1
|
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.
Collapse
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.
| |
Collapse
|
2
|
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: 34] [Impact Index Per Article: 34.0] [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.
Collapse
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.)
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Congenital Ophthalmoplegia and Late-Onset Limb Weakness Caused by MUSK Mutations. J Clin Neuromuscul Dis 2021; 21:222-224. [PMID: 32453097 DOI: 10.1097/cnd.0000000000000277] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Congenital myasthenic syndromes are clinically and genetically heterogeneous disorders characterized by a neuromuscular transmission defect. Mutations in novel genes have been described in recent years. Among these, MUSK gene mutations are extremely rare, with only 8 families identified worldwide to date. We report a Spanish case, a carrier of one known hetero-allelic missense mutation and one newly identified MUSK gene variant. Our patient presented with congenital onset ophthalmoplegia and palpebral ptosis associated with limb-girdle weakness and exercise intolerance without prominent fatigability, developed during his twenties. He was misdiagnosed as mitochondrial myopathy because of paraclinic and histologic findings, but detailed clinical examination prompted us to reassess him with repetitive stimulation technique, demonstrating decremental response and suggesting myasthenic syndrome. A genetic study confirmed the clinical diagnosis allowing us to started treatment with excellent clinical response.
Collapse
|
5
|
Xiao T, Wu LW. [Advances in the diagnosis and treatment of congenital myasthenic syndrome]. ZHONGGUO DANG DAI ER KE ZA ZHI = CHINESE JOURNAL OF CONTEMPORARY PEDIATRICS 2020; 22:672-676. [PMID: 32571471 PMCID: PMC7390217 DOI: 10.7499/j.issn.1008-8830.1912095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 04/24/2020] [Indexed: 06/11/2023]
Abstract
Congenital myasthenic syndrome (CMS) is a group of clinical and genetic heterogeneous diseases caused by impaired neuromuscular transmission due to genetic defects. At present, it has been reported that more than 30 genes can cause CMS. All CMS subtypes have the clinical features of fatigue and muscle weakness, but age of onset, symptoms, and treatment response vary with the molecular mechanisms underlying genetic defects. Pharmacotherapy and symptomatic/supportive treatment are the main methods for the treatment of CMS, and antisense oligonucleotide technology has been proven to be beneficial for CHRNA 1-related CMS in animals. Since CMS is a group of increasingly recognized clinical and genetic heterogeneous diseases, an understanding of the latest knowledge and research advances in its clinical features, genetic research, and treatment helps to give early diagnosis and treatment as well as gain a deeper understanding of the pathogenesis of CMS, so as to make new breakthroughs in the treatment of CMS.
Collapse
Affiliation(s)
- Ting Xiao
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha 410008, China.
| | | |
Collapse
|
6
|
Shen Y, Wang B, Zheng X, Zhang W, Wu H, Hei M. A Neonate With MuSK Congenital Myasthenic Syndrome Presenting With Refractory Respiratory Failure. Front Pediatr 2020; 8:166. [PMID: 32373561 PMCID: PMC7176811 DOI: 10.3389/fped.2020.00166] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Accepted: 03/24/2020] [Indexed: 12/04/2022] Open
Abstract
This was a Chinese neonatal congenital myasthenic syndromes case caused by muscle skeletal receptor tyrosine kinase gene mutations, which have not been recorded in the Human Gene Mutation Database. The newborn girl had refractory respiratory failure from birth to death, and failed extubation seven times. She had two heterozygous mutations: a non-sense mutation c.2062C>T (p.Q688X) inherited from father and a missense mutation c.2324T>C (p.F775S) inherited from mother, which was predicted pathogenic and harmful by bioinformatic softwares SIFT, PolyPhen_2 and REVEL. She positively responded to Neostigmine, but her parent quitted treatment when Pyridostigmine Bromide (2 mg/kg Q12 h) had been given for 8 days. She died 2 days after she was taken home by her parents on age of 56 days.
