151
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Novel roles for collagens in wiring the vertebrate nervous system. Curr Opin Cell Biol 2008; 20:508-13. [DOI: 10.1016/j.ceb.2008.05.003] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2008] [Revised: 05/15/2008] [Accepted: 05/16/2008] [Indexed: 01/06/2023]
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152
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Umemori H, Sanes JR. Signal regulatory proteins (SIRPS) are secreted presynaptic organizing molecules. J Biol Chem 2008; 283:34053-61. [PMID: 18819922 DOI: 10.1074/jbc.m805729200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Formation of chemical synapses requires exchange of organizing signals between the synaptic partners. Using synaptic vesicle aggregation in cultured neurons as a marker of presynaptic differentiation, we purified candidate presynaptic organizers from mouse brain. A major bioactive species was the extracellular domain of signal regulatory protein alpha (SIRP-alpha), a transmembrane immunoglobulin superfamily member concentrated at synapses. The extracellular domain of SIRP-alpha is cleaved and shed in a developmentally regulated manner. The presynaptic organizing activity of SIRP-alpha is mediated in part by CD47. SIRP-alpha homologues, SIRP-beta and -gamma also have synaptic vesicle clustering activity. The effects of SIRP-alpha are distinct from those of another presynaptic organizer, FGF22: the two proteins induced vesicle clusters of different sizes, differed in their ability to promote neurite branching, and acted through different receptors and signaling pathways. SIRP family proteins may act together with other organizing molecules to pattern synapses.
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Affiliation(s)
- Hisashi Umemori
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, Massachusetts 02138, USA.
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153
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Gordon T, Ly V, Hegedus J, Tyreman N. Early detection of denervated muscle fibers in hindlimb muscles after sciatic nerve transection in wild type mice and in the G93A mouse model of amyotrophic lateral sclerosis. Neurol Res 2008; 31:28-42. [PMID: 18768111 DOI: 10.1179/174313208x332977] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The cell adhesion molecule N-CAM is localized to the adult neuromuscular junction but is also expressed in the extrajunctional membrane of denervated muscles concurrent with extrajunctional acetylcholine receptors. Here we used N-CAM immunohistochemistry to determine whether we could detect early denervation in hindlimb muscles of the G93A transgenic mouse model of amyotrophic lateral sclerosis (ALS). In denervated wild type mouse muscles, N-CAM immunoreactivity on the sarcolemma of all fiber types and within the sarcoplasm of only type IIA fibers was detected at day 2: approximately 30% of the muscle fibers in cross-section were fully circumscribed by N-CAM immunoreactivity and approximately 25% of fibers were incompletely circumscribed. The proportion of the latter fibers remained constant over the next 8 days as the proportions of the former fibers increased exponentially. Thereafter, fully circumscribed muscle fibers increased to a maximum by 30 days with a concomitant fall in the incompletely circumscribed fibers. Hence, early muscle denervation was detected by the incomplete circumscription of fiber membranes by N-CAM immunoreactivity with full circumscription and intracellular localization indicating more long-term denervation. In the G93A transgenic mouse, rapid denervation of fast-twitch muscles was readily detected by a corresponding proportion of muscle fibers in cross-section with positive N-CAM immunoreactivity. The proportions of incompletely and completely circumscribed muscle fibers corresponded well with the rate of decline in intact motor units and reduced muscle contractile forces. Progressively more fully circumscribed muscle fibers became evident with age. We conclude that the N-CAM immunoreactivity on muscle fiber membranes in muscle cross-sections provides a sensitive means of detecting early muscle fiber denervation.
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Affiliation(s)
- T Gordon
- Division of Physical Medicine and Rehabilitation/Centre for Neuroscience, Faculty of Medicine, University of Alberta, Edmonton, Alta T6G 2S2, Canada.
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154
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Letellier M, Willson ML, Gautheron V, Mariani J, Lohof AM. Normal adult climbing fiber monoinnervation of cerebellar Purkinje cells in mice lacking MHC class I molecules. Dev Neurobiol 2008; 68:997-1006. [PMID: 18418877 DOI: 10.1002/dneu.20639] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Some immune system proteins have recently been implicated in the development and plasticity of neuronal connections. Notably, proteins of the major histocompatibility complex 1 (MHC class 1) have been shown to be involved in synaptic plasticity in the hippocampus and the development of projection patterns in the visual system. We examined the possible role for the MHC class 1 proteins in one well-characterized example of synaptic exuberance and subsequent refinement, the climbing fiber (CF) to Purkinje cell (PC) synapse. Cerebella from adult mice deficient for two MHC genes, H2-D1 and H2-K1, and for beta2-microglobulin gene were examined for evidence of deficient elimination of supernumerary CF synapses on their PCs. Electrophysiological and morphological evidence showed that, despite the absence of these MHC class 1 molecules, adult PCs in these transgenic mice are monoinnervated as in wild-type animals. These findings indicate that, at the level of restriction of afferent number at this synapse, functional MHC class 1 proteins are not required.
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Affiliation(s)
- Mathieu Letellier
- Centre National de la Recherche Scientifique, Université Pierre et Marie Curie-Paris, Unité Mixte de Recherche 7102-Neurobiologie des Processus Adaptatifs, F-75005 Paris, France
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155
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Linger RMA, Keating AK, Earp HS, Graham DK. TAM receptor tyrosine kinases: biologic functions, signaling, and potential therapeutic targeting in human cancer. Adv Cancer Res 2008; 100:35-83. [PMID: 18620092 DOI: 10.1016/s0065-230x(08)00002-x] [Citation(s) in RCA: 533] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Tyro-3, Axl, and Mer constitute the TAM family of receptor tyrosine kinases (RTKs) characterized by a conserved sequence within the kinase domain and adhesion molecule-like extracellular domains. This small family of RTKs regulates an intriguing mix of processes, including cell proliferation/survival, cell adhesion and migration, blood clot stabilization, and regulation of inflammatory cytokine release. Genetic or experimental alteration of TAM receptor function can contribute to a number of disease states, including coagulopathy, autoimmune disease, retinitis pigmentosa, and cancer. In this chapter, we first provide a comprehensive review of the structure, regulation, biologic functions, and downstream signaling pathways of these receptors. In addition, we discuss recent evidence which suggests a role for TAM receptors in oncogenic mechanisms as family members are overexpressed in a spectrum of human cancers and have prognostic significance in some. Possible strategies for targeted inhibition of the TAM family in the treatment of human cancer are described. Further research will be necessary to evaluate the full clinical implications of TAM family expression and activation in cancer.
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Affiliation(s)
- Rachel M A Linger
- Department of Pediatrics, University of Colorado at Denver and Health Sciences Center, Aurora, CO, USA
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156
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Tai CY, Kim SA, Schuman EM. Cadherins and synaptic plasticity. Curr Opin Cell Biol 2008; 20:567-75. [PMID: 18602471 DOI: 10.1016/j.ceb.2008.06.003] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Revised: 06/05/2008] [Accepted: 06/09/2008] [Indexed: 11/20/2022]
Abstract
Given their trans-synaptic localization, their persistent expression at mature synapses and their distinct biochemical and adhesive properties, cadherins are uniquely poised at the synapse to mediate synaptic plasticity, the ability to change synaptic function thought to underlie learning and memory. For example recent work suggests that cadherins may recruit and stabilize AMPA receptors at the synapse via direct interactions or through complex formation, revealing cross talk between postsynaptic signaling and adhesion. Moreover, the use of small interfering RNA knockdown of cadherin, the availability of N-cadherin-deficient embryonic stem cells and the acute disruption of cadherin function with peptide application in vivo have allowed for more precise dissection of the molecular mechanisms by which cadherins function in both structural and functional plasticity.
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Affiliation(s)
- Chin-Yin Tai
- Howard Hughes Medical Institute, Division of Biology, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
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157
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Activity-dependent regulation of synaptic AMPA receptor composition and abundance by beta3 integrins. Neuron 2008; 58:749-62. [PMID: 18549786 DOI: 10.1016/j.neuron.2008.04.011] [Citation(s) in RCA: 178] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 01/15/2008] [Accepted: 04/09/2008] [Indexed: 11/21/2022]
Abstract
At synapses, cell adhesion molecules (CAMs) provide the molecular framework for coordinating signaling events across the synaptic cleft. Among synaptic CAMs, the integrins, receptors for extracellular matrix proteins and counterreceptors on adjacent cells, are implicated in synapse maturation and plasticity and memory formation. However, little is known about the molecular mechanisms of integrin action at central synapses. Here, we report that postsynaptic beta3 integrins control synaptic strength by regulating AMPA receptors (AMPARs) in a subunit-specific manner. Pharmacological perturbation targeting beta3 integrins promotes endocytosis of GluR2-containing AMPARs via Rap1 signaling, and expression of beta3 integrins produces robust changes in the abundance and composition of synaptic AMPARs without affecting dendritic spine structure. Importantly, homeostatic synaptic scaling induced by activity deprivation elevates surface expression of beta3 integrins, and in turn, beta3 integrins are required for synaptic scaling. Our findings demonstrate a key role for integrins in the feedback regulation of excitatory synaptic strength.
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158
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Chen PL, Clandinin TR. The cadherin Flamingo mediates level-dependent interactions that guide photoreceptor target choice in Drosophila. Neuron 2008; 58:26-33. [PMID: 18400160 DOI: 10.1016/j.neuron.2008.01.007] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Revised: 11/30/2007] [Accepted: 01/04/2008] [Indexed: 11/17/2022]
Abstract
Quantitative differences in cadherin activity have been proposed to play important roles in patterning connections between pre- and postsynaptic neurons. However, no examples of such a function have yet been described, and the mechanisms that would allow such differences to direct growth cones to specific synaptic targets are unknown. In the Drosophila visual system, photoreceptors are genetically programmed to make a complex, stereotypic set of synaptic connections. Here we show that the atypical cadherin Flamingo functions as a short-range, homophilic signal, passing between specific R cell growth cones to influence their choice of postsynaptic partners. We find that individual growth cones are sensitive to differences in Flamingo activity through opposing interactions between neighboring cells and require these interactions to be balanced in order to extend along the appropriate trajectory.
