Promoter polymorphism -119C/G in MYG1 (C12orf10) gene is related to vitiligo susceptibility and Arg4Gln affects mitochondrial entrance of Myg1

Abstract

Background: MYG1 (Melanocyte proliferating gene 1, also C12orf10 in human) is a ubiquitous nucleo-mitochondrial protein, involved in early developmental processes and in adult stress/illness conditions. We recently showed that MYG1 mRNA expression is elevated in the skin of vitiligo patients. Our aim was to examine nine known polymorphisms in the MYG1 gene, to investigate their functionality, and to study their association with vitiligo susceptibility.

Methods: Nine single nucleotide polymorphisms (SNPs) in the MYG1 locus were investigated by SNPlex assay and/or sequencing in vitiligo patients (n = 124) and controls (n = 325). MYG1 expression in skin biopsies was detected by quantitative-real time PCR (Q-RT-PCR) and polymorphisms were further analysed using luciferase and YFP reporters in the cell culture.

Results: Control subjects with -119G promoter allele (rs1465073) exhibited significantly higher MYG1 mRNA levels than controls with -119C allele (P = 0.01). Higher activity of -119G promoter was confirmed by luciferase assay. Single marker association analysis showed that the -119G allele was more frequent in vitiligo patients (47.1%) compared to controls (39.3%, P < 0.05, OR 1.37, 95%CI 1.02-1.85). Analysis based on the stage of progression of the vitiligo revealed that the increased frequency of -119G allele occurred prevalently in the group of patients with active vitiligo (n = 86) compared to the control group (48.2% versus 39.3%, P < 0.05; OR 1.44, 95%CI 1.02-2.03). Additionally, we showed that glutamine in the fourth position (in Arg4Gln polymorphism) completely eliminated mitochondrial entrance of YFP-tagged Myg1 protein in cell culture. The analysis of available EST, cDNA and genomic DNA sequences revealed that Myg1 4Gln allele is remarkably present in human populations but is never detected in homozygous state according to the HapMap database.

Conclusions: Our study demonstrated that both MYG1 promoter polymorphism -119C/G and Arg4Gln polymorphism in the mitochondrial signal of Myg1 have a functional impact on the regulation of the MYG1 gene and promoter polymorphism (-119C/G) is related with suspectibility for actively progressing vitiligo.

Figure 1

Genomic localization of single nucleotide polymorphisms (SNPs) in the MYG1 gene that were examined in this study. Relative positions of selected SNPs are represented by their ID number from NCBI's dbSNP database. Grey boxes are representing exons and arrow indicates the direction of transcription of MYG1 gene.

Figure 2

Impact of MYG1 promoter SNP (-119C/G) on MYG1 mRNA expression. (A) MYG1 mRNA expression levels in the skin biopsies of healthy subjects and vitiligo patients; n indicates number of subjects in each group; the error bars present standard deviation of the mean. Abbreviations: HS - healthy skin; LS - lesioned skin. (B) MYG1 promoter activity in luciferase assay. Data is shown relative to the activity of empty pGL3-Basic. Pattern codes corresponding to three genotypes for both (A) and (B) are shown on the right. * P < 0.05; ** P < 0.01

Figure 3

Subcellular localization of full-length human MYG1 cDNA with both variants for Myg1 Arg4Gln polymorphism. Mitochondrial localization YFP tagged MYG1 cDNA with arginine in the position amino acid four (A) is completely eliminated if arginine is replaced with glutamine (B). Scale bars represent 10 μm.

Figure 4

Analysis of binding sites in the -119 promoter region using TRANSFAC software. (A) Sequence of -119G promoter allele. (B) Sequence of -119G promoter allele. Arrowhead points to a single nucleotide polymorphism, G in (A) and C in (B).