1
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Knittel LM, Swanson TL, Lee HJ, Copenhaver PF. Fasciclin 2 plays multiple roles in promoting cell migration within the developing nervous system of Manduca sexta. Dev Biol 2023; 499:31-46. [PMID: 37121309 DOI: 10.1016/j.ydbio.2023.04.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 04/07/2023] [Accepted: 04/27/2023] [Indexed: 05/02/2023]
Abstract
The coordination of neuronal and glial migration is essential to the formation of most nervous systems, requiring a complex interplay of cell-intrinsic responses and intercellular guidance cues. During the development of the enteric nervous system (ENS) in Manduca sexta (tobacco hornworm), the IgCAM Fasciclin 2 (Fas2) serves several distinct functions to regulate these processes. As the ENS forms, a population of 300 neurons (EP cells) undergoes sequential phases of migration along well-defined muscle pathways on the visceral mesoderm to form a branching Enteric Plexus, closely followed by a trailing wave of proliferating glial cells that enwrap the neurons. Initially, both the neurons and glial cells express a GPI-linked form of Fas2 (GPI-Fas2), which helps maintain cell-cell contact among the pre-migratory neurons and later promotes glial ensheathment. The neurons then switch isoforms, predominantly expressing a combination of transmembrane isoforms lacking an intracellular PEST domain (TM-Fas2 PEST-), while their muscle band pathways on the midgut transiently express transmembrane isoforms containing this domain (TM-Fas2 PEST+). Using intracellular injection protocols to manipulate Fas2 expression in cultured embryos, we found that TM-Fas2 promotes the directed migration and outgrowth of individual neurons in the developing ENS. Concurrently, TM-Fas2 expression by the underlying muscle bands is also required as a substrate cue to support normal migration, while glial expression of GPI-Fas2 helps support their ensheathment of the migratory neurons. These results demonstrate how a specific IgCAM can play multiple roles that help coordinate neuronal and glial migration in the developing nervous system.
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Affiliation(s)
- Laura M Knittel
- Department of Cell, Developmental and Cancer Biology L-215, Oregon Health & Sciences University, 3181 SW Sam Jackson Park Rd, Portland, OR, 97239, USA.
| | - Tracy L Swanson
- Department of Cell, Developmental and Cancer Biology L-215, Oregon Health & Sciences University, 3181 SW Sam Jackson Park Rd, Portland, OR, 97239, USA.
| | - Hun Joo Lee
- Department of Cell, Developmental and Cancer Biology L-215, Oregon Health & Sciences University, 3181 SW Sam Jackson Park Rd, Portland, OR, 97239, USA.
| | - Philip F Copenhaver
- Department of Cell, Developmental and Cancer Biology L-215, Oregon Health & Sciences University, 3181 SW Sam Jackson Park Rd, Portland, OR, 97239, USA.
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2
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Serna-Morales E, Sánchez-Sánchez BJ, Marcotti S, Nichols A, Bhargava A, Dragu A, Hirvonen LM, Díaz-de-la-Loza MDC, Mink M, Cox S, Rayfield E, Lee RM, Hobson CM, Chew TL, Stramer BM. Extracellular matrix assembly stress initiates Drosophila central nervous system morphogenesis. Dev Cell 2023; 58:825-835.e6. [PMID: 37086718 PMCID: PMC10390342 DOI: 10.1016/j.devcel.2023.03.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 12/12/2022] [Accepted: 03/05/2023] [Indexed: 04/24/2023]
Abstract
Forces controlling tissue morphogenesis are attributed to cellular-driven activities, and any role for extracellular matrix (ECM) is assumed to be passive. However, all polymer networks, including ECM, can develop autonomous stresses during their assembly. Here, we examine the morphogenetic function of an ECM before reaching homeostatic equilibrium by analyzing de novo ECM assembly during Drosophila ventral nerve cord (VNC) condensation. Asymmetric VNC shortening and a rapid decrease in surface area correlate with the exponential assembly of collagen IV (Col4) surrounding the tissue. Concomitantly, a transient developmentally induced Col4 gradient leads to coherent long-range flow of ECM, which equilibrates the Col4 network. Finite element analysis and perturbation of Col4 network formation through the generation of dominant Col4 mutations that affect assembly reveal that VNC morphodynamics is partially driven by a sudden increase in ECM-driven surface tension. These data suggest that ECM assembly stress and associated network instabilities can actively participate in tissue morphogenesis.
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Affiliation(s)
- Eduardo Serna-Morales
- Randall Centre for Cell and Molecular Biophysics, King's College London, SE1 1UL London, UK
| | | | - Stefania Marcotti
- Randall Centre for Cell and Molecular Biophysics, King's College London, SE1 1UL London, UK
| | - Angus Nichols
- Randall Centre for Cell and Molecular Biophysics, King's College London, SE1 1UL London, UK
| | - Anushka Bhargava
- Randall Centre for Cell and Molecular Biophysics, King's College London, SE1 1UL London, UK
| | - Anca Dragu
- Randall Centre for Cell and Molecular Biophysics, King's College London, SE1 1UL London, UK
| | - Liisa M Hirvonen
- Randall Centre for Cell and Molecular Biophysics, King's College London, SE1 1UL London, UK
| | | | - Matyas Mink
- Institute of Medical Biology, University of Szeged, 6720 Szeged, Hungary
| | - Susan Cox
- Randall Centre for Cell and Molecular Biophysics, King's College London, SE1 1UL London, UK
| | - Emily Rayfield
- School of Earth Sciences, University of Bristol, BS8 1QU Bristol, UK
| | - Rachel M Lee
- Advanced Imaging Center, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA
| | - Chad M Hobson
- Advanced Imaging Center, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA
| | - Teng-Leong Chew
- Advanced Imaging Center, Howard Hughes Medical Institute Janelia Research Campus, Ashburn, VA 20147, USA
| | - Brian M Stramer
- Randall Centre for Cell and Molecular Biophysics, King's College London, SE1 1UL London, UK.
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3
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Lépine S, Castellanos-Montiel MJ, Durcan TM. TDP-43 dysregulation and neuromuscular junction disruption in amyotrophic lateral sclerosis. Transl Neurodegener 2022; 11:56. [PMID: 36575535 PMCID: PMC9793560 DOI: 10.1186/s40035-022-00331-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 11/29/2022] [Indexed: 12/28/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a disease characterized by upper and lower motor neuron (MN) loss with a signature feature of cytoplasmic aggregates containing TDP-43, which are detected in nearly all patients. Mutations in the gene that encodes TDP-43 (TARBDP) are known to result in both familial and sporadic ALS. In ALS, disruption of neuromuscular junctions (NMJs) constitutes a critical event in disease pathogenesis, leading to denervation atrophy, motor impairments and disability. Morphological defects and impaired synaptic transmission at NMJs have been reported in several TDP-43 animal models and in vitro, linking TDP-43 dysregulation to the loss of NMJ integrity in ALS. Through the lens of the dying-back and dying-forward hypotheses of ALS, this review discusses the roles of TDP-43 related to synaptic function, with a focus on the potential molecular mechanisms occurring within MNs, skeletal muscles and glial cells that may contribute to NMJ disruption in ALS.
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Affiliation(s)
- Sarah Lépine
- grid.14709.3b0000 0004 1936 8649The Neuro’s Early Drug Discovery Unit (EDDU), Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, 3801 University Street, Montreal, QC H3A 2B4 Canada ,grid.14709.3b0000 0004 1936 8649Faculty of Medicine and Health Sciences, McGill University, 3605 De La Montagne, Montreal, QC H3G 2M1 Canada
| | - Maria José Castellanos-Montiel
- grid.14709.3b0000 0004 1936 8649The Neuro’s Early Drug Discovery Unit (EDDU), Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, 3801 University Street, Montreal, QC H3A 2B4 Canada
| | - Thomas Martin Durcan
- grid.14709.3b0000 0004 1936 8649The Neuro’s Early Drug Discovery Unit (EDDU), Department of Neurology and Neurosurgery, Montreal Neurological Institute-Hospital, McGill University, 3801 University Street, Montreal, QC H3A 2B4 Canada
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4
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Cammarota C, Finegan TM, Wilson TJ, Yang S, Bergstralh DT. An Axon-Pathfinding Mechanism Preserves Epithelial Tissue Integrity. Curr Biol 2020; 30:5049-5057.e3. [PMID: 33065006 DOI: 10.1016/j.cub.2020.09.061] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 08/21/2020] [Accepted: 09/18/2020] [Indexed: 01/09/2023]
Abstract
Epithelial tissues form the boundaries of organs, where they perform a range of functions, including secretion, absorption, and protection. These tissues are commonly composed of discrete cell layers-sheets of cells that are one-cell thick. In multiple systems examined, epithelial cells round up and move in the apical direction before dividing, likely in response to neighbor-cell crowding [1-6]. Because of this movement, daughter cells may be born displaced from the tissue layer. Reintegration of these displaced cells supports tissue growth and maintains tissue architecture [4]. Two conserved IgCAMs (immunoglobulin superfamily cell adhesion molecules), neuroglian (Nrg) and fasciclin 2 (Fas2), participate in cell reintegration in the Drosophila follicular epithelium [4]. Like their vertebrate orthologs L1CAM and NCAM1/2, respectively, Nrg and Fas2 are cell adhesion molecules primarily studied in the context of nervous system development [7-10]. Consistent with this, we identify another neural IgCAM, Fasciclin 3 (Fas3), as a reintegration factor. Nrg, Fas2, and Fas3 are components of the insect septate junction, the functional equivalent of the vertebrate tight junction, but proliferating follicle cells do not have mature septate junctions, and we find that the septate junction protein neurexin IV does not participate in reintegration [11, 12]. Here, we show that epithelial reintegration works in the same way as IgCAM-mediated axon growth and pathfinding; it relies not only on extracellular adhesion but also mechanical coupling between IgCAMs and the lateral spectrin-based membrane skeleton. Our work indicates that reintegration is mediated by a distinct epithelial adhesion assembly that is compositionally and functionally equivalent to junctions made between axons.
