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Du J, Zhao H, Song G, Pang Y, Jiang L, Zan L, Wang H. Overexpression of cholinergic receptor nicotinic gamma subunit inhibits proliferation and differentiation of bovine preadipocytes. Anim Biosci 2023; 36:200-208. [PMID: 36108684 PMCID: PMC9834735 DOI: 10.5713/ab.22.0144] [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: 04/09/2022] [Accepted: 08/14/2022] [Indexed: 02/03/2023] Open
Abstract
OBJECTIVE Muscle acetylcholine receptors have five alpha subunits (α, β, δ, ε, or γ), and cholinergic receptor nicotinic gamma subunit (CHRNG) is the γ subunit. It may also play an essential role in biological processes, including cell differentiation, growth, and survival, while the role of CHRNG has not been studied in the literature. Therefore, the purpose of this study is to clarify the effect of CHRNG on the proliferation and differentiation of bovine preadipocytes. METHODS We constructed a CHRNG overexpression adenovirus vector and successfully overexpressed it on bovine preadipocytes. The effects of CHRNG on bovine preadipocyte proliferation were detected by Edu assay, cell counting Kit-8 (CCK-8), real-time fluorescence quantitative polymerase chain reaction (RT-qPCR), Western blot and other techniques. We also performed oil red O, RT-qPCR, Western blot to explore its effect on the differentiation of preadipocytes. RESULTS The results of Edu proliferation experiments showed that the number of EDU-positive cells in the overexpression group was significantly less. CCK-8 experiments found that the optical density values of the cells in the overexpression group were lower than those of the control group, the mRNA levels of proliferating cell nuclear antigen (PCNA), cyclin A2 (CCNA2), cyclin B1 (CCNB1), cyclin D2 (CCND2) decreased significantly after CHRNG gene overexpression, the mRNA levels of cyclin dependent kinase inhibitor 1A (CDKN1A) increased significantly, and the protein levels of PCNA, CCNB1, CCND2 decreased significantly. Overexpression of CHRNG inhibited the differentiation of bovine preadipocytes. The results of oil red O and triglyceride determination showed that the size and speed of lipid droplets accumulation in the overexpression group were significantly lower. The mRNA and protein levels of peroxisome proliferator activated receptor gamma (PPARγ), CCAAT enhancer binding protein alpha (CEBPα), fatty acid binding protein 4 (FABP4), fatty acid synthase (FASN) decreased significantly. CONCLUSION Overexpression of CHRNG in bovine preadipocytes inhibits the proliferation and differentiation of bovine preadipocytes.
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Affiliation(s)
- Jiawei Du
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100,
China
| | - Hui Zhao
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100,
China
| | - Guibing Song
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100,
China
| | - Yuan Pang
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100,
China
| | - Lei Jiang
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100,
China
| | - Linsen Zan
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100,
China,National Beef Cattle Improvement Center, Northwest A&F University, Yangling, 712100,
China
| | - Hongbao Wang
- College of Animal Science and Technology, Northwest A&F University, Yangling, 712100,
China,National Beef Cattle Improvement Center, Northwest A&F University, Yangling, 712100,
China,Corresponding Author: Hongbao Wang, Tel: +86-158-2903-0403, E-mail:
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Liu Y, Chen Q, Bao J, Pu Y, Han J, Zhao H, Ma Y, Zhao Q. Genome-Wide Analysis of Circular RNAs Reveals circCHRNG Regulates Sheep Myoblast Proliferation via miR-133/SRF and MEF2A Axis. Int J Mol Sci 2022; 23:ijms232416065. [PMID: 36555706 PMCID: PMC9781509 DOI: 10.3390/ijms232416065] [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: 11/15/2022] [Revised: 12/08/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022] Open
Abstract
As relatively new members of the non-coding RNA family, circRNAs play important roles in a variety of biological processes. However, the temporal expression pattern and the function of circRNAs during sheep skeletal muscle development remains unclear. This study aimed to identify circRNAs related to sheep skeletal muscle development and explore their roles in myoblast proliferation. The circRNA expression profiles of longissimus dorsi of sheep from F90, L30, and A3Y were obtained by the RNA-seq method. The function and mechanisms of the novel circCHRNG in muscle satellite cell proliferation were explored using CCK-8 assay, Western blot, qPCR, and dual-luciferase reporter assay. We identified 12,375 circRNAs, including 476, 133, and 233 DEcircRNAs found among three comparative groups. KEGG results showed that DEcircRNAs were enriched in muscle contraction, the regulation of cell proliferation, and the AMPK, insulin, and PI3K-Akt signaling pathways. Notably, a novel circRNA, termed circRNA CHRNG, acts as a miR-133 sponge to promote skeletal muscle satellite cell proliferation. Our study provides a systematic description of circRNAs of ovine skeletal muscle across fetal, lamb, and adult stages. GO and KEGG analyses showed that DEcircRNAs were enriched in multiple pathways associated with muscle development, such as the PI3K-Akt and AMPK signaling pathways. In addition, we propose that circCHRNG acts as a miR-133 sponge to upregulate the expression levels of SRF and MEF2A, thereby promoting myoblast proliferation.
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Affiliation(s)
- Yue Liu
- Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Qian Chen
- Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Jingjing Bao
- Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Yabin Pu
- Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Jianlin Han
- CAAS-ILRI Joint Laboratory on Livestock and Forage Genetic Resources, Institute of Animal Science, Chinese Academy of Agricultural Sciences (CAAS), Beijing 100193, China
- International Livestock Research Institute (ILRI), Nairobi 00100, Kenya
| | - Huijing Zhao
- Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Yuehui Ma
- Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Qianjun Zhao
- Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China
- Correspondence:
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Lipovsek M, Marcovich I, Elgoyhen AB. The Hair Cell α9α10 Nicotinic Acetylcholine Receptor: Odd Cousin in an Old Family. Front Cell Neurosci 2021; 15:785265. [PMID: 34867208 PMCID: PMC8634148 DOI: 10.3389/fncel.2021.785265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 10/25/2021] [Indexed: 11/13/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are a subfamily of pentameric ligand-gated ion channels with members identified in most eumetazoan clades. In vertebrates, they are divided into three subgroups, according to their main tissue of expression: neuronal, muscle and hair cell nAChRs. Each receptor subtype is composed of different subunits, encoded by paralogous genes. The latest to be identified are the α9 and α10 subunits, expressed in the mechanosensory hair cells of the inner ear and the lateral line, where they mediate efferent modulation. α9α10 nAChRs are the most divergent amongst all nicotinic receptors, showing marked differences in their degree of sequence conservation, their expression pattern, their subunit co-assembly rules and, most importantly, their functional properties. Here, we review recent advances in the understanding of the structure and evolution of nAChRs. We discuss the functional consequences of sequence divergence and conservation, with special emphasis on the hair cell α9α10 receptor, a seemingly distant cousin of neuronal and muscle nicotinic receptors. Finally, we highlight potential links between the evolution of the octavolateral system and the extreme divergence of vertebrate α9α10 receptors.
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Affiliation(s)
- Marcela Lipovsek
- Ear Institute, Faculty of Brain Sciences, University College London, London, United Kingdom
| | - Irina Marcovich
- Departments of Otolaryngology & Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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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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5
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Cloning and characterization of nicotinic acetylcholine receptor γ-like gene in adult transparent Pristella maxillaris. Gene 2020; 769:145193. [PMID: 33007374 DOI: 10.1016/j.gene.2020.145193] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 08/26/2020] [Accepted: 09/24/2020] [Indexed: 11/23/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) play an important role in regulating the development and function of nervous system. The muscle AChR is composed of four homologous glycoprotein subunits with a stoichiometry α2βγδ in fetal or α2βεδ in adult. But the mechanism controlling the transition of fetal AChR γ-subunit to adult AChR ε is still unknown. Here a gene annoted AChR γ-like in Pristella maxillaris was first cloned by rapid amplification of cDNA ends (RACE) based on a transcriptome of dorsal fins. The full length of AChR γ-like was 1984 bp and it encoded 518 amino acids from 100 bp to 1653 bp. The multiple alignment analysis showed that AChR γ-like had 98% protein identity to AChR γ-like in Astyanax mexicanus. Then an 11647 bp DNA from 5'-UTR to 3'-UTR was cloned based on gene structure of AChR γ-like in A.mexicanus. Additionally a 2768 bp DNA upstream 5'-UTR was cloned by chromosome walking method. Furthermore, the results from semi-quantitative PCR showed that AChR γ-like was highly expressed in embryo and adult tissues, such as the muscle, eye, heart and intestine. While it showed low expression in the brain and gill. Significantly, the results of in situ hybridization showed strong diffused expression of AChR γ-like in the muscle of 1 dpf (day post-fertilization) embryo. And weak signal was observed in the muscle of 2-4 dpf embryos. All these data indicated that AChR γ-like could be one subunit of AChRs in the muscle and it could be used to study the development of the neuromuscular junction in adult transparent Pristella maxillaris. Thus our work will lay the foundation for using Pristella maxillaris to analyze the in vivo function of the nAChRs in adult vertebrate.
