1
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Rho GTPase-activating protein 17 (ARHGAP17) as additional autoimmune target in ARHGAP26-IgG/anti-Ca autoantibody-associated autoimmune encephalitis. J Neurol 2023; 270:1776-1780. [PMID: 36333454 PMCID: PMC9971044 DOI: 10.1007/s00415-022-11417-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 09/30/2022] [Accepted: 10/01/2022] [Indexed: 11/06/2022]
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2
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Ouyang L, Chen Y, Wang Y, Chen Y, Fu AKY, Fu WY, Ip NY. p39-associated Cdk5 activity regulates dendritic morphogenesis. Sci Rep 2020; 10:18746. [PMID: 33127972 PMCID: PMC7603351 DOI: 10.1038/s41598-020-75264-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Accepted: 09/22/2020] [Indexed: 12/13/2022] Open
Abstract
Dendrites, branched structures extending from neuronal cell soma, are specialized for processing information from other neurons. The morphogenesis of dendritic structures is spatiotemporally regulated by well-orchestrated signaling cascades. Dysregulation of these processes impacts the wiring of neuronal circuit and efficacy of neurotransmission, which contribute to the pathogeneses of neurological disorders. While Cdk5 (cyclin-dependent kinase 5) plays a critical role in neuronal dendritic development, its underlying molecular control is not fully understood. In this study, we show that p39, one of the two neuronal Cdk5 activators, is a key regulator of dendritic morphogenesis. Pyramidal neurons deficient in p39 exhibit aberrant dendritic morphology characterized by shorter length and reduced arborization, which is comparable to dendrites in Cdk5-deficient neurons. RNA sequencing analysis shows that the adaptor protein, WDFY1 (WD repeat and FYVE domain-containing 1), acts downstream of Cdk5/p39 to regulate dendritic morphogenesis. While WDFY1 is elevated in p39-deficient neurons, suppressing its expression rescues the impaired dendritic arborization. Further phosphoproteomic analysis suggests that Cdk5/p39 mediates dendritic morphogenesis by modulating various downstream signaling pathways, including PI3K/Akt-, cAMP-, or small GTPase-mediated signaling transduction pathways, thereby regulating cytoskeletal organization, protein synthesis, and protein trafficking.
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Affiliation(s)
- Li Ouyang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Molecular Neuroscience Center, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.,Hong Kong Center for Neurodegenerative Diseases, Hong Kong Science Park, Hong Kong, China
| | - Yu Chen
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Molecular Neuroscience Center, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.,Hong Kong Center for Neurodegenerative Diseases, Hong Kong Science Park, Hong Kong, China.,The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, 518055, Guangdong, China.,Guangdong Provincial Key Laboratory of Brain Science, Disease and Drug Development, HKUST Shenzhen Research Institute, Shenzhen-Hong Kong Institute of Brain Science, Shenzhen, 518057, Guangdong, China
| | - Ye Wang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Molecular Neuroscience Center, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.,Hong Kong Center for Neurodegenerative Diseases, Hong Kong Science Park, Hong Kong, China
| | - Yuewen Chen
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Molecular Neuroscience Center, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.,Hong Kong Center for Neurodegenerative Diseases, Hong Kong Science Park, Hong Kong, China.,The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, 518055, Guangdong, China.,Guangdong Provincial Key Laboratory of Brain Science, Disease and Drug Development, HKUST Shenzhen Research Institute, Shenzhen-Hong Kong Institute of Brain Science, Shenzhen, 518057, Guangdong, China
| | - Amy K Y Fu
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Molecular Neuroscience Center, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.,Hong Kong Center for Neurodegenerative Diseases, Hong Kong Science Park, Hong Kong, China.,Guangdong Provincial Key Laboratory of Brain Science, Disease and Drug Development, HKUST Shenzhen Research Institute, Shenzhen-Hong Kong Institute of Brain Science, Shenzhen, 518057, Guangdong, China
| | - Wing-Yu Fu
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Molecular Neuroscience Center, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.,Hong Kong Center for Neurodegenerative Diseases, Hong Kong Science Park, Hong Kong, China
| | - Nancy Y Ip
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Molecular Neuroscience Center, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China. .,Hong Kong Center for Neurodegenerative Diseases, Hong Kong Science Park, Hong Kong, China. .,Guangdong Provincial Key Laboratory of Brain Science, Disease and Drug Development, HKUST Shenzhen Research Institute, Shenzhen-Hong Kong Institute of Brain Science, Shenzhen, 518057, Guangdong, China.
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3
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Lv L, Liu Y, Xie J, Wu Y, Zhao J, Li Q, Zhong Y. Interplay between α2-chimaerin and Rac1 activity determines dynamic maintenance of long-term memory. Nat Commun 2019; 10:5313. [PMID: 31757963 PMCID: PMC6876637 DOI: 10.1038/s41467-019-13236-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2019] [Accepted: 10/22/2019] [Indexed: 12/05/2022] Open
Abstract
Memory consolidation theory suggests that once memory formation has been completed, memory is maintained at a stable strength and is incapable of further enhancement. However, the current study reveals that even long after formation, contextual fear memory could be further enhanced. Such unexpected enhancement is possible because memory is dynamically maintained at an intermediate level that allows for bidirectional regulation. Here we find that both Rac1 activation and expression of α2-chimaerin are stimulated by single-trial contextual fear conditioning. Such sustained Rac1 activity mediates reversible forgetting, and α2-chimaerin acts as a memory molecule that reverses forgetting to sustain memory through inhibition of Rac1 activity during the maintenance stage. Therefore, the balance between activated Rac1 and expressed α2-chimaerin defines dynamic long-term memory maintenance. Our findings demonstrate that consolidated memory maintains capacity for bidirectional regulation.
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Affiliation(s)
- Li Lv
- Peking University-Tsinghua University-National Institute Biological Science Joint Graduate Program, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Yunlong Liu
- Peking University-Tsinghua University-National Institute Biological Science Joint Graduate Program, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Jianxin Xie
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100101, China
| | - Yan Wu
- Peking University-Tsinghua University-National Institute Biological Science Joint Graduate Program, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Jianjian Zhao
- Peking University-Tsinghua University-National Institute Biological Science Joint Graduate Program, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Qian Li
- Peking University-Tsinghua University-National Institute Biological Science Joint Graduate Program, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Yi Zhong
- Peking University-Tsinghua University-National Institute Biological Science Joint Graduate Program, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
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4
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Hollern DP, Swiatnicki MR, Rennhack JP, Misek SA, Matson BC, McAuliff A, Gallo KA, Caron KM, Andrechek ER. E2F1 Drives Breast Cancer Metastasis by Regulating the Target Gene FGF13 and Altering Cell Migration. Sci Rep 2019; 9:10718. [PMID: 31341204 PMCID: PMC6656723 DOI: 10.1038/s41598-019-47218-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 07/12/2019] [Indexed: 12/27/2022] Open
Abstract
In prior work we demonstrated that loss of E2F transcription factors inhibits metastasis. Here we address the mechanisms for this phenotype and identify the E2F regulated genes that coordinate tumor cell metastasis. Transcriptomic profiling of E2F1 knockout tumors identified a role for E2F1 as a master regulator of a suite of pro-metastatic genes, but also uncovered E2F1 target genes with an unknown role in pulmonary metastasis. High expression of one of these genes, Fgf13, is associated with early human breast cancer metastasis in a clinical dataset. Together these data led to the hypothesis that Fgf13 is critical for breast cancer metastasis, and that upregulation of Fgf13 may partially explain how E2F1 promotes breast cancer metastasis. To test this hypothesis we ablated Fgf13 via CRISPR. Deletion of Fgf13 in a MMTV-PyMT breast cancer cell line reduces colonization of the lungs in a tail vein injection. In addition, loss of Fgf13 reduced in vitro cell migration, suggesting that Fgf13 may be critical for tumor cells to escape the primary tumor and to colonize the distal sites. The significance of this work is twofold: we have both uncovered genomic features by which E2F1 regulates metastasis and we have identified new pro-metastatic functions for the E2F1 target gene Fgf13.
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Affiliation(s)
- Daniel P Hollern
- Lineberger Comprehensive Cancer Center University of North Carolina, Chapel Hill, United States
| | - Matthew R Swiatnicki
- Department of Physiology, Michigan State University, East Lansing, United States
| | - Jonathan P Rennhack
- Department of Physiology, Michigan State University, East Lansing, United States
| | - Sean A Misek
- Department of Physiology, Michigan State University, East Lansing, United States
| | - Brooke C Matson
- University of North Carolina Department of Cell Biology, Chapel Hill, United States
| | - Andrew McAuliff
- Department of Physiology, Michigan State University, East Lansing, United States
| | - Kathleen A Gallo
- Department of Physiology, Michigan State University, East Lansing, United States
| | - Kathleen M Caron
- Lineberger Comprehensive Cancer Center University of North Carolina, Chapel Hill, United States
| | - Eran R Andrechek
- Department of Physiology, Michigan State University, East Lansing, United States.
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5
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The RacGAP β-Chimaerin is essential for cerebellar granule cell migration. Sci Rep 2018; 8:680. [PMID: 29330522 PMCID: PMC5766509 DOI: 10.1038/s41598-017-19116-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 12/21/2017] [Indexed: 11/08/2022] Open
Abstract
During mammalian cerebellar development, postnatal granule cell progenitors proliferate in the outer part of the External Granule Layer (EGL). Postmitotic granule progenitors migrate tangentially in the inner EGL before switching to migrate radially inward, past the Purkinje cell layer, to achieve their final position in the mature Granule Cell Layer (GCL). Here, we show that the RacGAP β-chimaerin is expressed by a small population of late-born, premigratory granule cells. β-chimaerin deficiency causes a subset of granule cells to become arrested in the EGL, where they differentiate and form ectopic neuronal clusters. These clusters of granule cells are able to recruit aberrantly projecting mossy fibers. Collectively, these data suggest a role for β-chimaerin as an intracellular mediator of Cerebellar Granule Cell radial migration.
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6
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Ba W, Nadif Kasri N. RhoGTPases at the synapse: An embarrassment of choice. Small GTPases 2017; 8:106-113. [PMID: 27492682 PMCID: PMC5464131 DOI: 10.1080/21541248.2016.1206352] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 06/22/2016] [Accepted: 06/22/2016] [Indexed: 12/14/2022] Open
Abstract
Activity-dependent modifications in the strength of excitatory synapses are considered to be major cellular mechanisms that contribute to the plasticity of neuronal networks underlying learning and memory. Key mechanisms for the regulation of synaptic efficacy involve the dynamic changes in size and number of dendritic spines, as well as the synaptic incorporation and removal of AMPA-type glutamate receptors (AMPAr). As key regulators of the actin cytoskeleton, the Rho subfamily of GTP-binding proteins play a critical role in synaptic development and plasticity. They shuttle between the active GTP-bound form and the inactive GDP-bound form under the regulation of dedicated guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). More than 80 human GEFs and 70 GAPs have been identified, most of which are expressed in the brain with a specific spatial and temporal expression pattern. However, the function of most GEFs and GAPs in the brain has not been elucidated. In this review, we highlight the novel neuronal function of the synaptic RhoGAP ARHGAP12 and the ID-associated RhoGEF TRIO and further propose 3 possible approaches of neurons utilizing Rho GTPase regulatory proteins to accurately modulate synaptic function.