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Affiliation(s)
- Pei-Ling Chen
- Department of Neurobiology, Stanford University, Stanford, CA 94305, USA
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159
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Abstract
Gradients of secreted small morphogenic molecules control cell proliferation and patterning throughout animal development. Recent years have seen the discovery of surprising roles for morphogens in later developmental processes, including axon pathfinding and synaptogenesis. The latest addition is a role for the TGF-beta superfamily morphogen Activin in synaptic patterning of the Drosophila visual system. In contrast to classical instructive and long-range morphogen gradients, Activin acts as a permissive and local motility restriction signal around several hundred individual photoreceptor axon terminals. Activin must therefore act in concert with other instructively attracting and repelling signals as part of a larger genetic program for brain wiring.
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Affiliation(s)
- W Ryan Williamson
- Department of Physiology and Green Center Division for Systems Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
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160
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Mukherjee K, Sharma M, Urlaub H, Bourenkov GP, Jahn R, Südhof TC, Wahl MC. CASK Functions as a Mg2+-independent neurexin kinase. Cell 2008; 133:328-39. [PMID: 18423203 DOI: 10.1016/j.cell.2008.02.036] [Citation(s) in RCA: 209] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Revised: 10/30/2007] [Accepted: 02/06/2008] [Indexed: 01/09/2023]
Abstract
CASK is a unique MAGUK protein that contains an N-terminal CaM-kinase domain besides the typical MAGUK domains. The CASK CaM-kinase domain is presumed to be a catalytically inactive pseudokinase because it lacks the canonical DFG motif required for Mg2+ binding that is thought to be indispensable for kinase activity. Here we show, however, that CASK functions as an active protein kinase even without Mg2+ binding. High-resolution crystal structures reveal that the CASK CaM-kinase domain adopts a constitutively active conformation that binds ATP and catalyzes phosphotransfer without Mg2+. The CASK CaM-kinase domain phosphorylates itself and at least one physiological interactor, the synaptic protein neurexin-1, to which CASK is recruited via its PDZ domain. Thus, our data indicate that CASK combines the scaffolding activity of MAGUKs with an unusual kinase activity that phosphorylates substrates recuited by the scaffolding activity. Moreover, our study suggests that other pseudokinases (10% of the kinome) could also be catalytically active.
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Affiliation(s)
- Konark Mukherjee
- Department of Neuroscience, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390-9111, USA.
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161
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Junghans D, Heidenreich M, Hack I, Taylor V, Frotscher M, Kemler R. Postsynaptic and differential localization to neuronal subtypes of protocadherin beta16 in the mammalian central nervous system. Eur J Neurosci 2008; 27:559-71. [PMID: 18279309 DOI: 10.1111/j.1460-9568.2008.06052.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The formation of synapses is dependent on the expression of surface adhesion molecules that facilitate correct recognition, stabilization and function. The more than 60 clustered protocadherins (Pcdhalpha, Pcdhbeta and Pcdhgamma) identified in human and mouse have attracted considerable attention because of their clustered genomic organization and the potential role of alpha- and gamma-Pcdhs in allocating a neuronal surface code specifying synaptic connectivity. Here, we investigated whether beta-Pcdhs also contribute to these processes. By performing RT-PCR, we found a striking parallel onset of expression of many beta-Pcdhs around the onset of neurogenesis and wide expression in the central nervous system. We generated antibodies specific to Pcdhb16 and showed localization of Pcdhb16 protein in the adult mouse cerebellum, hippocampus and cerebral cortex. Analysing the mouse retina in detail revealed localization of Pcdhb16 to specific cell types and, importantly, subsets of synapses. We show that Pcdhb16 localizes predominantly to postsynaptic compartments and the comparison with Pcdhb22 implies differential localization and functions of individual beta-Pcdhs in the mammalian central nervous system. Moreover, we provide evidence for a role of beta-Pcdhs in the outer segments and connecting cilia of photoreceptors. Our data show for the first time that beta-Pcdhs also localize to specific neuronal subpopulations and synapses, providing support for the hypothesis that clustered Pcdhs are candidate genes for the specification of synaptic connectivity and neuronal networks.
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Affiliation(s)
- Dirk Junghans
- Max-Planck Institute of Immunobiology, Department of Molecular Embryology, 79011 Freiburg, Germany
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162
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Cline H, Haas K. The regulation of dendritic arbor development and plasticity by glutamatergic synaptic input: a review of the synaptotrophic hypothesis. J Physiol 2008; 586:1509-17. [PMID: 18202093 PMCID: PMC2375708 DOI: 10.1113/jphysiol.2007.150029] [Citation(s) in RCA: 186] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2007] [Accepted: 01/10/2008] [Indexed: 01/15/2023] Open
Abstract
The synaptotropic hypothesis, which states that synaptic inputs control the elaboration of dendritic (and axonal) arbors was articulated by Vaughn in 1989. Today the role of synaptic inputs in controlling neuronal structural development remains an area of intense research activity. Several recent studies have applied modern molecular genetic, imaging and electrophysiological methods to this question and now provide strong evidence that maturation of excitatory synaptic inputs is required for the development of neuronal structure in the intact brain. Here we critically review data concerning the hypothesis with the expectation that understanding the circumstances when the data do and do not support the hypothesis will be most valuable. The synaptotrophic hypothesis contributes at both conceptual and mechanistic levels to our understanding of how relatively minor changes in levels or function of synaptic proteins may have profound effects on circuit development and plasticity.
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Affiliation(s)
- Hollis Cline
- Cold Spring Harbour Laboratory, 1 Bungtown Road, Cold Spring Harbour, NY 11724, USA.
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163
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Wahlin KJ, Moreira EF, Huang H, Yu N, Adler R. Molecular dynamics of photoreceptor synapse formation in the developing chick retina. J Comp Neurol 2008; 506:822-37. [PMID: 18076030 DOI: 10.1002/cne.21582] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The cellular and molecular mechanisms underlying photoreceptor synaptogenesis are poorly understood. Furthermore, a detailed picture of the molecular composition of photoreceptor synapses, or their subtypes, is not yet available, nor do we know what differences, if any, exist among those subtypes. To address these questions, we investigated temporal and spatial patterns of expression and assembly of photoreceptor presynaptic components during chick embryo retinal development and early posthatched life by using reverse transcriptase polymerase chain reaction (RT-PCR), dissociated retinal cells, laser-capture microdissection (LCM), immunocytochemistry and confocal microscopy. Immunocytochemistry in tissue sections and dissociated cells showed many similarities and few differences in the synaptic composition of rods and cone subtypes, which, however, were found to project to different strata within the outer plexiform layer. A striking finding was the precise timetable of expression of synaptic genes and proteins during synaptogenesis. Although mRNAs for some synaptic molecules appeared as early as embryonic day (ED) 5-8 (the time of inner retina synaptogenesis), others were undetectable before the time of onset of photoreceptor synaptogenesis on ED13, including CAST, rim2, synapsin-2, syntaxin-3, synaptotagmin, glutamate receptors -1, -4, and -5, homer-1 and -2, and tenascin-R. Most synaptic proteins in photoreceptors followed a similar sequence of expression: they were negative or weakly positive before ED13, appeared in inner segments between ED13 and ED15, became subsequently detectable in perinuclear and axonal regions, and by ED18 were assembled into synaptic terminals and became undetectable in the inner segments. The identity of the signals that regulate the coordinated expression of these synaptic components remains to be investigated.
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Affiliation(s)
- Karl J Wahlin
- Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-9257, USA
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164
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Budreck EC, Scheiffele P. Neuroligin-3 is a neuronal adhesion protein at GABAergic and glutamatergic synapses. Eur J Neurosci 2008; 26:1738-48. [PMID: 17897391 DOI: 10.1111/j.1460-9568.2007.05842.x] [Citation(s) in RCA: 227] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Synaptic adhesion molecules are thought to play a critical role in the formation, function and plasticity of neuronal networks. Neuroligins (NL1-4) are a family of presumptive postsynaptic cell adhesion molecules. NL1 and NL2 isoforms are concentrated at glutamatergic and GABAergic synapses, respectively, but the cellular expression and synaptic localization of the endogenous NL3 and NL4 isoforms are unknown. We generated a panel of NL isoform-specific antibodies and examined the expression, developmental regulation and synaptic specificity of NL3. We found that NL3 was enriched in brain, where NL3 protein levels increased during postnatal development, coinciding with the peak of synaptogenesis. Subcellular fractionation revealed a concentration of NL3 in synaptic plasma membranes and postsynaptic densities. In cultured hippocampal neurons, endogenous NL3 was highly expressed and was localized at both glutamatergic and GABAergic synapses. Clustering of NL3 in hippocampal neurons by neurexin-expressing cells resulted in coaggregation of NL3 with glutamatergic and GABAergic scaffolding proteins. Finally, individual synapses contained colocalized NL2 and NL3 proteins, and coimmunoprecipitation studies revealed the presence of NL1-NL3 and NL2-NL3 complexes in brain extracts. These findings suggest that rodent NL3 is a synaptic adhesion molecule that is a shared component of glutamatergic and GABAergic synapses.
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Affiliation(s)
- Elaine C Budreck
- Department of Physiology & Cellular Biophysics, Columbia University, College of Physicians & Surgeons, 630 West 168th Street, P&S 11-511, New York, NY 10032, USA
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165
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Seabold GK, Wang PY, Chang K, Wang CY, Wang YX, Petralia RS, Wenthold RJ. The SALM family of adhesion-like molecules forms heteromeric and homomeric complexes. J Biol Chem 2008; 283:8395-405. [PMID: 18227064 DOI: 10.1074/jbc.m709456200] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Synaptic adhesion-like molecules (SALMs) are a newly discovered family of adhesion molecules that play roles in synapse formation and neurite outgrowth. The SALM family is comprised of five homologous molecules that are expressed largely in the central nervous system. SALMs 1-3 contain PDZ-binding domains, whereas SALMs 4 and 5 do not. We are interested in characterizing the interactions of the SALMs both among the individual members and with other binding partners. In the present study, we focused on the interactions formed by the five SALM members in rat brain and heterologous cells. In brain, we found that SALMs 1-3 strongly co-immunoprecipitated with each other, whereas SALMs 4 and 5 did not, suggesting that SALMs 4 and 5 mainly form homomeric complexes. In heterologous cells transfected with SALMs, co-immunoprecipitation studies showed that all five SALMs form heteromeric and homomeric complexes. We also determined if SALMs could form trans-cellular associations between transfected heterologous cells. Both SALMs 4 and 5 formed homophilic, but not heterophilic associations, whereas no trans associations were formed by the other SALMs. The ability of SALM4 to form trans interactions is due to its extracellular N terminus because chimeras of SALM4 N terminus and SALM2 C terminus can form trans interactions, whereas chimeras of SALM2 N terminus and SALM4 C terminus cannot. Co-culture experiments using HeLa cells and rat hippocampal neurons expressing the SALMs showed that SALM4 is recruited to points of contact between the cells. In neurons, these points of contact were seen in both axons and dendrites.
