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Li H, Teng J, Hibbs RE. Structural switch in acetylcholine receptors in developing muscle. Nature 2024:10.1038/s41586-024-07774-6. [PMID: 39085615 DOI: 10.1038/s41586-024-07774-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 07/02/2024] [Indexed: 08/02/2024]
Abstract
During development, motor neurons originating in the brainstem and spinal cord form elaborate synapses with skeletal muscle fibres1. These neurons release acetylcholine (ACh), which binds to nicotinic ACh receptors (AChRs) on the muscle, initiating contraction. Two types of AChR are present in developing muscle cells, and their differential expression serves as a hallmark of neuromuscular synapse maturation2-4. The structural principles underlying the switch from fetal to adult muscle receptors are unknown. Here, we present high-resolution structures of both fetal and adult muscle nicotinic AChRs, isolated from bovine skeletal muscle in developmental transition. These structures, obtained in the absence and presence of ACh, provide a structural context for understanding how fetal versus adult receptor isoforms are tuned for synapse development versus the all-or-none signalling required for high-fidelity skeletal muscle contraction. We find that ACh affinity differences are driven by binding site access, channel conductance is tuned by widespread surface electrostatics and open duration changes result from intrasubunit interactions and structural flexibility. The structures further reveal pathogenic mechanisms underlying congenital myasthenic syndromes.
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Affiliation(s)
- Huanhuan Li
- Department of Neurobiology, University of California San Diego, La Jolla, CA, USA
| | - Jinfeng Teng
- Department of Neurobiology, University of California San Diego, La Jolla, CA, USA
| | - Ryan E Hibbs
- Department of Neurobiology, University of California San Diego, La Jolla, CA, USA.
- Department of Pharmacology, University of California San Diego, La Jolla, CA, USA.
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2
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Shen X, Nakata T, Mizuno S, Imoto I, Selcen D, Ohno K, Engel AG. Impaired gating of γ- and ε-AChR respectively causes Escobar syndrome and fast-channel myasthenia. Ann Clin Transl Neurol 2023; 10:732-743. [PMID: 36891870 PMCID: PMC10187723 DOI: 10.1002/acn3.51756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 02/27/2023] [Indexed: 03/10/2023] Open
Abstract
OBJECTIVE To dissect the kinetic defects of acetylcholine receptor (AChR) γ subunit variant in an incomplete form of the Escobar syndrome without pterygium and compare it with those of a variant of corresponding residue in the AChR ε subunit in a congenital myasthenic syndrome (CMS). METHODS Whole exome sequencing, α-bungarotoxin binding assay, single channel patch-clamp recordings, and maximum likelihood analysis of channel kinetics. RESULTS We identified compound heterozygous variants in AChR γ and ε subunits in three Escobar syndrome (1-3) and three CMS patients (4-6), respectively. Each Escobar syndrome patient carries γP121R along with γV221Afs*44 in patients 1 and 2, and γY63* in patient 3. Three CMS patients share εP121T along with εR20W, εG-8R, and εY15H in patients 4, 5, and 6, respectively. Surface expressions of γP121R- and εP121T-AChR were 80% and 138% of the corresponding wild-type AChR, whereas εR20W, εG-8R, and εY15H reduced receptor expression to 27%, 35%, and 30% of wild-type εAChR, respectively. γV221Afs*44 and γY63* are null variants. Thus, γP121R and εP121T determine the phenotype. γP121R and εP121T shorten channel opening burst duration to 28% and 18% of corresponding wild-type AChR by reducing the channel gating equilibrium constant 44- and 63-fold, respectively. INTERPRETATION Similar impairment of channel gating efficiency of a corresponding P121 residue in the acetylcholine-binding site of the AChR γ and ε subunits causes Escobar syndrome without pterygium and fast-channel CMS, respectively, suggesting that therapy for the fast-channel CMS will benefit Escobar syndrome.
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Affiliation(s)
- Xin‐Ming Shen
- Department of Neurology and Neuromuscular Research LaboratoryMayo ClinicRochesterMinnesotaUSA
| | - Tomohiko Nakata
- Division of Neurogenetics, Center for Neurological Diseases and CancerNagoya University Graduate School of MedicineNagoyaJapan
- Department of PediatricsNagoya University Graduate School of MedicineNagoyaJapan
| | - Seiji Mizuno
- Department of PediatricsCentral Hospital, Aichi Human Service CenterKasugaiJapan
| | - Issei Imoto
- Aichi Cancer Center Research InstituteNagoyaJapan
| | - Duygu Selcen
- Department of Neurology and Neuromuscular Research LaboratoryMayo ClinicRochesterMinnesotaUSA
| | - Kinji Ohno
- Division of Neurogenetics, Center for Neurological Diseases and CancerNagoya University Graduate School of MedicineNagoyaJapan
| | - Andrew G. Engel
- Department of Neurology and Neuromuscular Research LaboratoryMayo ClinicRochesterMinnesotaUSA
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Srivastava P, Kane A, Harrison C, Levin M. A Meta-Analysis of Bioelectric Data in Cancer, Embryogenesis, and Regeneration. Bioelectricity 2021; 3:42-67. [PMID: 34476377 DOI: 10.1089/bioe.2019.0034] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Developmental bioelectricity is the study of the endogenous role of bioelectrical signaling in all cell types. Resting potentials and other aspects of ionic cell physiology are known to be important regulatory parameters in embryogenesis, regeneration, and cancer. However, relevant quantitative measurement and genetic phenotyping data are distributed throughout wide-ranging literature, hampering experimental design and hypothesis generation. Here, we analyze published studies on bioelectrics and transcriptomic and genomic/phenotypic databases to provide a novel synthesis of what is known in three important aspects of bioelectrics research. First, we provide a comprehensive list of channelopathies-ion channel and pump gene mutations-in a range of important model systems with developmental patterning phenotypes, illustrating the breadth of channel types, tissues, and phyla (including man) in which bioelectric signaling is a critical endogenous aspect of embryogenesis. Second, we perform a novel bioinformatic analysis of transcriptomic data during regeneration in diverse taxa that reveals an electrogenic protein to be the one common factor specifically expressed in regeneration blastemas across Kingdoms. Finally, we analyze data on distinct Vmem signatures in normal and cancer cells, revealing a specific bioelectrical signature corresponding to some types of malignancies. These analyses shed light on fundamental questions in developmental bioelectricity and suggest new avenues for research in this exciting field.
