Differential tissue expression of sex steroid-synthesizing enzyme CYP11A1 in male Tibetan sheep ( <i>Ovis aries</i> )

Steroid metabolism is a fundament to testicular development and function. The cytochrome P450, family 11, subfamily A, polypeptide 1 (<i>CYP11A1</i>) is a key rate-limiting enzyme for catalyzing the conversion of cholesterol to pregnenolone. However, despite its importance, what expression and roles of <i>CYP11A1</i> possesses and how it regulates the testicular development and spermatogenesis in Tibetan sheep remains largely unknown. Based on this, we evaluated the expression and localization patterns of <i>CYP11A1</i> in testes and epididymides of Tibetan sheep at three developmental stages (three-month-old, pre-puberty; one-year-old, sexual maturity and three-year-old, adult) by quantitative real-time PCR (qPCR), western blot and immunofluorescence. The results showed that <i>CYP11A1</i> mRNA and protein were expressed in testes and epididymides throughout the development stages and obviously more intense in one- and three-year-old groups than three-month-old group (except for the caput epididymidis). Immunofluorescence assay showed that the CYP11A1 protein was mainly located in Leydig cells and epididymal epithelial cells. In addition, positive signals of CYP11A1 protein were observed in germ cells, epididymal connective tissue and sperms stored in the epididymal lumen. Collectively, these results suggested that the <i>CYP11A1</i> gene might be mainly involved in regulating spermatogenesis and androgen synthesis in developmental Tibetan sheep testis and epididymis.