Polymorphism of the ovine BMP15, INHBA and INHA candidate genes for litter size in four Iranian Indigenous sheep using PCR-sequencing

The inhibin α (INHA), inhibin βA (INHBA) and bone morphogenetic protein 15 (BMP-15) were investigated as candidate genes for reproductive traits in four Iranian sheep breeds (Bahmaei, Lak Ghashghaei, Lori-Bakhtiari and Karakul). Based on the ovine sequences of BMP-15, INHA and INHBA genes, three pairs of primers were designed to identify single nucleotide polymorphisms (SNPs) in exon 2 of BMP-15, INHA and INHBA in multiparous ewes by DNA sequencing. Two SNPs were detected in exon 2 of the ovine BMP15 gene at positions 367 and 430, which lead to amino acid substitutions at position 231 and 252 in the BMP15 protein sequence, respectively. Substitution of Leucine to Proline at position 252 is predicted to affect the protein function. A synonymous mutation was found in the amplified fragment of exon 2 at position 752 in ovine INHBA gene. In addition, the c752C T mutation was only found in heterozygous condition in only one Lori-Bakhtiari ewe, while other breeds were in wild type genotype for c752C T mutation. The INHA gene was shown to be highly polymorphic. A total of 7 SNPs including 6 nucleotide substitutions and one insertion were found in the amplified fragment of the INHA locus. The insertion mutation was found in two animals of Bahmaei and Karakul breeds. Interestingly, homozygous condition for the mutant alleles in all identified SNPs in BMP15, INHA and INHBA loci was absent in these breeds. Generally, these breeds showed different genetic structures with regard to the identified SNPs in BMP15, INHBA and INHA genes. However, further research with larger sample size and phenotype data on reproductive performance is required to investigate the definitive effect of the identified mutations in this study.