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Sawant N, Morton H, Kshirsagar S, Reddy AP, Reddy PH. Mitochondrial Abnormalities and Synaptic Damage in Huntington's Disease: a Focus on Defective Mitophagy and Mitochondria-Targeted Therapeutics. Mol Neurobiol 2021; 58:6350-6377. [PMID: 34519969 DOI: 10.1007/s12035-021-02556-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 09/05/2021] [Indexed: 12/12/2022]
Abstract
Huntington's disease (HD) is a fatal and pure genetic disease with a progressive loss of medium spiny neurons (MSN). HD is caused by expanded polyglutamine repeats in the exon 1 of HD gene. Clinically, HD is characterized by chorea, seizures, involuntary movements, dystonia, cognitive decline, intellectual impairment, and emotional disturbances. Several years of intense research revealed that multiple cellular changes, including defective axonal transport, protein-protein interactions, defective bioenergetics, calcium dyshomeostasis, NMDAR activation, synaptic damage, mitochondrial abnormalities, and selective loss of medium spiny neurons are implicated in HD. Recent research on mutant huntingtin (mHtt) and mitochondria has found that mHtt interacts with the mitochondrial division protein, dynamin-related protein 1 (DRP1), enhances GTPase DRP1 enzymatic activity, and causes excessive mitochondrial fragmentation and abnormal distribution, leading to defective axonal transport of mitochondria and selective synaptic degeneration. Recent research also revealed that failure to remove dead and/or dying mitochondria is an early event in the disease progression. Currently, efforts are being made to reduce abnormal protein interactions and enhance synaptic mitophagy as therapeutic strategies for HD. The purpose of this article is to discuss recent research in HD progression. This article also discusses recent developments of cell and mouse models, cellular changes, mitochondrial abnormalities, DNA damage, bioenergetics, oxidative stress, mitophagy, and therapeutics strategies in HD.
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Affiliation(s)
- Neha Sawant
- Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Hallie Morton
- Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Sudhir Kshirsagar
- Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Arubala P Reddy
- Nutritional Sciences Department, College of Human Sciences, Texas Tech University, 1301 Akron Ave, Lubbock, TX, USA
| | - P Hemachandra Reddy
- Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA. .,Neuroscience & Pharmacology, Texas Tech University Health Sciences Center, Lubbock, TX, USA. .,Neurology, Department of School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA. .,Public Health Department of Graduate School of Biomedical Sciences, Texas Tech University Health Sciences Center, Lubbock, TX, USA. .,Department of Speech, Language and Hearing Sciences, School Health Professions, Texas Tech University Health Sciences Center, Lubbock, TX, USA. .,Department of Internal Medicine, Cell Biology & Biochemistry, Public Health and School of Health Professions, Texas Tech University Health Sciences Center, Neuroscience & Pharmacology3601 4th Street, NeurologyLubbock, TX, 79430, USA.
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Pacitti D, Levene M, Garone C, Nirmalananthan N, Bax BE. Mitochondrial Neurogastrointestinal Encephalomyopathy: Into the Fourth Decade, What We Have Learned So Far. Front Genet 2018; 9:669. [PMID: 30627136 PMCID: PMC6309918 DOI: 10.3389/fgene.2018.00669] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 12/04/2018] [Indexed: 02/05/2023] Open
Abstract
Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an ultra-rare metabolic autosomal recessive disease, caused by mutations in the nuclear gene TYMP which encodes the enzyme thymidine phosphorylase. The resulting enzyme deficiency leads to a systemic accumulation of the deoxyribonucleosides thymidine and deoxyuridine, and ultimately mitochondrial failure due to a progressive acquisition of secondary mitochondrial DNA (mtDNA) mutations and mtDNA depletion. Clinically, MNGIE is characterized by gastrointestinal and neurological manifestations, including cachexia, gastrointestinal dysmotility, peripheral neuropathy, leukoencephalopathy, ophthalmoplegia and ptosis. The disease is progressively degenerative and leads to death at an average age of 37.6 years. As with the vast majority of rare diseases, patients with MNGIE face a number of unmet needs related to diagnostic delays, a lack of approved therapies, and non-specific clinical management. We provide here a comprehensive collation of the available knowledge of MNGIE since the disease was first described 42 years ago. This review includes symptomatology, diagnostic procedures and hurdles, in vitro and in vivo disease models that have enhanced our understanding of the disease pathology, and finally experimental therapeutic approaches under development. The ultimate aim of this review is to increase clinical awareness of MNGIE, thereby reducing diagnostic delay and improving patient access to putative treatments under investigation.
