Figure 2.
Depiction of Rates of DNA Methylation in Three Life Stages
(A) Rates of methylation change with age during three developmental life stages (the fetal period, childhood, and postchildhood/adult) at each CpG site for 27,578 CpG loci. A rate of change is plotted on the x axis. The −log10 p value is on the y axis, such that increasing values indicate more significant changes in methylation with age within a given stage. Red dots represent significant age-related methylation changes at FDR < 0.05. The fastest rates of methylation changes occurred during the fetal period, involving predominantly decreases in methylation (negative values on the x axis). In contrast, during the childhood and adulthood the changes were much slower and involved mainly increased methylation with aging (positive values on the x axis).
(B) Average rates of significant methylation changes with age within three developmental stages (red = the fetal period, green = childhood, blue = postchildhood). The absolute rate of the methylation change per year for the significant age-related CpG loci (FDR < 0.05) is on the y axis. The fastest changes in methylation occurred during the prenatal period, followed by childhood and postchildhood. The error bars represent standard deviations.
(C) Diagram showing the numbers of the CpG sites with significant age-related changes during the life stages. Of 27,578 CpG sites, significant age-related changes in DNA methylation (FDR < 0.05) were observed at 865 sites during the fetal period, 5,506 sites during childhood, and 10,578 sites during postchildhood. One hundred and thirty-eight sites out of the 252 sites that overlapped between the fetal period and the childhood and 188 sites out of the 3,529 sites that overlapped between children and postchildhood showed the opposite patterns of methylation (an increase followed by a decrease or vice versa) between these life stages. The transition from the fetal life to childhood is frequently associated with a reversal of direction in DNA methylation profile.