Collapse
Affiliation(s)
- Yanhua Shen
- Neonatal Center, Beijing Children's Hospital, Capital Medical University, Beijing, China
- National Center for Children's Health, Beijing, China
| | - Bo Wang
- Neonatal Center, Beijing Children's Hospital, Capital Medical University, Beijing, China
- National Center for Children's Health, Beijing, China
| | - Xia Zheng
- Neonatal Center, Beijing Children's Hospital, Capital Medical University, Beijing, China
- National Center for Children's Health, Beijing, China
| | - Wenwen Zhang
- Neonatal Center, Beijing Children's Hospital, Capital Medical University, Beijing, China
- National Center for Children's Health, Beijing, China
| | - Hailan Wu
- Neonatal Center, Beijing Children's Hospital, Capital Medical University, Beijing, China
- National Center for Children's Health, Beijing, China
| | - Mingyan Hei
- Neonatal Center, Beijing Children's Hospital, Capital Medical University, Beijing, China
- National Center for Children's Health, Beijing, China
| |
Collapse
|
7
|
Liu Y, Qiao K, Yan C, Song J, Huan X, Luo S, Lu J, Zhao C, Xi J. Congenital myasthenia syndrome in a Chinese family with mutations in MUSK: A hotspot mutation and literature review. J Clin Neurosci 2020; 76:161-165. [PMID: 32253145 DOI: 10.1016/j.jocn.2020.03.036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 03/01/2020] [Accepted: 03/20/2020] [Indexed: 11/30/2022]
Abstract
Congenital myasthenic syndrome (CMS) caused by mutations in MUSK is very rare and the genotype-phenotype relationship in MUSK related CMS is still unclear. Here we identified two patients carrying a homozygous hotspot mutation, c.308A > G in MUSK from a Chinese family. Both of them presented predominant bulbar weakness and atrophy of bilateral temporalis and masticatory muscles. To address the phenotype-genotype relationship, a total of 27 MUSK related CMS patients were reviewed. Patients with nonsense, frameshift or splicing mutations showed earlier onset (10/13 vs 2/14 neonatal onset, p = 0.0018) and more occurrence of vocal cord paralysis or stridor (8/13 vs 0/14, p = 0.0006), indicating a more severe phenotype. Comparing with patients carrying other missense mutations, the four patients carrying a homozygous c.308A > G mutation showed the female predominance (4/10 vs 4/4) and dramatic exacerbation after emotional or physiological stresses (2/10 vs 4/4) like pregnancy, menstrual periods and infection. All these indicated a genotype-phenotype relationship in MUSK-related CMS.
Collapse
Affiliation(s)
- Yiqi Liu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Kai Qiao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Chong Yan
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Jie Song
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Xiao Huan
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Sushan Luo
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Jiahong Lu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Chongbo Zhao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Jianying Xi
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China.
| |
Collapse
|
8
|
Guarino SR, Canciani A, Forneris F. Dissecting the Extracellular Complexity of Neuromuscular Junction Organizers. Front Mol Biosci 2020; 6:156. [PMID: 31998752 PMCID: PMC6966886 DOI: 10.3389/fmolb.2019.00156] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 12/13/2019] [Indexed: 12/20/2022] Open
Abstract
Synapse formation is a very elaborate process dependent upon accurate coordination of pre and post-synaptic specialization, requiring multiple steps and a variety of receptors and signaling molecules. Due to its relative structural simplicity and the ease in manipulation and observation, the neuromuscular synapse or neuromuscular junction (NMJ)-the connection between motor neurons and skeletal muscle-represents the archetype junction system for studying synapse formation and conservation. This junction is essential for survival, as it controls our ability to move and breath. NMJ formation requires coordinated interactions between motor neurons and muscle fibers, which ultimately result in the formation of a highly specialized post-synaptic architecture and a highly differentiated nerve terminal. Furthermore, to ensure a fast and reliable synaptic transmission following neurotransmitter release, ligand-gated channels (acetylcholine receptors, AChRs) are clustered on the post-synaptic muscle cell at high concentrations in sites opposite the presynaptic active zone, supporting a direct role for nerves in the organization of the post-synaptic membrane architecture. This organized clustering process, essential for NMJ formation and for life, relies on key signaling molecules and receptors and is regulated by soluble extracellular molecules localized within the synaptic cleft. Notably, several mutations as well as auto-antibodies against components of these signaling complexes have been related to neuromuscular disorders. The recent years have witnessed strong progress in the understanding of molecular identities, architectures, and functions of NMJ macromolecules. Among these, prominent roles have been proposed for neural variants of the proteoglycan agrin, its receptor at NMJs composed of the lipoprotein receptor-related protein 4 (LRP4) and the muscle-specific kinase (MuSK), as well as the regulatory soluble synapse-specific protease Neurotrypsin. In this review we summarize the current state of the art regarding molecular structures and (agrin-dependent) canonical, as well as (agrin-independent) non-canonical, MuSK signaling mechanisms that underscore the formation of neuromuscular junctions, with the aim of providing a broad perspective to further stimulate molecular, cellular and tissue biology investigations on this fundamental intercellular contact.
