1
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Bin JM, Suminaite D, Benito-Kwiecinski SK, Kegel L, Rubio-Brotons M, Early JJ, Soong D, Livesey MR, Poole RJ, Lyons DA. Importin 13-dependent axon diameter growth regulates conduction speeds along myelinated CNS axons. Nat Commun 2024; 15:1790. [PMID: 38413580 PMCID: PMC10899189 DOI: 10.1038/s41467-024-45908-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 02/06/2024] [Indexed: 02/29/2024] Open
Abstract
Axon diameter influences the conduction properties of myelinated axons, both directly, and indirectly through effects on myelin. However, we have limited understanding of mechanisms controlling axon diameter growth in the central nervous system, preventing systematic dissection of how manipulating diameter affects myelination and conduction along individual axons. Here we establish zebrafish to study axon diameter. We find that importin 13b is required for axon diameter growth, but does not affect cell body size or axon length. Using neuron-specific ipo13b mutants, we assess how reduced axon diameter affects myelination and conduction, and find no changes to myelin thickness, precision of action potential propagation, or ability to sustain high frequency firing. However, increases in conduction speed that occur along single myelinated axons with development are tightly linked to their growth in diameter. This suggests that axon diameter growth is a major driver of increases in conduction speeds along myelinated axons over time.
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Affiliation(s)
- Jenea M Bin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK.
| | - Daumante Suminaite
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | | | - Linde Kegel
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Maria Rubio-Brotons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Daniel Soong
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Matthew R Livesey
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, S10 2HQ, UK
- Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Richard J Poole
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, UK
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH16 4SB, UK.
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2
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El-Daher F, Early JJ, Richmond CE, Jamieson R, Becker T, Becker CG. Controlled Semi-Automated Lased-Induced Injuries for Studying Spinal Cord Regeneration in Zebrafish Larvae. J Vis Exp 2021. [PMID: 34866633 DOI: 10.3791/63259] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Zebrafish larvae possess a fully functional central nervous system (CNS) with a high regenerative capacity only a few days after fertilization. This makes this animal model very useful for studying spinal cord injury and regeneration. The standard protocol for inducing such lesions is to transect the dorsal part of the trunk manually. However, this technique requires extensive training and damages additional tissues. A protocol was developed for laser-induced lesions to circumvent these limitations, allowing for high reproducibility and completeness of spinal cord transection over many animals and between different sessions, even for an untrained operator. Furthermore, tissue damage is mainly limited to the spinal cord itself, reducing confounding effects from injuring different tissues, e.g., skin, muscle, and CNS. Moreover, hemi-lesions of the spinal cord are possible. Improved preservation of tissue integrity after laser injury facilitates further dissections needed for additional analyses, such as electrophysiology. Hence, this method offers precise control of the injury extent that is unachievable manually. This allows for new experimental paradigms in this powerful model in the future.
