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Libberecht K, Dirkx N, Vangansewinkel T, Vandendries W, Lambrichts I, Wolfs E. The Influence of Lysosomal Stress on Dental Pulp Stem Cell-Derived Schwann Cells. Biomolecules 2024; 14:405. [PMID: 38672423 PMCID: PMC11048368 DOI: 10.3390/biom14040405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 03/16/2024] [Accepted: 03/25/2024] [Indexed: 04/28/2024] Open
Abstract
BACKGROUND Dysregulation of the endo-lysosomal-autophagy pathway has been identified as a critical factor in the pathology of various demyelinating neurodegenerative diseases, including peripheral neuropathies. This pathway plays a crucial role in transporting newly synthesized myelin proteins to the plasma membrane in myelinating Schwann cells, making these cells susceptible to lysosome-related dysfunctions. Nevertheless, the specific impact of lysosomal dysfunction in Schwann cells and its contribution to neurodegeneration remain poorly understood. METHODS We aim to mimic lysosomal dysfunction in Schwann cells using chloroquine, a lysosomal dysfunction inducer, and to monitor lysosomal leakiness, Schwann cell viability, and apoptosis over time. Additionally, due to the ethical and experimental issues associated with cell isolation and the culturing of human Schwann cells, we use human dental pulp stem cell-derived Schwann cells (DPSC-SCs) as a model in our study. RESULTS Chloroquine incubation boosts lysosomal presence as demonstrated by an increased Lysotracker signal. Further in-depth lysosomal analysis demonstrated an increased lysosomal size and permeability as illustrated by a TEM analysis and GAL3-LAMP1 staining. Moreover, an Alamar blue assay and Caspase-3 staining demonstrates a reduced viability and increased apoptosis, respectively. CONCLUSIONS Our data indicate that prolonged lysosomal dysfunction leads to lysosomal permeability, reduced viability, and eventually apoptosis in human DPSC-SCs.
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Affiliation(s)
- Karen Libberecht
- Laboratory for Functional Imaging & Research on Stem Cells, Biomedical Research Institute (BIOMED), Faculty of Medicine and Life Sciences, Hasselt University, 3590 Diepenbeek, Belgium; (K.L.); (N.D.)
- VIB, Center for Brain & Disease Research, Laboratory of Neurobiology, 3000 Leuven, Belgium
| | - Nathalie Dirkx
- Laboratory for Functional Imaging & Research on Stem Cells, Biomedical Research Institute (BIOMED), Faculty of Medicine and Life Sciences, Hasselt University, 3590 Diepenbeek, Belgium; (K.L.); (N.D.)
| | - Tim Vangansewinkel
- Laboratory for Functional Imaging & Research on Stem Cells, Biomedical Research Institute (BIOMED), Faculty of Medicine and Life Sciences, Hasselt University, 3590 Diepenbeek, Belgium; (K.L.); (N.D.)
- VIB, Center for Brain & Disease Research, Laboratory of Neurobiology, 3000 Leuven, Belgium
- Laboratory for Histology and Regeneration, Biomedical Research Institute (BIOMED), Faculty of Medicine and Life Sciences, Hasselt University, 3590 Diepenbeek, Belgium;
| | - Wendy Vandendries
- Laboratory for Functional Imaging & Research on Stem Cells, Biomedical Research Institute (BIOMED), Faculty of Medicine and Life Sciences, Hasselt University, 3590 Diepenbeek, Belgium; (K.L.); (N.D.)
| | - Ivo Lambrichts
- Laboratory for Histology and Regeneration, Biomedical Research Institute (BIOMED), Faculty of Medicine and Life Sciences, Hasselt University, 3590 Diepenbeek, Belgium;
| | - Esther Wolfs
- Laboratory for Functional Imaging & Research on Stem Cells, Biomedical Research Institute (BIOMED), Faculty of Medicine and Life Sciences, Hasselt University, 3590 Diepenbeek, Belgium; (K.L.); (N.D.)
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2
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Touvier T, Veneri FA, Claessens A, Ferri C, Mastrangelo R, Sorgiati N, Bianchi F, Valenzano S, Del Carro U, Rivellini C, Duong P, Shy ME, Kelly JW, Svaren J, Wiseman RL, D'Antonio M. Activation of XBP1s attenuates disease severity in models of proteotoxic Charcot-Marie-Tooth type 1B. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.31.577760. [PMID: 38352425 PMCID: PMC10862880 DOI: 10.1101/2024.01.31.577760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
Mutations in myelin protein zero (MPZ) are generally associated with Charcot-Marie-Tooth type 1B (CMT1B) disease, one of the most common forms of demyelinating neuropathy. Pathogenesis of some MPZ mutants, such as S63del and R98C, involves the misfolding and retention of MPZ in the endoplasmic reticulum (ER) of myelinating Schwann cells. To cope with proteotoxic ER-stress, Schwann cells mount an unfolded protein response (UPR) characterized by activation of the PERK, ATF6 and IRE1α/XBP1 pathways. Previous results showed that targeting the PERK UPR pathway mitigates neuropathy in mouse models of CMT1B; however, the contributions of other UPR pathways in disease pathogenesis remains poorly understood. Here, we probe the importance of the IRE1α/XBP1 signalling during normal myelination and in CMT1B. In response to ER stress, IRE1α is activated to stimulate the non-canonical splicing of Xbp1 mRNA to generate spliced Xbp1 (Xbp1s). This results in the increased expression of the adaptive transcription factor XBP1s, which regulates the expression of genes involved in diverse pathways including ER proteostasis. We generated mouse models where Xbp1 is deleted specifically in Schwann cells, preventing XBP1s activation in these cells. We observed that Xbp1 is dispensable for normal developmental myelination, myelin maintenance and remyelination after injury. However, Xbp1 deletion dramatically worsens the hypomyelination and the electrophysiological and locomotor parameters observed in young and adult CMT1B neuropathic animals. RNAseq analysis suggested that XBP1s exerts its adaptive function in CMT1B mouse models in large part via the induction of ER proteostasis genes. Accordingly, the exacerbation of the neuropathy in Xbp1 deficient mice was accompanied by upregulation of ER-stress pathways and of IRE1-mediated RIDD signaling in Schwann cells, suggesting that the activation of XBP1s via IRE1 plays a critical role in limiting mutant protein toxicity and that this toxicity cannot be compensated by other stress responses. Schwann cell specific overexpression of XBP1s partially re-established Schwann cell proteostasis and attenuated CMT1B severity in both the S63del and R98C mouse models. In addition, the selective, pharmacologic activation of IRE1α/XBP1 signaling ameliorated myelination in S63del dorsal root ganglia explants. Collectively, these data show that XBP1 has an essential adaptive role in different models of proteotoxic CMT1B neuropathy and suggest that activation of the IRE1α/XBP1 pathway may represent a therapeutic avenue in CMT1B and possibly for other neuropathies characterized by UPR activation.
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Affiliation(s)
- Thierry Touvier
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Francesca A Veneri
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Anke Claessens
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Cinzia Ferri
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Rosa Mastrangelo
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Noémie Sorgiati
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Francesca Bianchi
- Institute of Experimental Neurology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Serena Valenzano
- Institute of Experimental Neurology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
- Department of Biomedical and Clinical Sciences "L. Sacco", University of Milan, 20157 Milan, Italy
- University of Camerino, Center for Neuroscience, 62032 Camerino, Italy
| | - Ubaldo Del Carro
- Institute of Experimental Neurology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Cristina Rivellini
- Division of Neuroscience, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Phu Duong
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Michael E Shy
- Department of Neurology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242 USA
| | - Jeffery W Kelly
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA 92037, USA
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - John Svaren
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - R Luke Wiseman
- Department of Molecular and Cellular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Maurizio D'Antonio
- Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
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3
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Therapeutic tools for inherited neuropathies. Rev Neurol (Paris) 2023; 179:5-9. [PMID: 36529569 DOI: 10.1016/j.neurol.2022.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Inherited neuropathies are a genetically and phenotypically heterogenous group of disorders leading to sensory and motor dysfunction. For years, these neuropathies have been considered as non-treatable diseases, as no drug is able to induce nerve regrowth. Progress in molecular tools has changed this view and several neuropathies can now be efficiently treated. Some more will be treatable in the upcoming years. Basically, these new treatments can be divided into four categories, depending on the target: gene therapy; gene expression therapy; protein modification or replacement (enzyme replacement therapy, ERT); downstream therapies. In this short review, we will provide a few examples for each of them in the field of peripheral neuropathies.
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4
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Veneri FA, Prada V, Mastrangelo R, Ferri C, Nobbio L, Passalacqua M, Milanesi M, Bianchi F, Del Carro U, Vallat JM, Duong P, Svaren J, Schenone A, Grandis M, D’Antonio M. A novel mouse model of CMT1B identifies hyperglycosylation as a new pathogenetic mechanism. Hum Mol Genet 2022; 31:4255-4274. [PMID: 35908287 PMCID: PMC9759335 DOI: 10.1093/hmg/ddac170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 07/19/2022] [Accepted: 07/20/2022] [Indexed: 01/21/2023] Open
Abstract
Mutations in the Myelin Protein Zero gene (MPZ), encoding P0, the major structural glycoprotein of peripheral nerve myelin, are the cause of Charcot-Marie-Tooth (CMT) type 1B neuropathy, and most P0 mutations appear to act through gain-of-function mechanisms. Here, we investigated how misglycosylation, a pathomechanism encompassing several genetic disorders, may affect P0 function. Using in vitro assays, we showed that gain of glycosylation is more damaging for P0 trafficking and functionality as compared with a loss of glycosylation. Hence, we generated, via CRISPR/Cas9, a mouse model carrying the MPZD61N mutation, predicted to generate a new N-glycosylation site in P0. In humans, MPZD61N causes a severe early-onset form of CMT1B, suggesting that hyperglycosylation may interfere with myelin formation, leading to pathology. We show here that MPZD61N/+ mice develop a tremor as early as P15 which worsens with age and correlates with a significant motor impairment, reduced muscular strength and substantial alterations in neurophysiology. The pathological analysis confirmed a dysmyelinating phenotype characterized by diffuse hypomyelination and focal hypermyelination. We find that the mutant P0D61N does not cause significant endoplasmic reticulum stress, a common pathomechanism in CMT1B, but is properly trafficked to myelin where it causes myelin uncompaction. Finally, we show that myelinating dorsal root ganglia cultures from MPZD61N mice replicate some of the abnormalities seen in vivo, suggesting that they may represent a valuable tool to investigate therapeutic approaches. Collectively, our data indicate that the MPZD61N/+ mouse represents an authentic model of severe CMT1B affirming gain-of-glycosylation in P0 as a novel pathomechanism of disease.
