Fig. 2

Methylation variations of significant CpG markers within the putative promoter regions. By referring to the RefSeq 41 annotation, we can determine a CpG marker’s distances to transcription start site (TSS) of a gene’s transcript. Then, we can also determine the relative locations of CpG markers within the putative promoter regions, which are the genomic regions ranging from − 5000 bp to + 3000 bp of a transcript’s TSS. a, c, e For each CpG marker, the X and Y axes denoted its distance to TSS and its methylation variation, respectively. Using the two arrows, the promoter was split into three sub-regions, the left, the core and the right sub-regions. The methylation variations (average ± S.D.) of the CpG markers located within each sub-region were labeled. The sample sizes for sub-figures a, c, e were 205,306, 393,023, and 385,840, respectively. b, d, f The box plots and t test demonstrated that the CpG markers within the core sub-region varied more than those within the other two sub-regions (P < 2.2E−16 for the six comparisons)