1
|
Jurecka A, Tylki-Szymanska A. Inborn errors of purine and pyrimidine metabolism: A guide to diagnosis. Mol Genet Metab 2022; 136:164-176. [PMID: 35216884 DOI: 10.1016/j.ymgme.2022.02.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 02/14/2022] [Accepted: 02/15/2022] [Indexed: 12/18/2022]
Abstract
Inborn errors of purine and pyrimidine (P/P) metabolism are under-reported and rarely mentioned in the general literature or in clinical practice, as well as in reviews dedicated to other inborn errors of metabolism (IEMs). However, their diagnosis is important because genetic counseling can be provided and, in some cases, specific treatment exists that may slow or even reverse clinical signs. The purpose of this review is to provide a practical guideline on the suspicion and investigation of inborn errors of P/P metabolism. Failure of a physician to recognize the presence of these disorders may be devastating for affected infants and children because of its permanent effects in the patient, and for their parents because of implications for future offspring. Diagnosis is crucial because genetic counseling can be provided and, in some cases, specific treatment can be offered that may slow or even reverse clinical symptoms. This review highlights the risk factors in the history, the important examination findings, and the appropriate biochemical investigation of the child. Herein we describe the approach to the diagnosis of P/P disorders and emphasize clinical situations in which physicians should consider these diseases as diagnostic possibilities.
Collapse
|
2
|
Manini A, Abati E, Comi GP, Corti S, Ronchi D. Mitochondrial DNA homeostasis impairment and dopaminergic dysfunction: A trembling balance. Ageing Res Rev 2022; 76:101578. [PMID: 35114397 DOI: 10.1016/j.arr.2022.101578] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 12/26/2021] [Accepted: 01/28/2022] [Indexed: 02/07/2023]
Abstract
Maintenance of mitochondrial DNA (mtDNA) homeostasis includes a variety of processes, such as mtDNA replication, repair, and nucleotides synthesis, aimed at preserving the structural and functional integrity of mtDNA molecules. Mutations in several nuclear genes (i.e., POLG, POLG2, TWNK, OPA1, DGUOK, MPV17, TYMP) impair mtDNA maintenance, leading to clinical syndromes characterized by mtDNA depletion and/or deletions in affected tissues. In the past decades, studies have demonstrated a progressive accumulation of multiple mtDNA deletions in dopaminergic neurons of the substantia nigra in elderly population and, to a greater extent, in Parkinson's disease patients. Moreover, parkinsonism has been frequently described as a prominent clinical feature in mtDNA instability syndromes. Among Parkinson's disease-related genes with a significant role in mitochondrial biology, PARK2 and LRRK2 specifically take part in mtDNA maintenance. Moreover, a variety of murine models (i.e., "Mutator", "MitoPark", "PD-mitoPstI", "Deletor", "Twinkle-dup" and "TwinkPark") provided in vivo evidence that mtDNA stability is required to preserve nigrostriatal integrity. Here, we review and discuss the clinical, genetic, and pathological background underlining the link between impaired mtDNA homeostasis and dopaminergic degeneration.
Collapse
|
3
|
Berardo A, Engelstad K, Hirano M. Advances in Thymidine Kinase 2 Deficiency: Clinical Aspects, Translational Progress, and Emerging Therapies. J Neuromuscul Dis 2022; 9:225-235. [PMID: 35094997 PMCID: PMC9028656 DOI: 10.3233/jnd-210786] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Defects in the replication, maintenance, and repair of mitochondrial DNA (mtDNA) constitute a growing and genetically heterogeneous group of mitochondrial disorders. Multiple genes participate in these processes, including thymidine kinase 2 (TK2) encoding the mitochondrial matrix protein TK2, a critical component of the mitochondrial nucleotide salvage pathway. TK2 deficiency (TK2d) causes mtDNA depletion, multiple deletions, or both, which manifest predominantly as mitochondrial myopathy. A wide clinical spectrum phenotype includes a severe, rapidly progressive, early onset form (median survival: < 2 years); a less severe childhood-onset form; and a late-onset form with a variably slower rate of progression. Clinical presentation typically includes progressive weakness of limb, neck, facial, oropharyngeal, and respiratory muscle, whereas limb myopathy with ptosis, ophthalmoparesis, and respiratory involvement is more common in the late-onset form. Deoxynucleoside monophosphates and deoxynucleosides that can bypass the TK2 enzyme defect have been assessed in a mouse model, as well as under open-label compassionate use (expanded access) in TK2d patients, indicating clinical efficacy with a favorable side-effect profile. This treatment is currently undergoing testing in clinical trials intended to support approval in the US and European Union (EU). In the early expanded access program, growth differentiation factor 15 (GDF-15) appears to be a useful biomarker that correlates with therapeutic response. With the advent of a specific treatment and given the high morbidity and mortality associated with TK2d, clinicians need to know how to recognize and diagnose this disorder. Here, we summarize translational research about this rare condition emphasizing clinical aspects.
Collapse
Affiliation(s)
- Andres Berardo
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
| | - Kristin Engelstad
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
| | - Michio Hirano
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
| |
Collapse
|
4
|
Preferent Diaphragmatic Involvement in TK2 Deficiency: An Autopsy Case Study. Int J Mol Sci 2021; 22:ijms22115598. [PMID: 34070501 PMCID: PMC8199166 DOI: 10.3390/ijms22115598] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 05/18/2021] [Accepted: 05/20/2021] [Indexed: 12/23/2022] Open
Abstract
Our goal was to analyze postmortem tissues of an adult patient with late-onset thymidine kinase 2 (TK2) deficiency who died of respiratory failure. Compared with control tissues, we found a low mtDNA content in the patient’s skeletal muscle, liver, kidney, small intestine, and particularly in the diaphragm, whereas heart and brain tissue showed normal mtDNA levels. mtDNA deletions were present in skeletal muscle and diaphragm. All tissues showed a low content of OXPHOS subunits, and this was especially evident in diaphragm, which also exhibited an abnormal protein profile, expression of non-muscular β-actin and loss of GAPDH and α-actin. MALDI-TOF/TOF mass spectrometry analysis demonstrated the loss of the enzyme fructose-bisphosphate aldolase, and enrichment for serum albumin in the patient’s diaphragm tissue. The TK2-deficient patient’s diaphragm showed a more profound loss of OXPHOS proteins, with lower levels of catalase, peroxiredoxin 6, cytosolic superoxide dismutase, p62 and the catalytic subunits of proteasome than diaphragms of ventilated controls. Strong overexpression of TK1 was observed in all tissues of the patient with diaphragm showing the highest levels. TK2 deficiency induces a more profound dysfunction of the diaphragm than of other tissues, which manifests as loss of OXPHOS and glycolytic proteins, sarcomeric components, antioxidants and overactivation of the TK1 salvage pathway that is not attributed to mechanical ventilation.
Collapse
|
5
|
James R, Chaytow H, Ledahawsky LM, Gillingwater TH. Revisiting the role of mitochondria in spinal muscular atrophy. Cell Mol Life Sci 2021; 78:4785-4804. [PMID: 33821292 PMCID: PMC8195803 DOI: 10.1007/s00018-021-03819-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 02/22/2021] [Accepted: 03/23/2021] [Indexed: 02/07/2023]
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive motor neuron disease of variable clinical severity that is caused by mutations in the survival motor neuron 1 (SMN1) gene. Despite its name, SMN is a ubiquitous protein that functions within and outside the nervous system and has multiple cellular roles in transcription, translation, and proteostatic mechanisms. Encouragingly, several SMN-directed therapies have recently reached the clinic, albeit this has highlighted the increasing need to develop combinatorial therapies for SMA to achieve full clinical efficacy. As a subcellular site of dysfunction in SMA, mitochondria represents a relevant target for a combinatorial therapy. Accordingly, we will discuss our current understanding of mitochondrial dysfunction in SMA, highlighting mitochondrial-based pathways that offer further mechanistic insights into the involvement of mitochondria in SMA. This may ultimately facilitate translational development of targeted mitochondrial therapies for SMA. Due to clinical and mechanistic overlaps, such strategies may also benefit other motor neuron diseases and related neurodegenerative disorders.
Collapse
Affiliation(s)
- Rachel James
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Helena Chaytow
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Leire M Ledahawsky
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Thomas H Gillingwater
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK.
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, EH16 4SB, UK.
| |
Collapse
|
6
|
Karakaidos P, Rampias T. Mitonuclear Interactions in the Maintenance of Mitochondrial Integrity. Life (Basel) 2020; 10:life10090173. [PMID: 32878185 PMCID: PMC7555762 DOI: 10.3390/life10090173] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 08/28/2020] [Indexed: 12/27/2022] Open
Abstract
In eukaryotic cells, mitochondria originated in an α-proteobacterial endosymbiont. Although these organelles harbor their own genome, the large majority of genes, originally encoded in the endosymbiont, were either lost or transferred to the nucleus. As a consequence, mitochondria have become semi-autonomous and most of their processes require the import of nuclear-encoded components to be functional. Therefore, the mitochondrial-specific translation has evolved to be coordinated by mitonuclear interactions to respond to the energetic demands of the cell, acquiring unique and mosaic features. However, mitochondrial-DNA-encoded genes are essential for the assembly of the respiratory chain complexes. Impaired mitochondrial function due to oxidative damage and mutations has been associated with numerous human pathologies, the aging process, and cancer. In this review, we highlight the unique features of mitochondrial protein synthesis and provide a comprehensive insight into the mitonuclear crosstalk and its co-evolution, as well as the vulnerabilities of the animal mitochondrial genome.
Collapse
|
7
|
Clinical exome sequencing in neuromuscular diseases: an experience from Turkey. Neurol Sci 2020; 41:2157-2164. [PMID: 32140910 DOI: 10.1007/s10072-020-04304-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 02/20/2020] [Indexed: 02/08/2023]
Abstract
Neuromuscular diseases (NMDs) encompass a variety of ailments from muscular dystrophies to ataxias, in the course of which the functioning of the muscles is eventually either directly or indirectly impaired. The clinical diagnosis of a particular NMD is not always straightforward due to the clinical and genetic heterogeneity of the disorders under investigation. Traditional diagnostic tools such as electrophysiological tests and muscle biopsies are both invasive and painful methods, causing the patients to be reluctant. Next-generation sequencing, on the other hand, emerged as an alternative method for the diagnosis of NMDs, both with its minimally invasive nature and fast processing period. In this study, clinical exome sequencing (CES) was applied to a cohort of 70 probands in Turkey, 44 of whom received a final diagnosis, representing a diagnostic rate of 62.9%. Out of the 50 mutations identified to be causal, 26 were novel in the known 27 NMD genes. Two probands had complex/blended phenotypes. Molecular confirmation of clinical diagnosis of NMDs has a major prognostic impact and is crucial for the management and the possibility of alternative reproductive options. CES, which has been increasingly adopted to diagnose single-gene disorders, is also a powerful tool for revealing the etiopathogenesis in complex/blended phenotypes, as observed in two probands of the cohort.
