Domestic yak is a special animal species in Qinghai-tibet plateau, which has good adaptability to the extreme environment of high cold. At present, we do not know much about reproductive physiology of yak, especially spermatogenesis.Spermatogenesis is a complex process of cell specialization, which includes mitosis of spermatocyte, meiosis of spermatocyte and sperm deformation.Sustained and stable spermatogenesis depend on the formation and maintenance of spermatogonial stem cells. Mammalian spermatogonial stem cells are derived from fetal progenitor cells that develop into spermatogonal stem cells and differentiated spermatogonial cells in the gonad after birth.
In the present study, we examined transcriptomes of testes from domestic yaks at four different stages (3, 5, 8 and 24 months of age) and attempted to identify genes that are associated with key developmental events of spermatogenesis. Histological analyses showed that the most advanced germ cells within seminiferous tubules of testes from 3, 5, 8 and 24 months old yaks were gonocytes, spermatogonia, spermatocytes and elongated spermatids, respectively. RNA-sequencing (RNA-seq) analyses revealed that 11904, 4381 and 2459 genes were differentially expressed during the gonocyte to spermatogonia transition, the mitosis to meiosis transition and the meiosis to post-meiosis transition. Further analyses identified a list of candidate genes than may regulate these important cellular processes. CXCR4, a previously identified SSC niche factor in mouse, was one of the up-regulated genes in the 5 months old yak testis. Results of immunohistochemical staining confirmed that CXCR4 was exclusively expressed in gonocytes and a subpopulation of spermatogonia in the yak testis.
The related paper "Gene expression dynamics during the gonocyte to spermatogonial transition and spermatogenesis in the domestic yak" was published online in the TOP Journal of Animal Science and Biotechnology on July 12, 2019. Doctoral candidate Wang Guowen is the first author of the paper, and researcher Yang Qien is the corresponding author.The research was supported by the national key research and development plan (2016YFC0501805), the key research and transformation project of Qinghai provincial department of science and technology (2017-nk-154), the STS project of the Chinese Academy of Sciences (kfj-sts-qyzd-113), and the "100-Talant plan" of the Chinese Academy of Sciences.The discipline group relies on the key laboratory of plateau adaptation and evolution of Chinese Academy of Sciences and Qinghai key laboratory of animal ecological genomics.
Paper link: https://jasbsci.biomedcentral.com/articles/10.1186/s40104-019-0360-7
Schematic diagram of yak germ cell development and gene expression differences