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Cabrera OH, Useinovic N, Maksimovic S, Near M, Quillinan N, Todorovic SM, Jevtovic-Todorovic V. Neonatal ketamine exposure impairs infrapyramidal bundle pruning and causes lasting increase in excitatory synaptic transmission in hippocampal CA3 neurons. Neurobiol Dis 2022; 175:105923. [PMID: 36371060 PMCID: PMC9831613 DOI: 10.1016/j.nbd.2022.105923] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 10/27/2022] [Accepted: 11/07/2022] [Indexed: 11/11/2022] Open
Abstract
Preclinical models demonstrate that nearly all anesthetics cause widespread neuroapoptosis in the developing brains of infant rodents and non-human primates. Anesthesia-induced developmental apoptosis is succeeded by prolonged neuropathology in the surviving neurons and lasting cognitive impairments, suggesting that anesthetics interfere with the normal developmental trajectory of the brain. However, little is known about effects of anesthetics on stereotyped axonal pruning, an important developmental algorithm that sculpts neural circuits for proper function. Here, we proposed that neonatal ketamine exposure may interfere with stereotyped axonal pruning of the infrapyramidal bundle (IPB) of the hippocampal mossy fiber system and that impaired pruning may be associated with alterations in the synaptic transmission of CA3 neurons. To test this hypothesis, we injected postnatal day 7 (PND7) mouse pups with ketamine or vehicle over 6 h and then studied them at different developmental stages corresponding to IPB pruning (PND20-40). Immunohistochemistry with synaptoporin (a marker of mossy fibers) revealed that in juvenile mice treated with ketamine at PND7, but not in vehicle-treated controls, positive IPB fibers extended farther into the stratum pyramidale of CA3 region. Furthermore, immunofluorescent double labeling for synaptoporin and PSD-95 strongly suggested that the unpruned IPB caused by neonatal ketamine exposure makes functional synapses. Importantly, patch-clamp electrophysiology for miniature excitatory postsynaptic currents (mEPSCs) in acute brain slices ex vivo revealed increased frequency and amplitudes of mEPSCs in hippocampal CA3 neurons in ketamine-treated groups when compared to vehicle controls. We conclude that neonatal ketamine exposure interferes with normal neural circuit development and that this interference leads to lasting increase in excitatory synaptic transmission in hippocampus.
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Affiliation(s)
- Omar Hoseá Cabrera
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA
| | - Nemanja Useinovic
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA
| | - Stefan Maksimovic
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA
| | - Michelle Near
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA
| | - Nidia Quillinan
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA,University of Colorado School of Medicine at Anschutz Medical Campus, Neuroscience Graduate Program, Aurora, CO, USA
| | - Slobodan M. Todorovic
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA,University of Colorado School of Medicine at Anschutz Medical Campus, Neuroscience Graduate Program, Aurora, CO, USA
| | - Vesna Jevtovic-Todorovic
- University of Colorado School of Medicine at Anschutz Medical Campus, Department of Anesthesiology, Aurora, CO, USA,University of Colorado School of Medicine at Anschutz Medical Campus, Department of Pharmacology, Aurora, CO, USA,Corresponding author. (V. Jevtovic-Todorovic)
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2
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Nakanishi Y, Akinaga S, Osawa K, Suzuki N, Sugeno A, Kolattukudy P, Goshima Y, Ohshima T. Regulation of axon pruning of mossy fiber projection in hippocampus by CRMP2 and CRMP4. Dev Neurobiol 2021; 82:138-146. [PMID: 34932871 DOI: 10.1002/dneu.22865] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 12/09/2021] [Accepted: 12/10/2021] [Indexed: 12/20/2022]
Abstract
Axon pruning facilitates the removal of ectopic and misguided axons and plays an important role in neural circuit formation during brain development. Sema3F and its receptor neuropilin-2 (Nrp2) have been shown to be involved in the stereotyped pruning of the infrapyramidal bundle (IPB) of mossy fibers of the dentate gyrus (DG) in the developing hippocampus. Collapsin response mediator proteins (CRMPs) were originally identified as an intracellular mediator of semaphorin signaling, and the defective pruning of IPB was recently reported in CRMP2-/- and CRMP3-/- mice. CRMP1 and CRMP4 have high homology to CRMP2 and CRMP3, and their expression in the developing mouse brain overlaps; however, their role in IPB pruning has not yet been examined. In this study, we report that CRMP4, but not CRMP1, is involved in IPB pruning during neural circuit formation in the hippocampus. Our genetic interaction analyses indicated that CRMP2 and CRMP4 have distinct functions and that CRMP2 mediates IPB pruning via Nrp2. We also observed the altered synaptic terminals of mossy fibers in CRMP2 and CRMP4 mutant mice. These results suggest that CRMP family members have a distinct function in the axon pruning and targeting of mossy fibers of the hippocampal DG in the developing mouse brain.
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Affiliation(s)
- Yurika Nakanishi
- Department of Life Science and Medical Bio-Science, Waseda University, Tokyo, Japan
| | - Satoshi Akinaga
- Department of Life Science and Medical Bio-Science, Waseda University, Tokyo, Japan
| | - Koki Osawa
- Department of Life Science and Medical Bio-Science, Waseda University, Tokyo, Japan
| | - Natusmi Suzuki
- Department of Life Science and Medical Bio-Science, Waseda University, Tokyo, Japan
| | - Ayaka Sugeno
- Department of Life Science and Medical Bio-Science, Waseda University, Tokyo, Japan
| | | | - Yoshio Goshima
- Department of Molecular Pharmacology and Neurobiology, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Toshio Ohshima
- Department of Life Science and Medical Bio-Science, Waseda University, Tokyo, Japan
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3
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An activity-dependent determinant of synapse elimination in the mammalian brain. Neuron 2021; 109:1333-1349.e6. [PMID: 33770504 DOI: 10.1016/j.neuron.2021.03.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/26/2021] [Accepted: 03/04/2021] [Indexed: 01/06/2023]
Abstract
To establish functional neural circuits in the brain, synaptic connections are refined by neural activity during development, where active connections are maintained and inactive ones are eliminated. However, the molecular signals that regulate synapse refinement remain to be elucidated. When we inactivate a subset of neurons in the mouse cingulate cortex, their callosal connections are eliminated through activity-dependent competition. Using this system, we identify JAK2 tyrosine kinase as a key regulator of inactive synapse elimination. We show that JAK2 is necessary and sufficient for elimination of inactive connections; JAK2 is activated at inactive synapses in response to signals from other active synapses; STAT1, a substrate of JAK2, mediates inactive synapse elimination; JAK2 signaling is critical for physiological refinement of synapses during normal development; and JAK2 regulates synapse refinement in multiple brain regions. We propose that JAK2 is an activity-dependent switch that serves as a determinant of inactive synapse elimination.
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4
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Chowdhury D, Watters K, Biederer T. Synaptic recognition molecules in development and disease. Curr Top Dev Biol 2021; 142:319-370. [PMID: 33706921 DOI: 10.1016/bs.ctdb.2020.12.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Synaptic connectivity patterns underlie brain functions. How recognition molecules control where and when neurons form synapses with each other, therefore, is a fundamental question of cellular neuroscience. This chapter delineates adhesion and signaling complexes as well as secreted factors that contribute to synaptic partner recognition in the vertebrate brain. The sections follow a developmental perspective and discuss how recognition molecules (1) guide initial synaptic wiring, (2) provide for the rejection of incorrect partner choices, (3) contribute to synapse specification, and (4) support the removal of inappropriate synapses once formed. These processes involve a rich repertoire of molecular players and key protein families are described, notably the Cadherin and immunoglobulin superfamilies, Semaphorins/Plexins, Leucine-rich repeat containing proteins, and Neurexins and their binding partners. Molecular themes that diversify these recognition systems are defined and highlighted throughout the text, including the neuron-type specific expression and combinatorial action of recognition factors, alternative splicing, and post-translational modifications. Methodological innovations advancing the field such as proteomic approaches and single cell expression studies are additionally described. Further, the chapter highlights the importance of choosing an appropriate brain region to analyze synaptic recognition factors and the advantages offered by laminated structures like the hippocampus or retina. In a concluding section, the profound disease relevance of aberrant synaptic recognition for neurodevelopmental and psychiatric disorders is discussed. Based on the current progress, an outlook is presented on research goals that can further advance insights into how recognition molecules provide for the astounding precision and diversity of synaptic connections.
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Affiliation(s)
| | - Katherine Watters
- Department of Neurology, Yale School of Medicine, New Haven, CT, United States; Neuroscience Graduate Program, Tufts University School of Medicine, Boston, MA, United States
| | - Thomas Biederer
- Department of Neurology, Yale School of Medicine, New Haven, CT, United States.
