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Blaise AM, Corcoran EE, Wattenberg ES, Zhang YL, Cottrell JR, Koleske AJ. In vitro fluorescence assay to measure GDP/GTP exchange of guanine nucleotide exchange factors of Rho family GTPases. Biol Methods Protoc 2021; 7:bpab024. [PMID: 35087952 PMCID: PMC8789339 DOI: 10.1093/biomethods/bpab024] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 12/14/2021] [Indexed: 11/14/2022] Open
Abstract
Guanine nucleotide exchange factors (GEFs) are enzymes that promote the activation of GTPases through GTP loading. Whole exome sequencing has identified rare variants in GEFs that are associated with disease, demonstrating that GEFs play critical roles in human development. However, the consequences of these rare variants can only be understood through measuring their effects on cellular activity. Here, we provide a detailed, user-friendly protocol for purification and fluorescence-based analysis of the two GEF domains within the protein, Trio. This analysis offers a straight-forward, quantitative tool to test the activity of GEF domains on their respective GTPases, as well as utilize high-throughput screening to identify regulators and inhibitors. This protocol can be adapted for characterization of other Rho family GEFs. Such analyses are crucial for the complete understanding of the roles of GEF genetic variants in human development and disease.
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Affiliation(s)
- Alyssa M Blaise
- Departments of Molecular Biophysics and Biochemistry, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
- Neuroscience, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
| | - Ellen E Corcoran
- Departments of Molecular Biophysics and Biochemistry, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
- Neuroscience, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
| | - Eve S Wattenberg
- Departments of Molecular Biophysics and Biochemistry, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
- Neuroscience, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
| | - Yan-Ling Zhang
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Jeffrey R Cottrell
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Anthony J Koleske
- Departments of Molecular Biophysics and Biochemistry, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
- Neuroscience, Yale School of Medicine, Yale University, New Haven, CT 06520-8024, USA
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2
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Sheehan CJ, McMahon JJ, Serdar LD, Silver DL. Dosage-dependent requirements of Magoh for cortical interneuron generation and survival. Development 2020; 147:dev.182295. [PMID: 31857347 DOI: 10.1242/dev.182295] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 11/30/2019] [Indexed: 12/15/2022]
Abstract
Embryonic interneuron development underlies cortical function and its disruption contributes to neurological disease. Yet the mechanisms by which viable interneurons are produced from progenitors remain poorly understood. Here, we demonstrate dosage-dependent requirements of the exon junction complex component Magoh for interneuron genesis in mouse. Conditional Magoh ablation from interneuron progenitors, but not post-mitotic neurons, depletes cortical interneuron number through adulthood, with increased severity in homozygotes. Using live imaging, we discover that Magoh deficiency delays progenitor mitotic progression in a dosage-sensitive fashion, with 40% of homozygous progenitors failing to divide. This shows that Magoh is required in progenitors for both generation and survival of newborn progeny. Transcriptome analysis implicates p53 signaling; moreover, p53 ablation in Magoh haploinsufficient progenitors rescues apoptosis, completely recovering interneuron number. In striking contrast, in Magoh homozygotes, p53 loss fails to rescue interneuron number and mitotic delay, further implicating mitotic defects in interneuron loss. Our results demonstrate that interneuron development is intimately dependent upon progenitor mitosis duration and uncover a crucial post-transcriptional regulator of interneuron fate relevant for neurodevelopmental pathologies.This article has an associated 'The people behind the papers' interview.
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Affiliation(s)
- Charles J Sheehan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - John J McMahon
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Lucas D Serdar
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Debra L Silver
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA .,Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA.,Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA.,Duke Institute for Brain Sciences, Duke University Medical Center, Durham, NC 27710, USA
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3
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Zengini E, Finan C, Wilkinson JM. The Genetic Epidemiological Landscape of Hip and Knee Osteoarthritis: Where Are We Now and Where Are We Going? J Rheumatol 2015; 43:260-6. [PMID: 26628593 DOI: 10.3899/jrheum.150710] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2015] [Indexed: 12/31/2022]
Abstract
Osteoarthritis (OA) is a complex disease that affects the whole joint, with multiple biological and environmental factors contributing to its development. The heritable component for primary OA accounts for ∼50% of susceptibility. So far, candidate gene studies and genome-wide association scans have established 18 OA-associated loci. These findings account for 11% of the heritability, explaining a rather small fraction of the genetic component. To further unravel the genetic architecture of OA, the field needs to facilitate more precise phenotypic definitions, high genome coverage, and large sample metaanalyses, expecting the identification of rare and low frequency variants with potentially higher penetrance, and more accurate methods for calculating phenotype-genotype correlation. Expression analysis, epigenetics, and investigation of interactions can also help clarify the implicated transcriptional regulatory pathways and provide insights into further novel pathogenic OA mechanisms leading to diagnostic biomarker identification and new, more focused therapeutic disease approaches.
