Global DNA methylation levels within the cell lines and methylation domain types. (A) The distribution of average percent methylation across 20-kb windows is shown for each of the three cell lines. (B) Average percent methylation within the four methylation domain types (N-HMD, L-HMD, B-PMD, or B-HMD) defined using the HMM. The H1 cell line is included for comparison. Error bars show standard deviations. (C) Average percent methylation of promoter CpG islands in human cerebral cortex and the SH-SY5Y and IMR90 cell lines. N-HMD, neuronal HMD; L-HMD, lung HMD; B-PMD, PMD in both cell lines; B-HMD, HMD in both cell lines.