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Shen MM, Rummey C, Lynch DR. Phenotypic variation of FXN compound heterozygotes in a Friedreich ataxia cohort. Ann Clin Transl Neurol 2024; 11:1110-1121. [PMID: 38396238 PMCID: PMC11093247 DOI: 10.1002/acn3.52027] [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: 12/13/2023] [Revised: 01/24/2024] [Accepted: 02/09/2024] [Indexed: 02/25/2024] Open
Abstract
OBJECTIVE Most individuals with Friedreich ataxia (FRDA) have homozygous GAA triplet repeat expansions in the FXN gene, correlating with a typical phenotype of ataxia and cardiomyopathy. A minority are compound heterozygotes carrying a GAA expansion on one allele and a mutation on the other. The study aim was to examine phenotypic variation among compound heterozygotes. METHODS Data on FXN mutations were obtained from the Friedreich Ataxia Clinical Outcome Measures Study (FA-COMS). We compared clinical features in a single-site FA-COMS cohort of 51 compound heterozygous and 358 homozygous patients, including quantitative measures of cardiac, neurologic, and visual disease progression. RESULTS Non-GAA repeat mutations were associated with reduced cardiac disease, and patients with minimal/no function mutations otherwise had a typical FRDA phenotype but with significantly more severe progression. The partial function mutation group was characterized by relative sparing of bulbar and upper limb function, as well as particularly low cardiac involvement. Other clinical features in this group, including optic atrophy and diabetes mellitus, varied widely depending on the specific type of partial function mutation. INTERPRETATION These data support that the typical FRDA phenotype is driven by frataxin deficiency, especially severe in compound heterozygotes with minimal/no function mutations, whereas the heterogeneous presentations of those with partial function mutations may indicate other contributing factors to FRDA pathogenesis.
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Affiliation(s)
- Megan M. Shen
- Division of NeurologyThe Children's Hospital of PhiladelphiaPhiladelphiaPennsylvaniaUSA
- Perelman School of Medicine, University of Pennsylvania.PhiladelphiaPennsylvaniaUSA
| | | | - David R. Lynch
- Division of NeurologyThe Children's Hospital of PhiladelphiaPhiladelphiaPennsylvaniaUSA
- Perelman School of Medicine, University of Pennsylvania.PhiladelphiaPennsylvaniaUSA
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Lynch DR, Rojsajjakul T, Subramony SH, Perlman SL, Keita M, Mesaros C, Blair IA. Frataxin analysis using triple quadrupole mass spectrometry: application to a large heterogeneous clinical cohort. J Neurol 2024; 271:1844-1849. [PMID: 38063871 DOI: 10.1007/s00415-023-12118-x] [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: 10/25/2023] [Revised: 11/13/2023] [Accepted: 11/14/2023] [Indexed: 01/23/2024]
Abstract
BACKGROUND Friedreich ataxia is a progressive multisystem disorder caused by deficiency of the protein frataxin; a small mitochondrial protein involved in iron sulfur cluster synthesis. Two types of frataxin exist: FXN-M, found in most cells, and FXN-E, found almost exclusively in red blood cells. Treatments in clinical trials include frataxin restoration by gene therapy, protein replacement, and epigenetic therapies, all of which necessitate sensitive assays for assessing frataxin levels. METHODS In the present study, we have used a triple quadrupole mass spectrometry-based assay to examine the features of both types of frataxin levels in blood in a large heterogenous cohort of 106 patients with FRDA. RESULTS Frataxin levels (FXN-E and FXN M) were predicted by GAA repeat length in regression models (R2 values = 0.51 and 0.27, respectively), and conversely frataxin levels predicted clinical status as determined by modified Friedreich Ataxia Rating scale scores and by disability status (R2 values = 0.13-0.16). There was no significant change in frataxin levels in individual subjects over time, and apart from start codon mutations, FXN-E and FXN-M levels were roughly equal. Accounting for hemoglobin levels in a smaller sub-cohort improved prediction of both FXN-E and FXN-M levels from R2 values of (0.3-0.38 to 0.20-0.51). CONCLUSION The present data show that assay of FXN-M and FXN-E levels in blood provides an appropriate biofluid for assessing their repletion in particular clinical contexts.
