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Mouihate A, Kalakh S. Breastfeeding promotes oligodendrocyte precursor cells division and myelination in the demyelinated corpus callosum. Brain Res 2023; 1821:148584. [PMID: 37717888 DOI: 10.1016/j.brainres.2023.148584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 09/12/2023] [Accepted: 09/14/2023] [Indexed: 09/19/2023]
Abstract
Demyelination alters the conduction of neuronal signals and hampers sensory-motor functions. Experimental and clinical evidence suggest that breastfeeding exerts a promyelinating impact on the maternal brain. The mechanism underlying this neuroprotective effect is not well-understood. In the present paper, we assessed the impact of rat lactation on lysolecithin-induced demyelination injury within the corpus callosum of lactating and non-lactating postpartum rats. We show that lactation enhanced the cell density of oligodendrocyte precursor cells (OPCs), but not that of activated microglia and astrocytes, within the demyelination lesion. Lactation also increased the expression of myelin markers involved in the initial stage of myelin recovery (Myelin-associated glycoprotein and 2',3'-cyclic nucleotide 3'-phosphodiesterase) and reduced the demyelination injury. Altogether, these data suggest that lactation creates a conducive promyelinating environment through increased OPCs cell division, enhanced expression of select myelin proteins, and reduced number of non-myelinated axons.
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Affiliation(s)
- Abdeslam Mouihate
- Department of Physiology, College of Medicine, Kuwait University, P.O. Box 24923, Safat 13110, Kuwait.
| | - Samah Kalakh
- Department of Physiology, College of Medicine, Kuwait University, P.O. Box 24923, Safat 13110, Kuwait
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2
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Xie Q, Zhang Y, Zhang J, Cui D, Zhou Q, Guo M. Promotion effect of the blend containing 2'-FL, OPN and DHA on oligodendrocyte progenitor cells myelination in vitro. Front Nutr 2022; 9:1054431. [DOI: 10.3389/fnut.2022.1054431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 10/17/2022] [Indexed: 11/11/2022] Open
Abstract
During early neurodevelopment of infant, myelination plays an essential role in brain connectivity and emergence of behavioral and cognitive function. Early life nutrition is an important factor to shape myelination and consequently cognitive appearance. To analyze the effects of additive nutrients, including 2'-fucosyllactose (2'-FL), osteopontin (OPN), docosahexaenoic acid (DHA), on neurocognitive function and brain structure, the current study evaluated the effects of different composition of breast milk nutrients on oligodendrocyte progenitor cells (OPCs) myelination with a neural primary cell model in vitro. The study showed that the three nutrients promoted the proliferation, maturation and differentiation of OPCs into mature oligodendrocytes (OLs) in each phage of the cell growth, and the effect of the nutrients blend is obviously stronger than that of the nutrient treatment alone, showing a synergistic effect in promotion of OPCs. The results of this experiment clarified the effects of 2′-FL OPN and DHA to promote myelination development of neural cells, and laid an experimental basis for further optimization of infant formula.
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3
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Anti-MAG neuropathy: From biology to clinical management. J Neuroimmunol 2021; 361:577725. [PMID: 34610502 DOI: 10.1016/j.jneuroim.2021.577725] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 09/20/2021] [Indexed: 12/19/2022]
Abstract
The acquired chronic demyelinating neuropathies include a growing number of disease entities that have characteristic, often overlapping, clinical presentations, mediated by distinct immune mechanisms, and responding to different therapies. After the discovery in the early 1980s, that the myelin associated glycoprotein (MAG) is a target antigen in an autoimmune demyelinating neuropathy, assays to measure the presence of anti-MAG antibodies were used as the basis to diagnose the anti-MAG neuropathy. The route was open for describing the clinical characteristics of this new entity as a chronic distal large fiber sensorimotor neuropathy, for studying its pathogenesis and devising specific treatment strategies. The initial use of chemotherapeutic agents was replaced by the introduction in the late 1990s of rituximab, a monoclonal antibody against CD20+ B-cells. Since then, other anti-B cells agents have been introduced. Recently a novel antigen-specific immunotherapy neutralizing the anti-MAG antibodies with a carbohydrate-based ligand mimicking the natural HNK-1 glycoepitope has been described.
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4
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Moss KR, Bopp TS, Johnson AE, Höke A. New evidence for secondary axonal degeneration in demyelinating neuropathies. Neurosci Lett 2021; 744:135595. [PMID: 33359733 PMCID: PMC7852893 DOI: 10.1016/j.neulet.2020.135595] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 10/31/2020] [Accepted: 12/19/2020] [Indexed: 12/28/2022]
Abstract
Development of peripheral nervous system (PNS) myelin involves a coordinated series of events between growing axons and the Schwann cell (SC) progenitors that will eventually ensheath them. Myelin sheaths have evolved out of necessity to maintain rapid impulse propagation while accounting for body space constraints. However, myelinating SCs perform additional critical functions that are required to preserve axonal integrity including mitigating energy consumption by establishing the nodal architecture, regulating axon caliber by organizing axonal cytoskeleton networks, providing trophic and potentially metabolic support, possibly supplying genetic translation materials and protecting axons from toxic insults. The intermediate steps between the loss of these functions and the initiation of axon degeneration are unknown but the importance of these processes provides insightful clues. Prevalent demyelinating diseases of the PNS include the inherited neuropathies Charcot-Marie-Tooth Disease, Type 1 (CMT1) and Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) and the inflammatory diseases Acute Inflammatory Demyelinating Polyneuropathy (AIDP) and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP). Secondary axon degeneration is a common feature of demyelinating neuropathies and this process is often correlated with clinical deficits and long-lasting disability in patients. There is abundant electrophysiological and histological evidence for secondary axon degeneration in patients and rodent models of PNS demyelinating diseases. Fully understanding the involvement of secondary axon degeneration in these diseases is essential for expanding our knowledge of disease pathogenesis and prognosis, which will be essential for developing novel therapeutic strategies.
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Affiliation(s)
- Kathryn R Moss
- Department of Neurology, Neuromuscular Division, Johns Hopkins School of Medicine, Baltimore, MD, United States
| | - Taylor S Bopp
- Department of Neurology, Neuromuscular Division, Johns Hopkins School of Medicine, Baltimore, MD, United States
| | - Anna E Johnson
- Department of Neurology, Neuromuscular Division, Johns Hopkins School of Medicine, Baltimore, MD, United States
| | - Ahmet Höke
- Department of Neurology, Neuromuscular Division, Johns Hopkins School of Medicine, Baltimore, MD, United States.
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5
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Sipione S, Monyror J, Galleguillos D, Steinberg N, Kadam V. Gangliosides in the Brain: Physiology, Pathophysiology and Therapeutic Applications. Front Neurosci 2020; 14:572965. [PMID: 33117120 PMCID: PMC7574889 DOI: 10.3389/fnins.2020.572965] [Citation(s) in RCA: 144] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 08/31/2020] [Indexed: 12/12/2022] Open
Abstract
Gangliosides are glycosphingolipids highly abundant in the nervous system, and carry most of the sialic acid residues in the brain. Gangliosides are enriched in cell membrane microdomains ("lipid rafts") and play important roles in the modulation of membrane proteins and ion channels, in cell signaling and in the communication among cells. The importance of gangliosides in the brain is highlighted by the fact that loss of function mutations in ganglioside biosynthetic enzymes result in severe neurodegenerative disorders, often characterized by very early or childhood onset. In addition, changes in the ganglioside profile (i.e., in the relative abundance of specific gangliosides) were reported in healthy aging and in common neurological conditions, including Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), stroke, multiple sclerosis and epilepsy. At least in HD, PD and in some forms of epilepsy, experimental evidence strongly suggests a potential role of gangliosides in disease pathogenesis and potential treatment. In this review, we will summarize ganglioside functions that are crucial to maintain brain health, we will review changes in ganglioside levels that occur in major neurological conditions and we will discuss their contribution to cellular dysfunctions and disease pathogenesis. Finally, we will review evidence of the beneficial roles exerted by gangliosides, GM1 in particular, in disease models and in clinical trials.
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Affiliation(s)
- Simonetta Sipione
- Department of Pharmacology, Faculty of Medicine and Dentistry, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
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6
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Schwann Cell Role in Selectivity of Nerve Regeneration. Cells 2020; 9:cells9092131. [PMID: 32962230 PMCID: PMC7563640 DOI: 10.3390/cells9092131] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 09/16/2020] [Accepted: 09/17/2020] [Indexed: 12/13/2022] Open
Abstract
Peripheral nerve injuries result in the loss of the motor, sensory and autonomic functions of the denervated segments of the body. Neurons can regenerate after peripheral axotomy, but inaccuracy in reinnervation causes a permanent loss of function that impairs complete recovery. Thus, understanding how regenerating axons respond to their environment and direct their growth is essential to improve the functional outcome of patients with nerve lesions. Schwann cells (SCs) play a crucial role in the regeneration process, but little is known about their contribution to specific reinnervation. Here, we review the mechanisms by which SCs can differentially influence the regeneration of motor and sensory axons. Mature SCs express modality-specific phenotypes that have been associated with the promotion of selective regeneration. These include molecular markers, such as L2/HNK-1 carbohydrate, which is differentially expressed in motor and sensory SCs, or the neurotrophic profile after denervation, which differs remarkably between SC modalities. Other important factors include several molecules implicated in axon-SC interaction. This cell–cell communication through adhesion (e.g., polysialic acid) and inhibitory molecules (e.g., MAG) contributes to guiding growing axons to their targets. As many of these factors can be modulated, further research will allow the design of new strategies to improve functional recovery after peripheral nerve injuries.
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Roles of Gangliosides in Hypothalamic Control of Energy Balance: New Insights. Int J Mol Sci 2020; 21:ijms21155349. [PMID: 32731387 PMCID: PMC7432706 DOI: 10.3390/ijms21155349] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 07/20/2020] [Accepted: 07/26/2020] [Indexed: 12/19/2022] Open
Abstract
Gangliosides are essential components of cell membranes and are involved in a variety of physiological processes, including cell growth, differentiation, and receptor-mediated signal transduction. They regulate functions of proteins in membrane microdomains, notably receptor tyrosine kinases such as insulin receptor (InsR) and epidermal growth factor receptor (EGFR), through lateral association. Studies during the past two decades using knockout (KO) or pharmacologically inhibited cells, or KO mouse models for glucosylceramide synthase (GCS; Ugcg), GM3 synthase (GM3S; St3gal5), and GD3 synthase (GD3S; St8sia1) have revealed essential roles of gangliosides in hypothalamic control of energy balance. The a-series gangliosides GM1 and GD1a interact with leptin receptor (LepR) and promote LepR signaling through activation of the JAK2/STAT3 pathway. Studies of GM3S KO cells have shown that the extracellular signal-regulated kinase (ERK) pathway, downstream of the LepR signaling pathway, is also modulated by gangliosides. Recent studies have revealed crosstalk between the LepR signaling pathway and other receptor signaling pathways (e.g., InsR and EGFR pathways). Gangliosides thus have the ability to modulate the effects of leptin by regulating functions of such receptors, and by direct interaction with LepR to control signaling.
