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Murtazina A, Borovikov A, Marakhonov A, Sharkov A, Sharkova I, Mirzoyan A, Kulikova S, Ganieva R, Zabnenkova V, Ryzhkova O, Nikitin S, Dadali E, Kutsev S. Mild phenotype of CHAT-associated congenital myasthenic syndrome: case series. Front Pediatr 2024; 12:1280394. [PMID: 38304750 PMCID: PMC10830679 DOI: 10.3389/fped.2024.1280394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Accepted: 01/02/2024] [Indexed: 02/03/2024] Open
Abstract
Congenital myasthenic syndrome with episodic apnea is associated with pathogenic variants in the CHAT gene. While respiratory disorders and oculomotor findings are commonly reported in affected individuals, a subset of patients only present with muscle weakness and/or ptosis but not apneic crises. In this case series, we describe five individuals with exercise intolerance caused by single nucleotide variants in the CHAT gene. The age of onset ranged from 1 to 2.5 years, and all patients exhibited a fluctuating course of congenital myasthenic syndrome without disease progression over several years. Notably, these patients maintained a normal neurological status, except for the presence of abnormal fatigability in their leg muscles following prolonged physical activity. We conducted a modified protocol of repetitive nerve stimulation on the peroneal nerve, revealing an increased decrement in amplitude and area of compound muscle action potentials of the tibialis anterior muscle after 15-20 min of exercise. Treatment with 3,4-diaminopyridine showed clear improvement in two children, while one patient experienced severe adverse effects and is currently receiving a combination of Salbutamol Syrup and pyridostigmine with slight positive effects. Based on our findings and previous cases of early childhood onset with muscle fatigability as the sole manifestation, we propose the existence of a mild phenotype characterized by the absence of apneic episodes.
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Affiliation(s)
| | | | | | - Artem Sharkov
- Veltischev Research and Clinical Institute for Pediatrics of the Pirogov Russian National Research Medical University, Moscow, Russia
- Genomed Ltd., Moscow, Russia
| | - Inna Sharkova
- Research Centre for Medical Genetics, Moscow, Russia
| | - Alena Mirzoyan
- Republican Research and Clinical Center of Neurology and Neurosurgery, Minsk, Belarus
| | - Sviatlana Kulikova
- Republican Research and Clinical Center of Neurology and Neurosurgery, Minsk, Belarus
| | | | | | | | | | - Elena Dadali
- Research Centre for Medical Genetics, Moscow, Russia
| | - Sergey Kutsev
- Research Centre for Medical Genetics, Moscow, Russia
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2
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Younger DS. Neonatal and infantile hypotonia. HANDBOOK OF CLINICAL NEUROLOGY 2023; 195:401-423. [PMID: 37562880 DOI: 10.1016/b978-0-323-98818-6.00011-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
The underlying etiology of neonatal and infantile hypotonia can be divided into primary peripheral and central nervous system and acquired or genetic disorders. The approach to identifying the likeliest cause of hypotonia begins with a bedside assessment followed by a careful review of the birth history and early development and family pedigree and obtaining available genetic studies and age- and disease-appropriate laboratory investigations. Until about a decade ago, the main goal was to identify the clinical signs and a battery of basic investigations including electrophysiology to confirm or exclude a given neuromuscular disorder, however the availability of whole-exome sequencing and next generation sequencing and transcriptome sequencing has simplified the identification of specific underlying genetic defect and improved the accuracy of diagnosis in many related Mendelian disorders.
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Affiliation(s)
- David S Younger
- Department of Clinical Medicine and Neuroscience, CUNY School of Medicine, New York, NY, United States; Department of Medicine, Section of Internal Medicine and Neurology, White Plains Hospital, White Plains, NY, United States.
