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Stovickova L, Hansikova H, Hanzalova J, Musova Z, Semjonov V, Stovicek P, Hadzic H, Novotna L, Simcik M, Strnad P, Serbina A, Karamazovova S, Schwabova Paulasova J, Vyhnalek M, Krsek P, Zumrova A. Exploring mitochondrial biomarkers for Friedreich's ataxia: a multifaceted approach. J Neurol 2024; 271:3439-3454. [PMID: 38520521 PMCID: PMC11136723 DOI: 10.1007/s00415-024-12223-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 01/24/2024] [Accepted: 01/24/2024] [Indexed: 03/25/2024]
Abstract
This study presents an in-depth analysis of mitochondrial enzyme activities in Friedreich's ataxia (FA) patients, focusing on the Electron Transport Chain complexes I, II, and IV, the Krebs Cycle enzyme Citrate Synthase, and Coenzyme Q10 levels. It examines a cohort of 34 FA patients, comparing their mitochondrial enzyme activities and clinical parameters, including disease duration and cardiac markers, with those of 17 healthy controls. The findings reveal marked reductions in complexes II and, specifically, IV, highlighting mitochondrial impairment in FA. Additionally, elevated Neurofilament Light Chain levels and cardiomarkers were observed in FA patients. This research enhances our understanding of FA pathophysiology and suggests potential biomarkers for monitoring disease progression. The study underscores the need for further clinical trials to validate these findings, emphasizing the critical role of mitochondrial dysfunction in FA assessment and treatment.
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Affiliation(s)
- Lucie Stovickova
- Department of Paediatric Neurology, Second Faculty of Medicine, Charles University, Motol University Hospital, V Uvalu 84, 15006, Prague 5, Czech Republic.
- Centre of Hereditary Ataxias, Second Faculty of Medicine, An Official EFACTS Site, a Member of European Reference Network for Rare Neurological Diseases (ERN-RND), Charles University, Motol University Hospital, Prague 5, Czech Republic.
| | - Hana Hansikova
- Department of Paediatrics and Inherited Metabolic Disorders, First Medical Faculty, Charles University and General University Hospital in Prague, Prague 2, Czech Republic
| | - Jitka Hanzalova
- Department of Immunology, Second Faculty of Medicine, Charles University, Motol University Hospital, Prague 5, Czech Republic
| | - Zuzana Musova
- Department of Biology and Medical Genetics, Second Faculty of Medicine, Charles University, Motol University Hospital, Prague 5, Czech Republic
- Centre of Hereditary Ataxias, Second Faculty of Medicine, An Official EFACTS Site, a Member of European Reference Network for Rare Neurological Diseases (ERN-RND), Charles University, Motol University Hospital, Prague 5, Czech Republic
| | - Valerij Semjonov
- Department of Paediatrics, Second Faculty of Medicine, Charles University and Motol University Hospital, Prague, Czech Republic
| | | | - Haris Hadzic
- Second Faculty of Medicine, Charles University, Prague 5, Czech Republic
| | - Ludmila Novotna
- Second Faculty of Medicine, Charles University, Prague 5, Czech Republic
| | - Martin Simcik
- Second Faculty of Medicine, Charles University, Prague 5, Czech Republic
| | - Pavel Strnad
- Second Faculty of Medicine, Charles University, Prague 5, Czech Republic
| | - Anastaziia Serbina
- Second Faculty of Medicine, Charles University, Prague 5, Czech Republic
| | - Simona Karamazovova
- Department of Neurology, Second Faculty of Medicine, Charles University, Motol University Hospital, Prague 5, Czech Republic
- Centre of Hereditary Ataxias, Second Faculty of Medicine, An Official EFACTS Site, a Member of European Reference Network for Rare Neurological Diseases (ERN-RND), Charles University, Motol University Hospital, Prague 5, Czech Republic
| | - Jaroslava Schwabova Paulasova
- Department of Neurology, Second Faculty of Medicine, Charles University, Motol University Hospital, Prague 5, Czech Republic
- Centre of Hereditary Ataxias, Second Faculty of Medicine, An Official EFACTS Site, a Member of European Reference Network for Rare Neurological Diseases (ERN-RND), Charles University, Motol University Hospital, Prague 5, Czech Republic
| | - Martin Vyhnalek
- Department of Neurology, Second Faculty of Medicine, Charles University, Motol University Hospital, Prague 5, Czech Republic
