Abstract
The conditional knockout of the small GTPase Cdc42 from neuroepithelial (NE) and radial glial (RG) cells in the mouse telencephalon has been shown to have a significant impact on brain development by causing these neural progenitor cells to detach from the apical/ventricular surface and to lose their cell identity. This has been attributed to the requirement for Cdc42 in establishing proper apical/basal cell polarity and cell-cell adhesions. In the present study, we provide new insights into the role played by Cdc42 in the maintenance of neural progenitor cells, using the mouse embryonal carcinoma P19 cell line as a model system. We show that the ability of P19 cells to undergo the transition from an Oct3/4-positive, undifferentiated status to microtubule-associated protein 2-positive neurons and glial fibrillary acidic protein-positive astrocytes, upon treatment with retinoic acid (RA), requires RA-induced activation of Cdc42 during the neural cell lineage specification phase. Experiments using chemical inhibitors and RNA interference suggest that the actions of Cdc42 are mediated through signaling pathways that start with fibroblast growth factors and Delta/Notch proteins and lead to Cdc42-dependent mTOR activation, culminating in the up-regulation of Hes5 and Pax6, two transcription factors that are essential for the maintenance of NE and RG cells. The constitutively active Cdc42(F28L) mutant was sufficient to up-regulate Hes5 and Pax6 in P19 cells, even in the absence of RA treatment, ultimately promoting their transition to neural progenitor cells. The ectopic Cdc42 expression also significantly augmented the RA-dependent up-regulation of these transcription factors, resulting in P19 cells maintaining their neural progenitor status but being unable to undergo terminal differentiation. These findings shed new light on how Cdc42 influences neural progenitor cell fate by regulating gene expression.
MeSH terms
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Animals
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Antineoplastic Agents / pharmacology*
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Astrocytes / metabolism
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Basic Helix-Loop-Helix Transcription Factors / genetics
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Basic Helix-Loop-Helix Transcription Factors / metabolism*
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Cell Adhesion / drug effects
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Cell Adhesion / physiology
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Cell Differentiation / drug effects*
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Cell Line, Tumor
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Cell Polarity / drug effects
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Cell Polarity / physiology
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Enzyme Activation / drug effects
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Enzyme Activation / physiology
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Enzyme Inhibitors / pharmacology
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Eye Proteins / genetics
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Eye Proteins / metabolism*
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Homeodomain Proteins / genetics
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Homeodomain Proteins / metabolism*
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Mice
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Mice, Knockout
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Microtubule-Associated Proteins
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Mutation
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Neurons / metabolism*
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Octamer Transcription Factor-3 / genetics
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Octamer Transcription Factor-3 / metabolism
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PAX6 Transcription Factor
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Paired Box Transcription Factors / genetics
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Paired Box Transcription Factors / metabolism*
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Phosphotransferases (Alcohol Group Acceptor) / genetics
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Phosphotransferases (Alcohol Group Acceptor) / metabolism*
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RNA, Small Interfering / genetics
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Receptors, Notch / genetics
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Receptors, Notch / metabolism
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Repressor Proteins / genetics
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Repressor Proteins / metabolism*
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Stem Cells / metabolism
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TOR Serine-Threonine Kinases
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Telencephalon / embryology
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Telencephalon / metabolism
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Tretinoin / pharmacology*
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Up-Regulation / drug effects
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Up-Regulation / physiology
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cdc42 GTP-Binding Protein / antagonists & inhibitors
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cdc42 GTP-Binding Protein / genetics
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cdc42 GTP-Binding Protein / metabolism*
Substances
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Antineoplastic Agents
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Basic Helix-Loop-Helix Transcription Factors
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Carrier Proteins
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Enzyme Inhibitors
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Eye Proteins
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Hes5 protein, mouse
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Homeodomain Proteins
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Microtubule-Associated Proteins
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Octamer Transcription Factor-3
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PAX6 Transcription Factor
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Paired Box Transcription Factors
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Pax6 protein, mouse
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Pou5f1 protein, mouse
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RNA, Small Interfering
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Receptors, Notch
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Repressor Proteins
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Tretinoin
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Phosphotransferases (Alcohol Group Acceptor)
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mTOR protein, mouse
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TOR Serine-Threonine Kinases
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cdc42 GTP-Binding Protein