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Lancaster MS, Graham BH. Succinyl-CoA Synthetase Dysfunction as a Mechanism of Mitochondrial Encephalomyopathy: More than Just an Oxidative Energy Deficit. Int J Mol Sci 2023; 24:10725. [PMID: 37445899 PMCID: PMC10342173 DOI: 10.3390/ijms241310725] [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: 05/12/2023] [Revised: 06/23/2023] [Accepted: 06/25/2023] [Indexed: 07/15/2023] Open
Abstract
Biallelic pathogenic variants in subunits of succinyl-CoA synthetase (SCS), a tricarboxylic acid (TCA) cycle enzyme, are associated with mitochondrial encephalomyopathy in humans. SCS catalyzes the interconversion of succinyl-CoA to succinate, coupled to substrate-level phosphorylation of either ADP or GDP, within the TCA cycle. SCS-deficient encephalomyopathy typically presents in infancy and early childhood, with many patients succumbing to the disease during childhood. Common symptoms include abnormal brain MRI, basal ganglia lesions and cerebral atrophy, severe hypotonia, dystonia, progressive psychomotor regression, and growth deficits. Although subunits of SCS were first identified as causal genes for progressive metabolic encephalomyopathy in the early 2000s, recent investigations are now beginning to unravel the pathomechanisms underlying this metabolic disorder. This article reviews the current understanding of SCS function within and outside the TCA cycle as it relates to the complex and multifactorial mechanisms underlying SCS-related mitochondrial encephalomyopathy.
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Affiliation(s)
| | - Brett H. Graham
- Department of Medical & Molecular Genetics, Indiana University School of Medicine, 975 W. Walnut St., Room IB257, Indianapolis, IN 46202, USA;
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2
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SUCLG1 mutations and mitochondrial encephalomyopathy: a case study and review of the literature. Mol Biol Rep 2020; 47:9699-9714. [PMID: 33230783 DOI: 10.1007/s11033-020-05999-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 11/11/2020] [Indexed: 10/22/2022]
Abstract
The mitochondrial encephalomyopathies represent a clinically heterogeneous group of neurodegenerative disorders. The clinical phenotype of patients could be explained by mutations of mitochondria-related genes, notably SUCLG1 and SUCLA2. Here, we presented a 5-year-old boy with clinical features of mitochondrial encephalomyopathy from Iran. Also, a systematic review was performed to explore the involvement of SUCLG1 mutations in published mitochondrial encephalomyopathies cases. Genotyping was performed by implementing whole-exome sequencing. Moreover, quantification of the mtDNA content was performed by real-time qPCR. We identified a novel, homozygote missense variant chr2: 84676796 A > T (hg19) in the SUCLG1 gene. This mutation substitutes Cys with Ser at the 60-position of the SUCLG1 protein. Furthermore, the in-silico analysis revealed that the mutated position in the genome is well conserved in mammalians, that implies mutation in this residue would possibly result in phenotypic consequences. Here, we identified a novel, homozygote missense variant chr2: 84676796 A > T in the SUCLG1 gene. Using a range of experimental and in silico analysis, we found that the mutation might explain the observed phenotype in the family.
