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Verissimo CS, Elands R, Cheng S, Saaltink DJ, ter Horst JP, Alme MN, Pont C, van de Water B, Håvik B, Fitzsimons CP, Vreugdenhil E. Silencing of doublecortin-like (DCL) results in decreased mitochondrial activity and delayed neuroblastoma tumor growth. PLoS One 2013; 8:e75752. [PMID: 24086625 PMCID: PMC3784435 DOI: 10.1371/journal.pone.0075752] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2013] [Accepted: 08/19/2013] [Indexed: 12/17/2022] Open
Abstract
Doublecortin-like (DCL) is a microtubule-binding protein crucial for neuroblastoma (NB) cell proliferation. We have investigated whether the anti-proliferative effect of DCL knockdown is linked to reduced mitochondrial activity. We found a delay in tumor development after DCL knockdown in vivo in doxycycline-inducible NB tumor xenografts. To understand the mechanisms underlying this tumor growth retardation we performed a series of in vitro experiments in NB cell lines. DCL colocalizes with mitochondria, interacts with the mitochondrial outer membrane protein OMP25/ SYNJ2BP and DCL knockdown results in decreased expression of genes involved in oxidative phosphorylation. Moreover, DCL knockdown decreases cytochrome c oxidase activity and ATP synthesis. We identified the C-terminal Serine/Proline-rich domain and the second microtubule-binding area as crucial DCL domains for the regulation of cytochrome c oxidase activity and ATP synthesis. Furthermore, DCL knockdown causes a significant reduction in the proliferation rate of NB cells under an energetic challenge induced by low glucose availability. Together with our previous studies, our results corroborate DCL as a key player in NB tumor growth in which DCL controls not only mitotic spindle formation and the stabilization of the microtubule cytoskeleton, but also regulates mitochondrial activity and energy availability, which makes DCL a promising molecular target for NB therapy.
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Affiliation(s)
- Carla S. Verissimo
- Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, Leiden, the Netherlands
- * E-mail: (CSV); (EV)
| | - Rachel Elands
- Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, Leiden, the Netherlands
| | - Sou Cheng
- Prosensa Therapeutics B.V., Leiden, the Netherlands
| | - Dirk-Jan Saaltink
- Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, Leiden, the Netherlands
| | - Judith P. ter Horst
- Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, Leiden, the Netherlands
| | - Maria N. Alme
- Department of Biomedicine, K. G. Jebsen Centre for Research on Neuropsychiatric Disorders, University of Bergen, Bergen, Norway
| | - Chantal Pont
- Division of Toxicology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, Leiden, the Netherlands
| | - Bob van de Water
- Division of Toxicology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, Leiden, the Netherlands
| | - Bjarte Håvik
- Dr. E. Martens Research Group for Biological Psychiatry, Department of Clinical Medicine, University of Bergen, Bergen, Norway
- Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway
| | - Carlos P. Fitzsimons
- Centre for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, the Netherlands
| | - Erno Vreugdenhil
- Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, Leiden, the Netherlands
- Department of Human Genetics, Migraine Research Group, Leiden University Medical Center, Leiden, the Netherlands
- * E-mail: (CSV); (EV)
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52
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Khalaf-Nazzal R, Bruel-Jungerman E, Rio JP, Bureau J, Irinopoulou T, Sumia I, Roumegous A, Martin E, Olaso R, Parras C, Cifuentes-Diaz C, Francis F. Organelle and cellular abnormalities associated with hippocampal heterotopia in neonatal doublecortin knockout mice. PLoS One 2013; 8:e72622. [PMID: 24023755 PMCID: PMC3759370 DOI: 10.1371/journal.pone.0072622] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Accepted: 07/11/2013] [Indexed: 11/18/2022] Open
Abstract
Heterotopic or aberrantly positioned cortical neurons are associated with epilepsy and intellectual disability. Various mouse models exist with forms of heterotopia, but the composition and state of cells developing in heterotopic bands has been little studied. Dcx knockout (KO) mice show hippocampal CA3 pyramidal cell lamination abnormalities, appearing from the age of E17.5, and mice suffer from spontaneous epilepsy. The Dcx KO CA3 region is organized in two distinct pyramidal cell layers, resembling a heterotopic situation, and exhibits hyperexcitability. Here, we characterized the abnormally organized cells in postnatal mouse brains. Electron microscopy confirmed that the Dcx KO CA3 layers at postnatal day (P) 0 are distinct and separated by an intermediate layer devoid of neuronal somata. We found that organization and cytoplasm content of pyramidal neurons in each layer were altered compared to wild type (WT) cells. Less regular nuclei and differences in mitochondria and Golgi apparatuses were identified. Each Dcx KO CA3 layer at P0 contained pyramidal neurons but also other closely apposed cells, displaying different morphologies. Quantitative PCR and immunodetections revealed increased numbers of oligodendrocyte precursor cells (OPCs) and interneurons in close proximity to Dcx KO pyramidal cells. Immunohistochemistry experiments also showed that caspase-3 dependent cell death was increased in the CA1 and CA3 regions of Dcx KO hippocampi at P2. Thus, unsuspected ultrastructural abnormalities and cellular heterogeneity may lead to abnormal neuronal function and survival in this model, which together may contribute to the development of hyperexcitability.
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Affiliation(s)
- Reham Khalaf-Nazzal
- INSERM UMRS 839, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Institut du Fer à Moulin, Paris, France
| | - Elodie Bruel-Jungerman
- INSERM UMRS 839, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Institut du Fer à Moulin, Paris, France
| | - Jean-Paul Rio
- INSERM UMRS 839, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Institut du Fer à Moulin, Paris, France
| | - Jocelyne Bureau
- INSERM UMRS 839, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Institut du Fer à Moulin, Paris, France
| | - Theano Irinopoulou
- INSERM UMRS 839, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Institut du Fer à Moulin, Paris, France
| | - Iffat Sumia
- INSERM UMRS 839, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Institut du Fer à Moulin, Paris, France
| | - Audrey Roumegous
- INSERM UMRS 839, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Institut du Fer à Moulin, Paris, France
| | - Elodie Martin
- Université Pierre et Marie Curie, Paris, France
- Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, Paris, France
- INSERM UMRS 975, Paris, France
- CNRS UMR 7225, Paris, France
| | - Robert Olaso
- Plateforme de Transcriptomique, Laboratoire de Recherche Translationnelle, CEA/DSV/IG-Centre National de Génotypage, Evry, France
| | - Carlos Parras
- Université Pierre et Marie Curie, Paris, France
- Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, Paris, France
- INSERM UMRS 975, Paris, France
- CNRS UMR 7225, Paris, France
| | - Carmen Cifuentes-Diaz
- INSERM UMRS 839, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Institut du Fer à Moulin, Paris, France
- * E-mail: (FF); (CCD)
| | - Fiona Francis
- INSERM UMRS 839, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Institut du Fer à Moulin, Paris, France
- * E-mail: (FF); (CCD)
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53
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Shin E, Kashiwagi Y, Kuriu T, Iwasaki H, Tanaka T, Koizumi H, Gleeson JG, Okabe S. Doublecortin-like kinase enhances dendritic remodelling and negatively regulates synapse maturation. Nat Commun 2013; 4:1440. [PMID: 23385585 PMCID: PMC4017031 DOI: 10.1038/ncomms2443] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Accepted: 01/03/2013] [Indexed: 11/09/2022] Open
Abstract
Dendritic morphogenesis and formation of synapses at appropriate dendritic locations are essential for the establishment of proper neuronal connectivity. Recent imaging studies provide evidence for stabilization of dynamic distal branches of dendrites by the addition of new synapses. However, molecules involved in both dendritic growth and suppression of synapse maturation remain to be identified. Here we report two distinct functions of doublecortin-like kinases, chimeric proteins containing both a microtubule-binding domain and a kinase domain in postmitotic neurons. First, doublecortin-like kinases localize to the distal dendrites and promote their growth by enhancing microtubule bundling. Second, doublecortin-like kinases suppress maturation of synapses through multiple pathways, including reduction of PSD-95 by the kinase domain and suppression of spine structural maturation by the microtubule-binding domain. Thus, doublecortin-like kinases are critical regulators of dendritic development by means of their specific targeting to the distal dendrites, and their local control of dendritic growth and synapse maturation.
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Affiliation(s)
- Euikyung Shin
- Department of Cellular Neurobiology, University of Tokyo, Tokyo 113-0033, Japan
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54
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Fibrinogen-induced perivascular microglial clustering is required for the development of axonal damage in neuroinflammation. Nat Commun 2013. [PMID: 23187627 PMCID: PMC3514498 DOI: 10.1038/ncomms2230] [Citation(s) in RCA: 424] [Impact Index Per Article: 38.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Blood-brain barrier disruption, microglial activation and neurodegeneration are hallmarks of multiple sclerosis. However, the initial triggers that activate innate immune responses and their role in axonal damage remain unknown. Here we show that the blood protein fibrinogen induces rapid microglial responses toward the vasculature and is required for axonal damage in neuroinflammation. Using in vivo two-photon microscopy, we demonstrate that microglia form perivascular clusters before myelin loss or paralysis onset and that, of the plasma proteins, fibrinogen specifically induces rapid and sustained microglial responses in vivo. Fibrinogen leakage correlates with areas of axonal damage and induces reactive oxygen species release in microglia. Blocking fibrin formation with anticoagulant treatment or genetically eliminating the fibrinogen binding motif recognized by the microglial integrin receptor CD11b/CD18 inhibits perivascular microglial clustering and axonal damage. Thus, early and progressive perivascular microglial clustering triggered by fibrinogen leakage upon blood-brain barrier disruption contributes to axonal damage in neuroinflammatory disease. Multiple sclerosis is characterized by the activation of microglia cells. Davalos et al. investigate the early stages of neuroinflammation in mice and reveal that the plasma protein fibrinogen induces microglial clustering around the brain vasculature, which facilitates lesion formation and focal axonal damage.
