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Kediha MI, Tazir M, Sternberg D, Eymard B, Ali Pacha L. Innovative Therapeutic Approaches in Congenital Myasthenic Syndromes. Neurol Clin Pract 2024; 14:e200277. [PMID: 38737513 PMCID: PMC11081764 DOI: 10.1212/cpj.0000000000200277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 01/10/2024] [Indexed: 05/14/2024]
Abstract
Background and Objectives To provide real-word clinical follow-up data on patients carrying variations of congenital myasthenic syndromes (CMS) and who respond to some innovative drugs. Methods Patients recruited from the Neurology Department of the Mustapha Bacha university hospital in Algiers. Treated with innovative drugs, they were monitored and their clinical progress was evaluated on the basis of clinical arguments suggestive of CMSs, but also para clinical arguments (electromyography and genetic study). Results Six patients carrying different mutations in different genes of CMSs were studied. They had different pathophysiologic profiles (slow or fast channel syndromes, low expressor of receptor). Their therapeutic management was based on innovative drugs, normally indicated in other, non-neurological pathologies. Their outcome was toward a clear clinical improvement. Discussion This work relates the interest of proposing treatments (outside of Pyridostigmine) in the management of CMSs. These therapies can greatly modify the prognosis of patients suffering from this orphan disease. Classification of Evidence This study provides Class IV evidence that for patients with congenital myasthenic syndromes, some innovative treatments are effective.
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Affiliation(s)
- Mohamed I Kediha
- Neurology Department (MIK, MT, LAP), Mustapha Bacha University Hospital Algiers, Algeria; Myology Department (DS), Pitié Salpetriere, Paris; and Functional Unit for Neuromuscular Pathology (BE), Pitié Salpetriere, France
| | - Meriem Tazir
- Neurology Department (MIK, MT, LAP), Mustapha Bacha University Hospital Algiers, Algeria; Myology Department (DS), Pitié Salpetriere, Paris; and Functional Unit for Neuromuscular Pathology (BE), Pitié Salpetriere, France
| | - Damien Sternberg
- Neurology Department (MIK, MT, LAP), Mustapha Bacha University Hospital Algiers, Algeria; Myology Department (DS), Pitié Salpetriere, Paris; and Functional Unit for Neuromuscular Pathology (BE), Pitié Salpetriere, France
| | - Bruno Eymard
- Neurology Department (MIK, MT, LAP), Mustapha Bacha University Hospital Algiers, Algeria; Myology Department (DS), Pitié Salpetriere, Paris; and Functional Unit for Neuromuscular Pathology (BE), Pitié Salpetriere, France
| | - Lamia Ali Pacha
- Neurology Department (MIK, MT, LAP), Mustapha Bacha University Hospital Algiers, Algeria; Myology Department (DS), Pitié Salpetriere, Paris; and Functional Unit for Neuromuscular Pathology (BE), Pitié Salpetriere, France
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Ohno K, Ohkawara B, Shen XM, Selcen D, Engel AG. Clinical and Pathologic Features of Congenital Myasthenic Syndromes Caused by 35 Genes-A Comprehensive Review. Int J Mol Sci 2023; 24:ijms24043730. [PMID: 36835142 PMCID: PMC9961056 DOI: 10.3390/ijms24043730] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 02/09/2023] [Accepted: 02/09/2023] [Indexed: 02/16/2023] Open
Abstract
Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders characterized by impaired neuromuscular signal transmission due to germline pathogenic variants in genes expressed at the neuromuscular junction (NMJ). A total of 35 genes have been reported in CMS (AGRN, ALG14, ALG2, CHAT, CHD8, CHRNA1, CHRNB1, CHRND, CHRNE, CHRNG, COL13A1, COLQ, DOK7, DPAGT1, GFPT1, GMPPB, LAMA5, LAMB2, LRP4, MUSK, MYO9A, PLEC, PREPL, PURA, RAPSN, RPH3A, SCN4A, SLC18A3, SLC25A1, SLC5A7, SNAP25, SYT2, TOR1AIP1, UNC13A, VAMP1). The 35 genes can be classified into 14 groups according to the pathomechanical, clinical, and therapeutic features of CMS patients. Measurement of compound muscle action potentials elicited by repetitive nerve stimulation is required to diagnose CMS. Clinical and electrophysiological features are not sufficient to identify a defective molecule, and genetic studies are always required for accurate diagnosis. From a pharmacological point of view, cholinesterase inhibitors are effective in most groups of CMS, but are contraindicated in some groups of CMS. Similarly, ephedrine, salbutamol (albuterol), amifampridine are effective in most but not all groups of CMS. This review extensively covers pathomechanical and clinical features of CMS by citing 442 relevant articles.
