51
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Li X, Li L, Sun Y, Lv F, Zhang G, Liu W, Zhang M, Jiang H, Liu S. Whole exome sequencing reveals two novel compound heterozygous mutations in TWNK as a cause of the hepatocerebral form of mitochondrial DNA depletion syndrome: a case report. BMC MEDICAL GENETICS 2019; 20:146. [PMID: 31455269 PMCID: PMC6712797 DOI: 10.1186/s12881-019-0875-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Accepted: 08/11/2019] [Indexed: 12/13/2022]
Abstract
BACKGROUND Although Mitochondrial DNA depletion syndrome (MDS) can be classified into three forms: myopathic, encephalomyopathic and hepatocerebral form, it is difficult to identify its form due to its clinical heterogeneity. Therefore, it is very important to conduct molecular genetic analysis on suspected patients. This study presented a male 38 weeks and 5 days infant with liver cytolysis and leukodystrophy. CASE PRESENTATION A male infant proband was admitted to the department of NICU for feeding intolerance, irregular rhythm of respiration, hypoglycemia, lactic acidosis, liver cytolysis and neurological abnormalities. He was onset of mild jaundice with leukodystrophy and high lactate and phenylderivatives for urine organic acids on the 7th day. Whole exome sequencing (WES) and Sanger sequencing were performed to screen and confirm the suspicious pathogenic mutations. The results revealed this proband carried two compound heterozygous mutations in TWNK: c.1186 C > T / p.Pro396Ser and c.1844 G > C / p.Gly615Ala inherited by an autosomal recessive form from his parents, of which protein conservative analysis and structural modeling supported the pathogenicity of the two mutations. Unfortunately, the conditions described above were not improved until he was discharged from the hospital on the 23rd day and died at 4 months of age. CONCLUSIONS In this study, we investigated a Chinese family with the hepatocerebral form of MDS and conducted WES and Sanger sequencing to explore the causative mutations for this proband born from non-consanguineous and healthy parents. We identified two novel TWNK c.1186 C > T/ c.1844 G > C compound heterozygous mutations which were probably the disease-causing mutations of hepatocerebral form of MDS and described the clinical manifestations of the proband, which expanded the phenotypic spectrum of MDS caused by variants in TWNK. This study also emphasized WES technology can provide the genetic diagnosis of Mendelian genetic disease.
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Affiliation(s)
- Xianghong Li
- Department of Neonatology, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China
| | - Liangshan Li
- Medical Genetic Department, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China
| | - Yaqi Sun
- Shandong Provincial Key Laboratory of Metabolic Diseases and Qingdao Key Laboratory of Gout, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China
| | - Fuyan Lv
- Qingdao Women and Children's Hospital, Qingdao, 266034, China
| | - Guoqing Zhang
- Department of Orthopaedic Surgery, the Affiliated Hospital of Qingdao University, Qingdao, 266000, China
| | - Wenmiao Liu
- Medical Genetic Department, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China
| | - Meiyan Zhang
- Department of Neonatology, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China
| | - Hong Jiang
- Department of Neonatology, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China.
| | - Shiguo Liu
- Medical Genetic Department, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China.
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52
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CPEO and Mitochondrial Myopathy in a Patient with DGUOK Compound Heterozygous Pathogenetic Variant and mtDNA Multiple Deletions. Case Rep Neurol Med 2019; 2019:5918632. [PMID: 30956829 PMCID: PMC6431376 DOI: 10.1155/2019/5918632] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Accepted: 02/19/2019] [Indexed: 11/21/2022] Open
Abstract
The classic features of deoxyguanosine kinase (DGUOK) deficiency are infantile onset hepatic failure with nystagmus and hypotonia; mitochondrial DNA studies on affected tissue reveal mitochondrial DNA depletion. Later, it has been shown that the mutations in the same gene may present with adult-onset mitochondrial myopathy and mitochondrial DNA multiple deletions in skeletal muscle. Here we report the case of a 42-year-old Italian woman presenting with a chronic progressive external ophthalmoplegia and myopathy with mtDNA multiple deletions and the compound heterozygous c.462T>A (p.Asn154Lys) and c.707+2T>G pathogenic variants in DGUOK.
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53
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Moreira-Silva H, Maio I, Bandeira A, Gomes-Martins E, Santos-Silva E. Metabolic liver diseases presenting with neonatal cholestasis: at the crossroad between old and new paradigms. Eur J Pediatr 2019; 178:515-523. [PMID: 30693370 DOI: 10.1007/s00431-019-03328-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 01/15/2019] [Accepted: 01/17/2019] [Indexed: 12/18/2022]
Abstract
Metabolic liver diseases (MLD) are an important group of disorders presenting with neonatal cholestasis (NC). The spectrum of liver involvement is wide and the presumptive diagnosis is traditionally based on clinical and laboratory findings. Recently, next-generation sequencing (NGS) panels have emerged as an appealing tool to diagnose neonatal/infantile cholestatic disorders. The aim of this study was to identify clinical phenotypes of liver injury and contribute to find a diagnostic methodology that integrates new molecular diagnostic tools. We retrospectively analyzed the clinical and biochemical features of 16 patients with MLD and NC. Patients were categorized into three groups: A-NC with liver failure (N = 8): tyrosinemia type I (n = 2), classic galactosemia (n = 5), mitochondrial DNA depletion syndrome (n = 1); B-NC evolving with chronic liver disease (N = 5): argininemia (n = 2); mitochondrial cytopathy (n = 1); congenital disorders of glycosylation type Ia (n = 1); Zellweger syndrome (n = 1); and C-transient NC (N = 3): Niemann-Pick type C (n = 2), citrullinemia type II (n = 1).Conclusion: MLD presenting with NC can be categorized into three main clinical phenotypes of liver injury. We highlight transient NC as a clue for MLD that must be pursued. New molecular diagnostic tools can play a key role, but application criteria must be established to make them cost-effective. What is Known: • Metabolic liver diseases are an important group of disorders presenting with neonatal cholestasis. • The diagnostic approach is challenging and traditionally based on clinical and laboratory findings. Next-generation sequencing is a recent and rapidly developing tool in pediatric hepatology. What is New: • We provide a liver-targeted characterization of metabolic liver diseases presenting with neonatal cholestasis, categorizing them into three clinical phenotypes that may narrow the diagnostic possibilities. • A clinical decision-making algorithm is proposed, in which the NGS technology is integrated.
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Affiliation(s)
- Helena Moreira-Silva
- Pediatric Gastroenterology Unit, Centro Materno Infantil do Norte - CMIN, Centro Hospitalar Universitário do Porto, Largo da Maternidade de Júlio Dinis, 4050-651, Porto, Portugal
| | - Inês Maio
- Pediatric Gastroenterology Unit, Centro Materno Infantil do Norte - CMIN, Centro Hospitalar Universitário do Porto, Largo da Maternidade de Júlio Dinis, 4050-651, Porto, Portugal
| | - Anabela Bandeira
- Pediatric Metabolic Unit, Centro Materno Infantil do Norte - CMIN, Centro Hospitalar Universitário do Porto, Porto, Portugal
| | - Esmeralda Gomes-Martins
- Pediatric Metabolic Unit, Centro Materno Infantil do Norte - CMIN, Centro Hospitalar Universitário do Porto, Porto, Portugal.,Instituto de Ciências Biomédicas Abel Salazar, Porto, Portugal
| | - Ermelinda Santos-Silva
- Pediatric Gastroenterology Unit, Centro Materno Infantil do Norte - CMIN, Centro Hospitalar Universitário do Porto, Largo da Maternidade de Júlio Dinis, 4050-651, Porto, Portugal. .,Instituto de Ciências Biomédicas Abel Salazar, Porto, Portugal.
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54
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Desler C, Lillenes MS, Tønjum T, Rasmussen LJ. The Role of Mitochondrial Dysfunction in the Progression of Alzheimer's Disease. Curr Med Chem 2019; 25:5578-5587. [PMID: 28618998 PMCID: PMC6446443 DOI: 10.2174/0929867324666170616110111] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Revised: 01/02/2017] [Accepted: 01/02/2017] [Indexed: 11/22/2022]
Abstract
The current molecular understanding of Alzheimer's disease (AD) has still not resulted in successful interventions. Mitochondrial dysfunction of the AD brain is currently emerging as a hallmark of this disease. One mitochondrial function often affected in AD is oxidative phosphorylation responsible for ATP production, but also for production of reactive oxygen species (ROS) and for the de novo synthesis of pyrimidines. This paper reviews the role of mitochondrial produced ROS and pyrimidines in the aetiology of AD and their proposed role in oxidative degeneration of macromolecules, synthesis of essential phospholipids and maintenance of mitochondrial viability in the AD brain.
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Affiliation(s)
- Claus Desler
- Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark
| | - Meryl S Lillenes
- Healthy Brain Aging Centre (HBAC), Department of Microbiology, Oslo University Hospital, Oslo, Norway
| | - Tone Tønjum
- Healthy Brain Aging Centre (HBAC), Department of Microbiology, Oslo University Hospital, Oslo, Norway
| | - Lene Juel Rasmussen
- Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark
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55
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Caporali L, Bello L, Tagliavini F, La Morgia C, Maresca A, Di Vito L, Liguori R, Valentino ML, Cecchin D, Pegoraro E, Carelli V. DGUOK recessive mutations in patients with CPEO, mitochondrial myopathy, parkinsonism and mtDNA deletions. Brain 2019; 141:e3. [PMID: 29228108 DOI: 10.1093/brain/awx301] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Affiliation(s)
- Leonardo Caporali
- IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Bologna, Italy
| | - Luca Bello
- Department of Neuroscience, University of Padova, Padova, Italy
| | - Francesca Tagliavini
- IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Bologna, Italy
| | - Chiara La Morgia
- IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Bologna, Italy.,Neurology Unit, Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy
| | - Alessandra Maresca
- IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Bologna, Italy
| | - Lidia Di Vito
- IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Bologna, Italy
| | - Rocco Liguori
- IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Bologna, Italy.,Neurology Unit, Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy
| | - Maria Lucia Valentino
- IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Bologna, Italy.,Neurology Unit, Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy
| | - Diego Cecchin
- Nuclear Medicine Unit, Department of Medicine - DIMED, University-Hospital of Padova, Italy.,Padova Neuroscience Center, University of Padova, Italy
| | - Elena Pegoraro
- Department of Neuroscience, University of Padova, Padova, Italy
| | - Valerio Carelli
- IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Bologna, Italy.,Neurology Unit, Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy
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56
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Munro B, Horvath R, Müller JS. Nucleoside supplementation modulates mitochondrial DNA copy number in the dguok -/- zebrafish. Hum Mol Genet 2019; 28:796-803. [PMID: 30428046 PMCID: PMC6381312 DOI: 10.1093/hmg/ddy389] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 10/25/2018] [Accepted: 10/31/2018] [Indexed: 01/07/2023] Open
Abstract
Deoxyguanosine kinase (dGK) is an essential rate-limiting component of the mitochondrial purine nucleotide salvage pathway, encoded by the nuclear gene encoding deoxyguanosine kinase (DGUOK). Mutations in DGUOK lead to mitochondrial DNA (mtDNA) depletion typically in the liver and brain, causing a hepatocerebral phenotype. Previous work has shown that in cultured DGUOK patient cells it is possible to rescue mtDNA depletion by increasing substrate amounts for dGK. In this study we developed a mutant dguok zebrafish (Danio rerio) line using CRISPR/Cas9 mediated mutagenesis; dguok-/- fish have significantly reduced mtDNA levels compared with wild-type (wt) fish. When supplemented with only one purine nucleoside (dGuo), mtDNA copy number in both mutant and wt juvenile animals was significantly reduced, contrasting with previous cell culture studies, possibly because of nucleotide pool imbalance. However, in adult dguok-/- fish we detected a significant increase in liver mtDNA copy number when supplemented with both purine nucleosides. This study further supports the idea that nucleoside supplementation has a potential therapeutic benefit in mtDNA depletion syndromes by substrate enhancement of the purine nucleoside salvage pathway and might improve the liver pathology in patients.
