1
|
Cheng YHH, Bohaczuk SC, Stergachis AB. Functional categorization of gene regulatory variants that cause Mendelian conditions. Hum Genet 2024; 143:559-605. [PMID: 38436667 PMCID: PMC11078748 DOI: 10.1007/s00439-023-02639-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 12/30/2023] [Indexed: 03/05/2024]
Abstract
Much of our current understanding of rare human diseases is driven by coding genetic variants. However, non-coding genetic variants play a pivotal role in numerous rare human diseases, resulting in diverse functional impacts ranging from altered gene regulation, splicing, and/or transcript stability. With the increasing use of genome sequencing in clinical practice, it is paramount to have a clear framework for understanding how non-coding genetic variants cause disease. To this end, we have synthesized the literature on hundreds of non-coding genetic variants that cause rare Mendelian conditions via the disruption of gene regulatory patterns and propose a functional classification system. Specifically, we have adapted the functional classification framework used for coding variants (i.e., loss-of-function, gain-of-function, and dominant-negative) to account for features unique to non-coding gene regulatory variants. We identify that non-coding gene regulatory variants can be split into three distinct categories by functional impact: (1) non-modular loss-of-expression (LOE) variants; (2) modular loss-of-expression (mLOE) variants; and (3) gain-of-ectopic-expression (GOE) variants. Whereas LOE variants have a direct corollary with coding loss-of-function variants, mLOE and GOE variants represent disease mechanisms that are largely unique to non-coding variants. These functional classifications aim to provide a unified terminology for categorizing the functional impact of non-coding variants that disrupt gene regulatory patterns in Mendelian conditions.
Collapse
Affiliation(s)
- Y H Hank Cheng
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA, USA
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Stephanie C Bohaczuk
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA, USA
| | - Andrew B Stergachis
- Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA, USA.
- Department of Genome Sciences, University of Washington, Seattle, WA, USA.
- Brotman Baty Institute for Precision Medicine, Seattle, WA, USA.
| |
Collapse
|
2
|
Feng X, Liu S, Li K, Bu F, Yuan H. NCAD v1.0: a database for non-coding variant annotation and interpretation. J Genet Genomics 2024; 51:230-242. [PMID: 38142743 DOI: 10.1016/j.jgg.2023.12.005] [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] [Received: 08/30/2023] [Revised: 12/15/2023] [Accepted: 12/18/2023] [Indexed: 12/26/2023]
Abstract
The application of whole genome sequencing is expanding in clinical diagnostics across various genetic disorders, and the significance of non-coding variants in penetrant diseases is increasingly being demonstrated. Therefore, it is urgent to improve the diagnostic yield by exploring the pathogenic mechanisms of variants in non-coding regions. However, the interpretation of non-coding variants remains a significant challenge, due to the complex functional regulatory mechanisms of non-coding regions and the current limitations of available databases and tools. Hence, we develop the non-coding variant annotation database (NCAD, http://www.ncawdb.net/), encompassing comprehensive insights into 665,679,194 variants, regulatory elements, and element interaction details. Integrating data from 96 sources, spanning both GRCh37 and GRCh38 versions, NCAD v1.0 provides vital information to support the genetic diagnosis of non-coding variants, including allele frequencies of 12 diverse populations, with a particular focus on the population frequency information for 230,235,698 variants in 20,964 Chinese individuals. Moreover, it offers prediction scores for variant functionality, five categories of regulatory elements, and four types of non-coding RNAs. With its rich data and comprehensive coverage, NCAD serves as a valuable platform, empowering researchers and clinicians with profound insights into non-coding regulatory mechanisms while facilitating the interpretation of non-coding variants.
