101
|
Letellier M, Szíber Z, Chamma I, Saphy C, Papasideri I, Tessier B, Sainlos M, Czöndör K, Thoumine O. A unique intracellular tyrosine in neuroligin-1 regulates AMPA receptor recruitment during synapse differentiation and potentiation. Nat Commun 2018; 9:3979. [PMID: 30266896 PMCID: PMC6162332 DOI: 10.1038/s41467-018-06220-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 08/13/2018] [Indexed: 01/08/2023] Open
Abstract
To better understand the molecular mechanisms by which early neuronal connections mature into synapses, we examined the impact of neuroligin-1 (Nlg1) phosphorylation on synapse differentiation, focusing on a unique intracellular tyrosine (Y782), which differentially regulates Nlg1 binding to PSD-95 and gephyrin. By expressing Nlg1 point mutants (Y782A/F) in hippocampal neurons, we show using imaging and electrophysiology that Y782 modulates the recruitment of functional AMPA receptors (AMPARs). Nlg1-Y782F impaired both dendritic spine formation and AMPAR diffusional trapping, but not NMDA receptor recruitment, revealing the assembly of silent synapses. Furthermore, replacing endogenous Nlg1 with either Nlg1-Y782A or -Y782F in CA1 hippocampal neurons impaired long-term potentiation (LTP), demonstrating a critical role of AMPAR synaptic retention. Screening of tyrosine kinases combined with pharmacological inhibitors point to Trk family members as major regulators of endogenous Nlg1 phosphorylation and synaptogenic function. Thus, Nlg1 tyrosine phosphorylation signaling is a critical event in excitatory synapse differentiation and LTP. Neuroligins are postsynaptic cell adhesion molecules thought to play roles in synaptic development and function. Here, authors show that phosphorylation of Y782 in neuroligin-1 modulates its role in differentiation and ability to recruit AMPARs including during long-term potentiation.
Collapse
Affiliation(s)
- Mathieu Letellier
- Interdisciplinary Institute for Neuroscience, UMR 5297, Univ. Bordeaux, F-33000, Bordeaux, France. .,Interdisciplinary Institute for Neuroscience, UMR 5297, CNRS, F-33000, Bordeaux, France.
| | - Zsófia Szíber
- Interdisciplinary Institute for Neuroscience, UMR 5297, Univ. Bordeaux, F-33000, Bordeaux, France.,Interdisciplinary Institute for Neuroscience, UMR 5297, CNRS, F-33000, Bordeaux, France
| | - Ingrid Chamma
- Interdisciplinary Institute for Neuroscience, UMR 5297, Univ. Bordeaux, F-33000, Bordeaux, France.,Interdisciplinary Institute for Neuroscience, UMR 5297, CNRS, F-33000, Bordeaux, France
| | - Camille Saphy
- Interdisciplinary Institute for Neuroscience, UMR 5297, Univ. Bordeaux, F-33000, Bordeaux, France.,Interdisciplinary Institute for Neuroscience, UMR 5297, CNRS, F-33000, Bordeaux, France
| | - Ioanna Papasideri
- Interdisciplinary Institute for Neuroscience, UMR 5297, Univ. Bordeaux, F-33000, Bordeaux, France.,Interdisciplinary Institute for Neuroscience, UMR 5297, CNRS, F-33000, Bordeaux, France
| | - Béatrice Tessier
- Interdisciplinary Institute for Neuroscience, UMR 5297, Univ. Bordeaux, F-33000, Bordeaux, France.,Interdisciplinary Institute for Neuroscience, UMR 5297, CNRS, F-33000, Bordeaux, France
| | - Matthieu Sainlos
- Interdisciplinary Institute for Neuroscience, UMR 5297, Univ. Bordeaux, F-33000, Bordeaux, France.,Interdisciplinary Institute for Neuroscience, UMR 5297, CNRS, F-33000, Bordeaux, France
| | - Katalin Czöndör
- Interdisciplinary Institute for Neuroscience, UMR 5297, Univ. Bordeaux, F-33000, Bordeaux, France.,Interdisciplinary Institute for Neuroscience, UMR 5297, CNRS, F-33000, Bordeaux, France
| | - Olivier Thoumine
- Interdisciplinary Institute for Neuroscience, UMR 5297, Univ. Bordeaux, F-33000, Bordeaux, France. .,Interdisciplinary Institute for Neuroscience, UMR 5297, CNRS, F-33000, Bordeaux, France.
| |
Collapse
|
102
|
Bragina L, Conti F. Expression of Neurofilament Subunits at Neocortical Glutamatergic and GABAergic Synapses. Front Neuroanat 2018; 12:74. [PMID: 30254572 PMCID: PMC6141662 DOI: 10.3389/fnana.2018.00074] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 08/27/2018] [Indexed: 11/29/2022] Open
Abstract
Neurofilaments (NFs) are neuron-specific heteropolymers that have long been considered as structural proteins. However, it has recently been documented that they may play a functional role at synapses. Indeed, the four NF subunits—NFL, NFM, NFH and α-internexin—are integral components of synapses in the striatum and hippocampus, since their elimination disrupts synaptic plasticity and impairs social memory, an observation that might have important implications for some neuropsychiatric diseases. Here, we studied NFs localization in VGLUT1-, VGLUT2-, VGAT-, PSD-95- and gephyrin-positive (+) puncta, and in glutamatergic and GABAergic synapses in the cerebral cortex of adult rats. Synapses were identified by pre- and postsynaptic markers: glutamatergic synapses by VGLUT1+ or VGLUT2+ puncta contacting PSD-95+ puncta; and GABAergic synapses by VGAT+ puncta contacting gephyrin+ puncta. In VGLUT1 glutamatergic synapses NF showed a greater expression in the compartment labeled by postsynaptic markers (20%–30%) than in those labeled by presynaptic markers (10%–20%), whereas in GABAergic synapses a similar expression was detected in both compartments (20%–30%). Moreover, NF expression was higher in the GABAergic (20%–30%) than in the glutamatergic (10%–15%) compartments labeled by presynaptic markers. Finally, a higher colocalization of VGLUT1+, VGLUT2+ and VGAT+ puncta with NFs was seen when presynaptic puncta contacted elements labeled by postsynaptic markers. These findings show that the four NF subunits are expressed at some neocortical synapses, and contribute to glutamatergic and GABAergic synapse heterogeneity.
Collapse
Affiliation(s)
- Luca Bragina
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, Italy.,Center for Neurobiology of Aging, IRCCS INRCA, Ancona, Italy
| | - Fiorenzo Conti
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle Marche, Ancona, Italy.,Center for Neurobiology of Aging, IRCCS INRCA, Ancona, Italy
| |
Collapse
|
103
|
Moutin E, Nikonenko I, Stefanelli T, Wirth A, Ponimaskin E, De Roo M, Muller D. Palmitoylation of cdc42 Promotes Spine Stabilization and Rescues Spine Density Deficit in a Mouse Model of 22q11.2 Deletion Syndrome. Cereb Cortex 2018; 27:3618-3629. [PMID: 27365300 DOI: 10.1093/cercor/bhw183] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
22q11.2 deletion syndrome (22q11DS) is associated with learning and cognitive dysfunctions and a high risk of developing schizophrenia. It has become increasingly clear that dendritic spine plasticity is tightly linked to cognition. Thus, understanding how genes involved in cognitive disorders affect synaptic networks is a major challenge of modern biology. Several studies have pointed to a spine density deficit in 22q11DS transgenic mice models. Using the LgDel mouse model, we first quantified spine deficit at different stages using electron microscopy. Next we performed repetitive confocal imaging over several days on hippocampal organotypic cultures of LgDel mice. We show no imbalanced ratio between daily spine formation and spine elimination, but a decreased spine life expectancy. We corrected this impaired spine stabilization process by overexpressing ZDHHC8 palmitoyltransferase, whose gene belongs to the LgDel microdeletion. Overexpression of one of its substrates, the cdc42 brain-specific variant, under a constitutively active form (cdc42-palm-CA) led to the same result. Finally, we could rescue spine density in vivo, in adult LgDel mice, by injecting pups with a vector expressing cdc42-palm-CA. This study reveals a new role of ZDHHC8-cdc42-palm molecular pathway in postsynaptic structural plasticity and provides new evidence in favor of the dysconnectivity hypothesis for schizophrenia.
Collapse
Affiliation(s)
- E Moutin
- Department of Basic Neurosciences, Medical School, University of Geneva, 1211 Geneva 4, Switzerland
| | - I Nikonenko
- Department of Basic Neurosciences, Medical School, University of Geneva, 1211 Geneva 4, Switzerland
| | - T Stefanelli
- Department of Basic Neurosciences, Medical School, University of Geneva, 1211 Geneva 4, Switzerland
| | - A Wirth
- Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - E Ponimaskin
- Cellular Neurophysiology, Hannover Medical School, 30625 Hannover, Germany
| | - M De Roo
- Department of Basic Neurosciences, Medical School, University of Geneva, 1211 Geneva 4, Switzerland
| | - D Muller
- Department of Basic Neurosciences, Medical School, University of Geneva, 1211 Geneva 4, Switzerland
| |
Collapse
|
104
|
Paradis-Isler N, Boehm J. NMDA receptor-dependent dephosphorylation of serine 387 in Argonaute 2 increases its degradation and affects dendritic spine density and maturation. J Biol Chem 2018; 293:9311-9325. [PMID: 29735530 DOI: 10.1074/jbc.ra117.001007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 04/26/2018] [Indexed: 01/01/2023] Open
Abstract
Argonaute (AGO) proteins are essential components of the microRNA (miRNA) pathway. AGO proteins are loaded with miRNAs to target mRNAs and thereby regulate mRNA stability and protein translation. As such, AGO proteins are important actors in controlling local protein synthesis, for instance, at dendritic spines and synapses. Although miRNA-mediated regulation of dendritic mRNAs has become a focus of intense interest over the past years, the mechanisms regulating neuronal AGO proteins remain largely unknown. Here, using rat hippocampal neurons, we report that dendritic Ago2 is down-regulated by the proteasome upon NMDA receptor activation. We found that Ser-387 in Ago2 is dephosphorylated upon NMDA treatment and that this dephosphorylation precedes Ago2 degradation. Expressing Ser-387 phosphorylation-deficient or phosphomimetic Ago2 in neurons, we observed that this phosphorylation site is involved in modulating dendritic spine morphology and postsynaptic density protein 95 (PSD-95) expression in spines. Collectively, our results point toward a signaling pathway linking NMDA receptor-dependent Ago2 dephosphorylation and turnover to postsynaptic structural changes. They support a model in which NMDA receptor-mediated dephosphorylation of Ago2 and Ago2 turnover contributes to the de-repression of mRNAs involved in spine growth and maturation.
Collapse
Affiliation(s)
- Nicolas Paradis-Isler
- From the Département Neurosciences, Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Jannic Boehm
- From the Département Neurosciences, Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| |
Collapse
|
105
|
Suresh A, Dunaevsky A. Relationship Between Synaptic AMPAR and Spine Dynamics: Impairments in the FXS Mouse. Cereb Cortex 2018; 27:4244-4256. [PMID: 28541473 PMCID: PMC6057510 DOI: 10.1093/cercor/bhx128] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 05/04/2017] [Indexed: 12/26/2022] Open
Abstract
Structural dynamics of dendritic spines are important for memory and learning and are impaired in neurodevelopmental disorders such as fragile X syndrome. Spine dynamics are regulated by activity-dependent mechanisms that involve modulation of AMPA receptors (AMPAR); however, the relationship between AMPAR and spine dynamics in vivo and how these are altered in FXS mouse model is not known. Here, we tracked AMPAR and spines over multiple days in vivo in the cortex and found that dendritic spines in the fmr1 KO mouse were denser, smaller, had higher turnover rates and contained less sGluA2 compared to littermate controls. Although, KO spines maintained the relationship between AMPAR and spine stability, AMPAR levels in the KO were more dynamic with larger proportion of spines showing multiple dynamic events of AMPAR. Directional changes in sGluA2 were also observed in newly formed and eliminated spines, with KO spines displaying greater loss of AMPAR before elimination. Thus, we demonstrate that AMPAR levels within spines not are only continuously dynamic, but are also predictive of spine behavior, with impairments observed in the fmr1 KO mice.
Collapse
Affiliation(s)
| | - Anna Dunaevsky
- Department of Developmental Neuroscience, Munroe-Meyer Institute, University of Nebraska Medical Center, 985960 Nebraska Medical Center, Omaha, NE 68198-5960, USA
| |
Collapse
|
106
|
Martínez-Torres NI, González-Tapia D, Flores-Soto M, Vázquez-Hernández N, Salgado-Ceballos H, González-Burgos I. Spinogenesis in spinal cord motor neurons following pharmacological lesions to the rat motor cortex. Neurologia 2018; 36:119-126. [PMID: 29555297 DOI: 10.1016/j.nrl.2017.12.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 12/01/2017] [Indexed: 11/19/2022] Open
Abstract
INTRODUCTION Motor function is impaired in multiple neurological diseases associated with corticospinal tract degeneration. Motor impairment has been linked to plastic changes at both the presynaptic and postsynaptic levels. However, there is no evidence of changes in information transmission from the cortex to spinal motor neurons. METHODS We used kainic acid to induce stereotactic lesions to the primary motor cortex of female adult rats. Fifteen days later, we evaluated motor function with the BBB scale and the rotarod and determined the density of thin, stubby, and mushroom spines of motor neurons from a thoracolumbar segment of the spinal cord. Spinophilin, synaptophysin, and β iii-tubulin expression was also measured. RESULTS Pharmacological lesions resulted in poor motor performance. Spine density and the proportion of thin and stubby spines were greater. We also observed increased expression of the 3 proteins analysed. CONCLUSION The clinical symptoms of neurological damage secondary to Wallerian degeneration of the corticospinal tract are associated with spontaneous, compensatory plastic changes at the synaptic level. Based on these findings, spontaneous plasticity is a factor to consider when designing more efficient strategies in the early phase of rehabilitation.