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Affiliation(s)
- Benjamin Munro
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE1 3BZ, UK
- Department of Clinical Neurosciences, University of Cambridge, John Van Geest Centre for Brain Repair, The ED Adrian Building, Forvie Site, Robinson Way, Cambridge, CB2 0PY, UK
| | - Rita Horvath
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE1 3BZ, UK
- Department of Clinical Neurosciences, University of Cambridge, John Van Geest Centre for Brain Repair, The ED Adrian Building, Forvie Site, Robinson Way, Cambridge, CB2 0PY, UK
| | - Juliane S Müller
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE1 3BZ, UK
- Department of Clinical Neurosciences, University of Cambridge, John Van Geest Centre for Brain Repair, The ED Adrian Building, Forvie Site, Robinson Way, Cambridge, CB2 0PY, UK
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57
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Jing R, Corbett JL, Cai J, Beeson GC, Beeson CC, Chan SS, Dimmock DP, Lazcares L, Geurts AM, Lemasters JJ, Duncan SA. A Screen Using iPSC-Derived Hepatocytes Reveals NAD + as a Potential Treatment for mtDNA Depletion Syndrome. Cell Rep 2018; 25:1469-1484.e5. [PMID: 30404003 PMCID: PMC6289059 DOI: 10.1016/j.celrep.2018.10.036] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 09/18/2018] [Accepted: 10/08/2018] [Indexed: 12/22/2022] Open
Abstract
Patients with mtDNA depletion syndrome 3 (MTDPS3) often die as children from liver failure caused by severe reduction in mtDNA content. The identification of treatments has been impeded by an inability to culture and manipulate MTDPS3 primary hepatocytes. Here we generated DGUOK-deficient hepatocyte-like cells using induced pluripotent stem cells (iPSCs) and used them to identify drugs that could improve mitochondrial ATP production and mitochondrial function. Nicotinamide adenine dinucleotide (NAD) was found to improve mitochondrial function in DGUOK-deficient hepatocyte-like cells by activating the peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α). NAD treatment also improved ATP production in MTDPS3-null rats and in hepatocyte-like cells that were deficient in ribonucleoside-diphosphate reductase subunit M2B (RRM2B), suggesting that it could be broadly effective. Our studies reveal that DGUOK-deficient iPSC-derived hepatocytes recapitulate the pathophysiology of MTDPS3 in culture and can be used to identify therapeutics for mtDNA depletion syndromes.
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Affiliation(s)
- Ran Jing
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - James L Corbett
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - Jun Cai
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - Gyda C Beeson
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - Craig C Beeson
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - Sherine S Chan
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA
| | - David P Dimmock
- Human Molecular Genetics Center and Division of Genetics, Department of Pediatrics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA; Rady Children's Institute for Genomic Medicine, 3020 Children's Way, San Diego, CA 92123, USA
| | - Lynn Lazcares
- Division of Pediatric Pathology, Department of Pathology and Laboratory Medicine, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - Aron M Geurts
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | - John J Lemasters
- Center for Cell Death, Injury and Regeneration, Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Stephen A Duncan
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, 173 Ashley Avenue, Charleston, SC 29425, USA; Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, Charleston, SC 29425, USA.
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58
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Reversing wrinkled skin and hair loss in mice by restoring mitochondrial function. Cell Death Dis 2018; 9:735. [PMID: 30026579 PMCID: PMC6053453 DOI: 10.1038/s41419-018-0765-9] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 04/27/2018] [Accepted: 06/08/2018] [Indexed: 12/12/2022]
Abstract
Mitochondrial DNA (mtDNA) depletion is involved in mtDNA depletion syndromes, mitochondrial diseases, aging and aging-associated chronic diseases, and other human pathologies. To evaluate the consequences of depletion of mtDNA in the whole animal, we created an inducible mtDNA-depleter mouse expressing, in the polymerase domain of POLG1, a dominant-negative mutation to induce depletion of mtDNA in various tissues. These mice showed reduced mtDNA content, reduced mitochondrial gene expression, and instability of supercomplexes involved in oxidative phosphorylation (OXPHOS) resulting in reduced OXPHOS enzymatic activities. We demonstrate that ubiquitous depletion of mtDNA in mice leads to predominant and profound effects on the skin resulting in wrinkles and visual hair loss with an increased number of dysfunctional hair follicles and inflammatory responses. Development of skin wrinkle was associated with the significant epidermal hyperplasia, hyperkeratosis, increased expression of matrix metalloproteinases, and decreased expression of matrix metalloproteinase inhibitor TIMP1. We also discovered markedly increased skin inflammation that appears to be a contributing factor in skin pathology. Histopathologic analyses revealed dysfunctional hair follicles. mtDNA-depleter mice also show changes in expression of aging-associated markers including IGF1R, KLOTHO, VEGF, and MRPS5. mtDNA-repleter mice showed that, by turning off the mutant POLG1 transgene expression, mitochondrial function, as well as the skin and hair pathology, is reversed to wild-type level. To our knowledge that restoration of mitochondrial functions can reverse the skin and hair pathology is unprecedented.
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59
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Molecular signature pathway of gene protein interaction in human mitochondrial DNA (mtDNA) metabolism linked disease. INDIAN JOURNAL OF MEDICAL SPECIALITIES 2018. [DOI: 10.1016/j.injms.2018.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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60
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The presence of rNTPs decreases the speed of mitochondrial DNA replication. PLoS Genet 2018; 14:e1007315. [PMID: 29601571 PMCID: PMC5895052 DOI: 10.1371/journal.pgen.1007315] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 04/11/2018] [Accepted: 03/19/2018] [Indexed: 11/19/2022] Open
Abstract
Ribonucleotides (rNMPs) are frequently incorporated during replication or repair by DNA polymerases and failure to remove them leads to instability of nuclear DNA (nDNA). Conversely, rNMPs appear to be relatively well-tolerated in mitochondrial DNA (mtDNA), although the mechanisms behind the tolerance remain unclear. We here show that the human mitochondrial DNA polymerase gamma (Pol γ) bypasses single rNMPs with an unprecedentedly high fidelity and efficiency. In addition, Pol γ exhibits a strikingly low frequency of rNMP incorporation, a property, which we find is independent of its exonuclease activity. However, the physiological levels of free rNTPs partially inhibit DNA synthesis by Pol γ and render the polymerase more sensitive to imbalanced dNTP pools. The characteristics of Pol γ reported here could have implications for forms of mtDNA depletion syndrome (MDS) that are associated with imbalanced cellular dNTP pools. Our results show that at the rNTP/dNTP ratios that are expected to prevail in such disease states, Pol γ enters a polymerase/exonuclease idling mode that leads to mtDNA replication stalling. This could ultimately lead to mtDNA depletion and, consequently, to mitochondrial disease phenotypes such as those observed in MDS.
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61
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Moss CF, Dalla Rosa I, Hunt LE, Yasukawa T, Young R, Jones AWE, Reddy K, Desai R, Virtue S, Elgar G, Voshol P, Taylor MS, Holt IJ, Reijns MAM, Spinazzola A. Aberrant ribonucleotide incorporation and multiple deletions in mitochondrial DNA of the murine MPV17 disease model. Nucleic Acids Res 2018; 45:12808-12815. [PMID: 29106596 PMCID: PMC5728394 DOI: 10.1093/nar/gkx1009] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 10/17/2017] [Indexed: 12/24/2022] Open
Abstract
All DNA polymerases misincorporate ribonucleotides despite their preference for deoxyribonucleotides, and analysis of cultured cells indicates that mammalian mitochondrial DNA (mtDNA) tolerates such replication errors. However, it is not clear to what extent misincorporation occurs in tissues, or whether this plays a role in human disease. Here, we show that mtDNA of solid tissues contains many more embedded ribonucleotides than that of cultured cells, consistent with the high ratio of ribonucleotide to deoxynucleotide triphosphates in tissues, and that riboadenosines account for three-quarters of them. The pattern of embedded ribonucleotides changes in a mouse model of Mpv17 deficiency, which displays a marked increase in rGMPs in mtDNA. However, while the mitochondrial dGTP is low in the Mpv17−/− liver, the brain shows no change in the overall dGTP pool, leading us to suggest that Mpv17 determines the local concentration or quality of dGTP. Embedded rGMPs are expected to distort the mtDNA and impede its replication, and elevated rGMP incorporation is associated with early-onset mtDNA depletion in liver and late-onset multiple deletions in brain of Mpv17−/− mice. These findings suggest aberrant ribonucleotide incorporation is a primary mtDNA abnormality that can result in pathology.
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Affiliation(s)
| | - Ilaria Dalla Rosa
- MRC Laboratory, Mill Hill, London NW7 1AA, UK.,Department of Clinical Neurosciences, Institute of Neurology, Royal Free Campus, University College London NW3 2PF, UK
| | - Lilian E Hunt
- Advanced Sequencing Facility, Francis Crick Institute, London NW1 1AT, UK
| | | | - Robert Young
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Aleck W E Jones
- MRC Laboratory, Mill Hill, London NW7 1AA, UK.,Department of Clinical Neurosciences, Institute of Neurology, Royal Free Campus, University College London NW3 2PF, UK
| | - Kaalak Reddy
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Radha Desai
- MRC Laboratory, Mill Hill, London NW7 1AA, UK
| | - Sam Virtue
- MRC Metabolic Diseases Unit, Wellcome Trust-MRC Institute of Metabolic Science, Cambridge CB2 0QQ, UK
| | - Greg Elgar
- Advanced Sequencing Facility, Francis Crick Institute, London NW1 1AT, UK
| | - Peter Voshol
- MRC Metabolic Diseases Unit, Wellcome Trust-MRC Institute of Metabolic Science, Cambridge CB2 0QQ, UK
| | - Martin S Taylor
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Ian J Holt
- MRC Laboratory, Mill Hill, London NW7 1AA, UK.,Department of Clinical Neurosciences, Institute of Neurology, Royal Free Campus, University College London NW3 2PF, UK.,Biodonostia Health Research Institute, 20014 San Sebastián, Spain and IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Martin A M Reijns
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Antonella Spinazzola
- MRC Laboratory, Mill Hill, London NW7 1AA, UK.,Department of Clinical Neurosciences, Institute of Neurology, Royal Free Campus, University College London NW3 2PF, UK.,MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK
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62
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Ribonucleotides incorporated by the yeast mitochondrial DNA polymerase are not repaired. Proc Natl Acad Sci U S A 2017; 114:12466-12471. [PMID: 29109257 DOI: 10.1073/pnas.1713085114] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Incorporation of ribonucleotides into DNA during genome replication is a significant source of genomic instability. The frequency of ribonucleotides in DNA is determined by deoxyribonucleoside triphosphate/ribonucleoside triphosphate (dNTP/rNTP) ratios, by the ability of DNA polymerases to discriminate against ribonucleotides, and by the capacity of repair mechanisms to remove incorporated ribonucleotides. To simultaneously compare how the nuclear and mitochondrial genomes incorporate and remove ribonucleotides, we challenged these processes by changing the balance of cellular dNTPs. Using a collection of yeast strains with altered dNTP pools, we discovered an inverse relationship between the concentration of individual dNTPs and the amount of the corresponding ribonucleotides incorporated in mitochondrial DNA, while in nuclear DNA the ribonucleotide pattern was only altered in the absence of ribonucleotide excision repair. Our analysis uncovers major differences in ribonucleotide repair between the two genomes and provides concrete evidence that yeast mitochondria lack mechanisms for removal of ribonucleotides incorporated by the mtDNA polymerase. Furthermore, as cytosolic dNTP pool imbalances were transmitted equally well into the nucleus and the mitochondria, our results support a view of the cytosolic and mitochondrial dNTP pools in frequent exchange.