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3
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Chinopoulos C, Batzios S, van den Heuvel LP, Rodenburg R, Smeets R, Waterham HR, Turkenburg M, Ruiter JP, Wanders RJA, Doczi J, Horvath G, Dobolyi A, Vargiami E, Wevers RA, Zafeiriou D. Mutated SUCLG1 causes mislocalization of SUCLG2 protein, morphological alterations of mitochondria and an early-onset severe neurometabolic disorder. Mol Genet Metab 2019; 126:43-52. [PMID: 30470562 DOI: 10.1016/j.ymgme.2018.11.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 11/14/2018] [Accepted: 11/14/2018] [Indexed: 11/19/2022]
Abstract
Succinate-CoA ligase (SUCL) is a heterodimer consisting of an alpha subunit encoded by SUCLG1, and a beta subunit encoded by either SUCLA2 or SUCLG2 catalyzing an ATP- or GTP-forming reaction, respectively, in the mitochondrial matrix. The deficiency of this enzyme represents an encephalomyopathic form of mtDNA depletion syndromes. We describe the fatal clinical course of a female patient with a pathogenic mutation in SUCLG1 (c.626C > A, p.Ala209Glu) heterozygous at the genomic DNA level, but homozygous at the transcriptional level. The patient exhibited early-onset neurometabolic abnormality culminating in severe brain atrophy and dystonia leading to death by the age of 3.5 years. Urine and plasma metabolite profiling was consistent with SUCL deficiency which was confirmed by enzyme analysis and lack of mitochondrial substrate-level phosphorylation (mSLP) in skin fibroblasts. Oxygen consumption- but not extracellular acidification rates were altered only when using glutamine as a substrate, and this was associated with mild mtDNA depletion and no changes in ETC activities. Immunoblot analysis revealed no detectable levels of SUCLG1, while SUCLA2 and SUCLG2 protein expressions were largely reduced. Confocal imaging of triple immunocytochemistry of skin fibroblasts showed that SUCLG2 co-localized only partially with the mitochondrial network which otherwise exhibited an increase in fragmentation compared to control cells. Our results outline the catastrophic consequences of the mutated SUCLG1 leading to strongly reduced SUCL activity, mSLP impairment, mislocalization of SUCLG2, morphological alterations in mitochondria and clinically to a severe neurometabolic disease, but in the absence of changes in mtDNA levels or respiratory complex activities.
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Affiliation(s)
| | - Spyros Batzios
- 1st Department of Pediatrics, "Hippokratio" General Hospital, Aristotle University, Thessaloniki, Greece; Department of Paediatric Metabolic Medicine, Great Ormond Street Hospital, London, UK
| | - Lambertus P van den Heuvel
- Department of Pediatrics, Radboud University Medical Centre, Nijmegen, The Netherlands; Translational Metabolic Laboratory, Department Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Richard Rodenburg
- Department of Pediatrics, Radboud University Medical Centre, Nijmegen, The Netherlands; Translational Metabolic Laboratory, Department Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Roel Smeets
- Translational Metabolic Laboratory, Department Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Hans R Waterham
- Laboratory Genetic Metabolic Diseases, Amsterdam University Medical Centers, University of Amsterdam, The Netherlands
| | - Marjolein Turkenburg
- Laboratory Genetic Metabolic Diseases, Amsterdam University Medical Centers, University of Amsterdam, The Netherlands
| | - Jos P Ruiter
- Laboratory Genetic Metabolic Diseases, Amsterdam University Medical Centers, University of Amsterdam, The Netherlands
| | - Ronald J A Wanders
- Laboratory Genetic Metabolic Diseases, Amsterdam University Medical Centers, University of Amsterdam, The Netherlands
| | - Judit Doczi
- Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary
| | - Gergo Horvath
- Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary
| | - Arpad Dobolyi
- MTA-ELTE Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences, Eotvos Lorand University, Budapest, Hungary; Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary
| | - Euthymia Vargiami
- 1st Department of Pediatrics, "Hippokratio" General Hospital, Aristotle University, Thessaloniki, Greece
| | - Ron A Wevers
- Translational Metabolic Laboratory, Department Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands.
| | - Dimitrios Zafeiriou
- 1st Department of Pediatrics, "Hippokratio" General Hospital, Aristotle University, Thessaloniki, Greece.