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5
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Furusawa K, Emoto K. Scrap and Build for Functional Neural Circuits: Spatiotemporal Regulation of Dendrite Degeneration and Regeneration in Neural Development and Disease. Front Cell Neurosci 2021; 14:613320. [PMID: 33505249 PMCID: PMC7829185 DOI: 10.3389/fncel.2020.613320] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 12/04/2020] [Indexed: 01/01/2023] Open
Abstract
Dendrites are cellular structures essential for the integration of neuronal information. These elegant but complex structures are highly patterned across the nervous system but vary tremendously in their size and fine architecture, each designed to best serve specific computations within their networks. Recent in vivo imaging studies reveal that the development of mature dendrite arbors in many cases involves extensive remodeling achieved through a precisely orchestrated interplay of growth, degeneration, and regeneration of dendritic branches. Both degeneration and regeneration of dendritic branches involve precise spatiotemporal regulation for the proper wiring of functional networks. In particular, dendrite degeneration must be targeted in a compartmentalized manner to avoid neuronal death. Dysregulation of these developmental processes, in particular dendrite degeneration, is associated with certain types of pathology, injury, and aging. In this article, we review recent progress in our understanding of dendrite degeneration and regeneration, focusing on molecular and cellular mechanisms underlying spatiotemporal control of dendrite remodeling in neural development. We further discuss how developmental dendrite degeneration and regeneration are molecularly and functionally related to dendrite remodeling in pathology, disease, and aging.
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Affiliation(s)
- Kotaro Furusawa
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Kazuo Emoto
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.,International Research Center for Neurointelligence (WPI-IRCN), The University of Tokyo, Tokyo, Japan
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6
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Mathews E, Dewees K, Diaz D, Favero C. White matter abnormalities in fetal alcohol spectrum disorders: Focus on axon growth and guidance. Exp Biol Med (Maywood) 2021; 246:812-821. [PMID: 33423552 DOI: 10.1177/1535370220980398] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Fetal Alcohol Spectrum Disorders (FASDs) describe a range of deficits, affecting physical, mental, cognitive, and behavioral function, arising from prenatal alcohol exposure. FASD causes widespread white matter abnormalities, with significant alterations of tracts in the cerebral cortex, cerebellum, and hippocampus. These brain regions present with white-matter volume reductions, particularly at the midline. Neural pathways herein are guided primarily by three guidance cue families: Semaphorin/Neuropilin, Netrin/DCC, and Slit/Robo. These guidance cue/receptor pairs attract and repulse axons and ensure that they reach the proper target to make functional connections. In several cases, these signals cooperate with each other and/or additional molecular partners. Effects of alcohol on guidance cue mechanisms and their associated effectors include inhibition of growth cone response to repellant cues as well as changes in gene expression. Relevant to the corpus callosum, specifically, developmental alcohol exposure alters GABAergic and glutamatergic cell populations and glial cells that serve as guidepost cells for callosal axons. In many cases, deficits seen in FASD mirror aberrancies in guidance cue/receptor signaling. We present evidence for the need for further study on how prenatal alcohol exposure affects the formation of neural connections which may underlie disrupted functional connectivity in FASD.
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Affiliation(s)
- Erin Mathews
- Biology Department, Ursinus College, Collegeville, PA 19426-1000, USA
| | - Kevyn Dewees
- Biology Department, Ursinus College, Collegeville, PA 19426-1000, USA
| | - Deborah Diaz
- Biology Department, Ursinus College, Collegeville, PA 19426-1000, USA
| | - Carlita Favero
- Biology Department, Ursinus College, Collegeville, PA 19426-1000, USA
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7
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Ahammad I. A comprehensive review of tumor proliferative and suppressive role of semaphorins and therapeutic approaches. Biophys Rev 2020; 12:1233-1247. [PMID: 32577918 PMCID: PMC7575654 DOI: 10.1007/s12551-020-00709-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 06/15/2020] [Indexed: 01/05/2023] Open
Abstract
Semaphorins have been traditionally known as axon guidance proteins that negatively regulate axonal growth. However, in the past couple of decades, their versatile role in so many other biological processes has come to prominence as well. One such example is their role in cancer. In this review article, the focus was on the tumor proliferative and tumor suppressive role of all 20 semaphorin family members under the 7 semaphorin classes found in vertebrates and invertebrates as well as the ongoing and emerging therapeutic approaches to combat semaphorin-mediated cancers. Except sema6C, 19 of the 20 non-viral semaphorin family members have been discovered to be associated with cancer in one way or another. Eleven semaphorin family members have been discovered to be tumor proliferative and 8 to be tumor suppressive. Six therapeutic avenues and their safety profiles have been discussed which are currently at use or at the various stages of development. Finally, perspectives on which approach is the best for treating cancers associated with semaphorins have been given.
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Affiliation(s)
- Ishtiaque Ahammad
- Department of Biochemistry and Microbiology, North South University, Dhaka, 1229, Bangladesh.
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8
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Rudnitskaya EA, Kozlova TA, Burnyasheva AO, Tarasova AE, Pankova TM, Starostina MV, Stefanova NA, Kolosova NG. Features of Postnatal Hippocampal Development in a Rat Model of Sporadic Alzheimer's Disease. Front Neurosci 2020; 14:533. [PMID: 32581685 PMCID: PMC7289999 DOI: 10.3389/fnins.2020.00533] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 04/29/2020] [Indexed: 12/26/2022] Open
Abstract
Aging is the major risk factor of the most common (∼95% of cases) sporadic Alzheimer’s disease (AD). Accumulating data indicate middle age as a critical period for the relevant pathological processes, however, the question of when AD starts to develop remains open. It has been reported only recently that in the early postnatal period—when brain development is completing—preconditions for a decrease in cognitive abilities and for accelerated aging can form. Here, we hypothesized that specific features of early postnatal brain development may be considered some of the prerequisites of AD development at an advanced age. To test this hypothesis, we used OXYS rats, which are a suitable model of sporadic AD. The duration of gestation, litter size, and weight at birth were lower in OXYS rats compared to control Wistar rats. The shortened duration of gestation may result in developmental retardation. Indeed, we noted decreased locomotor activity and increased anxiety in OXYS rats already at a young age: possible signs of altered brain development. We demonstrated retardation of the peak of postnatal neurogenesis in the hippocampal dentate gyrus of OXYS rats. Delayed neuronal maturation led to alterations of mossy-fiber formation: a shortened suprapyramidal bundle and longer infrapyramidal bundle, less pronounced fasciculation of granule cells’ axons, and smaller size and irregular shape of nuclei in the CA3 pyramidal layer. These changes were accompanied by altered astrocytic migration. The observed features of early development may be considered some of the risk factors of the AD-like pathology that manifests itself in OXYS rats late in life.
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Affiliation(s)
- Ekaterina A Rudnitskaya
- Laboratory of Molecular Mechanisms of Aging, The Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences (SB RAS), Novosibirsk, Russia
| | - Tatiana A Kozlova
- Laboratory of Molecular Mechanisms of Aging, The Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences (SB RAS), Novosibirsk, Russia
| | - Alena O Burnyasheva
- Laboratory of Molecular Mechanisms of Aging, The Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences (SB RAS), Novosibirsk, Russia
| | - Anna E Tarasova
- Laboratory of Central Mechanisms of Regulation, Institute of Molecular Biology and Biophysics, Federal Research Center of Fundamental and Translational Medicine, Novosibirsk, Russia
| | - Tatiana M Pankova
- Laboratory of Central Mechanisms of Regulation, Institute of Molecular Biology and Biophysics, Federal Research Center of Fundamental and Translational Medicine, Novosibirsk, Russia
| | - Marina V Starostina
- Laboratory of Central Mechanisms of Regulation, Institute of Molecular Biology and Biophysics, Federal Research Center of Fundamental and Translational Medicine, Novosibirsk, Russia
| | - Natalia A Stefanova
- Laboratory of Molecular Mechanisms of Aging, The Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences (SB RAS), Novosibirsk, Russia
| | - Nataliya G Kolosova
- Laboratory of Molecular Mechanisms of Aging, The Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences (SB RAS), Novosibirsk, Russia
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9
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McHail DG, Dumas TC. Hippocampal gamma rhythms during Y‐maze navigation in the juvenile rat. Hippocampus 2020; 30:505-525. [DOI: 10.1002/hipo.23168] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 09/01/2019] [Accepted: 09/17/2019] [Indexed: 12/20/2022]
Affiliation(s)
- Daniel G. McHail
- Interdisciplinary Program in NeuroscienceGeorge Mason University Fairfax Virginia
| | - Theodore C. Dumas
- Interdisciplinary Program in NeuroscienceGeorge Mason University Fairfax Virginia
- Psychology DepartmentGeorge Mason University Fairfax Virginia
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10
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Ziak J, Weissova R, Jeřábková K, Janikova M, Maimon R, Petrasek T, Pukajova B, Kleisnerova M, Wang M, Brill MS, Kasparek P, Zhou X, Alvarez-Bolado G, Sedlacek R, Misgeld T, Stuchlik A, Perlson E, Balastik M. CRMP2 mediates Sema3F-dependent axon pruning and dendritic spine remodeling. EMBO Rep 2020; 21:e48512. [PMID: 31919978 DOI: 10.15252/embr.201948512] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 12/11/2019] [Accepted: 12/12/2019] [Indexed: 11/09/2022] Open
Abstract
Regulation of axon guidance and pruning of inappropriate synapses by class 3 semaphorins are key to the development of neural circuits. Collapsin response mediator protein 2 (CRMP2) has been shown to regulate axon guidance by mediating semaphorin 3A (Sema3A) signaling; however, nothing is known about its role in synapse pruning. Here, using newly generated crmp2-/- mice we demonstrate that CRMP2 has a moderate effect on Sema3A-dependent axon guidance in vivo, and its deficiency leads to a mild defect in axon guidance in peripheral nerves and the corpus callosum. Surprisingly, crmp2-/- mice display prominent defects in stereotyped axon pruning in hippocampus and visual cortex and altered dendritic spine remodeling, which is consistent with impaired Sema3F signaling and with models of autism spectrum disorder (ASD). We demonstrate that CRMP2 mediates Sema3F signaling in primary neurons and that crmp2-/- mice display ASD-related social behavior changes in the early postnatal period as well as in adults. Together, we demonstrate that CRMP2 mediates Sema3F-dependent synapse pruning and its dysfunction shares histological and behavioral features of ASD.