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63
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Irwin CR, Hitt MM, Evans DH. Targeting Nucleotide Biosynthesis: A Strategy for Improving the Oncolytic Potential of DNA Viruses. Front Oncol 2017; 7:229. [PMID: 29018771 PMCID: PMC5622948 DOI: 10.3389/fonc.2017.00229] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 09/07/2017] [Indexed: 12/14/2022] Open
Abstract
The rapid growth of tumors depends upon elevated levels of dNTPs, and while dNTP concentrations are tightly regulated in normal cells, this control is often lost in transformed cells. This feature of cancer cells has been used to advantage to develop oncolytic DNA viruses. DNA viruses employ many different mechanisms to increase dNTP levels in infected cells, because the low concentration of dNTPs found in non-cycling cells can inhibit virus replication. By disrupting the virus-encoded gene(s) that normally promote dNTP biosynthesis, one can assemble oncolytic versions of these agents that replicate selectively in cancer cells. This review covers the pathways involved in dNTP production, how they are dysregulated in cancer cells, and the various approaches that have been used to exploit this biology to improve the tumor specificity of oncolytic viruses. In particular, we compare and contrast the ways that the different types of oncolytic virus candidates can directly modulate these processes. We limit our review to the large DNA viruses that naturally encode homologs of the cellular enzymes that catalyze dNTP biogenesis. Lastly, we consider how this knowledge might guide future development of oncolytic viruses.
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Affiliation(s)
- Chad R Irwin
- Faculty of Medicine and Dentistry, Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, Canada.,Faculty of Medicine and Dentistry, Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB, Canada
| | - Mary M Hitt
- Faculty of Medicine and Dentistry, Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB, Canada.,Faculty of Medicine and Dentistry, Department of Oncology, University of Alberta, Edmonton, AB, Canada
| | - David H Evans
- Faculty of Medicine and Dentistry, Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, Canada.,Faculty of Medicine and Dentistry, Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB, Canada
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64
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Fang W, Song P, Xie X, Wang J, Lu Y, Li G, Abuduxikuer K. A fatal case of mitochondrial DNA depletion syndrome with novel compound heterozygous variants in the deoxyguanosine kinase gene. Oncotarget 2017; 8:84309-84319. [PMID: 29137425 PMCID: PMC5663597 DOI: 10.18632/oncotarget.20905] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 08/17/2017] [Indexed: 12/02/2022] Open
Abstract
The deoxyguanosine kinase (DGUOK) gene controls mitochondrial DNA (mtDNA) maintenance, and variation in the gene can alter or abolish the anabolism of mitochondrial deoxyribonucleotides. A Chinese female infant, whose symptoms included weight stagnation, jaundice, hypoglycemia, coagulation disorders, abnormal liver function, and multiple abnormal signals in the brain, died at about 10 months old. Genetic testing revealed a compound heterozygote of alleles c.128T>C (p.I43T) and c.313C>T (p.R105*) of the DGUOK gene. c.128T>C (p.I43T) is a novel variant located in exon 1 (NM_080916) in the first beta sheet of DGUOK. Her mother was an allele c.313C>T (p.R105*) heterozygote, which is located in DGUOK exon 2 (NM_080916) between the third and fourth alpha helixes. c.313C>T (p.R105*) is predicted to result in a 173 amino acid residue truncation at the C terminus of DGUOK. There are as many as 112 infantile mtDNA depletion syndrome (MDS) cases in the literature related to DGUOK gene variants. These variants include missense mutations, nucleotide deletion, nucleotide insertion, and nucleotide duplication. Integrated data showed that mutations affected both conserved and non-conserved DGUOK amino acids and are associated with patient deaths.
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Affiliation(s)
- Weiyuan Fang
- The Center for Pediatric Liver Disease, Children's Hospital of Fudan University, Shanghai 201102, China
| | - Peng Song
- Advanced Training Program, Children's Hospital of Fudan University, Shanghai 201102, China.,Department of Infectious Diseases, Tangshan Maternal and Children Health Hospital, Tangshan City, Hebei Province 063000, China
| | - Xinbao Xie
- The Center for Pediatric Liver Disease, Children's Hospital of Fudan University, Shanghai 201102, China
| | - Jianshe Wang
- The Center for Pediatric Liver Disease, Children's Hospital of Fudan University, Shanghai 201102, China
| | - Yi Lu
- The Center for Pediatric Liver Disease, Children's Hospital of Fudan University, Shanghai 201102, China
| | - Gang Li
- Institute of Pediatrics, Children's Hospital of Fudan University, Shanghai 201102, China
| | - Kuerbanjiang Abuduxikuer
- The Center for Pediatric Liver Disease, Children's Hospital of Fudan University, Shanghai 201102, China
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Abstract
Mitochondria are intracellular organelles responsible for adenosine triphosphate production. The strict control of intracellular energy needs require proper mitochondrial functioning. The mitochondria are under dual controls of mitochondrial DNA (mtDNA) and nuclear DNA (nDNA). Mitochondrial dysfunction can arise from changes in either mtDNA or nDNA genes regulating function. There are an estimated ∼1500 proteins in the mitoproteome, whereas the mtDNA genome has 37 proteins. There are, to date, ∼275 genes shown to give rise to disease. The unique physiology of mitochondrial functioning contributes to diverse gene expression. The onset and range of phenotypic expression of disease is diverse, with onset from neonatal to seventh decade of life. The range of dysfunction is heterogeneous, ranging from single organ to multisystem involvement. The complexity of disease expression has severely limited gene discovery. Combining phenotypes with improvements in gene sequencing strategies are improving the diagnosis process. This chapter focuses on the interplay of the unique physiology and gene discovery in the current knowledge of genetically derived mitochondrial disease.
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Affiliation(s)
- Russell P Saneto
- Seattle Children's Hospital/University of Washington, Seattle, WA, United States.
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66
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Mitochondrial diseases: the contribution of organelle stress responses to pathology. Nat Rev Mol Cell Biol 2017; 19:77-92. [DOI: 10.1038/nrm.2017.66] [Citation(s) in RCA: 264] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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67
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Wang L. Mitochondrial purine and pyrimidine metabolism and beyond. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2017; 35:578-594. [PMID: 27906631 DOI: 10.1080/15257770.2015.1125001] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Carefully balanced deoxynucleoside triphosphate (dNTP) pools are essential for both nuclear and mitochondrial genome replication and repair. Two synthetic pathways operate in cells to produce dNTPs, e.g., the de novo and the salvage pathways. The key regulatory enzymes for de novo synthesis are ribonucleotide reductase (RNR) and thymidylate synthase (TS), and this process is considered to be cytosolic. The salvage pathway operates both in the cytosol (TK1 and dCK) and the mitochondria (TK2 and dGK). Mitochondrial dNTP pools are separated from the cytosolic ones owing to the double membrane structure of the mitochondria, and are formed by the salvage enzymes TK2 and dGK together with NMPKs and NDPK in postmitotic tissues, while in proliferating cells the mitochondrial dNTPs are mainly imported from the cytosol produced by the cytosolic pathways. Imbalanced mitochondrial dNTP pools lead to mtDNA depletion and/or deletions resulting in serious mitochondrial diseases. The mtDNA depletion syndrome is caused by deficiencies not only in enzymes in dNTP synthesis (TK2, dGK, p53R2, and TP) and mtDNA replication (mtDNA polymerase and twinkle helicase), but also in enzymes in other metabolic pathways such as SUCLA2 and SUCLG1, ABAT and MPV17. Basic questions are why defects in these enzymes affect dNTP synthesis and how important is mitochondrial nucleotide synthesis in the whole cell/organism perspective? This review will focus on recent studies on purine and pyrimidine metabolism, which have revealed several important links that connect mitochondrial nucleotide metabolism with amino acids, glucose, and fatty acid metabolism.
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Affiliation(s)
- Liya Wang
- a Department of Anatomy, Physiology and Biochemistry , Swedish University of Agricultural Sciences , Uppsala , Sweden
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68
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Berglund AK, Navarrete C, Engqvist MKM, Hoberg E, Szilagyi Z, Taylor RW, Gustafsson CM, Falkenberg M, Clausen AR. Nucleotide pools dictate the identity and frequency of ribonucleotide incorporation in mitochondrial DNA. PLoS Genet 2017; 13:e1006628. [PMID: 28207748 PMCID: PMC5336301 DOI: 10.1371/journal.pgen.1006628] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 03/03/2017] [Accepted: 02/09/2017] [Indexed: 01/22/2023] Open
Abstract
Previous work has demonstrated the presence of ribonucleotides in human mitochondrial DNA (mtDNA) and in the present study we use a genome-wide approach to precisely map the location of these. We find that ribonucleotides are distributed evenly between the heavy- and light-strand of mtDNA. The relative levels of incorporated ribonucleotides reflect that DNA polymerase γ discriminates the four ribonucleotides differentially during DNA synthesis. The observed pattern is also dependent on the mitochondrial deoxyribonucleotide (dNTP) pools and disease-causing mutations that change these pools alter both the absolute and relative levels of incorporated ribonucleotides. Our analyses strongly suggest that DNA polymerase γ-dependent incorporation is the main source of ribonucleotides in mtDNA and argues against the existence of a mitochondrial ribonucleotide excision repair pathway in human cells. Furthermore, we clearly demonstrate that when dNTP pools are limiting, ribonucleotides serve as a source of building blocks to maintain DNA replication. Increased levels of embedded ribonucleotides in patient cells with disturbed nucleotide pools may contribute to a pathogenic mechanism that affects mtDNA stability and impair new rounds of mtDNA replication. Human mitochondria contain a small double-stranded DNA genome (mtDNA) of only 16,569 base pairs (bp) that encodes 13 essential subunits of the oxidative phosphorylation system. Depletion of mtDNA and different types of mtDNA mutations cause mitochondrial disease, and are also implicated in biological ageing. For almost half a century it has been known that mtDNA contains ribonucleotides, but their identity and precise location are not known. The source of these ribonucleotides and their relevance for mitochondrial genome stability in healthy individuals and in patients with mitochondrial defects has not been addressed. We have used a combination of next-generation sequencing, and in vivo and in vitro biochemistry to address some of these questions. Our findings demonstrate that DNA polymerase γ-dependent incorporation is the main source of ribonucleotides in mtDNA and argues against the existence of ribonucleotide excision repair pathways in human mitochondria. Our data also reveal that when dNTP pools are limiting, ribonucleotides serves as a second line of building blocks for DNA synthesis. We also demonstrate increased levels of embedded ribonucleotides in patient cells with disturbed nucleotide pools, which may constitute a new pathogenic mechanism that affects mtDNA stability and impairs later rounds of mtDNA replication.
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Affiliation(s)
| | - Clara Navarrete
- Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | | | - Emily Hoberg
- Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Zsolt Szilagyi
- Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Robert W. Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | | | - Maria Falkenberg
- Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
- * E-mail: (MF); (ARC)
| | - Anders R. Clausen
- Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
- * E-mail: (MF); (ARC)
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69
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Pai CC, Kearsey SE. A Critical Balance: dNTPs and the Maintenance of Genome Stability. Genes (Basel) 2017; 8:genes8020057. [PMID: 28146119 PMCID: PMC5333046 DOI: 10.3390/genes8020057] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 01/24/2017] [Indexed: 01/14/2023] Open
Abstract
A crucial factor in maintaining genome stability is establishing deoxynucleoside triphosphate (dNTP) levels within a range that is optimal for chromosomal replication. Since DNA replication is relevant to a wide range of other chromosomal activities, these may all be directly or indirectly affected when dNTP concentrations deviate from a physiologically normal range. The importance of understanding these consequences is relevant to genetic disorders that disturb dNTP levels, and strategies that inhibit dNTP synthesis in cancer chemotherapy and for treatment of other disorders. We review here how abnormal dNTP levels affect DNA replication and discuss the consequences for genome stability.
