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Wang W, Lin L, Zhang Q, Yang J, Kamili E, Chu J, Li X, Yang S, Xu Y. Heteroplasmy and Individual Mitogene Pools: Characteristics and Potential Roles in Ecological Studies. BIOLOGY 2023; 12:1452. [PMID: 37998051 PMCID: PMC10669347 DOI: 10.3390/biology12111452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Revised: 11/09/2023] [Accepted: 11/15/2023] [Indexed: 11/25/2023]
Abstract
The mitochondrial genome (mitogenome or mtDNA), the extrachromosomal genome, is a multicopy circular DNA with high mutation rates due to replication and repair errors. A mitochondrion, cell, tissue, organ, or an individual body may hold multiple variants, both inherited and developed over a lifetime, which make up individual mitogene pools. This phenomenon is also called mtDNA heteroplasmy. MtDNA variants influence cellular and tissular functions and are consequently subjected to selection. Although it has long been recognized that only inheritable germline heteroplasmies have evolutionary significance, non-inheritable somatic heteroplasmies have been overlooked since they directly affect individual fitness and thus indirectly affect the fate of heritable germline variants. This review focuses on the characteristics, dynamics, and functions of mtDNA heteroplasmy and proposes the concept of individual mitogene pools to discuss individual genetic diversity from multiple angles. We provide a unique perspective on the relationship between individual genetic diversity and heritable genetic diversity and guide how the individual mitogene pool with novel genetic markers can be applied to ecological research.
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Affiliation(s)
| | | | | | | | | | | | | | - Shuhui Yang
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin 150040, China; (W.W.); (L.L.); (Q.Z.); (J.Y.); (E.K.); (J.C.); (X.L.)
| | - Yanchun Xu
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin 150040, China; (W.W.); (L.L.); (Q.Z.); (J.Y.); (E.K.); (J.C.); (X.L.)
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Creation of Mitochondrial Disease Models Using Mitochondrial DNA Editing. Biomedicines 2023; 11:biomedicines11020532. [PMID: 36831068 PMCID: PMC9953118 DOI: 10.3390/biomedicines11020532] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/07/2023] [Accepted: 02/10/2023] [Indexed: 02/15/2023] Open
Abstract
Mitochondrial diseases are a large class of human hereditary diseases, accompanied by the dysfunction of mitochondria and the disruption of cellular energy synthesis, that affect various tissues and organ systems. Mitochondrial DNA mutation-caused disorders are difficult to study because of the insufficient number of clinical cases and the challenges of creating appropriate models. There are many cellular models of mitochondrial diseases, but their application has a number of limitations. The most proper and promising models of mitochondrial diseases are animal models, which, unfortunately, are quite rare and more difficult to develop. The challenges mainly arise from the structural features of mitochondria, which complicate the genetic editing of mitochondrial DNA. This review is devoted to discussing animal models of human mitochondrial diseases and recently developed approaches used to create them. Furthermore, this review discusses mitochondrial diseases and studies of metabolic disorders caused by the mitochondrial DNA mutations underlying these diseases.
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A Novel MTTK Gene Variant m.8315A>C as a Cause of MERRF Syndrome. Genes (Basel) 2022; 13:genes13071245. [PMID: 35886028 PMCID: PMC9319148 DOI: 10.3390/genes13071245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 07/11/2022] [Accepted: 07/11/2022] [Indexed: 02/01/2023] Open
Abstract
In this study, we report on a novel heteroplasmic pathogenic variant in mitochondrial DNA (mtDNA). The studied patient had myoclonus, epilepsy, muscle weakness, and hearing impairment and harbored a heteroplasmic m.8315A>C variant in the MTTK gene with a mutation load ranging from 71% to >96% in tested tissues. In muscle mitochondria, markedly decreased activities of respiratory chain complex I + III and complex IV were observed together with mildly reduced amounts of complex I and complex V (with the detection of V*- and free F1-subcomplexes) and a diminished level of complex IV holoenzyme. This pattern was previously seen in other MTTK pathogenic variants. The novel variant was not present in internal and publicly available control databases. Our report further expands the spectrum of MTTK variants associated with mitochondrial encephalopathies in adults.
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Richter U, McFarland R, Taylor RW, Pickett SJ. The molecular pathology of pathogenic mitochondrial tRNA variants. FEBS Lett 2021; 595:1003-1024. [PMID: 33513266 PMCID: PMC8600956 DOI: 10.1002/1873-3468.14049] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 01/14/2021] [Accepted: 01/18/2021] [Indexed: 12/16/2022]
Abstract
Mitochondrial diseases are clinically and genetically heterogeneous disorders, caused by pathogenic variants in either the nuclear or mitochondrial genome. This heterogeneity is particularly striking for disease caused by variants in mitochondrial DNA‐encoded tRNA (mt‐tRNA) genes, posing challenges for both the treatment of patients and understanding the molecular pathology. In this review, we consider disease caused by the two most common pathogenic mt‐tRNA variants: m.3243A>G (within MT‐TL1, encoding mt‐tRNALeu(UUR)) and m.8344A>G (within MT‐TK, encoding mt‐tRNALys), which together account for the vast majority of all mt‐tRNA‐related disease. We compare and contrast the clinical disease they are associated with, as well as their molecular pathologies, and consider what is known about the likely molecular mechanisms of disease. Finally, we discuss the role of mitochondrial–nuclear crosstalk in the manifestation of mt‐tRNA‐associated disease and how research in this area not only has the potential to uncover molecular mechanisms responsible for the vast clinical heterogeneity associated with these variants but also pave the way to develop treatment options for these devastating diseases.
