Polymorphism of the exon 2 of transforming growth factor-β1 gene (TGF-β1) and its relationship with litter size in two goat breeds | 转化生长因子β1基因(TGF-β1)外显子2的单核苷酸多态性及其与两个山羊品种产羔数的相关分析

chinois. 为寻找与山羊(Capra hircus)产羔数密切相关的分子标记，加快山羊育种进程，研究转化生长因子β1基因(TGF-β1)遗传多态性与山羊产羔数的相关性，根据牛的TGF-β1基因序列设计3对引物, 采用 PCR-SSCP .和DNA测序技术检测山羊TGF-β1基因外显子2和内含子3的多态性, 同时用最小二乘法研究了其多态性与产羔数的关系。结果表明，在波尔山羊和陕南白山羊中，仅第二外显子148 bp位点碱基发生A→G 的突变，导致苏氨酸(Thr)变为丙氨酸 (Ala)；多态位点均以A为优势等位基因，基因频率分别为0.530和0.648。在波尔山羊的1~3胎产羔数中，AB型个体的产羔数显著高于BB和AA型个体(P0.05)；在第四胎产羔数和平均产羔数中，AB 型个体的产羔数显著高于AA(P0.05)，显著高于BB(P0.05)；BB型个体的平均产羔数显著高于AA型(P0.05)。在陕南白山羊中，AB型个体的2~4胎产羔数和平均产羔数显著高于 AA和BB型个体(P0.05)；在第一胎中，AB型个体显著高于AA 型个体(P0.05)。研究结果表明TGF-β1基因多态位点与产羔数显著相关，可以用于山羊分子遗传育种的候选基因。

anglais. In order to find the molecular marker used in marker-assisted selection (MAS) to accelerate goat (Capra hircus) breeding progress, the goat transforming growth factor-β1 gene(TGF-β1) was selected to study the association between its polymorphism and litter size. According to the sequence of bovine TGF-β1 gene, three pairs of primers were designed to detect SNPs of intron 3 and exon 2 of TGF-β1 gene in two goat breeds by PCR-SSCP and DNA sequencing. The least square mean and genetic variance of different genotypes at polymorphic loci were analyzed. The results showed that the PCR products of primer 1 (P1) had polymorphism. Three genotypes (AB, BB, and AA), and one single nucleotide mutation (A→G) was detected in two goat breeds, and this mutation resulted in an amino acid change: Thr→Ala. Allele A was the dominant allele. The frequencies of allele A were 0.530 and 0.648 in two goat breeds, respectively. In Boer goat, AB genotype had significantly higher (P0.05) litter size than that of BB and AA genotypes from the first to third parity. AB genotype was very significantly higher (P0.01) than that of AA genotype, and significantly higher (P0.05) than that of BB genotype, and BB genotype was significantly higher (P0.05) than that of AA genotype in the fourth parity and average litter size. In Shaannan goat, AB genotype had significantly higher (P0.05) litter size than that of AA and BB genotypes in the second, third, fourth and average parity, and AB and BB genotypes had significantly higher (P0.05) litter size than that of AA genotype in the first parity. The TGF-β1 gene had significant effects on litter size in two goat breeds. Therefore, these results suggest that the TGF-β1 gene is a strong candidate gene that affects litter size in goats.