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Ramdas S, Beeson D, Dong YY. Congenital myasthenic syndromes: increasingly complex. Curr Opin Neurol 2024; 37:493-501. [PMID: 39051439 PMCID: PMC11377046 DOI: 10.1097/wco.0000000000001300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2024]
Abstract
PURPOSE OF REVIEW Congenital myasthenia syndromes (CMS) are treatable, inherited disorders affecting neuromuscular transmission. We highlight that the involvement of an increasing number of proteins is making the understanding of the disease mechanisms and potential treatments progressively more complex. RECENT FINDINGS Although early studies identified mutations of proteins directly involved in synaptic transmission at the neuromuscular junction, recently, next-generation sequencing has facilitated the identification of many novel mutations in genes that encode proteins that have a far wider expression profile, some even ubiquitously expressed, but whose defective function leads to impaired neuromuscular transmission. Unsurprisingly, mutations in these genes often causes a wider phenotypic disease spectrum where defective neuromuscular transmission forms only one component. This has implications for the management of CMS patients. SUMMARY Given the widening nonneuromuscular junction phenotypes in the newly identified forms of CMS, new therapies need to include disease-modifying approaches that address not only neuromuscular weakness but also the multisystem involvement. Whilst the current treatments for CMS are highly effective for many subtypes there remains, in a proportion of CMS patients, an unmet need for more efficacious therapies.
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Affiliation(s)
- Sithara Ramdas
- MDUK Neuromuscular Centre, Department of Paediatrics, University of Oxford
- Department of Paediatric Neurology, John Radcliffe Hospital
| | - David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, The John Radcliffe, Oxford OX3 9DS
| | - Yin Yao Dong
- Neurosciences Group, Weatherall Institute of Molecular Medicine, The John Radcliffe, Oxford OX3 9DS
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Cocanougher BT, Liu SW, Francescatto L, Behura A, Anneling M, Jackson DG, Deak KL, Hornik CD, ElMallah MK, Pizoli CE, Smith EC, Tan KGQ, McDonald MT. The severity of MUSK pathogenic variants is predicted by the protein domain they disrupt. HGG ADVANCES 2024; 5:100288. [PMID: 38566418 PMCID: PMC11070630 DOI: 10.1016/j.xhgg.2024.100288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 03/27/2024] [Accepted: 03/27/2024] [Indexed: 04/04/2024] Open
Abstract
Biallelic loss-of-function variants in the MUSK gene result in two allelic disorders: (1) congenital myasthenic syndrome (CMS; OMIM: 616325), a neuromuscular disorder that has a range of severity from severe neonatal-onset weakness to mild adult-onset weakness, and (2) fetal akinesia deformation sequence (OMIM: 208150), a form of pregnancy loss characterized by severe muscle weakness in the fetus. The MUSK gene codes for muscle-specific kinase (MuSK), a receptor tyrosine kinase involved in the development of the neuromuscular junction. Here, we report a case of neonatal-onset MUSK-related CMS in a patient harboring compound heterozygous deletions in the MUSK gene, including (1) a deletion of exons 2-3 leading to an in-frame MuSK protein lacking the immunoglobulin 1 (Ig1) domain and (2) a deletion of exons 7-11 leading to an out-of-frame, truncated MuSK protein. Individual domains of the MuSK protein have been elucidated structurally; however, a complete MuSK structure generated by machine learning algorithms has clear inaccuracies. We modify a predicted AlphaFold structure and integrate previously reported domain-specific structural data to suggest a MuSK protein that dimerizes in two locations (Ig1 and the transmembrane domain). We analyze known pathogenic variants in MUSK to discover domain-specific genotype-phenotype correlations; variants that lead to a loss of protein expression, disruption of the Ig1 domain, or Dok-7 binding are associated with the most severe phenotypes. A conceptual model is provided to explain the severe phenotypes seen in Ig1 variants and the poor response of our patient to pyridostigmine.
