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Cha JH, Lee SH, Yun Y, Choi WH, Koo H, Jung SH, Chae HB, Lee DH, Lee SJ, Jo DH, Kim JH, Song JJ, Chae JH, Lee JH, Park J, Kang JY, Bae S, Lee SY. Discovery of novel disease-causing mutation in SSBP1 and its correction using adenine base editor to improve mitochondrial function. MOLECULAR THERAPY. NUCLEIC ACIDS 2024; 35:102257. [PMID: 39104869 PMCID: PMC11299580 DOI: 10.1016/j.omtn.2024.102257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 06/14/2024] [Indexed: 08/07/2024]
Abstract
Mutations in nuclear genes regulating mitochondrial DNA (mtDNA) replication are associated with mtDNA depletion syndromes. Using whole-genome sequencing, we identified a heterozygous mutation (c.272G>A:p.Arg91Gln) in single-stranded DNA-binding protein 1 (SSBP1), a crucial protein involved in mtDNA replisome. The proband manifested symptoms including sensorineural deafness, congenital cataract, optic atrophy, macular dystrophy, and myopathy. This mutation impeded multimer formation and DNA-binding affinity, leading to reduced efficiency of mtDNA replication, altered mitochondria dynamics, and compromised mitochondrial function. To correct this mutation, we tested two adenine base editor (ABE) variants on patient-derived fibroblasts. One variant, NG-Cas9-based ABE8e (NG-ABE8e), showed higher editing efficacy (≤30%) and enhanced mitochondrial replication and function, despite off-target editing frequencies; however, risks from bystander editing were limited due to silent mutations and off-target sites in non-translated regions. The other variant, NG-Cas9-based ABE8eWQ (NG-ABE8eWQ), had a safer therapeutic profile with very few off-target effects, but this came at the cost of lower editing efficacy (≤10% editing). Despite this, NG-ABE8eWQ-edited cells still restored replication and improved mtDNA copy number, which in turn recovery of compromised mitochondrial function. Taken together, base editing-based gene therapies may be a promising treatment for mitochondrial diseases, including those associated with SSBP1 mutations.
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Affiliation(s)
- Ju Hyuen Cha
- Department of Otorhinolaryngology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea
| | - Seok-Hoon Lee
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Yejin Yun
- Department of Otorhinolaryngology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea
| | - Won Hoon Choi
- Department of Otorhinolaryngology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea
| | - Hansol Koo
- Cancer Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Sung Ho Jung
- Department of Otorhinolaryngology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea
| | - Ho Byung Chae
- Department of Otorhinolaryngology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea
| | | | - Seok Jae Lee
- Fight Against Angiogenesis-Related Blindness (FARB) Laboratory, Clinical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Dong Hyun Jo
- Department of Anatomy and Cell Biology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Jeong Hun Kim
- Fight Against Angiogenesis-Related Blindness (FARB) Laboratory, Clinical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Jae-Jin Song
- Department of Otorhinolaryngology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Republic of Korea
| | - Jong-Hee Chae
- Department of Genomic Medicine, Seoul National University Hospital, Seoul, Republic of Korea
| | - Jun Ho Lee
- Department of Otorhinolaryngology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea
| | - Jiho Park
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Jin Young Kang
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Sangsu Bae
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, Republic of Korea
- Cancer Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea
- Medical Research Center of Genomic Medicine Institute, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Sang-Yeon Lee
- Department of Otorhinolaryngology, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea
- Department of Genomic Medicine, Seoul National University Hospital, Seoul, Republic of Korea
- Sensory Organ Research Institute, Seoul National University Medical Research Center, Seoul, Republic of Korea
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2
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Bretscher H, O’Connor MB. Glycogen homeostasis and mtDNA expression require motor neuron to muscle TGFβ/Activin Signaling in Drosophila. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.25.600699. [PMID: 39131342 PMCID: PMC11312462 DOI: 10.1101/2024.06.25.600699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/13/2024]
Abstract
Maintaining metabolic homeostasis requires coordinated nutrient utilization between intracellular organelles and across multiple organ systems. Many organs rely heavily on mitochondria to generate (ATP) from glucose, or stored glycogen. Proteins required for ATP generation are encoded in both nuclear and mitochondrial DNA (mtDNA). We show that motoneuron to muscle signaling by the TGFβ/Activin family member Actβ positively regulates glycogen levels during Drosophila development. Remarkably, we find that levels of stored glycogen are unaffected by altering cytoplasmic glucose catabolism. Instead, Actβ loss reduces levels of mtDNA and nuclearly encoded genes required for mtDNA replication, transcription and translation. Direct RNAi mediated knockdown of these same nuclearly encoded mtDNA expression factors also results in decreased glycogen stores. Lastly, we find that expressing an activated form of the type I receptor Baboon in muscle restores both glycogen and mtDNA levels in actβ mutants, thereby confirming a direct link between Actβ signaling, glycogen homeostasis and mtDNA expression.
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Affiliation(s)
- Heidi Bretscher
- Department of Genetics, Cell Biology and Development University of Minnesota, Minneapolis, MN 55455
| | - Michael B. O’Connor
- Department of Genetics, Cell Biology and Development University of Minnesota, Minneapolis, MN 55455
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Bernardino Gomes TM, Vincent AE, Menger KE, Stewart JB, Nicholls TJ. Mechanisms and pathologies of human mitochondrial DNA replication and deletion formation. Biochem J 2024; 481:683-715. [PMID: 38804971 PMCID: PMC11346376 DOI: 10.1042/bcj20230262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 05/13/2024] [Accepted: 05/14/2024] [Indexed: 05/29/2024]
Abstract
Human mitochondria possess a multi-copy circular genome, mitochondrial DNA (mtDNA), that is essential for cellular energy metabolism. The number of copies of mtDNA per cell, and their integrity, are maintained by nuclear-encoded mtDNA replication and repair machineries. Aberrant mtDNA replication and mtDNA breakage are believed to cause deletions within mtDNA. The genomic location and breakpoint sequences of these deletions show similar patterns across various inherited and acquired diseases, and are also observed during normal ageing, suggesting a common mechanism of deletion formation. However, an ongoing debate over the mechanism by which mtDNA replicates has made it difficult to develop clear and testable models for how mtDNA rearrangements arise and propagate at a molecular and cellular level. These deletions may impair energy metabolism if present in a high proportion of the mtDNA copies within the cell, and can be seen in primary mitochondrial diseases, either in sporadic cases or caused by autosomal variants in nuclear-encoded mtDNA maintenance genes. These mitochondrial diseases have diverse genetic causes and multiple modes of inheritance, and show notoriously broad clinical heterogeneity with complex tissue specificities, which further makes establishing genotype-phenotype relationships challenging. In this review, we aim to cover our current understanding of how the human mitochondrial genome is replicated, the mechanisms by which mtDNA replication and repair can lead to mtDNA instability in the form of large-scale rearrangements, how rearranged mtDNAs subsequently accumulate within cells, and the pathological consequences when this occurs.
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Affiliation(s)
- Tiago M. Bernardino Gomes
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- NHS England Highly Specialised Service for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne NE2 4HH, U.K
| | - Amy E. Vincent
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
| | - Katja E. Menger
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
| | - James B. Stewart
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
| | - Thomas J. Nicholls
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, U.K
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Castellaneta A, Losito I, Porcelli V, Barile S, Maresca A, Del Dotto V, Losacco V, Guadalupi LS, Calvano CD, Chan DC, Carelli V, Palmieri L, Cataldi TRI. Lipidomics reveals the reshaping of the mitochondrial phospholipid profile in cells lacking OPA1 and mitofusins. J Lipid Res 2024; 65:100563. [PMID: 38763493 PMCID: PMC11225846 DOI: 10.1016/j.jlr.2024.100563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Accepted: 05/09/2024] [Indexed: 05/21/2024] Open
Abstract
Depletion or mutations of key proteins for mitochondrial fusion, like optic atrophy 1 (OPA1) and mitofusins 1 and 2 (Mfn 1 and 2), are known to significantly impact the mitochondrial ultrastructure, suggesting alterations of their membranes' lipid profiles. In order to make an insight into this issue, we used hydrophilic interaction liquid chromatography coupled with electrospray ionization-high resolution MS to investigate the mitochondrial phospholipid (PL) profile of mouse embryonic fibroblasts knocked out for OPA1 and Mfn1/2 genes. One hundred sixty-seven different sum compositions were recognized for the four major PL classes of mitochondria, namely phosphatidylcholines (PCs, 63), phosphatidylethanolamines (55), phosphatidylinositols (21), and cardiolipins (28). A slight decrease in the cardiolipin/PC ratio was found for Mfn1/2-knockout mitochondria. Principal component analysis and hierarchical cluster analysis were subsequently used to further process hydrophilic interaction liquid chromatography-ESI-MS data. A progressive decrease in the incidence of alk(en)yl/acyl species in PC and phosphatidylethanolamine classes and a general increase in the incidence of unsaturated acyl chains across all the investigated PL classes was inferred in OPA1 and Mfn1/2 knockouts compared to WT mouse embryonic fibroblasts. These findings suggest a reshaping of the PL profile consistent with the changes observed in the mitochondrial ultrastructure when fusion proteins are absent. Based on the existing knowledge on the metabolism of mitochondrial phospholipids, we propose that fusion proteins, especially Mfns, might influence the PL transfer between the mitochondria and the endoplasmic reticulum, likely in the context of mitochondria-associated membranes.
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Affiliation(s)
- Andrea Castellaneta
- Dipartimento di Chimica- Università degli Studi di Bari Aldo Moro, Bari, Italy
| | - Ilario Losito
- Dipartimento di Chimica- Università degli Studi di Bari Aldo Moro, Bari, Italy; Centro Interdipartimentale SMART- Università degli Studi di Bari Aldo Moro, Bari, Italy.
| | - Vito Porcelli
- Dipartimento di Bioscienze, Biotecnologie e Ambiente - Università degli Studi di Bari Aldo Moro, Bari, Italy
| | - Serena Barile
- Dipartimento di Bioscienze, Biotecnologie e Ambiente - Università degli Studi di Bari Aldo Moro, Bari, Italy
| | - Alessandra Maresca
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy
| | - Valentina Del Dotto
- Dipartimento di Scienze Biomediche e Neuromotorie, Università degli Studi di Bologna, Bologna, Italy
| | - Valentina Losacco
- Dipartimento di Chimica- Università degli Studi di Bari Aldo Moro, Bari, Italy
| | | | - Cosima Damiana Calvano
- Dipartimento di Chimica- Università degli Studi di Bari Aldo Moro, Bari, Italy; Centro Interdipartimentale SMART- Università degli Studi di Bari Aldo Moro, Bari, Italy
| | - David C Chan
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Valerio Carelli
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy; Dipartimento di Scienze Biomediche e Neuromotorie, Università degli Studi di Bologna, Bologna, Italy
| | - Luigi Palmieri
- Dipartimento di Bioscienze, Biotecnologie e Ambiente - Università degli Studi di Bari Aldo Moro, Bari, Italy; CNR-Istituto di Biomembrane, Bioenergetica e Biotecnologie Molecolari, Bari, Italy
| | - Tommaso R I Cataldi
- Dipartimento di Chimica- Università degli Studi di Bari Aldo Moro, Bari, Italy; Centro Interdipartimentale SMART- Università degli Studi di Bari Aldo Moro, Bari, Italy
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Liang KX. The application of brain organoid for drug discovery in mitochondrial diseases. Int J Biochem Cell Biol 2024; 170:106556. [PMID: 38423381 DOI: 10.1016/j.biocel.2024.106556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 02/26/2024] [Accepted: 02/26/2024] [Indexed: 03/02/2024]
Abstract
Mitochondrial diseases are difficult to treat due to the complexity and multifaceted nature of mitochondrial dysfunction. Brain organoids are three-dimensional (3D) structures derived from human pluripotent stem cells designed to mimic brain-like development and function. Brain organoids have received a lot of attention in recent years as powerful tools for modeling human diseases, brain development, and drug screening. Screening compounds for mitochondrial diseases using brain organoids could provide a more physiologically relevant platform for drug discovery. Brain organoids offer the possibility of personalized medicine because they can be derived from patient-specific cells, allowing testing of drugs tailored to specific genetic mutations. In this article, we highlight how brain organoids offer a promising avenue for screening compounds for mitochondrial diseases and address the challenges and limitations associated with their use. We hope this review will provide new insights into the further progress of brain organoids for mitochondrial screening studies.
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Bermejo-Guerrero L, Hernández-Voth A, Serrano-Lorenzo P, Blázquez A, Martin-Jimenez P, Martin MA, Domínguez-González C. Remarkable clinical improvement with oral nucleoside treatment in a patient with adult-onset TK2 deficiency: A case report. Mitochondrion 2024; 76:101879. [PMID: 38599303 DOI: 10.1016/j.mito.2024.101879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 03/09/2024] [Accepted: 04/07/2024] [Indexed: 04/12/2024]
Abstract
OBJECTIVES Thymidine kinase 2 deficiency (TK2d) is a rare autosomal recessive mitochondrial disorder. It manifests as a continuous clinical spectrum, from fatal infantile mitochondrial DNA depletion syndromes to adult-onset mitochondrial myopathies characterized by ophthalmoplegia-plus phenotypes with early respiratory involvement. Treatment with pyrimidine nucleosides has recently shown striking effects on survival and motor outcomes in the more severe infantile-onset clinical forms. We present the response to treatment in a patient with adult-onset TK2d. METHODS An adult with ptosis, ophthalmoplegia, facial, neck, and proximal muscle weakness, non-invasive nocturnal mechanical ventilation, and dysphagia due to biallelic pathogenic variants in TK2 received treatment with 260 mg/kg/day of deoxycytidine (dC) and deoxythymidine (dT) under a Compassionate Use Program. Prospective motor and respiratory assessments are presented. RESULTS After 27 months of follow-up, the North Star Ambulatory Assessment improved by 11 points, he walked 195 m more in the 6 Minute-Walking-Test, ran 10 s faster in the 100-meter time velocity test, and the Forced Vital Capacity stabilized. Growth Differentiation Factor-15 (GDF15) levels, a biomarker of respiratory chain dysfunction, normalized. The only reported side effect was dose-dependent diarrhea. DISCUSSION Treatment with dC and dT can significantly improve motor performance and stabilize respiratory function safely in patients with adult-onset TK2d.
