HELICAL PROTEIN ZALPHA51

Abstract: Novel four-helix bundle polypeptides, materials and methods for making them, and method of use are disclosed. The polypeptides comprise at least nine contiguous amino acid residues of SEQ ID NO:2 and SEQ ID NO:5, and may be prepared as polypeptide fusions comprise heterologous sequences, such as affinity tags. The polypeptides and polynucleotides encoding them may be used within a variety of therapeutic, diagnostic, and research applications.

Description: Description HELICAL PROTEIN ZALPH A51 BACKGROUND OF THE INVENTION Cytokines are polypeptide hormones that are produced by a cell and affect cell growth or metabolism in either autocrine, paracrine or endocrine fashion. In multicellular animals, cytokines control cell growth, migration, differentiation, and maturation. Cytokines play a role in both normal development and pathogenesis, including the development of solid tumors. Cytokines are physicochemically diverse, ranging in size from 5 kDa (TGF-α) to 140 kDa (Mullerian-inhibiting substance). Structurally, cytokines include a group distinguished by their four-helix bundle conformation. They include single polypeptide chains, as well as disulfide-linked homodimers and heterodimers. Cytokines influence cellular events by binding to cell-surface receptors. Binding initiates a chain of signalling events within the cell, which ultimately resalts in phenotypic changes such as cell division, protease production, cell migration, expression of cell surface proteins, and production of additional growth factors. Cell differentiation and maturation are also under control of cytokines. For example, the hematopoietic factors erythropoietin, thrombopoietin, and G-CSF stimulate the production of erythrocytes, platelets, and neutrophils, respectively, from precursor cells in the bone marrow. Development of mature cells from pluripotent progenitors may require the presence of a plurality of factors. The role of cytokines in controlling cellular processes makes them likely candidates and targets for therapeutic intervention; indeed, a number of cytokines have been approved for clinical use. Interferon-alpha (IFN-α), for example, is used in the treatment of hairy cell leukemia, chronic myeloid leukemia, Kaposi's sarcoma, condylomata acuminata, chronic hepatitis C, and chronic hepatitis B (Aggarwal and Puri, "Common and Uncommon Features of Cytokines and Cytokine Receptors: An Overview", in Aggarwal and Puri, eds., Human Cytokines: Their Role in Disease and Therapy, Blackwell Science, Cambridge, MA, 1995, 3-24). Platelet-derived growth factor (PDGF) has been approved in the United States and other countries for the treatment of dermal ulcers in diabetic patients. The hematopoietic cytokine erythropoietin has been developed for the treatment of anemias (e.g., EP 613,683). G- CSF, GM-CSF, IFN-α, IFN-γ, and IL-2 have also been approved for use in humans (Aggarwal and Puri, ibid.). Experimental evidence supports additional therapeutic uses of cytokines and their inhibitors. Inhibition of PDGF receptor activity has been shown to reduce intimal ήyperplasia in injured baboon arteries (Giese et al., Restenosis Summit NHL Poster Session #23, 1996; U.S. Patent No. 5,620,687). Vascular endothelial growth factors (VEGFs) have been shown to promote the growth of blood vessels in ischemic limbs (Isner et al., The Lancet 348:370-374, 1996), and have been proposed for use as wound-healing agents, for treatment of periodontal disease, for promoting endothelialization in vascular graft surgery, and for promoting collateral circulation following myocardial infarction (WTPO Publication No. WO 95/24473; U.S. Patent No. 5,219,739). A soluble VEGF receptor (soluble flt-1) has been found to block binding of VEGF to cell-surface receptors and to inhibit the growth of vascular tissue in vitro (Biotechnology News 16(17):5-6, 1996). Experimental evidence suggests that inhibition of angiogenesis may be used to block tumor development (Biotechnology News, Nov. 13, 1997) and that angiogenesis is an early indicator of cervical cancer (Br. J. Cancer 76:1410-1415, 1997). More recently, thrombopoietin has been shown to stimulate the production of platelets in vivo (Kaushansky et al., Nature 369:568-571, 1994) and has been the subject of several clinical trials (reviewed by von dem Borne et al., Bailliere's Clin. Haematol. 11:427-445, 1998). In view of the proven clinical utility of cytokines, there is a need in the art for additional such molecules for use as both therapeutic agents and research tools and reagents. Cytokines are used in the laboratory to study developmental processes, and in laboratory and industry settings as components of cell culture media. BRIEF DESCRIPTION OF THE DRAWINGS The figure is a Hopp/Woods hydrophilicity profile of the amino acid sequence shown in SEQ ID NO:2. The profile is based on a sliding six-residue window. Buried G, S, and T residues and exposed H, Y, and W residues were ignored. These residues are indicated in the figure by lower case letters. DETAILED DESCRIPTION OF THE INVENTION Prior to setting forth the invention in detail, it may be helpful to the understanding thereof to define the following terms: The term "affinity tag" is used herein to denote a polypeptide segment that can be attached to a second polypeptide to provide for purification of the second polypeptide or provide sites for attachment of the second polypeptide to a substrate. In principal, any peptide or protein for which an antibody or other specific binding agent is available can be used as an affinity tag. Affinity tags include a poly-histidine tract, protein A (Nilsson et al., EMBO J. 4:1075, 1985; Nilsson et al., Methods Enzvmol. 198:3, 1991), glutathione S transferase (Smith and Johnson, Gene 67:31, 1988), Glu- Glu affinity tag (Grussenmeyer et al., Proc. Natl. Acad. Sci. USA 82:7952-4, 1985) (SEQ ID NO:5), substance P, Flag™ peptide (Hopp et al., Biotechnology 6:1204-1210, 1988), streptavidin binding peptide, maltose binding protein (Guan et al., Gene 67:21- 30, 1987), cellulose binding protein, thioredoxin, ubiquitin, T7 polymerase, or other antigenic epitope or binding domain. See, in general, Ford et al., Protein Expression and Purification 2: 95-107, 1991. DNAs encoding affinity tags and other reagents are available from commercial suppliers (e.g., Pharmacia Biotech, Piscataway, NJ; New England Biolabs, Beverly, MA; Eastman Kodak, New Haven, CT). The term "allelic variant" is used herein to denote any of two or more alternative forms of a gene occupying the same chromosomal locus. Allelic variation arises naturally through mutation, and may result in phenotypic polymorphism within populations. Gene mutations can be silent (no change in the encoded polypeptide) or may encode polypeptides having altered amino acid sequence. The term allelic variant is also used herein to denote a protein encoded by an allelic variant of a gene. The terms "arnino-terminal Λ and "carboxyl-terminal" are used herein to denote positions within polypeptides. Where the context allows, these terms are used with reference to a particular sequence or portion of a polypeptide to denote proximity or relative position. For example, a certain sequence positioned carboxyl-terminal to a reference sequence within a polypeptide is located proximal to the carboxyl terminus of the reference sequence, but is not necessarily at the carboxyl terminus of the complete polypeptide. A "complement" of a polynucleotide molecule is a polynucleotide molecule having a complementary base sequence and reverse orientation as compared to a reference sequence. For example, the sequence 5' ATGCAC 3' is complementary to 5' GTGCAT 3*. The term "corresponding to", when applied to positions of amino acid residues in sequences, means corresponding positions in a plurality of sequences when the sequences are optimally aligned. The term "degenerate nucleotide sequence" denotes a sequence of nucleotides that includes one or more degenerate codons (as compared to a reference polynucleotide molecule that encodes a polypeptide). Degenerate codons contain different triplets of nucleotides, but encode the same amino acid residue (i.e., GAU and GAC triplets each encode Asp). The term "expression vector" is used to denote a DNA molecule, linear or circular, that comprises a segment encoding a polypeptide of interest operably linked to additional segments that provide for its transcription. Such additional segments include promoter and terminator sequences, and may also include one or more origins of replication, one or more selectable markers, an enhancer, a polyadenylation signal, etc. Expression vectors are generally derived from plasmid or viral DNA, or may contain elements of both. The term "isolated", when applied to a polynucleotide, denotes that the polynucleotide has been removed from its natural genetic milieu and is thus free of other extraneous or unwanted coding sequences, and is in a form suitable for use within genetically engineered protein production systems. Such isolated molecules are those that are separated from their natural environment and include cDNA and genomic clones. Isolated DNA molecules of the present invention are free of other genes with which they are ordinarily associated, but may include naturally occurring 5' and 3' untranslated regions such as promoters and terminators. The identification of associated regions will be evident to one of ordinary skill in the art (see for example, Dynan and Tijan, Nature 316:774-78, 1985) An "isolated" polypeptide or protein is a polypeptide or protein that is found in a condition other than its native environment, such as apart from blood and animal tissue. In a preferred form, the isolated polypeptide or protein is substantially free of other polypeptides or proteins, particularly those of animal origin. It is preferred to provide the polypeptides and proteins in a highly purified form, i.e. greater than 95% pure, more preferably greater than 99% pure. When used in this context, the term "isolated" does not exclude the presence of the same polypeptide or protein in alternative physical forms, such as dimers or alternatively glycosylated or derivatized forms. "Operably linked" means that two or more entities are joined together such that they function in concert for their intended purposes. When referring to DNA segments, the phrase indicates, for example, that coding sequences are joined in the correct reading frame, and transcription initiates in the promoter and proceeds through the coding segment(s) to the terminator. When referring to polypeptides, "operably linked" includes both covalently (e.g., by disulfide bonding) and non-covalently (e.g., by hydrogen bonding, hydrophobic interactions, or salt-bridge interactions) linked sequences, wherein the desired function(s) of the sequences are retained. The term "ortholog" denotes a polypeptide or protein obtained from one species that is the functional counterpart of a polypeptide or protein from a different species. Sequence differences among orthologs are the result of speciation. A "polynucleotide" is a single- or double-stranded polymer of deoxyribonucleotide or ribonucleotide bases read from the 5' to the 3' end. Polynucleotides include RNA and DNA, and may be isolated from natural sources, synthesized in vitro, or prepared from a combination of natural and synthetic molecules. Sizes of polynucleotides are expressed as base pairs (abbreviated "bp"), nucleotides ("nt"), or kilobases ("kb"). Where the context allows, the latter two terms may describe polynucleotides that are single-stranded or double-stranded. When the term is applied to double-stranded molecules it is used to denote overall length and will be understood to be equivalent to the term "base pairs". It will be recognized by those skilled in the art that the two strands of a double-stranded polynucleotide may differ slightly in length and that the ends thereof may be staggered as a result of enzymatic cleavage; thus all nucleotides within a double-stranded polynucleotide molecule may not be paired. Such unpaired ends will in general not exceed 20 nt in length. A "polypeptide" is a polymer of amino acid residues joined by peptide bonds, whether produced naturally or synthetically. Polypeptides of less than about 10 amino acid residues are commonly referred to as "peptides". The term "promoter" is used herein for its art-recognized meaning to denote a portion of a gene containing DNA sequences that provide for the binding of RNA polymerase and initiation of transcription. Promoter sequences are commonly, but not always, found in the 5' non-coding regions of genes. A "protein" is a macromolecule comprising one or more polypeptide chains. A protein may also comprise non-peptidic components, such as carbohydrate groups. Carbohydrates and other non-peptidic substituents may be added to a protein by the cell in which the protein is produced, and will vary with the type of cell. Proteins are defined herein in terms of their amino acid backbone structures; substituents such as carbohydrate groups are generally not specified, but may be present nonetheless, thus, a protein "consisting of, for example, from 15 to 1500 amino acid residues may further contain one or more carbohydrate chains. A "secretory signal sequence" is a DNA sequence that encodes a polypeptide (a "secretory peptide") that, as a component of a larger polypeptide, directs the larger polypeptide through a secretory pathway of a cell in which it is synthesized. The larger polypeptide is commonly cleaved to remove the secretory peptide during transit through the secretory pathway. A "segment" is a portion of a larger molecule (e.g., polynucleotide or polypeptide) having specified attributes. For example, a DNA segment encoding a specified polypeptide is a portion of a longer DNA molecule, such as a plasmid or plasmid fragment, that, when read from the 5' to the 3' direction, encodes the sequence of amino acids of the specified polypeptide. Molecular weights and lengths of polymers determined by imprecise analytical methods (e.g., gel electrophoresis) will be understood to be approximate values. When such a value is expressed as "about" X or "approximately" X, the stated value of X will be understood to be accurate to ±10%. All references cited herein are incorporated by reference in their entirety. The present invention provides novel cytokine polypeptides and proteins. This novel cytokine, termed "zalpha51", was identified by the presence of polypeptide and polynucleotide features characteristic of four-helix bundle cytokines (e.g., erythropoietin, thrombopoietin, G-CSF, IL-2, IL-4, leptin, and growth hormone). Analysis of the amino acid sequence shown in SEQ ID NO:2 indicates the presence of four amphipathic, alpha-helical regions. These regions include at least amino acid residues 43 through 57 (helix A), 98 through 112 (helix B), 126 through 140 (helix C), and 192 through 206 (helix D). Within these helical regions, residues that are expected to lie within the core of the four-helix bundle occur at positions 43, 46, 47, 50, 53, 54, "57, 98, 101, 102, 105, 108, 109, 112, 126, 129, 130, 133, 136, 137, 140, 192, 195, 196, 199, 202, 203, and 206 of SEQ ID NO:2. Residues 44, 45, 49, 51, 52, 55, 56, 99, 100, 103, 104, 106, 107, 110, 111, 127, 128, 131, 134, 135, 138, 139, 193, 194, 197, 198, 200, 201, 204, and 205 of SEQ ID NO: 2 are expected to lie on the exposed surface of the bundle. Inter-helix loops comprise approximately residues 58 through 97 (loop A/B), residues 113 through 125 (loop B/C) and 141 through 191 (loop C D) as shown on SEQ ID NO: 2, with corresponding nucleotide sequence shown in SEQ ID NO: 1. The human zalpha51 cDNA (SEQ ID NO:l) encodes a polypeptide of at least 232 amino acid residues. This sequence is predicted to include a secretory peptide of at least 14 residues. Cleavage after residue 17 will result in a mature polypeptide (residues 18-232 of SEQ J-D NO:2; with corresponding nucleotide sequence shown in SEQ ID NO: 1) having a calculated molecular weight (exclusive of glycosylation) of approximately 26,234 Da. Those skilled in the art will recognize that predicted domain boundaries are somewhat imprecise and may vary by up to ± 5 amino acid residues. Those skilled in the art will recognize, however, that some cytokines (e.g., endothelial cell growth factor, basic FGF, and IL-lα) do not comprise conventional secretory peptides and are secreted by a mechanism that is not understood. Polypeptides of the present invention comprise at least 6, preferably at least 9, more preferably at least 15 contiguous amino acid residues of SEQ ID NO:2 or SEQ ID NO: 5. Within certain embodiments of the invention, the polypeptides comprise 20, 30, 40, 50, 100, or more contiguous residues of SEQ ID NO:2, up to the entire predicted mature polypeptide (residues 18 to 196 of SEQ ID NO:2) or the primary translation product (residues 1 to 198 of SEQ ID NO:2). I-n other embodiments, the primary translation product will include residues 1- 243 as shown in SEQ ID NO: 5. As disclosed in more detail below, these polypeptides can further comprise additional, non-zalpha51, polypeptide sequence(s). I-n a broader sense, the helical regions of the zalpha51 polypeptides must include from 15 to 23 contiguous amino acid residues comprising residues 54 (Ala) to 60 (Glu) as shown in SEQ ID NO: 5 (helix A); from 15 to 26 contiguous amino acid residues comprising residues 109 (He) to 114 (Gin) as shown in SEQ ID NO: 5 (helix B); from 15 to 23 contiguous amino acid residues comprising residues 146 (Asp) to 151 (Leu) as shown in SEQ ID NO: 5 (helix C); and from 15 to 27 contiguous amino acid residues comprising residues 205 (Arg) to 217 (Ala) as shown in SEQ ID NO: 5 (helix D). Therefore, helical regions of zalpha51 can include amino acid residues 38 (Leu) to 60 (Glu) as shown in SEQ ID NO: 5 (helix A); amino acid residues 91 (Ser) to 114 (Gin) as shown in SEQ ID NO: 5 (helix B); amino acid residues 136 (Gin) to 158 (Ala) as shown in SEQ T-D NO: 5 (helix C); and amino acid residues 203 (Thr) to 227 (Ala) as shown in SEQ ID NO: 5 (helix D). As would be recognized by those skilled in the art, the corresponding nucleotides encoding these regions can be found in SEQ ID NOS: 4 and 6. Within the polypeptides of the present invention are polypeptides that comprise an epitope-bearing portion of a protein as shown in SEQ ID NO:2. An "epitope" is a region of a protein to which an antibody can bind. See, for example, Geysen et al., Proc. Natl. Acad. Sci. USA 81:3998-4002, 1984. Epitopes can be linear or conformational, the latter being composed of discontinuous regions of the protein that form an epitope upon folding of the protein. Linear epitopes are generally at least nine amino acid residues in length. Relatively short synthetic peptides that mimic part of a protein sequence are routinely capable of eliciting an antiserum that reacts with the partially mimicked protein. See, Sutcliffe et al., Science 219:660-666, 1983. Antibodies that recognize short, linear epitopes are particularly useful in analytic and diagnostic applications that employ denatured protein, such as Western blotting (Tobin, Proc. Natl. Acad. Sci. USA 76:4350-4356, 1979), or in the analysis of fixed cells or tissue samples. Antibodies to linear epitopes are also useful for detecting fragments of zalpha51, such as might occur in body fluids or cell culture media. Antigenic, epitope-bearing polypeptides of the present invention are useful for raising antibodies, including monoclonal antibodies, that specifically bind to a zalpha51 protein. It is preferred that the amino acid sequence of the epitope-bearing polypeptide is selected to provide substantial solubility in aqueous solvents, that is the sequence includes relatively hydrophilic residues, and hydrophobic residues are substantially avoided, and are described herein. Of interest within the present invention are polypeptides that comprise the entire four-helix bundle of a zalpha51 polypeptide (e.g., residues 43-170 of SEQ ID NO:2) or portions thereof, including amino acid residues 43 through 57 (helix A), 98 through 112 (helix B), 126 through 140 (helix C), and 156 through 170 (helix D). Such polypeptides may further comprise all or part of one or both of the native zalpha51 amino-terminal (residues 18-42 of SEQ ID NO:2); carboxyl-terminal (residues 171-232 of SEQ J-D NO:2) regions, as well as non-zalpha51 amino acid residues or polypeptide sequences as disclosed in more detail below. I-n another embodiment, the present invention are polypeptides that comprise the residues 38-227 of SEQ ID NO:5, or portions thereof, including amino acid residues 38 through 60 (helix A), 91 through 114 (helix B), 136 through 158 (helix C), and 203 through 227 (helix D). Such polypeptides may further comprise all or part of one or both of the native zalpha51 amino-terminal (residues 29-37 of SEQ ID NO: 5); carboxyl-terminal (residues 228-243 of SEQ J-D NO:5) region. Polypeptides of the present invention can be prepared with one or more amino acid substitutions, deletions or additions as compared to SEQ ID NO:2. These changes are preferably of a minor nature, that is conservative amino acid substitutions and other changes that do not significantly affect the folding or activity of the protein or polypeptide, and include amino- or carboxyl-terminal extensions, such as an amino- terminal methionine residue, an amino or carboxyl-terminal cysteine residue to facilitate subsequent linking to maleimide-activated keyhole limpet hemocyanin, a small linker peptide of up to about 20-25 residues, or an extension that facilitates purification (an affinity tag) as disclosed above. Two or more affinity tags may be used in combination. Polypeptides comprising affinity tags can further comprise a polypeptide linker and/or a proteolytic cleavage site between the zalpha51 polypeptide and the affinity tag. Preferred cleavage sites include thrombin cleavage sites and factor Xa cleavage sites. Studies using CNTF and