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Prior R, Silva A, Vangansewinkel T, Idkowiak J, Tharkeshwar AK, Hellings TP, Michailidou I, Vreijling J, Loos M, Koopmans B, Vlek N, Agaser C, Kuipers TB, Michiels C, Rossaert E, Verschoren S, Vermeire W, de Laat V, Dehairs J, Eggermont K, van den Biggelaar D, Bademosi AT, Meunier FA, vandeVen M, Van Damme P, Mei H, Swinnen JV, Lambrichts I, Baas F, Fluiter K, Wolfs E, Van Den Bosch L. PMP22 duplication dysregulates lipid homeostasis and plasma membrane organization in developing human Schwann cells. Brain 2024; 147:3113-3130. [PMID: 38743588 PMCID: PMC11370802 DOI: 10.1093/brain/awae158] [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: 12/06/2023] [Revised: 04/08/2024] [Accepted: 04/19/2024] [Indexed: 05/16/2024] Open
Abstract
Charcot-Marie-Tooth disease type 1A (CMT1A) is the most common inherited peripheral neuropathy caused by a 1.5 Mb tandem duplication of chromosome 17 harbouring the PMP22 gene. This dose-dependent overexpression of PMP22 results in disrupted Schwann cell myelination of peripheral nerves. To obtain better insights into the underlying pathogenic mechanisms in CMT1A, we investigated the role of PMP22 duplication in cellular homeostasis in CMT1A mouse models and in patient-derived induced pluripotent stem cells differentiated into Schwann cell precursors (iPSC-SCPs). We performed lipidomic profiling and bulk RNA sequencing (RNA-seq) on sciatic nerves of two developing CMT1A mouse models and on CMT1A patient-derived iPSC-SCPs. For the sciatic nerves of the CMT1A mice, cholesterol and lipid metabolism was downregulated in a dose-dependent manner throughout development. For the CMT1A iPSC-SCPs, transcriptional analysis unveiled a strong suppression of genes related to autophagy and lipid metabolism. Gene ontology enrichment analysis identified disturbances in pathways related to plasma membrane components and cell receptor signalling. Lipidomic analysis confirmed the severe dysregulation in plasma membrane lipids, particularly sphingolipids, in CMT1A iPSC-SCPs. Furthermore, we identified reduced lipid raft dynamics, disturbed plasma membrane fluidity and impaired cholesterol incorporation and storage, all of which could result from altered lipid storage homeostasis in the patient-derived CMT1A iPSC-SCPs. Importantly, this phenotype could be rescued by stimulating autophagy and lipolysis. We conclude that PMP22 duplication disturbs intracellular lipid storage and leads to a more disordered plasma membrane owing to an alteration in the lipid composition, which might ultimately lead to impaired axo-glial interactions. Moreover, targeting lipid handling and metabolism could hold promise for the treatment of patients with CMT1A.
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Affiliation(s)
- Robert Prior
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven—University of Leuven, Leuven 3000, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
- Department of Ophthalmology, Medical Faculty, University of Bonn, Bonn 53127, Germany
| | - Alessio Silva
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven—University of Leuven, Leuven 3000, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
| | - Tim Vangansewinkel
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
- UHasselt—Hasselt University, Biomedical Research Institute, Diepenbeek 3590, Belgium
| | - Jakub Idkowiak
- Laboratory of Lipid Metabolism and Cancer, Department of Oncology, KU Leuven, Leuven 3000, Belgium
- Department of Analytical Chemistry, Faculty of Chemical Technology, University of Pardubice, Pardubice 532 10, Czech Republic
| | - Arun Kumar Tharkeshwar
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven—University of Leuven, Leuven 3000, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
| | - Tom P Hellings
- Department of Clinical Genetics, Leiden University Medical Center, Leiden 2333 ZA, The Netherlands
| | - Iliana Michailidou
- Department of Clinical Genetics, Leiden University Medical Center, Leiden 2333 ZA, The Netherlands
| | - Jeroen Vreijling
- Department of Clinical Genetics, Leiden University Medical Center, Leiden 2333 ZA, The Netherlands
| | - Maarten Loos
- InnoSer Nederland B.V., 2333 CK Leiden, The Netherlands
| | | | - Nina Vlek
- InnoSer Nederland B.V., 2333 CK Leiden, The Netherlands
| | - Cedrick Agaser
- Department of Biomedical Data Sciences, Sequencing Analysis Support Core, Leiden University Medical Center, Leiden 2333 ZA, The Netherlands
| | - Thomas B Kuipers
- Department of Biomedical Data Sciences, Sequencing Analysis Support Core, Leiden University Medical Center, Leiden 2333 ZA, The Netherlands
| | - Christine Michiels
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven—University of Leuven, Leuven 3000, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
| | - Elisabeth Rossaert
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven—University of Leuven, Leuven 3000, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
| | - Stijn Verschoren
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven—University of Leuven, Leuven 3000, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
| | - Wendy Vermeire
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven—University of Leuven, Leuven 3000, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
| | - Vincent de Laat
- Laboratory of Lipid Metabolism and Cancer, Department of Oncology, KU Leuven, Leuven 3000, Belgium
| | - Jonas Dehairs
- Laboratory of Lipid Metabolism and Cancer, Department of Oncology, KU Leuven, Leuven 3000, Belgium
| | - Kristel Eggermont
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven—University of Leuven, Leuven 3000, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
| | - Diede van den Biggelaar
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven—University of Leuven, Leuven 3000, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
| | - Adekunle T Bademosi
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Frederic A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Martin vandeVen
- UHasselt—Hasselt University, Biomedical Research Institute, Diepenbeek 3590, Belgium
| | - Philip Van Damme
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven—University of Leuven, Leuven 3000, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
- Department of Neurology, University Hospitals Leuven, Leuven 3000, Belgium
| | - Hailiang Mei
- Department of Biomedical Data Sciences, Sequencing Analysis Support Core, Leiden University Medical Center, Leiden 2333 ZA, The Netherlands
| | - Johannes V Swinnen
- Laboratory of Lipid Metabolism and Cancer, Department of Oncology, KU Leuven, Leuven 3000, Belgium
| | - Ivo Lambrichts
- UHasselt—Hasselt University, Biomedical Research Institute, Diepenbeek 3590, Belgium
| | - Frank Baas
- Department of Clinical Genetics, Leiden University Medical Center, Leiden 2333 ZA, The Netherlands
| | - Kees Fluiter
- Department of Clinical Genetics, Leiden University Medical Center, Leiden 2333 ZA, The Netherlands
| | - Esther Wolfs
- UHasselt—Hasselt University, Biomedical Research Institute, Diepenbeek 3590, Belgium
| | - Ludo Van Den Bosch
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven—University of Leuven, Leuven 3000, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Leuven 3000, Belgium
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2
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Moore SM, Jeong E, Zahid M, Gawron J, Arora S, Belin S, Sim F, Poitelon Y, Feltri ML. Loss of YAP in Schwann cells improves HNPP pathophysiology. Glia 2024. [PMID: 38989661 DOI: 10.1002/glia.24592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 05/29/2024] [Accepted: 06/29/2024] [Indexed: 07/12/2024]
Abstract
Rapid nerve conduction in the peripheral nervous system (PNS) is facilitated by the multilamellar myelin sheath encasing many axons of peripheral nerves. Charcot-Marie-Tooth type 1A (CMT1A), and hereditary neuropathy with liability to pressure palsy (HNPP) are common demyelinating inherited peripheral neuropathies and are caused by mutations in the peripheral myelin protein 22 (PMP22) gene. Duplication of PMP22 leads to its overexpression and causes CMT1A, while its deletion results in PMP22 under expression and causes HNPP. Here, we investigated novel targets for modulating the protein level of PMP22 in HNPP. We found that genetic attenuation of the transcriptional coactivator Yap in Schwann cells reduces p-TAZ levels, increased TAZ activity, and increases PMP22 in peripheral nerves. Based on these findings, we ablated Yap alleles in Schwann cells of the Pmp22-haploinsufficient mouse model of HNPP and identified fewer tomacula on morphological assessment and improved nerve conduction in peripheral nerves. These findings suggest YAP modulation may be a new avenue for treatment of HNPP.
