Screening for Causative Mutations of Major Prolificacy Genes in Iranian Fat-Tailed Sheep

Background: The presence of different missense mutations in sheep breeds have shown that the bone morphogenetic protein receptor 1B (BMPR1B), bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) genes play a vital role in ovulation rate and prolificacy in ewes. Therefore, the present study aims to investigate BMPR1B, BMP15 and GDF9 gene mutations in prolific ewes of Iranian fat-tailed Lori-Bakhtiari sheep. Materials and Methods: In the present experimental study, genomic DNA was extracted from whole blood of 10 prolific Lori-Bakhtiari ewes with at least two twinning records in the first four parities to identify point mutations of the BMPR1B, BMP15 and GDF9 genes, using DNA sequencing. Results: The results obtained from DNA sequencing showed a new synonymous mutation (g.66496G>A) in exon 8 of the BMPR1B gene, without any amino acid change. Sequencing of the BMP15 gene revealed a deletion of 3 bp (g.656_658delTTC) in exon 1, leading to an amino acid deletion (p.Leu19del). Four single nucleotide polymorphisms (G1:g.2118G>A, G2:g.3451T>C, G3:g.3457A>G and G4:g.3701G>A), were detected in exons 1 and 2 of the GDF9 gene, two of which caused amino acid substitutions (G1: p.87Arg>His and G4: p.241Glu>Lys). These amino acid alterations are proposed to have a benign impact on structure and function of the GDF9 polypeptide sequence. Conclusion: Three major prolificacy genes (BMPR1B, BMP15 and GDF9) were polymorphic in Lori-Bakhtiari sheep, although none of the major causative mutation was detected in this sheep type. Further studies using high throughput methods such as genome-wide association study (GWAS) and evaluation of other candidate genes are necessary in the future.