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Affiliation(s)
- Christian Cammarota
- Department of Physics & Astronomy, University of Rochester, Rochester, NY 14627, USA
| | - Tara M Finegan
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
| | - Tyler J Wilson
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
| | - Sifan Yang
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
| | - Dan T Bergstralh
- Department of Physics & Astronomy, University of Rochester, Rochester, NY 14627, USA; Department of Biology, University of Rochester, Rochester, NY 14627, USA; Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, NY 14627, USA.
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5
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Finegan TM, Bergstralh DT. Neuronal immunoglobulin superfamily cell adhesion molecules in epithelial morphogenesis: insights from Drosophila. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190553. [PMID: 32829687 PMCID: PMC7482216 DOI: 10.1098/rstb.2019.0553] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/19/2020] [Indexed: 12/25/2022] Open
Abstract
In this review, we address the function of immunoglobulin superfamily cell adhesion molecules (IgCAMs) in epithelia. Work in the Drosophila model system in particular has revealed novel roles for calcium-independent adhesion molecules in the morphogenesis of epithelial tissues. We review the molecular composition of lateral junctions with a focus on their IgCAM components and reconsider the functional roles of epithelial lateral junctions. The epithelial IgCAMs discussed in this review have well-defined roles in the nervous system, particularly in the process of axon guidance, suggesting functional overlap and conservation in mechanism between that process and epithelial remodelling. We expand on the hypothesis that epithelial occluding junctions and synaptic junctions are compositionally equivalent and present a novel hypothesis that the mechanism of epithelial cell (re)integration and synaptic junction formation are shared. We highlight the importance of considering non-cadherin-based adhesion in our understanding of the mechanics of epithelial tissues and raise questions to direct future work. This article is part of the discussion meeting issue 'Contemporary morphogenesis'.
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6
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Chou VT, Johnson SA, Van Vactor D. Synapse development and maturation at the drosophila neuromuscular junction. Neural Dev 2020; 15:11. [PMID: 32741370 PMCID: PMC7397595 DOI: 10.1186/s13064-020-00147-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 07/14/2020] [Indexed: 12/12/2022] Open
Abstract
Synapses are the sites of neuron-to-neuron communication and form the basis of the neural circuits that underlie all animal cognition and behavior. Chemical synapses are specialized asymmetric junctions between a presynaptic neuron and a postsynaptic target that form through a series of diverse cellular and subcellular events under the control of complex signaling networks. Once established, the synapse facilitates neurotransmission by mediating the organization and fusion of synaptic vesicles and must also retain the ability to undergo plastic changes. In recent years, synaptic genes have been implicated in a wide array of neurodevelopmental disorders; the individual and societal burdens imposed by these disorders, as well as the lack of effective therapies, motivates continued work on fundamental synapse biology. The properties and functions of the nervous system are remarkably conserved across animal phyla, and many insights into the synapses of the vertebrate central nervous system have been derived from studies of invertebrate models. A prominent model synapse is the Drosophila melanogaster larval neuromuscular junction, which bears striking similarities to the glutamatergic synapses of the vertebrate brain and spine; further advantages include the simplicity and experimental versatility of the fly, as well as its century-long history as a model organism. Here, we survey findings on the major events in synaptogenesis, including target specification, morphogenesis, and the assembly and maturation of synaptic specializations, with a emphasis on work conducted at the Drosophila neuromuscular junction.
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Affiliation(s)
- Vivian T Chou
- Department of Cell Biology and Program in Neuroscience, Blavatnik Institute, Harvard Medical School, Boston, MA, 02115, USA
| | - Seth A Johnson
- Department of Cell Biology and Program in Neuroscience, Blavatnik Institute, Harvard Medical School, Boston, MA, 02115, USA.
| | - David Van Vactor
- Department of Cell Biology and Program in Neuroscience, Blavatnik Institute, Harvard Medical School, Boston, MA, 02115, USA.
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7
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Strah N, Romano G, Introna C, Klima R, Marzullo M, Ciapponi L, Megighian A, Nizzardo M, Feiguin F. TDP-43 promotes the formation of neuromuscular synapses through the regulation of Disc-large expression in Drosophila skeletal muscles. BMC Biol 2020; 18:34. [PMID: 32216790 PMCID: PMC7099817 DOI: 10.1186/s12915-020-00767-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 03/10/2020] [Indexed: 12/12/2022] Open
Abstract
Background The ribonuclear protein TDP-43 has been implicated in the pathophysiology of amyotrophic lateral sclerosis (ALS), with genetic mutations being linked to the neurological symptoms of the disease. Though alterations in the intracellular distribution of TDP-43 have been observed in skeletal muscles of patients suffering from ALS, it is not clear whether such modifications play an active role in the disease or merely represent an expression of muscle homeostatic mechanisms. Also, the molecular and metabolic pathways regulated by TDP-43 in the skeletal muscle remain largely unknown. Here, we analyze the function of TBPH, the Drosophila melanogaster ortholog of TDP-43, in skeletal muscles. Results We modulated the activity of TDP-43 in Drosophila muscles by means of RNA interference and observed that it is required to promote the formation and growth of neuromuscular synapses. TDP-43 regulated the expression levels of Disc-large (Dlg), and restoring Dlg expression either in skeletal muscles or in motoneurons was sufficient to suppress the locomotive and synaptic defects of TDP-43-null flies. These results were validated by the observation of a decrease in Dlg levels in human neuroblastoma cells and iPSC-differentiated motoneurons derived from ALS patients, suggesting similar mechanisms may potentially be involved in the pathophysiology of the disease. Conclusions Our results help to unveil the physiological role of TDP-43 in skeletal muscles as well as the mechanisms responsible for the autonomous and non-autonomous behavior of this protein concerning the organization of neuromuscular synapses.
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Affiliation(s)
- Nina Strah
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149, Trieste, Italy
| | - Giulia Romano
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149, Trieste, Italy
| | - Clelia Introna
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149, Trieste, Italy
| | - Raffaella Klima
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149, Trieste, Italy
| | - Marta Marzullo
- Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, Rome, Italy.,Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza Università di Roma, Rome, Italy
| | - Laura Ciapponi
- Dipartimento di Biologia e Biotecnologie "C. Darwin", Sapienza Università di Roma, Rome, Italy
| | - Aram Megighian
- Department of Biomedical Sciences, University of Padova, via Marzolo 3, 35131, Padua, Italy
| | - Monica Nizzardo
- Department of Pathophysiology and Transplantation (DePT), Dino Ferrari Centre, University of Milan, Neuroscience Section, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy
| | - Fabian Feiguin
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149, Trieste, Italy.
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8
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Inal MA, Banzai K, Kamiyama D. Retrograde Tracing of Drosophila Embryonic Motor Neurons Using Lipophilic Fluorescent Dyes. J Vis Exp 2020. [PMID: 31984960 DOI: 10.3791/60716] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
We describe a technique for retrograde labeling of motor neurons in Drosophila. We use an oil-dissolved lipophilic dye and deliver a small droplet to an embryonic fillet preparation by a microinjector. Each motor neuron whose membrane is contacted by the droplet can then be rapidly labeled. Individual motor neurons are continuously labeled, enabling fine structural details to be clearly visualized. Given that lipophilic dyes come in various colors, the technique also provides a means to get adjacent neurons labeled in multicolor. This tracing technique is therefore useful for studying neuronal morphogenesis and synaptic connectivity in the motor neuron system of Drosophila.
