acids 33-397 of SEQ ID NO:4 (mature human LIG46); and an isolated LIG46 protein having an amino acid sequence that is at least about 85%, 95%, or 98% identical to a portion of LIG46 having homology to a galactosyltransferase (e.g., amino acids 192-353, 142-184, 201-296, 289-347, 140-183, 367- 391, 177-266, 299-343, or 140-184 of SEQ ID NO:2) or a neurogenic secreted signalling protein (e.g., amino acids 200-291, 270-354, 144-183, 380-394, or 211-248 of SEQ ID NO:2). Also within the invention are: an isolated LIG46 protein which is encoded by a nucleic acid molecule having a nucleotide sequence that is at least about 65%, preferably 75%, 85%, or 95% identical to SEQ ID NO:3; and an isolated LIG46 protein which is encoded by a nucleic acid molecule having a nucleotide sequence which hybridizes under stringent hybridization conditions to a nucleic acid molecule having the nucleotide sequence of the complement of SEQ ID NO:3. Another embodiment of the invention provides LIG46 nucleic acid molecules which specifically detect LIG46 nucleic acid molecules (e.g., a nucleic acid molecule encoding human LIG46) relative to nucleic acid molecules encoding other galactosyltransferases. For example, in one embodiment, a LIG46 nucleic acid molecule hybridizes under stringent conditions to a nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:l, SEQ ID NO:3, nucleotides 3-1193 of SEQ ID NO: 1, nucleotides 246 - 1436 of SEQ ID NO:3, or a complement thereof, but does not hybridize to unrelated galactosyltransferases. In another embodiment, the LIG46 nucleic acid molecule is at least 300 (325, 350, 375, 400, 425, 450, 500, 550, 600, 650, 700, 800, 900, 1000, or 1200) nucleotides in length and hybridizes under stringent conditions to a nucleic acid molecule comprising the nucleotide sequence shown in SEQ ID NO:l, SEQ ID NO:3, or a complement thereof.

Another aspect of the invention provides a vector, e.g., a recombinant expression vector, comprising a LIG46 nucleic acid molecule of the invention. In another embodiment the invention provides a host cell containing such a vector. The invention also provides a method for producing LIG46 protein by culturing, in a suitable medium, a host cell of the invention containing a recombinant expression vector such that a LIG46 protein is produced. Another aspect of this invention provides isolated or recombinant LIG46 proteins and polypeptides. Preferred LIG46 proteins and polypeptides possess at least one biological activity possessed by naturally occurring LIG46 (e.g., the ability to act as a galactosyl- transferase) and are induced by leptin. The LIG46 proteins of the present invention, or biologically active portions thereof, can be operatively linked to a non-LIG46 polypeptide (e.g., heterologous amino acid sequences) to form LIG46 fusion proteins. The invention further features antibodies that specifically bind LIG46 proteins, such as monoclonal or polyclonal antibodies. In addition, the LIG46 proteins or biologically active portions thereof can be incoφorated into pharmaceutical compositions, which optionally include pharmaceutically acceptable carriers. In another aspect, the present invention provides a method for detecting the presence of LIG46 activity or expression in a biological sample by contacting the biological sample with an agent capable of detecting an indicator of LIG46 activity such that the presence of LIG46 activity is detected in the biological sample. In another aspect, the invention provides a method for modulating LIG46 activity comprising contacting a cell with an agent that modulates (inhibits or stimulates) LIG46 activity or expression such that LIG46 activity or expression in the cell is modulated. In one embodiment, the agent is an antibody that specifically binds to LIG46 protein. In another embodiment, the agent modulates expression of LIG46 by modulating transcription of a LIG46 gene, splicing of a LIG46 mRNA, or translation of a LIG46 mRNA. In yet another embodiment, the agent is a nucleic acid molecule having a nucleotide sequence that is antisense to the coding strand of the LIG46 mRNA or the LIG46 gene.

In one embodiment, the methods of the present invention are used to treat a subject having a disorder characterized by and undesirable level of LIG46 protein or nucleic acid expression or activity by administering an agent that is a LIG46 modulator to the subject. In one embodiment, the LIG46 modulator is a LIG46 protein. In another embodiment the LIG46 modulator is a LIG46 nucleic acid molecule. In other embodiments, the LIG46 modulator is a peptide, peptidomimetic, or other small molecule. In a preferred embodiment, the disorder is obesity or cachexia. For treatment of obesity it is desirable to administer an agent which reduces the expression or activity of LIG46 (an LIG46 antagonist). Such an agent can be administered in conjunction with leptin. Preferably the amount of leptin administered is sufficient, in combination with any endogenous leptin, to render the subect being treated sensitive to the effects of the LIG46 antagonist. For treatment of low body weight it is desirable to administer an agent which increases the expression of activity of LIG46 (an LIG46 agonist).

The present invention also provides a diagnostic assay for identifying the presence or absence of a genetic lesion or mutation characterized by at least one of: (i) aberrant modification or mutation of a gene encoding a LIG46 protein; (ii) mis-regulation of a gene encoding a LIG46 protein; and (iii) aberrant post-translational modification of a LIG46 protein, wherein a wild-type form of the gene encodes a protein with a LIG46 activity. In another aspect, the invention provides a method for identifying a compound that binds to or modulates the activity of a LIG46 protein. In general, such methods entail measuring a biological activity of a LIG46 protein in the presence and absence of a test compound and identifying those compounds which alter the activity of the LIG46 protein. The invention also features methods for identifying a compound which modulates the expression of LIG46 by measuring the expression of LIG46 in the presence and absence of a compound.

Other features and advantages of the invention will be apparent from the following detailed description and claims.

DESCRIPTION OF DRAWINGS

Figures 1 A-AB depicts the cDNA sequence (SEQ ID NO:l ) and predicted amino acid sequence (SEQ ID NO:2) of murine LIG46.

Figures 2A-2C depict a series of alignments of the amino acid sequence of mouse

LIG46 (SEQ ID NO:2) with portions of a number of galactosyltransferases, including (from top to bottom): Mus musculus UDP-Gal: betaGlcNAc beta 1 ,3-galactosyltransferase-I

(Accession Number AF029790; SEQ ID NO:7); Mus musculus IPP-Gal: betaGlcNAc beta

1,3-galactosyltransferase-iπ (Accession Number AF029792; SEQ ID NO:8); Drosophila melanogaster neurogenic secreted signalling protein ("Brainiac"; Accession Number U41449;

SEQ ID NO:9); and Homo sapiens UDP-galactose: 2-acetamido-2-deoxy-D-glucose3beta- galactosyltransferase (Accession Number Y15014; SEQ ID NO:10). The amino acid sequence above the solid line is a majority sequence (SEQ ID NO:l 1).

Figure 3 is a hydropathy plot of mouse LIG46. The location of the predicted transmembrane (TM), cytoplasmic (IN), and extracellular (OUT) domains are indicated as are the position of cysteines (cys; vertical bars immediately below the plot). Relative hydrophobicity is shown above the dotted line, and relative hydrophilicity is shown below the dotted line.

Figure 4 is a graph depicting the effect of mouse LIG46 sense and antisense oligonucleotides on food intake of male obese (ob/ob) mice in the presence and absence of leptin. Figures 5 A -5B depict the cDNA sequence of human LIG46 (SEQ ID NO:3). Figure 6 depicts the predicted amino acid sequence of human LIG46 (SEQ ID NO:4).

Figures 7A-7B depict an alignment of the cDNA sequences of human LIG46 (upper sequence; SEQ ID NO:3) and mouse LIG46 (lower sequence; SEQ ID NO:l).

Figure 8 depicts an alignment of the predicted amino acid sequences of human LIG46 (upper sequence; SEQ ID NO:4) and mouse LIG46 (lower sequence; SEQ ID NO. 2).

Figure 9 is a graph depicting the effect of LIG46 sense and antisense oligonucleotides on food intake of male lean mice in the presence and absence of leptin.

DETAILED DESCRIPTION

The present invention is based, in part, on the identification of a gene, mouse LIG46, whose expression is induced by leptin.

A nucleotide sequence encoding murine LIG46 protein is shown in Figures 1 A- IB (SEQ ID NO:l). A predicted amino acid sequence of murine LIG46 protein is also shown in Figures 1 A-1B (SEQ ID NO: 2). The murine LIG46 cDNA of Figures 1 A-1B (SEQ ID NO:l) encodes a 397 amino acid protein. A nucleotide sequence encoding human LIG46 protein is shown in Figures 5A-5B

(SEQ ID NO:3). A predicted amino acid sequence of human LIG46 protein is shown in Figure 6. The human LIG46 cDNA of Figures 5A-5B encodes a 395 amino acid protein.

Murine LIG46 and human LIG46 are members of a family of molecules (the "LIG46 family") having certain conserved structural and functional features. The term "family" when referring to the protein and nucleic acid molecules of the invention is intended to mean two or more proteins or nucleic acid molecules having a common structural domain and having sufficient amino acid or nucleotide sequence identity as defined herein. Such family members can be naturally occurring and can be from either the same or different species. For example, a family can contain a first protein of murine origin and a homologue of that protein of human origin, as well as a second, distinct protein of human origin and a murine homologue of that protein. Members of a family may also have common functional characteristics.

I. Isolated Nucleic Acid Molecules

One aspect of the invention pertains to isolated nucleic acid molecules that encode LIG46 proteins or biologically active portions thereof, as well as nucleic acid molecules that can be used as hybridization probes to identify LIG46-encoding nucleic acid molecules (e.g., human LIG46) and fragments for use as PCR primers for the amplification or mutation of LIG46 nucleic acid molecules. As used herein, the term "nucleic acid molecule" is intended to include DNA molecules (e.g., cDNA or genomic DNA) and RNA molecules (e.g., mRNA) and analogs of the DNA or RNA generated using nucleotide analogs. The nucleic acid molecule can be single-stranded or double-stranded, but preferably is double-stranded DNA. An "isolated" nucleic acid molecule is one which is separated from other nucleic acid molecules which are present in the natural source of the nucleic acid. Preferably, an "isolated" nucleic acid is free of sequences (preferably protein encoding sequences) which naturally flank the nucleic acid (i.e., sequences located at the 5' and 3' ends of the nucleic acid) in the genomic DNA of the organism from which the nucleic acid is derived. For example, in various embodiments, the isolated LIG46 nucleic acid molecule can contain less than about 5 kb, 4 kb, 3 kb, 2 kb, 1 kb, 0.5 kb or 0.1 kb of nucleotide sequences which naturally flank the nucleic acid molecule in genomic DNA of the cell from which the nucleic acid is derived. Moreover, an "isolated" nucleic acid molecule, such as a cDNA molecule, can be substantially free of other cellular material, or culture medium when produced by recombinant techniques, or substantially free of chemical precursors or other chemicals when chemically synthesized.

A nucleic acid molecule of the present invention, e.g., a nucleic acid molecule having the nucleotide sequence of SEQ ID NO:l, SEQ ID NO:3, SEQ ID NO:5; SEQ ID NO:6, or a complement of any of these nucleotide sequences, can be isolated using standard molecular biology techniques and the sequence information provided herein. Using all or portion of the nucleic acid sequences of SEQ ID NO:l , SEQ ID NO:3, or all or a portion of the nucleic acid sequence of SEQ ID NO:5 or SEQ ID NO:6, as a hybridization probe, LIG46 and LIG56 nucleic acid molecules can be isolated using standard hybridization arid cloning techniques (e.g., as described in Sambrook et al., eds., Molecular Cloning: A Laboratory Manual. 2nd, ed., Cold Spring Harbor Laboratory , Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1989).

A nucleic acid of the invention can be amplified using cDNA, mRNA or genomic DNA as a template and appropriate oligonucleotide primers according to standard PCR amplification techniques. The nucleic acid so amplified can be cloned into an appropriate vector and characterized by DNA sequence analysis. Furthermore, oligonucleotides corresponding to LIG46 nucleotide sequences can be prepared by standard synthetic techniques, e.g., using an automated DNA synthesizer.

The isolated nucleic acid molecules of the invention comprise a nucleic acid molecule which is a complement of the nucleotide sequence shown in SEQ ID NO:l, SEQ ID NO:3, SEQ ID NO:5 or SEQ ID NO:6, or a portion thereof. A nucleic acid molecule which is complementary to a given nucleotide sequence is one which is sufficiently complementary to the given nucleotide sequence that it can hybridize to the given nucleotide sequence thereby forming a stable duplex. Moreover, the nucleic acid molecule of the invention can comprise only a portion of a nucleic acid sequence encoding LIG46, for example, a fragment that can be used as a probe or primer or a fragment encoding a biologically active portion of LIG46. The nucleotide sequence determined from the cloning of the murine and human LIG46 genes allows for the generation of probes and primers designed for use in identifying and/or cloning LIG46 homologues in other cell types, e.g., from other tissues, as well as LIG46 homologues from other mammals. The probe/primer typically comprises substantially purified oligonucleotide. The oligonucleotide typically comprises a region of nucleotide sequence that hybridizes under stringent conditions to at least about 12, preferably about 25, more preferably about 50, 75, 100, 125, 150, 175, 200, 250, 300, 350 or 400 consecutive nucleotides of the sense or anti- sense sequence of SEQ ID NO:l or SEQ ID NO:3, or of a naturally occurring mutant of SEQ ID NO:l or SEQ ID NO:3, or sense or anti-sense sequence of SEQ ID NO:5 or SEQ ID NO:6, or of a naturally occurring mutant of SEQ ID NO: 5 or SEQ ID NO:6.

Probes based on the LIG46 nucleotide sequence can be used to detect transcripts or genomic sequences encoding the same or related proteins. The probe comprises a label group attached thereto, e.g., a radioisotope, a fluorescent compound, an enzyme, or an enzyme co- factor. Such probes can be used as a part of a diagnostic test kit for identifying cells or tissue which mis-express a LIG46 protein, such as by measuring a level of a LIG46-encoding nucleic acid in a sample of cells from a subject, e.g., detecting LIG46 mRNA levels or determining whether a genomic LIG46 gene has been mutated or deleted. A nucleic acid fragment encoding a "biologically active portion of LIG46" can be prepared by isolating a portion of SEQ ID NO:l or SEQ ID NO:3 which encodes a polypeptide having a LIG46 biological activity, expressing the encoded portion of LIG46 (e.g., by recombinant expression in vitro) and assessing the activity of the encoded portion of LIG46. For example, a nucleic acid fragment encoding a biologically active portion of LIG46 includes a galactosyltransferase-like domain. The invention further encompasses nucleic acid molecules that differ from the nucleotide sequence of SEQ ID NO:l, SEQ ID NO:3, SEQ ID NO:5, or SEQ ID NO:6 due to degeneracy of the genetic code and thus encode the same LIG46 protein as that encoded by the nucleotide sequence shown in SEQ ID NO:l, SEQ ID NO:3, SEQ ID NO:5, or SEQ ID NO:6. In addition to the LIG46 nucleotide sequences shown in SEQ ID NO: 5 and SEQ ID

NO:6, it will be appreciated by those skilled in the art that DNA sequence polymoφhisms that lead to changes in the amino acid sequences of LIG46 may exist within a population. Such genetic polymoφhism in the LIG46 gene may exist among individuals within a population due to natural allelic variation. As used herein, the terms "gene" and "recombinant gene" refer to nucleic acid molecules comprising an open reading frame encoding a LIG46 protein, preferably a mammalian LIG46 protein. Such natural allelic variations can typically result in 1-5% variance in the nucleotide sequence of the LIG46 gene. Any and all such nucleotide variations and resulting amino acid polymoφhisms in LIG46 that are the result of natural allelic variation and that do not alter the functional activity of LIG46 are intended to be within the scope of the invention.

Moreover, nucleic acid molecules encoding LIG46 proteins from other species (LIG46 homologues), which have a nucleotide sequence which differs from that of the murine gene or human gene, are intended to be within the scope of the invention. Nucleic acid molecules corresponding to natural allelic variants and homologues of the LIG46 cDNA of the invention can be isolated based on their identity to the LIG46 nucleic acids disclosed herein using the murine cDNAs, or a portion thereof, as a hybridization probe according to standard hybridization techniques under stringent hybridization conditions. For example, a soluble LIG46 cDNA can be isolated based on its identity to murine or human membrane-bound LIG46. Accordingly, in another embodiment, an isolated nucleic acid molecule of the invention is at least 300 (325, 350, 375, 400, 425, 450, 500, 550, 600, 650, 700, 800, 900, 1000, or 1200) nucleotides in length and hybridizes under stringent conditions to the nucleic acid molecule comprising the nucleotide sequence, preferably the coding sequence, of SEQ IDNO:l, or SEQ ID NO:3, or SEQ ID NO:5 or SEQ ID NO:6.

As used herein, the term "hybridizes under stringent conditions" is intended to describe conditions for hybridization and washing under which nucleotide sequences at least 60% (65%, 70%, preferably 75%) identical to each other typically remain hybridized to each other. Such stringent conditions are known to those skilled in the art and can be found in Current Protocols in Molecular Biology, John Wiley & Sons, N.Y. (1989), 6.3.1-6.3.6. A preferred, non-limiting example of stringent hybridization conditions are hybridization in 6X sodium chloride/sodium citrate (SSC) at about 45°C, followed by one or more washes in 0.2 X SSC, 0.1% SDS at 50-65°C. Preferably, an isolated nucleic acid molecule of the invention that hybridizes under stringent conditions to the sequence of SEQ JO NO:l, SEQ ID NO:3, SEQ ID NO:5 or SEQ ID NO:6 corresponds to a naturally-occurring nucleic acid molecule. As used herein, a "naturally-occurring" nucleic acid molecule refers to an RNA or DNA molecule having a nucleotide sequence that occurs in nature (e.g., encodes a natural protein). In addition to naturally-occurring allelic variants of the LIG46 sequence that may exist in the population, the skilled artisan will further appreciate that changes can be introduced by mutation into the nucleotide sequences disclosed herein, thereby leading to changes in the amino acid sequence of the encoded LIG46 protein, without altering the functional ability of the LIG46 protein. For example, one can make nucleotide substitutions leading to amino acid substitutions at "non-essential" amino acid residues. A "non-essential" amino acid residue is a residue that can be altered from the wild-type sequence of LIG46 without altering the biological activity, whereas an "essential" amino acid residue is required for biological activity. For example, amino acid residues that are conserved among the LIG46 proteins of various species are predicted to be particularly unamenable to alteration.