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Affiliation(s)
- Seth M Moore
- Department of Biochemistry, University at Buffalo, Buffalo, New York, USA
- Institute for Myelin and Glia Exploration, Jacob's School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA
| | - Eunbi Jeong
- Department of Biochemistry, University at Buffalo, Buffalo, New York, USA
- Institute for Myelin and Glia Exploration, Jacob's School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA
| | - Muhammad Zahid
- Institute for Myelin and Glia Exploration, Jacob's School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA
- Department of Biological Sciences, University at Buffalo, Buffalo, New York, USA
| | - Joseph Gawron
- Department of Biochemistry, University at Buffalo, Buffalo, New York, USA
- Institute for Myelin and Glia Exploration, Jacob's School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA
| | - Simar Arora
- Albany Medical College, Department of Neuroscience and Experimental Therapeutics, Albany, New York, USA
| | - Sophie Belin
- Albany Medical College, Department of Neuroscience and Experimental Therapeutics, Albany, New York, USA
| | - Fraser Sim
- Department of Pharmacology and Toxicology, University at Buffalo, Buffalo, New York, USA
| | - Yannick Poitelon
- Albany Medical College, Department of Neuroscience and Experimental Therapeutics, Albany, New York, USA
| | - M Laura Feltri
- Department of Biochemistry, University at Buffalo, Buffalo, New York, USA
- Institute for Myelin and Glia Exploration, Jacob's School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA
- Department of Neurology, University at Buffalo, Buffalo, New York, USA
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Stefanski KM, Li GC, Marinko JT, Carter BD, Samuels DC, Sanders CR. How T118M peripheral myelin protein 22 predisposes humans to Charcot-Marie-Tooth disease. J Biol Chem 2023; 299:102839. [PMID: 36581210 PMCID: PMC9860121 DOI: 10.1016/j.jbc.2022.102839] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 12/19/2022] [Accepted: 12/21/2022] [Indexed: 12/27/2022] Open
Abstract
Data from gnomAD indicate that a missense mutation encoding the T118M variation in human peripheral myelin protein 22 (PMP22) is found in roughly one of every 75 genomes of western European lineage (1:120 in the overall human population). It is unusual among PMP22 variants that cause Charcot-Marie-Tooth (CMT) disease in that it is not 100% penetrant. Here, we conducted cellular and biophysical studies to determine why T118M PMP22 predisposes humans to CMT, but with only incomplete penetrance. We found that T118M PMP22 is prone to mistraffic but differs even from the WT protein in that increased expression levels do not result in a reduction in trafficking efficiency. Moreover, the T118M mutant exhibits a reduced tendency to form large intracellular aggregates relative to other disease mutants and even WT PMP22. NMR spectroscopy revealed that the structure and dynamics of T118M PMP22 resembled those of WT. These results show that the main consequence of T118M PMP22 in WT/T118M heterozygous individuals is a reduction in surface-trafficked PMP22, unaccompanied by formation of toxic intracellular aggregates. This explains the incomplete disease penetrance and the mild neuropathy observed for WT/T118M CMT cases. We also analyzed BioVU, a biobank linked to deidentified electronic medical records, and found a statistically robust association of the T118M mutation with the occurrence of long and/or repeated episodes of carpal tunnel syndrome. Collectively, our results illuminate the cellular effects of the T118M PMP22 variation leading to CMT disease and indicate a second disorder for which it is a risk factor.
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Affiliation(s)
- Katherine M Stefanski
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Geoffrey C Li
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Justin T Marinko
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Bruce D Carter
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - David C Samuels
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
| | - Charles R Sanders
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
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Prior R, Verschoren S, Vints K, Jaspers T, Rossaert E, Klingl YE, Silva A, Hersmus N, Van Damme P, Van Den Bosch L. HDAC3 Inhibition Stimulates Myelination in a CMT1A Mouse Model. Mol Neurobiol 2022; 59:3414-3430. [PMID: 35320455 PMCID: PMC9148289 DOI: 10.1007/s12035-022-02782-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 02/07/2022] [Indexed: 12/02/2022]
Abstract
Charcot-Marie-Tooth disease (CMT) is the most common inherited peripheral neuropathy, with currently no effective treatment or cure. CMT1A is caused by a duplication of the PMP22 gene, which leads to Schwann cell differentiation defects and dysmyelination of the peripheral nerves. The epigenetic regulator histone deacetylase 3 (HDAC3) has been shown to negatively regulate myelination as well as its associated signaling pathways, PI3K-AKT and MAPK-ERK. We showed that these signaling pathways are indeed downregulated in the C3-PMP22 mouse model, similar to what has been shown in the CMT1A rat model. We confirmed that early postnatal defects are present in the peripheral nerves of the C3-PMP22 mouse model, which led to a progressive reduction in axon caliber size and myelination. The aim of this study was to investigate whether pharmacological HDAC3 inhibition could be a valuable therapeutic approach for this CMT1A mouse model. We demonstrated that early treatment of CMT1A mice with the selective HDAC3 inhibitor RGFP966 increased myelination and myelin g-ratios, which was associated with improved electrophysiological recordings. However, a high dose of RGFP966 caused a decline in rotarod performance and a decline in overall grip strength. Additionally, macrophage presence in peripheral nerves was increased in RGFP966 treated CMT1A mice. We conclude that HDAC3 does not only play a role in regulating myelination but is also important in the neuroimmune modulation. Overall, our results indicate that correct dosing of HDAC3 inhibitors is of crucial importance if translated to a clinical setting for demyelinating forms of CMT or other neurological disorders.
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Affiliation(s)
- Robert Prior
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven - University of Leuven, B-3000, Leuven, Belgium.
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Campus Gasthuisberg O&N5, Herestraat 49, box 602, B-3000, Leuven, Belgium.
| | - Stijn Verschoren
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven - University of Leuven, B-3000, Leuven, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Campus Gasthuisberg O&N5, Herestraat 49, box 602, B-3000, Leuven, Belgium
| | - Katlijn Vints
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven - University of Leuven, B-3000, Leuven, Belgium
- Electron Microscopy Platform & VIB BioImaging Core, Herestraat 49, B-3000, Leuven, Belgium
| | - Tom Jaspers
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven - University of Leuven, B-3000, Leuven, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Campus Gasthuisberg O&N5, Herestraat 49, box 602, B-3000, Leuven, Belgium
| | - Elisabeth Rossaert
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven - University of Leuven, B-3000, Leuven, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Campus Gasthuisberg O&N5, Herestraat 49, box 602, B-3000, Leuven, Belgium
| | - Yvonne E Klingl
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven - University of Leuven, B-3000, Leuven, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Campus Gasthuisberg O&N5, Herestraat 49, box 602, B-3000, Leuven, Belgium
| | - Alessio Silva
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven - University of Leuven, B-3000, Leuven, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Campus Gasthuisberg O&N5, Herestraat 49, box 602, B-3000, Leuven, Belgium
| | - Nicole Hersmus
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven - University of Leuven, B-3000, Leuven, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Campus Gasthuisberg O&N5, Herestraat 49, box 602, B-3000, Leuven, Belgium
| | - Philip Van Damme
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven - University of Leuven, B-3000, Leuven, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Campus Gasthuisberg O&N5, Herestraat 49, box 602, B-3000, Leuven, Belgium
- Neurology, University Hospitals Leuven, B-3000, Leuven, Belgium
| | - Ludo Van Den Bosch
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI), KU Leuven - University of Leuven, B-3000, Leuven, Belgium.
- Laboratory of Neurobiology, VIB, Center for Brain & Disease Research, Campus Gasthuisberg O&N5, Herestraat 49, box 602, B-3000, Leuven, Belgium.
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5
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Pantera H, Hu B, Moiseev D, Dunham C, Rashid J, Moran JJ, Krentz K, Rubinstein CD, Won S, Li J, Svaren J. Pmp22 super-enhancer deletion causes tomacula formation and conduction block in peripheral nerves. Hum Mol Genet 2020; 29:1689-1699. [PMID: 32356557 PMCID: PMC7322568 DOI: 10.1093/hmg/ddaa082] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 04/07/2020] [Accepted: 04/24/2020] [Indexed: 11/12/2022] Open
Abstract
Copy number variation of the peripheral nerve myelin gene Peripheral Myelin Protein 22 (PMP22) causes multiple forms of inherited peripheral neuropathy. The duplication of a 1.4 Mb segment surrounding this gene in chromosome 17p12 (c17p12) causes the most common form of Charcot-Marie-Tooth disease type 1A, whereas the reciprocal deletion of this gene causes a separate neuropathy termed hereditary neuropathy with liability to pressure palsies (HNPP). PMP22 is robustly induced in Schwann cells in early postnatal development, and several transcription factors and their cognate regulatory elements have been implicated in coordinating the gene's proper expression. We previously found that a distal super-enhancer domain was important for Pmp22 expression in vitro, with particular impact on a Schwann cell-specific alternative promoter. Here, we investigate the consequences of deleting this super-enhancer in vivo. We find that loss of the super-enhancer in mice reduces Pmp22 expression throughout development and into adulthood, with greater impact on the Schwann cell-specific promoter. Additionally, these mice display tomacula formed by excessive myelin folding, a pathological hallmark of HNPP, as have been previously observed in heterozygous Pmp22 mice as well as sural biopsies from patients with HNPP. Our findings demonstrate a mechanism by which smaller copy number variations, not including the Pmp22 gene, are sufficient to reduce gene expression and phenocopy a peripheral neuropathy caused by the HNPP-associated deletion encompassing PMP22.