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Affiliation(s)
| | - Kota Banzai
- Department of Cellular Biology, University of Georgia
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9
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Sphingolipid-dependent Dscam sorting regulates axon segregation. Nat Commun 2019; 10:813. [PMID: 30778062 PMCID: PMC6379420 DOI: 10.1038/s41467-019-08765-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 01/17/2019] [Indexed: 12/22/2022] Open
Abstract
Neurons are highly polarized cells with distinct protein compositions in axonal and dendritic compartments. Cellular mechanisms controlling polarized protein sorting have been described for mature nervous system but little is known about the segregation in newly differentiated neurons. In a forward genetic screen for regulators of Drosophila brain circuit development, we identified mutations in SPT, an evolutionary conserved enzyme in sphingolipid biosynthesis. Here we show that reduced levels of sphingolipids in SPT mutants cause axonal morphology defects similar to loss of cell recognition molecule Dscam. Loss- and gain-of-function studies show that neuronal sphingolipids are critical to prevent aggregation of axonal and dendritic Dscam isoforms, thereby ensuring precise Dscam localization to support axon branch segregation. Furthermore, SPT mutations causing neurodegenerative HSAN-I disorder in humans also result in formation of stable Dscam aggregates and axonal branch phenotypes in Drosophila neurons, indicating a causal link between developmental protein sorting defects and neuronal dysfunction. Little is known about the initial segregation of axonal and dendritic proteins during the differentiation of newly generated neurons. Here authors use a forward genetic screen to identify the role of sphingolipids in regulating the sub-cellular distribution of Dscam for neuronal patterning in Drosophila Mushroom Bodies
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10
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Neuert H, Deing P, Krukkert K, Naffin E, Steffes G, Risse B, Silies M, Klämbt C. The Drosophila NCAM homolog Fas2 signals independent of adhesion. Development 2019; 147:dev.181479. [DOI: 10.1242/dev.181479] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 12/09/2019] [Indexed: 12/22/2022]
Abstract
The development of tissues and organs requires close interaction of cells. To do so, cells express adhesion proteins such as the neural cell adhesion molecule (NCAM) or its Drosophila orthologue Fasciclin 2 (Fas2). Both are members of the Ig-domain superfamily of proteins that mediate homophilic adhesion. These proteins are expressed as different isoforms differing in their membrane anchorage and their cytoplasmic domains. To study the function of single isoforms we have conducted a comprehensive genetic analysis of fas2. We reveal the expression pattern of all major Fas2 isoforms, two of which are GPI-anchored. The remaining five isoforms carry transmembrane domains with variable cytoplasmic tails. We generated fas2 mutants expressing only single isoforms. In contrast to the null mutation which causes embryonic lethality, these mutants are viable, indicating redundancy among the different isoforms. Cell type specific rescue experiments showed that glial secreted Fas2 can rescue the fas2 mutant phenotype to viability. This demonstrates cytoplasmic Fas2 domains have no apparent essential functions and indicate that Fas2 has function(s) other than homophilic adhesion. In conclusion, our data propose novel mechanistic aspects of a long studied adhesion protein.
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Affiliation(s)
- Helen Neuert
- University of Münster, Institute for Neuro- and Behavioral Biology, Badestr. 9, 48149 Münster, Germany
| | - Petra Deing
- University of Münster, Institute for Neuro- and Behavioral Biology, Badestr. 9, 48149 Münster, Germany
| | - Karin Krukkert
- University of Münster, Institute for Neuro- and Behavioral Biology, Badestr. 9, 48149 Münster, Germany
| | - Elke Naffin
- University of Münster, Institute for Neuro- and Behavioral Biology, Badestr. 9, 48149 Münster, Germany
| | - Georg Steffes
- University of Münster, Institute for Neuro- and Behavioral Biology, Badestr. 9, 48149 Münster, Germany
| | - Benjamin Risse
- University of Münster, Institute for Neuro- and Behavioral Biology, Badestr. 9, 48149 Münster, Germany
| | - Marion Silies
- University of Münster, Institute for Neuro- and Behavioral Biology, Badestr. 9, 48149 Münster, Germany
| | - Christian Klämbt
- University of Münster, Institute for Neuro- and Behavioral Biology, Badestr. 9, 48149 Münster, Germany
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11
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Sheng C, Javed U, Gibbs M, Long C, Yin J, Qin B, Yuan Q. Experience-dependent structural plasticity targets dynamic filopodia in regulating dendrite maturation and synaptogenesis. Nat Commun 2018; 9:3362. [PMID: 30135566 PMCID: PMC6105721 DOI: 10.1038/s41467-018-05871-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 07/27/2018] [Indexed: 11/21/2022] Open
Abstract
Highly motile dendritic protrusions are hallmarks of developing neurons. These exploratory filopodia sample the environment and initiate contacts with potential synaptic partners. To understand the role for dynamic filopodia in dendrite morphogenesis and experience-dependent structural plasticity, we analyzed dendrite dynamics, synapse formation, and dendrite volume expansion in developing ventral lateral neurons (LNvs) of the Drosophila larval visual circuit. Our findings reveal the temporal coordination between heightened dendrite dynamics with synaptogenesis in LNvs and illustrate the strong influence imposed by sensory experience on the prevalence of dendritic filopodia, which regulate the formation of synapses and the expansion of dendritic arbors. Using genetic analyses, we further identified Amphiphysin (Amph), a BAR (Bin/Amphiphysin/Rvs) domain-containing protein as a required component for tuning the dynamic state of LNv dendrites and promoting dendrite maturation. Taken together, our study establishes dynamic filopodia as the key cellular target for experience-dependent regulation of dendrite development. During development, dendrites display structural plasticity, as reflected in the appearance of long, thin and highly motile dendritic filopodia. Here, the authors examine dendritic dynamics of ventral lateral neurons in the developing Drosophila larva, and identify Amphiphysin as an important regulator of this process.
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Affiliation(s)
- Chengyu Sheng
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Uzma Javed
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Mary Gibbs
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Caixia Long
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Jun Yin
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Bo Qin
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Quan Yuan
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, 20892, USA.
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12
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Nahm M, Park S, Lee J, Lee S. MICAL-like Regulates Fasciclin II Membrane Cycling and Synaptic Development. Mol Cells 2016; 39:762-767. [PMID: 27770767 PMCID: PMC5104885 DOI: 10.14348/molcells.2016.0203] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 09/12/2016] [Accepted: 09/12/2016] [Indexed: 11/27/2022] Open
Abstract
Fasciclin II (FasII), the Drosophila ortholog of neural cell adhesion molecule (NCAM), plays a critical role in synaptic stabilization and plasticity. Although this molecule undergoes constitutive cycling at the synaptic membrane, how its membrane trafficking is regulated to ensure proper synaptic development remains poorly understood. In a genetic screen, we recovered a mutation in Drosophila mical-like that displays an increase in bouton numbers and a decrease in FasII levels at the neuromuscular junction (NMJ). Similar phenotypes were induced by presynaptic, but not postsynaptic, knockdown of mical-like expression. FasII trafficking assays revealed that the recycling of internalized FasII molecules to the cell surface was significantly impaired in mical-like-knockdown cells. Importantly, this defect correlated with an enhancement of endosomal sorting of FasII to the lysosomal degradation pathway. Similarly, synaptic vesicle exocytosis was also impaired in mical-like mutants. Together, our results identify Mical-like as a novel regulator of synaptic growth and FasII endocytic recycling.
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Affiliation(s)
- Minyeop Nahm
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul 08826,
Korea
- School of Dentistry and Dental Research Institute, Seoul National University, Seoul 08826,
Korea
| | - Sunyoung Park
- Interdisciplinary Graduate Program in Brain Science, College of Natural Sciences, Seoul National University, Seoul 08826,
Korea
| | - Jihye Lee
- Department of Oral Pathology and BK21 PLUS Project, School of Dentistry and Institute of Translational Dental Sciences, Pusan National University, Yangsan 50612,
Korea
| | - Seungbok Lee
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul 08826,
Korea
- School of Dentistry and Dental Research Institute, Seoul National University, Seoul 08826,
Korea
- Interdisciplinary Graduate Program in Brain Science, College of Natural Sciences, Seoul National University, Seoul 08826,
Korea
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13
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Harden N, Wang SJH, Krieger C. Making the connection – shared molecular machinery and evolutionary links underlie the formation and plasticity of occluding junctions and synapses. J Cell Sci 2016; 129:3067-76. [DOI: 10.1242/jcs.186627] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
ABSTRACT
The pleated septate junction (pSJ), an ancient structure for cell–cell contact in invertebrate epithelia, has protein components that are found in three more-recent junctional structures, the neuronal synapse, the paranodal region of the myelinated axon and the vertebrate epithelial tight junction. These more-recent structures appear to have evolved through alterations of the ancestral septate junction. During its formation in the developing animal, the pSJ exhibits plasticity, although the final structure is extremely robust. Similar to the immature pSJ, the synapse and tight junctions both exhibit plasticity, and we consider evidence that this plasticity comes at least in part from the interaction of members of the immunoglobulin cell adhesion molecule superfamily with highly regulated membrane-associated guanylate kinases. This plasticity regulation probably arose in order to modulate the ancestral pSJ and is maintained in the derived structures; we suggest that it would be beneficial when studying plasticity of one of these structures to consider the literature on the others. Finally, looking beyond the junctions, we highlight parallels between epithelial and synaptic membranes, which both show a polarized distribution of many of the same proteins – evidence that determinants of apicobasal polarity in epithelia also participate in patterning of the synapse.
