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Borrelli E, Bandello F, Boon CJF, Carelli V, Lenaers G, Reibaldi M, Sadda SR, Sadun AA, Sarraf D, Yu-Wai-Man P, Barboni P. Mitochondrial retinopathies and optic neuropathies: The impact of retinal imaging on modern understanding of pathogenesis, diagnosis, and management. Prog Retin Eye Res 2024; 101:101264. [PMID: 38703886 DOI: 10.1016/j.preteyeres.2024.101264] [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: 01/11/2024] [Revised: 03/18/2024] [Accepted: 04/26/2024] [Indexed: 05/06/2024]
Abstract
Advancements in ocular imaging have significantly broadened our comprehension of mitochondrial retinopathies and optic neuropathies by examining the structural and pathological aspects of the retina and optic nerve in these conditions. This article aims to review the prominent imaging characteristics associated with mitochondrial retinopathies and optic neuropathies, aiming to deepen our insight into their pathogenesis and clinical features. Preceding this exploration, the article provides a detailed overview of the crucial genetic and clinical features, which is essential for the proper interpretation of in vivo imaging. More importantly, we will provide a critical analysis on how these imaging modalities could serve as biomarkers for characterization and monitoring, as well as in guiding treatment decisions. However, these imaging methods have limitations, which will be discussed along with potential strategies to mitigate them. Lastly, the article will emphasize the potential advantages and future integration of imaging techniques in evaluating patients with mitochondrial eye disorders, considering the prospects of emerging gene therapies.
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Affiliation(s)
- Enrico Borrelli
- Department of Surgical Sciences, University of Turin, Turin, Italy; Department of Ophthalmology, "City of Health and Science" Hospital, Turin, Italy.
| | - Francesco Bandello
- Vita-Salute San Raffaele University, Milan, Italy; IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Camiel J F Boon
- Department of Ophthalmology, Amsterdam University Medical Centers, Amsterdam, the Netherlands; Department of Ophthalmology, Leiden University Medical Center, Leiden, the Netherlands
| | - Valerio Carelli
- Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna, Italy; IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy
| | - Guy Lenaers
- Equipe MitoLab, Unité MitoVasc, INSERM U1083, Université d'Angers, 49933, Angers, France; Service de Neurologie, CHU d'Angers, 49100, Angers, France
| | - Michele Reibaldi
- Department of Surgical Sciences, University of Turin, Turin, Italy; Department of Ophthalmology, "City of Health and Science" Hospital, Turin, Italy
| | - Srinivas R Sadda
- Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Doheny Eye Institute, Los Angeles, CA, USA
| | - Alfredo A Sadun
- Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Doheny Eye Institute, Los Angeles, CA, USA
| | - David Sarraf
- Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Retinal Disorders and Ophthalmic Genetics Division, Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Patrick Yu-Wai-Man
- John van Geest Centre for Brain Repair and MRC Mitochondrial Biology Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK; Cambridge Eye Unit, Addenbrooke's Hospital, Cambridge University Hospitals, Cambridge, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK; Institute of Ophthalmology, University College London, London, UK
| | - Piero Barboni
- IRCCS San Raffaele Scientific Institute, Milan, Italy; Studio Oculistico d'Azeglio, Bologna, Italy.
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de Souza FG, da Silva MB, de Araújo GS, Silva CS, Pinheiro AHG, Cáceres-Durán MÁ, Santana-da-Silva MN, Pinto P, Gobbo AR, da Costa PF, Salgado CG, Ribeiro-Dos-Santos Â, Cavalcante GC. Whole mitogenome sequencing uncovers a relation between mitochondrial heteroplasmy and leprosy severity. Hum Genomics 2023; 17:110. [PMID: 38062538 PMCID: PMC10704783 DOI: 10.1186/s40246-023-00555-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 11/15/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND In recent years, the mitochondria/immune system interaction has been proposed, so that variants of mitochondrial genome and levels of heteroplasmy might deregulate important metabolic processes in fighting infections, such as leprosy. METHODS We sequenced the whole mitochondrial genome to investigate variants and heteroplasmy levels, considering patients with different clinical forms of leprosy and household contacts. After sequencing, a specific pipeline was used for preparation and bioinformatics analysis to select heteroplasmic variants. RESULTS We found 116 variants in at least two of the subtypes of the case group (Borderline Tuberculoid, Borderline Lepromatous, Lepromatous), suggesting a possible clinical significance to these variants. Notably, 15 variants were exclusively found in these three clinical forms, of which five variants stand out for being missense (m.3791T > C in MT-ND1, m.5317C > A in MT-ND2, m.8545G > A in MT-ATP8, m.9044T > C in MT-ATP6 and m.15837T > C in MT-CYB). In addition, we found 26 variants shared only by leprosy poles, of which two are characterized as missense (m.4248T > C in MT-ND1 and m.8027G > A in MT-CO2). CONCLUSION We found a significant number of variants and heteroplasmy levels in the leprosy patients from our cohort, as well as six genes that may influence leprosy susceptibility, suggesting for the first time that the mitogenome might be involved with the leprosy process, distinction of clinical forms and severity. Thus, future studies are needed to help understand the genetic consequences of these variants.