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Affiliation(s)
- Dario Pacitti
- Molecular and Clinical Sciences Research Institute, St George's, University of London, London, United Kingdom
| | - Michelle Levene
- Molecular and Clinical Sciences Research Institute, St George's, University of London, London, United Kingdom
| | - Caterina Garone
- MRC Mitochondrial Biology Unit, Cambridge Biomedical, Cambridge, United Kingdom
| | | | - Bridget E. Bax
- Molecular and Clinical Sciences Research Institute, St George's, University of London, London, United Kingdom
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3
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Mitochondrial DNA Mutation-Elicited Oxidative Stress, Oxidative Damage, and Altered Gene Expression in Cultured Cells of Patients with MERRF Syndrome. Mol Neurobiol 2010; 41:256-66. [DOI: 10.1007/s12035-010-8123-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Accepted: 03/23/2010] [Indexed: 12/12/2022]
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4
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Sikorska M, Sandhu JK, Simon DK, Pathiraja V, Sodja C, Li Y, Ribecco-Lutkiewicz M, Lanthier P, Borowy-Borowski H, Upton A, Raha S, Pulst SM, Tarnopolsky MA. Identification of ataxia-associated mtDNA mutations (m.4052T>C and m.9035T>C) and evaluation of their pathogenicity in transmitochondrial cybrids. Muscle Nerve 2009; 40:381-94. [PMID: 19626676 DOI: 10.1002/mus.21355] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The potential pathogenicity of two homoplasmic mtDNA point mutations, 9035T>C and 4452T>C, found in a family afflicted with maternally transmitted cognitive developmental delay, learning disability, and progressive ataxia was evaluated using transmitochondrial cybrids. We confirmed that the 4452T>C transition in tRNA(Met) represented a polymorphism; however, 9035T>C conversion in the ATP6 gene was responsible for a defective F(0)-ATPase. Accordingly, mutant cybrids had a reduced oligomycin-sensitive ATP hydrolyzing activity. They had less than half of the steady-state content of ATP and nearly an 8-fold higher basal level of reactive oxygen species (ROS). Mutant cybrids were unable to cope with additional insults, i.e., glucose deprivation or tertiary-butyl hydroperoxide, and they succumbed to either apoptotic or necrotic cell death. Both of these outcomes were prevented by the antioxidants CoQ(10) and vitamin E, suggesting that the abnormally high levels of ROS were the triggers of cell death. In conclusion, the principal metabolic defects, i.e., energy deficiency and ROS burden, resulted from the 9035T>C mutation and could be responsible for the development of clinical symptoms in this family. Furthermore, antioxidant therapy might prove helpful in the management of this disease.
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Affiliation(s)
- Marianna Sikorska
- Neurogenesis and Brain Repair Group M54, Institute for Biological Sciences, National Research Council Canada, 1200 Montreal Road, Ottawa, Ontario, K1A 0R6, Canada.
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5
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Seppet E, Gruno M, Peetsalu A, Gizatullina Z, Nguyen HP, Vielhaber S, Wussling MH, Trumbeckaite S, Arandarcikaite O, Jerzembeck D, Sonnabend M, Jegorov K, Zierz S, Striggow F, Gellerich FN. Mitochondria and energetic depression in cell pathophysiology. Int J Mol Sci 2009; 10:2252-2303. [PMID: 19564950 PMCID: PMC2695278 DOI: 10.3390/ijms10052252] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Revised: 04/25/2009] [Accepted: 05/14/2009] [Indexed: 12/21/2022] Open
Abstract
Mitochondrial dysfunction is a hallmark of almost all diseases. Acquired or inherited mutations of the mitochondrial genome DNA may give rise to mitochondrial diseases. Another class of disorders, in which mitochondrial impairments are initiated by extramitochondrial factors, includes neurodegenerative diseases and syndromes resulting from typical pathological processes, such as hypoxia/ischemia, inflammation, intoxications, and carcinogenesis. Both classes of diseases lead to cellular energetic depression (CED), which is characterized by decreased cytosolic phosphorylation potential that suppresses the cell's ability to do work and control the intracellular Ca(2+) homeostasis and its redox state. If progressing, CED leads to cell death, whose type is linked to the functional status of the mitochondria. In the case of limited deterioration, when some amounts of ATP can still be generated due to oxidative phosphorylation (OXPHOS), mitochondria launch the apoptotic cell death program by release of cytochrome c. Following pronounced CED, cytoplasmic ATP levels fall below the thresholds required for processing the ATP-dependent apoptotic cascade and the cell dies from necrosis. Both types of death can be grouped together as a mitochondrial cell death (MCD). However, there exist multiple adaptive reactions aimed at protecting cells against CED. In this context, a metabolic shift characterized by suppression of OXPHOS combined with activation of aerobic glycolysis as the main pathway for ATP synthesis (Warburg effect) is of central importance. Whereas this type of adaptation is sufficiently effective to avoid CED and to control the cellular redox state, thereby ensuring the cell survival, it also favors the avoidance of apoptotic cell death. This scenario may underlie uncontrolled cellular proliferation and growth, eventually resulting in carcinogenesis.
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Affiliation(s)
- Enn Seppet
- Department of Pathophysiology, University of Tartu, Tartu, Estonia; E-Mail:
(M.G.)
| | - Marju Gruno
- Department of Pathophysiology, University of Tartu, Tartu, Estonia; E-Mail:
(M.G.)
| | - Ants Peetsalu
- Department of Surgery, University of Tartu, Tartu, Estonia; E-Mail:
(A.P.)
| | - Zemfira Gizatullina
- KeyNeurotek AG, ZENIT-Technology Park Magdeburg, Magdeburg, Germany; E-Mails:
(Z.G.);
(D.J.);
(M.S.);
(K.J.);
(F.S.);
(F.N.G.)
| | - Huu Phuc Nguyen
- Department of Medical Genetics, University of Tübingen, Tübingen, Germany; E-Mail:
(H.P.N.)
| | - Stefan Vielhaber
- Department of Neurology, Otto von Guericke University, Magdeburg, Germany; E-Mail:
(S.V.)
| | - Manfred H.P. Wussling
- Bernstein Institute for Physiology, Martin-Luther-University Halle-Wittenberg, Germany; E-Mail:
(M.H.P.W.)
| | - Sonata Trumbeckaite
- Institute for Biomedical Research, Kaunas University of Medicine, Kaunas, Lithuania; E-Mails:
(S.T.);
(O.A.)
| | - Odeta Arandarcikaite
- Institute for Biomedical Research, Kaunas University of Medicine, Kaunas, Lithuania; E-Mails:
(S.T.);
(O.A.)