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Affiliation(s)
- Francois El-Daher
- Centre for Discovery Brain Sciences, University of Edinburgh Medical School: Biomedical Sciences;
| | - Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh Medical School: Biomedical Sciences
| | - Claire E Richmond
- Centre for Discovery Brain Sciences, University of Edinburgh Medical School: Biomedical Sciences
| | - Rory Jamieson
- Centre for Discovery Brain Sciences, University of Edinburgh Medical School: Biomedical Sciences
| | - Thomas Becker
- Centre for Discovery Brain Sciences, University of Edinburgh Medical School: Biomedical Sciences; Center for Regenerative Therapies at the TU Dresden
| | - Catherina G Becker
- Centre for Discovery Brain Sciences, University of Edinburgh Medical School: Biomedical Sciences; Center for Regenerative Therapies at the TU Dresden
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3
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Madden ME, Suminaite D, Ortiz E, Early JJ, Koudelka S, Livesey MR, Bianco IH, Granato M, Lyons DA. CNS Hypomyelination Disrupts Axonal Conduction and Behavior in Larval Zebrafish. J Neurosci 2021; 41:9099-9111. [PMID: 34544838 PMCID: PMC8570833 DOI: 10.1523/jneurosci.0842-21.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 08/11/2021] [Accepted: 08/16/2021] [Indexed: 11/21/2022] Open
Abstract
Myelination is essential for central nervous system (CNS) formation, health and function. As a model organism, larval zebrafish have been extensively employed to investigate the molecular and cellular basis of CNS myelination, because of their genetic tractability and suitability for non-invasive live cell imaging. However, it has not been assessed to what extent CNS myelination affects neural circuit function in zebrafish larvae, prohibiting the integration of molecular and cellular analyses of myelination with concomitant network maturation. To test whether larval zebrafish might serve as a suitable platform with which to study the effects of CNS myelination and its dysregulation on circuit function, we generated zebrafish myelin regulatory factor (myrf) mutants with CNS-specific hypomyelination and investigated how this affected their axonal conduction properties and behavior. We found that myrf mutant larvae exhibited increased latency to perform startle responses following defined acoustic stimuli. Furthermore, we found that hypomyelinated animals often selected an impaired response to acoustic stimuli, exhibiting a bias toward reorientation behavior instead of the stimulus-appropriate startle response. To begin to study how myelination affected the underlying circuitry, we established electrophysiological protocols to assess various conduction properties along single axons. We found that the hypomyelinated myrf mutants exhibited reduced action potential conduction velocity and an impaired ability to sustain high-frequency action potential firing. This study indicates that larval zebrafish can be used to bridge molecular and cellular investigation of CNS myelination with multiscale assessment of neural circuit function.SIGNIFICANCE STATEMENT Myelination of CNS axons is essential for their health and function, and it is now clear that myelination is a dynamic life-long process subject to modulation by neuronal activity. However, it remains unclear precisely how changes to myelination affects animal behavior and underlying action potential conduction along axons in intact neural circuits. In recent years, zebrafish have been employed to study cellular and molecular mechanisms of myelination, because of their relatively simple, optically transparent, experimentally tractable vertebrate nervous system. Here we find that changes to myelination alter the behavior of young zebrafish and action potential conduction along individual axons, providing a platform to integrate molecular, cellular, and circuit level analyses of myelination using this model.
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Affiliation(s)
- M E Madden
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
| | - D Suminaite
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
| | - E Ortiz
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - J J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
| | - S Koudelka
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
| | - M R Livesey
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, The University of Sheffield, Sheffield S10 2HQ, United Kingdom
| | - I H Bianco
- Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - M Granato
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - D A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH16 4SB, United Kingdom
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4
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Almeida RG, Williamson JM, Madden ME, Early JJ, Voas MG, Talbot WS, Bianco IH, Lyons DA. Myelination induces axonal hotspots of synaptic vesicle fusion that promote sheath growth. Curr Biol 2021; 31:3743-3754.e5. [PMID: 34270947 PMCID: PMC8445327 DOI: 10.1016/j.cub.2021.06.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 05/17/2021] [Accepted: 06/11/2021] [Indexed: 02/08/2023]
Abstract
Myelination of axons by oligodendrocytes enables fast saltatory conduction. Oligodendrocytes are responsive to neuronal activity, which has been shown to induce changes to myelin sheaths, potentially to optimize conduction and neural circuit function. However, the cellular bases of activity-regulated myelination in vivo are unclear, partly due to the difficulty of analyzing individual myelinated axons over time. Activity-regulated myelination occurs in specific neuronal subtypes and can be mediated by synaptic vesicle fusion, but several questions remain: it is unclear whether vesicular fusion occurs stochastically along axons or in discrete hotspots during myelination and whether vesicular fusion regulates myelin targeting, formation, and/or growth. It is also unclear why some neurons, but not others, exhibit activity-regulated myelination. Here, we imaged synaptic vesicle fusion in individual neurons in living zebrafish and documented robust vesicular fusion along axons during myelination. Surprisingly, we found that axonal vesicular fusion increased upon and required myelination. We found that axonal vesicular fusion was enriched in hotspots, namely the heminodal non-myelinated domains into which sheaths grew. Blocking vesicular fusion reduced the stable formation and growth of myelin sheaths, and chemogenetically stimulating neuronal activity promoted sheath growth. Finally, we observed high levels of axonal vesicular fusion only in neuronal subtypes that exhibit activity-regulated myelination. Our results identify a novel "feedforward" mechanism whereby the process of myelination promotes the neuronal activity-regulated signal, vesicular fusion that, in turn, consolidates sheath growth along specific axons selected for myelination.
