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O'Connor K, Spendiff S, Lochmüller H, Horvath R. Mitochondrial Mutations Can Alter Neuromuscular Transmission in Congenital Myasthenic Syndrome and Mitochondrial Disease. Int J Mol Sci 2023; 24:ijms24108505. [PMID: 37239850 DOI: 10.3390/ijms24108505] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 04/28/2023] [Accepted: 05/02/2023] [Indexed: 05/28/2023] Open
Abstract
Congenital myasthenic syndromes (CMS) are a group of rare, neuromuscular disorders that usually present in childhood or infancy. While the phenotypic presentation of these disorders is diverse, the unifying feature is a pathomechanism that disrupts neuromuscular transmission. Recently, two mitochondrial genes-SLC25A1 and TEFM-have been reported in patients with suspected CMS, prompting a discussion about the role of mitochondria at the neuromuscular junction (NMJ). Mitochondrial disease and CMS can present with similar symptoms, and potentially one in four patients with mitochondrial myopathy exhibit NMJ defects. This review highlights research indicating the prominent roles of mitochondria at both the pre- and postsynapse, demonstrating the potential for mitochondrial involvement in neuromuscular transmission defects. We propose the establishment of a novel subcategorization for CMS-mitochondrial CMS, due to unifying clinical features and the potential for mitochondrial defects to impede transmission at the pre- and postsynapse. Finally, we highlight the potential of targeting the neuromuscular transmission in mitochondrial disease to improve patient outcomes.
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Affiliation(s)
- Kaela O'Connor
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, Canada
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
- Centre for Neuromuscular Disease, University of Ottawa Brain and Mind Research Institute, Ottawa, ON K1H 8M5, Canada
| | - Sally Spendiff
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, Canada
| | - Hanns Lochmüller
- Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 8L1, Canada
- Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, ON K1H 8L6, Canada
- Brain and Mind Research Institute, University of Ottawa, Ottawa, ON K1H 8M5, Canada
- Department of Neuropediatrics and Muscle Disorders, Faculty of Medicine, Medical Center-University of Freiburg, 79104 Freiburg, Germany
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), 08028 Barcelona, Catalonia, Spain
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge, Cambridge CB3 0FD, UK
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Tawfik CA, Zaitoun R, Farag AA. Harel Yoon syndrome: a novel mutation in ATAD3A gene and expansion of the clinical spectrum. Ophthalmic Genet 2023; 44:226-233. [PMID: 36856321 DOI: 10.1080/13816810.2023.2183223] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Abstract
BACKGROUND Harel-Yoon syndrome (HAYOS) is a recently described neurodevelopmental disorder characterized by psychomotor delay, truncal hypotonia, appendicular spasticity, and peripheral neuropathy. It is caused by mutations in ATAD3A gene located on chromosome 1p.36.33 whose functions include mitochondrial DNA stabilization, the regulation of mitochondrial fission/fusion, and cholesterol homeostasis. MATERIALS AND METHODS An 11-year-old male patient of consanguineous Egyptian parents, who present with neuroregression and ptosis along with progressive impaired vision, undergoes complete ophthalmological and neurological examination. Additionally, color fundus photography, fundus autofluorescence (FAF), spectral domain optical coherence tomography (SD-OCT) of both the macula and optic nerve head, full field electroretinogram (ERG), and visual field perimetry were obtained. Whole-exome sequencing and mitochondrial genome sequencing were done in a commercial laboratory from a peripheral blood sample. RESULTS A novel mutation in ATAD3A gene c.624_644del was identified by whole-exome sequencing consistent with a diagnosis of Harel-Yoon Syndrome (HAYOS). The 11-year-old boy had characteristic features of neurodevelopmental delay, hypotonia, and peripheral neuropathy. However, we documented some novel features as fatiguable ptosis, facial weakness, progressive bulbar palsy, obsessive-compulsive disorder (OCD) in addition to cone system dysfunction. CONCLUSION Our study reports a novel mutation in ATAD3A gene and expands the clinical spectrum of Harel-Yoon Syndrome. Future research aiming at better understanding of gene function will lead to better genotype-phenotype correlation and could pave the way to more treatment options.