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6
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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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7
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Progress in nicotinic receptor structural biology. Neuropharmacology 2020; 171:108086. [PMID: 32272141 DOI: 10.1016/j.neuropharm.2020.108086] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 03/31/2020] [Indexed: 02/07/2023]
Abstract
Here we begin by briefly reviewing landmark structural studies on the nicotinic acetylcholine receptor. We highlight challenges that had to be overcome to push through resolution barriers, then focus on what has been gleaned in the past few years from crystallographic and single particle cryo-EM studies of different nicotinic receptor subunit assemblies and ligand complexes. We discuss insights into ligand recognition, ion permeation, and allosteric gating. We then highlight some foundational aspects of nicotinic receptor structural biology that remain unresolved and are areas ripe for future exploration. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.
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8
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Kaplan MM, Sultana N, Benedetti A, Obermair GJ, Linde NF, Papadopoulos S, Dayal A, Grabner M, Flucher BE. Calcium Influx and Release Cooperatively Regulate AChR Patterning and Motor Axon Outgrowth during Neuromuscular Junction Formation. Cell Rep 2019; 23:3891-3904. [PMID: 29949772 DOI: 10.1016/j.celrep.2018.05.085] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 05/07/2018] [Accepted: 05/25/2018] [Indexed: 11/29/2022] Open
Abstract
Formation of synapses between motor neurons and muscles is initiated by clustering of acetylcholine receptors (AChRs) in the center of muscle fibers prior to nerve arrival. This AChR patterning is considered to be critically dependent on calcium influx through L-type channels (CaV1.1). Using a genetic approach in mice, we demonstrate here that either the L-type calcium currents (LTCCs) or sarcoplasmic reticulum (SR) calcium release is necessary and sufficient to regulate AChR clustering at the onset of neuromuscular junction (NMJ) development. The combined lack of both calcium signals results in loss of AChR patterning and excessive nerve branching. In the absence of SR calcium release, the severity of synapse formation defects inversely correlates with the magnitude of LTCCs. These findings highlight the importance of activity-dependent calcium signaling in early neuromuscular junction formation and indicate that both LTCC and SR calcium release individually support proper innervation of muscle by regulating AChR patterning and motor axon outgrowth.
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Affiliation(s)
- Mehmet Mahsum Kaplan
- Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Nasreen Sultana
- Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Ariane Benedetti
- Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Gerald J Obermair
- Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Nina F Linde
- Center of Physiology and Pathophysiology, Institute of Vegetative Physiology, University of Cologne, 50931 Cologne, Germany
| | - Symeon Papadopoulos
- Center of Physiology and Pathophysiology, Institute of Vegetative Physiology, University of Cologne, 50931 Cologne, Germany
| | - Anamika Dayal
- Department of Medical Genetics, Molecular and Clinical Pharmacology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Manfred Grabner
- Department of Medical Genetics, Molecular and Clinical Pharmacology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Bernhard E Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria.
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9
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Grassi F, Fucile S. Calcium influx through muscle nAChR-channels: One route, multiple roles. Neuroscience 2019; 439:117-124. [PMID: 30999028 DOI: 10.1016/j.neuroscience.2019.04.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 04/01/2019] [Accepted: 04/04/2019] [Indexed: 01/31/2023]
Abstract
Although Ca2+ influx through muscle nAChR-channels has been described over the past 40 years, its functions remain still poorly understood. In this review we suggest possible roles of Ca2+ entry at all stages of muscle development, summarizing the evidence present in literature. nAChRs are expressed in myoblasts prior to fusion, and can be activated in the absence of an ACh-releasing nerve terminal, with Ca2+ influx likely contributing to regulate cell fusion. Upon establishment of nerve-muscle contact, Ca2+ influx contributes to orchestrate the signaling required for the correct formation of the neuromuscular junction. Finally, in the mature synapse, Ca2+ entry through postsynaptic nAChR-channels - highly Ca2+ permeable, in particular in humans - acts on K+ and Na+ channels to shape endplate excitability. However, when genetic defects cause excessive channel activation, Ca2+ influx becomes toxic and causes endplate myopathy. Throughout the review, we highlight how Ricardo Miledi has contributed to construct this whole body of knowledge, from the initial description of Ca2+ permeability of endplate nAChR channels, to the rationale for the treatment of endplate excitotoxic damage under pathological conditions. This article is part of a Special Issue entitled: SI: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.
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Affiliation(s)
- Francesca Grassi
- Department of Physiology and Pharmacology, Sapienza University, piazzale Aldo Moro 5, 00185, Rome, Italy.
| | - Sergio Fucile
- Department of Physiology and Pharmacology, Sapienza University, piazzale Aldo Moro 5, 00185, Rome, Italy; IRCCS Neuromed, Viale dell'Elettronica, 86077, Pozzilli, Italy
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10
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Härönen H, Zainul Z, Naumenko N, Sormunen R, Miinalainen I, Shakirzyanova A, Santoleri S, Kemppainen AV, Giniatullin R, Pihlajaniemi T, Heikkinen A. Correct expression and localization of collagen XIII are crucial for the normal formation and function of the neuromuscular system. Eur J Neurosci 2019; 49:1491-1511. [PMID: 30667565 DOI: 10.1111/ejn.14346] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 01/08/2019] [Accepted: 01/08/2019] [Indexed: 11/28/2022]
Abstract
Transmembrane collagen XIII has been linked to maturation of the musculoskeletal system. Its absence in mice (Col13a1-/- ) results in impaired neuromuscular junction (NMJ) differentiation and function, while transgenic overexpression (Col13a1oe ) leads to abnormally high bone mass. Similarly, loss-of-function mutations in COL13A1 in humans produce muscle weakness, decreased motor synapse function and mild dysmorphic skeletal features. Here, analysis of the exogenous overexpression of collagen XIII in various muscles revealed highly increased transcript and protein levels, especially in the diaphragm. Unexpectedly, the main location of exogenous collagen XIII in the muscle was extrasynaptic, in fibroblast-like cells, while some motor synapses were devoid of collagen XIII, possibly due to a dominant negative effect. Concomitantly, phenotypical changes in the NMJs of the Col13a1oe mice partly resembled those previously observed in Col13a1-/- mice. Namely, the overall increase in collagen XIII expression in the muscle produced both pre- and postsynaptic abnormalities at the NMJ, especially in the diaphragm. We discovered delayed and compromised acetylcholine receptor (AChR) clustering, axonal neurofilament aggregation, patchy acetylcholine vesicle (AChV) accumulation, disrupted adhesion of the nerve and muscle, Schwann cell invagination and altered evoked synaptic function. Furthermore, the patterns of the nerve trunks and AChR clusters in the diaphragm were broader in the adult muscles, and already prenatally in the Col13a1oe mice, suggesting collagen XIII involvement in the development of the neuromuscular system. Overall, these results confirm the role of collagen XIII at the neuromuscular synapses and highlight the importance of its correct expression and localization for motor synapse formation and function.
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Affiliation(s)
- Heli Härönen
- Faculty of Biochemistry and Molecular Medicine, Center for Cell-Matrix Research, Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Zarin Zainul
- Department of Pediatrics, College of Medicine, University of Florida, Gainesville, Florida
| | - Nikolay Naumenko
- Department of Biotechnology and Molecular Medicine, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Raija Sormunen
- Biocenter Oulu Electron Microscopy Core Facility, University of Oulu, Oulu, Finland
| | - Ilkka Miinalainen
- Biocenter Oulu Electron Microscopy Core Facility, University of Oulu, Oulu, Finland
| | - Anastasia Shakirzyanova
- Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.,Laboratory of Neurobiology, Department of Physiology, Kazan Federal University, Kazan, Russia
| | - Sabrina Santoleri
- Faculty of Biology, Medicine and Health, Division of Cell Matrix Biology and Regenerative Medicine, University of Manchester, Manchester, UK
| | - Antti V Kemppainen
- Faculty of Biochemistry and Molecular Medicine, Center for Cell-Matrix Research, Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Rashid Giniatullin
- Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.,Laboratory of Neurobiology, Department of Physiology, Kazan Federal University, Kazan, Russia
| | - Taina Pihlajaniemi
- Faculty of Biochemistry and Molecular Medicine, Center for Cell-Matrix Research, Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Anne Heikkinen
- Faculty of Biochemistry and Molecular Medicine, Center for Cell-Matrix Research, Biocenter Oulu, University of Oulu, Oulu, Finland
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Li J, Ito M, Ohkawara B, Masuda A, Ohno K. Differential effects of spinal motor neuron-derived and skeletal muscle-derived Rspo2 on acetylcholine receptor clustering at the neuromuscular junction. Sci Rep 2018; 8:13577. [PMID: 30206360 PMCID: PMC6133930 DOI: 10.1038/s41598-018-31949-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 08/30/2018] [Indexed: 12/31/2022] Open
Abstract
We recently reported that R-spondin 2 (Rspo2), a secreted activator of Wnt/β-catenin signaling, promotes acetylcholine receptor (AChR) clustering and neuromuscular junction (NMJ) formation via its receptor, Lgr5. Rspo2 is expressed highly in spinal motor neurons (SMNs) and marginally in the skeletal muscle, but the origin of Rspo2 at the NMJ remains elusive. We rescued Rspo2-deficient (Rspo2-/-) mice by specifically expressing Rspo2 in the skeletal muscle and SMNs. SMN-specific Rspo2 mitigated or over-corrected abnormal features of the NMJs and AChR clusters observed in Rspo2-/- mice including (i) abnormal broadening of enlarged AChR clusters, (ii) three of six abnormal ultrastructural features, and (iii) abnormal expression of nine genes in SMNs and the diaphragm. In contrast, muscle-specific Rspo2 normalized all six abnormal ultrastructural features, but it had no effect on AChR clustering and NMJ formation at the light microscopy level or on abnormal gene expression in SMNs and the diaphragm. These results suggest that SMN-derived Rspo2 plays a major role in AChR clustering and NMJ formation in the postsynaptic region, and muscle-derived Rspo2 also plays a substantial role in juxtaposition of the active zones and synaptic folds.