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3
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Cacabelos R. Pharmacogenetic considerations when prescribing cholinesterase inhibitors for the treatment of Alzheimer's disease. Expert Opin Drug Metab Toxicol 2020; 16:673-701. [PMID: 32520597 DOI: 10.1080/17425255.2020.1779700] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
INTRODUCTION Cholinergic dysfunction, demonstrated in the late 1970s and early 1980s, led to the introduction of acetylcholinesterase inhibitors (AChEIs) in 1993 (Tacrine) to enhance cholinergic neurotransmission as the first line of treatment against Alzheimer's disease (AD). The new generation of AChEIs, represented by Donepezil (1996), Galantamine (2001) and Rivastigmine (2002), is the only treatment for AD to date, together with Memantine (2003). AChEIs are not devoid of side-effects and their cost-effectiveness is limited. An option to optimize the correct use of AChEIs is the implementation of pharmacogenetics (PGx) in the clinical practice. AREAS COVERED (i) The cholinergic system in AD, (ii) principles of AD PGx, (iii) PGx of Donepezil, Galantamine, Rivastigmine, Huperzine and other treatments, and (iv) practical recommendations. EXPERT OPINION The most relevant genes influencing AChEI efficacy and safety are APOE and CYPs. APOE-4 carriers are the worst responders to AChEIs. With the exception of Rivastigmine (UGT2B7, BCHE-K), the other AChEIs are primarily metabolized via CYP2D6, CYP3A4, and UGT enzymes, with involvement of ABC transporters and cholinergic genes (CHAT, ACHE, BCHE, SLC5A7, SLC18A3, CHRNA7) in most ethnic groups. Defective variants may affect the clinical response to AChEIs. PGx geno-phenotyping is highly recommended prior to treatment.
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Affiliation(s)
- Ramón Cacabelos
- Department of Genomic Medicine, EuroEspes Biomedical Research Center, International Center of Neuroscience and Genomic Medicine , Bergondo, Corunna, Spain
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4
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Zhang Y, Cheng X, Luo C, Lei M, Mao F, Shi Z, Cao W, Zhang J, Zhang Q. Congenital Myasthenic Syndrome Caused by a Novel Hemizygous CHAT Mutation. Front Pediatr 2020; 8:185. [PMID: 32411636 PMCID: PMC7198756 DOI: 10.3389/fped.2020.00185] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 03/30/2020] [Indexed: 02/02/2023] Open
Abstract
Congenital myasthenic syndrome (CMS) is a neuromuscular transmission disorder caused by mutations in genes encoding neuromuscular junction proteins. CMS due to choline acetyltransferase (CHAT) gene mutation is characterized by episodic apnoea. To date, 52 cases of CMS caused by CHAT gene mutations have been reported. Here, we report a neonate with the third hemizygous mutation [a 4.9 Mb deletion [10q11.22-10q11.23 (chr10: 46123781-51028772)] containing the whole CHAT gene and c.1976A>T (p.Gln659Leu in the CHAT gene)]. The c.1976A>T (p.Gln659Leu) variant had not been reported in the ExAC or gnomAD databases and was predicted to be pathogenic. The alignment of amino acid sequences revealed that glutamine at codon 659 is highly conserved in different species and causes structural changes in the substrate-binding site. Our female patient with neonate-onset CMS presented with apnoea, dyspnoea, feeding difficulties, weak crying, and seizure-like episodes, and her respiration was ventilator dependent. The prostigmine test was positive. This case may help to further elucidate clinical features and treatment methods in neonate-onset CMS caused by CHAT gene mutations.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Qian Zhang
- Neonatal Intensive Care Unit, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
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5
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Morey TM, Winick-Ng W, Seah C, Rylett RJ. Chaperone-Mediated Regulation of Choline Acetyltransferase Protein Stability and Activity by HSC/HSP70, HSP90, and p97/VCP. Front Mol Neurosci 2017; 10:415. [PMID: 29311808 PMCID: PMC5733026 DOI: 10.3389/fnmol.2017.00415] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 11/30/2017] [Indexed: 11/13/2022] Open
Abstract
Choline acetyltransferase (ChAT) synthesizes the neurotransmitter acetylcholine in cholinergic neurons, and mutations of this enzyme are linked to the neuromuscular disorder congenital myasthenic syndrome (CMS). One CMS-related mutation, V18M, reduces ChAT enzyme activity and cellular protein levels, and is located within a highly-conserved N-terminal proline-rich motif at residues 14PKLPVPP20. We showed previously that disruption of this proline-rich motif by either proline-to-alanine mutation (P17A/P19A) or mutation of residue Val18 (V18M) enhances ubiquitination and degradation of these mutant ChAT proteins expressed in cholinergic SN56 cells by an unknown mechanism. In this study, using proximity-dependent biotin identification (BioID), co-immunoprecipitation and in situ proximity-ligation assay (PLA), we identified the heat shock proteins (HSPs) HSC/HSP70 and HSP90 as novel ChAT protein-interactors. These molecular chaperones are well-known for promoting the folding and stabilization of cellular proteins. Thus, we found that inhibition of HSPs by treatment of cells with either the HSC/HSP70 inhibitors 2-phenylethynesulfonamide (PES) or VER-155008, or the HSP90 inhibitor 17-AAG reduced cellular ChAT activity and solubility, and enhanced the ubiquitination and proteasome-dependent loss of ChAT protein. Importantly, the effects of HSP inhibition were greater for mutant ChAT proteins (P17A/P19A-ChAT and CMS-related V18M- and A513T-ChAT) compared to wild-type ChAT. HSPs can promote ubiquitination and degradation of terminally misfolded proteins through cooperative interaction with the E3 ubiquitin ligase CHIP/Stub1, and while we show that ChAT interacts with CHIP in situ, siRNA-mediated knock-down of CHIP had no effect on either wild-type or mutant ChAT protein levels. However, inhibition of the endoplasmic reticulum (ER)- and HSP-associated co-chaperone p97/VCP prevented degradation of ubiquitinated ChAT. Together, these results identify novel mechanisms for the functional regulation of wild-type and CMS-related mutant ChAT by pro-stabilizing HSPs and the pro-degradative co-chaperone p97/VCP that may have broader implications for ChAT function during cellular stress and disease.
