Representative erythropoiesis profiles of bone marrow and spleen of 4.1R^−/− and phlebotomy-induced mice. (Top panel) Representative erythropoiesis profiles of bone marrow. Note that there is an increased proportion of nucleated erythroblasts (I+II+III+IV) which is accompanied by a decreased proportion of enucleated erythrocytes (V+VI) in both 4.1R^−/− and phlebotomy-induced WT bone marrow compared with WT bone marrow. (Bottom panel) Representative erythropoiesis profiles of spleen. Note that there are very few erythroblasts in WT spleen but a large proportion of nucleated erythroblasts in the spleens of both 4.1R^−/− and phlebotomy-induced WT anemic mice.