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Safran A, Proskorovski-Ohayon R, Eskin-Schwartz M, Yogev Y, Drabkin M, Eremenko E, Aharoni S, Freund O, Jean MM, Agam N, Hadar N, Loewenthal N, Staretz-Chacham O, Birk OS. Hyperinsulinism/hyperammonemia syndrome caused by biallelic SLC25A36 mutation. J Inherit Metab Dis 2023; 46:744-755. [PMID: 36695547 DOI: 10.1002/jimd.12594] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 01/06/2023] [Accepted: 01/19/2023] [Indexed: 01/26/2023]
Abstract
Hyperinsulinism/hyperammonemia (HI/HA) syndrome has been known to be caused by dominant gain-of-function mutations in GLUD1, encoding the mitochondrial enzyme glutamate dehydrogenase. Pathogenic GLUD1 mutations enhance enzymatic activity by reducing its sensitivity to allosteric inhibition by GTP. Two recent independent studies showed that a similar HI/HA phenotype can be caused by biallelic mutations in SLC25A36, encoding pyrimidine nucleotide carrier 2 (PNC2), a mitochondrial nucleotide carrier that transports pyrimidine and guanine nucleotides across the inner mitochondrial membrane: one study reported a single case caused by a homozygous truncating mutation in SLC25A36 resulting in lack of expression of SLC25A36 in patients' fibroblasts. A second study described two siblings with a splice site mutation in SLC25A36, causing reduction of mitochondrial GTP content, putatively leading to hyperactivation of glutamate dehydrogenase. In an independent study, through combined linkage analysis and exome sequencing, we demonstrate in four individuals of two Bedouin Israeli related families the same disease-causing SLC25A36 (NM_018155.3) c.284 + 3A > T homozygous splice-site mutation found in the two siblings. We demonstrate that the mutation, while causing skipping of exon 3, does not abrogate expression of mRNA and protein of the mutant SLC25A36 in patients' blood and fibroblasts. Affected individuals had hyperinsulinism, hyperammonemia, borderline low birth weight, tonic-clonic seizures commencing around 6 months of age, yet normal intellect and no significant other morbidities. Chronic constipation, hypothyroidism, and developmental delay previously described in a single patient were not found. We thus verify that biallelic SLC25A36 mutations indeed cause HI/HA syndrome and clearly delineate the disease phenotype.
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Affiliation(s)
- Amit Safran
- Morris Kahn Laboratory of Human Genetics at the Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and National Institute for Biotechnology in the Negev, Ben Gurion University, Beer Sheva, Israel
| | - Regina Proskorovski-Ohayon
- Morris Kahn Laboratory of Human Genetics at the Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and National Institute for Biotechnology in the Negev, Ben Gurion University, Beer Sheva, Israel
| | - Marina Eskin-Schwartz
- Morris Kahn Laboratory of Human Genetics at the Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and National Institute for Biotechnology in the Negev, Ben Gurion University, Beer Sheva, Israel
- Genetics Institute, Soroka Medical Center, Beer Sheva, Israel
| | - Yuval Yogev
- Morris Kahn Laboratory of Human Genetics at the Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and National Institute for Biotechnology in the Negev, Ben Gurion University, Beer Sheva, Israel
| | - Max Drabkin
- Morris Kahn Laboratory of Human Genetics at the Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and National Institute for Biotechnology in the Negev, Ben Gurion University, Beer Sheva, Israel
| | - Ekaterina Eremenko
- Department of Life Sciences and Shraga Segal Department of Microbiology, Immunology and Genetics, National Institute of Biotechnology in the Negev, Zlotowski Neuroscience Center and the Regenerative Medicine and Stem Cell Research Center, Ben-Gurion University, Beer Sheva, Israel
| | - Sarit Aharoni
- Morris Kahn Laboratory of Human Genetics at the Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and National Institute for Biotechnology in the Negev, Ben Gurion University, Beer Sheva, Israel
| | - Ofek Freund
- Morris Kahn Laboratory of Human Genetics at the Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and National Institute for Biotechnology in the Negev, Ben Gurion University, Beer Sheva, Israel
| | - Matan M Jean
- Morris Kahn Laboratory of Human Genetics at the Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and National Institute for Biotechnology in the Negev, Ben Gurion University, Beer Sheva, Israel
| | - Nadav Agam
- Morris Kahn Laboratory of Human Genetics at the Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and National Institute for Biotechnology in the Negev, Ben Gurion University, Beer Sheva, Israel
| | - Noam Hadar
- Morris Kahn Laboratory of Human Genetics at the Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and National Institute for Biotechnology in the Negev, Ben Gurion University, Beer Sheva, Israel
| | - Neta Loewenthal
- Pediatric Endocrinology Unit, Pediatric Division, Soroka Medical Center, Beer Sheva, Israel
- Faculty of Health Sciences, Ben Gurion University, Beer Sheva, Israel
| | - Orna Staretz-Chacham
- Faculty of Health Sciences, Ben Gurion University, Beer Sheva, Israel
