The Human Epigenome

Epigenetic mechanisms are responsible for the transmission of information that is “layered onto” the DNA from one cell division to the next. That is, epigenetic information is not contained in the DNA sequence itself, but it is nonetheless essential for normal development, for maintaining the overall integrity of the genome, and for modulating gene dosage via processes such as imprinting and X-chromosome inactivation in females. Epigenetic modifications are reversible, which makes them an attractive therapeutic target for cancer and other diseases. DNA methylation is affected by nutrition and by environmental stimuli, which lends the epigenome a remarkable level of plasticity. DNA methylation is profoundly disrupted in cancer, and several techniques have been developed to analyze the cancer epigenome both globally and at the single gene level. Importantly, DNA methylation has been shown to serve as a biomarker. A large body of research is currently under way in the hope of identifying sequences that could lead to clinical applications. It should also be noted that DNA methylation inhibitors have been used in the successful treatment of myelodysplastic syndrome in human patients. This opens a promising avenue for the clinical treatment of solid tumors in the future. Keywords: Major groove of DNA; CpG islands; Monozygotic twins; Lipotropes; Imprinted locus