IL-6 demonstrated that a CNTF helix can be exchanged for the equivalent helix in IL-6, conferring CTNF-binding properties to the chimera. Thus, it appears that functional domains of four-helical cytokines are determined on the basis of structural homology, irrespective of sequence identity, and can maintain functional integrity in a chimera (Kallen et al., J. Biol. Chem. 274:11859- 11867, 1999). Therefore, the helical domains of zalpha51 will be useful for preparing chimeric fusion molecules, particularly with other four-helix bundle cytokines to determine and modulate receptor binding specificity. Of particular interest are fusion proteins engineered with helix A and/or helix D, and fusion proteins that combine helical and loop domains from other four-helix bundle cytokines such as JJL-2, erythropoietin, and G-CSF. When preparing variants that are a composite of helical domains from zalpha51 and/or other four-helix bundle cytokines, maintaining structural geometry require loop domains that are taken from zalpha51 or another four-helix bundle cytokine. For example, loops can comprise approximately residues 58 through 97 (loop A/B), residues 113 through 125 (loop B/C), and 141 through 191 (loop C/D) from SEQ ID. NO: 2. In another embodiment, variants will require loop domains comprising residues 61-90 (loop A/B), residues 115-135 (loop B/C), and residues 159- 202 (loop C/D), all shown in SEQ ID NO: 5. The present invention further provides a variety of other polypeptide fusions. For example, a zalpha51 polypeptide can be prepared as a fusion to a dimerizing protein as disclosed in U.S. Patents Nos. 5,155,027 and 5,567,584. Preferred dimerizing proteins in this regard include immunoglobulin constant region domains. Immunoglobulin-zalpha51 polypeptide fusions can be expressed in genetically engineered cells to produce a variety of multimeric zalpha51 analogs. In addition, a zalpha51 polypeptide can be joined to another bioactive molecule, such as a cytokine, to provide a multi-functional molecule. One or more helices of a zalpha51 polypeptide can be joined to another cytokine to enhance or otherwise modify its biological properties. Auxiliary domains can be fused to zalpha51 polypeptides to target them to specific cells, tissues, or macromolecules (e.g., collagen). For example, a zalpha51 polypeptide or protein can be targeted to a predetermined cell type by fusing a zalpha51 polypeptide to a ligand that specifically binds to a receptor on the surface of the target cell. In this way, polypeptides and proteins can be targeted for therapeutic or diagnostic purposes. A zalpha51 polypeptide can be fused to two or more moieties, such as an affinity tag for purification and a targeting domain. Polypeptide fusions can also comprise one or more cleavage sites, particularly between domains. See, Tuan et al.. Connective Tissue Research 34:1-9, 1996. Polypeptide fusions of the present invention will generally contain not more than about 1,500 amino acid residues, preferably not more than about 1,200 residues, more preferably not more than about 1,000 residues, and will in many cases be considerably smaller. For example, a zalpha51 polypeptide of 215 residues (residues 18-232 of SEQ JO NO:2) can be fused to E. coli -galactosidase (1,021 residues; see Casadaban et al, J. Bacteriol. 143:971-980, 1980), a 10-residue spacer, and a 4-residue factor Xa cleavage site. In a second example, residues 18-232 of SEQ ID NO:2 can be fused to maltose binding protein (approximately 370 residues), a 4-residue cleavage site, and a 6-residue polyhistidine tag. As disclosed above, the polypeptides of the present invention comprise at least nine contiguous residues of SEQ ID NO:2. These polypeptides may further comprise additional residues as shown in SEQ J-D NO:2, a variant of SEQ J-D NO:2, or another protein as disclosed herein. When variants of SEQ ID NO:2 are employed, the resulting polypeptide certain embodiments will be at least 90%, other embodiments will be at least 95%, 96%, 97%, 98%, or 99% identical to the corresponding region of SEQ ID NO: 2. Percent sequence identity is determined by conventional methods. See, for example, Altschul et al., Bull. Math. Bio. 48:603-616, 1986, and Henikoff and Henikoff, Proc. Natl. Acad. Sci. USA 89:10915-10919. 1992. Briefly, two amino acid sequences are aligned to optimize the alignment scores using a gap opening penalty of 10, a gap extension penalty of 1, and the "BLOSUM62" scoring matrix of Henikoff and Henikoff (ibid.) as shown in Table 1 (amino acids are indicated by the standard one- letter codes). The percent identity is then calculated as: Total number of identical matches x lOO [length of the longer sequence plus the number of gaps introduced into the longer sequence in order to align the two sequences] <! K. si 1-3 ω TJ → -ϋ S « tr 1 H JU Ω M O D 3 ftf 1 1 1 1 1 1 1 1 I 1 1 1 o M oo o H 1 H to H H H t o H H o t to Φ If 1 1 1 I 1 1 1 I 1 1 00 -o oo H H 1 to OJ H t to 00 o to O h- 1 00 to o σi f 1 1 1 1 I ω -o O H 1 to OJ to o J OJ H o o O 00 H σ\ 3 1 1 1 1 1 1 1 1 I 00 ω H O H OJ 00 H Φ 0J H H to o oo Ch σ 1 1 1 I 1 1 1 1 1 1 1 1 to t H to H J H H 00 00 oo U3 o 1 1 1 1 1 1 1 1 to H t H O H OJ o H to 0J o to CO σi iO 1 1 1 1 1 1 I 1 t to oo H O H OJ t H oo oo o t on M 1 1 1 1 1 I 1 1 (- oo to DO O to OJ 00 to t σ\ Q 1 1 I 1 1 I 1 to to oo H o H OJ H on K 1 1 1 1 1 l-> H H H to σ Ul s 1 1 1 1 H oo H> t to en > χ | 1 1 1 1 t 00 . ■ H H 1 -J TJ 1 1 to to OJ H Φ ω I 1 o to to Ul H 1 H oo to SI - ττ C6t80/lOSfl/I3«-[ 9860 ./Ϊ0 OΛV The level of identity between amino acid sequences can be determined using the "FASTA" similarity search algorithm disclosed by Pearson and Lipman (Proc. Natl. Acad. Sci. USA 85:2444, 1988) and by Pearson (Meth. Enzymol. 183:63. 1990). Briefly, FASTA first characterizes sequence similarity by identifying regions shared by the query sequence (e.g., SEQ ID NO:2) and a test sequence that have either the highest density of identities (if the ktup variable is 1) or pairs of identities (if ktup=2), without considering conservative amino acid substitutions, insertions, or deletions. The ten regions with the highest density of identities are then rescored by comparing the similarity of all paired amino acids using an amino acid substitution matrix, and the ends of the regions are "trimmed" to include only those residues that contribute to the highest score. If there are several regions with scores greater than the "cutoff value (calculated by a predetermined formula based upon the length of the sequence and the ktup value), then the trimmed initial regions are examined to determine whether the regions can be joined to form an approximate alignment with gaps. Finally, the highest scoring regions of the two amino acid sequences are aligned using a modification of the Needleman-Wunsch-Sellers algorithm (Needleman and Wunsch, J. Mol. Biol. 48:444, 1970; Sellers, SIAM J. Appl. Math. 26:787, 1974), which allows for amino acid insertions and deletions. Preferred parameters for FASTA analysis are: ktup=l, gap opening penalty=10, gap extension penalty=l, and substitution matrix=BLOSUM62. These parameters can be introduced into a FASTA program by modifying the scoring matrix file ("SMATRLX"), as explained in Appendix 2 of Pearson, 1990 (ibid.). FASTA can also be used to determine the sequence identity of nucleic acid molecules using a ratio as disclosed above. For nucleotide sequence comparisons, the ktup value can range between one to six, preferably from three to six, most preferably three, with other parameters set as default. The present invention includes polypeptides having one or more conservative amino acid changes as compared with the amino acid sequence of SEQ ID NO:2. The BLOSUM62 matrix (Table 1) is an amino acid substitution matrix derived from about 2,000 local multiple alignments of protein sequence segments, representing highly conserved regions of more than 500 groups of related proteins (Henikoff and Henikoff, ibid.). Thus, the BLOSUM62 substitution frequencies can be used to define conservative amino acid substitutions that may be introduced into the amino acid sequences of the present invention. As used herein, the term "conservative amino acid substitution" refers to a substitution represented by a BLOSUM62 value of greater than -1. For example, an amino acid substitution is conservative if the substitution is characterized by a BLOSUM62 value of 0, 1, 2, or 3. Preferred conservative amino acid substitutions are characterized by a BLOSUM62 value of at least one 1 (e.g., 1, 2 or 3), while more preferred conservative amino acid substitutions are characterized by a BLOSUM62 value of at least 2 (e.g., 2 or 3). The proteins of the present invention can also comprise non-naturally occurring amino acid residues. Non-naturally occurring amino acids include, without limitation, tran^.-3-methylproline, 2,4-methanoproline, -.-4-hydroxyproline, trα/M-4- hydroxyproline, N-methylglycine, /Zo-threonine, methylthreonine, hydroxyethylcysteine, hydroxyethylhomocysteine, nitroglutamine, homoglutamine, pipecolic acid, tert-leucine, norvaline, 2-azaphenylalanine, 3-azaphenylalanine, 4- azaphenylalanine, and 4-fluorophenylalanine. Several methods are known in the art for incorporating non-naturally occuring amino acid residues into proteins. For example, an in vitro system can be employed wherein nonsense mutations are suppressed using chemically aminoacylated suppressor fRΝAs. Methods for synthesizing amino acids and aminoacylating tRΝA are known in the art. Transcription and translation of plasmids containing nonsense mutations is carried out in a cell-free system comprising an E. c li S30 extract and commercially available enzymes and other reagents. Proteins are purified by chromatography. See, for example, Robertson et al., J. Am. Chem. Soc. 113:2722, 1991; Εllman et al., Methods Εnzvmol. 202:301, 1991; Chung et al., Science 259:806-_809, 1993; and Chung et al., Proc. Νatl. Acad. Sci. USA 90:10145-10149- 1993). In a second method, translation is carried out in Xenopus oocytes by microinjection of mutated mRΝA and chemically aminoacylated suppressor tRΝAs (Turcatti et al., J. Biol. Chem. 271:19991-19998, 1996). Within a third method, E. coli cells are cultured in the absence of a natural amino acid that is to be replaced (e.g., phenylalanine) and in the presence of the desired non-naturally occurring amino acid(s) (e.g., 2-azaphenylalanine, 3- azaphenylalanine, 4-azaphenylalanine, or 4-fluorophenylalanine). The non-naturally occurring amino acid is incorporated into the protein in place of its natural counterpart. See, Koide et al., Biochem. 33:7470-7476, 1994. Naturally occurring amino acid residues can be converted to non-naturally occurring species by in vitro chemical modification. Chemical modification can be combined with site-directed mutagenesis to further expand the range of substitutions (Wynn and Richards, Protein Sci. 2:395-403, 1993). Amino acid sequence changes are made in zalpha51 polypeptides so as to minimize disruption of higher order structure essential to biological activity. Amino acid residues that are within regions or domains that are critical to maintaining structural integrity can be determined. Within these regions one can identify specific residues that will be more or less tolerant of change and maintain the overall tertiary structure of the molecule. Methods for analyzing sequence structure include, but are not limited to, alignment of multiple sequences with high amino acid or nucleotide identity, secondary structure propensities, binary patterns, complementary packing, and buried polar interactions (Barton, Current Opin. Struct. Biol. 5:372-376, 1995 and Cordes et al., Current Opin. Struct. Biol. 6:3-10, 1996). In general, determination of structure will be accompanied by evaluation of activity of modified molecules. For example, changes in amino acid residues will be made so as not to disrupt the four- helix bundle structure of the protein family. The effects of amino acid sequence changes can be predicted by, for example, computer modeling using available software (e.g., the Insight JJ® viewer and homology modeling tools; MSI, San Diego, CA) or determined by analysis of crystal structure (see, e.g., Lapthorn et al, Nature 369:455- 461, 1994; Lapthorn et al., Nat. Struct. Biol. 2:266-268, 1995). Protein folding can be measured by circular dichroism (CD). Measuring and comparing the CD spectra generated by a modified molecule and standard molecule are routine in the art (Johnson, Proteins 7:205-214, 1990). Crystallography is another well known and accepted method for analyzing folding and structure. Nuclear magnetic resonance (NMR), digestive peptide mapping and epitope mapping are other known methods for analyzing folding and structural similarities between proteins and polypeptides (Schaanan et al., Science 257:961-964, 1992). Mass spectrometry and chemical modification using reduction and alkylation can be used to identify cysteine residues that are associated with disulfide bonds or are free of such associations (Bean et al., Anal. Biochem. 201:216-226, 1992; Gray, Protein Sci. 2:1732-1748, 1993; and Patterson et al., Anal. Chem. 66:3727-3732, 1994). Alterations in disulfide bonding will be expected to affect protein folding. These techniques can be employed individually or in combination to analyze and compare the structural features that affect folding of a variant protein or polypeptide to a standard molecule to determine whether such modifications would be significant. A hydrophilicity profile of SEQ JJD NO:2 is shown in the attached figure. Those skilled in the art will recognize that this hydrophilicity will be taken into account when designing alterations in the amino acid sequence of a zalpha51 polypeptide, so as not to disrupt the overall profile. Residues within the core of the four-helix bundle can be replaced with a hydrophobic residue selected from the group consisting of Leu, JJe, Val, Met, Phe, Tip, Gly. The residues predicted to be on the exposed surface of the four-helix bundle will be relatively intolerant of substitution. The length and amino acid composition of the interdomain loops are also expected to be important for receptor binding (and therefore biological activity); conservative substitutions and relatively small insertions and deletions are thus preferred within the loops, and the insertion of bulky amino acid residues (e.g., Phe) will in general be avoided. Essential amino acids in the polypeptides of the present invention can be identified experimentally according to procedures known in the art, such as site- directed mutagenesis or alanine-scan ing mutagenesis (Cunningham and Wells, Science 244, 1081-1085, 1989; Bass et al.. Proc. Natl. Acad. Sci. USA 88:4498-4502, 1991). In the latter technique, single alanine mutations are introduced at every residue in the molecule, and the resultant mutant molecules are tested for biological activity as disclosed below to identify amino acid residues that are critical to the activity of the molecule. Multiple amino acid substitutions can be made and tested using known methods of mutagenesis and screening, such as those disclosed by Reidhaar-Olson and Sauer (Science 241:53-57, 1988) or Bowie and Sauer .Proc. Natl. Acad. Sci. USA 86:2152-2156, 1989). Briefly, these authors disclose o methods for simultaneously randomizing two or more positions in a polypeptide, selecting for functional polypeptide, and then sequencing the mutagenized polypeptides to determine the spectrum of allowable substitutions at each position. Other methods that can be used include phage display (e.g., Lowman et al., Biochem. 30:10832-10837, 1991; Ladner et al., U.S. Patent No. 5,223,409; Huse, WJPO Publication WO 92/06204) and region- directed mutagenesis (Derbyshire et al., Gene 46:145, 1986; Ner et al., DNA 7:127, 1988). Variants of the disclosed zalpha51 DNA and polypeptide sequences can be generated through DNA shuffling as disclosed by Stemmer, Nature 370:389-391, 1994 and Stemmer, Proc. Natl. Acad. Sci. USA 91:10747-10751, 1994. Briefly, variant genes are generated by in vitro homologous recombination by random fragmentation of a parent gene followed by reassembly using PCR, resulting in randomly introduced point mutations. This technique can be modified by using a family of parent genes, such as allelic variants or genes from different species, to introduce additional variability into the process. Selection or screening for the desired activity, followed by additional iterations of mutagenesis and assay provides for rapid "evolution" of sequences by selecting for desirable mutations while simultaneously selecting against detrimental changes. In many cases, the structure of the final polypeptide product will result from processing of the nascent polypeptide chain by the host cell, thus the final sequence of a zalpha51 polypeptide produced by a host cell will not always correspond to the full sequence encoded by the expressed polynucleotide. For example, expressing the complete zalpha51 sequence in a cultured mammalian cell is expected to result in removal of at least the secretory peptide, while the same polypeptide produced in a prokaryotic host would not be expected to be cleaved. Differential processing of individual chains may result in heterogeneity of expressed polypeptides. Mutagenesis methods as disclosed above can be combined with high volume or high-throughput screening methods to detect biological activity of zalpha51 variant polypeptides. Assays that can be scaled up for high throughput include mitogenesis assays, which can be run in a 96-well format. Mutagenized DNA molecules that encode active zalpha51 polypeptides can be recovered from the host cells and rapidly sequenced using modern equipment. These methods allow the rapid determination of the importance of individual amino acid residues in a polypeptide of interest, and can be applied to polypeptides of unknown structure. Using the methods discussed above, one of ordinary skill in the art can prepare a variety of polypeptide fragments or variants of SEQ ID NO:2 that retain the activity of wild-type zalpha51. The present invention also provides polynucleotide molecules, including DNA and RNA molecules, that encode the zalpha51 polypeptides disclosed above. A representative DNA sequence encoding the amino acid sequence of SEQ JJD NO:2 is shown in SEQ ID NO:l. Those skilled in the art will readily recognize that, in view of the degeneracy of the genetic code, considerable sequence variation is possible among these polynucleotide molecules. SEQ ID NO:3 is a degenerate DNA sequence that encompasses all DNAs that encode the zalpha51 polypeptide of SEQ J-D NO: 2. Those skilled in the art will recognize that the degenerate sequence of SEQ J-D NO:3 also provides all RNA sequences encoding SEQ ID NO:2 by substituting U for T. Thus, zalpha51 polypeptide-encoding polynucleotides comprising nucleotides 1 or 52 nucleotides 696 of SEQ ID NO:3, and their RNA equivalents are contemplated by the present invention, as are segments of SEQ ID NO: 3 encoding other zalpha51 polypeptides disclosed herein. Table 2 sets forth the one-letter codes used within SEQ J-D NO:3 to denote degenerate nucleotide positions. "Resolutions" are the nucleotides denoted by a code letter. "Complement" indicates the code for the complementary nucleotide(s). For example, the code Y denotes either C or T, and its complement R denotes A or G, A being complementary to T, and G being complementary to C. TABLE 2 Nucleotide Resolutions Complement Resolutions A A T T C C G G G G C C T T A A R A|G Y C|T Y C|T R A|G M A|C K G|T K G|T M A|C s C|G S C|G w A|T W A|T H A|C|T D A|G|T B C|G|T V A)C[G V A|C|G B C|G|T D A|G|T H A|C|T N A|C|G|T N A|C|G|T The degenerate codons used in SEQ ID NO:3, encompassing all possible codons for a given amino acid, are set forth in Table 3, below. TABLE 3 Amino One-Letter Degenerate Acid Code Codons Codon Cys C TGC TGT TGY Ser s AGC AGT TCA TCC TCG TCT WSN Thr T ACA ACC ACG ACT CAN Pro P CCA CCC CCG CCT CCN Ala A GCA GCC GCG GCT GCN Gly G GGA GGC GGG GGT GGN Asn N AAC AAT AAY Asp D GAC GAT GAY Glu E GAA GAG GAR Gin Q CAA CAG CAR His H CAC CAT CAY Arg R AGA AGG CGA CGC CGG CGT MGN Lys K AAA AAG AAR Met M ATG ATG Ee I ATA ATC ATT ATH Leu L CTA CTC CTG CTT TTA TTG YTN Val V GTA GTC GTG GTT GTN Phe F TTC TTT TTY Tyr Y TAC TAT TAY Tip w TGG TGG Ter . TAA TAG TGA TRR Asn|Asp B RAY Glu|Gln Z SAR Any X NNN Gap One of ordinary skill in the art will appreciate that some ambiguity is introduced in determining a degenerate codon, representative of all possible codons encoding each amino acid. For example, the degenerate codon for serine (WSN) can, in some circumstances, encode arginine (AGR), and the degenerate codon for arginine (MGN) can, in some circumstances, encode serine (AGY). A similar relationship exists between codons encoding phenylalanine and leucine. Thus, some polynucleotides encompassed by the degenerate sequence may encode variant amino acid sequences, but one of ordinary skill in the art can easily identify such variant sequences by reference to the amino acid sequence of SEQ ID NO: 2. Variant sequences can be readily tested for functionality as described herein. One of ordinary skill in the art will also appreciate that different species can exhibit preferential codon usage. See, in general, Grantham et al., Nuc. Acids Res. 8:1893-912, 1980; Haas et al. Curr. Biol. 6:315-24, 1996; Wain-Hobson et al., Gene 13:355-64, 1981; Grosjean and Fiers, Gene 18:199-209, 1982; Holm, Nuc. Acids Res. 14:3075-87, 1986; and H emura, J. Mol. Biol. 158:573-97, 1982. Introduction of preferred codon sequences into recombinant DNA can, for example, enhance production of the protein by making protein translation more efficient within a particular cell type or species. Therefore, the degenerate codon sequence disclosed in SEQ ID NO:3 serves as a template for optimizing expression of polynucleotides in various cell types and species commonly used in the art and disclosed herein. Within preferred embodiments of