Collapse
Affiliation(s)
- N I Martínez-Torres
- División de Neurociencias, Centro de Investigación Biomédica de Occidente, IMSS, Guadalajara, Jalisco, México; Centro Universitario del Norte, Universidad de Guadalajara, Colotlán, Jalisco, México
| | - D González-Tapia
- División de Neurociencias, Centro de Investigación Biomédica de Occidente, IMSS, Guadalajara, Jalisco, México; Instituto de Ciencias de la Rehabilitación Integral, Guadalajara, Jalisco, México; Universidad Politécnica de la Zona Metropolitana de Guadalajara, Tlajomulco de Zúñiga, Jalisco, México
| | - M Flores-Soto
- División de Neurociencias, Centro de Investigación Biomédica de Occidente, IMSS, Guadalajara, Jalisco, México
| | - N Vázquez-Hernández
- División de Neurociencias, Centro de Investigación Biomédica de Occidente, IMSS, Guadalajara, Jalisco, México
| | - H Salgado-Ceballos
- Unidad de Investigación Médica en Enfermedades Neurológicas, Hospital de Especialidades, Centro Médico Nacional S-XXI, IMSS, Ciudad de México, México; Proyecto Camina, A.C., Ciudad de México, México
| | - I González-Burgos
- División de Neurociencias, Centro de Investigación Biomédica de Occidente, IMSS, Guadalajara, Jalisco, México.
| |
Collapse
|
107
|
Perez-Rando M, Castillo-Gomez E, Bueno-Fernandez C, Nacher J. The TrkB agonist 7,8-dihydroxyflavone changes the structural dynamics of neocortical pyramidal neurons and improves object recognition in mice. Brain Struct Funct 2018; 223:2393-2408. [PMID: 29500536 DOI: 10.1007/s00429-018-1637-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 02/20/2018] [Indexed: 01/17/2023]
Abstract
BDNF and its receptor TrkB have important roles in neurodevelopment, neural plasticity, learning, and memory. Alterations in TrkB expression have been described in different CNS disorders. Therefore, drugs interacting with TrkB, specially agonists, are promising therapeutic tools. Among them, the recently described 7,8-dihydroxyflavone (DHF), an orally bioactive compound, has been successfully tested in animal models of these diseases. Recent studies have shown the influence of this drug on the structure of pyramidal neurons, specifically on dendritic spine density. However, there is no information yet on how DHF may alter the structural dynamics of these neurons (i.e., real-time study of the addition/elimination of dendritic spines and axonal boutons). To gain knowledge on these effects of DHF, we have performed a real-time analysis of spine and axonal dynamics in pyramidal neurons of barrel cortex, using cranial windows and 2-photon microscopy during a chronic oral treatment with this drug. After confirming TrkB expression in these neurons, we found that DHF increased the gain rates of spines and axonal boutons, as well as improved object recognition memory. These results help to understand how the activation of the BDNF-TrkB system can improve basic behavioral tasks through changes in the structural dynamics of pyramidal neurons. Moreover, they highlight DHF as a promising therapeutic vector for certain brain disorders in which this system is altered.
Collapse
Affiliation(s)
- Marta Perez-Rando
- Neurobiology Unit, Cell Biology Department, Program in Neurosciences and Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Dr. Moliner, 50, Burjassot, 46100, Spain
| | - Esther Castillo-Gomez
- Neurobiology Unit, Cell Biology Department, Program in Neurosciences and Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Dr. Moliner, 50, Burjassot, 46100, Spain. .,CIBERSAM: Spanish National Network for Research in Mental Health, Valencia, Spain. .,Department of Medicine, School of Medical Sciences, Universitat Jaume I, Vicente Sos Banyat s/n, 12071, Castellón de la Plana, Spain.
| | - Clara Bueno-Fernandez
- Neurobiology Unit, Cell Biology Department, Program in Neurosciences and Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Dr. Moliner, 50, Burjassot, 46100, Spain
| | - Juan Nacher
- Neurobiology Unit, Cell Biology Department, Program in Neurosciences and Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Dr. Moliner, 50, Burjassot, 46100, Spain. .,CIBERSAM: Spanish National Network for Research in Mental Health, Valencia, Spain. .,Fundación Investigación Hospital Clínico de Valencia, INCLIVA, Valencia, Spain.
| |
Collapse
|
108
|
Synaptic Tenacity or Lack Thereof: Spontaneous Remodeling of Synapses. Trends Neurosci 2018; 41:89-99. [DOI: 10.1016/j.tins.2017.12.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 11/22/2017] [Accepted: 12/04/2017] [Indexed: 11/18/2022]
|
109
|
Boivin JR, Piekarski DJ, Thomas AW, Wilbrecht L. Adolescent pruning and stabilization of dendritic spines on cortical layer 5 pyramidal neurons do not depend on gonadal hormones. Dev Cogn Neurosci 2018; 30:100-107. [PMID: 29413532 PMCID: PMC6294327 DOI: 10.1016/j.dcn.2018.01.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 01/12/2018] [Accepted: 01/19/2018] [Indexed: 12/30/2022] Open
Abstract
Pyramidal neurons in the neocortex receive a majority of their synapses on dendritic spines, whose growth, gain, and loss regulate the strength and identity of neural connections. Juvenile brains typically show higher spine density and turnover compared to adult brains, potentially enabling greater capacity for experience-dependent circuit 'rewiring'. Although spine pruning and stabilization in frontal cortex overlap with pubertal milestones, it is unclear if gonadal hormones drive these processes. To address this question, we used hormone manipulations and in vivo 2-photon microscopy to test for a causal relationship between pubertal hormones and spine pruning and stabilization in layer 5 neurons in the frontal cortex of female mice. We found that spine density, gains, and losses decreased from P27 to P60 and that these measures were not affected by pre-pubertal hormone injections or ovariectomy. Further analyses of spine morphology after manipulation of gonadal hormones suggest that gonadal hormones may play a role in morphological maturation and dynamics. Our data help to segregate hormone-sensitive and hormone-insensitive maturational processes that occur simultaneously in dorsomedial frontal cortex. These data provide more specific insight into adolescent development and may have implications for understanding the neurodevelopmental effects of changes in pubertal timing in humans.
Collapse
Affiliation(s)
- Josiah R Boivin
- UC San Francisco, Neuroscience Graduate Program, 1550 4th St., San Francisco, CA 94158, USA
| | - David J Piekarski
- UC Berkeley, Department of Psychology, 16 Barker Hall, Berkeley, CA 94720, USA
| | - A Wren Thomas
- UC Berkeley, Helen Wills Neuroscience Institute, 16 Barker Hall, Berkeley, CA 94720, USA
| | - Linda Wilbrecht
- UC Berkeley, Department of Psychology, 16 Barker Hall, Berkeley, CA 94720, USA; UC Berkeley, Helen Wills Neuroscience Institute, 16 Barker Hall, Berkeley, CA 94720, USA.
| |
Collapse
|
110
|
Abstract
During development, the environment exerts a profound influence on the wiring of brain circuits. Due to the limited resolution of studies in fixed tissue, this experience-dependent structural plasticity was once thought to be restricted to a specific developmental time window. The recent introduction of two-photon microscopy for in vivo imaging has opened the door to repeated monitoring of individual neurons and the study of structural plasticity mechanisms at a very fine scale. In this review, we focus on recent work showing that synaptic structural rearrangements are a key mechanism mediating neural circuit adaptation and behavioral plasticity in the adult brain. We examine this work in the context of classic studies in the visual systems of model organisms, which have laid much of the groundwork for our understanding of activity-dependent synaptic remodeling and its role in brain plasticity.
Collapse
Affiliation(s)
- Kalen P Berry
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; .,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Elly Nedivi
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; .,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| |
Collapse
|
111
|
Wegner W, Mott AC, Grant SGN, Steffens H, Willig KI. In vivo STED microscopy visualizes PSD95 sub-structures and morphological changes over several hours in the mouse visual cortex. Sci Rep 2018; 8:219. [PMID: 29317733 PMCID: PMC5760696 DOI: 10.1038/s41598-017-18640-z] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 12/14/2017] [Indexed: 12/23/2022] Open
Abstract
The post-synaptic density (PSD) is an electron dense region consisting of ~1000 proteins, found at the postsynaptic membrane of excitatory synapses, which varies in size depending upon synaptic strength. PSD95 is an abundant scaffolding protein in the PSD and assembles a family of supercomplexes comprised of neurotransmitter receptors, ion channels, as well as signalling and structural proteins. We use superresolution STED (STimulated Emission Depletion) nanoscopy to determine the size and shape of PSD95 in the anaesthetised mouse visual cortex. Adult knock-in mice expressing eGFP fused to the endogenous PSD95 protein were imaged at time points from 1 min to 6 h. Superresolved large assemblies of PSD95 show different sub-structures; most large assemblies were ring-like, some horse-shoe or figure-8 shaped, and shapes were continuous or made up of nanoclusters. The sub-structure appeared stable during the shorter (minute) time points, but after 1 h, more than 50% of the large assemblies showed a change in sub-structure. Overall, these data showed a sub-morphology of large PSD95 assemblies which undergo changes within the 6 hours of observation in the anaesthetised mouse.
Collapse
Affiliation(s)
- Waja Wegner
- Optical Nanoscopy in Neuroscience, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Alexander C Mott
- Optical Nanoscopy in Neuroscience, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany.,Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Seth G N Grant
- Genes to Cognition Program, Centre for Clinical Brain Sciences, Chancellor's Building, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Heinz Steffens
- Optical Nanoscopy in Neuroscience, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Katrin I Willig
- Optical Nanoscopy in Neuroscience, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany. .,Collaborative Research Center 889, University of Göttingen, Göttingen, Germany. .,Max Planck Institute of Experimental Medicine, Göttingen, Germany.
| |
Collapse
|
112
|
Dos Santos M, Salery M, Forget B, Garcia Perez MA, Betuing S, Boudier T, Vanhoutte P, Caboche J, Heck N. Rapid Synaptogenesis in the Nucleus Accumbens Is Induced by a Single Cocaine Administration and Stabilized by Mitogen-Activated Protein Kinase Interacting Kinase-1 Activity. Biol Psychiatry 2017; 82:806-818. [PMID: 28545678 DOI: 10.1016/j.biopsych.2017.03.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 03/10/2017] [Accepted: 03/14/2017] [Indexed: 12/21/2022]
Abstract
BACKGROUND Repeated cocaine exposure produces new spine formation in striatal projection neurons (SPNs) of the nucleus accumbens. However, an acute exposure to cocaine can trigger long-lasting synaptic plasticity in SPNs leading to behavioral alterations. This raises the intriguing question as to whether a single administration of cocaine could enduringly modify striatal connectivity. METHODS A three-dimensional morphometric analysis of presynaptic glutamatergic boutons and dendritic spines was performed on SPNs 1 hour and 1 week after a single cocaine administration. Time-lapse two-photon microscopy in adult slices was used to determine the precise molecular-events sequence responsible for the rapid spine formation. RESULTS A single injection triggered a rapid synaptogenesis and persistent increase in glutamatergic connectivity in SPNs from the shell part of the nucleus accumbens, specifically. Synapse formation occurred through clustered growth of active spines contacting pre-existing axonal boutons. Spine growth required extracellular signal-regulated kinase activation, while spine stabilization involved transcription-independent protein synthesis driven by mitogen-activated protein kinase interacting kinase-1, downstream from extracellular signal-regulated kinase. The maintenance of new spines driven by mitogen-activated protein kinase interacting kinase-1 was essential for long-term connectivity changes induced by cocaine in vivo. CONCLUSIONS Our study originally demonstrates that a single administration of cocaine is able to induce stable synaptic rewiring in the nucleus accumbens, which will likely influence responses to subsequent drug exposure. It also unravels a new functional role for cocaine-induced extracellular signal-regulated kinase pathway independently of nuclear targets. Finally, it reveals that mitogen-activated protein kinase interacting kinase-1 has a pivotal role in cocaine-induced connectivity.