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Affiliation(s)
- Harrison Pantera
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA
- Molecular and Cellular Pharmacology Graduate Program, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Bo Hu
- Department of Neurology and Translational Neuroscience Initiative, Wayne State University School of Medicine, Detroit, MI 48202, USA
| | - Daniel Moiseev
- Department of Neurology and Translational Neuroscience Initiative, Wayne State University School of Medicine, Detroit, MI 48202, USA
| | - Chris Dunham
- Department of Neurology and Translational Neuroscience Initiative, Wayne State University School of Medicine, Detroit, MI 48202, USA
| | - Jibraan Rashid
- Department of Neurology and Translational Neuroscience Initiative, Wayne State University School of Medicine, Detroit, MI 48202, USA
| | - John J Moran
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Kathleen Krentz
- Biotechnology Center, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - C Dustin Rubinstein
- Biotechnology Center, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Seongsik Won
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Jun Li
- Department of Neurology and Translational Neuroscience Initiative, Wayne State University School of Medicine, Detroit, MI 48202, USA
| | - John Svaren
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53705, USA
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6
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Zhou Y, Borchelt D, Bauson JC, Fazio S, Miles JR, Tavori H, Notterpek L. Subcellular diversion of cholesterol by gain- and loss-of-function mutations in PMP22. Glia 2020; 68:2300-2315. [PMID: 32511821 DOI: 10.1002/glia.23840] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2019] [Revised: 03/22/2020] [Accepted: 04/24/2020] [Indexed: 12/13/2022]
Abstract
Abnormalities of the peripheral myelin protein 22 (PMP22) gene, including duplication, deletion and point mutations are a major culprit in Type 1 Charcot-Marie-Tooth (CMT) diseases. The complete absence of PMP22 alters cholesterol metabolism in Schwann cells, which likely contributes to myelination deficits. Here, we examined the subcellular trafficking of cholesterol in distinct models of PMP22-linked neuropathies. In Schwann cells from homozygous Trembler J (TrJ) mice carrying a Leu16Pro mutation, cholesterol was retained with TrJ-PMP22 in the Golgi, alongside a corresponding reduction in its plasma membrane level. PMP22 overexpression, which models CMT1A caused by gene duplication, triggered cholesterol sequestration to lysosomes, and reduced ATP-binding cassette transporter-dependent cholesterol efflux. Conversely, lysosomal targeting of cholesterol by U18666A treatment increased wild type (WT)-PMP22 levels in lysosomes. Mutagenesis of a cholesterol recognition motif, or CRAC domain, in human PMP22 lead to increased levels of PMP22 in the ER and Golgi compartments, along with higher cytosolic, and lower membrane-associated cholesterol. Importantly, cholesterol trafficking defects observed in PMP22-deficient Schwann cells were rescued by WT but not CRAC-mutant-PMP22. We also observed that myelination deficits in dorsal root ganglia explants from heterozygous PMP22-deficient mice were improved by cholesterol supplementation. Collectively, these findings indicate that PMP22 is critical in cholesterol metabolism, and this mechanism is likely a contributing factor in PMP22-linked hereditary neuropathies. Our results provide a basis for understanding how altered expression of PMP22 impacts cholesterol metabolism.
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Affiliation(s)
- Ye Zhou
- Department of Neuroscience, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA
| | - David Borchelt
- Department of Neuroscience, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA
| | - Jodi C Bauson
- Department of Neuroscience, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA
| | - Sergio Fazio
- Department of Medicine, Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Oregon, Portland, USA
| | - Joshua R Miles
- Department of Medicine, Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Oregon, Portland, USA
| | - Hagai Tavori
- Department of Medicine, Knight Cardiovascular Institute, Center for Preventive Cardiology, Oregon Health and Science University, Oregon, Portland, USA
| | - Lucia Notterpek
- Department of Neuroscience, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA.,Department of Neurology, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA
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7
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Zambon AA, Pitt M, Laurà M, Polke JM, Reilly MM, Muntoni F. A novel homozygous variant extending the peripheral myelin protein 22 by 9 amino acids causes early‐onset
Charcot‐Marie‐Tooth
disease with predominant severe sensory ataxia. J Peripher Nerv Syst 2020; 25:303-307. [DOI: 10.1111/jns.12386] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 05/10/2020] [Accepted: 05/11/2020] [Indexed: 01/25/2023]
Affiliation(s)
- Alberto A. Zambon
- Dubowitz Neuromuscular CentreUCL Great Ormond Street Institute of Child Health & Great Ormond Street Hospital London UK
| | - Matthew Pitt
- Department of Clinical NeurophysiologyGreat Ormond Street Hospital for Children NHS Foundation Trust London UK
| | - Matilde Laurà
- MRC Centre for Neuromuscular DiseasesNational Hospital for Neurology and Neurosurgery and UCL Queen Square Institute of Neurology London UK
| | - James M. Polke
- MRC Centre for Neuromuscular DiseasesNational Hospital for Neurology and Neurosurgery and UCL Queen Square Institute of Neurology London UK
| | - Mary M. Reilly
- MRC Centre for Neuromuscular DiseasesNational Hospital for Neurology and Neurosurgery and UCL Queen Square Institute of Neurology London UK
| | - Francesco Muntoni
- Dubowitz Neuromuscular CentreUCL Great Ormond Street Institute of Child Health & Great Ormond Street Hospital London UK
- NIHR Great Ormond Street Hospital Biomedical Research Centre, Great Ormond Street Institute of Child HealthUniversity College London & Great Ormond Street Hospital Trust London UK
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8
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Chittoor-Vinod VG, Bazick H, Todd AG, Falk D, Morelli KH, Burgess RW, Foster TC, Notterpek L. HSP90 Inhibitor, NVP-AUY922, Improves Myelination in Vitro and Supports the Maintenance of Myelinated Axons in Neuropathic Mice. ACS Chem Neurosci 2019; 10:2890-2902. [PMID: 31017387 PMCID: PMC6588339 DOI: 10.1021/acschemneuro.9b00105] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
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Hereditary
demyelinating neuropathies linked to peripheral myelin
protein 22 (PMP22) involve the disruption of normal protein trafficking
and are therefore relevant targets for chaperone therapy. Using a
small molecule HSP90 inhibitor, EC137, in cell culture models, we
previously validated the chaperone pathway as a viable target for
therapy development. Here, we tested five commercially available inhibitors
of HSP90 and identified BIIB021 and AUY922 to support Schwann cell
viability and enhance chaperone expression. AUY922 showed higher efficacy,
compared to BIIB021, in enhancing myelin synthesis in dorsal root
ganglion explant cultures from neuropathic mice. For in vivo testing,
we randomly assigned 2–3 month old C22 and 6 week old Trembler
J (TrJ) mice to receive two weekly injections of either vehicle or
AUY922 (2 mg/kg). By the intraperitoneal (i.p.) route, the drug was
well-tolerated by all mice over the 5 month long study, without influence
on body weight or general grooming behavior. AUY922 improved the maintenance
of myelinated nerves of both neuropathic models and attenuated the
decline in rotarod performance and peak muscle force production in
C22 mice. These studies highlight the significance of proteostasis
in neuromuscular function and further validate the HSP90 pathway as
a therapeutic target for hereditary neuropathies.