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Affiliation(s)
- Kinji Ohno
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
- Correspondence: (K.O.); (A.G.E.)
| | - Bisei Ohkawara
- Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Xin-Ming Shen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
| | - Duygu Selcen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
| | - Andrew G. Engel
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
- Correspondence: (K.O.); (A.G.E.)
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Dejthevaporn C, Wetchaphanphesat S, Pulkes T, Rattanasiri S, Engel AG, Witoonpanich R. Treatment of slow-channel congenital myasthenic syndrome in a Thai family with fluoxetine. J Clin Neurosci 2022; 96:85-89. [PMID: 34999496 DOI: 10.1016/j.jocn.2021.12.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 11/11/2021] [Accepted: 12/12/2021] [Indexed: 11/30/2022]
Abstract
The slow-channel congenital myasthenic syndrome is an autosomal dominant neuromuscular disorder caused by mutations in different subunits of the acetylcholine receptor. Fluoxetine, a common antidepressant and long-lived open-channel blocker of acetylcholine receptor, has been reported to be beneficial in the slow-channel congenital myasthenic syndrome. Here we report a prospective open label study of fluoxetine treatment in some affected members of a Thai family with slow-channel congenital myasthenic syndrome caused by a novel p.Gly153Ala (c.518G > C) mutation in CHRNA1 in the AChR α subunit. These patients showed significant clinical improvement following fluoxetine treatment but their respiratory function responded variably.
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Affiliation(s)
- Charungthai Dejthevaporn
- Division of Neurology, Department of Medicine, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | | | - Teeratorn Pulkes
- Division of Neurology, Department of Medicine, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - Sasivimol Rattanasiri
- Clinical Epidemiology Unit, Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - Andrew G Engel
- Department of Neurology and Muscle Research Laboratory, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - Rawiphan Witoonpanich
- Division of Neurology, Department of Medicine, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
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Rare slow channel congenital myasthenic syndromes without repetitive compound muscle action potential and dramatic response to low dose fluoxetine. Acta Neurol Belg 2021; 121:1755-1760. [PMID: 33030681 DOI: 10.1007/s13760-020-01505-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 09/15/2020] [Indexed: 10/23/2022]
Abstract
Congenital myasthenic syndromes are rare hereditary disorders caused by mutations associated with proteins of the neuromuscular junction. Abnormal ''gain of function'' mutations result in prolonged nicotinic acetylcholine receptor channel open state causing a rare subtype of CMS, slow-channel CMS (SCCMS). Mutations in the delta subunit encoding the gene, CHRND, resulting in SCCMS are extremely rare. An important clue to the diagnosis of SCCMS is repetitive CMAP's. Fluoxetine, usually at high doses, is used to treat SCCMS. The mutation, recently described in one patient, was identified by whole exome sequencing and validated, and its segregation with the disease was ascertained by Sanger sequencing. Here, we describe clinical and genetic findings of an early onset SCCMS patient carrying a very rare missense mutation c.880C > T in CHRND causing a highly conserved leucine to phenylalanine substitution in the M2 domain of CHRND. The patient had no repetitive CMAP. He had a dramatic response to fluoxetine at low-moderate doses (40 mg/day), increasing over months: Being wheelchair bound, he could walk independently after treatment. Rare cases may offer insight into the pathological gating mechanism leading to CMS. SCCMS should be suspected even without a repetitive CMAP. Fluoxetine at relatively low doses can be a very effective treatment.
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Di L, Chen H, Lu Y, Selcen D, Engel AG, Da Y, Shen XM. Determinants of the repetitive-CMAP occurrence and therapy efficacy in slow-channel myasthenia. Neurology 2020; 95:e2781-e2793. [PMID: 32907971 DOI: 10.1212/wnl.0000000000010734] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Accepted: 06/22/2020] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To find determinants of the occurrence of repetitive compound muscle action potential (R-CMAP) and to assess the efficacy of channel blocker therapy in slow-channel congenital myasthenic syndrome (SCCMS). METHODS Neurologic examination, EMG study, laboratory test, muscle biopsy, and next-generation and Sanger sequencing; literature review of reported patients with SCCMS, including EMG, kinetics of mutant acetylcholine receptors (AChRs), and response to therapy; and simulation of the decay phase of endplate potential (EPP) were performed. RESULTS Three newly characterized and 57 reported patients with SCCMS with mutations of AChR subunits were included. In patients with R-CMAP, the length of channel opening bursts of mutant AChR was increased 8.68 ± 2.82 (mean ± SD)-fold compared to wild-type; in patients without R-CMAP, the length was increased 3.84 ± 0.65-fold (95% confidence interval 3.18-6.50, p = 0.000014). The EPP amplitude after refractory period of action potential in muscle fiber is above the threshold in patients with R-CMAP but below the threshold in patients without R-CMAP. In patients with good results from channel blocker therapy, treatment was initiated 11.60 ± 5.17 years after onset of symptoms; in patients with no to moderate benefit from channel blocker therapy, treatment was initiated 30.70 ± 12.72 years after onset (95% confidence interval -28.57 to -9.63, p = 0.00089). CONCLUSIONS In SCCMS, the R-CMAP occurrence is related to the extent of prolongation of the opening episodes of mutant AChR channel. Channel blocker treatment is more effective the sooner it is started after the onset of symptoms. CLASSIFICATION OF EVIDENCE This study provides Class IV evidence that channel blocker therapy in patients with SCCMS improves symptoms.
