High association of a novel variant in the adiponectin gene with the litter size in Awassi ewes

Abstract

Flock productivity is affected by reproductive traits controlled by many factors such as ovulation rate, hormones, and genetics. Many genes are associated with fertility and other features related to it such as melatonin receptor 1A ( MNTR1A ) gene, inhibin βA ( INHBA) gene, insulin-like growth factor-I ( IGF-1 ) gene, and prolactin gene, and many other new candidates, adiponectin gene ( ADIPOQ ) is one of them, which are associated with reproduction and fertility. This study aimed to evaluate the genetic variation of the ADIPOQ gene concerning the litter size of Awassi ewes. Genomic DNA isolated from 114 Awassi ewes produced single lambs and 84 Awassi ewes produced twin lambs. By polymerase chain reaction (PCR), we amplified all three exons (368 bp, 448 bp, and 363 bp) of the ADIPOQ gene (exons 1, 2, and 3). Three genotypes were found in the 368 bp amplicons, the CC, CA, and AA genotypes. Novel mutation c.198473337C > A was discovered in the CA genotype through a sequencing reaction. This single nucleotide polymorphism (SNP) showed a highly significant ( P ≤ 0.01) association with litter size, in that the sheep with this SNP had a larger litter size than those without it. The ewes with the AA genotype had 1.97 lambs more than those with the CC and CA genotypes. Using logistic regression, the c.198473337C > A SNP was confirmed to be responsible for increasing the litter size. In conclusion, the c.198473337C > A SNP appears to have an interesting and positive impact on reproductive traits (especially litter size) in Awassi sheep. In light of these data, the genetic variant of the ADIPOQ gene could be used for developing marker-assisted selection programs to improve litter size in Awassi sheep.