1
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Richardson K, Wessells R. A novel panel of Drosophila TAFAZZIN mutants in distinct genetic backgrounds as a resource for therapeutic testing. PLoS One 2023; 18:e0286380. [PMID: 37756350 PMCID: PMC10529581 DOI: 10.1371/journal.pone.0286380] [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: 04/05/2023] [Accepted: 05/16/2023] [Indexed: 09/29/2023] Open
Abstract
Barth Syndrome is a rare, X-linked disorder caused by mutation of the gene TAFAZZIN (TAZ). The corresponding Tafazzin protein is involved in the remodeling of cardiolipin, a phospholipid with critical roles in mitochondrial function. While recent clinical trials have been promising, there is still no cure for Barth Syndrome. Because TAZ is highly conserved, multiple animal and cell culture models exist for pre-clinical testing of therapeutics. However, since the same mutation in different patients can lead to different symptoms and responses to treatment, isogenized experimental models can't fully account for human disease conditions. On the other hand, isogenized animal models allow for sufficient numbers to thoroughly establish efficacy for a given genetic background. Therefore, a combined method for testing treatments in a panel of isogenized cohorts that are genetically distinct from each other would be transformative for testing emerging pre-clinical therapies. To aid in this effort, we've created a novel panel of 10 Drosophila lines, each with the same TAZ mutation in highly diverse genetic backgrounds, to serve as a helpful resource to represent natural variation in background genetics in pre-clinical studies. As a proof of principle, we test our panel here using nicotinamide riboside (NR), a treatment with established therapeutic value, to evaluate how robust this therapy is across the 10 genetic backgrounds in this novel reference panel. We find substantial variation in the response to NR across backgrounds. We expect this resource will be valuable in pre-clinical testing of emerging therapies for Barth Syndrome.
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Affiliation(s)
- Kristin Richardson
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, United States of America
| | - Robert Wessells
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI, United States of America
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2
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Takeda A, Ueki M, Abe J, Maeta K, Horiguchi T, Yamazawa H, Izumi G, Chida-Nagai A, Sasaki D, Tsujioka T, Sato I, Shiraishi M, Matsuo M. A case of infantile Barth syndrome with severe heart failure: Importance of splicing variants in the TAZ gene. Mol Genet Genomic Med 2023:e2190. [PMID: 37186429 DOI: 10.1002/mgg3.2190] [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: 04/09/2022] [Revised: 03/30/2023] [Accepted: 04/11/2023] [Indexed: 05/17/2023] Open
Abstract
Barth syndrome (BTHS) is an X-linked disorder characterized by cardiomyopathy, skeletal myopathy, and 3-methylglutaconic aciduria. The causative pathogenic variants for BTHS are in TAZ, which encodes a putative acyltransferase named tafazzin and is involved in the remodeling of cardiolipin in the inner mitochondrial membranes. Pathogenic variants in TAZ result in mitochondrial structural and functional abnormalities. We report a case of infantile BTHS with severe heart failure, left ventricular noncompaction, and lactic acidosis, having a missense c.640C>T (p.His214Tyr) variant in TAZ, which is considered a pathogenic variant based on the previously reported amino acid substitution at the same site (c.641A>G, p.His214Arg). However, in this previously reported case, heart function was compensated and not entirely similar to the present case. Silico prediction analysis suggested that c.640C>T could alter the TAZ messenger RNA (mRNA) splicing process. TAZ mRNAs in isolated peripheral mononuclear cells from the patient and in vitro splicing analysis using minigenes of TAZ found an 8 bp deletion at the 3' end of exon 8, which resulted in the formation of a termination codon in the coding region of exon 9 (H214Nfs*3). These findings suggest that splicing abnormalities should always be considered in BTHS.
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Affiliation(s)
- Atsuhito Takeda
- Department of Pediatrics, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Masahiro Ueki
- Department of Pediatrics, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Jiro Abe
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Kazuhiro Maeta
- KNC Department of Nucleic Acid Drug Discovery, Faculty of Rehabilitation, Kobe Gakuin University, Kobe, Japan
- Research Center for Locomotion Biology, Kobe Gakuin University, Kobe, Japan
| | - Tomoko Horiguchi
- KNC Department of Nucleic Acid Drug Discovery, Faculty of Rehabilitation, Kobe Gakuin University, Kobe, Japan
- Research Center for Locomotion Biology, Kobe Gakuin University, Kobe, Japan
| | - Hirokuni Yamazawa
- Department of Pediatrics, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Gaku Izumi
- Department of Pediatrics, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Ayako Chida-Nagai
- Department of Pediatrics, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Daisuke Sasaki
- Department of Pediatrics, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Takao Tsujioka
- Department of Pediatrics, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Itsumi Sato
- Department of Pediatrics, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Masahiro Shiraishi
- Department of Pediatrics, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Masafumi Matsuo
- KNC Department of Nucleic Acid Drug Discovery, Faculty of Rehabilitation, Kobe Gakuin University, Kobe, Japan
- Research Center for Locomotion Biology, Kobe Gakuin University, Kobe, Japan
- Faculty of Health Sciences, Kobe Tokiwa University, Kobe, Japan
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3
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Płatek T, Sordyl M, Polus A, Olszanecka A, Kroczka S, Solnica B. Analysis of tafazzin and deoxyribonuclease 1 like 1 transcripts and X chromosome sequencing in the evaluation of the effect of mosaicism in the TAZ gene on phenotypes in a family affected by Barth syndrome. Mutat Res 2022; 826:111812. [PMID: 36628843 DOI: 10.1016/j.mrfmmm.2022.111812] [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: 07/15/2022] [Revised: 11/11/2022] [Accepted: 12/23/2022] [Indexed: 12/31/2022]
Abstract
Barth syndrome is a rare disease affecting mitochondria structure and function in males. In our previous study, we have shown a new mutation (c.83T>A, p.Val28Glu) in the TAZ gene in two affected patients with congenital cardiomyopathy. Furthermore, women in this family had no mutations in their blood cells, whereas they only had mutations in the oral epithelial cells. The objective of the project was to evaluate the effect of intertissue mosaicisms on the Barth syndrome phenotypes, searching for another disease-related loci on chromosome X and finally to assess the consequences of the mutation. We conducted the advanced genetic study including cytogenetic research (constitutional karyotyping in blood and fibroblasts), NGS sequencing (with custom chromosome X sequencing together with the evaluation of loss of heterozygosity (LOH) and aberrations (CNV) in the whole genome) in four different tissues and sequencing of tafazzin and deoxyribonuclease 1 like 1 transcripts. The presence of deletions within the 5'untranslated region of the TAZ gene and/or the noncoding regions of the DNASE1L1 gene were detected in several tissues. Whereas, there is no intertissue mosaicism regarding point mutation in TAZ gene in all investigated tissues in female carriers. Only the male patient presented biochemical markers and neurological symptoms of Barth syndrome. All the female carriers are healthy and have normal tafazzin and deoxyribonuclease 1 like 1 transcripts in 2 analyzed tissues. The conclusion of this study is that we cannot rule out or confirm mosaicism in the noncoding regions of TAZ or DNASE1L1 genes, but this is not clinically relevant in female carriers because they are healthy. Finally, it has been proven that mutation (c.83T>A, p.Val28Glu) is responsible for disease in males in this family.