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Affiliation(s)
- Benjamin T Cocanougher
- Department of Pediatrics, Duke University, Durham, NC, USA; Division of Medical Genetics, Duke University, Durham, NC, USA.
| | - Samuel W Liu
- Department of Pediatrics, Duke University, Durham, NC, USA; Division of Medical Genetics, Duke University, Durham, NC, USA
| | | | - Alexander Behura
- Department of Pediatrics, Duke University, Durham, NC, USA; Division of Medical Genetics, Duke University, Durham, NC, USA
| | - Mariele Anneling
- Department of Pediatrics, Duke University, Durham, NC, USA; Division of Medical Genetics, Duke University, Durham, NC, USA
| | - David G Jackson
- Department of Pediatrics, Duke University, Durham, NC, USA; Division of Medical Genetics, Duke University, Durham, NC, USA
| | - Kristen L Deak
- Department of Pathology, Duke University, Durham, NC, USA
| | - Chi D Hornik
- Department of Pediatrics, Duke University, Durham, NC, USA
| | - Mai K ElMallah
- Department of Pediatrics, Duke University, Durham, NC, USA
| | - Carolyn E Pizoli
- Department of Pediatrics, Duke University, Durham, NC, USA; Division of Pediatric Neurology, Duke University, Durham, NC, USA
| | - Edward C Smith
- Department of Pediatrics, Duke University, Durham, NC, USA; Division of Pediatric Neurology, Duke University, Durham, NC, USA
| | - Khoon Ghee Queenie Tan
- Department of Pediatrics, Duke University, Durham, NC, USA; Division of Medical Genetics, Duke University, Durham, NC, USA
| | - Marie T McDonald
- Department of Pediatrics, Duke University, Durham, NC, USA; Division of Medical Genetics, Duke University, Durham, NC, USA.
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McLean A, Wilson I. Congenital myasthenic syndrome from a MUSK gene mutation. Pract Neurol 2024; 24:238-240. [PMID: 37985124 DOI: 10.1136/pn-2023-003945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/31/2023] [Indexed: 11/22/2023]
Abstract
Slowly progressive neuromuscular symptoms often have a genetic basis. We present the case of a woman in her 40s with gradually progressive symmetrical weakness and respiratory muscle involvement. Extensive investigation found no specific cause. After a novel neuromuscular gene panel became available, we identified a mutation in the MUSK gene (muscle-specific kinase), confirming a diagnosis of congenital myasthenic syndrome. This group of rare disorders are caused by mutations in genes encoding the neuromuscular junction.
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Affiliation(s)
- Antonia McLean
- Neurology, Cairns Hospital, Cairns, Queensland, Australia
| | - Ian Wilson
- Neurology, Cairns Hospital, Cairns, Queensland, Australia
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Henehan L, Beeson D, Palace J. Congenital myasthenic syndromes. Pract Neurol 2024; 24:185-187. [PMID: 38631903 DOI: 10.1136/pn-2024-004098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/01/2024] [Indexed: 04/19/2024]
Affiliation(s)
- Leighann Henehan
- Department of Clinical Neurology, John Radcliffe Hospital, Oxford, Oxfordshire, UK
| | - David Beeson
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Jacqueline Palace
- Department of Clinical Neurology, John Radcliffe Hospital, Oxford, Oxfordshire, UK
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Jiang L, Wang SC, Zhang J, Han FG, Zhao J, Xu Y. Case Report: Congenital Myasthenic Syndrome Presenting with Bilateral Vocal Cord Paralysis Caused by De-Novel Compound Heterozygous MUSK Mutation. Pharmgenomics Pers Med 2023; 16:373-379. [PMID: 37091828 PMCID: PMC10120818 DOI: 10.2147/pgpm.s398071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 03/21/2023] [Indexed: 04/25/2023] Open
Abstract
Background We report the genetic etiology of a case of bilateral vocal cord paralysis in a female infant. Case Description The female infant developed dyspnea after birth, which improved with treatment, allowing her to be discharged from the local hospital. At 2 months of age, the child experienced a recurrence of dyspnea and was treated in a local hospital with interventions such as tracheal intubation and mechanical ventilation. However, as the child continued to suffer from dyspnea, she was transferred to the neonatal intensive care unit of the Children's Hospital affiliated to Zhengzhou University for further treatment. A second electronic nasopharyngoscopy examination revealed bilateral vocal cord paralysis. The child underwent a tracheostomy due to a failure to wean from mechanical ventilation; after surgery, the respirator was effectively removed, and oxygen delivery ceased. The child and her parents underwent genetic testing with next-generation sequencing technology, which revealed that the child had two heterozygous variants in the MUSK gene, namely the c.2287G>A heterozygous mutation (p.Ala763Thr) and the c.790C>T heterozygous mutation. In addition, Sanger sequencing was performed, which confirmed that these two mutations were, respectively, inherited from the mother and father. Conclusion Congenital myasthenic syndrome caused by MUSK gene mutations can present clinically as bilateral vocal cord paralysis in neonates.
