HOXA9 and acute myeloid leukemia: We next turned our focus to early leukemia progression in a Hoxa9/Meis1-Ubiquitin-c-GFP (HA9M1) mouse model of AML, performing intravital imaging of the calvarium bone marrow between 1 and 3 days after transplanting 3 × 106 cells into non-irradiated recipients (Fig. 4a).