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Affiliation(s)
- Jin Li
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Mikako Ito
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Bisei Ohkawara
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Akio Masuda
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Kinji Ohno
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya, Japan.
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12
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Kariminejad A, Almadani N, Khoshaeen A, Olsson B, Moslemi AR, Tajsharghi H. Truncating CHRNG mutations associated with interfamilial variability of the severity of the Escobar variant of multiple pterygium syndrome. BMC Genet 2016; 17:71. [PMID: 27245440 PMCID: PMC4886457 DOI: 10.1186/s12863-016-0382-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 05/25/2016] [Indexed: 12/29/2022] Open
Abstract
Background In humans, muscle-specific nicotinergic acetylcholine receptor (AChR) is a transmembrane protein with five different subunits, coded by CHRNA1, CHRNB, CHRND and CHRNG/CHRNE. The gamma subunit of AChR encoded by CHRNG is expressed during early foetal development, whereas in the adult, the γ subunit is replaced by a ε subunit. Mutations in the CHRNG encoding the embryonal acetylcholine receptor may cause the non-lethal Escobar variant (EVMPS) and lethal form (LMPS) of multiple pterygium syndrome. The MPS is a condition characterised by prenatal growth failure with pterygium and akinesia leading to muscle weakness and severe congenital contractures, as well as scoliosis. Results Our whole exome sequencing studies have identified one novel and two previously reported homozygous mutations in CHRNG in three families affected by non-lethal EVMPS. The mutations consist of deletion of two nucleotides, cause a frameshift predicted to result in premature termination of the foetally expressed gamma subunit of the AChR. Conclusions Our data suggest that severity of the phenotype varies significantly both within and between families with MPS and that there is no apparent correlation between mutation position and clinical phenotype. Although individuals with CHRNG mutations can survive, there is an increased frequency of abortions and stillbirth in their families. Furthermore, genetic background and environmental modifiers might be of significance for decisiveness of the lethal spectrum, rather than the state of the mutation per se. Detailed clinical examination of our patients further indicates the changing phenotype from infancy to childhood.
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Affiliation(s)
| | - Navid Almadani
- Kariminejad-Najmabadi Pathology & Genetics Centre, Tehran, Iran
| | | | - Bjorn Olsson
- Systems Biology Research Centre, School of Bioscience, University of Skovde, SE-541 28, Skovde, Sweden
| | - Ali-Reza Moslemi
- Department of Pathology, University of Gothenburg, Sahlgrenska University Hospital, SE-413 45, Gothenburg, Sweden
| | - Homa Tajsharghi
- Systems Biology Research Centre, School of Bioscience, University of Skovde, SE-541 28, Skovde, Sweden. .,Department of Pathology, University of Gothenburg, Sahlgrenska University Hospital, SE-413 45, Gothenburg, Sweden.
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13
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Abstract
Neuromuscular diseases can affect the survival of peripheral neurons, their axons extending to peripheral targets, their synaptic connections onto those targets, or the targets themselves. Examples include motor neuron diseases such as Amyotrophic Lateral Sclerosis, peripheral neuropathies such as Charcot-Marie-Tooth diseases, myasthenias, and muscular dystrophies. Characterizing these phenotypes in mouse models requires an integrated approach, examining both the nerve and muscle histologically, anatomically, and functionally by electrophysiology. Defects observed at these levels can be related back to onset, severity, and progression, as assessed by "Quality of life measures" including tests of gross motor performance such as gait or grip strength. This chapter describes methods for assessing neuromuscular disease models in mice, and how interpretation of these tests can be complicated by the inter-relatedness of the phenotypes.
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Affiliation(s)
- Robert W Burgess
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME, 04609, USA.
| | - Gregory A Cox
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME, 04609, USA
| | - Kevin L Seburn
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME, 04609, USA
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14
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Tintignac LA, Brenner HR, Rüegg MA. Mechanisms Regulating Neuromuscular Junction Development and Function and Causes of Muscle Wasting. Physiol Rev 2015; 95:809-52. [DOI: 10.1152/physrev.00033.2014] [Citation(s) in RCA: 224] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The neuromuscular junction is the chemical synapse between motor neurons and skeletal muscle fibers. It is designed to reliably convert the action potential from the presynaptic motor neuron into the contraction of the postsynaptic muscle fiber. Diseases that affect the neuromuscular junction may cause failure of this conversion and result in loss of ambulation and respiration. The loss of motor input also causes muscle wasting as muscle mass is constantly adapted to contractile needs by the balancing of protein synthesis and protein degradation. Finally, neuromuscular activity and muscle mass have a major impact on metabolic properties of the organisms. This review discusses the mechanisms involved in the development and maintenance of the neuromuscular junction, the consequences of and the mechanisms involved in its dysfunction, and its role in maintaining muscle mass during aging. As life expectancy is increasing, loss of muscle mass during aging, called sarcopenia, has emerged as a field of high medical need. Interestingly, aging is also accompanied by structural changes at the neuromuscular junction, suggesting that the mechanisms involved in neuromuscular junction maintenance might be disturbed during aging. In addition, there is now evidence that behavioral paradigms and signaling pathways that are involved in longevity also affect neuromuscular junction stability and sarcopenia.
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Affiliation(s)
- Lionel A. Tintignac
- Biozentrum, University of Basel, Basel, Switzerland; Department of Biomedicine, University of Basel, Basel, Switzerland; and INRA, UMR866 Dynamique Musculaire et Métabolisme, Montpellier, France
| | - Hans-Rudolf Brenner
- Biozentrum, University of Basel, Basel, Switzerland; Department of Biomedicine, University of Basel, Basel, Switzerland; and INRA, UMR866 Dynamique Musculaire et Métabolisme, Montpellier, France
| | - Markus A. Rüegg
- Biozentrum, University of Basel, Basel, Switzerland; Department of Biomedicine, University of Basel, Basel, Switzerland; and INRA, UMR866 Dynamique Musculaire et Métabolisme, Montpellier, France
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15
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Chong J, Burrage L, Beck A, Marvin C, McMillin M, Shively K, Harrell T, Buckingham K, Bacino C, Jain M, Alanay Y, Berry S, Carey J, Gibbs R, Lee B, Krakow D, Shendure J, Nickerson D, Bamshad MJ, Bamshad M, Shendure J, Nickerson D, Abecasis G, Anderson P, Blue E, Annable M, Browning B, Buckingham K, Chen C, Chin J, Chong J, Cooper G, Davis C, Frazar C, Harrell T, He Z, Jain P, Jarvik G, Jimenez G, Johanson E, Jun G, Kircher M, Kolar T, Krauter S, Krumm N, Leal S, Luksic D, Marvin C, McMillin M, McGee S, O’Reilly P, Paeper B, Patterson K, Perez M, Phillips S, Pijoan J, Poel C, Reinier F, Robertson P, Santos-Cortez R, Shaffer T, Shephard C, Shively K, Siegel D, Smith J, Staples J, Tabor H, Tackett M, Underwood J, Wegener M, Wang G, Wheeler M, Yi Q. Autosomal-Dominant Multiple Pterygium Syndrome Is Caused by Mutations in MYH3. Am J Hum Genet 2015; 96:841-9. [PMID: 25957469 DOI: 10.1016/j.ajhg.2015.04.004] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 04/07/2015] [Indexed: 12/28/2022] Open
Abstract
Multiple pterygium syndrome (MPS) is a phenotypically and genetically heterogeneous group of rare Mendelian conditions characterized by multiple pterygia, scoliosis, and congenital contractures of the limbs. MPS typically segregates as an autosomal-recessive disorder, but rare instances of autosomal-dominant transmission have been reported. Whereas several mutations causing recessive MPS have been identified, the genetic basis of dominant MPS remains unknown. We identified four families affected by dominantly transmitted MPS characterized by pterygia, camptodactyly of the hands, vertebral fusions, and scoliosis. Exome sequencing identified predicted protein-altering mutations in embryonic myosin heavy chain (MYH3) in three families. MYH3 mutations underlie distal arthrogryposis types 1, 2A, and 2B, but all mutations reported to date occur in the head and neck domains. In contrast, two of the mutations found to cause MPS in this study occurred in the tail domain. The phenotypic overlap among persons with MPS, coupled with physical findings distinct from other conditions caused by mutations in MYH3, suggests that the developmental mechanism underlying MPS differs from that of other conditions and/or that certain functions of embryonic myosin might be perturbed by disruption of specific residues and/or domains. Moreover, the vertebral fusions in persons with MPS, coupled with evidence of MYH3 expression in bone, suggest that embryonic myosin plays a role in skeletal development.