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Affiliation(s)
- Francesca A Veneri
- Biology of Myelin Unit, Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy,Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genova, IRCCS AOU San Martino-IST, 16132 Genova, Italy
| | - Valeria Prada
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genova, IRCCS AOU San Martino-IST, 16132 Genova, Italy
| | - Rosa Mastrangelo
- Biology of Myelin Unit, Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Cinzia Ferri
- Biology of Myelin Unit, Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Lucilla Nobbio
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genova, IRCCS AOU San Martino-IST, 16132 Genova, Italy
| | - Mario Passalacqua
- Department of Experimental Medicine, University of Genova, 16132 Genova, Italy
| | - Maria Milanesi
- Experimental Oncology and Immunology, Department of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
| | - Francesca Bianchi
- Movement Disorders Unit, Division of Neuroscience, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Ubaldo Del Carro
- Movement Disorders Unit, Division of Neuroscience, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Jean-Michel Vallat
- Department and Laboratory of Neurology, National Reference Center for ‘Rare Peripheral Neuropathies’, University Hospital of Limoges (CHU Limoges), Dupuytren Hospital, 87000 Limoges, France
| | - Phu Duong
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - John Svaren
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Angelo Schenone
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genova, IRCCS AOU San Martino-IST, 16132 Genova, Italy,Department of Neurology, IRCCS Ospedale Policlinico San Martino, 16132 Genova, Italy
| | - Marina Grandis
- To whom correspondence should be addressed at: Department of Neurology, IRCCS Ospedale Policlinico San Martino, Largo Daneo 3, 16132 Genova, Italy. Tel: +39 010 3537562; (M.G.); San Raffaele Scientific Institute, DIBIT, via Olgettina 58, 20132 Milan, Italy. Tel: +39 02 26435307; (M.D.)
| | - Maurizio D’Antonio
- To whom correspondence should be addressed at: Department of Neurology, IRCCS Ospedale Policlinico San Martino, Largo Daneo 3, 16132 Genova, Italy. Tel: +39 010 3537562; (M.G.); San Raffaele Scientific Institute, DIBIT, via Olgettina 58, 20132 Milan, Italy. Tel: +39 02 26435307; (M.D.)
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5
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Abstract
Demyelinating forms of Charcot-Marie-Tooth disease (CMT) are genetically and phenotypically heterogeneous and result from highly diverse biological mechanisms including gain of function (including dominant negative effects) and loss of function. While no definitive treatment is currently available, rapid advances in defining the pathomechanisms of demyelinating CMT have led to promising pre-clinical studies, as well as emerging clinical trials. Especially promising are the recently completed pre-clinical genetic therapy studies in PMP-22, GJB1, and SH3TC2-associated neuropathies, particularly given the success of similar approaches in humans with spinal muscular atrophy and transthyretin familial polyneuropathy. This article focuses on neuropathies related to mutations in PMP-22, MPZ, and GJB1, which together comprise the most common forms of demyelinating CMT, as well as on select rarer forms for which promising treatment targets have been identified. Clinical characteristics and pathomechanisms are reviewed in detail, with emphasis on therapeutically targetable biological pathways. Also discussed are the challenges facing the CMT research community in its efforts to advance the rapidly evolving biological insights to effective clinical trials. These considerations include the limitations of currently available animal models, the need for personalized medicine approaches/allele-specific interventions for select forms of demyelinating CMT, and the increasing demand for optimal clinical outcome assessments and objective biomarkers.
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Affiliation(s)
- Vera Fridman
- Department of Neurology, University of Colorado Anschutz Medical Campus, 12631 E 17th Avenue, Mailstop B185, Room 5113C, Aurora, CO, 80045, USA.
| | - Mario A Saporta
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, USA
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6
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Sidoli M, Reed CB, Scapin C, Paez P, Cavener DR, Kaufman RJ, D'Antonio M, Feltri ML, Wrabetz L. Calcineurin Activity Is Increased in Charcot-Marie-Tooth 1B Demyelinating Neuropathy. J Neurosci 2021; 41:4536-4548. [PMID: 33879538 PMCID: PMC8152608 DOI: 10.1523/jneurosci.2384-20.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 03/08/2021] [Accepted: 03/17/2021] [Indexed: 11/21/2022] Open
Abstract
Schwann cells produce a considerable amount of lipids and proteins to form myelin in the PNS. For this reason, the quality control of myelin proteins is crucial to ensure proper myelin synthesis. Deletion of serine 63 from P0 (P0S63del) protein in myelin forming Schwann cells causes Charcot-Marie-Tooth type 1B neuropathy in humans and mice. Misfolded P0S63del accumulates in the ER of Schwann cells where it elicits the unfolded protein response (UPR). PERK is the UPR transducer that attenuates global translation and reduces ER stress by phosphorylating the translation initiation factor eIF2alpha. Paradoxically, Perk ablation in P0S63del Schwann cells (S63del/PerkSCKO ) reduced the level of P-eIF2alpha, leaving UPR markers upregulated, yet unexpectedly improved S63del myelin defects in vivo We therefore investigated the hypothesis that PERK may interfere with signals outside of the UPR and specifically with calcineurin/NFATc4 pro-myelinating pathway. Using mouse genetics including females and males in our experimental setting, we show that PERK and calcineurin interact in P0S63del nerves and that calcineurin activity and NFATc4 nuclear localization are increased in S63del Schwann cells, without altering EGR2/KROX20 expression. Moreover, genetic manipulation of the calcineurin subunits appears to be either protective or toxic in S63del in a context-dependent manner, suggesting that Schwann cells are highly sensitive to alterations of calcineurin activity.SIGNIFICANCE STATEMENT Our work shows a novel activity and function for calcineurin in Schwann cells in the context of ER stress. Schwann cells expressing the S63del mutation in P0 protein induce the unfolded protein response and upregulate calcineurin activity. Calcineurin interacts with the ER stress transducer PERK, but the relationship between the UPR and calcineurin in Schwann cells is unclear. Here we propose a protective role for calcineurin in S63del neuropathy, although Schwann cells appear to be very sensitive to its regulation. The paper uncovers a new important role for calcineurin in a demyelinating diseases.
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Affiliation(s)
- Mariapaola Sidoli
- Hunter James Kelly Research Institute, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
- Department of Developmental Biology, School of Medicine, Stanford University, Stanford, California 94305
| | - Chelsey B Reed
- Hunter James Kelly Research Institute, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
- Department of Neurology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
| | - Cristina Scapin
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, DIBIT, Milan 20132, Italy
| | - Pablo Paez
- Hunter James Kelly Research Institute, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
| | - Douglas R Cavener
- Department of Biology, Center for Cellular Dynamics, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037
| | - Maurizio D'Antonio
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, DIBIT, Milan 20132, Italy
| | - M Laura Feltri
- Hunter James Kelly Research Institute, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
- Department of Neurology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
| | - Lawrence Wrabetz
- Hunter James Kelly Research Institute, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
- Department of Neurology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14203
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7
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Howard P, Feely SME, Grider T, Bacha A, Scarlato M, Fazio R, Quattrini A, Shy ME, Previtali SC. Loss of function MPZ mutation causes milder CMT1B neuropathy. J Peripher Nerv Syst 2021; 26:177-183. [PMID: 33960567 DOI: 10.1111/jns.12452] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 04/29/2021] [Accepted: 05/01/2021] [Indexed: 02/06/2023]
Abstract
Mutations in Myelin Protein Zero (MPZ) cause CMT1B, the second leading cause of CMT1. Many of the >200 mutations cause neuropathy through a toxic gain of function by the mutant protein such as ER retention, activation of the Unfolded Protein Response (UPR) or disruption of myelin compaction. While there is extensive literature on the loss of function consequences of MPZ in heterozygous Mpz +/- null mice, there is little known of the consequences of MPZ haploinsufficiency in humans. We identified six patients from different families with p.Tyr68Ter or p.Asp104fs heterozygous mutations of MPZ that are predicted to cause a premature termination and nonsense mediated decay of the mutant allele. Five patients were evaluated in Milan and one in Iowa City; all should be haploinsufficient for MPZ. Patients were evaluated clinically and by electrophysiology. Sensory ataxia dominated the clinical presentation with only mild weakness present in five of the six patients. Symptoms presented in adulthood in all patients and only one individual had a CMTNSv2 >5. Deep tendon reflexes were absent in all patients. Patients with likely MPZ loss of function due to mutations that cause haplodeficiency in MPZ have a mild, predominantly large fiber sensory neuropathy that serves as a human equivalent to the neuropathy observed in heterozygous Mpz null mice. Successful therapeutic approaches in treating Mpz deficient mice may be candidates for trials in these and similar patients.
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Affiliation(s)
- Paige Howard
- Roy and Lucille Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | | | - Tiffany Grider
- University of Iowa Healthcare Neurology, Iowa City, Iowa, USA
| | - Alexa Bacha
- Roy and Lucille Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Marina Scarlato
- Institute of Experimental Neurology (InSpe) and Division of Neuroscience, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Raffaella Fazio
- Institute of Experimental Neurology (InSpe) and Division of Neuroscience, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Angelo Quattrini
- Institute of Experimental Neurology (InSpe) and Division of Neuroscience, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Michael E Shy
- Roy and Lucille Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Stefano C Previtali
- Institute of Experimental Neurology (InSpe) and Division of Neuroscience, IRCCS Ospedale San Raffaele, Milano, Italy
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8
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Wei GZ, Saraswat Ohri S, Khattar NK, Listerman AW, Doyle CH, Andres KR, Karuppagounder SS, Ratan RR, Whittemore SR, Hetman M. Hypoxia-inducible factor prolyl hydroxylase domain (PHD) inhibition after contusive spinal cord injury does not improve locomotor recovery. PLoS One 2021; 16:e0249591. [PMID: 33819286 PMCID: PMC8021188 DOI: 10.1371/journal.pone.0249591] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 03/19/2021] [Indexed: 12/12/2022] Open
Abstract
Traumatic spinal cord injury (SCI) is a devastating neurological condition that involves both primary and secondary tissue loss. Various cytotoxic events including hypoxia, hemorrhage and blood lysis, bioenergetic failure, oxidative stress, endoplasmic reticulum (ER) stress, and neuroinflammation contribute to secondary injury. The HIF prolyl hydroxylase domain (PHD/EGLN) family of proteins are iron-dependent, oxygen-sensing enzymes that regulate the stability of hypoxia inducible factor-1α (HIF-1α) and also mediate oxidative stress caused by free iron liberated from the lysis of blood. PHD inhibition improves outcome after experimental intracerebral hemorrhage (ICH) by reducing activating transcription factor 4 (ATF4)-driven neuronal death. As the ATF4-CHOP (CCAAT-enhancer-binding protein homologous protein) pathway plays a role in the pathogenesis of contusive SCI, we examined the effects of PHD inhibition in a mouse model of moderate T9 contusive SCI in which white matter damage is the primary driver of locomotor dysfunction. Pharmacological inhibition of PHDs using adaptaquin (AQ) moderately lowers acute induction of Atf4 and Chop mRNAs and prevents the acute decline of oligodendrocyte (OL) lineage mRNAs, but does not improve long-term recovery of hindlimb locomotion or increase chronic white matter sparing. Conditional genetic ablation of all three PHD isoenzymes in OLs did not affect Atf4, Chop or OL mRNAs expression levels, locomotor recovery, and white matter sparing after SCI. Hence, PHDs may not be suitable targets to improve outcomes in traumatic CNS pathologies that involve acute white matter injury.