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Affiliation(s)
- Felipe Gouvea de Souza
- Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, PA, 66075-110, Brazil
| | - Moisés Batista da Silva
- Laboratório de Dermato-Imunologia, Instituto de Ciências Biológicas, Universidade Federal do Pará, Marituba, PA, 67105-290, Brazil
| | - Gilderlanio S de Araújo
- Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, PA, 66075-110, Brazil
| | - Caio S Silva
- Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, PA, 66075-110, Brazil
| | - Andrey Henrique Gama Pinheiro
- Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, PA, 66075-110, Brazil
| | - Miguel Ángel Cáceres-Durán
- Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, PA, 66075-110, Brazil
| | - Mayara Natália Santana-da-Silva
- Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, PA, 66075-110, Brazil
| | - Pablo Pinto
- Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, PA, 66075-110, Brazil
| | - Angélica Rita Gobbo
- Laboratório de Dermato-Imunologia, Instituto de Ciências Biológicas, Universidade Federal do Pará, Marituba, PA, 67105-290, Brazil
| | - Patrícia Fagundes da Costa
- Laboratório de Dermato-Imunologia, Instituto de Ciências Biológicas, Universidade Federal do Pará, Marituba, PA, 67105-290, Brazil
| | - Claudio Guedes Salgado
- Laboratório de Dermato-Imunologia, Instituto de Ciências Biológicas, Universidade Federal do Pará, Marituba, PA, 67105-290, Brazil
| | - Ândrea Ribeiro-Dos-Santos
- Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, PA, 66075-110, Brazil.
| | - Giovanna C Cavalcante
- Laboratório de Genética Humana e Médica, Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, PA, 66075-110, Brazil.
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Valiente-Pallejà A, Tortajada J, Bulduk BK, Vilella E, Garrabou G, Muntané G, Martorell L. Comprehensive summary of mitochondrial DNA alterations in the postmortem human brain: A systematic review. EBioMedicine 2022; 76:103815. [PMID: 35085849 PMCID: PMC8790490 DOI: 10.1016/j.ebiom.2022.103815] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 12/24/2021] [Accepted: 01/05/2022] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Mitochondrial DNA (mtDNA) encodes 37 genes necessary for synthesizing 13 essential subunits of the oxidative phosphorylation system. mtDNA alterations are known to cause mitochondrial disease (MitD), a clinically heterogeneous group of disorders that often present with neuropsychiatric symptoms. Understanding the nature and frequency of mtDNA alterations in health and disease could be a cornerstone in disentangling the relationship between biochemical findings and clinical symptoms of brain disorders. This systematic review aimed to summarize the mtDNA alterations in human brain tissue reported to date that have implications for further research on the pathophysiological significance of mtDNA alterations in brain functioning. METHODS We searched the PubMed and Embase databases using distinct terms related to postmortem human brain and mtDNA up to June 10, 2021. Reports were eligible if they were empirical studies analysing mtDNA in postmortem human brains. FINDINGS A total of 158 of 637 studies fulfilled the inclusion criteria and were clustered into the following groups: MitD (48 entries), neurological diseases (NeuD, 55 entries), psychiatric diseases (PsyD, 15 entries), a miscellaneous group with controls and other clinical diseases (5 entries), ageing (20 entries), and technical issues (5 entries). Ten entries were ascribed to more than one group. Pathogenic single nucleotide variants (pSNVs), both homo- or heteroplasmic variants, have been widely reported in MitD, with heteroplasmy levels varying among brain regions; however, pSNVs are rarer in NeuD, PsyD and ageing. A lower mtDNA copy number (CN) in disease was described in most, but not all, of the identified studies. mtDNA deletions were identified in individuals in the four clinical categories and ageing. Notably, brain samples showed significantly more mtDNA deletions and at higher heteroplasmy percentages than blood samples, and several of the deletions present in the brain were not detected in the blood. Finally, mtDNA heteroplasmy, mtDNA CN and the deletion levels varied depending on the brain region studied. INTERPRETATION