For example, preferred LIG46 proteins of the present invention retain amino acids that are conserved among galactosyltransferases. Such conserved domains are less likely to be amenable to mutation. Other amino acid residues, however, (e.g., those that are not conserved or only semi-conserved among LIG46 of various species) may not be essential for activity and thus are likely to be amenable to alteration. Accordingly, another aspect of the invention pertains to nucleic acid molecules encoding LIG46 proteins that contain changes in amino acid residues that are not essential for activity. Such LIG46 proteins differ in amino acid sequence from those disclosed herein yet retain biological activity. In one embodiment, the isolated nucleic acid molecule includes a nucleotide sequence encoding a protein that includes an amino acid sequence that is at least about 45% identical, 65%, 75%, 85%, 95%, or 98% identical to the amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4.

An isolated nucleic acid molecule encoding a LIG46 protein having a sequence which differs from that disclosed herein can be created by introducing one or more nucleotide substitutions, additions or deletions into the nucleotide sequence disclosed herein such that one or more amino acid substitutions, additions or deletions are introduced into the encoded protein. Mutations can be introduced by standard techniques, such as site-directed mutagenesis and PCR-mediated mutagenesis. Preferably, conservative amino acid substitutions are made at one or more predicted non-essential amino acid residues. A "conservative amino acid substitution" is one in which the amino acid residue is replaced with an amino acid residue having a similar side chain. Families of amino acid residues having similar side chains have been defined in the art. These families include amino acids with basic side chains (e.g., lysine, arginine, histidine), acidic side chains (e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g., glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan), beta-branched side chains (e.g., threonine, valine, isoleucine) and aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine). Thus, a predicted nonessential amino acid residue in LIG46 is preferably replaced with another amino acid residue from the same side chain family. Alternatively, mutations can be introduced randomly along all or part of a LIG46 coding sequence, such as by saturation mutagenesis, and the resultant mutants can be screened for LIG46 biological activity to identify mutants that retain activity. Following mutagenesis, the encoded protein can be expressed recombinantly and the activity of the protein can be determined.

The present invention encompasses antisense nucleic acid molecules, i.e., molecules which are complementary to a sense nucleic acid encoding a protein, e.g., complementary to the coding strand of a double-stranded cDNA molecule or complementary to an mRNA sequence. Accordingly, an antisense nucleic acid can hydrogen bond to a sense nucleic acid. The antisense nucleic acid can be complementary to an entire LIG46 coding strand, or to only a portion thereof, e.g., all or part of the protein coding region (or open reading frame). An antisense nucleic acid molecule can be antisense to a noncoding region of the coding strand of a nucleotide sequence encoding LIG46 . The noncoding regions ("5' and 3' untranslated regions") are the 5' and 3' sequences which flank the coding region and are not translated into amino acids.

Given the coding strand sequences encoding LIG46 disclosed herein (e.g., SEQ ID NO:l, SEQ ID NO:3, SEQ ID NO:5, and SEQ ID NO:6), antisense nucleic acids of the invention can be designed according to the rules of Watson and Crick base pairing. The antisense nucleic acid molecule can be complementary to the entire coding region of LIG46 mRNA, but more preferably is an oligonucleotide which is antisense to only a portion of the coding or noncoding region of LIG46 mRNA For example, the antisense oligonucleotide can be complementary to the region surrounding the translation start site of LIG46 mRNA. An antisense oligonucleotide can be, for example, about 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50 nucleotides in length. An antisense nucleic acid of the invention can be constructed using chemical synthesis and enzymatic ligation reactions using procedures known in the art. For example, an antisense nucleic acid (e.g., an antisense oligonucleotide) can be chemically synthesized using naturally occurring nucleotides or variously modified nucleotides designed to increase the biological stability of the molecules or to increase the physical stability of the duplex formed between the antisense and sense nucleic acids, e.g., phosphorothioate derivatives and acridine substituted nucleotides can be used. Examples of modified nucleotides which can be used to generate the antisense nucleic acid include 5-fluorouracil, 5- bromouracil, 5-chlorouracil, 5-iodouracil, hypoxanthine, xanthine, 4-acetylcytosine, 5- (carboxyhydroxylmethyl) uracil, 5-carboxymethylaminomethyl-2-thiouridine, 5- carboxymethylaminomethyluracil, dihydrouracil, beta-D-galactosylqueosine, inosine, N6- isopentenyladenine, 1 -methylguanine, 1-methylinosine, 2,2-dimethylguanine, 2- methyladenine, 2-methylguanine, 3-methylcytosine, 5-methylcytosine, N6-adenine, 7- methylguanine, 5-methylaminomethyluracil, 5-methoxyaminomethyl-2-thiouracil, beta-D- mannosylqueosine, 5'-methoxycarboxymethyluraciL 5-methoxyuracil, 2-methylthio-N6- isopentenyladenine, uracil-5-oxyacetic acid (v), wybutoxosine, pseudouracil, queosine, 2- thiocytosine, 5-methyl-2-thiouracil, 2-thiouracil, 4-thiouracil, 5-methyluracil, uracil-5- oxyacetic acid methylester, uracil-5-oxyacetic acid (v), 5-methyl-2-thiouracil, 3-(3-amino-3- N-2-carboxypropyl) uracil, (acp3)w, and 2,6-diaminopurine. Alternatively, the antisense nucleic acid can be produced biologically using an expression vector into which a nucleic acid has been subcloned in an antisense orientation (i.e., RNA transcribed from the inserted nucleic acid will be of an antisense orientation to a target nucleic acid of interest, described further in the following subsection).

The antisense nucleic acid molecules of the invention are typically administered to a subject or generated in situ such that they hybridize with or bind to cellular mRNA and/or genomic DNA encoding the protein of interest to thereby inhibit expression of the protein, e.g., by inhibiting transcription and/or translation. The hybridization can be by conventional nucleotide complementarity to form a stable duplex, or, for example, in the case of an antisense nucleic acid molecule which binds to DNA duplexes, through specific interactions in the major groove of the double helix. An example of a route of administration of antisense nucleic acid molecules of the invention include direct injection at a tissue site. Alternatively, antisense nucleic acid molecules can be modified to target selected cells and then administered systemically. For example, for systemic administration, antisense molecules can be modified such that they specifically bind to receptors or antigens expressed on a selected cell surface, e.g., by linking the antisense nucleic acid molecules to peptides or antibodies which bind to cell surface receptors or antigens. The antisense nucleic acid molecules can also be delivered to cells using the vectors described herein. To achieve sufficient intracellular concentrations of the antisense molecules, vector constructs in which the antisense nucleic acid molecule is placed under the control of a strong pol II or pol IU promoter are preferred. An antisense nucleic acid molecule of the invention can be an α-anomeric nucleic acid molecule. An α-anomeric nucleic acid molecule forms specific double-stranded hybrids with complementary RNA in which, contrary to the usual β-units, the strands run parallel to each other (Gaultier et al. (1987) Nucleic Acids. Res. 15:6625-6641). The antisense nucleic acid molecule can also comprise a 2'-o-methylribonucleotide (L oue et al. (1987) Nucleic Acids Res. 15:6131-6148) or a chimeric RNA-DNA analogue (Inoue et al. (1987) FEBS Lett. 215:327-330). The invention also encompasses ribozymes. Ribozymes are catalytic RNA molecules with ribonuclease activity which are capable of cleaving a single-stranded nucleic acid, such as an mRNA, to which they have a complementary region. Thus, ribozymes (e.g., hammerhead ribozymes (described in Haselhoff and Gerlach (1988) Nature 334:585-591)) can be used to catalytically cleave LIG46 mRNA transcripts to thereby inhibit translation of LIG46 mRNA. A ribozyme having specificity for a LIG46-encoding nucleic acid can be designed based upon the nucleotide sequence of a LIG46 cDNA disclosed herein. For example, a derivative of a Tetrahymena L-19 IVS RNA can be constructed in which the nucleotide sequence of the active site is complementary to the nucleotide sequence to be cleaved in a LIG46-encoding mRNA. See, e.g., Cech et al. U.S. Patent No. 4,987,071 ; and Cech et al. U.S. Patent No. 5,116,742. Alternatively, LIG46 mRNA can be used to select a catalytic RNA having a specific ribonuclease activity from a pool of RNA molecules. See, e.g., Bartel and Szostak (1993) Science 261:1411-1418.

The invention also encompasses nucleic acid molecules which form triple helical structures. For example, LIG46 gene expression can be inhibited by targeting nucleotide sequences complementary to the regulatory region of the LIG46 (e.g., the LIG46 promoter and/or enhancers) to form triple helical structures that prevent transcription of the LIG46 gene in target cells. See generally, Helene (1991) Anticancer Drug Des. 6(6):569-84; Helene (1992)Λnn. N.Y. Acad. Sci. 660:27-36; and Maher (1992) Bioassays 14(12):807-15. In preferred embodiments, the nucleic acid molecules of the invention can be modified at the base moiety, sugar moiety or phosphate backbone to improve, e.g., the stability, hybridization, or solubility of the molecule. For example, the deoxyribose phosphate backbone of the nucleic acids can be modified to generate peptide nucleic acids (see Hyrup et al. (1996) Bioorganic &Medicinal Chemistry 4(1): 5-23). As used herein, the terms "peptide nucleic acids" or "PNAs" refer to nucleic acid mimics, e.g., DNA mimics, in which the deoxyribose phosphate backbone is replaced by a pseudopeptide backbone and only the four natural nucleobases are retained. The neutral backbone of PNAs has been shown to allow for specific hybridization to DNA and RNA under conditions of low ionic strength. The synthesis of PNA oligomers can be performed using standard solid phase peptide synthesis protocols as described in Hyrup et al. (1996) supra; Perry-O'Keefe et al. (1996) Proc. Natl. Acad. Sci. USA 93: 14670-675. PNAs of LIG46 can be used therapeutic and diagnostic applications. For example, PNAs can be used as antisense or antigene agents for sequence-specific modulation of gene expression by, e.g., inducing transcription or translation arrest or inhibiting replication. PNAs of LIG46 can also be used, e.g., in the analysis of single base pair mutations in a gene by, e.g., PNA directed PCR clamping; as 'artificial restriction enzymes when used in combination with other enzymes, e.g., SI nucleases (Hyrup (1996) supra; or as probes or primers for DNA sequence and hybridization (Hyrup (1996) supra; Peπy-O'Keefe et al. (1996) Proc. Natl. Acad. Sci. USA 93: 14670-675).

In another embodiment, PNAs of LIG46 can be modified, e.g., to enhance their stability or cellular uptake, by attaching lipophilic or other helper groups to PNA, by the formation of PNA-DNA chimeras, or by the use of liposomes or other techniques of drug delivery known in the art. For example, PNA-DNA chimeras of LIG46 can be generated which may combine the advantageous properties of PNA and DNA. Such chimeras allow DNA recognition enzymes, e.g., RNAse H and DNA polymerases, to interact with the DNA portion while the PNA portion would provide high binding affinity and specificity. PNA- DNA chimeras can be linked using linkers of appropriate lengths selected in terms of base stacking, number of bonds between the nucleobases, and orientation (Hyrup (1996) supra). The synthesis of PNA-DNA chimeras can be performed as described in Hyrup (1996) supra and Finn et al. (1996) Nucleic Acids Research 24(17):3357-63. For example, aDNA chain can be synthesized on a solid support using standard phosphoramidite coupling chemistry and modified nucleoside analogs, e.g., 5'-(4-methoxytrityl)amino-5'-deoxy-thymidine phosphoramidite, can be used as a between the PNA and the 5' end of DNA (Mag et al. (1989) Nucleic Acid Res. 17:5973-88). PNA monomers are then coupled in a stepwise manner to produce a chimeric molecule with a 5' PNA segment and a 3' DNA segment (Finn et al. (1996) Nucleic Acids Research 24(17):3357-63). Alternatively, chimeric molecules can be synthesized with a 5' DNA segment and a 3' PNA segment (Peterser et al. (1975) Bioorganic Med. Chem. Lett. 5:1119-11124).

In other embodiments, the oligonucleotide may include other appended groups such as peptides (e.g., for targeting host cell receptors in vivo), or agents facilitating transport across the cell membrane (see, e.g., Letsinger et al. (1989) Proc. Nail. Acad. Sci. USA 86:6553-6556; Lemaitre et al. (1987) Proc. Natl. Acad. Sci. USA 84:648-652; PCT Publication No. W0 88/09810) or the blood-brain barrier (see, e.g., PCT Publication No. W0 89/10134). In addition, oligonucleotides can be modified with hybridization-triggered cleavage agents (see, e.g., Krol et al. (1988) Bio/Techniques 6:958-976) or intercalating agents (see, e.g., Zon (1988) Pharm. Res. 5:539-549). To this end, the oligonucleotide may be conjugated to another molecule, e.g., a peptide, hybridization triggered cross-linking agent, transport agent, hybridization-triggered cleavage agent, etc.

TJ. Isolated LIG46 Proteins and Anti-LIG46 Antibodies

One aspect of the invention pertains to isolated LIG46 proteins, and biologically active portions thereof, as well as polypeptide fragments suitable for use as immunogens to raise anti-LIG46 antibodies. In one embodiment, native LIG46 proteins can be isolated from cells or tissue sources by an appropriate purification scheme using standard protein purification techniques. In another embodiment, LIG46 proteins are produced by recombinant DNA techniques. Alternative to recombinant expression, a LIG46 protein or polypeptide can be synthesized chemically using standard peptide synthesis techniques.

An "isolated" or "purified" protein or biologically active portion thereof is substantially free of cellular material or other contaminating proteins from the cell or tissue source from which the protein of interest is derived (e.g., LIG46), or substantially free from chemical precursors or other chemicals when chemically synthesized. The language "substantially free of cellular material" includes preparations in which the protein is separated from cellular components of the cells from which it is isolated or recombinantly produced. Thus, LIG46 protein that is substantially free of cellular material includes preparations of LIG46 protein having less than about 30%, 20%, 10%, or 5% (by dry weight) of non-LIG46 protein (also referred to herein as a "contaminating protein"). When the LIG46 protein or biologically active portion thereof is recombinantly produced, it is also preferably substantially free of culture medium, i.e., culture medium represents less than about 20%, 10%, or 5% of the volume of the protein preparation. When LIG46 protein is produced by chemical synthesis, it is preferably substantially free of chemical precursors or other chemicals, i.e., it is separated from chemical precursors or other chemicals which are involved in the synthesis of the protein. Accordingly such preparations of LIG46 protein have less than about 30%, 20%, 10%, 5% (by dry weight) of chemical precursors or non-LIG46 chemicals. Biologically active portions of a LIG46 protein include peptides comprising amino acid sequences sufficiently identical to or derived from the amino acid sequence of the LIG46 protein, which include less amino acids than the full length LIG46 proteins, and exhibit at least one activity of a LIG46 protein. Typically, biologically active portions comprise a domain or motif with at least one activity of the LIG46 protein. A biologically active portion of a LIG46 protein can be a polypeptide which is, for example, 10, 25, 50, 100 or more amino acids in length. Preferred biologically active polypeptides include one or more identified LIG46 structural domains.

Moreover, other biologically active portions, in which other regions of the protein are deleted, can be prepared by recombinant techniques and evaluated for one or more of the functional activities of a native LIG46 protein.

Preferred LIG46 proteins have or are substantially identical to the amino acid sequences disclosed herein. Preferred proteins are substantially identical to those disclosed herein and retain the functional activity of the protein yet differ in amino acid sequence due to natural allelic variation or mutagenesis.

Accordingly, a useful LIG46 protein is a protein which includes an amino acid sequence at least about 45%, preferably 55%, 65%, 75%, 85%, 95%, or 99% identical to the amino acid sequence of SEQ JO NO:4 (or SEQ JD NO:2) and retains the functional activity of the LIG46 protein of SEQ ID NO:4 (or SEQ JD NO:2). In other instances, the LIG46 protein is a protein having an amino acid sequence 55%, 65%, 75%, 85%, 95%, or 98% identical to a portion of LIG46 having homology to a galactosyltransferase (e.g., amino acids 192-353, 142- 184, 201-296, 289-347, 140-183, 367-391, 177-266, 299-343, or 140-184 of SEQ JD NO:2) or a neurogenic secreted signalling protein (e.g., amino acids 200-291, 270-354, 144-183, 380-394, or 211-248 of SEQ ID NO:2). In a preferred embodiment, the LIG46 protein retains a functional activity of the LIG46 protein of SEQ ID NO:4 (or SEQ JD NO:2).

To determine the percent identity of two amino acid sequences or of two nucleic acids, the sequences are aligned for optimal comparison puφoses (e.g., gaps can be introduced in the sequence of a first amino acid or nucleic acid sequence for optimal alignment with a second amino or nucleic acid sequence). The amino acid residues or nucleotides at corresponding amino acid positions or nucleotide positions are then compared. When a position in the first sequence is occupied by the same amino acid residue or nucleotide as the corresponding position in the second sequence, then the molecules are identical at that position. The percent identity between the two sequences is a function of the number of identical positions shared by the sequences (i.e., % identity = # of identical positions/total # of positions x 100). The determination of percent homology between two sequences can be accomplished using a mathematical algorithm. A preferred, non-limiting example of a mathematical algorithm utilized for the comparison of two sequences is the algorithm of Kariin and Altschul (1990) Proc. Nat'lAcad. Sci. USA 87:2264-2268, modified as in Kariin and Altschul (1993) Proc. Nat'lAcad. Sci. USA 90:5873-5877. Such an algorithm is incoφorated into the NBLAST and XBLAST programs of Altschul, etal. (1990) J. Mol. Biol. 215:403-410. BLAST nucleotide searches can be performed with the NBLAST program, score = 100, wordlength = 12 to obtain nucleotide sequences homologous to LIG46 nucleic acid molecules of the invention. BLAST protein searches can be performed with the XBLAST program, score = 50, wordlength = 3 to obtain amino acid sequences homologous to LIG46 protein molecules of the invention. To obtain gapped alignments for comparison puφoses, Gapped BLAST can be utilized as described in Altschul et al, (1997) Nucleic Acids Res. 25:3389- 3402. When utilizing BLAST and Gapped BLAST programs, the default parameters of the respective programs (e.g., XBLAST and NBLAST) can be used. See http://www.ncbi.nlm.nih.gov. Another preferred, non-limiting example of a mathematical algorithm utilized for the comparison of sequences is the algorithm of Myers and Miller,

CABIOS (1989). Such an algorithm is incoφorated into the ALIGN program (version 2.0) which is part of the GCG sequence alignment software package. When utilizing the ALIGN program for comparing amino acid sequences, a PAM120 weight residue table, a gap length penalty of 12, and a gap penalty of 4 can be used. The percent identity between two sequences can be determined using techniques similar to those described above, with or without allowing gaps. In calculating percent identity, only exact matches are counted.