Collapse
|
8
|
Bioavailability and cytosolic kinases modulate response to deoxynucleoside therapy in TK2 deficiency. EBioMedicine 2019; 46:356-367. [PMID: 31383553 PMCID: PMC6710986 DOI: 10.1016/j.ebiom.2019.07.037] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/10/2019] [Accepted: 07/15/2019] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND TK2 is a nuclear gene encoding the mitochondrial matrix protein thymidine kinase 2 (TK2), a critical enzyme in the mitochondrial nucleotide salvage pathway. Deficiency of TK2 activity causes mitochondrial DNA (mtDNA) depletion, which in humans manifests predominantly as a mitochondrial myopathy with onset typically in infancy and childhood. We previously showed that oral treatment of the Tk2 H126N knock-in mouse model (Tk2-/-) with the TK2 substrates, deoxycytidine (dCtd) and thymidine (dThd), delayed disease onset and prolonged median survival by 3-fold. Nevertheless, dCtd + dThd treated Tk2-/- mice showed mtDNA depletion in brain as early as postnatal day 13 and in virtually all other tissues at age 29 days. METHODS To enhance mechanistic understanding and efficacy of dCtd + dThd therapy, we studied the bioavailability of dCtd and dThd in various tissues as well as levels of the cytosolic enzymes, TK1 and dCK that convert the deoxynucleosides into dCMP and dTMP. FINDINGS Parenteral treatment relative to oral treatment produced higher levels of dCtd and dThd and improved mtDNA levels in liver and heart, but did not ameliorate molecular defects in brain or prolong survival. Down-regulation of TK1 correlated with temporal- and tissue-specificity of response to dCtd + dThd. Finally, we observed in human infant and adult muscle expression of TK1 and dCK, which account for the long-term efficacy to dCtd + dThd therapy in TK2 deficient patients. INTERPRETATIONS These data indicate that the cytosolic pyrimidine salvage pathway enzymes TK1 and dCK are critical for therapeutic efficacy of deoxynucleoside therapy for Tk2 deficiency. FUND: National Institutes of Health P01HD32062.
Collapse
|
9
|
Domínguez-González C, Madruga-Garrido M, Mavillard F, Garone C, Aguirre-Rodríguez FJ, Donati MA, Kleinsteuber K, Martí I, Martín-Hernández E, Morealejo-Aycinena JP, Munell F, Nascimento A, Kalko SG, Sardina MD, Álvarez Del Vayo C, Serrano O, Long Y, Tu Y, Levin B, Thompson JLP, Engelstad K, Uddin J, Torres-Torronteras J, Jimenez-Mallebrera C, Martí R, Paradas C, Hirano M. Deoxynucleoside Therapy for Thymidine Kinase 2-Deficient Myopathy. Ann Neurol 2019; 86:293-303. [PMID: 31125140 DOI: 10.1002/ana.25506] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 05/21/2019] [Accepted: 05/22/2019] [Indexed: 12/22/2022]
Abstract
OBJECTIVE Thymidine kinase 2, encoded by the nuclear gene TK2, is required for mitochondrial DNA maintenance. Autosomal recessive TK2 mutations cause depletion and multiple deletions of mtDNA that manifest predominantly as a myopathy usually beginning in childhood and progressing relentlessly. We investigated the safety and efficacy of deoxynucleoside monophosphate and deoxynucleoside therapies. METHODS We administered deoxynucleoside monophosphates and deoxynucleoside to 16 TK2-deficient patients under a compassionate use program. RESULTS In 5 patients with early onset and severe disease, survival and motor functions were better than historically untreated patients. In 11 childhood and adult onset patients, clinical measures stabilized or improved. Three of 8 patients who were nonambulatory at baseline gained the ability to walk on therapy; 4 of 5 patients who required enteric nutrition were able to discontinue feeding tube use; and 1 of 9 patients who required mechanical ventilation became able to breathe independently. In motor functional scales, improvements were observed in the 6-minute walk test performance in 7 of 8 subjects, Egen Klassifikation in 2 of 3, and North Star Ambulatory Assessment in all 5 tested. Baseline elevated serum growth differentiation factor 15 levels decreased with treatment in all 7 patients tested. A side effect observed in 8 of the 16 patients was dose-dependent diarrhea, which did not require withdrawal of treatment. Among 12 other TK2 patients treated with deoxynucleoside, 2 adults developed elevated liver enzymes that normalized following discontinuation of therapy. INTERPRETATION This open-label study indicates favorable side effect profiles and clinical efficacy of deoxynucleoside monophosphate and deoxynucleoside therapies for TK2 deficiency. ANN NEUROL 2019;86:293-303.
Collapse
Affiliation(s)
- Cristina Domínguez-González
- Neuromuscular Disorders Unit, Neurology Department, Hospital 12 de Octubre, Madrid, Spain.,Instituto de Investigación i + 12, Hospital 12 de Octubre, Madrid, Spain.,Center for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Marcos Madruga-Garrido
- Neuromuscular Disorders Unit, Pediatric Neurology Department, Instituto de Biomedicina de Sevilla, Hospital U. Virgen del Rocío, Consejo Superior de Investigaciones Científicas, University of Seville, Seville, Spain
| | - Fabiola Mavillard
- Neuromuscular Disorders Unit, Neurology Department, Instituto de Biomedicina de Sevilla, Hospital U. Virgen del Rocío, Consejo Superior de Investigaciones Científicas, University of Seville, Seville, Spain.,Center for Biomedical Network Research on Neurodegenerative Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Caterina Garone
- Medical Research Council Mitochondrial Biology Unit, Cambridge Biomedical Campus, Cambridge, UK
| | | | - M Alice Donati
- Metabolic and Neuromuscular Unit, Meyer Hospital, Florence, Italy
| | - Karin Kleinsteuber
- Pediatric Neurology Department, Faculty of Medicine, University of Chile, Las Condes Clinic, Santiago, Chile
| | - Itxaso Martí
- Pediatric Neurology Department, Donostia University Hospital, San Sebastian, Spain
| | - Elena Martín-Hernández
- Instituto de Investigación i + 12, Hospital 12 de Octubre, Madrid, Spain.,Center for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.,Hereditary Metabolic and Mitochondrial Disorders Unit, Pediatric Department, October 12 Hospital, Madrid, Spain
| | | | - Francina Munell
- Pediatric Department, Vall d'Hebron Hospital, Barcelona, Spain
| | - Andrés Nascimento
- Center for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.,Neuromuscular Unit, Neurology Department, Sant Joan de Déu Research Institute, Sant Joan de Déu Hospital, Barcelona, Spain
| | - Susana G Kalko
- Center for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.,Neuromuscular Unit, Neurology Department, Sant Joan de Déu Research Institute, Sant Joan de Déu Hospital, Barcelona, Spain
| | - M Dolores Sardina
- Pediatric Neurology Department, Badajoz Hospital Complex, Badajoz, Spain
| | - Concepcion Álvarez Del Vayo
- Center for Biomedical Network Research on Neurodegenerative Diseases, Instituto de Salud Carlos III, Madrid, Spain.,Pharmacy Department, Virgin of el Rocío University Hospital, Seville, Spain
| | - Olga Serrano
- Pharmacy Department, October 12 Hospital, Madrid, Spain
| | - Yuelin Long
- Department of Biostatistics, Mailman School of Public Health, Columbia University Medical Center, New York, NY
| | - Yuqi Tu
- Department of Biostatistics, Mailman School of Public Health, Columbia University Medical Center, New York, NY
| | - Bruce Levin
- Department of Biostatistics, Mailman School of Public Health, Columbia University Medical Center, New York, NY
| | - John L P Thompson
- Department of Biostatistics, Mailman School of Public Health, Columbia University Medical Center, New York, NY
| | - Kristen Engelstad
- Neurology Department, H. Houston Merritt Center, Columbia University Medical Center, New York, NY
| | - Jasim Uddin
- Neurology Department, H. Houston Merritt Center, Columbia University Medical Center, New York, NY
| | - Javier Torres-Torronteras
- Center for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.,Research Group on Neuromuscular and Mitochondrial Diseases, Vall d'Hebron Research Institute, Autonomous University of Barcelona, Barcelona, Spain
| | - Cecilia Jimenez-Mallebrera
- Center for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.,Neuromuscular Unit, Neurology Department, Sant Joan de Déu Research Institute, Sant Joan de Déu Hospital, Barcelona, Spain
| | - Ramon Martí
- Center for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.,Research Group on Neuromuscular and Mitochondrial Diseases, Vall d'Hebron Research Institute, Autonomous University of Barcelona, Barcelona, Spain
| | - Carmen Paradas
- Neuromuscular Disorders Unit, Neurology Department, Instituto de Biomedicina de Sevilla, Hospital U. Virgen del Rocío, Consejo Superior de Investigaciones Científicas, University of Seville, Seville, Spain.,Center for Biomedical Network Research on Neurodegenerative Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Michio Hirano
- Neurology Department, H. Houston Merritt Center, Columbia University Medical Center, New York, NY
| |
Collapse
|
10
|
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.
Collapse
|
11
|
Brockhage R, Slone J, Ma Z, Hegde MR, Valencia CA, Huang T. Validation of the diagnostic potential of mtDNA copy number derived from whole genome sequencing. J Genet Genomics 2018; 45:S1673-8527(18)30098-5. [PMID: 29910094 DOI: 10.1016/j.jgg.2018.06.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 06/03/2018] [Accepted: 06/04/2018] [Indexed: 02/05/2023]
Affiliation(s)
- Rachel Brockhage
- Division of Human Genetics, Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Jesse Slone
- Division of Human Genetics, Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Zeqiang Ma
- PerkinElmer Genomics, Branford, CT 06405, USA
| | - Madhuri R Hegde
- PerkinElmer Genomics, Branford, CT 06405, USA; Department of Human Genetics, Emory University, Atlanta, GA 30322, USA; School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - C Alexander Valencia
- PerkinElmer Genomics, Branford, CT 06405, USA; West China Hospital, Sichuan University, Chengdu 610041, China
| | - Taosheng Huang
- Division of Human Genetics, Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Human Aging Research Institute, Nanchang University, Nanchang 330031, China.
| |
Collapse
|
12
|
Wang J, Kim E, Dai H, Stefans V, Vogel H, Al Jasmi F, Schrier Vergano SA, Castro D, Bernes S, Bhambhani V, Long C, El-Hattab AW, Wong LJ. Clinical and molecular spectrum of thymidine kinase 2-related mtDNA maintenance defect. Mol Genet Metab 2018; 124:124-130. [PMID: 29735374 DOI: 10.1016/j.ymgme.2018.04.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 04/25/2018] [Accepted: 04/26/2018] [Indexed: 11/29/2022]
Abstract
Mitochondrial DNA maintenance (mtDNA) defects have a wide range of causes, each with a set of phenotypes that overlap with many other neurological or muscular diseases. Clinicians face the challenge of narrowing down a long list of differential diagnosis when encountered with non-specific neuromuscular symptoms. Biallelic pathogenic variants in the Thymidine Kinase 2 (TK2) gene cause a myopathic form of mitochondrial DNA maintenance defect. Since the first description in 2001, there have been 71 patients reported with 42 unique pathogenic variants. Here we are reporting 11 new cases with 5 novel pathogenic variants. We describe and analyze a total of 82 cases with 47 unique TK2 pathogenic variants in effort to formulate a comprehensive molecular and clinical spectrum of TK2-related mtDNA maintenance disorders.