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Affiliation(s)
- George Z Wei
- University of Louisville School of Medicine, Louisville, Kentucky, United States of America.,Department of Pharmacology & Toxicology, University of Louisville School of Medicine, Louisville, KY, United States of America.,Kentucky Spinal Cord Injury Research Center, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Sujata Saraswat Ohri
- Kentucky Spinal Cord Injury Research Center, University of Louisville School of Medicine, Louisville, KY, United States of America.,Department of Neurological Surgery, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Nicolas K Khattar
- Department of Pharmacology & Toxicology, University of Louisville School of Medicine, Louisville, KY, United States of America.,Kentucky Spinal Cord Injury Research Center, University of Louisville School of Medicine, Louisville, KY, United States of America.,Department of Neurological Surgery, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Adam W Listerman
- Kentucky Spinal Cord Injury Research Center, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Catherine H Doyle
- Kentucky Spinal Cord Injury Research Center, University of Louisville School of Medicine, Louisville, KY, United States of America.,Department of Neurological Surgery, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Kariena R Andres
- Kentucky Spinal Cord Injury Research Center, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Saravanan S Karuppagounder
- Sperling Center for Hemorrhagic Stroke Recovery, Burke Neurological Institute, White Plains, NY, United States of America.,Feil Family Brain and Mind Research Institute, Weill Medical College of Cornell University, New York, NY, United States of America
| | - Rajiv R Ratan
- Sperling Center for Hemorrhagic Stroke Recovery, Burke Neurological Institute, White Plains, NY, United States of America.,Feil Family Brain and Mind Research Institute, Weill Medical College of Cornell University, New York, NY, United States of America
| | - Scott R Whittemore
- Department of Pharmacology & Toxicology, University of Louisville School of Medicine, Louisville, KY, United States of America.,Kentucky Spinal Cord Injury Research Center, University of Louisville School of Medicine, Louisville, KY, United States of America.,Department of Neurological Surgery, University of Louisville School of Medicine, Louisville, KY, United States of America.,Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY, United States of America
| | - Michal Hetman
- University of Louisville School of Medicine, Louisville, Kentucky, United States of America.,Department of Pharmacology & Toxicology, University of Louisville School of Medicine, Louisville, KY, United States of America.,Kentucky Spinal Cord Injury Research Center, University of Louisville School of Medicine, Louisville, KY, United States of America.,Department of Neurological Surgery, University of Louisville School of Medicine, Louisville, KY, United States of America.,Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY, United States of America
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9
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Garcia LM, Hacker JL, Sase S, Adang L, Almad A. Glial cells in the driver seat of leukodystrophy pathogenesis. Neurobiol Dis 2020; 146:105087. [PMID: 32977022 DOI: 10.1016/j.nbd.2020.105087] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 08/16/2020] [Accepted: 09/18/2020] [Indexed: 01/24/2023] Open
Abstract
Glia cells are often viewed as support cells in the central nervous system, but recent discoveries highlight their importance in physiological functions and in neurological diseases. Central to this are leukodystrophies, a group of progressive, neurogenetic disease affecting white matter pathology. In this review, we take a closer look at multiple leukodystrophies, classified based on the primary glial cell type that is affected. While white matter diseases involve oligodendrocyte and myelin loss, we discuss how astrocytes and microglia are affected and impinge on oligodendrocyte, myelin and axonal pathology. We provide an overview of the leukodystrophies covering their hallmark features, clinical phenotypes, diverse molecular pathways, and potential therapeutics for clinical trials. Glial cells are gaining momentum as cellular therapeutic targets for treatment of demyelinating diseases such as leukodystrophies, currently with no treatment options. Here, we bring the much needed attention to role of glia in leukodystrophies, an integral step towards furthering disease comprehension, understanding mechanisms and developing future therapeutics.
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Affiliation(s)
- Luis M Garcia
- Department of Neurology, The Children's Hospital of Philadelphia, PA, Pennsylvania, USA
| | - Julia L Hacker
- Department of Neurology, The Children's Hospital of Philadelphia, PA, Pennsylvania, USA
| | - Sunetra Sase
- Department of Neurology, The Children's Hospital of Philadelphia, PA, Pennsylvania, USA
| | - Laura Adang
- Department of Neurology, The Children's Hospital of Philadelphia, PA, Pennsylvania, USA
| | - Akshata Almad
- Department of Neurology, The Children's Hospital of Philadelphia, PA, Pennsylvania, USA.
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10
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Mesentier-Louro LA, Shariati MA, Dalal R, Camargo A, Kumar V, Shamskhou EA, de Jesus Perez V, Liao YJ. Systemic hypoxia led to little retinal neuronal loss and dramatic optic nerve glial response. Exp Eye Res 2020; 193:107957. [PMID: 32032627 PMCID: PMC7673281 DOI: 10.1016/j.exer.2020.107957] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 12/19/2019] [Accepted: 02/03/2020] [Indexed: 01/23/2023]
Abstract
Vision loss is a devastating consequence of systemic hypoxia, but the cellular mechanisms are unclear. We investigated the impact of acute hypoxia in the retina and optic nerve. We induced systemic hypoxia (10% O2) in 6-8w mice for 48 h and performed in vivo imaging using optical coherence tomography (OCT) at baseline and after 48 h to analyze structural changes in the retina and optic nerve. We analyzed glial cellular and molecular changes by histology and immunofluorescence and the impact of pretreatment with 4-phenylbutyric acid (4-PBA) in oligodendroglia survival. After 48 h hypoxia, we found no change in ganglion cell complex thickness and no loss of retinal ganglion cells. Despite this, there was significantly increased expression of CCAAT-enhancer-binding protein homologous protein (CHOP), a marker of endoplasmic reticulum stress, in the retina and optic nerve. In addition, hypoxia induced obvious increase of GFAP expression in the anterior optic nerve, where it co-localized with CHOP, and significant loss of Olig2+ oligodendrocytes. Pretreatment with 4-PBA, which has been shown to reduce endoplasmic reticulum stress, rescued total Olig2+ oligodendrocytes and increased the pool of mature (CC-1+) but not of immature (PDGFRa+) oligodendrocytes. Consistent with a selective vulnerability of the retina and optic nerve in hypoxia, the most striking changes in the 48 h murine model of hypoxia were in glial cells in the optic nerve, including increased CHOP expression in the astrocytes and loss of oligodendrocytes. Our data support a model where glial dysfunction is among the earliest events in systemic hypoxia - suggesting that glia may be a novel target in treatment of hypoxia.
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Affiliation(s)
| | - Mohammed Ali Shariati
- Department of Ophthalmology, Stanford University, School of Medicine, Stanford, CA, USA
| | - Roopa Dalal
- Department of Ophthalmology, Stanford University, School of Medicine, Stanford, CA, USA
| | - Alexandra Camargo
- Department of Ophthalmology, Stanford University, School of Medicine, Stanford, CA, USA
| | - Varun Kumar
- Department of Ophthalmology, Stanford University, School of Medicine, Stanford, CA, USA
| | - Elya Ali Shamskhou
- Department of Pulmonary Medicine, Stanford University, School of Medicine, Stanford, CA, USA
| | - Vinicio de Jesus Perez
- Department of Pulmonary Medicine, Stanford University, School of Medicine, Stanford, CA, USA
| | - Yaping Joyce Liao
- Department of Ophthalmology, Stanford University, School of Medicine, Stanford, CA, USA; Department of Neurology, Stanford University, School of Medicine, Stanford, CA, USA.
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11
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Saraswat Ohri S, Bankston AN, Mullins SA, Liu Y, Andres KR, Beare JE, Howard RM, Burke DA, Riegler AS, Smith AE, Hetman M, Whittemore SR. Blocking Autophagy in Oligodendrocytes Limits Functional Recovery after Spinal Cord Injury. J Neurosci 2018; 38:5900-5912. [PMID: 29793971 PMCID: PMC6021994 DOI: 10.1523/jneurosci.0679-17.2018] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Revised: 05/15/2018] [Accepted: 05/17/2018] [Indexed: 01/21/2023] Open
Abstract
Autophagy mechanisms are well documented in neurons after spinal cord injury (SCI), but the direct functional role of autophagy in oligodendrocyte (OL) survival in SCI pathogenesis remains unknown. Autophagy is an evolutionary conserved lysosomal-mediated catabolic pathway that ensures degradation of dysfunctional cellular components to maintain homeostasis in response to various forms of stress, including nutrient deprivation, hypoxia, reactive oxygen species, DNA damage, and endoplasmic reticulum (ER) stress. Using pharmacological gain and loss of function and genetic approaches, we investigated the contribution of autophagy in OL survival and its role in the pathogenesis of thoracic contusive SCI in female mice. Although upregulation of Atg5 (an essential autophagy gene) occurs after SCI, autophagy flux is impaired. Purified myelin fractions of contused 8 d post-SCI samples show enriched protein levels of LC3B, ATG5, and BECLIN 1. Data show that, while the nonspecific drugs rapamycin (activates autophagy) and spautin 1 (blocks autophagy) were pharmacologically active on autophagy in vivo, their administration did not alter locomotor recovery after SCI. To directly analyze the role of autophagy, transgenic mice with conditional deletion of Atg5 in OLs were generated. Analysis of hindlimb locomotion demonstrated a significant reduction in locomotor recovery after SCI that correlated with a greater loss in spared white matter. Immunohistochemical analysis demonstrated that deletion of Atg5 from OLs resulted in decreased autophagic flux and was detrimental to OL function after SCI. Thus, our study provides evidence that autophagy is an essential cytoprotective pathway operating in OLs and is required for hindlimb locomotor recovery after thoracic SCI.SIGNIFICANCE STATEMENT This study describes the role of autophagy in oligodendrocyte (OL) survival and pathogenesis after thoracic spinal cord injury (SCI). Modulation of autophagy with available nonselective drugs after thoracic SCI does not affect locomotor recovery despite being pharmacologically active in vivo, indicating significant off-target effects. Using transgenic mice with conditional deletion of Atg5 in OLs, this study definitively identifies autophagy as an essential homeostatic pathway that operates in OLs and exhibits a direct functional role in SCI pathogenesis and recovery. Therefore, this study emphasizes the need to discover novel autophagy-specific drugs that specifically modulate autophagy for further investigation for clinical translation to treat SCI and other CNS pathologies related to OL survival.