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Affiliation(s)
- Rafael G Almeida
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.
| | - Jill M Williamson
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Megan E Madden
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Matthew G Voas
- Department of Developmental Biology, Stanford University, Stanford, CA, USA; National Cancer Institute, Frederick, MD, USA
| | - William S Talbot
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
| | - Isaac H Bianco
- Department of Neuroscience, Physiology and Pharmacology, UCL, London, UK
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.
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5
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Marshall-Phelps KLH, Kegel L, Baraban M, Ruhwedel T, Almeida RG, Rubio-Brotons M, Klingseisen A, Benito-Kwiecinski SK, Early JJ, Bin JM, Suminaite D, Livesey MR, Möbius W, Poole RJ, Lyons DA. Neuronal activity disrupts myelinated axon integrity in the absence of NKCC1b. J Cell Biol 2021; 219:151733. [PMID: 32364583 PMCID: PMC7337504 DOI: 10.1083/jcb.201909022] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 03/09/2020] [Accepted: 04/07/2020] [Indexed: 02/07/2023] Open
Abstract
Through a genetic screen in zebrafish, we identified a mutant with disruption to myelin in both the CNS and PNS caused by a mutation in a previously uncharacterized gene, slc12a2b, predicted to encode a Na+, K+, and Cl- (NKCC) cotransporter, NKCC1b. slc12a2b/NKCC1b mutants exhibited a severe and progressive pathology in the PNS, characterized by dysmyelination and swelling of the periaxonal space at the axon-myelin interface. Cell-type-specific loss of slc12a2b/NKCC1b in either neurons or myelinating Schwann cells recapitulated these pathologies. Given that NKCC1 is critical for ion homeostasis, we asked whether the disruption to myelinated axons in slc12a2b/NKCC1b mutants is affected by neuronal activity. Strikingly, we found that blocking neuronal activity completely prevented and could even rescue the pathology in slc12a2b/NKCC1b mutants. Together, our data indicate that NKCC1b is required to maintain neuronal activity-related solute homeostasis at the axon-myelin interface, and the integrity of myelinated axons.
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Affiliation(s)
| | - Linde Kegel
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Marion Baraban
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Torben Ruhwedel
- Electron Microscopy Core Unit, Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Rafael G Almeida
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | | | - Anna Klingseisen
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | | | - Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Jenea M Bin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Daumante Suminaite
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Matthew R Livesey
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Wiebke Möbius
- Electron Microscopy Core Unit, Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Richard J Poole
- Department of Cell and Developmental Biology, University College London, London, UK
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
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6
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Campbell JS, Davidson AJ, Todd H, Rodrigues FSLM, Elliot AM, Early JJ, Lyons DA, Feng Y, Wood W. PTPN21/Pez Is a Novel and Evolutionarily Conserved Key Regulator of Inflammation In Vivo. Curr Biol 2021; 31:875-883.e5. [PMID: 33296680 PMCID: PMC7902905 DOI: 10.1016/j.cub.2020.11.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 10/09/2020] [Accepted: 11/04/2020] [Indexed: 11/18/2022]
Abstract
