Variation in Follicle-Stimulating Hormone Receptor Expression Is Associated with the Twinning Rate QTL Located on...

Twin births in dairy cattle present challenges for producers, resulting in increased prevalence of health issues for both cows and calves, thereby impacting profitability. Genome-wide association study (GWAS) analyses of the twinning rate in Holstein cattle have reported the most significant genomic association with twinning rate in a region containing two strong candidate genes: follicle-stimulating hormone receptor (FSHR) and luteinizing hormone/chorionic gonadotropin receptor (LHCGR). Coding-sequence variants of these genes were not associated with the twinning rate, suggesting that one of the two genes is differentially expressed in association with the twinning rate. Granulosa cells were collected from 38 Holstein cows that were selected to provide similar representation of genotypes for the twinning rate quantitative trait locus (QTL). RNA was extracted from granulosa cells and gene expression was assessed by quantitative PCR with data analyzed by the ΔΔCT method. Association of gene expression with QTL genotype was tested by the Kruskal-Wallis test with the QTL genotype based on the SNP most significantly associated with twinning rate. QTL genotype was significantly associated (p = 1.88 × 10^-8) with the expression of FSHR but was not associated with LHCGR expression (p = 0.18). The increased FSHR expression was associated with an increasing copy number of the G allele and thus an increased twinning rate.