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Affiliation(s)
- Jakub Ziak
- Department of Molecular Neurobiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic.,Faculty of Science, Charles University in Prague, Prague, Czech Republic
| | - Romana Weissova
- Department of Molecular Neurobiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic.,Faculty of Science, Charles University in Prague, Prague, Czech Republic
| | - Kateřina Jeřábková
- Department of Transgenic Models of Diseases and Czech Centre for Phenogenomics, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martina Janikova
- Department of Neurophysiology of the Memory, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Roy Maimon
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Tomas Petrasek
- Department of Neurophysiology of the Memory, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Barbora Pukajova
- Department of Molecular Neurobiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic.,Faculty of Science, Charles University in Prague, Prague, Czech Republic
| | - Marie Kleisnerova
- Department of Molecular Neurobiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Mengzhe Wang
- Institute of Neuronal Cell Biology, Technical University Munich, Munich, Germany
| | - Monika S Brill
- Institute of Neuronal Cell Biology, Technical University Munich, Munich, Germany
| | - Petr Kasparek
- Department of Transgenic Models of Diseases and Czech Centre for Phenogenomics, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
| | - Xunlei Zhou
- Institute of Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
| | | | - Radislav Sedlacek
- Department of Transgenic Models of Diseases and Czech Centre for Phenogenomics, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
| | - Thomas Misgeld
- Institute of Neuronal Cell Biology, Technical University Munich, Munich, Germany.,German Center for Neurodegenerative Diseases and Munich Cluster for Systems Neurology, Munich, Germany
| | - Ales Stuchlik
- Department of Neurophysiology of the Memory, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Eran Perlson
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Martin Balastik
- Department of Molecular Neurobiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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11
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Li Z, Jagadapillai R, Gozal E, Barnes G. Deletion of Semaphorin 3F in Interneurons Is Associated with Decreased GABAergic Neurons, Autism-like Behavior, and Increased Oxidative Stress Cascades. Mol Neurobiol 2019; 56:5520-5538. [PMID: 30635860 PMCID: PMC6614133 DOI: 10.1007/s12035-018-1450-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 12/07/2018] [Indexed: 12/11/2022]
Abstract
Autism and epilepsy are diseases which have complex genetic inheritance. Genome-wide association and other genetic studies have implicated at least 500+ genes associated with the occurrence of autism spectrum disorders (ASD) including the human semaphorin 3F (Sema 3F) and neuropilin 2 (NRP2) genes. However, the genetic basis of the comorbid occurrence of autism and epilepsy is unknown. The aberrant development of GABAergic circuitry is a possible risk factor in autism and epilepsy. Molecular biological approaches were used to test the hypothesis that cell-specific genetic variation in mouse homologs affects the formation and function of GABAergic circuitry. The empirical analysis with mice homozygous null for one of these genes, Sema 3F, in GABAergic neurons substantiated these predictions. Notably, deletion of Sema 3F in interneurons but not excitatory neurons during early development decreased the number of interneurons/neurites and mRNAs for cell-specific GABAergic markers and increased epileptogenesis and autistic behaviors. Studies of interneuron cell-specific knockout of Sema 3F signaling suggest that deficient Sema 3F signaling may lead to neuroinflammation and oxidative stress. Further studies of mouse KO models of ASD genes such as Sema 3F or NRP2 may be informative to clinical phenotypes contributing to the pathogenesis in autism and epilepsy patients.
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Affiliation(s)
- Zhu Li
- Department of Neurology, Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Rekha Jagadapillai
- Department of Pediatrics, University of Louisville School of Medicine, Louisville, KY, USA
| | - Evelyne Gozal
- Department of Pediatrics, University of Louisville School of Medicine, Louisville, KY, USA
| | - Gregory Barnes
- Department of Pediatrics, University of Louisville School of Medicine, Louisville, KY, USA.
- Department of Neurology, University of Louisville School of Medicine, Louisville, KY, USA.
- Pediatric Research Institute, University of Louisville Autism Center, 1405 East Burnett Ave, Louisville, KY, 40217, USA.
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12
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Abstract
Mounting evidence suggests that prolonged exposure to general anesthesia (GA) during brain synaptogenesis damages the immature neurons and results in long-term neurocognitive impairments. Importantly, synaptogenesis relies on timely axon pruning to select axons that participate in active neural circuit formation. This process is in part dependent on proper homeostasis of neurotrophic factors, in particular brain-derived neurotrophic factor (BDNF). We set out to examine how GA may modulate axon maintenance and pruning and focused on the role of BDNF. We exposed post-natal day (PND)7 mice to ketamine using a well-established dosing regimen known to induce significant developmental neurotoxicity. We performed morphometric analyses of the infrapyramidal bundle (IPB) since IPB is known to undergo intense developmental modeling and as such is commonly used as a well-established model of in vivo pruning in rodents. When IPB remodeling was followed from PND10 until PND65, we noted a delay in axonal pruning in ketamine-treated animals when compared to controls; this impairment coincided with ketamine-induced downregulation in BDNF protein expression and maturation suggesting two conclusions: a surge in BDNF protein expression "signals" intense IPB pruning in control animals and ketamine-induced downregulation of BDNF synthesis and maturation could contribute to impaired IPB pruning. We conclude that the combined effects on BDNF homeostasis and impaired axon pruning may in part explain ketamine-induced impairment of neuronal circuitry formation.
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13
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Sapar ML, Han C. Die in pieces: How Drosophila sheds light on neurite degeneration and clearance. J Genet Genomics 2019; 46:187-199. [PMID: 31080046 PMCID: PMC6541534 DOI: 10.1016/j.jgg.2019.03.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 03/24/2019] [Accepted: 03/26/2019] [Indexed: 01/08/2023]
Abstract
Dendrites and axons are delicate neuronal membrane extensions that undergo degeneration after physical injuries. In neurodegenerative diseases, they often degenerate prior to neuronal death. Understanding the mechanisms of neurite degeneration has been an intense focus of neurobiology research in the last two decades. As a result, many discoveries have been made in the molecular pathways that lead to neurite degeneration and the cell-cell interactions responsible for the subsequent clearance of neuronal debris. Drosophila melanogaster has served as a prime in vivo model system for identifying and characterizing the key molecular players in neurite degeneration, thanks to its genetic tractability and easy access to its nervous system. The knowledge learned in the fly provided targets and fuel for studies in other model systems that have further enhanced our understanding of neurodegeneration. In this review, we will introduce the experimental systems developed in Drosophila to investigate injury-induced neurite degeneration, and then discuss the biological pathways that drive degeneration. We will also cover what is known about the mechanisms of how phagocytes recognize and clear degenerating neurites, and how recent findings in this area enhance our understanding of neurodegenerative disease pathology.
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Affiliation(s)
- Maria L Sapar
- Weill Institute for Cell and Molecular Biology, Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA
| | - Chun Han
- Weill Institute for Cell and Molecular Biology, Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14853, USA.
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14
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Bragina L, Conti F. Expression of Neurofilament Subunits at Neocortical Glutamatergic and GABAergic Synapses. Front Neuroanat 2018; 12:74. [PMID: 30254572 PMCID: PMC6141662 DOI: 10.3389/fnana.2018.00074] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 08/27/2018] [Indexed: 11/29/2022] Open
Abstract
Neurofilaments (NFs) are neuron-specific heteropolymers that have long been considered as structural proteins. However, it has recently been documented that they may play a functional role at synapses. Indeed, the four NF subunits—NFL, NFM, NFH and α-internexin—are integral components of synapses in the striatum and hippocampus, since their elimination disrupts synaptic plasticity and impairs social memory, an observation that might have important implications for some neuropsychiatric diseases. Here, we studied NFs localization in VGLUT1-, VGLUT2-, VGAT-, PSD-95- and gephyrin-positive (+) puncta, and in glutamatergic and GABAergic synapses in the cerebral cortex of adult rats. Synapses were identified by pre- and postsynaptic markers: glutamatergic synapses by VGLUT1+ or VGLUT2+ puncta contacting PSD-95+ puncta; and GABAergic synapses by VGAT+ puncta contacting gephyrin+ puncta. In VGLUT1 glutamatergic synapses NF showed a greater expression in the compartment labeled by postsynaptic markers (20%–30%) than in those labeled by presynaptic markers (10%–20%), whereas in GABAergic synapses a similar expression was detected in both compartments (20%–30%). Moreover, NF expression was higher in the GABAergic (20%–30%) than in the glutamatergic (10%–15%) compartments labeled by presynaptic markers. Finally, a higher colocalization of VGLUT1+, VGLUT2+ and VGAT+ puncta with NFs was seen when presynaptic puncta contacted elements labeled by postsynaptic markers. These findings show that the four NF subunits are expressed at some neocortical synapses, and contribute to glutamatergic and GABAergic synapse heterogeneity.