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Affiliation(s)
- Laura Bermejo-Guerrero
- Neurology Department, Neuromuscular Disorders Unit, Hospital 12 de Octubre, Madrid 28041, Spain
| | - Ana Hernández-Voth
- Pulmonology Department, Mechanical Ventilation and Neuromuscular Disorders Unit, Hospital 12 de Octubre, Madrid 28041, Spain
| | - Pablo Serrano-Lorenzo
- Spanish Network for Biomedical Research in Rare Diseases (CIBERER), Madrid 28029, Spain
| | - Alberto Blázquez
- Spanish Network for Biomedical Research in Rare Diseases (CIBERER), Madrid 28029, Spain; Mitochondrial and Neuromuscular Research Group '12 de Octubre', Hospital Research Institute (imas12), Madrid 28041, Spain
| | - Paloma Martin-Jimenez
- Neurology Department, Neuromuscular Disorders Unit, Hospital 12 de Octubre, Madrid 28041, Spain
| | - Miguel A Martin
- Spanish Network for Biomedical Research in Rare Diseases (CIBERER), Madrid 28029, Spain; Mitochondrial and Neuromuscular Research Group '12 de Octubre', Hospital Research Institute (imas12), Madrid 28041, Spain; Genetics Department, Hospital Universitario, 12 de Octubre, Madrid 28041, Spain
| | - Cristina Domínguez-González
- Neurology Department, Neuromuscular Disorders Unit, Hospital 12 de Octubre, Madrid 28041, Spain; Spanish Network for Biomedical Research in Rare Diseases (CIBERER), Madrid 28029, Spain; Mitochondrial and Neuromuscular Research Group '12 de Octubre', Hospital Research Institute (imas12), Madrid 28041, Spain.
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Wang Y, Hang L, Shou W, Li C, Dong F, Feng X, Jin R, Li B, Xiao S. Case Report: A novel RRM2B variant in a Chinese infant with mitochondrial DNA depletion syndrome and collective analyses of RRM2B variants for disease etiology. Front Pediatr 2024; 12:1363728. [PMID: 38737634 PMCID: PMC11084280 DOI: 10.3389/fped.2024.1363728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Accepted: 04/10/2024] [Indexed: 05/14/2024] Open
Abstract
Background There are few reports of infantile mitochondrial DNA depletion syndrome (MDDS) caused by variants in RRM2B and the correlation between genotype and phenotype has rarely been analyzed in detail. This study investigated an infantile patient with MDDS, from clinical characteristics to genetic causes. Methods Routine physical examinations, laboratory assays, which included gas chromatography-mass spectrometry of blood and urine, and MRI scans were performed to obtain an exact diagnosis. Whole-exome sequencing was used to pinpoint the abnormal gene and bioinformatic analyses were performed on the identified variant. Results The case presented with progressive neurologic deterioration, failure to thrive, respiratory distress and lactic acidosis. Sequencing revealed that the patient had a homozygous novel missense variant, c.155T>C (p.Ile52Thr), in exon 2 of the RRM2B gene. Multiple lines of bioinformatic evidence suggested that this was a likely detrimental variant. In addition, reported RRM2B variants were compiled from the relevant literature to analyze disease etiology. We found a distinctive distribution of genotypes across disease manifestations of different severity. Pathogenic alleles of RRM2B were significantly enriched in MDDS cases. Conclusion The novel variant is a likely genetic cause of MDDS. It expands our understanding of the pathogenic variant spectrum and the contribution of the RRM2B gene to the disease spectrum of MDDS.
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Affiliation(s)
- Yanjun Wang
- Pediatric Intensive Care Unit, Kunming Children’s Hospital, Children’s Hospital Affiliated to Kunming Medical University, Kunming, China
| | - Ling Hang
- Pediatric Intensive Care Unit, Kunming Children’s Hospital, Children’s Hospital Affiliated to Kunming Medical University, Kunming, China
| | - Weihua Shou
- Kunming Key Laboratory of Children Infection and Immunity, Yunnan Key Laboratory of Children’s Major Disease Research, Yunnan Medical Center for Pediatric Diseases, Yunnan Institute of Pediatrics, Kunming Children’s Hospital, Kunming, China
| | - Cuifen Li
- Pediatric Intensive Care Unit, Kunming Children’s Hospital, Children’s Hospital Affiliated to Kunming Medical University, Kunming, China
| | - Fangling Dong
- Pediatric Intensive Care Unit, Kunming Children’s Hospital, Children’s Hospital Affiliated to Kunming Medical University, Kunming, China
| | - Xingxing Feng
- Department of Clinical Laboratory, Kunming Children’s Hospital, Children’s Hospital Affiliated to Kunming Medical University, Kunming, China
| | - Ruohong Jin
- Pediatric Intensive Care Unit, Kunming Children’s Hospital, Children’s Hospital Affiliated to Kunming Medical University, Kunming, China
| | - Bin Li
- Pediatric Intensive Care Unit, Kunming Children’s Hospital, Children’s Hospital Affiliated to Kunming Medical University, Kunming, China
| | - Shufang Xiao
- Pediatric Intensive Care Unit, Kunming Children’s Hospital, Children’s Hospital Affiliated to Kunming Medical University, Kunming, China
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Brañas Casas R, Zuppardo A, Risato G, Dinarello A, Celeghin R, Fontana C, Grelloni E, Gilea AI, Viscomi C, Rasola A, Dalla Valle L, Lodi T, Baruffini E, Facchinello N, Argenton F, Tiso N. Zebrafish polg2 knock-out recapitulates human POLG-disorders; implications for drug treatment. Cell Death Dis 2024; 15:281. [PMID: 38643274 PMCID: PMC11032366 DOI: 10.1038/s41419-024-06622-9] [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: 11/30/2023] [Revised: 03/15/2024] [Accepted: 03/18/2024] [Indexed: 04/22/2024]
Abstract
The human mitochondrial DNA polymerase gamma is a holoenzyme, involved in mitochondrial DNA (mtDNA) replication and maintenance, composed of a catalytic subunit (POLG) and a dimeric accessory subunit (POLG2) conferring processivity. Mutations in POLG or POLG2 cause POLG-related diseases in humans, leading to a subset of Mendelian-inherited mitochondrial disorders characterized by mtDNA depletion (MDD) or accumulation of multiple deletions, presenting multi-organ defects and often leading to premature death at a young age. Considering the paucity of POLG2 models, we have generated a stable zebrafish polg2 mutant line (polg2ia304) by CRISPR/Cas9 technology, carrying a 10-nucleotide deletion with frameshift mutation and premature stop codon. Zebrafish polg2 homozygous mutants present slower development and decreased viability compared to wild type siblings, dying before the juvenile stage. Mutants display a set of POLG-related phenotypes comparable to the symptoms of human patients affected by POLG-related diseases, including remarkable MDD, altered mitochondrial network and dynamics, and reduced mitochondrial respiration. Histological analyses detected morphological alterations in high-energy demanding tissues, along with a significant disorganization of skeletal muscle fibres. Consistent with the last finding, locomotor assays highlighted a decreased larval motility. Of note, treatment with the Clofilium tosylate drug, previously shown to be effective in POLG models, could partially rescue MDD in Polg2 mutant animals. Altogether, our results point at zebrafish as an effective model to study the etiopathology of human POLG-related disorders linked to POLG2, and a suitable platform to screen the efficacy of POLG-directed drugs in POLG2-associated forms.
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Affiliation(s)
| | - Alessandro Zuppardo
- Department of Biomedical Sciences, University of Padova, Padova, 35131, Italy
| | - Giovanni Risato
- Department of Biology, University of Padova, Padova, 35131, Italy
- Department of Cardio-Thoraco-Vascular Sciences and Public Health, University of Padova, Padova, 35128, Italy
| | - Alberto Dinarello
- Department of Biology, University of Padova, Padova, 35131, Italy
- Novo Nordisk Foundation Center for Stem Cell Medicine (reNEW), University of Copenhagen, Copenhagen, 2200, Denmark
| | - Rudy Celeghin
- Department of Cardio-Thoraco-Vascular Sciences and Public Health, University of Padova, Padova, 35128, Italy
| | - Camilla Fontana
- Department of Biology, University of Padova, Padova, 35131, Italy
- Department of Animal and Aquatic Sciences, Faculty of Agriculture, Chiang Mai University, Chiang Mai, 50200, Thailand
| | | | - Alexandru Ionut Gilea
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parma, 43124, Italy
| | - Carlo Viscomi
- Department of Biomedical Sciences, University of Padova, Padova, 35131, Italy
| | - Andrea Rasola
- Department of Biomedical Sciences, University of Padova, Padova, 35131, Italy
| | | | - Tiziana Lodi
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parma, 43124, Italy
| | - Enrico Baruffini
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parma, 43124, Italy
| | - Nicola Facchinello
- Neuroscience Institute, Italian Research Council (CNR), 35131, Padova, Italy.
| | | | - Natascia Tiso
- Department of Biology, University of Padova, Padova, 35131, Italy.
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Shammas MK, Nie Y, Gilsrud A, Huang X, Narendra DP, Chinnery PF. CHCHD10 mutations induce tissue-specific mitochondrial DNA deletions with a distinct signature. Hum Mol Genet 2023; 33:91-101. [PMID: 37815936 PMCID: PMC10729859 DOI: 10.1093/hmg/ddad161] [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: 06/19/2023] [Revised: 09/11/2023] [Accepted: 09/19/2023] [Indexed: 10/12/2023] Open
Abstract
Mutations affecting the mitochondrial intermembrane space protein CHCHD10 cause human disease, but it is not known why different amino acid substitutions cause markedly different clinical phenotypes, including amyotrophic lateral sclerosis-frontotemporal dementia, spinal muscular atrophy Jokela-type, isolated autosomal dominant mitochondrial myopathy and cardiomyopathy. CHCHD10 mutations have been associated with deletions of mitochondrial DNA (mtDNA deletions), raising the possibility that these explain the clinical variability. Here, we sequenced mtDNA obtained from hearts, skeletal muscle, livers and spinal cords of WT and Chchd10 G58R or S59L knockin mice to characterise the mtDNA deletion signatures of the two mutant lines. We found that the deletion levels were higher in G58R and S59L mice than in WT mice in some tissues depending on the Chchd10 genotype, and the deletion burden increased with age. Furthermore, we observed that the spinal cord was less prone to the development of mtDNA deletions than the other tissues examined. Finally, in addition to accelerating the rate of naturally occurring deletions, Chchd10 mutations also led to the accumulation of a novel set of deletions characterised by shorter direct repeats flanking the deletion breakpoints. Our results indicate that Chchd10 mutations in mice induce tissue-specific deletions which may also contribute to the clinical phenotype associated with these mutations in humans.
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Affiliation(s)
- Mario K Shammas
- Department of Clinical Neurosciences, School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0QQ, United Kingdom
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, United Kingdom
- Inherited Movement Disorders Unit, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, Bethesda, MD 20892, United States
| | - Yu Nie
- Department of Clinical Neurosciences, School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0QQ, United Kingdom
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, United Kingdom
| | - Alexandra Gilsrud
- Inherited Movement Disorders Unit, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, Bethesda, MD 20892, United States
| | - Xiaoping Huang
- Inherited Movement Disorders Unit, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, Bethesda, MD 20892, United States
| | - Derek P Narendra
- Inherited Movement Disorders Unit, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 35 Convent Drive, Bethesda, MD 20892, United States
| | - Patrick F Chinnery
- Department of Clinical Neurosciences, School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0QQ, United Kingdom
- Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, United Kingdom
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10
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Serag M, Plutino M, Charles P, Azulay JP, Chaussenot A, Paquis-Flucklinger V, Ait-El-Mkadem Saadi S, Rouzier C. A Case Report of SYNE1 Deficiency-Mimicking Mitochondrial Disease and the Value of Pangenomic Investigations. Genes (Basel) 2023; 14:2154. [PMID: 38136976 PMCID: PMC10743207 DOI: 10.3390/genes14122154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 11/24/2023] [Accepted: 11/27/2023] [Indexed: 12/24/2023] Open
Abstract
Mitochondrial disorders are characterized by a huge clinical, biochemical, and genetic heterogeneity, which poses significant diagnostic challenges. Several studies report that more than 50% of patients with suspected mitochondrial disease could have a non-mitochondrial disorder. Thus, only the identification of the causative pathogenic variant can confirm the diagnosis. Herein, we describe the diagnostic journey of a family suspected of having a mitochondrial disorder who were referred to our Genetics Department. The proband presented with the association of cerebellar ataxia, COX-negative fibers on muscle histology, and mtDNA deletions. Whole exome sequencing (WES), supplemented by a high-resolution array, comparative genomic hybridization (array-CGH), allowed us to identify two pathogenic variants in the non-mitochondrial SYNE1 gene. The proband and her affected sister were found to be compound heterozygous for a known nonsense variant (c.13258C>T, p.(Arg4420Ter)), and a large intragenic deletion that was predicted to result in a loss of function. To our knowledge, this is the first report of a large intragenic deletion of SYNE1 in patients with cerebellar ataxia (ARCA1). This report highlights the interest in a pangenomic approach to identify the genetic basis in heterogeneous neuromuscular patients with the possible cause of mitochondrial disease. Moreover, even rare copy number variations should be considered in patients with a phenotype suggestive of SYNE1 deficiency.
