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Dong H, Ma X, Chen Z, Zhang H, Song J, Jin Y, Li M, Lu M, He R, Zhang Y, Yang Y. Clinical features and ALDH5A1 gene findings in 13 Chinese cases with succinic semialdehyde dehydrogenase deficiency. BMC Med Genomics 2024; 17:158. [PMID: 38862963 PMCID: PMC11165735 DOI: 10.1186/s12920-024-01925-4] [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: 11/04/2023] [Accepted: 06/04/2024] [Indexed: 06/13/2024] Open
Abstract
BACKGROUND AND AIMS To investigate the clinical features, ALDH5A1 gene variations, treatment, and prognosis of patients with succinic semialdehyde dehydrogenase (SSADH) deficiency. MATERIALS AND METHODS This retrospective study evaluated the findings in 13 Chinese patients with SSADH deficiency admitted to the Pediatric Department of Peking University First Hospital from September 2013 to September 2023. RESULTS Thirteen patients (seven male and six female patients; two sibling sisters) had the symptoms aged from 1 month to 1 year. Their urine 4-hydroxybutyrate acid levels were elevated and were accompanied by mildly increased serum lactate levels. Brain magnetic resonance imaging (MRI) showed symmetric abnormal signals in both sides of the globus pallidus and other areas. All 13 patients had psychomotor retardation, with seven showing epileptic seizures. Among the 18 variants of the ALDH5A1 gene identified in these 13 patients, six were previously reported, while 12 were novel variants. Among the 12 novel variants, three (c.85_116del, c.206_222dup, c.762C > G) were pathogenic variants; five (c.427delA, c.515G > A, c.637C > T, c.755G > T, c.1274T > C) were likely pathogenic; and the remaining four (c.454G > C, c.479C > T, c.1480G > A, c.1501G > C) were variants of uncertain significance. The patients received drugs such as L-carnitine, vigabatrin, and taurine, along with symptomatic treatment. Their urine 4-hydroxybutyric acid levels showed variable degrees of reduction. CONCLUSIONS A cohort of 13 cases with early-onset SSADH deficiency was analyzed. Onset of symptoms occurred from 1 month to 1 year of age. Twelve novel variants of the ALDH5A1 gene were identified.
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Affiliation(s)
- Hui Dong
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Xue Ma
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Zhehui Chen
- Department of Pediatrics, Women and Children's Hospital, School of Medicine, Xiamen University, Xiamen, 361003, China
| | - Huiting Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Jinqing Song
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Ying Jin
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Mengqiu Li
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Mei Lu
- Department of Pediatrics, Women and Children's Hospital, School of Medicine, Xiamen University, Xiamen, 361003, China
| | - Ruxuan He
- Department of Respiratory Medicine, Beijing Children's Hospital, National Centre for Children's Health, Capital Medical University, Beijing, 100045, China
| | - Yao Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China.
| | - Yanling Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China.
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Julia-Palacios NA, Kuseyri Hübschmann O, Olivella M, Pons R, Horvath G, Lücke T, Fung CW, Wong SN, Cortès-Saladelafont E, Rovira-Remisa MM, Yıldız Y, Mercimek-Andrews S, Assmann B, Stevanović G, Manti F, Brennenstuhl H, Jung-Klawitter S, Jeltsch K, Sivri HS, Garbade SF, García-Cazorla À, Opladen T. The continuously evolving phenotype of succinic semialdehyde dehydrogenase deficiency. J Inherit Metab Dis 2024; 47:447-462. [PMID: 38499966 DOI: 10.1002/jimd.12723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 02/15/2024] [Accepted: 02/20/2024] [Indexed: 03/20/2024]
Abstract
The objective of the study is to evaluate the evolving phenotype and genetic spectrum of patients with succinic semialdehyde dehydrogenase deficiency (SSADHD) in long-term follow-up. Longitudinal clinical and biochemical data of 22 pediatric and 9 adult individuals with SSADHD from the patient registry of the International Working Group on Neurotransmitter related Disorders (iNTD) were studied with in silico analyses, pathogenicity scores and molecular modeling of ALDH5A1 variants. Leading initial symptoms, with onset in infancy, were developmental delay and hypotonia. Year of birth and specific initial symptoms influenced the diagnostic delay. Clinical phenotype of 26 individuals (median 12 years, range 1.8-33.4 years) showed a diversifying course in follow-up: 77% behavioral problems, 76% coordination problems, 73% speech disorders, 58% epileptic seizures and 40% movement disorders. After ataxia, dystonia (19%), chorea (11%) and hypokinesia (15%) were the most frequent movement disorders. Involvement of the dentate nucleus in brain imaging was observed together with movement disorders or coordination problems. Short attention span (78.6%) and distractibility (71.4%) were the most frequently behavior traits mentioned by parents while impulsiveness, problems communicating wishes or needs and compulsive behavior were addressed as strongly interfering with family life. Treatment was mainly aimed to control epileptic seizures and psychiatric symptoms. Four new pathogenic variants were identified. In silico scoring system, protein activity and pathogenicity score revealed a high correlation. A genotype/phenotype correlation was not observed, even in siblings. This study presents the diversifying characteristics of disease phenotype during the disease course, highlighting movement disorders, widens the knowledge on the genotypic spectrum of SSADHD and emphasizes a reliable application of in silico approaches.