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8
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Darios F, Mochel F, Stevanin G. Lipids in the Physiopathology of Hereditary Spastic Paraplegias. Front Neurosci 2020; 14:74. [PMID: 32180696 PMCID: PMC7059351 DOI: 10.3389/fnins.2020.00074] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 01/20/2020] [Indexed: 12/12/2022] Open
Abstract
Hereditary spastic paraplegias (HSP) are a group of neurodegenerative diseases sharing spasticity in lower limbs as common symptom. There is a large clinical variability in the presentation of patients, partly underlined by the large genetic heterogeneity, with more than 60 genes responsible for HSP. Despite this large heterogeneity, the proteins with known function are supposed to be involved in a limited number of cellular compartments such as shaping of the endoplasmic reticulum or endolysosomal function. Yet, it is difficult to understand why alteration of such different cellular compartments can lead to degeneration of the axons of cortical motor neurons. A common feature that has emerged over the last decade is the alteration of lipid metabolism in this group of pathologies. This was first revealed by the identification of mutations in genes encoding proteins that have or are supposed to have enzymatic activities on lipid substrates. However, it also appears that mutations in genes affecting endoplasmic reticulum, mitochondria, or endolysosome function can lead to changes in lipid distribution or metabolism. The aim of this review is to discuss the role of lipid metabolism alterations in the physiopathology of HSP, to evaluate how such alterations contribute to neurodegenerative phenotypes, and to understand how this knowledge can help develop therapeutic strategy for HSP.
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Affiliation(s)
- Frédéric Darios
- Sorbonne Université, Paris, France.,Inserm, U1127, Paris, France.,CNRS, UMR 7225, Paris, France.,Institut du Cerveau et de la Moelle Epinière, Paris, France
| | - Fanny Mochel
- Sorbonne Université, Paris, France.,Inserm, U1127, Paris, France.,CNRS, UMR 7225, Paris, France.,Institut du Cerveau et de la Moelle Epinière, Paris, France.,National Reference Center for Neurometabolic Diseases, Pitié-Salpêtrière University Hospital, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - Giovanni Stevanin
- Sorbonne Université, Paris, France.,Inserm, U1127, Paris, France.,CNRS, UMR 7225, Paris, France.,Institut du Cerveau et de la Moelle Epinière, Paris, France.,Equipe de Neurogénétique, Ecole Pratique des Hautes Etudes, PSL Research University, Paris, France
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9
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Dong XZ, Wang DX, Zhang TY, Liu X, Liu P, Hu Y. Identification of protein targets for the antidepressant effects of Kai-Xin-San in Chinese medicine using isobaric tags for relative and absolute quantitation. Neural Regen Res 2019; 15:302-310. [PMID: 31552903 PMCID: PMC6905330 DOI: 10.4103/1673-5374.265555] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Kai-Xin-San consists of Ginseng Radix, Polygalae Radix, Acori Tatarinowii Rhizoma, and Poria at a ratio of 3:3:2:2. Kai-Xin-San has been widely used for the treatment of emotional disorders in China. However, no studies have identified the key proteins implicated in response to Kai-Xin-San treatment. In this study, rat models of chronic mild stress were established using different stress methods over 28 days. After 14 days of stress stimulation, rats received daily intragastric administrations of 600 mg/kg Kai-Xin-San. The sucrose preference test was used to determine depression-like behavior in rats, while isobaric tags were used for relative and absolute quantitation-based proteomics to identify altered proteins following Kai-Xin-San treatment. Kai-Xin-San treatment for 2 weeks noticeably improved depression-like behaviors in rats with chronic mild stress. We identified 33 differentially expressed proteins: 7 were upregulated and 26 were downregulated. Functional analysis showed that these differentially expressed proteins participate in synaptic plasticity, neurodevelopment, and neurogenesis. Our results indicate that Kai-Xin-San has an important role in regulating the key node proteins in the synaptic signaling network, and are helpful to better understand the mechanism of the antidepressive effects of Kai-Xin-San and to provide objective theoretical support for its clinical application. The study was approved by the Ethics Committee for Animal Research from the Chinese PLA General Hospital (approval No. X5-2016-07) on March 5, 2016.
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Affiliation(s)
- Xian-Zhe Dong
- Department of Clinical Pharmacology and Pharmacy, Center of Pharmacy, Chinese PLA General Hospital; Department of Pharmacy, Xuanwu Hospital of Capital Medical University, Beijing, China
| | - Dong-Xiao Wang
- Department of Clinical Pharmacology and Pharmacy, Center of Pharmacy, Chinese PLA General Hospital, Beijing, China
| | - Tian-Yi Zhang
- Department of Clinical Pharmacology and Pharmacy, Center of Pharmacy, Chinese PLA General Hospital, Beijing, China
| | - Xu Liu
- Department of Clinical Pharmacology and Pharmacy, Center of Pharmacy, Chinese PLA General Hospital, Beijing, China
| | - Ping Liu
- Department of Clinical Pharmacology and Pharmacy, Center of Pharmacy, Chinese PLA General Hospital, Beijing, China
| | - Yuan Hu
- Department of Clinical Pharmacology and Pharmacy, Center of Pharmacy, Chinese PLA General Hospital, Beijing, China
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10
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Siddiqui SS, Matar R, Merheb M, Hodeify R, Vazhappilly CG, Marton J, Shamsuddin SA, Al Zouabi H. Siglecs in Brain Function and Neurological Disorders. Cells 2019; 8:E1125. [PMID: 31546700 PMCID: PMC6829431 DOI: 10.3390/cells8101125] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 09/19/2019] [Accepted: 09/20/2019] [Indexed: 12/14/2022] Open
Abstract
Siglecs (Sialic acid-binding immunoglobulin-type lectins) are a I-type lectin that typically binds sialic acid. Siglecs are predominantly expressed in immune cells and generate activating or inhibitory signals. They are also shown to be expressed on the surface of cells in the nervous system and have been shown to play central roles in neuroinflammation. There has been a plethora of reviews outlining the studies pertaining to Siglecs in immune cells. However, this review aims to compile the articles on the role of Siglecs in brain function and neurological disorders. In humans, the most abundant Siglecs are CD33 (Siglec-3), Siglec-4 (myelin-associated glycoprotein/MAG), and Siglec-11, Whereas in mice the most abundant are Siglec-1 (sialoadhesin), Siglec-2 (CD22), Siglec-E, Siglec-F, and Siglec-H. This review is divided into three parts. Firstly, we discuss the general biological aspects of Siglecs that are expressed in nervous tissue. Secondly, we discuss about the role of Siglecs in brain function and molecular mechanism for their function. Finally, we collate the available information on Siglecs and neurological disorders. It is intriguing to study this family of proteins in neurological disorders because they carry immunoinhibitory and immunoactivating motifs that can be vital in neuroinflammation.
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Affiliation(s)
- Shoib Sarwar Siddiqui
- Department of Biotechnology, American University of Ras Al Khaimah (AURAK), Ras Al Khaimah 10021, UAE.
| | - Rachel Matar
- Department of Biotechnology, American University of Ras Al Khaimah (AURAK), Ras Al Khaimah 10021, UAE.
| | - Maxime Merheb
- Department of Biotechnology, American University of Ras Al Khaimah (AURAK), Ras Al Khaimah 10021, UAE.
| | - Rawad Hodeify
- Department of Biotechnology, American University of Ras Al Khaimah (AURAK), Ras Al Khaimah 10021, UAE.
| | - Cijo George Vazhappilly
- Department of Biotechnology, American University of Ras Al Khaimah (AURAK), Ras Al Khaimah 10021, UAE.
| | - John Marton
- Department of Biotechnology, American University of Ras Al Khaimah (AURAK), Ras Al Khaimah 10021, UAE.
| | | | - Hussain Al Zouabi
- Department of Biotechnology, American University of Ras Al Khaimah (AURAK), Ras Al Khaimah 10021, UAE.
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11
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Mouihate A, Kalakh S. Ganaxolone enhances microglial clearance activity and promotes remyelination in focal demyelination in the corpus callosum of ovariectomized rats. CNS Neurosci Ther 2019; 26:240-250. [PMID: 31332963 PMCID: PMC6978248 DOI: 10.1111/cns.13195] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 06/24/2019] [Accepted: 06/27/2019] [Indexed: 12/01/2022] Open
Abstract
Aim Experimental studies have shown that the progesterone metabolite, allopregnanolone, is endowed with promyelinating effects. The mechanisms underlying these promyelinating effects are not well understood. Therefore, we explored the impact of allopregnanolone's synthetic analogue, ganaxolone, on remyelination and microglial activation following focal demyelination in the corpus callosum of ovariectomized rats. Methods Ovariectomized adult Sprague Dawley rats received a stereotaxic injection of 2 µL of 1% lysolecithin solution in the corpus callosum followed by daily injections of either ganaxolone (intraperitoneal injection [i.p.], 2.5 mg/kg) or vehicle. The demyelination lesion was assessed 3 and 7 days postdemyelination insult using Luxol fast blue staining and transmission electron microscopy. The expression levels of myelin proteins (MBP, MAG, MOG, CNPase) were explored using Western blot. The inflammatory response and clearance of damaged myelin were evaluated using immunofluorescent staining (Iba1, dMBP, GFAP) and multiplex enzyme‐linked immunosorbent assay (IL‐1β, TNF‐α, IL‐4, IL‐10, IL‐6). Results Systemic administration of ganaxolone promoted remyelination of lysolecithin‐induced demyelination, upregulated the expression of major myelin proteins, and enhanced microglial clearance of damaged myelin. Astrocytosis, as well as locally produced pro‐ and antiinflammatory cytokines, was not affected by ganaxolone treatment. Conclusion Ganaxolone promotes remyelination in response to focal demyelination of the corpus callosum of ovariectomized rats. This effect is, at least in part, mediated by enhancing microglial clearance of myelin debris, which creates a conducive environment for a successful remyelination process.
