1
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Cárdenas-García SP, Ijaz S, Pereda AE. The components of an electrical synapse as revealed by expansion microscopy of a single synaptic contact. eLife 2024; 13:e91931. [PMID: 38994821 PMCID: PMC11333041 DOI: 10.7554/elife.91931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 07/08/2024] [Indexed: 07/13/2024] Open
Abstract
Most nervous systems combine both transmitter-mediated and direct cell-cell communication, known as 'chemical' and 'electrical' synapses, respectively. Chemical synapses can be identified by their multiple structural components. Electrical synapses are, on the other hand, generally defined by the presence of a 'gap junction' (a cluster of intercellular channels) between two neuronal processes. However, while gap junctions provide the communicating mechanism, it is unknown whether electrical transmission requires the contribution of additional cellular structures. We investigated this question at identifiable single synaptic contacts on the zebrafish Mauthner cells, at which gap junctions coexist with specializations for neurotransmitter release and where the contact unequivocally defines the anatomical limits of a synapse. Expansion microscopy of these single contacts revealed a detailed map of the incidence and spatial distribution of proteins pertaining to various synaptic structures. Multiple gap junctions of variable size were identified by the presence of their molecular components. Remarkably, most of the synaptic contact's surface was occupied by interleaving gap junctions and components of adherens junctions, suggesting a close functional association between these two structures. In contrast, glutamate receptors were confined to small peripheral portions of the contact, indicating that most of the synaptic area functions as an electrical synapse. Thus, our results revealed the overarching organization of an electrical synapse that operates with not one, but multiple gap junctions, in close association with structural and signaling molecules known to be components of adherens junctions. The relationship between these intercellular structures will aid in establishing the boundaries of electrical synapses found throughout animal connectomes and provide insight into the structural organization and functional diversity of electrical synapses.
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Affiliation(s)
- Sandra P Cárdenas-García
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of MedicineBronxUnited States
| | - Sundas Ijaz
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of MedicineBronxUnited States
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of MedicineBronxUnited States
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2
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Michel JC, Grivette MMB, Harshfield AT, Huynh L, Komons AP, Loomis B, McKinnis K, Miller BT, Nguyen EQ, Huang TW, Lauf S, Michel ES, Michel ME, Kissinger JS, Marsh AJ, Crow WE, Kaye LE, Lasseigne AM, Lukowicz-Bedford RM, Farnsworth DR, Martin EA, Miller AC. Electrical synapse structure requires distinct isoforms of a postsynaptic scaffold. PLoS Genet 2023; 19:e1011045. [PMID: 38011265 PMCID: PMC10703405 DOI: 10.1371/journal.pgen.1011045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 12/07/2023] [Accepted: 11/01/2023] [Indexed: 11/29/2023] Open
Abstract
Electrical synapses are neuronal gap junction (GJ) channels associated with a macromolecular complex called the electrical synapse density (ESD), which regulates development and dynamically modifies electrical transmission. However, the proteomic makeup and molecular mechanisms utilized by the ESD that direct electrical synapse formation are not well understood. Using the Mauthner cell of zebrafish as a model, we previously found that the intracellular scaffolding protein ZO1b is a member of the ESD, localizing postsynaptically, where it is required for GJ channel localization, electrical communication, neural network function, and behavior. Here, we show that the complexity of the ESD is further diversified by the genomic structure of the ZO1b gene locus. The ZO1b gene is alternatively initiated at three transcriptional start sites resulting in isoforms with unique N-termini that we call ZO1b-Alpha, -Beta, and -Gamma. We demonstrate that ZO1b-Beta and ZO1b-Gamma are broadly expressed throughout the nervous system and localize to electrical synapses. By contrast, ZO1b-Alpha is expressed mainly non-neuronally and is not found at synapses. We generate mutants in all individual isoforms, as well as double mutant combinations in cis on individual chromosomes, and find that ZO1b-Beta is necessary and sufficient for robust GJ channel localization. ZO1b-Gamma, despite its localization to the synapse, plays an auxiliary role in channel localization. This study expands the notion of molecular complexity at the ESD, revealing that an individual genomic locus can contribute distinct isoforms to the macromolecular complex at electrical synapses. Further, independent scaffold isoforms have differential contributions to developmental assembly of the interneuronal GJ channels. We propose that ESD molecular complexity arises both from the diversity of unique genes and from distinct isoforms encoded by single genes. Overall, ESD proteomic diversity is expected to have critical impacts on the development, structure, function, and plasticity of electrical transmission.
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Affiliation(s)
- Jennifer Carlisle Michel
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Margaret M. B. Grivette
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Amber T. Harshfield
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Lisa Huynh
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Ava P. Komons
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Bradley Loomis
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Kaitlan McKinnis
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Brennen T. Miller
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Ethan Q. Nguyen
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Tiffany W. Huang
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Sophia Lauf
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Elias S. Michel
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Mia E. Michel
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Jane S. Kissinger
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Audrey J. Marsh
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - William E. Crow
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Lila E. Kaye
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Abagael M. Lasseigne
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Rachel M. Lukowicz-Bedford
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Dylan R. Farnsworth
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - E. Anne Martin
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Adam C. Miller
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
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3
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Cárdenas-García SP, Ijaz S, Pereda AE. The components of an electrical synapse as revealed by expansion microscopy of a single synaptic contact. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.25.550347. [PMID: 37546897 PMCID: PMC10402082 DOI: 10.1101/2023.07.25.550347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Most nervous systems combine both transmitter-mediated and direct cell-cell communication, known as 'chemical' and 'electrical' synapses, respectively. Chemical synapses can be identified by their multiple structural components. Electrical synapses are, on the other hand, generally defined by the presence of a 'gap junction' (a cluster of intercellular channels) between two neuronal processes. However, while gap junctions provide the communicating mechanism, it is unknown whether electrical transmission requires the contribution of additional cellular structures. We investigated this question at identifiable single synaptic contacts on the zebrafish Mauthner cells, at which gap junctions coexist with specializations for neurotransmitter release and where the contact defines the anatomical limits of a synapse. Expansion microscopy of these contacts revealed a detailed map of the incidence and spatial distribution of proteins pertaining to various synaptic structures. Multiple gap junctions of variable size were identified by the presence of their molecular components. Remarkably, most of the synaptic contact's surface was occupied by interleaving gap junctions and components of adherens junctions, suggesting a close functional association between these two structures. In contrast, glutamate receptors were confined to small peripheral portions of the contact, indicating that most of the synaptic area works as an electrical synapse. Thus, our results revealed the overarching organization of an electrical synapse that operates with not one, but multiple gap junctions, in close association with structural and signaling molecules known to be components of AJs. The relationship between these intercellular structures will aid in establishing the boundaries of electrical synapses found throughout animal connectomes and provide insight into the structural organization and functional diversity of electrical synapses.