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Affiliation(s)
- W. Ba
- Department of Cognitive Neuroscience, Radboudumc, Nijmegen, the Netherlands
- Department of Human Genetics, Radboudumc, Nijmegen, the Netherlands
- Donders Institute for Brain, Cognition, and Behavior, Nijmegen, the Netherlands
| | - N. Nadif Kasri
- Department of Cognitive Neuroscience, Radboudumc, Nijmegen, the Netherlands
- Department of Human Genetics, Radboudumc, Nijmegen, the Netherlands
- Donders Institute for Brain, Cognition, and Behavior, Nijmegen, the Netherlands
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7
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Huang GH, Sun ZL, Li HJ, Feng DF. Rho GTPase-activating proteins: Regulators of Rho GTPase activity in neuronal development and CNS diseases. Mol Cell Neurosci 2017; 80:18-31. [PMID: 28163190 DOI: 10.1016/j.mcn.2017.01.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 01/06/2017] [Accepted: 01/29/2017] [Indexed: 12/22/2022] Open
Abstract
The Rho family of small GTPases was considered as molecular switches in regulating multiple cellular events, including cytoskeleton reorganization. The Rho GTPase-activating proteins (RhoGAPs) are one of the major families of Rho GTPase regulators. RhoGAPs were initially considered negative mediators of Rho signaling pathways via their GAP domain. Recent studies have demonstrated that RhoGAPs also regulate numerous aspects of neuronal development and are related to various neurodegenerative diseases in GAP-dependent and GAP-independent manners. Moreover, RhoGAPs are regulated through various mechanisms, such as phosphorylation. To date, approximately 70 RhoGAPs have been identified; however, only a small portion has been thoroughly investigated. Thus, the characterization of important RhoGAPs in the central nervous system is crucial to understand their spatiotemporal role during different stages of neuronal development. In this review, we summarize the current knowledge of RhoGAPs in the brain with an emphasis on their molecular function, regulation mechanism and disease implications in the central nervous system.
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Affiliation(s)
- Guo-Hui Huang
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China
| | - Zhao-Liang Sun
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China
| | - Hong-Jiang Li
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China
| | - Dong-Fu Feng
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China; Institute of Traumatic Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China.
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8
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Valdez CM, Murphy GG, Beg AA. The Rac-GAP alpha2-chimaerin regulates hippocampal dendrite and spine morphogenesis. Mol Cell Neurosci 2016; 75:14-26. [PMID: 27297944 DOI: 10.1016/j.mcn.2016.06.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 05/09/2016] [Accepted: 06/07/2016] [Indexed: 12/01/2022] Open
Abstract
Dendritic spines are fine neuronal processes where spatially restricted input can induce activity-dependent changes in one spine, while leaving neighboring spines unmodified. Morphological spine plasticity is critical for synaptic transmission and is thought to underlie processes like learning and memory. Significantly, defects in dendritic spine stability and morphology are common pathogenic features found in several neurodevelopmental and neuropsychiatric disorders. The remodeling of spines relies on proteins that modulate the underlying cytoskeleton, which is primarily composed of filamentous (F)-actin. The Rho-GTPase Rac1 is a major regulator of F-actin and is essential for the development and plasticity of dendrites and spines. However, the key molecules and mechanisms that regulate Rac1-dependent pathways at spines and synapses are not well understood. We have identified the Rac1-GTPase activating protein, α2-chimaerin, as a critical negative regulator of Rac1 in hippocampal neurons. The loss of α2-chimaerin significantly increases the levels of active Rac1 and induces the formation of aberrant polymorphic dendritic spines. Further, disruption of α2-chimaerin signaling simplifies dendritic arbor complexity and increases the presence of dendritic spines that appear poly-innervated. Our data suggests that α2-chimaerin serves as a "brake" to constrain Rac1-dependent signaling to ensure that the mature morphology of spines is maintained in response to network activity.
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Affiliation(s)
- Chris M Valdez
- Interdepartmental Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109, United States
| | - Geoffrey G Murphy
- Interdepartmental Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109, United States; Molecular and Behavioral Neuroscience Institute, Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, United States
| | - Asim A Beg
- Interdepartmental Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109, United States; Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, United States.
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9
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Couch G, Redman JE, Wernisch L, Newton R, Malhotra S, Dawsey SM, Lao-Sirieix P, Fitzgerald RC. The Discovery and Validation of Biomarkers for the Diagnosis of Esophageal Squamous Dysplasia and Squamous Cell Carcinoma. Cancer Prev Res (Phila) 2016; 9:558-66. [PMID: 27072986 DOI: 10.1158/1940-6207.capr-15-0379] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 03/11/2016] [Indexed: 02/07/2023]
Abstract
The 5-year survival rate of esophageal cancer is less than 10% in developing countries, where more than 90% of these cancers are esophageal squamous cell carcinomas (ESCC). Endoscopic screening is undertaken in high incidence areas. Biomarker analysis could reduce the subjectivity associated with histologic assessment of dysplasia and thus improve diagnostic accuracy. The aims of this study were therefore to identify biomarkers for esophageal squamous dysplasia and carcinoma. A publicly available dataset was used to identify genes with differential expression in ESCC compared with normal esophagus. Each gene was ranked by a support vector machine separation score. Expression profiles were examined, before validation by qPCR and IHC. We found that 800 genes were overexpressed in ESCC compared with normal esophagus (P < 10(-5)). Of the top 50 genes, 33 were expressed in ESCC epithelium and not in normal esophagus epithelium or stroma using the Protein Atlas website. These were taken to qPCR validation, and 20 genes were significantly overexpressed in ESCC compared with normal esophagus (P < 0.05). TNFAIP3 and CHN1 showed differential expression with IHC. TNFAIP3 expression increased gradually through normal esophagus, mild, moderate and severe dysplasia, and SCC (P < 0.0001). CHN1 staining was rarely present in the top third of normal esophagus epithelium and extended progressively towards the surface in mild, moderate, and severe dysplasia, and SCC (P < 0.0001). Two novel promising biomarkers for ESCC were identified, TNFAIP3 and CHN1. CHN1 and TNFAIP3 may improve diagnostic accuracy of screening methods for ESCC. Cancer Prev Res; 9(7); 558-66. ©2016 AACR.
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Affiliation(s)
- George Couch
- MRC Cancer Unit, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, United Kingdom
| | - James E Redman
- MRC Cancer Unit, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, United Kingdom
| | - Lorenz Wernisch
- MRC Biostatistics Unit, Robinson Way, Cambridge, United Kingdom
| | - Richard Newton
- MRC Biostatistics Unit, Robinson Way, Cambridge, United Kingdom
| | - Shalini Malhotra
- Department of Histopathology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom
| | - Sanford M Dawsey
- Division of Cancer Epidemiology & Genetics, NCI, Bethesda, Maryland
| | - Pierre Lao-Sirieix
- MRC Cancer Unit, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, United Kingdom
| | - Rebecca C Fitzgerald
- MRC Cancer Unit, Hutchison/MRC Research Centre, University of Cambridge, Cambridge, United Kingdom.
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10
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Ba W, Selten MM, van der Raadt J, van Veen H, Li LL, Benevento M, Oudakker AR, Lasabuda RSE, Letteboer SJ, Roepman R, van Wezel RJA, Courtney MJ, van Bokhoven H, Nadif Kasri N. ARHGAP12 Functions as a Developmental Brake on Excitatory Synapse Function. Cell Rep 2016; 14:1355-1368. [PMID: 26854232 DOI: 10.1016/j.celrep.2016.01.037] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 11/28/2015] [Accepted: 01/09/2016] [Indexed: 12/31/2022] Open
Abstract
The molecular mechanisms that promote excitatory synapse development have been extensively studied. However, the molecular events preventing precocious excitatory synapse development so that synapses form at the correct time and place are less well understood. Here, we report the functional characterization of ARHGAP12, a previously uncharacterized Rho GTPase-activating protein (RhoGAP) in the brain. ARHGAP12 is specifically expressed in the CA1 region of the hippocampus, where it localizes to the postsynaptic compartment of excitatory synapses. ARHGAP12 negatively controls spine size via its RhoGAP activity and promotes, by interacting with CIP4, postsynaptic AMPA receptor endocytosis. Arhgap12 knockdown results in precocious maturation of excitatory synapses, as indicated by a reduction in the proportion of silent synapses. Collectively, our data show that ARHGAP12 is a synaptic RhoGAP that regulates excitatory synaptic structure and function during development.
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Affiliation(s)
- W Ba
- Department of Cognitive Neuroscience, Radboudumc, 6500 HB Nijmegen, the Netherlands; Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands; Donders Institute for Brain, Cognition, and Behaviour, 6525 AJ Nijmegen, the Netherlands
| | - M M Selten
- Department of Cognitive Neuroscience, Radboudumc, 6500 HB Nijmegen, the Netherlands; Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands; Donders Institute for Brain, Cognition, and Behaviour, 6525 AJ Nijmegen, the Netherlands
| | - J van der Raadt
- Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands; Radboud Institute for Molecular Life Sciences, Radboudumc, 6525 GA Nijmegen, the Netherlands
| | - H van Veen
- Donders Institute for Brain, Cognition, and Behaviour, 6525 AJ Nijmegen, the Netherlands; Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, P.O. Box 80082, 30508 TB Utrecht, the Netherlands
| | - L-L Li
- Molecular Signalling Laboratory, Department of Neurobiology, A.I. Virtanen Institute, University of Eastern Finland, Kuopio 70210, Finland
| | - M Benevento
- Department of Cognitive Neuroscience, Radboudumc, 6500 HB Nijmegen, the Netherlands; Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands; Donders Institute for Brain, Cognition, and Behaviour, 6525 AJ Nijmegen, the Netherlands
| | - A R Oudakker
- Department of Cognitive Neuroscience, Radboudumc, 6500 HB Nijmegen, the Netherlands; Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands; Donders Institute for Brain, Cognition, and Behaviour, 6525 AJ Nijmegen, the Netherlands
| | - R S E Lasabuda
- Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands
| | - S J Letteboer
- Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands; Radboud Institute for Molecular Life Sciences, Radboudumc, 6525 GA Nijmegen, the Netherlands
| | - R Roepman
- Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands; Radboud Institute for Molecular Life Sciences, Radboudumc, 6525 GA Nijmegen, the Netherlands
| | - R J A van Wezel
- Donders Institute for Brain, Cognition, and Behaviour, 6525 AJ Nijmegen, the Netherlands; Biomedical Signal and Systems, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, 7500 AE Enschede, the Netherlands
| | - M J Courtney
- Molecular Signalling Laboratory, Department of Neurobiology, A.I. Virtanen Institute, University of Eastern Finland, Kuopio 70210, Finland; Turku Centre for Biotechnology, Abo Akademi University and University of Turku, Turku 20521, Finland
| | - H van Bokhoven
- Department of Cognitive Neuroscience, Radboudumc, 6500 HB Nijmegen, the Netherlands; Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands; Donders Institute for Brain, Cognition, and Behaviour, 6525 AJ Nijmegen, the Netherlands; Radboud Institute for Molecular Life Sciences, Radboudumc, 6525 GA Nijmegen, the Netherlands
| | - N Nadif Kasri
- Department of Cognitive Neuroscience, Radboudumc, 6500 HB Nijmegen, the Netherlands; Department of Human Genetics, Radboudumc, 6500 HB Nijmegen, the Netherlands; Donders Institute for Brain, Cognition, and Behaviour, 6525 AJ Nijmegen, the Netherlands.