- Centre of Hereditary Ataxias, Second Faculty of Medicine, An Official EFACTS Site, a Member of European Reference Network for Rare Neurological Diseases (ERN-RND), Charles University, Motol University Hospital, Prague 5, Czech Republic
| | - Pavel Krsek
- Department of Paediatric Neurology, Second Faculty of Medicine, Charles University, Motol University Hospital, V Uvalu 84, 15006, Prague 5, Czech Republic
| | - Alena Zumrova
- Department of Paediatric Neurology, Second Faculty of Medicine, Charles University, Motol University Hospital, V Uvalu 84, 15006, Prague 5, Czech Republic
- Centre of Hereditary Ataxias, Second Faculty of Medicine, An Official EFACTS Site, a Member of European Reference Network for Rare Neurological Diseases (ERN-RND), Charles University, Motol University Hospital, Prague 5, Czech Republic
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Koka M, Li H, Akther R, Perlman S, Wong D, Fogel BL, Lynch DR, Chandran V. Long non-coding RNA TUG1 is downregulated in Friedreich's ataxia. Brain Commun 2024; 6:fcae170. [PMID: 38846537 PMCID: PMC11154142 DOI: 10.1093/braincomms/fcae170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 03/25/2024] [Accepted: 05/14/2024] [Indexed: 06/09/2024] Open
Abstract
Friedreich's ataxia is a neurodegenerative disorder caused by reduced frataxin levels. It leads to motor and sensory impairments and has a median life expectancy of around 35 years. As the most common inherited form of ataxia, Friedreich's ataxia lacks reliable, non-invasive biomarkers, prolonging and inflating the cost of clinical trials. This study proposes TUG1, a long non-coding RNA, as a promising blood-based biomarker for Friedreich's ataxia, which is known to regulate various cellular processes. In a previous study using a frataxin knockdown mouse model, we observed several hallmark Friedreich's ataxia symptoms. Building on this, we hypothesized that a dual-source approach-comparing the data from peripheral blood samples from Friedreich's ataxia patients with tissue samples from affected areas in Friedreich's ataxia knockdown mice, tissues usually unattainable from patients-would effectively identify robust biomarkers. A comprehensive reanalysis was conducted on gene expression data from 183 age- and sex-matched peripheral blood samples of Friedreich's ataxia patients, carriers and controls and 192 tissue data sets from Friedreich's ataxia knockdown mice. Blood and tissue samples underwent RNA isolation and quantitative reverse transcription polymerase chain reaction, and frataxin knockdown was confirmed through enzyme-linked immunosorbent assays. Tug1 RNA interaction was explored via RNA pull-down assays. Validation was performed in serum samples on an independent set of 45 controls and 45 Friedreich's ataxia patients and in blood samples from 66 heterozygous carriers and 72 Friedreich's ataxia patients. Tug1 and Slc40a1 emerged as potential blood-based biomarkers, confirmed in the Friedreich's ataxia knockdown mouse model (one-way ANOVA, P ≤ 0.05). Tug1 was consistently downregulated after Fxn knockdown and correlated strongly with Fxn levels (R 2 = 0.71 during depletion, R 2 = 0.74 during rescue). Slc40a1 showed a similar but tissue-specific pattern. Further validation of Tug1's downstream targets strengthened its biomarker candidacy. In additional human samples, TUG1 levels were significantly downregulated in both whole blood and serum of Friedreich's ataxia patients compared with controls (Wilcoxon signed-rank test, P < 0.05). Regression analyses revealed a negative correlation between TUG1 fold-change and disease onset (P < 0.0037) and positive correlations with disease duration and functional disability stage score (P < 0.04). This suggests that elevated TUG1 levels correlate with earlier onset and more severe cases. This study identifies TUG1 as a potential blood-based biomarker for Friedreich's ataxia, showing consistent expression variance in human and mouse tissues related to disease severity and key Friedreich's ataxia pathways. It correlates with frataxin levels, indicating its promise as an early, non-invasive marker. TUG1 holds potential for Friedreich's ataxia monitoring and therapeutic development, meriting additional research.
