β-catenin deletion reverses myeloid and erythroid cell differentiation blockage and exhaustion induced by Apc loss. (A-B) Histograms represent the frequency of Mac-1⁺Gr⁺ (A) myeloid cells and (B) erythroblasts in BM from Apc^Δ/Δ and Apc^Δ/Δβ-catenin^Δ/Δ CM (left, 2 weeks after induction) or Apc^Δ/Δβ-catenin^Δ/Δ, β-catenin^Δ/Δ, and β-catenin^fl/fl (right, 5 weeks after induction). Mean ± standard deviation (SD); n = 4. (C) In vitro colony-forming unit (CFU) assays. The number of BM CFC, CFU-granulocyte-erythroid-monocyte-megakaryocyte, CFU-granulocyte-macrophage, CFU-granulocyte, CFU-megakaryocyte, and burst-forming unit-erythroid was examined in Mx1-Cre Apc^fl/fl, Mx1-Cre Apc^fl/flβ-catenin^fl/fl, Mx1-Cre β-catenin^fl/fl, and β-catenin^fl/fl mice 5 days after induction (mean ± SD, n = 3). (D) Representative histograms are shown for the frequency of subpopulations of myeloid progenitor cells in Apc^Δ/Δ and Apc^Δ/Δβ-catenin^Δ/Δ CM 2 weeks after induction. (E-F) Absolute number of myeloid progenitor cells in BM from (E) Apc^Δ/Δ and Apc^Δ/Δβ-catenin^Δ/Δ CM (mean ± SD; n = 6-7) 2 weeks after induction or (F) BM from Apc^Δ/Δβ-catenin^Δ/Δ, β-catenin^Δ/Δ, and β-catenin^fl/fl (mean ± SD; n = 3) 5 weeks after induction. *P < .05; **P < .01; ***P < .001.