DNA methylation in genomic imprinting, development, and disease.

Changes in DNA methylation profiles are common features of development and in a number of human diseases, such as cancer and imprinting disorders like Beckwith-Wiedemann and Prader-Willi/Angelman syndromes. This suggests that DNA methylation is required for proper gene regulation during development and in differentiated tissues and has clinical relevance. DNA methylation is also involved in X-chromosome inactivation and the allele-specific silencing of imprinted genes. This review describes possible mechanisms by which DNA methylation can regulate gene expression, using imprinted genes as examples. The molecular basis of methylation-mediated gene regulation is related to changes in chromatin structure and appears to be similar for both imprinted and biallelically expressed genes.