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Affiliation(s)
- Uwe Richter
- Wellcome Centre for Mitochondrial Research, The Medical School, Newcastle University, UK.,Molecular and Integrative Biosciences Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland.,Newcastle University Biosciences Institute, Newcastle University, UK
| | - Robert McFarland
- Wellcome Centre for Mitochondrial Research, The Medical School, Newcastle University, UK.,Newcastle University Translational and Clinical Research Institute, Newcastle University, UK
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, The Medical School, Newcastle University, UK.,Newcastle University Translational and Clinical Research Institute, Newcastle University, UK
| | - Sarah J Pickett
- Wellcome Centre for Mitochondrial Research, The Medical School, Newcastle University, UK.,Newcastle University Translational and Clinical Research Institute, Newcastle University, UK
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Montano V, Gruosso F, Simoncini C, Siciliano G, Mancuso M. Clinical features of mtDNA-related syndromes in adulthood. Arch Biochem Biophys 2020; 697:108689. [PMID: 33227288 DOI: 10.1016/j.abb.2020.108689] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 11/06/2020] [Accepted: 11/15/2020] [Indexed: 01/26/2023]
Abstract
Mitochondrial diseases are the most common inheritable metabolic diseases, due to defects in oxidative phosphorylation. They are caused by mutations of nuclear or mitochondrial DNA in genes involved in mitochondrial function. The peculiarity of "mitochondrial DNA genetics rules" in part explains the marked phenotypic variability, the complexity of genotype-phenotype correlations and the challenge of genetic counseling. The new massive genetic sequencing technologies have changed the diagnostic approach, enhancing mitochondrial DNA-related syndromes diagnosis and often avoiding the need of a tissue biopsy. Here we present the most common phenotypes associated with a mitochondrial DNA mutation with the recent advances in diagnosis and in therapeutic perspectives.
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Affiliation(s)
- V Montano
- Department of Clinical and Experimental Medicine, Neurological Clinic, University of Pisa, Italy
| | - F Gruosso
- Department of Clinical and Experimental Medicine, Neurological Clinic, University of Pisa, Italy
| | - C Simoncini
- Department of Clinical and Experimental Medicine, Neurological Clinic, University of Pisa, Italy
| | - G Siciliano
- Department of Clinical and Experimental Medicine, Neurological Clinic, University of Pisa, Italy
| | - M Mancuso
- Department of Clinical and Experimental Medicine, Neurological Clinic, University of Pisa, Italy.
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Hou Y, Zhao XT, Xie ZY, Yuan Y, Wang ZX. [Mitochondrial encephalopathy, lactic acidosis and stroke-like episodes / myoclonus epilepsy with ragged-red fibers /Leigh overlap syndrome caused by mitochondrial DNA 8344A>G mutation]. BEIJING DA XUE XUE BAO. YI XUE BAN = JOURNAL OF PEKING UNIVERSITY. HEALTH SCIENCES 2020. [PMID: 33047718 DOI: 10.19723/j.issn.1671-167x.2020.05.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Mitochondrial deoxyribonucleic acid (mtDNA) 8344 A>G (m.8344A>G) mutation is the common mutation associated with mitochondrial myoclonus epilepsy with ragged-red fibers (MERRF) syndrome. Herein we report a rare case with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes/MERRF/Leigh (MELAS/MERRF/Leigh) overlap syndrome caused by m.8344A>G mutation. METHODS The clinical and imaging data of the patient were collected and an open muscle biopsy was carried out. We further employed molecular genetic analyses to detect mtDNA mutation in the proband and his mother. And then a clinical and neuroimaging follow-up was performed. RESULTS This patient was a 25-year-old male, who developed exercise intolerance since the age of 6. At age 10, he suffered from acute episodes of hemianopia, and cranial magnetic resonance imaging (MRI) showed occipital stroke-like lesions and cranial magnetic resonance spectroscopy (MRS) revealed a lactate peak corresponding to the lesion. After that the patient presented slowly progressive psychomotor decline. He had myoclonic seizures and cerebellar ataxia since the age of 12. At age 21, he was admitted to our hospital because of confusion and cranial MRI revealed symmetrical lesions in bilateral posterior putamen, thalami and midbrain. Then repeated MRI showed progression of original lesions and new frontal multiple stroke-like lesions. Symptomatic and rehabilitation treatment relieved his condition. Follow-up cranial MRI at age 24 showed the lesions in basal ganglia and thalami diminished, and the midbrain lesions even completely vanished. Muscle pathology indicated the presence of numerous scattered ragged-red fibers (RRF), suggestive of a mitochondrial disorder. Polymerase chain reaction-restricted fragment length polymorphism (PCR-RFLP) detected the m.8344A>G mutation of the MT-TK gene encoding mitochondrial transfer RNA for lysine in the patient's blood. Next generation sequencing (NGS) of the whole mitochondrial genome identified that the proportion of m.8344A>G was 90%, and no other mtDNA mutation was detected. Sanger sequencing further identified this mutation both in the proband and his mother's blood, although the mutation load was much lower in his mother's blood with approximately 10% heteroplasmy. CONCLUSION The present study is the first to describe a patient with m.8344A>G mutation in association with the MELAS/MERRF/Leigh overlap syndrome, which expands the phenotypic spectrum of the m.8344A>G mutation.
