CpGs (n = 1829), which are differentially methylated in WBCs between BRCA1 mutation carriers and wild type controls and which comprise the ‘ BRCA1 -mutation DNA methylation signature’. Heatmap of normalised methylation values (blue = relative high methylation, yellow = relative low methylation) of CpGs comprising the BRCA1-mutation DNAme signature. The first colour bar at the top denotes the two main clusters where ‘red’ reflects the samples with a BRCA1 mutation whereas ‘green’ reflects samples without a mutation in BRCA1 or BRCA2 gene. The distribution of cancer cases is given in the second colour bar indicating women who had developed a breast cancer in purple. Right panel shows the enrichment of the top components of the gene set enrichment analysis in the hyper- and hypomethylated subset of CpGs; PCGT; Polycomb repressor complex 2 Group Target. Dashed line separates hypermethylated from hypomethylated CpGs.