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Affiliation(s)
- Gail K Seabold
- Laboratory of Neurochemistry, NIDCD, NIH, Bethesda, MD 20892-8027, USA
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166
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Neylon C. Small angle neutron and X-ray scattering in structural biology: recent examples from the literature. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2008; 37:531-41. [PMID: 18214466 DOI: 10.1007/s00249-008-0259-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 12/20/2007] [Accepted: 12/21/2007] [Indexed: 10/22/2022]
Abstract
Small angle scattering can provide unique structural information on the shape, domain organisation, and interactions of biomacromolecules in solution. Small angle neutron scattering (SANS) combined with deuterium labelling makes it possible to define the positions of specific components within a complex while small angle X-ray scattering (SAXS) provides more precise data on the overall shape. Here I review four recent publications, three of which were presented at the Neutrons in Biology meeting at the STFC Rutherford Appleton Laboratory in July 2007, that utilise SANS, SAXS, and complementary techniques to define the solution structure of large multidomain proteins and macromolecular complexes. These four papers emphasise the critical importance of sample quality and characterisation as well as the important role played by complementary techniques in building structural models based on small angle scattering data. They show the ability of SANS and SAXS in determining solution structures provides an important complementary structural technique for large, flexible, and glycosylated proteins where high resolution structural techniques, such as crystallography and NMR, cannot be applied.
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Affiliation(s)
- Cameron Neylon
- Science and Technology Facilities Council Rutherford Appleton Laboratory, Didcot OX 11 0QX, UK.
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167
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Abstract
Synapses are asymmetric cell junctions with precisely juxtaposed presynaptic and postsynaptic sides. Transsynaptic adhesion complexes are thought to organize developing synapses. The molecular composition of these complexes, however, remains incompletely understood, precluding us from understanding how adhesion across the synaptic cleft guides synapse development. Here, we define two immunoglobulin superfamily members, SynCAM 1 and 2, that are expressed in neurons in the developing brain and localize to excitatory and inhibitory synapses. They function as cell adhesion molecules and assemble with each other across the synaptic cleft into a specific, transsynaptic SynCAM 1/2 complex. Additionally, SynCAM 1 and 2 promote functional synapses as they increase the number of active presynaptic terminals and enhance excitatory neurotransmission. The interaction of SynCAM 1 and 2 is affected by glycosylation, indicating regulation of this adhesion complex by posttranslational modification. The SynCAM 1/2 complex is representative for the highly defined adhesive patterns of this protein family, the four members of which are expressed in neurons in divergent expression profiles. SynCAMs 1, 2, and 3 each can bind themselves, yet preferentially assemble into specific, heterophilic complexes as shown for the synaptic SynCAM 1/2 interaction and a second complex comprising SynCAM 3 and 4. Our results define SynCAM proteins as components of novel heterophilic transsynaptic adhesion complexes that set up asymmetric interactions, with SynCAM proteins contributing to synapse organization and function.
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168
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Kohsaka H, Takasu E, Nose A. In vivo induction of postsynaptic molecular assembly by the cell adhesion molecule Fasciclin2. ACTA ACUST UNITED AC 2007; 179:1289-300. [PMID: 18070911 PMCID: PMC2140041 DOI: 10.1083/jcb.200705154] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cell adhesion molecules (CAMs) are thought to mediate interactions between innervating axons and their targets. However, such interactions have not been directly observed in vivo. In this paper, we study the function and dynamics of Fasciclin2 (Fas2), a homophilic CAM expressed both pre- and postsynaptically during neuromuscular synapse formation in Drosophila melanogaster. We apply live imaging of functional fluorescent fusion proteins expressed in muscles and find that Fas2 and Discs-Large (Dlg; a scaffolding protein known to bind Fas2) accumulate at the synaptic contact site soon after the arrival of the nerve. Genetic, deletion, and photobleaching analyses suggest that Fas2-mediated trans-synaptic adhesion is important for the postsynaptic accumulation of both Fas2 itself and Dlg. In fas2 mutants, many aspects of synapse formation appear normal; however, we see a reduction in the synaptic accumulation of Scribble (another scaffolding protein) and glutamate receptor subunits GluRIIA and GluRIIB. We propose that Fas2 mediates trans-synaptic adhesion, which contributes to postsynaptic molecular assembly at the onset of synaptogenesis.
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Affiliation(s)
- Hiroshi Kohsaka
- Department of Physics, Graduate School of Science, Graduate School of Frontier Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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169
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Synaptic adhesion molecules and PSD-95. Prog Neurobiol 2007; 84:263-83. [PMID: 18206289 DOI: 10.1016/j.pneurobio.2007.10.011] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Revised: 08/31/2007] [Accepted: 10/26/2007] [Indexed: 11/21/2022]
Abstract
Synaptic adhesion molecules are known to participate in various steps of synapse development including initial contacts between dendrites and axons, formation of early synapses, and their maturation and plastic changes. Notably, a significant subset of synaptic adhesion molecules associates with synaptic scaffolding proteins, suggesting that they may act in concert to couple trans-synaptic adhesion to molecular organization of synaptic proteins. Here, we describe an emerging group of synaptic adhesion molecules that directly interact with the abundant postsynaptic scaffold PSD-95, which include neuroligins, NGLs, SALMs, and ADAM22, and discuss how these proteins and PSD-95 act together to regulate synaptic development. PSD-95 may be one of the central organizers of synaptic adhesion that recruits diverse proteins to sites of synaptic adhesion, promotes trans-synaptic signaling, and couples neuronal activity with changes in synaptic adhesion.
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170
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Kiryushko D, Bock E, Berezin V. Pharmacology of cell adhesion molecules of the nervous system. Curr Neuropharmacol 2007; 5:253-67. [PMID: 19305742 PMCID: PMC2644493 DOI: 10.2174/157015907782793658] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Revised: 04/27/2007] [Accepted: 07/17/2007] [Indexed: 12/15/2022] Open
Abstract
Cell adhesion molecules (CAMs) play a pivotal role in the development and maintenance of the nervous system under normal conditions. They also are involved in numerous pathological processes such as inflammation, degenerative disorders, and cancer, making them attractive targets for drug development. The majority of CAMs are signal transducing receptors. CAM-induced intracellular signalling is triggered via homophilic (CAM-CAM) and heterophilic (CAM - other counter-receptors) interactions, which both can be targeted pharmacologically. We here describe the progress in the CAM pharmacology focusing on cadherins and CAMs of the immunoglobulin (Ig) superfamily, such as NCAM and L1. Structural basis of CAM-mediated cell adhesion and CAM-induced signalling are outlined. Different pharmacological approaches to study functions of CAMs are presented including the use of specific antibodies, recombinant proteins, and synthetic peptides. We also discuss how unravelling of the 3D structure of CAMs provides novel pharmacological tools for dissection of CAM-induced signalling pathways and offers therapeutic opportunities for a range of neurological disorders.
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Affiliation(s)
- Darya Kiryushko
- Protein Laboratory, Department of Neuroscience and Pharmacology, Panum Institute Bld. 6.2, Blegdamsvej 3C, DK-2200, Copenhagen N, Denmark.
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171
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Mitsuhashi H, Futai E, Sasagawa N, Hayashi Y, Nishino I, Ishiura S. Csk-homologous kinase interacts with SHPS-1 and enhances neurite outgrowth of PC12 cells. J Neurochem 2007; 105:101-12. [PMID: 17999719 DOI: 10.1111/j.1471-4159.2007.05121.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
SHPS-1 is an immunoglobulin superfamily protein with four immunoreceptor tyrosine-based inhibitory motifs (ITIMs) in its cytoplasmic region. Various neurotrophic factors induce the tyrosine phosphorylation of SHPS-1 and the association of SHPS-1 with the protein tyrosine phosphatase SHP-2. Using a yeast two-hybrid screen, we identified a protein tyrosine kinase, Csk-homologous kinase (CHK), as an SHPS-1-interacting protein. Immunoprecipitation and pull-down assays using glutathione S-transferase (GST) fusion proteins containing the Src homology 2 (SH2) domain of CHK revealed that CHK associates with tyrosine-phosphorylated SHPS-1 via its SH2 domain. HIS3 assay in a yeast two-hybrid system using the tyrosine-to-phenylalanine mutants of SHPS-1 indicated that the first and second ITIMs of SHPS-1 are required to bind CHK. Over-expression of wild-type CHK, but not a kinase-inactive CHK mutant, enhanced the phosphorylation of SHPS-1 and its subsequent association with SHP-2. CHK phosphorylated each of four tyrosines in the cytoplasmic region of SHPS-1 in vitro. Co-expression of SHPS-1 and CHK enhanced neurite outgrowth in PC12 cells. Thus, CHK phosphorylates and associates with SHPS-1 and is involved in neural differentiation via SHP-2 activation.
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Affiliation(s)
- Hiroaki Mitsuhashi
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan
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172
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Li J, Ashley J, Budnik V, Bhat MA. Crucial role of Drosophila neurexin in proper active zone apposition to postsynaptic densities, synaptic growth, and synaptic transmission. Neuron 2007; 55:741-55. [PMID: 17785181 PMCID: PMC2039911 DOI: 10.1016/j.neuron.2007.08.002] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Revised: 07/17/2007] [Accepted: 08/07/2007] [Indexed: 10/22/2022]
Abstract
Neurexins have been proposed to function as major mediators of the coordinated pre- and postsynaptic apposition. However, key evidence for this role in vivo has been lacking, particularly due to gene redundancy. Here, we have obtained null mutations in the single Drosophila neurexin gene (dnrx). dnrx loss of function prevents the normal proliferation of synaptic boutons at glutamatergic neuromuscular junctions, while dnrx gain of function in neurons has the opposite effect. DNRX mostly localizes to the active zone of presynaptic terminals. Conspicuously, dnrx null mutants display striking defects in synaptic ultrastructure, with the presence of detachments between pre- and postsynaptic membranes, abnormally long active zones, and increased number of T bars. These abnormalities result in corresponding alterations in synaptic transmission with reduced quantal content. Together, our results provide compelling evidence for an in vivo role of neurexins in the modulation of synaptic architecture and adhesive interactions between pre- and postsynaptic compartments.