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Affiliation(s)
- Abdeslam Mouihate
- Department of Physiology, Faculty of Medicine, Kuwait University, Safat, Kuwait
| | - Samah Kalakh
- Department of Physiology, Faculty of Medicine, Kuwait University, Safat, Kuwait
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12
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Myllykoski M, Eichel MA, Jung RB, Kelm S, Werner HB, Kursula P. High-affinity heterotetramer formation between the large myelin-associated glycoprotein and the dynein light chain DYNLL1. J Neurochem 2018; 147:764-783. [PMID: 30261098 DOI: 10.1111/jnc.14598] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 08/21/2018] [Accepted: 09/16/2018] [Indexed: 12/13/2022]
Abstract
The close association of myelinated axons and their myelin sheaths involves numerous intercellular molecular interactions. For example, myelin-associated glycoprotein (MAG) mediates myelin-to-axon adhesion and signalling via molecules on the axonal surface. However, knowledge about intracellular binding partners of myelin proteins, including MAG, has remained limited. The two splice isoforms of MAG, S- and L-MAG, display distinct cytoplasmic domains and spatiotemporal expression profiles. We used yeast two-hybrid screening to identify interaction partners of L-MAG and found the dynein light chain DYNLL1 (also termed dynein light chain 8). DYNLL1 homodimers are known to facilitate dimerization of target proteins. L-MAG and DYNLL1 associate with high affinity, as confirmed with recombinant proteins in vitro. Structural analyses of the purified complex indicate that the DYNLL1-binding segment is localized close to the L-MAG C terminus, next to the Fyn kinase Tyr phosphorylation site. The crystal structure of the complex between DYNLL1 and its binding segment on L-MAG shows 2 : 2 binding in a parallel arrangement, indicating a heterotetrameric complex. The homology between L-MAG and previously characterized DYNLL1-ligands is limited, and some details of binding site interactions are unique for L-MAG. The structure of the complex between the entire L-MAG cytoplasmic domain and DYNLL1, as well as that of the extracellular domain of MAG, were modelled based on small-angle X-ray scattering data, allowing structural insights into L-MAG interactions on both membrane surfaces. Our data imply that DYNLL1 dimerizes L-MAG, but not S-MAG, through the formation of a specific 2 : 2 heterotetramer. This arrangement is likely to affect, in an isoform-specific manner, the functions of MAG in adhesion and myelin-to-axon signalling. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. Read the Editorial Highlight for this article on page 712.
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Affiliation(s)
- Matti Myllykoski
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Maria A Eichel
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Georg August University School of Science, University of Göttingen, Göttingen, Germany
| | - Ramona B Jung
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Sørge Kelm
- Centre for Biomolecular Interactions Bremen (CBIB), University of Bremen, Bremen, Germany
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Petri Kursula
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland.,Department of Biomedicine, University of Bergen, Bergen, Norway
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Ferrer I. Oligodendrogliopathy in neurodegenerative diseases with abnormal protein aggregates: The forgotten partner. Prog Neurobiol 2018; 169:24-54. [DOI: 10.1016/j.pneurobio.2018.07.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Revised: 07/24/2018] [Accepted: 07/27/2018] [Indexed: 12/31/2022]
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Mariano V, Domínguez-Iturza N, Neukomm LJ, Bagni C. Maintenance mechanisms of circuit-integrated axons. Curr Opin Neurobiol 2018; 53:162-173. [PMID: 30241058 DOI: 10.1016/j.conb.2018.08.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Accepted: 08/14/2018] [Indexed: 12/21/2022]
Abstract
Adult, circuit-integrated neurons must be maintained and supported for the life span of their host. The attenuation of either maintenance or plasticity leads to impaired circuit function and ultimately to neurodegenerative disorders. Over the last few years, significant discoveries of molecular mechanisms were made that mediate the formation and maintenance of axons. Here, we highlight intrinsic and extrinsic mechanisms that ensure the health and survival of axons. We also briefly discuss examples of mutations associated with impaired axonal maintenance identified in specific neurological conditions. A better understanding of these mechanisms will therefore help to define targets for therapeutic interventions.
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Affiliation(s)
- Vittoria Mariano
- Department of Fundamental Neurosciences, University of Lausanne, Switzerland; Department of Neurosciences KU Leuven, VIB Center for Brain and Disease Research, Leuven, Belgium
| | - Nuria Domínguez-Iturza
- Department of Fundamental Neurosciences, University of Lausanne, Switzerland; Department of Neurosciences KU Leuven, VIB Center for Brain and Disease Research, Leuven, Belgium
| | - Lukas J Neukomm
- Department of Fundamental Neurosciences, University of Lausanne, Switzerland.
| | - Claudia Bagni
- Department of Fundamental Neurosciences, University of Lausanne, Switzerland; Department of Biomedicine and Prevention, University of Rome Tor Vergata, Italy.
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15
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Correale J, Ysrraelit MC, Benarroch EE. Metabolic coupling of axons and glial cells. Neurology 2018; 90:737-744. [DOI: 10.1212/wnl.0000000000005339] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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16
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Lopez PH, Báez BB. Gangliosides in Axon Stability and Regeneration. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2018; 156:383-412. [DOI: 10.1016/bs.pmbts.2018.03.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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17
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Pan S, Chan JR. Regulation and dysregulation of axon infrastructure by myelinating glia. J Cell Biol 2017; 216:3903-3916. [PMID: 29114067 PMCID: PMC5716274 DOI: 10.1083/jcb.201702150] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 10/06/2017] [Accepted: 10/18/2017] [Indexed: 12/21/2022] Open
Abstract
Pan and Chan discuss the role of myelinating glia in axonal development and the impact of demyelination on axon degeneration. Axon loss and neurodegeneration constitute clinically debilitating sequelae in demyelinating diseases such as multiple sclerosis, but the underlying mechanisms of secondary degeneration are not well understood. Myelinating glia play a fundamental role in promoting the maturation of the axon cytoskeleton, regulating axon trafficking parameters, and imposing architectural rearrangements such as the nodes of Ranvier and their associated molecular domains. In the setting of demyelination, these changes may be reversed or persist as maladaptive features, leading to axon degeneration. In this review, we consider recent insights into axon–glial interactions during development and disease to propose that disruption of the cytoskeleton, nodal architecture, and other components of axon infrastructure is a potential mediator of pathophysiological damage after demyelination.
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Affiliation(s)
- Simon Pan
- Department of Neurology, University of California, San Francisco, San Francisco, CA .,Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA
| | - Jonah R Chan
- Department of Neurology, University of California, San Francisco, San Francisco, CA.,Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA
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18
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Granados-Durán P, López-Ávalos MD, Cifuentes M, Pérez-Martín M, Fernández-Arjona MDM, Hughes TR, Johnson K, Morgan BP, Fernández-Llebrez P, Grondona JM. Microbial Neuraminidase Induces a Moderate and Transient Myelin Vacuolation Independent of Complement System Activation. Front Neurol 2017; 8:78. [PMID: 28326060 PMCID: PMC5339270 DOI: 10.3389/fneur.2017.00078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 02/20/2017] [Indexed: 02/05/2023] Open
Abstract
AIMS Some central nervous system pathogens express neuraminidase (NA) on their surfaces. In the rat brain, a single intracerebroventricular (ICV) injection of NA induces myelin vacuolation in axonal tracts. Here, we explore the nature, the time course, and the role of the complement system in this damage. METHODS The spatiotemporal analysis of myelin vacuolation was performed by optical and electron microscopy. Myelin basic protein-positive area and oligodendrocyte transcription factor (Olig2)-positive cells were quantified in the damaged bundles. Neuronal death in the affected axonal tracts was assessed by Fluoro-Jade B and anti-caspase-3 staining. To evaluate the role of the complement, membrane attack complex (MAC) deposition on damaged bundles was analyzed using anti-C5b9. Rats ICV injected with the anaphylatoxin C5a were studied for myelin damage. In addition, NA-induced vacuolation was studied in rats with different degrees of complement inhibition: normal rats treated with anti-C5-blocking antibody and C6-deficient rats. RESULTS The stria medullaris, the optic chiasm, and the fimbria were the most consistently damaged axonal tracts. Vacuolation peaked 7 days after NA injection and reverted by day 15. Olig2+ cell number in the damaged tracts was unaltered, and neurodegeneration associated with myelin alterations was not detected. MAC was absent on damaged axonal tracts, as revealed by C5b9 immunostaining. Rats ICV injected with the anaphylatoxin C5a displayed no myelin injury. When the complement system was experimentally or constitutively inhibited, NA-induced myelin vacuolation was similar to that observed in normal rats. CONCLUSION Microbial NA induces a moderate and transient myelin vacuolation that is not caused either by neuroinflammation or complement system activation.
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Affiliation(s)
- Pablo Granados-Durán
- Laboratorio de Fisiología Animal, Facultad de Ciencias, Departamento de Biología Celular, Genética y Fisiología, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga , Málaga , Spain
| | - María Dolores López-Ávalos
- Laboratorio de Fisiología Animal, Facultad de Ciencias, Departamento de Biología Celular, Genética y Fisiología, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga , Málaga , Spain
| | - Manuel Cifuentes
- Laboratorio de Fisiología Animal, Facultad de Ciencias, Departamento de Biología Celular, Genética y Fisiología, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga, Málaga, Spain; Centro de Investigaciones Biomédicas en Red de Bioingeniería, Biomateriales y Nanomedicina, CIBER BBN, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
| | - Margarita Pérez-Martín
- Laboratorio de Fisiología Animal, Facultad de Ciencias, Departamento de Biología Celular, Genética y Fisiología, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga , Málaga , Spain
| | - María Del Mar Fernández-Arjona
- Laboratorio de Fisiología Animal, Facultad de Ciencias, Departamento de Biología Celular, Genética y Fisiología, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga , Málaga , Spain
| | - Timothy R Hughes
- Division of Infection and Immunity, School of Medicine, Cardiff University , Cardiff , UK
| | | | - B Paul Morgan
- Division of Infection and Immunity, School of Medicine, Cardiff University , Cardiff , UK
| | - Pedro Fernández-Llebrez
- Laboratorio de Fisiología Animal, Facultad de Ciencias, Departamento de Biología Celular, Genética y Fisiología, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga , Málaga , Spain
| | - Jesús M Grondona
- Laboratorio de Fisiología Animal, Facultad de Ciencias, Departamento de Biología Celular, Genética y Fisiología, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga , Málaga , Spain
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19
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Abstract
Antibodies reacting with carbohydrate epitopes on neural glycoconjugates are present in several forms of neuropathy. These include monoclonal antibodies to the myelin-associated glycoprotein (MAG) and to gan gliosides in patients with neuropathy in association with IgM gammopathy, as well as polyclonal antibodies to gangliosides in inflammatory polyneuropathies, such as Guillain-Barré syndrome and multifocal motor neuropathy. There are several correlations between antibody specificity and clinical symptoms, including anti-MAG antibodies with demyelinating sensory or sensorimotor neuropathy, anti-GM1 ganglioside anti bodies with motor nerve disorders, anti-GQ1b ganglioside antibodies with Miller-Fisher syndrome, and antibodies to gangliosides containing disialosyl moieties with sensory ataxic neuropathy. This review will emphasize recent developments concerning the origins of the anti-glycoconjugate antibodies in patients, pathogenic mechanisms by which the antibodies may cause the neuropathies, and the implications of these findings for therapy. NEUROSCIENTIST 3:195-204, 1997
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Affiliation(s)
- Richard H. Quarles
- Laboratory of Molecular and Cellular Neurobiology National
Institute of Neurological Disorders and Stroke National Institutes of Health
Bethesda, Maryland
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20
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Vallat JM, Magy L, Ciron J, Corcia P, Le Masson G, Mathis S. Therapeutic options and management of polyneuropathy associated with anti-MAG antibodies. Expert Rev Neurother 2016; 16:1111-9. [DOI: 10.1080/14737175.2016.1198257] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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21
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Bombeiro AL, Santini JC, Thomé R, Ferreira ERL, Nunes SLO, Moreira BM, Bonet IJM, Sartori CR, Verinaud L, Oliveira ALR. Enhanced Immune Response in Immunodeficient Mice Improves Peripheral Nerve Regeneration Following Axotomy. Front Cell Neurosci 2016; 10:151. [PMID: 27378849 PMCID: PMC4905955 DOI: 10.3389/fncel.2016.00151] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 05/27/2016] [Indexed: 12/21/2022] Open
Abstract
Injuries to peripheral nerves cause loss of motor and sensory function, greatly affecting life quality. Successful repair of the lesioned nerve requires efficient cell debris removal, followed by axon regeneration and reinnervation of target organs. Such process is orchestrated by several cellular and molecular events in which glial and immune cells actively participate. It is known that tissue clearance is largely improved by macrophages, which activation is potentiated by cells and molecules of the acquired immune system, such as T helper lymphocytes and antibodies, respectively. In the present work, we evaluated the contribution of lymphocytes in the regenerative process of crushed sciatic nerves of immunocompetent (wild-type, WT) and T and B-deficient (RAG-KO) mice. In Knockout animals, we found increased amount of macrophages under basal conditions and during the initial phase of the regenerative process, that was evaluated at 2, 4, and 8 weeks after lesion (wal). That parallels with faster axonal regeneration evidenced by the quantification of neurofilament and a growth associated protein immunolabeling. The motor function, evaluated by the sciatic function index, was fully recovered in both mouse strains within 4 wal, either in a progressive fashion, as observed for RAG-KO mice, or presenting a subtle regression, as seen in WT mice between 2 and 3 wal. Interestingly, boosting the immune response by early adoptive transference of activated WT lymphocytes at 3 days after lesion improved motor recovery in WT and RAG-KO mice, which was not ameliorated when cells were transferred at 2 wal. When monitoring lymphocytes by in vivo imaging, in both mouse strains, cells migrated to the lesion site shortly after transference, remaining in the injured limb up to its complete motor recovery. Moreover, a first peak of hyperalgesia, determined by von-Frey test, was coincident with increased lymphocyte infiltration in the damaged paw. Overall, the present results suggest that a wave of immune cell infiltration takes place during subacute phase of axonal regeneration, resulting in transient set back of motor recovery following peripheral axonal injury. Moreover, modulation of the immune response can be an efficient approach to speed up nerve regeneration.
