The Effect of Two Novel Amino Acid Substitutions of BMP15 Gene on Ovulation Rate in Awassi Ewes

Genetic variations in the bone morphogenetic protein 15 (BMP15) gene exert a major effect on the ovulation rate in sheep. This study was conducted to investigate the polymorphisms of the BMP15 gene and its association with twining performance in two breeds of Awassi: purebreds and crossbreds. Two loci were genotyped within the exon 2 of the BMP15 gene, B2 and B4 amplicons. PCR–single-strand conformation polymorphism (SSCP) method indicated the presence of two genotypes in B2 amplicons, TT in purebreds and TA in crossbreds. Two novel SNPs were identified in the B2 amplicons, Asp238Glu, which was detected in both studied breeds, and Phe255Leu, which was detected only in crossbreds. Asp238Glu was predicted to have a highly deleterious effect on protein structure and function. Sheep with TA genotype showed 87% of twining ratio compared with sheep with TT genotype that exhibited only 48.3%, signifying an obvious superiority of TA genotype over TT genotype. In conclusions, the non-deleterious Phe255Leu is associated with higher litter size in crossbreds, while the deleterious Asp238Glu is associated with the observed lower litter size on the purebreds. The present study demonstrated the presence of a highly positive effect of Phe255Leu on BMP15 protein, manifesting in a possible improved prolificacy in the ovine population.