Collapse
Affiliation(s)
- Xiaoshu Feng
- Institute of Rare Diseases, West China Hospital, Sichuan University, Chengdu, Sichuan 610044, China
| | - Sihan Liu
- Institute of Rare Diseases, West China Hospital, Sichuan University, Chengdu, Sichuan 610044, China
| | - Ke Li
- Institute of Rare Diseases, West China Hospital, Sichuan University, Chengdu, Sichuan 610044, China
| | - Fengxiao Bu
- Institute of Rare Diseases, West China Hospital, Sichuan University, Chengdu, Sichuan 610044, China.
| | - Huijun Yuan
- Institute of Rare Diseases, West China Hospital, Sichuan University, Chengdu, Sichuan 610044, China.
| |
Collapse
|
3
|
Rodríguez Cruz PM, Cossins J, Beeson D, Vincent A. The Neuromuscular Junction in Health and Disease: Molecular Mechanisms Governing Synaptic Formation and Homeostasis. Front Mol Neurosci 2020; 13:610964. [PMID: 33343299 PMCID: PMC7744297 DOI: 10.3389/fnmol.2020.610964] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 10/30/2020] [Indexed: 12/28/2022] Open
Abstract
The neuromuscular junction (NMJ) is a highly specialized synapse between a motor neuron nerve terminal and its muscle fiber that are responsible for converting electrical impulses generated by the motor neuron into electrical activity in the muscle fibers. On arrival of the motor nerve action potential, calcium enters the presynaptic terminal, which leads to the release of the neurotransmitter acetylcholine (ACh). ACh crosses the synaptic gap and binds to ACh receptors (AChRs) tightly clustered on the surface of the muscle fiber; this leads to the endplate potential which initiates the muscle action potential that results in muscle contraction. This is a simplified version of the events in neuromuscular transmission that take place within milliseconds, and are dependent on a tiny but highly structured NMJ. Much of this review is devoted to describing in more detail the development, maturation, maintenance and regeneration of the NMJ, but first we describe briefly the most important molecules involved and the conditions that affect their numbers and function. Most important clinically worldwide, are myasthenia gravis (MG), the Lambert-Eaton myasthenic syndrome (LEMS) and congenital myasthenic syndromes (CMS), each of which causes specific molecular defects. In addition, we mention the neurotoxins from bacteria, snakes and many other species that interfere with neuromuscular transmission and cause potentially fatal diseases, but have also provided useful probes for investigating neuromuscular transmission. There are also changes in NMJ structure and function in motor neuron disease, spinal muscle atrophy and sarcopenia that are likely to be secondary but might provide treatment targets. The NMJ is one of the best studied and most disease-prone synapses in the nervous system and it is amenable to in vivo and ex vivo investigation and to systemic therapies that can help restore normal function.
Collapse
Affiliation(s)
- Pedro M. Rodríguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Judith Cossins
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| |
Collapse
|
4
|
Belotti E, Schaeffer L. Regulation of Gene expression at the neuromuscular Junction. Neurosci Lett 2020; 735:135163. [PMID: 32553805 DOI: 10.1016/j.neulet.2020.135163] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Revised: 06/11/2020] [Accepted: 06/14/2020] [Indexed: 01/08/2023]
Abstract
Gene expression in skeletal muscle is profoundly changed upon innervation. 50 years of research on the neuromuscular system have greatly increased our understanding of the mechanisms underlying these changes. By controlling the expression and the activity of key transcription factors, nerve-evoked electrical activity in the muscle fiber positively and negatively regulates the expression of hundreds of genes. Innervation also compartmentalizes gene expression into synaptic and extra-synaptic regions of muscle fibers. In addition, electrically-evoked, release of several factors (e.g. Agrin, Neuregulin, Wnt ligands) induce the clustering of synaptic proteins and of a few muscle nuclei. The sub-synaptic nuclei acquire a particular chromatin organization and develop a specific gene expression program dedicated to building and maintaining a functional neuromuscular synapse. Deciphering synapse-specific, transcriptional regulation started with the identification of the N-box, a six base pair element present in the promoters of the acetylcholine δ and ε subunits. Most genes with synapse-specific expression turned out to contain at least one N-box in their promoters. The N-box is a response element for the synaptic signals Agrin and Neuregulins as well as a binding site for transcription factors of the Ets family. The Ets transcription factors GABP and Erm are implicated in the activation of post-synaptic genes via the N-box. In muscle fibers, Erm expression is restricted to the NMJ whereas GABP is expressed in all muscle nuclei but phosphorylated and activated by the JNK and ERK signaling pathways in response to Agrin and Neuregulins. Post-synaptic gene expression also correlates with chromatin modifications at the genomic level as evidenced by the strong enrichment of decondensed chromatin and acetylated histones in sub-synaptic nuclei. Here we discuss these transcriptional pathways for synaptic specialization at NMJs.