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11
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Developmental RacGAP α2-Chimaerin Signaling Is a Determinant of the Morphological Features of Dendritic Spines in Adulthood. J Neurosci 2016; 35:13728-44. [PMID: 26446225 DOI: 10.1523/jneurosci.0419-15.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Morphological characteristics of dendritic spines form the basis of cognitive ability. However, molecular mechanisms involved in fine-tuning of spine morphology during development are not fully understood. Moreover, it is unclear whether, and to what extent, these developmental mechanisms determine the normal adult spine morphological features. Here, we provide evidence that α2-isoform of Rac-specific GTPase-activating protein α-chimaerin (α2-chimaerin) is involved in spine morphological refinement during late postnatal period, and furthermore show that this developmental α2-chimaerin function affects adult spine morphologies. We used a series of mice with global and conditional knock-out of α-chimaerin isoforms (α1-chimaerin and α2-chimaerin). α2-Chimaerin disruption, but not α1-chimaerin disruption, in the mouse results in an increased size (and density) of spines in the hippocampus. In contrast, overexpression of α2-chimaerin in developing hippocampal neurons induces a decrease of spine size. Disruption of α2-chimaerin suppressed EphA-mediated spine morphogenesis in cultured developing hippocampal neurons. α2-Chimaerin disruption that begins during the juvenile stage results in an increased size of spines in the hippocampus. Meanwhile, spine morphologies are unaltered when α2-chimaerin is deleted only in adulthood. Consistent with these spine morphological results, disruption of α2-chimaerin beginning in the juvenile stage led to an increase in contextual fear learning in adulthood; whereas contextual learning was recently shown to be unaffected when α2-chimaerin was deleted only in adulthood. Together, these results suggest that α2-chimaerin signaling in developmental stages contributes to determination of the morphological features of adult spines and establishment of normal cognitive ability. SIGNIFICANCE STATEMENT Recent studies of neurodevelopmental disorders in humans and their animal models have led to an attractive hypothesis that spine morphogenesis during development forms the basis of adult cognition. In particular, the roles of Rac and its regulators, such as Rac-specific GTPase-activating proteins (RacGAPs) and Rac guanine nucleotide exchange factors, are a topic of focus in spine morphogenesis and cognitive ability. Using a series of mice with global and conditional knock-out (KO) of RacGAP α-chimaerin isoforms (α1-chimaerin and α2-chimaerin), we provide compelling evidence demonstrating that α2-chimaerin is involved in spine morphological refinement during late postnatal development and that this developmental α2-chimaerin function affects adult spine morphologies. Furthermore, our results clearly showed that α2-chimaerin signaling during late postnatal development contributes to normal cognitive ability in adult mice.
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12
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Regulating Rac in the nervous system: molecular function and disease implication of Rac GEFs and GAPs. BIOMED RESEARCH INTERNATIONAL 2015; 2015:632450. [PMID: 25879033 PMCID: PMC4388020 DOI: 10.1155/2015/632450] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 03/06/2015] [Indexed: 12/11/2022]
Abstract
Rho family GTPases, including RhoA, Rac1, and Cdc42 as the most studied members, are master regulators of actin cytoskeletal organization. Rho GTPases control various aspects of the nervous system and are associated with a number of neuropsychiatric and neurodegenerative diseases. The activity of Rho GTPases is controlled by two families of regulators, guanine nucleotide exchange factors (GEFs) as the activators and GTPase-activating proteins (GAPs) as the inhibitors. Through coordinated regulation by GEFs and GAPs, Rho GTPases act as converging signaling molecules that convey different upstream signals in the nervous system. So far, more than 70 members of either GEFs or GAPs of Rho GTPases have been identified in mammals, but only a small subset of them have well-known functions. Thus, characterization of important GEFs and GAPs in the nervous system is crucial for the understanding of spatiotemporal dynamics of Rho GTPase activity in different neuronal functions. In this review, we summarize the current understanding of GEFs and GAPs for Rac1, with emphasis on the molecular function and disease implication of these regulators in the nervous system.
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Kato T, Konishi Y, Shimohama S, Beach TG, Akatsu H, Tooyama I. Alpha1-chimaerin, a Rac1 GTPase-activating protein, is expressed at reduced mRNA levels in the brain of Alzheimer's disease patients. Neurosci Lett 2015; 591:19-24. [PMID: 25676811 PMCID: PMC4382517 DOI: 10.1016/j.neulet.2015.02.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 02/03/2015] [Accepted: 02/06/2015] [Indexed: 12/21/2022]
Abstract
Alpha1-chimaerin is a GTPase-activating protein (GAP) for Rac1, a member of the Rho small GTPase family, whose action leads to the inactivation of Rac1. Rac1 activity is upregulated in Alzheimer's disease, but little is known about the role of α1-chimaerin. In this study, we investigated the expression and localization of α1-chimaerin mRNA in postmortem human brains from patients with Alzheimer's disease and control subjects. In situ hybridization studies demonstrated that α1-chimaerin was expressed by neurons in the neo-cortex of the temporal lobe and the hippocampus of both controls and Alzheimer's disease cases, with the signal intensity dramatically decreased in patients with Alzheimer's disease. Real-time PCR analysis confirmed a significant reduction of α1-chimaerin mRNA expression in the temporal cortex of Alzheimer's disease cases. In contrast, α2-chimaerin mRNA levels showed no significant difference between the groups. The present study showed reduced α1-chimaerin expression in the brain of Alzheimer's disease cases, suggesting a role in the upregulation of Rac1 activity during the disease process.
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Affiliation(s)
- Tomoko Kato
- Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu 520-2192, Japan
| | - Yoshihiro Konishi
- Department of Clinical Research, Nishi-tottori National Hospital, Tottori 689-0202, Japan
| | - Shun Shimohama
- Department of Neurology, Sapporo Medical University, Sapporo 060-8556, Japan
| | - Thomas G Beach
- Banner Sun Health Research Institute, Sun City, AZ 85372, USA
| | - Hiroyasu Akatsu
- Department of Community-Based Medical Education, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
| | - Ikuo Tooyama
- Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu 520-2192, Japan.
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14
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Molecular regulation of synaptogenesis during associative learning and memory. Brain Res 2014; 1621:239-51. [PMID: 25485772 DOI: 10.1016/j.brainres.2014.11.054] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 11/24/2014] [Accepted: 11/25/2014] [Indexed: 01/06/2023]
Abstract
Synaptogenesis plays a central role in associative learning and memory. The biochemical pathways that underlie synaptogenesis are complex and incompletely understood. Nevertheless, research has so far identified three conceptually distinct routes to synaptogenesis: cell-cell contact mediated by adhesion proteins, cell-cell biochemical signaling from astrocytes and other cells, and neuronal signaling through classical ion channels and cell surface receptors. The cell adhesion pathways provide the physical substrate to the new synaptic connection, while cell-cell signaling may provide a global or regional signal, and the activity-dependent pathways provide the neuronal specificity that is required for the new synapses to produce functional neuronal networks capable of storing associative memories. These three aspects of synaptogenesis require activation of a variety of interacting biochemical pathways that converge on the actin cytoskeleton and strengthen the synapse in an information-dependent manner. This article is part of a Special Issue titled SI: Brain and Memory.
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Tian J, Tep C, Benedick A, Saidi N, Ryu JC, Kim ML, Sadasivan S, Oberdick J, Smeyne R, Zhu MX, Yoon SO. p75 regulates Purkinje cell firing by modulating SK channel activity through Rac1. J Biol Chem 2014; 289:31458-72. [PMID: 25253694 PMCID: PMC4223344 DOI: 10.1074/jbc.m114.589937] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 09/11/2014] [Indexed: 12/22/2022] Open
Abstract
p75 is expressed among Purkinje cells in the adult cerebellum, but its function has remained obscure. Here we report that p75 is involved in maintaining the frequency and regularity of spontaneous firing of Purkinje cells. The overall spontaneous firing activity of Purkinje cells was increased in p75(-/-) mice during the phasic firing period due to a longer firing period and accompanying reduction in silence period than in the wild type. We attribute these effects to a reduction in small conductance Ca(2+)-activated potassium (SK) channel activity in Purkinje cells from p75(-/-) mice compared with the wild type littermates. The mechanism by which p75 regulates SK channel activity appears to involve its ability to activate Rac1. In organotypic cultures of cerebellar slices, brain-derived neurotrophic factor increased RacGTP levels by activating p75 but not TrkB. These results correlate with a reduction in RacGTP levels in synaptosome fractions from the p75(-/-) cerebellum, but not in that from the cortex of the same animals, compared with wild type littermates. More importantly, we demonstrate that Rac1 modulates SK channel activity and firing patterns of Purkinje cells. Along with the finding that spine density was reduced in p75(-/-) cerebellum, these data suggest that p75 plays a role in maintaining normalcy of Purkinje cell firing in the cerebellum in part by activating Rac1 in synaptic compartments and modulating SK channels.
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Affiliation(s)
- JinBin Tian
- the Department of Neuroscience, Ohio State University, Columbus, Ohio 43210, the Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Chhavy Tep
- From the Department of Molecular and Cellular Biochemistry, the Biochemistry Program, and
| | - Alex Benedick
- From the Department of Molecular and Cellular Biochemistry
| | - Nabila Saidi
- From the Department of Molecular and Cellular Biochemistry
| | - Jae Cheon Ryu
- From the Department of Molecular and Cellular Biochemistry
| | - Mi Lyang Kim
- From the Department of Molecular and Cellular Biochemistry
| | - Shankar Sadasivan
- the Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, and
| | | | - Richard Smeyne
- the Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, and
| | - Michael X Zhu
- the Department of Neuroscience, Ohio State University, Columbus, Ohio 43210, the Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Sung Ok Yoon
- From the Department of Molecular and Cellular Biochemistry,
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16
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Iwata R, Ohi K, Kobayashi Y, Masuda A, Iwama M, Yasuda Y, Yamamori H, Tanaka M, Hashimoto R, Itohara S, Iwasato T. RacGAP α2-Chimaerin Function in Development Adjusts Cognitive Ability in Adulthood. Cell Rep 2014; 8:1257-64. [DOI: 10.1016/j.celrep.2014.07.047] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 06/20/2014] [Accepted: 07/25/2014] [Indexed: 11/24/2022] Open
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17
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Wang T, Mao J, Liu MJ, Choy KW, Li HB, Cram DS, Li H, Chen Y. A patient with five chromosomal rearrangements and a 2q31.1 microdeletion. Clin Chim Acta 2014; 430:129-33. [PMID: 24412318 DOI: 10.1016/j.cca.2014.01.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 01/02/2014] [Accepted: 01/03/2014] [Indexed: 11/30/2022]
Abstract
BACKGROUND Complex chromosomal rearrangements and chromosomal deletion and duplication syndromes are commonly associated with abnormal clinical phenotypes. The 2q31.1 microdeletion syndrome is a rare cytogenetic event that leads to limb and multi-internal organ anomalies. In this study we investigated the genetic basis of the physical and mental symptoms exhibited by a 4-year-old boy with a suspected 2q31.1 deletion. METHODS Cytogenetic and molecular techniques including karyotyping, array-based comparative genomic hybridization (aCGH), fluorescence in situ hybridization (FISH) and real-time PCR were used to identify the nature and extent of chromosome abnormalities in the patient. RESULTS A 3.6Mb interstitial microdeletion of 2q31.1 was identified in association with complex balanced genomic structural rearrangements involving chromosomes 2, 3, 6, 15 and 18. The 2q31.1 deletion resulted in the loss of one copy of several known disease genes, including GAD1, DCAF17, SLC25A12 and ITGA6 associated with mental retardation and facial abnormalities and DLX1/DLX2 partially associated with limb abnormalities. Two additional genes, HOXD13 and CHN1, required for normal limb and eye development that map immediately distal to the 2q31.1 deletion had normal copy numbers, although CHN1 was found to express at a lower level in patient's lymphocytes. CONCLUSIONS We speculated that the 2q31.1 deletion and/or translocation may have a positional effect which reduces expression of HOXD13 and CHN1 causing haplo-insufficiency, and in combination with the hemizygous expression of the disease genes at 2q31.1, provides a plausible explanation for the diverse clinical symptoms exhibited by the patient.