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Affiliation(s)
- Natalia Alexandra Julia-Palacios
- Inborn Errors of Metabolism Unit, Department of Neurology, Institut de Recerca Sant Joan de Déu and CIBERER-ISCIII, Barcelona, Spain
| | - Oya Kuseyri Hübschmann
- Center for Pediatric and Adolescent Medicine Department I, Division of Pediatric Neurology and Metabolic Medicine, Heidelberg University, Medical Faculty Heidelberg, Heidelberg, Germany
| | - Mireia Olivella
- Bioinfomatics and Medical Statistics Group, University of Vic-Central University of Catalonia, Vic, Spain
| | - Roser Pons
- First Department of Pediatrics, Aghia Sofia Hospital, University of Athens, Athens, Greece
| | - Gabriella Horvath
- Division of Biochemical Genetics, Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| | - Thomas Lücke
- St. Josef-Hospital, University Children's Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Cheuk-Wing Fung
- Department of Pediatrics and Adolescent Medicine, The Hong Kong Children's Hospital, Hong Kong, Hong Kong
| | - Suet-Na Wong
- Department of Pediatrics and Adolescent Medicine, The Hong Kong Children's Hospital, Hong Kong, Hong Kong
| | - Elisenda Cortès-Saladelafont
- Inborn Errors of Metabolism Unit, Department of Neurology, Institut de Recerca Sant Joan de Déu and CIBERER-ISCIII, Barcelona, Spain
- Unit of Inherited Metabolic Diseases and Child Neurology, Department of Pediatrics, Hospital Germans Trias i Pujol, Badalona and Faculty of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - M Mar Rovira-Remisa
- Unit of Inherited Metabolic Diseases and Child Neurology, Department of Pediatrics, Hospital Germans Trias i Pujol, Badalona and Faculty of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Yılmaz Yıldız
- Division of Pediatric Metabolism, Department of Pediatrics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Saadet Mercimek-Andrews
- The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Medical Genetics, Faculty of Medicine and Dentistry, Women and Children's Health Research Institute, Stollery Children's Hospital, University of Alberta, Edmonton, Alberta, Canada
| | - Birgit Assmann
- Center for Pediatric and Adolescent Medicine Department I, Division of Pediatric Neurology and Metabolic Medicine, Heidelberg University, Medical Faculty Heidelberg, Heidelberg, Germany
| | - Galina Stevanović
- Clinic of Neurology and Psychiatry for Children and Youth, School of Medicine, University of Belgrade, Belgrade, Serbia
| | - Filippo Manti
- Unit of Child Neurology and Psychiatry, Department of Human Neuroscience, Università degli Studi di Roma La Sapienza, Rome, Italy
| | - Heiko Brennenstuhl
- Center for Pediatric and Adolescent Medicine Department I, Division of Pediatric Neurology and Metabolic Medicine, Heidelberg University, Medical Faculty Heidelberg, Heidelberg, Germany
- Institute of Human Genetics, Heidelberg University, Medical Faculty Heidelberg, Heidelberg, Germany
| | - Sabine Jung-Klawitter
- Center for Pediatric and Adolescent Medicine Department I, Division of Pediatric Neurology and Metabolic Medicine, Heidelberg University, Medical Faculty Heidelberg, Heidelberg, Germany
| | - Kathrin Jeltsch
- Center for Pediatric and Adolescent Medicine Department I, Division of Pediatric Neurology and Metabolic Medicine, Heidelberg University, Medical Faculty Heidelberg, Heidelberg, Germany
| | - H Serap Sivri
- Division of Pediatric Metabolism, Department of Pediatrics, Faculty of Medicine, Hacettepe University, Ankara, Turkey
| | - Sven F Garbade
- Center for Pediatric and Adolescent Medicine Department I, Division of Pediatric Neurology and Metabolic Medicine, Heidelberg University, Medical Faculty Heidelberg, Heidelberg, Germany
| | - Àngels García-Cazorla
- Inborn Errors of Metabolism Unit, Department of Neurology, Institut de Recerca Sant Joan de Déu and CIBERER-ISCIII, Barcelona, Spain
| | - Thomas Opladen
- Center for Pediatric and Adolescent Medicine Department I, Division of Pediatric Neurology and Metabolic Medicine, Heidelberg University, Medical Faculty Heidelberg, Heidelberg, Germany
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Lee HHC, Latzer IT, Bertoldi M, Gao G, Pearl PL, Sahin M, Rotenberg A. Gene replacement therapies for inherited disorders of neurotransmission: Current progress in succinic semialdehyde dehydrogenase deficiency. J Inherit Metab Dis 2024; 47:476-493. [PMID: 38581234 PMCID: PMC11096052 DOI: 10.1002/jimd.12735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Revised: 03/06/2024] [Accepted: 03/20/2024] [Indexed: 04/08/2024]
Abstract
Neurodevelopment is a highly organized and complex process involving lasting and often irreversible changes in the central nervous system. Inherited disorders of neurotransmission (IDNT) are a group of genetic disorders where neurotransmission is primarily affected, resulting in abnormal brain development from early life, manifest as neurodevelopmental disorders and other chronic conditions. In principle, IDNT (particularly those of monogenic causes) are amenable to gene replacement therapy via precise genetic correction. However, practical challenges for gene replacement therapy remain major hurdles for its translation from bench to bedside. We discuss key considerations for the development of gene replacement therapies for IDNT. As an example, we describe our ongoing work on gene replacement therapy for succinic semialdehyde dehydrogenase deficiency, a GABA catabolic disorder.
