A human FSHB promoter SNP associated with low FSH levels in men impairs LHX3 binding and basal FSHB transcription.

FSH production is important for human gametogenesis. In addition to inactivating mutations in the FSHB gene, which result in infertility in both sexes, a G/T single-nucleotide polymorphism (SNP) at -211 relative to the transcription start site of the 5' untranslated region of FSHB has been reported to be associated with reduced serum FSH levels in men. In this study, we sought to identify the potential mechanism by which the -211 SNP reduces FSH levels. Although the SNP resides in a putative hormone response element, we showed that, unlike the murine gene, human FSHB was not induced by androgens or progestins in gonadotropes. On the other hand, we found that the LHX3 homeodomain transcription factor bound to an 11-bp element in the human FSHB promoter that includes the -211 nucleotide. Furthermore, we also demonstrated that LHX3 bound with greater affinity to the wild-type human FSHB promoter compared with the -211 G/T mutation and that LHX3 binding was more effectively competed with excess wild-type oligonucleotide than with the SNP. Finally, we showed that FSHB transcription was decreased in gonadotrope cells with the -211 G/T mutation compared with the wild-type FSHB promoter. Altogether, our results suggest that decreased serum FSH levels in men with the SNP likely result from reduced LHX3 binding and induction of FSHB transcription.