Applying whole-genome studies of epigenetic regulation to study human disease

Epigenetics may be broadly defined as the study of processes that produce a heritable phenotype that is not strictly dependent on DNA sequence. The definition has traditionally been restricted to processes that occur in the cell’s nucleus, with the term ‘heritable’ having a loose meaning that can be applied to either the entire organism or single cells. For example, a process that produces a phenotype only in a specific cell type (for instance, chromatin-mediated maintenance of a differentiated state) is usually considered epigenetic even if it is not directly inherited, but instead must be re-established or actively maintained at each cell division. Given this definition, the field of epigenetics has long focused on proteins that affect DNA packaging, and thereby affect the utilization of the genetic information encoded in the DNA template. This focus extends to the enzymatic modification of those proteins, and to the enzymatic modification of the DNA template itself, primarily DNA methylation