Methylierungsassays

Methylierungsassays, also known as DNA methylation assays, are methods to detect, quantify, or map the addition of a methyl group to cytosines in genomic DNA, most often at CpG sites. They are used to study epigenetic regulation, development, aging, and disease, and include targeted locus assays as well as genome-wide approaches.

Targeted bisulfite methods convert unmethylated cytosines to uracil while leaving methylated cytosines unchanged, enabling site-specific analysis by sequencing, PCR, or pyrosequencing. Common targeted techniques include bisulfite sequencing, methylation-specific PCR (MSP) and quantitative variants, pyrosequencing, and methylation-sensitive high-resolution melting (MS-HRM).

Non-bisulfite methods rely on antibodies or methyl-CpG binding domain proteins to enrich methylated DNA for sequencing or array analysis, examples being MeDIP-seq and MBD-seq.

Genome-wide approaches include whole-genome bisulfite sequencing (WGBS), reduced representation bisulfite sequencing (RRBS), and methylation arrays such as Infinium BeadChips.

Applications span cancer biomarker discovery, imprinting and X-chromosome inactivation studies, aging, and environmental exposure research, as well as basic studies of epigenetic regulation.

Limitations include DNA degradation from bisulfite treatment, incomplete conversion, and tissue heterogeneity; quantitative interpretation can be challenging, and costs and data analysis requirements are nontrivial.

Appropriate experimental design, controls, and validation are essential for reliable conclusions.