Reduction of Ape1 expression by siRNA in CD34⁺ day-10 EB cells abrogates definitive hematopoiesis. (A) CD34⁺ cells derived from day-10 CCE EBs were transfected with either Ape1 siRNA or scrambled siRNA, and plated for definitive erythroid progenitor (Ery-D) assays. (B) CD34⁺ EB cells derived from day-10 EBs were transfected with 25 nM or 50 nM Ape1 siRNA, or scrambled siRNA, and plated into granulocyte-macrophage colony (CFU-GM) assays, or (C) mixed lineage colony assays (CFU-Mix). CD34⁺ EB cells derived from day-10 EBs were transfected with 25 nM or 50 nM Ape1 siRNA, or scrambled siRNA, and plated into mixed progenitor colony (CFU-Mix) assay. Significantly fewer progenitors developed. (A-C) *P < .05 comparing cells transfected with Ape1 siRNA to that of scrambled siRNA for all progenitor assays conducted. Data represent the mean ± SD for 3 experiments.