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Affiliation(s)
- Pranjal Srivastava
- Rye High School, Rye, New York, USA; Current Affiliation: College of Chemistry, University of California, Berkeley, Berkeley, California, USA
| | - Anna Kane
- Department of Biology, Allen Discovery Center, Tufts University, Medford, Massachusetts, USA
| | - Christina Harrison
- Department of Biology, Allen Discovery Center, Tufts University, Medford, Massachusetts, USA
| | - Michael Levin
- Department of Biology, Allen Discovery Center, Tufts University, Medford, Massachusetts, USA
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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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Progress in nicotinic receptor structural biology. Neuropharmacology 2020; 171:108086. [PMID: 32272141 DOI: 10.1016/j.neuropharm.2020.108086] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [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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Vaughan SK, Sutherland NM, Valdez G. Attenuating Cholinergic Transmission Increases the Number of Satellite Cells and Preserves Muscle Mass in Old Age. Front Aging Neurosci 2019; 11:262. [PMID: 31616286 PMCID: PMC6768977 DOI: 10.3389/fnagi.2019.00262] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 09/05/2019] [Indexed: 12/13/2022] Open
Abstract
In addition to driving contraction of skeletal muscles, acetylcholine (ACh) acts as an anti-synaptogenic agent at neuromuscular junctions (NMJs). Previous studies suggest that aging is accompanied by increases in cholinergic activity at the NMJ, which may play a role in neuromuscular degeneration. In this study, we hypothesized that moderately and chronically reducing ACh could attenuate the deleterious effects of aging on NMJs and skeletal muscles. To test this hypothesis, we analyzed NMJs and muscle fibers from heterozygous transgenic mice with reduced expression of the vesicular ACh transporter (VAChT; VKDHet), which present with approximately 30% less synaptic ACh compared to control mice. Because ACh is constitutively decreased in VKDHet, we first analyzed developing NMJs and muscle fibers. We found no obvious morphological or molecular differences between NMJs and muscle fibers of VKDHet and control mice during development. In contrast, we found that moderately reducing ACh has various effects on adult NMJs and muscle fibers. VKDHet mice have significantly larger NMJs and muscle fibers compared to age-matched control mice. They also present with reduced expression of the pro-atrophy gene, Foxo1, and have more satellite cells in skeletal muscles. These molecular and cellular features may partially explain the increased size of NMJs and muscle fibers. Thus, moderately reducing ACh may be a therapeutic strategy to prevent the loss of skeletal muscle mass that occurs with advancing age.
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Affiliation(s)
- Sydney K Vaughan
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, United States.,Fralin Biomedical Research Institute, Virginia Tech Carilion, Roanoke, VA, United States.,Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA, United States
| | - Natalia M Sutherland
- Fralin Biomedical Research Institute, Virginia Tech Carilion, Roanoke, VA, United States
| | - Gregorio Valdez
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, United States.,Fralin Biomedical Research Institute, Virginia Tech Carilion, Roanoke, VA, United States.,Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
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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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Sugita S, Fleming LL, Wood C, Vaughan SK, Gomes MPSM, Camargo W, Naves LA, Prado VF, Prado MAM, Guatimosim C, Valdez G. VAChT overexpression increases acetylcholine at the synaptic cleft and accelerates aging of neuromuscular junctions. Skelet Muscle 2016; 6:31. [PMID: 27713817 PMCID: PMC5050580 DOI: 10.1186/s13395-016-0105-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 08/26/2016] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Cholinergic dysfunction occurs during aging and in a variety of diseases, including amyotrophic lateral sclerosis (ALS). However, it remains unknown whether changes in cholinergic transmission contributes to age- and disease-related degeneration of the motor system. Here we investigated the effect of moderately increasing levels of synaptic acetylcholine (ACh) on the neuromuscular junction (NMJ), muscle fibers, and motor neurons during development and aging and in a mouse model for amyotrophic lateral sclerosis (ALS). METHODS Chat-ChR2-EYFP (VAChTHyp) mice containing multiple copies of the vesicular acetylcholine transporter (VAChT), mutant superoxide dismutase 1 (SOD1G93A), and Chat-IRES-Cre and tdTomato transgenic mice were used in this study. NMJs, muscle fibers, and α-motor neurons' somata and their axons were examined using a light microscope. Transcripts for select genes in muscles and spinal cords were assessed using real-time quantitative PCR. Motor function tests were carried out using an inverted wire mesh and a rotarod. Electrophysiological recordings were collected to examine miniature endplate potentials (MEPP) in muscles. RESULTS We show that VAChT is elevated in the spinal cord and at NMJs of VAChTHyp mice. We also show that the amplitude of MEPPs is significantly higher in VAChTHyp muscles, indicating that more ACh is loaded into synaptic vesicles and released into the synaptic cleft at NMJs of VAChTHyp mice compared to control mice. While the development of NMJs was not affected in VAChTHyp mice, NMJs prematurely acquired age-related structural alterations in adult VAChTHyp mice. These structural changes at NMJs were accompanied by motor deficits in VAChTHyp mice. However, cellular features of muscle fibers and levels of molecules with critical functions at the NMJ and in muscle fibers were largely unchanged in VAChTHyp mice. In the SOD1G93A mouse model for ALS, increasing synaptic ACh accelerated degeneration of NMJs caused motor deficits and resulted in premature death specifically in male mice. CONCLUSIONS The data presented in this manuscript demonstrate that increasing levels of ACh at the synaptic cleft promote degeneration of adult NMJs, contributing to age- and disease-related motor deficits. We thus propose that maintaining normal cholinergic signaling in muscles will slow degeneration of NMJs and attenuate loss of motor function caused by aging and neuromuscular diseases.