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Primiano G, Brunetti V, Vollono C, Losurdo A, Moroni R, Della Marca G, Servidei S. Sleep-Disordered Breathing in Adult Patients With Mitochondrial Diseases: A Cohort Study. Neurology 2020; 96:e241-e249. [PMID: 33024021 DOI: 10.1212/wnl.0000000000011005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 08/25/2020] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To describe the prevalence and characteristics of sleep-disordered breathing (SDB) in a large cohort of patients with genetically confirmed mitochondrial diseases. METHODS This is a prospective observational study performed at the Neurophysiopatology Unit of Fondazione Policlinico Universitario A. Gemelli IRCCS. All participants had a defined mitochondrial disease and were investigated by full-night polysomnography. RESULTS One hundred three consecutive patients were enrolled. SDB was demonstrated in 49 patients (47.6%). Regarding phenotypes, we found differences in distribution between the groups: patients affected by progressive external ophthalmoplegia with single or multiple mtDNA deletions frequently had obstructive apneas (50% and 43.8%) or REM-related hypoventilation when associated with m.3243A>G mutations (75%). Furthermore, a high percentage of participants with maternally inherited diabetes and deafness and myoclonic epilepsy with ragged-red fibers syndromes were characterized by obstructive sleep apnea and REM-related hypoventilation, respectively. In contrast to what has been described in previous studies, central sleep apnea was rarely reported in our cohort. CONCLUSIONS SDB has a higher prevalence in mitochondrial diseases compared to general population-based data. Overall, these results suggest that patients characterized by a specific phenotype-genotype combination are most at risk of developing a specific subgroup of SDB. The early identification of this disorder is crucial in the management of these fragile patients.
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Affiliation(s)
- Guido Primiano
- From UOC Neurofisiopatologia (G.P., C.V., A.L., S.S.), UOC Neurologia (V.B., G.D.M.), and Direzione Scientifica (R.M.), Fondazione Policlinico Universitario A. Gemelli IRCCS; and Dipartimento Universitario di Neuroscienze (G.P., G.D.M., S.S.), Università Cattolica del Sacro Cuore, Rome, Italy.
| | - Valerio Brunetti
- From UOC Neurofisiopatologia (G.P., C.V., A.L., S.S.), UOC Neurologia (V.B., G.D.M.), and Direzione Scientifica (R.M.), Fondazione Policlinico Universitario A. Gemelli IRCCS; and Dipartimento Universitario di Neuroscienze (G.P., G.D.M., S.S.), Università Cattolica del Sacro Cuore, Rome, Italy
| | - Catello Vollono
- From UOC Neurofisiopatologia (G.P., C.V., A.L., S.S.), UOC Neurologia (V.B., G.D.M.), and Direzione Scientifica (R.M.), Fondazione Policlinico Universitario A. Gemelli IRCCS; and Dipartimento Universitario di Neuroscienze (G.P., G.D.M., S.S.), Università Cattolica del Sacro Cuore, Rome, Italy
| | - Anna Losurdo
- From UOC Neurofisiopatologia (G.P., C.V., A.L., S.S.), UOC Neurologia (V.B., G.D.M.), and Direzione Scientifica (R.M.), Fondazione Policlinico Universitario A. Gemelli IRCCS; and Dipartimento Universitario di Neuroscienze (G.P., G.D.M., S.S.), Università Cattolica del Sacro Cuore, Rome, Italy
| | - Rossana Moroni
- From UOC Neurofisiopatologia (G.P., C.V., A.L., S.S.), UOC Neurologia (V.B., G.D.M.), and Direzione Scientifica (R.M.), Fondazione Policlinico Universitario A. Gemelli IRCCS; and Dipartimento Universitario di Neuroscienze (G.P., G.D.M., S.S.), Università Cattolica del Sacro Cuore, Rome, Italy
| | - Giacomo Della Marca
- From UOC Neurofisiopatologia (G.P., C.V., A.L., S.S.), UOC Neurologia (V.B., G.D.M.), and Direzione Scientifica (R.M.), Fondazione Policlinico Universitario A. Gemelli IRCCS; and Dipartimento Universitario di Neuroscienze (G.P., G.D.M., S.S.), Università Cattolica del Sacro Cuore, Rome, Italy
| | - Serenella Servidei
- From UOC Neurofisiopatologia (G.P., C.V., A.L., S.S.), UOC Neurologia (V.B., G.D.M.), and Direzione Scientifica (R.M.), Fondazione Policlinico Universitario A. Gemelli IRCCS; and Dipartimento Universitario di Neuroscienze (G.P., G.D.M., S.S.), Università Cattolica del Sacro Cuore, Rome, Italy
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Ji K, Zhao B, Lin Y, Wang W, Liu F, Li W, Zhao Y, Yan C. “Myo-neuropathy” is commonly associated with mitochondrial tRNALysine mutation. J Neurol 2020; 267:3319-3328. [DOI: 10.1007/s00415-020-10017-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/18/2020] [Accepted: 06/18/2020] [Indexed: 11/24/2022]
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Evidence of diaphragmatic dysfunction with severe alveolar hypoventilation syndrome in mitochondrial respiratory chain deficiency. Neuromuscul Disord 2020; 30:593-598. [PMID: 32654952 DOI: 10.1016/j.nmd.2020.06.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 05/31/2020] [Accepted: 06/04/2020] [Indexed: 11/21/2022]
Abstract
Diaphragmatic dysfunction has been reported in congenital myopathies, muscular dystrophies, and occasionally, mitochondrial respiratory chain deficiency. Using a minimally invasive procedure in 3 young girls, 1 with a heteroplasmic MT-CYB mutation and 2 with biallelic pathogenic TK2 variants, we provided functional evidence of diaphragmatic dysfunction with global respiratory muscle weakness in mitochondrial respiratory chain deficiency. Analysis of respiratory muscle performance using esogastric pressures revealed paradoxical breathing and severe global inspiratory and expiratory muscle weakness with a sniff esophageal inspiratory pressure and a gastric pressure during cough averaging 50% and 40% of predicted values, respectively. This diaphragmatic dysfunction was responsible for severe undiagnosed nocturnal hypoventilation, requiring noninvasive ventilation. Our results underline the interest of this minimally invasive procedure for the evaluation of respiratory muscle performance and its potential value for the monitoring of future clinical trials in respiratory chain deficiency.