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Affiliation(s)
- Nicholas Harden
- Simon Fraser University, Department of Molecular Biology and Biochemistry, Burnaby, British Columbia V5A 1S6, Canada
| | - Simon Ji Hau Wang
- Simon Fraser University, Department of Molecular Biology and Biochemistry, Burnaby, British Columbia V5A 1S6, Canada
- Simon Fraser University, Department of Biomedical Physiology and Kinesiology, Burnaby, British Columbia V5A 1S6, Canada
| | - Charles Krieger
- Simon Fraser University, Department of Biomedical Physiology and Kinesiology, Burnaby, British Columbia V5A 1S6, Canada
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Halberg KA, Rainey SM, Veland IR, Neuert H, Dornan AJ, Klämbt C, Davies SA, Dow JAT. The cell adhesion molecule Fasciclin2 regulates brush border length and organization in Drosophila renal tubules. Nat Commun 2016; 7:11266. [PMID: 27072072 PMCID: PMC4833865 DOI: 10.1038/ncomms11266] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 03/08/2016] [Indexed: 12/20/2022] Open
Abstract
Multicellular organisms rely on cell adhesion molecules to coordinate cell–cell interactions, and to provide navigational cues during tissue formation. In Drosophila, Fasciclin 2 (Fas2) has been intensively studied due to its role in nervous system development and maintenance; yet, Fas2 is most abundantly expressed in the adult renal (Malpighian) tubule rather than in neuronal tissues. The role Fas2 serves in this epithelium is unknown. Here we show that Fas2 is essential to brush border maintenance in renal tubules of Drosophila. Fas2 is dynamically expressed during tubule morphogenesis, localizing to the brush border whenever the tissue is transport competent. Genetic manipulations of Fas2 expression levels impact on both microvilli length and organization, which in turn dramatically affect stimulated rates of fluid secretion by the tissue. Consequently, we demonstrate a radically different role for this well-known cell adhesion molecule, and propose that Fas2-mediated intermicrovillar homophilic adhesion complexes help stabilize the brush border. In Drosophila, Fasciclin 2 (Fas2) has been mainly studied in the nervous system, yet this adhesion protein is more abundant in the adult renal tubule. Here the authors show that Fas2 is essential for brush border maintenance in renal tubules through regulation of microvilli length and organization.
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Affiliation(s)
- Kenneth A Halberg
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Davidson Building Room 324, Glasgow G12 8QQ, UK.,Section for Cell &Neurobiology, Department of Biology, University of Copenhagen, Universitetsparken 15, Copenhagen DK-2100, Denmark
| | - Stephanie M Rainey
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Davidson Building Room 324, Glasgow G12 8QQ, UK.,MRC-University of Glasgow Centre for Virus Research, Henry Wellcome Building, 464 Bearsden Road, Glasgow G61 1QH, UK
| | - Iben R Veland
- Cancer Research UK
- Beatson Institute, Garscube Estate, Switchback road, Glasgow G61 1BD, UK.,Section of Cell Biology and Physiology, Department of Biology, University of Copenhagen, Universitetsparken 13, Copenhagen DK-2100, Denmark
| | - Helen Neuert
- Institut für Neuro- und Verhaltensbiologie, Universität Münster, Badestrasse 9, 48149 Münster, Germany
| | - Anthony J Dornan
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Davidson Building Room 324, Glasgow G12 8QQ, UK
| | - Christian Klämbt
- Institut für Neuro- und Verhaltensbiologie, Universität Münster, Badestrasse 9, 48149 Münster, Germany
| | - Shireen-Anne Davies
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Davidson Building Room 324, Glasgow G12 8QQ, UK
| | - Julian A T Dow
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Davidson Building Room 324, Glasgow G12 8QQ, UK
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15
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Sturgeon M, Davis D, Albers A, Beatty D, Austin R, Ferguson M, Tounsel B, Liebl FLW. The Notch ligand E3 ligase, Mind Bomb1, regulates glutamate receptor localization in Drosophila. Mol Cell Neurosci 2015; 70:11-21. [PMID: 26596173 DOI: 10.1016/j.mcn.2015.11.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Revised: 11/09/2015] [Accepted: 11/16/2015] [Indexed: 12/29/2022] Open
Abstract
The postsynaptic density (PSD) is a protein-rich network important for the localization of postsynaptic glutamate receptors (GluRs) and for signaling downstream of these receptors. Although hundreds of PSD proteins have been identified, many are functionally uncharacterized. We conducted a reverse genetic screen for mutations that affected GluR localization using Drosophila genes that encode homologs of mammalian PSD proteins. 42.8% of the mutants analyzed exhibited a significant change in GluR localization at the third instar larval neuromuscular junction (NMJ), a model synapse that expresses homologs of AMPA receptors. We identified the E3 ubiquitin ligase, Mib1, which promotes Notch signaling, as a regulator of synaptic GluR localization. Mib1 positively regulates the localization of the GluR subunits GluRIIA, GluRIIB, and GluRIIC. Mutations in mib1 and ubiquitous expression of Mib1 that lacks its ubiquitin ligase activity result in the loss of synaptic GluRIIA-containing receptors. In contrast, overexpression of Mib1 in all tissues increases postsynaptic levels of GluRIIA. Cellular levels of Mib1 are also important for the structure of the presynaptic motor neuron. While deficient Mib1 signaling leads to overgrowth of the NMJ, ubiquitous overexpression of Mib1 results in a reduction in the number of presynaptic motor neuron boutons and branches. These synaptic changes may be secondary to attenuated glutamate release from the presynaptic motor neuron in mib1 mutants as mib1 mutants exhibit significant reductions in the vesicle-associated protein cysteine string protein and in the frequency of spontaneous neurotransmission.
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Affiliation(s)
- Morgan Sturgeon
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Dustin Davis
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Amanda Albers
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Derek Beatty
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Rik Austin
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Matt Ferguson
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Brittany Tounsel
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Faith L W Liebl
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States.
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16
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Harris KP, Littleton JT. Transmission, Development, and Plasticity of Synapses. Genetics 2015; 201:345-75. [PMID: 26447126 PMCID: PMC4596655 DOI: 10.1534/genetics.115.176529] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/28/2015] [Indexed: 01/03/2023] Open
Abstract
Chemical synapses are sites of contact and information transfer between a neuron and its partner cell. Each synapse is a specialized junction, where the presynaptic cell assembles machinery for the release of neurotransmitter, and the postsynaptic cell assembles components to receive and integrate this signal. Synapses also exhibit plasticity, during which synaptic function and/or structure are modified in response to activity. With a robust panel of genetic, imaging, and electrophysiology approaches, and strong evolutionary conservation of molecular components, Drosophila has emerged as an essential model system for investigating the mechanisms underlying synaptic assembly, function, and plasticity. We will discuss techniques for studying synapses in Drosophila, with a focus on the larval neuromuscular junction (NMJ), a well-established model glutamatergic synapse. Vesicle fusion, which underlies synaptic release of neurotransmitters, has been well characterized at this synapse. In addition, studies of synaptic assembly and organization of active zones and postsynaptic densities have revealed pathways that coordinate those events across the synaptic cleft. We will also review modes of synaptic growth and plasticity at the fly NMJ, and discuss how pre- and postsynaptic cells communicate to regulate plasticity in response to activity.
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Affiliation(s)
- Kathryn P Harris
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - J Troy Littleton
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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17
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Abstract
Semaphorin family proteins are well-known axon guidance ligands. Recent studies indicate that certain transmembrane Semaphorins can also function as guidance receptors to mediate axon-axon attraction or repulsion. The mechanisms by which Semaphorin reverse signaling modulates axon-surface affinity, however, remain unknown. In this study, we reveal a novel mechanism underlying upregulation of axon-axon attraction by Semaphorin-1a (Sema1a) reverse signaling in the developing Drosophila visual system. Sema1a promotes the phosphorylation and activation of Moesin (Moe), a member of the ezrin/radixin/moesin family of proteins, and downregulates the level of active Rho1 in photoreceptor axons. We propose that Sema1a reverse signaling activates Moe, which in turn upregulates Fas2-mediated axon-axon attraction by inhibiting Rho1.