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Affiliation(s)
- David R Lynch
- Penn/CHOP Friedreich Ataxia Center of Excellence, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
- Children's Hospital of Philadelphia, University of Pennsylvania Perelman School of Medicine, 502F Abramson Research Center, 3615 Civic Center Blvd, Philadelphia, PA, 19104-4318, USA.
| | - Teerapat Rojsajjakul
- Penn/CHOP Friedreich Ataxia Center of Excellence, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - S H Subramony
- Department of Neurology, University of Florida, Gainesville, FL, 32608, USA
| | - Susan L Perlman
- Department of Neurology, David Geffen School of Medicine, UCLA, Los Angeles, CA, 90095, USA
| | - Medina Keita
- Penn/CHOP Friedreich Ataxia Center of Excellence, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Clementina Mesaros
- Penn/CHOP Friedreich Ataxia Center of Excellence, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Ian A Blair
- Penn/CHOP Friedreich Ataxia Center of Excellence, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
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3
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Ast T, Itoh Y, Sadre S, McCoy JG, Namkoong G, Wengrod JC, Chicherin I, Joshi PR, Kamenski P, Suess DLM, Amunts A, Mootha VK. METTL17 is an Fe-S cluster checkpoint for mitochondrial translation. Mol Cell 2024; 84:359-374.e8. [PMID: 38199006 PMCID: PMC11046306 DOI: 10.1016/j.molcel.2023.12.016] [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: 11/02/2022] [Revised: 08/13/2023] [Accepted: 12/12/2023] [Indexed: 01/12/2024]
Abstract
Friedreich's ataxia (FA) is a debilitating, multisystemic disease caused by the depletion of frataxin (FXN), a mitochondrial iron-sulfur (Fe-S) cluster biogenesis factor. To understand the cellular pathogenesis of FA, we performed quantitative proteomics in FXN-deficient human cells. Nearly every annotated Fe-S cluster-containing protein was depleted, indicating that as a rule, cluster binding confers stability to Fe-S proteins. We also observed depletion of a small mitoribosomal assembly factor METTL17 and evidence of impaired mitochondrial translation. Using comparative sequence analysis, mutagenesis, biochemistry, and cryoelectron microscopy, we show that METTL17 binds to the mitoribosomal small subunit during late assembly and harbors a previously unrecognized [Fe4S4]2+ cluster required for its stability. METTL17 overexpression rescued the mitochondrial translation and bioenergetic defects, but not the cellular growth, of FXN-depleted cells. These findings suggest that METTL17 acts as an Fe-S cluster checkpoint, promoting translation of Fe-S cluster-rich oxidative phosphorylation (OXPHOS) proteins only when Fe-S cofactors are replete.
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Affiliation(s)
- Tslil Ast
- Broad Institute, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Yuzuru Itoh
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden
| | - Shayan Sadre
- Broad Institute, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Jason G McCoy
- Broad Institute, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Gil Namkoong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jordan C Wengrod
- Broad Institute, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Ivan Chicherin
- Department of Biology, M.V.Lomonosov Moscow State University, Moscow 119234, Russia
| | - Pallavi R Joshi
- Broad Institute, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Piotr Kamenski
- Department of Biology, M.V.Lomonosov Moscow State University, Moscow 119234, Russia
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Alexey Amunts
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden
| | - Vamsi K Mootha
- Broad Institute, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
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Ast T, Wang H, Marutani E, Nagashima F, Malhotra R, Ichinose F, Mootha VK. Continuous, but not intermittent, regimens of hypoxia prevent and reverse ataxia in a murine model of Friedreich's ataxia. Hum Mol Genet 2023; 32:2600-2610. [PMID: 37260376 PMCID: PMC10407700 DOI: 10.1093/hmg/ddad091] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 05/08/2023] [Accepted: 05/22/2023] [Indexed: 06/02/2023] Open
Abstract
Friedreich's ataxia (FA) is a devastating, multi-systemic neurodegenerative disease affecting thousands of people worldwide. We previously reported that oxygen is a key environmental variable that can modify FA pathogenesis. In particular, we showed that chronic, continuous normobaric hypoxia (11% FIO2) prevents ataxia and neurological disease in a murine model of FA, although it did not improve cardiovascular pathology or lifespan. Here, we report the pre-clinical evaluation of seven 'hypoxia-inspired' regimens in the shFxn mouse model of FA, with the long-term goal of designing a safe, practical and effective regimen for clinical translation. We report three chief results. First, a daily, intermittent hypoxia regimen (16 h 11% O2/8 h 21% O2) conferred no benefit and was in fact harmful, resulting in elevated cardiac stress and accelerated mortality. The detrimental effect of this regimen is likely owing to transient tissue hyperoxia that results when daily exposure to 21% O2 combines with chronic polycythemia, as we could blunt this toxicity by pharmacologically inhibiting polycythemia. Second, we report that more mild regimens of chronic hypoxia (17% O2) confer a modest benefit by delaying the onset of ataxia. Third, excitingly, we show that initiating chronic, continuous 11% O2 breathing once advanced neurological disease has already started can rapidly reverse ataxia. Our studies showcase both the promise and limitations of candidate hypoxia-inspired regimens for FA and underscore the need for additional pre-clinical optimization before future translation into humans.