Collapse
Affiliation(s)
| | | | - Federico Forneris
- The Armenise-Harvard Laboratory of Structural Biology, Department Biology and Biotechnology, University of Pavia, Pavia, Italy
| |
Collapse
|
9
|
Pinto MV, Saw JL, Milone M. Congenital Vocal Cord Paralysis and Late-Onset Limb-Girdle Weakness in MuSK-Congenital Myasthenic Syndrome. Front Neurol 2019; 10:1300. [PMID: 31920924 PMCID: PMC6934021 DOI: 10.3389/fneur.2019.01300] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 11/26/2019] [Indexed: 12/19/2022] Open
Abstract
A 30-year-old woman with congenital vocal cord paralysis presented for evaluation of fatigable proximal upper limb weakness and difficulty maintaining the neck erect. Neurologic examination showed bilateral asymmetric eyelid ptosis, mild weakness (MRC 4/5), and atrophy of neck extensors and shoulder girdle muscles, whereas lower limb muscle strength was normal. Repetitive nerve stimulation revealed decremental responses in orbicularis oculis and trapezius. Needle electromyography demonstrated myopathic changes in proximal and paraspinal muscles. Acetylcholine receptor and muscle skeletal receptor tyrosine kinase (MuSK) antibodies, creatine kinase (CK), and lactate were negative or normal. Next-generation sequencing detected two heterozygous variants in the MUSK gene. One variant, c.79+2T>G, is a known pathogenic variant, and the other, c.2165T>C (p.V722A), is a novel missense variant, predicted to be pathogenic by in silico analysis. The two variants were proven to be in trans. This case expands the clinical and molecular spectrum of MuSK congenital myasthenic syndromes.
Collapse
Affiliation(s)
- Marcus V Pinto
- Department of Neurology, Mayo Clinic, Rochester, MN, United States
| | - Jacqui-Lyn Saw
- Department of Neurology, Mayo Clinic, Rochester, MN, United States
| | | |
Collapse
|
10
|
Alhammad RM, Naddaf E. Myopathies presenting with head drop: Clinical spectrum and treatment outcomes. Neuromuscul Disord 2019; 30:128-136. [PMID: 32005492 DOI: 10.1016/j.nmd.2019.12.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 11/23/2019] [Accepted: 12/09/2019] [Indexed: 11/25/2022]
Abstract
Dropped head syndrome can be the presenting feature of a wide spectrum of neurological conditions. In this study, we aimed to define the clinical characteristics and treatment outcomes of 107 patients, where head drop was the presenting or predominant clinical feature of a myopathy. Median age at presentation was 68 years (range 42-88). A specific diagnosis was reached in 53% of patients: Inflammatory myopathy (n = 16), myopathy with rimmed vacuoles (n = 10), radiation-induced myopathy (n = 8), sporadic late-onset nemaline myopathy (n = 7), myofibrillar myopathy (n = 4), facioscapulohumeral dystrophy (n = 3), inclusion body myositis (n = 2), mitochondrial myopathy (n = 2), scleroderma-associated myopathy (n = 2), and single cases of necrotizing autoimmune myopathy, drug-induced myopathy, and B-cell chronic lymphocytic leukemia-myopathy. Splenius capitis had the highest diagnostic yield for a muscle biopsy (67%). When tested, 31/35 (89%) of patients had abnormal pulmonary function tests, 15/30 (50%) abnormal swallow evaluation, 24/65 (37%) abnormal electrocardiogram and 5/38 (13%) abnormal transthoracic echocardiogram. 23/43 (53%) treated patients responded to treatment. Patient-reported limb weakness and neck flexion weakness on physical examination were associated with good response to treatment. A wide spectrum of acquired and hereditary myopathies can present with head drop, some of which are potentially treatable. Establishing a diagnosis is crucial for timely treatment administration, screening for swallowing and cardiorespiratory involvement, and counseling regarding prognosis.
