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Osso LA, Hughes EG. Dynamics of mature myelin. Nat Neurosci 2024; 27:1449-1461. [PMID: 38773349 DOI: 10.1038/s41593-024-01642-2] [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: 09/14/2023] [Accepted: 04/05/2024] [Indexed: 05/23/2024]
Abstract
Myelin, which is produced by oligodendrocytes, insulates axons to facilitate rapid and efficient action potential propagation in the central nervous system. Traditionally viewed as a stable structure, myelin is now known to undergo dynamic modulation throughout life. This Review examines these dynamics, focusing on two key aspects: (1) the turnover of myelin, involving not only the renewal of constituents but the continuous wholesale replacement of myelin membranes; and (2) the structural remodeling of pre-existing, mature myelin, a newly discovered form of neural plasticity that can be stimulated by external factors, including neuronal activity, behavioral experience and injury. We explore the mechanisms regulating these dynamics and speculate that myelin remodeling could be driven by an asymmetry in myelin turnover or reactivation of pathways involved in myelin formation. Finally, we outline how myelin remodeling could have profound impacts on neural function, serving as an integral component of behavioral adaptation.
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Affiliation(s)
- Lindsay A Osso
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Ethan G Hughes
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA.
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2
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Looser ZJ, Faik Z, Ravotto L, Zanker HS, Jung RB, Werner HB, Ruhwedel T, Möbius W, Bergles DE, Barros LF, Nave KA, Weber B, Saab AS. Oligodendrocyte-axon metabolic coupling is mediated by extracellular K + and maintains axonal health. Nat Neurosci 2024; 27:433-448. [PMID: 38267524 PMCID: PMC10917689 DOI: 10.1038/s41593-023-01558-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 12/13/2023] [Indexed: 01/26/2024]
Abstract
The integrity of myelinated axons relies on homeostatic support from oligodendrocytes (OLs). To determine how OLs detect axonal spiking and how rapid axon-OL metabolic coupling is regulated in the white matter, we studied activity-dependent calcium (Ca2+) and metabolite fluxes in the mouse optic nerve. We show that fast axonal spiking triggers Ca2+ signaling and glycolysis in OLs. OLs detect axonal activity through increases in extracellular potassium (K+) concentrations and activation of Kir4.1 channels, thereby regulating metabolite supply to axons. Both pharmacological inhibition and OL-specific inactivation of Kir4.1 reduce the activity-induced axonal lactate surge. Mice lacking oligodendroglial Kir4.1 exhibit lower resting lactate levels and altered glucose metabolism in axons. These early deficits in axonal energy metabolism are associated with late-onset axonopathy. Our findings reveal that OLs detect fast axonal spiking through K+ signaling, making acute metabolic coupling possible and adjusting the axon-OL metabolic unit to promote axonal health.
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Affiliation(s)
- Zoe J Looser
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University and ETH Zurich, Zurich, Switzerland
| | - Zainab Faik
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University and ETH Zurich, Zurich, Switzerland
| | - Luca Ravotto
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University and ETH Zurich, Zurich, Switzerland
| | - Henri S Zanker
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University and ETH Zurich, Zurich, Switzerland
| | - Ramona B Jung
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Torben Ruhwedel
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Wiebke Möbius
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Dwight E Bergles
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA
| | - L Felipe Barros
- Centro de Estudios Científicos (CECs), Valdivia, Chile
- Facultad de Medicina y Ciencia, Universidad San Sebastián, Valdivia, Chile
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Bruno Weber
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich, University and ETH Zurich, Zurich, Switzerland
| | - Aiman S Saab
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.
- Neuroscience Center Zurich, University and ETH Zurich, Zurich, Switzerland.
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3
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Liu S, Yang D, Dong S, Luo Y, Zhang T, Li S, Bai Y, Li L, Ma Y, Liu J. Effects of acrylamide exposure during pregnancy and lactation on the development of myelin sheath of corpus callosum in offspring rats. Toxicol Res (Camb) 2024; 13:tfae014. [PMID: 38314039 PMCID: PMC10836055 DOI: 10.1093/toxres/tfae014] [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: 10/20/2023] [Revised: 12/20/2023] [Accepted: 01/15/2023] [Indexed: 02/06/2024] Open
Abstract
Acrylamide is an alkene known to induce neurotoxicity in humans and experimental animals. However, the effects of acrylamide on the development of myelin sheath are unclear. The present study was to explore the effects of acrylamide exposure during pregnancy and lactation on the development of myelin sheath in offspring rats. Four groups of thirty-two pregnant Sprague-Dawley rats were exposed to 0, 4.5, 9 and 18 mg/kg BW acrylamide by gavage from gestational day 15 to postnatal day 13. The corpus callosum of nine offspring rats per group were dissected in postpartum day 14. Structural changes and lipid contents in myelin sheaths were examined by transmission electron microscopy(TEM) and Luxol Fast Blue staining(LFB). The expression of MBP and PLP was evaluated by immunohistochemistry and Western blotting. TEM showed that the myelin sheaths in the 18 mg/kg group were disordered compared with control group. Luxol Fast Blue staining gradually decreased with increasing acrylamide maternal exposure. The immunohistochemistry and Western Blotting results showed that maternal exposure to acrylamide caused a decreasing trend in MBP and PLP in the corpus callosum of rats at postnatal day 14. Furthermore, these reduced protein levels may be neurodevelopmental toxicity's mechanism in response to maternal exposure to acrylamide.
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Affiliation(s)
- Shuping Liu
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Guangdong Pharmaceutical University, No. 280, Outer Ring East Road, Guangzhou University City, Panyu District, Guangzhou City, Guangzhou 510006, PR China
| | - Dehui Yang
- Lianjiang People's Hospital, No. 30 Renmin Avenue Middle, Lianjiang City, Zhanjiang City, Guangdong Province, Lianjiang 524400, PR China
| | - Suqiu Dong
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Guangdong Pharmaceutical University, No. 280, Outer Ring East Road, Guangzhou University City, Panyu District, Guangzhou City, Guangzhou 510006, PR China
| | - Yuyou Luo
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Guangdong Pharmaceutical University, No. 280, Outer Ring East Road, Guangzhou University City, Panyu District, Guangzhou City, Guangzhou 510006, PR China
| | - Tong Zhang
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Guangdong Pharmaceutical University, No. 280, Outer Ring East Road, Guangzhou University City, Panyu District, Guangzhou City, Guangzhou 510006, PR China
| | - Siyuan Li
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Guangdong Pharmaceutical University, No. 280, Outer Ring East Road, Guangzhou University City, Panyu District, Guangzhou City, Guangzhou 510006, PR China
| | - Yanxian Bai
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Guangdong Pharmaceutical University, No. 280, Outer Ring East Road, Guangzhou University City, Panyu District, Guangzhou City, Guangzhou 510006, PR China
| | - Lixia Li
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Guangdong Pharmaceutical University, No. 280, Outer Ring East Road, Guangzhou University City, Panyu District, Guangzhou City, Guangzhou 510006, PR China
| | - Yuxin Ma
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Guangdong Pharmaceutical University, No. 280, Outer Ring East Road, Guangzhou University City, Panyu District, Guangzhou City, Guangzhou 510006, PR China
| | - Jing Liu
- Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Guangdong Pharmaceutical University, No. 280, Outer Ring East Road, Guangzhou University City, Panyu District, Guangzhou City, Guangzhou 510006, PR China
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4
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Louie AY, Kim JS, Drnevich J, Dibaeinia P, Koito H, Sinha S, McKim DB, Soto-Diaz K, Nowak RA, Das A, Steelman AJ. Influenza A virus infection disrupts oligodendrocyte homeostasis and alters the myelin lipidome in the adult mouse. J Neuroinflammation 2023; 20:190. [PMID: 37596606 PMCID: PMC10439573 DOI: 10.1186/s12974-023-02862-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 07/25/2023] [Indexed: 08/20/2023] Open
Abstract
BACKGROUND Recent data suggest that myelin may be altered by physiological events occurring outside of the central nervous system, which may cause changes to cognition and behavior. Similarly, peripheral infection by non-neurotropic viruses is also known to evoke changes to cognition and behavior. METHODS Mice were inoculated with saline or influenza A virus. Bulk RNA-seq, lipidomics, RT-qPCR, flow cytometry, immunostaining, and western blots were used to determine the effect of infection on OL viability, protein expression and changes to the lipidome. To determine if microglia mediated infection-induced changes to OL homeostasis, mice were treated with GW2580, an inhibitor of microglia activation. Additionally, conditioned medium experiments using primary glial cell cultures were also used to test whether secreted factors from microglia could suppress OL gene expression. RESULTS Transcriptomic and RT-qPCR analyses revealed temporal downregulation of OL-specific transcripts with concurrent upregulation of markers characteristic of cellular stress. OLs isolated from infected mice had reduced cellular expression of myelin proteins compared with those from saline-inoculated controls. In contrast, the expression of these proteins within myelin was not different between groups. Similarly, histological and immunoblotting analysis performed on various brain regions indicated that infection did not alter OL viability, but increased expression of a cellular stress marker. Shot-gun lipidomic analysis revealed that infection altered the lipid profile within the prefrontal cortex as well as in purified brain myelin and that these changes persisted after recovery from infection. Treatment with GW2580 during infection suppressed the expression of genes associated with glial activation and partially restored OL-specific transcripts to baseline levels. Finally, conditioned medium from activated microglia reduced OL-gene expression in primary OLs without altering their viability. CONCLUSIONS These findings show that peripheral respiratory viral infection with IAV is capable of altering OL homeostasis and indicate that microglia activation is likely involved in the process.