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Affiliation(s)
- André L Bombeiro
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas Campinas, Brazil
| | - Júlio C Santini
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas Campinas, Brazil
| | - Rodolfo Thomé
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas Campinas, Brazil
| | - Elisângela R L Ferreira
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas Campinas, Brazil
| | - Sérgio L O Nunes
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas Campinas, Brazil
| | - Bárbara M Moreira
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas Campinas, Brazil
| | - Ivan J M Bonet
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas Campinas, Brazil
| | - Cesar R Sartori
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas Campinas, Brazil
| | - Liana Verinaud
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas Campinas, Brazil
| | - Alexandre L R Oliveira
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas Campinas, Brazil
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22
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Al-Bashir N, Mellado W, Filbin MT. Sialic Acid Is Required for Neuronal Inhibition by Soluble MAG but not for Membrane Bound MAG. Front Mol Neurosci 2016; 9:21. [PMID: 27065798 PMCID: PMC4817280 DOI: 10.3389/fnmol.2016.00021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 03/14/2016] [Indexed: 11/13/2022] Open
Abstract
Myelin-Associated Glycoprotein (MAG), a major inhibitor of axonal growth, is a member of the immunoglobulin (Ig) super-family. Importantly, MAG (also known as Siglec-4) is a member of the Siglec family of proteins (sialic acid-binding, immunoglobulin-like lectins), MAG binds to complex gangliosides, specifically GD1a and/or GT1b. Therefore, it has been proposed as neuronal receptors for MAG inhibitory effect of axonal growth. Previously, we showed that MAG binds sialic acid through domain 1 at Arg118 and is able to inhibit axonal growth through domain 5. We developed a neurite outgrowth (NOG) assay, in which both wild type MAG and mutated MAG (MAG Arg118) are expressed on cells. In addition we also developed a soluble form NOG in which we utilized soluble MAG-Fc and mutated MAG (Arg118-Fc). Only MAG-Fc is able to inhibit NOG, but not mutated MAG (Arg118)-Fc that has been mutated at its sialic acid binding site. However, both forms of membrane bound MAG- and MAG (Arg118)- expressing cells still inhibit NOG. Here, we review various results from different groups regarding MAG’s inhibition of axonal growth. Also, we propose a model in which the sialic acid binding is not necessary for the inhibition induced by the membrane form of MAG, but it is necessary for the soluble form of MAG. This finding highlights the importance of understanding the different mechanisms by which MAG inhibits NOG in both the soluble fragmented form and the membrane-bound form in myelin debris following CNS damage.
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Affiliation(s)
- Najat Al-Bashir
- Biology Department, Hunter College, City University of New York New York, NY, USA
| | - Wilfredo Mellado
- Biology Department, Hunter College, City University of New YorkNew York, NY, USA; Burke-Cornell Medical Research Institute White Plains, NY, USA
| | - Marie T Filbin
- Biology Department, Hunter College, City University of New York New York, NY, USA
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23
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Wang LC, Almazan G. Cdon, a cell surface protein, mediates oligodendrocyte differentiation and myelination. Glia 2016; 64:1021-33. [PMID: 26988125 DOI: 10.1002/glia.22980] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 02/11/2016] [Indexed: 12/13/2022]
Abstract
During central nervous system development, oligodendrocyte progenitors (OLPs) establish multiple branched processes and axonal contacts to initiate myelination. A complete understanding of the molecular signals implicated in cell surface interaction to initiate myelination/remyelination is currently lacking. The objective of our study was to assess whether Cdon, a cell surface protein that was shown to participate in muscle and neuron cell development, is involved in oligodendrocyte (OLG) differentiation and myelination. Here, we demonstrate that endogenous Cdon protein is expressed in OLPs, increasing in the early differentiation stages and decreasing in mature OLGs. Immunocytochemistry of endogenous Cdon showed localization on both OLG cell membranes and cellular processes exhibiting puncta- or varicosity-like structures. Cdon knockdown with siRNA decreased protein levels by 62% as well as two myelin-specific proteins, MBP and MAG. Conversely, overexpression of full-length rat Cdon increased myelin proteins in OLGs. The complexity of OLGs branching and contact point numbers with axons were also increased in Cdon overexpressing cells growing alone or in coculture with dorsal root ganglion neurons (DRGNs). Furthermore, myelination of DRGNs was decreased when OLPs were transfected with Cdon siRNA. Altogether, our results suggest that Cdon participates in OLG differentiation and myelination, most likely in the initial stages of development.
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Affiliation(s)
- Li-Chun Wang
- Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada, H3G 1Y6
| | - Guillermina Almazan
- Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada, H3G 1Y6
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24
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Kraus A, Michalak M. Endoplasmic reticulum quality control and dysmyelination. Biomol Concepts 2015; 2:261-74. [PMID: 25962034 DOI: 10.1515/bmc.2011.028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Dysmyelination contributes to several human diseases including multiple sclerosis, Charcot-Marie-Tooth, leukodystrophies, and schizophrenia and can result in serious neurological disability. Properly formed, compacted myelin sheaths are required for appropriate nerve conduction velocities and the health and survival of neurons. Many different molecular mechanisms contribute to dysmyelination and many of these mechanisms originate at the level of the endoplasmic reticulum. The endoplasmic reticulum is a critical organelle for myelin biosynthesis and maintenance as the site of myelin protein folding quality control, Ca2+ homeostasis, cholesterol biosynthesis, and modulation of cellular stress. This review paper highlights the role of the endoplasmic reticulum and its resident molecules as an upstream and dynamic contributor to myelin and myelin pathologies.
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25
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Patzig J, Kusch K, Fledrich R, Eichel MA, Lüders KA, Möbius W, Sereda MW, Nave KA, Martini R, Werner HB. Proteolipid protein modulates preservation of peripheral axons and premature death when myelin protein zero is lacking. Glia 2015; 64:155-74. [PMID: 26393339 DOI: 10.1002/glia.22922] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 09/04/2015] [Indexed: 12/23/2022]
Abstract
Protein zero (P0) is the major structural component of peripheral myelin. Lack of this adhesion protein from Schwann cells causes a severe dysmyelinating neuropathy with secondary axonal degeneration in humans with the neuropathy Dejerine-Sottas syndrome (DSS) and in the corresponding mouse model (P0(null)-mice). In the mammalian CNS, the tetraspan-membrane protein PLP is the major structural myelin constituent and required for the long-term preservation of myelinated axons, which fails in hereditary spastic paraplegia (SPG type-2) and the relevant mouse model (Plp(null)-mice). The Plp-gene is also expressed in Schwann cells but PLP is of very low abundance in normal peripheral myelin; its function has thus remained enigmatic. Here we show that the abundance of PLP but not of other tetraspan myelin proteins is strongly increased in compact peripheral myelin of P0(null)-mice. To determine the functional relevance of PLP expression in the absence of P0, we generated P0(null)*Plp(null)-double-mutant mice. Compared with either single-mutant, P0(null)*Plp(null)-mice display impaired nerve conduction, reduced motor functions, and premature death. At the morphological level, axonal segments were frequently non-myelinated but in a one-to-one relationship with a hypertrophic Schwann cell. Importantly, axonal numbers were reduced in the vital phrenic nerve of P0(null)*Plp(null)-mice. In the absence of P0, thus, PLP also contributes to myelination by Schwann cells and to the preservation of peripheral axons. These data provide a link between the Schwann cell-dependent support of peripheral axons and the oligodendrocyte-dependent support of central axons.
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Affiliation(s)
- Julia Patzig
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Kathrin Kusch
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Robert Fledrich
- 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
| | - Katja A Lüders
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Wiebke Möbius
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
| | - Michael W Sereda
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Department of Clinical Neurophysiology, University Medical Center, Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Rudolf Martini
- Department of Neurology, Developmental Neurobiology, University Hospital, Würzburg, Germany
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
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26
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McKerracher L, Rosen KM. MAG, myelin and overcoming growth inhibition in the CNS. Front Mol Neurosci 2015; 8:51. [PMID: 26441514 PMCID: PMC4561339 DOI: 10.3389/fnmol.2015.00051] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 08/25/2015] [Indexed: 01/22/2023] Open
Abstract
While neurons in the central nervous system (CNS) have the capacity to regenerate their axons after injury, they fail to do so, in part because regeneration is limited by growth inhibitory proteins present in CNS myelin. Myelin-associated glycoprotein (MAG) was the first myelin-derived growth inhibitory protein identified, and its inhibitory activity was initially elucidated in 1994 independently by the Filbin lab and the McKerracher lab using cell-based and biochemical techniques, respectively. Since that time we have gained a wealth of knowledge concerning the numerous growth inhibitory proteins that are present in myelin, and we also have dissected many of the neuronal signaling pathways that act as stop signs for axon regeneration. Here we give an overview of the early research efforts that led to the identification of myelin-derived growth inhibitory proteins, and the importance of this family of proteins for understanding neurotrauma and CNS diseases. We further provide an update on how this knowledge has been translated towards current clinical studies in regenerative medicine.
