1
|
Saito A, Matsui S, Chino A, Sato S, Takeshita N. Discovery and pharmacological characterization of novel positive allosteric modulators acting on skeletal muscle-type nicotinic acetylcholine receptors. Biochem Biophys Res Commun 2023; 668:27-34. [PMID: 37235916 DOI: 10.1016/j.bbrc.2023.04.103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 04/21/2023] [Accepted: 04/27/2023] [Indexed: 05/28/2023]
Abstract
Skeletal muscle-type nicotinic acetylcholine receptors (m-nAChRs) are ligand-gated ion channels that open after activation by ACh and whose signals cause muscle contraction. Defects in neurotransmission are reported in disorders such as myasthenia gravis (MG) and congenital myasthenia syndromes (CMS). Although treatments for these disorders exist, therapies which significantly increase muscle strength have yet to be reported. Positive allosteric modulators (PAMs), which promote ACh signaling through AChRs, are expected to be promising therapeutic agents. In this study, we identified an m-nAChR PAM called AS3513678 by high-throughput screening using human myotube cells and modified it to obtain novel compounds (AS3566987 and AS3580239) that showed even stronger PAM activity. AS3580239 caused a leftward shift in the ACh concentration-response curve and was 14.0-fold potent at 10 μM compared with vehicle. Next, we examined the effect of AS3580239 on electrically-induced isometric contraction of the extensor digitorum longus (EDL) muscle in wild-type (WT) and MG model rats. AS3580239 enhanced EDL muscle contraction in both WT and MG model rats at 30 μM. These data suggest that AS3580239 improved neurotransmission and enhanced muscle strength. Thus, m-nAChR PAMs may be a useful treatment for neuromuscular diseases.
Collapse
Affiliation(s)
- Asako Saito
- Astellas Pharma Inc, 21, Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan.
| | - Shigeo Matsui
- Astellas Pharma Inc, 21, Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan
| | - Ayaka Chino
- Astellas Pharma Inc, 21, Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan
| | - Shota Sato
- Astellas Pharma Inc, 21, Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan
| | - Nobuaki Takeshita
- Astellas Pharma Inc, 21, Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan
| |
Collapse
|
2
|
GDP-Mannose Pyrophosphorylase B ( GMPPB)-Related Disorders. Genes (Basel) 2023; 14:genes14020372. [PMID: 36833299 PMCID: PMC9956253 DOI: 10.3390/genes14020372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 01/29/2023] [Accepted: 01/30/2023] [Indexed: 02/04/2023] Open
Abstract
GDP-mannose pyrophosphorylase B (GMPPB) is a cytoplasmic protein that catalyzes the formation of GDP-mannose. Impaired GMPPB function reduces the amount of GDP-mannose available for the O-mannosylation of α-dystroglycan (α-DG) and ultimately leads to disruptions of the link between α-DG and extracellular proteins, hence dystroglycanopathy. GMPPB-related disorders are inherited in an autosomal recessive manner and caused by mutations in either a homozygous or compound heterozygous state. The clinical spectrum of GMPPB-related disorders spans from severe congenital muscular dystrophy (CMD) with brain and eye abnormalities to mild forms of limb-girdle muscular dystrophy (LGMD) to recurrent rhabdomyolysis without overt muscle weakness. GMPPB mutations can also lead to the defect of neuromuscular transmission and congenital myasthenic syndrome due to altered glycosylation of the acetylcholine receptor subunits and other synaptic proteins. Such impairment of neuromuscular transmission is a unique feature of GMPPB-related disorders among dystroglycanopathies. LGMD is the most common phenotypic presentation, characterized by predominant proximal weakness involving lower more than upper limbs. Facial, ocular, bulbar, and respiratory muscles are largely spared. Some patients demonstrate fluctuating fatigable weakness suggesting neuromuscular junction involvement. Patients with CMD phenotype often also have structural brain defects, intellectual disability, epilepsy, and ophthalmic abnormalities. Creatine kinase levels are typically elevated, ranging from 2 to >50 times the upper limit of normal. Involvement of the neuromuscular junction is demonstrated by the decrement in the compound muscle action potential amplitude on low-frequency (2-3 Hz) repetitive nerve stimulation in proximal muscles but not in facial muscles. Muscle biopsies typically show myopathic changes with variable degrees of reduced α-DG expression. Higher mobility of β-DG on Western blotting represents a specific feature of GMPPB-related disorders, distinguishing it from other α-dystroglycanopathies. Patients with clinical and electrophysiologic features of neuromuscular transmission defect can respond to acetylcholinesterase inhibitors alone or combined with 3,4 diaminopyridine or salbutamol.
Collapse
|
3
|
Chen R, Yi Y, Xiao W, Zhong B, Zhang L, Zeng Y. Urinary protein biomarkers based on LC-MS/MS analysis to discriminate vascular dementia from Alzheimer's disease in Han Chinese population. Front Aging Neurosci 2023; 15:1070854. [PMID: 36761180 PMCID: PMC9905227 DOI: 10.3389/fnagi.2023.1070854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Accepted: 01/04/2023] [Indexed: 01/27/2023] Open
Abstract
Objective This study aimed to identify the potential urine biomarkers of vascular dementia (VD) and unravel the disease-associated mechanisms by applying Liquid chromatography tandem-mass spectrometry (LC-MS/MS). Methods LC-MS/MS proteomic analysis was applied to urine samples from 3 groups, including 14 patients with VD, 9 patients with AD, and 21 normal controls (NC). By searching the MS data by Proteome Discoverer software, analyzing the protein abundances qualitatively and quantitatively, comparing between groups, combining bioinformatics analysis using Gene Ontology (GO) and pathway crosstalk analysis using Kyoto Encyclopedia of Genes and Genomes (KEGG), and literature searching, the differentially expressed proteins (DEPs) of VD can be comprehensively determined at last and were further quantified by receiver operating characteristic (ROC) curve methods. Results The proteomic findings showed quantitative changes in patients with VD compared to patients with NC and AD groups; among 4,699 identified urine proteins, 939 and 1,147 proteins displayed quantitative changes unique to VD vs. NC and AD, respectively, including 484 overlapped common DEPs. Then, 10 unique proteins named in KEGG database (including PLOD3, SDCBP, SRC, GPRC5B, TSG101/STP22/VPS23, THY1/CD90, PLCD, CDH16, NARS/asnS, AGRN) were confirmed by a ROC curve method. Conclusion Our results suggested that urine proteins enable detection of VD from AD and VC, which may provide an opportunity for intervention.
Collapse
Affiliation(s)
- Ruijuan Chen
- Department of Geriatrics, Second Xiangya Hospital, Central South University, Changsha, Hunan, China,Department of Emergency, Central South University Xiangya School of Medicine Affiliated Haikou Hospital, Haikou, Hainan, China
| | - Yuanjing Yi
- Department of Geriatrics, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Wenbiao Xiao
- Department of Geriatrics, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Bowen Zhong
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, National Center for Protein Sciences (Beijing), Beijing Institute of Lifeomics, Beijing, China
| | - Le Zhang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Yi Zeng
- Department of Geriatrics, Second Xiangya Hospital, Central South University, Changsha, Hunan, China,*Correspondence: Yi Zeng,
| |
Collapse
|
4
|
Spendiff S, Howarth R, McMacken G, Davey T, Quinlan K, O'Connor E, Slater C, Hettwer S, Mäder A, Roos A, Horvath R, Lochmüller H. Modulation of the Acetylcholine Receptor Clustering Pathway Improves Neuromuscular Junction Structure and Muscle Strength in a Mouse Model of Congenital Myasthenic Syndrome. Front Mol Neurosci 2021; 13:594220. [PMID: 33390901 PMCID: PMC7773664 DOI: 10.3389/fnmol.2020.594220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 11/24/2020] [Indexed: 11/16/2022] Open
Abstract
Introduction: Congenital myasthenic syndromes (CMS) are a diverse group of inherited neuromuscular disorders characterized by a failure of synaptic transmission at the neuromuscular junction (NMJ). CMS often present early with fatigable weakness and can be fatal through respiratory complications. The AGRN gene is one of over 30 genes known to harbor mutations causative for CMS. In this study, we aimed to determine if a compound (NT1654), developed to stimulate the acetylcholine receptor (AChR) clustering pathway, would benefit a mouse model of CMS caused by a loss-of-function mutation in Agrn (Agrnnmf380 mouse). Methods:Agrnnmf380 mice received an injection of either NT1654 or vehicle compound daily, with wild-type litter mates used for comparison. Animals were weighed daily and underwent grip strength assessments. After 30 days of treatment animals were sacrificed, and muscles collected. Investigations into NMJ and muscle morphology were performed on collected tissue. Results: While minimal improvements in NMJ ultrastructure were observed with electron microscopy, gross NMJ structure analysis using fluorescent labelling and confocal microscopy revealed extensive postsynaptic improvements in Agrnnmf380 mice with NT1654 administration, with variables frequently returning to wild type levels. An improvement in muscle weight and myofiber characteristics helped increase forelimb grip strength and body weight. Conclusions: We conclude that NT1654 restores NMJ postsynaptic structure and improves muscle strength through normalization of muscle fiber composition and the prevention of atrophy. We hypothesize this occurs through the AChR clustering pathway in Agrnnmf380 mice. Future studies should investigate if this may represent a viable treatment option for patients with CMS, especially those with mutations in proteins of the AChR clustering pathway.
