TRANSIENT APPEARANCE OF CRES PROTEIN DURING SPERMATOGENESIS AND CAPUTEPIDIDYMAL SPERM MATURATION

In previous studies we identified an epididymal gene that exhibits hom ology to the cystatin family of cysteine protease inhibitors. The expr ession of this gene, termed CRES (cystatin-related epididymal and sper matogenic), was shown to be highly restricted to the proximal caput ep ididymal epithelium with less expression in the testis and no expressi on in the 24 other tissues examined. In this report, studies were carr ied out to examine CRES gene expression in the testis as well as to ch aracterize the CRES protein in the testis and epididymis. In situ hybr idization experiments revealed that within the testis CRES gene expres sion is stage-specific during spermatogenesis acid is exclusively expr essed by the round spermatids of Stages VII-VIII and the early elongat ing spermatids of Stages IX and X. Immunohistochemical studies demonst rated that CRES protein was transiently expressed in both the testis a nd epididymis. Within the testis the protein was localized to the elon gating spermatids, whereas within the epididymis CRES protein was excl usively synthesized by the proximal caput epithelium and then secreted into the lumen. Surprisingly, the secreted CRES protein had completel y disappeared from the epididymal lumen by the distal caput epididymid is. Western blot analysis of testicular and epididymal proteins showed that the CRES antibody specifically recognized a predominant 19 kDa C RES protein and a less abundant 14 kDa form. These observations sugges t that the CRES protein performs a specialized role during sperm devel opment and maturation. (C) 1995 Wiley-Liss, Inc.