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Pfeiffer P, Barreda Tomás FJ, Wu J, Schleimer JH, Vida I, Schreiber S. A dynamic clamp protocol to artificially modify cell capacitance. eLife 2022; 11:75517. [PMID: 35362411 PMCID: PMC9135398 DOI: 10.7554/elife.75517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 03/17/2022] [Indexed: 11/13/2022] Open
Abstract
Dynamics of excitable cells and networks depend on the membrane time constant, set by membrane resistance and capacitance. Whereas pharmacological and genetic manipulations of ionic conductances of excitable membranes are routine in electrophysiology, experimental control over capacitance remains a challenge. Here, we present capacitance clamp, an approach that allows electrophysiologists to mimic a modified capacitance in biological neurons via an unconventional application of the dynamic clamp technique. We first demonstrate the feasibility to quantitatively modulate capacitance in a mathematical neuron model and then confirm the functionality of capacitance clamp in in vitro experiments in granule cells of rodent dentate gyrus with up to threefold virtual capacitance changes. Clamping of capacitance thus constitutes a novel technique to probe and decipher mechanisms of neuronal signaling in ways that were so far inaccessible to experimental electrophysiology.
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Affiliation(s)
- Paul Pfeiffer
- Institute for Theoretical Biology, Department of Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | | | - Jiameng Wu
- Institute for Integrative Neuroanatomy, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jan-Hendrik Schleimer
- Institute of Theoretical Biology, Department of Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Imre Vida
- Institute for Integrative Neuroanatomy, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Susanne Schreiber
- Institute of Theoretical Biology, Department of Biology, Humboldt-Universität zu Berlin, Berlin, Germany
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2
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Velasco B, Mohamed E, Sato-Bigbee C. Endogenous and exogenous opioid effects on oligodendrocyte biology and developmental brain myelination. Neurotoxicol Teratol 2021; 86:107002. [PMID: 34126203 DOI: 10.1016/j.ntt.2021.107002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 05/26/2021] [Accepted: 06/09/2021] [Indexed: 12/27/2022]
Abstract
The elevated presence of opioid receptors and their ligands throughout the developing brain points to the existence of maturational functions of the endogenous opioid system that still remain poorly understood. The alarmingly increasing rates of opioid use and abuse underscore the urgent need for clear identification of those functions and the cellular bases and molecular mechanisms underlying their physiological roles under normal and pathological conditions. This review is focused on current knowledge on the direct and indirect regulatory roles that opioids may have on oligodendrocyte development and their generation of myelin, a complex insulating membrane that not only facilitates rapid impulse conduction but also participates in mechanisms of brain plasticity and adaptation. Information is examined in relation to the importance of endogenous opioid function, as well as direct and indirect effects of opioid analogues, which like methadone and buprenorphine are used in medication-assisted therapies for opioid addiction during pregnancy and pharmacotherapy in neonatal abstinence syndrome. Potential opioid effects are also discussed regarding late myelination of the brain prefrontal cortex in adolescents and young adults. Such knowledge is fundamental for the design of safer pharmacological interventions for opioid abuse, minimizing deleterious effects in the developing nervous system.
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Affiliation(s)
- Brandon Velasco
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA
| | - Esraa Mohamed
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA
| | - Carmen Sato-Bigbee
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA.
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3
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Zbili M, Debanne D. Myelination Increases the Spatial Extent of Analog-Digital Modulation of Synaptic Transmission: A Modeling Study. Front Cell Neurosci 2020; 14:40. [PMID: 32194377 PMCID: PMC7063086 DOI: 10.3389/fncel.2020.00040] [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: 08/26/2019] [Accepted: 02/10/2020] [Indexed: 12/31/2022] Open
Abstract
Analog-digital facilitations (ADFs) have been described in local excitatory brain circuits and correspond to a class of phenomena describing how subthreshold variations of the presynaptic membrane potential influence spike-evoked synaptic transmission. In many brain circuits, ADFs rely on the propagation of somatic membrane potential fluctuations to the presynaptic bouton where they modulate ion channels availability, inducing modifications of the presynaptic spike waveform, the spike-evoked Ca2+ entry, and the transmitter release. Therefore, one major requirement for ADFs to occur is the propagation of subthreshold membrane potential variations from the soma to the presynaptic bouton. To date, reported ADFs space constants are relatively short (250–500 μm) which limits their action to proximal synapses. However, ADFs have been studied either in unmyelinated axons or in juvenile animals in which myelination is incomplete. We examined here the potential gain of ADFs spatial extent caused by myelination using a realistic model of L5 pyramidal cell. Myelination of the axon was found to induce a 3-fold increase in the axonal length constant. As a result, the different forms of ADF were found to display a much longer spatial extent (up to 3,000 μm). In addition, while the internodal length displayed a mild effect, the number of myelin wraps ensheathing the internodes was found to play a critical role in the ADFs spatial extents. We conclude that axonal myelination induces an increase in ADFs spatial extent in our model, thus making ADFs plausible in long-distance connections.