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Affiliation(s)
- Lan Jiang
- Department of Otorhinolaryngology Head and Neck Surgery, Children’s Hospital Affiliated to Zhengzhou University; Henan Children’s Hospital; Zhengzhou Children’s Hospital, Zhengzhou, 450003, People’s Republic of China
| | - Sheng-Cai Wang
- National Center for Children’s Health, Department of Otolaryngology Head and Neck Surgery, Beijing Children’s Hospital, Capital Medical University, Beijing, 100045, People’s Republic of China
| | - Jie Zhang
- National Center for Children’s Health, Department of Otolaryngology Head and Neck Surgery, Beijing Children’s Hospital, Capital Medical University, Beijing, 100045, People’s Republic of China
| | - Fu-Gen Han
- Department of Otorhinolaryngology Head and Neck Surgery, Children’s Hospital Affiliated to Zhengzhou University; Henan Children’s Hospital; Zhengzhou Children’s Hospital, Zhengzhou, 450003, People’s Republic of China
| | - Jing Zhao
- National Center for Children’s Health, Department of Otolaryngology Head and Neck Surgery, Beijing Children’s Hospital, Capital Medical University, Beijing, 100045, People’s Republic of China
| | - Ying Xu
- Department of Otorhinolaryngology Head and Neck Surgery, Children’s Hospital Affiliated to Zhengzhou University; Henan Children’s Hospital; Zhengzhou Children’s Hospital, Zhengzhou, 450003, People’s Republic of China
- Correspondence: Ying Xu, Department of Otorhinolaryngology Head and Neck Surgery, Children’s Hospital Affiliated to Zhengzhou University; Henan Children’s Hospital; Zhengzhou Children’s Hospital, Zhengzhou, 450003, People’s Republic of China, Tel/Fax +86 3718939569373, Email
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Xi J, Wang X, Yue D, Dou T, Wu Q, Lu J, Liu Y, Yu W, Qiao K, Lin J, Luo S, Li J, Du A, Dong J, Chen Y, Luo L, Yang J, Niu Z, Liang Z, Zhao C, Lu J, Zhu W, Zhou Y. 5' UTR CGG repeat expansion in GIPC1 is associated with oculopharyngodistal myopathy. Brain 2021; 144:601-614. [PMID: 33374016 DOI: 10.1093/brain/awaa426] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 09/20/2020] [Accepted: 10/05/2020] [Indexed: 11/14/2022] Open
Abstract
Oculopharyngodistal myopathy is a late-onset degenerative muscle disorder characterized by ptosis and weakness of the facial, pharyngeal, and distal limb muscles. A recent report suggested a non-coding trinucleotide repeat expansion in LRP12 to be associated with the disease. Here we report a genetic study in a Chinese cohort of 41 patients with the clinical diagnosis of oculopharyngodistal myopathy (21 cases from seven families and 20 sporadic cases). In a large family with 12 affected individuals, combined haplotype and linkage analysis revealed a maximum two-point logarithm of the odds (LOD) score of 3.3 in chromosomal region chr19p13.11-p13.2 and narrowed the candidate region to an interval of 4.5 Mb. Using a comprehensive strategy combining whole-exome sequencing, long-read sequencing, repeat-primed polymerase chain reaction and GC-rich polymerase chain reaction, we identified an abnormal CGG repeat expansion in the 5' UTR of the GIPC1 gene that co-segregated with disease. Overall, the repeat expansion in GIPC1 was identified in 51.9% independent pedigrees (4/7 families and 10/20 sporadic cases), while the repeat expansion in LRP12 was only identified in one sporadic case (3.7%) in our cohort. The number of CGG repeats was <30 in controls but >60 in affected individuals. There was a slight correlation between repeat size and the age at onset. Both repeat expansion and retraction were observed during transmission but somatic instability was not evident. These results further support that non-coding CGG repeat expansion plays an essential role in the pathogenesis of oculopharyngodistal myopathy.
