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Zhang T, Xu Z, Zheng D, Wang X, He J, Zhang L, Zallocchi M. Novel biallelic variants in the PLEC gene are associated with severe hearing loss. Hear Res 2023; 436:108831. [PMID: 37393735 DOI: 10.1016/j.heares.2023.108831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Revised: 05/18/2023] [Accepted: 06/13/2023] [Indexed: 07/04/2023]
Abstract
Pediatric auditory neuropathy spectrum disorder is a particular type of hearing loss caused by abnormal sound transmission from the cochlea to the brain. It is due to defective peripheral synaptic function or improper neuronal conduction. Using trio whole-exome sequencing, we have identified novel biallelic variants in the PLEC gene in three individuals with profound deafness from two unrelated families. Among them, one pediatric patient diagnosed with auditory neuropathy spectrum disorder had a good cochlear implantation outcome. The other two adult patients were diagnosed with non-syndromic hearing loss. Studies in mice and zebrafish confirmed that plectin is developmentally expressed in the inner ear. Moreover, plectin's knockdown resulted in a reduction of synaptic mitochondrial potential and loss of ribbon synapses, reinforcing the idea of a role for plectin in neuronal transmission. Altogether, the results presented here, point to a new unconventional role for plectin in the inner ear. Contrary to the well-characterized association of plectin to skin and muscle diseases, we found that specific plectin mutations can result in hearing loss with no other clinical manifestations. This is important because 1) it provides evidence of plectin's involvement in inner ear function and 2) it will help clinicians at the time of diagnosis and treatment.
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Affiliation(s)
- Tianyang Zhang
- Department of Otolaryngology-Head and Neck Surgery, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong, China; Department of Otorhinolaryngology Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
| | - Zhenhang Xu
- Department of Biomedical Sciences, School of Medicine, Creighton University, Omaha, United States; Department of Otolaryngology, Xiangya Hospital, Central South University, Changsha, China.
| | - Danya Zheng
- Department of Otolaryngology-Head and Neck Surgery, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong, China.
| | - Xuechun Wang
- Department of Otolaryngology-Head and Neck Surgery, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong, China.
| | - Jingchun He
- Department of Otorhinolaryngology Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
| | - Luping Zhang
- Department of Otolaryngology-Head and Neck Surgery, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong, China.
| | - Marisa Zallocchi
- Department of Biomedical Sciences, School of Medicine, Creighton University, Omaha, United States.
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2
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Ohno K, Ohkawara B, Shen XM, Selcen D, Engel AG. Clinical and Pathologic Features of Congenital Myasthenic Syndromes Caused by 35 Genes-A Comprehensive Review. Int J Mol Sci 2023; 24:ijms24043730. [PMID: 36835142 PMCID: PMC9961056 DOI: 10.3390/ijms24043730] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 02/09/2023] [Accepted: 02/09/2023] [Indexed: 02/16/2023] Open
Abstract
Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders characterized by impaired neuromuscular signal transmission due to germline pathogenic variants in genes expressed at the neuromuscular junction (NMJ). A total of 35 genes have been reported in CMS (AGRN, ALG14, ALG2, CHAT, CHD8, CHRNA1, CHRNB1, CHRND, CHRNE, CHRNG, COL13A1, COLQ, DOK7, DPAGT1, GFPT1, GMPPB, LAMA5, LAMB2, LRP4, MUSK, MYO9A, PLEC, PREPL, PURA, RAPSN, RPH3A, SCN4A, SLC18A3, SLC25A1, SLC5A7, SNAP25, SYT2, TOR1AIP1, UNC13A, VAMP1). The 35 genes can be classified into 14 groups according to the pathomechanical, clinical, and therapeutic features of CMS patients. Measurement of compound muscle action potentials elicited by repetitive nerve stimulation is required to diagnose CMS. Clinical and electrophysiological features are not sufficient to identify a defective molecule, and genetic studies are always required for accurate diagnosis. From a pharmacological point of view, cholinesterase inhibitors are effective in most groups of CMS, but are contraindicated in some groups of CMS. Similarly, ephedrine, salbutamol (albuterol), amifampridine are effective in most but not all groups of CMS. This review extensively covers pathomechanical and clinical features of CMS by citing 442 relevant articles.
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Affiliation(s)
- Kinji Ohno
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
- Correspondence: (K.O.); (A.G.E.)
| | - Bisei Ohkawara
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Xin-Ming Shen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
| | - Duygu Selcen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
| | - Andrew G. Engel
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
- Correspondence: (K.O.); (A.G.E.)
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3
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Vahidnezhad H, Youssefian L, Harvey N, Tavasoli AR, Saeidian AH, Sotoudeh S, Varghaei A, Mahmoudi H, Mansouri P, Mozafari N, Zargari O, Zeinali S, Uitto J. Mutation update: The spectra of PLEC sequence variants and related plectinopathies. Hum Mutat 2022; 43:1706-1731. [PMID: 35815343 PMCID: PMC9771971 DOI: 10.1002/humu.24434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 06/23/2022] [Accepted: 07/07/2022] [Indexed: 01/24/2023]
Abstract
Plectin, encoded by PLEC, is a cytoskeletal linker of intermediate filaments expressed in many cell types. Plectin consists of three main domains that determine its functionality: the N-terminal domain, the Rod domain, and the C-terminal domain. Molecular defects of PLEC correlating with the functional aspects lead to a group of rare heritable disorders, plectinopathies. These multisystem disorders include an autosomal dominant form of epidermolysis bullosa simplex (EBS-Ogna), limb-girdle muscular dystrophy (LGMD), aplasia cutis congenita (ACC), and an autosomal recessive form of EBS, which may associate with muscular dystrophy (EBS-MD), pyloric atresia (EBS-PA), and/or congenital myasthenic syndrome (EBS-MyS). In this study, genotyping of over 600 Iranian patients with epidermolysis bullosa by next-generation sequencing identified 15 patients with disease-causing PLEC variants. This mutation update analyzes the clinical spectrum of PLEC in our cohort and in the literature and demonstrates the relationship between PLEC genotype and phenotypic manifestations. This study has integrated our seven novel PLEC variants and phenotypic findings with previously published data totaling 116 variants to provide the most complete overview of pathogenic PLEC variants and related disorders.
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Affiliation(s)
- Hassan Vahidnezhad
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
- Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA
| | - Leila Youssefian
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
- Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA
| | - Nailah Harvey
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
- Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA
- Philadelphia College of Osteopathic Medicine, Philadelphia, Pennsylvania, USA
| | - Ali Reza Tavasoli
- Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA
- Pediatric Neurology Division, Children’s Medical Center, Pediatric Center of Excellence, Tehran University of Medical Sciences, Tehran, Iran
| | - Amir Hossein Saeidian
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
- Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA
| | - Soheila Sotoudeh
- Department of Dermatology, Children’s Medical Center, Pediatric Center of Excellence, Tehran University of Medical Sciences, Tehran, Iran
| | - Aida Varghaei
- Department of Dermatology, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran
| | - Hamidreza Mahmoudi
- Department of Dermatology, Razi Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Parvin Mansouri
- Skin and Stem Cell Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Nikoo Mozafari
- Skin Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | | | | | - Jouni Uitto
- Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, USA
- Jefferson Institute of Molecular Medicine, Thomas Jefferson University, Philadelphia, PA
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4
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Wikramanayake TC, Chéret J, Sevilla A, Birch-Machin M, Paus R. Targeting mitochondria in dermatological therapy: Beyond oxidative damage and skin aging. Expert Opin Ther Targets 2022; 26:233-259. [PMID: 35249436 DOI: 10.1080/14728222.2022.2049756] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
INTRODUCTION The analysis of the role of the mitochondria in oxidative damage and skin aging is a significant aspect of dermatological research. Mitochondria generate most reactive oxygen species (ROS); however, excessive ROS are cytotoxic and DNA-damaging and promote (photo-)aging. ROS also possesses key physiological and regulatory functions and mitochondrial dysfunction is prominent in several skin diseases including skin cancers. Although many standard dermatotherapeutics modulate mitochondrial function, dermatological therapy rarely targets the mitochondria. Accordingly, there is a rationale for "mitochondrial dermatology"-based approaches to be applied to therapeutic research. AREAS COVERED This paper examines the functions of mitochondria in cutaneous physiology beyond energy (ATP) and ROS production. Keratinocyte differentiation and epidermal barrier maintenance, appendage morphogenesis and homeostasis, photoaging and skin cancer are considered. Based on related PubMed search results, the paper evaluates thyroid hormones, glucocorticoids, Vitamin D3 derivatives, retinoids, cannabinoid receptor agonists, PPARγ agonists, thyrotropin, and thyrotropin-releasing hormone as instructive lead compounds. Moreover, the mitochondrial protein MPZL3 as a promising new drug target for future "mitochondrial dermatology" is highlighted. EXPERT OPINION Future dermatological therapeutic research should have a mitochondrial medicine emphasis. Focusing on selected lead agents, protein targets, in silico drug design, and model diseases will fertilize a mito-centric approach.
