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Neuhofer CM, Prokisch H. Digenic Inheritance in Rare Disorders and Mitochondrial Disease-Crossing the Frontier to a More Comprehensive Understanding of Etiology. Int J Mol Sci 2024; 25:4602. [PMID: 38731822 PMCID: PMC11083678 DOI: 10.3390/ijms25094602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 04/10/2024] [Accepted: 04/12/2024] [Indexed: 05/13/2024] Open
Abstract
Our understanding of rare disease genetics has been shaped by a monogenic disease model. While the traditional monogenic disease model has been successful in identifying numerous disease-associated genes and significantly enlarged our knowledge in the field of human genetics, it has limitations in explaining phenomena like phenotypic variability and reduced penetrance. Widening the perspective beyond Mendelian inheritance has the potential to enable a better understanding of disease complexity in rare disorders. Digenic inheritance is the simplest instance of a non-Mendelian disorder, characterized by the functional interplay of variants in two disease-contributing genes. Known digenic disease causes show a range of pathomechanisms underlying digenic interplay, including direct and indirect gene product interactions as well as epigenetic modifications. This review aims to systematically explore the background of digenic inheritance in rare disorders, the approaches and challenges when investigating digenic inheritance, and the current evidence for digenic inheritance in mitochondrial disorders.
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Affiliation(s)
- Christiane M. Neuhofer
- Institute of Human Genetics, University Medical Center, Technical University of Munich, Trogerstr. 32, 81675 Munich, Germany
- Institute of Neurogenomics, Computational Health Center, Helmholtz Centre Munich Neuherberg, Ingolstädter Landstraße 1, 85764 Oberschleißheim, Germany
- Institute of Human Genetics, Salzburger Landeskliniken, University Hospital of the Paracelsus Medical University, Müllner Hauptstraße 48, 5020 Salzburg, Austria
| | - Holger Prokisch
- Institute of Human Genetics, University Medical Center, Technical University of Munich, Trogerstr. 32, 81675 Munich, Germany
- Institute of Neurogenomics, Computational Health Center, Helmholtz Centre Munich Neuherberg, Ingolstädter Landstraße 1, 85764 Oberschleißheim, Germany
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Uittenbogaard M, Gropman AL, Whitehead MT, Brantner CA, Gropman E, Chiaramello A. Dysfunctional Postnatal Mitochondrial Energy Metabolism in a Patient with Neurodevelopmental Defects Caused by Intrauterine Growth Restriction Due to Idiopathic Placental Insufficiency. Int J Mol Sci 2024; 25:1386. [PMID: 38338665 PMCID: PMC10855472 DOI: 10.3390/ijms25031386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/16/2024] [Accepted: 01/20/2024] [Indexed: 02/12/2024] Open
Abstract
We report the case of a four-year-old male patient with a complex medical history born prematurely as the result of intrauterine growth restriction due to placental insufficiency. His clinical manifestations included severe neurodevelopmental deficits, global developmental delay, Pierre-Robin sequence, and intractable epilepsy with both generalized and focal features. The proband's low levels of citrulline and lactic acidosis provoked by administration of Depakoke were evocative of a mitochondrial etiology. The proband's genotype-phenotype correlation remained undefined in the absence of nuclear and mitochondrial pathogenic variants detected by deep sequencing of both genomes. However, live-cell mitochondrial metabolic investigations provided evidence of a deficient oxidative-phosphorylation pathway responsible for adenosine triphosphate (ATP) synthesis, leading to chronic energy crisis in the proband. In addition, our metabolic analysis revealed metabolic plasticity in favor of glycolysis for ATP synthesis. Our mitochondrial morphometric analysis by transmission electron microscopy confirmed the suspected mitochondrial etiology, as the proband's mitochondria exhibited an immature morphology with poorly developed and rare cristae. Thus, our results support the concept that suboptimal levels of intrauterine oxygen and nutrients alter fetal mitochondrial metabolic reprogramming toward oxidative phosphorylation (OXPHOS) leading to a deficient postnatal mitochondrial energy metabolism. In conclusion, our collective studies shed light on the long-term postnatal mitochondrial pathophysiology caused by intrauterine growth restriction due to idiopathic placental insufficiency and its negative impact on the energy-demanding development of the fetal and postnatal brain.
