Cloning, characterization and identification of Rcet1-v1 and Rcet1-v2, two novel splice variants of mouse Rcet1 related to Cres subgroup of family 2 cystatins.

Cystatins are physiological cysteine proteinase inhibitors. We used digital differential display (DDD) to clone two novel splice variants Rcet1-v1 and Rcet1-v2 which were isolated from adult mouse testis cDNA library. Sequence analysis revealed that Rcet1-v1 and Rcet1-v2 cDNAs are 454 and 610 bp in length, respectively, and each has four exons, but the lengths of their second and third exons are different, with the results that these cDNAs encoded two different putative proteins. The deduced proteins were 88 amino acid residues (RCET1-v1) and 140 residues (RCET1-v2) in length and have one potential signal peptide and one cystatin domain, respectively, but lack part critical consensus sites important for cysteine protease inhibition. These characteristics are seen in CRES subgroup, which related to the family 2 cystatins and primarily expressed in reproductive tract. RT-PCR analysis showed that Rcet1-v1 and Rcet1-v2 were specifically expressed in adult mouse testis, epididymis and cerebrum, but higher in testis than in epididymis and cerebrum. RT-PCR analysis also showed that Rcet1-v1 and Rcet1-v2 were specifically expressed in adult mouse pituitary and spermatogonium, but not expressed in spermatozoa. Results of in situ hybridization showed that Rcet1 gene expressed abundantly in mouse spermatogonium, spermatocytes and round spermatids; did not expressed in spermatozoa. At mouse testis different development stages, Rcet1-v1 and Rcet1-v2 were expressed very low from postnatal 1 day to postnatal 3 weeks; after postnatal 4 weeks, expressed steadily increased from postnatal 4 to 7 weeks, highest in postnatal 7 to 8 weeks, then keeping on the expressing level of postnatal 6 weeks in postnatal 13-57 weeks. All these indicated that Rcet1-v1 and Rcet1-v2 primarily expressed in mouse male reproductive tract and may play important roles in mouse spermatocytes and round spermatid development. Rcet1-v1 and Rcet1-v2 may be new members of Cres subgroup of the family 2 cystatins.

Cloning of a novel gene, Cymg1, related to family 2 cystatins and expressed at specific stages of mouse testis development.

We have cloned a novel gene, Cymg1 (GenBank accession number AY600990), from a mouse testis cDNA library. Cymg1 is located in 2G3 of mouse chromosome 2. The cDNA includes an open reading frame that encodes 141 amino acid residues. The encoded polypeptide has a cysteine protease inhibitor domain found in the family 2 cystatins but lacks critical consensus sites important for cysteine protease inhibition. These characteristics are seen in the proteins of the CRES subfamily of the family 2 cystatins which are expressed specifically in the reproductive tract. CYMG1 protein shows 44% identity with mouse CRES and 30% identity with mouse cystatin C. Northern blot analysis showed that the Cymg1 gene was specifically expressed in adult mouse testis. RT-PCR also showed that Cymg1 was expressed in testis and spermatogonial cells. Cymg1 expression level varied in the different developmental stages of mouse testis, and were coincidental with spermatogenesis and sex maturation. These results indicate that Cymg1 may play important roles in mouse spermatogenesis and sex maturation.