牛α1-抗胰蛋白酶基因5′侧翼区新SNP的鉴定及其与中国荷斯坦奶牛产奶性状的相关性

Identification of New SNPs in Bovine α1-Antitrypsin Gene 5′ Flanking Region and Their Association with Milk Production Traits in Chinese Holstein Dairy Cattle

以中国荷斯坦奶牛(Chinese Holstein dairy cattle)为对象,以α1-抗胰蛋白酶基因(α1-AT)为候选基因,扩增5′侧翼区668 bp和999 bp的片段并进行测序.首次发现,在+3 142 bp处P1和+4 408 bp处P2分别发生C-T、T-C突变.随后采用PCR-RFLP方法对随机采自6个牛场,共计294头牛进行了检测,遗传变异和产奶性状分析结果显示:2个位点的等位基因在群体中都有分布,且处于中度多态.P1位点A和B等位基因的频率分别为50.34%和49.66%;AA、AB和BB基因型频率分别为23.81%、53.06%和23.13%;P2位点E和F等位基因的频率分别为30.61%和69.39%,EE、EF和FF基因型频率分别为11.90%、37.41%和50.68%.χ2适合性检验表明,该群体在P1位点的突变达到Hardy-Weinberg平衡状态(P>0.05),在P2位点未达到平衡.基因与产奶性状关联分析表明,AB基因型个体产奶量与脂蛋比显著高于AA基因型个体(P<0.05);FF基因型个体乳蛋白率显著高于EF基因型个体(P<0.05);9种单倍型组合与乳脂率、乳蛋白率、体细胞数、产奶量及脂蛋比均存在不同程度相关性.

α1-Antitrypsin（al-AT） gene is a candidate gene for milk production traits in Chinese Holstein dairy cattle. The 668-bp and 999-bp fragments of 5＇ flanking region were amplified by PCR. The C-T and T- C single nueleotide polymorphisms （SNPs） were identified at nucleotide ＋ 3 142 bp and ＋ 4 408 bp by sequencing, respectively. 294 random samples from 6 dairy farms were analyzed by PCR-RFLP. The result suggested that alleles （A and B, E and F） of two loci distributed in the population that showed middle polymorphism. The allele frequencies of A and B （P1） were 50.34 % and 49.66 % separately. The genotype frequencies of AA, AB and BB were 23.81 %, 53.06% and 23.13%, respectively. The allele frequencies of E and F （P2） were 30.61% and 69.39% separately. The genotype frequencies of EE, EF and FF were 11.90%, 37.41% and 50.68%, respectively. The statistical results via χ2 test indicated that P1 sites in the population fitted with Hardy-Weinberg equilibrium （P 〉0.05）, but P2 didn＇ t （ P 〈0.05）. Meanwhile, the effect of polymorphism of α1-AT gene on milk production traits was analyzed. The results indicated that the cows with genotype AB showed higher milk yield and fat protein ratio than those with genotype AA （ P 〈 0.05） ; with genotype FF showed higher protein percentage than those with genotype EF （ P 〈 0.05） ; different genotypes had no significant influence on fat percentage （ P 〉 0.05）. The relativities of varying degrees were existed among nine-haplotype combinations and fat percentage, protein percentage, somatic cell count, fatprotein ratio, and milk yield.