Epigenom

The epigenome (often written epigenom in some languages) refers to the complete set of chemical modifications to the genome and to the associated chromatin structure that regulate gene expression without changing the DNA sequence. It determines how genetic information is read in a given cell or tissue and is essential for development, differentiation, and cellular identity.

Key components of the epigenome include DNA methylation, histone post-translational modifications (such as methylation and acetylation), chromatin remodeling, regulatory non-coding RNAs, and higher-order three-dimensional genome organization. These layers work together to control when, where, and how genes are expressed, and they are dynamic across development and in response to environmental cues.

Epigenetic states are established during development and can be maintained through cell divisions by maintenance enzymes and chromatin-binding proteins. Some epigenetic marks can be altered or reset in response to stimuli or during germline reprogramming, leading to changes in gene expression patterns. While most epigenetic information is cell-type specific, some aspects can be inherited across generations in limited contexts.

Study of the epigenome employs a range of techniques, including bisulfite sequencing for DNA methylation, ChIP-sequencing for histone marks, ATAC-seq for chromatin accessibility, and Hi-C for 3D genome architecture. Epigenome-wide association studies (EWAS) examine links between epigenetic patterns and traits or diseases.

Biological and medical relevance is broad: epigenetic mechanisms underpin development, imprinting, X-chromosome inactivation, aging, and cancer, and are targets for therapies such as DNA methyltransferase and histone deacetylase inhibitors, as well as emerging epigenome-editing approaches.