Collapse
Affiliation(s)
- Sally Spendiff
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
| | - Rachel Howarth
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Grace McMacken
- Department of Neurosciences, Royal Victoria Hospital, Belfast, United Kingdom
| | - Tracey Davey
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Kaitlyn Quinlan
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
| | - Emily O'Connor
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada.,Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada
| | - Clarke Slater
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | | | | | - Andreas Roos
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada.,Department of Paediatric Neurology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Hanns Lochmüller
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada.,Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada.,Department of Neuropediatrics and Muscle Disorders, Medical Center - University of Freiburg, Freiburg, Germany.,Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| |
Collapse
|
5
|
Rodríguez Cruz PM, Cossins J, Beeson D, Vincent A. The Neuromuscular Junction in Health and Disease: Molecular Mechanisms Governing Synaptic Formation and Homeostasis. Front Mol Neurosci 2020; 13:610964. [PMID: 33343299 PMCID: PMC7744297 DOI: 10.3389/fnmol.2020.610964] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 10/30/2020] [Indexed: 12/28/2022] Open
Abstract
The neuromuscular junction (NMJ) is a highly specialized synapse between a motor neuron nerve terminal and its muscle fiber that are responsible for converting electrical impulses generated by the motor neuron into electrical activity in the muscle fibers. On arrival of the motor nerve action potential, calcium enters the presynaptic terminal, which leads to the release of the neurotransmitter acetylcholine (ACh). ACh crosses the synaptic gap and binds to ACh receptors (AChRs) tightly clustered on the surface of the muscle fiber; this leads to the endplate potential which initiates the muscle action potential that results in muscle contraction. This is a simplified version of the events in neuromuscular transmission that take place within milliseconds, and are dependent on a tiny but highly structured NMJ. Much of this review is devoted to describing in more detail the development, maturation, maintenance and regeneration of the NMJ, but first we describe briefly the most important molecules involved and the conditions that affect their numbers and function. Most important clinically worldwide, are myasthenia gravis (MG), the Lambert-Eaton myasthenic syndrome (LEMS) and congenital myasthenic syndromes (CMS), each of which causes specific molecular defects. In addition, we mention the neurotoxins from bacteria, snakes and many other species that interfere with neuromuscular transmission and cause potentially fatal diseases, but have also provided useful probes for investigating neuromuscular transmission. There are also changes in NMJ structure and function in motor neuron disease, spinal muscle atrophy and sarcopenia that are likely to be secondary but might provide treatment targets. The NMJ is one of the best studied and most disease-prone synapses in the nervous system and it is amenable to in vivo and ex vivo investigation and to systemic therapies that can help restore normal function.
Collapse
Affiliation(s)
- Pedro M Rodríguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Judith Cossins
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.,Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| |
Collapse
|
6
|
The Impact of Mitochondrial Deficiencies in Neuromuscular Diseases. Antioxidants (Basel) 2020; 9:antiox9100964. [PMID: 33050147 PMCID: PMC7600520 DOI: 10.3390/antiox9100964] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 09/23/2020] [Accepted: 09/24/2020] [Indexed: 02/06/2023] Open
Abstract
Neuromuscular diseases (NMDs) are a heterogeneous group of acquired or inherited rare disorders caused by injury or dysfunction of the anterior horn cells of the spinal cord (lower motor neurons), peripheral nerves, neuromuscular junctions, or skeletal muscles leading to muscle weakness and waste. Unfortunately, most of them entail serious or even fatal consequences. The prevalence rates among NMDs range between 1 and 10 per 100,000 population, but their rarity and diversity pose difficulties for healthcare and research. Some molecular hallmarks are being explored to elucidate the mechanisms triggering disease, to set the path for further advances. In fact, in the present review we outline the metabolic alterations of NMDs, mainly focusing on the role of mitochondria. The aim of the review is to discuss the mechanisms underlying energy production, oxidative stress generation, cell signaling, autophagy, and inflammation triggered or conditioned by the mitochondria. Briefly, increased levels of inflammation have been linked to reactive oxygen species (ROS) accumulation, which is key in mitochondrial genomic instability and mitochondrial respiratory chain (MRC) dysfunction. ROS burst, impaired autophagy, and increased inflammation are observed in many NMDs. Increasing knowledge of the etiology of NMDs will help to develop better diagnosis and treatments, eventually reducing the health and economic burden of NMDs for patients and healthcare systems.
Collapse
|
7
|
Gan S, Yang H, Xiao T, Pan Z, Wu L. AGRN Gene Mutation Leads to Congenital Myasthenia Syndromes: A Pediatric Case Report and Literature Review. Neuropediatrics 2020; 51:364-367. [PMID: 32221959 DOI: 10.1055/s-0040-1708534] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The congenital myasthenia syndromes (CMS) are a group of autosomal recessive or autosomal dominant diseases that affect neuromuscular junctions. CMS caused by AGRN mutations is very uncommon typically characterized by ptosis, mild weakness, and proximal limb weakness. We report the case of an 8-year-old female who exhibited the onset of motor development retardation from infancy and slow progression to proximal muscle weakness. Repeated nerve stimulation at 3 Hz showed a clear decrement with 17%. Whole exon sequencing showed an AGRN gene compound heterozygous mutation (c.5009C >T and c.5078T > C). She was treated with salbutamol but without improvement. Then pseudoephedrine was adapted as a treatment choice and obtained remarkable curative effect. We have summarized and analyzed 12 patients who have been reported in the literature. An early age of onset and muscle weakness in the lower limbs are the main feature of an early AGRN gene mutation. Both types of AGRN-related CMS respond favorably to ephedrine. This is the first report showing that pseudoephedrine is effective as a choice for the treatment of AGRN-related CMS.
Collapse
Affiliation(s)
- Siyi Gan
- Department of Pediatric Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, PR China
| | - Haiyan Yang
- Department of Pediatric Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, PR China
| | - Ting Xiao
- Department of Pediatric Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, PR China
| | - Zou Pan
- Department of Pediatric Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, PR China
| | - Liwen Wu
- Department of Pediatric Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, PR China
| |
Collapse
|
8
|
Ohkawara B, Shen X, Selcen D, Nazim M, Bril V, Tarnopolsky MA, Brady L, Fukami S, Amato AA, Yis U, Ohno K, Engel AG. Congenital myasthenic syndrome-associated agrin variants affect clustering of acetylcholine receptors in a domain-specific manner. JCI Insight 2020; 5:132023. [PMID: 32271162 DOI: 10.1172/jci.insight.132023] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 02/28/2020] [Indexed: 12/17/2022] Open
Abstract
Congenital myasthenic syndromes (CMS) are caused by mutations in molecules expressed at the neuromuscular junction. We report clinical, structural, ultrastructural, and electrophysiologic features of 4 CMS patients with 6 heteroallelic variants in AGRN, encoding agrin. One was a 7.9-kb deletion involving the N-terminal laminin-binding domain. Another, c.4744G>A - at the last nucleotide of exon 26 - caused skipping of exon 26. Four missense mutations (p.S1180L, p.R1509W, p.G1675S, and p.Y1877D) expressed in conditioned media decreased AChR clusters in C2C12 myotubes. The agrin-enhanced phosphorylation of MuSK was markedly attenuated by p.Y1877D in the LG3 domain and moderately attenuated by p.R1509W in the LG1 domain but not by the other 2 mutations. The p.S1180L mutation in the SEA domain facilitated degradation of secreted agrin. The p.G1675S mutation in the LG2 domain attenuated anchoring of agrin to the sarcolemma by compromising its binding to heparin. Anchoring of agrin with p.R1509W in the LG1 domain was similarly attenuated. Mutations of agrin affect AChR clustering by enhancing agrin degradation or by suppressing MuSK phosphorylation and/or by compromising anchoring of agrin to the sarcolemma of the neuromuscular junction.
Collapse
Affiliation(s)
- Bisei Ohkawara
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - XinMing Shen
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | - Duygu Selcen
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | - Mohammad Nazim
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Vera Bril
- Vera Bril, Department of Neurology, University of Toronto, Toronto, Canada
| | - Mark A Tarnopolsky
- Department of Pediatrics, McMaster University Medical Center, Hamilton, Ontario, Canada
| | - Lauren Brady
- Department of Pediatrics, McMaster University Medical Center, Hamilton, Ontario, Canada
| | - Sae Fukami
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Anthony A Amato
- Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Uluc Yis
- Division of Child Neurology, Department of Pediatrics, School of Medicine, Dokuz Eylul University, Izmir, Turkey
| | - Kinji Ohno
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Andrew G Engel
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| |
Collapse
|
9
|
Previtali SC, Zhao E, Lazarevic D, Pipitone GB, Fabrizi GM, Manganelli F, Mazzeo A, Pareyson D, Schenone A, Taroni F, Vita G, Bellone E, Ferrarini M, Garibaldi M, Magri S, Padua L, Pennisi E, Pisciotta C, Riva N, Scaioli V, Scarlato M, Tozza S, Geroldi A, Jordanova A, Ferrari M, Molineris I, Reilly MM, Comi G, Carrera P, Devoto M, Bolino A. Expanding the spectrum of genes responsible for hereditary motor neuropathies. J Neurol Neurosurg Psychiatry 2019; 90:1171-1179. [PMID: 31167812 DOI: 10.1136/jnnp-2019-320717] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 04/24/2019] [Accepted: 05/17/2019] [Indexed: 12/12/2022]
Abstract
BACKGROUND Inherited peripheral neuropathies (IPNs) represent a broad group of genetically and clinically heterogeneous disorders, including axonal Charcot-Marie-Tooth type 2 (CMT2) and hereditary motor neuropathy (HMN). Approximately 60%-70% of cases with HMN/CMT2 still remain without a genetic diagnosis. Interestingly, mutations in HMN/CMT2 genes may also be responsible for motor neuron disorders or other neuromuscular diseases, suggesting a broad phenotypic spectrum of clinically and genetically related conditions. Thus, it is of paramount importance to identify novel causative variants in HMN/CMT2 patients to better predict clinical outcome and progression. METHODS We designed a collaborative study for the identification of variants responsible for HMN/CMT2. We collected 15 HMN/CMT2 families with evidence for autosomal recessive inheritance, who had tested negative for mutations in 94 known IPN genes, who underwent whole-exome sequencing (WES) analyses. Candidate genes identified by WES were sequenced in an additional cohort of 167 familial or sporadic HMN/CMT2 patients using next-generation sequencing (NGS) panel analysis. RESULTS Bioinformatic analyses led to the identification of novel or very rare variants in genes, which have not been previously associated with HMN/CMT2 (ARHGEF28, KBTBD13, AGRN and GNE); in genes previously associated with HMN/CMT2 but in combination with different clinical phenotypes (VRK1 and PNKP), and in the SIGMAR1 gene, which has been linked to HMN/CMT2 in only a few cases. These findings were further validated by Sanger sequencing, segregation analyses and functional studies. CONCLUSIONS These results demonstrate the broad spectrum of clinical phenotypes that can be associated with a specific disease gene, as well as the complexity of the pathogenesis of neuromuscular disorders.
