The Genetic Diversity Of MSTN Gene In Horses And Donkeys

The myostatin gene (MSTN), also called Growth differentiation factor8, belongs to theTGF-β (Transforming Growth Factor-beta) superfamily as a negative regulator of skeletalmuscle growth. Variants of the MSTN gene are associated with muscle hypertrophyphenotypes, growth traits and performance traits in a range of mammalian species. To explorethe genetic diversity of MSTN gene in horses and donkeys, fifteen horse breeds and thirteendonkey breeds in China were analyzed in this study. Nine primer pairs were designed toPCR-amplify and sequence partial MSTN gene based on horse MSTN gene sequence fromGenBank. The sequence contains promoter region,5’-UTR, exon-1, intron-1and exon-2ofMSTN gene. PCR–RFLP methods were applied to identify and genotype the single nucleotidepolymorphisms (SNPs).1The genetic diversity of MSTN gene in horsesThe horse partial MSTN gene with3247bp was sequenced. Six SNPs (g.26Tâ†'C,g.156Tâ†'C, g.587Aâ†'G, g.598Câ†'T, g.1485Câ†'T, g.2115Aâ†'G) were detected in MSTN genein15Chinese horse breeds. Of all, g.26Tâ†'C, g.156Tâ†'C were in the promoter region,g.587Aâ†'G, g.598Câ†'T in the5’-UTR region, and g.1485Câ†'T, g.2115Aâ†'G in intron-1ofequine MSTN gene. Six mutations are digested with RsaΙ, SspI, TasΙ, BsmΙ, AccΙ and ScaΙ,respectively. g.26Tâ†'C, g.587Aâ†'G and g.1485Câ†'T have natural endonuclease restrictionsites, which can be as new PCR-RFLP genetic markers.Two novel SNPs includingg.587Aâ†'G and g.598Câ†'T were first detected in this study. g.2115Aâ†'G is associated withracing performances. We predated that most of Chinese horse breeds were more suitable forlong-distance races. Datong, Guanzhong, Guizhou and Yushu breeds with GG genotype werethe candidate horse breeds at short-distance races. Thirteen haplotypes were determined basedon six mutations. The haplotype H1was the most ancient in all breeds, which indicatedabundant genetic diversity of MSTN gene in Chinese horse breeds. The result showedg.156T>C and g.2115A>G deviated from the Hardy–Weinberg equilibrium, and Tajima testindicated population expansion and/or purifying selection in most of horse breeds.2The genetic diversity of MSTN gene in donkeysThe partial MSTN gene with3242bp was first sequenced in donkeys. Four SNPsincluding g.65Tâ†'C (promoter), g.872Aâ†'G (exon-1), g.2017Gâ†'A (intron-1) and g.2395 Câ†'G (intron-1) were detected. g.65Tâ†'C and g.2017Gâ†'A were digested with SmiΙ andMboΙ, respectively, which can be as new PCR-RFLP markers. g.872Aâ†'G only existed inXinjiang donkeys. The study revealed that six haplotypes were obtained based on fourmutations (LH1-LH6), which indicated abundant genetic diversity of MSTN gene in Chinesedonkey breeds. The haplotype H1was the most dominant and ancient in all breeds. In Chinesedonkey breeds, g.2115Aâ†'G deviated from the Hardy–Weinberg equilibrium. PositiveTajima’s D signified a decrease in population size and/or balancing selection balancingselection occurring at these loci.3The variation of MSTN gene between populationsAMOVA analysis indicated most of the genetic variance was attributable to differencesamong individuals in Chinese horse breeds and donkey breeds. Genetic variation caused bythe difference between breeds had little influence. The distribution of genotypes andhaplotypes had no obvious breed and type differences. The MP tree of MSTN gene amongdifferent species was constructed. Yak and cattle clustered, then goat and sheep clustered, nexthorse and donkey clustered, and pig, mouse and chicken belonged to a single branch,respectively. These are consistent with the fact of species differentiation. It can be used as thebasis to determine the genetic relationship between distantly related species.The study plays an important role to protect genetic resources of Chinese horses anddonkeys, and provides a reliable theoretical basis for the preservation, exploration andutilization in Chinese horse and donkey genetic resources.