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Affiliation(s)
- Lisa McKerracher
- BioAxone BioSciences Inc.Cambridge, MA, USA
- Department of Neurology and Neurosurgery, McGill UniversityMontreal, QC, Canada
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27
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Peluffo H, Solari-Saquieres P, Negro-Demontel ML, Francos-Quijorna I, Navarro X, López-Vales R, Sayós J, Lago N. CD300f immunoreceptor contributes to peripheral nerve regeneration by the modulation of macrophage inflammatory phenotype. J Neuroinflammation 2015; 12:145. [PMID: 26259611 PMCID: PMC4531482 DOI: 10.1186/s12974-015-0364-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 07/21/2015] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND It has recently become evident that activating/inhibitory cell surface immune receptors play a critical role in regulating immune and inflammatory processes in the central nervous system (CNS). The immunoreceptor CD300f expressed on monocytes, neutrophils, and mast cells modulates inflammation, phagocytosis, and outcome in models of autoimmune demyelination, allergy, and systemic lupus erythematosus. On the other hand, a finely regulated inflammatory response is essential to induce regeneration after injury to peripheral nerves since hematogenous macrophages, together with resident macrophages and de-differentiated Schwann cells, phagocyte distal axonal and myelin debris in a well-orchestrated inflammatory response. The possible roles and expression of CD300f and its ligands have not been reported under these conditions. METHODS By using quantitative PCR (QPCR) and CD300f-IgG2a fusion protein, we show the expression of CD300f and its ligands in the normal and crush injured sciatic nerve. The putative role of CD300f in peripheral nerve regeneration was analyzed by blocking receptor-ligand interaction with the same CD300f-IgG2a soluble receptor fusion protein in sciatic nerves of Thy1-YFP-H mice injected at the time of injury. Macrophage M1/M2 polarization phenotype was also analyzed by CD206 and iNOS expression. RESULTS We found an upregulation of CD300f mRNA and protein expression after injury. Moreover, the ligands are present in restricted membrane patches of Schwann cells, which remain stable after the lesion. The lesioned sciatic nerves of Thy1-YFP-H mice injected with a single dose of CD300f-IgG2a show long lasting effects on nerve regeneration characterized by a lower number of YFP-positive fibres growing into the tibial nerve after 10 days post lesion (dpl) and a delayed functional recovery when compared to PBS- or IgG2a-administered control groups. Animals treated with CD300f-IgG2a show at 10 dpl higher numbers of macrophages and CD206-positive cells and lower levels of iNOS expression than both control groups. At later time points (28 dpl), increased numbers of macrophages and iNOS expression occur. CONCLUSIONS Taken together, these results show that the pair CD300f ligand is implicated in Wallerian degeneration and nerve regeneration by modulating both the influx and phenotype of macrophages.
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Affiliation(s)
- Hugo Peluffo
- Neuroinflammation and Gene Therapy Laboratory, Institut Pasteur Montevideo, Mataojo 2020, CP 11400, Montevideo, Uruguay.
- Department of Histology and Embryology, Faculty of Medicine, UDELAR, Montevideo, Uruguay.
| | - Patricia Solari-Saquieres
- Neuroinflammation and Gene Therapy Laboratory, Institut Pasteur Montevideo, Mataojo 2020, CP 11400, Montevideo, Uruguay.
| | - Maria Luciana Negro-Demontel
- Neuroinflammation and Gene Therapy Laboratory, Institut Pasteur Montevideo, Mataojo 2020, CP 11400, Montevideo, Uruguay.
| | - Isaac Francos-Quijorna
- Institute of Neurosciences and Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain.
| | - Xavier Navarro
- Institute of Neurosciences and Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain.
| | - Ruben López-Vales
- Institute of Neurosciences and Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain.
| | - Joan Sayós
- Immunobiology Group, CIBBIM-Nanomedicine Program, Hospital Universitari Vall d'Hebron, Institut de Recerca (VHIR), Universitat Autonoma de Barcelona, Barcelona, Spain.
| | - Natalia Lago
- Neuroinflammation and Gene Therapy Laboratory, Institut Pasteur Montevideo, Mataojo 2020, CP 11400, Montevideo, Uruguay.
- Neurodegeneration Laboratory, Institut Pasteur Montevideo, Montevideo, Uruguay.
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28
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Lossos A, Elazar N, Lerer I, Schueler-Furman O, Fellig Y, Glick B, Zimmerman BE, Azulay H, Dotan S, Goldberg S, Gomori JM, Ponger P, Newman JP, Marreed H, Steck AJ, Schaeren-Wiemers N, Mor N, Harel M, Geiger T, Eshed-Eisenbach Y, Meiner V, Peles E. Myelin-associated glycoprotein gene mutation causes Pelizaeus-Merzbacher disease-like disorder. Brain 2015; 138:2521-36. [PMID: 26179919 DOI: 10.1093/brain/awv204] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 05/27/2015] [Indexed: 01/07/2023] Open
Abstract
Pelizaeus-Merzbacher disease is an X-linked hypomyelinating leukodystrophy caused by mutations or rearrangements in PLP1. It presents in infancy with nystagmus, jerky head movements, hypotonia and developmental delay evolving into spastic tetraplegia with optic atrophy and variable movement disorders. A clinically similar phenotype caused by recessive mutations in GJC2 is known as Pelizaeus-Merzbacher-like disease. Both genes encode proteins associated with myelin. We describe three siblings of a consanguineous family manifesting the typical infantile-onset Pelizaeus-Merzbacher disease-like phenotype slowly evolving into a form of complicated hereditary spastic paraplegia with mental retardation, dysarthria, optic atrophy and peripheral neuropathy in adulthood. Magnetic resonance imaging and spectroscopy were consistent with a demyelinating leukodystrophy. Using genetic linkage and exome sequencing, we identified a homozygous missense c.399C>G; p.S133R mutation in MAG. This gene, previously associated with hereditary spastic paraplegia, encodes myelin-associated glycoprotein, which is involved in myelin maintenance and glia-axon interaction. This mutation is predicted to destabilize the protein and affect its tertiary structure. Examination of the sural nerve biopsy sample obtained in childhood in the oldest sibling revealed complete absence of myelin-associated glycoprotein accompanied by ill-formed onion-bulb structures and a relatively thin myelin sheath of the affected axons. Immunofluorescence, cell surface labelling, biochemical analysis and mass spectrometry-based proteomics studies in a variety of cell types demonstrated a devastating effect of the mutation on post-translational processing, steady state expression and subcellular localization of myelin-associated glycoprotein. In contrast to the wild-type protein, the p.S133R mutant was retained in the endoplasmic reticulum and was subjected to endoplasmic reticulum-associated protein degradation by the proteasome. Our findings identify involvement of myelin-associated glycoprotein in this family with a disorder affecting the central and peripheral nervous system, and suggest that loss of the protein function is responsible for the unique clinical phenotype.
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Affiliation(s)
- Alexander Lossos
- 1 Department of Neurology and Agnes Ginges Centre for Human Neurogenetics, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Nimrod Elazar
- 2 Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Israela Lerer
- 3 Department of Genetics and Metabolic Diseases, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Ora Schueler-Furman
- 4 Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, Faculty of Medicine, Hebrew University, Jerusalem, Israel
| | - Yakov Fellig
- 5 Department of Pathology, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Benjamin Glick
- 6 Paediatric Neuromuscular Service, Alyn Paediatric Rehabilitation Centre, Jerusalem, Israel
| | - Bat-El Zimmerman
- 3 Department of Genetics and Metabolic Diseases, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Haim Azulay
- 5 Department of Pathology, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Shlomo Dotan
- 7 Department of Ophthalmology, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Sharon Goldberg
- 7 Department of Ophthalmology, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - John M Gomori
- 8 Department of Radiology, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Penina Ponger
- 1 Department of Neurology and Agnes Ginges Centre for Human Neurogenetics, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - J P Newman
- 1 Department of Neurology and Agnes Ginges Centre for Human Neurogenetics, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Hodaifah Marreed
- 3 Department of Genetics and Metabolic Diseases, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Andreas J Steck
- 9 Department of Biomedicine, University Hospital Basel, University of Basel, Switzerland
| | | | - Nofar Mor
- 2 Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Michal Harel
- 10 Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Tamar Geiger
- 10 Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Yael Eshed-Eisenbach
- 2 Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Vardiella Meiner
- 3 Department of Genetics and Metabolic Diseases, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Elior Peles
- 2 Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
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Baldwin KT, Giger RJ. Insights into the physiological role of CNS regeneration inhibitors. Front Mol Neurosci 2015; 8:23. [PMID: 26113809 PMCID: PMC4462676 DOI: 10.3389/fnmol.2015.00023] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 05/26/2015] [Indexed: 12/14/2022] Open
Abstract
The growth inhibitory nature of injured adult mammalian central nervous system (CNS) tissue constitutes a major barrier to robust axonal outgrowth and functional recovery following trauma or disease. Prototypic CNS regeneration inhibitors are broadly expressed in the healthy and injured brain and spinal cord and include myelin-associated glycoprotein (MAG), the reticulon family member NogoA, oligodendrocyte myelin glycoprotein (OMgp), and chondroitin sulfate proteoglycans (CSPGs). These structurally diverse molecules strongly inhibit neurite outgrowth in vitro, and have been most extensively studied in the context of nervous system injury in vivo. The physiological role of CNS regeneration inhibitors in the naïve, or uninjured, CNS remains less well understood, but has received growing attention in recent years and is the focus of this review. CNS regeneration inhibitors regulate myelin development and axon stability, consolidate neuronal structure shaped by experience, and limit activity-dependent modification of synaptic strength. Altered function of CNS regeneration inhibitors is associated with neuropsychiatric disorders, suggesting crucial roles in brain development and health.
