Environmental effects on chromatin repression at imprinted genes and endogenous retroviruses.

Environmental factors can perturb epigenetic regulation. In mammals, most studies have focused on repressive DNA methylation. Two attractive model systems to monitor environmentally triggered drifts in DNA methylation are genomic imprinting and endogenous retroviruses (ERVs), particularly intracisternal-A particles (IAPs). These systems show mechanistic similarities in their repressive chromatin organization, which in somatic cells is comparable between the DNA-methylated alleles of imprinted differentially methylated regions (DMRs) and repressed ERVs. Here, we present how during development, nutrition and chemical components can perturb DNA methylation at imprinted genes and ERVs, and discuss the still poorly understood underlying mechanisms.