Cooperation between both Wnt/{beta}-catenin and PTEN/PI3K/Akt signaling promotes primitive hematopoietic stem cell self-renewal and expansion

Genes Dev. 2011 Sep 15;25(18):1928-42. doi: 10.1101/gad.17421911. Epub 2011 Sep 2.


Although self-renewal is the central property of stem cells, the underlying mechanism remains inadequately defined. Using a hematopoietic stem and progenitor cell (HSPC)-specific conditional induction line, we generated a compound genetic model bearing both Pten deletion and β-catenin activation. These double mutant mice exhibit a novel phenotype, including expansion of phenotypic long-term hematopoietic stem cells (LT-HSCs) without extensive differentiation. Unexpectedly, constitutive activation of β-catenin alone results in apoptosis of HSCs. However, together, the Wnt/β-catenin and PTEN/PI3k/Akt pathways interact to drive phenotypic LT-HSC expansion by inducing proliferation while simultaneously inhibiting apoptosis and blocking differentiation, demonstrating the necessity of complementary cooperation between the two pathways in promoting self-renewal. Mechanistically, β-catenin activation reduces multiple differentiation-inducing transcription factors, blocking differentiation partially through up-regulation of Inhibitor of differentiation 2 (Id2). In double mutants, loss of Pten enhances the HSC anti-apoptotic factor Mcl-1. All of these contribute in a complementary way to HSC self-renewal and expansion. While permanent, genetic alteration of both pathways in double mutant mice leads to expansion of phenotypic HSCs, these HSCs cannot function due to blocked differentiation. We developed a pharmacological approach to expand normal, functional HSCs in culture using factors that reversibly activate both Wnt/β-catenin and PI3K/Akt signaling simultaneously. We show for the first time that activation of either single pathway is insufficient to expand primitive HSCs, but in combination, both pathways drive self-renewal and expansion of HSCs with long-term functional capacity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Cell Culture Techniques / methods
  • Cell Differentiation
  • Cell Line
  • Cell Proliferation
  • Cells, Cultured
  • Hematopoietic Stem Cell Transplantation
  • Hematopoietic Stem Cells / cytology*
  • Hematopoietic Stem Cells / enzymology
  • Hematopoietic Stem Cells / metabolism*
  • Mice
  • Mutation
  • PTEN Phosphohydrolase / genetics
  • PTEN Phosphohydrolase / metabolism*
  • Phenotype
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Signal Transduction*
  • Wnt Proteins / genetics
  • Wnt Proteins / metabolism*
  • beta Catenin / genetics
  • beta Catenin / metabolism*


  • Wnt Proteins
  • beta Catenin
  • Phosphatidylinositol 3-Kinases
  • PTEN Phosphohydrolase
  • Pten protein, mouse