Consistent with this claim, we determined methylation levels by bisulfite colony sequencing immediately upstream to the repeat (region F in ref. 14) and validated the binding of CTCF in an overlapping region (CTCF binding site I, CTCFI) by ChIP analysis in wild type, DM1 and Δ/Δ hESCs (Fig. S3b and S3c). The gene discussed is CTCF; the disease is myotonic dystrophy type 1.