DNA methylation changes in CpGs across the 14 chromatin states.

<p>To facilitate the visualization of aging-associated DNA methylation changes, we divided CpGs into five classes based on their regression coefficients from the linear model. CpGs that rarely exhibit DNA methylation alterations (absolute value of regression coefficients < 0.0002, 5% quantile), those slightly exhibit DNA methylation alterations with aging (absolute regression coefficients in [0.0002, 0.0034), 5~20% quantiles), CpGs that change DNA methylation medially (absolute regression coefficients between [0.0034, 0.0272), 20~80% quantiles), and CpGs that strongly (absolute regression coefficients between [0.0272, 0.0591), 80~95% quantile) and very strongly (absolute regression coefficients > = 0.0591, top 5%) alter DNA methylation are referred to as never (never), slightly (slight), medially (medium), strongly (strong) or very strongly (very strong), respectively. CpGs with fractional methylation levels between 0 ~ 0.05 and 0.05 ~ 0.2 are defined as unmethylated and hypo-methylated, respectively. CpGs with fractional methylation levels between 0.95 ~ 1.00 and 0.80 ~ 0.95 are defined as methylated and hyper-methylated, respectively. (A) The proportions of CpGs in different classes in genomic regions occupied by different chromatin states. (B) Changes of CpG methylation with aging across three individuals (newborn, 25 years old and 82 years old). (C) The mean regression slopes of the most significant (top 5% in regression coefficients, <i>P</i>-values < 10⁻³) aging CpGs reveal contrasting patterns of aging-associated DNA methylation changes between active versus poised/repressed chromatin states.