The invention also provides LIG46 chimeric or fusion proteins. As used herein, a LIG46 "chimeric protein" or "fusion protein" comprises a LIG46 polypeptide operatively linked to a non-LIG46 polypeptide. A "LIG46 polypeptide" refers to a polypeptide having an amino acid sequence corresponding to LIG46, whereas a "non-LIG46 polypeptide" refers to a polypeptide having an amino acid sequence corresponding to a protein which is not substantially identical to the LIG46 protein, e.g., a protein which is different from the LIG46 protein and which is derived from the same or a different organism. Within a LIG46 fusion protein the LIG46 polypeptide can correspond to all or a portion of a LIG46 protein, preferably at least one biologically active portion of a LIG46 protein. Within the fusion protein, the term "operatively linked" is intended to indicate that the LIG46 polypeptide and the non-LIG46 polypeptide are fused in-frame to each other. The non-LIG46 polypeptide can be fused to the N-terminus or C-terminus of the LIG46 polypeptide.

One useful fusion protein is a GST-LIG46 fusion protein in which the LIG46 sequences are fused to the C-terminus of the GST sequences. Such fusion proteins can facilitate the purification of recombinant LIG46.

In another embodiment, the fusion protein is a LIG46 protein containing a heterologous signal sequence at its N-terminus. For example, the native LIG46 signal sequence (i.e., about amino acids 1 to 32 of SEQ JD NO:2) can be removed and replaced with a signal sequence from another protein. In certain host cells (e.g., mammalian host cells), expression and/or secretion of LIG46 can be increased through use of a heterologous signal sequence. For example, the gp67 secretory sequence of the baculovirus envelope protein can be used as a heterologous signal sequence (Current Protocols in Molecular Biology, Ausubel et al., eds., John Wiley & Sons, 1992). Other examples of eukaryotic heterologous signal sequences include the secretory sequences of melittin and human placental alkaline phosphatase (Stratagene; La Jolla, California). In yet another example, useful prokaryotic heterologous signal sequences include the phoA secretory signal (Molecular cloning, Sambrook et al, second edition, Cold spring harbor laboratory press, 1989) and the protein A secretory signal (Pharmacia Biotech; Piscataway, New Jersey). In yet another embodiment, the fusion protein is an LIG46-immunoglobulin fusion protein in which all or part of LIG46 is fused to sequences derived from a member of the immunoglobulin protein family. The LIG46-immunoglobulin fusion proteins of the invention can be incoφorated into pharmaceutical compositions and administered to a subject to inhibit an interaction between a LIG46 ligand and a LIG46 protein on the surface of a cell, to thereby suppress LIG46-mediated signal transduction in vivo. The LIG46-immunoglobulin fusion proteins can be used to affect the bioavailabihty of a LIG46 cognate ligand. Moreover, the LIG56-immunoglobulin fusion proteins of the invention can be used as immunogens to produce LIG56 antibodies in a subject, to purify LIG46 ligands and in screening assays to identify molecules which inhibit the interaction of LIG46 with a LIG46 ligand.

Preferably, a LIG46 chimeric or fusion protein of the invention is produced by standard recombinant DNA techniques. For example, DNA fragments coding for the different polypeptide sequences are ligated together in-frame in accordance with conventional techniques, for example by employing blunt-ended or stagger-ended termini for ligation, restriction enzyme digestion to provide for appropriate termini, filling-in of cohesive ends as appropriate, alkaline phosphatase treatment to avoid undesirable joining, and enzymatic ligation. In another embodiment, the fusion gene can be synthesized by conventional techniques including automated DNA synthesizers. Alternatively, PCR amplification of gene fragments can be carried out using anchor primers which give rise to complementary overhangs between two consecutive gene fragments which can subsequently be annealed and reamplified to generate a chimeric gene sequence (see, e.g., Current Protocols in Molecular Biology, Ausubel et al. eds., John Wiley & Sons: 1992). Moreover, many expression vectors are commercially available that already encode a fusion moiety (e.g., a GST polypeptide). An LIG46-encoding nucleic acid can be cloned into such an expression vector such that the fusion moiety is linked in-frame to the LIG46 protein.

The present invention also pertains to variants of the LIG46 proteins which function as either LIG46 agonists (mimetics) or as LIG46 antagonists. Variants of the LIG46 protein can be generated by mutagenesis, e.g., discrete point mutation or truncation of the LIG46 protein. An agonist of the LIG46 protein can retain substantially the same, or a subset, of the biological activities of the naturally occurring form of the LIG46 protein. An antagonist of the LIG46 protein can inhibit one or more of the activities of the naturally occurring form of the LIG46 protein by, for example, competitively binding to a downstream or upstream member of a cellular signaling cascade which includes the LIG46 protein. Thus, specific biological effects can be elicited by treatment with a variant of limited function. Treatment of a subject with a variant having a subset of the biological activities of the naturally occurring form of the protein can have fewer side effects in a subject relative to treatment with Ihe naturally occurring form of the LIG46 proteins. Variants of the LIG46 protein which function as either LIG46 agonists (mimetics) or as LIG46 antagonists can be identified by screening combinatorial libraries of mutants, e.g., truncation mutants, of the LIG46 protein for LIG46 protein agonist or antagonist activity. In one embodiment, a variegated library of LIG46 variants is generated by combinatorial mutagenesis at the nucleic acid level and is encoded by a variegated gene library. A variegated library of LIG46 variants can be produced by, for example, enzymatically ligating a mixture of synthetic oligonucleotides into gene sequences such that a degenerate set of potential LIG46 sequences is expressible as individual polypeptides, or alternatively, as a set of larger fusion proteins (e.g., for phage display) containing the set of LIG46 sequences therein. There are a variety of methods which can be used to produce libraries of potential LIG46 variants from a degenerate oligonucleotide sequence. Chemical synthesis of a degenerate gene sequence can be performed in an automatic DNA synthesizer, and the synthetic gene then ligated into an appropriate expression vector. Use of a degenerate set of genes allows for the provision, in one mixture, of all of the sequences encoding the desired set of potential LIG46 sequences. Methods for synthesizing degenerate oligonucleotides are known in the art (see, e.g., Narang (1983) Tetrahedron 39:3; Itakura et al. (1984) Annu. Rev. Biochem. 53:323; Itakura et al. (1984) Science 198:1056; Ike et al. (1983) Nucleic Acid Res. 11 :477).

In addition, libraries of fragments of the LIG46 protein coding sequence can be used to generate a variegated population of LIG46 fragments for screening and subsequent selection of variants of a LIG46 protein. In one embodiment, a library of coding sequence fragments can be generated by treating a double stranded PCR fragment of a LIG46 coding sequence with a nuclease under conditions wherein nicking occurs only about once per molecule, denaturing the double stranded DNA, renaturing the DNA to form double stranded DNA which can include sense/antisense pairs from different nicked products, removing single stranded portions from reformed duplexes by treatment with SI nuclease, and ligating the resulting fragment library into an expression vector. By this method, an expression library can be derived which encodes N-terminal and internal fragments of various sizes of the LIG46 protein. Several techniques are known in the art for screening gene products of combinatorial libraries made by point mutations or truncation, and for screening cDNA libraries for gene products having a selected property. Such techniques are adaptable for rapid screening of the gene libraries generated by the combinatorial mutagenesis of LIG46 proteins. The most widely used techniques, which are amenable to high through-put analysis, for screening large gene libraries typically include cloning the gene library into replicable expression vectors, transforming appropriate cells with the resulting library of vectors, and expressing the combinatorial genes under conditions in which detection of a desired activity facilitates isolation of the vector encoding the gene whose product was detected. Recursive ensemble mutagenesis (REM), a technique which enhances the frequency of functional mutants in the libraries, can be used in combination with the screening assays to identify LIG46 variants (Arkin and Yourvan (1992) Proc. Natl. Acad. Sci. USA 59:7811-7815; Delgrave et al. (1993) Protein Engineering 6(3):327-331).

An isolated LIG46 protein, or a portion or fragment thereof, can be used as an immunogen to generate antibodies that bind LIG46 using standard techniques for polyclonal and monoclonal antibody preparation. The full-length LIG46 protein can be used or, alternatively, the invention provides antigenic peptide fragments of LIG46 for use as immunogens. The antigenic peptide of LIG46 comprises at least 8 (preferably 10, 15, 20, or 30) amino acid residues of the amino acid sequence shown in SEQ JD NO:2 and encompasses an epitope of LIG46 such that an antibody raised against the peptide forms a specific immune complex with LIG46 . Preferred epitopes encompassed by the antigenic peptide are regions of LIG46 that are located on the surface of the protein, e.g., hydrophilic regions. Hydrophilic regions and antigenic regions can be identified using standard analytical tools well-known to those skilled in the art.

A LIG46 immunogen typically is used to prepare antibodies by immunizing a suitable subject, (e.g., rabbit, goat, mouse or other mammal) with the immunogen. An appropriate immunogenic preparation can contain, for example, recombinantly expressed LIG46 protein or a chemically synthesized LIG46 polypeptide. The preparation can further include an adjuvant, such as Freund's complete or incomplete adjuvant, or similar immunostimulatory agent. Immunization of a suitable subject with an immunogenic LIG46 preparation induces a polyclonal anti-LIG46 antibody response. Accordingly, another aspect of the invention pertains to anti-LIG46 antibodies. The term "antibody" as used herein refers to immunoglobulin molecules and immunologically active portions of immunoglobulin molecules, i.e., molecules that contain an antigen-binding site which specifically binds an antigen, such as LIG46. A molecule which specifically binds to LIG46 is a molecule which binds LIG46, but does not substantially bind other molecules in a sample, e.g., a biological sample, which naturally contains LIG46. Examples of immunologically active portions of immunoglobulin molecules include F(ab) and F(ab')₂ fragments which can be generated by treating the antibody with an enzyme such as pepsin. The invention provides polyclonal and monoclonal antibodies that bind LIG46. The term "monoclonal antibody" or "monoclonal antibody composition", as used herein, refers to a population of antibody molecules that contain only one species of an antigen binding site capable of immunoreacting with a particular epitope of LIG46 . A monoclonal antibody composition thus typically displays a single binding affinity for a particular LIG46 protein with which it immunoreacts. Polyclonal anti-LIG46 antibodies can be prepared as described above by immunizing a suitable subject with a LIG46 immunogen. The anti-LIG46 antibody titer in the immunized subject can be monitored over time by standard techniques, such as with an enzyme linked immunosorbent assay (ELISA) using immobilized LIG46 . If desired, the antibody molecules directed against LIG46 can be isolated from the mammal (e.g., from the blood) and further purified by well-known techniques, such as protein A chromatography to obtain the IgG fraction. At an appropriate time after immunization, e.g., when the anti-LIG46 antibody titers are highest, antibody-producing cells can be obtained from the subject and used to prepare monoclonal antibodies by standard techniques, such as the hybridoma technique originally described by Kohler and Milstein (1975) Nature 256:495-497, the human B cell hybridoma technique (Kozbor et al. (1983) Immunol Today 4:72), the EBV-hybridoma technique (Cole et al. (1985), Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, Inc., pp. 77-96) or trioma techniques. The technology for producing various antibodies monoclonal antibody hybridomas is well known (see generally Current Protocols in Immunology (1994) Coligan et al. (eds.) John Wiley & Sons, Inc., New York, NY). Briefly, an immortal cell line (typically a myeloma) is fused to lymphocytes (typically splenocytes) from a mammal immunized with a LIG46 immunogen as described above, and the culture supernatants of the resulting hybridoma cells are screened to identify a hybridoma producing a monoclonal antibody that binds LIG46.

Any of the many well known protocols used for fusing lymphocytes and immortalized cell lines can be applied for the puφose of generating an anti-LIG46 monoclonal antibody (see, e.g., Current Protocols in Immunology, supra; Galfre et al. (1977) Nature 266:55052; R.H. Kenneth, in Monoclonal Antibodies: A New Dimension In Biological Analyses, Plenum Publishing Coφ., New York, New York (1980); and Lerner (1981 ) Yale J. Biol. Med., 54:387-402. Moreover, the ordinarily skilled worker will appreciate that there are many variations of such methods which also would be useful. Typically, the immortal cell line (e.g., a myeloma cell line) is derived from the same mammalian species as the lymphocytes. For example, murine hybridomas can be made by fusing lymphocytes from a mouse immunized with an immunogenic preparation of the present invention with an immortalized mouse cell line, e.g., a myeloma cell line that is sensitive to culture medium containing hypoxanthine, aminopterin and thymidine ("HAT medium"). Any of a number of myeloma cell lines can be used as a fusion partner according to standard techniques, e.g., the P3-NS1/1- Ag4-1, P3-x63-Ag8.653 or Sp2/O-Agl 4 myeloma lines. These myeloma lines are available from ATCC. Typically, HAT-sensitive mouse myeloma cells are fused to mouse splenocytes using polyethylene glycol ("PEG"). Hybridoma cells resulting from the fusion are then selected using HAT medium, which kills unfused and unproductively fused myeloma cells (unfused splenocytes die after several days because they are not transformed). Hybridoma cells producing a monoclonal antibody of the invention are detected by screening the hybridoma culture supernatants for antibodies that bind LIG46, e.g., using a standard ELISA assay.

Alternative to preparing monoclonal antibody-secreting hybridomas, a monoclonal anti-LIG46 antibody can be identified and isolated by screening a recombinant combinatorial immunoglobulin library (e.g., an antibody phage display library) with LIG46 to thereby isolate immunoglobulin library members that bind LIG46. Kits for generating and screening phage display libraries are commercially available (e.g., the Pharmacia Recombinant Phage Antibody System, Catalog No. 27-9400-01 ; and the Stratagene SurfZAP^® Phage Display Kit, Catalog No. 240612). Additionally, examples of methods and reagents particularly amenable for use in generating and screening antibody display library can be found in, for example, U.S. Patent No. 5,223,409; PCT Publication No. WO 92/18619; PCT Publication No. WO 91/17271; PCT Publication No. WO 92/20791; PCT Publication No. WO 92/15679; PCT Publication No. WO 93/01288; PCT Publication No. WO 92/01047; PCT Publication No. WO 92/09690; PCT Publication No. WO 90/02809; Fuchs et al. (1991) Bio/Technology 9:1370-1372; Hay et al. (1992) Hum. Antibod. Hybridomas 3:81-85; Huse et al. (1989) Science 246:1275-1281; Griffiths et al. (1993)E BOJ. 12:725-734.

Additionally, recombinant anti-LIG46 antibodies, such as chimeric and humanized monoclonal antibodies, comprising both human and non-human portions, which can be made using standard recombinant DNA techniques, are within the scope of the invention. Such chimeric and humanized monoclonal antibodies can be produced by recombinant DNA techniques known in the art, for example using methods described in PCT Publication No. WO 87/02671; European Patent Application 184,187; European Patent Application 171,496; European Patent Application 173,494; PCT Publication No. WO 86/01533; U.S. PatentNo. 4,816,567; European Patent Application 125,023; Better et al. (1988) Science 240:1041-1043; Liu et al. (1987) Proc. Natl. Acad. Sci. USA 84:3439-3443; Liu et al. (1987) J. Immunol. 139:3521-3526; Sun et al. (1987) Proc. Natl. Acad. Sci. USA 84:214-218; Nishimura et al. (1987) Cane. Res. 47:999-1005; Wood et al. (\985)Nature 314:446-449; and Shaw et al. (1988)J. Natl. Cancer Inst. 80:1553-1559); Morrison, (1985) Science 229:1202-1207; Oi et al. (1986) Bio/Techniques 4:214; U.S. Patent 5,225,539; Jones et al. (1986) Nature 321 :552- 525; Verhoeyan et al. (1988) Science 239:1534; and Beidler et al. (1988) J. Immunol. 141:4053-4060.

An anti-LIG46 antibody (e.g., monoclonal antibody) can be used to isolate LIG46 by standard techniques, such as affinity chromatography or immunoprecipitation. An anti-LIG46 antibody can facilitate the purification of natural LIG46 from cells and of recombinantly produced LIG46 expressed in host cells. Moreover, an anti-LIG46 antibody can be used to detect LIG46 protein (e.g., in a cellular lysate or cell supernatant) in order to evaluate the abundance and pattern of expression of the LIG46 protein. Anti-LIG46 antibodies can be used diagnostically to monitor protein levels in tissue as part of a clinical testing procedure, e.g., to, for example, determine the efficacy of a given treatment regimen. Detection can be facilitated by coupling the antibody to a detectable substance. Examples of detectable substances include various enzymes, prosthetic groups, fluorescent materials, luminescent materials, bioluminescent materials, and radioactive materials. Examples of suitable enzymes include horseradish peroxidase, alkaline phosphatase, β-galactosidase, or acetylcholinesterase; examples of suitable prosthetic group complexes include streptavidin/biotin and avidin/biotin; examples of suitable fluorescent materials include umbelliferone, fluorescein, fluorescein isothiocyanate, rhodamine, dichlorotriazinylamine fluorescein, dansyl chloride or phycoerythrin; an example of a luminescent material includes luminol; examples of bioluminescent materials include luciferase, luciferin, and aequorin, and examples of suitable radioactive material include I, I, S or H.