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Abstract
INTRODUCTION Epilepsy is a prominent feature of myoclonic epilepsy with ragged-red fibers (MERRF)-syndrome. The most frequent seizure type is myoclonic seizures, of which the treatment is challenging and empiric. AREAS COVERED Herein, the author summarises and discusses previous and recent findings of antiepileptic drug (AED) treatment in MERRF-syndrome. EXPERT OPINION MERRF-syndrome is a predominantly maternally inherited, multisystem mitochondrial disorder caused by pathogenic variants predominantly of the mitochondrial DNA (mtDNA). Canonical clinical features of MERRF include myoclonus, epilepsy, ataxia, and myopathy. Additionally, other manifestations in the CNS, peripheral nerves, eyes, ears, heart, gastrointestinal tract, and endocrine organs may occur (MERRF-plus). Today, MERRF is considered rather as myoclonic ataxia than as myoclonic epilepsy. Genotypically, MERRF is due to mutations in 13 mtDNA-located genes and 1 nDNA-located gene. According to the modified Smith-score, the strongest gene-disease relationship exists for MT-TK, MT-TL1, and POLG1. Epilepsy is the second most frequent phenotypic feature of MERRF. Seizure-types associated with MERRF include focal myoclonic, focal clonic, and focal atonic seizures, generalized myoclonic, tonic-clonic, atonic, and myoclonic-atonic seizures, or typical absences. Treatment of myoclonic epilepsy relies on expert judgments recommending levetiracetam, together with clonazepam, or topiramate, zonisamide, or piracetam in monotherapy as the first line AEDs.
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Affiliation(s)
- Josef Finsterer
- a Krankenanstalt Rudolfstiftung , Messerli Institute , Vienna , Austria
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Abstract
BACKGROUND Given the etiologic heterogeneity of disease classification using clinical phenomenology, we employed contemporary criteria to classify variants associated with myoclonic epilepsy with ragged-red fibers (MERRF) syndrome and to assess the strength of evidence of gene-disease associations. Standardized approaches are used to clarify the definition of MERRF, which is essential for patient diagnosis, patient classification, and clinical trial design. METHODS Systematic literature and database search with application of standardized assessment of gene-disease relationships using modified Smith criteria and of variants reported to be associated with MERRF using modified Yarham criteria. RESULTS Review of available evidence supports a gene-disease association for two MT-tRNAs and for POLG. Using modified Smith criteria, definitive evidence of a MERRF gene-disease association is identified for MT-TK. Strong gene-disease evidence is present for MT-TL1 and POLG. Functional assays that directly associate variants with oxidative phosphorylation impairment were critical to mtDNA variant classification. In silico analysis was of limited utility to the assessment of individual MT-tRNA variants. With the use of contemporary classification criteria, several mtDNA variants previously reported as pathogenic or possibly pathogenic are reclassified as neutral variants. CONCLUSIONS MERRF is primarily an MT-TK disease, with pathogenic variants in this gene accounting for ~90% of MERRF patients. Although MERRF is phenotypically and genotypically heterogeneous, myoclonic epilepsy is the clinical feature that distinguishes MERRF from other categories of mitochondrial disorders. Given its low frequency in mitochondrial disorders, myoclonic epilepsy is not explained simply by an impairment of cellular energetics. Although MERRF phenocopies can occur in other genes, additional data are needed to establish a MERRF disease-gene association. This approach to MERRF emphasizes standardized classification rather than clinical phenomenology, thus improving patient diagnosis and clinical trial design.