the invention the isolated polynucleotides will hybridize to similar sized regions of SEQ ID NO:l or a sequence complementary thereto under stringent conditions. In general, stringent conditions are selected to be about 5°C lower than the thermal melting point (T m ) for the specific sequence at a defined ionic strength and pH. The T m is the temperature (under defined ionic strength and pH) at which 50% of the target sequence hybridizes to a perfectly matched probe. Typical stringent conditions are those in which the salt concentration is up to about 0.03 M at pH 7 and the temperature is at least about 60°C. As previously noted, the isolated polynucleotides of the present invention include DNA and RNA. Methods for preparing DNA and RNA are well known in the art. In general, RNA is isolated from a tissue or cell that produces large amounts of zalpha51 RNA. Liver cells are preferred. Fibroblasts are another preferred source. Total RNA can be prepared using guanidine HC1 extraction followed by isolation by centrifugation in a CsCl gradient (Chirgwin et al., Biochemistry 18:52-94, 1979). Poly (A)+ RNA is prepared from total RNA using the method of Aviv and Leder (Proc. Natl. Acad. Sci. USA 69:1408-1412, 1972). Complementary DNA (cDNA) is prepared from poly(A) + RNA using known methods. J-n the alternative, genomic DNA can be isolated. Polynucleotides encoding zalpha51 polypeptides are then identified and isolated by, for example, hybridization or PCR. Full-length clones encoding zalpha51 can be obtained by conventional cloning procedures. Complementary DNA (cDNA) clones are preferred, although for some applications (e.g., expression in transgenic animals) it may be preferable to use a genomic clone, or to modify a cDNA clone to include at least one genomic intron. Methods for preparing cDNA and genomic clones are well known and within the level of ordinary skill in the art, and include the use of the sequence disclosed herein, or parts thereof, for probing or priming a library. Expression libraries can be probed with antibodies to zalpha51, receptor fragments, or other specific binding partners. Zalpha51 polynucleotide sequences disclosed herein can also be used as probes or primers to clone 5' non-coding regions of a zalpha51 gene. Promoter elements from a zalpha51 gene can thus be used to direct the expression of heterologous genes in, for example, transgenic animals or patients treated with gene therapy. Cloning of 5' flanking sequences also facilitates production of zalpha51 proteins by "gene activation" as disclosed in U.S. Patent No. 5,641,670. Briefly, expression of an endogenous zalpha51 gene in a cell is altered by introducing into the zalpha51 locus a DNA construct comprising at least a targeting sequence, a regulatory sequence, an exon, and an unpaired splice donor site. The targeting sequence is a zalpha51 5' non-coding sequence that permits homologous recombination of the construct with the endogenous zalpha51 locus, whereby the sequences within the construct become operably linked with the endogenous zalpha51 coding sequence. In this way, an endogenous zalpha51 promoter can be replaced or supplemented with other regulatory sequences to provide enhanced, tissue-specific, or otherwise regulated expression. Those skilled in the art will recognize that the sequences disclosed in SEQ ID NOS:l and 2 represent a single allele of human zalpha51. Allelic variants of these sequences can be cloned by probing cDNA or genomic libraries from different individuals according to standard procedures. The present invention further provides counterpart polypeptides and polynucleotides from other species ("orthologs"). Of particular interest are zalpha51 polypeptides from other mammalian species, including murine, porcine, ovine, bovine, canine, feline, equine, and other primate polypeptides. Orthologs of human zalpha51 can be cloned using information and compositions provided by the present invention in combination with conventional cloning techniques. For example, a cDNA can be cloned using mRNA obtained from a tissue or cell type that expresses zalpha51 as disclosed above. A library is then prepared from mRNA of a positive tissue or cell line. A zalpha51 -encoding cDNA can then be isolated by a variety of methods, such as by probing with a complete or partial human cDNA or with one or more sets of degenerate probes based on the disclosed sequence. A cDNA can also be cloned using the polymerase chain reaction, or PCR (Mullis, U.S. Patent No. 4,683,202), using primers designed from the representative human zalpha51 sequence disclosed herein. Within an additional method, the cDNA library can be used to transform or transfect host cells, and expression of the cDNA of interest can be detected with an antibody to zalpha51 polypeptide. Similar techniques can also be applied to the isolation of genomic clones. For any zalpha51 polypeptide, including variants and fusion proteins, one of ordinary skill in the art can readily generate a fully degenerate polynucleotide sequence encoding that variant using the information set forth in Tables 3 and 4, above. Moreover, those of skill in the art can use standard software to devise zalpha51 variants based upon the nucleotide and amino acid sequences described herein. The present invention thus provides ^ a computer-readable medium encoded with a data structure that provides at least one of the following sequences: SEQ ID NO:l, SEQ ID NO:2, and portions thereof. Suitable forms of computer-readable media include magnetic media and optically-readable media. Examples of magnetic media include a hard or fixed drive, a random access memory (RAM) chip, a floppy disk, digital linear tape (DLT), a disk cache, and a ZIP™ disk. Optically readable media are exemplified " by compact discs (e.g., CD-read only memory (ROM), CD-rewritable (RW), and CD- recordable), and digital versatile/video discs (DVD) (e.g., DVD-ROM, DVD-RAM, and DVD+RW). The zalpha51 polypeptides of the present invention, including full- length polypeptides, biologically active fragments, and fusion polypeptides can be produced according to conventional techniques using cells into which have been introduced an expression vector encoding the polypeptide. As used herein, "cells into which have been introduced an expression vector" include both cells that have been directly manipulated by the introduction of exogenous DNA molecules and progeny thereof that contain the introduced DNA. Suitable host cells are those cell types that can be transformed or transfected with exogenous DNA and grown in culture, and include bacteria, fungal cells, and cultured higher eukaryotic cells. Techniques for manipulating cloned DNA molecules and introducing exogenous DNA into a variety of host cells are disclosed by Sambrook et al., Molecular Cloning: A Laboratory Manual, 2nd ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1989, and Ausubel et al., eds., Current Protocols in Molecular Biology, John Wiley and Sons, Inc., NY, 1987. In general, a DNA sequence encoding a zalpha51 polypeptide is operably linked to other genetic elements required for its expression, generally including a transcription promoter and terminator, within an expression vector. The vector will also commonly contain one or more selectable markers and one or more origins of replication, although those skilled in the art will recognize that within certain systems selectable markers may be provided on separate vectors, and replication of the exogenous DNA may be provided by integration into the host cell genome. Selection of promoters, terminators, selectable markers, vectors and other elements is a matter of routine design within the level of ordinary skill in the art. Many such elements are described in the literature and are available through commercial suppliers. To direct a zalpha51 polypeptide into the secretory pathway of a host cell, a secretory signal sequence (also known as a leader sequence, prepro sequence or pre sequence) is provided in the expression vector. The secretory signal sequence may be that of zalpha51, or may be derived from another secreted protein (e.g., t-PA; see, U.S. Patent No. 5,641,655) or synthesized de novo. The secretory signal sequence is operably linked to the zalpha51 DNA sequence, i.e., the two sequences are joined in the correct reading frame and positioned to direct the newly synthesized polypeptide into the secretory pathway of the host cell. Secretory signal sequences are commonly positioned 5' to the DNA sequence encoding the polypeptide of interest, although certain signal sequences may be positioned elsewhere in the DNA sequence of interest (see, e.g., Welch et al., U.S. Patent No. 5,037,743; Holland et al., U.S. Patent No. 5,143,830). Cultured mammalian cells can be used as hosts within the present invention. Methods for introducing exogenous DNA into mammalian host cells include calcium phosphate-mediated transfection (Wigler et al., Cell 14:725, 1978; Corsaro and Pearson, Somatic Cell Genetics 7:603, 1981; Graham and Van der Eb, Virology 52:456, 1973), electroporation (Neumann et al., EMBO J. 1:841-845, 1982), DEAE-dextran mediated transfection (Ausubel et al., ibid.), and liposome-mediated transfection (Hawley-Nelson et al., Focus 15:73, 1993; Ciccarone et al., Focus 15:80, 1993). The production of recombinant polypeptides in cultured mammalian cells is disclosed, for example, by Levinson et al., U.S. Patent No. 4,713,339; Hagen et al., U.S. Patent No. 4,784,950; Palmiter et al., U.S. Patent No. 4,579,821; and Ringold, U.S. Patent No. 4,656,134. Suitable cultured mammalian cells include the COS-1 (ATCC No. CRL 1650), COS-7 (ATCC No. CRL 1651), BHK (ATCC No. CRL 1632), BHK 570 (ATCC No. CRL 10314), 293 (ATCC No. CRL 1573; Graham et al., J. Gen. Virol. 36:59-72, 1977) and Chinese hamster ovary (e.g. CHO-K1, ATCC No. CCL 61; or CHO DG44, Chasin et al., Som. Cell. Molec. Genet. 12:555, 1986) cell lines. Additional suitable cell lines are known in the art and available from public depositories such as the American Type Culture Collection, Manassas, VA. J-n general, strong transcription promoters are preferred, such as promoters from SV-40 or cytomegalovirus. See, e.g., U.S. Patent No. 4,956,288. Other suitable promoters include those from metallothionein genes (U.S. Patent Nos. 4,579,821 and 4,601,978) and the adenovirus major late promoter. Expression vectors for use in mammalian cells include pZP-1 and pZP-9, which have been deposited with the American Type Culture Collection, Manassas, VA USA under accession numbers 98669 and 98668, respectively, and derivatives thereof. Drug selection is generally used to select for cultured mammalian cells into which foreign DNA has been inserted. Such cells are commonly referred to as "transfectants". Cells that have been cultured in the presence of the selective agent and are able to pass the gene of interest to their progeny are referred to as "stable transfectants." A preferred selectable marker is a gene encoding resistance to the antibiotic neomycin. Selection is carried out in the presence of a neomycin-type drug, such as G-418 or the like. Selection systems can also be used to increase the expression level of the gene of interest, a process referred to as "amplification." Amplification is carried out by culturing transfectants in the presence of a low level of the selective agent and then increasing the amount of selective agent to select for cells that produce high levels of the products of the introduced genes. A preferred amplifiable selectable marker is dihydrofolate reductase, which confers resistance to methotrexate. Other drug resistance genes (e.g. hygromycin resistance, multi-drug resistance, puromycin acetyltransferase) can also be used. The adenovirus system can also be used for protein production in vitro. By culturing adenovirus-infected non-293 cells under conditions where the cells are not rapidly dividing, the cells can produce proteins for extended periods of time. For instance, BHK cells are grown to confluence in cell factories, then exposed to the adenoviral vector encoding the secreted protein of interest. The cells are then grown under serum-free conditions, which allows infected cells to survive for several weeks without significant cell division. In an alternative method, adenovirus vector-infected 293 cells can be grown as adherent cells or in suspension culture at relatively high cell density to produce significant amounts of protein (See Gamier et al., Cvtotechnol. 15:145-55, 1994). With either protocol, an expressed, secreted heterologous protein can be repeatedly isolated from the cell culture supernatant, lysate, or membrane fractions depending on the disposition of the expressed protein in the cell. Within the infected 293 cell production protocol, non-secreted proteins can also be effectively obtained. Insect cells can be infected with recombinant baculovirus, commonly derived from Autographa californica nuclear polyhedrosis virus (AcNPV) according to methods known in the art. Within a preferred method, recombinant baculovirus is produced through the use of a transposon-based system described by Luckow et al. (J. Virol 67:4566-4579, 1993). This system, which utilizes transfer vectors, is commercially available in kit form (Bac-to-Bac™ kit; Life Technologies, Rockville, MD). The transfer vector (e.g., pFasfBacl™; Life Technologies) contains a Tn7 transposon to move the DNA encoding the protein of interest into a baculovirus genome maintained in E. coli as a large plasmid called a "bacmid." See, Hill-Perkins and Possee, J. Gen. Virol. 71:971-976, 1990; Bonning et al., J. Gen. Virol. 75:1551- 1556, 1994; and Chazenbalk and Rapoport, J. Biol. Chem. 270:1543-1549, 1995. T-n addition, transfer vectors can include an in-frame fusion with DNA encoding a polypeptide extension or affinity tag as disclosed above. Using techniques known in the art, a transfer vector containing a zalpha51 -encoding sequence is transformed into E. coli host cells, and the cells are screened for bacmids which contain an interrupted lacZ gene indicative of recombinant baculovirus. The bacmid DNA containing the recombinant baculovirus genome is isolated, using common techniques, and used to transfect Spodoptera frugiperda cells, such as Sf9 cells. Recombinant virus that expresses zalpha51 protein is subsequently produced. Recombinant viral stocks are made by methods commonly used the art. For protein production, the recombinant virus is used to infect host cells, typically a cell line derived from the fall armyworm, Spodoptera frugiperda (e.g., Sf9 or Sf21 cells) or Trichoplusia ni (e.g., High Five™ cells; J-nvitrogen, Carlsbad, CA). See, for example, U.S. Patent No. 5,300,435. Serum-free media are used to grow and maintain the cells. Suitable media formulations are known in the art and can be obtained from commercial suppliers. The cells are grown up from an inoculation density of approximately 2-5 x 10 5 cells to a density of 1-2 x 10 6 cells, at which time a recombinant viral stock is added at a multiplicity of infection (MOI) of 0.1 to 10, more typically near 3. Procedures used are generally known in the art. Other higher eukaryotic cells can also be used as hosts, including plant cells and avian cells. The use of Agrobacterium rhizogenes as a vector for expressing genes in plant cells has been reviewed by Sinkar et al., J. Biosci. (Bangalore) 11 :47- 58, 1987. Fungal cells, including yeast cells, can also be used within the present invention. Yeast species of particular interest in this regard include Saccharomyces cerevisiae, Pichia pastoris, and Pichia methanolica. Methods for transforming S. cerevisiae cells with exogenous DNA and producing recombinant polypeptides therefrom are disclosed by, for example, Kawasaki, U.S. Patent No. 4,599,311; Kawasaki et al., U.S. Patent No. 4,931,373; Brake, U.S. Patent No. 4,870,008; Welch et al., U.S. Patent No. 5,037,743; and Murray et al., U.S. Patent No. 4,845,075. Transformed cells are selected by phenotype determined by the selectable marker, commonly drug resistance or the ability to grow in the absence of a particular nutrient (e.g., leucine). A preferred vector system for use in Saccharomyces cerevisiae is the POT1 vector system disclosed by Kawasaki et al. (U.S. Patent No. 4,931,373), which allows transformed cells to be selected by growth in glucose-containing media. Suitable promoters and terminators for use in yeast include those from glycolytic enzyme genes (see, e.g., Kawasaki, U.S. Patent No. 4,599,311; Kingsman et al., U.S. Patent No. 4,615,974; and Bitter, U.S. Patent No. 4,977,092) and alcohol dehydrogenase genes. See also U.S. Patents Nos. 4,990,446; 5,063,154; 5,139,936 and 4,661,454. Transformation systems for other yeasts, including Hansenula polymorpha, Schizosaccharomyces pombe, Kluyveromyces lactis, Kluyveromyces fragilis, Ustilago maydis, Pichia pastoris, Pichia methanolica, Pichia guillermondii and Candida maltosa are known in the art. See, for example, Gleeson et al., J. Gen. Microbiol. 132:3459-3465, 1986; Cregg, U.S. Patent No. 4,882,279; and Raymond et al., Yeast IA, 11-23, 1998. Aspergillus cells may be utilized according to the methods of McKnight et al., U.S. Patent No. 4,935,349. Methods for transforming Acremonium chrysogenum are disclosed by Sumino et al., U.S. Patent No. 5,162,228. Methods for transforming Neurospora are disclosed by Lambowitz, U.S. Patent No. 4,486,533. Production of recombinant proteins in Pichia methanolica is disclosed in U.S. Patents No. 5,716,808, 5,736,383, 5,854,039, and 5,888,768. Prokaryotic host cells, including strains of the bacteria Escherichia coli, Bacillus and other genera are also useful host cells within the present invention. Techniques for transforming these hosts and expressing foreign DNA sequences cloned therein are well known in the art (see, e.g., Sambrook et al., ibid.). When expressing a zalpha51 polypeptide in bacteria such as E. coli, the polypeptide may be retained in the cytoplasm, typically as insoluble granules, or may be directed to the periplasmic space by a bacterial secretion sequence. In the former case, the cells are lysed, and the granules are recovered and denatured using, for example, guanidine isothiocyanate or urea. The denatured polypeptide can then be refolded and dimerized by diluting the denaturant, such as by dialysis against a solution of urea and a combination of reduced and oxidized glutathione, followed by dialysis against a buffered saline solution. In the latter case, the polypeptide can be recovered from the periplasmic space in a soluble and functional form by disrupting the cells (by, for example, sonication or osmotic shock) to release the contents of the periplasmic space and recovering the protein, thereby obviating the need for denaturation and refolding. Transformed or transfected host cells are cultured according to conventional procedures in a culture medium containing nutrients and other components required for the growth of the chosen host cells. A variety of suitable media, including defined media and complex media, are known in the art and generally include a carbon source, a nitrogen source, essential amino acids, vitamins and minerals. Media may also contain such components as growth factors or serum, as required. 4 The growth medium will generally select for cells β containing the exogenously added DNA by, for example, drug selection or deficiency in an essential nutrient which is complemented by the selectable marker carried on the expression vector or co-transfected into the host cell. Liquid cultures are provided with sufficient aeration by conventional means, such as shaking of small flasks or sparging of fermentors. It is preferred to purify the polypeptides and proteins of the present invention to >80% purity, more preferably to >90% purity, even more preferably >95% purity, and particularly preferred is a pharmaceutically pure state, that is greater than 99.9% pure with respect to contaminating macromolecules, particularly other proteins and nucleic acids, and free of infectious and pyrogenic agents. Preferably, a purified polypeptide or protein is substantially free of other polypeptides or proteins, particularly those of animal origin. Expressed recombinant zalpha51 proteins (including chimeric polypeptides and multimeric proteins) are purified by conventional protein purification methods, typically by a combination of chromatographic techniques. See, in general, Affinity Chromatography: Principles & Methods, Pharmacia LKB Biotechnology, Uppsala, Sweden, 1988; and Scopes, Protein Purification: Principles and Practice. Springer- Verlag, New York, 1994. Proteins comprising a polyhistidine affinity tag (typically about 6 histidine residues) are purified by affinity chromatography on a nickel chelate resin. See, for example, Houchuli et al., Bio/Technol. 