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Affiliation(s)
- Chen-Chun Pai
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford OX3 7DQ, UK.
| | - Stephen E Kearsey
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
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70
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Dai H, Zhang VW, El-Hattab AW, Ficicioglu C, Shinawi M, Lines M, Schulze A, McNutt M, Gotway G, Tian X, Chen S, Wang J, Craigen WJ, Wong LJ. FBXL4 defects are common in patients with congenital lactic acidemia and encephalomyopathic mitochondrial DNA depletion syndrome. Clin Genet 2017; 91:634-639. [PMID: 27743463 DOI: 10.1111/cge.12894] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 10/11/2016] [Accepted: 10/11/2016] [Indexed: 11/30/2022]
Abstract
Mutations in FBXL4 have recently been recognized to cause a mitochondrial disorder, with clinical features including early onset lactic acidosis, hypotonia, and developmental delay. FBXL4 sequence analysis was performed in 808 subjects suspected to have a mitochondrial disorder. In addition, 28 samples from patients with early onset of lactic acidosis, but without identifiable mutations in 192 genes known to cause mitochondrial diseases, were examined for FBXL4 mutations. Definitive diagnosis was made in 10 new subjects with a total of 7 novel deleterious variants; 5 null and 2 missense substitutions. All patients exhibited congenital lactic acidemia, most of them with severe encephalopathic presentation, and global developmental delay. Overall, FBXL4 defects account for at least 0.7% (6 out of 808) of subjects suspected to have a mitochondrial disorder, and as high as 14.3% (4 out of 28) in young children with congenital lactic acidosis and clinical features of mitochondrial disease. Including FBLX4 in the mitochondrial diseases panel should be particularly important for patients with congenital lactic acidosis.
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Affiliation(s)
- H Dai
- Baylor Genetics, Houston, TX, USA
| | - V W Zhang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - A W El-Hattab
- Division of Clinical Genetics and Metabolic Disorders, Pediatric Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - C Ficicioglu
- Division of Human Genetics and Metabolism, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - M Shinawi
- Division of Genetics and Genomics, Washington University School of Medicine, St. Louis, MO, USA
| | - M Lines
- Department of Genetics, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
| | - A Schulze
- Division of Clinical and Metabolic Genetics, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada
| | - M McNutt
- Children's Medical Center, Dallas, TX, USA
| | - G Gotway
- Children's Medical Center, Dallas, TX, USA
| | - X Tian
- Baylor Genetics, Houston, TX, USA
| | - S Chen
- Baylor Genetics, Houston, TX, USA
| | - J Wang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - W J Craigen
- Baylor Genetics, Houston, TX, USA.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - L-J Wong
- Baylor Genetics, Houston, TX, USA.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
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71
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Pereira CV, Moraes CT. Current strategies towards therapeutic manipulation of mtDNA heteroplasmy. Front Biosci (Landmark Ed) 2017; 22:991-1010. [PMID: 27814659 DOI: 10.2741/4529] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Mitochondrial disease is a multifactorial disorder involving both nuclear and mitochondrial genomes. Over the past 20 years, great progress was achieved in the field of gene editing which raised the possibility of partial or complete elimination of mutant mtDNA that causes disease phenotypes. Each cell contains thousands of copies of mtDNA which can be either wild-type (WT) or mutant, a condition called heteroplasmy. As there are multiple copies of mtDNA inside a cell, the percentage of mutant mtDNA can vary and a directional shift in the heteroplasmy ratio towards an increase of WT mtDNA copies would have therapeutic value. Gene editing tools have been adapted to translocate to mitochondria and were able to change heteroplasmy in a predictable manner. These include mitochondrial targeted restriction endonucleases, Zinc-finger nucleases, and TAL-effector nucleases. These procedures could also be adapted to reduce the levels of mutant mtDNA in embryos, offering an option to the controversial mitochondrial replacement techniques during in vitro fertilization. The current strategies to induce heteroplasmy shift of mtDNA and its implications will be comprehensively discussed.
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Affiliation(s)
- Claudia V Pereira
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Carlos T Moraes
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL 33136, USA,
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72
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Campolina-Sampaio GP, Lasmar LMDLBF, Ribeiro BSV, Gurgel-Giannetti J. The Newcastle Pediatric Mitochondrial Disease Scale: translation and cultural adaptation for use in Brazil. ARQUIVOS DE NEURO-PSIQUIATRIA 2016; 74:909-913. [DOI: 10.1590/0004-282x20160137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Accepted: 06/13/2016] [Indexed: 11/22/2022]
Abstract
ABSTRACT Objective The aim of this study was to translate and adapt the Newcastle Paediatric Mitochondrial Disease Scale (NPMDS) to Portuguese for use in Brazil. Methods The scale was applied in 20 pediatric patients with mitochondrial disease, in three groups: myopathy (n = 4); Leigh syndrome (n = 8); and encephalomyopathy (n = 8). Scores were obtained for the various dimensions of the NPMDS, and comparisons were drawn between the groups. Results There was a statistically significant difference between the myopathy group and the Leigh syndrome group (p = 0.0085), as well as between the myopathy and encephalomyopathy groups (p = 0.01). Conclusions The translation of the NPMDS, and its adaptation to the socioeconomic and cultural conditions in Brazil, make the NPMDS score useful as an additional parameter in the evaluation and monitoring of pediatric patients with MD in Brazil.
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73
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Abstract
Ten years ago, there was an emerging view that the molecular basis for adult mitochondrial disorders was largely known and that the clinical phenotypes had been well described. Nothing could have been further from the truth. The establishment of large cohorts of patients has revealed new aspects of the clinical presentation that were not previously appreciated. Over time, this approach is starting to provide an accurate understanding of the natural history of mitochondrial disease in adults. Advances in molecular diagnostics, underpinned by next generation sequencing technology, have identified novel molecular mechanisms. Recently described mitochondrial disease phenotypes have disparate causes, and yet share common mechanistic themes. In particular, disorders of mtDNA maintenance have emerged as a major cause of mitochondrial disease in adults. Progressive mtDNA depletion and the accumulation of mtDNA mutations explain some of the clinical features, but the genetic and cellular processes responsible for the mtDNA abnormalities are not entirely clear in each instance. Unfortunately, apart from a few specific examples, treatments for adult mitochondrial disease have not been forthcoming. However, the establishment of international consortia, and the first multinational randomised controlled trial, have paved the way for major progress in the near future, underpinned by growing interest from the pharmaceutical industry. Adult mitochondrial medicine is, therefore, in its infancy, and the challenge is to harness the new understanding of its molecular and cellular basis to develop treatments of real benefit to patients.
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Affiliation(s)
- Patrick F Chinnery
- Department of Clinical Neurosciences, School of Clinical Medicine, University of Cambridge, Cambridge, UK Medical Research Council - Mitochondrial Biology Unit, Cambridge Biomedical Campus, Cambridge, UK
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74
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Vilarinho S, Sari S, Yilmaz G, Stiegler AL, Boggon TJ, Jain D, Akyol G, Dalgic B, Günel M, Lifton RP. Recurrent recessive mutation in deoxyguanosine kinase causes idiopathic noncirrhotic portal hypertension. Hepatology 2016; 63:1977-86. [PMID: 26874653 PMCID: PMC4874872 DOI: 10.1002/hep.28499] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2015] [Accepted: 02/10/2016] [Indexed: 12/30/2022]
Abstract
UNLABELLED Despite advances in the diagnosis and management of idiopathic noncirrhotic portal hypertension, its pathogenesis remains elusive. Insight may be gained from study of early-onset familial idiopathic noncirrhotic portal hypertension, in which Mendelian mutations may account for disease. We performed exome sequencing of eight subjects from six kindreds with onset of portal hypertension of indeterminate etiology during infancy or childhood. Three subjects from two consanguineous families shared the identical rare homozygous p.N46S mutation in DGUOK, a deoxyguanosine kinase required for mitochondrial DNA replication; haplotype sharing demonstrated that the mutation in the two families was inherited from a remote common ancestor. All three affected subjects had stable portal hypertension with noncirrhotic liver disease for 6-16 years of follow-up. This mutation impairs adenosine triphosphate binding and reduces catalytic activity. Loss-of-function mutations in DGUOK have previously been implicated in cirrhosis and liver failure but not in isolated portal hypertension. Interestingly, treatment of patients with human immunodeficiency viral infection with the nucleoside analogue didanosine is known to cause portal hypertension in a subset of patients and lowers deoxyguanosine kinase levels in vitro; the current findings implicate these effects on deoxyguanosine kinase in the causal mechanism. CONCLUSION Our findings provide new insight into the mechanisms mediating inherited and acquired noncirrhotic portal hypertension, expand the phenotypic spectrum of DGUOK deficiency, and provide a new genetic test for a specific cause of idiopathic noncirrhotic portal hypertension. (Hepatology 2016;63:1977-1986).
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Affiliation(s)
- Sílvia Vilarinho
- Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, New Haven, Connecticut, USA,Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA,Correspondence should be addressed to: Richard P. Lifton, M.D., Ph.D., Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 333 Cedar St., SHM I308, New Haven, CT 06510, USA. Telephone: +1-203-737-4420, Fax: +1-203-785-7560, ; or Sílvia Vilarinho, M.D., Ph.D., Departments of Genetics and Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, 333 Cedar St., LMP1080, New Haven, CT 06510, USA. Telephone: +1-203-737-1833, Fax: +1-203-737-1755,
| | - Sinan Sari
- Department of Pediatrics, Division of Gastroenterology, Gazi University, Faculty of Medicine, Ankara, Turkey
| | - Güldal Yilmaz
- Department of Pathology, Gazi University, Faculty of Medicine, Ankara, Turkey
| | - Amy L. Stiegler
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Titus J. Boggon
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut, USA,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA
| | - Dhanpat Jain
- Department of Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, New Haven, Connecticut, USA,Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA,Department of Pathology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Gulen Akyol
- Department of Pathology, Gazi University, Faculty of Medicine, Ankara, Turkey
| | - Buket Dalgic
- Department of Pediatrics, Division of Gastroenterology, Gazi University, Faculty of Medicine, Ankara, Turkey
| | - Murat Günel
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA,Department of Neurosurgery, Yale Program in Brain Tumor Research, Yale University School of Medicine, New Haven, Connecticut, USA,Yale Center for Mendelian Genomics, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Richard P. Lifton
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA,Department of Neurosurgery, Yale Program in Brain Tumor Research, Yale University School of Medicine, New Haven, Connecticut, USA,Department of Internal Medicine and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, USA,Correspondence should be addressed to: Richard P. Lifton, M.D., Ph.D., Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 333 Cedar St., SHM I308, New Haven, CT 06510, USA. Telephone: +1-203-737-4420, Fax: +1-203-785-7560, ; or Sílvia Vilarinho, M.D., Ph.D., Departments of Genetics and Internal Medicine, Section of Digestive Diseases, Yale University School of Medicine, 333 Cedar St., LMP1080, New Haven, CT 06510, USA. Telephone: +1-203-737-1833, Fax: +1-203-737-1755,
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Sadat R, Barca E, Masand R, Donti TR, Naini A, De Vivo DC, DiMauro S, Hanchard NA, Graham BH. Functional cellular analyses reveal energy metabolism defect and mitochondrial DNA depletion in a case of mitochondrial aconitase deficiency. Mol Genet Metab 2016; 118:28-34. [PMID: 26992325 PMCID: PMC4833660 DOI: 10.1016/j.ymgme.2016.03.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Revised: 03/07/2016] [Accepted: 03/07/2016] [Indexed: 01/06/2023]
Abstract
Defects in the tricarboxylic acid cycle (TCA) are associated with a spectrum of neurological phenotypes that are often difficult to diagnose and manage. Whole-exome sequencing (WES) led to a rapid expansion of diagnostic capabilities in such disorders and facilitated a better understanding of disease pathogenesis, although functional characterization remains a bottleneck to the interpretation of potential pathological variants. We report a 2-year-old boy of Afro-Caribbean ancestry, who presented with neuromuscular symptoms without significant abnormalities on routine diagnostic evaluation. WES revealed compound heterozygous missense variants of uncertain significance in mitochondrial aconitase (ACO2), which encodes the TCA enzyme ACO2. Pathogenic variants in ACO2 have been described in a handful of families as the cause of infantile cerebellar-retinal degeneration syndrome. Using biochemical and cellular assays in patient fibroblasts, we found that ACO2 expression was quantitatively normal, but ACO2 enzyme activity was <20% of that observed in control cells. We also observed a deficiency in cellular respiration and, for the first time, demonstrate evidence of mitochondrial DNA depletion and altered expression of some TCA components and electron transport chain subunits. The observed cellular defects were completely restored with ACO2 gene rescue. Our findings demonstrate the pathogenicity of two VUS in ACO2, provide novel mechanistic insights to TCA disturbances in ACO2 deficiency, and implicate mitochondrial DNA depletion in the pathogenesis of this recently described disorder.
