Conditional ablation of DNMT3A in mice has been shown to increase the stem cell pool and to impair differentiation.7 The relevance of DNMT3A is further supported by frequent mutations in acute myeloid leukemia (AML)8, 9 and myelodysplastic syndromes.10 About 22% of AML patients harbor mutations in DNMT3A, either at the highly recurrent position R882 or at other sites within the gene.8 Yan et al.11 have recently reported that mutations in DNMT3A are associated with alterations of DNAm and gene expression profiles (such as HOXB genes). The gene discussed is DNMT3A; the disease is acute myeloid leukemia.