6: 1321-1325, 1988. Proteins comprising a glu-glu tag can be purified by immunoaffinity chromatography according to conventional procedures. See, for example, Grussenmeyer et al., ibid. Maltose binding protein fusions are purified on an amylose column according to methods known in the art. Zalpha51 polypeptides can also be prepared through chemical synthesis according to methods known in the art, including exclusive solid phase synthesis, partial solid phase methods, fragment condensation or classical solution synthesis. See, for example, Merrifield, J. Am. Chem. Soc. 85:2149, 1963; Stewart et al., Solid Phase Peptide Synthesis (2nd edition), Pierce Chemical Co., Rockford, IL, 1984; Bayer and Rapp, Chem. Pept. Prot. 3:3, 1986; and Atherton et al., Solid Phase Peptide Synthesis: A Practical Approach, J-RL Press, Oxford, 1989. In vitro synthesis is particularly advantageous for the preparation of smaller polypeptides. Using methods known in the art, zalpha51 proteins can be prepared as monomers or multimers; glycosylated or non-glycosylated; pegylated or non- pegylated; and may or may not include an initial methionine amino acid residue. Target cells for use in zalpha51 activity assays include, without limitation, vascular cells (especially endothelial cells and smooth muscle cells), hematopoietic (myeloid and lymphoid) cells, liver cells (including hepatocytes, fenestrated endothelial cells, Kupffer cells, and Ito cells), fibroblasts (including human dermal fibroblasts and lung fibroblasts), fetal lung cells, articular synoviocytes, pericytes, chondrocytes, osteoblasts, and prostate epithelial cells. Endothelial cells and hematopoietic cells are derived from a common ancestral cell, the hemangioblast (Choi et al„ Development 125:725-732, 1998). Zalpha51 proteins of the present invention are characterized by their activity, that is, modulation of the proliferation, differentiation, migration, adhesion, or metabolism of responsive cell types. Biological activity of zalpha51 proteins is assayed using in vitro or in vivo assays designed to detect cell proliferation, differentiation, migration or adhesion; or changes in cellular metabolism (e.g., production of other growth factors or other macromolecules). Many suitable assays are known in the art, and representative assays are disclosed herein. Assays using cultured cells are most convenient for screening, such as for determining the effects of amino acid substitutions, deletions, or insertions. However, in view of the complexity of developmental processes (e.g., angiogenesis, wound healing), in vivo assays will generally be employed to confirm and further characterize biological activity. Certain in vitro models, such as the three-dimensional collagen gel matrix model of Pepper et al. (Biochem. Biophys. Res. Comm. 189:824-831, 1992), are sufficiently complex to assay histological effects. Assays can be performed using exogenously produced proteins, or may be carried out in vivo or in vitro using cells expressing the polypeptide(s) of interest. Assays can be conducted using zalpha51 proteins alone or in combination with other growth factors, such as members of the VEGF family or hematopoietic cytokines (e.g., EPO, TPO, G-CSF, stem cell factor). Representative assays are disclosed below. Activity of zalpha51 proteins can be measured in vitro using cultured cells or in vivo by administering molecules of the claimed invention to an appropriate animal model. Assays measuring cell proliferation or differentiation are well known in the art. For example, assays measuring proliferation include such assays as chemosensitivity to neutral red dye (Cavanaugh et al., Investigational New Drugs 8:347-354, 1990), incorporation of radiolabelled nucleotides (as disclosed by, e.g., Raines and Ross, Methods Enzymol. 109:749-773, 1985; Wahl et al, Mol. Cell Biol. 8:5016-5025, 1988; and Cook et al., Analytical Biochem. 179:1-7, 1989), incorporation of 5-bromo-2'-deoxyuridine (BrdU) in the DNA of proliferating cells (Porstmann et al., J. Immunol. Methods 82:169-179, 1985), and use of tetrazolium salts (Mosmann, J. Immunol. Methods 65:55-63, 1983; Alley et al., Cancer Res. 48:589-601, 1988; Marshall et al., Growth Reg. 5:69-84, 1995; and Scudiero et al., Cancer Res. 48:4827-4833, 1988). Differentiation can be assayed using suitable precursor cells that can be induced to differentiate into a more mature phenotype. Assays measuring differentiation include, for example, measuring cell-surface markers associated with stage-specific expression of a tissue, enzymatic activity, functional activity or morphological changes (Watt, FASEB, 5:281-284, 1991; Francis, Differentiation 57:63-75, 1994; Raes, Adv. Anim. Cell Biol. Technol. Bioprocesses, 161-171, 1989; all incorporated herein by reference). Zalpha51 activity may also be detected using assays designed to measure zalpha51 -induced production of one or more additional growth factors or other macromolecules. Preferred such assays include those for determining the presence of hepatocyte growth factor (HGF), epidermal growth factor (EGF), transforming growth factor alpha (TGFα), interleukin-6 (IL-6), VEGF, acidic fibroblast growth factor (aFGF), angiogenin, and other macromolecules produced by the liver. Suitable assays include mitogenesis assays using target cells responsive to the macromolecule of interest, receptor-binding assays, competition binding assays, immunological assays (e.g., ELISA), and other formats known in the art. Metalloprotease secretion is measured from treated primary human dermal fibroblasts, synoviocytes and chondrocytes. The relative levels of collagenase, gelatinase and stromalysin produced in response to culturing in the presence of a zalpha51 protein is measured using zymogram gels (Loita and Stetler-Stevenson, Cancer Biology 1_:96- 106, 1990). Procollagen collagen synthesis by dermal fibroblasts and chondrocytes in response to a test protein is measured using 3 H-proline incorporation into nascent secreted collagen. 3 H-labeled collagen is visualized by SDS-PAGE followed by autoradiography (Unemori and Amento, J. Biol. Chem. 265: 10681-10685, 1990). Glycosaminoglycan (GAG) secretion from dermal fibroblasts and chondrocytes is measured using a 1,9-dimethylmethylene blue dye binding assay (Farndale et al., Biochim. Biophvs. Acta 883:173-177, 1986). Collagen and GAG assays are also carried out in the presence of JJ -lo. or TGF-α to examine the ability of zalpha51 protein to modify the established responses to these cytokines. Monocyte activation assays are carried out (1) to look for the ability of zalpha51 proteins to further stimulate monocyte activation, and (2) to examine the ability of zalpha51 proteins to modulate attachment-induced or endotoxin-induced monocyte activation (Fuhlbrigge et al., J. Immunol. 138: 3799-3802, 1987). DL-lα and TNF levels produced in response to activation are measured by ELISA (Biosource, Inc. Camarillo, CA). Monocyte/macrophage cells, by virtue of CD14 (LPS receptor), are exquisitely sensitive to endotoxin, and proteins with moderate levels of endotoxin-like activity will activate these cells. Hematopoietic activity of zalpha51 proteins can be assayed on various hematopoietic cells in culture. Preferred assays include primary bone marrow colony assays and later stage lineage-restricted colony assays, which are known in the art (e.g., Holly et al., WJPO Publication WO 95/21920). Marrow cells plated on a suitable semi-solid medium (e.g., 50% methylcellulose containing 15% fetal bovine serum, 10% bovine serum albumin, and 0.6% PSN antibiotic mix) are incubated in the presence of test polypeptide, then examined microscopically for colony formation. Known hematopoietic factors are used as controls. Mitogenic activity of zalpha51 polypeptides on hematopoietic cell lines can be measured as disclosed above. Cell migration is assayed essentially as disclosed by Kahler et al. (Arteriosclerosis, Thrombosis, and Vascular Biology 17:932-939, 1997). A protein is considered to be chemotactic if it induces migration of cells from an area of low protein concentration to an area of high protein concentration. A typical assay is performed using modified Boyden chambers with a polystryrene membrane separating the two chambers (Transwell; Corning Costar Corp.). The test sample, diluted in medium containing 1% BSA, is added to the lower chamber of a 24-well plate containing Transwells. Cells are then placed on the Transwell insert that has been pretreated with 0.2% gelatin. Cell migration is measured after 4 hours of incubation at 37°C. Non-migrating cells are wiped off the top of the Transwell membrane, and cells attached to the lower face of the membrane are fixed and stained with 0.1% crystal violet. Stained cells are then extracted with 10% acetic acid and absorbance is measured at 600 nm. Migration is then calculated from a standard calibration curve. Cell migration can also be measured using the matrigel method of Grant et al. ("Angiogenesis as a component of epithelial-mesenchymal interactions" in Goldberg and Rosen, Epithelial-Mesenchymal Interaction in Cancer, Birkhauser Verlag, 1995, 235-248; Baatout, Anticancer Research 17:451-456, 1997). Cell adhesion activity is assayed essentially as disclosed by LaFleur et al. (J. Biol. Chem. 272:32798-32803, 1997). Briefly, microtiter plates are coated with the test protein, non-specific sites are blocked with BSA, and cells (such as smooth muscle cells, leukocytes, or endothelial cells) are plated at a density of approximately 10 4 - 10 5 cells/well. The wells are incubated at 37°C (typically for about 60 minutes), then non-adherent cells are removed by gentle washing. Adhered cells are quantitated by conventional methods (e.g.^by staining with crystal violet, lysing the cells, and determining the optical density of the lysate). Control wells are coated with a known adhesive protein, such as fibronectin or vitronectin. The activity of zalpha51 proteins can be measured with a silicon-based biosensor microphysiometer that measures the extracellular acidification rate or proton excretion associated with receptor binding and subsequent physiologic cellular responses. An exemplary such device is the Cytosensor™ Microphysiometer manufactured by Molecular Devices, Sunnyvale, CA. A variety of cellular responses, such as cell proliferation, ion transport, energy production, inflammatory response, regulatory and receptor activation, and the like, can be measured by this method. See, for example, McConnell et al., Science 257:1906-1912, 1992; Pitchford et al., Meth. Enzvmol. 228:84-108, 1997; Arimilli et al., J. Immunol. Meth. 212:49-59, 1998; and Van Liefde et al., Eur. J. Pharmacol. 346:87-95, 1998. The microphysiometer can be used for assaying adherent or non-adherent eukaryotic or prokaryotic cells. By measuring extracellular acidification changes in cell media over time, the microphysiometer directly measures cellular responses to various stimuli, including zalpha51 proteins, their agonists, and antagonists. Preferably, the microphysiometer is used to measure responses of a zalpha51 -responsive eukaryotic cell, compared to a control eukaryotic cell that does not respond to zalpha51 polypeptide. Zalpha51- responsive eukaryotic cells comprise cells into which a receptor for zalpha51 has been transfected, thereby creating a cell that is responsive to zalpha51, as well as cells naturally responsive to zalpha51. Differences, measured by a change, for example, an increase or diminution in extracellular acidification, in the response of cells exposed to zalpha51 polypeptide, relative to a control not exposed to zalpha51, are a direct measurement of zalpha51 -modulated cellular responses. Moreover, such zalpha51- modulated responses can be assayed under a variety of stimuli. The present invention thus provides methods of identifying agonists and antagonists of zalpha51 proteins, comprising providing cells responsive to a zalpha51 polypeptide, culturing a first portion of the cells in the absence of a test compound, culturing a second portion of the cells in the presence of a test compound, and detecting a change, for example, an increase or diminution, in a cellular response of the second portion of the cells as compared to the first portion of the cells. The change in cellular response is shown as a measurable change in extracellular acidification rate. Culturing a third portion of the cells in the presence of a zalpha51 protein and the absence of a test compound provides a positive control for the zalpha51 -responsive cells and a control to compare the agonist activity of a test compound with that of the zalpha51 polypeptide. Antagonists of zalpha51 can be identified by; exposing the cells to zalpha51 protein in the presence and absence of the test compound, whereby a reduction in zalpha51- stimulated activity is indicative of antagonist activity in the test compound. Expression of zalpha51 polynucleotides in animals provides models for further study of the biological effects of overproduction or inhibition of protein activity in vivo. Zalpha51 -encoding polynucleotides and antisense polynucleotides can be introduced into test animals, such as mice, using viral vectors or naked DNA, or transgenic animals can be produced. One in vivo approach for assaying proteins of the present invention utilizes viral delivery systems. Exemplary viruses for this purpose include adenovirus, herpesvirus, retroviruses, vaccinia virus, and adeno-associated virus (AAV). Adenovirus, a double-stranded DNA virus, is currently the best studied gene transfer vector for delivery of heterologous nucleic acids. For review, see Becker et al., Meth. Cell Biol. 43:161-89, 1994; and Douglas and Curiel, Science & Medicine 4:44-53, 1997. The adenovirus system offers several advantages. Adenovirus can (i) accommodate relatively large DNA inserts; (ii) be grown to high-titer; (iii) infect a broad range of mammalian cell types; and (iv) be used with many different promoters including ubiquitous, tissue specific, and regulatable promoters. Because adenoviruses are stable in the bloodstream, they can be administered by intravenous injection. By deleting portions of the adenovirus genome, larger inserts (up to 7 kb) of heterologous DNA can be accommodated. These inserts can be incorporated into the viral DNA by direct ligation or by homologous recombination with a co- transfected plasmid. In an exemplary system, the essential El gene is deleted from the viral vector, and the virus will not replicate unless the El gene is provided by the host cell (e.g., the human 293 cell line). When intravenously administered to intact animals, adenovirus primarily targets the liver. If the adenoviral delivery system has an El gene deletion, the virus cannot replicate in the host cells. However, the host's tissue (e.g., liver) will express and process (and, if a signal sequence is present, secrete) the heterologous protein. Secreted proteins will enter the circulation in the highly vascularized liver, and effects on the infected animal can be determined. An alternative method of gene delivery comprises removing cells from the body and introducing a vector into the cells as a naked DNA plasmid. The transformed cells are then re-implanted in the body. Naked DNA vectors are introduced into host cells by methods known in the art, including transfection, electroporation, microinjection, transduction, cell fusion, DEAE dextran, calcium phosphate precipitation, use of a gene gun, or use of a DNA vector transporter. See, Wu et al., J. Biol. Chem. 263:14621-14624, 1988; Wu et al., J. Biol. Chem. 267:963- 967, 1992; and Johnston and Tang, Meth. Cell Biol. 43:353-365, 1994. Transgenic mice, engineered to express a zalpha51 gene, and mice that exhibit a complete absence of zalpha51 gene function, referred to as "knockout mice" (Snouwaert et al., Science 257:1083, 1992), can also be generated (Lowell et al., Nature 366:740-742, 1993). These mice can be employed to study the zalpha51 gene and the protein encoded thereby in an in vivo system. Transgenic mice are particularly useful for investigating the role of zalpha51 proteins in early development in that they allow the identification of developmental abnormalities or blocks resulting from the over- or underexpression of a specific factor. See also, Maisonpierre et al., Science 277:55-60, 1997 and Hanahan, Science 277:48-50, 1997. Preferred promoters for transgenic expression include promoters from metallothionein and albumin genes. Transgenic mice expressing zalpha51 had severe locomotion disabilities. Microscopic examination of the brain found severe necrosis in the cerebellar folia (encephalomalacia). The necrotic cells were primarily located in the granular and Purkinje cell layers of the cerebellum. Acute perivasculitis was observed in the pons and cerebellar folia of the mice and in the ventral spinal cord of one of the mice. No significant changes were found in the tissues of the nontransgenic control. The lesions in the zalpha51 transgenic mice were similar to lesions observed in chicks with vitamin E deficiency (Riddell, Avian Histopathology, p.76. AAVP, Kennett Square, PA, 1987.) A form of spinocerebellar ataxia in humans has been associated with a severe deficiency of this vitamin. The rapid onset of rigor mortis in these transgenic mice suggests a metabolic derangement. Mitochondrial disorders can cause metabolism-related changes in a variety of tissue (e.g. the MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke)). These data suggest that zalpha51 may have some role in inducing apoptosis, based on the cell death observed in the cerebellum and other tissues. See, Heffner and Schochet, "Skeletal muscle" in Anderson's Pathology, tenth edition, Damjanov and Linder, eds., pp 2653-2690. Mosby Year-Book, Inc., St. Louis, 1990 and Cotran, Kumar, and Robbins, Pathologic Basis of Disease, fifth edition, pp 418-419. W.B. Saunders Co., Philadelphia, 1994. In addition, inflammation which is associated with many of the cytokines, has been identified as a secondary contributor to certain neurodegenerative diseases (Owens et al., Nature Medicine, 7:161-166, 2001.) A loss of normal inhibitory control of muscle contraction has been associated with damage or perturbation of selected gamma-aminobutryric acid- secreting neurons. For example, Stiff Man Syndrome exhibit remarkable stiffness of musculature, believed to be mediated through interference of the functioning of their garrmia-aminobutryric acid (GAB A) producing neurons. Other related neuromuscular disorders include myotonia, metabolic myopathies, Isaac's syndrome, dystonia, and tetanic spasms (Valldeoriola, J. Neurol 246:423-431, 1999). These disorders exhibit phenotypic similarities to those seen in zalpha51 -expressing mice, and antagonists of zalpha51 can serve as candidate therapies for such disorders. Similarly, direct measurement of zalpha51 polypeptide, or its loss of expression in a tissue can be determined in a tissue or cells as they undergo tumor progression, increases in invasiveness and motility of cells, or the gain or loss of expression of zalpha51 in a pre-cancerous or cancerous condition, in comparison to normal tissue, can serve as a diagnostic for transformation, invasion and metastasis in tumor progression. As such, knowledge of a tumor's stage of progression or metastasis will aid the physician in choosing the most proper therapy, or aggressiveness of treatment, for a given individual cancer patient. Methods of measuring gain and loss of expression (of either mRNA or protein) are well known in the art and described herein and can be applied to zalpha51 expression. For example, appearance or disappearance of polypeptides that regulate cell motility can be used to aid diagnosis and prognosis of prostate cancer (Banyard, J. and Zetter, B.R., Cancer and Metast. Rev. 17:449-458, 1999). As an effector of cell motility, or as a liver- specific marker, zalpha51 gain or loss of expression may serve as a diagnostic for liver, neuroblastoma, endothelial, brain, and other cancers. Moreover, analogous to the prostate specific antigen (PSA), as a naturally-expressed liver marker, increased levels of zalpha51 polypeptides, or anti-zalpha51 antibodies in a patient, relative to a normal control can be indicative of liver, neuroblastoma, endothelial, brain, and other cancers (See, e.g., Mulders, TMT, et al., Eur. J. Surgical Oncol. 