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Nguyen LT, Aprico A, Nwoke E, Walsh AD, Blades F, Avneri R, Martin E, Zalc B, Kilpatrick TJ, Binder MD. Mertk-expressing microglia influence oligodendrogenesis and myelin modelling in the CNS. J Neuroinflammation 2023; 20:253. [PMID: 37926818 PMCID: PMC10626688 DOI: 10.1186/s12974-023-02921-8] [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: 07/28/2023] [Accepted: 10/04/2023] [Indexed: 11/07/2023] Open
Abstract
BACKGROUND Microglia, an immune cell found exclusively within the CNS, initially develop from haematopoietic stem cell precursors in the yolk sac and colonise all regions of the CNS early in development. Microglia have been demonstrated to play an important role in the development of oligodendrocytes, the myelin producing cells in the CNS, as well as in myelination. Mertk is a receptor expressed on microglia that mediates immunoregulatory functions, including myelin efferocytosis. FINDINGS Here we demonstrate an unexpected role for Mertk-expressing microglia in both oligodendrogenesis and myelination. The selective depletion of Mertk from microglia resulted in reduced oligodendrocyte production in early development and the generation of pathological myelin. During demyelination, mice deficient in microglial Mertk had thinner myelin and showed signs of impaired OPC differentiation. We established that Mertk signalling inhibition impairs oligodendrocyte repopulation in Xenopus tadpoles following demyelination. CONCLUSION These data highlight the importance of microglia in myelination and are the first to identify Mertk as a regulator of oligodendrogenesis and myelin ultrastructure.
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Affiliation(s)
- Linda T Nguyen
- The Florey Institute of Neuroscience and Mental Health, Parkville, Melbourne, Australia
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Melbourne, Australia
| | - Andrea Aprico
- The Florey Institute of Neuroscience and Mental Health, Parkville, Melbourne, Australia
| | - Eze Nwoke
- The Florey Institute of Neuroscience and Mental Health, Parkville, Melbourne, Australia
- Crux Biolabs, Bayswater, VIC, 3153, Australia
| | - Alexander D Walsh
- The Florey Institute of Neuroscience and Mental Health, Parkville, Melbourne, Australia
- Cognitive Neuroepigenetics Laboratory, Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia
| | - Farrah Blades
- The Florey Institute of Neuroscience and Mental Health, Parkville, Melbourne, Australia
- Centre for Solar Biotechnology, Institute for Molecular Biosciences, University of Queensland, St Lucia, Brisbane, Australia
| | - Raphael Avneri
- Inserm, CNRS, Institut du Cerveau, AP-HP Pitié-Salpêtrière Hospital, Sorbonne Université, Paris, France
- Department of Molecular Biology, Ariel University, 40700, Ariel, Israel
| | - Elodie Martin
- Inserm, CNRS, Institut du Cerveau, AP-HP Pitié-Salpêtrière Hospital, Sorbonne Université, Paris, France
| | - Bernard Zalc
- Inserm, CNRS, Institut du Cerveau, AP-HP Pitié-Salpêtrière Hospital, Sorbonne Université, Paris, France
| | - Trevor J Kilpatrick
- The Florey Institute of Neuroscience and Mental Health, Parkville, Melbourne, Australia
| | - Michele D Binder
- The Florey Institute of Neuroscience and Mental Health, Parkville, Melbourne, Australia.
- Department of Anatomy and Physiology, University of Melbourne, Parkville, Melbourne, Australia.
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Arinrad S, Depp C, Siems SB, Sasmita AO, Eichel MA, Ronnenberg A, Hammerschmidt K, Lüders KA, Werner HB, Ehrenreich H, Nave KA. Isolated catatonia-like executive dysfunction in mice with forebrain-specific loss of myelin integrity. eLife 2023; 12:70792. [PMID: 36892455 PMCID: PMC9998085 DOI: 10.7554/elife.70792] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 01/24/2023] [Indexed: 03/10/2023] Open
Abstract
A key feature of advanced brain aging includes structural defects of intracortical myelin that are associated with secondary neuroinflammation. A similar pathology is seen in specific myelin mutant mice that model 'advanced brain aging' and exhibit a range of behavioral abnormalities. However, the cognitive assessment of these mutants is problematic because myelin-dependent motor-sensory functions are required for quantitative behavioral readouts. To better understand the role of cortical myelin integrity for higher brain functions, we generated mice lacking Plp1, encoding the major integral myelin membrane protein, selectively in ventricular zone stem cells of the mouse forebrain. In contrast to conventional Plp1 null mutants, subtle myelin defects were restricted to the cortex, hippocampus, and underlying callosal tracts. Moreover, forebrain-specific Plp1 mutants exhibited no defects of basic motor-sensory performance at any age tested. Surprisingly, several behavioral alterations reported for conventional Plp1 null mice (Gould et al., 2018) were absent and even social interactions appeared normal. However, with novel behavioral paradigms, we determined catatonia-like symptoms and isolated executive dysfunction in both genders. This suggests that loss of myelin integrity has an impact on cortical connectivity and underlies specific defects of executive function. These observations are likewise relevant for human neuropsychiatric conditions and other myelin-related diseases.
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Affiliation(s)
- Sahab Arinrad
- Clinical Neuroscience, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Constanze Depp
- Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Sophie B Siems
- Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | | | - Maria A Eichel
- Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Anja Ronnenberg
- Clinical Neuroscience, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | | | - Katja A Lüders
- Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Hauke B Werner
- Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Hannelore Ehrenreich
- Clinical Neuroscience, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Klaus-Armin Nave
- Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
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3
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Boahen F, Doyon N, Deteix J. Sensitivity of the electrical response of a node of Ranvier model to alterations of the myelin sheath geometry. J Math Biol 2022; 86:17. [PMID: 36534161 DOI: 10.1007/s00285-022-01841-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 08/31/2022] [Accepted: 11/21/2022] [Indexed: 12/23/2022]
Abstract
Nodes of Ranvier play critical roles in the generation and transmission of action potentials. Alterations in node properties during pathology and/or development are known to affect the speed and quality of electrical transmission. From a modelling standpoint, nodes of Ranvier are often described by systems of ordinary differential equations neglecting or greatly simplifying their geometric structure. These approaches fail to accurately describe how fine scale alteration in the node geometry or in myelin thickness in the paranode region will impact action potential generation and transmission. Here, we rely on a finite element approximation to describe the three dimensional geometry of a node of Ranvier. With this, we are able to investigate how sensitive is the electrical response to alterations in the myelin sheath and paranode geometry. We could in particular investigate irregular loss of myelin, which might be more physiologically relevant than the uniform loss often described through simpler modelling approaches.
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Affiliation(s)
- Frank Boahen
- Groupe Interdisciplinaire de Recherche en Éléments Finis (GIREF), Département de mathématiques et statistique, Université Laval Pavillon Vachon, 1045 Avenue de la médecine, Université Laval, Québec, QC, Canada
| | - Nicolas Doyon
- Groupe Interdisciplinaire de Recherche en Éléments Finis (GIREF), Département de mathématiques et statistique, Université Laval Pavillon Vachon, 1045 Avenue de la médecine, Université Laval, Québec, QC, Canada.
| | - Jean Deteix
- Groupe Interdisciplinaire de Recherche en Éléments Finis (GIREF), Département de mathématiques et statistique, Université Laval Pavillon Vachon, 1045 Avenue de la médecine, Université Laval, Québec, QC, Canada
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4
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Yadav A, Verhaegen S, Filis P, Domanska D, Lyle R, Sundaram AYM, Leithaug M, Østby GC, Aleksandersen M, Berntsen HF, Zimmer KE, Fowler PA, Paulsen RE, Ropstad E. Exposure to a human relevant mixture of persistent organic pollutants or to perfluorooctane sulfonic acid alone dysregulates the developing cerebellum of chicken embryo. ENVIRONMENT INTERNATIONAL 2022; 166:107379. [PMID: 35792514 DOI: 10.1016/j.envint.2022.107379] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 05/07/2022] [Accepted: 06/24/2022] [Indexed: 06/15/2023]
Abstract
Prenatal exposure to persistent organic pollutants (POPs) is associated with neurodevelopmental disorders. In the present study, we explored whether a human-relevant POP mixture affects the development of chicken embryo cerebellum. We used a defined mixture of 29 POPs, with chemical composition and concentrations based on blood levels in the Scandinavian population. We also evaluated exposure to a prominent compound in the mixture, perfluorooctane sulfonic acid (PFOS), alone. Embryos (n = 7-9 per exposure group) were exposed by injection directly into the allantois at embryonic day 13 (E13). Cerebella were isolated at E17 and subjected to morphological, RNA-seq and shot-gun proteomics analyses. There was a reduction in thickness of the molecular layer of cerebellar cortex in both exposure scenarios. Exposure to the POP mixture significantly affected expression of 65 of 13,800 transcripts, and 43 of 2,568 proteins, when compared to solvent control. PFOS alone affected expression of 80 of 13,859 transcripts, and 69 of 2,555 proteins. Twenty-five genes and 15 proteins were common for both exposure groups. These findings point to alterations in molecular events linked to retinoid X receptor (RXR) signalling, neuronal cell proliferation and migration, cellular stress responses including unfolded protein response, lipid metabolism, and myelination. Exposure to the POP mixture increased methionine oxidation, whereas PFOS decreased oxidation. Several of the altered genes and proteins are involved in a wide variety of neurological disorders. We conclude that POP exposure can interfere with fundamental aspects of neurodevelopment, altering molecular pathways that are associated with adverse neurocognitive and behavioural outcomes.
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Affiliation(s)
- Ajay Yadav
- Department of Production Animal Clinical Sciences, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway; Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, University of Oslo, P.O. Box 1068, Blindern, NO-0316 Oslo, Norway.
| | - Steven Verhaegen
- Department of Production Animal Clinical Sciences, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway.
| | - Panagiotis Filis
- Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
| | - Diana Domanska
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway; Department of Pathology, Oslo University Hospital-Rikshospitalet, Oslo, Norway.
| | - Robert Lyle
- Department of Medical Genetics, Oslo University Hospital and University of Oslo, Oslo, Norway; Centre for Fertility and Health, Norwegian Institute of Public Health, Oslo, Norway.
| | - Arvind Y M Sundaram
- Department of Medical Genetics, Oslo University Hospital and University of Oslo, Oslo, Norway.
| | - Magnus Leithaug
- Department of Medical Genetics, Oslo University Hospital and University of Oslo, Oslo, Norway.
| | - Gunn Charlotte Østby
- Department of Production Animal Clinical Sciences, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway.
| | - Mona Aleksandersen
- Department of Preclinical Sciences and Pathology, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway.
| | - Hanne Friis Berntsen
- Department of Production Animal Clinical Sciences, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway; National Institute of Occupational Health, P.O. Box 5330 Majorstuen, NO-0304, Oslo, Norway.
| | - Karin Elisabeth Zimmer
- Department of Preclinical Sciences and Pathology, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway.
| | - Paul A Fowler
- Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
| | - Ragnhild Elisabeth Paulsen
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, University of Oslo, P.O. Box 1068, Blindern, NO-0316 Oslo, Norway.
| | - Erik Ropstad
- Department of Production Animal Clinical Sciences, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway.