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Affiliation(s)
- Vinita G. Chittoor-Vinod
- Departments of Neuroscience and Neurology, College of Medicine, McKnight Brain Institute, 1149 Newell Drive, Box 100244, Gainesville, Florida 32610-0244, United States
| | - Hannah Bazick
- Departments of Neuroscience and Neurology, College of Medicine, McKnight Brain Institute, 1149 Newell Drive, Box 100244, Gainesville, Florida 32610-0244, United States
| | - Adrian G. Todd
- Department of Pediatrics, Powell Gene Therapy Center, University of Florida, Gainesville, Florida 32611, United States
| | - Darin Falk
- Department of Pediatrics, Powell Gene Therapy Center, University of Florida, Gainesville, Florida 32611, United States
| | - Kathryn H. Morelli
- The Graduate School of Biomedical Science and Engineering, University of Maine, Orono, Maine 04469, United States
- The Jackson Laboratory, Bar Harbor, Maine 04609, United States
| | - Robert W. Burgess
- The Graduate School of Biomedical Science and Engineering, University of Maine, Orono, Maine 04469, United States
- The Jackson Laboratory, Bar Harbor, Maine 04609, United States
| | - Thomas C. Foster
- Departments of Neuroscience and Neurology, College of Medicine, McKnight Brain Institute, 1149 Newell Drive, Box 100244, Gainesville, Florida 32610-0244, United States
| | - Lucia Notterpek
- Departments of Neuroscience and Neurology, College of Medicine, McKnight Brain Institute, 1149 Newell Drive, Box 100244, Gainesville, Florida 32610-0244, United States
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9
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Jouaud M, Mathis S, Richard L, Lia AS, Magy L, Vallat JM. Rodent models with expression of PMP22: Relevance to dysmyelinating CMT and HNPP. J Neurol Sci 2019; 398:79-90. [PMID: 30685714 DOI: 10.1016/j.jns.2019.01.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 12/26/2018] [Accepted: 01/16/2019] [Indexed: 02/02/2023]
Abstract
BACKGROUND Charcot-Marie-Tooth diseases (CMT) are due to abnormalities of many genes, the most frequent being linked to PMP22 (Peripheral Myelin Protein 22). In the past, only spontaneous genetic anomalies occurring in mouse mutants such as Trembler (Tr) mice were available; more recently, several rodent models have been generated for exploration of the pathophysiological mechanisms underlying these neuropathies. METHODS Based on the personal experience of our team, we describe here the pathological hallmarks of most of these animal models and compare them to the pathological features observed in some CMT patient nerves (CMT types 1A and E; hereditary neuropathy with liability to pressure palsies, HNPP). RESULTS We describe clinical data and detailed pathological analysis mainly by electron microscopy of the sciatic nerves of these animal models conducted in our laboratory; lesions of PMP22 deficient animals (KO and mutated PMP22) and PMP22 overexpressed models are described and compared to ultrastructural anomalies of nerve biopsies from CMT patients due to PMP22 gene anomalies. It is of note that while there are some similarities, there are also significant differences between the lesions in animal models and human cases. Such observations highlight the complex roles played by PMP22 in nerve development. CONCLUSION It should be borne in mind that we require additional correlations between animal models of hereditary neuropathies and CMT patients to rationalize the development of efficient drugs.
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Affiliation(s)
- Maxime Jouaud
- Equipe d'accueil 6309, Maintenance myélinique et Neuropathies périphériques, University of Limoges, 2 rue du Docteur Raymond Marcland, 87000 Limoges, France
| | - Stéphane Mathis
- Department of Neurology, Nerve-Muscle Unit, CHU Bordeaux (Pellegrin University Hospital), place Amélie Raba-Léon, 33000 Bordeaux, France; National Reference Center 'maladies neuromusculaires du Grand Sud-ouest', CHU Bordeaux (Pellegrin University Hospital), place Amélie Raba-Léon, 33000 Bordeaux, France
| | - Laurence Richard
- Department of Neurology, CHU Limoges, Dupuytren University Hospital, 2 avenue Martin Luther King, 87042 Limoges, France; National Reference Center for 'Rare Peripheral Neuropathies', CHU Limoges, Dupuytren University Hospital, 2 avenue Martin Luther King, 87042 Limoges, France
| | - Anne-Sophie Lia
- Equipe d'accueil 6309, Maintenance myélinique et Neuropathies périphériques, University of Limoges, 2 rue du Docteur Raymond Marcland, 87000 Limoges, France; Department of Biochemistry and Molecular Genetics, CHU Limoges, Dupuytren University Hospital, 2 avenue Martin Luther King, 87042 Limoges, France
| | - Laurent Magy
- Department of Neurology, CHU Limoges, Dupuytren University Hospital, 2 avenue Martin Luther King, 87042 Limoges, France; National Reference Center for 'Rare Peripheral Neuropathies', CHU Limoges, Dupuytren University Hospital, 2 avenue Martin Luther King, 87042 Limoges, France
| | - Jean-Michel Vallat
- Department of Neurology, CHU Limoges, Dupuytren University Hospital, 2 avenue Martin Luther King, 87042 Limoges, France; National Reference Center for 'Rare Peripheral Neuropathies', CHU Limoges, Dupuytren University Hospital, 2 avenue Martin Luther King, 87042 Limoges, France.
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10
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Sinha AA, Sajda T. The Evolving Story of Autoantibodies in Pemphigus Vulgaris: Development of the "Super Compensation Hypothesis". Front Med (Lausanne) 2018; 5:218. [PMID: 30155465 PMCID: PMC6102394 DOI: 10.3389/fmed.2018.00218] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Accepted: 07/16/2018] [Indexed: 12/11/2022] Open
Abstract
Emerging data and innovative technologies are re-shaping our understanding of the scope and specificity of the autoimmune response in Pemphigus vulgaris (PV), a prototypical humorally mediated autoimmune skin blistering disorder. Seminal studies identified the desmosomal proteins Desmoglein 3 and 1 (Dsg3 and Dsg1), cadherin family proteins which function to maintain cell adhesion, as the primary targets of pathogenic autoAbs. Consequently, pathogenesis in PV has primarily considered to be the result of anti-Dsg autoAbs alone. However, accumulating data suggesting that anti-Dsg autoAbs by themselves cannot adequately explain the loss of cell-cell adhesion seen in PV, nor account for the disease heterogeneity exhibited across PV patients has spurred the notion that additional autoAb specificities may contribute to disease. To investigate the role of non-Dsg autoAbs in PV, an increasing number of studies have attempted to characterize additional targets of PV autoAbs. The recent advent of protein microarray technology, which allows for the rapid, highly sensitive, and multiplexed assessment of autoAb specificity has facilitated the comprehensive classification of the scope and specificity of the autoAb response in PV. Such detailed deconstruction of the autoimmune response in PV, beyond simply tracking anti-Dsg autoAbs, has provided invaluable new insights concerning disease mechanisms and enhanced disease classification which could directly translate into superior tools for prognostics and clinical management, as well as the development of novel, disease specific treatments.
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Affiliation(s)
- Animesh A Sinha
- Department of Dermatology, University at Buffalo, Buffalo, NY, United States
| | - Thomas Sajda
- Department of Dermatology, University at Buffalo, Buffalo, NY, United States
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11
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Ren G, You J, Gong X, Zhang X, Zhao L, Wei X, Jin T, Chen M. SP110 and PMP22 polymorphisms are associated with tuberculosis risk in a Chinese-Tibetan population. Oncotarget 2018; 7:66100-66108. [PMID: 27623071 PMCID: PMC5323218 DOI: 10.18632/oncotarget.11847] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 07/19/2016] [Indexed: 12/21/2022] Open
Abstract
Susceptibility to tuberculosis (TB) is partially dependent on host genetic variability. SP110 and PMP22 are candidate genes identified in this study as associated with human susceptibility to TB. Here we performed an association analysis in a case-control study of a Tibetan population (217 cases and 383 controls). Using bioinformatics methods, we identified two SNPs in SP110 that may decrease susceptibility to TB (rs4327230, p<0.001, OR: 0.37, 95%CI: 0.25-0.55; rs2114591, p<0.001, OR: 0.59, 95%CI: 0.45-0.78), whereas one SNP in PMP22 appeared to increase TB risk (rs13422, p=0.003, OR: 1.45, 95%CI: 1.14-1.84). SNPs rs4327230 and rs2114591 remained significant after Bonferroni correction (p<0.00178). We found that the “GC” haplotype in SP110 was protective against TB, with a 64% reduction in disease risk. “CA” and “CG” in PMP22 were also associated with a protective effect. Our study indicates there is an association between specific gene polymorphisms and TB risk in a Tibetan population, and may help to identify those TB-affected individuals most susceptible to disease.