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Affiliation(s)
- Satoshi Sugita
- Virginia Tech Carilion Research Institute, Virginia Tech, Roanoke, VA USA
| | - Leland L. Fleming
- Virginia Tech Carilion Research Institute, Virginia Tech, Roanoke, VA USA
- Virginia Tech Postbaccalaureate Research and Education (VT PREP) Scholar, Virginia Tech, Blacksburg, VA USA
| | - Caleb Wood
- Virginia Tech Carilion Research Institute, Virginia Tech, Roanoke, VA USA
| | - Sydney K. Vaughan
- Virginia Tech Carilion Research Institute, Virginia Tech, Roanoke, VA USA
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA USA
| | - Matheus P. S. M. Gomes
- Departamento de Morfologia, Instiuto Ciencias Biologicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais Brazil
| | - Wallace Camargo
- Departamento de Fisiologia e Biofísica, Instiuto Ciencias Biologicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais Brazil
| | - Ligia A. Naves
- Departamento de Fisiologia e Biofísica, Instiuto Ciencias Biologicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais Brazil
| | - Vania F. Prado
- Robarts Research Institute, Department of Physiology and Pharmacology, Department of Anatomy & Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON N6A5K8 Canada
| | - Marco A. M. Prado
- Robarts Research Institute, Department of Physiology and Pharmacology, Department of Anatomy & Cell Biology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON N6A5K8 Canada
| | - Cristina Guatimosim
- Departamento de Morfologia, Instiuto Ciencias Biologicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais Brazil
| | - Gregorio Valdez
- Virginia Tech Carilion Research Institute, Virginia Tech, Roanoke, VA USA
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA USA
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Structural correlates of affinity in fetal versus adult endplate nicotinic receptors. Nat Commun 2016; 7:11352. [PMID: 27101778 PMCID: PMC4845029 DOI: 10.1038/ncomms11352] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 03/17/2016] [Indexed: 11/24/2022] Open
Abstract
Adult-type nicotinic acetylcholine receptors (AChRs) mediate signalling at mature neuromuscular junctions and fetal-type AChRs are necessary for proper synapse development. Each AChR has two neurotransmitter binding sites located at the interface of a principal and a complementary subunit. Although all agonist binding sites have the same core of five aromatic amino acids, the fetal site has ∼30-fold higher affinity for the neurotransmitter ACh. Here we use molecular dynamics simulations of adult versus fetal homology models to identify complementary-subunit residues near the core that influence affinity, and use single-channel electrophysiology to corroborate the results. Four residues in combination determine adult versus fetal affinity. Simulations suggest that at lower-affinity sites, one of these unsettles the core directly and the others (in loop E) increase backbone flexibility to unlock a key, complementary tryptophan from the core. Swapping only four amino acids is necessary and sufficient to exchange function between adult and fetal AChRs. Adult and fetal nicotinic acetylcholine receptors (AChRs) have different functional requirements and affinity for ACh. Here, the authors use molecular dynamics and electrophysiology to investigate this affinity, and identify four amino acids that when swapped exchange function between adult and fetal AChRs.