| | - Doreen Jerzembeck
- KeyNeurotek AG, ZENIT-Technology Park Magdeburg, Magdeburg, Germany; E-Mails:
(Z.G.);
(D.J.);
(M.S.);
(K.J.);
(F.S.);
(F.N.G.)
| | - Maria Sonnabend
- KeyNeurotek AG, ZENIT-Technology Park Magdeburg, Magdeburg, Germany; E-Mails:
(Z.G.);
(D.J.);
(M.S.);
(K.J.);
(F.S.);
(F.N.G.)
| | - Katharina Jegorov
- KeyNeurotek AG, ZENIT-Technology Park Magdeburg, Magdeburg, Germany; E-Mails:
(Z.G.);
(D.J.);
(M.S.);
(K.J.);
(F.S.);
(F.N.G.)
| | - Stephan Zierz
- Department of Neurology, Martin-Luther-University Halle-Wittenberg, Germany; E-Mail:
(S.Z.)
| | - Frank Striggow
- KeyNeurotek AG, ZENIT-Technology Park Magdeburg, Magdeburg, Germany; E-Mails:
(Z.G.);
(D.J.);
(M.S.);
(K.J.);
(F.S.);
(F.N.G.)
| | - Frank N. Gellerich
- KeyNeurotek AG, ZENIT-Technology Park Magdeburg, Magdeburg, Germany; E-Mails:
(Z.G.);
(D.J.);
(M.S.);
(K.J.);
(F.S.);
(F.N.G.)
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Katayama Y, Maeda K, Iizuka T, Hayashi M, Hashizume Y, Sanada M, Kawai H, Kashiwagi A. Accumulation of oxidative stress around the stroke-like lesions of MELAS patients. Mitochondrion 2009; 9:306-13. [PMID: 19393775 DOI: 10.1016/j.mito.2009.04.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Revised: 04/04/2009] [Accepted: 04/15/2009] [Indexed: 02/05/2023]
Abstract
To investigate the relationship between oxidative stress and progressive spread of the stroke-like lesions in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) with 3243A>G mutation, we retrospectively analyzed the spread frequency in patients with and without treatment with the radical scavenger edaravone. Oxidative damage and defensive enzymes were histologically evaluated. Spread was significantly less frequent in the patients treated with edaravone. Although 8-hydroxy-2'-deoxyguanosine, a marker for oxidative damage of DNA, was obviously accumulated in peri-lesional surviving neurons, manganese superoxide dismutase and 8-oxoguanine glycosylase 1 were not up-regulated in those neurons. Increased oxidative stress and insufficient defense could be involved in the pathogenesis of the spreading lesions in MELAS.
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Affiliation(s)
- Yuri Katayama
- Division of Neurology, Department of Internal Medicine, Shiga University of Medical Science, Seta-Tsukinowa, Otsu, Shiga 520-2192, Japan
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Di Leo R, Musumeci O, de Gregorio C, Recupero A, Grimaldi P, Messina C, Coglitore S, Vita G, Toscano A. Evidence of cardiovascular autonomic impairment in mitochondrial disorders. J Neurol 2007; 254:1498-503. [PMID: 17987253 DOI: 10.1007/s00415-007-0536-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 10/01/2006] [Accepted: 01/17/2007] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To investigate autonomic nervous system (ANS) function in mitochondrial disorders (MD). BACKGROUND MD are characterized by a wide range of clinical features, including heart abnormalities and peripheral and central nervous systems involvement. Rarely autonomic symptoms have been reported. METHODS 22 patients with MD underwent a battery of cardiovascular reflex tests including five tests of parasympathetic function and four tests of sympathetic function. Power spectral analyses (PSA) of heart rate variability in the supine and upright positions were also evaluated. Plasma levels of adrenaline, noradrenaline and dopamine were determined in the standing and lying positions. RESULTS Only 4/22 patients referred symptoms related to ANS dysfunction. 46% of patients had a definite autonomic damage (i. e. an autonomic score >/= 4). 36% showed moderate alterations with an autonomic score in the range 2-3 and 18 % had a normal autonomic function. MD patients had a significantly (p <0.03) lower increase of adrenaline level after standing. CONCLUSIONS Our data indicate an autonomic dysfunction in more than 80% of MD patients, even in the absence of a clinically manifested autonomic involvement. Cardiovascular autonomic investigation might be systematically employed in the characterization of MD.
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Affiliation(s)
- Rita Di Leo
- Department of Neurosciences Psychiatry and Anaesthesiology, University of Messina, Via Consolare Valeria 98125, Messina, Italy
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8
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Iizuka T, Sakai F, Ide T, Miyakawa S, Sato M, Yoshii S. Regional cerebral blood flow and cerebrovascular reactivity during chronic stage of stroke-like episodes in MELAS -- implication of neurovascular cellular mechanism. J Neurol Sci 2007; 257:126-38. [PMID: 17316689 DOI: 10.1016/j.jns.2007.01.040] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
BACKGROUND Ischemic vascular hypothesis as a causative role in the pathogenesis of stroke-like episodes in MELAS remains to be debated. METHODS This study consisted of two parts. Part 1 is a clinicoradiological study during acute stage of 18 consecutive stroke-like episodes in six patients with MELAS. Part 2 is a SPECT study to assess the regional cerebrovascular reactivity (rCVR) to acetazolamide during chronic stage in five patients with MELAS. RESULTS Headache and epileptic seizure were the most common presenting symptoms. Unique features of acute stroke-like lesions included progressive spread of cortical lesions with vasogenic edema, focal periodic epileptiform discharges, focal hyperperfusion, and cortical laminar necrosis during subacute stage. During chronic stage, SPECT showed hypoperfusion in non-affected occipital cortex in three patients as well as in previously affected regions in four. The rCVR was preserved in three patients, focally impaired in one, and extensively impaired in one, but relatively preserved in the occipital cortex in all patients. CONCLUSIONS Stroke-like episodes could be non-ischemic neurovascular events initiated by neuronal hyperexcitability. Once neuronal hyperexcitability develops in a focal brain region, epileptic activities depolarize adjacent neurons, leading to a propagation of epileptic activities into the surrounding cortex, and resulting in energy imbalance. The mechanisms for neuronal hyperexcitability remain to be elucidated.