- Pediatric Metabolic Clinic, Pediatric Division, Soroka Medical Center, Ben-Gurion University, Beer Sheva, Israel
| | - Ohad S Birk
- Morris Kahn Laboratory of Human Genetics at the Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences and National Institute for Biotechnology in the Negev, Ben Gurion University, Beer Sheva, Israel
- Genetics Institute, Soroka Medical Center, Beer Sheva, Israel
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Molina-Granada D, González-Vioque E, Dibley MG, Cabrera-Pérez R, Vallbona-Garcia A, Torres-Torronteras J, Sazanov LA, Ryan MT, Cámara Y, Martí R. Most mitochondrial dGTP is tightly bound to respiratory complex I through the NDUFA10 subunit. Commun Biol 2022; 5:620. [PMID: 35739187 PMCID: PMC9226000 DOI: 10.1038/s42003-022-03568-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 06/08/2022] [Indexed: 12/30/2022] Open
Abstract
Imbalanced mitochondrial dNTP pools are known players in the pathogenesis of multiple human diseases. Here we show that, even under physiological conditions, dGTP is largely overrepresented among other dNTPs in mitochondria of mouse tissues and human cultured cells. In addition, a vast majority of mitochondrial dGTP is tightly bound to NDUFA10, an accessory subunit of complex I of the mitochondrial respiratory chain. NDUFA10 shares a deoxyribonucleoside kinase (dNK) domain with deoxyribonucleoside kinases in the nucleotide salvage pathway, though no specific function beyond stabilizing the complex I holoenzyme has been described for this subunit. We mutated the dNK domain of NDUFA10 in human HEK-293T cells while preserving complex I assembly and activity. The NDUFA10E160A/R161A shows reduced dGTP binding capacity in vitro and leads to a 50% reduction in mitochondrial dGTP content, proving that most dGTP is directly bound to the dNK domain of NDUFA10. This interaction may represent a hitherto unknown mechanism regulating mitochondrial dNTP availability and linking oxidative metabolism to DNA maintenance.
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Affiliation(s)
- David Molina-Granada
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Emiliano González-Vioque
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
- Department of Clinical Biochemistry, Hospital Universitario Puerta del Hierro-Majadahonda, Madrid, Spain
| | - Marris G Dibley
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Raquel Cabrera-Pérez
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Antoni Vallbona-Garcia
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
| | - Javier Torres-Torronteras
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Leonid A Sazanov
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Michael T Ryan
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia
| | - Yolanda Cámara
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain.
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.
| | - Ramon Martí
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain.
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.
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Berardo A, Engelstad K, Hirano M. Advances in Thymidine Kinase 2 Deficiency: Clinical Aspects, Translational Progress, and Emerging Therapies. J Neuromuscul Dis 2022; 9:225-235. [PMID: 35094997 PMCID: PMC9028656 DOI: 10.3233/jnd-210786] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Defects in the replication, maintenance, and repair of mitochondrial DNA (mtDNA) constitute a growing and genetically heterogeneous group of mitochondrial disorders. Multiple genes participate in these processes, including thymidine kinase 2 (TK2) encoding the mitochondrial matrix protein TK2, a critical component of the mitochondrial nucleotide salvage pathway. TK2 deficiency (TK2d) causes mtDNA depletion, multiple deletions, or both, which manifest predominantly as mitochondrial myopathy. A wide clinical spectrum phenotype includes a severe, rapidly progressive, early onset form (median survival: < 2 years); a less severe childhood-onset form; and a late-onset form with a variably slower rate of progression. Clinical presentation typically includes progressive weakness of limb, neck, facial, oropharyngeal, and respiratory muscle, whereas limb myopathy with ptosis, ophthalmoparesis, and respiratory involvement is more common in the late-onset form. Deoxynucleoside monophosphates and deoxynucleosides that can bypass the TK2 enzyme defect have been assessed in a mouse model, as well as under open-label compassionate use (expanded access) in TK2d patients, indicating clinical efficacy with a favorable side-effect profile. This treatment is currently undergoing testing in clinical trials intended to support approval in the US and European Union (EU). In the early expanded access program, growth differentiation factor 15 (GDF-15) appears to be a useful biomarker that correlates with therapeutic response. With the advent of a specific treatment and given the high morbidity and mortality associated with TK2d, clinicians need to know how to recognize and diagnose this disorder. Here, we summarize translational research about this rare condition emphasizing clinical aspects.