Drosophila provides a powerful model in which to study inflammation in vivo, and previous studies have revealed many of the key signaling events critical for recruitment of immune cells to tissue damage. In the fly, wounding stimulates the rapid production of hydrogen peroxide (H2O2).1,2 This then acts as an activation signal by triggering a signaling pathway within responding macrophages by directly activating the Src family kinase (SFK) Src42A,3 which in turn phosphorylates the damage receptor Draper. Activated Draper then guides macrophages to the wound through the detection of an as-yet unidentified chemoattractant.3-5 Similar H2O2-activated signaling pathways are also critical for leukocyte recruitment following wounding in larval zebrafish,6-9 where H2O2 activates the SFK Lyn to drive neutrophil chemotaxis. In this study, we combine proteomics, live imaging, and genetics in the fly to identify a novel regulator of inflammation in vivo; the PTP-type phosphatase Pez. Pez is expressed in macrophages and is critical for their efficient migration to wounds. Pez functions within activated macrophages downstream of damage-induced H2O2 and operates, via its band 4.1 ezrin, radixin, and moesin (FERM) domain, together with Src42A and Draper to ensure effective inflammatory cell recruitment to wounds. We show that this key role is conserved in vertebrates, because "crispant" zebrafish larvae of the Draper ortholog (MEGF10) or the Pez ortholog (PTPN21) exhibit a failure in leukocyte recruitment to wounds. This study demonstrates evolutionary conservation of inflammatory signaling and identifies MEGF10 and PTPN21 as potential therapeutic targets for the treatment of inflammatory disorders.
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Affiliation(s)
- Jennie S Campbell
- Centre for Inflammation Research, University of Edinburgh, Queens Medical Research Institute, 47 Little France Crescent, Edinburgh BioQuarter, Edinburgh EH16 4TJ, UK; School of Cellular and Molecular Medicine, Faculty of Biomedical Sciences, University of Bristol, Bristol BS8 1TD, UK.
| | - Andrew J Davidson
- Centre for Inflammation Research, University of Edinburgh, Queens Medical Research Institute, 47 Little France Crescent, Edinburgh BioQuarter, Edinburgh EH16 4TJ, UK
| | - Henry Todd
- Centre for Inflammation Research, University of Edinburgh, Queens Medical Research Institute, 47 Little France Crescent, Edinburgh BioQuarter, Edinburgh EH16 4TJ, UK
| | - Frederico S L M Rodrigues
- School of Cellular and Molecular Medicine, Faculty of Biomedical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Abigail M Elliot
- Centre for Inflammation Research, University of Edinburgh, Queens Medical Research Institute, 47 Little France Crescent, Edinburgh BioQuarter, Edinburgh EH16 4TJ, UK
| | - Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Yi Feng
- Centre for Inflammation Research, University of Edinburgh, Queens Medical Research Institute, 47 Little France Crescent, Edinburgh BioQuarter, Edinburgh EH16 4TJ, UK
| | - Will Wood
- Centre for Inflammation Research, University of Edinburgh, Queens Medical Research Institute, 47 Little France Crescent, Edinburgh BioQuarter, Edinburgh EH16 4TJ, UK.
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7
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Early JJ, Cole KL, Williamson JM, Swire M, Kamadurai H, Muskavitch M, Lyons DA. An automated high-resolution in vivo screen in zebrafish to identify chemical regulators of myelination. eLife 2018; 7:35136. [PMID: 29979149 PMCID: PMC6056238 DOI: 10.7554/elife.35136] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 07/05/2018] [Indexed: 12/23/2022] Open
Abstract
Myelinating oligodendrocytes are essential for central nervous system (CNS) formation and function. Their disruption is implicated in numerous neurodevelopmental, neuropsychiatric and neurodegenerative disorders. However, recent studies have indicated that oligodendrocytes may be tractable for treatment of disease. In recent years, zebrafish have become well established for the study of myelinating oligodendrocyte biology and drug discovery in vivo. Here, by automating the delivery of zebrafish larvae to a spinning disk confocal microscope, we were able to automate high-resolution imaging of myelinating oligodendrocytes in vivo. From there, we developed an image analysis pipeline that facilitated a screen of compounds with epigenetic and post-translational targets for their effects on regulating myelinating oligodendrocyte number. This screen identified novel compounds that strongly promote myelinating oligodendrocyte formation in vivo. Our imaging platform and analysis pipeline is flexible and can be employed for high-resolution imaging-based screens of broad interest using zebrafish.