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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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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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Wilbe M, Ekvall S, Eurenius K, Ericson K, Casar-Borota O, Klar J, Dahl N, Ameur A, Annerén G, Bondeson ML. MuSK: a new target for lethal fetal akinesia deformation sequence (FADS). J Med Genet 2015; 52:195-202. [PMID: 25612909 DOI: 10.1136/jmedgenet-2014-102730] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
BACKGROUND Fetal akinesia deformation sequence syndrome (FADS, OMIM 208150) is characterised by decreased fetal movement (fetal akinesia) as well as intrauterine growth restriction, arthrogryposis, and developmental anomalies (eg, cystic hygroma, pulmonary hypoplasia, cleft palate, and cryptorchidism). Mutations in components of the acetylcholine receptor (AChR) pathway have previously been associated with FADS. METHODS AND RESULTS We report on a family with recurrent fetal loss, where the parents had five affected fetuses/children with FADS and one healthy child. The fetuses displayed no fetal movements from the gestational age of 17 weeks, extended knee joints, flexed hips and elbows, and clenched hands. Whole exome sequencing of one affected fetus and the parents was performed. A novel homozygous frameshift mutation was identified in muscle, skeletal receptor tyrosine kinase (MuSK), c.40dupA, which segregated with FADS in the family. Haplotype analysis revealed a conserved haplotype block suggesting a founder mutation. MuSK (muscle-specific tyrosine kinase receptor), a component of the AChR pathway, is a main regulator of neuromuscular junction formation and maintenance. Missense mutations in MuSK have previously been reported to cause congenital myasthenic syndrome (CMS) associated with AChR deficiency. CONCLUSIONS To our knowledge, this is the first report showing that a mutation in MuSK is associated with FADS. The results support previous findings that CMS and/or FADS are caused by complete or severe functional disruption of components located in the AChR pathway. We propose that whereas milder mutations of MuSK will cause a CMS phenotype, a complete loss is lethal and will cause FADS.
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Affiliation(s)
- Maria Wilbe
- Science for Life Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Sara Ekvall
- Science for Life Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Karin Eurenius
- Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden
| | - Katharina Ericson
- Science for Life Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden Department of Pathology and Cytology, Uppsala University Hospital, Uppsala, Sweden
| | - Olivera Casar-Borota
- Science for Life Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden Department of Pathology and Cytology, Uppsala University Hospital, Uppsala, Sweden
| | - Joakim Klar
- Science for Life Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Niklas Dahl
- Science for Life Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Adam Ameur
- Science for Life Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Göran Annerén
- Science for Life Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Marie-Louise Bondeson
- Science for Life Laboratory, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
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Kask K, Ruisu K, Tikker L, Karis K, Saare M, Meier R, Karis A, Tõnissoo T, Pooga M. Deletion of RIC8A in neural precursor cells leads to altered neurogenesis and neonatal lethality of mouse. Dev Neurobiol 2015; 75:984-1002. [DOI: 10.1002/dneu.22264] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 12/10/2014] [Accepted: 12/29/2014] [Indexed: 12/14/2022]
Affiliation(s)
- Keiu Kask
- Department of Developmental Biology; Institute of Molecular and Cell Biology, University of Tartu; 23 Riia St., Tartu 51010 Estonia
| | - Katrin Ruisu
- Department of Developmental Biology; Institute of Molecular and Cell Biology, University of Tartu; 23 Riia St., Tartu 51010 Estonia
| | - Laura Tikker
- Department of Developmental Biology; Institute of Molecular and Cell Biology, University of Tartu; 23 Riia St., Tartu 51010 Estonia
| | - Kirstin Karis
- Department of Developmental Biology; Institute of Molecular and Cell Biology, University of Tartu; 23 Riia St., Tartu 51010 Estonia
| | - Merly Saare
- Department of Developmental Biology; Institute of Molecular and Cell Biology, University of Tartu; 23 Riia St., Tartu 51010 Estonia
| | - Riho Meier
- Department of Developmental Biology; Institute of Molecular and Cell Biology, University of Tartu; 23 Riia St., Tartu 51010 Estonia
| | - Alar Karis
- Department of Developmental Biology; Institute of Molecular and Cell Biology, University of Tartu; 23 Riia St., Tartu 51010 Estonia
| | - Tambet Tõnissoo
- Department of Developmental Biology; Institute of Molecular and Cell Biology, University of Tartu; 23 Riia St., Tartu 51010 Estonia
| | - Margus Pooga
- Department of Developmental Biology; Institute of Molecular and Cell Biology, University of Tartu; 23 Riia St., Tartu 51010 Estonia
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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: 36] [Impact Index Per Article: 3.6] [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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Functional differences between neurotransmitter binding sites of muscle acetylcholine receptors. Proc Natl Acad Sci U S A 2014; 111:17660-5. [PMID: 25422413 DOI: 10.1073/pnas.1414378111] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A muscle acetylcholine receptor (AChR) has two neurotransmitter binding sites located in the extracellular domain, at αδ and either αε (adult) or αγ (fetal) subunit interfaces. We used single-channel electrophysiology to measure the effects of mutations of five conserved aromatic residues at each site with regard to their contribution to the difference in free energy of agonist binding to active versus resting receptors (ΔGB1). The two binding sites behave independently in both adult and fetal AChRs. For four different agonists, including ACh and choline, ΔGB1 is ∼-2 kcal/mol more favorable at αγ compared with at αε and αδ. Only three of the aromatics contribute significantly to ΔGB1 at the adult sites (αY190, αY198, and αW149), but all five do so at αγ (as well as αY93 and γW55). γW55 makes a particularly large contribution only at αγ that is coupled energetically to those contributions of some of the α-subunit aromatics. The hydroxyl and benzene groups of loop C residues αY190 and αY198 behave similarly with regard to ΔGB1 at all three kinds of site. ACh binding energies estimated from molecular dynamics simulations are consistent with experimental values from electrophysiology and suggest that the αγ site is more compact, better organized, and less dynamic than αε and αδ. We speculate that the different sensitivities of the fetal αγ site versus the adult αε and αδ sites to choline and ACh are important for the proper maturation and function of the neuromuscular synapse.
