ESPE Abstracts

Genomic imprinting in mammals is controlled by DNA methylation. This essential epigenetic phenomenon mediates the mono-allelic expression of about hundred autosomal protein-coding genes and hundreds of regulatory non-coding RNAs, such that these become expressed from one of the two parental alleles only. Although the first imprinted genes were discovered less than thirty years ago, given their key roles in fetal development, homeostasis and brain functions, these exceptional genes have been studied in great detail. For many, dosage is critical and environmentally-induced or stochastic perturbations cause disease. Evolutionarily, imprinting is a young phenomenon which arose at the time that placentation became more important for development with a growing dependence on maternal resources postnatally. Amongst the youngest, most recently evolved, imprinted genes many are imprinted in the placenta only, and different studies have linked their expression to fetal growth. The recent discovery of polymorphic imprinting in humans suggests that the evolutionary process is still ongoing. The underlying reasons are debated and different evolutionary theories have been proposed. Imprinting research evolves fast as well and has boosted our understanding of endocrine and other imprinting-related disorders. A challenge for the future will be to unravel the relative importance of genetic versus epigenetic alterations in the emergence of imprinted gene expression, and in its pathological perturbation in animals and humans.