Impaired proliferation of PU.1G/G FL erythroid precursors. (A) Ex vivo expansion of erythroid progenitors. The 13.5-dpc FL cells (2 × 106) were plated in erythroid medium at day 0, and cell numbers were counted each following day. Graph represents 1 of more than 5 experiments with similar results. (B) Optimal proliferation of PU.1G/G FL erythroid precursors requires Epo, SCF, and Dex. The 13.5-dpc FL cells (2.2 × 105 WT, 1.8 × 105 PU.1G/G) were plated in erythroid medium at day 0 in the presence of Epo, SCF, Dex, and IGF or in the absence of the indicated factors. Cell numbers were counted each following day. Graphs represent 1 of 3 independent experiments. (C) Impaired proliferation of PU.1+/G and PU.1G/G erythroid progenitors. The experiment was performed as depicted. Forty-eight hours after CFSE loading, cells were harvested and analyzed for TER119, CD71, and CFSE expression. White histograms represent the CFSE intensities of the gated CD71+TER119– cells; black histograms represent the CFSE intensity of a control population that had not divided.