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Affiliation(s)
- Sandra P. Cárdenas-García
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Sundas Ijaz
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Alberto E. Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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4
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Hamling KR, Harmon K, Schoppik D. The Nature and Origin of Synaptic Inputs to Vestibulospinal Neurons in the Larval Zebrafish. eNeuro 2023; 10:ENEURO.0090-23.2023. [PMID: 37268420 PMCID: PMC10241381 DOI: 10.1523/eneuro.0090-23.2023] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 04/24/2023] [Accepted: 04/27/2023] [Indexed: 06/04/2023] Open
Abstract
Vestibulospinal neurons integrate sensed imbalance to regulate postural reflexes. As an evolutionarily conserved neural population, understanding their synaptic and circuit-level properties can offer insight into vertebrate antigravity reflexes. Motivated by recent work, we set out to verify and extend the characterization of vestibulospinal neurons in the larval zebrafish. Using current-clamp recordings together with stimulation, we observed that larval zebrafish vestibulospinal neurons are silent at rest, yet capable of sustained spiking following depolarization. Neurons responded systematically to a vestibular stimulus (translation in the dark); responses were abolished after chronic or acute loss of the utricular otolith. Voltage-clamp recordings at rest revealed strong excitatory inputs with a characteristic multimodal distribution of amplitudes, as well as strong inhibitory inputs. Excitatory inputs within a particular mode (amplitude range) routinely violated refractory period criteria and exhibited complex sensory tuning, suggesting a nonunitary origin. Next, using a unilateral loss-of-function approach, we characterized the source of vestibular inputs to vestibulospinal neurons from each ear. We observed systematic loss of high-amplitude excitatory inputs after utricular lesions ipsilateral, but not contralateral, to the recorded vestibulospinal neuron. In contrast, while some neurons had decreased inhibitory inputs after either ipsilateral or contralateral lesions, there were no systematic changes across the population of recorded neurons. We conclude that imbalance sensed by the utricular otolith shapes the responses of larval zebrafish vestibulospinal neurons through both excitatory and inhibitory inputs. Our findings expand our understanding of how a vertebrate model, the larval zebrafish, might use vestibulospinal input to stabilize posture. More broadly, when compared with recordings in other vertebrates, our data speak to conserved origins of vestibulospinal synaptic input.
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Affiliation(s)
- Kyla R Hamling
- Departments of Otolaryngology and Neuroscience & Physiology, and Neuroscience Institute, New York University Grossman School of Medicine, New York, New York 10016
| | - Katherine Harmon
- Departments of Otolaryngology and Neuroscience & Physiology, and Neuroscience Institute, New York University Grossman School of Medicine, New York, New York 10016
| | - David Schoppik
- Departments of Otolaryngology and Neuroscience & Physiology, and Neuroscience Institute, New York University Grossman School of Medicine, New York, New York 10016
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5
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Martin EA, Michel JC, Kissinger JS, Echeverry FA, Lin YP, O'Brien J, Pereda AE, Miller AC. Neurobeachin controls the asymmetric subcellular distribution of electrical synapse proteins. Curr Biol 2023; 33:2063-2074.e4. [PMID: 37172585 PMCID: PMC10266475 DOI: 10.1016/j.cub.2023.04.049] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 01/27/2023] [Accepted: 04/19/2023] [Indexed: 05/15/2023]
Abstract
The subcellular positioning of synapses and their specialized molecular compositions form the fundamental basis of neural circuits. Like chemical synapses, electrical synapses are constructed from an assortment of adhesion, scaffolding, and regulatory molecules, yet little is known about how these molecules localize to specific neuronal compartments. Here, we investigate the relationship between the autism- and epilepsy-associated gene Neurobeachin, the neuronal gap junction channel-forming Connexins, and the electrical synapse scaffold ZO1. Using the zebrafish Mauthner circuit, we find Neurobeachin localizes to the electrical synapse independently of ZO1 and Connexins. By contrast, we show Neurobeachin is required postsynaptically for the robust localization of ZO1 and Connexins. We demonstrate that Neurobeachin binds ZO1 but not Connexins. Finally, we find Neurobeachin is required to restrict electrical postsynaptic proteins to dendrites, but not electrical presynaptic proteins to axons. Together, the results reveal an expanded understanding of electrical synapse molecular complexity and the hierarchical interactions required to build neuronal gap junctions. Further, these findings provide novel insight into the mechanisms by which neurons compartmentalize the localization of electrical synapse proteins and provide a cell biological mechanism for the subcellular specificity of electrical synapse formation and function.
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Affiliation(s)
- E Anne Martin
- Institute of Neuroscience, University of Oregon, Eugene, OR 97403, USA.
| | | | - Jane S Kissinger
- Institute of Neuroscience, University of Oregon, Eugene, OR 97403, USA
| | - Fabio A Echeverry
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Ya-Ping Lin
- Department of Ophthalmology & Visual Science, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - John O'Brien
- Department of Ophthalmology & Visual Science, University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Adam C Miller
- Institute of Neuroscience, University of Oregon, Eugene, OR 97403, USA.
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6
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Hamling KR, Harmon K, Schoppik D. The nature and origin of synaptic inputs to vestibulospinal neurons in the larval zebrafish. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.15.532859. [PMID: 36993365 PMCID: PMC10055124 DOI: 10.1101/2023.03.15.532859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Vestibulospinal neurons integrate sensed imbalance to regulate postural reflexes. As an evolutionarily-conserved neural population, understanding their synaptic and circuit-level properties can offer insight into vertebrate antigravity reflexes. Motivated by recent work, we set out to verify and extend the characterization of vestibulospinal neurons in the larval zebrafish. Using current clamp recordings together with stimulation, we observed that larval zebrafish vestibulospinal neurons are silent at rest, yet capable of sustained spiking following depolarization. Neurons responded systematically to a vestibular stimulus (translation in the dark); responses were abolished after chronic or acute loss of the utricular otolith. Voltage clamp recordings at rest revealed strong excitatory inputs with a characteristic multimodal distribution of amplitudes, as well as strong inhibitory inputs. Excitatory inputs within a particular mode (amplitude range) routinely violated refractory period criteria and exhibited complex sensory tuning, suggesting a non-unitary origin. Next, using a unilateral loss-of-function approach, we characterized the source of vestibular inputs to vestibulospinal neurons from each ear. We observed systematic loss of high-amplitude excitatory inputs after utricular lesions ipsilateral, but not contralateral to the recorded vestibulospinal neuron. In contrast, while some neurons had decreased inhibitory inputs after either ipsilateral or contralateral lesions, there were no systematic changes across the population of recorded neurons. We conclude that imbalance sensed by the utricular otolith shapes the responses of larval zebrafish vestibulospinal neurons through both excitatory and inhibitory inputs. Our findings expand our understanding of how a vertebrate model, the larval zebrafish, might use vestibulospinal input to stabilize posture. More broadly, when compared to recordings in other vertebrates, our data speak to conserved origins of vestibulospinal synaptic input.