mtDNA alterations are well known to affect human tissues, including the brain. In general, we found that studies of MitD, NeuD, PsyD, and ageing were highly variable in terms of the type of disease or ageing process investigated, number of screened individuals, studied brain regions and technology used. In NeuD and PsyD, no particular type of mtDNA alteration could be unequivocally assigned to any specific disease or diagnostic group. However, the presence of mtDNA deletions and mtDNA CN variation imply a role for mtDNA in NeuD and PsyD. Heteroplasmy levels and threshold effects, affected brain regions, and mitotic segregation patterns of mtDNA alterations may be involved in the complex inheritance of NeuD and PsyD and in the ageing process. Therefore, more information is needed regarding the type of mtDNA alteration, the affected brain regions, the heteroplasmy levels, and their relationship with clinical phenotypes and the ageing process. FUNDING Hospital Universitari Institut Pere Mata; Institut d'Investigació Sanitària Pere Virgili; Instituto de Salud Carlos III, Ministerio de Ciencia e Innovación (PI18/00514).
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Affiliation(s)
- Alba Valiente-Pallejà
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain
| | - Juan Tortajada
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain
| | - Bengisu K Bulduk
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain
| | - Elisabet Vilella
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain
| | - Glòria Garrabou
- Laboratory of Muscle Research and Mitochondrial Function, Department of Internal Medicine-Hospital Clínic of Barcelona (HCB); Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS); Faculty of Medicine and Health Sciences, Universitat de Barcelona (UB), 08036 Barcelona, Catalonia, Spain; Biomedical Network Research Centre on Rare Diseases (CIBERER), 28029 Madrid, Spain
| | - Gerard Muntané
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain; Institute of Evolutionary Biology (IBE), Universitat Pompeu Fabra (UPF), 08003 Barcelona, Catalonia, Spain
| | - Lourdes Martorell
- Research Department, Hospital Universitari Institut Pere Mata (HUIPM); Institut d'Investigació Sanitària Pere Virgili (IISPV); Faculty of Medicine and Health Sciences, Universitat Rovira i Virgili (URV), 43201 Reus, Catalonia, Spain; Biomedical Network Research Centre on Mental Health (CIBERSAM), 28029 Madrid, Spain.
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Lundquist AA, Farholt S, Børresen ML, Dunø M, Wibrand F, Witting N, Østergaard E. A novel homoplasmic mt-tRNA Glu m.14701C>T variant presenting with a partially reversible infantile respiratory chain deficiency. Eur J Med Genet 2021; 64:104306. [PMID: 34400372 DOI: 10.1016/j.ejmg.2021.104306] [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: 12/18/2020] [Revised: 06/16/2021] [Accepted: 08/12/2021] [Indexed: 11/19/2022]
Abstract
BACKGROUND Reversible infantile respiratory chain deficiency (RIRCD) is a rare mitochondrial disorder associated with variable penetrance and partial to full remission of symptoms. OBJECTIVE To describe features of maternally related individuals with a novel variant associated with RIRCD. MATERIALS AND METHODS Nine maternally related individuals aged 23 months to 64 years are described through physical examinations, muscle biopsies, histochemical and biochemical analyses, genome sequencing, and cerebral imaging. RESULTS A homoplasmic mitochondrial transfer ribonucleic acid for glutamic acid (mt-tRNAGlu) m.14701C>T variant was identified in eight tested individuals out of nine maternally related individuals. Two individuals presented with hypotonia, muscle weakness, feeding difficulties and lactic acidosis at age 3-4 months, and improvement around age 15-23 months with mild residual symptoms at last examination. One individual with less severe symptoms had unknown age at onset and improved around age 4-5 years. Five individuals developed lipoma on the upper back, and one adult individual developed ataxia, while one was unaffected. CONCLUSIONS We have identified a novel homoplasmic mt-tRNAGlu m.14701C>T variant presenting with phenotypic and paraclinical features associated with RIRCD as well as ataxia and lipomas, which to our knowledge are new features associated to RIRCD.