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Affiliation(s)
- Jingjun Li
- Curriculum in Neurobiology, Department of Cell and Molecular Physiology, UNC-Neuroscience Center, Neurodevelopmental Disorders Research Center, University of North Carolina School of Medicine Chapel Hill, NC 27599-7545
| | - James Ashley
- Department of Neurobiology University of Massachusetts Medical School Worcester, MA 01605
| | - Vivian Budnik
- Department of Neurobiology University of Massachusetts Medical School Worcester, MA 01605
| | - Manzoor A. Bhat
- Curriculum in Neurobiology, Department of Cell and Molecular Physiology, UNC-Neuroscience Center, Neurodevelopmental Disorders Research Center, University of North Carolina School of Medicine Chapel Hill, NC 27599-7545
- *To whom correspondence should be addressed: Manzoor Bhat, Ph.D., Neuroscience Research Building, Room #5109, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7545, Tel: (919) 966-1018, Fax: (919) 843-2777,
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173
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Coleman B, de Silva MG, Shepherd RK. Concise Review: The Potential of Stem Cells for Auditory Neuron Generation and Replacement. Stem Cells 2007; 25:2685-94. [PMID: 17656641 DOI: 10.1634/stemcells.2007-0393] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Sensory hair cells in the mammalian cochlea are sensitive to many insults including loud noise, ototoxic drugs, and ageing. Damage to these hair cells results in deafness and sets in place a number of irreversible changes that eventually result in the progressive degeneration of auditory neurons, the target cells of the cochlear implant. Techniques designed to preserve the density and integrity of auditory neurons in the deafened cochlea are envisaged to provide improved outcomes for cochlear implant recipients. This review examines the potential of embryonic stem cells to generate new neurons for the deafened mammalian cochlea, including the directed differentiation of stem cells toward a sensory neural lineage and the engraftment of exogenous stem cells into the deafened auditory system. Although still in its infancy the aim of this therapy is to restore a critical number of auditory neurons, thereby improving the benefits derived from a cochlear implant.
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Affiliation(s)
- Bryony Coleman
- Department of Otolaryngology, University of Melbourne, East Melbourne, Victoria, Australia.
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174
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Aricescu AR, Jones EY. Immunoglobulin superfamily cell adhesion molecules: zippers and signals. Curr Opin Cell Biol 2007; 19:543-50. [PMID: 17935964 DOI: 10.1016/j.ceb.2007.09.010] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 09/14/2007] [Accepted: 09/14/2007] [Indexed: 11/17/2022]
Abstract
The latest structural studies of immunoglobulin superfamily cell adhesion molecules are driving a shift in perspective; increasingly the view is not focused solely on the individual molecule but rather is on the molecular assembly. Two common themes are emerging, revealing mechanisms for ectodomain-dependent regulation of cell surface receptors' signalling abilities. The first is the propensity of many such molecules to arrange in zipper-type or array-type assemblies driven by a network of highly specific cis and trans interactions. The second is the use of the extracellular dimensions of a molecule or adhesion complex as properties which, in combination with characteristic intercellular spacings, can determine the co-localisation or exclusion of particular protein populations at cell interfaces and junctions.
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Affiliation(s)
- A Radu Aricescu
- Cancer Research UK Receptor Structure Research Group, Division of Structural Biology, The Henry Wellcome Building for Genomic Medicine, Roosevelt Drive, Headington, Oxford OX3 7BN, UK
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175
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Shapiro L, Love J, Colman DR. Adhesion molecules in the nervous system: structural insights into function and diversity. Annu Rev Neurosci 2007; 30:451-74. [PMID: 17600523 DOI: 10.1146/annurev.neuro.29.051605.113034] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The unparalleled complexity of intercellular connections in the nervous system presents requirements for high levels of both specificity and diversity for the proteins that mediate cell adhesion. Here we describe recent advances toward understanding the molecular mechanisms that underlie adhesive binding, specificity, and diversity for several well-characterized families of adhesion molecules in the nervous system. Although many families of adhesion proteins, including cadherins and immunoglobulin superfamily members, are utilized in neural and nonneural contexts, nervous system-specific diversification mechanisms, such as precisely regulated alternative splicing, provide an important means to enable their function in the complex context of the nervous system.
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Affiliation(s)
- Lawrence Shapiro
- Department of Biochemistry and Molecular Biophysics, 2Edward S. Harkness Eye Institute, Columbia University, New York, New York 10032 USA.
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176
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Abstract
Excitatory (glutamatergic) synapses in the mammalian brain are usually situated on dendritic spines, a postsynaptic microcompartment that also harbors organelles involved in protein synthesis, membrane trafficking, and calcium metabolism. The postsynaptic membrane contains a high concentration of glutamate receptors, associated signaling proteins, and cytoskeletal elements, all assembled by a variety of scaffold proteins into an organized structure called the postsynaptic density (PSD). A complex machine made of hundreds of distinct proteins, the PSD dynamically changes its structure and composition during development and in response to synaptic activity. The molecular size of the PSD and the stoichiometry of many major constituents have been recently measured. The structures of some intact PSD proteins, as well as the spatial arrangement of several proteins within the PSD, have been determined at low resolution by electron microscopy. On the basis of such studies, a more quantitative and geometrically realistic view of PSD architecture is emerging.
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Affiliation(s)
- Morgan Sheng
- The Picower Institute for Learning and Memory, Howard Hughes Medical Institute, Departments of Brain and Cognitive Sciences, and Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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177
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Furutani Y, Matsuno H, Kawasaki M, Sasaki T, Mori K, Yoshihara Y. Interaction between telencephalin and ERM family proteins mediates dendritic filopodia formation. J Neurosci 2007; 27:8866-76. [PMID: 17699668 PMCID: PMC6672168 DOI: 10.1523/jneurosci.1047-07.2007] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Dendritic filopodia are long, thin, actin-rich, and dynamic protrusions that are thought to play a critical role as a precursor of spines during neural development. We reported previously that a telencephalon-specific cell adhesion molecule, telencephalin (TLCN) [intercellular adhesion molecule-5 (ICAM-5)], is highly expressed in dendritic filopodia, facilitates the filopodia formation, and slows spine maturation. Here we demonstrate that TLCN cytoplasmic region binds ERM (ezrin/radixin/moesin) family proteins that link membrane proteins to actin cytoskeleton. In cultured hippocampal neurons, phosphorylated active forms of ERM proteins are colocalized with TLCN in dendritic filopodia, whereas alpha-actinin, another binding partner of TLCN, is colocalized with TLCN at surface membranes of soma and dendritic shafts. Expression of constitutively active ezrin induces dendritic filopodia formation, whereas small interference RNA-mediated knockdown of ERM proteins decreases filopodia density and accelerates spine maturation. These results indicate the important role of TLCN-ERM interaction in the formation of dendritic filopodia, which leads to subsequent synaptogenesis and establishment of functional neural circuitry in the developing brain.
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Affiliation(s)
- Yutaka Furutani
- Laboratory for Neurobiology of Synapse, RIKEN Brain Science Institute, Saitama 351-0198, Japan
- Core Research Evolutional Science and Technology, Japan Science and Technology Agency, Osaka 560-0082, Japan
| | - Hitomi Matsuno
- Laboratory for Neurobiology of Synapse, RIKEN Brain Science Institute, Saitama 351-0198, Japan
- Core Research Evolutional Science and Technology, Japan Science and Technology Agency, Osaka 560-0082, Japan
| | - Miwa Kawasaki
- Laboratory for Neurobiology of Synapse, RIKEN Brain Science Institute, Saitama 351-0198, Japan
| | - Takehiko Sasaki
- Department of Pathology and Immunology, Akita University School of Medicine, Akita 010-8543, Japan, and
| | - Kensaku Mori
- Department of Physiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Yoshihiro Yoshihara
- Laboratory for Neurobiology of Synapse, RIKEN Brain Science Institute, Saitama 351-0198, Japan
- Core Research Evolutional Science and Technology, Japan Science and Technology Agency, Osaka 560-0082, Japan
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178
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Hishimoto A, Liu QR, Drgon T, Pletnikova O, Walther D, Zhu XG, Troncoso JC, Uhl GR. Neurexin 3 polymorphisms are associated with alcohol dependence and altered expression of specific isoforms. Hum Mol Genet 2007; 16:2880-91. [PMID: 17804423 DOI: 10.1093/hmg/ddm247] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Neurexins are cell adhesion molecules that help to specify and stabilize synapses and provide receptors for neuroligins, neurexophilins, dystroglycans and alpha-latrotoxins. We previously reported significant allele frequency differences for single nucleotide polymorphisms (SNPs) in the neurexin 3 (NRXN3) gene in each of two comparisons between individuals who were dependent on illegal substances and controls. We now report work clarifying details of NRXN3's gene structure and variants and documenting association of NRXN3 SNPs with alcohol dependence. We localize this association signal with the vicinity of the NRXN3 splicing site 5 (SS#5). A splicing site SNP, rs8019381, that is located 23 bp from the SS#5 exon 23 donor site displays association with P = 0.0007 (odds ratio = 2.46). Including or excluding exon 23 at SS#5 produces soluble or transmembrane NRXN3 isoforms. We thus examined expression of these NRXN3 isoforms in postmortem human cerebral cortical brain samples from individuals with varying rs8019381 genotypes. Two of the splice variants that encode transmembrane NRXN3 isoforms were expressed at significantly lower levels in individuals with the addiction-associated rs8019381 'T' allele than in CC homozygotes. Taken together with recent reports of NRXN3 association with nicotine dependence and linkage with opiate dependence, these data support roles for NRXN3 haplotypes that alter expression of specific NRXN3 isoforms in genetic vulnerabilities to dependence on a variety of addictive substances.