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Affiliation(s)
- Ting Wang
- Center for Reproduction and Genetics, Nanjing Medical University Affiliated Suzhou Hospital, Suzhou 215002, China
| | - Jun Mao
- Center for Reproduction and Genetics, Nanjing Medical University Affiliated Suzhou Hospital, Suzhou 215002, China
| | - Min-Juan Liu
- Center for Reproduction and Genetics, Nanjing Medical University Affiliated Suzhou Hospital, Suzhou 215002, China
| | - Kwong Wai Choy
- Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, Hong Kong, China; Joint Centre with Utrecht University-Genetic Core, The Chinese University of Hong Kong, Hong Kong, China
| | - Hai-Bo Li
- Center for Reproduction and Genetics, Nanjing Medical University Affiliated Suzhou Hospital, Suzhou 215002, China
| | | | - Hong Li
- Center for Reproduction and Genetics, Nanjing Medical University Affiliated Suzhou Hospital, Suzhou 215002, China
| | - Ying Chen
- Center for Reproduction and Genetics, Nanjing Medical University Affiliated Suzhou Hospital, Suzhou 215002, China.
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18
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Raynaud F, Moutin E, Schmidt S, Dahl J, Bertaso F, Boeckers TM, Homburger V, Fagni L. Rho-GTPase-activating protein interacting with Cdc-42-interacting protein 4 homolog 2 (Rich2): a new Ras-related C3 botulinum toxin substrate 1 (Rac1) GTPase-activating protein that controls dendritic spine morphogenesis. J Biol Chem 2013; 289:2600-9. [PMID: 24352656 DOI: 10.1074/jbc.m113.534636] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Development of dendritic spines is important for synaptic function, and alteration in spine morphogenesis is often associated with mental disorders. Rich2 was an uncharacterized Rho-GAP protein. Here we searched for a role of this protein in spine morphogenesis. We found that it is enriched in dendritic spines of cultured hippocampal pyramidal neurons during early stages of development. Rich2 specifically stimulated the Rac1 GTPase in these neurons. Inhibition of Rac1 by EHT 1864 increased the size and decreased the density of dendritic spines. Similarly, Rich2 overexpression increased the size and decreased the density of dendritic spines, whereas knock-down of the protein by specific si-RNA decreased both size and density of spines. The morphological changes were reflected by the increased amplitude and decreased frequency of miniature EPSCs induced by Rich2 overexpression, while si-RNA treatment decreased both amplitude and frequency of these events. Finally, treatment of neurons with EHT 1864 rescued the phenotype induced by Rich2 knock-down. These results suggested that Rich2 controls dendritic spine morphogenesis and function via inhibition of Rac1.
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Affiliation(s)
- Fabrice Raynaud
- From CNRS, UMR-5203, Institut de Génomique Fonctionnelle, F-34000 Montpellier, France
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19
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Breaking it down: the ubiquitin proteasome system in neuronal morphogenesis. Neural Plast 2013; 2013:196848. [PMID: 23476809 PMCID: PMC3586504 DOI: 10.1155/2013/196848] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 12/31/2012] [Indexed: 01/20/2023] Open
Abstract
The ubiquitin-proteasome system (UPS) is most widely known for its role in intracellular protein degradation; however, in the decades since its discovery, ubiquitination has been associated with the regulation of a wide variety of cellular processes. The addition of ubiquitin tags, either as single moieties or as polyubiquitin chains, has been shown not only to mediate degradation by the proteasome and the lysosome, but also to modulate protein function, localization, and endocytosis. The UPS plays a particularly important role in neurons, where local synthesis and degradation work to balance synaptic protein levels at synapses distant from the cell body. In recent years, the UPS has come under increasing scrutiny in neurons, as elements of the UPS have been found to regulate such diverse neuronal functions as synaptic strength, homeostatic plasticity, axon guidance, and neurite outgrowth. Here we focus on recent advances detailing the roles of the UPS in regulating the morphogenesis of axons, dendrites, and dendritic spines, with an emphasis on E3 ubiquitin ligases and their identified regulatory targets.
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20
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The RacGAP β2-Chimaerin selectively mediates axonal pruning in the hippocampus. Cell 2012; 149:1594-606. [PMID: 22726444 DOI: 10.1016/j.cell.2012.05.018] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 04/03/2012] [Accepted: 05/01/2012] [Indexed: 02/08/2023]
Abstract
Axon pruning and synapse elimination promote neural connectivity and synaptic plasticity. Stereotyped pruning of axons that originate in the hippocampal dentate gyrus (DG) and extend along the infrapyramidal tract (IPT) occurs during postnatal murine development by neurite retraction and resembles axon repulsion. The chemorepellent Sema3F is required for IPT axon pruning, dendritic spine remodeling, and repulsion of DG axons. The signaling events that regulate IPT axon pruning are not known. We find that inhibition of the small G protein Rac1 by the Rac GTPase-activating protein (GAP) β2-Chimaerin (β2Chn) mediates Sema3F-dependent pruning. The Sema3F receptor neuropilin-2 selectively binds β2Chn, and ligand engagement activates this GAP to ultimately restrain Rac1-dependent effects on cytoskeletal reorganization. β2Chn is necessary for axon pruning both in vitro and in vivo, but it is dispensable for axon repulsion and spine remodeling. Therefore, a Npn2/β2Chn/Rac1 signaling axis distinguishes DG axon pruning from the effects of Sema3F on repulsion and dendritic spine remodeling.
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21
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Gonzalez-Billault C, Muñoz-Llancao P, Henriquez DR, Wojnacki J, Conde C, Caceres A. The role of small GTPases in neuronal morphogenesis and polarity. Cytoskeleton (Hoboken) 2012; 69:464-85. [PMID: 22605667 DOI: 10.1002/cm.21034] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 04/12/2012] [Accepted: 04/16/2012] [Indexed: 12/21/2022]
Abstract
The highly dynamic remodeling and cross talk of the microtubule and actin cytoskeleton support neuronal morphogenesis. Small RhoGTPases family members have emerged as crucial regulators of cytoskeletal dynamics. In this review we will comprehensively analyze findings that support the participation of RhoA, Rac, Cdc42, and TC10 in different neuronal morphogenetic events ranging from migration to synaptic plasticity. We will specifically address the contribution of these GTPases to support neuronal polarity and axonal elongation.
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Affiliation(s)
- Christian Gonzalez-Billault
- Faculty of Sciences, Laboratory of Cell and Neuronal Dynamics, Department of Biology and Institute for Cell Dynamics and Biotechnology, Universidad de Chile, Santiago, Chile.
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22
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Ligeti E, Welti S, Scheffzek K. Inhibition and Termination of Physiological Responses by GTPase Activating Proteins. Physiol Rev 2012; 92:237-72. [DOI: 10.1152/physrev.00045.2010] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Physiological processes are strictly organized in space and time. However, in cell physiology research, more attention is given to the question of space rather than to time. To function as a signal, environmental changes must be restricted in time; they need not only be initiated but also terminated. In this review, we concentrate on the role of one specific protein family involved in biological signal termination. GTPase activating proteins (GAPs) accelerate the endogenously low GTP hydrolysis rate of monomeric guanine nucleotide-binding proteins (GNBPs), limiting thereby their prevalence in the active, GTP-bound form. We discuss cases where defective or excessive GAP activity of specific proteins causes significant alteration in the function of the nervous, endocrine, and hemopoietic systems, or contributes to development of infections and tumors. Biochemical and genetic data as well as observations from human pathology support the notion that GAPs represent vital elements in the spatiotemporal fine tuning of physiological processes.
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Affiliation(s)
- Erzsébet Ligeti
- Department of Physiology, Semmelweis University, Budapest, Hungary; Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany; and Division of Biological Chemistry, Biocenter, Innsbruck Medical University, Innsbruck, Austria
| | - Stefan Welti
- Department of Physiology, Semmelweis University, Budapest, Hungary; Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany; and Division of Biological Chemistry, Biocenter, Innsbruck Medical University, Innsbruck, Austria
| | - Klaus Scheffzek
- Department of Physiology, Semmelweis University, Budapest, Hungary; Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany; and Division of Biological Chemistry, Biocenter, Innsbruck Medical University, Innsbruck, Austria
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23
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Yang CB, Zheng YT, Kiser PJ, Mower GD. Identification of α-Chimaerin as a Candidate Gene for Critical Period Neuronal Plasticity in Cat and Mouse Visual Cortex. BMC Neurosci 2011; 12:70. [PMID: 21767388 PMCID: PMC3155490 DOI: 10.1186/1471-2202-12-70] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Accepted: 07/18/2011] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
In cat visual cortex, critical period neuronal plasticity is minimal until approximately 3 postnatal weeks, peaks at 5 weeks, gradually declines to low levels at 20 weeks, and disappears by 1 year of age. Dark rearing slows the entire time course of this critical period, such that at 5 weeks of age, normal cats are more plastic than dark reared cats, whereas at 20 weeks, dark reared cats are more plastic. Thus, a stringent criterion for identifying genes that are important for plasticity in visual cortex is that they show differences in expression between normal and dark reared that are of opposite direction in young versus older animals.
Results
The present study reports the identification by differential display PCR of a novel gene, α-chimaerin, as a candidate visual cortex critical period plasticity gene that showed bidirectional regulation of expression due to age and dark rearing. Northern blotting confirmed the bidirectional expression and 5'RACE sequencing identified the gene. There are two alternatively-spliced α-chimaerin isoforms: α1 and α2. Western blotting extended the evidence for bidirectional regulation of visual cortex α-chimaerin isoform expression to protein in cats and mice. α1- and α2-Chimaerin were elevated in dark reared compared to normal visual cortex at the peak of the normal critical period and in normal compared to dark reared visual cortex at the nadir of the normal critical period. Analysis of variance showed a significant interaction in both cats and mice for both α-chimaerin isoforms, indicating that the effect of dark rearing depended on age. This differential expression was not found in frontal cortex.