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Affiliation(s)
- Trevor M Morey
- Molecular Medicine Research Laboratories, Robarts Research Institute, University of Western Ontario, London, ON, Canada.,Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
| | - Warren Winick-Ng
- Molecular Medicine Research Laboratories, Robarts Research Institute, University of Western Ontario, London, ON, Canada.,Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada.,Epigenetic Regulation and Chromatin Architecture Group, Berlin Institute for Medical Systems Biology, Max-Delbrück Centre for Molecular Medicine, Berlin, Germany
| | - Claudia Seah
- Molecular Medicine Research Laboratories, Robarts Research Institute, University of Western Ontario, London, ON, Canada
| | - R Jane Rylett
- Molecular Medicine Research Laboratories, Robarts Research Institute, University of Western Ontario, London, ON, Canada.,Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, ON, Canada
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Schwartz M, Sternberg D, Whalen S, Afenjar A, Isapof A, Chabrol B, Portnoï MF, Heide S, Keren B, Chantot-Bastaraud S, Siffroi JP. How chromosomal deletions can unmask recessive mutations? Deletions in 10q11.2 associated with CHAT or SLC18A3 mutations lead to congenital myasthenic syndrome. Am J Med Genet A 2017; 176:151-155. [PMID: 29130637 DOI: 10.1002/ajmg.a.38515] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Revised: 09/24/2017] [Accepted: 09/26/2017] [Indexed: 11/06/2022]
Abstract
A congenital myasthenia was suspected in two unrelated children with very similar phenotypes including several episodes of severe dyspnea. Both children had a 10q11.2 deletion revealed by Single Nucleotide Polymorphisms array or by Next Generation Sequencing analysis. The deletion was inherited from the healthy mother in the first case. These deletions unmasked a recessive mutation at the same locus in both cases, but in two different genes: CHAT and SLC18A3.