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Affiliation(s)
- Teresa Płatek
- Department of Clinical Biochemistry, Jagiellonian University Medical College, Kraków, Poland.
| | - Maria Sordyl
- Department of Clinical Biochemistry, Jagiellonian University Medical College, Kraków, Poland
| | - Anna Polus
- Department of Clinical Biochemistry, Jagiellonian University Medical College, Kraków, Poland
| | - Agnieszka Olszanecka
- 1st Department of Cardiology, Interventional Electrocardiology and Hypertension, Faculty of Medicine, Jagiellonian University Medical College, Krakow, Poland
| | - Sławomir Kroczka
- Department of Child and Adolescent Neurology, Jagiellonian University Medical College, Krakow, Poland; Department of Child Neurology, University Children's Hospital, Krakow, Poland
| | - Bogdan Solnica
- Department of Clinical Biochemistry, Jagiellonian University Medical College, Kraków, Poland
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4
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Petit PX, Ardilla-Osorio H, Penalvia L, Nathan E. R. Tafazzin Mutation Affecting Cardiolipin Leads to Increased Mitochondrial Superoxide Anions and Mitophagy Inhibition in Barth Syndrome. Cells 2020; 9:cells9102333. [PMID: 33096711 PMCID: PMC7589545 DOI: 10.3390/cells9102333] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/19/2020] [Accepted: 10/20/2020] [Indexed: 01/01/2023] Open
Abstract
Tafazzin is a phospholipid transacylase that catalyzes the remodeling of cardiolipin, a mitochondrial phospholipid required for oxidative phosphorylation. Mutations of the tafazzin gene cause Barth syndrome, which is characterized by mitochondrial dysfunction and dilated cardiomyopathy, leading to premature death. However, the molecular mechanisms underlying the cause of mitochondrial dysfunction in Barth syndrome remain poorly understood. We again highlight the fact that the tafazzin deficiency is also linked to defective oxidative phosphorylation associated with oxidative stress. All the mitochondrial events are positioned in a context where mitophagy is a key element in mitochondrial quality control. Here, we investigated the role of tafazzin in mitochondrial homeostasis dysregulation and mitophagy alteration. Using a HeLa cell model of tafazzin deficiency, we show that dysregulation of tafazzin in HeLa cells induces alteration of mitophagy. Our findings provide some additional insights into mitochondrial dysfunction associated with Barth syndrome, but also show that mitophagy inhibition is concomitant with apoptosis dysfunction through the inability of abnormal mitochondrial cardiolipin to assume its role in cytoplasmic signal transduction. Our work raises hope that pharmacological manipulation of the mitophagic pathway together with mitochondrially targeted antioxidants may provide new insights leading to promising treatment for these highly lethal conditions.
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Affiliation(s)
- Patrice X. Petit
- SSPIN Saints-Pères Paris Institut de Neurosciences, CNRS UMR 8003, “Mitochondria, Apoptosis and Autophagy Signalling” Université de Paris—Campus Saint-Germain, 45 rue des Saints-Pères, 75006 Paris, France; (L.P.); (R.N.E.)
- Correspondence: or ; Tel.: +33(0)6-78-24-80-87
| | - Hector Ardilla-Osorio
- Laboratoire Cellules Souches et Prions, INSERM-S 1124, Université de Paris—Campus Saint-Germain, 45 rue des Saints Pères, 75006 Paris, France;
| | - Lucile Penalvia
- SSPIN Saints-Pères Paris Institut de Neurosciences, CNRS UMR 8003, “Mitochondria, Apoptosis and Autophagy Signalling” Université de Paris—Campus Saint-Germain, 45 rue des Saints-Pères, 75006 Paris, France; (L.P.); (R.N.E.)
| | - Rainey Nathan E.
- SSPIN Saints-Pères Paris Institut de Neurosciences, CNRS UMR 8003, “Mitochondria, Apoptosis and Autophagy Signalling” Université de Paris—Campus Saint-Germain, 45 rue des Saints-Pères, 75006 Paris, France; (L.P.); (R.N.E.)