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Affiliation(s)
- Martine Uittenbogaard
- Department of Anatomy and Cell Biology, School of Medicine and Health Sciences, George Washington University, 2300 I Street N.W., Washington, DC 20037, USA; (M.U.); (E.G.)
| | - Andrea L. Gropman
- Children’s National Medical Center, Division of Neurogenetics and Neurodevelopmental Pediatrics, Washington, DC 20010, USA;
| | - Matthew T. Whitehead
- Division on Neuroradiology, Department of Radiology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA;
| | - Christine A. Brantner
- Electron Microscopy Core Imaging Facility, School of Dentistry and School of Medicine, University of Maryland Baltimore, Baltimore, MD 21201, USA;
| | - Eliana Gropman
- Department of Anatomy and Cell Biology, School of Medicine and Health Sciences, George Washington University, 2300 I Street N.W., Washington, DC 20037, USA; (M.U.); (E.G.)
| | - Anne Chiaramello
- Department of Anatomy and Cell Biology, School of Medicine and Health Sciences, George Washington University, 2300 I Street N.W., Washington, DC 20037, USA; (M.U.); (E.G.)
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Gropman AL, Uittenbogaard MN, Chiaramello AE. Challenges and opportunities to bridge translational to clinical research for personalized mitochondrial medicine. Neurotherapeutics 2024; 21:e00311. [PMID: 38266483 PMCID: PMC10903101 DOI: 10.1016/j.neurot.2023.e00311] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 12/08/2023] [Accepted: 12/13/2023] [Indexed: 01/26/2024] Open
Abstract
Mitochondrial disorders are a group of rare and heterogeneous genetic diseases characterized by dysfunctional mitochondria leading to deficient adenosine triphosphate synthesis and chronic energy deficit in patients. The majority of these patients exhibit a wide range of phenotypic manifestations targeting several organ systems, making their clinical diagnosis and management challenging. Bridging translational to clinical research is crucial for improving the early diagnosis and prognosis of these intractable mitochondrial disorders and for discovering novel therapeutic drug candidates and modalities. This review provides the current state of clinical testing in mitochondrial disorders, discusses the challenges and opportunities for converting basic discoveries into clinical settings, explores the most suited patient-centric approaches to harness the extraordinary heterogeneity among patients affected by the same primary mitochondrial disorder, and describes the current outlook of clinical trials.
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Affiliation(s)
- Andrea L Gropman
- Children's National Medical Center, Division of Neurogenetics and Neurodevelopmental Pediatrics, Washington, DC 20010, USA
| | - Martine N Uittenbogaard
- Department of Anatomy and Cell Biology, George Washington University School of Medicine and Health Sciences, Washington, DC 20037, USA
| | - Anne E Chiaramello
- Department of Anatomy and Cell Biology, George Washington University School of Medicine and Health Sciences, Washington, DC 20037, USA.