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55
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Prokop A, Beaven R, Qu Y, Sánchez-Soriano N. Using fly genetics to dissect the cytoskeletal machinery of neurons during axonal growth and maintenance. J Cell Sci 2013; 126:2331-41. [PMID: 23729743 DOI: 10.1242/jcs.126912] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The extension of long slender axons is a key process of neuronal circuit formation, both during brain development and regeneration. For this, growth cones at the tips of axons are guided towards their correct target cells by signals. Growth cone behaviour downstream of these signals is implemented by their actin and microtubule cytoskeleton. In the first part of this Commentary, we discuss the fundamental roles of the cytoskeleton during axon growth. We present the various classes of actin- and microtubule-binding proteins that regulate the cytoskeleton, and highlight the important gaps in our understanding of how these proteins functionally integrate into the complex machinery that implements growth cone behaviour. Deciphering such machinery requires multidisciplinary approaches, including genetics and the use of simple model organisms. In the second part of this Commentary, we discuss how the application of combinatorial genetics in the versatile genetic model organism Drosophila melanogaster has started to contribute to the understanding of actin and microtubule regulation during axon growth. Using the example of dystonin-linked neuron degeneration, we explain how knowledge acquired by studying axonal growth in flies can also deliver new understanding in other aspects of neuron biology, such as axon maintenance in higher animals and humans.
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Affiliation(s)
- Andreas Prokop
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
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56
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Kremer T, Jagasia R, Herrmann A, Matile H, Borroni E, Francis F, Kuhn HG, Czech C. Analysis of adult neurogenesis: evidence for a prominent "non-neurogenic" DCX-protein pool in rodent brain. PLoS One 2013; 8:e59269. [PMID: 23690918 PMCID: PMC3653925 DOI: 10.1371/journal.pone.0059269] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 02/13/2013] [Indexed: 11/19/2022] Open
Abstract
Here, we have developed a highly sensitive immunoassay for Dcx to characterize expression in brain and cerebrospinal fluid (CSF) of rodents. We demonstrate that Dcx is widely expressed during development in various brain regions and as well can be detected in cerebrospinal fluid of rats (up to 30 days postnatal). While Dcx protein level decline in adulthood and were detectable in neurogenic regions of the adult rodent brain, similar levels were also detectable in brain regions expected to bear no neurogenesis including the cerebral cortex and CA1/CA3 enriched hippocampus. We monitored DCX protein levels after paradigms to increase or severely decrease adult hippocampal neurogenesis, namely physical activity and cranial radiation, respectively. In both paradigms, Dcx protein- and mRNA-levels clearly reflected changes in neurogenesis in the hippocampus. However, basal Dcx-levels are unaffected in non-neurogenic regions (e.g. CA1/CA3 enriched hippocampus, cortex). These data suggest that there is a substantial "non-neurogenic" pool of Dcx- protein, whose regulation can be uncoupled from adult neurogenesis suggesting caution for the interpretation of such studies.
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Affiliation(s)
- Thomas Kremer
- F. Hoffmann-La Roche AG, Pharma Research & Early Development, DTA Neuroscience, Basel, Switzerland.
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57
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Reiner O. LIS1 and DCX: Implications for Brain Development and Human Disease in Relation to Microtubules. SCIENTIFICA 2013; 2013:393975. [PMID: 24278775 PMCID: PMC3820303 DOI: 10.1155/2013/393975] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 02/07/2013] [Indexed: 05/29/2023]
Abstract
Proper lamination of the cerebral cortex requires the orchestrated motility of neurons from their place of birth to their final destination. Improper neuronal migration may result in a wide range of diseases, including brain malformations, such as lissencephaly, mental retardation, schizophrenia, and autism. Ours and other studies have implicated that microtubules and microtubule-associated proteins play an important role in the regulation of neuronal polarization and neuronal migration. Here, we will review normal processes of brain development and neuronal migration, describe neuronal migration diseases, and will focus on the microtubule-associated functions of LIS1 and DCX, which participate in the regulation of neuronal migration and are involved in the human developmental brain disease, lissencephaly.
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Affiliation(s)
- Orly Reiner
- Department of Molecular Genetics, The Weizmann Institute of Science, 76100 Rehovot, Israel
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58
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Doublecortin (Dcx) family proteins regulate filamentous actin structure in developing neurons. J Neurosci 2013; 33:709-21. [PMID: 23303949 DOI: 10.1523/jneurosci.4603-12.2013] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Doublecortin (Dcx) is the causative gene for X-linked lissencephaly, which encodes a microtubule-binding protein. Axon tracts are abnormal in both affected individuals and in animal models. To determine the reason for the axon tract defect, we performed a semiquantitative proteomic analysis of the corpus callosum in mice mutant for Dcx. In axons from mice mutant for Dcx, widespread differences are found in actin-associated proteins as compared with wild-type axons. Decreases in actin-binding proteins α-actinin-1 and α-actinin-4 and actin-related protein 2/3 complex subunit 3 (Arp3), are correlated with dysregulation in the distribution of filamentous actin (F-actin) in the mutant neurons with increased F-actin around the cell body and decreased F-actin in the neurites and growth cones. The actin distribution defect can be rescued by full-length Dcx and further enhanced by Dcx S297A, the unphosphorylatable mutant, but not with the truncation mutant of Dcx missing the C-terminal S/P-rich domain. Thus, the C-terminal region of Dcx dynamically regulates formation of F-actin features in developing neurons, likely through interaction with spinophilin, but not through α-actinin-4 or Arp3. We show with that the phenotype of Dcx/Doublecortin-like kinase 1 deficiency is consistent with actin defect, as these axons are selectively deficient in axon guidance, but not elongation.
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59
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Esteves SLC, Korrodi-Gregório L, Cotrim CZ, van Kleeff PJM, Domingues SC, da Cruz e Silva OAB, Fardilha M, da Cruz e Silva EF. Protein phosphatase 1γ isoforms linked interactions in the brain. J Mol Neurosci 2012; 50:179-97. [PMID: 23080069 DOI: 10.1007/s12031-012-9902-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 10/03/2012] [Indexed: 01/03/2023]
Abstract
Posttranslational protein modifications, in particular reversible protein phosphorylation, are important regulatory mechanisms involved in cellular signaling transduction pathways. Thousands of human proteins are phosphorylatable and the tight regulation of phosphorylation states is crucial for cell maintenance and development. Protein phosphorylation occurs primarily on serine, threonine, and tyrosine residues, through the antagonistic actions of protein kinases and phosphatases. The catalytic subunit of protein phosphatase 1 (PP1), a major Ser/Thr-phosphatase, associates with a large variety of regulatory subunits that define substrate specificity and determine specific cellular pathway responses. PP1 has been shown to bind to different proteins in the brain in order to execute key and differential functions. This work reports the identification of proteins expressed in the human brain that interact with PP1γ1 and PP1γ2 isoforms by the yeast two-hybrid method. An extensive search of PP1-binding motifs was performed for the proteins identified, revealing already known PP1 regulators but also novel interactors. Moreover, our results were integrated with the data of PP1γ interacting proteins from several public web databases, permitting the development of physical maps of the novel interactions. The PP1γ interactome thus obtained allowed for the identification of novel PP1 interacting proteins, supporting novel functions of PP1γ isoforms in the human brain.
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Affiliation(s)
- Sara L C Esteves
- Signal Transduction Laboratory, Centre for Cell Biology, Biology Department, University of Aveiro, 3810-193 Aveiro, Portugal
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60
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Rao S, Ge S, Shelly M. Centrosome positioning and primary cilia assembly orchestrate neuronal development. ACTA ACUST UNITED AC 2012. [DOI: 10.1007/s11515-012-1231-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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61
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Jean DC, Baas PW, Black MM. A novel role for doublecortin and doublecortin-like kinase in regulating growth cone microtubules. Hum Mol Genet 2012; 21:5511-27. [PMID: 23001563 DOI: 10.1093/hmg/dds395] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Doublecortin (DCX) and doublecortin-like kinase (DCLK), closely related family members, are microtubule-associated proteins with overlapping functions in both neuronal migration and axonal outgrowth. In growing axons, these proteins appear to have their primary functions in the growth cone. Here, we used siRNA to deplete these proteins from cultured rat sympathetic neurons. Normally, microtubules in the growth cone exhibit a gently curved contour as they extend from the base of the cone toward its periphery. However, following depletion of DCX and DCLK, microtubules throughout the growth cone become much more curvy, with many microtubules exhibiting multiple prominent bends over relatively short distances, creating a configuration that we termed wave-like folds. Microtubules with these folds appeared as if they were buckling in response to powerful forces. Indeed, inhibition of myosin-II, which generates forces on the actin cytoskeleton to push microtubules in the growth cone back toward the axonal shaft, significantly decreases the frequency of these wave-like folds. In addition, in the absence of DCX and DCLK, the depth of microtubule invasion into filopodia is reduced compared with controls, and at a functional level, growth cone responses to substrate guidance cues are altered. Conversely, overexpression of DCX results in microtubules that are straighter than usual, suggesting that higher levels of these proteins can enable an even greater resistance to folding. These findings support a role for DCX and DCLK in enabling microtubules to overcome retrograde actin-based forces, thereby facilitating the ability of the growth cone to carry out its crucial path-finding functions.