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Affiliation(s)
- Tongyu C Wikramanayake
- Frost Department of Dermatology & Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, FL, U.S.A.,Molecular Cell and Developmental Biology Program, University of Miami Miller School of Medicine, Miami, FL, U.S.A
| | - Jérémy Chéret
- Frost Department of Dermatology & Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, FL, U.S.A
| | - Alec Sevilla
- Frost Department of Dermatology & Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, FL, U.S.A
| | - Mark Birch-Machin
- Dermatological Sciences, Translational and Clinical Research Institute, and The UK National Innovation Centre for Ageing, Newcastle University, Newcastle upon Tyne, UK
| | - Ralf Paus
- Frost Department of Dermatology & Cutaneous Surgery, University of Miami Miller School of Medicine, Miami, FL, U.S.A.,Monasterium Laboratory, Münster, Germany.,Centre for Dermatology Research, University of Manchester, and NIHR Manchester Biomedical Research Centre, Manchester, UK
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5
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Abstract
Plectin is a multi-faceted, 500 kDa-large protein, which due to its expression in different isoforms and distinct organs acts diversely as a cytoskeletal crosslinker and signaling scaffold. It functions as a mediator of keratinocyte mechanical stability in the skin, primarily through linking intermediate filaments to hemidesmosomes. Skin fragility may occur through the presence of mutations in the gene encoding for plectin, PLEC, or through the presence of autoantibodies against the molecule. Below, we review the cutaneous manifestations of plectinopathies as well as their systemic involvement in specific disease subtypes. We summarize the known roles of plectin in keratinocytes and fibroblasts and provide an outlook on future perspectives for plectin-associated skin disorders.
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Affiliation(s)
- Dimitra Kiritsi
- Department of Dermatology, Faculty of Medicine, Medical Center-University of Freiburg, 79104 Freiburg, Germany;
- Correspondence:
| | | | - Franziska Schauer
- Department of Dermatology, Faculty of Medicine, Medical Center-University of Freiburg, 79104 Freiburg, Germany;
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6
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Walter MC, Reilich P, Krause S, Hiebeler M, Gehling S, Goebel HH, Schoser B, Abicht A. Congenital myopathy and epidermolysis bullosa due to PLEC variant. Neuromuscul Disord 2021; 31:1212-1217. [PMID: 34702657 DOI: 10.1016/j.nmd.2021.09.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 06/29/2021] [Accepted: 09/24/2021] [Indexed: 10/20/2022]
Abstract
We report on an adult Turkish patient with mild myopathy with a fiber-type disproportion and mitochondrial disorganization caused by genetic variants in the plectin gene (PLEC). Molecular genetic panel testing revealed two homozygous variants in PLEC (NM_000445.4): c.8306C>G (p.Pro2769Arg) and c.7506 + 5C>G (p. ?) that were classified as variants of unknown significance (class 3) following ACMG guidelines for variant classification in genetic diagnostics. A thorough reassessment of the patient revealed mild skin blistering (epidermolysis bullosa simplex, EBS). This illustrates the importance of deep phenotyping of neuromuscular patients.
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Affiliation(s)
- Maggie C Walter
- Department of Neurology, Friedrich-Baur-Institute LMU Klinikum, Munich, Germany.
| | - Peter Reilich
- Department of Neurology, Friedrich-Baur-Institute LMU Klinikum, Munich, Germany
| | - Sabine Krause
- Department of Neurology, Friedrich-Baur-Institute LMU Klinikum, Munich, Germany
| | - Miriam Hiebeler
- Department of Neurology, Friedrich-Baur-Institute LMU Klinikum, Munich, Germany
| | | | - Hans H Goebel
- Department of Neuropathology, Charité University, Berlin, and Johannes-Gutenberg University, Mainz, Germany
| | - Benedikt Schoser
- Department of Neurology, Friedrich-Baur-Institute LMU Klinikum, Munich, Germany
| | - Angela Abicht
- Department of Neurology, Friedrich-Baur-Institute LMU Klinikum, Munich, Germany; Medical Genetics Centre, Munich, Germany
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7
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Abstract
Plectin is a giant cytoskeletal crosslinker and intermediate filament stabilizing protein. Mutations in the human plectin gene (PLEC) cause several rare diseases that are grouped under the term plectinopathies. The most common disorder is autosomal recessive disease epidermolysis bullosa simplex with muscular dystrophy (EBS-MD), which is characterized by skin blistering and progressive muscle weakness. Besides EBS-MD, PLEC mutations lead to EBS with nail dystrophy, EBS-MD with a myasthenic syndrome, EBS with pyloric atresia, limb-girdle muscular dystrophy type R17, or EBS-Ogna. In this review, we focus on the clinical and pathological manifestations caused by PLEC mutations on skeletal and cardiac muscle. Skeletal muscle biopsies from EBS-MD patients and plectin-deficient mice revealed severe dystrophic features with variation in fiber size, degenerative myofibrillar changes, mitochondrial alterations, and pathological desmin-positive protein aggregates. Ultrastructurally, PLEC mutations lead to a disorganization of myofibrils and sarcomeres, Z- and I-band alterations, autophagic vacuoles and cytoplasmic bodies, and misplaced and degenerating mitochondria. We also summarize a variety of genetically manipulated mouse and cell models, which are either plectin-deficient or that specifically lack a skeletal muscle-expressed plectin isoform. These models are powerful tools to study functional and molecular consequences of PLEC defects and their downstream effects on the skeletal muscle organization.
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8
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Valencia RG, Mihailovska E, Winter L, Bauer K, Fischer I, Walko G, Jorgacevski J, Potokar M, Zorec R, Wiche G. Plectin dysfunction in neurons leads to tau accumulation on microtubules affecting neuritogenesis, organelle trafficking, pain sensitivity and memory. Neuropathol Appl Neurobiol 2021; 47:73-95. [PMID: 32484610 PMCID: PMC7891324 DOI: 10.1111/nan.12635] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 05/19/2020] [Indexed: 12/26/2022]
Abstract
AIMS Plectin, a universally expressed multi-functional cytolinker protein, is crucial for intermediate filament networking, including crosstalk with actomyosin and microtubules. In addition to its involvement in a number of diseases affecting skin, skeletal muscle, heart, and other stress-exposed tissues, indications for a neuropathological role of plectin have emerged. Having identified P1c as the major isoform expressed in neural tissues in previous studies, our aim for the present work was to investigate whether, and by which mechanism(s), the targeted deletion of this isoform affects neuritogenesis and proper nerve cell functioning. METHODS For ex vivo phenotyping, we used dorsal root ganglion and hippocampal neurons derived from isoform P1c-deficient and plectin-null mice, complemented by in vitro experiments using purified proteins and cell fractions. To assess the physiological significance of the phenotypic alterations observed in P1c-deficient neurons, P1c-deficient and wild-type littermate mice were subjected to standard behavioural tests. RESULTS We demonstrate that P1c affects axonal microtubule dynamics by isoform-specific interaction with tubulin. P1c deficiency in neurons leads to altered dynamics of microtubules and excessive association with tau protein, affecting neuritogenesis, neurite branching, growth cone morphology, and translocation and directionality of movement of vesicles and mitochondria. On the organismal level, we found P1c deficiency manifesting as impaired pain sensitivity, diminished learning capabilities and reduced long-term memory of mice. CONCLUSIONS Revealing a regulatory role of plectin scaffolds in microtubule-dependent nerve cell functions, our results have potential implications for cytoskeleton-related neuropathies.