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Abstract
PURPOSE OF REVIEW Understanding the mechanisms and abnormalities of respiratory function in neuromuscular disease is critical to supporting the patient and maintaining ventilation in the face of acute or chronic progressive impairment. RECENT FINDINGS Retrospective clinical studies reviewing the care of patients with Guillain-Barré syndrome and myasthenia have shown a disturbingly high mortality following step-down from intensive care. This implies high dependency and rehabilitation management is failing despite evidence that delayed improvement can occur with long-term care. A variety of mechanisms of phrenic nerve impairment have been recognized with newer investigation techniques, including EMG and ultrasound. Specific treatment for progressive neuromuscular and muscle disease has been increasingly possible particularly for the treatment of myasthenia, metabolic myopathies, and Duchenne muscular dystrophy. For those conditions without specific treatment, it has been increasingly possible to support ventilation in the domiciliary setting with newer techniques of noninvasive ventilation and better airway clearance. There remained several areas of vigorous debates, including the role for tracheostomy care and the place of respiratory muscle training and phrenic nerve/diaphragm pacing. SUMMARY Recent studies and systematic reviews have defined criteria for anticipating, recognizing, and managing ventilatory failure because of acute neuromuscular disease. The care of patients requiring long-term noninvasive ventilatory support for chronic disorders has also evolved. This has resulted in significantly improved survival for patients requiring domiciliary ventilatory support.
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Scarpelli M, Carreño-Gago L, Russignan A, de Luna N, Carnicer-Cáceres C, Ariatti A, Verriello L, Devigili G, Tonin P, Garcia-Arumi E, Pinós T. Identification and characterization of the novel m.8305C>T MTTK and m.4440G>A MTTM gene mutations causing mitochondrial myopathies. Neuromuscul Disord 2017; 28:137-143. [PMID: 29174468 DOI: 10.1016/j.nmd.2017.10.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 10/19/2017] [Accepted: 10/23/2017] [Indexed: 01/20/2023]
Abstract
We report on two novel mtDNA mutations in patients affected with mitochondrial myopathy. The first patient, a 44-year-old woman, had bilateral eyelid ptosis and the m.8305C>T mutation in the MTTK gene. The second patient, a 56-year-old man, had four-limb muscle weakness and the MTTM gene m.4440G>A mutation. Muscle biopsies in both patients showed ragged red fibers and numerous COX-negative fibers as well as a combined defect of complex I, III and IV activities. The two mutations were heteroplasmic and detected only in muscle tissue, with a higher mutation load in COX-negative fibers. Additionally, both mutations occurred in highly conserved mt-tRNA sites, and were not found by an in silico search in 30,589 human mtDNA sequences. Our report further expands the mutational and phenotypic spectrum of diseases associated with mutations in mitochondrial tRNA genes and reinforces the notion that mutations in mitochondrial tRNAs represent hot spots for mitochondrial myopathies in adults.
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Affiliation(s)
- Mauro Scarpelli
- Section of Neurology, Department of Neurological, Biomedical and Movement Sciences, University of Verona, Verona, Italy
| | - Lidia Carreño-Gago
- Mitochondrial Disorders Unit, Vall d'Hebron Institut de Recerca, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Anna Russignan
- Section of Neurology, Department of Neurological, Biomedical and Movement Sciences, University of Verona, Verona, Italy
| | - Noemi de Luna
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain; Laboratori de Malalties Neuromusculars, Institut de Recerca Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona, Spain
| | - Clara Carnicer-Cáceres
- Unidad de Metabolopatías, Servicio de Bioquímica, Hospital Universitari Vall d'Hebron, Barcelona, Spain
| | - Alessandra Ariatti
- Department of Neurosciences and Department of Onco-Haematology, University Hospitals of Modena & Reggio Emilia, Italy
| | - Lorenzo Verriello
- Division of Neurology, Department of Neuroscience, Azienda Ospedaliero Universitaria, Udine, Italy
| | - Grazia Devigili
- Division of Neurology, Department of Neuroscience, Azienda Ospedaliero Universitaria, Udine, Italy
| | - Paola Tonin
- Section of Neurology, Department of Neurological, Biomedical and Movement Sciences, University of Verona, Verona, Italy
| | - Elena Garcia-Arumi
- Mitochondrial Disorders Unit, Vall d'Hebron Institut de Recerca, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain; Àrea de Genètica Clínica i Molecular, Hospital Universitari Vall d'Hebron, Barcelona, Spain.
| | - Tomàs Pinós
- Mitochondrial Disorders Unit, Vall d'Hebron Institut de Recerca, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.
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Zhou Y, Yi J, Liu L, Wang X, Dong L, Du A. Acute mitochondrial myopathy with respiratory insufficiency and motor axonal polyneuropathy. Int J Neurosci 2017; 128:231-236. [PMID: 28969510 DOI: 10.1080/00207454.2017.1387113] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
BACKGROUND Mitochondrial myopathies (MMs) are mainly presented with chronic muscle weakness and accompanied with other syndromes. MM with acute respiratory insufficiency is rare. AIMS To reveal the clinical, pathological and molecular characteristics of a life-threatening MM. METHODS Muscle biopsy and enzyme staining were performed in skeletal muscles. Mitochondrial DNA (mtDNA) sequencing was analyzed and heteroplasmy were quantified by pyrosequencing. RESULTS All three patients had tachycardia, acute lactic acidosis, dyspnea and sudden severe muscle weakness. Two patients had calf edema and abdominal pain, and one had a heart attack. Electromyography in two patients showed dramatically decreased axonal amplitudes of motor nerves. Muscle biopsies showed ragged red fibers and dramatic mitochondrial abnormality. A mtDNA m.3243A>G mutation was identified in Patient 1 (mutation load: 29% in blood and 73% in muscle) and Patient 3 (79% in blood and 89% in muscle). A mtDNA m.8344A>G mutation was found in Patient 2 (mutation load 80.4% in blood). CONCLUSION MM characterized by lactic acidosis, respiratory failure and acute motor axonal neuropathy is life threatening.