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5
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Ruskamo S, Raasakka A, Pedersen JS, Martel A, Škubník K, Darwish T, Porcar L, Kursula P. Human myelin proteolipid protein structure and lipid bilayer stacking. Cell Mol Life Sci 2022; 79:419. [PMID: 35829923 PMCID: PMC9279222 DOI: 10.1007/s00018-022-04428-6] [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: 03/14/2022] [Revised: 05/28/2022] [Accepted: 06/13/2022] [Indexed: 11/03/2022]
Abstract
The myelin sheath is an essential, multilayered membrane structure that insulates axons, enabling the rapid transmission of nerve impulses. The tetraspan myelin proteolipid protein (PLP) is the most abundant protein of compact myelin in the central nervous system (CNS). The integral membrane protein PLP adheres myelin membranes together and enhances the compaction of myelin, having a fundamental role in myelin stability and axonal support. PLP is linked to severe CNS neuropathies, including inherited Pelizaeus-Merzbacher disease and spastic paraplegia type 2, as well as multiple sclerosis. Nevertheless, the structure, lipid interaction properties, and membrane organization mechanisms of PLP have remained unidentified. We expressed, purified, and structurally characterized human PLP and its shorter isoform DM20. Synchrotron radiation circular dichroism spectroscopy and small-angle X-ray and neutron scattering revealed a dimeric, α-helical conformation for both PLP and DM20 in detergent complexes, and pinpoint structural variations between the isoforms and their influence on protein function. In phosphatidylcholine membranes, reconstituted PLP and DM20 spontaneously induced formation of multilamellar myelin-like membrane assemblies. Cholesterol and sphingomyelin enhanced the membrane organization but were not crucial for membrane stacking. Electron cryomicroscopy, atomic force microscopy, and X-ray diffraction experiments for membrane-embedded PLP/DM20 illustrated effective membrane stacking and ordered organization of membrane assemblies with a repeat distance in line with CNS myelin. Our results shed light on the 3D structure of myelin PLP and DM20, their structure-function differences, as well as fundamental protein-lipid interplay in CNS compact myelin.
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Affiliation(s)
- Salla Ruskamo
- Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Oulu, Finland.
| | - Arne Raasakka
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Jan Skov Pedersen
- Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
| | - Anne Martel
- Institut Laue-Langevin (ILL), Grenoble, France
| | - Karel Škubník
- Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Tamim Darwish
- National Deuteration Facility, The Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, Sydney, NSW, 2232, Australia
| | | | - Petri Kursula
- Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Oulu, Finland.
- Department of Biomedicine, University of Bergen, Bergen, Norway.
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6
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Abstract
Schwann cells in the peripheral nervous system (PNS) are essential for the support and myelination of axons, ensuring fast and accurate communication between the central nervous system and the periphery. Schwann cells and related glia accompany innervating axons in virtually all tissues in the body, where they exhibit remarkable plasticity and the ability to modulate pathology in extraordinary, and sometimes surprising, ways. Here, we provide a brief overview of the various glial cell types in the PNS and describe the cornerstone cellular and molecular processes that enable Schwann cells to perform their canonical functions. We then dive into discussing exciting noncanonical functions of Schwann cells and related PNS glia, which include their role in organizing the PNS, in regulating synaptic activity and pain, in modulating immunity, in providing a pool of stem cells for different organs, and, finally, in influencing cancer.
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Affiliation(s)
- Carla Taveggia
- Axo-Glial Interaction Unit, Division of Neuroscience, IRCCS Ospedale San Raffaele, Milan, Italy;
| | - M. Laura Feltri
- Institute for Myelin and Glia Exploration, Departments of Biochemistry and Neurology, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York, USA
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7
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Structural myelin defects are associated with low axonal ATP levels but rapid recovery from energy deprivation in a mouse model of spastic paraplegia. PLoS Biol 2020; 18:e3000943. [PMID: 33196637 PMCID: PMC7704050 DOI: 10.1371/journal.pbio.3000943] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 11/30/2020] [Accepted: 10/22/2020] [Indexed: 11/19/2022] Open
Abstract
In several neurodegenerative disorders, axonal pathology may originate from impaired oligodendrocyte-to-axon support of energy substrates. We previously established transgenic mice that allow measuring axonal ATP levels in electrically active optic nerves. Here, we utilize this technique to explore axonal ATP dynamics in the Plpnull/y mouse model of spastic paraplegia. Optic nerves from Plpnull/y mice exhibited lower and more variable basal axonal ATP levels and reduced compound action potential (CAP) amplitudes, providing a missing link between axonal pathology and a role of oligodendrocytes in brain energy metabolism. Surprisingly, when Plpnull/y optic nerves are challenged with transient glucose deprivation, both ATP levels and CAP decline slower, but recover faster upon reperfusion of glucose. Structurally, myelin sheaths display an increased frequency of cytosolic channels comprising glucose and monocarboxylate transporters, possibly facilitating accessibility of energy substrates to the axon. These data imply that complex metabolic alterations of the axon–myelin unit contribute to the phenotype of Plpnull/y mice. Imaging of ATP dynamics in the optic nerve axons of mice lacking the major myelin protein PLP (a model of spastic paraplegia) reveals complex alterations in the metabolic interaction between oligodendrocytes and axons, associated with structural deficits of myelin.
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8
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The Integrated UPR and ERAD in Oligodendrocytes Maintain Myelin Thickness in Adults by Regulating Myelin Protein Translation. J Neurosci 2020; 40:8214-8232. [PMID: 32958569 DOI: 10.1523/jneurosci.0604-20.2020] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 08/09/2020] [Accepted: 09/10/2020] [Indexed: 12/12/2022] Open
Abstract
Myelin proteins, which are produced in the endoplasmic reticulum (ER), are essential and necessary for maintaining myelin structure. The integrated unfold protein response (UPR) and ER-associated degradation (ERAD) are the primary ER quality control mechanism. The adaptor protein Sel1L (Suppressor/Enhancer of Lin-12-like) controls the stability of the E3 ubiquitin ligase Hrd1 (hydroxymethylglutaryl reductase degradation protein 1), and is necessary for the ERAD activity of the Sel1L-Hrd1 complex. Herein, we showed that Sel1L deficiency specifically in oligodendrocytes caused ERAD impairment, the UPR activation, and attenuation of myelin protein biosynthesis; and resulted in late-onset, progressive myelin thinning in the CNS of adult mice (both male and female). The pancreatic ER kinase (PERK) branch of the UPR functions as the master regulator of protein translation in ER-stressed cells. Importantly, PERK inactivation reversed attenuation of myelin protein biosynthesis in oligodendrocytes and restored myelin thickness in the CNS of oligodendrocyte-specific Sel1L-deficient mice (both male and female). Conversely, blockage of proteolipid protein production exacerbated myelin thinning in the CNS of oligodendrocyte-specific Sel1L-deficient mice (both male and female). These findings suggest that impaired ERAD in oligodendrocytes reduces myelin thickness in the adult CNS through suppression of myelin protein translation by activating PERK.SIGNIFICANCE STATEMENT Myelin is an enormous extended plasma membrane of oligodendrocytes that wraps and insulates axons. Myelin structure, including thickness, was thought to be extraordinarily stable in adults. Myelin proteins, which are produced in the endoplasmic reticulum (ER), are essential and necessary for maintaining myelin structure. The integrated unfolded protein response (UPR) and ER-associated degradation (ERAD) are the primary mechanism that maintains ER protein homeostasis. Herein, we explored the role of the integrated UPR and ERAD in oligodendrocytes in regulating myelin protein production and maintaining myelin structure using mouse models. The results presented in this study imply that the integrated UPR and ERAD in oligodendrocytes maintain myelin thickness in adults by regulating myelin protein production.
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Steyer AM, Ruhwedel T, Nardis C, Werner HB, Nave KA, Möbius W. Pathology of myelinated axons in the PLP-deficient mouse model of spastic paraplegia type 2 revealed by volume imaging using focused ion beam-scanning electron microscopy. J Struct Biol 2020; 210:107492. [PMID: 32156581 PMCID: PMC7196930 DOI: 10.1016/j.jsb.2020.107492] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 02/28/2020] [Accepted: 03/06/2020] [Indexed: 11/26/2022]
Abstract
Advances in electron microscopy including improved imaging techniques and state-of-the-art detectors facilitate imaging of larger tissue volumes with electron microscopic resolution. In combination with genetic tools for the generation of mouse mutants this allows assessing the three-dimensional (3D) characteristics of pathological features in disease models. Here we revisited the axonal pathology in the central nervous system of a mouse model of spastic paraplegia type 2, the Plp-/Y mouse. Although PLP is a bona fide myelin protein, the major hallmark of the disease in both SPG2 patients and mouse models are axonal swellings comprising accumulations of numerous organelles including mitochondria, gradually leading to irreversible axonal loss. To assess the number and morphology of axonal mitochondria and the overall myelin preservation we evaluated two sample preparation techniques, chemical fixation or high-pressure freezing and freeze substitution, with respect to the objective of 3D visualization. Both methods allowed visualizing distribution and morphological details of axonal mitochondria. In Plp-/Y mice the number of mitochondria is 2-fold increased along the entire axonal length. Mitochondria are also found in the excessive organelle accumulations within axonal swellings. In addition, organelle accumulations were detected within the myelin sheath and the inner tongue. We find that 3D electron microscopy is required for a comprehensive understanding of the size, content and frequency of axonal swellings, the hallmarks of axonal pathology.
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Affiliation(s)
- Anna M Steyer
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
| | - Torben Ruhwedel
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Christos Nardis
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Wiebke Möbius
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany.
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10
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Stone S, Wu S, Nave KA, Lin W. The UPR preserves mature oligodendrocyte viability and function in adults by regulating autophagy of PLP. JCI Insight 2020; 5:132364. [PMID: 32053121 DOI: 10.1172/jci.insight.132364] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 02/06/2020] [Indexed: 01/03/2023] Open
Abstract
Maintaining cellular proteostasis is essential for oligodendrocyte viability and function; however, its underlying mechanisms remain unexplored. Unfolded protein response (UPR), which comprises 3 parallel branches, inositol requiring enzyme 1 (IRE1), pancreatic ER kinase (PERK), and activating transcription factor 6α (ATF6α), is a major mechanism that maintains cellular proteostasis by facilitating protein folding, attenuating protein translation, and enhancing autophagy and ER-associated degradation. Here we report that impaired UPR in oligodendrocytes via deletion of PERK and ATF6α did not affect developmental myelination but caused late-onset mature oligodendrocyte dysfunction and death in young adult mice. The detrimental effects of the impaired UPR on mature oligodendrocytes were accompanied by autophagy impairment and intracellular proteolipid protein (PLP) accumulation and were rescued by PLP deletion. Data indicate that PLP was degraded by autophagy and that intracellular PLP accumulation was cytotoxic to oligodendrocytes. Thus, these findings imply that the UPR is required for maintaining cellular proteostasis and the viability and function of mature oligodendrocytes in adults by regulating autophagy of PLP.