Collapse
Affiliation(s)
| | - Elie Naddaf
- Department of Neurology, Mayo Clinic, Rochester, MN, USA.
| |
Collapse
|
11
|
Rodríguez Cruz PM, Cossins J, Cheung J, Maxwell S, Jayawant S, Herbst R, Waithe D, Kornev AP, Palace J, Beeson D. Congenital myasthenic syndrome due to mutations in MUSK suggests that the level of MuSK phosphorylation is crucial for governing synaptic structure. Hum Mutat 2019; 41:619-631. [PMID: 31765060 PMCID: PMC7028094 DOI: 10.1002/humu.23949] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 09/08/2019] [Accepted: 11/05/2019] [Indexed: 11/18/2022]
Abstract
MUSK encodes the muscle‐specific receptor tyrosine kinase (MuSK), a key component of the agrin‐LRP4‐MuSK‐DOK7 signaling pathway, which is essential for the formation and maintenance of highly specialized synapses between motor neurons and muscle fibers. We report a patient with severe early‐onset congenital myasthenic syndrome and two novel missense mutations in MUSK (p.C317R and p.A617V). Functional studies show that MUSK p.C317R, located at the frizzled‐like cysteine‐rich domain of MuSK, disrupts an integral part of MuSK architecture resulting in ablated MuSK phosphorylation and acetylcholine receptor (AChR) cluster formation. MUSK p.A617V, located at the kinase domain of MuSK, enhances MuSK phosphorylation resulting in anomalous AChR cluster formation. The identification and evidence for pathogenicity of MUSK mutations supported the initiation of treatment with β2‐adrenergic agonists with a dramatic improvement of muscle strength in the patient. This work suggests uncharacterized mechanisms in which control of the precise level of MuSK phosphorylation is crucial in governing synaptic structure.
Collapse
Affiliation(s)
- Pedro M Rodríguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.,Neurosciences Group, The John Radcliffe Hospital, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Judith Cossins
- Neurosciences Group, The John Radcliffe Hospital, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Jonathan Cheung
- Neurosciences Group, The John Radcliffe Hospital, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Susan Maxwell
- Neurosciences Group, The John Radcliffe Hospital, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Sandeep Jayawant
- Department of Paediatric Neurology, Children's Hospital, John Radcliffe Hospital, Oxford, UK
| | - Ruth Herbst
- Center for Pathophysiology, Infectiology and Immunology, Medical Science Divisions, Medical University of Vienna, Vienna, Austria
| | - Dominic Waithe
- MRC Centre for Computational Biology and Wolfson Imaging Centre, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Alexandr P Kornev
- Department of Pharmacology, University of California at San Diego, La Jolla, California
| | - Jacqueline Palace
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.,Neurosciences Group, The John Radcliffe Hospital, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| |
Collapse
|
12
|
Rivner MH, Pasnoor M, Dimachkie MM, Barohn RJ, Mei L. Muscle-Specific Tyrosine Kinase and Myasthenia Gravis Owing to Other Antibodies. Neurol Clin 2019; 36:293-310. [PMID: 29655451 DOI: 10.1016/j.ncl.2018.01.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Around 20% of patients with myasthenia gravis are acetylcholine receptor antibody negative; muscle-specific tyrosine kinase antibodies (MuSK) were identified as the cause of myasthenia gravis in 30% to 40% of these cases. Anti MuSK myasthenia gravis is associated with specific clinical phenotypes. One is a bulbar form with fewer ocular symptoms. Others show an isolated head drop or symptoms indistinguishable from acetylcholine receptor-positive myasthenia gravis. These patients usually respond well to immunosuppressive therapy, but not as well to cholinesterase inhibitors. Other antibodies associated with myasthenia gravis, including low-density lipoprotein receptor-related protein 4, are discussed.
