title: shRNA knockdown of Bmi-1 reveals a critical role for p21-Rb pathway in NSC self-renewal during development.
abstract: 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.
authors: Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA.
authors: Christopher A
authors: CA
authors: Fasano
authors: Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
authors: John T
authors: JT
authors: Dimos
authors: Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
authors: Natalia B
authors: NB
authors: Ivanova
authors: Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA.
authors: Natalia
authors: N
authors: Lowry
authors: Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
authors: Ihor R
authors: IR
authors: Lemischka
authors: Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA. Electronic address: temples@mail.amc.edu.
authors: Sally
authors: S
authors: Temple
mesh_terms: D000818:Animals; D002455:Cell Division; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000502:physiology*; D018274:Electroporation; D005260:Female; D051379:Mice; D009420:Nervous System / Q000166:cytology*; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D063150:Polycomb Repressive Complex 1; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D012313:RNA / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D016160:Retinoblastoma Protein / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology*
chemical_list: C489421:Bmi1 protein, mouse; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D016160:Retinoblastoma Protein; D012313:RNA; D063150:Polycomb Repressive Complex 1