Collapse
Affiliation(s)
- Marc Dos Santos
- Neurosciences Paris Seine, Institut de Biologie Paris Seine, University Pierre and Marie Curie University of Paris 06, Sorbonne Universités, Centre National pour la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Paris, France
| | - Marine Salery
- Neurosciences Paris Seine, Institut de Biologie Paris Seine, University Pierre and Marie Curie University of Paris 06, Sorbonne Universités, Centre National pour la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Paris, France
| | - Benoit Forget
- Neurosciences Paris Seine, Institut de Biologie Paris Seine, University Pierre and Marie Curie University of Paris 06, Sorbonne Universités, Centre National pour la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Paris, France
| | - Maria Alexandra Garcia Perez
- Neurosciences Paris Seine, Institut de Biologie Paris Seine, University Pierre and Marie Curie University of Paris 06, Sorbonne Universités, Centre National pour la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Paris, France
| | - Sandrine Betuing
- Neurosciences Paris Seine, Institut de Biologie Paris Seine, University Pierre and Marie Curie University of Paris 06, Sorbonne Universités, Centre National pour la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Paris, France
| | - Thomas Boudier
- Neurosciences Paris Seine, Institut de Biologie Paris Seine, University Pierre and Marie Curie University of Paris 06, Sorbonne Universités, Centre National pour la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Paris, France; Bioinformatics Institute, Agency for Science, Technology, and Research, Singapore
| | - Peter Vanhoutte
- Neurosciences Paris Seine, Institut de Biologie Paris Seine, University Pierre and Marie Curie University of Paris 06, Sorbonne Universités, Centre National pour la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Paris, France
| | - Jocelyne Caboche
- Neurosciences Paris Seine, Institut de Biologie Paris Seine, University Pierre and Marie Curie University of Paris 06, Sorbonne Universités, Centre National pour la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Paris, France.
| | - Nicolas Heck
- Neurosciences Paris Seine, Institut de Biologie Paris Seine, University Pierre and Marie Curie University of Paris 06, Sorbonne Universités, Centre National pour la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Paris, France
| |
Collapse
|
113
|
Reumann R, Vierk R, Zhou L, Gries F, Kraus V, Mienert J, Romswinkel E, Morellini F, Ferrer I, Nicolini C, Fahnestock M, Rune G, Glatzel M, Galliciotti G. The serine protease inhibitor neuroserpin is required for normal synaptic plasticity and regulates learning and social behavior. Learn Mem 2017; 24:650-659. [PMID: 29142062 PMCID: PMC5688962 DOI: 10.1101/lm.045864.117] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 08/25/2017] [Indexed: 01/22/2023]
Abstract
The serine protease inhibitor neuroserpin regulates the activity of tissue-type plasminogen activator (tPA) in the nervous system. Neuroserpin expression is particularly prominent at late stages of neuronal development in most regions of the central nervous system (CNS), whereas it is restricted to regions related to learning and memory in the adult brain. The physiological expression pattern of neuroserpin, its high degree of colocalization with tPA within the CNS, together with its dysregulation in neuropsychiatric disorders, suggest a role in formation and refinement of synapses. In fact, studies in cell culture and mice point to a role for neuroserpin in dendritic branching, spine morphology, and modulation of behavior. In this study, we investigated the physiological role of neuroserpin in the regulation of synaptic density, synaptic plasticity, and behavior in neuroserpin-deficient mice. In the absence of neuroserpin, mice show a significant decrease in spine-synapse density in the CA1 region of the hippocampus, while expression of the key postsynaptic scaffold protein PSD-95 is increased in this region. Neuroserpin-deficient mice show decreased synaptic potentiation, as indicated by reduced long-term potentiation (LTP), whereas presynaptic paired-pulse facilitation (PPF) is unaffected. Consistent with altered synaptic plasticity, neuroserpin-deficient mice exhibit cognitive and sociability deficits in behavioral assays. However, although synaptic dysfunction is implicated in neuropsychiatric disorders, we do not detect alterations in expression of neuroserpin in fusiform gyrus of autism patients or in dorsolateral prefrontal cortex of schizophrenia patients. Our results identify neuroserpin as a modulator of synaptic plasticity, and point to a role for neuroserpin in learning and memory.
Collapse
Affiliation(s)
- Rebecca Reumann
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Ricardo Vierk
- Institute of Neuroanatomy, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Lepu Zhou
- Institute of Neuroanatomy, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Frederice Gries
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Vanessa Kraus
- Research Group Behavioral Biology, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Julia Mienert
- Research Group Behavioral Biology, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Eva Romswinkel
- Research Group Behavioral Biology, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Fabio Morellini
- Research Group Behavioral Biology, Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Isidre Ferrer
- Institute of Neuropathology, Bellvitge University Hospital, University of Barcelona, CIBERNED, 08907 Hospitalet de Llobregat, Spain
| | - Chiara Nicolini
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Margaret Fahnestock
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Gabriele Rune
- Institute of Neuroanatomy, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Markus Glatzel
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Giovanna Galliciotti
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| |
Collapse
|
114
|
Berry KP, Nedivi E. Spine Dynamics: Are They All the Same? Neuron 2017; 96:43-55. [PMID: 28957675 DOI: 10.1016/j.neuron.2017.08.008] [Citation(s) in RCA: 314] [Impact Index Per Article: 44.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 05/03/2017] [Accepted: 08/04/2017] [Indexed: 11/19/2022]
Abstract
Since Cajal's first drawings of Golgi stained neurons, generations of researchers have been fascinated by the small protrusions, termed spines, studding many neuronal dendrites. Most excitatory synapses in the mammalian CNS are located on dendritic spines, making spines convenient proxies for excitatory synaptic presence. When in vivo imaging revealed that dendritic spines are dynamic structures, their addition and elimination were interpreted as excitatory synapse gain and loss, respectively. Spine imaging has since become a popular assay for excitatory circuit remodeling. In this review, we re-evaluate the validity of using spine dynamics as a straightforward reflection of circuit rewiring. Recent studies tracking both spines and synaptic markers in vivo reveal that 20% of spines lack PSD-95 and are short lived. Although they account for most spine dynamics, their remodeling is unlikely to impact long-term network structure. We discuss distinct roles that spine dynamics can play in circuit remodeling depending on synaptic content.
Collapse
Affiliation(s)
- Kalen P Berry
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Elly Nedivi
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| |
Collapse
|
115
|
de Vivo L, Bellesi M, Marshall W, Bushong EA, Ellisman MH, Tononi G, Cirelli C. Ultrastructural evidence for synaptic scaling across the wake/sleep cycle. Science 2017; 355:507-510. [PMID: 28154076 DOI: 10.1126/science.aah5982] [Citation(s) in RCA: 361] [Impact Index Per Article: 51.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 10/20/2016] [Indexed: 02/01/2023]
Abstract
It is assumed that synaptic strengthening and weakening balance throughout learning to avoid runaway potentiation and memory interference. However, energetic and informational considerations suggest that potentiation should occur primarily during wake, when animals learn, and depression should occur during sleep. We measured 6920 synapses in mouse motor and sensory cortices using three-dimensional electron microscopy. The axon-spine interface (ASI) decreased ~18% after sleep compared with wake. This decrease was proportional to ASI size, which is indicative of scaling. Scaling was selective, sparing synapses that were large and lacked recycling endosomes. Similar scaling occurred for spine head volume, suggesting a distinction between weaker, more plastic synapses (~80%) and stronger, more stable synapses. These results support the hypothesis that a core function of sleep is to renormalize overall synaptic strength increased by wake.
Collapse
Affiliation(s)
- Luisa de Vivo
- Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Boulevard, Madison, WI 53719, USA
| | - Michele Bellesi
- Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Boulevard, Madison, WI 53719, USA.,Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, Università Politecnica delle Marche, Ancona, Italy
| | - William Marshall
- Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Boulevard, Madison, WI 53719, USA
| | - Eric A Bushong
- National Center for Microscopy and Imaging Research, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Mark H Ellisman
- National Center for Microscopy and Imaging Research, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.,Department of Neurosciences, School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Giulio Tononi
- Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Boulevard, Madison, WI 53719, USA.
| | - Chiara Cirelli
- Department of Psychiatry, University of Wisconsin-Madison, 6001 Research Park Boulevard, Madison, WI 53719, USA.
| |
Collapse
|
116
|
Tsai NP, Wilkerson JR, Guo W, Huber KM. FMRP-dependent Mdm2 dephosphorylation is required for MEF2-induced synapse elimination. Hum Mol Genet 2017; 26:293-304. [PMID: 28025327 DOI: 10.1093/hmg/ddw386] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 11/03/2016] [Indexed: 11/12/2022] Open
Abstract
The Myocyte Enhancer Factor 2 (MEF2) transcription factors suppress an excitatory synapse number by promoting degradation of the synaptic scaffold protein, postsynaptic density protein 95 (PSD-95), a process that is deficient in the mouse model of Fragile X Syndrome, Fmr1 KO. How MEF2 activation results in PSD-95 degradation and why this is defective in Fmr1 KO neurons is unknown. Here we report that MEF2 induces a Protein phosphatase 2A (PP2A)-mediated dephosphorylation of murine double minute-2 (Mdm2), the ubiquitin E3 ligase for PSD-95, which results in nuclear export and synaptic accumulation of Mdm2 as well as PSD-95 degradation and synapse elimination. In Fmr1 KO neurons, Mdm2 is hyperphosphorylated, nuclear localized basally, and unaffected by MEF2 activation, which our data suggest due to an enhanced interaction with Eukaryotic Elongation Factor 1α (EF1α), whose protein levels are elevated in Fmr1 KO. Expression of a dephosphomimetic of Mdm2 rescues PSD-95 ubiquitination, degradation and synapse elimination in Fmr1 KO neurons. This work reveals detailed mechanisms of synapse elimination in health and a developmental brain disorder.
Collapse
Affiliation(s)
- Nien-Pei Tsai
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Molecular and Integrative Physiology, School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.,Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Julia R Wilkerson
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Weirui Guo
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Kimberly M Huber
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA
| |
Collapse
|
117
|
Soltani A, Lebrun S, Carpentier G, Zunino G, Chantepie S, Maïza A, Bozzi Y, Desnos C, Darchen F, Stettler O. Increased signaling by the autism-related Engrailed-2 protein enhances dendritic branching and spine density, alters synaptic structural matching, and exaggerates protein synthesis. PLoS One 2017; 12:e0181350. [PMID: 28809922 PMCID: PMC5557355 DOI: 10.1371/journal.pone.0181350] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 06/29/2017] [Indexed: 12/13/2022] Open
Abstract
Engrailed 1 (En1) and 2 (En2) code for closely related homeoproteins acting as transcription factors and as signaling molecules that contribute to midbrain and hindbrain patterning, to development and maintenance of monoaminergic pathways, and to retinotectal wiring. En2 has been suggested to be an autism susceptibility gene and individuals with autism display an overexpression of this homeogene but the mechanisms remain unclear. We addressed in the present study the effect of exogenously added En2 on the morphology of hippocampal cells that normally express only low levels of Engrailed proteins. By means of RT-qPCR, we confirmed that En1 and En2 were expressed at low levels in hippocampus and hippocampal neurons, and observed a pronounced decrease in En2 expression at birth and during the first postnatal week, a period characterized by intense synaptogenesis. To address a putative effect of Engrailed in dendritogenesis or synaptogenesis, we added recombinant En1 or En2 proteins to hippocampal cell cultures. Both En1 and En2 treatment increased the complexity of the dendritic tree of glutamatergic neurons, but only En2 increased that of GABAergic cells. En1 increased the density of dendritic spines both in vitro and in vivo. En2 had similar but less pronounced effect on spine density. The number of mature synapses remained unchanged upon En1 treatment but was reduced by En2 treatment, as well as the area of post-synaptic densities. Finally, both En1 and En2 elevated mTORC1 activity and protein synthesis in hippocampal cells, suggesting that some effects of Engrailed proteins may require mRNA translation. Our results indicate that Engrailed proteins can play, even at low concentrations, an active role in the morphogenesis of hippocampal cells. Further, they emphasize the over-regulation of GABA cell morphology and the vulnerability of excitatory synapses in a pathological context of En2 overexpression.
