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Yahya V, Dilena R, Del Bo R, Magni M, Biella F, Salani S, Fortunato F, Scola E, Di Fonzo A, Monfrini E. Soft cerebellar signs unveil RARS2-related epilepsy. Epileptic Disord 2024. [PMID: 38733322 DOI: 10.1002/epd2.20237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 03/30/2024] [Accepted: 04/22/2024] [Indexed: 05/13/2024]
Affiliation(s)
- Vidal Yahya
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Robertino Dilena
- Neurophysiopathology Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Roberto Del Bo
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Manuela Magni
- Neurology Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Fabio Biella
- Neurology Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Sabrina Salani
- Neurology Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Francesco Fortunato
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Elisa Scola
- Neuroradiology Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Alessio Di Fonzo
- Neurology Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Edoardo Monfrini
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
- Neurology Unit, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
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2
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Nicolle R, Altin N, Siquier-Pernet K, Salignac S, Blanc P, Munnich A, Bole-Feysot C, Malan V, Caron B, Nitschké P, Desguerre I, Boddaert N, Rio M, Rausell A, Cantagrel V. A non-coding variant in the Kozak sequence of RARS2 strongly decreases protein levels and causes pontocerebellar hypoplasia. BMC Med Genomics 2023; 16:143. [PMID: 37344844 DOI: 10.1186/s12920-023-01582-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 06/16/2023] [Indexed: 06/23/2023] Open
Abstract
Bi-allelic variants in the mitochondrial arginyl-transfer RNA synthetase (RARS2) gene have been involved in early-onset encephalopathies classified as pontocerebellar hypoplasia (PCH) type 6 and in epileptic encephalopathy. A variant (NM_020320.3:c.-2A > G) in the promoter and 5'UTR of the RARS2 gene has been previously identified in a family with PCH. Only a mild impact of this variant on the mRNA level has been detected. As RARS2 is non-dosage-sensitive, this observation is not conclusive in regard of the pathogenicity of the variant.We report and describe here a new patient with the same variant in the RARS2 gene, at the homozygous state. This patient presents with a clinical phenotype consistent with PCH6 although in the absence of lactic acidosis. In agreement with the previous study, we measured RARS2 mRNA levels in patient's fibroblasts and detected a partially preserved gene expression compared to control. Importantly, this variant is located in the Kozak sequence that controls translation initiation. Therefore, we investigated the impact on protein translation using a bioinformatic approach and western blotting. We show here that this variant, additionally to its effect on the transcription, also disrupts the consensus Kozak sequence, and has a major impact on RARS2 protein translation. Through the identification of this additional case and the characterization of the molecular consequences, we clarified the involvement of this Kozak variant in PCH and on protein synthesis. This work also points to the current limitation in the pathogenicity prediction of variants located in the translation initiation region.
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Affiliation(s)
- Romain Nicolle
- Developmental Brain Disorders Laboratory, Université Paris Cité, INSERM UMR1163, Imagine Institute, 75015, Paris, France
- Clinical Bioinformatics Laboratory, Université Paris Cité, INSERM UMR 1163, Imagine Institute, Paris, 75015, France
| | - Nami Altin
- Developmental Brain Disorders Laboratory, Université Paris Cité, INSERM UMR1163, Imagine Institute, 75015, Paris, France
| | - Karine Siquier-Pernet
- Developmental Brain Disorders Laboratory, Université Paris Cité, INSERM UMR1163, Imagine Institute, 75015, Paris, France
| | - Sherlina Salignac
- Developmental Brain Disorders Laboratory, Université Paris Cité, INSERM UMR1163, Imagine Institute, 75015, Paris, France
| | - Pierre Blanc
- Developmental Brain Disorders Laboratory, Université Paris Cité, INSERM UMR1163, Imagine Institute, 75015, Paris, France
- Fédération de Génétique et Médecine Génomique, Service de Médecine Génomique des Maladies Rares, AP-HP, Necker Hospital for Sick Children, Paris, 75015, France
| | - Arnold Munnich
- Fédération de Génétique et Médecine Génomique, Service de Médecine Génomique des Maladies Rares, AP-HP, Necker Hospital for Sick Children, Paris, 75015, France
| | - Christine Bole-Feysot
- Genomics Platform, Université Paris Cité, INSERM UMR 1163, Imagine Institute, Paris, 75015, France
| | - Valérie Malan
- Developmental Brain Disorders Laboratory, Université Paris Cité, INSERM UMR1163, Imagine Institute, 75015, Paris, France
- Fédération de Génétique et Médecine Génomique, Service de Médecine Génomique des Maladies Rares, AP-HP, Necker Hospital for Sick Children, Paris, 75015, France
| | - Barthélémy Caron
- Clinical Bioinformatics Laboratory, Université Paris Cité, INSERM UMR 1163, Imagine Institute, Paris, 75015, France
| | - Patrick Nitschké
- Bioinformatics Core Facility, Université Paris Cité, INSERM UMR 1163, Imagine Institute, 75015, Paris, France
| | - Isabelle Desguerre
- Département de Neurologie Pédiatrique, AP-HP, Necker Hospital for Sick Children, 75015, Paris, France
| | - Nathalie Boddaert
- Département de Radiologie Pédiatrique, AP-HP, Necker Hospital for Sick Children and Université Paris Cité, INSERM UMR 1163 and INSERM U1299, Imagine Institute, Paris, 75015, France
| | - Marlène Rio
- Developmental Brain Disorders Laboratory, Université Paris Cité, INSERM UMR1163, Imagine Institute, 75015, Paris, France
- Fédération de Génétique et Médecine Génomique, Service de Médecine Génomique des Maladies Rares, AP-HP, Necker Hospital for Sick Children, Paris, 75015, France
| | - Antonio Rausell
- Clinical Bioinformatics Laboratory, Université Paris Cité, INSERM UMR 1163, Imagine Institute, Paris, 75015, France
- Fédération de Génétique et Médecine Génomique, Service de Médecine Génomique des Maladies Rares, AP-HP, Necker Hospital for Sick Children, Paris, 75015, France
| | - Vincent Cantagrel
- Developmental Brain Disorders Laboratory, Université Paris Cité, INSERM UMR1163, Imagine Institute, 75015, Paris, France.
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3
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Sekulovski S, Trowitzsch S. What connects splicing of transfer RNA precursor molecules with pontocerebellar hypoplasia? Bioessays 2023; 45:e2200130. [PMID: 36517085 DOI: 10.1002/bies.202200130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 11/28/2022] [Accepted: 11/30/2022] [Indexed: 01/19/2023]
Abstract
Transfer RNAs (tRNAs) represent the most abundant class of RNA molecules in the cell and are key players during protein synthesis and cellular homeostasis. Aberrations in the extensive tRNA biogenesis pathways lead to severe neurological disorders in humans. Mutations in the tRNA splicing endonuclease (TSEN) and its associated RNA kinase cleavage factor polyribonucleotide kinase subunit 1 (CLP1) cause pontocerebellar hypoplasia (PCH), a heterogeneous group of neurodegenerative disorders, that manifest as underdevelopment of specific brain regions typically accompanied by microcephaly, profound motor impairments, and child mortality. Recently, we demonstrated that mutations leading to specific PCH subtypes destabilize TSEN in vitro and cause imbalances of immature to mature tRNA ratios in patient-derived cells. However, how tRNA processing defects translate to disease on a systems level has not been understood. Recent findings suggested that other cellular processes may be affected by mutations in TSEN/CLP1 and obscure the molecular mechanisms of PCH emergence. Here, we review PCH disease models linked to the TSEN/CLP1 machinery and discuss future directions to study neuropathogenesis.
