Continuing role for mouse Numb and Numbl in maintaining progenitor cells during cortical neurogenesis.
Neural progenitor cells in the developing neocortex change over time to produce different neurons, a phenomenon that is also observed in other regions of the nervous system. Mouse Numb (also known as m-numb) and Numbl (also known as numblike or Nbl) are redundant but essential in maintaining virtually all progenitor cells during early neurogenesis. They do this by allowing cells to choose progenitor over neuronal fates. To determine whether their roles change as neurogenesis progresses, we conditionally ablated both genes in the embryonic dorsal forebrain after initial waves of neurogenesis. Here we report that these proteins continue to be required for progenitor-cell maintenance, contrary to recently reported findings. As occurs during early neurogenesis, the loss of Numb and Numbl causes premature progenitor-cell depletion and, consequently, a highly specific malformation of the neocortex and hippocampus. Because progenitor cells can proliferate without Numb and Numbl before neurogenesis, we propose that Numb-mediated asymmetric cell divisions, which diversify many cell fates in Drosophila melanogaster, represent a general mechanism in mammals for stem cells to balance self-renewal and differentiation.
Petersen
Petur H
PH
Department of Molecular, Cellular and Developmental Biology, Yale University, P.O. Box 208103, New Haven, Connecticut 06520, USA.
Zou
Kaiyong
K
Krauss
Stefan
S
Zhong
Weimin
W
D000818:Animals; D004622:Embryo, Mammalian; D018390:Gene Targeting; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D020287:In Situ Nick-End Labeling; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D019579:Neocortex / Q000196:embryology*; D009419:Nerve Tissue Proteins / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D013234:Stem Cells
D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C106293:Numb protein, mouse; C106292:Numbl protein, mouse