Figure 1: Genetic and environmental influences on genome-wide DNA methylation levels.
From: Genetic and environmental influences interact with age and sex in shaping the human methylome
Estimates from classical twin modelling in 769 MZ and 424 DZ twin pairs. (a) Histograms of genome-wide ACE model estimates: variance explained by additive genetic effects (a2, red), common environmental effects (c2, purple) and unique environmental effects (e2, green). (b) Histograms of genome-wide ADE model estimates: variance explained by additive genetic effects (a2, red), non-additive genetic effects (d2, dark purple) and unique environmental effects (e2, green). Y axes are truncated. (c) Scatterplots of DNA methylation levels in MZ and DZ twin pairs at four exemplary CpG sites. The DNA methylation level in twin 2 (y axis) is plotted against the DNA methylation level in twin 1 (x axis) for all MZ twin pairs and all DZ twin pairs. For illustrative purposes, methylation β-values (which represent methylation proportion) obtained after normalization are plotted in this figure, whereas all analyses were performed on normalized methylation M values, corrected for a number of covariates (see Methods section). Four examples of CpG sites were selected from the most variable CpG sites (s.d.>0.03) with high heritability (h2=0.56; upper left), high SNP heritability (h2SNPs=0.81; upper right), low heritability (h2=0.18; lower left) and low SNP heritability (h2SNPs=0.00, lower right). Note that the larger the difference between the correlation in MZ twins and in DZ twins (stronger correlation in MZ twins), the higher the total heritability. The resemblance of MZ and DZ twins is not informative with respect to the amount of variance explained by genome-wide SNPs. Additional examples are plotted in Supplementary Figs 10–13.