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5
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Chin MT, Conway SJ. Role of Tafazzin in Mitochondrial Function, Development and Disease. J Dev Biol 2020; 8:jdb8020010. [PMID: 32456129 PMCID: PMC7344621 DOI: 10.3390/jdb8020010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 05/19/2020] [Accepted: 05/20/2020] [Indexed: 12/19/2022] Open
Abstract
Tafazzin, an enzyme associated with the rare inherited x-linked disorder Barth Syndrome, is a nuclear encoded mitochondrial transacylase that is highly conserved across multiple species and plays an important role in mitochondrial function. Numerous studies have elucidated the mechanisms by which Tafazzin affects mitochondrial function, but its effects on development and susceptibility to adult disease are incompletely understood. The purpose of this review is to highlight previous functional studies across a variety of model organisms, introduce recent studies that show an important role in development, and also to provide an update on the role of Tafazzin in human disease. The profound effects of Tafazzin on cardiac development and adult cardiac homeostasis will be emphasized. These studies underscore the importance of mitochondrial function in cardiac development and disease, and also introduce the concept of Tafazzin as a potential therapeutic modality.
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Affiliation(s)
- Michael T. Chin
- Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA 02111, USA
- Correspondence: (M.T.C.); (S.J.C.); Tel.: +1-617-636-8776 (M.T.C.); +1-317-278-8780 (S.J.C.)
| | - Simon J. Conway
- Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Correspondence: (M.T.C.); (S.J.C.); Tel.: +1-617-636-8776 (M.T.C.); +1-317-278-8780 (S.J.C.)
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6
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Schlame M, Xu Y. The Function of Tafazzin, a Mitochondrial Phospholipid-Lysophospholipid Acyltransferase. J Mol Biol 2020; 432:5043-5051. [PMID: 32234310 DOI: 10.1016/j.jmb.2020.03.026] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Revised: 03/13/2020] [Accepted: 03/25/2020] [Indexed: 12/21/2022]
Abstract
Tafazzin is a mitochondrial enzyme that exchanges fatty acids between phospholipids by phospholipid-lysophospholipid transacylation. The reaction alters the molecular species composition and, as a result, the physical properties of lipids. In vivo, the most important substrate of tafazzin is the mitochondria-specific lipid cardiolipin. Tafazzin mutations cause the human disease Barth syndrome, which presents with cardiomyopathy, skeletal muscle weakness, fatigue, and other symptoms, probably all related to mitochondrial dysfunction. The reason why mitochondria require tafazzin is still not known, but recent evidence suggests that tafazzin may lower the energy cost associated with protein crowding in the inner mitochondrial membrane.
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Affiliation(s)
- Michael Schlame
- Departments of Anesthesiology and Cell Biology, New York University School of Medicine, New York, NY 10016, USA.
| | - Yang Xu
- Departments of Anesthesiology and Cell Biology, New York University School of Medicine, New York, NY 10016, USA
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Shilovsky GA, Putyatina TS, Ashapkin VV, Yamskova OV, Lyubetsky VA, Sorokina EV, Shram SI, Markov AV, Vyssokikh MY. Biological Diversity and Remodeling of Cardiolipin in Oxidative Stress and Age-Related Pathologies. BIOCHEMISTRY (MOSCOW) 2020; 84:1469-1483. [PMID: 31870251 DOI: 10.1134/s000629791912006x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Age-related dysfunctions are accompanied by impairments in the mitochondrial morphology, activity of signaling pathway, and protein interactions. Cardiolipin is one of the most important phospholipids that maintains the curvature of the cristae and facilitates assembly and interaction of complexes and supercomplexes of the mitochondrial respiratory chain. The fatty acid composition of cardiolipin influences the biophysical properties of the membrane and, therefore, is crucial for the mitochondrial bioenergetics. The presence of unsaturated fatty acids in cardiolipin is the reason of its susceptibility to oxidative damage. Damaged cardiolipin undergoes remodeling by phospholipases, acyltransferases, and transacylases, creating a highly specific fatty acyl profile for each tissue. In this review, we discuss the variability of cardiolipin fatty acid composition in various species and different tissues of the same species, both in the norm and at various pathologies (e.g., age-related diseases, oxidative and traumatic stresses, knockouts/knockdowns of enzymes of the cardiolipin synthesis pathway). Progressive pathologies, including age-related ones, are accompanied by cardiolipin depletion and decrease in the efficiency of its remodeling, as well as the activation of an alternative way of pathological remodeling, which causes replacement of cardiolipin fatty acids with polyunsaturated ones (e.g., arachidonic or docosahexaenoic acids). Drugs or special diet can contribute to the partial restoration of the cardiolipin acyl profile to the one rich in fatty acids characteristic of an intact organ or tissue, thereby correcting the consequences of pathological or insufficient cardiolipin remodeling. In this regard, an urgent task of biomedicine is to study the mechanism of action of mitochondria-targeted antioxidants effective in the treatment of age-related pathologies and capable of accumulating not only in vitro, but also in vivo in the cardiolipin-enriched membrane fragments.
