Abstract
The Small Tailed Han sheep and Hu sheep are two prolific local sheep in China. In this study, the polymorphisms of BMPR-IB (Bone morphogenetic protein receptor IB), BMP-15 (Bone morphogenetic protein 15) and FSHR (follicle stimulating hormone receptor) were investigated to check whether they are associated with litter size in Small Tailed Han sheep and Hu sheep. Consequently, three polymorphisms, FecB mutation in BMPR-IB (c.746A>G), FecG mutation in BMP-15 (c.718C>T) and the mutation (g. 47C>T) in FSHR were found in the above two sheep breeds with a total number of 1630 individuals. The single marker association analysis showed that the three mutations were significantly associated with litter size. The ewes with genotype FecBB/FecBB and FecBB/FecB+ had 0.78 and 0.58 more lambs (p < 0.01) than those with genotype FecB+/FecB+, respectively. The heterozygous Han and Hu ewes with FecXG/FecX+ genotype showed 0.30 (p = 0.05) more lambs than those with the FecX+/FecX+ genotype. For FSHR gene, the ewes with genotype CC had 0.52 (p < 0.01) and 0.75 (p < 0.01) more lambs than those with genotypes TC and TT, respectively. Combined effect analyses indicated an extremely significant interaction (p < 0.01) between the random combinations of BMPR-IB, BMP-15 and FSHR genes on litter size. In addition, the Han and Hu ewes with BB/G+/CC genotype harbor the highest litter size among ewes analyzed in current study. In conclusion, BMPR-IB, BMP-15 and FSHR polymorphisms could be used as genetic markers in multi-gene pyramiding for improving litter size in sheep husbandry.
Highlights
The FecB (Fec = Fecundity, B = Booroola) mutation plays a vital role in increasing ovulation rate and prolificacy in ewes
BMP-15 (Bone morphogenetic protein 15) gene belongs to the TGFβ (Transforming growth factor-β) family, which acts as a key regulator of granulosa cell (GC) processes in ovarian follicular development [4,5]
The 141 bp PCR product of the c.718C>T polymorphism of the BMP-15 gene was digested with Hinf I, generating two fragments: the 141 bp + 111 bp + 30 bp and 111 bp + 30 bp bands represented G+ and ++ genotypes, respectively (Figure 2)
Summary
The FecB (Fec = Fecundity, B = Booroola) mutation plays a vital role in increasing ovulation rate and prolificacy in ewes. This mutation (c.746A>G) was in BMPR-IB (Bone morphogenetic protein receptor IB) gene that located on chromosome 6,which was first found to be significantly associated with litter size in Booroola Merino ewes [1,2,3]. The c.718C>T mutation (named FecXG; Galway mutation) in BMP-15 gene was first identified in Cambridge and Belclare sheep, which increased ovulation rate and infertility [6]. FSHR (Follicle stimulating hormone receptor) gene was first identified in rat Sertoli cells and may have an influence on the FSH (follicle stimulating hormone) signal transduction [7]. A variety of mutations were found in the 5' flanking region of ovine FSHR gene, which were significantly associated with litter size in Australian sheep, Hu sheep and Small Tailed Han sheep [10,11,12]
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