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Yamamoto S, Kanca O, Wangler MF, Bellen HJ. Integrating non-mammalian model organisms in the diagnosis of rare genetic diseases in humans. Nat Rev Genet 2024; 25:46-60. [PMID: 37491400 DOI: 10.1038/s41576-023-00633-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2023] [Indexed: 07/27/2023]
Abstract
Next-generation sequencing technology has rapidly accelerated the discovery of genetic variants of interest in individuals with rare diseases. However, showing that these variants are causative of the disease in question is complex and may require functional studies. Use of non-mammalian model organisms - mainly fruitflies (Drosophila melanogaster), nematode worms (Caenorhabditis elegans) and zebrafish (Danio rerio) - enables the rapid and cost-effective assessment of the effects of gene variants, which can then be validated in mammalian model organisms such as mice and in human cells. By probing mechanisms of gene action and identifying interacting genes and proteins in vivo, recent studies in these non-mammalian model organisms have facilitated the diagnosis of numerous genetic diseases and have enabled the screening and identification of therapeutic options for patients. Studies in non-mammalian model organisms have also shown that the biological processes underlying rare diseases can provide insight into more common mechanisms of disease and the biological functions of genes. Here, we discuss the opportunities afforded by non-mammalian model organisms, focusing on flies, worms and fish, and provide examples of their use in the diagnosis of rare genetic diseases.
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Affiliation(s)
- Shinya Yamamoto
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Oguz Kanca
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX, USA
| | - Michael F Wangler
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX, USA.
| | - Hugo J Bellen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX, USA.
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.
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2
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Singh V, Sharma RK, Athilingam T, Sinha P, Sinha N, Thakur AK. NMR Spectroscopy-based Metabolomics of Drosophila Model of Huntington's Disease Suggests Altered Cell Energetics. J Proteome Res 2017; 16:3863-3872. [PMID: 28871787 DOI: 10.1021/acs.jproteome.7b00491] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Huntington's disease (HD) is a neurodegenerative disorder induced by aggregation of the pathological form of Huntingtin protein that has expanded polyglutamine (polyQ) repeats. In the Drosophila model, for instance, expression of transgenes with polyQ repeats induces HD-like pathologies, progressively correlating with the increasing lengths of these repeats. Previous studies on both animal models and clinical samples have revealed metabolite imbalances during HD progression. To further explore the physiological processes linked to metabolite imbalances during HD, we have investigated the 1D 1H NMR spectroscopy-based metabolomics profile of Drosophila HD model. Using multivariate analysis (PCA and PLS-DA) of metabolites obtained from methanolic extracts of fly heads displaying retinal deformations due to polyQ overexpression, we show that the metabolite imbalance during HD is likely to affect cell energetics. Six out of the 35 metabolites analyzed, namely, nicotinamide adenine dinucleotide (NAD), lactate, pyruvate, succinate, sarcosine, and acetoin, displayed segregation with progressive severity of HD. Specifically, HD progression was seen to be associated with reduction in NAD and increase in lactate-to-pyruvate ratio. Furthermore, comparative analysis of fly HD metabolome with those of mouse HD model and HD human patients revealed comparable metabolite imbalances, suggesting altered cellular energy homeostasis. These findings thus raise the possibility of therapeutic interventions for HD via modulation of cellular energetics.
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Affiliation(s)
- Virender Singh
- Biological Science and Bioengineering, Indian Institute of Technology Kanpur , Kanpur 208016, India
| | - Raj Kumar Sharma
- Centre of Biomedical Research, SGPGIMS Campus , Lucknow 226014, India
| | | | - Pradip Sinha
- Biological Science and Bioengineering, Indian Institute of Technology Kanpur , Kanpur 208016, India
| | - Neeraj Sinha
- Centre of Biomedical Research, SGPGIMS Campus , Lucknow 226014, India
| | - Ashwani Kumar Thakur
- Biological Science and Bioengineering, Indian Institute of Technology Kanpur , Kanpur 208016, India
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3
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Guarani V, Jardel C, Chrétien D, Lombès A, Bénit P, Labasse C, Lacène E, Bourillon A, Imbard A, Benoist JF, Dorboz I, Gilleron M, Goetzman ES, Gaignard P, Slama A, Elmaleh-Bergès M, Romero NB, Rustin P, Ogier de Baulny H, Paulo JA, Harper JW, Schiff M. QIL1 mutation causes MICOS disassembly and early onset fatal mitochondrial encephalopathy with liver disease. eLife 2016; 5. [PMID: 27623147 PMCID: PMC5021520 DOI: 10.7554/elife.17163] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 08/24/2016] [Indexed: 12/16/2022] Open
Abstract
Previously, we identified QIL1 as a subunit of mitochondrial contact site (MICOS) complex and demonstrated a role for QIL1 in MICOS assembly, mitochondrial respiration, and cristae formation critical for mitochondrial architecture (Guarani et al., 2015). Here, we identify QIL1 null alleles in two siblings displaying multiple clinical symptoms of early-onset fatal mitochondrial encephalopathy with liver disease, including defects in respiratory chain function in patient muscle. QIL1 absence in patients' fibroblasts was associated with MICOS disassembly, abnormal cristae, mild cytochrome c oxidase defect, and sensitivity to glucose withdrawal. QIL1 expression rescued cristae defects, and promoted re-accumulation of MICOS subunits to facilitate MICOS assembly. MICOS assembly and cristae morphology were not efficiently rescued by over-expression of other MICOS subunits in patient fibroblasts. Taken together, these data provide the first evidence of altered MICOS assembly linked with a human mitochondrial disease and confirm a central role for QIL1 in stable MICOS complex formation.
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Affiliation(s)
- Virginia Guarani
- Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Claude Jardel
- Inserm U1016, Institut Cochin, CNRS UMR 8104, Paris, France.,Department of Biochemistry, APHP, GHU Pitié-Salpêtrière, Paris, France.,Université Paris-Descartes, Paris, France
| | - Dominique Chrétien
- UMR1141, PROTECT, INSERM, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
| | - Anne Lombès
- Inserm U1016, Institut Cochin, CNRS UMR 8104, Paris, France.,Department of Biochemistry, APHP, GHU Pitié-Salpêtrière, Paris, France.,Université Paris-Descartes, Paris, France
| | - Paule Bénit
- UMR1141, PROTECT, INSERM, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
| | - Clémence Labasse
- Neuromuscular morphology unit, Institut de Myologie, GHU Pitié-Salpêtrière, APHP, Paris, France
| | - Emmanuelle Lacène
- Neuromuscular morphology unit, Institut de Myologie, GHU Pitié-Salpêtrière, APHP, Paris, France
| | - Agnès Bourillon
- Department of Biochemistry, Hôpital Robert Debré, APHP, Paris, France
| | - Apolline Imbard
- Department of Biochemistry, Hôpital Robert Debré, APHP, Paris, France
| | | | - Imen Dorboz
- UMR1141, PROTECT, INSERM, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
| | - Mylène Gilleron
- Inserm U1016, Institut Cochin, CNRS UMR 8104, Paris, France.,Department of Biochemistry, APHP, GHU Pitié-Salpêtrière, Paris, France.,Université Paris-Descartes, Paris, France
| | - Eric S Goetzman
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, United States.,University of Pittsburgh, Pittsburgh, United States.,Children's Hospital of Pittsburgh of UPMC, Pittsburgh, United States
| | - Pauline Gaignard
- Department of Biochemistry, Hôpital Bicêtre, APHP, Paris, France
| | - Abdelhamid Slama
- Department of Biochemistry, Hôpital Bicêtre, APHP, Paris, France
| | | | - Norma B Romero
- Neuromuscular morphology unit, Institut de Myologie, GHU Pitié-Salpêtrière, APHP, Paris, France
| | - Pierre Rustin
- UMR1141, PROTECT, INSERM, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France
| | - Hélène Ogier de Baulny
- Reference Center for Inborn Errors of Metabolism, Robert Debré University Hospital, APHP, Paris, France
| | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, Boston, United States
| | - J Wade Harper
- Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Manuel Schiff
- UMR1141, PROTECT, INSERM, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France.,Reference Center for Inborn Errors of Metabolism, Robert Debré University Hospital, APHP, Paris, France
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4
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Kanabus M, Heales SJ, Rahman S. Development of pharmacological strategies for mitochondrial disorders. Br J Pharmacol 2014; 171:1798-817. [PMID: 24116962 PMCID: PMC3976606 DOI: 10.1111/bph.12456] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 09/21/2013] [Accepted: 09/26/2013] [Indexed: 01/19/2023] Open
Abstract
Mitochondrial diseases are an unusually genetically and phenotypically heterogeneous group of disorders, which are extremely challenging to treat. Currently, apart from supportive therapy, there are no effective treatments for the vast majority of mitochondrial diseases. Huge scientific effort, however, is being put into understanding the mechanisms underlying mitochondrial disease pathology and developing potential treatments. To date, a variety of treatments have been evaluated by randomized clinical trials, but unfortunately, none of these has delivered breakthrough results. Increased understanding of mitochondrial pathways and the development of many animal models, some of which are accurate phenocopies of human diseases, are facilitating the discovery and evaluation of novel prospective treatments. Targeting reactive oxygen species has been a treatment of interest for many years; however, only in recent years has it been possible to direct antioxidant delivery specifically into the mitochondria. Increasing mitochondrial biogenesis, whether by pharmacological approaches, dietary manipulation or exercise therapy, is also currently an active area of research. Modulating mitochondrial dynamics and mitophagy and the mitochondrial membrane lipid milieu have also emerged as possible treatment strategies. Recent technological advances in gene therapy, including allotopic and transkingdom gene expression and mitochondrially targeted transcription activator-like nucleases, have led to promising results in cell and animal models of mitochondrial diseases, but most of these techniques are still far from clinical application.