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18
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Hahn A, Stevanovic M, Brouwer E, Bublak D, Tripp J, Schorge T, Karas M, Schleiff E. Secretome analysis of Anabaena sp. PCC 7120 and the involvement of the TolC-homologue HgdD in protein secretion. Environ Microbiol 2014; 17:767-80. [PMID: 24890022 DOI: 10.1111/1462-2920.12516] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 05/18/2014] [Indexed: 12/01/2022]
Abstract
Secretion of proteins is a central strategy of bacteria to influence and respond to their environment. Until now, there has been very few discoveries regarding the cyanobacterial secrotome or the secretion machineries involved. For a mutant of the outer membrane channel TolC-homologue HgdD of Anabaena sp. PCC 7120, a filamentous and heterocyst-forming cyanobacterium, an altered secretome profile was reported. To define the role of HgdD in protein secretion, we have developed a method to isolate extracellular proteins of Anabaena sp. PCC 7120 wild type and an hgdD loss-of-function mutant. We identified 51 proteins of which the majority is predicted to have an extracellular secretion signal, while few seem to be localized in the periplasmic space. Eight proteins were exclusively identified in the secretome of wild-type cells, which coincides with the distribution of type I secretion signal. We selected three candidates and generated hemagglutinin-tagged fusion proteins which could be exclusively detected in the extracellular protein fraction. However, these proteins are not secreted in the hgdD-mutant background, where they are rapidly degraded. This confirms a direct function of HgdD in protein secretion and points to the existence of a quality control mechanism at least for proteins secreted in an HgdD-dependent pathway.
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Affiliation(s)
- Alexander Hahn
- Institute of Molecular Biosciences, Cell Biology of Plants, Goethe University, Max-von-Laue Str. 9, Frankfurt/am Main, 60438, Germany
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19
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Gomez JM, Wang Y, Riechmann V. Tao controls epithelial morphogenesis by promoting Fasciclin 2 endocytosis. ACTA ACUST UNITED AC 2013; 199:1131-43. [PMID: 23266957 PMCID: PMC3529531 DOI: 10.1083/jcb.201207150] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Tao initiates morphogenesis of a squamous epithelium by promoting the endocytosis of the adhesion molecule Fasciclin 2 from the lateral membrane. Regulation of epithelial cell shape, for example, changes in relative sizes of apical, basal, and lateral membranes, is a key mechanism driving morphogenesis. However, it is unclear how epithelial cells control the size of their membranes. In the epithelium of the Drosophila melanogaster ovary, cuboidal precursor cells transform into a squamous epithelium through a process that involves lateral membrane shortening coupled to apical membrane extension. In this paper, we report a mutation in the gene Tao, which resulted in the loss of this cuboidal to squamous transition. We show that the inability of Tao mutant cells to shorten their membranes was caused by the accumulation of the cell adhesion molecule Fasciclin 2, the Drosophila N-CAM (neural cell adhesion molecule) homologue. Fasciclin 2 accumulation at the lateral membrane of Tao mutant cells prevented membrane shrinking and thereby inhibited morphogenesis. In wild-type cells, Tao initiated morphogenesis by promoting Fasciclin 2 endocytosis at the lateral membrane. Thus, we identify here a mechanism controlling the morphogenesis of a squamous epithelium.
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Affiliation(s)
- Juan Manuel Gomez
- Department of Cell and Molecular Biology, Medical Faculty Mannheim, Heidelberg University, D-68167 Mannheim, Germany
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20
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Voigt B, Hieu CX, Hempel K, Becher D, Schlüter R, Teeling H, Glöckner FO, Amann R, Hecker M, Schweder T. Cell surface proteome of the marine planctomycete Rhodopirellula baltica. Proteomics 2012; 12:1781-91. [PMID: 22623273 DOI: 10.1002/pmic.201100512] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The surface proteome (surfaceome) of the marine planctomycete Rhodopirellula baltica SH1(T) was studied using a biotinylation and a proteinase K approach combined with SDS-PAGE and mass spectrometry. 52 of the proteins identified in both approaches could be assigned to the group of potential surface proteins. Among them are some high molecular weight proteins, potentially involved in cell-cell attachment, that contain domains shown before to be typical for surface proteins like cadherin/dockerin domains, a bacterial adhesion domain or the fasciclin domain. The identification of proteins with enzymatic functions in the R. baltica surfaceome provides further clues for the suggestion that some degradative enzymes may be anchored onto the cell surface. YTV proteins, which have been earlier supposed to be components of the proteinaceous cell wall of R. baltica, were detected in the surface proteome. Additionally, 8 proteins with a novel protein structure combining a conserved type IV pilin/N-methylation domain and a planctomycete-typical DUF1559 domain were identified.
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Affiliation(s)
- Birgit Voigt
- Institute for Microbiology, Ernst-Moritz-Arndt-University, Greifswald, Germany
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21
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Zhou Y, Cameron S, Chang WT, Rao Y. Control of directional change after mechanical stimulation in Drosophila. Mol Brain 2012; 5:39. [PMID: 23107101 PMCID: PMC3514245 DOI: 10.1186/1756-6606-5-39] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 10/23/2012] [Indexed: 11/11/2022] Open
Abstract
Background Proper adjustment of moving direction after external mechanical stimulation is essential for animals to avoid danger (e.g. predators), and thus is vital for survival. This process involves sensory inputs, central processing and motor outputs. Recent studies have made considerable progress in identifying mechanosensitive neurons and mechanosensation receptor proteins. Our understandings of molecular and cellular mechanisms that link mechanosensation with the changes in moving direction, however, remain limited. Results In this study, we investigate the control of movement adjustment in Drosophila. In response to gentle touch at the anterior segments, Drosophila larvae reorient and select a new direction for forward movement. The extent of change in moving direction is correlated with the intensity of tactile stimuli. Sensation of gentle touch requires chordotonal organs and class IV da neurons. Genetic analysis indicates an important role for the evolutionarily conserved immunoglobulin (Ig) superfamily protein Turtle (Tutl) to regulate touch-initiated directional change. Tutl is required specifically in post-mitotic neurons at larval stage after the completion of embryonic development. Circuit breaking analysis identified a small subset of Tutl-positive neurons that are involved in the adjustment of moving direction. Conclusion We identify Tutl and a small subset of CNS neurons in modulating directional change in response to gentle touch. This study presents an excellent starting point for further dissection of molecular and cellular mechanisms controlling directional adjustment after mechanical stimulation.
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Affiliation(s)
- Yating Zhou
- McGill Centre for Research in Neuroscience, McGill University Health Centre, Montreal, Quebec, Canada
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22
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Kohsaka H, Okusawa S, Itakura Y, Fushiki A, Nose A. Development of larval motor circuits in Drosophila. Dev Growth Differ 2012; 54:408-19. [PMID: 22524610 DOI: 10.1111/j.1440-169x.2012.01347.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
How are functional neural circuits formed during development? Despite recent advances in our understanding of the development of individual neurons, little is known about how complex circuits are assembled to generate specific behaviors. Here, we describe the ways in which Drosophila motor circuits serve as an excellent model system to tackle this problem. We first summarize what has been learned during the past decades on the connectivity and development of component neurons, in particular motor neurons and sensory feedback neurons. We then review recent progress in our understanding of the development of the circuits as well as studies that apply optogenetics and other innovative techniques to dissect the circuit diagram. New approaches using Drosophila as a model system are now making it possible to search for developmental rules that regulate the construction of neural circuits.
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Affiliation(s)
- Hiroshi Kohsaka
- Department of Physics, Graduate School of Science, University of Tokyo, 7-3-1, Hongo, Tokyo 113-0033, Japan
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23
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Synaptic functions of invertebrate varicosities: what molecular mechanisms lie beneath. Neural Plast 2012; 2012:670821. [PMID: 22655209 PMCID: PMC3359714 DOI: 10.1155/2012/670821] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Accepted: 02/27/2012] [Indexed: 11/26/2022] Open
Abstract
In mammalian brain, the cellular and molecular events occurring in both synapse formation and plasticity are difficult to study due to the large number of factors involved in these processes and because the contribution of each component is not well defined. Invertebrates, such as Drosophila, Aplysia, Helix, Lymnaea, and Helisoma, have proven to be useful models for studying synaptic assembly and elementary forms of learning. Simple nervous system, cellular accessibility, and genetic simplicity are some examples of the invertebrate advantages that allowed to improve our knowledge about evolutionary neuronal conserved mechanisms. In this paper, we present an overview of progresses that elucidates cellular and molecular mechanisms underlying synaptogenesis and synapse plasticity in invertebrate varicosities and their validation in vertebrates. In particular, the role of invertebrate synapsin in the formation of presynaptic terminals and the cell-to-cell interactions that induce specific structural and functional changes in their respective targets will be analyzed.