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Affiliation(s)
- Luca Bragina
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, Italy.,Center for Neurobiology of Aging, IRCCS INRCA, Ancona, Italy
| | - Fiorenzo Conti
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, Italy.,Center for Neurobiology of Aging, IRCCS INRCA, Ancona, Italy
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15
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Tawarayama H, Yamada H, Shinmyo Y, Tanaka H, Ikawa S. The chemorepellent draxin is involved in hippocampal mossy fiber projection. Biochem Biophys Res Commun 2018; 500:217-223. [PMID: 29634927 DOI: 10.1016/j.bbrc.2018.04.043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 04/06/2018] [Indexed: 02/05/2023]
Abstract
Lamina-specific afferent innervation of the mammalian hippocampus is critical for its function. We investigated the relevance of the chemorepellent draxin to the laminar projections of three principal hippocampal afferents: mossy fibers, entorhinal, and associational/commissural fibers. We observed that draxin deficiency led to abnormal projection of mossy fibers but not other afferents. Immunohistochemical analysis indicated that draxin is expressed in the dentate gyrus and cornu ammonis (CA) 3 at postnatal day 0, when dentate granule cells begin to extend mossy fibers towards CA3. Furthermore, a neurite growth assay using dissociated cells of the neonatal dentate gyrus revealed that draxin inhibited the growth of calbindin-D28k-expressing mossy fibers in vitro. Taken together, we conclude that draxin is a key molecule in the regulation of mossy fiber projections.
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Affiliation(s)
- Hiroshi Tawarayama
- Department of Developmental Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan; Department of Project Programs, Institute of Development, Aging and Cancer (IDAC), Tohoku University, Sendai 980-8575, Japan; Department of Ecology and Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan.
| | - Hirohisa Yamada
- Department of Developmental Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Yohei Shinmyo
- Department of Developmental Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Hideaki Tanaka
- Department of Developmental Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Shuntaro Ikawa
- Department of Project Programs, Institute of Development, Aging and Cancer (IDAC), Tohoku University, Sendai 980-8575, Japan
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16
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Hippocampal Pathophysiology: Commonality Shared by Temporal Lobe Epilepsy and Psychiatric Disorders. NEUROSCIENCE JOURNAL 2018; 2018:4852359. [PMID: 29610762 PMCID: PMC5828345 DOI: 10.1155/2018/4852359] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 12/02/2017] [Accepted: 12/20/2017] [Indexed: 11/18/2022]
Abstract
Accumulating evidence points to the association of epilepsy, particularly, temporal lobe epilepsy (TLE), with psychiatric disorders, such as schizophrenia. Among these illnesses, the hippocampus is considered the regional focal point of the brain, playing an important role in cognition, psychosis, and seizure activity and potentially suggesting common etiologies and pathophysiology of TLE and schizophrenia. In the present review, we overview abnormal network connectivity between the dentate gyrus (DG) and the Cornus Ammonis area 3 (CA3) subregions of the hippocampus relative to the induction of epilepsy and schizophrenia. In light of our recent finding on the misguidance of hippocampal mossy fiber projection in the rodent model of schizophrenia, we discuss whether ectopic mossy fiber projection is a commonality in order to evoke TLE as well as symptoms related to schizophrenia.
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17
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Nakahara S, Matsumoto M, Ito H, Tajinda K. Ectopic Mossy Fiber Pathfinding in the Hippocampus Caused the Abnormal Neuronal Transmission in the Mouse Models of Psychiatric Disease. Biol Pharm Bull 2018; 41:138-141. [PMID: 29311476 DOI: 10.1248/bpb.b17-00643] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Appropriate axonal pathfinding is a necessary step for the function of neuronal circuits. The mossy fibers (MFs) in the hippocampus of CaMKIIα heterozygous knockout (CaMKIIα-hKO) psychiatric model mice project onto not only the stratum lucidum but also the stratum oriens region in the CA3, which is a projection pattern distinct from that in normal mice. Thus, we examined the electrophysiological properties of the MF-CA3 connection in this mutant mouse on field recordings and found a lower synaptic connection. This study suggested that the phenotype of abnormal MF pathfindings could induce aberrant neuronal functions, which may link to cognition and memory.
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Affiliation(s)
- Soichiro Nakahara
- Unit 2, Candidate Discovery Science Labs, Drug Discovery Research, Astellas Pharma Inc
| | - Mitsuyuki Matsumoto
- Unit 2, Candidate Discovery Science Labs, Drug Discovery Research, Astellas Pharma Inc
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18
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Marcotulli D, Fattorini G, Bragina L, Perugini J, Conti F. Levetiracetam Affects Differentially Presynaptic Proteins in Rat Cerebral Cortex. Front Cell Neurosci 2017; 11:389. [PMID: 29311825 PMCID: PMC5732259 DOI: 10.3389/fncel.2017.00389] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 11/24/2017] [Indexed: 01/23/2023] Open
Abstract
Presynaptic proteins are potential therapeutic targets for epilepsy and other neurological diseases. We tested the hypothesis that chronic treatment with the SV2A ligand levetiracetam affects the expression of other presynaptic proteins. Results showed that in rat neocortex no significant difference was detected in SV2A protein levels in levetiracetam treated animals compared to controls, whereas levetiracetam post-transcriptionally decreased several vesicular proteins and increased LRRK2, without any change in mRNA levels. Analysis of SV2A interactome indicates that the presynaptic proteins regulation induced by levetiracetam reported here is mediated by this interactome, and suggests that LRRK2 plays a role in forging the pattern of effects.
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Affiliation(s)
- Daniele Marcotulli
- Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, Italy
| | - Giorgia Fattorini
- Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, Italy.,Center for Neurobiology of Aging, INRCA IRCCS, Ancona, Italy
| | - Luca Bragina
- Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, Italy.,Center for Neurobiology of Aging, INRCA IRCCS, Ancona, Italy
| | - Jessica Perugini
- Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, Italy
| | - Fiorenzo Conti
- Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, Italy.,Center for Neurobiology of Aging, INRCA IRCCS, Ancona, Italy
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19
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Gamboa NT, Taussky P, Park MS, Couldwell WT, Mahan MA, Kalani MYS. Neurovascular patterning cues and implications for central and peripheral neurological disease. Surg Neurol Int 2017; 8:208. [PMID: 28966815 PMCID: PMC5609400 DOI: 10.4103/sni.sni_475_16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 06/28/2017] [Indexed: 12/20/2022] Open
Abstract
The highly branched nervous and vascular systems run along parallel trajectories throughout the human body. This stereotyped pattern of branching shared by the nervous and vascular systems stems from a common reliance on specific cues critical to both neurogenesis and angiogenesis. Continually emerging evidence supports the notion of later-evolving vascular networks co-opting neural molecular mechanisms to ensure close proximity and adequate delivery of oxygen and nutrients to nervous tissue. As our understanding of these biologic pathways and their phenotypic manifestations continues to advance, identification of where pathways go awry will provide critical insight into central and peripheral nervous system pathology.
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Affiliation(s)
- Nicholas T Gamboa
- Department of Neurosurgery, Clinical Neurosciences Center, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - Philipp Taussky
- Department of Neurosurgery, Clinical Neurosciences Center, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - Min S Park
- Department of Neurosurgery, Clinical Neurosciences Center, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - William T Couldwell
- Department of Neurosurgery, Clinical Neurosciences Center, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - Mark A Mahan
- Department of Neurosurgery, Clinical Neurosciences Center, University of Utah School of Medicine, Salt Lake City, Utah, USA
| | - M Yashar S Kalani
- Department of Neurosurgery, Clinical Neurosciences Center, University of Utah School of Medicine, Salt Lake City, Utah, USA
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20
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Abstract
Abstract
Axonal loss is an important process both during development and diseases of the nervous system. While the molecular mechanisms that mediate axonal loss are largely elusive, modern imaging technology affords an increasingly clear view of the cellular processes that allow nerve cells to shed individiual axon branches or even dismantle entire parts of their axonal projections. The present review discusses the characteristics of post-traumatic Wallerian degeneration, the process of axonal loss currently best understood. Subsequently, the properties of a number of recently discovered axonal loss phenomena are described. These phenomena explain some of the axonal loss that occurs locally after axon transection, during neuro-inflammatory insults, and as part of normal neurodevelopment.
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21
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Abstract
The assembly of functional neural circuits requires the combined action of progressive and regressive events. Regressive events encompass a variety of inhibitory developmental processes, including axon and dendrite pruning, which facilitate the removal of exuberant neuronal connections. Most axon pruning involves the removal of axons that had already made synaptic connections; thus, axon pruning is tightly associated with synapse elimination. In many instances, these developmental processes are regulated by the interplay between neurons and glial cells that act instructively during neural remodeling. Owing to the importance of axon and dendritic pruning, these remodeling events require precise spatial and temporal control, and this is achieved by a range of distinct molecular mechanisms. Disruption of these mechanisms results in abnormal pruning, which has been linked to brain dysfunction. Therefore, understanding the mechanisms of axon and dendritic pruning will be instrumental in advancing our knowledge of neural disease and mental disorders.