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Affiliation(s)
- Li Di
- From the Department of Neurology (L.D., H.C., Y.L., Y.D.), Xuanwu Hospital, Capital Medical University, Beijing, China; and Department of Neurology and Neuromuscular Research Laboratory (L.D., D.S., A.G.E., X.-M.S.), Mayo Clinic, Rochester, MN
| | - Hai Chen
- From the Department of Neurology (L.D., H.C., Y.L., Y.D.), Xuanwu Hospital, Capital Medical University, Beijing, China; and Department of Neurology and Neuromuscular Research Laboratory (L.D., D.S., A.G.E., X.-M.S.), Mayo Clinic, Rochester, MN
| | - Yan Lu
- From the Department of Neurology (L.D., H.C., Y.L., Y.D.), Xuanwu Hospital, Capital Medical University, Beijing, China; and Department of Neurology and Neuromuscular Research Laboratory (L.D., D.S., A.G.E., X.-M.S.), Mayo Clinic, Rochester, MN
| | - Duygu Selcen
- From the Department of Neurology (L.D., H.C., Y.L., Y.D.), Xuanwu Hospital, Capital Medical University, Beijing, China; and Department of Neurology and Neuromuscular Research Laboratory (L.D., D.S., A.G.E., X.-M.S.), Mayo Clinic, Rochester, MN
| | - Andrew G Engel
- From the Department of Neurology (L.D., H.C., Y.L., Y.D.), Xuanwu Hospital, Capital Medical University, Beijing, China; and Department of Neurology and Neuromuscular Research Laboratory (L.D., D.S., A.G.E., X.-M.S.), Mayo Clinic, Rochester, MN
| | - Yuwei Da
- From the Department of Neurology (L.D., H.C., Y.L., Y.D.), Xuanwu Hospital, Capital Medical University, Beijing, China; and Department of Neurology and Neuromuscular Research Laboratory (L.D., D.S., A.G.E., X.-M.S.), Mayo Clinic, Rochester, MN.
| | - Xin-Ming Shen
- From the Department of Neurology (L.D., H.C., Y.L., Y.D.), Xuanwu Hospital, Capital Medical University, Beijing, China; and Department of Neurology and Neuromuscular Research Laboratory (L.D., D.S., A.G.E., X.-M.S.), Mayo Clinic, Rochester, MN.
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Shen XM, Milone M, Wang HL, Banwell B, Selcen D, Sine SM, Engel AG. Slow-channel myasthenia due to novel mutation in M2 domain of AChR delta subunit. Ann Clin Transl Neurol 2019; 6:2066-2078. [PMID: 31560172 PMCID: PMC6801167 DOI: 10.1002/acn3.50902] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 09/01/2019] [Indexed: 11/09/2022] Open
Abstract
OBJECTIVE To characterize the molecular and phenotypic basis of a severe slow-channel congenital myasthenic syndrome (SCCMS). METHODS Intracellular and single-channel recordings from patient endplates; alpha-bungarotoxin binding studies; direct sequencing of AChR genes; microsatellite analysis; kinetic analysis of AChR activation; homology modeling of adult human AChR structure. RESULTS Among 24 variants reported to cause SCCMS only two appear in the AChR δ-subunit. We here report a 16-year-old patient harboring a novel δL273F mutation (δL294F in HGVS nomenclature) in the second transmembrane domain (M2) of the AChR δ subunit. Kinetic analyses with ACh and the weak agonist choline indicate that δL273F prolongs the channel opening bursts 9.4-fold due to a 75-fold increase in channel gating efficiency, whereas a previously identified εL269F mutation (εL289F in HGVS nomenclature) at an equivalent location in the AChR ε-subunit prolongs channel opening bursts 4.4-fold due to a 30-fold increase in gating efficiency. Structural modeling of AChR predicts that inter-helical hydrophobic interactions between the mutant residue in the δ and ε subunit and nearby M2 domain residues in neighboring α subunits contribute to structural stability of the open relative to the closed channel states. INTERPRETATION The greater increase in gating efficiency by δL273F than by εL269F explains why δL273F has more severe clinical effects. Both δL273F and εL269F impair channel gating by disrupting hydrophobic interactions with neighboring α-subunits. Differences in the extent of impairment of channel gating in δ and ε mutant receptors suggest unequal contributions of ε/α and δ/α subunit pairs to gating efficiency.
