Abstract
Aldehyde dehydrogenase 2 (ALDH2) protects cells from ethanol toxicity by metabolizing acetaldehyde. We studied the single nucleotide polymorphism (SNP) rs886205s located between a negative and a positive regulating promoter element in the ALDH2 gene. The negative regulatory region was already associated with differential DNA methylation in the two allele variations of rs886205 SNP. Another CpG island, in the positive regulatory region of the ALDH2 promoter, extends through the SNP rs886205 and a nuclear receptor response element. We assessed rs886305 genotype and DNA methylation using bisulfite sequencing in a cohort of 83 male alcohol-dependent patients undergoing detoxification treatment (Days 1, 7 and 14) and in 33 male age-matched controls. Luciferase reporter assays were performed to address the functional significance of genotype and methylation. We observed a higher methylation in alcohol-dependent patients compared to controls. Patients with AA (n = 52) or GG/GA (n = 31) genotype differed significantly in baseline methylation levels as well as in methylation kinetics during withdrawal. AA carriers display an increase in methylation from low baseline levels while GG/GA showed the inverse pattern. The reporter gene assays corroborate these data by showing a significant effect of genotype on ALDH2 expression as well as an interaction between genotype and methylation. Our results describe a new regulatory role of rs886205 in the methylation of ALDH2 promoter region and provide additional insight into the complex regulation of ALDH2 under the condition of alcohol dependence. Genetic variations have been described to influence DNA promoter methylation of various genes. We investigated the association between the polymorphism rs886205, located on ALDH2 promoter and methylation kinetics of the neighboring CpG island in alcohol-dependent patients. Luciferase reporter assays showed functional significance of genotype, methylation and a genotype-epigenotype interaction in vitro.
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