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Affiliation(s)
- Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom.,United Kingdom Zebrafish screening facility, University of Edinburgh, Edinburgh, United Kingdom
| | - Katy Lh Cole
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Jill M Williamson
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Matthew Swire
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom.,MRC Centre for Regenerative Medicine, Edinburgh, United Kingdom
| | | | | | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom.,United Kingdom Zebrafish screening facility, University of Edinburgh, Edinburgh, United Kingdom
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8
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Almeida RG, Pan S, Cole KLH, Williamson JM, Early JJ, Czopka T, Klingseisen A, Chan JR, Lyons DA. Myelination of Neuronal Cell Bodies when Myelin Supply Exceeds Axonal Demand. Curr Biol 2018; 28:1296-1305.e5. [PMID: 29628374 PMCID: PMC5912901 DOI: 10.1016/j.cub.2018.02.068] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 02/02/2018] [Accepted: 02/23/2018] [Indexed: 01/10/2023]
Abstract
The correct targeting of myelin is essential for nervous system formation and function. Oligodendrocytes in the CNS myelinate some axons, but not others, and do not myelinate structures including cell bodies and dendrites [1]. Recent studies indicate that extrinsic signals, such as neuronal activity [2, 3] and cell adhesion molecules [4], can bias myelination toward some axons and away from cell bodies and dendrites, indicating that, in vivo, neuronal and axonal cues regulate myelin targeting. In vitro, however, oligodendrocytes have an intrinsic propensity to myelinate [5, 6, 7] and can promiscuously wrap inert synthetic structures resembling neuronal processes [8, 9] or cell bodies [4]. A current therapeutic goal for the treatment of demyelinating diseases is to greatly promote oligodendrogenesis [10, 11, 12, 13]; thus, it is important to test how accurately extrinsic signals regulate the oligodendrocyte’s intrinsic program of myelination in vivo. Here, we test the hypothesis that neurons regulate myelination with sufficient stringency to always ensure correct targeting. Surprisingly, however, we find that myelin targeting in vivo is not very stringent and that mistargeting occurs readily when oligodendrocyte and myelin supply exceed axonal demand. We find that myelin is mistargeted to neuronal cell bodies in zebrafish mutants with fewer axons and independently in drug-treated zebrafish with increased oligodendrogenesis. Additionally, by increasing myelin production of oligodendrocytes in zebrafish and mice, we find that excess myelin is also inappropriately targeted to cell bodies. Our results suggest that balancing oligodendrocyte-intrinsic programs of myelin supply with axonal demand is essential for correct myelin targeting in vivo and highlight potential liabilities of strongly promoting oligodendrogenesis. Balance between axons and myelin production regulates its targeting in vivo Excess myelin is mistargeted to cell bodies Low, but not zero, level of mistargeting during normal development Potential implications for myelin-promoting therapies
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Affiliation(s)
- Rafael G Almeida
- Centre for Discovery Brain Sciences, University of Edinburgh, 49 Little France Crescent, Edinburgh EH16 4SB, UK
| | - Simon Pan
- Department of Neurology and Program in Neuroscience, University of California, San Francisco, 675 Nelson Rising Lane, San Francisco, CA 94143, USA
| | - Katy L H Cole
- Centre for Discovery Brain Sciences, University of Edinburgh, 49 Little France Crescent, Edinburgh EH16 4SB, UK
| | - Jill M Williamson
- Centre for Discovery Brain Sciences, University of Edinburgh, 49 Little France Crescent, Edinburgh EH16 4SB, UK
| | - Jason J Early
- Centre for Discovery Brain Sciences, University of Edinburgh, 49 Little France Crescent, Edinburgh EH16 4SB, UK
| | - Tim Czopka
- Centre for Discovery Brain Sciences, University of Edinburgh, 49 Little France Crescent, Edinburgh EH16 4SB, UK; Institute of Neuronal Cell Biology, Technical University of Munich, Biedersteiner Strasse 29, 80802 Munich, Germany; Munich Cluster of Systems Neurology (SyNergy), Feodor-Lynen Strasse 17, 81377 Munich, Germany
| | - Anna Klingseisen
- Centre for Discovery Brain Sciences, University of Edinburgh, 49 Little France Crescent, Edinburgh EH16 4SB, UK
| | - Jonah R Chan
- Department of Neurology and Program in Neuroscience, University of California, San Francisco, 675 Nelson Rising Lane, San Francisco, CA 94143, USA
| | - David A Lyons
- Centre for Discovery Brain Sciences, University of Edinburgh, 49 Little France Crescent, Edinburgh EH16 4SB, UK.