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Affiliation(s)
- Samoil Sekulovski
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Frankfurt/Main, Germany
| | - Simon Trowitzsch
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Frankfurt/Main, Germany
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Koç Yekedüz M, Şen Akova B, Köse E, Doğulu N, Öncül Ü, Okulu E, Arsan S, Fitöz S, Eminoğlu FT. Early neuroimaging findings of infants diagnosed with inherited metabolic disorders in neonatal period: A case-control study. Clin Neurol Neurosurg 2022; 222:107474. [DOI: 10.1016/j.clineuro.2022.107474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 06/26/2022] [Accepted: 09/27/2022] [Indexed: 11/16/2022]
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Abstract
The human brain consumes five orders of magnitude more energy than the sun by unit of mass and time. This staggering bioenergetic cost serves mostly synaptic transmission and actin cytoskeleton dynamics. The peak of both brain bioenergetic demands and the age of onset for neurodevelopmental disorders is approximately 5 years of age. This correlation suggests that defects in the machinery that provides cellular energy would be causative and/or consequence of neurodevelopmental disorders. We explore this hypothesis from the perspective of the machinery required for the synthesis of the electron transport chain, an ATP-producing and NADH-consuming enzymatic cascade. The electron transport chain is constituted by nuclear- and mitochondrial-genome-encoded subunits. These subunits are synthesized by the 80S and the 55S ribosomes, which are segregated to the cytoplasm and the mitochondrial matrix, correspondingly. Mitochondrial protein synthesis by the 55S ribosome is the rate-limiting step in the synthesis of electron transport chain components, suggesting that mitochondrial protein synthesis is a bottleneck for tissues with high bionergetic demands. We discuss genetic defects in the human nuclear and mitochondrial genomes that affect these protein synthesis machineries and cause a phenotypic spectrum spanning autism spectrum disorders to neurodegeneration during neurodevelopment. We propose that dysregulated mitochondrial protein synthesis is a chief, yet understudied, causative mechanism of neurodevelopmental and behavioral disorders.
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Zhang Y, Yu Y, Zhao X, Xu Y, Chen L, Li N, Yao R, Wang J, Yu T. Novel RARS2 Variants: Updating the Diagnosis and Pathogenesis of Pontocerebellar Hypoplasia Type 6. Pediatr Neurol 2022; 131:30-41. [PMID: 35468344 DOI: 10.1016/j.pediatrneurol.2022.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 03/13/2022] [Accepted: 04/06/2022] [Indexed: 12/30/2022]
Abstract
BACKGROUND Pontocerebellar hypoplasia type 6 (PCH6) is an early-onset encephalopathy with/without mitochondrial respiratory complex defects caused by recessive mutations in mitochondrial arginyl-tRNA synthetase (RARS2). Highly heterogeneous clinical phenotypes and numerous missense variations of uncertain significance make diagnosis difficult. Pathogenesis of PCH6 remains unclear. METHODS Facial characteristics of patients were assessed. Genetic tests were performed. Structure prediction was based on the template from AlphaFold Protein Structure Database. Expression of mutant RARS2 was tested in HEK293T cells. Patient-derived induced pluripotent stem cells (iPSCs) were detected for human mitochondrial tRNAArg (hmtRNAArg) steady-state level, mitochondrial respiratory complex (MRC) activity, oxygen consumption rate (OCR), extracellular acidification rate (ECAR), mitochondrial membrane potential (MMP), reactive oxygen species (ROS) abundance, and apoptosis level. RESULTS The three pedigrees were diagnosed as PCH6 caused by compound heterozygous RARS2 variations. Five RARS2 variants were identified: c.3G>C(p.M1?), c.685C>T(p.R229∗), c.1060T>A(p.F354I), c.1210A>G(p.M404V), and c.1369G>A(p.G457R). RARS2 c.3G>C disrupted protein expression. RARS2 c.685C>T created a truncated protein lacking complete catalytic core and anticodon-binding domain. RARS2 c.1060T>A and c.1369G>A were predicted to cause structural abnormality. The hmtRNAArg steady-state abundance in a patient's iPSCs was unaffected. Mitochondrial energy metabolism was normal, including MRC activity, OCR, ECAR, and MMP, while mitochondria-related cellular characteristics, including ROS (P < 0.001) and apoptosis levels (P < 0.001), increased. CONCLUSIONS This study reports five RARS2 variations among which c.3G>C and c.1060T>A are novel. Summarized facial features of PCH6 patients will facilitate diagnosis. Defective mitochondrial energy metabolism may not be key points, but mitochondria-related abnormal cellular physiology, including apoptosis, may be an underlying pathogenesis.
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Affiliation(s)
- Yi Zhang
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Yafen Yu
- Department of Children's Health Prevention, Tianshui First People's Hospital, Gansu, People's Republic of China
| | - Xiangyue Zhao
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Yufei Xu
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Lina Chen
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Niu Li
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Ruen Yao
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Jian Wang
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
| | - Tingting Yu
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
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7
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Chuan Z, Ruikun C, Qian L, Shiyue M, Shengju H, Yong Y, Haibo L, Neng X, Yong Z, Huiqin X, Weijia W, Ling H, Bingbo Z, Zhang Q, Yan W, Zongfu C, Xu M. Genetic and Phenotype Analysis of a Chinese Cohort of Infants and Children With Epilepsy. Front Genet 2022; 13:869210. [PMID: 35571021 PMCID: PMC9091957 DOI: 10.3389/fgene.2022.869210] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 04/12/2022] [Indexed: 11/13/2022] Open
Abstract
Background: Epilepsy in childhood is a common and diverse neurological disorder. We conducted a genetic and phenotype analysis of a Chinese cohort of infants and children with epilepsy. Methods: We conducted a pedigree analysis of 260 Chinese patients with epilepsy onset during infancy or childhood by whole exome sequencing (WES). Results: Of the 260 probands analyzed, a genetic diagnosis was established in 135 patients. One-hundred eighty-eight phenotypes were detected in those 135 positive/likely positive patients, 106 patients had more than two phenotypes, and 67 patients had more than three phenotypes. A total of 142 variants of 81 genes were detected among the positive/likely positive patients. Among these 142 variants, of which 87 of 66 genes were novel. Conclusion: Our findings extend the variant spectrum of genes related to epilepsy. Our results will be useful for genetic testing and counseling for patients with epilepsy.