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Affiliation(s)
- Katherine T Baldwin
- Department of Cell and Developmental Biology, University of Michigan School of Medicine Ann Arbor, MI, USA ; Cellular and Molecular Biology Graduate Program, University of Michigan School of Medicine Ann Arbor, MI, USA
| | - Roman J Giger
- Department of Cell and Developmental Biology, University of Michigan School of Medicine Ann Arbor, MI, USA ; Department of Neurology, University of Michigan School of Medicine Ann Arbor, MI, USA
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Yoo SW, Motari MG, Susuki K, Prendergast J, Mountney A, Hurtado A, Schnaar RL. Sialylation regulates brain structure and function. FASEB J 2015; 29:3040-53. [PMID: 25846372 DOI: 10.1096/fj.15-270983] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 03/11/2015] [Indexed: 11/11/2022]
Abstract
Every cell expresses a molecularly diverse surface glycan coat (glycocalyx) comprising its interface with its cellular environment. In vertebrates, the terminal sugars of the glycocalyx are often sialic acids, 9-carbon backbone anionic sugars implicated in intermolecular and intercellular interactions. The vertebrate brain is particularly enriched in sialic acid-containing glycolipids termed gangliosides. Human congenital disorders of ganglioside biosynthesis result in paraplegia, epilepsy, and intellectual disability. To better understand sialoglycan functions in the nervous system, we studied brain anatomy, histology, biochemistry, and behavior in mice with engineered mutations in St3gal2 and St3gal3, sialyltransferase genes responsible for terminal sialylation of gangliosides and some glycoproteins. St3gal2/3 double-null mice displayed dysmyelination marked by a 40% reduction in major myelin proteins, 30% fewer myelinated axons, a 33% decrease in myelin thickness, and molecular disruptions at nodes of Ranvier. In part, these changes may be due to dysregulation of ganglioside-mediated oligodendroglial precursor cell proliferation. Neuronal markers were also reduced up to 40%, and hippocampal neurons had smaller dendritic arbors. Young adult St3gal2/3 double-null mice displayed impaired motor coordination, disturbed gait, and profound cognitive disability. Comparisons among sialyltransferase mutant mice provide insights into the functional roles of brain gangliosides and sialoglycoproteins consistent with related human congenital disorders.
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Affiliation(s)
- Seung-Wan Yoo
- *Department of Pharmacology and Molecular Sciences, Department of Neurology, and Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA; Brain Trauma Neuroprotection and Neurorestoration Branch, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA; and International Center for Spinal Cord Injury, Hugo W. Moser Research Institute, Kennedy Krieger, Baltimore, Maryland, USA
| | - Mary G Motari
- *Department of Pharmacology and Molecular Sciences, Department of Neurology, and Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA; Brain Trauma Neuroprotection and Neurorestoration Branch, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA; and International Center for Spinal Cord Injury, Hugo W. Moser Research Institute, Kennedy Krieger, Baltimore, Maryland, USA
| | - Keiichiro Susuki
- *Department of Pharmacology and Molecular Sciences, Department of Neurology, and Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA; Brain Trauma Neuroprotection and Neurorestoration Branch, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA; and International Center for Spinal Cord Injury, Hugo W. Moser Research Institute, Kennedy Krieger, Baltimore, Maryland, USA
| | - Jillian Prendergast
- *Department of Pharmacology and Molecular Sciences, Department of Neurology, and Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA; Brain Trauma Neuroprotection and Neurorestoration Branch, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA; and International Center for Spinal Cord Injury, Hugo W. Moser Research Institute, Kennedy Krieger, Baltimore, Maryland, USA
| | - Andrea Mountney
- *Department of Pharmacology and Molecular Sciences, Department of Neurology, and Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA; Brain Trauma Neuroprotection and Neurorestoration Branch, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA; and International Center for Spinal Cord Injury, Hugo W. Moser Research Institute, Kennedy Krieger, Baltimore, Maryland, USA
| | - Andres Hurtado
- *Department of Pharmacology and Molecular Sciences, Department of Neurology, and Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA; Brain Trauma Neuroprotection and Neurorestoration Branch, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA; and International Center for Spinal Cord Injury, Hugo W. Moser Research Institute, Kennedy Krieger, Baltimore, Maryland, USA
| | - Ronald L Schnaar
- *Department of Pharmacology and Molecular Sciences, Department of Neurology, and Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Neuroscience, Baylor College of Medicine, Houston, Texas, USA; Brain Trauma Neuroprotection and Neurorestoration Branch, Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA; and International Center for Spinal Cord Injury, Hugo W. Moser Research Institute, Kennedy Krieger, Baltimore, Maryland, USA
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31
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Abstract
The sialic acids N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) differ by a single oxygen atom and are widely found at the terminal position of glycans on vertebrate cell surfaces. In animals capable of synthesizing Neu5Gc, most tissues and cell types express both sialic acids, in proportions that vary between species. However, it has long been noted that Neu5Gc is consistently expressed at trace to absent levels in the brains of all vertebrates studied to date. Although several reports have claimed to find low levels of Neu5Gc-containing glycans in neural tissue, no study definitively excludes the possibility of contamination with glycans from non-neural cell types. This distribution of a molecule - prominently but variably expressed in extraneural tissues but very low or absent in the brain - is, to our knowledge, unique. The evolutionarily conserved brain-specific suppression of Neu5Gc may indicate that its presence is toxic to this organ; however, no studies to date have directly addressed this very interesting question. Here we provide a historical background to this issue and discuss potential mechanisms causing the suppression of Neu5Gc expression in brain tissue, as well as mechanisms by which Neu5Gc may exert the presumed toxicity. Finally, we discuss future approaches towards understanding the mechanisms and implications of this unusual finding.
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Affiliation(s)
- Leela R L Davies
- Glycobiology Research and Training Center, Center for Academic Research and Training in Anthropogeny, Biomedical Sciences Graduate Program, Departments of Medicine and Cellular and Molecular Medicine, University of California at San Diego, 9500 Gilman Dr., MC 0687, La Jolla, CA, 92093-0687, USA
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Progressive disorganization of paranodal junctions and compact myelin due to loss of DCC expression by oligodendrocytes. J Neurosci 2014; 34:9768-78. [PMID: 25031414 DOI: 10.1523/jneurosci.0448-14.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Paranodal axoglial junctions are critical for maintaining the segregation of axonal domains along myelinated axons; however, the proteins required to organize and maintain this structure are not fully understood. Netrin-1 and its receptor Deleted in Colorectal Cancer (DCC) are proteins enriched at paranodes that are expressed by neurons and oligodendrocytes. To identify the specific function of DCC expressed by oligodendrocytes in vivo, we selectively eliminated DCC from mature myelinating oligodendrocytes using an inducible cre regulated by the proteolipid protein promoter. We demonstrate that DCC deletion results in progressive disruption of the organization of axonal domains, myelin ultrastructure, and myelin protein composition. Conditional DCC knock-out mice develop balance and coordination deficits and exhibit decreased conduction velocity. We conclude that DCC expression by oligodendrocytes is required for the maintenance and stability of myelin in vivo, which is essential for proper signal conduction in the CNS.
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Schnaar RL, Gerardy-Schahn R, Hildebrandt H. Sialic acids in the brain: gangliosides and polysialic acid in nervous system development, stability, disease, and regeneration. Physiol Rev 2014; 94:461-518. [PMID: 24692354 DOI: 10.1152/physrev.00033.2013] [Citation(s) in RCA: 497] [Impact Index Per Article: 49.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Every cell in nature carries a rich surface coat of glycans, its glycocalyx, which constitutes the cell's interface with its environment. In eukaryotes, the glycocalyx is composed of glycolipids, glycoproteins, and proteoglycans, the compositions of which vary among different tissues and cell types. Many of the linear and branched glycans on cell surface glycoproteins and glycolipids of vertebrates are terminated with sialic acids, nine-carbon sugars with a carboxylic acid, a glycerol side-chain, and an N-acyl group that, along with their display at the outmost end of cell surface glycans, provide for varied molecular interactions. Among their functions, sialic acids regulate cell-cell interactions, modulate the activities of their glycoprotein and glycolipid scaffolds as well as other cell surface molecules, and are receptors for pathogens and toxins. In the brain, two families of sialoglycans are of particular interest: gangliosides and polysialic acid. Gangliosides, sialylated glycosphingolipids, are the most abundant sialoglycans of nerve cells. Mouse genetic studies and human disorders of ganglioside metabolism implicate gangliosides in axon-myelin interactions, axon stability, axon regeneration, and the modulation of nerve cell excitability. Polysialic acid is a unique homopolymer that reaches >90 sialic acid residues attached to select glycoproteins, especially the neural cell adhesion molecule in the brain. Molecular, cellular, and genetic studies implicate polysialic acid in the control of cell-cell and cell-matrix interactions, intermolecular interactions at cell surfaces, and interactions with other molecules in the cellular environment. Polysialic acid is essential for appropriate brain development, and polymorphisms in the human genes responsible for polysialic acid biosynthesis are associated with psychiatric disorders including schizophrenia, autism, and bipolar disorder. Polysialic acid also appears to play a role in adult brain plasticity, including regeneration. Together, vertebrate brain sialoglycans are key regulatory components that contribute to proper development, maintenance, and health of the nervous system.
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Puttini S, Panaite PA, Mermod N, Renaud S, Steck AJ, Kuntzer T. Gene expression changes in chronic inflammatory demyelinating polyneuropathy skin biopsies. J Neuroimmunol 2014; 270:61-6. [PMID: 24657030 DOI: 10.1016/j.jneuroim.2014.03.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 02/15/2014] [Accepted: 03/02/2014] [Indexed: 11/25/2022]
Abstract
Chronic-inflammatory demyelinating polyneuropathy (CIDP) is an immune-mediated disease with no known biomarkers for diagnosing the disease or assessing its prognosis. We performed transcriptional profiling microarray analysis on skin punch biopsies from 20 CIDP patients and 17 healthy controls to identify disease-associated gene expression changes. We demonstrate changes in expression of genes involved in immune and chemokine regulation, growth and repair. We also found a combination of two upregulated genes that can be proposed as a novel biomarker of the disorder.
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Affiliation(s)
- Stefania Puttini
- Department of Clinical Neurosciences, Nerve-Muscle Unit, Lausanne University Hospital (CHUV), rue du Bugnon 46, CH-1011 Lausanne, Switzerland; Institute of Biotechnology, University of Lausanne (UNIL), chemin des Alambiques, CH-1015 Lausanne, Switzerland
| | - Petrica-Adrian Panaite
- Department of Clinical Neurosciences, Nerve-Muscle Unit, Lausanne University Hospital (CHUV), rue du Bugnon 46, CH-1011 Lausanne, Switzerland
| | - Nicolas Mermod
- Institute of Biotechnology, University of Lausanne (UNIL), chemin des Alambiques, CH-1015 Lausanne, Switzerland
| | - Susanne Renaud
- Department of Clinical Neurosciences, Nerve-Muscle Unit, Lausanne University Hospital (CHUV), rue du Bugnon 46, CH-1011 Lausanne, Switzerland; Neurology Division, Hôpital Neuchâtelois, Maladière 45, CH-2000 Neuchâtel, Switzerland
| | - Andreas J Steck
- Department of Clinical Neurosciences, Nerve-Muscle Unit, Lausanne University Hospital (CHUV), rue du Bugnon 46, CH-1011 Lausanne, Switzerland; Department of Neurology, Basel University Hospital, Spitalstrasse 21, 4031 Basel, Switzerland
| | - Thierry Kuntzer
- Department of Clinical Neurosciences, Nerve-Muscle Unit, Lausanne University Hospital (CHUV), rue du Bugnon 46, CH-1011 Lausanne, Switzerland.