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Affiliation(s)
- G A Shilovsky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia. .,Lomonosov Moscow State University, Faculty of Biology, Moscow, 119234, Russia.,Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, 127051, Russia
| | - T S Putyatina
- Lomonosov Moscow State University, Faculty of Biology, Moscow, 119234, Russia
| | - V V Ashapkin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - O V Yamskova
- Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991, Russia
| | - V A Lyubetsky
- Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, 127051, Russia
| | - E V Sorokina
- Lomonosov Moscow State University, Faculty of Biology, Moscow, 119234, Russia
| | - S I Shram
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow, 123182, Russia
| | - A V Markov
- Lomonosov Moscow State University, Faculty of Biology, Moscow, 119234, Russia
| | - M Y Vyssokikh
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
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8
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New C-Terminal Conserved Regions of Tafazzin, a Catalyst of Cardiolipin Remodeling. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2019; 2019:2901057. [PMID: 31781330 PMCID: PMC6855050 DOI: 10.1155/2019/2901057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 08/16/2019] [Indexed: 12/20/2022]
Abstract
Cardiolipin interacts with many proteins of the mitochondrial inner membrane and, together with cytochrome C and creatine kinase, activates them. It can be considered as an integrating factor for components of the mitochondrial respiratory chain, which provides for an efficient transfer of electrons and protons. The major, if not the only, factor of cardiolipin maturation is tafazzin. Variations of isoform proportions of this enzyme can cause severe diseases such as Barth syndrome. Using bioinformatic methods, we have found conserved C-terminal regions in many tafazzin isoforms and identified new mammalian species that acquired exon 5 as well as rare occasions of intron retention between exons 8 and 9. The regions in the C-terminal part arise from frameshifts relative to the full-length TAZ transcript after skipping exon 9 or retention of the intron between exons 10 and 11. These modifications demonstrate specific distribution among the orders of mammals. The dependence of the species maximum lifespan, body weight, and mitochondrial metabolic rate on the modifications has been demonstrated. Arguably, unconventional tafazzin isoforms provide for the optimal balance between the increased biochemical activity of mitochondria (resulting from specific environmental or nutritional conditions) and lifespan maintenance; and the functional role of such isoforms is linked to the modification of the primary and secondary structures at their C-termini.
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9
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Ren M, Miller PC, Schlame M, Phoon CKL. A critical appraisal of the tafazzin knockdown mouse model of Barth syndrome: what have we learned about pathogenesis and potential treatments? Am J Physiol Heart Circ Physiol 2019; 317:H1183-H1193. [PMID: 31603701 DOI: 10.1152/ajpheart.00504.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Pediatric heart failure remains poorly understood, distinct in many aspects from adult heart failure. Limited data point to roles of altered mitochondrial functioning and, in particular, changes in mitochondrial lipids, especially cardiolipin. Barth syndrome is a mitochondrial disorder caused by tafazzin mutations that lead to abnormal cardiolipin profiles. Patients are afflicted by cardiomyopathy, skeletal myopathy, neutropenia, and growth delay. A mouse model of Barth syndrome was developed a decade ago, which relies on a doxycycline-inducible short hairpin RNA to knock down expression of tafazzin mRNA (TAZKD). Our objective was to review published data from the TAZKD mouse to determine its contributions to our pathogenetic understanding of, and potential treatment strategies for, Barth syndrome. In regard to the clinical syndrome, the reported physiological, biochemical, and ultrastructural abnormalities of the mouse model mirror those in Barth patients. Using this model, the peroxisome proliferator-activated receptor pan-agonist bezafibrate has been suggested as potential therapy because it ameliorated the cardiomyopathy in TAZKD mice, while increasing mitochondrial biogenesis. A clinical trial is now underway to test bezafibrate in Barth syndrome patients. Thus the TAZKD mouse model of Barth syndrome has led to important insights into disease pathogenesis and therapeutic targets, which can potentially translate to pediatric heart failure.
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Affiliation(s)
- Mindong Ren
- Department of Anesthesiology, New York University School of Medicine, New York, New York.,Department of Cell Biology, New York University School of Medicine, New York, New York
| | - Paighton C Miller
- Department of Pediatrics, Division of Pediatric Cardiology, New York University School of Medicine, New York, New York
| | - Michael Schlame
- Department of Anesthesiology, New York University School of Medicine, New York, New York.,Department of Cell Biology, New York University School of Medicine, New York, New York
| | - Colin K L Phoon
- Department of Pediatrics, Division of Pediatric Cardiology, New York University School of Medicine, New York, New York
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10
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Finsterer J. Barth syndrome: mechanisms and management. APPLICATION OF CLINICAL GENETICS 2019; 12:95-106. [PMID: 31239752 PMCID: PMC6558240 DOI: 10.2147/tacg.s171481] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 05/04/2019] [Indexed: 12/21/2022]
Abstract
Objectives: Barth syndrome is an ultra-rare, infantile-onset, X-linked recessive mitochondrial disorder, primarily affecting males, due to variants in TAZ encoding for the cardiolipin transacylase tafazzin. This review aimed to summarize and discuss recent and earlier findings concerning the etiology, pathogenesis, clinical presentation, diagnosis, treatment, and outcome of Barth syndrome. Method: A literature review was undertaken through a MEDLINE search. Results: The phenotype of Barth syndrome is highly variable but most frequently patients present with hypertrophic/dilated/non-compaction cardiomyopathy, fibroelastosis, arrhythmias, neutropenia, mitochondrial myopathy, growth retardation, dysmorphism, cognitive impairment, and other, rarer features. Lactic acid and creatine kinase, and blood and urine organic acids, particularly 3-methylglutaconic acid and monolysocardiolipin, are often elevated. Cardiolipin is decreased. Biochemical investigations may show decreased activity of various respiratory chain complexes. The diagnosis is confirmed by documentation of a causative TAZ variant. Treatment is symptomatic and directed toward treating heart failure, arrhythmias, neutropenia, and mitochondrial myopathy. Conclusions: Although Barth syndrome is still an orphan disease, with fewer than 200 cases described so far, there is extensive ongoing research with regard to its pathomechanism and new therapeutic approaches. Although most of these approaches are still experimental, it can be expected that causative strategies will be developed in the near future.
