epigenomewide

Epigenomewide refers to research approaches that survey epigenetic modifications across the genome to identify associations with phenotypes, exposures, or diseases. Like genome-wide association studies (GWAS), epigenomewide studies aim to be comprehensive, but they examine epigenetic marks rather than DNA sequence. The most common focus is DNA methylation at CpG dinucleotides, though other epigenetic features such as histone modifications and chromatin accessibility can be explored in broader epigenome-wide analyses.

Typically, epigenomewide studies use high-throughput platforms such as array-based assays (for example, Illumina Infinium 450K or EPIC methylation arrays) or sequencing-based approaches (e.g., bisulfite sequencing). Data are summarized as methylation levels or related metrics and tested for associations with the trait of interest using regression models, often with covariates to adjust for confounders. Because millions of sites may be tested, rigorous multiple-testing correction is applied, and analysis frequently accounts for cell-type composition and other sources of technical variation.

Study designs span cross-sectional and longitudinal projects. Results must be interpreted with caution due to tissue specificity, environmental factors, and the dynamic nature of epigenetic marks. Associations do not imply causality; methods such as Mendelian randomization or experimental validation are used to explore potential causal links.

Applications include discovery of epigenetic biomarkers for disease risk, exposure history, or treatment response, and investigations into aging through epigenetic clocks. Public resources, such as the EWAS Catalog and data from Roadmap Epigenomics, support replication and meta-analysis across cohorts.