Conclusions
Chimaerins are RhoGTPase-activating proteins that are EphA4 effectors and have been implicated in a number of processes including growth cone collapse, axon guidance, dendritic spine development and the formation of corticospinal motor circuits. The present results identify α-chimaerin as a candidate molecule for a role in the postnatal critical period of visual cortical plasticity.
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24
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Shaping up the membrane: diacylglycerol coordinates spatial orientation of signaling. Trends Biochem Sci 2011; 36:593-603. [PMID: 21798744 DOI: 10.1016/j.tibs.2011.06.005] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2011] [Revised: 06/21/2011] [Accepted: 06/23/2011] [Indexed: 11/23/2022]
Abstract
Diacylglycerol signals by binding and activating C1 domain-containing proteins expressed principally in neuronal and immune tissues. This restricted expression profile suggests that diacylglycerol-regulated signals are particularly relevant in cell-cell communication processes in which active endocytosis and exocytosis take place. Not surprisingly, various experimental approaches have demonstrated a crucial role for diacylglycerol effectors and metabolizing enzymes in the control of immune responses, neuron communication and phagocytosis. Current research delineates a scenario in which coordinated decoding of diacylglycerol signals is translated into complex biological responses such as neuronal plasticity, T cell development or cytolytic killing. Diacylglycerol functions reach maximal diversity in these highly specialized systems in which signal intensity directly regulates distinct biological outcomes. This review brings together the most recent studies, emphasizing the contribution of compartmentalized DAG metabolism to orientated signaling events.
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25
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Tolias KF, Duman JG, Um K. Control of synapse development and plasticity by Rho GTPase regulatory proteins. Prog Neurobiol 2011; 94:133-48. [PMID: 21530608 DOI: 10.1016/j.pneurobio.2011.04.011] [Citation(s) in RCA: 197] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 04/13/2011] [Accepted: 04/15/2011] [Indexed: 12/21/2022]
Abstract
Synapses are specialized cell-cell contacts that mediate communication between neurons. Most excitatory synapses in the brain are housed on dendritic spines, small actin-rich protrusions extending from dendrites. During development and in response to environmental stimuli, spines undergo marked changes in shape and number thought to underlie processes like learning and memory. Improper spine development, in contrast, likely impedes information processing in the brain, since spine abnormalities are associated with numerous brain disorders. Elucidating the mechanisms that regulate the formation and plasticity of spines and their resident synapses is therefore crucial to our understanding of cognition and disease. Rho-family GTPases, key regulators of the actin cytoskeleton, play essential roles in orchestrating the development and remodeling of spines and synapses. Precise spatio-temporal regulation of Rho GTPase activity is critical for their function, since aberrant Rho GTPase signaling can cause spine and synapse defects as well as cognitive impairments. Rho GTPases are activated by guanine nucleotide exchange factors (GEFs) and inhibited by GTPase-activating proteins (GAPs). We propose that Rho-family GEFs and GAPs provide the spatiotemporal regulation and signaling specificity necessary for proper Rho GTPase function based on the following features they possess: (i) existence of multiple GEFs and GAPs per Rho GTPase, (ii) developmentally regulated expression, (iii) discrete localization, (iv) ability to bind to and organize specific signaling networks, and (v) tightly regulated activity, perhaps involving GEF/GAP interactions. Recent studies describe several Rho-family GEFs and GAPs that uniquely contribute to spinogenesis and synaptogenesis. Here, we highlight several of these proteins and discuss how they occupy distinct biochemical niches critical for synaptic development.
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Affiliation(s)
- Kimberley F Tolias
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA.
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26
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Regulation of synaptic Rac1 activity, long-term potentiation maintenance, and learning and memory by BCR and ABR Rac GTPase-activating proteins. J Neurosci 2010; 30:14134-44. [PMID: 20962234 DOI: 10.1523/jneurosci.1711-10.2010] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Rho family small GTPases are important regulators of neuronal development. Defective Rho regulation causes nervous system dysfunctions including mental retardation and Alzheimer's disease. Rac1, a member of the Rho family, regulates dendritic spines and excitatory synapses, but relatively little is known about how synaptic Rac1 is negatively regulated. Breakpoint cluster region (BCR) is a Rac GTPase-activating protein known to form a fusion protein with the c-Abl tyrosine kinase in Philadelphia chromosome-positive chronic myelogenous leukemia. Despite the fact that BCR mRNAs are abundantly expressed in the brain, the neural functions of BCR protein have remained obscure. We report here that BCR and its close relative active BCR-related (ABR) localize at excitatory synapses and directly interact with PSD-95, an abundant postsynaptic scaffolding protein. Mice deficient for BCR or ABR show enhanced basal Rac1 activity but only a small increase in spine density. Importantly, mice lacking BCR or ABR exhibit a marked decrease in the maintenance, but not induction, of long-term potentiation, and show impaired spatial and object recognition memory. These results suggest that BCR and ABR have novel roles in the regulation of synaptic Rac1 signaling, synaptic plasticity, and learning and memory, and that excessive Rac1 activity negatively affects synaptic and cognitive functions.
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27
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Marland JRK, Pan D, Buttery PC. Rac GTPase-activating protein (Rac GAP) α1-Chimaerin undergoes proteasomal degradation and is stabilized by diacylglycerol signaling in neurons. J Biol Chem 2010; 286:199-207. [PMID: 21056981 DOI: 10.1074/jbc.m110.166728] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
α1-Chimaerin is a neuron-specific member of the Rho GTPase-activating protein family that selectively inactivates the small GTPase Rac. It is known to regulate the structure of dendrites and dendritic spines. We describe here that under basal conditions α1-chimaerin becomes polyubiquitinated and undergoes rapid proteasomal degradation. This degradation is partly dependent on the N-terminal region that is unique to this isoform. Mimicking diacylglycerol (DAG) signaling with a phorbol ester stabilizes endogenous α1-chimaerin against degradation and causes accumulation of the protein. The stabilization requires phorbol ester binding via the C1 domain of the protein and is independent of PKC activity. In addition, overexpression of a constitutively active Rac1 mutant is sufficient to cause an accumulation of α1-chimaerin through a phospholipase C-dependent mechanism, showing that endogenous DAG signaling can also stabilize the protein. These results suggest that signaling via DAG may regulate the abundance of α1-chimaerin under physiological conditions, providing a new model for understanding how its activity could be controlled.
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Affiliation(s)
- Jamie R K Marland
- Centre for Brain Repair, University of Cambridge, Cambridge CB2 0PY, United Kingdom
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28
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Mitter D, Chiaie BD, Lüdecke HJ, Gillessen-Kaesbach G, Bohring A, Kohlhase J, Caliebe A, Siebert R, Roepke A, Ramos-Arroyo MA, Nieva B, Menten B, Loeys B, Mortier G, Wieczorek D. Genotype-phenotype correlation in eight new patients with a deletion encompassing 2q31.1. Am J Med Genet A 2010; 152A:1213-24. [PMID: 20425826 DOI: 10.1002/ajmg.a.33344] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Microdeletions of the 2q31.1 region are rare. We present the clinical and molecular findings of eight previously unreported patients with overlapping deletions in 2q31.1. The patients have a variable clinical phenotype and present with developmental delay (7/8), growth retardation (5/8), seizures (2/8) and a craniofacial dysmorphism consisting of microcephaly (4/8), short palpebral fissures (7/8), broad eyebrows with lateral flare (7/8), low-set ears with thickened helices and lobules (5/8), and micrognathia (6/8). Additional congenital anomalies were noted, including limb abnormalities (8/8), heart defects (3/8), genital anomalies (3/8), and craniosynostosis (1/8). Six of these microdeletions, ranging in size from 1.24 to 8.35 Mb, were identified by array CGH, one larger deletion (19.7 Mb) was detected by conventional karyotyping and further characterized by array CGH analysis. The smallest region of overlap in all eight patients spans at most 88 kb and includes only the WIPF1 gene. This gene codes for the WAS/WASL interacting protein family member 1. The patients described here do not present with clinical signs of the Wiskott-Aldrich syndrome and the deletion of this single gene does not allow explaining the phenotype in our patients. It is likely that the deletion of different but overlapping sets of genes from 2q31 is responsible for the clinical variability in these patients. To further dissect the complex phenotype associated with deletions in 2q31, additional patients with overlapping phenotypes should be examined with array CGH. This should help to link particular phenotypes to specific genes, and add to our understanding of the underlying developmental processes.
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MESH Headings
- Adult
- Child
- Child, Preschool
- Chromosome Breakage
- Chromosome Deletion
- Chromosomes, Human, Pair 2/genetics
- Comparative Genomic Hybridization
- Female
- Foot Deformities, Congenital/complications
- Foot Deformities, Congenital/diagnostic imaging
- Foot Deformities, Congenital/genetics
- Genetic Association Studies
- Hand Deformities, Congenital/complications
- Hand Deformities, Congenital/diagnostic imaging
- Hand Deformities, Congenital/genetics
- Humans
- Infant
- Infant, Newborn
- Karyotyping
- Male
- Pregnancy
- Radiography
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Affiliation(s)
- Diana Mitter
- Institut für Humangenetik, Universitätsklinikum Essen, Essen, Germany.
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Campbell NR, Fernandes CC, Halff AW, Berg DK. Endogenous signaling through alpha7-containing nicotinic receptors promotes maturation and integration of adult-born neurons in the hippocampus. J Neurosci 2010; 30:8734-44. [PMID: 20592195 PMCID: PMC2905643 DOI: 10.1523/jneurosci.0931-10.2010] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Revised: 04/19/2010] [Accepted: 05/12/2010] [Indexed: 12/20/2022] Open
Abstract
Neurogenesis in the dentate gyrus occurs throughout adult mammalian life and is essential for proper hippocampal function. Early in their development, adult-born neurons express homomeric alpha7-containing nicotinic acetylcholine receptors (alpha7-nAChRs) and receive direct cholinergic innervation. We show here that functional alpha7-nAChRs are necessary for normal survival, maturation, and integration of adult-born neurons in the dentate gyrus. Stereotaxic retroviral injection into the dentate gyrus of wild-type and alpha7-knock-out (alpha7KO) male and female mice was used to label and birthdate adult-born neurons for morphological and electrophysiological measures; BrdU (5-bromo-2-deoxyuridine) injections were used to quantify cell survival. In alpha7KO mice, we find that adult-born neurons develop with truncated, less complex dendritic arbors and display GABAergic postsynaptic currents with immature kinetics. The neurons also have a prolonged period of GABAergic depolarization characteristic of an immature state. In this condition, they receive fewer spontaneous synaptic currents and are more prone to die during the critical period when adult-born neurons are normally integrated into behaviorally relevant networks. Even those adult-born neurons that survive the critical period retain long-term dendritic abnormalities in alpha7KO mice. Interestingly, local infection with retroviral constructs to knockdown alpha7-mRNA mimics the alpha7KO phenotype, demonstrating that the relevant alpha7-nAChR signaling is cell autonomous. The results indicate a profound role for alpha7-nAChRs in adult neurogenesis and predict that alpha7-nAChR loss will cause progressive impairment in hippocampal circuitry and function over time as fewer neurons are added to the dentate gyrus and those that are added integrate less well.