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Affiliation(s)
- Mickaël Zbili
- Lyon Neuroscience Research Center, INSERM U1028-CNRS UMR5292-Université Claude Bernard Lyon1, Lyon, France.,UNIS UMR 1072 INSERM, AMU, Marseille, France
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4
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Eshed-Eisenbach Y, Peles E. The clustering of voltage-gated sodium channels in various excitable membranes. Dev Neurobiol 2020; 81:427-437. [PMID: 31859465 DOI: 10.1002/dneu.22728] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 11/27/2019] [Accepted: 12/16/2019] [Indexed: 01/19/2023]
Abstract
In excitable membranes, the clustering of voltage-gated sodium channels (VGSC) serves to enhance excitability at critical sites. The two most profoundly studied sites of channel clustering are the axon initial segment, where action potentials are generated and the node of Ranvier, where action potentials propagate along myelinated axons. The clustering of VGSC is found, however, in other highly excitable sites such as axonal terminals, postsynaptic membranes of dendrites and muscle fibers, and pre-myelinated axons. In this review, different examples of axonal as well as non-axonal clustering of VGSC are discussed and the underlying mechanisms are compared. Whether the clustering of channels is intrinsically or extrinsically induced, it depends on the submembranous actin-based cytoskeleton that organizes these highly specialized membrane microdomains through specific adaptor proteins.
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Affiliation(s)
- Yael Eshed-Eisenbach
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot, Israel
| | - Elior Peles
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot, Israel
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5
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Kanda H, Ling J, Tonomura S, Noguchi K, Matalon S, Gu JG. TREK-1 and TRAAK Are Principal K + Channels at the Nodes of Ranvier for Rapid Action Potential Conduction on Mammalian Myelinated Afferent Nerves. Neuron 2019; 104:960-971.e7. [PMID: 31630908 DOI: 10.1016/j.neuron.2019.08.042] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 07/30/2019] [Accepted: 08/27/2019] [Indexed: 12/22/2022]
Abstract
Rapid conduction of nerve impulses is critical in life and relies on action potential (AP) leaps through the nodes of Ranvier (NRs) along myelinated nerves. While NRs are the only sites where APs can be regenerated during nerve conduction on myelinated nerves, ion channel mechanisms underlying the regeneration and conduction of APs at mammalian NRs remain incompletely understood. Here, we show that TREK-1 and TRAAK, the thermosensitive and mechanosensitive two-pore-domain potassium (K2P) channels, are clustered at NRs of rat trigeminal Aβ-afferent nerves with a density over 3,000-fold higher than that on their somas. These K2P channels, but not voltage-gated K+ channels as in other parts of nerves, are required for rapid AP repolarization at the NRs. Furthermore, these channels permit high-speed and high-frequency AP conduction along the myelinated afferent nerves, and loss of function of these channels at NRs retards nerve conduction and impairs sensory behavioral responses in animals.
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Affiliation(s)
- Hirosato Kanda
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Jennifer Ling
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Sotatsu Tonomura
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Koichi Noguchi
- Department of Anatomy and Neuroscience, Hyogo College of Medicine, Nishinomiya, Hyogo 663-8501, Japan
| | - Sadis Matalon
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Jianguo G Gu
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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6
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Abstract
Axons functionally link the somato-dendritic compartment to synaptic terminals. Structurally and functionally diverse, they accomplish a central role in determining the delays and reliability with which neuronal ensembles communicate. By combining their active and passive biophysical properties, they ensure a plethora of physiological computations. In this review, we revisit the biophysics of generation and propagation of electrical signals in the axon and their dynamics. We further place the computational abilities of axons in the context of intracellular and intercellular coupling. We discuss how, by means of sophisticated biophysical mechanisms, axons expand the repertoire of axonal computation, and thereby, of neural computation.