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Affiliation(s)
- R. G. Valencia
- Max F. Perutz LaboratoriesDepartment of Biochemistry and Cell BiologyUniversity of ViennaViennaAustria
- Present address:
Department of ImmunologyUniversity Children’s Hospital ZurichZurichSwitzerland
| | - E. Mihailovska
- Max F. Perutz LaboratoriesDepartment of Biochemistry and Cell BiologyUniversity of ViennaViennaAustria
- Present address:
AFFiRiS AGViennaAustria
| | - L. Winter
- Max F. Perutz LaboratoriesDepartment of Biochemistry and Cell BiologyUniversity of ViennaViennaAustria
- Neuromuscular Research DepartmentCenter for Anatomy and Cell BiologyMedical University of ViennaViennaAustria
| | - K. Bauer
- Max F. Perutz LaboratoriesDepartment of Biochemistry and Cell BiologyUniversity of ViennaViennaAustria
| | - I. Fischer
- Max F. Perutz LaboratoriesDepartment of Biochemistry and Cell BiologyUniversity of ViennaViennaAustria
| | - G. Walko
- Max F. Perutz LaboratoriesDepartment of Biochemistry and Cell BiologyUniversity of ViennaViennaAustria
- Present address:
Department of Biology and BiochemistryUniversity of BathBathUK
| | - J. Jorgacevski
- Laboratory of Neuroendocrinology – Molecular Cell PhysiologyFaculty of MedicineInstitute of PathophysiologyUniversity of LjubljanaLjubljanaSlovenia
- Celica Biomedical SloveniaLjubljanaSlovenia
| | - M. Potokar
- Laboratory of Neuroendocrinology – Molecular Cell PhysiologyFaculty of MedicineInstitute of PathophysiologyUniversity of LjubljanaLjubljanaSlovenia
- Celica Biomedical SloveniaLjubljanaSlovenia
| | - R. Zorec
- Laboratory of Neuroendocrinology – Molecular Cell PhysiologyFaculty of MedicineInstitute of PathophysiologyUniversity of LjubljanaLjubljanaSlovenia
- Celica Biomedical SloveniaLjubljanaSlovenia
| | - G. Wiche
- Max F. Perutz LaboratoriesDepartment of Biochemistry and Cell BiologyUniversity of ViennaViennaAustria
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9
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Argente-Escrig H, Schultheis D, Kamm L, Schowalter M, Thiel C, Türk M, Clemen CS, Muelas N, Castañón MJ, Wiche G, Herrmann H, Vilchez JJ, Schröder R. Plectin-related scapuloperoneal myopathy with treatment-responsive myasthenic syndrome. Neuropathol Appl Neurobiol 2020; 47:352-356. [PMID: 32757300 DOI: 10.1111/nan.12652] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 07/28/2020] [Indexed: 12/26/2022]
Affiliation(s)
- H Argente-Escrig
- Neuromuscular Reference Centre - ERN EURO-NMD, Hospital Universitari i Politècnic La Fe, Valencia, Spain.,Neuromuscular Pathology and Ataxia Research Group, Health Research Institute Hospital La Fe, Valencia, Spain
| | - D Schultheis
- Institute of Neuropathology, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - L Kamm
- Institute of Neuropathology, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - M Schowalter
- Institute of Neuropathology, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - C Thiel
- Institute of Human Genetics, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - M Türk
- Department of Neurology, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - C S Clemen
- Institute of Neuropathology, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany.,Institute of Aerospace Medicine, German Aerospace Centre (DLR), Cologne, Germany.,Centre for Physiology and Pathophysiology, Institute of Vegetative Physiology, Medical Faculty, University of Cologne, Cologne, Germany
| | - N Muelas
- Neuromuscular Reference Centre - ERN EURO-NMD, Hospital Universitari i Politècnic La Fe, Valencia, Spain.,Neuromuscular Pathology and Ataxia Research Group, Health Research Institute Hospital La Fe, Valencia, Spain
| | - M J Castañón
- Max F. Perutz Laboratories, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
| | - G Wiche
- Max F. Perutz Laboratories, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
| | - H Herrmann
- Institute of Neuropathology, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - J J Vilchez
- Neuromuscular Reference Centre - ERN EURO-NMD, Hospital Universitari i Politècnic La Fe, Valencia, Spain.,CIBERER and Department of Medicine, School of Medicine, University of Valencia, Valencia, Spain
| | - R Schröder
- Institute of Neuropathology, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
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10
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Mroczek M, Durmus H, Töpf A, Parman Y, Straub V. Four Individuals with a Homozygous Mutation in Exon 1f of the PLEC Gene and Associated Myasthenic Features. Genes (Basel) 2020; 11:genes11070716. [PMID: 32605089 PMCID: PMC7397187 DOI: 10.3390/genes11070716] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Revised: 06/23/2020] [Accepted: 06/24/2020] [Indexed: 11/17/2022] Open
Abstract
We identified the known c.1_9del mutation in the PLEC gene in four unrelated females from consanguineous families of Turkish origin. All individuals presented with slowly progressive limb-girdle weakness without any dermatological findings, and dystrophic changes observed in their muscle biopsies. Additionally, the neurological examination revealed ptosis, facial weakness, fatigability, and muscle cramps in all four cases. In two patients, repetitive nerve stimulation showed a borderline decrement and a high jitter was detected in all patients by single-fiber electromyography. Clinical improvement was observed after treatment with pyridostigmine and salbutamol was started. We further characterize the phenotype of patients with limb-girdle muscular dystrophy R17 clinically, by muscle magnetic resonance imaging (MRI) features and by describing a common 3.8 Mb haplotype in three individuals from the same geographical region. In addition, we review the neuromuscular symptoms associated with PLEC mutations and the role of plectin in the neuromuscular junction.
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Affiliation(s)
- Magdalena Mroczek
- John Walton Muscular Dystrophy Research Centre, Translational and Clinical Research Institute, Newcastle University and Newcastle Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 3BZ, UK; (M.M.); (A.T.)
| | - Hacer Durmus
- Department of Neurology, Istanbul Faculty of Medicine, Istanbul University, Istanbul 34093, Turkey; (H.D.); (Y.P.)
| | - Ana Töpf
- John Walton Muscular Dystrophy Research Centre, Translational and Clinical Research Institute, Newcastle University and Newcastle Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 3BZ, UK; (M.M.); (A.T.)
| | - Yesim Parman
- Department of Neurology, Istanbul Faculty of Medicine, Istanbul University, Istanbul 34093, Turkey; (H.D.); (Y.P.)
| | - Volker Straub
- John Walton Muscular Dystrophy Research Centre, Translational and Clinical Research Institute, Newcastle University and Newcastle Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 3BZ, UK; (M.M.); (A.T.)
- Correspondence: ; Tel.: +44-19124-18762-8655
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11
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Abstract
The skin is a high turnover organ, and its constant renewal depends on the rapid proliferation of its progenitor cells. The energy requirement for these metabolically active cells is met by mitochondrial respiration, an ATP generating process driven by a series of protein complexes collectively known as the electron transport chain (ETC) that is located on the inner membrane of the mitochondria. However, reactive oxygen species (ROS) like superoxide, singlet oxygen, peroxides are inevitably produced during respiration and disrupt macromolecular and cellular structures if not quenched by the antioxidant system. The oxidative damage caused by mitochondrial ROS production has been established as the molecular basis of multiple pathophysiological conditions, including aging and cancer. Not surprisingly, the mitochondria are the primary organelle affected during chronological and UV-induced skin aging, the phenotypic manifestations of which are the direct consequence of mitochondrial dysfunction. Also, deletions and other aberrations in the mitochondrial DNA (mtDNA) are frequent in photo-aged skin and skin cancer lesions. Recent studies have revealed a more innate role of the mitochondria in maintaining skin homeostasis and pigmentation, which are affected when the essential mitochondrial functions are impaired. Some common and rare skin disorders have a mitochondrial involvement and include dermal manifestations of primary mitochondrial diseases as well as congenital skin diseases caused by damaged mitochondria. With studies increasingly supporting the close association between mitochondria and skin health, its therapeutic targeting in the skin-either via an ATP production boost or free radical scavenging-has gained attention from clinicians and aestheticians alike. Numerous bioactive compounds have been identified that improve mitochondrial functions and have proved effective against aged and diseased skin. In this review, we discuss the essential role of mitochondria in regulating normal and abnormal skin physiology and the possibility of targeting this organelle in various skin disorders.