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Affiliation(s)
- M Kanabus
- Clinical and Molecular Genetics Unit, UCL Institute of Child Health, London, UK
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5
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Vernau KM, Runstadler JA, Brown EA, Cameron JM, Huson HJ, Higgins RJ, Ackerley C, Sturges BK, Dickinson PJ, Puschner B, Giulivi C, Shelton GD, Robinson BH, DiMauro S, Bollen AW, Bannasch DL. Genome-wide association analysis identifies a mutation in the thiamine transporter 2 (SLC19A3) gene associated with Alaskan Husky encephalopathy. PLoS One 2013; 8:e57195. [PMID: 23469184 PMCID: PMC3587633 DOI: 10.1371/journal.pone.0057195] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 01/18/2013] [Indexed: 11/28/2022] Open
Abstract
Alaskan Husky Encephalopathy (AHE) has been previously proposed as a mitochondrial encephalopathy based on neuropathological similarities with human Leigh Syndrome (LS). We studied 11 Alaskan Husky dogs with AHE, but found no abnormalities in respiratory chain enzyme activities in muscle and liver, or mutations in mitochondrial or nuclear genes that cause LS in people. A genome wide association study was performed using eight of the affected dogs and 20 related but unaffected control AHs using the Illumina canine HD array. SLC19A3 was identified as a positional candidate gene. This gene controls the uptake of thiamine in the CNS via expression of the thiamine transporter protein THTR2. Dogs have two copies of this gene located within the candidate interval (SLC19A3.2 – 43.36–43.38 Mb and SLC19A3.1 – 43.411–43.419 Mb) on chromosome 25. Expression analysis in a normal dog revealed that one of the paralogs, SLC19A3.1, was expressed in the brain and spinal cord while the other was not. Subsequent exon sequencing of SLC19A3.1 revealed a 4bp insertion and SNP in the second exon that is predicted to result in a functional protein truncation of 279 amino acids (c.624 insTTGC, c.625 C>A). All dogs with AHE were homozygous for this mutation, 15/41 healthy AH control dogs were heterozygous carriers while 26/41 normal healthy AH dogs were wild type. Furthermore, this mutation was not detected in another 187 dogs of different breeds. These results suggest that this mutation in SLC19A3.1, encoding a thiamine transporter protein, plays a critical role in the pathogenesis of AHE.
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Affiliation(s)
- Karen M Vernau
- University of California Davis, Davis, California, United States of America.
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Siriwardena K, Mackay N, Levandovskiy V, Blaser S, Raiman J, Kantor PF, Ackerley C, Robinson BH, Schulze A, Cameron JM. Mitochondrial citrate synthase crystals: novel finding in Sengers syndrome caused by acylglycerol kinase (AGK) mutations. Mol Genet Metab 2013; 108:40-50. [PMID: 23266196 DOI: 10.1016/j.ymgme.2012.11.282] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Accepted: 11/24/2012] [Indexed: 11/16/2022]
Abstract
We report on two families with Sengers syndrome and mutations in the acylglycerol kinase gene (AGK). In the first family, two brothers presented with vascular strokes, lactic acidosis, cardiomyopathy and cataracts, abnormal muscle cell histopathology and mitochondrial function. One proband had very abnormal mitochondria with citrate synthase crystals visible in electron micrographs, associated with markedly high citrate synthase activity. Exome sequencing was used to identify mutations in the AGK gene in the index patient. Targeted sequencing confirmed the same homozygous mutation (c.3G>A, p.M1I) in the brother. The second family had four affected members, of which we examined two. They also presented with similar clinical symptoms, but no strokes. Postmortem heart and skeletal muscle tissues showed low complex I, III and IV activities in the heart, but normal in the muscle. Skin fibroblasts showed elevated lactate/pyruvate ratios and low complex I+III activity. Targeted sequencing led to identification of a homozygous c.979A>T, p.K327* mutation. AGK is located in the mitochondria and phosphorylates monoacylglycerol and diacylglycerol to lysophosphatidic acid and phosphatidic acid. Disruption of these signaling molecules affects the mitochondria's response to superoxide radicals, resulting in oxidative damage to mitochondrial DNA, lipids and proteins, and stimulation of cellular detoxification pathways. High levels of manganese superoxide dismutase protein were detected in all four affected individuals, consistent with increased free radical damage. Phosphatidic acid is also involved in the synthesis of phospholipids and its loss will result in changes to the lipid composition of the inner mitochondrial membrane. These effects manifest as cataract formation in the eye, respiratory chain dysfunction and cardiac hypertrophy in heart tissue. These two pedigrees confirm that mutation of AGK is responsible for the severe neonatal presentation of Sengers syndrome. The identification of citrate synthase precipitates by electron microscopy and the presence of vascular strokes in two siblings may expand the cellular and clinical phenotype of this disease.
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Affiliation(s)
- Komudi Siriwardena
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, ON, Canada M5G 1X8
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7
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LRPPRC mutation suppresses cytochrome oxidase activity by altering mitochondrial RNA transcript stability in a mouse model. Biochem J 2012; 441:275-83. [PMID: 21880015 DOI: 10.1042/bj20110985] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
LRPPRC (leucine-rich pentatricopeptide repeat-containing) has been shown to be essential for the maturation of COX (cytochrome c oxidase), possibly by stabilizing RNA transcripts of COXI, COXII and COXIII genes encoded in mtDNA (mitochondrial DNA). We established a mouse 'gene-trap' model using ES cells (embryonic stem cells) in which the C-terminus of LRPPRC has been replaced with a β-geo construct. Mice homozygous for this modification were found to be subject to embryonic lethality, with death before 12.5 dpc (days post-coitum). Biochemical analysis of MEFs (mouse embryonic fibroblasts) isolated from homozygous mutants showed a major decrease in COX activity, with slight reductions in other respiratory chain complexes with mtDNA encoded components. Constructs of LRPPRC containing different numbers of PPRs (pentatricopeptide repeats) were expressed as recombinant proteins and tested for their ability to bind to the COXI mRNA transcript. Full binding required the first 19 PPR motifs. A specific segment of COXI mRNA was identified as the binding target for LRPPRC, encoded by mouse mtDNA nucleotides 5961-6020. These data strongly suggest that LRPPRC is involved in the maturation of COX, and is involved in stabilizing of mitochondrial mRNAs encoding COX transcripts.
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8
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Maj M, Sriskandarajah N, Hung V, Browne I, Shah B, Weadge A, Jamieson NL, Tropak M, Cameron JM, Addis JB, Robinson BH. Identification of drug candidates which increase cytochrome c oxidase activity in deficient patient fibroblasts. Mitochondrion 2010; 11:264-72. [PMID: 21050896 DOI: 10.1016/j.mito.2010.10.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Revised: 10/21/2010] [Accepted: 10/25/2010] [Indexed: 12/25/2022]
Abstract
Cytochrome c oxidase (COX) activity reflects the expressed level of respiratory chain complexes, mtDNA levels, titer and mass of mitochondria. Activity is also indicative of the overall fitness of mt-transcription factors and the import, transcription and translation of mt-proteins. We have developed a high-throughput assay to measure COX activity using live cells to screen chemical libraries for compounds capable of increasing COX activity. These libraries have revealed four examples which elevated the activities of COX in NIH-3T3 fibroblasts and in fibroblasts from patients with COX defects independent of the peroxisome proliferator activated receptor family.
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Affiliation(s)
- Mary Maj
- Metabolism Research Programme, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
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Cameron JM, Levandovskiy V, Mackay N, Ackerley C, Chitayat D, Raiman J, Halliday WH, Schulze A, Robinson BH. Complex V TMEM70 deficiency results in mitochondrial nucleoid disorganization. Mitochondrion 2010; 11:191-9. [PMID: 20920610 DOI: 10.1016/j.mito.2010.09.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Revised: 08/23/2010] [Accepted: 09/22/2010] [Indexed: 10/19/2022]
Abstract
Mutations in the TMEM70 gene are responsible for a familial form of complex V deficiency presenting with 3-methylglutaconic aciduria, lactic acidosis, cardiomyopathy and mitochondrial myopathy. Here we present a case of TMEM70 deficiency due to compound heterozygous mutations, who displayed abnormal mitochondria with whorled cristae in muscle. Immunogold electron microscopy and tomography shows for the first time that nucleoid clusters of mtDNA are disrupted in the abnormal mitochondria, with both nucleoids and mitochondrial respiratory chain complexes confined to the outer rings of the whorls. This could explain the differential effects on the expression and assembly of complex V in different tissues.
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Affiliation(s)
- Jessie M Cameron
- Genetics and Genome Biology, The Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
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10
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Maj MC, Tkachyova I, Patel P, Addis JB, Mackay N, Levandovskiy V, Lee J, Lang AE, Cameron JM, Robinson BH. Oxidative stress alters the regulatory control of p66Shc and Akt in PINK1 deficient cells. Biochem Biophys Res Commun 2010; 399:331-5. [PMID: 20637729 DOI: 10.1016/j.bbrc.2010.07.033] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Accepted: 07/12/2010] [Indexed: 02/08/2023]
Abstract
Mitochondrial dysfunction is involved in the underlying pathology of Parkinson's Disease (PD). PINK1 deficiency, which gives rise to familial early-onset PD, is associated with this dysfunction as well as increased oxidative stress. We have established primary fibroblast cell lines from two patients with PD who carry mutations in the PINK1 gene. The phosphorylation of Akt is abrogated in the presence of oxidative stressors in the complete absence of PINK1 suggesting enhanced apoptotic signalling. We have found an imbalance between the production of reactive oxygen species where the capacity of the cell to remove these toxins by anti-oxidative enzymes is greatly reduced. The expression levels of the anti-oxidant enzymes glutathione peroxidase-1, MnSOD, peroxiredoxin-3 and thioredoxin-2 were diminished. The p66(Shc) adaptor protein has recently been identified to become activated by oxidative stress by phosphorylation at residue Ser36 which then translocates to the mitochondrial inner membrane space. The phosphorylation of p66(Shc) at Ser36 is significantly increased in PINK1 deficient cell lines under normal tissue culture conditions, further still in the presence of compounds which elicit oxidative stress. The stable transfection of PINK1 in the fibroblasts which display the null phenotype ameliorates the hyper-phosphorylation of p66(Shc).
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Affiliation(s)
- Mary C Maj
- Metabolism Research Programme, Research Institute, The Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada M5G 1X8
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11
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Inborn errors of energy metabolism associated with myopathies. J Biomed Biotechnol 2010; 2010:340849. [PMID: 20589068 PMCID: PMC2877206 DOI: 10.1155/2010/340849] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 01/19/2010] [Accepted: 02/22/2010] [Indexed: 12/31/2022] Open
Abstract
Inherited neuromuscular disorders affect approximately one in 3,500 children. Structural muscular defects are most common; however functional impairment of skeletal and cardiac muscle in both children and adults may be caused by inborn errors of energy metabolism as well. Patients suffering from metabolic myopathies due to compromised energy metabolism may present with exercise intolerance, muscle pain, reversible or progressive muscle weakness, and myoglobinuria. In this review, the physiology of energy metabolism in muscle is described, followed by the presentation of distinct disorders affecting skeletal and cardiac muscle: glycogen storage diseases types III, V, VII, fatty acid oxidation defects, and respiratory chain defects (i.e., mitochondriopathies). The diagnostic work-up and therapeutic options in these disorders are discussed.