Collapse
Affiliation(s)
- Edwige Belotti
- INMG, Inserm U1217, CNRS UMR5310, Université Lyon 1, Université De Lyon, Lyon, France
| | - Laurent Schaeffer
- INMG, Inserm U1217, CNRS UMR5310, Université Lyon 1, Université De Lyon, Lyon, France; Centre De Biotechnologie Cellulaire, Hospices Civils De Lyon, Lyon, France.
| |
Collapse
|
5
|
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.
Collapse
Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic College of Medicine, Rochester, MN, United States.
| |
Collapse
|
6
|
Eiber N, Simeone L, Hashemolhosseini S. Ablation of Protein Kinase CK2β in Skeletal Muscle Fibers Interferes with Their Oxidative Capacity. Pharmaceuticals (Basel) 2017; 10:ph10010013. [PMID: 28106831 PMCID: PMC5374417 DOI: 10.3390/ph10010013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Revised: 01/13/2017] [Accepted: 01/14/2017] [Indexed: 11/16/2022] Open
Abstract
The tetrameric protein kinase CK2 was identified playing a role at neuromuscular junctions by studying CK2β-deficient muscle fibers in mice, and in cultured immortalized C2C12 muscle cells after individual knockdown of CK2α and CK2β subunits. In muscle cells, CK2 activity appeared to be at least required for regular aggregation of nicotinic acetylcholine receptors, which serves as a hallmark for the presence of a postsynaptic apparatus. Here, we set out to determine whether any other feature accompanies CK2β-deficient muscle fibers. Hind limb muscles gastrocnemius, plantaris, and soleus of adult wildtype and CK2β-deficient mice were dissected, cross-sectioned, and stained histochemically by Gomori trichrome and for nicotinamide adenine dinucleotide (NADH) dehydrogenase and succinate dehydrogenase (SDH) enzymatic activities. A reduction of oxidative enzymatic activity was determined for CK2β-deficient muscle fibers in comparison with wildtype controls. Importantly, the CK2β-deficient fibers, muscle fibers that typically exhibit high NADH dehydrogenase and SDH activities, like slow-type fibers, showed a marked reduction in these activities. Altogether, our data indicate additional impairments in the absence of CK2β in skeletal muscle fibers, pointing to an eventual mitochondrial myopathy.
Collapse
Affiliation(s)
- Nane Eiber
- Institute of Biochemistry, Friedrich-Alexander University of Erlangen-Nuremberg, Fahrstrasse 17, 91054 Erlangen, Germany.
| | - Luca Simeone
- Institute of Biochemistry, Friedrich-Alexander University of Erlangen-Nuremberg, Fahrstrasse 17, 91054 Erlangen, Germany.
| | - Said Hashemolhosseini
- Institute of Biochemistry, Friedrich-Alexander University of Erlangen-Nuremberg, Fahrstrasse 17, 91054 Erlangen, Germany.
| |
Collapse
|
7
|
Aygun N. Correlations between long inverted repeat (LIR) features, deletion size and distance from breakpoint in human gross gene deletions. Sci Rep 2015; 5:8300. [PMID: 25657065 PMCID: PMC4319165 DOI: 10.1038/srep08300] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 01/14/2015] [Indexed: 11/09/2022] Open
Abstract
Long inverted repeats (LIRs) have been shown to induce genomic deletions in yeast. In this study, LIRs were investigated within ±10 kb spanning each breakpoint from 109 human gross deletions, using Inverted Repeat Finder (IRF) software. LIR number was significantly higher at the breakpoint regions, than in control segments (P < 0.001). In addition, it was found that strong correlation between 5' and 3' LIR numbers, suggesting contribution to DNA sequence evolution (r = 0.85, P < 0.001). 138 LIR features at ±3 kb breakpoints in 89 (81%) of 109 gross deletions were evaluated. Significant correlations were found between distance from breakpoint and loop length (r = -0.18, P < 0.05) and stem length (r = -0.18, P < 0.05), suggesting DNA strands are potentially broken in locations closer to bigger LIRs. In addition, bigger loops cause larger deletions (r = 0.19, P < 0.05). Moreover, loop length (r = 0.29, P < 0.02) and identity between stem copies (r = 0.30, P < 0.05) of 3' LIRs were more important in larger deletions. Consequently, DNA breaks may form via LIR-induced cruciform structure during replication. DNA ends may be later repaired by non-homologous end-joining (NHEJ), with following deletion.