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Affiliation(s)
- Sarrabeth Stone
- Department of Neuroscience and.,Institute for Translational Neuroscience, University of Minnesota, Minneapolis, Minnesota, USA
| | - Shuangchan Wu
- Department of Neuroscience and.,Institute for Translational Neuroscience, University of Minnesota, Minneapolis, Minnesota, USA
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Wensheng Lin
- Department of Neuroscience and.,Institute for Translational Neuroscience, University of Minnesota, Minneapolis, Minnesota, USA
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11
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The wmN1 Enhancer Region of the Mouse Myelin Proteolipid Protein Gene (mPlp1) is Indispensable for Expression of an mPlp1-lacZ Transgene in Both the CNS and PNS. Neurochem Res 2019; 45:663-671. [PMID: 31782102 DOI: 10.1007/s11064-019-02919-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 11/19/2019] [Accepted: 11/22/2019] [Indexed: 10/25/2022]
Abstract
The myelin proteolipid protein gene (PLP1) encodes the most abundant protein in CNS myelin. Expression of the gene must be strictly regulated, as evidenced by human X-linked leukodystrophies resulting from variations in PLP1 copy number, including elevated dosages as well as deletions. Recently, we showed that the wmN1 region in human PLP1 (hPLP1) intron 1 is required to promote high levels of an hPLP1-lacZ transgene in mice, using a Cre-lox approach. The current study tests whether loss of the wmN1 region from a related transgene containing mouse Plp1 (mPlp1) DNA produces similar results. In addition, we investigated the effects of loss of another region (ASE) in mPlp1 intron 1. Previous studies have shown that the ASE is required to promote high levels of mPlp1-lacZ expression by transfection analysis, but had no effect when removed from the native gene in mouse. Whether this is due to compensation by another regulatory element in mPlp1 that was not included in the mPlp1-lacZ constructs, or to differences in methodology, is unclear. Two transgenic mouse lines were generated that harbor mPLP(+)Z/FL. The parental transgene utilizes mPlp1 sequences (proximal 2.3 kb of 5'-flanking DNA to the first 37 bp of exon 2) to drive expression of a lacZ reporter cassette. Here we demonstrate that mPLP(+)Z/FL is expressed in oligodendrocytes, oligodendrocyte precursor cells, olfactory ensheathing cells and neurons in brain, and Schwann cells in sciatic nerve. Loss of the wmN1 region from the parental transgene abolished expression, whereas removal of the ASE had no effect.
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12
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Unal DB, Caliari SR, Lampe KJ. Engineering biomaterial microenvironments to promote myelination in the central nervous system. Brain Res Bull 2019; 152:159-174. [PMID: 31306690 DOI: 10.1016/j.brainresbull.2019.07.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Revised: 06/09/2019] [Accepted: 07/08/2019] [Indexed: 01/01/2023]
Abstract
Promoting remyelination and/or minimizing demyelination are key therapeutic strategies under investigation for diseases and injuries like multiple sclerosis (MS), spinal cord injury, stroke, and virus-induced encephalopathy. Myelination is essential for efficacious neuronal signaling. This myelination process is originated by oligodendrocyte progenitor cells (OPCs) in the central nervous system (CNS). Resident OPCs are capable of both proliferation and differentiation, and also migration to demyelinated injury sites. OPCs can then engage with these unmyelinated or demyelinated axons and differentiate into myelin-forming oligodendrocytes (OLs). However this process is frequently incomplete and often does not occur at all. Biomaterial strategies can now be used to guide OPC and OL development with the goal of regenerating healthy myelin sheaths in formerly damaged CNS tissue. Growth and neurotrophic factors delivered from such materials can promote proliferation of OPCs or differentiation into OLs. While cell transplantation techniques have been used to replace damaged cells in wound sites, they have also resulted in poor transplant cell viability, uncontrollable differentiation, and poor integration into the host. Biomaterial scaffolds made from extracellular matrix (ECM) mimics that are naturally or synthetically derived can improve transplanted cell survival, support both transplanted and endogenous cell populations, and direct their fate. In particular, stiffness and degradability of these scaffolds are two parameters that can influence the fate of OPCs and OLs. The future outlook for biomaterials research includes 3D in vitro models of myelination / remyelination / demyelination to better mimic and study these processes. These models should provide simple relationships of myelination to microenvironmental biophysical and biochemical properties to inform improved therapeutic approaches.
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Affiliation(s)
- Deniz B Unal
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22903, United States
| | - Steven R Caliari
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22903, United States; Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22903, United States
| | - Kyle J Lampe
- Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22903, United States.
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13
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Marinko J, Huang H, Penn WD, Capra JA, Schlebach JP, Sanders CR. Folding and Misfolding of Human Membrane Proteins in Health and Disease: From Single Molecules to Cellular Proteostasis. Chem Rev 2019; 119:5537-5606. [PMID: 30608666 PMCID: PMC6506414 DOI: 10.1021/acs.chemrev.8b00532] [Citation(s) in RCA: 153] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Indexed: 12/13/2022]
Abstract
Advances over the past 25 years have revealed much about how the structural properties of membranes and associated proteins are linked to the thermodynamics and kinetics of membrane protein (MP) folding. At the same time biochemical progress has outlined how cellular proteostasis networks mediate MP folding and manage misfolding in the cell. When combined with results from genomic sequencing, these studies have established paradigms for how MP folding and misfolding are linked to the molecular etiologies of a variety of diseases. This emerging framework has paved the way for the development of a new class of small molecule "pharmacological chaperones" that bind to and stabilize misfolded MP variants, some of which are now in clinical use. In this review, we comprehensively outline current perspectives on the folding and misfolding of integral MPs as well as the mechanisms of cellular MP quality control. Based on these perspectives, we highlight new opportunities for innovations that bridge our molecular understanding of the energetics of MP folding with the nuanced complexity of biological systems. Given the many linkages between MP misfolding and human disease, we also examine some of the exciting opportunities to leverage these advances to address emerging challenges in the development of therapeutics and precision medicine.
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Affiliation(s)
- Justin
T. Marinko
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Hui Huang
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Wesley D. Penn
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - John A. Capra
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
- Department
of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37245, United States
| | - Jonathan P. Schlebach
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Charles R. Sanders
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
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14
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Erwig MS, Patzig J, Steyer AM, Dibaj P, Heilmann M, Heilmann I, Jung RB, Kusch K, Möbius W, Jahn O, Nave KA, Werner HB. Anillin facilitates septin assembly to prevent pathological outfoldings of central nervous system myelin. eLife 2019; 8:43888. [PMID: 30672734 PMCID: PMC6344079 DOI: 10.7554/elife.43888] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 01/11/2019] [Indexed: 12/15/2022] Open
Abstract
Myelin serves as an axonal insulator that facilitates rapid nerve conduction along axons. By transmission electron microscopy, a healthy myelin sheath comprises compacted membrane layers spiraling around the cross-sectioned axon. Previously we identified the assembly of septin filaments in the innermost non-compacted myelin layer as one of the latest steps of myelin maturation in the central nervous system (CNS) (Patzig et al., 2016). Here we show that loss of the cytoskeletal adaptor protein anillin (ANLN) from oligodendrocytes disrupts myelin septin assembly, thereby causing the emergence of pathological myelin outfoldings. Since myelin outfoldings are a poorly understood hallmark of myelin disease and brain aging we assessed axon/myelin-units in Anln-mutant mice by focused ion beam-scanning electron microscopy (FIB-SEM); myelin outfoldings were three-dimensionally reconstructed as large sheets of multiple compact membrane layers. We suggest that anillin-dependent assembly of septin filaments scaffolds mature myelin sheaths, facilitating rapid nerve conduction in the healthy CNS.
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Affiliation(s)
- Michelle S Erwig
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Julia Patzig
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Anna M Steyer
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
| | - Payam Dibaj
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Mareike Heilmann
- Department of Cellular Biochemistry, Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle, Germany
| | - Ingo Heilmann
- Department of Cellular Biochemistry, Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Halle, Germany
| | - Ramona B Jung
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Kathrin Kusch
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Wiebke Möbius
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Olaf Jahn
- Proteomics Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
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15
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Inoue K. Pelizaeus-Merzbacher Disease: Molecular and Cellular Pathologies and Associated Phenotypes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1190:201-216. [PMID: 31760646 DOI: 10.1007/978-981-32-9636-7_13] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Pelizaeus-Merzbacher disease (PMD) represents a group of disorders known as hypomyelinating leukodystrophies, which are characterized by abnormal development and maintenance of myelin in the central nervous system. PMD is caused by different types of mutations in the proteolipid protein 1 (PLP1) gene, which encodes a major myelin membrane lipoprotein. These mutations in the PLP1 gene result in distinct cellular and molecular pathologies and a spectrum of clinical phenotypes. In this chapter, I discuss the historical aspects and current understanding of the mechanisms underlying how different PLP1 mutations disrupt the normal process of myelination and result in PMD and other disorders.
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Affiliation(s)
- Ken Inoue
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan.
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16
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Hamdan H, Patyal P, Kockara NT, Wight PA. The wmN1 enhancer region in intron 1 is required for expression of human PLP1. Glia 2018; 66:1763-1774. [PMID: 29683207 DOI: 10.1002/glia.23339] [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: 02/01/2017] [Revised: 03/10/2018] [Accepted: 03/22/2018] [Indexed: 12/13/2022]
Abstract
The myelin proteolipid protein gene (PLP1) encodes the most abundant protein present in myelin from the central nervous system (CNS). Its expression must be tightly controlled as evidenced by mutations that alter PLP1 dosage; both overexpression (elevated PLP1 copy number) and lack thereof (PLP1 deletion) result in X-linked genetic disorders in man. However, not much is known about the mechanisms that govern expression of the human gene. To address this, transgenic mice were generated which utilize human PLP1 (hPLP1) sequences (proximal 6.2 kb of 5'-flanking DNA to the first 38 bp of exon 2) to drive expression of a lacZ reporter cassette. LoxP sites were incorporated around a 1.5-kb section of hPLP1 intron 1 since it contains sequence orthologous to the wmN1 region from mouse which, previously, was shown to augment expression of a minimally-promoted transgene coincident with the active myelination period of CNS development. Eight transgenic lines were generated with the parental, 6.2hPLP(+)Z/FL, transgene. All lines expressed the transgene appropriately in brain as evidenced by staining with X-gal in white matter regions and olfactory bulb. Removal of the "wmN1" region from 6.2hPLP(+)Z/FL with a ubiquitously expressed Cre-driver caused a dramatic reduction in transgene activity. These results demonstrate for the first time that the wmN1 enhancer region: (1) is functional in hPLP1; (2) works in collaboration with its native promoter-not just a basal heterologous promoter; (3) is required for high levels of hPLP1 gene activity; (4) has a broader effect, both spatially and temporally, than originally projected with mPlp1.
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Affiliation(s)
- Hamdan Hamdan
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Pankaj Patyal
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Neriman T Kockara
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Patricia A Wight
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
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17
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Wight PA. Effects of Intron 1 Sequences on Human PLP1 Expression: Implications for PLP1-Related Disorders. ASN Neuro 2017; 9:1759091417720583. [PMID: 28735559 PMCID: PMC5528184 DOI: 10.1177/1759091417720583] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Alterations in the myelin proteolipid protein gene ( PLP1) may result in rare X-linked disorders in humans such as Pelizaeus-Merzbacher disease and spastic paraplegia type 2. PLP1 expression must be tightly regulated since null mutations, as well as elevated PLP1 copy number, both lead to disease. Previous studies with Plp1-lacZ transgenic mice have demonstrated that mouse Plp1 ( mPlp1) intron 1 DNA (which accounts for slightly more than half of the gene) is required for the mPlp1 promoter to drive significant levels of reporter gene expression in brain. However not much is known about the mechanisms that control expression of the human PLP1 gene ( hPLP1). Therefore this review will focus on sequences in hPLP1 intron 1 DNA deemed important for hPLP1 gene activity as well as a couple of "human-specific" supplementary exons within the first intron which are utilized to generate novel splice variants, and the potential role that these sequences may play in PLP1-linked disorders.
