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.