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Affiliation(s)
- Mounir Serag
- Service de Génétique Médicale, Hôpital l’Archet 2, CHU de Nice, 151 Route Saint-Antoine de Ginestière, 06202 Nice, France; (M.S.); (M.P.); (A.C.); (V.P.-F.); (S.A.-E.-M.S.)
- CNRS UMR7284/ INSERM U1081, Faculté de Médecine, Université Côte d’Azur, 06107 Nice, France
| | - Morgane Plutino
- Service de Génétique Médicale, Hôpital l’Archet 2, CHU de Nice, 151 Route Saint-Antoine de Ginestière, 06202 Nice, France; (M.S.); (M.P.); (A.C.); (V.P.-F.); (S.A.-E.-M.S.)
- CNRS UMR7284/ INSERM U1081, Faculté de Médecine, Université Côte d’Azur, 06107 Nice, France
| | - Perrine Charles
- Service de Génétique, La Pitié-Salpêtrière, AP-HP, 75610 Paris, France;
| | | | - Annabelle Chaussenot
- Service de Génétique Médicale, Hôpital l’Archet 2, CHU de Nice, 151 Route Saint-Antoine de Ginestière, 06202 Nice, France; (M.S.); (M.P.); (A.C.); (V.P.-F.); (S.A.-E.-M.S.)
- CNRS UMR7284/ INSERM U1081, Faculté de Médecine, Université Côte d’Azur, 06107 Nice, France
| | - Véronique Paquis-Flucklinger
- Service de Génétique Médicale, Hôpital l’Archet 2, CHU de Nice, 151 Route Saint-Antoine de Ginestière, 06202 Nice, France; (M.S.); (M.P.); (A.C.); (V.P.-F.); (S.A.-E.-M.S.)
- CNRS UMR7284/ INSERM U1081, Faculté de Médecine, Université Côte d’Azur, 06107 Nice, France
| | - Samira Ait-El-Mkadem Saadi
- Service de Génétique Médicale, Hôpital l’Archet 2, CHU de Nice, 151 Route Saint-Antoine de Ginestière, 06202 Nice, France; (M.S.); (M.P.); (A.C.); (V.P.-F.); (S.A.-E.-M.S.)
- CNRS UMR7284/ INSERM U1081, Faculté de Médecine, Université Côte d’Azur, 06107 Nice, France
| | - Cécile Rouzier
- Service de Génétique Médicale, Hôpital l’Archet 2, CHU de Nice, 151 Route Saint-Antoine de Ginestière, 06202 Nice, France; (M.S.); (M.P.); (A.C.); (V.P.-F.); (S.A.-E.-M.S.)
- CNRS UMR7284/ INSERM U1081, Faculté de Médecine, Université Côte d’Azur, 06107 Nice, France
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11
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Corrà S, Checchetto V, Brischigliaro M, Rampazzo C, Bottani E, Gagliani C, Cortese K, De Pittà C, Roverso M, De Stefani D, Bogialli S, Zeviani M, Viscomi C, Szabò I, Costa R. Drosophila Mpv17 forms an ion channel and regulates energy metabolism. iScience 2023; 26:107955. [PMID: 37810222 PMCID: PMC10558772 DOI: 10.1016/j.isci.2023.107955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 07/15/2023] [Accepted: 09/14/2023] [Indexed: 10/10/2023] Open
Abstract
Mutations in MPV17 are a major contributor to mitochondrial DNA (mtDNA) depletion syndromes, a group of inherited genetic conditions due to mtDNA instability. To investigate the role of MPV17 in mtDNA maintenance, we generated and characterized a Drosophila melanogaster Mpv17 (dMpv17) KO model showing that the absence of dMpv17 caused profound mtDNA depletion in the fat body but not in other tissues, increased glycolytic flux and reduced lifespan in starvation. Accordingly, the expression of key genes of glycogenolysis and glycolysis was upregulated in dMpv17 KO flies. In addition, we demonstrated that dMpv17 formed a channel in planar lipid bilayers at physiological ionic conditions, and its electrophysiological hallmarks were affected by pathological mutations. Importantly, the reconstituted channel translocated uridine but not orotate across the membrane. Our results indicate that dMpv17 forms a channel involved in translocation of key metabolites and highlight the importance of dMpv17 in energy homeostasis and mitochondrial function.
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Affiliation(s)
- Samantha Corrà
- Veneto Institute of Molecular Medicine (VIMM), Padova, Italy
| | | | | | | | - Emanuela Bottani
- Department of Diagnostic and Public Health, University of Verona, Verona, Italy
| | - Cristina Gagliani
- Department of Experimental Medicine, University of Genova, Genova, Italy
| | - Katia Cortese
- Department of Experimental Medicine, University of Genova, Genova, Italy
| | | | - Marco Roverso
- Department of Chemical Sciences, University of Padova, Padova, Italy
| | - Diego De Stefani
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Sara Bogialli
- Department of Chemical Sciences, University of Padova, Padova, Italy
| | - Massimo Zeviani
- Department of Neurosciences, University of Padova, Padova, Italy
- IRCCS Materno Infantile Burlo Garofolo, Trieste, Italy
| | - Carlo Viscomi
- Veneto Institute of Molecular Medicine (VIMM), Padova, Italy
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Ildiko Szabò
- Department of Biology, University of Padova, Padova, Italy
| | - Rodolfo Costa
- Department of Biology, University of Padova, Padova, Italy
- Institute of Neuroscience, National Research Council of Italy (CNR), Padova, Italy
- Chronobiology Section, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
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12
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Wu H, Zhang W, Xu F, Peng K, Liu X, Ding W, Ma Q, Cheng H, Wang X. C17orf80 binds the mitochondrial genome to promote its replication. J Cell Biol 2023; 222:e202302037. [PMID: 37676315 PMCID: PMC10484793 DOI: 10.1083/jcb.202302037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 06/26/2023] [Accepted: 07/17/2023] [Indexed: 09/08/2023] Open
Abstract
Serving as the power plant and signaling hub of a cell, mitochondria contain their own genome which encodes proteins essential for energy metabolism and forms DNA-protein assemblies called nucleoids. Mitochondrial DNA (mtDNA) exists in multiple copies within each cell ranging from hundreds to tens of thousands. Maintaining mtDNA homeostasis is vital for healthy cells, and its dysregulation causes multiple human diseases. However, the players involved in regulating mtDNA maintenance are largely unknown though the core components of its replication machinery have been characterized. Here, we identify C17orf80, a functionally uncharacterized protein, as a critical player in maintaining mtDNA homeostasis. C17orf80 primarily localizes to mitochondrial nucleoid foci and exhibits robust double-stranded DNA binding activity throughout the mitochondrial genome, thus constituting a bona fide new mitochondrial nucleoid protein. It controls mtDNA levels by promoting mtDNA replication and plays important roles in mitochondrial metabolism and cell proliferation. Our findings provide a potential target for therapeutics of human diseases associated with defective mtDNA control.
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Affiliation(s)
- Hao Wu
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing, China
- Academy of Advanced Interdisciplinary Study, Peking University, Beijing, China
| | - Wenshuo Zhang
- Peking-Tsinghua Center for Life Sciences, College of Life Sciences, Peking University, Beijing, China
| | - Fengli Xu
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing, China
| | - Kun Peng
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing, China
| | - Xiaoyu Liu
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing, China
| | - Wanqiu Ding
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing, China
| | - Qi Ma
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing, China
| | - Heping Cheng
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing, China
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational Medicine, Nanjing, China
| | - Xianhua Wang
- State Key Laboratory of Membrane Biology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, College of Future Technology, Peking University, Beijing, China
- Research Unit of Mitochondria in Brain Diseases, Chinese Academy of Medical Sciences, PKU-Nanjing Institute of Translational Medicine, Nanjing, China
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13
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Chen C, Guan MX. Induced pluripotent stem cells: ex vivo models for human diseases due to mitochondrial DNA mutations. J Biomed Sci 2023; 30:82. [PMID: 37737178 PMCID: PMC10515435 DOI: 10.1186/s12929-023-00967-7] [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: 04/05/2023] [Accepted: 08/16/2023] [Indexed: 09/23/2023] Open
Abstract
Mitochondria are essential organelles for cellular metabolism and physiology in eukaryotic cells. Human mitochondria have their own genome (mtDNA), which is maternally inherited with 37 genes, encoding 13 polypeptides for oxidative phosphorylation, and 22 tRNAs and 2 rRNAs for translation. mtDNA mutations are associated with a wide spectrum of degenerative and neuromuscular diseases. However, the pathophysiology of mitochondrial diseases, especially for threshold effect and tissue specificity, is not well understood and there is no effective treatment for these disorders. Especially, the lack of appropriate cell and animal disease models has been significant obstacles for deep elucidating the pathophysiology of maternally transmitted diseases and developing the effective therapy approach. The use of human induced pluripotent stem cells (iPSCs) derived from patients to obtain terminally differentiated specific lineages such as inner ear hair cells is a revolutionary approach to deeply understand pathogenic mechanisms and develop the therapeutic interventions of mitochondrial disorders. Here, we review the recent advances in patients-derived iPSCs as ex vivo models for mitochondrial diseases. Those patients-derived iPSCs have been differentiated into specific targeting cells such as retinal ganglion cells and eventually organoid for the disease modeling. These disease models have advanced our understanding of the pathophysiology of maternally inherited diseases and stepped toward therapeutic interventions for these diseases.
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Affiliation(s)
- Chao Chen
- Center for Mitochondrial Biomedicine, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Min-Xin Guan
- Center for Mitochondrial Biomedicine, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
- Division of Medical Genetics and Genomics, The Children's Hospital, Zhejiang University School of Medicine and National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China.
- Institute of Genetics, Zhejiang University International School of Medicine, 866 Yuhangtang Road, Hangzhou, 310058, Zhejiang, China.
- Zhejiang Provincial Key Laboratory of Genetic and Developmental Disorders, Hangzhou, Zhejiang, China.
- Key Lab of Reproductive Genetics, Ministry of Education of PRC, Zhejiang University, Hangzhou, Zhejiang, China.
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14
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Picca A, Guerra F, Calvani R, Coelho-Júnior HJ, Leeuwenburgh C, Bucci C, Marzetti E. The contribution of mitochondrial DNA alterations to aging, cancer, and neurodegeneration. Exp Gerontol 2023; 178:112203. [PMID: 37172915 DOI: 10.1016/j.exger.2023.112203] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 04/24/2023] [Accepted: 05/09/2023] [Indexed: 05/15/2023]
Abstract
Mitochondrial DNA (mtDNA) is as a double-stranded molecule existing in hundreds to thousands copies in cells depending on cell metabolism and exposure to endogenous and/or environmental stressors. The coordination of mtDNA replication and transcription regulates the pace of mitochondrial biogenesis to guarantee the minimum number of organelles per cell. mtDNA inheritance follows a maternal lineage, although bi-parental inheritance has been reported in some species and in the case of mitochondrial diseases in humans. mtDNA mutations (e.g., point mutations, deletions, copy number variations) have been identified in the setting of several human diseases. For instance, sporadic and inherited rare disorders involving the nervous system as well higher risk of developing cancer and neurodegenerative conditions, including Parkinson's and Alzheimer's disease, have been associated with polymorphic mtDNA variants. An accrual of mtDNA mutations has also been identified in several tissues and organs, including heart and muscle, of old experimental animals and humans, which may contribute to the development of aging phenotypes. The role played by mtDNA homeostasis and mtDNA quality control pathways in human health is actively investigated for the possibility of developing targeted therapeutics for a wide range of conditions.
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Affiliation(s)
- Anna Picca
- Department of Medicine and Surgery, LUM University, 70100 Casamassima, Italy; Fondazione Policlinico Universitario "Agostino Gemelli" IRCCS, 00168 Rome, Italy
| | - Flora Guerra
- Department of Biological and Environmental Sciences and Technologies, University of Salento, 73100 Lecce, Italy
| | - Riccardo Calvani
- Fondazione Policlinico Universitario "Agostino Gemelli" IRCCS, 00168 Rome, Italy; Department of Geriatrics and Orthopedics, Università Cattolica del Sacro Cuore, 00168 Rome, Italy.
| | - Hélio José Coelho-Júnior
- Department of Geriatrics and Orthopedics, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
| | | | - Cecilia Bucci
- Department of Biological and Environmental Sciences and Technologies, University of Salento, 73100 Lecce, Italy
| | - Emanuele Marzetti
- Fondazione Policlinico Universitario "Agostino Gemelli" IRCCS, 00168 Rome, Italy; Department of Geriatrics and Orthopedics, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
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15
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Haque S, Crawley K, Shrestha R, Schofield D, Sue CM. Healthcare resource utilization of patients with mitochondrial disease in an outpatient hospital setting. Orphanet J Rare Dis 2023; 18:129. [PMID: 37246228 DOI: 10.1186/s13023-023-02746-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 05/18/2023] [Indexed: 05/30/2023] Open
Abstract
BACKGROUND AND OBJECTIVES Mitochondrial diseases present as multi-system disorders requiring a comprehensive multidisciplinary approach. The data on healthcare resource utilization associated with mitochondrial diseases and the clinical drivers of these costs are limited including for the out-patient setting where the majority of the clinical care for mitochondrial disease patients occurs. We performed a cross-sectional retrospective study of out-patient healthcare resource utilization and costs for patients with a confirmed diagnosis of mitochondrial disease. METHODS We recruited participants from the Mitochondrial Disease Clinic in Sydney and stratified them into three groups: those with mitochondrial DNA (mtDNA) mutations (Group 1), those with nuclear DNA (nDNA) mutations and the predominant phenotype of chronic progressive external ophthalmoplegia (CPEO) or optic atrophy (Group 2) and those without a confirmed genetic diagnosis but clinical criteria and muscle biopsy findings supportive of a diagnosis of mitochondrial disease (Group 3). Data was collected through retrospective chart review and out-patient costs were calculated using the Medicare Benefits Schedule. RESULTS We analyzed the data from 91 participants and found that Group 1 had the greatest average out-patient costs per person per annum ($838.02; SD 809.72). Neurological investigations were the largest driver of outpatient healthcare costs in all groups (average costs per person per annum:-Group 1: $364.11; SD 340.93, Group 2: $247.83; SD 113.86 and Group 3: $239.57; SD 145.69) consistent with the high frequency (94.5%) of neurological symptoms. Gastroenterological and cardiac-related out-patient costs were also major contributors to out-patient healthcare resource utilization in Groups 1 and 3. In Group 2, ophthalmology was the second-most resource intensive specialty ($136.85; SD 173.35). The Group 3 had the greatest average healthcare resource utilization per person over the entire duration of out-patient clinic care ($5815.86; SD 3520.40) most likely due to the lack of a molecular diagnosis and a less customized management approach. CONCLUSION The drivers of healthcare resource utilization are dependent on the phenotype-genotype characteristics. Neurological, cardiac, and gastroenterological costs were the top three drivers in the out-patient clinics unless the patient had nDNA mutations with predominant phenotype of CPEO and/or optic atrophy wherein ophthalmological-related costs were the second most resource intensive driver.
