In some reports, in vivo deletion of Asxl1 led to mild phenotypes of myeloid and lymphoid cell frequencies (7), while in other reports, Asxl1-knockout mice had systemic developmental defects and MDS-like presentation, suggesting a loss-of-function effect particularly in hematopoietic progenitor cells (11, 36). The gene discussed is ASXL1; the disease is myelodysplastic syndrome.