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Affiliation(s)
| | | | - Keshav K Singh
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
- Integartive Center For Aging Research and O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
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12
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Gonzalez Garcia A, Tutmaher MS, Upadhyayula SR, Sanchez Russo R, Verma S. Novel PLEC gene variants causing congenital myasthenic syndrome. Muscle Nerve 2019; 60:E40-E43. [PMID: 31509265 DOI: 10.1002/mus.26703] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 09/05/2019] [Accepted: 09/08/2019] [Indexed: 11/11/2022]
Affiliation(s)
- Aixa Gonzalez Garcia
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
| | - Michelle S Tutmaher
- Department of Pediatrics and Neurology, Emory University School of Medicine, Atlanta, Georgia
| | - Saila R Upadhyayula
- Department of Pediatrics and Neurology, Emory University School of Medicine, Atlanta, Georgia
| | | | - Sumit Verma
- Department of Pediatrics and Neurology, Emory University School of Medicine, Atlanta, Georgia
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Nicolau S, Kao JC, Liewluck T. Trouble at the junction: When myopathy and myasthenia overlap. Muscle Nerve 2019; 60:648-657. [PMID: 31449669 DOI: 10.1002/mus.26676] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 08/18/2019] [Accepted: 08/20/2019] [Indexed: 12/22/2022]
Abstract
Although myopathies and neuromuscular junction disorders are typically distinct, their coexistence has been reported in several inherited and acquired conditions. Affected individuals have variable clinical phenotypes but typically display both a decrement on repetitive nerve stimulation and myopathic findings on muscle biopsy. Inherited causes include myopathies related to mutations in BIN1, DES, DNM2, GMPPB, MTM1, or PLEC and congenital myasthenic syndromes due to mutations in ALG2, ALG14, COL13A1, DOK7, DPAGT1, or GFPT1. Additionally, a decrement due to muscle fiber inexcitability is observed in certain myotonic disorders. The identification of a defect of neuromuscular transmission in an inherited myopathy may assist in establishing a molecular diagnosis and in selecting patients who would benefit from pharmacological correction of this defect. Acquired cases meanwhile stem from the co-occurrence of myasthenia gravis or Lambert-Eaton myasthenic syndrome with an immune-mediated myopathy, which may be due to paraneoplastic disorders or exposure to immune checkpoint inhibitors.
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Affiliation(s)
- Stefan Nicolau
- Department of Neurology, Mayo Clinic, Rochester, Minnesota
| | - Justin C Kao
- Department of Neurology, Auckland City Hospital, Auckland, New Zealand
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Abstract
PURPOSE OF REVIEW Summarize features of the currently recognized congenital myasthenic syndromes (CMS) with emphasis on novel findings identified in the past 6 years. RECENT FINDINGS Since the last review of the CMS in this journal in 2012, several novel CMS were identified. The identified disease proteins are SNAP25B, synaptotagmin 2, Munc13-1, synaptobrevin-1, GFPT1, DPAGT1, ALG2, ALG14, Agrin, GMPPB, LRP4, myosin 9A, collagen 13A1, the mitochondrial citrate carrier, PREPL, LAMA5, the vesicular ACh transporter, and the high-affinity presynaptic choline transporter. Exome sequencing has provided a powerful tool for identifying novel CMS. Identifying the disease genes is essential for determining optimal therapy. The landscape of the CMS is still unfolding.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA.
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16
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Abstract
The congenital myasthenic syndromes (CMS) are heterogeneous disorders in which the safety margin of neuromuscular transmission is compromised by one or more specific mechanisms. The disease proteins reside in the nerve terminal, the synaptic basal lamina, or in the postsynaptic region, or at multiple sites at the neuromuscular junction as well as in other tissues. Targeted mutation analysis by Sanger or exome sequencing has been facilitated by characteristic phenotypic features of some CMS. No fewer than 20 disease genes have been recognized to date. In one-half of the currently identified probands, the disease stems from mutations in genes encoding subunits of the muscle form of the acetylcholine receptor (CHRNA1, CHRNB, CHRNAD1, and CHRNE). In 10-14% of the probands the disease is caused by mutations in RAPSN, DOK 7, or COLQ, and in 5% by mutations in CHAT. Other less frequently identified disease genes include LAMB2, AGRN, LRP4, MUSK, GFPT1, DPAGT1, ALG2, and ALG 14 as well as SCN4A, PREPL, PLEC1, DNM2, and MTM1. Identification of the genetic basis of each CMS is important not only for genetic counseling and disease prevention but also for therapy, because therapeutic agents that benefit one type of CMS can be harmful in another.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic College of Medicine, Rochester, MN, United States.
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Thorolfsdottir RB, Sveinbjornsson G, Sulem P, Helgadottir A, Gretarsdottir S, Benonisdottir S, Magnusdottir A, Davidsson OB, Rajamani S, Roden DM, Darbar D, Pedersen TR, Sabatine MS, Jonsdottir I, Arnar DO, Thorsteinsdottir U, Gudbjartsson DF, Holm H, Stefansson K. A Missense Variant in PLEC Increases Risk of Atrial Fibrillation. J Am Coll Cardiol 2017; 70:2157-2168. [PMID: 29050564 DOI: 10.1016/j.jacc.2017.09.005] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 08/07/2017] [Accepted: 09/05/2017] [Indexed: 01/19/2023]
Abstract
BACKGROUND Genome-wide association studies (GWAS) have yielded variants at >30 loci that associate with atrial fibrillation (AF), including rare coding mutations in the sarcomere genes MYH6 and MYL4. OBJECTIVES The aim of this study was to search for novel AF associations and in doing so gain insights into the mechanisms whereby variants affect AF risk, using electrocardiogram (ECG) measurements. METHODS The authors performed a GWAS of 14,255 AF cases and 374,939 controls, using whole-genome sequence data from the Icelandic population, and tested novel signals in 2,002 non-Icelandic cases and 12,324 controls. They then tested the AF variants for effect on cardiac electrical function by using measurements in 289,297 ECGs from 62,974 individuals. RESULTS The authors discovered 2 novel AF variants, the intergenic variant rs72700114, between the genes LINC01142 and METTL11B (risk allele frequency = 8.1%; odds ratio [OR]: 1.26; p = 3.1 × 10-18), and the missense variant p.Gly4098Ser in PLEC (frequency = 1.2%; OR: 1.55; p = 8.0 × 10-10), encoding plectin, a cytoskeletal cross-linking protein that contributes to integrity of cardiac tissue. The authors also confirmed 29 reported variants. p.Gly4098Ser in PLEC significantly affects various ECG measurements in the absence of AF. Other AF variants have diverse effects on the conduction system, ranging from none to extensive. CONCLUSIONS The discovery of a missense variant in PLEC affecting AF combined with recent discoveries of variants in the sarcomere genes MYH6 and MYL4 points to an important role of myocardial structure in the pathogenesis of the disease. The diverse associations between AF variants and ECG measurements suggest fundamentally different categories of mechanisms contributing to the development of AF.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Dan M Roden
- Departments of Medicine, Pharmacology, and Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Dawood Darbar
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Terje R Pedersen
- Center For Preventive Medicine, Oslo University Hospital and Medical Faculty, University of Oslo, Oslo, Norway
| | - Marc S Sabatine
- TIMI Study Group, Division of Cardiovascular Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Ingileif Jonsdottir
- deCODE genetics/Amgen, Inc., Reykjavik, Iceland; Faculty of Medicine, University of Iceland, Reykjavik, Iceland; Department of Immunology, Landspitali University Hospital, Reykjavik, Iceland
| | - David O Arnar
- deCODE genetics/Amgen, Inc., Reykjavik, Iceland; Faculty of Medicine, University of Iceland, Reykjavik, Iceland; Department of Medicine, Landspitali University Hospital, Reykjavik, Iceland
| | - Unnur Thorsteinsdottir
- deCODE genetics/Amgen, Inc., Reykjavik, Iceland; Faculty of Medicine, University of Iceland, Reykjavik, Iceland
| | - Daniel F Gudbjartsson
- deCODE genetics/Amgen, Inc., Reykjavik, Iceland; School of Engineering and Natural Sciences, University of Iceland, Reykjavik, Iceland
| | - Hilma Holm
- deCODE genetics/Amgen, Inc., Reykjavik, Iceland
| | - Kari Stefansson
- deCODE genetics/Amgen, Inc., Reykjavik, Iceland; Faculty of Medicine, University of Iceland, Reykjavik, Iceland.
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Kyrova J, Kopeckova L, Buckova H, Mrazova L, Vesely K, Hermanova M, Oslejskova H, Fajkusova L. Epidermolysis bullosa simplex with muscular dystrophy. Review of the literature and a case report. J Dermatol Case Rep 2016; 10:39-48. [PMID: 28400893 DOI: 10.3315/jdcr.2016.1231] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 09/06/2016] [Indexed: 11/11/2022]
Abstract
BACKGROUND Epidermolysis bullosa simplex associated with muscular dystrophy is a genetic skin disease caused by plectin deficiency. A case of a 19-year-old Czech patient affected with this disease and a review all previously published clinical cases are presented. MAIN OBSERVATIONS In our patient, skin signs of the disease developed after birth. Bilateral ptosis at the age of 8 years was considered as the first specific symptom of muscular dystrophy. Since then, severe scoliosis, urological and psychiatric complication have quickly developed. The signs of plectin deficiency were found by histopathological studies, electron microscopy and antigen mapping of the skin and muscular samples. Two autosomal recessive mutations in the plectin gene leading to premature termination codon were disclosed by mutation analysis. By review of all published clinical cases, 49 patients with this disease were found. 54 different mutations in the plectin gene were published, p.(Arg2319*) in exon 31 being the most frequently found. Median age of muscular dystrophy development was 9.5 years. Hoarseness and respiratory complications were the most often complications beside skin involvement. CONCLUSION Epidermolysis bullosa simplex with muscular dystrophy was diagnosed based on clinical, histopathological (skin and muscle biopsy) and mutation analysis of the plectin gene. Overview of the genetic and clinical characteristic of this disease could be presented by review of all previously published clinical cases.