Collapse
Affiliation(s)
- Julia Wang
- Medical Scientist Training Program, Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States.
| | - Emily Kim
- Department of BioSciences, Rice University, 6100 Main Street, Houston, TX 77005, United States
| | - Honzheng Dai
- Department of Human and Molecular Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States
| | - Vikki Stefans
- UAMS College of Medicine, Arkansas Children's Hospital, 1 Children's Way, Little Rock, AR 72202, United States
| | - Hannes Vogel
- Pathology, Stanford University School of Medicine, R241 Edwards Building, 300 Pasteur Drive, Palo Alto, CA 94305, United States
| | - Fatma Al Jasmi
- Division of Clinical Genetics and Metabolic Disorders, Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - Samantha A Schrier Vergano
- Division of Medical Genetics and Metabolism, Children's Hospital of The King's Daughters, 601 Children's Lane, Norfolk, VA 23507, United States
| | - Diana Castro
- Department of Pediatric, Neurology and Neurotherapeutics, Children's Health Dallas, University of Texas Southwestern, 2350 N Stemmons Freeway, Dallas, TX 75207, United States
| | - Saunder Bernes
- Department of Neurology, Phoenix Children's Hospital, Barrows Neurological Institute, 1919 East Thomas Road, Phoenix, AZ 85016, United States
| | - Vikas Bhambhani
- Genomics Medicine Program, Children's Hospital Minnesota, 2525 Chicago Ave S, Minneapolis, MN 55404, United States
| | - Catherine Long
- Genomics Medicine Program, Children's Hospital Minnesota, 2525 Chicago Ave S, Minneapolis, MN 55404, United States
| | - Ayman W El-Hattab
- Division of Clinical Genetics and Metabolic Disorders, Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - Lee-Jun Wong
- Department of Human and Molecular Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, United States.
| |
Collapse
|
13
|
Garone C, Taylor RW, Nascimento A, Poulton J, Fratter C, Domínguez-González C, Evans JC, Loos M, Isohanni P, Suomalainen A, Ram D, Hughes MI, McFarland R, Barca E, Lopez Gomez C, Jayawant S, Thomas ND, Manzur AY, Kleinsteuber K, Martin MA, Kerr T, Gorman GS, Sommerville EW, Chinnery PF, Hofer M, Karch C, Ralph J, Cámara Y, Madruga-Garrido M, Domínguez-Carral J, Ortez C, Emperador S, Montoya J, Chakrapani A, Kriger JF, Schoenaker R, Levin B, Thompson JLP, Long Y, Rahman S, Donati MA, DiMauro S, Hirano M. Retrospective natural history of thymidine kinase 2 deficiency. J Med Genet 2018; 55:515-521. [PMID: 29602790 PMCID: PMC6073909 DOI: 10.1136/jmedgenet-2017-105012] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Revised: 03/02/2018] [Accepted: 03/11/2018] [Indexed: 12/21/2022]
Abstract
Background Thymine kinase 2 (TK2) is a mitochondrial matrix protein encoded in nuclear DNA and phosphorylates the pyrimidine nucleosides: thymidine and deoxycytidine. Autosomal recessive TK2 mutations cause a spectrum of disease from infantile onset to adult onset manifesting primarily as myopathy. Objective To perform a retrospective natural history study of a large cohort of patients with TK2 deficiency. Methods The study was conducted by 42 investigators across 31 academic medical centres. Results We identified 92 patients with genetically confirmed diagnoses of TK2 deficiency: 67 from literature review and 25 unreported cases. Based on clinical and molecular genetics findings, we recognised three phenotypes with divergent survival: (1) infantile-onset myopathy (42.4%) with severe mitochondrial DNA (mtDNA) depletion, frequent neurological involvement and rapid progression to early mortality (median post-onset survival (POS) 1.00, CI 0.58 to 2.33 years); (2) childhood-onset myopathy (40.2%) with mtDNA depletion, moderate-to-severe progression of generalised weakness and median POS at least 13 years; and (3) late-onset myopathy (17.4%) with mild limb weakness at onset and slow progression to respiratory insufficiency with median POS of 23 years. Ophthalmoparesis and facial weakness are frequent in adults. Muscle biopsies show multiple mtDNA deletions often with mtDNA depletion. Conclusions In TK2 deficiency, age at onset, rate of weakness progression and POS are important variables that define three clinical subtypes. Nervous system involvement often complicates the clinical course of the infantile-onset form while extraocular muscle and facial involvement are characteristic of the late-onset form. Our observations provide essential information for planning future clinical trials in this disorder.
Collapse
Affiliation(s)
- Caterina Garone
- Department of Neurology, Columbia University Medical Center, New York City, New York, USA.,MRC Mitochondrial Biology Unit, Cambridge Biomedical Campus, Cambridge, UK
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Andrés Nascimento
- Neuromuscular Unit, Hospital Universitario 12 de Octubre, Madrid, Spain
| | - Joanna Poulton
- Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Oxford, UK
| | - Carl Fratter
- Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Cristina Domínguez-González
- Neuromuscular Unit, Hospital Universitario 12 de Octubre, Madrid, Spain.,Centre for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.,Instituto de Investigación, Hospital Universitario 12 de Octubre, Madrid, Spain
| | - Julie C Evans
- Oxford Medical Genetics Laboratories, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Mariana Loos
- Neurology Department, Hospital de Pediatría 'Prof. Dr JP Garrahan', Buenos Aires, Argentina
| | - Pirjo Isohanni
- Research Programs Unit, Molecular Neurology, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland.,Department of Child Neurology, Children's Hospital, University of Helsinki, Helsinki University Hospital, Helsinki, Finland
| | - Anu Suomalainen
- Research Programs Unit, Molecular Neurology, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland.,Neuroscience Center, University of Helsinki, Helsinki, Finland.,Department of Neurology, Helsinki University Hospital, Helsinki, Finland
| | - Dipak Ram
- Department of Paediatric Neurology, Royal Manchester Children's Hospital, Manchester, UK
| | - M Imelda Hughes
- Department of Paediatric Neurology, Royal Manchester Children's Hospital, Manchester, UK
| | - Robert McFarland
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Emanuele Barca
- Department of Neurology, Columbia University Medical Center, New York City, New York, USA.,UOC Neurology and Neuromuscular Diseases, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Carlos Lopez Gomez
- Department of Neurology, Columbia University Medical Center, New York City, New York, USA
| | - Sandeep Jayawant
- Paediatric Neurology, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Neil D Thomas
- Paediatric Neurology, University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Adnan Y Manzur
- Dubowitz Neuromuscular Centre, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Karin Kleinsteuber
- Pediatric Neurology, Faculty of Medicine, Universidad de Chile, Clínica Las Condes, Santiago, Chile
| | - Miguel A Martin
- Centre for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.,Instituto de Investigación, Hospital Universitario 12 de Octubre, Madrid, Spain
| | - Timothy Kerr
- Paediatric Neurology, St George's University Hospitals NHS Foundation Trust, London, UK
| | - Grainne S Gorman
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Ewen W Sommerville
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Patrick F Chinnery
- MRC Mitochondrial Biology Unit, Cambridge Biomedical Campus, Cambridge, UK.,Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - Monika Hofer
- Department of Neuropathology, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Christoph Karch
- Department of Neurology, University of California San Francisco, San Francisco, California, USA
| | - Jeffrey Ralph
- Department of Neurology, University of California San Francisco, San Francisco, California, USA
| | - Yolanda Cámara
- Research Group on Neuromuscular and Mitochondrial Disorders, Vall d'Hebron Institut de Recerca, Barcelona, Spain.,Centre for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
| | - Marcos Madruga-Garrido
- Sección de Neuropediatría, Hospital Universitario Virgen del Rocío, Instituto de Biomedicina de Sevilla, Seville, Spain
| | - Jana Domínguez-Carral
- Neuromuscular Unit, Department of Neurology, Hospital Sant Joan de Déu, CIBERER, ISCIII, Universitat de Barcelona, Barcelona, Spain
| | - Carlos Ortez
- Neuromuscular Unit, Hospital Universitario 12 de Octubre, Madrid, Spain
| | - Sonia Emperador
- Department of Biochemistry and Molecular Biology, University of Zaragoza-CIBERER-Instituto de investigaciones Sanitarias de Aragón, Zaragoza, Spain
| | - Julio Montoya
- Department of Biochemistry and Molecular Biology, University of Zaragoza-CIBERER-Instituto de investigaciones Sanitarias de Aragón, Zaragoza, Spain
| | - Anupam Chakrapani
- Metabolic Unit, Great Ormond Street Hospital NHS Foundation Trust, London, UK
| | - Joshua F Kriger
- Department of Biostatistics, Mailman School of Public Health, Columbia University Medical Center, New York City, New York, USA
| | - Robert Schoenaker
- Department of Neurology, Columbia University Medical Center, New York City, New York, USA
| | - Bruce Levin
- Department of Biostatistics, Mailman School of Public Health, Columbia University Medical Center, New York City, New York, USA
| | - John L P Thompson
- Department of Biostatistics, Mailman School of Public Health, Columbia University Medical Center, New York City, New York, USA
| | - Yuelin Long
- Department of Biostatistics, Mailman School of Public Health, Columbia University Medical Center, New York City, New York, USA
| | - Shamima Rahman
- Metabolic Unit, Great Ormond Street Hospital NHS Foundation Trust, London, UK.,Mitochondrial Research Group, Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, London, UK
| | | | - Salvatore DiMauro
- Department of Neurology, Columbia University Medical Center, New York City, New York, USA
| | - Michio Hirano
- Department of Neurology, Columbia University Medical Center, New York City, New York, USA
| |
Collapse
|
14
|
Barbé C, Bray F, Gueugneau M, Devassine S, Lause P, Tokarski C, Rolando C, Thissen JP. Comparative Proteomic and Transcriptomic Analysis of Follistatin-Induced Skeletal Muscle Hypertrophy. J Proteome Res 2017; 16:3477-3490. [PMID: 28810121 DOI: 10.1021/acs.jproteome.7b00069] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Skeletal muscle, the most abundant body tissue, plays vital roles in locomotion and metabolism. Myostatin is a negative regulator of skeletal muscle mass. In addition to increasing muscle mass, Myostatin inhibition impacts muscle contractility and energy metabolism. To decipher the mechanisms of action of the Myostatin inhibitors, we used proteomic and transcriptomic approaches to investigate the changes induced in skeletal muscles of transgenic mice overexpressing Follistatin, a physiological Myostatin inhibitor. Our proteomic workflow included a fractionation step to identify weakly expressed proteins and a comparison of fast versus slow muscles. Functional annotation of altered proteins supports the phenotypic changes induced by Myostatin inhibition, including modifications in energy metabolism, fiber type, insulin and calcium signaling, as well as membrane repair and regeneration. Less than 10% of the differentially expressed proteins were found to be also regulated at the mRNA level but the Biological Process annotation, and the KEGG pathways analysis of transcriptomic results shows a great concordance with the proteomic data. Thus this study describes the most extensive omics analysis of muscle overexpressing Follistatin, providing molecular-level insights to explain the observed muscle phenotypic changes.