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Affiliation(s)
- Allison Y Louie
- Neuroscience Program, 2325/21 Beckman Institute, 405 North Mathews Ave., Urbana, IL, 61801, USA
| | - Justin S Kim
- Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, 1201 W. Gregory Dr., Urbana, IL, 61801, USA
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 3306, IBB, Parker H. Petit Institute for Bioengineering and Biosciences, 315 Fernst Dr. NW, Atlanta, GA, 30332, USA
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, 3516 Veterinary Medicine Basic Sciences Bldg., 2001 South Lincoln Avenue, Urbana, IL, 61802, USA
| | - Jenny Drnevich
- Roy J. Carver Biotechnology Center, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Payam Dibaeinia
- Department of Computer Science, University of Illinois at Urbana-Champaign, 201 North Goodwin Avenue, Urbana, IL, 61801, USA
| | - Hisami Koito
- Department of Pharmaceutical Sciences, Josai University, 1-1 Keyakidai, Sakado-shi, Saitama, 350-0295, Japan
| | - Saurabh Sinha
- Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, 1201 W. Gregory Dr., Urbana, IL, 61801, USA
- Department of Computer Science, University of Illinois at Urbana-Champaign, 201 North Goodwin Avenue, Urbana, IL, 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Dr., Urbana, IL, 61801, USA
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, USA
| | - Daniel B McKim
- Neuroscience Program, 2325/21 Beckman Institute, 405 North Mathews Ave., Urbana, IL, 61801, USA
- Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, 1201 W. Gregory Dr., Urbana, IL, 61801, USA
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, 1201 W. Gregory Dr., Urbana, IL, 61801, USA
| | - Katiria Soto-Diaz
- Neuroscience Program, 2325/21 Beckman Institute, 405 North Mathews Ave., Urbana, IL, 61801, USA
| | - Romana A Nowak
- Department of Computer Science, University of Illinois at Urbana-Champaign, 201 North Goodwin Avenue, Urbana, IL, 61801, USA
- Department of Bioengineering, Cancer Center at Illinois, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave., Urbana, IL, 61801, USA
| | - Aditi Das
- Neuroscience Program, 2325/21 Beckman Institute, 405 North Mathews Ave., Urbana, IL, 61801, USA.
- Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, 1201 W. Gregory Dr., Urbana, IL, 61801, USA.
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 3306, IBB, Parker H. Petit Institute for Bioengineering and Biosciences, 315 Fernst Dr. NW, Atlanta, GA, 30332, USA.
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, 3516 Veterinary Medicine Basic Sciences Bldg., 2001 South Lincoln Avenue, Urbana, IL, 61802, USA.
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Dr., Urbana, IL, 61801, USA.
| | - Andrew J Steelman
- Neuroscience Program, 2325/21 Beckman Institute, 405 North Mathews Ave., Urbana, IL, 61801, USA.
- Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, 1201 W. Gregory Dr., Urbana, IL, 61801, USA.
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Dr., Urbana, IL, 61801, USA.
- Department of Bioengineering, Cancer Center at Illinois, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave., Urbana, IL, 61801, USA.
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5
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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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6
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Steyer AM, Buscham TJ, Lorenz C, Hümmert S, Eichel-Vogel MA, Schadt LC, Edgar JM, Köster S, Möbius W, Nave KA, Werner HB. Focused ion beam-scanning electron microscopy links pathological myelin outfoldings to axonal changes in mice lacking Plp1 or Mag. Glia 2023; 71:509-523. [PMID: 36354016 DOI: 10.1002/glia.24290] [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: 07/11/2022] [Revised: 10/10/2022] [Accepted: 10/17/2022] [Indexed: 11/11/2022]
Abstract
Healthy myelin sheaths consist of multiple compacted membrane layers closely encasing the underlying axon. The ultrastructure of CNS myelin requires specialized structural myelin proteins, including the transmembrane-tetraspan proteolipid protein (PLP) and the Ig-CAM myelin-associated glycoprotein (MAG). To better understand their functional relevance, we asked to what extent the axon/myelin-units display similar morphological changes if PLP or MAG are lacking. We thus used focused ion beam-scanning electron microscopy (FIB-SEM) to re-investigate axon/myelin-units side-by-side in Plp- and Mag-null mutant mice. By three-dimensional reconstruction and morphometric analyses, pathological myelin outfoldings extend up to 10 μm longitudinally along myelinated axons in both models. More than half of all assessed outfoldings emerge from internodal myelin. Unexpectedly, three-dimensional reconstructions demonstrated that both models displayed complex axonal pathology underneath the myelin outfoldings, including axonal sprouting. Axonal anastomosing was additionally observed in Plp-null mutant mice. Importantly, normal-appearing axon/myelin-units displayed significantly increased axonal diameters in both models according to quantitative assessment of electron micrographs. These results imply that healthy CNS myelin sheaths facilitate normal axonal diameters and shape, a function that is impaired when structural myelin proteins PLP or MAG are lacking.
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Affiliation(s)
- Anna M Steyer
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.,Electron Microscopy-City Campus, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Tobias J Buscham
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Charlotta Lorenz
- Institute for X-Ray Physics, University of Göttingen, Göttingen, Germany
| | - Sophie Hümmert
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Maria A Eichel-Vogel
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Leonie C Schadt
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Julia M Edgar
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.,Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Sarah Köster
- Institute for X-Ray Physics, University of Göttingen, Göttingen, Germany.,Cluster of Excellence 'Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells' (MBExC), University of Göttingen, Göttingen, Germany
| | - Wiebke Möbius
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.,Electron Microscopy-City Campus, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.,Cluster of Excellence 'Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells' (MBExC), University of Göttingen, Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
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7
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Barnes-Vélez JA, Aksoy Yasar FB, Hu J. Myelin lipid metabolism and its role in myelination and myelin maintenance. Innovation (N Y) 2023; 4:100360. [PMID: 36588745 PMCID: PMC9800635 DOI: 10.1016/j.xinn.2022.100360] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 12/03/2022] [Indexed: 12/12/2022] Open
Abstract
Myelin is a specialized cell membrane indispensable for rapid nerve conduction. The high abundance of membrane lipids is one of myelin's salient features that contribute to its unique role as an insulator that electrically isolates nerve fibers across their myelinated surface. The most abundant lipids in myelin include cholesterol, glycosphingolipids, and plasmalogens, each playing critical roles in myelin development as well as function. This review serves to summarize the role of lipid metabolism in myelination and myelin maintenance, as well as the molecular determinants of myelin lipid homeostasis, with an emphasis on findings from genetic models. In addition, the implications of myelin lipid dysmetabolism in human diseases are highlighted in the context of hereditary leukodystrophies and neuropathies as well as acquired disorders such as Alzheimer's disease.