Collapse
Affiliation(s)
- Stefano C Previtali
- Institute of Experimental Neurology (InSpe), Division of Neuroscience, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Edward Zhao
- Division of Genetics, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Dejan Lazarevic
- Center for Translational Genomics and Bioinformatics, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Giovanni Battista Pipitone
- Laboratory of Clinical and Molecular Biology and Unit of Genomics for Diagnosis of Genetic Diseases, Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Gian Maria Fabrizi
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Fiore Manganelli
- Department of Neurosciences, Reproductive Sciences and Odontostomatology, University Federico II of Naples, Napoli, Italy
| | - Anna Mazzeo
- Unit of Neurology and Neuromuscular Diseases, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Davide Pareyson
- Unit of Rare Neurodegenerative and Neurometabolic Diseases, Department of Clinical Neurosciences, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Angelo Schenone
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetic and Maternal Infantile Sciences, University of Genoa, and IRCCS Policlinico San Martino, Genova, Italy
| | - Franco Taroni
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Giuseppe Vita
- Unit of Neurology and Neuromuscular Diseases, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Emilia Bellone
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetic and Maternal Infantile Sciences, University of Genoa, and IRCCS Policlinico San Martino, Genova, Italy
| | - Moreno Ferrarini
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Matteo Garibaldi
- Unit of Neuromuscular Disorders, Department of Neuroscience, Mental Health and Sensory Organs (NESMOS), Sapienza University of Rome, Sant'Andrea Hospital, Roma, Italy
| | - Stefania Magri
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Luca Padua
- Policlinico Universitario Agostino Gemelli IRCCS, Università Cattolica, Roma, Italy
| | | | - Chiara Pisciotta
- Unit of Rare Neurodegenerative and Neurometabolic Diseases, Department of Clinical Neurosciences, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Nilo Riva
- Institute of Experimental Neurology (InSpe), Division of Neuroscience, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Vidmer Scaioli
- Neurophysiopathology Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milano, Italy
| | - Marina Scarlato
- Institute of Experimental Neurology (InSpe), Division of Neuroscience, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Stefano Tozza
- Department of Neurosciences, Reproductive Sciences and Odontostomatology, University Federico II of Naples, Napoli, Italy
| | - Alessandro Geroldi
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetic and Maternal Infantile Sciences, University of Genoa, and IRCCS Policlinico San Martino, Genova, Italy
| | - Albena Jordanova
- VIB-UAntwerp Center for Molecular Neurology, Antwerp, Belgium
- Department of Medical Chemistry and Biochemistry, Medical University-Sofia, Sofia, Bulgaria
| | - Maurizio Ferrari
- Laboratory of Clinical and Molecular Biology and Unit of Genomics for Diagnosis of Genetic Diseases, Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Ivan Molineris
- Center for Translational Genomics and Bioinformatics, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Mary M Reilly
- MRC Centre for Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Giancarlo Comi
- Institute of Experimental Neurology (InSpe), Division of Neuroscience, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Paola Carrera
- Laboratory of Clinical and Molecular Biology and Unit of Genomics for Diagnosis of Genetic Diseases, Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Marcella Devoto
- Division of Genetics, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Translational and Precision Medicine, University La Sapienza, Roma, Italy
| | - Alessandra Bolino
- Institute of Experimental Neurology (InSpe), Division of Neuroscience, IRCCS Ospedale San Raffaele, Milano, Italy
| |
Collapse
|
10
|
Xing G, Jing H, Zhang L, Cao Y, Li L, Zhao K, Dong Z, Chen W, Wang H, Cao R, Xiong WC, Mei L. A mechanism in agrin signaling revealed by a prevalent Rapsyn mutation in congenital myasthenic syndrome. eLife 2019; 8:e49180. [PMID: 31549961 PMCID: PMC6779466 DOI: 10.7554/elife.49180] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Accepted: 09/23/2019] [Indexed: 12/15/2022] Open
Abstract
Neuromuscular junction is a synapse between motoneurons and skeletal muscles, where acetylcholine receptors (AChRs) are concentrated to control muscle contraction. Studies of this synapse have contributed to our understanding of synapse assembly and pathological mechanisms of neuromuscular disorders. Nevertheless, underlying mechanisms of NMJ formation was not well understood. To this end, we took a novel approach - studying mutant genes implicated in congenital myasthenic syndrome (CMS). We showed that knock-in mice carrying N88K, a prevalent CMS mutation of Rapsyn (Rapsn), died soon after birth with profound NMJ deficits. Rapsn is an adapter protein that bridges AChRs to the cytoskeleton and possesses E3 ligase activity. In investigating how N88K impairs the NMJ, we uncovered a novel signaling pathway by which Agrin-LRP4-MuSK induces tyrosine phosphorylation of Rapsn, which is required for its self-association and E3 ligase activity. Our results also provide insight into pathological mechanisms of CMS.
Collapse
Affiliation(s)
- Guanglin Xing
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Hongyang Jing
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Lei Zhang
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Yu Cao
- Department of Neuroscience and Regenerative MedicineAugusta UniversityAugustaUnited States
| | - Lei Li
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Kai Zhao
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
- Department of Neuroscience and Regenerative MedicineAugusta UniversityAugustaUnited States
| | - Zhaoqi Dong
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Wenbing Chen
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Hongsheng Wang
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Rangjuan Cao
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
| | - Wen-Cheng Xiong
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
- Louis Stokes Cleveland Veterans Affairs Medical CenterClevelandUnited States
| | - Lin Mei
- Department of Neurosciences, School of MedicineCase Western Reserve UniversityClevelandUnited States
- Louis Stokes Cleveland Veterans Affairs Medical CenterClevelandUnited States
| |
Collapse
|
11
|
Rivner MH, Pasnoor M, Dimachkie MM, Barohn RJ, Mei L. Muscle-Specific Tyrosine Kinase and Myasthenia Gravis Owing to Other Antibodies. Neurol Clin 2019; 36:293-310. [PMID: 29655451 DOI: 10.1016/j.ncl.2018.01.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Around 20% of patients with myasthenia gravis are acetylcholine receptor antibody negative; muscle-specific tyrosine kinase antibodies (MuSK) were identified as the cause of myasthenia gravis in 30% to 40% of these cases. Anti MuSK myasthenia gravis is associated with specific clinical phenotypes. One is a bulbar form with fewer ocular symptoms. Others show an isolated head drop or symptoms indistinguishable from acetylcholine receptor-positive myasthenia gravis. These patients usually respond well to immunosuppressive therapy, but not as well to cholinesterase inhibitors. Other antibodies associated with myasthenia gravis, including low-density lipoprotein receptor-related protein 4, are discussed.
Collapse
Affiliation(s)
- Michael H Rivner
- EMG Lab, Augusta University, 1120 15th Street, BP-4390, Augusta, GA 30912, USA.
| | - Mamatha Pasnoor
- Department of Neurology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | - Mazen M Dimachkie
- Department of Neurology, University of Kansas Medical Center, 3599 Rainbow Boulevard, Mail Stop 2012, Kansas City, KS 66103, USA
| | - Richard J Barohn
- Department of Neurology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Mail Stop 4017, Kansas City, KS 66160, USA
| | - Lin Mei
- Department of Neuroscience and Regenerative Medicine, Augusta University, 1120 15th Street, CA-2014, Augusta, GA 30912, USA
| |
Collapse
|
12
|
Modulation of Agrin and RhoA Pathways Ameliorates Movement Defects and Synapse Morphology in MYO9A-Depleted Zebrafish. Cells 2019; 8:cells8080848. [PMID: 31394789 PMCID: PMC6721702 DOI: 10.3390/cells8080848] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 07/24/2019] [Accepted: 08/02/2019] [Indexed: 12/14/2022] Open
Abstract
Congenital myasthenic syndromes (CMS) are a group of rare, inherited disorders characterised by impaired function of the neuromuscular junction (NMJ). This is due to defects in one of the many proteins associated with the NMJ. In three patients with CMS, missense mutations in a gene encoding an unconventional myosin protein, MYO9A, were identified as likely causing their disorder. Preliminary studies revealed a potential involvement of the RhoA/ROCK pathway and of a key NMJ protein, agrin, in the pathophysiology of MYO9A-depletion. In this study, a CRISPR/Cas9 approach was used to generate genetic mutants of MYO9A zebrafish orthologues, myo9aa/ab, to expand and refine the morphological analysis of the NMJ. Injection of NT1654, a synthetic agrin fragment compound, improved NMJ structure and zebrafish movement in the absence of Myo9aa/ab. In addition, treatment of zebrafish with fasudil, a ROCK inhibitor, also provided improvements to the morphology of NMJs in early development, as well as rescuing movement defects, but not to the same extent as NT1654 and not at later time points. Therefore, this study highlights a role for MYO9A at the NMJ, the first unconventional myosin motor protein associated with a neuromuscular disease, and provides a potential mechanism of action of MYO9A-pathophysiology.
