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Chen A, Yangzom T, Hong Y, Lundberg BC, Sullivan GJ, Tzoulis C, Bindoff LA, Liang KX. Hallmark Molecular and Pathological Features of POLG Disease are Recapitulated in Cerebral Organoids. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2307136. [PMID: 38445970 PMCID: PMC11095234 DOI: 10.1002/advs.202307136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 11/26/2023] [Indexed: 03/07/2024]
Abstract
In this research, a 3D brain organoid model is developed to study POLG-related encephalopathy, a mitochondrial disease stemming from POLG mutations. Induced pluripotent stem cells (iPSCs) derived from patients with these mutations is utilized to generate cortical organoids, which exhibited typical features of the diseases with POLG mutations, such as altered morphology, neuronal loss, and mitochondiral DNA (mtDNA) depletion. Significant dysregulation is also identified in pathways crucial for neuronal development and function, alongside upregulated NOTCH and JAK-STAT signaling pathways. Metformin treatment ameliorated many of these abnormalities, except for the persistent affliction of inhibitory dopamine-glutamate (DA GLU) neurons. This novel model effectively mirrors both the molecular and pathological attributes of diseases with POLG mutations, providing a valuable tool for mechanistic understanding and therapeutic screening for POLG-related disorders and other conditions characterized by compromised neuronal mtDNA maintenance and complex I deficiency.
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Affiliation(s)
- Anbin Chen
- Department of Clinical Medicine (K1)University of BergenBergen5021Norway
- Department of NeurosurgeryXinhua Hospital Affiliated to Shanghai Jiaotong University School of MedicineShanghai20092China
| | - Tsering Yangzom
- Department of Clinical Medicine (K1)University of BergenBergen5021Norway
- Centre for International HealthUniversity of BergenBergen5020Norway
| | - Yu Hong
- Department of Clinical Medicine (K1)University of BergenBergen5021Norway
| | - Bjørn Christian Lundberg
- Department of Clinical Medicine (K1)University of BergenBergen5021Norway
- Department of BiomedicineUniversity of BergenBergen5009Norway
| | | | - Charalampos Tzoulis
- Department of Clinical Medicine (K1)University of BergenBergen5021Norway
- Neuro‐SysMedCenter of Excellence for Clinical Research in Neurological DiseasesHaukeland University HospitalBergen5021Norway
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Salemi M, Lanza G, Salluzzo MG, Schillaci FA, Di Blasi FD, Cordella A, Caniglia S, Lanuzza B, Morreale M, Marano P, Tripodi M, Ferri R. A Next-Generation Sequencing Study in a Cohort of Sicilian Patients with Parkinson's Disease. Biomedicines 2023; 11:3118. [PMID: 38137339 PMCID: PMC10740523 DOI: 10.3390/biomedicines11123118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 11/20/2023] [Accepted: 11/21/2023] [Indexed: 12/24/2023] Open
Abstract
Parkinson's disease (PD) is a multisystem and multifactorial disorder and, therefore, the application of modern genetic techniques may assist in unraveling its complex pathophysiology. We conducted a clinical-demographic evaluation of 126 patients with PD, all of whom were Caucasian and of Sicilian ancestry. DNA was extracted from the peripheral blood for each patient, followed by sequencing using a Next-Generation Sequencing system. This system was based on a custom gene panel comprising 162 genes. The sample underwent further filtering, taking into account the allele frequencies of genetic variants, their presence in the Human Gene Mutation Database, and their association in the literature with PD or other movement/neurodegenerative disorders. The largest number of variants was identified in the leucine-rich repeat kinase 2 (LRRK2) gene. However, variants in other genes, such as acid beta-glucosidase (GBA), DNA polymerase gamma catalytic subunit (POLG), and parkin RBR E3 ubiquitin protein ligase (PRKN), were also discovered. Interestingly, some of these variants had not been previously associated with PD. Enhancing our understanding of the genetic basis of PD and identifying new variants possibly linked to the disease will contribute to improved diagnostic accuracy, therapeutic developments, and prognostic insights for affected individuals.
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Affiliation(s)
- Michele Salemi
- Oasi Research Institute—IRCCS, 94018 Troina, EN, Italy; (M.S.); (M.G.S.); (F.A.S.); (F.D.D.B.); (S.C.); (B.L.); (M.M.); (P.M.); (M.T.); (R.F.)
| | - Giuseppe Lanza
- Oasi Research Institute—IRCCS, 94018 Troina, EN, Italy; (M.S.); (M.G.S.); (F.A.S.); (F.D.D.B.); (S.C.); (B.L.); (M.M.); (P.M.); (M.T.); (R.F.)
- Department of Surgery and Medical-Surgical Specialties, University of Catania, 95123 Catania, CT, Italy
| | - Maria Grazia Salluzzo
- Oasi Research Institute—IRCCS, 94018 Troina, EN, Italy; (M.S.); (M.G.S.); (F.A.S.); (F.D.D.B.); (S.C.); (B.L.); (M.M.); (P.M.); (M.T.); (R.F.)
| | - Francesca A. Schillaci
- Oasi Research Institute—IRCCS, 94018 Troina, EN, Italy; (M.S.); (M.G.S.); (F.A.S.); (F.D.D.B.); (S.C.); (B.L.); (M.M.); (P.M.); (M.T.); (R.F.)
| | - Francesco Domenico Di Blasi
- Oasi Research Institute—IRCCS, 94018 Troina, EN, Italy; (M.S.); (M.G.S.); (F.A.S.); (F.D.D.B.); (S.C.); (B.L.); (M.M.); (P.M.); (M.T.); (R.F.)
| | - Angela Cordella
- Genomix4Life Srl, 84081 Baronissi, SA, Italy;
- Genome Research Center for Health—CRGS, 84081 Baronissi, SA, Italy
| | - Salvatore Caniglia
- Oasi Research Institute—IRCCS, 94018 Troina, EN, Italy; (M.S.); (M.G.S.); (F.A.S.); (F.D.D.B.); (S.C.); (B.L.); (M.M.); (P.M.); (M.T.); (R.F.)
| | - Bartolo Lanuzza
- Oasi Research Institute—IRCCS, 94018 Troina, EN, Italy; (M.S.); (M.G.S.); (F.A.S.); (F.D.D.B.); (S.C.); (B.L.); (M.M.); (P.M.); (M.T.); (R.F.)
| | - Manuela Morreale
- Oasi Research Institute—IRCCS, 94018 Troina, EN, Italy; (M.S.); (M.G.S.); (F.A.S.); (F.D.D.B.); (S.C.); (B.L.); (M.M.); (P.M.); (M.T.); (R.F.)
| | - Pietro Marano
- Oasi Research Institute—IRCCS, 94018 Troina, EN, Italy; (M.S.); (M.G.S.); (F.A.S.); (F.D.D.B.); (S.C.); (B.L.); (M.M.); (P.M.); (M.T.); (R.F.)
| | - Mariangela Tripodi
- Oasi Research Institute—IRCCS, 94018 Troina, EN, Italy; (M.S.); (M.G.S.); (F.A.S.); (F.D.D.B.); (S.C.); (B.L.); (M.M.); (P.M.); (M.T.); (R.F.)
| | - Raffaele Ferri
- Oasi Research Institute—IRCCS, 94018 Troina, EN, Italy; (M.S.); (M.G.S.); (F.A.S.); (F.D.D.B.); (S.C.); (B.L.); (M.M.); (P.M.); (M.T.); (R.F.)
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Park J, Herrmann GK, Mitchell PG, Sherman MB, Yin YW. Polγ coordinates DNA synthesis and proofreading to ensure mitochondrial genome integrity. Nat Struct Mol Biol 2023; 30:812-823. [PMID: 37202477 PMCID: PMC10920075 DOI: 10.1038/s41594-023-00980-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 03/28/2023] [Indexed: 05/20/2023]
Abstract
Accurate replication of mitochondrial DNA (mtDNA) by DNA polymerase γ (Polγ) is essential for maintaining cellular energy supplies, metabolism, and cell cycle control. To illustrate the structural mechanism for Polγ coordinating polymerase (pol) and exonuclease (exo) activities to ensure rapid and accurate DNA synthesis, we determined four cryo-EM structures of Polγ captured after accurate or erroneous incorporation to a resolution of 2.4-3.0 Å. The structures show that Polγ employs a dual-checkpoint mechanism to sense nucleotide misincorporation and initiate proofreading. The transition from replication to error editing is accompanied by increased dynamics in both DNA and enzyme, in which the polymerase relaxes its processivity and the primer-template DNA unwinds, rotates, and backtracks to shuttle the mismatch-containing primer terminus 32 Å to the exo site for editing. Our structural and functional studies also provide a foundation for analyses of Polγ mutation-induced human diseases and aging.
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Affiliation(s)
- Joon Park
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA
| | - Geoffrey K Herrmann
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA
| | - Patrick G Mitchell
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center National Accelerator Laboratory, Stanford University, Menlo Park, CA, USA
| | - Michael B Sherman
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA
| | - Y Whitney Yin
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA.
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA.
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA.
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Abstract
Progressive external ophthalmoplegia (PEO), characterized by ptosis and impaired eye movements, is a clinical syndrome with an expanding number of etiologically distinct subtypes. Advances in molecular genetics have revealed numerous pathogenic causes of PEO, originally heralded in 1988 by the detection of single large-scale deletions of mitochondrial DNA (mtDNA) in skeletal muscle of people with PEO and Kearns-Sayre syndrome. Since then, multiple point variants of mtDNA and nuclear genes have been identified to cause mitochondrial PEO and PEO-plus syndromes, including mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) and sensory ataxic neuropathy dysarthria ophthalmoplegia (SANDO). Intriguingly, many of those nuclear DNA pathogenic variants impair maintenance of the mitochondrial genome causing downstream mtDNA multiple deletions and depletion. In addition, numerous genetic causes of nonmitochondrial PEO have been identified.
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Affiliation(s)
- Michio Hirano
- H. Houston Merritt Neuromuscular Research Center, Neuromuscular Medicine Division, Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States.
| | - Robert D S Pitceathly
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom; NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, London, United Kingdom
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5
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A new pathogenic POLG variant. Mol Genet Metab Rep 2022; 32:100890. [PMID: 35860755 PMCID: PMC9289853 DOI: 10.1016/j.ymgmr.2022.100890] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 06/22/2022] [Accepted: 06/23/2022] [Indexed: 11/20/2022] Open
Abstract
POLG gene mutations are the most common causes of inherited mitochondrial disorders. The enzyme produced by this gene is responsible for the replication and repair of mitochondrial DNA. To date, around 300 pathogenic variants have been described in this gene. The resulting clinical outcomes of POLG mutations are widely variable in both phenotype and severity. There is considerable overlap in the phenotype of the so-called POLG syndromes with no clear genotype-phenotype correlation. Here we describe a newly discovered pathogenic variant in the POLG gene in a 7-year-old male that died of uncontrollable refractory status epilepticus. Genetic epilepsy panel sequencing identified two variants in the POLG gene, the common p.A467T pathological mutation and a novel p.S809R POLG variant found in trans with the p.A467T POLG that accompanied a severely reduced mitochondrial DNA level in the patient's tissues.
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Dunn PJ, Harvey NR, Maksemous N, Smith RA, Sutherland HG, Haupt LM, Griffiths LR. Investigation of Mitochondrial Related Variants in a Cerebral Small Vessel Disease Cohort. Mol Neurobiol 2022; 59:5366-5378. [PMID: 35699875 PMCID: PMC9395495 DOI: 10.1007/s12035-022-02914-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 06/03/2022] [Indexed: 11/25/2022]
Abstract
Monogenic forms of cerebral small vessel disease (CSVD) can be caused by both variants in nuclear DNA and mitochondrial DNA (mtDNA). Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is known to have a phenotype similar to Cerebral Autosomal Dominant Arteriopathy with Sub-cortical Infarcts and Leukoencephalopathy (CADASIL), and can be caused by variants in the mitochondrial genome and in several nuclear-encoded mitochondrial protein (NEMP) genes. The aim of this study was to screen for variants in the mitochondrial genome and NEMP genes in a NOTCH3-negative CADASIL cohort, to identify a potential link between mitochondrial dysfunction and CSVD pathology. Whole exome sequencing was performed for 50 patients with CADASIL-like symptomology on the Ion Torrent system. Mitochondrial sequencing was performed using an in-house designed protocol with sequencing run on the Ion GeneStudio S5 Plus (S5 +). NEMP genes and mitochondrial sequencing data were examined for rare (MAF < 0.001), non-synonymous variants that were predicted to have a deleterious effect on the protein. We identified 29 candidate NEMP variants that had links to either MELAS-, encephalopathy-, or Alzheimer’s disease–related phenotypes. Based on these changes, variants affecting POLG, MTO1, LONP1, NDUFAF6, NDUFB3, and TCIRG1 were thought to play a potential role in CSVD pathology in this cohort. Overall, the exploration of the mitochondrial genome identified a potential role for mitochondrial related proteins and mtDNA variants contributing to CSVD pathologies.