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17
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Ellis-Hutchings RG, Rasoulpour RJ, Terry C, Carney EW, Billington R. Human relevance framework evaluation of a novel rat developmental toxicity mode of action induced by sulfoxaflor. Crit Rev Toxicol 2014; 44 Suppl 2:45-62. [DOI: 10.3109/10408444.2014.910752] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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18
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Robinson KG, Viereck MJ, Margiotta MV, Gripp KW, Abdul-Rahman OA, Akins RE. Neuromotor synapses in Escobar syndrome. Am J Med Genet A 2013; 161A:3042-8. [PMID: 24038971 DOI: 10.1002/ajmg.a.36154] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 06/10/2013] [Indexed: 11/10/2022]
Abstract
The Escobar variant of multiple pterygium syndrome (OMIM #265000) is a rare, autosomal recessive disorder associated with mutations in the γ-subunit of the nicotinic acetylcholine receptor (CHRNG). CHRNG is expressed in fetal muscle during motor development and contributes to the formation of neuromuscular junctions (NMJs). Anomalies in NMJ structure and function have not been investigated in patients with Escobar syndrome. We report five patients identified as having Escobar syndrome, from four families. In three families, the same mutation (c.459dupA) was identified in CHRNG. A biopsy from brachioradialis muscle was collected from a patient from one of these families and analyzed for NMJ organization using fluorescence microscopy. Compared to spinalis muscle from control patients with idiopathic scoliosis or cerebral palsy (CP), the patient with Escobar syndrome had a significantly higher degree of acetylcholine receptor present outside acetylcholinesterase and significantly less acetylcholinesterase outside acetylcholine receptors. Given the role of the acetylcholine receptor γ-subunit in fetal neuromuscular signal transduction and in establishing the primary encounter of muscle and motor nerve terminal, the CHRNG mutations described in Escobar syndrome may cause a broader disruption of postsynaptic proteins and result in aberrant development of the NMJ due to impaired prenatal neuromuscular transmission and/or abnormal neuromuscular synaptogenesis.
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Affiliation(s)
- Karyn G Robinson
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, Delaware
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19
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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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20
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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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21
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Postnatal changes in vagal control of esophageal muscle contractions in rats. Life Sci 2012; 90:495-501. [PMID: 22285836 DOI: 10.1016/j.lfs.2012.01.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2011] [Revised: 12/21/2011] [Accepted: 01/09/2012] [Indexed: 12/23/2022]
Abstract
AIMS Replacement of smooth muscles by striated muscles occurs in the esophagus during the early postnatal period. The aim of this study was to clarify postnatal changes in vagal control of esophageal muscle contractions in rats. MAIN METHODS An isolated segment of the neonatal rat esophagus was placed in an organ bath and the contractile responses were recorded using a force transducer. KEY FINDINGS Electrical stimulation of the vagus trunk evoked a biphasic contractile response in the neonatal esophageal segment. The first and second components of the contractions were inhibited by α-bungarotoxin and atropine, respectively. Ganglion blockers, hexamethonium and mecamylamine, did not affect vagally mediated contractions. The first component gradually enlarged with age in days, whereas the second component declined during the first week after birth. Application of d-tubocurarine or acetylcholine caused an apparent contraction in the esophageal striated muscle at postnatal day 0, but responses to these drugs were not observed at 1 week after birth. The neonatal esophagus expressed the γ-subunit of nicotinic acetylcholine receptors. In contrast, the ε-subunit was dominantly expressed in the adult esophagus. SIGNIFICANCE The vagus nerves directly innervate both the esophageal striated muscles and smooth muscles in the early neonatal period. During the process of muscle rearrangement, the property of the striated muscles is altered substantially. The specific features of striated muscles in the neonatal rat esophagus might compensate for immature formation of neuromuscular junctions. Unsuccessful conversion of the striated muscle property during postnatal muscle rearrangement would be related to disorders of esophageal motility.
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22
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Acetylcholine negatively regulates development of the neuromuscular junction through distinct cellular mechanisms. Proc Natl Acad Sci U S A 2010; 107:10702-7. [PMID: 20498043 DOI: 10.1073/pnas.1004956107] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Emerging evidence suggests that the neurotransmitter acetylcholine (ACh) negatively regulates the development of the neuromuscular junction, but it is not clear if ACh exerts its effects exclusively through muscle ACh receptors (AChRs). Here, we used genetic methods to remove AChRs selectively from muscle. Similar to the effects of blocking ACh biosynthesis, eliminating postsynaptic AChRs increased motor axon branching and expanded innervation territory, suggesting that ACh negatively regulates synaptic growth through postsynaptic AChRs. However, in contrast to the effects of blocking ACh biosynthesis, eliminating postsynaptic AChRs in agrin-deficient mice failed to restore deficits in pre- and postsynaptic differentiation, suggesting that ACh negatively regulates synaptic differentiation through nonpostsynaptic receptors. Consistent with this idea, the ACh agonist carbachol inhibited presynaptic specialization of motorneurons in vitro. Together, these data suggest that ACh negatively regulates axon growth and presynaptic specialization at the neuromuscular junction through distinct cellular mechanisms.