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Affiliation(s)
| | - Andrew N Bankston
- Kentucky Spinal Cord Injury Research Center
- Departments of Neurological Surgery
| | - S Ashley Mullins
- Kentucky Spinal Cord Injury Research Center
- Departments of Neurological Surgery
| | - Yu Liu
- Kentucky Spinal Cord Injury Research Center
- Departments of Neurological Surgery
| | - Kariena R Andres
- Kentucky Spinal Cord Injury Research Center
- Departments of Neurological Surgery
| | - Jason E Beare
- Kentucky Spinal Cord Injury Research Center
- Cardiovascular Innovation Institute, University of Louisville, School of Medicine, Louisville, Kentucky 40292
| | - Russell M Howard
- Kentucky Spinal Cord Injury Research Center
- Departments of Neurological Surgery
| | - Darlene A Burke
- Kentucky Spinal Cord Injury Research Center
- Departments of Neurological Surgery
| | - Amberly S Riegler
- Kentucky Spinal Cord Injury Research Center
- Departments of Neurological Surgery
| | - Allison E Smith
- Kentucky Spinal Cord Injury Research Center
- Departments of Neurological Surgery
| | - Michal Hetman
- Kentucky Spinal Cord Injury Research Center
- Departments of Neurological Surgery
- Pharmacology & Toxicology
- Anatomical Sciences & Neurobiology, and
| | - Scott R Whittemore
- Kentucky Spinal Cord Injury Research Center,
- Departments of Neurological Surgery
- Pharmacology & Toxicology
- Anatomical Sciences & Neurobiology, and
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12
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Moon SL, Sonenberg N, Parker R. Neuronal Regulation of eIF2α Function in Health and Neurological Disorders. Trends Mol Med 2018; 24:575-589. [PMID: 29716790 DOI: 10.1016/j.molmed.2018.04.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 04/04/2018] [Accepted: 04/05/2018] [Indexed: 12/12/2022]
Abstract
A key site of translation control is the phosphorylation of the eukaryotic translation initiation factor 2α (eIF2α), which reduces the rate of GDP to GTP exchange by eIF2B, leading to altered translation. The extent of eIF2α phosphorylation within neurons can alter synaptic plasticity. Phosphorylation of eIF2α is triggered by four stress-responsive kinases, and as such eIF2α is often phosphorylated during neurological perturbations or disease. Moreover, in some cases decreasing eIF2α phosphorylation mitigates neurodegeneration, suggesting that this could be a therapeutic target. Mutations in the γ subunit of eIF2, the guanine exchange factor eIF2B, an eIF2α phosphatase, or in two eIF2α kinases can cause disease in humans, demonstrating the importance of proper regulation of eIF2α phosphorylation for health.
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Affiliation(s)
- Stephanie L Moon
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80303, USA
| | - Nahum Sonenberg
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, QC H3A 1A3, Canada
| | - Roy Parker
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80303, USA; Howard Hughes Medical Institute, University of Colorado, Boulder, CO 80303, USA.
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13
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Saraswat Ohri S, Mullins A, Hetman M, Whittemore SR. Activating Transcription Factor-6α Deletion Modulates the Endoplasmic Reticulum Stress Response after Spinal Cord Injury but Does Not Affect Locomotor Recovery. J Neurotrauma 2017; 35:486-491. [PMID: 26842780 DOI: 10.1089/neu.2015.3993] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The endoplasmic reticulum stress response (ERSR) is activated in a variety of neurodegenerative diseases and/or traumatic injuries. Subsequent restoration of ER homeostasis may contribute to improvement in the functional outcome of these diseases. We recently demonstrated improvements in hindlimb locomotion after thoracic spinal cord injury (SCI) and implicated oligodendrocyte survival as a potential mechanism using genetic and pharmacological inhibition of the protein kinase ribonucleic acid-like ER kinase- CCAAT/enhancer binding homologous protein (PERK-CHOP) arm of the ERSR. Here, we investigated the contribution of activating transcription factor-6 (ATF6), an ERSR signaling effector comprising the second arm of ERSR, in the pathogenesis of SCI. In contrast to what was seen after attenuation of PERK-CHOP signaling, genetic ablation of ATF6 results in modulation of ERSR and decreased survival in oligodendrocyte precursor cells against ER stress. Further, ATF6 loss delays the ERSR after SCI, potentiates PERK-ATF4-CHOP signaling and fails to improve locomotor deficits. These data suggest that deleting ATF6 levels is unlikely to be a viable therapeutic target to improve functional recovery after SCI.
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Affiliation(s)
- Sujata Saraswat Ohri
- 1 Kentucky Spinal Cord Injury Research Center, University of Louisville , Louisville, Kentucky.,2 Department of Neurological Surgery, University of Louisville , Louisville, Kentucky
| | - Ashley Mullins
- 1 Kentucky Spinal Cord Injury Research Center, University of Louisville , Louisville, Kentucky.,2 Department of Neurological Surgery, University of Louisville , Louisville, Kentucky
| | - Michal Hetman
- 1 Kentucky Spinal Cord Injury Research Center, University of Louisville , Louisville, Kentucky.,2 Department of Neurological Surgery, University of Louisville , Louisville, Kentucky.,3 Department of Pharmacology and Toxicology, University of Louisville , Louisville, Kentucky.,4 Department of Anatomical Sciences and Neurobiology, University of Louisville , Louisville, Kentucky
| | - Scott R Whittemore
- 1 Kentucky Spinal Cord Injury Research Center, University of Louisville , Louisville, Kentucky.,2 Department of Neurological Surgery, University of Louisville , Louisville, Kentucky.,4 Department of Anatomical Sciences and Neurobiology, University of Louisville , Louisville, Kentucky
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14
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VerPlank JJS, Lokireddy S, Feltri ML, Goldberg AL, Wrabetz L. Impairment of protein degradation and proteasome function in hereditary neuropathies. Glia 2017; 66:379-395. [PMID: 29076578 DOI: 10.1002/glia.23251] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 09/10/2017] [Accepted: 10/09/2017] [Indexed: 01/02/2023]
Abstract
In several neurodegenerative diseases in which misfolded proteins accumulate there is impairment of the ubiquitin proteasome system (UPS). We tested if a similar disruption of proteostasis occurs in hereditary peripheral neuropathies. In sciatic nerves from mouse models of two human neuropathies, Myelin Protein Zero mutation (S63del) and increased copy number (P0 overexpression), polyubiquitinated proteins accumulated, and the overall rates of protein degradation were decreased. 26S proteasomes affinity-purified from sciatic nerves of S63del mice were defective in degradation of peptides and a ubiquitinated protein, unlike proteasomes from P0 overexpression, which appeared normal. Nevertheless, cellular levels of 26S proteasomes were increased in both, through the proteolytic-activation of the transcription factor Nrf1, as occurs in response to proteasome inhibitors. In S63del, increased amounts of the deubiquitinating enzymes USP14, UCH37, and USP5 were associated with proteasomes, the first time this has been reported in a human disease model. Inhibitors of USP14 increased the rate of protein degradation in S63del sciatic nerves and unexpectedly increased the phosphorylation of eIF2α by Perk. Thus, proteasome content, composition and activity are altered in these diseases and USP14 inhibitors have therapeutic potential in S63del neuropathy.
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Affiliation(s)
- Jordan J S VerPlank
- Hunter James Kelly Research Institute and Departments of, Biochemistry and Neurology, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York.,Harvard Medical School, Boston, Massachusetts
| | | | - M Laura Feltri
- Hunter James Kelly Research Institute and Departments of, Biochemistry and Neurology, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York
| | | | - Lawrence Wrabetz
- Hunter James Kelly Research Institute and Departments of, Biochemistry and Neurology, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York
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15
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Inoue K. Cellular Pathology of Pelizaeus-Merzbacher Disease Involving Chaperones Associated with Endoplasmic Reticulum Stress. Front Mol Biosci 2017; 4:7. [PMID: 28286750 PMCID: PMC5323380 DOI: 10.3389/fmolb.2017.00007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Accepted: 02/09/2017] [Indexed: 11/23/2022] Open
Abstract
Disease-causing mutations in genes encoding membrane proteins may lead to the production of aberrant polypeptides that accumulate in the endoplasmic reticulum (ER). These mutant proteins have detrimental conformational changes or misfolding events, which result in the triggering of the unfolded protein response (UPR). UPR is a cellular pathway that reduces ER stress by generally inhibiting translation, increasing ER chaperones levels, or inducing cell apoptosis in severe ER stress. This process has been implicated in the cellular pathology of many neurological disorders, including Pelizaeus-Merzbacher disease (PMD). PMD is a rare pediatric disorder characterized by the failure in the myelination process of the central nervous system (CNS). PMD is caused by mutations in the PLP1 gene, which encodes a major myelin membrane protein. Severe clinical PMD phenotypes appear to be the result of cell toxicity, due to the accumulation of PLP1 mutant proteins and not due to the lack of functional PLP1. Therefore, it is important to clarify the pathological mechanisms by which the PLP1 mutants negatively impact the myelin-generating cells, called oligodendrocytes, to overcome this devastating disease. This review discusses how PLP1 mutant proteins change protein homeostasis in the ER of oligodendrocytes, especially focusing on the reaction of ER chaperones against the accumulation of PLP1 mutant proteins that cause PMD.
