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Association of novel single-nucleotide polymorphisms of the vascular endothelial growth factor-A gene with high-altitude adaptation in yak (Bos grunniens)

Author(s): X.Y. Wu1,2, C.N. Liang1,2, X.Z. Ding1,2, X. Guo1,2, P.J. Bao1,2, M. Chu1,2, W.B. Liu1,2 and P. Yan1,2

Vascular endothelial growth factor-A gene (VEGF-A) is a key regulator of angiogenesis and an endothelial cell mitogen that plays an important role in high-altitude adaptation. In this study, we detected 2 novel single-nucleotide polymorphisms (SNPs) of VEGF-A by screening for genetic variation in 700 individuals of 3 domestic Chinese yak breeds - namely Gannan (GN), Datong (DT), and Tianzhu white (TZW) - using polymerase chain reaction-restriction fragment length polymorphism and DNA sequencing techniques. GN and DT yaks live at high altitude and TZW yaks live at low altitude on the Qinghai-Tibetan Plateau. SNP g.8430T>C is located in intron 4 of VEGF-A. SNP g.14853G>A is located in the 3' untranslated region of VEGF-A. Frequencies of the GA and AA genotypes and the A allele of SNP g.14853G>A observed in GN and DT yaks were significantly higher than that in TZW yaks (P < 0.01). No significant difference among the breeds was observed for SNP g.8430T>C. The frequency of haplotype TA was significantly higher (P < 0.01), whereas the frequency of TG (P < 0.01) was significantly lower in GN and DT yaks compared with that in TZW yaks. The 2 SNPs were in moderate linkage disequilibrium in GN and DT yaks, but not in TZW yaks. The fixation index (FST) pairwise value was significantly different among the breeds studied. The neutral test result indicated that the region between the 2 SNPs may have been subjected to positive or balancing selection, and the high-altitude hypoxia environment might be the main determinant for selection. These results suggest that VEGF-A might contribute to the high-altitude adaptability of yak.