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Affiliation(s)
- Mathias Schwartz
- AP-HP, Département de Génétique Médicale, Hôpital Armand Trousseau, UPMC, Paris, France
| | - Damien Sternberg
- AP-HP, Hôpital Pitié-Salpêtrière, Biochimie et Génétique, Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06 UMR S 1127, ICM, Paris, France
| | - Sandra Whalen
- AP-HP, Hôpital Armand Trousseau, UF de Génétique Clinique, UPMC, Paris, France
| | - Alexandra Afenjar
- AP-HP, Hôpital Armand Trousseau, UF de Génétique Clinique, UPMC, Paris, France
| | - Arnaud Isapof
- AP-HP, Hôpital Armand Trousseau, Unité de Neuropédiatrie et Pathologie du Développement, UPMC, Paris, France
| | - Brigitte Chabrol
- CHU de Marseille, Hôpital de la Timone, Service de Neurologie Pédiatrique, Inserm U1127, CNRS UMR 7225, UPMC, Centre de Recherche de l'Institut du Cerveau et de la Moëlle épinière, Paris, France
| | - Marie-France Portnoï
- AP-HP, Département de Génétique Médicale, Hôpital Armand Trousseau, UPMC, Paris, France
| | - Solveig Heide
- AP-HP, Département de Génétique Médicale, Hôpital Armand Trousseau, UPMC, Paris, France
| | - Boris Keren
- AP-HP, Département de Génétique, Hôpital de la Pitié Salpêtrière, Paris, France
| | | | - Jean-Pierre Siffroi
- AP-HP, Département de Génétique Médicale, Hôpital Armand Trousseau, UPMC, Paris, France
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7
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Pitt MC. Use of stimulated electromyography in the analysis of the neuromuscular junction in children. Muscle Nerve 2017; 56:841-847. [DOI: 10.1002/mus.25685] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 04/18/2017] [Accepted: 05/01/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Matthew C. Pitt
- Department of Clinical NeurophysiologyGreat Ormond Street Hospital for Children NHS Foundation TrustGreat Ormond Street, LondonWC1N 3JH United Kingdom
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8
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Tan JS, Ambang T, Ahmad-Annuar A, Rajahram GS, Wong KT, Goh KJ. Congenital myasthenic syndrome due to novel CHAT
mutations in an ethnic kadazandusun family. Muscle Nerve 2016; 53:822-6. [DOI: 10.1002/mus.25037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/08/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Joo-San Tan
- Division of Neurology, Department of Medicine, Faculty of Medicine; University of Malaya; Kuala Lumpur Malaysia
| | - Tomica Ambang
- Division of Neurology, Department of Medicine, Faculty of Medicine; University of Malaya; Kuala Lumpur Malaysia
| | - Azlina Ahmad-Annuar
- Department of Biomedical Science, Faculty of Medicine; University of Malaya; Kuala Lumpur Malaysia
| | - Giri Shan Rajahram
- Department of Medicine; Hospital Queen Elizabeth; Kota Kinabalu Sabah Malaysia
| | - Kum Thong Wong
- Department of Pathology, Faculty of Medicine; University of Malaya; Kuala Lumpur Malaysia
| | - Khean Jin Goh
- Division of Neurology, Department of Medicine, Faculty of Medicine; University of Malaya; Kuala Lumpur Malaysia
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9
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Morey TM, Albers S, Shilton BH, Rylett RJ. Enhanced ubiquitination and proteasomal degradation of catalytically deficient human choline acetyltransferase mutants. J Neurochem 2016; 137:630-46. [PMID: 26871972 DOI: 10.1111/jnc.13574] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 02/03/2016] [Accepted: 02/09/2016] [Indexed: 11/30/2022]
Abstract
Choline acetyltransferase (ChAT) is essential for cholinergic neuron function as it mediates synthesis of the neurotransmitter acetylcholine. ChAT mutations have been linked to the neuromuscular disorder congenital myasthenic syndrome (CMS). One CMS-related ChAT mutation, V18M, reduces enzyme activity and cellular protein levels, and is positioned within a highly conserved proline-rich motif with the sequence 14 PKLPVPP20 . We demonstrate that N-terminal truncation that includes this proline-rich motif, as well as mutation of prolines-17/19 together to alanine (P17A/P19A), dramatically reduces ChAT steady-state protein levels and cellular activity when expressed in cholinergic SN56 neural cells. The in vitro activity of bacterially expressed recombinant P17A/P19A-ChAT is also reduced, although this is not caused by changes in protein secondary structure or thermal stability. Treatment of SN56 cells with the proteasome inhibitor MG132 increases cellular P17A/P19A-ChAT steady-state protein levels, and by immunoprecipitation we found that ChAT is ubiquitinated and that polyubiquitination of P17A/P19A-ChAT is increased compared to wild-type (WT) ChAT. Using a novel fluorescent-biorthogonal pulse-chase protocol in SN56 cells, we determined that the protein half-life of P17A/P19A-ChAT (2.2 h) is substantially reduced compared to WT-ChAT (19.7 h). Lastly, we show that two CMS-related ChAT mutants (V18M and A513T) have enhanced ubiquitination, and that treatment with MG132 can partially restore both the steady-state protein levels as well as cellular activity of some CMS-mutant ChAT. These results identify a novel mechanism for regulation of ChAT through the ubiquitin-proteasome system that is influenced by the conserved N-terminal proline-rich motif of ChAT and may be implicated in CMS pathology. Choline acetyltransferase (ChAT) synthesizes acetylcholine in cholinergic neurons. In this study we find that steady-state protein levels of human 69-kDa ChAT are regulated by the ubiquitin-proteasome system. Mutation of a highly conserved N-terminal proline-rich motif in human 69-kDa ChAT reduces both cellular ChAT protein levels, through enhanced ubiquitination and proteasomal degradation, and enzyme activity. Ubiquitination of catalytically deficient congenital myasthenic syndrome (CMS)-mutant ChAT is increased in cells, and importantly proteasome inhibition partially restores steady-state protein levels as well as cellular activity of some CMS-mutant ChAT proteins.
