Yu, B.; Yang, Y.; Li, Y.; Gao, R.; Ma, M.; Wang, X.

The Tibetan sheep is a typical hypoxia-tolerant mammal, which lives on the plateau, an altitude of between 2,500 and 5,000 meters above sea level, the study of its hypoxic adaptation mechanism provides reference for exploring the hypoxic adaptation mechanism of other animals. To grope for the genetic mechanism of adaptation to hypoxic environment at the transcriptional level in Tibetan sheep testicular tissue, and to identify candidate genes and key pathways related to sheep adaptation. Histological observation of testicular tissues from two sheep breeds was carried out using hematoxylin-eosin (HE) conventional staining. A total of 277 differentially expressed genes (DEGs) were authenticated at high altitude Tibetan sheep (ZYH) and low altitude Tibetan sheep (ZYM) by RNA sequencing technology (RNA-Seq), which included 165 up-regulated genes and 112 down-regulated genes. Functional analyses revealed several terms and pathways, such as were closely related with testis adaptation to plateau. Several genes (including GGT5, AGTR2, EDN1, LPAR3, CYP2C19, IGFBP3, APOC3 and PKC1) were remarkably enriched in several pathways and terms, which may impact the Plateau adaptability of sheep by adjusting its reproductive activity and sexual maturation, and protecting Sertoli cells, various spermatocytes and spermatogenesis processes. The results make a reasonable case for a better understanding of the molecular mechanisms of adaptation to altitude in sheep.