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Affiliation(s)
- Kyla R Hamling
- Departments of Otolaryngology, Neuroscience & Physiology, and the Neuroscience Institute, New York University Grossman School of Medicine
| | - Katherine Harmon
- Departments of Otolaryngology, Neuroscience & Physiology, and the Neuroscience Institute, New York University Grossman School of Medicine
| | - David Schoppik
- Departments of Otolaryngology, Neuroscience & Physiology, and the Neuroscience Institute, New York University Grossman School of Medicine
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7
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Shoenhard H, Jain RA, Granato M. The calcium-sensing receptor (CaSR) regulates zebrafish sensorimotor decision making via a genetically defined cluster of hindbrain neurons. Cell Rep 2022; 41:111790. [PMID: 36476852 PMCID: PMC9813870 DOI: 10.1016/j.celrep.2022.111790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 09/21/2022] [Accepted: 11/15/2022] [Indexed: 12/12/2022] Open
Abstract
Decision making is a fundamental nervous system function that ranges widely in complexity and speed of execution. We previously established larval zebrafish as a model for sensorimotor decision making and identified the G-protein-coupled calcium-sensing receptor (CaSR) to be critical for this process. Here, we report that CaSR functions in neurons to dynamically regulate the bias between two behavioral outcomes: escapes and reorientations. By employing a computational guided transgenic strategy, we identify a genetically defined neuronal cluster in the hindbrain as a key candidate site for CaSR function. Finally, we demonstrate that transgenic CaSR expression targeting this cluster consisting of a few hundred neurons shifts behavioral bias in wild-type animals and restores decision making deficits in CaSR mutants. Combined, our data provide a rare example of a G-protein-coupled receptor that biases vertebrate sensorimotor decision making via a defined neuronal cluster.
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Affiliation(s)
- Hannah Shoenhard
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Roshan A Jain
- Department of Biology, Haverford College, Haverford, PA 19041, USA
| | - Michael Granato
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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8
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Michel JC, Lasseigne AM, Marsh AJ, Miller AC. The disconnect2 mutation disrupts the tjp1b gene that is required for electrical synapse formation. MICROPUBLICATION BIOLOGY 2022; 2022:10.17912/micropub.biology.000593. [PMID: 35855444 PMCID: PMC9288654 DOI: 10.17912/micropub.biology.000593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 01/01/1970] [Accepted: 06/29/2022] [Indexed: 11/17/2022]
Abstract
To investigate electrical synapse formation in vivo we used forward genetics to disrupt genes affecting Mauthner cell electrical synapses in larval zebrafish. We identify the disconnect2 ( dis2 ) mutation for its failure to localize neural gap junction channels at electrical synapses. We mapped this mutation to chromosome 25 and identified a splice-altering mutation in the tjp1b gene. We demonstrated that the dis2 mutation disrupts tjp1b function using complementation analysis with CRISPR generated mutants. We conclude that the dis2 mutation disrupts the tjp1b gene that is required for electrical synapse formation.
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Affiliation(s)
| | | | - Audrey J. Marsh
- Institute of Neuroscience, University of Oregon, Eugene, OR USA
| | - Adam C. Miller
- Institute of Neuroscience, University of Oregon, Eugene, OR USA
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9
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Ahmed KT, Amin MR, Razmara P, Roy B, Cai R, Tang J, Chen XZ, Ali DW. Expression and Development of TARP γ-4 in Embryonic Zebrafish. Dev Neurosci 2022; 44:518-531. [PMID: 35728564 DOI: 10.1159/000525578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Accepted: 05/19/2022] [Indexed: 11/19/2022] Open
Abstract
Fast excitatory synaptic transmission in the CNS is mediated by the neurotransmitter glutamate, binding to and activating AMPA receptors (AMPARs). AMPARs are known to interact with auxiliary proteins that modulate their behavior. One such family of proteins is the transmembrane AMPAR-related proteins, known as TARPs. Little is known about the role of TARPs during development or about their function in nonmammalian organisms. Here, we report on the presence of TARP γ-4 in developing zebrafish. We find that zebrafish express 2 forms of TARP γ-4: γ-4a and γ-4b as early as 12 h post-fertilization. Sequence analysis shows that both γ-4a and γ-4b shows great level of variation particularly in the intracellular C-terminal domain compared to rat, mouse, and human γ-4. RT-qPCR showed a gradual increase in the expression of γ-4a throughout the first 5 days of development, whereas γ-4b levels were constant until day 5 when levels increased significantly. Knockdown of TARP γ-4a and γ-4b via either splice-blocking morpholinos or translation-blocking morpholinos resulted in embryos that exhibited deficits in C-start escape responses, showing reduced C-bend angles. Morphant larvae displayed reduced bouts of swimming. Whole-cell patch-clamp recordings of AMPAR-mediated currents from Mauthner cells showed a reduction in the frequency of mEPCs but no change in amplitude or kinetics. Together, these results suggest that γ-4a and γ-4b are required for proper neuronal development.
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Affiliation(s)
- Kazi Tanveer Ahmed
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Md Ruhul Amin
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Parastoo Razmara
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Birbickram Roy
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Ruiqi Cai
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
| | - Jingfeng Tang
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Hubei University of Technology, Wuhan, China
| | - Xing-Zhen Chen
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Hubei University of Technology, Wuhan, China
| | - Declan William Ali
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Hubei University of Technology, Wuhan, China
- Centre for Neuroscience, University of Alberta, Edmonton, Alberta, Canada
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10
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Meserve JH, Nelson JC, Marsden KC, Hsu J, Echeverry FA, Jain RA, Wolman MA, Pereda AE, Granato M. A forward genetic screen identifies Dolk as a regulator of startle magnitude through the potassium channel subunit Kv1.1. PLoS Genet 2021; 17:e1008943. [PMID: 34061829 PMCID: PMC8195410 DOI: 10.1371/journal.pgen.1008943] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 06/11/2021] [Accepted: 05/04/2021] [Indexed: 11/19/2022] Open
Abstract
The acoustic startle response is an evolutionarily conserved avoidance behavior. Disruptions in startle behavior, particularly startle magnitude, are a hallmark of several human neurological disorders. While the neural circuitry underlying startle behavior has been studied extensively, the repertoire of genes and genetic pathways that regulate this locomotor behavior has not been explored using an unbiased genetic approach. To identify such genes, we took advantage of the stereotypic startle behavior in zebrafish larvae and performed a forward genetic screen coupled with whole genome analysis. We uncovered mutations in eight genes critical for startle behavior, including two genes encoding proteins associated with human neurological disorders, Dolichol kinase (Dolk), a broadly expressed regulator of the glycoprotein biosynthesis pathway, and the potassium Shaker-like channel subunit Kv1.1. We demonstrate that Kv1.1 and Dolk play critical roles in the spinal cord to regulate movement magnitude during the startle response and spontaneous swim movements. Moreover, we show that Kv1.1 protein is mislocalized in dolk mutants, suggesting they act in a common genetic pathway. Combined, our results identify a diverse set of eight genes, all associated with human disorders, that regulate zebrafish startle behavior and reveal a previously unappreciated role for Dolk and Kv1.1 in regulating movement magnitude via a common genetic pathway.