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Affiliation(s)
- Trevor M Morey
- Molecular Medicine Research Group, Robarts Research Institute, Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Shawn Albers
- Molecular Medicine Research Group, Robarts Research Institute, Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Brian H Shilton
- Department of Biochemistry, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
| | - R Jane Rylett
- Molecular Medicine Research Group, Robarts Research Institute, Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada
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10
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Engel AG, Shen XM, Selcen D, Sine SM. Congenital myasthenic syndromes: pathogenesis, diagnosis, and treatment. Lancet Neurol 2015; 14:420-34. [PMID: 25792100 PMCID: PMC4520251 DOI: 10.1016/s1474-4422(14)70201-7] [Citation(s) in RCA: 333] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The congenital myasthenic syndromes (CMS) are a diverse group of genetic disorders caused by abnormal signal transmission at the motor endplate, a special synaptic contact between motor axons and each skeletal muscle fibre. Most CMS stem from molecular defects in the muscle nicotinic acetylcholine receptor, but they can also be caused by mutations in presynaptic proteins, mutations in proteins associated with the synaptic basal lamina, defects in endplate development and maintenance, or defects in protein glycosylation. The specific diagnosis of some CMS can sometimes be reached by phenotypic clues pointing to the mutated gene. In the absence of such clues, exome sequencing is a useful technique for finding the disease gene. Greater understanding of the mechanisms of CMS have been obtained from structural and electrophysiological studies of the endplate, and from biochemical studies. Present therapies for the CMS include cholinergic agonists, long-lived open-channel blockers of the acetylcholine receptor ion channel, and adrenergic agonists. Although most CMS are treatable, caution should be exercised as some drugs that are beneficial in one syndrome can be detrimental in another.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, Rochester, MN, USA.
| | - Xin-Ming Shen
- Department of Neurology, Mayo Clinic, Rochester, MN, USA
| | - Duygu Selcen
- Department of Neurology, Mayo Clinic, Rochester, MN, USA
| | - Steven M Sine
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
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Abstract
The neuromuscular junction (NMJ) is a synapse between motor neurons and skeletal muscle fibers, and is critical for control of muscle contraction. Its formation requires neuronal agrin that acts by binding to LRP4 to stimulate MuSK. Mutations have been identified in agrin, MuSK, and LRP4 in patients with congenital myasthenic syndrome, and patients with myasthenia gravis develop antibodies against agrin, LRP4, and MuSK. However, it remains unclear whether the agrin signaling pathway is critical for NMJ maintenance because null mutation of any of the three genes is perinatal lethal. In this study, we generated imKO mice, a mutant strain whose LRP4 gene can be deleted in muscles by doxycycline (Dox) treatment. Ablation of the LRP4 gene in adult muscle enabled studies of its role in NMJ maintenance. We demonstrate that Dox treatment of P30 mice reduced muscle strength and compound muscle action potentials. AChR clusters became fragmented with diminished junctional folds and synaptic vesicles. The amplitude and frequency of miniature endplate potentials were reduced, indicating impaired neuromuscular transmission and providing cellular mechanisms of adult LRP4 deficiency. We showed that LRP4 ablation led to the loss of synaptic agrin and the 90 kDa fragments, which occurred ahead of other prejunctional and postjunctional components, suggesting that LRP4 may regulate the stability of synaptic agrin. These observations demonstrate that LRP4 is essential for maintaining the structural and functional integrity of the NMJ and that loss of muscle LRP4 in adulthood alone is sufficient to cause myasthenic symptoms.
