HRI knockdown cooperates with pomalidomide and UNC0638 to significantly increase HbF levels. (A) The 3-phase CD34⁺ differentiation system used in combinatorial HbF pharmacologic induction and shRNA-mediated HRI depletion. (B) HRI transcript levels vs fold γ-globin induction using HRI shRNAs #1 and #2 titrated to various levels of HRI depletion (n = 6 independent donors). (C) HRI transcript levels vs fold γ-globin induction (single donor with 6 independent samples). Linear regression goodness of fit is displayed as the coefficient of determination (R²). (D) γ-Globin transcript levels (expressed as γ-globin/γ-globin+β-globin) in healthy CD34⁺ donors as measured by qRT-PCR after shRNA scrambled control or HRI depletion with 2 independent shRNAs combined with either vehicle control or HbF pharmacologic induction (50 μM hydroxyurea [HU], 1 μM pomalidomide [Pom], or 0.125 μM UNC0638). (E) Representative HbF flow cytometric plots. The percentage of F-cells is quantified for each