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Affiliation(s)
- Sameen Haque
- Nepean Hospital, Derby Street, Kingswood, NSW, 2747, Australia.
- The Kolling Institute, Royal North Shore Hospital, Reserve Road, St Leonards, NSW, 2065, Australia.
| | - Karen Crawley
- The Kolling Institute, Royal North Shore Hospital, Reserve Road, St Leonards, NSW, 2065, Australia
| | - Rupendra Shrestha
- Centre for Economic Impacts of Genomic Medicine (GenIMPACT), Macquarie Business School, Macquarie University, Eastern Rd, Macquarie Park, NSW, 2109, Australia
| | - Deborah Schofield
- Centre for Economic Impacts of Genomic Medicine (GenIMPACT), Macquarie Business School, Macquarie University, Eastern Rd, Macquarie Park, NSW, 2109, Australia
| | - Carolyn M Sue
- The Kolling Institute, Royal North Shore Hospital, Reserve Road, St Leonards, NSW, 2065, Australia
- Neuroscience Research Australia, University of New South Wales, Sydney, Australia
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16
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Zhao K, Wu Y, Zhao D, Zhang H, Lin J, Wang Y. Six mitophagy-related hub genes as peripheral blood biomarkers of Alzheimer's disease and their immune cell infiltration correlation. Front Neurosci 2023; 17:1125281. [PMID: 37274215 PMCID: PMC10232817 DOI: 10.3389/fnins.2023.1125281] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 03/30/2023] [Indexed: 06/06/2023] Open
Abstract
Background Alzheimer's disease (AD), a neurodegenerative disorder with progressive symptoms, seriously endangers human health worldwide. AD diagnosis and treatment are challenging, but molecular biomarkers show diagnostic potential. This study aimed to investigate AD biomarkers in the peripheral blood. Method Utilizing three microarray datasets, we systematically analyzed the differences in expression and predictive value of mitophagy-related hub genes (MRHGs) in the peripheral blood mononuclear cells of patients with AD to identify potential diagnostic biomarkers. Subsequently, a protein-protein interaction network was constructed to identify hub genes, and functional enrichment analyses were performed. Using consistent clustering analysis, AD subtypes with significant differences were determined. Finally, infiltration patterns of immune cells in AD subtypes and the relationship between MRHGs and immune cells were investigated by two algorithms, CIBERSORT and single-sample gene set enrichment analysis (ssGSEA). Results Our study identified 53 AD- and mitophagy-related differentially expressed genes and six MRHGs, which may be potential biomarkers for diagnosing AD. Functional analysis revealed that six MRHGs significantly affected biologically relevant functions and signaling pathways such as IL-4 Signaling Pathway, RUNX3 Regulates Notch Signaling Pathway, IL-1 and Megakaryocytes in Obesity Pathway, and Overview of Leukocyteintrinsic Hippo Pathway. Furthermore, CIBERSORT and ssGSEA algorithms were used for all AD samples to analyze the abundance of infiltrating immune cells in the two disease subtypes. The results showed that these subtypes were significantly related to immune cell types such as activated mast cells, regulatory T cells, M0 macrophages, and neutrophils. Moreover, specific MRHGs were significantly correlated with immune cell levels. Conclusion Our findings suggest that MRHGs may contribute to the development and prognosis of AD. The six identified MRHGs could be used as valuable diagnostic biomarkers for further research on AD. This study may provide new promising diagnostic and therapeutic targets in the peripheral blood of patients with AD.
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Affiliation(s)
- Kun Zhao
- Department of Neurology, Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu, China
| | - Yinyan Wu
- Department of Neurology, Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu, China
| | - Dongliang Zhao
- Department of Neurology, Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu, China
| | - Hui Zhang
- Fujian Center for Safety Evaluation of New Drug, Fujian Medical University, Fuzhou, Fujian, China
| | - Jianyang Lin
- Department of General Surgery, Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu, China
| | - Yuanwei Wang
- Department of Neurology, Shuyang Hospital Affiliated to Xuzhou Medical University, Shuyang, Jiangsu, China
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Restrepo-Vera JL, Rovira-Moreno E, Ramón J, Codina-Sola M, Llauradó A, Salvadó M, Sánchez-Tejerina D, Sotoca J, Martínez-Sáez E, Martí R, García-Arumí E, Juntas-Morales R. Identification of two novel RRM2B variants associated with autosomal recessive progressive external ophthalmoplegia in a family with pseudodominant inheritance pattern. J Hum Genet 2023:10.1038/s10038-023-01144-2. [PMID: 36959467 DOI: 10.1038/s10038-023-01144-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 02/07/2023] [Accepted: 02/28/2023] [Indexed: 03/25/2023]
Abstract
RRM2B encodes the p53-inducible small subunit (p53R2) of ribonucleotide reductase, a key protein for mitochondrial DNA (mtDNA) synthesis. Pathogenic variants in this gene result in familial mitochondrial disease in adults and children, secondary to a maintenance disorder of mtDNA. This study describes two patients, mother and son, with early-onset chronic progressive external ophthalmoplegia (PEO). Skeletal muscle biopsy from the latter was examined: cytochrome c oxidase (COX)-negative fibres were shown, and molecular studies revealed multiple mtDNA deletions. A next-generation sequencing gene panel for nuclear-encoded mitochondrial maintenance genes identified two unreported heterozygous missense variants (c.514 G > A and c.682 G > A) in the clinically affected son. The clinically affected mother harboured the first variant in homozygous state, and the clinically unaffected father harboured the remaining variant in heterozygous state. In silico analyses predicted both variants as deleterious. Cell culture studies revealed that patients' skin fibroblasts, but not fibroblasts from healthy controls, responded to nucleoside supplementation with enhanced mtDNA repopulation, thus suggesting an in vitro functional difference in patients' cells. Our results support the pathogenicity of two novel RRM2B variants found in two patients with autosomal recessive PEO with multiple mtDNA deletions inherited with a pseudodominant pattern.
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Affiliation(s)
- Juan Luis Restrepo-Vera
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Eulàlia Rovira-Moreno
- Department of Clinical and Molecular Genetics, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
- Medicine Genetics Group, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Javier Ramón
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Marta Codina-Sola
- Department of Clinical and Molecular Genetics, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
- Medicine Genetics Group, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Arnau Llauradó
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Maria Salvadó
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Daniel Sánchez-Tejerina
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Javier Sotoca
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Elena Martínez-Sáez
- Department of Pathology, Hospital Vall d'Hebron, Universitat Autònoma Barcelona, 08035, Barcelona, Spain
| | - Ramon Martí
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Elena García-Arumí
- Department of Clinical and Molecular Genetics, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain.
- Research Group on Neuromuscular and Mitochondrial Diseases, Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain.
- Biomedical Network Research Centre on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain.
| | - Raul Juntas-Morales
- Neuromuscular Diseases Unit, European Reference Network on Rare Neuromuscular Diseases, Department of Neurology, Hospital Vall d'Hebron, Universitat Autònoma de Barcelona, Barcelona, Spain.
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18
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Xie X, Zhu X. Visualization of mtDNA Using FISH. Methods Mol Biol 2023; 2615:89-98. [PMID: 36807786 DOI: 10.1007/978-1-0716-2922-2_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Proper mitochondrial DNA (mtDNA) levels are critical for many cellular biological functions and are associated with aging and many mitochondria disorders. Defects in core subunits of the mtDNA replication machinery lead to decreased mtDNA levels. Other indirect mitochondrial contexts including ATP concentration, lipid composition, and nucleotide composition also contribute to mtDNA maintenance. Furthermore, mtDNA molecules are distributed evenly throughout the mitochondrial network. This uniform distribution pattern is required for oxidative phosphorylation and ATP production and has been linked to many diseases when perturbed. Thus, it is important to visualize mtDNA in the cellular context. Here we provide detailed protocols for cellular visualization of mtDNA using fluorescence in situ hybridization (FISH). The fluorescent signals are targeted to the mtDNA sequence directly, ensuring both sensitivity and specificity. This mtDNA FISH method can be combined with immunostaining and used for visualizing mtDNA-protein interactions and dynamics.
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Affiliation(s)
- Xie Xie
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Gothenburg, Sweden
| | - Xuefeng Zhu
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Gothenburg, Sweden.
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19
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Misic J, Milenkovic D. Studying Mitochondrial Nucleic Acid Synthesis Utilizing Intact Isolated Mitochondria. Methods Mol Biol 2023; 2615:219-228. [PMID: 36807795 DOI: 10.1007/978-1-0716-2922-2_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Mitochondria are eukaryotic organelles of endosymbiotic origin that contain their own genetic material, mitochondrial DNA (mtDNA), and dedicated systems for mtDNA maintenance and expression. MtDNA molecules encode a limited number of proteins that are nevertheless all essential subunits of the mitochondrial oxidative phosphorylation system. Here, we describe protocols to monitor DNA and RNA synthesis in intact, isolated mitochondria. These in organello synthesis protocols are valuable techniques for studying the mechanisms and regulation of mtDNA maintenance and expression.
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Affiliation(s)
- Jelena Misic
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
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20
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Wu S, Longley MJ, Lujan SA, Kunkel TA, Copeland WC. Mitochondrial DNA Enrichment for Sensitive Next-Generation Sequencing. Methods Mol Biol 2023; 2615:427-441. [PMID: 36807807 DOI: 10.1007/978-1-0716-2922-2_28] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Mitochondrial DNA (mtDNA) encodes components essential for cellular respiration. Low levels of point mutations and deletions accumulate in mtDNA during normal aging. However, improper maintenance of mtDNA results in mitochondrial diseases, stemming from progressive loss of mitochondrial function through the accelerated formation of deletions and mutations in mtDNA. To better understand the molecular mechanisms underlying the creation and propagation of mtDNA deletions, we developed the LostArc next-generation DNA sequencing pipeline to detect and quantify rare mtDNA species in small tissue samples. LostArc procedures are designed to minimize PCR amplification of mtDNA and instead achieve enrichment of mtDNA by selective destruction of nuclear DNA. This approach leads to cost-effective, high-depth sequencing of mtDNA with a sensitivity sufficient to identify one mtDNA deletion per million mtDNA circles. Here, we describe detailed protocols for isolation of genomic DNA from mouse tissues, enrichment of mtDNA through enzymatic destruction of linear nuclear DNA, and preparation of libraries for unbiased next-generation sequencing of mtDNA.
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Affiliation(s)
- Shilan Wu
- Genome Integrity and Structural Biology Laboratory, Mitochondrial DNA Replication Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Matthew J Longley
- Genome Integrity and Structural Biology Laboratory, Mitochondrial DNA Replication Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Scott A Lujan
- Genome Integrity and Structural Biology Laboratory, DNA Replication Fidelity Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - Thomas A Kunkel
- Genome Integrity and Structural Biology Laboratory, DNA Replication Fidelity Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA
| | - William C Copeland
- Genome Integrity and Structural Biology Laboratory, Mitochondrial DNA Replication Group, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA.
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21
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Synofzik M, Rugarli E, Reid E, Schüle R. Ataxia and spastic paraplegia in mitochondrial disease. HANDBOOK OF CLINICAL NEUROLOGY 2023; 194:79-98. [PMID: 36813322 DOI: 10.1016/b978-0-12-821751-1.00009-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Degenerative ataxias and hereditary spastic paraplegias (HSPs) form a continuous, often overlapping disease spectrum sharing not only phenotypic features and underlying genes, but also cellular pathways and disease mechanisms. Mitochondrial metabolism presents a major molecular theme underlying both multiple ataxias and HSPs, thus indicating a heightened vulnerability of Purkinje cells, spinocerebellar tracts, and motor neurons to mitochondrial dysfunction, which is of particular interest for translational approaches. Mitochondrial dysfunction might be the primary (upstream) or secondary (downstream) result of a genetic defect, with underlying genetic defects in nuclear-encoded genes being much more frequent than in mtDNA genes in both, ataxias and HSPs. Here, we outline the substantial number of ataxias, spastic ataxias and HSPs caused by mutated genes implicated in (primary or secondary) mitochondrial dysfunction, highlighting several key "mitochondrial" ataxias and HSPs which are of particular interest for their frequency, pathogenesis and translational opportunities. We then showcase prototypic mitochondrial mechanisms by which disruption of these ataxia and HSP genes contributes to Purkinje cells or corticospinal neuron dysfunction, thus elucidating hypotheses on Purkinje cells and corticospinal neuron vulnerability to mitochondrial dysfunction.