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Affiliation(s)
- Martin M Riccomagno
- Department of Cell Biology and Neuroscience, University of California, Riverside, California 92521;
| | - Alex L Kolodkin
- Solomon H. Snyder Department of Neuroscience, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205;
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22
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Bragina L, Bonifacino T, Bassi S, Milanese M, Bonanno G, Conti F. Differential expression of metabotropic glutamate and GABA receptors at neocortical glutamatergic and GABAergic axon terminals. Front Cell Neurosci 2015; 9:345. [PMID: 26388733 PMCID: PMC4559644 DOI: 10.3389/fncel.2015.00345] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 08/18/2015] [Indexed: 12/04/2022] Open
Abstract
Metabotropic glutamate (Glu) receptors (mGluRs) and GABAB receptors are highly expressed at presynaptic sites. To verify the possibility that the two classes of metabotropic receptors contribute to axon terminals heterogeneity, we studied the localization of mGluR1α, mGluR5, mGluR2/3, mGluR7, and GABAB1 in VGLUT1-, VGLUT2-, and VGAT- positive terminals in the cerebral cortex of adult rats. VGLUT1-positive puncta expressed mGluR1α (∼5%), mGluR5 (∼6%), mGluR2/3 (∼22%), mGluR7 (∼17%), and GABAB1 (∼40%); VGLUT2-positive terminals expressed mGluR1α (∼10%), mGluR5 (∼11%), mGluR2/3 (∼20%), mGluR7 (∼28%), and GABAB1 (∼25%); whereas VGAT-positive puncta expressed mGluR1α (∼27%), mGluR5 (∼24%), mGluR2/3 (∼38%), mGluR7 (∼31%), and GABAB1 (∼19%). Control experiments ruled out the possibility that postsynaptic mGluRs and GABAB1 might have significantly biased our results. We also performed functional assays in synaptosomal preparations, and showed that all agonists modify Glu and GABA levels, which return to baseline upon exposure to antagonists. Overall, these findings indicate that mGluR1α, mGluR5, mGluR2/3, mGluR7, and GABAB1 expression differ significantly between glutamatergic and GABAergic axon terminals, and that the robust expression of heteroreceptors may contribute to the homeostatic regulation of the balance between excitation and inhibition.
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Affiliation(s)
- Luca Bragina
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle MarcheAncona, Italy
- Center for Neurobiology of Aging, Istituto Nazionale di Riposo e Cura per Anziani – Istituto di Ricovero e Cura a Carattere ScientificoAncona, Italy
| | - Tiziana Bonifacino
- Department of Pharmacy, Unit of Pharmacology and Toxicology, University of GenoaGenoa, Italy
| | - Silvia Bassi
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle MarcheAncona, Italy
| | - Marco Milanese
- Department of Pharmacy, Unit of Pharmacology and Toxicology, University of GenoaGenoa, Italy
| | - Giambattista Bonanno
- Department of Pharmacy, Unit of Pharmacology and Toxicology, University of GenoaGenoa, Italy
- Center of Excellence for Biomedical Research, University of GenoaGenoa, Italy
| | - Fiorenzo Conti
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle MarcheAncona, Italy
- Center for Neurobiology of Aging, Istituto Nazionale di Riposo e Cura per Anziani – Istituto di Ricovero e Cura a Carattere ScientificoAncona, Italy
- Fondazione di Medicina Molecolare, Università Politecnica delle MarcheAncona, Italy
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23
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Nakahara S, Miyake S, Tajinda K, Ito H. Mossy fiber mis-pathfinding and semaphorin reduction in the hippocampus of α-CaMKII hKO mice. Neurosci Lett 2015; 598:47-51. [DOI: 10.1016/j.neulet.2015.05.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 04/24/2015] [Accepted: 05/08/2015] [Indexed: 11/25/2022]
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24
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Julien DP, Sagasti A. Synaptic specificity: when the neighbors are away, sensory axons turn promiscuous. Curr Biol 2014; 24:R1168-70. [PMID: 25514010 DOI: 10.1016/j.cub.2014.11.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A new study describes cellular mechanisms establishing synaptic specificity during development and remodeling of a zebrafish mechanosensory organ. Coordination amongst postsynaptic neurons and interactions between presynaptic and postsynaptic cells together promote the segregation of circuits responding to distinct sensory stimuli.
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Affiliation(s)
- Donald P Julien
- Department of Molecular, Cell, and Developmental Biology, UCLA, Los Angeles, CA 90095-1606, USA
| | - Alvaro Sagasti
- Department of Molecular, Cell, and Developmental Biology, UCLA, Los Angeles, CA 90095-1606, USA.
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25
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Schuldiner O, Yaron A. Mechanisms of developmental neurite pruning. Cell Mol Life Sci 2014; 72:101-19. [PMID: 25213356 DOI: 10.1007/s00018-014-1729-6] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 09/02/2014] [Accepted: 09/04/2014] [Indexed: 12/19/2022]
Abstract
The precise wiring of the nervous system is a combined outcome of progressive and regressive events during development. Axon guidance and synapse formation intertwined with cell death and neurite pruning sculpt the mature circuitry. It is now well recognized that pruning of dendrites and axons as means to refine neuronal networks, is a wide spread phenomena required for the normal development of vertebrate and invertebrate nervous systems. Here we will review the arising principles of cellular and molecular mechanisms of neurite pruning. We will discuss these principles in light of studies in multiple neuronal systems, and speculate on potential explanations for the emergence of neurite pruning as a mechanism to sculpt the nervous system.
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Affiliation(s)
- Oren Schuldiner
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, 7610001, Rehovot, Israel,
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26
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Abstract
Precise connectivity in neuronal circuits is a prerequisite for proper brain function. The dauntingly complex environment encountered by axons and dendrites, even after navigation to their target area, prompts the question of how specificity of synaptic connections arises during development. We review developmental strategies and molecular mechanisms that are used by neurons to ensure their precise matching of pre- and postsynaptic elements. The emerging theme is that each circuit uses a combination of simple mechanisms to achieve its refined, often complex connectivity pattern. At increasing levels of resolution, from lamina choice to subcellular targeting, similar signaling concepts are reemployed to narrow the choice of potential matches. Temporal control over synapse development and synapse elimination further ensures the specificity of connections in the nervous system.
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Affiliation(s)
- Shaul Yogev
- Department of Biology, Howard Hughes Medical Institute, Stanford University, Stanford, California 94305;
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27
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Focal adhesion kinase function in neuronal development. Curr Opin Neurobiol 2014; 27:89-95. [DOI: 10.1016/j.conb.2014.03.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 02/17/2014] [Accepted: 03/09/2014] [Indexed: 11/21/2022]
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28
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Van Battum EY, Gunput RAF, Lemstra S, Groen EJN, Yu KL, Adolfs Y, Zhou Y, Hoogenraad CC, Yoshida Y, Schachner M, Akhmanova A, Pasterkamp RJ. The intracellular redox protein MICAL-1 regulates the development of hippocampal mossy fibre connections. Nat Commun 2014; 5:4317. [PMID: 25007825 DOI: 10.1038/ncomms5317] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 06/05/2014] [Indexed: 02/05/2023] Open
Abstract
Mical is a reduction-oxidation (redox) enzyme that functions as an unusual F-actin disassembly factor during Drosophila development. Although three Molecule interacting with CasL (MICAL) proteins exist in vertebrate species, their mechanism of action remains poorly defined and their role in vivo unknown. Here, we report that vertebrate MICAL-1 regulates the targeting of secretory vesicles containing immunoglobulin superfamily cell adhesion molecules (IgCAMs) to the neuronal growth cone membrane through its ability to control the actin cytoskeleton using redox chemistry, thereby maintaining appropriate IgCAM cell surface levels. This precise regulation of IgCAMs by MICAL-1 is essential for the lamina-specific targeting of mossy fibre axons onto CA3 pyramidal neurons in the developing mouse hippocampus in vivo. These findings reveal the first in vivo role for a vertebrate MICAL protein, expand the repertoire of cellular functions controlled through MICAL-mediated effects on the cytoskeleton, and provide insights into the poorly characterized mechanisms underlying neuronal protein cell surface expression and lamina-specific axonal targeting.
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Affiliation(s)
- Eljo Y Van Battum
- 1] Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands [2]
| | - Rou-Afza F Gunput
- 1] Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands [2] [3]
| | - Suzanne Lemstra
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands
| | - Ewout J N Groen
- 1] Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands [2] Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3508 GA, Utrecht, The Netherlands
| | - Ka Lou Yu
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Youri Adolfs
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands
| | - Yeping Zhou
- 1] Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands [2]
| | - Casper C Hoogenraad
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Yukata Yoshida
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA
| | - Melitta Schachner
- Center for Neuroscience, Shantou University Medical College, Shantou, Guangdong 515041, China
| | - Anna Akhmanova
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - R Jeroen Pasterkamp
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands
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29
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Christensen MH, Ishibashi M, Nielsen ML, Leonard CS, Kohlmeier KA. Age-related changes in nicotine response of cholinergic and non-cholinergic laterodorsal tegmental neurons: implications for the heightened adolescent susceptibility to nicotine addiction. Neuropharmacology 2014; 85:263-83. [PMID: 24863041 DOI: 10.1016/j.neuropharm.2014.05.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 04/30/2014] [Accepted: 05/05/2014] [Indexed: 02/06/2023]
Abstract
The younger an individual starts smoking, the greater the likelihood that addiction to nicotine will develop, suggesting that neurobiological responses vary across age to the addictive component of cigarettes. Cholinergic neurons of the laterodorsal tegmental nucleus (LDT) are importantly involved in the development of addiction, however, the effects of nicotine on LDT neuronal excitability across ontogeny are unknown. Nicotinic effects on LDT cells across different age groups were examined using calcium imaging and whole-cell patch clamping. Within the youngest age group (P7-P15), nicotine induced larger intracellular calcium transients and inward currents. Nicotine induced a greater number of excitatory synaptic currents in the youngest animals, whereas larger amplitude inhibitory synaptic events were induced in cells from the oldest animals (P15-P34). Nicotine increased neuronal firing of cholinergic cells to a greater degree in younger animals, possibly linked to development associated differences found in nicotinic effects on action potential shape and afterhyperpolarization. We conclude that in addition to age-associated alterations of several properties expected to affect resting cell excitability, parameters affecting cell excitability are altered by nicotine differentially across ontogeny. Taken together, our data suggest that nicotine induces a larger excitatory response in cholinergic LDT neurons from the youngest animals, which could result in a greater excitatory output from these cells to target regions involved in development of addiction. Such output would be expected to be promotive of addiction; therefore, ontogenetic differences in nicotine-mediated increases in the excitability of the LDT could contribute to the differential susceptibility to nicotine addiction seen across age.
