Polymorphisms in BMPR-IB gene and their association with litter size trait in Chinese Hu sheep

Identification and utilization of sheep major fecundity genes offer opportunities for the increase in litter size, as well as the improvement of production efficiency in livestock industry. BMPR-IB gene belongs to the TGF-β superfamily, and is also considered as a regulator for sheep reproductive performance due to its involvement in the mammalian gametogenesis pathway. This study aimed to detect the variations of BMPR-IB gene in Hu sheep (N = 934) and to evaluate their effects on the litter size trait. qRT-PCR results showed that the mRNA expression level of BMPR-IB in kidney was the highest. And in the tissues of ovary and pituitary, the expression levels of prolific group were significantly higher than that of non-prolific group (p < 0.05). Through DNA sequencing and PCR-RFLP, three SNPs were identified in the genomic region of BMPR-IB gene; the individuals with CC in g.29362047T > C, AA in g.29427689G > A and GG in FecB had better fecundity characterization. Additionally, association analysis indicated that two diplotypes of Hap2/2 and Hap2/4 showed larger litter size. Overall, our results verified several useful markers which would contribute to further development of sheep breeding strategies.