Collapse
Affiliation(s)
- Asma Soltani
- UMR 8250, Centre National de la Recherche Scientifique, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Solène Lebrun
- UMR 8250, Centre National de la Recherche Scientifique, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Gilles Carpentier
- Laboratoire Croissance, Réparation et Régénération Tissulaires (CRRET), EA 4397 / ERL 9215, Centre National de la Recherche Scientifique, Université Paris Est Créteil, Créteil, France
| | - Giulia Zunino
- Centre for Integrative Biology, University of Trento, Trento, Italy
| | - Sandrine Chantepie
- Laboratoire Croissance, Réparation et Régénération Tissulaires (CRRET), EA 4397 / ERL 9215, Centre National de la Recherche Scientifique, Université Paris Est Créteil, Créteil, France
| | - Auriane Maïza
- Laboratoire Croissance, Réparation et Régénération Tissulaires (CRRET), EA 4397 / ERL 9215, Centre National de la Recherche Scientifique, Université Paris Est Créteil, Créteil, France
| | - Yuri Bozzi
- Centre for Integrative Biology, University of Trento, Trento, Italy
| | - Claire Desnos
- UMR 8250, Centre National de la Recherche Scientifique, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - François Darchen
- UMR 8250, Centre National de la Recherche Scientifique, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Olivier Stettler
- UMR 8250, Centre National de la Recherche Scientifique, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
- Laboratoire Croissance, Réparation et Régénération Tissulaires (CRRET), EA 4397 / ERL 9215, Centre National de la Recherche Scientifique, Université Paris Est Créteil, Créteil, France
| |
Collapse
|
118
|
Cooperative stochastic binding and unbinding explain synaptic size dynamics and statistics. PLoS Comput Biol 2017; 13:e1005668. [PMID: 28704399 PMCID: PMC5546711 DOI: 10.1371/journal.pcbi.1005668] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 08/07/2017] [Accepted: 06/30/2017] [Indexed: 11/28/2022] Open
Abstract
Synapses are dynamic molecular assemblies whose sizes fluctuate significantly over time-scales of hours and days. In the current study, we examined the possibility that the spontaneous microscopic dynamics exhibited by synaptic molecules can explain the macroscopic size fluctuations of individual synapses and the statistical properties of synaptic populations. We present a mesoscopic model, which ties the two levels. Its basic premise is that synaptic size fluctuations reflect cooperative assimilation and removal of molecules at a patch of postsynaptic membrane. The introduction of cooperativity to both assimilation and removal in a stochastic biophysical model of these processes, gives rise to features qualitatively similar to those measured experimentally: nanoclusters of synaptic scaffolds, fluctuations in synaptic sizes, skewed, stable size distributions and their scaling in response to perturbations. Our model thus points to the potentially fundamental role of cooperativity in dictating synaptic remodeling dynamics and offers a conceptual understanding of these dynamics in terms of central microscopic features and processes. Neurons communicate through specialized sites of cell–cell contact known as synapses. This vast set of connections is believed to be crucial for sensory processing, motor function, learning and memory. Experimental data from recent years suggest that synapses are not static structures, but rather dynamic assemblies of molecules that move in, out and between nearby synapses, with these dynamics driving changes in synaptic properties over time. Thus, in addition to changes directed by activity or other physiological signals, synapses also exhibit spontaneous changes that have particular dynamical and statistical signatures. Given the immense complexity of synapses at the molecular scale, how can one hope to understand the principles that govern these spontaneous changes and statistical signatures? Here we offer a mesoscopic modelling approach—situated between detailed microscopic and abstract macroscopic approaches—to advance this understanding. Our model, based on simplified biophysical assumptions, shows that spontaneous cooperative binding and unbinding of proteins at synaptic sites can give rise to dynamic and statistical signatures similar to those measured in experiments. Importantly, we find cooperativity to be indispensable in this regard. Our model thus offers a conceptual understanding of synaptic dynamics and statistical features in terms of a fundamental biological principle, namely cooperativity.
Collapse
|
119
|
Tjia M, Yu X, Jammu LS, Lu J, Zuo Y. Pyramidal Neurons in Different Cortical Layers Exhibit Distinct Dynamics and Plasticity of Apical Dendritic Spines. Front Neural Circuits 2017; 11:43. [PMID: 28674487 PMCID: PMC5474458 DOI: 10.3389/fncir.2017.00043] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Accepted: 05/30/2017] [Indexed: 01/28/2023] Open
Abstract
The mammalian cerebral cortex is typically organized in six layers containing multiple types of neurons, with pyramidal neurons (PNs) being the most abundant. PNs in different cortical layers have distinct morphology, physiology and functional roles in neural circuits. Therefore, their development and synaptic plasticity may also differ. Using in vivo transcranial two-photon microscopy, we followed the structural dynamics of dendritic spines on apical dendrites of layer (L) 2/3 and L5 PNs at different developmental stages. We show that the density and dynamics of spines are significantly higher in L2/3 PNs than L5 PNs in both adolescent (1 month old) and adult (4 months old) mice. While spine density of L5 PNs decreases during adolescent development due to a higher rate of spine elimination than formation, there is no net change in the spine density along apical dendrites of L2/3 PNs over this period. In addition, experiences exert differential impact on the dynamics of apical dendritic spines of PNs resided in different cortical layers. While motor skill learning promotes spine turnover on L5 PNs in the motor cortex, it does not change the spine dynamics on L2/3 PNs. In addition, neonatal sensory deprivation decreases the spine density of both L2/3 and L5 PNs, but leads to opposite changes in spine dynamics among these two populations of neurons in adolescence. In summary, our data reveal distinct dynamics and plasticity of apical dendritic spines on PNs in different layers in the living mouse cortex, which may arise from their distinct functional roles in cortical circuits.
Collapse
Affiliation(s)
- Michelle Tjia
- Department of Molecular, Cell and Developmental Biology, University of CaliforniaSanta Cruz, CA, United States
| | - Xinzhu Yu
- Department of Molecular, Cell and Developmental Biology, University of CaliforniaSanta Cruz, CA, United States
| | - Lavpreet S Jammu
- Department of Molecular, Cell and Developmental Biology, University of CaliforniaSanta Cruz, CA, United States
| | - Ju Lu
- Department of Molecular, Cell and Developmental Biology, University of CaliforniaSanta Cruz, CA, United States
| | - Yi Zuo
- Department of Molecular, Cell and Developmental Biology, University of CaliforniaSanta Cruz, CA, United States
| |
Collapse
|
120
|
Perez-Rando M, Castillo-Gómez E, Guirado R, Blasco-Ibañez JM, Crespo C, Varea E, Nacher J. NMDA Receptors Regulate the Structural Plasticity of Spines and Axonal Boutons in Hippocampal Interneurons. Front Cell Neurosci 2017; 11:166. [PMID: 28659763 PMCID: PMC5466979 DOI: 10.3389/fncel.2017.00166] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 05/29/2017] [Indexed: 11/13/2022] Open
Abstract
N-methyl-D-aspartate receptors (NMDARs) are present in both pyramidal neurons and interneurons of the hippocampus. These receptors play an important role in the adult structural plasticity of excitatory neurons, but their impact on the remodeling of interneurons is unknown. Among hippocampal interneurons, somatostatin-expressing cells located in the stratum oriens are of special interest because of their functional importance and structural characteristics: they display dendritic spines, which change density in response to different stimuli. In order to understand the role of NMDARs on the structural plasticity of these interneurons, we have injected acutely MK-801, an NMDAR antagonist, to adult mice which constitutively express enhanced green fluorescent protein (EGFP) in these cells. We have behaviorally tested the animals, confirming effects of the drug on locomotion and anxiety-related behaviors. NMDARs were expressed in the somata and dendritic spines of somatostatin-expressing interneurons. Twenty-four hours after the injection, the density of spines did not vary, but we found a significant increase in the density of their en passant boutons (EPB). We have also used entorhino-hippocampal organotypic cultures to study these interneurons in real-time. There was a rapid decrease in the apparition rate of spines after MK-801 administration, which persisted for 24 h and returned to basal levels afterwards. A similar reversible decrease was detected in spine density. Our results show that both spines and axons of interneurons can undergo remodeling and highlight NMDARs as regulators of this plasticity. These results are specially relevant given the importance of all these players on hippocampal physiology and the etiopathology of certain psychiatric disorders.
Collapse
Affiliation(s)
- Marta Perez-Rando
- Neurobiology Unit, Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de ValènciaValència, Spain
| | - Esther Castillo-Gómez
- Neurobiology Unit, Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de ValènciaValència, Spain
| | - Ramon Guirado
- Neurobiology Unit, Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de ValènciaValència, Spain
| | - José Miguel Blasco-Ibañez
- Neurobiology Unit, Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de ValènciaValència, Spain
| | - Carlos Crespo
- Neurobiology Unit, Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de ValènciaValència, Spain
| | - Emilio Varea
- Neurobiology Unit, Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de ValènciaValència, Spain
| | - Juan Nacher
- Neurobiology Unit, Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), Universitat de ValènciaValència, Spain.,CIBERSAM: Spanish National Network for Research in Mental HealthMadrid, Spain.,Fundación Investigación Hospital Clínico de Valencia, Instituto de Investigación Sanitaria (INCLIVA)València, Spain
| |
Collapse
|
121
|
MacDonald ML, Alhassan J, Newman JT, Richard M, Gu H, Kelly RM, Sampson AR, Fish KN, Penzes P, Wills ZP, Lewis DA, Sweet RA. Selective Loss of Smaller Spines in Schizophrenia. Am J Psychiatry 2017; 174:586-594. [PMID: 28359200 PMCID: PMC5800878 DOI: 10.1176/appi.ajp.2017.16070814] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
OBJECTIVE Decreased density of dendritic spines in adult schizophrenia subjects has been hypothesized to result from increased pruning of excess synapses in adolescence. In vivo imaging studies have confirmed that synaptic pruning is largely driven by the loss of large or mature synapses. Thus, increased pruning throughout adolescence would likely result in a deficit of large spines in adulthood. Here, the authors examined the density and volume of dendritic spines in deep layer 3 of the auditory cortex of 20 schizophrenia and 20 matched comparison subjects as well as aberrant voltage-gated calcium channel subunit protein expression linked to spine loss. METHOD Primary auditory cortex deep layer 3 spine density and volume was assessed in 20 pairs of schizophrenia and matched comparison subjects in an initial and replication cohort (12 and eight pairs) by immunohistochemistry-confocal microscopy. Targeted mass spectrometry was used to quantify postsynaptic density and voltage-gated calcium channel protein expression. The effect of increased voltage-gated calcium channel subunit protein expression on spine density and volume was assessed in primary rat neuronal culture. RESULTS Only the smallest spines are lost in deep layer 3 of the primary auditory cortex in subjects with schizophrenia, while larger spines are retained. Levels of the tryptic peptide ALFDFLK, found in the schizophrenia risk gene CACNB4, are inversely correlated with the density of smaller, but not larger, spines in schizophrenia subjects. Consistent with this observation, CACNB4 overexpression resulted in a lower density of smaller spines in primary neuronal cultures. CONCLUSIONS These findings require a rethinking of the overpruning hypothesis, demonstrate a link between small spine loss and a schizophrenia risk gene, and should spur more in-depth investigations of the mechanisms that govern new or small spine generation and stabilization under normal conditions as well as how this process is impaired in schizophrenia.
Collapse
Affiliation(s)
- Matthew L. MacDonald
- Translational Neuroscience Program, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Jamil Alhassan
- Translational Neuroscience Program, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Jason T. Newman
- Translational Neuroscience Program, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Michelle Richard
- Translational Neuroscience Program, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Hong Gu
- Department of Statistics, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Ryan M. Kelly
- Department of Statistics, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Alan R. Sampson
- Department of Statistics, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Kenneth N. Fish
- Translational Neuroscience Program, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Peter Penzes
- Department of Physiology, Northwestern University Feinberg School of Medicine
- Department of Psychiatry and Behavioral Sciences, Northwestern University Feinberg School of Medicine
| | - Zachary P. Wills
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - David A. Lewis
- Translational Neuroscience Program, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Robert A. Sweet
- Translational Neuroscience Program, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA
- Mental Illness Research, Education, and Clinical Center, VA Pittsburgh Healthcare System, Pittsburgh, PA
| |
Collapse
|
122
|
Lambert JT, Hill TC, Park DK, Culp JH, Zito K. Protracted and asynchronous accumulation of PSD95-family MAGUKs during maturation of nascent dendritic spines. Dev Neurobiol 2017; 77:1161-1174. [PMID: 28388013 DOI: 10.1002/dneu.22503] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 02/27/2017] [Accepted: 04/03/2017] [Indexed: 11/10/2022]
Abstract
The formation and stabilization of new dendritic spines is a key component of the experience-dependent neural circuit plasticity that supports learning, but the molecular maturation of nascent spines remains largely unexplored. The PSD95-family of membrane-associated guanylate kinases (PSD-MAGUKs), most notably PSD95, has a demonstrated role in promoting spine stability. However, nascent spines contain low levels of PSD95, suggesting that other members of the PSD-MAGUK family might act to stabilize nascent spines in the early stages of spiny synapse formation. Here, we used GFP-fusion constructs to quantitatively define the molecular composition of new spines, focusing on the PSD-MAGUK family. We found that PSD95 levels in new spines were as low as those previously associated with rapid subsequent spine elimination, and new spines did not achieve mature levels of PSD95 until between 12 and 20 h following new spine identification. Surprisingly, we found that the PSD-MAGUKs PSD93, SAP97, and SAP102 were also substantially less enriched in new spines. However, they accumulated in new spines more quickly than PSD95: SAP102 enriched to mature levels within 3 h, SAP97 and PSD93 enriched gradually over the course of 6 h. Intriguingly, when we restricted our analysis to only those new spines that persisted, SAP97 was the only PSD-MAGUK already present at mature levels in persistent new spines when first identified. Our findings uncover a key structural difference between nascent and mature spines, and suggest a mechanism for the stabilization of nascent spines through the sequential arrival of PSD-MAGUKs. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1161-1174, 2017.