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Affiliation(s)
- Jana Kyrova
- Department of Pediatric Dermatology, Pediatric Clinic, University Hospital Brno and Masaryk University Brno, Brno, Czech Republic; ; EB Centre Czech Republic, University Hospital Brno and Masaryk University Brno, Brno, Czech Republic
| | - Lenka Kopeckova
- Centre of Molecular Biology and Gene Therapy, University Hospital Brno and Masaryk University Brno, Brno, Czech Republic
| | - Hana Buckova
- Department of Pediatric Dermatology, Pediatric Clinic, University Hospital Brno and Masaryk University Brno, Brno, Czech Republic; ; EB Centre Czech Republic, University Hospital Brno and Masaryk University Brno, Brno, Czech Republic
| | - Lenka Mrazova
- Clinic of Pediatric Neurology, University Hospital and Masaryk University Brno, Brno, Czech Republic
| | - Karel Vesely
- 1st Department of Pathological Anatomy, St. Anne´s University Hospital Brno and Masaryk University Brno, Brno, Czech Republic
| | - Marketa Hermanova
- 1st Department of Pathological Anatomy, St. Anne´s University Hospital Brno and Masaryk University Brno, Brno, Czech Republic
| | - Hana Oslejskova
- Clinic of Pediatric Neurology, University Hospital and Masaryk University Brno, Brno, Czech Republic
| | - Lenka Fajkusova
- Centre of Molecular Biology and Gene Therapy, University Hospital Brno and Masaryk University Brno, Brno, Czech Republic
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Affiliation(s)
- Kinji Ohno
- Division of Neurogenetics; Center for Neurological Diseases and Cancer; Nagoya University Graduate School of Medicine; Nagoya Japan
| | - Bisei Ohkawara
- Division of Neurogenetics; Center for Neurological Diseases and Cancer; Nagoya University Graduate School of Medicine; Nagoya Japan
| | - Mikako Ito
- Division of Neurogenetics; Center for Neurological Diseases and Cancer; Nagoya University Graduate School of Medicine; Nagoya Japan
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20
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Affiliation(s)
- S. Jackson
- Department of Neurology; Technische Universität Dresden; Dresden Germany
| | - J. Schaefer
- Department of Neurology; Technische Universität Dresden; Dresden Germany
| | - M. Meinhardt
- Department of Pathology; Technische Universität Dresden; Dresden Germany
| | - H. Reichmann
- Department of Neurology; Technische Universität Dresden; Dresden Germany
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21
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Abstract
The congenital myasthenic syndromes (CMS) are a diverse group of genetic disorders caused by abnormal signal transmission at the motor endplate, a special synaptic contact between motor axons and each skeletal muscle fibre. Most CMS stem from molecular defects in the muscle nicotinic acetylcholine receptor, but they can also be caused by mutations in presynaptic proteins, mutations in proteins associated with the synaptic basal lamina, defects in endplate development and maintenance, or defects in protein glycosylation. The specific diagnosis of some CMS can sometimes be reached by phenotypic clues pointing to the mutated gene. In the absence of such clues, exome sequencing is a useful technique for finding the disease gene. Greater understanding of the mechanisms of CMS have been obtained from structural and electrophysiological studies of the endplate, and from biochemical studies. Present therapies for the CMS include cholinergic agonists, long-lived open-channel blockers of the acetylcholine receptor ion channel, and adrenergic agonists. Although most CMS are treatable, caution should be exercised as some drugs that are beneficial in one syndrome can be detrimental in another.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, Rochester, MN, USA.
| | - Xin-Ming Shen
- Department of Neurology, Mayo Clinic, Rochester, MN, USA
| | - Duygu Selcen
- Department of Neurology, Mayo Clinic, Rochester, MN, USA
| | - Steven M Sine
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
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22
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Rodríguez Cruz PM, Sewry C, Beeson D, Jayawant S, Squier W, McWilliam R, Palace J. Congenital myopathies with secondary neuromuscular transmission defects; A case report and review of the literature. Neuromuscul Disord 2014; 24:1103-10. [DOI: 10.1016/j.nmd.2014.07.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 06/27/2014] [Accepted: 07/18/2014] [Indexed: 01/14/2023]
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23
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Abstract
Plectin has been characterized as a linker protein that is expressed in many cell types and is distinctive in various isoforms in the N-terminus and around the rod domain due to complicated alternative splicing of PLEC, the gene encoding plectin. Plectin deficiency causes autosomal recessive epidermolysis bullosa simplex (EBS) with involvement of the skin and other organs, such as muscle and gastrointestinal tract, depending on the expression pattern of the defective protein. In addition, a point mutation in the rod domain of plectin leads to autosomal dominant EBS, called as EBS-Ogna. Plectin can be targeted by circulating autoantibodies in subepidermal autoimmune blistering diseases. This review summarizes plectin-related skin diseases, from congenital to autoimmune disorders.
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24
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Mihailovska E, Raith M, Valencia RG, Fischer I, Al Banchaabouchi M, Herbst R, Wiche G. Neuromuscular synapse integrity requires linkage of acetylcholine receptors to postsynaptic intermediate filament networks via rapsyn-plectin 1f complexes. Mol Biol Cell 2014; 25:4130-49. [PMID: 25318670 PMCID: PMC4263455 DOI: 10.1091/mbc.e14-06-1174] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
P1f, a specific isoform of the cytolinker protein plectin, bridges AChRs to the desmin IF network of myofibers via direct interaction with the AChR-scaffolding protein rapsyn. P1f-mediated IF linkage is crucial for the formation and maintenance of AChR clusters, postsynaptic organization of the NMJ, and body locomotion. Mutations in the cytolinker protein plectin lead to grossly distorted morphology of neuromuscular junctions (NMJs) in patients suffering from epidermolysis bullosa simplex (EBS)-muscular dystrophy (MS) with myasthenic syndrome (MyS). Here we investigated whether plectin contributes to the structural integrity of NMJs by linking them to the postsynaptic intermediate filament (IF) network. Live imaging of acetylcholine receptors (AChRs) in cultured myotubes differentiated ex vivo from immortalized plectin-deficient myoblasts revealed them to be highly mobile and unable to coalesce into stable clusters, in contrast to wild-type cells. We found plectin isoform 1f (P1f) to bridge AChRs and IFs via direct interaction with the AChR-scaffolding protein rapsyn in an isoform-specific manner; forced expression of P1f in plectin-deficient cells rescued both compromised AChR clustering and IF network anchoring. In conditional plectin knockout mice with gene disruption in muscle precursor/satellite cells (Pax7-Cre/cKO), uncoupling of AChRs from IFs was shown to lead to loss of postsynaptic membrane infoldings and disorganization of the NMJ microenvironment, including its invasion by microtubules. In their phenotypic behavior, mutant mice closely mimicked EBS-MD-MyS patients, including impaired body balance, severe muscle weakness, and reduced life span. Our study demonstrates that linkage to desmin IF networks via plectin is crucial for formation and maintenance of AChR clusters, postsynaptic NMJ organization, and body locomotion.