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Affiliation(s)
- Xin-Ming Shen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Margherita Milone
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Hang-Long Wang
- Department of Neurology and Vesicular Biology Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Brenda Banwell
- Division of Neurology, Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Duygu Selcen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, Minnesota
| | - Steven M Sine
- Department of Physiology and Biomedical Engineering and Receptor Biology Laboratory, Mayo Clinic, Rochester, Minnesota.,Department of Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota.,Department of Neurology, Mayo Clinic, Rochester, Minnesota
| | - Andrew G Engel
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, Minnesota
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Angelini C, Lispi L, Salvoro C, Mostacciuolo ML, Vazza G. Clinical and genetic characterization of an Italian family with slow-channel syndrome. Neurol Sci 2018; 40:503-507. [PMID: 30542963 DOI: 10.1007/s10072-018-3645-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 11/09/2018] [Indexed: 02/07/2023]
Abstract
INTRODUCTION The slow-channel congenital myasthenic syndrome (SCCMS) is a postsynaptic form of congenital myasthenic syndromes (CMSs), a clinically heterogeneous group of disorders caused by genetic defects leading to an abnormal signal transmission at the endplate. METHODS We report clinical and molecular data of a multigenerational family in which the presentation of a progressive proximal-distal weakness with ocular involvement led to a number of different clinical diagnoses. RESULTS A comprehensive genetic study which included whole-genome linkage analysis and whole-exome sequencing identified a heterozygous missense substitution (c.721C>T, p.L241F) in the ε subunit of the acetylcholine receptor (CHRNE) that was consistent with clinical weakness in all patients. DISCUSSION SCCMS is characterized by a broad and heterogeneous clinical phenotype in which disease onset, symptoms, severity, and progression can be highly variable even between family members. The identification of a CHRNE mutation allowed to make the definitive diagnosis of CMS in this family and contributed to define the clinical spectrum of this disease.
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Affiliation(s)
- Corrado Angelini
- Fondazione Hospital S.Camillo Institute for Research and Health Care, Venice, Italy.
| | - Ludovico Lispi
- Neurology and Neurophysiopathology Unit, ASO San Camillo-Forlanini Hospital of Rome, Rome, Italy
| | | | | | - Giovanni Vazza
- Department of Biology, University of Padova, Padova, Italy
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Idikuda V, Gao W, Su Z, Liu Q, Zhou L. cAMP binds to closed, inactivated, and open sea urchin HCN channels in a state-dependent manner. J Gen Physiol 2018; 151:200-213. [PMID: 30541772 PMCID: PMC6363418 DOI: 10.1085/jgp.201812019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 07/08/2018] [Accepted: 11/13/2018] [Indexed: 01/11/2023] Open
Abstract
Mammalian hyperpolarization-activated cyclic-nucleotide–modulated (HCN) channels bind cAMP preferably in the open state. Using sea urchin HCN channels, Idikuda et al. reveal less cAMP binding to the closed state and further reduced binding to the inactivated state and thus demonstrate intricate communication between the gate and ligand-binding domain. Hyperpolarization-activated cyclic-nucleotide–modulated (HCN) channels are nonselective cation channels that regulate electrical activity in the heart and brain. Previous studies of mouse HCN2 (mHCN2) channels have shown that cAMP binds preferentially to and stabilizes these channels in the open state—a simple but elegant implementation of ligand-dependent gating. Distinct from mammalian isoforms, the sea urchin (spHCN) channel exhibits strong voltage-dependent inactivation in the absence of cAMP. Here, using fluorescently labeled cAMP molecules as a marker for cAMP binding, we report that the inactivated spHCN channel displays reduced cAMP binding compared with the closed channel. The reduction in cAMP binding is a voltage-dependent process but proceeds at a much slower rate than the movement of the voltage sensor. A single point mutation in the last transmembrane domain near the channel’s gate, F459L, abolishes inactivation and concurrently reverses the response to hyperpolarizing voltage steps from a decrease to an increase in cAMP binding. ZD7288, an open channel blocker that interacts with a region close to the activation/inactivation gate, dampens the reduction of cAMP binding to inactivated spHCN channels. In addition, compared with closed and “locked” closed channels, increased cAMP binding is observed in channels purposely locked in the open state upon hyperpolarization. Thus, the order of cAMP-binding affinity, measured by the fluorescence signal from labeled cAMP, ranges from high in the open state to intermediate in the closed state to low in the inactivated state. Our work on spHCN channels demonstrates intricate state-dependent communications between the gate and ligand-binding domain and provides new mechanistic insight into channel inactivation/desensitization.