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16
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Seo J, Choi IH, Lee JS, Yoo Y, Kim NKD, Choi M, Ko JM, Shin YB. Rare cases of congenital arthrogryposis multiplex caused by novel recurrent CHRNG mutations. J Hum Genet 2015; 60:213-5. [PMID: 25608830 DOI: 10.1038/jhg.2015.2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2014] [Revised: 11/28/2014] [Accepted: 12/18/2014] [Indexed: 11/09/2022]
Abstract
Multiple pterygium syndrome (MPS) is an autosomal recessively inherited condition that becomes evident before birth, with pterygium at multiple joints and akinesia. There are two forms of this syndrome that are differentiated by clinical severity: the milder form, Escobar type (OMIM#265000), and the more severe form, lethal type (OMIM#253290). Mutations in CHRNG, which encode the acetylcholine receptor gamma subunit, cause most cases of MPS. Here, we present three patients from two unrelated families showing multiple joint contractures in both the upper and lower limbs. High-arched palates with malocclusion, short neck and micrognathia were observed in all patients. Peripheral blood karyotypes were normal. Whole-exome sequencing analysis of the patients' genomes led to the discovery of identical missense (p.Pro143Arg) and frameshift deletion variants (p.Pro251fs*45) on CHRNG. These were rare cases of congenital arthrogryposis multiplex related to novel recessive CHRNG variants in two Korean kindred without apparent relatedness.
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Affiliation(s)
- Jieun Seo
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea
| | - In-Ho Choi
- Department of Orthopedic Surgery, Seoul National University Children's Hospital, Seoul, Korea
| | - Je Sang Lee
- Department of Rehabilitative Medicine, Pusan National University Hospital, Pusan National University School of Medicine, Pusan, Korea
| | - Yongjin Yoo
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea
| | - Nayoung K D Kim
- Samsung Genome Institute, Samsung Medical Center, Seoul, Korea
| | - Murim Choi
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Korea
| | - Jung Min Ko
- Department of Pediatrics, Seoul National University Children's Hospital, Seoul, Korea
| | - Yong Beom Shin
- Department of Rehabilitative Medicine, Pusan National University Hospital, Pusan National University School of Medicine, Pusan, Korea
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17
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Hacohen Y, Jacobson LW, Byrne S, Norwood F, Lall A, Robb S, Dilena R, Fumagalli M, Born AP, Clarke D, Lim M, Vincent A, Jungbluth H. Fetal acetylcholine receptor inactivation syndrome: A myopathy due to maternal antibodies. NEUROLOGY-NEUROIMMUNOLOGY & NEUROINFLAMMATION 2014; 2:e57. [PMID: 25566546 PMCID: PMC4277302 DOI: 10.1212/nxi.0000000000000057] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Accepted: 11/03/2014] [Indexed: 11/15/2022]
Abstract
Background: Transient neonatal myasthenia gravis (TNMG) affects a proportion of infants born to mothers with myasthenia gravis (MG). Symptoms usually resolve completely within the first few months of life, but persistent myopathic features have been reported in a few isolated cases. Methods: Here we report 8 patients from 4 families born to mothers with clinically manifest MG or mothers who were asymptomatic but had elevated acetylcholine receptor (AChR) antibody levels. Results: Clinical features in affected infants ranged from a mild predominantly facial and bulbar myopathy to arthrogryposis multiplex congenita. Additional clinical findings included hearing impairment, pyloric stenosis, and mild CNS involvement. In all cases, antibodies against the AChR were markedly elevated, although not always specific for the fetal AChR γ subunit. There was a correlation between maternal symptoms; the timing, intensity, and frequency of maternal treatment; and neonatal outcome. Conclusions: These findings suggest that persistent myopathic features following TNMG may be more common than currently recognized. Fetal AChR inactivation syndrome should be considered in the differential diagnosis of infants presenting with unexplained myopathic features, in particular marked dysarthria and velopharyngeal incompetence. Correct diagnosis requires a high degree of suspicion if the mother is asymptomatic but is crucial considering the high recurrence risk for future pregnancies and the potentially treatable nature of this condition. Infants with a history of TNMG should be followed up for subtle myopathic signs and associated complications.
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Affiliation(s)
- Yael Hacohen
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Leslie W Jacobson
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Susan Byrne
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Fiona Norwood
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Abhimanu Lall
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Stephanie Robb
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Robertino Dilena
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Monica Fumagalli
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Alfred Peter Born
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Debbie Clarke
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Ming Lim
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Angela Vincent
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Heinz Jungbluth
- Department of Pediatric Neurology (Y.H., S.B., D.C., M.L., H.J.), Evelina's Children Hospital, Guy's & St. Thomas' Hospital NHS Foundation Trust, London, United Kingdom; Department of Clinical Neurology (Y.H., L.W.J., A.V.), Oxford University, Oxford; Department of Neurology (F.N.), Department of Neonatology (A.L.), Randall Division for Cell and Molecular Biophysics (H.J.), Muscle Signaling Section, and Department of Basic and Clinical Neuroscience Division (H.J.), IoP, King's College, London, United Kingdom; Dubowitz Neuromuscular Centre (S.R.), Great Ormond Street Hospital for Children, London, United Kingdom; Unit of Clinical Neurophysiology (R.D.), Department of Neuroscience and Mental Health and Neonatal Intensive Care Unit (M.F.), IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Università degli Studi di Milano, Milan, Italy; and Department of Pediatrics (A.P.B.), Rigshospitalet, Copenhagen University Hospital, Denmark
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Asymmetric transmitter binding sites of fetal muscle acetylcholine receptors shape their synaptic response. Proc Natl Acad Sci U S A 2013; 110:13654-9. [PMID: 23898191 DOI: 10.1073/pnas.1308247110] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Neuromuscular acetylcholine receptors (AChRs) have two transmitter binding sites: at α-δ and either α-γ (fetal) or α-ε (adult) subunit interfaces. The γ-subunit of fetal AChRs is indispensable for the proper development of neuromuscular synapses. We estimated parameters for acetylcholine (ACh) binding and gating from single channel currents of fetal mouse AChRs expressed in tissue-cultured cells. The unliganded gating equilibrium constant is smaller and less voltage-dependent than in adult AChRs. However, the α-γ binding site has a higher affinity for ACh and provides more binding energy for gating compared with α-ε; therefore, the diliganded gating equilibrium constant at -100 mV is comparable for both receptor subtypes. The -2.2 kcal/mol extra binding energy from α-γ compared with α-δ and α-ε is accompanied by a higher resting affinity for ACh, mainly because of slower transmitter dissociation. End plate current simulations suggest that the higher affinity and increased energy from α-γ are essential for generating synaptic responses at low pulse [ACh].
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19
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The neuromuscular junction: Selective remodeling of synaptic regulators at the nerve/muscle interface. Mech Dev 2013; 130:402-11. [DOI: 10.1016/j.mod.2012.09.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 09/18/2012] [Accepted: 09/21/2012] [Indexed: 11/19/2022]
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20
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Wu X, Tuzun E, Li J, Xiao T, Saini SS, Qi H, Allman W, Christadoss P. Ocular and generalized myasthenia gravis induced by human acetylcholine receptor γ subunit immunization. Muscle Nerve 2012; 45:209-16. [DOI: 10.1002/mus.22273] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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21
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Scheffer D, Sage C, Plazas PV, Huang M, Wedemeyer C, Zhang DS, Chen ZY, Elgoyhen AB, Corey DP, Pingault V. The α1 subunit of nicotinic acetylcholine receptors in the inner ear: transcriptional regulation by ATOH1 and co-expression with the γ subunit in hair cells. J Neurochem 2011; 103:2651-64. [PMID: 17961150 DOI: 10.1111/j.1471-4159.2007.04980.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Acetylcholine is a key neurotransmitter of the inner ear efferent system. In this study, we identify two novel nAChR subunits in the inner ear: α1 and γ, encoded by Chrna1 and Chrng, respectively. In situ hybridization shows that the messages of these two subunits are present in vestibular and cochlear hair cells during early development. Chrna1 and Chrng expression begin at embryonic stage E13.5 in the vestibular system and E17.5 in the organ of Corti. Chrna1 message continues through P7, whereas Chrng is undetectable at post-natal stage P6. The α1 and γ subunits are known as muscle-type nAChR subunits and are surprisingly expressed in hair cells which are sensory-neural cells. We also show that ATOH1/MATH1, a transcription factor essential for hair cell development, directly activates CHRNA1 transcription. Electrophoretic mobility-shift assays and supershift assays showed that ATOH1/E47 heterodimers selectively bind on two E boxes located in the proximal promoter of CHRNA1. Thus, Chrna1 could be the first transcriptional target of ATOH1 in the inner ear. Co-expression in Xenopus oocytes of the α1 subunit does not change the electrophysiological properties of the α9α10 receptor. We suggest that hair cells transiently express α1γ-containing nAChRs in addition to α9α10, and that these may have a role during development of the inner ear innervation.