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Affiliation(s)
- Patricia A Wight
- 1 Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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18
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Ishimoto T, Ninomiya K, Inoue R, Koike M, Uchiyama Y, Mori H. Mice lacking BCAS1, a novel myelin-associated protein, display hypomyelination, schizophrenia-like abnormal behaviors, and upregulation of inflammatory genes in the brain. Glia 2017; 65:727-739. [PMID: 28230289 DOI: 10.1002/glia.23129] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 01/30/2017] [Accepted: 02/01/2017] [Indexed: 12/22/2022]
Abstract
The abnormal expression and function of myelin-related proteins contribute to nervous system dysfunction associated with neuropsychiatric disorders; however, the underlying mechanism of this remains unclear. We found here that breast carcinoma amplified sequence 1 (BCAS1), a basic protein abundant in the brain, was expressed specifically in oligodendrocytes and Schwann cells, and that its expression level was decreased by demyelination. This suggests that BCAS1 is a novel myelin-associated protein. BCAS1 knockout mice displayed schizophrenia-like behavioral abnormalities and a tendency toward reduced anxiety-like behaviors. Moreover, we found that the loss of BCAS1 specifically induced hypomyelination and the expression of inflammation-related genes in the brain. These observations provide a novel insight into the functional link between oligodendrocytes and inflammation and/or abnormal behaviors.
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Affiliation(s)
- Tetsuya Ishimoto
- Department of Molecular Neuroscience, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
| | - Kensuke Ninomiya
- Department of Anatomy and Developmental Biology, Graduate School of Medicine, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Ran Inoue
- Department of Molecular Neuroscience, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
| | - Masato Koike
- Department of Cell Biology and Neuroscience, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan
| | - Yasuo Uchiyama
- Department of Cell Biology and Neuroscience, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan
| | - Hisashi Mori
- Department of Molecular Neuroscience, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
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19
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Clayton BLL, Popko B. Endoplasmic reticulum stress and the unfolded protein response in disorders of myelinating glia. Brain Res 2016; 1648:594-602. [PMID: 27055915 PMCID: PMC5036997 DOI: 10.1016/j.brainres.2016.03.046] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 03/25/2016] [Accepted: 03/26/2016] [Indexed: 12/12/2022]
Abstract
Myelin is vital to the proper function of the nervous system. Oligodendrocytes in the CNS and Schwann cells in the PNS are the glial cells responsible for generating the myelin sheath. Myelination requires the production of a vast amount of proteins and lipid-rich membrane, which puts a heavy load on the secretory pathway of myelinating glia and leaves them susceptible to endoplasmic reticulum (ER) stress. Cells respond to ER stress by activating the unfolded protein response (UPR). The UPR is initially protective but in situations of prolonged unresolved stress the UPR can lead to the apoptotic death of the stressed cell. There is strong evidence that ER stress and the UPR play a role in a number of disorders of myelin and myelinating glia, including multiple sclerosis, Pelizaeus-Merzbacher disease, Vanishing White Matter Disease, and Charcot-Marie-Tooth disease. In this review we discuss the role that ER stress and the UPR play in these disorders of myelin. In addition, we discuss the progress that has been made in our understanding of the effect genetic and pharmacological manipulation of the UPR has in mouse models of these disorders and the novel therapeutic potential of targeting the UPR that these studies support. This article is part of a Special Issue entitled SI:ER stress.
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Affiliation(s)
- Benjamin L L Clayton
- Department of Neurology, The University of Chicago Center for Peripheral Neuropathy, The University of Chicago, IL 60637, United States
| | - Brian Popko
- Department of Neurology, The University of Chicago Center for Peripheral Neuropathy, The University of Chicago, IL 60637, United States.
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20
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Laukka JJ, Kamholz J, Bessert D, Skoff RP. Novel pathologic findings in patients with Pelizaeus-Merzbacher disease. Neurosci Lett 2016; 627:222-32. [PMID: 27222925 PMCID: PMC4948744 DOI: 10.1016/j.neulet.2016.05.028] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 05/13/2016] [Accepted: 05/14/2016] [Indexed: 10/21/2022]
Abstract
Pelizaeus-Merzbacher disease (PMD) is an X-linked inherited hypomyelinating disorder caused by mutations in the gene encoding proteolipid protein (PLP), the major structural protein in central nervous system (CNS) myelin. Prior to our study, whether hypomyelination in PMD was caused by demyelination, abnormally thin sheaths or failure to form myelin was unknown. In this study, we compared the microscopic pathology of myelin from brain tissue of 3 PMD patients with PLP1 duplications to that of a patient with a complete PLP1 deletion. Autopsy tissue procured from PMD patients was embedded in paraffin for immunocytochemistry and plastic for electron microscopy to obtain highresolution fiber pathology of cerebrum and corpus callosum. Through histological stains, immunocytochemistry and electron microscopy, our study illustrates unique pathologic findings between the two different types of mutations. Characteristic of the patient with a PLP1 deletion, myelin sheaths showed splitting and decompaction of myelin, confirming for the first time that myelin in PLP1 deletion patients is similar to that of rodent models with gene deletions. Myelin thickness and g-ratios of some fibers, in relation to axon diameter was abnormally thin, suggesting that oligodendrocytes remain metabolically functional and/or are attempting to make myelin. Many fibers showed swollen, progressive degenerative changes to axons in addition to the dissolution of myelin. All three duplication cases shared remarkable fiber pathology including swellings, constriction and/or transection and involution of myelin. Characteristic of PLP1 duplication patients, many axons showed segmental demyelination along their length. Still other axons had abnormally thick myelin sheaths, suggestive of continued myelination. Thus, each type of mutation exhibited unique pathology even though commonality to both mutations included involution of myelin, myelin balls and degeneration of axons. This pathology study describes findings unique to each mutation that suggests the mechanism causing fiber pathology is likewise heterogeneous.
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Affiliation(s)
- Jeremy J Laukka
- Department of Neuroscience, University of Toledo, College of Medicine and Life Science, Toledo, OH 43614, United States; Department of Neurology, University of Toledo, College of Medicine and Life Science, Toledo, OH 43614, United States.
| | - John Kamholz
- Center for Molecular Medicine and Genetics, Wayne State University, School of Medicine, Detroit, MI 48201, United States; Department of Neurology, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, United States
| | - Denise Bessert
- Department of Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI 48201, United States
| | - Robert P Skoff
- Center for Molecular Medicine and Genetics, Wayne State University, School of Medicine, Detroit, MI 48201, United States; Department of Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI 48201, United States
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21
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Myelin Proteolipid Protein Complexes with αv Integrin and AMPA Receptors In Vivo and Regulates AMPA-Dependent Oligodendrocyte Progenitor Cell Migration through the Modulation of Cell-Surface GluR2 Expression. J Neurosci 2015; 35:12018-32. [PMID: 26311781 DOI: 10.1523/jneurosci.5151-14.2015] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED In previous studies, stimulation of ionotropic AMPA/kainate glutamate receptors on cultured oligodendrocyte cells induced the formation of a signaling complex that includes the AMPA receptor, integrins, calcium-binding proteins, and, surprisingly, the myelin proteolipid protein (PLP). AMPA stimulation of cultured oligodendrocyte progenitor cells (OPCs) also caused an increase in OPC migration. The current studies focused primarily on the formation of the PLP-αv integrin-AMPA receptor complex in vivo and whether complex formation impacts OPC migration in the brain. We found that in wild-type cerebellum, PLP associates with αv integrin and the calcium-impermeable GluR2 subunit of the AMPA receptor, but in mice lacking PLP, αv integrin did not associate with GluR2. Live imaging studies of OPC migration in ex vivo cerebellar slices demonstrated altered OPC migratory responses to neurotransmitter stimulation in the absence of PLP and GluR2 or when αv integrin levels were reduced. Chemotaxis assays of purified OPCs revealed that AMPA stimulation was neither attractive nor repulsive but clearly increased the migration rate of wild-type but not PLP null OPCs. AMPA receptor stimulation of wild-type OPCs caused decreased cell-surface expression of the GluR2 AMPA receptor subunit and increased intracellular Ca(2+) signaling, whereas PLP null OPCs did not reduce GluR2 at the cell surface or increase Ca(2+) signaling in response to AMPA treatment. Together, these studies demonstrate that PLP is critical for OPC responses to glutamate signaling and has important implications for OPC responses when levels of glutamate are high in the extracellular space, such as following demyelination. SIGNIFICANCE STATEMENT After demyelination, such as occurs in multiple sclerosis, remyelination of axons is often incomplete, leading to loss of neuronal function and clinical disability. Remyelination may fail because oligodendrocyte precursor cells (OPCs) do not completely migrate into demyelinated areas or OPCs in lesions may not mature into myelinating oligodendrocytes. We have found that the myelin proteolipid protein is critical to regulating OPC migratory responses to the neurotransmitter glutamate through modulation of cell-surface expression of the calcium-impermeable GluR2 subunit of the AMPA glutamate receptor and increased intercellular Ca(2+) signaling. Altered glutamate homeostasis has been reported in demyelinated lesions. Therefore, understanding how OPCs respond to glutamate has important implications for treatment after white matter injury and disease.
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22
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Kim MY, Kim HY, Hong J, Kim D, Lee H, Cheong E, Lee Y, Roth J, Kim DG, Min DS, Choi KY. CXXC5 plays a role as a transcription activator for myelin genes on oligodendrocyte differentiation. Glia 2015; 64:350-62. [DOI: 10.1002/glia.22932] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 09/07/2015] [Accepted: 09/24/2015] [Indexed: 12/19/2022]
Affiliation(s)
- Mi-Yeon Kim
- Translational Research Center for Protein Function Control; Yonsei University; Seoul 120-749 Korea
- Department of Biotechnology; College of Life Science and Biotechnology, Yonsei University; Seoul 120-749 Korea
| | - Hyun-Yi Kim
- Translational Research Center for Protein Function Control; Yonsei University; Seoul 120-749 Korea
- Department of Biotechnology; College of Life Science and Biotechnology, Yonsei University; Seoul 120-749 Korea
| | - Jiso Hong
- Biological Sciences; Korea Advanced Institute of Science and Technology (KAIST); Daejeon 305-701 Korea
| | - Daesoo Kim
- Biological Sciences; Korea Advanced Institute of Science and Technology (KAIST); Daejeon 305-701 Korea
| | - Hyojung Lee
- Translational Research Center for Protein Function Control; Yonsei University; Seoul 120-749 Korea
- Department of Biotechnology; College of Life Science and Biotechnology, Yonsei University; Seoul 120-749 Korea
| | - Eunji Cheong
- Translational Research Center for Protein Function Control; Yonsei University; Seoul 120-749 Korea
- Department of Biotechnology; College of Life Science and Biotechnology, Yonsei University; Seoul 120-749 Korea
| | - Yangsin Lee
- Department of Integrated OMICS For Biomedical Science; WCU Program of Graduate School, Yonsei University; Seoul 120-749 Korea
| | - Jürgen Roth
- Department of Integrated OMICS For Biomedical Science; WCU Program of Graduate School, Yonsei University; Seoul 120-749 Korea
| | - Dong Goo Kim
- Department of Pharmacology; Brain Research Institute, Brain Korea 21 Project for Medical Science, Severance Biomedical Science Institute, Yonsei University, College of Medicine; Seoul 120-749 Korea
| | - Do Sik Min
- Translational Research Center for Protein Function Control; Yonsei University; Seoul 120-749 Korea
- Department of Molecular Biology; College of Natural Science, Pusan National University; Busan 609-735 Korea
| | - Kang-Yell Choi
- Translational Research Center for Protein Function Control; Yonsei University; Seoul 120-749 Korea
- Department of Biotechnology; College of Life Science and Biotechnology, Yonsei University; Seoul 120-749 Korea
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23
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Abstract
Myelination of axons in the nervous system of vertebrates enables fast, saltatory impulse propagation, one of the best-understood concepts in neurophysiology. However, it took a long while to recognize the mechanistic complexity both of myelination by oligodendrocytes and Schwann cells and of their cellular interactions. In this review, we highlight recent advances in our understanding of myelin biogenesis, its lifelong plasticity, and the reciprocal interactions of myelinating glia with the axons they ensheath. In the central nervous system, myelination is also stimulated by axonal activity and astrocytes, whereas myelin clearance involves microglia/macrophages. Once myelinated, the long-term integrity of axons depends on glial supply of metabolites and neurotrophic factors. The relevance of this axoglial symbiosis is illustrated in normal brain aging and human myelin diseases, which can be studied in corresponding mouse models. Thus, myelinating cells serve a key role in preserving the connectivity and functions of a healthy nervous system.