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Affiliation(s)
- Joseph A. Barnes-Vélez
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX 77054-1901, USA
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Science, Houston, TX 77225-0334, USA
- University of Puerto Rico Medical Sciences Campus, School of Medicine, San Juan, PR 00936-5067, USA
| | - Fatma Betul Aksoy Yasar
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX 77054-1901, USA
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Science, Houston, TX 77225-0334, USA
| | - Jian Hu
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX 77054-1901, USA
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Science, Houston, TX 77225-0334, USA
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8
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Lam M, Takeo K, Almeida RG, Cooper MH, Wu K, Iyer M, Kantarci H, Zuchero JB. CNS myelination requires VAMP2/3-mediated membrane expansion in oligodendrocytes. Nat Commun 2022; 13:5583. [PMID: 36151203 PMCID: PMC9508103 DOI: 10.1038/s41467-022-33200-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 09/07/2022] [Indexed: 11/08/2022] Open
Abstract
Myelin is required for rapid nerve signaling and is emerging as a key driver of CNS plasticity and disease. How myelin is built and remodeled remains a fundamental question of neurobiology. Central to myelination is the ability of oligodendrocytes to add vast amounts of new cell membrane, expanding their surface areas by many thousand-fold. However, how oligodendrocytes add new membrane to build or remodel myelin is not fully understood. Here, we show that CNS myelin membrane addition requires exocytosis mediated by the vesicular SNARE proteins VAMP2/3. Genetic inactivation of VAMP2/3 in myelinating oligodendrocytes caused severe hypomyelination and premature death without overt loss of oligodendrocytes. Through live imaging, we discovered that VAMP2/3-mediated exocytosis drives membrane expansion within myelin sheaths to initiate wrapping and power sheath elongation. In conjunction with membrane expansion, mass spectrometry of oligodendrocyte surface proteins revealed that VAMP2/3 incorporates axon-myelin adhesion proteins that are collectively required to form nodes of Ranvier. Together, our results demonstrate that VAMP2/3-mediated membrane expansion in oligodendrocytes is indispensable for myelin formation, uncovering a cellular pathway that could sculpt myelination patterns in response to activity-dependent signals or be therapeutically targeted to promote regeneration in disease.
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Affiliation(s)
- Mable Lam
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Koji Takeo
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
- Pharmaceutical Research Laboratories, Toray Industries, Inc., Kamakura, Kanagawa, Japan
| | - Rafael G Almeida
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Madeline H Cooper
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Kathryn Wu
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Manasi Iyer
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - Husniye Kantarci
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
| | - J Bradley Zuchero
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA.
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9
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Dermitzakis I, Manthou ME, Meditskou S, Miliaras D, Kesidou E, Boziki M, Petratos S, Grigoriadis N, Theotokis P. Developmental Cues and Molecular Drivers in Myelinogenesis: Revisiting Early Life to Re-Evaluate the Integrity of CNS Myelin. Curr Issues Mol Biol 2022; 44:3208-3237. [PMID: 35877446 PMCID: PMC9324160 DOI: 10.3390/cimb44070222] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/14/2022] [Accepted: 07/17/2022] [Indexed: 02/07/2023] Open
Abstract
The mammalian central nervous system (CNS) coordinates its communication through saltatory conduction, facilitated by myelin-forming oligodendrocytes (OLs). Despite the fact that neurogenesis from stem cell niches has caught the majority of attention in recent years, oligodendrogenesis and, more specifically, the molecular underpinnings behind OL-dependent myelinogenesis, remain largely unknown. In this comprehensive review, we determine the developmental cues and molecular drivers which regulate normal myelination both at the prenatal and postnatal periods. We have indexed the individual stages of myelinogenesis sequentially; from the initiation of oligodendrocyte precursor cells, including migration and proliferation, to first contact with the axon that enlists positive and negative regulators for myelination, until the ultimate maintenance of the axon ensheathment and myelin growth. Here, we highlight multiple developmental pathways that are key to successful myelin formation and define the molecular pathways that can potentially be targets for pharmacological interventions in a variety of neurological disorders that exhibit demyelination.
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Affiliation(s)
- Iasonas Dermitzakis
- Department of Histology-Embryology, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; (I.D.); (M.E.M.); (S.M.); (D.M.)
| | - Maria Eleni Manthou
- Department of Histology-Embryology, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; (I.D.); (M.E.M.); (S.M.); (D.M.)
| | - Soultana Meditskou
- Department of Histology-Embryology, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; (I.D.); (M.E.M.); (S.M.); (D.M.)
| | - Dimosthenis Miliaras
- Department of Histology-Embryology, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; (I.D.); (M.E.M.); (S.M.); (D.M.)
| | - Evangelia Kesidou
- Laboratory of Experimental Neurology and Neuroimmunology, Second Department of Neurology, AHEPA University Hospital, 54621 Thessaloniki, Greece; (E.K.); (M.B.); (N.G.)
| | - Marina Boziki
- Laboratory of Experimental Neurology and Neuroimmunology, Second Department of Neurology, AHEPA University Hospital, 54621 Thessaloniki, Greece; (E.K.); (M.B.); (N.G.)
| | - Steven Petratos
- Department of Neuroscience, Central Clinical School, Monash University, Prahran, VIC 3004, Australia;
| | - Nikolaos Grigoriadis
- Laboratory of Experimental Neurology and Neuroimmunology, Second Department of Neurology, AHEPA University Hospital, 54621 Thessaloniki, Greece; (E.K.); (M.B.); (N.G.)
| | - Paschalis Theotokis
- Department of Histology-Embryology, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; (I.D.); (M.E.M.); (S.M.); (D.M.)
- Laboratory of Experimental Neurology and Neuroimmunology, Second Department of Neurology, AHEPA University Hospital, 54621 Thessaloniki, Greece; (E.K.); (M.B.); (N.G.)
- Correspondence:
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10
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Wu YQ, Xiong J, He ZL, Yuan Y, Wang BN, Xu JY, Wu M, Zhang SS, Cai SF, Zhao JX, Xu K, Zhang HY, Xiao J. Metformin promotes microglial cells to facilitate myelin debris clearance and accelerate nerve repairment after spinal cord injury. Acta Pharmacol Sin 2022; 43:1360-1371. [PMID: 34480113 PMCID: PMC9160053 DOI: 10.1038/s41401-021-00759-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 08/08/2021] [Indexed: 02/07/2023] Open
Abstract
Spinal cord injury (SCI) is one kind of severe trauma for central nervous system. Myelin debris clearance and axon regeneration are essential for nerve regeneration after SCI. Metformin, a glucose-lowering drug, has been demonstrated to promote the locomotor functional recovery after SCI. In this study, we investigated the role and molecular mechanism of metformin on myelin preservation in a rat SCI model. SCI was induced in rats by compression at T9 level using a vascular clip. We showed that administration of metformin (50 mg·kg-1·d-1, ip) for 28 days significantly improved locomotor function in SCI rats. Metformin also ameliorated SCI-induced neuronal apoptosis and promoted axon regeneration in the spinal cord. Using co-immunofluorescence of IBa-1 and MBP, and luxol fasting blue (LFB) staining, we demonstrated that metformin promoted the transformation of M1 to M2 phenotype polarization of microglial cells, then greatly facilitated myelin debris clearance and protected the myelin in SCI rats. Furthermore, metformin ameliorated SCI-induced blockade of autophagic flux in the spinal cord, and enhanced the fusion of autophagosome and lysosome by inhibiting the AMPK-mTOR signaling pathway. Moreover, metformin significantly attenuated inflammatory responses in the spinal cord. In LPS-treated BV2 cells, pretreatment with metformin (2 mM) significantly enhanced autophagy level, suppressed inflammation and cell apoptosis. The protective effects were blocked in the presence of an autophagy inhibitor 3-methyladenine (3-MA, 5 mM), suggesting that the effect of metformin on autophagy in microglial cells is essential for the myelin preservation during nerve recovery. This study reveals a novel therapeutic effect of metformin in SCI recovery by regulating the activation of microglial cells and enhancing its autophagy level.
