Doublecortin-like, a microtubule-associated protein expressed in radial glia, is crucial for neuronal precursor division and radial process stability

Authors

  • Erno Vreugdenhil,

    1. Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, PO Box 9502, 2300 RA Leiden, The Netherlands
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  • Sharon M. Kolk,

    1. Department of Pharmacology and Anatomy, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, The Netherlands
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  • Karin Boekhoorn,

    1. Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, The Netherlands
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  • Carlos P. Fitzsimons,

    1. Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, PO Box 9502, 2300 RA Leiden, The Netherlands
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  • Marcel Schaaf,

    1. Institute for Biology, Clusius Laboratory, Leiden University, The Netherlands
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  • Theo Schouten,

    1. Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, PO Box 9502, 2300 RA Leiden, The Netherlands
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  • Angela Sarabdjitsingh,

    1. Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, PO Box 9502, 2300 RA Leiden, The Netherlands
    2. Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, The Netherlands
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  • Rosana Sibug,

    1. Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, PO Box 9502, 2300 RA Leiden, The Netherlands
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  • Paul J. Lucassen

    1. Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, The Netherlands
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Dr E. Vreugdenhil, 1Division of Medical Pharmacology, as above.
E-mail: vreugden@lacdr.leidenuniv.nl

Abstract

During corticogenesis, progenitors divide within the ventricular zone where they rely on radial process extensions, formed by radial glial cell (RG) scaffolds, along which they migrate to the proper layers of the cerebral cortex. Although the microtubule-associated proteins doublecortin (DCX) and doublecortin-like kinase (DCLK) are critically involved in dynamic rearrangement of the cytoskeletal machinery that allow migration, little is known about their role in early corticogenesis. Here we have functionally characterized a mouse splice-variant of DCLK, doublecortin-like (DCL), exhibiting 73% amino acid sequence identity with DCX over its entire length. Unlike DCX, DCL is expressed from embryonic day 8 onwards throughout the early neuroepithelium. It is localized in mitotic cells, RGs and radial processes. DCL knockdown using siRNA in vitro induces spindle collapse in dividing neuroblastoma cells, whereas overexpression results in elongated and asymmetrical mitotic spindles. In vivo knockdown of the DCLK gene by in utero electroporation significantly reduced cell numbers in the inner proliferative zones and dramatically disrupted most radial processes. Our data emphasize the unique role of the DCLK gene in mitotic spindle integrity during early neurogenesis. In addition, they indicate crucial involvement of DCLK in RG proliferation and their radial process stability, a finding that has thus far not been attributed to DCX or DCLK.

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