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Affiliation(s)
- Mert Koka
- Department of Pediatrics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Hui Li
- Department of Pediatrics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Rumana Akther
- Department of Pediatrics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Susan Perlman
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Darice Wong
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
- Clinical Neurogenomics Research Center, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - Brent L Fogel
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
- Clinical Neurogenomics Research Center, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
| | - David R Lynch
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Vijayendran Chandran
- Department of Pediatrics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Department of Neuroscience, College of Medicine, University of Florida, and McKnight Brain Institute, Gainesville, FL 32610, USA
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Rojsajjakul T, Selvan N, De B, Rosenberg JB, Kaminsky SM, Sondhi D, Janki P, Crystal RG, Mesaros C, Khanna R, Blair IA. Expression and processing of mature human frataxin after gene therapy in mice. Sci Rep 2024; 14:8391. [PMID: 38600238 PMCID: PMC11006666 DOI: 10.1038/s41598-024-59060-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 04/06/2024] [Indexed: 04/12/2024] Open
Abstract
Friedreich's ataxia is a degenerative and progressive multisystem disorder caused by mutations in the highly conserved frataxin (FXN) gene that results in FXN protein deficiency and mitochondrial dysfunction. While gene therapy approaches are promising, consistent induction of therapeutic FXN protein expression that is sub-toxic has proven challenging, and numerous therapeutic approaches are being tested in animal models. FXN (hFXN in humans, mFXN in mice) is proteolytically modified in mitochondria to produce mature FXN. However, unlike endogenous hFXN, endogenous mFXN is further processed into N-terminally truncated, extra-mitochondrial mFXN forms of unknown function. This study assessed mature exogenous hFXN expression levels in the heart and liver of C57Bl/6 mice 7-10 months after intravenous administration of a recombinant adeno-associated virus encoding hFXN (AAVrh.10hFXN) and examined the potential for hFXN truncation in mice. AAVrh.10hFXN induced dose-dependent expression of hFXN in the heart and liver. Interestingly, hFXN was processed into truncated forms, but found at lower levels than mature hFXN. However, the truncations were at different positions than mFXN. AAVrh.10hFXN induced mature hFXN expression in mouse heart and liver at levels that approximated endogenous mFXN levels. These results suggest that AAVrh.10hFXN can likely induce expression of therapeutic levels of mature hFXN in mice.
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Affiliation(s)
- Teerapat Rojsajjakul
- Department of Systems Pharmacology and Translational Therapeutics Perelman School of Medicine, Penn/CHOP Friedreich's Ataxia Center of Excellence, Center of Excellence in Environmental Toxicology, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Bishnu De
- Department of Genetic Medicine, Weill Cornell College of Medicine, New York, NY, USA
| | - Jonathan B Rosenberg
- Department of Genetic Medicine, Weill Cornell College of Medicine, New York, NY, USA
| | - Stephen M Kaminsky
- Department of Genetic Medicine, Weill Cornell College of Medicine, New York, NY, USA
| | - Dolan Sondhi
- Department of Genetic Medicine, Weill Cornell College of Medicine, New York, NY, USA
| | | | - Ronald G Crystal
- Department of Genetic Medicine, Weill Cornell College of Medicine, New York, NY, USA
| | - Clementina Mesaros
- Department of Systems Pharmacology and Translational Therapeutics Perelman School of Medicine, Penn/CHOP Friedreich's Ataxia Center of Excellence, Center of Excellence in Environmental Toxicology, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Ian A Blair
- Department of Systems Pharmacology and Translational Therapeutics Perelman School of Medicine, Penn/CHOP Friedreich's Ataxia Center of Excellence, Center of Excellence in Environmental Toxicology, University of Pennsylvania, Philadelphia, PA, USA.
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4
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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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5
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Rojsajjakul T, Selvan N, De B, Rosenberg JB, Kaminsky SM, Sondhi D, Janki P, Crystal RG, Mesaros C, Khanna R, Blair IA. Expression and processing of mature human frataxin after gene therapy in mice. RESEARCH SQUARE 2023:rs.3.rs-3788652. [PMID: 38234818 PMCID: PMC10793484 DOI: 10.21203/rs.3.rs-3788652/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Friedreich's ataxia is a degenerative and progressive multisystem disorder caused by mutations in the highly conserved frataxin (FXN) gene that results in FXN protein deficiency and mitochondrial dysfunction. While gene therapy approaches are promising, consistent induction of therapeutic FXN protein expression that is sub-toxic has proven challenging, and numerous therapeutic approaches are being tested in animal models. FXN (hFXN in humans, mFXN in mice) is proteolytically modified in mitochondria to produce mature FXN. However, unlike endogenous hFXN, endogenous mFXN is further processed into N-terminally truncated, extra-mitochondrial mFXN forms of unknown function. This study assessed mature exogenous hFXN expression levels in the heart and liver of C57Bl/6 mice 7-10 months after intravenous administration of a recombinant adeno-associated virus encoding hFXN (AAVrh.10hFXN) and examined the potential for hFXN truncation in mice. AAVrh.10hFXN induced dose-dependent expression of hFXN in the heart and liver. Interestingly, hFXN was processed into truncated forms, but found at lower levels than mature hFXN. However, the truncations were at different positions than mFXN. AAVrh.10hFXN induced mature hFXN expression in mouse heart and liver at levels that approximated endogenous mFXN levels. These results demonstrate that AAVrh.10hFXN may induce expression of therapeutic levels of mature hFXN in mice.