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Nose A. Generation of neuromuscular specificity in Drosophila: novel mechanisms revealed by new technologies. Front Mol Neurosci 2012; 5:62. [PMID: 22586369 PMCID: PMC3347465 DOI: 10.3389/fnmol.2012.00062] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 04/23/2012] [Indexed: 11/13/2022] Open
Abstract
The Drosophila larval neuromuscular system is one of the best-characterized model systems for axon targeting. In each abdominal hemisegment, only 36 identified motor neurons form synaptic connections with just 30 target muscles in a highly specific and stereotypic manner. Studies in the 1990s identified several cell-surface and secreted proteins that are expressed in specific muscles and contribute to target specificity. Emerging evidence suggests that target selection is determined not only by attraction to the target cells but also by exclusion from non-target cells. Proteins with leucine-rich repeats (LRR proteins) appear to be a major molecular family of proteins responsible for the targeting. While the demonstrated roles of the target-derived cues point to active recognition by presynaptic motor neurons, postsynaptic muscles also reach out and recognize specific motor neurons by sending out cellular protrusions called myopodia. Simultaneous live imaging of myopodia and growth cones has revealed that local and mutual recognition at the tip of myopodia is critical for selective synapse formation. A large number of candidate target cues have been identified on a single muscle, suggesting that target specificity is determined by the partially redundant and combinatorial function of multiple cues. Analyses of the seemingly simple neuromuscular system in Drosophila have revealed an unexpected complexity in the mechanisms of axon targeting.
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Affiliation(s)
- Akinao Nose
- Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, University of Tokyo, Kashiwanoha, Kashiwa Chiba, Japan
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25
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Sarto-Jackson I, Milenkovic I, Smalla KH, Gundelfinger ED, Kaehne T, Herrera-Molina R, Thomas S, Kiebler MA, Sieghart W. The cell adhesion molecule neuroplastin-65 is a novel interaction partner of γ-aminobutyric acid type A receptors. J Biol Chem 2012; 287:14201-14. [PMID: 22389504 DOI: 10.1074/jbc.m111.293175] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
γ-Aminobutyric acid type A (GABA(A)) receptors are pentameric ligand-gated ion channels that mediate fast inhibition in the central nervous system. Depending on their subunit composition, these receptors exhibit distinct pharmacological properties and differ in their ability to interact with proteins involved in receptor anchoring at synaptic or extra-synaptic sites. Whereas GABA(A) receptors containing α1, α2, or α3 subunits are mainly located synaptically where they interact with the submembranous scaffolding protein gephyrin, receptors containing α5 subunits are predominantly found extra-synaptically and seem to interact with radixin for anchorage. Neuroplastin is a cell adhesion molecule of the immunoglobulin superfamily that is involved in hippocampal synaptic plasticity. Our results reveal that neuroplastin and GABA(A) receptors can be co-purified from rat brain and exhibit a direct physical interaction as demonstrated by co-precipitation and Förster resonance energy transfer (FRET) analysis in a heterologous expression system. The brain-specific isoform neuroplastin-65 co-localizes with GABA(A) receptors as shown in brain sections as well as in neuronal cultures, and such complexes can either contain gephyrin or be devoid of gephyrin. Neuroplastin-65 specifically co-localizes with α1 or α2 but not with α3 subunits at GABAergic synapses. In addition, neuroplastin-65 also co-localizes with GABA(A) receptor α5 subunits at extra-synaptic sites. Down-regulation of neuroplastin-65 by shRNA causes a loss of GABA(A) receptor α2 subunits at GABAergic synapses. These results suggest that neuroplastin-65 can co-localize with a subset of GABA(A) receptor subtypes and might contribute to anchoring and/or confining GABA(A) receptors to particular synaptic or extra-synaptic sites, thus affecting receptor mobility and synaptic strength.
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Affiliation(s)
- Isabella Sarto-Jackson
- Center for Brain Research, Department of Biochemistry and Molecular Biology of the Nervous System, Medical University of Vienna, 1090 Vienna, Austria
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26
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Fukui A, Inaki M, Tonoe G, Hamatani H, Homma M, Morimoto T, Aburatani H, Nose A. Lola regulates glutamate receptor expression at the Drosophila neuromuscular junction. Biol Open 2012; 1:362-75. [PMID: 23213426 PMCID: PMC3509458 DOI: 10.1242/bio.2012448] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Communication between pre- and post-synaptic cells is a key process in the development and modulation of synapses. Reciprocal induction between pre- and postsynaptic cells involves regulation of gene transcription, yet the underlying genetic program remains largely unknown. To investigate how innervation-dependent gene expression in postsynaptic cells supports synaptic differentiation, we performed comparative microarray analysis of Drosophila muscles before and after innervation, and of prospero mutants, which show a delay in motor axon outgrowth. We identified 84 candidate genes that are potentially up- or downregulated in response to innervation. By systematic functional analysis, we found that one of the downregulated genes, longitudinals lacking (lola), which encodes a BTB-Zn-finger transcription factor, is required for proper expression of glutamate receptors. When the function of lola was knocked down in muscles by RNAi, the abundance of glutamate receptors (GluRs), GluRIIA, GluRIIB and GluRIII, as well as that of p-21 activated kinase (PAK), was greatly reduced at the neuromuscular junctions (NMJs). Recordings of the synaptic response revealed a decrease in postsynaptic quantal size, consistent with the reduction in GluR levels. Lola appears to regulate the expression of GluRs and PAK at the level of transcription, because the amount of mRNAs encoding these molecules was also reduced in the mutants. The transcriptional level of lola, in turn, is downregulated by increased neural activity. We propose that Lola coordinates expression of multiple postsynaptic components by transcriptional regulation.
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Affiliation(s)
- Ai Fukui
- Department of Physics, Graduate School of Science, University of Tokyo , Hongo, Bunkyo-ku, Tokyo 113-0033 , Japan
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27
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Sun M, Xie W. Cell adhesion molecules in Drosophila synapse development and function. SCIENCE CHINA-LIFE SCIENCES 2012; 55:20-6. [PMID: 22314487 DOI: 10.1007/s11427-012-4273-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 09/15/2011] [Indexed: 12/11/2022]
Abstract
Synapse is a highly specialized inter-cellular structure between neurons or between a neuron and its target cell that mediates cell-cell communications. Ample results indicate that synaptic adhesion molecules are critically important in modulating the complexity and specificity of the synapse. And disruption of adhesive properties of synapses may lead to neurodevelopmental or neurodegenerative diseases. In this review, we will use the Drosophila NMJ as a model system for glutamatergic synapses to discuss the structure and function of homophilic and heterophilic synaptic adhesion molecules with special focus on recent findings in neurexins and neuroligins in Drosophila.
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Affiliation(s)
- Mingkuan Sun
- Key Laboratory of DGHD, MOE, Institute of Life Sciences, Southeast University, Nanjing 210096, China.
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Glutamate receptors in synaptic assembly and plasticity: case studies on fly NMJs. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 970:3-28. [PMID: 22351049 DOI: 10.1007/978-3-7091-0932-8_1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The molecular and cellular mechanisms that control the composition and functionality of ionotropic glutamate receptors may be considered as most important "set screws" for adjusting excitatory transmission in the course of developmental and experience-dependent changes within neural networks. The Drosophila larval neuromuscular junction has emerged as one important invertebrate model system to study the formation, maintenance, and plasticity-related remodeling of glutamatergic synapses in vivo. By exploiting the unique genetic accessibility of this organism combined with diverse tools for manipulation and analysis including electrophysiology and state of the art imaging, considerable progress has been made to characterize the role of glutamate receptors during the orchestration of junctional development, synaptic activity, and synaptogenesis. Following an introduction to basic features of this model system, we will mainly focus on conceptually important findings such as the selective impact of glutamate receptor subtypes on the formation of new synapses, the coordination of presynaptic maturation and receptor subtype composition, the role of nonvesicularly released glutamate on the synaptic localization of receptors, or the homeostatic feedback of receptor functionality on presynaptic transmitter release.
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Zhong Y, Shtineman-Kotler A, Nguyen L, Iliadi KG, Boulianne GL, Rotin D. A splice isoform of DNedd4, DNedd4-long, negatively regulates neuromuscular synaptogenesis and viability in Drosophila. PLoS One 2011; 6:e27007. [PMID: 22110599 PMCID: PMC3215714 DOI: 10.1371/journal.pone.0027007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 10/07/2011] [Indexed: 11/29/2022] Open
Abstract
Background Neuromuscular (NM) synaptogenesis is a tightly regulated process. We previously showed that in flies, Drosophila Nedd4 (dNedd4/dNedd4S) is required for proper NM synaptogenesis by promoting endocytosis of commissureless from the muscle surface, a pre-requisite step for muscle innervation. DNedd4 is an E3 ubiquitin ligase comprised of a C2-WW(x3)-Hect domain architecture, which includes several splice isoforms, the most prominent ones are dNedd4-short (dNedd4S) and dNedd4-long (dNedd4Lo). Methodology/Principal Findings We show here that while dNedd4S is essential for NM synaptogenesis, the dNedd4Lo isoform inhibits this process and causes lethality. Our results reveal that unlike dNedd4S, dNedd4Lo cannot rescue the lethality of dNedd4 null (DNedd4T121FS) flies. Moreover, overexpression of UAS-dNedd4Lo specifically in wildtype muscles leads to NM synaptogenesis defects, impaired locomotion and larval lethality. These negative effects of dNedd4Lo are ameliorated by deletion of two regions (N-terminus and Middle region) unique to this isoform, and by inactivating the catalytic activity of dNedd4Lo, suggesting that these unique regions, as well as catalytic activity, are responsible for the inhibitory effects of dNedd4Lo on synaptogenesis. In accord with these findings, we demonstrate by sqRT-PCR an increase in dNedd4S expression relative to the expression of dNedd4Lo during embryonic stages when synaptogenesis takes place. Conclusion/Significance Our studies demonstrate that splice isoforms of the same dNedd4 gene can lead to opposite effects on NM synaptogenesis.