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Affiliation(s)
- Ying Zhou
- a Department of Cardiology , Second Affiliated Hospital, Zhejiang University School of Medicine , Hangzhou , China
| | - Jianhua Yi
- b Department of Emergency Medicine , Second Affiliated Hospital, Zhejiang University School of Medicine , Hangzhou , China
| | - Li Liu
- c Mitochondrial Disease Research Center, Institute of Genetics , College of Life Science, Zhejiang University , Hangzhou , China
| | - Xiaoping Wang
- d Department of Neurology , Tongren Hospital, Shanghai Jiaotong University School of Medicine , Shanghai , China
| | - Liang Dong
- a Department of Cardiology , Second Affiliated Hospital, Zhejiang University School of Medicine , Hangzhou , China
| | - Ailian Du
- d Department of Neurology , Tongren Hospital, Shanghai Jiaotong University School of Medicine , Shanghai , China
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Mitochondrial tRNA genes are hotspots for mutations in a cohort of patients with exercise intolerance and mitochondrial myopathy. J Neurol Sci 2017; 379:137-143. [DOI: 10.1016/j.jns.2017.05.056] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 05/28/2017] [Accepted: 05/29/2017] [Indexed: 11/22/2022]
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Finsterer J, Zarrouk-Mahjoub S. Management of epilepsy in MERRF syndrome. Seizure 2017; 50:166-170. [DOI: 10.1016/j.seizure.2017.06.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 05/26/2017] [Accepted: 06/13/2017] [Indexed: 11/28/2022] Open
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Sommerville EW, Ng YS, Alston CL, Dallabona C, Gilberti M, He L, Knowles C, Chin SL, Schaefer AM, Falkous G, Murdoch D, Longman C, de Visser M, Bindoff LA, Rawles JM, Dean JCS, Petty RK, Farrugia ME, Haack TB, Prokisch H, McFarland R, Turnbull DM, Donnini C, Taylor RW, Gorman GS. Clinical Features, Molecular Heterogeneity, and Prognostic Implications in YARS2-Related Mitochondrial Myopathy. JAMA Neurol 2017; 74:686-694. [PMID: 28395030 PMCID: PMC5822212 DOI: 10.1001/jamaneurol.2016.4357] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 08/25/2016] [Indexed: 01/09/2023]
Abstract
Importance YARS2 mutations have been associated with a clinical triad of myopathy, lactic acidosis, and sideroblastic anemia in predominantly Middle Eastern populations. However, the identification of new patients expands the clinical and molecular spectrum of mitochondrial disorders. Objectives To review the clinical, molecular, and genetic features of YARS2-related mitochondrial disease and to demonstrate a new Scottish founder variant. Design, Setting, and Participants An observational case series study was conducted at a national diagnostic center for mitochondrial disease in Newcastle upon Tyne, England, and review of cases published in the literature. Six adults in a well-defined mitochondrial disease cohort and 11 additional cases described in the literature were identified with YARS2 variants between January 1, 2000, and January 31, 2015. Main Outcome and Measures The spectrum of clinical features and disease progression in unreported and reported patients with pathogenic YARS2 variants. Results Seventeen patients (median [interquartile range] age at onset, 1.5 [9.8] years) with YARS2-related mitochondrial myopathy were identified. Fifteen individuals (88%) exhibited an elevated blood lactate level accompanied by generalized myopathy; only 12 patients (71%) manifested with sideroblastic anemia. Hypertrophic cardiomyopathy (9 [53%]) and respiratory insufficiency (8 [47%]) were also prominent clinical features. Central nervous system involvement was rare. Muscle studies showed global cytochrome-c oxidase deficiency in all patients tested and severe, combined respiratory chain complex activity deficiencies. Microsatellite genotyping demonstrated a common founder effect shared between 3 Scottish patients with a p.Leu392Ser variant. Immunoblotting from fibroblasts and myoblasts of an affected Scottish patient showed normal YARS2 protein levels and mild respiratory chain complex defects. Yeast modeling of novel missense YARS2 variants closely correlated with the severity of clinical phenotypes. Conclusions and Relevance The p.Leu392Ser variant is likely a newly identified founder YARS2 mutation. Testing for pathogenic YARS2 variants should be considered in patients presenting with mitochondrial myopathy, characterized by exercise intolerance and muscle weakness even in the absence of sideroblastic anemia irrespective of ethnicity. Regular surveillance and early treatment for cardiomyopathy and respiratory muscle weakness is advocated because early treatment may mitigate the significant morbidity and mortality associated with this genetic disorder.