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12
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Singh RR, Tan SV, Hanna MG, Robb SA, Clarke A, Jungbluth H. Mutations in SCN4A: a rare but treatable cause of recurrent life-threatening laryngospasm. Pediatrics 2014; 134:e1447-50. [PMID: 25311598 DOI: 10.1542/peds.2013-3727] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Laryngospasm is a rare but potentially life-threatening occurrence in infants and usually has infective, allergic, metabolic, or anatomic causes. Underlying genetic conditions are rarely considered. Mutations in SCN4A encoding the voltage-gated sodium channel NaV1.4 have been implicated in a wide spectrum of neuromuscular disorders with variable onset, ranging from a rare form of congenital myasthenic syndrome to both hypokalemic and hyperkalemic forms of periodic paralysis and paramyotonia congenita. Here we report on 3 unrelated patients without family history presenting with recurrent, life-threatening episodes of laryngospasm from the first months of life. Clinical features more typically associated with SCN4A-related disorders such as generalized muscle hypertrophy with clinical or electrical myotonia evolved later in life. All patients were found to be heterozygous for the same SCN4A mutation, c.3917G>A; p.Gly1306Glu. Treatment with carbamazepine resulted in complete abolition of recurrent laryngospasm and alleviated symptoms associated with myotonia and muscle stiffness. We conclude that SCN4A mutations ought to be considered in the differential diagnosis of recurrent infantile laryngospasm because timely institution of treatment can be life-saving.
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Affiliation(s)
- Rahul R Singh
- Departments of Paediatric Neurology, Neuromuscular Service, Evelina's Children Hospital, and
| | - S Veronica Tan
- Neurology & Neurophysiology, Guy's & St Thomas' Hospital NHS Foundation Trust, London, United Kingdom
| | - Michael G Hanna
- MRC Centre for Neuromuscular Disease and National Hospital for Neurology and Neurosurgery, Queen's Square, London, United Kingdom
| | - Stephanie A Robb
- Dubowitz Neuromuscular Centre, Institute of Child Health and Great Ormond Street Hospital for Children, London, United Kingdom
| | - Antonia Clarke
- Department of Paediatric Neurology, St George's Hospital, London, United Kingdom; and
| | - Heinz Jungbluth
- Departments of Paediatric Neurology, Neuromuscular Service, Evelina's Children Hospital, and Randall Division for Cell and Molecular Biophysics, Muscle Signalling Section, and Clinical Neuroscience Division, IOP, King's College, London, United Kingdom
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13
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Prenatal diagnosis of an interstitial deletion of 10q (10q11.21 → q21.1): array comparative genomic hybridization characterization and literature review. Taiwan J Obstet Gynecol 2013; 51:672-6. [PMID: 23276582 DOI: 10.1016/j.tjog.2012.09.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/10/2012] [Indexed: 11/23/2022] Open
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14
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Abstract
This article reviews the use of electrodiagnostic testing in disorders of neuromuscular transmission and discusses the differences between various presynaptic and postsynaptic disorders. Attention is paid to quality control issues that influence the sensitivity of repetitive nerve stimulation and single fiber electromyography. Electrodiagnostic testing, when used as an extension of the clinician's history and physical examination, will provide appropriate direction in establishing the diagnosis.
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Affiliation(s)
- James F Howard
- Neuromuscular Disorders Section, Department of Neurology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7025, USA.
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15
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Engel AG. Current status of the congenital myasthenic syndromes. Neuromuscul Disord 2012; 22:99-111. [PMID: 22104196 PMCID: PMC3269564 DOI: 10.1016/j.nmd.2011.10.009] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2011] [Revised: 10/11/2011] [Accepted: 10/13/2011] [Indexed: 01/04/2023]
Abstract
Congenital myasthenic syndromes (CMS) are heterogeneous disorders in which the safety margin of neuromuscular transmission is compromised by one or more specific mechanisms. Clinical, electrophysiologic, and morphologic studies have paved the way for detecting CMS-related mutations in proteins residing in the nerve terminal, the synaptic basal lamina, and in the postsynaptic region of the motor endplate. The disease proteins identified to date include choline acetyltransferase (ChAT), the endplate species of acetylcholinesterase (AChE), β2-laminin, the acetylcholine receptor (AChR), rapsyn, plectin, Na(v)1.4, the muscle specific protein kinase (MuSK), agrin, downstream of tyrosine kinase 7 (Dok-7), and glutamine-fructose-6-phosphate transaminase 1 (GFPT1). Myasthenic syndromes associated with centronuclear myopathies were recently recognized. Analysis of properties of expressed mutant proteins contributed to finding improved therapy for most CMS. Despite these advances, the molecular basis of some phenotypically characterized CMS remains elusive. Moreover, other types of CMS and disease genes likely exist and await discovery.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, Rochester, MN 55905, United States.