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Affiliation(s)
- Daphney C Jean
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA
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62
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Spectraplakins promote microtubule-mediated axonal growth by functioning as structural microtubule-associated proteins and EB1-dependent +TIPs (tip interacting proteins). J Neurosci 2012; 32:9143-58. [PMID: 22764224 DOI: 10.1523/jneurosci.0416-12.2012] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The correct outgrowth of axons is essential for the development and regeneration of nervous systems. Axon growth is primarily driven by microtubules. Key regulators of microtubules in this context are the spectraplakins, a family of evolutionarily conserved actin-microtubule linkers. Loss of function of the mouse spectraplakin ACF7 or of its close Drosophila homolog Short stop/Shot similarly cause severe axon shortening and microtubule disorganization. How spectraplakins perform these functions is not known. Here we show that axonal growth-promoting roles of Shot require interaction with EB1 (End binding protein) at polymerizing plus ends of microtubules. We show that binding of Shot to EB1 requires SxIP motifs in Shot's C-terminal tail (Ctail), mutations of these motifs abolish Shot functions in axonal growth, loss of EB1 function phenocopies Shot loss, and genetic interaction studies reveal strong functional links between Shot and EB1 in axonal growth and microtubule organization. In addition, we report that Shot localizes along microtubule shafts and stabilizes them against pharmacologically induced depolymerization. This function is EB1-independent but requires net positive charges within Ctail which essentially contribute to the microtubule shaft association of Shot. Therefore, spectraplakins are true members of two important classes of neuronal microtubule regulating proteins: +TIPs (tip interacting proteins; plus end regulators) and structural MAPs (microtubule-associated proteins). From our data we deduce a model that relates the different features of the spectraplakin C terminus to the two functions of Shot during axonal growth.
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63
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Bellanger JM, Cueva JG, Baran R, Tang G, Goodman MB, Debant A. The doublecortin-related gene zyg-8 is a microtubule organizer in Caenorhabditis elegans neurons. J Cell Sci 2012; 125:5417-27. [PMID: 22956537 DOI: 10.1242/jcs.108381] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Doublecortin-domain containing (DCDC) genes play key roles in the normal and pathological development of the human brain cortex. The origin of the cellular specialisation and the functional redundancy of these microtubule (MT)-associated proteins (MAPs), especially those of Doublecortin (DCX) and Doublecortin-like kinase (DCLKs) genes, is still unclear. The DCX domain has the ability to control MT architecture and bundling. However, the physiological significance of such properties is not fully understood. To address these issues, we sought post-mitotic roles for zyg-8, the sole representative of the DCX-DCLK subfamily of genes in C. elegans. Previously, zyg-8 has been shown to control anaphase-spindle positioning in one-cell stage embryos, but functions of the gene later in development have not been investigated. Here we show that wild-type zyg-8 is required beyond early embryonic divisions for proper development, spontaneous locomotion and touch sensitivity of adult worms. Consistently, we find zyg-8 expression in the six touch receptor neurons (TRNs), as well as in a subset of other neuronal and non-neuronal cells. In TRNs and motoneurons, zyg-8 controls cell body shape/polarity and process outgrowth and morphology. Ultrastructural analysis of mutant animals reveals that zyg-8 promotes structural integrity, length and number of individual MTs, as well as their bundled organisation in TRNs, with no impact on MT architecture.
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Affiliation(s)
- Jean-Michel Bellanger
- CRBM-CNRS, Université Montpellier 2, 1919, route de Mende, 34293 Montpellier, France.
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64
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Molecular basis for specific regulation of neuronal kinesin-3 motors by doublecortin family proteins. Mol Cell 2012; 47:707-21. [PMID: 22857951 PMCID: PMC3549492 DOI: 10.1016/j.molcel.2012.06.025] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2012] [Revised: 05/14/2012] [Accepted: 06/15/2012] [Indexed: 11/22/2022]
Abstract
Doublecortin (Dcx) defines a growing family of microtubule (MT)-associated proteins (MAPs) involved in neuronal migration and process outgrowth. We show that Dcx is essential for the function of Kif1a, a kinesin-3 motor protein that traffics synaptic vesicles. Neurons lacking Dcx and/or its structurally conserved paralogue, doublecortin-like kinase 1 (Dclk1), show impaired Kif1a-mediated transport of Vamp2, a cargo of Kif1a, with decreased run length. Human disease-associated mutations in Dcx's linker sequence (e.g., W146C, K174E) alter Kif1a/Vamp2 transport by disrupting Dcx/Kif1a interactions without affecting Dcx MT binding. Dcx specifically enhances binding of the ADP-bound Kif1a motor domain to MTs. Cryo-electron microscopy and subnanometer-resolution image reconstruction reveal the kinesin-dependent conformational variability of MT-bound Dcx and suggest a model for MAP-motor crosstalk on MTs. Alteration of kinesin run length by MAPs represents a previously undiscovered mode of control of kinesin transport and provides a mechanism for regulation of MT-based transport by local signals.
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65
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Slepak T, Salay L, Lemmon V, Bixby J. Dyrk kinases regulate phosphorylation of doublecortin, cytoskeletal organization, and neuronal morphology. Cytoskeleton (Hoboken) 2012; 69:514-27. [PMID: 22359282 PMCID: PMC3556588 DOI: 10.1002/cm.21021] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 02/15/2012] [Accepted: 02/16/2012] [Indexed: 11/06/2022]
Abstract
In a neuronal overexpression screen focused on kinases and phosphatases, one "hit" was the dual specificity tyrosine phosphorylation-regulated kinase (Dyrk4), which increased the number of dendritic branches in hippocampal neurons. Overexpression of various Dyrk family members in primary neurons significantly changed neuronal morphology. Dyrk1A decreased axon growth, Dyrk3 and Dyrk4 increased dendritic branching, and Dyrk2 decreased both axon and dendrite growth and branching. Kinase-deficient mutants revealed that most of these effects depend on kinase activity. Because doublecortin (DCX), a microtubule-binding protein, regulates cytoskeletal dynamics and neuronal morphogenesis, we investigated the possibility that DCX is a target of Dyrks. We found that overexpression of Dyrk2 and Dyrk3, but not Dyrk1A or Dyrk4, can change DCX phosphorylation status. Mutation of a consensus phosphorylation site for Dyrk kinases at Serine 306 (Ser306) in DCX indicated that this is one target site for Dyrk2 and Dyrk3. Overexpression of Dyrk2 restored altered DCX distribution in the growth cones of dendrites and axons, and partially reversed the morphological effects of DCX overexpression; some of these effects were abrogated by mutation of Ser306 to alanine. These studies implicate Dyrks in the regulation of cytoskeletal organization and process outgrowth in neurons, and suggest that DCX is one relevant Dyrk target.
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Affiliation(s)
- T.I. Slepak
- Miami Project to Cure Paralysis, University of Miami Miller School of Medicine
| | - L.D. Salay
- Miami Project to Cure Paralysis, University of Miami Miller School of Medicine
| | - V.P. Lemmon
- Miami Project to Cure Paralysis, University of Miami Miller School of Medicine
- Department of Neurological Surgery, University of Miami Miller School of Medicine
| | - J.L. Bixby
- Miami Project to Cure Paralysis, University of Miami Miller School of Medicine
- Department of Neurological Surgery, University of Miami Miller School of Medicine
- Department of Molecular & Cellular Pharmacology, University of Miami Miller School of Medicine
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66
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Devaux S, Poulain FE, Devignot V, Lachkar S, Irinopoulou T, Sobel A. Specific serine-proline phosphorylation and glycogen synthase kinase 3β-directed subcellular targeting of stathmin 3/Sclip in neurons. J Biol Chem 2012; 287:22341-53. [PMID: 22577147 DOI: 10.1074/jbc.m112.344044] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
During nervous system development, neuronal growth, migration, and functional morphogenesis rely on the appropriate control of the subcellular cytoskeleton including microtubule dynamics. Stathmin family proteins play major roles during the various stages of neuronal differentiation, including axonal growth and branching, or dendritic development. We have shown previously that stathmins 2 (SCG10) and 3 (SCLIP) fulfill distinct, independent and complementary regulatory roles in axonal morphogenesis. Although the two proteins have been proposed to display the four conserved phosphorylation sites originally identified in stathmin 1, we show here that they possess distinct phosphorylation sites within their specific proline-rich domains (PRDs) that are differentially regulated by phosphorylation by proline-directed kinases involved in the control of neuronal differentiation. ERK2 or CDK5 phosphorylate the two proteins but with different site specificities. We also show for the first time that, unlike stathmin 2, stathmin 3 is a substrate for glycogen synthase kinase (GSK) 3β both in vitro and in vivo. Interestingly, stathmin 3 phosphorylated at its GSK-3β target site displays a specific subcellular localization at neuritic tips and within the actin-rich peripheral zone of the growth cone of differentiating hippocampal neurons in culture. Finally, pharmacological inhibition of GSK-3β induces a redistribution of stathmin 3, but not stathmin 2, from the periphery toward the Golgi region of neurons. Stathmin proteins can thus be either regulated locally or locally targeted by specific phosphorylation, each phosphoprotein of the stathmin family fulfilling distinct and specific roles in the control of neuronal differentiation.