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9
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Cole KLH, Early JJ, Lyons DA. Drug discovery for remyelination and treatment of MS. Glia 2017; 65:1565-1589. [PMID: 28618073 DOI: 10.1002/glia.23166] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/20/2017] [Accepted: 04/24/2017] [Indexed: 12/19/2022]
Abstract
Glia constitute the majority of the cells in our nervous system, yet there are currently no drugs that target glia for the treatment of disease. Given ongoing discoveries of the many roles of glia in numerous diseases of the nervous system, this is likely to change in years to come. Here we focus on the possibility that targeting the oligodendrocyte lineage to promote regeneration of myelin (remyelination) represents a therapeutic strategy for the treatment of the demyelinating disease multiple sclerosis, MS. We discuss how hypothesis driven studies have identified multiple targets and pathways that can be manipulated to promote remyelination in vivo, and how this work has led to the first ever remyelination clinical trials. We also highlight how recent chemical discovery screens have identified a host of small molecule compounds that promote oligodendrocyte differentiation in vitro. Some of these compounds have also been shown to promote myelin regeneration in vivo, with one already being trialled in humans. Promoting oligodendrocyte differentiation and remyelination represents just one potential strategy for the treatment of MS. The pathology of MS is complex, and its complete amelioration may require targeting multiple biological processes in parallel. Therefore, we present an overview of new technologies and models for phenotypic analyses and screening that can be exploited to study complex cell-cell interactions in in vitro and in vivo systems. Such technological platforms will provide insight into fundamental mechanisms and increase capacities for drug-discovery of relevance to glia and currently intractable disorders of the CNS.
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Affiliation(s)
- Katy L H Cole
- Centre for Neuroregeneration, MS Society Centre for Translational Research, Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, EH16 4SB, United Kingdom
| | - Jason J Early
- Centre for Neuroregeneration, MS Society Centre for Translational Research, Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, EH16 4SB, United Kingdom
| | - David A Lyons
- Centre for Neuroregeneration, MS Society Centre for Translational Research, Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, EH16 4SB, United Kingdom
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10
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Karttunen MJ, Czopka T, Goedhart M, Early JJ, Lyons DA. Regeneration of myelin sheaths of normal length and thickness in the zebrafish CNS correlates with growth of axons in caliber. PLoS One 2017; 12:e0178058. [PMID: 28542521 PMCID: PMC5444792 DOI: 10.1371/journal.pone.0178058] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 05/08/2017] [Indexed: 01/17/2023] Open
Abstract
Demyelination is observed in numerous diseases of the central nervous system, including multiple sclerosis (MS). However, the endogenous regenerative process of remyelination can replace myelin lost in disease, and in various animal models. Unfortunately, the process of remyelination often fails, particularly with ageing. Even when remyelination occurs, it is characterised by the regeneration of myelin sheaths that are abnormally thin and short. This imperfect remyelination is likely to have implications for the restoration of normal circuit function and possibly the optimal metabolic support of axons. Here we describe a larval zebrafish model of demyelination and remyelination. We employ a drug-inducible cell ablation system with which we can consistently ablate 2/3rds of oligodendrocytes in the larval zebrafish spinal cord. This leads to a concomitant demyelination of 2/3rds of axons in the spinal cord, and an innate immune response over the same time period. We find restoration of the normal number of oligodendrocytes and robust remyelination approximately two weeks after induction of cell ablation, whereby myelinated axon number is restored to control levels. Remarkably, we find that myelin sheaths of normal length and thickness are regenerated during this time. Interestingly, we find that axons grow significantly in caliber during this period of remyelination. This suggests the possibility that the active growth of axons may stimulate the regeneration of myelin sheaths of normal dimensions.