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Rojsajjakul T, Hordeaux JJ, Choudhury GR, Hinderer CJ, Mesaros C, Wilson JM, Blair IA. Quantification of human mature frataxin protein expression in nonhuman primate hearts after gene therapy. Commun Biol 2023; 6:1093. [PMID: 37891254 PMCID: PMC10611776 DOI: 10.1038/s42003-023-05472-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Accepted: 10/16/2023] [Indexed: 10/29/2023] Open
Abstract
Deficiency in human mature frataxin (hFXN-M) protein is responsible for the devastating neurodegenerative and cardiodegenerative disease of Friedreich's ataxia (FRDA). It results primarily through epigenetic silencing of the FXN gene by GAA triplet repeats on intron 1 of both alleles. GAA repeat lengths are most commonly between 600 and 1200 but can reach 1700. A subset of approximately 3% of FRDA patients have GAA repeats on one allele and a mutation on the other. FRDA patients die most commonly in their 30s from heart disease. Therefore, increasing expression of heart hFXN-M using gene therapy offers a way to prevent early mortality in FRDA. We used rhesus macaque monkeys to test the pharmacology of an adeno-associated virus (AAV)hu68.CB7.hFXN therapy. The advantage of using non-human primates for hFXN-M gene therapy studies is that hFXN-M and monkey FXN-M (mFXN-M) are 98.5% identical, which limits potential immunologic side-effects. However, this presented a formidable bioanalytical challenge in quantification of proteins with almost identical sequences. This could be overcome by the development of a species-specific quantitative mass spectrometry-based method, which has revealed for the first time, robust transgene-specific human protein expression in monkey heart tissue. The dose response is non-linear resulting in a ten-fold increase in monkey heart hFXN-M protein expression with only a three-fold increase in dose of the vector.
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Affiliation(s)
- Teerapat Rojsajjakul
- Penn/CHOP Friedreich's Ataxia Center of Excellence and Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Juliette J Hordeaux
- Gene Therapy Program, Departments of Medicine and Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Gourav R Choudhury
- Gene Therapy Program, Departments of Medicine and Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Christian J Hinderer
- Gene Therapy Program, Departments of Medicine and Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Clementina Mesaros
- Penn/CHOP Friedreich's Ataxia Center of Excellence and Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - James M Wilson
- Gene Therapy Program, Departments of Medicine and Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
| | - Ian A Blair
- Penn/CHOP Friedreich's Ataxia Center of Excellence and Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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7
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Blair I, Rojsajjakul T, Hordeaux J, Chaudhary G, Hinderer C, Mesaros C, Wilson J. Quantification of human mature frataxin protein expression in nonhuman primate hearts after gene therapy. RESEARCH SQUARE 2023:rs.3.rs-3121549. [PMID: 37461697 PMCID: PMC10350221 DOI: 10.21203/rs.3.rs-3121549/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Deficiency in human mature frataxin (hFXN-M) protein is responsible for the devastating neurodegenerative and cardiodegenerative disease of Friedreich's ataxia (FRDA). It results primarily by epigenetic silencing the FXN gene due to up to 1400 GAA triplet repeats in intron 1 of both alleles of the gene; a subset of approximately 3% of FRDA patients have a mutation on one allele. FRDA patients die most commonly in their 30s from heart disease. Therefore, increasing expression of heart hFXN-M using gene therapy offers a way to prevent early mortality in FRDA. We used rhesus macaque monkeys to test the pharmacology of an adeno-associated virus (AAV)hu68.CB7.hFXN therapy. The advantage of using non-human primates for hFXN-M gene therapy studies is that hFXN-M and monkey FXN-M (mFXN-M) are 98.5% identical, which limits potential immunologic side-effects. However, this presented a formidable bioanalytical challenge in quantification of proteins with almost identical sequences. This was overcome by development of a species-specific quantitative mass spectrometry-based method, which revealed for the first time, robust transgene-specific human protein expression in monkey heart tissue. The dose response was non-linear resulting in a ten-fold increase in monkey heart hFXN-M protein expression with only a three-fold increase in dose of the vector.