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Schara U, Christen HJ, Durmus H, Hietala M, Krabetz K, Rodolico C, Schreiber G, Topaloglu H, Talim B, Voss W, Pihko H, Abicht A, Müller JS, Lochmüller H. Long-term follow-up in patients with congenital myasthenic syndrome due to CHAT mutations. Eur J Paediatr Neurol 2010; 14:326-33. [PMID: 19900826 DOI: 10.1016/j.ejpn.2009.09.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Revised: 09/19/2009] [Accepted: 09/28/2009] [Indexed: 10/20/2022]
Abstract
BACKGROUND Congenital myasthenic syndromes (CMSs) are a group of clinically and genetically heterogeneous inherited disorders of the neuromuscular junction. Mutations in the acetylcholine transferase (CHAT) gene cause a pre-synaptic CMS, typically associated with episodic apnoea and worsening of myasthenic symptoms during crises caused by infections, fever or stress. Between crises symptoms may be mild and variable. Acetylcholinesterase - inhibitor therapy is reported to improve clinical symptoms and reduce crises. PATIENTS AND METHODS We present data on the long-term follow-up of 11 patients with a congenital myasthenic syndrome due to nine different CHAT mutations; ten of the patients have not been previously reported. RESULTS AND CONCLUSIONS Manifestation varied from the neonatal period to the age of two years, follow-up time from nine months to 12 years. This cohort of CHAT patients studied here enabled us to describe two distinct phenotypes: The neonatal-onset group suffers from apnoeic crises, respirator dependency and bulbar weakness. Apnoea should be carefully distinguished from seizures; a CMS should be taken into account early to start appropriate therapy. Infantile-onset patients show mild permanent weakness, but experience apnoeic crises and worsening which resolve with Acetylcholinesterase - inhibitor treatment. However, after several years of treatment proximal muscle strength may decrease and lead to wheelchair dependency despite the continuation of Acetylcholinesterase - inhibitor therapy.
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Affiliation(s)
- Ulrike Schara
- Dept. of Paediatric Neurology, University of Essen, Hufelandstr. 55, D-45122 Essen, Germany.
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Engel AG, Shen XM, Selcen D, Sine SM. What have we learned from the congenital myasthenic syndromes. J Mol Neurosci 2010; 40:143-53. [PMID: 19688192 PMCID: PMC3050586 DOI: 10.1007/s12031-009-9229-0] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Accepted: 07/20/2009] [Indexed: 10/20/2022]
Abstract
The congenital myasthenic syndromes have now been traced to an array of molecular targets at the neuromuscular junction encoded by no fewer than 11 disease genes. The disease genes were identified by the candidate gene approach, using clues derived from clinical, electrophysiological, cytochemical, and ultrastructural features. For example, electrophysiologic studies in patients suffering from sudden episodes of apnea pointed to a defect in acetylcholine resynthesis and CHAT as the candidate gene (Ohno et al., Proc Natl Acad Sci USA 98:2017-2022, 2001); refractoriness to anticholinesterase medications and partial or complete absence of acetylcholinesterase (AChE) from the endplates (EPs) has pointed to one of the two genes (COLQ and ACHE ( T )) encoding AChE, though mutations were observed only in COLQ. After a series of patients carrying mutations in a disease gene have been identified, the emerging genotype-phenotype correlations provided clues for targeted mutation analysis in other patients. Mutations in EP-specific proteins also prompted expression studies that proved pathogenicity, highlighted important functional domains of the abnormal proteins, and pointed to rational therapy.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology and Muscle Research Laboratory, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
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Yis U, Kurul SH, Oztura I, Ozden O, Akinci G, Dirik E. Temporary diazepam responsive apneic attacks and congenital myasthenic syndrome. J Child Neurol 2009; 24:895-8. [PMID: 19289695 DOI: 10.1177/0883073808331083] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Congenital myasthenic syndromes are a genetically and phenotypically heterogeneous group of hereditary disorders affecting neuromuscular junction. Mutations in the gene encoding choline acetyltransferase cause presynaptic defects. The missense mutation I336T has been identified in Turkish population, and most of the cases carrying this mutation present with exercise-induced fatigability and ptosis. Although apneic attacks occur in these cases during febrile illness in childhood, the number of reported respiratory distress episodes during infancy is scarce. Another important feature of these cases is that response to esterase inhibitors is satisfactory. We present a case of congenital myasthenic syndrome with I336T choline acetyltransferase mutation who presented with numerous attacks of respiratory distress in the infancy period. Interestingly, the patient had myopathic findings on electromyography and diazepam decreased severity of apneic attacks. There was also no improvement with esterase inhibitors.