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Affiliation(s)
- Yunan Zhong
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada
- Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Alina Shtineman-Kotler
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada
- Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Leo Nguyen
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada
- Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Konstantin G. Iliadi
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Gabrielle L. Boulianne
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Daniela Rotin
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada
- Department of Biochemistry, University of Toronto, Toronto, Canada
- * E-mail:
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Mochizuki H, Toda H, Ando M, Kurusu M, Tomoda T, Furukubo-Tokunaga K. Unc-51/ATG1 controls axonal and dendritic development via kinesin-mediated vesicle transport in the Drosophila brain. PLoS One 2011; 6:e19632. [PMID: 21589871 PMCID: PMC3093397 DOI: 10.1371/journal.pone.0019632] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 04/11/2011] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND Members of the evolutionary conserved Ser/Thr kinase Unc-51 family are key regulatory proteins that control neural development in both vertebrates and invertebrates. Previous studies have suggested diverse functions for the Unc-51 protein, including axonal elongation, growth cone guidance, and synaptic vesicle transport. METHODOLOGY/PRINCIPAL FINDINGS In this work, we have investigated the functional significance of Unc-51-mediated vesicle transport in the development of complex brain structures in Drosophila. We show that Unc-51 preferentially accumulates in newly elongating axons of the mushroom body, a center of olfactory learning in flies. Mutations in unc-51 cause disintegration of the core of the developing mushroom body, with mislocalization of Fasciclin II (Fas II), an IgG-family cell adhesion molecule important for axonal guidance and fasciculation. In unc-51 mutants, Fas II accumulates in the cell bodies, calyx, and the proximal peduncle. Furthermore, we show that mutations in unc-51 cause aberrant overshooting of dendrites in the mushroom body and the antennal lobe. Loss of unc-51 function leads to marked accumulation of Rab5 and Golgi components, whereas the localization of dendrite-specific proteins, such as Down syndrome cell adhesion molecule (DSCAM) and No distributive disjunction (Nod), remains unaltered. Genetic analyses of kinesin light chain (Klc) and unc-51 double heterozygotes suggest the importance of kinesin-mediated membrane transport for axonal and dendritic development. Moreover, our data demonstrate that loss of Klc activity causes similar axonal and dendritic defects in mushroom body neurons, recapitulating the salient feature of the developmental abnormalities caused by unc-51 mutations. CONCLUSIONS/SIGNIFICANCE Unc-51 plays pivotal roles in the axonal and dendritic development of the Drosophila brain. Unc-51-mediated membrane vesicle transport is important in targeted localization of guidance molecules and organelles that regulate elongation and compartmentalization of developing neurons.
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Affiliation(s)
- Hiroaki Mochizuki
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Hirofumi Toda
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
- Division of Neurosciences, Beckman Research Institute of the City of Hope, Duarte, California, United States of America
| | - Mai Ando
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Mitsuhiko Kurusu
- Structural Biology Center, National Institute of Genetics, and Department of Genetics, The Graduate University for Advanced Studies, Shizuoka, Japan
| | - Toshifumi Tomoda
- Division of Neurosciences, Beckman Research Institute of the City of Hope, Duarte, California, United States of America
| | - Katsuo Furukubo-Tokunaga
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
- * E-mail:
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31
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Zheng CY, Seabold GK, Horak M, Petralia RS. MAGUKs, synaptic development, and synaptic plasticity. Neuroscientist 2011; 17:493-512. [PMID: 21498811 DOI: 10.1177/1073858410386384] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
MAGUKs are proteins that act as key scaffolds in surface complexes containing receptors, adhesion proteins, and various signaling molecules. These complexes evolved prior to the appearance of multicellular animals and play key roles in cell-cell intercommunication. A major example of this is the neuronal synapse, which contains several presynaptic and postsynaptic MAGUKs including PSD-95, SAP102, SAP97, PSD-93, CASK, and MAGIs. Here, they play roles in both synaptic development and in later synaptic plasticity events. During development, MAGUKs help to organize the postsynaptic density via associations with other scaffolding proteins, such as Shank, and the actin cytoskeleton. They affect the clustering of glutamate receptors and other receptors, and these associations change with development. MAGUKs are involved in long-term potentiation and depression (e.g., via their phosphorylation by kinases and phosphorylation of other proteins associated with MAGUKs). Importantly, synapse development and function are dependent on the kind of MAGUK present. For example, SAP102 shows high mobility and is present in early synaptic development. Later, much of SAP102 is replaced by PSD-95, a more stable synaptic MAGUK; this is associated with changes in glutamate receptor types that are characteristic of synaptic maturation.
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Affiliation(s)
- Chan-Ying Zheng
- National Institute on Deafness and Other Communication Disorders/National Institutes of Health, Bethesda, MD 20892-8027, USA
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32
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Abstract
Synapse formation is tightly associated with neuronal excitability. We found striking synaptic overgrowth caused by Drosophila K(+)-channel mutations of the seizure and slowpoke genes, encoding Erg and Ca(2+)-activated large-conductance (BK) channels, respectively. These mutants display two distinct patterns of "satellite" budding from larval motor terminus synaptic boutons. Double-mutant analysis indicates that BK and Erg K(+) channels interact with separate sets of synaptic proteins to affect distinct growth steps. Post-synaptic L-type Ca(2+) channels, Dmca1D, and PSD-95-like scaffold protein, Discs large, are required for satellite budding induced by slowpoke and seizure mutations. Pre-synaptic cacophony Ca(2+) channels and the NCAM-like adhesion molecule, Fasciclin II, take part in a maturation step that is partially arrested by seizure mutations. Importantly, slowpoke and seizure satellites were both suppressed by rutabaga mutations that disrupt Ca(2+)/CaM-dependent adenylyl cyclase, demonstrating a convergence of K(+) channels of different functional categories in regulation of excitability-dependent Ca(2+) influx for triggering cAMP-mediated growth plasticity.
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APC/C(Fzr/Cdh1)-dependent regulation of cell adhesion controls glial migration in the Drosophila PNS. Nat Neurosci 2010; 13:1357-64. [PMID: 20890296 DOI: 10.1038/nn.2656] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 08/31/2010] [Indexed: 12/13/2022]
Abstract
Interactions between neurons and glia are a key feature during the assembly of the nervous system. During development, glial cells often follow extending axons, implying that axonal outgrowth and glial migration are precisely coordinated. We found that the anaphase-promoting complex/cyclosome (APC/C) co-activator fizzy-related/Cdh1 (Fzr/Cdh1) is involved in the non-autonomous control of peripheral glial migration in postmitotic Drosophila neurons. APC/C(Fzr/Cdh1) is a cell-cycle regulator that targets proteins that are required for G1 arrest for ubiquitination and subsequent degradation. We found that Fzr/Cdh1 function is mediated by the immunoglobulin superfamily cell adhesion molecule Fasciclin2 (Fas2). In motor neurons Fzr/Cdh1 is crucial for the establishment of a graded axonal distribution of Fas2. Axonal Fas2 interacts homophilically with a glial isoform of Fas2. Glial migration is initiated along axonal segments that have low levels of Fas2 but stalls in axonal domains with high levels of Fas2 on their surfaces. This represents a simple mechanism by which a subcellular gradient of adhesiveness can coordinate glial migration with axonal growth.
