无角牦牛Hesx1基因多态性及其与生长性状的关联分析

Association Analysis of Hesx1 Gene Polymorphism and Growth Traits in Polled Yak

为了研究Hesx1(Homeobox expressed in ES cells)基因单核苷酸多态性(Single nucleotide polymorphisms,SNP)对无角牦牛各时期生长性状的影响,采用PCR-SSCP(Polymerase chain reaction-single strand conformation polymorphism)和DNA测序技术,对364头无角牦牛Hesx1基因hⅠ与hⅡ基因座的遗传多态性进行研究,并进一步分析Hesx1基因多态性对无角牦牛生长性状的遗传效应。结果表明,在hⅠ基因座(5′UTR)第-618位发生单个碱基突变(G→C),出现GG与GC共2种基因型;在hⅡ基因座(Intron1)第+226位发生单个碱基突变(T→C),出现TT与TC共2种基因型。通过与6、12、18月龄无角牦牛的生长性状(体质量、体高、体斜长、胸围)进行关联分析发现,hⅠ基因座对6月龄无角牦牛的体质量、体高、胸围均有极显著影响(P<0.01),但对体斜长影响不显著(P>0.05);对12月龄无角牦牛的体质量有显著影响(P<0.05),对体斜长、胸围均有极显著影响(P<0.01),但对体高影响不显著(P>0.05);对18月龄无角牦牛的体质量有显著影响(P<0.05),对体高、体斜长、胸围均无显著影响(P>0.05)。hⅡ基因座对6月龄无角牦牛的体质量、体高、体斜长、胸围均无显著影响(P>0.05);对12月龄无角牦牛的体质量有极显著影响(P<0.01),对体高、胸围均有显著影响(P<0.05),对体斜长无显著影响(P>0.05);对18月龄无角牦牛的体质量、体高、体斜长、胸围均无显著影响(P>0.05)。与此同时,hⅠ与hⅡ基因座的突变杂合型GC与TC是无角牦牛生长的优势基因型。卡方适合性检验表明,牦牛群体显著偏离哈代-温伯格平衡(P<0.05)。综上,可初步判定hⅠ与hⅡ多态基因座可以作为牦牛辅助育种的分子标记。

In order to study the effect of single nucleotide polymorphisms(SNP) of Hesx 1 gene on growth traits of polled yaks at different stages,PCR-SSCP and DNA sequencing techniques were used in this study.The genetic polymorphisms of hⅠ and hⅡ loci of Hesx 1 gene in 364 yaks were studied,and the genetic effects of Hesx 1 gene polymorphisms on growth traits of polled yaks were analyzed.The results showed that a single base mutation(G→C) occurred at the -618 th position of hⅠ locus (5′UTR),and there were two genotypes of GG and GC.A single base mutation(T→C) occurred at the 226 th position of hⅡ locus(Intron1),and there were two genotypes of TT and TC.By correlation analysis with growth traits(body weight,body height,body oblique length,chest circumference) of 6,12 and 18 months old polled yaks,it was found that hⅠ locus had a very significant effect on body weight,body height and chest cir-cumference of 6 months old polled yaks( P <0.01), but had no significant effect on body oblique length( P >0.05).hⅠ locus had a significant effect on body weight of 12 months old polled yaks( P <0.05),and had a very significant effect on body oblique length and chest circumference( P <0.01).And hⅠ locus had a significant effect on body weight of 18 months old polled yaks( P <0.05), but had no significant effect on body height,body oblique length and chest circumference( P >0.05).hⅡ locus had no significant effect on body weight,body height,body oblique length and chest circumference of 6 months old polled yaks( P >0.05).hⅡ locus had a very significant effect on body weight of 12 months old polled yaks( P <0.01), and had a significant effect on body height and chest circumference( P <0.05),but had no significant effect on oblique length( P >0.05).And hⅡ locus had no significant effects on body weight,body height,body oblique length and chest circumference of 18 months old polled yaks( P > 0.05 ).The heterozygous GC and TC of hⅠ and hⅡ loci were both dominant genotypes.Chi-square fitness test showed that the yak population deviated significantly from the Hardy-Weinberg equilibrium( P < 0.05 ).The results showed that the hⅠ and hⅡ loci could be used as reference for molecular marker-assisted breeding in yak.