Collapse
Affiliation(s)
- Michael H Rivner
- EMG Lab, Augusta University, 1120 15th Street, BP-4390, Augusta, GA 30912, USA.
| | - Mamatha Pasnoor
- Department of Neurology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
| | - Mazen M Dimachkie
- Department of Neurology, University of Kansas Medical Center, 3599 Rainbow Boulevard, Mail Stop 2012, Kansas City, KS 66103, USA
| | - Richard J Barohn
- Department of Neurology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Mail Stop 4017, Kansas City, KS 66160, USA
| | - Lin Mei
- Department of Neuroscience and Regenerative Medicine, Augusta University, 1120 15th Street, CA-2014, Augusta, GA 30912, USA
| |
Collapse
|
13
|
Abstract
OBJECTIVES Congenital myasthenic syndromes (CMSs) are a genotypically and phenotypically heterogeneous group of neuromuscular disorders, which have in common an impaired neuromuscular transmission. Since the field of CMSs is steadily expanding, the present review aimed at summarizing and discussing current knowledge and recent advances concerning the etiology, clinical presentation, diagnosis, and treatment of CMSs. METHODS Systematic literature review. RESULTS Currently, mutations in 32 genes are made responsible for autosomal dominant or autosomal recessive CMSs. These mutations concern 8 presynaptic, 4 synaptic, 15 post-synaptic, and 5 glycosilation proteins. These proteins function as ion-channels, enzymes, or structural, signalling, sensor, or transporter proteins. The most common causative genes are CHAT, COLQ, RAPSN, CHRNE, DOK7, and GFPT1. Phenotypically, these mutations manifest as abnormal fatigability or permanent or fluctuating weakness of extra-ocular, facial, bulbar, axial, respiratory, or limb muscles, hypotonia, or developmental delay. Cognitive disability, dysmorphism, neuropathy, or epilepsy are rare. Low- or high-frequency repetitive nerve stimulation may show an abnormal increment or decrement, and SF-EMG an increased jitter or blockings. Most CMSs respond favourably to acetylcholine-esterase inhibitors, 3,4-diamino-pyridine, salbutamol, albuterol, ephedrine, fluoxetine, or atracurium. CONCLUSIONS CMSs are an increasingly recognised group of genetically transmitted defects, which usually respond favorably to drugs enhancing the neuromuscular transmission. CMSs need to be differentiated from neuromuscular disorders due to muscle or nerve dysfunction.
Collapse
Affiliation(s)
- Josef Finsterer
- Krankenanstalt Rudolfstiftung, Messerli Institute, Veterinary University of Vienna, Postfach 20, 1180, Vienna, Austria.
| |
Collapse
|
14
|
Murali C, Li D, Grand K, Hakonarson H, Bhoj E. Isolated vocal cord paralysis in two siblings with compound heterozygous variants in MUSK: Expanding the phenotypic spectrum. Am J Med Genet A 2019; 179:655-658. [PMID: 30719842 DOI: 10.1002/ajmg.a.61060] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 01/09/2019] [Accepted: 01/10/2019] [Indexed: 01/19/2023]
Abstract
The congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders caused by perturbations in signal transduction at the neuromuscular junction. Defects in muscle, skeletal, receptor tyrosine kinase (MuSK) cause two distinct phenotypes: fetal akinesia with multiple congenital anomalies (Fetal akinesia deformation sequence [MIM:208150]) and early onset congenital myasthenia (myasthenic syndrome, congenital, 9, associated with acetylcholine receptor deficiency [MIM:616325]). Myasthenia due to MuSK deficiency has variable clinical features, ranging from a milder presentation of isolated late-onset proximal muscle weakness; to a severe presentation of prenatal-onset diffuse weakness, ophthalmoplegia, respiratory failure, and vocal cord paralysis (VCP). Here, we propose to expand the phenotypic spectrum for MuSK deficiency to include isolated VCP with the absence of other classical myasthenic symptoms. We evaluated two brothers who presented in the neonatal period with respiratory failure secondary to isolated VCP. Research-based exome sequencing revealed biallelic likely pathogenic variants in MUSK (MIM:601296). Both children had normal gross motor and fine motor development. One brother had speech delay, likely due to a combination of tracheostomy status and ankyloglossia. This case report suggests that CMS should be on the differential diagnosis for familial recurrence of VCP.