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22
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Pacifici PG, Peter C, Yampolsky P, Koenen M, McArdle JJ, Witzemann V. Novel mouse model reveals distinct activity-dependent and -independent contributions to synapse development. PLoS One 2011; 6:e16469. [PMID: 21305030 PMCID: PMC3031568 DOI: 10.1371/journal.pone.0016469] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 12/20/2010] [Indexed: 11/18/2022] Open
Abstract
The balanced action of both pre- and postsynaptic organizers regulates the formation of neuromuscular junctions (NMJ). The precise mechanisms that control the regional specialization of acetylcholine receptor (AChR) aggregation, guide ingrowing axons and contribute to correct synaptic patterning are unknown. Synaptic activity is of central importance and to understand synaptogenesis, it is necessary to distinguish between activity-dependent and activity-independent processes. By engineering a mutated fetal AChR subunit, we used homologous recombination to develop a mouse line that expresses AChR with massively reduced open probability during embryonic development. Through histological and immunochemical methods as well as electrophysiological techniques, we observed that endplate anatomy and distribution are severely aberrant and innervation patterns are completely disrupted. Nonetheless, in the absence of activity AChRs form postsynaptic specializations attracting motor axons and permitting generation of multiple nerve/muscle contacts on individual fibers. This process is not restricted to a specialized central zone of the diaphragm and proceeds throughout embryonic development. Phenotypes can be attributed to separate activity-dependent and -independent pathways. The correct patterning of synaptic connections, prevention of multiple contacts and control of nerve growth require AChR-mediated activity. In contrast, myotube survival and acetylcholine-mediated dispersal of AChRs are maintained even in the absence of AChR-mediated activity. Because mouse models in which acetylcholine is entirely absent do not display similar effects, we conclude that acetylcholine binding to the AChR initiates activity-dependent and activity-independent pathways whereby the AChR modulates formation of the NMJ.
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Affiliation(s)
- Pier Giorgio Pacifici
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Christoph Peter
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Pessah Yampolsky
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Michael Koenen
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Joseph J. McArdle
- Department of Pharmacology and Physiology, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Veit Witzemann
- Department of Molecular Neurobiology, Max Planck Institute for Medical Research, Heidelberg, Germany
- * E-mail:
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Abstract
Neuromuscular diseases can affect the survival of peripheral neurons, their axons extending to peripheral targets, their synaptic connections onto those targets, or the targets themselves. Examples include motor neuron diseases such as amyotrophic lateral sclerosis, peripheral neuropathies, such as Charcot-Marie-Tooth diseases, myasthenias, and muscular dystrophies. Characterizing these phenotypes in mouse models requires an integrated approach, examining both the nerve and the muscle histologically, anatomically, and functionally by electrophysiology. Defects observed at these levels can be related back to onset, severity, and progression, as assessed by "quality-of-life measures" including tests of gross motor performance such as gait or grip strength. This chapter describes methods for assessing neuromuscular disease models in mice, and how interpretation of these tests can be complicated by the inter-relatedness of the phenotypes.
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Liu Y, Sugiura Y, Padgett D, Lin W. Postsynaptic development of the neuromuscular junction in mice lacking the gamma-subunit of muscle nicotinic acetylcholine receptor. J Mol Neurosci 2009; 40:21-6. [PMID: 19672725 DOI: 10.1007/s12031-009-9248-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Accepted: 07/20/2009] [Indexed: 12/22/2022]
Abstract
The mammalian muscle nicotinic acetylcholine receptor (AChR) is composed of five membrane-spanning subunits and its composition differs between embryonic and adult muscles. In embryonic muscles, it is composed of two alpha-, one beta-, one delta-, and one gamma-subunit; the gamma-subunit is later replaced by the epsilon-subunit during postnatal development. This unique temporal expression pattern of the gamma-subunit suggests it may play specific roles in embryonic muscles. To address this issue, we examined the formation and function of the neuromuscular junction in mouse embryos deficient in the gamma-subunit. At embryonic day 15.5, AChR clusters were absent and the spontaneous miniature endplate potentials were undetectable in the mutant muscles. However, electrical stimulation of the nerves triggered muscle contraction and elicited postsynaptic endplate potential (EPP) in the mutant muscles, although the magnitude of the muscle contraction and the amplitudes of the EPPs were smaller in the mutant compared to the wild-type muscles. Reintroducing a wild-type gamma-subunit into the mutant myotubes restored the formation of AChR clusters in vitro. Together, these results have demonstrated that functional AChRs were present in the mutant muscle membrane, but at reduced levels. Thus, in the absence of the gamma-subunit, a combination of alpha, beta, and delta subunits may assemble into functional receptors in vivo. These results also suggest that the gamma-subunit maybe involved in interacting with rapsyn, a cytoplasmic protein required for AChR clustering.
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Affiliation(s)
- Yun Liu
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX 75390-9111, USA
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25
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Liu Y, Oppenheim RW, Sugiura Y, Lin W. Abnormal development of the neuromuscular junction in Nedd4-deficient mice. Dev Biol 2009; 330:153-66. [PMID: 19345204 DOI: 10.1016/j.ydbio.2009.03.023] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Revised: 03/23/2009] [Accepted: 03/25/2009] [Indexed: 11/28/2022]
Abstract
Nedd4 (neural precursor cell expressed developmentally down-regulated gene 4) is an E3 ubiquitin ligase highly conserved from yeast to humans. The expression of Nedd4 is developmentally down-regulated in the mammalian nervous system, but the role of Nedd4 in mammalian neural development remains poorly understood. Here we show that a null mutation of Nedd4 in mice leads to perinatal lethality: mutant mice were stillborn and many of them died in utero before birth (between E15.5-E18.5). In Nedd4 mutant embryos, skeletal muscle fiber sizes and motoneuron numbers are significantly reduced. Surviving motoneurons project axons to their target muscles on schedule, but motor nerves defasciculate upon reaching the muscle surface, suggesting that Nedd4 plays a critical role in fine-tuning the interaction between the nerve and the muscle. Electrophysiological analyses of the neuromuscular junction (NMJ) demonstrate an increased spontaneous miniature endplate potential (mEPP) frequency in Nedd4 mutants. However, the mutant neuromuscular synapses are less responsive to membrane depolarization, compared to the wildtypes. Ultrastructural analyses further reveal that the pre-synaptic nerve terminal branches at the NMJs of Nedd4 mutants are increased in number, but decreased in diameter compared to the wildtypes. These ultrastructural changes are consistent with functional alternation of the NMJs in Nedd4 mutants. Unexpectedly, Nedd4 is not expressed in motoneurons, but is highly expressed in skeletal muscles and Schwann cells. Together, these results demonstrate that Nedd4 is involved in regulating the formation and function of the NMJs through non-cell autonomous mechanisms.
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Affiliation(s)
- Yun Liu
- Department of Neuroscience, UT Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75390-9111, USA
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26
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Méjat A, Decostre V, Li J, Renou L, Kesari A, Hantaï D, Stewart CL, Xiao X, Hoffman E, Bonne G, Misteli T. Lamin A/C-mediated neuromuscular junction defects in Emery-Dreifuss muscular dystrophy. ACTA ACUST UNITED AC 2009; 184:31-44. [PMID: 19124654 PMCID: PMC2615092 DOI: 10.1083/jcb.200811035] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The LMNA gene encodes lamins A and C, two intermediate filament-type proteins that are important determinants of interphase nuclear architecture. Mutations in LMNA lead to a wide spectrum of human diseases including autosomal dominant Emery-Dreifuss muscular dystrophy (AD-EDMD), which affects skeletal and cardiac muscle. The cellular mechanisms by which mutations in LMNA cause disease have been elusive. Here, we demonstrate that defects in neuromuscular junctions (NMJs) are part of the disease mechanism in AD-EDMD. Two AD-EDMD mouse models show innervation defects including misexpression of electrical activity–dependent genes and altered epigenetic chromatin modifications. Synaptic nuclei are not properly recruited to the NMJ because of mislocalization of nuclear envelope components. AD-EDMD patients with LMNA mutations show the same cellular defects as the AD-EDMD mouse models. These results suggest that lamin A/C–mediated NMJ defects contribute to the AD-EDMD disease phenotype and provide insights into the cellular and molecular mechanisms for the muscle-specific phenotype of AD-EDMD.