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Affiliation(s)
- Henry HC Lee
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA 02115, USA
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children’s Hospital, Boston, MA 02115, USA
| | - Itay Tokatly Latzer
- Division of Epilepsy & Clinical Neurophysiology, Department of Neurology, Boston Children’s Hospital, Boston, MA 02115, USA
- Tel-Aviv University Faculty of Medicine, Tel-Aviv, Israel
| | - Mariarita Bertoldi
- Dept. of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Guangping Gao
- The Horae Gene Therapy Center, UMass Medical School, MA 01605, USA
| | - Phillip L Pearl
- Division of Epilepsy & Clinical Neurophysiology, Department of Neurology, Boston Children’s Hospital, Boston, MA 02115, USA
| | - Mustafa Sahin
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA 02115, USA
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children’s Hospital, Boston, MA 02115, USA
| | - Alexander Rotenberg
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA 02115, USA
- Division of Epilepsy & Clinical Neurophysiology, Department of Neurology, Boston Children’s Hospital, Boston, MA 02115, USA
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Tokatly Latzer I, Bertoldi M, Blau N, DiBacco ML, Elsea SH, García-Cazorla À, Gibson KM, Gropman AL, Hanson E, Hoffman C, Jeltsch K, Juliá-Palacios N, Knerr I, Lee HHC, Malaspina P, McConnell A, Opladen T, Oppebøen M, Rotenberg A, Walterfang M, Wang-Tso L, Wevers RA, Roullet JB, Pearl PL. Consensus guidelines for the diagnosis and management of succinic semialdehyde dehydrogenase deficiency. Mol Genet Metab 2024; 142:108363. [PMID: 38452608 PMCID: PMC11073920 DOI: 10.1016/j.ymgme.2024.108363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 02/27/2024] [Accepted: 02/29/2024] [Indexed: 03/09/2024]
Abstract
Succinic semialdehyde dehydrogenase deficiency (SSADHD) (OMIM #271980) is a rare autosomal recessive metabolic disorder caused by pathogenic variants of ALDH5A1. Deficiency of SSADH results in accumulation of γ-aminobutyric acid (GABA) and other GABA-related metabolites. The clinical phenotype of SSADHD includes a broad spectrum of non-pathognomonic symptoms such as cognitive disabilities, communication and language deficits, movement disorders, epilepsy, sleep disturbances, attention problems, anxiety, and obsessive-compulsive traits. Current treatment options for SSADHD remain supportive, but there are ongoing attempts to develop targeted genetic therapies. This study aimed to create consensus guidelines for the diagnosis and management of SSADHD. Thirty relevant statements were initially addressed by a systematic literature review, resulting in different evidence levels of strength according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria. The highest level of evidence (level A), based on randomized controlled trials, was unavailable for any of the statements. Based on cohort studies, Level B evidence was available for 12 (40%) of the statements. Thereupon, through a process following the Delphi Method and directed by the Appraisal of Guidelines for Research and Evaluation (AGREE II) criteria, expert opinion was sought, and members of an SSADHD Consensus Group evaluated all the statements. The group consisted of neurologists, epileptologists, neuropsychologists, neurophysiologists, metabolic disease specialists, clinical and biochemical geneticists, and laboratory scientists affiliated with 19 institutions from 11 countries who have clinical experience with SSADHD patients and have studied the disorder. Representatives from parent groups were also included in the Consensus Group. An analysis of the survey's results yielded 25 (83%) strong and 5 (17%) weak agreement strengths. These first-of-their-kind consensus guidelines intend to consolidate and unify the optimal care that can be provided to individuals with SSADHD.