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Macken WL, Falabella M, Pizzamiglio C, Woodward CE, Scotchman E, Chitty LS, Polke JM, Bugiardini E, Hanna MG, Vandrovcova J, Chandler N, Labrum R, Pitceathly RDS. Enhanced mitochondrial genome analysis: bioinformatic and long-read sequencing advances and their diagnostic implications. Expert Rev Mol Diagn 2023; 23:797-814. [PMID: 37642407 DOI: 10.1080/14737159.2023.2241365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 07/24/2023] [Indexed: 08/31/2023]
Abstract
INTRODUCTION Primary mitochondrial diseases (PMDs) comprise a large and heterogeneous group of genetic diseases that result from pathogenic variants in either nuclear DNA (nDNA) or mitochondrial DNA (mtDNA). Widespread adoption of next-generation sequencing (NGS) has improved the efficiency and accuracy of mtDNA diagnoses; however, several challenges remain. AREAS COVERED In this review, we briefly summarize the current state of the art in molecular diagnostics for mtDNA and consider the implications of improved whole genome sequencing (WGS), bioinformatic techniques, and the adoption of long-read sequencing, for PMD diagnostics. EXPERT OPINION We anticipate that the application of PCR-free WGS from blood DNA will increase in diagnostic laboratories, while for adults with myopathic presentations, WGS from muscle DNA may become more widespread. Improved bioinformatic strategies will enhance WGS data interrogation, with more accurate delineation of mtDNA and NUMTs (nuclear mitochondrial DNA segments) in WGS data, superior coverage uniformity, indirect measurement of mtDNA copy number, and more accurate interpretation of heteroplasmic large-scale rearrangements (LSRs). Separately, the adoption of diagnostic long-read sequencing could offer greater resolution of complex LSRs and the opportunity to phase heteroplasmic variants.
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Affiliation(s)
- William L Macken
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery, London, UK
| | - Micol Falabella
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Chiara Pizzamiglio
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery, London, UK
| | - Cathy E Woodward
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery, London, UK
- Rare and Inherited Disease Laboratory, North Thames Genomic Laboratory Hub, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Elizabeth Scotchman
- Rare and Inherited Disease Laboratory, North Thames Genomic Laboratory Hub, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Lyn S Chitty
- Rare and Inherited Disease Laboratory, North Thames Genomic Laboratory Hub, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - James M Polke
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery, London, UK
- Rare and Inherited Disease Laboratory, North Thames Genomic Laboratory Hub, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Enrico Bugiardini
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery, London, UK
| | - Michael G Hanna
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery, London, UK
| | - Jana Vandrovcova
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Natalie Chandler
- Rare and Inherited Disease Laboratory, North Thames Genomic Laboratory Hub, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Robyn Labrum
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery, London, UK
- Rare and Inherited Disease Laboratory, North Thames Genomic Laboratory Hub, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Robert D S Pitceathly
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, The National Hospital for Neurology and Neurosurgery, London, UK
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Seed LM, Dean A, Krishnakumar D, Phyu P, Horvath R, Harijan PD. Molecular and neurological features of MELAS syndrome in paediatric patients: A case series and review of the literature. Mol Genet Genomic Med 2022; 10:e1955. [PMID: 35474314 PMCID: PMC9266612 DOI: 10.1002/mgg3.1955] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 03/21/2022] [Accepted: 04/04/2022] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome is one of the most well-known mitochondrial diseases, with most cases attributed to m.3243A>G. MELAS syndrome patients typically present in the first two decades of life with a broad, multi-systemic phenotype that predominantly features neurological manifestations--stroke-like episodes. However, marked phenotypic variability has been observed among paediatric patients, creating a clinical challenge and delaying diagnoses. METHODS A literature review of paediatric MELAS syndrome patients and a retrospective analysis in a UK tertiary paediatric neurology centre were performed. RESULTS Three children were included in this case series. All patients presented with seizures and had MRI changes not confined to a single vascular territory. Blood heteroplasmy varied considerably, and one patient required a muscle biopsy. Based on a literature review of 114 patients, the mean age of presentation is 8.1 years and seizures are the most prevalent manifestation of stroke-like episodes. Heteroplasmy is higher in a tissue other than blood in most cases. CONCLUSION The threshold for investigating MELAS syndrome in children with suspicious neurological symptoms should be low. If blood m.3243A>G analysis is negative, yet clinical suspicion remains high, invasive testing or further interrogation of the mitochondrial genome should be considered.