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Affiliation(s)
- Nolan R. Campbell
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357, and
| | - Catarina C. Fernandes
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357, and
- Institute of Pharmacology and Neurosciences, Faculty of Medicine and Unit of Neurosciences, Institute of Molecular Medicine, University of Lisbon, 1649-028 Lisbon, Portugal
| | - Andrew W. Halff
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357, and
| | - Darwin K. Berg
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357, and
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30
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Griner EM, Caino MC, Sosa MS, Colón-González F, Chalmers MJ, Mischak H, Kazanietz MG. A novel cross-talk in diacylglycerol signaling: the Rac-GAP beta2-chimaerin is negatively regulated by protein kinase Cdelta-mediated phosphorylation. J Biol Chem 2010; 285:16931-41. [PMID: 20335173 DOI: 10.1074/jbc.m109.099036] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although the family of chimaerin Rac-GAPs has recently gained significant attention for their involvement in development, cancer, and neuritogenesis, little is known about their molecular regulation. Chimaerins are activated by the lipid second messenger diacylglycerol via their C1 domain upon activation of tyrosine kinase receptors, thereby restricting the magnitude of Rac signaling in a receptor-regulated manner. Here we identified a novel regulatory mechanism for beta2-chimaerin via phosphorylation. Epidermal growth factor or the phorbol ester phorbol 12-myristate 13-acetate caused rapid phosphorylation of beta2-chimaerin on Ser(169) located in the SH2-C1 domain linker region via protein kinase Cdelta, which retained beta2-chimaerin in the cytosol and prevented its C1 domain-mediated translocation to membranes. Furthermore, despite the fact that Ser(169) phosphorylation did not alter intrinsic Rac-GAP activity in vitro, a non-phosphorylatable beta2-chimaerin mutant was highly sensitive to translocation, and displayed enhanced association with activated Rac, enhanced Rac-GAP activity, and anti-migratory properties when expressed in cells. Our results not only revealed a novel regulatory mechanism that facilitates Rac activation, but also identified a novel mechanism of cross-talk between diacylglycerol receptors that restricts beta2-chimaerin relocalization and activation.
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Affiliation(s)
- Erin M Griner
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6160, USA
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31
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32
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Sosa MS, Lewin NE, Choi SH, Blumberg PM, Kazanietz MG. Biochemical characterization of hyperactive beta2-chimaerin mutants revealed an enhanced exposure of C1 and Rac-GAP domains. Biochemistry 2009; 48:8171-8. [PMID: 19618918 DOI: 10.1021/bi9010623] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent studies established that the Rac-GAP beta2-chimaerin plays important roles in development, neuritogenesis, and cancer progression. A unique feature of beta2-chimaerin is that it can be activated by phorbol esters and the lipid second messenger diacylglycerol (DAG), which bind with high affinity to its C1 domain and promote beta2-chimaerin translocation to membranes, leading to the inactivation of the small G-protein Rac. Crystallographic evidence and cellular studies suggest that beta2-chimaerin remains in an inactive conformation in the cytosol with the C1 domain inaccessible to ligands. We developed a series of beta2-chimaerin point mutants in which intramolecular contacts that occlude the C1 domain have been disrupted. These mutants showed enhanced translocation in response to phorbol 12-myristate 13-acetate (PMA) in cells. Binding assays using [(3)H]phorbol 12,13-dibutyrate ([(3)H]PDBu) revealed that internal contact mutants have a reduced acidic phospholipid requirement for phorbol ester binding. Moreover, disruption of intramolecular contacts enhances binding of beta2-chimaerin to acidic phospholipid vesicles and confers enhanced Rac-GAP activity in vitro. These studies suggest that beta2-chimaerin must undergo a conformational rearrangement in order to expose its lipid binding sites and become activated.
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Affiliation(s)
- Maria Soledad Sosa
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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33
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Corty MM, Matthews BJ, Grueber WB. Molecules and mechanisms of dendrite development in Drosophila. Development 2009; 136:1049-61. [PMID: 19270170 DOI: 10.1242/dev.014423] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Neurons are one of the most morphologically diverse cell types, in large part owing to their intricate dendrite branching patterns. Dendrites are structures that are specialized to receive and process inputs in neurons, thus their specific morphologies reflect neural connectivity and influence information flow through circuits. Recent studies in Drosophila on the molecular basis of dendrite diversity, dendritic guidance, the cell biology of dendritic branch patterning and territory formation have identified numerous intrinsic and extrinsic cues that shape diverse features of dendrites. As we discuss in this review, many of the mechanisms that are being elucidated show conservation in diverse systems.
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Affiliation(s)
- Megan M Corty
- Center for Neurobiology and Behavior, Columbia University Medical Center, New York, NY 10032, USA.
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34
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Affiliation(s)
- Samuel G Frere
- Department of Pathology and Cell Biology, Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, NY, USA
| | - Gilbert Di Paolo
- Department of Pathology and Cell Biology, Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University Medical Center, New York, NY, USA
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35
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Kim K, Yang J, Zhong XP, Kim MH, Kim YS, Lee HW, Han S, Choi J, Han K, Seo J, Prescott SM, Topham MK, Bae YC, Koretzky G, Choi SY, Kim E. Synaptic removal of diacylglycerol by DGKzeta and PSD-95 regulates dendritic spine maintenance. EMBO J 2009; 28:1170-9. [PMID: 19229292 DOI: 10.1038/emboj.2009.44] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Accepted: 01/27/2009] [Indexed: 12/22/2022] Open
Abstract
Diacylglycerol (DAG) is an important lipid signalling molecule that exerts an effect on various effector proteins including protein kinase C. A main mechanism for DAG removal is to convert it to phosphatidic acid (PA) by DAG kinases (DGKs). However, it is not well understood how DGKs are targeted to specific subcellular sites and tightly regulates DAG levels. The neuronal synapse is a prominent site of DAG production. Here, we show that DGKzeta is targeted to excitatory synapses through its direct interaction with the postsynaptic PDZ scaffold PSD-95. Overexpression of DGKzeta in cultured neurons increases the number of dendritic spines, which receive the majority of excitatory synaptic inputs, in a manner requiring its catalytic activity and PSD-95 binding. Conversely, DGKzeta knockdown reduces spine density. Mice deficient in DGKzeta expression show reduced spine density and excitatory synaptic transmission. Time-lapse imaging indicates that DGKzeta is required for spine maintenance but not formation. We propose that PSD-95 targets DGKzeta to synaptic DAG-producing receptors to tightly couple synaptic DAG production to its conversion to PA for the maintenance of spine density.
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Affiliation(s)
- Karam Kim
- National Creative Research Initiative Center for Synaptogenesis and Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, Republic of Korea
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36
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Nikolic M. Unravelling the complex role of Cdk5 in the developing cerebral cortex. FUTURE NEUROLOGY 2008. [DOI: 10.2217/14796708.3.6.729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The normal development of the mammalian CNS is entirely dependent on the coordinated behavior of its cellular components. Particular importance is attributed to the correct morphology, migration and communication of neurons. Recent years have seen the identification of many extracellular, cell surface and intracellular signaling molecules that are important for normal CNS development, consequently triggering huge progress in our understanding of the complex processes involved. A key molecule to emerge is Cdk5. To date, Cdk5 has been functionally linked with controlled neuronal morphology, migration, synaptic function, cognition, drug addiction, neuronal death and neurodegeneration. The complexity of its function has been confirmed by the ever increasing number of diverse upstream regulators, protein substrates and biological consequences of altered catalytic function. The aim of this review is to consolidate recent findings concerning the role of Cdk5 in the developing nervous system, particularly the cerebral cortex, where its importance is most clearly evidenced.
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Affiliation(s)
- Margareta Nikolic
- Department of Cellular & Molecular Neuroscience, Division of Neuroscience & Mental Health, School of Medicine, Imperial College London, Burlington Danes Building, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK
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37
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Miyake N, Chilton J, Psatha M, Cheng L, Andrews C, Chan WM, Law K, Crosier M, Lindsay S, Cheung M, Allen J, Gutowski NJ, Ellard S, Young E, Iannaccone A, Appukuttan B, Stout JT, Christiansen S, Ciccarelli ML, Baldi A, Campioni M, Zenteno JC, Davenport D, Mariani LE, Sahin M, Guthrie S, Engle EC. Human CHN1 mutations hyperactivate alpha2-chimaerin and cause Duane's retraction syndrome. Science 2008; 321:839-43. [PMID: 18653847 PMCID: PMC2593867 DOI: 10.1126/science.1156121] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Duane's retraction syndrome (DRS) is a complex congenital eye movement disorder caused by aberrant innervation of the extraocular muscles by axons of brainstem motor neurons. Studying families with a variant form of the disorder (DURS2-DRS), we have identified causative heterozygous missense mutations in CHN1, a gene on chromosome 2q31 that encodes alpha2-chimaerin, a Rac guanosine triphosphatase-activating protein (RacGAP) signaling protein previously implicated in the pathfinding of corticospinal axons in mice. We found that these are gain-of-function mutations that increase alpha2-chimaerin RacGAP activity in vitro. Several of the mutations appeared to enhance alpha2-chimaerin translocation to the cell membrane or enhance its ability to self-associate. Expression of mutant alpha2-chimaerin constructs in chick embryos resulted in failure of oculomotor axons to innervate their target extraocular muscles. We conclude that alpha2-chimaerin has a critical developmental function in ocular motor axon pathfinding.