Collapse
Affiliation(s)
- Caroline Barbé
- Pole of Endocrinology, Diabetes and Nutrition, Institute of Experimental and Clinical Research, Université Catholique de Louvain , 1200 Brussels, Belgium
| | - Fabrice Bray
- Miniaturisation pour la Synthèse, l'Analyse & la Protéomique (MSAP), CNRS, USR 3290, Université de Lille; Biochimie Structurale & Fonctionnelle des Assemblages Biomoléculaires, CNRS, FR 3688, FRABIO, Université de Lille and Institut Eugène-Michel Chevreul, CNRS, FR 2638, Université de Lille, 59000 Lille, France
| | - Marine Gueugneau
- Pole of Endocrinology, Diabetes and Nutrition, Institute of Experimental and Clinical Research, Université Catholique de Louvain , 1200 Brussels, Belgium
| | - Stéphanie Devassine
- Miniaturisation pour la Synthèse, l'Analyse & la Protéomique (MSAP), CNRS, USR 3290, Université de Lille; Biochimie Structurale & Fonctionnelle des Assemblages Biomoléculaires, CNRS, FR 3688, FRABIO, Université de Lille and Institut Eugène-Michel Chevreul, CNRS, FR 2638, Université de Lille, 59000 Lille, France
| | - Pascale Lause
- Pole of Endocrinology, Diabetes and Nutrition, Institute of Experimental and Clinical Research, Université Catholique de Louvain , 1200 Brussels, Belgium
| | - Caroline Tokarski
- Miniaturisation pour la Synthèse, l'Analyse & la Protéomique (MSAP), CNRS, USR 3290, Université de Lille; Biochimie Structurale & Fonctionnelle des Assemblages Biomoléculaires, CNRS, FR 3688, FRABIO, Université de Lille and Institut Eugène-Michel Chevreul, CNRS, FR 2638, Université de Lille, 59000 Lille, France
| | - Christian Rolando
- Miniaturisation pour la Synthèse, l'Analyse & la Protéomique (MSAP), CNRS, USR 3290, Université de Lille; Biochimie Structurale & Fonctionnelle des Assemblages Biomoléculaires, CNRS, FR 3688, FRABIO, Université de Lille and Institut Eugène-Michel Chevreul, CNRS, FR 2638, Université de Lille, 59000 Lille, France
| | - Jean-Paul Thissen
- Pole of Endocrinology, Diabetes and Nutrition, Institute of Experimental and Clinical Research, Université Catholique de Louvain , 1200 Brussels, Belgium
| |
Collapse
|
15
|
Mitochondrial Diseases as Model of Neurodegeneration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1007:129-155. [DOI: 10.1007/978-3-319-60733-7_8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
|
16
|
Thymidine kinase 2 and alanyl-tRNA synthetase 2 deficiencies cause lethal mitochondrial cardiomyopathy: case reports and review of the literature. Cardiol Young 2017; 27:936-944. [PMID: 27839525 DOI: 10.1017/s1047951116001876] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Cardiomyopathy is a common manifestation in neonates and infants with mitochondrial disorders. In this study, we report two cases manifesting with fatal mitochondrial hypertrophic cardiomyopathy, which include the third known patient with thymidine kinase 2 deficiency and the ninth patient with alanyl-tRNA synthetase 2 deficiency. The girl with thymidine kinase 2 deficiency had hypertrophic cardiomyopathy together with regression of gross motor development at the age of 13 months. Neurological symptoms and cardiac involvement progressed into severe myopathy, psychomotor arrest, and cardiorespiratory failure at the age of 22 months. The imaging methods and autoptic studies proved that she suffered from unique findings of leucoencephalopathy, severe, mainly cerebellar neuronal degeneration, and hepatic steatosis. The girl with alanyl-tRNA synthetase 2 deficiency presented with cardiac failure and underlying hypertrophic cardiomyopathy within 12 hours of life and subsequently died at 9 weeks of age. Muscle biopsy analyses demonstrated respiratory chain complex I and IV deficiencies, and histological evaluation revealed massive mitochondrial accumulation and cytochrome c oxidase-negative fibres in both cases. Exome sequencing in the first case revealed compound heterozygozity for one novel c.209T>C and one previously published c.416C>T mutation in the TK2 gene, whereas in the second case homozygozity for the previously described mutation c.1774C>T in the AARS2 gene was determined. The thymidine kinase 2 mutations resulted in severe mitochondrial DNA depletion (to 12% of controls) in the muscle. We present, for the first time, severe leucoencephalopathy and hepatic steatosis in a patient with thymidine kinase 2 deficiency and the finding of a ragged red fibre-like image in the muscle biopsy in a patient with alanyl-tRNA synthetase 2 deficiency.
Collapse
|
17
|
Abstract
Paediatric motor neuron diseases encompass a group of neurodegenerative diseases characterised by the onset of muscle weakness and atrophy before the age of 18 years, attributable to motor neuron loss across various neuronal networks in the brain and spinal cord. While the genetic underpinnings are diverse, advances in next generation sequencing have transformed diagnostic paradigms. This has reinforced the clinical phenotyping and molecular genetic expertise required to navigate the complexities of such diagnoses. In turn, improved genetic technology and subsequent gene identification have enabled further insights into the mechanisms of motor neuron degeneration and how these diseases form part of a neurodegenerative disorder spectrum. Common pathophysiologies include abnormalities in axonal architecture and function, RNA processing, and protein quality control. This review incorporates an overview of the clinical manifestations, genetics, and pathophysiology of inherited paediatric motor neuron disorders beyond classic SMN1-related spinal muscular atrophy and describes recent advances in next generation sequencing and its clinical application. Specific disease-modifying treatment is becoming a clinical reality in some disorders of the motor neuron highlighting the importance of a timely and specific diagnosis.
Collapse
|
18
|
Lopez-Gomez C, Levy RJ, Sanchez-Quintero MJ, Juanola-Falgarona M, Barca E, Garcia-Diaz B, Tadesse S, Garone C, Hirano M. Deoxycytidine and Deoxythymidine Treatment for Thymidine Kinase 2 Deficiency. Ann Neurol 2017; 81:641-652. [PMID: 28318037 DOI: 10.1002/ana.24922] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 03/09/2017] [Accepted: 03/09/2017] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Thymidine kinase 2 (TK2), a critical enzyme in the mitochondrial pyrimidine salvage pathway, is essential for mitochondrial DNA (mtDNA) maintenance. Mutations in the nuclear gene, TK2, cause TK2 deficiency, which manifests predominantly in children as myopathy with mtDNA depletion. Molecular bypass therapy with the TK2 products, deoxycytidine monophosphate (dCMP) and deoxythymidine monophosphate (dTMP), prolongs the life span of Tk2-deficient (Tk2-/- ) mice by 2- to 3-fold. Because we observed rapid catabolism of the deoxynucleoside monophosphates to deoxythymidine (dT) and deoxycytidine (dC), we hypothesized that: (1) deoxynucleosides might be the major active agents and (2) inhibition of deoxycytidine deamination might enhance dTMP+dCMP therapy. METHODS To test these hypotheses, we assessed two therapies in Tk2-/- mice: (1) dT+dC and (2) coadministration of the deaminase inhibitor, tetrahydrouridine (THU), with dTMP+dCMP. RESULTS We observed that dC+dT delayed disease onset, prolonged life span of Tk2-deficient mice and restored mtDNA copy number as well as respiratory chain enzyme activities and levels. In contrast, dCMP+dTMP+THU therapy decreased life span of Tk2-/- animals compared to dCMP+dTMP. INTERPRETATION Our studies demonstrate that deoxynucleoside substrate enhancement is a novel therapy, which may ameliorate TK2 deficiency in patients. Ann Neurol 2017;81:641-652.
Collapse
Affiliation(s)
- Carlos Lopez-Gomez
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
| | - Rebecca J Levy
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
| | - Maria J Sanchez-Quintero
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
| | - Martí Juanola-Falgarona
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
| | - Emanuele Barca
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY.,Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Beatriz Garcia-Diaz
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY.,Unidad de Gestión Clínica de Neurociencias, Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga, Spain
| | - Saba Tadesse
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
| | - Caterina Garone
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY.,MRC Mitochondrial Biology Unit, Cambridge University, Cambridge, United Kingdom
| | - Michio Hirano
- Department of Neurology, H. Houston Merritt Neuromuscular Research Center, Columbia University Medical Center, New York, NY
| |
Collapse
|
19
|
Abstract
Mitochondrial diseases are a group of genetic disorders that are characterized by defects in oxidative phosphorylation and caused by mutations in genes in the nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) that encode structural mitochondrial proteins or proteins involved in mitochondrial function. Mitochondrial diseases are the most common group of inherited metabolic disorders and are among the most common forms of inherited neurological disorders. One of the challenges of mitochondrial diseases is the marked clinical variation seen in patients, which can delay diagnosis. However, advances in next-generation sequencing techniques have substantially improved diagnosis, particularly in children. Establishing a genetic diagnosis allows patients with mitochondrial diseases to have reproductive options, but this is more challenging for women with pathogenetic mtDNA mutations that are strictly maternally inherited. Recent advances in in vitro fertilization techniques, including mitochondrial donation, will offer a better reproductive choice for these women in the future. The treatment of patients with mitochondrial diseases remains a challenge, but guidelines are available to manage the complications of disease. Moreover, an increasing number of therapeutic options are being considered, and with the development of large cohorts of patients and biomarkers, several clinical trials are in progress.
Collapse
|
20
|
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.
Collapse
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
| |
Collapse
|
21
|
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.
Collapse
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:
| |
Collapse
|
22
|
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.