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Affiliation(s)
- Vinay Idikuda
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA
| | - Weihua Gao
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA
| | - Zhuocheng Su
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA
| | - Qinglian Liu
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA
| | - Lei Zhou
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA
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Visco DB, Manhães-de-Castro R, Chaves WF, Lacerda DC, Pereira SDC, Ferraz-Pereira KN, Toscano AE. Selective serotonin reuptake inhibitors affect structure, function and metabolism of skeletal muscle: A systematic review. Pharmacol Res 2018; 136:194-204. [DOI: 10.1016/j.phrs.2018.09.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 09/01/2018] [Accepted: 09/04/2018] [Indexed: 12/14/2022]
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Kudryavtsev DS, Spirova EN, Shelukhina IV, Son LV, Makarova YV, Utkina NK, Kasheverov IE, Tsetlin VI. Makaluvamine G from the Marine Sponge Zyzzia fuliginosa Inhibits Muscle nAChR by Binding at the Orthosteric and Allosteric Sites. Mar Drugs 2018; 16:md16040109. [PMID: 29597332 PMCID: PMC5923396 DOI: 10.3390/md16040109] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Revised: 03/16/2018] [Accepted: 03/23/2018] [Indexed: 12/19/2022] Open
Abstract
Diverse ligands of the muscle nicotinic acetylcholine receptor (nAChR) are used as muscle relaxants during surgery. Although a plethora of such molecules exists in the market, there is still a need for new drugs with rapid on/off-set, increased selectivity, and so forth. We found that pyrroloiminoquinone alkaloid Makaluvamine G (MG) inhibits several subtypes of nicotinic receptors and ionotropic γ-aminobutiric acid receptors, showing a higher affinity and moderate selectivity toward muscle nAChR. The action of MG on the latter was studied by a combination of electrophysiology, radioligand assay, fluorescent microscopy, and computer modeling. MG reveals a combination of competitive and un-competitive inhibition and caused an increase in the apparent desensitization rate of the murine muscle nAChR. Modeling ion channel kinetics provided evidence for MG binding in both orthosteric and allosteric sites. We also demonstrated that theα1 (G153S) mutant of the receptor, associated with the myasthenic syndrome, is more prone to inhibition by MG. Thus, MG appears to be a perspective hit molecule for the design of allosteric drugs targeting muscle nAChR, especially for treating slow-channel congenital myasthenic syndromes.
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Affiliation(s)
- Denis S Kudryavtsev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Ekaterina N Spirova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Irina V Shelukhina
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Lina V Son
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
- Moscow Institute of Physics and Technology, Institutsky Per. 9, Dolgoprudny, 141700 Moscow Region, Russia.
| | - Yana V Makarova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Natalia K Utkina
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry (PIBOC), Russian Academy of Sciences, Prospect 100 let Vladivostoku, 159, 690022 Vladivostok, Russia.
| | - Igor E Kasheverov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Victor I Tsetlin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
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Engel AG. Genetic basis and phenotypic features of congenital myasthenic syndromes. HANDBOOK OF CLINICAL NEUROLOGY 2018; 148:565-589. [PMID: 29478601 DOI: 10.1016/b978-0-444-64076-5.00037-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
Abstract
The congenital myasthenic syndromes (CMS) are heterogeneous disorders in which the safety margin of neuromuscular transmission is compromised by one or more specific mechanisms. The disease proteins reside in the nerve terminal, the synaptic basal lamina, or in the postsynaptic region, or at multiple sites at the neuromuscular junction as well as in other tissues. Targeted mutation analysis by Sanger or exome sequencing has been facilitated by characteristic phenotypic features of some CMS. No fewer than 20 disease genes have been recognized to date. In one-half of the currently identified probands, the disease stems from mutations in genes encoding subunits of the muscle form of the acetylcholine receptor (CHRNA1, CHRNB, CHRNAD1, and CHRNE). In 10-14% of the probands the disease is caused by mutations in RAPSN, DOK 7, or COLQ, and in 5% by mutations in CHAT. Other less frequently identified disease genes include LAMB2, AGRN, LRP4, MUSK, GFPT1, DPAGT1, ALG2, and ALG 14 as well as SCN4A, PREPL, PLEC1, DNM2, and MTM1. Identification of the genetic basis of each CMS is important not only for genetic counseling and disease prevention but also for therapy, because therapeutic agents that benefit one type of CMS can be harmful in another.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic College of Medicine, Rochester, MN, United States.