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Affiliation(s)
- Uluç Yis
- Division of Child Neurology, Gaziantep Children's Hospital, Gaziantep, Turkey.
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Proschowsky HF, Flagstad A, Cirera S, Joergensen CB, Fredholm M. Identification of a mutation in the CHAT gene of Old Danish Pointing Dogs affected with congenital myasthenic syndrome. ACTA ACUST UNITED AC 2007; 98:539-43. [PMID: 17586598 DOI: 10.1093/jhered/esm026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The presence of a recessive inherited muscle disease in Old Danish Pointing Dogs has been well known for years. Comparisons of this disease with myasthenic diseases of other dog breeds and humans have pointed toward a defect in the synthesis of the neurotransmitter acetylcholine possibly due to decreased activity of the enzyme choline acetyltransferase. We sequenced exons 5-18 of the gene encoding choline acetyltransferase (CHAT) in 2 affected and 2 unaffected dogs and identified a G to A missense mutation in exon 6. The mutation causes a valine to methionine substitution and segregates in agreement with the inheritance of the disease. The mutation was not detected in 50 dogs representing 25 other dog breeds. A DNA test has been developed and is now available to the breeders of Old Danish Pointing Dogs.
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Affiliation(s)
- Helle Friis Proschowsky
- Department of Animal and Veterinary Basic Sciences, Groennegaardsvej 3, the Royal Veterinary and Agricultural University, 1870 Frederiksberg C, Denmark.
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Diagnose und Therapie der kongenitalen Myastheniesyndrome. Monatsschr Kinderheilkd 2005. [DOI: 10.1007/s00112-003-0874-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Cai Y, Cronin CN, Engel AG, Ohno K, Hersh LB, Rodgers DW. Choline acetyltransferase structure reveals distribution of mutations that cause motor disorders. EMBO J 2004; 23:2047-58. [PMID: 15131697 PMCID: PMC424412 DOI: 10.1038/sj.emboj.7600221] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Accepted: 04/05/2004] [Indexed: 11/09/2022] Open
Abstract
Choline acetyltransferase (ChAT) synthesizes acetylcholine in neurons and other cell types. Decreases in ChAT activity are associated with a number of disease states, and mutations in ChAT cause congenital neuromuscular disorders. The crystal structure of ChAT reported here shows the enzyme divided into two domains with the active site in a solvent accessible tunnel at the domain interface. A low-resolution view of the complex with one substrate, coenzyme A, defines its binding site and suggests an additional interaction not found in the related carnitine acetyltransferase. Also, the preference for choline over carnitine as an acetyl acceptor is seen to result from both electrostatic and steric blocks to carnitine binding at the active site. While half of the mutations that cause motor disorders are positioned to affect enzyme activity directly, the remaining changes are surprisingly distant from the active site and must exert indirect effects. The structure indicates how ChAT is regulated by phosphorylation and reveals an unusual pattern of basic surface patches that may mediate membrane association or macromolecular interactions.
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Affiliation(s)
- Yiying Cai
- Department of Molecular and Cellular Biochemistry, and Center for Structural Biology, University of Kentucky, Lexington, KY, USA
| | | | - Andrew G Engel
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN, USA
| | - Kinji Ohno
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN, USA
| | - Louis B Hersh
- Department of Molecular and Cellular Biochemistry, and Center for Structural Biology, University of Kentucky, Lexington, KY, USA
- Department of Molecular and Cellular Biochemistry, University of Kentucky, 800 Rose St, Lexington, KY 40536, USA. Tel.: +1 859 257 5205; Fax: +1 859 323 1037; E-mail:
| | - David W Rodgers
- Department of Molecular and Cellular Biochemistry, and Center for Structural Biology, University of Kentucky, Lexington, KY, USA
- Department of Molecular and Cellular Biochemistry, University of Kentucky, 800 Rose St, Lexington, KY 40536, USA. Tel.: +1 859 257 5205; Fax: +1 859 323 1037; E-mail:
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