Absence of Sirtuin 1 impairs the testicular development in cattleyak by inactivating SF-1.

Cattleyak, which are interspecific hybrids between cattle and yak, display much higher growth performances than yak. However, F1 male cattleyak are infertile due to defective testicular development. Sirtuin 1 (SIRT1) is a histone deacetylase that is essential for various biological processes, while the roles of testicular SIRT1 in yak and cattleyak are still poorly understood. Here, we found that SIRT1 was localized in various kinds of yak testicular cells except elongated spermatids while it was deficient in cattleyak testis. Further studies indicated that cattleyak testis exhibited decreased histone acetylation levels on H3 and H4. One of SIRT1 co-factors, steroidogenic factor-1 (SF-1), was lost in cattleyak testis at protein level. Expressions of several SF-1 target genes responsible for Sertoli cell development and steroidogenesis, including STAR, CYP11A1, CYP26B1, FDX1 and HSD3B, decreased significantly in cattleyak testis. In addition, SIRT1-mediated P53 acetylation was not responsible for the cell apoptosis in cattleyak testis. Taken together, our results suggested the deficiency of SIRT1 in yak testis caused inactivation of SF-1 and the impairment of testicular development. This research provides theoretical bases for understanding the mechanism of cattleyak sterility and gives new insights in revealing the roles of SIRT1 in regulating yak testicular development.