Collapse
Affiliation(s)
- Nevim Aygun
- Department of Medical Biology, Faculty of Medicine, Dokuz Eylul University, Inciralti, Izmir, Turkey
| |
Collapse
|
8
|
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]
|
9
|
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.
Collapse
Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, Rochester, MN 55905, United States.
| |
Collapse
|
10
|
|
11
|
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.
Collapse
Affiliation(s)
- Juliane S Müller
- Friedrich-Baur-Institute, Department of Neurology, Ludwig-Maximilians-University, Munich, Germany
| | | | | | | |
Collapse
|
12
|
Beeson D, Hantaï D, Lochmüller H, Engel AG. 126th International Workshop: congenital myasthenic syndromes, 24-26 September 2004, Naarden, the Netherlands. Neuromuscul Disord 2005; 15:498-512. [PMID: 15951177 DOI: 10.1016/j.nmd.2005.05.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2005] [Indexed: 11/16/2022]
Affiliation(s)
- David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, The John Radcliff, Oxford, UK
| | | | | | | |
Collapse
|
13
|
Abstract
PURPOSE OF REVIEW Congenital myasthenic syndromes are a heterogeneous group of diseases caused by genetic defects affecting neuromuscular transmission. In this article, a strategy that leads to the diagnosis of congenital myasthenic syndromes is presented, and recent advances in the clinical, genetic and molecular aspects of congenital myasthenic syndrome are outlined. RECENT FINDINGS Besides the identification of new mutations in genes already known to be implicated in congenital myasthenic syndromes (genes for the acetylcholine receptor subunits and the collagen tail of acetylcholinesterase), mutations in other genes have more recently been discovered and characterized (genes for choline acetyltransferase, rapsyn, and the muscle sodium channel SCN4A). Fluoxetine has recently been proposed as an alternative treatment for 'slow channel' congenital myasthenic syndrome. SUMMARY The characterization of congenital myasthenic syndromes comprises two complementary steps: establishing the diagnosis and identifying the pathophysiological type of congenital myasthenic syndrome. Characterization of the type of congenital myasthenic syndrome has allowed it to be classified as caused by presynaptic, synaptic and postsynaptic defects. A clinically and muscle histopathologically oriented genetic study has identified several genes in which mutations cause the disease. Despite comprehensive characterization, the phenotypic expression of one given gene involved is variable, and the aetiology of many congenital myasthenic syndromes remains to be discovered.
Collapse
Affiliation(s)
- Daniel Hantaï
- Inserm U582 and Unité Clinique de Pathologie Neuromusculaire, Institut de Myologie, Hôpital de la Salpêtrière, Paris, France.