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Affiliation(s)
- Matthis Synofzik
- Department of Neurodegenerative Diseases, Center for Neurology & Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany; German Center of Neurodegenerative Diseases (DZNE), Tübingen, Germany.
| | - Elena Rugarli
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, and Center for Molecular Medicine, University of Cologne, Cologne, Germany
| | - Evan Reid
- Cambridge Institute for Medical Research and Department of Medical Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Rebecca Schüle
- Department of Neurodegenerative Diseases, Center for Neurology & Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany; German Center of Neurodegenerative Diseases (DZNE), Tübingen, Germany
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22
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De Nicolo B, Cataldi-Stagetti E, Diquigiovanni C, Bonora E. Calcium and Reactive Oxygen Species Signaling Interplays in Cardiac Physiology and Pathologies. Antioxidants (Basel) 2023; 12:antiox12020353. [PMID: 36829912 PMCID: PMC9952851 DOI: 10.3390/antiox12020353] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 01/27/2023] [Accepted: 01/31/2023] [Indexed: 02/05/2023] Open
Abstract
Mitochondria are key players in energy production, critical activity for the smooth functioning of energy-demanding organs such as the muscles, brain, and heart. Therefore, dysregulation or alterations in mitochondrial bioenergetics primarily perturb these organs. Within the cell, mitochondria are the major site of reactive oxygen species (ROS) production through the activity of different enzymes since it is one of the organelles with the major availability of oxygen. ROS can act as signaling molecules in a number of different pathways by modulating calcium (Ca2+) signaling. Interactions among ROS and calcium signaling can be considered bidirectional, with ROS regulating cellular Ca2+ signaling, whereas Ca2+ signaling is essential for ROS production. In particular, we will discuss how alterations in the crosstalk between ROS and Ca2+ can lead to mitochondrial bioenergetics dysfunctions and the consequent damage to tissues at high energy demand, such as the heart. Changes in Ca2+ can induce mitochondrial alterations associated with reduced ATP production and increased production of ROS. These changes in Ca2+ levels and ROS generation completely paralyze cardiac contractility. Thus, ROS can hinder the excitation-contraction coupling, inducing arrhythmias, hypertrophy, apoptosis, or necrosis of cardiac cells. These interplays in the cardiovascular system are the focus of this review.
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Affiliation(s)
- Bianca De Nicolo
- Department of Medical and Surgical Sciences, University of Bologna, 40138 Bologna, Italy
| | - Erica Cataldi-Stagetti
- Department of Medical and Surgical Sciences, University of Bologna, 40138 Bologna, Italy
| | - Chiara Diquigiovanni
- Department of Medical and Surgical Sciences, University of Bologna, 40138 Bologna, Italy
- Correspondence: ; Tel.: +39-051209476
| | - Elena Bonora
- Department of Medical and Surgical Sciences, University of Bologna, 40138 Bologna, Italy
- Medical Genetics Unit, IRCCS Azienda Ospedaliero-Universitaria di Bologna, 40138 Bologna, Italy
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23
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Abstract
Progressive external ophthalmoplegia (PEO), characterized by ptosis and impaired eye movements, is a clinical syndrome with an expanding number of etiologically distinct subtypes. Advances in molecular genetics have revealed numerous pathogenic causes of PEO, originally heralded in 1988 by the detection of single large-scale deletions of mitochondrial DNA (mtDNA) in skeletal muscle of people with PEO and Kearns-Sayre syndrome. Since then, multiple point variants of mtDNA and nuclear genes have been identified to cause mitochondrial PEO and PEO-plus syndromes, including mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) and sensory ataxic neuropathy dysarthria ophthalmoplegia (SANDO). Intriguingly, many of those nuclear DNA pathogenic variants impair maintenance of the mitochondrial genome causing downstream mtDNA multiple deletions and depletion. In addition, numerous genetic causes of nonmitochondrial PEO have been identified.
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Affiliation(s)
- Michio Hirano
- H. Houston Merritt Neuromuscular Research Center, Neuromuscular Medicine Division, Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States.
| | - Robert D S Pitceathly
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom; NHS Highly Specialised Service for Rare Mitochondrial Disorders, Queen Square Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, London, United Kingdom
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24
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Maiorana A, Tagliaferri F, Dionisi-Vici C. Current understanding on pathogenesis and effective treatment of glycogen storage disease type Ib with empagliflozin: new insights coming from diabetes for its potential implications in other metabolic disorders. Front Endocrinol (Lausanne) 2023; 14:1145111. [PMID: 37152929 PMCID: PMC10160627 DOI: 10.3389/fendo.2023.1145111] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Accepted: 04/10/2023] [Indexed: 05/09/2023] Open
Abstract
Glycogen storage type Ib (GSDIb) is a rare inborn error of metabolism caused by glucose-6-phosphate transporter (G6PT, SLC37A4) deficiency. G6PT defect results in excessive accumulation of glycogen and fat in the liver, kidney, and intestinal mucosa and into both glycogenolysis and gluconeogenesis impairment. Clinical features include hepatomegaly, hypoglycemia, lactic acidemia, hyperuricemia, hyperlipidemia, and growth retardation. Long-term complications are liver adenoma, hepatocarcinoma, nephropathy and osteoporosis. The hallmark of GSDIb is neutropenia, with impaired neutrophil function, recurrent infections and inflammatory bowel disease. Alongside classical nutritional therapy with carbohydrates supplementation and immunological therapy with granulocyte colony-stimulating factor, the emerging role of 1,5-anhydroglucitol in the pathogenesis of neutrophil dysfunction led to repurpose empagliflozin, an inhibitor of the renal glucose transporter SGLT2: the current literature of its off-label use in GSDIb patients reports beneficial effects on neutrophil dysfunction and its clinical consequences. Surprisingly, this glucose-lowering drug ameliorated the glycemic and metabolic control in GSDIb patients. Furthermore, numerous studies from big cohorts of type 2 diabetes patients showed the efficacy of empagliflozin in reducing the cardiovascular risk, the progression of kidney disease, the NAFLD and the metabolic syndrome. Beneficial effects have also been described on peripheral neuropathy in a prediabetic rat model. Increasing evidences highlight the role of empagliflozin in regulating the cellular energy sensors SIRT1/AMPK and Akt/mTOR, which leads to improvement of mitochondrial structure and function, stimulation of autophagy, decrease of oxidative stress and suppression of inflammation. Modulation of these pathways shift the oxidative metabolism from carbohydrates to lipids oxidation and results crucial in reducing insulin levels, insulin resistance, glucotoxicity and lipotoxicity. For its pleiotropic effects, empagliflozin appears to be a good candidate for drug repurposing also in other metabolic diseases presenting with hypoglycemia, organ damage, mitochondrial dysfunction and defective autophagy.
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Affiliation(s)
- Arianna Maiorana
- Division of Metabolism, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy
- *Correspondence: Arianna Maiorana,
| | - Francesco Tagliaferri
- SCDU of Pediatrics, Azienda Ospedaliero-Universitaria Maggiore della Carità, University of Piemonte Orientale, Novara, Italy
| | - Carlo Dionisi-Vici
- Division of Metabolism, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy
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25
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Shiraishi W, Tateishi T, Hashimoto Y, Yamasaki R, Kira JI, Isobe N. [Chronic progressive external ophthalmoplegia that could not be diagnosed by biceps muscle biopsy, but was genetically diagnosed by extraocular muscle biopsy]. Rinsho Shinkeigaku 2022; 62:946-951. [PMID: 36450492 DOI: 10.5692/clinicalneurol.cn-001798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
A 48-year-old Japanese male experienced slowly progressive diplopia. He had no family history and was negative for the edrophonium chloride test. Blood analysis showed elevated lactic acid and pyruvic acid levels, suggesting mitochondrial disease. A muscle biopsy from the biceps brachii was performed, but no pathological or genetical mitochondrial abnormalities were detected. Subsequently, he underwent muscle plication for diplopia in which the right inferior rectus muscle was biopsied. Genetic examination of genomic DNA extracted from the extraocular muscle tissue revealed multiple mitochondrial gene deletions, with a heteroplasmy rate of approximately 35%, resulting in the diagnosis of chronic progressive external ophthalmoplegia. In mitochondrial diseases, the tissue distribution of mitochondria with disease-associated variants in mtDNA should be noted, and it is important to select the affected muscle when performing a biopsy for an accurate diagnosis.
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Affiliation(s)
- Wataru Shiraishi
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University
- Department of Neurology, Kokura Memorial Hospital
- Shiraishi Internal Medicine Clinic
| | - Takahisa Tateishi
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University
- Department of Medicine, Kurume University School of Medicine
| | - Yu Hashimoto
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University
| | - Ryo Yamasaki
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University
| | - Jun-Ichi Kira
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University
- Translational Neuroscience Center, Graduate School of Medicine, and School of Pharmacy at Fukuoka, International University of Health and Welfare
- Department of Neurology, Brain and Nerve Center, Fukuoka Central Hospital
| | - Noriko Isobe
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University
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26
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Qian J, Zheng M, Wang L, Song Y, Yan J, Hsu YF. Arabidopsis mitochondrial single-stranded DNA-binding proteins SSB1 and SSB2 are essential regulators of mtDNA replication and homologous recombination. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2022; 64:1952-1965. [PMID: 35925893 DOI: 10.1111/jipb.13338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 08/04/2022] [Indexed: 06/15/2023]
Abstract
Faithful DNA replication is one of the most essential processes in almost all living organisms. However, the proteins responsible for organellar DNA replication are still largely unknown in plants. Here, we show that the two mitochondrion-targeted single-stranded DNA-binding (SSB) proteins SSB1 and SSB2 directly interact with each other and act as key factors for mitochondrial DNA (mtDNA) maintenance, as their single or double loss-of-function mutants exhibit severe germination delay and growth retardation. The mtDNA levels in mutants lacking SSB1 and/or SSB2 function were two- to four-fold higher than in the wild-type (WT), revealing a negative role for SSB1/2 in regulating mtDNA replication. Genetic analysis indicated that SSB1 functions upstream of mitochondrial DNA POLYMERASE IA (POLIA) or POLIB in mtDNA replication, as mutation in either gene restored the high mtDNA copy number of the ssb1-1 mutant back to WT levels. In addition, SSB1 and SSB2 also participate in mitochondrial genome maintenance by influencing mtDNA homologous recombination (HR). Additional genetic analysis suggested that SSB1 functions upstream of ORGANELLAR SINGLE-STRANDED DNA-BINDING PROTEIN1 (OSB1) during mtDNA replication, while SSB1 may act downstream of OSB1 and MUTS HOMOLOG1 for mtDNA HR. Overall, our results yield new insights into the roles of the plant mitochondrion-targeted SSB proteins and OSB1 in maintaining mtDNA stability via affecting DNA replication and DNA HR.
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Affiliation(s)
- Jie Qian
- School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Min Zheng
- School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Lingyu Wang
- School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Yu Song
- School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Jiawen Yan
- School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Yi-Feng Hsu
- School of Life Sciences, Southwest University, Chongqing, 400715, China
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27
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Winters SJ. Hypogonadism in Males With Genetic Neurodevelopmental Syndromes. J Clin Endocrinol Metab 2022; 107:e3974-e3989. [PMID: 35913018 DOI: 10.1210/clinem/dgac421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Indexed: 11/19/2022]
Abstract
Genetic syndromes that affect the nervous system may also disrupt testicular function, and the mechanisms for these effects may be interrelated. Most often neurological signs and symptoms predominate and hypogonadism remains undetected and untreated, while in other cases, a thorough evaluation of a hypogonadal male reveals previously unrecognized ataxia, movement disorder, muscle weakness, tremor, or seizures, leading to a syndromic diagnosis. Androgen deficiency in patients with neurological diseases may aggravate muscle weakness and fatigue and predispose patients to osteoporosis and obesity. The purpose of this mini review is to provide a current understanding of the clinical, biochemical, histologic, and genetic features of syndromes in which male hypogonadism and neurological dysfunction may coexist and may be encountered by the clinical endocrinologist.
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Affiliation(s)
- Stephen J Winters
- Division of Endocrinology, Metabolism & Diabetes, University of Louisville, Louisville, KY, USA
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28
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Akbari M, Nilsen HL, Montaldo NP. Dynamic features of human mitochondrial DNA maintenance and transcription. Front Cell Dev Biol 2022; 10:984245. [PMID: 36158192 PMCID: PMC9491825 DOI: 10.3389/fcell.2022.984245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 08/02/2022] [Indexed: 12/03/2022] Open
Abstract
Mitochondria are the primary sites for cellular energy production and are required for many essential cellular processes. Mitochondrial DNA (mtDNA) is a 16.6 kb circular DNA molecule that encodes only 13 gene products of the approximately 90 different proteins of the respiratory chain complexes and an estimated 1,200 mitochondrial proteins. MtDNA is, however, crucial for organismal development, normal function, and survival. MtDNA maintenance requires mitochondrially targeted nuclear DNA repair enzymes, a mtDNA replisome that is unique to mitochondria, and systems that control mitochondrial morphology and quality control. Here, we provide an overview of the current literature on mtDNA repair and transcription machineries and discuss how dynamic functional interactions between the components of these systems regulate mtDNA maintenance and transcription. A profound understanding of the molecular mechanisms that control mtDNA maintenance and transcription is important as loss of mtDNA integrity is implicated in normal process of aging, inflammation, and the etiology and pathogenesis of a number of diseases.