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Affiliation(s)
- P J Dunn
- Centre for Genomics and Personalised Health, Genomics Research Centre, School of Biomedical Sciences, Queensland University of Technology (QUT), 60 Musk Ave., Kelvin Grove, Queensland, 4059, Australia
- Health Sciences and Medicine Faculty, Bond University, 14 University Drive, Robina, Queensland, Australia
| | - N R Harvey
- Centre for Genomics and Personalised Health, Genomics Research Centre, School of Biomedical Sciences, Queensland University of Technology (QUT), 60 Musk Ave., Kelvin Grove, Queensland, 4059, Australia
- Health Sciences and Medicine Faculty, Bond University, 14 University Drive, Robina, Queensland, Australia
- Department of Medical and Molecular Genetics, Guy's Hospital, Kings College London, London, SE1 9RT, England
| | - N Maksemous
- Centre for Genomics and Personalised Health, Genomics Research Centre, School of Biomedical Sciences, Queensland University of Technology (QUT), 60 Musk Ave., Kelvin Grove, Queensland, 4059, Australia
| | - R A Smith
- Centre for Genomics and Personalised Health, Genomics Research Centre, School of Biomedical Sciences, Queensland University of Technology (QUT), 60 Musk Ave., Kelvin Grove, Queensland, 4059, Australia
| | - H G Sutherland
- Centre for Genomics and Personalised Health, Genomics Research Centre, School of Biomedical Sciences, Queensland University of Technology (QUT), 60 Musk Ave., Kelvin Grove, Queensland, 4059, Australia
| | - L M Haupt
- Centre for Genomics and Personalised Health, Genomics Research Centre, School of Biomedical Sciences, Queensland University of Technology (QUT), 60 Musk Ave., Kelvin Grove, Queensland, 4059, Australia
| | - L R Griffiths
- Centre for Genomics and Personalised Health, Genomics Research Centre, School of Biomedical Sciences, Queensland University of Technology (QUT), 60 Musk Ave., Kelvin Grove, Queensland, 4059, Australia.
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Roy A, Kandettu A, Ray S, Chakrabarty S. Mitochondrial DNA replication and repair defects: Clinical phenotypes and therapeutic interventions. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148554. [PMID: 35341749 DOI: 10.1016/j.bbabio.2022.148554] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 03/06/2022] [Accepted: 03/16/2022] [Indexed: 12/15/2022]
Abstract
Mitochondria is a unique cellular organelle involved in multiple cellular processes and is critical for maintaining cellular homeostasis. This semi-autonomous organelle contains its circular genome - mtDNA (mitochondrial DNA), that undergoes continuous cycles of replication and repair to maintain the mitochondrial genome integrity. The majority of the mitochondrial genes, including mitochondrial replisome and repair genes, are nuclear-encoded. Although the repair machinery of mitochondria is quite efficient, the mitochondrial genome is highly susceptible to oxidative damage and other types of exogenous and endogenous agent-induced DNA damage, due to the absence of protective histones and their proximity to the main ROS production sites. Mutations in replication and repair genes of mitochondria can result in mtDNA depletion and deletions subsequently leading to mitochondrial genome instability. The combined action of mutations and deletions can result in compromised mitochondrial genome maintenance and lead to various mitochondrial disorders. Here, we review the mechanism of mitochondrial DNA replication and repair process, key proteins involved, and their altered function in mitochondrial disorders. The focus of this review will be on the key genes of mitochondrial DNA replication and repair machinery and the clinical phenotypes associated with mutations in these genes.
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Affiliation(s)
- Abhipsa Roy
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Amoolya Kandettu
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Swagat Ray
- Department of Life Sciences, School of Life and Environmental Sciences, University of Lincoln, Lincoln LN6 7TS, United Kingdom
| | - Sanjiban Chakrabarty
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India.
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Manini A, Abati E, Comi GP, Corti S, Ronchi D. Mitochondrial DNA homeostasis impairment and dopaminergic dysfunction: A trembling balance. Ageing Res Rev 2022; 76:101578. [PMID: 35114397 DOI: 10.1016/j.arr.2022.101578] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 12/26/2021] [Accepted: 01/28/2022] [Indexed: 02/07/2023]
Abstract
Maintenance of mitochondrial DNA (mtDNA) homeostasis includes a variety of processes, such as mtDNA replication, repair, and nucleotides synthesis, aimed at preserving the structural and functional integrity of mtDNA molecules. Mutations in several nuclear genes (i.e., POLG, POLG2, TWNK, OPA1, DGUOK, MPV17, TYMP) impair mtDNA maintenance, leading to clinical syndromes characterized by mtDNA depletion and/or deletions in affected tissues. In the past decades, studies have demonstrated a progressive accumulation of multiple mtDNA deletions in dopaminergic neurons of the substantia nigra in elderly population and, to a greater extent, in Parkinson's disease patients. Moreover, parkinsonism has been frequently described as a prominent clinical feature in mtDNA instability syndromes. Among Parkinson's disease-related genes with a significant role in mitochondrial biology, PARK2 and LRRK2 specifically take part in mtDNA maintenance. Moreover, a variety of murine models (i.e., "Mutator", "MitoPark", "PD-mitoPstI", "Deletor", "Twinkle-dup" and "TwinkPark") provided in vivo evidence that mtDNA stability is required to preserve nigrostriatal integrity. Here, we review and discuss the clinical, genetic, and pathological background underlining the link between impaired mtDNA homeostasis and dopaminergic degeneration.
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Over-Mutated Mitochondrial, Lysosomal and TFEB-Regulated Genes in Parkinson's Disease. J Clin Med 2022; 11:jcm11061749. [PMID: 35330074 PMCID: PMC8951534 DOI: 10.3390/jcm11061749] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 03/17/2022] [Accepted: 03/18/2022] [Indexed: 02/04/2023] Open
Abstract
The association between Parkinson's disease (PD) and mutations in genes involved in lysosomal and mitochondrial function has been previously reported. However, little is known about the involvement of other genes or cellular mechanisms. We aim to identify novel genetic associations to better understand the pathogenesis of PD. We performed WES in a cohort of 32 PD patients and 30 age-matched controls. We searched for rare variants in 1667 genes: PD-associated, related to lysosomal function and mitochondrial function and TFEB-regulated. When comparing the PD patient cohort with that of age matched controls, a statistically significant burden of rare variants in the previous group of genes were identified. In addition, the Z-score calculation, using the European population database (GnomAD), showed an over-representation of particular variants in 36 genes. Interestingly, 11 of these genes are implicated in mitochondrial function and 18 are TFEB-regulated genes. Our results suggest, for the first time, an involvement of TFEB-regulated genes in the genetic susceptibility to PD. This is remarkable as TFEB factor has been reported to be sequestered inside Lewy bodies, pointing to a role of TFEB in the pathogenesis of PD. Our data also reinforce the involvement of lysosomal and mitochondrial mechanisms in PD.
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Mitochondrial Neurodegeneration. Cells 2022; 11:cells11040637. [PMID: 35203288 PMCID: PMC8870525 DOI: 10.3390/cells11040637] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 01/28/2022] [Accepted: 02/06/2022] [Indexed: 01/27/2023] Open
Abstract
Mitochondria are cytoplasmic organelles, which generate energy as heat and ATP, the universal energy currency of the cell. This process is carried out by coupling electron stripping through oxidation of nutrient substrates with the formation of a proton-based electrochemical gradient across the inner mitochondrial membrane. Controlled dissipation of the gradient can lead to production of heat as well as ATP, via ADP phosphorylation. This process is known as oxidative phosphorylation, and is carried out by four multiheteromeric complexes (from I to IV) of the mitochondrial respiratory chain, carrying out the electron flow whose energy is stored as a proton-based electrochemical gradient. This gradient sustains a second reaction, operated by the mitochondrial ATP synthase, or complex V, which condensates ADP and Pi into ATP. Four complexes (CI, CIII, CIV, and CV) are composed of proteins encoded by genes present in two separate compartments: the nuclear genome and a small circular DNA found in mitochondria themselves, and are termed mitochondrial DNA (mtDNA). Mutations striking either genome can lead to mitochondrial impairment, determining infantile, childhood or adult neurodegeneration. Mitochondrial disorders are complex neurological syndromes, and are often part of a multisystem disorder. In this paper, we divide the diseases into those caused by mtDNA defects and those that are due to mutations involving nuclear genes; from a clinical point of view, we discuss pediatric disorders in comparison to juvenile or adult-onset conditions. The complementary genetic contributions controlling organellar function and the complexity of the biochemical pathways present in the mitochondria justify the extreme genetic and phenotypic heterogeneity of this new area of inborn errors of metabolism known as ‘mitochondrial medicine’.
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Dohrn MF, Heller C, Zengeler D, Obermaier CD, Biskup S, Weis J, Nikolin S, Claeys KG, Schöne U, Beijer D, Winter N, Achenbach P, Gess B, Schulz JB, Mulahasanovic L. Heterozygous POLG variant Ser1181Asn co-segregating in a family with autosomal dominant axonal neuropathy, proximal muscle fatigability, ptosis, and ragged red fibers. Neurol Res Pract 2022; 4:5. [PMID: 35101151 PMCID: PMC8805222 DOI: 10.1186/s42466-022-00169-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 12/30/2021] [Indexed: 11/25/2022] Open
Abstract
By whole-exome sequencing, we found the heterozygous POLG variant c.3542G>A; p.Ser1181Asn in a family of four affected individuals, presenting with a mixed neuro-myopathic phenotype. The variant is located within the active site of polymerase gamma, in a cluster region associated with an autosomal dominant inheritance. In adolescence, the index developed distal atrophies and weakness, sensory loss, afferent ataxia, double vision, and bilateral ptosis. One older sister presented with Charcot-Marie-Tooth-like symptoms, while the youngest sister and father reported exercise-induced muscle pain and proximal weakness. In none of the individuals, we observed any involvement of the central nervous system. Muscle biopsies obtained from the father and the older sister showed ragged-red fibers, and electron microscopy confirmed mitochondrial damage. We conclude that this novel POLG variant explains this family’s phenotype.
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Whole-Exome Sequencing Identifies a Novel POLG Frameshift Variant in an Adult Patient Presenting with Progressive External Ophthalmoplegia and Mitochondrial DNA Depletion. Case Rep Genet 2021; 2021:9969071. [PMID: 34777884 PMCID: PMC8589515 DOI: 10.1155/2021/9969071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 10/16/2021] [Indexed: 11/30/2022] Open
Abstract
Mitochondrial DNA (mtDNA) depletion syndromes are a group of autosomal recessive disorders associated with a spectrum of clinical diseases, which include progressive external ophthalmoplegia (PEO). They are caused by variants in nuclear DNA (nDNA) encoded genes, and the gene that encodes for mtDNA polymerase gamma (POLG) is commonly involved. A splice-site mutation in POLG, c.3104+3A > T, was previously identified in three families with findings of PEO, and studies demonstrated this variant to result in skipping of exon 19. Here, we report a 57-year-old female who presented with ophthalmoplegia, ptosis, muscle weakness, and exercise intolerance with a subsequent muscle biopsy demonstrating mitochondrial myopathy on histopathologic evaluation and multiple mtDNA deletions by southern blot analysis. Whole-exome sequencing identified the previously characterized c. 3104+3A > T splice-site mutation in compound heterozygosity with a novel frameshift variant, p.Gly23Serfs∗236 (c.67_88del). mtDNA copy number analysis performed on the patient's muscle showed mtDNA depletion, as expected in a patient with biallelic pathogenic mutations in POLG. This is the first reported case with POLG p.Gly23Serfs∗236, discovered in a patient presenting with features of PEO.
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NGS in Hereditary Ataxia: When Rare Becomes Frequent. Int J Mol Sci 2021; 22:ijms22168490. [PMID: 34445196 PMCID: PMC8395181 DOI: 10.3390/ijms22168490] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/03/2021] [Accepted: 08/04/2021] [Indexed: 12/17/2022] Open
Abstract
The term hereditary ataxia (HA) refers to a heterogeneous group of neurological disorders with multiple genetic etiologies and a wide spectrum of ataxia-dominated phenotypes. Massive gene analysis in next-generation sequencing has entered the HA scenario, broadening our genetic and clinical knowledge of these conditions. In this study, we employed a targeted resequencing panel (TRP) in a large and highly heterogeneous cohort of 377 patients with a clinical diagnosis of HA, but no molecular diagnosis on routine genetic tests. We obtained a positive result (genetic diagnosis) in 33.2% of the patients, a rate significantly higher than those reported in similar studies employing TRP (average 19.4%), and in line with those performed using exome sequencing (ES, average 34.6%). Moreover, 15.6% of the patients had an uncertain molecular diagnosis. STUB1, PRKCG, and SPG7 were the most common causative genes. A comparison with published literature data showed that our panel would have identified 97% of the positive cases reported in previous TRP-based studies and 92% of those diagnosed by ES. Proper use of multigene panels, when combined with detailed phenotypic data, seems to be even more efficient than ES in clinical practice.