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67
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Bonni S, Bonni A. SnoN signaling in proliferating cells and postmitotic neurons. FEBS Lett 2012; 586:1977-83. [PMID: 22710173 DOI: 10.1016/j.febslet.2012.02.048] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2012] [Revised: 02/27/2012] [Accepted: 02/28/2012] [Indexed: 01/28/2023]
Abstract
The transcriptional regulator SnoN plays a fundamental role as a modulator of transforming growth factor beta (TGFβ)-induced signal transduction and biological responses. In recent years, novel functions of SnoN have been discovered in both TGFβ-dependent and TGFβ-independent settings in proliferating cells and postmitotic neurons. Accumulating evidence suggests that SnoN plays a dual role as a corepressor or coactivator of TGFβ-induced transcription. Accordingly, SnoN exerts oncogenic or tumor-suppressive effects in epithelial tissues. At the cellular level, SnoN antagonizes or mediates the ability of TGFβ to induce cell cycle arrest in a cell-type specific manner. SnoN also exerts key effects on epithelial-mesenchymal transition (EMT), with implications in cancer biology. Recent studies have expanded SnoN functions to postmitotic neurons, where SnoN orchestrates key aspects of neuronal development in the mammalian brain, from axon growth and branching to neuronal migration and positioning. In this review, we will highlight our understanding of SnoN biology at the crossroads of cancer biology and neurobiology.
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Affiliation(s)
- Shirin Bonni
- Department of Biochemistry and Molecular Biology, Southern Alberta Cancer Research Institute, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
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68
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Toriyama M, Mizuno N, Fukami T, Iguchi T, Toriyama M, Tago K, Itoh H. Phosphorylation of doublecortin by protein kinase A orchestrates microtubule and actin dynamics to promote neuronal progenitor cell migration. J Biol Chem 2012; 287:12691-702. [PMID: 22367209 DOI: 10.1074/jbc.m111.316307] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Doublecortin (DCX) is a microtubule-associated protein that is specifically expressed in neuronal cells. Genetic mutation of DCX causes lissencephaly disease. Although the abnormal cortical lamination in lissencephaly is thought to be attributable to neuronal cell migration defects, the regulatory mechanisms governing interactions between DCX and cytoskeleton in the migration of neuronal progenitor cells remain obscure. In this study we found that the G(s) and protein kinase A (PKA) signal elicited by pituitary adenylate cyclase-activating polypeptide promotes neuronal progenitor cells migration. Stimulation of G(s)-PKA signaling prevented microtubule bundling and induced the dissociation of DCX from microtubules in cells. PKA phosphorylated DCX at Ser-47, and the phospho-mimicking mutant DCX-S47E promoted cell migration. Activation of PKA and DCX-S47E induced lamellipodium formation. Pituitary adenylate cyclase-activating polypeptide and DCX-S47E stimulated the activation of Rac1, and DCX-S47E interacted with Asef2, a guanine nucleotide exchange factor for Rac1. Our data reveal a dual reciprocal role for DCX phosphorylation in the regulation of microtubule and actin dynamics that is indispensable for proper brain lamination.
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Affiliation(s)
- Manami Toriyama
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
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69
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Okabe S. Molecular Dynamics of the Excitatory Synapse. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 970:131-52. [DOI: 10.1007/978-3-7091-0932-8_6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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70
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Kim YT, Hur EM, Snider WD, Zhou FQ. Role of GSK3 Signaling in Neuronal Morphogenesis. Front Mol Neurosci 2011; 4:48. [PMID: 22131966 PMCID: PMC3222852 DOI: 10.3389/fnmol.2011.00048] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 11/06/2011] [Indexed: 01/28/2023] Open
Abstract
Glycogen synthase kinase 3 (GSK3) is emerging as a key regulator of several aspects of neuronal morphogenesis including neuronal polarization, axon growth, and axon branching. Multiple signaling pathways have been identified that control neuronal polarization, including PI3K, Rho-GTPases, Par3/6, TSC–mTOR, and PKA–LKB1. However, how these pathways are coordinated is not clear. As GSK3 signaling exhibits crosstalk with each of these pathways it has the potential to integrate these polarity signals in the control neuronal polarization. After neurons establish polarity, GSK3 acts as an important signaling mediator in the regulation of axon extension and axon branching by transducing upstream signaling to reorganization of the axonal cytoskeleton, especially microtubules. Here we review the roles of GSK3 signaling in neuronal morphogenesis and discuss the underlying molecular mechanisms.
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Affiliation(s)
- Yun Tai Kim
- Department of Orthopaedic Surgery, The Johns Hopkins University School of Medicine Baltimore, MD, USA
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71
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Molina-Pinelo S, Ferrer I, Blanco-Aparicio C, Peregrino S, Pastor MD, Alvarez-Vega J, Suarez R, Verge M, Marin JJ, Hernandez-Losa J, Ramon y Cajal S, Paz-Ares L, Carnero A. Down-regulation of spinophilin in lung tumours contributes to tumourigenesis. J Pathol 2011; 225:73-82. [PMID: 21598252 DOI: 10.1002/path.2905] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Revised: 03/01/2011] [Accepted: 03/17/2011] [Indexed: 01/22/2023]
Abstract
The scaffold protein spinophilin (Spn, PPP1R9B) is one of the regulatory subunits of phosphatase-1a (PP1), targeting it to distinct subcellular locations and to its target. Loss of Spn reduces PPP1CA levels, thereby maintaining higher levels of phosphorylated pRb. This effect contributes to an increase in p53 activity. However, in the absence of p53, reduced levels of Spn increase the tumourigenic properties of cells. In addition, Spn knockout mice have a reduced lifespan, an increased number of tumours and increased cellular proliferation in some tissues, such as the mammary ducts. In addition, the combined loss of Spn and p53 activity leads to an increase in mammary carcinomas, confirming the functional relationship between p53 and Spn. In this paper, we report that Spn is absent in 20% and reduced in another 37% of human lung tumours. Spn reduction correlates with malignant grade. Furthermore, the loss of Spn also correlates with p53 mutations. Analysis of miRNAs in a series of lung tumours showed that miRNA106a* targeting Spn is over-expressed in some patients, correlating with decreased Spn levels. Proof-of-concept experiments over-expressing miRNA106a* or Spn shRNA in lung tumour cells showed increased tumourigenicity. In conclusion, our data showed that miRNA106a* over-expression found in lung tumours might contribute to tumourigenesis through Spn down-regulation in the absence of p53.
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72
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Huynh MA, Ikeuchi Y, Netherton S, de la Torre-Ubieta L, Kanadia R, Stegmüller J, Cepko C, Bonni S, Bonni A. An isoform-specific SnoN1-FOXO1 repressor complex controls neuronal morphogenesis and positioning in the mammalian brain. Neuron 2011; 69:930-44. [PMID: 21382553 DOI: 10.1016/j.neuron.2011.02.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/21/2010] [Indexed: 12/17/2022]
Abstract
Control of neuronal positioning is fundamental to normal brain development. However, the cell-intrinsic mechanisms that govern neuronal positioning remain to be elucidated. Here, we report that the spliced protein products of the transcriptional regulator SnoN, SnoN1 and SnoN2, harbor opposing functions in the coordinate regulation of neuronal branching and positioning. Knockdown of SnoN2 stimulates axon branching in primary neurons and impairs migration of granule neurons in the rat cerebellar cortex in vivo. By contrast, SnoN1 knockdown suppresses SnoN2 knockdown-induced neuronal branching and strikingly triggers excessive migration of granule neurons in the cerebellar cortex. We also find that SnoN1 forms a complex with the transcription factor FOXO1 that represses the X-linked lissencephaly gene encoding doublecortin (DCX). Accordingly, repression of DCX mediates the ability of SnoN1 to regulate branching in primary neurons and granule neuron migration in vivo. These data define an isoform-specific SnoN1-FOXO1 transcriptional complex that orchestrates neuronal branching and positioning in the brain with important implications for the study of developmental disorders of cognition and epilepsy.
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Affiliation(s)
- Mai Anh Huynh
- Department of Pathology, Harvard Medical School, Boston, MA 02115, USA
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73
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Dent EW, Gupton SL, Gertler FB. The growth cone cytoskeleton in axon outgrowth and guidance. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a001800. [PMID: 21106647 DOI: 10.1101/cshperspect.a001800] [Citation(s) in RCA: 402] [Impact Index Per Article: 30.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Axon outgrowth and guidance to the proper target requires the coordination of filamentous (F)-actin and microtubules (MTs), the dynamic cytoskeletal polymers that promote shape change and locomotion. Over the past two decades, our knowledge of the many guidance cues, receptors, and downstream signaling cascades involved in neuronal outgrowth and guidance has increased dramatically. Less is known, however, about how those cascades of information converge and direct appropriate remodeling and interaction of cytoskeletal polymers, the ultimate effectors of movement and guidance. During development, much of the communication that occurs between environmental guidance cues and the cytoskeleton takes place at the growing tip of the axon, the neuronal growth cone. Several articles on this topic focus on the "input" to the growth cone, the myriad of receptor types, and their corresponding cognate ligands. Others investigate the signaling cascades initiated by receptors and propagated by second messenger pathways (i.e., kinases, phosphatases, GTPases). Ultimately, this plethora of information converges on proteins that associate directly with the actin and microtubule cytoskeletons. The role of these cytoskeletal-associated proteins, as well as the cytoskeleton itself in axon outgrowth and guidance, is the subject of this article.