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Affiliation(s)
- Ken Inoue
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry Kodaira, Japan
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16
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Volpi VG, Touvier T, D'Antonio M. Endoplasmic Reticulum Protein Quality Control Failure in Myelin Disorders. Front Mol Neurosci 2017; 9:162. [PMID: 28101003 PMCID: PMC5209374 DOI: 10.3389/fnmol.2016.00162] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 12/16/2016] [Indexed: 12/24/2022] Open
Abstract
Reaching the correct three-dimensional structure is crucial for the proper function of a protein. The endoplasmic reticulum (ER) is the organelle where secreted and transmembrane proteins are synthesized and folded. To guarantee high fidelity of protein synthesis and maturation in the ER, cells have evolved ER-protein quality control (ERQC) systems, which assist protein folding and promptly degrade aberrant gene products. Only correctly folded proteins that pass ERQC checkpoints are allowed to exit the ER and reach their final destination. Misfolded glycoproteins are detected and targeted for degradation by the proteasome in a process known as endoplasmic reticulum-associated degradation (ERAD). The excess of unstructured proteins in the ER triggers an adaptive signal transduction pathway, called unfolded protein response (UPR), which in turn potentiates ERQC activities in order to reduce the levels of aberrant molecules. When the situation cannot be restored, the UPR drives cells to apoptosis. Myelin-forming cells of the central and peripheral nervous system (oligodendrocytes and Schwann cells) synthesize a large amount of myelin proteins and lipids and therefore are particularly susceptible to ERQC failure. Indeed, deficits in ERQC and activation of ER stress/UPR have been implicated in several myelin disorders, such as Pelizaeus-Merzbacher and Krabbe leucodystrophies, vanishing white matter disease and Charcot-Marie-Tooth neuropathies. Here we discuss recent evidence underlying the importance of proper ERQC functions in genetic disorders of myelinating glia.
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Affiliation(s)
- Vera G Volpi
- Biology of Myelin Unit, Division of Genetics and Cell Biology, San Raffaele Scientific Institute, DIBIT Milan, Italy
| | - Thierry Touvier
- Biology of Myelin Unit, Division of Genetics and Cell Biology, San Raffaele Scientific Institute, DIBIT Milan, Italy
| | - Maurizio D'Antonio
- Biology of Myelin Unit, Division of Genetics and Cell Biology, San Raffaele Scientific Institute, DIBIT Milan, Italy
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17
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Clayton BLL, Popko B. Endoplasmic reticulum stress and the unfolded protein response in disorders of myelinating glia. Brain Res 2016; 1648:594-602. [PMID: 27055915 PMCID: PMC5036997 DOI: 10.1016/j.brainres.2016.03.046] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 03/25/2016] [Accepted: 03/26/2016] [Indexed: 12/12/2022]
Abstract
Myelin is vital to the proper function of the nervous system. Oligodendrocytes in the CNS and Schwann cells in the PNS are the glial cells responsible for generating the myelin sheath. Myelination requires the production of a vast amount of proteins and lipid-rich membrane, which puts a heavy load on the secretory pathway of myelinating glia and leaves them susceptible to endoplasmic reticulum (ER) stress. Cells respond to ER stress by activating the unfolded protein response (UPR). The UPR is initially protective but in situations of prolonged unresolved stress the UPR can lead to the apoptotic death of the stressed cell. There is strong evidence that ER stress and the UPR play a role in a number of disorders of myelin and myelinating glia, including multiple sclerosis, Pelizaeus-Merzbacher disease, Vanishing White Matter Disease, and Charcot-Marie-Tooth disease. In this review we discuss the role that ER stress and the UPR play in these disorders of myelin. In addition, we discuss the progress that has been made in our understanding of the effect genetic and pharmacological manipulation of the UPR has in mouse models of these disorders and the novel therapeutic potential of targeting the UPR that these studies support. This article is part of a Special Issue entitled SI:ER stress.
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Affiliation(s)
- Benjamin L L Clayton
- Department of Neurology, The University of Chicago Center for Peripheral Neuropathy, The University of Chicago, IL 60637, United States
| | - Brian Popko
- Department of Neurology, The University of Chicago Center for Peripheral Neuropathy, The University of Chicago, IL 60637, United States.
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18
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Musner N, Sidoli M, Zambroni D, Del Carro U, Ungaro D, D'Antonio M, Feltri ML, Wrabetz L. Perk Ablation Ameliorates Myelination in S63del-Charcot-Marie-Tooth 1B Neuropathy. ASN Neuro 2016; 8:8/2/1759091416642351. [PMID: 27095827 PMCID: PMC4844932 DOI: 10.1177/1759091416642351] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 02/18/2016] [Indexed: 12/31/2022] Open
Abstract
In peripheral nerves, P0 glycoprotein accounts for more than 20% of myelin protein content. P0 is synthesized by Schwann cells, processed in the endoplasmic reticulum (ER) and enters the secretory pathway. However, the mutant P0 with S63 deleted (P0S63del) accumulates in the ER lumen and induces a demyelinating neuropathy in Charcot–Marie–Tooth disease type 1B (CMT1B)–S63del mice. Accumulation of P0S63del in the ER triggers a persistent unfolded protein response. Protein kinase RNA-like endoplasmic reticulum kinase (PERK) is an ER stress sensor that phosphorylates eukaryotic initiation factor 2 alpha (eIF2alpha) in order to attenuate protein synthesis. We have shown that increasing phosphophorylated-eIF2alpha (P-eIF2alpha) is a potent therapeutic strategy, improving myelination and motor function in S63del mice. Here, we explore the converse experiment: Perk haploinsufficiency reduces P-eIF2alpha in S63del nerves as expected, but surprisingly, ameliorates, rather than worsens S63del neuropathy. Motor performance and myelin abnormalities improved in S63del//Perk+/− compared with S63del mice. These data suggest that mechanisms other than protein translation might be involved in CMT1B/S63del neuropathy. In addition, Perk deficiency in other cells may contribute to demyelination in a non–Schwann-cell autonomous manner.
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Affiliation(s)
- Nicolò Musner
- Hunter James Kelly Research Institute, University at Buffalo, NY, USA
| | - Mariapaola Sidoli
- Hunter James Kelly Research Institute, University at Buffalo, NY, USA Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, NY, USA
| | - Desireè Zambroni
- Division of Neuroscience, San Raffaele Scientific Institute, DIBIT, Milan, Italy
| | - Ubaldo Del Carro
- Division of Neuroscience, San Raffaele Scientific Institute, DIBIT, Milan, Italy
| | - Daniela Ungaro
- Division of Neuroscience, San Raffaele Scientific Institute, DIBIT, Milan, Italy
| | - Maurizio D'Antonio
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, DIBIT, Milan, Italy
| | - Maria L Feltri
- Hunter James Kelly Research Institute, University at Buffalo, NY, USA Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, NY, USA Department of Neurology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, NY, USA
| | - Lawrence Wrabetz
- Hunter James Kelly Research Institute, University at Buffalo, NY, USA Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, NY, USA Department of Neurology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, NY, USA
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19
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Stone S, Lin W. The unfolded protein response in multiple sclerosis. Front Neurosci 2015; 9:264. [PMID: 26283904 PMCID: PMC4518158 DOI: 10.3389/fnins.2015.00264] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 07/14/2015] [Indexed: 01/08/2023] Open
Abstract
The unfolded protein response (UPR) occurs in response to endoplasmic reticulum (ER) stress caused by the accumulation of unfolded or misfolded proteins in the ER. The UPR is comprised of three signaling pathways that promote cytoprotective functions to correct ER stress; however, if ER stress cannot be resolved the UPR results in apoptosis of affected cells. The UPR is an important feature of various human diseases, including multiple sclerosis (MS). Recent studies have shown several components of the UPR are upregulated in the multiple cell types in MS lesions, including oligodendrocytes, T cells, microglia/macrophages, and astrocytes. Data from animal model studies, particularly studies of experimental autoimmune encephalomyelitis (EAE) and the cuprizone model, imply an important role of the UPR activation in oligodendrocytes in the development of MS. In this review we will cover current literature on the UPR and the evidence for its role in the development of MS.
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Affiliation(s)
- Sarrabeth Stone
- Department of Neuroscience, University of Minnesota Minneapolis, MN, USA ; Institute for Translational Neuroscience, University of Minnesota Minneapolis, MN, USA
| | - Wensheng Lin
- Department of Neuroscience, University of Minnesota Minneapolis, MN, USA ; Institute for Translational Neuroscience, University of Minnesota Minneapolis, MN, USA
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20
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Sypecka J, Ziemka-Nalecz M, Dragun-Szymczak P, Zalewska T. A simple, xeno-free method for oligodendrocyte generation from human neural stem cells derived from umbilical cord: engagement of gelatinases in cell commitment and differentiation. J Tissue Eng Regen Med 2015; 11:1442-1455. [DOI: 10.1002/term.2042] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 02/03/2015] [Accepted: 04/29/2015] [Indexed: 12/31/2022]
Affiliation(s)
- Joanna Sypecka
- Neurorepair Department, Mossakowski Medical Research Centre; Polish Academy of Sciences; Warsaw Poland
| | - Małgorzata Ziemka-Nalecz
- Neurorepair Department, Mossakowski Medical Research Centre; Polish Academy of Sciences; Warsaw Poland
| | - Patrycja Dragun-Szymczak
- Neurorepair Department, Mossakowski Medical Research Centre; Polish Academy of Sciences; Warsaw Poland
| | - Teresa Zalewska
- Neurorepair Department, Mossakowski Medical Research Centre; Polish Academy of Sciences; Warsaw Poland
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21
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Abstract
Myelinated nerve fibers are essential for the rapid propagation of action potentials by saltatory conduction. They form as the result of reciprocal interactions between axons and Schwann cells. Extrinsic signals from the axon, and the extracellular matrix, drive Schwann cells to adopt a myelinating fate, whereas myelination reorganizes the axon for its role in conduction and is essential for its integrity. Here, we review our current understanding of the development, molecular organization, and function of myelinating Schwann cells. Recent findings into the extrinsic signals that drive Schwann cell myelination, their cognate receptors, and the downstream intracellular signaling pathways they activate will be described. Together, these studies provide important new insights into how these pathways converge to activate the transcriptional cascade of myelination and remodel the actin cytoskeleton that is critical for morphogenesis of the myelin sheath.
