KLF1-GATA1 fusion protein upregulates δ-globin gene and HbA2 expression in erythroid cells cultured from human CD34⁺ sickle cells. Human CD34⁺ sickle cells were lentivirus transduced with vector only, KLF1, or KLF1-GATA1 fusion protein, then grown in an erythroid culture system for 3 weeks. (A) Cultured cells stained with Giemsa showing erythroid differentiation progression from erythroblast to normoblast at days 7 and 14 to a mostly uniform population of enucleated reticulocytes and erythrocytes at day 21. Original magnification, ×40. (B) Experimental schema, with the time course of expansion and differentiation phases indicated. Time points are indicated for the specific analyses (C) Quantitative-PCR (QT-PCR) analysis of globin-chain gene expression in cultured erythroid cells. ∗P < .05, ∗∗P < .01 vs vector control-transduced cells. Error bars represent the mean ± standard deviation (SD) of 3 independent experiments. (D) HPLC analysis of HbA, HbA2, and HbF expression in cultured erythroid cells. At least 3 independent experiments were performed. HPLC, high performance liquid chromatography; KG-M, medium-form KLF1-GATA1; KG-L, long-form KLF1-GATA1.