The DNA methylation profile of three human chromosomes is reported in a study to be published in the December 2006 issue of Nature Genetics, marking substantial progress towards a complete accounting of the human 'epigenome', the collection of modifications to the human genetic code that occur without changing the original DNA sequence.
DNA methylation refers to the chemical modification of DNA by the addition of methyl groups, which consist of one carbon and three hydrogen atoms. This process can affect the expression of nearby genes, usually silencing or switching them off, and is potentially an important factor in the development of some cancers when it occurs aberrantly. The Human Epigenome Project (a consortium that includes the Welcome Trust Sanger Institute, UK; Epigenomics AG, Germany; and The Centre National de Génotypage, France), whose goal is to catalog all of the sites of methylation in the human genome in all major tissues, have now done so in 12 different tissues for chromosomes 6, 20 and 22.
In addition to providing the catalog as a publicly available resource for other investigators, the authors also report that there are only very small differences in the methylation patterns between male and females and between young and old individuals. Significant differences were observed between different tissues, however.
Finally, by examining some of the corresponding regions in the mouse genome, they concluded that the pattern of methylation has been generally conserved during evolution, at least among mammals.
Florian Eckhardt (Epigenomics AG, Berlin, Germany)
Stephan Beck (Wellcome Trust Sanger Institute, Hinxton, UK)
Abstract available online.
(C) Nature Genetics press release.
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