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Li X, Xu Y, Si JX, Gu F, Ma YY. Role of Agrin in tissue repair and regeneration: From mechanisms to therapeutic opportunities (Review). Int J Mol Med 2024; 54:98. [PMID: 39301653 PMCID: PMC11410309 DOI: 10.3892/ijmm.2024.5422] [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: 03/05/2024] [Accepted: 08/01/2024] [Indexed: 09/22/2024] Open
Abstract
Tissue regeneration is a complex process that involves the recruitment of various types of cells for healing after injury; it is mediated by numerous precise interactions. However, the identification of effective targets for improving tissue regeneration remains a challenge. As an extracellular matrix protein, Agrin plays a critical role in neuromuscular junction formation. Furthermore, recent studies have revealed the role of Agrin in regulating tissue proliferation and regeneration, which contributes to the repair process of injured tissues. An in‑depth understanding of the role of Agrin will therefore be of value. Given that repair and regeneration processes occur in various parts of the human body, the present systematic review focuses on the role of Agrin in typical tissue and highlights the potential signaling pathways that are involved in Agrin‑induced repair and regeneration. This review offers important insight into novel strategies for the future clinical applications of Agrin‑based therapies, which may represent a feasible treatment option for patients who require organ replacement or repair.
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Affiliation(s)
- Xiang Li
- Center for Plastic and Reconstructive Surgery, Department of Plastic and Reconstructive Surgery, Zhejiang Provincial People's Hospital (Affiliated People's Hospital), Hangzhou Medical College, Hangzhou, Zhejiang 310014, P.R. China
- Key Laboratory of Gastroenterology of Zhejiang Province, Zhejiang Provincial People's Hospital (Affiliated People's Hospital), Hangzhou Medical College, Hangzhou, Zhejiang 310014, P.R. China
| | - Yuan Xu
- Department of Gastrointestinal Surgery, Ningbo Medical Center Lihuili Hospital, Ningbo, Zhejiang 315048, P.R. China
| | - Jing-Xing Si
- Center for Plastic and Reconstructive Surgery, Department of Plastic and Reconstructive Surgery, Zhejiang Provincial People's Hospital (Affiliated People's Hospital), Hangzhou Medical College, Hangzhou, Zhejiang 310014, P.R. China
| | - Fang Gu
- Department of Paediatrics, Zhejiang Provincial People's Hospital, Affiliated People's Hospital, Hangzhou Medical College, Hangzhou, Zhejiang 310014, P.R. China
| | - Ying-Yu Ma
- Center for Plastic and Reconstructive Surgery, Department of Plastic and Reconstructive Surgery, Zhejiang Provincial People's Hospital (Affiliated People's Hospital), Hangzhou Medical College, Hangzhou, Zhejiang 310014, P.R. China
- Key Laboratory of Gastroenterology of Zhejiang Province, Zhejiang Provincial People's Hospital (Affiliated People's Hospital), Hangzhou Medical College, Hangzhou, Zhejiang 310014, P.R. China
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2
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Herbst R, Huijbers MG, Oury J, Burden SJ. Building, Breaking, and Repairing Neuromuscular Synapses. Cold Spring Harb Perspect Biol 2024; 16:a041490. [PMID: 38697654 PMCID: PMC11065174 DOI: 10.1101/cshperspect.a041490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2024]
Abstract
A coordinated and complex interplay of signals between motor neurons, skeletal muscle cells, and Schwann cells controls the formation and maintenance of neuromuscular synapses. Deficits in the signaling pathway for building synapses, caused by mutations in critical genes or autoantibodies against key proteins, are responsible for several neuromuscular diseases, which cause muscle weakness and fatigue. Here, we describe the role that four key genes, Agrin, Lrp4, MuSK, and Dok7, play in this signaling pathway, how an understanding of their mechanisms of action has led to an understanding of several neuromuscular diseases, and how this knowledge has contributed to emerging therapies for treating neuromuscular diseases.
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Affiliation(s)
- Ruth Herbst
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, 1090 Vienna, Austria
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Centre LUMC, 2300 RC Leiden, the Netherlands
- Department of Neurology, Leiden University Medical Centre LUMC, 2333 ZA Leiden, the Netherlands
| | - Julien Oury
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU School of Medicine, New York, New York 10016, USA
| | - Steven J Burden
- Neurology Department, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA
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3
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Eguchi T, Tezuka T, Watanabe Y, Inoue-Yamauchi A, Sagara H, Ozawa M, Yamanashi Y. Calcium-binding protein 7 expressed in muscle negatively regulates age-related degeneration of neuromuscular junctions in mice. iScience 2024; 27:108997. [PMID: 38327785 PMCID: PMC10847746 DOI: 10.1016/j.isci.2024.108997] [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: 08/30/2023] [Revised: 12/05/2023] [Accepted: 01/19/2024] [Indexed: 02/09/2024] Open
Abstract
The neuromuscular junction (NMJ) forms centrally in myotubes and, as the only synapse between motor neuron and myotube, are indispensable for motor activity. The midmuscle formation of NMJs, including midmuscle-restricted expression of NMJ-related genes, is governed by the muscle-specific kinase (MuSK). However, mechanisms underlying MuSK-mediated signaling are unclear. Here, we find that the Calcium-binding protein 7 (Cabp7) gene shows midmuscle-restricted expression, and muscle-specific depletion of Cabp7 in mice accelerated age-related NMJ degeneration, muscle weakness/atrophy, and motor dysfunction. Surprisingly, forced expression in muscle of CIP, an inhibitory peptide of the negative regulator of NMJ formation cyclin-dependent kinase 5 (Cdk5), restored NMJ integrity and muscle strength, and healed muscle atrophy in muscle-specific Cabp7-deficient mice, which showed increased muscle expression of the Cdk5 activator p25. These findings together demonstrate that MuSK-mediated signaling induces muscle expression of Cabp7, which suppresses age-related NMJ degeneration likely by attenuating p25 expression, providing insights into prophylactic/therapeutic intervention against age-related motor dysfunction.
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Affiliation(s)
- Takahiro Eguchi
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Tohru Tezuka
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Yuji Watanabe
- Medical Proteomics Laboratory, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Akane Inoue-Yamauchi
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Hiroshi Sagara
- Medical Proteomics Laboratory, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Manabu Ozawa
- Laboratory of Reproductive Systems Biology, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
- Core Laboratory for Developing Advanced Animal Models, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Yuji Yamanashi
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
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Chen BH, Lin ZY, Zeng XX, Jiang YH, Geng F. LRP4-related signalling pathways and their regulatory role in neurological diseases. Brain Res 2024; 1825:148705. [PMID: 38065285 DOI: 10.1016/j.brainres.2023.148705] [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: 10/04/2023] [Revised: 11/17/2023] [Accepted: 12/03/2023] [Indexed: 01/28/2024]
Abstract
The mechanism of action of low-density lipoprotein receptor related protein 4 (LRP4) is mediated largely via the Agrin-LRP4-MuSK signalling pathway in the nervous system. LRP4 contributes to the development of synapses in the peripheral nervous system (PNS). It interacts with signalling molecules such as the amyloid beta-protein precursor (APP) and the wingless type protein (Wnt). Its mechanisms of action are complex and mediated via interaction between the pre-synaptic motor neuron and post-synaptic muscle cell in the PNS, which enhances the development of the neuromuscular junction (NMJ). LRP4 may function differently in the central nervous system (CNS) than in the PNS, where it regulates ATP and glutamate release via astrocytes. It mayaffect the growth and development of the CNS by controlling the energy metabolism. LRP4 interacts with Agrin to maintain dendrite growth and density in the CNS. The goal of this article is to review the current studies involving relevant LRP4 signaling pathways in the nervous system. The review also discusses the clinical and etiological roles of LRP4 in neurological illnesses, such as myasthenia gravis, Alzheimer's disease and epilepsy. In this review, we provide a theoretical foundation for the pathogenesis and therapeutic application of LRP4 in neurologic diseases.
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Affiliation(s)
- Bai-Hui Chen
- Department of Physiology, Shantou University Medical College, Shantou 515041, China
| | - Ze-Yu Lin
- Department of Physiology, Shantou University Medical College, Shantou 515041, China
| | - Xiao-Xue Zeng
- Department of Physiology, Shantou University Medical College, Shantou 515041, China
| | - Yi-Han Jiang
- Department of Physiology, Shantou University Medical College, Shantou 515041, China
| | - Fei Geng
- Department of Physiology, Shantou University Medical College, Shantou 515041, China; Guangdong Provincial Key Laboratory of Infectious Diseases and Molecular Immunopathology, Shantou University Medical College, Shantou 515041, China.
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5
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Wang M, Fan J, Shao Z. Cellular and Molecular Mechanisms Underlying Synaptic Subcellular Specificity. Brain Sci 2024; 14:155. [PMID: 38391729 PMCID: PMC10886843 DOI: 10.3390/brainsci14020155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 01/03/2024] [Accepted: 01/09/2024] [Indexed: 02/24/2024] Open
Abstract
Chemical synapses are essential for neuronal information storage and relay. The synaptic signal received or sent from spatially distinct subcellular compartments often generates different outcomes due to the distance or physical property difference. Therefore, the final output of postsynaptic neurons is determined not only by the type and intensity of synaptic inputs but also by the synaptic subcellular location. How synaptic subcellular specificity is determined has long been the focus of study in the neurodevelopment field. Genetic studies from invertebrates such as Caenorhabditis elegans (C. elegans) have uncovered important molecular and cellular mechanisms required for subcellular specificity. Interestingly, similar molecular mechanisms were found in the mammalian cerebellum, hippocampus, and cerebral cortex. This review summarizes the comprehensive advances in the cellular and molecular mechanisms underlying synaptic subcellular specificity, focusing on studies from C. elegans and rodents.
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Affiliation(s)
- Mengqing Wang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Neurosurgery, Zhongshan Hospital, Fudan University, 131 Dong An Rd, Research Building B4017, Shanghai 200032, China
| | - Jiale Fan
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Neurosurgery, Zhongshan Hospital, Fudan University, 131 Dong An Rd, Research Building B4017, Shanghai 200032, China
| | - Zhiyong Shao
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Neurosurgery, Zhongshan Hospital, Fudan University, 131 Dong An Rd, Research Building B4017, Shanghai 200032, China
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6
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Chen D, Philippidou P, Brenha BDF, Schaffer AE, Miranda HC. Scalable, optically-responsive human neuromuscular junction model reveals convergent mechanisms of synaptic dysfunction in familial ALS. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.11.575304. [PMID: 38260655 PMCID: PMC10802619 DOI: 10.1101/2024.01.11.575304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Neuromuscular junctions (NMJs) are specialized synapses that mediate communication between motor neurons and skeletal muscles and are essential for movement. The degeneration of this system can lead to symptoms observed in neuromuscular and motor neuron diseases. Studying these synapses and their degeneration has proven challenging. Prior NMJ studies heavily relied upon the use of mouse, chick, or isolated primary human cells, which have demonstrated limited fidelity for disease modeling. To enable the study of NMJ dysfunction and model genetic diseases, we, and others, have developed methods to generate human NMJs from pluripotent stem cells (PSCs), embryonic stem cells, and induced pluripotent stem cells. However, published studies have highlighted technical limitations associated with these complex in vitro NMJ models. In this study, we developed a robust PSC-derived motor neuron and skeletal muscle co-culture method, and demonstrated its sensitivity in modeling motor neuron disease. Our method spontaneously and reproducibly forms human NMJs. We developed multiwell-multielectrode array (MEA) parameters to quantify the activity of PSC-derived skeletal muscles, as well as measured the electrophysiological activity of functional human PSC-derived NMJs. We further leveraged our method to morphologically and functionally assess NMJs from the familial amyotrophic lateral sclerosis (fALS) PSCs, C9orf72 hexanucleotide (G4C2)n repeat expansion (HRE), SOD1 A5V , and TDP43 G298S to define the reproducibility and sensitivity of our system. We observed a significant decrease in the numbers and activity of PSC-derived NMJs developed from the different ALS lines compared to their respective controls. Furthermore, we evaluated a therapeutic candidate undergoing clinical trials and observed a variant-dependent rescue of functionality of NMJs. Our newly developed method provides a platform for the systematic investigation of genetic causes of NMJ neurodegeneration and highlights the need for therapeutic avenues to consider patient genotype.