Collapse
|
13
|
Nicolau S, Liewluck T, Shen XM, Selcen D, Engel AG, Milone M. A homozygous mutation in GMPPB leads to centronuclear myopathy with combined pre- and postsynaptic defects of neuromuscular transmission. Neuromuscul Disord 2019; 29:614-617. [PMID: 31378432 DOI: 10.1016/j.nmd.2019.07.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 06/14/2019] [Accepted: 07/02/2019] [Indexed: 11/26/2022]
Abstract
Mutations in GMPPB cause a wide spectrum of neuromuscular syndromes, including muscular dystrophies and congenital myasthenic syndrome. The mechanisms by which GMPPB mutations impair neuromuscular transmission however remain incompletely understood. We expand here upon a previous report of one such patient presenting with a myopathy-congenital myasthenic syndrome overlap phenotype. Fatigable proximal muscle weakness developed gradually between 13 and 25 years of age, with subsequent stabilization. Low-frequency repetitive nerve stimulation showed a decrement, while a muscle biopsy demonstrated the presence of a centronuclear myopathy. Genetic testing identified a homozygous c.458C > T (p.Thr153Ile) variant in GMPPB. In-vitro microelectrode recordings and ultrastructural studies showed impairment of both pre- and postsynaptic neuromuscular transmission, thus demonstrating the presence of not only postsynaptic, but also presynaptic pathology in GMPPB-related disorders.
Collapse
Affiliation(s)
- Stefan Nicolau
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States
| | - Teerin Liewluck
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States
| | - Xin-Ming Shen
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States
| | - Duygu Selcen
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States
| | - Andrew G Engel
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States
| | - Margherita Milone
- Department of Neurology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, United States.
| |
Collapse
|
14
|
Tadenev ALD, Burgess RW. Model validity for preclinical studies in precision medicine: precisely how precise do we need to be? Mamm Genome 2019; 30:111-122. [PMID: 30953144 PMCID: PMC6606658 DOI: 10.1007/s00335-019-09798-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Accepted: 03/27/2019] [Indexed: 12/15/2022]
Abstract
The promise of personalized medicine is that each patient’s treatment can be optimally tailored to their disease. In turn, their disease, as well as their response to the treatment, is determined by their genetic makeup and the “environment,” which relates to their general health, medical history, personal habits, and surroundings. Developing such optimized treatment strategies is an admirable goal and success stories include examples such as switching chemotherapy agents based on a patient’s tumor genotype. However, it remains a challenge to apply precision medicine to diseases for which there is no known effective treatment. Such diseases require additional research, often using experimentally tractable models. Presumably, models that recapitulate as much of the human pathophysiology as possible will be the most predictive. Here we will discuss the considerations behind such “precision models.” What sort of precision is required and under what circumstances? How can the predictive validity of such models be improved? Ultimately, there is no perfect model, but our continually improving ability to genetically engineer a variety of systems allows the generation of more and more precise models. Furthermore, our steadily increasing awareness of risk alleles, genetic background effects, multifactorial disease processes, and gene by environment interactions also allows increasingly sophisticated models that better reproduce patients’ conditions. In those cases where the research has progressed sufficiently far, results from these models appear to often be translating to effective treatments for patients.
Collapse
Affiliation(s)
- Abigail L D Tadenev
- The Center for Precision Genetics, The Jackson Laboratory, 600 Main Street, Bar Harbor, ME, 04609, USA
| | - Robert W Burgess
- The Center for Precision Genetics, The Jackson Laboratory, 600 Main Street, Bar Harbor, ME, 04609, USA.
| |
Collapse
|
15
|
Issop Y, Hathazi D, Khan MM, Rudolf R, Weis J, Spendiff S, Slater CR, Roos A, Lochmüller H. GFPT1 deficiency in muscle leads to myasthenia and myopathy in mice. Hum Mol Genet 2019; 27:3218-3232. [PMID: 29905857 PMCID: PMC6121184 DOI: 10.1093/hmg/ddy225] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Accepted: 06/05/2018] [Indexed: 11/13/2022] Open
Abstract
Glutamine-fructose-6-phosphate transaminase 1 (GFPT1) is the rate-limiting enzyme in the hexosamine biosynthetic pathway which yields precursors required for protein and lipid glycosylation. Mutations in GFPT1 and other genes downstream of this pathway cause congenital myasthenic syndrome (CMS) characterized by fatigable muscle weakness owing to impaired neurotransmission. The precise pathomechanisms at the neuromuscular junction (NMJ) owing to a deficiency in GFPT1 is yet to be discovered. One of the challenges we face is the viability of Gfpt1−/− knockout mice. In this study, we use Cre/LoxP technology to generate a muscle-specific GFPT1 knockout mouse model, Gfpt1tm1d/tm1d, characteristic of the human CMS phenotype. Our data suggest a critical role for muscle derived GFPT1 in the development of the NMJ, neurotransmission, skeletal muscle integrity and highlight that a deficiency in skeletal muscle alone is sufficient to cause morphological postsynaptic NMJ changes that are accompanied by presynaptic alterations despite the conservation of neuronal GFPT1 expression. In addition to the conventional morphological NMJ changes and fatigable muscle weakness, Gfpt1tm1d/tm1d mice display a progressive myopathic phenotype with the presence of tubular aggregates in muscle, characteristic of the GFPT1-CMS phenotype. We further identify an upregulation of skeletal muscle proteins glypican-1, farnesyltransferase/geranylgeranyltransferase type-1 subunit α and muscle-specific kinase, which are known to be involved in the differentiation and maintenance of the NMJ. The Gfpt1tm1d/tm1d model allows for further investigation of pathophysiological consequences on genes and pathways downstream of GFPT1 likely to involve misglycosylation or hypoglycosylation of NMJs and muscle targets.
Collapse
Affiliation(s)
- Yasmin Issop
- John Walton Muscular Dystrophy Research Centre, MRC Centre for Neuromuscular Diseases, Institute of Genetic Medicine, Newcastle University, Newcastle, UK
| | - Denisa Hathazi
- Leibniz-Institut für Analytische Wissenschaften-ISAS e.V, Dortmund, Germany
| | - Muzamil Majid Khan
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
| | - Rüdiger Rudolf
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany.,Interdisciplinary Center for Neurosciences, University of Heidelberg, Heidelberg, Germany.,Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, Mannheim, Germany
| | - Joachim Weis
- Institute of Neuropathology, RWTH Aachen University Hospital, Aachen, Germany
| | - Sally Spendiff
- John Walton Muscular Dystrophy Research Centre, MRC Centre for Neuromuscular Diseases, Institute of Genetic Medicine, Newcastle University, Newcastle, UK
| | - Clarke R Slater
- Institute of Neuroscience, Newcastle University, Newcastle, UK
| | - Andreas Roos
- John Walton Muscular Dystrophy Research Centre, MRC Centre for Neuromuscular Diseases, Institute of Genetic Medicine, Newcastle University, Newcastle, UK.,Leibniz-Institut für Analytische Wissenschaften-ISAS e.V, Dortmund, Germany
| | - Hanns Lochmüller
- John Walton Muscular Dystrophy Research Centre, MRC Centre for Neuromuscular Diseases, Institute of Genetic Medicine, Newcastle University, Newcastle, UK.,Department of Neuropediatrics and Muscle Disorders,Faculty of Medicine, Medical Center - University of Freiburg, Freiburg, Germany.,Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia, Spain
| |
Collapse
|
16
|
Animal Models of the Neuromuscular Junction, Vitally Informative for Understanding Function and the Molecular Mechanisms of Congenital Myasthenic Syndromes. Int J Mol Sci 2018; 19:ijms19051326. [PMID: 29710836 PMCID: PMC5983836 DOI: 10.3390/ijms19051326] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 04/24/2018] [Accepted: 04/25/2018] [Indexed: 01/16/2023] Open
Abstract
The neuromuscular junction is the point of contact between motor nerve and skeletal muscle, its vital role in muscle function is reliant on the precise location and function of many proteins. Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders of neuromuscular transmission with 30 or more implicated proteins. The use of animal models has been instrumental in determining the specific role of many CMS-related proteins. The mouse neuromuscular junction (NMJ) has been extensively studied in animal models of CMS due to its amenability for detailed electrophysiological and histological investigations and relative similarity to human NMJ. As well as their use to determine the precise molecular mechanisms of CMS variants, where an animal model accurately reflects the human phenotype they become useful tools for study of therapeutic interventions. Many of the animal models that have been important in deconvolving the complexities of neuromuscular transmission and revealing the molecular mechanisms of disease are highlighted.
Collapse
|
17
|
O'Connor E, Töpf A, Zahedi RP, Spendiff S, Cox D, Roos A, Lochmüller H. Clinical and research strategies for limb-girdle congenital myasthenic syndromes. Ann N Y Acad Sci 2018; 1412:102-112. [PMID: 29315608 DOI: 10.1111/nyas.13520] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/05/2017] [Accepted: 09/12/2017] [Indexed: 12/21/2022]
Abstract
Congenital myasthenic syndromes (CMS) are a group of rare disorders that cause fatigable muscle weakness due to defective signal transmission at the neuromuscular junction, a specialized synapse between peripheral motor neurons and their target muscle fibers. There are now over 30 causative genes that have been reported for CMS. Of these, there are 10 that are associated with a limb-girdle pattern of muscle weakness and are thus classed as LG-CMS. Next-generation sequencing and advanced methods of data sharing are likely to uncover further genes that are associated with similar clinical phenotypes, contributing to better diagnosis and effective treatment of LG-CMS patients. This review highlights clinical and pathological hallmarks of LG-CMS in relation to the underlying genetic defects and pathways. Tailored animal and cell models are essential to elucidate the exact function and pathomechanisms at the neuromuscular synapse that underlie LG-CMS. The integration of genomics and proteomics data derived from these models and patients reveals new and often unexpected insights that are relevant beyond the rare genetic disorder of LG-CMS and may extend to the functioning of mammalian synapses in health and disease more generally.