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Affiliation(s)
- Eleni Zengini
- From the Dromokaiteio Psychiatric Hospital of Athens, Athens, Greece; Department of Human Metabolism, University of Sheffield, Sheffield; Wellcome Trust Sanger Institute, Hinxton, UK.E. Zengini, BSc, PhD Student, Dromokaiteio Psychiatric Hospital of Athens, and Department of Human Metabolism, University of Sheffield; C. Finan, PhD, Research Excellence Fellow, PhD, Wellcome Trust Sanger Institute; J.M. Wilkinson, FRCS (Tr&Orth), PhD, Professor of Orthopaedics, Department of Human Metabolism, University of Sheffield, Honorary Consultant Orthopaedic Surgeon, Sheffield Teaching Hospitals National Health Service Foundation Trust
| | - Chris Finan
- From the Dromokaiteio Psychiatric Hospital of Athens, Athens, Greece; Department of Human Metabolism, University of Sheffield, Sheffield; Wellcome Trust Sanger Institute, Hinxton, UK.E. Zengini, BSc, PhD Student, Dromokaiteio Psychiatric Hospital of Athens, and Department of Human Metabolism, University of Sheffield; C. Finan, PhD, Research Excellence Fellow, PhD, Wellcome Trust Sanger Institute; J.M. Wilkinson, FRCS (Tr&Orth), PhD, Professor of Orthopaedics, Department of Human Metabolism, University of Sheffield, Honorary Consultant Orthopaedic Surgeon, Sheffield Teaching Hospitals National Health Service Foundation Trust
| | - J Mark Wilkinson
- From the Dromokaiteio Psychiatric Hospital of Athens, Athens, Greece; Department of Human Metabolism, University of Sheffield, Sheffield; Wellcome Trust Sanger Institute, Hinxton, UK.E. Zengini, BSc, PhD Student, Dromokaiteio Psychiatric Hospital of Athens, and Department of Human Metabolism, University of Sheffield; C. Finan, PhD, Research Excellence Fellow, PhD, Wellcome Trust Sanger Institute; J.M. Wilkinson, FRCS (Tr&Orth), PhD, Professor of Orthopaedics, Department of Human Metabolism, University of Sheffield, Honorary Consultant Orthopaedic Surgeon, Sheffield Teaching Hospitals National Health Service Foundation Trust.
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4
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van Unen J, Reinhard NR, Yin T, Wu YI, Postma M, Gadella TWJ, Goedhart J. Plasma membrane restricted RhoGEF activity is sufficient for RhoA-mediated actin polymerization. Sci Rep 2015; 5:14693. [PMID: 26435194 PMCID: PMC4592971 DOI: 10.1038/srep14693] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Accepted: 09/04/2015] [Indexed: 01/08/2023] Open
Abstract
The small GTPase RhoA is involved in cell morphology and migration. RhoA activity is tightly regulated in time and space and depends on guanine exchange factors (GEFs). However, the kinetics and subcellular localization of GEF activity towards RhoA are poorly defined. To study the mechanism underlying the spatiotemporal control of RhoA activity by GEFs, we performed single cell imaging with an improved FRET sensor reporting on the nucleotide loading state of RhoA. By employing the FRET sensor we show that a plasma membrane located RhoGEF, p63RhoGEF, can rapidly activate RhoA through endogenous GPCRs and that localized RhoA activity at the cell periphery correlates with actin polymerization. Moreover, synthetic recruitment of the catalytic domain derived from p63RhoGEF to the plasma membrane, but not to the Golgi apparatus, is sufficient to activate RhoA. The synthetic system enables local activation of endogenous RhoA and effectively induces actin polymerization and changes in cellular morphology. Together, our data demonstrate that GEF activity at the plasma membrane is sufficient for actin polymerization via local RhoA signaling.