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Affiliation(s)
- Mark H Christensen
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health Sciences, Universitetsparken 2, Copenhagen 2100, Denmark
| | - Masaru Ishibashi
- Department of Physiology, New York Medical College, Valhalla, NY 10595, USA
| | - Michael L Nielsen
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health Sciences, Universitetsparken 2, Copenhagen 2100, Denmark
| | | | - Kristi A Kohlmeier
- University of Copenhagen, Department of Drug Design and Pharmacology, Faculty of Health Sciences, Universitetsparken 2, Copenhagen 2100, Denmark.
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30
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Semaphorins and the dynamic regulation of synapse assembly, refinement, and function. Curr Opin Neurobiol 2014; 27:1-7. [PMID: 24598309 DOI: 10.1016/j.conb.2014.02.005] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 01/21/2014] [Accepted: 02/06/2014] [Indexed: 01/13/2023]
Abstract
Semaphorins are phylogenetically conserved proteins expressed in most organ systems, including the nervous system. Following their description as axon guidance cues, semaphorins have been implicated in multiple aspects of nervous system development. Semaphorins are key regulators of neural circuit assembly, neuronal morphogenesis, assembly of excitatory and inhibitory synapses, and synaptic refinement. Semaphorins contribute to the balance between excitatory and inhibitory synaptic transmission, and electrical activity can modulate semaphorin signaling in neurons. This interplay between guidance cue signaling and electrical activity has the potential to sculpt the wiring of neural circuits and to modulate their function.
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31
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Plum, an immunoglobulin superfamily protein, regulates axon pruning by facilitating TGF-β signaling. Neuron 2013; 78:456-68. [PMID: 23664613 DOI: 10.1016/j.neuron.2013.03.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/26/2013] [Indexed: 11/22/2022]
Abstract
Axon pruning during development is essential for proper wiring of the mature nervous system, but its regulation remains poorly understood. We have identified an immunoglobulin superfamily (IgSF) transmembrane protein, Plum, that is cell autonomously required for axon pruning of mushroom body (MB) γ neurons and for ectopic synapse refinement at the developing neuromuscular junction in Drosophila. Plum promotes MB γ neuron axon pruning by regulating the expression of Ecdysone Receptor-B1, a key initiator of axon pruning. Genetic analyses indicate that Plum acts to facilitate signaling of Myoglianin, a glial-derived TGF-β, on MB γ neurons upstream of the type-I TGF-β receptor Baboon. Myoglianin, Baboon, and Ecdysone Receptor-B1 are also required for neuromuscular junction ectopic synapse refinement. Our study highlights both IgSF proteins and TGF-β facilitation as key promoters of developmental axon elimination and demonstrates a mechanistic conservation between MB axon pruning during metamorphosis and the refinement of ectopic larval neuromuscular connections.
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The endogenous regenerative capacity of the damaged newborn brain: boosting neurogenesis with mesenchymal stem cell treatment. J Cereb Blood Flow Metab 2013; 33:625-34. [PMID: 23403379 PMCID: PMC3652688 DOI: 10.1038/jcbfm.2013.3] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Neurogenesis continues throughout adulthood. The neurogenic capacity of the brain increases after injury by, e.g., hypoxia-ischemia. However, it is well known that in many cases brain damage does not resolve spontaneously, indicating that the endogenous regenerative capacity of the brain is insufficient. Neonatal encephalopathy leads to high mortality rates and long-term neurologic deficits in babies worldwide. Therefore, there is an urgent need to develop more efficient therapeutic strategies. The latest findings indicate that stem cells represent a novel therapeutic possibility to improve outcome in models of neonatal encephalopathy. Transplanted stem cells secrete factors that stimulate and maintain neurogenesis, thereby increasing cell proliferation, neuronal differentiation, and functional integration. Understanding the molecular and cellular mechanisms underlying neurogenesis after an insult is crucial for developing tools to enhance the neurogenic capacity of the brain. The aim of this review is to discuss the endogenous capacity of the neonatal brain to regenerate after a cerebral ischemic insult. We present an overview of the molecular and cellular mechanisms underlying endogenous regenerative processes during development as well as after a cerebral ischemic insult. Furthermore, we will consider the potential to use stem cell transplantation as a means to boost endogenous neurogenesis and restore brain function.
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Ma Y, Ramachandran A, Ford N, Parada I, Prince DA. Remodeling of dendrites and spines in the C1q knockout model of genetic epilepsy. Epilepsia 2013; 54:1232-9. [PMID: 23621154 DOI: 10.1111/epi.12195] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2013] [Indexed: 12/24/2022]
Abstract
PURPOSE To determine whether developmental synaptic pruning defects in epileptic C1q-knockout (KO) mice are accompanied by postsynaptic abnormalities in dendrites and/or spines. METHODS Immunofluorescence staining was performed on biocytin-filled layer Vb pyramidal neurons in sensorimotor cortex. Basal dendritic arbors and their spines were reconstructed with NEUROLUCIDA software, and their morphologic characteristics were quantitated in Neuroexplorer. KEY FINDINGS Seven to nine completely filled pyramidal neurons were analyzed from the wild-type (WT) and C1q KO groups. Compared to WT controls, KO mice showed significant structural modifications in their basal dendrites including (1) higher density of dendritic spines (0.60 ± 0.03/μm vs. 0.49 ± 0.03/μm dendritic length in WT, p < 0.05); (2) remarkably increased occurrence of thin spines (0.26 ± 0.02/μm vs. 0.14 ± 0.02/μm dendritic length in control, p < 0.01); (3) longer dendritic length (2,680 ± 159 μm vs. 2,119 ± 108 μm in control); and (4) increased branching (22.6 ± 1.9 vs. 16.2 ± 1.3 in WT at 80 μm from soma center, p < 0.05; 12.4 ± 1.4 vs. 8.2 ± 0.6 in WT at 120 μm from soma center, respectively, p < 0.05). Dual immunolabeling demonstrated the expression of putative glutamate receptor 2 (GluR2) on some thin spines. These dendritic alterations are likely postsynaptic structural consequences of failure of synaptic pruning in the C1q KO mice. SIGNIFICANCE Failure to prune excessive excitatory synapses in C1q KO mice is a likely mechanism underlying abnormalities in postsynaptic dendrites, including increased branching and alterations in spine type and density. It is also possible that seizure activity contributes to these abnormalities. These structural abnormalities, together with increased numbers of excitatory synapses, likely contribute to epileptogenesis in C1q KO mice.
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Affiliation(s)
- Yunyong Ma
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California 94305-5122, USA
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Mizumoto K, Shen K. Interaxonal interaction defines tiled presynaptic innervation in C. elegans. Neuron 2013; 77:655-66. [PMID: 23439119 DOI: 10.1016/j.neuron.2012.12.031] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/07/2012] [Indexed: 10/27/2022]
Abstract
VIDEO ABSTRACT Cellular interactions between neighboring axons are essential for global topographic map formation. Here we show that axonal interactions also precisely instruct the location of synapses. Motoneurons form en passant synapses in Caenorhabditis elegans. Although axons from the same neuron class significantly overlap, each neuron innervates a unique and tiled segment of the muscle field by restricting its synapses to a distinct subaxonal domain-a phenomenon we term synaptic tiling. Using DA8 and DA9 motoneurons, we found that the synaptic tiling requires the PlexinA4 homolog, PLX-1, and two transmembrane semaphorins. In the plexin or semaphorin mutants, synaptic domains from both neurons expand and overlap with each other without guidance defects. In a semaphorin-dependent manner, PLX-1 is concentrated at the synapse-free axonal segment, delineating the tiling border. Furthermore, plexin inhibits presynapse formation by suppressing synaptic F-actin through its cytoplasmic GTPase-activating protein (GAP) domain. Hence, contact-dependent, intra-axonal plexin signaling specifies synaptic circuits by inhibiting synapse formation at the subcellular loci.
