The interaction of genetic and epigenetic mechanisms is one of the underlying causes of phenotypic variability in complex diseases such as type 2 diabetes (T2D). To explore the influence of genetic and epigenetic changes in T2D, we examined the effect of methylation of CpG-SNP sites on allele-specific expression (ASE) in one-carbon metabolism pathway genes in T2D. Case-control study was conducted on 860 individuals (430 T2D and 430 controls). CpG-SNPs shortlisted through in silico analysis were genotyped using tetra ARMS PCR and validated using Sanger DNA sequencing.

Global DNA methylation was carried out using RP-HPLC. Promoter DNA methylation and CpG site-specific methylation were carried out using bisulfite sequencing. mRNA expression and ASE were examined by SYBR green and TaqMan assay, respectively. Four exonic CpG-SNPs of MTHFD1, MTRR, and GGH genes were identified in folate…