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Affiliation(s)
- Tslil Ast
- Broad Institute, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Hong Wang
- Broad Institute, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Eizo Marutani
- Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Fumiaki Nagashima
- Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Rajeev Malhotra
- Cardiology Division, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Fumito Ichinose
- Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Vamsi K Mootha
- Broad Institute, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
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Rodden LN, McIntyre K, Keita M, Wells M, Park C, Profeta V, Waldman A, Rummey C, Balcer LJ, Lynch DR. Retinal hypoplasia and degeneration result in vision loss in Friedreich ataxia. Ann Clin Transl Neurol 2023; 10:1397-1406. [PMID: 37334854 PMCID: PMC10424660 DOI: 10.1002/acn3.51830] [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: 12/23/2022] [Revised: 02/16/2023] [Accepted: 05/26/2023] [Indexed: 06/21/2023] Open
Abstract
OBJECTIVE Friedreich ataxia (FRDA) is an inherited condition caused by a GAA triplet repeat (GAA-TR) expansion in the FXN gene. Clinical features of FRDA include ataxia, cardiomyopathy, and in some, vision loss. In this study, we characterize features of vision loss in a large cohort of adults and children with FRDA. METHODS Using optical coherence tomography (OCT), we measured peripapillary retinal nerve fiber layer (RNFL) thickness in 198 people with FRDA, and 77 controls. Sloan letter charts were used to determine visual acuity. RNFL thickness and visual acuity were compared to measures of disease severity obtained from the Friedreich Ataxia Clinical Outcomes Measures Study (FACOMS). RESULTS The majority of patients, including children, had pathologically thin RNFLs (mean = 73 ± 13 μm in FRDA; 98 ± 9 μm in controls) and low-contrast vision deficits early in the disease course. Variability in RNFL thickness in FRDA (range: 36 to 107 μm) was best predicted by disease burden (GAA-TR length X disease duration). Significant deficits in high-contrast visual acuity were apparent in patients with an RNFL thickness of ≤68 μm. RNFL thickness decreased at a rate of -1.2 ± 1.4 μm/year and reached 68 μm at a disease burden of approximately 12,000 GAA years, equivalent to disease duration of 17 years for participants with 700 GAAs. INTERPRETATION These data suggest that both hypoplasia and subsequent degeneration of the RNFL may be responsible for the optic nerve dysfunction in FRDA and support the development of a vision-directed treatment for selected patients early in the disease to prevent RNFL loss from reaching the critical threshold.
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Affiliation(s)
- Layne N. Rodden
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Kellie McIntyre
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Medina Keita
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Mckenzie Wells
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Courtney Park
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Victoria Profeta
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Amy Waldman
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | | | - Laura J. Balcer
- Departments of Neurology, Population Health and OphthalmologyNYU Grossman School of MedicineNew YorkNew YorkUSA
| | - David R. Lynch
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
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Profeta V, McIntyre K, Wells M, Park C, Lynch DR. Omaveloxolone: an activator of Nrf2 for the treatment of Friedreich ataxia. Expert Opin Investig Drugs 2023; 32:5-16. [PMID: 36708320 DOI: 10.1080/13543784.2023.2173063] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
INTRODUCTION Friedreich ataxia (FRDA) is a rare autosomal recessive degenerative disorder characterized by ataxia, dysarthria, diabetes, cardiomyopathy, scoliosis, and occasionally vision loss in late-stage disease. The discovery of the abnormal gene in FRDA and its product frataxin has provided insight into the pathophysiology and mechanisms of treatment. AREAS COVERED Although the neurologic phenotype of FRDA is well defined, there are currently no established pharmacological treatments. Omaveloxolone, a nuclear factor erythroid 2-related factor 2 (Nrf2) activator, is currently under review by the Food and Drug Administration (FDA) and has the potential to be the first approved treatment for FRDA. In the present report, we have reviewed the basic and clinical literature on Nrf2 deficiency in FRDA, and evidence for the benefit of omaveloxolone. EXPERT OPINION The present perspective suggests that omaveloxolone is a rational and efficacious therapy that is possibly disease modifying in treatment of FRDA.
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Affiliation(s)
- Victoria Profeta
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Kellie McIntyre
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - McKenzie Wells
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Courtney Park
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - David R Lynch
- Departments of Pediatrics and Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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Keita M, McIntyre K, Rodden LN, Schadt K, Lynch DR. Friedreich ataxia: clinical features and new developments. Neurodegener Dis Manag 2022; 12:267-283. [PMID: 35766110 PMCID: PMC9517959 DOI: 10.2217/nmt-2022-0011] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 06/15/2022] [Indexed: 11/21/2022] Open
Abstract
Friedreich's ataxia (FRDA), a neurodegenerative disease characterized by ataxia and other neurological features, affects 1 in 50,000-100,000 individuals in the USA. However, FRDA also includes cardiac, orthopedic and endocrine dysfunction, giving rise to many secondary disease characteristics. The multifaceted approach for clinical care has necessitated the development of disease-specific clinical care guidelines. New developments in FRDA include the advancement of clinical drug trials targeting the NRF2 pathway and frataxin restoration. Additionally, a novel understanding of gene silencing in FRDA, reflecting a variegated silencing pattern, will have applications to current and future therapeutic interventions. Finally, new perspectives on the neuroanatomy of FRDA and its developmental features will refine the time course and anatomical targeting of novel approaches.
