BMP4 and juvenile myelomonocytic leukemia: Unsupervised hierarchical clustering of the 111 JMML cases according to methylation levels at the most variable 6 CpG sites (Supplemental Table 2) revealed two major groups of samples, one with BMP4 CpG sites exhibiting low-methylation levels (83 samples) and one with increased methylation (28 samples) (Fig. 2).