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Affiliation(s)
- Alberte A Lundquist
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Stense Farholt
- Centre for Rare Diseases, Pediatric and Adolescent Medicine, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark; Centre for Rare Diseases, Pediatric and Adolescent Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Malene L Børresen
- Centre for Rare Diseases, Pediatric and Adolescent Medicine, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Morten Dunø
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Flemming Wibrand
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Nanna Witting
- Copenhagen Neuromuscular Center, Department of Neurology, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Elsebet Østergaard
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark.
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Finsterer J, Zarrouk-Mahjoub S. Involvement of the Spinal Cord in Mitochondrial Disorders. J Neurosci Rural Pract 2019; 9:245-251. [PMID: 29725177 PMCID: PMC5912032 DOI: 10.4103/jnrp.jnrp_446_17] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
This review aims at summarising and discussing the current status concerning the clinical presentation, pathogenesis, diagnosis, and treatment of spinal cord affection in mitochondrial disorders (MIDs). A literature search using the database Pubmed was carried out by application of appropriate search terms and their combinations. Involvement of the spinal cord in MIDs is more frequent than anticipated. It occurs in specific and non-specific MIDs. Among the specific MIDs it has been most frequently described in LBSL, LS, MERRF, KSS, IOSCA, MIRAS, and PCH and only rarely in MELAS, CPEO, and LHON. Clinically, spinal cord involvement manifests as monoparesis, paraparesis, quadruparesis, sensory disturbances, hypotonia, spasticity, urinary or defecation dysfunction, spinal column deformities, or as transverse syndrome. Diagnosing spinal cord involvement in MIDs requires a thoroughly taken history, clinical exam, and imaging studies. Additionally, transcranial magnetic stimulation, somato-sensory-evoked potentials, and cerebro-spinal fluid can be supportive. Treatment is generally not at variance compared to the underlying MID but occasionally surgical stabilisation of the spinal column may be necessary. It is concluded that spinal cord involvement in MIDs is more frequent than anticipated but may be missed if cerebral manifestations prevail. Spinal cord involvement in MIDs may strongly determine the mobility of these patients.
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Affiliation(s)
- Josef Finsterer
- Department of Neurology, Krankenanstalt Rudolfstiftung, Vienna, Austria
| | - Sinda Zarrouk-Mahjoub
- Pasteur Institute of Tunis, University of Tunis El Manar and Genomics Platform, Pasteur Institute of Tunis, Tunis, Tunisia
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6
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Sallevelt SCEH, de Die-Smulders CEM, Hendrickx ATM, Hellebrekers DMEI, de Coo IFM, Alston CL, Knowles C, Taylor RW, McFarland R, Smeets HJM. De novo mtDNA point mutations are common and have a low recurrence risk. J Med Genet 2016; 54:73-83. [PMID: 27450679 PMCID: PMC5502310 DOI: 10.1136/jmedgenet-2016-103876] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 06/02/2016] [Accepted: 06/09/2016] [Indexed: 12/25/2022]
Abstract
Background Severe, disease-causing germline mitochondrial (mt)DNA mutations are maternally inherited or arise de novo. Strategies to prevent transmission are generally available, but depend on recurrence risks, ranging from high/unpredictable for many familial mtDNA point mutations to very low for sporadic, large-scale single mtDNA deletions. Comprehensive data are lacking for de novo mtDNA point mutations, often leading to misconceptions and incorrect counselling regarding recurrence risk and reproductive options. We aim to study the relevance and recurrence risk of apparently de novo mtDNA point mutations. Methods Systematic study of prenatal diagnosis (PND) and recurrence of mtDNA point mutations in families with de novo cases, including new and published data. ‘De novo’ based on the absence of the mutation in multiple (postmitotic) maternal tissues is preferred, but mutations absent in maternal blood only were also included. Results In our series of 105 index patients (33 children and 72 adults) with (likely) pathogenic mtDNA point mutations, the de novo frequency was 24.6%, the majority being paediatric. PND was performed in subsequent pregnancies of mothers of four de novo cases. A fifth mother opted for preimplantation genetic diagnosis because of a coexisting Mendelian genetic disorder. The mtDNA mutation was absent in all four prenatal samples and all 11 oocytes/embryos tested. A literature survey revealed 137 de novo cases, but PND was only performed for 9 (including 1 unpublished) mothers. In one, recurrence occurred in two subsequent pregnancies, presumably due to germline mosaicism. Conclusions De novo mtDNA point mutations are a common cause of mtDNA disease. Recurrence risk is low. This is relevant for genetic counselling, particularly for reproductive options. PND can be offered for reassurance.