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Affiliation(s)
- Medina Keita
- Departments of Pediatrics & Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Kellie McIntyre
- Departments of Pediatrics & Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Layne N Rodden
- Departments of Pediatrics & Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Kim Schadt
- Departments of Pediatrics & Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - David R Lynch
- Departments of Pediatrics & Neurology, Children's Hospital of Philadelphia, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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8
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Lynch DR, Schadt K, Kichula E, McCormack S, Lin KY. Friedreich Ataxia: Multidisciplinary Clinical Care. J Multidiscip Healthc 2021; 14:1645-1658. [PMID: 34234452 PMCID: PMC8253929 DOI: 10.2147/jmdh.s292945] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 06/04/2021] [Indexed: 12/17/2022] Open
Abstract
Friedreich ataxia (FRDA) is a multisystem disorder affecting 1 in 50,000-100,000 person in the United States. Traditionally viewed as a neurodegenerative disease, FRDA patients also develop cardiomyopathy, scoliosis, diabetes and other manifestation. Although it usually presents in childhood, it continues throughout life, thus requiring expertise from both pediatric and adult subspecialist in order to provide optimal management. The phenotype of FRDA is unique, giving rise to specific loss of neuronal pathways, a unique form of cardiomyopathy with early hypertrophy and later fibrosis, and diabetes incorporating components of both type I and type II disease. Vision loss, hearing loss, urinary dysfunction and depression also occur in FRDA. Many agents are reaching Phase III trials; if successful, these will provide a variety of new treatments for FRDA that will require many specialists who are not familiar with FRDA to provide clinical therapy. This review provides a summary of the diverse manifestation of FRDA, existing symptomatic therapies, and approaches for integrative care for future therapy in FRDA.
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Affiliation(s)
- David R Lynch
- Division of Neurology, Departments of Pediatrics and Neurology, Children’s Hospital of Philadelphia and the Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Kim Schadt
- Division of Neurology, Departments of Pediatrics and Neurology, Children’s Hospital of Philadelphia and the Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Elizabeth Kichula
- Division of Neurology, Departments of Pediatrics and Neurology, Children’s Hospital of Philadelphia and the Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Shana McCormack
- Division of Endocrinology, Department of Pediatrics, Children’s Hospital of Philadelphia and the Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Kimberly Y Lin
- Division of Cardiology, Department of Pediatrics, Children’s Hospital of Philadelphia and the Perelman School of Medicine, Philadelphia, PA, 19104, USA
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Neil AJ, Liang MU, Khristich AN, Shah KA, Mirkin SM. RNA-DNA hybrids promote the expansion of Friedreich's ataxia (GAA)n repeats via break-induced replication. Nucleic Acids Res 2019; 46:3487-3497. [PMID: 29447396 PMCID: PMC5909440 DOI: 10.1093/nar/gky099] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 02/05/2018] [Indexed: 12/21/2022] Open
Abstract
Expansion of simple DNA repeats is responsible for numerous hereditary diseases in humans. The role of DNA replication, repair and transcription in the expansion process has been well documented. Here we analyzed, in a yeast experimental system, the role of RNA–DNA hybrids in genetic instability of long (GAA)n repeats, which cause Friedreich’s ataxia. Knocking out both yeast RNase H enzymes, which counteract the formation of RNA–DNA hybrids, increased (GAA)n repeat expansion and contraction rates when the repetitive sequence was transcribed. Unexpectedly, we observed a similar increase in repeat instability in RNase H-deficient cells when we either changed the direction of transcription-replication collisions, or flipped the repeat sequence such that the (UUC)n run occurred in the transcript. The increase in repeat expansions in RNase H-deficient strains was dependent on Rad52 and Pol32 proteins, suggesting that break-induced replication (BIR) is responsible for this effect. We conclude that expansions of (GAA)n repeats are induced by the formation of RNA–DNA hybrids that trigger BIR. Since this stimulation is independent of which strand of the repeat (homopurine or homopyrimidine) is in the RNA transcript, we hypothesize that triplex H-DNA structures stabilized by an RNA–DNA hybrid (H-loops), rather than conventional R-loops, could be responsible.
