GFI1 and leukemia: We could not observe an increase in survival or significant changes in pathological parameters like spleen size or organ infiltration in mice over-expressing GFI1 but observed a clear reduction of cKit+ cells, which is a fraction of cells, in which leukemic stem cells are enriched27, giving a first hint that upregulation of GFI1 also alters in vivo the characteristics of leukaemia (Supplementary Fig. S4).