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Qaisar R. Targeting neuromuscular junction to treat neuromuscular disorders. Life Sci 2023; 333:122186. [PMID: 37858716 DOI: 10.1016/j.lfs.2023.122186] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Revised: 10/07/2023] [Accepted: 10/16/2023] [Indexed: 10/21/2023]
Abstract
The integrity and preservation of the neuromuscular junction (NMJ), the interface between the motor neuron and skeletal muscle, is critical for maintaining a healthy skeletal muscle. The structural and/or functional defects in the three cellular components of NMJ, namely the pre-synaptic terminal, synaptic cleft, and post-synaptic region, negatively affect skeletal muscle mass and/or strength. Therefore, NMJ repair appears to be an appropriate therapy for muscle disorders. Mouse models provide a detailed molecular characterization of various cellular components of NMJ with relevance to human diseases. This review discusses different molecular targets on the three cellular components of NMJ for treating muscle diseases. The potential effects of these therapies on NMJ morphology and motor performance, their therapeutic efficacy, and clinical relevance are discussed. Collectively, the available data supports targeting NMJ alone or as an adjunct therapy in treating muscle disorders. However, the potential impact of such interventions on human patients with muscle disorders requires further investigation.
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Affiliation(s)
- Rizwan Qaisar
- Basic Medical Sciences, College of Medicine, University of Sharjah, Sharjah, United Arab Emirates; Space Medicine Research Group, Sharjah Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates; Cardiovascular Research Group, Sharjah Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates.
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8
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He Y, Wang HP, Pan FY, Xu SH, Gao YF. Plasticity changes in neuromuscular junction morphology and related regulatory proteins in the hibernating ground squirrel. J Appl Physiol (1985) 2023; 135:1082-1091. [PMID: 37795532 DOI: 10.1152/japplphysiol.00334.2023] [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: 05/24/2023] [Revised: 09/28/2023] [Accepted: 10/03/2023] [Indexed: 10/06/2023] Open
Abstract
Skeletal muscle disuse atrophy can cause degenerative changes in neuromuscular junction morphology. Although Daurian ground squirrels (Spermophilus dauricus) are a natural anti-disuse animal model for studying muscle atrophy during hibernation, little is known about the morphological and regulatory mechanisms of their neuromuscular junctions. Here, we found that morphological indices of the soleus muscle were significantly lower during hibernation (torpor and interbout arousal) compared with pre-hibernation but recovered during post-hibernation. In the extensor digitorum longus muscle, neuromuscular junction morphology did not change significantly during hibernation. Agrin-Lrp4-MuSK is a key pathway for the formation and maintenance of the neuromuscular junction. Our results showed that low-density lipoprotein receptor-associated protein 4 (Lrp4) expression in the soleus (slow muscle) decreased by 46.2% in the interbout arousal group compared with the pre-hibernation group (P = 0.019), with recovery in the post-hibernation group. Compared with the pre-hibernation group, agrin expression in the extensor digitorum longus (fast muscle) increased by 67.0% in the interbout arousal group (P = 0.016). In conclusion, periodic up-regulation in agrin expression during interbout arousal may be involved in the maintenance of neuromuscular junction morphology in the extensor digitorum longus muscle during hibernation. The degenerative changes in neuromuscular junction morphology and the periodic decrease in Lrp4 protein expression in the soleus during hibernation, these changes recovered to the pre-hibernation levels in the post-hibernation group, exhibiting significant plasticity. This plasticity may be one of the important mechanisms for resisting disuse atrophy in hibernating animals.NEW & NOTEWORTHY This study is the first to explore the neuromuscular junction morphology of slow- and fast-twitch muscles in Daurian ground squirrels during different periods of hibernation. Results showed that the neuromuscular junction maintained stable morphology in the extensor digitorum longus muscle. The degenerative changes in neuromuscular junction morphology and the periodic decrease in Lrp4 protein expression in the soleus muscle during hibernation recovered in post-hibernation, exhibiting significant plasticity.
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Affiliation(s)
- Yue He
- Shaanxi Key Laboratory for Animal Conservation, College of Life Sciences, Northwest University, Xi'an, People's Republic of China
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, Xi'an, People's Republic of China
| | - Hui-Ping Wang
- Shaanxi Key Laboratory for Animal Conservation, College of Life Sciences, Northwest University, Xi'an, People's Republic of China
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, Xi'an, People's Republic of China
| | - Fang-Yang Pan
- Shaanxi Key Laboratory for Animal Conservation, College of Life Sciences, Northwest University, Xi'an, People's Republic of China
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, Xi'an, People's Republic of China
| | - Shen-Hui Xu
- Shaanxi Key Laboratory for Animal Conservation, College of Life Sciences, Northwest University, Xi'an, People's Republic of China
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, Xi'an, People's Republic of China
- Department of Digestive Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, People's Republic of China
- State Key Laboratory of Cancer Biology, Department of Pathology, Xijing Hospital and School of Basic Medicine, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Yun-Fang Gao
- Shaanxi Key Laboratory for Animal Conservation, College of Life Sciences, Northwest University, Xi'an, People's Republic of China
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Northwest University, Xi'an, People's Republic of China
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Navarro-Martínez A, Vicente-García C, Carvajal JJ. NMJ-related diseases beyond the congenital myasthenic syndromes. Front Cell Dev Biol 2023; 11:1216726. [PMID: 37601107 PMCID: PMC10436495 DOI: 10.3389/fcell.2023.1216726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 07/21/2023] [Indexed: 08/22/2023] Open
Abstract
Neuromuscular junctions (NMJs) are a special type of chemical synapse that transmits electrical stimuli from motor neurons (MNs) to their innervating skeletal muscle to induce a motor response. They are an ideal model for the study of synapses, given their manageable size and easy accessibility. Alterations in their morphology or function lead to neuromuscular disorders, such as the congenital myasthenic syndromes, which are caused by mutations in proteins located in the NMJ. In this review, we highlight novel potential candidate genes that may cause or modify NMJs-related pathologies in humans by exploring the phenotypes of hundreds of mouse models available in the literature. We also underscore the fact that NMJs may differ between species, muscles or even sexes. Hence the importance of choosing a good model organism for the study of NMJ-related diseases: only taking into account the specific features of the mammalian NMJ, experimental results would be efficiently translated to the clinic.
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Affiliation(s)
| | - Cristina Vicente-García
- Centro Andaluz de Biología del Desarrollo, CSIC-UPO-JA, Universidad Pablo de Olavide, Sevilla, Spain
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Li L, Chen S, Yokoyama H, Kaburagi H, Hirai T, Tsuji K, Enomoto M, Wakabayashi Y, Okawa A. Remodeling of Neuromuscular Junctions in Target Muscle Following Nerve Regeneration in Mice After Delayed Peripheral Nerve Repair. Neuroscience 2023; 524:197-208. [PMID: 37201862 DOI: 10.1016/j.neuroscience.2023.05.008] [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: 07/31/2022] [Revised: 05/05/2023] [Accepted: 05/10/2023] [Indexed: 05/20/2023]
Abstract
Peripheral nerve injury (PNI) induces severe functional loss in extremities. Progressive denervation and atrophy occur in the muscles if the nerve repair is delayed for long periods of the time. To overcome these difficulties, detailed mechanisms should be determined for neuromuscular junction (NMJ) degeneration in target muscles after PNI and regeneration after nerve repair. We established two models of end-to-end neurorrhaphy and allogeneic nerve grafting in the chronic phase after common peroneal nerve injury in female mice (n = 100 in total). We evaluated motor function, histology, and gene expression in the target muscles during their regeneration processes and compared the models. We found that the functional recovery with allogeneic nerve grafting was superior to that with end-to-end neurorrhaphy, and the number of reinnervated NMJs and Schwann cells was increased at 12 weeks after allograft. In addition, NMJ- and Schwann cell-related molecules showed high expression in the target muscle in the allograft model. These results suggest that Schwann cell migrating from the allograft might play a crucial role in nerve regeneration in the chronic phase after PNI. The relationship between the NMJ and Schwann cells should be further investigated in the target muscle.
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Affiliation(s)
- Leyang Li
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan; Department of Traumatic Orthopaedics, The Affiliated Yantai Yuhuangding Hospital of Qingdao University, Yantai, China.
| | - Su Chen
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Hiroyuki Yokoyama
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Hidetoshi Kaburagi
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Takashi Hirai
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Kunikazu Tsuji
- Department of Cartilage Regeneration, Tokyo Medical and Dental University, Tokyo, Japan.
| | - Mitsuhiro Enomoto
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Yoshiaki Wakabayashi
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
| | - Atsushi Okawa
- Department of Orthopaedic and Spinal Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo, Tokyo 113-8519, Japan.
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11
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Kwan HLR, Chan ZCK, Bi X, Kutkowska J, Prószyński TJ, Chan CB, Lee CW. Nerve-independent formation of membrane infoldings at topologically complex postsynaptic apparatus by caveolin-3. SCIENCE ADVANCES 2023; 9:eadg0183. [PMID: 37327338 PMCID: PMC10275590 DOI: 10.1126/sciadv.adg0183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 05/12/2023] [Indexed: 06/18/2023]
Abstract
Junctional folds are unique membrane specializations developed progressively during the postnatal maturation of vertebrate neuromuscular junctions (NMJs), but how they are formed remains elusive. Previous studies suggested that topologically complex acetylcholine receptor (AChR) clusters in muscle cultures undergo a series of transformations, resembling the postnatal maturation of NMJs in vivo. We first demonstrated the presence of membrane infoldings at AChR clusters in cultured muscles. Live-cell super-resolution imaging further revealed that AChRs are gradually redistributed to the crest regions and spatially segregated from acetylcholinesterase along the elongating membrane infoldings over time. Mechanistically, lipid raft disruption or caveolin-3 knockdown not only inhibits membrane infolding formation at aneural AChR clusters and delays agrin-induced AChR clustering in vitro but also affects junctional fold development at NMJs in vivo. Collectively, this study demonstrated the progressive development of membrane infoldings via nerve-independent, caveolin-3-dependent mechanisms and identified their roles in AChR trafficking and redistribution during the structural maturation of NMJs.