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Affiliation(s)
- Takahiro Iizuka
- Department of Neurology, School of Medicine, Kitasato University, 1-15-1 Kitasato, Sagamihara, Kanagawa, 228-8555, Japan.
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Zhadanov SI, Grechanina EY, Grechanina YB, Gusar VA, Fedoseeva NP, Lebon S, Münnich A, Schurr TG. Fatal manifestation of a de novo ND5 mutation: Insights into the pathogenetic mechanisms of mtDNA ND5 gene defects. Mitochondrion 2007; 7:260-6. [PMID: 17317336 DOI: 10.1016/j.mito.2007.01.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Revised: 01/08/2007] [Accepted: 01/10/2007] [Indexed: 11/23/2022]
Abstract
We report the de novo occurrence of a heteroplasmic 12706T-->C (12705C) ND5 mutation associated with the clinical expression of fatal Leigh syndrome. Phylogenetic analysis of several cases having the 12706C mutation confirmed that this mutation occurred independently in distinctive mtDNA backgrounds. In each of these cases, the low level of heteroplasmy and the association of the mutation with a deleterious phenotype indicated that the 12706C had a primary role in the expression of LS/MELAS in its carriers. Secondary structure analysis of the ND5 protein further supported the deleterious role of the 12706C mutation, as it was found to affect a functionally significant transmembrane domain that is likely responsible for the proton-translocation function of complex I.
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Affiliation(s)
- Sergey I Zhadanov
- Department of Anthropology, University of Pennsylvania, 325 University Museum, 3260 South Street, Philadelphia, PA 19104-6398, USA.
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Lenaz G, Baracca A, Fato R, Genova ML, Solaini G. New insights into structure and function of mitochondria and their role in aging and disease. Antioxid Redox Signal 2006; 8:417-37. [PMID: 16677088 DOI: 10.1089/ars.2006.8.417] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This review covers some novel findings on mitochondrial biochemistry and discusses diseases due to mitochondrial DNA mutations as a model of the changes occurring during physiological aging. The random collision model of organization of the mitochondrial respiratory chain has been recently challenged on the basis of findings of supramolecular organization of respiratory chain complexes. The source of superoxide in Complex I is discussed on the basis of laboratory experiments using a series of specific inhibitors and is presumably iron sulfur center N2. Maternally inherited diseases due to mutations of structural genes in mitochondrial DNA are surveyed as a model of alterations mimicking those occurring during normal aging. The molecular defects in senescence are surveyed on the basis of the "Mitochondrial Theory of Aging", establishing mitochondrial DNA somatic mutations, caused by accumulation of oxygen radical damage, to be at the basis of cellular senescence. Mitochondrial production of reactive oxygen species increases with aging and mitochondrial DNA mutations and deletions accumulate and may be responsible for oxidative phosphorylation defects. Evidence is presented favoring the mitochondrial theory, with primary mitochondrial alterations, although the problem is made more complex by changes in the cross-talk between nuclear and mitochondrial DNA.
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Affiliation(s)
- Giorgio Lenaz
- Dipartimento di Biochimica, Università di Bologna, Bologna, Italy.
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11
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Pulkes T, Liolitsa D, Eunson LH, Rose M, Nelson IP, Rahman S, Poulton J, Marchington DR, Landon DN, Debono AG, Morgan-Hughes JA, Hanna MG. New phenotypic diversity associated with the mitochondrial tRNA(SerUCN) gene mutation. Neuromuscul Disord 2005; 15:364-71. [PMID: 15833431 DOI: 10.1016/j.nmd.2005.01.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Revised: 01/15/2005] [Accepted: 01/21/2005] [Indexed: 01/29/2023]
Abstract
We performed detailed clinical, histopathological, biochemical, in vitro translation and molecular genetic analysis in patients from two unrelated families harbouring the tRNA(SerUCN) 7472C-insertion mutation. Proband 1 developed a progressive neurodegenerative phenotype characterised by myoclonus, epilepsy, cerebellar ataxia and progressive hearing loss. Proband 2 had a comparatively benign phenotype characterised by isolated myopathy with exercise intolerance. Both patients had the 7472C-insertion mutation in identical proportions and they exhibited a similar muscle biochemical and histopathological phenotype. However, proband 2 also had a previously unreported homoplasmic A to C transition at nucleotide position 7472 in the tRNA(SerUCN) gene. This change lengthens further the homopolymeric C run already expanded by the 7472C-insertion. These data extend the phenotypic range associated with the 7472C-insertion to include isolated skeletal myopathy, as well as a MERRF-like phenotype.