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Affiliation(s)
- Pepe Alcami
- Division of Neurobiology, Department of Biology II, Ludwig-Maximilians-Universitaet Muenchen, Martinsried, Germany
- Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany
| | - Ahmed El Hady
- Princeton Neuroscience Institute, Princeton University, Princeton, NJ, United States
- Howard Hughes Medical Institute, Princeton University, Princeton, NJ, United States
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7
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Mitew S, Gobius I, Fenlon LR, McDougall SJ, Hawkes D, Xing YL, Bujalka H, Gundlach AL, Richards LJ, Kilpatrick TJ, Merson TD, Emery B. Pharmacogenetic stimulation of neuronal activity increases myelination in an axon-specific manner. Nat Commun 2018; 9:306. [PMID: 29358753 PMCID: PMC5778130 DOI: 10.1038/s41467-017-02719-2] [Citation(s) in RCA: 195] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 12/19/2017] [Indexed: 11/09/2022] Open
Abstract
Mounting evidence suggests that neuronal activity influences myelination, potentially allowing for experience-driven modulation of neural circuitry. The degree to which neuronal activity is capable of regulating myelination at the individual axon level is unclear. Here we demonstrate that stimulation of somatosensory axons in the mouse brain increases proliferation and differentiation of oligodendrocyte progenitor cells (OPCs) within the underlying white matter. Stimulated axons display an increased probability of being myelinated compared to neighboring non-stimulated axons, in addition to being ensheathed with thicker myelin. Conversely, attenuating neuronal firing reduces axonal myelination in a selective activity-dependent manner. Our findings reveal that the process of selecting axons for myelination is strongly influenced by the relative activity of individual axons within a population. These observed cellular changes are consistent with the emerging concept that adaptive myelination is a key mechanism for the fine-tuning of neuronal circuitry in the mammalian CNS.
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Affiliation(s)
- Stanislaw Mitew
- The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, 3052, Australia.,Department of Anatomy & Neuroscience, The University of Melbourne, Parkville, VIC, 3010, Australia.,Australian Regenerative Medicine Institute, Monash University, Clayton, VIC, 3800, Australia
| | - Ilan Gobius
- Queensland Brain Institute, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Laura R Fenlon
- Queensland Brain Institute, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Stuart J McDougall
- The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, 3052, Australia
| | - David Hawkes
- The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, 3052, Australia.,Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Yao Lulu Xing
- The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, 3052, Australia.,Australian Regenerative Medicine Institute, Monash University, Clayton, VIC, 3800, Australia
| | - Helena Bujalka
- Department of Anatomy & Neuroscience, The University of Melbourne, Parkville, VIC, 3010, Australia.,Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Andrew L Gundlach
- The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, 3052, Australia.,Florey Department of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Linda J Richards
- Queensland Brain Institute, The University of Queensland, St Lucia, QLD, 4072, Australia.,Schools of Biomedical Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Trevor J Kilpatrick
- The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, 3052, Australia.,Melbourne Neuroscience Institute, The University of Melbourne, Parkville, VIC, 3010, Australia
| | - Tobias D Merson
- The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, 3052, Australia. .,Australian Regenerative Medicine Institute, Monash University, Clayton, VIC, 3800, Australia. .,Florey Department of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC, 3010, Australia.
| | - Ben Emery
- The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, 3052, Australia. .,Department of Anatomy & Neuroscience, The University of Melbourne, Parkville, VIC, 3010, Australia. .,Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health and Science University, Portland, OR, 97239, USA.
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8
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Daneshi Kohan E, Lashkari BS, Sparrey CJ. The effects of paranodal myelin damage on action potential depend on axonal structure. Med Biol Eng Comput 2017; 56:395-411. [PMID: 28770425 DOI: 10.1007/s11517-017-1691-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 07/17/2017] [Indexed: 12/31/2022]
Abstract
Biophysical computational models of axons provide an important tool for quantifying the effects of injury and disease on signal conduction characteristics. Several studies have used generic models to study the average behavior of healthy and injured axons; however, few studies have included the effects of normal structural variation on the simulated axon's response to injury. The effects of variations in physiological characteristics on axonal function were mapped by altering the structure of the nodal, paranodal, and juxtaparanodal regions across reported values in three different caliber axons (1, 2, and 5.7 μm). Myelin detachment and retraction were simulated to quantify the effects of each injury mechanism on signal conduction. Conduction velocity was most affected by axonal fiber diameter (89%), while membrane potential amplitude was most affected by nodal length (86%) in healthy axons. Postinjury axonal functionality was most affected by myelin detachment in the paranodal and juxtaparanodal regions when retraction and detachment were modeled simultaneously. The efficacy of simulated potassium channel blockers on restoring membrane potential and velocity varied with axonal caliber and injury type. The structural characteristics of axons affect their functional response to myelin retraction and detachment and their subsequent response to potassium channel blocker treatment.
