DNA METHYLATION FROM EMBRYO TO ADULT

This chapter discusses the deoxyribonucleic acid (DNA) methylation from embryo to adult. The existence of tissue-specific methylation patterns and the results of the transfection experiments, taken together, clearly prove that once ethylation patterns are formed, they are propagated in somatic tissues. The methyltransferase found in mammalian tissues is suitable for directing such a maintenance activity, as it shows preferential activity, with hemimethylated DNA as a substrate. Embryonic cells are capable of demethylating and de novo methylating their DNA. These activities allow the embryo to erase the methylation patterns inherited from the gametes and create a new methylation pattern. This characteristic of embryonic cells prompted studies aimed at elucidation of the mechanisms involved in the formation of gene-specific methylation patterns during the embryonic development and gametogenesis. The presumed role of methylation in parental imprinting and the recent finding that target mutation of the murine DNA methyltransferase gene results in embryonic lethality, strongly suggest that the dynamic changes in DNA methylation patterns during embryo development play a role in reprogramming the genome in the developing embryo. © 1994 Academic Press Inc.