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Affiliation(s)
- Hui-Lam Rachel Kwan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Zora Chui-Kuen Chan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Xinyi Bi
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- School of Biological Sciences, Faculty of Science, The University of Hong Kong, Hong Kong, China
| | - Justyna Kutkowska
- Łukasiewicz Research Network – PORT Polish Center for Technology Development, Wrocław, Poland
| | - Tomasz J. Prószyński
- Łukasiewicz Research Network – PORT Polish Center for Technology Development, Wrocław, Poland
| | - Chi Bun Chan
- School of Biological Sciences, Faculty of Science, The University of Hong Kong, Hong Kong, China
| | - Chi Wai Lee
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- Golden Meditech Centre for NeuroRegeneration Sciences, Hong Kong Baptist University, Hong Kong, China
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12
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Ozes B, Tong L, Myers M, Moss K, Ridgley A, Sahenk Z. AAV1.NT-3 gene therapy prevents age-related sarcopenia. Aging (Albany NY) 2023; 15:1306-1329. [PMID: 36897179 PMCID: PMC10042697 DOI: 10.18632/aging.204577] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Accepted: 03/02/2023] [Indexed: 03/11/2023]
Abstract
Sarcopenia is progressive loss of muscle mass and strength, occurring during normal aging with significant consequences on the quality of life for elderly. Neurotrophin 3 (NT-3) is an important autocrine factor supporting Schwann cell survival and differentiation and stimulating axon regeneration and myelination. NT-3 is involved in the maintenance of neuromuscular junction (NMJ) integrity, restoration of impaired radial growth of muscle fibers through activation of the Akt/mTOR pathway. We tested the efficacy of NT-3 gene transfer therapy in wild type (WT)-aged C57BL/6 mice, a model for natural aging and sarcopenia, via intramuscular injection 1 × 1011 vg AAV1.tMCK.NT-3, at 18 months of age. The treatment efficacy was assessed at 6 months post-injection using run to exhaustion and rotarod tests, in vivo muscle contractility assay, and histopathological studies of the peripheral nervous system, including NMJ connectivity and muscle. AAV1.NT-3 gene therapy in WT-aged C57BL/6 mice resulted in functional and in vivo muscle physiology improvements, supported by quantitative histology from muscle, peripheral nerves and NMJ. Hindlimb and forelimb muscles in the untreated cohort showed the presence of a muscle- and sex-dependent remodeling and fiber size decrease with aging, which was normalized toward values obtained from 10 months old WT mice with treatment. The molecular studies assessing the NT-3 effect on the oxidative state of distal hindlimb muscles, accompanied by western blot analyses for mTORC1 activation were in accordance with the histological findings. Considering the cost and quality of life to the individual, we believe our study has important implications for management of age-related sarcopenia.
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Affiliation(s)
- Burcak Ozes
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Lingying Tong
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Morgan Myers
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Kyle Moss
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Alicia Ridgley
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children’s Hospital, Columbus, OH 43205, USA
| | - Zarife Sahenk
- Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children’s Hospital, Columbus, OH 43205, USA
- Department of Pediatrics and Neurology, Nationwide Children’s Hospital and The Ohio State University, Columbus, OH 43205, USA
- Department of Pathology and Laboratory Medicine, Nationwide Children’s Hospital, Columbus, OH 43205, USA
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13
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Hicks MR, Pyle AD. The emergence of the stem cell niche. Trends Cell Biol 2023; 33:112-123. [PMID: 35934562 PMCID: PMC9868094 DOI: 10.1016/j.tcb.2022.07.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 07/06/2022] [Accepted: 07/11/2022] [Indexed: 02/03/2023]
Abstract
Stem cell niches are composed of dynamic microenvironments that support stem cells over a lifetime. The emerging niche is distinct from the adult because its main role is to support the progenitors that build organ systems in development. Emerging niches mature through distinct stages to form the adult niche and enable proper stem cell support. As a model of emerging niches, this review highlights how differences in the skeletal muscle microenvironment influence emerging versus satellite cell (SC) niche formation in skeletal muscle, which is among the most regenerative tissue systems. We contrast how stem cell niches regulate intrinsic properties between progenitor and stem cells throughout development to adulthood. We describe new applications for generating emerging niches from human pluripotent stem cells (hPSCs) using developmental principles and highlight potential applications for regeneration and therapeutics.
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Affiliation(s)
- Michael R Hicks
- Physiology and Biophysics, University of California, Irvine, Irvine, CA, USA
| | - April D Pyle
- Microbiology, Immunology, and Molecular Genetics, Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA, USA.
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14
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Luderman LN, Michaels MT, Levic DS, Knapik EW. Zebrafish Erc1b mediates motor innervation and organization of craniofacial muscles in control of jaw movement. Dev Dyn 2023; 252:104-123. [PMID: 35708710 DOI: 10.1002/dvdy.511] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 05/31/2022] [Accepted: 06/03/2022] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Movement of the lower jaw, a common behavior observed among vertebrates, is required for eating and processing food. This movement is controlled by signals sent from the trigeminal motor nerve through neuromuscular junctions (NMJs) to the masticatory muscles. Dysfunctional jaw movements contribute to craniomandibular disorders, yet the pathophysiology of these disorders is not well understood, as limited studies have been conducted on the molecular mechanisms of jaw movement. RESULTS Using erc1b/kimm533 genetic loss of function mutant, we evaluated lower jaw muscle organization and innervation by the cranial motor nerves in developing zebrafish. Using time-lapse confocal imaging of the erc1b mutant in a transgenic fluorescent reporter line, we found delayed trigeminal nerve growth and disrupted nerve branching architecture during muscle innervation. By automated 3D image analysis of NMJ distribution, we identified an increased number of small, disorganized NMJ clusters in erc1b mutant larvae compared to WT siblings. Using genetic replacement experiments, we determined the Rab GTPase binding domain of Erc1b is required for cranial motor nerve branching, but not NMJ organization or muscle attachment. CONCLUSIONS We identified Erc1b/ERC1 as a novel component of a genetic pathway contributing to muscle organization, trigeminal nerve outgrowth, and NMJ spatial distribution during development that is required for jaw movement.
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Affiliation(s)
- Lauryn N Luderman
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, USA
| | - Mackenzie T Michaels
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Daniel S Levic
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, USA
- Neuroscience Graduate Program, Vanderbilt Brain Institute, Vanderbilt University, Nashville, Tennessee, USA
| | - Ela W Knapik
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, USA
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15
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Younger DS. Neurogenetic motor disorders. HANDBOOK OF CLINICAL NEUROLOGY 2023; 195:183-250. [PMID: 37562870 DOI: 10.1016/b978-0-323-98818-6.00003-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
Advances in the field of neurogenetics have practical applications in rapid diagnosis on blood and body fluids to extract DNA, obviating the need for invasive investigations. The ability to obtain a presymptomatic diagnosis through genetic screening and biomarkers can be a guide to life-saving disease-modifying therapy or enzyme replacement therapy to compensate for the deficient disease-causing enzyme. The benefits of a comprehensive neurogenetic evaluation extend to family members in whom identification of the causal gene defect ensures carrier detection and at-risk counseling for future generations. This chapter explores the many facets of the neurogenetic evaluation in adult and pediatric motor disorders as a primer for later chapters in this volume and a roadmap for the future applications of genetics in neurology.
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Affiliation(s)
- David S Younger
- Department of Clinical Medicine and Neuroscience, CUNY School of Medicine, New York, NY, United States; Department of Medicine, Section of Internal Medicine and Neurology, White Plains Hospital, White Plains, NY, United States.
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16
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Gessler L, Kurtek C, Merholz M, Jian Y, Hashemolhosseini S. In Adult Skeletal Muscles, the Co-Receptors of Canonical Wnt Signaling, Lrp5 and Lrp6, Determine the Distribution and Size of Fiber Types, and Structure and Function of Neuromuscular Junctions. Cells 2022; 11:cells11243968. [PMID: 36552732 PMCID: PMC9777411 DOI: 10.3390/cells11243968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 12/01/2022] [Accepted: 12/04/2022] [Indexed: 12/14/2022] Open
Abstract
Canonical Wnt signaling is involved in skeletal muscle cell biology. The exact way in which this pathway exerts its contribution to myogenesis or neuromuscular junctions (NMJ) is a matter of debate. Next to the common co-receptors of canonical Wnt signaling, Lrp5 and Lrp6, the receptor tyrosine kinase MuSK was reported to bind at NMJs WNT glycoproteins by its extracellular cysteine-rich domain. Previously, we reported canonical Wnt signaling being active in fast muscle fiber types. Here, we used conditional Lrp5 or Lrp6 knockout mice to investigate the role of these receptors in muscle cells. Conditional double knockout mice died around E13 likely due to ectopic expression of the Cre recombinase. Phenotypes of single conditional knockout mice point to a very divergent role for the two receptors. First, muscle fiber type distribution and size were changed. Second, canonical Wnt signaling reporter mice suggested less signaling activity in the absence of Lrps. Third, expression of several myogenic marker genes was changed. Fourth, NMJs were of fragmented phenotype. Fifth, recordings revealed impaired neuromuscular transmission. In sum, our data show fundamental differences in absence of each of the Lrp co-receptors and suggest a differentiated view of canonical Wnt signaling pathway involvement in adult skeletal muscle cells.
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Affiliation(s)
- Lea Gessler
- Institute of Biochemistry, Medical Faculty, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Christopher Kurtek
- Institute of Biochemistry, Medical Faculty, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Mira Merholz
- Institute of Biochemistry, Medical Faculty, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Yongzhi Jian
- Institute of Biochemistry, Medical Faculty, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Said Hashemolhosseini
- Institute of Biochemistry, Medical Faculty, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
- Muscle Research Center, Friedrich-Alexander-University of Erlangen-Nürnberg, 91054 Erlangen, Germany
- Correspondence: ; Tel.: +49-9131-85-24634
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In Skeletal Muscle Fibers, Protein Kinase Subunit CSNK2A1/CK2α Is Required for Proper Muscle Homeostasis and Structure and Function of Neuromuscular Junctions. Cells 2022; 11:cells11243962. [PMID: 36552726 PMCID: PMC9776919 DOI: 10.3390/cells11243962] [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: 10/31/2022] [Revised: 12/03/2022] [Accepted: 12/05/2022] [Indexed: 12/13/2022] Open
Abstract
CSNK2 tetrameric holoenzyme is composed of two subunits with catalytic activity (CSNK2A1 and/or CSNK2A2) and two regulatory subunits (CSNK2B) and is involved in skeletal muscle homeostasis. Up-to-date, constitutive Csnk2a2 knockout mice demonstrated mild regenerative impairments in skeletal muscles, while conditional Csnk2b mice were linked to muscle weakness, impaired neuromuscular transmission, and metabolic and autophagic compromises. Here, for the first time, skeletal muscle-specific conditional Csnk2a1 mice were generated and characterized. The ablation of Csnk2a1 expression was ensured using a human skeletal actin-driven Cre reporter. In comparison with control mice, first, conditional knockout of CSNK2A1 resulted in age-dependent reduced grip strength. Muscle weakness was accompanied by impaired neuromuscular transmission. Second, the protein amount of other CSNK2 subunits was aberrantly changed. Third, the number of central nuclei in muscle fibers indicative of regeneration increased. Fourth, oxidative metabolism was impaired, reflected by an increase in cytochrome oxidase and accumulation of mitochondrial enzyme activity underneath the sarcolemma. Fifth, autophagic processes were stimulated. Sixth, NMJs were fragmented and accompanied by increased synaptic gene expression levels. Altogether, knockout of Csnk2a1 or Csnk2b results in diverse impairments of skeletal muscle biology.
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18
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Xu J, Zhu J, Li Y, Yao Y, Xuan A, Li D, Yu T, Zhu D. Three-dimensional mapping reveals heterochronic development of the neuromuscular system in postnatal mouse skeletal muscles. Commun Biol 2022; 5:1200. [PMID: 36347940 PMCID: PMC9643545 DOI: 10.1038/s42003-022-04159-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 10/24/2022] [Indexed: 11/09/2022] Open
Abstract
The development of the neuromuscular system, including muscle growth and intramuscular neural development, in addition to central nervous system maturation, determines motor ability improvement. Motor development occurs asynchronously from cephalic to caudal. However, whether the structural development of different muscles is heterochronic is unclear. Here, based on the characteristics of motor behavior in postnatal mice, we examined the 3D structural features of the neuromuscular system in different muscles by combining tissue clearing with optical imaging techniques. Quantitative analyses of the structural data and related mRNA expression revealed that there was continued myofiber hyperplasia of the forelimb and hindlimb muscles until around postnatal day 3 (P3) and P6, respectively, as well as continued axonal arborization and neuromuscular junction formation until around P3 and P9, respectively; feature alterations of the cervical muscle ended at birth. Such structural heterochrony of muscles in different body parts corresponds to their motor function. Structural data on the neuromuscular system of neonatal muscles provide a 3D perspective in the understanding of the structural status during motor development.
