Polymorphism Of Candidate Gene GnRHR And ESR And Its Association With Prolificacy In Goats

The gonadotropin-releasing hormone receptor (GnRHR) is a member of the seven-transmembrane, G-protein coupled receptor (GPCR) family. It is expressed on the surface of pituitary gonadotrope cells as well as lymphocytes, breast, ovary, and prostate. This receptor is a G protein-coupled receptor and resides primarily in the pituitary and is responsible for advancing the development and maturation of gonad and regulating the reproduction of mammal after its release from the hypothalamus.The estrogen receptor (ESR) is a member of the nuclear receptor superfamily.ESR is a transcription factor that is ligand-activated in animals.The development of follicle was affected by ESR,which is associated with the estrogen for its gene expression and regulation in the reproduction cycle of female vertebrate.The purpose of this study was to detect single nucleotide polymorphisms (SNPs) within GnRHR and ESR gene, to analyze the genetic structure of two goat breeds, and to investigate the effects of the gene on litter size of Huanghuai goats. Based on the sheep DNA sequences in GenBank, four primer pairs for GnRHR and ESR gene, respectively, were designed to clone the partial sequence of GnRHR and ESR gene. Detecting mutation location of exon 1,2 of GnRHR gene and exon 4 of ESR gene in Huanghuai goat and Bore goat by PCR-SSCP, and the associations of the gene polymorphism with the litter size of Huanghuai goat does were also explored. The results are as follows:1. The PCR products of one pairs of primer among those of 4 pair primers were polymorphic. And the polymorphic site was on exon 1 of GnRHR gene.2. The nucleotide sequences,located on the exon 1 of GnRHR gene, have a mutation of 3 bases. Homological analysis suggested that the identity of the nucleotide sequences were 98% among Huanghuai goat,Boer goat and Sheep.3. Three genotypes (AA, AB and AC) were observed in Huanghuai goat and Boer goat. Compared to the BB genotype, there were mutation (A→C) at 58 bp, which gave rise to amino acid changes (Lys→Gln), in the AA genotype by sequencing analysis.4. Genetic analysis suggested that, two allelics were detected in Huanghuai goat and the allelic frequencies were 0.825 and 0.175, respectively, three genotype (AA,AB and BB) frequencies were 0.725,0.200 and 0.075, respectively.χ2 fitness test showed that the distribution of different genotype with primer 2 in Huanghuai goat was not in Hardy-Weinberg equilibrium. In Bore goat, the allelic frequencies were 0.868和0.132, respectively; Genotype (AA,AB and BB) frequencies were0.765,0.206和0.029, respectively.χ2 fitness test showed that the distribution of different genotype with primer 2 in Huanghuai goat was in Hardy-Weinberg equilibrium.5. In the Huanghuai goat population, least square analysis showed that the does with genotype BB had 0.66 (P<0.05) or 0.39 (P>0.05) kids more than those with genotype AA or AB, respectively; the difference between genotype AB and genotype AA was not significantly.