Association of FOXP3 and GAGE10 promoter polymorphisms and decreased FOXP3 expression in regulatory T cells with susceptibility to generalized vitiligo in Gujarat population.

Abstract

Alterations in regulatory T (Treg) cells have been observed in generalized vitiligo (GV) patients and decreased Forkhead Box P3 (FOXP3) has been implicated in the disease pathogenesis. The present study examined FOXP3 rs3761547(A>G), rs3761548(C>A), rs2232365(A>G) and GAGE10 rs11798415(A>T) promoter single nucleotide polymorphisms (SNPs) in 419 GV patients and 429 controls from Gujarat population using PCR-RFLP and ARMS-PCR. Real-time PCR and flow cytometry were used for assessment of FOXP3 mRNA and protein levels respectively in 96 GV patients and 90 controls. The frequency of genotypes (p<0.001) and alleles (p=0.012 & p=0.040) for rs3761547(A>G) and rs11798415(A>T) SNPs significantly differed between GV patients and controls. FOXP3 mRNA and protein levels were significantly decreased (p<0.001) in GV Tregs compared to controls. Active vitiligo (AV) Tregs showed significantly reduced FOXP3 mRNA and protein levels compared to that of stable vitiligo (SV) (p=0.02 & p=0.039). The correlation of genotype-phenotype of FOXP3 SNPs suggested reduced FOXP3 mRNA (p=0.019, p<0.001 & p<0.001) and protein (p=0.028, p<0.001 & p=0.022) levels in patients with susceptible GG, AA and GG genotypes respectively. The GAGT, GCGT & ACGT haplotypes were prevalent in GV patients (p=0.004, p=0.004 & p=0.016); however, GAGT & GCGT were overrepresented in patients with AV (p=0.044 & p=0.024). The susceptible GAGT and GCGT haplotypes in patients exhibited reduction in FOXP3 mRNA (p=0.014 & p=0.019) and protein (p=0.024 & p=0.028). DNA-protein docking analysis revealed reduced binding for transcription factor C/EBP to the susceptible allele 'G' (rs3761547) compared to A allele. For the first time, the study suggests significant association of FOXP3 rs3761547(A>G) & GAGE10 rs11798415(A>T) SNPs with susceptibility to GV in Gujarat population. In addition, the likely role of these SNPs in altered FOXP3 expression of Tregs may possibly affect Treg suppressive function in GV.