Collapse
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.
| |
Collapse
|
23
|
Ripolone M, Ronchi D, Violano R, Vallejo D, Fagiolari G, Barca E, Lucchini V, Colombo I, Villa L, Berardinelli A, Balottin U, Morandi L, Mora M, Bordoni A, Fortunato F, Corti S, Parisi D, Toscano A, Sciacco M, DiMauro S, Comi GP, Moggio M. Impaired Muscle Mitochondrial Biogenesis and Myogenesis in Spinal Muscular Atrophy. JAMA Neurol 2015; 72:666-75. [PMID: 25844556 PMCID: PMC4944827 DOI: 10.1001/jamaneurol.2015.0178] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
IMPORTANCE The important depletion of mitochondrial DNA (mtDNA) and the general depression of mitochondrial respiratory chain complex levels (including complex II) have been confirmed, implying an increasing paucity of mitochondria in the muscle from patients with types I, II, and III spinal muscular atrophy (SMA-I, -II, and -III, respectively). OBJECTIVE To investigate mitochondrial dysfunction in a large series of muscle biopsy samples from patients with SMA. DESIGN, SETTING, AND PARTICIPANTS We studied quadriceps muscle samples from 24 patients with genetically documented SMA and paraspinal muscle samples from 3 patients with SMA-II undergoing surgery for scoliosis correction. Postmortem muscle samples were obtained from 1 additional patient. Age-matched controls consisted of muscle biopsy specimens from healthy children aged 1 to 3 years who had undergone analysis for suspected myopathy. Analyses were performed at the Neuromuscular Unit, Istituto di Ricovero e Cura a Carattere Scientifico Foundation Ca' Granda Ospedale Maggiore Policlinico-Milano, from April 2011 through January 2015. EXPOSURES We used histochemical, biochemical, and molecular techniques to examine the muscle samples. MAIN OUTCOMES AND MEASURES Respiratory chain activity and mitochondrial content. RESULTS Results of histochemical analysis revealed that cytochrome-c oxidase (COX) deficiency was more evident in muscle samples from patients with SMA-I and SMA-II. Residual activities for complexes I, II, and IV in muscles from patients with SMA-I were 41%, 27%, and 30%, respectively, compared with control samples (P < .005). Muscle mtDNA content and cytrate synthase activity were also reduced in all 3 SMA types (P < .05). We linked these alterations to downregulation of peroxisome proliferator-activated receptor coactivator 1α, the transcriptional activators nuclear respiratory factor 1 and nuclear respiratory factor 2, mitochondrial transcription factor A, and their downstream targets, implying depression of the entire mitochondrial biogenesis. Results of Western blot analysis confirmed the reduced levels of the respiratory chain subunits that included mitochondrially encoded COX1 (47.5%; P = .004), COX2 (32.4%; P < .001), COX4 (26.6%; P < .001), and succinate dehydrogenase complex subunit A (65.8%; P = .03) as well as the structural outer membrane mitochondrial porin (33.1%; P < .001). Conversely, the levels of expression of 3 myogenic regulatory factors-muscle-specific myogenic factor 5, myoblast determination 1, and myogenin-were higher in muscles from patients with SMA compared with muscles from age-matched controls (P < .05). CONCLUSIONS AND RELEVANCE Our results strongly support the conclusion that an altered regulation of myogenesis and a downregulated mitochondrial biogenesis contribute to pathologic change in the muscle of patients with SMA. Therapeutic strategies should aim at counteracting these changes.
Collapse
Affiliation(s)
- Michela Ripolone
- Neuromuscular Unit, Dino Ferrari Centre, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Dario Ronchi
- Neurology Unit, Neuroscience Section, Department of Pathophysiology and Transplantation, Dino Ferrari Centre, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Raffaella Violano
- Neuromuscular Unit, Dino Ferrari Centre, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Dionis Vallejo
- Sien-Servicios Integrales en Neurologia, Universidad de Antioquia, Medellin, Colombia
| | - Gigliola Fagiolari
- Neuromuscular Unit, Dino Ferrari Centre, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Emanuele Barca
- Department of Neurology, Columbia University Medical Center, New York, New York
| | - Valeria Lucchini
- Neuromuscular Unit, Dino Ferrari Centre, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Irene Colombo
- Neuromuscular Unit, Dino Ferrari Centre, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Luisa Villa
- Neuromuscular Unit, Dino Ferrari Centre, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Angela Berardinelli
- Child Neuropsychiatry Unit, C. Mondino National Neurological Institute, Pavia, Italy
| | - Umberto Balottin
- Child Neuropsychiatry Unit, C. Mondino National Neurological Institute, Pavia, Italy
| | - Lucia Morandi
- Neuromuscular Diseases and Neuroimmunology Unit, Department of Clinical Neurosciences, IRCCS Foundation, Carlo Besta Neurological Institute, Milan, Italy
| | - Marina Mora
- Neuromuscular Diseases and Neuroimmunology Unit, Department of Clinical Neurosciences, IRCCS Foundation, Carlo Besta Neurological Institute, Milan, Italy
| | - Andreina Bordoni
- Neurology Unit, Neuroscience Section, Department of Pathophysiology and Transplantation, Dino Ferrari Centre, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Francesco Fortunato
- Neurology Unit, Neuroscience Section, Department of Pathophysiology and Transplantation, Dino Ferrari Centre, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Stefania Corti
- Neurology Unit, Neuroscience Section, Department of Pathophysiology and Transplantation, Dino Ferrari Centre, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Daniela Parisi
- Reference Center for Rare Neuromuscular Disorders, Department of Neurosciences, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy
| | - Antonio Toscano
- Reference Center for Rare Neuromuscular Disorders, Department of Neurosciences, University of Messina, Azienda Ospedaliera Universitaria Policlinico G. Martino, Messina, Italy
| | - Monica Sciacco
- Neuromuscular Unit, Dino Ferrari Centre, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Salvatore DiMauro
- Department of Neurology, Columbia University Medical Center, New York, New York
| | - Giacomo P Comi
- Neurology Unit, Neuroscience Section, Department of Pathophysiology and Transplantation, Dino Ferrari Centre, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| | - Maurizio Moggio
- Neuromuscular Unit, Dino Ferrari Centre, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Foundation Ca' Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy
| |
Collapse
|
24
|
Sun R, Wang L. Thymidine Kinase 2 Enzyme Kinetics Elucidate the Mechanism of Thymidine-Induced Mitochondrial DNA Depletion. Biochemistry 2014; 53:6142-50. [DOI: 10.1021/bi5006877] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Ren Sun
- Department
of Anatomy, Physiology
and Biochemistry, Swedish University of Agricultural Sciences, Box 7011, SE-750 07 Uppsala, Sweden
| | - Liya Wang
- Department
of Anatomy, Physiology
and Biochemistry, Swedish University of Agricultural Sciences, Box 7011, SE-750 07 Uppsala, Sweden
| |
Collapse
|
25
|
Balasubramaniam S, Duley JA, Christodoulou J. Inborn errors of pyrimidine metabolism: clinical update and therapy. J Inherit Metab Dis 2014; 37:687-98. [PMID: 25030255 DOI: 10.1007/s10545-014-9742-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 06/05/2014] [Accepted: 06/24/2014] [Indexed: 10/25/2022]
Abstract
Inborn errors involving enzymes essential for pyrimidine nucleotide metabolism have provided new insights into their fundamental physiological roles as vital constituents of nucleic acids as well as substrates of lipid and carbohydrate metabolism and in oxidative phosphorylation. Genetic aberrations of pyrimidine pathways lead to diverse clinical manifestations including neurological, immunological, haematological, renal impairments, adverse reactions to analogue therapy and association with malignancies. Maintenance of cellular nucleotides depends on the three aspects of metabolism of pyrimidines: de novo synthesis, catabolism and recycling of these metabolites. Of the ten recognised disorders of pyrimidine metabolism treatment is currently restricted to only two disorders: hereditary orotic aciduria (oral uridine therapy) and mitochondrial neurogastrointestinal encephalomyopathy (MNGIE; allogeneic hematopoetic stem cell transplant and enzyme replacement). The ubiquitous role that pyrimidine metabolism plays in human life highlights the importance of improving diagnostic evaluation in suggestive clinical settings, which will contribute to the elucidation of new defects, future development of novel drugs and therapeutic strategies. Limited awareness of the expanding phenotypic spectrum, with relatively recent descriptions of newer disorders, compounded by considerable genetic heterogeneity has often contributed to the delays in the diagnosis of this group of disorders. The lack of an easily recognisable, easily measurable end product, akin to uric acid in purine metabolism, has contributed to the under-recognition of these disorders.This review describes the currently known inborn errors of pyrimidine metabolism, their variable phenotypic presentations, established diagnostic methodology and recognised treatment options.
Collapse
Affiliation(s)
- Shanti Balasubramaniam
- Metabolic Unit, Princess Margaret Hospital, Roberts Road, Subiaco, Perth, WA, 6008, Australia
| | | | | |
Collapse
|
26
|
Zhang H, Singh KK. Global genetic determinants of mitochondrial DNA copy number. PLoS One 2014; 9:e105242. [PMID: 25170845 PMCID: PMC4149433 DOI: 10.1371/journal.pone.0105242] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 05/19/2014] [Indexed: 11/18/2022] Open
Abstract
Many human diseases including development of cancer is associated with depletion of mitochondrial DNA (mtDNA) content. These diseases are collectively described as mitochondrial DNA depletion syndrome (MDS). High similarity between yeast and human mitochondria allows genomic study of the budding yeast to be used to identify human disease genes. In this study, we systematically screened the pre-existing respiratory-deficient Saccharomyces cerevisiae yeast strains using fluorescent microscopy and identified 102 nuclear genes whose deletions result in a complete mtDNA loss, of which 52 are not reported previously. Strikingly, these genes mainly encode protein products involved in mitochondrial protein biosynthesis process (54.9%). The rest of these genes either encode protein products associated with nucleic acid metabolism (14.7%), oxidative phosphorylation (3.9%), or other protein products (13.7%) responsible for bud-site selection, mitochondrial intermembrane space protein import, assembly of cytochrome-c oxidase, vacuolar protein sorting, protein-nucleus import, calcium-mediated signaling, heme biosynthesis and iron homeostasis. Thirteen (12.7%) of the genes encode proteins of unknown function. We identified human orthologs of these genes, conducted the interaction between the gene products and linked them to human mitochondrial disorders and other pathologies. In addition, we screened for genes whose defects affect the nuclear genome integrity. Our data provide a systematic view of the nuclear genes involved in maintenance of mitochondrial DNA. Together, our studies i) provide a global view of the genes regulating mtDNA content; ii) provide compelling new evidence toward understanding novel mechanism involved in mitochondrial genome maintenance and iii) provide useful clues in understanding human diseases in which mitochondrial defect and in particular depletion of mitochondrial genome plays a critical role.