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12
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Cameron JM, Levandovskiy V, MacKay N, Utgikar R, Ackerley C, Chiasson D, Halliday W, Raiman J, Robinson BH. Identification of a novel mutation in GYS1 (muscle-specific glycogen synthase) resulting in sudden cardiac death, that is diagnosable from skin fibroblasts. Mol Genet Metab 2009; 98:378-82. [PMID: 19699667 DOI: 10.1016/j.ymgme.2009.07.012] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 07/21/2009] [Accepted: 07/22/2009] [Indexed: 11/17/2022]
Abstract
We report here the identification of a patient with muscle-specific glycogen synthase deficiency. The 8-year-old patient showed no prior signs of distress before collapsing during a bout of exercise, resulting in death. Initial post-mortem analysis of tissues suggested death was due to metabolic complications of mitochondrial myopathy, but upon further examination it was found that the anomalies were indicative of mitochondrial proliferation and oxidative compensation. A homozygous two base pair deletion was identified in exon 2 of GYS1, and the parents and sibling were confirmed as heterozygous carriers of the deletion. This case highlights the importance of differentiating between mitochondrial compensatory phenomena and true mitochondrial disease, and suggests that GYS1 deficiency could be a common cause of sudden cardiac death in children. Children with abnormal cardiac responses to increased workloads as well as those with defined myocardial disease should therefore be tested for GYS1 deficiency.
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Affiliation(s)
- Jessie M Cameron
- Genetics and Genome Biology, The Research Institute, The Hospital for Sick Children, Toronto, Canada
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13
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Rolandic mitochondrial encephalomyelopathy and MT-ND3 mutations. Pediatr Neurol 2009; 41:27-33. [PMID: 19520270 DOI: 10.1016/j.pediatrneurol.2009.02.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Revised: 02/09/2009] [Accepted: 02/16/2009] [Indexed: 11/22/2022]
Abstract
Mitochondrial encephalopathies may be caused by mutations in the respiratory chain complex I subunit genes. Described here are the cases of two pediatric patients who presented with MELAS-like calcarine lesions in addition to novel, bilateral rolandic lesions and epilepsia partialis continua, secondary to MT-ND3 mutations. Data were collected included neurologic symptoms, serial brain imaging, metabolic evaluations, skeletal muscle biopsies, mitochondrial biochemical and molecular testing. Permission for publication was given by the families. Muscle histology revealed nonspecific changes, with no ragged red or blue or COX-negative fibers. Sequencing of the mitochondrial DNA indicated patient 2 to be homoplasmic in muscle for the mt.10158T>C mutation in the ND3 subunit and Patient 1 to be 75% heteroplasmic for the mt.10191T>C mutation, also in ND3. Bilateral rolandic lesions and epilepsia partialis continua accompanied by suspicion of mitochondrial disease are indications to search for an underlying mutation in the MT-ND3 gene.
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14
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Cameron JM, Maj M, Levandovskiy V, Barnett CP, Blaser S, Mackay N, Raiman J, Feigenbaum A, Schulze A, Robinson BH. Pyruvate dehydrogenase phosphatase 1 (PDP1) null mutation produces a lethal infantile phenotype. Hum Genet 2009; 125:319-26. [PMID: 19184109 DOI: 10.1007/s00439-009-0629-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Accepted: 01/18/2009] [Indexed: 11/30/2022]
Abstract
Pyruvate dehydrogenase phosphatase deficiency has previously only been confirmed at the molecular level in two brothers and two breeds of dog with exercise intolerance. A female patient, who died at 6 months, presented with lactic acidemia in the neonatal period with serum lactate levels ranging from 2.5 to 17 mM. Failure of dichloroacetate to activate the PDH complex in skin fibroblasts was evident, but not in early passages. A homozygous c.277G > T (p.E93X) nonsense mutation in the PDP1 gene was identified in genomic DNA and immunoblotting showed a complete absence of PDP1 protein in mitochondria. Native PDHC activity could be restored by the addition of either recombinant PDP1 or PDP2. This highlights the role of PDP2, the second phosphatase isoform, in PDP1-deficient patients for the first time. We conclude that the severity of the clinical course associated with PDP1 deficiency can be quite variable depending on the exact nature of the molecular defect.
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Affiliation(s)
- J M Cameron
- The Research Institute, The Hospital for Sick Children, Toronto, Canada
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15
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Disruption of a mitochondrial RNA-binding protein gene results in decreased cytochrome b expression and a marked reduction in ubiquinol–cytochrome c reductase activity in mouse heart mitochondria. Biochem J 2008; 416:15-26. [DOI: 10.1042/bj20080847] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mice homozygous for a defect in the PTCD2 (pentatricopeptide repeat domain protein 2) gene were generated in order to study the role of this protein in mitochondrial RNA metabolism. These mice displayed specific but variable reduction of ubiquinol–cytochrome c reductase complex activity in mitochondria of heart, liver and skeletal muscle due to a decrease in the expression of mitochondrial DNA-encoded cytochrome b, the catalytic core of the complex. This reduction in mitochondrial function has a profound effect on the myocardium, with replacement of ventricular cardiomyocytes by fibro-fatty tissue. Northern blotting showed a reduction in the mRNA for the mitochondrial DNA encoded proteins cytochrome b (cytb) and ND5 (NADH dehydrogenase subunit 5) and an elevation in a combined pre-processed ND5-CYTB transcript. This suggests that the PTCD2 protein is involved in processing RNA transcripts involving cytochrome b derived from mitochondrial DNA. This defines the site for PTCD2 action in mammalian mitochondria and suggests a possible role for dysfunction of this protein in the aetiology of heart failure.
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16
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Haas RH, Parikh S, Falk MJ, Saneto RP, Wolf NI, Darin N, Wong LJ, Cohen BH, Naviaux RK. The in-depth evaluation of suspected mitochondrial disease. Mol Genet Metab 2008; 94:16-37. [PMID: 18243024 PMCID: PMC2810849 DOI: 10.1016/j.ymgme.2007.11.018] [Citation(s) in RCA: 249] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Revised: 11/21/2007] [Accepted: 11/21/2007] [Indexed: 12/12/2022]
Abstract
Mitochondrial disease confirmation and establishment of a specific molecular diagnosis requires extensive clinical and laboratory evaluation. Dual genome origins of mitochondrial disease, multi-organ system manifestations, and an ever increasing spectrum of recognized phenotypes represent the main diagnostic challenges. To overcome these obstacles, compiling information from a variety of diagnostic laboratory modalities can often provide sufficient evidence to establish an etiology. These include blood and tissue histochemical and analyte measurements, neuroimaging, provocative testing, enzymatic assays of tissue samples and cultured cells, as well as DNA analysis. As interpretation of results from these multifaceted investigations can become quite complex, the Diagnostic Committee of the Mitochondrial Medicine Society developed this review to provide an overview of currently available and emerging methodologies for the diagnosis of primary mitochondrial disease, with a focus on disorders characterized by impairment of oxidative phosphorylation. The aim of this work is to facilitate the diagnosis of mitochondrial disease by geneticists, neurologists, and other metabolic specialists who face the challenge of evaluating patients of all ages with suspected mitochondrial disease.
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Affiliation(s)
- Richard H. Haas
- Departments of Neurosciences & Pediatrics, University of California San Diego, La Jolla, CA and Rady Children's Hospital San Diego, San Diego, CA
- Corresponding Author: Richard H. Haas, MB, BChir, MRCP, Professor of Neurosciences and Pediatrics, University of California San Diego, T. 858-822-6700; F. 858-822-6707;
| | - Sumit Parikh
- Division of Neuroscience, The Cleveland Clinic, Cleveland, OH
| | - Marni J. Falk
- Division of Human Genetics, The Children's Hospital of Philadelphia and University of Pennsylvania, Philadelphia, PA
| | - Russell P. Saneto
- Division of Pediatric Neurology, Children's Hospital and Regional Medical Center, University of Washington, Seattle, WA
| | - Nicole I. Wolf
- Department of Child Neurology, University Children's Hospital, Heidelberg, Germany
| | - Niklas Darin
- Division of Child Neurology, The Queen Silvia Children's Hospital, Göteborg, Sweden
| | - Lee-Jun Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas
| | - Bruce H. Cohen
- Division of Neuroscience, The Cleveland Clinic, Cleveland, OH
| | - Robert K. Naviaux
- Departments of Medicine and Pediatrics, Division of Medical and Biochemical Genetics, University of California San Diego, La Jolla, CA and Rady Children's Hospital San Diego, San Diego, CA
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17
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Abstract
The subtle balance between proinflammatory and antiinflammatory cytokines plays an important role in determining the severity of the inflammatory reaction and in the anomalous iron handling associated with infection. Conversely, iron deficiency per se appears to limit the severity of the inflammatory response. All of these considerations are at present highly speculative and in need of further experimental and epidemiologic support. If confirmed, the beneficial biological effects of iron depletion may have a defensive role in inflammation and may be perturbed by the nonselective administration of iron to iron-replete patients who would not benefit from such treatment in the first place. In view of the importance of non-transferrin-bound plasma iron (NTBI) in iron toxicity and its rapid cellular uptake, it may play an important role in the harmful effects of iron in infection, and this is illustrated by the infectious complications of parenteral iron therapy in tropical countries.
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Affiliation(s)
- Chaim Hershko
- Department of Hematology, Hebrew University Hadassah Medical School, Shaare Zedek Medical Center, Jerusalem, Israel.
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18
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Wittig I, Carrozzo R, Santorelli FM, Schägger H. Functional assays in high-resolution clear native gels to quantify mitochondrial complexes in human biopsies and cell lines. Electrophoresis 2007; 28:3811-20. [DOI: 10.1002/elps.200700367] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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19
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Diomedi-Camassei F, Di Giandomenico S, Santorelli FM, Caridi G, Piemonte F, Montini G, Ghiggeri GM, Murer L, Barisoni L, Pastore A, Muda AO, Valente ML, Bertini E, Emma F. COQ2 nephropathy: a newly described inherited mitochondriopathy with primary renal involvement. J Am Soc Nephrol 2007; 18:2773-80. [PMID: 17855635 DOI: 10.1681/asn.2006080833] [Citation(s) in RCA: 243] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Primary coenzyme Q(10) (CoQ(10)) deficiency includes a group of rare autosomal recessive disorders primarily characterized by neurological and muscular symptoms. Rarely, glomerular involvement has been reported. The COQ2 gene encodes the para-hydroxybenzoate-polyprenyl-transferase enzyme of the CoQ(10) synthesis pathway. We identified two patients with early-onset glomerular lesions that harbored mutations in the COQ2 gene. The first patient presented with steroid-resistant nephrotic syndrome at the age of 18 months as a result of collapsing glomerulopathy, with no extrarenal symptoms. The second patient presented at five days of life with oliguria, had severe extracapillary proliferation on renal biopsy, rapidly developed end-stage renal disease, and died at the age of 6 months after a course complicated by progressive epileptic encephalopathy. Ultrastructural examination of renal specimens from these cases, as well as from two previously reported patients, showed an increased number of dysmorphic mitochondria in glomerular cells. Biochemical analyses demonstrated decreased activities of respiratory chain complexes [II+III] and decreased CoQ(10) concentrations in skeletal muscle and renal cortex. In conclusion, we suggest that inherited COQ2 mutations cause a primary glomerular disease with renal lesions that vary in severity and are not necessarily associated with neurological signs. COQ2 nephropathy should be suspected when electron microscopy shows an increased number of abnormal mitochondria in podocytes and other glomerular cells.