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Affiliation(s)
- Alexander J Neil
- Department of Biology, Tufts University, Medford, MA 02155, USA.,Genetics Program, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA 02111, USA
| | - Miranda U Liang
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | | | - Kartik A Shah
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, MA 02155, USA
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Ouellet DL, Cherif K, Rousseau J, Tremblay JP. Deletion of the GAA repeats from the human frataxin gene using the CRISPR-Cas9 system in YG8R-derived cells and mouse models of Friedreich ataxia. Gene Ther 2017; 24:265-274. [PMID: 28024081 DOI: 10.1038/gt.2016.89] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 12/19/2016] [Indexed: 02/07/2023]
Abstract
The Friedreich ataxia is a monogenic disease due to a hyperexpanded GAA triplet located within the first intron of the frataxin gene that causes transcriptional issues. The resulting frataxin protein deficiency leads to a Fe-S cluster biosynthesis dysfunction in the mitochondria and to oxidative stress and cell death. Here we use the CRISPR-Cas9 system to remove the mutated GAA expansion and restore the frataxin gene transcriptional activity and protein level. Both YG8R and YG8sR mouse models and cell lines derived from these mice were used to CRISPR-edited successfully the GAA expansion in vitro and in vivo. Nevertheless, our results suggest the YG8sR as a better and more suitable model for the study of the CRISPR-Cas9 edition of the mutated frataxin gene.
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Affiliation(s)
- D L Ouellet
- Centre de Recherche, Centre Hospitalier, Universitaire de Québec, Quebec City, QC, Canada
- Département de Médecine Moléculaire, Faculté de Médecine, CHU de Québec, Université Laval, Québec City, QC, Canada
| | - K Cherif
- Centre de Recherche, Centre Hospitalier, Universitaire de Québec, Quebec City, QC, Canada
- Département de Médecine Moléculaire, Faculté de Médecine, CHU de Québec, Université Laval, Québec City, QC, Canada
| | - J Rousseau
- Centre de Recherche, Centre Hospitalier, Universitaire de Québec, Quebec City, QC, Canada
- Département de Médecine Moléculaire, Faculté de Médecine, CHU de Québec, Université Laval, Québec City, QC, Canada
| | - J P Tremblay
- Centre de Recherche, Centre Hospitalier, Universitaire de Québec, Quebec City, QC, Canada
- Département de Médecine Moléculaire, Faculté de Médecine, CHU de Québec, Université Laval, Québec City, QC, Canada
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Costantini A, Laureti T, Pala MI, Colangeli M, Cavalieri S, Pozzi E, Brusco A, Salvarani S, Serrati C, Fancellu R. Long-term treatment with thiamine as possible medical therapy for Friedreich ataxia. J Neurol 2016; 263:2170-2178. [PMID: 27488863 DOI: 10.1007/s00415-016-8244-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 07/21/2016] [Accepted: 07/22/2016] [Indexed: 01/13/2023]
Abstract
Thiamine (vitamin B1) is a cofactor of fundamental enzymes of cell energetic metabolism; its deficiency causes disorders affecting both the peripheral and central nervous system. Previous studies reported low thiamine levels in cerebrospinal fluid and pyruvate dehydrogenase dysfunction in Friedreich ataxia (FRDA). We investigated the effect of long-term treatment with thiamine in FRDA, evaluating changes in neurological symptoms, echocardiographic parameters, and plasma FXN mRNA levels. Thirty-four consecutive FRDA patients have been continuously treated with intramuscular thiamine 100 mg twice a week and have been assessed with the Scale for the Assessment and Rating of Ataxia (SARA) at baseline, after 1 month, and then every 3 months during treatment. Thiamine administration ranged from 80 to 930 days and was effective in improving total SARA scores from 26.6 ± 7.7 to 21.5 ± 6.2 (p < 0.02). Moreover, deep tendon reflexes reappeared in 57 % of patients with areflexia at baseline, and swallowing improved in 63 % of dysphagic patients. Clinical improvement was stable in all patients, who did not show worsening even after 2 years of treatment. In a subgroup of 13 patients who performed echocardiogram before and during treatment, interventricular septum thickness reduced significantly (p < 0.02). Frataxin mRNA blood levels were modestly increased in one-half of treated patients. We suppose that a focal thiamine deficiency may contribute to a selective neuronal damage in the areas involved in FRDA. Further studies are mandatory to evaluate thiamine role on FXN regulation, to exclude placebo effect, to verify our clinical results, and to confirm restorative and neuroprotective action of thiamine in FRDA.
