Loss of Cul4A in the bone marrow is sufficient to cause hematopoietic failure and is lethal. (A) Cul4A deletion in transplant recipients of mutant bone marrow causes a dramatic loss of bone marrow and spleen cellularity. Recipients of either mutant or control bone marrow LDMNCs were induced with pIpC and monitored daily. Sick, near-death recipients of mutant cells were killed along with a control recipient and sections of tibia, spleen, and duodenum were prepared. For each tissue, mutant and control images are shown at the same magnification. The same microscope and camera were used as described for Figure 2. (B) For transplant recipients described in panel A, blood counts from recipients of mutant (■) and control (□) bone marrow were graphed versus days after induction. Asterisks denote time points where mutant and control count differences were statistically significant (P ≤ .03). Results from 3 independent experiments were combined.