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Affiliation(s)
- Noriko Miyake
- Department of Medicine (Genetics), Children’s Hospital Boston, Boston, MA 02115, USA
- Harvard Medical School, Boston, MA 02115, USA
| | - John Chilton
- Institute of Biomedical and Clinical Science, Peninsula Medical School, Research Way, Plymouth PL6 8BU, UK
| | - Maria Psatha
- MRC Centre for Developmental Neurobiology, King's College, Guy's Campus, London SE1 1UL, UK
| | - Long Cheng
- Department of Medicine (Genetics), Children’s Hospital Boston, Boston, MA 02115, USA
- Harvard Medical School, Boston, MA 02115, USA
| | - Caroline Andrews
- Department of Medicine (Genetics), Children’s Hospital Boston, Boston, MA 02115, USA
- Department of Neurology, Children’s Hospital Boston, Boston, MA 02115, USA
- Harvard Medical School, Boston, MA 02115, USA
| | - Wai-Man Chan
- Department of Medicine (Genetics), Children’s Hospital Boston, Boston, MA 02115, USA
| | - Krystal Law
- Department of Medicine (Genetics), Children’s Hospital Boston, Boston, MA 02115, USA
| | - Moira Crosier
- MRC-Wellcome Trust Human Developmental Biology Resource (Newcastle), Institute of Human Genetics, Newcastle University, International Centre for Life, Newcastle upon Tyne, NE1 3BZ, UK
| | - Susan Lindsay
- MRC-Wellcome Trust Human Developmental Biology Resource (Newcastle), Institute of Human Genetics, Newcastle University, International Centre for Life, Newcastle upon Tyne, NE1 3BZ, UK
| | - Michelle Cheung
- MRC Centre for Developmental Neurobiology, King's College, Guy's Campus, London SE1 1UL, UK
| | - James Allen
- Institute of Biomedical and Clinical Science, Peninsula Medical School, Research Way, Plymouth PL6 8BU, UK
| | - Nick J Gutowski
- Department of Neurology, Royal Devon and Exeter Hospital, Barrack Road, Exeter, Devon, EX2 5DW, UK
- Peninsula Medical School, Barrack Road, Exeter EX2 5DW, UK
| | - Sian Ellard
- Department of Molecular Genetics, Royal Devon and Exeter Hospital, Barrack Road, Exeter, Devon, EX2 5DW, UK
- Peninsula Medical School, Barrack Road, Exeter EX2 5DW, UK
| | | | - Alessandro Iannaccone
- University of Tennessee Health Science Center, Hamilton Eye Institute, 930 Madison Avenue, Suite 731, Memphis, TN 38163, USA
| | - Binoy Appukuttan
- Casey Eye Institute, Oregon Health and Science University, 3375 SW Terwilliger Blvd, Portland, OR 97239, USA
| | - J. Timothy Stout
- Casey Eye Institute, Oregon Health and Science University, 3375 SW Terwilliger Blvd, Portland, OR 97239, USA
| | - Stephen Christiansen
- Department of Ophthalmology, University of Minnesota, MMC 493, 420 Delaware St, SE, Minneapolis, MN 55455-0501, USA
| | | | - Alfonso Baldi
- Department of Biochemistry 'F. Cedrangolo', Section of Pathologic Anatomy, Second University of Naples, Naples, Italy
| | - Mara Campioni
- Department of Biochemistry 'F. Cedrangolo', Section of Pathologic Anatomy, Second University of Naples, Naples, Italy
| | - Juan C. Zenteno
- Department of Genetics and Research Unit, Institute of Ophthalmology “Conde de Valenciana”, Mexico City, Mexico
| | - Dominic Davenport
- MRC Centre for Developmental Neurobiology, King's College, Guy's Campus, London SE1 1UL, UK
| | - Laura E. Mariani
- Department of Neurology, Children’s Hospital Boston, Boston, MA 02115, USA
| | - Mustafa Sahin
- Department of Neurology, Children’s Hospital Boston, Boston, MA 02115, USA
- Harvard Medical School, Boston, MA 02115, USA
| | - Sarah Guthrie
- MRC Centre for Developmental Neurobiology, King's College, Guy's Campus, London SE1 1UL, UK
| | - Elizabeth C. Engle
- Department of Medicine (Genetics), Children’s Hospital Boston, Boston, MA 02115, USA
- Department of Neurology, Children’s Hospital Boston, Boston, MA 02115, USA
- Department of Ophthalmology, Children’s Hospital Boston, Boston, MA 02115, USA
- Harvard Medical School, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
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38
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Beg AA, Sommer JE, Martin JH, Scheiffele P. alpha2-Chimaerin is an essential EphA4 effector in the assembly of neuronal locomotor circuits. Neuron 2007; 55:768-78. [PMID: 17785183 DOI: 10.1016/j.neuron.2007.07.036] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 07/23/2007] [Accepted: 07/31/2007] [Indexed: 10/22/2022]
Abstract
The assembly of neuronal networks during development requires tightly controlled cell-cell interactions. Multiple cell surface receptors that control axon guidance and synapse maturation have been identified. However, the signaling mechanisms downstream of these receptors have remained unclear. Receptor signals might be transmitted through dedicated signaling lines defined by specific effector proteins. Alternatively, a single cell surface receptor might couple to multiple effectors with overlapping functions. We identified the neuronal RacGAP alpha2-chimaerin as an effector for the receptor tyrosine kinase EphA4. alpha2-Chimaerin interacts with activated EphA4 and is required for ephrin-induced growth cone collapse in cortical neurons. alpha2-Chimaerin mutant mice exhibit a rabbit-like hopping gait with synchronous hindlimb movements that phenocopies mice lacking EphA4 kinase activity. Anatomical and functional analyses of corticospinal and spinal interneuron projections reveal that loss of alpha2-chimaerin results in impairment of EphA4 signaling in vivo. These findings identify alpha2-chimaerin as an indispensable effector for EphA4 in cortical and spinal motor circuits.
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Affiliation(s)
- Asim A Beg
- Department of Physiology and Cellular Biophysics, Department of Neuroscience, Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA
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39
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Abstract
In two manuscripts published in Neuron (Beg et al. and Wegmeyer et al.) and one published in Cell (Iwasato et al.), investigators have found that a particular GAP, alpha-chimaerin, is required in vivo for ephrinB3/EphA4-dependent motor circuit formation.
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Affiliation(s)
- Matthew B Dalva
- Department of Neuroscience, University of Pennsylvania Medical Center, Philadelphia, PA 19104, USA.
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40
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Tachikawa K, Sasaki S, Maeda T, Nakajima K. Identification of molecules preferentially expressed beneath the marginal zone in the developing cerebral cortex. Neurosci Res 2007; 60:135-46. [PMID: 18055048 DOI: 10.1016/j.neures.2007.10.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Revised: 10/03/2007] [Accepted: 10/10/2007] [Indexed: 12/17/2022]
Abstract
During cerebral cortical development, the majority of excitatory neurons are born near the ventricle and migrate radially toward the marginal zone (MZ). Since the cells invariably stop migrating beneath the MZ, neurons are aligned in an "inside-out" manner in the cortical plate (CP); that is, the early-born and late-born neurons are ultimately positioned in the deep and superficial layers, respectively. Since dramatic morphological changes occur in cells beneath the MZ, several events critical for proper neuronal maturation and layer formation must take place. In this study, we screened for molecules strongly expressed beneath the MZ, and identified 28 genes that are preferentially expressed in the upper half of the mouse CP on both embryonic day (E) 16.5 and E18.5. Expression analyses in reeler and yotari mice, in which neurons terminate migration throughout the CP, suggested that these genes were indeed related to the events beneath the MZ rather than unrelatedly induced by the structures near the brain surface. Pathway analyses suggested calcium signaling to have an important role in cells beneath the MZ. The gene list presented here will be useful for clarifying the molecular mechanisms that control cortical development.
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Affiliation(s)
- Kashiko Tachikawa
- Department of Anatomy, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan
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41
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Iwasato T, Katoh H, Nishimaru H, Ishikawa Y, Inoue H, Saito YM, Ando R, Iwama M, Takahashi R, Negishi M, Itohara S. Rac-GAP alpha-chimerin regulates motor-circuit formation as a key mediator of EphrinB3/EphA4 forward signaling. Cell 2007; 130:742-53. [PMID: 17719550 DOI: 10.1016/j.cell.2007.07.022] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Revised: 05/24/2007] [Accepted: 07/16/2007] [Indexed: 11/16/2022]
Abstract
The ephrin/Eph system plays a central role in neuronal circuit formation; however, its downstream effectors are poorly understood. Here we show that alpha-chimerin Rac GTPase-activating protein mediates ephrinB3/EphA4 forward signaling. We discovered a spontaneous mouse mutation, miffy (mfy), which results in a rabbit-like hopping gait, impaired corticospinal axon guidance, and abnormal spinal central pattern generators. Using positional cloning, transgene rescue, and gene targeting, we demonstrated that loss of alpha-chimerin leads to mfy phenotypes similar to those of EphA4(-/-) and ephrinB3(-/-) mice. alpha-chimerin interacts with EphA4 and, in response to ephrinB3/EphA4 signaling, inactivates Rac, which is a positive regulator of process outgrowth. Moreover, downregulation of alpha-chimerin suppresses ephrinB3-induced growth cone collapse in cultured neurons. Our findings indicate that ephrinB3/EphA4 signaling prevents growth cone extension in motor circuit formation via alpha-chimerin-induced inactivation of Rac. They also highlight the role of a Rho family GTPase-activating protein as a key mediator of ephrin/Eph signaling.
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MESH Headings
- Animals
- Animals, Newborn
- Cells, Cultured
- Cerebral Cortex/cytology
- Chimerin 1/metabolism
- Chromosomes, Mammalian
- Crosses, Genetic
- Ephrin-B3/genetics
- Ephrin-B3/metabolism
- Genes, Recessive
- Genetic Linkage
- Mice
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Mice, Knockout
- Mice, Transgenic
- Molecular Sequence Data
- Motor Activity/genetics
- Mutation
- N-Methylaspartate/pharmacology
- Neurons/cytology
- Neurons/metabolism
- Polymorphism, Single Nucleotide
- Serotonin/pharmacology
- Signal Transduction
- Spinal Cord/drug effects
- rac GTP-Binding Proteins/physiology
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Affiliation(s)
- Takuji Iwasato
- Laboratory for Behavioral Genetics, RIKEN Brain Science Institute (BSI), 2-1 Hirosawa Wako-shi, Saitama 351-0198, Japan
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42
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Willets JM, Nelson CP, Nahorski SR, Challiss RAJ. The regulation of M1 muscarinic acetylcholine receptor desensitization by synaptic activity in cultured hippocampal neurons. J Neurochem 2007; 103:2268-80. [PMID: 17908240 PMCID: PMC2658029 DOI: 10.1111/j.1471-4159.2007.04931.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
To better understand metabotropic/ionotropic integration in neurons we have examined the regulation of M1 muscarinic acetylcholine (mACh) receptor signalling in mature (> 14 days in vitro), synaptically-active hippocampal neurons in culture. Using a protocol where neurons are exposed to an EC(50) concentration of the muscarinic agonist methacholine (MCh) prior to (R1), and following (R2) a desensitizing pulse of a high concentration of this agonist, we have found that the reduction in M(1) mACh receptor responsiveness is decreased in quiescent (+tetrodotoxin) neurons and increased when synaptic activity is enhanced by blocking GABA(A) receptors with picrotoxin. The picrotoxin-mediated effect on M1 mACh receptor responsiveness was completely prevented by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor blockade. Inhibition of endogenous G protein-coupled receptor kinase 2 by transfection with the non-G(q/11)alpha-binding, catalytically-inactive (D110A,K220R)G protein-coupled receptor kinase 2 mutant, decreased the extent of M1 mACh receptor desensitization under all conditions. Pharmacological inhibition of protein kinase C (PKC) activity, or chronic phorbol ester-induced PKC down-regulation had no effect on agonist-mediated receptor desensitization in quiescent or spontaneously synaptically active neurons, but significantly decreased the extent of receptor desensitization in picrotoxin-treated neurons. MCh stimulated the translocation of diacylglycerol- sensitive eGFP-PKCepsilon, but not Ca2+/diacylglycerol-sensitive eGFP-PKCbetaII in both the absence, and presence of tetrodotoxin. Under these conditions, MCh-stimulated eGFP-myristoylated, alanine-rich C kinase substrate translocation was dependent on PKC activity, but not Ca2+/calmodulin. In contrast, picrotoxin-driven translocation of myristoylated, alanine-rich C kinase substrate was accompanied by translocation of PKCbetaII, but not PKCepsilon, and was dependent on PKC and Ca2+/calmodulin. Taken together these data suggest that the level of synaptic activity may determine the different kinases recruited to regulate M1 mACh receptor desensitization in neurons.