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Affiliation(s)
- Andres Berardo
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
| | - Kristin Engelstad
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
| | - Michio Hirano
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
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Ramón J, Vila-Julià F, Molina-Granada D, Molina-Berenguer M, Melià MJ, García-Arumí E, Torres-Torronteras J, Cámara Y, Martí R. Therapy Prospects for Mitochondrial DNA Maintenance Disorders. Int J Mol Sci 2021; 22:6447. [PMID: 34208592 PMCID: PMC8234938 DOI: 10.3390/ijms22126447] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 06/10/2021] [Accepted: 06/11/2021] [Indexed: 02/07/2023] Open
Abstract
Mitochondrial DNA depletion and multiple deletions syndromes (MDDS) constitute a group of mitochondrial diseases defined by dysfunctional mitochondrial DNA (mtDNA) replication and maintenance. As is the case for many other mitochondrial diseases, the options for the treatment of these disorders are rather limited today. Some aggressive treatments such as liver transplantation or allogeneic stem cell transplantation are among the few available options for patients with some forms of MDDS. However, in recent years, significant advances in our knowledge of the biochemical pathomechanisms accounting for dysfunctional mtDNA replication have been achieved, which has opened new prospects for the treatment of these often fatal diseases. Current strategies under investigation to treat MDDS range from small molecule substrate enhancement approaches to more complex treatments, such as lentiviral or adenoassociated vector-mediated gene therapy. Some of these experimental therapies have already reached the clinical phase with very promising results, however, they are hampered by the fact that these are all rare disorders and so the patient recruitment potential for clinical trials is very limited.
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Affiliation(s)
- Javier Ramón
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Ferran Vila-Julià
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - David Molina-Granada
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Miguel Molina-Berenguer
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Maria Jesús Melià
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Elena García-Arumí
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Javier Torres-Torronteras
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Yolanda Cámara
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Ramon Martí
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d’Hebron Research Institute, Universitat Autònoma de Barcelona, 08035 Barcelona, Spain; (J.R.); (F.V.-J.); (D.M.-G.); (M.M.-B.); (M.J.M.); (E.G.-A.); (J.T.-T.); (Y.C.)
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, 28029 Madrid, Spain
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Drosophila melanogaster Mitochondrial Carriers: Similarities and Differences with the Human Carriers. Int J Mol Sci 2020; 21:ijms21176052. [PMID: 32842667 PMCID: PMC7504413 DOI: 10.3390/ijms21176052] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 08/19/2020] [Accepted: 08/19/2020] [Indexed: 12/15/2022] Open
Abstract
Mitochondrial carriers are a family of structurally related proteins responsible for the exchange of metabolites, cofactors and nucleotides between the cytoplasm and mitochondrial matrix. The in silico analysis of the Drosophila melanogaster genome has highlighted the presence of 48 genes encoding putative mitochondrial carriers, but only 20 have been functionally characterized. Despite most Drosophila mitochondrial carrier genes having human homologs and sharing with them 50% or higher sequence identity, D. melanogaster genes display peculiar differences from their human counterparts: (1) in the fruit fly, many genes encode more transcript isoforms or are duplicated, resulting in the presence of numerous subfamilies in the genome; (2) the expression of the energy-producing genes in D. melanogaster is coordinated from a motif known as Nuclear Respiratory Gene (NRG), a palindromic 8-bp sequence; (3) fruit-fly duplicated genes encoding mitochondrial carriers show a testis-biased expression pattern, probably in order to keep a duplicate copy in the genome. Here, we review the main features, biological activities and role in the metabolism of the D. melanogaster mitochondrial carriers characterized to date, highlighting similarities and differences with their human counterparts. Such knowledge is very important for obtaining an integrated view of mitochondrial function in D. melanogaster metabolism.