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14
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Bender F, Timmann D, van de Warrenburg BP, Adarmes-Gómez AD, Bender B, Thieme A, Synofzik M, Schöls L. Natural History of Polymerase Gamma-Related Ataxia. Mov Disord 2021; 36:2642-2652. [PMID: 34288125 DOI: 10.1002/mds.28713] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 05/31/2021] [Accepted: 06/16/2021] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Mutations in the mitochondrial DNA polymerase gamma are causing a wide phenotypic spectrum including ataxia as one of the most common presentations. OBJECTIVE The objective of this study was to determine the course of disease of polymerase gamma-related ataxia. METHODS In a prospective natural history study, we assessed 24 adult ataxia patients with biallelic polymerase gamma mutations for (1) severity of cerebellar dysfunction using the Scale for the Assessment and Rating of Ataxia score, (2) presence of nonataxia signs using the Inventory of Non-Ataxia Symptoms, (3) gray- and white-matter changes in brain MRI, and (4) findings in nerve conduction studies. RESULTS Assessment included follow-up visits up to 11.6 years. The Scale for the Assessment and Rating of Ataxia showed a mean annual increase of 1.02 ± 0.78 points/year. Disease progression was faster in patients with age at onset ≤ 30 years (1.5 Scale for the Assessment and Rating of Ataxia points/year) than with later onset (0.5 points/year); P = 0.008. The Inventory of Non-Ataxia Symptoms count increased by 0.30 ± 0.4 points/year. External ophthalmoplegia, brain stem oculomotor signs, areflexia, and sensory deficits were the most common nonataxic features. On MRI cerebellar atrophy was mild. T2 signal alterations affected mostly cerebellar white matter, middle cerebellar peduncles, thalamus, brain stem, and occipital and frontal white matter. Within 4 years, progression was primarily observed in the context of repeated epileptic seizures. Nerve conduction studies revealed axonal sensory peripheral neuropathy with mild motor nerve involvement. Exploratory sample size calculation implied 38 patients per arm as sufficient to detect a reduction of progression by 50% in hypothetical interventions within a 1-year trial. CONCLUSION The results recommend the Scale for the Assessment and Rating of Ataxia as a primary outcome measure for future interventional trials in polymerase gamma-related ataxia. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Friedemann Bender
- Department of Neurodegenerative Diseases, Hertie-Institute for Clinical Brain Research & Center of Neurology, University of Tuebingen, Tuebingen, Germany.,German Center for Neurodegenerative Diseases (DZNE), Tuebingen, Germany
| | - Dagmar Timmann
- Department of Neurology and Center for Translational Neuro- and Behavioral Sciences (C-TNBS), University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Bart P van de Warrenburg
- Department of Neurology, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
| | - Astrid D Adarmes-Gómez
- Unidad de Trastornos del Movimiento, Servicio de Neurología y Neurofisiología Clínica, Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Benjamin Bender
- Department of Diagnostics and Interventional Neuroradiology, University of Tuebingen, Tuebingen, Germany
| | - Andreas Thieme
- Department of Neurology and Center for Translational Neuro- and Behavioral Sciences (C-TNBS), University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Matthis Synofzik
- Department of Neurodegenerative Diseases, Hertie-Institute for Clinical Brain Research & Center of Neurology, University of Tuebingen, Tuebingen, Germany.,German Center for Neurodegenerative Diseases (DZNE), Tuebingen, Germany
| | - Ludger Schöls
- Department of Neurodegenerative Diseases, Hertie-Institute for Clinical Brain Research & Center of Neurology, University of Tuebingen, Tuebingen, Germany.,German Center for Neurodegenerative Diseases (DZNE), Tuebingen, Germany
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15
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Franklin AD, Chaudhari BP, Koboldt DC, Machut KZ. Polymerase Gamma Mitochondrial DNA Depletion Syndrome Initially Presenting as Disproportionate Respiratory Distress in a Moderately Premature Neonate: A Case Report. Front Genet 2021; 12:664278. [PMID: 34194468 PMCID: PMC8238196 DOI: 10.3389/fgene.2021.664278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 05/04/2021] [Indexed: 11/13/2022] Open
Abstract
A 32-week premature infant presented with respiratory failure, later progressing to pulmonary hypertension (PH), liver failure, lactic acidosis, and encephalopathy. Using exome sequencing, this patient was diagnosed with a rare Polymerase Gamma (POLG)-related mitochondrial DNA (mtDNA) depletion syndrome. This case demonstrates that expanding the differential to uncommon diagnoses is important for complex infants, even in premature neonates whose condition may be explained partially by their gestational age (GA). It also shows that patients with complex neonatal diseases with significant family history may benefit from exome sequencing for diagnosis.
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Affiliation(s)
- Andrew D Franklin
- Division of Neonatology, NorthShore University HealthSystem, Evanston, IL, United States
| | - Bimal P Chaudhari
- Division of Genetic and Genomic Medicine, Nationwide Children's Hospital, Columbus, OH, United States.,Division of Neonatology, Nationwide Children's Hospital, Columbus, OH, United States.,The Steve and Cindy Rasmussen Institute for Genomic Medicine at Nationwide Children's Hospital, Columbus, OH, United States.,Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, United States
| | - Daniel C Koboldt
- The Steve and Cindy Rasmussen Institute for Genomic Medicine at Nationwide Children's Hospital, Columbus, OH, United States
| | - Kerri Z Machut
- Division of Neonatology, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, United States.,Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
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16
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Genetic etiologic analysis in 74 Chinese Han women with idiopathic premature ovarian insufficiency by combined molecular genetic testing. J Assist Reprod Genet 2021; 38:965-978. [PMID: 33538981 DOI: 10.1007/s10815-021-02083-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Accepted: 01/19/2021] [Indexed: 12/24/2022] Open
Abstract
PURPOSE To identify the disease-causing genes of Chinese Han women with idiopathic premature ovarian insufficiency (POI). METHODS Seventy-four Chinese Han women with idiopathic POI were collected to analyze the genetic etiology. Triplet repeat-primed polymerase chain reaction (TP-PCR) was performed to screen the FMR1 (CGG)n premutation, and then 60 POI-related genes were sequenced by targeted next-generation sequencing (NGS) in POI patients with normal FMR1. RESULTS A total of one patient (1/74) with FMR1 premutation was identified. Targeted NGS revealed that 15.07% (11/73) patients had pathogenic or likely pathogenic variants of Mendelian genes (FOXL2, EIF2B2, CYP17A1, CLPP, MCM9, GDF9, MSH5, ERCC6, POLG). Ten novel variants in six Mendelian genes were identified, such as CLPP c.355A>C (p.I119L) and c.688A>C (p.M230L), MCM9 c.1157C>T (p.T386M) and c.1291A>G (p.M431V), GDF9 c. 238C>T (p.Q80X), MSH5 c.604G>C (p.G202R) and c.2063T>C (p.I688T), ERCC6 c.C1769C>T (p.P590L), POLG c.2832G>C (p.E944D), and c.2821A>G (p.I941V). CONCLUSION This study suggested targeted NGS was an efficient etiologic test for idiopathic POI patients without FMR1 premutation and enriched the variant spectrum of POI-related genes.
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17
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Müller‐Nedebock AC, Westhuizen FH, Kõks S, Bardien S. Nuclear Genes Associated with Mitochondrial
DNA
Processes as Contributors to Parkinson's Disease Risk. Mov Disord 2021; 36:815-831. [DOI: 10.1002/mds.28475] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 12/07/2020] [Accepted: 12/16/2020] [Indexed: 12/11/2022] Open
Affiliation(s)
- Amica C. Müller‐Nedebock
- Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences Stellenbosch University Cape Town South Africa
| | | | - Sulev Kõks
- Perron Institute for Neurological and Translational Science Nedlands Western Australia Australia
- Centre for Molecular Medicine and Innovative Therapeutics Murdoch University Murdoch Western Australia Australia
| | - Soraya Bardien
- Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences Stellenbosch University Cape Town South Africa
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18
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Zhou Y, Zhang J, Wang X, Peng Q, Shang X. Paroxysmal kinesigenic dyskinesia associated with a novel POLG variant: A case report. Medicine (Baltimore) 2021; 100:e24395. [PMID: 33530235 PMCID: PMC7850660 DOI: 10.1097/md.0000000000024395] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 12/29/2020] [Indexed: 01/05/2023] Open
Abstract
INTRODUCTION Paroxysmal kinesigenic dyskinesia (PKD) is a rare neurological disease characterized by recurrent dyskinesia or choreoathetosis triggered by sudden movements. Pathogenic variants in PRRT2 are the main cause of PKD. However, only about half of clinically diagnosed PKD patients have PRRT2 mutations, indicating that additional undiscovered causative genes could be implicated. PKD associated with POLG variant has not been reported. PATIENT CONCERNS A 14-year-old boy presented with a 2-month history of involuntary dystonic movements triggered by sudden activities. He was conscious during the attacks. Neurological examination, laboratory tests, brain magnetic resonance imaging (MRI), electroencephalogram (EEG) were all normal. Genetic analysis showed a novel variant of POLG (c.440G>T, p.Ser147Ile), which was considered to be a likely pathogenic variant in this case. DIAGNOSES The patient was diagnosed with PKD. INTERVENTIONS Low dose carbamazepine was used orally for treatment. OUTCOMES The patient achieved complete resolution of symptoms without any dyskinesia during the 6-month follow up. CONCLUSION Our study identified the novel POLG variant (c.440G>T, p.Ser147Ile) to be a likely pathogenic variant in PKD.
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19
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Maghbooli M, Ghaffarpour M, Ghazizadeh T, Shalbaf NA, MalekMahmoudi G. Clinicogenetical Variants of Progressive External Ophthalmoplegia - An Especial Review of Non-ophthalmic Manifestations. Neurol India 2020; 68:760-768. [PMID: 32859811 DOI: 10.4103/0028-3886.293454] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Progressive external ophthalmoplegia (PEO) is a slowly progressive myopathy characterized by extraocular muscles involvement, leading to frozen eyes without diplopia. The pattern of inheritance may be mitochondrial, autosomal dominant or, rarely, autosomal recessive. Sporadic forms were also reported. Muscular involvement other than extraocular muscles may occur with varying degrees of weakness, but this mostly happens many years after the disease begins. There are also scattered data about systemic signs besides ophthalmoplegia. This article aims to review non-ophthalmic findings of PEO from a clinicogenetical point of view.
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Affiliation(s)
- Mehdi Maghbooli
- Department of Neurology, Zanjan University of Medical Sciences, Vali-e-Asr Hospital, Zanjan, Iran
| | - Majid Ghaffarpour
- Department of Neurology, Tehran University of Medical Sciences, Iranian Center of Neurological Research, Tehran, Iran
| | - Taher Ghazizadeh
- Department of Neurology, Zanjan University of Medical Sciences, Vali-e-Asr Hospital, Zanjan, Iran
| | - Nazanin Azizi Shalbaf
- Department of Neurology, Zanjan University of Medical Sciences, Vali-e-Asr Hospital, Zanjan, Iran
| | - Ghazal MalekMahmoudi
- Department of Neurology, Zanjan University of Medical Sciences, Vali-e-Asr Hospital, Zanjan, Iran
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20
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Liang KX, Kristiansen CK, Mostafavi S, Vatne GH, Zantingh GA, Kianian A, Tzoulis C, Høyland LE, Ziegler M, Perez RM, Furriol J, Zhang Z, Balafkan N, Hong Y, Siller R, Sullivan GJ, Bindoff LA. Disease-specific phenotypes in iPSC-derived neural stem cells with POLG mutations. EMBO Mol Med 2020; 12:e12146. [PMID: 32840960 PMCID: PMC7539330 DOI: 10.15252/emmm.202012146] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 07/30/2020] [Accepted: 07/31/2020] [Indexed: 12/12/2022] Open
Abstract
Mutations in POLG disrupt mtDNA replication and cause devastating diseases often with neurological phenotypes. Defining disease mechanisms has been hampered by limited access to human tissues, particularly neurons. Using patient cells carrying POLG mutations, we generated iPSCs and then neural stem cells. These neural precursors manifested a phenotype that faithfully replicated the molecular and biochemical changes found in patient post‐mortem brain tissue. We confirmed the same loss of mtDNA and complex I in dopaminergic neurons generated from the same stem cells. POLG‐driven mitochondrial dysfunction led to neuronal ROS overproduction and increased cellular senescence. Loss of complex I was associated with disturbed NAD+ metabolism with increased UCP2 expression and reduced phosphorylated SirT1. In cells with compound heterozygous POLG mutations, we also found activated mitophagy via the BNIP3 pathway. Our studies are the first that show it is possible to recapitulate the neuronal molecular and biochemical defects associated with POLG mutation in a human stem cell model. Further, our data provide insight into how mitochondrial dysfunction and mtDNA alterations influence cellular fate determining processes.