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Affiliation(s)
- Zhang Chuan
- National Research Institute for Family Planning, National Human Genetic Resources Center, Beijing, China
- Gansu Province Medical Genetics Center, Gansu Provincial Clinical Research Center for Birth Defects and Rare Diseases, Gansu Provincial Maternity and Child-Care Hospital, Lanzhou, China
- Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Cai Ruikun
- National Research Institute for Family Planning, National Human Genetic Resources Center, Beijing, China
| | - Li Qian
- National Research Institute for Family Planning, National Human Genetic Resources Center, Beijing, China
| | - Mei Shiyue
- Department of Intensive Care Unit, Henan Provincial Key Laboratory of Children’s Genetics and Metabolic Diseases, Children’s Hospital Affiliated to Zhengzhou University, Zhengzhou, China
| | - Hao Shengju
- Gansu Province Medical Genetics Center, Gansu Provincial Clinical Research Center for Birth Defects and Rare Diseases, Gansu Provincial Maternity and Child-Care Hospital, Lanzhou, China
| | - Yuan Yong
- Zhongshan City People’s Hospital, Affiliated Zhongshan Hospital of Sun Yat-Sen University, Guangzhou, China
| | - Li Haibo
- The Central Laboratory of Birth Defects Prevention and Control, Ningbo Women and Children’s Hospital, Ningbo, China
| | - Xiao Neng
- Department of Pediatric Neurology, Chenzhou First People’s Hospital, Chenzhou, China
| | - Zhao Yong
- Foshan Women and Children Hospital, Foshan, China
| | - Xue Huiqin
- Children’s Hospital of Shanxi, Women Health Center of Shanxi, Taiyuan, China
| | - Wang Weijia
- Zhongshan City People’s Hospital, Affiliated Zhongshan Hospital of Sun Yat-Sen University, Guangzhou, China
| | - Hui Ling
- Gansu Province Medical Genetics Center, Gansu Provincial Clinical Research Center for Birth Defects and Rare Diseases, Gansu Provincial Maternity and Child-Care Hospital, Lanzhou, China
| | - Zhou Bingbo
- Gansu Province Medical Genetics Center, Gansu Provincial Clinical Research Center for Birth Defects and Rare Diseases, Gansu Provincial Maternity and Child-Care Hospital, Lanzhou, China
| | - Qinghua Zhang
- Gansu Province Medical Genetics Center, Gansu Provincial Clinical Research Center for Birth Defects and Rare Diseases, Gansu Provincial Maternity and Child-Care Hospital, Lanzhou, China
| | - Wang Yan
- Gansu Province Medical Genetics Center, Gansu Provincial Clinical Research Center for Birth Defects and Rare Diseases, Gansu Provincial Maternity and Child-Care Hospital, Lanzhou, China
| | - Cao Zongfu
- National Research Institute for Family Planning, National Human Genetic Resources Center, Beijing, China
- Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
- *Correspondence: Cao Zongfu, ; Ma Xu,
| | - Ma Xu
- National Research Institute for Family Planning, National Human Genetic Resources Center, Beijing, China
- Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
- *Correspondence: Cao Zongfu, ; Ma Xu,
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8
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Sevinç S, İnci A, Ezgü FS, Eminoğlu FT. A Patient with a Novel RARS2 Variant Exhibiting Liver Involvement as a New Clinical Feature and Review of the Literature. Mol Syndromol 2022; 13:226-234. [DOI: 10.1159/000519604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 09/13/2021] [Indexed: 11/19/2022] Open
Abstract
Pontocerebellar hypoplasia (PCH) is a heterogeneous neurodevelopmental disorder that is characterized by decreased brainstem and cerebellum volume. Pontocerebellar hypoplasia type 6 (PCH6) is a mitochondrial disease associated with autosomal recessive inheritance that results from mutations in the <i>RARS2</i> gene. In this case report, we describe a new clinical presentation with a novel <i>RARS2</i> pathogenic variant. We report here on 2 siblings who presented with neonatal lactic acidosis, microcephaly, growth retardation, persistent seizures, and cholestasis with a previously undefined <i>RARS2</i> pathogenic variant. In our literature review, we evaluated the clinical features and pathogenic variants of 34 patients reported in 16 publications since the initial identification of <i>RARS2</i> pathogenic variants in PCH6 in 2007. Both siblings were detected with c.1564G>A (p.Val522Ile), a novel homozygous pathogenic variant of the <i>RARS2</i> gene. Imaging revealed advanced cerebral atrophy and cerebellar hypoplasia, while the basal ganglia and pons were preserved. At follow-up, the elevations in liver function test results and cholestasis had regressed while the LDH and GGT elevations persisted. Both siblings showed microcephaly on follow-up and started to suffer seizures. Severe developmental delay and nutritional problems were observed, and both died in infancy. <i>RARS2</i> pathogenic variant is a mitochondrial disease that causes severe mental, motor, and developmental retardation, as well as short life expectancy. Our patients are the first cases with liver involvement in PCH6 and a novel homozygous <i>RARS2</i> pathogenic variant to be reported in the literature. This additional phenotype can be considered as making a valid contribution to the literature.
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9
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de Valles-Ibáñez G, Hildebrand MS, Bahlo M, King C, Coleman M, Green TE, Goldsmith J, Davis S, Gill D, Mandelstam S, Scheffer IE, Sadleir LG. Infantile-onset myoclonic developmental and epileptic encephalopathy: A new RARS2 phenotype. Epilepsia Open 2021; 7:170-180. [PMID: 34717047 PMCID: PMC8886097 DOI: 10.1002/epi4.12553] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 09/29/2021] [Accepted: 10/25/2021] [Indexed: 11/11/2022] Open
Abstract
Recessive variants in RARS2, a nuclear gene encoding a mitochondrial protein, were initially reported in pontocerebellar hypoplasia. Subsequently, a recessive RARS2 early-infantile (<12 weeks) developmental and epileptic encephalopathy was described with hypoglycaemia and lactic acidosis. Here, we describe two unrelated patients with a novel RARS2 phenotype and reanalyse the published RARS2 epilepsy phenotypes and variants. Our novel cases had infantile-onset myoclonic developmental and epileptic encephalopathy, presenting with a progressive movement disorder from 9 months on a background of normal development. Development plateaued and regressed thereafter, with mild to profound impairment. Multiple drug-resistant generalized and focal seizures occurred with episodes of non-convulsive status epilepticus. Seizure types included absence, atonic, myoclonic, and focal seizures. Electroencephalograms showed diffuse slowing, multifocal, and generalised spike-wave activity, activated by sleep. Both patients had compound heterozygous RARS2 variants with likely impact on splicing and transcription. Remarkably, of the now 52 RARS2 variants reported in 54 patients, our reanalysis found that 44 (85%) have been shown to or are predicted to affect splicing or gene expression leading to protein truncation or nonsense-mediated decay. We expand the RARS2 phenotypic spectrum to include infantile encephalopathy and suggest this gene is enriched for pathogenic variants that disrupt splicing.
