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Barbosa-Gouveia S, González-Vioque E, Hermida Á, Suarez MU, Martínez-González MJ, Borges F, Wintjes L, Kappen A, Rodenburg R, Couce ML. Identification of a Novel Variant in EARS2 Associated with a Severe Clinical Phenotype Expands the Clinical Spectrum of LTBL. Genes (Basel) 2020; 11:E1028. [PMID: 32887222 DOI: 10.3390/genes11091028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 08/21/2020] [Accepted: 08/31/2020] [Indexed: 12/30/2022] Open
Abstract
The EARS2 nuclear gene encodes mitochondrial glutamyl-tRNA synthetase, a member of the class I family of aminoacyl-tRNA synthetases (aaRSs) that plays a crucial role in mitochondrial protein biosynthesis by catalyzing the charging of glutamate to mitochondrial tRNA(Glu). Pathogenic EARS2 variants have been associated with a rare mitochondrial disorder known as leukoencephalopathy with thalamus and brainstem involvement and high lactate (LTBL). The targeted sequencing of 150 nuclear genes encoding respiratory chain complex subunits and proteins implicated in the oxidative phosphorylation (OXPHOS) function was performed. The oxygen consumption rate (OCR), and the extracellular acidification rate (ECAR), were measured. The enzymatic activities of Complexes I-V were analyzed spectrophotometrically. We describe a patient carrying two heterozygous EARS2 variants, c.376C>T (p.Gln126*) and c.670G>A (p.Gly224Ser), with infantile-onset disease and a severe clinical presentation. We demonstrate a clear defect in mitochondrial function in the patient’s fibroblasts, suggesting the molecular mechanism underlying the pathogenicity of these EARS2 variants. Experimental validation using patient-derived fibroblasts allowed an accurate characterization of the disease-causing variants, and by comparing our patient’s clinical presentation with that of previously reported cases, new clinical and radiological features of LTBL were identified, expanding the clinical spectrum of this disease.
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Oliveira R, Sommerville EW, Thompson K, Nunes J, Pyle A, Grazina M, Chinnery PF, Diogo L, Garcia P, Taylor RW. Lethal Neonatal LTBL Associated with Biallelic EARS2 Variants: Case Report and Review of the Reported Neuroradiological Features. JIMD Rep 2016; 33:61-68. [PMID: 27571996 DOI: 10.1007/8904_2016_581] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 08/04/2016] [Accepted: 08/09/2016] [Indexed: 02/06/2023] Open
Abstract
Mitochondrial translation defects are important causes of early onset mitochondrial disease. Although the biochemical (combined respiratory chain deficiency) signature and neuroimaging are usually distinctive, they are not diagnostic as the genetic origin of mitochondrial translation defects is heterogeneous. We report a female child, born at term to non-consanguineous parents, who exhibited global hypotonia, failure to thrive, persistent and progressive hyperlactacidaemia with lactic acidosis, liver dysfunction and encephalopathy and died at the age of 5 months. Brain MRI revealed hypogenesis of the corpus callosum, T2 signal abnormalities in the medulla oblongata, pons, midbrain, thalami, cerebellar white matter, and a lactate peak on MRS. Muscle histochemistry showed cytochrome c oxidase (COX)-deficient and ragged-red fibres, while muscle biochemical studies showed decreased activities of mitochondrial respiratory chain complexes I and IV. Whole exome sequencing (WES) identified biallelic EARS2 (NM_001083614) variants, a previously reported start-loss (c.1>G, p.Met1?) variant and a novel missense (c.184A>T, p.Ile62Phe) variant. Patient fibroblasts and muscle homogenate displayed markedly decreased EARS2 protein levels, although decreased steady-state levels of complex I (NDUFB8) and complex IV (MT-CO1 and MT-CO2) subunits were only observed in muscle. Pathogenic variants in EARS2, encoding mitochondrial glutamyl-tRNA synthetase (mtGluR), are associated with Leukoencephalopathy involving the Thalamus and Brainstem with high Lactate (LTBL), a mitochondrial disorder characterised by a distinctive brain MRI pattern and a biphasic clinical course. We further outline the unique phenotypic spectrum of LTBL and review the neuroradiological features reported in all patients documented in the literature.
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Affiliation(s)
- Renata Oliveira
- Human Genetics Department, Centro Hospitalar de São João, Alameda Prof. Hernâni Monteiro, 4200, Porto, Portugal.
| | - Ewen W Sommerville
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Kyle Thompson
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Joana Nunes
- Imaging Department, Centro Hospitalar Vila Nova de Gaia/Espinho, Vila Nova de Gaia, Portugal
| | - Angela Pyle
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Manuela Grazina
- CNC - Center for Neuroscience and Cell Biology, Laboratory of Biochemical Genetics, University of Coimbra, Coimbra, Portugal
- Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Patrick F Chinnery
- Department of Clinical Neurosciences, School of Clinical Medicine, University of Cambridge, Cambridge, UK
- MRC Mitochondrial Biology Unit, Cambridge Biomedical Campus, Cambridge, UK
| | - Luísa Diogo
- Metabolic Unit - Child Development Center, Hospital Pediátrico, Centro Hospitalar e Universitário de Coimbra (CHUC), Coimbra, Portugal
| | - Paula Garcia
- Metabolic Unit - Child Development Center, Hospital Pediátrico, Centro Hospitalar e Universitário de Coimbra (CHUC), Coimbra, Portugal
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
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Danhauser K, Haack TB, Alhaddad B, Melcher M, Seibt A, Strom TM, Meitinger T, Klee D, Mayatepek E, Prokisch H, Distelmaier F. EARS2 mutations cause fatal neonatal lactic acidosis, recurrent hypoglycemia and agenesis of corpus callosum. Metab Brain Dis 2016; 31:717-21. [PMID: 26780086 DOI: 10.1007/s11011-016-9793-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 01/08/2016] [Indexed: 11/25/2022]
Abstract
Mitochondrial aminoacyl tRNA synthetases are essential for organelle protein synthesis. Genetic defects affecting the function of these enzymes may cause pediatric mitochondrial disease. Here, we report on a child with fatal neonatal lactic acidosis and recurrent hypoglycemia caused by mutations in EARS2, encoding mitochondrial glutamyl-tRNA synthetase 2. Brain ultrasound revealed agenesis of corpus callosum. Studies on patient-derived skin fibroblasts showed severely decreased EARS2 protein levels, elevated reactive oxygen species (ROS) production, and altered mitochondrial morphology. Our report further illustrates the clinical spectrum of the severe neonatal-onset form of EARS2 mutations. Moreover, in this case the live-cell parameters appeared to be more sensitive to mitochondrial dysfunction compared to standard diagnostics, which indicates the potential relevance of fibroblast studies in children with mitochondrial diseases.