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Affiliation(s)
- Lydia M. Seed
- School of Clinical MedicineUniversity of CambridgeCambridgeUK
| | - Andrew Dean
- Department of Clinical NeuroscienceUniversity of CambridgeCambridgeUK
- Department of HistopathologyCambridge University Hospitals NHS Foundation TrustCambridgeUK
| | - Deepa Krishnakumar
- Department of Paediatric NeurosciencesCambridge University Hospitals NHS Foundation TrustCambridgeUK
| | - Poe Phyu
- Department of Clinical NeuroradiologyCambridge University Hospitals NHS Foundation TrustCambridgeUK
| | - Rita Horvath
- Department of Clinical NeuroscienceUniversity of CambridgeCambridgeUK
| | - Pooja Devi Harijan
- Department of Paediatric NeurosciencesCambridge University Hospitals NHS Foundation TrustCambridgeUK
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Li H, Uittenbogaard M, Navarro R, Ahmed M, Gropman A, Chiaramello A, Hao L. Integrated proteomic and metabolomic analyses of the mitochondrial neurodegenerative disease MELAS. Mol Omics 2022; 18:196-205. [PMID: 34982085 PMCID: PMC11334596 DOI: 10.1039/d1mo00416f] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
MELAS (mitochondrial encephalomyopathy, lactic acidosis, stroke-like episodes) is a progressive neurodegenerative disease caused by pathogenic mitochondrial DNA variants. The pathogenic mechanism of MELAS remains enigmatic due to the exceptional clinical heterogeneity and the obscure genotype-phenotype correlation among MELAS patients. To gain insights into the pathogenic signature of MELAS, we designed a comprehensive strategy integrating proteomics and metabolomics in patient-derived dermal fibroblasts harboring the ultra-rare MELAS pathogenic variant m.14453G>A, specifically affecting the mitochondrial respiratory complex I. Global proteomics was achieved by data-dependent acquisition (DDA) and verified by data-independent acquisition (DIA) using both Spectronaut and the recently launched MaxDIA platforms. Comprehensive metabolite coverage was achieved for both polar and nonpolar metabolites in both reverse phase and HILIC LC-MS/MS analyses. Our proof-of-principle MELAS study with multi-omics integration revealed OXPHOS dysregulation with a predominant deficiency of complex I subunits, as well as alterations in key bioenergetic pathways, glycolysis, tricarboxylic acid cycle, and fatty acid β-oxidation. The most clinically relevant discovery is the downregulation of the arginine biosynthesis pathway, likely due to blocked argininosuccinate synthase, which is congruent with the MELAS cardinal symptom of stroke-like episodes and its current treatment by arginine infusion. In conclusion, we demonstrated an integrated proteomic and metabolomic strategy for patient-derived fibroblasts, which has great clinical potential to discover therapeutic targets and design personalized interventions after validation with a larger patient cohort in the future.
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Affiliation(s)
- Haorong Li
- Department of Chemistry, The George Washington University, Science and Engineering Hall, 800 22nd St., NW, Washington, DC 20052, USA.
| | - Martine Uittenbogaard
- Department of Anatomy and Cell Biology, George Washington University School of Medicine and Health Sciences, Washington, DC 20037, USA
| | - Ryan Navarro
- Department of Chemistry, The George Washington University, Science and Engineering Hall, 800 22nd St., NW, Washington, DC 20052, USA.
| | - Mustafa Ahmed
- Department of Chemistry, The George Washington University, Science and Engineering Hall, 800 22nd St., NW, Washington, DC 20052, USA.
| | - Andrea Gropman
- Division of Neurogenetics and Neurodevelopmental Pediatrics, Children's National Medical Center, Washington, DC 20010, USA
| | - Anne Chiaramello
- Department of Anatomy and Cell Biology, George Washington University School of Medicine and Health Sciences, Washington, DC 20037, USA
| | - Ling Hao
- Department of Chemistry, The George Washington University, Science and Engineering Hall, 800 22nd St., NW, Washington, DC 20052, USA.
