methylomics

Methylomics refers to the genome-wide study of DNA methylation patterns, collectively known as the methylome, and encompasses the acquisition, distribution, and functional consequences of methyl groups added to nucleic acids. In mammals, the primary modification is 5-methylcytosine at CpG dinucleotides; in plants and some other organisms, non-CpG methylation and methylation in various contexts also occur. Methylomics is a core component of epigenomics and interacts with other chromatin marks to regulate gene expression.

The field aims to map methylation landscapes across tissues, developmental stages, environmental conditions, and disease states, and to relate methylation to transcriptional activity, replication timing, and chromatin structure.

Methods include sequencing-based approaches such as whole-genome bisulfite sequencing (WGBS) and reduced representation bisulfite sequencing (RRBS), as well as enrichment-based (MeDIP-seq) and array-based platforms such as Infinium methylation arrays. Single-cell methylomics is advancing, with scBS-seq and snmC-seq.

Applications encompass cancer epigenetics, where abnormal methylation patterns are common, studies of development and aging, imprinting disorders, and exposure biology. Methylation profiles serve as biomarkers and as the basis for therapies targeting methylation, such as DNA methyltransferase inhibitors; and methylation clocks estimate biological age.

Challenges include tissue heterogeneity, sample quality, data analysis complexity, and cross-study comparability. Data resources and consortia such as ENCODE, Roadmap Epigenomics, and MethBase provide reference methylomes and tools for interpretation.