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Affiliation(s)
- Alexandre Méjat
- National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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27
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Röder IV, Petersen Y, Choi KR, Witzemann V, Hammer JA, Rudolf R. Role of Myosin Va in the plasticity of the vertebrate neuromuscular junction in vivo. PLoS One 2008; 3:e3871. [PMID: 19057648 PMCID: PMC2587709 DOI: 10.1371/journal.pone.0003871] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Accepted: 11/10/2008] [Indexed: 01/07/2023] Open
Abstract
Background Myosin Va is a motor protein involved in vesicular transport and its absence leads to movement disorders in humans (Griscelli and Elejalde syndromes) and rodents (e.g. dilute lethal phenotype in mice). We examined the role of myosin Va in the postsynaptic plasticity of the vertebrate neuromuscular junction (NMJ). Methodology/Principal Findings Dilute lethal mice showed a good correlation between the propensity for seizures, and fragmentation and size reduction of NMJs. In an aneural C2C12 myoblast cell culture, expression of a dominant-negative fragment of myosin Va led to the accumulation of punctate structures containing the NMJ marker protein, rapsyn-GFP, in perinuclear clusters. In mouse hindlimb muscle, endogenous myosin Va co-precipitated with surface-exposed or internalised acetylcholine receptors and was markedly enriched in close proximity to the NMJ upon immunofluorescence. In vivo microscopy of exogenous full length myosin Va as well as a cargo-binding fragment of myosin Va showed localisation to the NMJ in wildtype mouse muscles. Furthermore, local interference with myosin Va function in live wildtype mouse muscles led to fragmentation and size reduction of NMJs, exclusion of rapsyn-GFP from NMJs, reduced persistence of acetylcholine receptors in NMJs and an increased amount of punctate structures bearing internalised NMJ proteins. Conclusions/Significance In summary, our data show a crucial role of myosin Va for the plasticity of live vertebrate neuromuscular junctions and suggest its involvement in the recycling of internalised acetylcholine receptors back to the postsynaptic membrane.
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Affiliation(s)
- Ira Verena Röder
- Institute of Toxicology and Genetics, Research Center Karlsruhe, Eggenstein-Leopoldshafen, Germany
| | - Yvonne Petersen
- Institute of Toxicology and Genetics, Research Center Karlsruhe, Eggenstein-Leopoldshafen, Germany
| | - Kyeong Rok Choi
- Institute of Toxicology and Genetics, Research Center Karlsruhe, Eggenstein-Leopoldshafen, Germany
| | - Veit Witzemann
- Max-Planck-Institute for Medical Research, Heidelberg, Germany
| | - John A. Hammer
- Laboratory of Cell Biology, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Rüdiger Rudolf
- Institute of Toxicology and Genetics, Research Center Karlsruhe, Eggenstein-Leopoldshafen, Germany
- * E-mail:
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28
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Loss of transforming growth factor-beta 2 leads to impairment of central synapse function. Neural Dev 2008; 3:25. [PMID: 18854036 PMCID: PMC2576228 DOI: 10.1186/1749-8104-3-25] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Accepted: 10/14/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The formation of functional synapses is a crucial event in neuronal network formation, and with regard to regulation of breathing it is essential for life. Members of the transforming growth factor-beta (TGF-beta) superfamily act as intercellular signaling molecules during synaptogenesis of the neuromuscular junction of Drosophila and are involved in synaptic function of sensory neurons of Aplysia. RESULTS Here we show that while TGF-beta2 is not crucial for the morphology and function of the neuromuscular junction of the diaphragm muscle of mice, it is essential for proper synaptic function in the pre-Bötzinger complex, a central rhythm organizer located in the brainstem. Genetic deletion of TGF-beta2 in mice strongly impaired both GABA/glycinergic and glutamatergic synaptic transmission in the pre-Bötzinger complex area, while numbers and morphology of central synapses of knock-out animals were indistinguishable from their wild-type littermates at embryonic day 18.5. CONCLUSION The results demonstrate that TGF-beta2 influences synaptic function, rather than synaptogenesis, specifically at central synapses. The functional alterations in the respiratory center of the brain are probably the underlying cause of the perinatal death of the TGF-beta2 knock-out mice.
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Chevessier F, Girard E, Molgo J, Bartling S, Koenig J, Hantai D, Witzemann V. A mouse model for congenital myasthenic syndrome due to MuSK mutations reveals defects in structure and function of neuromuscular junctions. Hum Mol Genet 2008; 17:3577-95. [DOI: 10.1093/hmg/ddn251] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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30
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Muscle-wide secretion of a miniaturized form of neural agrin rescues focal neuromuscular innervation in agrin mutant mice. Proc Natl Acad Sci U S A 2008; 105:11406-11. [PMID: 18685098 DOI: 10.1073/pnas.0801683105] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Agrin and its receptor MuSK are required for the formation of the postsynaptic apparatus at the neuromuscular junction (NMJ). In the current model the local deposition of agrin by the nerve and the resulting local activation of MuSK are responsible for creating and maintaining the postsynaptic apparatus including clusters of acetylcholine receptors (AChRs). Concomitantly, the release of acetylcholine (ACh) and the resulting depolarization disperses those postsynaptic structures that are not apposed by the nerve and thus not stabilized by agrin-MuSK signaling. Here we show that a miniaturized form of agrin, consisting of the laminin-binding and MuSK-activating domains, is sufficient to fully restore NMJs in agrin mutant mice when expressed by developing muscle. Although miniagrin is expressed uniformly throughout muscle fibers and induces ectopic AChR clusters, the size and the number of those AChR clusters contacted by the motor nerve increase during development. We provide experimental evidence that this is due to ACh, because the AChR agonist carbachol stabilizes AChR clusters in organotypic cultures of embryonic diaphragms. In summary, our results show that agrin function in NMJ development requires only two small domains, and that this function does not depend on the local deposition of agrin at synapses. Finally, they suggest a novel local function of ACh in stabilizing postsynaptic structures.
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31
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Oppenheim RW, Calderó J, Cuitat D, Esquerda J, McArdle JJ, Olivera BM, Prevette D, Teichert RW. The rescue of developing avian motoneurons from programmed cell death by a selective inhibitor of the fetal muscle-specific nicotinic acetylcholine receptor. Dev Neurobiol 2008; 68:972-80. [PMID: 18418876 DOI: 10.1002/dneu.20636] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In an attempt to determine whether the rescue of developing motoneurons (MNS) from programmed cell death (PCD) in the chick embryo following reductions in neuromuscular function involves muscle or neuronal nicotinic acetylcholine receptors (nAChRs), we have employed a novel cone snail toxin alphaA-OIVA that acts selectively to antagonize the embryonic/fetal form of muscle nAChRs. The results demonstrate that alphaA-OIVA is nearly as effective as curare or alpha-bungarotoxin (alpha-BTX) in reducing neuromuscular function and is equally effective in increasing MN survival and intramuscular axon branching. Together with previous reports, we also provide evidence consistent with a transition between the embryonic/fetal form to the adult form of muscle nAChRs in chicken that involves the loss of the gamma subunit in the adult receptor. We conclude that selective inhibition of the embryonic/fetal form of the chicken muscle nAChR is sufficient to rescue MNs from PCD without any involvement of neuronal nAChRs.
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Affiliation(s)
- Ronald W Oppenheim
- Department of Neurobiology and Anatomy and The Neuroscience Program, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
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McArdle PF, Rutherford S, Mitchell BD, Damcott CM, Wang Y, Ramachandran V, Ott S, Chang YPC, Levy D, Steinle N. Nicotinic acetylcholine receptor subunit variants are associated with blood pressure; findings in the Old Order Amish and replication in the Framingham Heart Study. BMC MEDICAL GENETICS 2008; 9:67. [PMID: 18625075 PMCID: PMC2478679 DOI: 10.1186/1471-2350-9-67] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Accepted: 07/14/2008] [Indexed: 11/10/2022]
Abstract
BACKGROUND Systemic blood pressure, influenced by both genetic and environmental factors, is regulated via sympathetic nerve activity. We assessed the role of genetic variation in three subunits of the neuromuscular nicotinic acetylcholine receptor positioned on chromosome 2q, a region showing replicated evidence of linkage to blood pressure. METHODS We sequenced CHRNA1, CHRND and CHRNG in 24 Amish subjects from the Amish Family Diabetes Study (AFDS) and identified 20 variants. We then performed association analysis of non-redundant variants (n = 12) in the complete AFDS cohort of 1,189 individuals, and followed by genotyping blood pressure-associated variants (n = 5) in a replication sample of 1,759 individuals from the Framingham Heart Study (FHS). RESULTS The minor allele of a synonymous coding SNP, rs2099489 in CHRNG, was associated with higher systolic blood pressure in both the Amish (p = 0.0009) and FHS populations (p = 0.009) (minor allele frequency = 0.20 in both populations). CONCLUSION CHRNG is currently thought to be expressed only during fetal development. These findings support the Barker hypothesis, that fetal genotype and intra-uterine environment influence susceptibility to chronic diseases later in life. Additional studies of this variant in other populations, as well as the effect of this variant on acetylcholine receptor expression and function, are needed to further elucidate its potential role in the regulation of blood pressure. This study suggests for the first time in humans, a possible role for genetic variation in the neuromuscular nicotinic acetylcholine receptor, particularly the gamma subunit, in systolic blood pressure regulation.