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8
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Rojsajjakul T, Wu L, Grady CB, Hwang WT, Mesaros C, Lynch DR, Blair IA. Liquid Chromatography-Mass Spectrometry Analysis of Frataxin Proteoforms in Whole Blood as Biomarkers of the Genetic Disease Friedreich's Ataxia. Anal Chem 2023; 95:4251-4260. [PMID: 36800320 PMCID: PMC9979142 DOI: 10.1021/acs.analchem.3c00091] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Friedreich's ataxia (FRDA) is caused primarily by expanded GAA repeats in intron 1 of both alleles of the FXN gene, which causes transcriptional silencing and reduced expression of frataxin mRNA and protein. FRDA is characterized by slowly progressive ataxia and cardiomyopathy. Symptoms generally appear during adolescence, and patients slowly progress to wheelchair dependency usually in the late teens or early twenties with death on average in the 4th decade. There are two known mature proteoforms of frataxin. Mitochondrial frataxin (frataxin-M) is a 130-amino acid protein with a molecular weight of 14,268 Da, and there is an alternatively spliced N-terminally acetylated 135-amino acid form (frataxin-E) with a molecular weight of 14,953 Da found in erythrocytes. There is reduced expression of frataxin in the heart and brain, but frataxin is not secreted into the systemic circulation, so it cannot be analyzed in serum or plasma. Blood is a readily accessible biofluid that contains numerous different cell types that express frataxin. We have found that pig blood can serve as an excellent surrogate matrix to validate an assay for frataxin proteoforms because pig frataxin is lost during the immunoprecipitation step used to isolate human frataxin. Frataxin-M is expressed in blood cells that contain mitochondria, whereas extra-mitochondrial frataxin-E is found in erythrocytes. This means that the analysis of frataxin in whole blood provides information on the concentration of both proteoforms without having to isolate the individual cell types. In the current study, we observed that the distributions of frataxin levels for a sample of 25 healthy controls and 50 FRDA patients were completely separated from each other, suggesting 100% specificity and 100% sensitivity for distinguishing healthy controls from FRDA cases, a very unusual finding for a biomarker assay. Additionally, frataxin levels were significantly correlated with the GAA repeat length and age of onset with higher correlations for extra-mitochondrial frataxin-E than those for mitochondrial frataxin-M. These findings auger well for using frataxin levels measured by the validated stable isotope dilution ultrahigh-performance liquid chromatography-multiple reaction monitoring/mass spectrometry assay to monitor therapeutic interventions and the natural history of FRDA. Our study also illustrates the utility of using whole blood for protein disease biomarker discovery and validation.
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Affiliation(s)
- Teerapat Rojsajjakul
- Penn/CHOP
Friedreich’s Ataxia Center of Excellence, Philadelphia, Pennsylvania 19104, United States,Center
of Excellence in Environmental Toxicology, Department of Systems Pharmacology
and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Linfeng Wu
- Agilent
Technologies Inc., 5301
Stevens Creek Blvd., Santa Clara, California 95051, United States
| | - Connor B. Grady
- Center
for Clinical Epidemiology and Biostatistics, Department of Biostatistics,
Epidemiology and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, 19104, United States
| | - Wei-Ting Hwang
- Center
for Clinical Epidemiology and Biostatistics, Department of Biostatistics,
Epidemiology and Informatics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, 19104, United States
| | - Clementina Mesaros
- Penn/CHOP
Friedreich’s Ataxia Center of Excellence, Philadelphia, Pennsylvania 19104, United States,Center
of Excellence in Environmental Toxicology, Department of Systems Pharmacology
and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - David R. Lynch
- Penn/CHOP
Friedreich’s Ataxia Center of Excellence, Philadelphia, Pennsylvania 19104, United States,Departments
of Pediatrics and Neurology, Children’s
Hospital of Philadelphia and University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Ian A. Blair
- Penn/CHOP
Friedreich’s Ataxia Center of Excellence, Philadelphia, Pennsylvania 19104, United States,Center
of Excellence in Environmental Toxicology, Department of Systems Pharmacology
and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States,. Phone: +1-610-529-0610. Fax: +1-215-573-9889
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