A Functional Polymorphism c.-712C>T in the FGF9 Promoter Is Associated with Sertoli Cell-Only Syndrome.

Abstract

Fibroblast growth factor 9 (FGF9) is an autocrine/paracrine growth factor considered to be important for a variety of biological processes, including proliferation, differentiation and cell survival activities in embryogenesis and adult. Recent studies from Fgf9 knockout mice emphasized the importance of FGF9 in male sex determination and differentiation. The reproductive system phenotypes of Fgf9-/- null mice range from testicular hypoplasia to male-to-female sex reversal and gonadal dysgenesis, suggesting the crucial role for FGF9 signaling in sex determination and testicular development. The RNA and protein expressions of FGF9 in the testes of Sertoli cell-only syndrome (SCOS) were significantly decreased, compared to controls. We further systematically examined the sequences of FGF9 gene in 29 SCOS infertile men and 79 unrelated healthy controls to test whether sequence variants of FGF9 gene play a pathological role in SCOS phenotype. A single nucleotide polymorphism and two polymorphic microsatellites were detected. The allelic and genotypic frequencies of the c.-712C>T in the promoter region of FGF9 were significantly different between SCOS patients and controls (P = 0.005 and 0.0008, respectively), while the microsatellites c.-124dupT(8_10) in the 5'UTR and c.*275_76TG(13_17) in the 3'UTR did not show any difference between these two groups. Reporter assay demonstrated that the polymorphism c.-712C>T dramatically attenuated promoter activity. By transcription element search system (TESS), E2F transcription factor 1 (E2F-1) was predicted to bound to -712C and this binding was confirmed by chromatin immuno-precipitation (ChIP) assay. Moreover, in electrophoretic mobility shift assay (EMSA), substitutional mutation of E2F-1 binding site (i.e. -712C>T) reduced DNA-protein complex formation. Collectively, our data suggest the functional polymorphism c.-712C>T within the promoter region of FGF9 gene, which results in decreased FGF9 expression and may contribute to one of the causes of SCOS. (poster)