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Franssen H, Straver DCG. Pathophysiology of immune-mediated demyelinating neuropathies--Part II: Neurology. Muscle Nerve 2013; 49:4-20. [PMID: 24037667 DOI: 10.1002/mus.24068] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2013] [Indexed: 12/13/2022]
Abstract
In the second part of this review we deal with the clinical aspects of immune-mediated demyelinating neuropathies. We describe the relationship between pathophysiology and symptoms and discuss the pathophysiology of specific disease entities, including Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy, anti-myelin-associated glycoprotein neuropathy, and POEMS syndrome.
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Affiliation(s)
- Hessel Franssen
- Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Heidelberglaan 100, 3584, CX Utrecht, The Netherlands
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36
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Tu TW, Kim JH, Yin FQ, Jakeman LB, Song SK. The impact of myelination on axon sparing and locomotor function recovery in spinal cord injury assessed using diffusion tensor imaging. NMR IN BIOMEDICINE 2013; 26:1484-1495. [PMID: 23775778 PMCID: PMC3800477 DOI: 10.1002/nbm.2981] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 04/24/2013] [Accepted: 05/10/2013] [Indexed: 05/31/2023]
Abstract
The dysmyelinated axons of shiverer mice exhibit impaired conduction characteristics, similar to early postnatal axons before myelination, whereas the patterns of neuronal activity and connectivity are relatively comparable with those of wild-type myelinated axons. This unique dysmyelination pattern is exploited in the present study to determine the role of compact myelin in the loss and recovery of function following traumatic spinal cord injury (SCI). We applied in vivo diffusion tensor imaging (DTI) and post-mortem immunohistochemistry analysis to examine changes in myelin and axonal integrity, and evaluated these changes in concert with the analysis of locomotor function from 1 to 4 weeks following a mid-thoracic contusion injury in homozygous shiverer and heterozygous littermate mice. The DTI biomarkers, axial and radial diffusivities, are noninvasive indicators of axon and myelin integrity in response to SCI of both myelinated and dysmyelinated spinal cord. We show that myelin is critical for normal hind limb function in open field locomotion. However, when the functional outcome is limited during chronic SCI, the extent of recovery is associated with residual axonal integrity and independent of the extent of intact myelin at the lesion epicenter.
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Affiliation(s)
- Tsang-Wei Tu
- Radiology and Imaging Sciences, Clinical Center, National Institute of Health, MD, USA
| | - Joong H. Kim
- Department of Radiology, Washington University in St. Louis, MO, USA
| | - Feng Qin Yin
- Department of Physiology & Cell Biology and Center for Brain and Spinal Cord Repair, Ohio State University, Columbus, OH, USA
| | - Lyn B. Jakeman
- Department of Physiology & Cell Biology and Center for Brain and Spinal Cord Repair, Ohio State University, Columbus, OH, USA
| | - Sheng-Kwei Song
- Department of Radiology, Washington University in St. Louis, MO, USA
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37
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Aung WY, Mar S, Benzinger TL. Diffusion tensor MRI as a biomarker in axonal and myelin damage. ACTA ACUST UNITED AC 2013; 5:427-440. [PMID: 24795779 DOI: 10.2217/iim.13.49] [Citation(s) in RCA: 217] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Diffusion tensor imaging has been used extensively as a research tool to understand the structural changes associated with white matter pathology. Using water diffusion as the basis to construct anatomic details, diffusion tensor imaging offers the potential to identify structural and functional adaptations before gross anatomical changes, such as lesions and tumors, become apparent on conventional MRI. Over the past 10 years, further parameters, such as axial and radial diffusivity, have been developed to characterize white matter changes specific to axons and myelin. In this paper, the potential application and outstanding issues on the use of diffusion tensor imaging directional diffusivity as a biomarker in axonal and myelin damage in neurological disorders will be reviewed.
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Affiliation(s)
- Wint Yan Aung
- Department of Radiology, Washington University, School of Medicine, 510 South Kingshighway Boulevard, St Louis, MO 63110, USA
| | - Soe Mar
- Department of Pediatric & Developmental Neurology, Washington University School of Medicine, St Louis, MO, USA
| | - Tammie Ls Benzinger
- Department of Radiology, Washington University, School of Medicine, 510 South Kingshighway Boulevard, St Louis, MO 63110, USA ; Department of Neurological Surgery, Washington University School of Medicine, St Louis, MO, USA
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39
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Abstract
The identification of autoantibodies associated with dysimmune neuropathies was a major contribution to the characterization of peripheral nerve disorders, the understanding of their pathophysiology, and the clinical diagnosis of neuropathies. Antibodies directed to GM1, GQ1b, and disyalilated gangliosides, and anti-MAG antibodies are very useful in the diagnosis of acute or chronic motor or sensory-motor neuropathies with or without monoclonal IgM. Anti-onconeural anti-Hu and anti-CV2/CRMP antibodies allow when they are detected the diagnosis of paraneoplastic neuropathies. This chapter focuses on the description of these antibodies as diagnostic markers and on their immunopathogenesis. We give a background overview on the origin of these antibodies, their detection, and review those studies, which clearly show that these antibodies are capable of binding to the target tissues in peripheral nerve and thereby can exert a variety of pathophysiological effects. The corresponding electrophysiological and histological changes observed both in human and animal models are exemplified in order to get a better understanding of the immune mechanisms of these antibody-mediated neuropathies.
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Affiliation(s)
- Andreas Steck
- Department of Neurology, University Hospital Basel, Basel, Switzerland.
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Abstract
A peripheral nerve trunk is composed of nerve fascicles supported in a fibrous collagenous sheath and defined by concentric layers of cells (the perineurium) that separate the contents (the endoneurium) from its fibrous collagen support (the epineurium). In the endoneurium are myelinated and unmyelinated fibers that are axons combined with their supporting Schwann cells to provide physical and electrical connections with end-organs such as muscle fibers and sensory endings. Axons are tubular neuronal extensions with a cytoskeleton of neurotubules and tubulin along which organelles and proteins can travel between the neuronal cell body and the axon terminal. During development some axons enlarge and are covered by a chain of Schwann cells each associated with just one axon. As the axons grow in diameter, the Schwann cells wrap round them to produce a myelin sheath. This consists of many layers of compacted Schwann cell membrane plus some additional proteins. Adjacent myelin segments connect at highly specialized structures, the nodes of Ranvier. Myelin insulates the axon so that the nerve impulse can jump from one node to the next. The region adjacent to the node, the paranodal segment, is the site of myelin terminations on the axolemma. There are connections here between the Schwann cell and the axon via a complex chain of proteins. The Schwann cell cytoplasm in the adjacent segment, the juxtaparanode, contains most of the Schwann cell mitochondria. In addition to the node, continuity of myelin lamellae is broken at intervals along the internode by helical regions of decompaction known as Schmidt-Lanterman incisures; these are seen as paler conical segments in suitably stained microscopical preparations and provide a pathway between the adaxonal and abaxonal cytoplasm. Smaller axons without a myelin sheath conduct very much more slowly and have a more complex relationship with their supporting Schwann cells that has important implications for repair.
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Affiliation(s)
- Rosalind King
- Department of Clinical Neurosciences, Institute of Neurology, University College London, Royal Free Campus, London, UK.
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41
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Abstract
The fundamental roles of Schwann cells during peripheral nerve formation and regeneration have been recognized for more than 100 years, but the cellular and molecular mechanisms that integrate Schwann cell and axonal functions continue to be elucidated. Derived from the embryonic neural crest, Schwann cells differentiate into myelinating cells or bundle multiple unmyelinated axons into Remak fibers. Axons dictate which differentiation path Schwann cells follow, and recent studies have established that axonal neuregulin1 signaling via ErbB2/B3 receptors on Schwann cells is essential for Schwann cell myelination. Extracellular matrix production and interactions mediated by specific integrin and dystroglycan complexes are also critical requisites for Schwann cell-axon interactions. Myelination entails expansion and specialization of the Schwann cell plasma membrane over millimeter distances. Many of the myelin-specific proteins have been identified, and transgenic manipulation of myelin genes have provided novel insights into myelin protein function, including maintenance of axonal integrity and survival. Cellular events that facilitate myelination, including microtubule-based protein and mRNA targeting, and actin based locomotion, have also begun to be understood. Arguably, the most remarkable facet of Schwann cell biology, however, is their vigorous response to axonal damage. Degradation of myelin, dedifferentiation, division, production of axonotrophic factors, and remyelination all underpin the substantial regenerative capacity of the Schwann cells and peripheral nerves. Many of these properties are not shared by CNS fibers, which are myelinated by oligodendrocytes. Dissecting the molecular mechanisms responsible for the complex biology of Schwann cells continues to have practical benefits in identifying novel therapeutic targets not only for Schwann cell-specific diseases but other disorders in which axons degenerate.
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Affiliation(s)
- Grahame J Kidd
- Department of Neuroscience, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA.
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Abstract
Multiple sclerosis (MS) is an inflammatory demyelinating disease that is considered by many people to have an autoimmune aetiology. In recent years, new data emerging from histopathology, imaging and other studies have expanded our understanding of the disease and may change the way in which it is treated. Conceptual shifts have included: first, an appreciation of the extent to which the neuron and its axon are affected in MS, and second, elucidation of how the neurobiology of axon-glial and, particularly, axon-myelin interaction may influence disease progression. In this article, we review advances in both areas, focusing on the molecular mechanisms underlying axonal loss in acute inflammation and in chronic demyelination, and discussing how the restoration of myelin sheaths via the regenerative process of remyelination might prevent axon degeneration. An understanding of these processes could lead to better strategies for the prevention and treatment of axonal loss, which will ultimately benefit patients with MS.
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Lopez PHH, Ahmad AS, Mehta NR, Toner M, Rowland EA, Zhang J, Doré S, Schnaar RL. Myelin-associated glycoprotein protects neurons from excitotoxicity. J Neurochem 2011; 116:900-8. [PMID: 21214567 DOI: 10.1111/j.1471-4159.2010.07069.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In addition to supporting rapid nerve conduction, myelination nurtures and stabilizes axons and protects them from acute toxic insults. One myelin molecule that protects and sustains axons is myelin-associated glycoprotein (MAG). MAG is expressed on the innermost wrap of myelin, apposed to the axon surface, where it interacts with axonal receptors that reside in lateral membrane domains including gangliosides, the glycosylphosphatidylinositol-anchored Nogo receptors, and β1-integrin. We report here that MAG protection extends beyond the axon to the neurons from which those axons emanate, protecting them from excitotoxicity. Compared to wild type mice, Mag-null mice displayed markedly increased seizure activity in response to intraperitoneal injection of kainic acid, an excitotoxic glutamate receptor agonist. Mag-null mice also had larger lesion volumes in response to intrastriatal injection of the excitotoxin NMDA. Prior injection of a soluble form of MAG partially protected Mag-null mice from NMDA-induced lesions. Hippocampal neurons plated on proteins extracted from wild-type rat or mouse myelin were resistant to kainic acid-induced excitotoxicity, whereas neurons plated on proteins from Mag-null myelin were not. Protection was reversed by anti-MAG antibody and replicated by addition of soluble MAG. MAG-mediated protection from excitotoxicity was dependent on Nogo receptors and β1-integrin. We conclude that MAG engages membrane-domain resident neuronal receptors to protect neurons from excitotoxicity, and that soluble MAG mitigates excitotoxic damage in vivo.
