Activation of Wnt/β-Catenin Protein Signaling Induces Mitochondria-mediated Apoptosis in Hematopoietic Progenitor Cells

The canonical Wnt/β-catenin signaling is activated during development, tumorigenesis, and in adult homeostasis, yet its role in maintenance of hematopoietic stem/progenitor cells is not firmly established. Here, we demonstrate that conditional expression of an active form of β-catenin in vivo induces a marked increase in the frequency of apoptosis in hematopoietic stem/progenitor cells (HSCs/HPCs). Activation of Wnt/β-catenin signaling in HPCs in vitro elevates the activity of caspases 3 and 9 and leads to a loss of mitochondrial membrane potential (ΔΨm), indicating that it induces the intrinsic mitochondrial apoptotic pathway. In vivo, expression of activated β-catenin in HPCs is associated with down-regulation of Bcl2 and expression of Casp3. Bone marrow transplantation assays reveal that enhanced cell survival by a Bcl2 transgene re-establishes the reconstitution capacity of HSCs/HPCs that express activated β-catenin. In addition, a Bcl2 transgene prevents exhaustion of these HSCs/HPCs in vivo. Our data suggest that activation of the Wnt/β-catenin pathway contributes to the defective function of HPCs in part by deregulating their survival.Background: Wnt/β-catenin signaling plays a strong role in maintaining homeostasis of hematopoietic progenitor cells (HPCs).Results: Activated β-catenin deregulates the survival of HPCs by induction of the mitochondrial apoptotic pathway.Conclusion: Wnt/β-catenin signaling is critical for HPC pool maintenance.Significance: This study clarifies the role of the Wnt/β-catenin signaling in HPCs by showing that it has negative impact on the function and survival of the cells.