Collapse
Affiliation(s)
- Emily O'Connor
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - Ana Töpf
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - René P Zahedi
- Leibniz-Institut für Analytische Wissenschaften, ISAS e.V., Dortmund, Germany
| | - Sally Spendiff
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - Daniel Cox
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - Andreas Roos
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK.,Leibniz-Institut für Analytische Wissenschaften, ISAS e.V., Dortmund, Germany
| | - Hanns Lochmüller
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| |
Collapse
|
18
|
Xi J, Yan C, Liu WW, Qiao K, Lin J, Tian X, Wu H, Lu J, Wong LJ, Beeson D, Zhao C. Novel SEA and LG2 Agrin mutations causing congenital Myasthenic syndrome. Orphanet J Rare Dis 2017; 12:182. [PMID: 29258548 PMCID: PMC5735900 DOI: 10.1186/s13023-017-0732-z] [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: 09/13/2017] [Accepted: 12/04/2017] [Indexed: 11/17/2022] Open
Abstract
Background Congenital myasthenic syndrome caused by mutations in AGRN, a gene encoding a protein with a crucial function at the neuromuscular junction, is a rare disorder. There are few studies in this area. We here present two cases with novel mutations of AGRN of which we further investigated possible pathogenesis. Results Patient 1 had general limb weakness with fluctuation and deterioration in the afternoon and in hot weather. Patient 2 had early-onset weakness of lower extremities with suspected fluctuation in the early stages, which then progressed to the upper limbs. Both distal and proximal muscles were involved. Repetitive stimulation on EMG in both patients showed decrement in proximal and distal limbs. Patient 2 showed a marked response to salbutamol while Patient 1 did not. By targeted exome sequencing, two novel homozygous missense variants, p.L1176P and p.R1698C, in the SEA and LG2 domain of agrin were identified respectively. Further functional analysis revealed instability of the protein and impaired clustering of the acetylcholine receptor (AChR) by both mutations. Conclusions The mutations identified in AGRN in our study may cause congenital myasthenic syndrome by damaging protein stability and interfering with AChR clustering. These results broaden the understandings on the phenotype, genotype and pathogenesis of this rare disorder. Electronic supplementary material The online version of this article (10.1186/s13023-017-0732-z) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Jianying Xi
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Chong Yan
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Wei-Wei Liu
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK
| | - Kai Qiao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Jie Lin
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Xia Tian
- Baylor Genetics Laboratories, Houston, Texas, USA
| | - Hui Wu
- Department of Neurology, Jing'an District Center Hospital of Shanghai, Shanghai, China
| | - Jiahong Lu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Lee-Jun Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - David Beeson
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK.
| | - Chongbo Zhao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China.,Department of Neurology, Jing'an District Center Hospital of Shanghai, Shanghai, China
| |
Collapse
|
19
|
MacDonald R, Barbat-Artigas S, Cho C, Peng H, Shang J, Moustaine A, Carbonetto S, Robitaille R, Chalifour LE, Paudel H. A Novel Egr-1-Agrin Pathway and Potential Implications for Regulation of Synaptic Physiology and Homeostasis at the Neuromuscular Junction. Front Aging Neurosci 2017; 9:258. [PMID: 28824419 PMCID: PMC5541023 DOI: 10.3389/fnagi.2017.00258] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 07/19/2017] [Indexed: 12/11/2022] Open
Abstract
Synaptic transmission requires intricate coordination of the components involved in processing of incoming signals, formation and stabilization of synaptic machinery, neurotransmission and in all related signaling pathways. Changes to any of these components cause synaptic imbalance and disruption of neuronal circuitry. Extensive studies at the neuromuscular junction (NMJ) have greatly aided in the current understanding of synapses and served to elucidate the underlying physiology as well as associated adaptive and homeostatic processes. The heparan sulfate proteoglycan agrin is a vital component of the NMJ, mediating synaptic formation and maintenance in both brain and muscle, but very little is known about direct control of its expression. Here, we investigated the relationship between agrin and transcription factor early growth response-1 (Egr-1), as Egr-1 regulates the expression of many genes involved in synaptic homeostasis and plasticity. Using chromatin immunoprecipitation (ChIP), cell culture with cell lines derived from brain and muscle, and animal models, we show that Egr-1 binds to the AGRN gene locus and suppresses its expression. When compared with wild type (WT), mice deficient in Egr-1 (Egr-1−/−) display a marked increase in AGRN mRNA and agrin full-length and cleavage fragment protein levels, including the 22 kDa, C-terminal fragment in brain and muscle tissue homogenate. Because agrin is a crucial component of the NMJ, we explored possible physiological implications of the Egr-1-agrin relationship. In the diaphragm, Egr-1−/− mice display increased NMJ motor endplate density, individual area and area of innervation. In addition to increased density, soleus NMJs also display an increase in fragmented and faint endplates in Egr-1−/− vs. WT mice. Moreover, the soleus NMJ electrophysiology of Egr-1−/− mice revealed increased quantal content and motor testing showed decreased movement and limb muscle strength compared with WT. This study provides evidence for the potential involvement of a novel Egr-1-agrin pathway in synaptic homeostatic and compensatory mechanisms at the NMJ. Synaptic homeostasis is greatly affected by the process of aging. These and other data suggest that changes in Egr-1 expression may directly or indirectly promote age-related pathologies.
Collapse
Affiliation(s)
- Ryen MacDonald
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada
| | | | - Chulmin Cho
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada
| | - Huashan Peng
- Center for Research in NeuroscienceMontreal, QC, Canada
| | - Jijun Shang
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada
| | - Ayman Moustaine
- Département de neurosciences, Université de MontréalMontreal, QC, Canada
| | - Salvatore Carbonetto
- Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada.,Center for Research in NeuroscienceMontreal, QC, Canada.,Department of Medicine, McGill UniversityMontreal, QC, Canada
| | - Richard Robitaille
- Département de neurosciences, Université de MontréalMontreal, QC, Canada
| | - Lorraine E Chalifour
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Department of Medicine, McGill UniversityMontreal, QC, Canada
| | - Hemant Paudel
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada.,Department of Medicine, McGill UniversityMontreal, QC, Canada
| |
Collapse
|
20
|
Dietary supplementation with bovine-derived milk fat globule membrane lipids promotes neuromuscular development in growing rats. Nutr Metab (Lond) 2017; 14:9. [PMID: 28127382 PMCID: PMC5259894 DOI: 10.1186/s12986-017-0161-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 01/15/2017] [Indexed: 12/11/2022] Open
Abstract
Background The milk fat globule membrane (MFGM) is primarily composed of polar phospho- and sphingolipids, which have established biological effects on neuroplasticity. The present study aimed to investigate the effect of dietary MFGM supplementation on the neuromuscular system during post-natal development. Methods Growing rats received dietary supplementation with bovine-derived MFGM mixtures consisting of complex milk lipids (CML), beta serum concentrate (BSC) or a complex milk lipid concentrate (CMLc) (which lacks MFGM proteins) from post-natal day 10 to day 70. Results Supplementation with MFGM mixtures enriched in polar lipids (BSC and CMLc, but not CML) increased the plasma phosphatidylcholine (PC) concentration, with no effect on plasma phosphatidylinositol (PI), phosphatidylethanolamine (PE), phosphatidylserine (PS) or sphingomyelin (SM). In contrast, muscle PC was reduced in rats receiving supplementation with both BSC and CMLc, whereas muscle PI, PE, PS and SM remained unchanged. Rats receiving BSC and CMLc (but not CML) displayed a slow-to-fast muscle fibre type profile shift (MyHCI → MyHCIIa) that was associated with elevated expression of genes involved in myogenic differentiation (myogenic regulatory factors) and relatively fast fibre type specialisation (Myh2 and Nfatc4). Expression of neuromuscular development genes, including nerve cell markers, components of the synaptogenic agrin–LRP4 pathway and acetylcholine receptor subunits, was also increased in muscle of rats supplemented with BSC and CMLc (but not CML). Conclusions These findings demonstrate that dietary supplementation with bovine-derived MFGM mixtures enriched in polar lipids can promote neuromuscular development during post-natal growth in rats, leading to shifts in adult muscle phenotype. Electronic supplementary material The online version of this article (doi:10.1186/s12986-017-0161-y) contains supplementary material, which is available to authorized users.
Collapse
|
21
|
Li L, Cao Y, Wu H, Ye X, Zhu Z, Xing G, Shen C, Barik A, Zhang B, Xie X, Zhi W, Gan L, Su H, Xiong WC, Mei L. Enzymatic Activity of the Scaffold Protein Rapsyn for Synapse Formation. Neuron 2016; 92:1007-1019. [PMID: 27839998 DOI: 10.1016/j.neuron.2016.10.023] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 07/21/2016] [Accepted: 10/07/2016] [Indexed: 12/22/2022]
Abstract
Neurotransmission is ensured by a high concentration of neurotransmitter receptors at the postsynaptic membrane. This is mediated by scaffold proteins that bridge the receptors with cytoskeleton. One such protein is rapsyn (receptor-associated protein at synapse), which is essential for acetylcholine receptor (AChR) clustering and NMJ (neuromuscular junction) formation. We show that the RING domain of rapsyn contains E3 ligase activity. Mutation of the RING domain that abolishes the enzyme activity inhibits rapsyn- as well as agrin-induced AChR clustering in heterologous and muscle cells. Further biological and genetic studies support a working model where rapsyn, a classic scaffold protein, serves as an E3 ligase to induce AChR clustering and NMJ formation, possibly by regulation of AChR neddylation. This study identifies a previously unappreciated enzymatic function of rapsyn and a role of neddylation in synapse formation, and reveals a potential target of therapeutic intervention for relevant neurological disorders.