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Affiliation(s)
- Yan-Qing Wu
- The Institute of Life Sciences, Engineering Laboratory of Zhejiang Province for Pharmaceutical Development of Growth Factors, Biomedical Collaborative Innovation Center of Wenzhou, Wenzhou University, Wenzhou, 325035, China
| | - Jun Xiong
- Molecular Pharmacology Research Center, School of Pharmaceutical Science Wenzhou Medical University, Wenzhou, 325035, China
| | - Zi-Li He
- Molecular Pharmacology Research Center, School of Pharmaceutical Science Wenzhou Medical University, Wenzhou, 325035, China
| | - Yuan Yuan
- Department of Pharmacy, Hangzhou Red Cross Hospital, Zhejiang Province Hospital of Integrated Traditional Chinese and Western Medicine, Hangzhou, 310003, China
| | - Bei-Ni Wang
- Molecular Pharmacology Research Center, School of Pharmaceutical Science Wenzhou Medical University, Wenzhou, 325035, China
| | - Jing-Yu Xu
- The Institute of Life Sciences, Engineering Laboratory of Zhejiang Province for Pharmaceutical Development of Growth Factors, Biomedical Collaborative Innovation Center of Wenzhou, Wenzhou University, Wenzhou, 325035, China
| | - Man Wu
- Molecular Pharmacology Research Center, School of Pharmaceutical Science Wenzhou Medical University, Wenzhou, 325035, China
| | - Su-Su Zhang
- Molecular Pharmacology Research Center, School of Pharmaceutical Science Wenzhou Medical University, Wenzhou, 325035, China
| | - Shu-Fang Cai
- The Institute of Life Sciences, Engineering Laboratory of Zhejiang Province for Pharmaceutical Development of Growth Factors, Biomedical Collaborative Innovation Center of Wenzhou, Wenzhou University, Wenzhou, 325035, China
| | - Jia-Xin Zhao
- Molecular Pharmacology Research Center, School of Pharmaceutical Science Wenzhou Medical University, Wenzhou, 325035, China
| | - Ke Xu
- The Institute of Life Sciences, Engineering Laboratory of Zhejiang Province for Pharmaceutical Development of Growth Factors, Biomedical Collaborative Innovation Center of Wenzhou, Wenzhou University, Wenzhou, 325035, China
| | - Hong-Yu Zhang
- Molecular Pharmacology Research Center, School of Pharmaceutical Science Wenzhou Medical University, Wenzhou, 325035, China.
| | - Jian Xiao
- Molecular Pharmacology Research Center, School of Pharmaceutical Science Wenzhou Medical University, Wenzhou, 325035, China.
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11
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Buscham TJ, Eichel-Vogel MA, Steyer AM, Jahn O, Strenzke N, Dardawal R, Memhave TR, Siems SB, Müller C, Meschkat M, Sun T, Ruhwedel T, Möbius W, Krämer-Albers EM, Boretius S, Nave KA, Werner HB. Progressive axonopathy when oligodendrocytes lack the myelin protein CMTM5. eLife 2022; 11:75523. [PMID: 35274615 PMCID: PMC8916772 DOI: 10.7554/elife.75523] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 02/27/2022] [Indexed: 11/26/2022] Open
Abstract
Oligodendrocytes facilitate rapid impulse propagation along the axons they myelinate and support their long-term integrity. However, the functional relevance of many myelin proteins has remained unknown. Here, we find that expression of the tetraspan-transmembrane protein CMTM5 (chemokine-like factor-like MARVEL-transmembrane domain containing protein 5) is highly enriched in oligodendrocytes and central nervous system (CNS) myelin. Genetic disruption of the Cmtm5 gene in oligodendrocytes of mice does not impair the development or ultrastructure of CNS myelin. However, oligodendroglial Cmtm5 deficiency causes an early-onset progressive axonopathy, which we also observe in global and tamoxifen-induced oligodendroglial Cmtm5 mutants. Presence of the WldS mutation ameliorates the axonopathy, implying a Wallerian degeneration-like pathomechanism. These results indicate that CMTM5 is involved in the function of oligodendrocytes to maintain axonal integrity rather than myelin biogenesis.
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Affiliation(s)
- Tobias J Buscham
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Maria A Eichel-Vogel
- 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
| | - Olaf Jahn
- Proteomics Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Translational Neuroproteomics Group, Department of Psychiatry and Psychotherapy, University Medical Center Göttingen, Georg-August-University, Göttingen, Germany
| | - Nicola Strenzke
- Institute for Auditory Neuroscience, University Medicine Göttingen, Göttingen, Germany
| | - Rakshit Dardawal
- Functional Imaging Laboratory, German Primate Center, Leibniz Institute for Primate Research, Göttingen, Germany
| | - Tor R Memhave
- Functional Imaging Laboratory, German Primate Center, Leibniz Institute for Primate Research, Göttingen, Germany
| | - Sophie B Siems
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Christina Müller
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University, Mainz, Germany
| | - Martin Meschkat
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Abberior Instruments Gmbh, Göttingen, Germany
| | - Ting Sun
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Torben Ruhwedel
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Electron Microscopy Core Unit, 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
| | - Eva-Maria Krämer-Albers
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University, Mainz, Germany
| | - Susann Boretius
- Functional Imaging Laboratory, German Primate Center, Leibniz Institute for Primate Research, 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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12
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Meschkat M, Steyer AM, Weil MT, Kusch K, Jahn O, Piepkorn L, Agüi-Gonzalez P, Phan NTN, Ruhwedel T, Sadowski B, Rizzoli SO, Werner HB, Ehrenreich H, Nave KA, Möbius W. White matter integrity in mice requires continuous myelin synthesis at the inner tongue. Nat Commun 2022; 13:1163. [PMID: 35246535 PMCID: PMC8897471 DOI: 10.1038/s41467-022-28720-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 01/24/2022] [Indexed: 12/18/2022] Open
Abstract
Myelin, the electrically insulating sheath on axons, undergoes dynamic changes over time. However, it is composed of proteins with long lifetimes. This raises the question how such a stable structure is renewed. Here, we study the integrity of myelinated tracts after experimentally preventing the formation of new myelin in the CNS of adult mice, using an inducible Mbp null allele. Oligodendrocytes survive recombination, continue to express myelin genes, but they fail to maintain compacted myelin sheaths. Using 3D electron microscopy and mass spectrometry imaging we visualize myelin-like membranes failing to incorporate adaxonally, most prominently at juxta-paranodes. Myelinoid body formation indicates degradation of existing myelin at the abaxonal side and the inner tongue of the sheath. Thinning of compact myelin and shortening of internodes result in the loss of about 50% of myelin and axonal pathology within 20 weeks post recombination. In summary, our data suggest that functional axon-myelin units require the continuous incorporation of new myelin membranes. Myelin is formed of proteins of long half-lives. The mechanisms of renewal of such a stable structure are unclear. Here, the authors show that myelin integrity requires continuous myelin synthesis at the inner tongue, contributing to the maintenance of a functional axon-myelin unit.