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Affiliation(s)
- Eva Mihailovska
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
| | - Marianne Raith
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
| | - Rocio G Valencia
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
| | - Irmgard Fischer
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
| | - Mumna Al Banchaabouchi
- Preclinical Phenotyping Facility, Campus Science Support Facilities, 1030 Vienna, Austria
| | - Ruth Herbst
- Center for Brain Research and Institute of Immunology, Medical University of Vienna, 1030 Vienna, Austria
| | - Gerhard Wiche
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, 1030 Vienna, Austria
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25
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Abstract
Aberrant mitochondrial structure and function influence tissue homeostasis and thereby contribute to multiple human disorders and ageing. Ten per cent of patients with primary mitochondrial disorders present skin manifestations that can be categorized into hair abnormalities, rashes, pigmentation abnormalities and acrocyanosis. Less attention has been paid to the fact that several disorders of the skin are linked to alterations of mitochondrial energy metabolism. This review article summarizes the contribution of mitochondrial pathology to both common and rare skin diseases. We explore the intriguing observation that a wide array of skin disorders presents with primary or secondary mitochondrial pathology and that a variety of molecular defects can cause dysfunctional mitochondria. Among them are mutations in mitochondrial- and nuclear DNA-encoded subunits and assembly factors of oxidative phosphorylation (OXPHOS) complexes; mutations in intermediate filament proteins involved in linking, moving and shaping of mitochondria; and disorders of mitochondrial DNA metabolism, fatty acid metabolism and heme synthesis. Thus, we assume that mitochondrial involvement is the rule rather than the exception in skin diseases. We conclude the article by discussing how improving mitochondrial function can be beneficial for aged skin and can be used as an adjunct therapy for certain skin disorders. Consideration of mitochondrial energy metabolism in the skin creates a new perspective for both dermatologists and experts in metabolic disease.
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Affiliation(s)
- René G Feichtinger
- Research Program for Receptor Biochemistry and Tumor Metabolism, Department of Pediatrics, University Hospital Salzburg, Paracelsus Medical University, Salzburg, Austria
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26
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Bouameur JE, Favre B, Borradori L. Plakins, a versatile family of cytolinkers: roles in skin integrity and in human diseases. J Invest Dermatol 2013; 134:885-894. [PMID: 24352042 DOI: 10.1038/jid.2013.498] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 10/16/2013] [Accepted: 10/25/2013] [Indexed: 11/09/2022]
Abstract
The plakin family consists of giant proteins involved in the cross-linking and organization of the cytoskeleton and adhesion complexes. They further modulate several fundamental biological processes, such as cell adhesion, migration, and polarization or signaling pathways. Inherited and acquired defects of plakins in humans and in animal models potentially lead to dramatic manifestations in the skin, striated muscles, and/or nervous system. These observations unequivocally demonstrate the key role of plakins in the maintenance of tissue integrity. Here we review the characteristics of the mammalian plakin members BPAG1 (bullous pemphigoid antigen 1), desmoplakin, plectin, envoplakin, epiplakin, MACF1 (microtubule-actin cross-linking factor 1), and periplakin, highlighting their role in skin homeostasis and diseases.
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Affiliation(s)
- Jamal-Eddine Bouameur
- Departments of Dermatology and Clinical Research, Inselspital, Bern University Hospital, and University of Bern, Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Bertrand Favre
- Departments of Dermatology and Clinical Research, Inselspital, Bern University Hospital, and University of Bern, Bern, Switzerland.
| | - Luca Borradori
- Departments of Dermatology and Clinical Research, Inselspital, Bern University Hospital, and University of Bern, Bern, Switzerland
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27
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Abstract
Plectin is a large, 500-kDa, intermediate filament (IF)-associated protein. It acts as a cytoskeletal crosslinker and signaling scaffold, affecting mechanical as well as dynamic properties of the cytoskeleton. As a member of the plakin family of cytolinker proteins, plectin has a multidomain structure that is responsible for its vast binding portfolio. It not only binds to all types of IFs, actin filaments and microtubules, but also to transmembrane receptors, proteins of the subplasma membrane protein skeleton, components of the nuclear envelope, and several kinases with known roles in migration, proliferation, and energy metabolism of cells. Due to alternative splicing, plectin is expressed as various isoforms with differing N-terminal heads that dictate their differential subcellular targeting. Through specific interactions with other proteins at their target sites and their ability to bind to all types of IFs, plectin molecules provide strategically located IF anchorage sites within the cytoplasm of cells. In this review, we will present an overview of the structural features and functional properties of plectin and discuss recent progress in defining the role of its isoforms in stress-prone tissues and the implicated diseases, with focus on skin, skeletal muscle, and Schwann cells of peripheral nerve.
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Affiliation(s)
- Maria J. Castañón
- Max F. Perutz Laboratories, Department of Biochemistry and Cell Biology, University of Vienna, 1030 Vienna, Austria
| | - Gernot Walko
- Max F. Perutz Laboratories, Department of Biochemistry and Cell Biology, University of Vienna, 1030 Vienna, Austria
- Present Address: Centre for Stem Cells and Regenerative Medicine, King’s College London School of Medicine, 28th Floor, Tower Wing, Guy’s Hospital, Great Maze Pond, London, SE1 9RT UK
| | - Lilli Winter
- Max F. Perutz Laboratories, Department of Biochemistry and Cell Biology, University of Vienna, 1030 Vienna, Austria
- Present Address: Institute of Neuropathology, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany
| | - Gerhard Wiche
- Max F. Perutz Laboratories, Department of Biochemistry and Cell Biology, University of Vienna, 1030 Vienna, Austria
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28
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Abstract
During the past five years an increasing number of patients have been diagnosed with congenital myasthenic syndromes (CMS) and a number of novel syndromes have been recognized and investigated. This presentation focuses on the CMS caused by defects in choline acetyltransferase, novel fast-channel syndromes that hinder isomerization of the acetylcholine receptor from the closed to the open state, the consequences of deleterious mutations in the intermediate filament linker plectin, altered neuromuscular transmission in a centronuclear myopathy, and two recently identified CMS caused by congenital defects in glycosylation.
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Affiliation(s)
- Andrew G Engel
- Neuromuscular Research Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.
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29
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Abstract
Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders caused by genetic defects affecting neuromuscular transmission and leading to muscle weakness accentuated by exertion. The characterization of CMS comprises two complementary steps: establishing the diagnosis and identifying the pathophysiological type of CMS. The combination of clinical, electrophysiological, and morphological studies allows the physician to refer a given CMS to mutation(s) in one of the 18 causative genes discovered to date and, in turn, to classify the CMS according to the location of the mutated proteins at the neuromuscular junction into presynaptic compartment, synaptic basal lamina, and postsynaptic compartment CMS. This complete characterization is essential for counseling and therapy of the patient, depending on the molecular background of the respective CMS. Despite comprehensive characterization, the phenotypic expression of one given gene involved is variable, and the etiology of many CMS remains to be discovered.
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Affiliation(s)
- Bruno Eymard
- Reference Center for Neuromuscular Diseases, Institute of Myology, Pitié-Salpêtrière Hospital, Paris, France
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30
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Winter L, Wiche G. The many faces of plectin and plectinopathies: pathology and mechanisms. Acta Neuropathol 2013; 125:77-93. [PMID: 22864774 DOI: 10.1007/s00401-012-1026-0] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Revised: 07/12/2012] [Accepted: 07/23/2012] [Indexed: 12/20/2022]
Abstract
Plectin, a giant multifunctional cytolinker protein, plays a crucial role in stabilizing and orchestrating intermediate filament networks in cells. Mutations in the human plectin gene result in multiple diseases manifesting with muscular dystrophy, skin blistering, and signs of neuropathy. The most common disease caused by plectin deficiency is epidermolysis bullosa simplex (EBS)-MD, a rare autosomal-recessive skin blistering disorder with late-onset muscular dystrophy. EBS-MD patients and plectin-deficient mice display pathologic desmin-positive protein aggregates, degenerated myofibrils, and mitochondrial abnormalities, the hallmarks of myofibrillar myopathies. In addition to EBS-MD, plectin mutations have been shown to cause EBS-MD with a myasthenic syndrome, limb-girdle muscular dystrophy type 2Q, EBS with pyloric atresia, and EBS-Ogna. This review focuses on clinical and pathological manifestations of these plectinopathies. It addresses especially plectin's role in skeletal muscle, where a loss of muscle fiber integrity and profound changes of myofiber cytoarchitecture are observed in its absence. Furthermore, the highly complex genetic and molecular structure of plectin is discussed; a high number of differentially spliced exons give rise to a variety of different isoforms, which fulfill distinct functions in different cell types and tissues. Plectin's abilities to act as a dynamic organizer of intermediate filament networks and to interact with a multitude of different interaction partners are the basis for its function as a scaffolding platform for proteins involved in signaling. Finally, the article addresses a series of genetically manipulated mouse lines that were generated to serve as powerful models to study functional and molecular consequences of plectin gene defects.
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Affiliation(s)
- Lilli Winter
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, Dr. Bohrgasse 9, 1030 Vienna, Austria
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31
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Abstract
This article reviews the use of electrodiagnostic testing in disorders of neuromuscular transmission and discusses the differences between various presynaptic and postsynaptic disorders. Attention is paid to quality control issues that influence the sensitivity of repetitive nerve stimulation and single fiber electromyography. Electrodiagnostic testing, when used as an extension of the clinician's history and physical examination, will provide appropriate direction in establishing the diagnosis.