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Sommerville EW, Dalla Rosa I, Rosenberg MM, Bruni F, Thompson K, Rocha M, Blakely EL, He L, Falkous G, Schaefer AM, Yu‐Wai‐Man P, Chinnery PF, Hedstrom L, Spinazzola A, Taylor RW, Gorman GS. Identification of a novel heterozygous guanosine monophosphate reductase (GMPR) variant in a patient with a late-onset disorder of mitochondrial DNA maintenance. Clin Genet 2020; 97:276-286. [PMID: 31600844 PMCID: PMC7004030 DOI: 10.1111/cge.13652] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 09/18/2019] [Accepted: 09/27/2019] [Indexed: 12/18/2022]
Abstract
Autosomal dominant progressive external ophthalmoplegia (adPEO) is a late-onset, Mendelian mitochondrial disorder characterised by paresis of the extraocular muscles, ptosis, and skeletal-muscle restricted multiple mitochondrial DNA (mtDNA) deletions. Although dominantly inherited, pathogenic variants in POLG, TWNK and RRM2B are among the most common genetic defects of adPEO, identification of novel candidate genes and the underlying pathomechanisms remains challenging. We report the clinical, genetic and molecular investigations of a patient who presented in the seventh decade of life with PEO. Oxidative histochemistry revealed cytochrome c oxidase-deficient fibres and occasional ragged red fibres showing subsarcolemmal mitochondrial accumulation in skeletal muscle, while molecular studies identified the presence of multiple mtDNA deletions. Negative candidate screening of known nuclear genes associated with PEO prompted diagnostic exome sequencing, leading to the prioritisation of a novel heterozygous c.547G>C variant in GMPR (NM_006877.3) encoding guanosine monophosphate reductase, a cytosolic enzyme required for maintaining the cellular balance of adenine and guanine nucleotides. We show that the novel c.547G>C variant causes aberrant splicing, decreased GMPR protein levels in patient skeletal muscle, proliferating and quiescent cells, and is associated with subtle changes in nucleotide homeostasis protein levels and evidence of disturbed mtDNA maintenance in skeletal muscle. Despite confirmation of GMPR deficiency, demonstrating marked defects of mtDNA replication or nucleotide homeostasis in patient cells proved challenging. Our study proposes that GMPR is the 19th locus for PEO and highlights the complexities of uncovering disease mechanisms in late-onset PEO phenotypes.
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Affiliation(s)
- Ewen W. Sommerville
- Wellcome Centre for Mitochondrial Research, Institute of NeuroscienceNewcastle UniversityNewcastle upon TyneUK
| | - Ilaria Dalla Rosa
- Department of Clinical and Movement Neurosciences, UCL Queens Square Institute of Neurology, Royal Free CampusUniversity College LondonLondonUK
| | | | - Francesco Bruni
- Wellcome Centre for Mitochondrial Research, Institute of NeuroscienceNewcastle UniversityNewcastle upon TyneUK
- Department of Biosciences, Biotechnologies and BiopharmaceuticsUniversity of Bari “ldo Moro”BariItaly
| | - Kyle Thompson
- Wellcome Centre for Mitochondrial Research, Institute of NeuroscienceNewcastle UniversityNewcastle upon TyneUK
| | - Mariana Rocha
- Wellcome Centre for Mitochondrial Research, Institute of NeuroscienceNewcastle UniversityNewcastle upon TyneUK
| | - Emma L. Blakely
- Wellcome Centre for Mitochondrial Research, Institute of NeuroscienceNewcastle UniversityNewcastle upon TyneUK
| | - Langping He
- Wellcome Centre for Mitochondrial Research, Institute of NeuroscienceNewcastle UniversityNewcastle upon TyneUK
| | - Gavin Falkous
- Wellcome Centre for Mitochondrial Research, Institute of NeuroscienceNewcastle UniversityNewcastle upon TyneUK
| | - Andrew M. Schaefer
- Wellcome Centre for Mitochondrial Research, Institute of NeuroscienceNewcastle UniversityNewcastle upon TyneUK
| | - Patrick Yu‐Wai‐Man
- NIHR Biomedical Research Centre at Moorfields Eye Hospital and UCL Institute of OphthalmologyLondonUK
- MRC Mitochondrial Biology UnitUniversity of CambridgeCambridgeUK
- Cambridge Centre for Brain Repair, Department of Clinical NeurosciencesUniversity of CambridgeCambridgeUK
| | - Patrick F. Chinnery
- Department of Clinical Neuroscience & Medical Research Council Mitochondrial Biology UnitSchool of Clinical Medicine, University of CambridgeCambridgeUK
| | - Lizbeth Hedstrom
- Department of BiologyBrandeis UniversityWalthamMA
- Department of ChemistryBrandeis University, 415 South St.WalthamMA
| | - Antonella Spinazzola
- Department of Clinical and Movement Neurosciences, UCL Queens Square Institute of Neurology, Royal Free CampusUniversity College LondonLondonUK