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Affiliation(s)
- Martin Meschkat
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Göttingen Graduate Center for Neurosciences, Biophysics, and Molecular Biosciences (GGNB), Göttingen, Germany.,DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany.,Abberior Instruments GmbH, 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.,DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany.,Imaging Centre, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Marie-Theres Weil
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
| | - Kathrin Kusch
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Olaf Jahn
- DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany.,Proteomics Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Translational Neuroproteomics Group, Department of Psychiatry and Psychotherapy, University Medical Center Göttingen, Göttingen, Germany
| | - Lars Piepkorn
- Proteomics Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Translational Neuroproteomics Group, Department of Psychiatry and Psychotherapy, University Medical Center Göttingen, Göttingen, Germany
| | - Paola Agüi-Gonzalez
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Center for Biostructural Imaging of Neurodegeneration, Göttingen, Germany
| | - Nhu Thi Ngoc Phan
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Center for Biostructural Imaging of Neurodegeneration, Göttingen, Germany.,Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
| | - Torben Ruhwedel
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Boguslawa Sadowski
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
| | - Silvio O Rizzoli
- DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany.,Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Center for Biostructural Imaging of Neurodegeneration, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Hannelore Ehrenreich
- DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany.,Clinical Neuroscience, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 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. .,DFG Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany. .,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany.
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13
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Ahmed S, Travis SD, Díaz-Bahamonde FV, Porter DDL, Henry SN, Mykins J, Ravipati A, Booker A, Ju J, Ding H, Ramesh AK, Pickrell AM, Wang M, LaConte S, Howell BR, Yuan L, Morton PD. Early Influences of Microbiota on White Matter Development in Germ-Free Piglets. Front Cell Neurosci 2022; 15:807170. [PMID: 35027884 PMCID: PMC8751630 DOI: 10.3389/fncel.2021.807170] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 11/29/2021] [Indexed: 11/13/2022] Open
Abstract
Abnormalities in the prefrontal cortex (PFC), as well as the underlying white matter (WM) tracts, lie at the intersection of many neurodevelopmental disorders. The influence of microorganisms on brain development has recently been brought into the clinical and research spotlight as alterations in commensal microbiota are implicated in such disorders, including autism spectrum disorders, schizophrenia, depression, and anxiety via the gut-brain axis. In addition, gut dysbiosis is common in preterm birth patients who often display diffuse WM injury and delayed WM maturation in critical tracts including those within the PFC and corpus callosum. Microbial colonization of the gut aligns with ongoing postnatal processes of oligodendrogenesis and the peak of brain myelination in humans; however, the influence of microbiota on gyral WM development remains elusive. Here, we develop and validate a neonatal germ-free swine model to address these issues, as piglets share key similarities in WM volume, developmental trajectories, and distribution to humans. We find significant region-specific reductions, and sexually dimorphic trends, in WM volume, oligodendrogenesis, and mature oligodendrocyte numbers in germ-free piglets during a key postnatal epoch of myelination. Our findings indicate that microbiota plays a critical role in promoting WM development during early life when the brain is vulnerable to environmental insults that can result in an array of disabilities manifesting later in life.
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Affiliation(s)
- Sadia Ahmed
- Graduate Studies in Biomedical and Veterinary Sciences, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States
| | - Sierrah D Travis
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States
| | - Francisca V Díaz-Bahamonde
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States
| | - Demisha D L Porter
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States.,Virginia Tech Graduate Program in Translational Biology, Medicine and Health, Virginia Tech, Roanoke, VA, United States
| | - Sara N Henry
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States
| | - Julia Mykins
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States
| | - Aditya Ravipati
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States
| | - Aryn Booker
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States
| | - Jing Ju
- Graduate Studies in Biomedical and Veterinary Sciences, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States
| | - Hanzhang Ding
- Virginia Tech Graduate Program in Translational Biology, Medicine and Health, Virginia Tech, Roanoke, VA, United States
| | - Ashwin K Ramesh
- Graduate Studies in Biomedical and Veterinary Sciences, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States.,Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States.,Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, United States
| | - Alicia M Pickrell
- School of Neuroscience, Virginia Tech, Blacksburg, VA, United States
| | - Maosen Wang
- Fralin Biomedical Research Institute at Virginia Tech Carilion (VTC), Virginia Tech, Roanoke, VA, United States
| | - Stephen LaConte
- Fralin Biomedical Research Institute at Virginia Tech Carilion (VTC), Virginia Tech, Roanoke, VA, United States.,Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, United States
| | - Brittany R Howell
- Fralin Biomedical Research Institute at Virginia Tech Carilion (VTC), Virginia Tech, Roanoke, VA, United States.,Department of Human Development and Family Science, Virginia Tech, Roanoke, VA, United States
| | - Lijuan Yuan
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States
| | - Paul D Morton
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, United States
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14
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Kister A, Kister I. Overview of myelin, major myelin lipids, and myelin-associated proteins. Front Chem 2022; 10:1041961. [PMID: 36896314 PMCID: PMC9989179 DOI: 10.3389/fchem.2022.1041961] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 12/23/2022] [Indexed: 02/23/2023] Open
Abstract
Myelin is a modified cell membrane that forms a multilayer sheath around the axon. It retains the main characteristics of biological membranes, such as lipid bilayer, but differs from them in several important respects. In this review, we focus on aspects of myelin composition that are peculiar to this structure and differentiate it from the more conventional cell membranes, with special attention to its constituent lipid components and several of the most common and important myelin proteins: myelin basic protein, proteolipid protein, and myelin protein zero. We also discuss the many-fold functions of myelin, which include reliable electrical insulation of axons to ensure rapid propagation of nerve impulses, provision of trophic support along the axon and organization of the unmyelinated nodes of Ranvier, as well as the relationship between myelin biology and neurologic disease such as multiple sclerosis. We conclude with a brief history of discovery in the field and outline questions for future research.
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Affiliation(s)
- Alexander Kister
- Department of Neurology, New York University Grossman School of Medicine, New York, NY, United States
| | - Ilya Kister
- Department of Neurology, New York University Grossman School of Medicine, New York, NY, United States
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15
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Kim D, An H, Fan C, Park Y. Identifying oligodendrocyte enhancers governing Plp1 expression. Hum Mol Genet 2021; 30:2225-2239. [PMID: 34230963 PMCID: PMC8600034 DOI: 10.1093/hmg/ddab184] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 06/29/2021] [Accepted: 07/01/2021] [Indexed: 11/13/2022] Open
Abstract
Oligodendrocytes (OLs) produce myelin in the central nervous system (CNS), which accelerates the propagation of action potentials and supports axonal integrity. As a major component of CNS myelin, proteolipid protein 1 (Plp1) is indispensable for the axon-supportive function of myelin. Notably, this function requires the continuous high-level expression of Plp1 in OLs. Equally important is the controlled expression of Plp1, as illustrated by Pelizaeus-Merzbacher disease for which the most common cause is PLP1 overexpression. Despite a decade-long search, promoter-distal OL enhancers that govern Plp1 remain elusive. We have recently developed an innovative method that maps promoter-distal enhancers to genes in a principled manner. Here, we applied it to Plp1, uncovering two OL enhancers for it (termed Plp1-E1 and Plp1-E2). Remarkably, clustered regularly interspaced short palindromic repeats (CRISPR) interference epigenome editing showed that Plp1-E1 and Plp1-E2 do not regulate two genes in their vicinity, highlighting their exquisite specificity to Plp1. Assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) and chromatin immunoprecipitation with high-throughput sequencing (ChIP-seq) data show that Plp1-E1 and Plp1-E2 are OL-specific enhancers that are conserved among human, mouse and rat. Hi-C data reveal that the physical interactions between Plp1-E1/2 and PLP1 are among the strongest in OLs and specific to OLs. We also show that Myrf, a master regulator of OL development, acts on Plp1-E1 and Plp1-E2 to promote Plp1 expression.
