GnRHR基因多态性及其与小尾寒羊高繁殖力关系的研究

设计8对引物，应用聚合酶链式反应-单链构象多态性（PCR-SSCP）技术检测促性腺激素释放激素受体（gonadotropin releasing hormone receptor, GnRHR）基因外显子1、外显子2和外显子3在高繁殖力品种（小尾寒羊和湖羊）和低繁殖力品种（南非肉用美利奴、考力代和中国美利奴绵羊）中的单核苷酸多态性，同时研究该基因对小尾寒羊高繁殖力的影响。结果发现引物P4和P7扩增片段具有多态性，其余6对引物的扩增片段都不存在多态性。对于P4扩增片段，在湖羊中检测到AA和BB基因型，在其余4个绵羊品种中只检测到AA基因型，BB型与AA型相比在外显子1有5个突变（+692G→A、+706T→A、+747T→C、+748A→T和+802T→A），并引起氨基酸改变（Gly→Ser、Asp→Glu和Leu→Pro）。对于P7扩增片段，在小尾寒羊和湖羊中都检测到CC和DD基因型，在低繁殖力的3个绵羊品种中均只检测到CC基因型，DD型与CC型相比在外显子2有+50A→G和+101A→C两个突变，并引起氨基酸改变（Glu→Gly和Gln→Pro）；小尾寒羊CC和DD基因型频率分别为0.87和0.13，突变纯合型（DD）小尾寒羊平均产羔数比野生型（CC）多0.81只（P<0.01）。

Polymorphism of GnRHR Gene and Its Relationship with Prolificacy of Small Tail Han Sheep

The gonadotropin releasing hormone receptor (GnRHR) gene was studied as a candidate gene for the prolificacy of Small Tail Han sheep. Eight pairs of primers were designed to detect single nucleotide polymorphisms of exon 1, exon 2 and exon 3 of GnRHR gene in both high fecundity breeds (Small Tail Han and Hu sheep) and low fecundity breeds (South African Mutton Merino, Corriedale and Chinese Merino sheep) by PCR-SSCP. Only the products amplified by primers P4 and P7 displayed polymorphisms. For primer P4, two genotypes (AA and BB) were detected in Hu sheep, only one genotype AA was detected in other four sheep breeds. Sequencing revealed five mutations (+692G→A, +706T→A, +747T→C, +748A→T and +802T→A) of exon 1 in genotype BB compared with genotype AA, which gave rise to amino acid changes (Gly→Ser, Asp→Glu and Leu→Pro). For primer P7, two genotypes (CC and DD) were detected in prolific Small Tail Han and Hu sheep, only one genotype CC was detected in three low fecundity sheep breeds. Sequencing revealed two mutations (+50A→G and +101A→C) of exon 2 in genotype DD compared with genotype CC, which resulted in amino acid changes (Glu→Gly and Gln→Pro). In Small Tail Han sheep, frequency of CC and DD genotypes was 0.87 and 0.13, respectively. The Small Tail Han ewes with mutant homozygous genotype DD had 0.81 (P<0.01) lambs more than those with wild type CC.