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

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.

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.

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.

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.