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Affiliation(s)
- Dongkyeong Kim
- Hunter James Kelly Research Institute, Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, USA
| | - Hongjoo An
- Hunter James Kelly Research Institute, Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, USA
| | - Chuandong Fan
- Hunter James Kelly Research Institute, Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, USA
| | - Yungki Park
- Hunter James Kelly Research Institute, Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14203, USA
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16
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Riedhammer KM, Stockler S, Ploski R, Wenzel M, Adis-Dutschmann B, Ahting U, Alhaddad B, Blaschek A, Haack TB, Kopajtich R, Lee J, Murcia Pienkowski V, Pollak A, Szymanska K, Tarailo-Graovac M, van der Lee R, van Karnebeek CD, Meitinger T, Krägeloh-Mann I, Vill K. De novo stop-loss variants in CLDN11 cause hypomyelinating leukodystrophy. Brain 2021; 144:411-419. [PMID: 33313762 DOI: 10.1093/brain/awaa410] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 09/17/2020] [Accepted: 09/28/2020] [Indexed: 11/13/2022] Open
Abstract
Claudin-11, a tight junction protein, is indispensable in the formation of the radial component of myelin. Here, we report de novo stop-loss variants in the gene encoding claudin-11, CLDN11, in three unrelated individuals presenting with an early-onset spastic movement disorder, expressive speech disorder and eye abnormalities including hypermetropia. Brain MRI showed a myelin deficit with a discrepancy between T1-weighted and T2-weighted images and some progress in myelination especially involving the central and peripheral white matter. Exome sequencing identified heterozygous stop-loss variants c.622T>C, p.(*208Glnext*39) in two individuals and c.622T>G, p.(*208Gluext*39) in one individual, all occurring de novo. At the RNA level, the variant c.622T>C did not lead to a loss of expression in fibroblasts, indicating this transcript is not subject to nonsense-mediated decay and most likely translated into an extended protein. Extended claudin-11 is predicted to form an alpha helix not incorporated into the cytoplasmic membrane, possibly perturbing its interaction with intracellular proteins. Our observations suggest that stop-loss variants in CLDN11 expand the genetically heterogeneous spectrum of hypomyelinating leukodystrophies.
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Affiliation(s)
- Korbinian M Riedhammer
- Institute of Human Genetics, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, Munich, 81675, Germany.,Department of Nephrology, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, Munich, 81675, Germany
| | - Sylvia Stockler
- Division of Biochemical Diseases, Department of Pediatrics, B.C. Children's Hospital, The University of British Columbia, Vancouver, BC V6H 0B3, Canada
| | - Rafal Ploski
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, 02-106, Poland
| | - Maren Wenzel
- Genetikum, Genetic Counseling and Diagnostics, Neu-Ulm, 89231, Germany
| | | | - Uwe Ahting
- Institute of Human Genetics, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, Munich, 81675, Germany
| | - Bader Alhaddad
- Institute of Human Genetics, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, Munich, 81675, Germany
| | - Astrid Blaschek
- Dr. v. Hauner Children's Hospital, Department of Pediatric Neurology and Developmental Medicine, LMU - University of Munich, 80337, Germany
| | - Tobias B Haack
- Institute of Human Genetics, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, Munich, 81675, Germany.,Institute of Medical Genetics and Applied Genomics, University of Tübingen, 72076 Tübingen, Germany
| | - Robert Kopajtich
- Institute of Human Genetics, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, Munich, 81675, Germany.,Institute of Neurogenomics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, 85764, Germany
| | - Jessica Lee
- Centre for Molecular Medicine and Therapeutics, BC Children's Hospital Research Institute, Department of Medical Genetics and Pediatrics, The University of British Columbia, Vancouver, BC V6H 0B3, Canada
| | | | - Agnieszka Pollak
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, 02-106, Poland
| | - Krystyna Szymanska
- Department of Experimental and Clinical Neuropathology, Mossakowski Medical Research Center, Polish Academy of Sciences, Warsaw, 02-106, Poland
| | - Maja Tarailo-Graovac
- Department of Medical Genetics, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada.,Department of Biochemistry and Molecular Biology, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Robin van der Lee
- Centre for Molecular Medicine and Therapeutics, BC Children's Hospital Research Institute, Department of Medical Genetics and Pediatrics, The University of British Columbia, Vancouver, BC V6H 0B3, Canada
| | - Clara D van Karnebeek
- Centre for Molecular Medicine and Therapeutics, BC Children's Hospital Research Institute, Department of Medical Genetics and Pediatrics, The University of British Columbia, Vancouver, BC V6H 0B3, Canada.,Department of Pediatric Metabolic Diseases, Amalia Children's Hospital, Radboud University Medical centre, Nijmegen, 6525 GA, The Netherlands
| | - Thomas Meitinger
- Institute of Human Genetics, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, Munich, 81675, Germany
| | - Ingeborg Krägeloh-Mann
- Department of Pediatric Neurology and Developmental Medicine, University Children's Hospital, Tübingen, 72076, Germany
| | - Katharina Vill
- Dr. v. Hauner Children's Hospital, Department of Pediatric Neurology and Developmental Medicine, LMU - University of Munich, 80337, Germany
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17
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Siems SB, Jahn O, Hoodless LJ, Jung RB, Hesse D, Möbius W, Czopka T, Werner HB. Proteome Profile of Myelin in the Zebrafish Brain. Front Cell Dev Biol 2021; 9:640169. [PMID: 33898427 PMCID: PMC8060510 DOI: 10.3389/fcell.2021.640169] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 03/05/2021] [Indexed: 12/14/2022] Open
Abstract
The velocity of nerve conduction along vertebrate axons depends on their ensheathment with myelin. Myelin membranes comprise specialized proteins well characterized in mice. Much less is known about the protein composition of myelin in non-mammalian species. Here, we assess the proteome of myelin biochemically purified from the brains of adult zebrafish (Danio rerio), considering its increasing popularity as model organism for myelin biology. Combining gel-based and gel-free proteomic approaches, we identified > 1,000 proteins in purified zebrafish myelin, including all known constituents. By mass spectrometric quantification, the predominant Ig-CAM myelin protein zero (MPZ/P0), myelin basic protein (MBP), and the short-chain dehydrogenase 36K constitute 12%, 8%, and 6% of the total myelin protein, respectively. Comparison with previously established mRNA-abundance profiles shows that expression of many myelin-related transcripts coincides with the maturation of zebrafish oligodendrocytes. Zebrafish myelin comprises several proteins that are not present in mice, including 36K, CLDNK, and ZWI. However, a surprisingly large number of ortholog proteins is present in myelin of both species, indicating partial evolutionary preservation of its constituents. Yet, the relative abundance of CNS myelin proteins can differ markedly as exemplified by the complement inhibitor CD59 that constitutes 5% of the total zebrafish myelin protein but is a low-abundant myelin component in mice. Using novel transgenic reporter constructs and cryo-immuno electron microscopy, we confirm the incorporation of CD59 into myelin sheaths. These data provide the first proteome resource of zebrafish CNS myelin and demonstrate both similarities and heterogeneity of myelin composition between teleost fish and rodents.