Collapse
Affiliation(s)
- Chaya Murali
- Department of Pediatrics, Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Dong Li
- Department of Pediatrics, Center for Applied Genomics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Katheryn Grand
- Department of Pediatrics, Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Hakon Hakonarson
- Department of Pediatrics, Center for Applied Genomics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Elizabeth Bhoj
- Department of Pediatrics, Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.,Department of Pediatrics, Center for Applied Genomics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| |
Collapse
|
15
|
Wadwekar V, Pillai RR, Sesh S, Nair SS, Nair M. Pregnancy-associated respiratory failure in muscle specific kinase congenital myasthenic syndrome. Muscle Nerve 2019; 59:E24-E26. [PMID: 30635923 DOI: 10.1002/mus.26410] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Revised: 12/19/2018] [Accepted: 12/22/2018] [Indexed: 11/07/2022]
Affiliation(s)
- Vaibhav Wadwekar
- Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - Rajit Remanan Pillai
- Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - S Sesh
- Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - Sruthi S Nair
- Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| | - Muralidharan Nair
- Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India
| |
Collapse
|
16
|
Owen D, Töpf A, Preethish-Kumar V, Lorenzoni PJ, Vroling B, Scola RH, Dias-Tosta E, Geraldo A, Polavarapu K, Nashi S, Cox D, Evangelista T, Dawson J, Thompson R, Senderek J, Laurie S, Beltran S, Gut M, Gut I, Nalini A, Lochmüller H. Recessive variants of MuSK are associated with late onset CMS and predominant limb girdle weakness. Am J Med Genet A 2018; 176:1594-1601. [PMID: 29704306 DOI: 10.1002/ajmg.a.38707] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 02/26/2018] [Accepted: 03/20/2018] [Indexed: 11/07/2022]
Abstract
Congenital myasthenic syndrome (CMS) is a heterogeneous disorder that causes fatigable muscle weakness. CMS has been associated with variants in the MuSK gene and, to date, 16 patients have been reported. MuSK-CMS patients present a different phenotypic pattern of limb girdle weakness. Here, we describe four additional patients and discuss the phenotypic and clinical relationship with those previously reported. Two novel damaging missense variants are described: c.1742T > A; p.I581N found in homozygosis, and c.1634T > C; p.L545P found in compound heterozygosis with p.R166*. The reported patients had predominant limb girdle weakness with symptom onset at 12, 17, 18, and 30 years of age, and the majority exhibited a good clinical response to Salbutamol therapy, but not to esterase inhibitors. Meta-analysis including previously reported variants revealed an increased likelihood of a severe, respiratory phenotype with null alleles. Missense variants exclusively affecting the kinase domain, but not the catalytic site, are associated with late onset. These data refine the phenotype associated with MuSK-related CMS.
Collapse
Affiliation(s)
- David Owen
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Ana Töpf
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Veeramani Preethish-Kumar
- Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, Karnataka, India
| | - Paulo José Lorenzoni
- Service of Neuromuscular Disorders, Division of Neurology, Department of Internal Medicine, Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, Brazil
| | | | - Rosana Herminia Scola
- Service of Neuromuscular Disorders, Division of Neurology, Department of Internal Medicine, Hospital de Clínicas, Universidade Federal do Paraná, Curitiba, Brazil
| | - Elza Dias-Tosta
- Unidade de Neurologia Clínica, Hospital de Base do Distrito Federal, Brasília, Brazil
| | - Argemiro Geraldo
- Serviço de Neurologia, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
| | - Kiran Polavarapu
- Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, Karnataka, India
| | - Saraswati Nashi
- Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, Karnataka, India
| | - Daniel Cox
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Teresinha Evangelista
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - John Dawson
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Rachel Thompson
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Jan Senderek
- Friedrich-Baur-Institut, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Steven Laurie
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Sergi Beltran
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Marta Gut
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Ivo Gut
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Atchayaram Nalini
- Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, Karnataka, India
| | - Hanns Lochmüller
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
- CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
- Department of Neuropediatrics and Muscle Disorders, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| |
Collapse
|
17
|
Yang K, Cheng H, Yuan F, Meng L, Yin R, Zhang Y, Wang S, Wang C, Lu Y, Xi J, Lu Q, Chen Y. CHRNE compound heterozygous mutations in congenital myasthenic syndrome: A case report. Medicine (Baltimore) 2018; 97:e0347. [PMID: 29702980 PMCID: PMC5944527 DOI: 10.1097/md.0000000000010347] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
RATIONALE Congenital myasthenic syndrome (CMSs) are a group of rare genetic disorders of the neurological junction, which can result in structural or functional weakness. Here, we characterized a case of CMS in order to clarify the diagnosis and expand the understanding of it. The molecular diagnosis had implications for choice of treatment and genetic counseling. PATIENT CONCERNS A 3-year-old male patient with CMS had ptosis and limb weakness for 2 months after birth. Clinical course and electrophysiological, imaging, and genetic findings were assessed. Protein structure/function was predicted. A novel mutation of c.295C>T (exon 4) and another known mutation of c.442T>A (exon 5) were found in CHRNE. Both mutations localized in conserved sequences. The c.442T>A (p.C148S) missense mutation in CHRNE was predicted to be damaging/deleterious. The iterative threading assembly refinement (I-TASSER) server generated vastly different 3-dimensional (3D) atomic models based on protein sequences from wide-type and novel nonsense mutation of c.295C>T (p.R99X) in CHRNE. DIAGNOSES The diagnosis of CMS with CHRNE mutations in Han Chinese was confirmed. INTERVENTIONS The patient was given prednisone (10 mg, once daily, taken orally) and pyridostigmine (15 mg, three times a day, taken orally). OUTCOMES The patient had a moderate response to prednisone and pyridostigmine. LESSONS We expanded the genotype and phenotype of CMS with CHRNE mutations in Han Chinese and provided new insights into the molecular mechanism of CMS and help to the diagnosis and treatment of CMS.
