Cell-autonomous thrombocytopenia in mice lacking NF-E2 function. (a) Platelet counts from adult mice of the indicated p45 NF-E2 genotype (left 2 bars, dark shading) are reproduced after fetal liver cell transplantation. Lethally irradiated wild-type recipients were transplanted with fetal liver cells from p45 NF-E2^+/+ or NF-E2^−/− mice and hematologic profiles followed for 3 to 9 weeks. Severe thrombocytopenia is evident in recipients of p45 NF-E2^−/− transplants. (b) Southern blot analysis of hematopoietic tissues from representative fetal liver transplant recipients verifies reconstitution in these animals by cells of the transplanted genotype. The wild-type allele is represented by a 5-kb band, and the knockout allele is represented by a 7-kb band. (c) Hematoxylin and eosin-stained microscopic sections of the spleen from representative recipient mice reconstituted with fetal liver cells from wild-type (left panel) or p45 NF-E2^−/−(right 2 panels) donors. The numbers and morphology of the megakaryocytes are similar to those seen in adults of the donor genotypes. Original magnifications: for left two panels, ×40; for right panel, ×100.