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Affiliation(s)
- Mansour Akbari
- Department of Medical Biology, Faculty of Health Sciences, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Hilde Loge Nilsen
- Department of Clinical Molecular Biology, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- Unit for precision medicine, Akershus University Hospital, Nordbyhagen, Norway
- Department of Microbiology, Oslo University Hospital, Oslo, Norway
| | - Nicola Pietro Montaldo
- Department of Clinical Molecular Biology, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
- *Correspondence: Nicola Pietro Montaldo,
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29
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Almannai M, El-Hattab AW, Azamian MS, Ali M, Scaglia F. Mitochondrial DNA maintenance defects: potential therapeutic strategies. Mol Genet Metab 2022; 137:40-48. [PMID: 35914366 PMCID: PMC10401187 DOI: 10.1016/j.ymgme.2022.07.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 07/03/2022] [Accepted: 07/03/2022] [Indexed: 10/17/2022]
Abstract
Mitochondrial DNA (mtDNA) replication depends on the mitochondrial import of hundreds of nuclear encoded proteins that control the mitochondrial genome maintenance and integrity. Defects in these processes result in an expanding group of disorders called mtDNA maintenance defects that are characterized by mtDNA depletion and/or multiple mtDNA deletions with variable phenotypic manifestations. As it applies for mitochondrial disorders in general, current treatment options for mtDNA maintenance defects are limited. Lately, with the development of model organisms, improved understanding of the pathophysiology of these disorders, and a better knowledge of their natural history, the number of preclinical studies and existing and planned clinical trials has been increasing. In this review, we discuss recent preclinical studies and current and future clinical trials concerning potential therapeutic options for the different mtDNA maintenance defects.
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Affiliation(s)
- Mohammed Almannai
- Genetics and Precision Medicine Department (GPM), King Abdullah Specialized Children's Hospital (KASCH), King Abdulaziz Medical City, Ministry of National Guard Health Affairs (MNG-HA), Riyadh, Saudi Arabia
| | - Ayman W El-Hattab
- Department of Clinical Sciences, College of Medicine, University of Sharjah, Sharjah, United Arab Emirates
| | - Mahshid S Azamian
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - May Ali
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA; Texas Children's Hospital, Houston, TX, USA; Joint BCM-CUHK Center of Medical Genetics, Prince of Wales Hospital, Shatin, Hong Kong.
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30
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A novel RRM2B mutation associated with mitochondrial DNA depletion syndrome. Mol Genet Metab Rep 2022; 32:100887. [PMID: 35756861 PMCID: PMC9218228 DOI: 10.1016/j.ymgmr.2022.100887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 06/10/2022] [Accepted: 06/10/2022] [Indexed: 11/22/2022] Open
Abstract
Mitochondrial DNA (mtDNA) depletion syndromes are disorders characterized by infantile-onset, severe progression, and the drastic loss of mtDNA content in affected tissues. In a patient who showed severe hypotonia, proximal tubulopathy and sensorineural hearing loss after birth, we observed severe mtDNA depletion and impaired respiratory chain activity in muscle due to heterozygous variants c.686G > T and c.551-2A > G in RRM2B, encoding the p53R2 subunit of the ribonucleotide reductase.
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31
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Richard P, Stojkovic T, Metay C, Lacau St Guily J, Trollet C. Distrofia muscolare oculofaringea. Neurologia 2022. [DOI: 10.1016/s1634-7072(22)46725-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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32
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Abstract
Mitochondrial hepatopathies are a subset of mitochondrial diseases defined by primary dysfunction of hepatocyte mitochondria leading to a phenotype of hepatocyte cell injury, steatosis, or liver failure. Increasingly, the diagnosis is established by new sequencing approaches that combine analysis of both nuclear DNA and mitochondrial DNA and allow for timely diagnosis in most patients. Despite advances in diagnostics, for most affected children their disorders are relentlessly progressive, and result in substantial morbidity and mortality. Treatment remains mainly supportive; however, novel therapeutics and a more definitive role for liver transplantation hold promise for affected children.
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Affiliation(s)
- Mary Ayers
- University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Simon P Horslen
- University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Anna María Gómez
- University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - James E Squires
- University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224, USA.
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33
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Chen YM, Chen W, Xu Y, Lu CS, Zhu MM, Sun RY, Wang Y, Chen Y, Shi J, Wang D. Novel compound heterozygous SUCLG1 variants may contribute to mitochondria DNA depletion syndrome-9. Mol Genet Genomic Med 2022; 10:e2010. [PMID: 35762302 PMCID: PMC9482404 DOI: 10.1002/mgg3.2010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 05/18/2022] [Accepted: 06/08/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Succinate-CoA ligase/synthetase (SCS) deficiency is responsible for encephalomyopathy with mitochondrial DNA depletion and mild methylmalonic aciduria. Variants in SUCLG1, the nuclear gene encoding the alpha subunit of the SCS enzyme playing a pivotal role in maintaining mtDNA integrity and stability, are associated with mitochondrial DNA depletion syndrome 9 (MTDPS9). METHODS In this study, we reported an infant with clinical features of MTDPS9 from China. Whole exome sequencing (WES) was used to identify the genetic cause. Bioinformatic analysis and mtDNA level detection were performed to assess pathogenicity. RESULTS The proband manifested with hypotonia, lactic acidosis, mild methylmalonic aciduria, hearing loss and psychomotor retardation. WES identified new compound heterozygous SUCLG1 variants of c.601A>G (p.R201G) in exon 6 and c.871G>C (p.A291P) in exon 8. Computational analysis predicted that these missense variants might alter structure stability and mitochondrial translocation of SUCLG1. qRT-PCR showed 68% depletion of mtDNA content in proband as compared to controls. CONCLUSION Novel compound heterozygous variants c.601A>G (p.R201G) and c.871G>C (p.A291P) in SUCLG1 may cause MTDPS9 in this family. Our finding should be helpful for molecular diagnosis, genetic counseling and clinical management of SCS deficiency disorders.
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Affiliation(s)
- Yi-Ming Chen
- Department of Surgery, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Wei Chen
- Department of Radiology, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yue Xu
- Department of Pediatrics, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Chao-Sheng Lu
- Department of Pediatrics, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Mian-Mian Zhu
- Department of Pediatrics, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Rong-Yue Sun
- Department of Pediatrics, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yihong Wang
- Department of Pediatrics, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Yuan Chen
- Department of Pediatrics, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Jiaming Shi
- Department of Pediatrics, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Dan Wang
- Department of Pediatrics, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
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34
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Manini A, Caporali L, Meneri M, Zanotti S, Piga D, Arena IG, Corti S, Toscano A, Comi GP, Musumeci O, Carelli V, Ronchi D. Case Report: Rare Homozygous RNASEH1 Mutations Associated With Adult-Onset Mitochondrial Encephalomyopathy and Multiple Mitochondrial DNA Deletions. Front Genet 2022; 13:906667. [PMID: 35711919 PMCID: PMC9194440 DOI: 10.3389/fgene.2022.906667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 04/25/2022] [Indexed: 12/02/2022] Open
Abstract
Mitochondrial DNA (mtDNA) maintenance disorders embrace a broad range of clinical syndromes distinguished by the evidence of mtDNA depletion and/or deletions in affected tissues. Among the nuclear genes associated with mtDNA maintenance disorders, RNASEH1 mutations produce a homogeneous phenotype, with progressive external ophthalmoplegia (PEO), ptosis, limb weakness, cerebellar ataxia, and dysphagia. The encoded enzyme, ribonuclease H1, is involved in mtDNA replication, whose impairment leads to an increase in replication intermediates resulting from mtDNA replication slowdown. Here, we describe two unrelated Italian probands (Patient 1 and Patient 2) affected by chronic PEO, ptosis, and muscle weakness. Cerebellar features and severe dysphagia requiring enteral feeding were observed in one patient. In both cases, muscle biopsy revealed diffuse mitochondrial abnormalities and multiple mtDNA deletions. A targeted next-generation sequencing analysis revealed the homozygous RNASEH1 mutations c.129-3C>G and c.424G>A in patients 1 and 2, respectively. The c.129-3C>G substitution has never been described as disease-related and resulted in the loss of exon 2 in Patient 1 muscle RNASEH1 transcript. Overall, we recommend implementing the use of high-throughput sequencing approaches in the clinical setting to reach genetic diagnosis in case of suspected presentations with impaired mtDNA homeostasis.
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Affiliation(s)
- Arianna Manini
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Leonardo Caporali
- Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy
| | - Megi Meneri
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy.,Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Department of Neuroscience, Milan, Italy
| | - Simona Zanotti
- Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neuromuscular and Rare Diseases Unit, Department of Neuroscience, Milan, Italy
| | - Daniela Piga
- Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Department of Neuroscience, Milan, Italy
| | - Ignazio Giuseppe Arena
- Unit of Neurology and Neuromuscular disorders, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Stefania Corti
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy.,Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Department of Neuroscience, Milan, Italy
| | - Antonio Toscano
- Unit of Neurology and Neuromuscular disorders, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Giacomo Pietro Comi
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy.,Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neuromuscular and Rare Diseases Unit, Department of Neuroscience, Milan, Italy
| | - Olimpia Musumeci
- Unit of Neurology and Neuromuscular disorders, Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Valerio Carelli
- Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy.,Dipartimento di Scienze Biomediche e Neuromotorie (DIBINEM), University of Bologna, Bologna, Italy
| | - Dario Ronchi
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy.,Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Department of Neuroscience, Milan, Italy
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35
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Roy A, Kandettu A, Ray S, Chakrabarty S. Mitochondrial DNA replication and repair defects: Clinical phenotypes and therapeutic interventions. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2022; 1863:148554. [PMID: 35341749 DOI: 10.1016/j.bbabio.2022.148554] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 03/06/2022] [Accepted: 03/16/2022] [Indexed: 12/15/2022]
Abstract
Mitochondria is a unique cellular organelle involved in multiple cellular processes and is critical for maintaining cellular homeostasis. This semi-autonomous organelle contains its circular genome - mtDNA (mitochondrial DNA), that undergoes continuous cycles of replication and repair to maintain the mitochondrial genome integrity. The majority of the mitochondrial genes, including mitochondrial replisome and repair genes, are nuclear-encoded. Although the repair machinery of mitochondria is quite efficient, the mitochondrial genome is highly susceptible to oxidative damage and other types of exogenous and endogenous agent-induced DNA damage, due to the absence of protective histones and their proximity to the main ROS production sites. Mutations in replication and repair genes of mitochondria can result in mtDNA depletion and deletions subsequently leading to mitochondrial genome instability. The combined action of mutations and deletions can result in compromised mitochondrial genome maintenance and lead to various mitochondrial disorders. Here, we review the mechanism of mitochondrial DNA replication and repair process, key proteins involved, and their altered function in mitochondrial disorders. The focus of this review will be on the key genes of mitochondrial DNA replication and repair machinery and the clinical phenotypes associated with mutations in these genes.
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Affiliation(s)
- Abhipsa Roy
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Amoolya Kandettu
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Swagat Ray
- Department of Life Sciences, School of Life and Environmental Sciences, University of Lincoln, Lincoln LN6 7TS, United Kingdom
| | - Sanjiban Chakrabarty
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal 576104, Karnataka, India.
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36
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Ng YS, Lim AZ, Panagiotou G, Turnbull DM, Walker M. Endocrine Manifestations and New Developments in Mitochondrial Disease. Endocr Rev 2022; 43:583-609. [PMID: 35552684 PMCID: PMC9113134 DOI: 10.1210/endrev/bnab036] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Indexed: 11/19/2022]
Abstract
Mitochondrial diseases are a group of common inherited diseases causing disruption of oxidative phosphorylation. Some patients with mitochondrial disease have endocrine manifestations, with diabetes mellitus being predominant but also include hypogonadism, hypoadrenalism, and hypoparathyroidism. There have been major developments in mitochondrial disease over the past decade that have major implications for all patients. The collection of large cohorts of patients has better defined the phenotype of mitochondrial diseases and the majority of patients with endocrine abnormalities have involvement of several other systems. This means that patients with mitochondrial disease and endocrine manifestations need specialist follow-up because some of the other manifestations, such as stroke-like episodes and cardiomyopathy, are potentially life threatening. Also, the development and follow-up of large cohorts of patients means that there are clinical guidelines for the management of patients with mitochondrial disease. There is also considerable research activity to identify novel therapies for the treatment of mitochondrial disease. The revolution in genetics, with the introduction of next-generation sequencing, has made genetic testing more available and establishing a precise genetic diagnosis is important because it will affect the risk for involvement for different organ systems. Establishing a genetic diagnosis is also crucial because important reproductive options have been developed that will prevent the transmission of mitochondrial disease because of mitochondrial DNA variants to the next generation.