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Affiliation(s)
| | - Michael S Hildebrand
- Department of Medicine, Epilepsy Research Centre, University of Melbourne, Austin Health, Melbourne, Victoria, Australia.,Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Melanie Bahlo
- Population Health and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Chontelle King
- Department of Paediatrics and Child Health, University of Otago, Wellington, New Zealand
| | - Matthew Coleman
- Department of Medicine, Epilepsy Research Centre, University of Melbourne, Austin Health, Melbourne, Victoria, Australia.,Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Timothy E Green
- Department of Medicine, Epilepsy Research Centre, University of Melbourne, Austin Health, Melbourne, Victoria, Australia.,Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - John Goldsmith
- Waikids Paediatric Service, Waikato District Health Board, Hamilton, New Zealand
| | | | - Deepak Gill
- T.Y. Nelson Department of Neurology and Neurosurgery, The Children's Hospital at Westmead, Sydney, New South Wales, Australia
| | - Simone Mandelstam
- Department of Medical Imaging, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Ingrid E Scheffer
- Department of Medicine, Epilepsy Research Centre, University of Melbourne, Austin Health, Melbourne, Victoria, Australia.,Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria, Australia.,Departments of Paediatrics, University of Melbourne, Austin Health and Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Lynette G Sadleir
- Department of Paediatrics and Child Health, University of Otago, Wellington, New Zealand
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10
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Fraga de Andrade I, Mehta C, Bresnick EH. Post-transcriptional control of cellular differentiation by the RNA exosome complex. Nucleic Acids Res 2020; 48:11913-11928. [PMID: 33119769 PMCID: PMC7708067 DOI: 10.1093/nar/gkaa883] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 09/21/2020] [Accepted: 09/30/2020] [Indexed: 12/12/2022] Open
Abstract
Given the complexity of intracellular RNA ensembles and vast phenotypic remodeling intrinsic to cellular differentiation, it is instructive to consider the role of RNA regulatory machinery in controlling differentiation. Dynamic post-transcriptional regulation of protein-coding and non-coding transcripts is vital for establishing and maintaining proteomes that enable or oppose differentiation. By contrast to extensively studied transcriptional mechanisms governing differentiation, many questions remain unanswered regarding the involvement of post-transcriptional mechanisms. Through its catalytic activity to selectively process or degrade RNAs, the RNA exosome complex dictates the levels of RNAs comprising multiple RNA classes, thereby regulating chromatin structure, gene expression and differentiation. Although the RNA exosome would be expected to control diverse biological processes, studies to elucidate its biological functions and how it integrates into, or functions in parallel with, cell type-specific transcriptional mechanisms are in their infancy. Mechanistic analyses have demonstrated that the RNA exosome confers expression of a differentiation regulatory receptor tyrosine kinase, downregulates the telomerase RNA component TERC, confers genomic stability and promotes DNA repair, which have considerable physiological and pathological implications. In this review, we address how a broadly operational RNA regulatory complex interfaces with cell type-specific machinery to control cellular differentiation.
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Affiliation(s)
- Isabela Fraga de Andrade
- Wisconsin Blood Cancer Research Institute, Department of Cell and Regenerative Biology, Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, 4009 WIMR, Madison, WI 53705, USA
| | - Charu Mehta
- Wisconsin Blood Cancer Research Institute, Department of Cell and Regenerative Biology, Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, 4009 WIMR, Madison, WI 53705, USA
| | - Emery H Bresnick
- Wisconsin Blood Cancer Research Institute, Department of Cell and Regenerative Biology, Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Avenue, 4009 WIMR, Madison, WI 53705, USA
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11
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Xu Y, Wu BB, Wang HJ, Zhou SZ, Cheng GQ, Zhou YF. A term neonate with early myoclonic encephalopathy caused by RARS2 gene variants: a case report. Transl Pediatr 2020; 9:707-712. [PMID: 33209735 PMCID: PMC7658767 DOI: 10.21037/tp-20-110] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The RARS2 gene encodes mitochondrial arginine-tRNA synthetase. Patients with variants of the RARS2 gene have pontocerebellar hypoplasia type 6 (PCH6), which is characterized by early onset seizures, progressive microcephaly, and developmental delay. PCH6 is a rare mitochondrial encephalopathy. To the best of our knowledge, the onset seizure type which the ictal video-electroencephalogram (VEEG) was compatible with early myoclonic encephalopathy (EME) has not been reported. Here we reported a term female neonate with EME caused by heterozygous variants of the RARS2 gene [NM_020320: exon10: c.773G>A (p. R258H) Maternal, NM_020320: exon4: c.282_285delAGAG Paternal]. Groan was the first symptom manifested, followed by metabolic disorders, and early marked cerebral atrophy. Metabolic disorders were corrected after feeding with extensively hydrolyzed protein formula. Seizures started at the 19th day of life. Interictal VEEG showed a suppression-burst (SB) pattern and ictal VEEG revealed myoclonic seizures that were compatible with early myoclonic encephalopathy (EME). She had frequent myoclonic seizures resistant to multi-antiepileptic drugs including phenobarbital, levetiracetam and oxcarbazepine, and soon developed into convulsive status epilepticus. At 7 months of age, she had severe developmental delay, and developed infantile spasms. Our case report expands the phenotypic spectrum of the PCH6, meanwhile, RARS2 should be considered be a causative gene in patients with EME.