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Affiliation(s)
- Kristina Xiao Liang
- Neuro-SysMed, Center of Excellence for Clinical Research in Neurological Diseases, Haukeland University Hospital, Bergen, Norway.,Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | | | - Sepideh Mostafavi
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Guro Helén Vatne
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Gina Alien Zantingh
- Leiden University Medical Centre, Leiden University, Leiden, The Netherlands
| | - Atefeh Kianian
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Charalampos Tzoulis
- Neuro-SysMed, Center of Excellence for Clinical Research in Neurological Diseases, Haukeland University Hospital, Bergen, Norway.,Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | | | - Mathias Ziegler
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | | | - Jessica Furriol
- Department of Clinical Medicine, University of Bergen, Bergen, Norway.,Department of Medicine, Haukeland University Hospital, Bergen, Norway
| | - Zhuoyuan Zhang
- State Key Laboratory of Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, China.,Department of Head and Neck Cancer Surgery, West China School of Stomatology, Sichuan University, Chengdu, China
| | - Novin Balafkan
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Yu Hong
- Neuro-SysMed, Center of Excellence for Clinical Research in Neurological Diseases, Haukeland University Hospital, Bergen, Norway.,Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Richard Siller
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.,Norwegian Center for Stem Cell Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Gareth John Sullivan
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.,Norwegian Center for Stem Cell Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,Institute of Immunology, Oslo University Hospital, Oslo, Norway.,Hybrid Technology Hub - Centre of Excellence, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.,Department of Pediatric Research, Oslo University Hospital, Oslo, Norway
| | - Laurence A Bindoff
- Neuro-SysMed, Center of Excellence for Clinical Research in Neurological Diseases, Haukeland University Hospital, Bergen, Norway.,Department of Clinical Medicine, University of Bergen, Bergen, Norway
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21
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Sanderson KG, Millar E, Tumber A, Klatt R, Sondheimer N, Vincent A. Rod bipolar cell dysfunction in POLG retinopathy. Doc Ophthalmol 2020; 142:111-118. [PMID: 32567010 DOI: 10.1007/s10633-020-09777-w] [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: 04/21/2020] [Accepted: 06/09/2020] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To report the clinical and novel electrophysiological features in a child with POLG-related sensory ataxic neuropathy, dysarthria and ophthalmoparesis (SANDO). METHODS The proband, a male child of Indian descent, underwent serial systemic and ophthalmological evaluations from birth until 14 years of age. Eye examinations included visual acuity and extraocular movement assessments, fundus photography, spectral domain optical coherence tomography and full-field electroretinography (ERG). Detailed genetic testing was also performed. RESULTS The child carried a homozygous mutation in POLG (c.911T > G/p.Leu304Arg) and manifested systemic features such as seizures, headaches, areflexia, hypotonia, myopathy and vomiting. The child's distance visual acuity was 0.50 and 0.40 LogMAR in the right and left eyes, respectively. Bilateral ophthalmoplegia and ptosis were observed at 5 years of age. The dark-adapted (DA) ERG responses to 2.29 cd s m-2 and 7.6 cd s m-2 stimuli showed a markedly reduced b/a ratio; an electronegative configuration was noted to a DA 7.6 ERG. CONCLUSION This is the first documented case of an electronegative ERG in a POLG-related disorder consistent with generalized rod ON-bipolar dysfunction. The rest of the proband's systemic and ophthalmological features were consistent with SANDO but some features overlapped with other POLG-related disorders such as Alpers-Huttenlocher syndrome and autosomal dominant progressive external ophthalmoplegia demonstrating the wide phenotypic overlap expected due to POLG mutations.
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Affiliation(s)
- Kit Green Sanderson
- Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Canada
| | - Eoghan Millar
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, University of Toronto, Toronto, Canada
| | - Anupreet Tumber
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, University of Toronto, Toronto, Canada
| | - Regan Klatt
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, University of Toronto, Toronto, Canada
| | - Neal Sondheimer
- Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Canada.,Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Canada
| | - Ajoy Vincent
- Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Canada. .,Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, University of Toronto, Toronto, Canada.
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22
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Awd-Allah NA, Ismail SM, Salah El-Dine MM, Mohammed MM. Association between POLG and XRCC1 gene polymorphisms and keratoconus occurrence among Egyptian patients. ACTA ACUST UNITED AC 2020; 95:439-446. [PMID: 32414513 DOI: 10.1016/j.oftal.2020.03.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/29/2020] [Accepted: 03/24/2020] [Indexed: 12/28/2022]
Abstract
BACKGROUND Keratoconus is a progressive disorder distinguished by thinning of the corneal tissue and bulging forward into a cone-shaped fashion. Yet its etiology, which is multifactorial, despite intensive research remains elusive. Corneal exposure a reactive oxygen species causing oxidative DNA damage has been reported to be associated with KC and therefore suggesting that DNA base excision repair mechanism might lie behind the pathogenesis of the disease. METHODS We studied the association of three variants in two BER genes (XRCC1 and POLG) and QC occurrence in a cohort of patients from Egypt. Genotyping of the three variants was performed using PCR and restriction enzymes analysis. RESULTS We observed that A allele and A/A genotype of the c.1196A>G variant in the XRCC1 gene were significantly associated with increased KC occurrence while the G allele was associated with decreased KC occurrence. Similarly, the A/A genotype of the c.-1370T>A polymorphism in the POLG gene and the A allele were associated with increased occurrence of KC, while T/A genotype and the T allele were accompanied with decreased occurrence of KC. On the other hand, no association was observed between the c.580C>T variant in the XRCC1 gene and KC occurrence among the studied group of patients. CONCLUSION Our results suggest that c.1196A>G variant of the XRCC1 and c.-1370T>A variant of the POLG gene may be involved in KC pathogenesis and might be considered as a genetic risk factors of the disease among Egyptian population.
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Affiliation(s)
- N A Awd-Allah
- Biochemistry Department, Faculty of Science, Ain Shams University, Cairo, Egipto.
| | - S M Ismail
- Medical Molecular Genetics Department, Human Genetics and Genome Research Division, National Research Centre, Cairo, Egipto
| | | | - M M Mohammed
- Biochemistry Department, Faculty of Science, Ain Shams University, Cairo, Egipto
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23
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Pauly MG, Tunc S, Bäumer T, Gillessen-Kaesbach G, Münchau A. "Twitching" and Stiffness in POLG1 Mutation Carriers: Red Flag or Red Herring? Mov Disord Clin Pract 2019; 7:91-93. [PMID: 31970219 DOI: 10.1002/mdc3.12860] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 10/04/2019] [Accepted: 10/16/2019] [Indexed: 11/11/2022] Open
Affiliation(s)
- Martje G Pauly
- Institute of Neurogenetics University of Lübeck Lübeck Germany
| | - Sinem Tunc
- Institute of Neurogenetics University of Lübeck Lübeck Germany.,Department of Neurology University of Lübeck Lübeck Germany
| | - Tobias Bäumer
- Institute of Neurogenetics University of Lübeck Lübeck Germany
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24
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Heighton JN, Brady LI, Sadikovic B, Bulman DE, Tarnopolsky MA. Genotypes of chronic progressive external ophthalmoplegia in a large adult-onset cohort. Mitochondrion 2019; 49:227-231. [PMID: 31521625 DOI: 10.1016/j.mito.2019.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 03/28/2019] [Accepted: 09/11/2019] [Indexed: 12/11/2022]
Abstract
Chronic progressive external ophthalmoplegia (CPEO) is a common presentation of mitochondrial disease. We performed a retrospective evaluation of the molecular genetic testing and genotype-phenotype correlations in a large cohort of adult-onset CPEO patients (N = 111). One hundred percent of patients tested had at least one mitochondrial DNA (mtDNA) deletion. Genetic testing of nuclear genes encoding mitochondrial proteins identified pathogenic/likely pathogenic variants likely to be associated with CPEO in 7.6% of patients. As expected, the nuclear gene most associated with DNA variation was POLG. A single likely pathogenic mitochondrial DNA variant (m.12278T>C) was identified in two unrelated patients. No significant differences were noted in the clinical phenotypes of patients with pathogenic or likely pathogenic nuclear variants in comparison to those with negative nuclear gene testing. Analysis of deletion size and heteroplasmy in muscle-derived mtDNA showed significant correlations with age of symptom onset but not disease severity (number of canonical CPEO features). Results suggest that smaller mtDNA deletions (p = 0.0127, r2 = 0.1201) and higher heteroplasmy of single mtDNA deletions (p = 0.0112, r2 = 0.2483) are associated with an earlier age of onset in CPEO patients.
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Affiliation(s)
- Julia N Heighton
- Department of Pediatrics, McMaster University, Hamilton, ON, Canada
| | - Lauren I Brady
- Department of Pediatrics, McMaster University, Hamilton, ON, Canada
| | - Bekim Sadikovic
- Department of Pathology and Laboratory Medicine, Western University, London, ON, Canada; Molecular Genetics Laboratory, Molecular Diagnostics Division, London Health Sciences Centre, London, ON, Canada
| | - Dennis E Bulman
- Newborn Screening Ontario and CHEO Research Institute, Children's Hospital of Eastern Ontario, Ottawa, ON, Canada
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25
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Souza PVS, Bortholin T, Teixeira CAC, Seneor DD, Marin VDGB, Dias RB, Farias IB, Badia BML, Silva LHL, Pinto WBVR, Oliveira ASB, DiMauro S. Leigh syndrome caused by mitochondrial DNA-maintenance defects revealed by whole exome sequencing. Mitochondrion 2019; 49:25-34. [PMID: 31271879 DOI: 10.1016/j.mito.2019.06.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 11/17/2018] [Accepted: 06/24/2019] [Indexed: 01/30/2023]
Abstract
Leigh syndrome represents a complex inherited neurometabolic and neurodegenerative disorder associated with different clinical, genetic and neuroimaging findings in the context of bilateral symmetrical lesions involving the brainstem and basal ganglia. Heterogeneous neurological manifestations such as spasticity, cerebellar ataxia, dystonia, choreoathetosis and parkinsonism are associated with multisystemic and ophthalmological abnormalities due to >75 different monogenic causes. Here, we describe the clinical and genetic features of a Brazilian cohort of patients with Leigh Syndrome in which muscle biopsy analysis showed mitochondrial DNA defects and determine the utility of whole exome sequencing for a final genetic diagnostic in this cohort.
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Affiliation(s)
- P V S Souza
- Division of Neuromuscular Diseases, Department of Neurology, Department of Neurosurgery, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil.
| | - Thiago Bortholin
- Division of Neuromuscular Diseases, Department of Neurology, Department of Neurosurgery, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Carlos Alberto Castro Teixeira
- Division of Neuromuscular Diseases, Department of Neurology, Department of Neurosurgery, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Daniel Delgado Seneor
- Division of Neuromuscular Diseases, Department of Neurology, Department of Neurosurgery, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Vitor Dias Gomes Barrios Marin
- Division of Neuromuscular Diseases, Department of Neurology, Department of Neurosurgery, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Renan Braido Dias
- Division of Neuromuscular Diseases, Department of Neurology, Department of Neurosurgery, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Igor Braga Farias
- Division of Neuromuscular Diseases, Department of Neurology, Department of Neurosurgery, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - B M L Badia
- Division of Neuromuscular Diseases, Department of Neurology, Department of Neurosurgery, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Luiz Henrique Libardi Silva
- Division of Neuromuscular Diseases, Department of Neurology, Department of Neurosurgery, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - W B V R Pinto
- Division of Neuromuscular Diseases, Department of Neurology, Department of Neurosurgery, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Acary Souza Bulle Oliveira
- Division of Neuromuscular Diseases, Department of Neurology, Department of Neurosurgery, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Salvatore DiMauro
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
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26
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Wheeler JH, Young CKJ, Young MJ. Analysis of Human Mitochondrial DNA Content by Southern Blotting and Nonradioactive Probe Hybridization. CURRENT PROTOCOLS IN TOXICOLOGY 2019; 80:e75. [PMID: 30982231 PMCID: PMC6581606 DOI: 10.1002/cptx.75] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A single cell can contain several thousand copies of the mitochondrial DNA genome or mtDNA. Tools for assessing mtDNA content are necessary for clinical and toxicological research, as mtDNA depletion is linked to genetic disease and drug toxicity. For instance, mtDNA depletion syndromes are typically fatal childhood disorders that are characterized by severe declines in mtDNA content in affected tissues. Mitochondrial toxicity and mtDNA depletion have also been reported in human immunodeficiency virus-infected patients treated with certain nucleoside reverse transcriptase inhibitors. Further, cell culture studies have demonstrated that exposure to oxidative stress stimulates mtDNA degradation. Here we outline a Southern blot and nonradioactive digoxigenin-labeled probe hybridization method to estimate mtDNA content in human genomic DNA samples. © 2019 by John Wiley & Sons, Inc.
