Studies On SNPs Of GnRHR As Candidate Genes For Fecundity Of Sheep And Their Association With Prolificacy

The purpose of this study was to detect single nucleotide polymorphisms(SNPs) within GnRHR gene in Small Tail Han sheep,Hu sheep,South African Mutton Merino, Chinese Merino sheep and Corriedale using PCR-SSCP.According to the average litter size,Small Tail Han sheep and Hu sheep were high fecundity sheep breeds,others were low fecundity sheep breeds.Based on the sequence of ovine GnRHR gene in GenBank, eight pairs of primers were designed to detect SNPs of exons of GnRHR gene in different fecundity sheep breeds.The results showed that the products amplified only with primer P4 and P7 displayed polymorphisms in GnRHR gene.For primer P4,two genotypes(AA and BB) were detected in Hu sheep,only one genotype AA was detected in other four sheep breeds.Sequence of genotype BB compared with genotype AA revealed five mutations(+692G→A,+706T→A, +747T→C,+748A→T and+802T→A) in exon 1,which gave rise to relevant amino acid changes(Gly→Ser,Asp→Glu and Leu→Pro) in GnRHR.In Hu sheep,frequencies of AA and BB genotypes were 0.74 and 0.26.For primer P7,two genotypes(CC and DD) were detected in prolific Small Tail Han and Hu sheep,but one genotype CC was detected in three low fecundity sheep breeds.Sequence of genotype DD compared with genotype CC revealed two mutations(+50A→G and+101A→C) of exon 2,which resulted in the amino acid changes(Glu→Gly and Gln→Pro).In Small Tail Han sheep,frequencies of CC and DD genotypes were 0.87 and 0.13,respectively.In Hu sheep,frequencies of CC and DD genotypes were 0.79 and 0.21.The Small Tall Han ewes with mutant homozygous genotype DD had 0.81(P＜0.01) lambs more than those with wild type CC.