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Affiliation(s)
- Suzanne C E H Sallevelt
- Department of Clinical Genetics, Maastricht University Medical Centre (MUMC), Maastricht, The Netherlands
| | - Christine E M de Die-Smulders
- Department of Clinical Genetics, Maastricht University Medical Centre (MUMC), Maastricht, The Netherlands.,Research School for Developmental Biology (GROW), Maastricht University, Maastricht, The Netherlands
| | - Alexandra T M Hendrickx
- Department of Clinical Genetics, Maastricht University Medical Centre (MUMC), Maastricht, The Netherlands
| | - Debby M E I Hellebrekers
- Department of Clinical Genetics, Maastricht University Medical Centre (MUMC), Maastricht, The Netherlands
| | - Irenaeus F M de Coo
- Department of Neurology, Erasmus MC-Sophia Children's Hospital Rotterdam, Rotterdam, The Netherlands
| | - Charlotte L Alston
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Charlotte Knowles
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Robert McFarland
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Hubert J M Smeets
- Department of Clinical Genetics, Maastricht University Medical Centre (MUMC), Maastricht, The Netherlands.,Research School for Developmental Biology (GROW), Maastricht University, Maastricht, The Netherlands.,Research School for Cardiovascular Diseases in Maastricht, CARIM, Maastricht University, Maastricht, The Netherlands
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7
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A mutation in the THG1L gene in a family with cerebellar ataxia and developmental delay. Neurogenetics 2016; 17:219-225. [PMID: 27307223 DOI: 10.1007/s10048-016-0487-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 05/29/2016] [Indexed: 12/31/2022]
Abstract
Autosomal-recessive cerebellar atrophy is usually associated with inactivating mutations and early-onset presentation. The underlying molecular diagnosis suggests the involvement of neuronal survival pathways, but many mechanisms are still lacking and most patients elude genetic diagnosis. Using whole exome sequencing, we identified homozygous p.Val55Ala in the THG1L (tRNA-histidine guanylyltransferase 1 like) gene in three siblings who presented with cerebellar signs, developmental delay, dysarthria, and pyramidal signs and had cerebellar atrophy on brain MRI. THG1L protein was previously reported to participate in mitochondrial fusion via its interaction with MFN2. Abnormal mitochondrial fragmentation, including mitochondria accumulation around the nuclei and confinement of the mitochondrial network to the nuclear vicinity, was observed when patient fibroblasts were cultured in galactose containing medium. Culturing cells in galactose containing media promotes cellular respiration by oxidative phosphorylation and the action of the electron transport chain thus stimulating mitochondrial activity. The growth defect of the yeast thg1Δ strain was rescued by the expression of either yeast Thg1 or human THG1L; however, clear growth defect was observed following the expression of the human p.Val55Ala THG1L or the corresponding yeast mutant. A defect in the protein tRNAHis guanylyltransferase activity was excluded by the normal in vitro G-1 addition to either yeast tRNAHis or human mitochondrial tRNAHis in the presence of the THG1L mutation. We propose that homozygosity for the p.Val55Ala mutation in THG1L is the cause of the abnormal mitochondrial network in the patient fibroblasts, likely by interfering with THG1L activity towards MFN2. This may result in lack of mitochondria in the cerebellar Purkinje dendrites, with degeneration of Purkinje cell bodies and apoptosis of granule cells, as reported for MFN2 deficient mice.
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8
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Alsemari A, Al-Hindi HN. Large-scale mitochondrial DNA deletion underlying familial multiple system atrophy of the cerebellar subtype. Clin Case Rep 2015; 4:111-7. [PMID: 26862402 PMCID: PMC4736521 DOI: 10.1002/ccr3.435] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Revised: 09/03/2015] [Accepted: 09/29/2015] [Indexed: 11/29/2022] Open
Abstract
A family with mitochondrial inheritance of multiple system atrophy of the cerebellar subtype. MRI brain shows significant cerebellar atrophy with mild pontine atrophy and the classical hot cross bun sign in Pons. The muscle biopsy was indicative of mitochondrial myopathy. Mitochondrial DNA analysis revealed a low‐level large mtDNA deletion, m.3264_1607del12806 bp.