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23
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Ten Broek RW, Grefte S, Von den Hoff JW. Regulatory factors and cell populations involved in skeletal muscle regeneration. J Cell Physiol 2010; 224:7-16. [PMID: 20232319 DOI: 10.1002/jcp.22127] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Skeletal muscle regeneration is a complex process, which is not yet completely understood. Satellite cells, the skeletal muscle stem cells, become activated after trauma, proliferate, and migrate to the site of injury. Depending on the severity of the myotrauma, activated satellite cells form new multinucleated myofibers or fuse to damaged myofibers. The specific microenvironment of the satellite cells, the niche, controls their behavior. The niche contains several components that maintain satellite cells quiescence until they are activated. In addition, a great diversity of stimulatory and inhibitory growth factors such as IGF-1 and TGF-beta1 regulate their activity. Donor-derived satellite cells are able to improve muscle regeneration, but their migration through the muscle tissue and across endothelial layers is limited. Less than 1% of their progeny, the myoblasts, survive the first days upon intra-muscular injection. However, a range of other multipotent muscle- and non-muscle-derived stem cells are involved in skeletal muscle regeneration. These stem cells can occupy the satellite cell niche and show great potential for the treatment of skeletal muscle injuries and diseases. The aim of this review is to discuss the niche factors, growth factors, and other stem cells, which are involved in skeletal muscle regeneration. Knowledge about the factors regulating satellite cell activity and skeletal muscle regeneration can be used to improve the treatment of muscle injuries and diseases.
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Affiliation(s)
- Roel W Ten Broek
- Department of Orthodontics and Oral Biology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
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Yampolsky P, Pacifici PG, Witzemann V. Differential muscle-driven synaptic remodeling in the neuromuscular junction after denervation. Eur J Neurosci 2010; 31:646-58. [DOI: 10.1111/j.1460-9568.2010.07096.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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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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Turgeon B, Meloche S. Interpreting neonatal lethal phenotypes in mouse mutants: insights into gene function and human diseases. Physiol Rev 2009; 89:1-26. [PMID: 19126753 DOI: 10.1152/physrev.00040.2007] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The mouse represents the model of choice to study the biological function of mammalian genes through mutation of its genome. However, the biggest challenge of mouse geneticists remains the phenotypic analysis of mouse mutants. A survey of mouse mutant databases reveals a surprisingly high number of gene mutations leading to neonatal death. These genetically modified mouse mutants have been instrumental in elucidating gene function and have become important models of congenital human diseases. The main complication when phenotyping mutant mice dying during the neonatal period is the large spectrum of physiological systems whose defects can challenge neonatal survival. Here, we present a comprehensive review of gene mutations leading to neonatal lethality and discuss the impact of these mutations on the major physiological processes critical to mouse newborn survival: parturition, breathing, suckling, and homeostasis. Selected examples of mouse mutants are highlighted to illustrate how the precise identification of the timing and cause of death associated with these physiological processes allows for a more profound understanding of the underlying cellular and molecular defects. This review provides a guide for the analysis of neonatal lethal phenotypes in mutant mice that will be helpful for dissecting out the function of specific genes during mouse development.
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Affiliation(s)
- Benjamin Turgeon
- Department of Pharmacology and Molecular Biology, Université de Montréal, Montreal, Quebec, Canada
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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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The role of nerve- versus muscle-derived factors in mammalian neuromuscular junction formation. J Neurosci 2008; 28:3333-40. [PMID: 18367600 DOI: 10.1523/jneurosci.5590-07.2008] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neuromuscular junctions (NMJs) normally form in the central region of developing muscle. In this process, agrin released from motor neurons has been considered to initiate the formation of synaptic acetylcholine receptor (AChR) clusters (neurocentric model). However, in muscle developing in the absence of nerves and thus of agrin, AChR clusters still form in the muscle center. This raises the possibility that the region of NMJ formation is determined by muscle-derived cues that spatially restrict the nerve to form synapses from aneural AChR clusters, e.g., by patterned expression of the agrin receptor MuSK (muscle-specific kinase) (myocentric model). Here we examine at initial stages of synaptogenesis whether the responsiveness of myotubes to agrin is spatially restricted, whether the regions of NMJ formation in wild-type muscle and of aneural AChR cluster formation in agrin-deficient animals correlate, and whether AChR cluster growth depends on the presence of agrin. We show that primary myotubes form AChR clusters in response to exogenous agrin in their central region only, a pattern that can spatially restrict NMJ formation. However, the nerve also makes synapses in regions in which aneural AChR clusters do not form, and agrin promotes synaptic cluster growth from the first stages of neuromuscular contact formation. These data indicate that aneural AChR clusters per se are not required for NMJ formation. A model is proposed that explains either the neurocentric or the myocentric mode of NMJ formation depending on a balance between the levels of MuSK expression and the availability of nerve-released agrin.