16:37-41, 1990). Moreover, as zalpha51 expression appears to be restricted to liver, neuroblastoma, endothelial, brain, and other cancers in normal human tissues, lack of zalpha51 expression in liver or strong zalpha51 expression in non-liver tissue would serve as a diagnostic of an abnormality in the cell or tissue type, of invasion or metastasis of cancerous liver tissue into non-liver tissue, and could aid a physician in directing further testing or investigation, or aid in directing therapy. In addition, as zalpha51 is liver-specific, polynucleotide probes, anti- zalpha51 antibodies, and detection the presence of zalpha51 polypeptides in tissue can be used to assess whether liver tissue is present, for example, after surgery involving the excision of a diseased or cancerous liver or neuronal tissue. As such, the β polynucleotides, polypeptides, and antibodies of the present invention can be used as an aid to determine whether all liver-derived tissue is excised after surgery, for example, after surgery for liver, neuroblastoma, endothelial, brain, and other cancers. In such instances, it is especially important to remove all potentially diseased tissue to maximize recovery from the cancer, and to minimize recurrence. Preferred embodiments include fluorescent, radiolabeled, or calorimetrically labeled anti- zalpha51 antibodies and zalpha51 polypeptide binding partners, that can be used histologically or in situ. Moreover, the activity and effect of zalpha51 on tumor progression and metastasis can be measured in vivo. Several syngeneic mouse models have been developed to study the influence of polypeptides, compounds or other treatments on tumor progression. In these models, tumor cells passaged in culture are implanted into mice of the same strain as the tumor donor. The cells will develop into tumors having similar characteristics in the recipient mice, and metastasis will also occur in some of the models. Appropriate tumor models for our studies include the Lewis lung carcinoma (ATCC No. CRL- 1642) and B16 melanoma (ATCC No. CRL-6323), amongst others. These are both commonly used tumor lines, syngeneic to the C57BL6 mouse, that are readily cultured and manipulated in vitro. Tumors resulting from implantation of either of these cell lines are capable of metastasis to the lung in C57BL6 mice. The Lewis lung carcinoma model has recently been used in mice to identify an inhibitor of angiogenesis (O'Reilly MS, et al. Cell 79: 315-328,1994). C57BL6/J mice are treated with an experimental agent either through daily injection of recombinant protein, agonist or antagonist or a one-time injection of recombinant adenovirus. Three days following this treatment, 10 to 10 cells are implanted under the dorsal skin. Alternatively, the cells themselves may be infected with recombinant adenovirus, such as one expressing zalpha51, before implantation so that the protein is synthesized at the tumor site or intracellularly, rather than systemically. The mice normally develop visible tumors within 5 days. The tumors are allowed to grow for a 3 period of up to 3 weeks, during which time they may reach a size of 1500 - 1800 mm in the control treated group. Tumor size and body weight are carefully monitored throughout the experiment. At the time of sacrifice, the tumor is removed and weighed along with the lungs and the liver. The lung weight has been shown to correlate well with metastatic tumor burden. As an additional measure, lung surface metastases are counted. The resected tumor, lungs and liver are prepared for histopathological examination, immunohistochemistry, and in situ hybridization, using methods known in the art and described herein. The influence of the expressed polypeptide in question, e.g., zalpha51, on the ability of the tumor to recruit vasculature and undergo metastasis can thus be assessed. In addition, aside from using adenovirus, the implanted cells can be transiently transfected with zalpha51. Use of stable zalpha51 transfectants as well as use of induceable promoters to activate zalpha51 expression in vivo are known in the art and can be used in this system to assess z*** induction of metastasis. Moreover, purified zalpha51 or zalpha51- conditioned media can be directly injected in to this mouse model, and hence be used in this system. For general reference see, O'Reilly MS, et al. Cell 79:315-328, 1994; and Rusciano D, et al. Murine Models of Liver Metastasis. Invasion Metastasis 14:349-361, 1995. Antisense methodology can be used to inhibit zalpha51 gene transcription to examine the effects of such inhibition in vivo. Polynucleotides that are complementary to a segment of a zalpha51 -encoding polynucleotide (e.g., a polynucleotide as set forth in SEQ ID NO:l) are designed to bind to zalpha51- encoding mRNA and to inhibit translation of such mRNA. Such antisense oligonucleotides can also be used to inhibit expression of zalpha51 polypeptide- encoding genes in cell culture. Most four-helix bundle cytokines as well as other proteins produced by activated lymphocytes play an important biological role in cell differentiation, activation, recruitment and homeostasis of cells throughout the body. Zalpha51 and inhibitors of zalpha51 activity are expected to have a variety of therapeutic applications. These therapeutic applications include treatment of diseases which require immune regulation, including autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, myasthenia gravis, systemic lupus erythematosis, and diabetes. Zalpha51 may be important in the regulation of inflammation, and therefore would be useful in treating rheumatoid arthritis, asthma and sepsis. There may be a role of zalpha51 in mediating tumorgenesis, whereby a zalpha51 antagonist would be useful in the treatment of cancer. Zalpha51 may be useful in modulating the immune system, whereby zalpha51 and zalpha51 antagonists may be used for reducing graft rejection, preventing graft- vs-host disease, boosting immunity to infectious diseases, treating immunocompromised patients (e.g., HJN + patients), or in improving vaccines. Zalpha51 polypeptides can be administered alone or in combination with other vasculogenic or angiogenic agents, including NEGF. When using zalpha51 in combination with an additional agent, the two compounds can be administered simultaneously or sequentially as appropriate for the specific condition being treated. For pharmaceutical use, zalpha51 proteins are formulated for topical or parenteral, particularly intravenous or subcutaneous, delivery according to conventional methods. In general, pharmaceutical formulations will include a zalpha51 polypeptide in combination with a pharmaceutically acceptable vehicle, such as saline, buffered saline, 5% dextrose in water, or the like. Formulations may further include one or more excipients, preservatives, solubilizers, buffering agents, albumin to prevent protein loss on vial surfaces, etc. Methods of formulation are well known in the art and are disclosed, for example, in Remington: The Science and Practice of Pharmacy, Gennaro, ed., Mack Publishing Co., Easton, PA, 19th ed., 1995. Zalpha51 will preferably be used in a concentration of about 10 to 100 μg/ml of total volume, although concentrations in the range of 1 ng/ml to 1000 μg/ml may be used. For topical application, such as for the promotion of wound healing, the protein will be applied in the range of 0.1-10 μg/cm 2 of wound area, with the exact dose determined by the clinician according to accepted standards, taking into account the nature and severity of the condition to be treated, patient traits, etc. Determination of dose is within the level of ordinary skill in the art. Dosing is daily or intermittently over the period of treatment. Intravenous administration will be by bolus injection or infusion over a typical period of one to several hours. Sustained release formulations can also be employed. In general, a therapeutically effective amount of zalpha51 is an amount sufficient to produce a clinically significant change in the treated condition, such as a clinically significant change in hematopoietic or immune function, a significant reduction in morbidity, or a significantly increased histological score. Zalpha51 proteins, agonists, and antagonists are useful for modulating the expansion, proliferation, activation, differentiation, migration, or metabolism of responsive cell types, which include both primary cells and cultured cell lines. Of particular interest in this regard are hematopoietic cells, mesenchymal cells (including stem cells and mature myeloid and lymphoid cells), endothelial cells, smooth muscle cells, fibroblasts, hepatocytes, neural cells and embryonic stem cells. Zalpha51 polypeptides are added to tissue culture media for these cell types at a concentration of about 10 pg/ml to about 100 ng/ml. Those skilled in the art will recognize that zalpha51 proteins can be advantageously combined with other growth factors in culture media. Within the laboratory research field, zalpha51 proteins can also be used as molecular weight standards or as reagents in assays for determining circulating levels of the protein, such as in the diagnosis of disorders characterized by over- or under-production of zalpha51 protein or in the analysis of cell phenotype. Zalpha51 proteins can also be used to identify inhibitors of their activity. Test compounds are added to the assays disclosed above to identify compounds that inhibit the activity of zalpha51 protein. In addition to those assays disclosed above, samples can be tested for inhibition of zalpha51 activity within a variety of assays designed to measure receptor binding or the stimulation/inhibition of zalpha51 -dependent cellular responses. For example, zalpha51 -responsive cell lines can be transfected with a reporter gene construct that is responsive to a zalpha51- stimulated cellular pathway. Reporter gene constructs of this type are known in the art, and will generally comprise a zalpha51 -activated serum response element (SRE) operably linked to a gene encoding an assayable protein, such as luciferase. Candidate compounds, solutions, mixtures or extracts are tested for the ability to inhibit the activity of zalpha51 on the target cells as evidenced by a decrease in zalpha51 stimulation of reporter gene expression. Assays of this type will detect compounds that directly block zalpha51 binding to cell-surface receptors, as well as compounds that block processes in the cellular pathway subsequent to receptor-ligand binding. In the alternative, compounds or other samples can be tested for direct blocking of zalpha51 binding to receptor using zalpha51 tagged with a detectable label (e.g., 125 I, biotin, horseradish peroxidase, FITC, and the like). Within assays of this type, the ability of a test sample to inhibit the binding of labeled zalpha51 to the receptor is indicative of inhibitory activity, which can be confirmed through secondary assays. Receptors used within binding assays may be cellular receptors or isolated, immobilized receptors. As used herein, the term "antibodies" includes polyclonal antibodies, monoclonal antibodies, antigen-binding fragments thereof such as F(ab')2 and Fab fragments, single chain antibodies, and the like, including genetically engineered antibodies. Non-human antibodies may be humanized by grafting non-human CDRs onto human framework and constant regions, or by incorporating the entire non- human variable domains (optionally "cloaking" them with a human-like surface by replacement of exposed residues, wherein the result is a "veneered" antibody). In some instances, humanized antibodies may retain non-human residues within the human variable region framework domains to enhance proper binding characteristics. Through humanizing antibodies, biological half-life may be increased, and the potential for adverse immune reactions upon administration to humans is reduced. One skilled in the art can generate humanized antibodies with specific and different constant domains (i.e., different Ig subclasses) to facilitate or inhibit various immune functions associated with particular antibody constant domains. Antibodies are defined to be specifically binding if they bind to a zalpha51 polypeptide or protein with an affinity at least 10-fold greater than the binding affinity to control (non- zalpha51) polypeptide or protein. The affinity of a monoclonal antibody can be readily determined by one of ordinary skill in the art (see, for example, Scatchard, Ann. NY Acad. Sci. 51: 660-672, 1949). Methods for preparing polyclonal and monoclonal antibodies are well known in the art (see for example, Hurrell, J. G. R., Ed., Monoclonal Hybridoma Antibodies: Techniques and Applications, CRC Press, Inc., Boca Raton, FL, 1982, which is incorporated herein by reference). Of particular interest are generating antibodies to hydrophilic antigenic sites which include, for example, residues 30-35, residues 135-140, residues 87-92, residues 168-173 and residues 19-24 of SEQ ID NO: 2. As would be evident to one of ordinary skill in the art, polyclonal antibodies can be generated from a variety of warm-blooded animals such as horses, cows, goats, sheep, dogs, chickens, rabbits, mice, and rats. The immunogenicity of a zalpha51 polypeptide may be increased through the use of an adjuvant such as alum (aluminum hydroxide) or Freund's complete or incomplete adjuvant. Polypeptides useful for immunization also include fusion polypeptides, such as fusions of a zalpha51 polypeptide or a portion thereof with an immunoglobulin polypeptide or with maltose binding protein. The polypeptide immunogen may be a full-length molecule or a portion thereof. Jf the polypeptide portion is "hapten-like", such portion may be advantageously joined or linked to a macromolecular carrier (such as keyhole limpet hemocyanin (KLH), bovine serum albumin (BSA) or tetanus toxoid) for immunization. Alternative techniques for generating or selecting antibodies include in vitro exposure of lymphocytes to zalpha51 polypeptides, and selection of antibody display libraries in phage or similar vectors (e.g., through the use of immobilized or labeled zalpha51 polypeptide). Human antibodies can be produced in transgenic, non- human animals that have been engineered to contain human immunoglobulin genes as disclosed in WD?O Publication WO 98/24893. It is preferred that the endogenous immunoglobulin genes in these animals be inactivated or eliminated, such as by homologous recombination. A variety of assays known to those skilled in the art can be utilized to detect antibodies which specifically bind to zalpha51 polypeptides. Exemplary assays are described in detail in Antibodies: A Laboratory Manual, Harlow and Lane (Eds.), Cold Spring Harbor Laboratory Press, 1988. Representative examples of such assays include: concurrent immunoelectrophoresis, radio-immunoassays, radio- immunoprecipitations, enzyme-linked immunosorbent assays (ELISA), dot blot assays, Western blot assays, inhibition or competition assays, and sandwich assays. Antibodies to zalpha51 may be used for affinity purification of the protein, within diagnostic assays for determining circulating levels of the protein; for detecting or quantitating soluble zalpha51 polypeptide as a marker of underlying pathology or disease; for immunolocalization within whole animals or tissue sections, including immunodiagnostic applications; for irnmunohistochernistry; and as antagonists to block protein activity in vitro and in vivo. Antibodies to zalpha51 may also be used for tagging cells that express zalpha51; for affinity purification of zalpha51 polypeptides and proteins; in analytical methods employing FACS; for screening expression libraries; and for generating anti-idiotypic antibodies. Antibodies can be linked to other compounds, including therapeutic and diagnostic agents, using known methods to provide for targeting of those compounds to cells expressing receptors for zalpha51. For certain applications, including in vitro and in vivo diagnostic uses, it is advantageous to employ labeled antibodies. Suitable direct tags or labels include radionuclides, enzymes, substrates, cofactors, inhibitors, fluorescent markers, chemiluminescent markers, magnetic particles and the like; indirect tags or labels may feature use of biotin-avidin or other complement/anti- complement pairs as intermediates. Antibodies of the present invention may also be directly or indirectly conjugated to drugs, toxins, radionuclides and the like, and these conjugates used for in vivo diagnostic or therapeutic applications(e.g., inhibition of cell proliferation). See, in general, Ramakrishnan et al., Cancer Res. 56:1324-1330, 1996. Polypeptides and proteins of the present invention can be used to identify and isolate receptors. Zalpha51 receptors may be involved in growth regulation in the liver, blood vessel formation, and other developmental processes. For example, zalpha51 proteins and polypeptides can be immobilized on a column, and membrane preparations run over the column (as generally disclosed in immobilized Affinity Ligand Techniques, Hermanson et al., eds., Academic Press, San Diego, CA, 1992, pp.195-202). Proteins and polypeptides can also be radiolabeled (Methods Enzymol., vol. 182, "Guide to Protein Purification", M. Deutscher, ed., Academic Press, San Diego, 1990, 721-737) or photoaffinity labeled (Brunner et al., Ann. Rev. Biochem. 62:483-514, 1993 and Fedan et al., Biochem. Pharmacol. 33:1167-1180, 1984) and used to tag specific cell-surface proteins. In a similar manner, radiolabeled zalpha51 proteins and polypeptides can be used to clone the cognate receptor in binding assays using cells transfected with an expression cDNA library. Zalpha51 gene has been mapped to a chromosomal location of 16pl2.1. This chromosomal locus has been identified with several neuromuscular diseases or defects, a phenotype that has been seen with zalpha51 transgenic mice. When there is a concentration of multiple pathologies, all having some related etiology, that have been correlated to a chromosomal locus, identification of a new gene within that cluster has scientific and medical value by providing a possible candidate gene for an inheritable disease which shows linkage in that chromosomal region. Further elucidation of the role of that chromosomal region facilitates the use of genetics as a diagnostic for neuromuscular disease. For example, benign familial infantile convulsions (BFIC) has been linked to the locus 16pl2-ql2 (Lee et al., Human Genet. 103:608-612, 1998 and Szepetowski et al., Am. J. Hum. Genet. 61:889-898, 1997). Brody disease, which is characterized by progressive impairment of muscular relaxation, has been localized to chromosome 16 (MacLenna et al., Somat. Cell Molec. Genet. 13:341-346, 1987). Furthermore, 16pl2-pl3 has also been identified as the familial neuroblastoma locus, which results in a predisposition for neuroblastoma, the most common form of solid tumors in children. It has been suggested that the tumor is an embryonic lethal gene mutation. (Furuta et al., Medical and Pediatric Oncol. 35:531-533, 2000 and Weiss et al., Medical and Pediatric Oncol. 35:526-530, 2000.) Zalpha51 maps to this region of the chromosome, and overexpression in mice resulted in severe neuronal damage in specific regions of the brain, making zalpha51 a candidate gene for involvement in neurological disease, such as neuroblastoma. Defects in the zalpha51 gene itself may result in a heritable human disease state. Molecules of the present invention, such as the polypeptides, antagonists, agonists, polynucleotides and antibodies of the present invention would aid in the detection, diagnosis prevention, and treatment of diseases associated with a zalpha51 genetic defect. One of skill in the art would recognize that of zalpha51 polynucleotide probes are particularly useful for diagnosis of gross chromosomal abnormalities associated with loss of heterogeneity (LOH), chromosome gain (e.g. trisomy), translocation, DNA amplification, and the like. In addition, zalpha51 polynucleotide probes can be used to detect allelic differences between diseased or non-diseased individuals at the zalpha51 chromosomal locus. As such, the zalpha51 sequences can be used as diagnostics in forensic DNA profiling. A diagnostic could assist physicians in determining the type of disease and appropriate associated therapy, or assistance in genetic counseling. As such, the inventive anti-zalpha51 antibodies, polynucleotides, and polypeptides can be used for the detection of zalpha51 polypeptide, mRNA or anti- zalpha51 antibodies, thus serving as markers and be directly used for detecting or genetic diseases or cancers, as described herein, using methods known in the art and described herein. In general, the diagnostic methods used in genetic linkage analysis, to detect a genetic abnormality or aberration in a patient, are known in the art. Most diagnostic methods comprise the steps of (i) obtaining a genetic sample from a potentially diseased patient, diseased patient or potential non-diseased carrier of a recessive disease allele; (ii) producing a first reaction product by incubating the genetic sample with a zalpha51 polynucleotide probe wherein the polynucleotide will hybridize to complementary polynucleotide sequence, such as in RFLP analysis or by incubating the genetic sample with sense and antisense primers in a PCR reaction under appropriate PCR reaction conditions; (iii) Nisualizing the first reaction product by gel electrophoresis and/or other known method such as visualizing the first reaction product with a zalpha51 polynucleotide probe wherein the polynucleotide will hybridize to the complementary polynucleotide sequence of the first reaction; and (iv) comparing the visualized first reaction product to a second control reaction product of a genetic sample from a normal or control individual. A difference between the first reaction product and the control reaction product is indicative of a genetic abnormality in the diseased or potentially diseased patient, or the presence of a heterozygous recessive carrier phenotype for a non-diseased patient, or the presence of a genetic defect in a tumor from a diseased patient, or the presence of a genetic abnormality in a fetus or pre-implantation embryo. For example, a difference in restriction fragment pattern, length of PCR products, length of repetitive sequences at the zalpha51 genetic locus, and the like, are indicative of a genetic abnormality, genetic aberration, or allelic difference in comparison to the normal control. Controls can be from unaffected family members, or unrelated individuals, depending on the test and availability of samples. Genetic samples for use within the present invention include genomic DNA, mRNA, and cDNA isolated fromm any tissue or other biological sample from a patient, such as but not limited to, blood, saliva, semen, embryonic cells, amniotic fluid, and the like. The polynucleotide probe or primer can be RNA or DNA, and will comprise a portion of SEQ ID NO:l, the complement of SEQ J-D NO:l, or an RNA equivalent thereof. Such methods of showing genetic linkage analysis to human disease phenotypes are well known in the art. For reference to PCR based methods in diagnostics see, generally, Mathew (ed.), Protocols in Human Molecular Genetics (Humana Press, Inc. 1991), White (ed.), PCR Protocols: Current Methods and Applications (Humana Press, Inc. 1993), Cotter (ed.), Molecular Diagnosis of Cancer (Humana Press, Inc. 1996), Hanausek and Walaszek (eds.), Tumor Marker Protocols (Humana Press, Inc. 1998), Lo (ed.), Clinical Applications of PCR (Humana Press, Inc. 1998), and Meltzer (ed.), PCR in Bioanalysis (Humana Press, Inc. 1998)). Mutations associated with the zalpha51 locus can be detected using nucleic acid molecules of the present invention by employing standard methods for direct mutation analysis, such as restriction fragment length polymorphism analysis, short tandem repeat analysis employing PCR techniques, amplification-refractory mutation system analysis, single-strand conformation polymorphism detection, RNase cleavage methods, denaturing gradient gel electrophoresis, fluorescence-assisted mismatch analysis, and other genetic analysis techniques known in the art (see, for example, Mathew (ed.), Protocols in Human Molecular Genetics (Humana Press, Inc. 1991), Marian, Chest 108:255 (1995), Coleman and Tsongalis, Molecular Diagnostics (Human Press, Inc. 1996), Elles (ed.) Molecular Diagnosis of Genetic Diseases (Humana Press, Inc. 1996), Landegren (ed.), Laboratory Protocols for Mutation Detection (Oxford University Press 1996), Birren et al. (eds.), Genome Analysis, Vol. 2: Detecting Genes (Cold Spring Harbor Laboratory Press 1998), Dracopoli et al. (eds.), Current Protocols in Human Genetics (John Wiley & Sons 1998), and Richards and Ward, "Molecular Diagnostic Testing," in