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Affiliation(s)
- Caroline Atef Tawfik
- Department of ophthalmology, Ain Shams University, Cairo, Egypt
- Watany Eye Hospital, Cairo, Egypt
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Olimpio C, Tiet MY, Horvath R. Primary mitochondrial myopathies in childhood. Neuromuscul Disord 2021; 31:978-987. [PMID: 34736635 DOI: 10.1016/j.nmd.2021.08.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 07/29/2021] [Accepted: 08/05/2021] [Indexed: 12/30/2022]
Abstract
Primary mitochondrial myopathies are genetic metabolic disorders of mitochondrial dysfunction affecting mainly, but not exclusively, skeletal muscle. Although individually rare, they are the most common inherited metabolic disorders in childhood. They can be similar to other childhood muscle diseases such as congenital myopathies, dystrophies, myasthenic syndromes or metabolic myopathies and a muscle biopsy and genetic testing are important in the differential diagnosis. Mitochondrial myopathies can present at any age but typically childhood onset myopathies have more significant muscle involvement and are caused by genes encoded in the nuclear DNA. Mitochondrial myopathy in infants presents with hypotonia, muscle weakness and difficulty feeding. In toddlers and older children delayed motor development, exercise intolerance and premature fatigue are common. A number of nuclear DNA and mitochondrial DNA encoded genes are known to cause isolated myopathy in childhood and they are important in a range of mitochondrial functions such as oxidative phosphorylation, mitochondrial transcription/translation and mitochondrial fusion/fission. A rare cause of isolated myopathy in children, reversible infantile respiratory chain deficiency myopathy, is non-progressive and typically associated with spontaneous full recovery. Promising targeted treatments have been reported for a number or mitochondrial myopathies including riboflavin in ACAD9 and ETFDH-myopathies and deoxynucleoside for TK2-related disease.
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Affiliation(s)
- Catarina Olimpio
- East Anglian Medical Genetics Service, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom
| | - May Yung Tiet
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom.
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Baty K, Farrugia ME, Hopton S, Falkous G, Schaefer AM, Stewart W, Willison HJ, Reilly MM, Blakely EL, Taylor RW, Ng YS. A novel MT-CO2 variant causing cerebellar ataxia and neuropathy: The role of muscle biopsy in diagnosis and defining pathogenicity. Neuromuscul Disord 2021; 31:1186-1193. [PMID: 34325999 PMCID: PMC8708152 DOI: 10.1016/j.nmd.2021.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 05/21/2021] [Accepted: 05/28/2021] [Indexed: 11/22/2022]
Abstract
Pathogenic variants in mitochondrial DNA (mtDNA) are associated with significant clinical heterogeneity with neuromuscular involvement commonly reported. Non-syndromic presentations of mtDNA disease continue to pose a diagnostic challenge and with genomic testing still necessitating a muscle biopsy in many cases. Here we describe an adult patient who presented with progressive ataxia, neuropathy and exercise intolerance in whom the application of numerous Mendelian gene panels had failed to make a genetic diagnosis. Muscle biopsy revealed characteristic mitochondrial pathology (cytochrome c oxidase deficient, ragged-red fibers) prompting a thorough investigation of the mitochondrial genome. Two heteroplasmic MT-CO2 gene variants (NC_012920.1: m.7887G>A and m.8250G>A) were identified, necessitating single fiber segregation and familial studies - including the biopsy of the patient's clinically-unaffected mother - to demonstrate pathogenicity of the novel m.7887G>A p.(Gly101Asp) variant and establishing this as the cause of the mitochondrial biochemical defects and clinical presentation. In the era of high throughput whole exome and genome sequencing, muscle biopsy remains a key investigation in the diagnosis of patients with non-syndromic presentations of adult-onset mitochondrial disease and fully defining the pathogenicity of novel mtDNA variants.