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Affiliation(s)
- Abdulaziz Alsemari
- Department of Neurosciences King Faisal Specialist Hospital and Research Centre PO box 3354 Riyadh 11211 Saudi Arabia
| | - Hindi Nasser Al-Hindi
- Department of Pathology and Laboratory Medicine King Faisal Specialist Hospital and Research Centre PO box 3354 Riyadh 11211 Saudi Arabia
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9
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Neuropathologic Characterization of Pontocerebellar Hypoplasia Type 6 Associated With Cardiomyopathy and Hydrops Fetalis and Severe Multisystem Respiratory Chain Deficiency due to Novel RARS2 Mutations. J Neuropathol Exp Neurol 2015; 74:688-703. [PMID: 26083569 PMCID: PMC4470523 DOI: 10.1097/nen.0000000000000209] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Autosomal recessive mutations in the RARS2 gene encoding the mitochondrial arginyl-transfer RNA synthetase cause infantile-onset myoencephalopathy pontocerebellar hypoplasia type 6 (PCH6). We describe 2 sisters with novel compound heterozygous RARS2 mutations who presented perinatally with neurologic features typical of PCH6 but with additional features including cardiomyopathy, hydrops, and pulmonary hypoplasia and who died at 1 day and 14 days of age. Magnetic resonance imaging findings included marked cerebellar hypoplasia, gyral immaturity, punctate lesions in cerebral white matter, and unfused deep cerebral grey matter. Enzyme histochemistry of postmortem tissues revealed a near-global cytochrome c oxidase-deficiency; assessment of respiratory chain enzyme activities confirmed severe deficiencies involving complexes I, III, and IV. Molecular genetic studies revealed 2 RARS2 gene mutations: a c.1A>G, p.? variant predicted to abolish the initiator methionine, and a deep intronic c.613-3927C>T variant causing skipping of exons 6-8 in the mature RARS2 transcript. Neuropathologic investigation included low brain weights, small brainstem and cerebellum, deep cerebral white matter pathology, pontine nucleus neuron loss (in 1 sibling), and peripheral nerve pathology. Mitochondrial respiratory chain immunohistochemistry in brain tissues confirmed an absence of complexes I and IV immunoreactivity with sparing of mitochondrial numbers. These cases expand the clinical spectrum of RARS2 mutations, including antenatal features and widespread mitochondrial respiratory chain deficiencies in postmortem brain tissues.
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10
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Boczonadi V, Bansagi B, Horvath R. Reversible infantile mitochondrial diseases. J Inherit Metab Dis 2015; 38:427-35. [PMID: 25407320 DOI: 10.1007/s10545-014-9784-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 10/09/2014] [Accepted: 10/14/2014] [Indexed: 11/30/2022]
Abstract
Mitochondrial diseases are usually severe and progressive conditions; however, there are rare forms that show remarkable spontaneous recoveries. Two homoplasmic mitochondrial tRNA mutations (m.14674T>C/G in mt-tRNA(Glu)) have been reported to cause severe infantile mitochondrial myopathy in the first months of life. If these patients survive the first year of life by extensive life-sustaining measures they usually recover and develop normally. Another mitochondrial disease due to deficiency of the 5-methylaminomethyl-2-thiouridylate methyltransferase (TRMU) causes severe liver failure in infancy, but similar to the reversible mitochondrial myopathy, within the first year of life these infants may also recover completely. Partial recovery has been noted in some other rare forms of mitochondrial disease due to deficiency of mitochondrial tRNA synthetases and mitochondrial tRNA modifying enzymes. Here we summarize the clinical presentation of these unique reversible mitochondrial diseases and discuss potential molecular mechanisms behind the reversibility. Understanding these mechanisms may provide the key to treatments of potential broader relevance in mitochondrial disease, where for the majority of the patients no effective treatment is currently available.