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MESH Headings
- Adolescent
- Adult
- DNA Mutational Analysis/methods
- DNA, Mitochondrial/genetics
- Electron Transport Complex IV/metabolism
- Electrophoresis/methods
- Female
- Humans
- Male
- Microscopy, Electron, Transmission/methods
- Mitochondria, Muscle/pathology
- Mitochondrial Encephalomyopathies/enzymology
- Mitochondrial Encephalomyopathies/genetics
- Mitochondrial Encephalomyopathies/pathology
- Mitochondrial Encephalomyopathies/physiopathology
- Mitochondrial Proteins/metabolism
- Muscle, Skeletal/enzymology
- Muscle, Skeletal/pathology
- Muscle, Skeletal/ultrastructure
- Mutation
- Nucleic Acid Conformation
- Phenotype
- RNA, Transfer, Ser/chemistry
- RNA, Transfer, Ser/genetics
- Serine/metabolism
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Affiliation(s)
- T Pulkes
- Centre for Neuromuscular Disease, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
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12
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Taylor RD, Pfanner N. The protein import and assembly machinery of the mitochondrial outer membrane. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2004; 1658:37-43. [PMID: 15282172 DOI: 10.1016/j.bbabio.2004.04.017] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2004] [Accepted: 04/19/2004] [Indexed: 12/21/2022]
Abstract
The process of mitochondrial protein import has been studied for many years. Despite this attention, many processes associated with mitochondrial biogenesis are poorly understood. Insight into one of these processes, assembly of beta-barrel proteins into the mitochondrial outer membrane, will be discussed. This review focuses on recent data that suggest that assembly of beta-barrel proteins into the outer mitochondrial membrane is dependent on a newly identified protein complex termed the sorting and assembly machinery (SAM complex). Members of the SAM complex have been identified in both eukaryotic and prokaryotic organisms, suggesting that the process of beta-barrel assembly into membranes has been conserved through evolution.
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Affiliation(s)
- Rebecca D Taylor
- Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany
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13
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Gellerich FN, Trumbeckaite S, Müller T, Deschauer M, Chen Y, Gizatullina Z, Zierz S. Energetic depression caused by mitochondrial dysfunction. Mol Cell Biochem 2004; 256-257:391-405. [PMID: 14977198 DOI: 10.1023/b:mcbi.0000009885.34498.e6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Mitochondria, providing most of ATP needed for cell work, realizing numerous specific functions as biosyntheses or degradations, contributing to Ca2+ signalling also play a key role in the pathways to cell death. Impairment of mitochondrial functions caused by mutations of mt-genome and by acute processes are responsible for numerous diseases. The relations between changes on the level of molecules and the clinical state are rather complex, and the prediction of thresholds is difficult. Therefore investigations on different levels of an organismus (genome, metabolites, enzymes, mitochondrial function in vivo and in vitro) are necessary (multi level approach). Metabolic control theory is a valuable tool for understanding the different effects of mutations on the level of enzyme activities and mitochondrial function. Decreased concentrations of adenine nucleotides, leaky outer and inner mitochondrial membranes, decreased rates of mitochondrial linked pathways and decreased activities of respiratory chain enzymes contribute to depression of cellular energy metabolism characterized by decreased cytosolic phosphorylation potentials as one of the most important consequences of mitochondrial impairments. This review regards classical bioenergetic mechanisms of mitochondrial impairment which contribute to energetic depression.
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Affiliation(s)
- Frank Norbert Gellerich
- Muskellabor der Neurologischen Klinik, Martin-Luther-Universität Halle-Wittenberg, Halle/Saale, Germany.
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14
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Lenaz G, Baracca A, Carelli V, D'Aurelio M, Sgarbi G, Solaini G. Bioenergetics of mitochondrial diseases associated with mtDNA mutations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2004; 1658:89-94. [PMID: 15282179 DOI: 10.1016/j.bbabio.2004.03.013] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2004] [Revised: 03/22/2004] [Accepted: 03/22/2004] [Indexed: 11/18/2022]
Abstract
This mini-review summarizes our present view of the biochemical alterations associated with mitochondrial DNA (mtDNA) point mutations. Mitochondrial cytopathies caused by mutations of mtDNA are well-known genetic and clinical entities, but the biochemical pathogenic mechanisms are often obscure. Leber's hereditary optic neuropathy (LHON) is due to three main mutations in genes for complex I subunits. Even if the catalytic activity of complex I is maintained except in cells carrying the 3460/ND1 mutation, in all cases there is a change in sensitivity to complex I inhibitors and an impairment of mitochondrial respiration, eliciting the possibility of generation of reactive oxygen species (ROS) by the complex. Neurogenic muscle weakness, Ataxia and Retinitis Pigmentosa (NARP), is due to a mutation in the ATPase-6 gene. In NARP patients ATP synthesis is strongly depressed to an extent proportional to the mutation load; nevertheless, ATP hydrolysis and ATP-driven proton translocation are not affected. It is suggested that the NARP mutation affects the ability of the enzyme to couple proton transport to ATP synthesis. A point mutation in subunit III of cytochrome c oxidase is accompanied by a syndrome resembling MELAS: however, no major biochemical defect is found, if we except an enhanced production of ROS. The mechanism of such enhancement is at present unknown. In this review, we draw attention to a few examples in which the overproduction of ROS might represent a common step in the induction of clinical phenotypes and/or in the progression of several human pathologies associated with mtDNA point mutations.