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Affiliation(s)
- Joel H. Wheeler
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901
| | - Carolyn K. J. Young
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901
| | - Matthew J. Young
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901
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Blázquez-Bermejo C, Carreño-Gago L, Molina-Granada D, Aguirre J, Ramón J, Torres-Torronteras J, Cabrera-Pérez R, Martín MÁ, Domínguez-González C, de la Cruz X, Lombès A, García-Arumí E, Martí R, Cámara Y. Increased dNTP pools rescue mtDNA depletion in human POLG-deficient fibroblasts. FASEB J 2019; 33:7168-7179. [PMID: 30848931 DOI: 10.1096/fj.201801591r] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Polymerase γ catalytic subunit (POLG) gene encodes the enzyme responsible for mitochondrial DNA (mtDNA) synthesis. Mutations affecting POLG are the most prevalent cause of mitochondrial disease because of defective mtDNA replication and lead to a wide spectrum of clinical phenotypes characterized by mtDNA deletions or depletion. Enhancing mitochondrial deoxyribonucleoside triphosphate (dNTP) synthesis effectively rescues mtDNA depletion in different models of defective mtDNA maintenance due to dNTP insufficiency. In this study, we studied mtDNA copy number recovery rates following ethidium bromide-forced depletion in quiescent fibroblasts from patients harboring mutations in different domains of POLG. Whereas control cells spontaneously recovered initial mtDNA levels, POLG-deficient cells experienced a more severe depletion and could not repopulate mtDNA. However, activation of deoxyribonucleoside (dN) salvage by supplementation with dNs plus erythro-9-(2-hydroxy-3-nonyl) adenine (inhibitor of deoxyadenosine degradation) led to increased mitochondrial dNTP pools and promoted mtDNA repopulation in all tested POLG-mutant cells independently of their specific genetic defect. The treatment did not compromise POLG fidelity because no increase in multiple deletions or point mutations was detected. Our study suggests that physiologic dNTP concentration limits the mtDNA replication rate. We thus propose that increasing mitochondrial dNTP availability could be of therapeutic interest for POLG deficiency and other conditions in which mtDNA maintenance is challenged.-Blázquez-Bermejo, C., Carreño-Gago, L., Molina-Granada, D., Aguirre, J., Ramón, J., Torres-Torronteras, J., Cabrera-Pérez, R., Martín, M. Á., Domínguez-González, C., de la Cruz, X., Lombès, A., García-Arumí, E., Martí, R., Cámara, Y. Increased dNTP pools rescue mtDNA depletion in human POLG-deficient fibroblasts.
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Affiliation(s)
- Cora Blázquez-Bermejo
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca-Universitat Autònoma de Barcelona, Barcelona, Spain.,Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Lidia Carreño-Gago
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca-Universitat Autònoma de Barcelona, Barcelona, Spain.,Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - David Molina-Granada
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca-Universitat Autònoma de Barcelona, Barcelona, Spain.,Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Josu Aguirre
- Translational Bioinformatics Group, Vall d'Hebron Institut de Recerca-Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Javier Ramón
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca-Universitat Autònoma de Barcelona, Barcelona, Spain.,Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Javier Torres-Torronteras
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca-Universitat Autònoma de Barcelona, Barcelona, Spain.,Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Raquel Cabrera-Pérez
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca-Universitat Autònoma de Barcelona, Barcelona, Spain.,Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Miguel Ángel Martín
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.,Laboratorio de Enfermedades Mitocondriales, Instituto de Investigación Hospital 12 de Octubre (i+12), Madrid, Spain
| | - Cristina Domínguez-González
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.,Unidad de Neuromuscular, Instituto de Investigación Hospital 12 de Octubre (i+12), Madrid, Spain
| | - Xavier de la Cruz
- Translational Bioinformatics Group, Vall d'Hebron Institut de Recerca-Universitat Autònoma de Barcelona, Barcelona, Spain.,Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain; and
| | - Anne Lombès
- Institut Cochin, INSERM Unité 1016-Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 8104-Service de Biochimie Métabolique et Centre de Génétique Moléculaire et Chromosomique, Groupement Hospitalier Universitaire (GHU) Pitié-Salpétrière, Assistance Publique-Hôpitaux de Paris (AP-HP)-Université Paris Descartes, Paris, France
| | - Elena García-Arumí
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca-Universitat Autònoma de Barcelona, Barcelona, Spain.,Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Ramon Martí
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca-Universitat Autònoma de Barcelona, Barcelona, Spain.,Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Yolanda Cámara
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca-Universitat Autònoma de Barcelona, Barcelona, Spain.,Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
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Ogunbona OB, Claypool SM. Emerging Roles in the Biogenesis of Cytochrome c Oxidase for Members of the Mitochondrial Carrier Family. Front Cell Dev Biol 2019; 7:3. [PMID: 30766870 PMCID: PMC6365663 DOI: 10.3389/fcell.2019.00003] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 01/10/2019] [Indexed: 12/11/2022] Open
Abstract
The mitochondrial carrier family (MCF) is a group of transport proteins that are mostly localized to the inner mitochondrial membrane where they facilitate the movement of various solutes across the membrane. Although these carriers represent potential targets for therapeutic application and are repeatedly associated with human disease, research on the MCF has not progressed commensurate to their physiologic and pathophysiologic importance. Many of the 53 MCF members in humans are orphans and lack known transport substrates. Even for the relatively well-studied members of this family, such as the ADP/ATP carrier and the uncoupling protein, there exist fundamental gaps in our understanding of their biological roles including a clear rationale for the existence of multiple isoforms. Here, we briefly review this important family of mitochondrial carriers, provide a few salient examples of their diverse metabolic roles and disease associations, and then focus on an emerging link between several distinct MCF members, including the ADP/ATP carrier, and cytochrome c oxidase biogenesis. As the ADP/ATP carrier is regarded as the paradigm of the entire MCF, its newly established role in regulating translation of the mitochondrial genome highlights that we still have a lot to learn about these metabolite transporters.
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Affiliation(s)
- Oluwaseun B. Ogunbona
- Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, MD, United States
- Department of Pathology & Laboratory Medicine, School of Medicine, Emory University, Atlanta, GA, United States
| | - Steven M. Claypool
- Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, MD, United States
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Chen B, Li L, Wang J, Zhou Y, Zhu J, Li T, Pan H, Liu B, Cao Y, Wang B. Identification of the first homozygous POLG mutation causing non-syndromic ovarian dysfunction. Climacteric 2018; 21:467-471. [PMID: 29992832 DOI: 10.1080/13697137.2018.1467891] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
OBJECTIVE To investigate the genetic cause of non-syndromic ovarian dysfunction in a patient from a consanguineous family. METHODS This study examined a patient with irregular menstrual cycles and abnormal oocytes. The patient had undergone irregular hormone replacement therapy over 3 years to adjust the menstrual cycle and improve ovarian function. Prior to ovarian stimulation in our hospital, 3 months of androgen and regular hormone therapy were used as an intervention method. No follicular development was detected in the subsequent three cycles using letrozole treatment. The patient then received a constantly adjusted dose of menotropins, but produced only one oocyte. RESULTS Whole-exome sequencing analysis identified the first homozygous POLG mutation (c.2890C > T; p.R964C) associated with ovarian dysfunction. Sanger sequencing was used to validate. In silico analysis suggested that the p.R964C mutation was pathogenic. Conservation analysis demonstrated that R964 was an important site for the DNA polymerase function of POLG. CONCLUSIONS Biallelic mutations in POLG may be associated with ovarian dysfunction. This study has improved our understanding of POLG-related genetic mutations in ovarian dysfunction, and the mode of inheritance of certain sequence variants. This information will assist genetic counseling and precision medicine in the future.
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Affiliation(s)
- B Chen
- a Department of Obstetrics and Gynecology , Reproductive Medicine Center, The First Affiliated Hospital of Anhui Medical University , Hefei , China.,b Institute of Reproductive Genetics , Anhui Medical University , Hefei , China.,c Anhui Provincial Engineering Technology Research Center for Biopreservation and Artificial Organs , Hefei , China
| | - L Li
- d Central Laboratory, Beijing Obstetrics and Gynecology Hospital , Capital Medical University , Beijing , China
| | - J Wang
- e Department of Medical Genetics and Developmental Biology , School of Basic Medical Sciences, Capital Medical University , Beijing , China
| | - Y Zhou
- a Department of Obstetrics and Gynecology , Reproductive Medicine Center, The First Affiliated Hospital of Anhui Medical University , Hefei , China.,b Institute of Reproductive Genetics , Anhui Medical University , Hefei , China.,c Anhui Provincial Engineering Technology Research Center for Biopreservation and Artificial Organs , Hefei , China
| | - J Zhu
- a Department of Obstetrics and Gynecology , Reproductive Medicine Center, The First Affiliated Hospital of Anhui Medical University , Hefei , China.,b Institute of Reproductive Genetics , Anhui Medical University , Hefei , China.,c Anhui Provincial Engineering Technology Research Center for Biopreservation and Artificial Organs , Hefei , China
| | - T Li
- f Center for Genetics , National Research Institute for Family Planning , Beijing , China
| | - H Pan
- f Center for Genetics , National Research Institute for Family Planning , Beijing , China
| | - B Liu
- f Center for Genetics , National Research Institute for Family Planning , Beijing , China
| | - Y Cao
- a Department of Obstetrics and Gynecology , Reproductive Medicine Center, The First Affiliated Hospital of Anhui Medical University , Hefei , China.,b Institute of Reproductive Genetics , Anhui Medical University , Hefei , China.,c Anhui Provincial Engineering Technology Research Center for Biopreservation and Artificial Organs , Hefei , China
| | - B Wang
- a Department of Obstetrics and Gynecology , Reproductive Medicine Center, The First Affiliated Hospital of Anhui Medical University , Hefei , China.,f Center for Genetics , National Research Institute for Family Planning , Beijing , China.,g Key Laboratory of Family Planning and Reproductive Genetics , National Health and Family Planning Commission, Hebei Research Institute for Family Planning , Hebei , China
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30
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Nuclear genes involved in mitochondrial diseases caused by instability of mitochondrial DNA. J Appl Genet 2018; 59:43-57. [PMID: 29344903 PMCID: PMC5799321 DOI: 10.1007/s13353-017-0424-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 12/20/2017] [Indexed: 02/07/2023]
Abstract
Mitochondrial diseases are defined by a respiratory chain dysfunction and in most of the cases manifest as multisystem disorders with predominant expression in muscles and nerves and may be caused by mutations in mitochondrial (mtDNA) or nuclear (nDNA) genomes. Most of the proteins involved in respiratory chain function are nuclear encoded, although 13 subunits of respiratory chain complexes (together with 2 rRNAs and 22 tRNAs necessary for their translation) encoded by mtDNA are essential for cell function. nDNA encodes not only respiratory chain subunits but also all the proteins responsible for mtDNA maintenance, especially those involved in replication, as well as other proteins necessary for the transcription and copy number control of this multicopy genome. Mutations in these genes can cause secondary instability of the mitochondrial genome in the form of depletion (decreased number of mtDNA molecules in the cell), vast multiple deletions or accumulation of point mutations which in turn leads to mitochondrial diseases inherited in a Mendelian fashion. The list of genes involved in mitochondrial DNA maintenance is long, and still incomplete.
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Abstract
Ataxia is one of the most frequent symptoms of mitochondrial disease. In most cases it occurs as part of a syndromic disorder and the combination of ataxia with other neurologic involvement such as epilepsy is common. Mitochondrial ataxias can be caused by disturbance of the cerebellum and its connections, involvement of proprioception (i.e., sensory ataxia) or a combination of both (spinocerebellar). There are no specific features that define an ataxia as mitochondrial, except perhaps the tendency for it to occur together with involvement of multiple other sites, both in the nervous system and outside. In this review we will concentrate on the mitochondrial disorders in which ataxia is a prominent and consistent feature and focus on the clinical features and genetic causes.
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Affiliation(s)
- Hilary J Vernon
- McKusick-Nathans Institute of Genetic Medicine, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Laurence A Bindoff
- Department of Clinical Medicine, University of Bergen and Department of Neurology, Haukeland University Hospital, Bergen, Norway.
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32
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Coutelier M, Coarelli G, Monin ML, Konop J, Davoine CS, Tesson C, Valter R, Anheim M, Behin A, Castelnovo G, Charles P, David A, Ewenczyk C, Fradin M, Goizet C, Hannequin D, Labauge P, Riant F, Sarda P, Sznajer Y, Tison F, Ullmann U, Van Maldergem L, Mochel F, Brice A, Stevanin G, Durr A. A panel study on patients with dominant cerebellar ataxia highlights the frequency of channelopathies. Brain 2017; 140:1579-1594. [PMID: 28444220 DOI: 10.1093/brain/awx081] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 02/05/2017] [Indexed: 12/21/2022] Open
Abstract
Autosomal dominant cerebellar ataxias have a marked heterogeneous genetic background, with mutations in 34 genes identified so far. This large amount of implicated genes accounts for heterogeneous clinical presentations, making genotype-phenotype correlations a major challenge in the field. While polyglutamine ataxias, linked to CAG repeat expansions in genes such as ATXN1, ATXN2, ATXN3, ATXN7, CACNA1A and TBP, have been extensively characterized in large cohorts, there is a need for comprehensive assessment of frequency and phenotype of more 'conventional' ataxias. After exclusion of CAG/polyglutamine expansions in spinocerebellar ataxia genes in 412 index cases with dominantly inherited cerebellar ataxias, we aimed to establish the relative frequencies of mutations in other genes, with an approach combining panel sequencing and TaqMan® polymerase chain reaction assay. We found relevant genetic variants in 59 patients (14.3%). The most frequently mutated were channel genes [CACNA1A (n = 16), KCND3 (n = 4), KCNC3 (n = 2) and KCNA1 (n = 2)]. Deletions in ITPR1 (n = 11) were followed by biallelic variants in SPG7 (n = 9). Variants in AFG3L2 (n = 7) came next in frequency, and variants were rarely found in STBN2 (n = 2), ELOVL5, FGF14, STUB1 and TTBK2 (n = 1 each). Interestingly, possible risk factor variants were detected in SPG7 and POLG. Clinical comparisons showed that ataxias due to channelopathies had a significantly earlier age at onset with an average of 24.6 years, versus 40.9 years for polyglutamine expansion spinocerebellar ataxias and 37.8 years for SPG7-related forms (P = 0.001). In contrast, disease duration was significantly longer in the former (20.5 years versus 9.3 and 13.7, P=0.001), though for similar functional stages, indicating slower progression of the disease. Of interest, intellectual deficiency was more frequent in channel spinocerebellar ataxias, while cognitive impairment in adulthood was similar among the three groups. Similar differences were found among a single gene group, comparing 23 patients with CACNA1A expansions (spinocerebellar ataxia 6) to 22 patients with CACNA1A point mutations, which had lower average age at onset (25.2 versus 47.3 years) with longer disease duration (18.7 versus 10.9), but lower severity indexes (0.39 versus 0.44), indicating slower progression of the disease. In conclusion, we identified relevant genetic variations in up to 15% of cases after exclusion of polyglutamine expansion spinocerebellar ataxias, and confirmed CACNA1A and SPG7 as major ataxia genes. We could delineate firm genotype-phenotype correlations that are important for genetic counselling and of possible prognostic value.