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Affiliation(s)
- Jakobus van Unen
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, P.O. Box 94215, NL-1090 GE Amsterdam, The Netherlands
| | - Nathalie R Reinhard
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, P.O. Box 94215, NL-1090 GE Amsterdam, The Netherlands
| | - Taofei Yin
- Center for Cell Analysis and Modeling, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06032-6406
| | - Yi I Wu
- Center for Cell Analysis and Modeling, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06032-6406
| | - Marten Postma
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, P.O. Box 94215, NL-1090 GE Amsterdam, The Netherlands
| | - Theodorus W J Gadella
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, P.O. Box 94215, NL-1090 GE Amsterdam, The Netherlands
| | - Joachim Goedhart
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, P.O. Box 94215, NL-1090 GE Amsterdam, The Netherlands
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5
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Evans JC, Robinson CM, Shi M, Webb DJ. The guanine nucleotide exchange factor (GEF) Asef2 promotes dendritic spine formation via Rac activation and spinophilin-dependent targeting. J Biol Chem 2015; 290:10295-308. [PMID: 25750125 DOI: 10.1074/jbc.m114.605543] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2014] [Indexed: 11/06/2022] Open
Abstract
Dendritic spines are actin-rich protrusions that establish excitatory synaptic contacts with surrounding neurons. Reorganization of the actin cytoskeleton is critical for the development and plasticity of dendritic spines, which is the basis for learning and memory. Rho family GTPases are emerging as important modulators of spines and synapses, predominantly through their ability to regulate actin dynamics. Much less is known, however, about the function of guanine nucleotide exchange factors (GEFs), which activate these GTPases, in spine and synapse development. In this study we show that the Rho family GEF Asef2 is found at synaptic sites, where it promotes dendritic spine and synapse formation. Knockdown of endogenous Asef2 with shRNAs impairs spine and synapse formation, whereas exogenous expression of Asef2 causes an increase in spine and synapse density. This effect of Asef2 on spines and synapses is abrogated by expression of GEF activity-deficient Asef2 mutants or by knockdown of Rac, suggesting that Asef2-Rac signaling mediates spine development. Because Asef2 interacts with the F-actin-binding protein spinophilin, which localizes to spines, we investigated the role of spinophilin in Asef2-promoted spine formation. Spinophilin recruits Asef2 to spines, and knockdown of spinophilin hinders spine and synapse formation in Asef2-expressing neurons. Furthermore, inhibition of N-methyl-d-aspartate receptor (NMDA) activity blocks spinophilin-mediated localization of Asef2 to spines. These results collectively point to spinophilin-Asef2-Rac signaling as a novel mechanism for the development of dendritic spines and synapses.
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Affiliation(s)
- J Corey Evans
- From the Department of Biological Sciences and the Kennedy Center for Research on Human Development and
| | - Cristina M Robinson
- From the Department of Biological Sciences and the Kennedy Center for Research on Human Development and
| | - Mingjian Shi
- From the Department of Biological Sciences and the Kennedy Center for Research on Human Development and
| | - Donna J Webb
- From the Department of Biological Sciences and the Kennedy Center for Research on Human Development and the Department of Cancer Biology, Vanderbilt University, Nashville, Tennessee 37235
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6
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Omelchenko T, Rabadan MA, Hernández-Martínez R, Grego-Bessa J, Anderson KV, Hall A. β-Pix directs collective migration of anterior visceral endoderm cells in the early mouse embryo. Genes Dev 2015; 28:2764-77. [PMID: 25512563 PMCID: PMC4265679 DOI: 10.1101/gad.251371.114] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Rac1 is essential for generating the protrusive activity that drives the collective migration of anterior visceral endoderm (AVE) cells in the early mouse embryo. Omelchenko et al. identified β-Pix as a potential regulator of Rac1. Genetic deletion of β-Pix in mice disrupts collective AVE migration. Collective epithelial migration is important throughout embryonic development. The underlying mechanisms are poorly understood but likely involve spatially localized activation of Rho GTPases. We previously reported that Rac1 is essential for generating the protrusive activity that drives the collective migration of anterior visceral endoderm (AVE) cells in the early mouse embryo. To identify potential regulators of Rac1, we first performed an RNAi screen of Rho family exchange factors (guanine nucleotide exchange factor [GEF]) in an in vitro collective epithelial migration assay and identified β-Pix. Genetic deletion of β-Pix in mice disrupts collective AVE migration, while high-resolution live imaging revealed that this is associated with randomly directed protrusive activity. We conclude that β-Pix controls the spatial localization of Rac1 activity to drive collective AVE migration at a critical stage in mouse development.