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Affiliation(s)
- Joy H. Meserve
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Jessica C. Nelson
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Kurt C. Marsden
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Jerry Hsu
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Fabio A. Echeverry
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Roshan A. Jain
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Marc A. Wolman
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Alberto E. Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Michael Granato
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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11
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Lasseigne AM, Echeverry FA, Ijaz S, Michel JC, Martin EA, Marsh AJ, Trujillo E, Marsden KC, Pereda AE, Miller AC. Electrical synaptic transmission requires a postsynaptic scaffolding protein. eLife 2021; 10:e66898. [PMID: 33908867 PMCID: PMC8081524 DOI: 10.7554/elife.66898] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 03/30/2021] [Indexed: 02/06/2023] Open
Abstract
Electrical synaptic transmission relies on neuronal gap junctions containing channels constructed by Connexins. While at chemical synapses neurotransmitter-gated ion channels are critically supported by scaffolding proteins, it is unknown if channels at electrical synapses require similar scaffold support. Here, we investigated the functional relationship between neuronal Connexins and Zonula Occludens 1 (ZO1), an intracellular scaffolding protein localized to electrical synapses. Using model electrical synapses in zebrafish Mauthner cells, we demonstrated that ZO1 is required for robust synaptic Connexin localization, but Connexins are dispensable for ZO1 localization. Disrupting this hierarchical ZO1/Connexin relationship abolishes electrical transmission and disrupts Mauthner cell-initiated escape responses. We found that ZO1 is asymmetrically localized exclusively postsynaptically at neuronal contacts where it functions to assemble intercellular channels. Thus, forming functional neuronal gap junctions requires a postsynaptic scaffolding protein. The critical function of a scaffolding molecule reveals an unanticipated complexity of molecular and functional organization at electrical synapses.
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Affiliation(s)
| | - Fabio A Echeverry
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of MedicineBronxUnited States
| | - Sundas Ijaz
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of MedicineBronxUnited States
| | | | - E Anne Martin
- Institute of Neuroscience, University of OregonEugeneUnited States
| | - Audrey J Marsh
- Institute of Neuroscience, University of OregonEugeneUnited States
| | - Elisa Trujillo
- Institute of Neuroscience, University of OregonEugeneUnited States
| | - Kurt C Marsden
- Department of Biological Sciences, NC State UniversityRaleighUnited States
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of MedicineBronxUnited States
| | - Adam C Miller
- Institute of Neuroscience, University of OregonEugeneUnited States
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12
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Brunal AA, Clark KC, Ma M, Woods IG, Pan YA. Effects of Constitutive and Acute Connexin 36 Deficiency on Brain-Wide Susceptibility to PTZ-Induced Neuronal Hyperactivity. Front Mol Neurosci 2021; 13:587978. [PMID: 33505244 PMCID: PMC7829467 DOI: 10.3389/fnmol.2020.587978] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 11/25/2020] [Indexed: 11/13/2022] Open
Abstract
Connexins are transmembrane proteins that form hemichannels allowing the exchange of molecules between the extracellular space and the cell interior. Two hemichannels from adjacent cells dock and form a continuous gap junction pore, thereby permitting direct intercellular communication. Connexin 36 (Cx36), expressed primarily in neurons, is involved in the synchronous activity of neurons and may play a role in aberrant synchronous firing, as seen in seizures. To understand the reciprocal interactions between Cx36 and seizure-like neural activity, we examined three questions: (a) does Cx36 deficiency affect seizure susceptibility, (b) does seizure-like activity affect Cx36 expression patterns, and (c) does acute blockade of Cx36 conductance increase seizure susceptibility. We utilize the zebrafish pentylenetetrazol [PTZ; a GABA(A) receptor antagonist] induced seizure model, taking advantage of the compact size and optical translucency of the larval zebrafish brain to assess how PTZ affects brain-wide neuronal activity and Cx36 protein expression. We exposed wild-type and genetic Cx36-deficient (cx35.5-/-) zebrafish larvae to PTZ and subsequently mapped neuronal activity across the whole brain, using phosphorylated extracellular-signal-regulated kinase (pERK) as a proxy for neuronal activity. We found that cx35.5-/- fish exhibited region-specific susceptibility and resistance to PTZ-induced hyperactivity compared to wild-type controls, suggesting that genetic Cx36 deficiency may affect seizure susceptibility in a region-specific manner. Regions that showed increased PTZ sensitivity include the dorsal telencephalon, which is implicated in human epilepsy, and the lateral hypothalamus, which has been underexplored. We also found that PTZ-induced neuronal hyperactivity resulted in a rapid reduction of Cx36 protein levels within 30 min. This Cx36 reduction persists after 1-h of recovery but recovered after 3–6 h. This acute downregulation of Cx36 by PTZ is likely maladaptive, as acute pharmacological blockade of Cx36 by mefloquine results in increased susceptibility to PTZ-induced neuronal hyperactivity. Together, these results demonstrate a reciprocal relationship between Cx36 and seizure-associated neuronal hyperactivity: Cx36 deficiency contributes region-specific susceptibility to neuronal hyperactivity, while neuronal hyperactivity-induced downregulation of Cx36 may increase the risk of future epileptic events.
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Affiliation(s)
- Alyssa A Brunal
- Center for Neurobiology Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Virginia Tech, Roanoke, VA, United States.,Translational Biology Medicine and Health Graduate Program, Virginia Tech, Blacksburg, VA, United States
| | - Kareem C Clark
- Center for Neurobiology Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Virginia Tech, Roanoke, VA, United States
| | - Manxiu Ma
- Center for Neurobiology Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Virginia Tech, Roanoke, VA, United States
| | - Ian G Woods
- Department of Biology, Ithaca College, Ithaca, NY, United States
| | - Y Albert Pan
- Center for Neurobiology Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Virginia Tech, Roanoke, VA, United States.,Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States.,Department of Psychiatry and Behavioral Medicine, Virginia Tech Carilion School of Medicine, Roanoke, VA, United States
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13
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Nelson JC, Witze E, Ma Z, Ciocco F, Frerotte A, Randlett O, Foskett JK, Granato M. Acute Regulation of Habituation Learning via Posttranslational Palmitoylation. Curr Biol 2020; 30:2729-2738.e4. [PMID: 32502414 PMCID: PMC8446937 DOI: 10.1016/j.cub.2020.05.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 01/06/2020] [Accepted: 05/05/2020] [Indexed: 12/16/2022]
Abstract
Habituation is an adaptive learning process that enables animals to adjust innate behaviors to changes in their environment. Despite its well-documented implications for a wide diversity of behaviors, the molecular and cellular basis of habituation learning is not well understood. Using whole-genome sequencing of zebrafish mutants isolated in an unbiased genetic screen, we identified the palmitoyltransferase Huntingtin interacting protein 14 (Hip14) as a critical regulator of habituation learning. We demonstrate that Hip14 regulates depression of sensory inputs onto an identified hindbrain neuron and provide evidence that Hip14 palmitoylates the Shaker-like K+ voltage-gated channel subunit (Kv1.1), thereby regulating Kv1.1 subcellular localization. Furthermore, we show that, like for Hip14, loss of Kv1.1 leads to habituation deficits and that Hip14 is dispensable in development and instead acts acutely to promote habituation. Combined, these results uncover a previously unappreciated role for acute posttranslational palmitoylation at defined circuit components to regulate learning.
