Cited by 53Myasthenia Gravis and ThymomaMuscle Physiology and DisordersNeurogenetic and Muscular Disorders Research

Impaired synaptic development, maintenance, and neuromuscular transmission in LRP4-related myasthenia

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Selcen, Duygu, Ohkawara, Bisei, Shen, Xin-Ming, McEvoy, Kathleen, Ohno, Kinji, Engel, Andrew G.·2015·JAMA Neurology

Abstract

IMPORTANCE: Congenital myasthenic syndromes (CMS) are heterogeneous disorders. Defining the phenotypic features, genetic basis, and pathomechanisms of a CMS is relevant to prognosis, genetic counseling, and therapy. OBJECTIVES: To characterize clinical, structural, electrophysiologic, and genetic features of a CMS and to search for optimal therapy. DESIGN, SETTINGS, AND PARTICIPANTS: Two sisters with CMS affecting the limb-girdle muscles were investigated between 2012 and 2014 at an academic medical center by clinical observation, in vitro analysis of neuromuscular transmission, cytochemical and electron microscopy studies of the neuromuscular junction, exome sequencing, expression studies in HEK293 and COS7 cells, and for response to therapy, and they were compared with 15 historical control participants. MAIN OUTCOMES AND MEASURES: We identified the disease gene and mutation, confirmed pathogenicity of the mutation by expression studies, and instituted optimal pharmacotherapy. RESULTS: Quantitative analysis of single EP regions was done for all 15 control participants and microelectrode studies of neuromuscular transmission and α-bgt binding sites per EP was conducted for 13 control participants. Examination of the older sister's intercostal muscle end plates (EPs) showed them to be abnormally small, with attenuated reactivities for the acetylcholine receptor and acetylcholinesterase. Most EPs had poorly differentiated or degenerate junctional folds, and some appeared denuded of nerve terminals. The amplitude of the EP potential (EPP), the miniature EPP, and the quantal content of the EPP were all markedly reduced. Exome sequencing identified a novel homozygous p.Glu1233Ala mutation in low-density lipoprotein receptor-related protein 4 (LRP4), a coreceptor for agrin to activate muscle-specific tyrosine kinase (MuSK), which is required for EP development and maintenance. Expression studies indicate that the mutation compromises the ability of LRP4 to bind to, phosphorylate, and activate MuSK. Treatment with albuterol sulfate improved the patients' symptoms. A previously identified patient harboring 2 heterozygous mutations in LRP4 had structurally abnormal intercostal EPs but no identifiable defect of neuromuscular transmission at these EPs. CONCLUSIONS AND RELEVANCE: We identified a second CMS kinship harboring mutations in LRP4, identified the mechanisms that impair neuromuscular transmission, and mitigated the disease by appropriate therapy.

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Crossref · 10.1001/jamaneurol.2015.0853

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  1. [15]Engel AG Engel AG Franzini-Armstrong C Quantitative morphological studies of muscle Myology 1994 2nd ed New York McGraw-Hill 1018 1045

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Authors
Selcen, D., Ohkawara, B., Shen, X.-M., McEvoy, K., Ohno, K., & Engel, A. G.
Affiliations
  • Mayo Clinic (US)
  • Nagoya University (JP)
Corresponding author
Engel, Andrew G.
Venue
JAMA Neurology
Published
2015-08-01
Volume
72
Issue
8
Pages
889
ISSN
2168-6149 (ISSN-L)
OpenAlex
W1567347505
Cited by
53
References
27
Citations by year
2026: 5 · 2025: 5 · 2024: 1 · 2023: 4 · 2022: 2 · 2021: 2 · 2020: 4 · 2019: 3 · 2018: 12 · 2017: 6 · 2016: 6 · 2015: 1 · 2013: 1
FWCI
5.85
Type
journal article
Language
en
Open access
Locations
  • JAMA Neurology (publishedVersion)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (acceptedVersion)
  • PubMed Central (acceptedVersion)
Funders
  • Japan Society for the Promotion of Science (15H04840)
  • National Institute of Neurological Disorders and Stroke (NS-62777, R01NS006277, R56NS006277)
Topics
  • Health Sciences › Medicine › Neurology › Myasthenia Gravis and Thymoma
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Muscle Physiology and Disorders
  • Health Sciences › Medicine › Genetics › Neurogenetic and Muscular Disorders Research
Keywords
congenital myasthenic syndrome, LRP4, neuromuscular transmission, neuromuscular junction, agrin, musk, acetylcholine receptor, acetylcholinesterase, intercostal muscles, homozygous mutation
MeSH terms
Adult, Female, Humans, Mutation, Myasthenia Gravis, Synaptic Transmission, Neuromuscular Junction, Muscle Weakness, Myasthenic Syndromes, Congenital, LDL-Receptor Related Proteins, Young Adult, HEK293 Cells

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