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Affiliation(s)
- Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, D-37075 Göttingen, Germany; ,
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24
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García-Díaz B, Riquelme R, Varela-Nieto I, Jiménez AJ, de Diego I, Gómez-Conde AI, Matas-Rico E, Aguirre JÁ, Chun J, Pedraza C, Santín LJ, Fernández O, Rodríguez de Fonseca F, Estivill-Torrús G. Loss of lysophosphatidic acid receptor LPA1 alters oligodendrocyte differentiation and myelination in the mouse cerebral cortex. Brain Struct Funct 2014; 220:3701-20. [PMID: 25226845 DOI: 10.1007/s00429-014-0885-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 09/08/2014] [Indexed: 12/16/2022]
Abstract
Lysophosphatidic acid (LPA) is an intercellular signaling lipid that regulates multiple cellular functions, acting through specific G-protein coupled receptors (LPA(1-6)). Our previous studies using viable Malaga variant maLPA1-null mice demonstrated the requirement of the LPA1 receptor for normal proliferation, differentiation, and survival of the neuronal precursors. In the cerebral cortex LPA1 is expressed extensively in differentiating oligodendrocytes, in parallel with myelination. Although exogenous LPA-induced effects have been investigated in myelinating cells, the in vivo contribution of LPA1 to normal myelination remains to be demonstrated. This study identified a relevant in vivo role for LPA1 as a regulator of cortical myelination. Immunochemical analysis in adult maLPA1-null mice demonstrated a reduction in the steady-state levels of the myelin proteins MBP, PLP/DM20, and CNPase in the cerebral cortex. The myelin defects were confirmed using magnetic resonance spectroscopy and electron microscopy. Stereological analysis limited the defects to adult differentiating oligodendrocytes, without variation in the NG2+ precursor cells. Finally, a possible mechanism involving oligodendrocyte survival was demonstrated by the impaired intracellular transport of the PLP/DM20 myelin protein which was accompanied by cellular loss, suggesting stress-induced apoptosis. These findings describe a previously uncharacterized in vivo functional role for LPA1 in the regulation of oligodendrocyte differentiation and myelination in the CNS, underlining the importance of the maLPA1-null mouse as a model for the study of demyelinating diseases.
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Affiliation(s)
- Beatriz García-Díaz
- Laboratorio de Investigación, UGC Intercentros de Neurociencias, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospitales Universitarios Regional de Málaga y Virgen de la Victoria, Hospital Civil, Pabellón 5, Planta Sótano, Plaza del Hospital Civil s/n, 29009, Málaga, Spain.,Department of Neurology, H. Houston Merritt Clinical Research Center, Columbia University Medical Center, New York, NY, 10032, USA
| | - Raquel Riquelme
- Instituto de Investigaciones Biomédicas 'Alberto Sols', Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid (UAM), 28029, Madrid, Spain
| | - Isabel Varela-Nieto
- Instituto de Investigaciones Biomédicas 'Alberto Sols', Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid (UAM), 28029, Madrid, Spain
| | - Antonio Jesús Jiménez
- Departamento de Biología Celular, Genética y Fisiología, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga, 29071, Málaga, Spain
| | - Isabel de Diego
- Departamento de Anatomía y Medicina Legal, Universidad de Málaga, 29071, Málaga, Spain
| | - Ana Isabel Gómez-Conde
- ECAI de Microscopía, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospitales Universitarios Regional de Málaga y Virgen de la Victoria, 29010, Málaga, Spain
| | - Elisa Matas-Rico
- Laboratorio de Investigación, UGC Intercentros de Neurociencias, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospitales Universitarios Regional de Málaga y Virgen de la Victoria, Hospital Civil, Pabellón 5, Planta Sótano, Plaza del Hospital Civil s/n, 29009, Málaga, Spain.,Division of Cell Biology I, The Netherlands Cancer Institute, 1066CX, Amsterdam, The Netherlands
| | - José Ángel Aguirre
- Departamento de Fisiología Humana y Educación Físico Deportiva, Universidad de Málaga, 29071, Málaga, Spain
| | - Jerold Chun
- Department of Molecular and Cellular Neuroscience, Dorris Neuroscience Centre, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Carmen Pedraza
- Departamento de Psicobiología y Metodología de las Ciencias del Comportamiento, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga, 29071, Málaga, Spain
| | - Luis Javier Santín
- Departamento de Psicobiología y Metodología de las Ciencias del Comportamiento, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga, 29071, Málaga, Spain
| | - Oscar Fernández
- Neurology Service, UGC Intercentros de Neurociencias, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospitales Universitarios Regional de Málaga y Virgen de la Victoria, Universidad de Málaga, 29010, Málaga, Spain
| | - Fernando Rodríguez de Fonseca
- Laboratorio de Medicina Regenerativa, UGC de Salud Mental, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Universitario Regional de Málaga, 29010, Málaga, Spain
| | - Guillermo Estivill-Torrús
- Laboratorio de Investigación, UGC Intercentros de Neurociencias, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospitales Universitarios Regional de Málaga y Virgen de la Victoria, Hospital Civil, Pabellón 5, Planta Sótano, Plaza del Hospital Civil s/n, 29009, Málaga, Spain. .,ECAI de Microscopía, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospitales Universitarios Regional de Málaga y Virgen de la Victoria, 29010, Málaga, Spain.
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Laukka JJ, Makki MI, Lafleur T, Stanley J, Kamholz J, Garbern JY. Diffusion tensor imaging of patients with proteolipid protein 1 gene mutations. J Neurosci Res 2014; 92:1723-32. [PMID: 25156430 DOI: 10.1002/jnr.23458] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 06/10/2014] [Accepted: 07/05/2014] [Indexed: 11/08/2022]
Abstract
Pelizaeus-Merzbacher disease (PMD) is an X-linked disorder of the central nervous system (CNS) caused by a wide variety of mutations affecting proteolipid protein 1 (PLP1). We assessed the effects of PLP1 mutations on water diffusion in CNS white matter by using diffusion tensor imaging. Twelve patients with different PLP1 point mutations encompassing a range of clinical phenotypes were analyzed, and the results were compared with a group of 12 age-matched controls. The parallel (λ// ), perpendicular (λ⊥ ), and apparent diffusion coefficients (ADC) and fractional anisotropy were measured in both limbs of the internal capsule, the genu and splenium of corpus callosum, the base of the pons, and the cerebral peduncles. The mean ADC and λ⊥ in the PMD patient group were both significantly increased in all selected structures, except for the base of the pons, compared with controls. PMD patients with the most severe disease, however, had a significant increase of both λ// and λ⊥ . In contrast, more mildly affected patients had much smaller changes in λ// and λ⊥ . These data suggest that myelin, the structure responsible in part for the λ⊥ barrier, is the major site of disease pathogenesis in this heterogeneous group of patients. Axons, in contrast, the structures mainly responsible for λ// , are much less affected, except within the subgroup of patients with the most severe disease. Clinical disability in patients with PLP1 point mutation is thus likely determined by the extent of pathological involvement of both myelin and axons, with alterations of both structures causing the most severe disease. © 2014 Wiley Periodicals, Inc.
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Affiliation(s)
- Jeremy J Laukka
- Department of Neuroscience, University of Toledo, Toledo, Ohio; Center of Molecular Medicine and Genetics, Wayne State University, Detroit, Michigan
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Petit B, Giraudet F, Béchon C, Bardin L, Avan P, Boespflug-Tanguy O, Bégou M. Mice with a deletion of the major central myelin protein exhibit hypersensitivity to noxious thermal stimuli: involvement of central sensitization. Neurobiol Dis 2014; 65:55-68. [DOI: 10.1016/j.nbd.2014.01.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 12/10/2013] [Accepted: 01/04/2014] [Indexed: 01/10/2023] Open
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Bakhti M, Aggarwal S, Simons M. Myelin architecture: zippering membranes tightly together. Cell Mol Life Sci 2014; 71:1265-77. [PMID: 24165921 PMCID: PMC11113231 DOI: 10.1007/s00018-013-1492-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Revised: 09/11/2013] [Accepted: 10/07/2013] [Indexed: 12/12/2022]
Abstract
Rapid nerve conduction requires the coating of axons by a tightly packed multilayered myelin membrane. In the central nervous system, myelin is formed from cellular processes that extend from oligodendrocytes and wrap in a spiral fashion around an axon, resulting in the close apposition of adjacent myelin membrane bilayers. In this review, we discuss the physical principles underlying the zippering of the plasma membrane of oligodendrocytes at the cytoplasmic and extracellular leaflet. We propose that the interaction of the myelin basic protein with the cytoplasmic leaflet of the myelin bilayer triggers its polymerization into a fibrous network that drives membrane zippering and protein extrusion. In contrast, the adhesion of the extracellular surfaces of myelin requires the down-regulation of repulsive components of the glycocalyx, in order to uncover weak and unspecific attractive forces that bring the extracellular surfaces into close contact. Unveiling the mechanisms of myelin membrane assembly at the cytoplasmic and extracelluar sites may help to understand how the myelin bilayers are disrupted and destabilized in the different demyelinating diseases.
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Affiliation(s)
- Mostafa Bakhti
- Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, Göttingen, Germany
- Department of Neurology, University of Göttingen, Robert-Koch-Str. 40, Göttingen, Germany
- Present Address: Institute of Diabetes and Regeneration Research, Helmholtz Zentrum München, Neuherberg, Germany
| | - Shweta Aggarwal
- Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, Göttingen, Germany
- Department of Neurology, University of Göttingen, Robert-Koch-Str. 40, Göttingen, Germany
| | - Mikael Simons
- Max-Planck-Institute of Experimental Medicine, Hermann-Rein-Str. 3, Göttingen, Germany
- Department of Neurology, University of Göttingen, Robert-Koch-Str. 40, Göttingen, Germany
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Beirowski B. Concepts for regulation of axon integrity by enwrapping glia. Front Cell Neurosci 2013; 7:256. [PMID: 24391540 PMCID: PMC3867696 DOI: 10.3389/fncel.2013.00256] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 11/25/2013] [Indexed: 12/16/2022] Open
Abstract
Long axons and their enwrapping glia (EG; Schwann cells (SCs) and oligodendrocytes (OLGs)) form a unique compound structure that serves as conduit for transport of electric and chemical information in the nervous system. The peculiar cytoarchitecture over an enormous length as well as its substantial energetic requirements make this conduit particularly susceptible to detrimental alterations. Degeneration of long axons independent of neuronal cell bodies is observed comparatively early in a range of neurodegenerative conditions as a consequence of abnormalities in SCs and OLGs . This leads to the most relevant disease symptoms and highlights the critical role that these glia have for axon integrity, but the underlying mechanisms remain elusive. The quest to understand why and how axons degenerate is now a crucial frontier in disease-oriented research. This challenge is most likely to lead to significant progress if the inextricable link between axons and their flanking glia in pathological situations is recognized. In this review I compile recent advances in our understanding of the molecular programs governing axon degeneration, and mechanisms of EG’s non-cell autonomous impact on axon-integrity. A particular focus is placed on emerging evidence suggesting that EG nurture long axons by virtue of their intimate association, release of trophic substances, and neurometabolic coupling. The correction of defects in these functions has the potential to stabilize axons in a variety of neuronal diseases in the peripheral nervous system and central nervous system (PNS and CNS).