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Affiliation(s)
| | | | - Rocío Hernández-Martínez
- Developmental Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Joaquim Grego-Bessa
- Developmental Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Kathryn V Anderson
- Developmental Biology Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
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7
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Jaiswal M, Dvorsky R, Ahmadian MR. Deciphering the molecular and functional basis of Dbl family proteins: a novel systematic approach toward classification of selective activation of the Rho family proteins. J Biol Chem 2012; 288:4486-500. [PMID: 23255595 DOI: 10.1074/jbc.m112.429746] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The diffuse B-cell lymphoma (Dbl) family of the guanine nucleotide exchange factors is a direct activator of the Rho family proteins. The Rho family proteins are involved in almost every cellular process that ranges from fundamental (e.g. the establishment of cell polarity) to highly specialized processes (e.g. the contraction of vascular smooth muscle cells). Abnormal activation of the Rho proteins is known to play a crucial role in cancer, infectious and cognitive disorders, and cardiovascular diseases. However, the existence of 74 Dbl proteins and 25 Rho-related proteins in humans, which are largely uncharacterized, has led to increasing complexity in identifying specific upstream pathways. Thus, we comprehensively investigated sequence-structure-function-property relationships of 21 representatives of the Dbl protein family regarding their specificities and activities toward 12 Rho family proteins. The meta-analysis approach provides an unprecedented opportunity to broadly profile functional properties of Dbl family proteins, including catalytic efficiency, substrate selectivity, and signaling specificity. Our analysis has provided novel insights into the following: (i) understanding of the relative differences of various Rho protein members in nucleotide exchange; (ii) comparing and defining individual and overall guanine nucleotide exchange factor activities of a large representative set of the Dbl proteins toward 12 Rho proteins; (iii) grouping the Dbl family into functionally distinct categories based on both their catalytic efficiencies and their sequence-structural relationships; (iv) identifying conserved amino acids as fingerprints of the Dbl and Rho protein interaction; and (v) defining amino acid sequences conserved within, but not between, Dbl subfamilies. Therefore, the characteristics of such specificity-determining residues identified the regions or clusters conserved within the Dbl subfamilies.
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Affiliation(s)
- Mamta Jaiswal
- Institut für Biochemie and Molekularbiologie II, Medizinische Fakultät der Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
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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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9
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Reddy-Alla S, Schmitt B, Birkenfeld J, Eulenburg V, Dutertre S, Böhringer C, Götz M, Betz H, Papadopoulos T. PH-domain-driven targeting of collybistin but not Cdc42 activation is required for synaptic gephyrin clustering. Eur J Neurosci 2010; 31:1173-84. [PMID: 20345913 DOI: 10.1111/j.1460-9568.2010.07149.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Collybistin (Cb) is a brain-specific guanine nucleotide exchange factor (GEF) that is essential for the synaptic clustering of gephyrin and GABAA receptors in selected regions of the mammalian central nervous system. It has been previously proposed that Cb regulates gephyrin clustering by activating Cdc42, and thus acts as a signal transducer in a membrane activation process which labels postsynaptic membrane domains for inhibitory synapse formation. Here, we dissected the functional roles of the Dbl-homology (DH) and pleckstrin homology (PH) domains of the constitutively active splice variant Cb II by substituting conserved amino acid residues that are required for GEF activity towards Cdc42 and phosphoinositide binding, respectively. A Cb II mutant lacking any detectable GEF activity towards Cdc42 was still fully active in inducing gephyrin scaffold formation, both in transfected NIH-3T3 cells and in cultured hippocampal neurons. Furthermore, mice with a forebrain-specific inactivation of the Cdc42 gene displayed normal densities of gephyrin and GABA(A) receptor clusters in the hippocampus. In contrast, substitution of Cb II PH-domain residues essential for phosphoinositide binding abolished gephyrin recruitment to synaptic sites. Our results provide evidence that the formation of gephyrin scaffolds at inhibitory synapses requires an intact Cb II PH-domain but is Cdc42-independent.