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Affiliation(s)
- Veronika Boczonadi
- Institute of Human Genetics, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
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Nesbitt V, Alston CL, Blakely EL, Fratter C, Feeney CL, Poulton J, Brown GK, Turnbull DM, Taylor RW, McFarland R. A national perspective on prenatal testing for mitochondrial disease. Eur J Hum Genet 2014; 22:1255-9. [PMID: 24642831 PMCID: PMC4200441 DOI: 10.1038/ejhg.2014.35] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 12/17/2013] [Accepted: 01/16/2014] [Indexed: 01/30/2023] Open
Abstract
Mitochondrial diseases affect >1 in 7500 live births and may be due to mutations in either mitochondrial DNA (mtDNA) or nuclear DNA (nDNA). Genetic counselling for families with mitochondrial diseases, especially those due to mtDNA mutations, provides unique and difficult challenges particularly in relation to disease transmission and prevention. We have experienced an increasing demand for prenatal diagnostic testing from families affected by mitochondrial disease since we first offered this service in 2007. We review the diagnostic records of the 62 prenatal samples (17 mtDNA and 45 nDNA) analysed since 2007, the reasons for testing, mutation investigated and the clinical outcome. Our findings indicate that prenatal testing for mitochondrial disease is reliable and informative for the nuclear and selected mtDNA mutations we have tested. Where available, the results of mtDNA heteroplasmy analyses from other family members are helpful in interpreting the prenatal mtDNA test result. This is particularly important when the mutation is rare or the mtDNA heteroplasmy is observed at intermediate levels. At least 11 cases of mitochondrial disease were prevented following prenatal testing, 3 of which were mtDNA disease. On the basis of our results, we believe that prenatal testing for mitochondrial disease is an important option for couples where appropriate genetic analyses and pre/post-test counselling can be provided.
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Affiliation(s)
- Victoria Nesbitt
- Wellcome Trust Centre for Mitochondrial Research, The Medical School, Institute for Ageing and Health, Newcastle University, Newcastle-upon-Tyne, UK
| | - Charlotte L Alston
- NHS Specialised Services for Rare Mitochondrial Disorders of Adults and Children UK, Oxford, UK
| | - Emma L Blakely
- NHS Specialised Services for Rare Mitochondrial Disorders of Adults and Children UK, Oxford, UK
| | - Carl Fratter
- NHS Specialised Services for Rare Mitochondrial Disorders of Adults and Children UK, Oxford, UK
- Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Trust, Oxford, UK
| | - Catherine L Feeney
- NHS Specialised Services for Rare Mitochondrial Disorders of Adults and Children UK, Oxford, UK
| | - Joanna Poulton
- NHS Specialised Services for Rare Mitochondrial Disorders of Adults and Children UK, Oxford, UK
- Nuffield Department of Obstetrics and Gynaecology, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Garry K Brown
- NHS Specialised Services for Rare Mitochondrial Disorders of Adults and Children UK, Oxford, UK
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Doug M Turnbull
- Wellcome Trust Centre for Mitochondrial Research, The Medical School, Institute for Ageing and Health, Newcastle University, Newcastle-upon-Tyne, UK
- NHS Specialised Services for Rare Mitochondrial Disorders of Adults and Children UK, Oxford, UK
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research, The Medical School, Institute for Ageing and Health, Newcastle University, Newcastle-upon-Tyne, UK
- NHS Specialised Services for Rare Mitochondrial Disorders of Adults and Children UK, Oxford, UK
| | - Robert McFarland
- Wellcome Trust Centre for Mitochondrial Research, The Medical School, Institute for Ageing and Health, Newcastle University, Newcastle-upon-Tyne, UK
- NHS Specialised Services for Rare Mitochondrial Disorders of Adults and Children UK, Oxford, UK
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Lehmann D, Schubert K, Joshi PR, Baty K, Blakely EL, Zierz S, Taylor RW, Deschauer M. A novel m.7539C>T point mutation in the mt-tRNA(Asp) gene associated with multisystemic mitochondrial disease. Neuromuscul Disord 2014; 25:81-4. [PMID: 25447692 PMCID: PMC4317191 DOI: 10.1016/j.nmd.2014.09.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 09/03/2014] [Accepted: 09/17/2014] [Indexed: 11/18/2022]
Abstract
Mitochondrial transfer RNA (mt-tRNA) mutations are the commonest sub-type of mitochondrial (mtDNA) mutations associated with human disease. We report a patient with multisytemic disease characterised by myopathy, spinal ataxia, sensorineural hearing loss, cataract and cognitive impairment in whom a novel m.7539C>T mt-tRNA(Asp) transition was identified. Muscle biopsy revealed extensive histopathological findings including cytochrome c oxidase (COX)-deficient fibres. Pyrosequencing confirmed mtDNA heteroplasmy for the mutation whilst single muscle fibre segregation studies revealed statistically significant higher mutation loads in COX-deficient fibres than in COX-positive fibres. Absence from control databases, hierarchical mt-tRNA mutation segregation within tissues, and occurrence at conserved sequence positions, further confirm this novel mt-tRNA mutation to be pathogenic. To date only three mt-tRNA(Asp) gene mutations have been described with clear evidence of pathogenicity. The novel m.7539C>T mt-tRNA(Asp) gene mutation extends the spectrum of pathogenic mutations in this gene, further supporting the notion that mt-tRNA(Asp) gene mutations are associated with multisystemic disease presentations.