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Affiliation(s)
- Katharina Danhauser
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital, Heinrich-Heine-University Düsseldorf, Moorenstr 5, 40225, Düsseldorf, Germany
| | - Tobias B Haack
- Institute of Human Genetics, Technische Universität München, Trogerstr 32, 81675, Munich, Germany
- Institute of Human Genetics, Helmholtz Zentrum München, Ingolstädter Landstr 1, 85764, Neuherberg, Germany
| | - Bader Alhaddad
- Institute of Human Genetics, Technische Universität München, Trogerstr 32, 81675, Munich, Germany
- Institute of Human Genetics, Helmholtz Zentrum München, Ingolstädter Landstr 1, 85764, Neuherberg, Germany
| | - Marlen Melcher
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital, Heinrich-Heine-University Düsseldorf, Moorenstr 5, 40225, Düsseldorf, Germany
| | - Annette Seibt
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital, Heinrich-Heine-University Düsseldorf, Moorenstr 5, 40225, Düsseldorf, Germany
| | - Tim M Strom
- Institute of Human Genetics, Technische Universität München, Trogerstr 32, 81675, Munich, Germany
- Institute of Human Genetics, Helmholtz Zentrum München, Ingolstädter Landstr 1, 85764, Neuherberg, Germany
| | - Thomas Meitinger
- Institute of Human Genetics, Technische Universität München, Trogerstr 32, 81675, Munich, Germany
- Institute of Human Genetics, Helmholtz Zentrum München, Ingolstädter Landstr 1, 85764, Neuherberg, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Dirk Klee
- Medical Faculty, Department of Diagnostic and Interventional Radiology, University Düsseldorf, Moorenstr 5, 40225, Düsseldorf, Germany
| | - Ertan Mayatepek
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital, Heinrich-Heine-University Düsseldorf, Moorenstr 5, 40225, Düsseldorf, Germany
| | - Holger Prokisch
- Institute of Human Genetics, Technische Universität München, Trogerstr 32, 81675, Munich, Germany.
- Institute of Human Genetics, Helmholtz Zentrum München, Ingolstädter Landstr 1, 85764, Neuherberg, Germany.
| | - Felix Distelmaier
- Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital, Heinrich-Heine-University Düsseldorf, Moorenstr 5, 40225, Düsseldorf, Germany.
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Şahin S, Cansu A, Kalay E, Dinçer T, Kul S, Çakır İM, Kamaşak T, Budak GY. Leukoencephalopathy with thalamus and brainstem involvement and high lactate caused by novel mutations in the EARS2 gene in two siblings. J Neurol Sci 2016; 365:54-8. [PMID: 27206875 DOI: 10.1016/j.jns.2016.04.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 03/29/2016] [Accepted: 04/06/2016] [Indexed: 11/18/2022]
Abstract
Leukoencephalopathy with thalamus and brainstem involvement, and high lactate (LTBL) is a recently identified disease related to mutations in the EARS2 gene encoding glutamyl-tRNA synthetase. We report clinical and radiological findings for two siblings with new pathogenic mutations in the EARS2 gene. Both patients showed symptoms of mild-type disease, but there were clinical differences between the two siblings. While the older brother had hypotonia and delayed developmental milestones, the younger brother had seizures and spasticity in the lower extremities. Brain magnetic resonance imaging (MRI) findings were quite similar for the two siblings. MRI findings were specific to LTBL. MRI lesions of the older sibling had regressed over time. Clinical and radiological improvement, as in the previously reported patients with LTBL, may be an important clue for diagnosis.
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Affiliation(s)
- Sevim Şahin
- Department of Pediatric Neurology, Karadeniz Technical University Faculty of Medicine, Trabzon, Turkey.
| | - Ali Cansu
- Department of Pediatric Neurology, Karadeniz Technical University Faculty of Medicine, Trabzon, Turkey
| | - Ersan Kalay
- Department of Medical Biology, Karadeniz Technical University Faculty of Medicine, Trabzon, Turkey
| | - Tuba Dinçer
- Department of Medical Biology, Karadeniz Technical University Faculty of Medicine, Trabzon, Turkey
| | - Sibel Kul
- Department of Radiology, Karadeniz Technical University Faculty of Medicine, Trabzon, Turkey
| | - İsmet Miraç Çakır
- Department of Radiology, Karadeniz Technical University Faculty of Medicine, Trabzon, Turkey
| | - Tülay Kamaşak
- Department of Pediatric Neurology, Karadeniz Technical University Faculty of Medicine, Trabzon, Turkey
| | - Gülden Yorgancıoğlu Budak
- Department of Medical Biology, Karadeniz Technical University Health Science Institute, Trabzon, Turkey
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