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Affiliation(s)
- Patrick F McArdle
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, USA.
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33
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Mutant forms of the extracellular domain of the human acetylcholine receptor gamma-subunit with improved solubility and enhanced antigenicity. The importance of the Cys-loop. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:1226-33. [PMID: 18502212 DOI: 10.1016/j.bbapap.2008.04.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2007] [Revised: 04/06/2008] [Accepted: 04/28/2008] [Indexed: 11/21/2022]
Abstract
The muscle nicotinic acetylcholine receptor (AChR) is the prototype of the ligand-gated ion channels (or Cys-loop receptors), formed by 5 homologous subunits (alpha2betagammadelta or alpha2betagammaepsilon), and is the major autoantigen in the autoimmune disease, myasthenia gravis. Previously, we expressed the wild-type extracellular domain (ECD) of the gamma-subunit (gammaECD) of the AChR in yeast Pichia pastoris at 0.3-0.8 mg/L, in soluble but microaggregate form, to use as starting material for structural and antigenicity studies. To optimize these characteristics, we constructed and characterized four gammaECD variants: (a) mutants-1 (gammaC61S) and -2 (gammaC106S-C115S), where the non-conserved Cys of gammaECD were replaced by serines, (b) mutant-3 (gammaCysLoop), where the gamma Cys-loop region was substituted by the cognate region of the acetylcholine binding protein (AChBP) and (c) mutant-4 (gammaCysLoop-C106S-C115S), where both the C106S-C115S and Cys-loop mutations were combined. None of mutants-1 and -2 displayed any improvement, while mutant-3 and -4 were mostly in dimeric form and expressed at much higher levels (2.5 mg/L and 3.5 mg/L respectively). All four mutants and wild-type gammaECD were recognized by sera from myasthenic patients, but mutants-3 and -4 exhibited higher efficiency, compared to wild-type or mutants-1 and -2. These results suggest that the substitution of the Cys-loop region of any AChR ECD with the AChBP counterpart leads to AChR ECD of improved conformation, more suitable for structural and therapeutic studies.
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Liu Y, Padgett D, Takahashi M, Li H, Sayeed A, Teichert RW, Olivera BM, McArdle JJ, Green WN, Lin W. Essential roles of the acetylcholine receptor gamma-subunit in neuromuscular synaptic patterning. Development 2008; 135:1957-67. [PMID: 18434415 DOI: 10.1242/dev.018119] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Formation of the vertebrate neuromuscular junction (NMJ) takes place in a stereotypic pattern in which nerves terminate at select sarcolemmal sites often localized to the central region of the muscle fibers. Several lines of evidence indicate that the muscle fibers may initiate postsynaptic differentiation independent of the ingrowing nerves. For example, nascent acetylcholine receptors (AChRs) are pre-patterned at select regions of the muscle during the initial stage of neuromuscular synaptogenesis. It is not clear how these pre-patterned AChR clusters are assembled, and to what extent they contribute to pre- and post-synaptic differentiation during development. Here, we show that genetic deletion of the AChR gamma-subunit gene in mice leads to an absence of pre-patterned AChR clusters during initial stages of neuromuscular synaptogenesis. The absence of pre-patterned AChR clusters was associated with excessive nerve branching, increased motoneuron survival, as well as aberrant distribution of acetylcholinesterase (AChE) and rapsyn. However, clustering of muscle specific kinase (MuSK) proceeded normally in the gamma-null muscles. AChR clusters emerged at later stages owing to the expression of the AChR epsilon-subunit, but these delayed AChR clusters were broadly distributed and appeared at lower level compared with the wild-type muscles. Interestingly, despite the abnormal pattern, synaptic vesicle proteins were progressively accumulated at individual nerve terminals, and neuromuscular synapses were ultimately established in gamma-null muscles. These results demonstrate that the gamma-subunit is required for the formation of pre-patterned AChR clusters, which in turn play an essential role in determining the subsequent pattern of neuromuscular synaptogenesis.
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Affiliation(s)
- Yun Liu
- Department of Neuroscience, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75235-9111, USA
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35
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AChR channel conversion and AChR-adjusted neuronal survival during embryonic development. Mol Cell Neurosci 2008; 37:634-45. [DOI: 10.1016/j.mcn.2007.12.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2007] [Revised: 11/16/2007] [Accepted: 12/06/2007] [Indexed: 11/21/2022] Open
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Tessitore A, Pfelsticker LN, Paschoal JR. Aspectos neurofisiológicos da musculatura facial visando a reabilitação na paralisia facial. REVISTA CEFAC 2008. [DOI: 10.1590/s1516-18462008000100010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
OBJETIVO: revisão teórica dos aspectos e particularidades neurofisiológicas relevantes da musculatura orofacial, visando a reabilitação na paralisia facial periférica. MÉTODOS: revisão da literatura sobre neuro-anatomofisiologia da musculatura orofacial mediante pesquisa dos artigos dos periódicos nacionais e internacionais e nos livros científicos sobre o tema, no período entre 1995 a 2005. RESULTADOS: foram revistas 50 referências neste trabalho. Destas, 20 sobre neurofisiologia, 14 sobre neuroanatomia. As demais sobre fonoaudiologia e paralisia facial. Os artigos de neurofisiologia e neuroanatomia estudados foram divididos em três grupos: I - Aspectos do complexo neuromuscular; II - Características morfológicas e histoquímicas dos músculos da face e III - Denervação e atrofia muscular. CONCLUSÃO: a partir dos achados, procurou-se sistematizar didaticamente as particularidades da neuro-anatomofisiologia, cujo conhecimento, na impressão dos autores, são relevantes para o sucesso na reabilitação da paralisia facial.
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37
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Li XM, Dong XP, Luo SW, Zhang B, Lee DH, Ting AKL, Neiswender H, Kim CH, Carpenter-Hyland E, Gao TM, Xiong WC, Mei L. Retrograde regulation of motoneuron differentiation by muscle beta-catenin. Nat Neurosci 2008; 11:262-8. [PMID: 18278041 DOI: 10.1038/nn2053] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2007] [Accepted: 01/23/2008] [Indexed: 01/19/2023]
Abstract
Synapse formation requires proper interaction between pre- and postsynaptic cells. In anterograde signaling, neurons release factors to guide postsynaptic differentiation. However, less is known about how postsynaptic targets retrogradely regulate presynaptic differentiation or function. We found that muscle-specific conditional knockout of beta-catenin (Ctnnb1, also known as beta-cat) in mice caused both morphologic and functional defects in motoneuron terminals of neuromuscular junctions (NMJs). In the absence of muscle beta-catenin, acetylcholine receptor clusters were increased in size and distributed throughout a wider region. Primary nerve branches were mislocated, whereas secondary or intramuscular nerve branches were elongated and reduced in number. Both spontaneous and evoked neurotransmitter release was reduced at the mutant NMJs. Furthermore, short-term plasticity and calcium sensitivity of neurotransmitter release were compromised in beta-catenin-deficient muscle. In contrast, the NMJ was normal in morphology and function in motoneuron-specific beta-catenin-deficient mice. Taken together, these observations indicate a role for muscle beta-catenin in presynaptic differentiation and function, identifying a previously unknown retrograde signaling in the synapse formation and synaptic plasticity.