Completely human antibodies are particularly desirable for therapeutic treatment of human patients. Such antibodies can be produced using transgenic mice which are incapable of expressing endogenous immunoglobulin heavy and light chains genes, but which can express human heavy and light chain genes. The transgenic mice are immunized in the normal fashion with a selected antigen. Monoclonal antibodies directed against the antigen can be obtain using conventional hybridoma technology. The human immunoglobulin transgenes of harbored by the transgenic mice rearrange during B cell differentiation, subsequently undergo class switching and somatic mutation. Thus, using such a technique, it is possible to produce therapeutically useful IgG, IgA and IgE antibodies. For an overview of this technology for producing human antibodies, see Lonberg and Huszar (1995, Int. Rev. Immunol. 13:65-93). For a detailed discussion of this technology for producing human antibodies and human monoclonal antibodies and protocols for producing such antibodies, see, e.g., U.S. Patent 5,625,126; U.S. Patent 5,633,425; U.S. Patent 5,569,825; U.S. Patent 5,661,016; and U.S. Patent 5,545,806. Human antibodies directed against a selected antigen can be provided by Abgenix, Inc. (Fremont, CA) and GenPharm, Inc. (Palo Alto, CA).

HI. Recombinant Expression Vectors and Host Cells

Another aspect of the invention pertains to vectors, preferably expression vectors, containing a nucleic acid encoding LIG46 (or a portion thereof).

As used herein, the term "vector" refers to a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked. One type of vector is a "plasmid", which refers to a circular double stranded DNA loop into which additional DNA segments can be ligated. Another type of vector is a viral vector, wherein additional DNA segments can be ligated into the viral genome. Certain vectors are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial vectors having a bacterial origin of replication and episomal mammalian vectors). Other vectors (e.g., non- episomal mammalian vectors) are integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome. Moreover, certain vectors, expression vectors, are capable of directing the expression of genes to which they are operatively linked. In general, expression vectors of utility in recombinant DNA techniques are often in the form of plasmids (vectors). However, the invention is intended to include such other forms of expression vectors, such as viral vectors (e.g., replication defective retroviruses, adenoviruses and adeno-associated viruses), which serve equivalent functions. The recombinant expression vectors of the invention comprise a nucleic acid of the invention in a form suitable for expression of the nucleic acid in a host cell, which means that the recombinant expression vectors include one or more regulatory sequences, selected on the basis of the host cells to be used for expression, which is operatively linked to the nucleic acid sequence to be expressed. Within a recombinant expression vector, "operably linked" is intended to mean that the nucleotide sequence of interest is linked to the regulatory sequence(s) in a manner which allows for expression of the nucleotide sequence (e.g., in an in vitro transcription/translation system or in a host cell when the vector is introduced into the host cell). The term "regulatory sequence" is intended to include promoters, enhancers and other expression control elements (e.g., polyadenylation signals). Such regulatory sequences are described, for example, in Goeddel; Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, CA (1990). Regulatory sequences include those which direct constitutive expression of a nucleotide sequence in many types of host cell and those which direct expression of the nucleotide sequence only in certain host cells (e.g., tissue-specific regulatory sequences). It will be appreciated by those skilled in the art that the design of the expression vector can depend on such factors as the choice of the host cell to be transformed, the level of expression of protein desired, etc. The expression vectors of the invention can be introduced into host cells to thereby produce proteins or peptides, including fusion proteins or peptides, encoded by nucleic acids as described herein (e.g., LIG46 proteins, mutant forms of LIG46, fusion proteins, etc.). The recombinant expression vectors of the invention can be designed for expression of LIG46 in prokaryotic or eukaryotic cells, e.g., bacterial cells such as E. coli, insect cells (using baculovirus expression vectors) yeast cells or mammalian cells. Suitable host cells are discussed further in Goeddel, Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, CA (1990). Alternatively, the recombinant expression vector can be transcribed and translated in vitro, for example using T7 promoter regulatory sequences and T7 polymerase.

Expression of proteins in prokaryotes is most often carried out inE. coli with vectors containing constitutive or inducible promoters directing the expression of either fusion or non-fusion proteins. Fusion vectors add a number of amino acids to a protein encoded therein, usually to the amino terminus of the recombinant protein. Such fusion vectors typically serve three puφoses: 1) to increase expression of recombinant protein; 2) to increase the solubility of the recombinant protein; and 3) to aid in the purification of the recombinant protein by acting as a ligand in affinity purification. Often, in fusion expression vectors, a proteolytic cleavage site is introduced at the junction of the fusion moiety and the recombinant protein to enable separation of the recombinant protein from the fusion moiety subsequent to purification of the fusion protein. Such enzymes, and their cognate recognition sequences, include Factor Xa, thrombin and enterokinase. Typical fusion expression vectors include pGEX (Pharmacia Biotech Inc; Smith and Johnson (1988) Gene 67:31-40), pMAL (New England Biolabs, Beverly, MA) and pRIT5 (Pharmacia, Piscataway, NJ) which fuse glutathione S-transferase (GST), maltose E binding protein, or protein A, respectively, to the target recombinant protein.

Examples of suitable inducible non-fusion E. coli expression vectors include pTrc (Amann et al., (1988) Gene 69:301-315) and pET 1 Id (Studier et al., Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, California (1990) 60- 89). Target gene expression from the pTrc vector relies on host RNA polymerase transcription from a hybrid tφ-lac fusion promoter. Target gene expression from the pET l id vector relies on transcription from a T7 gnlO-lac fusion promoter mediated by a coexpressed viral RNA polymerase (T7 gnl). This viral polymerase is supplied by host strains BL21(DE3) or HMS174(DE3) from a resident λ prophage harboring a T7 gnl gene under the transcriptional control of the lacUV 5 promoter. particular promoters of T cell receptors (Winoto and Baltimore (1989) EMBOJ. 8:729-733) and immunoglobulins (Banerji et al. (1983) Cell 33:729-740; Queen and Baltimore (1983) Cell 33:741-748), neuron-specific promoters (e.g., the neurofilament promoter; Byrne and Ruddle (1989) Proc. Natl. Acad. Sci. USA 86:5473-5477), pancreas-specific promoters (Edlund et al. (1985) Science 230:912-916), and mammary gland-specific promoters (e.g., milk whey promoter; U.S. Patent No. 4,873,316 and European Application Publication No. 264,166). Developmentally-regulated promoters are also encompassed, for example the murine hox promoters (Kessel and Gruss (1990) Science 249:374-379) and the α-fetoprotein promoter (Campes and Tilghman (1989) Genes Dev. 3:537-546). The invention further provides a recombinant expression vector comprising a DNA molecule of the invention cloned into the expression vector in an antisense orientation. That is, the DNA molecule is operatively linked to a regulatory sequence in a manner which allows for expression (by transcription of the DNA molecule) of an RNA molecule which is antisense to LIG46 mRNA. Regulatory sequences operatively linked to a nucleic acid cloned in the antisense orientation can be chosen which direct the continuous expression of the antisense RNA molecule in a variety of cell types, for instance viral promoters and/or enhancers, or regulatory sequences can be chosen which direct constitutive, tissue specific or cell type specific expression of antisense RNA. The antisense expression vector can be in the form of a recombinant plasmid, phagemid or attenuated virus in which antisense nucleic acids are produced under the control of a high efficiency regulatory region, the activity of which can be determined by the cell type into which the vector is introduced. For a discussion of the regulation of gene expression using antisense genes see Weintraub et al. (Reviews - Trends in Genetics, o\. 1(1) 1986).

Another aspect of the invention pertains to host cells into which a recombinant expression vector of the invention has been introduced. The terms "host cell" and

"recombinant host cell" are used interchangeably herein. It is understood that such terms refer not only to the particular subject cell but to the progeny or potential progeny of such a cell. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope of the term as used herein.

31 One strategy to maximize recombinant protein expression in E. coli is to express the protein in host bacteria with an impaired capacity to proteolytically cleave the recombinant protein (Gottesman, Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, California (1990) 119-128). Another strategy is to alter the nucleic acid sequence of the nucleic acid to be inserted into an expression vector so that the individual codons for each amino acid are those preferentially utilized in E. coli (Wada et al. (1992) Nucleic Acids Res. 20:2111-2118). Such alteration of nucleic acid sequences of the invention can be carried out by standard DNA synthesis techniques.

In another embodiment, the LIG46 expression vector is a yeast expression vector. Examples of vectors for expression in yeast S. cerivisae include pYepSecl (Baldari et al. (1987) EMBOJ. 6:229-234), pMFa (Kurjan and Herskowitz, (1982) Cell 30:933-943), pJRY88 (Schultz et al. (1987) Gene 54:113-123), pYES2 (Invitrogen Coφoration, San Diego, CA), and picZ (InVitrogen Coφ, San Diego, CA).

Alternatively, LIG46 can be expressed in insect cells using baculovirus expression vectors. Baculovirus vectors available for expression of proteins in cultured insect cells (e.g., Sf 9 cells) include the pAc series (Smith et al. (1983) Mol. Cell Biol. 3:2156-2165) and the pVL series (Lucklowand Summers (1989) Virology 170:31-39).

In yet another embodiment, a nucleic acid of the invention is expressed in mammalian cells using a mammalian expression vector. Examples of mammalian expression vectors include pCDM8 (Seed (1987) Nature 329:840) and pMT2PC (Kaufman et al. (1987) EMBOJ. 6:187-195). When used in mammalian cells, the expression vector's control functions are often provided by viral regulatory elements. For example, commonly used promoters are derived from polyoma, Adenovirus 2, cytomegalovirus and Simian Virus 40. For other suitable expression systems for both prokaryotic and eukaryotic cells see chapters 16 and 17 of Sambrook et al. (supra).

In another embodiment, the recombinant mammalian expression vector is capable of directing expression of the nucleic acid preferentially in a particular cell type (e.g., tissue- specific regulatory elements are used to express the nucleic acid). Tissue-specific regulatory elements are known in the art. Non-limiting examples of suitable tissue-specific promoters include the albumin promoter (liver-specific; Pinkert et al. (1987) Genes Dev. 1 :268-277), lymphoid-specific promoters (Calame and Eaton (1988) A dv. Immunol. 43:235-275), in

- 30 - A host cell can be any prokaryotic or eukaryotic cell. For example, LIG46 protein can be expressed in bacterial cells such as E. coli, insect cells, yeast or mammalian cells (such as Chinese hamster ovary cells (CHO) or COS cells). Other suitable host cells are known to those skilled in the art. Vector DNA can be introduced into prokaryotic or eukaryotic cells via conventional transformation or transfection techniques. As used herein, the terms "transformation" and "transfection" are intended to refer to a variety of art-recognized techniques for introducing foreign nucleic acid (e.g., DNA) into a host cell, including calcium phosphate or calcium chloride co-precipitation, DEAE-dextran-mediated transfection, lipofection, or electroporation. Suitable methods for transforming or transfecting host cells can be found in Sambrook, et al. (supra), and other laboratory manuals.

For stable transfection of mammalian cells, it is known that, depending upon the expression vector and transfection technique used, only a small fraction of cells may integrate the foreign DNA into their genome. In order to identify and select these integrants, a gene that encodes a selectable marker (e.g., resistance to antibiotics) is generally introduced into the host cells along with the gene of interest. Preferred selectable markers include those which confer resistance to drugs, such as G418, hygromycin and methotrexate. Nucleic acid encoding a selectable marker can be introduced into a host cell on the same vector as that encoding LIG46 or can be introduced on a separate vector. Cells stably transfected with the introduced nucleic acid can be identified by drug selection (e.g., cells that have incorporated the selectable marker gene will survive, while the other cells die).

A host cell of the invention, such as a prokaryotic or eukaryotic host cell in culture, can be used to produce (i.e., express) LIG46 protein. Accordingly, the invention further provides methods for producing LIG46 protein using the host cells of the invention. In one embodiment, the method comprises culturing the host cell of invention (into which a recombinant expression vector encoding LIG46 has been introduced) in a suitable medium such that LIG46 protein is produced. In another embodiment, the method further comprises isolating LIG46 from the medium or the host cell.

The host cells of the invention can also be used to produce non-human transgenic animals which over-express a protein of interest. For example, in one embodiment, a host cell of the invention is a fertilized oocyte or an embryonic stem cell into which a nucleic acid molecule which directs high-level expression of LIG46 has been introduced. Such host cells can then be used to create non-human transgenic animals in which LIG46 sequences have been introduced into their genome or homologous recombinant animals in which endogenous LIG46 sequences have been altered. Such animals are useful for studying the function and/or activity of LIG46 and for identifying and/or evaluating modulators of LIG46 activity. As used herein, a "transgenic animal" is a non-human animal, preferably a mammal, more preferably a rodent such as a rat or mouse, in which one or more of the cells of the animal includes a transgene. Other examples of transgenic animals include non-human primates, sheep, dogs, cows, goats, chickens, amphibians, etc. A transgene is exogenous DNA which is integrated into the genome of a cell from which a transgenic animal develops and which remains in the genome of the mature animal, thereby directing the expression of an encoded gene product in one or more cell types or tissues of the transgenic animal. As used herein, an "homologous recombinant animal" is a non-human animal, preferably a mammal, more preferably a mouse, in which an endogenous LIG46 gene has been altered by homologous recombination between the endogenous gene and an exogenous DNA molecule introduced into a cell of the animal, e.g., an embryonic cell of the animal, prior to development of the animal.

A transgenic animal of the invention can be created by introducing a nucleic acid molecule encoding a desired protein into the male pronuclei of a fertilized oocyte, e.g., by microinjection, retroviral infection, and allowing the oocyte to develop in a pseudopregnant female foster animal. The cDNA sequence can be introduced as a transgene into the genome of a non-human animal. Alternatively, a human homologue of the LIG46 gene can be isolated based on hybridization to the murine LIG46 cDNA and used as a transgene. Iritronic sequences and polyadenylation signals can also be included in the transgene to increase the efficiency of expression of the transgene. A tissue-specific regulatory sequence(s) can be operably linked to the transgene to direct expression of the protein to particular cells. Methods for generating transgenic animals via embryo manipulation and microinjection, particularly animals such as mice, have become conventional in the art and are described, for example, in U.S. Patent Nos. 4,736,866 and 4,870,009, U.S. Patent No. 4,873,191 and in Hogan, Manipulating the Mouse Embryo, (Cold Spring Harbor Laboratory Press, Cold Spring

Harbor, N.Y., 1986). Similar methods are used for production of other transgenic animals. A transgenic founder animal can be identified based upon the presence of the transgene in its genome and/or expression of the mRNA in tissues or cells of the animals. A transgenic founder animal can then be used to breed additional animals carrying the transgene. Moreover, transgenic animals carrying a transgene encoding LIG46 can further be bred to other transgenic animals carrying other transgenes.

To create an homologous recombinant animal, a vector is prepared which contains at least a portion of a LIG46 gene into which a deletion, addition or substitution has been introduced to thereby alter, e.g., functionally disrupt, the gene. In a preferred embodiment, the vector is designed such that, upon homologous recombination, the endogenous gene is functionally disrupted (i.e., no longer encodes a functional protein; also referred to as a

"knock out" vector). Alternatively, the vector can be designed such that, upon homologous recombination, the endogenous gene is mutated or otherwise altered but still encodes functional protein (e.g., the upstream regulatory region can be altered to thereby alter the expression of the endogenous protein). In the homologous recombination vector, the altered portion of the gene is flanked at its 5' and 3' ends by additional nucleic acids of the gene to allow for homologous recombination to occur between the exogenous gene carried by the vector and an endogenous gene in an embryonic stem cell. The additional flanking nucleic acid is of sufficient length for successful homologous recombination with the endogenous gene. Typically, several kilobases of flanking DNA (both at the 5' and 3' ends) are included in the vector (see, e.g., Thomas and Capecchi (1987) Cell 51:503 for a description of homologous recombination vectors). The vector is introduced into an embryonic stem cell line (e.g., by electroporation) and cells in which the introduced gene has homologously recombined with the endogenous gene are selected (see, e.g., Li et al. (1992) Cell 69:915). The selected cells are then injected into a blastocyst of an animal (e.g., a mouse) to form aggregation chimeras (see, e.g., Bradley in Teratocarcinomas and Embryonic Stem Cells: A Practical Approach, Robertson, ed. (IRL, Oxford, 1987) pp. 113-152). A chimeric embryo can then be implanted into a suitable pseudopregnant female foster animal and the embryo brought to term. Progeny harboring the homologously recombined DNA in their germ cells can be used to breed animals in which all cells of the animal contain the homologously recombined DNA by germline transmission of the transgene. Methods for constructing homologous recombination vectors and homologous recombinant animals are described further in Bradley (1991) Current Opinion in Bio/Technology 2:823-829 and in PCT Publication Nos. WO 90/11354, WO 91/01140, WO 92/0968, and WO 93/04169.

In another embodiment, transgenic non-humans animals can be produced which contain selected systems which allow for regulated expression of the transgene. One example of such a system is the cre/loxP recombinase system of bacteriophage PI. For a description of the cre/loxP recombinase system, see, e.g., Lakso et al. (1992) Proc. Natl. Acad. Sci. USA 89:6232-6236. Another example of a recombinase system is the FLP recombinase system of Saccharomyces cerevisiae (O'Gorman et al. (1991) Science 251:1351-1355. If a cre/loxP recombinase system is used to regulate expression of the transgene, animals containing transgenes encoding both the Cre recombinase and a selected protein are required. Such animals can be provided through the construction of "double" transgenic animals, e.g., by mating two transgenic animals, one containing a transgene encoding a selected protein and the other containing a transgene encoding a recombinase.

Clones of the non-human transgenic animals described herein can also be produced according to the methods described in Wilmut et al. (1997) Nature 385:810-813 and PCT

Publication Nos. WO 97/07668 and WO 97/07669. In brief, a cell, e.g., a somatic cell, from the transgenic animal can be isolated and induced to exit the growth cycle and enter G₀ phase. The quiescent cell can then be fused, e.g., through the use of electrical pulses, to an enucleated oocyte from an animal of the same species from which the quiescent cell is isolated. The reconstructed oocyte is then cultured such that it develops to morula or blastocyte and then transferred to pseudopregnant female foster animal. The offspring borne of this female foster animal will be a clone of the animal from which the cell, e.g., the somatic cell, is isolated.