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Affiliation(s)
- Akitoyo Hishimoto
- Molecular Neurobiology Branch, NIDA-IRP, NIH, DHSS, Baltimore, MD 21224, USA
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179
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Silverman JB, Restituito S, Lu W, Lee-Edwards L, Khatri L, Ziff EB. Synaptic anchorage of AMPA receptors by cadherins through neural plakophilin-related arm protein AMPA receptor-binding protein complexes. J Neurosci 2007; 27:8505-16. [PMID: 17687028 PMCID: PMC6672939 DOI: 10.1523/jneurosci.1395-07.2007] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cadherins function in the adhesion of presynaptic and postsynaptic membranes at excitatory synapses. Here we show that the cadherin-associated protein neural plakophilin-related arm protein (NPRAP; also called delta-catenin) binds via a postsynaptic density-95 (PSD-95)/discs large/zona occludens-1 (PDZ) interaction to AMPA receptor (AMPAR)-binding protein (ABP) and the related glutamate receptor (GluR)-interacting protein (GRIP), two multi-PDZ proteins that bind the GluR2 and GluR3 AMPAR subunits. The resulting cadherin-NPRAP-ABP/GRIP complexes serve as anchorages for AMPARs. Exogenous NPRAP that was bound to cadherins at adherens junctions of Madin-Darby canine kidney cells recruited ABP from the cytosol to form cadherin-NPRAP-ABP complexes, dependent on NPRAP interaction with the ABP PDZ domain 2. The cadherin-NPRAP-ABP complexes also bound GluR2. In cultured hippocampal neurons, dominant-negative mutants of NPRAP designed to disrupt tethering of ABP to NPRAP-cadherin complexes reduced surface levels of endogenous GluR2, indicating that interaction with cadherin-NPRAP-ABP complexes stabilized GluR2 at the neuronal plasma membrane. Cadherins, NPRAP, GRIP, and GluR2 copurified in the fractionation of synaptosomes and the postsynaptic density, two fractions enriched in synaptic proteins. Furthermore, synaptosomes contain NPRAP-GRIP complexes, and NPRAP localizes with the postsynaptic marker PSD-95 and with AMPARs and GRIP at spines of hippocampal neurons. Thus, tethering is likely to take place at synaptic or perisynaptic sites. NPRAP also binds PSD-95, which is a scaffold for NMDA receptors, for AMPARs in complexes with auxiliary subunits, the TARPs (transmembrane AMPA receptor regulator proteins), and for adhesion molecules. Thus, the interaction of scaffolding proteins with cadherin-NPRAP complexes may anchor diverse signaling and adhesion molecules at cadherins.
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Affiliation(s)
| | | | - Wei Lu
- Program in Neuroscience and Physiology, New York University School of Medicine, New York, New York 10016
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180
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Chubykin AA, Atasoy D, Etherton MR, Brose N, Kavalali ET, Gibson JR, Südhof TC. Activity-dependent validation of excitatory versus inhibitory synapses by neuroligin-1 versus neuroligin-2. Neuron 2007; 54:919-31. [PMID: 17582332 PMCID: PMC3738748 DOI: 10.1016/j.neuron.2007.05.029] [Citation(s) in RCA: 450] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Revised: 09/29/2006] [Accepted: 05/31/2007] [Indexed: 01/08/2023]
Abstract
Neuroligins enhance synapse formation in vitro, but surprisingly are not required for the generation of synapses in vivo. We now show that in cultured neurons, neuroligin-1 overexpression increases excitatory, but not inhibitory, synaptic responses, and potentiates synaptic NMDAR/AMPAR ratios. In contrast, neuroligin-2 overexpression increases inhibitory, but not excitatory, synaptic responses. Accordingly, deletion of neuroligin-1 in knockout mice selectively decreases the NMDAR/AMPAR ratio, whereas deletion of neuroligin-2 selectively decreases inhibitory synaptic responses. Strikingly, chronic inhibition of NMDARs or CaM-Kinase II, which signals downstream of NMDARs, suppresses the synapse-boosting activity of neuroligin-1, whereas chronic inhibition of general synaptic activity suppresses the synapse-boosting activity of neuroligin-2. Taken together, these data indicate that neuroligins do not establish, but specify and validate, synapses via an activity-dependent mechanism, with different neuroligins acting on distinct types of synapses. This hypothesis reconciles the overexpression and knockout phenotypes and suggests that neuroligins contribute to the use-dependent formation of neural circuits.
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Affiliation(s)
- Alexander A Chubykin
- Department of Neuroscience, The University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
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181
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Okuda T, Yu LMY, Cingolani LA, Kemler R, Goda Y. beta-Catenin regulates excitatory postsynaptic strength at hippocampal synapses. Proc Natl Acad Sci U S A 2007; 104:13479-84. [PMID: 17679699 PMCID: PMC1948936 DOI: 10.1073/pnas.0702334104] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The precise contribution of the cadherin-beta-catenin synapse adhesion complex in the functional and structural changes associated with the pre- and postsynaptic terminals remains unclear. Here we report a requirement for endogenous beta-catenin in regulating synaptic strength and dendritic spine morphology in cultured hippocampal pyramidal neurons. Ablating beta-catenin after the initiation of synaptogenesis in the postsynaptic neuron reduces the amplitude of spontaneous excitatory synaptic responses without a concurrent change in their frequency and synapse density. The normal glutamatergic synaptic response is maintained by postsynaptic beta-catenin in a cadherin-dependent manner and requires the C-terminal PDZ-binding motif of beta-catenin but not the link to the actin cytoskeleton. In addition, ablating beta-catenin in postsynaptic neurons accompanies a block of bidirectional quantal scaling of glutamatergic responses induced by chronic activity manipulation. In older cultures at a time when neurons have abundant dendritic spines, neurons ablated for beta-catenin show thin, elongated spines and reduced proportion of mushroom spines without a change in spine density. Collectively, these findings suggest that the cadherin-beta-catenin complex is an integral component of synaptic strength regulation and plays a basic role in coupling synapse function and spine morphology.
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Affiliation(s)
- Takashi Okuda
- *Medical Research Council Laboratory for Molecular Cell Biology and Cell Biology Unit
| | - Lily M. Y. Yu
- *Medical Research Council Laboratory for Molecular Cell Biology and Cell Biology Unit
- Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom; and
| | - Lorenzo A. Cingolani
- *Medical Research Council Laboratory for Molecular Cell Biology and Cell Biology Unit
| | - Rolf Kemler
- Department of Molecular Embryology, Max Planck Institute of Immunobiology, Stuebeweg 51, D-79108 Freiburg, Germany
| | - Yukiko Goda
- *Medical Research Council Laboratory for Molecular Cell Biology and Cell Biology Unit
- Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom; and
- To whom correspondence should be addressed at:
Medical Research Council Laboratory for Molecular Cell Biology and Cell Biology Unit, University College London, Gower Street, London WC1E 6BT, United Kingdom. E-mail:
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182
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Besse F, Mertel S, Kittel RJ, Wichmann C, Rasse TM, Sigrist SJ, Ephrussi A. The Ig cell adhesion molecule Basigin controls compartmentalization and vesicle release at Drosophila melanogaster synapses. ACTA ACUST UNITED AC 2007; 177:843-55. [PMID: 17548512 PMCID: PMC2064284 DOI: 10.1083/jcb.200701111] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Synapses can undergo rapid changes in size as well as in their vesicle release function during both plasticity processes and development. This fundamental property of neuronal cells requires the coordinated rearrangement of synaptic membranes and their associated cytoskeleton, yet remarkably little is known of how this coupling is achieved. In a GFP exon-trap screen, we identified Drosophila melanogaster Basigin (Bsg) as an immunoglobulin domain-containing transmembrane protein accumulating at periactive zones of neuromuscular junctions. Bsg is required pre- and postsynaptically to restrict synaptic bouton size, its juxtamembrane cytoplasmic residues being important for that function. Bsg controls different aspects of synaptic structure, including distribution of synaptic vesicles and organization of the presynaptic cortical actin cytoskeleton. Strikingly, bsg function is also required specifically within the presynaptic terminal to inhibit nonsynchronized evoked vesicle release. We thus propose that Bsg is part of a transsynaptic complex regulating synaptic compartmentalization and strength, and coordinating plasma membrane and cortical organization.
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Affiliation(s)
- Florence Besse
- Developmental Biology Unit, European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
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183
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Liu J, Lewohl JM, Harris RA, Dodd PR, Mayfield RD. Altered gene expression profiles in the frontal cortex of cirrhotic alcoholics. Alcohol Clin Exp Res 2007; 31:1460-6. [PMID: 17625000 DOI: 10.1111/j.1530-0277.2007.00444.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Cirrhosis is the result of chronic liver disease that causes scarring and dysfunction of the liver. The disease is a common concomitant condition resulting from sustained exposure to alcohol. Heavy alcohol use results in brain damage that is generally more severe in cirrhotic compared with noncirrhotic alcoholics. We examined, at the cellular level, gene expression in the frontal cortex of cirrhotic alcoholics. METHODS Gene expression profiles were compared between cirrhotic and noncirrhotic alcoholics using approximately 47,000 element cDNA microarrays. RESULTS Widespread differences in transcriptome patterns were observed in cirrhotic compared with noncirrhotic alcoholics and these differences in gene expression accurately distinguished cirrhotic from noncirrhotic alcoholics. Functionally related groups of genes were identified that are involved in cell adhesion, mitochondrial function, synaptic transmission, apoptosis, and cell proliferation. Both astrocytes and neuronal cells were affected at the transcriptional level. The regulated genes are involved in neurite growth, neuronal cell adhesion, synaptic vesicle release, and postsynaptic neurotransmission. CONCLUSIONS These changes in the transcriptome likely contribute to the more severe brain dysfunction in cirrhotic alcoholics.