- MRC Centre for Neuromuscular DiseasesUCL Institute of Neurology and National Hospital for Neurology and NeurosurgeryLondonUK
| | - Robert W. Taylor
- Wellcome Centre for Mitochondrial Research, Institute of NeuroscienceNewcastle UniversityNewcastle upon TyneUK
| | - Gráinne S. Gorman
- Wellcome Centre for Mitochondrial Research, Institute of NeuroscienceNewcastle UniversityNewcastle upon TyneUK
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Bioavailability and cytosolic kinases modulate response to deoxynucleoside therapy in TK2 deficiency. EBioMedicine 2019; 46:356-367. [PMID: 31383553 PMCID: PMC6710986 DOI: 10.1016/j.ebiom.2019.07.037] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/10/2019] [Accepted: 07/15/2019] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND TK2 is a nuclear gene encoding the mitochondrial matrix protein thymidine kinase 2 (TK2), a critical enzyme in the mitochondrial nucleotide salvage pathway. Deficiency of TK2 activity causes mitochondrial DNA (mtDNA) depletion, which in humans manifests predominantly as a mitochondrial myopathy with onset typically in infancy and childhood. We previously showed that oral treatment of the Tk2 H126N knock-in mouse model (Tk2-/-) with the TK2 substrates, deoxycytidine (dCtd) and thymidine (dThd), delayed disease onset and prolonged median survival by 3-fold. Nevertheless, dCtd + dThd treated Tk2-/- mice showed mtDNA depletion in brain as early as postnatal day 13 and in virtually all other tissues at age 29 days. METHODS To enhance mechanistic understanding and efficacy of dCtd + dThd therapy, we studied the bioavailability of dCtd and dThd in various tissues as well as levels of the cytosolic enzymes, TK1 and dCK that convert the deoxynucleosides into dCMP and dTMP. FINDINGS Parenteral treatment relative to oral treatment produced higher levels of dCtd and dThd and improved mtDNA levels in liver and heart, but did not ameliorate molecular defects in brain or prolong survival. Down-regulation of TK1 correlated with temporal- and tissue-specificity of response to dCtd + dThd. Finally, we observed in human infant and adult muscle expression of TK1 and dCK, which account for the long-term efficacy to dCtd + dThd therapy in TK2 deficient patients. INTERPRETATIONS These data indicate that the cytosolic pyrimidine salvage pathway enzymes TK1 and dCK are critical for therapeutic efficacy of deoxynucleoside therapy for Tk2 deficiency. FUND: National Institutes of Health P01HD32062.
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Slc25a36 modulates pluripotency of mouse embryonic stem cells by regulating mitochondrial function and glutathione level. Biochem J 2019; 476:1585-1604. [PMID: 31036718 DOI: 10.1042/bcj20190057] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/09/2019] [Accepted: 04/29/2019] [Indexed: 01/01/2023]
Abstract
Mitochondria play a central role in the maintenance of the naive state of embryonic stem cells. Many details of the mechanism remain to be fully elucidated. Solute carrier family 25 member 36 (Slc25a36) might regulate mitochondrial function through transporting pyrimidine nucleotides for mtDNA/RNA synthesis. Its physical role in this process remains unknown; however, Slc25a36 was recently found to be highly expressed in naive mouse embryonic stem cells (mESCs). Here, the function of Slc25a36 was characterized as a maintenance factor of mESCs pluripotency. Slc25a36 deficiency (via knockdown) has been demonstrated to result in mitochondrial dysfunction, which induces the differentiation of mESCs. The expression of key pluripotency markers (Pou5f1, Sox2, Nanog, and Utf1) decreased, while that of key TE genes (Cdx2, Gata3, and Hand1) increased. Cdx2-positive cells emerged in Slc25a36-deficient colonies under trophoblast stem cell culture conditions. As a result of Slc25a36 deficiency, mtDNA of knockdown cells declined, leading to impaired mitochondria with swollen morphology, decreased mitochondrial membrane potential, and low numbers. The key transcription regulators of mitochondrial biogenesis also decreased. These results indicate that mitochondrial dysfunction leads to an inability to support the pluripotency maintenance. Moreover, down-regulated glutathione metabolism and up-regulated focal adhesion reinforced and stabilized the process of differentiation by separately enhancing OCT4 degradation and promoting cell spread. This study improves the understanding of the function of Slc25a36, as well as the relationship of mitochondrial function with naive pluripotency maintenance and stem cell fate decision.
