Cdc42 deletion decreases erythroid progenitor activity. (A) BFU-E and CFU-E activities in the WT or KO bone marrow cells were assayed as described in “Erythroid progenitor assays.” (B) The relative apoptotic erythroid cells stained positive for annexin V and Ter119 were analyzed by FACS in freshly harvested bone marrow cells. *P < .05; **P < .01; and ***P < .001.