| | | | | | | |
Collapse
|
14
|
Müller JS, Abicht A, Christen HJ, Stucka R, Schara U, Mortier W, Huebner A, Lochmüller H. A newly identified chromosomal microdeletion of the rapsyn gene causes a congenital myasthenic syndrome. Neuromuscul Disord 2005; 14:744-9. [PMID: 15482960 DOI: 10.1016/j.nmd.2004.06.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2004] [Revised: 06/01/2004] [Accepted: 06/09/2004] [Indexed: 10/26/2022]
Abstract
The objective is mutation analysis of the RAPSN gene in a patient with sporadic congenital myasthenic syndrome (CMS). Mutations in various genes encoding proteins expressed at the neuromuscular junction may cause CMS. Most mutations affect the epsilon subunit gene of the acetylcholine receptor (AChR) leading to endplate AChR deficiency. Recently, mutations in the RAPSN gene have been identified in several CMS patients with AChR deficiency. In most patients, RAPSN N88K was identified, either homozygously or heteroallelic to a second missense mutation. A sporadic CMS patient from Germany was analyzed for RAPSN mutations by RFLP, long-range PCR and sequence analysis. Clinically, the patient presents with an early onset CMS, associated with arthrogryposis multiplex congenita, recurrent episodes of respiratory insufficiency provoked by infections, and a moderate general weakness, responsive to anticholinesterase treatment. The mutation RAPSN N88K was found heterozygously to a large deletion of about 4.5 kb disrupting the RAPSN gene. Interestingly, an Alu-mediated unequal homologous recombination may have caused the deletion. We hypothesize that numerous interspersed Alu elements may predispose the RAPSN locus for genetic rearrangements.
Collapse
Affiliation(s)
- Juliane S Müller
- Department of Neurology and Gene Center, Friedrich-Baur-Institute, Ludwig-Maximilians-University, Munich, Germany
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Rodova M, Kelly KF, VanSaun M, Daniel JM, Werle MJ. Regulation of the rapsyn promoter by kaiso and delta-catenin. Mol Cell Biol 2004; 24:7188-96. [PMID: 15282317 PMCID: PMC479716 DOI: 10.1128/mcb.24.16.7188-7196.2004] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rapsyn is a synapse-specific protein that is required for clustering acetylcholine receptors at the neuromuscular junction. Analysis of the rapsyn promoter revealed a consensus site for the transcription factor Kaiso within a region that is mutated in a subset of patients with congenital myasthenic syndrome. Kaiso is a POZ-zinc finger family transcription factor which recognizes the specific core consensus sequence CTGCNA (where N is any nucleotide). Previously, the only known binding partner for Kaiso was the cell adhesion cofactor, p120 catenin. Here we show that delta-catenin, a brain-specific member of the p120 catenin subfamily, forms a complex with Kaiso. Antibodies against Kaiso and delta-catenin recognize proteins in the nuclei of C2C12 myocytes and at the postsynaptic domain of the mouse neuromuscular junction. Endogenous Kaiso in C2C12 cells coprecipitates with the rapsyn promoter in vivo as shown by chromatin immunoprecipitation assay. Minimal promoter assays demonstrated that the rapsyn promoter can be activated by Kaiso and delta-catenin; this activation is apparently muscle specific. These results provide the first experimental evidence that rapsyn is a direct sequence-specific target of Kaiso and delta-catenin. We propose a new model of synapse-specific transcription that involves the interaction of Kaiso, delta-catenin, and myogenic transcription factors at the neuromuscular junction.
Collapse
MESH Headings
- Active Transport, Cell Nucleus/physiology
- Animals
- Antibiotics, Antineoplastic/pharmacology
- Armadillo Domain Proteins
- Base Sequence
- Catenins
- Cell Adhesion Molecules
- Cell Line
- Chickens
- Cytoskeletal Proteins/metabolism
- Fatty Acids, Unsaturated/pharmacology
- Gene Expression Regulation
- Genes, Reporter
- Humans
- Macromolecular Substances
- Mice
- Molecular Sequence Data
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/drug effects
- Muscle Fibers, Skeletal/metabolism
- Muscle Proteins/genetics
- Muscle Proteins/metabolism
- Muscle, Skeletal/chemistry
- Muscle, Skeletal/cytology
- Muscle, Skeletal/metabolism
- Myasthenic Syndromes, Congenital/genetics
- Myasthenic Syndromes, Congenital/metabolism
- Neuromuscular Junction/physiology
- Phosphoproteins
- Promoter Regions, Genetic
- Sequence Alignment
- Transcription Factors/metabolism
- Delta Catenin
Collapse
Affiliation(s)
- Marianna Rodova
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, 66160-7421, USA
| | | | | | | | | |
Collapse
|
16
|
Spuler S, Lehmann TN, Engel AG. [Differential congenital myasthenia syndrome diagnosis]. DER NERVENARZT 2004; 75:141-4. [PMID: 14770284 DOI: 10.1007/s00115-003-1614-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Among myopathies and disorders of neuromuscular transmission, the congenital myasthenic syndromes (CMS) are particularly rare. However, because of the available therapeutic options, it is still clinically important to achieve a correct diagnosis in these patients. We report an adult patient with ophthalmoplegia and nonfluctuating limb-girdle syndrome. For almost 20 years, a congenital myopathy or mitochondriopathy had been suspected before CMS was diagnosed caused by an epsilon subunit mutation of the acetylcholine receptor (epsilon1276delG).