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Affiliation(s)
- Antonio Costantini
- Department of Neurological Rehabilitation, "Villa Immacolata" Clinic, Strada Sammartinese 65A, 01100, Viterbo, Italy
| | - Tiziana Laureti
- Department of Economics and Management, University of Tuscia, Via del Paradiso 47, 01100, Viterbo, Italy
| | - Maria Immacolata Pala
- Department of Neurological Rehabilitation, "Villa Immacolata" Clinic, Strada Sammartinese 65A, 01100, Viterbo, Italy
| | - Marco Colangeli
- University Studies Abroad Consortium, University of Tuscia, Via Santa Maria in Gradi 4, 01100, Viterbo, Italy
| | - Simona Cavalieri
- Department of Medical Sciences, University of Turin, 10126, Turin, Italy
| | - Elisa Pozzi
- Department of Medical Sciences, University of Turin, 10126, Turin, Italy
| | - Alfredo Brusco
- Department of Medical Sciences, University of Turin, 10126, Turin, Italy.,Medical Genetics Unit, Città della Salute e della Scienza University Hospital, 10126, Turin, Italy
| | - Sandro Salvarani
- Unit of Neurology, ASL3 Villa Scassi Hospital, Corso O. Scassi 1, 16149, Genoa, Italy
| | - Carlo Serrati
- Unit of Neurology, IRCCS San Martino University Hospital IST, Largo Rosanna Benzi 10, 16132, Genoa, Italy
| | - Roberto Fancellu
- Unit of Neurology, ASL3 Villa Scassi Hospital, Corso O. Scassi 1, 16149, Genoa, Italy. .,Unit of Neurology, IRCCS San Martino University Hospital IST, Largo Rosanna Benzi 10, 16132, Genoa, Italy.
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12
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Wedding IM, Kroken M, Henriksen SP, Selmer KK, Fiskerstrand T, Knappskog PM, Berge T, Tallaksen CME. Friedreich ataxia in Norway - an epidemiological, molecular and clinical study. Orphanet J Rare Dis 2015; 10:108. [PMID: 26338206 PMCID: PMC4559212 DOI: 10.1186/s13023-015-0328-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 08/25/2015] [Indexed: 01/06/2023] Open
Abstract
Background Friedreich ataxia is an autosomal recessive hereditary spinocerebellar disorder, characterized by progressive limb and gait ataxia due to proprioceptive loss, often complicated by cardiomyopathy, diabetes and skeletal deformities. Friedreich ataxia is the most common hereditary ataxia, with a reported prevalence of 1:20 000 – 1:50 000 in Central Europe. Previous reports from south Norway have found a prevalence varying from 1:100 000 – 1:1 350 000; no studies are previously done in the rest of the country. Methods In this cross-sectional study, Friedreich ataxia patients were identified through colleagues in neurological, pediatric and genetic departments, hospital archives searches, patients’ associations, and National Centre for Rare Disorders. All included patients, carriers and controls were investigated clinically and molecularly with genotype characterization including size determination of GAA repeat expansions and frataxin measurements. 1376 healthy blood donors were tested for GAA repeat expansion for carrier frequency analysis. Results Twenty-nine Friedreich ataxia patients were identified in Norway, of which 23 were ethnic Norwegian, corresponding to a prevalence of 1:176 000 and 1:191 000, respectively. The highest prevalence was seen in the north. Carrier frequency of 1:196 (95 % CI = [1:752–1:112]) was found. Homozygous GAA repeat expansions in the FXN gene were found in 27/29, while two patients were compound heterozygous with c.467 T < C, L157P and the deletion (g.120032_122808del) including exon 5a. Two additional patients were heterozygous for GAA repeat expansions only. Significant differences in the level of frataxin were found between the included patients (N = 27), carriers (N = 37) and controls (N = 27). Conclusions In this first thorough study of a complete national cohort of Friedreich ataxia patients, and first nation-wide study of Friedreich ataxia in Norway, the prevalence of Friedreich ataxia in Norway is lower than in Central Europe, but higher than in the last Norwegian report, and as expected from migration studies. A south–north prevalence gradient is present. Based on Hardy Weinberg’s equilibrium, the carrier frequency of 1:196 is consistent with the observed prevalence. All genotypes, and typical and atypical phenotypes were present in the Norwegian population. The patients were phenotypically similar to European cohorts. Frataxin was useful in the diagnostic work-up of heterozygous symptomatic cases. Electronic supplementary material The online version of this article (doi:10.1186/s13023-015-0328-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Iselin Marie Wedding
- Department of Neurology, Oslo University Hospital, Ullevaal, 0407, Oslo, Norway. .,University of Oslo, Faculty of Medicine, Oslo, Norway.
