title: Cdk5 and its substrates, Dcx and p27kip1, regulate cytoplasmic dilation formation and nuclear elongation in migrating neurons.
abstract: Neuronal migration is crucial for development of the mammalian-specific six-layered cerebral cortex. Migrating neurons are known to exhibit distinct features; they form a cytoplasmic dilation, a structure specific to migrating neurons, at the proximal region of the leading process, followed by nuclear elongation and forward movement. However, the molecular mechanisms of dilation formation and nuclear elongation remain unclear. Using ex vivo chemical inhibitor experiments, we show here that rottlerin, which is widely used as a specific inhibitor for PKCδ, suppresses the formation of a cytoplasmic dilation and nuclear elongation in cortical migrating neurons. Although our previous study showed that cortical neuronal migration depends on Jnk, another downstream target of rottlerin, Jnk inhibition disturbs only the nuclear elongation and forward movement, but not the dilation formation. We found that an unconventional cyclin-dependent kinase, Cdk5, is a novel downstream target of rottlerin, and that pharmacological or knockdown-mediated inhibition of Cdk5 suppresses both the dilation formation and nuclear elongation. We also show that Cdk5 inhibition perturbs endocytic trafficking as well as microtubule organization, both of which have been shown to be required for dilation formation. Furthermore, knockdown of Dcx, a Cdk5 substrate involved in microtubule organization and membrane trafficking, or p27(kip1), another Cdk5 substrate involved in actin and microtubule organization, disturbs the dilation formation and nuclear elongation. These data suggest that Cdk5 and its substrates, Dcx and p27(kip1), characterize migrating neuron-specific features, cytoplasmic dilation formation and nuclear elongation in the mouse cerebral cortex, possibly through the regulation of microtubule organization and an endocytic pathway.
authors.affiliation: Department of Anatomy, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan Laboratory of Neural Differentiation, Graduate School of Brain Science, Doshisha University, 4-1-1 Kizugawa-dai, Kizugawa-shi, Kyoto 619-0225, Japan Department of Molecular Neurobiology, Institute for Developmental Research, Aichi Human Service Center, 713-8 Kamiya, Kasugai, Aichi 480-0392, Japan.
authors.forename: Yoshiaki V
authors.initials: YV
authors.lastname: Nishimura
authors.affiliation: Department of Anatomy, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan Department of Physiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Mima
authors.initials: M
authors.lastname: Shikanai
authors.affiliation: Department of Biochemistry and Cellular Biology, National Institute of Neuroscience, NCNP, Tokyo 187-8502, Japan.
authors.forename: Mikio
authors.initials: M
authors.lastname: Hoshino
authors.affiliation: Department of Life Science and Medical Bioscience, Waseda University, Tokyo 162-8430, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Ohshima
authors.affiliation: Laboratory of Molecular Life Science, Foundation for Biomedical Research and Innovation, Kobe 650-0047, Japan.
authors.forename: Yo-ichi
authors.initials: Y
authors.lastname: Nabeshima
authors.affiliation: Laboratory of Neural Differentiation, Graduate School of Brain Science, Doshisha University, 4-1-1 Kizugawa-dai, Kizugawa-shi, Kyoto 619-0225, Japan.
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Mizutani
authors.affiliation: Department of Molecular Neurobiology, Institute for Developmental Research, Aichi Human Service Center, 713-8 Kamiya, Kasugai, Aichi 480-0392, Japan.
authors.forename: Koh-Ichi
authors.initials: K
authors.lastname: Nagata
authors.affiliation: Department of Anatomy, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Nakajima
authors.affiliation: Department of Anatomy, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan Department of Physiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Saitama 332-0012, Japan takeshi-kawauchi@umin.ac.jp.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kawauchi
mesh_terms: D000818:Animals; D002465:Cell Movement / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism*; D051360:Cyclin-Dependent Kinase 5 / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000502:physiology; D017931:DNA Primers / Q000235:genetics; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D018274:Electroporation; D007150:Immunohistochemistry; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics
chemical_list: C493961:Cdkn1b protein, mouse; C000714328:DCX protein, human; D017931:DNA Primers; C000714847:Dcx protein, mouse; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides; D050760:Cyclin-Dependent Kinase Inhibitor p27; D051360:Cyclin-Dependent Kinase 5; C495906:Cdk5 protein, mouse
keywords: C-jun N-terminal kinase; Cdkn1b; Cell migration; Cytoskeleton; Doublecortin; Endocytosis; Mouse; Rab5