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Affiliation(s)
- Marie Coutelier
- INSERM U 1127, 75013, Paris, France.,Centre National de la Recherche Scientifique UMR 7225, 75013, Paris, France.,UMRS 1127, Université Pierre et Marie Curie (Paris 06), Sorbonne Universités, 75013, Paris, France.,Institut du Cerveau et de la Moelle Epinière, 75013, Paris, France.,Laboratory of Human Molecular Genetics, de Duve Institute, Université catholique de Louvain, 1200, Brussels, Belgium.,Ecole Pratique des Hautes Etudes, PSL Research University, 75014, Paris, France
| | - Giulia Coarelli
- INSERM U 1127, 75013, Paris, France.,Centre National de la Recherche Scientifique UMR 7225, 75013, Paris, France.,UMRS 1127, Université Pierre et Marie Curie (Paris 06), Sorbonne Universités, 75013, Paris, France.,Institut du Cerveau et de la Moelle Epinière, 75013, Paris, France.,Centre de Référence de Neurogénétique, Hôpital de la Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris, 75013, Paris, France
| | - Marie-Lorraine Monin
- Centre de Référence de Neurogénétique, Hôpital de la Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris, 75013, Paris, France
| | - Juliette Konop
- INSERM U 1127, 75013, Paris, France.,Centre National de la Recherche Scientifique UMR 7225, 75013, Paris, France.,UMRS 1127, Université Pierre et Marie Curie (Paris 06), Sorbonne Universités, 75013, Paris, France.,Institut du Cerveau et de la Moelle Epinière, 75013, Paris, France.,Ecole Pratique des Hautes Etudes, PSL Research University, 75014, Paris, France
| | - Claire-Sophie Davoine
- INSERM U 1127, 75013, Paris, France.,Centre National de la Recherche Scientifique UMR 7225, 75013, Paris, France.,UMRS 1127, Université Pierre et Marie Curie (Paris 06), Sorbonne Universités, 75013, Paris, France.,Institut du Cerveau et de la Moelle Epinière, 75013, Paris, France
| | - Christelle Tesson
- INSERM U 1127, 75013, Paris, France.,Centre National de la Recherche Scientifique UMR 7225, 75013, Paris, France.,UMRS 1127, Université Pierre et Marie Curie (Paris 06), Sorbonne Universités, 75013, Paris, France.,Institut du Cerveau et de la Moelle Epinière, 75013, Paris, France.,Ecole Pratique des Hautes Etudes, PSL Research University, 75014, Paris, France
| | - Rémi Valter
- INSERM U 1127, 75013, Paris, France.,Centre National de la Recherche Scientifique UMR 7225, 75013, Paris, France.,UMRS 1127, Université Pierre et Marie Curie (Paris 06), Sorbonne Universités, 75013, Paris, France.,Institut du Cerveau et de la Moelle Epinière, 75013, Paris, France.,Ecole Pratique des Hautes Etudes, PSL Research University, 75014, Paris, France
| | - Mathieu Anheim
- Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, 67200, Strasbourg, France.,Département de Neurologie, Hôpital de Hautepierre, CHU de Strasbourg, 67100, Strasbourg, France.,Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM-U964/CNRS-UMR7104/Université de Strasbourg, 67400, Illkirch, France
| | - Anthony Behin
- AP-HP, Centre de Référence de Pathologie Neuromusculaire Paris-Est, Institut de Myologie, GHU Pitié-Salpêtrière, 75013, Paris, France
| | - Giovanni Castelnovo
- Service de Neurologie, Centre Hospitalier Universitaire Caremeau, 30900, Nîmes, France
| | - Perrine Charles
- Centre de Référence de Neurogénétique, Hôpital de la Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris, 75013, Paris, France
| | - Albert David
- Service de Génétique Médicale Centre Hospitalier Universitaire de Nantes, 44093, Nantes, France
| | - Claire Ewenczyk
- Centre de Référence de Neurogénétique, Hôpital de la Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris, 75013, Paris, France
| | - Mélanie Fradin
- Service de Génétique Médicale, CHU de Rennes, 35033, Rennes, France.,Service de Génétique Médicale, Centre Hospitalier de Saint Brieuc, 22000, Saint-Brieuc, France
| | - Cyril Goizet
- INSERM U1211, Université de Bordeaux, Laboratoire Maladies Rares, Génétique et Métabolisme, 33000, Bordeaux, France.,CHU Bordeaux, Service de Génétique Médicale, 33000, Bordeaux, France
| | - Didier Hannequin
- Service de Génétique, Service de Neurologie, Inserm U1079, Rouen University Hospital, 76031, Rouen, France
| | - Pierre Labauge
- Service de Neurologie, Hopital Gui de Chauliac, CHU de Montpellier, 34295, Montpellier Cedex 5, France
| | - Florence Riant
- Assistance Publique - Hôpitaux de Paris, Groupe Hospitalier Lariboisiere-Fernand Widal, Laboratoire de Génétique, 75010, Paris, France
| | - Pierre Sarda
- Département de Génétique Médicale, Hôpital Arnaud de Villeneuve, CHU de Montpellier, 34295 Montpellier, France
| | - Yves Sznajer
- Cliniques Universitaires Saint-Luc, Centre for Human Genetics, 1200, Brussels, Belgium
| | - François Tison
- Institut des Maladies Neurodégénératives, CHU de Bordeaux, Université de Bordeaux, CNRS UMR 5293, 33076, Bordeaux, France
| | - Urielle Ullmann
- Centre de génétique humaine, Institut de Pathologie et de Génétique, 6041, Gosselies, Belgium
| | - Lionel Van Maldergem
- Centre de Génétique Humaine, Université de Franche-Comté, 25000, Besançon, France.,Centre de Référence pour les Maladies Métaboliques, Université de Liège, 4000, Liège, Belgium
| | - Fanny Mochel
- INSERM U 1127, 75013, Paris, France.,Centre National de la Recherche Scientifique UMR 7225, 75013, Paris, France.,UMRS 1127, Université Pierre et Marie Curie (Paris 06), Sorbonne Universités, 75013, Paris, France.,Institut du Cerveau et de la Moelle Epinière, 75013, Paris, France.,Centre de Référence de Neurogénétique, Hôpital de la Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris, 75013, Paris, France.,Neurometabolic Research Group, University Pierre and Marie Curie, 75013, Paris, France
| | - Alexis Brice
- INSERM U 1127, 75013, Paris, France.,Centre National de la Recherche Scientifique UMR 7225, 75013, Paris, France.,UMRS 1127, Université Pierre et Marie Curie (Paris 06), Sorbonne Universités, 75013, Paris, France.,Institut du Cerveau et de la Moelle Epinière, 75013, Paris, France.,Centre de Référence de Neurogénétique, Hôpital de la Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris, 75013, Paris, France
| | - Giovanni Stevanin
- INSERM U 1127, 75013, Paris, France.,Centre National de la Recherche Scientifique UMR 7225, 75013, Paris, France.,UMRS 1127, Université Pierre et Marie Curie (Paris 06), Sorbonne Universités, 75013, Paris, France.,Institut du Cerveau et de la Moelle Epinière, 75013, Paris, France.,Ecole Pratique des Hautes Etudes, PSL Research University, 75014, Paris, France.,Centre de Référence de Neurogénétique, Hôpital de la Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris, 75013, Paris, France
| | - Alexandra Durr
- INSERM U 1127, 75013, Paris, France.,Centre National de la Recherche Scientifique UMR 7225, 75013, Paris, France.,UMRS 1127, Université Pierre et Marie Curie (Paris 06), Sorbonne Universités, 75013, Paris, France.,Institut du Cerveau et de la Moelle Epinière, 75013, Paris, France.,Centre de Référence de Neurogénétique, Hôpital de la Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris, 75013, Paris, France
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Viscomi C, Zeviani M. MtDNA-maintenance defects: syndromes and genes. J Inherit Metab Dis 2017; 40:587-599. [PMID: 28324239 PMCID: PMC5500664 DOI: 10.1007/s10545-017-0027-5] [Citation(s) in RCA: 123] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 02/10/2017] [Accepted: 02/13/2017] [Indexed: 02/02/2023]
Abstract
A large group of mitochondrial disorders, ranging from early-onset pediatric encephalopathic syndromes to late-onset myopathy with chronic progressive external ophthalmoplegia (CPEOs), are inherited as Mendelian disorders characterized by disturbed mitochondrial DNA (mtDNA) maintenance. These errors of nuclear-mitochondrial intergenomic signaling may lead to mtDNA depletion, accumulation of mtDNA multiple deletions, or both, in critical tissues. The genes involved encode proteins belonging to at least three pathways: mtDNA replication and maintenance, nucleotide supply and balance, and mitochondrial dynamics and quality control. In most cases, allelic mutations in these genes may lead to profoundly different phenotypes associated with either mtDNA depletion or multiple deletions.
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Affiliation(s)
- Carlo Viscomi
- MRC-Mitochondrial Biology Unit, MRC MBU, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Massimo Zeviani
- MRC-Mitochondrial Biology Unit, MRC MBU, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK.
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El-Hattab AW, Craigen WJ, Scaglia F. Mitochondrial DNA maintenance defects. Biochim Biophys Acta Mol Basis Dis 2017; 1863:1539-1555. [PMID: 28215579 DOI: 10.1016/j.bbadis.2017.02.017] [Citation(s) in RCA: 185] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 01/31/2017] [Accepted: 02/14/2017] [Indexed: 01/12/2023]
Abstract
The maintenance of mitochondrial DNA (mtDNA) depends on a number of nuclear gene-encoded proteins including a battery of enzymes forming the replisome needed to synthesize mtDNA. These enzymes need to be in balanced quantities to function properly that is in part achieved by exchanging intramitochondrial contents through mitochondrial fusion. In addition, mtDNA synthesis requires a balanced supply of nucleotides that is achieved by nucleotide recycling inside the mitochondria and import from the cytosol. Mitochondrial DNA maintenance defects (MDMDs) are a group of diseases caused by pathogenic variants in the nuclear genes involved in mtDNA maintenance resulting in impaired mtDNA synthesis leading to quantitative (mtDNA depletion) and qualitative (multiple mtDNA deletions) defects in mtDNA. Defective mtDNA leads to organ dysfunction due to insufficient mtDNA-encoded protein synthesis, resulting in an inadequate energy production to meet the needs of affected organs. MDMDs are inherited as autosomal recessive or dominant traits, and are associated with a broad phenotypic spectrum ranging from mild adult-onset ophthalmoplegia to severe infantile fatal hepatic failure. To date, pathogenic variants in 20 nuclear genes known to be crucial for mtDNA maintenance have been linked to MDMDs, including genes encoding enzymes of mtDNA replication machinery (POLG, POLG2, TWNK, TFAM, RNASEH1, MGME1, and DNA2), genes encoding proteins that function in maintaining a balanced mitochondrial nucleotide pool (TK2, DGUOK, SUCLG1, SUCLA2, ABAT, RRM2B, TYMP, SLC25A4, AGK, and MPV17), and genes encoding proteins involved in mitochondrial fusion (OPA1, MFN2, and FBXL4).