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Tan JZ, Man Y, Xiao F. A Missense Mutation in Epsilon-subunit of Acetylcholine Receptor Causing Autosomal Dominant Slow-channel Congenital Myasthenic Syndrome in a Chinese Family. Chin Med J (Engl) 2017; 129:2596-2602. [PMID: 27779167 PMCID: PMC5125339 DOI: 10.4103/0366-6999.192780] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Congenital myasthenic syndromes are a group of rare disorders that are clinically and genetically heterogeneous and caused by mutations in the genes encoding proteins of the neuromuscular junction. Here, we described a Chinese family that presented with phenotypes of classic slow-channel congenital myasthenic syndrome (SCCMS). METHODS Clinical characteristics and electrophysiological features of three patients from a Chinese family were examined, and next-generation sequencing followed by direct sequencing was carried out. RESULTS The patients revealed variability in clinical and electrophysiological features. However, weakness, scoliosis, and repetitive-compound muscle action potential were found in all affected members in the family. A heterozygous C>T missense mutation at nucleotide 865 in acetylcholine receptor epsilon-subunit (CHRNE) gene that causes a leucine-to-phenylalanine substitution at position 289 (L289F) was found. CONCLUSIONS We reported a SCCMS family of Chinese origin. In the family, classical clinical phenotype with phenotypic variability among different members was found. Genetic testing could help diagnose this rare disease.
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Affiliation(s)
- Jia-Ze Tan
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Yuan Man
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Fei Xiao
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
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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: 329] [Impact Index Per Article: 36.6] [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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15
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Zhu H, Grajales-Reyes GE, Alicea-Vázquez V, Grajales-Reyes JG, Robinson K, Pytel P, Báez-Pagán CA, Lasalde-Dominicci JA, Gomez CM. Fluoxetine is neuroprotective in slow-channel congenital myasthenic syndrome. Exp Neurol 2014; 270:88-94. [PMID: 25448156 DOI: 10.1016/j.expneurol.2014.10.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 09/30/2014] [Accepted: 10/17/2014] [Indexed: 11/19/2022]
Abstract
The slow-channel congenital myasthenic syndrome (SCS) is an inherited neurodegenerative disease that caused mutations in the acetylcholine receptor (AChR) affecting neuromuscular transmission. Leaky AChRs lead to Ca(2+) overload and degeneration of the neuromuscular junction (NMJ) attributed to activation of cysteine proteases and apoptotic changes of synaptic nuclei. Here we use transgenic mouse models expressing two different mutations found in SCS to demonstrate that inhibition of prolonged opening of mutant AChRs using fluoxetine not only improves motor performance and neuromuscular transmission but also prevents Ca(2+) overload, the activation of cysteine proteases, calpain, caspase-3 and 9 at endplates, and as a consequence, reduces subsynaptic DNA damage at endplates, suggesting a long term benefit to therapy. These studies suggest that prolonged treatment of SCS patients with open ion channel blockers that preferentially block mutant AChRs is neuroprotective.
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Affiliation(s)
- Haipeng Zhu
- Department of Neurology, The University of Chicago, Chicago, IL, USA
| | | | | | | | - KaReisha Robinson
- Department of Neurology, The University of Chicago, Chicago, IL, USA
| | - Peter Pytel
- Department of Pathology, The University of Chicago, Chicago, IL, USA
| | - Carlos A Báez-Pagán
- Department of Biology, The University of Puerto Rico, San Juan, Puerto Rico, USA
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16
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Abicht A, Dusl M, Gallenmüller C, Guergueltcheva V, Schara U, Della Marina A, Wibbeler E, Almaras S, Mihaylova V, von der Hagen M, Huebner A, Chaouch A, Müller JS, Lochmüller H. Congenital myasthenic syndromes: Achievements and limitations of phenotype-guided gene-after-gene sequencing in diagnostic practice: A study of 680 patients. Hum Mutat 2012; 33:1474-84. [DOI: 10.1002/humu.22130] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 04/30/2012] [Indexed: 11/09/2022]
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17
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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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18
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Chaouch A, Müller JS, Guergueltcheva V, Dusl M, Schara U, Rakocević-Stojanović V, Lindberg C, Scola RH, Werneck LC, Colomer J, Nascimento A, Vilchez JJ, Muelas N, Argov Z, Abicht A, Lochmüller H. A retrospective clinical study of the treatment of slow-channel congenital myasthenic syndrome. J Neurol 2011; 259:474-81. [PMID: 21822932 DOI: 10.1007/s00415-011-6204-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 07/19/2011] [Accepted: 07/24/2011] [Indexed: 10/17/2022]
Abstract
Slow-channel congenital myasthenic syndrome (CMS) is a rare subtype of CMS caused by dominant "gain of function" mutations in the acetylcholine receptor. Clinically, the cervical and forearm extensor muscles seem to be preferentially weaker; and conventional treatment with anticholinesterases fails to improve symptoms. In contrast, open channel blockers such as fluoxetine and quinidine have been shown to be of benefit. The objectives of our study were to provide further insight into the clinical features of slow-channel CMS and evaluate response to recommended therapy. We carried out a retrospective clinical follow up study of 15 slow-channel CMS patients referred to the Munich CMS Centre. Detailed clinical data were collected by clinicians involved in the care of each patient, with a particular focus on response and tolerability to recommended therapy. Patients varied widely as regard onset of symptoms, severity of disease and mutations involved. Patients received up to four different medications and some had none. Our results strengthen previous reported findings in terms of clinical phenotype variability and the poor response to pyridostigmine. Although treatment with fluoxetine was beneficial in most patients, a number of our patients suffered significant adverse effects that hindered optimum dose titration or led to treatment cessation. Slow-channel CMS is rare and exhibits distinct clinical and genetic characteristics. Our study suggests that fluoxetine, despite being effective in most patients, can be associated with significant side effects, thus reducing treatment effectiveness in clinical practice.