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Affiliation(s)
- Ehsan Daneshi Kohan
- Mechatronic Systems Engineering, Simon Fraser University, 250-13450 102 Avenue, Surrey, BC, V3T 0A3, Canada.,International Collaboration on Repair Discoveries (ICORD), Faculty of Medicine, University of British Columbia, 5th floor, 5200, 818 West 10th Avenue, Vancouver, BC, V5Z 1M9, Canada
| | - Behnia Shadab Lashkari
- International Collaboration on Repair Discoveries (ICORD), Faculty of Medicine, University of British Columbia, 5th floor, 5200, 818 West 10th Avenue, Vancouver, BC, V5Z 1M9, Canada
| | - Carolyn Jennifer Sparrey
- Mechatronic Systems Engineering, Simon Fraser University, 250-13450 102 Avenue, Surrey, BC, V3T 0A3, Canada. .,International Collaboration on Repair Discoveries (ICORD), Faculty of Medicine, University of British Columbia, 5th floor, 5200, 818 West 10th Avenue, Vancouver, BC, V5Z 1M9, Canada.
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9
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Myelin structure in unfixed, single nerve fibers: Scanning X-ray microdiffraction with a beam size of 200nm. J Struct Biol 2017; 200:229-243. [PMID: 28698109 DOI: 10.1016/j.jsb.2017.07.001] [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: 04/25/2017] [Revised: 06/27/2017] [Accepted: 07/07/2017] [Indexed: 11/21/2022]
Abstract
Previous raster-scanning with a 1μm X-ray beam of individual, myelinated fibers from glutaraldehyde-fixed rat sciatic nerve revealed a spatially-dependent variation in the diffraction patterns from single fibers. Analysis indicated differences in the myelin periodicity, membrane separations, distribution of proteins, and orientation of membrane lamellae. As chemical fixation is known to produce structural artifacts, we sought to determine in the current study whether the structural heterogeneity is intrinsic to unfixed myelin. Using a 200nm-beam that was about five-fold smaller than before, we raster-scanned individual myelinated fibers from both the peripheral (PNS; mouse and rat sciatic nerves) and central (CNS; rat corpus callosum) nervous systems. As expected, the membrane stacking in the internodal region was nearly parallel to the fiber axis and in the paranodal region it was perpendicular to the axis. A myelin lattice was also frequently observed when the incident beam was injected en face to the sheath. Myelin periodicity and diffracted intensity varied with axial position along the fiber, as did the calculated membrane profiles. Raster-scanning with an X-ray beam at sub-micron resolution revealed for the first time that the individual myelin sheaths in unfixed nerve are heterogeneous in both membrane structure and packing.
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10
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Evolution of rapid nerve conduction. Brain Res 2016; 1641:11-33. [PMID: 26879248 DOI: 10.1016/j.brainres.2016.02.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 02/04/2016] [Accepted: 02/05/2016] [Indexed: 01/29/2023]
Abstract
Rapid conduction of nerve impulses is a priority for organisms needing to react quickly to events in their environment. While myelin may be viewed as the crowning innovation bringing about rapid conduction, the evolution of rapid communication mechanisms, including those refined and enhanced in the evolution of myelin, has much deeper roots. In this review, a sequence is traced starting with diffusional communication, followed by transport-facilitated communication, the rise of electrical signaling modalities, the invention of voltage-gated channels and "all-or-none" impulses, the emergence of elongate nerve axons specialized for communication and their fine-tuning to enhance impulse conduction speeds. Finally within the evolution of myelin itself, several innovations have arisen and have been interactively refined for speed enhancement, including the addition and sealing of layers, their limitation by space availability, and the optimization of key parameters: channel density, lengths of exposed nodes and lengths of internodes. We finish by suggesting several design principles that appear to govern the evolution of rapid conduction. This article is part of a Special Issue entitled SI: Myelin Evolution.
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11
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Tomassy GS, Dershowitz LB, Arlotta P. Diversity Matters: A Revised Guide to Myelination. Trends Cell Biol 2016; 26:135-147. [PMID: 26442841 PMCID: PMC4727993 DOI: 10.1016/j.tcb.2015.09.002] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/28/2015] [Accepted: 09/01/2015] [Indexed: 11/28/2022]
Abstract
The evolutionary success of the vertebrate nervous system is largely due to a unique structural feature--the myelin sheath, a fatty envelope that surrounds the axons of neurons. By increasing the speed by which electrical signals travel along axons, myelin facilitates neuronal communication between distant regions of the nervous system. We review the cellular and molecular mechanisms that regulate the development of myelin as well as its homeostasis in adulthood. We discuss how finely tuned neuron-oligodendrocyte interactions are central to myelin formation during development and in the adult, and how these interactions can have profound implications for the plasticity of the adult brain. We also speculate how the functional diversity of both neurons and oligodendrocytes may impact on the myelination process in both health and disease.
