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McMacken G, Whittaker RG, Wake R, Lochmuller H, Horvath R. Neuromuscular junction involvement in inherited motor neuropathies: genetic heterogeneity and effect of oral salbutamol treatment. J Neurol 2023; 270:3112-3119. [PMID: 36869887 DOI: 10.1007/s00415-023-11643-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 02/01/2023] [Accepted: 02/22/2023] [Indexed: 03/05/2023]
Abstract
OBJECTIVES Inherited defects of the neuromuscular junction (NMJ) comprise an increasingly diverse range of diseases. Several recently identified genes highlight the overlap between peripheral neuropathies and congenital myasthenic syndromes (CMS). The beta-2 adrenergic receptor agonist salbutamol has been shown to provide symptomatic benefit in CMS, while improving structural defects at the NMJ. Based on these findings, we identified cases of motor neuropathy with NMJ dysfunction and assessed the effect of salbutamol on motor function. METHODS Cases of motor neuropathy with significant NMJ dysfunction, were identified using repetitive nerve stimulation and single fibre electromyography. Oral salbutamol was administered for 12 months. Repeat neurophysiological and clinical assessments were undertaken at baseline, 6 months and 12 months. RESULTS Significant defects of neuromuscular transmission were identified in 15 patients harbouring a range of genetic defects, including mutations in GARS1, DNM2, SYT2 and DYNC1H. No clear benefit on motor function was seen following the administration of 12 months of oral salbutamol; however, there was a significant improvement in patient reported fatigue. In addition, no clear effect on neurophysiological parameters was seen in patients treated with salbutamol. Side-effects due to off-target beta-adrenergic effects were significant in the patient cohort. CONCLUSION These results highlight the involvement of the NMJ in several subtypes of motor neuropathies, including subtypes of neuropathy due to deficits in mitochondrial fusion-fission, synaptic vesicle transport, calcium channels and tRNA synthetases. Whether the NMJ dysfunction is simply due to muscle reinnervation or a pathology unrelated to denervation is unknown. The involvement of the NMJ may represent a novel therapeutic target in these conditions. However, treatment regimens will need to be more targeted for patients with primary inherited defects of neuromuscular transmission.
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Affiliation(s)
- Grace McMacken
- Department of Neurology, Royal Victoria Hospital, Belfast Health and Social Care Trust, Belfast, UK
| | - Roger G Whittaker
- Translational and Clinical Research Institute, Newcastle University, Newcastle Upon Tyne, UK
| | - Ruth Wake
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, UK
| | - Hanns Lochmuller
- Division of Neurology, Department of Medicine, Children's Hospital of Eastern Ontario Research Institute, The Ottawa Hospital and Brain and Mind Research Institute, University of Ottawa, Ottawa, Canada
| | - Rita Horvath
- Department of Clinical Neurosciences, John Van Geest Centre for Brain Repair, University of Cambridge School of Clinical Medicine, Level 3 A Block, Box 165, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK.
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Cahalan SD, Boehm I, Jones RA, Piercy RJ. Recognising the potential of large animals for modelling neuromuscular junction physiology and disease. J Anat 2022; 241:1120-1132. [PMID: 36056593 PMCID: PMC9558152 DOI: 10.1111/joa.13749] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 08/05/2022] [Accepted: 08/08/2022] [Indexed: 12/28/2022] Open
Abstract
The aetiology and pathophysiology of many diseases of the motor unit remain poorly understood and the role of the neuromuscular junction (NMJ) in this group of disorders is particularly overlooked, especially in humans, when these diseases are comparatively rare. However, elucidating the development, function and degeneration of the NMJ is essential to uncover its contribution to neuromuscular disorders, and to explore potential therapeutic avenues to treat these devastating diseases. Until now, an understanding of the role of the NMJ in disease pathogenesis has been hindered by inherent differences between rodent and human NMJs: stark contrasts in body size and corresponding differences in associated axon length underpin some of the translational issues in animal models of neuromuscular disease. Comparative studies in large mammalian models, including examination of naturally occurring, highly prevalent animal diseases and evaluation of their treatment, might provide more relevant insights into the pathogenesis and therapy of equivalent human diseases. This review argues that large animal models offer great potential to enhance our understanding of the neuromuscular system in health and disease, and in particular, when dealing with diseases for which nerve length dependency might underly the pathogenesis.
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Affiliation(s)
- Stephen D Cahalan
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Science and Services, Royal Veterinary College, University of London, London, UK
| | - Ines Boehm
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK.,Biozentrum University of Basel, Basel, Switzerland
| | - Ross A Jones
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
| | - Richard J Piercy
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Science and Services, Royal Veterinary College, University of London, London, UK
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Wu C, Xiang H, Chen R, Zheng Y, Zhu M, Chen S, Yu Y, Peng Y, Yu Y, Deng J, Zhou M, Hong D. Genetic spectrum in a cohort of patients with distal hereditary motor neuropathy. Ann Clin Transl Neurol 2022; 9:633-643. [PMID: 35297556 PMCID: PMC9082376 DOI: 10.1002/acn3.51543] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 02/08/2022] [Accepted: 02/26/2022] [Indexed: 12/26/2022] Open
Abstract
Background Distal hereditary motor neuropathy (dHMN) is a heterogeneous group of diseases characterized by exclusive degeneration of peripheral motor nerves, while only 20.0–47.8% of dHMN patients are genetically identified. Recently, GGC expansion in the 5’UTR of NOTCH2NLC has been associated with dHMN. Accordingly, short tandem repeat (STR) should be further explored in genetically unsolved patients with dHMN. Methods A total of 128 patients from 90 unrelated families were clinically diagnosed as dHMN, and underwent a comprehensively genetic screening. Skin biopsies were conducted with routine protocols. Results Most patients showed chronic distal weakness of lower limbs (121/128), while 20 patients initially had asymmetrical involvements, 14 had subclinical sensory abnormalities, 11 had pyramidal impairments, five had cerebellar disturbance, and four had hyperCKmia. The rate of genetic detection was achieved in 36.7% (33/90), and the rate increased to 46.7% (42/90) if patients with variants uncertain significance were included. The most common causative genes included chaperone‐related genes (8/33, 24.2%), tRNA synthetase genes (4/33, 12.1%), and cytoskeleton‐related genes (4/33, 12.1%). Additionally, two dominant inherited families were attributed to abnormal expansion of GGC repeats in the 5‘UTR of NOTCH2NLC; and a patient with dHMN and cerebellar symptoms had CAG repeat expansion in the ATXN2 gene. Skin biopsy from patients with GGC expansion in NOTCH2NLC revealed typical intranuclear inclusions on histological and ultrastructural examinations. Interpretations This study further extends the genetic heterogeneity of dHMN. Given some dHMN patients may be associated with nucleotides repeat expansion, STR screening is necessary to perform in genetically unsolved patients.
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Affiliation(s)
- Chengsi Wu
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Haijie Xiang
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Ran Chen
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Yilei Zheng
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Min Zhu
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China.,Department of Medical Genetics, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Shuyun Chen
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Yanyan Yu
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China.,Department of Medical Genetics, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Yun Peng
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China.,Department of Medical Genetics, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Yaqing Yu
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Jianwen Deng
- Department of Neurology, Peking University First Hospital, Beijing, 100034, China
| | - Meihong Zhou
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Daojun Hong
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China.,Department of Medical Genetics, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China.,Department of Neurology, Peking University People Hospital, Beijing, 100044, China
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