LSD1 inhibition activates γ-globin transcription but blocks erythroid differentiation. (A) Representative flow cytometry plots of human CD34⁺ HSPCs undergoing erythroid differentiation after 11, 14, and 18 days (d) in culture. Cells were treated with DMSO or with 1.1 μM, 370 nM, or 120 nM LSD1i (CCG050). Cells were monitored for CD71 and CD235a cell surface markers, whose acquisition reflect maturing erythroid differentiation stages.³³ Numbers in each quadrant indicate the percentage of gated cells. Results are representative of experiments performed using CD34⁺ HSPCs from 2 healthy adult donors. (B) Representative HPLC chromatograms of day-18 cells cultured or not with CCG050 from panel A. HbF percentages are indicated in parentheses. (C) Percentage of γ-globin transcripts in total β-like (γ+β) globin mRNAs at day 14. (D) mRNA abundance of γ-globin and β-globin (normalized to OAZ1 internal control mRNA)¹⁵ at day 14. The γ-globin transcript abundance in DMSO-treated cells was arbitrarily set at 1. (E) Transcript levels of key erythroid TFs GATA1, KLF1, and TAL1 (normalized to OAZ1 mRNA) were reduced in day-14 cells treated with 370 nM LSD1i CCG050. Transcript levels of each mRNA in DMSO-treated cells were arbitrarily set at 1. Data are mean ± standard deviation from 3 replicates. ***P < .001, unpaired Student t test. h, human.