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Affiliation(s)
- Francesca Diomedi-Camassei
- Divisions of Pathology , Department of Laboratory Medicine, Bambino Gesù Children's Hospital and Research Institute, Rome, Italy
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20
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Castagna AE, Addis J, McInnes RR, Clarke JTR, Ashby P, Blaser S, Robinson BH. Late onset Leigh syndrome and ataxia due to a T to C mutation at bp 9,185 of mitochondrial DNA. Am J Med Genet A 2007; 143A:808-16. [PMID: 17352390 DOI: 10.1002/ajmg.a.31637] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A T-to-C missense mutation at nucleotide position 9,185 in the protein-coding ATP6 gene of the mitochondrial genome was present at high heteroplasmy in members of a Canadian family with Leigh syndrome with predominant ataxia and peripheral neuropathy. This mutation results in the substitution of a proline residue for an evolutionary-conserved leucine at position of amino acid 220 near the carboxyl terminus of the mitochondrial protein. The index patient and brother, who had an identical clinical presentation, had >90% mutant mtDNA in cultured skin fibroblasts, lymphocytes, and whole blood. Their mother and a maternal uncle, symptomatic with a peripheral neuropathy alone, had 86% and 85% heteroplasmy, respectively. Symptomatic maternal cousins with early onset revealed 90% and 91% mutant mtDNA in all tissues analyzed. Studies of lymphoblasts from the asymptomatic maternal grandmother and eldest brother of the proband were heteroplasmic for mutant mtDNA with 56% and 17%, respectively. Biochemical analysis demonstrated normal respiratory chain enzyme activity in muscle and fibroblasts, normal ATP synthesis, but reduced oligomycin-sensitive H(+)ATPase in cultured lymphoblast mitochondria. We propose that the 9,185T > C mtDNA mutation is pathogenic even though the initial phenotype is mild and the biochemical phenotype not easily detectable.
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Affiliation(s)
- Avril E Castagna
- Scarborough General Hospital, Hospital for Sick Children, Toronto, Ontario
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21
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Cameron JM, Maj MC, Levandovskiy V, MacKay N, Shelton GD, Robinson BH. Identification of a canine model of pyruvate dehydrogenase phosphatase 1 deficiency. Mol Genet Metab 2007; 90:15-23. [PMID: 17095275 DOI: 10.1016/j.ymgme.2006.09.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Revised: 09/26/2006] [Accepted: 09/27/2006] [Indexed: 12/01/2022]
Abstract
Exercise intolerance syndromes are well known to be associated with inborn errors of metabolism affecting glycolysis (phosphorylase and phosphofructokinase deficiency) and fatty acid oxidation (palmitoyl carnitine transferase deficiency). We have identified a canine model for profound exercise intolerance caused by a deficit in PDP1 (EC 3.1.3.43), the phosphatase enzyme that activates the pyruvate dehydrogenase complex (PDHc). The Clumber spaniel breed was originated in 1760 by the Duc de Noailles, as a hunting dog with a gentle temperament suitable for the 'elderly gentleman'. Here we report that 20% of the current Clumber and Sussex spaniel population are carriers for a null mutation in PDP1, and that homozygosity produces severe exercise intolerance. Human pyruvate dehydrogenase phosphatase deficiency was recently characterized at the molecular level. However, the nature of the human mutation (loss of a single amino acid altering PDP1 activity) made it impossible to discern the role of the second phosphatase isoform, PDP2, in the deficient phenotype. Here we show that the null mutation in dogs provides a valuable animal model with which to study the effects of dysregulation of the PDHc. Knowledge of the molecular defect has allowed for the institution of a rapid restriction enzyme test for the canine mutation that will allow for selective breeding and has led to a suggested dietary therapy for affected dogs that has proven to be beneficial. Pharmacological and genetic therapies for PDP1 deficiency can now be investigated and the role of PDP2 can be fully characterized.
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Affiliation(s)
- Jessie M Cameron
- Metabolic Research Programme, Research Institute, The Hospital for Sick Children, 555 University Avenue, Toronto, Ont., Canada M5G 1X8
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22
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Timmermans EC, Tebas P, Ruiter JPN, Wanders RJA, de Ronde A, de Baar MP. Real-Time Nucleic Acid Sequence–Based Amplification Assay to Quantify Changes in Mitochondrial DNA Concentrations in Cell Cultures and Blood Cells from HIV-Infected Patients Receiving Antiviral Therapy. Clin Chem 2006; 52:979-87. [PMID: 16601068 DOI: 10.1373/clinchem.2005.062901] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Abstract
Background: To study the clinical relevance of changes in mitochondrial DNA (mtDNA) in peripheral blood mononuclear cells (PBMCs) attributable to HIV infection and/or combination antiretroviral therapy (cART), a high-throughput molecular assay to quantify mtDNA is required.
Methods: We developed a quantitative real-time duplex nucleic acid sequence–based amplification assay in which both mtDNA and nuclear DNA are simultaneously amplified in 1 tube. The assay could accurately quantify mtDNA in a range of 15–1500 copies of mtDNA per 2 genomic copies with an intrarun variation of 11% and an interrun variation of 16%. We compared this real-time assay with the lactate/pyruvate ratios in fibroblasts incubated with glucose and exposed to zalcitabine. Additionally, we studied the effects of platelet contamination and the in vivo effects of cART on mtDNA in PBMCs from a small group of patients.
Results: Decreases in mtDNA preceded the increase in lactate/pyruvate ratios and vice versa when zalcitabine was eliminated from the culture. Platelets affected the mtDNA in PBMCs if >5 platelets per PBMC were present. Within 12 weeks, mtDNA increased and remained increased in PBMCs from patients on continuous treatment with zidovudine/lamivudine/indinavir therapy (P = 0.03), but increased if patients were switched to stavudine/didanosine therapy (P = 0.008).
Conclusion: After drug exposure, the mtDNA assay can detect changes in mtDNA concentrations in cell lines and PBMCs, when properly controlled for platelet effects, earlier than traditional assays.
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23
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Sue CM, Schon EA. Mitochondrial respiratory chain diseases and mutations in nuclear DNA: a promising start? Brain Pathol 2006; 10:442-50. [PMID: 10885663 PMCID: PMC8098584 DOI: 10.1111/j.1750-3639.2000.tb00276.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Affiliation(s)
- Carolyn M. Sue
- Department of Neurology, Columbia University, New York, NY, USA
| | - Eric A. Schon
- Department of Neurology, Columbia University, New York, NY, USA
- Department of Genetics and Development, Columbia University, New York, NY, USA
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24
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Tarnopolsky MA, Raha S. Mitochondrial myopathies: diagnosis, exercise intolerance, and treatment options. Med Sci Sports Exerc 2006; 37:2086-93. [PMID: 16331134 DOI: 10.1249/01.mss.0000177341.89478.06] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mitochondrial myopathies are caused by genetic mutations that directly influence the functioning of the electron transport chain (ETC). It is estimated that 1 of 8,000 people have pathology inducing mutations affecting mitochondrial function. Diagnosis often requires a multifaceted approach with measurements of serum lactate and pyruvate, urine organic acids, magnetic resonance spectroscopy (MRS), muscle histology and ultrastructure, enzymology, genetic analysis, and exercise testing. The ubiquitous distribution of the mitochondria in the human body explains the multiple organ involvement. Exercise intolerance is a common but often an overlooked hallmark of mitochondrial myopathies. The muscle consequences of ETC dysfunction include increased reliance on anaerobic metabolism (lactate generation, phosphocreatine degradation), enhanced free radical production, reduced oxygen extraction and electron flux through ETC, and mitochondrial proliferation or biogenesis (see article by Hood in current issue). Treatments have included antioxidants (vitamin E, alpha lipoic acid), electron donors and acceptors (coenzyme Q10, riboflavin), alternative energy sources (creatine monohydrate), lactate reduction strategies (dichloroacetate) and exercise training. Exercise is a particularly important modality in diagnosis as well as therapy (see article by Taivassalo in current issue). Increased awareness of these disorders by exercise physiologists and sports medicine practitioners should lead to more accurate and more rapid diagnosis and the opportunity for therapy and genetic counseling.
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25
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Mannucci L, Pastore A, Rizzo C, Piemonte F, Rizzoni G, Emma F. Impaired activity of the gamma-glutamyl cycle in nephropathic cystinosis fibroblasts. Pediatr Res 2006; 59:332-5. [PMID: 16439602 DOI: 10.1203/01.pdr.0000196370.57200.da] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Cystinotic patients have been shown to excrete in their urine high levels of pyroglutamate, an intermediate metabolite of the adenosine triphosphate (ATP)-dependent gamma-glutamyl cycle, which is responsible for glutathione (GSH) synthesis. Human fibroblasts were used to study the mechanisms leading to pyroglutamate accumulation in nephropathic cystinosis (NC). We show that inhibition of ATP synthesis caused a marked intracellular accumulation of pyroglutamate, reflecting decreased GSH synthesis. Despite similar degrees of ATP depletion, pyroglutamate increased more in cystinotic fibroblasts than in controls, while GSH decreased to lower levels. In addition, cystinotic cells exposed to oxidative stress (hydrogen peroxide) were unable to increase their GSH concentration above baseline. These results could not be attributed to differences in mitochondrial oxidative activity or to increased apoptotic cell death. Together, these results support the hypothesis that cysteine derived from lysosomal cystine efflux limits the activity of the gamma-glutamyl cycle and GSH synthesis.
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Affiliation(s)
- Liliana Mannucci
- Department of Nephrology and Urology, Bambino Gesù Children's Hospital and Research Institute, Rome, Italy
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26
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Setterfield K, Williams AJ, Donald J, Thorburn DR, Kirby DM, Trounce I, Christodoulou J. Flow cytometry in the study of mitochondrial respiratory chain disorders. Mitochondrion 2005; 1:437-45. [PMID: 16120296 DOI: 10.1016/s1567-7249(02)00008-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2001] [Revised: 01/01/2002] [Accepted: 02/25/2002] [Indexed: 11/29/2022]
Abstract
We have developed a flow cytometric assay to measure the oxidative capacity of cultured lymphoblasts as a possible screening test for patients suspected of having a defect of the mitochondrial respiratory chain. Cells were incubated overnight in serum free media, followed by incubation with dihydroethidium with and without rotenone, and then analysed using flow cytometry to measure fluorescence. Inhibition with rotenone gave an increase in fluorescence compared to uninhibited cells. The change in fluorescence was significantly lower in four of the six patient cell lines, with a correlation between the activity of complex I and change in fluorescence. This method may be applicable to cell lines with defects in other complexes of the respiratory chain.