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Affiliation(s)
- Pablo H H Lopez
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Pupil-involving third nerve palsy as a manifestation of anti-myelin-associated glycoprotein neuropathy. J Neuroophthalmol 2010; 31:29-33. [PMID: 21164358 DOI: 10.1097/wno.0b013e3181f2e27a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A 56-year-old man developed a pupil-involving left third nerve palsy. Imaging studies of the brain and intracranial vessels were normal. Neurological examination demonstrated a sensory polyneuropathy and mild distal weakness. Nerve conduction studies showed prolonged distal motor latencies. An enzyme-linked immunosorbent assay test detected high titers of anti-myelin-associated glycoprotein (MAG) antibodies. The patient improved with prednisone and rituximab treatment. Anti-MAG neuropathy should be considered when evaluating a patient with an undiagnosed cranial neuropathy, especially in the setting of a sensory neuropathy.
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Khazaei MR, Halfter H, Karimzadeh F, Koo JH, Margolis FL, Young P. Bex1 is involved in the regeneration of axons after injury. J Neurochem 2010; 115:910-20. [PMID: 20731761 DOI: 10.1111/j.1471-4159.2010.06960.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Successful axonal regeneration is a complex process determined by both axonal environment and endogenous neural capability of the regenerating axons in the central and the peripheral nervous systems. Numerous external inhibitory factors inhibit axonal regeneration after injury. In response, neurons express various regeneration-associated genes to overcome this inhibition and increase the intrinsic growth capacity. In the present study, we show that the brain-expressed X-linked (Bex1) protein was over-expressed as a result of peripheral axonal damage. Bex1 antagonized the axon outgrowth inhibitory effect of myelin-associated glycoprotein. The involvement of Bex1 in axon regeneration was further confirmed in vivo. We have demonstrated that Bex1 knock-out mice showed lower capability for regeneration after peripheral nerve injury than wild-type animals. Wild-type mice could recover from sciatic nerve injury much faster than Bex1 knock-out mice. Our findings suggest that Bex1 could be considered as regeneration-associated gene.
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Affiliation(s)
- Mohammad R Khazaei
- Department of Neurology, University Hospital of Münster, Münster, Germany
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Piaton G, Gould RM, Lubetzki C. Axon-oligodendrocyte interactions during developmental myelination, demyelination and repair. J Neurochem 2010; 114:1243-60. [PMID: 20524961 DOI: 10.1111/j.1471-4159.2010.06831.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In multiple sclerosis, CNS demyelination is often followed by spontaneous repair, mostly achieved by adult oligodendrocyte precursor cells. Extent of this myelin repair differs, ranging from very low, limited to the plaque border, to extensive, with remyelination throughout the 'shadow plaques.' In addition to restoring neuronal connectivity, new myelin is neuroprotective. It reduces axonal loss and thus disability progression. Reciprocal communication between neurons and oligodendrocytes is essential for both myelin biogenesis and myelin repair. Hence, deciphering neuron-oligodendrocyte communication is not only important for understanding myelination per se, but also the pathophysiology that underlies demyelinating diseases and the development of innovative therapeutic strategies.
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Mehta NR, Nguyen T, Bullen JW, Griffin JW, Schnaar RL. Myelin-associated glycoprotein (MAG) protects neurons from acute toxicity using a ganglioside-dependent mechanism. ACS Chem Neurosci 2010; 1:215-222. [PMID: 20436925 DOI: 10.1021/cn900029p] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Myelin-associated glycoprotein (MAG), a protein expressed on the innermost wrap of myelin, contributes to long-term axon stability as evidenced by progressive axon degeneration in Mag-null mice. Recently, MAG was also found to protect axons from acute toxic insults. In the current study, rat dorsal root ganglion neurons were cultured on control substrata and substrata adsorbed with myelin proteins. Neurons on myelin-adsorbed surfaces were resistant to acute degeneration of neurites induced by vincristine, a cancer chemotherapeutic agent with neuropathic side effects. Myelin-mediated protection was reversed by anti-MAG antibody and was absent when cells were cultured on extracts from Mag-null mouse myelin, confirming the protective role of MAG. Gangliosides (sialylated glycosphingolipids) are one functional class of axonal receptors for MAG. In the current studies, a direct role for gangliosides in mediating the acute protective effects of MAG was established. Treatment of neurons with sialidase, an enzyme that cleaves the terminal sialic acids required for MAG binding, reversed MAG's protective effect, as did treatment with (1R,2R)-1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol, an inhibitor of glycosphingolipid biosynthesis. In contrast, treatment with phosphatidylinositol-specific phospholipase C, an enzyme that cleaves Nogo receptors (NgR, another class of MAG receptor), or with a peptide inhibitor of an NgR-associated signaling molecule p75(NTR), failed to diminish MAG-mediated protection. Inhibiting the Rho-associated protein kinase ROCK reversed protection. We conclude that MAG protects neurites from acute toxic insult via a ganglioside-mediated signaling pathway that involves activation of RhoA. Understanding MAG-mediated protection may provide opportunities to reduce axonal damage and loss.
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Piccinini M, Scandroglio F, Prioni S, Buccinnà B, Loberto N, Aureli M, Chigorno V, Lupino E, DeMarco G, Lomartire A, Rinaudo MT, Sonnino S, Prinetti A. Deregulated sphingolipid metabolism and membrane organization in neurodegenerative disorders. Mol Neurobiol 2010; 41:314-40. [PMID: 20127207 DOI: 10.1007/s12035-009-8096-6] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Accepted: 12/22/2009] [Indexed: 12/13/2022]
Abstract
Sphingolipids are polar membrane lipids present as minor components in eukaryotic cell membranes. Sphingolipids are highly enriched in nervous cells, where they exert important biological functions. They deeply affect the structural and geometrical properties and the lateral order of cellular membranes, modulate the function of several membrane-associated proteins, and give rise to important intra- and extracellular lipid mediators. Sphingolipid metabolism is regulated along the differentiation and development of the nervous system, and the expression of a peculiar spatially and temporarily regulated sphingolipid pattern is essential for the maintenance of the functional integrity of the nervous system: sphingolipids in the nervous system participate to several signaling pathways controlling neuronal survival, migration, and differentiation, responsiveness to trophic factors, synaptic stability and synaptic transmission, and neuron-glia interactions, including the formation and stability of central and peripheral myelin. In several neurodegenerative diseases, sphingolipid metabolism is deeply deregulated, leading to the expression of abnormal sphingolipid patterns and altered membrane organization that participate to several events related to the pathogenesis of these diseases. The most impressive consequence of this deregulation is represented by anomalous sphingolipid-protein interactions that are at least, in part, responsible for the misfolding events that cause the fibrillogenic and amyloidogenic processing of disease-specific protein isoforms, such as amyloid beta peptide in Alzheimer's disease, huntingtin in Huntington's disease, alpha-synuclein in Parkinson's disease, and prions in transmissible encephalopathies. Targeting sphingolipid metabolism represents today an underexploited but realistic opportunity to design novel therapeutic strategies for the intervention in these diseases.
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Affiliation(s)
- Marco Piccinini
- Section of Biochemistry, Department of Medicine and Experimental Oncology, University of Turin, Turin, Italy
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Schnaar RL, Lopez PHH. Myelin-associated glycoprotein and its axonal receptors. J Neurosci Res 2010; 87:3267-76. [PMID: 19156870 DOI: 10.1002/jnr.21992] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Myelin-associated glycoprotein (MAG) is expressed on the innermost myelin membrane wrap, directly apposed to the axon surface. Although it is not required for myelination, MAG enhances long-term axon-myelin stability, helps to structure nodes of Ranvier, and regulates the axon cytoskeleton. In addition to its role in axon-myelin stabilization, MAG inhibits axon regeneration after injury; MAG and a discrete set of other molecules on residual myelin membranes at injury sites actively signal axons to halt elongation. Both the stabilizing and the axon outgrowth inhibitory effects of MAG are mediated by complementary MAG receptors on the axon surface. Two MAG receptor families have been described, sialoglycans (specifically gangliosides GD1a and GT1b) and Nogo receptors (NgRs). Controversies remain about which receptor(s) mediates which of MAG's biological effects. Here we review the findings and challenges in associating MAG's biological effects with specific receptors.
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Affiliation(s)
- Ronald L Schnaar
- Department of Pharmacology, The Johns Hopkins School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA.
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Inhibitory activity of myelin-associated glycoprotein on sensory neurons is largely independent of NgR1 and NgR2 and resides within Ig-Like domains 4 and 5. PLoS One 2009; 4:e5218. [PMID: 19367338 PMCID: PMC2666269 DOI: 10.1371/journal.pone.0005218] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Accepted: 02/23/2009] [Indexed: 12/16/2022] Open
Abstract
Myelin-associated glycoprotein (MAG) is a sialic acid binding Ig-like lectin (Siglec) which has been characterized as potent myelin-derived inhibitor of neurite outgrowth. Two members of the Nogo-receptor (NgR) family, NgR1 and NgR2, have been identified as neuronal binding proteins of MAG. In addition, gangliosides have been proposed to bind to and confer the inhibitory activity of MAG on neurons. In this study, we investigated the individual contribution of NgRs and gangliosides to MAG-mediated inhibition of sensory neurons derived from dorsal root ganglia (DRG) of ngr1, ngr2 or ngr1/ngr2 deletion mutants. We found no disinhibition of neurite growth in the absence of either NgR1 or NgR2. Sensory neurons deficient for both NgR proteins displayed only a moderate reduction of MAG-mediated inhibition of neurite growth. If treated with Vibrio cholerae neuraminidase (VCN), inhibition by MAG is further attenuated but still not annulled. Thus, disrupting all known protein and ganglioside receptors for MAG in sensory neurons does not fully abolish its inhibitory activity pointing to the existence of as yet unidentified receptors for MAG. Moreover, by employing a variety of protein mutants, we identified the Ig-like domains 4 or 5 of MAG as necessary and sufficient for growth arrest, whereas abolishing MAG's ability to bind to sialic acid did not interfere with its inhibitory activity. These findings provide new insights into the inhibitory function of MAG and suggest similarities but also major differences in MAG inhibition between sensory and central nervous system (CNS) neurons.
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