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Affiliation(s)
- Suneel Reddy-Alla
- Department of Neurochemistry, Max-Planck Institute for Brain Research, 60528 Frankfurt/Main, Germany
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10
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Matsushita T, Ashikawa K, Yonemoto K, Hirakawa Y, Hata J, Amitani H, Doi Y, Ninomiya T, Kitazono T, Ibayashi S, Iida M, Nakamura Y, Kiyohara Y, Kubo M. Functional SNP of ARHGEF10 confers risk of atherothrombotic stroke. Hum Mol Genet 2009; 19:1137-46. [DOI: 10.1093/hmg/ddp582] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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11
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Gauthier-Fisher A, Lin DC, Greeve M, Kaplan DR, Rottapel R, Miller FD. Lfc and Tctex-1 regulate the genesis of neurons from cortical precursor cells. Nat Neurosci 2009; 12:735-44. [DOI: 10.1038/nn.2339] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Accepted: 03/31/2009] [Indexed: 12/20/2022]
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12
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Fujiyama T, Yamada M, Terao M, Terashima T, Hioki H, Inoue YU, Inoue T, Masuyama N, Obata K, Yanagawa Y, Kawaguchi Y, Nabeshima YI, Hoshino M. Inhibitory and excitatory subtypes of cochlear nucleus neurons are defined by distinct bHLH transcription factors, Ptf1a and Atoh1. Development 2009; 136:2049-58. [PMID: 19439493 DOI: 10.1242/dev.033480] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The cochlear nucleus (CN), which consists of dorsal and ventral cochlear nuclei (DCN and VCN), plays pivotal roles in processing and relaying auditory information to the brain. Although it contains various types of neurons, the origins of the distinct subtypes and their developmental molecular machinery are still elusive. Here we reveal that two basic helix-loop-helix transcription factors play crucial roles in specifying neuron subtypes in the CN. Pancreatic transcription factor 1a (Ptf1a) and atonal homolog 1 (Atoh1) were found to be expressed in discrete dorsolateral regions of the embryonic neuroepithelia of the middle hindbrain (rhombomeres 2-5). Genetic lineage tracing using mice that express Cre recombinase from the Ptf1a locus or under the control of the Atoh1 promoter revealed that inhibitory (GABAergic and glycinergic) or excitatory (glutamatergic) neurons of both DCN and VCN are derived from the Ptf1a- and Atoh1-expressing neuroepithelial regions, respectively. In the Ptf1a or Atoh1 null embryos, production of inhibitory or excitatory neurons, respectively, was severely inhibited in the CN. These findings suggest that inhibitory and excitatory subtypes of CN neurons are defined by Ptf1a and Atoh1, respectively and, furthermore, provide important insights into understanding the machinery of neuron subtype specification in the dorsal hindbrain.
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Affiliation(s)
- Tomoyuki Fujiyama
- Department of Biochemistry and Cellular Biology, National Institute of Neuroscience, NCNP, Kodaira, Tokyo 187-8502, Japan
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13
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Abstract
Climbing fiber (CF) neurons in the inferior olivary nucleus (ION) extend their axons to Purkinje cells, playing a crucial role in regulating cerebellar function. However, little is known about their precise place of birth and developmental molecular machinery. Here, we describe the origin of the CF neuron lineage and the involvement of Ptf1a (pancreatic transcription factor 1a) in CF neuron development. Ptf1a protein was found to be expressed in a discrete dorsolateral region of the embryonic caudal hindbrain neuroepithelium. Because expression of Ptf1a is not overlapping other transcription factors such as Math1 (mouse atonal homolog 1) and Neurogenin1, which are suggested to define domains within caudal hindbrain neuroepithelium (Landsberg et al., 2005), we named the neuroepithelial region the Ptf1a domain. Analysis of mice that express beta-galactosidase from the Ptf1a locus revealed that CF neurons are derived from the Ptf1a domain. In contrast, retrograde labeling of precerebellar neurons indicated that mossy fiber neurons are not derived from Ptf1a-expressing progenitors. We could observe a detailed migratory path of CF neurons from the Ptf1a domain to the ION during embryogenesis. In Ptf1a null mutants, putative immature CF neurons produced from this domain were unable to migrate or differentiate appropriately, resulting in a failure of ION formation. Apoptotic cells were observed in the mutant hindbrain. Furthermore, the fate of some cells in the Ptf1a lineage were changed to mossy fiber neurons in Ptf1a null mutants. These findings clarify the precise origin of CF neurons and suggest that Ptf1a controls their fate, survival, differentiation, and migration during development.
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14
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Tolias KF, Bikoff JB, Kane CG, Tolias CS, Hu L, Greenberg ME. The Rac1 guanine nucleotide exchange factor Tiam1 mediates EphB receptor-dependent dendritic spine development. Proc Natl Acad Sci U S A 2007; 104:7265-70. [PMID: 17440041 PMCID: PMC1855368 DOI: 10.1073/pnas.0702044104] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Dendritic spines are small, actin-rich protrusions on the surface of dendrites that receive the majority of excitatory synaptic inputs in the brain. The formation and remodeling of spines, processes that underlie synaptic development and plasticity, are regulated in part by Eph receptor tyrosine kinases. However, the mechanism by which Ephs regulate actin cytoskeletal remodeling necessary for spine development is not fully understood. Here, we report that the Rac1 guanine nucleotide exchange factor Tiam1 interacts with the EphB2 receptor in a kinase-dependent manner. Activation of EphBs by their ephrinB ligands induces the tyrosine phosphorylation and recruitment of Tiam1 to EphB complexes containing NMDA-type glutamate receptors. Either knockdown of Tiam1 protein by RNAi or inhibition of Tiam1 function with a dominant-negative Tiam1 mutant blocks dendritic spine formation induced by ephrinB1 stimulation. Taken together, these findings suggest that EphBs regulate spine development in part by recruiting, phosphorylating, and activating Tiam1. Tiam1 can then promote Rac1-dependent actin cytoskeletal remodeling required for dendritic spine morphogenesis.
