Remarkably, Vav-iCre-controlled inactivation of the Nsd1 (Nsd1-/-) gene in the hematopoietic system of the mouse induced a fully penetrant erythroleukemia-like disease characterized by anemia, thrombocytopenia and multi-organ erythroblast infiltration. The gene discussed is NSD1; the disease is erythroleukemia.