Erythropoiesis is severely impaired in FLVCR-deleted bone marrow with a maturation block at the proerythroblast stage. (A) Competitive repopulation assay using FLVCR-deleted or control bone marrow cells and GFP⁺ competitor cells. The contribution of each donor population to erythropoiesis was determined by flow cytometry of peripheral blood. (B) Competitive transplantation with 95:5 ratio of FLVCR-deleted:GFP⁺ bone marrow cells. Hematopoietic recovery is determined by granulocyte recovery by flow cytometry. The contribution of FLVCR-deleted cells to erythropoiesis is determined by flow cytometry. (C) Proerythroblast populations were identified by flow cytometry. (C-D) The extent of apoptosis was determined by staining with 7-AAD and Annexin V. Bone marrow was harvested 24 weeks after transplant.