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7
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Li H, Uittenbogaard M, Hao L, Chiaramello A. Clinical Insights into Mitochondrial Neurodevelopmental and Neurodegenerative Disorders: Their Biosignatures from Mass Spectrometry-Based Metabolomics. Metabolites 2021; 11:233. [PMID: 33920115 PMCID: PMC8070181 DOI: 10.3390/metabo11040233] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 04/01/2021] [Accepted: 04/07/2021] [Indexed: 02/07/2023] Open
Abstract
Mitochondria are dynamic multitask organelles that function as hubs for many metabolic pathways. They produce most ATP via the oxidative phosphorylation pathway, a critical pathway that the brain relies on its energy need associated with its numerous functions, such as synaptic homeostasis and plasticity. Therefore, mitochondrial dysfunction is a prevalent pathological hallmark of many neurodevelopmental and neurodegenerative disorders resulting in altered neurometabolic coupling. With the advent of mass spectrometry (MS) technology, MS-based metabolomics provides an emerging mechanistic understanding of their global and dynamic metabolic signatures. In this review, we discuss the pathogenetic causes of mitochondrial metabolic disorders and the recent MS-based metabolomic advances on their metabolomic remodeling. We conclude by exploring the MS-based metabolomic functional insights into their biosignatures to improve diagnostic platforms, stratify patients, and design novel targeted therapeutic strategies.
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Affiliation(s)
- Haorong Li
- Department of Chemistry, George Washington University, Science and Engineering Hall 4000, 800 22nd St., NW, Washington, DC 20052, USA;
| | - Martine Uittenbogaard
- Department of Anatomy and Cell Biology, School of Medicine and Health Sciences, George Washington University, 2300 I Street N.W. Ross Hall 111, Washington, DC 20037, USA;
| | - Ling Hao
- Department of Chemistry, George Washington University, Science and Engineering Hall 4000, 800 22nd St., NW, Washington, DC 20052, USA;
| | - Anne Chiaramello
- Department of Anatomy and Cell Biology, School of Medicine and Health Sciences, George Washington University, 2300 I Street N.W. Ross Hall 111, Washington, DC 20037, USA;
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Macken WL, Vandrovcova J, Hanna MG, Pitceathly RDS. Applying genomic and transcriptomic advances to mitochondrial medicine. Nat Rev Neurol 2021; 17:215-230. [PMID: 33623159 DOI: 10.1038/s41582-021-00455-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/06/2021] [Indexed: 02/07/2023]
Abstract
Next-generation sequencing (NGS) has increased our understanding of the molecular basis of many primary mitochondrial diseases (PMDs). Despite this progress, many patients with suspected PMD remain without a genetic diagnosis, which restricts their access to in-depth genetic counselling, reproductive options and clinical trials, in addition to hampering efforts to understand the underlying disease mechanisms. Although they represent a considerable improvement over their predecessors, current methods for sequencing the mitochondrial and nuclear genomes have important limitations, and molecular diagnostic techniques are often manual and time consuming. However, recent advances in genomics and transcriptomics offer realistic solutions to these challenges. In this Review, we discuss the current genetic testing approach for PMDs and the opportunities that exist for increased use of whole-genome NGS of nuclear and mitochondrial DNA (mtDNA) in the clinical environment. We consider the possible role for long-read approaches in sequencing of mtDNA and in the identification of novel nuclear genomic causes of PMDs. We examine the expanding applications of RNA sequencing, including the detection of cryptic variants that affect splicing and gene expression and the interpretation of rare and novel mitochondrial transfer RNA variants.
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Affiliation(s)
- William L Macken
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, UK
| | - Jana Vandrovcova
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, UK
| | - Michael G Hanna
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, UK
| | - Robert D S Pitceathly
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, UK.