Collapse
Affiliation(s)
- S Spuler
- Neurologische Klinik, Charité, Berlin.
| | | | | |
Collapse
|
17
|
Beeson D, Webster R, Ealing J, Croxen R, Brownlow S, Brydson M, Newsom-Davis J, Slater C, Hatton C, Shelley C, Colquhoun D, Vincent A. Structural abnormalities of the AChR caused by mutations underlying congenital myasthenic syndromes. Ann N Y Acad Sci 2003; 998:114-24. [PMID: 14592868 DOI: 10.1196/annals.1254.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The objective was to define the molecular mechanisms underlying congenital myasthenic syndromes (CMS) by studying mutations within genes encoding the acetylcholine receptor (AChR) and related proteins at the neuromuscular junction. It was found that mutations within muscle AChRs are the most common cause of CMS. The majority are located within the epsilon-subunit gene and result in AChR deficiency.
Collapse
MESH Headings
- Alleles
- Animals
- Cell Line
- DNA Mutational Analysis
- Exons
- Extracellular Space/genetics
- Extracellular Space/metabolism
- Female
- Humans
- In Situ Hybridization/methods
- Male
- Mutation
- Myasthenic Syndromes, Congenital/classification
- Myasthenic Syndromes, Congenital/diagnosis
- Myasthenic Syndromes, Congenital/genetics
- Myasthenic Syndromes, Congenital/physiopathology
- Neuromuscular Junction/abnormalities
- Neuromuscular Junction/genetics
- Neuromuscular Junction/metabolism
- Patch-Clamp Techniques
- Polymorphism, Single-Stranded Conformational
- Protein Structure, Secondary
- Protein Subunits/genetics
- Protein Subunits/metabolism
- Receptors, Cholinergic/chemistry
- Receptors, Cholinergic/deficiency
- Receptors, Cholinergic/genetics
- Receptors, Cholinergic/physiology
- Reverse Transcriptase Polymerase Chain Reaction
- Transfection
Collapse
Affiliation(s)
- David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, The John Radcliffe, Headington, Oxford OX3 9DS, United Kingdom.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Méjat A, Ravel-Chapuis A, Vandromme M, Schaeffer L. Synapse-specific gene expression at the neuromuscular junction. Ann N Y Acad Sci 2003; 998:53-65. [PMID: 14592863 DOI: 10.1196/annals.1254.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Agrin is the key neural factor that controls muscle postsynaptic differentiation, including the induction of synapse-specific transcription via neuregulins. In 1995, the promoter element responsible for the targeting of AChR delta and epsilon gene transcription to the skeletal muscle subsynaptic area was identified. This element, named N-box, recruits the Ets-related transcription factor GABP to AChR delta and epsilon promoters, and both the N-box and GABP are required to obtain transcriptional stimulation by neuregulins. The physiological importance of the N-box has been definitively established with the discovery of myasthenic families carrying single-point mutations in the N-box of the AChR epsilon gene promoter and showing reduced levels of AChR epsilon subunit expression. The control of synapse-specific transcription by agrin and neuregulins through the N-box and GABP is not restricted to the case of AChR genes. The same regulation holds true for the ACh esterase and utrophin genes, thus showing that nerve-induced transcriptional activation of several synapse-specific genes is triggered by a common mechanism involving agrin, neuregulins, and ultimately the N-box and Ets-related transcription factors.