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Affiliation(s)
- Erik W Dent
- Department of Anatomy, University of Wisconsin-Madison, 53706, USA
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74
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Pramparo T, Libiger O, Jain S, Li H, Youn YH, Hirotsune S, Schork NJ, Wynshaw-Boris A. Global developmental gene expression and pathway analysis of normal brain development and mouse models of human neuronal migration defects. PLoS Genet 2011; 7:e1001331. [PMID: 21423666 PMCID: PMC3053345 DOI: 10.1371/journal.pgen.1001331] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Accepted: 02/08/2011] [Indexed: 01/01/2023] Open
Abstract
Heterozygous LIS1 mutations are the most common cause of human lissencephaly, a human neuronal migration defect, and DCX mutations are the most common cause of X-linked lissencephaly. LIS1 is part of a protein complex including NDEL1 and 14-3-3ε that regulates dynein motor function and microtubule dynamics, while DCX stabilizes microtubules and cooperates with LIS1 during neuronal migration and neurogenesis. Targeted gene mutations of Lis1, Dcx, Ywhae (coding for 14-3-3ε), and Ndel1 lead to neuronal migration defects in mouse and provide models of human lissencephaly, as well as aid the study of related neuro-developmental diseases. Here we investigated the developing brain of these four mutants and wild-type mice using expression microarrays, bioinformatic analyses, and in vivo/in vitro experiments to address whether mutations in different members of the LIS1 neuronal migration complex lead to similar and/or distinct global gene expression alterations. Consistent with the overall successful development of the mutant brains, unsupervised clustering and co-expression analysis suggested that cell cycle and synaptogenesis genes are similarly expressed and co-regulated in WT and mutant brains in a time-dependent fashion. By contrast, focused co-expression analysis in the Lis1 and Ndel1 mutants uncovered substantial differences in the correlation among pathways. Differential expression analysis revealed that cell cycle, cell adhesion, and cytoskeleton organization pathways are commonly altered in all mutants, while synaptogenesis, cell morphology, and inflammation/immune response are specifically altered in one or more mutants. We found several commonly dysregulated genes located within pathogenic deletion/duplication regions, which represent novel candidates of human mental retardation and neurocognitive disabilities. Our analysis suggests that gene expression and pathway analysis in mouse models of a similar disorder or within a common pathway can be used to define novel candidates for related human diseases.
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Affiliation(s)
- Tiziano Pramparo
- Department of Pediatrics and Institute for Human Genetics, School of Medicine, University of California San Francisco, San Francisco, California, United States of America
- Departments of Pediatrics and Medicine, Center for Human Genetics and Genomics, School of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Ondrej Libiger
- The Scripps Research Institute and the Scripps Translational Science Institute, La Jolla, California United States of America
| | - Sonia Jain
- Department of Family and Preventive Medicine, Division of Biostatistics and Bioinformatics, School of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Hong Li
- Departments of Pediatrics and Medicine, Center for Human Genetics and Genomics, School of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Yong Ha Youn
- Department of Pediatrics and Institute for Human Genetics, School of Medicine, University of California San Francisco, San Francisco, California, United States of America
- Departments of Pediatrics and Medicine, Center for Human Genetics and Genomics, School of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Shinji Hirotsune
- Department of Genetic Disease Research, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Nicholas J. Schork
- The Scripps Research Institute and the Scripps Translational Science Institute, La Jolla, California United States of America
| | - Anthony Wynshaw-Boris
- Department of Pediatrics and Institute for Human Genetics, School of Medicine, University of California San Francisco, San Francisco, California, United States of America
- Departments of Pediatrics and Medicine, Center for Human Genetics and Genomics, School of Medicine, University of California San Diego, La Jolla, California, United States of America
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75
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Role of cytoskeletal abnormalities in the neuropathology and pathophysiology of type I lissencephaly. Acta Neuropathol 2011; 121:149-70. [PMID: 21046408 PMCID: PMC3037170 DOI: 10.1007/s00401-010-0768-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 10/01/2010] [Accepted: 10/23/2010] [Indexed: 01/24/2023]
Abstract
Type I lissencephaly or agyria-pachygyria is a rare developmental disorder which results from a defect of neuronal migration. It is characterized by the absence of gyri and a thickening of the cerebral cortex and can be associated with other brain and visceral anomalies. Since the discovery of the first genetic cause (deletion of chromosome 17p13.3), six additional genes have been found to be responsible for agyria–pachygyria. In this review, we summarize the current knowledge concerning these genetic disorders including clinical, neuropathological and molecular results. Genetic alterations of LIS1, DCX, ARX, TUBA1A, VLDLR, RELN and more recently WDR62 genes cause migrational abnormalities along with more complex and subtle anomalies affecting cell proliferation and differentiation, i.e., neurite outgrowth, axonal pathfinding, axonal transport, connectivity and even myelination. The number and heterogeneity of clinical, neuropathological and radiological defects suggest that type I lissencephaly now includes several forms of cerebral malformations. In vitro experiments and mutant animal studies, along with neuropathological abnormalities in humans are of invaluable interest for the understanding of pathophysiological mechanisms, highlighting the central role of cytoskeletal dynamics required for a proper achievement of cell proliferation, neuronal migration and differentiation.
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76
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Bilimoria PM, de la Torre-Ubieta L, Ikeuchi Y, Becker EBE, Reiner O, Bonni A. A JIP3-regulated GSK3β/DCX signaling pathway restricts axon branching. J Neurosci 2010; 30:16766-76. [PMID: 21159948 PMCID: PMC3409248 DOI: 10.1523/jneurosci.1362-10.2010] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 06/21/2010] [Accepted: 06/27/2010] [Indexed: 01/26/2023] Open
Abstract
Axon branching plays a critical role in establishing the accurate patterning of neuronal circuits in the brain. However, the mechanisms that control axon branching remain poorly understood. Here we report that knockdown of the brain-enriched signaling protein JNK-interacting protein 3 (JIP3) triggers exuberant axon branching and self-contact in primary granule neurons of the rat cerebellar cortex. JIP3 knockdown in cerebellar slices and in postnatal rat pups in vivo leads to the formation of ectopic branches in granule neuron parallel fiber axons in the cerebellar cortex. We also find that JIP3 restriction of axon branching is mediated by the protein kinase glycogen synthase kinase 3β (GSK3β). JIP3 knockdown induces the downregulation of GSK3β in neurons, and GSK3β knockdown phenocopies the effect of JIP3 knockdown on axon branching and self-contact. Finally, we establish doublecortin (DCX) as a novel substrate of GSK3β in the control of axon branching and self-contact. GSK3β phosphorylates DCX at the distinct site of Ser327 and thereby contributes to DCX function in the restriction of axon branching. Together, our data define a JIP3-regulated GSK3β/DCX signaling pathway that restricts axon branching in the mammalian brain. These findings may have important implications for our understanding of neuronal circuitry during development, as well as the pathogenesis of neurodevelopmental disorders of cognition.
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Affiliation(s)
- Parizad M. Bilimoria
- Department of Pathology and
- Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115, and
| | - Luis de la Torre-Ubieta
- Department of Pathology and
- Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115, and
| | | | | | - Orly Reiner
- Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Azad Bonni
- Department of Pathology and
- Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115, and
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77
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Fourniol FJ, Sindelar CV, Amigues B, Clare DK, Thomas G, Perderiset M, Francis F, Houdusse A, Moores CA. Template-free 13-protofilament microtubule-MAP assembly visualized at 8 A resolution. ACTA ACUST UNITED AC 2010; 191:463-70. [PMID: 20974813 PMCID: PMC3003314 DOI: 10.1083/jcb.201007081] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Microtubule-associated proteins (MAPs) are essential for regulating and organizing cellular microtubules (MTs). However, our mechanistic understanding of MAP function is limited by a lack of detailed structural information. Using cryo-electron microscopy and single particle algorithms, we solved the 8 Å structure of doublecortin (DCX)-stabilized MTs. Because of DCX's unusual ability to specifically nucleate and stabilize 13-protofilament MTs, our reconstruction provides unprecedented insight into the structure of MTs with an in vivo architecture, and in the absence of a stabilizing drug. DCX specifically recognizes the corner of four tubulin dimers, a binding mode ideally suited to stabilizing both lateral and longitudinal lattice contacts. A striking consequence of this is that DCX does not bind the MT seam. DCX binding on the MT surface indirectly stabilizes conserved tubulin-tubulin lateral contacts in the MT lumen, operating independently of the nucleotide bound to tubulin. DCX's exquisite binding selectivity uncovers important insights into regulation of cellular MTs.
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Affiliation(s)
- Franck J Fourniol
- Institute of Structural and Molecular Biology, Birkbeck College, London, England, UK
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78
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Marsh JA, Dancheck B, Ragusa MJ, Allaire M, Forman-Kay JD, Peti W. Structural diversity in free and bound states of intrinsically disordered protein phosphatase 1 regulators. Structure 2010; 18:1094-103. [PMID: 20826336 PMCID: PMC2936704 DOI: 10.1016/j.str.2010.05.015] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 05/07/2010] [Accepted: 05/19/2010] [Indexed: 10/19/2022]
Abstract
Complete folding is not a prerequisite for protein function, as disordered and partially folded states of proteins frequently perform essential biological functions. In order to understand their functions at the molecular level, we utilized diverse experimental measurements to calculate ensemble models of three nonhomologous, intrinsically disordered proteins: I-2, spinophilin, and DARPP-32, which bind to and regulate protein phosphatase 1 (PP1). The models demonstrate that these proteins have dissimilar propensities for secondary and tertiary structure in their unbound forms. Direct comparison of these ensemble models with recently determined PP1 complex structures suggests a significant role for transient, preformed structure in the interactions of these proteins with PP1. Finally, we generated an ensemble model of partially disordered I-2 bound to PP1 that provides insight into the relationship between flexibility and biological function in this dynamic complex.