IV. Pharmaceutical Compositions

The LIG46 nucleic acid molecules, LIG46 proteins, and anti-LIG46 antibodies, and inhibitors and activators of LIG46 expression or activity (also referred to herein as "active compounds") can be incoφorated into pharmaceutical compositions suitable for administration. Therapeutic compositions typically comprise the nucleic acid molecule, protein, or antibody and a pharmaceutically acceptable carrier. As used herein the language "pharmaceutically acceptable carrier" is intended to include any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absoφtion delaying agents, and the like, compatible with pharmaceutical administration. The use of such media and agents for pharmaceutically active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active compound, use thereof in the compositions is contemplated. Supplementary active compounds can also be incoφorated into the compositions.

A pharmaceutical composition of the invention is formulated to be compatible with its intended route of administration. Examples of routes of administration include parenteral, e.g., intravenous, intradermal, subcutaneous, oral (e.g., inhalation), transdermal (topical), transmucosal, and rectal administration. Solutions or suspensions used for parenteral, intradermal, or subcutaneous application can include the following components: a sterile diluent such as water for injection, saline solution, fixed oils, polyethylene glycols, glycerine, propylene glycol or other synthetic solvents; antibacterial agents such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. pH can be adjusted with acids or bases, such as hydrochloric acid or sodium hydroxide. The parenteral preparation can be enclosed in ampoules, disposable syringes or multiple dose vials made of glass or plastic.

Pharmaceutical compositions suitable for injectable use include sterile aqueous solutions (where water soluble) or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersion. For intravenous administration, suitable carriers include physiological saline, bacteriostatic water, Cremophor EL (BASF; Parsippany, NJ) or phosphate buffered saline (PBS). In all cases, the composition must be sterile and should be fluid to the extent that easy syringability exists. It must be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms such as bacteria and fungi. The carrier can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyetheylene glycol, and the like), and suitable mixtures thereof. The proper fluidity can be maintained, for example, by the use of a coating such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. Prevention of the action of microorganisms can be achieved by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, ascorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars, polyalcohols such as mannitol, sorbitol, sodium chloride in the composition. Prolonged absoφtion of the injectable compositions can be brought about by including in the composition an agent which delays absoφtion, for example, aluminum monostearate and gelatin.

Sterile injectable solutions can be prepared by incoφorating the active compound (e.g., a LIG46 protein or anti-LIG46 antibody) in the required amount in an appropriate solvent with one or a combination of ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incoφorating the active compound into a sterile vehicle which contains a basic dispersion medium and the required other ingredients from those enumerated above. Jxi the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum drying and freeze-drying which yields a powder of the active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof.

Oral compositions generally include an inert diluent or an edible carrier. They can be enclosed in gelatin capsules or compressed into tablets. For the puφose of oral therapeutic administration, the active compound can be incorporated with excipients and used in the form of tablets, troches, or capsules. Oral compositions can also be prepared using a fluid carrier for use as a mouthwash, wherein the compound in the fluid carrier is applied orally and swished and expectorated or swallowed. Pharmaceutically compatible binding agents, and/or adjuvant materials can be included as part of the composition. The tablets, pills, capsules, troches and the like can contain any of the following ingredients, or compounds of a similar nature: a binder such as microcrystalline cellulose, gum tragacanth or gelatin; an excipient such as starch or lactose, a disintegrating agent such as alginic acid, Primogel, or corn starch; a lubricant such as magnesium stearate or Sterotes; a glidant such as colloidal silicon dioxide; a sweetening agent such as sucrose or saccharin; or a flavoring agent such as peppermint, methyl salicylate, or orange flavoring. For administration by inhalation, the compounds are delivered in the form of an aerosol spray from pressured container or dispenser which contains a suitable propellant, e.g., a gas such as carbon dioxide, or a nebulizer.

Systemic administration can also be by transmucosal or transdermal means. For transmucosal or transdermal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art, and include, for example, for transmucosal administration, detergents, bile salts, and fusidic acid derivatives. Transmucosal administration can be accomplished through the use of nasal sprays or suppositories. For transdermal administration, the active compounds are formulated into ointments, salves, gels, or creams as generally known in the art.

The compounds can also be prepared in the form of suppositories (e.g., with conventional suppository bases such as cocoa butter and other glycerides) or retention enemas for rectal delivery.

In one embodiment, the active compounds are prepared with carriers that will protect the compound against rapid elimination from the body, such as a controlled release formulation, including implants and microencapsulated delivery systems. Biodegradable, biocompatible polymers can be used, such as ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, and polylactic acid. Methods for preparation of such formulations will be apparent to those skilled in the art. The materials can also be obtained commercially from Alza Coφoration and Nova Pharmaceuticals, Inc. Liposomal suspensions (including liposomes targeted to infected cells with monoclonal antibodies to viral antigens) can also be used as pharmaceutically acceptable carriers. These can be prepared according to methods known to those skilled in the art, for example, as described in U.S. Patent No. 4,522,811. It is especially advantageous to formulate oral or parenteral compositions in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the subject to be treated; each unit containing a predetermined quantity of active compound calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. The specification for the dosage unit forms of the invention are dictated by and directly dependent on the unique characteristics of the active compound and the particular therapeutic effect to be achieved, and the limitations inherent in the art of compounding such an active compound for the treatment of individuals.

The nucleic acid molecules of the invention can be inserted into vectors and used as gene therapy vectors. Gene therapy vectors can be delivered to a subject by, for example, intravenous injection, local administration (U.S. Patent 5,328,470) or by stereotactic injection (see, e.g., Chen et al. (1994) Proc. Natl. Acad. Sci. USA 91 :3054-3057). The pharmaceutical preparation of the gene therapy vector can include the gene therapy vector in an acceptable diluent, or can comprise a slow release matrix in which the gene delivery vehicle is imbedded. Alternatively, where the complete gene delivery vector can be produced intact from recombinant cells, e.g. retroviral vectors, the pharmaceutical preparation can include one or more cells which produce the gene delivery system.

The pharmaceutical compositions can be included in a container, pack, or dispenser together with instructions for administration.

V. Uses and Methods of the Invention

The LIG46 nucleic acid molecules, proteins, protein homologues, and antibodies described herein can be used in one or more of the following methods: a) screening assays; b) detection assays (e.g., chromosomal mapping, tissue typing, forensic biology); and c) methods of treatment (e.g., therapeutic and prophylactic). The isolated nucleic acid molecules of the invention can be used to express LIG46 protein (e.g., via a recombinant expression vector in a host cell in gene therapy applications or transgenic animals), to detect LIG46 mRNA (e.g., in a biological sample) or a genetic lesion in a LIG46 gene, and to modulate LIG46 activity or expression. In addition, LIG46 protein can be used to screen drugs or compounds which modulate LIG46 activity or expression as well as to treat disorders characterized by insufficient or excessive production of LIG46 protein or production of LIG46 protein forms which have an undesirable level of activity compared to the wild type protein. In addition, the anti-LIG46 antibodies of the invention can be used to detect and isolate LIG46 protein and modulate LIG46 activity.

This invention further pertains to novel agents identified by the above-described screening assays and uses thereof for treatments as described herein. A. Screening Assays

The invention provides a method (also referred to herein as a "screening assay") for identifying modulators, i.e., candidate or test compounds or agents (e.g., peptides, peptidomimetics, small molecules or other drugs) which bind to a LIG46 protein and/or have a stimulatory or inhibitory effect on, for example, LIG46 expression or activity.

The invention provides assays for screening candidate or test compounds which bind to or modulate the activity of the membrane-bound form of a LIG46 protein or polypeptide or biologically active portion thereof. Other embodiments entail the use of a soluble form of LIG46. The test compounds of the present invention can be obtained using any of the numerous approaches in combinatorial library methods known in the art, including: biological libraries; spatially addressable parallel solid phase or solution phase libraries; synthetic library methods requiring deconvolution; the "one-bead one-compound" library method; and synthetic library methods using affinity chromatography selection. The biological library approach is limited to peptide libraries, while the other four approaches are applicable to peptide, non-peptide oligomer or small molecule libraries of compounds (Lam (1997) Anticancer Drug Des. 12:145).

Examples of methods for the synthesis of molecular libraries can be found in the art, for example in: DeWitt et al. (1993) Proc. Natl. Acad. Sci. U.S.A. 90:6909; Erb et al. (1994) Proc. Natl. Acad. Sci. USA 91:11422; Zuckermann et al. (1994). J. Med. Chem. 37:2678; Cho et al. (1993) Science 261 :1303; Carrell et al. (1994) Angew. Chem. Int. Ed. Engl 33:2059; Carell et al. (1994) Angew. Chem. Int. Ed. Engl 33:2061; and Gallop et al. (1994) J. Med. Chem. 37:1233.

Libraries of compounds may be presented in solution (e.g., Houghten (1992) Bio/Techniques 13:412-421), or on beads (Lam (1991) Nature 354:82-84), chips (Fodor (1993) Nature 364:555-556), bacteria (U.S. Patent No. 5,223,409), spores (Patent Nos. 5,571,698; 5,403,484; and 5,223,409), plasmids (Cull etal. (1992) roc. Natl. Acad. Sci. USA 89:1865-1869) or on phage (Scott and Smith (1990) Science 249:386-390; Devlin (1990) Science 249:404-406; Cwirla et al. (1990) Proc. Natl. Acad. Sci. 87:6378-6382; and Felici (1991) J. Mol. Biol. 222:301-310). The invention includes assays employing soluble LIG46. Such assays entail contacting a LIG46 protein or biologically active portion thereof with a test compound and determining the ability of the test compound to bind to LIG46 protein or biologically active portion thereof. Binding of the test compound to LIG46 protein can be determined either directly or indirectly using the approaches described above. In a preferred embodiment, the assay includes contacting LIG46 protein or biologically active portion thereof with a known compound which binds LIG46 to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability of the test compound to interact with LIG46 protein, wherein determining the ability of the test compound to interact with LIG46 protein comprises determining the ability of the test compound to preferentially bind to LIG46 or biologically active portion thereof as compared to the known compound.

Jn another embodiment, an assay is a cell-free assay comprising contacting LIG46 protein or biologically active portion thereof with a test compound and determining the ability of the test compound to modulate (e.g., stimulate or inhibit) the activity of LIG46 or a biologically active portion thereof. Determining the ability of the test compound to modulate the activity of LIG46 can be accomplished, for example, by determining the ability of LIG46 to bind to a test compound by one of the methods described herein for determining direct binding. In an alternative embodiment, determining the ability of the test compound to modulate the activity of LIG46 can be accomplished by determining the ability of the agent to alter the activity of a LIG46 target molecule. For example, the catalytic/enzymatic activity of the target molecule on an appropriate substrate can be determined.

In yet another embodiment, the cell-free assay comprises contacting the LIG46 protein or biologically active portion thereof with a known compound which binds LIG46 to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability of the test compound to interact with a LIG46 protein, wherein determining the ability of the test compound to interact with a LIG46 protein comprises determining the ability of the LIG46 protein to preferentially bind to or modulate the activity of a LIG46 target molecule.

It is possible that a membrane-bound form of LIG46 is present in, e.g., golgi. Thus, in one embodiment, an assay is a cell-based assay in which a cell which expresses a membrane- bound form of LIG46 protein, or a biologically active portion thereof, on the cell surface is contacted with a test compound and the ability of the test compound to bind to a LIG46 protein determined. The cell, for example, can be a yeast cell or a cell of mammalian origin. Determining the ability of the test compound to bind to the LIG46 protein can be accomplished, for example, by coupling the test compound with a radioisotope or enzymatic label such that binding of the test compound to the LIG46 protein or biologically active portion thereof can be determined by detecting the labeled compound in a complex. For example, test compounds can be labeled with ¹²⁵I, ³⁵S, ¹⁴C, or ³H, either directly or indirectly, and the radioisotope detected by direct counting of radioemmission or by scintillation counting. Alternatively, test compounds can be enzymatically labeled with, for example, horseradish peroxidase, alkaline phosphatase, or luciferase, and the enzymatic label detected by determination of conversion of an appropriate substrate to product. In a preferred embodiment, the assay comprises contacting a cell which expresses a membrane-bound form of LIG46 protein, or a biologically active portion thereof, on the cell surface with a known compound which binds LIG46 to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability of the test compound to interact with a LIG46 protein, wherein determining the ability of the test compound to interact with a LIG46 protein comprises determining the ability of the test compound to preferentially bind to LIG46 or a biologically active portion thereof as compared to the known compound.

In another embodiment, an assay is a cell-based assay comprising contacting a cell expressing a membrane-bound form of LIG46 protein, or a biologically active portion thereof, on the cell surface with a test compound and determining the ability of the test compound to modulate (e.g., stimulate or inhibit) the activity of the LIG46 protein or biologically active portion thereof. Determining the ability of the test compound to modulate the activity of LIG46 or a biologically active portion thereof can be accomplished, for example, by determining the ability of the LIG46 protein to bind to or interact with a LIG46 target molecule. As used herein, a "target molecule" is a molecule with which a LIG46 protein binds or interacts in nature, for example, a molecule on the surface of a cell which expresses a LIG46 protein, a molecule on the surface of a second cell, a molecule in the extracellular milieu, a molecule associated with the internal surface of a cell membrane or a cytoplasmic molecule. A LIG46 target molecule can be a non-LIG46 molecule or a LIG46 protein or polypeptide of the present invention. In one embodiment, a LIG46 target molecule is a component of a signal transduction pathway that facilitates transduction of an extracellular signal (e.g., a signal generated by binding of a compound to a membrane-bound LIG46 molecule) through the cell membrane and into the cell. The target, for example, can be a second intercellular protein that has catalytic activity or a protein that facilitates the association of downstream signaling molecules with LIG46.

Determining the ability of a membrane bound form of LIG46 protein to bind to or interact with a LIG46 target molecule can be accomplished by one of the methods described above for determining direct binding. In a preferred embodiment, determining the ability of the LIG46 protein to bind to or interact with a LIG46 target molecule can be accomplished by determining the activity of the target molecule. For example, the activity of the target molecule can be determined by detecting catalytic/enzymatic activity or detecting a cellular response.

The cell-free assays of the present invention are amenable to use of both the soluble form or the membrane-bound form of LIG46. In the case of cell-free assays comprising the membrane-bound form of LIG46, it may be desirable to utilize a solubilizing agent such that the membrane-bound form of LIG46 is maintained in solution. Examples of such solubilizing agents include non-ionic detergents such as n-octylglucoside, n-dodecylglucoside, n- dodecylmaltoside, octanoyl-N-methylglucamide, decanoyl-N-methylglucamide, Triton^® X- 100, Triton^® X-l 14, Thesit^®, Isotridecypoly (ethylene glycol ether)n, 3-[(3- cholamidopropyl)dimethylamminio]-l -propane sulfonate (CHAPS), 3 -[(3 - cholamidopropyl)dimethylamminio]-2-hydroxy-l -propane sulfonate (CHAPSO), or N- dodecyl=N,N-dimethyl-3-ammonio-l -propane sulfonate.

In more than one embodiment of the above assay methods of the present invention, it may be desirable to immobilize either LIG46 or the corresponding target molecule to facilitate separation of complexed from uncomplexed forms of one or both of the proteins, as well as to accommodate automation of the assay. Binding of a test compound to LIG46 or interaction of LIG46 with a target molecule in the presence and absence of a candidate compound, can be accomplished in any vessel suitable for containing the reactants. Examples of such vessels include microtitre plates, test tubes, and micro-centrifuge tubes. In one embodiment, a fusion protein can be provided which adds a domain that allows one or both of the proteins to be bound to a matrix. For example, glutathione-S-transferase/ fusion proteins or glutathione-S- transferase/target fusion proteins can be adsorbed onto glutathione sepharose beads (Sigma Chemical; St. Louis, MO) or glutathione derivatized microtitre plates, which are then combined with the test compound or the test compound and either the non-adsorbed target protein or LIG46 protein, and the mixture incubated under conditions conducive to complex formation (e.g., at physiological conditions for salt and pH). Following incubation, the beads or microtitre plate wells are washed to remove any unbound components, the matrix immobilized in the case of beads, complex determined either directly or indirectly, for example, as described above. Alternatively, the complexes can be dissociated from the matrix, and the level of LIG46 binding or activity determined using standard techniques. Other techniques for immobilizing proteins on matrices can also be used in the screening assays of the invention. For example, either LIG46 or the corresponding target molecule can be immobilized utilizing conjugation of biotin and streptavidin. Biotinylated LIG46 or the corresponding target molecule can be prepared from biotin-NHS (N-hydroxy- succinimide) using techniques well known in the art (e.g., biotinylation kit, Pierce Chemicals; Rockford, JL), and immobilized in the wells of streptavidin-coated 96 well plates (Pierce Chemical). Alternatively, antibodies reactive with LIG46 or the corresponding target molecule but which do not interfere with binding of the LIG46 protein to its target molecule can be derivatized to the wells of the plate, and unbound target or LIG46 trapped in the wells by antibody conjugation. Methods for detecting such complexes, in addition to those described above for the GST-immobilized complexes, include immunodetection of complexes using antibodies reactive with the LIG46 or corresponding target molecule, as well as enzyme-linked assays which rely on detecting an enzymatic activity associated with the LIG46 or corresponding target molecule.

In another embodiment, modulators of LIG46 expression are identified in a cell-based assay in which a cell is contacted with a candidate compound and the expression of LIG46 mRNA or protein in the cell is determined. The level of expression of LIG46 mRNA or protein in the presence of the candidate compound is compared to the level of expression of LIG46 mRNA or protein in the absence of the candidate compound. The candidate compound can then be identified as a modulator of LIG46 expression based on this comparison. For example, when expression of LIG46 mRNA or protein is greater

(statistically significantly greater) in the presence of the candidate compound than in its absence, the candidate compound is identified as a stimulator of LIG46 mRNA or protein expression. Alternatively, when expression of LIG46 mRNA or protein is less (statistically significantly less) in the presence of the candidate compound than in its absence, the candidate compound is identified as an inhibitor of LIG46 mRNA or protein expression. The level of LIG46 mRNA or protein expression in the cells can be determined by methods described herein for detecting LIG46 mRNA or protein.

In another embodiment, modulators of LIG46 activity are identified in a cell-based assay in which a cell is contacted with a candidate compound and the activity of LIG46 mRNA or protein in the cell is determined. The level of activity of LIG46 mRNA or protein in the presence of the candidate compound is compared to the level of activity of LIG46 mRNA or protein in the absence of the candidate compound. The candidate compound can then be identified as a modulator of LIG46 activity based on this comparison.