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Affiliation(s)
- Giorgio Lenaz
- Dipartimento di Biochimica G. Moruzzi, Università di Bologna, Via Irnerio 48, Bologna 40126, Italy
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Senoo-Matsuda N, Hartman PS, Akatsuka A, Yoshimura S, Ishii N. A complex II defect affects mitochondrial structure, leading to ced-3- and ced-4-dependent apoptosis and aging. J Biol Chem 2003; 278:22031-6. [PMID: 12672828 DOI: 10.1074/jbc.m211377200] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mev-1(kn1) mutation of Caenorhabditis elegans is in Cyt-1, which encodes a subunit of succinate-coenzyme Q oxidoreductase in the mitochondrial electron transport chain. Mutants are hypersensitive to oxidative stress and age precociously in part because of increased superoxide anion production. Here, we show that mev-1 mutants are defective in succinate-coenzyme Q oxidoreductase, possess ultrastructural mitochondrial abnormalities (especially in muscle cells), show a loss of membrane potential, have altered CED-9 and Cyt-1 protein levels under hyperoxia, and contain ced-3-and ced-4-dependent supernumerary apoptotic cells. These defects likely explain the failure of mev-1 to complete embryonic development under hyperoxia as well as its reduced life span.
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Affiliation(s)
- Nanami Senoo-Matsuda
- Department of Molecular Life Science, Tokai University School of Medicine, Isehara, Kanagawa 259-1193, Japan
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16
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Liolitsa D, Hanna MG. Models of mitochondrial disease. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2003; 53:429-66. [PMID: 12512349 DOI: 10.1016/s0074-7742(02)53016-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Danae Liolitsa
- Centre for Neuromuscular Disease, Institute of Neurology, Queen Square, London, WC1N 3BG, United Kingdom
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17
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Gellerich FN, Deschauer M, Chen Y, Müller T, Neudecker S, Zierz S. Mitochondrial respiratory rates and activities of respiratory chain complexes correlate linearly with heteroplasmy of deleted mtDNA without threshold and independently of deletion size. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1556:41-52. [PMID: 12351217 DOI: 10.1016/s0005-2728(02)00305-5] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To clarify the importance of deleted protein and tRNA genes on the impairment of mitochondrial function, we performed a quantitative analysis of biochemical, genetic and morphological findings in skeletal muscles of 16 patients with single deletions and 5 patients with multiple deletions of mtDNA. Clinically, all patients showed chronic progressive external ophthalmoplegia (CPEO). The size of deletions varied between 2.5 and 9 kb, and heteroplasmy between 31% and 94%. In patients with single deletions, the citrate synthase (CS) activity was nearly doubled. Decreased ratios of pyruvate- and succinate-dependent respiration were detected in fibers of all patients in comparison to controls. Inverse and linear correlations without thresholds were established between heteroplasmy and (i) CS referenced activities of the complexes of respiratory chain, (ii) CS referenced maximal respiratory rates, (iii) and cytochrome-c-oxidase (COX) negative fibers. In patients with single and multiple deletions, all respiratory chain complexes as well as the respiratory rates were decreased to a similar extent. All changes detected in patients with single deletions were independent of deletion size. In one patient, only genes of ND5, ND4L as well as tRNA(Leu(CUN)), tRNA(Ser(AGY)), and tRNA(His) were deleted. The pronounced decrease in COX activity in this patient points to the high pathological impact of these missing tRNA genes. The activity of nuclear encoded SDH was also significantly decreased in patients, but to a lesser extent. This is an indication of secondary disturbances of mitochondria at CPEO. In conclusion, we have shown that different deletions cause mitochondrial impairments of the same phenotype correlating with heteroplasmy. The missing threshold at the level of mitochondrial function seems to be characteristic for large-scale deletions were tRNA and protein genes are deleted.
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Affiliation(s)
- Frank Norbert Gellerich
- Muskellabor der Neurologischen Klinik der Martin-Luther-Universität Halle-Wittenb., Julius-Kühn-Strasse 7, D-06079, Halle an der Saale, Germany.
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18
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Biomedical vignette. J Biomed Sci 2002. [DOI: 10.1007/bf02254974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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19
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Funalot B, Reynier P, Vighetto A, Ranoux D, Bonnefont JP, Godinot C, Malthièry Y, Mas JL. Leigh-like encephalopathy complicating Leber's hereditary optic neuropathy. Ann Neurol 2002; 52:374-7. [PMID: 12205655 DOI: 10.1002/ana.10299] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Leber's hereditary optic neuropathy is a mitochondrial disease caused by point mutations in mitochondrial DNA. It usually presents as severe bilateral visual loss in young adults. We report on a neurological disorder resembling Leigh syndrome, which complicated Leber's hereditary optic neuropathy in three unrelated male patients harboring mitochondrial DNA mutations at nucleotide positions 3460, 14459, and 14484, respectively. This Leigh-like encephalopathy appears to be associated with a much more severe outcome than isolated Leber's hereditary optic neuropathy.
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Affiliation(s)
- Benoît Funalot
- Service de Neurologie, Hôpital Sainte-Anne, Paris, France.
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20
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Thorburn DR, Dahl HH. Mitochondrial disorders: genetics, counseling, prenatal diagnosis and reproductive options. AMERICAN JOURNAL OF MEDICAL GENETICS 2002; 106:102-14. [PMID: 11579429 DOI: 10.1002/ajmg.1380] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Most patients with mitochondrial disorders are diagnosed by finding a respiratory chain enzyme defect or a mutation in the mitochondrial DNA (mtDNA). The provision of accurate genetic counseling and reproductive options to these families is complicated by the unique genetic features of mtDNA that distinguish it from Mendelian genetics. These include maternal inheritance, heteroplasmy, the threshold effect, the mitochondrial bottleneck, tissue variation, and selection. Although we still have much to learn about mtDNA genetics, it is now possible to provide useful guidance to families with an mtDNA mutation or a respiratory chain enzyme defect. We describe a range of current reproductive options that may be considered for prevention of transmission of mtDNA mutations, including the use of donor oocytes, prenatal diagnosis (by chorionic villus sampling or amniocentesis), and preimplantation genetic diagnosis, plus possible future options such as nuclear transfer and cytoplasmic transfer. For common mtDNA mutations associated with mitochondrial cytopathies (such as NARP, Leigh Disease, MELAS, MERRF, Leber's Hereditary Optic Neuropathy, CPEO, Kearns-Sayre syndrome, and Pearson syndrome), we summarize the available data on recurrence risk and discuss the relative advantages and disadvantages of reproductive options.
