The scl^RER/RER adult surviving mice present with mild anemia. (A) (i,ii) Blood films obtained from 2-month-old wild-type and scl^RER/RER mice were stained with MGG (original magnification, ×400). Black arrows indicate target cells; red arrows, reticulocytes. (iii,iv) BCB staining confirms the presence of reticulocytes in mutant scl^RER/RER blood (arrows) (original magnification, ×400). (v,vi) Representative CFU-E colonies from wild-type and scl^RER/RER total bone marrow replating (200× objective). Note the poor hemoglobinization of the mutant CFU-E colony (vi). (vii,viii) MGG/benzidine staining of CFU-E colonies (magnification, ×400). Note the lack of benzidine positive scl^RER/RER erythrocytes (viii). (B) Characterization of adult bone marrow hematopoietic cells. (Top) See legend for Figure 3C. (Bottom) Bone marrow cells derived from wild-type, heterozygous, and homozygous 2-month-old mice were analyzed by FACS according to expression of various combinations of cell surface markers. The percentage of total bone marrow cells for each cellular population is indicated. Error bars indicate plus or minus 1 SD from at least 3 independent experiments. (C) Splenomegaly in scl^RER/RER mice. (D) Splenocytes harvested from wild-type and scl^RER/RER mice were analyzed for expression of the cell surface markers CD71 and Ter119 by FACS. Populations I to IV represent progressive maturation of erythroid cells. Representative FACS plots with the percentage of cells for each population are shown. (E) Cell populations as shown in panel D were sorted and stained with MGG/benzidine. Populations are mainly characterized by I, proerythroblasts; II, basophilic normoblasts; III, late normoblasts; and IV, enucleated red blood cells. Red arrowheads show enucleated cells frequently observed in wild-type population III but not in the corresponding mutant sample. Note the irregular shape of the mutant late normoblasts and the small size of the mutant enucleated cells (scl^RER/RER, III and IV, respectively; original magnification, ×400).