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Affiliation(s)
- Jessica C Nelson
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, Philadelphia, PA 19104, USA
| | - Eric Witze
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, Philadelphia, PA 19104, USA
| | - Zhongming Ma
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 415 Curie Boulevard, Philadelphia, PA 19104, USA
| | - Francesca Ciocco
- Department of Biology, Haverford College, 370 Lancaster Avenue, Haverford, PA 19041, USA
| | - Abigaile Frerotte
- Department of Biology, Haverford College, 370 Lancaster Avenue, Haverford, PA 19041, USA
| | - Owen Randlett
- Institut NeuroMyoGène, Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U1217, Lyon 69008, France
| | - J Kevin Foskett
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 415 Curie Boulevard, Philadelphia, PA 19104, USA
| | - Michael Granato
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, Philadelphia, PA 19104, USA.
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14
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Martin EA, Lasseigne AM, Miller AC. Understanding the Molecular and Cell Biological Mechanisms of Electrical Synapse Formation. Front Neuroanat 2020; 14:12. [PMID: 32372919 PMCID: PMC7179694 DOI: 10.3389/fnana.2020.00012] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 03/09/2020] [Indexed: 12/20/2022] Open
Abstract
In this review article, we will describe the recent advances made towards understanding the molecular and cell biological mechanisms of electrical synapse formation. New evidence indicates that electrical synapses, which are gap junctions between neurons, can have complex molecular compositions including protein asymmetries across joined cells, diverse morphological arrangements, and overlooked similarities with other junctions, all of which indicate new potential roles in neurodevelopmental disease. Aquatic organisms, and in particular the vertebrate zebrafish, have proven to be excellent models for elucidating the molecular mechanisms of electrical synapse formation. Zebrafish will serve as our main exemplar throughout this review and will be compared with other model organisms. We highlight the known cell biological processes that build neuronal gap junctions and compare these with the assemblies of adherens junctions, tight junctions, non-neuronal gap junctions, and chemical synapses to explore the unknown frontiers remaining in our understanding of the critical and ubiquitous electrical synapse.
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Affiliation(s)
- E Anne Martin
- Department of Biology, Institute of Neuroscience, University of Oregon, Eugene, OR, United States
| | - Abagael M Lasseigne
- Department of Biology, Institute of Neuroscience, University of Oregon, Eugene, OR, United States
| | - Adam C Miller
- Department of Biology, Institute of Neuroscience, University of Oregon, Eugene, OR, United States
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15
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Marquart GD, Tabor KM, Bergeron SA, Briggman KL, Burgess HA. Prepontine non-giant neurons drive flexible escape behavior in zebrafish. PLoS Biol 2019; 17:e3000480. [PMID: 31613896 PMCID: PMC6793939 DOI: 10.1371/journal.pbio.3000480] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 09/10/2019] [Indexed: 11/18/2022] Open
Abstract
Many species execute ballistic escape reactions to avoid imminent danger. Despite fast reaction times, responses are often highly regulated, reflecting a trade-off between costly motor actions and perceived threat level. However, how sensory cues are integrated within premotor escape circuits remains poorly understood. Here, we show that in zebrafish, less precipitous threats elicit a delayed escape, characterized by flexible trajectories, which are driven by a cluster of 38 prepontine neurons that are completely separate from the fast escape pathway. Whereas neurons that initiate rapid escapes receive direct auditory input and drive motor neurons, input and output pathways for delayed escapes are indirect, facilitating integration of cross-modal sensory information. These results show that rapid decision-making in the escape system is enabled by parallel pathways for ballistic responses and flexible delayed actions and defines a neuronal substrate for hierarchical choice in the vertebrate nervous system.
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Affiliation(s)
- Gregory D. Marquart
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, United States of America
- Neuroscience and Cognitive Science Program, University of Maryland, Maryland, United States of America
| | - Kathryn M. Tabor
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, United States of America
| | - Sadie A. Bergeron
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, United States of America
| | - Kevin L. Briggman
- Circuit Dynamics and Connectivity Unit, National Institute of Neurological Disorders and Stroke, Bethesda, Maryland, United States of America
| | - Harold A. Burgess
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, United States of America
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16
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Marsden KC, Jain RA, Wolman MA, Echeverry FA, Nelson JC, Hayer KE, Miltenberg B, Pereda AE, Granato M. A Cyfip2-Dependent Excitatory Interneuron Pathway Establishes the Innate Startle Threshold. Cell Rep 2019; 23:878-887. [PMID: 29669291 PMCID: PMC6642828 DOI: 10.1016/j.celrep.2018.03.095] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 12/13/2017] [Accepted: 03/20/2018] [Indexed: 11/18/2022] Open
Abstract
Sensory experiences dynamically modify whether animals respond to a given stimulus, but it is unclear how innate behavioral thresholds are established. Here, we identify molecular and circuit-level mechanisms underlying the innate threshold of the zebrafish startle response. From a forward genetic screen, we isolated five mutant lines with reduced innate startle thresholds. Using whole-genome sequencing, we identify the causative mutation for one line to be in the fragile X mental retardation protein (FMRP)-interacting protein cyfip2. We show that cyfip2 acts independently of FMRP and that reactivation of cyfip2 restores the baseline threshold after phenotype onset. Finally, we show that cyfip2 regulates the innate startle threshold by reducing neural activity in a small group of excitatory hindbrain interneurons. Thus, we identify a selective set of genes critical to establishing an innate behavioral threshold and uncover a circuit-level role for cyfip2 in this process. Using forward genetics, electrophysiology, and combined behavior and Ca2+ imaging in zebrafish, Marsden et al. show that cyfip2 regulates the acoustic startle threshold by controlling the activity of excitatory spiral fiber interneurons.