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Franzolin E, Salata C, Bianchi V, Rampazzo C. The Deoxynucleoside Triphosphate Triphosphohydrolase Activity of SAMHD1 Protein Contributes to the Mitochondrial DNA Depletion Associated with Genetic Deficiency of Deoxyguanosine Kinase. J Biol Chem 2015; 290:25986-96. [PMID: 26342080 PMCID: PMC4646252 DOI: 10.1074/jbc.m115.675082] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Indexed: 11/22/2022] Open
Abstract
The dNTP triphosphohydrolase SAMHD1 is a nuclear antiviral host restriction factor limiting HIV-1 infection in macrophages and a major regulator of dNTP concentrations in human cells. In normal human fibroblasts its expression increases during quiescence, contributing to the small dNTP pool sizes of these cells. Down-regulation of SAMHD1 by siRNA expands all four dNTP pools, with dGTP undergoing the largest relative increase. The deoxyguanosine released by SAMHD1 from dGTP can be phosphorylated inside mitochondria by deoxyguanosine kinase (dGK) or degraded in the cytosol by purine nucleoside phosphorylase. Genetic mutations of dGK cause mitochondrial (mt) DNA depletion in noncycling cells and hepato-cerebral mtDNA depletion syndrome in humans. We studied if SAMHD1 and dGK interact in the regulation of the dGTP pool during quiescence employing dGK-mutated skin fibroblasts derived from three unrelated patients. In the presence of SAMHD1 quiescent mutant fibroblasts manifested mt dNTP pool imbalance and mtDNA depletion. When SAMHD1 was silenced by siRNA transfection the composition of the mt dNTP pool approached that of the controls, and mtDNA copy number increased, compensating the depletion to various degrees in the different mutant fibroblasts. Chemical inhibition of purine nucleoside phosphorylase did not improve deoxyguanosine recycling by dGK in WT cells. We conclude that the activity of SAMHD1 contributes to the pathological phenotype of dGK deficiency. Our results prove the importance of SAMHD1 in the regulation of all dNTP pools and suggest that dGK inside mitochondria has the function of recycling the deoxyguanosine derived from endogenous dGTP degraded by SAMHD1 in the nucleus.
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Affiliation(s)
- Elisa Franzolin
- From the Department of Biology, University of Padova, 35131 Padova, Italy and
| | - Cristiano Salata
- Department of Molecular Medicine, University of Padova, 35121 Padova, Italy
| | - Vera Bianchi
- From the Department of Biology, University of Padova, 35131 Padova, Italy and
| | - Chiara Rampazzo
- From the Department of Biology, University of Padova, 35131 Padova, Italy and
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10
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Garone C, Garcia-Diaz B, Emmanuele V, Lopez LC, Tadesse S, Akman HO, Tanji K, Quinzii CM, Hirano M. Deoxypyrimidine monophosphate bypass therapy for thymidine kinase 2 deficiency. EMBO Mol Med 2015; 6:1016-27. [PMID: 24968719 PMCID: PMC4154130 DOI: 10.15252/emmm.201404092] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Autosomal recessive mutations in the thymidine kinase 2 gene (TK2) cause mitochondrial DNA depletion, multiple deletions, or both due to loss of TK2 enzyme activity and ensuing unbalanced deoxynucleotide triphosphate (dNTP) pools. To bypass Tk2 deficiency, we administered deoxycytidine and deoxythymidine monophosphates (dCMP+dTMP) to the Tk2 H126N (Tk2(-/-)) knock-in mouse model from postnatal day 4, when mutant mice are phenotypically normal, but biochemically affected. Assessment of 13-day-old Tk2(-/-) mice treated with dCMP+dTMP 200 mg/kg/day each (Tk2(-/-200dCMP/) (dTMP)) demonstrated that in mutant animals, the compounds raise dTTP concentrations, increase levels of mtDNA, ameliorate defects of mitochondrial respiratory chain enzymes, and significantly prolong their lifespan (34 days with treatment versus 13 days untreated). A second trial of dCMP+dTMP each at 400 mg/kg/day showed even greater phenotypic and biochemical improvements. In conclusion, dCMP/dTMP supplementation is the first effective pharmacologic treatment for Tk2 deficiency.