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Affiliation(s)
- James L Salzer
- Department of Neuroscience and Physiology, New York University Neuroscience Institute, New York University School of Medicine, New York, New York 10016
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22
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Frid K, Einstein O, Friedman-Levi Y, Binyamin O, Ben-Hur T, Gabizon R. Aggregation of MBP in chronic demyelination. Ann Clin Transl Neurol 2015; 2:711-21. [PMID: 26273684 PMCID: PMC4531054 DOI: 10.1002/acn3.207] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 03/26/2015] [Indexed: 12/14/2022] Open
Abstract
Objectives Misfolding of key disease proteins to an insoluble state is associated with most neurodegenerative conditions, such as prion, Parkinson, and Alzheimer’s diseases. In this work, and by studying animal models of multiple sclerosis, we asked whether this is also the case for myelin basic protein (MBP) in the late and neurodegenerative phases of demyelinating diseases. Methods To this effect, we tested whether MBP, an essential myelin component, present prion-like properties in animal models of MS, as is the case for Cuprizone-induced chronic demyelination or chronic phases of Experimental Autoimmune Encephalomyelitis (EAE). Results We show here that while total levels of MBP were not reduced following extensive demyelination, part of these molecules accumulated thereafter as aggregates inside oligodendrocytes or around neuronal cells. In chronic EAE, MBP precipitated concomitantly with Tau, a marker of diverse neurodegenerative conditions, including MS. Most important, analysis of fractions from Triton X-100 floatation gradients suggest that the lipid composition of brain membranes in chronic EAE differs significantly from that of naïve mice, an effect which may relate to oxidative insults and subsequently prevent the appropriate insertion and compaction of new MBP in the myelin sheath, thereby causing its misfolding and aggregation. Interpretation Prion-like aggregation of MBP following chronic demyelination may result from an aberrant lipid composition accompanying this pathological status. Such aggregation of MBP may contribute to neuronal damage that occurs in the progressive phase of MS.
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Affiliation(s)
- Kati Frid
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah University Hospital Jerusalem, 91120, Israel
| | - Ofira Einstein
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah University Hospital Jerusalem, 91120, Israel
| | - Yael Friedman-Levi
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah University Hospital Jerusalem, 91120, Israel
| | - Orli Binyamin
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah University Hospital Jerusalem, 91120, Israel
| | - Tamir Ben-Hur
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah University Hospital Jerusalem, 91120, Israel
| | - Ruth Gabizon
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah University Hospital Jerusalem, 91120, Israel
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Abstract
The leukodystrophies are a heterogeneous group of inherited disorders with broad clinical manifestations and variable pathologic mechanisms. Improved diagnostic methods have allowed identification of the underlying cause of these diseases, facilitating identification of their pathologic mechanisms. Clinicians are now able to prioritize treatment strategies and advance research in therapies for specific disorders. Although only a few of these disorders have well-established treatments or therapies, a number are on the verge of clinical trials. As investigators are able to shift care from symptomatic management of disorders to targeted therapeutics, the unmet therapeutic needs could be reduced for these patients.
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Affiliation(s)
- Guy Helman
- Department of Neurology, Children's National Health System, 111 Michigan Avenue, Northwest, Washington, DC 20010, USA; Center for Genetic Medicine Research, Children's National Health System, 111 Michigan Avenue, Northwest, Washington, DC 20010, USA
| | - Keith Van Haren
- Department of Neurology, Lucile Packard Children's Hospital, Stanford University School of Medicine, 730 Welch Rd, Palo Alto, CA 94304, USA
| | - Maria L Escolar
- Department of Integrated Systems Biology, George Washington University School of Medicine, 2150 Pennsylvania Ave NW, Washington, DC 20037, USA
| | - Adeline Vanderver
- Department of Neurology, Children's National Health System, 111 Michigan Avenue, Northwest, Washington, DC 20010, USA; Center for Genetic Medicine Research, Children's National Health System, 111 Michigan Avenue, Northwest, Washington, DC 20010, USA; Department of Integrated Systems Biology, George Washington University School of Medicine, 2150 Pennsylvania Ave NW, Washington, DC 20037, USA.
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24
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Helman G, Van Haren K, Bonkowsky JL, Bernard G, Pizzino A, Braverman N, Suhr D, Patterson MC, Ali Fatemi S, Leonard J, van der Knaap MS, Back SA, Damiani S, Goldman SA, Takanohashi A, Petryniak M, Rowitch D, Messing A, Wrabetz L, Schiffmann R, Eichler F, Escolar ML, Vanderver A. Disease specific therapies in leukodystrophies and leukoencephalopathies. Mol Genet Metab 2015; 114:527-36. [PMID: 25684057 PMCID: PMC4390468 DOI: 10.1016/j.ymgme.2015.01.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 01/30/2015] [Accepted: 01/30/2015] [Indexed: 10/24/2022]
Abstract
Leukodystrophies are a heterogeneous, often progressive group of disorders manifesting a wide range of symptoms and complications. Most of these disorders have historically had no etiologic or disease specific therapeutic approaches. Recently, a greater understanding of the pathologic mechanisms associated with leukodystrophies has allowed clinicians and researchers to prioritize treatment strategies and advance research in therapies for specific disorders, some of which are on the verge of pilot or Phase I/II clinical trials. This shifts the care of leukodystrophy patients from the management of the complex array of symptoms and sequelae alone to targeted therapeutics. The unmet needs of leukodystrophy patients still remain an overwhelming burden. While the overwhelming consensus is that these disorders collectively are symptomatically treatable, leukodystrophy patients are in need of advanced therapies and if possible, a cure.
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Affiliation(s)
- Guy Helman
- Department of Neurology, Children's National Health System, Washington, DC, USA
| | - Keith Van Haren
- Department of Neurology, Lucile Packard Children's Hospital and Stanford University School of Medicine, Stanford, CA, USA
| | - Joshua L Bonkowsky
- Department of Pediatrics and Neurology, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Genevieve Bernard
- Department of Pediatrics, Montreal Children's Hospital/McGill University Health Center, Montreal, Canada; Department of Neurology and Neurosurgery, Montreal Children's Hospital/McGill University Health Center, Montreal, Canada
| | - Amy Pizzino
- Department of Neurology, Lucile Packard Children's Hospital and Stanford University School of Medicine, Stanford, CA, USA
| | - Nancy Braverman
- Department of Human Genetics and Pediatrics, McGill University and the Montreal Children's Hospital Research Institute, Montreal, Canada
| | | | - Marc C Patterson
- Department of Neurology, Mayo Clinic, Rochester, MN, USA; Department of Pediatrics and Medical Genetics, Mayo Clinic, Rochester, MN, USA
| | - S Ali Fatemi
- The Moser Center for Leukodystrophies and Neurogenetics Service, The Kennedy Krieger Institute, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | | | - Marjo S van der Knaap
- Department of Child Neurology, VU University Medical Center, and Neuroscience Campus Amsterdam, Amsterdam, The Netherlands
| | - Stephen A Back
- Department of Pediatrics and Neurology, Oregon Health and Science University, Portland, OR, USA
| | - Stephen Damiani
- Mission Massimo Foundation Inc., Melbourne, VIC, Australia; Mission Massimo Foundation Inc., Los Angeles, CA, USA
| | - Steven A Goldman
- Center for Translational Neuromedicine and the Department of Neurology of the University of Rochester Medical Center, Rochester, NY, USA
| | - Asako Takanohashi
- Center for Genetic Medicine Research, Children's National Health System, Washington, DC USA
| | - Magdalena Petryniak
- Department of Pediatrics, Papé Family Pediatric Research Institute, Oregon Health and Science University, Portland, OR, USA
| | - David Rowitch
- Department of Pediatrics, University of California, San Francisco, San Francisco, CA, USA; Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA, USA
| | - Albee Messing
- Waisman Center and Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI, USA
| | - Lawrence Wrabetz
- Department of Neurology, Hunter James Kelly Research Institute-HJRKI, University of Buffalo School of Medicine and Biomedical Sciences, Buffalo, NY, USA; Department of Biochemistry, Hunter James Kelly Research Institute-HJRKI, University of Buffalo School of Medicine and Biomedical Sciences, Buffalo, NY, USA
| | - Raphael Schiffmann
- Institute of Metabolic Disease, Baylor Research Institute, Dallas, TX, USA
| | - Florian Eichler
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Maria L Escolar
- Department of Pediatrics, University of Pittsburgh, One Children's Hospital Drive, Pittsburgh, PA, USA
| | - Adeline Vanderver
- Department of Neurology, Children's National Health System, Washington, DC, USA; Center for Genetic Medicine Research, Children's National Health System, Washington, DC USA; Department of Integrated Systems Biology, George Washington University School of Medicine, Washington, DC, USA.
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25
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Tanner DC, Campbell A, O'Banion KM, Noble M, Mayer-Pröschel M. cFLIP is critical for oligodendrocyte protection from inflammation. Cell Death Differ 2015; 22:1489-501. [PMID: 25633192 DOI: 10.1038/cdd.2014.237] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 12/15/2014] [Accepted: 12/17/2014] [Indexed: 11/09/2022] Open
Abstract
Neuroinflammation associated with degenerative central nervous system disease and injury frequently results in oligodendrocyte death. While promoting oligodendrocyte viability is a major therapeutic goal, little is known about protective signaling strategies. We report that in highly purified rat oligodendrocytes, interferon gamma (IFNγ) activates a signaling pathway that protects these cells from tumor necrosis factor alpha (TNFα)-induced cytotoxicity. IFNγ protection requires Jak (Janus kinase) activation, components of the integrated stress response and NF-κB activation. Although NF-κB activation also occurred transiently in the absence of IFNγ and presence of TNFα, this activation was not sufficient to prevent induction of the TNFα-responsive cell death pathway. Genetic inhibition of NF-κB translocation to the nucleus abrogated IFNγ-mediated protection and did not change the cell death induced by TNFα, suggesting that NF-κB activation via IFNγ induces a different set of responses than activation of NF-κB via TNFα. A promising candidate is the NF-κB target cFLIP (cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein), which is protease-deficient caspase homolog that inhibits caspase-3 activation. We show that IFNγ-mediated protection led to upregulation of cFLIP. Overexpression of cFLIP was sufficient for oligodendrocyte protection from TNFα and short hairpin RNA knockdown of cFLIP-abrogated IFNγ -mediated protection. To determine the relevance of our in vitro finding to the more complex in vivo situation, we determined the impact on oligodendrocyte death of regional cFLIP loss of function in a murine model of neuroinflammation. Our data show that downregulation of cFLIP during inflammation leads to death of oligodendrocytes and decrease of myelin in vivo. Taken together, we show that IFNγ-mediated induction of cFLIP expression provides a new mechanism by which this cytokine can protect oligodendrocytes from TNFα-induced cell death.