Principles of Molecular Medicine, pages 83-88 (Humana Press, Inc. 1998). Direct analysis of an zalpha51 gene for a mutation can be performed using a subject's genomic DNA. Methods for amplifying genomic DNA, obtained for example from peripheral blood lymphocytes, are well- known to those of skill in the art (see, for example, Dracopoli et al. (eds.), Current Protocols in Human Genetics, at pages 7.1.6 to 7.1.7 (John Wiley & Sons 1998)). Radiation hybrid mapping is a somatic cell genetic technique developed for constructing high-resolution, contiguous maps of mammalian chromosomes (Cox et al., Science 250:245-50, 1990). Partial or full knowledge of a gene's sequence allows one to design PCR primers suitable for use with chromosomal radiation hybrid mapping panels. Radiation hybrid mapping panels that cover the entire human genome are commercially available, such as the Stanford G3 RH Panel and the GeneBridge 4 RH Panel (Research Genetics, Inc., Huntsville, AL). These panels enable rapid, PCR-based chromosomal localizations and ordering of genes, sequence- tagged sites (STSs), and other nonpolymorphic and polymorphic markers within a region of interest, and the establishment of directly proportional physical distances between newly discovered genes of interest and previously mapped markers. The precise knowledge of a gene's position can be useful for a number of purposes, including: 1) determining if a sequence is part of an β existing contig and obtaining additional surrounding genetic sequences in various forms, such as YACs, BACs or cDNA clones; 2) providing a possible candidate gene for an inheritable disease which shows linkage to the same chromosomal region; and 3) cross-referencing model organisms, such as mouse, which may aid in determining what function a particular gene might have. Sequence tagged sites (STSs) can also be used independently for chromosomal localization. An STS is a DNA sequence that is unique in the human genome and can be used as a reference point for a particular chromosome or region of a chromosome. An STS is defined by a pair of oligonucleotide primers that are used in a polymerase chain reaction to specifically detect this site in the presence of all other genomic sequences. Since STSs are based solely on DNA sequence they can be completely described within an electronic database, for example, Database of Sequence Tagged Sites (dbSTS), Ge Bank (National Center for Biological Information, National Institutes of Health, Bethesda, MD), and can be searched with a gene sequence of interest for the mapping data contained within these short genomic landmark STS sequences. The polypeptides, nucleic acid and/or antibodies of the present invention may be used in diagnosis or treatment of disorders associated with cell loss or abnormal cell proliferation (including cancer). Labeled zalpha51 polypeptides may be used for imaging tumors or other sites of abnormal cell proliferation. Inhibitors of zalpha51 activity (zalpha51 antagonists) include anti- zalpha51 antibodies and soluble zalpha51 receptors, as well as other peptidic and non- peptidic agents (including ribozymes). Such antagonists can be used to block the effects of zalpha51 on cells or tissues. Of particular interest is the use of antagonists of zalpha51 activity in cancer therapy. As early detection methods improve it becomes possible to intervene at earlier times in tumor development, making it feasible to use inhibitors of growth factors to block cell proliferation, angiogenesis, and other events that lead to tumor development and metastasis. Inhibitors are also expected to be useful in adjunct therapy after surgery to prevent the growth of residual cancer cells. Inhibitors can also be used in combination with other cancer therapeutic agents. In addition to antibodies, zalpha51 inhibitors include small molecule inhibitors and inactive receptor-binding fragments of zalpha51 polypeptides. Inhibitors are formulated for pharmaceutical use as generally disclosed above, taking into account the precise chemical and physical nature of the inhibitor and the condition to be treated. The relevant determinations are within the level of ordinary skill in the formulation art. Alternatively, zalpha51 may activate the immune system which would be important in boosting immunity to infectious diseases, treating immunocompromised patients, such as HJN+ patients, or in improving vaccines. J-n particular, zalpha51 stimulation or expansion of hematopoietic cells, or their progenitors, would provide therapeutic value in treatment of bacterial or viral infection, and as an anti-neoplastic factor. zalpha51 stimulation of the immune response against viral and non- viral pathogenic agents (including bacteria, protozoa, and fungi) would provide therapeutic value in treatment of such infections by inhibiting the growth of such infections agents. Determining directly or indirectly the levels of a pathogen or antigen, such as a tumor cell, present in the body can be achieved by a number of methods known in the art and described herein. The present invention include a method of stimulating an immune response in a mammal exposed to an antigen or pathogen comprising the steps of: (1) determining directly or indirectly the level of antigen or pathogen present in said mammal; (2) administering a composition comprising zalpha51 polypeptide in an acceptable pharmaceutical vehicle; (3) determining directly or indirectly the level of antigen or pathogen in said mammal; and (4) comparing the level of the antigen or pathogen in step 1 to the antigen or pathogen level in step 3, wherein a change in the level is indicative of stimulating an immune response. J-n another embodiment the zalpha51 composition is re-administered. In other embodiments, the antigen is a B cell tumor; a virus; a parasite or a bacterium. In another aspect, the present invention provides a method of stimulating an immune response in a mammal exposed to an antigen or pathogen comprising: (1) determining a level of an antigen- or pathogen-specific antibody; (2) administering a composition comprising zalpha51 polypeptide in an acceptable pharmaceutical vehicle; (3) determining a post administration level of antigen- or pathogen-specific antibody; (4) comparing the level of antibody in step (1) to the level of antibody in step (3), wherein an increase in antibody level is indicative of stimulating an immune response. Polynucleotides encoding zalpha51 polypeptides are useful within gene therapy applications where it is desired to increase or inhibit zalpha51 activity. If a mammal has a mutated or absent zalpha51 gene, a zalpha51 gene can be introduced into the cells of the mammal. In one embodiment, a gene encoding a zalpha51 polypeptide is introduced in vivo in a viral vector. Such vectors include an attenuated or defective DNA virus, such as, but not limited to, herpes simplex virus (HSV), papillomavirus, Epstein Barr virus (EBV), adenovirus, adeno-associated virus (AAV), and the like. Defective viruses, which entirely or almost entirely lack viral genes, are preferred. A defective virus is not infective after introduction into a cell. Use of defective viral vectors allows for administration to cells in a specific, localized area, without concern that the vector can infect other cells. Examples of particular vectors include, but are not limited to, a defective herpes simplex virus 1 (HSN1) vector (Kaplitt et al., Molec. Cell. Νeurosci. 2:320-330, 1991); an attenuated adenovirus vector, such as the vector described by Stratford-Perricaudet et al., J. Clin. Invest. 90:626-630, 1992; and a defective adeno-associated virus vector (Samulski et al., J. Virol. 61:3096-3101, 1987; Samulski et al, J. Virol. 63:3822-3888, 1989). Within another embodiment, a zalpha51 gene can be introduced in a retroviral vector as described, for example, by Anderson et al., U.S. Patent No. 5,399,346; Mann et al. Cell 33:153, 1983; Temin et al., U.S. Patent No. 4,650,764; Temin et al., U.S. Patent No. 4,980,289; Markowitz et al., J. Virol. 62:1120, 1988; Temin et al., U.S. Patent No. 5,124,263; Dougherty et al., WJ-PO Publication WO 95/07358; and Kuo et al., Blood 82:845, 1993. Alternatively, the vector can be introduced by liposome-mediated transfection ("lipofection"). Synthetic cationic lipids can be used to prepare liposomes for in vivo transfection of a gene encoding a marker (Feigner et al., Proc. Natl. Acad. Sci. USA 84:7413-7417, 1987; Mackey et al., Proc. Natl. Acad. Sci. USA 85:8027- 8031, 1988). The use of lipofection to introduce exogenous genes into specific organs in vivo has certain practical advantages, including molecular targeting of liposomes to specific cells. Directing transfection to particular cell types is particularly advantageous in a tissue with cellular heterogeneity, such as the pancreas, liver, kidney, and brain. Lipids may be chemically coupled to other molecules for the purpose of targeting. Peptidic and non-peptidic molecules can be coupled to liposomes chemically. Within another embodiment, cells are removed from the body, a vector is introduced into the cells as a naked DNA plasmid, and the transformed cells are re-implanted into the body as disclosed above. Antisense methodology can be used to inhibit zalpha51 gene transcription in a patient as generally disclosed above. Zalpha51 polypeptides and anti-zalpha51 antibodies can be directly or indirectly conjugated to drugs, toxins, radionuclides and the like, and these conjugates used for in vivo diagnostic or therapeutic applications. For instance, polypeptides or antibodies of the present invention may be used to identify or treat tissues or organs that express a corresponding anti-complementary molecule (receptor or antigen, respectively, for instance). More specifically, zalpha51 polypeptides or anti-zalpha51 antibodies, or bioactive fragments or portions thereof, can be coupled to ^ detectable or cytotoxic molecules and delivered to a mammal having cells, tissues, or organs that express the anti-complementary molecule. Suitable detectable molecules can be directly or indirectly attached to the polypeptide or antibody, and include radionuclides, enzymes, substrates, cofactors, inhibitors, fluorescent markers, chemiluminescent markers, magnetic particles, and the like. Suitable cytotoxic molecules can be directly or indirectly attached to the polypeptide or antibody, and include bacterial or plant toxins (for instance, diphtheria toxin, Pseudomonas exotoxin, ricin, abrin, saporin, and the like), as well as therapeutic radionuclides, such as iodine-131, rhenium-188 or yttrium-90. These can be either directly attached to the polypeptide or antibody, or indirectly attached according to known methods, such as through a chelating moiety. Polypeptides or antibodies can also be conjugated to cytotoxic drugs, such as adriamycin. For indirect attachment of a detectable or cytotoxic molecule, the detectable or cytotoxic molecule may be conjugated with a member of a complementary/anticomplementary pair, where the other member is bound to the polypeptide or antibody portion. For these purposes,, biotin/streptavidin is an exemplary complementary/anticomplementary pair. Polypeptide-toxin fusion proteins or antibody/fragment-toxin fusion proteins may be used for targeted cell or tissue inhibition or ablation, such as in cancer therapy. Of particular interest in this regard are conjugates of a zalpha51 polypeptide and a cytotoxin, which can be used to target the cytotoxin to a tumor or other tissue that is undergoing undesired angiogenesis or neovascularization. Target cells (i.e., those displaying the zalpha51 receptor) bind the zalpha51 -toxin conjugate, which is then internalized, killing the cell. The effects of receptor-specific cell killing (target ablation) are revealed by changes in whole animal physiology or through histological examination. Thus, ligand-dependent, receptor-directed cyotoxicity can be used to enhance understanding of the physiological significance of a protein ligand. A preferred such toxin is saporin. Mammalian cells have no receptor for saporin, which is non-toxic when it remains extracellular. In another embodiment, zalpha51 -cytokine fusion proteins or antibody/fragment-cytokine fusion proteins may be used for enhancing in vitro cytotoxicity (for instance, that mediated by monoclonal antibodies against tumor targets) and for enhancing in vivo killing of target tissues (for example, blood and bone marrow cancers). See, generally, Hornick et al., Blood 89:4437-4447, 1997). In general, cytokines are toxic if administered systemically. The described fusion proteins enable targeting of a cytokine to a desired site of action, such as a cell having binding sites for zalpha51, thereby providing an elevated local concentration of cytokine. Suitable cytokines for this purpose include, for example, interleukin-2 and granulocyte-macrophage colony-stimulating factor (GM-CSF). Such fusion proteins may be used to cause cytokine-induced killing of tumors and other tissues undergoing angiogenesis or neovascularization. The bioactive polypeptide or antibody conjugates described herein can be delivered intravenously, intra-arterially or intraductally, or may be introduced locally at the intended site of action. In summary, the present inventions provides, but is not limited to, certain embodiments described herein. I-n one aspect, the present invention provides an isolated polypeptide comprising at least nine contiguous amino acid residues of SEQ ID NO:2. In another embodiment at least nine contiguous amino acid residues of SEQ ID NO: 2 are operably linked via a peptide bond or polypeptide linker to a second polypeptide selected from the group consisting of maltose binding protein and an immunoglobulin constant region. In other embodiments, the polypeptides are from 15 to 232 amino acid residues, are at least 30 contiguous residues of SEQ J-D NO:2, comprise residues 43-206 of SEQ ID NO:2, comprise residues 18-232 of SEQ JD NO: 2. In another embodiment, the present invention provides an isolated polypeptide comprising a sequence of amino acid residues selected from the group consisting of: (a) residues 1-17 of SEQ ID NO:2; (b) residues 43-57 of SEQ JO NO:2; (c) residues 98-112 of SEQ ID NO:2; (d) residues 126-140 of SEQ ID NO:2; and (e) residues 192- 206 of SEQ ID NO:2. In a broader sense, the helical regions of the zalpha51 polypeptides must include from 15 to 23 contiguous amino acid residues comprising residues 54 (Ala) to 60 (Glu) as shown in SEQ J-D NO: 5 (helix A); from 15 to 26 contiguous amino acid residues comprising residues 109 (He) to 114 (Gin) as shown in SEQ J-D NO: 5 (helix B); from 15 to 23 contiguous amino acid residues comprising residues 146 (Asp) to 151 (Leu) as shown in SEQ ID NO: 5 (helix C); and from 15 to 27 contiguous amino acid residues comprising residues 205 (Arg) to 217 (Ala) as shown in SEQ ID NO: 5 (helix D). Therefore, helical regions of zalpha51 can include amino acid residues 38 (Leu) to 60 (Glu) as shown in SEQ J-D NO: 5 (helix A); amino acid residues 91 (Ser) to 114 (Gin) as shown in SEQ J-D NO: 5 (helix B); amino acid residues 136 (Gin) to 158 (Ala) as shown in SEQ J-D NO: 5 (helix C); and amino acid residues 203 (Thr) to 227 (Ala) as shown in SEQ J_D NO: 5 (helix D). As would be recognized by those skilled in the art, the corresponding nucleotides encoding these regions can be found in SEQ J-D NOS: 4 and 6. Furthermore, the present invention includes an isolated polypeptide comprising a sequence of amino acid residues as shown in SEQ J-D NO: 5 from residue 1 to residue 243. In other aspects, the present invention includes a fusion polypeptide comprising a four-helix bundle cytokine wherein at least one or more of helices A, B, C, or D within the polypeptide comprise a sequence of amino acid residues selected from the group consisting of: (a) amino acid residues 38 (Leu) to 60 (Glu) as shown in SEQ ID NO: 5; (b) amino acid residues 91 (Ser) to 114 (Gin) as shown in SEQ J-D NO: 5; (c) amino acid residues 136 (Gin) to 158 (Ala) as shown in SEQ J-D NO: 5; and (d) amino acid residues 203 (Thr) to 227 (Ala) as shown in SEQ J-D NO: 5. In another embodiment, at least two of helices A, B, C, or D within the fusion polypeptide comprises a sequence of amino acids selected from the group consisting of: (a) amino acid residues 38 (Leu) to 60 (Glu) as shown in SEQ ID NO: 5; (b) amino acid residues 91 (Ser) to 114 (Gin) as shown in SEQ J-D NO: 5; (c) amino acid residues 136 (Gin) to 158 (Ala) as shown in SEQ ID NO: 5; and (d) amino acid residues 203 (Thr) to 227 (Ala) as shown in SEQ ID NO: 5. In other aspects, polynucleotide molecules encoding the polypeptides and fusion polypeptides described herein are provided using the corresponding nucleotide sequences as shown in SEQ J-D NOS: 1, 3, 4, and 6. These nucleotide sequences include polynucleotide molecules as shown in SEQ J-D NO: 4 from nucleotide 35 to nucleotide 766 or SEQ J-D NO: 6 from nucleotide 1 to nucleotide 729. The present invention includes expression vectors comprising the following operably linked elements: a transcription promoter; a DNA segments encoding polypeptides described herein, and a transcription terminator. Also provided are cultured cells into which has been introduced the expression vectors, and express the DNA segments. The present invention provides methods of making a protein comprising: culturing a cell into which has been introduced the expression vectors described herein under conditions whereby the DNA segment is expressed and the polypeptide is produced; and recovering the protein from the cell. In other aspects, the present invention includes antibodies that specifically binds to the polypeptides described herein. The present invention includes methods of using the polynucleotides and polypeptides provided herein. These include a method of detecting the presence of an RNA encoding SEQ J-D NO: 5 in a biological sample, comprising the steps of : (a) contacting a zalpha51 nucleic acid probe under hybridizing conditions with either (i) test RNA molecules from the biological sample, or (ii) nucleic acid molecules synthesized from the RNA molecules, wherein the probe has a nucleotide sequence comprising either a portion of the nucleotide sequence of the nucleic acid molecule of claim 17, or its complement, and (b) detecting the formation of hybrids of the nucleic acid probe with either the test RNA molecules or the synthesized nucleic acid molecules, wherein the presence of the hybrids indicates the presence of RNA encoding SEQ ID NO: 5 in the biological sample. In another embodiment, the biological sample is taken from a mammal with a neuromuscular disorder, or the mammal has a locomotion disorder. Also included is a method of detecting the presence of a polypeptide as shown in SEQ J-D NO: 5, or portion thereof, in a biological sample, comprising the steps of: (a) contacting the biological sample with an antibody, or an antibody fragment, of claim 34, wherein the contacting is performed under conditions that allow the binding of the antibody or antibody fragment to the biological sample, and (b) detecting any of the bound antibody or bound antibody fragment. In another aspect, the present invention includes a method for detecting a genetic abnormality in a patient, comprising: obtaining a genetic sample from a patient; producing a first reaction product by incubating the genetic sample with a polynucleotide comprising at least 14 contiguous nucleotides of SEQ ID NO:l or the complement of SEQ J-D NO:l, under conditions wherein said polynucleotide will hybridize to complementary polynucleotide sequence; visualizing the first reaction product; and comparing said first reaction product to a control reaction product from a wild type patient, wherein a difference between said first reaction product and said control reaction product is indicative of a genetic abnormality in the patient. Other methods include a method for detecting liver tissue in a patient sample, comprising: obtaining a tissue or biological sample from a patient; incubating the tissue or biological sample with an antibody as described herein under conditions wherein the antibody binds to its complementary polypeptide in the tissue or biological sample; visualizing the antibody bound in the tissue or biological sample; and comparing levels and localization of antibody bound in the tissue or biological sample from the patient to a non-liver control tissue or biological sample, wherein an increase in the level or localization of antibody bound to the patient tissue or biological sample relative to the non-liver control tissue or biological sample is indicative of liver tissue in a patient sample. Also included is a method for detecting liver tissue in a patient sample, comprising: obtaining a tissue or biological sample from a patient; labeling a polynucleotide comprising at least 14 contiguous nucleotides of SEQ ID NO:5 or the complement of SEQ ID NO:5; incubating the tissue or biological sample with under conditions wherein the polynucleotide will hybridize to complementary polynucleotide sequence; visualizing the labeled polynucleotide in the tissue or biological sample; and comparing the level and localization of labeled polynucleotide hybridization in the tissue or biological sample from the patient to a control non-liver tissue or biological sample, wherein an increase in the level or localization of the labeled polynucleotide hybridization to the patient tissue or biological sample relative to the control non-liver tissue or biological sample is indicative of liver tissue in a patient sample. The invention is further illustrated by the following non-limiting examples. Examples Example 1 An expression plasmid containing all or part of a polynucleotide encoding zalpha51 is constructed via homologous recombination. A fragment of zalpha51 cDNA is isolated by PCR using the polynucleotide sequence of SEQ ID NO: 1 with flanking regions at the 5' and 3' ends corresponding to the vector sequences flanking the zalpha51 