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Affiliation(s)
- Josef Finsterer
- Krankenanstalt Rudolfstiftung, Messerli Institute, Vienna, Austria
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11
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Imai-Okazaki A, Kishita Y, Kohda M, Yatsuka Y, Hirata T, Mizuno Y, Harashima H, Hirono K, Ichida F, Noguchi A, Yoshida M, Tokorodani C, Nishiuchi R, Takeda A, Nakaya A, Sakata Y, Murayama K, Ohtake A, Okazaki Y. Barth Syndrome: Different Approaches to Diagnosis. J Pediatr 2018; 193:256-260. [PMID: 29249525 DOI: 10.1016/j.jpeds.2017.09.075] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 07/18/2017] [Accepted: 09/27/2017] [Indexed: 12/28/2022]
Abstract
The diagnosis of Barth syndrome is challenging owing to the wide phenotypic spectrum with allelic heterogeneity. Here we report 3 cases of Barth syndrome with phenotypic and allelic heterogeneity that were diagnosed by different approaches, including whole exome sequencing and final confirmation by reverse-transcription polymease chain reaction.
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Affiliation(s)
- Atsuko Imai-Okazaki
- Department of Genome Informatics, Graduate School of Medicine, Osaka University, Osaka, Japan; Department of Cardiovascular Medicine, Graduate School of Medicine, Osaka University, Osaka, Japan; Division of Genomic Medicine Research, Medical Genomics Center, National Center for Global Health and Medicine, Tokyo, Japan
| | - Yoshihito Kishita
- Division of Functional Genomics and Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Masakazu Kohda
- Division of Translational Research, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Yukiko Yatsuka
- Division of Functional Genomics and Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Tomoko Hirata
- Division of Translational Research, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Yosuke Mizuno
- Division of Functional Genomics and Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Hiroko Harashima
- Department of Pediatrics, Saitama Medical University, Saitama, Japan
| | - Keiichi Hirono
- Department of Pediatrics, Graduate School of Medicine, University of Toyama, Toyama, Japan
| | - Fukiko Ichida
- Department of Pediatrics, Graduate School of Medicine, University of Toyama, Toyama, Japan
| | - Atsuko Noguchi
- Department of Pediatrics, Graduate School of Medicine, Akita University, Akita, Japan
| | - Masayuki Yoshida
- Department of Molecular Pathology and Tumor Pathology, Graduate School of Medicine, Akita University, Akita, Japan
| | - Chiho Tokorodani
- Department of Pediatrics, Kochi Health Sciences Center, Kochi, Japan
| | - Ritsuo Nishiuchi
- Department of Pediatrics, Kochi Health Sciences Center, Kochi, Japan
| | - Atsuhito Takeda
- Department of Pediatrics, Graduate School of Medicine, Hokkaido University, Hokkaido, Japan
| | - Akihiro Nakaya
- Department of Genome Informatics, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Yasushi Sakata
- Department of Cardiovascular Medicine, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Kei Murayama
- Department of Metabolism, Chiba Children's Hospital, Chiba, Japan
| | - Akira Ohtake
- Department of Pediatrics, Saitama Medical University, Saitama, Japan; Center for Intractable Diseases, Saitama Medical University Hospital, Saitama, Japan
| | - Yasushi Okazaki
- Division of Functional Genomics and Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan; Division of Translational Research, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan.
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12
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Dinca AA, Chien WM, Chin MT. Identification of novel mitochondrial localization signals in human Tafazzin, the cause of the inherited cardiomyopathic disorder Barth syndrome. J Mol Cell Cardiol 2018; 114:83-92. [PMID: 29129703 PMCID: PMC5801207 DOI: 10.1016/j.yjmcc.2017.11.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 10/30/2017] [Accepted: 11/08/2017] [Indexed: 01/15/2023]
Abstract
Mutations in the gene tafazzin (TAZ) result in Barth syndrome (BTHS). Patients present with hypotonia, cyclic neutropenia, 3-methyglutaconic aciduria, and cardiomyopathy, which is the major cause of mortality. The recessive, X-linked TAZ gene encodes a mitochondrial membrane-associated phospholipid modifying enzyme, which adds unsaturated fatty acid species to monolysocardiolipin to generate mature cardiolipin in the mitochondrial membrane that is essential for mitochondrial morphology and function. To identify intrinsic mitochondrial localization sequences in the human TAZ protein, we made sequential TAZ peptide-eGFP fusion protein expression constructs and analyzed the localization of eGFP fluorescence by confocal microscopy. We assessed these fusion proteins for mitochondrial localization through cotransfection of H9c2 cells with plasmids encoding organellar markers linked to TdTomato. We have identified two peptides of TAZ that are independently responsible for mitochondrial localization. Using CRISPR-generated TAZ knock out cell lines, we found that these peptides are able to direct proteins to mitochondria in the absence of endogenous TAZ. These peptides are not located within the predicted enzymatic clefts of TAZ, implying that some BTHS disease causing mutations may affect mitochondrial localization without affecting transacylase activity. These novel peptides improve our understanding of TAZ intracellular trafficking, provide insight into the molecular basis of BTHS and provide molecular reagents for developing targeted mitochondrial therapies.
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Affiliation(s)
- Ana A Dinca
- Department of Pathology, Division of Cardiology, University of Washington, Seattle, Washington, United States
| | - Wei-Ming Chien
- Department of Medicine, Division of Cardiology, University of Washington, Seattle, Washington, United States
| | - Michael T Chin
- Department of Pathology, Division of Cardiology, University of Washington, Seattle, Washington, United States; Department of Medicine, Division of Cardiology, University of Washington, Seattle, Washington, United States.