For example, when activity of LIG46 is greater (statistically significantly greater) in the presence of the candidate compound than in its absence, the candidate compound is identified as a stimulator of LIG46 mRNA or protein expression. Alternatively, when the activity of LIG46 is less (statistically significantly less) in the presence of the candidate compound than in its absence, the candidate compound is identified as an inhibitor of LIG46 activity.

In yet another aspect of the invention, LIG46 protein can be used a "bait protein" in a two-hybrid assay or three hybrid assay (see, e.g., U.S. Patent No. 5,283,317; Zervos et al. (1993) Cell 72:223-232; Madura et al. (1993) J. Biol. Chem. 268:12046-12054; Barrel et al. (1993) Bio/Techniques 14:920-924; Iwabuchi et al. (1993) Oncogene 8:1693-1696; and PCT Publication No. WO 94/10300), to identify other proteins, which bind to or interact with LIG46 and modulate activity. The two-hybrid system is based on the modular nature of most transcription factors, which consist of separable DNA-binding and activation domains. Briefly, the assay utilizes two different DNA constructs. In one construct, the gene that codes for the protein of interest, e.g., LIG46, is fused to a gene encoding the DNA binding domain of a known transcription factor (e.g., GAL-4). In the other construct, a DNA sequence, from a library of DNA sequences, that encodes an unidentified protein ("prey" or "sample") is fused to a gene that codes for the activation domain of the known transcription factor. If the "bait" and the "prey" proteins are able to interact, in vivo, forming a complex, the DNA-binding and activation domains of the transcription factor are brought into close proximity. This proximity allows transcription of a reporter gene (e.g., LacZ) which is operably linked to a transcriptional regulatory site responsive to the transcription factor. Expression of the reporter gene can be detected and cell colonies containing the functional transcription factor can be isolated and used to obtain the cloned gene which encodes the protein which interacts with LIG46.

This invention further pertains to novel agents identified by the above-described screening assays and uses thereof for treatments as described herein. B. Detection Assays Portions or fragments of the LIG46 sequences identified herein (and the corresponding complete gene sequences) can be used in numerous ways as polynucleotide reagents. For example, these sequences can be used to: (i) map their respective genes on a chromosome; and, thus, locate gene regions associated with genetic disease; (ii) identify an individual from a minute biological sample (tissue typing); and (iii) aid in forensic identification of a biological sample. These applications are described in the subsections below.

1. Chromosome Mapping

Once the sequence (or a portion of the sequence) of a gene has been isolated, this sequence can be used to map the location of the gene on a chromosome. Accordingly, LIG46 nucleic acid molecules described herein or fragments thereof, can be used to map the location of LIG46 genes on a chromosome. The mapping of the LIG46 sequences to chromosomes is an important first step in correlating these sequences with genes associated with disease. Briefly, LIG46 genes can be mapped to chromosomes by preparing PCR primers (preferably 15-25 bp in length) from the LIG46 sequences. Computer analysis of LIG46 sequences can be used to rapidly select primers that do not span more than one exon in the genomic DNA, thus complicating the amplification process. These primers can then be used for PCR screening of somatic cell hybrids containing individual human chromosomes. Only those hybrids containing the human gene corresponding to the LIG46 sequences will yield an amplified fragment. Somatic cell hybrids are prepared by fusing somatic cells from different mammals

(e.g., human and mouse cells). As hybrids of human and mouse cells grow and divide, they gradually lose human chromosomes in random order, but retain the mouse chromosomes. By using media in which mouse cells cannot grow, because they lack a particular enzyme, but human cells can, the one human chromosome that contains the gene encoding the needed enzyme, will be retained. By using various media, panels of hybrid cell lines can be established. Each cell line in a panel contains either a single human chromosome or a small number of human chromosomes, and a full set of mouse chromosomes, allowing easy mapping of individual genes to specific human chromosomes. (D'Eustachio et al. (1983) Science 220:919-924). Somatic cell hybrids containing only fragments of human chromosomes can also be produced by using human chromosomes with translocations and deletions.

PCR mapping of somatic cell hybrids is a rapid procedure for assigning a particular sequence to a particular chromosome. Three or more sequences can be assigned per day using a single thermal cycler. Using the LIG46 sequences to design oligonucleotide primers, sublocalization can be achieved with panels of fragments from specific chromosomes. Other mapping strategies which can similarly be used to map a LIG46 sequence to its chromosome include in situ hybridization (described in Fan et al. (1990) Proc. Natl. Acad. Sci. USA 87:6223-27), pre-screening with labeled flow-sorted chromosomes, and pre-selection by hybridization to chromosome specific cDNA libraries.

Fluorescence in situ hybridization (FISH) of a DNA sequence to a metaphase chromosomal spread can further be used to provide a precise chromosomal location in one step. Chromosome spreads can be made using cells whose division has been blocked in metaphase by a chemical like colcemid that disrupts the mitotic spindle. The chromosomes can be treated briefly with trypsin, and then stained with Giemsa. A pattern of light and dark bands develops on each chromosome, so that the chromosomes can be identified individually. The FISH technique can be used with a DNA sequence as short as 500 or 600 bases.

However, clones larger than 1,000 bases have a higher likelihood of binding to a unique chromosomal location with sufficient signal intensity for simple detection. Preferably 1,000 bases, and more preferably 2,000 bases will suffice to get good results at a reasonable amount of time. For a review of this technique, see Verma et al., (Human Chromosomes: A Manual of Basic Techniques (Pergamon Press, New York, 1988)). Reagents for chromosome mapping can be used individually to mark a single chromosome or a single site on that chromosome, or panels of reagents can be used for marking multiple sites and/or multiple chromosomes. Reagents corresponding to noncoding regions of the genes actually are preferred for mapping puφoses. Coding sequences are more likely to be conserved within gene families, thus increasing the chance of cross hybridizations during chromosomal mapping.

Once a sequence has been mapped to a precise chromosomal location, the physical position of the sequence on the chromosome can be correlated with genetic map data. (Such data are found, for example, in V. McKusick, Mendelian Inheritance in Man, available on-line through Johns Hopkins University Welch Medical Library). The relationship between genes and disease, mapped to the same chromosomal region, can then be identified through linkage analysis (co-inheritance of physically adjacent genes), described in, e.g., Egeland et al. (1987) Nature, 325:783-787.

Moreover, differences in the DNA sequences between individuals affected and unaffected with a disease associated with the LIG46 gene can be determined. If a mutation is observed in some or all of the affected individuals but not in any unaffected individuals, then the mutation is likely to be the causative agent of the particular disease. Comparison of affected and unaffected individuals generally involves first looking for structural alterations in the chromosomes such as deletions or translocations that are visible from chromosome spreads or detectable using PCR based on that DNA sequence. Ultimately, complete sequencing of genes from several individuals can be performed to confirm the presence of a mutation and to distinguish mutations from polymoφhisms. 2. Tissue Typing

The LIG46 sequences of the present invention can also be used to identify individuals from minute biological samples. The United States military, for example, is considering the use of restriction fragment length polymoφhism (RFLP) for identification of its personnel. In this technique, an individual's genomic DNA is digested with one or more restriction enzymes, and probed on a Southern blot to yield unique bands for identification. This method does not suffer from the current limitations of "Dog Tags" which can be lost, switched, or stolen, making positive identification difficult. The sequences of the present invention are useful as additional DNA markers for RFLP (described in U.S. Patent 5,272,057). Furthermore, the sequences of the present invention can be used -to provide an_r alternative technique which determines the actual base-by-base DNA sequence of selected portions of an individual's genome. Thus, the LIG46 sequences described herein can be used to prepare two PCR primers from the 5' and 3' ends of the sequences. These primers can then be used to amplify an individual's DNA and subsequently sequence it.

Panels of corresponding DNA sequences from individuals, prepared in this manner, can provide unique individual identifications, as each individual will have a unique set of such DNA sequences due to allelic differences. The sequences of the present invention can be used to obtain such identification sequences from individuals and from tissue. The LIG46 sequences of the invention uniquely represent portions of the human genome. Allelic variation occurs to some degree in the coding regions of these sequences, and to a greater degree in the non-coding regions. It is estimated that allelic variation between individual humans occurs with a frequency of about once per each 500 bases. Each of the sequences described herein can, to some degree, be used as a standard against which DNA from an individual can be compared for identification puφoses. Because greater numbers of polymoφhisms occur in the non-coding regions, fewer sequences are necessary to differentiate individuals. The non-coding sequences of SEQ JD NO:3 can comfortably provide positive individual identification with a panel of perhaps 10 to 1,000 primers which each yield a non-coding amplified sequence of 100 bases. J predicted coding sequences present in SEQ JD NO:3 are used, a more appropriate number of primers for positive individual identification would be 500-2,000.

If a panel of reagents from LIG46 sequences described herein is used to generate a unique identification database for an individual, those same reagents can later be used to identify tissue from that individual. Using the unique identification database, positive identification of the individual, living or dead, can be made from extremely small tissue samples.

3. Use of Partial LIG46 Sequences in Forensic Biology

DNA-based identification techniques can also be used in forensic biology. Forensic biology is a scientific field employing genetic typing of biological evidence found at a crime scene as a means for positively identifying, for example, a peφetrator of a crime. To make such an identification, PCR technology can be used to amplify DNA sequences taken from very small biological samples such as tissues, e.g., hair or skin, or body fluids, e.g., blood, saliva, or semen found at a crime scene. The amplified sequence can then be compared to a standard, thereby allowing identification of the origin of the biological sample.

The sequences of the present invention can be used to provide polynucleotide reagents, e.g., PCR primers, targeted to specific loci in the human genome, which can enhance the reliability of DNA-based forensic identifications by, for example, providing another "identification marker" (i.e. another DNA sequence that is unique to a particular individual). As mentioned above, actual base sequence information can be used for identification as an accurate alternative to patterns formed by restriction enzyme generated fragments. Sequences targeted to non-coding regions of SEQ JD NO:3 are particularly appropriate for this use as greater numbers of polymoφhisms occur in the non-coding regions, making it easier to differentiate individuals using this technique. Examples of polynucleotide reagents include the LIG46 sequences or portions thereof, e.g., fragments derived from the non-coding regions of SEQ ID NO:3 having a length of at least 20 or 30 bases.

The LIG46 sequences described herein can further be used to provide polynucleotide reagents, e.g., labeled or labelable probes which can be used in, for example, an in situ hybridization technique, to identify a specific tissue, e.g., brain tissue. This can be very useful in cases where a forensic pathologist is presented with a tissue of unknown origin. Panels of such LIG46 probes can be used to identify tissue by species and/or by organ type.

In a similar fashion, these reagents, e.g., LIG46 primers or probes can be used to screen tissue culture for contamination (i.e., screen for the presence of a mixture of different types of cells in a culture).

This invention is further illustrated by the following examples which should not be construed as limiting. The contents of all references, patents and published patent applications cited throughout this application are hereby incoφorated by reference.

EXAMPLES

Example 1: Identification of Leptin Induced Genes The LIG46 gene was identified by comparing the expression pattern of leptin-treated murine neuronal cells expressing the long form of the leptin receptor with the expression pattern of otherwise identically treated cells not expressing leptin receptor.

Preparation of Ob Receptor Expressing Neuronal Cells An adenovirus vector expressing long form murine OB receptor (ObR-L) (Bauman et al. (1996) Proc. Nat'l. Acad. Sci. USA 93:8374-78) was prepared using standard techniques. A high titer viral stock carrying this vector was prepared and used to infect GT1 -7 murine neuronal cells. The infected cells were incubated in standard growth medium for 48 hours and then tested for ObR-L expression by measuring binding of labelled leptin ((1995) Cell 83:1263 -71). This assay demonstrated that the infected cells express ObR-L.

Preparation of a Subtracted Library

The ObR-L expressing murine neuronal cells described above were starved were four hours by growth in serum-free medium. A sample of the starved cells was stimulated by incubation in the presence of 200 ng/ml murine leptin for three hours. A second sample of starved cells was mock-stimulated. Total RNA was isolated from both cell samples and used to create cDNA using the SMART PCR^® cDNA synthesis kit (Clontech, Inc.; Palo Alto, CA). The two cDNA pools (generated from total RNA harvested from untreated and leptin-treated cells) created as described above were used to create a subtracted library using the Clontech PCR-Select cDNA Subtraction Kit (Clontech, Inc.). Screening of the Subtracted Library and Analysis of Positive Clones

The clones in the subtracted library were cloned into T/A vector plasmid T-Adv (Advantage PCR Cloning Kit; Clontech, Inc.). Plasmid specific flanking primers were used to PCR amplify cDNA inserts from the library. The PCR products were then used to create microarrays on nylon filters. The microarrays were probed with labeled cDNA from the subtracted library. Positive clones identified on the the microarray were sequenced, and differential expression of the positive clones was confirmed by virtual Northern analysis on the original treated and untreated samples (pre-subtracted cDNA generated from from the original cell samples). Additionally, a subset of these clones were analyzed for brain and peripheral tissue distribution by Nothern blotting. Two positive clones which appeared to represent novel genes were used to probe a murine whole brain library in order to identify full-length clones. This resulted in the identification of LIG46 and another novel gene.

Example 2: Characterization of Murine and Human LIG46 cDNA and Protein

The murine LIG46 cDNA isolated as described above (SEQ JD NO:l) has a 1191 nucleotide open reading frame (nucleotides 3-1193 of SEQ ID NO:l; SEQ ID NO:5) which encodes a 397 amino acid protein (SEQ JD NO:2). This protein includes a predicted signal sequence of about 32 amino acids (from amino acid 1 to about amino acid 32 of SEQ JD NO:2) and a predicted mature protein of about 365 amino acids (from about amino acid 33 to amino acid 397 of SEQ JD NO:2). The extracellular domain of LIG46 extends from about amino acid 33 to about amino acid 302. LIG46 protein possesses one predicted transmembrane domain which extends from about amino acid 303 (extracellular end) to about 320 (intracellular end) of SEQ JD NO:2. The cytoplasmic domain of LIG46 extends from about amino acid 321 to about amino acid 397.

LIG46 protein has some sequence similarity to a number of galactosyltransferases. Galactosyltransferases have been implicated in developmental processes. In addition, galactosyltransferases may play a role in cell to cell signaling by modifying the carbohydrate repertoire on cell surface receptors to activate, inhibit or otherwise modify (e.g., by alter receptor affinity for a ligand) receptor activity. Thus, LIG46 may play a role body weight regulation by influencing cell to cell signaling mediated by molecules involved in body weight regulation, e.g., leptin.

The LIG46 polypeptide sequence of SEQ JD NO:2 includes potential N-glycosylation sites at amino acids 30-33, 79-82, 89-92, 127-173, and 219-222; potential protein kinase C phosphorylation sites at amino acids 54-56, 202-204, 221 -223, 323-325, and 377-379; potential casein kinase II phosphorylation sites at amino acids 31-34, 94-97, 185-188, 221- 224, 234-237, and 368-371 ; a potential tyrosine kinase phosphorylation site at amino acids 115-122; and a potential amidation site at amino acids 3-6.

Portions of LIG46 are similar to certain galactosyltransferases. Figures 2A-2C depict a series of alignments of portions of the amino acid sequence of LIG46 with portions of a number of galactosyltransferases, including: Mus musculus UDP-Gal: betaGlcNAc beta 1,3- galactosyltransferase-I (Accession Number AF029790; SEQ JD NO:7); Mus musculus UDP- Gal: betaGlcNAc beta 1,3-galactosyltransferase-iπ (Accession Number AF029792; SEQ JD NO:8); Drosophila melanogaster neurogenic secreted signalling protein (Accession Number U41449; SEQ ID NO:9); and Homo sapiens UDP-galactose: 2-acetamido-2-deoxy-D- glucose3beta-galactosyltransferase (Accession Number Y15014; SEQ JD NO:10). A majority sequence is depicted above the solid line (SEQ ID NO:l 1). Conserved residues are shaded. These residues are more likely conserved in functional variants of LIG46.

Figure 3 is a hydropathy plot of murine LIG46. Relative hydrophobicity is shown above the dotted line, and relative hydrophilicity is shown below the dotted line. Figures 5A-5B depict the cDNA sequence of a full-length human LIG46 clone.

Figure 6 depicts the predicted amino acid sequence of human LIG46. The human LIG46 cDNA depicted in Figures 5A-5B (SEQ JD NO:3) has a 1191 nucleotide open reading frame which encodes a 397 amino acid protein (SEQ JD NO:4). This protein includes a predicted signal sequence of about 32 amino acids (from amino acid 1 to about amino acid 32 of SEQ JD NO:4) and a predicted mature protein of about 365 amino acids (from about amino acid 33 to amino acid 397 of SEQ JD NO:4).

Figures 7A-7B depict an alignment of the cDNA sequences of human LIG46 (upper sequence) and murine LIG46 (lower sequence). Figure 8 depicts an alignment of the predicted amino acid sequences of human LIG46 (upper sequence) and murine LIG46 (lower sequence).

The cDNA sequence of human LIG46 was constructed as follows. Proprietary and public databases were searched with the sequence of the coding region of murine LIG46. All identified overlapping sequences were merged and a composite sequence was designed. This 1191 nucleotide open reading frame is predicted to encode a 397 amino acid protein.

Example 3: Genomic Mapping of LIG46

LIG46 was mapped to human chromosome 2, 17.9 cR₃₀oo telomeric to the Whitehead Institute framework marker D2S290 (LOD score = 15.5) and 23.5 cR₃ooo centromeric of the Whitehead framework marker WI-6130 (LOD score = 13.6). This region corresponds to cytogenic location 2pl2-13, within or just outside the minimal interval for Alstrόm syndrome (Macari et al. (1998) Human Genet. 103:658-61). Alstrόm syndrome is an autosomal recessive disorder characterized by childhood obesity, retinal pigment degeneration, neurogenic deafness, non-insulin dependent diabetes mellitus, chronic nephropathy, and hyperlipidemia. Other symptoms include: cardiomyopathy, acanthosis nigricans, hypothyroidism, growth hormone deficiency, progressive baldness, hyperuricemia, gynecomastia, and reduced fertility (Russell-Eggitt et al. (1998) Oph thalmology 105:1274- 80).