Collapse
Affiliation(s)
| | | | | | - Linyi Meng
- Department of Pharmacy, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai, China
| | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Morren J, Li Y. Myasthenia gravis with muscle-specific tyrosine kinase antibodies: A narrative review. Muscle Nerve 2018; 58:344-358. [DOI: 10.1002/mus.26107] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 02/09/2018] [Accepted: 02/18/2018] [Indexed: 12/14/2022]
Affiliation(s)
- John Morren
- Neuromuscular Center, Neurological Institute, Cleveland Clinic, 9500 Euclid Avenue, Desk S90; Cleveland Ohio 44195 USA
| | - Yuebing Li
- Neuromuscular Center, Neurological Institute, Cleveland Clinic, 9500 Euclid Avenue, Desk S90; Cleveland Ohio 44195 USA
| |
Collapse
|
19
|
Nickel J, Ten Dijke P, Mueller TD. TGF-β family co-receptor function and signaling. Acta Biochim Biophys Sin (Shanghai) 2018; 50:12-36. [PMID: 29293886 DOI: 10.1093/abbs/gmx126] [Citation(s) in RCA: 123] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 11/08/2017] [Indexed: 01/04/2023] Open
Abstract
Transforming growth factor-β (TGF-β) family members, which include TGF-βs, activins and bone morphogenetic proteins, are pleiotropic cytokines that elicit cell type-specific effects in a highly context-dependent manner in many different tissues. These secreted protein ligands signal via single-transmembrane Type I and Type II serine/threonine kinase receptors and intracellular SMAD transcription factors. Deregulation in signaling has been implicated in a broad array of diseases, and implicate the need for intricate fine tuning in cellular signaling responses. One important emerging mechanism by which TGF-β family receptor signaling intensity, duration, specificity and diversity are regulated and/or mediated is through cell surface co-receptors. Here, we provide an overview of the co-receptors that have been identified for TGF-β family members. While some appear to be specific to TGF-β family members, others are shared with other pathways and provide possible ways for signal integration. This review focuses on novel functions of TGF-β family co-receptors, which continue to be discovered.
Collapse
Affiliation(s)
- Joachim Nickel
- Universitätsklinikum Würzburg, Lehrstuhl für Tissue Engineering und Regenerative Medizin und Fraunhofer Institut für Silicatforschung (ISC), Translationszentrum "Regenerative Therapien", Röntgenring 11, D-97070 Würzburg, Germany
| | - Peter Ten Dijke
- Department of Molecular and Cell Biology and Cancer Genomics Centre Netherlands, Leiden University Medical Center, Einthovenweg 20, 2300 RC Leiden, The Netherlands
| | - Thomas D Mueller
- Lehrstuhl für molekulare Pflanzenphysiologie und Biophysik, Julius-von-Sachs Institut für Biowissenschaften, Universität Würzburg, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany
| |
Collapse
|
20
|
Luan X, Tian W, Cao L. Limb-girdle congenital myasthenic syndrome in a Chinese family with novel mutations in MUSK gene and literature review. Clin Neurol Neurosurg 2016; 150:41-45. [DOI: 10.1016/j.clineuro.2016.08.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Revised: 08/04/2016] [Accepted: 08/21/2016] [Indexed: 11/16/2022]
|