Aberrant DOT1L activity is found in various hematopoietic malignancies including AML with KMT2A (MLL) gene rearrangements (Okada et al., 2005; Bernt et al., 2011; Jo et al., 2011), partial tandem duplications (Kühn et al., 2015), NPM1 mutations (Kühn et al., 2016), MLLT10 (AF10) gene fusions (Chen et al., 2013), and NUP98-rearranged AML (Deshpande et al., 2014). The gene discussed is KMT2A; the disease is acute myeloid leukemia.