| | - Mette Kroken
- Department of Medical Genetics, Oslo University Hospital, Ullevaal, 0407, Oslo, Norway
| | | | - Kaja Kristine Selmer
- Department of Medical Genetics, Oslo University Hospital, Ullevaal, 0407, Oslo, Norway.,University of Oslo, Faculty of Medicine, Oslo, Norway
| | - Torunn Fiskerstrand
- Department of Clinical Science, University of Bergen, Bergen, Norway.,Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway
| | - Per Morten Knappskog
- Department of Clinical Science, University of Bergen, Bergen, Norway.,Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway
| | - Tone Berge
- Department of Neurology, Oslo University Hospital, Ullevaal, 0407, Oslo, Norway
| | - Chantal M E Tallaksen
- Department of Neurology, Oslo University Hospital, Ullevaal, 0407, Oslo, Norway.,University of Oslo, Faculty of Medicine, Oslo, Norway
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An AAV9 coding for frataxin clearly improved the symptoms and prolonged the life of Friedreich ataxia mouse models. MOLECULAR THERAPY-METHODS & CLINICAL DEVELOPMENT 2014; 1:14044. [PMID: 26015982 PMCID: PMC4362356 DOI: 10.1038/mtm.2014.44] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 07/30/2014] [Indexed: 12/13/2022]
Abstract
Friedreich ataxia (FRDA) is a genetic disease due to increased repeats of the GAA trinucleotide in intron 1 of the frataxin gene. This mutation leads to a reduced expression of frataxin. We have produced an adeno-associated virus (AAV)9 coding for human frataxin (AAV9-hFXN). This AAV was delivered by intraperitoneal (IP) injection to young conditionally knockout mice in which the frataxin gene had been knocked-out in some tissues during embryogenesis by breeding them with mice expressing the Cre recombinase gene under the muscle creatine kinase (MCK) or the neuron-specific enolase (NSE) promoter. In the first part of the study, different doses of virus were tested from 6 × 1011 v.p. to 6 × 109 v.p. in NSE-cre mice and all leading to an increase in life spent of the mice. The higher and the lower dose were also tested in MCK-cre mice. A single administration of the AAV9-hFXN at 6 × 1011 v.p. more than doubled the life of these mice. In fact the MCK-cre mice treated with the AAV9-hFXN were sacrificed for further molecular investigations at the age of 29 weeks without apparent symptoms. Echography analysis of the heart function clearly indicated that the cardiac systolic function was better preserved in the mice that received 6 × 1011 v.p. of AAV9-hFXN. The human frataxin protein was detected by ELISA in the heart, brain, muscles, kidney, and liver with the higher dose of virus in both mouse models. Thus, gene therapy with an AAV9-hFXN is a potential treatment of FRDA.
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Ygland E, Taroni F, Gellera C, Caldarazzo S, Duno M, Soller M, Puschmann A. Atypical Friedreich ataxia in patients with FXN p.R165P point mutation or comorbid hemochromatosis. Parkinsonism Relat Disord 2014; 20:919-23. [PMID: 24816001 DOI: 10.1016/j.parkreldis.2014.04.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 03/28/2014] [Accepted: 04/14/2014] [Indexed: 11/29/2022]
Abstract
BACKGROUND Compound heterozygosity for a trinucleotide repeat expansion and a point mutation in the FXN gene is a rare cause of Friedreich ataxia (FRDA). METHODS We identified three Swedish FRDA patients with an FXN p.R165P missense mutation and compared their clinical features with six homozygote trinucleotide repeat expansion carriers. Patients were assessed clinically. Trinucleotide expansion length was determined and lymphocyte frataxin levels measured. RESULTS p.R165P mutation carriers became wheelchair bound early, but had retained reflexes, better arm function, milder dysarthria, and were more independent in activities of daily living. One p.R165P mutation carrier developed psychosis. Frataxin levels were higher than in homozygous trinucleotide expansion patients. One patient with homozygous trinucleotide repeat expansions and comorbid hemochromatosis had more severe FRDA symptoms than his sibling without hemochromatosis. CONCLUSION p.R165P patients progress to a less disabling disease state than typical FRDA. Comorbid hemochromatosis may worsen FRDA symptoms through additive effects on iron metabolism.
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Affiliation(s)
- Emil Ygland
- Department of Neurology, Skåne University Hospital, Lund, Sweden; Department of Neurology, Clinical Sciences, Lund University, Lund, Sweden
| | - Franco Taroni
- Unit of Genetics of Neurodegenerative and Metabolic Disease, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Cinzia Gellera
- Unit of Genetics of Neurodegenerative and Metabolic Disease, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Serena Caldarazzo
- Unit of Genetics of Neurodegenerative and Metabolic Disease, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Morten Duno
- Department of Clinical Genetics, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Maria Soller
- Department of Clinical Genetics, Skåne University Hospital, University and Regional Laboratories, Lund University, Lund, Sweden
| | - Andreas Puschmann
- Department of Neurology, Skåne University Hospital, Lund, Sweden; Department of Neurology, Clinical Sciences, Lund University, Lund, Sweden.