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Affiliation(s)
- Guoxia Ren
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of School of Medicine of Xi'an Jiaotong University, Xi'an 710061, People's Republic of China.,Department of Intergrated Traditional Chinese and Western Medicine, Xi'an Chest Hospital, Xi'an 710061, People's Republic of China
| | - Jiangtao You
- Department of Thoracic Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, People's Republic of China
| | - Xianfeng Gong
- Department of Intergrated Traditional Chinese and Western Medicine, Xi'an Chest Hospital, Xi'an 710061, People's Republic of China
| | - Xiucheng Zhang
- Department of Intergrated Traditional Chinese and Western Medicine, Xi'an Chest Hospital, Xi'an 710061, People's Republic of China
| | - Lin Zhao
- Department of Intergrated Traditional Chinese and Western Medicine, Xi'an Chest Hospital, Xi'an 710061, People's Republic of China
| | - Xianglan Wei
- Department of Intergrated Traditional Chinese and Western Medicine, Xi'an Chest Hospital, Xi'an 710061, People's Republic of China
| | - Tianbo Jin
- School of Life Sciences, Northwest University, Xi'an 710069, People's Republic of China.,Key Laboratory of High Altitude Environment and Genes Related to Diseases of Tibet Autonomous Region, School of Medicine, Tibet University for Nationalities, Xianyang 712082, People's Republic of China.,Xi'an Tiangen Precision Medical Institute, Xi'an 710075, People's Republic of China
| | - Mingwei Chen
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of School of Medicine of Xi'an Jiaotong University, Xi'an 710061, People's Republic of China
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12
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Poitelon Y, Matafora V, Silvestri N, Zambroni D, McGarry C, Serghany N, Rush T, Vizzuso D, Court FA, Bachi A, Wrabetz L, Feltri ML. A dual role for Integrin α6β4 in modulating hereditary neuropathy with liability to pressure palsies. J Neurochem 2018; 145:245-257. [PMID: 29315582 DOI: 10.1111/jnc.14295] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 12/14/2017] [Accepted: 12/21/2017] [Indexed: 12/23/2022]
Abstract
Peripheral myelin protein 22 (PMP22) is a component of compact myelin in the peripheral nervous system. The amount of PMP22 in myelin is tightly regulated, and PMP22 over or under-expression cause Charcot-Marie-Tooth 1A (CMT1A) and Hereditary Neuropathy with Pressure Palsies (HNPP). Despite the importance of PMP22, its function remains largely unknown. It was reported that PMP22 interacts with the β4 subunit of the laminin receptor α6β4 integrin, suggesting that α6β4 integrin and laminins may contribute to the pathogenesis of CMT1A or HNPP. Here we asked if the lack of α6β4 integrin in Schwann cells influences myelin stability in the HNPP mouse model. Our data indicate that PMP22 and β4 integrin may not interact directly in myelinating Schwann cells, however, ablating β4 integrin delays the formation of tomacula, a characteristic feature of HNPP. In contrast, ablation of integrin β4 worsens nerve conduction velocities and non-compact myelin organization in HNPP animals. This study demonstrates that indirect interactions between an extracellular matrix receptor and a myelin protein influence the stability and function of myelinated fibers.
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Affiliation(s)
- Yannick Poitelon
- Hunter James Kelly Research Institute, University at Buffalo, Buffalo, New York, USA.,Department of Biochemistry, University at Buffalo, Buffalo, New York, USA
| | - Vittoria Matafora
- Division of Genetics and Cell Biology, San Raffaele Hospital, Milan, Italy
| | | | - Desirée Zambroni
- Division of Genetics and Cell Biology, San Raffaele Hospital, Milan, Italy
| | - Claire McGarry
- Department of Biochemistry, University at Buffalo, Buffalo, New York, USA
| | - Nora Serghany
- Department of Biochemistry, University at Buffalo, Buffalo, New York, USA
| | - Thomas Rush
- Department of Biochemistry, University at Buffalo, Buffalo, New York, USA
| | - Domenica Vizzuso
- Hunter James Kelly Research Institute, University at Buffalo, Buffalo, New York, USA.,Division of Genetics and Cell Biology, San Raffaele Hospital, Milan, Italy
| | - Felipe A Court
- Division of Genetics and Cell Biology, San Raffaele Hospital, Milan, Italy.,Center for Integrative Biology, Universidad Mayor de Chile, Santiago, Chile
| | - Angela Bachi
- Division of Genetics and Cell Biology, San Raffaele Hospital, Milan, Italy
| | - Lawrence Wrabetz
- Hunter James Kelly Research Institute, University at Buffalo, Buffalo, New York, USA.,Department of Biochemistry, University at Buffalo, Buffalo, New York, USA.,Division of Genetics and Cell Biology, San Raffaele Hospital, Milan, Italy.,Department of Neurology, University at Buffalo, Buffalo, New York, USA
| | - Maria Laura Feltri
- Hunter James Kelly Research Institute, University at Buffalo, Buffalo, New York, USA.,Department of Biochemistry, University at Buffalo, Buffalo, New York, USA.,Division of Genetics and Cell Biology, San Raffaele Hospital, Milan, Italy.,Department of Neurology, University at Buffalo, Buffalo, New York, USA
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13
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Rosso G, Young P, Shahin V. Implications of Schwann Cells Biomechanics and Mechanosensitivity for Peripheral Nervous System Physiology and Pathophysiology. Front Mol Neurosci 2017; 10:345. [PMID: 29118694 PMCID: PMC5660964 DOI: 10.3389/fnmol.2017.00345] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 10/11/2017] [Indexed: 12/21/2022] Open
Abstract
The presence of bones around the central nervous system (CNS) provides it with highly effective physiologically crucial mechanical protection. The peripheral nervous system (PNS), in contrast, lacks this barrier. Consequently, the long held belief is that the PNS is mechanically vulnerable. On the other hand, the PNS is exposed to a variety of physiological mechanical stresses during regular daily activities. This fact prompts us to question the dogma of PNS mechanical vulnerability. As a matter of fact, impaired mechanics of PNS nerves is associated with neuropathies with the liability to mechanical stresses paralleled by significant impairment of PNS physiological functions. Our recent biomechanical integrity investigations on nerve fibers from wild-type and neuropathic mice lend strong support in favor of natural mechanical protection of the PNS and demonstrate a key role of Schwann cells (SCs) therein. Moreover, recent works point out that SCs can sense mechanical properties of their microenvironment and the evidence is growing that SCs mechanosensitivity is important for PNS development and myelination. Hence, SCs exhibit mechanical strength necessary for PNS mechanoprotection as well as mechanosensitivity necessary for PNS development and myelination. This mini review reflects on the intriguing dual ability of SCs and implications for PNS physiology and pathophysiology.
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Affiliation(s)
- Gonzalo Rosso
- Institute of Physiology II, University of Münster, Münster, Germany
| | - Peter Young
- Department of Sleep Medicine and Neuromuscular Disorders, University of Münster, Münster, Germany
| | - Victor Shahin
- Institute of Physiology II, University of Münster, Münster, Germany
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14
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Abstract
Haploinsufficiency of peripheral myelin protein 22 (PMP22) causes hereditary neuropathy with liability to pressure palsies, a peripheral nerve lesion induced by minimal trauma or compression. As PMP22 is localized to cholesterol-enriched membrane domains that are closely linked with the underlying actin network, we asked whether the myelin instability associated with PMP22 deficiency could be mediated by involvement of the protein in actin-dependent cellular functions and/or lipid raft integrity. In peripheral nerves and cells from mice with PMP22 deletion, we assessed the organization of filamentous actin (F-actin), and actin-dependent cellular functions. Using in vitro models, we discovered that, in the absence of PMP22, the migration and adhesion capacity of Schwann cells and fibroblasts are similarly impaired. Furthermore, PMP22-deficient Schwann cells produce shortened myelin internodes, and display compressed axial cell length and collapsed lamellipodia. During early postnatal development, F-actin-enriched Schmidt-Lanterman incisures do not form properly in nerves from PMP22(-/-) mice, and the expression and localization of molecules associated with uncompacted myelin domains and lipid rafts, including flotillin-1, cholesterol, and GM1 ganglioside, are altered. In addition, we identified changes in the levels and distribution of cholesterol and ApoE when PMP22 is absent. Significantly, cholesterol supplementation of the culture medium corrects the elongation and migration deficits of PMP22(-/-) Schwann cells, suggesting that the observed functional impairments are directly linked with cholesterol deficiency of the plasma membrane. Our findings support a novel role for PMP22 in the linkage of the actin cytoskeleton with the plasma membrane, likely through regulating the cholesterol content of lipid rafts.
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15
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Tae HJ, Rahman MM, Park BY. Temporal and spatial expression analysis of peripheral myelin protein 22 (Pmp22) in developing Xenopus. Gene Expr Patterns 2015; 17:26-30. [PMID: 25616247 DOI: 10.1016/j.gep.2015.01.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 01/10/2015] [Accepted: 01/11/2015] [Indexed: 11/18/2022]
Abstract
Peripheral myelin protein 22 (Pmp22), a member of the junction protein family Claudin/EMP/PMP22, contributes to the formation and maintenance of myelin sheaths in the peripheral nervous system. Apart from the establishment and maintenance of peripheral nerves, Pmp22 and its family member have also participated in a broad range of more general processes including cell cycle regulation and apoptosis during development. Pmp22 has been identified from several vertebrate species including mouse, human and zebrafish. However, Pmp22 has not been identified from Xenopus embryos yet. In this paper, we cloned Pmp22 from Xenopus laevis and evaluated its expression during embryogenesis. We found that Pmp22 was initially expressed in the mesoderm and cement gland during the neurula stage. At early tailbud stage, strong expression of Pmp22 was detected in the trigeminal and profundal ganglia as well as developing somites and branchial arches. Later in development, Pmp22 was expressed specifically in cranio-facial cartilage, roof plate and floor plate of the developing brain, otic vesicle and lens. Pmp22 is also strongly expressed in the developing trachea and lungs. Based on its expression in facial tissues, we propose that Pmp22 may be involved in the formation of head structure in addition to the maintenance of functional peripheral nerves in Xenopus embryos.