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Affiliation(s)
- Kurt C Marsden
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, 1157 BRB II/III, 421 Curie Blvd., Philadelphia, PA 19104, USA; Department of Biological Sciences, W.M. Keck Center for Behavioral Biology, North Carolina State University, 127 David Clark Labs, 100 Brooks Ave., Raleigh, NC 27607, USA
| | - Roshan A Jain
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, 1157 BRB II/III, 421 Curie Blvd., Philadelphia, PA 19104, USA; Department of Biology, Haverford College, S108 Sharpless Hall, 370 Lancaster Ave., Haverford, PA 19041, USA
| | - Marc A Wolman
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, 1157 BRB II/III, 421 Curie Blvd., Philadelphia, PA 19104, USA; Department of Zoology, 213 Zoology Research Building, 1117 West Johnson St., University of Wisconsin, Madison, WI 53706, USA
| | - Fabio A Echeverry
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 431 Rose F. Kennedy Center, 1410 Pelham Parkway South, Bronx, NY 10461, USA
| | - Jessica C Nelson
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, 1157 BRB II/III, 421 Curie Blvd., Philadelphia, PA 19104, USA
| | - Katharina E Hayer
- Department of Biomedical and Health Informatics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Ben Miltenberg
- Department of Biology, Haverford College, S108 Sharpless Hall, 370 Lancaster Ave., Haverford, PA 19041, USA
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 431 Rose F. Kennedy Center, 1410 Pelham Parkway South, Bronx, NY 10461, USA
| | - Michael Granato
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, 1157 BRB II/III, 421 Curie Blvd., Philadelphia, PA 19104, USA.
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17
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Liu W, Kämpfe Nordström C, Danckwardt-Lillieström N, Rask-Andersen H. Human Inner Ear Immune Activity: A Super-Resolution Immunohistochemistry Study. Front Neurol 2019; 10:728. [PMID: 31354608 PMCID: PMC6635812 DOI: 10.3389/fneur.2019.00728] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 06/19/2019] [Indexed: 12/20/2022] Open
Abstract
Background: Like the brain, the human inner ear was long thought to be devoid of immune activity. Only the endolymphatic sac (ES) was known to be endowed with white blood cells that could process antigens and serve as an immunologic defense organ for the entire inner ear. Unexpectedly, the cochlear and vestibular organs, including the eighth cranial nerve, were recently shown to contain macrophages whose functions and implication in ear disease are somewhat undefined. Here, we review recent inner ear findings in man and extend the analyses to the vestibular nerve using super-resolution structured illumination microscopy (SR-SIM). Materials and Methods: Human ESs and cochleae were collected during surgery to treat patients with vestibular schwannoma and life-threatening petro-clival meningioma compressing the brainstem. The ESs and cochleae were placed in fixative, decalcified, and rapidly frozen and cryostat sectioned. Antibodies against ionized calcium-binding adaptor molecule 1-expressing cells (IBA1 cells), laminin β2 and type IV collagen TUJ1, cytokine fractalkine (CX3CL1), toll-like receptor 4 (TLR4), CD68, CD11b, CD4, CD8, the major histocompatibility complex type II (MHCII), and the microglial marker TEME119 were used. Results: IBA1-positive cells were present in the ESs, the cochlea, central and peripheral axons of the cochlear nerve, and the vestibular nerve trunk. IBA1 cells were found in the cochlear lateral wall, spiral limbus, and spiral ganglion. Notable variants of IBA1 cells adhered to neurons with “synapse-like” specializations and cytoplasmic projections. Slender IBA1 cells occasionally protracted into the basal lamina of the Schwann cells and had intimate contact with surrounding axons. Discussion: The human eighth nerve may be under the control of a well-developed macrophage cell system. A small number of CD4+ and CD8+ cells were found in the ES and occasionally in the cochlea, mostly located in the peripheral region of Rosenthal's canal. A neuro-immunologic axis may exist in the human inner ear that could play a role in the protection of the auditory nerve. The implication of the macrophage system during disease, surgical interventions, and cell-based transplantation should be further explored.
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Affiliation(s)
- Wei Liu
- Section of Otolaryngology, Department of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden
| | - Charlotta Kämpfe Nordström
- Section of Otolaryngology, Department of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden
| | | | - Helge Rask-Andersen
- Section of Otolaryngology, Department of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden
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18
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Tabor KM, Smith TS, Brown M, Bergeron SA, Briggman KL, Burgess HA. Presynaptic Inhibition Selectively Gates Auditory Transmission to the Brainstem Startle Circuit. Curr Biol 2018; 28:2527-2535.e8. [PMID: 30078569 DOI: 10.1016/j.cub.2018.06.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 06/11/2018] [Accepted: 06/12/2018] [Indexed: 12/25/2022]
Abstract
Filtering mechanisms prevent a continuous stream of sensory information from swamping perception, leading to diminished focal attention and cognitive processing. Mechanisms for sensory gating are commonly studied using prepulse inhibition, a paradigm that measures the regulated transmission of auditory information to the startle circuit; however, the underlying neuronal pathways are unresolved. Using large-scale calcium imaging, optogenetics, and laser ablations, we reveal a cluster of 30 morphologically identified neurons in zebrafish that suppress the transmission of auditory signals during prepulse inhibition. These neurons project to a key sensorimotor interface in the startle circuit-the termination zone of auditory afferents on the dendrite of a startle command neuron. Direct measurement of auditory nerve neurotransmitter release revealed selective presynaptic inhibition of sensory transmission to the startle circuit, sparing signaling to other brain regions. Our results provide the first cellular resolution circuit for prepulse inhibition in a vertebrate, revealing a central role for presynaptic gating of sensory information to a brainstem motor circuit.
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Affiliation(s)
- Kathryn M Tabor
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA.
| | - Trevor S Smith
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Mary Brown
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Sadie A Bergeron
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | - Kevin L Briggman
- Circuit Dynamics and Connectivity Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Harold A Burgess
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA.
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19
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Marsh AJ, Michel JC, Adke AP, Heckman EL, Miller AC. Asymmetry of an Intracellular Scaffold at Vertebrate Electrical Synapses. Curr Biol 2017; 27:3561-3567.e4. [PMID: 29103941 PMCID: PMC5698123 DOI: 10.1016/j.cub.2017.10.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 09/27/2017] [Accepted: 10/03/2017] [Indexed: 12/25/2022]
Abstract
Neuronal synaptic connections are either chemical or electrical, and these two types of synapses work together to dynamically define neural circuit function [1]. Although we know a great deal about the molecules that support chemical synapse formation and function, we know little about the macromolecular complexes that regulate electrical synapses. Electrical synapses are created by gap junction (GJ) channels that provide direct ionic communication between neurons [2]. Although they are often molecularly and functionally symmetric, recent work has found that pre- and postsynaptic neurons can contribute different GJ-forming proteins, creating molecularly asymmetric channels that are correlated with functional asymmetry at the synapse [3, 4]. Associated with the GJs are structures observed by electron microscopy termed the electrical synapse density (ESD) [5]. The ESD has been suggested to be critical for the formation and function of the electrical synapse, yet the biochemical makeup of these structures is poorly understood. Here we find that electrical synapse formation in vivo requires an intracellular scaffold called Tight Junction Protein 1b (Tjp1b). Tjp1b is localized to the electrical synapse, where it is required for the stabilization of the GJs and for electrical synapse function. Strikingly, we find that Tjp1b protein localizes and functions asymmetrically, exclusively on the postsynaptic side of the synapse. Our findings support a novel model of electrical synapse molecular asymmetry at the level of an intracellular scaffold that is required for building the electrical synapse. We propose that such ESD asymmetries could be used by all nervous systems to support molecular and functional asymmetries at electrical synapses.