Collapse
Affiliation(s)
- Hengshan Zhang
- Hengshan Zhang, Department of Central Laboratory, First Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Keshav K. Singh
- Departments of Genetics, Pathology, Environmental Health, Center for Free Radical Biology, Center for Aging and UAB Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, Alabama, and Birmingham Veterans Affairs Medical Center, Birmingham, Alabama, United States of America
- * E-mail:
| |
Collapse
|
27
|
Roos S, Lindgren U, Ehrstedt C, Moslemi A, Oldfors A. Mitochondrial DNA depletion in single fibers in a patient with novel TK2 mutations. Neuromuscul Disord 2014; 24:713-20. [DOI: 10.1016/j.nmd.2014.05.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 05/09/2014] [Accepted: 05/20/2014] [Indexed: 11/30/2022]
|
28
|
Chaussenot A, Paquis-Flucklinger V. An overview of neurological and neuromuscular signs in mitochondrial diseases. Rev Neurol (Paris) 2014; 170:323-38. [DOI: 10.1016/j.neurol.2014.03.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 03/24/2014] [Indexed: 01/10/2023]
|
29
|
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]
|
30
|
Kalko SG, Paco S, Jou C, Rodríguez MA, Meznaric M, Rogac M, Jekovec-Vrhovsek M, Sciacco M, Moggio M, Fagiolari G, De Paepe B, De Meirleir L, Ferrer I, Roig-Quilis M, Munell F, Montoya J, López-Gallardo E, Ruiz-Pesini E, Artuch R, Montero R, Torner F, Nascimento A, Ortez C, Colomer J, Jimenez-Mallebrera C. Transcriptomic profiling of TK2 deficient human skeletal muscle suggests a role for the p53 signalling pathway and identifies growth and differentiation factor-15 as a potential novel biomarker for mitochondrial myopathies. BMC Genomics 2014; 15:91. [PMID: 24484525 PMCID: PMC3937154 DOI: 10.1186/1471-2164-15-91] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 01/28/2014] [Indexed: 02/08/2023] Open
Abstract
Background Mutations in the gene encoding thymidine kinase 2 (TK2) result in the myopathic form of mitochondrial DNA depletion syndrome which is a mitochondrial encephalomyopathy presenting in children. In order to unveil some of the mechanisms involved in this pathology and to identify potential biomarkers and therapeutic targets we have investigated the gene expression profile of human skeletal muscle deficient for TK2 using cDNA microarrays. Results We have analysed the whole transcriptome of skeletal muscle from patients with TK2 mutations and compared it to normal muscle and to muscle from patients with other mitochondrial myopathies. We have identified a set of over 700 genes which are differentially expressed in TK2 deficient muscle. Bioinformatics analysis reveals important changes in muscle metabolism, in particular, in glucose and glycogen utilisation, and activation of the starvation response which affects aminoacid and lipid metabolism. We have identified those transcriptional regulators which are likely to be responsible for the observed changes in gene expression. Conclusion Our data point towards the tumor suppressor p53 as the regulator at the centre of a network of genes which are responsible for a coordinated response to TK2 mutations which involves inflammation, activation of muscle cell death by apoptosis and induction of growth and differentiation factor 15 (GDF-15) in muscle and serum. We propose that GDF-15 may represent a potential novel biomarker for mitochondrial dysfunction although further studies are required.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Cecilia Jimenez-Mallebrera
- Neuromuscular Unit, Neurology Department, Fundación Sant Joan de Déu, Hospital Sant Joan de Déu, Barcelona, Spain.
| |
Collapse
|
31
|
Chanprasert S, Wang J, Weng SW, Enns GM, Boué DR, Wong BL, Mendell JR, Perry DA, Sahenk Z, Craigen WJ, Alcala FJC, Pascual JM, Melancon S, Zhang VW, Scaglia F, Wong LJC. Molecular and clinical characterization of the myopathic form of mitochondrial DNA depletion syndrome caused by mutations in the thymidine kinase (TK2) gene. Mol Genet Metab 2013; 110:153-61. [PMID: 23932787 DOI: 10.1016/j.ymgme.2013.07.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 07/10/2013] [Accepted: 07/10/2013] [Indexed: 11/26/2022]
Abstract
Mitochondrial DNA (mtDNA) depletion syndromes (MDSs) are a clinically and molecularly heterogeneous group of mitochondrial cytopathies characterized by severe mtDNA copy number reduction in affected tissues. Clinically, MDSs are mainly categorized as myopathic, encephalomyopathic, hepatocerebral, or multi-systemic forms. To date, the myopathic form of MDS is mainly caused by mutations in the TK2 gene, which encodes thymidine kinase 2, the first and rate limiting step enzyme in the phosphorylation of pyrimidine nucleosides. We analyzed 9 unrelated families with 11 affected subjects exhibiting the myopathic form of MDS, by sequencing the TK2 gene. Twelve mutations including 4 novel mutations were detected in 9 families. Skeletal muscle specimens were available from 7 out of 11 subjects. Respiratory chain enzymatic activities in skeletal muscle were measured in 6 subjects, and enzymatic activities were reduced in 3 subjects. Quantitative analysis of mtDNA content in skeletal muscle was performed in 5 subjects, and marked mtDNA content reduction was observed in each. In addition, we outline the molecular and clinical characteristics of this syndrome in a total of 52 patients including those previously reported, and a total of 36 TK2 mutations are summarized. Clinically, hypotonia and proximal muscle weakness are the major phenotypes present in all subjects. In summary, our study expands the molecular and clinical spectrum associated with TK2 deficiency.
Collapse
Affiliation(s)
- Sirisak Chanprasert
- Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Katsetos CD, Koutzaki S, Melvin JJ. Mitochondrial dysfunction in neuromuscular disorders. Semin Pediatr Neurol 2013; 20:202-15. [PMID: 24331362 DOI: 10.1016/j.spen.2013.10.010] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
This review deciphers aspects of mitochondrial (mt) dysfunction among nosologically, pathologically, and genetically diverse diseases of the skeletal muscle, lower motor neuron, and peripheral nerve, which fall outside the traditional realm of mt cytopathies. Special emphasis is given to well-characterized mt abnormalities in collagen VI myopathies (Ullrich congenital muscular dystrophy and Bethlem myopathy), megaconial congenital muscular dystrophy, limb-girdle muscular dystrophy type 2 (calpainopathy), centronuclear myopathies, core myopathies, inflammatory myopathies, spinal muscular atrophy, Charcot-Marie-Tooth neuropathy type 2, and drug-induced peripheral neuropathies. Among inflammatory myopathies, mt abnormalities are more prominent in inclusion body myositis and a subset of polymyositis with mt pathology, both of which are refractory to corticosteroid treatment. Awareness is raised about instances of phenotypic mimicry between cases harboring primary mtDNA depletion, in the context of mtDNA depletion syndrome, and established neuromuscular disorders such as spinal muscular atrophy. A substantial body of experimental work, derived from animal models, attests to a major role of mitochondria (mt) in the early process of muscle degeneration. Common mechanisms of mt-related cell injury include dysregulation of the mt permeability transition pore opening and defective autophagy. The therapeutic use of mt permeability transition pore modifiers holds promise in various neuromuscular disorders, including muscular dystrophies.
Collapse
Affiliation(s)
- Christos D Katsetos
- Department of Pediatrics, Drexel University College of Medicine, St. Christopher's Hospital for Children, Philadelphia, PA; Department of Pathology and Laboratory Medicine, Drexel University College of Medicine, Philadelphia, PA; Department of Neurology, Drexel University College of Medicine, Philadelphia, PA.
| | - Sirma Koutzaki
- Department of Pathology and Laboratory Medicine, Drexel University College of Medicine, Philadelphia, PA
| | - Joseph J Melvin
- Department of Pediatrics, Drexel University College of Medicine, St. Christopher's Hospital for Children, Philadelphia, PA; Department of Neurology, Drexel University College of Medicine, Philadelphia, PA
| |
Collapse
|
33
|
Zhou X, Kannisto K, Curbo S, von Döbeln U, Hultenby K, Isetun S, Gåfvels M, Karlsson A. Thymidine kinase 2 deficiency-induced mtDNA depletion in mouse liver leads to defect β-oxidation. PLoS One 2013; 8:e58843. [PMID: 23505564 PMCID: PMC3591375 DOI: 10.1371/journal.pone.0058843] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 02/07/2013] [Indexed: 02/06/2023] Open
Abstract
Thymidine kinase 2 (TK2) deficiency in humans causes mitochondrial DNA (mtDNA) depletion syndrome. To study the molecular mechanisms underlying the disease and search for treatment options, we previously generated and described a TK2 deficient mouse strain (TK2−/−) that progressively loses its mtDNA. The TK2−/− mouse model displays symptoms similar to humans harboring TK2 deficient infantile fatal encephalomyopathy. Here, we have studied the TK2−/− mouse model to clarify the pathological role of progressive mtDNA depletion in liver for the severe outcome of TK2 deficiency. We observed that a gradual depletion of mtDNA in the liver of the TK2−/− mice was accompanied by increasingly hypertrophic mitochondria and accumulation of fat vesicles in the liver cells. The levels of cholesterol and nonesterified fatty acids were elevated and there was accumulation of long chain acylcarnitines in plasma of the TK2−/− mice. In mice with hepatic mtDNA levels below 20%, the blood sugar and the ketone levels dropped. These mice also exhibited reduced mitochondrial β-oxidation due to decreased transport of long chain acylcarnitines into the mitochondria. The gradual loss of mtDNA in the liver of the TK2−/− mice causes impaired mitochondrial function that leads to defect β-oxidation and, as a result, insufficient production of ketone bodies and glucose. This study provides insight into the mechanism of encephalomyopathy caused by TK2 deficiency-induced mtDNA depletion that may be used to explore novel therapeutic strategies.
Collapse
Affiliation(s)
- Xiaoshan Zhou
- Division of Clinical Microbiology F-68, Karolinska Institutet, Department of Laboratory Medicine, Karolinska University Hospital, Huddinge, Sweden
| | - Kristina Kannisto
- Division of Clinical Chemistry, C1-72, Karolinska Institutet, Department of Laboratory Medicine, Karolinska University Hospital, Huddinge, Sweden
| | - Sophie Curbo
- Division of Clinical Microbiology F-68, Karolinska Institutet, Department of Laboratory Medicine, Karolinska University Hospital, Huddinge, Sweden
- * E-mail:
| | - Ulrika von Döbeln
- Division of Metabolic Diseases, Karolinska Institutet, Department of Laboratory Medicine, Karolinska University Hospital, Huddinge, Sweden
| | - Kjell Hultenby
- Division of Clinical Research Center, Karolinska Institutet, Department of Laboratory Medicine, Karolinska University Hospital, Huddinge, Sweden
| | - Sindra Isetun
- Division of Metabolic Diseases, Karolinska Institutet, Department of Laboratory Medicine, Karolinska University Hospital, Huddinge, Sweden
| | - Mats Gåfvels
- Division of Clinical Chemistry, C1-72, Karolinska Institutet, Department of Laboratory Medicine, Karolinska University Hospital, Huddinge, Sweden
- Division of Clinical Chemistry, Department of Laboratory Medicine, Lund University, Lund, Sweden
| | - Anna Karlsson
- Division of Clinical Microbiology F-68, Karolinska Institutet, Department of Laboratory Medicine, Karolinska University Hospital, Huddinge, Sweden
| |
Collapse
|
34
|
Navarro-Sastre A, Tort F, Garcia-Villoria J, Pons MR, Nascimento A, Colomer J, Campistol J, Yoldi ME, López-Gallardo E, Montoya J, Unceta M, Martinez MJ, Briones P, Ribes A. Mitochondrial DNA depletion syndrome: new descriptions and the use of citrate synthase as a helpful tool to better characterise the patients. Mol Genet Metab 2012; 107:409-15. [PMID: 22980518 DOI: 10.1016/j.ymgme.2012.08.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Accepted: 08/25/2012] [Indexed: 01/21/2023]
Abstract
Mitochondrial DNA depletion syndrome (MDS) is a clinically heterogeneous group of mitochondrial disorders characterised by a quantitative reduction of the mitochondrial DNA copy number. Three main clinical forms of MDS: myopathic, encephalomyopathic and hepatocerebral have been defined, although patients may present with other MDS associated clinical symptoms and signs that cover a wide spectrum of onset age and disease. We studied 52 paediatric individuals suspected to have MDS. These patients have been divided into three different groups, and the appropriate MDS genes have been screened according to their clinical and biochemical phenotypes. Mutational study of DGUOK, MPV17, SUCLA2, SUCLG1 and POLG allowed us to identify 3 novel mutations (c.1048G>A and c.1049G>T in SUCLA2 and c.531+4A>T in SUCLG1) and 7 already known mutations in 10 patients (8 families). Seventeen patients presented with mtDNA depletion in liver or muscle, but the cause of mtDNA depletion still remains unknown in 8 of them. When possible, we quantified mtDNA/nDNA and CS activity in the same tissue sample, providing an additional tool for the study of MDS. The ratio (mtDNA/nDNA)/CS has shed some light in the discrepant results between the mtDNA copy number and the enzymatic respiratory chain activities of some cases.