Collapse
Affiliation(s)
- Lei Li
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Yu Cao
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Haitao Wu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Xinchun Ye
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Zhihui Zhu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Guanglin Xing
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Chengyong Shen
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Arnab Barik
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Bin Zhang
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Xiaoling Xie
- Department of Ophthalmology, University of Rochester, Rochester, NY 14642, USA
| | - Wenbo Zhi
- Center for Biotechnology and Genomic Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Lin Gan
- Department of Ophthalmology, University of Rochester, Rochester, NY 14642, USA
| | - Huabo Su
- Vascular Biology Center, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Wen-Cheng Xiong
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA; Department of Neurology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA; Charlie Norwood VA Medical Center, Augusta, GA 30912, USA
| | - Lin Mei
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA; Department of Neurology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA; Charlie Norwood VA Medical Center, Augusta, GA 30912, USA.
| |
Collapse
|
22
|
Bais P, Beebe K, Morelli KH, Currie ME, Norberg SN, Evsikov AV, Miers KE, Seburn KL, Guergueltcheva V, Kremensky I, Jordanova A, Bult CJ, Burgess RW. Metabolite profile of a mouse model of Charcot-Marie-Tooth type 2D neuropathy: implications for disease mechanisms and interventions. Biol Open 2016; 5:908-20. [PMID: 27288508 PMCID: PMC4958279 DOI: 10.1242/bio.019273] [Citation(s) in RCA: 6] [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
Charcot–Marie–Tooth disease encompasses a genetically heterogeneous class of heritable polyneuropathies that result in axonal degeneration in the peripheral nervous system. Charcot–Marie–Tooth type 2D neuropathy (CMT2D) is caused by dominant mutations in glycyl tRNA synthetase (GARS). Mutations in the mouse Gars gene result in a genetically and phenotypically valid animal model of CMT2D. How mutations in GARS lead to peripheral neuropathy remains controversial. To identify putative disease mechanisms, we compared metabolites isolated from the spinal cord of Gars mutant mice and their littermate controls. A profile of altered metabolites that distinguish the affected and unaffected tissue was determined. Ascorbic acid was decreased fourfold in the spinal cord of CMT2D mice, but was not altered in serum. Carnitine and its derivatives were also significantly reduced in spinal cord tissue of mutant mice, whereas glycine was elevated. Dietary supplementation with acetyl-L-carnitine improved gross motor performance of CMT2D mice, but neither acetyl-L-carnitine nor glycine supplementation altered the parameters directly assessing neuropathy. Other metabolite changes suggestive of liver and kidney dysfunction in the CMT2D mice were validated using clinical blood chemistry. These effects were not secondary to the neuromuscular phenotype, as determined by comparison with another, genetically unrelated mouse strain with similar neuromuscular dysfunction. However, these changes do not seem to be causative or consistent metabolites of CMT2D, because they were not observed in a second mouse Gars allele or in serum samples from CMT2D patients. Therefore, the metabolite ‘fingerprint’ we have identified for CMT2D improves our understanding of cellular biochemical changes associated with GARS mutations, but identification of efficacious treatment strategies and elucidation of the disease mechanism will require additional studies. Summary: A metabolomics analysis of a mouse model of Charcot–Marie–Tooth type 2D neuropathy revealed a clear distinction between mutant and control samples, and the therapeutic potential of a subset of these changes was explored.
Collapse
Affiliation(s)
- Preeti Bais
- The Jackson Laboratory, Bar Harbor, 04609 ME, USA
| | | | - Kathryn H Morelli
- The Jackson Laboratory, Bar Harbor, 04609 ME, USA Graduate School of Biomedical Science and Engineering, University of Maine, Orono, 04469 ME, USA
| | | | | | - Alexei V Evsikov
- The Jackson Laboratory, Bar Harbor, 04609 ME, USA Department of Molecular Medicine, USF Health, University of South Florida, Tampa, 33620 FL, USA
| | | | | | | | - Ivo Kremensky
- National Genetics Laboratory, Department of Obstetrics and Gynecology, University Hospital of Obstetrics and Gynecology, Medical University-Sofia, 1431 Sofia, Bulgaria
| | - Albena Jordanova
- Molecular Neurogenomics Group, VIB Department of Molecular Genetics, University of Antwerp, 2610 Antwerpen, Belgium Molecular Medicine Center, Department of Medical Chemistry and Biochemistry, Medical University-Sofia, 1431 Sofia, Bulgaria
| | - Carol J Bult
- The Jackson Laboratory, Bar Harbor, 04609 ME, USA
| | - Robert W Burgess
- The Jackson Laboratory, Bar Harbor, 04609 ME, USA Graduate School of Biomedical Science and Engineering, University of Maine, Orono, 04469 ME, USA
| |
Collapse
|
23
|
Shen C, Xiong WC, Mei L. LRP4 in neuromuscular junction and bone development and diseases. Bone 2015; 80:101-108. [PMID: 26071838 DOI: 10.1016/j.bone.2015.05.012] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Revised: 05/04/2015] [Accepted: 05/08/2015] [Indexed: 02/08/2023]
Abstract
Low-density lipoprotein receptor-related protein 4 (LRP4) is a member of the low-density lipoprotein receptor (LDLR) family. Recent studies have revealed multiple functions and complex signaling mechanisms of LRP4 in different organs and tissues. LPR4 mutation or malfunction has been implicated in neurological disorders including congenital myasthenic syndrome, myasthenia gravis, and diseases of bone or kidney. This article is part of a Special Issue entitled "Muscle Bone Interactions".
Collapse
Affiliation(s)
- Chengyong Shen
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912, USA; Department of Neurology, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912, USA
| | - Wen-Cheng Xiong
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912, USA; Department of Neurology, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912, USA
| | - Lin Mei
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912, USA; Department of Neurology, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912, USA.
| |
Collapse
|
24
|
Evangelista T, Hanna M, Lochmüller H. Congenital Myasthenic Syndromes with Predominant Limb Girdle Weakness. J Neuromuscul Dis 2015; 2:S21-S29. [PMID: 26870666 PMCID: PMC4746746 DOI: 10.3233/jnd-150098] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Congenital myasthenic syndromes are a heterogeneous group of genetically determined disorders characterized by impaired neuromuscular transmission. They usually present from birth to childhood and are characterised by exercise induced weakness and fatigability. Genotype-phenotype correlations are difficult. However, in some patients particular phenotypic aspects may point towards a specific genetic defect. The absence of ptosis and ophthalmoparesis in patients with limb-girdle weakness makes the diagnosis of a neuromuscular transmission defect particularly challenging (LG-CMS). This is illustrated by a well-documented case published by Walton in 1956. The diagnosis of LG-CMS is secured by demonstrating a neuromuscular transmission defect with single fibre EMG or repetitive nerve stimulation, in the absence of auto-antibodies. Ultimately, a genetic test is required to identify the underlying cause and assure counselling and optimization of treatment. LG-CMS are inherited in autosomal recessive traits, and are often associated with mutations in DOK7 and GFPT1, and less frequently with mutations in COLQ, ALG2, ALG14 and DPAGT. Genetic characterization of CMS is of the upmost importance when choosing the adequate treatment. Some of the currently used drugs can either ameliorate or aggravate the symptoms depending on the underlying genetic defect. The drug most frequently used for the treatment of CMS is pyridostigmine an acetylcholinesterase inhibitor. However, pyridostigmine is not effective or is even detrimental in DOK7- and COLQ-related LG-CMS, while beta-adrenergic agonists (ephedrine, salbutamol) show some sustained benefit. Standard clinical trials may be difficult, but standardized follow-up of patients and international collaboration may help to improve the standards of care of these conditions.
Collapse
Affiliation(s)
- Teresinha Evangelista
- John Walton Muscular Dystrophy Research Centre, MRC Centre for Neuromuscular Diseases, Newcastle University, Newcastle upon Tyne, UK
| | - Mike Hanna
- UCL MRC Centre for Neuromuscular Disease, Institute of Neurology and National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom
| | - Hanns Lochmüller
- John Walton Muscular Dystrophy Research Centre, MRC Centre for Neuromuscular Diseases, Newcastle University, Newcastle upon Tyne, UK
| |
Collapse
|
25
|
MuSK frizzled-like domain is critical for mammalian neuromuscular junction formation and maintenance. J Neurosci 2015; 35:4926-41. [PMID: 25810523 DOI: 10.1523/jneurosci.3381-14.2015] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The muscle-specific kinase MuSK is one of the key molecules orchestrating neuromuscular junction (NMJ) formation. MuSK interacts with the Wnt morphogens, through its Frizzled-like domain (cysteine-rich domain [CRD]). Dysfunction of MuSK CRD in patients has been recently associated with the onset of myasthenia, common neuromuscular disorders mainly characterized by fatigable muscle weakness. However, the physiological role of Wnt-MuSK interaction in NMJ formation and function remains to be elucidated. Here, we demonstrate that the CRD deletion of MuSK in mice caused profound defects of both muscle prepatterning, the first step of NMJ formation, and synapse differentiation associated with a drastic deficit in AChR clusters and excessive growth of motor axons that bypass AChR clusters. Moreover, adult MuSKΔCRD mice developed signs of congenital myasthenia, including severe NMJs dismantlement, muscle weakness, and fatigability. We also report, for the first time, the beneficial effects of lithium chloride, a reversible inhibitor of the glycogen synthase kinase-3, that rescued NMJ defects in MuSKΔCRD mice and therefore constitutes a novel therapeutic reagent for the treatment of neuromuscular disorders linked to Wnt-MuSK signaling pathway deficiency. Together, our data reveal that MuSK CRD is critical for NMJ formation and plays an unsuspected role in NMJ maintenance in adulthood.
