DNA methylation and mammalian epigenetics

Epigenetic modifications of DNA such as methylation are important for genom e function during development and in adults, DNA methylation has central im portance for genomic imprinting and other aspects of epigenetic control of gene expression, and during development methylation patterns are largely ma intained in somatic lineages. The mammalian genome undergoes major reprogra mming of methylation patterns in the germ cells and in the early embryo. So me of the factors that are involved both in maintenance and in reprogrammin g, such as methyltransferases, are being identified. Epigenetic changes are likely to be important in animal cloning, and influence the occurrence of epimutations and of epigenetic inheritance. Environmental factors can alter epigenetic modifications and may thus have long lasting effects on phenoty pe. Epigenetic engineering is likely to play an important role in medicine in the future.