The contribution of additive genetic and environmental factors to levels of DNA methylation.

Shown are the results from structural equation models to estimate the mean proportion of variance in DNA methylation explained by additive genetic effects (A), shared environmental effects (C) and unshared (or unique) environmental effects (E) across Illumina 450K probes. Results are presented separately for DNA methylation sites located on the autosomes and X-chromosome, and stratified by whether they have intermediate levels of DNAm and/or are “variable”.