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Affiliation(s)
- Jianyi Xu
- Britton Chance Center for Biomedical Photonics - MoE Key Laboratory for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics - Advanced Biomedical Imaging Facility, Huazhong University of Science and Technology, 430074, Wuhan, Hubei, China
- Optics Valley Laboratory, 430074, Wuhan, Hubei, China
| | - Jingtan Zhu
- Britton Chance Center for Biomedical Photonics - MoE Key Laboratory for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics - Advanced Biomedical Imaging Facility, Huazhong University of Science and Technology, 430074, Wuhan, Hubei, China
- Optics Valley Laboratory, 430074, Wuhan, Hubei, China
| | - Yusha Li
- Britton Chance Center for Biomedical Photonics - MoE Key Laboratory for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics - Advanced Biomedical Imaging Facility, Huazhong University of Science and Technology, 430074, Wuhan, Hubei, China
- Optics Valley Laboratory, 430074, Wuhan, Hubei, China
| | - Yingtao Yao
- Britton Chance Center for Biomedical Photonics - MoE Key Laboratory for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics - Advanced Biomedical Imaging Facility, Huazhong University of Science and Technology, 430074, Wuhan, Hubei, China
- Optics Valley Laboratory, 430074, Wuhan, Hubei, China
| | - Ang Xuan
- Britton Chance Center for Biomedical Photonics - MoE Key Laboratory for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics - Advanced Biomedical Imaging Facility, Huazhong University of Science and Technology, 430074, Wuhan, Hubei, China
- Optics Valley Laboratory, 430074, Wuhan, Hubei, China
| | - Dongyu Li
- Britton Chance Center for Biomedical Photonics - MoE Key Laboratory for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics - Advanced Biomedical Imaging Facility, Huazhong University of Science and Technology, 430074, Wuhan, Hubei, China
- Optics Valley Laboratory, 430074, Wuhan, Hubei, China
| | - Tingting Yu
- Britton Chance Center for Biomedical Photonics - MoE Key Laboratory for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics - Advanced Biomedical Imaging Facility, Huazhong University of Science and Technology, 430074, Wuhan, Hubei, China.
- Optics Valley Laboratory, 430074, Wuhan, Hubei, China.
| | - Dan Zhu
- Britton Chance Center for Biomedical Photonics - MoE Key Laboratory for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics - Advanced Biomedical Imaging Facility, Huazhong University of Science and Technology, 430074, Wuhan, Hubei, China.
- Optics Valley Laboratory, 430074, Wuhan, Hubei, China.
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Bai L, Tu WY, Xiao Y, Zhang K, Shen C. Motoneurons innervation determines the distinct gene expressions in multinucleated myofibers. Cell Biosci 2022; 12:140. [PMID: 36042463 PMCID: PMC9429338 DOI: 10.1186/s13578-022-00876-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 08/09/2022] [Indexed: 11/22/2022] Open
Abstract
Background Neuromuscular junctions (NMJs) are peripheral synapses connecting motoneurons and skeletal myofibers. At the postsynaptic side in myofibers, acetylcholine receptor (AChR) proteins are clustered by the neuronal agrin signal. Meanwhile, several nuclei in each myofiber are specially enriched around the NMJ for postsynaptic gene transcription. It remains mysterious that how gene expressions in these synaptic nuclei are systematically regulated, especially by motoneurons. Results We found that synaptic nuclei have a distinctive chromatin structure and gene expression profiling. Synaptic nuclei are formed during NMJ development and maintained by motoneuron innervation. Transcriptome analysis revealed that motoneuron innervation determines the distinct expression patterns in the synaptic region and non-synaptic region in each multinucleated myofiber, probably through epigenetic regulation. Myonuclei in synaptic and non-synaptic regions have different responses to denervation. Weighted gene co-expression network analysis revealed that the histone lysine demethylases Kdm1a is a negative regulator of synaptic gene expression. Inhibition of Kdm1a promotes AChR expression but impairs motor functions. Conclusion These results demonstrate that motoneurons innervation determines the distinct gene expressions in multinucleated myofibers. Thus, dysregulation of nerve-controlled chromatin structure and muscle gene expression might cause muscle weakness and atrophy in motoneuron degenerative disorders. Supplementary Information The online version contains supplementary material available at 10.1186/s13578-022-00876-6.
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20
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Control of CRK-RAC1 activity by the miR-1/206/133 miRNA family is essential for neuromuscular junction function. Nat Commun 2022; 13:3180. [PMID: 35676269 PMCID: PMC9178026 DOI: 10.1038/s41467-022-30778-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 05/07/2022] [Indexed: 11/08/2022] Open
Abstract
Formation and maintenance of neuromuscular junctions (NMJs) are essential for skeletal muscle function, allowing voluntary movements and maintenance of the muscle tone, thereby preventing atrophy. Generation of NMJs depends on the interaction of motor neurons with skeletal muscle fibers, which initiates a cascade of regulatory events that is essential for patterning of acetylcholine receptor (AChR) clusters at specific sites of the sarcolemma. Here, we show that muscle-specific miRNAs of the miR-1/206/133 family are crucial regulators of a signaling cascade comprising DOK7-CRK-RAC1, which is critical for stabilization and anchoring of postsynaptic AChRs during NMJ development and maintenance. We describe that posttranscriptional repression of CRK by miR-1/206/133 is essential for balanced activation of RAC1. Failure to adjust RAC1 activity severely compromises NMJ function, causing respiratory failure in neonates and neuromuscular symptoms in adult mice. We conclude that miR-1/206/133 serve a specific function for NMJs but are dispensable for skeletal muscle development. The miR-1/133/206 gene family codes for the most abundant microRNAs in striated muscles. Here, Klockner et al show that inactivation of all family members in skeletal muscle prevents formation of normal neuromuscular junctions due to increased expression of the adaptor protein CRK.
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21
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Novel treatment strategies for acetylcholine receptor antibody-positive myasthenia gravis and related disorders. Autoimmun Rev 2022; 21:103104. [PMID: 35452851 DOI: 10.1016/j.autrev.2022.103104] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 04/18/2022] [Indexed: 11/21/2022]
Abstract
The presence of autoantibodies directed against the muscle nicotinic acetylcholine receptor (AChR) is the most common cause of myasthenia gravis (MG). These antibodies damage the postsynaptic membrane of the neuromuscular junction and cause muscle weakness by depleting AChRs and thus impairing synaptic transmission. As one of the best-characterized antibody-mediated autoimmune diseases, AChR-MG has often served as a reference model for other autoimmune disorders. Classical pharmacological treatments, including broad-spectrum immunosuppressive drugs, are effective in many patients. However, complete remission cannot be achieved in all patients, and 10% of patients do not respond to currently used therapies. This may be attributed to production of autoantibodies by long-lived plasma cells which are resistant to conventional immunosuppressive drugs. Hence, novel therapies specifically targeting plasma cells might be a suitable therapeutic approach for selected patients. Additionally, in order to reduce side effects of broad-spectrum immunosuppression, targeted immunotherapies and symptomatic treatments will be required. This review presents established therapies as well as novel therapeutic approaches for MG and related conditions, with a focus on AChR-MG.
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22
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Kaplan MM, Flucher BE. Counteractive and cooperative actions of muscle β-catenin and CaV1.1 during early neuromuscular synapse formation. iScience 2022; 25:104025. [PMID: 35340430 PMCID: PMC8941212 DOI: 10.1016/j.isci.2022.104025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 01/07/2022] [Accepted: 03/01/2022] [Indexed: 11/29/2022] Open
Abstract
Activity-dependent calcium signals in developing muscle play a crucial role in neuromuscular junction (NMJ) formation. However, its downstream effectors and interactions with other regulators of pre- and postsynaptic differentiation are poorly understood. Here, we demonstrate that the skeletal muscle calcium channel CaV1.1 and β-catenin interact in various ways to control NMJ development. They differentially regulate nerve branching and presynaptic innervation patterns during the initial phase of NMJ formation. Conversely, they cooperate in regulating postsynaptic AChR clustering, synapse formation, and the proper organization of muscle fibers in mouse diaphragm. CaV1.1 does not directly regulate β-catenin expression but differentially controls the activity of its transcriptional co-regulators TCF/Lef and YAP. These findings suggest a crosstalk between CaV1.1 and β-catenin in the activity-dependent transcriptional regulation of genes involved in specific pre- and postsynaptic aspects of NMJ formation. Neuromuscular junction formation requires either muscle calcium or β-catenin signaling Complementary actions of CaV1.1 and β-catenin control presynaptic innervation patterns Parallel actions of CaV1.1 and β-catenin are crucial for postsynaptic AChR clustering Loss of CaV1.1 differentially regulates activity of β-catenin targets TCF/Lef and YAP
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Affiliation(s)
- Mehmet Mahsum Kaplan
- Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
- Corresponding author
| | - Bernhard E. Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
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23
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Lei L, Fan Z, Su S, Xu M, Chen H, Zhu W, Luan Q, Da Y. Involvement of Ocular Muscles in Patients With Myasthenia Gravis With Nonocular Onset. J Neuroophthalmol 2022; 42:e260-e266. [PMID: 34369469 DOI: 10.1097/wno.0000000000001325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Myasthenia gravis (MG) is an autoimmune disorder involving neuromuscular junctions and more than half of MG patients manifested with extraocular muscle weakness initially. In the remained patients, ocular weakness may occur later in the course of the disease. However, little data are available about ocular involvement in such patients. Therefore, the study aims to investigate ocular weakness in MG patients with nonocular onset and evaluate the associated factors influencing it. METHODS In our monocentric retrospective study, 54 adult-onset patients with MG with nonocular onset were included and were followed up for at least 2 years from the onset. The primary outcome was the occurrence of ptosis, diplopia, or both. Kaplan-Meier analysis was performed to estimate the time to the ocular weakness, and log-rank tests were used to analyze the association between clinical characteristics and ocular weakness. Multivariate Cox proportional hazards regression models were used to identify factors associated with ocular involvement. RESULTS A total of 47 (87.0%) patients developed ocular weakness during the study period. The median time to ocular weakness was 6.0 months. Time to the ocular involvement was earlier in patients with bulbar onset (P = 0.007), whereas patients receiving pyridostigmine monotherapy and immunomodulatory therapy had a longer median time of ocular weakness (P < 0.0001). No significant difference was noted between ocular weakness and age of onset, gender, and thymoma. The Cox analysis showed that bulbar onset was a risk factor of ocular weakness (adjusted hazard ratio [HR] 2.65, 95% confidence interval [CI] 1.41-4.99), whereas pyridostigmine monotherapy (adjusted HR 0.28, 95% CI 0.13-0.60) and immunotherapy (adjusted HR 0.09, 95% CI 0.04-0.22) were protective factors. CONCLUSIONS Eighty-seven percent of patients with MG with nonocular onset developed ocular weakness. Bulbar onset was an independent risk factor for ocular involvement, whereas pyridostigmine and immunotherapy were protective factors.
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Affiliation(s)
- Lin Lei
- Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing, China
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Fralish Z, Lotz EM, Chavez T, Khodabukus A, Bursac N. Neuromuscular Development and Disease: Learning From in vitro and in vivo Models. Front Cell Dev Biol 2021; 9:764732. [PMID: 34778273 PMCID: PMC8579029 DOI: 10.3389/fcell.2021.764732] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Accepted: 10/06/2021] [Indexed: 01/02/2023] Open
Abstract
The neuromuscular junction (NMJ) is a specialized cholinergic synaptic interface between a motor neuron and a skeletal muscle fiber that translates presynaptic electrical impulses into motor function. NMJ formation and maintenance require tightly regulated signaling and cellular communication among motor neurons, myogenic cells, and Schwann cells. Neuromuscular diseases (NMDs) can result in loss of NMJ function and motor input leading to paralysis or even death. Although small animal models have been instrumental in advancing our understanding of the NMJ structure and function, the complexities of studying this multi-tissue system in vivo and poor clinical outcomes of candidate therapies developed in small animal models has driven the need for in vitro models of functional human NMJ to complement animal studies. In this review, we discuss prevailing models of NMDs and highlight the current progress and ongoing challenges in developing human iPSC-derived (hiPSC) 3D cell culture models of functional NMJs. We first review in vivo development of motor neurons, skeletal muscle, Schwann cells, and the NMJ alongside current methods for directing the differentiation of relevant cell types from hiPSCs. We further compare the efficacy of modeling NMDs in animals and human cell culture systems in the context of five NMDs: amyotrophic lateral sclerosis, myasthenia gravis, Duchenne muscular dystrophy, myotonic dystrophy, and Pompe disease. Finally, we discuss further work necessary for hiPSC-derived NMJ models to function as effective personalized NMD platforms.