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Affiliation(s)
- Kimberley F. Tolias
- *Neurobiology Program, Children's Hospital, and
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115
| | - Jay B. Bikoff
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115
| | | | | | - Linda Hu
- *Neurobiology Program, Children's Hospital, and
| | - Michael E. Greenberg
- *Neurobiology Program, Children's Hospital, and
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115
- To whom correspondence should be addressed. E-mail:
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15
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Mohl M, Winkler S, Wieland T, Lutz S. Gef10--the third member of a Rho-specific guanine nucleotide exchange factor subfamily with unusual protein architecture. Naunyn Schmiedebergs Arch Pharmacol 2006; 373:333-41. [PMID: 16896804 DOI: 10.1007/s00210-006-0083-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2006] [Accepted: 06/13/2006] [Indexed: 10/24/2022]
Abstract
According to cDNA sequence homologies, Gef10 is related to the Rho-specific guanine nucleotide exchange factors GrinchGEF and p164-RhoGEF. Like these GEFs, Gef10 exhibits only weak homology to known pleckstrin homology domains, but contains a putative WD40-like domain. As detected by RT-PCR, Gef10 is transcribed in at least two splice variants in different human tissues. Although the Gef10 sequence contains two putative transmembrane segments, recombinantly expressed Gef10 displays a cytosolic localisation. As detected by guanine nucleotide exchange activity assay, precipitation assay of GTP-bound Rho proteins and serum response element dependent gene transcription Gef10 activates RhoA-C, but not Rac1 or Cdc42. In the reporter gene assay, Gef10 preferentially activated RhoB. When expressed in NIH3T3 cells, Gef10 induced actin stress fibre, but not lamellipodia or filopodia formation. We conclude that Gef10 is the third member of a Rho-specific GEF family with unusual protein architecture.
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Affiliation(s)
- M Mohl
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität Heidelberg, Maybachstr 14, D-68169 Mannheim, Germany
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16
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Yoshizawa M, Kawauchi T, Sone M, Nishimura YV, Terao M, Chihama K, Nabeshima YI, Hoshino M. Involvement of a Rac activator,P-Rex1, in neurotrophin-derived signaling and neuronal migration. J Neurosci 2006; 25:4406-19. [PMID: 15858067 PMCID: PMC6725123 DOI: 10.1523/jneurosci.4955-04.2005] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Rho-family GTPases play key roles in regulating cytoskeletal reorganization, contributing to many aspects of nervous system development. Their activities are known to be regulated by guanine nucleotide exchange factors (GEFs), in response to various extracellular cues. P-Rex1, a GEF for Rac, has been mainly investigated in neutrophils, in which this molecule contributes to reactive oxygen species formation. However, its role in the nervous system is essentially unknown. Here we describe the expression profile and a physiological function of P-Rex1 in nervous system development. In situ hybridization revealed that P-Rex1 is dynamically expressed in a variety of cells in the developing mouse brain, including some cortical and DRG neurons. In migrating neurons in the intermediate zone, P-Rex1 protein was found to localize in the leading process and adjacent cytoplasmic region. When transfected in pheochromocytoma PC12 cells, P-Rex1 can be activated by NGF, causing an increase in GTP-bound Rac1 and cell motility. Deletion analyses suggested roles for distinct domains of this molecule. Experiments using a P-Rex1 mutant lacking the Dbl-homology domain, a dominant-negative-like form, and small interfering RNA showed that endogenous P-Rex1 was involved in cell migration of PC12 cells and primary cultured neurons from the embryonic day 14 cerebral cortices, induced by extracellular stimuli (NGF, BDNF, and epidermal growth factor). Furthermore, in utero electroporation of the mutant protein into the embryonic cerebral cortex perturbed radial neuronal migration. These findings suggest that P-Rex1, which is expressed in a variety of cell types, is activated by extracellular cues such as neurotrophins and contributes to neuronal migration in the developing nervous system.
