Imprinted by Eed

Imprinted genes are subject to epigenetic regulation and undergo parent-of-origin-specific allelic silencing. Many imprinted genes have been shown to contain a differentially methylated region (DMR). In an Advanced Online Publication in Nature Genetics, Jesse Mager and colleagues at the University of North Carolina at Chapel Hill, US, report a role for the Polycomb group protein Eed (embryonic ectoderm development) — a histone methyltransferase — in epigenetic regulation at imprinted loci (Nature Genetics, DOI:10.1038/ng1125,10 March 2003).

Eed^-/- knockout embryos showed upregulation of a subset of paternally-repressed imprinted genes. Loss-of-imprinting may account in part for the lethality of Eed knockout embryos. Eed mutation did not affect parent-of-origin methylation, but did cause changes in the methylation of certain CpG dinucleotides in the DMR of imprinted genes. These data provide the first link between mammalian Polycomb group genes and genome imprinting.