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El-Hattab AW, Craigen WJ, Scaglia F. Mitochondrial DNA maintenance defects. Biochim Biophys Acta Mol Basis Dis 2017; 1863:1539-1555. [PMID: 28215579 DOI: 10.1016/j.bbadis.2017.02.017] [Citation(s) in RCA: 166] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 01/31/2017] [Accepted: 02/14/2017] [Indexed: 01/12/2023]
Abstract
The maintenance of mitochondrial DNA (mtDNA) depends on a number of nuclear gene-encoded proteins including a battery of enzymes forming the replisome needed to synthesize mtDNA. These enzymes need to be in balanced quantities to function properly that is in part achieved by exchanging intramitochondrial contents through mitochondrial fusion. In addition, mtDNA synthesis requires a balanced supply of nucleotides that is achieved by nucleotide recycling inside the mitochondria and import from the cytosol. Mitochondrial DNA maintenance defects (MDMDs) are a group of diseases caused by pathogenic variants in the nuclear genes involved in mtDNA maintenance resulting in impaired mtDNA synthesis leading to quantitative (mtDNA depletion) and qualitative (multiple mtDNA deletions) defects in mtDNA. Defective mtDNA leads to organ dysfunction due to insufficient mtDNA-encoded protein synthesis, resulting in an inadequate energy production to meet the needs of affected organs. MDMDs are inherited as autosomal recessive or dominant traits, and are associated with a broad phenotypic spectrum ranging from mild adult-onset ophthalmoplegia to severe infantile fatal hepatic failure. To date, pathogenic variants in 20 nuclear genes known to be crucial for mtDNA maintenance have been linked to MDMDs, including genes encoding enzymes of mtDNA replication machinery (POLG, POLG2, TWNK, TFAM, RNASEH1, MGME1, and DNA2), genes encoding proteins that function in maintaining a balanced mitochondrial nucleotide pool (TK2, DGUOK, SUCLG1, SUCLA2, ABAT, RRM2B, TYMP, SLC25A4, AGK, and MPV17), and genes encoding proteins involved in mitochondrial fusion (OPA1, MFN2, and FBXL4).
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Affiliation(s)
- Ayman W El-Hattab
- Division of Clinical Genetics and Metabolic Disorders, Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - William J Craigen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
| | - Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
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Donti TR, Masand R, Scott DA, Craigen WJ, Graham BH. Expanding the phenotypic spectrum of Succinyl-CoA ligase deficiency through functional validation of a new SUCLG1 variant. Mol Genet Metab 2016; 119:68-74. [PMID: 27484306 PMCID: PMC5031536 DOI: 10.1016/j.ymgme.2016.07.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 07/17/2016] [Accepted: 07/18/2016] [Indexed: 11/21/2022]
Abstract
Deficiency of the TCA cycle enzyme Succinyl-CoA Synthetase/Ligase (SCS), due to pathogenic variants in subunits encoded by SUCLG1 and SUCLA2, causes mitochondrial encephalomyopathy, methylmalonic acidemia, and mitochondrial DNA (mtDNA) depletion. In this study, we report an 11year old patient who presented with truncal ataxia, chorea, hypotonia, bilateral sensorineural hearing loss and preserved cognition. Whole exome sequencing identified a heterozygous known pathogenic variant and a heterozygous novel missense variant of uncertain clinical significance (VUS) in SUCLG1. To validate the suspected pathogenicity of the novel VUS, molecular and biochemical analyses were performed using primary skin fibroblasts from the patient. The patient's cells lack the SUCLG1 protein, with significantly reduced levels of SUCLA2 and SUCLG2 protein. This leads to essentially undetectable SCS enzyme activity, mtDNA depletion, and cellular respiration defects. These abnormal phenotypes are rescued upon ectopic expression of wild-type SUCLG1 in the patient's fibroblasts, thus functionally confirming the pathogenic nature of the SUCLG1 VUS identified in this patient and expanding the phenotypic spectrum for SUCLG1 deficiency.
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Affiliation(s)
- Taraka R Donti
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Ruchi Masand
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Daryl A Scott
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - William J Craigen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Brett H Graham
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
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6
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Huang J, Fraser ME. Structural basis for the binding of succinate to succinyl-CoA synthetase. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2016; 72:912-21. [PMID: 27487822 DOI: 10.1107/s2059798316010044] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 06/20/2016] [Indexed: 01/19/2023]
Abstract
Succinyl-CoA synthetase catalyzes the only step in the citric acid cycle that provides substrate-level phosphorylation. Although the binding sites for the substrates CoA, phosphate, and the nucleotides ADP and ATP or GDP and GTP have been identified, the binding site for succinate has not. To determine this binding site, pig GTP-specific succinyl-CoA synthetase was crystallized in the presence of succinate, magnesium ions and CoA, and the structure of the complex was determined by X-ray crystallography to 2.2 Å resolution. Succinate binds in the carboxy-terminal domain of the β-subunit. The succinate-binding site is near both the active-site histidine residue that is phosphorylated in the reaction and the free thiol of CoA. The carboxy-terminal domain rearranges when succinate binds, burying this active site. However, succinate is not in position for transfer of the phosphoryl group from phosphohistidine. Here, it is proposed that when the active-site histidine residue has been phosphorylated by GTP, the phosphohistidine displaces phosphate and triggers the movement of the carboxylate of succinate into position to be phosphorylated. The structure shows why succinyl-CoA synthetase is specific for succinate and does not react appreciably with citrate nor with the other C4-dicarboxylic acids of the citric acid cycle, fumarate and oxaloacetate, but shows some activity with L-malate.