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Uittenbogaard M, Sen K, Whitehead M, Brantner CA, Wang Y, Wong LJ, Gropman A, Chiaramello A. Genetic and Mitochondrial Metabolic Analyses of an Atypical Form of Leigh Syndrome. Front Cell Dev Biol 2021; 9:767407. [PMID: 35004675 PMCID: PMC8728009 DOI: 10.3389/fcell.2021.767407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 12/10/2021] [Indexed: 11/13/2022] Open
Abstract
In this study, we aimed to establish the mitochondrial etiology of the proband's progressive neurodegenerative disease suggestive of an atypical Leigh syndrome, by determining the proband's pathogenic variants. Brain MRI showed a constellation of multifocal temporally disparate lesions in the cerebral deep gray nuclei, brainstem, cerebellum, spinal cord along with rhombencephalic atrophy, and optic nerve atrophy. Single voxel 1H MRS performed concurrently over the left cerebral deep gray nuclei showed a small lactate peak, increased glutamate and citrate elevation, elevating suspicion of a mitochondrial etiology. Whole exome sequencing revealed three heterozygous nuclear variants mapping in three distinct genes known to cause Leigh syndrome. Our mitochondrial bioenergetic investigations revealed an impaired mitochondrial energy metabolism. The proband's overall ATP deficit is further intensified by an ineffective metabolic reprogramming between oxidative phosphorylation and glycolysis. The deficient metabolic adaptability and global energy deficit correlate with the proband's neurological symptoms congruent with an atypical Leigh syndrome. In conclusion, our study provides much needed insights to support the development of molecular diagnostic and therapeutic strategies for atypical Leigh syndrome.
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Affiliation(s)
- Martine Uittenbogaard
- Department of Anatomy and Cell Biology, George Washington University School of Medicine and Health Sciences, Washington, DC, United States
| | - Kuntal Sen
- Children’s National Medical Center, Division of Neurogenetics and Developmental Pediatrics, Washington, DC, United States
| | - Matthew Whitehead
- Children’s National Medical Center, Division of Radiology, Washington, DC, United States
| | - Christine A. Brantner
- GW Nanofabrication and Imaging Center, Office of the Vice President for Research, George Washington University, Washington, DC, United States
| | - Yue Wang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
| | - Lee-Jun Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
| | - Andrea Gropman
- Children’s National Medical Center, Division of Neurogenetics and Developmental Pediatrics, Washington, DC, United States
| | - Anne Chiaramello
- Department of Anatomy and Cell Biology, George Washington University School of Medicine and Health Sciences, Washington, DC, United States
- *Correspondence: Anne Chiaramello, , orcid.org/0000-0001-8424-0826
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Uittenbogaard M, Chiaramello A. Maternally inherited mitochondrial respiratory disorders: from pathogenetic principles to therapeutic implications. Mol Genet Metab 2020; 131:38-52. [PMID: 32624334 PMCID: PMC7749081 DOI: 10.1016/j.ymgme.2020.06.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 06/22/2020] [Accepted: 06/23/2020] [Indexed: 01/19/2023]
Abstract
Maternally inherited mitochondrial respiratory disorders are rare, progressive, and multi-systemic diseases that remain intractable, with no effective therapeutic interventions. Patients share a defective oxidative phosphorylation pathway responsible for mitochondrial ATP synthesis, in most cases due to pathogenic mitochondrial variants transmitted from mother to child or to a rare de novo mutation or large-scale deletion of the mitochondrial genome. The clinical diagnosis of these mitochondrial diseases is difficult due to exceptionally high clinical variability, while their genetic diagnosis has improved with the advent of next-generation sequencing. The mechanisms regulating the penetrance of the mitochondrial variants remain unresolved with the patient's nuclear background, epigenomic regulation, heteroplasmy, mitochondrial haplogroups, and environmental factors thought to act as rheostats. The lack of animal models mimicking the phenotypic manifestations of these disorders has hampered efforts toward curative therapies. Patient-derived cellular paradigms provide alternative models for elucidating the pathogenic mechanisms and screening pharmacological small molecules to enhance mitochondrial function. Recent progress has been made in designing promising approaches to curtail the negative impact of dysfunctional mitochondria and alleviate clinical symptoms: 1) boosting mitochondrial biogenesis; 2) shifting heteroplasmy; 3) reprogramming metabolism; and 4) administering hypoxia-based treatment. Here, we discuss their varying efficacies and limitations and provide an outlook on their therapeutic potential and clinical application.