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Affiliation(s)
- Jianwen Liu
- Waggoner Center for Alcohol and Addiction Research, University of Texas at Austin, Austin, Texas 78712, USA
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184
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Abstract
The assembly of synapses in the vertebrate central nervous system requires bidirectional signaling across the synaptic cleft that directs the differentiation of pre- and postsynaptic membrane domains. Biochemical and genetic studies have identified several adhesion and signaling molecules that localize to synapses and might participate in organizing synaptic structures. Understanding how individual proteins contribute to synaptic organization is complicated by the fact that there are significant numbers of separate signals that cooperate in this process. This protocol describes an assay system that permits examination of synaptogenic activities of individual cell-surface proteins in isolation. Besides the time needed for preparation and growth of primary neuronal cultures (6-14 days), the execution and analysis of the assay is rapid, requiring approximately 2 days. Using this assay, recent studies revealed that single synaptic adhesion complexes can direct a remarkable degree of synaptic differentiation and provided new insights into the cell biological mechanisms of synaptogenesis.
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Affiliation(s)
- Thomas Biederer
- Department of Molecular Biophysics and Biochemistry, Yale University, Sterling Hall of Medicine C127, 333 Cedar Street, New Haven, Connecticut 06520, USA.
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185
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Gingras J, Rassadi S, Cooper E, Ferns M. Synaptic transmission is impaired at neuronal autonomic synapses in agrin-null mice. Dev Neurobiol 2007; 67:521-34. [PMID: 17443806 DOI: 10.1002/dneu.20304] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Neuronal synapse formation is a multistep process regulated by several pre- and postsynaptic adhesion and signaling proteins. Recently, we found that agrin acts as one such synaptogenic factor at neuronal synapses in the PNS by demonstrating that structural synapse formation is impaired in the superior cervical ganglia (SCG) of z+ agrin-deficient mice and in SCG cultures derived from those animals. Here, we tested whether synaptic function is defective in agrin-null (AGD-/-) ganglia and began to define agrin's mechanism of action. Our electrophysiological recordings of compound action potentials showed that presynaptic stimulation evoked action potentials in approximately 40% of AGD-/- ganglionic neurons compared to 90% of wild-type neurons; moreover, transmission could not be potentiated as in wild-type or z+ agrin-deficient ganglia. Intracellular recordings also showed that nerve-evoked excitatory postsynaptic potentials in AGD-/- neurons were only 1/3 the size of those in wild-type neurons and mostly subthreshold. Consistent with these defects in transmission, we found an approximately 40-50% decrease in synapse number in AGD-/- ganglia and cultures, and decreased levels of differentiation at the residual synapses in culture. Furthermore, surface levels of acetylcholine receptors (AChRs) were equivalent in cultured AGD-/- and wild-type neurons, and depolarization reduced the synaptic localization of AChRs in AGD-/- but not wild-type neurons. These findings provide the first direct demonstration that agrin is required for proper structural and functional development of an interneuronal synapse in vivo. Moreover, they suggest a novel role for agrin, in stabilizing the postsynaptic density of nAChR at nascent neuronal synapses.
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Affiliation(s)
- Jacinthe Gingras
- Center for Research in Neuroscience, McGill University Health Center, Montreal, QC, H3G 1A4, Canada
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186
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Tai CY, Mysore SP, Chiu C, Schuman EM. Activity-Regulated N-Cadherin Endocytosis. Neuron 2007; 54:771-85. [PMID: 17553425 DOI: 10.1016/j.neuron.2007.05.013] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2006] [Revised: 03/23/2007] [Accepted: 05/09/2007] [Indexed: 11/25/2022]
Abstract
Enduring forms of synaptic plasticity are thought to require ongoing regulation of adhesion molecules, such as N-cadherin, at synaptic junctions. Little is known about the activity-regulated trafficking of adhesion molecules. Here we demonstrate that surface N-cadherin undergoes a surprisingly high basal rate of internalization. Upon activation of NMDA receptors (NMDAR), the rate of N-cadherin endocytosis is significantly reduced, resulting in an accumulation of N-cadherin in the plasma membrane. Beta-catenin, an N-cadherin binding partner, is a primary regulator of N-cadherin endocytosis. Following NMDAR stimulation, beta-catenin accumulates in spines and exhibits increased binding to N-cadherin. Overexpression of a mutant form of beta-catenin, Y654F, prevents the NMDAR-dependent regulation of N-cadherin internalization, resulting in stabilization of surface N-cadherin molecules. Furthermore, the stabilization of surface N-cadherin blocks NMDAR-dependent synaptic plasticity. These results indicate that NMDAR activity regulates N-cadherin endocytosis, providing a mechanistic link between structural plasticity and persistent changes in synaptic efficacy.
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Affiliation(s)
- Chin-Yin Tai
- Division of Biology 114-96, California Institute of Technology, Pasadena, CA 91125, USA
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187
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Letellier M, Bailly Y, Demais V, Sherrard RM, Mariani J, Lohof AM. Reinnervation of late postnatal Purkinje cells by climbing fibers: neosynaptogenesis without transient multi-innervation. J Neurosci 2007; 27:5373-83. [PMID: 17507559 PMCID: PMC6672351 DOI: 10.1523/jneurosci.0452-07.2007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Synaptic partner selection and refinement of projections are important in the development of precise and functional neuronal connections. We investigated the formation of new synaptic connections in a relatively mature system to test whether developmental events can be recapitulated at later stages (i.e., after the mature synaptic organization has been established), using a model of postlesional reinnervation in the olivo-cerebellar pathway. During the development of this pathway, synaptic connections between climbing fibers (CFs) and Purkinje cells (PCs) are diffuse and redundant before synapse elimination refines the pattern. The regression of CFs during the first 2 postnatal weeks in the rat leads to mono-innervation of each PC. After unilateral transection of the rat olivo-cerebellar pathway and intracerebellar injection of BDNF 24 h after lesion, axons from the remaining inferior olive can sprout into the deafferented hemicerebellum and establish new contacts with denervated PCs at later developmental stages. We found that these contacts are first established on somatic thorns before the CFs translocate to the PC dendrites, recapitulating the morphological steps of normal CF-PC synaptogenesis, but on a relatively mature PC. However, electrophysiology of PC reinnervation by transcommissural CFs in these animals showed that each PC is reinnervated by only one CF. This mono-innervation contrasts with the reinnervation of grafted immature PCs in the same cerebellum. Our results provide evidence that relatively mature PCs do not receive several olivary afferents during late reinnervation, suggesting a critical role of the target cell state in the control of CF-PC synaptogenesis. Thus, synapse exuberance and subsequent elimination are not a prerequisite to reach a mature relationship between synaptic partners.
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Affiliation(s)
- Mathieu Letellier
- Université Pierre et Marie Curie-Paris, Unité Mixte de Recherche (UMR) 7102–Neurobiologie des Processus Adaptatifs (NPA), and Centre National de la Recherche Scientifique (CNRS), UMR 7102–NPA, F-75005 Paris, France
| | - Yannick Bailly
- Neurotransmission et Sécrétion Neuroendocrine, UMR 7168 Institut des Neurosciences Cellulaires et Intégratives, CNRS, and
| | - Valérie Demais
- Plateforme d'Imagerie In Vitro, Institut Fédératif de Recherche 37 des Neurosciences, Université Louis Pasteur, F-67084 Strasbourg, France
| | - Rachel M. Sherrard
- School of Anatomy and Human Biology, University of Western Australia, Crawley 6009, Australia, and
| | - Jean Mariani
- Université Pierre et Marie Curie-Paris, Unité Mixte de Recherche (UMR) 7102–Neurobiologie des Processus Adaptatifs (NPA), and Centre National de la Recherche Scientifique (CNRS), UMR 7102–NPA, F-75005 Paris, France
- Assistance Publique–Hôpitaux de Paris Hôpital Charles Foix, Unité d'Explorations Fonctionnelles, F-94200, Ivry sur Seine, France
| | - Ann M. Lohof
- Université Pierre et Marie Curie-Paris, Unité Mixte de Recherche (UMR) 7102–Neurobiologie des Processus Adaptatifs (NPA), and Centre National de la Recherche Scientifique (CNRS), UMR 7102–NPA, F-75005 Paris, France
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188
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Lardi-Studler B, Fritschy JM. Matching of pre- and postsynaptic specializations during synaptogenesis. Neuroscientist 2007; 13:115-26. [PMID: 17404372 DOI: 10.1177/1073858406296803] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Formation of chemical synapses in the central nervous system is a highly regulated, multistep process that requires bidirectional communication across the synaptic cleft. Neurotransmitter receptors, scaffolding proteins, and signaling molecules need to be concentrated in the postsynaptic density, a specialized membrane microdomain apposed to the active zone of presynaptic terminals, where transmitter release occurs. This precise, synapse-specific matching implicates that sorting and targeting mechanisms exist for the molecular constituents of different types of synapses to ensure correct formation of neuronal circuits in the brain. There is considerable evidence from in vitro and in vivo studies that neurotransmitter signaling is not required for proper sorting during synapse formation, whereas active neurotransmission is essential for long-term synapse maintenance. Here, the authors review recent studies on the role of cell adhesion molecules in synaptogenesis and on possible mechanisms ensuring correct matching of pre- and postsynaptic sites. They discuss the role of neurotransmitter receptors and scaffolding proteins in these processes, focusing on fundamental differences between synapse formation during development and synapse maintenance and plasticity in adulthood.
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Affiliation(s)
- Barbara Lardi-Studler
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
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189
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Johansson T, Elfverson M, Birgner C, Frändberg PA, Nyberg F, Le Grevès P. Neurosteroids alter glutamate-induced changes in neurite morphology of NG108-15 cells. J Steroid Biochem Mol Biol 2007; 104:215-9. [PMID: 17512193 DOI: 10.1016/j.jsbmb.2007.03.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Activation of the NMDA receptor leads to increased intracellular Ca2+ levels ([Ca2+]i) which induces outgrowth of and morphologic changes in the neurites of the NG108-15 cell line. This effect can be blocked by antagonists for this glutamate receptor subtype (e.g. ifenprodil or AP5). We have previously shown that nanomolar concentrations of various neurosteroids modulate ifenprodil binding to the NMDA receptor. To investigate whether this interaction affects the functioning of the receptor, we studied the effect of 24 and 48 h of pregnenolone sulphate (PS) or pregnanolone sulphate (3alpha5betaS) on glutamate-stimulated NG108-15 cells. Unexpectedly, the neurosteroids themselves had an inhibitory effect on glutamate-induced changes in neurite patterns. This effect was comparable to that of ifenprodil or AP5. Moreover, the effect of combined treatment with 3alpha5betaS and ifenprodil on neurite morphology indicated a functional interaction between the substances. Interestingly, PS induced cell detachment over time, an effect that was further enhanced by ifenprodil. Cell detachment was also seen after 48 h of treatment with 3alpha5betaS; however, the effect was blocked by ifenprodil and weaker than that of PS. The interaction with the NR2B-selective antagonist ifenprodil indicates that this NMDA receptor subunit may be involved in neurosteroid-induced NG108-15 cell detachment.