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Tafazzin (TAZ) promotes the tumorigenicity of cervical cancer cells and inhibits apoptosis. PLoS One 2017; 12:e0177171. [PMID: 28489874 PMCID: PMC5425199 DOI: 10.1371/journal.pone.0177171] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Accepted: 04/24/2017] [Indexed: 11/19/2022] Open
Abstract
Tafazzin (TAZ) is often aberrantly expressed in some cancers, including rectal cancer and thyroid neoplasms. However, the function of TAZ in cervical cancer cells remains unknown. This study aims to explore the expression and function of TAZ in cervical cancer cells. Here, we determined the expression of TAZ protein in normal cervical tissue (NC, n = 27), high-grade squamous intraepithelial lesions (HSIL, n = 26) and squamous cervical carcinoma (SCC, n = 41) by immunohistochemistry, the expression of TAZ protein gradually increased from NC to HSIL to SCC. TAZ was overexpressed or down-regulated in cervical cancer cells by stably transfecting a TAZ-expressing plasmid or a shRNA plasmid targeting TAZ. In vitro, the cell growth curves and MTT assays showed that TAZ may promote the growth and viability of cervical cancer cells. In vivo, xenografts experiment showed that TAZ may increase tumor-forming ability. The percentage of apoptosis cells analyzed by FACS and TUNEL assays consistently showed that TAZ inhibits apoptosis in cervical cancer cells. Furthermore, the Cleaved Caspase 9 and Cleaved Caspase 3 were down-regulated by TAZ in cervical cancer cells. Taken together, this study demonstrated that TAZ is overexpressed in cervical cancer and may promote tumorigenicity of cervical cancer cells and inhibit apoptosis.
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Wang J, Guo Y, Huang M, Zhang Z, Zhu J, Liu T, Shi L, Li F, Huang H, Fu L. Identification of TAZ mutations in pediatric patients with cardiomyopathy by targeted next-generation sequencing in a Chinese cohort. Orphanet J Rare Dis 2017; 12:26. [PMID: 28183324 PMCID: PMC5301434 DOI: 10.1186/s13023-016-0562-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 12/23/2016] [Indexed: 12/31/2022] Open
Abstract
Background Barth syndrome (BTHS) is a rare X-linked recessive disease characterized by cardiomyopathy, neutropenia, skeletal myopathy and growth delay. Early diagnosis and appropriate treatment may improve the prognosis of this disease. The purpose of this study is to determine the role of targeted next-generation sequencing (NGS) in the early diagnosis of BTHS in children with cardiomyopathy. Methods During the period between 2012 and 2015, a gene panel-based NGS approach was used to search for potentially disease-causing genetic variants in all patients referred to our institution with a clinical diagnosis of primary cardiomyopathy. NGS was performed using the Illumina sequencing system. Results A total of 180 Chinese pediatric patients (114 males and 66 females) diagnosed with primary cardiomyopathy were enrolled in this study. TAZ mutations were identified in four of the male index patients, including two novel mutations (c.527A > G, p.H176R and c.134_136delinsCC, p.H45PfsX38). All four probands and two additional affected male family members were born at full term with a median birth weight of 2350 g (range, 2000–2850 g). The median age at diagnosis of cardiomyopathy was 3.0 months (range, 1.0–20.0 months). The baseline echocardiography revealed prominent dilation and trabeculations of the left ventricle with impaired systolic function in the six patients, four of which fulfilled the diagnostic criteria of left ventricular noncompaction. Other aspects of their clinical presentations included hypotonia (6/6), growth delay (6/6), neutropenia (3/6) and 3-methylglutaconic aciduria (4/5). Five patients died at a median age of 7.5 months (range, 7.0–12.0 months). The cause of death was heart failure associated with infection in three patients and cardiac arrhythmia in two patients. The remaining one patient survived beyond infancy but had fallen into a persistent vegetative state after suffering from cardiac arrest. Conclusions This is the first report of systematic mutation screening of TAZ in a large cohort of pediatric patients with primary cardiomyopathy using the NGS approach. TAZ mutations were found in 4/114 (3.5%) male patients with primary cardiomyopathy. Our findings indicate that the inclusion of TAZ gene testing in cardiomyopathy genetic testing panels may contribute to the early diagnosis of BTHS.
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Affiliation(s)
- Jian Wang
- Research Division of Birth Defects, Institute of Pediatric Translational Medicine, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai, 200127, People's Republic of China
| | - Ying Guo
- Department of Cardiology, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, 1678 Dongfang Road, Pudong, Shanghai, 200127, People's Republic of China
| | - Meirong Huang
- Department of Cardiology, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, 1678 Dongfang Road, Pudong, Shanghai, 200127, People's Republic of China
| | - Zhen Zhang
- Research Division of cardiovascular disease, Institute of Pediatric Translational Medicine, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai, 200127, People's Republic of China
| | - Junxue Zhu
- Department of Cardiology, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, 1678 Dongfang Road, Pudong, Shanghai, 200127, People's Republic of China
| | - Tingliang Liu
- Department of Cardiology, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, 1678 Dongfang Road, Pudong, Shanghai, 200127, People's Republic of China
| | - Lin Shi
- Department of Cardiology, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, 1678 Dongfang Road, Pudong, Shanghai, 200127, People's Republic of China
| | - Fen Li
- Department of Cardiology, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, 1678 Dongfang Road, Pudong, Shanghai, 200127, People's Republic of China
| | - Huimin Huang
- Department of Cardiothoracic Surgery, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai, 200127, People's Republic of China
| | - Lijun Fu
- Department of Cardiology, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, 1678 Dongfang Road, Pudong, Shanghai, 200127, People's Republic of China. .,Research Division of cardiovascular disease, Institute of Pediatric Translational Medicine, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai, 200127, People's Republic of China.
