a library containing cdna or genomic clones can be screened with one or more polynucleotide probes based upon seq id no 1 using standard methods see for example ausubel 1995 at pages 6 1 to 6 11 nucleic acid molecules that encode a zvnr4 gene can also be obtained using the polymerase chain reaction pcr with oligonucleotide primers having nucleotide sequences that are based upon the nucleotide sequences of the zvnr4 gene as described herein general methods for screening libraries with pcr are provided by for example yu et al u201c use of the polymerase chain reaction to screen phage libraries u201d in methods in molecular biology vol 15 pcr protocols current methods and applications white ed pages 211 215 humana press inc 1993 moreover techniques for using pcr to isolate related genes are described by for example preston u201c use of degenerate oligonucleotide primers and the polymerase chain reaction to clone gene family members u201d in methods in molecular biology vol 15 pcr protocols current methods and applications white ed pages 317 337 humana press inc 1993 anti zvnr4 antibodies produced as described below can also be used to isolate dna sequences that encode zvnr4 genes from cdna libraries for example the antibodies can be used to screen u03bbgt11 expression libraries or the antibodies can be used for immunoscreening following hybrid selection and translation see for example ausubel 1995 at pages 6 12 to 6 16 margolis et al u201c screening u03bb expression libraries with antibody and protein probes u201d in dna cloning.