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Affiliation(s)
- Audrey J Marsh
- University of Oregon, Institute of Neuroscience, Department of Biology, 1254 University of Oregon, Eugene, OR 97403, USA
| | - Jennifer Carlisle Michel
- University of Oregon, Institute of Neuroscience, Department of Biology, 1254 University of Oregon, Eugene, OR 97403, USA
| | - Anisha P Adke
- University of Oregon, Institute of Neuroscience, Department of Biology, 1254 University of Oregon, Eugene, OR 97403, USA
| | - Emily L Heckman
- University of Oregon, Institute of Neuroscience, Department of Biology, 1254 University of Oregon, Eugene, OR 97403, USA
| | - Adam C Miller
- University of Oregon, Institute of Neuroscience, Department of Biology, 1254 University of Oregon, Eugene, OR 97403, USA.
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20
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Takahashi M, Inoue M, Tanimoto M, Kohashi T, Oda Y. Short-term desensitization of fast escape behavior associated with suppression of Mauthner cell activity in larval zebrafish. Neurosci Res 2017; 121:29-36. [DOI: 10.1016/j.neures.2017.03.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 03/13/2017] [Accepted: 03/21/2017] [Indexed: 01/12/2023]
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21
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Miller AC, Whitebirch AC, Shah AN, Marsden KC, Granato M, O'Brien J, Moens CB. A genetic basis for molecular asymmetry at vertebrate electrical synapses. eLife 2017; 6. [PMID: 28530549 PMCID: PMC5462537 DOI: 10.7554/elife.25364] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 05/20/2017] [Indexed: 01/18/2023] Open
Abstract
Neural network function is based upon the patterns and types of connections made between neurons. Neuronal synapses are adhesions specialized for communication and they come in two types, chemical and electrical. Communication at chemical synapses occurs via neurotransmitter release whereas electrical synapses utilize gap junctions for direct ionic and metabolic coupling. Electrical synapses are often viewed as symmetrical structures, with the same components making both sides of the gap junction. By contrast, we show that a broad set of electrical synapses in zebrafish, Danio rerio, require two gap-junction-forming Connexins for formation and function. We find that one Connexin functions presynaptically while the other functions postsynaptically in forming the channels. We also show that these synapses are required for the speed and coordination of escape responses. Our data identify a genetic basis for molecular asymmetry at vertebrate electrical synapses and show they are required for appropriate behavioral performance. DOI:http://dx.doi.org/10.7554/eLife.25364.001
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Affiliation(s)
- Adam C Miller
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Alex C Whitebirch
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Arish N Shah
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Kurt C Marsden
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, United States
| | - Michael Granato
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, United States
| | - John O'Brien
- Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas Health Sciences Center at Houston, Houston, United States
| | - Cecilia B Moens
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States
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22
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Troconis EL, Ordoobadi AJ, Sommers TF, Aziz‐Bose R, Carter AR, Trapani JG. Intensity-dependent timing and precision of startle response latency in larval zebrafish. J Physiol 2017; 595:265-282. [PMID: 27228964 PMCID: PMC5199724 DOI: 10.1113/jp272466] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 05/17/2016] [Indexed: 01/12/2023] Open
Abstract
KEY POINTS Using high-speed videos time-locked with whole-animal electrical recordings, simultaneous measurement of behavioural kinematics and field potential parameters of C-start startle responses allowed for discrimination between short-latency and long-latency C-starts (SLCs vs. LLCs) in larval zebrafish. Apart from their latencies, SLC kinematics and SLC field potential parameters were intensity independent. Increasing stimulus intensity increased the probability of evoking an SLC and decreased mean SLC latencies while increasing their precision; subtraction of field potential latencies from SLC latencies revealed a fixed time delay between the two measurements that was intensity independent. The latency and the precision in the latency of the SLC field potentials were linearly correlated to the latencies and precision of the first evoked action potentials (spikes) in hair-cell afferent neurons of the lateral line. Together, these findings indicate that first spike latency (FSL) is a fast encoding mechanism that can serve to precisely initiate startle responses when speed is critical for survival. ABSTRACT Vertebrates rely on fast sensory encoding for rapid and precise initiation of startle responses. In afferent sensory neurons, trains of action potentials (spikes) encode stimulus intensity within the onset time of the first evoked spike (first spike latency; FSL) and the number of evoked spikes. For speed of initiation of startle responses, FSL would be the more advantageous mechanism to encode the intensity of a threat. However, the intensity dependence of FSL and spike number and whether either determines the precision of startle response initiation is not known. Here, we examined short-latency startle responses (SLCs) in larval zebrafish and tested the hypothesis that first spike latencies and their precision (jitter) determine the onset time and precision of SLCs. We evoked startle responses via activation of Channelrhodopsin (ChR2) expressed in ear and lateral line hair cells and acquired high-speed videos of head-fixed larvae while simultaneously recording underlying field potentials. This method allowed for discrimination between primary SLCs and less frequent, long-latency startle responses (LLCs). Quantification of SLC kinematics and field potential parameters revealed that, apart from their latencies, they were intensity independent. We found that increasing stimulus intensity decreased SLC latencies while increasing their precision, which was significantly correlated with corresponding changes in field potential latencies and their precision. Single afferent neuron recordings from the lateral line revealed a similar intensity-dependent decrease in first spike latencies and their jitter, which could account for the intensity-dependent changes in timing and precision of startle response latencies.
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Affiliation(s)
| | | | | | | | - Ashley R. Carter
- Department of Physics and AstronomyAmherst CollegeAmherstMA01002USA
| | - Josef G. Trapani
- Department of BiologyAmherst CollegeAmherstMA01002USA
- Neuroscience ProgramAmherst CollegeAmherstMA01002USA
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23
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Liu Z, Ciarleglio CM, Hamodi AS, Aizenman CD, Pratt KG. A population of gap junction-coupled neurons drives recurrent network activity in a developing visual circuit. J Neurophysiol 2016; 115:1477-86. [PMID: 26763780 DOI: 10.1152/jn.01046.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 01/08/2016] [Indexed: 01/04/2023] Open
Abstract
In many regions of the vertebrate brain, microcircuits generate local recurrent activity that aids in the processing and encoding of incoming afferent inputs. Local recurrent activity can amplify, filter, and temporally and spatially parse out incoming input. Determining how these microcircuits function is of great interest because it provides glimpses into fundamental processes underlying brain computation. Within the Xenopus tadpole optic tectum, deep layer neurons display robust recurrent activity. Although the development and plasticity of this local recurrent activity has been well described, the underlying microcircuitry is not well understood. Here, using a whole brain preparation that allows for whole cell recording from neurons of the superficial tectal layers, we identified a physiologically distinct population of excitatory neurons that are gap junctionally coupled and through this coupling gate local recurrent network activity. Our findings provide a novel role for neuronal coupling among excitatory interneurons in the temporal processing of visual stimuli.
