We retrovirally transduced Lin− BM cells derived from GFI1-KD or GFI1-KD; Mx1-Cre transgenic mice with a vector encoding the MLL-AF9 fusion protein, the product of the t(9;11)(p22;q23) translocation, found in a subset of human leukaemia and described to induce an aggressive form of AML in mice, similar to the situation found in human patients33. The gene discussed is MLLT3; the disease is leukemia.