Collapse
|
26
|
Abstract
The neuromuscular junction (NMJ) is a synapse between motor neurons and skeletal muscle fibers, and is critical for control of muscle contraction. Its formation requires neuronal agrin that acts by binding to LRP4 to stimulate MuSK. Mutations have been identified in agrin, MuSK, and LRP4 in patients with congenital myasthenic syndrome, and patients with myasthenia gravis develop antibodies against agrin, LRP4, and MuSK. However, it remains unclear whether the agrin signaling pathway is critical for NMJ maintenance because null mutation of any of the three genes is perinatal lethal. In this study, we generated imKO mice, a mutant strain whose LRP4 gene can be deleted in muscles by doxycycline (Dox) treatment. Ablation of the LRP4 gene in adult muscle enabled studies of its role in NMJ maintenance. We demonstrate that Dox treatment of P30 mice reduced muscle strength and compound muscle action potentials. AChR clusters became fragmented with diminished junctional folds and synaptic vesicles. The amplitude and frequency of miniature endplate potentials were reduced, indicating impaired neuromuscular transmission and providing cellular mechanisms of adult LRP4 deficiency. We showed that LRP4 ablation led to the loss of synaptic agrin and the 90 kDa fragments, which occurred ahead of other prejunctional and postjunctional components, suggesting that LRP4 may regulate the stability of synaptic agrin. These observations demonstrate that LRP4 is essential for maintaining the structural and functional integrity of the NMJ and that loss of muscle LRP4 in adulthood alone is sufficient to cause myasthenic symptoms.
Collapse
|
27
|
The MuSK activator agrin has a separate role essential for postnatal maintenance of neuromuscular synapses. Proc Natl Acad Sci U S A 2014; 111:16556-61. [PMID: 25368159 DOI: 10.1073/pnas.1408409111] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The motoneural control of skeletal muscle contraction requires the neuromuscular junction (NMJ), a midmuscle synapse between the motor nerve and myotube. The formation and maintenance of NMJs are orchestrated by the muscle-specific receptor tyrosine kinase (MuSK). Motor neuron-derived agrin activates MuSK via binding to MuSK's coreceptor Lrp4, and genetic defects in agrin underlie a congenital myasthenic syndrome (an NMJ disorder). However, MuSK-dependent postsynaptic differentiation of NMJs occurs in the absence of a motor neuron, indicating a need for nerve/agrin-independent MuSK activation. We previously identified the muscle protein Dok-7 as an essential activator of MuSK. Although NMJ formation requires agrin under physiological conditions, it is dispensable for NMJ formation experimentally in the absence of the neurotransmitter acetylcholine, which inhibits postsynaptic specialization. Thus, it was hypothesized that MuSK needs agrin together with Lrp4 and Dok-7 to achieve sufficient activation to surmount inhibition by acetylcholine. Here, we show that forced expression of Dok-7 in muscle enhanced MuSK activation in mice lacking agrin or Lrp4 and restored midmuscle NMJ formation in agrin-deficient mice, but not in Lrp4-deficient mice, probably due to the loss of Lrp4-dependent presynaptic differentiation. However, these NMJs in agrin-deficient mice rapidly disappeared after birth, and postsynaptic specializations emerged ectopically throughout myotubes whereas exogenous Dok-7-mediated MuSK activation was maintained. These findings demonstrate that the MuSK activator agrin plays another role essential for the postnatal maintenance, but not for embryonic formation, of NMJs and also for the postnatal, but not prenatal, midmuscle localization of postsynaptic specializations, providing physiological and pathophysiological insight into NMJ homeostasis.
Collapse
|
28
|
Nicole S, Chaouch A, Torbergsen T, Bauché S, de Bruyckere E, Fontenille MJ, Horn MA, van Ghelue M, Løseth S, Issop Y, Cox D, Müller JS, Evangelista T, Stålberg E, Ioos C, Barois A, Brochier G, Sternberg D, Fournier E, Hantaï D, Abicht A, Dusl M, Laval SH, Griffin H, Eymard B, Lochmüller H. Agrin mutations lead to a congenital myasthenic syndrome with distal muscle weakness and atrophy. Brain 2014; 137:2429-43. [DOI: 10.1093/brain/awu160] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
29
|
Abstract
PURPOSE OF REVIEW Congenital myasthenic syndromes (CMSs) form a heterogeneous group of genetic diseases characterized by a dysfunction of neuromuscular transmission because of mutations in numerous genes. This review will focus on the causative genes recently identified and on the therapy of CMSs. RECENT FINDINGS Advances in exome sequencing allowed the discovery of a new group of genes that did not code for the known molecular components of the neuromuscular junction, and the definition of a new group of glycosylation-defective CMS. Rather than the specific drugs used, some of them having been known for decades, it is the rigorous therapeutic strategy that is now offered to the patient in relation to the identified mutated gene that is novel and promising. SUMMARY In addition to the above main points, we also present new data on the genes that were already known with an emphasis on the clinic and on animal models that may be of use to understand the pathophysiology of the disease. We also stress not only the diagnosis difficulties between congenital myopathies and CMSs, but also the continuum that may exist between the two.
Collapse
|
30
|
Sleigh JN, Burgess RW, Gillingwater TH, Cader MZ. Morphological analysis of neuromuscular junction development and degeneration in rodent lumbrical muscles. J Neurosci Methods 2014; 227:159-65. [PMID: 24530702 DOI: 10.1016/j.jneumeth.2014.02.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 02/04/2014] [Accepted: 02/05/2014] [Indexed: 10/25/2022]
Abstract
BACKGROUND The neuromuscular junction (NMJ) is a specialised synapse formed between a lower motor neuron and a skeletal muscle fibre, and is an early pathological target in numerous nervous system disorders, including amyotrophic lateral sclerosis (ALS), Charcot-Marie-Tooth disease (CMT), and spinal muscular atrophy (SMA). Being able to accurately visualise and quantitatively characterise the NMJ in rodent models of neurological conditions, particularly during the early stages of disease, is thus of clear importance. NEW METHOD We present a method for dissection of rodent deep lumbrical muscles located in the hind-paw, and describe how to perform immunofluorescent morphological analysis of their NMJs. RESULTS These techniques allow the temporal assessment of a number of developmental and pathological NMJ phenotypes in lumbrical muscles. COMPARISON WITH EXISTING METHODS Small muscles, such as the distal hind-limb lumbrical muscles, possess a major advantage over larger muscles, such as gastrocnemius, in that they can be whole-mounted and the entire innervation pattern visualised. This reduces preparation time and ambiguity when evaluating important neuromuscular phenotypes. CONCLUSIONS Together, these methods will allow the reader to perform a detailed and accurate analysis of the neuromuscular system in rodent models of disease in order to identify pertinent features of neuropathology.
Collapse
Affiliation(s)
- James N Sleigh
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK; The Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | | | - Thomas H Gillingwater
- Centre for Integrative Physiology & Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - M Zameel Cader
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK; The Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK.
| |
Collapse
|
31
|
Hettwer S, Lin S, Kucsera S, Haubitz M, Oliveri F, Fariello RG, Ruegg MA, Vrijbloed JW. Injection of a soluble fragment of neural agrin (NT-1654) considerably improves the muscle pathology caused by the disassembly of the neuromuscular junction. PLoS One 2014; 9:e88739. [PMID: 24520420 PMCID: PMC3919806 DOI: 10.1371/journal.pone.0088739] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 01/10/2014] [Indexed: 01/13/2023] Open
Abstract
Treatment of neuromuscular diseases is still an unsolved problem. Evidence over the last years strongly indicates the involvement of malformation and dysfunction of neuromuscular junctions in the development of such medical conditions. Stabilization of NMJs thus seems to be a promising approach to attenuate the disease progression of muscle wasting diseases. An important pathway for the formation and maintenance of NMJs is the agrin/Lrp4/MuSK pathway. Here we demonstrate that the agrin biologic NT-1654 is capable of activating the agrin/Lrp4/MuSK system in vivo, leading to an almost full reversal of the sarcopenia-like phenotype in neurotrypsin-overexpressing (SARCO) mice. We also show that injection of NT-1654 accelerates muscle re-innervation after nerve crush. This report demonstrates that a systemically administered agrin fragment has the potential to counteract the symptoms of neuromuscular disorders.
Collapse
Affiliation(s)
| | - Shuo Lin
- Biozentrum, University of Basel, Basel, Switzerland
| | | | | | | | | | | | | |
Collapse
|
32
|
Almenar-Queralt A, Kim SN, Benner C, Herrera CM, Kang DE, Garcia-Bassets I, Goldstein LSB. Presenilins regulate neurotrypsin gene expression and neurotrypsin-dependent agrin cleavage via cyclic AMP response element-binding protein (CREB) modulation. J Biol Chem 2013; 288:35222-36. [PMID: 24145027 DOI: 10.1074/jbc.m113.513705] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Presenilins, the catalytic components of the γ-secretase complex, are upstream regulators of multiple cellular pathways via regulation of gene transcription. However, the underlying mechanisms and the genes regulated by these pathways are poorly characterized. In this study, we identify Tequila and its mammalian ortholog Prss12 as genes negatively regulated by presenilins in Drosophila larval brains and mouse embryonic fibroblasts, respectively. Prss12 encodes the serine protease neurotrypsin, which cleaves the heparan sulfate proteoglycan agrin. Altered neurotrypsin activity causes serious synaptic and cognitive defects; despite this, the molecular processes regulating neurotrypsin expression and activity are poorly understood. Using γ-secretase drug inhibitors and presenilin mutants in mouse embryonic fibroblasts, we found that a mature γ-secretase complex was required to repress neurotrypsin expression and agrin cleavage. We also determined that PSEN1 endoproteolysis or processing of well known γ-secretase substrates was not essential for this process. At the transcriptional level, PSEN1/2 removal induced cyclic AMP response element-binding protein (CREB)/CREB-binding protein binding, accumulation of activating histone marks at the neurotrypsin promoter, and neurotrypsin transcriptional and functional up-regulation that was dependent on GSK3 activity. Upon PSEN1/2 reintroduction, this active epigenetic state was replaced by a methyl CpG-binding protein 2 (MeCP2)-containing repressive state and reduced neurotrypsin expression. Genome-wide analysis revealed hundreds of other mouse promoters in which CREB binding is similarly modulated by the presence/absence of presenilins. Our study thus identifies Tequila and neurotrypsin as new genes repressed by presenilins and reveals a novel mechanism used by presenilins to modulate CREB signaling based on controlling CREB recruitment.