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15
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Ugarte M, Osborne NN, Brown LA, Bishop PN. Iron, zinc, and copper in retinal physiology and disease. Surv Ophthalmol 2013; 58:585-609. [DOI: 10.1016/j.survophthal.2012.12.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 12/09/2012] [Accepted: 12/11/2012] [Indexed: 12/26/2022]
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Chapdelaine P, Coulombe Z, Chikh A, Gérard C, Tremblay JP. A Potential New Therapeutic Approach for Friedreich Ataxia: Induction of Frataxin Expression With TALE Proteins. MOLECULAR THERAPY. NUCLEIC ACIDS 2013; 2:e119. [PMID: 24002729 PMCID: PMC4028015 DOI: 10.1038/mtna.2013.41] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 06/04/2013] [Indexed: 12/31/2022]
Abstract
TALEs targeting a promoter sequence and fused with a transcription activation domain (TAD) may be used to specifically induce the expression of a gene as a potential treatment for haploinsufficiency. This potential therapeutic approach was applied to increase the expression of frataxin in fibroblasts of Friedreich ataxia (FRDA) patients. FRDA fibroblast cells were nucleofected with a pCR3.1 expression vector coding for TALEFrat#8 fused with VP64. A twofold increase of the frataxin mRNA (detected by quantitative reverse transcription-PCR (qRT-PCR)) associated with a similar increase of the mature form of the frataxin protein was observed. The frataxin mRNA and protein were also increased by this TALE in the fibroblasts of the YG8R mouse model. The addition of 5-aza-2′-deoxycytidine (5-Aza-dC) or of valproic acid (VPA) to the TALE treatment did not produce significant improvement. Other TADs (i.e., p65, TFAP2α, SRF, SP1, and MyoD) fused with the TALEFrat#8 gene did not produce a significant increase in the frataxin protein. Thus the TALEFrat#8-VP64 recombinant protein targeting the frataxin promoter could eventually be used to increase the frataxin expression and alleviate the FRDA symptoms.
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Affiliation(s)
- Pierre Chapdelaine
- 1] Centre de Recherche du Centre Hospitalier Universitaire de Québec, Québec, Québec, Canada [2] Département de Médecine Moléculaire, Faculté de Médecine, Université Laval, Québec, Québec, Canada
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17
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Lane DJR, Huang MLH, Ting S, Sivagurunathan S, Richardson DR. Biochemistry of cardiomyopathy in the mitochondrial disease Friedreich's ataxia. Biochem J 2013; 453:321-36. [PMID: 23849057 DOI: 10.1042/bj20130079] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
FRDA (Friedreich's ataxia) is a debilitating mitochondrial disorder leading to neural and cardiac degeneration, which is caused by a mutation in the frataxin gene that leads to decreased frataxin expression. The most common cause of death in FRDA patients is heart failure, although it is not known how the deficiency in frataxin potentiates the observed cardiomyopathy. The major proposed biochemical mechanisms for disease pathogenesis and the origins of heart failure in FRDA involve metabolic perturbations caused by decreased frataxin expression. Additionally, recent data suggest that low frataxin expression in heart muscle of conditional frataxin knockout mice activates an integrated stress response that contributes to and/or exacerbates cardiac hypertrophy and the loss of cardiomyocytes. The elucidation of these potential mechanisms will lead to a more comprehensive understanding of the pathogenesis of FRDA, and will contribute to the development of better treatments and therapeutics.
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Affiliation(s)
- Darius J R Lane
- Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, Blackburn Building, D06, University of Sydney, Sydney, NSW 2006, Australia
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Tremblay JP, Chapdelaine P, Coulombe Z, Rousseau J. Transcription activator-like effector proteins induce the expression of the frataxin gene. Hum Gene Ther 2012; 23:883-90. [PMID: 22587705 DOI: 10.1089/hum.2012.034] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Genes encoding transcription activator-like effector (TALE) proteins may be engineered to target specific DNA sequences. TALEs fused with a transcription activator can be used to specifically induce the expression of a gene. This could lead to completely new therapies for several diseases. We have applied this potential therapeutic approach to Friedreich ataxia (FRDA), as an example. FRDA is due to reduced expression of frataxin because of elongation of a trinucleotide (GAA) repeat in intron 1. Our aim was to develop a potential treatment for FRDA by increasing the expression of the frataxin gene. We engineered 12 TALE genes (TALE(Frat)) encoding TALE(Frat) proteins, each specifically targeting different 14-bp DNA sequences within the proximal region of the human frataxin promoter. When the genes encoding these TALE(Frat) proteins were fused with a transcription activator, that is, four VP16 peptides (i.e., VP64), the resulting TALE(Frat)-VP64 proteins induced the expression of an mCherry reporter gene fused to a mini-cytomegalovirus promoter able to be activated by the insertion of the frataxin proximal promoter upstream to the minipromoter. These TALE(Frat)-VP64 proteins also increased, by 2- to 3-fold, frataxin gene expression (detected by qRT-PCR) in the cells. We conclude that TALE(Frat) proteins targeting the frataxin promoter may be used to increase the expression of frataxin mRNA and potentially could alleviate the symptoms of Friedreich ataxia. TALE methodology opens a new field of research, which could be used to develop TALE proteins to treat other diseases by inducing the expression of specific genes.
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Affiliation(s)
- Jacques P Tremblay
- Department of Molecular Medicine, Laval University, and Centre de Recherche du Centre Hospitalier Universitaire de, 2705 boul. Laurier Québec, PQ G1V4G2, Canada.
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