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Affiliation(s)
- Yi Shiau Ng
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Albert Zishen Lim
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Grigorios Panagiotou
- Department of Diabetes and Endocrinology, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Doug M Turnbull
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
- NHS Highly Specialised Service for Rare Mitochondrial Disorders, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK
| | - Mark Walker
- Department of Diabetes and Endocrinology, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
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Milenkovic D, Sanz-Moreno A, Calzada-Wack J, Rathkolb B, Veronica Amarie O, Gerlini R, Aguilar-Pimentel A, Misic J, Simard ML, Wolf E, Fuchs H, Gailus-Durner V, de Angelis MH, Larsson NG. Mice lacking the mitochondrial exonuclease MGME1 develop inflammatory kidney disease with glomerular dysfunction. PLoS Genet 2022; 18:e1010190. [PMID: 35533204 PMCID: PMC9119528 DOI: 10.1371/journal.pgen.1010190] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 05/19/2022] [Accepted: 04/05/2022] [Indexed: 12/27/2022] Open
Abstract
Mitochondrial DNA (mtDNA) maintenance disorders are caused by mutations in ubiquitously expressed nuclear genes and lead to syndromes with variable disease severity and tissue-specific phenotypes. Loss of function mutations in the gene encoding the mitochondrial genome and maintenance exonuclease 1 (MGME1) result in deletions and depletion of mtDNA leading to adult-onset multisystem mitochondrial disease in humans. To better understand the in vivo function of MGME1 and the associated disease pathophysiology, we characterized a Mgme1 mouse knockout model by extensive phenotyping of ageing knockout animals. We show that loss of MGME1 leads to de novo formation of linear deleted mtDNA fragments that are constantly made and degraded. These findings contradict previous proposal that MGME1 is essential for degradation of linear mtDNA fragments and instead support a model where MGME1 has a critical role in completion of mtDNA replication. We report that Mgme1 knockout mice develop a dramatic phenotype as they age and display progressive weight loss, cataract and retinopathy. Surprisingly, aged animals also develop kidney inflammation, glomerular changes and severe chronic progressive nephropathy, consistent with nephrotic syndrome. These findings link the faulty mtDNA synthesis to severe inflammatory disease and thus show that defective mtDNA replication can trigger an immune response that causes age-associated progressive pathology in the kidney. We have addressed the controversy of the role of the mitochondrial genome and maintenance exonuclease 1 (MGME1) in mtDNA metabolism by characterization of knockout mice. Our findings show that loss of MGME1 leads to increased de novo formation of linear deleted mtDNA, thus contradicting previous report that MGME1 degrades long linear mtDNA molecules. In addition, we report that loss of MGME1 leads to age-associated pathology manifested as progressive weight loss, cataract and retinopathy. Aged knockout mice also develop kidney inflammation leading to glomerular changes, fibrosis and nephrotic syndrome. Defective mtDNA replication causing the formation of linear deleted mtDNA can thus trigger an immune response that leads to the development of progressive kidney disease in ageing animals.
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Affiliation(s)
| | - Adrián Sanz-Moreno
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Julia Calzada-Wack
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Birgit Rathkolb
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
- Institute of Molecular Animal Breeding and Biotechnology, Gene Center, Ludwig-Maximilians-University Munich, Munich, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Oana Veronica Amarie
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Raffaele Gerlini
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Antonio Aguilar-Pimentel
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Jelena Misic
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | | | - Eckhard Wolf
- Institute of Molecular Animal Breeding and Biotechnology, Gene Center, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Helmut Fuchs
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Valerie Gailus-Durner
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
| | - Martin Hrabě de Angelis
- Institute of Experimental Genetics, German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health GmbH, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Chair of Experimental Genetics, TUM School of Life Sciences, Technische Universität München, Freising, Germany
- * E-mail: (NGL); (MH)
| | - Nils-Göran Larsson
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
- * E-mail: (NGL); (MH)
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Hou Y, Zhao X, Xie Z, Yu M, Lv H, Zhang W, Yuan Y, Wang Z. Novel and recurrent nuclear gene variations in a cohort of Chinese progressive external ophthalmoplegia patients with multiple mtDNA deletions. Mol Genet Genomic Med 2022; 10:e1921. [PMID: 35289132 PMCID: PMC9034679 DOI: 10.1002/mgg3.1921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 12/30/2021] [Accepted: 02/25/2022] [Indexed: 11/07/2022] Open
Abstract
Objectives This study aimed to investigate the clinical and genetic spectrum in Chinese patients with multiple mtDNA deletions presenting with autosomal‐inherited mitochondrial progressive external ophthalmoplegia (PEO). Methods Long‐range polymerase chain reaction and massively parallel sequencing of the mitochondrial genome were performed to detect deletions in muscle mtDNA of 274 unrelated families. Then, targeted next generation sequencing was used to detect nuclear gene variations in patients with multiple mtDNA deletions. Results A total of 40 Chinese PEO patients (10 males and 30 females) from 20 families were found to have multiple mtDNA deletions in this study, and the median age at onset was 35 (1–70) years. PEO and positive family history were the two prominent features of these patients, and ataxia, neuropathy, and hypogonadism were also present as onset symptoms in some patients. Fifteen of 20 probands with multiple mtDNA deletions were identified to carry nuclear gene variants; eight (40.0%) probands had variants within POLG, two (10.0%) within TWNK, two (10.0%) within RRM2B, two (10.0%) within TK2, and one (5.0%) within POLG2. A total of 24 variants were found in these five nuclear genes, of which 19 were novel. The causal nuclear genetic factors in five pedigrees remain undetermined. Conclusions The POLG gene is the most common disease‐causing gene in this group of PEO patients with multiple mtDNA deletions. While inherited PEO is the most prominent symptoms in these patients, genotypic and phenotypic heterogeneity still exist, for example in onset age, initial symptoms, and accompanying manifestations.
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Affiliation(s)
- Yue Hou
- Department of Neurology, Peking University First Hospital, Beijing, China.,Department of Geriatrics, Peking University First Hospital, Beijing, China
| | - Xutong Zhao
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Zhiying Xie
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Meng Yu
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - He Lv
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Wei Zhang
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Yun Yuan
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Zhaoxia Wang
- Department of Neurology, Peking University First Hospital, Beijing, China.,Beijing Key Laboratory of Neurovascular Disease Discovery, Beijing, China
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39
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Carvalho G, Repolês BM, Mendes I, Wanrooij PH. Mitochondrial DNA Instability in Mammalian Cells. Antioxid Redox Signal 2022; 36:885-905. [PMID: 34015960 PMCID: PMC9127837 DOI: 10.1089/ars.2021.0091] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 05/11/2021] [Indexed: 02/06/2023]
Abstract
Significance: The small, multicopy mitochondrial genome (mitochondrial DNA [mtDNA]) is essential for efficient energy production, as alterations in its coding information or a decrease in its copy number disrupt mitochondrial ATP synthesis. However, the mitochondrial replication machinery encounters numerous challenges that may limit its ability to duplicate this important genome and that jeopardize mtDNA stability, including various lesions in the DNA template, topological stress, and an insufficient nucleotide supply. Recent Advances: An ever-growing array of DNA repair or maintenance factors are being reported to localize to the mitochondria. We review current knowledge regarding the mitochondrial factors that may contribute to the tolerance or repair of various types of changes in the mitochondrial genome, such as base damage, incorporated ribonucleotides, and strand breaks. We also discuss the newly discovered link between mtDNA instability and activation of the innate immune response. Critical Issues: By which mechanisms do mitochondria respond to challenges that threaten mtDNA maintenance? What types of mtDNA damage are repaired, and when are the affected molecules degraded instead? And, finally, which forms of mtDNA instability trigger an immune response, and how? Future Directions: Further work is required to understand the contribution of the DNA repair and damage-tolerance factors present in the mitochondrial compartment, as well as the balance between mtDNA repair and degradation. Finally, efforts to understand the events underlying mtDNA release into the cytosol are warranted. Pursuing these and many related avenues can improve our understanding of what goes wrong in mitochondrial disease. Antioxid. Redox Signal. 36, 885-905.
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Affiliation(s)
- Gustavo Carvalho
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Bruno Marçal Repolês
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Isabela Mendes
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Paulina H. Wanrooij
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
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40
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Organization and expression of the mammalian mitochondrial genome. Nat Rev Genet 2022; 23:606-623. [PMID: 35459860 DOI: 10.1038/s41576-022-00480-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/21/2022] [Indexed: 02/07/2023]
Abstract
The mitochondrial genome encodes core subunits of the respiratory chain that drives oxidative phosphorylation and is, therefore, essential for energy conversion. Advances in high-throughput sequencing technologies and cryoelectron microscopy have shed light on the structure and organization of the mitochondrial genome and revealed unique mechanisms of mitochondrial gene regulation. New animal models of impaired mitochondrial protein synthesis have shown how the coordinated regulation of the cytoplasmic and mitochondrial translation machineries ensures the correct assembly of the respiratory chain complexes. These new technologies and disease models are providing a deeper understanding of mitochondrial genome organization and expression and of the diseases caused by impaired energy conversion, including mitochondrial, neurodegenerative, cardiovascular and metabolic diseases. They also provide avenues for the development of treatments for these conditions.
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41
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Lopriore P, Ricciarini V, Siciliano G, Mancuso M, Montano V. Mitochondrial Ataxias: Molecular Classification and Clinical Heterogeneity. Neurol Int 2022; 14:337-356. [PMID: 35466209 PMCID: PMC9036286 DOI: 10.3390/neurolint14020028] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 03/26/2022] [Accepted: 03/28/2022] [Indexed: 01/25/2023] Open
Abstract
Ataxia is increasingly being recognized as a cardinal manifestation in primary mitochondrial diseases (PMDs) in both paediatric and adult patients. It can be caused by disruption of cerebellar nuclei or fibres, its connection with the brainstem, or spinal and peripheral lesions leading to proprioceptive loss. Despite mitochondrial ataxias having no specific defining features, they should be included in hereditary ataxias differential diagnosis, given the high prevalence of PMDs. This review focuses on the clinical and neuropathological features and genetic background of PMDs in which ataxia is a prominent manifestation.
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42
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Zaman M, Shutt TE. The Role of Impaired Mitochondrial Dynamics in MFN2-Mediated Pathology. Front Cell Dev Biol 2022; 10:858286. [PMID: 35399520 PMCID: PMC8989266 DOI: 10.3389/fcell.2022.858286] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 03/07/2022] [Indexed: 12/17/2022] Open
Abstract
The Mitofusin 2 protein (MFN2), encoded by the MFN2 gene, was first described for its role in mediating mitochondrial fusion. However, MFN2 is now recognized to play additional roles in mitochondrial autophagy (mitophagy), mitochondrial motility, lipid transfer, and as a tether to other organelles including the endoplasmic reticulum (ER) and lipid droplets. The tethering role of MFN2 is an important mediator of mitochondrial-ER contact sites (MERCs), which themselves have many important functions that regulate mitochondria, including calcium homeostasis and lipid metabolism. Exemplifying the importance of MFN2, pathogenic variants in MFN2 are established to cause the peripheral neuropathy Charcot-Marie-Tooth Disease Subtype 2A (CMT2A). However, the mechanistic basis for disease is not clear. Moreover, additional pathogenic phenotypes such as lipomatosis, distal myopathy, optic atrophy, and hearing loss, can also sometimes be present in patients with CMT2A. Given these variable patient phenotypes, and the many cellular roles played by MFN2, the mechanistic underpinnings of the cellular impairments by which MFN2 dysfunction leads to disease are likely to be complex. Here, we will review what is known about the various functions of MFN2 that are impaired by pathogenic variants causing CMT2A, with a specific emphasis on the ties between MFN2 variants and MERCs.
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Affiliation(s)
- Mashiat Zaman
- Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB, Canada
- Alberta Children's Hospital Research Institute (ACHRI), Calgary, AB, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | - Timothy E Shutt
- Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB, Canada
- Alberta Children's Hospital Research Institute (ACHRI), Calgary, AB, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
- Department of Medical Genetics, University of Calgary, Calgary, AB, Canada
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43
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Sayles NM, Southwell N, McAvoy K, Kim K, Pesini A, Anderson CJ, Quinzii C, Cloonan S, Kawamata H, Manfredi G. Mutant CHCHD10 causes an extensive metabolic rewiring that precedes OXPHOS dysfunction in a murine model of mitochondrial cardiomyopathy. Cell Rep 2022; 38:110475. [PMID: 35263592 PMCID: PMC9013208 DOI: 10.1016/j.celrep.2022.110475] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 11/01/2021] [Accepted: 02/10/2022] [Indexed: 12/13/2022] Open
Abstract
Mitochondrial cardiomyopathies are fatal diseases, with no effective treatment. Alterations of heart mitochondrial function activate the mitochondrial integrated stress response (ISRmt), a transcriptional program affecting cell metabolism, mitochondrial biogenesis, and proteostasis. In humans, mutations in CHCHD10, a mitochondrial protein with unknown function, were recently associated with dominant multi-system mitochondrial diseases, whose pathogenic mechanisms remain to be elucidated. Here, in CHCHD10 knockin mutant mice, we identify an extensive cardiac metabolic rewiring triggered by proteotoxic ISRmt. The stress response arises early on, before the onset of bioenergetic impairments, triggering a switch from oxidative to glycolytic metabolism, enhancement of transsulfuration and one carbon (1C) metabolism, and widespread metabolic imbalance. In parallel, increased NADPH oxidases elicit antioxidant responses, leading to heme depletion. As the disease progresses, the adaptive metabolic stress response fails, resulting in fatal cardiomyopathy. Our findings suggest that early interventions to counteract metabolic imbalance could ameliorate mitochondrial cardiomyopathy associated with proteotoxic ISRmt. Sayles et al. report that mutant CHCHD10 proteotoxicity activates the mitochondrial integrated stress response (ISRmt) in a mouse model of mitochondrial cardiomyopathy. Chronic ISRmt causes profound metabolic imbalances, culminating in oxidative stress and iron dysregulation, ultimately resulting in mitochondrial dysfunction and contributing to disease pathogenesis.