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Affiliation(s)
- Joseph A. Marsh
- Molecular Structure & Function, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada & Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Barbara Dancheck
- Department of Molecular Pharmacology, Physiology and Biotechnology & Department of Chemistry, Brown University, Providence, RI, 02912, USA
| | - Michael J. Ragusa
- Department of Molecular Pharmacology, Physiology and Biotechnology & Department of Chemistry, Brown University, Providence, RI, 02912, USA
| | - Marc Allaire
- National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA
| | - Julie D. Forman-Kay
- Molecular Structure & Function, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada & Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Wolfgang Peti
- Department of Molecular Pharmacology, Physiology and Biotechnology & Department of Chemistry, Brown University, Providence, RI, 02912, USA
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79
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Bush JR, Wevrick R. Loss of Necdin impairs myosin activation and delays cell polarization. Genesis 2010; 48:540-53. [DOI: 10.1002/dvg.20658] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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80
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Clustering of excess growth resources within leading growth cones underlies the recurrent "deposition" of varicosities along developing neurites. Exp Neurol 2010; 225:140-53. [PMID: 20558161 DOI: 10.1016/j.expneurol.2010.06.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2010] [Revised: 05/30/2010] [Accepted: 06/07/2010] [Indexed: 11/21/2022]
Abstract
Varicosities (VRs) are ubiquitous neuronal structures that are considered to serve as presynaptic structures. The mechanisms of their assembly are unknown. Using cultured Aplysia neurons, we found that in the absence of postsynaptic targets, VRs form at the leading edge of extending neurites when anterogradely transported organelles accumulate within the palm of the growth cone (GC) at a rate that exceeds their utilization by the GC machinery. The aggregation of excess organelles at the palm of the GC leads to slowdown of the GC's advance. As the size of the organelle clusters increases, the rate of organelle sequestration diminishes and the supply of building blocks to the GC resumes. The GCs' advance is re-initiated, "leaving behind" an organelle-loaded nascent VR. These mechanisms account for the recurrent "deposition" of almost equally spaced VRs by advancing GCs. Consistent with the view that VRs serve as "ready-to-go" presynaptic terminals, we found that a short train of action potentials leads to exocytosis of labeled vesicles within the varicosities. We propose that the formation and spacing of VRs by advancing GCs is the default outcome of the balance between the rate of supply of growth-supporting resources and the usage of these resources by the GC's machinery at the leading edges of specific neurites.
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81
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Peng YJ, He WQ, Tang J, Tao T, Chen C, Gao YQ, Zhang WC, He XY, Dai YY, Zhu NC, Lv N, Zhang CH, Qiao YN, Zhao LP, Gao X, Zhu MS. Trio is a key guanine nucleotide exchange factor coordinating regulation of the migration and morphogenesis of granule cells in the developing cerebellum. J Biol Chem 2010; 285:24834-44. [PMID: 20516067 DOI: 10.1074/jbc.m109.096537] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Orchestrated regulation of neuronal migration and morphogenesis is critical for neuronal development and establishment of functional circuits, but its regulatory mechanism is incompletely defined. We established and analyzed mice with neural-specific knock-out of Trio, a guanine nucleotide exchange factor with multiple guanine nucleotide exchange factor domains. Knock-out mice showed defective cerebella and severe signs of ataxia. Mutant cerebella had no granule cells in the internal granule cell layer due to aberrant granule cell migration as well as abnormal neurite growth. Trio-deficient granule cells showed reduced extension of neurites and highly branched and misguided processes with perturbed stabilization of actin and microtubules. Trio deletion caused down-regulation of the activation of Rac1, RhoA, and Cdc42, and mutant granule cells appeared to be unresponsive to neurite growth-promoting molecules such as Netrin-1 and Semaphorin 6A. These results suggest that Trio may be a key signal module for the orchestrated regulation of neuronal migration and morphogenesis during cerebellar development. Trio may serve as a signal integrator decoding extrinsic signals to Rho GTPases for cytoskeleton organization.
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Affiliation(s)
- Ya-Jing Peng
- Model Animal Research Center and Moe Key Laboratory of Model Animal for Disease Study, Nanjing University, Nanjing 210061, China
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82
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Bollen M, Peti W, Ragusa MJ, Beullens M. The extended PP1 toolkit: designed to create specificity. Trends Biochem Sci 2010; 35:450-8. [PMID: 20399103 DOI: 10.1016/j.tibs.2010.03.002] [Citation(s) in RCA: 383] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Revised: 03/03/2010] [Accepted: 03/04/2010] [Indexed: 01/03/2023]
Abstract
Protein Ser/Thr phosphatase-1 (PP1) catalyzes the majority of eukaryotic protein dephosphorylation reactions in a highly regulated and selective manner. Recent studies have identified an unusually diversified PP1 interactome with the properties of a regulatory toolkit. PP1-interacting proteins (PIPs) function as targeting subunits, substrates and/or inhibitors. As targeting subunits, PIPs contribute to substrate selection by bringing PP1 into the vicinity of specific substrates and by modulating substrate specificity via additional substrate docking sites or blocking substrate-binding channels. Many of the nearly 200 established mammalian PIPs are predicted to be intrinsically disordered, a property that facilitates their binding to a large surface area of PP1 via multiple docking motifs. These novel insights offer perspectives for the therapeutic targeting of PP1 by interfering with the binding of PIPs or substrates.
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Affiliation(s)
- Mathieu Bollen
- Laboratory of Biosignaling & Therapeutics, Department of Molecular Cell Biology, University of Leuven, B-3000 Leuven, Belgium.
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83
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Rouwette TPH, Kozicz T, Olde Loohuis NFM, Gaszner B, Vreugdenhil E, Scheffer GJ, Roubos EW, Vissers KC, Scheenen WJJM. Acute pain increases phosphorylation of DCLK-long in the Edinger-Westphal nucleus but not in the hypothalamic paraventricular nucleus of the rat. THE JOURNAL OF PAIN 2010; 11:930-40. [PMID: 20418180 DOI: 10.1016/j.jpain.2009.12.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 12/01/2009] [Accepted: 12/24/2009] [Indexed: 01/14/2023]
Abstract
UNLABELLED The doublecortin-like kinase (DCLK) gene is crucially involved in neuronal plasticity and microtubule-guided retrograde transport of signaling molecules. We have explored the possibility that DCLK is involved in pain-induced signaling events in adult male Wistar rats. Our results show that both DCLK-short and DCLK-long splice variants are present in the cell body and proximal dendrites of neurons in stress-related nuclei, ie, the paraventricular nucleus of the hypothalamus (PVN) and the non-preganglionic Edinger-Westphal nucleus (npEW) in the rostroventral periaqueductal grey. We found that DCLK-long but not DCLK-short is phosphorylated in its serine/proline-rich domain. Furthermore, we demonstrate that phosphorylation of DCLK-long in the npEW is increased by acute pain, whereas DCLK-long phosphorylation in the PVN remains unaffected. This is the first report revealing that DCLK isoforms in the PVN and npEW occur in the adult mammalian brain and that pain differentially affects DCLK-long-mediated neuronal plasticity in these 2 stress-sensitive brain centers. PERSPECTIVE Pain is a burden for society and the individual, and although the mechanisms underlying pain are relatively well known, its treatment remains difficult and incomplete. Pain stress can lead to diseases like chronic pain and depression. The differential DCLK-phosphorylation in stress-sensitive brain areas is a potential novel therapeutic target in pain research.
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Affiliation(s)
- Tom P H Rouwette
- Department of Cellular Animal Physiology, Donders Institute for Brain, Cognition and Behaviour, Center for Neuroscience, Radboud University Nijmegen, Nijmegen, The Netherlands.
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84
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Ragusa MJ, Dancheck B, Critton DA, Nairn AC, Page R, Peti W. Spinophilin directs protein phosphatase 1 specificity by blocking substrate binding sites. Nat Struct Mol Biol 2010; 17:459-64. [PMID: 20305656 PMCID: PMC2924587 DOI: 10.1038/nsmb.1786] [Citation(s) in RCA: 148] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Accepted: 02/08/2010] [Indexed: 01/14/2023]
Abstract
The serine/threonine Protein Phosphatase 1 (PP1) dephosphorylates hundreds of key biological targets. PP1 associates with ≥200 regulatory proteins to form highly specific holoenzymes. These regulatory proteins target PP1 to its point of action within the cell and prime its enzymatic specificity for particular substrates. However, how they direct PP1’s specificity is not understood. Here we show that spinophilin, a neuronal PP1 regulator, is entirely unstructured in its unbound form and binds PP1, through a folding-upon-binding mechanism, in an elongated fashion, blocking one of PP1’s three putative substrate binding sites, without altering its active site. This mode of binding is sufficient for spinophilin to restrict PP1’s activity toward a model substrate in vitro, without affecting its ability to dephosphorylate its neuronal substrate GluR1. Thus, our work provides the molecular basis for the ability of spinophilin to dictate PP1 substrate specificity.
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Affiliation(s)
- Michael J Ragusa
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island, USA
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85
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Blackmore MG, Moore DL, Smith RP, Goldberg JL, Bixby JL, Lemmon VP. High content screening of cortical neurons identifies novel regulators of axon growth. Mol Cell Neurosci 2010; 44:43-54. [PMID: 20159039 DOI: 10.1016/j.mcn.2010.02.002] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Revised: 01/28/2010] [Accepted: 02/08/2010] [Indexed: 12/14/2022] Open
Abstract
Neurons in the central nervous system lose their intrinsic capacity for axon regeneration as they mature, and it is widely hypothesized that changes in gene expression are responsible. Testing this hypothesis and identifying the relevant genes has been challenging because hundreds to thousands of genes are developmentally regulated in CNS neurons, but only a small subset are likely relevant to axon growth. Here we used automated high content analysis (HCA) methods to functionally test 743 plasmids encoding developmentally regulated genes in neurite outgrowth assays using postnatal cortical neurons. We identified both growth inhibitors (Ephexin, Aldolase A, Solute Carrier 2A3, and Chimerin), and growth enhancers (Doublecortin, Doublecortin-like, Kruppel-like Factor 6, and CaM-Kinase II gamma), some of which regulate established growth mechanisms like microtubule dynamics and small GTPase signaling. Interestingly, with only one exception the growth-suppressing genes were developmentally upregulated, and the growth-enhancing genes downregulated. These data provide important support for the hypothesis that developmental changes in gene expression control neurite outgrowth, and identify potential new gene targets to promote neurite outgrowth.
