EpoR-GFPCre–mediated inactivation of Rb and E2f8 in the erythroid compartment results in severe anemia and enhanced but ineffective erythropoiesis. (A-D) Peripheral blood RBC numbers (A), hemoglobin (B), hematocrit (C), and spleen weights (D) of mice with the indicated genotypes. (E-K) Flow cytometric analysis of spleens (E-F) and BM (G-K) using lineage-specific cell-surface markers. (I-L) Erythroid staging by flow cytometric analysis of Ter119⁺ BM (I-J) and spleen cells (K-L) sorted by CD71 and cell size (forward scatter, FSC). (I,K) Representative flow cytometric profiles. (J,L) Percentages of different erythroid subpopulations normalized to total Ter119⁺ cells.