Gata1 knockout in mice (Pevny et al., 1991) results in embryonic lethality around E10.5–E11.5 due to severe anemia, with GATA1-null cells undergoing massive apoptosis at the proerythroblastic stage (Pevny et al., 1995; Fujiwara et al., 1996). Here, GATA1 is linked to anemia (phenotype).