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Ricci FS, Stanga S, Mezzanotte M, Marinaccio C, D'Alessandro R, Somà A, Sottemano S, Conio A, Morana G, Spada M, Boido M, Mongini TE. Biochemical characterization on muscle tissue of a novel biallelic ACO2 mutation in an infant with progressive encephalopathy. JIMD Rep 2024; 65:3-9. [PMID: 38186851 PMCID: PMC10764196 DOI: 10.1002/jmd2.12400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 10/06/2023] [Accepted: 10/10/2023] [Indexed: 01/09/2024] Open
Abstract
The ACO2 gene encodes the mitochondrial protein aconitate hydratase, which is responsible for catalyzing the interconversion of citrate into isocitrate in the tricarboxylic acid (TCA) cycle. Mitochondrial aconitase is expressed ubiquitously, and deficiencies in TCA-cycle enzymes have been reported to cause various neurodegenerative diseases due to disruption of cellular energy metabolism and development of oxidative stress. We investigated a severe early infantile-onset neurometabolic syndrome due to a homozygous novel variant in exon 13 of the ACO2 gene. The in vitro pathogenicity of this variant of unknown significance was demonstrated by the loss of both protein expression and its enzymatic activity on muscle tissue sample taken from the patient. The patient presented with progressive encephalopathy soon after birth, characterized by hypotonia, progressive severe muscle atrophy, and respiratory failure. Serial brain magnetic resonance imaging showed progressive abnormalities compatible with a metabolic disorder, possibly mitochondrial. Muscle biopsy disclosed moderate myopathic alterations and features consistent with a mitochondriopathy albeit nonspecific. The course was characterized by progressive worsening of the clinical and neurological picture, and the patient died at 5 months of age. This study provides the first report on the validation in muscle from human subjects regarding in vitro analysis for mitochondrial aconitase activity. To our knowledge, no prior reports have demonstrated a correlation of phenotypic and diagnostic characteristics with in vitro muscle enzymatic activity of mitochondrial aconitase in humans. In conclusion, this case further expands the genetic spectrum of ACO2 variants and defines a complex case of severe neonatal neurometabolic disorder.
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Affiliation(s)
- Federica Silvia Ricci
- Division of Child and Adolescent Neuropsychiatry, Department of Public Health and Pediatric SciencesUniversity of TurinTurinItaly
| | - Serena Stanga
- Department of Neuroscience “Rita Levi Montalcini”Neuroscience Institute Cavalieri Ottolenghi, University of TurinTurinItaly
| | - Mariarosa Mezzanotte
- Department of Neuroscience “Rita Levi Montalcini”Neuroscience Institute Cavalieri Ottolenghi, University of TurinTurinItaly
| | - Cristina Marinaccio
- Division of Child and Adolescent Neuropsychiatry, Department of Child Care and PathologyChildren Hospital “Regina Margherita”TurinItaly
| | - Rossella D'Alessandro
- Division of Child and Adolescent Neuropsychiatry, Department of Child Care and PathologyChildren Hospital “Regina Margherita”TurinItaly
| | - Alessandra Somà
- Division of Child and Adolescent Neuropsychiatry, Department of Public Health and Pediatric SciencesUniversity of TurinTurinItaly
| | - Stefano Sottemano
- Division of Child and Adolescent Neuropsychiatry, Department of Public Health and Pediatric SciencesUniversity of TurinTurinItaly
| | - Alessandra Conio
- Pediatric Intensive Care Unit, Anesthesia, Resuscitation and Emergency DepartmentUniversity of TurinTurinItaly
| | - Giovanni Morana
- Neuroradiology Unit, Department of Neuroscience “Rita Levi Montalcini”University of TurinTurinItaly
| | - Marco Spada
- Division of Child and Adolescent Neuropsychiatry, Department of Child Care and PathologyChildren Hospital “Regina Margherita”TurinItaly
| | - Marina Boido
- Department of Neuroscience “Rita Levi Montalcini”Neuroscience Institute Cavalieri Ottolenghi, University of TurinTurinItaly
| | - Tiziana E. Mongini
- Division of Neurology 1, Department of Neuroscience “Rita Levi Montalcini”University of TurinTurinItaly
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Ha DJ, Park J, Seo GH, Lee K, Kwon YS, Lee JE, Kim SJ. Case Report: Infantile Cerebellar-Retinal Degeneration With Compound Heterozygous Variants in ACO2 Gene-Long-Term Follow-Up of a Sibling. Front Genet 2022; 13:729980. [PMID: 35368710 PMCID: PMC8965713 DOI: 10.3389/fgene.2022.729980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 02/09/2022] [Indexed: 11/13/2022] Open
Abstract
Infantile cerebellar-retinal degeneration (ICRD) is an extremely rare, infantile-onset neuro-degenerative disease, characterized by autosomal recessive inherited, global developmental delay (GDD), progressive cerebellar and cortical atrophy, and retinal degeneration. In 2012, a biallelic pathogenic variant in ACO2 gene (NM_001098.3) was found to be causative of this disease. To date, approximately 44 variants displaying various clinical features have been reported. Here, we report a case of two siblings with compound heterozygous variants in the ACO2 gene. Two siblings without perinatal problems were born to healthy non-consanguineous Korean parents. They showed GDD and seizures since infancy. Their first brain magnetic resonance imaging (MRI), electroencephalography, and metabolic workup revealed no abnormal findings. As they grew, they developed symptoms including ataxia, dysmetria, poor sitting balance, and myopia. Follow-up brain MRI findings revealed atrophy of the cerebellum and optic nerve. Through exome sequencing of both siblings and their parents, we identified the following compound heterozygous variants in the ACO2: c.85C > T (p.Arg29Trp) and c.2303C > A (p.Ala768Asp). These two variants were categorized as likely pathogenic based on ACMG/AMP guidelines. In conclusion, this case help to broaden the genetic and clinical spectrum of the ACO2 variants associated with ICRD. We have also documented the long-term clinical course and serial brain MRI findings for two patients with this extremely rare disease.
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Affiliation(s)
- Dong Jun Ha
- Department of Pediatrics, Inha University Hospital, Inha University College of Medicine, Incheon, South Korea
| | - Jisun Park
- Department of Pediatrics, Inha University Hospital, Inha University College of Medicine, Incheon, South Korea.,Northwest Gyeonggi Regional Center for Rare Disease, Inha University Hospital, Incheon, Korea
| | | | | | - Young Se Kwon
- Department of Pediatrics, Inha University Hospital, Inha University College of Medicine, Incheon, South Korea.,Northwest Gyeonggi Regional Center for Rare Disease, Inha University Hospital, Incheon, Korea
| | - Ji Eun Lee
- Department of Pediatrics, Inha University Hospital, Inha University College of Medicine, Incheon, South Korea.,Northwest Gyeonggi Regional Center for Rare Disease, Inha University Hospital, Incheon, Korea
| | - Su Jin Kim
- Department of Pediatrics, Inha University Hospital, Inha University College of Medicine, Incheon, South Korea.,Northwest Gyeonggi Regional Center for Rare Disease, Inha University Hospital, Incheon, Korea
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