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Affiliation(s)
- Itay Tokatly Latzer
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; School of Medicine, Faculty of Medicine and Health Sciences, Tel-Aviv University, Tel Aviv, Israel.
| | - Mariarita Bertoldi
- Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Italy.
| | - Nenad Blau
- Division of Metabolism, University Children's Hospital, Zürich, Switzerland; Children's Research Center, University Children's Hospital Zurich, Switzerland.
| | - Melissa L DiBacco
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
| | - Sarah H Elsea
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
| | - Àngels García-Cazorla
- Neurometabolic Unit, Neurology Department, Institut de Recerca, Hospital Sant Joan de Déu, Barcelona, Spain.
| | - K Michael Gibson
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA.
| | - Andrea L Gropman
- Division of Neurogenetics and Neurodevelopmental Disabilities, Children's National Hospital, Washington, D.C, USA.
| | - Ellen Hanson
- Human Neurobehavioral Core, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA; Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, MA 02115, USA.
| | | | - Kathrin Jeltsch
- Heidelberg University, Medical Faculty Heidelberg, Center for Pediatric and Adolescent Medicine, Department I, Division of Pediatric Neurology and Metabolic Medicine, Heidelberg, Germany.
| | - Natalia Juliá-Palacios
- Neurometabolic Unit, Neurology Department, Institut de Recerca, Hospital Sant Joan de Déu, Barcelona, Spain.
| | - Ina Knerr
- National Centre for Inherited Metabolic Disorders, Children's Health Ireland, Temple Street, Dublin, Ireland.
| | - Henry H C Lee
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, MA 02115, USA; F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA.
| | - Patrizia Malaspina
- Department of Biology, Tor Vergata University, Via della Ricerca Scientifica s.n.c., Rome 00133, Italy.
| | | | - Thomas Opladen
- Heidelberg University, Medical Faculty Heidelberg, Center for Pediatric and Adolescent Medicine, Department I, Division of Pediatric Neurology and Metabolic Medicine, Heidelberg, Germany.
| | | | - Alexander Rotenberg
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA.
| | - Mark Walterfang
- Neuropsychiatry, Royal Melbourne Hospital, Melbourne, Australia; Department of Psychiatry, University of Melbourne, Melbourne, Australia; Florey Institute of Neuroscience and Mental Health, Melbourne, Australia; Department of Health and Medical Sciences, Edith Cowan University, Perth, Australia.
| | - Lee Wang-Tso
- Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan
| | - Ron A Wevers
- Translational Metabolic Laboratory, Department Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands.
| | - Jean-Baptiste Roullet
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA.
| | - Phillip L Pearl
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
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Tokatly Latzer I, Roullet JB, Afshar-Saber W, Lee HHC, Bertoldi M, McGinty GE, DiBacco ML, Arning E, Tsuboyama M, Rotenberg A, Opladen T, Jeltsch K, García-Cazorla À, Juliá-Palacios N, Gibson KM, Sahin M, Pearl PL. Clinical and molecular outcomes from the 5-Year natural history study of SSADH Deficiency, a model metabolic neurodevelopmental disorder. J Neurodev Disord 2024; 16:21. [PMID: 38658850 PMCID: PMC11044349 DOI: 10.1186/s11689-024-09538-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 04/09/2024] [Indexed: 04/26/2024] Open
Abstract
BACKGROUND Succinic semialdehyde dehydrogenase deficiency (SSADHD) represents a model neurometabolic disease at the fulcrum of translational research within the Boston Children's Hospital Intellectual and Developmental Disabilities Research Centers (IDDRC), including the NIH-sponsored natural history study of clinical, neurophysiological, neuroimaging, and molecular markers, patient-derived induced pluripotent stem cells (iPSC) characterization, and development of a murine model for tightly regulated, cell-specific gene therapy. METHODS SSADHD subjects underwent clinical evaluations, neuropsychological assessments, biochemical quantification of γ-aminobutyrate (GABA) and related metabolites, electroencephalography (standard and high density), magnetoencephalography, transcranial magnetic stimulation, magnetic resonance imaging and spectroscopy, and genetic tests. This was parallel to laboratory molecular investigations of in vitro GABAergic neurons derived from induced human pluripotent stem cells (hiPSCs) of SSADHD subjects and biochemical analyses performed on a versatile murine model that uses an inducible and reversible rescue strategy allowing on-demand and cell-specific gene therapy. RESULTS The 62 SSADHD subjects [53% females, median (IQR) age of 9.6 (5.4-14.5) years] included in the study had a reported symptom onset at ∼ 6 months and were diagnosed at a median age of 4 years. Language developmental delays were more prominent than motor. Autism, epilepsy, movement disorders, sleep disturbances, and various psychiatric behaviors constituted the core of the disorder's clinical phenotype. Lower clinical severity scores, indicating worst severity, coincided with older age (R= -0.302, p = 0.03), as well as age-adjusted lower values of plasma γ-aminobutyrate (GABA) (R = 0.337, p = 0.02) and γ-hydroxybutyrate (GHB) (R = 0.360, p = 0.05). While epilepsy and psychiatric behaviors increase in severity with age, communication abilities and motor function tend to improve. iPSCs, which were differentiated into GABAergic neurons, represent the first in vitro neuronal model of SSADHD and express the neuronal marker microtubule-associated protein 2 (MAP2), as well as GABA. GABA-metabolism in induced GABAergic neurons could be reversed using CRISPR correction of the pathogenic variants or mRNA transfection and SSADHD iPSCs were associated with excessive glutamatergic activity and related synaptic excitation. CONCLUSIONS Findings from the SSADHD Natural History Study converge with iPSC and animal model work focused on a common disorder within our IDDRC, deepening our knowledge of the pathophysiology and longitudinal clinical course of a complex neurodevelopmental disorder. This further enables the identification of biomarkers and changes throughout development that will be essential for upcoming targeted trials of enzyme replacement and gene therapy.