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Affiliation(s)
- Caterina Garone
- Department of Neurology, Columbia University Medical Center, New York, NY, USA Human Genetics Joint PhD Program, University of Bologna and Turin, Turin, Italy
| | - Beatriz Garcia-Diaz
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | - Valentina Emmanuele
- Department of Neurology, Columbia University Medical Center, New York, NY, USA Pediatric Clinic University of Genoa IRCCS G. Gaslini Institute, Genoa, Italy
| | - Luis C Lopez
- Instituto de Biotecnología, Centro de Investigación Biomédica, Universidad de Granada Parque Tecnológico de Ciencias de la Salud, Armilla, Spain
| | - Saba Tadesse
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | - Hasan O Akman
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | - Kurenai Tanji
- Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY, USA
| | - Catarina M Quinzii
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | - Michio Hirano
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
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11
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Kamath VG, Hsiung CH, Lizenby ZJ, McKee EE. Heart mitochondrial TTP synthesis and the compartmentalization of TMP. J Biol Chem 2014; 290:2034-41. [PMID: 25505243 DOI: 10.1074/jbc.m114.624213] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The primary pathway of TTP synthesis in the heart requires thymidine salvage by mitochondrial thymidine kinase 2 (TK2). However, the compartmentalization of this pathway and the transport of thymidine nucleotides are not well understood. We investigated the metabolism of [(3)H]thymidine or [(3)H]TMP as precursors of [(3)H]TTP in isolated intact or broken mitochondria from the rat heart. The results demonstrated that [(3)H]thymidine was readily metabolized by the mitochondrial salvage enzymes to TTP in intact mitochondria. The equivalent addition of [(3)H]TMP produced far less [(3)H]TTP than the amount observed with [(3)H]thymidine as the precursor. Using zidovudine to inhibit TK2, the synthesis of [(3)H]TTP from [(3)H]TMP was effectively blocked, demonstrating that synthesis of [(3)H]TTP from [(3)H]TMP arose solely from the dephosphorysynthase pathway that includes deoxyuridine triphosphatelation of [(3)H]TMP to [(3)H]thymidine. To determine the role of the membrane in TMP metabolism, mitochondrial membranes were disrupted by freezing and thawing. In broken mitochondria, [(3)H]thymidine was readily converted to [(3)H]TMP, but further phosphorylation was prevented even though the energy charge was well maintained by addition of oligomycin A, phosphocreatine, and creatine phosphokinase. The failure to synthesize TTP in broken mitochondria was not related to a loss of membrane potential or inhibition of the electron transport chain, as confirmed by addition of carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone and potassium cyanide, respectively, in intact mitochondria. In summary, these data, taken together, suggest that the thymidine salvage pathway is compartmentalized so that TMP kinase prefers TMP synthesized by TK2 over medium TMP and that this is disrupted in broken mitochondria.
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Affiliation(s)
- Vasudeva G Kamath
- From the Department of Foundational Sciences, College of Medicine, Central Michigan University, Mount Pleasant, Michigan 48859
| | - Chia-Heng Hsiung
- From the Department of Foundational Sciences, College of Medicine, Central Michigan University, Mount Pleasant, Michigan 48859
| | - Zachary J Lizenby
- From the Department of Foundational Sciences, College of Medicine, Central Michigan University, Mount Pleasant, Michigan 48859
| | - Edward E McKee
- From the Department of Foundational Sciences, College of Medicine, Central Michigan University, Mount Pleasant, Michigan 48859
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12
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Di Noia MA, Todisco S, Cirigliano A, Rinaldi T, Agrimi G, Iacobazzi V, Palmieri F. The human SLC25A33 and SLC25A36 genes of solute carrier family 25 encode two mitochondrial pyrimidine nucleotide transporters. J Biol Chem 2014; 289:33137-48. [PMID: 25320081 DOI: 10.1074/jbc.m114.610808] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human genome encodes 53 members of the solute carrier family 25 (SLC25), also called the mitochondrial carrier family, many of which have been shown to transport inorganic anions, amino acids, carboxylates, nucleotides, and coenzymes across the inner mitochondrial membrane, thereby connecting cytosolic and matrix functions. Here two members of this family, SLC25A33 and SLC25A36, have been thoroughly characterized biochemically. These proteins were overexpressed in bacteria and reconstituted in phospholipid vesicles. Their transport properties and kinetic parameters demonstrate that SLC25A33 transports uracil, thymine, and cytosine (deoxy)nucleoside di- and triphosphates by an antiport mechanism and SLC25A36 cytosine and uracil (deoxy)nucleoside mono-, di-, and triphosphates by uniport and antiport. Both carriers also transported guanine but not adenine (deoxy)nucleotides. Transport catalyzed by both carriers was saturable and inhibited by mercurial compounds and other inhibitors of mitochondrial carriers to various degrees. In confirmation of their identity (i) SLC25A33 and SLC25A36 were found to be targeted to mitochondria and (ii) the phenotypes of Saccharomyces cerevisiae cells lacking RIM2, the gene encoding the well characterized yeast mitochondrial pyrimidine nucleotide carrier, were overcome by expressing SLC25A33 or SLC25A36 in these cells. The main physiological role of SLC25A33 and SLC25A36 is to import/export pyrimidine nucleotides into and from mitochondria, i.e. to accomplish transport steps essential for mitochondrial DNA and RNA synthesis and breakdown.
