shRNA knockdown of Bmi-1 reveals a critical role for p21-Rb pathway in NSC self-renewal during development

Cell Stem Cell. 2007 Jun 7;1(1):87-99. doi: 10.1016/j.stem.2007.04.001.


Knockout studies have shown that the polycomb gene Bmi-1 is important for postnatal, but not embryonic, neural stem cell (NSC) self-renewal and have identified the cell-cycle inhibitors p16/p19 as molecular targets. Here, using lentiviral-delivered shRNAs in vitro and in vivo, we determined that Bmi-1 is also important for NSC self-renewal in the embryo. We found that neural progenitors depend increasingly on Bmi-1 for proliferation as development proceeds from embryonic through adult stages. Acute shRNA-mediated Bmi-1 reduction causes defects in embryonic and adult NSC proliferation and self-renewal that, unexpectedly, are mediated by a different cell-cycle inhibitor, p21. Gene array analyses revealed developmental differences in Bmi-1-controlled expression of genes in the p21-Rb cell cycle regulatory pathway. Our data therefore implicate p21 as an important Bmi-1 target in NSCs, potentially with stage-related differences. Understanding stage-related mechanisms underlying NSC self-renewal has important implications for development of stem cell-based therapies.

Publication types

  • Research Support, N.I.H., Extramural
  • Retracted Publication

MeSH terms

  • Animals
  • Cell Division*
  • Cell Proliferation
  • Cyclin-Dependent Kinase Inhibitor p21 / physiology*
  • Electroporation
  • Female
  • Mice
  • Nervous System / cytology*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / physiology*
  • Polycomb Repressive Complex 1
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / physiology*
  • RNA / genetics*
  • Repressor Proteins / genetics
  • Repressor Proteins / physiology*
  • Retinoblastoma Protein / physiology*
  • Stem Cells / cytology*


  • Bmi1 protein, mouse
  • Cdkn1a protein, mouse
  • Cyclin-Dependent Kinase Inhibitor p21
  • Nuclear Proteins
  • Proto-Oncogene Proteins
  • Repressor Proteins
  • Retinoblastoma Protein
  • RNA
  • Polycomb Repressive Complex 1