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Affiliation(s)
- Bogdan Beirowski
- Department of Genetics, Washington University School of Medicine Saint Louis, MO, USA
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Clinically relevant intronic splicing enhancer mutation in myelin proteolipid protein leads to progressive microglia and astrocyte activation in white and gray matter regions of the brain. J Neuroinflammation 2013; 10:146. [PMID: 24314267 PMCID: PMC3906979 DOI: 10.1186/1742-2094-10-146] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 11/27/2013] [Indexed: 02/06/2023] Open
Abstract
INTRODUCTION Mutations in proteolipid protein (PLP), the most abundant myelin protein in the CNS, cause the X-linked dysmyelinating leukodystrophies, Pelizaeus-Merzbacher disease (PMD) and spastic paraplegia type 2 (SPG2). Point mutations, deletion, and duplication of the PLP1 gene cause PMD/SPG2 with varying clinical presentation. Deletion of an intronic splicing enhancer (ISEdel) within intron 3 of the PLP1 gene is associated with a mild form of PMD. Clinical and preclinical studies have indicated that mutations in myelin proteins, including PLP, can induce neuroinflammation, but the temporal and spatial onset of the reactive glia response in a clinically relevant mild form of PMD has not been defined. METHODS A PLP-ISEdel knockin mouse was used to examine the behavioral and neuroinflammatory consequences of a deletion within intron 3 of the PLP gene, at two time points (two and four months old) early in the pathological progression. Mice were characterized functionally using the open field task, elevated plus maze, and nesting behavior. Quantitative neuropathological analysis was for markers of astrocytes (GFAP), microglia (IBA1, CD68, MHCII) and axons (APP). The Aperio ScanScope was used to generate a digital, high magnification photomicrograph of entire brain sections. These digital slides were used to quantify the immunohistochemical staining in ten different brain regions to assess the regional heterogeneity in the reactive astrocyte and microglial response. RESULTS The PLP-ISEdel mice exhibited behavioral deficits in the open field and nesting behavior at two months, which did not worsen by four months of age. A marker of axonal injury (APP) increased from two months to four months of age. Striking was the robust reactive astrocyte and microglia response which was also progressive. In the two-month-old mice, the astrocyte and microglia reactivity was most apparent in white matter rich regions of the brain. By four months of age the gliosis had become widespread and included both white as well as gray matter regions of the brain. CONCLUSIONS Our results indicate, along with other preclinical models of PMD, that an early reactive glia response occurs following mutations in the PLP gene, which may represent a potentially clinically relevant, oligodendrocyte-independent therapeutic target for PMD.
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Heng MY, Lin ST, Verret L, Huang Y, Kamiya S, Padiath QS, Tong Y, Palop JJ, Huang EJ, Ptácχek LJ, Fu YH. Lamin B1 mediates cell-autonomous neuropathology in a leukodystrophy mouse model. J Clin Invest 2013; 123:2719-29. [PMID: 23676464 PMCID: PMC3668844 DOI: 10.1172/jci66737] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 03/19/2013] [Indexed: 01/20/2023] Open
Abstract
Adult-onset autosomal-dominant leukodystrophy (ADLD) is a progressive and fatal neurological disorder characterized by early autonomic dysfunction, cognitive impairment, pyramidal tract and cerebellar dysfunction, and white matter loss in the central nervous system. ADLD is caused by duplication of the LMNB1 gene, which results in increased lamin B1 transcripts and protein expression. How duplication of LMNB1 leads to myelin defects is unknown. To address this question, we developed a mouse model of ADLD that overexpresses lamin B1. These mice exhibited cognitive impairment and epilepsy, followed by age-dependent motor deficits. Selective overexpression of lamin B1 in oligodendrocytes also resulted in marked motor deficits and myelin defects, suggesting these deficits are cell autonomous. Proteomic and genome-wide transcriptome studies indicated that lamin B1 overexpression is associated with downregulation of proteolipid protein, a highly abundant myelin sheath component that was previously linked to another myelin-related disorder, Pelizaeus-Merzbacher disease. Furthermore, we found that lamin B1 overexpression leads to reduced occupancy of Yin Yang 1 transcription factor at the promoter region of proteolipid protein. These studies identify a mechanism by which lamin B1 overexpression mediates oligodendrocyte cell-autonomous neuropathology in ADLD and implicate lamin B1 as an important regulator of myelin formation and maintenance during aging.
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Affiliation(s)
- Mary Y. Heng
- Department of Neurology, UCSF, San Francisco, California, USA.
Gladstone Institute of Neurological Disease, San Francisco,
California, USA. Howard Hughes Medical Institute, San Francisco,
California, USA. Department of Pathology, UCSF, San Francisco,
California, USA. Veterans Affairs Medical Center, San Francisco,
California, USA
| | - Shu-Ting Lin
- Department of Neurology, UCSF, San Francisco, California, USA.
Gladstone Institute of Neurological Disease, San Francisco,
California, USA. Howard Hughes Medical Institute, San Francisco,
California, USA. Department of Pathology, UCSF, San Francisco,
California, USA. Veterans Affairs Medical Center, San Francisco,
California, USA
| | - Laure Verret
- Department of Neurology, UCSF, San Francisco, California, USA.
Gladstone Institute of Neurological Disease, San Francisco,
California, USA. Howard Hughes Medical Institute, San Francisco,
California, USA. Department of Pathology, UCSF, San Francisco,
California, USA. Veterans Affairs Medical Center, San Francisco,
California, USA
| | - Yong Huang
- Department of Neurology, UCSF, San Francisco, California, USA.
Gladstone Institute of Neurological Disease, San Francisco,
California, USA. Howard Hughes Medical Institute, San Francisco,
California, USA. Department of Pathology, UCSF, San Francisco,
California, USA. Veterans Affairs Medical Center, San Francisco,
California, USA
| | - Sherry Kamiya
- Department of Neurology, UCSF, San Francisco, California, USA.
Gladstone Institute of Neurological Disease, San Francisco,
California, USA. Howard Hughes Medical Institute, San Francisco,
California, USA. Department of Pathology, UCSF, San Francisco,
California, USA. Veterans Affairs Medical Center, San Francisco,
California, USA
| | - Quasar S. Padiath
- Department of Neurology, UCSF, San Francisco, California, USA.
Gladstone Institute of Neurological Disease, San Francisco,
California, USA. Howard Hughes Medical Institute, San Francisco,
California, USA. Department of Pathology, UCSF, San Francisco,
California, USA. Veterans Affairs Medical Center, San Francisco,
California, USA
| | - Ying Tong
- Department of Neurology, UCSF, San Francisco, California, USA.
Gladstone Institute of Neurological Disease, San Francisco,
California, USA. Howard Hughes Medical Institute, San Francisco,
California, USA. Department of Pathology, UCSF, San Francisco,
California, USA. Veterans Affairs Medical Center, San Francisco,
California, USA
| | - Jorge J. Palop
- Department of Neurology, UCSF, San Francisco, California, USA.
Gladstone Institute of Neurological Disease, San Francisco,
California, USA. Howard Hughes Medical Institute, San Francisco,
California, USA. Department of Pathology, UCSF, San Francisco,
California, USA. Veterans Affairs Medical Center, San Francisco,
California, USA
| | - Eric J. Huang
- Department of Neurology, UCSF, San Francisco, California, USA.
Gladstone Institute of Neurological Disease, San Francisco,
California, USA. Howard Hughes Medical Institute, San Francisco,
California, USA. Department of Pathology, UCSF, San Francisco,
California, USA. Veterans Affairs Medical Center, San Francisco,
California, USA
| | - Louis J. Ptácχek
- Department of Neurology, UCSF, San Francisco, California, USA.
Gladstone Institute of Neurological Disease, San Francisco,
California, USA. Howard Hughes Medical Institute, San Francisco,
California, USA. Department of Pathology, UCSF, San Francisco,
California, USA. Veterans Affairs Medical Center, San Francisco,
California, USA
| | - Ying-Hui Fu
- Department of Neurology, UCSF, San Francisco, California, USA.
Gladstone Institute of Neurological Disease, San Francisco,
California, USA. Howard Hughes Medical Institute, San Francisco,
California, USA. Department of Pathology, UCSF, San Francisco,
California, USA. Veterans Affairs Medical Center, San Francisco,
California, USA
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Han H, Myllykoski M, Ruskamo S, Wang C, Kursula P. Myelin-specific proteins: a structurally diverse group of membrane-interacting molecules. Biofactors 2013; 39:233-41. [PMID: 23780694 DOI: 10.1002/biof.1076] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 11/15/2012] [Indexed: 12/15/2022]
Abstract
The myelin sheath is a multilayered membrane in the nervous system, which has unique biochemical properties. Myelin carries a set of specific high-abundance proteins, the structure and function of which are still poorly understood. The proteins of the myelin sheath are involved in a number of neurological diseases, including autoimmune diseases and inherited neuropathies. In this review, we briefly discuss the structural properties and functions of selected myelin-specific proteins (P0, myelin oligodendrocyte glycoprotein, myelin-associated glycoprotein, myelin basic protein, myelin-associated oligodendrocytic basic protein, P2, proteolipid protein, peripheral myelin protein of 22 kDa, 2',3'-cyclic nucleotide 3'-phosphodiesterase, and periaxin); such properties include, for example, interactions with lipid bilayers and the presence of large intrinsically disordered regions in some myelin proteins. A detailed understanding of myelin protein structure and function at the molecular level will be required to fully grasp their physiological roles in the myelin sheath.
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Affiliation(s)
- Huijong Han
- Department of Biochemistry and Biocenter Oulu, University of Oulu, Oulu, Finland
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Loss of electrostatic cell-surface repulsion mediates myelin membrane adhesion and compaction in the central nervous system. Proc Natl Acad Sci U S A 2013; 110:3143-8. [PMID: 23382229 DOI: 10.1073/pnas.1220104110] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
During the development of the central nervous system (CNS), oligodendrocytes wrap their plasma membrane around axons to form a multilayered stack of tightly attached membranes. Although intracellular myelin compaction and the role of myelin basic protein has been investigated, the forces that mediate the close interaction of myelin membranes at their external surfaces are poorly understood. Such extensive bilayer-bilayer interactions are usually prevented by repulsive forces generated by the glycocalyx, a dense and confluent layer of large and negatively charged oligosaccharides. Here we investigate the molecular mechanisms underlying myelin adhesion and compaction in the CNS. We revisit the role of the proteolipid protein and analyze the contribution of oligosaccharides using cellular assays, biophysical tools, and transgenic mice. We observe that differentiation of oligodendrocytes is accompanied by a striking down-regulation of components of their glycocalyx. Both in vitro and in vivo experiments indicate that the adhesive properties of the proteolipid protein, along with the reduction of sialic acid residues from the cell surface, orchestrate myelin membrane adhesion and compaction in the CNS. We suggest that loss of electrostatic cell-surface repulsion uncovers weak and unspecific attractive forces in the bilayer that bring the extracellular surfaces of a membrane into close contact over long distances.
