Figure 2: Sites having significantly different methylation patterns in women with FM compared to healthy controls. (a) A heatmap shows the 69 DM sites detected in the study. The women who have FM (F) are grouped on the left of the figure, with controls (C) being grouped on the right. Each row (CpG site) is scaled to represent methylation where lower levels are represented in green while higher levels are represented in red. The majority of significant differences resulted from women with FM (upper left red cluster) having higher levels compared to controls (upper cluster), with a smaller cluster (lower left green) showing lower methylation levels in the cases with FM compared to healthy controls. (b) Pie charts showing the percentage of DM sites according to their relationship to CpG islands. Nearly half (46.4%) of the sites that were significantly different between the women with FM compared to controls were localized to CpG islands (top pie chart), whereas CpG islands account for only about one third (31%) of the sites interrogated on the 450 K HumanMethylation array (bottom pie chart). The proportion of DM sites localized to shores that were recognized in this study (29%) closely paralleled the proportion of sites localized to shores that are interrogated in the array (23%). Sites associated with a location distant to CpG islands accounted for 24.5% of the DM sites identified in this study but accounted for 46% of the total sites interrogated on the array.