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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: 44] [Impact Index Per Article: 2.8] [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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32
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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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Vogt J, Harrison BJ, Spearman H, Cossins J, Vermeer S, ten Cate LN, Morgan NV, Beeson D, Maher ER. Mutation analysis of CHRNA1, CHRNB1, CHRND, and RAPSN genes in multiple pterygium syndrome/fetal akinesia patients. Am J Hum Genet 2008; 82:222-7. [PMID: 18179903 DOI: 10.1016/j.ajhg.2007.09.016] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Revised: 09/06/2007] [Accepted: 09/12/2007] [Indexed: 01/12/2023] Open
Abstract
Multiple pterygium syndromes (MPS) comprise a group of multiple congenital anomaly disorders characterized by webbing (pterygia) of the neck, elbows, and/or knees and joint contractures (arthrogryposis). MPS are phenotypically and genetically heterogeneous but are traditionally divided into prenatally lethal and nonlethal (Escobar) types. Previously, we and others reported that recessive mutations in the embryonal acetylcholine receptor g subunit (CHRNG) can cause both lethal and nonlethal MPS, thus demonstrating that pterygia resulted from fetal akinesia. We hypothesized that mutations in acetylcholine receptor-related genes might also result in a MPS/fetal akinesia phenotype and so we analyzed 15 cases of lethal MPS/fetal akinesia without CHRNG mutations for mutations in the CHRNA1, CHRNB1, CHRND, and rapsyn (RAPSN) genes. No CHRNA1, CHRNB1, or CHRND mutations were detected, but a homozygous RAPSN frameshift mutation, c.1177-1178delAA, was identified in a family with three children affected with lethal fetal akinesia sequence. Previously, RAPSN mutations have been reported in congenital myasthenia. Functional studies were consistent with the hypothesis that whereas incomplete loss of rapsyn function may cause congenital myasthenia, more severe loss of function can result in a lethal fetal akinesia phenotype.
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Affiliation(s)
- Julie Vogt
- Department of Medical and Molecular Genetics and WellChild Paediatric Research Centre, Division of Reproductive and Child Health, University of Birmingham, Birmingham B15 2TT, UK
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34
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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: 216] [Impact Index Per Article: 12.7] [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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35
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Steinlein OK. Genetic disorders caused by mutated acetylcholine receptors. Life Sci 2007; 80:2186-90. [PMID: 17434185 DOI: 10.1016/j.lfs.2007.03.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2006] [Revised: 02/20/2007] [Accepted: 03/13/2007] [Indexed: 10/23/2022]
Abstract
The nicotinic acetylcholine receptors (nAChRs) are members of the large family of ligand-gated ion channels and are constituted by the assembly of five subunits arranged pseudosymmetrically around the central axis that forms a cation-selective ion pore. They are widely distributed in both the nervous system and non-neuronal tissues, and can be activated by endogenous agonists such as acetylcholine or exogenous ligands such as nicotine. Mutations in neuronal nAChRs are found in a rare form of familial nocturnal frontal lobe epilepsy (ADNFLE), while mutations in the neuromuscular subtype of the nAChR are responsible for either congenital myasthenia syndromes (adult subtype of neuromuscular nAChR) or a form of arthrogryposis multiplex congenita type Escobar (fetal subtype of neuromuscular nAChR).
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Affiliation(s)
- Ortrud K Steinlein
- Institute of Human Genetics, University Hospital, Ludwig-Maximillians-University, Goethestr. 29, 80336 Munich, Germany.
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36
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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: 110] [Impact Index Per Article: 6.1] [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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37
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Morgan NV, Brueton LA, Cox P, Greally MT, Tolmie J, Pasha S, Aligianis IA, van Bokhoven H, Marton T, Al-Gazali L, Morton JEV, Oley C, Johnson CA, Trembath RC, Brunner HG, Maher ER. Mutations in the embryonal subunit of the acetylcholine receptor (CHRNG) cause lethal and Escobar variants of multiple pterygium syndrome. Am J Hum Genet 2006; 79:390-5. [PMID: 16826531 PMCID: PMC1559492 DOI: 10.1086/506256] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Accepted: 05/16/2006] [Indexed: 01/24/2023] Open
Abstract
Multiple pterygium syndromes (MPSs) comprise a group of multiple-congenital-anomaly disorders characterized by webbing (pterygia) of the neck, elbows, and/or knees and joint contractures (arthrogryposis). In addition, a variety of developmental defects (e.g., vertebral anomalies) may occur. MPSs are phenotypically and genetically heterogeneous but are traditionally divided into prenatally lethal and nonlethal (Escobar) types. To elucidate the pathogenesis of MPS, we undertook a genomewide linkage scan of a large consanguineous family and mapped a locus to 2q36-37. We then identified germline-inactivating mutations in the embryonal acetylcholine receptor gamma subunit (CHRNG) in families with both lethal and nonlethal MPSs. These findings extend the role of acetylcholine receptor dysfunction in human disease and provide new insights into the pathogenesis and management of fetal akinesia syndromes.
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Affiliation(s)
- Neil V Morgan
- Section of Medical and Molecular Genetics, University of Birmingham, Institute of Biomedical Research, Edgbaston, Birmingham, B15 2TT, UK
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38
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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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39
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de Jonge HW, van der Wiel CW, Eizema K, Weijs WA, Everts ME. Presence of SERCA and calcineurin during fetal development of porcine skeletal muscle. J Histochem Cytochem 2006; 54:641-8. [PMID: 16714421 DOI: 10.1369/jhc.5a6812.2006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Mechanisms involved in skeletal myofiber differentiation during fetal development of large animals are poorly understood. Studies in small animals suggest that the calcineurin (Cn) pathway is involved in myofiber differentiation. Neural activity is a prerequisite for Cn activity, implying maintenance of sustained low intracellular Ca(2+) concentrations. To study the role of Cn in fetal myofiber differentiation, we monitored the temporal and spatial distribution of Cn subunits, sarcoplasmic reticulum Ca(2+) ATPase (SERCA), phospholamban (PLB), and myosin heavy chain (MyHC) isoforms in relation to ingrowing nerves in porcine semitendinosus muscle (m. semitendinosus) at 55 and 75 days of gestation (dg) and at term. Immunofluorescence analysis revealed the presence of Cn subunits and SERCA isoforms at all analyzed stages. Cn distribution was not fiber-type specific, but expression became more prominent at term. At 75 dg, differential SERCA2 expression was accompanied by perinuclear PLB in primary fibers. SERCA1 was expressed in all fiber types at all stages. No specific MyHC isoform distribution was seen in relation to neuromuscular contacts, although neuromuscular contacts were present. From these results we speculate that in porcine m. semitendinosus differential SERCA2 expression precedes differential Cn expression. The question whether the Cn pathway is involved in prenatal myofiber differentiation needs further studies.