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Affiliation(s)
- Jianying Xi
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, 200040, China
| | - Xilu Wang
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Dongyue Yue
- Department of Neurology, Jing'an District Center Hospital of Shanghai, Shanghai, 200040, China
| | - Tonghai Dou
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Qunfeng Wu
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Jun Lu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, 200040, China
| | - Yiqi Liu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, 200040, China
| | - Wenbo Yu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, 200040, China
| | - Kai Qiao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, 200040, China
| | - Jie Lin
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, 200040, China
| | - Sushan Luo
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, 200040, China
| | - Jing Li
- Department of Radiology, Jing'an District Center Hospital of Shanghai, Shanghai, 200040, China
| | - Ailian Du
- Department of Neurology, Tongren Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, 200336, China
| | - Jihong Dong
- Department of Neurology, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Yan Chen
- Department of Neurology, Tongji Hospital, Tongji University, Shanghai, 200065, China
| | - Lijun Luo
- Department of Neurology, Wuhan No.1 Hospital, Wuhan, 430021, China
| | - Jie Yang
- Department of Neurology, Wuhan No.1 Hospital, Wuhan, 430021, China
| | - Zhenmin Niu
- Shanghai-MOST Key Laboratory of Health and Disease Genomics, Chinese National Human Genome Center at Shanghai, Shanghai, 201203, China
| | - Zonghui Liang
- Department of Radiology, Jing'an District Center Hospital of Shanghai, Shanghai, 200040, China
| | - Chongbo Zhao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, 200040, China
| | - Jiahong Lu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, 200040, China
| | - Wenhua Zhu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, 200040, China
| | - Yan Zhou
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China.,Shanghai-MOST Key Laboratory of Health and Disease Genomics, Chinese National Human Genome Center at Shanghai, Shanghai, 201203, China
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Fernandes M, Caetano A, Pinto M, Medeiros E, Santos L. Diagnosis of DOK7 congenital myasthenic syndrome during pregnancy: A case report and literature review. Clin Neurol Neurosurg 2021; 203:106591. [PMID: 33714798 DOI: 10.1016/j.clineuro.2021.106591] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 02/14/2021] [Accepted: 02/27/2021] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Pregnancy among patients with congenital myasthenic syndrome (CMS) is a rare occurrence. Since most of the patients with CMS reach adulthood, questions regarding clinical outcome with pregnancy arise. CASE REPORT We describe a 38-year-old Portuguese female who presented in the second trimester of pregnancy with proximal fluctuating limb-girdle weakness, hyperlordosis, waddling gait, dysphagia, dysphonia and ptosis, with no ophthalmoparesis. Initial diagnosis of seronegative myasthenia, supported by neurophysiology findings, led to unsuccessful treatment with intravenous immunoglobulin, pyridostigmine, prednisolone and plasmapheresis, and the patient slowly progressed to a severe tetraparesis with facial and bulbar involvement. Genetic testing for CMS identified a novel compound heterozygous mutation (c.1124_1127dupTGCC and c.935_936del) in the DOK7 gene. Subsequent treatment with salbutamol resulted in substantial clinical benefit. CONCLUSIONS This case underlines the importance of considering the diagnosis of CMS in patients with fluctuating weakness during pregnancy. Patients of child-bearing potential diagnosed with CMS, particularly due to DOK7 mutations, should be counseled in advance and closely followed during pregnancy.