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Affiliation(s)
- Zachary Fralish
- Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, NC, United States
| | - Ethan M Lotz
- Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, NC, United States
| | - Taylor Chavez
- Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, NC, United States
| | - Alastair Khodabukus
- Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, NC, United States
| | - Nenad Bursac
- Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, NC, United States
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25
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Ozes B, Moss K, Myers M, Ridgley A, Chen L, Murrey D, Sahenk Z. AAV1.NT-3 gene therapy in a CMT2D model: phenotypic improvements in GarsP278KY/+ mice. Brain Commun 2021; 3:fcab252. [PMID: 34755111 PMCID: PMC8568849 DOI: 10.1093/braincomms/fcab252] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/24/2021] [Accepted: 09/28/2021] [Indexed: 12/15/2022] Open
Abstract
Glycyl-tRNA synthetase mutations are associated to the Charcot-Marie-Tooth disease type-2D. The GarsP278KY/+ model for Charcot-Marie-Tooth disease type-2D is known best for its early onset severe neuropathic phenotype with findings including reduced axon size, slow conduction velocities and abnormal neuromuscular junction. Muscle involvement remains largely unexamined. We tested the efficacy of neurotrophin 3 gene transfer therapy in two Gars mutants with severe (GarsP278KY/+ ) and milder (GarsΔETAQ/+ ) phenotypes via intramuscular injection of adeno-associated virus setoype-1, triple tandem muscle creatine kinase promoter, neurotrophin 3 (AAV1.tMCK.NT-3) at 1 × 1011 vg dose. In the GarsP278KY/+ mice, the treatment efficacy was assessed at 12 weeks post-injection using rotarod test, electrophysiology and detailed quantitative histopathological studies of the peripheral nervous system including neuromuscular junction and muscle. Neurotrophin 3 gene transfer therapy in GarsP278KY/+ mice resulted in significant functional and electrophysiological improvements, supported with increases in myelin thickness and improvements in the denervated status of neuromuscular junctions as well as increases in muscle fibre size along with attenuation of myopathic changes. Improvements in the milder phenotype GarsΔETAQ/+ was less pronounced. Furthermore, oxidative enzyme histochemistry in muscles from Gars mutants revealed alterations in the content and distribution of oxidative enzymes with increased expression levels of Pgc1a. Cox1, Cox3 and Atp5d transcripts were significantly decreased suggesting that the muscle phenotype might be related to mitochondrial dysfunction. Neurotrophin 3 gene therapy attenuated these abnormalities in the muscle. This study shows that neurotrophin 3 gene transfer therapy has disease modifying effect in a mouse model for Charcot-Marie-Tooth disease type-2D, leading to meaningful improvements in peripheral nerve myelination and neuromuscular junction integrity as well as in a unique myopathic process, associated with mitochondria dysfunction, all in combination contributing to functional outcome. Based on the multiple biological effects of this versatile molecule, we predict neurotrophin 3 has the potential to be beneficial in other aminoacyl-tRNA synthetase-linked Charcot-Marie-Tooth disease subtypes.
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Affiliation(s)
- Burcak Ozes
- Department of Pediatrics, Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Kyle Moss
- Department of Pediatrics, Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Morgan Myers
- Department of Pediatrics, Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Alicia Ridgley
- Department of Pediatrics, Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Lei Chen
- Department of Pediatrics, Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Darren Murrey
- Department of Pediatrics, Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, Columbus, OH 43205, USA
| | - Zarife Sahenk
- Department of Pediatrics, Center for Gene Therapy, The Abigail Wexner Research Institute, Nationwide Children's Hospital, Columbus, OH 43205, USA.,Department of Pediatrics and Neurology, Nationwide Children's Hospital and The Ohio State University, Columbus, OH 43205, USA.,Department of Pathology and Laboratory Medicine, Nationwide Children's Hospital, Columbus, OH 43205, USA
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26
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Walker LJ, Roque RA, Navarro MF, Granato M. Agrin/Lrp4 signal constrains MuSK-dependent neuromuscular synapse development in appendicular muscle. Development 2021; 148:272655. [PMID: 34714331 PMCID: PMC8602948 DOI: 10.1242/dev.199790] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 09/24/2021] [Indexed: 12/17/2022]
Abstract
The receptor tyrosine kinase MuSK, its co-receptor Lrp4 and the Agrin ligand constitute a signaling pathway that is crucial in axial muscle for neuromuscular synapse development, yet whether this pathway functions similarly in appendicular muscle is unclear. Here, using the larval zebrafish pectoral fin, equivalent to tetrapod forelimbs, we show that, similar to axial muscle, developing appendicular muscles form aneural acetylcholine receptor (AChR) clusters prior to innervation. As motor axons arrive, neural AChR clusters form, eventually leading to functional synapses in a MuSK-dependent manner. We find that loss of Agrin or Lrp4 function, which abolishes synaptic AChR clusters in axial muscle, results in enlarged presynaptic nerve regions and progressively expanding appendicular AChR clusters, mimicking the consequences of motoneuron ablation. Moreover, musk depletion in lrp4 mutants partially restores synaptic AChR patterning. Combined, our results provide compelling evidence that, in addition to the canonical pathway in which Agrin/Lrp4 stimulates MuSK activity, Agrin/Lrp4 signaling in appendicular muscle constrains MuSK-dependent neuromuscular synapse organization. Thus, we reveal a previously unappreciated role for Agrin/Lrp4 signaling, thereby highlighting distinct differences between axial and appendicular synapse development.
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27
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Luttrell SM, Smith AST, Mack DL. Creating stem cell-derived neuromuscular junctions in vitro. Muscle Nerve 2021; 64:388-403. [PMID: 34328673 PMCID: PMC9292444 DOI: 10.1002/mus.27360] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 05/28/2021] [Accepted: 06/21/2021] [Indexed: 12/14/2022]
Abstract
Recent development of novel therapies has improved mobility and quality of life for people suffering from inheritable neuromuscular disorders. Despite this progress, the majority of neuromuscular disorders are still incurable, in part due to a lack of predictive models of neuromuscular junction (NMJ) breakdown. Improvement of predictive models of a human NMJ would be transformative in terms of expanding our understanding of the mechanisms that underpin development, maintenance, and disease, and as a testbed with which to evaluate novel therapeutics. Induced pluripotent stem cells (iPSCs) are emerging as a clinically relevant and non‐invasive cell source to create human NMJs to study synaptic development and maturation, as well as disease modeling and drug discovery. This review will highlight the recent advances and remaining challenges to generating an NMJ capable of eliciting contraction of stem cell‐derived skeletal muscle in vitro. We explore the advantages and shortcomings of traditional NMJ culturing platforms, as well as the pioneering technologies and novel, biomimetic culturing systems currently in use to guide development and maturation of the neuromuscular synapse and extracellular microenvironment. Then, we will explore how this NMJ‐in‐a‐dish can be used to study normal assembly and function of the efferent portion of the neuromuscular arc, and how neuromuscular disease‐causing mutations disrupt structure, signaling, and function.
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Affiliation(s)
- Shawn M Luttrell
- Department of Rehabilitation Medicine, University of Washington, Seattle, Washington, USA.,Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, Washington, USA
| | - Alec S T Smith
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, Washington, USA.,Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - David L Mack
- Department of Rehabilitation Medicine, University of Washington, Seattle, Washington, USA.,Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, Washington, USA.,Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
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28
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Jing H, Chen P, Hui T, Yu Z, Zhou J, Fei E, Wang S, Ren D, Lai X, Li B. Synapse-specific Lrp4 mRNA enrichment requires Lrp4/MuSK signaling, muscle activity and Wnt non-canonical pathway. Cell Biosci 2021; 11:105. [PMID: 34090516 PMCID: PMC8180081 DOI: 10.1186/s13578-021-00619-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Accepted: 05/25/2021] [Indexed: 11/10/2022] Open
Abstract
Background The neuromuscular junction (NMJ) is a peripheral synapse critical to muscle contraction. Like acetylcholine receptors (AChRs), many essential proteins of NMJ are extremely concentrated at the postjunctional membrane. However, the mechanisms of synapse-specific concentration are not well understood; furthermore, it is unclear whether signaling molecules critical to NMJ formation and maintenance are also locally transcribed. Results We studied the β-gal activity encoded by a lacZ cassette driven by the promoter of the Lrp4 gene. As reported for Lrp4 mRNA, β-gal was in the central region in embryonic muscles and at the NMJ after its formation. However, β-gal was no longer in the central areas of muscle fibers in Lrp4 or MuSK mutant mice, indicating a requirement of Lrp4/MuSK signaling. This phenotype could be rescued by transgenic expression of LRP4 with a transmembrane domain but not soluble ECD in Lrp4 mutant mice. β-gal and AChR clusters were distributed in a broader region in lacZ/ECD than that of heterozygous lacZ/+ mice, indicating an important role of the transmembrane domain in Lrp4 signaling. Synaptic β-gal activity became diffused after denervation or treatment with µ-conotoxin, despite its mRNA was increased, indicating synaptic Lrp4 mRNA enrichment requires muscle activity. β-gal was also diffused in aged mice but became re-concentrated after muscle stimulation. Finally, Lrp4 mRNA was increased in C2C12 myotubes by Wnt ligands in a manner that could be inhibited by RKI-1447, an inhibitor of ROCK in Wnt non-canonical signaling. Injecting RKI-1447 into muscles of adult mice diminished Lrp4 synaptic expression. Conclusions This study demonstrates that synapse-specific enrichment of Lrp4 mRNA requires a coordinated interaction between Lrp4/MuSK signaling, muscle activity, and Wnt non-canonical signaling. Thus, the study provides a new mechanism for Lrp4 mRNA enrichment. It also provides a potential target for the treatment of NMJ aging and other NMJ-related diseases. Supplementary Information The online version contains supplementary material available at 10.1186/s13578-021-00619-z.
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Affiliation(s)
- Hongyang Jing
- School of Life Science, Nanchang University, Nanchang, 330031, China.,Institute of Life Science, Nanchang University, Nanchang, 330031, China
| | - Peng Chen
- School of Life Science, Nanchang University, Nanchang, 330031, China.,Institute of Life Science, Nanchang University, Nanchang, 330031, China
| | - Tiankun Hui
- School of Life Science, Nanchang University, Nanchang, 330031, China.,Institute of Life Science, Nanchang University, Nanchang, 330031, China
| | - Zheng Yu
- School of Life Science, Nanchang University, Nanchang, 330031, China.,Institute of Life Science, Nanchang University, Nanchang, 330031, China
| | - Jin Zhou
- School of Life Science, Nanchang University, Nanchang, 330031, China.,Human Aging Research Institute, Nanchang University, Nanchang, 330031, China
| | - Erkang Fei
- School of Life Science, Nanchang University, Nanchang, 330031, China.,Institute of Life Science, Nanchang University, Nanchang, 330031, China
| | - Shunqi Wang
- School of Life Science, Nanchang University, Nanchang, 330031, China.,Institute of Life Science, Nanchang University, Nanchang, 330031, China
| | - Dongyan Ren
- School of Life Science, Nanchang University, Nanchang, 330031, China.,Institute of Life Science, Nanchang University, Nanchang, 330031, China
| | - Xinsheng Lai
- School of Life Science, Nanchang University, Nanchang, 330031, China. .,Institute of Life Science, Nanchang University, Nanchang, 330031, China.
| | - Baoming Li
- School of Life Science, Nanchang University, Nanchang, 330031, China. .,Institute of Life Science, Nanchang University, Nanchang, 330031, China. .,Department of Psychology and Institute of Brain Science, School of Education, Hangzhou Normal University, Hangzhou, 311121, China.