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Affiliation(s)
- Roa Sadat
- USDA/ARS/Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX, USA
| | - Emanuele Barca
- Department of Neuroscience, University of Messina, Messina, Italy; Houston Merritt Center, Columbia University Medical Center, New York, NY, USA
| | - Ruchi Masand
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Taraka R Donti
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Ali Naini
- Houston Merritt Center, Columbia University Medical Center, New York, NY, USA
| | - Darryl C De Vivo
- Pediatric Neurology, Columbia University Medical Center, New York, NY, USA
| | - Salvatore DiMauro
- Houston Merritt Center, Columbia University Medical Center, New York, NY, USA
| | - Neil A Hanchard
- USDA/ARS/Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Brett H Graham
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
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76
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Mitochondrial DNA Replication Defects Disturb Cellular dNTP Pools and Remodel One-Carbon Metabolism. Cell Metab 2016; 23:635-48. [PMID: 26924217 DOI: 10.1016/j.cmet.2016.01.019] [Citation(s) in RCA: 197] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 12/07/2015] [Accepted: 01/28/2016] [Indexed: 01/12/2023]
Abstract
Mitochondrial dysfunction affects cellular energy metabolism, but less is known about the consequences for cytoplasmic biosynthetic reactions. We report that mtDNA replication disorders caused by TWINKLE mutations-mitochondrial myopathy (MM) and infantile onset spinocerebellar ataxia (IOSCA)-remodel cellular dNTP pools in mice. MM muscle shows tissue-specific induction of the mitochondrial folate cycle, purine metabolism, and imbalanced and increased dNTP pools, consistent with progressive mtDNA mutagenesis. IOSCA-TWINKLE is predicted to hydrolyze dNTPs, consistent with low dNTP pools and mtDNA depletion in the disease. MM muscle also modifies the cytoplasmic one-carbon cycle, transsulfuration, and methylation, as well as increases glucose uptake and its utilization for de novo serine and glutathione biosynthesis. Our evidence indicates that the mitochondrial replication machinery communicates with cytoplasmic dNTP pools and that upregulation of glutathione synthesis through glucose-driven de novo serine biosynthesis contributes to the metabolic stress response. These results are important for disorders with primary or secondary mtDNA instability and offer targets for metabolic therapy.
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77
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Dalla Rosa I, Cámara Y, Durigon R, Moss CF, Vidoni S, Akman G, Hunt L, Johnson MA, Grocott S, Wang L, Thorburn DR, Hirano M, Poulton J, Taylor RW, Elgar G, Martí R, Voshol P, Holt IJ, Spinazzola A. MPV17 Loss Causes Deoxynucleotide Insufficiency and Slow DNA Replication in Mitochondria. PLoS Genet 2016; 12:e1005779. [PMID: 26760297 PMCID: PMC4711891 DOI: 10.1371/journal.pgen.1005779] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Accepted: 12/08/2015] [Indexed: 11/21/2022] Open
Abstract
MPV17 is a mitochondrial inner membrane protein whose dysfunction causes mitochondrial DNA abnormalities and disease by an unknown mechanism. Perturbations of deoxynucleoside triphosphate (dNTP) pools are a recognized cause of mitochondrial genomic instability; therefore, we determined DNA copy number and dNTP levels in mitochondria of two models of MPV17 deficiency. In Mpv17 ablated mice, liver mitochondria showed substantial decreases in the levels of dGTP and dTTP and severe mitochondrial DNA depletion, whereas the dNTP pool was not significantly altered in kidney and brain mitochondria that had near normal levels of DNA. The shortage of mitochondrial dNTPs in Mpv17-/- liver slows the DNA replication in the organelle, as evidenced by the elevated level of replication intermediates. Quiescent fibroblasts of MPV17-mutant patients recapitulate key features of the primary affected tissue of the Mpv17-/- mice, displaying virtual absence of the protein, decreased dNTP levels and mitochondrial DNA depletion. Notably, the mitochondrial DNA loss in the patients’ quiescent fibroblasts was prevented and rescued by deoxynucleoside supplementation. Thus, our study establishes dNTP insufficiency in the mitochondria as the cause of mitochondrial DNA depletion in MPV17 deficiency, and identifies deoxynucleoside supplementation as a potential therapeutic strategy for MPV17-related disease. Moreover, changes in the expression of factors involved in mitochondrial deoxynucleotide homeostasis indicate a remodeling of nucleotide metabolism in MPV17 disease models, which suggests mitochondria lacking functional MPV17 have a restricted purine mitochondrial salvage pathway. Mitochondrial DNA depletion syndrome (MDS) is a genetically heterogeneous condition characterized by a decrease of mitochondrial DNA (mtDNA) copy number and decreased activities of respiratory chain enzymes. Depletion of mtDNA has been associated with mutations in several genes, which encode either proteins directly involved in mtDNA replication or factors regulating the homeostasis of the mitochondrial deoxynucleotide pool. However, for some genes the mechanism linking mutations and mtDNA depletion is not known. One such gene is MPV17, whose loss-of-function causes mtDNA abnormalities in human, mouse and yeast. Here we show that MPV17 dysfunction leads to a shortage of the precursors for DNA synthesis in the mitochondria, slowing DNA replication in the organelle. Not only does mtDNA copy number correlate with dNTP pool size in both mouse tissues and human cells, deoxynucleoside supplementation of the growth medium prevents depletion and restores mtDNA copy number in quiescent MPV17-deficient cells. Hence, our study links MPV17 deficiency, insufficiency of mitochondrial dNTPs, and slow replication in mitochondria to depletion of mtDNA manifesting in the human disease, and places MPV17-related disease firmly in the category of mtDNA disorders caused by deoxynucleotide perturbation. The prevention and reversal of mtDNA loss in MPV17 patient-derived cells identifies potential therapeutic strategy for a currently untreatable disease.
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Affiliation(s)
| | - Yolanda Cámara
- Laboratory of Mitochondrial Disorders, Vall d’Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Catalonia
- Biomedical Network Research Centre on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | | | | | - Sara Vidoni
- MRC Mitochondrial Biology Unit, Wellcome Trust-MRC Building, Cambridge, United Kingdom
| | - Gokhan Akman
- MRC Mill Hill Laboratory, London, United Kingdom
| | - Lilian Hunt
- MRC Mill Hill Laboratory, London, United Kingdom
| | - Mark A. Johnson
- MRC Mitochondrial Biology Unit, Wellcome Trust-MRC Building, Cambridge, United Kingdom
| | - Sarah Grocott
- Mitochondrial Genetics Group, Nuffield Department of Obstetrics and Gynaecology, Women's Centre, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Liya Wang
- Department of Anatomy, Physiology and Biochemistry, The Swedish University of Agricultural Sciences, Biomedical Center, Uppsala, Sweden
| | - David R. Thorburn
- Murdoch Childrens Research Institute and University of Melbourne Department of Paediatrics, Royal Children's Hospital, Flemington Road, Parkville, Victoria, Australia
| | - Michio Hirano
- Department of Neurology, Columbia University Medical Center, New York, New York, United States of America
| | - Joanna Poulton
- Mitochondrial Genetics Group, Nuffield Department of Obstetrics and Gynaecology, Women's Centre, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Robert W. Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, The Medical School, Newcastle upon Tyne, United Kingdom
| | - Greg Elgar
- MRC Mill Hill Laboratory, London, United Kingdom
| | - Ramon Martí
- Laboratory of Mitochondrial Disorders, Vall d’Hebron Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona, Catalonia
- Biomedical Network Research Centre on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Peter Voshol
- Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom
| | - Ian J. Holt
- MRC Mill Hill Laboratory, London, United Kingdom
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78
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Singh B, Owens KM, Bajpai P, Desouki MM, Srinivasasainagendra V, Tiwari HK, Singh KK. Mitochondrial DNA Polymerase POLG1 Disease Mutations and Germline Variants Promote Tumorigenic Properties. PLoS One 2015; 10:e0139846. [PMID: 26468652 PMCID: PMC4607296 DOI: 10.1371/journal.pone.0139846] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 09/17/2015] [Indexed: 02/04/2023] Open
Abstract
Germline mutations in mitochondrial DNA polymerase gamma (POLG1) induce mitochondrial DNA (mtDNA) mutations, depletion, and decrease oxidative phosphorylation. Earlier, we identified somatic mutations in POLG1 and the contribution of these mutations in human cancer. However, a role for germline variations in POLG1 in human cancers is unknown. In this study, we examined a role for disease associated germline variants of POLG1, POLG1 gene expression, copy number variation and regulation in human cancers. We analyzed the mutations, expression and copy number variation in POLG1 in several cancer databases and validated the analyses in primary breast tumors and breast cancer cell lines. We discovered 5-aza-2'-deoxycytidine led epigenetic regulation of POLG1, mtDNA-encoded genes and increased mitochondrial respiration. We conducted comprehensive race based bioinformatics analyses of POLG1 gene in more than 33,000 European-Americans and 5,000 African-Americans. We identified a mitochondrial disease causing missense variation in polymerase domain of POLG1 protein at amino acid 1143 (E1143G) to be 25 times more prevalent in European-Americans (allele frequency 0.03777) when compared to African-American (allele frequency 0.00151) population. We identified T251I and P587L missense variations in exonuclease and linker region of POLG1 also to be more prevalent in European-Americans. Expression of these variants increased glucose consumption, decreased ATP production and increased matrigel invasion. Interestingly, conditional expression of these variants revealed that matrigel invasion properties conferred by these germline variants were reversible suggesting a role of epigenetic regulators. Indeed, we identified a set of miRNA whose expression was reversible after variant expression was turned off. Together, our studies demonstrate altered genetic and epigenetic regulation of POLG1 in human cancers and suggest a role for POLG1 germline variants in promoting tumorigenic properties.
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Affiliation(s)
- Bhupendra Singh
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Kjerstin M. Owens
- Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, NY, United States of America
| | - Prachi Bajpai
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Mohamed Mokhtar Desouki
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN, United States of America
| | - Vinodh Srinivasasainagendra
- Section on Statistical Genetics, Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Hemant K. Tiwari
- Section on Statistical Genetics, Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL, United States of America
| | - Keshav K. Singh
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, United States of America
- Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Department of Environmental Health, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Center for Aging, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- UAB Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Birmingham Veterans Affairs Medical Center, Birmingham, AL, 35294, United States of America
- * E-mail:
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79
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Cabrera-Pérez R, Torres-Torronteras J, Vila-Julià F, Ortega FJ, Cámara Y, Barquinero J, Martí R. Prospective therapeutic approaches in mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). Expert Opin Orphan Drugs 2015. [DOI: 10.1517/21678707.2015.1090307] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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80
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Hänninen RL, Ahonen S, Màrquez M, Myöhänen MJ, Hytönen MK, Lohi H. Canine MPV17 truncation without clinical manifestations. Biol Open 2015; 4:1253-8. [PMID: 26353863 PMCID: PMC4610228 DOI: 10.1242/bio.013870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mitochondrial DNA depletion syndromes (MDS) are often serious autosomal recessively inherited disorders characterized by tissue-specific mtDNA copy number reduction. Many genes, including MPV17, are associated with the hepatocerebral form of MDS. MPV17 encodes for a mitochondrial inner membrane protein with a poorly characterized function. Several MPV17 mutations have been reported in association with a heterogeneous group of early-onset manifestations, including liver disease and neurological problems. Mpv17-deficient mice present renal and hearing defects. We describe here a MPV17 truncation mutation in dogs. We found a 1-bp insertion in exon 4 of the MPV17 gene, resulting in a frameshift and early truncation of the encoded protein. The mutation halves MPV17 expression in the lymphocytes of the homozygous dogs and the truncated protein is not translated in transfected cells. The insertion mutation is recurrent and exists in many unrelated breeds, although is highly enriched in the Boxer breed. Unexpectedly, despite the truncation of MPV17, we could not find any common phenotypes in the genetically affected dogs. The lack of observable phenotype could be due to a late onset, mild symptoms or potential tissue-specific compensatory mechanisms. This study suggests species-specific differences in the manifestation of the MPV17 defects and establishes a novel large animal model to further study MPV17 function and role in mitochondrial biology.