Collapse
Affiliation(s)
- Jason T Lambert
- Center for Neuroscience, University of California Davis, Davis, California, 95618
| | - Travis C Hill
- Center for Neuroscience, University of California Davis, Davis, California, 95618
| | - Deborah K Park
- Center for Neuroscience, University of California Davis, Davis, California, 95618
| | - Julie H Culp
- Center for Neuroscience, University of California Davis, Davis, California, 95618
| | - Karen Zito
- Center for Neuroscience, University of California Davis, Davis, California, 95618
| |
Collapse
|
123
|
Roth RH, Zhang Y, Huganir RL. Dynamic imaging of AMPA receptor trafficking in vitro and in vivo. Curr Opin Neurobiol 2017; 45:51-58. [PMID: 28411409 DOI: 10.1016/j.conb.2017.03.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 03/03/2017] [Accepted: 03/15/2017] [Indexed: 10/19/2022]
Abstract
Modulation of synaptic strength through trafficking of AMPA receptors is a fundamental mechanism underlying synaptic plasticity and has been shown to be an important process in higher brain functions such as learning and memory. Many studies have used live time-lapse imaging of fluorescently tagged AMPA receptors to directly monitor their membrane trafficking in the basal state as well as during synaptic plasticity. While most of these studies are performed in vitro using neuronal cell cultures, in the past years technological advances have enabled the imaging of synaptic proteins in vivo in intact organisms. This has allowed for visualization of synaptic plasticity on a molecular level in living and behaving animals. Here, we discuss key studies and approaches using dynamic imaging to visualize AMPA receptor trafficking in vitro as well as imaging synaptic proteins, including AMPA receptors, in vivo.
Collapse
Affiliation(s)
- Richard H Roth
- Solomon H. Snyder Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Yong Zhang
- Neuroscience Research Institute, Key Laboratory for Neuroscience, Ministry of Education/National Health and Family Planning Commission, Peking University, Beijing 100191, China. PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Richard L Huganir
- Solomon H. Snyder Department of Neuroscience, Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA.
| |
Collapse
|
124
|
Vannini E, Maltese F, Olimpico F, Fabbri A, Costa M, Caleo M, Baroncelli L. Progression of motor deficits in glioma-bearing mice: impact of CNF1 therapy at symptomatic stages. Oncotarget 2017; 8:23539-23550. [PMID: 28212563 PMCID: PMC5410325 DOI: 10.18632/oncotarget.15328] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 01/23/2017] [Indexed: 11/25/2022] Open
Abstract
Glioblastoma (GBM) is the most aggressive type of brain tumor. In this context, animal models represent excellent tools for the early detection and longitudinal mapping of neuronal dysfunction, that are critical in the preclinical validation of new therapeutic strategies. In a mouse glioma model, we developed sensitive behavioral readouts that allow early recognizing and following neurological symptoms. We injected GL261 cells into the primary motor cortex of syngenic mice and we used a battery of behavioral tests to longitudinally monitor the dysfunction induced by tumor growth. Grip strength test revealed an early onset of functional deficit associated to the glioma growth, with a significant forelimb weakness appearing 9 days after tumor inoculation. A later deficit was observed in the rotarod and in the grid walk tasks. Using this model, we found reduced tumor growth and maintenance of behavioral functions following treatment with Cytotoxic Necrotizing Factor 1 (CNF1) at a symptomatic stage. Our data provide a detailed and precise examination of how tumor growth reverberates on the behavioral functions of glioma-bearing mice, providing normative data for the study of therapeutic strategies for glioma treatment. The reduced tumor volume and robust functional sparing observed in CNF1-treated, glioma-bearing mice strengthen the notion that CNF1 delivery is a promising strategy for glioma therapy.
Collapse
Affiliation(s)
- Eleonora Vannini
- Institute of Neuroscience, National Research Council (CNR), Pisa, Italy
| | - Federica Maltese
- Institute of Neuroscience, National Research Council (CNR), Pisa, Italy
| | | | | | - Mario Costa
- Institute of Neuroscience, National Research Council (CNR), Pisa, Italy
| | - Matteo Caleo
- Institute of Neuroscience, National Research Council (CNR), Pisa, Italy
| | - Laura Baroncelli
- Institute of Neuroscience, National Research Council (CNR), Pisa, Italy
| |
Collapse
|
125
|
Ohta KI, Suzuki S, Warita K, Kaji T, Kusaka T, Miki T. Prolonged maternal separation attenuates BDNF-ERK signaling correlated with spine formation in the hippocampus during early brain development. J Neurochem 2017; 141:179-194. [PMID: 28178750 DOI: 10.1111/jnc.13977] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 01/27/2017] [Accepted: 02/03/2017] [Indexed: 12/18/2022]
Abstract
Maternal separation (MS) is known to affect hippocampal function such as learning and memory, yet the molecular mechanism remains unknown. We hypothesized that these impairments are attributed to abnormities of neural circuit formation by MS, and focused on brain-derived neurotrophic factor (BDNF) as key factor because BDNF signaling has an essential role in synapse formation during early brain development. Using rat offspring exposed to MS for 6 h/day during postnatal days (PD) 2-20, we estimated BDNF signaling in the hippocampus during brain development. Our results show that MS attenuated BDNF expression and activation of extracellular signal-regulated kinase (ERK) around PD 7. Moreover, plasticity-related immediate early genes, which are transcriptionally regulated by BDNF-ERK signaling, were also reduced by MS around PD 7. Interestingly, detailed analysis revealed that MS particularly reduced expression of BDNF gene and immediate early genes in the cornu ammonis 1 (CA1) of hippocampus at PD 7. Considering that BDNF-ERK signaling is involved in spine formation, we next evaluated spine formation in the hippocampus during the weaning period. Our results show that MS particularly reduced mature spine density in proximal apical dendrites of CA1 pyramidal neurons at PD 21. These results suggest that MS could attenuate BDNF-ERK signaling during primary synaptogenesis with a region-specific manner, which is likely to lead to decreased spine formation and maturation observed in the hippocampal CA1 region. It is speculated that this incomplete spine formation during early brain development has an influence on learning capabilities throughout adulthood.
Collapse
Affiliation(s)
- Ken-Ichi Ohta
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Shingo Suzuki
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Katsuhiko Warita
- Department of Veterinary Anatomy, Faculty of Agriculture, Tottori University, Tottori, Japan
| | - Tomohiro Kaji
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Takashi Kusaka
- Department of Pediatrics, Faculty of Medicine, Kagawa University, Kagawa, Japan
| | - Takanori Miki
- Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University, Kagawa, Japan
| |
Collapse
|
126
|
Fasoli A, Dang J, Johnson JS, Gouw AH, Fogli Iseppe A, Ishida AT. Somatic and neuritic spines on tyrosine hydroxylase-immunopositive cells of rat retina. J Comp Neurol 2017; 525:1707-1730. [PMID: 28035673 DOI: 10.1002/cne.24166] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Revised: 12/13/2016] [Accepted: 12/27/2016] [Indexed: 12/27/2022]
Abstract
Dopamine- and tyrosine hydroxylase-immunopositive cells (TH cells) modulate visually driven signals as they flow through retinal photoreceptor, bipolar, and ganglion cells. Previous studies suggested that TH cells release dopamine from varicose axons arborizing in the inner and outer plexiform layers after glutamatergic synapses depolarize TH cell dendrites in the inner plexiform layer and these depolarizations propagate to the varicosities. Although it has been proposed that these excitatory synapses are formed onto appendages resembling dendritic spines, spines have not been found on TH cells of most species examined to date or on TH cell somata that release dopamine when exposed to glutamate receptor agonists. By use of protocols that preserve proximal retinal neuron morphology, we have examined the shape, distribution, and synapse-related immunoreactivity of adult rat TH cells. We report here that TH cell somata, tapering and varicose inner plexiform layer neurites, and varicose outer plexiform layer neurites all bear spines, that some of these spines are immunopositive for glutamate receptor and postsynaptic density proteins (viz., GluR1, GluR4, NR1, PSD-95, and PSD-93), that TH cell somata and tapering neurites are also immunopositive for a γ-aminobutyric acid (GABA) receptor subunit (GABAA Rα1 ), and that a synaptic ribbon-specific protein (RIBEYE) is found adjacent to some colocalizations of GluR1 and TH in the inner plexiform layer. These results identify previously undescribed sites at which glutamatergic and GABAergic inputs may stimulate and inhibit dopamine release, especially at somata and along varicose neurites that emerge from these somata and arborize in various levels of the retina. J. Comp. Neurol. 525:1707-1730, 2017. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Anna Fasoli
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
| | - James Dang
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
| | - Jeffrey S Johnson
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
| | - Aaron H Gouw
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
| | - Alex Fogli Iseppe
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
| | - Andrew T Ishida
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California.,Department of Ophthalmology and Vision Science, University of California, Sacramento, California
| |
Collapse
|
127
|
Fasulo L, Brandi R, Arisi I, La Regina F, Berretta N, Capsoni S, D'Onofrio M, Cattaneo A. ProNGF Drives Localized and Cell Selective Parvalbumin Interneuron and Perineuronal Net Depletion in the Dentate Gyrus of Transgenic Mice. Front Mol Neurosci 2017; 10:20. [PMID: 28232789 PMCID: PMC5299926 DOI: 10.3389/fnmol.2017.00020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 01/16/2017] [Indexed: 01/12/2023] Open
Abstract
ProNGF, the precursor of mature Nerve Growth Factor (NGF), is the most abundant NGF form in the brain and increases markedly in the cortex in Alzheimer's Disease (AD), relative to mature NGF. A large body of evidence shows that the actions of ProNGF and mature NGF are often conflicting, depending on the receptors expressed in target cells. TgproNGF#3 mice, expressing furin-cleavage resistant proNGF in CNS neurons, directly reveal consequences of increased proNGF levels on brain homeostasis. Their phenotype clearly indicates that proNGF can be a driver of neurodegeneration, including severe learning and memory behavioral deficits, cholinergic deficits, and diffuse immunoreactivity for A-beta and A-beta-oligomers. In aged TgproNGF#3 mice spontaneous epileptic-like events are detected in entorhinal cortex-hippocampal slices, suggesting occurrence of excitatory/inhibitory (E/I) imbalance. In this paper, we investigate the molecular events linking increased proNGF levels to the epileptiform activity detected in hippocampal slices. The occurrence of spontaneous epileptiform discharges in the hippocampal network in TgproNGF#3 mice suggests an impaired inhibitory interneuron homeostasis. In the present study, we detect the onset of hippocampal epileptiform events at 1-month of age. Later, we observe a regional- and cellular-selective Parvalbumin interneuron and perineuronal net (PNN) depletion in the dentate gyrus (DG), but not in other hippocampal regions of TgproNGF#3 mice. These results demonstrate that, in the hippocampus, the DG is selectively vulnerable to altered proNGF/NGF signaling. Parvalbumin interneuron depletion is also observed in the amygdala, a region strongly connected to the hippocampus and likewise receiving cholinergic afferences. Transcriptome analysis of TgproNGF#3 hippocampus reveals a proNGF signature with broad down-regulation of transcription. The most affected mRNAs modulated at early times belong to synaptic transmission and plasticity and extracellular matrix (ECM) gene families. Moreover, alterations in the expression of selected BDNF splice variants were observed. Our results provide further mechanistic insights into the vicious negative cycle linking proNGF and neurodegeneration, confirming the regulation of E/I homeostasis as a crucial mediating mechanism.
Collapse
Affiliation(s)
- Luisa Fasulo
- Bio@SNS Laboratory, Scuola Normale SuperiorePisa, Italy; European Brain Research Institute Rita Levi-MontalciniRome, Italy
| | - Rossella Brandi
- European Brain Research Institute Rita Levi-Montalcini Rome, Italy
| | - Ivan Arisi
- European Brain Research Institute Rita Levi-Montalcini Rome, Italy
| | | | - Nicola Berretta
- Department of Experimental Neurology, Fondazione Santa Lucia IRCCS Rome, Italy
| | - Simona Capsoni
- Bio@SNS Laboratory, Scuola Normale Superiore Pisa, Italy
| | - Mara D'Onofrio
- European Brain Research Institute Rita Levi-Montalcini Rome, Italy
| | - Antonino Cattaneo
- Bio@SNS Laboratory, Scuola Normale SuperiorePisa, Italy; European Brain Research Institute Rita Levi-MontalciniRome, Italy
| |
Collapse
|
128
|
OKABE S. Fluorescence imaging of synapse dynamics in normal circuit maturation and in developmental disorders. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2017; 93:483-497. [PMID: 28769018 PMCID: PMC5713177 DOI: 10.2183/pjab.93.029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 05/26/2017] [Indexed: 06/07/2023]
Abstract
One of the most fundamental questions in neurobiology is how proper synaptic connections are established in the developing brain. Live-cell imaging of the synaptic structure and functional molecules can reveal the time course of synapse formation, molecular dynamics, and functional maturation. Using postsynaptic scaffolding proteins as a marker of synapse development, fluorescence time-lapse imaging revealed rapid formation of individual synapses that occurred within hours and their remodeling in culture preparations. In vivo two-photon excitation microscopy development enabled us to directly measure synapse turnover in living animals. In vivo synapse dynamics were suppressed in the adult rodent brain, but were maintained at a high level during the early postnatal period. This transition in synapse dynamics is biologically important and can be linked to the pathology of juvenile-onset psychiatric diseases. Indeed, the upregulation of synapse dynamics was observed in multiple mouse models of autism spectrum disorders. Fluorescence imaging of synapses provides new information regarding the physiology and pathology of neural circuit construction.