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Affiliation(s)
- Karen Setterfield
- Department of Biological Sciences, Macquarie University, North Ryde, Sydney, NSW, Australia
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27
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Tadiboyina VT, Rupar A, Atkison P, Feigenbaum A, Kronick J, Wang J, Hegele RA. Novel mutation in DGUOK in hepatocerebral mitochondrial DNA depletion syndrome associated with cystathioninuria. Am J Med Genet A 2005; 135:289-91. [PMID: 15887277 DOI: 10.1002/ajmg.a.30748] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Mitochondrial depletion syndrome (MDS) refers to a heterogeneous group of mitochondrial disorders characterized by a reduction of the mtDNA copy number in affected tissues. Mutations in DGUOK encoding deoxyguanosine kinase (MIM 601465) cause the hepatocerebral form of MDS (MIM 251880). Cystathioninuria (MIM 219500) can result from mutations in CTH encoding cystathionine gamma lyase (MIM 607657) or can be a secondary finding in several diverse clinical conditions. We present three patients from two apparently unrelated old colony Mennonite families, each of whom had the hepatocerebral form of MDS together with cystathioninuria. Each affected child was homozygous for the novel DGUOK p.D255Y mutation, but had no CTH mutation, indicating that the hepatocerebral form of MDS might be associated with secondary cystathioninuria.
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Affiliation(s)
- Venu T Tadiboyina
- Robarts Research Institute and University of Western Ontario, London, Ontario, Canada
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28
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Pallotti F, Baracca A, Hernandez-Rosa E, Walker W, Solaini G, Lenaz G, Melzi d'ERIL G, DiMAURO S, Schon E, Davidson M. Biochemical analysis of respiratory function in cybrid cell lines harbouring mitochondrial DNA mutations. Biochem J 2005; 384:287-93. [PMID: 15324306 PMCID: PMC1134112 DOI: 10.1042/bj20040561] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We analysed key biochemical features that reflect the balance between glycolysis and glucose oxidation in cybrids (cytoplasmic hybrids) harbouring a representative sample of mitochondrial DNA point mutations and deletions. The cybrids analysed had the same 143B cell nuclear background and were isogenic for the mitochondrial background. The 143B cell line and its rho(0) counterpart were used as controls. All cells analysed were in a dynamic state, and cell number, time of plating, culture medium, extracellular volume and time of harvest and assay were strictly controlled. Intra- and extra-cellular lactate and pyruvate levels were measured in homoplasmic wild-type and mutant cells, and correlated with rates of ATP synthesis and O2 consumption. In all mutant cell lines, except those with the T8993C mutation in the ATPase 6 gene, glycolysis was increased even under conditions of low glucose, as demonstrated by increased levels of extracellular lactate and pyruvate. Extracellular lactate levels were strictly and inversely correlated with rates of ATP synthesis and O2 consumption. These results show increased glycolysis and defective oxidative phosphorylation, irrespective of the type or site of the point mutation or deletion in the mitochondrial genome. The different biochemical consequences of the T8993C mutation suggest a uniquely different pathogenic mechanism for this mutation. However, the distinct clinical features associated with some of these mutations still remain to be elucidated.
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Affiliation(s)
- Francesco Pallotti
- *Department of Neurology, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, U.S.A
- †Dipartimento Scienze Biomediche Sperimentali e Cliniche, Università degli Studi dell'Insubria, Via Dunant 5, 21100 Varese, Italy
| | - Alessandra Baracca
- ‡Dipartimento Biochimica ‘G. Moruzzi’, Università degli Studi di Bologna, Via Irnerio 48, 40126 Bologna, Italy
| | - Evelyn Hernandez-Rosa
- *Department of Neurology, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, U.S.A
| | - Winsome F. Walker
- *Department of Neurology, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, U.S.A
| | - Giancarlo Solaini
- §Scuola Superiore di Studi Universitari e di Perfezionamento ‘S. Anna’, Piazza dei Martiri 33, Pisa, Italy
| | - Giorgio Lenaz
- ‡Dipartimento Biochimica ‘G. Moruzzi’, Università degli Studi di Bologna, Via Irnerio 48, 40126 Bologna, Italy
| | - Gian Vico Melzi d'ERIL
- †Dipartimento Scienze Biomediche Sperimentali e Cliniche, Università degli Studi dell'Insubria, Via Dunant 5, 21100 Varese, Italy
| | - Salvatore DiMAURO
- *Department of Neurology, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, U.S.A
| | - Eric A. Schon
- *Department of Neurology, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, U.S.A
- ∥Department of Genetics and Development, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, U.S.A
| | - Mercy M. Davidson
- *Department of Neurology, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, U.S.A
- To whom correspondence should be addressed (email )
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29
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Koopman WJH, Verkaart S, Visch HJ, van der Westhuizen FH, Murphy MP, van den Heuvel LWPJ, Smeitink JAM, Willems PHGM. Inhibition of complex I of the electron transport chain causes O2-. -mediated mitochondrial outgrowth. Am J Physiol Cell Physiol 2005; 288:C1440-50. [PMID: 15647387 DOI: 10.1152/ajpcell.00607.2004] [Citation(s) in RCA: 221] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Recent evidence indicates that oxidative stress is central to the pathogenesis of a wide variety of degenerative diseases, aging, and cancer. Oxidative stress occurs when the delicate balance between production and detoxification of reactive oxygen species is disturbed. Mammalian cells respond to this condition in several ways, among which is a change in mitochondrial morphology. In the present study, we have used rotenone, an inhibitor of complex I of the respiratory chain, which is thought to increase mitochondrial O(2)(-)* production, and mitoquinone (MitoQ), a mitochondria-targeted antioxidant, to investigate the relationship between mitochondrial O(2)(-)* production and morphology in human skin fibroblasts. Video-rate confocal microscopy of cells pulse loaded with the mitochondria-specific cation rhodamine 123, followed by automated analysis of mitochondrial morphology, revealed that chronic rotenone treatment (100 nM, 72 h) significantly increased mitochondrial length and branching without changing the number of mitochondria per cell. In addition, this treatment caused a twofold increase in lipid peroxidation as determined with C11-BODIPY(581/591). Finally, digital imaging microscopy of cells loaded with hydroethidine, which is oxidized by O(2)(-)* to yield fluorescent ethidium, revealed that chronic rotenone treatment caused a twofold increase in the rate of O(2)(-)* production. MitoQ (10 nM, 72 h) did not interfere with rotenone-induced ethidium formation but abolished rotenone-induced outgrowth and lipid peroxidation. These findings show that increased mitochondrial O(2)(-)* production as a consequence of, for instance, complex I inhibition leads to mitochondrial outgrowth and that MitoQ acts downstream of this O(2)(-)* to prevent alterations in mitochondrial morphology.
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Affiliation(s)
- Werner J H Koopman
- Microscopal Imaging Center, Department of Biochemistry, Nijmegen Center for Molecular Life Sciences, Radboud University Medical Center, PO Box 9101, NL-6500 HB Nijmegen, The Netherlands
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30
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Visch HJ, Rutter GA, Koopman WJH, Koenderink JB, Verkaart S, de Groot T, Varadi A, Mitchell KJ, van den Heuvel LP, Smeitink JAM, Willems PHGM. Inhibition of mitochondrial Na+-Ca2+ exchange restores agonist-induced ATP production and Ca2+ handling in human complex I deficiency. J Biol Chem 2004; 279:40328-36. [PMID: 15269216 DOI: 10.1074/jbc.m408068200] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human mitochondrial complex I (NADH:ubiquinone oxidoreductase) of the oxidative phosphorylation system is a multiprotein assembly comprising both nuclear and mitochondrially encoded subunits. Deficiency of this complex is associated with numerous clinical syndromes ranging from highly progressive, often early lethal encephalopathies, of which Leigh disease is the most frequent, to neurodegenerative disorders in adult life, including Leber's hereditary optic neuropathy and Parkinson disease. We show here that the cytosolic Ca2+ signal in response to hormonal stimulation with bradykinin was impaired in skin fibroblasts from children between the ages of 0 and 5 years with an isolated complex I deficiency caused by mutations in nuclear encoded structural subunits of the complex. Inhibition of mitochondrial Na+-Ca2+ exchange by the benzothiazepine CGP37157 completely restored the aberrant cytosolic Ca2+ signal. This effect of the inhibitor was paralleled by complete restoration of the bradykinin-induced increases in mitochondrial Ca2+ concentration and ensuing ATP production. Thus, impaired mitochondrial Ca2+ accumulation during agonist stimulation is a major consequence of human complex I deficiency, a finding that may provide the basis for the development of new therapeutic approaches to this disorder.
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Affiliation(s)
- Henk-Jan Visch
- Department of Biochemistry and Pediatrics, University Medical Center Nijmegen, The Netherlands
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31
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Marriage BJ, Clandinin MT, Macdonald IM, Glerum DM. Cofactor treatment improves ATP synthetic capacity in patients with oxidative phosphorylation disorders. Mol Genet Metab 2004; 81:263-72. [PMID: 15059613 DOI: 10.1016/j.ymgme.2003.12.008] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2003] [Revised: 12/18/2003] [Accepted: 12/18/2003] [Indexed: 11/29/2022]
Abstract
Marked progress has been made over the past 15 years in defining the specific biochemical defects and underlying molecular mechanisms of oxidative phosphorylation disorders, but limited information is currently available on the development and evaluation of effective treatment approaches. Metabolic therapies that have been reported to produce a positive effect include coenzyme Q(10) (ubiquinone), other antioxidants such as ascorbic acid and vitamin E, riboflavin, thiamine, niacin, vitamin K (phylloquinone and menadione), and carnitine. The goal of these therapies is to increase mitochondrial ATP production, and to slow or arrest the progression of clinical symptoms. In the present study, we demonstrate for the first time that there is a significant increase in ATP synthetic capacity in lymphocytes from patients undergoing cofactor treatment. We also examined in vitro cofactor supplementation in control lymphocytes in order to determine the effect of the individual components of the cofactor treatment on ATP synthesis. A dose-dependent increase in ATP synthesis with CoQ(10) incubation was demonstrated, which supports the proposal that CoQ(10) may have a beneficial effect in the treatment of oxidative phosphorylation (OXPHOS) disorders.
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Affiliation(s)
- Barbara J Marriage
- Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.