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Affiliation(s)
- Ji Huang
- Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Marie E Fraser
- Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
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Carrozzo R, Verrigni D, Rasmussen M, de Coo R, Amartino H, Bianchi M, Buhas D, Mesli S, Naess K, Born AP, Woldseth B, Prontera P, Batbayli M, Ravn K, Joensen F, Cordelli DM, Santorelli FM, Tulinius M, Darin N, Duno M, Jouvencel P, Burlina A, Stangoni G, Bertini E, Redonnet-Vernhet I, Wibrand F, Dionisi-Vici C, Uusimaa J, Vieira P, Osorio AN, McFarland R, Taylor RW, Holme E, Ostergaard E. Succinate-CoA ligase deficiency due to mutations in SUCLA2 and SUCLG1: phenotype and genotype correlations in 71 patients. J Inherit Metab Dis 2016; 39:243-52. [PMID: 26475597 DOI: 10.1007/s10545-015-9894-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 09/04/2015] [Accepted: 09/08/2015] [Indexed: 11/28/2022]
Abstract
BACKGROUND The encephalomyopathic mtDNA depletion syndrome with methylmalonic aciduria is associated with deficiency of succinate-CoA ligase, caused by mutations in SUCLA2 or SUCLG1. We report here 25 new patients with succinate-CoA ligase deficiency, and review the clinical and molecular findings in these and 46 previously reported patients. PATIENTS AND RESULTS Of the 71 patients, 50 had SUCLA2 mutations and 21 had SUCLG1 mutations. In the newly-reported 20 SUCLA2 patients we found 16 different mutations, of which nine were novel: two large gene deletions, a 1 bp duplication, two 1 bp deletions, a 3 bp insertion, a nonsense mutation and two missense mutations. In the newly-reported SUCLG1 patients, five missense mutations were identified, of which two were novel. The median onset of symptoms was two months for patients with SUCLA2 mutations and at birth for SUCLG1 patients. Median survival was 20 years for SUCLA2 and 20 months for SUCLG1. Notable clinical differences between the two groups were hepatopathy, found in 38% of SUCLG1 cases but not in SUCLA2 cases, and hypertrophic cardiomyopathy which was not reported in SUCLA2 patients, but documented in 14% of cases with SUCLG1 mutations. Long survival, to age 20 years or older, was reported in 12% of SUCLA2 and in 10% of SUCLG1 patients. The most frequent abnormality on neuroimaging was basal ganglia involvement, found in 69% of SUCLA2 and 80% of SUCLG1 patients. Analysis of respiratory chain enzyme activities in muscle generally showed a combined deficiency of complexes I and IV, but normal histological and biochemical findings in muscle did not preclude a diagnosis of succinate-CoA ligase deficiency. In five patients, the urinary excretion of methylmalonic acid was only marginally elevated, whereas elevated plasma methylmalonic acid was consistently found. CONCLUSIONS To our knowledge, this is the largest study of patients with SUCLA2 and SUCLG1 deficiency. The most important findings were a significantly longer survival in patients with SUCLA2 mutations compared to SUCLG1 mutations and a trend towards longer survival in patients with missense mutations compared to loss-of-function mutations. Hypertrophic cardiomyopathy and liver involvement was exclusively found in patients with SUCLG1 mutations, whereas epilepsy was much more frequent in patients with SUCLA2 mutations compared to patients with SUCLG1 mutations. The mutation analysis revealed a number of novel mutations, including a homozygous deletion of the entire SUCLA2 gene, and we found evidence of two founder mutations in the Scandinavian population, in addition to the known SUCLA2 founder mutation in the Faroe Islands.
