Mouse Dnajc5b and Cymg1 genes are new genes that we cloned specifically in mouse testis.Dnajc5b is a homolog of DNAJ(HSP40),subfamily C,and the second of member 5,so named Dnajc5b,which is located on chromosome 3 of mouse and contains five exons with a total length of 947 bp.The reading frame is 597 bp and encodes a total of 199 amino acids.Dnajc5b was specifically expressed in mouse testis as shown by multi-tissue RT-PCR.Dnajc5b was weakly expressed in the first week and the second week after the mice were born,and the expression was enhanced in the third week.The greatest expression was in the eighth week of sexual maturity.At the same time,in situ hybridization results showed that Dnajc5b gene was specifically expressed in mouse spermatogonia,and its expression was positively correlated with testicular development.Cymg1(GenBank accession No.AY600990),which has a full length of 0.78 kb,and contains four exons and three introns,was cloned from a mouse testis cDNA library.The gene is located in the 2G3 area of chromosome 2.The full cDNA encompasses the entire open reading frame,encoding 141 amino acid residues.CYMG1 has a 44%(48/108)identity with mouse CRES and 30%(42/140)identity with mouse cystatin C.Northern blot analysis showed that the Cymg1 is specifically expressed in adult mouse testes.Immunohistochemistry revealed that the CYMG1 protein was expressed in mouse testes spermatogonium,spermatocytes,round spermatids,elongating spermatids and spermatozoa.RT-PCR results also showed that Cymg1 was expressed in mouse testes and spermatogonium.The Cymg1 expression level varied in different developmental stages.The Cymg1 expression level in the testes over different developmental stages correlates with the mouse spermatogenesis and sexual maturation process.