Detection Of The Q249R Mutation In Ovine Bone Morphogenetic Protein Receptor-â… B(BMPR-â… B) And Its Effect On Litter Size In Small-tailed Han Sheep

The Q249R mutation in bone morphogenetic protein receptor-â…  B(BMPR- â…  B) is associated with the high prolificacy of Booroola Merino sheep. Small-tailed Han sheep is a highly prolific sheep breed in China. The genes controlling the prolificacy in Small-tailed Han sheep are still unknown.The present study selected BMPR-â…  B as candidate gene, characterized the Q249R mutation frequency in a randomly selected populations of Small-tailed Han sheep, Large-tailed Han sheep, Wadi sheep and the Mongolia sheep breeds. The effect of the mutation on litter size in Small-tailed Han sheep and its linkage relationship with microsatellite OARJL36, which is fully associated with Booroola Merino FecB locus, were also invesigated. For BMPR-â…  B Q249R mutation, which is caused by A746G substitution, we established a PCR-SSCP detection method. The effect estimation was performed with S AS GLM procedure.The results indicated that the frequency of B allele is 0.716, 0.471 and 0.486 in Small-tailed Han sheep, Large-tailed Han Sheep and Wadi Sheep populations respectively. The frequency of mutation allele B in Wadi and Large-tailed Han Sheep were both lower than in Small-tailed Han Sheep population (P<0.01), whereas, no difference was observed between the Large-tailed Han Sheep and the Wadi Sheep populations (P>0.05). No B allele was detected in the Mongolia sheep. Hardy-Weinberg equilibrium test indicated that, for BMPR-â… B Q249R mutation, the populations of Large-tailed Han Sheep, Wadi Sheep were in a state of equilibrium; however, the Small-tailed Han sheep population was not (P<0.01).The allele substitution effect and dominance effect of the mutation were estimated to be 0.21 and 0.01 for the first, and 0.31 and 0.18 for the second parities respectively. In contrast to that in Booroola Merino sheep, the B allele was not fully associated with certain OARJL36 allele (180bp in size), indicating that recombinations had occurred on Small-tailed Han sheep, Large-tailed Han sheep and Wadi sheep between the Q249R mutation and OARJL36 during the breed development.