Collapse
|
33
|
Choi HY, Liu Y, Tennert C, Sugiura Y, Karakatsani A, Kröger S, Johnson EB, Hammer RE, Lin W, Herz J. APP interacts with LRP4 and agrin to coordinate the development of the neuromuscular junction in mice. eLife 2013; 2:e00220. [PMID: 23986861 PMCID: PMC3748711 DOI: 10.7554/elife.00220] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 07/18/2013] [Indexed: 12/22/2022] Open
Abstract
ApoE, ApoE receptors and APP cooperate in the pathogenesis of Alzheimer’s disease. Intriguingly, the ApoE receptor LRP4 and APP are also required for normal formation and function of the neuromuscular junction (NMJ). In this study, we show that APP interacts with LRP4, an obligate co-receptor for muscle-specific tyrosine kinase (MuSK). Agrin, a ligand for LRP4, also binds to APP and co-operatively enhances the interaction of APP with LRP4. In cultured myotubes, APP synergistically increases agrin-induced acetylcholine receptor (AChR) clustering. Deletion of the transmembrane domain of LRP4 (LRP4 ECD) results in growth retardation of the NMJ, and these defects are markedly enhanced in APP−/−;LRP4ECD/ECD mice. Double mutant NMJs are significantly reduced in size and number, resulting in perinatal lethality. Our findings reveal novel roles for APP in regulating neuromuscular synapse formation through hetero-oligomeric interaction with LRP4 and agrin and thereby provide new insights into the molecular mechanisms that govern NMJ formation and maintenance. DOI:http://dx.doi.org/10.7554/eLife.00220.001 One of the hallmarks of Alzheimer’s disease is the formation of plaques in the brain by a protein called β-amyloid. This protein is generated by the cleavage of a precursor protein, and mutations in the gene that encodes amyloid precursor protein greatly increase the risk of developing a familial, early-onset form of Alzheimer’s disease in middle age. Individuals with a particular variant of a lipoprotein called ApoE (ApoE4) are also more likely to develop Alzheimer’s disease at a younger age than the rest of the population. Due to its prevalence—approximately 20% of the world’s population are carriers of at least one allele—ApoE4 is the single-most important risk factor for the late-onset form of Alzheimer’s disease. Amyloid precursor protein and the receptors for ApoE—in particular one called LRP4—are also essential for the development of the specialized synapse that forms between motor neurons and muscles. However, the mechanisms by which they, individually or together, contribute to the formation of these neuromuscular junctions are incompletely understood. Now, Choi et al. have shown that amyloid precursor protein and LRP4 interact at the developing neuromuscular junction. A protein called agrin, which is produced by motor neurons and which must bind to LRP4 to induce neuromuscular junction formation, also binds directly to amyloid precursor protein. This latter interaction leads to the formation of a complex between LRP4 and amyloid precursor protein that robustly promotes the formation of the neuromuscular junction. Mutations that remove the part of LRP4 that anchors it to the cell membrane weaken this complex and thus reduce the development of neuromuscular junctions in mice, especially if the animals also lack amyloid precursor protein. These three proteins thus seem to influence the development and maintenance of neuromuscular junctions by regulating the activity of a fourth protein, called MuSK, which is present on the surface of muscle cells. Activation of MuSK by agrin bound to LRP4 promotes the clustering of acetylcholine receptors in the membrane, which is a crucial step in the formation of the neuromuscular junction. Intriguingly, Choi et al. have now shown that amyloid precursor protein can, by interacting directly with LRP4, also activate MuSK even in the absence of agrin, albeit only to a small extent. The work of Choi et al. suggests that the complex formed between agrin, amyloid precursor protein and LRP4 helps to focus the activation of MuSK, and thus the clustering of acetylcholine receptors, to the site of the developing neuromuscular junction. Since all four proteins are also found in the central nervous system, similar processes might well be at work during the development and maintenance of synapses in the brain. Further studies of these interactions, both at the neuromuscular junction and in the brain, should shed new light on both normal synapse formation and the synaptic dysfunction that is seen in Alzheimer’s disease. DOI:http://dx.doi.org/10.7554/eLife.00220.002
Collapse
Affiliation(s)
- Hong Y Choi
- Department of Molecular Genetics , University of Texas Southwestern Medical Center , Dallas , United States
| | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Bogdanik LP, Sleigh JN, Tian C, Samuels ME, Bedard K, Seburn KL, Burgess RW. Loss of the E3 ubiquitin ligase LRSAM1 sensitizes peripheral axons to degeneration in a mouse model of Charcot-Marie-Tooth disease. Dis Model Mech 2013; 6:780-92. [PMID: 23519028 PMCID: PMC3634660 DOI: 10.1242/dmm.010942] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Charcot-Marie-Tooth disease (CMT) is a clinically and genetically heterogeneous condition characterized by peripheral axon degeneration with subsequent motor and sensory deficits. Several CMT gene products function in endosomal sorting and trafficking to the lysosome, suggesting that defects in this cellular pathway might present a common pathogenic mechanism for these conditions. LRSAM1 is an E3 ubiquitin ligase that is implicated in this process, and mutations in LRSAM1 have recently been shown to cause CMT. We have generated mouse mutations in Lrsam1 to create an animal model of this form of CMT (CMT2P). Mouse Lrsam1 is abundantly expressed in the motor and sensory neurons of the peripheral nervous system. Both homozygous and heterozygous mice have largely normal neuromuscular performance and only a very mild neuropathy phenotype with age. However, Lrsam1 mutant mice are more sensitive to challenge with acrylamide, a neurotoxic agent that causes axon degeneration, indicating that the axons in the mutant mice are indeed compromised. In transfected cells, LRSAM1 primarily localizes in a perinuclear compartment immediately beyond the Golgi and shows little colocalization with components of the endosome to lysosome trafficking pathway, suggesting that other cellular mechanisms also merit consideration.
Collapse
|
35
|
Maselli RA, Fernandez JM, Arredondo J, Navarro C, Ngo M, Beeson D, Cagney Ó, Williams DC, Wollmann RL, Yarov-Yarovoy V, Ferns MJ. LG2 agrin mutation causing severe congenital myasthenic syndrome mimics functional characteristics of non-neural (z-) agrin. Hum Genet 2012; 131:1123-35. [PMID: 22205389 PMCID: PMC4795461 DOI: 10.1007/s00439-011-1132-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 12/11/2011] [Indexed: 10/14/2022]
Abstract
We describe a severe form of congenital myasthenic syndrome (CMS) caused by two heteroallelic mutations: a nonsense and a missense mutation in the gene encoding agrin (AGRN). The identified mutations, Q353X and V1727F, are located at the N-terminal and at the second laminin G-like (LG2) domain of agrin, respectively. A motor-point muscle biopsy demonstrated severe disruption of the architecture of the neuromuscular junction (NMJ), including: dispersion and fragmentation of endplate areas with normal expression of acetylcholinesterase; simplification of postsynaptic membranes; pronounced reduction of the axon terminal size; widening of the primary synaptic cleft; and, collection of membranous debris material in the primary synaptic cleft and in the subsynaptic cytoplasm. Expression studies in heterologous cells revealed that the Q353X mutation abolished expression of full-length agrin. Moreover, the V1727F mutation decreased agrin-induced clustering of the acetylcholine receptor (AChR) in cultured C2 muscle cells by >100-fold, and phosphorylation of the MuSK receptor and AChR beta subunit by ~tenfold. Surprisingly, the V1727F mutant also displayed increased binding to α-dystroglycan but decreased binding to a neural (z+) agrin-specific antibody. Our findings demonstrate that agrin mutations can associate with a severe form of CMS and cause profound distortion of the architecture and function of the NMJ. The impaired ability of V1727F agrin to activate MuSK and cluster AChRs, together with its increased affinity to α-dystroglycan, mimics non-neural (z-) agrin and are important determinants of the pathogenesis of the disease.
Collapse
MESH Headings
- Acetylcholinesterase/metabolism
- Adult
- Agrin/chemistry
- Agrin/genetics
- Agrin/metabolism
- Base Sequence
- Cell Line
- Codon, Nonsense
- Dystroglycans/metabolism
- Female
- HEK293 Cells
- Humans
- Male
- Models, Molecular
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/pathology
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Mutation, Missense
- Myasthenic Syndromes, Congenital/genetics
- Myasthenic Syndromes, Congenital/metabolism
- Neuromuscular Junction/metabolism
- Neuromuscular Junction/pathology
- Pedigree
- Receptors, Cholinergic/genetics
- Receptors, Cholinergic/metabolism
- Sequence Analysis, DNA
Collapse
Affiliation(s)
- Ricardo A. Maselli
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - Jose M. Fernandez
- Service of Clinical Neurophysiology. University Hospital of Vigo, Vigo (Pontevedra), Spain
| | - Juan Arredondo
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - Carmen Navarro
- Department of Pathology, University Hospital of Vigo and CIBERER (Centro de Investigacion Biomedica en Red en Enfermedades Raras), Vigo (Pontevedra), Spain
| | - Maian Ngo
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Órla Cagney
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - D. Colette Williams
- Veterinary Medical Teaching Hospital, University of California Davis, Davis, California, 95616, USA
| | - Robert L. Wollmann
- Department of Pathology, University of Chicago, Chicago, Illinois, 60637, USA
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California Davis, Davis, California 95616, USA
| | - Michael J Ferns
- Department of Physiology and Membrane Biology, University of California Davis, Davis, California 95616, USA
- Department of Anesthesiology, University of California Davis, Davis, California 95616, USA
| |
Collapse
|