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Affiliation(s)
- Yan Xu
- Department of Neurology, Children's Hospital of Fudan University, Shanghai, China
| | - Bing-Bing Wu
- The Molecular Genetic Diagnosis Center, Shanghai Key Lab of Birth Defects, Pediatrics Research Institute, Children's Hospital of Fudan University, Shanghai, China
| | - Hui-Jun Wang
- The Molecular Genetic Diagnosis Center, Shanghai Key Lab of Birth Defects, Pediatrics Research Institute, Children's Hospital of Fudan University, Shanghai, China
| | - Shui-Zhen Zhou
- Department of Neurology, Children's Hospital of Fudan University, Shanghai, China
| | - Guo-Qiang Cheng
- Department of Neonatology, Children's Hospital of Fudan University, Shanghai, China
| | - Yuan-Feng Zhou
- Department of Neurology, Children's Hospital of Fudan University, Shanghai, China
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12
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A patient with pontocerebellar hypoplasia type 6: Novel RARS2 mutations, comparison to previously published patients and clinical distinction from PEHO syndrome. Eur J Med Genet 2020; 63:103766. [DOI: 10.1016/j.ejmg.2019.103766] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 09/15/2019] [Accepted: 09/15/2019] [Indexed: 12/15/2022]
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13
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Kahn-Kirby AH, Amagata A, Maeder CI, Mei JJ, Sideris S, Kosaka Y, Hinman A, Malone SA, Bruegger JJ, Wang L, Kim V, Shrader WD, Hoff KG, Latham JC, Ashley EA, Wheeler MT, Bertini E, Carrozzo R, Martinelli D, Dionisi-Vici C, Chapman KA, Enns GM, Gahl W, Wolfe L, Saneto RP, Johnson SC, Trimmer JK, Klein MB, Holst CR. Targeting ferroptosis: A novel therapeutic strategy for the treatment of mitochondrial disease-related epilepsy. PLoS One 2019; 14:e0214250. [PMID: 30921410 PMCID: PMC6438538 DOI: 10.1371/journal.pone.0214250] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 03/08/2019] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Mitochondrial disease is a family of genetic disorders characterized by defects in the generation and regulation of energy. Epilepsy is a common symptom of mitochondrial disease, and in the vast majority of cases, refractory to commonly used antiepileptic drugs. Ferroptosis is a recently-described form of iron- and lipid-dependent regulated cell death associated with glutathione depletion and production of lipid peroxides by lipoxygenase enzymes. Activation of the ferroptosis pathway has been implicated in a growing number of disorders, including epilepsy. Given that ferroptosis is regulated by balancing the activities of glutathione peroxidase-4 (GPX4) and 15-lipoxygenase (15-LO), targeting these enzymes may provide a rational therapeutic strategy to modulate seizure. The clinical-stage therapeutic vatiquinone (EPI-743, α-tocotrienol quinone) was reported to reduce seizure frequency and associated morbidity in children with the mitochondrial disorder pontocerebellar hypoplasia type 6. We sought to elucidate the molecular mechanism of EPI-743 and explore the potential of targeting 15-LO to treat additional mitochondrial disease-associated epilepsies. METHODS Primary fibroblasts and B-lymphocytes derived from patients with mitochondrial disease-associated epilepsy were cultured under standardized conditions. Ferroptosis was induced by treatment with the irreversible GPX4 inhibitor RSL3 or a combination of pharmacological glutathione depletion and excess iron. EPI-743 was co-administered and endpoints, including cell viability and 15-LO-dependent lipid oxidation, were measured. RESULTS EPI-743 potently prevented ferroptosis in patient cells representing five distinct pediatric disease syndromes with associated epilepsy. Cytoprotection was preceded by a dose-dependent decrease in general lipid oxidation and the specific 15-LO product 15-hydroxyeicosatetraenoic acid (15-HETE). CONCLUSIONS These findings support the continued clinical evaluation of EPI-743 as a therapeutic agent for PCH6 and other mitochondrial diseases with associated epilepsy.
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Affiliation(s)
- Amanda H. Kahn-Kirby
- BioElectron Technology Corporation, Mountain View, California, United States of America
- * E-mail:
| | - Akiko Amagata
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Celine I. Maeder
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Janet J. Mei
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Steve Sideris
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Yuko Kosaka
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Andrew Hinman
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Stephanie A. Malone
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Joel J. Bruegger
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Leslie Wang
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Virna Kim
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - William D. Shrader
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Kevin G. Hoff
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Joey C. Latham
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Euan A. Ashley
- Stanford Center for Undiagnosed Diseases, Stanford University School of Medicine, Stanford, California, United States of America
| | - Matthew T. Wheeler
- Stanford Center for Undiagnosed Diseases, Stanford University School of Medicine, Stanford, California, United States of America
| | - Enrico Bertini
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesù Children’s Research Hospital, Rome, Italy
| | - Rosalba Carrozzo
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesù Children’s Research Hospital, Rome, Italy
| | - Diego Martinelli
- Unit of Neuromuscular and Neurodegenerative Disorders, Bambino Gesù Children’s Research Hospital, Rome, Italy
| | - Carlo Dionisi-Vici
- Clinical Division and Research Unit of Metabolic Diseases, Bambino Gesù Children's Hospital, Rome, Italy
| | - Kimberly A. Chapman
- Children’s National Rare Disease Institute, Children's National Health System, Washington, D.C., United States of America
| | - Gregory M. Enns
- Department of Pediatrics, Division of Medical Genetics, Stanford University School of Medicine, Stanford, California, United States of America
| | - William Gahl
- NIH Undiagnosed Diseases Program, National Human Genome Research Institute (NHGRI), National Institutes of Health, Bethesda, Maryland, United States of America
| | - Lynne Wolfe
- NIH Undiagnosed Diseases Program, National Human Genome Research Institute (NHGRI), National Institutes of Health, Bethesda, Maryland, United States of America
| | - Russell P. Saneto
- Division of Pediatric Neurology, Department of Neurology, Neuroscience Institute, Seattle Children's Hospital, Seattle, Washington, United States of America
| | - Simon C. Johnson
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, Washington, United States of America
- Department of Neurology, University of Washington, Seattle, Washington, United States of America
| | - Jeffrey K. Trimmer
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Matthew B. Klein
- BioElectron Technology Corporation, Mountain View, California, United States of America
| | - Charles R. Holst
- BioElectron Technology Corporation, Mountain View, California, United States of America
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14
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Mitochondrial DNA transcription and translation: clinical syndromes. Essays Biochem 2018; 62:321-340. [PMID: 29980628 PMCID: PMC6056718 DOI: 10.1042/ebc20170103] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/17/2018] [Accepted: 05/21/2018] [Indexed: 01/15/2023]
Abstract
Diagnosing primary mitochondrial diseases is challenging in clinical practice. Although, defective oxidative phosphorylation (OXPHOS) is the common final pathway, it is unknown why different mtDNA or nuclear mutations result in largely heterogeneous and often tissue -specific clinical presentations. Mitochondrial tRNA (mt-tRNA) mutations are frequent causes of mitochondrial diseases both in children and adults. However numerous nuclear mutations involved in mitochondrial protein synthesis affecting ubiquitously expressed genes have been reported in association with very tissue specific clinical manifestations suggesting that there are so far unknown factors determining the tissue specificity in mitochondrial translation. Most of these gene defects result in histological abnormalities and multiple respiratory chain defects in the affected organs. The clinical phenotypes are usually early-onset, severe, and often fatal, implying the importance of mitochondrial translation from birth. However, some rare, reversible infantile mitochondrial diseases are caused by very specific defects of mitochondrial translation. An unbiased genetic approach (whole exome sequencing, RNA sequencing) combined with proteomics and functional studies revealed novel factors involved in mitochondrial translation which contribute to the clinical manifestation and recovery in these rare reversible mitochondrial conditions.
