Expression and localization of BMP6/SMAD5 in Tibetan sheep testis

Bone morphogenetic protein 6 (BMP6) is one of the bone morphogenetic proteins (BMPs), which can promote DNA synthesis and cell proliferation in Sertoli cells. SMAD family member 5 (SMAD5) is a downstream signaling mediator that inhibits apoptosis. BMP6 and SMAD5 play key roles in male reproduction. To study the role of BMP6/SMAD5 in testicular development and spermatogenesis of Tibetan sheep (Ovis aries), Tibetan sheep at different developmental stages (3 months, 1 year, and 3 years old) were used as the research objects. PCR (Quantitative real time PCR, qRT-PCR), western blot, and immunohistochemical staining were used to detect the expression and distribution patterns of BMP6 and SMAD5 at different developmental stages of Tibetan sheep testis from transcription and translation levels. The results showed that the relative expression and protein expression of BMP6 mRNA in the testis of Tibetan sheep at 1 year (sexual maturity stage) and 3 years (adult stage) were significantly higher than those at 3 months (pre-sexual maturity) (P < 0.01), and both of them tended to be stable after sexual maturity. With increasing age, the relative expression of SMAD5 mRNA in the testis of Tibetan sheep decreased significantly (P < 0.01), whereas the expression level of SMAD5 protein increased very significantly (P < 0.01). Both BMP6 and SMAD5 proteins were expressed in sertoli cells and leydig cells at different developmental stages of Tibetan sheep testis. It is speculated that the BMP6/SMAD5 pathway plays a role in the process of spermatogenesis.