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Affiliation(s)
- D R Thorburn
- Mitochondrial Research Laboratory, Murdoch Children's Research Institute, Parkville, Victoria, Australia.
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Hsieh RH, Li JY, Pang CY, Wei YH. A novel mutation in the mitochondrial 16S rRNA gene in a patient with MELAS syndrome, diabetes mellitus, hyperthyroidism and cardiomyopathy. J Biomed Sci 2001; 8:328-35. [PMID: 11455195 DOI: 10.1007/bf02258374] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Using RNase protection analysis, we found a novel C to G mutation at nucleotide position 3093 of mitochondrial DNA (mtDNA) in a previously reported 35-year-old woman exhibiting clinical features of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome together with diabetes mellitus, hyperthyroidism and cardiomyopathy. The patient also had an A3243G mutation in the tRNA(Leu(UUR)) gene and a 260-base pair duplication in the D-loop of mtDNA. The fibroblasts of the patient were cultured and used for the construction of cybrids using cytoplasmic transfer of the patient's mtDNA to the mtDNA-less rho(0) cells. RNA isolated from the cybrids was subjected to RNase protection analysis, and a C3093G transversion at the 16S rRNA gene and a MELAS-associated A3243G mutation of mtDNA were detected. The novel C3093G mutation together with the A3243G transition were found in muscle biopsies, hair follicles and blood cells of this patient and also in her skin fibroblasts and cybrids. The proportion of the C3093G mutant mtDNA in muscle biopsies of the patient was 51%. In contrast, the mutation was not detected in three sons of the proband. To characterize the impact of the mtDNA mutation-associated defects on mitochondrial function, we determined the respiratory enzyme activities of the primary culture of fibroblasts established from the proband, her mother and her three sons. The proportions of mtDNA with the C3093G transversion and the A3243G transition in the fibroblasts of the proband were 45 and 58%, respectively. However, the fibroblasts of the proband's mother and children harbored lower levels of mtDNA with the A3243G mutation but did not contain the C3093G mutation. The complex I activity in the proband's fibroblasts was decreased to 47% of the control but those of the fibroblasts of the mother and three sons of the proband were not significantly changed. These findings suggest that the C3093G transversion together with the A3243G transition of mtDNA impaired the respiratory function of mitochondria and caused the atypical MELAS syndrome associated with diabetes mellitus, hyperthyroidism and cardiomyopathy in this patient.
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Affiliation(s)
- R H Hsieh
- Department of Biochemistry and Center for Cellular and Molecular Biology, School of Life Science, National Yang-Ming University, Taipei, Taiwan, ROC
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Kunz WS, Kudin A, Vielhaber S, Elger CE, Attardi G, Villani G. Flux control of cytochrome c oxidase in human skeletal muscle. J Biol Chem 2000; 275:27741-5. [PMID: 10869362 DOI: 10.1074/jbc.m004833200] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
In the present work, by titrating cytochrome c oxidase (COX) with the specific inhibitor KCN, the flux control coefficient and the metabolic reserve capacity of COX have been determined in human saponin-permeabilized muscle fibers. In the presence of the substrates glutamate and malate, a 2.3 +/- 0.2-fold excess capacity of COX was observed in ADP-stimulated human skeletal muscle fibers. This value was found to be dependent on the mitochondrial substrate supply. In the combined presence of glutamate, malate, and succinate, which supported an approximately 1.4-fold higher rate of respiration, only a 1.4 +/- 0.2-fold excess capacity of COX was determined. In agreement with these findings, the flux control of COX increased, in the presence of the three substrates, from 0.27 +/- 0.03 to 0.36 +/- 0.08. These results indicate a tight in vivo control of respiration by COX in human skeletal muscle. This tight control may have significant implications for mitochondrial myopathies. In support of this conclusion, the analysis of skeletal muscle fibers from two patients with chronic progressive external ophthalmoplegia, which carried deletions in 11 and 49% of their mitochondrial DNA, revealed a substantially lowered reserve capacity and increased flux control coefficient of COX, indicating severe rate limitations of oxidative phosphorylation by this enzyme.
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MESH Headings
- Adenosine Diphosphate/metabolism
- Adult
- Blotting, Southern
- Cell Membrane Permeability
- DNA, Mitochondrial/genetics
- Electron Transport Complex IV/antagonists & inhibitors
- Electron Transport Complex IV/genetics
- Electron Transport Complex IV/metabolism
- Humans
- Kinetics
- Middle Aged
- Mitochondria, Muscle/enzymology
- Mitochondrial Myopathies/enzymology
- Muscle Fibers, Skeletal/enzymology
- Muscle Fibers, Skeletal/pathology
- Muscle, Skeletal/enzymology
- Muscle, Skeletal/pathology
- Ophthalmoplegia, Chronic Progressive External/enzymology
- Ophthalmoplegia, Chronic Progressive External/genetics
- Ophthalmoplegia, Chronic Progressive External/pathology
- Oxygen Consumption/drug effects
- Potassium Cyanide/pharmacology
- Sequence Deletion
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Affiliation(s)
- W S Kunz
- Department of Epileptology, University Bonn Medical Center, Sigmund-Freud-Strasse 25, D-53105 Bonn, Germany.
