Integrative genomic viewer (IGV)

To visualize the methylation region, we used the IGV tool that enables real-time exploration of large datasets including methylation [84]. All data files submitted to IGV are represented in horizontal rows called track. Figure 3D–3E display various tracks including the Genome reference Hg19 (RefSeq Genes), all human promoters (gene promoters), all existing CG probes (Illumina CG probes) together with all differentially methylated probes between control and PAH patients (Control vs all). Moreover, additional files from the heatmap analysis were loaded showing the hypo-methylated (cluster 1, Figure ​Figure3D)3D) or hyper-methylated (cluster 2, Figure ​Figure3E)3E) promoters in PAH patients compared to controls. By evaluating the methylation level (numbers of modified probes) for each promoter, IGV allowed us to focus on the most important genes.