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Borna NN, Kishita Y, Ishikawa K, Nakada K, Hayashi JI, Tokuzawa Y, Kohda M, Nyuzuki H, Yamashita-Sugahara Y, Nasu T, Takeda A, Murayama K, Ohtake A, Okazaki Y. A novel mutation in TAZ causes mitochondrial respiratory chain disorder without cardiomyopathy. J Hum Genet 2017; 62:539-547. [PMID: 28123175 DOI: 10.1038/jhg.2016.165] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Revised: 11/17/2016] [Accepted: 12/08/2016] [Indexed: 12/15/2022]
Abstract
Tafazzin, encoded by the TAZ gene, is a mitochondrial membrane-associated protein that remodels cardiolipin (CL), an important mitochondrial phospholipid. TAZ mutations are associated with Barth syndrome (BTHS). BTHS is an X-linked multisystemic disorder affecting usually male patients. Through sequence analysis of TAZ, we found one novel mutation c.39_60del p.(Pro14Alafs*19) by whole-exome sequencing and a reported missense mutation c.280C>T p.(Arg94Cys) by Sanger sequencing in two male patients (Pt1 and Pt2). Patient with c.280C>T mutation had dilated cardiomyopathy, while another patient with c.39_60del mutation had no feature of cardiomyopathy. A reported m.1555A>G homoplasmic variant was also identified in the patient having mutation c.39_60del by whole mitochondrial DNA sequencing method. This variant was not considered to be the main cause of mitochondrial dysfunction based on a cytoplasmic hybrid (cybrid) assay. Tafazzin expression was absent in both patient-derived fibroblast cells. Complementation of TAZ expression in fibroblasts from the patient with the novel mutation c.39_60del restored mitochondrial respiratory complex assembly. High-performance liquid chromatography-tandem mass spectrometry-based metabolic analysis revealed the decline of CL and the accumulation of monolysocardiolipin, indicating the loss of tafazzin activity. Owing to phenotypic variability, it is difficult to diagnose BTHS based on clinical features only. We conclude that genetic analysis should be performed to avoid underdiagnosis of this potentially life-threatening inborn error of metabolism.
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Affiliation(s)
- Nurun N Borna
- Division of Functional Genomics & Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Yoshihito Kishita
- Division of Functional Genomics & Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Kaori Ishikawa
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Kazuto Nakada
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Jun-Ichi Hayashi
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Yoshimi Tokuzawa
- Division of Functional Genomics & Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Masakazu Kohda
- Division of Translational Research, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Hiromi Nyuzuki
- Division of Functional Genomics & Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Yzumi Yamashita-Sugahara
- Division of Functional Genomics & Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Takashi Nasu
- Department of Pediatrics, Obihiro Kosei General Hospital, Obihiro, Japan
| | - Atsuhito Takeda
- Department of Pediatrics, Hokkaido University Graduate School of Medicine, Hokkaido, Japan
| | - Kei Murayama
- Department of Metabolism, Chiba Children's Hospital, Chiba, Japan
| | - Akira Ohtake
- Department of Pediatrics, Saitama Medical University, Saitama, Japan
| | - Yasushi Okazaki
- Division of Functional Genomics & Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan.,Division of Translational Research, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
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Saric A, Andreau K, Armand AS, Møller IM, Petit PX. Barth Syndrome: From Mitochondrial Dysfunctions Associated with Aberrant Production of Reactive Oxygen Species to Pluripotent Stem Cell Studies. Front Genet 2016; 6:359. [PMID: 26834781 PMCID: PMC4719219 DOI: 10.3389/fgene.2015.00359] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 12/15/2015] [Indexed: 12/22/2022] Open
Abstract
Mutations in the gene encoding the enzyme tafazzin, TAZ, cause Barth syndrome (BTHS). Individuals with this X-linked multisystem disorder present cardiomyopathy (CM) (often dilated), skeletal muscle weakness, neutropenia, growth retardation, and 3-methylglutaconic aciduria. Biopsies of the heart, liver and skeletal muscle of patients have revealed mitochondrial malformations and dysfunctions. It is the purpose of this review to summarize recent results of studies on various animal or cell models of Barth syndrome, which have characterized biochemically the strong cellular defects associated with TAZ mutations. Tafazzin is a mitochondrial phospholipidlysophospholipid transacylase that shuttles acyl groups between phospholipids and regulates the remodeling of cardiolipin (CL), a unique inner mitochondrial membrane phospholipid dimer consisting of two phosphatidyl residues linked by a glycerol bridge. After their biosynthesis, the acyl chains of CLs may be modified in remodeling processes involving up to three different enzymes. Their characteristic acyl chain composition depends on the function of tafazzin, although the enzyme itself surprisingly lacks acyl specificity. CLs are crucial for correct mitochondrial structure and function. In addition to their function in the basic mitochondrial function of ATP production, CLs play essential roles in cardiac function, apoptosis, autophagy, cell cycle regulation and Fe-S cluster biosynthesis. Recent developments in tafazzin research have provided strong insights into the link between mitochondrial dysfunction and the production of reactive oxygen species (ROS). An important tool has been the generation of BTHS-specific induced pluripotent stem cells (iPSCs) from BTHS patients. In a complementary approach, disease-specific mutations have been introduced into wild-type iPSC lines enabling direct comparison with isogenic controls. iPSC-derived cardiomyocytes were then characterized using biochemical and classical bioenergetic approaches. The cells are tested in a "heart-on-chip" assay to model the pathophysiology in vitro, to characterize the underlying mechanism of BTHS deriving from TAZ mutations, mitochondrial deficiencies and ROS production and leading to tissue defects, and to evaluate potential therapies with the use of mitochondrially targeted antioxidants.