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Affiliation(s)
- Xiao-Ming Li
- Program of Developmental Neurobiology, Institute of Molecular Medicine and Genetics, Department of Neurology, Medical College of Georgia, 1120 15th Street, Augusta, Georgia 30912, USA
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38
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Kalamida D, Poulas K, Avramopoulou V, Fostieri E, Lagoumintzis G, Lazaridis K, Sideri A, Zouridakis M, Tzartos SJ. Muscle and neuronal nicotinic acetylcholine receptors. FEBS J 2007; 274:3799-845. [PMID: 17651090 DOI: 10.1111/j.1742-4658.2007.05935.x] [Citation(s) in RCA: 219] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are integral membrane proteins and prototypic members of the ligand-gated ion-channel superfamily, which has precursors in the prokaryotic world. They are formed by the assembly of five transmembrane subunits, selected from a pool of 17 homologous polypeptides (alpha1-10, beta1-4, gamma, delta, and epsilon). There are many nAChR subtypes, each consisting of a specific combination of subunits, which mediate diverse physiological functions. They are widely expressed in the central nervous system, while, in the periphery, they mediate synaptic transmission at the neuromuscular junction and ganglia. nAChRs are also found in non-neuronal/nonmuscle cells (keratinocytes, epithelia, macrophages, etc.). Extensive research has determined the specific function of several nAChR subtypes. nAChRs are now important therapeutic targets for various diseases, including myasthenia gravis, Alzheimer's and Parkinson's diseases, and schizophrenia, as well as for the cessation of smoking. However, knowledge is still incomplete, largely because of a lack of high-resolution X-ray structures for these molecules. Nevertheless, electron microscopy studies on 2D crystals of nAChR from fish electric organs and the determination of the high-resolution X-ray structure of the acetylcholine binding protein (AChBP) from snails, a homolog of the extracellular domain of the nAChR, have been major steps forward and the data obtained have important implications for the design of subtype-specific drugs. Here, we review some of the latest advances in our understanding of nAChRs and their involvement in physiology and pathology.
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Affiliation(s)
- Dimitra Kalamida
- Department of Pharmacy, University of Patras, Rio Patras, Greece
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Hoffmann K, Muller JS, Stricker S, Megarbane A, Rajab A, Lindner TH, Cohen M, Chouery E, Adaimy L, Ghanem I, Delague V, Boltshauser E, Talim B, Horvath R, Robinson PN, Lochmüller H, Hübner C, Mundlos S. Escobar syndrome is a prenatal myasthenia caused by disruption of the acetylcholine receptor fetal gamma subunit. Am J Hum Genet 2006; 79:303-12. [PMID: 16826520 PMCID: PMC1559482 DOI: 10.1086/506257] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Accepted: 05/12/2006] [Indexed: 11/03/2022] Open
Abstract
Escobar syndrome is a form of arthrogryposis multiplex congenita and features joint contractures, pterygia, and respiratory distress. Similar findings occur in newborns exposed to nicotinergic acetylcholine receptor (AChR) antibodies from myasthenic mothers. We performed linkage studies in families with Escobar syndrome and identified eight mutations within the gamma -subunit gene (CHRNG) of the AChR. Our functional studies show that gamma -subunit mutations prevent the correct localization of the fetal AChR in human embryonic kidney-cell membranes and that the expression pattern in prenatal mice corresponds to the human clinical phenotype. AChRs have five subunits. Two alpha, one beta, and one delta subunit are always present. By switching gamma to epsilon subunits in late fetal development, fetal AChRs are gradually replaced by adult AChRs. Fetal and adult AChRs are essential for neuromuscular signal transduction. In addition, the fetal AChRs seem to be the guide for the primary encounter of axon and muscle. Because of this important function in organogenesis, human mutations in the gamma subunit were thought to be lethal, as they are in gamma -knockout mice. In contrast, many mutations in other subunits have been found to be viable but cause postnatally persisting or beginning myasthenic syndromes. We conclude that Escobar syndrome is an inherited fetal myasthenic disease that also affects neuromuscular organogenesis. Because gamma expression is restricted to early development, patients have no myasthenic symptoms later in life. This is the major difference from mutations in the other AChR subunits and the striking parallel to the symptoms found in neonates with arthrogryposis when maternal AChR auto-antibodies crossed the placenta and caused the transient inactivation of the AChR pathway.
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Affiliation(s)
- Katrin Hoffmann
- Institute of Medical Genetics, Charite University Medical School, Humboldt University, 13353 Berlin, Germany.
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40
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Witzemann V. Development of the neuromuscular junction. Cell Tissue Res 2006; 326:263-71. [PMID: 16819627 DOI: 10.1007/s00441-006-0237-x] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Accepted: 05/05/2006] [Indexed: 11/30/2022]
Abstract
The differentiation of the neuromuscular junction is a multistep process requiring coordinated interactions between nerve terminals and muscle. Although innervation is not needed for muscle production, the formation of nerve-muscle contacts, intramuscular nerve branching, and neuronal survival require reciprocal signals from nerve and muscle to regulate the formation of synapses. Following the production of muscle fibers, clusters of acetylcholine receptors (AChRs) are concentrated in the central regions of the myofibers via a process termed "prepatterning". The postsynaptic protein MuSK is essential for this process activating possibly its own expression, in addition to the expression of AChR. AChR complexes (aggregated and stabilized by rapsyn) are thus prepatterned independently of neuronal signals in developing myofibers. ACh released by branching motor nerves causes AChR-induced postsynaptic potentials and positively regulates the localization and stabilization of developing synaptic contacts. These "active" contact sites may prevent AChRs clustering in non-contacted regions and counteract the establishment of additional contacts. ACh-induced signals also cause the dispersion of non-synaptic AChR clusters and possibly the removal of excess AChR. A further neuronal factor, agrin, stabilizes the accumulation of AChR at synaptic sites. Agrin released from the branching motor nerve may form a structural link specifically to the ACh-activated endplates, thereby enhancing MuSK kinase activity and AChR accumulation and preventing dispersion of postsynaptic specializations. The successful stabilization of prepatterned AChR clusters by agrin and the generation of singly innervated myofibers appear to require AChR-mediated postsynaptic potentials indicating that the differentiation of the nerve terminal proceeds only after postsynaptic specializations have formed.
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Affiliation(s)
- Veit Witzemann
- Max-Planck-Institut fur medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany.
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Fucile S, Sucapane A, Grassi F, Eusebi F, Engel AG. The human adult subtype ACh receptor channel has high Ca2+ permeability and predisposes to endplate Ca2+ overloading. J Physiol 2006; 573:35-43. [PMID: 16527851 PMCID: PMC1779694 DOI: 10.1113/jphysiol.2006.108092] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Slow-channel congenital myasthenic syndrome, caused by mutations in subunits of the endplate ACh receptor (AChR), results in prolonged synaptic currents and excitotoxic injury of the postsynaptic region by Ca2+ overloading. The Ca2+ overloading could be due entirely to the prolonged openings of the AChR channel or could be abetted by enhanced Ca2+ permeability of the mutant channels. We therefore measured the fractional Ca2+ current, defined as the percentage of the total ACh-evoked current carried by Ca2+ ions (Pf), for AChRs harbouring the alphaG153S or the alphaV249F slow-channel mutation, and for wild-type human AChRs in which Pf has not yet been determined. Experiments were performed in transiently transfected GH4C1 cells and human myotubes with simultaneous recording of ACh-evoked whole-cell currents and fura-2 fluorescence signals. We found that the Pf of the wild-type human endplate AChR was unexpectedly high (Pf approximately 7%), but neither the alphaV249F nor the alphaG153S mutation altered Pf. Fetal human AChRs containing either the wild-type or the mutated alpha subunit had a much lower Pf (2-3%). We conclude that the Ca2+ permeability of human endplate AChRs is higher than that reported for any other human nicotinic AChR, with the exception of alpha7-containing AChRs (Pf > 10%); and that neither the alphaG153S nor the alphaV249F mutations affect the Pf of fetal or adult endplate AChRs. However, the intrinsically high Ca2+ permeability of human AChRs probably predisposes to development of the endplate myopathy when opening events of the AChR channel are prolonged by altered AChR-channel kinetics.
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Affiliation(s)
- Sergio Fucile
- Pasteur Institute -Cenci Bolognetti Foundation & Department of Human Physiology and Pharmacology & Centre of Excellence for Biology and Molecular Medicine, University of Rome La Sapienza, Piazzale Aldo Moro 5; I-00185 Rome, Italy
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Hesser BA, Henschel O, Witzemann V. Synapse disassembly and formation of new synapses in postnatal muscle upon conditional inactivation of MuSK. Mol Cell Neurosci 2005; 31:470-80. [PMID: 16337809 DOI: 10.1016/j.mcn.2005.10.020] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Revised: 10/21/2005] [Accepted: 10/28/2005] [Indexed: 10/25/2022] Open
Abstract
The muscle-specific-kinase MuSK is required for the formation of acetylcholine receptor clusters during embryonic development, but its physiological role in adult muscle is not known. We used the loxP/Cre system in mice to conditionally inactivate MuSK whereby expression of Cre recombinase increases during postnatal development. The MuSK-inactivated mice develop myasthenic symptoms and die prematurely due to severe muscle weakness. The postnatal inactivation of MuSK causes loss of acetylcholine receptors and disassembly of the postsynaptic organization and innervating axons retract but start to grow and branch extensively. Due to the mosaic expression of Cre recombinase, MuSK is not globally inactivated and new synapses are formed aberrantly patterned across the diaphragm. Our findings demonstrate that MuSK kinase activity is required throughout postnatal development to hold up MuSK and AChR levels at endplates. Thus, MuSK and AChR together maintain the functional and structural integrity of the postsynaptic architecture and prevent axon growth.
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Affiliation(s)
- Boris A Hesser
- Max-Planck-Institut für medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany
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