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Affiliation(s)
- Rosalba Carrozzo
- Unit of Muscular and Neurodegenerative Diseases, Laboratory of Molecular Medicine, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Daniela Verrigni
- Unit of Muscular and Neurodegenerative Diseases, Laboratory of Molecular Medicine, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Magnhild Rasmussen
- Department of Clinical Neurosciences for Children, Oslo University Hospital, Oslo, Norway
| | - Rene de Coo
- Department of Neurology, Erasmus Medical Centre, Rotterdam, The Netherlands
| | - Hernan Amartino
- Servicio de Neurología Infantil, Hospital Universitario Austral, Buenos Aires, Argentina
| | - Marzia Bianchi
- Unit of Muscular and Neurodegenerative Diseases, Laboratory of Molecular Medicine, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Daniela Buhas
- Department of Medical Genetics, Montreal Children's Hospital, Montréal, Quebéc, Canada
| | - Samir Mesli
- Biochemistry, CHU de Bordeaux, Bordeaux, France
| | - Karin Naess
- Department of Laboratory Medicine and Centre for Inherited Metabolic Diseases, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - Alfred Peter Born
- Department of Pediatrics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Berit Woldseth
- Department of Medical Biochemistry, Oslo University Hospital, Oslo, Norway
| | - Paolo Prontera
- Centro di Riferimento Regionale di Genetica Medica, Azienda Ospedaliera di Perugia, CREO, Perugia, Italy
| | - Mustafa Batbayli
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Kirstine Ravn
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Fróði Joensen
- Department of Pediatrics, National Hospital of the Faroe Islands, Tórshavn, Faroe Islands
| | - Duccio M Cordelli
- U.O. Neuropsichiatria Infantile - Franzoni, Policlinico S. Orsola Malpighi, Bologna, Italy
| | | | - Mar Tulinius
- Department of Pediatrics, University of Gothenburg, The Queen Silvia's Children Hospital, Gothenburg, Sweden
| | - Niklas Darin
- Department of Pediatrics, University of Gothenburg, The Queen Silvia's Children Hospital, Gothenburg, Sweden
| | - Morten Duno
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Philippe Jouvencel
- Neonatal and Pediatric Intensive Care Unit, Children's Hospital, Bordeaux, France
| | - Alberto Burlina
- Division of Inherited Metabolic Diseases, Department of Pediatrics, University Hospital of Padua, Padua, Italy
| | - Gabriela Stangoni
- Centro di Riferimento Regionale di Genetica Medica, Azienda Ospedaliera di Perugia, CREO, Perugia, Italy
| | - Enrico Bertini
- Unit of Muscular and Neurodegenerative Diseases, Laboratory of Molecular Medicine, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | | | - Flemming Wibrand
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Carlo Dionisi-Vici
- Division of Metabolism, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Johanna Uusimaa
- Institute of Clinical Medicine/Department of Paediatrics, Finland and Medical Research Center, University of Oulu, Oulu University Hospital, Oulu, Finland
| | - Paivi Vieira
- Institute of Clinical Medicine/Department of Paediatrics, Finland and Medical Research Center, University of Oulu, Oulu University Hospital, Oulu, Finland
| | - Andrés Nascimento Osorio
- Unidad de patología neuromuscular, Servicio de Neurología, Hospital Sant Joan de Déu. Hospital Sant Joan de Déu and CIBERER, ISCIII, Barcelona, Spain
| | - Robert McFarland
- Wellcome Trust Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Elisabeth Holme
- Department of Clinical Chemistry, Institute of Biomedicine, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Elsebet Ostergaard
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark.