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29
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Xing G, Jing H, Yu Z, Chen P, Wang H, Xiong WC, Mei L. Membraneless condensates by Rapsn phase separation as a platform for neuromuscular junction formation. Neuron 2021; 109:1963-1978.e5. [PMID: 34033754 DOI: 10.1016/j.neuron.2021.04.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 03/27/2021] [Accepted: 04/22/2021] [Indexed: 12/29/2022]
Abstract
Our daily life depends on muscle contraction, a process that is controlled by the neuromuscular junction (NMJ). However, the mechanisms of NMJ assembly remain unclear. Here we show that Rapsn, a protein critical for NMJ formation, undergoes liquid-liquid phase separation (LLPS) and condensates into liquid-like assemblies. Such assemblies can recruit acetylcholine receptors (AChRs), cytoskeletal proteins, and signaling proteins for postsynaptic differentiation. Rapsn LLPS requires multivalent binding of tetratricopeptide repeats (TPRs) and is increased by Musk signaling. The capacity of Rapsn to condensate and co-condensate with interaction proteins is compromised by mutations of congenital myasthenic syndromes (CMSs). NMJ formation is impaired in mutant mice carrying a CMS-associated, LLPS-deficient mutation. These results reveal a critical role of Rapsn LLPS in forming a synaptic semi-membraneless compartment for NMJ formation.
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Affiliation(s)
- Guanglin Xing
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Hongyang Jing
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Zheng Yu
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Peng Chen
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Hongsheng Wang
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Wen-Cheng Xiong
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH 44106, USA.
| | - Lin Mei
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH 44106, USA.
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30
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Dobrowolny G, Barbiera A, Sica G, Scicchitano BM. Age-Related Alterations at Neuromuscular Junction: Role of Oxidative Stress and Epigenetic Modifications. Cells 2021; 10:1307. [PMID: 34074012 PMCID: PMC8225025 DOI: 10.3390/cells10061307] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 05/19/2021] [Accepted: 05/22/2021] [Indexed: 12/11/2022] Open
Abstract
With advancing aging, a decline in physical abilities occurs, leading to reduced mobility and loss of independence. Although many factors contribute to the physio-pathological effects of aging, an important event seems to be related to the compromised integrity of the neuromuscular system, which connects the brain and skeletal muscles via motoneurons and the neuromuscular junctions (NMJs). NMJs undergo severe functional, morphological, and molecular alterations during aging and ultimately degenerate. The effect of this decline is an inexorable decrease in skeletal muscle mass and strength, a condition generally known as sarcopenia. Moreover, several studies have highlighted how the age-related alteration of reactive oxygen species (ROS) homeostasis can contribute to changes in the neuromuscular junction morphology and stability, leading to the reduction in fiber number and innervation. Increasing evidence supports the involvement of epigenetic modifications in age-dependent alterations of the NMJ. In particular, DNA methylation, histone modifications, and miRNA-dependent gene expression represent the major epigenetic mechanisms that play a crucial role in NMJ remodeling. It is established that environmental and lifestyle factors, such as physical exercise and nutrition that are susceptible to change during aging, can modulate epigenetic phenomena and attenuate the age-related NMJs changes. This review aims to highlight the recent epigenetic findings related to the NMJ dysregulation during aging and the role of physical activity and nutrition as possible interventions to attenuate or delay the age-related decline in the neuromuscular system.
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Affiliation(s)
- Gabriella Dobrowolny
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics (DAHFMO)-Unit of Histology and Medical Embryology, Sapienza University of Rome, Laboratory Affiliated to Istituto Pasteur Italia-Fondazione Cenci Bolognetti, 00161 Rome, Italy;
| | - Alessandra Barbiera
- Department of Life Sciences and Public Health, Histology and Embryology Unit, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy; (A.B.); (G.S.)
| | - Gigliola Sica
- Department of Life Sciences and Public Health, Histology and Embryology Unit, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy; (A.B.); (G.S.)
| | - Bianca Maria Scicchitano
- Department of Life Sciences and Public Health, Histology and Embryology Unit, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy; (A.B.); (G.S.)
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31
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Sun X, Malandraki-Miller S, Kennedy T, Bassat E, Klaourakis K, Zhao J, Gamen E, Vieira JM, Tzahor E, Riley PR. The extracellular matrix protein agrin is essential for epicardial epithelial-to-mesenchymal transition during heart development. Development 2021; 148:261801. [PMID: 33969874 PMCID: PMC8172119 DOI: 10.1242/dev.197525] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 04/03/2021] [Indexed: 12/15/2022]
Abstract
During heart development, epicardial cells residing within the outer layer undergo epithelial-mesenchymal transition (EMT) and migrate into the underlying myocardium to support organ growth and morphogenesis. Disruption of epicardial EMT results in embryonic lethality, yet its regulation is poorly understood. Here, we report epicardial EMT within the mesothelial layer of the mouse embryonic heart at ultra-high resolution using scanning electron microscopy combined with immunofluorescence analyses. We identified morphologically active EMT regions that associated with key components of the extracellular matrix, including the basement membrane-associated proteoglycan agrin. Deletion of agrin resulted in impaired EMT and compromised development of the epicardium, accompanied by downregulation of Wilms' tumor 1. Agrin enhanced EMT in human embryonic stem cell-derived epicardial-like cells by decreasing β-catenin and promoting pFAK localization at focal adhesions, and promoted the aggregation of dystroglycan within the Golgi apparatus in murine epicardial cells. Loss of agrin resulted in dispersal of dystroglycan in vivo, disrupting basement membrane integrity and impairing EMT. Our results provide new insights into the role of the extracellular matrix in heart development and implicate agrin as a crucial regulator of epicardial EMT.
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Affiliation(s)
- Xin Sun
- Burdon-Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.,British Heart Foundation - Oxbridge Centre of Regenerative Medicine, CRM, University of Oxford, Oxford OX1 3PT, UK
| | - Sophia Malandraki-Miller
- Burdon-Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.,British Heart Foundation - Oxbridge Centre of Regenerative Medicine, CRM, University of Oxford, Oxford OX1 3PT, UK
| | - Tahnee Kennedy
- Burdon-Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.,British Heart Foundation - Oxbridge Centre of Regenerative Medicine, CRM, University of Oxford, Oxford OX1 3PT, UK
| | - Elad Bassat
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Konstantinos Klaourakis
- Burdon-Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.,British Heart Foundation - Oxbridge Centre of Regenerative Medicine, CRM, University of Oxford, Oxford OX1 3PT, UK
| | - Jia Zhao
- Burdon-Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.,British Heart Foundation - Oxbridge Centre of Regenerative Medicine, CRM, University of Oxford, Oxford OX1 3PT, UK
| | - Elisabetta Gamen
- Burdon-Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.,British Heart Foundation - Oxbridge Centre of Regenerative Medicine, CRM, University of Oxford, Oxford OX1 3PT, UK
| | - Joaquim Miguel Vieira
- Burdon-Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.,British Heart Foundation - Oxbridge Centre of Regenerative Medicine, CRM, University of Oxford, Oxford OX1 3PT, UK
| | - Eldad Tzahor
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Paul R Riley
- Burdon-Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.,British Heart Foundation - Oxbridge Centre of Regenerative Medicine, CRM, University of Oxford, Oxford OX1 3PT, UK
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32
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Prasad V, Millay DP. Skeletal muscle fibers count on nuclear numbers for growth. Semin Cell Dev Biol 2021; 119:3-10. [PMID: 33972174 DOI: 10.1016/j.semcdb.2021.04.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/30/2021] [Accepted: 04/19/2021] [Indexed: 02/06/2023]
Abstract
Skeletal muscle cells are noteworthy for their syncytial nature, with each myofiber accumulating hundreds or thousands of nuclei derived from resident muscle stem cells (MuSCs). These nuclei are accrued through cell fusion, which is controlled by the two essential fusogens Myomaker and Myomerger that are transiently expressed within the myogenic lineage. While the absolute requirement of fusion for muscle development has been known for decades, the underlying need for the magnitude of multinucleation in muscle remains mysterious. Possible advantages of multinucleation include the potential it affords for transcriptional diversity within these massive cells, and as a means of increasing DNA content to support optimal cell size and function. In this article, we review recent advances that elucidate the relationship between myonuclear numbers and establishment of myofiber size, and discuss how this new information refines our understanding of the concept of myonuclear domains (MND), the cytoplasmic volumes that each resident myonucleus can support. Finally, we explore the potential consequences and costs of multinucleation and its impacts on myonuclear transcriptional reserve capacity, growth potential, myofiber size regulation, and muscle adaptability. We anticipate this report will not only serve to highlight the latest advances in the basic biology of syncytial muscle cells but also provide information to help design the next generation of therapeutic strategies to maintain muscle mass and function.
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Affiliation(s)
- Vikram Prasad
- Division of Molecular Cardiovascular Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Douglas P Millay
- Division of Molecular Cardiovascular Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA.
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33
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Fuertes-Alvarez S, Izeta A. Terminal Schwann Cell Aging: Implications for Age-Associated Neuromuscular Dysfunction. Aging Dis 2021; 12:494-514. [PMID: 33815879 PMCID: PMC7990373 DOI: 10.14336/ad.2020.0708] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 07/08/2020] [Indexed: 12/11/2022] Open
Abstract
Action potential is transmitted to muscle fibers through specialized synaptic interfaces called neuromuscular junctions (NMJs). These structures are capped by terminal Schwann cells (tSCs), which play essential roles during formation and maintenance of the NMJ. tSCs are implicated in the correct communication between nerves and muscles, and in reinnervation upon injury. During aging, loss of muscle mass and strength (sarcopenia and dynapenia) are due, at least in part, to the progressive loss of contacts between muscle fibers and nerves. Despite the important role of tSCs in NMJ function, very little is known on their implication in the NMJ-aging process and in age-associated denervation. This review summarizes the current knowledge about the implication of tSCs in the age-associated degeneration of NMJs. We also speculate on the possible mechanisms underlying the observed phenotypes.
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Affiliation(s)
- Sandra Fuertes-Alvarez
- 1Biodonostia, Tissue Engineering Group, Paseo Dr. Begiristain, s/n, San Sebastian 20014, Spain
| | - Ander Izeta
- 1Biodonostia, Tissue Engineering Group, Paseo Dr. Begiristain, s/n, San Sebastian 20014, Spain.,2Tecnun-University of Navarra, School of Engineering, Department of Biomedical Engineering and Science, Paseo Mikeletegi, 48, San Sebastian 20009, Spain
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34
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Joviano-Santos JV, Kljakic O, Magalhães-Gomes MPS, Valadão PAC, de Oliveira LR, Prado MAM, Prado VF, Guatimosim C. Motoneuron-specific loss of VAChT mimics neuromuscular defects seen in congenital myasthenic syndrome. FEBS J 2021; 288:5331-5349. [PMID: 33730374 DOI: 10.1111/febs.15825] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 03/03/2021] [Accepted: 03/16/2021] [Indexed: 11/28/2022]
Abstract
Motoneurons (MNs) control muscle activity by releasing the neurotransmitter acetylcholine (ACh) at the level of neuromuscular junctions. ACh is packaged into synaptic vesicles by the vesicular ACh transporter (VAChT), and disruptions in its release can impair muscle contraction, as seen in congenital myasthenic syndromes (CMS). Recently, VAChT gene mutations were identified in humans displaying varying degrees of myasthenia. Moreover, mice with a global deficiency in VAChT expression display several characteristics of CMS. Despite these findings, little is known about how a long-term decrease in VAChT expression in vivo affects MNs structure and function. Using Cre-loxP technology, we generated a mouse model where VAChT is deleted in select groups of MNs (mnVAChT-KD). Molecular analysis revealed that the VAChT deletion was specific to MNs and affected approximately 50% of its population in the brainstem and spinal cord, with alpha-MNs primarily targeted (70% in spinal cord). Within each animal, the cell body area of VAChT-deleted MNs was significantly smaller compared to MNs with VAChT preserved. Likewise, muscles innervated by VAChT-deleted MNs showed atrophy while muscles innervated by VAChT-containing neurons appeared normal. In addition, mnVAChT KD mice had decreased muscle strength, were hypoactive, leaner and exhibited kyphosis. This neuromuscular dysfunction was evident at 2 months of age and became progressively worse by 6 months. Treatment of mutants with a cholinesterase inhibitor was able to improve some of the motor deficits. As these observations mimic what is seen in CMS, this new line could be valuable for assessing the efficacy of potential CMS drugs.