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Affiliation(s)
- Maria Antonietta Di Noia
- From the Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, via Orabona 4, 70125 Bari, Italy, Department of Sciences, University of Basilicata, via N. Sauro 85, 85100 Potenza, Italy
| | - Simona Todisco
- From the Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, via Orabona 4, 70125 Bari, Italy
| | - Angela Cirigliano
- Pasteur Institute-Cenci Bolognetti Foundation, Department of Biology and Biotechnology "Charles Darwin," University of Rome La Sapienza, 00185 Rome, Italy, Associazione Gian Franco Lupo "Un Sorriso alla Vita," ASM Azienda Sanitaria Locale di Matera, via Montescaglioso 75100 Matera, Italy, and
| | - Teresa Rinaldi
- Pasteur Institute-Cenci Bolognetti Foundation, Department of Biology and Biotechnology "Charles Darwin," University of Rome La Sapienza, 00185 Rome, Italy
| | - Gennaro Agrimi
- From the Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, via Orabona 4, 70125 Bari, Italy
| | - Vito Iacobazzi
- From the Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, via Orabona 4, 70125 Bari, Italy, Center of Excellence in Comparative Genomics, University of Bari, via Orabona 4, 70125 Bari, Italy
| | - Ferdinando Palmieri
- From the Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, via Orabona 4, 70125 Bari, Italy, Center of Excellence in Comparative Genomics, University of Bari, via Orabona 4, 70125 Bari, Italy
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13
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Da-Rè C, Franzolin E, Biscontin A, Piazzesi A, Pacchioni B, Gagliani MC, Mazzotta G, Tacchetti C, Zordan MA, Zeviani M, Bernardi P, Bianchi V, De Pittà C, Costa R. Functional characterization of drim2, the Drosophila melanogaster homolog of the yeast mitochondrial deoxynucleotide transporter. J Biol Chem 2014; 289:7448-59. [PMID: 24469456 PMCID: PMC3953259 DOI: 10.1074/jbc.m113.543926] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 01/22/2014] [Indexed: 12/03/2022] Open
Abstract
The CG18317 gene (drim2) is the Drosophila melanogaster homolog of the Saccharomyces cerevisiae Rim2 gene, which encodes a pyrimidine (deoxy)nucleotide carrier. Here, we tested if the drim2 gene also encodes for a deoxynucleotide transporter in the fruit fly. The protein was localized to mitochondria. Drosophila S2R(+) cells, silenced for drim2 expression, contained markedly reduced pools of both purine and pyrimidine dNTPs in mitochondria, whereas cytosolic pools were unaffected. In vivo drim2 homozygous knock-out was lethal at the larval stage, preceded by the following: (i) impaired locomotor behavior; (ii) decreased rates of oxygen consumption, and (iii) depletion of mtDNA. We conclude that the Drosophila mitochondrial carrier dRIM2 transports all DNA precursors and is essential to maintain mitochondrial function.
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Affiliation(s)
| | | | | | | | | | - Maria Cristina Gagliani
- the MicroScoBio Research Center, Department of Experimental Medicine, University of Genova, 16132 Genova, Italy
| | | | - Carlo Tacchetti
- the MicroScoBio Research Center, Department of Experimental Medicine, University of Genova, 16132 Genova, Italy
- the Experimental Imaging Center, San Raffaele Scientific Institute, 20132 Milano, Italy
| | | | - Massimo Zeviani
- the MRC Mitocondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - Paolo Bernardi
- the Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy, and
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14
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Cámara Y, González-Vioque E, Scarpelli M, Torres-Torronteras J, Martí R. Feeding the deoxyribonucleoside salvage pathway to rescue mitochondrial DNA. Drug Discov Today 2013; 18:950-7. [DOI: 10.1016/j.drudis.2013.06.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 05/27/2013] [Accepted: 06/19/2013] [Indexed: 12/16/2022]
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