KLF1-GATA1 fusion protein upregulates δ-globin gene and HbA2 expression in erythroid cells cultured from SCD mouse HSCs. Sca-1⁺c-Kit⁺Lin^/low HSCs isolated from SCD mice were transduced with vector only, KLF1, or KLF1-GATA1 fusion protein, then grown in an erythroid culture system for 3 weeks. (A) Giemsa staining at the cell-culture time points indicated, showing the progression of erythroid differentiation from HSCs to enucleated reticulocytes and erythrocytes. Original magnification, ×40. (B) The time course of expansion and differentiation phases. Time points are indicated for the specific analyses conducted. (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 indicate the mean ± SD results of 3 independent experiments. (D) Representative HPLC analysis of HbA2 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.