Polymorphisms Of Bovine Mx Gene And Its Correlation With Somatic Cell Score Of Holstein Cows

Mx gene was first found in inbred mouse strains of A2G in1962, and its encodingantiviral protein with GTPase activity was induced by interferon type Ⅰ(α/β) and Interferontype Ⅲ(λ). The known researchs show thatMx genes have rich polymorphism and Mxproteins have antiviral activity against RNA viruses, even DNA viruses. The results of celltransfection tests in vitro show that cattle Mx1gene and Mx2gene all have resistance forvesicular stomatitis virus (VSV), and the disease-resistant activity is different among severalgenotypes of Mx gene. In this study,31pair primers were designed based on previouslypublished bovine Mx gene sequences, to amplify and sequence exons of Mx1and Mx2genesof12Chinese cattle breeds, Qinghai Yaks and Holstein cows in Shaanxi Province. PCR-directsequencing and PCR-RFLP methods were applied to analyze the polymorphisms of Mx genes.In addition, the correlation between Mx gene polymorphisms and somatic cell score (SCS)among Holstein cows in Shannxi Province was analyzed based on least square method bySPSS software. The main results were as follows:1. There is rich polymorphism in the Mx1gene of Qinghai Yak. Four SNPs were detectedincluding exon5(g.847433C/T), exon6(g.848181A/G), exon7(g.851208A/G) andexon14(g.866793T/G), which were all missense mutations. Three kinds of genotypes werecharacterized at SNP sites located in exon5(g.847433C/T), exon6(g.848181A/G) andexon14(g.866793T/G), but in exon7(g.851208A/G) only two kinds of homozygousgenotypes were found.2. Rich polymorphisms were found in Mx1genes and Mx2genes of12Chinese cattlebreeds including Mongolian, Qinchuan, Anxi, Jinnan, Luxi, Jiaxian, Hainan, Zaosheng,Xuanhan, Nanyang, Wannan and Leizhou cattle. Thirteen SNPs including7missensemutations,5synonymous mutations and1nonsense mutation were detected in Mx1gene of12cattle breeds. There were three kinds of genotypes at12SNP sites and two kinds ofhomozygous genotypes in exon1(g.838066C/T). In addition, a deletion mutation of12bpsiting at5’-UTR zone of exon4in the Mx1gene was detected in this study. Furthermore,23 SNPs including11missense mutations,10synonymous mutations and2nonsense mutationswere detected in Mx2gene of12cattle breeds. There are three kinds of genotypes at all SNPsites.3. Four SNPs including3missense mutations and1synonymous mutation were detectedin the Mx1gene of Holstein cows in Shaanxi Province. There were three kinds of genotypes atfour SNP sites and the heterozygote was predominant.11haplotypes (H1-H11) were obtainedbased on four SNP mutations, in which the haplotype H6(0.362) was predominant. Inaddition, a deletion mutation of12bp siting at5’-UTR zone of exon4was detected in thisstudy. The analysis based on the least square method shows that the SCS of individuals withgenotype CT and TT significantly higher than those of individuals with genotype CC (P<0.05),which illustrated that the site is associated with SCS of Holstein cows and it could be used asthe candidate loci of mastitis resistance. In addition, three SNPs including2missensemutations and1synonymous mutation were detected in Mx2gene of Shaanxi Province’sHolstein cows. There were three kinds of genotypes at all SNP sites and heterozygote waspredominant. The Analysis based on the least square method shows that all SNP sites have nocorrelation with the SCS of Holstein cows.In recent years, the structure and function of Mx gene is constantly explored. But theresearch on Mx gene of Chinese local cattle breeds has not yet been reported. In this study, theMx gene polymorphisms of12cattle breeds and Qinghai Yaks were analyzed, which washelpful to the research on the structure and function of Mx genes and its application inpractice in the future. The polymorphisms of Mx gene and its correlation with SCS amongShaanxi Province’s Holstein cows were also analyzed, which would provide fundamentaldatas for the disease-resistant breeding of dairy cow.