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Affiliation(s)
- Reetta L Hänninen
- Department of Veterinary Biosciences and Research Programs Unit, Molecular Neurology, University of Helsinki and Folkhälsan Research Center, Helsinki 00014, Finland
| | - Saija Ahonen
- Department of Veterinary Biosciences and Research Programs Unit, Molecular Neurology, University of Helsinki and Folkhälsan Research Center, Helsinki 00014, Finland
| | - Merce Màrquez
- Banc de Teixits Animals de Catalunya (BTAC), Department Medicina i Cirurgia Animals, Facultat de Veterinària, Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Barcelona 08193, Spain
| | - Maarit J Myöhänen
- Research Programs Unit, Molecular Neurology, University of Helsinki, Helsinki 00014, Finland
| | - Marjo K Hytönen
- Department of Veterinary Biosciences and Research Programs Unit, Molecular Neurology, University of Helsinki and Folkhälsan Research Center, Helsinki 00014, Finland
| | - Hannes Lohi
- Department of Veterinary Biosciences and Research Programs Unit, Molecular Neurology, University of Helsinki and Folkhälsan Research Center, Helsinki 00014, Finland
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81
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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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82
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Disease-associated mutation in SRSF2 misregulates splicing by altering RNA-binding affinities. Proc Natl Acad Sci U S A 2015; 112:E4726-34. [PMID: 26261309 DOI: 10.1073/pnas.1514105112] [Citation(s) in RCA: 149] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Serine/arginine-rich splicing factor 2 (SRSF2) is an RNA-binding protein that plays important roles in splicing of mRNA precursors. SRSF2 mutations are frequently found in patients with myelodysplastic syndromes and certain leukemias, but how these mutations affect SRSF2 function has only begun to be examined. We used clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 nuclease to introduce the P95H mutation to SRSF2 in K562 leukemia cells, generating an isogenic model so that splicing alterations can be attributed solely to mutant SRSF2. We found that SRSF2 (P95H) misregulates 548 splicing events (<1% of total). Of these events, 374 involved the inclusion of cassette exons, and the inclusion was either increased (206) or decreased (168). We detected a specific motif (UCCA/UG) enriched in the more-included exons and a distinct motif (UGGA/UG) in the more-excluded exons. RNA gel shift assays showed that a mutant SRSF2 derivative bound more tightly than its wild-type counterpart to RNA sites containing UCCAG but bound less tightly to UGGAG sites. Thus in most cases the pattern of exon inclusion or exclusion correlated with stronger or weaker RNA binding, respectively. We further show that the P95H mutation does not affect other functions of SRSF2, i.e., protein-protein interactions with key splicing factors. Our results thus demonstrate that the P95H mutation positively or negatively alters the binding affinity of SRSF2 for cognate RNA sites in target transcripts, leading to misregulation of exon inclusion. Our findings shed light on the mechanism of the disease-associated SRSF2 mutation in splicing regulation and also reveal a group of misspliced mRNA isoforms for potential therapeutic targeting.
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83
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Ahmed N, Ronchi D, Comi GP. Genes and Pathways Involved in Adult Onset Disorders Featuring Muscle Mitochondrial DNA Instability. Int J Mol Sci 2015; 16:18054-76. [PMID: 26251896 PMCID: PMC4581235 DOI: 10.3390/ijms160818054] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 07/27/2015] [Accepted: 07/28/2015] [Indexed: 12/31/2022] Open
Abstract
Replication and maintenance of mtDNA entirely relies on a set of proteins encoded by the nuclear genome, which include members of the core replicative machinery, proteins involved in the homeostasis of mitochondrial dNTPs pools or deputed to the control of mitochondrial dynamics and morphology. Mutations in their coding genes have been observed in familial and sporadic forms of pediatric and adult-onset clinical phenotypes featuring mtDNA instability. The list of defects involved in these disorders has recently expanded, including mutations in the exo-/endo-nuclease flap-processing proteins MGME1 and DNA2, supporting the notion that an enzymatic DNA repair system actively takes place in mitochondria. The results obtained in the last few years acknowledge the contribution of next-generation sequencing methods in the identification of new disease loci in small groups of patients and even single probands. Although heterogeneous, these genes can be conveniently classified according to the pathway to which they belong. The definition of the molecular and biochemical features of these pathways might be helpful for fundamental knowledge of these disorders, to accelerate genetic diagnosis of patients and the development of rational therapies. In this review, we discuss the molecular findings disclosed in adult patients with muscle pathology hallmarked by mtDNA instability.
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Affiliation(s)
- Naghia Ahmed
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Dino Ferrari Centre, Department of Pathophysiology and Transplantation, Università degli Studi di Milano, via Francesco Sforza 35, Milan 20122, Italy.
| | - Dario Ronchi
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Dino Ferrari Centre, Department of Pathophysiology and Transplantation, Università degli Studi di Milano, via Francesco Sforza 35, Milan 20122, Italy.
| | - Giacomo Pietro Comi
- Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Dino Ferrari Centre, Department of Pathophysiology and Transplantation, Università degli Studi di Milano, via Francesco Sforza 35, Milan 20122, Italy.
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84
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Mitochondrial DNA Depletion and Deletions in Paediatric Patients with Neuromuscular Diseases: Novel Phenotypes. JIMD Rep 2015; 23:91-100. [PMID: 25940035 PMCID: PMC4484910 DOI: 10.1007/8904_2015_438] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Revised: 03/02/2015] [Accepted: 03/31/2015] [Indexed: 02/05/2023] Open
Abstract
OBJECTIVE To study the clinical manifestations and occurrence of mtDNA depletion and deletions in paediatric patients with neuromuscular diseases and to identify novel clinical phenotypes associated with mtDNA depletion or deletions. METHODS Muscle DNA samples from patients presenting with undefined encephalomyopathies or myopathies were analysed for mtDNA content by quantitative real-time PCR and for deletions by long-range PCR. Direct sequencing of mtDNA maintenance genes and whole-exome sequencing were used to study the genetic aetiologies of the diseases. Clinical and laboratory findings were collected. RESULTS Muscle samples were obtained from 104 paediatric patients with neuromuscular diseases. mtDNA depletion was found in three patients with severe early-onset encephalomyopathy or myopathy. Two of these patients presented with novel types of mitochondrial DNA depletion syndromes associated with increased serum creatine kinase (CK) and multiorgan disease without mutations in any of the known mtDNA maintenance genes; one patient had pathologic endoplasmic reticulum (ER) membranes in muscle. The third patient with mtDNA depletion was diagnosed with merosine-deficient muscular dystrophy caused by a homozygous mutation in the LAMA2 gene. Two patients with an early-onset Kearns-Sayre/Pearson-like phenotype harboured a large-scale mtDNA deletion, minor multiple deletions and high mtDNA content. CONCLUSIONS Novel encephalomyopathic mtDNA depletion syndrome with structural alterations in muscle ER was identified. mtDNA depletion may also refer to secondary mitochondrial changes related to muscular dystrophy. We suggest that a large-scale mtDNA deletion, minor multiple deletions and high mtDNA content associated with Kearns-Sayre/Pearson syndromes may be secondary changes caused by mutations in an unknown nuclear gene.
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85
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Fasullo M, Endres L. Nucleotide salvage deficiencies, DNA damage and neurodegeneration. Int J Mol Sci 2015; 16:9431-49. [PMID: 25923076 PMCID: PMC4463597 DOI: 10.3390/ijms16059431] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Revised: 03/16/2015] [Accepted: 04/03/2015] [Indexed: 12/20/2022] Open
Abstract
Nucleotide balance is critically important not only in replicating cells but also in quiescent cells. This is especially true in the nervous system, where there is a high demand for adenosine triphosphate (ATP) produced from mitochondria. Mitochondria are particularly prone to oxidative stress-associated DNA damage because nucleotide imbalance can lead to mitochondrial depletion due to low replication fidelity. Failure to maintain nucleotide balance due to genetic defects can result in infantile death; however there is great variability in clinical presentation for particular diseases. This review compares genetic diseases that result from defects in specific nucleotide salvage enzymes and a signaling kinase that activates nucleotide salvage after DNA damage exposure. These diseases include Lesch-Nyhan syndrome, mitochondrial depletion syndromes, and ataxia telangiectasia. Although treatment options are available to palliate symptoms of these diseases, there is no cure. The conclusions drawn from this review include the critical role of guanine nucleotides in preventing neurodegeneration, the limitations of animals as disease models, and the need to further understand nucleotide imbalances in treatment regimens. Such knowledge will hopefully guide future studies into clinical therapies for genetic diseases.
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Affiliation(s)
- Michael Fasullo
- Colleges of Nanoscale Sciences and Engineering, State University of New York Polytechnic University, Albany, NY 12203, USA.
| | - Lauren Endres
- Colleges of Nanoscale Sciences and Engineering, State University of New York Polytechnic University, Albany, NY 12203, USA.
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86
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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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87
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Besse A, Wu P, Bruni F, Donti T, Graham BH, Craigen WJ, McFarland R, Moretti P, Lalani S, Scott KL, Taylor RW, Bonnen PE. The GABA transaminase, ABAT, is essential for mitochondrial nucleoside metabolism. Cell Metab 2015; 21:417-27. [PMID: 25738457 PMCID: PMC4757431 DOI: 10.1016/j.cmet.2015.02.008] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 12/18/2014] [Accepted: 02/06/2015] [Indexed: 01/12/2023]
Abstract
ABAT is a key enzyme responsible for catabolism of principal inhibitory neurotransmitter γ-aminobutyric acid (GABA). We report an essential role for ABAT in a seemingly unrelated pathway, mitochondrial nucleoside salvage, and demonstrate that mutations in this enzyme cause an autosomal recessive neurometabolic disorder and mtDNA depletion syndrome (MDS). We describe a family with encephalomyopathic MDS caused by a homozygous missense mutation in ABAT that results in elevated GABA in subjects' brains as well as decreased mtDNA levels in subjects' fibroblasts. Nucleoside rescue and co-IP experiments pinpoint that ABAT functions in the mitochondrial nucleoside salvage pathway to facilitate conversion of dNDPs to dNTPs. Pharmacological inhibition of ABAT through the irreversible inhibitor Vigabatrin caused depletion of mtDNA in photoreceptor cells that was prevented through addition of dNTPs in cell culture media. This work reveals ABAT as a connection between GABA metabolism and nucleoside metabolism and defines a neurometabolic disorder that includes MDS.
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Affiliation(s)
- Arnaud Besse
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX 77030, USA
| | - Ping Wu
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Francesco Bruni
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Taraka Donti
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Brett H Graham
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - William J Craigen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Robert McFarland
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Paolo Moretti
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Seema Lalani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Kenneth L Scott
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Penelope E Bonnen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX 77030, USA.
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88
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Sezer T, Ozçay F, Balci O, Alehan F. Novel deoxyguanosine kinase gene mutations in the hepatocerebral form of mitochondrial DNA depletion syndrome. J Child Neurol 2015; 30:124-8. [PMID: 24423689 DOI: 10.1177/0883073813517000] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Deoxyguanosine kinase (DGUOK) gene mutations have been identified in the hepatocerebral form of mitochondrial DNA depletion syndromes. We report here clinical and laboratory features of 3 infants with novel DGUOK gene mutations, c.130G>A (Glu44Lys), c.493G>A (Glu165Lys), and c.707+3_6delTAAG.