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Pereira GB, Meng F, Kockara NT, Yang B, Wight PA. Targeted deletion of the antisilencer/enhancer (ASE) element from intron 1 of the myelin proteolipid protein gene (Plp1) in mouse reveals that the element is dispensable for Plp1 expression in brain during development and remyelination. J Neurochem 2012; 124:454-65. [PMID: 23157328 DOI: 10.1111/jnc.12092] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 11/01/2012] [Accepted: 11/03/2012] [Indexed: 01/16/2023]
Abstract
Myelin proteolipid protein gene (Plp1) expression is temporally regulated in brain, which peaks during the active myelination period of CNS development. Previous studies with Plp1-lacZ transgenic mice demonstrated that (mouse) Plp1 intron 1 DNA is required for high levels of expression in oligodendrocytes. Deletion-transfection analysis revealed the intron contains a single positive regulatory element operative in the N20.1 oligodendroglial cell line, which was named ASE (antisilencer/enhancer) based on its functional properties in these cells. To investigate the role of the ASE in vivo, the element was deleted from the native gene in mouse using a Cre/lox strategy. Although removal of the ASE from Plp1-lacZ constructs profoundly decreased expression in transfected oligodendroglial cell lines (N20.1 and Oli-neu), the element was dispensable to achieve normal levels of Plp1 gene expression in mouse during development (except perhaps at postnatal day 15) and throughout the remyelination period following cuprizone-induced (acute) demyelination. Thus, it is possible that the ASE is non-functional in vivo, or that loss of the ASE from the native gene in mouse can be compensated for by the presence of other regulatory elements within the Plp1 gene.
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Affiliation(s)
- Glauber B Pereira
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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Proteolipid protein dimerization at cysteine 108: Implications for protein structure. Neurosci Res 2012; 74:144-55. [PMID: 22902553 DOI: 10.1016/j.neures.2012.07.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2011] [Revised: 07/30/2012] [Accepted: 07/30/2012] [Indexed: 11/24/2022]
Abstract
Proteolipid protein (PLP) and its alternatively spliced isoform DM20 comprise ∼50% of central nervous system (CNS) myelin protein. The two proteins are identical in sequence except for the presence of a 35 amino sequence within the intracellular loop of PLP that is absent in DM20. In this work, we compared the expression of PLP/DM20 in transfected cells, oligodendrocytes and brain. In all 3 tissues, PLP exists as both a monomer and a disulfide-linked dimer; in contrast, DM20 is found mainly as a monomer. PLP dimers were increased by both chemical crosslinking and incubation with hydrogen peroxide, and were mediated by a cysteine at amino acid 108, located within the proximal intracellular loop of both PLP and DM20. The PLP-specific sequence thus influences the accessibility of this cysteine to chemical modification, perhaps as a result of altering protein structure. Consistent with these findings, several mutant PLPs known to cause Pelizaeus-Merzbacher disease form predominantly disulfide-linked, high molecular weight aggregates in transfected COS7 cells that are arrested in the ER and are associated with increased expression of CHOP, a part of the cellular response to unfolded proteins. In contrast, the same mutations in DM20 accumulate fewer high molecular weight disulfide-linked species that are expressed at the cell surface, and are not associated with increased CHOP. Taken together, these data suggest that mutant PLP multimerization, mediated in part by way of cysteine 108, may be part of the pathogenesis of Pelizaeus-Merzbacher disease.
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Saher G, Quintes S, Nave KA. Cholesterol: a novel regulatory role in myelin formation. Neuroscientist 2011; 17:79-93. [PMID: 21343408 DOI: 10.1177/1073858410373835] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Myelin consists of tightly compacted membranes that form an insulating sheath around axons. The function of myelin for rapid saltatory nerve conduction is dependent on its unique composition, highly enriched in glycosphingolipids and cholesterol. Cholesterol emerged as the only integral myelin component that is essential and rate limiting for the development of CNS and PNS myelin. Experiments with conditional mouse mutants that lack cholesterol biosynthesis in oligodendrocytes revealed that only minimal changes of the CNS myelin lipid composition are tolerated. In Schwann cells of the PNS, protein trafficking and myelin compaction depend on cholesterol. In this review, the authors summarize the role of cholesterol in myelin biogenesis and myelin disease.
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Affiliation(s)
- Gesine Saher
- Max Planck Institute of Experimental Medicine, Neurogenetics, Göttingen, Germany.
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36
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Gruenenfelder FI, Thomson G, Penderis J, Edgar JM. Axon-glial interaction in the CNS: what we have learned from mouse models of Pelizaeus-Merzbacher disease. J Anat 2011; 219:33-43. [PMID: 21401588 DOI: 10.1111/j.1469-7580.2011.01363.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
In the central nervous system (CNS) the majority of axons are surrounded by a myelin sheath, which is produced by oligodendrocytes. Myelin is a lipid-rich insulating material that facilitates the rapid conduction of electrical impulses along the myelinated nerve fibre. Proteolipid protein and its isoform DM20 constitute the most abundant protein component of CNS myelin. Mutations in the PLP1 gene encoding these myelin proteins cause Pelizaeus-Merzbacher disease and the related allelic disorder, spastic paraplegia type 2. Animal models of these diseases, particularly models lacking or overexpressing Plp1, have shed light on the interplay between axons and oligodendrocytes, and how one component influences the other.
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Affiliation(s)
- Fredrik I Gruenenfelder
- Applied Neurobiology Group, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Scotland, UK
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Lee X, Hu Y, Zhang Y, Yang Z, Shao Z, Qiu M, Pepinsky B, Miller RH, Mi S. Oligodendrocyte differentiation and myelination defects in OMgp null mice. Mol Cell Neurosci 2011; 46:752-61. [PMID: 21352918 DOI: 10.1016/j.mcn.2011.02.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2011] [Revised: 02/13/2011] [Accepted: 02/15/2011] [Indexed: 11/30/2022] Open
Abstract
OMgp is selectively expressed in CNS by oligodendrocyte. However, its potential role(s) in oligodendrocyte development and myelination remain unclear. We show that OMgp null mice are hypomyelinated in their spinal cords, resulting in slower ascending and descending conduction velocities compared to wild-type mice. Consistent with the hypomyelination, in the MOG induced EAE model, OMgp null mice show a more severe EAE clinical disease and slower nerve conduction velocity compared to WT animals. The contribution of OMgp to oligodendrocyte differentiation and myelination was verified using cultured oligodendrocytes from null mice. Oligodendrocytes isolated from OMgp null mice show a significant decrease in the number of MBP(+) cells and in myelination compared to wild-type mice. The dramatic effects of the OMgp KO in oligodendrocyte maturation in vivo and in vitro reveal a new and important function for OMgp in regulating CNS myelination.
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Affiliation(s)
- Xinhua Lee
- Biogen Idec Inc, 14 Cambridge Center, Cambridge, MA 02142, USA
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38
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Gow A. Using temporal genetic switches to synchronize the unfolded protein response in cell populations in vivo. Methods Enzymol 2011; 491:143-61. [PMID: 21329799 DOI: 10.1016/b978-0-12-385928-0.00009-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
In recent years, recognition of the importance of protein aggregation in human diseases has increasingly come to the fore and it is clear that many degenerative disorders involve activation of a metabolic signaling cascade known as the unfolded protein response (UPR). The UPR encompasses conserved mechanisms in cells to monitor and react to changes in metabolic flux through the secretory pathway. Such changes reflect an imbalance in cell homeostasis and the UPR integrates several signaling cascades to restore homeostasis. As such, the UPR is simply interpreted as a protection mechanism for cells as they perform their normal functions. A number of groups have suggested that the UPR also can eliminate cells in which homeostasis is lost, for example, during disease. This notion has kindled the rather paradoxical concept that inhibiting the UPR will ameliorate degenerative disease. However, several in vivo studies in the nervous system indicate that curtailing UPR function either exacerbates disease or may reduce severity through unexpected or unidentified pathways. Perhaps the notion that the UPR protects cells or eliminates them stems from widespread use of suboptimal paradigms to characterize the UPR; thus, too little is currently known about this homeostatic pathway. Herein, I describe the development of genetic switch technology (GST) to generate a novel model for studying UPR diseases. The model is geared toward obtaining high resolution in vivo detail for oligodendrocytes of the central nervous system, but it can be adapted to study other cell types and other UPR diseases.
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Affiliation(s)
- Alexander Gow
- Center for Molecular Medicine and Genetics, Carman and Ann Adams Department of Pediatrics, Department of Neurology, Wayne State University School of Medicine, Detroit, Michigan, USA
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Abstract
The myelination of axons by glial cells was the last major step in the evolution of cells in the vertebrate nervous system, and white-matter tracts are key to the architecture of the mammalian brain. Cell biology and mouse genetics have provided insight into axon-glia signalling and the molecular architecture of the myelin sheath. Glial cells that myelinate axons were found to have a dual role by also supporting the long-term integrity of those axons. This function may be independent of myelin itself. Myelin abnormalities cause a number of neurological diseases, and may also contribute to complex neuropsychiatric disorders.
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Affiliation(s)
- Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany.
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40
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Velumian AA, Samoilova M, Fehlings MG. Visualization of cytoplasmic diffusion within living myelin sheaths of CNS white matter axons using microinjection of the fluorescent dye Lucifer Yellow. Neuroimage 2010; 56:27-34. [PMID: 21073961 DOI: 10.1016/j.neuroimage.2010.11.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2010] [Revised: 08/10/2010] [Accepted: 11/04/2010] [Indexed: 01/16/2023] Open
Abstract
The compactness of myelin allows for efficient insulation defining rapid propagation of action potentials, but also raises questions about how cytoplasmic access to its membranes is achieved, which is critical for physiological activity. Understanding the organization of cytoplasmic ('water') spaces of myelin is also important for diffusion MRI studies of CNS white matter. Using longitudinal slices of mature rat spinal cord, we monitored the diffusion of the water-soluble fluorescent dye Lucifer Yellow injected into individual oligodendrocytes or internodal myelin. We show that living myelin sheaths on CNS axons are fenestrated by a network of diffusionally interconnected cytoplasmic 'pockets' (1.9 ± 0.2 pockets per 10μm sheath length, n=58) that included Schmidt-Lanterman clefts (SLCs) and numerous smaller compartments. 3-D reconstructions of these cytoplasmic networks show that the outer cytoplasmic layer of CNS myelin is cylindrically 'encuffing', which differs from EM studies using fixed tissue. SLCs were found in different 'open states' and remained stable within a 1-2hour observation period. Unlike the peripheral nervous system, where similarly small (<500Da) molecules diffuse along the whole myelin segment within a few minutes, in mature CNS this takes more than one hour. The slower cytoplasmic diffusion in CNS myelin possibly contributes to its known vulnerability to injury and limited capacity for repair. Our findings point to an elaborate cytoplasmic access to compact CNS myelin. These results could be of relevance to MRI studies of CNS white matter and to CNS repair/regeneration strategies.
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Affiliation(s)
- Alexander A Velumian
- Division of Genetics and Development, Toronto Western Research Institute, Canada.
