Research On Genetic Mutations Of GnRH And GDF9 Genes And Their Correlation With Little Size In Goats

In this study, we used PCR-SSCP technology, molecular cloning, and DNA sequencing to detect the genetic variations of GnRH gene, GnRHR gene, GDF9 gene and STAT5A gene. Meanwhile, we analyzed whether the mutations in these genes might be responsible for little size or milk yield in Xinong Sannen Dairy Goat and Boer Goat. The important results were showing in the followings:1. the genetic mutation of GnRH gene and its effect on little size in this two goat breeds4 pairs of primers were uesed to amply 4 exons of GnRH gene. No polymorphism was detected in products amplified by primers 1, 2 and 3, while three genotypes (CC, CT and TT) were detected in products amplified by primers 4 both in Xinong Saanen Dairy Goat and Boer Goat. Sequencing revealed two mutations (185bp C→T and 336bp C→T) in genotype CC compared with genotype TT. The first, second, third birth little size and the average little size of individuals with genotype CC and CT were significant or extremely significant higher than that of genotype TT (P<0.05) both in Xinong Saanen Dairy Goat and Boer goat.2. the genetic mutation of GnRHR gene and its effect on little size in this two goat breeds2 pairs of primers were designed to detect single nucleotide polymorphisms in exon 3 and 3'UTR of GnRHR gene. However, there was no any single nucleotide polymorphisms detected both in Xinong Saanen Dairy Goat and Boer Goat. We proposed that the exon 3 and 3'UTR of GnRHR gene were rather conservative in these breeds.3. the genetic mutation of GDF9 gene and its effect on little size in this two goat breeds6 pairs of primers were designed to detect single nucleotide polymorphisms in exon 1, exon 2 and 3'UTR of GDF9 gene. Only the product amplified by primer 3 was detected three genotypes (AA, AG and GG) both in Xinong Saanen Dairy Goat and Boer Goat. Compared with genotype GG, there was a mutation (G→A) at the 127bp of amplified product for genotype AA. In Xinong Saanen Dairy Goat, the second, third and average little size of individuals with genotype AA were extremely significant higher than that of genotype AG and GG (P<0.01), and the first, second, third and average little size of individuals with genotype AG were extremely significant higher than that of genotype GG (P<0.01). In Boer Goat, the first, second, third and average little size of individuals with genotype AA were extremely significant higher than that of genotype AG and GG(P<0.01), and only the first little size of individuals with genotype AG were significant higher than that of genotype GG (P<0.05). 4. the genetic mutation of STAT5A gene and its effect on milk yield in Xinong Sannen dairy goat12 pairs of primers were, respectively, designed to detect single nucleotide polymorphisms in exon 7, 9, 11, 12, 13, 14, 15, 16 and 19 of STAT5A gene. Only the product amplified by primer 1 was detected two genotypes (CC and CT) in Xinong Saanen Dairy Goat. Compared with genotype CC, there was a mutation (C→T) at the 126bp of amplified product. We proposed that the studied exons except for exon 7 of STAT5A gene were rather conservative in Xinong Saanen Dairy Goat. The milk yield of each lactation and average milk yield of individuals with genotype CC were not significantly higher than that of genotype CT (P>0.05). It needs further research to decide whether STAT5A gene could be a candidate gene to select milk trait of Xinong Saanen Dairy Goat.The results showed that the polymorphisms of GnRH and GDF9 gene can be used as the assisted selection marker for little size in Xinong Saanen Dairy Goat and Boer Goat. Whether STAT5A gene could be a candidate gene to select milk trait of Xinong Saanen Dairy Goat needs further research.