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Affiliation(s)
- Ana Saric
- INSERM U 1124 "Toxicologie, Pharmacologie et Signalisation Cellulaire" and "FR 3567" CNRS Chimie, Toxicologie, Signalisation Cellulaire et Cibles Thérapeutiques, Université Paris Descartes - Centre Universitaire des Saints-PèresParis, France; Division of Molecular Medicine, Ruđer Bošković InstituteZagreb, Croatia
| | - Karine Andreau
- INSERM U 1124 "Toxicologie, Pharmacologie et Signalisation Cellulaire" and "FR 3567" CNRS Chimie, Toxicologie, Signalisation Cellulaire et Cibles Thérapeutiques, Université Paris Descartes - Centre Universitaire des Saints-Pères Paris, France
| | - Anne-Sophie Armand
- INSERM U 1124 "Toxicologie, Pharmacologie et Signalisation Cellulaire" and "FR 3567" CNRS Chimie, Toxicologie, Signalisation Cellulaire et Cibles Thérapeutiques, Université Paris Descartes - Centre Universitaire des Saints-Pères Paris, France
| | - Ian M Møller
- Department of Molecular Biology and Genetics, Aarhus University Slagelse, Denmark
| | - Patrice X Petit
- INSERM U 1124 "Toxicologie, Pharmacologie et Signalisation Cellulaire" and "FR 3567" CNRS Chimie, Toxicologie, Signalisation Cellulaire et Cibles Thérapeutiques, Université Paris Descartes - Centre Universitaire des Saints-Pères Paris, France
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Reynolds S. Successful management of Barth syndrome: a systematic review highlighting the importance of a flexible and multidisciplinary approach. J Multidiscip Healthc 2015; 8:345-58. [PMID: 26251611 PMCID: PMC4524586 DOI: 10.2147/jmdh.s54802] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
This review describes and summarizes the available evidence related to the treatment and management of Barth syndrome. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standards were used to identify articles published between December 2004 and January 2015. The Cochrane Population, Intervention, Control, Outcome, Study Design (PICOS) approach was used to guide the article selection and evaluation process. Of the 128 articles screened, 28 articles matched the systematic review inclusion criteria. The results of this review indicate the need for a flexible and multidisciplinary approach to manage the symptoms most commonly associated with Barth syndrome. It is recommended that a comprehensive care team should include individuals with Barth syndrome, their family members and caregivers, as well as medical, rehabilitative, nutritional, psychological, and educational professionals. The evidence for specific treatments, therapies, and techniques for individuals with Barth syndrome is currently lacking in both quality and quantity.
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Affiliation(s)
- Stacey Reynolds
- Department of Occupational Therapy, Virginia Commonwealth University, Richmond, VA, USA
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18
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Vaz-Drago R, Pinheiro MT, Martins S, Enguita FJ, Carmo-Fonseca M, Custódio N. Transcription-coupled RNA surveillance in human genetic diseases caused by splice site mutations. Hum Mol Genet 2015; 24:2784-95. [PMID: 25652404 DOI: 10.1093/hmg/ddv039] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 01/31/2015] [Indexed: 12/15/2022] Open
Abstract
Current estimates indicate that approximately one-third of all disease-causing mutations are expected to disrupt splicing. Abnormal splicing often leads to disruption of the reading frame with introduction of a premature termination codon (PTC) that targets the mRNA for degradation in the cytoplasm by nonsense mediated decay (NMD). In addition to NMD there are RNA surveillance mechanisms that act in the nucleus while transcripts are still associated with the chromatin template. However, the significance of nuclear RNA quality control in the context of human genetic diseases is unknown. Here we used patient-derived lymphoblastoid cell lines as disease models to address how biogenesis of mRNAs is affected by splice site mutations. We observed that most of the mutations analyzed introduce PTCs and trigger mRNA degradation in the cytoplasm. However, for some mutant transcripts, RNA levels associated with chromatin were found down-regulated. Quantification of nascent transcripts further revealed that a subset of genes containing splicing mutations (SM) have reduced transcriptional activity. Following treatment with the translation inhibitor cycloheximide the cytoplasmic levels of mutant RNAs increased, while the levels of chromatin-associated transcripts remained unaltered. These results suggest that transcription-coupled surveillance mechanisms operate independently from NMD to reduce cellular levels of abnormal RNAs caused by SM.
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Affiliation(s)
- Rita Vaz-Drago
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
| | - Marco T Pinheiro
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
| | - Sandra Martins
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
| | - Francisco J Enguita
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
| | - Maria Carmo-Fonseca
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
| | - Noélia Custódio
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
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Kassahn KS, Scott HS, Caramins MC. Integrating massively parallel sequencing into diagnostic workflows and managing the annotation and clinical interpretation challenge. Hum Mutat 2014; 35:413-23. [PMID: 24510514 DOI: 10.1002/humu.22525] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 01/30/2014] [Indexed: 11/07/2022]
Abstract
Massively parallel sequencing has become a powerful tool for the clinical management of patients with applications in diagnosis, guidance of treatment, prediction of drug response, and carrier screening. A considerable challenge for the clinical implementation of these technologies is the management of the vast amount of sequence data generated, in particular the annotation and clinical interpretation of genomic variants. Here, we describe annotation steps that can be automated and common strategies employed for variant prioritization. The definition of best practice standards for variant annotation and prioritization is still ongoing; at present, there is limited consensus regarding an optimal clinical sequencing pipeline. We provide considerations to help define these. For the first time, clinical genetics and genomics is not limited by our ability to sequence, but our ability to clinically interpret and use genomic information in health management. We argue that the development of standardized variant annotation and interpretation approaches and software tools implementing these warrants further support. As we gain a better understanding of the significance of genomic variation through research, patients will be able to benefit from the full scope that these technologies offer.
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Affiliation(s)
- Karin S Kassahn
- Genetic and Molecular Pathology, SA Pathology, Women's and Children's Hospital, North Adelaide, South Australia, 5006, Australia; School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia, 5000, Australia
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