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Affiliation(s)
- Diana Lehmann
- Department of Neurology, University of Halle-Wittenberg, Ernst-Grube-Str. 40, Halle/Saale 06097, Germany
| | - Kathrin Schubert
- Department of Neurology, University of Halle-Wittenberg, Ernst-Grube-Str. 40, Halle/Saale 06097, Germany
| | - Pushpa R Joshi
- Department of Neurology, University of Halle-Wittenberg, Ernst-Grube-Str. 40, Halle/Saale 06097, Germany
| | - Karen Baty
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, UK
| | - Emma L Blakely
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, UK
| | - Stephan Zierz
- Department of Neurology, University of Halle-Wittenberg, Ernst-Grube-Str. 40, Halle/Saale 06097, Germany
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, UK
| | - Marcus Deschauer
- Department of Neurology, University of Halle-Wittenberg, Ernst-Grube-Str. 40, Halle/Saale 06097, Germany.
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Abbott JA, Francklyn CS, Robey-Bond SM. Transfer RNA and human disease. Front Genet 2014; 5:158. [PMID: 24917879 PMCID: PMC4042891 DOI: 10.3389/fgene.2014.00158] [Citation(s) in RCA: 150] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 05/14/2014] [Indexed: 12/25/2022] Open
Abstract
Pathological mutations in tRNA genes and tRNA processing enzymes are numerous and result in very complicated clinical phenotypes. Mitochondrial tRNA (mt-tRNA) genes are “hotspots” for pathological mutations and over 200 mt-tRNA mutations have been linked to various disease states. Often these mutations prevent tRNA aminoacylation. Disrupting this primary function affects protein synthesis and the expression, folding, and function of oxidative phosphorylation enzymes. Mitochondrial tRNA mutations manifest in a wide panoply of diseases related to cellular energetics, including COX deficiency (cytochrome C oxidase), mitochondrial myopathy, MERRF (Myoclonic Epilepsy with Ragged Red Fibers), and MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes). Diseases caused by mt-tRNA mutations can also affect very specific tissue types, as in the case of neurosensory non-syndromic hearing loss and pigmentary retinopathy, diabetes mellitus, and hypertrophic cardiomyopathy. Importantly, mitochondrial heteroplasmy plays a role in disease severity and age of onset as well. Not surprisingly, mutations in enzymes that modify cytoplasmic and mitochondrial tRNAs are also linked to a diverse range of clinical phenotypes. In addition to compromised aminoacylation of the tRNAs, mutated modifying enzymes can also impact tRNA expression and abundance, tRNA modifications, tRNA folding, and even tRNA maturation (e.g., splicing). Some of these pathological mutations in tRNAs and processing enzymes are likely to affect non-canonical tRNA functions, and contribute to the diseases without significantly impacting on translation. This chapter will review recent literature on the relation of mitochondrial and cytoplasmic tRNA, and enzymes that process tRNAs, to human disease. We explore the mechanisms involved in the clinical presentation of these various diseases with an emphasis on neurological disease.
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Affiliation(s)
- Jamie A Abbott
- Department of Biochemistry, College of Medicine, University of Vermont Burlington, VT, USA
| | | | - Susan M Robey-Bond
- Department of Biochemistry, College of Medicine, University of Vermont Burlington, VT, USA
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