Ga. Cornwall et Sr. Hann, TRANSIENT APPEARANCE OF CRES PROTEIN DURING SPERMATOGENESIS AND CAPUTEPIDIDYMAL SPERM MATURATION, Molecular reproduction and development, 41(1), 1995, pp. 37-46
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.