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Affiliation(s)
- Nicole M Sayles
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, 407 East 61st Street, New York, NY 10065, USA; Neuroscience Graduate Program, Weill Cornell Graduate School of Medical Sciences, 1300 York Avenue, New York, NY 10065, USA
| | - Nneka Southwell
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, 407 East 61st Street, New York, NY 10065, USA; Neuroscience Graduate Program, Weill Cornell Graduate School of Medical Sciences, 1300 York Avenue, New York, NY 10065, USA
| | - Kevin McAvoy
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, 407 East 61st Street, New York, NY 10065, USA
| | - Kihwan Kim
- Department of Medicine, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA
| | - Alba Pesini
- Department of Neurology, Columbia University, 710 West 168th Street, New York, NY 10032, USA
| | - Corey J Anderson
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, 407 East 61st Street, New York, NY 10065, USA
| | - Catarina Quinzii
- Department of Neurology, Columbia University, 710 West 168th Street, New York, NY 10032, USA
| | - Suzanne Cloonan
- Department of Medicine, Weill Cornell Medicine, 1300 York Avenue, New York, NY 10065, USA; The School of Medicine, Trinity Biomedical Science Institute, Trinity College Dublin, Pearse St, Dublin 2 52-160, Ireland; Tallaght University Hospital, Tallaght, Dublin 24 D24 NR0A, Ireland
| | - Hibiki Kawamata
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, 407 East 61st Street, New York, NY 10065, USA
| | - Giovanni Manfredi
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, 407 East 61st Street, New York, NY 10065, USA.
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44
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Mitochondrial Neurodegeneration. Cells 2022; 11:cells11040637. [PMID: 35203288 PMCID: PMC8870525 DOI: 10.3390/cells11040637] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 01/28/2022] [Accepted: 02/06/2022] [Indexed: 01/27/2023] Open
Abstract
Mitochondria are cytoplasmic organelles, which generate energy as heat and ATP, the universal energy currency of the cell. This process is carried out by coupling electron stripping through oxidation of nutrient substrates with the formation of a proton-based electrochemical gradient across the inner mitochondrial membrane. Controlled dissipation of the gradient can lead to production of heat as well as ATP, via ADP phosphorylation. This process is known as oxidative phosphorylation, and is carried out by four multiheteromeric complexes (from I to IV) of the mitochondrial respiratory chain, carrying out the electron flow whose energy is stored as a proton-based electrochemical gradient. This gradient sustains a second reaction, operated by the mitochondrial ATP synthase, or complex V, which condensates ADP and Pi into ATP. Four complexes (CI, CIII, CIV, and CV) are composed of proteins encoded by genes present in two separate compartments: the nuclear genome and a small circular DNA found in mitochondria themselves, and are termed mitochondrial DNA (mtDNA). Mutations striking either genome can lead to mitochondrial impairment, determining infantile, childhood or adult neurodegeneration. Mitochondrial disorders are complex neurological syndromes, and are often part of a multisystem disorder. In this paper, we divide the diseases into those caused by mtDNA defects and those that are due to mutations involving nuclear genes; from a clinical point of view, we discuss pediatric disorders in comparison to juvenile or adult-onset conditions. The complementary genetic contributions controlling organellar function and the complexity of the biochemical pathways present in the mitochondria justify the extreme genetic and phenotypic heterogeneity of this new area of inborn errors of metabolism known as ‘mitochondrial medicine’.
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Molecular Genetics Overview of Primary Mitochondrial Myopathies. J Clin Med 2022; 11:jcm11030632. [PMID: 35160083 PMCID: PMC8836969 DOI: 10.3390/jcm11030632] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/13/2022] [Accepted: 01/20/2022] [Indexed: 12/29/2022] Open
Abstract
Mitochondrial disorders are the most common inherited conditions, characterized by defects in oxidative phosphorylation and caused by mutations in nuclear or mitochondrial genes. Due to its high energy request, skeletal muscle is typically involved. According to the International Workshop of Experts in Mitochondrial Diseases held in Rome in 2016, the term Primary Mitochondrial Myopathy (PMM) should refer to those mitochondrial disorders affecting principally, but not exclusively, the skeletal muscle. The clinical presentation may include general isolated myopathy with muscle weakness, exercise intolerance, chronic ophthalmoplegia/ophthalmoparesis (cPEO) and eyelids ptosis, or multisystem conditions where there is a coexistence with extramuscular signs and symptoms. In recent years, new therapeutic targets have been identified leading to the launch of some promising clinical trials that have mainly focused on treating muscle symptoms and that require populations with defined genotype. Advantages in next-generation sequencing techniques have substantially improved diagnosis. So far, an increasing number of mutations have been identified as responsible for mitochondrial disorders. In this review, we focused on the principal molecular genetic alterations in PMM. Accordingly, we carried out a comprehensive review of the literature and briefly discussed the possible approaches which could guide the clinician to a genetic diagnosis.
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Maiorana A, Lepri FR, Novelli A, Dionisi-Vici C. Hypoglycaemia Metabolic Gene Panel Testing. Front Endocrinol (Lausanne) 2022; 13:826167. [PMID: 35422763 PMCID: PMC9001947 DOI: 10.3389/fendo.2022.826167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 02/21/2022] [Indexed: 12/31/2022] Open
Abstract
A large number of inborn errors of metabolism present with hypoglycemia. Impairment of glucose homeostasis may arise from different biochemical pathways involving insulin secretion, fatty acid oxidation, ketone bodies formation and degradation, glycogen metabolism, fructose and galactose metabolism, branched chain aminoacids and tyrosine metabolism, mitochondrial function and glycosylation proteins mechanisms. Historically, genetic analysis consisted of highly detailed molecular testing of nominated single genes. However, more recently, the genetic heterogeneity of these conditions imposed to perform extensive molecular testing within a useful timeframe via new generation sequencing technology. Indeed, the establishment of a rapid diagnosis drives specific nutritional and medical therapies. The biochemical and clinical phenotypes are critical to guide the molecular analysis toward those clusters of genes involved in specific pathways, and address data interpretation regarding the finding of possible disease-causing variants at first reported as variants of uncertain significance in known genes or the discovery of new disease genes. Also, the trio's analysis allows genetic counseling for recurrence risk in further pregnancies. Besides, this approach is allowing to expand the phenotypic characterization of a disease when pathogenic variants give raise to unexpected clinical pictures. Multidisciplinary input and collaboration are increasingly key for addressing the analysis and interpreting the significance of the genetic results, allowing rapidly their translation from bench to bedside.
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Affiliation(s)
- Arianna Maiorana
- Division of Metabolism, Department of Pediatrics Subspecialties, Ospedale Pediatrico Bambino Gesù, IRCCS (Istituto di Ricovero e Cura a Carattere Scientifico), Rome, Italy
- *Correspondence: Arianna Maiorana,
| | - Francesca Romana Lepri
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unity, Ospedale Pediatrico Bambino Gesù, IRCCS (Istituto di Ricovero e Cura a Carattere Scientifico), Rome, Italy
| | - Antonio Novelli
- Laboratory of Medical Genetics, Translational Cytogenomics Research Unity, Ospedale Pediatrico Bambino Gesù, IRCCS (Istituto di Ricovero e Cura a Carattere Scientifico), Rome, Italy
| | - Carlo Dionisi-Vici
- Division of Metabolism, Department of Pediatrics Subspecialties, Ospedale Pediatrico Bambino Gesù, IRCCS (Istituto di Ricovero e Cura a Carattere Scientifico), Rome, Italy
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Finsterer J. Survival from liver transplantation in mitochondrial disorders not only depends on periprocedural complications but also on the genotype and on mitochondrion-toxic drugs. Pediatr Transplant 2021; 25:e14137. [PMID: 34505738 DOI: 10.1111/petr.14137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Jurkute N, D'Esposito F, Robson AG, Pitceathly RDS, Cordeiro F, Raymond FL, Moore AT, Michaelides M, Yu-Wai-Man P, Webster AR, Arno G. SSBP1-Disease Update: Expanding the Genetic and Clinical Spectrum, Reporting Variable Penetrance and Confirming Recessive Inheritance. Invest Ophthalmol Vis Sci 2021; 62:12. [PMID: 34905022 PMCID: PMC8684315 DOI: 10.1167/iovs.62.15.12] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 11/19/2021] [Indexed: 11/24/2022] Open
Abstract
Purpose To report novel genotypes and expand the phenotype spectrum of SSBP1-disease and explore potential disease mechanism. Methods Five families with previously unsolved optic atrophy and retinal dystrophy underwent whole genome sequencing as part of the National Institute for Health Research BioResource Rare-Diseases and the UK's 100,000 Genomes Project. In silico analysis and protein modelling was performed on the identified variants. Deep phenotyping including retinal imaging and International Society for Clinical Electrophysiology of Vision standard visual electrophysiology was performed. Results Seven individuals from five unrelated families with bilateral optic atrophy and/or retinal dystrophy with extraocular signs and symptoms in some are described. In total, 6 SSBP1 variants were identified including the previously unreported variants: c.151A>G, p.(Lys51Glu), c.335G>A p.(Gly112Glu), and c.380G>A, p.(Arg127Gln). One individual was found to carry biallelic variants (c.380G>A p.(Arg127Gln); c.394A>G p.(Ile132Val)) associated with likely autosomal recessive SSBP1-disease. In silico analysis predicted all variants to be pathogenic and Three-dimensional protein modelling suggested possible disease mechanisms via decreased single-stranded DNA binding affinity or impaired higher structure formation. Conclusions SSBP1 is essential for mitochondrial DNA replication and maintenance, with defects leading to a spectrum of disease that includes optic atrophy and/or retinal dystrophy, occurring with or without extraocular features. This study provides evidence of intrafamilial variability and confirms the existence of an autosomal recessive inheritance in SSBP1-disease consequent upon a previously unreported genotype.
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Affiliation(s)
- Neringa Jurkute
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Fabiana D'Esposito
- Imperial College Ophthalmic Research Unit, Western Eye Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
- Eye Clinic, Department of Neurosciences, Reproductive Sciences and Dentistry, Federico II University, Naples, Italy
| | - Anthony G. Robson
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Robert D. S. Pitceathly
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, United Kingdom
| | - Francesca Cordeiro
- Imperial College Ophthalmic Research Unit, Western Eye Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
| | - F. Lucy Raymond
- NIHR BioResource - Rare Diseases, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, United Kingdom
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Anthony T. Moore
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States
| | - Michel Michaelides
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Patrick Yu-Wai-Man
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
- Cambridge Eye Unit, Addenbrooke's Hospital, Cambridge University Hospitals, Cambridge, United Kingdom
- John van Geest Centre for Brain Repair and MRC Mitochondrial Biology Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Andrew R. Webster
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Gavin Arno
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
- North Thames Genomic Laboratory Hub, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - for the Genomics England Research Consortium
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
- Imperial College Ophthalmic Research Unit, Western Eye Hospital, Imperial College Healthcare NHS Trust, London, United Kingdom
- Eye Clinic, Department of Neurosciences, Reproductive Sciences and Dentistry, Federico II University, Naples, Italy
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, United Kingdom
- NIHR BioResource - Rare Diseases, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, United Kingdom
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States
- Cambridge Eye Unit, Addenbrooke's Hospital, Cambridge University Hospitals, Cambridge, United Kingdom
- John van Geest Centre for Brain Repair and MRC Mitochondrial Biology Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
- North Thames Genomic Laboratory Hub, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
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Saccharomyces cerevisiae as a Tool for Studying Mutations in Nuclear Genes Involved in Diseases Caused by Mitochondrial DNA Instability. Genes (Basel) 2021; 12:genes12121866. [PMID: 34946817 PMCID: PMC8701800 DOI: 10.3390/genes12121866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 11/20/2021] [Accepted: 11/23/2021] [Indexed: 01/03/2023] Open
Abstract
Mitochondrial DNA (mtDNA) maintenance is critical for oxidative phosphorylation (OXPHOS) since some subunits of the respiratory chain complexes are mitochondrially encoded. Pathological mutations in nuclear genes involved in the mtDNA metabolism may result in a quantitative decrease in mtDNA levels, referred to as mtDNA depletion, or in qualitative defects in mtDNA, especially in multiple deletions. Since, in the last decade, most of the novel mutations have been identified through whole-exome sequencing, it is crucial to confirm the pathogenicity by functional analysis in the appropriate model systems. Among these, the yeast Saccharomyces cerevisiae has proved to be a good model for studying mutations associated with mtDNA instability. This review focuses on the use of yeast for evaluating the pathogenicity of mutations in six genes, MPV17/SYM1, MRM2/MRM2, OPA1/MGM1, POLG/MIP1, RRM2B/RNR2, and SLC25A4/AAC2, all associated with mtDNA depletion or multiple deletions. We highlight the techniques used to construct a specific model and to measure the mtDNA instability as well as the main results obtained. We then report the contribution that yeast has given in understanding the pathogenic mechanisms of the mutant variants, in finding the genetic suppressors of the mitochondrial defects and in the discovery of molecules able to improve the mtDNA stability.
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A new automated tool to quantify nucleoid distribution within mitochondrial networks. Sci Rep 2021; 11:22755. [PMID: 34815439 PMCID: PMC8610998 DOI: 10.1038/s41598-021-01987-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Accepted: 11/08/2021] [Indexed: 11/09/2022] Open
Abstract
Mitochondrial DNA (mtDNA) maintenance is essential to sustain a functionally healthy population of mitochondria within cells. Proper mtDNA replication and distribution within mitochondrial networks are essential to maintain mitochondrial homeostasis. However, the fundamental basis of mtDNA segregation and distribution within mitochondrial networks is still unclear. To address these questions, we developed an algorithm, Mitomate tracker to unravel the global distribution of nucleoids within mitochondria. Using this tool, we decipher the semi-regular spacing of nucleoids across mitochondrial networks. Furthermore, we show that mitochondrial fission actively regulates mtDNA distribution by controlling the distribution of nucleoids within mitochondrial networks. Specifically, we found that primary cells bearing disease-associated mutations in the fission proteins DRP1 and MYH14 show altered nucleoid distribution, and acute enrichment of enlarged nucleoids near the nucleus. Further analysis suggests that the altered nucleoid distribution observed in the fission mutants is the result of both changes in network structure and nucleoid density. Thus, our study provides novel insights into the role of mitochondria fission in nucleoid distribution and the understanding of diseases caused by fission defects.
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