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Affiliation(s)
- Jonathon M Willets
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, UK
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Wegmeyer H, Egea J, Rabe N, Gezelius H, Filosa A, Enjin A, Varoqueaux F, Deininger K, Schnütgen F, Brose N, Klein R, Kullander K, Betz A. EphA4-Dependent Axon Guidance Is Mediated by the RacGAP α2-Chimaerin. Neuron 2007; 55:756-67. [PMID: 17785182 DOI: 10.1016/j.neuron.2007.07.038] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Revised: 07/20/2007] [Accepted: 07/30/2007] [Indexed: 01/19/2023]
Abstract
Neuronal network formation in the developing nervous system is dependent on the accurate navigation of nerve cell axons and dendrites, which is controlled by attractive and repulsive guidance cues. Ephrins and their cognate Eph receptors mediate many repulsive axonal guidance decisions by intercellular interactions resulting in growth cone collapse and axon retraction of the Eph-presenting neuron. We show that the Rac-specific GTPase-activating protein alpha2-chimaerin binds activated EphA4 and mediates EphA4-triggered axonal growth cone collapse. alpha-Chimaerin mutant mice display a phenotype similar to that of EphA4 mutant mice, including aberrant midline axon guidance and defective spinal cord central pattern generator activity. Our results reveal an alpha-chimaerin-dependent signaling pathway downstream of EphA4, which is essential for axon guidance decisions and neuronal circuit formation in vivo.
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Affiliation(s)
- Heike Wegmeyer
- Department of Molecular Neurobiology and DFG Center for Molecular Physiology of the Brain, Max Planck Institute of Experimental Medicine, D-37075 Göttingen, Germany
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Ramos B, Gaudillière B, Bonni A, Gill G. Transcription factor Sp4 regulates dendritic patterning during cerebellar maturation. Proc Natl Acad Sci U S A 2007; 104:9882-7. [PMID: 17535924 PMCID: PMC1887555 DOI: 10.1073/pnas.0701946104] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Integration of inputs by a neuron depends on dendritic arborization patterns. In mammals, the genetic programs that regulate dynamic remodeling of dendrites during development and in response to activity are incompletely understood. Here we report that knockdown of the transcription factor Sp4 led to an increased number of highly branched dendrites during maturation of cerebellar granule neurons in dissociated cultures and in cerebellar cortex. Time-course analysis revealed that depletion of Sp4 led to persistent generation of dendritic branches and a failure in resorption of transient dendrites. Depolarization induced a reduction in the number of dendrites, and knockdown of Sp4 blocked depolarization-induced remodeling. Furthermore, overexpression of Sp4 wild type, but not a mutant lacking the DNA-binding domain, was sufficient to promote dendritic pruning in nondepolarizing conditions. These findings indicate that the transcription factor Sp4 controls dendritic patterning during cerebellar development by limiting branch formation and promoting activity-dependent pruning.
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Affiliation(s)
- Belén Ramos
- Department of Pathology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115
| | - Brice Gaudillière
- Department of Pathology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115
| | - Azad Bonni
- Department of Pathology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115
| | - Grace Gill
- Department of Pathology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115
- *To whom correspondence should be addressed. E-mail:
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Yang C, Kazanietz MG. Chimaerins: GAPs that bridge diacylglycerol signalling and the small G-protein Rac. Biochem J 2007; 403:1-12. [PMID: 17346241 DOI: 10.1042/bj20061750] [Citation(s) in RCA: 243] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Chimaerins are the only known RhoGAPs (Rho GTPase-activating proteins) that bind phorbol ester tumour promoters and the lipid second messenger DAG (diacylglycerol), and show specific GAP activity towards the small GTPase Rac. This review summarizes our knowledge of the structure, biochemical and biological properties of chimaerins. Recent findings have established that chimaerins are regulated by tyrosine kinase and GPCRs (G-protein-coupled receptors) via PLC (phospholipase C) activation and DAG generation to promote Rac inactivation. The finding that chimaerins, along with some other proteins, are receptors for DAG changed the prevalent view that PKC (protein kinase C) isoenzymes are the only cellular molecules regulated by DAG. In addition, vigorous recent studies have begun to decipher the critical roles of chimaerins in the central nervous system, development and tumour progression.
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Affiliation(s)
- Chengfeng Yang
- Department of Pharmacology and Institute for Translational Medicine and Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6160, USA.
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Abstract
Almost three decades after the discovery of protein kinase C (PKC), we still have only a partial understanding of how this family of serine/threonine kinases is involved in tumour promotion. PKC isozymes - effectors of diacylglycerol (DAG) and the main targets of phorbol-ester tumour promoters - have important roles in cell-cycle regulation, cellular survival, malignant transformation and apoptosis. How do PKC isozymes regulate these diverse cellular processes and what are their contributions to carcinogenesis? Moreover, what is the contribution of all phorbol-ester effectors, which include PKCs and small G-protein regulators? We now face the challenge of dissecting the relative contribution of each DAG signal to cancer progression.
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Affiliation(s)
- Erin M Griner
- Department of Pharmacology and Institute for Translational Medicine and Therapeutics (ITMAT), University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6160, USA
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Horton AC, Yi JJ, Ehlers MD. Cell type-specific dendritic polarity in the absence of spatially organized external cues. ACTA ACUST UNITED AC 2007; 35:29-38. [DOI: 10.1007/s11068-006-9003-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 09/15/2006] [Accepted: 10/04/2006] [Indexed: 10/23/2022]
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Wang H, Kazanietz MG. The lipid second messenger diacylglycerol as a negative regulator of Rac signalling. Biochem Soc Trans 2007; 34:855-7. [PMID: 17052214 DOI: 10.1042/bst0340855] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have established a novel role for the second messenger DAG (diacylglycerol), a product of PtdIns(4,5)P2 hydrolysis by PLC (phospholipase C). In addition to its well-known function as a protein kinase C activator, DAG produced by stimulation of the epidermal growth factor receptor causes the redistribution of the Rac-GAP (GTPase-activating protein) beta2-chimaerin to the plasma membrane, where it associates with the active form of Rac1 and promotes the inactivation of this small G-protein. This represents the first example of a Rac-GAP regulated directly by DAG in response to the activation of a tyrosine kinase receptor, and suggests a previously unappreciated role for this lipid as a negative modulator of Rac signalling.
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Affiliation(s)
- H Wang
- Department of Pharmacology, University of Pennsylvania School of Medicine, 816 BRB II/III, 421 Curie Blvd, Philadelphia, PA 19104-6160, USA
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Pathways and genes differentially expressed in the motor cortex of patients with sporadic amyotrophic lateral sclerosis. BMC Genomics 2007; 8:26. [PMID: 17244347 PMCID: PMC1796866 DOI: 10.1186/1471-2164-8-26] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2006] [Accepted: 01/23/2007] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Amyotrophic lateral sclerosis (ALS) is a fatal disorder caused by the progressive degeneration of motoneurons in brain and spinal cord. Despite identification of disease-linked mutations, the diversity of processes involved and the ambiguity of their relative importance in ALS pathogenesis still represent a major impediment to disease models as a basis for effective therapies. Moreover, the human motor cortex, although critical to ALS pathology and physiologically altered in most forms of the disease, has not been screened systematically for therapeutic targets. RESULTS By whole-genome expression profiling and stringent significance tests we identify genes and gene groups de-regulated in the motor cortex of patients with sporadic ALS, and interpret the role of individual candidate genes in a framework of differentially expressed pathways. Our findings emphasize the importance of defense responses and cytoskeletal, mitochondrial and proteasomal dysfunction, reflect reduced neuronal maintenance and vesicle trafficking, and implicate impaired ion homeostasis and glycolysis in ALS pathogenesis. Additionally, we compared our dataset with publicly available data for the SALS spinal cord, and show a high correlation of changes linked to the diseased state in the SALS motor cortex. In an analogous comparison with data for the Alzheimer's disease hippocampus we demonstrate a low correlation of global changes and a moderate correlation for changes specifically linked to the SALS diseased state. CONCLUSION Gene and sample numbers investigated allow pathway- and gene-based analyses by established error-correction methods, drawing a molecular portrait of the ALS motor cortex that faithfully represents many known disease features and uncovers several novel aspects of ALS pathology. Contrary to expectations for a tissue under oxidative stress, nuclear-encoded mitochondrial genes are uniformly down-regulated. Moreover, the down-regulation of mitochondrial and glycolytic genes implies a combined reduction of mitochondrial and cytoplasmic energy supply, with a possible role in the death of ALS motoneurons. Identifying candidate genes exclusively expressed in non-neuronal cells, we also highlight the importance of these cells in disease development in the motor cortex. Notably, some pathways and candidate genes identified by this study are direct or indirect targets of medication already applied to unrelated illnesses and point the way towards the rapid development of effective symptomatic ALS therapies.
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Haas K, Li J, Cline HT. AMPA receptors regulate experience-dependent dendritic arbor growth in vivo. Proc Natl Acad Sci U S A 2006; 103:12127-31. [PMID: 16882725 PMCID: PMC1525049 DOI: 10.1073/pnas.0602670103] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The size and shape of neuronal dendritic arbors affect the number and type of synaptic inputs, as well as the complexity and function of brain circuits. In the intact brain, dendritic arbor growth and the development of excitatory glutamatergic synapse are concurrent. Consequently, it has been difficult to resolve whether synaptic inputs drive dendritic arbor development. Here, we test the role of AMPA receptor (AMPAR)-mediated glutamatergic transmission in dendrite growth by expressing peptides corresponding to the intracellular C-terminal domains of AMPAR subunits GluR1 (GluR1Ct) and GluR2 (GluR2Ct) in optic tectal neurons of the Xenopus retinotectal system. These peptides significantly reduce AMPAR synaptic transmission in transfected neurons while leaving visual system circuitry intact. Daily in vivo imaging over 5 days revealed that GluR1Ct or GluR2Ct expression dramatically impaired dendrite growth, resulting in less complex arbors than controls. Time-lapse images collected at 2-h intervals over 6 h show that both GluR1Ct and GluR2Ct decrease branch lifetimes. Ultrastructural analysis indicates that synapses formed onto neurons expressing the GluRCt are less mature than synapses onto control neurons. These data suggest that the failure to form complex arbors is due to reduced stabilization of new synapses and dendritic branches. Although visual stimulation increases dendritic arbor growth rates in control tectal neurons, a weak postsynaptic response to visual experience in GluRCt-expressing cells leads to retraction of branches. These results indicate that AMPAR-mediated transmission underlies experience-dependent dendritic arbor growth by stabilizing branches, and support a competition-based model for dendrite growth.
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Affiliation(s)
- Kurt Haas
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724
| | - Jianli Li
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724
| | - Hollis T. Cline
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724
- To whom correspondence should be addressed. E-mail:
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