Collapse
Affiliation(s)
- Aleix Navarro-Sastre
- Division of Inborn Errors of Metabolism, Department of Biochemistry and Molecular Genetics, Hospital Clinic, Instituto de Investigación Biomédica Pi Sunyer, 08028 Barcelona, Spain
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Ronchi D, Garone C, Bordoni A, Gutierrez Rios P, Calvo SE, Ripolone M, Ranieri M, Rizzuti M, Villa L, Magri F, Corti S, Bresolin N, Mootha VK, Moggio M, DiMauro S, Comi GP, Sciacco M. Next-generation sequencing reveals DGUOK mutations in adult patients with mitochondrial DNA multiple deletions. Brain 2012; 135:3404-15. [PMID: 23043144 DOI: 10.1093/brain/aws258] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The molecular diagnosis of mitochondrial disorders still remains elusive in a large proportion of patients, but advances in next generation sequencing are significantly improving our chances to detect mutations even in sporadic patients. Syndromes associated with mitochondrial DNA multiple deletions are caused by different molecular defects resulting in a wide spectrum of predominantly adult-onset clinical presentations, ranging from progressive external ophthalmoplegia to multi-systemic disorders of variable severity. The mutations underlying these conditions remain undisclosed in half of the affected subjects. We applied next-generation sequencing of known mitochondrial targets (MitoExome) to probands presenting with adult-onset mitochondrial myopathy and harbouring mitochondrial DNA multiple deletions in skeletal muscle. We identified autosomal recessive mutations in the DGUOK gene (encoding mitochondrial deoxyguanosine kinase), which has previously been associated with an infantile hepatocerebral form of mitochondrial DNA depletion. Mutations in DGUOK occurred in five independent subjects, representing 5.6% of our cohort of patients with mitochondrial DNA multiple deletions, and impaired both muscle DGUOK activity and protein stability. Clinical presentations were variable, including mitochondrial myopathy with or without progressive external ophthalmoplegia, recurrent rhabdomyolysis in a young female who had received a liver transplant at 9 months of age and adult-onset lower motor neuron syndrome with mild cognitive impairment. These findings reinforce the concept that mutations in genes involved in deoxyribonucleotide metabolism can cause diverse clinical phenotypes and suggest that DGUOK should be screened in patients harbouring mitochondrial DNA deletions in skeletal muscle.
Collapse
Affiliation(s)
- Dario Ronchi
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation, University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Selim L, Mehaney D, Hassan F, Sabry R, Zeyada R, Hassan S, Eldin IG, Bertini E. Mitochondrial DNA depletion syndrome presenting with ataxia and external ophthalmoplegia: Case report. EGYPTIAN JOURNAL OF MEDICAL HUMAN GENETICS 2012. [DOI: 10.1016/j.ejmhg.2012.05.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
|
37
|
Yiu EM, Ryan MM. Genetic axonal neuropathies and neuronopathies of pre-natal and infantile onset. J Peripher Nerv Syst 2012; 17:285-300. [DOI: 10.1111/j.1529-8027.2012.00412.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
|
38
|
Abstract
Mitochondrial DNA (mtDNA) is replicated by the DNA polymerase g in concert with accessory proteins such as the mtDNA helicase, single stranded DNA binding protein, topoisomerase, and initiating factors. Nucleotide precursors for mtDNA replication arise from the mitochondrial salvage pathway originating from transport of nucleosides, or alternatively from cytoplasmic reduction of ribonucleotides. Defects in mtDNA replication or nucleotide metabolism can cause mitochondrial genetic diseases due to mtDNA deletions, point mutations, or depletion which ultimately cause loss of oxidative phosphorylation. These genetic diseases include mtDNA depletion syndromes such as Alpers or early infantile hepatocerebral syndromes, and mtDNA deletion disorders, such as progressive external ophthalmoplegia (PEO), ataxia-neuropathy, or mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). This review focuses on our current knowledge of genetic defects of mtDNA replication (POLG, POLG2, C10orf2) and nucleotide metabolism (TYMP, TK2, DGOUK, and RRM2B) that cause instability of mtDNA and mitochondrial disease.
Collapse
Affiliation(s)
- William C Copeland
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Durham, North Carolina 27709, USA.
| |
Collapse
|
39
|
Abstract
Most mitochondrial cytopathies in infants are caused by mutations in nuclear genes encoding proteins targeted to the mitochondria rather than by primary mutations in the mitochondrial DNA. Over the past few years, the awareness of the number of disease-causing mutations in different nuclear genes has grown exponentially. These genes encode the various subunits of each respiratory chain complex, the ancillary proteins involved in the assembly of these subunits, proteins involved in mitochondrial DNA replication and maintenance, proteins involved in mitochondrial protein synthesis, and proteins involved in mitochondrial dynamics. This increased awareness has added a challenging dimension to the current diagnostic workup of mitochondrial cytopathies. The advent of new technologies such as next-generation sequencing should facilitate the resolution of this dilemma.
Collapse
Affiliation(s)
- Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
| |
Collapse
|
40
|
Villarroya J, Dorado B, Vilà MR, Garcia-Arumí E, Domingo P, Giralt M, Hirano M, Villarroya F. Thymidine kinase 2 deficiency-induced mitochondrial DNA depletion causes abnormal development of adipose tissues and adipokine levels in mice. PLoS One 2011; 6:e29691. [PMID: 22216345 PMCID: PMC3246498 DOI: 10.1371/journal.pone.0029691] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 12/02/2011] [Indexed: 12/13/2022] Open
Abstract
Mammal adipose tissues require mitochondrial activity for proper development and differentiation. The components of the mitochondrial respiratory chain/oxidative phosphorylation system (OXPHOS) are encoded by both mitochondrial and nuclear genomes. The maintenance of mitochondrial DNA (mtDNA) is a key element for a functional mitochondrial oxidative activity in mammalian cells. To ascertain the role of mtDNA levels in adipose tissue, we have analyzed the alterations in white (WAT) and brown (BAT) adipose tissues in thymidine kinase 2 (Tk2) H126N knockin mice, a model of TK2 deficiency-induced mtDNA depletion. We observed respectively severe and moderate mtDNA depletion in TK2-deficient BAT and WAT, showing both tissues moderate hypotrophy and reduced fat accumulation. Electron microscopy revealed altered mitochondrial morphology in brown but not in white adipocytes from TK2-deficient mice. Although significant reduction in mtDNA-encoded transcripts was observed both in WAT and BAT, protein levels from distinct OXPHOS complexes were significantly reduced only in TK2-deficient BAT. Accordingly, the activity of cytochrome c oxidase was significantly lowered only in BAT from TK2-deficient mice. The analysis of transcripts encoding up to fourteen components of specific adipose tissue functions revealed that, in both TK2-deficient WAT and BAT, there was a consistent reduction of thermogenesis related gene expression and a severe reduction in leptin mRNA. Reduced levels of resistin mRNA were found in BAT from TK2-deficient mice. Analysis of serum indicated a dramatic reduction in circulating levels of leptin and resistin. In summary, our present study establishes that mtDNA depletion leads to a moderate impairment in mitochondrial respiratory function, especially in BAT, causes substantial alterations in WAT and BAT development, and has a profound impact in the endocrine properties of adipose tissues.
Collapse
Affiliation(s)
- Joan Villarroya
- Departament de Bioquímica i Biologia Molecular, and Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain.
| | | | | | | | | | | | | | | |
Collapse
|
41
|
Moran MM, Allen NM, Treacy EP, King MD. "Stiff neonate" with mitochondrial DNA depletion and secondary neurotransmitter defects. Pediatr Neurol 2011; 45:403-5. [PMID: 22115005 DOI: 10.1016/j.pediatrneurol.2011.08.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 08/24/2011] [Indexed: 10/15/2022]
Abstract
Mitochondrial disorders comprise a heterogenous group. A neonate who presented with episodes of severe truncal hypertonia and apnea progressed to a hypokinetic rigid syndrome characterized by hypokinesia, tremulousness, profound head lag, absent suck and gag reflexes, brisk deep tendon reflexes, ankle and jaw clonus, and evidence of autonomic dysfunction. Analysis of cerebrospinal fluid neurotransmitters from age 7 weeks demonstrated low levels of amine metabolites (homovanillic acid and 5-hydroxyindoleacetic acid), tetrahydrobiopterin, and pyridoxal phosphate. Mitochondrial DNA quantitative studies on muscle homogenate demonstrated a mitochondrial DNA depletion disorder. Respiratory chain enzymology demonstrated decreased complex IV activity. Screening for mitochondrial DNA rearrangement disorders and sequencing relevant mitochondrial genes produced negative results. No clinical or biochemical response to treatment with pyridoxal phosphate, tetrahydrobiopterin, or l-dopa occurred. The clinical course was progressive, and the patient died at age 19 months. Mitochondrial disorders causing secondary neurotransmitter diseases are usually severe, but are rarely reported. This diagnosis should be considered in neonates or infants who present with hypertonia, hypokinesia rigidity, and progressive neurodegeneration.