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Affiliation(s)
- Murray G Blackmore
- The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami, 1400 NW 12th Ave, Miami, FL 33136, USA.
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86
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Baucum AJ, Jalan-Sakrikar N, Jiao Y, Gustin RM, Carmody LC, Tabb DL, Ham AJL, Colbran RJ. Identification and validation of novel spinophilin-associated proteins in rodent striatum using an enhanced ex vivo shotgun proteomics approach. Mol Cell Proteomics 2010; 9:1243-59. [PMID: 20124353 DOI: 10.1074/mcp.m900387-mcp200] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Spinophilin regulates excitatory postsynaptic function and morphology during development by virtue of its interactions with filamentous actin, protein phosphatase 1, and a plethora of additional signaling proteins. To provide insight into the roles of spinophilin in mature brain, we characterized the spinophilin interactome in subcellular fractions solubilized from adult rodent striatum by using a shotgun proteomics approach to identify proteins in spinophilin immune complexes. Initial analyses of samples generated using a mouse spinophilin antibody detected 23 proteins that were not present in an IgG control sample; however, 12 of these proteins were detected in complexes isolated from spinophilin knock-out tissue. A second screen using two different spinophilin antibodies and either knock-out or IgG controls identified a total of 125 proteins. The probability of each protein being specifically associated with spinophilin in each sample was calculated, and proteins were ranked according to a chi(2) analysis of the probabilities from analyses of multiple samples. Spinophilin and the known associated proteins neurabin and multiple isoforms of protein phosphatase 1 were specifically detected. Multiple, novel, spinophilin-associated proteins (myosin Va, calcium/calmodulin-dependent protein kinase II, neurofilament light polypeptide, postsynaptic density 95, alpha-actinin, and densin) were then shown to interact with GST fusion proteins containing fragments of spinophilin. Additional biochemical and transfected cell imaging studies showed that alpha-actinin and densin directly interact with residues 151-300 and 446-817, respectively, of spinophilin. Taken together, we have developed a multi-antibody, shotgun proteomics approach to characterize protein interactomes in native tissues, delineating the importance of knock-out tissue controls and providing novel insights into the nature and function of the spinophilin interactome in mature striatum.
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Affiliation(s)
- Anthony J Baucum
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232-0615, USA.
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87
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Hammond JW, Huang CF, Kaech S, Jacobson C, Banker G, Verhey KJ. Posttranslational modifications of tubulin and the polarized transport of kinesin-1 in neurons. Mol Biol Cell 2009; 21:572-83. [PMID: 20032309 PMCID: PMC2820422 DOI: 10.1091/mbc.e09-01-0044] [Citation(s) in RCA: 221] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
During the development of neuronal polarity, the Kinesin-1 motor translocates preferentially to the axon. We show that Kinesin-1 selectivity does not depend on differences between axons and dendrites in microtubule stability or tubulin acetylation, but is likely specified by other tubulin posttranslational modifications. Polarized transport by microtubule-based motors is critical for neuronal development and function. Selective translocation of the Kinesin-1 motor domain is the earliest known marker of axonal identity, occurring before morphological differentiation. Thus, Kinesin-1–mediated transport may contribute to axonal specification. We tested whether posttranslational modifications of tubulin influence the ability of Kinesin-1 motors to distinguish microtubule tracks during neuronal development. We detected no difference in microtubule stability between axons and minor neurites in polarized stage 3 hippocampal neurons. In contrast, microtubule modifications were enriched in a subset of neurites in unpolarized stage 2 cells and the developing axon in polarized stage 3 cells. This enrichment correlated with the selective accumulation of constitutively active Kinesin-1 motors. Increasing tubulin acetylation, without altering the levels of other tubulin modifications, did not alter the selectivity of Kinesin-1 accumulation in polarized cells. However, globally enhancing tubulin acetylation, detyrosination, and polyglutamylation by Taxol treatment or inhibition of glycogen synthase kinase 3β decreased the selectivity of Kinesin-1 translocation and led to the formation of multiple axons. Although microtubule acetylation enhances the motility of Kinesin-1, the preferential translocation of Kinesin-1 on axonal microtubules in polarized neuronal cells is not determined by acetylation alone but is probably specified by a combination of tubulin modifications.
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Affiliation(s)
- Jennetta W Hammond
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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88
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Müller M, Lutter D, Püschel AW. Persistence of the cell-cycle checkpoint kinase Wee1 in SadA- and SadB-deficient neurons disrupts neuronal polarity. J Cell Sci 2009; 123:286-94. [PMID: 20026642 DOI: 10.1242/jcs.058230] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Wee1 is well characterized as a cell-cycle checkpoint kinase that regulates the entry into mitosis in dividing cells. Here we identify a novel function of Wee1 in postmitotic neurons during the establishment of distinct axonal and dendritic compartments, which is an essential step during neuronal development. Wee1 is expressed in unpolarized neurons but is downregulated after neurons have extended an axon. Suppression of Wee1 impairs the formation of minor neurites but does not interfere with axon formation. However, neuronal polarity is disrupted when neurons fail to downregulate Wee1. The kinases SadA and SadB (Sad kinases) phosphorylate Wee1 and are required to initiate its downregulation in polarized neurons. Wee1 expression persists in neurons that are deficient in SadA and SadB and disrupts neuronal polarity. Knockdown of Wee1 rescues the Sada(-/-);Sadb(-/-) mutant phenotype and restores normal polarity in these neurons. Our results demonstrate that the regulation of Wee1 by SadA and SadB kinases is essential for the differentiation of polarized neurons.
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Affiliation(s)
- Myriam Müller
- Abteilung Molekularbiologie, Institut für Allgemeine Zoologie und Genetik, Westfälische Wilhelms-Universität Münster, Schlossplatz 5, D-48149 Münster, Germany
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89
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Abstract
Interactions between dynamic microtubules and actin filaments are essential to a wide range of cell biological processes including cell division, motility and morphogenesis. In neuronal growth cones, interactions between microtubules and actin filaments in filopodia are necessary for growth cones to make a turn. Growth-cone turning is a fundamental behaviour during axon guidance, as correct navigation of the growth cone through the embryo is required for it to locate an appropriate synaptic partner. Microtubule-actin filament interactions also occur in the transition zone and central domain of the growth cone, where actin arcs exert compressive forces to corral microtubules into the core of the growth cone and thereby facilitate microtubule bundling, a requirement for axon formation. We now have a fairly comprehensive understanding of the dynamic behaviour of the cytoskeleton in growth cones, and the stage is set for discovering the molecular machinery that enables microtubule-actin filament coupling in growth cones, as well as the intracellular signalling pathways that regulate these interactions. Furthermore, recent experiments suggest that microtubule-actin filament interactions might also be important for the formation of dendritic spines from filopodia in mature neurons. Therefore, the mechanisms coupling microtubules to actin filaments in growth-cone turning and dendritic-spine maturation might be conserved.
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Affiliation(s)
- Sara Geraldo
- The MRC Centre for Developmental Neurobiology, New Hunts House, Guy's Campus, King's College London, London SE1 1UL, UK
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90
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Doublecortin associates with microtubules preferentially in regions of the axon displaying actin-rich protrusive structures. J Neurosci 2009; 29:10995-1010. [PMID: 19726658 DOI: 10.1523/jneurosci.3399-09.2009] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Here we studied doublecortin (DCX) in cultured hippocampal and sympathetic neurons during axonal development. In both types of neurons, DCX is abundant in the growth cone, in which it primarily localizes with microtubules. Its abundance is lowest on microtubules in the neck region of the growth cone and highest on microtubules extending into the actin-rich lamellar regions. Interestingly, the microtubule polymer richest in DCX is also deficient in tau. In hippocampal neurons but not sympathetic neurons, discrete focal patches of microtubules rich in DCX and deficient in tau are present along the axonal shaft. Invariably, these patches have actin-rich protrusions resembling those of growth cones. Many of the DCX/actin filament patches exhibit vigorous protrusive activity and also undergo a proximal-to-distal redistribution within the axon at average rates approximately 2 microm/min and thus closely resemble the growth-cone-like waves described by previous authors. Depletion of DCX using small interfering RNA had little effect on the appearance of the growth cone or on axonal growth in either type of neuron. However, DCX depletion significantly delayed collateral branching in hippocampal neurons and also significantly lowered the frequency of actin-rich patches along hippocampal axons. Branching by sympathetic neurons, which occurs by growth cone splitting, was not impaired by DCX depletion. These findings reveal a functional relationship between the DCX/actin filament patches and collateral branching. Based on the striking resemblance of these patches to growth cones, we discuss the possibility that they reflect a mechanism for locally boosting morphogenetic activity to facilitate axonal growth and collateral branching.