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Ferreirinha F, Quattrini A, Pirozzi M, Valsecchi V, Dina G, Broccoli V, Auricchio A, Piemonte F, Tozzi G, Gaeta L, Casari G, Ballabio A, Rugarli EI. Axonal degeneration in paraplegin-deficient mice is associated with abnormal mitochondria and impairment of axonal transport. J Clin Invest 2004; 113:231-42. [PMID: 14722615 PMCID: PMC311437 DOI: 10.1172/jci20138] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2003] [Accepted: 11/04/2003] [Indexed: 11/17/2022] Open
Abstract
In several neurodegenerative diseases, axonal degeneration occurs before neuronal death and contributes significantly to patients' disability. Hereditary spastic paraplegia (HSP) is a genetically heterogeneous condition characterized by selective degeneration of axons of the corticospinal tracts and fasciculus gracilis. HSP may therefore be considered an exemplary disease to study the local programs mediating axonal degeneration. We have developed a mouse model for autosomal recessive HSP due to mutations in the SPG7 gene encoding the mitochondrial ATPase paraplegin. Paraplegin-deficient mice are affected by a distal axonopathy of spinal and peripheral axons, characterized by axonal swelling and degeneration. We found that mitochondrial morphological abnormalities occurred in synaptic terminals and in distal regions of axons long before the first signs of swelling and degeneration and correlated with onset of motor impairment during a rotarod test. Axonal swellings occur through massive accumulation of organelles and neurofilaments, suggesting impairment of anterograde axonal transport. Retrograde axonal transport is delayed in symptomatic mice. We speculate that local failure of mitochondrial function may affect axonal transport and cause axonal degeneration. Our data suggest that a timely therapeutic intervention may prevent the loss of axons.
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Ferreirinha F, Quattrini A, Pirozzi M, Valsecchi V, Dina G, Broccoli V, Auricchio A, Piemonte F, Tozzi G, Gaeta L, Casari G, Ballabio A, Rugarli EI. Axonal degeneration in paraplegin-deficient mice is associated with abnormal mitochondria and impairment of axonal transport. J Clin Invest 2004. [DOI: 10.1172/jci200420138] [Citation(s) in RCA: 217] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Hershko C, Link G, Konijn AM. Cardioprotective effect of iron chelators. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 509:77-89. [PMID: 12572990 DOI: 10.1007/978-1-4615-0593-8_5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Chaim Hershko
- Shaare Zedek Medical Center, Jerusalem, Israel 91031
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Liet JM, Pelletier V, Robinson BH, Laryea MD, Wendel U, Morneau S, Morin C, Mitchell G, Lacroix J. The effect of short-term dimethylglycine treatment on oxygen consumption in cytochrome oxidase deficiency: a double-blind randomized crossover clinical trial. J Pediatr 2003; 142:62-6. [PMID: 12520257 DOI: 10.1067/mpd.2003.mpd0333] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE To study the effectiveness of dimethylglycine (DMG) on oxygen consumption (VO(2)) in children with Saguenay-Lac-Saint-Jean cytochrome-c oxidase (SLSJ-COX) deficiency (OMIM 220111). STUDY DESIGN In a crossover randomized double-blind clinical trial, 5 children with SLSJ-COX deficiency, who were stable and old enough to comply with VO(2) measurement, were treated with placebo or DMG for 3 days, and with the alternate treatment after a 2-week washout period. VO(2) was measured by indirect calorimetry before and after treatment. Dietary caloric intake was calculated for 3 days before each measurement. Mean caloric intakes per day were 1562 and 1342 kcal x m(-2) before and during placebo, 1,336 and 1,380 before and during DMG, respectively. RESULTS DMG was well tolerated and, in all cases, resulted in markedly increased blood DMG levels (617 + 203 mmol x L(-1)), versus 0 to 2 mmol x L(-1) without treatment. Mean VO(2) was lower after administration of either DMG (-1 +/- 3 mL x min(-1) x m(-2)) or placebo (-6 +/- 4), but neither difference was statistically significant. There was no detectable effect of DMG treatment on blood levels of lactate, pyruvate, bicarbonate, or pH. VO(2) values of patients (range, 101-135 mL x min(-1) x m(-2)) were lower than published norms (150-160 mL x min(-1) x m(-2)). CONCLUSION This study suggests that treatment with DMG does not substantially change VO(2) in children with SLSJ-COX deficiency.
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Affiliation(s)
- Jean-Michel Liet
- Department of Pediatrics, Sainte-Justine Hospital, Montreal, Canada
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Chapter 3 Molecular Genetic Basis of the Mitochondrial Encephalomyopathies. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1877-3419(09)70062-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Piemonte F, Casali C, Carrozzo R, Schägger H, Patrono C, Tessa A, Tozzi G, Cricchi F, Di Capua M, Siciliano G, Amabile GA, Morocutti C, Bertini E, Santorelli FM. Respiratory chain defects in hereditary spastic paraplegias. Neuromuscul Disord 2001; 11:565-9. [PMID: 11525886 DOI: 10.1016/s0960-8966(01)00214-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hereditary Spastic Paraplegias (HSPs) are heterogeneous neurodegenerative disorders whose etiopathogenesis is still unclear. The identification of pathogenic mutations in a gene (SPG7) encoding a mitochondrial metalloprotease suggested that oxidative phosphorylation (OXPHOS) alterations might underlie HSP in a subgroup of patients. We performed clinical, morphological, biochemical, and molecular genetic studies in six HSP patients and in six sporadic patients to investigate OXPHOS in muscle biopsies. Complicated and pure forms were included in our study. Morphological alterations of the type seen in OXPHOS-related disorders were found in three patients. Five patients showed an isolated defect of complex I activity. No mutations in the SPG7 gene were detected. Our results suggest that OXPHOS defects in HSP patients are more common than previously believed.
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Affiliation(s)
- F Piemonte
- Molecular Medicine and Neurology, IRCCS-Ospedale Bambino Gesù, Piazza S. Onofrio 4, 00165 Rome, Italy
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Seyda A, Newbold RF, Hudson TJ, Verner A, MacKay N, Winter S, Feigenbaum A, Malaney S, Gonzalez-Halphen D, Cuthbert AP, Robinson BH. A novel syndrome affecting multiple mitochondrial functions, located by microcell-mediated transfer to chromosome 2p14-2p13. Am J Hum Genet 2001; 68:386-96. [PMID: 11156534 PMCID: PMC1235272 DOI: 10.1086/318196] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2000] [Accepted: 11/28/2000] [Indexed: 11/03/2022] Open
Abstract
We have studied cultured skin fibroblasts from three siblings and one unrelated individual, all of whom had fatal mitochondrial disease manifesting soon after birth. After incubation with 1 mM glucose, these four cell strains exhibited lactate/pyruvate ratios that were six times greater than those of controls. On further analysis, enzymatic activities of the pyruvate dehydrogenase complex, the 2-oxoglutarate dehydrogenase complex, NADH cytochrome c reductase, succinate dehydrogenase, and succinate cytochrome c reductase were severely deficient. In two of the siblings the enzymatic activity of cytochrome oxidase was mildly decreased (by approximately 50%). Metabolite analysis performed on urine samples taken from these patients revealed high levels of glycine, leucine, valine, and isoleucine, indicating abnormalities of both the glycine-cleavage system and branched-chain alpha-ketoacid dehydrogenase. In contrast, the activities of fibroblast pyruvate carboxylase, mitochondrial aconitase, and citrate synthase were normal. Immunoblot analysis of selected complex III subunits (core 1, cyt c(1), and iron-sulfur protein) and of the pyruvate dehydrogenase complex subunits revealed no visible changes in the levels of all examined proteins, decreasing the possibility that an import and/or assembly factor is involved. To elucidate the underlying molecular defect, analysis of microcell-mediated chromosome-fusion was performed between the present study's fibroblasts (recipients) and a panel of A9 mouse:human hybrids (donors) developed by Cuthbert et al. (1995). Complementation was observed between the recipient cells from both families and the mouse:human hybrid clone carrying human chromosome 2. These results indicate that the underlying defect in our patients is under the control of a nuclear gene, the locus of which is on chromosome 2. A 5-cM interval has been identified as potentially containing the critical region for the unknown gene. This interval maps to region 2p14-2p13.