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Affiliation(s)
- Taner Sezer
- Division of Pediatric Neurology, Baskent University School of Medicine, Ankara, Turkey
| | - Figen Ozçay
- Division of Pediatric Gastroenterology Hepatology and Nutrition, Baskent University School of Medicine, Ankara, Turkey
| | - Oya Balci
- Division of Pediatric Gastroenterology Hepatology and Nutrition, Baskent University School of Medicine, Ankara, Turkey
| | - Füsun Alehan
- Division of Pediatric Neurology, Baskent University School of Medicine, Ankara, Turkey
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89
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Parikh S, Goldstein A, Koenig MK, Scaglia F, Enns GM, Saneto R, Anselm I, Cohen BH, Falk MJ, Greene C, Gropman AL, Haas R, Hirano M, Morgan P, Sims K, Tarnopolsky M, Van Hove JLK, Wolfe L, DiMauro S. Diagnosis and management of mitochondrial disease: a consensus statement from the Mitochondrial Medicine Society. Genet Med 2014; 17:689-701. [PMID: 25503498 DOI: 10.1038/gim.2014.177] [Citation(s) in RCA: 327] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 11/06/2014] [Indexed: 12/13/2022] Open
Abstract
PURPOSE The purpose of this statement is to review the literature regarding mitochondrial disease and to provide recommendations for optimal diagnosis and treatment. This statement is intended for physicians who are engaged in diagnosing and treating these patients. METHODS The Writing Group members were appointed by the Mitochondrial Medicine Society. The panel included members with expertise in several different areas. The panel members utilized a comprehensive review of the literature, surveys, and the Delphi method to reach consensus. We anticipate that this statement will need to be updated as the field continues to evolve. RESULTS Consensus-based recommendations are provided for the diagnosis and treatment of mitochondrial disease. CONCLUSION The Delphi process enabled the formation of consensus-based recommendations. We hope that these recommendations will help standardize the evaluation, diagnosis, and care of patients with suspected or demonstrated mitochondrial disease.
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Affiliation(s)
- Sumit Parikh
- Department of Neurology, Center for Child Neurology, Cleveland Clinic Children's Hospital, Cleveland, Ohio, USA
| | - Amy Goldstein
- Department of Pediatrics, Division of Child Neurology, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Mary Kay Koenig
- Department of Pediatrics, Division of Child and Adolescent Neurology, University of Texas Medical School at Houston, Houston, Texas, USA
| | - Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine and Texas Children's Hospital, Houston, Texas, USA
| | - Gregory M Enns
- Department of Pediatrics, Division of Medical Genetics, Stanford University Lucile Packard Children's Hospital, Palo Alto, California, USA
| | - Russell Saneto
- Department of Neurology, Seattle Children's Hospital, University of Washington, Seattle, Washington, USA.,Department of Pediatrics, Seattle Children's Hospital, University of Washington, Seattle, Washington, USA
| | - Irina Anselm
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, USA
| | - Bruce H Cohen
- Department of Pediatrics, NeuroDevelopmental Science Center, Children's Hospital Medical Center of Akron, Akron, Ohio, USA
| | - Marni J Falk
- Division of Human Genetics, Department of Pediatrics, The Children's Hospital of Philadelphia and University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
| | - Carol Greene
- Department of Pediatrics, University of Maryland Medical Center, Baltimore, Maryland, USA
| | - Andrea L Gropman
- Department of Neurology, Children's National Medical Center and the George Washington University of the Health Sciences, Washington, DC, USA
| | - Richard Haas
- Department of Neurosciences and Pediatrics, UCSD Medical Center and Rady Children's Hospital San Diego, La Jolla, California, USA
| | - Michio Hirano
- Department of Neurology, Columbia University Medical Center, New York, New York, USA
| | - Phil Morgan
- Department of Anesthesiology, Seattle Children's Hospital, Seattle, Washington, USA
| | - Katherine Sims
- Department of Neurology, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Mark Tarnopolsky
- Department of Pediatrics and Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Johan L K Van Hove
- Department of Pediatrics, Clinical Genetics and Metabolism, Children's Hospital Colorado, Denver, Colorado, USA
| | - Lynne Wolfe
- National Institutes of Health, Bethesda, Maryland, USA
| | - Salvatore DiMauro
- Department of Neurology, Columbia University Medical Center, New York, New York, USA
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90
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Zidovudine induces downregulation of mitochondrial deoxynucleoside kinases: implications for mitochondrial toxicity of antiviral nucleoside analogs. Antimicrob Agents Chemother 2014; 58:6758-66. [PMID: 25182642 DOI: 10.1128/aac.03613-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Mitochondrial thymidine kinase 2 (TK2) and deoxyguanosine kinase (dGK) catalyze the initial phosphorylation of deoxynucleosides in the synthesis of the DNA precursors required for mitochondrial DNA (mtDNA) replication and are essential for mitochondrial function. Antiviral nucleosides are known to cause toxic mitochondrial side effects. Here, we examined the effects of 3'-azido-2',3'-dideoxythymidine (AZT) (zidovudine) on mitochondrial TK2 and dGK levels and found that AZT treatment led to downregulation of mitochondrial TK2 and dGK in U2OS cells, whereas cytosolic deoxycytidine kinase (dCK) and thymidine kinase 1 (TK1) levels were not affected. The AZT effects on mitochondrial TK2 and dGK were similar to those of oxidants (e.g., hydrogen peroxide); therefore, we examined the oxidative effects of AZT. We found a modest increase in cellular reactive oxygen species (ROS) levels in the AZT-treated cells. The addition of uridine to AZT-treated cells reduced ROS levels and protein oxidation and prevented the degradation of mitochondrial TK2 and dGK. In organello studies indicated that the degradation of mitochondrial TK2 and dGK is a mitochondrial event. These results suggest that downregulation of mitochondrial TK2 and dGK may lead to decreased mitochondrial DNA precursor pools and eventually mtDNA depletion, which has significant implications for the regulation of mitochondrial nucleotide biosynthesis and for antiviral therapy using nucleoside analogs.
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91
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Ansoleaga B, Jové M, Schlüter A, Garcia-Esparcia P, Moreno J, Pujol A, Pamplona R, Portero-Otín M, Ferrer I. Deregulation of purine metabolism in Alzheimer's disease. Neurobiol Aging 2014; 36:68-80. [PMID: 25311278 DOI: 10.1016/j.neurobiolaging.2014.08.004] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 08/05/2014] [Indexed: 12/30/2022]
Abstract
The neuroprotective role of adenosine and the deregulation of adenosine receptors in Alzheimer's disease (AD) have been extensively studied in recent years. However, little is known about the involvement of purine metabolism in AD. We started by analyzing gene expression in the entorhinal cortex of human controls and AD cases with whole-transcript expression arrays. Once we identified deregulation of the cluster purine metabolism, messenger RNA expression levels of 23 purine metabolism genes were analyzed with qRT-PCR in the entorhinal cortex, frontal cortex area 8, and precuneus at stages I-II, III-IV, and V-VI of Braak and Braak and controls. APRT, DGUOK, POLR3B, ENTPD3, AK5, NME1, NME3, NME5, NME7, and ENTPD2 messenger RNAs were deregulated, with regional variations, in AD cases when compared with controls. In addition, liquid chromatography mass spectrometry based metabolomics in the entorhinal cortex identified altered levels of dGMP, glycine, xanthosine, inosine diphosphate, guanine, and deoxyguanosine, all implicated in this pathway. Our results indicate stage- and region-dependent deregulation of purine metabolism in AD.
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Affiliation(s)
- Belén Ansoleaga
- Institute of Neuropathology, Bellvitge University Hospital-Bellvitge Biomedical Research Institute (IDIBELL), L'Hospitalet de Llobregat, Spain
| | - Mariona Jové
- Department of Experimental Medicine, University of Lleida-Biomedical Research Institute of Lleida, Lleida, Spain
| | - Agatha Schlüter
- Neurometabolic Diseases Laboratory, IDIBELL, L'Hospitalet de Llobregat, Spain
| | - Paula Garcia-Esparcia
- Institute of Neuropathology, Bellvitge University Hospital-Bellvitge Biomedical Research Institute (IDIBELL), L'Hospitalet de Llobregat, Spain
| | - Jesús Moreno
- Institute of Neuropathology, Bellvitge University Hospital-Bellvitge Biomedical Research Institute (IDIBELL), L'Hospitalet de Llobregat, Spain
| | - Aurora Pujol
- Neurometabolic Diseases Laboratory, IDIBELL, L'Hospitalet de Llobregat, Spain; Centre for Biomedical Research on Rare Diseases (CIBERER), Institute Carlos III, Madrid, Spain; Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
| | - Reinald Pamplona
- Department of Experimental Medicine, University of Lleida-Biomedical Research Institute of Lleida, Lleida, Spain
| | - Manuel Portero-Otín
- Department of Experimental Medicine, University of Lleida-Biomedical Research Institute of Lleida, Lleida, Spain
| | - Isidre Ferrer
- Institute of Neuropathology, Bellvitge University Hospital-Bellvitge Biomedical Research Institute (IDIBELL), L'Hospitalet de Llobregat, Spain; University of Barcelona, Bellvitge Campus, L'Hospitalet de Llobregat, Spain; Centre for Networked Biomedical Research in Neurodegenerative Diseases (CIBERNED), Institute Carlos III, Madrid, Spain.
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92
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Sun R, Eriksson S, Wang L. Down-regulation of mitochondrial thymidine kinase 2 and deoxyguanosine kinase by didanosine: Implication for mitochondrial toxicities of anti-HIV nucleoside analogs. Biochem Biophys Res Commun 2014; 450:1021-6. [DOI: 10.1016/j.bbrc.2014.06.098] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 06/20/2014] [Indexed: 12/14/2022]
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93
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Nicholls TJ, Zsurka G, Peeva V, Schöler S, Szczesny RJ, Cysewski D, Reyes A, Kornblum C, Sciacco M, Moggio M, Dziembowski A, Kunz WS, Minczuk M. Linear mtDNA fragments and unusual mtDNA rearrangements associated with pathological deficiency of MGME1 exonuclease. Hum Mol Genet 2014; 23:6147-62. [PMID: 24986917 PMCID: PMC4222359 DOI: 10.1093/hmg/ddu336] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
MGME1, also known as Ddk1 or C20orf72, is a mitochondrial exonuclease found to be involved in the processing of mitochondrial DNA (mtDNA) during replication. Here, we present detailed insights on the role of MGME1 in mtDNA maintenance. Upon loss of MGME1, elongated 7S DNA species accumulate owing to incomplete processing of 5′ ends. Moreover, an 11-kb linear mtDNA fragment spanning the entire major arc of the mitochondrial genome is generated. In contrast to control cells, where linear mtDNA molecules are detectable only after nuclease S1 treatment, the 11-kb fragment persists in MGME1-deficient cells. In parallel, we observed characteristic mtDNA duplications in the absence of MGME1. The fact that the breakpoints of these mtDNA rearrangements do not correspond to either classical deletions or the ends of the linear 11-kb fragment points to a role of MGME1 in processing mtDNA ends, possibly enabling their repair by homologous recombination. In agreement with its functional involvement in mtDNA maintenance, we show that MGME1 interacts with the mitochondrial replicase PolgA, suggesting that it is a constituent of the mitochondrial replisome, to which it provides an additional exonuclease activity. Thus, our results support the viewpoint that MGME1-mediated mtDNA processing is essential for faithful mitochondrial genome replication and might be required for intramolecular recombination of mtDNA.
