Differentiation and proliferation of erythroid progenitors. (A) Flow cytometry analysis of CD71 and TER119 expression of freshly harvested hematopoietic cells, with regions of maturing erythroid cells indicated as described.²⁰  Table S1 presents the quantification. (B) CD71 and TER119 expression of E14.5 fetal liver cells after in vitro induction of Kras^G12D for 4 days (day 0), then after 1 day of EPO stimulation (day +1), or after 2 days of EPO stimulation and 1 day of EPO withdrawal (day +3). (C) BrdU incorporation in vivo by CD71⁺TER119⁺ bone marrow cells. Note that the CD71/TER119 staining profile reflects lysis of erythrocytes and fixation required for BrdU staining. Mean percentage BrdU⁺ cells ± SEM is shown.