Genetic Diversity Of KIT Gene And Y Chromosome In Horses

Horse is the herbivorous livestock which was domesticated4000years ago.Genetic diversity and the origins in horses were mainly focused on the mitochondrialgenome and autosome. However, only limited papers on horse Y chromosome werepublicated. In this dissertation, equine KIT gene and Y chromosome genetic diversitywere analyzed.1、Genetic diversity and origins in Horse Y chromosomeTwenty nine pairs of horse Y chromosome-specific primers were designed,13Chinese domestic breeds (Baise, Balikun, Chaidamu, Chakouyi, Datong, Debao pony,Guanzhong, Guizhou, Kazakh, Hequ, Ningqiang, Yanqi and Yushu) and23foreignbreeds and Equus przewalskii, with905individuals in all, were analyzed to detect theY-SNP and paternal origins. The results were as follows.(1) For the first time, a Y-SNP (C�'A) was detected in Chinese horses. In326samples from13Chinese domestic horse breeds,12samples from four breeds includingBaise Hequ, Yanqi and Debao pony indicated the unique Y-SNP.(2) Two Y chromosome haplotypes weredetermined in the Y-SNP marker in Chinesehorses. The sequence containing the A base was named ECAY1haplotype, containing theC base named ECAY2haplotype. Pyrosequencing technique corrobrated that12individuals belonged to ECAY2haplotype, the remaining samples belonged to ECAY1haplotype in Chinese domestic horses. Twenty three foreign domestic horse breeds onlyindicated ECAY1haplotype. Przewalskii was a multiple copy gene in this Y-SNP locus.(3) The ECAY2haplotype was mainly distributed in Northwest China. The resultsshowed that the ECAY2haplotype was present in the southwest horse, Hequ horse,mongolian horse and Hasake horse type, respectively, but ECAY2haplotype was mainlydistributed in Northwest China. The reason was likely associated with Silk Road andTea-Horse ancient Road.4）There was a second paternal origin in Chinese domestic horses. One Y-SNP wasfound in Chinese domestic horses, including two haplotype, suggested multi-paternalorigins in Chinese domestic horse, and rejected the viewpoint of the single paternalorigin in horses. 2、 The KIT gene genetic diversity in Chinese domestic horsesIn total,21exons and part of the intronic regions in KIT gene were sequenced for649samples of15Chinese domestic horse breeds. Six SNP were found, one was in5’-UTR region (g.91214T>G), two in intron6and20(g.143245T>G, g.171356C>G),and the other three in exon15,20and21(g.164297C>T, g.170189C>T,g.171471G>A, p.Ala960Thr), respectively.649individuals were genotyped usingPCR-RFLP method. Three genotypes (TT, CT and CC) were found in exon15, three(TT, CT and CC) in exon20and two (GG and GA) in exon21, and all of the wildtype as the dominant genotype. The genetic diversity analysis showed that theGuanzhong breed had both the highest nucleotide diversity (π=0.051%) andhaplotype diversity (h=0.724), whereas the Chaidamu breed had both the lowestnucleotide diversity (π=0.024%) and haplotype diversity (h=0.397), respectively.