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Affiliation(s)
- Itay Tokatly Latzer
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA, 02115, USA
- School of Medicine, Faculty of Medical and Health Sciences, Tel-Aviv University, Tel Aviv, Israel
| | - Jean-Baptiste Roullet
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - Wardiya Afshar-Saber
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, Boston, MA, 02115, USA
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Henry H C Lee
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, Boston, MA, 02115, USA
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Mariarita Bertoldi
- Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Gabrielle E McGinty
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Melissa L DiBacco
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA, 02115, USA
| | - Erland Arning
- Institute of Metabolic Disease, Baylor Scott & White Research Institute, Dallas, TX, USA
| | - Melissa Tsuboyama
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA, 02115, USA
| | - Alexander Rotenberg
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA, 02115, USA
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Thomas Opladen
- Division of Neuropediatrics & Metabolic Medicine, University Children's Hospital Heidelberg, Im Neuenheimer Feld 430, 69120, Heidelberg, Germany
| | - Kathrin Jeltsch
- Division of Neuropediatrics & Metabolic Medicine, University Children's Hospital Heidelberg, Im Neuenheimer Feld 430, 69120, Heidelberg, Germany
| | - Àngels García-Cazorla
- Neurometabolic Unit, Neurology Department, Institut de Recerca, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Natalia Juliá-Palacios
- Neurometabolic Unit, Neurology Department, Institut de Recerca, Hospital Sant Joan de Déu, Barcelona, Spain
| | - K Michael Gibson
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - Mustafa Sahin
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA, 02115, USA
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, Boston, MA, 02115, USA
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Phillip L Pearl
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA, 02115, USA.
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Tokatly Latzer I, Roullet JB, Cesaro S, DiBacco ML, Arning E, Rotenberg A, Lee HHC, Opladen T, Jeltsch K, García-Cazorla À, Juliá-Palacios N, Gibson KM, Bertoldi M, Pearl PL. Phenotypic correlates of structural and functional protein impairments resultant from ALDH5A1 variants. Hum Genet 2023; 142:1755-1776. [PMID: 37962671 DOI: 10.1007/s00439-023-02613-6] [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: 06/26/2023] [Accepted: 10/27/2023] [Indexed: 11/15/2023]
Abstract
To investigate the genotype-to-protein-to-phenotype correlations of succinic semialdehyde dehydrogenase deficiency (SSADHD), an inherited metabolic disorder of γ-aminobutyric acid catabolism. Bioinformatics and in silico mutagenesis analyses of ALDH5A1 variants were performed to evaluate their impact on protein stability, active site and co-factor binding domains, splicing, and homotetramer formation. Protein abnormalities were then correlated with a validated disease-specific clinical severity score and neurological, neuropsychological, biochemical, neuroimaging, and neurophysiological metrics. A total of 58 individuals (1:1 male/female ratio) were affected by 32 ALDH5A1 pathogenic variants, eight of which were novel. Compared to individuals with single homotetrameric or multiple homo and heterotetrameric proteins, those predicted not to synthesize any functional enzyme protein had significantly lower expression of ALDH5A1 (p = 0.001), worse overall clinical outcomes (p = 0.008) and specifically more severe cognitive deficits (p = 0.01), epilepsy (p = 0.04) and psychiatric morbidity (p = 0.04). Compared to individuals with predictions of having no protein or a protein impaired in catalytic functions, subjects whose proteins were predicted to be impaired in stability, folding, or oligomerization had a better overall clinical outcome (p = 0.02) and adaptive skills (p = 0.04). The quantity and type of enzyme proteins (no protein, single homotetramers, or multiple homo and heterotetramers), as well as their structural and functional impairments (catalytic or stability, folding, or oligomerization), contribute to phenotype severity in SSADHD. These findings are valuable for assessment of disease prognosis and management, including patient selection for gene replacement therapy. Furthermore, they provide a roadmap to determine genotype-to-protein-to-phenotype relationships in other autosomal recessive disorders.