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Affiliation(s)
- James F Howard
- Neuromuscular Disorders Section, Department of Neurology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7025, USA.
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32
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Abstract
Congenital myasthenic syndromes comprise heterogeneous genetic diseases characterized by compromised neuromuscular transmission. Congenital myasthenic syndromes are classified as presynaptic, synaptic, or postsynaptic, depending on the primary defect's location within the neuromuscular junction. Presynaptic forms are the rarest, affecting an estimated 7-8% of patients; synaptic forms account for approximately 14-15% of patients; and the remaining 75-80% are attributable to postsynaptic defects. Clinical manifestations vary by congenital myasthenic syndrome subtype. Electrophysiologic, morphologic, and molecular descriptions of various forms of congenital myasthenic syndromes have led to an enhanced understanding of clinical manifestations and disease pathophysiology. Although congenital myasthenic syndromes are indicated by clinical manifestations, family history, electrophysiologic studies, and responses to acetylcholinesterase inhibitors, overlap in some presentations occurs. Therefore, genetic testing may be necessary to identify specific mutations in CHAT, COLQ, LAMB2, CHRNA, CHRNB, CHRND, CHRNE, CHRNG, RAPSN, DOK7, MUSK, AGRN, SCN4A, GFPT1, or PLEC1 genes. The identification of congenital myasthenic syndromes subtypes will prove important in the treatment of these patients. Different drugs may be beneficial, or should be avoided because they are ineffective or worsen some forms of congenital myasthenic syndromes. We explore the classification, clinical manifestations, electrophysiologic features, genetics, and treatment responses of each congenital myasthenic syndrome subtype.
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Affiliation(s)
- Paulo José Lorenzoni
- Neuromuscular Disorders Unit, Division of Neurology, Department of Internal Medicine, Hospital de Clínicas da Universidade Federal do Paraná, Curitiba, PR, Brazil
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Abstract
Congenital myasthenic syndromes (CMS) represent a heterogeneous group of disorders in which the safety margin of neuromuscular transmission is compromised by one or more specific mechanisms. Clinical, electrophysiologic, and morphologic studies have paved the way for detecting CMS-related mutations in proteins residing in the nerve terminal, the synaptic basal lamina, or in the postsynaptic region of the motor endplate. The disease proteins identified to date include the acetylcholine receptor, acetylcholinesterase, choline acetyltransferase, rapsyn, and Na(v)1.4, muscle-specific kinase, agrin, β2-laminin, downstream of tyrosine kinase 7, and glutamine-fructose-6-phosphate transaminase 1. Analysis of electrophysiologic and biochemical properties of mutant proteins expressed in heterologous systems have contributed crucially to defining the molecular consequences of the observed mutations and have resulted in improved therapy of most CMS.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
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Abstract
Congenital myasthenic syndromes (CMS) are heterogeneous disorders in which the safety margin of neuromuscular transmission is compromised by one or more specific mechanisms. Clinical, electrophysiologic, and morphologic studies have paved the way for detecting CMS-related mutations in proteins residing in the nerve terminal, the synaptic basal lamina, and in the postsynaptic region of the motor endplate. The disease proteins identified to date include choline acetyltransferase (ChAT), the endplate species of acetylcholinesterase (AChE), β2-laminin, the acetylcholine receptor (AChR), rapsyn, plectin, Na(v)1.4, the muscle specific protein kinase (MuSK), agrin, downstream of tyrosine kinase 7 (Dok-7), and glutamine-fructose-6-phosphate transaminase 1 (GFPT1). Myasthenic syndromes associated with centronuclear myopathies were recently recognized. Analysis of properties of expressed mutant proteins contributed to finding improved therapy for most CMS. Despite these advances, the molecular basis of some phenotypically characterized CMS remains elusive. Moreover, other types of CMS and disease genes likely exist and await discovery.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, Rochester, MN 55905, United States.
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Abstract
Nemaline myopathy constitutes a continuous spectrum of primary skeletal muscle disorders named after the Greek word for thread, nema. The diagnosis is based on muscle weakness, combined with visualization of nemaline bodies on muscle biopsy. The patients' muscle weakness is usually generalized, but there may be a selective pattern of more pronounced weakness, and, most importantly, respiratory muscles may be especially weak. Histologically, additional features may coexist with the nemaline bodies. There are 7 known causative genes. The function of the most recently identified gene is unknown, but the other 6 encoded proteins are associated with the muscle thin filament. The 2 most common causes of nemaline myopathy are recessive mutations in nebulin and de novo dominant mutations in skeletal muscle α-actin. At least 1 further gene remains to be identified. Patient care is based on managing the clinical symptoms. Animal models are helping to gain insight into pathogenesis, and a variety of therapeutic approaches are being investigated.
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Affiliation(s)
- Carina Wallgren-Pettersson
- The Folkhälsan Institute of Genetics and Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland.
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Liewluck T, Selcen D, Engel AG. Beneficial effects of albuterol in congenital endplate acetylcholinesterase deficiency and Dok-7 myasthenia. Muscle Nerve 2011; 44:789-94. [PMID: 21952943 DOI: 10.1002/mus.22176] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2011] [Indexed: 12/20/2022]
Abstract
INTRODUCTION Congenital myasthenic syndromes (CMS) are disabling but treatable disorders. Anticholinesterase therapy is effective in most of them, but is contraindicated in endplate (EP) acetylcholinesterase (AChE) deficiency, the slow-channel syndrome, Dok-7 myasthenia, and β(2) -laminin deficiency, and is not useful in CMS due to defects in muscle-specific kinase (MuSK), agrin, and plectin. EP AChE, Dok-7, and β(2)-laminin deficiencies respond favorably to ephedrine, but ephedrine can no longer be prescribed in the USA. METHODS We used albuterol, another sympathomimetic agent, to treat 3 patients with EP AChE deficiency and 15 with Dok-7 myasthenia. Response to therapy was evaluated by a 9-point questionnaire pertaining to activities of daily life. RESULTS Comparison of the pre- and posttreatment responses indicated a beneficial response to albuterol (P < 0.001) in both patient groups. The adverse effects of therapy were like those of ephedrine. CONCLUSION Our observations should spur controlled, prospective clinical trials of albuterol in these as well as other CMS.
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Affiliation(s)
- Teerin Liewluck
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, Minnesota 55905, USA
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Yiu EM, Klausegger A, Waddell LB, Grasern N, Lloyd L, Tran K, North KN, Bauer JW, McKelvie P, Chow C, Ryan MM, Murrell DF. Epidermolysis bullosa with late-onset muscular dystrophy and plectin deficiency. Muscle Nerve 2011; 44:135-41. [DOI: 10.1002/mus.22076] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Barišić N, Chaouch A, Müller JS, Lochmüller H. Genetic heterogeneity and pathophysiological mechanisms in congenital myasthenic syndromes. Eur J Paediatr Neurol 2011; 15:189-96. [PMID: 21498094 DOI: 10.1016/j.ejpn.2011.03.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Accepted: 03/20/2011] [Indexed: 10/18/2022]
Abstract
Congenital myasthenic syndromes (CMS) are a rare heterogeneous group of inherited neuromuscular disorders associated with distinctive clinical, electrophysiological, ultrastructural and genetic abnormalities. These genetic defects either impair neuromuscular transmission directly or result in secondary impairments, which eventually compromise the safety margin of neuromuscular transmission. In this report we will explore the significant progress made in understanding the molecular pathogenesis of CMS, which is important for both patients and clinicians in terms of reaching a definite diagnosis and selecting the most appropriate treatment.
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Affiliation(s)
- Nina Barišić
- Department of Pediatrics, Medical School, University of Zagreb, 10000 Zagreb, Rebro, Kišpatićeva 12, Zagreb, Croatia.