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Affiliation(s)
- Sophie B Siems
- Department of Neurogenetics, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Olaf Jahn
- Proteomics Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Laura J Hoodless
- Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, United Kingdom
| | - Ramona B Jung
- Department of Neurogenetics, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Dörte Hesse
- Proteomics Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Wiebke Möbius
- Department of Neurogenetics, Max Planck Institute for Experimental Medicine, Göttingen, Germany.,Electron Microscopy Core Unit, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Tim Czopka
- Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, United Kingdom
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute for Experimental Medicine, Göttingen, Germany
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18
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Abstract
Myelination of axons provides the structural basis for rapid saltatory impulse propagation along vertebrate fiber tracts, a well-established neurophysiological concept. However, myelinating oligodendrocytes and Schwann cells serve additional functions in neuronal energy metabolism that are remarkably similar to those of axon-ensheathing glial cells in unmyelinated invertebrates. Here we discuss myelin evolution and physiological glial functions, beginning with the role of ensheathing glia in preventing ephaptic coupling, axoglial metabolic support, and eliminating oxidative radicals. In both vertebrates and invertebrates, axoglial interactions are bidirectional, serving to regulate cell fate, nerve conduction, and behavioral performance. One key step in the evolution of compact myelin in the vertebrate lineage was the emergence of the open reading frame for myelin basic protein within another gene. Several other proteins were neofunctionalized as myelin constituents and help maintain a healthy nervous system. Myelination in vertebrates became a major prerequisite of inhabiting new ecological niches.
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Affiliation(s)
- Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, D-37075 Göttingen, Germany; ,
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, D-37075 Göttingen, Germany; ,
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19
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Duncan GJ, Simkins TJ, Emery B. Neuron-Oligodendrocyte Interactions in the Structure and Integrity of Axons. Front Cell Dev Biol 2021; 9:653101. [PMID: 33763430 PMCID: PMC7982542 DOI: 10.3389/fcell.2021.653101] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 02/15/2021] [Indexed: 12/12/2022] Open
Abstract
The myelination of axons by oligodendrocytes is a highly complex cell-to-cell interaction. Oligodendrocytes and axons have a reciprocal signaling relationship in which oligodendrocytes receive cues from axons that direct their myelination, and oligodendrocytes subsequently shape axonal structure and conduction. Oligodendrocytes are necessary for the maturation of excitatory domains on the axon including nodes of Ranvier, help buffer potassium, and support neuronal energy metabolism. Disruption of the oligodendrocyte-axon unit in traumatic injuries, Alzheimer's disease and demyelinating diseases such as multiple sclerosis results in axonal dysfunction and can culminate in neurodegeneration. In this review, we discuss the mechanisms by which demyelination and loss of oligodendrocytes compromise axons. We highlight the intra-axonal cascades initiated by demyelination that can result in irreversible axonal damage. Both the restoration of oligodendrocyte myelination or neuroprotective therapies targeting these intra-axonal cascades are likely to have therapeutic potential in disorders in which oligodendrocyte support of axons is disrupted.
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Affiliation(s)
- Greg J. Duncan
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health & Science University, Portland, OR, United States
| | - Tyrell J. Simkins
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health & Science University, Portland, OR, United States
- Vollum Institute, Oregon Health & Science University, Portland, OR, United States
- Department of Neurology, VA Portland Health Care System, Portland, OR, United States
| | - Ben Emery
- Jungers Center for Neurosciences Research, Department of Neurology, Oregon Health & Science University, Portland, OR, United States
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20
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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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21
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Wolfe T, Hoffman K, Hogan MK, Salazar B, Tang X, Chaboub L, Quini CC, Lu ZL, Horner PJ. Quantification of Myelinated Nerve Fraction and Degeneration in Spinal Cord Neuropil by SHIFT MRI. J Magn Reson Imaging 2020; 53:1162-1174. [PMID: 33098256 DOI: 10.1002/jmri.27397] [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: 06/05/2020] [Revised: 09/29/2020] [Accepted: 09/30/2020] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Neurodegeneration is a complex cellular process linked to prompt changes in myelin integrity and gradual neuron loss. Current imaging techniques offer estimations of myelin volumes in lesions/remyelinated areas but are limited to detect subtle injury. PURPOSE To investigate whether measurements detected by a signal hierarchically isolated as a function of time-to-echo (SHIFT) MRI technique can determine changes in myelin integrity and fiber axolemma. STUDY TYPE Prospective animal model. ANIMAL MODEL Surgically demyelinated spinal cord (SC) injury model in rodents (n = 6). FIELD STRENGTH/SEQUENCE Gradient-echo spin-echo at 3T. ASSESSMENT Multicompartment T2 relaxations were computed by SHIFT MRI in 75-microns-resolution images of the SC injury penumbra region 2 weeks post-trauma. G-ratio and axolemma delamination were assessed by transmission electron microscopy (TEM) in intact and injured samples. SC myelinated nerve fraction was computed by SHIFT MRI prospectively and assessed histologically. STATISTICAL TESTS Relations between SHIFT-isolated T2 -components and TEM measurements were studied using linear regression and t-tests. Pearson's correlation and significance were computed to determine the SHIFT's sensitivity to detect myelinated fibers ratio in gray matter. Regularized least-squares-based ranking analysis was employed to determine SHIFT MRI's ability to discern intact and injured myelinated nerves. RESULTS Biexponential signals isolated by SHIFT MRI for intact vs. lesion penumbra exhibited changes in T2 , shifting from intermediate components (25 ± 2 msec) to long (43 ± 11 msec) in white matter, and similarly in gray matter regions-of-interest (31 ± 2 to 46 ± 16 msec). These changes correlated highly with TEM g-ratio and axon delamination measurements (P < 0.05). Changes in short T2 components were observed but not statistically significant (8.5 ± 0.5 to 7 ± 3 msec, P = 0.445, and 4.0 ± 0.9 to 7 ± 3 msec, P = 0.075, respectively). SHIFT MRI's ability to detect myelinated fibers within gray matter was confirmed (P < 0.001). DATA CONCLUSION Changes detected by SHIFT MRI are associated with abnormal intermembrane spaces formed upon mild injury, directly correlated with early neuro integrity loss. Level of Evidence 1 Technical Efficacy Stage 2.
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Affiliation(s)
- Tatiana Wolfe
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Kristopher Hoffman
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Matthew K Hogan
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Betsy Salazar
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Xiufeng Tang
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Lesley Chaboub
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
| | - Caio C Quini
- Department of Biological Physics, Universidade Estadual Paulista UNESP, Botucatu, Sao Paulo, Brazil
| | - Zhong-Lin Lu
- Division of Arts and Sciences, NYU Shanghai, Shanghai, China, NYU-ECNU Institute of Cognitive Neuroscience at NYU Shanghai, Shanghai, China, Center for Neural Science and Department of Psychology, New York University, New York, USA
| | - Philip J Horner
- Center for Neuroregneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston Methodist Hospital, Houston, Texas, USA
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22
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Alcover-Sanchez B, Garcia-Martin G, Escudero-Ramirez J, Gonzalez-Riano C, Lorenzo P, Gimenez-Cassina A, Formentini L, de la Villa-Polo P, Pereira MP, Wandosell F, Cubelos B. Absence of R-Ras1 and R-Ras2 causes mitochondrial alterations that trigger axonal degeneration in a hypomyelinating disease model. Glia 2020; 69:619-637. [PMID: 33010069 DOI: 10.1002/glia.23917] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 08/18/2020] [Accepted: 09/21/2020] [Indexed: 12/11/2022]
Abstract
Fast synaptic transmission in vertebrates is critically dependent on myelin for insulation and metabolic support. Myelin is produced by oligodendrocytes (OLs) that maintain multilayered membrane compartments that wrap around axonal fibers. Alterations in myelination can therefore lead to severe pathologies such as multiple sclerosis. Given that hypomyelination disorders have complex etiologies, reproducing clinical symptoms of myelin diseases from a neurological perspective in animal models has been difficult. We recently reported that R-Ras1-/- and/or R-Ras2-/- mice, which lack GTPases essential for OL survival and differentiation processes, present different degrees of hypomyelination in the central nervous system with a compounded hypomyelination in double knockout (DKO) mice. Here, we discovered that the loss of R-Ras1 and/or R-Ras2 function is associated with aberrant myelinated axons with increased numbers of mitochondria, and a disrupted mitochondrial respiration that leads to increased reactive oxygen species levels. Consequently, aberrant myelinated axons are thinner with cytoskeletal phosphorylation patterns typical of axonal degeneration processes, characteristic of myelin diseases. Although we observed different levels of hypomyelination in a single mutant mouse, the combined loss of function in DKO mice lead to a compromised axonal integrity, triggering the loss of visual function. Our findings demonstrate that the loss of R-Ras function reproduces several characteristics of hypomyelinating diseases, and we therefore propose that R-Ras1-/- and R-Ras2-/- neurological models are valuable approaches for the study of these myelin pathologies.