Collapse
Affiliation(s)
- Shigeo OKABE
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| |
Collapse
|
129
|
Karreman MA, Hyenne V, Schwab Y, Goetz JG. Intravital Correlative Microscopy: Imaging Life at the Nanoscale. Trends Cell Biol 2016; 26:848-863. [DOI: 10.1016/j.tcb.2016.07.003] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 07/12/2016] [Accepted: 07/15/2016] [Indexed: 01/04/2023]
|
130
|
Dvorkin R, Ziv NE. Relative Contributions of Specific Activity Histories and Spontaneous Processes to Size Remodeling of Glutamatergic Synapses. PLoS Biol 2016; 14:e1002572. [PMID: 27776122 PMCID: PMC5077109 DOI: 10.1371/journal.pbio.1002572] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Accepted: 09/27/2016] [Indexed: 11/18/2022] Open
Abstract
The idea that synaptic properties are defined by specific pre- and postsynaptic activity histories is one of the oldest and most influential tenets of contemporary neuroscience. Recent studies also indicate, however, that synaptic properties often change spontaneously, even in the absence of specific activity patterns or any activity whatsoever. What, then, are the relative contributions of activity history-dependent and activity history-independent processes to changes synapses undergo? To compare the relative contributions of these processes, we imaged, in spontaneously active networks of cortical neurons, glutamatergic synapses formed between the same axons and neurons or dendrites under the assumption that their similar activity histories should result in similar size changes over timescales of days. The size covariance of such commonly innervated (CI) synapses was then compared to that of synapses formed by different axons (non-CI synapses) that differed in their activity histories. We found that the size covariance of CI synapses was greater than that of non-CI synapses; yet overall size covariance of CI synapses was rather modest. Moreover, momentary and time-averaged sizes of CI synapses correlated rather poorly, in perfect agreement with published electron microscopy-based measurements of mouse cortex synapses. A conservative estimate suggested that ~40% of the observed size remodeling was attributable to specific activity histories, whereas ~10% and ~50% were attributable to cell-wide and spontaneous, synapse-autonomous processes, respectively. These findings demonstrate that histories of naturally occurring activity patterns can direct glutamatergic synapse remodeling but also suggest that the contributions of spontaneous, possibly stochastic, processes are at least as great.
Collapse
Affiliation(s)
- Roman Dvorkin
- Technion Faculty of Medicine, Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Technion, Haifa, Israel
| | - Noam E Ziv
- Technion Faculty of Medicine, Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Technion, Haifa, Israel.,Rappaport Family Institute for Research in the Medical Sciences, Haifa, Israel
| |
Collapse
|
131
|
Functional and structural underpinnings of neuronal assembly formation in learning. Nat Neurosci 2016; 19:1553-1562. [PMID: 27749830 DOI: 10.1038/nn.4418] [Citation(s) in RCA: 141] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 09/14/2016] [Indexed: 02/07/2023]
Abstract
Learning and memory are associated with the formation and modification of neuronal assemblies: populations of neurons that encode what has been learned and mediate memory retrieval upon recall. Functional studies of neuronal assemblies have progressed dramatically thanks to recent technological advances. Here we discuss how a focus on assembly formation and consolidation has provided a powerful conceptual framework to relate mechanistic studies of synaptic and circuit plasticity to behaviorally relevant aspects of learning and memory. Neurons are likely recruited to particular learning-related assemblies as a function of their relative excitabilities and synaptic activation, followed by selective strengthening of pre-existing synapses, formation of new connections and elimination of outcompeted synapses to ensure memory formation. Mechanistically, these processes involve linking transcription to circuit modification. They include the expression of immediate early genes and specific molecular and cellular events, supported by network-wide activities that are shaped and modulated by local inhibitory microcircuits.
Collapse
|
132
|
Oh WC, Lutzu S, Castillo PE, Kwon HB. De novo synaptogenesis induced by GABA in the developing mouse cortex. Science 2016; 353:1037-1040. [PMID: 27516412 PMCID: PMC5104171 DOI: 10.1126/science.aaf5206] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 08/03/2016] [Indexed: 12/23/2022]
Abstract
Dendrites of cortical pyramidal neurons contain intermingled excitatory and inhibitory synapses. We studied the local mechanisms that regulate the formation and distribution of synapses. We found that local γ-aminobutyric acid (GABA) release on dendrites of mouse cortical layer 2/3 pyramidal neurons could induce gephyrin puncta and dendritic spine formation via GABA type A receptor activation and voltage-gated calcium channels during early postnatal development. Furthermore, the newly formed inhibitory and excitatory synaptic structures rapidly gained functions. Bidirectional manipulation of GABA release from somatostatin-positive interneurons increased and decreased the number of gephyrin puncta and dendritic spines, respectively. These results highlight a noncanonical function of GABA as a local synaptogenic element shaping the early establishment of neuronal circuitry in mouse cortex.
Collapse
Affiliation(s)
- Won Chan Oh
- Max Planck Florida Institute for Neuroscience (MPFI), Jupiter, FL 33458, USA
| | - Stefano Lutzu
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Pablo E Castillo
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Hyung-Bae Kwon
- Max Planck Florida Institute for Neuroscience (MPFI), Jupiter, FL 33458, USA. Max Planck Institute of Neurobiology, Martinsried 82152, Germany.
| |
Collapse
|
133
|
Della Sala G, Putignano E, Chelini G, Melani R, Calcagno E, Michele Ratto G, Amendola E, Gross CT, Giustetto M, Pizzorusso T. Dendritic Spine Instability in a Mouse Model of CDKL5 Disorder Is Rescued by Insulin-like Growth Factor 1. Biol Psychiatry 2016; 80:302-311. [PMID: 26452614 DOI: 10.1016/j.biopsych.2015.08.028] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Revised: 08/12/2015] [Accepted: 08/12/2015] [Indexed: 11/25/2022]
Abstract
BACKGROUND CDKL5 (cyclin-dependent kinase-like 5) is mutated in many severe neurodevelopmental disorders, including atypical Rett syndrome. CDKL5 was shown to interact with synaptic proteins, but an in vivo analysis of the role of CDKL5 in dendritic spine dynamics and synaptic molecular organization is still lacking. METHODS In vivo two-photon microscopy of the somatosensory cortex of Cdkl5(-/y) mice was applied to monitor structural dynamics of dendritic spines. Synaptic function and plasticity were measured using electrophysiological recordings of excitatory postsynaptic currents and long-term potentiation in brain slices and assessing the expression of synaptic postsynaptic density protein 95 (PSD-95). Finally, we studied the impact of insulin-like growth factor 1 (IGF-1) treatment on CDKL5 null mice to restore the synaptic deficits. RESULTS Adult mutant mice showed a significant reduction in spine density and PSD-95-positive synaptic puncta, a reduction of persistent spines, and impaired long-term potentiation. In juvenile mutants, short-term spine elimination, but not formation, was dramatically increased. Exogenous administration of IGF-1 rescued defective rpS6 phosphorylation, spine density, and PSD-95 expression. Endogenous cortical IGF-1 levels were unaffected by CDKL5 deletion. CONCLUSIONS These data demonstrate that dendritic spine stabilization is strongly regulated by CDKL5. Moreover, our data suggest that IGF-1 treatment could be a promising candidate for clinical trials in CDKL5 patients.
Collapse
Affiliation(s)
- Grazia Della Sala
- Department of Neuroscience, Psychology, Drug Research, and Child Health-Neurofarba, University of Florence, Florence
| | - Elena Putignano
- Institute of Neuroscience (EP, TP), National Research Council, Pisa
| | - Gabriele Chelini
- Department of Neuroscience, Psychology, Drug Research, and Child Health-Neurofarba, University of Florence, Florence
| | - Riccardo Melani
- Department of Neuroscience, Psychology, Drug Research, and Child Health-Neurofarba, University of Florence, Florence
| | - Eleonora Calcagno
- Department of Neuroscience and National Institute of Neuroscience (EC, MG), University of Turin, Turin
| | - Gian Michele Ratto
- National Enterprise for Nanoscience and Nanotechnology (GMR), Institute of Nanoscience of the National Research Council, and Scuola Normale Superiore, Pisa
| | - Elena Amendola
- Mouse Biology Unit (EA, CTG), European Molecular Biology Laboratory, Monterotondo, Italy
| | - Cornelius T Gross
- Mouse Biology Unit (EA, CTG), European Molecular Biology Laboratory, Monterotondo, Italy
| | - Maurizio Giustetto
- Department of Neuroscience and National Institute of Neuroscience (EC, MG), University of Turin, Turin
| | - Tommaso Pizzorusso
- Department of Neuroscience, Psychology, Drug Research, and Child Health-Neurofarba, University of Florence, Florence; Institute of Neuroscience (EP, TP), National Research Council, Pisa.
| |
Collapse
|
134
|
Parajuli LK, Tanaka S, Okabe S. Insights into age-old questions of new dendritic spines: From form to function. Brain Res Bull 2016; 129:3-11. [PMID: 27491624 DOI: 10.1016/j.brainresbull.2016.07.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 07/18/2016] [Accepted: 07/31/2016] [Indexed: 11/30/2022]
Abstract
Principal neurons in multiple brain regions receive a vast majority of excitatory synaptic contacts on the tiny dendritic appendages called dendritic spines. These structures are believed to be the locus of memory storage in the brain. Indeed, neurological diseases leading to impairment in memory and cognitive capabilities are often associated with structural alteration of dendritic spines. While several landmark studies in the past have provided a great deal of information on the structure, function and molecular composition of prototypical mature dendritic spines, we still have a limited knowledge of nascent spines. In recent years there has been a surge of interest to understand the nascent spines and the increasing technical advances in the genetic, molecular and imaging methods have opened avenues for systematic and thorough investigation. In this review, by discussing studies from several labs including ours, we provide a systematic summary of the development, structure, molecular expression and function of nascent spines and highlight some of the potentially important and interesting research questions that remain to be answered.
Collapse
Affiliation(s)
- Laxmi Kumar Parajuli
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shinji Tanaka
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shigeo Okabe
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
| |
Collapse
|
135
|
Persistent Structural Plasticity Optimizes Sensory Information Processing in the Olfactory Bulb. Neuron 2016; 91:384-96. [PMID: 27373833 DOI: 10.1016/j.neuron.2016.06.004] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 04/14/2016] [Accepted: 05/19/2016] [Indexed: 11/23/2022]
Abstract
In the mammalian brain, the anatomical structure of neural circuits changes little during adulthood. As a result, adult learning and memory are thought to result from specific changes in synaptic strength. A possible exception is the olfactory bulb (OB), where activity guides interneuron turnover throughout adulthood. These adult-born granule cell (GC) interneurons form new GABAergic synapses that have little synaptic strength plasticity. In the face of persistent neuronal and synaptic turnover, how does the OB balance flexibility, as is required for adapting to changing sensory environments, with perceptual stability? Here we show that high dendritic spine turnover is a universal feature of GCs, regardless of their developmental origin and age. We find matching dynamics among postsynaptic sites on the principal neurons receiving the new synaptic inputs. We further demonstrate in silico that this coordinated structural plasticity is consistent with stable, yet flexible, decorrelated sensory representations. Together, our study reveals that persistent, coordinated synaptic structural plasticity between interneurons and principal neurons is a major mode of functional plasticity in the OB.
Collapse
|
136
|
Dendrites In Vitro and In Vivo Contain Microtubules of Opposite Polarity and Axon Formation Correlates with Uniform Plus-End-Out Microtubule Orientation. J Neurosci 2016; 36:1071-85. [PMID: 26818498 DOI: 10.1523/jneurosci.2430-15.2016] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
UNLABELLED In cultured vertebrate neurons, axons have a uniform arrangement of microtubules with plus-ends distal to the cell body (plus-end-out), whereas dendrites contain mixed polarity orientations with both plus-end-out and minus-end-out oriented microtubules. Rather than non-uniform microtubules, uniparallel minus-end-out microtubules are the signature of dendrites in Drosophila and Caenorhabditis elegans neurons. To determine whether mixed microtubule organization is a conserved feature of vertebrate dendrites, we used live-cell imaging to systematically analyze microtubule plus-end orientations in primary cultures of rat hippocampal and cortical neurons, dentate granule cells in mouse organotypic slices, and layer 2/3 pyramidal neurons in the somatosensory cortex of living mice. In vitro and in vivo, all microtubules had a plus-end-out orientation in axons, whereas microtubules in dendrites had mixed orientations. When dendritic microtubules were severed by laser-based microsurgery, we detected equal numbers of plus- and minus-end-out microtubule orientations throughout the dendritic processes. In dendrites, the minus-end-out microtubules were generally more stable and comparable with plus-end-out microtubules in axons. Interestingly, at early stages of neuronal development in nonpolarized cells, newly formed neurites already contained microtubules of opposite polarity, suggesting that the establishment of uniform plus-end-out microtubules occurs during axon formation. We propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization. SIGNIFICANCE STATEMENT Live-cell imaging was used to systematically analyze microtubule organization in primary cultures of rat hippocampal neurons, dentate granule cells in mouse organotypic slices, and layer 2/3 pyramidal neuron in somatosensory cortex of living mice. In vitro and in vivo, all microtubules have a plus-end-out orientation in axons, whereas microtubules in dendrites have mixed orientations. Interestingly, newly formed neurites of nonpolarized neurons already contain mixed microtubules, and the specific organization of uniform plus-end-out microtubules only occurs during axon formation. Based on these findings, the authors propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization.
