Expression of EpoR-tdTomato in mouse FL and BM erythroid cells. FL (A) and BM (B) progenitors. (a) Plot of CD71 vs c-Kit of 7AAD^–Linages^–CD16^–CD32^–CD41^–CD34^–Sca1^– cells revealing 3 populations in FL (I: BFU-E; II: BFU-E/CFU-E mixture; and III: CFU-E) and 4 populations in BM (I: c-Kit⁺CD71^–; II: c-Kit⁺CD71^Low; III: c-Kit⁺CD71^High; and IV: c-Kit^–CD71^–). (b) Histogram of EpoR-tdTomato showing EpoR-tdTomato expression levels in indicated cell populations. (c) Quantification of mean fluorescence intensity of EpoR-tdTomato. (C) BM erythroblasts. (a) Left panel: Representative plot of CD44 vs FSC-A of Ter119⁺ cells revealing different staged erythroid cells; right panel: histogram of EpoR-Tdtomato of the indicated cell population revealing progressive decrease of EpoR-tdTomato from Pro to RBC. (b) Representative images of IFC analysis showing expression of EpoR-tdTomato as well as changes in cell size, Ter119, and CD44 from Pro to RBC. (D) FL erythroblasts. (a) Left panel: Representative plot of CD44 vs FSC-A of Ter119⁺ cells revealing different staged erythroid cells. Right panel: histogram of EpoR-Tdtomato of the indicated cell populations. (b) Composite representative cytospin images of the sorted erythroblasts. (c) Representative images of IFC analysis. (E) Quantification of mean fluorescence intensity of EpoR-tdTomato. N = 3. FSC-A, forward scatter area; WT, wild type; IFC, imaging flow cytometry.