After a long period of adaptive evolution, Tibetan sheep have adapted to the plateau environment in terms of genetics, physiology and biochemistry, but the mechanism of hypoxia adaptation has not been fully elucidated, and the functional genes and molecular mechanisms regulating the hypoxia adaptation of Tibetan sheep need to be further studied. In this study, Tibetan sheep were selected as the research object, and the mRNA expression levels of the hypoxa-related gene EPO in heart, lung, kidney, liver, spleen and longissimus dorsi muscle of Hu sheep (100 m) and Tibetan sheep at different altitudes (2500 m, 3500 m, 4500 m) were assessed by RT-qPCR. The SNPs loci were detected by sequencing and Kompetitive Allele-Specific PCR (KASP) technology, then the correlation between genetic polymorphism and blood gas was analyzed. The results show that the expression of the EPO gene was the highest in the kidney, indicating that the expression of EPO gene had tissue differences. The expression levels of the EPO gene in the heart, lung and liver of Tibetan sheep at a 4500 m altitude were significantly higher than those in Hu sheep (p < 0.05), and the levels in the hearts of Tibetan sheep increased with the increase in altitude. Three mutations were identified in the EPO gene, the SNPs (g.855 A > C) in exon 1 and the SNPs (g.1985 T > G and g.2115 G > C) in exon 4, which were named EPO-SNP1, EPO-SNP2 and EPO-SNP3, respectively, and all three SNPs showed three genotypes. Correlation analysis showed that g.2115 G > C sites were significantly correlated with pO2 (p < 0.05), and haplotype combinations were significantly correlated with pO2 (p < 0.05). Thesee results suggest that the expression of the EPO gene is altitude-differentiated and organ-differentiated, and the EPO gene variants have significant effects on pO2, which may be beneficial to the adaptation of Tibetan sheep to hypoxia stress.
Keywords: EPO; SNPs; Tibetan sheep; adaptation; oxygen metabolism.