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Affiliation(s)
- Julliane V Joviano-Santos
- Robarts Research Institute, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada.,Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Ornela Kljakic
- Robarts Research Institute, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada.,Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada
| | - Matheus P S Magalhães-Gomes
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.,Departamento de Medicina, Faculdade Ciências Médicas de Minas Gerais, FCMMG, Belo Horizonte, Brasil
| | - Priscila Aparecida C Valadão
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Leonardo R de Oliveira
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Marco A M Prado
- Robarts Research Institute, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada.,Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada.,Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada.,Brain and Mind Institute, University of Western Ontario, London, Canada
| | - Vania F Prado
- Robarts Research Institute, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada.,Department of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada.,Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Canada.,Brain and Mind Institute, University of Western Ontario, London, Canada
| | - Cristina Guatimosim
- Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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35
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Ohkawara B, Ito M, Ohno K. Secreted Signaling Molecules at the Neuromuscular Junction in Physiology and Pathology. Int J Mol Sci 2021; 22:ijms22052455. [PMID: 33671084 PMCID: PMC7957818 DOI: 10.3390/ijms22052455] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 02/22/2021] [Accepted: 02/25/2021] [Indexed: 02/08/2023] Open
Abstract
Signal transduction at the neuromuscular junction (NMJ) is affected in many human diseases, including congenital myasthenic syndromes (CMS), myasthenia gravis, Lambert–Eaton myasthenic syndrome, Isaacs’ syndrome, Schwartz–Jampel syndrome, Fukuyama-type congenital muscular dystrophy, amyotrophic lateral sclerosis, and sarcopenia. The NMJ is a prototypic cholinergic synapse between the motor neuron and the skeletal muscle. Synaptogenesis of the NMJ has been extensively studied, which has also been extrapolated to further understand synapse formation in the central nervous system. Studies of genetically engineered mice have disclosed crucial roles of secreted molecules in the development and maintenance of the NMJ. In this review, we focus on the secreted signaling molecules which regulate the clustering of acetylcholine receptors (AChRs) at the NMJ. We first discuss the signaling pathway comprised of neural agrin and its receptors, low-density lipoprotein receptor-related protein 4 (Lrp4) and muscle-specific receptor tyrosine kinase (MuSK). This pathway drives the clustering of acetylcholine receptors (AChRs) to ensure efficient signal transduction at the NMJ. We also discuss three secreted molecules (Rspo2, Fgf18, and connective tissue growth factor (Ctgf)) that we recently identified in the Wnt/β-catenin and fibroblast growth factors (FGF) signaling pathways. The three secreted molecules facilitate the clustering of AChRs by enhancing the agrin-Lrp4-MuSK signaling pathway.
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Affiliation(s)
- Bisei Ohkawara
- Correspondence: ; Tel.: +81-52-744-2447; Fax: +81-52-744-2449
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36
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Zelada D, Bermedo-García F, Collao N, Henríquez JP. Motor function recovery: deciphering a regenerative niche at the neuromuscular synapse. Biol Rev Camb Philos Soc 2020; 96:752-766. [PMID: 33336525 PMCID: PMC7986695 DOI: 10.1111/brv.12675] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 11/20/2020] [Accepted: 11/25/2020] [Indexed: 12/13/2022]
Abstract
The coordinated movement of many organisms relies on efficient nerve–muscle communication at the neuromuscular junction (NMJ), a peripheral synapse composed of a presynaptic motor axon terminal, a postsynaptic muscle specialization, and non‐myelinating terminal Schwann cells. NMJ dysfunctions are caused by traumatic spinal cord or peripheral nerve injuries as well as by severe motor pathologies. Compared to the central nervous system, the peripheral nervous system displays remarkable regenerating abilities; however, this capacity is limited by the denervation time frame and depends on the establishment of permissive regenerative niches. At the injury site, detailed information is available regarding the cells, molecules, and mechanisms involved in nerve regeneration and repair. However, a regenerative niche at the final functional step of peripheral motor innervation, i.e. at the mature neuromuscular synapse, has not been deciphered. In this review, we integrate classic and recent evidence describing the cells and molecules that could orchestrate a dynamic ecosystem to accomplish successful NMJ regeneration. We propose that such a regenerative niche must ensure at least two fundamental steps for successful NMJ regeneration: the proper arrival of incoming regenerating axons to denervated postsynaptic muscle domains, and the resilience of those postsynaptic domains, in morphological and functional terms. We here describe and combine the main cellular and molecular responses involved in each of these steps as potential targets to help successful NMJ regeneration.
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Affiliation(s)
- Diego Zelada
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
| | - Francisca Bermedo-García
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
| | - Nicolás Collao
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
| | - Juan P Henríquez
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
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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: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [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.
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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
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Barbeau S, Tahraoui-Bories J, Legay C, Martinat C. Building neuromuscular junctions in vitro. Development 2020; 147:147/22/dev193920. [PMID: 33199350 DOI: 10.1242/dev.193920] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The neuromuscular junction (NMJ) has been the model of choice to understand the principles of communication at chemical synapses. Following groundbreaking experiments carried out over 60 years ago, many studies have focused on the molecular mechanisms underlying the development and physiology of these synapses. This Review summarizes the progress made to date towards obtaining faithful models of NMJs in vitro We provide a historical approach discussing initial experiments investigating NMJ development and function from Xenopus to mice, the creation of chimeric co-cultures, in vivo approaches and co-culture methods from ex vivo and in vitro derived cells, as well as the most recent developments to generate human NMJs. We discuss the benefits of these techniques and the challenges to be addressed in the future for promoting our understanding of development and human disease.
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Affiliation(s)
- Susie Barbeau
- Université de Paris, CNRS, SPPIN - Saints-Pères Paris Institute for the Neurosciences, F-75006 Paris, France
| | - Julie Tahraoui-Bories
- INSERM/UEPS UMR 861, Paris Saclay Université, I-STEM, 91100 Corbeil-Essonnes, France
| | - Claire Legay
- Université de Paris, CNRS, SPPIN - Saints-Pères Paris Institute for the Neurosciences, F-75006 Paris, France
| | - Cécile Martinat
- INSERM/UEPS UMR 861, Paris Saclay Université, I-STEM, 91100 Corbeil-Essonnes, France
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Lin SS, Hsieh TL, Liou GG, Li TN, Lin HC, Chang CW, Wu HY, Yao CK, Liu YW. Dynamin-2 Regulates Postsynaptic Cytoskeleton Organization and Neuromuscular Junction Development. Cell Rep 2020; 33:108310. [DOI: 10.1016/j.celrep.2020.108310] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 09/23/2020] [Accepted: 10/05/2020] [Indexed: 11/30/2022] Open
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40
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Cetin H, Beeson D, Vincent A, Webster R. The Structure, Function, and Physiology of the Fetal and Adult Acetylcholine Receptor in Muscle. Front Mol Neurosci 2020; 13:581097. [PMID: 33013323 PMCID: PMC7506097 DOI: 10.3389/fnmol.2020.581097] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 08/13/2020] [Indexed: 12/31/2022] Open
Abstract
The neuromuscular junction (NMJ) is a highly developed synapse linking motor neuron activity with muscle contraction. A complex of molecular cascades together with the specialized NMJ architecture ensures that each action potential arriving at the motor nerve terminal is translated into an action potential in the muscle fiber. The muscle-type nicotinic acetylcholine receptor (AChR) is a key molecular component located at the postsynaptic muscle membrane responsible for the generation of the endplate potential (EPP), which usually exceeds the threshold potential necessary to activate voltage-gated sodium channels and triggers a muscle action potential. Two AChR isoforms are found in mammalian muscle. The fetal isoform is present in prenatal stages and is involved in the development of the neuromuscular system whereas the adult isoform prevails thereafter, except after denervation when the fetal form is re-expressed throughout the muscle. This review will summarize the structural and functional differences between the two isoforms and outline congenital and autoimmune myasthenic syndromes that involve the isoform specific AChR subunits.
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Affiliation(s)
- Hakan Cetin
- Department of Neurology, Medical University of Vienna, Vienna, Austria.,Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Richard Webster
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
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41
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Grp94 Regulates the Recruitment of Aneural AChR Clusters for the Assembly of Postsynaptic Specializations by Modulating ADF/Cofilin Activity and Turnover. eNeuro 2020; 7:ENEURO.0025-20.2020. [PMID: 32747457 PMCID: PMC7540925 DOI: 10.1523/eneuro.0025-20.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 07/27/2020] [Accepted: 07/27/2020] [Indexed: 11/21/2022] Open
Abstract
Temperature is a physiological factor that affects neuronal growth and synaptic homeostasis at the invertebrate neuromuscular junctions (NMJs); however, whether temperature stress could also regulate the structure and function of the vertebrate NMJs remains unclear. In this study, we use Xenopus laevis primary cultures as a vertebrate model system for investigating the involvement of heat shock protein 90 (HSP90) family of stress proteins in NMJ development. First, cold temperature treatment or HSP90 inhibition attenuates the formation of aneural acetylcholine receptor (AChR) clusters, but increases their stability after they are formed, in cultured muscles. HSP90 inhibition specifically affects the stability of aneural AChR clusters and their associated intracellular scaffolding protein rapsyn, instead of causing a global change in cell metabolism and protein expression in Xenopus muscle cultures. Upon synaptogenic stimulation, a specific HSP90 family member, glucose-regulated protein 94 (Grp94), modulates the phosphorylation and dynamic turnover of actin depolymerizing factor (ADF)/cofilin at aneural AChR clusters, leading to the recruitment of AChR molecules from aneural clusters to the assembly of agrin-induced postsynaptic specializations. Finally, postsynaptic Grp94 knock-down significantly inhibits nerve-induced AChR clustering and postsynaptic activity in nerve-muscle co-cultures as demonstrated by live-cell imaging and electrophysiological recording, respectively. Collectively, this study suggests that temperature-dependent alteration in Grp94 expression and activity inhibits the assembly of postsynaptic specializations through modulating ADF/cofilin phosphorylation and activity at aneural AChR clusters, which prevents AChR molecules from being recruited to the postsynaptic sites via actin-dependent vesicular trafficking, at developing vertebrate NMJs.