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Affiliation(s)
- Ayman W El-Hattab
- Division of Clinical Genetics and Metabolic Disorders, Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - William J Craigen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
| | - Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
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DeBalsi KL, Longley MJ, Hoff KE, Copeland WC. Synergistic Effects of the in cis T251I and P587L Mitochondrial DNA Polymerase γ Disease Mutations. J Biol Chem 2017; 292:4198-4209. [PMID: 28154168 DOI: 10.1074/jbc.m116.773341] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 01/26/2017] [Indexed: 01/28/2023] Open
Abstract
Human mitochondrial DNA (mtDNA) polymerase γ (Pol γ) is the only polymerase known to replicate the mitochondrial genome. The Pol γ holoenzyme consists of the p140 catalytic subunit (POLG) and the p55 homodimeric accessory subunit (POLG2), which enhances binding of Pol γ to DNA and promotes processivity of the holoenzyme. Mutations within POLG impede maintenance of mtDNA and cause mitochondrial diseases. Two common POLG mutations usually found in cis in patients primarily with progressive external ophthalmoplegia generate T251I and P587L amino acid substitutions. To determine whether T251I or P587L is the primary pathogenic allele or whether both substitutions are required to cause disease, we overproduced and purified WT, T251I, P587L, and T251I + P587L double variant forms of recombinant Pol γ. Biochemical characterization of these variants revealed impaired DNA binding affinity, reduced thermostability, diminished exonuclease activity, defective catalytic activity, and compromised DNA processivity, even in the presence of the p55 accessory subunit. However, physical association with p55 was unperturbed, suggesting intersubunit affinities similar to WT. Notably, although the single mutants were similarly impaired, a dramatic synergistic effect was found for the double mutant across all parameters. In conclusion, our analyses suggest that individually both T251I and P587L substitutions functionally impair Pol γ, with greater pathogenicity predicted for the single P587L variant. Combining T251I and P587L induces extreme thermal lability and leads to synergistic nucleotide and DNA binding defects, which severely impair catalytic activity and correlate with presentation of disease in patients.
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Affiliation(s)
- Karen L DeBalsi
- From the Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Matthew J Longley
- From the Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Kirsten E Hoff
- From the Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - William C Copeland
- From the Genome Integrity and Structural Biology Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709
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DeBalsi KL, Hoff KE, Copeland WC. Role of the mitochondrial DNA replication machinery in mitochondrial DNA mutagenesis, aging and age-related diseases. Ageing Res Rev 2017; 33:89-104. [PMID: 27143693 DOI: 10.1016/j.arr.2016.04.006] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 04/19/2016] [Accepted: 04/19/2016] [Indexed: 12/19/2022]
Abstract
As regulators of bioenergetics in the cell and the primary source of endogenous reactive oxygen species (ROS), dysfunctional mitochondria have been implicated for decades in the process of aging and age-related diseases. Mitochondrial DNA (mtDNA) is replicated and repaired by nuclear-encoded mtDNA polymerase γ (Pol γ) and several other associated proteins, which compose the mtDNA replication machinery. Here, we review evidence that errors caused by this replication machinery and failure to repair these mtDNA errors results in mtDNA mutations. Clonal expansion of mtDNA mutations results in mitochondrial dysfunction, such as decreased electron transport chain (ETC) enzyme activity and impaired cellular respiration. We address the literature that mitochondrial dysfunction, in conjunction with altered mitochondrial dynamics, is a major driving force behind aging and age-related diseases. Additionally, interventions to improve mitochondrial function and attenuate the symptoms of aging are examined.
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Affiliation(s)
- Karen L DeBalsi
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Kirsten E Hoff
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
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Sánchez I, Balagué E, Matilla-Dueñas A. Ataxin-1 regulates the cerebellar bioenergetics proteome through the GSK3β-mTOR pathway which is altered in Spinocerebellar ataxia type 1 (SCA1). Hum Mol Genet 2016; 25:4021-4040. [PMID: 27466200 DOI: 10.1093/hmg/ddw242] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 06/21/2016] [Accepted: 07/11/2016] [Indexed: 12/17/2022] Open
Abstract
A polyglutamine expansion within the ataxin-1 protein (ATXN1) underlies spinocerebellar ataxia type-1 (SCA1), a neurological disorder mainly characterized by ataxia and cerebellar deficits. In SCA1, both loss and gain of ATXN1 biological functions contribute to cerebellar pathogenesis. However, the critical ATXN1 functions and pathways involved remain unclear. To further investigate the early signalling pathways regulated by ATXN1, we performed an unbiased proteomic study of the Atxn1-KO 5-week-old mice cerebellum. Here, we show that lack of ATXN1 expression induces early alterations in proteins involved in glycolysis [pyruvate kinase, muscle, isoform 1 protein (PKM-i1), citrate synthase (CS), glycerol-3-phosphate dehydrogenase 2 (GPD2), glucose-6-phosphate isomerase (GPI), alpha -: enolase (ENO1)], ATP synthesis [CS, Succinate dehydrogenase complex,subunit A (SDHA), ATP synthase subunit d, mitochondrial (ATP5H)] and oxidative stress [peroxiredoxin-6 (PRDX6), aldehyde dehydrogenase family 1, subfamily A1, 10-formyltetrahydrofolate dehydrogenase]. In the SCA1 mice, several of these proteins (PKM-i1, ATP5H, PRDX6, proteome subunit A6) were down-regulated and ATP levels decreased. The underlying mechanism does not involve modulation of mitochondrial biogenesis, but dysregulation of the activity of the metabolic regulators glycogen synthase kinase 3B (GSK3β), decreased in Atxn1-KO and increased in SCA1 mice, and mechanistic target of rapamycin (serine/threonine kinase) (mTOR), unchanged in the Atxn1-KO and decreased in SCA1 mice cerebellum before the onset of ataxic symptoms. Pharmacological inhibition of GSK3β and activation of mTOR in a SCA1 cell model ameliorated identified ATXN1-regulated metabolic proteome and ATP alterations. Taken together, these results point to an early role of ATXN1 in the regulation of bioenergetics homeostasis in the mouse cerebellum. Moreover, data suggest GSK3β and mTOR pathways modulate this ATXN1 function in SCA1 pathogenesis that could be targeted therapeutically prior to the onset of disease symptoms in SCA1 and other pathologies involving dysregulation of ATXN1 functions.
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Affiliation(s)
- Ivelisse Sánchez
- Functional and Translational Neurogenetics Unit, Department of Neurosciences, Health Sciences Research Institute Germans Trias i Pujol (IGTP)-Universitat Autonoma de Barcelona, Crta. de Can Ruti, camí de les escoles s/n, 08916 Badalona, Barcelona, Spain
| | - Eudald Balagué
- Functional and Translational Neurogenetics Unit, Department of Neurosciences, Health Sciences Research Institute Germans Trias i Pujol (IGTP)-Universitat Autonoma de Barcelona, Crta. de Can Ruti, camí de les escoles s/n, 08916 Badalona, Barcelona, Spain
| | - Antoni Matilla-Dueñas
- Functional and Translational Neurogenetics Unit, Department of Neurosciences, Health Sciences Research Institute Germans Trias i Pujol (IGTP)-Universitat Autonoma de Barcelona, Crta. de Can Ruti, camí de les escoles s/n, 08916 Badalona, Barcelona, Spain
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Rossi M, Medina Escobar A, Radrizzani M, Tenembaum S, Perandones C, Merello M. Dystonia in a Patient with Autosomal-Dominant Progressive External Ophthalmoplegia Type 1 Caused by Mutation in the POLG Gene. Mov Disord Clin Pract 2016; 4:266-269. [PMID: 30838265 DOI: 10.1002/mdc3.12397] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 05/14/2016] [Accepted: 05/16/2016] [Indexed: 11/11/2022] Open
Affiliation(s)
- Malco Rossi
- Movement Disorders Section Neuroscience Department Raul Carrea Institute for Neurological Research (FLENI) Buenos Aires Argentina
| | - Alex Medina Escobar
- Movement Disorders Section Neuroscience Department Raul Carrea Institute for Neurological Research (FLENI) Buenos Aires Argentina
| | - Martin Radrizzani
- Laboratory of Neuro and Molecular Cytogenetic (CONICET) School of Sciences and Technology CESyMA National University of San Martin Buenos Aires Argentina
| | - Silvia Tenembaum
- Department of Pediatric Neurology National Pediatric Hospital Dr. Juan P. Garrahan Buenos Aires Argentina
| | - Claudia Perandones
- Scientific and Technological Coordination Unit of the ANLIS Directorate National Administration of Laboratories and Institutes of Health, Dr. Carlos G. Malbran Buenos Aires Argentina.,Argentine National Scientific and Technological Research Council (CONICET) Buenos Aires Argentina
| | - Marcelo Merello
- Movement Disorders Section Neuroscience Department Raul Carrea Institute for Neurological Research (FLENI) Buenos Aires Argentina.,Argentine National Scientific and Technological Research Council (CONICET) Buenos Aires Argentina
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Rygiel KA, Tuppen HA, Grady JP, Vincent A, Blakely EL, Reeve AK, Taylor RW, Picard M, Miller J, Turnbull DM. Complex mitochondrial DNA rearrangements in individual cells from patients with sporadic inclusion body myositis. Nucleic Acids Res 2016; 44:5313-29. [PMID: 27131788 PMCID: PMC4914118 DOI: 10.1093/nar/gkw382] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 04/26/2016] [Indexed: 01/26/2023] Open
Abstract
Mitochondrial DNA (mtDNA) rearrangements are an important cause of mitochondrial disease and age related mitochondrial dysfunction in tissues including brain and skeletal muscle. It is known that different mtDNA deletions accumulate in single cells, but the detailed nature of these rearrangements is still unknown. To evaluate this we used a complementary set of sensitive assays to explore the mtDNA rearrangements in individual cells from patients with sporadic inclusion body myositis, a late-onset inflammatory myopathy with prominent mitochondrial changes. We identified large-scale mtDNA deletions in individual muscle fibres with 20% of cytochrome c oxidase-deficient myofibres accumulating two or more mtDNA deletions. The majority of deletions removed only the major arc but ∼10% of all deletions extended into the minor arc removing the origin of light strand replication (OL) and a variable number of genes. Some mtDNA molecules contained two deletion sites. Additionally, we found evidence of mitochondrial genome duplications allowing replication and clonal expansion of these complex rearranged molecules. The extended spectrum of mtDNA rearrangements in single cells provides insight into the process of clonal expansion which is fundamental to our understanding of the role of mtDNA mutations in ageing and disease.
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Affiliation(s)
- Karolina A Rygiel
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK Newcastle University Centre for Ageing and Vitality, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Helen A Tuppen
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - John P Grady
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Amy Vincent
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK Newcastle University Centre for Ageing and Vitality, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Emma L Blakely
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Amy K Reeve
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK Newcastle University Centre for Ageing and Vitality, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Martin Picard
- Division of Behavioral Medicine, Department of Psychiatry, Department of Neurology and CTNI, College of Physicians and Surgeons, Columbia University Medical Center, New York, NY 10032, USA
| | - James Miller
- Department of Neurology, Newcastle upon Tyne Hospitals NHS Foundation Trust Royal Victoria Infirmary, Newcastle upon Tyne, NE1 4LP, UK
| | - Doug M Turnbull
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK Newcastle University Centre for Ageing and Vitality, Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
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40
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41
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Henao AI, Pira S, Herrera DA, Vargas SA, Montoya J, Castillo M. Characteristic brain MRI findings in ataxia-neuropathy spectrum related to POLG mutation. Neuroradiol J 2016; 29:46-8. [PMID: 26755490 DOI: 10.1177/1971400915621324] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Patients with mutations in the polymerase gamma gene (POLG) may present with progressive ataxia and in such situations neuroimaging findings may suggest the diagnosis. Herein we report a patient with a POLG gene W748S homozygous mutation and characteristic lesions in the thalamus, cerebellum and inferior olivary nucleus seen on magnetic resonance imaging.
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Affiliation(s)
- Adriana I Henao
- Department of Pediatric Neurology, Universidad de Antioquia, Medellín, Colombia
| | - Sonia Pira
- Department of Pediatric Neurology, Universidad de Antioquia, Medellín, Colombia
| | - Diego A Herrera
- Department of Radiology, Universidad de Antioquia, Medellín, Colombia Department of Radiology, CediMed (Centro Avanzado de Diagnóstico Médico), Medellín, Colombia
| | - Sergio A Vargas
- Department of Radiology, Universidad de Antioquia, Medellín, Colombia Department of Radiology, CediMed (Centro Avanzado de Diagnóstico Médico), Medellín, Colombia
| | - Jorge Montoya
- Department of Genetics, Universidad de Antioquia, Medellín, Colombia
| | - Mauricio Castillo
- Department of Radiology, University of North Carolina, Chapel Hill, NC, USA
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Rajakulendran S, Pitceathly RDS, Taanman JW, Costello H, Sweeney MG, Woodward CE, Jaunmuktane Z, Holton JL, Jacques TS, Harding BN, Fratter C, Hanna MG, Rahman S. A Clinical, Neuropathological and Genetic Study of Homozygous A467T POLG-Related Mitochondrial Disease. PLoS One 2016; 11:e0145500. [PMID: 26735972 PMCID: PMC4703200 DOI: 10.1371/journal.pone.0145500] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 12/06/2015] [Indexed: 02/06/2023] Open
Abstract
Mutations in the nuclear gene POLG (encoding the catalytic subunit of DNA polymerase gamma) are an important cause of mitochondrial disease. The most common POLG mutation, A467T, appears to exhibit considerable phenotypic heterogeneity. The mechanism by which this single genetic defect results in such clinical diversity remains unclear. In this study we evaluate the clinical, neuropathological and mitochondrial genetic features of four unrelated patients with homozygous A467T mutations. One patient presented with the severe and lethal Alpers-Huttenlocher syndrome, which was confirmed on neuropathology, and was found to have a depletion of mitochondrial DNA (mtDNA). Of the remaining three patients, one presented with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), one with a phenotype in the Myoclonic Epilepsy, Myopathy and Sensory Ataxia (MEMSA) spectrum and one with Sensory Ataxic Neuropathy, Dysarthria and Ophthalmoplegia (SANDO). All three had secondary accumulation of multiple mtDNA deletions. Complete sequence analysis of muscle mtDNA using the MitoChip resequencing chip in all four cases demonstrated significant variation in mtDNA, including a pathogenic MT-ND5 mutation in one patient. These data highlight the variable and overlapping clinical and neuropathological phenotypes and downstream molecular defects caused by the A467T mutation, which may result from factors such as the mtDNA genetic background, nuclear genetic modifiers and environmental stressors.