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Abstract
BACKGROUND Plectin crosslinks intermediate filaments to their targets in different tissues. Defects in plectin cause epidermolysis bullosa simplex (EBS), muscular dystrophy (MD), and sometimes pyloric atresia. Association of EBS with a myasthenic syndrome (MyS) was documented in a single patient in 1999. OBJECTIVES To analyze the clinical, structural, and genetic aspects of a second and fatal case of EBS associated with a MyS and search for the genetic basis of the disease in a previously reported patient with EBS-MD-MyS. METHODS Clinical observations; histochemical, immunocytochemical, and electron microscopy studies of skeletal muscle and neuromuscular junction; and mutation analysis. RESULTS An African American man had EBS since early infancy, and progressive muscle weakness, hyperCKemia, and myasthenic symptoms refractory to therapy since age 3 years. Eventually he became motionless and died at age 42 years. At age 15 years, he had a marked EMG decrement, and a reduced miniature endplate potential amplitude. The myopathy was associated with dislocated muscle fiber organelles, structurally abnormal nuclei, focal plasmalemmal defects, and focal calcium ingress into muscle fibers. The neuromuscular junctions showed destruction of the junctional folds, and remodeling. Mutation analysis demonstrated a known p.Arg2319X and a novel c.12043dupG mutation in PLEC1. The EBS-MD-MyS patient reported in 1999 also carried c.12043dupG and a novel p.Gln2057X mutation. The novel mutations were absent in 200 Caucasian and 100 African American subjects. CONCLUSIONS The MyS in plectinopathy is attributed to destruction of the junctional folds and the myopathy to defective anchoring of muscle fiber organelles and defects in sarcolemmal integrity.
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Affiliation(s)
- D Selcen
- Department of Neurology, Mayo Clinic, Rochester, MN 55905, USA
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Maselli RA, Arredondo J, Cagney O, Mozaffar T, Skinner S, Yousif S, Davis RR, Gregg JP, Sivak M, Konia TH, Thomas K, Wollmann RL. Congenital myasthenic syndrome associated with epidermolysis bullosa caused by homozygous mutations in PLEC1 and CHRNE. Clin Genet 2010; 80:444-51. [PMID: 21175599 DOI: 10.1111/j.1399-0004.2010.01602.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Mutations in the plectin gene (PLEC1) cause epidermolysis bullosa simplex (EBS), which may associate with muscular dystrophy (EBS-MD) or pyloric atresia (EBS-PA). The association of EBS with congenital myasthenic syndrome (CMS) is also suspected to result from PLEC1 mutations. We report here a consanguineous patient with EBS and CMS for whom mutational analysis of PLEC1 revealed a homozygous 36 nucleotide insertion (1506_1507ins36) that results in a reduced expression of PLEC1 mRNA and plectin in the patient muscle. In addition, mutational analysis of CHRNE revealed a homozygous 1293insG, which is a well-known low-expressor receptor mutation. A skin biopsy revealed signs of EBS, and an anconeus muscle biopsy showed signs of a mild myopathy. Endplate studies showed fragmentation of endplates, postsynaptic simplification, and large collections of thread-like mitochondria. Amplitudes of miniature endplate potentials were diminished, but the endplate quantal content was actually increased. The complex phenotype presented here results from mutations in two separate genes. While the skin manifestations are because of the PLEC1 mutation, footprints of mutations in PLEC1 and CHRNE are present at the neuromuscular junction of the patient indicating that abnormalities in both genes contribute to the CMS phenotype.
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Affiliation(s)
- R A Maselli
- Department of Neurology, University of California Davis, USA.
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Gundesli H, Talim B, Korkusuz P, Balci-Hayta B, Cirak S, Akarsu NA, Topaloglu H, Dincer P. Mutation in exon 1f of PLEC, leading to disruption of plectin isoform 1f, causes autosomal-recessive limb-girdle muscular dystrophy. Am J Hum Genet 2010; 87:834-41. [PMID: 21109228 DOI: 10.1016/j.ajhg.2010.10.017] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 10/12/2010] [Accepted: 10/18/2010] [Indexed: 01/02/2023] Open
Abstract
Limb-girdle muscular dystrophy (LGMD) is a genetically heterogeneous group of inherited muscular disorders manifesting symmetric, proximal, and slowly progressive muscle weakness. Using Affymetrix 250K SNP Array genotyping and homozygosity mapping, we mapped an autosomal-recessive LGMD phenotype to the telomeric portion of chromosome 8q in a consanguineous Turkish family with three affected individuals. DNA sequence analysis of PLEC identified a homozygous c.1_9del mutation containing an initiation codon in exon 1f, which is an isoform-specific sequence of plectin isoform 1f. The same homozygous mutation was also detected in two additional families during the analysis of 72 independent LGMD2-affected families. Moreover, we showed that the expression of PLEC was reduced in the patient's muscle and that there was almost no expression for plectin 1f mRNA as a result of the mutation. In addition to dystrophic changes in muscle, ultrastructural alterations, such as membrane duplications, an enlarged space between the membrane and sarcomere, and misalignment of Z-disks, were observed by transmission electron microscopy. Unlike the control skeletal muscle, no sarcolemmal staining of plectin was detected in the patient's muscle. We conclude that as a result of plectin 1f deficiency, the linkage between the sarcolemma and sarcomere is broken, which could affect the structural organization of the myofiber. Our data show that one of the isoforms of plectin plays a key role in skeletal muscle function and that disruption of the plectin 1f can cause the LGMD2 phenotype without any dermatologic component as was previously reported with mutations in constant exons of PLEC.
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Forrest K, Mellerio JE, Robb S, Dopping-Hepenstal PJ, McGrath JA, Liu L, Buk SJ, Al-Sarraj S, Wraige E, Jungbluth H. Congenital muscular dystrophy, myasthenic symptoms and epidermolysis bullosa simplex (EBS) associated with mutations in the PLEC1 gene encoding plectin. Neuromuscul Disord 2010; 20:709-11. [PMID: 20624679 DOI: 10.1016/j.nmd.2010.06.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2010] [Revised: 05/10/2010] [Accepted: 06/10/2010] [Indexed: 11/20/2022]
Abstract
Mutations in the PLEC1 gene encoding plectin have been reported in neonatal epidermolysis bullosa simplex with muscular dystrophy of later-onset (EBS-MD). A neuromuscular transmission defect has been reported in one previous patient. We report a boy presenting from birth with features of a congenital muscular dystrophy and late-onset myasthenic symptoms. Repetitive nerve stimulation showed significant decrement, and strength improved with pyridostigmine. Subtle blistering noticed only retrospectively prompted further genetic testing, revealing recessive PLEC1 mutations. We conclude that PLEC1 should be considered in the differential diagnosis of congenital muscular dystrophies and myasthenic syndromes, even in the absence of prominent skin involvement.
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Nogajski JH, Kiernan MC, Ouvrier RA, Andrews PI. Congenital myasthenic syndromes. J Clin Neurosci 2008; 16:1-11. [PMID: 19017561 DOI: 10.1016/j.jocn.2008.05.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2006] [Revised: 04/10/2008] [Accepted: 05/04/2008] [Indexed: 10/21/2022]
Abstract
Congenital myasthenic syndromes (CMS) are a heterogeneous group of uncommon, inherited disorders affecting the neuromuscular junction. The defects interfere with presynaptic, synaptic, or postsynaptic function and compromise neuromuscular transmission. Most patients with CMS have similar clinical features regardless of the underlying defect, but attention to clinical and electrodiagnostic parameters can narrow the diagnostic spectrum. Recent advances in our understanding of the cellular mechanisms underlying specific syndromes allow DNA testing for some forms of CMS. Diagnosis of CMS enables a rationale for management to be developed. Two cases of genetically determined CMS as well as an undiagnosed infant are presented to highlight the clinical and electrophysiological difficulties associated with the diagnosis and management of such syndromes.
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Affiliation(s)
- Joseph H Nogajski
- Institute of Neurological Sciences, Prince of Wales Hospital, Randwick, New South Wales, Australia
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Konieczny P, Wiche G. Muscular Integrity—A Matter of Interlinking Distinct Structures via Plectin. Advances in Experimental Medicine and Biology 2008. [DOI: 10.1007/978-0-387-84847-1_12] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, Rochester, MN, USA.
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Abstract
In recent years, understanding of the pathogenesis and clinical presentation of distinct myasthenia subtypes has increased significantly. This article reviews the clinical manifestations of autoimmune myasthenia gravis (including myasthenia associated with anti-muscle-specific kinase antibodies), ocular myasthenia, and antibody negative myasthenia. The following treatments are examined: cholinesterase inhibitors, immunosuppressants, and thymectomy. Inherited congenital myasthenic syndromes (CMS) are now increasingly recognized, and most commonly present during childhood. This article outlines the presynaptic, synaptic basal lamina-associated, and postsynaptic classification of CMS and the clinical presentation and aetiology of individual syndromes. Relevant investigations and treatment options (including the role of pyridostigmine, 3,4-diaminopyridine, fluoxetine, and ephedrine) are discussed.
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Affiliation(s)
- J R Parr
- University of Oxford Department of Paediatrics, Children's Hospital, Oxford, UK.
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