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Affiliation(s)
- Hyun-Jin Tae
- Department of Biomedical Science and Research Institute for Bioscience and Biotechnology, Hallym University, 1 Hallymdaehak-gil, Chunchon 200-702, South Korea
| | - Md Mahfujur Rahman
- Bio-Safety Research Institute, College of Veterinary Medicine, Chonbuk National University, 567 Baekje-Daero, Jeonju 561-756, Republic of Korea
| | - Byung-Yong Park
- Bio-Safety Research Institute, College of Veterinary Medicine, Chonbuk National University, 567 Baekje-Daero, Jeonju 561-756, Republic of Korea.
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16
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Rosso G, Liashkovich I, Gess B, Young P, Kun A, Shahin V. Unravelling crucial biomechanical resilience of myelinated peripheral nerve fibres provided by the Schwann cell basal lamina and PMP22. Sci Rep 2014; 4:7286. [PMID: 25446378 PMCID: PMC4250911 DOI: 10.1038/srep07286] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 11/14/2014] [Indexed: 11/09/2022] Open
Abstract
There is an urgent need for the research of the close and enigmatic relationship between nerve biomechanics and the development of neuropathies. Here we present a research strategy based on the application atomic force and confocal microscopy for simultaneous nerve biomechanics and integrity investigations. Using wild-type and hereditary neuropathy mouse models, we reveal surprising mechanical protection of peripheral nerves. Myelinated peripheral wild-type fibres promptly and fully recover from acute enormous local mechanical compression while maintaining functional and structural integrity. The basal lamina which enwraps each myelinated fibre separately is identified as the major contributor to the striking fibre's resilience and integrity. In contrast, neuropathic fibres lacking the peripheral myelin protein 22 (PMP22), which is closely connected with several hereditary human neuropathies, fail to recover from light compression. Interestingly, the structural arrangement of the basal lamina of Pmp22−/− fibres is significantly altered compared to wild-type fibres. In conclusion, the basal lamina and PMP22 act in concert to contribute to a resilience and integrity of peripheral nerves at the single fibre level. Our findings and the presented technology set the stage for a comprehensive research of the links between nerve biomechanics and neuropathies.
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Affiliation(s)
- Gonzalo Rosso
- Institute of Physiology II, WWU Münster, Robert-Koch-Straße 27b 48149 Münster, Germany
| | - Ivan Liashkovich
- Institute of Physiology II, WWU Münster, Robert-Koch-Straße 27b 48149 Münster, Germany
| | - Burkhard Gess
- Department of Sleep Medicine and Neuromuscular Disorders, Albert-Schweitzer Campus 1, Geb. A1, 48149 Münster, Germany
| | - Peter Young
- Department of Sleep Medicine and Neuromuscular Disorders, Albert-Schweitzer Campus 1, Geb. A1, 48149 Münster, Germany
| | - Alejandra Kun
- Department of Proteins and Nucleic Acids, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
| | - Victor Shahin
- Institute of Physiology II, WWU Münster, Robert-Koch-Straße 27b 48149 Münster, Germany
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17
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Mittendorf KF, Kroncke BM, Meiler J, Sanders CR. The homology model of PMP22 suggests mutations resulting in peripheral neuropathy disrupt transmembrane helix packing. Biochemistry 2014; 53:6139-41. [PMID: 25243937 PMCID: PMC4188248 DOI: 10.1021/bi500809t] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
![]()
Peripheral myelin protein 22 (PMP22)
is a tetraspan membrane protein
strongly expressed in myelinating Schwann cells of the peripheral
nervous system. Myriad missense mutations in PMP22 result in varying
degrees of peripheral neuropathy. We used Rosetta 3.5 to generate
a homology model of PMP22 based on the recently published crystal
structure of claudin-15. The model suggests that several mutations
known to result in neuropathy act by disrupting transmembrane helix
packing interactions. Our model also supports suggestions from previous
studies that the first transmembrane helix is not tightly associated
with the rest of the helical bundle.
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Affiliation(s)
- Kathleen F Mittendorf
- Department of Biochemistry, ‡Center for Structural Biology, and §Departments of Pharmacology and Bioinformatics, Vanderbilt University School of Medicine , Nashville, Tennessee 37232, United States
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18
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Affiliation(s)
- Karen G. Fleming
- T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218;
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19
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Biochemical characterization of protein quality control mechanisms during disease progression in the C22 mouse model of CMT1A. ASN Neuro 2013; 5:e00128. [PMID: 24175617 PMCID: PMC3848555 DOI: 10.1042/an20130024] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Charcot–Marie–Tooth disease type 1A (CMT1A) is a hereditary demyelinating neuropathy linked with duplication of the peripheral myelin protein 22 (PMP22) gene. Transgenic C22 mice, a model of CMT1A, display many features of the human disease, including slowed nerve conduction velocity and demyelination of peripheral nerves. How overproduction of PMP22 leads to compromised myelin and axonal pathology is not fully understood, but likely involves subcellular alterations in protein homoeostatic mechanisms within affected Schwann cells. The subcellular response to abnormally localized PMP22 includes the recruitment of the ubiquitin–proteasome system (UPS), autophagosomes and heat-shock proteins (HSPs). Here we assessed biochemical markers of these protein homoeostatic pathways in nerves from PMP22-overexpressing neuropathic mice between the ages of 2 and 12 months to ascertain their potential contribution to disease progression. In nerves of 3-week-old mice, using endoglycosidases and Western blotting, we found altered processing of the exogenous human PMP22, an abnormality that becomes more prevalent with age. Along with the ongoing accrual of misfolded PMP22, the activity of the proteasome becomes compromised and proteins required for autophagy induction and lysosome biogenesis are up-regulated. Moreover, cytosolic chaperones are consistently elevated in nerves from neuropathic mice, with the most prominent change in HSP70. The gradual alterations in protein homoeostatic response are accompanied by Schwann cell de-differentiation and macrophage infiltration. Together, these results show that while subcellular protein quality control mechanisms respond appropriately to the presence of the overproduced PMP22, with aging they are unable to prevent the accrual of misfolded proteins. In peripheral nerves of neuropathic C22 mice the frequency of cytosolic PMP22 aggregates increases with age, which elicits a response from protein quality control mechanisms. The combined effects of aging and neuropathic genotype exacerbate disease progression leading to nerve defects.
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20
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Walko G, Wögenstein KL, Winter L, Fischer I, Feltri ML, Wiche G. Stabilization of the dystroglycan complex in Cajal bands of myelinating Schwann cells through plectin-mediated anchorage to vimentin filaments. Glia 2013; 61:1274-87. [PMID: 23836526 DOI: 10.1002/glia.22514] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2012] [Accepted: 03/28/2013] [Indexed: 11/06/2022]
Abstract
Previous studies have unmasked plectin, a uniquely versatile intermediate filament-associated cytolinker protein, to be essential for skin and skeletal muscle integrity. Different sets of isoforms of the protein were found to stabilize cells mechanically, regulate cytoskeletal dynamics, and serve as a scaffolding platform for signaling molecules. Here, we investigated whether a similar scenario prevails in myelinating Schwann cells. Using isoform-specific antibodies, the two plectin variants predominantly expressed in the cytoplasmic compartment (Cajal bands) of Schwann cells were identified as plectin (P)1 and P1c. Coimmunoprecipitation and immunolocalization experiments revealed complex formation of Cajal band plectin with β-dystroglycan, the core component of the dystrophin glycoprotein complex that in Schwann cells is crucial for the compartmentalization and stabilization of the myelin sheath. To study the functional implications of Schwann cell-specific plectin-β-dystroglycan interaction, we generated conditional (Schwann cell-restricted) plectin knockout mice. Ablation of plectin in myelinating Schwann cells (SCs) was found not to affect myelin sheath formation but to abrogate the tight association of the dystroglycan complex with the intermediate filament cytoskeleton. We show that the disruption of this association leads to the destabilization of the dystroglycan complex combined with increased myelin sheath deformations observed in the peripheral nerve during ageing of the animal.
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Affiliation(s)
- Gernot Walko
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, Center for Molecular Biology, University of Vienna, Vienna, Austria
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21
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Schlebach JP, Peng D, Kroncke BM, Mittendorf KF, Narayan M, Carter BD, Sanders CR. Reversible folding of human peripheral myelin protein 22, a tetraspan membrane protein. Biochemistry 2013; 52:3229-41. [PMID: 23639031 DOI: 10.1021/bi301635f] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Misfolding of the α-helical membrane protein peripheral myelin protein 22 (PMP22) has been implicated in the pathogenesis of the common neurodegenerative disease known as Charcot-Marie-Tooth disease (CMTD) and also several other related peripheral neuropathies. Emerging evidence suggests that the propensity of PMP22 to misfold in the cell may be due to an intrinsic lack of conformational stability. Therefore, quantitative studies of the conformational equilibrium of PMP22 are needed to gain insight into the molecular basis of CMTD. In this work, we have investigated the folding and unfolding of wild type (WT) human PMP22 in mixed micelles. Both kinetic and thermodynamic measurements demonstrate that the denaturation of PMP22 by n-lauroyl sarcosine (LS) in dodecylphosphocholine (DPC) micelles is reversible. Assessment of the conformational equilibrium indicates that a significant fraction of unfolded PMP22 persists even in the absence of the denaturing detergent. However, we find the stability of PMP22 is increased by glycerol, which facilitates quantitation of thermodynamic parameters. To our knowledge, this work represents the first report of reversible unfolding of a eukaryotic multispan membrane protein. The results indicate that WT PMP22 possesses minimal conformational stability in micelles, which parallels its poor folding efficiency in the endoplasmic reticulum. Folding equilibrium measurements for PMP22 in micelles may provide an approach to assess the effects of cellular metabolites or potential therapeutic agents on its stability. Furthermore, these results pave the way for future investigation of the effects of pathogenic mutations on the conformational equilibrium of PMP22.