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Affiliation(s)
- Kota Mizumoto
- Department of Biology, Howard Hughes Medical Institute, Stanford University, 385 Serra Mall, Stanford, CA 94305, USA
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Baudet ML, Bellon A, Holt CE. Role of microRNAs in Semaphorin function and neural circuit formation. Semin Cell Dev Biol 2012; 24:146-55. [PMID: 23219835 DOI: 10.1016/j.semcdb.2012.11.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 10/19/2012] [Accepted: 11/28/2012] [Indexed: 01/23/2023]
Abstract
Since the discovery of the first microRNA (miRNA) almost 20 years ago, insight into their functional role has gradually been accumulating. This class of non-coding RNAs has recently been implicated as key molecular regulators in the biology of most eukaryotic cells, contributing to the physiology of various systems including immune, cardiovascular, nervous systems and also to the pathophysiology of cancers. Interestingly, Semaphorins, a class of evolutionarily conserved signalling molecules, are acknowledged to play major roles in these systems also. This, combined with the fact that Semaphorin signalling requires tight spatiotemporal regulation, a hallmark of miRNA expression, suggests that miRNAs could be crucial regulators of Semaphorin function. Here, we review evidence suggesting that Semaphorin signalling is regulated by miRNAs in various systems in health and disease. In particular, we focus on neural circuit formation, including axon guidance, where Semaphorin function was first discovered.
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Browne K, Wang W, Liu RQ, Piva M, O’Connor TP. Transmembrane semaphorin5B is proteolytically processed into a repulsive neural guidance cue. J Neurochem 2012; 123:135-46. [DOI: 10.1111/j.1471-4159.2012.07885.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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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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Yoshida Y. Semaphorin signaling in vertebrate neural circuit assembly. Front Mol Neurosci 2012; 5:71. [PMID: 22685427 PMCID: PMC3368236 DOI: 10.3389/fnmol.2012.00071] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 05/17/2012] [Indexed: 11/13/2022] Open
Abstract
Neural circuit formation requires the coordination of many complex developmental processes. First, neurons project axons over long distances to find their final targets and then establish appropriate connectivity essential for the formation of neuronal circuitry. Growth cones, the leading edges of axons, navigate by interacting with a variety of attractive and repulsive axon guidance cues along their trajectories and at final target regions. In addition to guidance of axons, neuronal polarization, neuronal migration, and dendrite development must be precisely regulated during development to establish proper neural circuitry. Semaphorins consist of a large protein family, which includes secreted and cell surface proteins, and they play important roles in many steps of neural circuit formation. The major semaphorin receptors are plexins and neuropilins, however other receptors and co-receptors also mediate signaling by semaphorins. Upon semaphorin binding to their receptors, downstream signaling molecules transduce this event within cells to mediate further events, including alteration of microtubule and actin cytoskeletal dynamics. Here, I review recent studies on semaphorin signaling in vertebrate neural circuit assembly, with the goal of highlighting how this diverse family of cues and receptors imparts exquisite specificity to neural complex connectivity.
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Affiliation(s)
- Yutaka Yoshida
- Division of Developmental Biology, Cincinnati Children's Hospital Medical Center Cincinnati, OH, USA
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Bragina L, Fattorini G, Giovedí S, Melone M, Bosco F, Benfenati F, Conti F. Analysis of Synaptotagmin, SV2, and Rab3 Expression in Cortical Glutamatergic and GABAergic Axon Terminals. Front Cell Neurosci 2012; 5:32. [PMID: 22275882 PMCID: PMC3254050 DOI: 10.3389/fncel.2011.00032] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Accepted: 12/25/2011] [Indexed: 11/13/2022] Open
Abstract
We investigated whether cortical glutamatergic and GABAergic release machineries can be differentiated on the basis of the nature and amount of proteins they express, by performing a quantitative analysis of the degree of co-localization of synaptotagmin (SYT) 1 and 2, synaptic vesicle protein 2 (SV2) A and B, and Rab3a and c in VGLUT1+, VGLUT2+, and VGAT+ terminals and synaptic vesicles (SVs) in rat cerebral cortex. Co-localization studies showed that VGLUT1 puncta had high levels of SV2A and B and of Rab3c, intermediate levels of SYT1, and low levels of SYT2 and Rab3c; VGLUT2 puncta exhibited intermediate levels of all presynaptic proteins studied; whereas vesicular GABA transporter (VGAT) puncta had high levels of SV2A and SYT2, intermediate levels of SYT1, Rab3a, and Rab3c, and low levels of SV2B. Since SV2B is reportedly expressed by glutamatergic neurons and we observed SV2B expression in VGAT puncta, we performed electron microscopic studies and found SV2B positive axon terminals forming symmetric synapses. Immunoisolation studies showed that the expression levels of the protein isoforms varied in the three populations of SVs. Expression of SYT1 was highest in VGLUT1–SVs, while SYT2 expression was similar in the three SV groups. Expression of SV2A was similarly high in all three SV populations, except for SV2B levels that were very low in VGAT SVs. Finally, Rab3a levels were similar in the three SV groups, while Rab3c levels were highest in VGLUT1–SVs. These quantitative results extend our previous studies on the differential expression of presynaptic proteins involved in neurotransmitter release in GABAergic and glutamatergic terminals and indicate that heterogeneity of the respective release machineries can be generated by the differential complement of SV proteins involved in distinct stages of the release process.
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Affiliation(s)
- Luca Bragina
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche Ancona, Italy
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Neufeld SQ, Hibbert AD, Chen BE. Opposing roles of PlexinA and PlexinB in axonal branch and varicosity formation. Mol Brain 2011; 4:15. [PMID: 21489263 PMCID: PMC3094289 DOI: 10.1186/1756-6606-4-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Accepted: 04/13/2011] [Indexed: 01/01/2023] Open
Abstract
Establishing precise synaptic connectivity during development is crucial for neural circuit function. However, very few molecules have been identified that are involved in determining where and how many synapses form. The Plexin cell-surface molecules are a conserved family of axon guidance receptors that mediate axon fasciculation and repulsion during neural development, and later in development PlexinA receptors are involved in eliminating axonal branches and synapse numbers. Here we investigate the roles of PlexinA and PlexinB receptors in axonal branch and varicosity formation in Drosophila. We knocked down PlexinA or PlexinB expression using RNAi in identified mechanosensory neurons and analyzed axonal branching patterns and varicosity formations. Reducing PlexinA expression increased the axonal arbor complexity by increasing the number of branches and varicosities along the axon. In contrast, knocking down PlexinB expression decreased morphological complexity by decreasing the number of branches and the overall size of the axonal arbor, but did not reduce the number of varicosities. Our results demonstrate opposing roles for PlexinA and PlexinB in local wiring within a target region, where PlexinA functions to suppress excessive axonal branches and synapses and PlexinB facilitates axonal growth.
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Affiliation(s)
- Shay Q Neufeld
- Research Institute of the McGill University Health Centre, Centre for Research in Neuroscience, Montréal, Québec, Canada
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41
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Abstract
The assembly of specific synaptic connections during development of the nervous system represents a remarkable example of cellular recognition and differentiation. Neurons employ several different cellular signaling strategies to solve this puzzle, which successively limit unwanted interactions and reduce the number of direct recognition events that are required to result in a specific connectivity pattern. Specificity mechanisms include the action of contact-mediated and long-range signals that support or inhibit synapse formation, which can take place directly between synaptic partners or with transient partners and transient cell populations. The molecular signals that drive the synaptic differentiation process at individual synapses in the central nervous system are similarly diverse and act through multiple, parallel differentiation pathways. This molecular complexity balances the need for central circuits to be assembled with high accuracy during development while retaining plasticity for local and dynamic regulation.
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Affiliation(s)
- Kang Shen
- Howard Hughes Medical Institute, Department of Biology and Pathology, Stanford University, Stanford, California 94305, USA.
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42
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Genetic dissection of synaptic specificity. Curr Opin Neurobiol 2010; 21:93-9. [PMID: 21087855 DOI: 10.1016/j.conb.2010.10.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Revised: 10/04/2010] [Accepted: 10/21/2010] [Indexed: 11/22/2022]
Abstract
Nervous systems are built of a myriad of neurons connected by an even larger number of synapses. While it has been long known that neurons specifically select their synaptic partners among many possible choices during development, we only begin to understand how they make those decisions. Recent findings have started to elucidate the molecular mechanisms underlying synaptic target selection including positive as well as negative cues from synaptic partners, intermediate targets and surrounding tissues. Furthermore, emerging evidence suggests that synaptic connections are not only formed among specific sets of neurons, but also targeted to specific subcellular domains. Finally, spatial and temporal transcriptional regulation of these molecular cues represents an additional, versatile mechanism to provide wiring specificity.
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Stoneham ET, Sanders EM, Sanyal M, Dumas TC. Rules of engagement: factors that regulate activity-dependent synaptic plasticity during neural network development. THE BIOLOGICAL BULLETIN 2010; 219:81-99. [PMID: 20972254 DOI: 10.1086/bblv219n2p81] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Overproduction and pruning during development is a phenomenon that can be observed in the number of organisms in a population, the number of cells in many tissue types, and even the number of synapses on individual neurons. The sculpting of synaptic connections in the brain of a developing organism is guided by its personal experience, which on a neural level translates to specific patterns of activity. Activity-dependent plasticity at glutamatergic synapses is an integral part of neuronal network formation and maturation in developing vertebrate and invertebrate brains. As development of the rodent forebrain transitions away from an over-proliferative state, synaptic plasticity undergoes modification. Late developmental changes in synaptic plasticity signal the establishment of a more stable network and relate to pronounced perceptual and cognitive abilities. In large part, activation of glutamate-sensitive N-methyl-d-aspartate (NMDA) receptors regulates synaptic stabilization during development and is a necessary step in memory formation processes that occur in the forebrain. A developmental change in the subunits that compose NMDA receptors coincides with developmental modifications in synaptic plasticity and cognition, and thus much research in this area focuses on NMDA receptor composition. We propose that there are additional, equally important developmental processes that influence synaptic plasticity, including mechanisms that are upstream (factors that influence NMDA receptors) and downstream (intracellular processes regulated by NMDA receptors) from NMDA receptor activation. The goal of this review is to summarize what is known and what is not well understood about developmental changes in functional plasticity at glutamatergic synapses, and in the end, attempt to relate these changes to maturation of neural networks.
