Epigenetics in mental illness: Hope or hype?

Recently there has been increasing interest in genome-wide epigenetics (or epigenomics) of healthy controls (reference) compared to samples with a specific mental illness,based in part on evidence from rodent models that alterations in epigenetic modifications are implicated in behavioural phenotypes related to mental illness.1-3 unlike genetic sequences,epigenetic modifications are variable and depend on cellular phenotype and environmental conditions.4 genetics is considered insensitive to these conditions,since the same genetic sequence is present in the organism through out life,with the exception of sporadic mutations. epigenetics includes a large number of reversible covalent modifications that do not alter the genome (dna sequence),which include covalent modification of dna (dna methylation) and acetylation,methylation and phosphorylation of histones and dna-associated proteins. typically,dna methylation is associated with regions of condensed chromatin structure and silencing of gene expression,and is often associated with histone deacetylation and histone methylation (especially at lys-9).5-7 specific epigenetic changes at discrete sites in candidate genes have been correlated with alterations in specific gene expression,leading to altered lifelong behavioural phenotypes.1-3 the implication is that by understanding the full spectrum of epigenetic modifications across the genome,valuable markers of behavioural or disease phenotypes will emerge,using bioinformatics analysis to reveal specific changes that correlate with behaviour. © 2010 canadian medical association.