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Affiliation(s)
| | - Gábor Zsurka
- Department of Epileptology, Life and Brain Center and
| | | | | | - Roman J Szczesny
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland and
| | - Dominik Cysewski
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland and
| | - Aurelio Reyes
- Mitochondrial Biology Unit, Medical Research Council, Cambridge, UK
| | - Cornelia Kornblum
- Department of Neurology, University of Bonn Medical Center, Bonn, Germany
| | - Monica Sciacco
- Neuromuscular Unit, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Centro Dino Ferrari, University of Milan, Milan, Italy
| | - Maurizio Moggio
- Neuromuscular Unit, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Centro Dino Ferrari, University of Milan, Milan, Italy
| | - Andrzej Dziembowski
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland and
| | | | - Michal Minczuk
- Mitochondrial Biology Unit, Medical Research Council, Cambridge, UK,
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94
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Aye Y, Li M, Long MJC, Weiss RS. Ribonucleotide reductase and cancer: biological mechanisms and targeted therapies. Oncogene 2014; 34:2011-21. [PMID: 24909171 DOI: 10.1038/onc.2014.155] [Citation(s) in RCA: 276] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 04/25/2014] [Accepted: 04/26/2014] [Indexed: 12/16/2022]
Abstract
Accurate DNA replication and repair is essential for proper development, growth and tumor-free survival in all multicellular organisms. A key requirement for the maintenance of genomic integrity is the availability of adequate and balanced pools of deoxyribonucleoside triphosphates (dNTPs), the building blocks of DNA. Notably, dNTP pool alterations lead to genomic instability and have been linked to multiple human diseases, including mitochondrial disorders, susceptibility to viral infection and cancer. In this review, we discuss how a key regulator of dNTP biosynthesis in mammals, the enzyme ribonucleotide reductase (RNR), impacts cancer susceptibility and serves as a target for anti-cancer therapies. Because RNR-regulated dNTP production can influence DNA replication fidelity while also supporting genome-protecting DNA repair, RNR has complex and stage-specific roles in carcinogenesis. Nevertheless, cancer cells are dependent on RNR for de novo dNTP biosynthesis. Therefore, elevated RNR expression is a characteristic of many cancers, and an array of mechanistically distinct RNR inhibitors serve as effective agents for cancer treatment. The dNTP metabolism machinery, including RNR, has been exploited for therapeutic benefit for decades and remains an important target for cancer drug development.
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Affiliation(s)
- Y Aye
- 1] Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA [2] Department of Biochemistry, Weill Cornell Medical College, New York, NY, USA
| | - M Li
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA
| | - M J C Long
- Graduate Program in Biochemistry, Brandeis University, Waltham, MA, USA
| | - R S Weiss
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA
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95
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Genetics of mitochondrial respiratory chain deficiencies. Rev Neurol (Paris) 2014; 170:309-22. [DOI: 10.1016/j.neurol.2013.11.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 11/27/2013] [Indexed: 01/21/2023]
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96
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Garcia-Diaz B, Garone C, Barca E, Mojahed H, Gutierrez P, Pizzorno G, Tanji K, Arias-Mendoza F, Quinzii CM, Hirano M. Deoxynucleoside stress exacerbates the phenotype of a mouse model of mitochondrial neurogastrointestinal encephalopathy. ACTA ACUST UNITED AC 2014; 137:1337-49. [PMID: 24727567 PMCID: PMC3999724 DOI: 10.1093/brain/awu068] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Balanced pools of deoxyribonucleoside triphosphate precursors are required for DNA replication, and alterations of this balance are relevant to human mitochondrial diseases including mitochondrial neurogastrointestinal encephalopathy. In this disease, autosomal recessive TYMP mutations cause severe reductions of thymidine phosphorylase activity; marked elevations of the pyrimidine nucleosides thymidine and deoxyuridine in plasma and tissues, and somatic multiple deletions, depletion and site-specific point mutations of mitochondrial DNA. Thymidine phosphorylase and uridine phosphorylase double knockout mice recapitulated several features of these patients including thymidine phosphorylase activity deficiency, elevated thymidine and deoxyuridine in tissues, mitochondrial DNA depletion, respiratory chain defects and white matter changes. However, in contrast to patients with this disease, mutant mice showed mitochondrial alterations only in the brain. To test the hypothesis that elevated levels of nucleotides cause unbalanced deoxyribonucleoside triphosphate pools and, in turn, pathogenic mitochondrial DNA instability, we have stressed double knockout mice with exogenous thymidine and deoxyuridine, and assessed clinical, neuroradiological, histological, molecular, and biochemical consequences. Mutant mice treated with exogenous thymidine and deoxyuridine showed reduced survival, body weight, and muscle strength, relative to untreated animals. Moreover, in treated mutants, leukoencephalopathy, a hallmark of the disease, was enhanced and the small intestine showed a reduction of smooth muscle cells and increased fibrosis. Levels of mitochondrial DNA were depleted not only in the brain but also in the small intestine, and deoxyribonucleoside triphosphate imbalance was observed in the brain. The relative proportion, rather than the absolute amount of deoxyribonucleoside triphosphate, was critical for mitochondrial DNA maintenance. Thus, our results demonstrate that stress of exogenous pyrimidine nucleosides enhances the mitochondrial phenotype of our knockout mice. Our mouse studies provide insights into the pathogenic role of thymidine and deoxyuridine imbalance in mitochondrial neurogastrointestinal encephalopathy and an excellent model to study new therapeutic approaches.
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Affiliation(s)
- Beatriz Garcia-Diaz
- 1 Department of Neurology, Columbia University Medical Centre, New York, NY, 10032, USA
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97
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Nogueira C, Almeida LS, Nesti C, Pezzini I, Videira A, Vilarinho L, Santorelli FM. Syndromes associated with mitochondrial DNA depletion. Ital J Pediatr 2014; 40:34. [PMID: 24708634 PMCID: PMC3985578 DOI: 10.1186/1824-7288-40-34] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 03/28/2014] [Indexed: 01/21/2023] Open
Abstract
Mitochondrial dysfunction accounts for a large group of inherited metabolic disorders most of which are due to a dysfunctional mitochondrial respiratory chain (MRC) and, consequently, deficient energy production. MRC function depends on the coordinated expression of both nuclear (nDNA) and mitochondrial (mtDNA) genomes. Thus, mitochondrial diseases can be caused by genetic defects in either the mitochondrial or the nuclear genome, or in the cross-talk between the two. This impaired cross-talk gives rise to so-called nuclear-mitochondrial intergenomic communication disorders, which result in loss or instability of the mitochondrial genome and, in turn, impaired maintenance of qualitative and quantitative mtDNA integrity. In children, most MRC disorders are associated with nuclear gene defects rather than alterations in the mtDNA itself. The mitochondrial DNA depletion syndromes (MDSs) are a clinically heterogeneous group of disorders with an autosomal recessive pattern of transmission that have onset in infancy or early childhood and are characterized by a reduced number of copies of mtDNA in affected tissues and organs. The MDSs can be divided into least four clinical presentations: hepatocerebral, myopathic, encephalomyopathic and neurogastrointestinal. The focus of this review is to offer an overview of these syndromes, listing the clinical phenotypes, together with their relative frequency, mutational spectrum, and possible insights for improving diagnostic strategies.
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Affiliation(s)
| | | | | | | | | | - Laura Vilarinho
- National Institute of Health, Genetics Department, Research and Development Unit, Porto, Portugal.
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98
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Menezes MJ, Riley LG, Christodoulou J. Mitochondrial respiratory chain disorders in childhood: Insights into diagnosis and management in the new era of genomic medicine. Biochim Biophys Acta Gen Subj 2014; 1840:1368-79. [DOI: 10.1016/j.bbagen.2013.12.025] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2013] [Revised: 12/10/2013] [Accepted: 12/18/2013] [Indexed: 12/26/2022]
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99
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Yamazaki T, Murayama K, Compton AG, Sugiana C, Harashima H, Amemiya S, Ajima M, Tsuruoka T, Fujinami A, Kawachi E, Kurashige Y, Matsushita K, Wakiguchi H, Mori M, Iwasa H, Okazaki Y, Thorburn DR, Ohtake A. Molecular diagnosis of mitochondrial respiratory chain disorders in Japan: focusing on mitochondrial DNA depletion syndrome. Pediatr Int 2014; 56:180-7. [PMID: 24266892 DOI: 10.1111/ped.12249] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 08/19/2013] [Accepted: 10/21/2013] [Indexed: 01/08/2023]
Abstract
BACKGROUND Although mitochondrial respiratory chain disorders (MRCD) are one of the most common congenital metabolic diseases, there is no cumulative data on enzymatic diagnosis and clinical manifestation for MRCD in Japan and Asia. METHODS We evaluated 675 Japanese patients having profound lactic acidemia, or patients having symptoms or signs of multiple-organ origin simultaneously without lactic acidemia on respiratory chain enzyme activity assay and blue native polyacrylamide gel electrophoresis. Quantitative polymerase chain reaction was used to diagnose mitochondrial DNA depletion syndrome (MTDPS). Mutation analysis of several genes responsible for MTDPS was also performed. RESULTS A total of 232 patients were diagnosed with a probable or definite MRCD. MRCD are common, afflicting one in every several thousand people in Japan. More than one in 10 of the patients diagnosed lacked lactic acidemia. A subsequent analysis of the causative genes of MTDPS identified novel mutations in six of the patients. A 335 bp deletion in deoxyguanosine kinase (DGUOK; g.11692_12026del335 (p.A48fsX90)) was noted in two unrelated families, and may therefore be a common mutation in Japanese people. The proportion of all patients with MTDPS, and particularly those with recessive DNA polymerase γ (POLG) mutations, appears to be lower in Japan than in other studies. This is most likely due to the relatively high prevalence of ancient European POLG mutations in Caucasian populations. No other significant differences were identified in a comparison of the enzymatic diagnoses, disease classifications or prognoses in Japanese and Caucasian patients with MRCD. CONCLUSION MTDPS and other MRCD are common, but serious, diseases that occur across all races.
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Affiliation(s)
- Taro Yamazaki
- Department of Pediatrics, Faculty of Medicine, Saitama Medical University, Saitama, Japan; Murdoch Childrens Research Institute, Royal Children's Hospital and Department of Paediatrics, University of Melbourne, Melbourne, Australia
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100
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Grabhorn E, Tsiakas K, Herden U, Fischer L, Freisinger P, Marquardt T, Ganschow R, Briem-Richter A, Santer R. Long-term outcomes after liver transplantation for deoxyguanosine kinase deficiency: a single-center experience and a review of the literature. Liver Transpl 2014; 20:464-72. [PMID: 24478274 DOI: 10.1002/lt.23830] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 01/05/2014] [Indexed: 01/05/2023]
Abstract
Deoxyguanosine kinase (DGUOK) deficiency is a well-known cause of hepatocerebral mitochondrial DNA depletion syndromes, which include a broad spectrum of clinical presentations. Affected patients often develop life-threatening liver failure, but the benefits of liver transplantation (LT) are controversial because of the frequently severe neurological involvement due to the underlying mitochondrial disease. We describe the long-term clinical course of 2 patients from our institution and provide an update on their outcomes after LT with this condition. Another 12 pediatric patients were identified through a systematic search of the literature. All 14 reported patients underwent transplantation in infancy despite mild to moderate neurological impairment in some cases. The 2 DGUOK-deficient patients from our center displayed liver failure and mild to moderate neurological involvement. At the time of this writing, they had been followed for 5 and 8 years after LT, both patients were alive, and they had only mild neurological symptoms. Three of the 12 patients identified through the literature review survived for a long time (17, 12, and 23 years); 8 died during early follow-up; and for 1 patient, no follow-up information was available. The 1-year survival rate was 64%; 36% survived for more than 5 years. The long-term survivors had good quality of life. In conclusion, although survival after LT for DGUOK deficiency is lower than survival after LT for other indications, a significant proportion of patients benefit from LT with long-term survival and a stable neurological situation despite initial neurological abnormalities. Nevertheless, a decision to carry out LT for patients with DGUOK deficiency remains difficult because neurological symptoms may occur and worsen after LT despite their absence before transplantation.
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Affiliation(s)
- Enke Grabhorn
- Department of Pediatric Hepatology and Liver Transplantation, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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