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Affiliation(s)
- Sanjeev Rajakulendran
- UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery and the MRC Centre for Neuromuscular Diseases, Queen Square, London WC1N 3BG, United Kingdom
| | - Robert D. S. Pitceathly
- UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, United Kingdom and Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King’s College London SE5 8AF, United Kingdom
| | - Jan-Willem Taanman
- Department of Clinical Neurosciences, UCL Institute of Neurology, London NW3 2PF, United Kingdom
| | - Harry Costello
- Mitochondrial Research Group, Genetics and Genomic Medicine, UCL Institute of Child Health, London WC1N 1EH, United Kingdom
| | - Mary G. Sweeney
- Department of Neurogenetics, UCL Institute of Neurology and National Hospital for Neurology, Queen Square, London WC1N 3BG, United Kingdom
| | - Cathy E. Woodward
- Department of Neurogenetics, UCL Institute of Neurology and National Hospital for Neurology, Queen Square, London WC1N 3BG, United Kingdom
| | - Zane Jaunmuktane
- Division of Neuropathology, UCL Institute of Neurology and National Hospital for Neurology, Queen Square, London WC1N 3BG, United Kingdom
| | - Janice L. Holton
- Division of Neuropathology, UCL Institute of Neurology and National Hospital for Neurology, Queen Square, London WC1N 3BG, United Kingdom
| | - Thomas S. Jacques
- Developmental Biology and Cancer Programme, UCL Institute of Child Health and Department of Histopathology, Great Ormond Street Hospital for Children Foundation Trust, London WC1N 1EH, United Kingdom
| | - Brian N. Harding
- Division of Neuropathology, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Carl Fratter
- Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Trust, Churchill Hospital, Oxford OX3 7LE, United Kingdom
| | - Michael G. Hanna
- UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery and the MRC Centre for Neuromuscular Diseases, Queen Square, London WC1N 3BG, United Kingdom
| | - Shamima Rahman
- Mitochondrial Research Group, Genetics and Genomic Medicine, UCL Institute of Child Health, London WC1N 1EH, United Kingdom
- Metabolic Unit, Great Ormond Street Hospital, London WC1N 3JH, United Kingdom
- * E-mail:
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Ramakrishnan S, Yadav R, Adwani S, Mustare V, Kulkarni GB, Narayanappa G, Periyasamy G, Kumarasamy T. Vocal cord palsy in a case of chronic progressive external ophthalmoplegia. Ann Indian Acad Neurol 2015; 18:481-3. [PMID: 26713034 PMCID: PMC4683901 DOI: 10.4103/0972-2327.165463] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Affiliation(s)
- Subasree Ramakrishnan
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India
| | - Ravi Yadav
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India
| | - Sikander Adwani
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India
| | - Veerendrakumar Mustare
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India
| | - Girish B Kulkarni
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India
| | - Gayathri Narayanappa
- Department of Neuropathology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India
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Yeast model analysis of novel polymerase gamma variants found in patients with autosomal recessive mitochondrial disease. Hum Genet 2015; 134:951-66. [PMID: 26077851 PMCID: PMC4529462 DOI: 10.1007/s00439-015-1578-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 06/03/2015] [Indexed: 12/18/2022]
Abstract
Replication of the mitochondrial genome depends on the single DNA polymerase (pol gamma). Mutations in the POLG gene, encoding the catalytic subunit of the human polymerase gamma, have been linked to a wide variety of mitochondrial disorders that show remarkable heterogeneity, with more than 200 sequence variants, often very rare, found in patients. The pathogenicity and dominance status of many such mutations remain, however, unclear. Remarkable structural and functional conservation of human POLG and its S. cerevisiae ortholog (Mip1p) led to the development of many successful yeast models, enabling to study the phenotype of putative pathogenic mutations. In a group of patients with suspicion of mitochondrial pathology, we identified five novel POLG sequence variants, four of which (p.Arg869Ter, p.Gln968Glu, p.Thr1053Argfs*6, and p.Val1106Ala), together with one previously known but uncharacterised variant (p.Arg309Cys), were amenable to modelling in yeast. Familial analysis indicated causal relationship of these variants with disease, consistent with autosomal recessive inheritance. To investigate the effect of these sequence changes on mtDNA replication, we obtained the corresponding yeast mip1 alleles (Arg265Cys, Arg672Ter, Arg770Glu, Thr809Ter, and Val863Ala, respectively) and tested their effect on mitochondrial genome stability and replication fidelity. For three of them (Arg265Cys, Arg672Ter, and Thr809Ter), we observed a strong, partially dominant phenotype of a complete loss of functional mtDNA, whereas the remaining two led to partial mtDNA depletion and significant increase in point mutation frequencies. These results show good correlation with the severity of symptoms observed in patients and allow to establish these variants as pathogenic mutations.
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Mukai M, Sugaya K, Matsubara S, Cai H, Yabe I, Sasaki H, Nakano I. [Familial progressive external opthalmoplegia, parkinsonism and polyneuropathy associated with POLG1 mutation]. Rinsho Shinkeigaku 2015; 54:417-22. [PMID: 24943079 DOI: 10.5692/clinicalneurol.54.417] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Multiple mitochondrial DNA (mtDNA) deletions usually occur secondarily to a mutation in one of the enzymes involved in mtDNA maintenance, such as polymerase γ, which is encoded by the nuclear polymerase γ1 gene (POLG1) and POLG2. Patients with multiple mtDNA deletion disorders show clinical heterogeneity of symptoms, in addition to usually seen progressive external ophthalmoplegia (PEO). We conducted clinical, histological and genetic analyses of two affected sisters in a family with the autosomal dominant inheritance pattern of PEO. A 73-year-old woman (patient 1) with congenital hypogonadism and PEO developed L-dopa responsive parkinsonism about the age of 60. Neurological examination revealed mild proximal muscle weakness and polyneuropathy too. Her 69-year-old sister (patient 2) also showed PEO, parkinsonism and polyneuropathy. Histopathological studies of biopsied muscle specimens from patient 1 revealed numerous ragged red fibers as well as fibers with increased succinate dehydrogenase activity and decreased cytochrome c oxidase activity. Multiple mtDNA deletions were detected, both by Southern blot and long-range PCR assays of total DNA from the biopsied muscle specimens. A systemic mutational analysis in both sisters revealed a heterozygous p.Y955C (c.2864A>G) mutation in POLG1. This is the first Japanese family identified with this mutation. We reviewed cases with this mutation highlighting a wide phenotypic spectrum of this disorder.
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Affiliation(s)
- Masako Mukai
- Department of Neurology, Tokyo Metropolitan Neurological Hospital
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46
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Abstract
Because of their high-energy metabolism, neurons are strictly dependent on mitochondria, which generate cellular ATP through oxidative phosphorylation. The mitochondrial genome encodes for critical components of the oxidative phosphorylation pathway machinery, and therefore, mutations in mitochondrial DNA (mtDNA) cause energy production defects that frequently have severe neurological manifestations. Here, we review the principles of mitochondrial genetics and focus on prototypical mitochondrial diseases to illustrate how primary defects in mtDNA or secondary defects in mtDNA due to nuclear genome mutations can cause prominent neurological and multisystem features. In addition, we discuss the pathophysiological mechanisms underlying mitochondrial diseases, the cellular mechanisms that protect mitochondrial integrity, and the prospects for therapy.
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Affiliation(s)
- Valerio Carelli
- IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Bologna, Italy; Neurology Unit, Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - David C Chan
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
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47
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Linkowska K, Jawień A, Marszałek A, Malyarchuk BA, Tońska K, Bartnik E, Skonieczna K, Grzybowski T. Mitochondrial DNA Polymerase γ Mutations and Their Implications in mtDNA Alterations in Colorectal Cancer. Ann Hum Genet 2015; 79:320-328. [PMID: 25850945 DOI: 10.1111/ahg.12111] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Accepted: 01/26/2015] [Indexed: 01/16/2023]
Abstract
Mitochondrial DNA was found to be highly mutated in colorectal cancer cells. One of the key molecules involved in the maintenance of the mitochondrial genome is the nuclear-encoded polymerase gamma. The aim of our study was to determine if there is a link between polymorphisms within the polymerase gamma gene (POLG) and somatic mutations within the mitochondrial genome in cancer cells. We investigated POLG sequence variability in 50 colorectal cancer patients whose complete mitochondrial genome sequences were determined. Relative mtDNA copy number was also determined. We identified 251 sequence variants in the POLG gene. Most of them were germline-specific (∼92%). Twenty-one somatic changes in POLG were found in 10 colorectal cancer patients. We have found no association between the occurrence of mtDNA somatic mutations and the somatically occurring variants in POLG. MtDNA content was reduced in patients carrying somatic variants in POLG or germline nucleotide variants located in the region encoding the POLG polymerase domain, but the difference did not reach statistical significance. Our findings suggest that somatic mtDNA mutations occurring in colorectal cancer are not a consequence of somatic mutations in POLG. Nevertheless, POLG nucleotide variants may lead to a decrease in mtDNA content, and consequently result in mitochondrial dysfunction.
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Affiliation(s)
- Katarzyna Linkowska
- Department of Molecular and Forensic Genetics, Institute of Forensic Medicine, Ludwik Rydygier Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz, Poland
| | - Arkadiusz Jawień
- Chair of Vascular Surgery and Angiology, Ludwik Rydygier Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz, Poland
| | - Andrzej Marszałek
- Chair & Department of Clinical Pathomorphology, Ludwik Rydygier Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz, Poland
| | - Boris A Malyarchuk
- Institute of Biological Problems of the North, Far-East Branch of the Russian Academy of Sciences, Magadan, Russia
| | - Katarzyna Tońska
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Ewa Bartnik
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland.,Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Katarzyna Skonieczna
- Department of Molecular and Forensic Genetics, Institute of Forensic Medicine, Ludwik Rydygier Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz, Poland
| | - Tomasz Grzybowski
- Department of Molecular and Forensic Genetics, Institute of Forensic Medicine, Ludwik Rydygier Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz, Poland
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The in cis T251I and P587L POLG1 base changes: Description of a new family and literature review. Neuromuscul Disord 2015; 25:333-9. [DOI: 10.1016/j.nmd.2015.01.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 01/07/2015] [Accepted: 01/14/2015] [Indexed: 11/19/2022]
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Miguel R, Gago MF, Martins J, Barros P, Vale J, Rosas MJ. POLG1-related levodopa-responsive parkinsonism. Clin Neurol Neurosurg 2014; 126:47-54. [DOI: 10.1016/j.clineuro.2014.08.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 07/17/2014] [Accepted: 08/05/2014] [Indexed: 11/30/2022]
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50
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Polymorphism of the DNA base excision repair genes in keratoconus. Int J Mol Sci 2014; 15:19682-99. [PMID: 25356504 PMCID: PMC4264133 DOI: 10.3390/ijms151119682] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 10/08/2014] [Accepted: 10/16/2014] [Indexed: 01/12/2023] Open
Abstract
Keratoconus (KC) is a degenerative corneal disorder for which the exact pathogenesis is not yet known. Oxidative stress is reported to be associated with this disease. The stress may damage corneal biomolecules, including DNA, and such damage is primarily removed by base excision repair (BER). Variation in genes encoding BER components may influence the effectiveness of corneal cells to cope with oxidative stress. In the present work we genotyped 5 polymorphisms of 4 BER genes in 284 patients and 353 controls. The A/A genotype of the c.–1370T>A polymorphism of the DNA polymerase γ (POLG) gene was associated with increased occurrence of KC, while the A/T genotype was associated with decreased occurrence of KC. The A/G genotype and the A allele of the c.1196A>G polymorphism of the X-ray repair cross-complementing group 1 (XRCC1) were associated with increased, and the G/G genotype and the G allele, with decreased KC occurrence. Also, the C/T and T as well as C/C genotypes and alleles of the c.580C>T polymorphism of the same gene displayed relationship with KC occurrence. Neither the g.46438521G>C polymorphism of the Nei endonuclease VIII-like 1 (NEIL1) nor the c.2285T>C polymorphism of the poly(ADP-ribose) polymerase-1 (PARP-1) was associated with KC. In conclusion, the variability of the XRCC1 and POLG genes may play a role in KC pathogenesis and determine the risk of this disease.
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