Polymorphisms Of GDF9 And BMP15 Genes And Their Relationships With Prolificacy In Small Tail Han Sheep

Bone morphogenetic protein 15 (BMP15) gene which controls the fecundity of Belclare, Cambridge, Hanna and Inverdale ewes and growth differentiation factor 9 (GDF9) gene which controls the fecundity of Belclare and Cambridge ewes were studied as candidate genes for the prolificacy of Small Tail Han sheep.According to the sequence of ovine BMP15 gene and GDF9 gene, six pairs of primers were designed respectively to detect single nucleotide polymorphisms of exon 1 and exon 2 of BMP15 gene and GDF9 gene in both high fecundity breed (Small Tail Han sheep) and low fecundity breed (Dorset sheep) by PCR-SSCP. Two pairs of primers (primer 1-1 and primer 1-2) were used to amplify the exon 1. Four pairs of primers (primer 2-1, primer 2-2, primer 2-3 and primer 2-4) were used to amplify the exon 2.The results of GDF9 gene were as follows. Only the products amplified by primers 2-1 and 2-2 displayed polymorphism. For primer 2-1, three genotypes (AA, AB and BB) were detected in both sheep breeds. In Small Tail Han and Dorset sheep, frequency of genotype AA was 0. 302, 0.100, frequency of genotype AB was 0.603, 0.467, frequency of genotype BB was 0.095, 0.433, respectively. Sequencing revealed one single nucleotide mutation (G—A) at 477 bp of exon 2 of GDF9 gene in the genotype BB in comparison to the genotype AA. There was the same G477A mutation of GDF9 gene in both Small Tail Han and Dorset sheep as that in Belclare and Cambridge ewes, but this mutation did not cause amino acid change. The relationship of least squares means for litter size was AA>AB>BB in Small Tail Han sheep, but difference among the three genotypes didn't differ significantly (P>0. 05). For primer 2-2, two genotypes (CC and CD) were detected in both sheep breeds. In Small Tail Han and Dorset sheep, frequency of genotype CC was 0. 817, 0. 933, frequency of genotype CD was 0. 183, 0.067, respectively. Sequencing revealed one single nucleotide mutation (G—T) at 729 bp of exon 2 of GDF9 gene in the genotype CD in comparison, to the genotype CC, and this mutation resulted in an amino acid change of glutamine-histidine. The Small Tail Han ewes with mutation heterozygous genotype CD had 0.77 (P<0.01) lambs more than those with wild type CC. These results preliminarily showed that the GDF9 gene is either a major gene that influences the prolificacy of Small Tail Han sheep or a molecular genetic marker in close linkage with such a gene.The results of BMP15 gene were as follows. Only the products amplified by primer1-1 displayed polymorphism. Two genotypes (AA, AB) were detected in both sheep breeds. In Small Tail Han and Dorset sheep, frequency of genotype AA was 0.638, 0.800, frequency of genotype AB was 0. 362, 0.200, respectively. Sequencing revealed a CTT deletion mutation at 28-30 bp of exon 1 of BMP15 gene in the genotype AB in comparison to the genotype AA. There was the same CTT deletion mutation of BMP15 gene in both Small Tail Han and Dorset sheep as that in Belclare, Cambridge, Hanna and Inverdale ewes. The ewes with mutation heterozygous genotype AB had 0.20 (P>0. 05) lambs more than those with wild type AA in Small Tail Han sheep. These results indicated the CTT deletion mutation of BMP15 gene had no significant effect on prolificacy of Small Tail Han sheep.