Epigenetic selection and the DNA methylation signatures of adverse prenatal environments

Maternal adversity is associated with long-term physiological changes in offspring. These are believed to be mediated through epigenetic mechanisms, including DNA methylation (DNAm). Changes in DNAm are often interpreted as damage or as part of plastic responses of the embryo. We propose that selection on stochastic DNAm differences generated during epigenetic reprogramming after fertilization contributes to the effects of maternal adversity on DNAm. Using a mathematical model of epigenetic reprogramming in the early embryo we predict that this “epigenetic selection” will generate a characteristic reduction in variance of DNAm at selected loci in populations exposed to maternal adversity. We tested this prediction using DNAm data from a human cohort prenatally exposed to the Dutch Famine and confirmed the reduction in DNAm variance, suggesting that epigenetic selection may have occurred. Epigenetic selection should be considered as a possible mechanism linking adversity in pregnancy to offspring health and may have implications for the likely effectiveness of intervention strategies.