Histone lysine methylation in genomic imprinting

Genomic imprinting is an epigenetic phenomenon that causes parent-of-origin-specific expression of a small subset of genes in mammals. DNA methylation is believed to be the primary epigenetic signal that controls genomic imprinting. These methylation imprints are established during gametogenesis in male and female germ cells and maintained and interpreted during embryogenesis and in somatic tissues. Based on recent studies, histone lysine methylation plays an important role in the regulation of imprinted gene expression and, more intriguingly, may also be involved in the establishment and maintenance of DNA methylation imprints. In this point of view, we discuss these studies and their implications.