insertion point. The primers for PCR each include from 5' to 3' end: 40 bp of flanking sequence from the vector and 17 bp corresponding to the amino and carboxyl termini from the open reading frame of zalpha51. Ten μl of the 100 μl PCR reaction mixture is run on a 0.8% low- melting-temperature agarose (SeaPlaque GTG®; FMC BioProducts. Rockland, ME) gel with 1 x TBE buffer for analysis. The remaining 90 μl of the reaction misture is precipitated with the addition of 5 μl 1 M NaCl and 250 μl of absolute ethanol. The plasmid pZMP6, which has been cut with Smal, is used for recombination with the PCR fragment. Plamid pZMP6 is a mammalian expression vector containing an expression cassette having the cytomegalovirus immediate early promoter, multiple restriction sites for insertion of coding sequences, a stop codon, and a human growth hormone terminator; an E. coli origin of replication; a mammalian selectable marker expression unit comprising an S V40 promoter, enhancer and origin of replication, a DHFR gene, and the SV40 terminator; and URA3 and CEN-ARS sequences required for selection and replication in S. cerevisiae. It was constructed from pZP9 (deposited at the American Type Culture Collection, 10801 University Boulevard, Manassas, VA 20110-2209, under Accession No. 98668) with the yeast genetic elements taken from pRS316 (deposited at the American Type Culture Collection, 10801 University Boulevard, Manassas, VA 20110-2209, under Accession No. 77145), an internal ribosome entry site (IRES) element from poliovirus, arid the extracellular domain of CD8 truncated at the C-terminal end of the transmembrane domain. One hundred microliters of competent yeast (S. cerevisiae) cells are independently combined with 10 μl of the various DNA mixtures from above and transferred to a 0.2-cm electroporation cuvette. The yeast/DNA mixtures are electropulsed using power supply (BioRad Laboratories, Hercules, CA) settings of 0.75 kV (5 kV/cm), ∞ ohms, 25 μF. To each cuvette is added 600 μl of 1.2 M sorbitol, and the yeast is plated in two 300-μl aliquots onto two URA-D plates and incubated at 30°C. After about 48 hours, the Ura + yeast transformants from a single plate are resuspended in 1 ml H2O and spun briefly to pellet the yeast cells. The cell pellet is resuspended in 1 ml of lysis buffer (2% Triton X-100, 1% SDS, 100 mM NaCl, 10 mM Tris, pH 8.0, 1 mM EDTA). Five hundred microliters of the lysis mixture is added to an Eppendorf tube containing 300 μl acid-washed glass beads and 200 μl phenol-chloroform, vortexed for 1 minute intervals two or three times, and spun for 5 minutes in an Eppendorf centrifuge at maximum speed. Three hundred microliters of the aqueous phase is transferred to a fresh tube, and the DNA is precipitated with 600 μl ethanol (EtOH), followed by centrifugation for 10 minutes at 4°C. The DNA pellet is resuspended in 10 μl H2O. Transformation of electrocompetent E. coli host cells (Electromax DH10B™ cells; obtained from Life Technologies, Inc., Gaithersburg, MD) is done with 0.5-2 ml yeast DNA prep and 40 μl of cells. The cells are electropulsed at 1.7 kN, 25 μF, and 400 ohms. Following electroporation, 1 ml SOC (2% Bacto™ Tryptone (Difco, Detroit, MI), 0.5% yeast extract (Difco), 10 mM ΝaCl, 2.5 mM KC1, 10 mM MgCl 2 , 10 mM MgSO 4 , 20 mM glucose) is plated in 250-μl aliquots on four LB AMP plates (LB broth (Lennox), 1.8% Bacto™ Agar (Difco), 100 mg/L Ampicillin). Individual clones harboring the correct expression construct for zalpha51 are identified by restriction digest to verify the presence of the zalpha51 insert and to confirm that the various DΝA sequences have been joined correctly to one another. The inserts of positive clones are subjected to sequence analysis. Larger scale plasmid DΝA is isolated using a commercially available kit (QIAGEΝ Plasmid Maxi Kit, Qiagen, Valencia, CA) according to manufacturer's instructions. The correct construct is designated pZMP6/zalpha51. Example 2 CHO DG44 cells (Chasin et al, Som. Cell. Molec. Genet. 12:555-666, 1986) are plated in 10-cm tissue culture dishes and allowed to grow to approximately 50% to 70% confluency overnight at 37°C, 5% CO2, in Ham's F12/FBS media (Ham's F12 medium (Life Technologies), 5% fetal bovine serum (Hyclone, Logan, UT), 1% L-glutamine (JRH Biosciences, Lenexa, KS), 1% sodium pyruvate (Life Technologies)). The cells are then transfected with the plasmid zalpha51/pZMP6 by liposome-mediated transfection using a 3:1 (w/w) liposome formulation of the polycationic lipid 2,3-dioleyloxy-N-[2(sperininecarboxamido)ethyl]-N,N-dimethyl-l- propaniminium-trifluoroacetate and the neutral lipid dioleoyl phosphatidylethanolamine in membrane-filetered water (Lipofectamine™ Reagent, Life Technologies), in serum free (SF) media formulation (Ham's F12, 10 mg/ml transferrin, 5 mg/ml insulin, 2 mg/ml fetuin, 1% L-glutamine and 1% sodium pyruvate). Zalpha51/pZMP6 is diluted into 15-ml tubes to a total final volume of 640 μl with SF media. 35 μl of Lipofectamine™ is mixed with 605 μl of SF medium. The resulting mixture is added to the DNA mixture and allowed to incubate approximately 30 minutes at room temperature. Five ml of SF media is added to the DNA:Lipofectamine™ mixture. The cells are rinsed once with 5 ml of SF media, aspirated, and the DNA:Lipofectamine™ mixture is added. The cells are incubated at 37°C for five hours, then 6.4 ml of Ham's F12/10% FBS, 1% PSN media is added to each plate. The plates are incubated at 37°C overnight, and the DNA:Lipofectamine™ mixture is replaced with fresh 5% FBS/Ham's media the next day. On day 3 post- transfection, the cells are split into T-175 flasks in growth medium. On day 7 postransfection, the cells are stained with FITC-anti-CD8 monoclonal antibody (Pharmingen, San Diego, CA) followed by anti-FlTC-conjugated magnetic beads (Miltenyi Biotec). The CD8-positive cells are separated using commercially available columns (mini-MACS columns; Miltenyi Biotec) according to the manufacturer's directions and put into DMEM/Ham's F12/5% FBS without nucleosides but with 50 nM methotrexate (selection medium). Cells are plated for subcloning at a density of 0.5, 1 and 5 cells per well in 96-well dishes in selection medium and allowed to grow out for approximately two weeks. The wells are checked for evaporation of medium and brought back to 200 μl per well as necessary during this process. When a large percentage of the colonies in the plate are near confluency, 100 μl of medium is collected from each well for analysis by dot blot, and the cells are fed with fresh selection medium. The supernatant is applied to a nitrocellulose filter in a dot blot apparatus, and the filter is treated at 100°C in a vacuum oven to denature the protein. The filter is incubated in 625 mM Tris-glycine, pH 9.1, 5mM β-mercaptoethanol, at 65°C, 10 minutes, then in 2.5% nonfat dry milk Western A Buffer (0.25% gelatin, 50 mM Tris-HCl pH 7.4, 150 mM NaCl, 5 mM EDTA, 0.05% Igepal CA-630) overnight at 4°C on a rotating shaker. The filter is incubated with the antibody-HRP conjugate in 2.5% non-fat dry milk Western A buffer for 1 hour at room temperature on a rotating shaker. The filter is then washed three times at room temperature in PBS plus 0.01% Tween 20, 15 minutes per wash. The filter is developed with chemiluminescence reagents (ECL™ direct labelling kit; Amersham Corp., Arlington Heights, JL) according to the manufacturer's directions and exposed to film (Hyperfilm ECL, Amersham Corp.) for approximately 5 minutes. Positive clones are trypsinized from the 96-well dish and transferred to 6-well dishes in selection medium for scaleup and analysis by Western blot. Example 3 Full-length zalpha51 protein is produced in BHK cells transfected with pZMP6/zalpha51 (Example 1). BHK 570 cells (ATCC CRL-10314) are plated in 10- cm tissue culture dishes and allowed to grow to approximately 50 to 70% confluence overnight at 37°C, 5% CO 2 , in DMEM/FBS media (DMEM, Gibco/BRL High Glucose; Life Technologies), 5% fetal bovine serum (Hyclone, Logan, UT), 1 mM L- glutamine (JRH Biosciences, Lenexa, KS), 1 mM sodium pyruvate (Life Technologies). The cells are then transfected with pZMP6/zalpha51 by liposome- mediated transfection (using Lipofectamine™; Life Technologies), in serum free (SF) media (DMEM supplemented with 10 mg/ml transferrin, 5 mg/ml insulin, 2 mg/ml fetuin, 1% L-glutamine and 1% sodium pyruvate). The plasmid is diluted into 15-ml tubes to a total final volume of 640 μl with SF media. 35 μl of the lipid mixture is mixed with 605 μl of SF medium, and the resulting mixture is allowed to incubate approximately 30 minutes at room temperature. Five milliliters of SF media is then added to the DNA:lipid mixture. The cells are rinsed once with 5 ml of SF media, aspirated, and the DNA:lipid mixture is added. The cells are incubated at 37°C for five hours, then 6.4 ml of DMEM/10% FBS, 1% PSN media is added to each plate. The plates are incubated at 37°C overnight, and the DNA:lipid mixture is replaced with fresh 5% FBS/DMEM media the next day. On day 5 post-transfection, the cells are split into T-162 flasks in selection medium (DMEM + 5% FBS, 1% L-Gln, 1% NaPyr, 1 μM methotrexate). Approximately 10 days post-transfection, two 150-mm culture dishes of methotrexate-resistant colonies from each transfection are trypsinized, and the cells are pooled and plated into a T-162 flask and transferred to large-scale culture. Example 4 For construction of adenovirus vectors, the protein coding region of human zalpha51 is amplified by PCR using primers that add Pmel and Ascl restriction sites at the 5' and 3' termini respectively. Amplification is performed with a full- length zalpha51 cDNA template in a PCR reaction as follows: one cycle at 95 °C for 5 minutes; followed by 15 cycles at 95°C for 1 min., 61°C for 1 min., and 72°C for 1.5 min.; followed by 72°C for 7 min.; followed by a 4°C soak. The PCR reaction product is loaded onto a 1.2% low-melting-temperature agarose gel in TAE buffer (0.04 M Tris-acetate, 0.001 M EDTA). The zalpha51 PCR product is excised from the gel and purified using a commercially available kit comprising a silica gel mambrane spin column (QIAquick® PCR Purification Kit and gel cleanup kit; Qiagen, Inc.) as per kit instructions. The PCR product is then digested with Pmel and Ascl, phenol/chloroform extracted, EtOH precipitated, and rehydrated in 20 ml TE (Tris/EDTA pH 8). The zalpha51 fragment is then ligated into the Pmel- Ascl sites of the transgenic vector pTG12-8 and transformed into E. coli DH10B™ competent cells by electroporation. Vector pTG12-8 was derived from p2999B4 (Palmiter et al., Mol Cell Biol. 13:5266-5275, 1993) by insertion of a rat insulin II intron (ca. 200 bp) and polylinker (Fse ITPme I Asc I) into the Nru I site. The vector comprises a mouse metallothionein (MT-1) promoter (ca. 750 bp) and human growth hormone (hGH) untranslated region and polyadenylation signal (ca. 650 bp) flanked by 10 kb of MT-1 5' flanking sequence and 7 kb of MT-1 3' flanking sequence. The cDNA is inserted between the insulin II and hGH sequences. Clones containing zalpha51 are identified by plasmid DNA miniprep followed by digestion with Pmel and Ascl. A positive clone is sequenced to insure that there were no deletions or other anomalies in the construct. DNA is prepared using a commercially available kit (Maxi Kit, Qiagen, Inc.), and the zalpha51 cDNA is released from the pTG12-8 vector using Pmel and Ascl enzymes. The cDNA is isolated on a 1% low melting temperature agarose gel and excised from the gel. The gel slice is melted at 70μC, and the DNA is extracted twice with an equal volume of Tris-buffered phenol, precipitated with EtOH, and resuspended in 10 μl H2O. The zalpha51 cDNA is cloned into the EcoRV-AscI sites of a modified pAdTrack-CMV (He, T-C. et al., Proc. Natl. Acad. Sci. USA 95:2509-2514, 1998). This construct contains the green fluorescent protein (GFP) marker gene. The CMV promoter driving GFP expression is replaced with the SV40 promoter, and the SV40 polyadenylation signal is replaced with the human growth hormone polyadenylation signal. In addition, the native polylinker is replaced with Fsel, EcoRV, and Ascl sites. This modified form of pAdTrack-CMV is named pZyTrack. Ligation is performed using a commercially available DNA ligation and screening kit (Fast-Link® kit; Epicentre Technologies, Madison, WI). Clones containing zalpha51 are identified by digestion of mini prep DNA with Fsel and Ascl. In order to linearize the plasmid, approximately 5 μg of the resulting pZyTrack zalpha51 plasmid is digested with Pmel. Approximately 1 μg of the linearized plasmid is cotransformed with 200 ng of supercoiled pAdEasy (He et al., ibid.) into E. coli BJ5183 cells (He et al., ibid.). The co-transformation is done using a Bio-Rad Gene Pulser at 2.5 kN, 200 ohms and 25 μFa. The entire co-transformation mixture is plated on 4 LB plates containing 25 μg/ml kanamycin. The smallest colonies are picked and expanded in LB/kanamycin, and recombinant adenovirus DNA is identified by standard DNA miniprep procedures. The recombinant adenovirus miniprep DNA is transformed into E. coli DH10B™ competent cells, and DNA is prepared using a Maxi Kit (Qiagen, Inc.) aaccording to kit instructions. Approximately 5 μg of recombinant adenoviral DNA is digested with Pad enzyme (New England Biolabs) for 3 hours at 37°C in a reaction volume of 100 μl containing 20-30U of Pad. The digested DNA is extracted twice with an equal volume of phenol/chloroform and precipitated with ethanol. The DNA pellet is resuspended in 10 μl distilled water. A T25 flask of QBI-293A cells (Quantum Biotechnologies, Inc. Montreal, Qc. Canada), inoculated the day before and grown to 60-70% confluence, is transfected with the Pad digested DNA. The Pad-digested DNA is diluted up to a total volume of 50 μl with sterile HBS (150mM NaCl, 20mM HEPES). J-n a separate tube, 20 μl of lmg/ml N-[l-(2,3-Dioleoyloxy)propyl]-N,N,N- trimethyl-ammonium salts (DOTAP) (Boehringer Mannheim, Indianapolis, IN) is diluted to a total volume of 100 μl with HBS. The DNA is added to the DOTAP, mixed gently by pipeting up and down, and left at room temperature for 15 minutes. The media is removed from the 293A cells and washed with 5 ml serum-free minimum essential medium (MEM) alpha containing ImM sodium pyruvate, 0.1 mM MEM non-essential amino acids, and 25mM HEPES buffer (reagents obtained from Life Technologies, Gaithersburg, MD). 5 ml of serum-free MEM is added to the 293A cells and held at 37°C. The DNA/lipid mixture is added drop-wise to the T25 flask of 293A cells, mixed gently, and incubated at 37°C for 4 hours. After 4 hours the media containing the DNA/lipid mixture is aspirated off and replaced with 5 ml complete MEM containing 5% fetal bovine serum. The transfected cells are monitored for GFP expression and formation of foci (viral plaques). Seven days after transfection of 293A cells with the recombinant adenoviral DNA, the cells express the GFP protein and start to form foci (viral "plaques"). The crude viral lysate is collected using a cell scraper to collect all of the 293 A cells. The lysate is transferred to a 50-ml conical tube. To release most of the virus particles from the cells, three freeze/thaw cycles are done in a dry ice/ethanol bath and a 37°C waterbath. The crude lysate is amplified (Primary (1°) amplification) to obtain a working "stock" of zalpha51 rAdV lysate. Ten 10cm plates of nearly confluent (80- 90%) 293 A cells are set up 20 hours previously, 200 ml of crude rAdV lysate is added to each 10-cm plate, and the cells are monitored for 48 to 72 hours for CPE (cytopathic effect) under the white light microscope and expression of GFP under the fluorescent microscope. When all of the 293A cells show CPE, this stock lysate is collected and freeze/thaw cycles performed as described above. A secondary (2°) amplification of zalpha51 rAdV is then performed. Twenty 15-cm tissue culture dishes of 293A cells are prepared so that the cells are 80- 90% confluent. All but 20 ml of 5% MEM media is removed, and each dish is inoculated with 300-500 ml of the 1° amplified rAdv lysate. After 48 hours the 293 A cells are lysed from virus production, the lysate is collected into 250-ml polypropylene centrifuge bottles, and the rAdV is purified. NP-40 detergent is added to a final concentration of 0.5% to the bottles of crude lysate in order to lyse all cells. Bottles are placed on a rotating platform for 10 minutes agitating as fast as possible without the bottles falling over. The debris is pelleted by centrifugation at 20,000 X G for 15 minutes. The supernatant is transferred to 250-ml polycarbonate centrifuge bottles, and 0.5 volume of 20% PEG8000/2.5 M NaCl solution is added. The bottles are shaken overnight on ice. The bottles are centrifuged at 20,000 X G for 15 minutes, and the supernatant is discarded into a bleach solution. Using a sterile cell scraper, the white, virus/PEG precipitate from 2 bottles is resuspended in 2.5 ml PBS. The resulting virus solution is placed in 2-ml microcentrifuge tubes and centrifuged at 14,000 X G in the microcentrifuge for 10 minutes to remove any additional cell debris. The supernatant from the 2-ml microcentrifuge tubes is transferred into a 15-ml polypropylene snapcap tube and adjusted to a density of 1.34 g/ml with CsCl. The solution is transferred to 3.2-ml, polycarbonate, thick-walled centrifuge tubes and spun at 348,000 X G for 3-4 hours at 25μC. The virus forms a white band. Using wide-bore pipette tips, the virus band is collected. A commercially available ion-exchange columns (e.g., PD-10 columns ^ prepacked with Sephadex® G-25M; Pharmacia Biotech, Piscataway, NJ) is used to desalt the virus preparation. The column is equilibrated with 20 ml of PBS. The virus is loaded and allowed to run into the column. 5 ml of PBS is added to the column, and fractions of 8-10 drops are collected. The optical densities of 1:50 dilutions of each fraction are determined at 260 nm on a spectrophotometer. Peak fractions are pooled, and the optical density (OD) of a 1:25 dilution is determined. OD is converted to virus concentration using the formula: (OD at 260nm)(25)(l.l x 10 12 ) = virions/ml. To store the virus, glycerol is added to the purified virus to a final concentration of 15%, mixed gently but effectively, and stored in aliquots at -80μC. A protocol developed by Quantum Biotechnologies, Inc. (Montreal, Canada) is followed to measure recombinant virus infectivity. Briefly, two 96-well 4 tissue culture plates are seeded with 1 X 10 293 A cells per well in MEM containing 2% fetal bovine serum for each recombinant virus to be assayed. After 24 hours 10- fold dilutions of each virus from 1X10 -2 to 1X10 -14 are made in MEM containing 2% fetal bovine serum. 100 μl of each dilution is placed in each of 20 wells. After 5 days at 37°C, wells are read either positive or negative for CPE, and a value for "Plaque Forming Units/ml" (PFU) is calculated. Example 5 Transgenic zalpha51 mice Trangenic animals expressing zalpha51 genes are producing using adult, fertile males (studs) (B6C3fl, 2-8 months of age (Taconic Farms, Germantown, NY)), vasectomized males (duds) (CDl, 2-8 months, (Taconic Farms)), prepubescent fertile females (donors) (B6C3fl, 4-5 weeks, (Taconic Farms)) and adult fertile females (recipients) (CDl, 2-4 months, (Taconic Farms)). The donors are acclimated for 1 week and then injected with approximately 8 IU/mouse of Pregnant Mare's Serum gonadotrophin (Sigma, St. Louis, MO) IP., and 46-47 hours later, 8 IU/mouse of human Chorionic Gonadotropin (hCG (Sigma)) IP. to induce superovulation. Donors are mated with studs subsequent to hormone injections. Ovulation generally occurs within 13 hours of hCG injection. Copulation is confirmed by the presence of a vaginal plug the morning following mating. Fertilized eggs are collected under a surgical scope (Leica MZ12 Stereo Microscope, Leica, Wetzlar, DE). The oviducts are collected and eggs are released into urinanalysis slides containing hyaluronidase (Sigma). Eggs are washed once in hyaluronidase, and twice in Whitten's W640 medium (Table 4) that has been incubated with 5% CO2, 5% O2, and 90% N2 at 37°C. The eggs are then stored in a 37°C/5% CO2 incubator until microinjection. 