DNA methylation of the β-like globin gene promoters. (A) Target region (gray) in the γ-globin (HBG) promoter with CpG dinucleotide sites that were analyzed for methylation by mass spectrometry. Due to high sequence homology, the assay did not discriminate between HBG1 and HBG2. (B) γ-globin promoter CpG methylation (mean of 6 CpG sites) in GPEP cells of adults, newborns, JMML patients classified as normal HbF, and JMML patients classified as elevated HbF. (C) Correlation between globin expression [γ/(γ+β) mRNA quotient] and γ-globin promoter methylation in GPEP cells of patients with JMML. r, Pearson coefficient. (D) γ-globin promoter CpG methylation (mean of 6 CpG sites) in non-GPEP cell populations of adults, newborns, and patients with JMML. (E) Target region (gray) in the β-globin (HBB) promoter with CpG dinucleotide sites that were analyzed for methylation by bisulfite sequencing. (F) β-globin promoter CpG methylation in GPEP cells of 6 JMML patients assessed by bisulfite sequencing. Lines represent individual alleles; filled circles, methylated cytosines; open circles, unmethylated cytosines. The average level of methylation across CpG sites and alleles is indicated at the top for each patient. Mann-Whitney test: **p ≤ 0.01; ***p ≤ 0.001.