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Affiliation(s)
- Henriëtte W de Jonge
- Division of Anatomy and Physiology, Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, PO Box 80.158, NL-3508 TD, Utrecht, The Netherlands.
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Koenen M, Peter C, Villarroel A, Witzemann V, Sakmann B. Acetylcholine receptor channel subtype directs the innervation pattern of skeletal muscle. EMBO Rep 2005; 6:570-6. [PMID: 15905852 PMCID: PMC1369094 DOI: 10.1038/sj.embor.7400429] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2004] [Accepted: 04/15/2005] [Indexed: 11/08/2022] Open
Abstract
Acetylcholine receptors (AChRs) mediate synaptic transmission at the neuromuscular junction, and structural and functional analysis has assigned distinct functions to the fetal (alpha2beta(gamma)delta) and adult types of AChR (alpha2beta(epsilon)delta). Mice lacking the epsilon-subunit gene die prematurely, showing that the adult type is essential for maintenance of neuromuscular synapses in adult muscle. It has been suggested that the fetally and neonatally expressed AChRs are crucial for muscle differentiation and for the formation of the neuromuscular synapses. Here, we show that substitution of the fetal-type AChR with an adult-type AChR preserves myoblast fusion, muscle and end-plate differentiation, whereas it substantially alters the innervation pattern of muscle by the motor nerve. Mutant mice form functional neuromuscular synapses outside the central, narrow end-plate band region in the diaphragm, with synapses scattered over a wider muscle territory. We suggest that one function of the fetal type of AChR is to ensure an orderly innervation pattern of skeletal muscle.
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Affiliation(s)
- Michael Koenen
- Abteilung Zellphysiologie, Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany.
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Ono F, Mandel G, Brehm P. Acetylcholine receptors direct rapsyn clusters to the neuromuscular synapse in zebrafish. J Neurosci 2004; 24:5475-81. [PMID: 15201319 PMCID: PMC6729331 DOI: 10.1523/jneurosci.0851-04.2004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Clustering of nicotinic muscle acetylcholine receptors (AChRs) requires association with intracellular rapsyn, a protein with an intrinsic ability to self-cluster. Previous studies on sofa potato (sop), an AChR null line of zebrafish, have suggested that AChRs may play an active role in subsynaptic localization of rapsyn clusters. To test this proposal directly, we identified and cloned the gene responsible for the sop phenotype and then attempted to rescue subsynaptic localization of the receptor-rapsyn complex in mutant fish. sop contains a leucine to proline mutation at position 28, near the N terminus of the zebrafish AChR delta subunit. Transient expression of mutant delta subunit in sop fish was unable to restore surface expression of muscle AChRs. In contrast, expression of wild-type delta subunit restored the ability of muscle to assemble surface receptors along with the ability of fish to swim. Most importantly, the ability of rapsyn clusters to localize effectively to subsynaptic sites also was rescued in large part. Our results point to direct involvement of the AChR molecule in restricting receptor-rapsyn clusters to the synapse.
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Affiliation(s)
- Fumihito Ono
- The Whitney Laboratory, University of Florida, St. Augustine, Florida 32080, USA.
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Cossins J, Webster R, Maxwell S, Burke G, Vincent A, Beeson D. A mouse model of AChR deficiency syndrome with a phenotype reflecting the human condition. Hum Mol Genet 2004; 13:2947-57. [PMID: 15471888 DOI: 10.1093/hmg/ddh320] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The two subtypes of mammalian muscle nicotinic acetylcholine receptors (AChR) are generated by the substitution of the epsilon (adult) subunit for the gamma (fetal) subunit within the AChR pentamer. Null mutations of the adult AChR epsilon-subunit gene are the most common cause of the AChR deficiency syndrome. This is a disorder of neuromuscular transmission characterized by non-progressive fatigable muscle weakness present throughout life. In contrast with the human disorder, mice with AChR epsilon-subunit null mutations die between 10 and 14 weeks of age. We generated transgenic mice that constitutively express the human AChR gamma-subunit in an AChR epsilon-subunit 'knock-out' background. These mice, in which neuromuscular transmission is mediated by fetal AChR, live well into adult life but show striking similarities to human AChR deficiency syndrome. They display fatigable muscle weakness, reduced miniature endplate potentials and endplate potentials, reduced motor endplate AChR number and altered endplate morphology. Our results illustrate how species differences in the control of ion-channel gene expression may affect disease phenotype, demonstrate that expression of adult AChR subtype is not essential for long-term survival, and suggest that in patients with AChR deficiency syndrome, up-regulation of the gamma-subunit could be a beneficial therapeutic strategy.
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Affiliation(s)
- Judy Cossins
- Neuroscience Group, Weatherall Institute of Molecular Medicine, The John Radcliffe, Oxford, UK
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