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Affiliation(s)
- Agnieszka Seyda
- Metabolism Research Programme, Research Institute and Division of Clinical Genetics, Hospital for Sick Children, and Departments of Biochemistry and Paediatrics, University of Toronto, Toronto; Department of Biology and Biochemistry, Brunel University, Uxbridge, UK, Montréal General Hospital, Montréal; Medical Genetics/Metabolism, Valley Children’s Hospital, Fresno, CA; Garvin Institute of Medical Research, Darlinghurst, Australia; Departamento de Bioenergetica, Universidad Nacional Autonoma de Mexico, Mexico City; and Division of Medical and Molecular Genetics, Guy’s, King’s and St. Thomas’ School of Medicine, Guy’s Hospital, London
| | - Robert F. Newbold
- Metabolism Research Programme, Research Institute and Division of Clinical Genetics, Hospital for Sick Children, and Departments of Biochemistry and Paediatrics, University of Toronto, Toronto; Department of Biology and Biochemistry, Brunel University, Uxbridge, UK, Montréal General Hospital, Montréal; Medical Genetics/Metabolism, Valley Children’s Hospital, Fresno, CA; Garvin Institute of Medical Research, Darlinghurst, Australia; Departamento de Bioenergetica, Universidad Nacional Autonoma de Mexico, Mexico City; and Division of Medical and Molecular Genetics, Guy’s, King’s and St. Thomas’ School of Medicine, Guy’s Hospital, London
| | - Thomas J. Hudson
- Metabolism Research Programme, Research Institute and Division of Clinical Genetics, Hospital for Sick Children, and Departments of Biochemistry and Paediatrics, University of Toronto, Toronto; Department of Biology and Biochemistry, Brunel University, Uxbridge, UK, Montréal General Hospital, Montréal; Medical Genetics/Metabolism, Valley Children’s Hospital, Fresno, CA; Garvin Institute of Medical Research, Darlinghurst, Australia; Departamento de Bioenergetica, Universidad Nacional Autonoma de Mexico, Mexico City; and Division of Medical and Molecular Genetics, Guy’s, King’s and St. Thomas’ School of Medicine, Guy’s Hospital, London
| | - Andrei Verner
- Metabolism Research Programme, Research Institute and Division of Clinical Genetics, Hospital for Sick Children, and Departments of Biochemistry and Paediatrics, University of Toronto, Toronto; Department of Biology and Biochemistry, Brunel University, Uxbridge, UK, Montréal General Hospital, Montréal; Medical Genetics/Metabolism, Valley Children’s Hospital, Fresno, CA; Garvin Institute of Medical Research, Darlinghurst, Australia; Departamento de Bioenergetica, Universidad Nacional Autonoma de Mexico, Mexico City; and Division of Medical and Molecular Genetics, Guy’s, King’s and St. Thomas’ School of Medicine, Guy’s Hospital, London
| | - Neviana MacKay
- Metabolism Research Programme, Research Institute and Division of Clinical Genetics, Hospital for Sick Children, and Departments of Biochemistry and Paediatrics, University of Toronto, Toronto; Department of Biology and Biochemistry, Brunel University, Uxbridge, UK, Montréal General Hospital, Montréal; Medical Genetics/Metabolism, Valley Children’s Hospital, Fresno, CA; Garvin Institute of Medical Research, Darlinghurst, Australia; Departamento de Bioenergetica, Universidad Nacional Autonoma de Mexico, Mexico City; and Division of Medical and Molecular Genetics, Guy’s, King’s and St. Thomas’ School of Medicine, Guy’s Hospital, London
| | - Susan Winter
- Metabolism Research Programme, Research Institute and Division of Clinical Genetics, Hospital for Sick Children, and Departments of Biochemistry and Paediatrics, University of Toronto, Toronto; Department of Biology and Biochemistry, Brunel University, Uxbridge, UK, Montréal General Hospital, Montréal; Medical Genetics/Metabolism, Valley Children’s Hospital, Fresno, CA; Garvin Institute of Medical Research, Darlinghurst, Australia; Departamento de Bioenergetica, Universidad Nacional Autonoma de Mexico, Mexico City; and Division of Medical and Molecular Genetics, Guy’s, King’s and St. Thomas’ School of Medicine, Guy’s Hospital, London
| | - Annette Feigenbaum
- Metabolism Research Programme, Research Institute and Division of Clinical Genetics, Hospital for Sick Children, and Departments of Biochemistry and Paediatrics, University of Toronto, Toronto; Department of Biology and Biochemistry, Brunel University, Uxbridge, UK, Montréal General Hospital, Montréal; Medical Genetics/Metabolism, Valley Children’s Hospital, Fresno, CA; Garvin Institute of Medical Research, Darlinghurst, Australia; Departamento de Bioenergetica, Universidad Nacional Autonoma de Mexico, Mexico City; and Division of Medical and Molecular Genetics, Guy’s, King’s and St. Thomas’ School of Medicine, Guy’s Hospital, London
| | - Suzann Malaney
- Metabolism Research Programme, Research Institute and Division of Clinical Genetics, Hospital for Sick Children, and Departments of Biochemistry and Paediatrics, University of Toronto, Toronto; Department of Biology and Biochemistry, Brunel University, Uxbridge, UK, Montréal General Hospital, Montréal; Medical Genetics/Metabolism, Valley Children’s Hospital, Fresno, CA; Garvin Institute of Medical Research, Darlinghurst, Australia; Departamento de Bioenergetica, Universidad Nacional Autonoma de Mexico, Mexico City; and Division of Medical and Molecular Genetics, Guy’s, King’s and St. Thomas’ School of Medicine, Guy’s Hospital, London
| | - Diego Gonzalez-Halphen
- Metabolism Research Programme, Research Institute and Division of Clinical Genetics, Hospital for Sick Children, and Departments of Biochemistry and Paediatrics, University of Toronto, Toronto; Department of Biology and Biochemistry, Brunel University, Uxbridge, UK, Montréal General Hospital, Montréal; Medical Genetics/Metabolism, Valley Children’s Hospital, Fresno, CA; Garvin Institute of Medical Research, Darlinghurst, Australia; Departamento de Bioenergetica, Universidad Nacional Autonoma de Mexico, Mexico City; and Division of Medical and Molecular Genetics, Guy’s, King’s and St. Thomas’ School of Medicine, Guy’s Hospital, London
| | - Andrew P. Cuthbert
- Metabolism Research Programme, Research Institute and Division of Clinical Genetics, Hospital for Sick Children, and Departments of Biochemistry and Paediatrics, University of Toronto, Toronto; Department of Biology and Biochemistry, Brunel University, Uxbridge, UK, Montréal General Hospital, Montréal; Medical Genetics/Metabolism, Valley Children’s Hospital, Fresno, CA; Garvin Institute of Medical Research, Darlinghurst, Australia; Departamento de Bioenergetica, Universidad Nacional Autonoma de Mexico, Mexico City; and Division of Medical and Molecular Genetics, Guy’s, King’s and St. Thomas’ School of Medicine, Guy’s Hospital, London
| | - Brian H. Robinson
- Metabolism Research Programme, Research Institute and Division of Clinical Genetics, Hospital for Sick Children, and Departments of Biochemistry and Paediatrics, University of Toronto, Toronto; Department of Biology and Biochemistry, Brunel University, Uxbridge, UK, Montréal General Hospital, Montréal; Medical Genetics/Metabolism, Valley Children’s Hospital, Fresno, CA; Garvin Institute of Medical Research, Darlinghurst, Australia; Departamento de Bioenergetica, Universidad Nacional Autonoma de Mexico, Mexico City; and Division of Medical and Molecular Genetics, Guy’s, King’s and St. Thomas’ School of Medicine, Guy’s Hospital, London
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Abstract
The human cytochrome oxidase complex is a multisubunit assembly in the inner mitochondrial membrane responsible for the terminal event in electron transport in which molecular oxygen is reduced. Various phenotypic forms of cytochrome oxidase deficiency have been recognized, the major varieties involving degeneration of the brain stem and basal ganglia (Leigh syndrome) and lactic acidemia. Others include a fatal infantile form, a benign reversible form, and forms with cardiomyopathy. Early recognition of complementation groups within, for instance, the Leigh syndrome group has recently been followed up with a description of the gene defect for three of the nuclear-encoded forms of cytochrome c oxidase (COX) deficiency. The three genes indicted, SURF1 for Leigh syndrome, COX 10 for leukodystrophy and tubulopathy, and SCO2 for the cardiomyopathic form, all have a role in the assembly of the mature cytochrome oxidase complex. The description of these gene defects and the role these genes play are discussed in terms of what can be learned about COX assembly and about the etiology of the different phenotypic forms of the disease.
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Affiliation(s)
- B H Robinson
- Metabolism Research Programme, The Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
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Procaccio V, Mousson B, Beugnot R, Duborjal H, Feillet F, Putet G, Pignot-Paintrand I, Lombès A, De Coo R, Smeets H, Lunardi J, Issartel JP. Nuclear DNA origin of mitochondrial complex I deficiency in fatal infantile lactic acidosis evidenced by transnuclear complementation of cultured fibroblasts. J Clin Invest 1999; 104:83-92. [PMID: 10393702 PMCID: PMC408404 DOI: 10.1172/jci6184] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We have studied complex I (NADH-ubiquinone reductase) defects of the mitochondrial respiratory chain in 2 infants who died in the neonatal period from 2 different neurological forms of severe neonatal lactic acidosis. Specific and marked decrease in complex I activity was documented in muscle, liver, and cultured skin fibroblasts. Biochemical characterization and study of the genetic origin of this defect were performed using cultured fibroblasts. Immunodetection of 6 nuclear DNA-encoded (20, 23, 24, 30, 49, and 51 kDa) and 1 mitochondrial DNA-encoded (ND1) complex I subunits in fibroblast mitochondria revealed 2 distinct patterns. In 1 patient, complex I contained reduced amounts of the 24- and 51-kDa subunits and normal amounts of all the other investigated subunits. In the second patient, amounts of all the investigated subunits were severely decreased. The data suggest partial or extensive impairment of complex I assembly in both patients. Cell fusion experiments between 143B206 rho degrees cells, fully depleted of mitochondrial DNA, and fibroblasts from both patients led to phenotypic complementation of the complex I defects in mitochondria of the resulting cybrid cells. These results indicate that the complex I defects in the 2 reported cases are due to nuclear gene mutations.
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Affiliation(s)
- V Procaccio
- Laboratoire de Bioénergétique Cellulaire et Pathologique, EA2411 UJF/LRA6V CEA, DBMS, CEA Grenoble, 38054 Grenoble, France
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41
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Merante F, Mickle DA, Weisel RD, Li RK, Tumiati LC, Rao V, Williams WG, Robinson BH. Myocardial aerobic metabolism is impaired in a cell culture model of cyanotic heart disease. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:H1673-81. [PMID: 9815075 DOI: 10.1152/ajpheart.1998.275.5.h1673] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A human pediatric cardiomyocyte cell culture model of chronic cyanosis was used to assess the effects of low oxygen tension on mitochondrial enzyme activity to address the postoperative increase in lactate and decreased ATP in the myocardium and the high incidence of low-output failure with restoration of normal oxygen tension, after technically successful corrective cardiac surgery. Chronically hypoxic cells (PO2 = 40 mmHg for 7 days) exhibited significantly reduced activities for pyruvate dehydrogenase, cytochrome-c oxidase, succinate cytochrome c reductase, succinate dehydrogenase, and citrate synthase. The activity of NADH-cytochrome c reductase was unaffected. Lactate production and the lactate-to-pyruvate ratio were significantly greater in hypoxic cardiomyocytes. Western and Northern analysis demonstrated a decrease in the levels of various mRNA and corresponding polypeptides in hypoxic cells. Thus hypoxia influences mitochondrial metabolism through acute and chronic adaptive mechanisms, reflecting allosteric (posttranscriptional) and transcriptional modulation. Transcriptional downregulation of key mitochondrial enzyme systems can explain the insufficient myocardial aerobic metabolism and low-output failure in children with cyanotic heart disease after cardiac surgery.
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Affiliation(s)
- F Merante
- Centre for Cardiovascular Research, The Toronto Hospital and the University of Toronto, Toronto, Ontario, Canada M5G 2C4
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Denis-Gay M, Petit JM, Mazat JP, Ratinaud MH. Modifications of oxido-reductase activities in adriamycin-resistant leukaemia K562 cells. Biochem Pharmacol 1998; 56:451-7. [PMID: 9763220 DOI: 10.1016/s0006-2952(98)00084-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Adriamycin (ADR), a well-known antitumoral drug, interacts with DNA (nuclear and mitochondrial) and cardiolipin. Moreover, ADR induces numerous mitochondrial modifications in sensitive cells. However, no results have yet been obtained as to the repercussions of drug effects on oxido-reductase activities in ADR-resistant cells. To analyze mitochondrial damage induced by ADR treatment, we investigated lactate content, oxygen consumption, respiratory chain activities, and cytochrome content in ADR-sensitive K562 cells and two ADR-resistant variants (K562/R0.2 and K562/R0.5 cells). Biochemical investigations in ADR-resistant cells showed several mitochondrial modifications (in comparison to the parental cell line) according to the variant line and the physiologic state. More particularly, in K562/R0.5 cells cytochrome c (cyt c) oxidase (COX; EC 1.9.3.1) activity and cytochrome aa3 content dramatically decreased since cells enter into the stationary phase. Regardless of the number of multidrug-resistant cell subcultures in ADR-free medium, the cytochrome c oxidase activity in the stationary phase remained unchanged, indicating an irreversible effect of the drug. These alterations could correspond to several modifications of the nuclear and/or mitochondrial genome(s) following acquisition of the ADR resistance phenotype by K562 cells.