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Affiliation(s)
- Emily T Stoneham
- Molecular Neuroscience Department, George MasonUniversity, Fairfax, Virginia 22030, USA
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Roles of semaphorin-6B and plexin-A2 in lamina-restricted projection of hippocampal mossy fibers. J Neurosci 2010; 30:7049-60. [PMID: 20484647 DOI: 10.1523/jneurosci.0073-10.2010] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Hippocampal mossy fibers project preferentially to the proximal-most lamina of the suprapyramidal region of CA3, the stratum lucidum, and proximal-most parts of the infrapyrmidal region of CA3c. Molecular mechanisms that govern the lamina-restricted projection of mossy fibers, however, have not been fully understood. We previously studied functions of neural repellent Semaphorin-6A (Sema6A), a class 6 transmembrane semaphorin, and its receptors, plexin-A2 (PlxnA2) and PlxnA4, in mossy fiber projection and have proposed that PlxnA4-expressing mossy fibers are principally prevented from entering the Sema6A-expressing suprapyramidal and infrapyramidal regions of CA3 but are permitted to grow into proximal parts of the regions, where repulsive activity of Sema6A is competitively suppressed by PlxnA2 (Suto et al., 2007). In the present study we demonstrate that Sema6B, another class 6 transmembrane semaphorin, is expressed in CA3 and repels mossy fibers in a PlxnA4-dependent manner in vitro. In Sema6B-deficient mice several mossy fibers aberrantly project to the stratum radiatum and the stratum oriens. The number of aberrant mossy fibers is increased in Sema6A;Sema6B double knock-out mice, indicating that Sema6A and Sema6B function additively to regulate proper projection of mossy fibers. PlxnA2 does not suppress the Sema6B response, but itself promotes growth of mossy fibers. Based on these results, we propose that the balance between mossy fiber repulsion by Sema6A and Sema6B and attraction by PlxnA2 and unknown molecule(s) prescribes the areas permissive for mossy fibers to innervate.
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Abstract
Axon pruning and neuronal cell death constitute two major regressive events that enable the establishment of fully mature brain architecture and connectivity. Although the cellular mechanisms for these two events are thought to be distinct, recent evidence has indicated the direct involvement of axon guidance molecules, including semaphorins, netrins, and ephrins, in controlling both processes. Here, we review how axon guidance cues regulate regressive events in paradigmatic models of neural development, from early control of apoptosis of neural progenitors, to later maintenance of neuronal survival and stereotyped pruning of axonal branches. These new findings are also discussed in the context of neural diseases and the potential links between axon pruning and degeneration.
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46
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Setting up presynaptic structures at specific positions. Curr Opin Neurobiol 2010; 20:489-93. [PMID: 20471244 DOI: 10.1016/j.conb.2010.04.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Revised: 04/14/2010] [Accepted: 04/15/2010] [Indexed: 11/21/2022]
Abstract
Precise formation of presynaptic structures at specific loci is critical for correctly wiring neuronal circuits. Recent findings have gradually revealed how essential cues from different sources inform the axon to define the presynaptic domain and to choose its postsynaptic target. Here, we review key molecular regulators which mediate instructive or repellent signals from multiple sources including the target cells, local guidepost cells, and distal guiding tissues.
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47
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Abstract
The hippocampus is a region of the mammalian brain that shows an impressive capacity for structural reorganization. Preexisting neural circuits undergo modifications in dendritic complexity and synapse number, and entirely novel neural connections are formed through the process of neurogenesis. These types of structural change were once thought to be restricted to development. However, it is now generally accepted that the hippocampus remains structurally plastic throughout life. This article reviews structural plasticity in the hippocampus over the lifespan, including how it is investigated experimentally. The modulation of structural plasticity by various experiential factors as well as the possible role it may have in hippocampal functions such as learning and memory, anxiety, and stress regulation are also considered. Although significant progress has been made in many of these areas, we highlight some of the outstanding issues that remain.
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Affiliation(s)
- Benedetta Leuner
- Department of Psychology, Neuroscience Institute, Princeton University, Princeton, New Jersey 08544, USA
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Woronowicz A, Cawley NX, Chang SY, Koshimizu H, Phillips AW, Xiong ZG, Loh YP. Carboxypeptidase E knockout mice exhibit abnormal dendritic arborization and spine morphology in central nervous system neurons. J Neurosci Res 2010; 88:64-72. [PMID: 19598241 DOI: 10.1002/jnr.22174] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Carboxypeptidase E (CPE) is involved in maturation of neuropeptides and sorting of brain-derived neurotrophic factor (BDNF) to the regulated pathway for activity-dependent secretion from CNS neurons. CPE knockout (CPE-KO) mice have many neurological deficits, including deficits in learning and memory. Here, we analyzed the dendritic arborization and spine morphology of CPE-KO mice to determine a possible correlation of defects in such structures with the neurological deficits observed in these animals. Analysis of pyramidal neurons in layer V of cerebral cortex and in hippocampal CA1 region in 14-week-old CPE-KO mice showed more dendritic complexity compared with wild type (WT) mice. There were more dendritic intersections and more branch points in CPE-KO vs. WT neurons. Comparison of pyramidal cortical neurons in 6- vs. 14-week-old WT mice showed a decrease in dendritic arborization, reflecting the occurrence of normal dendritic pruning. However, this did not occur in CPE-KO neurons. Furthermore, analysis of spine morphology demonstrated a significant increase in the number of D-type spines regarded as nonfunctional in the cortical neurons of CPE-KO animals. Our findings suggest that CPE is an important, novel player in mediating appropriate dendritic patterning and spine formation in CNS neurons.
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Affiliation(s)
- Alicja Woronowicz
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
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Heterogeneity of glutamatergic and GABAergic release machinery in cerebral cortex: analysis of synaptogyrin, vesicle-associated membrane protein, and syntaxin. Neuroscience 2009; 165:934-43. [PMID: 19909789 DOI: 10.1016/j.neuroscience.2009.11.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Revised: 10/16/2009] [Accepted: 11/04/2009] [Indexed: 11/21/2022]
Abstract
To define whether cortical glutamatergic and GABAergic release machineries can be differentiated on the basis of the nature and amount of proteins they express, we studied the degree of co-localization of synaptogyrin (SGYR) 1 and 3, vesicle-associated membrane protein (VAMP) 1 and 2, syntaxin (STX) 1A and 1B in vesicular glutamate transporter (VGLUT)1-, VGLUT2- and vesicular GABA transporter (VGAT)-positive (+) puncta and synaptic vesicles in the rat cerebral cortex. Co-localization studies showed that SGYR1 and 3 were expressed in about 90% of VGLUT1+, 70% of VGLUT2+ and 80% of VGAT+ puncta; VAMP1 was expressed in approximately 45% of VGLUT1+, 55% of VGLUT2+, and 80% of VGAT+ puncta; VAMP2 in about 95% of VGLUT1+, 75% of VGLUT2+, and 80% of VGAT+ puncta; STX1A in about 65% of VGLUT1+, 30% of VGLUT2+, and 3% of VGAT+ puncta, and STX1B in approximately 45% of VGLUT1+, 35% of VGLUT2+, and 70% of VGAT+ puncta. Immunoisolation studies showed that while STX1A was completely segregated and virtually absent from VGAT synaptic vesicles, STX1B, VAMP1/VAMP2, SGYR1/SGYR3 showed a similar pattern with the highest expression in VGLUT1 immunoisolated vesicles and the lowest in VGAT immunoisolated vesicles. Moreover, we studied the localization of STX1B at the electron microscope and found that a population of axon terminals forming symmetric synapses were STX1B-positive.These results extend our previous observations on the differential expression of presynaptic proteins involved in neurotransmitter release in GABAergic and glutamatergic terminals and indicate that heterogeneity of glutamatergic and GABAergic release machinery can be contributed by both the presence or absence of a given protein in a nerve terminal and the amount of protein expressed by synaptic vesicles.
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50
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Chen SY, Cheng HJ. Functions of axon guidance molecules in synapse formation. Curr Opin Neurobiol 2009; 19:471-8. [PMID: 19828311 DOI: 10.1016/j.conb.2009.09.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Accepted: 09/23/2009] [Indexed: 11/18/2022]
Abstract
Axon guidance and synapse formation are important developmental events for establishing a functional neuronal circuitry. These two related cellular processes occur in a coordinated fashion but previous studies from multiple model organisms seemed to suggest that axon guidance and synapse formation are mediated by distinct molecular cues. Thus, axon guidance molecules are responsible for guiding the navigating axon toward its target area, while other adhesion or ligand-receptor molecules specify the synapse formation within the target area. However, accumulative evidence has shown that axon guidance molecules can regulate the localization and formation of pre-synaptic and post-synaptic components during synapse formation. These results demonstrate a role for axon guidance molecules in synapse formation and provide insight into how axon guidance and synapse formation are coordinated at the molecular level.
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Affiliation(s)
- Shih-Yu Chen
- Center for Neuroscience, Department of Neurobiology, Physiology and Behavior, United States
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