始丰微型牛GH基因的遗传特性分析

Geneticfeatures at the dwarfing site on the GH gene in Shifeng miniature cattle(Bos Indicus)

为考察始丰微型牛生长激素(GH)基因的遗传特性及与其小体型的关联性,采集12头始丰微型牛、5头雷琼牛和4头蒙古牛血液,提取血样的基因组DNA,PCR扩增GH基因编码区外显子5部分区段,序列测定后采用DNAstar、Meg Align软件进行序列分析和同源比对分析,结果表明:所检测3个家牛群体的GH基因部分区段含2个多态位点。始丰微型牛在GH基因649位存在一个SNP:C649A,矮小型Brahman在该位点的等位基因为C649,正常体型普通牛为A649,正常体型瘤牛及雷琼牛为C649,而在641位除了矮小型Brahman的等位基因为T641,其他牛均无多态,均为C。本研究在GH基因第5外显子649位处的A→C有突变,但未发生氨基酸的改变。而矮小型Brahman在641位与其他群体相比有C→T的突变,使苏氨酸(Thr)变为蛋氨酸(Met),引起蛋白质构象及功能发生变异。始丰微型牛在649位有AA、AB两种基因型个体,其基因型频率分别0.8333、0.1667,该位点上基因型与体型大小无关。本研究表明始丰微型牛不含有报道的矮化基因(T641),且GH基因座上的SNP(C649A)似乎与小体型无关联,其矮小化机制可能来源于GH或生长激素受体(GHR)基因座上的其他位点,本研究为进一步阐明始丰微型牛的矮化机制作了铺垫。

To explore the genetic property of GH gene and its relationship with small body size in Shifeng miniature cattle,we collected the blood samples of 12 Shifeng miniature cattle,5 Leiqiong cattle and 4 Menggu cattle,extracted the genomic DNA,amplified a partial region on the exon 5 of the GH gene by PCR,and conducted sequencing and homologous sequence analysis by comparing with other populations,using the DNAstar and MegAlign software.The results showed that there were two polymorphic sites,641 and 649,on the gene fragments among these three populations.Shifeng miniature cattle had only one SNP:C649 A,while dwarfing Bramhman had one allele C,the normal Bos Taurus had A649,and the normal zebu and Leiqiong had C649 with no polymorphism.At the site 641,also regarded as the dwarfing site,the dwarfing Brahman had the dwarfing allele,T641,and all the other populations had C641 with no polymorphism.The SNP C649 A would not cause the change in amino acid,while at position 641,the dwarfing Brahman had a mutation from C to T,causing the change in amino acid from Thr to Met,compared with the other cattle breeds,which led to a change in protein conformation and function.The SNP C649 A defined two genotypes,AA and AB,with frequencies of 0.8333 and 0.1667,respectively,but the genotype had no relationship with the body size.This study indicated that Shifeng miniature cattle did not contain the dwarfing allele(T 641) reported in the literature,and SNP(C649 A) appeared to be unrelated with the small body size.This research laid the foundation for further exploration into the dwarfing mechanism of Shifeng miniature cattle.