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Affiliation(s)
- Karen Baty
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Services for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 4LP, UK
| | - Maria E Farrugia
- Department of Neurology, Institute of Neurological Sciences, Queen Elizabeth University Hospital, Glasgow G51 4TF, UK
| | - Sila Hopton
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Services for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 4LP, UK
| | - Gavin Falkous
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Services for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 4LP, UK
| | - Andrew M Schaefer
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Services for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 4LP, UK; Directorate of Neurosciences, Royal Victoria Infirmary, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 4LP, UK
| | - William Stewart
- Department of Neuropathology, Queen Elizabeth University Hospital, Glasgow G51 4TF and Institute of Neuroscience and Psychology, University of Glasgow, G12 8QQ, UK
| | - Hugh J Willison
- Department of Neurology and Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow G51 4TF, UK
| | - Mary M Reilly
- MRC Centre for Neuromuscular Diseases, Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
| | - Emma L Blakely
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Services for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 4LP, UK
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Services for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 4LP, UK
| | - Yi Shiau Ng
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; NHS Highly Specialised Services for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 4LP, UK; Directorate of Neurosciences, Royal Victoria Infirmary, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE1 4LP, UK.
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Kuthethur R, Prasad K, Chakrabarty S, Kabekkodu SP, Singh KK, Thangaraj K, Satyamoorthy K. Advances in mitochondrial medicine and translational research. Mitochondrion 2021; 61:62-68. [PMID: 34363984 DOI: 10.1016/j.mito.2021.09.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/20/2021] [Accepted: 09/22/2021] [Indexed: 10/20/2022]
Abstract
Current knowledge of mitochondrial biology and function has provided tools and technologies that helped a better understanding of the molecular etiology of complex mitochondrial disorders. Dual genetic control of this subcellular organelle function regulates various signaling mechanisms which are essential for metabolism, bioenergetics, fatty acid biosynthesis, and DNA replication & repair. Understanding nuclear mitochondrial crosstalk through advanced genomics as well as clinical perspectives is the overall basis of mitochondrial research and medicine, also the sole objective of Society for Mitochondrial Medicine and Research (SMRM) - India. The eighth virtual international conference on 'Advances in Mitochondrial Medicine and Translational Research' was organized at the Manipal School of Life Sciences, MAHE, Manipal, India, during 6 - 7 November 2020. The aim of the virtual conference was to highlight the recent advances and future perspectives that represent comprehensive clinical and fundamental research interests in the area of mitochondrial biology of human diseases. To systematically present the various findings in mitochondrial biology, the meeting was themed with specific aspects comprising (a) mitochondrial disorders: clinical & genomic perspectives, (b) mitochondria in cancer, (c) mitochondrial metabolism & disorders, and (d) mitochondrial diseases & therapy. This report provides an overview of the recent advancements in the area of mitochondrial biology and medicine that was discussed at the conference.
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Affiliation(s)
- Raviprasad Kuthethur
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, India
| | - Keshava Prasad
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, India
| | - Sanjiban Chakrabarty
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, India
| | - Shama Prasada Kabekkodu
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, India
| | - Keshav K Singh
- Department of Genetics, School of Medicine, The University of Alabama at Birmingham, Kaul Genetics Building, Rm. 620, 720 20th St. South, Birmingham, AL, 35294, United States
| | - Kumarasamy Thangaraj
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007, India; Centre for DNA Fingerprinting and Diagnostics, Uppal, Hyderabad 500 039, India
| | - Kapaettu Satyamoorthy
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, India.
