Interspecies hybridization exists widely in nature and plays an important role in animal evolution and adaptation. It is commonly recognized that male offspring of interspecies hybrid are often sterile, which presents a crucial way of reproductive isolation. Currently, the mechanisms underlying interspecies hybrid male sterility are not well understood.
Cattle-yak, progeny of yak (Bos grunniens) and cattle (Bos taurus) cross, is a unique animal model for investigating hybrid male sterility. The research Group of Plateau animal’s Reproductive Biology examined expressions of histone methyltransferases (HMTs) and distributions of histone methylations in the yak and cattle-yak testis. Histological examination of seminiferous tubules revealed that gonocytes and spermatocytes were established normally, however, spermatogenesis was arrested at the meiosis phase began at 10 months after birth in the hybrids. SUV420H1 was the only HMT examined showing a significant enrichment in cattle-yak testes at 3 months. Relative expressions of MLL5, SETDB1 and SUV420H1 were increased while SETDB2 and EZH2 were decreased in cattle-yak testes at 10 months. Relative concentrations of MLL5 and SUV420H1 were again increased while EHMT2 and PRDM9 expressions were decreased at 24 months. Immunofluorescent detection of selected histone methylations in cross-sections of testicular tissues or meiotic chromosomes demonstrated that depletion of H3K4me3 and significant enrichment of H3K27me3 and H4K20me3 were observed in Sertoli cells of cattle-yak. Levels and localizations of H3K4me3, H3K9me1, H3K9me3 and H4K20me3 were strikingly different in meiotic chromosomes of cattle-yak spermatocytes. The study highlighted the potential roles of histone methylations in spermatogenic failure and hybrid male sterility.
The result was published in Theriogenology with the title of “The expression of histone methyltransferases and distribution of selected histone methylations in testes of yak and cattle-yak hybrid” on January 7,2020.LI Yongchang, postgraduate student at University of Chinese Academy of Sciences (institute: Northwest Institute of Plateau Biology, CAS) is the first author of the paper, and Prof. YANG Qien is the corresponding author. The research is funded by the General Program of the National Natural Science Foundation of China (31972574) and the Strategic Leading Science and Technology Program of the Chinese Academy of Sciences (2016YFC0501805). The subject group relies on the Key Laboratory of Plateau Biological Adaptation and Evolution of the Chinese Academy of Sciences and the Key Laboratory of Animal Ecogenomics in Qinghai Province.