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Affiliation(s)
- Berta Alcover-Sanchez
- Departamento de Biología Molecular and Centro Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid - Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Gonzalo Garcia-Martin
- Departamento de Biología Molecular and Centro Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid - Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Juan Escudero-Ramirez
- Departamento de Biología Molecular and Centro Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid - Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Carolina Gonzalez-Riano
- CEMBIO (Centre for Metabolomics and Bioanalysis), Facultad de Farmacia, Universidad San Pablo-CEU, CEU Universities, Madrid, Spain
| | - Paz Lorenzo
- CEMBIO (Centre for Metabolomics and Bioanalysis), Facultad de Farmacia, Universidad San Pablo-CEU, CEU Universities, Madrid, Spain
| | - Alfredo Gimenez-Cassina
- Departamento de Biología Molecular and Centro Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid - Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Laura Formentini
- Departamento de Biología Molecular and Centro Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid - Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Pedro de la Villa-Polo
- Departamento de Biología de Sistemas, Universidad de Alcalá, Madrid, Spain.,Grupo de Neurofisiología Visual, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Madrid, Spain
| | - Marta P Pereira
- Departamento de Biología Molecular and Centro Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid - Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Francisco Wandosell
- Departamento de Biología Molecular and Centro Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid - Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Beatriz Cubelos
- Departamento de Biología Molecular and Centro Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid - Consejo Superior de Investigaciones Científicas, Madrid, Spain
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23
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Aparicio GI, Formoso K, León A, Frasch AC, Scorticati C. Identification of Potential Interacting Proteins With the Extracellular Loops of the Neuronal Glycoprotein M6a by TMT/MS. Front Synaptic Neurosci 2020; 12:28. [PMID: 32848694 PMCID: PMC7396582 DOI: 10.3389/fnsyn.2020.00028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 06/15/2020] [Indexed: 12/21/2022] Open
Abstract
Nowadays, great efforts are made to gain insight into the molecular mechanisms that underlie structural neuronal plasticity. Moreover, the identification of signaling pathways involved in the development of psychiatric disorders aids the screening of possible therapeutic targets. Genetic variations or alterations in GPM6A expression are linked to neurological disorders such as schizophrenia, depression, and Alzheimer's disease. GPM6A encodes the neuronal surface glycoprotein M6a that promotes filopodia/spine, dendrite, and synapse formation by unknown mechanisms. A substantial body of evidence suggests that the extracellular loops of M6a command its function. However, the proteins that associate with them and that modulate neuronal plasticity have not been determined yet. To address this question, we generated a chimera protein that only contains the extracellular loops of M6a and performed a co-immunoprecipitation with rat hippocampus samples followed by TMT/MS. Here, we report 72 proteins, which are good candidates to interact with M6a's extracellular loops and modify its function. Gene ontology (GO) analysis showed that 63% of the potential M6a's interactor proteins belong to the category "synapse," at both sides of the synaptic cleft, "neuron projections" (51%) and "presynapse" (49%). In this sense, we showed that endogenous M6a interacts with piccolo, synaptic vesicle protein 2B, and synapsin 1 in mature cultured hippocampal neurons. Interestingly, about 28% of the proteins left were related to the "myelin sheath" annotation, suggesting that M6a could interact with proteins at the surface of oligodendrocytes. Indeed, we demonstrated the (cis and trans) interaction between M6a and proteolipid protein (PLP) in neuroblastoma N2a cells. Finally, the 72 proteins were subjected to disease-associated genes and variants screening by DisGeNET. Apart from the diseases that have already been associated with M6a, most of the proteins are also involved in "autistic disorder," "epilepsy," and "seizures" increasing the spectrum of disorders in which M6a could play a role. Data are available via ProteomeXchange with identifier PXD017347.
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Affiliation(s)
- Gabriela I Aparicio
- Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín (IIBio-UNSAM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Martín, Argentina
| | - Karina Formoso
- Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín (IIBio-UNSAM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Martín, Argentina.,Instituto de Investigaciones Biomédicas (BIOMED), Facultad de Ciencias Médicas, Pontificia Universidad Católica Argentina (UCA), CONICET, San Martín, Argentina
| | - Antonella León
- Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín (IIBio-UNSAM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Martín, Argentina
| | - Alberto C Frasch
- Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín (IIBio-UNSAM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Martín, Argentina.,Vicerrectorado, Edificio de Gobierno, Universidad Nacional de San Martín (UNSAM), San Martín, Argentina
| | - Camila Scorticati
- Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín (IIBio-UNSAM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Martín, Argentina
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24
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Abstract
Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. We review the two core MS features, myelin instability, fragmentation, and remyelination failure, and dominance of pathogenic CD4+ Th17 cells over protective CD4+ Treg cells. To better understand myelin pathology, we describe myelin biosynthesis, structure, and function, then highlight stearoyl-CoA desaturase (SCD) in nervonic acid biosynthesis and nervonic acid's contribution to myelin stability. Noting that vitamin D deficiency decreases SCD in the periphery, we propose it also decreases SCD in oligodendrocytes, disrupting the nervonic acid supply and causing myelin instability and fragmentation. To better understand the distorted Th17/Treg cell balance, we summarize Th17 cell contributions to MS pathogenesis, then highlight how 1,25-dihydroxyvitamin D3 signaling from microglia to CD4+ T cells restores Treg cell dominance. This signaling rapidly increases flux through the methionine cycle, removing homocysteine, replenishing S-adenosyl-methionine, and improving epigenetic marking. Noting that DNA hypomethylation and inappropriate DRB1*1501 expression were observed in MS patient CD4+ T cells, we propose that vitamin D deficiency thwarts epigenetic downregulation of DRB1*1501 and Th17 cell signature genes, and upregulation of Treg cell signature genes, causing dysregulation within the CD4+ T cell compartment. We explain how obesity reduces vitamin D status, and how estrogen and vitamin D collaborate to promote Treg cell dominance in females. Finally, we discuss the implications of this new knowledge concerning myelin and the Th17/Treg cell balance, and advocate for efforts to address the global epidemics of obesity and vitamin D deficiency in the expectation of reducing the impact of MS.
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Affiliation(s)
- Colleen E. Hayes
- Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706, USA
| | - James M. Ntambi
- Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706, USA
- Department of Nutritional Sciences, University of Wisconsin-Madison, 1415 Linden Drive, Madison, WI 53706, USA
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25
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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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26
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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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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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Abstract
Neural plasticity in the adult central nervous system involves the adaptation of myelination, including the formation of novel myelin sheaths by adult-born oligodendrocytes. Yet, mature oligodendrocytes slowly but constantly turn over their pre-existing myelin sheaths, thereby establishing an equilibrium of replenishment and degradation that may also be subject to adaptation with consequences for nerve conduction velocity. In this short review we highlight selected approaches to the normal turnover of adult myelin in vivo, from injecting radioactive precursors of myelin constituents in the 1960s to current strategies involving isotope labeling and tamoxifen-induced gene targeting.
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Affiliation(s)
- Tobias J Buscham
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Maria A Eichel
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Sophie B Siems
- 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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