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Affiliation(s)
- M Denis-Gay
- Institut de Biotechnologie, Faculté des Sciences, Limoges, France
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Robinson BH. Human complex I deficiency: clinical spectrum and involvement of oxygen free radicals in the pathogenicity of the defect. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1364:271-86. [PMID: 9593934 DOI: 10.1016/s0005-2728(98)00033-4] [Citation(s) in RCA: 160] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- B H Robinson
- Departments of Biochemistry and Paediatrics, The University of Toronto, Toronto, Ontario, Canada.
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Link G, Saada A, Pinson A, Konijn AM, Hershko C. Mitochondrial respiratory enzymes are a major target of iron toxicity in rat heart cells. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 1998; 131:466-74. [PMID: 9605112 DOI: 10.1016/s0022-2143(98)90148-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Our previous studies in iron-loaded rat heart cells showed that in vitro iron loading results in peroxidative injury, manifested in a marked decrease in rate and amplitude of heart cell contractility and rhythmicity, which is correctable by treatment with deferoxamine (DF). In the present studies we explored the role of mitochondrial damage in myocardial iron toxicity. Iron loading by 24-hour incubation with 0.36 mmol/L ferric ammonium citrate resulted in a decrease in the activity of nicotinamide adenine dinucleotide (NADH)-cytochrome c oxidoreductase (complex I+III) to 35.3%+/-11.2% of the value in untreated controls; of succinate-cytochrome c oxidoreductase (complex II+III) to 57.4%+/-3.1%; and of succinate dehydrogenase to 63.5%+/-12.6% (p < 0.001 in all cases). The decrease in activity of other mitochondrial enzymes, including NADH-ferricyanide reductase, succinate ubiquinone oxidoreductase (complex II), cytochrome c oxidase (complex IV), and ubiquinol cytochrome c oxidoreductase (complex III), was less impressive and ranged from 71.5%+/-15.8% to 91.5%+/-14.6% of controls. That the observed loss of respiratory enzyme activity was a specific effect of iron toxicity was clearly demonstrated by the complete restoration of enzyme activities by in vitro iron chelation therapy. Sequential treatment with iron and doxorubicin caused a loss of complex I+III and complex II+III activity that was greater than that seen with either agent alone but was only partially correctable by DF treatment. Alterations in cellular adenosine triphosphate measurements paralleled very closely the changes observed in respiratory complex activity. These findings demonstrate for the first time the impairment of cardiac mitochondrial respiratory enzyme activity caused by iron loading at conditions formerly shown to produce severe abnormalities in contractility and rhythmicity.
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Affiliation(s)
- G Link
- Laboratory of Myocardial Research, Hebrew University, Hadassah Medical School, Jerusalem, Israel
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Luo X, Pitkänen S, Kassovska-Bratinova S, Robinson BH, Lehotay DC. Excessive formation of hydroxyl radicals and aldehydic lipid peroxidation products in cultured skin fibroblasts from patients with complex I deficiency. J Clin Invest 1997; 99:2877-82. [PMID: 9185510 PMCID: PMC508138 DOI: 10.1172/jci119481] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Previous studies suggest oxygen free radicals' involvement in the etiology of cardiomyopathy with cataracts. To investigate the role of free radicals in the pathogenesis of the cardiomyopathy with cataracts and complex I deficiency, fibroblasts from patients were assessed for hydroxyl radical formation and aldehydic lipid peroxidation products with and without redox active agents that increase free radicals. The rate of hydroxyl radical formation in patient cells was increased over 2-10-fold under basal conditions, and up to 20-fold after menadione or doxorubicin treatment compared with normal cells. We also found an overproduction of aldehydes in patient cells both under basal conditions and after treatment. Both hydroxyl radicals and toxic aldehydes such as hexanal, 4-hydroxynon-2-enal, and malondialdehyde were elevated in cells from patients with three types of complex I deficiency. In contrast, acyloins, the less toxic conjugated products of pyruvate and saturated aldehydes, were lower in the patient cells. Our data provide direct evidence for the first time that complex I deficiency is associated with excessive production of hydroxyl radicals and lipid peroxidation. The resultant damage may contribute to the early onset of cardiomyopathy and cataracts and death in early infancy in affected patients with this disease.
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Affiliation(s)
- X Luo
- Department of Pediatric Laboratory Medicine, Division of Clinical Biochemistry, University of Toronto
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Merante F, Duncan AM, Mitchell G, Duff C, Rommens J, Robinson BH. Chromosomal localization of the human liver form cytochrome c oxidase subunit VIIa gene. Genome 1997; 40:318-24. [PMID: 9202412 DOI: 10.1139/g97-044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The chromosomal loci corresponding to human cytochrome c oxidase (COX) subunit VIIa Liver (VIIa-L) isoform genes were determined utilizing a combined approach of genomic cloning, in situ hybridization, and somatic hybrid genetics. In contrast to the proposal of E. Arnaudo et al. (Gene (Amst.), 119: 299-305, 1992) that COX VIIa-L sequences are located on chromosomes 4 and 14, we found that COX VIIa-L related sequences reside on chromosome 6, while an additional COX VIIa-L cross-reacting sequence psi-gene) was located on chromosome 4.
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Affiliation(s)
- F Merante
- Centre for Cardiovascular Research, Toronto Hospital, ON, Canada
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Koroshetz WJ, Jenkins BG, Rosen BR, Beal MF. Energy metabolism defects in Huntington's disease and effects of coenzyme Q10. Ann Neurol 1997; 41:160-5. [PMID: 9029064 DOI: 10.1002/ana.410410206] [Citation(s) in RCA: 269] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We investigated whether the Huntington's disease (HD) gene mutation may produce either primary or secondary effects on energy metabolism. 31P magnetic resonance spectroscopy demonstrated a significant decrease in the phosphocreatine to inorganic phosphate ratio in resting muscle of 8 patients as compared with 8 control subjects. The cerebrospinal fluid lactate-pyruvate ratio was significantly increased in 15 patients as compared with 13 control subjects. Lactate concentrations assessed using 1H magnetic resonance spectroscopy are increased in Huntington's disease cerebral cortex. Treatment with coenzyme Q10, an essential cofactor of the electron transport chain, resulted in significant decreases in cortical lactate concentrations in 18 patients, which reversed following withdrawal of therapy. These findings provide evidence for a generalized energy defect in Huntington's disease, and suggest a possible therapy.
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Affiliation(s)
- W J Koroshetz
- Neurology Service, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA
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Handran SD, Werth JL, DeVivo DC, Rothman SM. Mitochondrial morphology and intracellular calcium homeostasis in cytochrome oxidase-deficient human fibroblasts. Neurobiol Dis 1997; 3:287-98. [PMID: 9173926 DOI: 10.1006/nbdi.1996.0125] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Mitochondrial encephalomyopathies arise from mutations in the mitochondrial or nuclear genome and result in defective energy metabolism. Investigation of cellular pathophysiology in these disorders has been limited to nonneuronal explant cultures such as fibroblasts and myoblasts. While investigating mitochondrial structure and function in fibroblasts obtained from control and cytochrome oxidase-deficient (COX) patients, we observed possible abnormalities by vital dye confocal microscopy. Most notable were swelling, reticulation (e.g., intricate fusion of mitochondria), and proliferation of mitochondria. However, a detailed quantitative comparison of mitochondrial morphology in age-, sex-, and passage-matched cultures revealed no significant differences between control and cytochrome oxidase-deficient fibroblasts, nor any differences with passage. In addition, COX fibroblasts exhibited no obvious impairment of intracellular calcium handling, measured by fura-2. These results indicate that cytochrome oxidase deficiency, at the level in these cultures, does not produce structural or ionic concentration alterations in fibroblasts. Future investigation of the pathophysiology of this respiratory chain disorder may require excitable tissue.
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Affiliation(s)
- S D Handran
- Center for the Study of Nervous System Injury and Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
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Pitkanen S, Robinson BH. Mitochondrial complex I deficiency leads to increased production of superoxide radicals and induction of superoxide dismutase. J Clin Invest 1996; 98:345-51. [PMID: 8755643 PMCID: PMC507436 DOI: 10.1172/jci118798] [Citation(s) in RCA: 292] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Mitochondria were isolated from skin fibroblast cultures derived from healthy individuals (controls) and from a group patients with complex I (NADH-CoQ reductase) deficiency of the mitochondrial respiratory chain. The complex I deficient patients included those with fatal infantile lactic acidosis (FILA), cardiomyopathy with cataracts (CC), hepatopathy with tubulopathy (HT), Leigh's disease (LD), cataracts and developmental delay (CD), and lactic acidemia in the neonatal period followed by mild symptoms (MS). Production of superoxide radicals, on addition of NADH, were measured using the luminometric probe lucigenin with isolated fibroblast mitochondrial membranes. Superoxide production rates were highest with CD and decreased in the order CD >> MS > LD > control > HT > FILA = CC. The quantity of Mn-superoxide dismutase (MnSOD), as measured by ELISA techniques, however, was highest in CC and FILA and lowest in CD. Plots of MnSOD quantity versus superoxide production showed an inverse relationship for most conditions with complex I deficiency. We hypothesize that oxygen radical production is increased when complex I activity is compromised. However, the observed superoxide production rates are modulated by the variant induction of MnSOD which decreases the rates, sometimes below those seen in control fibroblast mitochondria. In turn, we show that the variant induction of MnSOD is most likely a function of the change in the redox state of the cell experienced rather than a result of the complex I defect per se.
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Affiliation(s)
- S Pitkanen
- Department of Pediatrics, University of Toronto, Ontario, Canada
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Schägger H, Bentlage H, Ruitenbeek W, Pfeiffer K, Rotter S, Rother C, Böttcher-Purkl A, Lodemann E. Electrophoretic separation of multiprotein complexes from blood platelets and cell lines: technique for the analysis of diseases with defects in oxidative phosphorylation. Electrophoresis 1996; 17:709-14. [PMID: 8738332 DOI: 10.1002/elps.1150170415] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A two-dimensional electrophoretic technique combining blue native polyacrylamide gel electrophoresis (BN-PAGE) with Tricine sodium dodecyl sulfate (SDS)-PAGE was previously used for the localization of oxidative phosphorylation (OXPHOS) defects in human diseases starting from biopsy or autopsy tissues (Schägger, H., Electrophoresis 1995, 16, 763-770). In the present work the technique was extended for the resolution of OXPHOS enzymes from platelets and tissue-cultured cells. Silver staining is required to detect the protein subunits of OXPHOS complexes in two-dimensional gels. However, the use of cultured cells has major implications for patients with mitochondrial encephalomyopathies since it will reduce the number of invasive muscle biopsies. The ease of isolating the platelet membrane glycoprotein complex from a few milliliters of blood makes it possible to analyze this complex and its protein subunits in bleeding disorders like Glanzmann's thrombasthenia.
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Affiliation(s)
- H Schägger
- Zentrum der Biologischen Chemie, Universitätsklinikum Frankfurt, Germany
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