The Association of Genes Hemoglobin and EPAS1 with Hypoxia Adaptation in the Tibetan Sheep

PurposeTo screen the hypoxic positive selection sites of hemoglobin and EPAS1 gene, and to analyze the genetic effects of these loci, revealing the role of the two genes in hypoxia adaptation in Tibetan sheep.

MethodHemoglobin and EPAS1 were used as candidate genes to screen the dominant SNPs in Tibetan sheep, and the expanded samples were used to detect the altitudinal trend sites and blood physiological parameters in three populations of altitudinal gradients (1 500, 2 500 and 3 500 m) for analyzing the association between genotypes and blood physiological indexes.

ResultsSix and twelve SNPs were respectively detected in the Tibetan sheep hemoglobin and EPAS1 genes, respectively. Those SNPs of hemoglobin were synonymous, and their gene frequencies did not show an altitudinal trend. The allele (T) frequency of the C871T loci in the 8^th intron of EPAS1 gene showed a significant altitudinal trend. The TT genotype of this locus had a genetic effect of increasing hemoglobin content (HGB), erythrocyte mean hemoglobin content (MCH) and blood viscosity (P<0.05). This mutation resulted in loss of GATA (hematopoietic regulatory factor) binding sites based on the prediction of transcription factor binding site. The G1001A site in the 9^th exon of EPAS1 gene was a nonsynonymous mutation VAL352MET, but the frequency of the mutant allele was only 0.34. There was no significant association between the three genotypes and the blood physiological indexes (P>0.05), and no change in protein structure function was found through protein structure homology prediction.

ConclusionThe frequency of the allele (T) of C871T locus in the 8^th intron of the EPAS1 gene increased with altitudes, and its TT genotype significantly increased the hemoglobin concentration (14.14 g/L) in Tibetan sheep, suggesting a potentially associated site for high hemoglobin concentration.