Polymorphism and Bioinformatics Analysis of Growth Differentiation Factor 9 Gene in Lori Sheep

Growth differentiation factor 9 (GDF9) is a fecundity major gene affecting prolificacy in sheep. In the present study, genetic variation of a 380-bp fragment in GDF9 gene exon 1 was investigated in 100 Lori ewes. Single-strand conformational polymorphism (SSCP) and DNA sequencing methods were used to detect single nucleotide polymorphism (SNP) of the studied fragment. A SNP (g.306G>A), known as G1 mutation, with two genotypes (GG and AG) was found in two different SSCP patterns of GDF9 gene exon 1, deducing an amino acid (AA) exchange (p.Arg87His). Frequencies of the AG and GG genotypes were 37.65% and 62.35%, respectively. Also, the estimated allelic frequencies for the A and G alleles were 18.825% and 81.175%, respectively. The observed nucleotide sequences were subjected to alignment analysis and it was found that the studied fragment had more than 99.7% similarity with some sequences reported for other breeds of sheep. Two different secondary and 3D protein structures were predicted for A and G alleles. Moreover, the A and G alleles had different isoelectric pH values (8.7 and 9, respectively). The observed genotypes tended to have a significant association with litter size (P<0.10) where average litter size of GG ewes was slightly (20%) higher than for AG animals. With respect to the results of the present study, it seems that more studies are needed to evaluate the mutations in other fragments of this gene or other genes in Lori sheep.