Genomic imprinting and mammalian development.

Genomic imprinting, which results in the mono-allelic expression of certain genes in a parent of origin-dependent manner, represents a specialized form of gene regulation which may be vitally important for mammalian development. The mechanisms which underlie imprinting and the molecular nature of the imprint itself remain elusive but most likely include epigenetic modifications of DNA, such as methylation and chromatin structure changes. It is clear, however, that many of the known imprinted genes play important developmental roles and that changes in the functional imprinting of some of these genes may have important pathological consequences, including placental abnormalities.