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Affiliation(s)
- Tobias Johansson
- Department of Pharmaceutical Biosciences, Division of Biological Research on Drug Dependence, Uppsala University, S-751 24 Uppsala, Sweden
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190
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Shcherbakova OG, Hurt CM, Xiang Y, Dell'Acqua ML, Zhang Q, Tsien RW, Kobilka BK. Organization of beta-adrenoceptor signaling compartments by sympathetic innervation of cardiac myocytes. ACTA ACUST UNITED AC 2007; 176:521-33. [PMID: 17296797 PMCID: PMC2063986 DOI: 10.1083/jcb.200604167] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The sympathetic nervous system regulates cardiac function through the activation of adrenergic receptors (ARs). β1 and β2ARs are the primary sympathetic receptors in the heart and play different roles in regulating cardiac contractile function and remodeling in response to injury. In this study, we examine the targeting and trafficking of β1 and β2ARs at cardiac sympathetic synapses in vitro. Sympathetic neurons form functional synapses with neonatal cardiac myocytes in culture. The myocyte membrane develops into specialized zones that surround contacting axons and contain accumulations of the scaffold proteins SAP97 and AKAP79/150 but are deficient in caveolin-3. The β1ARs are enriched within these zones, whereas β2ARs are excluded from them after stimulation of neuronal activity. The results indicate that specialized signaling domains are organized in cardiac myocytes at sites of contact with sympathetic neurons and that these domains are likely to play a role in the subtype-specific regulation of cardiac function by β1 and β2ARs in vivo.
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MESH Headings
- A Kinase Anchor Proteins
- Adaptor Proteins, Signal Transducing/metabolism
- Animals
- Caveolin 3/metabolism
- Cell Compartmentation
- Cells, Cultured
- Coculture Techniques
- Discs Large Homolog 1 Protein
- Guanylate Kinases
- Heart/innervation
- Heart/physiology
- Membrane Microdomains/metabolism
- Membrane Microdomains/ultrastructure
- Membrane Proteins/metabolism
- Mice
- Myocardium/metabolism
- Myocardium/ultrastructure
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/ultrastructure
- Neuromuscular Junction/metabolism
- Neuromuscular Junction/ultrastructure
- Receptors, Adrenergic, beta/drug effects
- Receptors, Adrenergic, beta/metabolism
- Receptors, Adrenergic, beta-1/drug effects
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, Adrenergic, beta-2/drug effects
- Receptors, Adrenergic, beta-2/metabolism
- Signal Transduction/physiology
- Sympathetic Fibers, Postganglionic/metabolism
- Sympathetic Fibers, Postganglionic/ultrastructure
- Synaptic Membranes/metabolism
- Synaptic Membranes/ultrastructure
- Synaptic Transmission/physiology
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Affiliation(s)
- Olga G Shcherbakova
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 95305, USA
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191
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Bonn S, Seeburg PH, Schwarz MK. Combinatorial expression of alpha- and gamma-protocadherins alters their presenilin-dependent processing. Mol Cell Biol 2007; 27:4121-32. [PMID: 17403907 PMCID: PMC1900011 DOI: 10.1128/mcb.01708-06] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alpha- and gamma-protocadherins (Pcdhs) are type I transmembrane receptors expressed predominantly in the central nervous system and located in part in synapses. They are transcribed from complex genomic loci, giving rise in the mouse to 14 alpha-Pcdh and 22 gamma-Pcdh isoforms consisting of variable domains, each encompassing the extracellular region, the transmembrane region, and part of the intracellular region harboring the alpha- or gamma-Pcdh-specific invariant cytoplasmic domain. Presenilin-dependent intramembrane proteolysis (PS-IP) of gamma-Pcdhs and the formation of alpha/gamma-Pcdh heteromers led us to investigate the effects of homo- and heteromer formation on gamma- and putative alpha-Pcdh membrane processing and signaling. We find that upon surface delivery, alpha-Pcdhs, like gamma-Pcdhs, are subject to matrix metallo-protease cleavage followed by PS-IP in neurons. We further demonstrate that the combinatorial expression of alpha- and gamma-Pcdhs modulates the extent of their PS-IP, indicating the formation of alpha/gamma-Pcdh heteromers with an altered susceptibility to processing. Cell-specific expression of alpha/gamma-Pcdh isoforms could thus determine cell and synapse adhesive properties as well as intracellular and nuclear signaling by their soluble cytoplasmic cleavage products, alpha C-terminal fragment 2 (alpha-CTF-2) and gamma-CTF-2.
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Affiliation(s)
- Stefan Bonn
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany
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192
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Coward RJM, Welsh GI, Koziell A, Hussain S, Lennon R, Ni L, Tavaré JM, Mathieson PW, Saleem MA. Nephrin is critical for the action of insulin on human glomerular podocytes. Diabetes 2007; 56:1127-35. [PMID: 17395751 DOI: 10.2337/db06-0693] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The leading causes of albuminuria and end-stage renal failure are secondary to abnormalities in the production or cellular action of insulin, including diabetes and hyperinsulinemic metabolic syndrome. The human glomerular podocyte is a critical cell for maintaining the filtration barrier of the kidney and preventing albuminuria. We have recently shown this cell to be insulin sensitive with respect to glucose uptake, with kinetics similar to muscle cells. We now show that the podocyte protein nephrin is essential for this process. Conditionally immortalized podocytes from two different patients with nephrin mutations (natural human nephrin mutant models) were unresponsive to insulin. Knocking nephrin down with siRNA in wild-type podocytes abrogated the insulin response, and stable nephrin transfection of nephrin-deficient podocytes rescued their insulin response. Mechanistically, we show that nephrin allows the GLUT1- and GLUT4-rich vesicles to fuse with the membrane of this cell. Furthermore, we show that the COOH of nephrin interacts with the vesicular SNARE protein VAMP2 in vitro and ex vivo (using yeast-2 hybrid and coimmunoprecipitation studies). This work demonstrates a previously unsuspected role of nephrin in vesicular docking and insulin responsiveness of podocytes.
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193
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Taniguchi H, Gollan L, Scholl FG, Mahadomrongkul V, Dobler E, Limthong N, Peck M, Aoki C, Scheiffele P. Silencing of neuroligin function by postsynaptic neurexins. J Neurosci 2007; 27:2815-24. [PMID: 17360903 PMCID: PMC2839889 DOI: 10.1523/jneurosci.0032-07.2007] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2006] [Revised: 02/02/2007] [Accepted: 02/02/2007] [Indexed: 12/24/2022] Open
Abstract
The formation of neuronal circuits during development involves a combination of synapse stabilization and elimination events. Synaptic adhesion molecules are thought to play an important role in synaptogenesis, and several trans-synaptic adhesion systems that promote the formation and maturation of synapses have been identified. The neuroligin-neurexin complex is a heterophilic adhesion system that promotes assembly and maturation of synapses through bidirectional signaling. In this protein complex, postsynaptic neuroligins are thought to interact trans-synaptically with presynaptic neurexins. However, the subcellular localization of neurexins has not been determined. Using immunoelectron microscopy, we found that endogenous neurexins and epitope-tagged neurexin-1beta are localized to axons and presynaptic terminals in vivo. Unexpectedly, neurexins are also abundant in the postsynaptic density. cis-expression of neurexin-1beta with neuroligin-1 inhibits trans-binding to recombinant neurexins, blocks the synaptogenic activity of neuroligin-1, and reduces the density of presynaptic terminals in cultured hippocampal neurons. Our results demonstrate that the function of neurexin proteins is more diverse than previously anticipated and suggest that postsynaptic cis-interactions might provide a novel mechanism for silencing the activity of a synaptic adhesion complex.
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Affiliation(s)
- Hiroki Taniguchi
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
| | - Leora Gollan
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
| | - Francisco G. Scholl
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
| | | | - Elizabeth Dobler
- Center for Neural Science, New York University, New York, New York 10003
| | - Nicolas Limthong
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
| | - Morgen Peck
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
| | - Chiye Aoki
- Center for Neural Science, New York University, New York, New York 10003
| | - Peter Scheiffele
- Department of Physiology and Cellular Biophysics, Center for Neurobiology and Behavior, Columbia University, Physicians and Surgeons 11-511, New York, New York 10032, and
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194
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Ledda F, Paratcha G, Sandoval-Guzmán T, Ibáñez CF. GDNF and GFRalpha1 promote formation of neuronal synapses by ligand-induced cell adhesion. Nat Neurosci 2007; 10:293-300. [PMID: 17310246 DOI: 10.1038/nn1855] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2006] [Accepted: 01/22/2007] [Indexed: 12/12/2022]
Abstract
The establishment of synaptic connections requires precise alignment of pre- and postsynaptic terminals. The glial cell line-derived neurotrophic factor (GDNF) receptor GFRalpha1 is enriched at pre- and postsynaptic compartments in hippocampal neurons, suggesting that it has a function in synapse formation. GDNF triggered trans-homophilic binding between GFRalpha1 molecules and cell adhesion between GFRalpha1-expressing cells. This represents the first example of a cell-cell interaction being mediated by a ligand-induced cell adhesion molecule (LICAM). In the presence of GDNF, ectopic GFRalpha1 induced localized presynaptic differentiation in hippocampal neurons, as visualized by clustering of vesicular proteins and neurotransmitter transporters, and by activity-dependent vesicle recycling. Presynaptic differentiation induced by GDNF was markedly reduced in neurons lacking GFRalpha1. Gdnf mutant mice showed reduced synaptic localization of presynaptic proteins and a marked decrease in the density of presynaptic puncta, indicating a role for GDNF signaling in hippocampal synaptogenesis in vivo. We propose that GFRalpha1 functions as a LICAM to establish precise synaptic contacts and induce presynaptic differentiation.