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Affiliation(s)
- Martine Uittenbogaard
- George Washington University School of Medicine and Health Sciences, Department of Anatomy and Cell Biology, 2300 I Street N.W., Washington, DC 20037, USA
| | - Anne Chiaramello
- George Washington University School of Medicine and Health Sciences, Department of Anatomy and Cell Biology, 2300 I Street N.W., Washington, DC 20037, USA.
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11
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Gropman A, Uittenbogaard M, Brantner CA, Wang Y, Wong LJ, Chiaramello A. Molecular genetic and mitochondrial metabolic analyses confirm the suspected mitochondrial etiology in a pediatric patient with an atypical form of alternating hemiplegia of childhood. Mol Genet Metab Rep 2020; 24:100609. [PMID: 32489883 PMCID: PMC7262444 DOI: 10.1016/j.ymgmr.2020.100609] [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: 05/21/2020] [Accepted: 05/21/2020] [Indexed: 02/05/2023] Open
Abstract
Alternative hemiplegia of childhood (AHC) is a rare neurodevelopmental disorder with an extensive phenotypic variability, resulting in a challenging clinical diagnosis. About 75% of AHC cases are caused by pathogenic variants mapping in the ATP1A3, ATP1A2 or GLUT1 gene, leaving many AHC patients clinically and genetically undiagnosed. In this study, we report the case of a 9-year old proband clinically diagnosed with an atypical form of AHC presenting a suspected mitochondrial etiology and an obscure genetic diagnosis. Long-range PCR followed by next generation sequencing of the proband's mitochondrial genome identified a novel mitochondrial variant, m.12302C > A, mapping in the MT-TL2 gene with a low heteroplasmic level in blood and fibroblasts. Whole exome sequencing revealed three known and novel pathogenic variants with different parental inheritance, all involved in the mitochondrial energy metabolism and thus far not associated with AHC. Live-cell mitochondrial metabolic study showed dysregulated mitochondrial oxidative phosphorylation pathway and metabolic plasticity preventing an efficient switch to glycolysis to sustain ATP homeostasis, congruent with the suspected mitochondrial etiology. In conclusion, our comprehensive genetic and metabolic analyses suggest an oligogenic inheritance among the nuclear and mitochondrial variants for the mitochondrial etiology of proband's atypical form of AHC, thereby providing critical insight in terms of genetic clues and bioenergetic deficit. This approach also improves the diagnostic process of atypical form of AHC with an unclear genotype-phenotype correlation to personalize therapeutic interventions.
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Affiliation(s)
- Andrea Gropman
- Children's National Medical Center, Division of Neurogenetics and Developmental Pediatrics, Washington, DC 20010, USA
| | - Martine Uittenbogaard
- Department of Anatomy and Regenerative Biology, George Washington University School of Medicine and Health Sciences, Washington, DC 20037, USA
| | - Christine A Brantner
- GW Nanofabrication and Imaging Center, Office of the Vice-President for Research, George Washington University, Washington, DC 20052, USA
| | - Yue Wang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Lee-Jun Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Anne Chiaramello
- Department of Anatomy and Regenerative Biology, George Washington University School of Medicine and Health Sciences, Washington, DC 20037, USA
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12
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Wong LJC, Chen T, Schmitt ES, Wang J, Zhang S, Landsverk M, Li F, Tang S, Wang Y, Zhang VW, Craigen WJ. Response to Bai et al. Genet Med 2020; 22:1420-1421. [PMID: 32418988 DOI: 10.1038/s41436-020-0805-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 03/31/2020] [Indexed: 11/09/2022] Open
Affiliation(s)
- Lee-Jun C Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA. .,Baylor Genetics Laboratory, Houston, TX, USA.
