Microsatellite in the 3′ untranslated region of human fibroblast growth factor 9 (FGF9) gene exhibits pleiotropic effect on modulating FGF9 protein expression

Abstract

Fibroblast growth factor 9 (FGF9) is a member of secreted polypeptide families and involved in many important biological processes, including implantation and morphogenesis during embryogenesis and adult life. Recently, Fgf9-knockout mice exhibited male-to-female sex reversal, demonstrating a novel function for FGF9 in testicular development. We hypothesized that FGF9 is involved in sex development at an early embryonic stage in humans. In this study, we systematically screened sequences of the FGF9 gene in 21 XY females and 72 XX females and XY males to examine whether sequence variants of the FGF9 gene play a pathophysiological role on human gonadal dysgenesis. No mutation was identified, but a single nucleotide variant and two microsatellites were found. The allelic distribution of polymorphic microsatellite in the 3'-UTR of FGF9 between patients and controls was slightly different with Bonferroni correction (P = 0.06). We further applied reporter gene system and quantitative RT-PCR to study the function of this microsatellite motif and results demonstrated that the (TG) n motif modulated gene expression at both preand post-transcriptional levels. The (TG) 14 allele, which showed a potential association with male-to-female sex reversal (odds ratio = 6.08, 95% confidence interval = 1.39-26.63), displayed the strongest promoter activity and longest mRNA stability. These data demonstrated that 3'-UTR microsatellite of the FGF9 is a functional polymorphism that plays dual roles in regulating FGF9 expression. Although our preliminary result suggested a possible association between FGF9 and human gonadal dysgenesis, the major limitation of small dataset in this study points out the requirement for further investigation.

Association between IGF1 CA microsatellites and mammographic density, anthropometric measures, and circulating IGF-I levels in premenopausal Caucasian women

“…Similarly, if our 3 0 polymorphism were functional and in weak linkage disequilibrium or linkage equilibrium with SNPs examined in other studies, the association we found with mammographic density may be either stronger or only detectable in our study. Functional significance has been demonstrated for some microsatellites in non-coding regions, including the 3 0 untranslated region [44]. However, we have no evidence that our 3 0 polymorphism is functional, and its association with mammographic density still needs to be confirmed.…”

Family-based genetic association study of insulin-like growth factor I microsatellite markers and premenopausal breast cancer risk

“…Experimental assays indicate that for some dinucleotide repeat variants in the promoter and other non-coding regions, alleles of different length influence transcription activity of specific genes [36][37][38], although there are no studies that indicate that the IGF1 promoter region 5 0 CA has functional effects. Associations between specific allele length groupings and breast cancer risk could also occur because of linkage disequilibrium between alleles within a grouping and an ungenotyped polymorphism that influences risk.…”

Absence of inactivating mutations and deletions in the DMRT1 and FGF9 genes in a large cohort of 46,XY patients with gonadal dysgenesis

“…They identified four different alleles, (TG 13e16 ) (c.*275TG)n. The (TG) 14 motif was identified in their patients with 46,XY DSD of different aetiologies and rarely in controls (P ¼ 0.01). Functional studies demonstrated that the (TG) 14 allele had the greatest promoter activity in luciferase expression assays and also longer mRNA stability than the other alleles [17].…”

“…The region from c.*127 to c.*395 (from 932 to 1199 bp relative to the transcription start site of FGF9), was amplified and sequenced as described by Chen et al [17].…”