Imprinting in mammals

Abstract

Genomic imprinting is an epigenetic gene-marking process which allows a subset of mammalian genes to be monoallelically expressed in a parent-of-origin specific manner. The regulation of this imprinted gene expression involves DNA methylation and chromatin modifications, marking parental alleles differentially. Imprints are established in accordance to the sex of the parent in the germline, and are subsequently maintained throughout development and adult life, and are erased prior to establishment during germ cell development. As imprinted gene expression plays an essential role in normal growth and development, genetic and epigenetic disruption altering the dosage of imprinted genes are associated with several developmental defects and diseases. Over the last few decades, after the discovery of the first imprinted gene, many different mechanisms have been implicated in the regulation of imprinted gene expression. This review summarizes the current understanding of the main molecular players and mechanisms in the life cycle of imprinting, and the regulation of the imprinted genes and clusters described so far, the diseases associated with imprinting, and finally the relevance of imprinting in assisted reprogramming technology (ART) or cell reprogramming.