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Affiliation(s)
- Itay Tokatly Latzer
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA, 02115, USA
- Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Jean-Baptiste Roullet
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - Samuele Cesaro
- Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Strada Le Grazie 8, 37134, Verona, VR, Italy
| | - Melissa L DiBacco
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA, 02115, USA
| | - Erland Arning
- Institute of Metabolic Disease, Baylor Scott & White Research Institute, Dallas, TX, USA
| | - Alexander Rotenberg
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA, 02115, USA
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Henry H C Lee
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, 02115, USA
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Thomas Opladen
- Division of Neuropediatrics and Metabolic Medicine, University Children's Hospital Heidelberg, Im Neuenheimer Feld 430, 69120, Heidelberg, Germany
| | - Kathrin Jeltsch
- Division of Neuropediatrics and Metabolic Medicine, University Children's Hospital Heidelberg, Im Neuenheimer Feld 430, 69120, Heidelberg, Germany
| | - Àngels García-Cazorla
- Neurometabolic Unit, Neurology Department, Institut de Recerca, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Natalia Juliá-Palacios
- Neurometabolic Unit, Neurology Department, Institut de Recerca, Hospital Sant Joan de Déu, Barcelona, Spain
| | - K Michael Gibson
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - Mariarita Bertoldi
- Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Strada Le Grazie 8, 37134, Verona, VR, Italy.
| | - Phillip L Pearl
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA, 02115, USA.
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Tokatly Latzer I, Hanson E, Bertoldi M, García-Cazorla À, Tsuboyama M, MacMullin P, Rotenberg A, Roullet JB, Pearl PL. Autism spectrum disorder and GABA levels in children with succinic semialdehyde dehydrogenase deficiency. Dev Med Child Neurol 2023; 65:1596-1606. [PMID: 37246331 DOI: 10.1111/dmcn.15659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 04/30/2023] [Accepted: 05/03/2023] [Indexed: 05/30/2023]
Abstract
AIM To elucidate the etiological aspects of autism spectrum disorder (ASD) in succinic semialdehyde dehydrogenase deficiency (SSADHD), related to dysregulation of γ-aminobutyric acid (GABA) and the imbalance of excitatory and inhibitory neurotransmission. METHOD In this prospective, international study, individuals with SSADHD underwent neuropsychological assessments, as well as biochemical, neurophysiological, and neuroimaging evaluations. RESULTS Of the 29 individuals (17 females) enrolled (median age [IQR] 10 years 5 months [5 years 11 months-18 years 1 month]), 16 were diagnosed with ASD. ASD severity significantly increased with age (r = 0.67, p < 0.001) but was inversely correlated with plasma GABA (r = -0.67, p < 0.001) and γ-hydroxybutyrate levels (r = -0.538, p = 0.004), and resting motor threshold as measured by transcranial magnetic stimulation (r = -0.44, p = 0.03). A discriminative analysis indicated that an age older than 7 years 2 months (p = 0.004) and plasma GABA levels less than 2.47 μM (p = 0.01) are the threshold values beyond which the likelihood of ASD presenting in individuals with SSADHD is increased. INTERPRETATION ASD is prevalent but not universal in SSADHD, and it can be predicted by lower levels of plasma GABA and GABA-related metabolites. ASD severity in SSADHD increases with age and the loss of cortical inhibition. These findings add insight into the pathophysiology of ASD and may facilitate its early diagnosis and intervention in individuals with SSADHD.
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Affiliation(s)
- Itay Tokatly Latzer
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
- Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Ellen Hanson
- Human Neurobehavioral Core Services, Division of Neurology, Boston Children's Hospital, Boston, MA, USA
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children's Hospital, MA, USA
| | - Mariarita Bertoldi
- Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Àngeles García-Cazorla
- Neurometabolic Unit, Neurology Department, Institut de Recerca, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Melissa Tsuboyama
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Paul MacMullin
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Alexander Rotenberg
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
- FM Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, USA
| | - Jean-Baptiste Roullet
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - Phillip L Pearl
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
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Koh W, Kwak H, Cheong E, Lee CJ. GABA tone regulation and its cognitive functions in the brain. Nat Rev Neurosci 2023; 24:523-539. [PMID: 37495761 DOI: 10.1038/s41583-023-00724-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2023] [Indexed: 07/28/2023]
Abstract
γ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter released at GABAergic synapses, mediating fast-acting phasic inhibition. Emerging lines of evidence unequivocally indicate that a small amount of extracellular GABA - GABA tone - exists in the brain and induces a tonic GABA current that controls neuronal activity on a slow timescale relative to that of phasic inhibition. Surprisingly, studies indicate that glial cells that synthesize GABA, such as astrocytes, release GABA through non-vesicular mechanisms, such as channel-mediated release, and thereby act as the source of GABA tone in the brain. In this Review, we first provide an overview of major advances in our understanding of the cell-specific molecular and cellular mechanisms of GABA synthesis, release and clearance that regulate GABA tone in various brain regions. We next examine the diverse ways in which the tonic GABA current regulates synaptic transmission and synaptic plasticity through extrasynaptic GABAA-receptor-mediated mechanisms. Last, we discuss the physiological mechanisms through which tonic inhibition modulates cognitive function on a slow timescale. In this Review, we emphasize that the cognitive functions of tonic GABA current extend beyond mere inhibition, laying a foundation for future research on the physiological and pathophysiological roles of GABA tone regulation in normal and abnormal psychiatric conditions.
