Increased Epo-independent viability and delayed differentiation of erythroid Lyn^+/up cells compared with Lyn^+/+ cells. (A) Similar cell morphology of J2-WT and J2-Lyn^+/up cell lines. Morphology of immortalized fetal liver erythroid J2-WT and J2-Lyn^+/up cell lines stained with Wright-Giemsa (scale bar = 5 µm). (B) Equivalent cell surface marker expression in J2-WT and J2-Lyn^+up cells. Flow cytometric profiles of J2-WT and J2-Lyn^+/up cells stained for cell surface expression of Sca1, c-Kit, CD71, Ter119, CD11b, and CD44. (C) J2-Lyn^+up cells (UP) have increased Epo-independent viability and delayed Epo-induced differentiation compared with J2-WT cells (WT). (i) Viable cell counts, (ii) viability (eosin dye exclusion), and (iii) differentiation (hemoglobin benzidine positive) analysis of J2-WT (WT) and J2-Lyn^+/up (UP) cell lines in differentiation media (T₃-depleted)²¹  in the presence (+E) or absence (−E) of Epo (5 U/mL). (D) Dose-response analysis of Epo on (i) viable cell counts, (ii) viability, and (iii) differentiation in differentiation media of J2-WT and J2-Lyn^+/up cell lines. Cell culture conditions as for C, with the indicated concentrations of Epo at 48 (viable cells and viability) and 72 hours (differentiation).