10-20 micrograms of plasmid DNA containing a cDNA of the zalpha51gene is linearized, gel-purified, and resuspended in 10 mM Tris pH 7.4, 0.25 mM EDTA pH 8.0, at a final concentration of 5-10 nanograms per microliter for microinjection. Plasmid DNA is microinjected into harvested eggs contained in a drop of W640 medium overlaid by warm, CO2 -equilibrated mineral oil. The DNA is drawn into an injection needle (pulled from a 0.75mm ID, 1mm OD borosilicate glass capillary), and injected into individual eggs. Each egg is penetrated with the injection needle, into one or both of the haploid pronuclei. Picoliters of DNA are injected into the pronuclei, and the injection needle withdrawn without coming into contact with the nucleoli. The procedure is repeated until all the eggs are injected. Successfully microinjected eggs are transferred into an organ tissue-culture dish with pregassed W640 medium for storage overnight in a 37°C/5% CO2 incubator. The following day, 12-17 healthy 2-cell embryos from the previous day's injection are transferred into the recipient. The swollen ampulla is located and holding the oviduct between the ampulla and the bursa, a nick in the oviduct is made with a 28 g needle close to the bursa, making sure not to tear the ampulla or the bursa. The embryos are implanted through this nick, and by holding onto the peritoneal wall, the reproductive organs are guided back into the abdominal cavity. The recipients are returned to cages in pairs, and allowed 19-21 days gestation. After birth, 19-21 days postpartum is allowed before weaning. The weanlings are sexed and placed into separate sex cages, and a 0.5 cm biopsy (used for genotyping) is snipped off the tail with clean scissors. Genomic DNA is prepared from the tail snips using a Qiagen Dneasy kit following the manufacturer's instructions. Genomic DNA is analyzed by PCR using primers designed to the human growth hormone (hGH) 3' UTR portion of the transgenic vector. A region unique to the human sequence was identified from an alignment of the human and mouse growth hormone 3' UTR DNA sequences, ensuring that the PCR reaction does not amplify the mouse sequence. Primers which amplify a 368 base pair fragment of hGH and primers which hybridize to vector sequences and amplify the cDNA insert, are often used along with the hGH primers. In these experiments, DNA from animals positive for the transgene will generate two bands, a 368 base pair band corresponding to the hGH 3' UTR fragment and a band of variable size corresponding to the cDNA insert. Once animals are confirmed to be transgenic (TG), they may be back- crossed into an inbred strain by placing a TG female with a wild-type male, or a TG male with one or two wild-type female(s). As pups are born and weaned, the sexes are separated, and their tails snipped for genotyping. Analysis of the mRNA expression level of each transgene is done using an RNA solution hybridization assay or real-time PCR on an ABI Prism 7700 (PE Applied Biosystems, Inc., Foster City, CA) following manufacturer's instructions. Table 4 WHΓΓTEN'S 640 MEDIA mgs/200m mgs/500/ml NaCl 1280 3200 KC1 72 180 KH 2 PO 4 32 80 MgSO 4 «7H 2 O 60 150 Glucose 200 500 Ca 2+ Lactate 106 265 K Penn 15 37.5 Streptomycin SO 10 25 NaHCO 3 380 950 Na Pyruvate 5 12.5 H 2 0 200 500 EDTA 100 μl 250 μl 5%> Phenol Red 200 μl 500 μl BSA 600 1500 All reagents are available from Sigma. Example 6 Histological evaluation of zalpha51 transgenic mice Three 4 week old male zalpha51 transgenics and an age-matched nontransgenic male control from the same litter were necropsied and their tissues microscopically evaluated. Prior to death, 2 of the mice were noticed to have abnormal locomotion. The two affected mice rapidly developed rigor mortis after being humanely euthanitized by anesthetic overdose. Following euthanasia, the mice were immediately necropsied and tissues collected into 10% neutral buffered formalin. After fixation, the following tissues were routinely processed, sectioned at 5μ and stained with hematoxylina and eosin for histopathology: brain, spinal cord, skull including teeth, nasal passages, eye and Harderian gland, liver, heart, kidney, lung, thymus, spleen, mesenteric lymph node, salivary gland, pancreas, stomach, small and large intestine, accessory sex glands, prostate, vas deferens, epididymis, testis, pituitary, adrenal, trachea, esophagus, skin, skeletal muscle, sciatic nerve, femur and bone marrow. Tissues were evaluated under a light microscope (Nikon Eclipse E600, Nikon Corporation, Tokyo). On microscopic examination of the brain, the transgenics with ambulatory difficulties were found to have severe necrosis in the cerebellar folia (encephalomalacia). The necrotic cells were primarily located in the granular and Purkinje cell layers of the cerebellum. Acute perivasculitis was observed in the pons and cerebellar folia in both mice and in the ventral spinal cord of one of the mice. Both mice also had diffuse moderate lymphoid depletion in the thymus, necrosis of scattered acinar cells in the pancreas (common in transgenics with the metallothionein promoter) and minimal degeneration of the sciatic nerve. One of the mice also had mild swelling of scattered fibers in the skeletal muscle of the rear leg (myopathy). No significant changes were found in the tissues of the nontransgenic control or third transgenic mouse. Expression analysis revealed that the two affected mice were high expressors while the third transgenic had no detectable expression of zalpha51. The microscopic changes found in the central nervous system were extremely uncommon in mice. The microscopic appearance of the lesions was similar to those observed in chicks with vitamin E deficiency. A form of spinocerebellar ataxia in humans has been associated with a severe deficiency of this vitamin. The rapid onset of rigor mortis in these transgenic mice suggested a metabolic derangement. Mitochondrial disorders can cause metabolism-related changes in a variety of tissue (e.g. the MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke)). These data ^ suggest that zalpha51 may have some role in inducing apoptosis, based on the cell death observed in the cerebellum and other tissues. Example 7 Expression of zalpha51 A panel of cDNAs from human tissues is screened for zalpha51 expression using PCR. The panel is made in-house and contained 94 marathon cDNA and cDNA samples from various normal and cancerous human tissues and cell lines is shown in Table 5, below. The cDNAs come from in-house libraries or marathon cDNAs from in-house RNA preps, Clontech RNA, or Invitrogen RNA. The marathon cDNAs are made using the marathon-Ready™ kit (Clontech, Palo Alto, CA) and QC tested with clathrin primers, and then diluted based on the intensity of the clathrin band. To assure quality of the panel samples, three tests for quality control (QC) are run: (1) To assess the RNA quality used for the libraries, the in-house cDNAs are tested for average insert size by PCR with vector oligonucleotides that are specific for the vector sequences for an individual cDNA library; (2) Standardization of the concentration of the cDNA in panel samples is achieved using standard PCR methods to amplify full length alpha tubulin or G3PDH cDNA using a 5' vector oligonucleotide and 3' alpha tubulin specific oligonucleotide primer or 3' G3PDH specific oligo primer; and (3) a sample is sequenced to check for possible ribosomal or mitochondrial DNA contamination. The panel is set up in a 96-well format that included a human genomic DNA (Clontech, Palo Alto, CA) positive control sample. Each well contains approximately 0.2-100 pg/μl of cDNA. The PCR reactions are set up using appropriate oligonucleotides, TaKaRa Ex Taq™ (TAKARA Shuzo Co LTD, Biomedicals Group, Japan), and Rediload dye (Research Genetics, Inc., Huntsville, AL). The typical amplification is carried out as follows: 1 cycle at 94°C for 2 minutes, 35 cycles of 94°C for 30 seconds, 66.3°C for 30 seconds and 72°C for 30 seconds, followed by 1 cycle at 72°C for 5 minutes. About 10 μl of the PCR reaction product is subjected to standard Agarose gel electrophoresis using a 4% agarose gel. The correct predicted DNA fragment size is observed in: (1) fetal liver; (2) normal tissues from liver, placenta, spinal cord, spleen, testis, and trachea; and (3) cancerous tissues from esophagus, stomach, kidney, liver, lung, ovary, and rectum. Furthermore, Northern data confirmed that expression of a 1.35 kb mRNA was highly expressed in liver. Table 5 Example 8 Tissue Distribution of mouse zalpha51 in tissue panels using PCR A panel of cDNAs from murine tissues was screened for mouse zalpha51 expression using PCR. The panel was made in-house and contained 72 marathon cDNA and cDNA samples from various normal and cancerous murine tissues and cell lines are shown in Table 6, below. The cDNAs came from in-house libraries or marathon cDNAs from in-house RNA preps, Clontech RNA (Clontech, Palo Alto, CA), or Invitrogen RNA (Invitrogen, Carlsbad, CA). The mouse marathon cDNAs were made using the marathon-Ready kit (Clontech) and quality control tested with mouse transferrin receptor primers, and then diluted based on the intensity of the transferrin band. To assure quality of the amplified library samples in the panel, three tests for quality control (QC) were run: (1) To assess the RNA quality used for the libraries, the in-house cDNAs were tested for average insert size by PCR with vector oligonucleotides that were specific for the vector sequences for an individual cDNA library; (2) Standardization of the concentration of the cDNA in panel samples was achieved using standard PCR methods to amplify full length alpha tubulin or G3PDH cDNA using a 5' vector oligonucleotides, and 3' alpha tubulin specific oligonucleotide primer, or 3' G3PDH specific oligo primer, and (3) a sample was sent to sequencing to check for possible ribosomal or mitochondrial DNA contamination. The panel was set up in a 96-well format that included a mouse genomic DNA (Clontech) positive control sample. Each well contained approximately 0.2-100 pg/μl of cDNA. The PCR amplification used Advantage 2 Taq Polymerase™ (Clontech), and Rediload dye (Research Genetics, Inc., Huntsville, AL). The amplification was carried out as follows: 1 cycle at 94°C for 2 minutes; 35 cycles of 94°C for 10 seconds, 66°C for 20 seconds and 68°C for 30 seconds, followed by 1 cycle at 68°C for 7 minutes. About 5 μl of the PCR reaction product was subjected to standard Agarose gel electrophoresis using a 4% E-gel. The correct predicted DNA fragment size was observed in all the samples except for Cell Line 229, OC10B, one Testis sample, and possibly ρ388Dl. The DNA fragment for Adipocytes was excised and purified using a Gel Extraction Kit (Qiagen, Chatsworth, CA) according to manufacturer's instructions. Fragments were confirmed by sequencing to show that they were indeed mouse zalpha51. Table 6 From the foregoing, it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

Claims: CLA S What is claimed is: 1. An isolated polypeptide comprising at least nine contiguous amino acid residues of SEQ J-D NO:2. 2. The isolated polypeptide of claim 1 having from 15 to 232 amino acid residues. 3. The isolated polypeptide of claim 2, wherein said at least nine contiguous amino acid residues of SEQ ID NO:2 are operably linked via a peptide bond or polypeptide linker to a second polypeptide selected from the group consisting of maltose binding protein and an immunoglobulin constant region. 4. The isolated polypeptide of claim 1 comprising at least 30 contiguous residues of SEQ J-D NO:2. 5. The isolated polypeptide of claim 1 comprising residues 43-206 of SEQ J-D NO:2. 6 The isolated polypeptide of claim 1 comprising residues 18-232 of SEQ ID NO: 2. 7. An isolated polypeptide comprising a sequence of amino acid residues selected from the group consisting of: (a) residues 1-17 of SEQ J-D NO:2; (b) residues 43-57 of SEQ ID NO:2; (c) residues 98-112 of SEQ ID NO:2; (d) residues 126-140 of SEQ ID NO:2; and (e) residues 192-206 of SEQ ID NO:2. 8. An isolated polypeptide comprising a sequence of amino acid residues as shown in SEQ J-D NO: 5 from residue 1 to residue 243. 9. An isolated polypeptide comprising a sequence of amino acid residues selected from the group consisting of: (a) from 15 to 23 contiguous amino acid residues comprising residues 54 (Ala) to 60 (Glu) as shown in SEQ J-D NO: 5; (b) from 15 to 26 contiguous amino acid residues comprising residues 109 (He) to 114 (Gin) as shown in SEQ J-D NO: 5; (c) from 15 to 23 contiguous amino acid residues comprising residues 146 (Asp) to 151 (Leu) as shown in SEQ ID NO: 5; and (d) from 15 to 27 contiguous amino acid residues comprising residues 205 (Arg) to 217 (Ala) as shown in SEQ JD NO: 5. 10. An isolated polypeptide comprising a sequence of amino acid residues selected from the group consisting of: (a) amino acid residues 38 (Leu) to 60 (Glu) as shown in SEQ ID NO: 5; (b) amino acid residues 91 (Ser) to 114 (Gin) as shown in SEQ ID NO: 5; (c) amino acid residues 136 (Gin) to 158 (Ala) as shown in SEQ ID NO: 5; and (d) amino acid residues 203 (Thr) to 227 (Ala) as shown in SEQ ID NO: 5. 11. A fusion polypeptide comprising a four-helix bundle cytokine wherein at least one or more of helices A, B, C, or D within the polypeptide comprise a sequence of amino acid residues selected from the group consisting of: (a) amino acid residues 38 (Leu) to 60 (Glu) as shown in SEQ J-D NO: 5; (b) amino acid residues 91 (Ser) to 114 (Gin) as shown in SEQ J-D NO: 5; (c) amino acid residues 136 (Gin) to 158 (Ala) as shown in SEQ J-D NO: 5; and (d) amino acid residues 203 (Thr) to 227 (Ala) as shown in SEQ JD NO: 5. 12. The fusion polypeptide of claim 11, wherein at least two of helices A, B, C, or D within the polypeptide comprises a sequence of amino acids selected from the group consisting of: (a) amino acid residues 38 (Leu) to 60 (Glu) as shown in SEQ J-D NO: 5; (b) amino acid residues 91 (Ser) to 114 (Gin) as shown in SEQ ID NO: 5; (c) amino acid residues 136 (Gin) to 158 (Ala) as shown in SEQ J-D NO: 5; and (d) amino acid residues 203 (Thr) to 227 (Ala) as shown in SEQ J-D NO: 5. 13. An isolated polynucleotide molecule comprising a sequence of nucleotides that encode a polypeptide selected from the group consisting of: residues 1-17 of SEQ J-D NO:2; residues 43-57 of SEQ ID NO:2; residues 98-112 of SEQ ID NO:2; residues 126-140 of SEQ ID NO:2; and residues 192-206 of SEQ ID NO:2. 14. An isolated polynucleotide molecule comprising a sequence of nucleotides that encode a polypeptide that is at least nine contiguous amino acid residues of SEQ ID NO:2. 15. The isolated polynucleotide molecule of claim 14 comprising residues 43-206 of SEQ ID NO:2. 16. The isolated polynucleotide molecule of claim 14 comprising residues 18-232 of SEQ TD NO: 2. 17. An isolated polynucleotide molecule comprising a sequence of nucleotides that encode a polypeptide as shown in SEQ J-D NO: 5 from residue 1 to residue 243. 18. An isolated polynucleotide molecule comprising a sequence of nucleotides that encode a sequence of amino acid residues selected from the group consisting of: (a) from 15 to 23 contiguous amino acid residues comprising residues 54 (Ala) to 60 (Glu) as shown in SEQ J-D NO: 5; (b) from 15 to 26 contiguous amino acid residues comprising residues 109 (lie) to 114 (Gin) as shown in SEQ J-D NO: 5; (c) from 15 to 23 contiguous amino acid residues comprising residues 146 (Asp) to 151 (Leu) as shown in SEQ J-D NO: 5; and (d) from 15 to 27 contiguous amino acid residues comprising residues 205 (Arg) to 217 (Ala) as shown in SEQ J-D NO: 5. 19. An isolated polynucleotide molecule comprising a sequence of nucleotides that encode a sequence of amino acid residues selected from the group consisting of: (a) amino acid residues 38 (Leu) to 60 (Glu) as shown in SEQ ID NO: 5; (b) amino acid residues 91 (Ser) to 114 (Gin) as shown in SEQ JD NO: 5; (c) amino acid residues 136 (Gin) to 158 (Ala) as shown in SEQ ID NO: 5; and (d) amino acid residues 203 (Thr) to 227 (Ala) as shown in SEQ ID NO: 5. 20. An expression vector comprising the following operably linked elements: a transcription promoter; a DNA segment encoding a polypeptide comprising a sequence of amino acid residues selected from the group consisting of: residues 1-17 of SEQ ID NO:2; residues 43-57 of SEQ ID NO:2; residues 98-112 of SEQ JD NO:2; residues 126-140 of SEQ ID NO:2; and residues 192-206 of SEQ ID NO:2; and a transcription terminator. 21. An expression vector comprising the following operably linked elements: a transcription promoter; a DNA segment encoding a polypeptide comprising a sequence of amino acid residues as shown in SEQ ID NO: 5 from residue 1 to residue 243; and a transcription terminator. 22. An expression vector comprising the following operably linked elements: a transcription promoter; a DNA segment encoding a polypeptide comprising a sequence of amino acid residues selected from the group consisting of: (a) from 15 to 23 contiguous amino acid residues comprising residues 54 (Ala) to 60 (Glu) as shown in SEQ JD NO: 5; (b) from 15 to 26 contiguous amino acid residues comprising residues 109 (lie) to 114 (Gin) as shown in SEQ JD NO: 5; (c) from 15 to 23 contiguous amino acid residues comprising residues 146 (Asp) to 151 (Leu) as shown in SEQ ID NO: 5; and (d) from 15 to 27 contiguous amino acid residues comprising residues 205 (Arg) to 217 (Ala) as shown in SEQ ID NO: 5; and a transcription terminator. 23. An expression vector comprising the following operably linked elements: a transcription promoter; a DNA segment encoding a polypeptide comprising a sequence of amino acid residues selected from the group consisting of: (a) amino acid residues 38 (Leu) to 60 (Glu) as shown in SEQ JD NO: 5; (b) amino acid residues 91 (Ser) to 114 (Gin) as shown in SEQ ID NO: 5; (c) amino acid residues 136 (Gin) to 158 (Ala) as shown in SEQ ID NO: 5; and (d) amino acid residues 203 (Thr) to 227 (Ala) as shown in SEQ ID NO: 5; and a transcription terminator. 24. A cultured cell into which has been introduced the expression vector of claim 21, wherein said cell expresses said DNA segment. 25. A cultured cell into which has been introduced the expression vector of claim 22, wherein said cell expresses said DNA segment. 26. A cultured cell into which has been introduced the expression vector of claim 23, wherein said cell expresses said DNA segment. 27. An isolated polynucleotide molecule as shown in SEQ ID NO: 1 from nucleotide 269 to nucleotide 924, or SEQ JD NO: 1 from nucleotide 278 to nucleotide 924. 28. An isolated polynucleotide molecule as shown in SEQ ID NO: 4 from nucleotide 35 to nucleotide 766 or SEQ ID NO: 6 from nucleotide 1 to nucleotide 729. 30. A method of making a protein comprising: culturing a cell into which has been introduced the expression vector of claim 20 under conditions whereby the DNA segment is expressed and the polypeptide is produced; and recovering the protein from the cell. 31. A method of making a protein comprising: culturing a cell into which has been introduced the expression vector of claim 21 under conditions whereby the DNA segment is expressed and the polypeptide is produced; and recovering the protein from the cell. 32. A method of making a protein comprising: culturing a cell into which has been introduced the expression vector of claim 22 under conditions whereby the DNA segment is expressed and the polypeptide is produced; and recovering the protein from the cell. 3 * 3. An antibody that specifically binds to the polypeptide of claim 7. 34. An antibody that specifically binds to the polypeptide of claim 8. 35. A method of detecting the presence of an RNA encoding SEQ JD NO: 5 in a biological sample, comprising the steps of : (a) contacting a nucleic acid probe as shown in SEQ ID NO: 4, or portions thereof, under hybridizing conditions with either (i) test RNA molecules from the biological sample, or (ii) nucleic acid molecules synthesized from the RNA molecules, wherein the probe has a nucleotide sequence comprising either a portion of the nucleotide sequence of the nucleic acid molecule of claim 17, or its complement, and (b) detecting the formation of hybrids of the nucleic acid probe with either the test RNA molecules or the synthesized nucleic acid molecules, wherein the presence of the hybrids indicates the presence of RNA encoding SEQ JD NO: 5 in the biological sample. 36. The method of claim 35, wherein the biological sample is taken from a mammal with a neuromuscular disorder. 38. The method of claim 35, wherein the mammal has a locomotion disorder. 39. A method of detecting the presence of a polypeptide as shown in SEQ JD NO: 5, or portion thereof, in a biological sample, comprising the steps of: (a) contacting the biological sample with an antibody, or an antibody fragment, of claim 34, wherein the contacting is performed under conditions that allow the binding of the antibody or antibody fragment to the biological sample, and (b) detecting any of the bound antibody or bound antibody fragment. 40. The method of claim 39, wherein the biological sample is taken from a mammal with a neuromuscular disorder. 41. The method of claim 39, wherein the mammal has a locomotion disorder. 42. A method for detecting a genetic abnormality in a patient, comprising: obtaining a genetic sample from a patient; producing a first reaction product by incubating the genetic sample with a polynucleotide comprising at least 14 contiguous nucleotides of SEQ ID NO: 5 or the complement of SEQ ID NO:5, under conditions wherein said polynucleotide will hybridize to complementary polynucleotide sequence; visualizing the first reaction product; and comparing said first reaction product to a control reaction product from a wild type patient, wherein a difference between said first reaction product and said control reaction product is indicative of a genetic abnormality in the patient. 43. A method for detecting liver tissue in a patient sample, comprising: obtaining a tissue or biological sample from a patient; incubating the tissue or biological sample with an antibody of claim 34 under conditions wherein the antibody binds to its complementary polypeptide in the tissue or biological sample; visualizing the antibody bound in the tissue or biological sample; and comparing levels and localization of antibody bound in the tissue or biological sample from the patient to a non-liver control tissue or biological sample, wherein an increase in the level or localization of antibody bound to the patient tissue or biological sample relative to the non-liver control tissue or biological sample is indicative of liver tissue in a patient sample. 44. A method for detecting liver tissue in a patient sample, comprising: obtaining a tissue or biological sample from a patient; labeling a polynucleotide comprising at least 14 contiguous nucleotides of SEQ JD NO:5 or the complement of SEQ JD NO:5; incubating the tissue or biological sample with under conditions wherein the polynucleotide will hybridize to complementary polynucleotide sequence; visualizing the labeled polynucleotide in the tissue or biological sample; and comparing the level and localization of labeled polynucleotide hybridization in the tissue or biological sample from the patient to a control non-liver tissue or biological sample, wherein an increase in the level or localization of the labeled polynucleotide hybridization to the patient tissue or biological sample relative to the control non-liver tissue or biological sample is indicative of liver tissue in a patient sample.

Inventors: CONKLIN DARRELL C, PRESNELL SCOTT R, CONKLIN, DARRELL, C., PRESNELL, SCOTT, R.
Applicants: ZYMOGENETICS INC, ZYMOGENETICS, INC.
Application year: 2001
Main classification: C12N15
IPC codes: A61K38, C07K14, C12N15