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Affiliation(s)
- Marja J. Karttunen
- Centre for Neuroregeneration, MS Society Centre for Translational Research, Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Tim Czopka
- Centre for Neuroregeneration, MS Society Centre for Translational Research, Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, United Kingdom
- Institute of Neuronal Cell Biology, Technische Universität München, München, Germany
| | - Marieke Goedhart
- Centre for Neuroregeneration, MS Society Centre for Translational Research, Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Jason J. Early
- Centre for Neuroregeneration, MS Society Centre for Translational Research, Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, United Kingdom
| | - David A. Lyons
- Centre for Neuroregeneration, MS Society Centre for Translational Research, Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail:
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Abstract
OBJECTIVE To report a case of weight loss and mood stabilization in a patient being treated with the antiepileptic drug topiramate. CASE SUMMARY A 37-year-old obese white woman with affective instability and obesity was being treated with adjunctive topiramate therapy. The patient lost 10 kg over 10 weeks of treatment with topiramate and improved clinically, as evidenced by a reduction in the number of times that she had to be admitted to a management unit for constant observation, and a decrease in the number of times that mechanical restraints or medication interventions were required for aggressive outbursts. Furthermore, the patient successfully completed two home visits while receiving topiramate therapy and was out of the hospital on her third home visit at the time of this writing. DISCUSSION This case further strengthens previous reports that topiramate may be useful in treating affective disorders as well as inducing weight loss in a patient population in which weight gain is common. The patient discussed in this case report had no acute illnesses or changes in health status, no changes in diet, and no changes in her medications that could have accounted for the sudden weight loss. In addition, the patient's behavior did not improve until topiramate was added as adjunctive therapy of valproic acid, citalopram, and chlorpromazine during an adequate trial period. CONCLUSIONS Controlled studies need to be performed to evaluate the use of topiramate in the psychiatric population and, in particular, the benefits of topiramate therapy in psychiatric patients with an additional diagnosis of obesity.
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Affiliation(s)
- C J Teter
- College of Pharmacy, University of Michigan, Ann Arbor 48109-1065, USA.
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12
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Teter CJ, Early JJ, Frachtling RJ. Olanzapine-induced neutropenia in patients with history of clozapine treatment: two case reports from a state psychiatric institution. J Clin Psychiatry 2000; 61:872-3. [PMID: 11105743 DOI: 10.4088/jcp.v61n1111b] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Matzke GR, Frye RF, Early JJ, Straka RJ, Carson SW. Evaluation of the influence of diabetes mellitus on antipyrine metabolism and CYP1A2 and CYP2D6 activity. Pharmacotherapy 2000; 20:182-90. [PMID: 10678296 DOI: 10.1592/phco.20.3.182.34775] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
STUDY OBJECTIVE To evaluate the metabolism of antipyrine, a general metabolic probe, caffeine, a probe for cytochrome P450 (CYP) 1A2 and N-acetyltransferase activity, and dextromethorphan, a specific probe for CYP2D6 activity in patients with type 1 or 2 diabetes mellitus. DESIGN Prospective, controlled study. SETTING Research facility. Patients. Fifteen patients with type 1 and 16 with type 2 diabetes, and 16 healthy controls. INTERVENTION Each subject simultaneously received antipyrine 10 mg/kg, caffeine 100 mg, and dextromethorphan 30 mg. MEASUREMENTS AND MAIN RESULTS The pharmacokinetics of antipyrine and its primary metabolites were determined from saliva and urine samples. Type 1 diabetes had marked effects on antipyrine metabolism whereas type 2 disease did not alter the metabolism of any of the probe drugs. The apparent oral clearance of antipyrine was increased 72% in patients with type 1 disease compared with controls (p=0.0001). In addition, formation clearances of 4-hydroxyantipyrine and 3-hydroxymethylantipyrine were increased by 74% and 137% in those patients relative to controls. The caffeine metabolic index (paraxanthine/caffeine) was increased 34% (p=0.11), and N-acetylation and CYP2D6 phenotype were not altered. CONCLUSION The metabolism of antipyrine is increased in patients with type 1 diabetes. Based on in vitro reports of antipyrine metabolism and current caffeine metabolic index data, the predominant effect of type 1 diabetes appears to be an increase in CYP1A2 activity. Assessment of the effect of the disease on other specific CYP metabolic pathways is warranted.
