Before the discovery of GATA2 as a disease gene in humans, the first Gata2 knockout (KO‐Gata2−/−) mice generated showed embryonic lethality at 10.5 days post coitum due to lack of definitive hematopoiesis and severe anemia (Tsai et al., 1994). The gene discussed is GATA2; the disease is anemia (phenotype).