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Affiliation(s)
- Ewen W. Sommerville
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
| | - Yi Shiau Ng
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
| | - Charlotte L. Alston
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
| | | | - Micol Gilberti
- Department of Life Sciences, University of Parma, Parma, Italy
| | - Langping He
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
| | - Charlotte Knowles
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
| | - Sophie L. Chin
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
| | - Andrew M. Schaefer
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
| | - Gavin Falkous
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
| | - David Murdoch
- Department of Cardiology, Queen Elizabeth University Hospital, Glasgow, Scotland
| | - Cheryl Longman
- West of Scotland Regional Genetics Service, Queen Elizabeth University Hospital, Glasgow, Scotland
| | - Marianne de Visser
- Department of Neurology, Academic Medical Centre, Amsterdam, the Netherlands
| | - Laurence A. Bindoff
- Department of Clinical Medicine, Department of Clinical Medicine, University of Bergen, Bergen, Norway
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
| | - John M. Rawles
- Department of Medicine, University of Aberdeen, Aberdeen, Scotland (retired)
| | - John C. S. Dean
- Department of Medical Genetics, Medical School Building, University of Aberdeen, Aberdeen, Scotland
| | - Richard K. Petty
- Institute of Neurological Sciences, Queen Elizabeth University Hospital, Glasgow, Scotland
| | - Maria E. Farrugia
- Institute of Neurological Sciences, Queen Elizabeth University Hospital, Glasgow, Scotland
| | - Tobias B. Haack
- Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany
- Institute of Human Genetics, Technische Universität München, Munich, Germany
| | - Holger Prokisch
- Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany
- Institute of Human Genetics, Technische Universität München, Munich, Germany
| | - Robert McFarland
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
| | - Douglass M. Turnbull
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
| | - Claudia Donnini
- Department of Life Sciences, University of Parma, Parma, Italy
| | - Robert W. Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
| | - Gráinne S. Gorman
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, England
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Finsterer J, Kovacs GG. Psoriasis, bulbar involvement, and diarrhea in late myoclonic epilepsy with ragged-red fibers-syndrome due to the m.8344A > G tRNA (Lys) mutation. IRANIAN JOURNAL OF NEUROLOGY 2017; 16:45-49. [PMID: 28717435 PMCID: PMC5506757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
| | - Gabor Geza Kovacs
- Institute of Neurology, Medical University of Vienna, Vienna, Austria
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Finsterer J, Zarrouk-Mahjoub S. Mitochondrial multiorgan disorder syndrome score generated from definite mitochondrial disorders. Neuropsychiatr Dis Treat 2017; 13:2569-2579. [PMID: 29062232 PMCID: PMC5638572 DOI: 10.2147/ndt.s149067] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
OBJECTIVES Mitochondrial disorders (MIDs) frequently present as mitochondrial multiorgan disorder syndrome (MIMODS) at onset or evolve into MIMODS during the course. This study aimed to find which organs and/or tissues are most frequently affected by MIMODS, which are the most frequent abnormalities within an affected organ, whether there are typical MIMODS patterns, and to generate an MIMODS score to assess the diagnostic probability for an MID. METHODS This is a retrospective evaluation of clinical, biochemical, and genetic investigations of adult patients with definite MIDs. A total of 36 definite MID patients, 19 men and 17 women, aged 29-82 years were included in this study. The diagnosis was based on genetic testing (n=21), on biochemical investigations (n=17), or on both (n=2). RESULTS The number of organs most frequently affected was 4 ranging from 1 to 9. MIMODS was diagnosed in 97% of patients. The organs most frequently affected were the muscle (97%), central nervous system (CNS; 72%), endocrine glands (69%), heart (58%), intestines (55%), and peripheral nerves (50%). The most frequent CNS abnormalities were leukoencephalopathy, prolonged visually evoked potentials, and atrophy. The most frequent endocrine abnormalities included thyroid dysfunction, short stature, and diabetes. The most frequent cardiac abnormalities included arrhythmias, systolic dysfunction, and hypertrophic cardiomyopathy. The most frequent MIMODS patterns were encephalomyopathy, encephalo-myo-endocrinopathy, and encepalo-myo-endocrino-cardiopathy. The mean ± 2SD MIMODS score was 35.97±27.6 (range =11-71). An MIMODS score >10 was regarded as indicative of an MID. CONCLUSION Adult MIDs manifest as MIMODS in the vast majority of the cases. The organs most frequently affected in MIMODS are muscles, CNS, endocrine glands, and heart. An MIMODS score >10 suggests an MID.
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Pereira CV, Moraes CT. Current strategies towards therapeutic manipulation of mtDNA heteroplasmy. Front Biosci (Landmark Ed) 2017; 22:991-1010. [PMID: 27814659 DOI: 10.2741/4529] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Mitochondrial disease is a multifactorial disorder involving both nuclear and mitochondrial genomes. Over the past 20 years, great progress was achieved in the field of gene editing which raised the possibility of partial or complete elimination of mutant mtDNA that causes disease phenotypes. Each cell contains thousands of copies of mtDNA which can be either wild-type (WT) or mutant, a condition called heteroplasmy. As there are multiple copies of mtDNA inside a cell, the percentage of mutant mtDNA can vary and a directional shift in the heteroplasmy ratio towards an increase of WT mtDNA copies would have therapeutic value. Gene editing tools have been adapted to translocate to mitochondria and were able to change heteroplasmy in a predictable manner. These include mitochondrial targeted restriction endonucleases, Zinc-finger nucleases, and TAL-effector nucleases. These procedures could also be adapted to reduce the levels of mutant mtDNA in embryos, offering an option to the controversial mitochondrial replacement techniques during in vitro fertilization. The current strategies to induce heteroplasmy shift of mtDNA and its implications will be comprehensively discussed.
