DNMT3A and myelodysplastic syndrome: When Dnmt3a KO HSCs were transplanted into lethally irradiated mice without healthy bone marrow cells, all the mice died within one year of a range of hematologic malignancies such as MDS, AML, and T- and B-cell acute lymphoblastic leukemia (Table 1), the diseases also frequently observed in patients with DNMT3A mutations, and the sick mice acquired a variety of cooperating mutations [87,88].