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Affiliation(s)
- Amina Chaouch
- Institute of Genetic Medicine, Newcastle University, NE1 3BZ, Newcastle upon Tyne, UK
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19
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Kullyev A, Dempsey CM, Miller S, Kuan CJ, Hapiak VM, Komuniecki RW, Griffin CT, Sze JY. A genetic survey of fluoxetine action on synaptic transmission in Caenorhabditis elegans. Genetics 2010; 186:929-41. [PMID: 20739712 PMCID: PMC2975281 DOI: 10.1534/genetics.110.118877] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 08/13/2010] [Indexed: 11/18/2022] Open
Abstract
Fluoxetine is one of the most commonly prescribed medications for many behavioral and neurological disorders. Fluoxetine acts primarily as an inhibitor of the serotonin reuptake transporter (SERT) to block the removal of serotonin from the synaptic cleft, thereby enhancing serotonin signals. While the effects of fluoxetine on behavior are firmly established, debate is ongoing whether inhibition of serotonin reuptake is a sufficient explanation for its therapeutic action. Here, we provide evidence of two additional aspects of fluoxetine action through genetic analyses in Caenorhabditis elegans. We show that fluoxetine treatment and null mutation in the sole SERT gene mod-5 eliminate serotonin in specific neurons. These neurons do not synthesize serotonin but import extracellular serotonin via MOD-5/SERT. Furthermore, we show that fluoxetine acts independently of MOD-5/SERT to regulate discrete properties of acetylcholine (Ach), gamma-aminobutyric acid (GABA), and glutamate neurotransmission in the locomotory circuit. We identified that two G-protein-coupled 5-HT receptors, SER-7 and SER-5, antagonistically regulate the effects of fluoxetine and that fluoxetine binds to SER-7. Epistatic analyses suggest that SER-7 and SER-5 act upstream of AMPA receptor GLR-1 signaling. Our work provides genetic evidence that fluoxetine may influence neuronal functions and behavior by directly targeting serotonin receptors.
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Affiliation(s)
- Andrey Kullyev
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Catherine M. Dempsey
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Sarah Miller
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Chih-Jen Kuan
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Vera M. Hapiak
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Richard W. Komuniecki
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Christine T. Griffin
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
| | - Ji Ying Sze
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461 Department of Biology, National University of Ireland, Maynooth, County Kilare, Ireland Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606
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Abstract
Congenital myasthenic syndromes (CMS) are classified in terms of the located defect: presynaptic, postsynaptic, and synaptic. They are inherited disorders caused by various genetic defects, all but the slow-channel CMS by recessive inheritance. To date, 10 different CMS are known and further CMS subtypes and their genetic cause may be disclosed by future investigations. Prognosis in CMS is variable and largely depends on the pathophysiological and genetic defect. Subtypes showing progression and life-threatening crises with apneas are generally less favorable than others. Therapeutic agents used in CMS depend on the underlying defect and include acetylcholinesterase inhibitor, 3,4-diaminopyridine, quinidine sulfate, fluoxetine, acetazolamide, and ephedrine. Although there are no double-blind, placebo-controlled clinical trials for CMS, several drugs have shown convincingly positive clinical effects. It is therefore necessary to start a rational therapy regime as early as possible. In most CMS, however, mild and severe clinical courses are reported, which makes assessment on an individual basis necessary. This review emphasizes therapeutic strategies in CMS.
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Affiliation(s)
- Ulrike Schara
- Department of Pediatric Neurology, University of Essen, Essen, Germany.