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Affiliation(s)
- Masato Yoshizawa
- Department of Pathology and Tumor Biology, Kyoto University Graduate School of Medicine, Kyoto 606-8501, Japan
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17
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Tse SW, Broderick JA, Wei ML, Luo MH, Smith D, McCaffery P, Stamm S, Andreadis A. Identification, expression analysis, genomic organization and cellular location of a novel protein with a RhoGEF domain. Gene 2005; 359:63-72. [PMID: 16143467 DOI: 10.1016/j.gene.2005.06.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2005] [Revised: 05/17/2005] [Accepted: 06/03/2005] [Indexed: 11/30/2022]
Abstract
In this study we describe the identification and characterization of a novel cytosolic protein of the guanine exchange factor (GEF) family. The human cDNA corresponds to predicted human protein FLJ00128/FLJ10357 located on chromosome 14q11.2. The deduced protein sequence contains in its C-terminus a RhoGEF domain followed by a pleckstrin domain. Its N-terminus, central region and RhoGEF/pleckstrin domain are homologous to the recently identified zebrafish Quattro protein, which is involved in morphogenetic movements mediated by the actin cytoskeleton. Based on the homology of our protein's RhoGEF domain to the RhoGEF domains of Trio, Duo and Duet and its homology with Quattro, we named it Solo. The Solo mRNA is ubiquitously expressed but enriched in brain, its expression peaks perinatally and it undergoes extensive alternative splicing. In both myoblasts and neuroblastoma cells, the Solo protein is concentrated around the nucleus.
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MESH Headings
- Amino Acid Sequence
- Animals
- Blood Proteins/genetics
- Blood Proteins/metabolism
- Blotting, Northern
- Blotting, Western
- Brain/embryology
- Brain/growth & development
- Brain/metabolism
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cell Line
- Cell Line, Tumor
- Cloning, Molecular
- Cytoplasm/metabolism
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Exons
- Gene Expression Profiling
- Guanine Nucleotide Exchange Factors/genetics
- Guanine Nucleotide Exchange Factors/metabolism
- Humans
- Immunohistochemistry
- Immunoprecipitation
- Introns
- Male
- Mice
- Molecular Sequence Data
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- Protein Binding
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Reverse Transcriptase Polymerase Chain Reaction
- Rho Guanine Nucleotide Exchange Factors
- Saccharomyces cerevisiae/genetics
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Two-Hybrid System Techniques
- tau Proteins/genetics
- tau Proteins/metabolism
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Affiliation(s)
- Sze-Wah Tse
- Department of Biomedical Sciences, E.K. Shriver Center for Mental Retardation, Waltham, MA 02452, USA
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18
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Hoshino M, Nakamura S, Mori K, Kawauchi T, Terao M, Nishimura YV, Fukuda A, Fuse T, Matsuo N, Sone M, Watanabe M, Bito H, Terashima T, Wright CVE, Kawaguchi Y, Nakao K, Nabeshima YI. Ptf1a, a bHLH transcriptional gene, defines GABAergic neuronal fates in cerebellum. Neuron 2005; 47:201-13. [PMID: 16039563 DOI: 10.1016/j.neuron.2005.06.007] [Citation(s) in RCA: 363] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Revised: 03/30/2005] [Accepted: 06/02/2005] [Indexed: 11/21/2022]
Abstract
The molecular machinery governing glutamatergic-GABAergic neuronal subtype specification is unclear. Here we describe a cerebellar mutant, cerebelless, which lacks the entire cerebellar cortex in adults. The primary defect of the mutant brains was a specific inhibition of GABAergic neuron production from the cerebellar ventricular zone (VZ), resulting in secondary and complete loss of external germinal layer, pontine, and olivary nuclei during development. We identified the responsible gene, Ptf1a, whose expression was lost in the cerebellar VZ but was maintained in the pancreas in cerebelless. Lineage tracing revealed that two types of neural precursors exist in the cerebellar VZ: Ptf1a-expressing and -nonexpressing precursors, which generate GABAergic and glutamatergic neurons, respectively. Introduction of Ptf1a into glutamatergic neuron precursors in the dorsal telencephalon generated GABAergic neurons with representative morphological and migratory features. Our results suggest that Ptf1a is involved in driving neural precursors to differentiate into GABAergic neurons in the cerebellum.
