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Splicing-related SNP of RABL2B jeopardizes semen quality in Chinese Holstein bulls
RABL2B is a member of a poorly characterized clade of RAS GTPase superfamily, which plays an essential role in male fertility, sperm intra-flagellar transport, and tail assembly. In this study, we identified a novel RABL2B splice variant in bovine testis and sperm; this splice variant, designated as RABL2B-TV, is characterized by exon 2 skipping. Moreover, a single-nucleotide polymorphism (SNP) c.125 G > A was found within the exonic splicing enhancer (ESE) motif, indicating that SNP caused the production of RABL2B-TV aberrant splice variant; we demonstrated this phenomenon by constructing pSPL3 exon capturing vector with different genotypes and transfecting these vectors in cells. Expression of RABL2B-TV transcript was lower in high-performance bull semen than in low-performance bull semen. Association analysis showed that sperm deformity rate was significantly lower in Chinese Holstein bulls with GG or GA genotype than in bulls with AA genotype (P < 0.05); additionally, the initial sperm motility was significantly higher in individuals with GG or GA genotype than in individuals with AA genotype (P < 0.05). Our findings suggest that the difference in semen quality in bulls with different RABL2B genotypes are generated via an alternative splicing mechanism caused by a functional SNP within the ESE motif.
RD17111 Accepted 18 April 2017
© CSIRO 2017