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Affiliation(s)
- Wuhyun Koh
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, South Korea
| | - Hankyul Kwak
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul, South Korea
| | - Eunji Cheong
- Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul, South Korea.
| | - C Justin Lee
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, South Korea.
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Tokatly Latzer I, Roullet JB, Gibson KM, Pearl PL. Establishment and validation of a clinical severity scoring system for succinic semialdehyde dehydrogenase deficiency. J Inherit Metab Dis 2023; 46:992-1003. [PMID: 37219411 DOI: 10.1002/jimd.12635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 05/16/2023] [Accepted: 05/19/2023] [Indexed: 05/24/2023]
Abstract
Succinic semialdehyde dehydrogenase deficiency (SSADHD) is an inherited metabolic disorder with a variable phenotype and rate of progression. We aimed to develop and validate a clinical severity scoring (CSS) system applicable to the clinical setting and composed of five domains reflecting the principal manifestations of this disorder: cognitive, communication, motor, epilepsy, and psychiatry. A prospectively characterized cohort of 27 SSADHD subjects (55% females, median [IQR] age 9.2 [4.6-16.2] years) who enrolled in the SSADHD Natural History Study were included. The CSS was validated by comparison to an objective severity scoring (OSS) system based on comprehensive neuropsychologic and neurophysiologic assessments, which mirror and complement the domains of the CSS. The total CSS was sex and age-independent, and 80% of its domains lacked interdependence. With increasing age, there was a significant improvement in communication abilities (p = 0.05) and a worsening of epilepsy and psychiatric manifestations (p = 0.004 and p = 0.02, respectively). There was a significant correlation between all the CSS and OSS domain scores, as well as between the total CSS and OSS (R = 0.855, p < 0.001). Additionally, there were no significant demographic or clinical differences in the ratio of individuals in the upper quartile to the lower three quartiles of the CSS and OSS. The SSADHD CSS is validated using objective measures and offers a reliable condition-specific instrument universally applicable in clinical settings. This severity score may be utilized for family and patient counseling, genotype-phenotype correlations, biomarker development, clinical trials, and objective descriptions of the natural history of SSADHD.
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Affiliation(s)
- Itay Tokatly Latzer
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
- Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Jean-Baptiste Roullet
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington, USA
| | - K Michael Gibson
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington, USA
| | - Phillip L Pearl
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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Latzer IT, Bertoldi M, DiBacco ML, Arning E, Tsuboyama M, MacMullin P, Sachee D, Rotenberg A, Lee HHC, Aygun D, Opladen T, Jeltsch K, García-Cazorla À, Roullet JB, Gibson KM, Pearl PL. The presence and severity of epilepsy coincide with reduced γ-aminobutyrate and cortical excitatory markers in succinic semialdehyde dehydrogenase deficiency. Epilepsia 2023; 64:1516-1526. [PMID: 36961285 PMCID: PMC10471137 DOI: 10.1111/epi.17592] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/21/2023] [Accepted: 03/21/2023] [Indexed: 03/25/2023]
Abstract
OBJECTIVE Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a rare inherited metabolic disorder caused by a defect of γ-aminobutyrate (GABA) catabolism. Despite the resultant hyper-GABAergic environment facilitated by the metabolic defect, individuals with this disorder have a paradoxically high prevalence of epilepsy. We aimed to study the characteristics of epilepsy in SSADHD and its concordance with GABA-related metabolites and neurophysiologic markers of cortical excitation. METHODS Subjects in an international natural history study of SSADHD underwent clinical assessments, electroencephalography, transcranial magnetic stimulation (TMS), magnetic resonance spectroscopy for GABA/N-acetyl aspartate quantification, and plasma GABA-related metabolite measurements. RESULTS A total of 61 subjects with SSADHD and 42 healthy controls were included in the study. Epilepsy was present in 49% of the SSADHD cohort. Over time, there was an increase in severity in 33% of the subjects with seizures. The presence of seizures was associated with increasing age (p = .001) and lower levels of GABA (p = .002), γ-hydroxybutyrate (GHB; p = .004), and γ-guanidinobutyrate (GBA; p = .003). Seizure severity was associated with increasing age and lower levels of GABA-related metabolites as well as lower TMS-derived resting motor thresholds (p = .04). The cutoff values with the highest discriminative ability to predict seizures were age > 9.2 years (p = .001), GABA < 2.57 μmol·L-1 (p = .002), GHB < 143.6 μmol·L-1 (p = .004), and GBA < .075 μmol·L-1 (p = .007). A prediction model for seizures in SSADHD was comprised of the additive effect of older age and lower plasma GABA, GHB, and GBA (area under the receiver operating characteristic curve of .798, p = .008). SIGNIFICANCE Epilepsy is highly prevalent in SSADHD, and its onset and severity correlate with an age-related decline in GABA and GABA-related metabolite levels as well as TMS markers of reduced cortical inhibition. The reduction of GABAergic activity in this otherwise hyper-GABAergic disorder demonstrates a concordance between epileptogenesis and compensatory responses. These findings may furthermore inform the timing of molecular interventions for SSADHD.
