Effects of novel single nucleotide polymorphisms of the FSH beta-subunit gene on semen quality and fertility in bulls.

The follicle-stimulating hormone (FSH) acts on the Sertoli cells in the seminiferous tubules of the testis and regulates spermatogenesis up to the secondary spermatocyte stage. This study aimed to investigate molecular genetic characteristics of the bovine FSH beta-subunit gene (FSHB) and elucidate the effects of single nucleotide polymorphisms (SNPs) of FSHB on the quality of fresh and frozen semen and on fertility in bulls. We used polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) and sequencing of the FSHB gene in 56 bulls belonging to three breeds. We identified 13 substitutions and 1 insertion in the upstream regulation region and in the coding region of exon 3, which were all linked together. Bioinformatics analysis suggested that mutations of the 5'-upstream regulation region altered the binding sites for transcription factors, and radioimmunoassay demonstrated that mutations may result in alterations in the serum FSH concentrations. The least-squares analysis revealed that bulls with this genotype exhibited a significantly lower sperm concentration in fresh semen and a lower percentage of acrosome integrity in both fresh and frozen semen (P<0.05). These bulls also exhibited a significantly higher percentage of sperm deformity in fresh semen (P<0.05), which was more pronounced in frozen semen (P<0.01), and a significantly lower sperm motility in frozen semen (P<0.05). For fertility evaluation, the nonreturn rates obtained from 14,416 inseminations with the analyzed batches revealed that bulls with this genotype showed significantly lower nonreturn rates (P<0.05). In other words, bulls with this genotype exhibited lower semen quality, poor freeze resistance, and lower fertility. These results suggest that the SNPs in bovine FSHB are associated with semen quality and fertility in bulls.