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15
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van Dijk T, Baas F, Barth PG, Poll-The BT. What's new in pontocerebellar hypoplasia? An update on genes and subtypes. Orphanet J Rare Dis 2018; 13:92. [PMID: 29903031 PMCID: PMC6003036 DOI: 10.1186/s13023-018-0826-2] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 05/16/2018] [Indexed: 12/25/2022] Open
Abstract
Background Pontocerebellar hypoplasia (PCH) describes a rare, heterogeneous group of neurodegenerative disorders mainly with a prenatal onset. Patients have severe hypoplasia or atrophy of cerebellum and pons, with variable involvement of supratentorial structures, motor and cognitive impairments. Based on distinct clinical features and genetic causes, current classification comprises 11 types of PCH. Main text In this review we describe the clinical, neuroradiological and genetic characteristics of the different PCH subtypes, summarize the differential diagnosis and reflect on potential disease mechanisms in PCH. Seventeen PCH-related genes are now listed in the OMIM database, most of them have a function in RNA processing or translation. It is unknown why defects in these apparently ubiquitous processes result in a brain-specific phenotype. Conclusions Many new PCH related genes and phenotypes have been described due to the appliance of next generation sequencing techniques. By including such a broad range of phenotypes, including non-degenerative and postnatal onset disorders, the current classification gives rise to confusion. Despite the discovery of new pathways involved in PCH, treatment is still symptomatic. However, correct diagnosis of PCH is important to provide suitable care and counseling regarding prognosis, and offer appropriate (prenatal) genetic testing to families.
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Affiliation(s)
- Tessa van Dijk
- Department of Clinical Genetics, Academic Medical Center, Amsterdam, The Netherlands.,Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Frank Baas
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Peter G Barth
- Department of Pediatric Neurology, Academic Medical Center, Amsterdam, The Netherlands
| | - Bwee Tien Poll-The
- Department of Pediatric Neurology, Academic Medical Center, Amsterdam, The Netherlands.
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16
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Mathew T, Avati A, D'Souza D, Therambil M. Expanding spectrum of RARS2 gene disorders: Myoclonic epilepsy, mental retardation, spasticity, and extrapyramidal features. Epilepsia Open 2018; 3:270-275. [PMID: 29881806 PMCID: PMC5983106 DOI: 10.1002/epi4.12108] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/15/2018] [Indexed: 12/21/2022] Open
Abstract
Pontocerebellar hypoplasia type 6 (PCH6) is an autosomal recessive mitochondrial disease, typically characterized by pontine atrophy, vermian hypoplasia, infantile encephalopathy, generalized hypotonia, and intractable seizures. The purpose of this study is to describe the seizures and other neurological manifestations of RARS2 gene mutations and to compare the clinical features with other causes of progressive myoclonic epilepsy. Detailed history, physical examination, and clinical and genetic work‐up were performed in 2 siblings who presented with progressive myoclonic epilepsy. One sibling, a 20‐year‐old woman, and the other a 24‐year‐old man, had a homozygous missense variant (c.848T>A; p.Leu283Gln) in exon 10 of the RARS2 gene. The female patient had action and audiogenic myoclonic jerks, postural tremors, spastic dysarthria, and bradykinesia, and her male sibling had similar features with oculomotor apraxia. The RARS2 gene mutation can present with myoclonic epilepsy, mental retardation, and pyramidal and extrapyramidal features, and is an important differential for causes of progressive myoclonic epilepsy.
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Affiliation(s)
- Thomas Mathew
- Department of Neurology St. John's Medical College Hospital Bengaluru Karnataka India
| | - Amrutha Avati
- Department of Neurology St. John's Medical College Hospital Bengaluru Karnataka India
| | - Delon D'Souza
- Department of Neurology St. John's Medical College Hospital Bengaluru Karnataka India
| | - Manjusha Therambil
- Department of Neurology St. John's Medical College Hospital Bengaluru Karnataka India
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17
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Zhang J, Zhang Z, Zhang Y, Wu Y. Distinct magnetic resonance imaging features in a patient with novel RARS2 mutations: A case report and review of the literature. Exp Ther Med 2017; 15:1099-1104. [PMID: 29434700 DOI: 10.3892/etm.2017.5491] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 07/14/2017] [Indexed: 01/30/2023] Open
Abstract
Pontocerebellar hypoplasia type 6 (PCH6) is a rare autosomal recessive disease that occurs due to mutations in the mitochondrial arginyl-tRNA synthetase 2 (RARS2) gene. To the best of our knowledge, 23 cases with relatively complete clinical data have been reported thus far. In the present study, a case with PCH6 caused by novel RARS2 mutations is described, in which distinct magnetic resonance imaging (MRI) features were identified. In addition, 23 PCH6 cases found in the literature were reviewed. Early onset hypotonia (43.48%), epileptic seizures (34.78%), encephalopathy (26.08%) and feeding difficulties (17.39%) were common initial symptoms of PCH6. During disease progression, the patients presented refractory epileptic seizures (94.12%), feeding problems (60.87%), severe developmental delay (100%), microcephaly (88.89%) and hyperlactacidemia (76.47%). The clinical features of the present patient were suggestive of PCH6, with early onset epilepsy, feeding difficulties, severe developmental delay, microcephaly, hearing loss and hyperlactacidemia. According to available MRI data from 20 reported cases with PCH6, the characteristic finding in MRI was pontocerebellar dysplasia or progressive cerebral/pontocerebellar atrophy in 16 cases, while 4 cases did not present pontocerebellar hypoplasia, and no basal ganglia involvement was observed in any of the cases. Distinctive MRI features were also identified in the present case, including pontocerebellar preservation after 1 year of age, as well as a high diffusion-weighted imaging signal suggesting intracellular edema in the cerebellar hemispheres, basal ganglia, thalamus and corpus callosum. Progressive loss of cerebral white matter and cortical volume were common features shared by all patients. In conclusion, in the present study, two novel heterozygous mutations were identified in RARS2, namely c.1718C>T(p.Thr573Ile) and c.991A>G (p.Ile331Val). Thus, the present case enriched the phenotypic and genotypic spectrum of the RARS2 mutations.
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Affiliation(s)
- Jie Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, P.R. China
| | - Zhongbin Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, P.R. China
| | - Yao Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, P.R. China
| | - Ye Wu
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, P.R. China
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18
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Meyer-Schuman R, Antonellis A. Emerging mechanisms of aminoacyl-tRNA synthetase mutations in recessive and dominant human disease. Hum Mol Genet 2017; 26:R114-R127. [PMID: 28633377 PMCID: PMC5886470 DOI: 10.1093/hmg/ddx231] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 06/09/2017] [Accepted: 06/12/2017] [Indexed: 12/29/2022] Open
Abstract
Aminoacyl-tRNA synthetases (ARSs) are responsible for charging amino acids to cognate tRNA molecules, which is the essential first step of protein translation. Interestingly, mutations in genes encoding ARS enzymes have been implicated in a broad spectrum of human inherited diseases. Bi-allelic mutations in ARSs typically cause severe, early-onset, recessive diseases that affect a wide range of tissues. The vast majority of these mutations show loss-of-function effects and impair protein translation. However, it is not clear how a subset cause tissue-specific phenotypes. In contrast, dominant ARS-mediated diseases specifically affect the peripheral nervous system-most commonly causing axonal peripheral neuropathy-and usually manifest later in life. These neuropathies are linked to heterozygosity for missense mutations in five ARS genes, which points to a shared mechanism of disease. However, it is not clear if a loss-of-function mechanism or a toxic gain-of-function mechanism is responsible for ARS-mediated neuropathy, or if a combination of these mechanisms operate on a mutation-specific basis. Here, we review our current understanding of recessive and dominant ARS-mediated disease. We also propose future directions for defining the molecular mechanisms of ARS mutations toward designing therapies for affected patient populations.