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Schröder R, Vielhaber S, Wiedemann FR, Kornblum C, Papassotiropoulos A, Broich P, Zierz S, Elger CE, Reichmann H, Seibel P, Klockgether T, Kunz WS. New insights into the metabolic consequences of large-scale mtDNA deletions: a quantitative analysis of biochemical, morphological, and genetic findings in human skeletal muscle. J Neuropathol Exp Neurol 2000; 59:353-60. [PMID: 10888364 DOI: 10.1093/jnen/59.5.353] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In order to study putative genotype phenotype correlations in mitochondrial disorders due to large-scale mtDNA deletions we performed a quantitative analysis of biochemical, morphological, and genetic findings in 20 patients. The size of the mtDNA deletions varied from 2 to 7.5 kb with a degree of heteroplasmy ranging from 16% to 78%. Applying improved methods for measuring respiratory chain enzyme activities, we found highly significant inverse correlations between the percentage of cytochrome c oxidase (COX)- negative fibers and citrate synthase (CS) normalized COX ratios. Significant correlations were also established between CS normalized complex I and complex IV ratios as well as between the degree of heteroplasmy of mtDNA deletions and the percentage of ragged red fibers, COX-negative fibers, and CS normalized complex I and complex IV ratios. Our results indicate that the degree of heteroplasmy of mtDNA deletions is mirrored on the histological as well as the biochemical level. Furthermore, our findings suggest that single large-scale deletions equally influence the activities of all mitochondrially encoded respiratory chain enzymes. Even low degrees of heteroplasmy of mtDNA deletions were found to result in biochemical abnormalities indicating the absence of any well-defined mtDNA deletion threshold in skeletal muscle.
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MESH Headings
- Adolescent
- Adult
- DNA, Mitochondrial/genetics
- Electron Transport Complex IV/metabolism
- Female
- Gene Deletion
- Humans
- Kearns-Sayre Syndrome/genetics
- Kearns-Sayre Syndrome/metabolism
- Kearns-Sayre Syndrome/pathology
- Kearns-Sayre Syndrome/physiopathology
- Male
- Middle Aged
- Mitochondria, Muscle/genetics
- Mitochondrial Myopathies/enzymology
- Mitochondrial Myopathies/genetics
- Mitochondrial Myopathies/pathology
- Mitochondrial Myopathies/physiopathology
- Muscle Fibers, Skeletal/pathology
- Muscle, Skeletal/enzymology
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Ophthalmoplegia, Chronic Progressive External/enzymology
- Ophthalmoplegia, Chronic Progressive External/genetics
- Ophthalmoplegia, Chronic Progressive External/pathology
- Ophthalmoplegia, Chronic Progressive External/physiopathology
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Affiliation(s)
- R Schröder
- Department of Neurology, University Bonn Medical Center, Germany
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Wiedemann FR, Vielhaber S, Schröder R, Elger CE, Kunz WS. Evaluation of methods for the determination of mitochondrial respiratory chain enzyme activities in human skeletal muscle samples. Anal Biochem 2000; 279:55-60. [PMID: 10683230 DOI: 10.1006/abio.1999.4434] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The quantification of mitochondrial enzyme activities in skeletal muscle samples of patients suspected of having mitochondrial myopathies is problematic. Therefore, we have evaluated different methods for the determination of activities cytochrome c oxidase and NADH:CoQ oxidoreductase in human skeletal muscle samples. The measurement of cytochrome c oxidase activity in the presence of 200 microM ferrocytochrome c and the detection of NADH:CoQ oxidoreductase as rotenone-sensitive NADH:CoQ(1) reductase resulted in comparable citrate synthase-normalized respiratory chain enzyme activities of both isolated mitochondria and homogenates from control human skeletal muscle samples. These methods allowed the precise detection of deficiencies of respiratory chain enzymes in skeletal muscle of two patients harboring only 20 and 27% of deleted mitochondrial DNA, respectively. Therefore, citrate synthase-normalized respiratory chain activities can serve as stable reference values for the determination of a putative mitochondrial defect in human skeletal muscle.
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Affiliation(s)
- F R Wiedemann
- Department of Epileptology, Department of Neurology, University Bonn Medical Center, Sigmund-Freud-Strasse 25, Bonn, D-53105, Germany
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Melov S, Schneider JA, Coskun PE, Bennett DA, Wallace DC. Mitochondrial DNA rearrangements in aging human brain and in situ PCR of mtDNA. Neurobiol Aging 1999; 20:565-71. [PMID: 10638530 DOI: 10.1016/s0197-4580(99)00092-5] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Deletions of the mitochondrial DNA (mtDNA) have been shown to accumulate with age in a variety of species regardless of mean or maximal life span. This implies that such mutations are either a molecular biomarker of senescence or that they are more causally linked to senescence itself. One assay that can be used to detect these mtDNA mutations is the long-extension polymerase chain reaction assay. This assay amplifies approximately 16 kb of the mtDNA in mammalian mitochondria and preferentially amplifies mtDNAs that are either deleted or duplicated. We have applied this assay to the aging human brain and found a heterogeneous array of rearranged mtDNAs. In addition, we have developed in situ polymerase chain reaction to detect mtDNA within individual cells of both the mouse and the human brain as a first step in identifying and enumerating cells containing mutant mtDNAs in situ.
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Affiliation(s)
- S Melov
- Center For Molecular Medicine, Emory University, Atlanta, GA 30322, USA.
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26
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Affiliation(s)
- H Cock
- University Department of Clinical Neurosciences, Royal Free and University College School of Medicine, London, England, UK
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