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Aplysia cell adhesion molecule and a novel protein kinase C activity in the postsynaptic neuron are required for presynaptic growth and initial formation of specific synapses. J Neurosci 2010; 30:8353-66. [PMID: 20573882 DOI: 10.1523/jneurosci.0546-10.2010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
To explore the role of both Aplysia cell adhesion molecule (ApCAM) and activity of specific protein kinase C (PKC) isoforms in the initial formation of sensory neuron synapses with specific postsynaptic targets (L7 but not L11), we examined presynaptic growth, initial synapse formation, and the expression of the presynaptic neuropeptide sensorin following cell-specific reduction of ApCAM or of a novel PKC activity. Synapse formation between sensory neurons and L7 begins by 3 h after plating and is accompanied by a rapid accumulation of a novel PKC to sites of synaptic interaction. Reducing ApCAM expression specifically from the surface of L7 blocks presynaptic growth and initial synapse formation, target-induced increase of sensorin in sensory neuron cell bodies and the rapid accumulation of the novel PKC to sites of interaction. Selective blockade of the novel PKC activity in L7, but not in sensory neurons, with injection of a dominant negative construct that interferes with the novel PKC activity, produces the same actions as downregulating ApCAM; blockade of presynaptic growth and initial synapse formation, and the target-induced increase of sensorin in sensory neuron cell bodies. The results indicate that signals initiated by postsynaptic cell adhesion molecule ApCAM coupled with the activation of a novel PKC in the appropriate postsynaptic neuron produce the retrograde signals required for presynaptic growth associated with initial synapse formation, and the target-induced expression of a presynaptic neuropeptide critical for synapse maturation.
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35
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Thomas U, Kobler O, Gundelfinger ED. TheDrosophilaLarval Neuromuscular Junction as a Model for Scaffold Complexes at Glutamatergic Synapses: Benefits and Limitations. J Neurogenet 2010; 24:109-19. [DOI: 10.3109/01677063.2010.493589] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Abstract
The most impressive structural feature of the nervous system is the specificity of its synaptic connections. Even after axons have navigated long distances to reach target areas, they must still choose appropriate synaptic partners from the many potential partners within easy reach. In many cases, axons also select a particular domain of the postsynaptic cell on which to form a synapse. Thus, synapse formation is selective at both cellular and subcellular levels. Unsurprisingly, the nervous system uses multiple mechanisms to ensure proper connectivity; these include complementary labels, coordinated growth of synaptic partners, sorting of afferents, prohibition or elimination of inappropriate synapses, respecification of targets, and use of short-range guidance mechanisms or intermediate targets. Specification of any circuit is likely to involve integration of multiple mechanisms. Recent studies of vertebrate and invertebrate systems have led to the identification of molecules that mediate a few of these interactions.
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Affiliation(s)
- Joshua R Sanes
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
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37
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Xiao MF, Xu JC, Tereshchenko Y, Novak D, Schachner M, Kleene R. Neural cell adhesion molecule modulates dopaminergic signaling and behavior by regulating dopamine D2 receptor internalization. J Neurosci 2009; 29:14752-63. [PMID: 19940170 PMCID: PMC6666007 DOI: 10.1523/jneurosci.4860-09.2009] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Accepted: 10/01/2009] [Indexed: 12/15/2022] Open
Abstract
The dopaminergic system plays an important role in the etiology of schizophrenia, and most antipsychotic drugs exert their functions by blocking dopamine D(2) receptors (D(2)Rs). Since the signaling strength mediated by D(2)Rs is regulated by internalization and degradation processes, it is crucial to identify molecules that modulate D(2)R localization at the cell surface. Here, we show that the neural cell adhesion molecule (NCAM) promotes D(2)R internalization/desensitization and subsequent degradation via direct interaction with a short peptide in the third intracellular loop of the D(2)R. NCAM deficiency in mice leads to increased numbers of D(2)Rs at the cell surface and augmented D(2)R signaling as a result of impaired D(2)R internalization. Furthermore, NCAM-deficient mice show higher sensitivity to the psychostimulant apomorphine and exaggerated activity of dopamine-related locomotor behavior. These results demonstrate that, in addition to its classical function in cell adhesion, NCAM is involved in regulating the trafficking of the neurotransmitter receptor D(2)R as well as receptor-mediated signaling and behavior, thus implicating NCAM as modulator of the dopaminergic system and a potential pharmacological target for dopamine-related neurological and psychiatric disorders.
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Affiliation(s)
- Mei-Fang Xiao
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, D-20246 Hamburg, Germany
| | - Jin-Chong Xu
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, D-20246 Hamburg, Germany
| | - Yuliya Tereshchenko
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, D-20246 Hamburg, Germany
| | - Daniel Novak
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, D-20246 Hamburg, Germany
| | - Melitta Schachner
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, D-20246 Hamburg, Germany
- Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey 08854, and
- Center for Neuroscience, Shantou University Medical College, Shantou 515041, China
| | - Ralf Kleene
- Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, D-20246 Hamburg, Germany
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38
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Katsuki T, Ailani D, Hiramoto M, Hiromi Y. Intra-axonal patterning: intrinsic compartmentalization of the axonal membrane in Drosophila neurons. Neuron 2009; 64:188-99. [PMID: 19874787 DOI: 10.1016/j.neuron.2009.08.019] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 08/20/2009] [Accepted: 08/20/2009] [Indexed: 10/20/2022]
Abstract
In the developing nervous system, distribution of membrane molecules, particularly axon guidance receptors, is often restricted to specific segments of axons. Such localization of membrane molecules can be important for the formation and function of neural networks; however, how this patterning within axons is achieved remains elusive. Here we show that Drosophila neurons in culture establish intra-axonal patterns in a cell-autonomous manner; several membrane molecules localize to either proximal or distal axon segments without cell-cell contacts. This distinct patterning of membrane proteins is not explained by a simple temporal control of expression, and likely involves spatially controlled vesicular targeting or retrieval. Mobility of transmembrane molecules is restricted at the boundary of intra-axonal segments, indicating that the axonal membrane is compartmentalized by a barrier mechanism. We propose that this intra-axonal compartmentalization is an intrinsic property of Drosophila neurons that provides a basis for the structural and functional development of the nervous system.
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Affiliation(s)
- Takeo Katsuki
- Department of Developmental Genetics, National Institute of Genetics, Mishima, Shizuoka, Japan
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Kohsaka H, Nose A. Target recognition at the tips of postsynaptic filopodia: accumulation and function of Capricious. Development 2009; 136:1127-35. [PMID: 19270171 DOI: 10.1242/dev.027920] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
While much evidence suggests that postsynaptic dynamism contributes to the formation of synapses, few studies have addressed its possible role in target selection. Do postsynaptic motile structures seek specific synaptic partner cells, as does the presynaptic growth cone? Here we studied the dynamics of myopodia, postsynaptic filopodia in Drosophila muscles, and the role of Capricious (CAPS) during the process of synaptic matchmaking. CAPS is a target recognition molecule with an extracellular domain containing leucine-rich repeat sequences. It is expressed in specific subsets of embryonic/larval body wall muscles, including muscle 12 (M12). We provide evidence that implicates the tips of myopodia as loci of initial neuromuscular recognition: (1) CAPS, expressed as a GFP-fusion protein in M12, accumulated at the tips of myopodia; and (2) simultaneous live imaging of presynaptic motoneurons and postsynaptic myopodia revealed that initial neuromuscular contacts occur at the tips of myopodia. The live imaging also showed that individual postsynaptic myopodia appear to be able to discriminate partner and non-partner presynaptic cells: whereas many myopodial contacts with the partner motoneurons are stabilized to form synapses, those with non-partner neurons are retracted. In caps mutants, or in double mutants lacking both CAPS and the closely related protein Tartan, we observed fewer contacts between myopodia of M12 and the presynaptic growth cones during the process of initial neuromuscular interaction. The nascent synaptic sites of M12 were also reduced. These results provide evidence for the sensing function of postsynaptic filopodia, and implicate Caps-mediated recognition at the tips of myopodia in synaptic matching.
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Affiliation(s)
- Hiroshi Kohsaka
- Department of Complexity Science and Engineering, University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
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Bizzoca A, Corsi P, Gennarini G. The mouse F3/contactin glycoprotein: structural features, functional properties and developmental significance of its regulated expression. Cell Adh Migr 2009; 3:53-63. [PMID: 19372728 PMCID: PMC2675150 DOI: 10.4161/cam.3.1.7462] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2008] [Accepted: 11/19/2008] [Indexed: 12/18/2022] Open
Abstract
F3/Contactin is an immunoglobulin superfamily component expressed in the nervous tissue of several species. Here we focus on the structural and functional properties of its mouse relative, on the mechanisms driving its regulated expression and on its developmental role. F3/Contactin is differentially expressed in distinct populations of central and peripheral neurons and in some non-neuronal cells. Accordingly, the regulatory region of the underlying gene includes promoter elements undergoing differential activation, associated with an intricate splicing profile, indicating that transcriptional and posttranscriptional mechanisms contribute to its expression. Transgenic models allowed to follow F3/Contactin promoter activation in vivo and to modify F3/Contactin gene expression under a heterologous promoter, which resulted in morphological and functional phenotypes. Besides axonal growth and pathfinding, these concerned earlier events, including precursor proliferation and commitment. This wide role in neural ontogenesis is consistent with the recognized interaction of F3/Contactin with developmental control genes belonging to the Notch pathway.
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Affiliation(s)
- Antonella Bizzoca
- Department of Pharmacology and Human Physiology, Medical School, University of Bari, Bari, Italy
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