Briefly, the LIG46 gene was mapped using the Genebridge 4 Radiation Hybrid Panel. A pair of primers within the 3' untranslated region of LIG46 (forward- CCATGTTGGGGTCTCACATTAGAG, SEQ JD NO: 12; and reverse- GGTAAGTCAGACCAATATCCTGCC, SEQ JD NO:13) were used to amplify DNA from the Genebridge 4 panel. The PCR products were run on a 2% agarose gel, stained with SYBR Gold and scanned. Linkage analysis was performed using the Map Manager QT623 software package.

LIG46 nucleic acid molecules can be used in the diagnosis of Alstrόm syndrome. Moreover, it is possible that mutations in LIG46 cause Alstrόm syndrome. Jf so, LIG46 polypeptide and nucleic acid molecules as well as antibodies directed against LIG46 and modulators of LIG46 expression or activity can be used to treat Alstrόm syndrome and/or various symptoms of Alstrόm syndrome.

Example 4: Distribution of LIG46 mRNA

The expression of LIG46 in murine tissue was analyzed using Northern blot hybridization. Analysis of total tissue blots revealed that LIG46 is expressed at the highest level in heart and liver followed by lung and kidney, then brain, then spleen testis, and skeletal muscle. Analysis of LIG46 expression in murine brain revealed that LIG46 is expressed at least in the hypothalamus (including: the arcuate nucleus, the ventral/medial hypothalamus, and the superchiasmatic nucleus, the hippocampus, the cortex, and the striatum).

Example 5: Secretion of LIG46 LIG46 protein is homologous to D. melanogaster brainiac (Goode et al., (1996)

Development 122:3863-79), a secreted protein (Figs. 2A-2C). As discussed above, LIG46 has a predicted signal sequence at its amino terminus. Therefore, to determine whether LIG46 protein is secreted, full-length LIG46 (amino acids 1-397) was fused to alkaline phosphatase using methods similar to those previously described (Cheng and Flanagan (1994) Cell 79:157- 168; Tartaglia et al. (1995) Cell 83:1263-71). This construct was transiently transfected into human 293T cells.

At 48 hrs post transfection, the growth media was assayed for alkaline phosphatase activity (White et al., (1997) Proc. Natl. Acad. Sci USA 94:10657-10662) using the Great EscAPe alkaline phosphatase detection kit (Clontech, Inc.). A large increase in alkaline phosphatase activity was observed in the growth medium from transfected cells compared to mock tranfected cells, indicating that LIG46 protein is secreted and that the signal sequence of LIG46 is functional.

Example 6: LIG46 Expression is Induced by Leptin in vivo

C57BL6 oblob mice were injected (via the inteφeritoneum (IP)) with 100 μl of either phosphate buffered saline (PBS) (sham injected) or PBS supplemented with 100 μg leptin

(leptin injected) (R&D Systems Inc., Minneapolis, MN). Following a 1 or 3 hr treatment, the animals were euthanized by CO₂ asphyxiation, the brains were harvested, sliced, and the hypothalamus analyzed by in situ hybridization using a 386 base pair radiolabeled antisense probe to the coding region of LIG46. Comparative analysis of hypothalamic slices from sham injected and leptin-injected animals indicates that LIG46 transcript is induced in the arcuate nucleus and the ventromedial hypothalamus by leptin.

Example 7: The Effect of Antisense LIG46 on Feeding of Obese (ob/ob) Male Mice

For this study, a phosphothioate-protected antisense oligodeoxynucleotide and its respective control sequence (sense) were synthesized. The antisense oligodeoxynucleotide targets the murine LIG46 start codon mRNA at position 39.

Antisense: 5' CTT CGA CGC CCC ACA CTC AT 3' (SEQ ID NO:14) Sense: 5' ATG AGT GTG GGG CGT CGA AG 3' (SEQ ID NO:15) Male obese oblob C57BL/6J (45 g) mice were individually housed in macrolon cages (222 D C; 12:12 h light/dark cycle with lights off at 6 pm). Tap water and mouse chow diet were given ad libitum. Mice were stereotaxically implanted with a chronic guide cannula aimed to the third ventricle (intracerebroventricular) one week prior to this experiment.

The effect of LIG46 antisense treatment on leptin-induced decrease in food intake was studied on day 5. Therefore, mice were treated intracerebroventricularly on days 1 and 3 with 18 μg LIG46 antisense oligodeoxyribonucleotide, 18 μg sense (control) oligodeoxyribonucleotide or 2 μl RNAse-free water. Intracerebroventricular injections were performed at 3 pm. Control and oligodeoxyribonucleotide pre-treatments were followed by an intraperitoneal injection of 1 mg/kg leptin or phosphate-buffered saline (vehicle), performed at 5 pm on day 5 and food intake was measured each four hour after leptin or vehicle application. The results of this study are shown in Figure 4. The leptin-induced decrease in food intake was far greater in the presence of LIG46 antisense oligodeoxynucleotide than LIG46 sense nucleotide or PBS control.

Example 8: The Effect of Antisense LIG46 on Feeding of Lean Male Mice For this study, a phosphothioate-protected antisense oligodeoxynucleotide and its respective control sequence (sense) were synthesized. The antisense oligodeoxynucleotide targets the murine LIG46 start codon mRNA at position 39.

Antisense: 5' CTT CGA CGC CCC ACA CTC AT 3' (SEQ ID NO:l 6) Sense: 5' ATG AGT GTG GGG CGT CGA AG 3' (SEQ ID NO:17) Male lean C57BL/6J (24 g) mice were individually housed in macrolon cages (222 C;

12:12 h light/dark cycle with lights off at 6 pm). Tap water and mouse chow diet were given ad libitum. Mice were stereotaxically implanted with a chronic guide cannula aimed to the third ventricle (intracerebroventricular) one week prior to this experiment.

The effect of LIG46 antisense treatment on leptin-induced decrease in food intake was studied on day 5. Therefore, mice were treated intracerebroventricularly on days 1 and 3 with 18 μg LIG46 antisense oligodeoxyribonucleotide, 18 μg sense (control) oligodeoxyribonucleotide or 2 μl RNAse-free water. Intracerebroventricular injections were performed at 3 pm. Control and oligodeoxyribonucleotide pre-treatments were followed by an intraperitoneal injection of 1 mg/kg leptin or phosphate-buffered saline (vehicle), performed at 5 pm on day 5 and food intake was measured each four hour after leptin or vehicle application. The results of this study are shown in Figure 9. The LIG46 antisense- induced decrease in food intake was far greater in the presence of leptin than PBS control. Thus, food intake can be decreased in lean mice by decreasing LIG46 protein expression. Moreover, this decrease in food intake is increased when leptin is administered, demonstrating that leptin can sensitize lean mice to the effects of a LIG46 antagonist.

Example 9: Enzymatic Activity of LIG46

As discussed above, LIG46 shows significant sequence similarity to a gene family of mammalian galactosyltransferases. Several members of this gene family have been expressed and demonstrated to encode active βl,3-galactosyltransferases that transfer galactose from UDP-Gal to β-N-acetylglucosamine terminating saccharide structures as well as glycolipids and glycoproteins (β3Gal-Tl, β3Gal-T2, β3Gal-T3, β3Gal-T5). One member of this family was shown to transfer galactose to β-N-acetylgalactosamine terminating ganglioside glycolipids (β3Gal-T4). One less closely related member of the gene family encodes a βl,3- N-acetylglucosaminyltransferase that can transfer GlcNAc to Galβl-4Glc(NAc)-terminating saccharides (β3 GnT) (Zhou et al., 1999, Proc. Nat 7. Acad. Sci. USA 96:406-11 ).

LIG46 possesses a number of features that are characteristic of homologous glycosyltransferases, including i) a predicted type JJ transmembrane topology as evidenced by an N-terminal hydrophobic leader sequence/golgi retention signal, ii) conserved sequence motifs spaced throughout the central and C-terminal region including a DxD motif, and iii) conserved spacing of cysteine residues. LIG46 shares these features with all the four β3 Gal- Ts (β3Gal-Tl, β3Gal-T2, β3Gal-T3, and β3Gal-T5). The more distant β3GnT shares only weak sequence similarity with the β3Gal-Ts and LIG46. In particular, β3GnT includes only one of the conserved C-terminal cysteine residues. This analysis suggests that LIG46 is likely a glycosyltransferase that has an enzymatic activity similar to that of the β3Gal-Ts and utilize UDP-Gal and transfer Gal into GlcNAc and/or Gal.

Based on the reasoning described above, a series of studies, described below, was conducted using combinations of the donors UDP-Gal, UDP-GalNAc, UDP-Glc, UDP- GlcNAc, and UDP-Gal with varying concentrations of monosaccharide aglycon derivatives (benzyl, p-nitrophenyl, umbrelliferyl, and O-Me). Somewhat suφrisingly, no activity was found. In a second series of studies, also described below, employing very high concentrations of donors and monosaccharides (0.5-1 M Gal, GalNAc, Glc, GlcNAc, Man, Xyl, Fuc) was conducted. This series of studies revealed low activity (approximately 2-fold over background) for the combination UDP-GlcNAc and Gal. Next, the reactions conditions were optimized and a panel of disaccharide and more complex structures was tested. This revealed higher activity with Galβl-4GlcNAc/Man structures. Further studies of glycolipids and N-linked glycoproteins with terminal Galβl-4GlcNAc/Man sequences, also described below, revealed that glycolipids are relatively poor substrates. These studies also revealed that N-linked glycoproteins, preferably with one Galβl-4GlcNAc lactosamine unit on biantennary or multiantennary structures are very good substrates. Additional studies, described below, revealed that the extracellular domain of the leptin receptor served as an efficient substrate.

Importantly, the enzymatic activity of LIG46 differs significantly from that of the homologous β3GnT (Zhou et al, supra) as well as from the non-homologous iGnT (Sasaki et al, supra). The non-homologous iGnT was cloned by transfection cloning with the identifying characteristic being that the gene directed poly-N-acetyllactosamine synthesis defined by anti-i antibodies and lectins. Recombinant iGnT functions with the extended tetrasaccharide structure neo-lactosyl-tetraose (Galβl-4GlcNAcβl-3Galβl-4Glc, nLc4) representing the simplest form of poly-N-acetyllactosamine. However, in vitro iGnT in vitro did not show activity with the simple Galβl -4GlcNAc disaccharide unit (Sasaki et al. supra). The homologous β3GnT was also suggested to represent a poly-N-acetyllactosamine synthase. For example, β3GnT exhibits slightly higher activity with the tetrasaccharide nLc4 structure compared to the Galβl -4GlcNAc disaccharide unit. In addition, transfection of HeLa cells with the β3GnT gene leads to increased expression of i-structures as evaluated by anti-i and tomato lectin staining (Zhou et al, supra). Extensive in vitro studies of the i- synthase function of iGnT have confirmed that it functions exclusively as an i-extention enzyme.

In striking contrast to β3GnT, LIG46 clearly exhibits highest activity with the single disaccharide Galβl -4GlcNAc unit and with N-linked glycoproteins known to carry a single lactosamine unit on N-glycans. These data clearly indicate that the primary function of LIG46, in contrast to iGnT and β3GnT, is to initiate the initial extension of the first lactosamine unit and not in further poly-N-acetyllactosamine extension. Thus, it appears that multiple β3GlcNAc-transferases function at different steps in poly-N-acetyllactosamine synthesis.

Another highly unusual aspect of LIG46 is its apparent strong preference for N-linked glycoproteins compared to glycolipids. Thus, extension of the first lactosamine unit on these two different types of glycoconjugates must be directed by different b3GlcNAc-transferases, a distinction that has not been previously appreciated.

In sum, the present data confirm that LIG46 has glycosyltransferase activity and appears to function in synthesis of poly-N-acetyllactosamine chains of glycoproteins by performing the first initiation step.

N-acetyllactosamine is the repeated "building block" of oligosaccharide chains on N- linked and mucin-type O-linked glycoproteins as well as on lactoseries glycospingolipids, when these are extended and branched. Linear poly-N-acetyllactosamine structures [(Galβl -

4GlcNAcβl-3)_{n = 1}.₁₀] or branched through GlcNAcβl -3 [GlcNAcβl-6] Galβl -4GlcNAc linkages constitute the backbone of glycans on glycoconjugates to which sialic acids, fucose and other monosaccharides are attached to form biologically important epitopes such as the sialyl-Lex selectin ligands and blood group specificities.

The biosynthesis of poly-N-acetyllactosamine structures has recently been unraveled as being potentially a very complex step with a high degree of regulation through differential usage of multiple isoenzymes. Thus, at least four distinct β4Gal-transferases capable of forming the Galβl -4GlcNAc linkage have been characterized (Almeida et al, supra;

Schwientek et al, 1999, J. Biol. Chem. 274:4504-12). At least two β6GlcNAc-transferases capable of forming the branching linkage have been identified (Fukuda et al, supra;

Schwientek et al, supra). Including LIG46, at least three β3GlcNAc-transferases forming the linear extension GlcNAcβl -3Galβl -4GlcNAc required for poly-N-acetyllactosamine synthesis have been identified (Fukuda et al, supra; Hennet et al, 1999, Proc. Nat 'I. Acad.

Sci. USA 406-411). The formation of poly-N-acetyllactosamine structures on N-linked and branched O-linked glycans has been studied in great detail, and it has been shown that distinct isoforms of β4Gal-transferases have superior functions in vitro with different types of glycans (Ujita et al, 1999, J. Biol. Chem. 274:9296-9304). The first cloned β3GlcNAc-transferase was identified by its in vivo ability to produce poly-N-acetyllactosamine structures and termed iGnT (Fukuda et al. supra), and this enzyme has been extensively used in in vitro assays as well as in studies determining the functions of different β4galatosyltransferases (Ujita et al, supra) enzyme. In contrast to iGnT, which does not transfer to a single N-acetyllactosamine unit and therefore appears to represent a true poly-N-acetyllactosamine polymerization enzyme, the β3GnT (Hennet et al, supra) and LIG46 both accept a single N-acetyllactosamine or lactose unit. However, in contrast to β3GnT (Zhou et al, supra), LIG46 shows significantly higher activity with N- acetyllactosamine compared to neolactotetrasaccharide. Although no direct comparisons have been made and neither the β3GnT or iGnT enzymes have been tested on glycoconjugates, the available data suggests that LIG46 in contrast to iGnt and β3GnT functions in the initial phase of poly-N-acetyllactosamine formation by making the first GlcNAcβl -3 Galβl -4Glc(NAc) linkage, which after galactosylation will serve as substrate for other β3GlcNAc-transferases. The homologous Drosophilia melanogaster genes, fringe and brainiac, were initially considered secreted signaling molecules (Yuan et al, 1997, Cell 88:9-11), but recently it was shown that a Golgi-tethered form of fringe was fully capable of exerting its receptor modulating activity on Notch (Bruckner et al, 2000, Nature 406:411 -5). Thus, it was concluded that fringe functions by directing a unique glycosylation pathway on O-glycans found in Notch EGF repeats. However, another study demonstrated that fringe in fact interacts with and can be co-immunoprecipitated with Notch (Ju et al, 2000, Nature 405:191- 5). These seemingly different activities of fringe could be reconciled in a model in which the catalytic domain also has a lectin-like binding activity for either the acceptor sugar (fucose) or the immediate product formed by the catalytic action (GlcNAcβl -3Fuc). Ju et al. (2000) did not investigate the nature of the interaction identified between fringe and Notch, e.g. by inhibition studies with sugars, but found in agreement with Bruckner et al. (2000) that fringe only functions if co-expressed in the same cell with Notch. Lectin-like binding activities of glycosyltransferases have been postulated for other glycosyltransferases (β4Gal-Tl), but no conclusive in vivo data to this effect have been reported. LIG46 is secreted at least in some cell types, and may form a complex with cell surface receptors similarly to that claimed for fringe. Expression of LIG46

Human LIG46 cDNAs encoding either full length (amino acids 1-397) or a truncated form of LIG46 (amino acids 33-397) lacking the amino terminal signal sequence were cloned into pyl 1392 or pAcGP67, (BD PharMingen; San Diego, CA) for expression in insect cells. Briefly, plasmids encoding full-length or truncated LIG46 and Baculo-Gold DNA (BD PharMingen) were co-transfected into Sf9 insect cells, and recombinant Baculo virus was generated by two successive amplifications in Sf9 cells grown in serum-containing medium essentially as previously described (Amado et al, 1998, J. Biol. Chem. 273:12770-8).

Glycosyltransferase Assay

Human LIG46 enzyme was purified using sequential ion-exchange chromatography using techniques as described in Wandall et al, 1997, J. Biol. Chem. 272:23503-14. Standard LIG46 glycosyltransferase assays are performed in a reaction volume of 50-100μl containing 1-5 μl of purified human LIG46 enzyme (soluble secreted fraction), 25 mM cacodylate (pH

7.4), 10 mM MnCl², 0.25% Triton X-100, and ether 100 μM UDP-[14C]-GlcNAc or 7.79 μM UDP-GlcNAc-³H and various non-labeled acceptor concentrations. The reaction is incubated at 37°C for 30-60 minutes. Reactions were terminated by the addition of 1 ml of ice-cold 10 mM EDTA and the mixture is placed on ice for 10 minutes. The reaction mix is then added to a freshly prepared Dowex 1 x 4 resin column which is then washed with 500 μl of 10 mM EDTA. All flow-through (containing the reaction product) is collected and counted for radiolabel using a standard scintillation counter.

Assays using Glycolipids Assays to detect activity on glycolipids were performed using purified enzyme according to methods described in Amado et al. (1998, supra).

Assays using Glycoproteins

Assays to detect activity on glycoproteins were performed using standard reaction mixtures modified to contain excess of UDP-[¹⁴C]-GlcNAc (600-3500 cpm/nmol) and 50 μg (unless indicated otherwise) of various acceptor proteins. Identification of Catalytic Activity and Donor/Acceptor Sugar Substrates Initial studies were performed using the secreted form of LIG46 expressed in insect cells with a large panel of monosaccharide aglycon (benzyl, umb, O-methyl, and nitrophenyl) derivatives combined with different UDP donor sugar-nucleotides (UDP-Gal, UDP-GalNAc, UDP-Glc, UDP-GlcNAc, UDP-Xyl). This analysis did not reveal significant catalytic activity.

