DNA methylation signatures: Biomarkers of drug and alcohol abuse.

DNA sequence is a powerful tool that can be used for an individual's identification and investigation of various abnormalities in the genome. However, recent studies have identified other heritable changes by epigenetic mechanisms that cause changes in gene expression without altering the DNA sequence itself. In particular, DNA methylation mediates long-lasting changes in gene promoters, which makes it an appealing epigenetic mechanism to study variation in methylation status that characterizes the extent of drug abuse. We summarize recent findings on methylation alterations in a number of genes caused by various drugs including cocaine, opioids, cannabinoids, amphetamine, phenobarbital, and alcohol in various human and animal model studies. Additionally, a minimal discussion of the basic concepts of methylation is provided. The determination of possible DNA methylation alterations can assist in finding the cause and circumstances of death or ailment, and gene markers can be potentially used as biomarkers in the future.