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Liu Y, Li X, Wang Q, Ding Y, Song J, Yang Y. Five novel SUCLG1 mutations in three Chinese patients with succinate-CoA ligase deficiency noticed by mild methylmalonic aciduria. Brain Dev 2016; 38:61-7. [PMID: 26028457 DOI: 10.1016/j.braindev.2015.05.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2014] [Revised: 05/02/2015] [Accepted: 05/07/2015] [Indexed: 01/28/2023]
Abstract
OBJECTIVE Methylmalonic aciduria is the most common organic aciduria in mainland China. Succinate-CoA ligase deficiency causes encephalomyopathy with mitochondrial DNA depletion and mild methylmalonic aciduria. Patients usually present with severe encephalomyopathy, infantile lactic acidosis, which can be fatal, and mild methylmalonic aciduria. PATIENTS AND METHODS Three Chinese patients (two boys and one girl) were hospitalized because of severe encephalomyopathy between 7 and 9 months. They presented with severe psychomotor retardation, hypotonia, dystonia, athetoid movements, seizures, feeding problems and failure to thrive. Mild elevated urine methylmalonic acid and blood propionylcarnitine indicated methylmalonic aciduria. Gene capture and high-throughput genomic sequencing was carried out. RESULTS Five novel mutations in SUCLG1 were identified in these patients: c.550G>A (p.G184S) in exon 5, c.751C>T (p.G251S) in exon 7, c.809A>C (p.L270W) in exon 7, c.961C>G (p.A321P) in exon 8 and c.826-2A>G (Splicing) in exon 9. Significant depletion of mtDNA was not observed in the peripheral leukocytes of the three patients in spite of mild decreasing of mitochondrial respiratory chain complex I in two patients and complex V in one patient. After treatment with cobalamin, calcium folinate, L-carnitine, vitamin B1, C, and coenzyme Q10, and nutrition intervention, the patients improved. CONCLUSIONS Succinate-CoA ligase deficiency due to SUCLG1 mutations is a rare cause of methylmalonic aciduria. Biochemical and gene studies are keys for the differential diagnoses. Three Chinese patients with mild methylmalonic aciduria were genetically diagnosed using high-throughput genomic sequencing. Five novel pathogenic mutations in SUCLG1 were identified.
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Affiliation(s)
- Yupeng Liu
- Peking University First Hospital, Beijing 100034, China
| | - Xiyuan Li
- Peking University First Hospital, Beijing 100034, China
| | - Qiao Wang
- Peking University First Hospital, Beijing 100034, China
| | - Yuan Ding
- Peking University First Hospital, Beijing 100034, China
| | - Jinqing Song
- Peking University First Hospital, Beijing 100034, China
| | - Yanling Yang
- Peking University First Hospital, Beijing 100034, China.
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9
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Landsverk ML, Zhang VW, Wong LJC, Andersson HC. A SUCLG1 mutation in a patient with mitochondrial DNA depletion and congenital anomalies. Mol Genet Metab Rep 2014; 1:451-454. [PMID: 27896121 PMCID: PMC5121340 DOI: 10.1016/j.ymgmr.2014.09.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 09/25/2014] [Accepted: 09/25/2014] [Indexed: 02/05/2023] Open
Abstract
Defects in two subunits of succinate-CoA ligase encoded by the genes SUCLG1 and SUCLA2 have been identified in mitochondrial DNA (mtDNA) depletion syndromes. Patients generally present with encephalomyopathy and mild methylmalonic acidemia (MMA), however mutations in SUCLG1 normally appear to result in a more severe clinical phenotype. In this report, we describe a patient with fatal infantile lactic acidosis and multiple congenital anomalies (MCAs) including renal and cardiac defects. Molecular studies showed a defective electron transport chain (ETC), mtDNA depletion, and a novel homozygous mutation in the SUCLG1 gene. Although our patient's clinical biochemical phenotype is consistent with a SUCLG1 mutation, it is unclear whether the MCAs observed in our patient are a result of the SUCLG1 mutation or alterations in a second gene. An increasing number of reports have described MCAs associated with mitochondrial disorders and SUCLG1 specifically. Additional studies such as whole exome sequencing will further define whether additional genes are responsible for the observed MCAs.