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Affiliation(s)
- Itay Tokatly Latzer
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
- Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Mariarita Bertoldi
- Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Italy
| | - Melissa L. DiBacco
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Erland Arning
- Institute of Metabolic Disease, Baylor Scott & White Research Institute, Dallas, Texas, USA
| | - Melissa Tsuboyama
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Paul MacMullin
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Daniyal Sachee
- Harvard College, Harvard University, Cambridge, MA 02138, USA
| | - Alexander Rotenberg
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA 02115, USA
| | - Henry H C Lee
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA 02115, USA
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children’s Hospital, MA 02115, USA
| | - Deniz Aygun
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Thomas Opladen
- Division of Neuropediatrics & Metabolic Medicine, University Children’s Hospital Heidelberg, Im Neuenheimer Feld 430, 69120, Heidelberg, Germany
| | - Kathrin Jeltsch
- Division of Neuropediatrics & Metabolic Medicine, University Children’s Hospital Heidelberg, Im Neuenheimer Feld 430, 69120, Heidelberg, Germany
| | - Àngels García-Cazorla
- Neurometabolic Unit, Neurology Department, Institut de Recerca, Hospital Sant Joan de Déu, Barcelona, Spain
| | - Jean-Baptiste Roullet
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - K. Michael Gibson
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, WA, USA
| | - Phillip L. Pearl
- Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
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Tokatly Latzer I, Pearl PL. Treatment of neurometabolic epilepsies: Overview and recent advances. Epilepsy Behav 2023; 142:109181. [PMID: 37001467 DOI: 10.1016/j.yebeh.2023.109181] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 03/11/2023] [Accepted: 03/12/2023] [Indexed: 05/08/2023]
Abstract
The rarity and heterogeneity of neurometabolic diseases make it challenging to reach evidence-based principles for their specific treatments. Indeed, current treatments for many of these diseases remain symptomatic and supportive. However, an ongoing scientific and medical revolution has led to dramatic breakthroughs in molecular sciences and genetics, revealing precise pathophysiologic mechanisms. Accordingly, this has led to significant progress in the development of novel therapeutic approaches aimed at treating epilepsy resulting from these conditions, as well as their other manifestations. We overview recent notable treatment advancements, from vitamins, trace minerals, and diets to unique medications targeting the elemental pathophysiology at a molecular or cellular level, including enzyme replacement therapy, enzyme enhancing therapy, antisense oligonucleotide therapy, stem cell transplantation, and gene therapy.
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Affiliation(s)
- Itay Tokatly Latzer
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Phillip L Pearl
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
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12
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Lee HHC, McGinty GE, Pearl PL, Rotenberg A. Understanding the Molecular Mechanisms of Succinic Semialdehyde Dehydrogenase Deficiency (SSADHD): Towards the Development of SSADH-Targeted Medicine. Int J Mol Sci 2022; 23:2606. [PMID: 35269750 PMCID: PMC8910003 DOI: 10.3390/ijms23052606] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 02/18/2022] [Accepted: 02/21/2022] [Indexed: 11/21/2022] Open
Abstract
Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a rare genetic disorder caused by inefficient metabolic breakdown of the major inhibitory neurotransmitter, γ-aminobutyric acid (GABA). Pathologic brain accumulation of GABA and γ-hydroxybutyrate (GHB), a neuroactive by-product of GABA catabolism, leads to a multitude of molecular abnormalities beginning in early life, culminating in multifaceted clinical presentations including delayed psychomotor development, intellectual disability, hypotonia, and ataxia. Paradoxically, over half of patients with SSADHD also develop epilepsy and face a significant risk of sudden unexpected death in epilepsy (SUDEP). Here, we review some of the relevant molecular mechanisms through which impaired synaptic inhibition, astrocytic malfunctions and myelin defects might contribute to the complex SSADHD phenotype. We also discuss the gaps in knowledge that need to be addressed for the implementation of successful gene and enzyme replacement SSADHD therapies. We conclude with a description of a novel SSADHD mouse model that enables 'on-demand' SSADH restoration, allowing proof-of-concept studies to fine-tune SSADH restoration in preparation for eventual human trials.
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Affiliation(s)
- Henry H. C. Lee
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA 02115, USA; (G.E.M.); (A.R.)
- Rosamund Stone Zander Translational Neuroscience Center, Boston Children’s Hospital, Boston, MA 02115, USA
| | - Gabrielle E. McGinty
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA 02115, USA; (G.E.M.); (A.R.)
| | - Phillip L. Pearl
- Division of Epilepsy & Clinical Neurophysiology, Department of Neurology, Boston Children’s Hospital, Boston, MA 02115, USA;
| | - Alexander Rotenberg
- F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Boston, MA 02115, USA; (G.E.M.); (A.R.)
- Division of Epilepsy & Clinical Neurophysiology, Department of Neurology, Boston Children’s Hospital, Boston, MA 02115, USA;
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