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Kinali M, Beeson D, Pitt M, Jungbluth H, Simonds A, Aloysius A, Cockerill H, Davis T, Palace J, Manzur A, Jimenez-Mallebrera C, Sewry C, Muntoni F, Robb S. Congenital Myasthenic Syndromes in childhood: Diagnostic and management challenges. J Neuroimmunol 2008; 201-202:6-12. [DOI: 10.1016/j.jneuroim.2008.06.026] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Revised: 06/07/2008] [Accepted: 06/09/2008] [Indexed: 10/21/2022]
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Effect of fluoxetine on neuromuscular function in acetylcholinesterase (AChE) knockout mice. Chem Biol Interact 2008; 175:113-4. [PMID: 18550043 DOI: 10.1016/j.cbi.2008.04.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Revised: 03/25/2008] [Accepted: 04/01/2008] [Indexed: 11/23/2022]
Abstract
Congenital myasthenic syndromes (CMS) are a heterogeneous group of diseases caused by genetic defects affecting neuromuscular transmission. The causal mutations have been described in number of cases. The slow channel myasthenic syndrome (slow-channel-CMS) results in a marked prolongation of channel opening in stimulated receptors (nAChR) and the end plate acetylcholinesterase (AChE) deficiency congenital myasthenic syndrome (ColQ-CMS) results in an increased action of acetylcholine (ACh) at the synapse. Anticholinesterase medication is detrimental in these cases. The successful treatment of slow-channel-CMS patients with the antidepressant serotonin re-uptake inhibitor fluoxetine has been reported. At high concentration it has a non-depolarizing effect on nicotinic receptors. This led us to the idea that fluoxetine could protect AChR from a relative excess of ACh. We investigated the possible use of fluoxetine as treatment in the AChE KO mouse. Treatment at 6 mg/kg from 3 weeks to 2 months increased slightly the daily weight gain but not the final weight at 2 months in AChE-/- mice. Isometric force production of Tibialis anterior in response to electric nerve stimulation was measured in situ in AChE-/- and wild type mice treated or not by fluoxetine. The results show that the maximum twitch force in response to a single nerve stimulation, the maximal tetanic force (P0) in response to repetitive nerve stimulation and the tetanic fade are not changed in AChE-/- mice treated with fluoxetine versus control AChE-/- mice.
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23
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Mihaylova V, Müller JS, Vilchez JJ, Salih MA, Kabiraj MM, D’Amico A, Bertini E, Wölfle J, Schreiner F, Kurlemann G, Rasic VM, Siskova D, Colomer J, Herczegfalvi A, Fabriciova K, Weschke B, Scola R, Hoellen F, Schara U, Abicht A, Lochmüller H. Clinical and molecular genetic findings in COLQ-mutant congenital myasthenic syndromes. Brain 2008; 131:747-59. [DOI: 10.1093/brain/awm325] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Müller JS, Mihaylova V, Abicht A, Lochmüller H. Congenital myasthenic syndromes: spotlight on genetic defects of neuromuscular transmission. Expert Rev Mol Med 2007; 9:1-20. [PMID: 17686188 DOI: 10.1017/s1462399407000427] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The neuromuscular junction (NMJ) is a complex structure that efficiently communicates the electrical impulse from the motor neuron to the skeletal muscle to induce muscle contraction. Genetic and autoimmune disorders known to compromise neuromuscular transmission are providing further insights into the complexities of NMJ function. Congenital myasthenic syndromes (CMSs) are a genetically and phenotypically heterogeneous group of rare hereditary disorders affecting neuromuscular transmission. The understanding of the molecular basis of the different types of CMSs has evolved rapidly in recent years. Mutations were first identified in the subunits of the nicotinic acetylcholine receptor (AChR), but now mutations in ten different genes - encoding post-, pre- or synaptic proteins - are known to cause CMSs. Pathogenic mechanisms leading to an impaired neuromuscular transmission modify AChRs or endplate structure or lead to decreased acetylcholine synthesis and release. However, the genetic background of many CMS forms is still unresolved. A precise molecular classification of CMS type is of paramount importance for the diagnosis, counselling and therapy of a patient, as different drugs may be beneficial or deleterious depending on the molecular background of the particular CMS.
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Affiliation(s)
- Juliane S Müller
- Friedrich-Baur-Institute, Department of Neurology, Ludwig-Maximilians-University, Munich, Germany
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26
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Abstract
In recent years, understanding of the pathogenesis and clinical presentation of distinct myasthenia subtypes has increased significantly. This article reviews the clinical manifestations of autoimmune myasthenia gravis (including myasthenia associated with anti-muscle-specific kinase antibodies), ocular myasthenia, and antibody negative myasthenia. The following treatments are examined: cholinesterase inhibitors, immunosuppressants, and thymectomy. Inherited congenital myasthenic syndromes (CMS) are now increasingly recognized, and most commonly present during childhood. This article outlines the presynaptic, synaptic basal lamina-associated, and postsynaptic classification of CMS and the clinical presentation and aetiology of individual syndromes. Relevant investigations and treatment options (including the role of pyridostigmine, 3,4-diaminopyridine, fluoxetine, and ephedrine) are discussed.
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Affiliation(s)
- J R Parr
- University of Oxford Department of Paediatrics, Children's Hospital, Oxford, UK.
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