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Affiliation(s)
- D C Tanner
- Department of Biomedical Genetics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA
| | - A Campbell
- Department of Biomedical Genetics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA
| | - K M O'Banion
- Department of Neurobiology and Anatomy, School of Medicine and Dentistry, University of Rochester, 601 Elmwood Avenue, Box 633, Rochester, NY 14642, USA
| | - M Noble
- Department of Biomedical Genetics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA
| | - M Mayer-Pröschel
- Department of Biomedical Genetics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA
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26
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Ohri SS, Mullins A, Hetman M, Whittemore SR. Inhibition of GADD34, the stress-inducible regulatory subunit of the endoplasmic reticulum stress response, does not enhance functional recovery after spinal cord injury. PLoS One 2014; 9:e109703. [PMID: 25386686 PMCID: PMC4227638 DOI: 10.1371/journal.pone.0109703] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 08/11/2014] [Indexed: 11/30/2022] Open
Abstract
Activation of the endoplasmic reticulum stress response (ERSR) is a hallmark of various pathological diseases and/or traumatic injuries. Restoration of ER homeostasis can contribute to improvement in the functional outcome of these diseases. Using genetic and pharmacological inhibition of the PERK-CHOP arm of the ERSR, we recently demonstrated improvements in hindlimb locomotion after spinal cord injury (SCI) and implicated oligodendrocyte survival as a potential mechanism. Here, we investigated the contribution of stress-inducible PPP1R15A/GADD34, an ERSR signaling effector downstream of CHOP that dephosphorylates eIF2α, in the pathogenesis of SCI. We show that although genetic ablation of GADD34 protects oligodendrocyte precursor cells (OPCs) against ER stress-mediated cell death in vitro and results in differential ERSR attenuation in vivo after SCI, there is no improvement in hindlimb locomotor function. Guanabenz, a FDA approved antihypertensive drug, was recently shown to reduce the burden of misfolded proteins in the ER by directly targeting GADD34. Guanabenz protected OPCs from ER stress-mediated cell death in vitro and attenuated the ERSR in vivo after SCI. However, guanabenz administration failed to rescue the locomotor deficits after SCI. These data suggest that deletion of GADD34 alone is not sufficient to improve functional recovery after SCI.
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Affiliation(s)
- Sujata Saraswat Ohri
- Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, United States of America; Department of Neurological Surgery, University of Louisville, Louisville, Kentucky, United States of America
| | - Ashley Mullins
- Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, United States of America; Department of Neurological Surgery, University of Louisville, Louisville, Kentucky, United States of America
| | - Michal Hetman
- Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, United States of America; Department of Neurological Surgery, University of Louisville, Louisville, Kentucky, United States of America; Department of Pharmacology & Toxicology, University of Louisville, Louisville, Kentucky, United States of America; Department of Anatomical Sciences & Neurobiology, University of Louisville, Louisville, Kentucky, United States of America
| | - Scott R Whittemore
- Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, United States of America; Department of Neurological Surgery, University of Louisville, Louisville, Kentucky, United States of America; Department of Anatomical Sciences & Neurobiology, University of Louisville, Louisville, Kentucky, United States of America
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27
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Torii T, Miyamoto Y, Yamauchi J, Tanoue A. Pelizaeus-Merzbacher disease: cellular pathogenesis and pharmacologic therapy. Pediatr Int 2014; 56:659-66. [PMID: 25040584 DOI: 10.1111/ped.12450] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 06/30/2014] [Accepted: 07/07/2014] [Indexed: 01/18/2023]
Abstract
Pelizaeus-Merzbacher disease (PMD) is a rare leukodystrophy that causes severe dysmyelination in the central nervous system in infancy and early childhood. Many previous studies showed that various proteolipid protein 1 (plp1) mutations, including duplications, point mutations, and deletions, lead to oligodendrocyte dysfunction in patients with PMD. PMD onset and clinical severity range widely, depending on the type of plp1 mutation. Patients with PMD exhibit a delayed mental and physical development phenotype, but specific pharmacological therapy and clinical treatment for PMD are not yet well established. This review describes PMD pathology and establishment of new clinical treatment for PMD. These findings support the development of a new therapy for PMD and these treatments may improve the quality of life in patients with PMD.
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Affiliation(s)
- Tomohiro Torii
- Department of Pharmacology, National Research Institute for Child Health and Development, Tokyo, Japan
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28
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Autophagy promotes oligodendrocyte survival and function following dysmyelination in a long-lived myelin mutant. J Neurosci 2013; 33:8088-100. [PMID: 23637198 DOI: 10.1523/jneurosci.0233-13.2013] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The Long-Evans shaker (les) rat has a mutation in myelin basic protein that results in severe CNS dysmyelination and subsequent demyelination during development. During this time, les oligodendrocytes accumulate cytoplasmic vesicles, including lysosomes and membrane-bound organelles. However, the mechanism and functional relevance behind these oligodendrocyte abnormalities in les have not been investigated. Using high-magnification electron microscopy, we identified the accumulations in les oligodendrocytes as early and late autophagosomes. Additionally, immunohistochemistry and Western blots showed an increase in autophagy markers in les. However, autophagy did not precede the death of les oligodendrocytes. Instead, upregulating autophagy promoted membrane extensions in les oligodendrocytes in vitro. Furthermore, upregulating autophagy in les rats via intermittent fasting increased the proportion of myelinated axons as well as myelin sheath thickness in les and control rats. Overall, this study provides insight into the abnormalities described in les as well as identifying a novel mechanism that promotes the survival and function of oligodendrocytes.
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29
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D'Antonio M, Musner N, Scapin C, Ungaro D, Del Carro U, Ron D, Feltri ML, Wrabetz L. Resetting translational homeostasis restores myelination in Charcot-Marie-Tooth disease type 1B mice. ACTA ACUST UNITED AC 2013; 210:821-38. [PMID: 23547100 PMCID: PMC3620355 DOI: 10.1084/jem.20122005] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Reduction of the CHOP target Gadd34 restores motor function in P0S63del mice with demyelinating neuropathy. P0 glycoprotein is an abundant product of terminal differentiation in myelinating Schwann cells. The mutant P0S63del causes Charcot-Marie-Tooth 1B neuropathy in humans, and a very similar demyelinating neuropathy in transgenic mice. P0S63del is retained in the endoplasmic reticulum of Schwann cells, where it promotes unfolded protein stress and elicits an unfolded protein response (UPR) associated with translational attenuation. Ablation of Chop, a UPR mediator, from S63del mice completely rescues their motor deficit and reduces active demyelination by half. Here, we show that Gadd34 is a detrimental effector of CHOP that reactivates translation too aggressively in myelinating Schwann cells. Genetic or pharmacological limitation of Gadd34 function moderates translational reactivation, improves myelination in S63del nerves, and reduces accumulation of P0S63del in the ER. Resetting translational homeostasis may provide a therapeutic strategy in tissues impaired by misfolded proteins that are synthesized during terminal differentiation.
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Affiliation(s)
- Maurizio D'Antonio
- Division of Genetics and Cell Biology and 2 Division of Neuroscience, San Raffaele Scientific Institute, DIBIT, 20132 Milan, Italy
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30
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Follow-up study of 22 Chinese children with Alexander disease and analysis of parental origin of de novo GFAP mutations. J Hum Genet 2013; 58:183-8. [DOI: 10.1038/jhg.2012.152] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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31
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Numata Y, Morimura T, Nakamura S, Hirano E, Kure S, Goto YI, Inoue K. Depletion of molecular chaperones from the endoplasmic reticulum and fragmentation of the Golgi apparatus associated with pathogenesis in Pelizaeus-Merzbacher disease. J Biol Chem 2013; 288:7451-7466. [PMID: 23344956 DOI: 10.1074/jbc.m112.435388] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Missense mutations in the proteolipid protein 1 (PLP1) gene cause a wide spectrum of hypomyelinating disorders, from mild spastic paraplegia type 2 to severe Pelizaeus-Merzbacher disease (PMD). Mutant PLP1 accumulates in the endoplasmic reticulum (ER) and induces ER stress. However, the link between the clinical severity of PMD and the cellular response induced by mutant PLP1 remains largely unknown. Accumulation of misfolded proteins in the ER generally leads to up-regulation of ER chaperones to alleviate ER stress. Here, we found that expression of the PLP1-A243V mutant, which causes severe disease, depletes some ER chaperones with a KDEL (Lys-Asp-Glu-Leu) motif, in HeLa cells, MO3.13 oligodendrocytic cells, and primary oligodendrocytes. The same PLP1 mutant also induces fragmentation of the Golgi apparatus (GA). These organelle changes are less prominent in cells with milder disease-associated PLP1 mutants. Similar changes are also observed in cells expressing another disease-causing gene that triggers ER stress, as well as in cells treated with brefeldin A, which induces ER stress and GA fragmentation by inhibiting GA to ER trafficking. We also found that mutant PLP1 disturbs localization of the KDEL receptor, which transports the chaperones with the KDEL motif from the GA to the ER. These data show that PLP1 mutants inhibit GA to ER trafficking, which reduces the supply of ER chaperones and induces GA fragmentation. We propose that depletion of ER chaperones and GA fragmentation induced by mutant misfolded proteins contribute to the pathogenesis of inherited ER stress-related diseases and affect the disease severity.
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Affiliation(s)
- Yurika Numata
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), 4-1-1 Ogawahigashi-machi, Kodaira-shi, Tokyo 187-8502; Department of Pediatrics, Tohoku University School of Medicine, 1-1 Seiryomachi, Aobaku, Sendai 980-8574
| | - Toshifumi Morimura
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), 4-1-1 Ogawahigashi-machi, Kodaira-shi, Tokyo 187-8502; Unit for Neurobiology and Therapeutics, Molecular Neuroscience Research Center, Shiga University of Medical Science, Seta-Tsukinowa-cho, Otsu, Shiga 520-2192, Japan
| | - Shoko Nakamura
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), 4-1-1 Ogawahigashi-machi, Kodaira-shi, Tokyo 187-8502
| | - Eriko Hirano
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), 4-1-1 Ogawahigashi-machi, Kodaira-shi, Tokyo 187-8502
| | - Shigeo Kure
- Department of Pediatrics, Tohoku University School of Medicine, 1-1 Seiryomachi, Aobaku, Sendai 980-8574
| | - Yu-Ich Goto
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), 4-1-1 Ogawahigashi-machi, Kodaira-shi, Tokyo 187-8502
| | - Ken Inoue
- Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP), 4-1-1 Ogawahigashi-machi, Kodaira-shi, Tokyo 187-8502.