| | - Ting Chen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,Department of Endocrinology, Genetics and Metabolism, Children's Hospital of Soochow University, Suzhou, China
| | - Eric S Schmitt
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,Baylor Genetics Laboratory, Houston, TX, USA
| | - Jing Wang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Shulin Zhang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,Department of Pathology and Laboratory Medicine, UKHealthCare, University of Kentucky, Lexington, USA
| | - Megan Landsverk
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,Global Laboratory Services/Diagnostics, Perkin Elmer, Waltham, MA, USA
| | - Fangyuan Li
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,Sema4, Branford, CT, USA
| | - Sha Tang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,WuXi NextCODE, Cambridge, MA, USA
| | - Yue Wang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,Baylor Genetics Laboratory, Houston, TX, USA
| | - Victor Wei Zhang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,AmCare Genomics Lab, Guangzhou, China
| | - William J Craigen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.,Baylor Genetics Laboratory, Houston, TX, USA
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Mejia-Vergara AJ, Seleme N, Sadun AA, Karanjia R. Pathophysiology of Conversion to Symptomatic Leber Hereditary Optic Neuropathy and Therapeutic Implications: a Review. Curr Neurol Neurosci Rep 2020; 20:11. [DOI: 10.1007/s11910-020-01032-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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14
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Interpretation of mitochondrial tRNA variants. Genet Med 2020; 22:917-926. [PMID: 31965079 DOI: 10.1038/s41436-019-0746-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 12/26/2019] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To develop criteria to interpret mitochondrial transfer RNA (mt-tRNA) variants based on unique characteristics of mitochondrial genetics and conserved structural/functional properties of tRNA. METHODS We developed rules on a set of established pathogenic/benign variants by examining heteroplasmy correlations with phenotype, tissue distribution, family members, and among unrelated families from published literature. We validated these deduced rules using our new cases and applied them to classify novel variants. RESULTS Evaluation of previously reported pathogenic variants found that 80.6% had sufficient evidence to support phenotypic correlation with heteroplasmy levels among and within families. The remaining variants were downgraded due to the lack of similar evidence. Application of the verified criteria resulted in rescoring 80.8% of reported variants of uncertain significance (VUS) to benign and likely benign. Among 97 novel variants, none met pathogenic criteria. A large proportion of novel variants (84.5%) remained as VUS, while only 10.3% were likely pathogenic. Detection of these novel variants in additional individuals would facilitate their classification. CONCLUSION Proper interpretation of mt-tRNA variants is crucial for accurate clinical diagnosis and genetic counseling. Correlations with tissue distribution, heteroplasmy levels, predicted perturbations to tRNA structure, and phenotypes provide important evidence for determining the clinical significance of mt-tRNA variants.
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15
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The importance of the nuclear background on the phenotypic signature caused by the MELAS m.1630 A>G variant. Mol Genet Metab Rep 2019; 19:100462. [PMID: 30815362 PMCID: PMC6378903 DOI: 10.1016/j.ymgmr.2019.100462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 02/12/2019] [Indexed: 11/20/2022] Open
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16
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Finsterer J. Pathogenicity of the m.1630A > G variant remains elusive if related mutation carriers with similar heteroplasmy rates are asymptomatic. Mol Genet Metab Rep 2019; 19:100461. [PMID: 30809469 PMCID: PMC6375060 DOI: 10.1016/j.ymgmr.2019.100461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 02/07/2019] [Indexed: 02/06/2023] Open
Affiliation(s)
- Josef Finsterer
- Krankenanstalt Rudolfstiftung, Messerli Institute, Veterinary University of Vienna, Vienna, Austria
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