Collapse
|
137
|
Rapid and continuous activity-dependent plasticity of olfactory sensory input. Nat Commun 2016; 7:10729. [PMID: 26898529 PMCID: PMC4764868 DOI: 10.1038/ncomms10729] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 01/15/2016] [Indexed: 02/01/2023] Open
Abstract
Incorporation of new neurons enables plasticity and repair of circuits in the adult brain. Adult neurogenesis is a key feature of the mammalian olfactory system, with new olfactory sensory neurons (OSNs) wiring into highly organized olfactory bulb (OB) circuits throughout life. However, neither when new postnatally generated OSNs first form synapses nor whether OSNs retain the capacity for synaptogenesis once mature, is known. Therefore, how integration of adult-born OSNs may contribute to lifelong OB plasticity is unclear. Here, we use a combination of electron microscopy, optogenetic activation and in vivo time-lapse imaging to show that newly generated OSNs form highly dynamic synapses and are capable of eliciting robust stimulus-locked firing of neurons in the mouse OB. Furthermore, we demonstrate that mature OSN axons undergo continuous activity-dependent synaptic remodelling that persists into adulthood. OSN synaptogenesis, therefore, provides a sustained potential for OB plasticity and repair that is much faster than OSN replacement alone.
Collapse
|
138
|
Villa KL, Berry KP, Subramanian J, Cha JW, Oh WC, Kwon HB, Kubota Y, So PTC, Nedivi E. Inhibitory Synapses Are Repeatedly Assembled and Removed at Persistent Sites In Vivo. Neuron 2016; 89:756-69. [PMID: 26853302 PMCID: PMC4760889 DOI: 10.1016/j.neuron.2016.01.010] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 06/11/2015] [Accepted: 12/24/2015] [Indexed: 11/24/2022]
Abstract
Older concepts of a hard-wired adult brain have been overturned in recent years by in vivo imaging studies revealing synaptic remodeling, now thought to mediate rearrangements in microcircuit connectivity. Using three-color labeling and spectrally resolved two-photon microscopy, we monitor in parallel the daily structural dynamics (assembly or removal) of excitatory and inhibitory postsynaptic sites on the same neurons in mouse visual cortex in vivo. We find that dynamic inhibitory synapses often disappear and reappear again in the same location. The starkest contrast between excitatory and inhibitory synapse dynamics is on dually innervated spines, where inhibitory synapses frequently recur while excitatory synapses are stable. Monocular deprivation, a model of sensory input-dependent plasticity, shortens inhibitory synapse lifetimes and lengthens intervals to recurrence, resulting in a new dynamic state with reduced inhibitory synaptic presence. Reversible structural dynamics indicate a fundamentally new role for inhibitory synaptic remodeling--flexible, input-specific modulation of stable excitatory connections.
Collapse
Affiliation(s)
- Katherine L Villa
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Kalen P Berry
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jaichandar Subramanian
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jae Won Cha
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Won Chan Oh
- Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - Hyung-Bae Kwon
- Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA; Max Planck Institute of Neurobiology, Martinsried 82152, Germany
| | - Yoshiyuki Kubota
- Division of Cerebral Circuitry, National Institute for Physiological Sciences, Okazaki 444-8585, Japan; Department of Physiological Science, Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan; JST, CREST, Tokyo 102-0076, Japan
| | - Peter T C So
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Elly Nedivi
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
| |
Collapse
|
139
|
Yau KW, Schätzle P, Tortosa E, Pagès S, Holtmaat A, Kapitein LC, Hoogenraad CC. Dendrites In Vitro and In Vivo Contain Microtubules of Opposite Polarity and Axon Formation Correlates with Uniform Plus-End-Out Microtubule Orientation. J Neurosci 2016. [PMID: 26818498 DOI: 10.1523/jneurosci.2430-15.20166] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023] Open
Abstract
UNLABELLED In cultured vertebrate neurons, axons have a uniform arrangement of microtubules with plus-ends distal to the cell body (plus-end-out), whereas dendrites contain mixed polarity orientations with both plus-end-out and minus-end-out oriented microtubules. Rather than non-uniform microtubules, uniparallel minus-end-out microtubules are the signature of dendrites in Drosophila and Caenorhabditis elegans neurons. To determine whether mixed microtubule organization is a conserved feature of vertebrate dendrites, we used live-cell imaging to systematically analyze microtubule plus-end orientations in primary cultures of rat hippocampal and cortical neurons, dentate granule cells in mouse organotypic slices, and layer 2/3 pyramidal neurons in the somatosensory cortex of living mice. In vitro and in vivo, all microtubules had a plus-end-out orientation in axons, whereas microtubules in dendrites had mixed orientations. When dendritic microtubules were severed by laser-based microsurgery, we detected equal numbers of plus- and minus-end-out microtubule orientations throughout the dendritic processes. In dendrites, the minus-end-out microtubules were generally more stable and comparable with plus-end-out microtubules in axons. Interestingly, at early stages of neuronal development in nonpolarized cells, newly formed neurites already contained microtubules of opposite polarity, suggesting that the establishment of uniform plus-end-out microtubules occurs during axon formation. We propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization. SIGNIFICANCE STATEMENT Live-cell imaging was used to systematically analyze microtubule organization in primary cultures of rat hippocampal neurons, dentate granule cells in mouse organotypic slices, and layer 2/3 pyramidal neuron in somatosensory cortex of living mice. In vitro and in vivo, all microtubules have a plus-end-out orientation in axons, whereas microtubules in dendrites have mixed orientations. Interestingly, newly formed neurites of nonpolarized neurons already contain mixed microtubules, and the specific organization of uniform plus-end-out microtubules only occurs during axon formation. Based on these findings, the authors propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization.
Collapse
Affiliation(s)
- Kah Wai Yau
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands, and
| | - Philipp Schätzle
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands, and
| | - Elena Tortosa
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands, and
| | - Stéphane Pagès
- Department of Basic Neurosciences, Faculty of Medicine and the Center for Neuroscience, University of Geneva, 1211 Geneva, Switzerland
| | - Anthony Holtmaat
- Department of Basic Neurosciences, Faculty of Medicine and the Center for Neuroscience, University of Geneva, 1211 Geneva, Switzerland
| | - Lukas C Kapitein
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands, and
| | - Casper C Hoogenraad
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH, Utrecht, The Netherlands, and
| |
Collapse
|
140
|
Abstract
Dynamic remodeling of connectivity is a fundamental feature of neocortical circuits. Unraveling the principles underlying these dynamics is essential for the understanding of how neuronal circuits give rise to computations. Moreover, as complete descriptions of the wiring diagram in cortical tissues are becoming available, deciphering the dynamic elements in these diagrams is crucial for relating them to cortical function. Here, we used chronic in vivo two-photon imaging to longitudinally follow a few thousand dendritic spines in the mouse auditory cortex to study the determinants of these spines' lifetimes. We applied nonlinear regression to quantify the independent contribution of spine age and several morphological parameters to the prediction of the future survival of a spine. We show that spine age, size, and geometry are parameters that can provide independent contributions to the prediction of the longevity of a synaptic connection. In addition, we use this framework to emulate a serial sectioning electron microscopy experiment and demonstrate how incorporation of morphological information of dendritic spines from a single time-point allows estimation of future connectivity states. The distinction between predictable and nonpredictable connectivity changes may be used in the future to identify the specific adaptations of neuronal circuits to environmental changes. The full dataset is publicly available for further analysis. Significance statement: The neural architecture in the neocortex exhibits constant remodeling. The functional consequences of these modifications are poorly understood, in particular because the determinants of these changes are largely unknown. Here, we aimed to identify those modifications that are predictable from current network state. To that goal, we repeatedly imaged thousands of dendritic spines in the auditory cortex of mice to assess the morphology and lifetimes of synaptic connections. We developed models based on morphological features of dendritic spines that allow predicting future turnover of synaptic connections. The dynamic models presented in this paper provide a quantitative framework for adding putative temporal dynamics to the static description of a neuronal circuit from single time-point connectomics experiments.
Collapse
|
141
|
Remodeling and Tenacity of Inhibitory Synapses: Relationships with Network Activity and Neighboring Excitatory Synapses. PLoS Comput Biol 2015; 11:e1004632. [PMID: 26599330 PMCID: PMC4658206 DOI: 10.1371/journal.pcbi.1004632] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Accepted: 10/29/2015] [Indexed: 11/19/2022] Open
Abstract
Glutamatergic synapse size remodeling is governed not only by specific activity forms but also by apparently stochastic processes with well-defined statistics. These spontaneous remodeling processes can give rise to skewed and stable synaptic size distributions, underlie scaling of these distributions and drive changes in glutamatergic synapse size "configurations". Where inhibitory synapses are concerned, however, little is known on spontaneous remodeling dynamics, their statistics, their activity dependence or their long-term consequences. Here we followed individual inhibitory synapses for days, and analyzed their size remodeling dynamics within the statistical framework previously developed for glutamatergic synapses. Similar to glutamatergic synapses, size distributions of inhibitory synapses were skewed and stable; at the same time, however, sizes of individual synapses changed considerably, leading to gradual changes in synaptic size configurations. The suppression of network activity only transiently affected spontaneous remodeling dynamics, did not affect synaptic size configuration change rates and was not followed by the scaling of inhibitory synapse size distributions. Comparisons with glutamatergic synapses within the same dendrites revealed a degree of coupling between nearby inhibitory and excitatory synapse remodeling, but also revealed that inhibitory synapse size configurations changed at considerably slower rates than those of their glutamatergic neighbors. These findings point to quantitative differences in spontaneous remodeling dynamics of inhibitory and excitatory synapses but also reveal deep qualitative similarities in the processes that control their sizes and govern their remodeling dynamics.
Collapse
|
142
|
Hruska M, Henderson NT, Xia NL, Le Marchand SJ, Dalva MB. Anchoring and synaptic stability of PSD-95 is driven by ephrin-B3. Nat Neurosci 2015; 18:1594-605. [PMID: 26479588 PMCID: PMC5396457 DOI: 10.1038/nn.4140] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 09/17/2015] [Indexed: 02/07/2023]
Abstract
Organization of signaling complexes at excitatory synapses by Membrane Associated Guanylate Kinase (MAGUK) proteins regulates synapse development, plasticity, senescence, and disease. Post-translational modification of MAGUK family proteins can drive their membrane localization, yet it is unclear how these intracellular proteins are targeted to sites of synaptic contact. Here we show using super-resolution imaging, biochemical approaches, and in vivo models that the trans-synaptic organizing protein, ephrin-B3, controls the synaptic localization and stability of PSD-95 and links these events to changes in neuronal activity via negative regulation of a novel MAPK-dependent phosphorylation site on ephrin-B3 (S332). Unphosphorylated ephrin-B3 is enriched at synapses, interacts directly with and stabilizes PSD-95 at synapses. Activity induced phosphorylation of S332 disperses ephrin-B3 from synapses, prevents the interaction with, and enhances the turnover of PSD-95. Thus, ephrin-B3 specifies the synaptic localization of PSD-95 and likely links the synaptic stability of PSD-95 to changes in neuronal activity.
Collapse
Affiliation(s)
- Martin Hruska
- Department of Neuroscience and the Farber Institute for Neuroscience, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA
| | - Nathan T Henderson
- Department of Neuroscience and the Farber Institute for Neuroscience, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA
| | - Nan L Xia
- Department of Neuroscience and the Farber Institute for Neuroscience, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA
| | - Sylvain J Le Marchand
- Department of Neuroscience and the Farber Institute for Neuroscience, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA
| | - Matthew B Dalva
- Department of Neuroscience and the Farber Institute for Neuroscience, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA
| |
Collapse
|
143
|
Korogod N, Petersen CCH, Knott GW. Ultrastructural analysis of adult mouse neocortex comparing aldehyde perfusion with cryo fixation. eLife 2015; 4. [PMID: 26259873 PMCID: PMC4530226 DOI: 10.7554/elife.05793] [Citation(s) in RCA: 242] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 07/03/2015] [Indexed: 12/18/2022] Open
Abstract
Analysis of brain ultrastructure using electron microscopy typically relies on chemical fixation. However, this is known to cause significant tissue distortion including a reduction in the extracellular space. Cryo fixation is thought to give a truer representation of biological structures, and here we use rapid, high-pressure freezing on adult mouse neocortex to quantify the extent to which these two fixation methods differ in terms of their preservation of the different cellular compartments, and the arrangement of membranes at the synapse and around blood vessels. As well as preserving a physiological extracellular space, cryo fixation reveals larger numbers of docked synaptic vesicles, a smaller glial volume, and a less intimate glial coverage of synapses and blood vessels compared to chemical fixation. The ultrastructure of mouse neocortex therefore differs significantly comparing cryo and chemical fixation conditions.