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Affiliation(s)
- Megan L Landsverk
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA; Sanford Health, Sioux Falls, SD, USA
| | - Victor Wei Zhang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Lee-Jun C Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Hans C Andersson
- Hayward Genetics Center, Tulane University, New Orleans, LA, USA; Department of Pediatrics, Tulane University, New Orleans, LA, USA
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10
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Abstract
Most mitochondrial cytopathies in infants are caused by mutations in nuclear genes encoding proteins targeted to the mitochondria rather than by primary mutations in the mitochondrial DNA. Over the past few years, the awareness of the number of disease-causing mutations in different nuclear genes has grown exponentially. These genes encode the various subunits of each respiratory chain complex, the ancillary proteins involved in the assembly of these subunits, proteins involved in mitochondrial DNA replication and maintenance, proteins involved in mitochondrial protein synthesis, and proteins involved in mitochondrial dynamics. This increased awareness has added a challenging dimension to the current diagnostic workup of mitochondrial cytopathies. The advent of new technologies such as next-generation sequencing should facilitate the resolution of this dilemma.
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Affiliation(s)
- Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
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11
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Sakamoto O, Ohura T, Murayama K, Ohtake A, Harashima H, Abukawa D, Takeyama J, Haginoya K, Miyabayashi S, Kure S. Neonatal lactic acidosis with methylmalonic aciduria due to novel mutations in the SUCLG1 gene. Pediatr Int 2011; 53:921-5. [PMID: 21639866 DOI: 10.1111/j.1442-200x.2011.03412.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND Succinyl-coenzyme A ligase (SUCL) is a mitochondrial enzyme that catalyses the reversible conversion of succinyl-coenzyme A to succinate. SUCL consists of an α subunit, encoded by SUCLG1, and a β subunit, encoded by either SUCLA2 or SUCLG2. Recently, mutations in SUCLG1 or SUCLA2 have been identified in patients with infantile lactic acidosis showing elevated urinary excretion of methylmalonate, mitochondrial respiratory chain (MRC) deficiency, and mitochondrial DNA depletion. METHODS Case description of a Japanese female patient who manifested a neonatal-onset lactic acidosis with urinary excretion of methylmalonic acid. Enzymatic analyses (MRC enzyme assay and Western blotting) and direct sequencing analysis of SUCLA2 and SUCLG1 were performed. RESULTS MRC enzyme assay and Western blotting showed that MRC complex I was deficient. SUCLG1 mutation analysis showed that the patient was a compound heterozygote for disease-causing mutations (p.M14T and p.S200F). CONCLUSION For patients showing neonatal lactic acidosis and prolonged mild methylmalonic aciduria, MRC activities and mutations of SUCLG1 or SUCLA2 should be screened for.
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Affiliation(s)
- Osamu Sakamoto
- Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan.
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Hanchard NA, Shchelochkov OA, Roy A, Wiszniewska J, Wang J, Popek EJ, Karpen S, Wong LJC, Scaglia F. Deoxyguanosine kinase deficiency presenting as neonatal hemochromatosis. Mol Genet Metab 2011; 103:262-7. [PMID: 21478040 DOI: 10.1016/j.ymgme.2011.03.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2011] [Revised: 03/07/2011] [Accepted: 03/08/2011] [Indexed: 11/24/2022]
Abstract
Mutations in DGUOK result in mitochondrial DNA (mtDNA) depletion and may present as neonatal liver failure. Neonatal hemochromatosis (NH(1)) is a liver disorder of uncertain and varied etiology characterized by hepatic and non-reticuloendothelial siderosis. To date, deoxyguanosine kinase (dGK(2)) deficiency has not been formally recognized in cases of NH. We report an African American female neonate with clinical and autopsy findings consistent with NH, and mtDNA depletion due to a homozygous mutation in DGUOK. This report highlights hepatocerebral mtDNA depletion in the differential of neonatal tyrosinemia, advocates considering dGK deficiency in cases of NH, and posits mitochondrial oxidative processes in the pathogenesis of NH.
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Affiliation(s)
- Neil A Hanchard
- Department of Human and Molecular Genetics, Baylor College of Medicine, Houston, TX, USA
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