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Chen A, Bai L, Zhong K, Shu X, Wang A, Xiao Y, Zhang K, Shen C. APC2
CDH1
negatively regulates agrin signaling by promoting the ubiquitination and proteolytic degradation of DOK7. FASEB J 2020; 34:12009-12023. [PMID: 32687671 DOI: 10.1096/fj.202000485r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 06/24/2020] [Accepted: 06/25/2020] [Indexed: 01/28/2023]
Affiliation(s)
- Aizhong Chen
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Lei Bai
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Keke Zhong
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Xiaoqiu Shu
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Ailian Wang
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Yatao Xiao
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Kejing Zhang
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
| | - Chengyong Shen
- The First Affiliated Hospital Institute of Translational Medicine School of Medicine Zhejiang University Zhejiang China
- Department of Neurobiology Key Laboratory of Medical Neurobiology of Zhejiang Province School of Medicine Zhejiang University Zhejiang China
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43
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Brzoska E, Kalkowski L, Kowalski K, Michalski P, Kowalczyk P, Mierzejewski B, Walczak P, Ciemerych MA, Janowski M. Muscular Contribution to Adolescent Idiopathic Scoliosis from the Perspective of Stem Cell-Based Regenerative Medicine. Stem Cells Dev 2020; 28:1059-1077. [PMID: 31170887 DOI: 10.1089/scd.2019.0073] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Adolescent idiopathic scoliosis (AIS) is a relatively frequent disease within a range 0.5%-5.0% of population, with higher frequency in females. While a resultant spinal deformity is usually medically benign condition, it produces far going psychosocial consequences, which warrant attention. The etiology of AIS is unknown and current therapeutic approaches are symptomatic only, and frequently inconvenient or invasive. Muscular contribution to AIS is widely recognized, although it did not translate to clinical routine as yet. Muscle asymmetry has been documented by pathological examinations as well as systemic muscle disorders frequently leading to scoliosis. It has been also reported numerous genetic, metabolic and radiological alterations in patients with AIS, which are linked to muscular and neuromuscular aspects. Therefore, muscles might be considered an attractive and still insufficiently exploited therapeutic target for AIS. Stem cell-based regenerative medicine is rapidly gaining momentum based on the tremendous progress in understanding of developmental biology. It comes also with a toolbox of various stem cells such as satellite cells or mesenchymal stem cells, which could be transplanted; also, the knowledge acquired in research on regenerative medicine can be applied to manipulation of endogenous stem cells to obtain desired therapeutic goals. Importantly, paravertebral muscles are located relatively superficially; therefore, they can be an easy target for minimally invasive approaches to treatment of AIS. It comes in pair with a fast progress in image guidance, which allows for precise delivery of therapeutic agents, including stem cells to various organs such as brain, muscles, and others. Summing up, it seems that there is a link between AIS, muscles, and stem cells, which might be worth of further investigations with a long-term goal of setting foundations for eventual bench-to-bedside translation.
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Affiliation(s)
- Edyta Brzoska
- 1Department of Cytology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Lukasz Kalkowski
- 2Department of Neurology and Neurosurgery, Faculty of Medical Sciences, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland
| | - Kamil Kowalski
- 1Department of Cytology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Pawel Michalski
- 3Spine Surgery Department, Institute of Mother and Child, Warsaw, Poland
| | - Pawel Kowalczyk
- 4Department of Neurosurgery, Children's Memorial Health Institute, Warsaw, Poland
| | - Bartosz Mierzejewski
- 1Department of Cytology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Piotr Walczak
- 5Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,6Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Maria A Ciemerych
- 1Department of Cytology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Miroslaw Janowski
- 5Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland.,6Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland
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Abstract
Thirty to fifty percent of patients with acetylcholine receptor (AChR) antibody (Ab)-negative myasthenia gravis (MG) have Abs to muscle specific kinase (MuSK) and are referred to as having MuSK-MG. MuSK is a 100 kD single-pass post-synaptic transmembrane receptor tyrosine kinase crucial to the development and maintenance of the neuromuscular junction. The Abs in MuSK-MG are predominantly of the IgG4 immunoglobulin subclass. MuSK-MG differs from AChR-MG, in exhibiting more focal muscle involvement, including neck, shoulder, facial and bulbar-innervated muscles, as well as wasting of the involved muscles. MuSK-MG is highly associated with the HLA DR14-DQ5 haplotype and occurs predominantly in females with onset in the fourth decade of life. Some of the standard treatments of AChR-MG have been found to have limited effectiveness in MuSK-MG, including thymectomy and cholinesterase inhibitors. Therefore, current treatment involves immunosuppression, primarily by corticosteroids. In addition, patients respond especially well to B cell depletion agents, e.g., rituximab, with long-term remissions. Future treatments will likely derive from the ongoing analysis of the pathogenic mechanisms underlying this disease, including histologic and physiologic studies of the neuromuscular junction in patients as well as information derived from the development and study of animal models of the disease.
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Affiliation(s)
| | - David P. Richman
- Department of Neurology, University of California, Davis, Davis, CA, United States
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45
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Multiple MuSK signaling pathways and the aging neuromuscular junction. Neurosci Lett 2020; 731:135014. [PMID: 32353380 DOI: 10.1016/j.neulet.2020.135014] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 04/23/2020] [Accepted: 04/24/2020] [Indexed: 12/16/2022]
Abstract
The neuromuscular junction (NMJ) is the vehicle for fast, reliable and robust communication between motor neuron and muscle. The unparalleled accessibility of this synapse to morphological, electrophysiological and genetic analysis has yielded an in depth understanding of many molecular components mediating its formation, maturation and stability. However, key questions surrounding the signaling pathways mediating these events and how they play out across the lifetime of the synapse remain unanswered. Such information is critical since the NMJ is necessary for normal movement and is compromised in several settings including myasthenia gravis, amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), muscular dystrophy, sarcopenia and aging. Muscle specific kinase (MuSK) is a central player in most if not all contexts of NMJ formation and stability. However, elucidating the function of this receptor in this range of settings is challenging since MuSK participates in at least three signaling pathways: as a tyrosine kinase-dependent receptor for agrin-LRP4 and Wnts; and, as a kinase-independent BMP co-receptor. Here we focus on NMJ stability during aging and discuss open questions regarding the molecular mechanisms that govern active maintenance of the NMJ, with emphasis on MuSK and the potential role of its multiple signaling contexts.
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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.
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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
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Chan ZCK, Kwan HLR, Wong YS, Jiang Z, Zhou Z, Tam KW, Chan YS, Chan CB, Lee CW. Site-directed MT1-MMP trafficking and surface insertion regulate AChR clustering and remodeling at developing NMJs. eLife 2020; 9:54379. [PMID: 32208136 PMCID: PMC7093154 DOI: 10.7554/elife.54379] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 02/10/2020] [Indexed: 12/12/2022] Open
Abstract
At vertebrate neuromuscular junctions (NMJs), the synaptic basal lamina contains different extracellular matrix (ECM) proteins and synaptogenic factors that induce and maintain synaptic specializations. Here, we report that podosome-like structures (PLSs) induced by ubiquitous ECM proteins regulate the formation and remodeling of acetylcholine receptor (AChR) clusters via focal ECM degradation. Mechanistically, ECM degradation is mediated by PLS-directed trafficking and surface insertion of membrane-type 1 matrix metalloproteinase (MT1-MMP) to AChR clusters through microtubule-capturing mechanisms. Upon synaptic induction, MT1-MMP plays a crucial role in the recruitment of aneural AChR clusters for the assembly of postsynaptic specializations. Lastly, the structural defects of NMJs in embryonic MT1-MMP-/- mice further demonstrate the physiological role of MT1-MMP in normal NMJ development. Collectively, this study suggests that postsynaptic MT1-MMP serves as a molecular switch to synaptogenesis by modulating local ECM environment for the deposition of synaptogenic signals that regulate postsynaptic differentiation at developing NMJs.
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Affiliation(s)
- Zora Chui-Kuen Chan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Hiu-Lam Rachel Kwan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Yin Shun Wong
- School of Biological Sciences, Faculty of Science, The University of Hong Kong, Hong Kong, China
| | - Zhixin Jiang
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Zhongjun Zhou
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Kin Wai Tam
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Ying-Shing Chan
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Chi Bun Chan
- School of Biological Sciences, Faculty of Science, The University of Hong Kong, Hong Kong, China
| | - Chi Wai Lee
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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Pęziński M, Daszczuk P, Pradhan BS, Lochmüller H, Prószyński TJ. An improved method for culturing myotubes on laminins for the robust clustering of postsynaptic machinery. Sci Rep 2020; 10:4524. [PMID: 32161296 PMCID: PMC7066178 DOI: 10.1038/s41598-020-61347-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 02/20/2020] [Indexed: 01/03/2023] Open
Abstract
Motor neurons form specialized synapses with skeletal muscle fibers, called neuromuscular junctions (NMJs). Cultured myotubes are used as a simplified in vitro system to study the postsynaptic specialization of muscles. The stimulation of myotubes with the glycoprotein agrin or laminin-111 induces the clustering of postsynaptic machinery that contains acetylcholine receptors (AChRs). When myotubes are grown on laminin-coated surfaces, AChR clusters undergo developmental remodeling to form topologically complex structures that resemble mature NMJs. Needing further exploration are the molecular processes that govern AChR cluster assembly and its developmental maturation. Here, we describe an improved protocol for culturing muscle cells to promote the formation of complex AChR clusters. We screened various laminin isoforms and showed that laminin-221 was the most potent for inducing AChR clusters, whereas laminin-121, laminin-211, and laminin-221 afforded the highest percentages of topologically complex assemblies. Human primary myotubes that were formed by myoblasts obtained from patient biopsies also assembled AChR clusters that underwent remodeling in vitro. Collectively, these results demonstrate an advancement of culturing myotubes that can facilitate high-throughput screening for potential therapeutic targets for neuromuscular disorders.
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Affiliation(s)
- Marcin Pęziński
- Laboratory of Synaptogenesis, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Patrycja Daszczuk
- Laboratory of Synaptogenesis, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Bhola Shankar Pradhan
- Laboratory of Synaptogenesis, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.,Łukasiewicz Research Network - PORT Polish Center for Technology Development, Wrocław, Poland
| | - Hanns Lochmüller
- Department of Neuropediatrics and Muscle Disorders, Faculty of Medicine, Medical Centre, University of Freiburg, Freiburg, Germany.,Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Canada.,Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, Canada
| | - Tomasz J Prószyński
- Laboratory of Synaptogenesis, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland. .,Łukasiewicz Research Network - PORT Polish Center for Technology Development, Wrocław, Poland.
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The role of the dystrophin glycoprotein complex on the neuromuscular system. Neurosci Lett 2020; 722:134833. [DOI: 10.1016/j.neulet.2020.134833] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Revised: 02/07/2020] [Accepted: 02/09/2020] [Indexed: 12/26/2022]
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MMP-mediated modulation of ECM environment during axonal growth and NMJ development. Neurosci Lett 2020; 724:134822. [PMID: 32061716 DOI: 10.1016/j.neulet.2020.134822] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Revised: 01/31/2020] [Accepted: 02/04/2020] [Indexed: 12/19/2022]
Abstract
Motor neurons, skeletal muscles, and perisynaptic Schwann cells interact with extracellular matrix (ECM) to form the tetrapartite synapse in the peripheral nervous system. Dynamic remodeling of ECM composition is essential to diversify its functions for distinct cellular processes during neuromuscular junction (NMJ) development. In this review, we give an overview of the proteolytic regulation of ECM proteins, particularly by secreted and membrane-type matrix metalloproteinases (MMPs), in axonal growth and NMJ development. It is suggested that MMP-2, MMP-9, and membrane type 1-MMP (MT1-MMP) promote axonal outgrowth and regeneration upon injury by clearing the glial scars at the lesion site. In addition, these MMPs also play roles in neuromuscular synaptogenesis, ranging from spontaneous formation of synaptic specializations to activity-dependent synaptic elimination, via proteolytic cleavage or degradation of growth factors, neurotrophic factors, and ECM molecules. For instance, secreted MMP-3 has been known to cleave agrin, the main postsynaptic differentiation inducer, further highlighting the importance of MMPs in NMJ formation and maintenance. Furthermore, the increased level of several MMPs in myasthenia gravis (MG) patient suggest the pathophysiological mechanisms of MMP-mediated proteolytic degradation in MG pathogenesis. Finally, we speculate on potential major future directions for studying the regulatory functions of MMP-mediated ECM remodeling in axonal growth and NMJ development.
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