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Affiliation(s)
- Jonathan P Schlebach
- Department of Biochemistry and ‡Center for Structural Biology, Vanderbilt University School of Medicine , Nashville, Tennessee 37232, United States
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22
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Li J, Parker B, Martyn C, Natarajan C, Guo J. The PMP22 gene and its related diseases. Mol Neurobiol 2012; 47:673-98. [PMID: 23224996 DOI: 10.1007/s12035-012-8370-x] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Accepted: 10/22/2012] [Indexed: 10/27/2022]
Abstract
Peripheral myelin protein-22 (PMP22) is primarily expressed in the compact myelin of the peripheral nervous system. Levels of PMP22 have to be tightly regulated since alterations of PMP22 levels by mutations of the PMP22 gene are responsible for >50 % of all patients with inherited peripheral neuropathies, including Charcot-Marie-Tooth type-1A (CMT1A) with trisomy of PMP22, hereditary neuropathy with liability to pressure palsies (HNPP) with heterozygous deletion of PMP22, and CMT1E with point mutations of PMP22. While overexpression and point-mutations of the PMP22 gene may produce gain-of-function phenotypes, deletion of PMP22 results in a loss-of-function phenotype that reveals the normal physiological functions of the PMP22 protein. In this article, we will review the basic genetics, biochemistry and molecular structure of PMP22, followed by discussion of the current understanding of pathogenic mechanisms involving in the inherited neuropathies with mutations in PMP22 gene.
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Affiliation(s)
- Jun Li
- VA Tennessee Valley Healthcare System, 1310 24th Avenue South, Nashville, TN 37212, USA.
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23
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Abstract
PMP22 (peripheral myelin protein 22), also known as GAS 3 (growth-arrest-specific protein 3), is a disease-linked tetraspan glycoprotein of peripheral nerve myelin and constituent of intercellular junctions in epithelia. To date, our knowledge of the post-translational modification of PMP22 is limited. Using the CSS-Palm 2.0 software we predicted that C85 (cysteine 85), a highly conserved amino acid located between the second and third transmembrane domains, is a potential site for palmitoylation. To test this, we mutated C85S (C85 to serine) and established stable cells lines expressing the WT (wild-type) or the C85S-PMP22. In Schwann and MDCK (Madin–Darby canine kidney) cells mutating C85 blocked the palmitoylation of PMP22, which we monitored using 17-ODYA (17-octadecynoic acid). While palmitoylation was not necessary for processing the newly synthesized PMP22 through the secretory pathway, overexpression of C85S-PMP22 led to pronounced cell spreading and uneven monolayer thinning. To further investigate the functional significance of palmitoylated PMP22, we evaluated MDCK cell migration in a wound-healing assay. While WT-PMP22 expressing cells were resistant to migration, C85S cells displayed lamellipodial protrusions and migrated at a similar rate to vector control. These findings indicate that palmitoylation of PMP22 at C85 is critical for the role of the protein in modulating epithelial cell shape and motility.
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Saporta MA, Katona I, Zhang X, Roper HP, McClelland L, Macdonald F, Brueton L, Blake J, Suter U, Reilly MM, Shy ME, Li J. Neuropathy in a human without the PMP22 gene. ACTA ACUST UNITED AC 2011; 68:814-21. [PMID: 21670407 DOI: 10.1001/archneurol.2011.110] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND Haploinsufficiency of PMP22 causes hereditary neuropathy with liability to pressure palsies. However, the biological functions of the PMP22 protein in humans have largely been unexplored owing to the absence of patients with PMP22-null mutations. OBJECTIVE To investigate the function of PMP22 in the peripheral nervous system by studying a boy without the PMP22 gene and mice without the Pmp22 gene. DESIGN The clinical and pathological features of a patient with a PMP22 homozygous deletion are compared with those of Pmp22-null mice. SETTING Clinical evaluation was performed at tertiary hospitals in the United Kingdom. Molecular diagnosis was performed at the West Midlands Regional Genetics Laboratory. Immunohistochemistry and electron microscopy analyses were conducted at Wayne State University, Detroit, Michigan. Analysis of the Pmp22 +/- and null mice was performed at Vanderbilt University, Nashville, Tennessee. PARTICIPANT A 7-year-old boy without the PMP22 gene. RESULTS Motor and sensory deficits in the proband were nonlength-dependent. Weakness was found in cranial muscles but not in the limbs. Large fiber sensory modalities were profoundly abnormal, which started prior to the maturation of myelin. This is in line with the temporal pattern of PMP22 expression predominantly in cranial motor neurons and dorsal root ganglia during embryonic development, becoming undetectable in adulthood. Moreover, there were conspicuous maturation defects of myelinating Schwann cells; these defects were more significant in motor nerve fibers than in sensory nerve fibers. CONCLUSIONS Taken together, the data suggest that PMP22 is important for the normal function of neurons that express PMP22 during early development, such as cranial motor neurons and spinal sensory neurons. Moreover, PMP22 deficiency differentially affects myelination between motor and sensory nerves, which may have contributed to the unique clinical phenotype in the patient with an absence of PMP22.
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25
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Rapamycin activates autophagy and improves myelination in explant cultures from neuropathic mice. J Neurosci 2010; 30:11388-97. [PMID: 20739560 DOI: 10.1523/jneurosci.1356-10.2010] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Misexpression and cytosolic retention of peripheral myelin protein 22 (PMP22) within Schwann cells (SCs) is associated with a genetically heterogeneous group of demyelinating peripheral neuropathies. PMP22 overproducer C22 and spontaneous mutant Trembler J (TrJ) mice display neuropathic phenotypes and affected nerves contain abnormally localized PMP22. Nutrient deprivation-induced autophagy is able to suppress the formation of PMP22 aggregates in a toxin-induced cellular model, and improve locomotor performance and myelination in TrJ mice. As a step toward therapies, we assessed whether pharmacological activation of autophagy by rapamycin (RM) could facilitate the processing of PMP22 within neuropathic SCs and enhance their capacity to myelinate peripheral axons. Exposure of mouse SCs to RM induced autophagy in a dose- and time-dependent manner and decreased the accumulation of poly-ubiquitinated substrates. The treatment of myelinating dorsal root ganglion (DRG) explant cultures from neuropathic mice with RM (25 nm) improved the processing of PMP22 and increased the abundance and length of myelin internodes, as well as the expression of myelin proteins. Notably, RM is similarly effective in both the C22 and TrJ model, signifying that the benefit overlaps among distinct genetic models of PMP22 neuropathies. Furthermore, lentivirus-mediated shRNA knockdown of the autophagy-related gene 12 (Atg12) abolished the activation of autophagy and the increase in myelin proteins, demonstrating that autophagy is critical for the observed improvement. Together, these results support the potential use of RM and other autophagy-enhancing compounds as therapeutic agents for PMP22-associated demyelinating neuropathies.
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26
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Saporta MA, Katona I, Lewis RA, Masse S, Shy ME, Li J. Shortened internodal length of dermal myelinated nerve fibres in Charcot-Marie-Tooth disease type 1A. Brain 2010; 132:3263-73. [PMID: 19923170 DOI: 10.1093/brain/awp274] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Charcot-Marie-Tooth disease type 1A is the most common inherited neuropathy and is caused by duplication of chromosome 17p11.2 containing the peripheral myelin protein-22 gene. This disease is characterized by uniform slowing of conduction velocities and secondary axonal loss, which are in contrast with non-uniform slowing of conduction velocities in acquired demyelinating disorders, such as chronic inflammatory demyelinating polyradiculoneuropathy. Mechanisms responsible for the slowed conduction velocities and axonal loss in Charcot-Marie-Tooth disease type 1A are poorly understood, in part because of the difficulty in obtaining nerve samples from patients, due to the invasive nature of nerve biopsies. We have utilized glabrous skin biopsies, a minimally invasive procedure, to evaluate these issues systematically in patients with Charcot-Marie-Tooth disease type 1A (n = 32), chronic inflammatory demyelinating polyradiculoneuropathy (n = 4) and healthy controls (n = 12). Morphology and molecular architecture of dermal myelinated nerve fibres were examined using immunohistochemistry and electron microscopy. Internodal length was uniformly shortened in patients with Charcot-Marie-Tooth disease type 1A, compared with those in normal controls (P < 0.0001). Segmental demyelination was absent in the Charcot-Marie-Tooth disease type 1A group, but identifiable in all patients with chronic inflammatory demyelinating polyradiculoneuropathy. Axonal loss was measurable using the density of Meissner corpuscles and associated with an accumulation of intra-axonal mitochondria. Our study demonstrates that skin biopsy can reveal pathological and molecular architectural changes that distinguish inherited from acquired demyelinating neuropathies. Uniformly shortened internodal length in Charcot-Marie-Tooth disease type 1A suggests a potential developmental defect of internodal lengthening. Intra-axonal accumulation of mitochondria provides new insights into the pathogenesis of axonal degeneration in Charcot-Marie-Tooth disease type 1A.