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Affiliation(s)
- Fernanda Ledda
- Division of Molecular Neurobiology, Department of Neuroscience, Karolinska Institute, 17177 Stockholm, Sweden.
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195
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Bernstein HG, Smalla KH, Bogerts B, Gordon-Weeks PR, Beesley PW, Gundelfinger ED, Kreutz MR. The immunolocalization of the synaptic glycoprotein neuroplastin differs substantially between the human and the rodent brain. Brain Res 2007; 1134:107-12. [PMID: 17196182 DOI: 10.1016/j.brainres.2006.11.090] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2006] [Revised: 11/25/2006] [Accepted: 11/28/2006] [Indexed: 10/23/2022]
Abstract
Neuroplastin is a cell adhesion molecule of the immunoglobulin superfamily that exists in two splice isoforms, np65/np55, and that was reported to play a prominent role in synaptic plasticity processes. The splice isoform np65 associates with synapses in an activity-dependent manner and has been shown to play a role for the induction of hippocampal long-term potentiation in rodents. We have therefore analyzed the distribution of neuroplastins in human brain. Neuroplastin is present in many neuronal cell types of the forebrain and cerebellum and immunoreactive label covers the cell soma, neurites and also puncta in the neuropil were visible. Interestingly, we found some remarkable species differences in the expression patterns of neuroplastins between the human and the rodent brain. In human brain np65 is prominently present in cerebellum while np55 is the predominant isoform in mouse and rat cerebellum. Moreover, the parasagittal stripe-type of staining seen with np55 in mouse cerebellum is not found in human brain. In addition we found no segregation of np65 immunolabel in hippocampal subregions like it was reported previously for the rat. These results might indicate different cellular functions of the molecule in different species.
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Affiliation(s)
- Hans-Gert Bernstein
- Department of Psychiatry, Faculty of Medicine, Otto-von-Guericke University, Magdeburg, Germany
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196
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Kato K. Glycobiological Approach to Understanding Neural Plasticity. TRENDS GLYCOSCI GLYC 2007. [DOI: 10.4052/tigg.19.99] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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197
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Zou C, Huang W, Ying G, Wu Q. Sequence analysis and expression mapping of the rat clustered protocadherin gene repertoires. Neuroscience 2007; 144:579-603. [PMID: 17110050 DOI: 10.1016/j.neuroscience.2006.10.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Revised: 09/14/2006] [Accepted: 10/04/2006] [Indexed: 11/30/2022]
Abstract
Three closely-linked clusters of protocadherin (Pcdh) genes (alpha, beta, and gamma) encoding more than 50 distinct mRNAs have been identified in humans and mice, and proposed to play important roles in neuronal connectivity in the CNS. The human and mouse Pcdh alpha and gamma clusters each span a region of about 300 kb genomic DNA, and are each organized into a tandem array of more than a dozen highly-similar "variable" exons, and three downstream "constant" exons. Little is known about the expression patterns of the alpha and gamma repertoires in the CNS. Here, we comprehensively analyzed the one megabase rat Pcdh genomic DNA sequences at the nucleotide level using various computational methods. We found that the clustered rat Pcdh genes display strict orthologous relationships with those of mice but not humans. Moreover, each rat Pcdh variable exon is preceded by a distinct promoter. We designed two complete sets of isoform-specific probes and extensively mapped the expression patterns for each member of the alpha and gamma repertoires in the adult rat CNS by non-isotopic in situ hybridization experiments. We found that most alpha and gamma mRNA isoforms are broadly expressed in similar patterns in subsets of cells (with some displaying interesting cortical layer-specific expression) throughout various CNS regions, including the olfactory bulb, cerebral cortex, hippocampus, cerebellum, and spinal cord. The broad expression of most alpha or gamma mRNAs throughout various regions of the CNS is consistent with the hypothesis that these genes may be used for neurons to establish their individuality and also provide the adhesive diversity required for complex synaptic connectivity in the mammalian CNS.
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Affiliation(s)
- C Zou
- Department of Human Genetics, University of Utah Medical School, Salt Lake City, UT 84112, USA
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198
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Lein ES, Hawrylycz MJ, Ao N, Ayres M, Bensinger A, Bernard A, Boe AF, Boguski MS, Brockway KS, Byrnes EJ, Chen L, Chen L, Chen TM, Chin MC, Chong J, Crook BE, Czaplinska A, Dang CN, Datta S, Dee NR, Desaki AL, Desta T, Diep E, Dolbeare TA, Donelan MJ, Dong HW, Dougherty JG, Duncan BJ, Ebbert AJ, Eichele G, Estin LK, Faber C, Facer BA, Fields R, Fischer SR, Fliss TP, Frensley C, Gates SN, Glattfelder KJ, Halverson KR, Hart MR, Hohmann JG, Howell MP, Jeung DP, Johnson RA, Karr PT, Kawal R, Kidney JM, Knapik RH, Kuan CL, Lake JH, Laramee AR, Larsen KD, Lau C, Lemon TA, Liang AJ, Liu Y, Luong LT, Michaels J, Morgan JJ, Morgan RJ, Mortrud MT, Mosqueda NF, Ng LL, Ng R, Orta GJ, Overly CC, Pak TH, Parry SE, Pathak SD, Pearson OC, Puchalski RB, Riley ZL, Rockett HR, Rowland SA, Royall JJ, Ruiz MJ, Sarno NR, Schaffnit K, Shapovalova NV, Sivisay T, Slaughterbeck CR, Smith SC, Smith KA, Smith BI, Sodt AJ, Stewart NN, Stumpf KR, Sunkin SM, Sutram M, Tam A, Teemer CD, Thaller C, Thompson CL, Varnam LR, Visel A, Whitlock RM, Wohnoutka PE, Wolkey CK, Wong VY, Wood M, Yaylaoglu MB, Young RC, Youngstrom BL, Yuan XF, Zhang B, Zwingman TA, Jones AR. Genome-wide atlas of gene expression in the adult mouse brain. Nature 2006; 445:168-76. [PMID: 17151600 DOI: 10.1038/nature05453] [Citation(s) in RCA: 3898] [Impact Index Per Article: 216.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Accepted: 11/15/2006] [Indexed: 11/09/2022]
Abstract
Molecular approaches to understanding the functional circuitry of the nervous system promise new insights into the relationship between genes, brain and behaviour. The cellular diversity of the brain necessitates a cellular resolution approach towards understanding the functional genomics of the nervous system. We describe here an anatomically comprehensive digital atlas containing the expression patterns of approximately 20,000 genes in the adult mouse brain. Data were generated using automated high-throughput procedures for in situ hybridization and data acquisition, and are publicly accessible online. Newly developed image-based informatics tools allow global genome-scale structural analysis and cross-correlation, as well as identification of regionally enriched genes. Unbiased fine-resolution analysis has identified highly specific cellular markers as well as extensive evidence of cellular heterogeneity not evident in classical neuroanatomical atlases. This highly standardized atlas provides an open, primary data resource for a wide variety of further studies concerning brain organization and function.
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Affiliation(s)
- Ed S Lein
- Allen Institute for Brain Science, Seattle, Washington 98103, USA.
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199
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Dai Y, Taru H, Deken SL, Grill B, Ackley B, Nonet ML, Jin Y. SYD-2 Liprin-α organizes presynaptic active zone formation through ELKS. Nat Neurosci 2006; 9:1479-87. [PMID: 17115037 DOI: 10.1038/nn1808] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Accepted: 10/27/2006] [Indexed: 12/12/2022]
Abstract
A central event in synapse development is formation of the presynaptic active zone in response to positional cues. Three active zone proteins, RIM, ELKS (also known as ERC or CAST) and Liprin-alpha, bind each other and are implicated in linking active zone formation to synaptic vesicle release. Loss of function in Caenorhabditis elegans syd-2 Liprin-alpha alters the size of presynaptic specializations and disrupts synaptic vesicle accumulation. Here we report that a missense mutation in the coiled-coil domain of SYD-2 causes a gain of function. In HSN synapses, the syd-2(gf) mutation promotes synapse formation in the absence of syd-1, which is essential for HSN synapse formation. syd-2(gf) also partially suppresses the synaptogenesis defects in syg-1 and syg-2 mutants. The activity of syd-2(gf) requires elks-1, an ELKS homolog; but not unc-10, a RIM homolog. The mutant SYD-2 shows increased association with ELKS. These results establish a functional dependency for assembly of the presynaptic active zone in which SYD-2 plays a key role.
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Affiliation(s)
- Ya Dai
- Department of Molecular, Cell and Developmental Biology, Sinsheimer Laboratories, University of California, 1156 High Street, Santa Cruz, California 95064, USA
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Varoqueaux F, Aramuni G, Rawson RL, Mohrmann R, Missler M, Gottmann K, Zhang W, Südhof TC, Brose N. Neuroligins determine synapse maturation and function. Neuron 2006; 51:741-54. [PMID: 16982420 DOI: 10.1016/j.neuron.2006.09.003] [Citation(s) in RCA: 598] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Revised: 07/31/2006] [Accepted: 09/01/2006] [Indexed: 11/22/2022]
Abstract
Synaptogenesis, the generation and maturation of functional synapses between nerve cells, is an essential step in the development of neuronal networks in the brain. It is thought to be triggered by members of the neuroligin family of postsynaptic cell adhesion proteins, which may form transsynaptic contacts with presynaptic alpha- and beta-neurexins and have been implicated in the etiology of autism. We show that deletion mutant mice lacking neuroligin expression die shortly after birth due to respiratory failure. This respiratory failure is a consequence of reduced GABAergic/glycinergic and glutamatergic synaptic transmission and network activity in brainstem centers that control respiration. However, the density of synaptic contacts is not altered in neuroligin-deficient brains and cultured neurons. Our data show that neuroligins are required for proper synapse maturation and brain function, but not for the initial formation of synaptic contacts.
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Affiliation(s)
- Frédérique Varoqueaux
- Department of Molecular Neurobiology and Center for the Molecular Physiology of the Brain, Max Planck Institute of Experimental Medicine, D-37075 Göttingen, Germany
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