DMOG synergizes with Dex to increase the number of erythroblasts formed from a BFU-E cell 300-fold. The experimental protocol was similar to that used in Figure 2A and B except that the CFU-E and BFU-E cells were purer (CD71andCD24a^20%high and CD71andCD24a^10%low, respectively). The improved method provided a BFU-E population that formed 94% BFU-E, 5% CFU-E, and 1% other myeloid colonies in colony-forming assays with a plating efficiency of 70% (supplemental Table 2). Cultures contained or not 100nM Dex and/or 333μM DMOG. (A) Proliferation of sorted CFU-E cells. Cells do not increase proliferation in response to Dex or DMOG alone, whereas a combination of both Dex and DMOG increase proliferation 1.7-fold (P < .05; n = 6). Error bars show 1 SD. (B) Proliferation of sorted BFU-E cells (n = 4). The maximum increase in proliferation (compared with day 6 with no Dex or DMOG) was 2-fold with DMOG (day 7), 42-fold with 100nM Dex (day 9), and 306-fold with both Dex and DMOG (day 10). The synergistic effect is shown by the fact that DMOG increases the stimulatory effect of Dex on proliferation 7.3-fold (more than the additive 1.7-fold increase). Error bars show 1 SD. (C) BFU-E cells were cultured in SFELE medium containing 0nM, 1nM. 10nM, or 100nM Dex with different concentrations of DMOG. Cells were counted from day 4 until the day cell counts dropped. The y-axis shows the average expansion of several thousand BFU-E cells plated in each experiment. Without Dex 333μM DMOG had little effect on BFU-E proliferation, whereas adding 1nM Dex allows 333μM DMOG to enhance maximum BFU-E proliferation 12-fold. (n = 4) At the endpoint of the BFU-E cell cultures, 95% of cells were erythroblasts (Figure 6C; supplemental Figure 6B,D).