Collapse
Affiliation(s)
- Alexandre Méjat
- Equipe Différenciation Neuromusculaire, UMR 5161 CNRS/ENS, Ecole Normale Supérieure de Lyon, Lyon, France
| | | | | | | |
Collapse
|
19
|
Abstract
Although the genetic neurologic channelopathies are uncommon, they serve as models that further understanding of disease mechanisms in paroxysmal disorders. Many other neurologic channelopathies likely will be identified in the future.
Collapse
Affiliation(s)
- Hemant K Pandey
- West Virginia University School of Medicine, Morgantown, West Virginia, USA
| | | |
Collapse
|
20
|
Engel AG, Ohno K, Shen XM, Sine SM. Congenital Myasthenic Syndromes: Multiple Molecular Targets at the Neuromuscular Junction. Ann N Y Acad Sci 2003; 998:138-60. [PMID: 14592871 DOI: 10.1196/annals.1254.016] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Congenital myasthenic syndromes (CMS) stem from defects in presynaptic, synaptic, and postsynaptic proteins. The presynaptic CMS are associated with defects that curtail the evoked release of acetylcholine (ACh) quanta or ACh resynthesis. Defects in ACh resynthesis have now been traced to mutations in choline acetyltransferase. A synaptic CMS is caused by mutations in the collagenic tail subunit (ColQ) of the endplate species of acetylcholinesterase that prevent the tail subunit from associating with catalytic subunits or from becoming inserted into the synaptic basal lamina. Most postsynaptic CMS are caused by mutations in subunits of the acetylcholine receptor (AChR) that alter the kinetic properties or decrease the expression of AChR. The kinetic mutations increase or decrease the synaptic response to ACh and result in slow- and fast-channel syndromes, respectively. Most low-expressor mutations reside in the AChR epsilon subunit and are partially compensated by residual expression of the fetal-type gamma subunit. In a subset of CMS patients, endplate AChR deficiency is caused by mutations in rapsyn, a molecule that plays a critical role in concentrating AChR in the postsynaptic membrane.
Collapse
Affiliation(s)
- Andrew G Engel
- Neuromuscular Disease Research Laboratory, Department of Neurology, Mayo Clinic, Rochester, Minnesota 55905, USA.
| | | | | | | |
Collapse
|
21
|
Engel AG, Ohno K, Sine SM. Sleuthing molecular targets for neurological diseases at the neuromuscular junction. Nat Rev Neurosci 2003; 4:339-52. [PMID: 12728262 DOI: 10.1038/nrn1101] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Andrew G Engel
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, Minnesota 55905, USA.
| | | | | |
Collapse
|
22
|
Briguet A, Bleckmann D, Bettan M, Mermod N, Meier T. Transcriptional activation of the utrophin promoter B by a constitutively active Ets-transcription factor. Neuromuscul Disord 2003; 13:143-50. [PMID: 12565912 DOI: 10.1016/s0960-8966(02)00217-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Duchenne muscular dystrophy is an X-linked genetic disease caused by the absence of functional dystrophin. Pharmacological upregulation of utrophin, the autosomal homologue of dystrophin, offers a potential therapeutic approach to treat Duchenne patients. Full-length utrophin mRNA is transcribed from two alternative promoters, called A and B. In contrast to the utrophin promoter A, little is known about the factors regulating the activity of the utrophin promoter B. Computer analysis of this second promoter revealed the presence of several conserved binding motives for Ets-transcription factors. Using electrotransfer of cDNA into mouse muscles, we demonstrate that a genetically modified beta-subunit of the Ets-transcription factor GA-binding protein potently activates a utrophin promoter B reporter construct in innervated muscle fibers in vivo. These results make the GA-binding protein and the signaling cascade regulating its activity in muscle cells, potential targets for the pharmacological modulation of utrophin expression in Duchenne patients.
Collapse
|
23
|
Affiliation(s)
- Kinji Ohno
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA
| | | |
Collapse
|
24
|
Millichap JG. Multi-Minicore and Central Core Disease. Pediatr Neurol Briefs 2002. [DOI: 10.15844/pedneurbriefs-16-6-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|