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Affiliation(s)
- Mario A Saporta
- Department of Neurology, Wayne State University, Detroit 48201, USA
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Abstract
Patients with PMP22 deficiency present with focal sensory and motor deficits when peripheral nerves are stressed by mechanical force. It has been hypothesized that these focal deficits are due to mechanically induced conduction block (CB). To test this hypothesis, we induced 60-70% CB (defined by electrophysiological criteria) by nerve compression in an authentic mouse model of hereditary neuropathy with liability to pressure palsies (HNPP) with an inactivation of one of the two pmp22 alleles (pmp22(+/-)). Induction time for the CB was significantly shorter in pmp22(+/-) mice than that in pmp22(+/+) mice. This shortened induction was also found in myelin-associated glycoprotein knock-out mice, but not in the mice with deficiency of myelin protein zero, a major structural protein of compact myelin. Pmp22(+/-) nerves showed intact tomacula with no segmental demyelination in both noncompressed and compressed conditions, normal molecular architecture, and normal concentration of voltage-gated sodium channels by [(3)H]-saxitoxin binding assay. However, focal constrictions were observed in the axonal segments enclosed by tomacula, a pathological hallmark of HNPP. The constricted axons increase axial resistance to action potential propagation, which may hasten the induction of CB in Pmp22 deficiency. Together, these results demonstrate that a function of Pmp22 is to protect the nerve from mechanical injury.
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Rangaraju S, Hankins D, Madorsky I, Madorsky E, Lee WH, Carter CS, Leeuwenburgh C, Notterpek L. Molecular architecture of myelinated peripheral nerves is supported by calorie restriction with aging. Aging Cell 2009; 8:178-91. [PMID: 19239416 DOI: 10.1111/j.1474-9726.2009.00460.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Peripheral nerves from aged animals exhibit features of degeneration, including marked fiber loss, morphological irregularities in myelinated axons and notable reduction in the expression of myelin proteins. To investigate how protein homeostatic mechanisms change with age within the peripheral nervous system, we isolated Schwann cells from the sciatic nerves of young and old rats. The responsiveness of cells from aged nerves to stress stimuli is weakened, which in part may account for the observed age-associated alterations in glial and axonal proteins in vivo. Although calorie restriction is known to slow the aging process in the central nervous system, its influence on peripheral nerves has not been investigated in detail. To determine if dietary restriction is beneficial for peripheral nerve health and glial function, we studied sciatic nerves from rats of four distinct ages (8, 18, 29 and 38 months) kept on an ad libitum (AL) or a 40% calorie restricted diet. Age-associated reduction in the expression of the major myelin proteins and widening of the nodes of Ranvier are attenuated by the dietary intervention, which is paralleled with the maintenance of a differentiated Schwann cell phenotype. The improvements in nerve architecture with diet restriction, in part, are underlined by sustained expression of protein chaperones and markers of the autophagy-lysosomal pathway. Together, the in vitro and in vivo results suggest that there might be an age-limit by which dietary intervention needs to be initiated to elicit a beneficial response on peripheral nerve health.
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Affiliation(s)
- Sunitha Rangaraju
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL 32610-0244, USA
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29
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Rangaraju S, Madorsky I, Pileggi JG, Kamal A, Notterpek L. Pharmacological induction of the heat shock response improves myelination in a neuropathic model. Neurobiol Dis 2008; 32:105-15. [PMID: 18655835 DOI: 10.1016/j.nbd.2008.06.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 06/19/2008] [Accepted: 06/20/2008] [Indexed: 11/16/2022] Open
Abstract
Misexpression and intracellular retention of peripheral myelin protein 22 (PMP22) is associated with hereditary neuropathies in humans, including Charcot-Marie-Tooth disease type 1A (CMT1A). Mice expressing extra copies of the human PMP22, termed C22, display morphologic and behavioral characteristics of CMT1A. In neuropathic Schwann cells, the turnover of the newly-synthesized PMP22 is decreased, leading to the formation of cytosolic protein aggregates. To aid the processing of PMP22 and alleviate the associated myelin defects, we pharmacologically stimulated the expression of protein chaperones by synthetic small-molecule inhibitors of heat shock protein 90 (HSP90). The exposure of Schwann cells to these compounds enhanced the levels of cytosolic chaperones in a time- and dose-dependent manner, with minimal cytotoxicity. Treatment of dorsal root ganglion (DRG) explants from neuropathic mice improved myelin formation and the processing of PMP22. These results warrant further studies with HSP90 inhibitors as potential therapeutic candidates for hereditary demyelinating neuropathies.
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Affiliation(s)
- Sunitha Rangaraju
- Department of Neuroscience, College of Medicine, McKnight Brain Institute, University of Florida, Gainesville, FL 32610-0244, USA
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30
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Iacobas DA, Iacobas S, Werner P, Scemes E, Spray DC. Alteration of transcriptomic networks in adoptive-transfer experimental autoimmune encephalomyelitis. Front Integr Neurosci 2007; 1:10. [PMID: 18958238 PMCID: PMC2526015 DOI: 10.3389/neuro.07.010.2007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Accepted: 12/03/2007] [Indexed: 01/09/2023] Open
Abstract
Adoptive transfer experimental autoimmune encephalomyelitis (AT-EAE) is an inflammatory demyelination that recapitulates in mouse spinal cord (SC) the human multiple sclerosis disease. We now analyze previously reported cDNA array data from age-matched young female adult control and passively myelin antigen-sensitized EAE mice with regard to organizational principles of the SC transcriptome in autoimmune demyelination. Although AT-EAE had a large impact on immune response genes, broader functional and chromosomal gene cohorts were neither significantly regulated nor showed significant changes in expression coordination. However, overall transcriptional control was increased in AT-EAE and the proportions of transcript abundances were perturbed within each cohort. Striking likenesses and oppositions were identified in the coordination profiles of genes related to myelination, calcium signaling, and inflammatory response in controls that were substantially altered in AT-EAE. We propose that up- or down-regulation of genes linked to those targeted by the disease could potentially compensate for the pathological transcriptomic changes.
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Affiliation(s)
- Dumitru A Iacobas
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine USA.
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31
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Mobley CK, Myers JK, Hadziselimovic A, Ellis CD, Sanders CR. Purification and initiation of structural characterization of human peripheral myelin protein 22, an integral membrane protein linked to peripheral neuropathies. Biochemistry 2007; 46:11185-95. [PMID: 17824619 DOI: 10.1021/bi700855j] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Gene duplications, deletions, and point mutations in peripheral myelin protein 22 (PMP22) are linked to several inherited peripheral neuropathies. However, the structural and biochemical properties of this very hydrophobic putative tetraspan integral membrane protein have received little attention, in part because of difficulties in obtaining milligram quantities of wild type and disease-linked mutant forms of the protein. In this study a fusion protein was constructed consisting of a fragment of lambda repressor, a decahistidine tag, an intervening TEV protease cleavage site, a Strep tag, and the human PMP22 sequence. This fusion protein was expressed in Escherichia coli at a level of 10-20 mg/L of protein. Following TEV cleavage of the fusion partner, PMP22 was purified and its structural properties were examined in several different types of detergent micelles using cross-linking, near and far-UV circular dichroism, and nuclear magnetic resonance (NMR) spectroscopy. PMP22 is highly helical and, in certain detergents, shows evidence of stable tertiary structure. The protein exhibits a strong tendency to dimerize. The 1H-15N TROSY NMR spectrum is well dispersed and contains signals from all regions of the protein. It appears that detergent-solubilized PMP22 is amenable to detailed structural characterization via crystallography or NMR. This work sets the stage for more detailed studies of the structure, folding, and misfolding of wild type and disease-linked mutants in order to unravel the molecular defects underlying peripheral neuropathies.
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Affiliation(s)
- Charles K Mobley
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-8725, USA
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