Igbp1 expression delays and impedes TGF-β–induced differentiation in Epo/SCF-treated erythroblasts. Three clones transduced with empty vector (EV; A,C,E) or Igbp1 expression constructs (Igbp1; B,D,F) were cultured in the presence of Epo and SCF but without Dex, supplemented (black symbols) or not supplemented (white symbols) with 20 ng/mL of TGF-β. Cumulative cell numbers (A,B), mean cell volume (C,D), hemoglobin per cell volume (E,F), and cell morphology (G) were examined at day 4 (t96) or 5 (t120) after differentiation induction. (See also legend to Figure 3).