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Affiliation(s)
- G R Matzke
- Department of Pharmaceutical Sciences, School of Pharmacy, and Center for Clinical Pharmacology, University of Pittsburgh, Pennsylvania 15261, USA
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14
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Abstract
The impact of replacing divalproex sodium with valproic acid on patient outcomes and direct drug costs was studied. Before-and-after medical chart review was performed in a state-supported facility for mentally retarded adults in which a pharmacy and therapeutics (P&T) committee recommended replacement of divalproex with valproic acid. Patients were studied if they had received divalproex for at least three months and if their antiepileptic drug was changed from divalproex to valproic acid between October 1993 and June 1994. Clinical, economic, and prescribing-pattern data were recorded for the periods extending 12 months before and 18 months after the change in therapy. Data for 46 patients were analyzed. Replacing divalproex with valproic acid was effective in 41 (89%) of the patients. There was no significant difference between the divalproex and valproic acid periods in seizure rate or frequency of new drug therapy for GI disorders. Between fiscal year 1992-93 and fiscal year 1995-96 there was a 56% decrease in total direct divalproex plus valproic acid costs, including drug products and packaging materials and labor. The rate of valproic acid prescriptions increased steadily after the replacement was recommended, and then plateaued. Replacing divalproex sodium with valproic acid in a group of institutionalized mentally retarded adults with epilepsy was clinically effective and economically advantageous.
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Affiliation(s)
- C W Cranor
- School of Public Health, University of North Carolina (UNC), Chapel Hill 27599-7360, USA.
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Shinohara T, Dietzschold B, Craft CM, Wistow G, Early JJ, Donoso LA, Horwitz J, Tao R. Primary and secondary structure of bovine retinal S antigen (48-kDa protein). Proc Natl Acad Sci U S A 1987; 84:6975-9. [PMID: 3478675 PMCID: PMC299211 DOI: 10.1073/pnas.84.20.6975] [Citation(s) in RCA: 159] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The complete amino acid sequence of bovine S antigen (48-kDa protein) has been determined by cDNA and partial amino acid sequencing. A 1623-base-pair (bp) cDNA contains an open reading frame coding for a protein of 404 amino acids (45,275 Da). Tryptic peptides and cyanogen bromide peptides of native bovine S antigen were purified and partially sequenced. All of these peptides were accounted for in the long open reading frame. Searching of the National Biomedical Research Foundation data bank revealed no extensive sequence homology between S antigen and other proteins. However, there are local regions of sequence similarity with alpha transducin, including the sites subject to ADP-ribosylation by Bordetella pertussis and cholera toxins and the phosphoryl binding-sites. Secondary structure prediction and circular dichroic spectroscopy show that S antigen is composed predominantly of beta-sheet conformation. Acid-catalyzed methanolysis suggests the presence of low levels of carbohydrate in the molecule.
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Affiliation(s)
- T Shinohara
- Laboratory of Molecular and Developmental Biology, National Eye Institute, Bethesda, MD 20892
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