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Affiliation(s)
- Giulio Srubek Tomassy
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA.
| | - Lori Bowe Dershowitz
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA
| | - Paola Arlotta
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA.
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12
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Freeman SA, Desmazières A, Fricker D, Lubetzki C, Sol-Foulon N. Mechanisms of sodium channel clustering and its influence on axonal impulse conduction. Cell Mol Life Sci 2016; 73:723-35. [PMID: 26514731 PMCID: PMC4735253 DOI: 10.1007/s00018-015-2081-1] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 10/21/2015] [Accepted: 10/22/2015] [Indexed: 12/16/2022]
Abstract
The efficient propagation of action potentials along nervous fibers is necessary for animals to interact with the environment with timeliness and precision. Myelination of axons is an essential step to ensure fast action potential propagation by saltatory conduction, a process that requires highly concentrated voltage-gated sodium channels at the nodes of Ranvier. Recent studies suggest that the clustering of sodium channels can influence axonal impulse conduction in both myelinated and unmyelinated fibers, which could have major implications in disease, particularly demyelinating pathology. This comprehensive review summarizes the mechanisms governing the clustering of sodium channels at the peripheral and central nervous system nodes and the specific roles of their clustering in influencing action potential conduction. We further highlight the classical biophysical parameters implicated in conduction timing, followed by a detailed discussion on how sodium channel clustering along unmyelinated axons can impact axonal impulse conduction in both physiological and pathological contexts.
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Affiliation(s)
- Sean A Freeman
- ICM-GHU Pitié-Salpêtrière, Sorbonne Universités UPMC Univ Paris 06, UMR_S 1127, 75013, Paris, France.
- Inserm U1127, 75013, Paris, France.
- CNRS UMR7225, 75013, Paris, France.
| | - Anne Desmazières
- ICM-GHU Pitié-Salpêtrière, Sorbonne Universités UPMC Univ Paris 06, UMR_S 1127, 75013, Paris, France.
- Inserm U1127, 75013, Paris, France.
- CNRS UMR7225, 75013, Paris, France.
| | - Desdemona Fricker
- ICM-GHU Pitié-Salpêtrière, Sorbonne Universités UPMC Univ Paris 06, UMR_S 1127, 75013, Paris, France.
- Inserm U1127, 75013, Paris, France.
- CNRS UMR7225, 75013, Paris, France.
| | - Catherine Lubetzki
- ICM-GHU Pitié-Salpêtrière, Sorbonne Universités UPMC Univ Paris 06, UMR_S 1127, 75013, Paris, France.
- Inserm U1127, 75013, Paris, France.
- CNRS UMR7225, 75013, Paris, France.
- Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, Paris, France.
| | - Nathalie Sol-Foulon
- ICM-GHU Pitié-Salpêtrière, Sorbonne Universités UPMC Univ Paris 06, UMR_S 1127, 75013, Paris, France.
- Inserm U1127, 75013, Paris, France.
- CNRS UMR7225, 75013, Paris, France.
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13
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Abstract
Myelin is probably one of the most fascinating and innovative biological acquisition: a glia plasma membrane tightly wrapped around an axon and insulating it. Chondrichthyans (cartilaginous fishes) form a large group of vertebrates, and they are among oldest extant jawed vertebrate lineage. It has been known from studies 150 years ago, that they are positioned at the root of the successful appearance of compact myelin and main adhesive proteins in vertebrates. More importantly, the ultrastructure of their compact myelin is indistinguishable from the one observed in tetrapods and the first true myelin basic protein (MBP) and myelin protein zero (MPZ) seem to have originated on cartilaginous fish or their ancestors, the placoderms. Thus, the study of their myelin formation would bring new insights in vertebrate׳s myelin evolution. Chondrichthyans central nervous system (CNS) myelin composition is also very similar to peripheral nervous system (PNS) myelin composition. And while they lack true proteolipid protein (PLP) like tetrapods, they express a DM-like protein in their myelin. This article is part of a Special Issue entitled SI: Myelin Evolution.
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Affiliation(s)
- Maria Elena de Bellard
- California State University Northridge, Biology Department, MC 8303, 18111 Nordhoff Street, Northridge, CA 91330, USA.
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