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Affiliation(s)
- Zhenyu Liu
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming; and
| | | | - Ali S Hamodi
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming; and
| | - Carlos D Aizenman
- Department of Neuroscience, Brown University, Providence, Rhode Island
| | - Kara G Pratt
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming; and
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24
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Marsden KC, Granato M. In Vivo Ca(2+) Imaging Reveals that Decreased Dendritic Excitability Drives Startle Habituation. Cell Rep 2015; 13:1733-40. [PMID: 26655893 DOI: 10.1016/j.celrep.2015.10.060] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 09/15/2015] [Accepted: 10/20/2015] [Indexed: 01/12/2023] Open
Abstract
Exposure to repetitive startling stimuli induces habitation, a simple form of learning. Despite its simplicity, the precise cellular mechanisms by which repeated stimulation converts a robust behavioral response to behavioral indifference are unclear. Here, we use head-restrained zebrafish larvae to monitor subcellular Ca(2+) dynamics in Mauthner neurons, the startle command neurons, during startle habituation in vivo. Using the Ca(2+) reporter GCaMP6s, we find that the amplitude of Ca(2+) signals in the lateral dendrite of the Mauthner neuron determines startle probability and that depression of this dendritic activity rather than downstream inhibition mediates glycine and N-methyl-D-aspartate (NMDA)-receptor-dependent short-term habituation. Combined, our results suggest a model for habituation learning in which increased inhibitory drive from feedforward inhibitory neurons combined with decreased excitatory input from auditory afferents decreases dendritic and Mauthner neuron excitability.
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Affiliation(s)
- Kurt C Marsden
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Michael Granato
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
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25
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Roy B, Ahmed KT, Cunningham ME, Ferdous J, Mukherjee R, Zheng W, Chen XZ, Ali DW. Zebrafish TARP Cacng2 is required for the expression and normal development of AMPA receptors at excitatory synapses. Dev Neurobiol 2015; 76:487-506. [PMID: 26178704 DOI: 10.1002/dneu.22327] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 07/01/2015] [Accepted: 07/14/2015] [Indexed: 01/03/2023]
Abstract
Fast excitatory synaptic transmission in the CNS is mediated by the neurotransmitter glutamate, binding to and activating AMPA receptors (AMPARs). AMPARs are known to interact with auxiliary proteins that modulate their behavior. One such family of proteins is the transmembrane AMPA receptor-related proteins, known as TARPs. Little is known about the role of TARPs during development, or about their function in non-mammalian organisms. Here we report the presence of TARPs, specifically the prototypical TARP, stargazin, in developing zebrafish. We find that zebrafish express two forms of stargazin, Cacng2a and Cacng2b from as early as 12-h post fertilization (hpf). Knockdown of Cacng2a and Cacng2b via splice-blocking morpholinos resulted in embryos that exhibited deficits in C-start escape responses, showing reduced C-bend angles, smaller tail velocities and aberrant C-bend turning directions. Injection of the morphants with Cacng2a or 2b mRNA rescued the morphological phenotype and the synaptic deficits. To investigate the effect of reduced Cacng2a and 2b levels on synaptic physiology, we performed whole cell patch clamp recordings of AMPA mEPSCs from zebrafish Mauthner cells. Knockdown of Cacng2a results in reduced AMPA currents and lower mEPSC frequencies, whereas knockdown of Cacng2b displayed no significant change in mEPSC amplitude or frequency. Non-stationary fluctuation analysis confirmed a reduction in the number of active synaptic receptors in the Cacng2a but not in the Cacng2b morphants. Together, these results suggest that Cacng2a is required for normal trafficking and function of synaptic AMPARs, while Cacng2b is largely non-functional with respect to the development of AMPA synaptic transmission.
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Affiliation(s)
- Birbickram Roy
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9
| | - Kazi T Ahmed
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9
| | - Marcus E Cunningham
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9
| | - Jannatul Ferdous
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9
| | - Rajarshi Mukherjee
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9
| | - Wang Zheng
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada, T6G 2H7
| | - Xing-Zhen Chen
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada, T6G 2H7
| | - Declan W Ali
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.,Department of Physiology, University of Alberta, Edmonton, Alberta, Canada, T6G 2H7.,Centre for Neuroscience, University of Alberta, Edmonton, Alberta, Canada, T6G 2E1
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26
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Heterotypic gap junctions at glutamatergic mixed synapses are abundant in goldfish brain. Neuroscience 2014; 285:166-93. [PMID: 25451276 DOI: 10.1016/j.neuroscience.2014.10.057] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 10/28/2014] [Accepted: 10/29/2014] [Indexed: 11/22/2022]
Abstract
Gap junctions provide for direct intercellular electrical and metabolic coupling. The abundance of gap junctions at "large myelinated club ending (LMCE)" synapses on Mauthner cells (M-cells) of the teleost brain provided a convenient model to correlate anatomical and physiological properties of electrical synapses. There, presynaptic action potentials were found to evoke short-latency electrical "pre-potentials" immediately preceding their accompanying glutamate-induced depolarizations, making these the first unambiguously identified "mixed" (i.e., chemical plus electrical) synapses in the vertebrate CNS. We recently showed that gap junctions at these synapses exhibit asymmetric electrical resistance (i.e., electrical rectification), which we correlated with total molecular asymmetry of connexin composition in their apposing gap junction hemiplaques, with connexin35 (Cx35) restricted to axon terminal hemiplaques and connexin34.7 (Cx34.7) restricted to apposing M-cell plasma membranes. We now show that similarly heterotypic neuronal gap junctions are abundant throughout goldfish brain, with labeling exclusively for Cx35 in presynaptic hemiplaques and exclusively for Cx34.7 in postsynaptic hemiplaques. Moreover, the vast majority of these asymmetric gap junctions occur at glutamatergic axon terminals. The widespread distribution of heterotypic gap junctions at glutamatergic mixed synapses throughout goldfish brain and spinal cord implies that pre- vs. postsynaptic asymmetry at electrical synapses evolved early in the chordate lineage. We propose that the advantages of the molecular and functional asymmetry of connexins at electrical synapses that are so prominently expressed in the teleost CNS are unlikely to have been abandoned in higher vertebrates. However, to create asymmetric coupling in mammals, where most gap junctions are composed of connexin36 (Cx36) on both sides, would require some other mechanism, such as differential phosphorylation of connexins on opposite sides of the same gap junction or on asymmetric differences in the complement of their scaffolding and regulatory proteins.
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