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Affiliation(s)
- Rebecca Meyer-Schuman
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Anthony Antonellis
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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19
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Ognjenović J, Simonović M. Human aminoacyl-tRNA synthetases in diseases of the nervous system. RNA Biol 2017; 15:623-634. [PMID: 28534666 PMCID: PMC6103678 DOI: 10.1080/15476286.2017.1330245] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 05/05/2017] [Accepted: 05/10/2017] [Indexed: 12/21/2022] Open
Abstract
Aminoacyl-tRNA synthetases (AaRSs) are ubiquitously expressed enzymes that ensure accurate translation of the genetic information into functional proteins. These enzymes also execute a variety of non-canonical functions that are significant for regulation of diverse cellular processes and that reside outside the realm of protein synthesis. Associations between faults in AaRS-mediated processes and human diseases have been long recognized. Most recent research findings strongly argue that 10 cytosolic and 14 mitochondrial AaRSs are implicated in some form of pathology of the human nervous system. The advent of modern whole-exome sequencing makes it all but certain that similar associations between the remaining 15 ARS genes and neurologic illnesses will be defined in future. It is not surprising that an intense scientific debate about the role of translational machinery, in general, and AaRSs, in particular, in the development and maintenance of the healthy human neural cell types and the brain is sparked. Herein, we summarize the current knowledge about causative links between mutations in human AaRSs and diseases of the nervous system and briefly discuss future directions.
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Affiliation(s)
- Jana Ognjenović
- Department of Biochemistry and Molecular Genetics, College of Medicine, The University of Illinois at Chicago, Chicago, IL, USA
| | - Miljan Simonović
- Department of Biochemistry and Molecular Genetics, College of Medicine, The University of Illinois at Chicago, Chicago, IL, USA
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20
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Lühl S, Bode H, Schlötzer W, Bartsakoulia M, Horvath R, Abicht A, Stenzel M, Kirschner J, Grünert SC. Novel homozygous RARS2 mutation in two siblings without pontocerebellar hypoplasia - further expansion of the phenotypic spectrum. Orphanet J Rare Dis 2016; 11:140. [PMID: 27769281 PMCID: PMC5073905 DOI: 10.1186/s13023-016-0525-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 10/11/2016] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Pontocerebellar hypoplasia type 6 (PCH6) is a mitochondrial disease caused by mutations in the RARS2 gene. RARS2 encodes mitochondrial arginyl transfer RNA synthetase, an enzyme involved in mitochondrial protein translation. A total of 27 patients from 14 families have been reported so far. Characteristic clinical features comprise neonatal lactic acidosis, severe encephalopathy, intractable seizures, feeding problems and profound developmental delay. Most patients show typical neuroradiologic abnormalities including cerebellar hypoplasia and progressive pontocerebellar atrophy. METHODS We describe the clinical, biochemical and molecular features of 2 siblings with a novel homozygous mutation in RARS2. Both patients presented neonatally with lactic acidosis. While the older sibling had severe neurological symptoms with microcephaly, seizures and developmental delay, the younger patient was still neurologically asymptomatic at the age of 2 months. RESULTS MRI studies in both children lacked pontocerebellar involvement. The expression of the OXPHOS complex proteins was decreased in both patients, whereas oxygen consumption was increased. CONCLUSIONS Characteristic neuroradiological abnormalities of PCH6 such as vermis and cerebellar hypoplasia and progressive pontocerebellar atrophy may be missing in patients with RARS2 mutations. RARS2 testing should therefore also be performed in patients without pontocerebellar hypoplasia but otherwise typical clinical symptoms.
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Affiliation(s)
- S Lühl
- Department of Pediatrics and Adolescent Medicine, University Medical Center, Ulm, Germany
| | - H Bode
- Department of Pediatrics and Adolescent Medicine, University Medical Center, Ulm, Germany
| | - W Schlötzer
- Department of Diagnostic and Interventional Radiology, Section Neuroradiology, University Medical Center, Ulm, Germany
| | - M Bartsakoulia
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - R Horvath
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - A Abicht
- Medical Genetics Centre, Munich, Germany
| | - M Stenzel
- Department of Pediatric Radiology, Kliniken der Stadt Köln, Köln, Germany
| | - J Kirschner
- Department of Neuropediatrics and Muscle Disorders, Medical Center - University of Freiburg, Faculty of Medicine, Freiburg, Germany
| | - S C Grünert
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Medical Center - University of Freiburg, Faculty of Medicine, Freiburg, Germany.
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21
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van Dijk T, van Ruissen F, Jaeger B, Rodenburg RJ, Tamminga S, van Maarle M, Baas F, Wolf NI, Poll-The BT. RARS2 Mutations: Is Pontocerebellar Hypoplasia Type 6 a Mitochondrial Encephalopathy? JIMD Rep 2016; 33:87-92. [PMID: 27683254 DOI: 10.1007/8904_2016_584] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 08/23/2016] [Accepted: 08/24/2016] [Indexed: 12/23/2022] Open
Abstract
Mutations in the mitochondrial arginyl tRNA synthetase (RARS2) gene are associated with Pontocerebellar Hypoplasia type 6 (PCH6). Here we report two patients, compound heterozygous for RARS2 mutations, presenting with early onset epileptic encephalopathy and (progressive) atrophy of both supra- and infratentorial structures. Early pontocerebellar hypoplasia was virtually absent and respiratory chain (RC) defects could not be detected in muscle biopsies. Both patients carried a novel missense mutation c.1544A>G (p.(Asp515Gly)) in combination with either a splice site (c.297+2T>G) or a frameshift (c.452_454insC) mutation. The splice site mutation induced skipping of exon 4.These two patients expand the phenotypical spectrum associated with RARS2 mutations beyond the first report of PCH6 by Edvardson and colleagues. We propose to classify RARS2-associated phenotypes as an early onset mitochondrial encephalopathy, since this is more in agreement with both clinical presentation and underlying genetic cause.
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Affiliation(s)
- Tessa van Dijk
- Department of Clinical Genetics, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands
| | - Fred van Ruissen
- Department of Clinical Genetics, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands
| | - Bregje Jaeger
- Department of Pediatric Neurology, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands
| | - Richard J Rodenburg
- Radboud Center for Mitochondrial Medicine, Radboud University Medical Center, 6500 HB, Nijmegen, The Netherlands
| | - Saskia Tamminga
- Department of Clinical Genetics, VU University Medical Center, 1081 HZ, Amsterdam, The Netherlands
| | - Merel van Maarle
- Department of Clinical Genetics, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands
| | - Frank Baas
- Department of Clinical Genetics, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands
| | - Nicole I Wolf
- Department of Pediatric Neurology, VU University Medical Center, and Neuroscience Campus Amsterdam, 1081 HZ, Amsterdam, The Netherlands
| | - Bwee Tien Poll-The
- Department of Pediatric Neurology, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands.
