Reduction of Ape1 expression by siRNA abrogates primitive and definitive hematopoiesis. (A) Cells derived from day-6 CCE EBs were transfected with either Ape1 siRNA or scrambled siRNA, and plated for primitive progenitor assays (Ery-P). (B) Cells derived from day-10 EBs were transfected with 25 nM or 50 nM Ape1 siRNA1, or scrambled siRNA, and plated for either definitive erythroid progenitor assays (Ery-D) or (C) granulocyte-macrophage colony assays (CFU-GM). At both 25 nM and 50 nM Ape1 siRNA in all assays conducted, 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.