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Monk KR, Voas MG, Franzini-Armstrong C, Hakkinen IS, Talbot WS. Mutation of sec63 in zebrafish causes defects in myelinated axons and liver pathology. Dis Model Mech 2013; 6:135-45. [PMID: 22864019 PMCID: PMC3529346 DOI: 10.1242/dmm.009217] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 07/19/2012] [Indexed: 12/17/2022] Open
Abstract
Mutations in SEC63 cause polycystic liver disease in humans. Sec63 is a member of the endoplasmic reticulum (ER) translocon machinery, although it is unclear how mutations in SEC63 lead to liver cyst formation in humans. Here, we report the identification and characterization of a zebrafish sec63 mutant, which was discovered in a screen for mutations that affect the development of myelinated axons. Accordingly, we show that disruption of sec63 in zebrafish leads to abnormalities in myelinating glia in both the central and peripheral nervous systems. In the vertebrate nervous system, segments of myelin are separated by the nodes of Ranvier, which are unmyelinated regions of axonal membrane containing a high density of voltage-gated sodium channels. We show that sec63 mutants have morphologically abnormal and reduced numbers of clusters of voltage-gated sodium channels in the spinal cord and along peripheral nerves. Additionally, we observed reduced myelination in both the central and peripheral nervous systems, as well as swollen ER in myelinating glia. Markers of ER stress are upregulated in sec63 mutants. Finally, we show that sec63 mutants develop liver pathology. As in glia, the primary defect, detectable at 5 dpf, is fragmentation and swelling of the ER, indicative of accumulation of proteins in the lumen. At 8 dpf, ER swelling is severe; other pathological features include disrupted bile canaliculi, altered cytoplasmic matrix and accumulation of large lysosomes. Together, our analyses of sec63 mutant zebrafish highlight the possible role of ER stress in polycystic liver disease and suggest that these mutants will serve as a model for understanding the pathophysiology of this disease and other abnormalities involving ER stress.
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Affiliation(s)
- Kelly R. Monk
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
- Department of Developmental Biology, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Matthew G. Voas
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Clara Franzini-Armstrong
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058, USA
| | - Ian S. Hakkinen
- Department of Developmental Biology, Washington University School of Medicine, St Louis, MO 63110, USA
| | - William S. Talbot
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
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33
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Relationship between energy dense diets and white adipose tissue inflammation in metabolic syndrome. Nutr Res 2013; 33:1-11. [DOI: 10.1016/j.nutres.2012.11.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Revised: 10/19/2012] [Accepted: 11/20/2012] [Indexed: 12/25/2022]
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Fledrich R, Stassart RM, Sereda MW. Murine therapeutic models for Charcot-Marie-Tooth (CMT) disease. Br Med Bull 2012; 102:89-113. [PMID: 22551516 DOI: 10.1093/bmb/lds010] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
INTRODUCTION OR BACKGROUND Charcot-Marie-Tooth (CMT) disease represents a broad group of inherited motor and sensory neuropathies which can originate from various genetic aberrations, e.g. mutations, deletions and duplications. SOURCES OF DATA We performed a literature review on murine animal models of CMT disease with regard to experimental therapeutic approaches. Hereby, we focussed on the demyelinating subforms of CMT (CMT1). PubMed items were CMT, animal model, demyelination and therapy. AREAS OF AGREEMENT Patients affected by CMT suffer from slowly progressive, distally pronounced muscle atrophy caused by an axonal loss. The disease severity is highly variable and impairments may result in wheelchair boundness. No therapy is available yet. AREAS OF CONTROVERSY Numerous rodent models for the various CMT subtypes are available today. The selection of the correct animal model for the specific CMT subtype provides an important prerequisite for the successful translation of experimental findings in patients. GROWING POINTS Despite more than 20 years of remarkable progress in CMT research, the disease is still left untreatable. There is a growing number of experimental therapeutic strategies that may be translated into future clinical trials in patients with CMT. AREAS TIMELY FOR DEVELOPING RESEARCH The slow disease progression and insensitive outcome measures hamper clinical therapy trials in CMT. Biomarkers may provide powerful tools to monitor therapeutic efficacy. Recently, we have shown that transcriptional profiling can be utilized to assess and predict the disease severity in a transgenic rat model and in affected humans.
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Affiliation(s)
- Robert Fledrich
- Research Group 'Molecular and Translational Neurology', Department of Neurogenetics, Max-Planck-Institute of Experimental Medicine, Göttingen, Germany
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35
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Groh J, Weis J, Zieger H, Stanley ER, Heuer H, Martini R. Colony-stimulating factor-1 mediates macrophage-related neural damage in a model for Charcot-Marie-Tooth disease type 1X. Brain 2012; 135:88-104. [PMID: 22094537 PMCID: PMC3267979 DOI: 10.1093/brain/awr283] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 08/19/2011] [Accepted: 08/26/2011] [Indexed: 12/22/2022] Open
Abstract
Previous studies in our laboratory have shown that in models for three distinct forms of the inherited and incurable nerve disorder, Charcot-Marie-Tooth neuropathy, low-grade inflammation implicating phagocytosing macrophages mediates demyelination and perturbation of axons. In the present study, we focus on colony-stimulating factor-1, a cytokine implicated in macrophage differentiation, activation and proliferation and fostering neural damage in a model for Charcot-Marie-Tooth neuropathy 1B. By crossbreeding a model for the X-linked form of Charcot-Marie-Tooth neuropathy with osteopetrotic mice, a spontaneous null mutant for colony-stimulating factor-1, we demonstrate a robust and persistent amelioration of demyelination and axon perturbation. Furthermore, functionally important domains of the peripheral nervous system, such as juxtaparanodes and presynaptic terminals, were preserved in the absence of colony-stimulating factor-1-dependent macrophage activation. As opposed to other Schwann cell-derived cytokines, colony-stimulating factor-1 is expressed by endoneurial fibroblasts, as revealed by in situ hybridization, immunocytochemistry and detection of β-galactosidase expression driven by the colony-stimulating factor-1 promoter. By both light and electron microscopic studies, we detected extended cell-cell contacts between the colony-stimulating factor-1-expressing fibroblasts and endoneurial macrophages as a putative prerequisite for the effective and constant activation of macrophages by fibroblasts in the chronically diseased nerve. Interestingly, in human biopsies from patients with Charcot-Marie-Tooth type 1, we also found frequent cell-cell contacts between macrophages and endoneurial fibroblasts and identified the latter as main source for colony-stimulating factor-1. Therefore, our study provides strong evidence for a similarly pathogenic role of colony-stimulating factor-1 in genetically mediated demyelination in mice and Charcot-Marie-Tooth type 1 disease in humans. Thus, colony-stimulating factor-1 or its cognate receptor are promising target molecules for treating the detrimental, low-grade inflammation of several inherited neuropathies in humans.
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Affiliation(s)
- Janos Groh
- Department of Neurology, Section of Developmental Neurobiology, University of Würzburg, Josef-Schneiderstr. 11, 97080 Würzburg, Germany
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Groh J, Heinl K, Kohl B, Wessig C, Greeske J, Fischer S, Martini R. Attenuation of MCP-1/CCL2 expression ameliorates neuropathy in a mouse model for Charcot-Marie-Tooth 1X. Hum Mol Genet 2010; 19:3530-43. [PMID: 20591826 DOI: 10.1093/hmg/ddq269] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The chemokine monocyte chemoattractant protein-1 (MCP-1/CCL2) has been previously shown to be an important mediator of macrophage-related neural damage in models of two distinct inherited neuropathies, Charcot-Marie-Tooth (CMT) 1A and 1B. In mice deficient in the gap junction protein connexin 32 (Cx32def), an established model for the X-chromosome-linked dominant form of CMT (CMT1X), we investigated the role of the chemokine in macrophage immigration and neural damage by crossbreeding the Cx32def mice with MCP-1 knockout mutants. In Cx32def mutants typically expressing increased levels of MCP-1, macrophage numbers were strongly elevated, caused by an MCP-1-mediated influx of haematogenous macrophages. Curiously, the complete genetic deletion of MCP-1 did not cause reduced macrophage numbers in the nerves due to compensatory proliferation of resident macrophages. In contrast, and as already seen in other CMT models, heterozygous deletion of MCP-1 led to reduced numbers of phagocytosing macrophages and an alleviation of demyelination. Whereas alleviated demyelination was transient, axonal damage was persistently improved and even robust axonal sprouting was detectable at 12 months. Other axon-related features were alleviated electrophysiological parameters, reduced muscle denervation and atrophy, and increased muscle strength. Similar to models for CMT1A and CMT1B, we identified MEK-ERK signalling as mediating MCP-1 expression in Cx32-deficient Schwann cells. Blocking this pathway by the inhibitor CI-1040 caused reduced MCP-1 expression, attenuation of macrophage increase and amelioration of myelin- and axon-related alterations. Thus, attenuation of MCP-1 upregulation by inhibiting ERK phosphorylation might be a promising approach to treat CMT1X and other so far untreatable inherited peripheral neuropathies in humans.
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Affiliation(s)
- Janos Groh
- Department of Neurology, University of Wuerzburg, Wuerzburg, Germany
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Gow A, Wrabetz L. CHOP and the endoplasmic reticulum stress response in myelinating glia. Curr Opin Neurobiol 2009; 19:505-10. [PMID: 19744850 DOI: 10.1016/j.conb.2009.08.007] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Revised: 08/24/2009] [Accepted: 08/24/2009] [Indexed: 10/20/2022]
Abstract
The unfolded protein response (UPR) comprises kinase signaling and transcription factor activation cascades delineated over the past 20 years. Most studies conclude that this stress response is adaptive but, nevertheless, includes maladaptive programs involving CHOP expression that drives cell-autonomous apoptosis. Herein, we highlight several studies of UPR diseases involving myelinating glia of the central and peripheral nervous systems that do not support a primary role for CHOP in apoptosis. In oligodendrocytes, CHOP expression apparently protects against death whereas in Schwann cells, CHOP promotes demyelination in the absence of cell death. Together, these studies demonstrate that CHOP should be viewed more broadly as a cell-specific and context-specific mediator of adaptive or maladaptive responses to stress rather than a proapoptotic transcription factor.
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Affiliation(s)
- Alexander Gow
- Wayne State University, 3217 Scott Hall, 540 E Canfield, Detroit, MI, USA.
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