A screen using 0.5 M free sugars (Glc, GlcNAc, Gal, GalNAc, Man, Xyl, and Fuc) revealed significant activity above background only with the combination Gal and UDP- GlacNAc. Further studies with dissacharides and dissacharide aglycon derivatives revealed activity with several Gal terminated structures including lactose, benzyl-lactose, N- acetyllactosamine, and Galβl -4Man-benzoyl, but Galβl -3 GlcNAc was not a substrate (Table I). Interestingly, neo-lactotetraose was a poorer substrate than N-acetyllactosamine.

The kinetic properties of LIG46 are similar to many glycoslytransferase with an apparent Km for UDP-GlcNAc using N-acetyllactosamine as acceptor substrate of 24 μM. The apparent Km for N-acetyllactosamine is 6.2 mM, and the apparent Km for lactose is 9.8 mM.

Interestingly, LIG46 exhibits striking inhibition by excess disaccharide acceptor substrates with no detectable activity at 50 mM of lactose and N-acetyllactosamine, which initially lead to failure of recognizing the activity at high concentrations of these substrates.

Table I: Substrate specificity of LIG46a with saccharide acceptors

Substrate concentration Substrate structure 1 mM 5 mM nmol/min/ml nmol/min/ml

D-Gal 10.45

(0.5M free sugar)

β-D-Gal-(l-3)-D-GalNAc 0 β-D-Gal-(l -3)-α-D-GalNAc-Bzl 0 0 β-D-Gal-(l -3)-D-GlcNAc 0 0.55 β-D-Gal-(l -4)-β-D-Glc-Bzl 16.1 61.1 β-D-Gal-(l -4)-β-D-Glc-l -OMe 15.9 23.1 β-D-Gal-(l -4)-β-D-Glc-l -OPr 14.9 30.0 β-D-Gal-(l-4)-D-GlcNAc 21.0 71.0

Lacto-N-neo-tetraose 18.6 49.2 β-D-Gal-(l -4)-β-D-Gal-(l -4)-D-Glc 0 β-D-Gal-(l-4)-D-Man 16.0 46.0 β-D-Gal-(l-6)-D-Gal 0 1.8 β-D-Gal-(l -6)-D-GlcNAc 0 0.2 α-D-Man-(l -4)-α-D-Man-l -OMe 0 0.9 α-L-Fuc-(l-2)-β-D-Gal-(l-4)-D-Glc 0 α-L-Fuc-(l -3)-β-D-Gal-(l -4)-D-Glc 0 β-D-Gal-(l-4)- D-Glc 9.65 32.0

^*Lacto-N-neo-tetraose = β-D-Gal-(l-4)-β-D-GlcNAc-(l-3)-β-D-Gal-(l-4)-β-D-Glc

Characterization of Glycolipid Specificity

LIG46 was expressed in High Five cells and partially purified using sequential ion- exchange chromatographies (Wandall et al, supra). The purified enzyme was used to analyze activity with glycolipid acceptors as previously described (Amado et al, supra ). Although both CDH and nLc4-Ceramide could act as substrates, only partial conversions could be obtained. Approximately 30% conversion was achieved with CDH, and analysis of the mixture of product and unused substrate by lH-NMR clearly revealed that Lc3Cer was formed. This suggests that the linkage produced by LIG46 is GlcNAcβl -3 Gal. The activity of LIG46 with glycolipids was relatively poor compared to other homologous glycosyltransferases including β3Gal-Tl and β3Gal-T2.

Characterization of Glycoprotein Specificity As shown in Table JI, below, relatively high activity was found with glycoproteins. Asialo-fetuin and asialo-transferrin were efficient substrates, indicating that N-glycans with terminal Galbl-4GlcNAc residues are acceptors.

In the studies reported in Table JJ, the assays were performed in 50-100 μl of total reaction mixture containing 25 mM cacodylate (pH 7.4), 10 mM MnCl₂, 0.20% Triton X-l 00 reduced, 50 μg acceptor protein (except with GP130, where 10 μg was used) and excess UDP- [¹⁴C]-GlcNAc (600-3500 cpm nmol) as donor substrate. The acceptor protein concentration was determined using bradford protein assay. For asialo-transferrin, asialofetuin, and asialo mOBR-FC by concentration was confirmed by OD₂₈o on FPLC S-12 gel filtration. The molecular weight of transferrin, mObR-FC and GP130 are known. The molecular weight of fetuin, ovalbumin, acid glycoprotein and glycophorin A was calculated from the amino acid sequence and the known carbohydrate content. This calculation was verified by SDS-PAGE molecular weight determination.

Table II : Substrate specificities with different protein acceptors

Substrate nmol of incorporated GlcNAc

N-glycan Type of N-glycan O-glycan GlcNAc * /acceptor substrate

Transferrin complex - biantennarj

AsialoTransferrin 2

2.45 3.9

Fetuin complex - 1/3 0.00 0.00

3 biantennary and 2/3

Asialofetuin triantennary 4.8 3.7

Ovalbumin 0.23 0.2

Asialo Ovalbumin hybrid/high-mannose

1 0.36 0.3

Acidic glycoprotein

0.18 0.2

Asialo Acidic complex - bi/tri/tetra/

Glycoprotein antennary 5.99 6.8

5

Asialo Glycophorin

A 1 n.i. 15 3.67 1.5

Asialo mObR-FC

4.82¹ 12.7 '

Asialo GP130 n.i. n.i. 1.30² 8.55²

* in 40-50 ug of acceptor protein with 12 hrs of incubation 1. results obtained with 28 ug of acceptor substrate.

2. results obtained with 6 ug of acceptor substrate n.i. = no information in literature

Example 10: Asialo-Leptin Receptor as a LIG46 Substrate

Leptin receptor is a highly N-glycosylated glycoprotein. A recombinant fusion protein containing the extracellular domain of murine leptin receptor and an immunoglobulin constant region (mObR-FC) was an efficient substrate for LIG46 only after removal of sialic acid with neuraminidase pretreatment. As shown in Table II, preparative glycosylation reactions allowed incoφoration of nearly 18 GlcNAc residues mole/mole in asialo-mObR-FC, while other N-linked glycoproteins, asialo-transferrin and asialo-fetuin, incoφorated nearly 4 residues mole/mole. The latter is close to the predicted maximum value of 4. The GlcNAc residues were incoporated into the intact glycoproteins as radiolabel (¹⁴C-GlcNAc) was tightly associated with the glycoproteins both in gel permeation (S12) and SDS-PAGE. This is consistent with the fact that the products formed served de novo as substrates for a b4galactosltransferase, b4Gal-T2, having acceptor substrate specificity for GlcNAcβl -R including asialo-agalacto-transferrin (Almeida et al, supra; Schwientek et al, supra).

The structures of N-glycans found on leptin receptor are not known. The relative high ratio (GlcNAc/N-glycans mole/mole) of incoφoration into only asialo-leptin receptor suggests that the receptor carries N-glycans fully sialylated. It is likely that there is high degree of heterogeneity in branching status of these N-glycans. Incompletely processed glycans of hybrid and/or high mannose type would reduce the actual number of N- acetyllactosamine termini that could serve as acceptors. This may at least partially explain why the GlcNAc/N-glycans mole/mole incorporation ratio is lower than 2:1. It is also possible that some termini carry poly-N-acetyllactosamine repeating structures, and LIG46 has preference for a single N-acetyllactosamine unit. In this respect LIG46 differs from the non-homologous iGnT enzyme (Sasaki et al, supra), which only functions in vitro with Galbl-4GlcNAcbl-3Galbl-4Glc or longer poly-N-acetyllactosamine structures. Thus, iGnT carries out poly-N-acetyllactosamine extensions, while LIG46 may function in the initial priming of Galbl -4GlcNAcbl residues to form the first di-N-acetyllactosamine extension.

Example 11 : LIG46 Activity Assays A LIG 46 activity assay can be used to identify both inhibitors and activators of LIG 46 activity. A LIG 46 activity assay can be based on the transfer of GlcNAc from UDP- GlcNAc (uridine 5'-diphosphate-N-acetylglucosamine) to LacNac (2-acetamide-2-deoxy-4- O-beta-D-glactopyranosyl-D-glucopyranose. The assay can be formatted in any suitable manner. For example, the UDP-GlcNAc may be radioactively labeled (e.g., by ³H or ¹⁴C labeling GlcNAc) and the transfer of the label to LacNac can be assayed. The reaction product can be separated from UDP-GlcNAc by column chromatography, thin layer chromatography or any other suitable means. The LacNac can be modified so that the reaction production can be readily partially or completely purified. Thus, LacNAc can be linked to biotin via a spacer. The reaction product can then be separated from other material using strepavidin.

A LIG46 assay can be conducted as follows. An aliquot of LIG46 (1-5 μl) and a sample of a test compound are combined with 10 μl of 25 mM LacNAc, 10 μl of 5X reaction mix (125 mM cacodylate pH 7.4) 50 M MnCl₂, 1.25% Triton X-100) and 3 μl of UDP- GlcNAc-³H (7.7 μM/50μl reaction). The total reaction volume is 50 μl. The reaction is incubated at 37°C for 30-60 min. To stop the reaction, 1 ml of ice-cold 10 mMEDTA is added and the reaction is place on ice for 10 min. The reaction mix is added to a freshly- prepared Dowex 1x4 resin column which is then washed with 500 μl of 10 mM EDTA. All of the flow-through is collected and counted for ³H activity. Alternatively, the LIG46 activity assay can also be performed in a non-radioactive format by exchanging the radiolabeled substrate (UDP-[¹⁴C]-GlcNAc or UDP-GlcNAc-³H) for a non-radiolabeled version (UDP-GlcNAc). Total enzymatic activity can be calculated by measuring the amount of post reaction UDP (uridine diphosphate) that is generated. This can be determined by treating the reaction product with calf intestinal phophatase and subsequently detecting the liberated free phosphate using a malachite green reagent and absorbance measurements of the product at 650nm. This assay is amenable to automation using robotics and can accommodate the high throughput analysis of a large compound library in the screen for potential LIG46 inhibitors.

Equivalents Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.

What is claimed is:

Claims

1. A method for determining whether a compound is a candidate compound for use in modulating body weight, comprising: a) measuring the expression level of LIG46 in a cell sample in the presence and absence of the compound; and b) identifying the compound as a candidate compound for use in modulating body weight when the expression level of LIG in the presence of the compound differs from the expression level of LIG46 in the absence of the compound.

2. The method of claim 1 wherein the cells in the cell sample are neuronal cells.

3. The method of claim 1 wherein the cells express Ob receptor.

4. The method of claim 3 wherein expression is measured in the presence of leptin.

5. A method for determining whether a compound is a candidate compound for use in modulating body weight, comprising: a) measuring activity of LIG46 in a sample in the presence and absence of the compound; and b) identifying the compound as a candidate compound for use in modulating body weight when the activity of LIG46 in the presence of the compound differs from the activity of LIG46 in the absence of the compound.

6. The method of claim 5 wherein the sample comprises cells.

7. The method of claim 6 wherein the cells express Ob receptor.

8. The method of claim 7 wherein activity is measured in the presence of leptin.

9. A method for determining whether a compound is a candidate compound for use in modulating body weight, comprising: a) measuring expression level of LIG46 in sample of cells isolated from a mammal treated with the compound and in a sample of cells isolated from an untreated mammal; and b) identifying the compound as a candidate compound for use in modulating body weight when the expression level of LIG46 in the sample of cells isolated from the treated mammal differs from the expression of LIG46 in the sample of cells isolated from the untreated mammal.

10. The method of claim 9 wherein the cells in the sample are neuronal cells.

11. The method of claim 9 wherein the mammal is a mouse.

12. A method for determining whether a compound is a candidate compound for use in modulating body weight, comprising: a) measuring activity level of LIG46 in sample of cells isolated from a mammal treated with the compound and in a sample of cells isolated from an untreated mammal; and b) identifying the compound as a candidate compound for use in modulating body weight when the activity level of in the sample of cells isolated from the treated mammal differs from the activity level of LIG46 in the sample of cells isolated from the untreated mammal.

13. The method of claim 12 wherein the cells in the sample are neuronal cells.

14. The method of claim 12 wherein said mammal is a mouse.

15. An isolated nucleic acid molecule selected from the group consisting of: a) a nucleic acid molecule comprising a nucleotide sequence which is at least 75% identical to the nucleotide sequence of SEQ ID NO:l, SEQ JD NO:3, SEQ JD NO:5, or SEQ JD NO:6, or a complement thereof; b) a nucleic acid molecule comprising a fragment of at least 300 nucleotides of the nucleotide sequence of SEQ JD NO:l, SEQ ID NO:3, SEQ JD NO:5, or SEQ ID NO:6, or a complement thereof; c) nucleic acid molecule which encodes a polypeptide comprising the amino acid sequence of SEQ JD NO:2 or SEQ ID NO:4; d) a nucleic acid molecule which encodes a fragment of a polypeptide comprising the amino acid sequence of SEQ JD NO:2 or SEQ JD NO:4, wherein the fragment comprises at least 15 contiguous amino acids of SEQ JD NO:2 or SEQ JD NO:4; and e) a nucleic acid molecule which encodes a naturally occurring allelic variant of a polypeptide comprising the amino acid sequence of SEQ ID NO:2 or SEQ JD NO:4, wherein the nucleic acid molecule hybridizes to a nucleic acid molecule comprising SEQ JD NO:l or SEQ JD NO:3 under stringent conditions.

16. The isolated nucleic acid molecule of claim 15, which is selected from the group consisting of: a) a nucleic acid comprising the nucleotide sequence of SEQ JD NO: 1 , SEQ JD NO:3, SEQ ID NO:5, or SEQ ID NO:6, or a complement thereof; and b) a nucleic acid molecule which encodes a polypeptide comprising the amino acid sequence of SEQ JD NO :2 or SEQ JD NO :4.

17. The nucleic acid molecule of claim 15 further comprising vector nucleic acid sequences.

18. The nucleic acid molecule of claim 15 further comprising nucleic acid sequences encoding a heterologous polypeptide.

19. A host cell which contains the nucleic acid molecule of claim 15.

20. The host cell of claim 19 which is a mammalian host cell.

21. A non-human mammalian host cell containing the nucleic acid molecule of claim 15.

22. An isolated polypeptide selected from the group consisting of: a) a fragment of a polypeptide comprising the amino acid sequence of SEQ ID NO :2 or SEQ JD NO:4, wherein the fragment comprises at least 15 contiguous amino acids of SEQ JD NO:2 or SEQ JD NO:4 b) a naturally occurring allelic variant of a polypeptide comprising the amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4 wherein the polypeptide is encoded by a nucleic acid molecule which hybridizes to a nucleic acid molecule comprising SEQ JD NO:l , SEQ JD NO:3, SEQ ID NO:5, or SEQ JD NO:6 under stringent conditions; c) a polypeptide which is encoded by a nucleic acid molecule comprising a nucleotide sequence which is at least 75% identical to a nucleic acid consisting of the nucleotide sequence of SEQ ID NO:l or SEQ JD NO:3.

23. The isolated polypeptide of claim 22 comprising the amino acid sequence of SEQ JDNO:2 or SEQ JD NO:4.

24. The polypeptide of claim 22 further comprising heterologous amino acid sequences.

25. An antibody that selectively binds to a polypeptide of claim 22.

26. A method for producing a polypeptide selected from the group consisting of: a) a polypeptide comprising the amino acid sequence of SEQ JD NO:2 or SEQ ID NO:4; b) a fragment of a polypeptide comprising the amino acid sequence of SEQ ID NO:2 or SEQ JD NO:4, wherein the fragment comprises at least 15 contiguous amino acids of SEQ

TD NO:2 or SEQ ID NO:4; and c) a naturally occurring allelic variant of a polypeptide comprising the amino acid sequence of SEQ ID NO:2 or SEQ JD NO:4, wherein the polypeptide is encoded by a nucleic acid molecule which hybridizes to a nucleic acid molecule consisting of SEQ JD NO:l or SEQ JD NO:3 under stringent conditions; comprising culturing a host comprising a DNA molecule encoding the polypeptide under conditions in which the nucleic acid molecule is expressed.

27. The isolated polypeptide of claim 22 comprising the amino acid sequence of SEQ ID NO:2 or SEQ JD NO:4.

28. A method for detecting the presence of a polypeptide of claim 22 in a sample, comprising: a) contacting the sample with a compound which selectively binds to a polypeptide ofclaim 22; and b) determining whether the compound binds to the polypeptide in the sample.

29. The method of claim 28, wherein the compound which binds to the polypeptide is an antibody.

30. A kit comprising a compound which selectively binds to a polypeptide of claim

22 and instructions for use.

31. A method for detecting the presence of a nucleic acid molecule of claim 15 in a sample, comprising the steps of: a) contacting the sample with a nucleic acid probe or primer which selectively hybridizes to the nucleic acid molecule; and b) determining whether the nucleic acid probe or primer binds to a nucleic acid molecule in the sample.

32. The method of claim 31, wherein the sample comprises mRNA molecules and is contacted with a nucleic acid probe.

33. A kit comprising a compound which selectively hybridizes to a nucleic acid molecule of claim 15 and instructions for use.

34. A method for identifying a compound which binds to a polypeptide of claim 22 comprising the steps of: a) contacting a polypeptide, or a cell expressing a polypeptide of claim 22 with a test compound; and b) determining whether the polypeptide binds to the test compound.

35. The method of claim 34, wherein the binding of the test compound to the polypeptide is detected by a method selected from the group consisting of: a) detection of binding by direct detecting of test compound/polypeptide binding; and b) detection of binding using a competition binding assay.

36. A method for modulating the activity of a polypeptide of claim 22 comprising contacting a polypeptide or a cell expressing a polypeptide of claim 22 with a compound which binds to the polypeptide in a sufficient concentration to modulate the activity of the polypeptide.

37. A method for treating a weight disorder comprising administering a molecule which reduces expression of activity of LIG46.

38. The method of claim 37 wherein said molecule is an antisense molecule.

39. The method of claim 37 further comprising administering leptin.