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91
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Sanchez-Soriano N, Travis M, Dajas-Bailador F, Gonçalves-Pimentel C, Whitmarsh AJ, Prokop A. Mouse ACF7 and drosophila short stop modulate filopodia formation and microtubule organisation during neuronal growth. J Cell Sci 2009; 122:2534-42. [PMID: 19571116 DOI: 10.1242/jcs.046268] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Spectraplakins are large actin-microtubule linker molecules implicated in various processes, including gastrulation, wound healing, skin blistering and neuronal degeneration. Expression data for the mammalian spectraplakin ACF7 and genetic analyses of the Drosophila spectraplakin Short stop (Shot) suggest an important role during neurogenesis. Using three parallel neuronal culture systems we demonstrate that, like Shot, ACF7 is essential for axon extension and describe, for the first time, their subcellular functions during axonal growth. Firstly, both ACF7 and Shot regulate the organisation of neuronal microtubules, a role dependent on both the F-actin- and microtubule-binding domains. This role in microtubule organisation is probably the key mechanism underlying the roles of Shot and ACF7 in growth cone advance. Secondly, we found a novel role for ACF7 and Shot in regulating the actin cytoskeleton through their ability to control the formation of filopodia. This function in F-actin regulation requires EF-hand motifs and interaction with the translational regulator Krasavietz/eIF5C, indicating that the underlying mechanisms are completely different from those used to control microtubules. Our data provide the basis for the first mechanistic explanation for the role of Shot and ACF7 in the developing nervous system and demonstrate their ability to coordinate the organisation of both actin and microtubule networks during axonal growth.
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Affiliation(s)
- Natalia Sanchez-Soriano
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Manchester M13 9PT, UK
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92
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The microtubule network and neuronal morphogenesis: Dynamic and coordinated orchestration through multiple players. Mol Cell Neurosci 2009; 43:15-32. [PMID: 19660553 DOI: 10.1016/j.mcn.2009.07.012] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2009] [Accepted: 07/27/2009] [Indexed: 11/24/2022] Open
Abstract
Nervous system function and plasticity rely on the complex architecture of neuronal networks elaborated during development, when neurons acquire their specific and complex shape. During neuronal morphogenesis, the formation and outgrowth of functionally and structurally distinct axons and dendrites require a coordinated and dynamic reorganization of the microtubule cytoskeleton involving numerous regulators. While most of these factors act directly on microtubules to stabilize them or promote their assembly, depolymerization or fragmentation, others are now emerging as essential regulators of neuronal differentiation by controlling tubulin availability and modulating microtubule dynamics. In this review, we recapitulate how the microtubule network is actively regulated during the successive phases of neuronal morphogenesis, and what are the specific roles of the various microtubule-regulating proteins in that process. We then describe the specific signaling pathways and inter-regulations that coordinate the different activities of these proteins to sustain neuronal development in response to environmental cues.
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93
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Chou A, Boerkoel C, du Souich C, Rupps R. Phenotypic and molecular characterization of a novelDCXdeletion and a review of the literature. Clin Genet 2009; 76:214-8. [DOI: 10.1111/j.1399-0004.2009.01206.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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94
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Microtubule assembly, organization and dynamics in axons and dendrites. Nat Rev Neurosci 2009; 10:319-32. [PMID: 19377501 DOI: 10.1038/nrn2631] [Citation(s) in RCA: 762] [Impact Index Per Article: 50.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
During the past decade enormous advances have been made in our understanding of the basic molecular machinery that is involved in the development of neuronal polarity. Far from being mere structural elements, microtubules are emerging as key determinants of neuronal polarity. Here we review the current understanding of the regulation of microtubule assembly, organization and dynamics in axons and dendrites. These studies provide new insight into microtubules' function in neuronal development and their potential contribution to plasticity.
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95
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Abstract
The central component in the road trip of axon guidance is the growth cone, a dynamic structure that is located at the tip of the growing axon. During its journey, the growth cone comprises both 'vehicle' and 'navigator'. Whereas the 'vehicle' maintains growth cone movement and contains the cytoskeletal structural elements of its framework, a motor to move forward and a mechanism to provide traction on the 'road', the 'navigator' aspect guides this system with spatial bias to translate environmental signals into directional movement. The understanding of the functions and regulation of the vehicle and navigator provides new insights into the cell biology of growth cone guidance.
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96
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Santra M, Santra S, Roberts C, Zhang RL, Chopp M. Doublecortin induces mitotic microtubule catastrophe and inhibits glioma cell invasion. J Neurochem 2009; 108:231-45. [PMID: 19094064 DOI: 10.1111/j.1471-4159.2008.05758.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Doublecortin (DCX) is a microtubule (MT) binding protein that induces growth arrest at the G2-M phase of cell cycle in glioma and suppresses tumor xenograft in immunocompromised hosts. DCX expression was found in neuronal cells, but lacking in glioma cells. We tested the hypothesis that DCX inhibits glioma U87 cell mitosis and invasion. Our data showed that DCX synthesizing U87 cells underwent mitotic MT spindle catastrophe in a neurabin II dependent pathway. Synthesis of both DCX and neurabin II were required to induce apoptosis in U87 and human embryonic kidney 293T cells. In DCX expressing U87 cells, association of phosphorylated DCX with protein phosphatase-1 (PP1) in the cytosol disrupted the interaction between kinesin-13 and PP1 in the nucleus and yielded spontaneously active kinesin-13. The activated kinesin-13 caused mitotic MT catastrophe in spindle checkpoint. Phosphorylated-DCX induced depolymerization of actin filaments in U87 cells, down-regulated matrix metalloproteinases-2 and -9, and inhibited glioma U87 cell invasion in a neurabin II dependent pathway. Thus, localization of the DCX-neurabin II-PP1 complex in the cytosol of U87 tumor cells inhibited PP1 phosphatase activities leading to anti-glioma effects via (1) mitotic MT spindle catastrophe that blocks mitosis and (2) depolymerization of actin that inhibits glioma cell invasion.
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Affiliation(s)
- Manoranjan Santra
- Department of Neurology, Henry Ford Health System, Detroit, Michigan, USA
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97
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Reiner O, Sapir T. Polarity regulation in migrating neurons in the cortex. Mol Neurobiol 2009; 40:1-14. [PMID: 19330467 DOI: 10.1007/s12035-009-8065-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Accepted: 03/12/2009] [Indexed: 12/25/2022]
Abstract
The formation of the cerebral cortex requires migration of billions of cells from their birth position to their final destination. A motile cell must have internal polarity in order to move in a specified direction. Locomotory polarity requires the coordinated polymerization of cytoskeletal elements such as microtubules and actin combined with regulated activities of the associated molecular motors. This review is focused on migrating neurons in the developing cerebral cortex, which need to attain internal polarity in order to reach their proper target. The position and dynamics of the centrosome plays an important function in this directed motility. We highlight recent interesting findings connecting polarity proteins with neuronal migration events regulated by the microtubule-associated molecular motor, cytoplasmic dynein.
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Affiliation(s)
- Orly Reiner
- Department of Molecular Genetics, The Weizmann Institute of Science, 76100 Rehovot, Israel.
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98
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The adenomatous polyposis coli protein is an essential regulator of radial glial polarity and construction of the cerebral cortex. Neuron 2009; 61:42-56. [PMID: 19146812 DOI: 10.1016/j.neuron.2008.10.053] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Revised: 09/30/2008] [Accepted: 10/31/2008] [Indexed: 11/23/2022]
Abstract
Radial glia are highly polarized cells that serve as neuronal progenitors and as scaffolds for neuronal migration during construction of the cerebral cortex. How radial glial cells establish and maintain their morphological polarity is unknown. Using conditional gene targeting in mice, we demonstrate that adenomatous polyposis coli (APC) serves an essential function in the maintenance of polarized radial glial scaffold during brain development. In the absence of APC, radial glial cells lose their polarity and responsiveness to the extracellular polarity maintenance cues, such as neuregulin-1. Elimination of APC further leads to marked instability of the radial glial microtubule cytoskeleton. The resultant changes in radial glial function and loss of APC in radial glial progeny lead to defective generation and migration of cortical neurons, severely disrupted cortical layer formation, and aberrant axonal tract development. Thus, APC is an essential regulator of radial glial polarity and is critical for the construction of cerebral cortex in mammals.
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99
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Abstract
Abnormal neuronal migration is manifested in brain malformations such as lissencephaly. The impairment in coordinated cell motility likely reflects a faulty mechanism of cell polarization or coupling between polarization and movement. Here we report on the relationship between the polarity kinase MARK2/Par-1 and its substrate, the well-known lissencephaly-associated gene doublecortin (DCX), during cortical radial migration. We have previously shown using in utero electroporation that reduced MARK2 levels resulted in multipolar neurons stalled at the intermediate zone border, similar to the phenotype observed in the case of DCX silencing. However, whereas reduced MARK2 stabilized microtubules, we show here that knock-down of DCX increased microtubule dynamics. This led to the hypothesis that simultaneous reduction may alleviate the phenotype. Coreduction of MARK2 and DCX resulted in a partial restoration of the normal neuronal migration phenotype in vivo. The kinetic behavior of the centrosomes reflected the different molecular mechanisms activated when either protein was reduced. In the case of reducing MARK2 processive motility of the centrosome was hindered, whereas when DCX was reduced, centrosomes moved quickly but bidirectionally. Our results stress the necessity for successful coupling between the polarity pathway and cytoplasmic dynein-dependent activities for proper neuronal migration.
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100
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Meng X, Kanwar N, Du Q, Goping IS, Bleackley RC, Wilkins JA. PPP1R9B (Neurabin 2): Involvement and dynamics in the NK immunological synapse. Eur J Immunol 2009; 39:552-60. [DOI: 10.1002/eji.200838474] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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