Collapse
Affiliation(s)
- Margaret M Moran
- Department of Paediatric Neurology and Clinical Neurophysiology, Children's University Hospital, Dublin, Ireland
| | | | | | | |
Collapse
|
42
|
Spinazzola A. Mitochondrial DNA mutations and depletion in pediatric medicine. Semin Fetal Neonatal Med 2011; 16:190-6. [PMID: 21652274 DOI: 10.1016/j.siny.2011.04.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Mitochondrial disorders are a group of diseases traditionally ascribed to defects of the respiratory chain, which is the only metabolic pathway in the cell that is under the control of the two separate genetic systems, the mitochondrial genome (mtDNA) and the nuclear genome (nDNA). Therefore the genetic classification of the primary mitochondrial diseases distinguishes disorders due to mutations in mtDNA, which are sporadic or maternal inherited, from disorders due to mutations in nDNA, which are governed by the stricter rules of mendelian genetics. Pathological alterations of mtDNA fall into two main categories: primary mutations of mitochondrial DNA (point mutations and rearrangements) and mtDNA perturbation, due to mutations in nuclear genes whose products are involved in mtDNA maintenance or replication. This article will focus on the primary mitochondrial DNA mutations and mtDNA depletion syndromes related to neonatal-infant human pathology.
Collapse
Affiliation(s)
- A Spinazzola
- MRC, Mitochondrial Biology Unit, Wellcome Trust, MRC Building, Hills Road, Cambridge CB2 0XY, UK.
| |
Collapse
|
43
|
Abstract
During the last decade rapid development has occurred in defining nuclear gene mutations causing mitochondrial disease. Some of these newly defined gene mutations cause neonatal or early infantile onset of disease, often associated with severe progressive encephalomyopathy combined with other multi-organ involvement such as cardiomyopathy or hepatopathy and with early death. Findings suggesting myopathy in neonates are hypotonia, muscle weakness and wasting, and arthrogryposis. We aim to describe the clinical findings of patients with mitochondrial disease presenting with muscular manifestations in the neonatal period or in early infancy and in whom the genetic defect has been characterized. The majority of patients with neonatal onset of mitochondrial disease have mutations in nuclear genes causing dysfunction of the mitochondrial respiratory chain, leading to defective oxidative phosphorylation.
Collapse
Affiliation(s)
- Már Tulinius
- Department of Pediatrics, University of Gothenburg, The Queen Silvia Children's Hospital, S-416 85 Göteborg, Sweden.
| | | |
Collapse
|
44
|
Abstract
Understanding mitochondrial role in normal physiology and pathological conditions has proven to be of high importance as mitochondrial dysfunction is connected with a number of disorders as well as some of the most common diseases (e.g. diabetes or Parkinson's disease). Modeling mitochondrial dysfunction has been difficult mainly due to unique features of mitochondrial genetics. Here we discuss some of the most important mouse models generated so far and lessons learned from them.
Collapse
Affiliation(s)
- S A Dogan
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | | |
Collapse
|
45
|
Nogueira C, Carrozzo R, Vilarinho L, Santorelli FM. Infantile-onset disorders of mitochondrial replication and protein synthesis. J Child Neurol 2011; 26:866-75. [PMID: 21572058 DOI: 10.1177/0883073811402072] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Most inherited mitochondrial diseases in infants result from mutations in nuclear genes encoding proteins with specific functions targeted to the mitochondria rather than primary mutations in the mitochondrial DNA (mtDNA) itself. In the past decade, a growing number of syndromes associated with dysfunction resulting from tissue-specific depletion of mtDNA have been reported in infants. MtDNA depletion syndrome is transmitted as an autosomal recessive trait and causes respiratory chain dysfunction with prominent neurological, muscular, and hepatic involvement. Mendelian diseases characterized by defective mitochondrial protein synthesis and combined respiratory chain defects have also been described in infants and are associated with mutations in nuclear genes that encode components of the translational machinery. In the present work, we reviewed current knowledge of clinical phenotypes, their relative frequency, spectrum of mutations, and possible pathogenic mechanisms responsible for infantile disorders of oxidative metabolism involved in correct mtDNA maintenance and protein production.
Collapse
Affiliation(s)
- Célia Nogueira
- Department of Genetics, Centro de Genética Médica Jacinto de Magalhães/INSA, Porto, Portugal
| | | | | | | |
Collapse
|
46
|
Dorado B, Area E, Akman HO, Hirano M. Onset and organ specificity of Tk2 deficiency depends on Tk1 down-regulation and transcriptional compensation. Hum Mol Genet 2010; 20:155-64. [PMID: 20940150 PMCID: PMC3000681 DOI: 10.1093/hmg/ddq453] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Deficiency of thymidine kinase 2 (TK2) is a frequent cause of isolated myopathy or encephalomyopathy in children with mitochondrial DNA (mtDNA) depletion. To determine the bases of disease onset, organ specificity and severity of TK2 deficiency, we have carefully characterized Tk2 H126N knockin mice (Tk2-/-). Although normal until postnatal day 8, Tk2-/- mice rapidly develop fatal encephalomyopathy between postnatal days 10 and 13. We have observed that wild-type Tk2 activity is constant in the second week of life, while Tk1 activity decreases significantly between postnatal days 8 and 13. The down-regulation of Tk1 activity unmasks Tk2 deficiency in Tk2-/- mice and correlates with the onset of mtDNA depletion in the brain and the heart. Resistance to pathology in Tk2 mutant organs depends on compensatory mechanisms to the reduced mtDNA level. Our analyses at postnatal day 13 have revealed that Tk2-/- heart significantly increases mitochondrial transcript levels relative to the mtDNA content. This transcriptional compensation allows the heart to maintain normal levels of mtDNA-encoded proteins. The up-regulation in mitochondrial transcripts is not due to increased expression of the master mitochondrial biogenesis regulators peroxisome proliferator-activated receptor-gamma coactivator 1 alpha and nuclear respiratory factors 1 and 2, or to enhanced expression of the mitochondrial transcription factors A, B1 or B2. Instead, Tk2-/- heart compensates for mtDNA depletion by down-regulating the expression of the mitochondrial transcriptional terminator transcription factor 3 (MTERF3). Understanding the molecular mechanisms that allow Tk2 mutant organs to be spared may help design therapies for Tk2 deficiency.
Collapse
Affiliation(s)
- Beatriz Dorado
- Department of Neurology, Columbia University Medical Center, New York, NY 10032, USA
| | | | | | | |
Collapse
|
47
|
Martí R, Nascimento A, Colomer J, Lara MC, López-Gallardo E, Ruiz-Pesini E, Montoya J, Andreu AL, Briones P, Pineda M. Hearing loss in a patient with the myopathic form of mitochondrial DNA depletion syndrome and a novel mutation in the TK2 gene. Pediatr Res 2010; 68:151-4. [PMID: 20421844 DOI: 10.1203/pdr.0b013e3181e33bbe] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Mitochondrial DNA (mtDNA) depletion syndrome (MDS) is a devastating disorder of infancy caused by a significant reduction of the number of copies of mitochondrial DNA in one or more tissues. We report a Spanish patient with the myopathic form of MDS, harboring two mutations in the thymidine kinase 2 gene (TK2): a previously reported deletion (p.K244del) and a novel nucleotide duplication in the exon 2, generating a frameshift and premature stop codon. Sensorineural hearing loss was a predominant symptom in the patient and a novel feature of MDS due to TK2 mutations. The patient survived up to the age of 8.5 y, which confirms that survival above the age of 5 y is not infrequent in patients with MDS due to TK2 deficiency.
Collapse
Affiliation(s)
- Ramon Martí
- Laboratory of Mitochondrial Disorders, Institut de Recerca Hospital Universitari Vall d'Hebron, 08035 Barcelona, Spain
| | | | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Suomalainen A, Isohanni P. Mitochondrial DNA depletion syndromes--many genes, common mechanisms. Neuromuscul Disord 2010; 20:429-37. [PMID: 20444604 DOI: 10.1016/j.nmd.2010.03.017] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Revised: 03/25/2010] [Accepted: 03/29/2010] [Indexed: 02/07/2023]
Abstract
Mitochondrial DNA depletion syndrome has become an important cause of inherited metabolic disorders, especially in children, but also in adults. The manifestations vary from tissue-specific mtDNA depletion to wide-spread multisystemic disorders. Nine genes are known to underlie this group of disorders, and many disease genes are still unidentified. However, the disease mechanisms seem to be intimately associated with mtDNA replication and nucleotide pool regulation. We review here the current knowledge on the clinical and molecular genetic features of mitochondrial DNA depletion syndrome.
Collapse
Affiliation(s)
- Anu Suomalainen
- Research Program of Molecular Neurology, Biomedicum-Helsinki, University of Helsinki, Helsinki, Finland.
| | | |
Collapse
|
49
|
Bartesaghi S, Betts-Henderson J, Cain K, Dinsdale D, Zhou X, Karlsson A, Salomoni P, Nicotera P. Loss of thymidine kinase 2 alters neuronal bioenergetics and leads to neurodegeneration. Hum Mol Genet 2010; 19:1669-77. [PMID: 20123860 DOI: 10.1093/hmg/ddq043] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mutations of thymidine kinase 2 (TK2), an essential component of the mitochondrial nucleotide salvage pathway, can give rise to mitochondrial DNA (mtDNA) depletion syndromes (MDS). These clinically heterogeneous disorders are characterized by severe reduction in mtDNA copy number in affected tissues and are associated with progressive myopathy, hepatopathy and/or encephalopathy, depending in part on the underlying nuclear genetic defect. Mutations of TK2 have previously been associated with an isolated myopathic form of MDS (OMIM 609560). However, more recently, neurological phenotypes have been demonstrated in patients carrying TK2 mutations, thus suggesting that loss of TK2 results in neuronal dysfunction. Here, we directly address the role of TK2 in neuronal homeostasis using a knockout mouse model. We demonstrate that in vivo loss of TK2 activity leads to a severe ataxic phenotype, accompanied by reduced mtDNA copy number and decreased steady-state levels of electron transport chain proteins in the brain. In TK2-deficient cerebellar neurons, these abnormalities are associated with impaired mitochondrial bioenergetic function, aberrant mitochondrial ultrastructure and degeneration of selected neuronal types. Overall, our findings demonstrate that TK2 deficiency leads to neuronal dysfunction in vivo, and have important implications for understanding the mechanisms of neurological impairment in MDS.
Collapse
|
50
|
Genetic bases of mitochondrial respiratory chain disorders. DIABETES & METABOLISM 2010; 36:97-107. [PMID: 20093061 DOI: 10.1016/j.diabet.2009.11.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 11/09/2009] [Accepted: 11/10/2009] [Indexed: 01/21/2023]
Abstract
Oxidative phosphorylation - ATP synthesis by the oxygen-consuming respiratory chain (RC) - supplies most organs and tissues with a readily usable energy source, and is already fully functioning at birth. This means that, in theory, RC deficiency can give rise to any symptom in any organ or tissue at any age and with any mode of inheritance, due to the two-fold genetic origin of RC components (nuclear DNA and mitochondrial DNA). It has long been erroneously believed that RC disorders originate from mutations of mtDNA as, for some time, only mutations or deletions of mtDNA could be identified. However, the number of disease-causing mutations in nuclear genes is now steadily growing. These genes not only encode the various subunits of each complex, but also the ancillary proteins involved in the different stages of holoenzyme biogenesis, including transcription, translation, chaperoning, addition of prosthetic groups and assembly of proteins, as well as the various enzymes involved in mtDNA metabolism.
Collapse
|