Figure 1.
Comparative methylation profiling of the X chromosome in 45,X and 46,XX individuals shows that X inactivation results in increased methylation of CpG islands at gene promoters. Regions containing high densities of CpG dinucleotides, corresponding with the transcription start sites of genes subject to X inactivation, show raised methylation levels on the Xi. The image shows the screenshot of a 250-kb region of Xp11.3 (chrX:46,475,000–46,725,000, hg18), with methylation data uploaded as custom tracks in the UCSC Genome Browser.