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22
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Puppala AK, French RL, Matthies D, Baxa U, Subramaniam S, Simonović M. Structural basis for early-onset neurological disorders caused by mutations in human selenocysteine synthase. Sci Rep 2016; 6:32563. [PMID: 27576344 PMCID: PMC5006159 DOI: 10.1038/srep32563] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 08/09/2016] [Indexed: 01/09/2023] Open
Abstract
Selenocysteine synthase (SepSecS) catalyzes the terminal reaction of selenocysteine, and is vital for human selenoproteome integrity. Autosomal recessive inheritance of mutations in SepSecS-Ala239Thr, Thr325Ser, Tyr334Cys and Tyr429*-induced severe, early-onset, neurological disorders in distinct human populations. Although harboring different mutant alleles, patients presented remarkably similar phenotypes typified by cerebellar and cerebral atrophy, seizures, irritability, ataxia, and extreme spasticity. However, it has remained unclear how these genetic alterations affected the structure of SepSecS and subsequently elicited the development of a neurological pathology. Herein, our biophysical and structural characterization demonstrates that, with the exception of Tyr429*, pathogenic mutations decrease protein stability and trigger protein misfolding. We propose that the reduced stability and increased propensity towards misfolding are the main causes for the loss of SepSecS activity in afflicted patients, and that these factors contribute to disease progression. We also suggest that misfolding of enzymes regulating protein synthesis should be considered in the diagnosis and study of childhood neurological disorders.
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Affiliation(s)
- Anupama K Puppala
- Department of Biochemistry an Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607, USA
| | - Rachel L French
- Department of Biochemistry an Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607, USA
| | - Doreen Matthies
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ulrich Baxa
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sriram Subramaniam
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Miljan Simonović
- Department of Biochemistry an Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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23
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Alkhateeb AM, Aburahma SK, Habbab W, Thompson IR. Novel mutations in WWOX, RARS2, and C10orf2 genes in consanguineous Arab families with intellectual disability. Metab Brain Dis 2016; 31:901-7. [PMID: 27121845 DOI: 10.1007/s11011-016-9827-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 04/19/2016] [Indexed: 02/06/2023]
Abstract
Intellectual disability is a heterogeneous disease with many genes and mutations influencing the phenotype. Consanguineous families constitute a rich resource for the identification of rare variants causing autosomal recessive disease, due to the effects of inbreeding. Here, we examine three consanguineous Arab families, recruited in a quest to identify novel genes/mutations. All the families had multiple offspring with non-specific intellectual disability. We identified homozygosity (autozygosity) intervals in those families through SNP genotyping and whole exome sequencing, with variants filtered using Ingenuity Variant Analysis (IVA) software. The families showed heterogeneity and novel mutations in three different genes known to be associated with intellectual disability. These mutations were not found in 514 ethnically matched control chromosomes. p.G410C in WWOX, p.H530Y in RARS2, and p.I69F in C10orf2 are novel changes that affect protein function and could give new insights into the development and function of the central nervous system.
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Affiliation(s)
- Asem M Alkhateeb
- Qatar Biomedical Research Institute, Hamad Bin Khalifa University, Doha, P.O. Box 5825, Qatar.
- Biotechnology and Genetics Department, Jordan University of Science and Technology, P.O. Box 3030, Irbid, 22110, Jordan.
| | - Samah K Aburahma
- Neurosciences Department, Jordan University of Science and Technology, P.O. Box 3030, Irbid, 22110, Jordan
| | - Wesal Habbab
- Qatar Biomedical Research Institute, Hamad Bin Khalifa University, Doha, P.O. Box 5825, Qatar
| | - I Richard Thompson
- Qatar Biomedical Research Institute, Hamad Bin Khalifa University, Doha, P.O. Box 5825, Qatar
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24
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Ngoh A, Bras J, Guerreiro R, Meyer E, McTague A, Dawson E, Mankad K, Gunny R, Clayton P, Mills PB, Thornton R, Lai M, Forsyth R, Kurian MA. RARS2 mutations in a sibship with infantile spasms. Epilepsia 2016; 57:e97-e102. [PMID: 27061686 PMCID: PMC4864753 DOI: 10.1111/epi.13358] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/18/2016] [Indexed: 02/04/2023]
Abstract
Pontocerebellar hypoplasia is a group of heterogeneous neurodevelopmental disorders characterized by reduced volume of the brainstem and cerebellum. We report two male siblings who presented with early infantile clonic seizures, and then developed infantile spasms associated with prominent isolated cerebellar hypoplasia/atrophy on magnetic resonance imaging (MRI). Using whole exome sequencing techniques, both were found to be compound heterozygotes for one previously reported and one novel mutation in the gene encoding mitochondrial arginyl‐tRNA synthetase 2 (RARS2). Mutations in this gene have been classically described in pontocerebellar hypoplasia type six (PCH6), a phenotype characterized by early (often intractable) seizures, profound developmental delay, and progressive pontocerebellar atrophy. The electroclinical spectrum of PCH6 is broad and includes a number of seizure types: myoclonic, generalized tonic–clonic, and focal clonic seizures. Our report expands the characterization of the PCH6 disease spectrum and presents infantile spasms as an associated electroclinical phenotype.
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Affiliation(s)
- Adeline Ngoh
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL-Institute of Child Health, London, United Kingdom.,Department of Neurology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - Jose Bras
- Department of Molecular Neuroscience, UCL-Institute of Neurology, London, United Kingdom
| | - Rita Guerreiro
- Department of Molecular Neuroscience, UCL-Institute of Neurology, London, United Kingdom.,Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland, U.S.A
| | - Esther Meyer
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL-Institute of Child Health, London, United Kingdom
| | - Amy McTague
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL-Institute of Child Health, London, United Kingdom.,Department of Neurology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - Eleanor Dawson
- Department of Paediatric Neurology, Great North Children's Hospital, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Kshitij Mankad
- Department of Radiology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - Roxana Gunny
- Department of Radiology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - Peter Clayton
- Genetics and Genomic Medicine Programme, UCL-Institute of Child Health, London, United Kingdom.,Metabolic Medicine Unit, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - Philippa B Mills
- Genetics and Genomic Medicine Programme, UCL-Institute of Child Health, London, United Kingdom
| | - Rachel Thornton
- Department of Neurophysiology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - Ming Lai
- Department of Neurophysiology, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
| | - Robert Forsyth
- Department of Paediatric Neurology, Great North Children's Hospital, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom.,Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Manju A Kurian
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL-Institute of Child Health, London, United Kingdom.,Department of Neurology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
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