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Kuthethur R, Prasad K, Chakrabarty S, Prasada Kabekkodu S, Singh KK, Thangaraj K, Satyamoorthy K. Advances in Mitochondrial Medicine and Translational Research. Mitochondrion 2021:S1567-7249(21)00102-1. [PMID: 34363984 DOI: 10.1016/j.mito.2021.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Current knowledge of mitochondrial biology and function has provided with tools and technologies that helped a better understanding of the molecular etiology of complex mitochondrial disorders. Dual genetic control of this subcellular organelle function regulates various signaling mechanisms which are essential for metabolism, bioenergetics, fatty acid biosynthesis, and DNA replication & repair. Understanding nuclear mitochondrial crosstalk through advanced genomics as well as clinical perspectives is the overall basis of mitochondrial research and medicine, also the sole objective of Society for Mitochondrial Medicine and Research (SMRM) - India. The eighth virtual international conference on 'Advances in Mitochondrial Medicine and Translational Research' was organized at the Manipal School of Life Sciences, MAHE, Manipal, India, during 6 - 7 November 2020. The aim of the virtual conference was to highlight the recent advances and future perspectives that represent comprehensive clinical and fundamental research interests in the area of mitochondrial biology of human diseases. To systematically present the various findings in mitochondrial biology, the meeting was themed with specific aspects comprising (a) mitochondrial disorders: clinical & genomic perspectives, (b) mitochondria in cancer, (c) mitochondrial metabolism & disorders, and (d) mitochondrial diseases & therapy. This report provides an overview of the recent advancements in the area of mitochondrial biology and medicine that was discussed at the conference.
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Affiliation(s)
- Raviprasad Kuthethur
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, India
| | - Keshava Prasad
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, India
| | - Sanjiban Chakrabarty
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, India
| | - Shama Prasada Kabekkodu
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, India
| | - Keshav K Singh
- Department of Genetics, School of Medicine, The University of Alabama at Birmingham, Kaul Genetics Building, Rm. 620, 720 20th St. South, Birmingham, AL 35294, USA
| | - Kumarasamy Thangaraj
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007, India; Centre for DNA Fingerprinting and Diagnostics, Uppal, Hyderabad, 500 039, India
| | - Kapaettu Satyamoorthy
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, India.
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Bernardino Gomes TM, Ng YS, Pickett SJ, Turnbull DM, Vincent AE. Mitochondrial DNA disorders: From pathogenic variants to preventing transmission. Hum Mol Genet 2021; 30:R245-R253. [PMID: 34169319 PMCID: PMC8490015 DOI: 10.1093/hmg/ddab156] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 05/28/2021] [Accepted: 06/01/2021] [Indexed: 11/27/2022] Open
Abstract
Mitochondrial DNA (mtDNA) disorders are recognized as one of the most common causes of inherited metabolic disorders. The mitochondrial genome occurs in multiple copies resulting in both homoplasmic and heteroplasmic pathogenic mtDNA variants. A biochemical defect arises when the pathogenic variant level reaches a threshold, which differs between variants. Moreover, variants can segregate, clonally expand, or be lost from cellular populations resulting in a dynamic and tissue-specific mosaic pattern of oxidative deficiency. MtDNA is maternally inherited but transmission patterns of heteroplasmic pathogenic variants are complex. During oogenesis, a mitochondrial bottleneck results in offspring with widely differing variant levels to their mother, whilst highly deleterious variants, such as deletions, are not transmitted. Complemented by a complex interplay between mitochondrial and nuclear genomes, these peculiar genetics produce marked phenotypic variation, posing challenges to the diagnosis and clinical management of patients. Novel therapeutic compounds and several genetic therapies are currently under investigation, but proven disease-modifying therapies remain elusive. Women who carry pathogenic mtDNA variants require bespoke genetic counselling to determine their reproductive options. Recent advances in in vitro fertilization techniques, have greatly improved reproductive choices, but are not without their challenges. Since the first pathogenic mtDNA variants were identified over 30 years ago, there has been remarkable progress in our understanding of these diseases. However, many questions remain unanswered and future studies are required to investigate the mechanisms of disease progression and to identify new disease-specific therapeutic targets.
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Affiliation(s)
- Tiago M Bernardino Gomes
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.,NHS Highly Specialised Service for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, NE2 4HH, UK
| | - Yi Shiau Ng
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.,NHS Highly Specialised Service for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, NE2 4HH, UK
| | - Sarah J Pickett
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Doug M Turnbull
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Amy E Vincent
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
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