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Affiliation(s)
- Claudia V Pereira
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Carlos T Moraes
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL 33136, USA,
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22
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Altmann J, Büchner B, Nadaj-Pakleza A, Schäfer J, Jackson S, Lehmann D, Deschauer M, Kopajtich R, Lautenschläger R, Kuhn KA, Karle K, Schöls L, Schulz JB, Weis J, Prokisch H, Kornblum C, Claeys KG, Klopstock T. Expanded phenotypic spectrum of the m.8344A>G "MERRF" mutation: data from the German mitoNET registry. J Neurol 2016; 263:961-972. [PMID: 26995359 DOI: 10.1007/s00415-016-8086-3] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 02/28/2016] [Accepted: 02/29/2016] [Indexed: 11/24/2022]
Abstract
The m.8344A>G mutation in the MTTK gene, which encodes the mitochondrial transfer RNA for lysine, is traditionally associated with myoclonic epilepsy and ragged-red fibres (MERRF), a multisystemic mitochondrial disease that is characterised by myoclonus, seizures, cerebellar ataxia, and mitochondrial myopathy with ragged-red fibres. We studied the clinical and paraclinical phenotype of 34 patients with the m.8344A>G mutation, mainly derived from the nationwide mitoREGISTER, the multicentric registry of the German network for mitochondrial disorders (mitoNET). Mean age at symptom onset was 24.5 years ±10.9 (6-48 years) with adult onset in 75 % of the patients. In our cohort, the canonical features seizures, myoclonus, cerebellar ataxia and ragged-red fibres that are traditionally associated with MERRF, occurred in only 61, 59, 70, and 63 % of the patients, respectively. In contrast, other features such as hearing impairment were even more frequently present (72 %). Other common features in our cohort were migraine (52 %), psychiatric disorders (54 %), respiratory dysfunction (45 %), gastrointestinal symptoms (38 %), dysarthria (36 %), and dysphagia (35 %). Brain MRI revealed cerebral and/or cerebellar atrophy in 43 % of our patients. There was no correlation between the heteroplasmy level in blood and age at onset or clinical phenotype. Our findings further broaden the clinical spectrum of the m.8344A>G mutation, document the large clinical variability between carriers of the same mutation, even within families and indicate an overlap of the phenotype with other mitochondrial DNA-associated syndromes.
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Affiliation(s)
- Judith Altmann
- Department of Neurology, RWTH Aachen University, Aachen, Germany.,Institute of Neuropathology, RWTH Aachen University, Aachen, Germany
| | - Boriana Büchner
- Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University, München, Germany
| | | | - Jochen Schäfer
- Department of Neurology, University Hospital Carl Gustav Carus, Dresden, Germany
| | - Sandra Jackson
- Department of Neurology, University Hospital Carl Gustav Carus, Dresden, Germany
| | - Diana Lehmann
- Department of Neurology, University of Halle-Wittenberg, Halle/Saale, Germany
| | - Marcus Deschauer
- Department of Neurology, University of Halle-Wittenberg, Halle/Saale, Germany.,Department of Neurology, University of Technology München, München, Germany
| | - Robert Kopajtich
- Institute of Human Genetics, Helmholtz Centre München, München, Germany.,Institute of Human Genetics, Technical University München, München, Germany
| | - Ronald Lautenschläger
- Institute for Medical Statistics and Epidemiology, University of Technology München, München, Germany
| | - Klaus A Kuhn
- Institute for Medical Statistics and Epidemiology, University of Technology München, München, Germany
| | - Kathrin Karle
- Institute of Clinical Neurogenetics, Department of Neurology and Hertie Institute for Clinical Brain Research, Tübingen, Germany
| | - Ludger Schöls
- Institute of Clinical Neurogenetics, Department of Neurology and Hertie Institute for Clinical Brain Research, Tübingen, Germany
| | - Jörg B Schulz
- Department of Neurology, RWTH Aachen University, Aachen, Germany.,JARA - Translational Brain Medicine, Aachen, Germany
| | - Joachim Weis
- Institute of Neuropathology, RWTH Aachen University, Aachen, Germany
| | - Holger Prokisch
- Institute of Human Genetics, Helmholtz Centre München, München, Germany.,Institute of Human Genetics, Technical University München, München, Germany
| | - Cornelia Kornblum
- Department of Neurology, University Hospital of Bonn, Bonn, Germany.,Center for Rare Diseases Bonn (ZSEB), University Hospital of Bonn, Bonn, Germany
| | - Kristl G Claeys
- Department of Neurology, RWTH Aachen University, Aachen, Germany. .,Institute of Neuropathology, RWTH Aachen University, Aachen, Germany. .,Department of Neurology, University Hospitals Leuven and University of Leuven (KU Leuven), Leuven, Belgium.
| | - Thomas Klopstock
- Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University, München, Germany.,German Center for Neurodegenerative Diseases (DZNE), München, Germany.,Munich Cluster for Systems Neurology (SyNergy), München, Germany
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