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Lee DH, Jeong JY, Kim YS, Kim JS, Cho YW, Roh GS, Kim HJ, Kang SS, Cho GJ, Choi WS. Ethanol down regulates the expression of myelin proteolipid protein in the rat hippocampus. Anat Cell Biol 2010; 43:194-200. [PMID: 21212859 PMCID: PMC3015037 DOI: 10.5115/acb.2010.43.3.194] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 09/02/2010] [Accepted: 09/06/2010] [Indexed: 12/03/2022] Open
Abstract
It is well known that chronic ethanol treatment affects the synthesis of RNA and protein in the brain and the maintenance and function of nervous system. The changes in myelination-related genes are most prominent in human alcoholics. Previously, our cDNA microarray study showed altered Proteolipid protein (PLP), a major protein of central myelin. The present study aimed to gain more understanding of the expression of PLP after chronic ethanol treatment. Male Sprague-Dawley rats were daily treated with ethanol (15% in saline, 3 g/kg, i.p.) or saline for 14 days. Messenger RNAs from hippocampus of each group were subjected to cDNA expression array hybridization to determine the differential gene expressions. Among many ethanol responsive genes, PLP was negatively regulated by ethanol treatment, which is one of the most abundant proteins in the CNS and has an important role in the stabilization of myelin sheath. Using northern blot and immunohistochemical analysis, we showed the change in expression level of PLP mRNA and protein after ethanol treatment. PLP mRNA and protein were decreased in hippocampus of rat with chronic ethanol exposure, suggesting that ethanol may affect the stabilization of myelin sheath through the modulation of PLP expression and induce the pathophysiology of alcoholic brain.
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Affiliation(s)
- Dong Hoon Lee
- Department of Anatomy & Neurobiology, Institute of Health Sciences, Medical Research Center for Neural Dysfunction, Gyeongsang National University School of Medicine, Jinju, Korea
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42
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Abstract
In addition to their role in providing myelin for rapid impulse propagation, the glia that ensheath long axons are required for the maintenance of normal axon transport and long-term survival. This presumably ancestral function seems to be independent of myelin membrane wrapping. Here, I propose that ensheathing glia provide trophic support to axons that are metabolically isolated, and that myelin itself might cause such isolation. This glial support of axonal integrity may be relevant for a number of neurological and psychiatric diseases.
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Affiliation(s)
- Klaus-Armin Nave
- Klaus-Armin Nave is at the Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Herrmann-Rein-Strasse 3, D-37075 Goettingen, Germany.
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Izawa T, Yamate J, Franklin RJ, Kuwamura M. Abnormal myelinogenesis both in the white and gray matter of the attractin-deficient mv rat. Brain Res 2010; 1312:145-55. [DOI: 10.1016/j.brainres.2009.11.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 11/10/2009] [Accepted: 11/11/2009] [Indexed: 10/20/2022]
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Devaux J, Fykkolodziej B, Gow A. Claudin Proteins And Neuronal Function. CURRENT TOPICS IN MEMBRANES 2010; 65:229-253. [PMID: 25013353 DOI: 10.1016/s1063-5823(10)65010-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The identification and characterization of the claudin family of tight junction (TJ) proteins in the late 1990s ushered in a new era for research into the molecular and cellular biology of intercellular junctions. Since that time, TJs have been studied in the contexts of many diseases including deafness, male infertility, cancer, bacterial invasion and liver and kidney disorders. In this review, we consider the role of claudins in the nervous system focusing on the mechanisms by which TJs in glial cells are involved in neuronal function. Electrophysiological evidence suggests that claudins may operate in the central nervous system (CNS) in a manner similar to polarized epithelia. We also evaluate hypotheses that TJs are the gatekeepers of an immune-privileged myelin compartment and that TJs emerged during evolution to form major adhesive forces within the myelin sheath. Finally, we consider the implications of CNS myelin TJs in the contexts of behavioral disorders (schizophrenia) and demyelinating/hypomyelinating diseases (multiple sclerosis and the leukodystrophies), and explore evidence of a possible mechanism governing affective disorder symptoms in patients with white matter abnormalities.
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Affiliation(s)
- Jérôme Devaux
- Département Signalisation Neuronale, CRN2M, UMR 6231, CNRS, Université de la Méditerranée-Université Paul Cézanne, IFR Jean Roche, Marseille, France
| | - Bozena Fykkolodziej
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI, 48201, USA
| | - Alexander Gow
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI, 48201, USA. ; Carman and Ann Adams Dept of Pediatrics, Wayne State University School of Medicine, Detroit, MI, 48201, USA. ; Dept of Neurology, Wayne State University School of Medicine, Detroit, MI, 48201, USA
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45
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Rosenbluth J. Multiple functions of the paranodal junction of myelinated nerve fibers. J Neurosci Res 2009; 87:3250-8. [DOI: 10.1002/jnr.22013] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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46
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Morfini GA, Burns M, Binder LI, Kanaan NM, LaPointe N, Bosco DA, Brown RH, Brown H, Tiwari A, Hayward L, Edgar J, Nave KA, Garberrn J, Atagi Y, Song Y, Pigino G, Brady ST. Axonal transport defects in neurodegenerative diseases. J Neurosci 2009; 29:12776-86. [PMID: 19828789 PMCID: PMC2801051 DOI: 10.1523/jneurosci.3463-09.2009] [Citation(s) in RCA: 335] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Accepted: 08/04/2009] [Indexed: 12/26/2022] Open
Abstract
Adult-onset neurodegenerative diseases (AONDs) comprise a heterogeneous group of neurological disorders characterized by a progressive, age-dependent decline in neuronal function and loss of selected neuronal populations. Alterations in synaptic function and axonal connectivity represent early and critical pathogenic events in AONDs, but molecular mechanisms underlying these defects remain elusive. The large size and complex subcellular architecture of neurons render them uniquely vulnerable to alterations in axonal transport (AT). Accordingly, deficits in AT have been documented in most AONDs, suggesting a common defect acquired through different pathogenic pathways. These observations suggest that many AONDs can be categorized as dysferopathies, diseases in which alterations in AT represent a critical component in pathogenesis. Topics here address various molecular mechanisms underlying alterations in AT in several AONDs. Illumination of such mechanisms provides a framework for the development of novel therapeutic strategies aimed to prevent axonal and synaptic dysfunction in several major AONDs.
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Affiliation(s)
- Gerardo A Morfini
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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Mayer CA, Macklin WB, Avishai N, Balan K, Wilson CG, Miller MJ. Mutation in the myelin proteolipid protein gene alters BK and SK channel function in the caudal medulla. Respir Physiol Neurobiol 2009; 169:303-14. [PMID: 19808102 DOI: 10.1016/j.resp.2009.09.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 09/24/2009] [Accepted: 09/25/2009] [Indexed: 12/31/2022]
Abstract
Proteolipid protein (Plp) gene mutation in rodents causes severe CNS dysmyelination, early death, and lethal hypoxic ventilatory depression (Miller et al., 2004). To determine if Plp mutation alters neuronal function critical for control of breathing, the nucleus tractus solitarii (nTS) of four rodent strains were studied: myelin deficient rats (MD), myelin synthesis deficient (Plp(msd)), and Plp(null) mice, as well as shiverer (Mbp(shi)) mice, a myelin basic protein mutant. Current-voltage relationships were analyzed using whole-cell patch-clamp in 300 microm brainstem slices. Voltage steps were applied, and inward and outward currents quantified. MD, Plp(msd), and Plp(null), but not Mbp(shi) neurons exhibited reduced outward current in nTS at P21. Apamin blockade of SK calcium-dependent currents and iberiotoxin blockade of BK calcium-dependent currents in the P21 MD rat demonstrated reduced outward current due to dysfunction of these channels. These results provide evidence that Plp mutation specifically alters neuronal excitability through calcium-dependent potassium channels in nTS.
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Affiliation(s)
- Catherine A Mayer
- Department of Pediatrics, Case Western Reserve University, 11100 Euclid Ave, Cleveland, OH 44106, United States.
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The role of CNS glia in preserving axon function. Curr Opin Neurobiol 2009; 19:498-504. [PMID: 19765974 DOI: 10.1016/j.conb.2009.08.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Accepted: 08/19/2009] [Indexed: 11/23/2022]
Abstract
Axons are the physical conduits by which information is relayed within the nervous system and as such, are essential for normal neurological function. In the central nervous system (CNS), axons comprise the bulk of the white matter, where they are closely associated with glial cells. Primary alterations of glial cell functions can have detrimental secondary consequences for axons, demonstrating that white matter glia are important custodians of axonal integrity. For example, genetic ablation of key oligodendroglial molecules abrogates the oligodendrocytes' supportive function, while expression of mutant super oxide dismutase in astrocytes expedites progression of motor neuron disease. Here we review some of the recent literature on the role of CNS glia in axonal health.
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Phylogeny of proteolipid proteins: divergence, constraints, and the evolution of novel functions in myelination and neuroprotection. ACTA ACUST UNITED AC 2009; 4:111-27. [PMID: 19497142 DOI: 10.1017/s1740925x0900009x] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The protein composition of myelin in the central nervous system (CNS) has changed at the evolutionary transition from fish to tetrapods, when a lipid-associated transmembrane-tetraspan (proteolipid protein, PLP) replaced an adhesion protein of the immunoglobulin superfamily (P0) as the most abundant constituent. Here, we review major steps of proteolipid evolution. Three paralog proteolipids (PLP/DM20/DMalpha, M6B/DMgamma and the neuronal glycoprotein M6A/DMbeta) exist in vertebrates from cartilaginous fish to mammals, and one (M6/CG7540) can be traced in invertebrate bilaterians including the planktonic copepod Calanus finmarchicus that possess a functional myelin equivalent. In fish, DMalpha and DMgamma are coexpressed in oligodendrocytes but are not major myelin components. PLP emerged at the root of tetrapods by the acquisition of an enlarged cytoplasmic loop in the evolutionary older DMalpha/DM20. Transgenic experiments in mice suggest that this loop enhances the incorporation of PLP into myelin. The evolutionary recruitment of PLP as the major myelin protein provided oligodendrocytes with the competence to support long-term axonal integrity. We suggest that the molecular shift from P0 to PLP also correlates with the concentration of adhesive forces at the radial component, and that the new balance between membrane adhesion and dynamics was favorable for CNS myelination.
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Rosenbluth J, Schiff R, Lam P. Effects of osmolality on PLP-null myelin structure: implications re axon damage. Brain Res 2008; 1253:191-7. [PMID: 19094971 DOI: 10.1016/j.brainres.2008.11.066] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Revised: 11/14/2008] [Accepted: 11/18/2008] [Indexed: 10/21/2022]
Abstract
In order to test the adhesiveness of PLP-null compact myelin lamellae we soaked aldehyde-fixed CNS specimens from PLP-null and control mice overnight in distilled water, in Ringer's solution or in Ringer's solution with added 1 M sucrose. Subsequent examination of the tissue by EM showed that both PLP-null and control white matter soaked in Ringer remained largely compact. After the distilled water soak, control myelin was virtually unchanged, but PLP-null myelin showed some decompaction, i.e., separation of myelin lamellae from one another. After the sucrose/Ringer soak, normal myelin developed foci of decompaction, but the great majority of lamellae remained compact. In the PLP-null specimens, in contrast, many of the myelin sheaths became almost completely decompacted. Such sheaths became thicker overall and were comprised of lamellae widely separated from one another by irregular spaces. Thus, in normal animals, fixed CNS myelin lamellae are firmly adherent and resist separation; PLP-null myelin lamellae, in contrast, are poorly adherent and more readily separated. Mechanisms by which impaired adhesiveness of PLP-null myelin lamellae and fluctuations in osmolality in vivo might underlie slowing of conduction and axon damage are discussed.
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Affiliation(s)
- Jack Rosenbluth
- Department of Physiology and Neuroscience, New York University School of Medicine, New York, NY 10016, USA.
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