Thus, for AML onset, additional class II mutations such as chromosome rearrangements are probably required,3 e.g. promyelocytic leukemia-retinoic acid receptor-alpha (PML-RARa), core binding factor/smooth muscle myosin heavy chain (CBFß/SMMHC), mixed-lineage leukemia (MLL) and acute myeloid leukemia-1 transcription factor/eight-twenty-one corepressor (AML1/ETO). The gene discussed is RUNX1; the disease is acute myeloid leukemia.