MLL 5′-CpG island methylation status. Genomic DNA was extracted from bone marrow cells enriched for CD34⁺ cells from 2 disease-free donors and peripheral blood mononuclear cells from 1 disease-free donor. DNA was extracted from diagnostic bone marrow (BM) cells obtained from 2 AML cases with the MLL^PTD/WT and 1 AML case with the MLL^WT//WT and all with greater than 50% blasts prior to enrichment. BS-PCR sequencing was performed as described in “Materials and methods.” The CpG sites (indicated by vertical lines on a horizontal line representing DNA sequence) evaluated are numbered relative to the known transcriptional initiation site of MLL (arrow above horizontal line). The total number of plasmid subclones sequenced for each sample was 10. Percentage of methylation status (number of times methylation was observed for a particular CpG site of 10 sequenced clones × 100%) is indicated by shading of circles.