Collapse
Affiliation(s)
- Natalya Korogod
- BioEM Facility, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Carl C H Petersen
- Laboratory of Sensory Processing, Brain Mind Institute, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Graham W Knott
- BioEM Facility, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| |
Collapse
|
144
|
Abstract
To create a presynaptic terminal, molecular signaling events must be orchestrated across a number of subcellular compartments. In the soma, presynaptic proteins need to be synthesized, packaged together, and attached to microtubule motors for shipment through the axon. Within the axon, transport of presynaptic packages is regulated to ensure that developing synapses receive an adequate supply of components. At individual axonal sites, extracellular interactions must be translated into intracellular signals that can incorporate mobile transport vesicles into the nascent presynaptic terminal. Even once the initial recruitment process is complete, the components and subsequent functionality of presynaptic terminals need to constantly be remodeled. Perhaps most remarkably, all of these processes need to be coordinated in space and time. In this review, we discuss how these dynamic cellular processes occur in neurons of the central nervous system in order to generate presynaptic terminals in the brain.
Collapse
Affiliation(s)
- Luke A D Bury
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Shasta L Sabo
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, USA Department of Neuroscience, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| |
Collapse
|
145
|
Bosch C, Martínez A, Masachs N, Teixeira CM, Fernaud I, Ulloa F, Pérez-Martínez E, Lois C, Comella JX, DeFelipe J, Merchán-Pérez A, Soriano E. FIB/SEM technology and high-throughput 3D reconstruction of dendritic spines and synapses in GFP-labeled adult-generated neurons. Front Neuroanat 2015; 9:60. [PMID: 26052271 PMCID: PMC4440362 DOI: 10.3389/fnana.2015.00060] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 04/29/2015] [Indexed: 12/24/2022] Open
Abstract
The fine analysis of synaptic contacts is usually performed using transmission electron microscopy (TEM) and its combination with neuronal labeling techniques. However, the complex 3D architecture of neuronal samples calls for their reconstruction from serial sections. Here we show that focused ion beam/scanning electron microscopy (FIB/SEM) allows efficient, complete, and automatic 3D reconstruction of identified dendrites, including their spines and synapses, from GFP/DAB-labeled neurons, with a resolution comparable to that of TEM. We applied this technology to analyze the synaptogenesis of labeled adult-generated granule cells (GCs) in mice. 3D reconstruction of dendritic spines in GCs aged 3–4 and 8–9 weeks revealed two different stages of dendritic spine development and unexpected features of synapse formation, including vacant and branched dendritic spines and presynaptic terminals establishing synapses with up to 10 dendritic spines. Given the reliability, efficiency, and high resolution of FIB/SEM technology and the wide use of DAB in conventional EM, we consider FIB/SEM fundamental for the detailed characterization of identified synaptic contacts in neurons in a high-throughput manner.
Collapse
Affiliation(s)
- Carles Bosch
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology and Parc Cientific de Barcelona, University of Barcelona Barcelona, Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Insituto de Salul Carlos III Madrid, Spain ; Institut de Recerca de l'Hospital Universitari de la Vall d'Hebron (VHIR) Barcelona, Spain
| | - Albert Martínez
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology and Parc Cientific de Barcelona, University of Barcelona Barcelona, Spain
| | - Nuria Masachs
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology and Parc Cientific de Barcelona, University of Barcelona Barcelona, Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Insituto de Salul Carlos III Madrid, Spain
| | - Cátia M Teixeira
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology and Parc Cientific de Barcelona, University of Barcelona Barcelona, Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Insituto de Salul Carlos III Madrid, Spain
| | - Isabel Fernaud
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Insituto de Salul Carlos III Madrid, Spain ; Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Campus de Montegancedo Madrid, Spain ; Instituto Cajal (Consejo Superior de Investigaciones Científicas) Madrid, Spain
| | - Fausto Ulloa
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology and Parc Cientific de Barcelona, University of Barcelona Barcelona, Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Insituto de Salul Carlos III Madrid, Spain
| | - Esther Pérez-Martínez
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology and Parc Cientific de Barcelona, University of Barcelona Barcelona, Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Insituto de Salul Carlos III Madrid, Spain
| | - Carlos Lois
- Department of Neurobiology, University of Massachusetts Medical School Worcester, MA, USA
| | - Joan X Comella
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Insituto de Salul Carlos III Madrid, Spain ; Institut de Recerca de l'Hospital Universitari de la Vall d'Hebron (VHIR) Barcelona, Spain ; Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona Bellaterra, Spain
| | - Javier DeFelipe
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Insituto de Salul Carlos III Madrid, Spain ; Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Campus de Montegancedo Madrid, Spain ; Instituto Cajal (Consejo Superior de Investigaciones Científicas) Madrid, Spain
| | - Angel Merchán-Pérez
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Insituto de Salul Carlos III Madrid, Spain ; Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Campus de Montegancedo Madrid, Spain ; Departamento de Arquitectura y Tecnología de Sistemas Informáticos, Escuela Técnica Superior de Ingenieros Informáticos, Universidad Politécnica de Madrid Madrid, Spain
| | - Eduardo Soriano
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology and Parc Cientific de Barcelona, University of Barcelona Barcelona, Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Insituto de Salul Carlos III Madrid, Spain ; Institut de Recerca de l'Hospital Universitari de la Vall d'Hebron (VHIR) Barcelona, Spain ; Institució Catalana de Recerca i Estudis Avançats Academia Barcelona, Spain
| |
Collapse
|
146
|
Pagès S, Cane M, Randall J, Capello L, Holtmaat A. Single cell electroporation for longitudinal imaging of synaptic structure and function in the adult mouse neocortex in vivo. Front Neuroanat 2015; 9:36. [PMID: 25904849 PMCID: PMC4387926 DOI: 10.3389/fnana.2015.00036] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 03/09/2015] [Indexed: 11/13/2022] Open
Abstract
Longitudinal imaging studies of neuronal structures in vivo have revealed rich dynamics in dendritic spines and axonal boutons. Spines and boutons are considered to be proxies for synapses. This implies that synapses display similar dynamics. However, spines and boutons do not always bear synapses, some may contain more than one, and dendritic shaft synapses have no clear structural proxies. In addition, synaptic strength is not always accurately revealed by just the size of these structures. Structural and functional dynamics of synapses could be studied more reliably using fluorescent synaptic proteins as markers for size and function. These proteins are often large and possibly interfere with circuit development, which renders them less suitable for conventional transfection or transgenesis methods such as viral vectors, in utero electroporation, and germline transgenesis. Single cell electroporation (SCE) has been shown to be a potential alternative for transfection of recombinant fluorescent proteins in adult cortical neurons. Here we provide proof of principle for the use of SCE to express and subsequently image fluorescently tagged synaptic proteins over days to weeks in vivo.
Collapse
Affiliation(s)
- Stéphane Pagès
- Department of Basic Neurosciences and The Center for Neuroscience, Centre Médical Universitaire (CMU), University of Geneva Geneva, Switzerland
| | - Michele Cane
- Department of Basic Neurosciences and The Center for Neuroscience, Centre Médical Universitaire (CMU), University of Geneva Geneva, Switzerland
| | - Jérôme Randall
- Department of Basic Neurosciences and The Center for Neuroscience, Centre Médical Universitaire (CMU), University of Geneva Geneva, Switzerland
| | - Luca Capello
- Itopie Informatique, Société Coopérative Geneva, Switzerland
| | - Anthony Holtmaat
- Department of Basic Neurosciences and The Center for Neuroscience, Centre Médical Universitaire (CMU), University of Geneva Geneva, Switzerland
| |
Collapse
|
147
|
Modeling maintenance of long-term potentiation in clustered synapses: long-term memory without bistability. Neural Plast 2015; 2015:185410. [PMID: 25945261 PMCID: PMC4402204 DOI: 10.1155/2015/185410] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Revised: 03/17/2015] [Accepted: 03/18/2015] [Indexed: 11/25/2022] Open
Abstract
Memories are stored, at least partly, as patterns of strong synapses. Given molecular turnover, how can synapses maintain strong for the years that memories can persist? Some models postulate that biochemical bistability maintains strong synapses. However, bistability should give a bimodal distribution of synaptic strength or weight, whereas current data show unimodal distributions for weights and for a correlated variable, dendritic spine volume. Thus it is important for models to simulate both unimodal distributions and long-term memory persistence. Here a model is developed that connects ongoing, competing processes of synaptic growth and weakening to stochastic processes of receptor insertion and removal in dendritic spines. The model simulates long-term (>1 yr) persistence of groups of strong synapses. A unimodal weight distribution results. For stability of this distribution it proved essential to incorporate resource competition between synapses organized into small clusters. With competition, these clusters are stable for years. These simulations concur with recent data to support the “clustered plasticity hypothesis” which suggests clusters, rather than single synaptic contacts, may be a fundamental unit for storage of long-term memory. The model makes empirical predictions and may provide a framework to investigate mechanisms maintaining the balance between synaptic plasticity and stability of memory.
Collapse
|
148
|
Cytokine-Induced GAPDH Sulfhydration Affects PSD95 Degradation and Memory. Mol Cell 2014; 56:786-95. [DOI: 10.1016/j.molcel.2014.10.019] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 09/12/2014] [Accepted: 10/22/2014] [Indexed: 12/28/2022]
|
149
|
Statman A, Kaufman M, Minerbi A, Ziv NE, Brenner N. Synaptic size dynamics as an effectively stochastic process. PLoS Comput Biol 2014; 10:e1003846. [PMID: 25275505 PMCID: PMC4183425 DOI: 10.1371/journal.pcbi.1003846] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2014] [Accepted: 07/18/2014] [Indexed: 11/18/2022] Open
Abstract
Long-term, repeated measurements of individual synaptic properties have revealed that synapses can undergo significant directed and spontaneous changes over time scales of minutes to weeks. These changes are presumably driven by a large number of activity-dependent and independent molecular processes, yet how these processes integrate to determine the totality of synaptic size remains unknown. Here we propose, as an alternative to detailed, mechanistic descriptions, a statistical approach to synaptic size dynamics. The basic premise of this approach is that the integrated outcome of the myriad of processes that drive synaptic size dynamics are effectively described as a combination of multiplicative and additive processes, both of which are stochastic and taken from distributions parametrically affected by physiological signals. We show that this seemingly simple model, known in probability theory as the Kesten process, can generate rich dynamics which are qualitatively similar to the dynamics of individual glutamatergic synapses recorded in long-term time-lapse experiments in ex-vivo cortical networks. Moreover, we show that this stochastic model, which is insensitive to many of its underlying details, quantitatively captures the distributions of synaptic sizes measured in these experiments, the long-term stability of such distributions and their scaling in response to pharmacological manipulations. Finally, we show that the average kinetics of new postsynaptic density formation measured in such experiments is also faithfully captured by the same model. The model thus provides a useful framework for characterizing synapse size dynamics at steady state, during initial formation of such steady states, and during their convergence to new steady states following perturbations. These findings show the strength of a simple low dimensional statistical model to quantitatively describe synapse size dynamics as the integrated result of many underlying complex processes.
Collapse
Affiliation(s)
- Adiel Statman
- Department of Chemical Engineering, Technion, Haifa, Israel
- Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Technion, Haifa, Israel
| | - Maya Kaufman
- Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Technion, Haifa, Israel
- Faculty of Medicine, Technion, Haifa, Israel
| | - Amir Minerbi
- Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Technion, Haifa, Israel
- Faculty of Medicine, Technion, Haifa, Israel
| | - Noam E. Ziv
- Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Technion, Haifa, Israel
- Faculty of Medicine, Technion, Haifa, Israel
| | - Naama Brenner
- Department of Chemical Engineering, Technion, Haifa, Israel
- Network Biology Research Laboratories, Lorry Lokey Center for Life Sciences and Engineering, Technion, Haifa, Israel
- * E-mail:
| |
Collapse
|
150
|
Caroni P, Chowdhury A, Lahr M. Synapse rearrangements upon learning: from divergent-sparse connectivity to dedicated sub-circuits. Trends Neurosci 2014; 37:604-14. [PMID: 25257207 DOI: 10.1016/j.tins.2014.08.011] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 08/26/2014] [Accepted: 08/27/2014] [Indexed: 01/24/2023]
Abstract
Learning can involve formation of new synapses and loss of synapses, providing memory traces of learned skills. Recent findings suggest that these synapse rearrangements reflect assembly of task-related sub-circuits from initially broadly distributed and sparse connectivity in the brain. These local circuit remodeling processes involve rapid emergence of synapses upon learning, followed by protracted validation involving strengthening of some new synapses, and selective elimination of others. The timing of these consolidation processes can vary. Here, we review these findings, focusing on how molecular/cellular mechanisms of synapse assembly, strengthening, and elimination might interface with circuit/system mechanisms of learning and memory consolidation. An integrated understanding of these learning-related processes should provide a better basis to elucidate how experience, genetic background, and disease influence brain function.
Collapse
Affiliation(s)
- Pico Caroni
- Friedrich Miescher Institut, Basel, Switzerland.
| | | | - Maria Lahr
- Friedrich Miescher Institut, Basel, Switzerland
| |
Collapse
|