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Affiliation(s)
- Mikio Hoshino
- Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
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19
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Winkler S, Mohl M, Wieland T, Lutz S. GrinchGEF—A novel Rho-specific guanine nucleotide exchange factor. Biochem Biophys Res Commun 2005; 335:1280-6. [PMID: 16112081 DOI: 10.1016/j.bbrc.2005.08.025] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Accepted: 08/03/2005] [Indexed: 10/25/2022]
Abstract
RhoGTPases, which are activated by specific guanine nucleotide exchange factors (GEFs), play pivotal roles in several cellular functions. We identified a new RhoGEF (GrinchGEF) containing the typical Dbl homology domain, a putative WD40-like domain, and two predicted transmembrane helices. In contrast to most other RhoGEFs, it exhibits no sequence similarities to known pleckstrin homology domains. GrinchGEF mRNA was highly abundant in skeletal muscle and pancreas. Despite the predicted transmembrane domains, subcellular localization studies revealed a cytosolic distribution. In vitro, GrinchGEF induced the GDP/GTP exchange at RhoA, but not at Rac1 or Cdc42. In intact cells, GrinchGEF induced specifically Rho activation and enhanced RhoA-C-specific downstream effects.
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Affiliation(s)
- Stefan Winkler
- Institut für Pharmakologie und Toxikologie, Fakultät für Klinische Medizin Mannheim, Universität Heidelberg, D-68169 Mannheim, Germany
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20
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Ethell IM, Pasquale EB. Molecular mechanisms of dendritic spine development and remodeling. Prog Neurobiol 2005; 75:161-205. [PMID: 15882774 DOI: 10.1016/j.pneurobio.2005.02.003] [Citation(s) in RCA: 264] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2004] [Revised: 01/28/2005] [Accepted: 02/22/2005] [Indexed: 12/19/2022]
Abstract
Dendritic spines are small protrusions that cover the surface of dendrites and bear the postsynaptic component of excitatory synapses. Having an enlarged head connected to the dendrite by a narrow neck, dendritic spines provide a postsynaptic biochemical compartment that separates the synaptic space from the dendritic shaft and allows each spine to function as a partially independent unit. Spines develop around the time of synaptogenesis and are dynamic structures that continue to undergo remodeling over time. Changes in spine morphology and density influence the properties of neural circuits. Our knowledge of the structure and function of dendritic spines has progressed significantly since their discovery over a century ago, but many uncertainties still remain. For example, several different models have been put forth outlining the sequence of events that lead to the genesis of a spine. Although spines are small and apparently simple organelles with a cytoskeleton mainly composed of actin filaments, regulation of their morphology and physiology appears to be quite sophisticated. A multitude of molecules have been implicated in dendritic spine development and remodeling, suggesting that intricate networks of interconnected signaling pathways converge to regulate actin dynamics in spines. This complexity is not surprising, given the likely importance of dendritic spines in higher brain functions. In this review, we discuss the molecules that are currently known to mediate the exquisite sensitivity of spines to perturbations in their environment and we outline how these molecules interface with each other to mediate cascades of signals flowing from the spine surface to the actin cytoskeleton.
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Affiliation(s)
- Iryna M Ethell
- Division of Biomedical Sciences, University of California Riverside, Riverside, CA 92521, USA
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Kawauchi T, Chihama K, Nabeshima YI, Hoshino M. The in vivo roles of STEF/Tiam1, Rac1 and JNK in cortical neuronal migration. EMBO J 2003; 22:4190-201. [PMID: 12912917 PMCID: PMC175802 DOI: 10.1093/emboj/cdg413] [Citation(s) in RCA: 245] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The coordinated migration of neurons is a pivotal step for functional architectural formation of the mammalian brain. To elucidate its molecular mechanism, gene transfer by means of in utero electroporation was applied in the developing murine brain, revealing the crucial roles of Rac1, its activators, STEF/Tiam1, and its downstream molecule, c-Jun N-terminal kinase (JNK), in the cerebral cortex. Functional repression of these molecules resulted in inhibition of radial migration of neurons without affecting their proper differentiation. Interestingly, distinct morphological phenotypes were observed; suppression of Rac1 activity caused loss of the leading process, whereas repression of JNK activity did not, suggesting the complexity of the signaling cascade. In cultured neurons from the intermediate zone, activated JNK was detected along microtubules in the processes. Application of a JNK inhibitor caused irregular morphology and increased stable microtubules in processes, and decreased phosphorylation of microtubule associated protein 1B, raising a possibility of the involvement of JNK in controlling tubulin dynamics in migrating neurons. Our data thus provide important clues for understanding the intracellullar signaling machinery for cortical neuronal migration.
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Affiliation(s)
- Takeshi Kawauchi
- Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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