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Affiliation(s)
- Marco Fernandes
- Department of Neurology, Hospital de Egas Moniz, Centro Hospitalar de Lisboa Ocidental, Rua da Junqueira 126, 1349-019, Lisbon, Portugal.
| | - André Caetano
- Department of Neurology, Hospital de Egas Moniz, Centro Hospitalar de Lisboa Ocidental, Rua da Junqueira 126, 1349-019, Lisbon, Portugal; CEDOC Chronic Diseases Research Centre, Nova Medical School / Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisbon, Portugal
| | - Miguel Pinto
- Department of Neurology, Hospital de Egas Moniz, Centro Hospitalar de Lisboa Ocidental, Rua da Junqueira 126, 1349-019, Lisbon, Portugal
| | - Elmira Medeiros
- Department of Neurology, Hospital de Egas Moniz, Centro Hospitalar de Lisboa Ocidental, Rua da Junqueira 126, 1349-019, Lisbon, Portugal; CEDOC Chronic Diseases Research Centre, Nova Medical School / Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisbon, Portugal
| | - Luís Santos
- Department of Neurology, Hospital de Egas Moniz, Centro Hospitalar de Lisboa Ocidental, Rua da Junqueira 126, 1349-019, Lisbon, Portugal; CEDOC Chronic Diseases Research Centre, Nova Medical School / Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisbon, Portugal
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Ohkawara B, Ito M, Ohno K. Secreted Signaling Molecules at the Neuromuscular Junction in Physiology and Pathology. Int J Mol Sci 2021; 22:ijms22052455. [PMID: 33671084 PMCID: PMC7957818 DOI: 10.3390/ijms22052455] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 02/22/2021] [Accepted: 02/25/2021] [Indexed: 02/08/2023] Open
Abstract
Signal transduction at the neuromuscular junction (NMJ) is affected in many human diseases, including congenital myasthenic syndromes (CMS), myasthenia gravis, Lambert–Eaton myasthenic syndrome, Isaacs’ syndrome, Schwartz–Jampel syndrome, Fukuyama-type congenital muscular dystrophy, amyotrophic lateral sclerosis, and sarcopenia. The NMJ is a prototypic cholinergic synapse between the motor neuron and the skeletal muscle. Synaptogenesis of the NMJ has been extensively studied, which has also been extrapolated to further understand synapse formation in the central nervous system. Studies of genetically engineered mice have disclosed crucial roles of secreted molecules in the development and maintenance of the NMJ. In this review, we focus on the secreted signaling molecules which regulate the clustering of acetylcholine receptors (AChRs) at the NMJ. We first discuss the signaling pathway comprised of neural agrin and its receptors, low-density lipoprotein receptor-related protein 4 (Lrp4) and muscle-specific receptor tyrosine kinase (MuSK). This pathway drives the clustering of acetylcholine receptors (AChRs) to ensure efficient signal transduction at the NMJ. We also discuss three secreted molecules (Rspo2, Fgf18, and connective tissue growth factor (Ctgf)) that we recently identified in the Wnt/β-catenin and fibroblast growth factors (FGF) signaling pathways. The three secreted molecules facilitate the clustering of AChRs by enhancing the agrin-Lrp4-MuSK signaling pathway.
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Affiliation(s)
- Bisei Ohkawara
- Correspondence: ; Tel.: +81-52-744-2447; Fax: +81-52-744-2449
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