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GRIN2A-related epilepsy and speech disorders: A comprehensive overview with a focus on the role of precision therapeutics. Epilepsy Res 2023; 189:107065. [PMID: 36516565 DOI: 10.1016/j.eplepsyres.2022.107065] [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: 08/18/2022] [Revised: 10/27/2022] [Accepted: 12/08/2022] [Indexed: 12/14/2022]
Abstract
Language dysfunction is a common and serious comorbidity of epilepsy, especially in individuals with epilepsy aphasia spectrum syndromes. Childhood epilepsy with centrotemporal spikes is on the mild end of the spectrum, while epileptic encephalopathy with continuous spike-and-wave during sleep syndrome is on the severe end. Traditional antiseizure medicines and immunotherapy are currently used to treat severely affected patients, but the results are usually disappointing. The discovery that GRIN2A is the primary monogenic etiology of these diseases has opened the door to precision treatments. The GRIN2A gene encodes GluN2A protein, which constitutes a subunit of the NMDA receptor (NMDAR). The GRIN2A pathogenic variants cause gain or loss of function of NMDAR; the former can be treated with uncompetitive NMDAR antagonists, such as memantine, while the latter with NMDAR co-agonist serine. Hyper-precision therapies with various other effective agents are likely to be developed shortly to target the diverse functional effects of different variants. Precision treatments for GRIN2A-related disorders will benefit those who suffer from the condition and pave the way for new therapeutic approaches to a variety of other NMDAR-linked neurodegenerative and psychiatric diseases (schizophrenia, Parkinson's disease, Alzheimer's disease, and so on). Furthermore, more research into GRIN2A-related disorders will help us better understand the neuroinflammatory and neuroimmunological basis of epilepsy, as well as the pathological and physiological network activation mechanisms that cause sleep activation of central-temporal spikes and language impairment.
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Liu XR, Xu XX, Lin SM, Fan CY, Ye TT, Tang B, Shi YW, Su T, Li BM, Yi YH, Luo JH, Liao WP. GRIN2A Variants Associated With Idiopathic Generalized Epilepsies. Front Mol Neurosci 2021; 14:720984. [PMID: 34720871 PMCID: PMC8551482 DOI: 10.3389/fnmol.2021.720984] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Accepted: 08/30/2021] [Indexed: 12/16/2022] Open
Abstract
Objective: The objective of this study is to explore the role of GRIN2A gene in idiopathic generalized epilepsies and the potential underlying mechanism for phenotypic variation. Methods: Whole-exome sequencing was performed in a cohort of 88 patients with idiopathic generalized epilepsies. Electro-physiological alterations of the recombinant N-methyl-D-aspartate receptors (NMDARs) containing GluN2A mutants were examined using two-electrode voltage-clamp recordings. The alterations of protein expression were detected by immunofluorescence staining and biotinylation. Previous studies reported that epilepsy related GRIN2A missense mutations were reviewed. The correlation among phenotypes, functional alterations, and molecular locations was analyzed. Results: Three novel heterozygous missense GRIN2A mutations (c.1770A > C/p.K590N, c.2636A > G/p.K879R, and c.3199C > T/p.R1067W) were identified in three unrelated cases. Electrophysiological analysis demonstrated R1067W significantly increased the current density of GluN1/GluN2A NMDARs. Immunofluorescence staining indicated GluN2A mutants had abundant distribution in the membrane and cytoplasm. Western blotting showed the ratios of surface and total expression of the three GluN2A-mutants were significantly increased comparing to the wild type. Further analysis on the reported missense mutations demonstrated that mutations with severe gain-of-function were associated with epileptic encephalopathy, while mutations with mild gain of function were associated with mild phenotypes, suggesting a quantitative correlation between gain-of-function and phenotypic severity. The mutations located around transmembrane domains were more frequently associated with severe phenotypes and absence seizure-related mutations were mostly located in carboxyl-terminal domain, suggesting molecular sub-regional effects. Significance: This study revealed GRIN2A gene was potentially a candidate pathogenic gene of idiopathic generalized epilepsies. The functional quantitative correlation and the molecular sub-regional implication of mutations helped in explaining the relatively mild clinical phenotypes and incomplete penetrance associated with GRIN2A variants.
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Affiliation(s)
- Xiao-Rong Liu
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Xing-Xing Xu
- Department of Physiology, Wenzhou Medical University, Wenzhou, China
| | - Si-Mei Lin
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Cui-Ying Fan
- NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang University School of Medicine, Hangzhou, China
| | - Ting-Ting Ye
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Bin Tang
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Yi-Wu Shi
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Tao Su
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Bing-Mei Li
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Yong-Hong Yi
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Jian-Hong Luo
- NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang University School of Medicine, Hangzhou, China
| | - Wei-Ping Liao
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
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Sapuppo A, Portale L, Massimino CR, Presti S, Tardino L, Marino S, Polizzi A, Falsaperla R, Praticò AD. GRIN2A and GRIN2B and Their Related Phenotypes. JOURNAL OF PEDIATRIC NEUROLOGY 2021. [DOI: 10.1055/s-0041-1727146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
AbstractGlutamate is the most relevant excitatory neurotransmitter of the central nervous system; it binds with several receptors, including N-methyl-D-aspartate receptors (NMDARs), a subtype of ionotropic glutamate receptor that displays voltage-dependent block by Mg2+ and a high permeability to Ca2+. GRIN2A and GRIN2B genes encode the GluN2A and GluN2B subunits of the NMDARs, which play important roles in synaptogenesis, synaptic transmission, and synaptic plasticity, as well as contributing to neuronal loss and dysfunction in several neurological disorders. Recently, individuals with a range of childhood-onset drug-resistant epilepsies, such as Landau–Kleffner or Lennox–Gastaut syndrome, intellectual disability (ID), and other neurodevelopmental abnormalities have been found to carry mutations in GRIN2A and GRIN2B, with high variable expressivity in phenotype. The first one is found mainly in epilepsy-aphasia syndromes, while the second one mainly in autism, schizophrenia, and ID, such as autism spectrum disorders. Brain magnetic resonance imaging alterations are found in some patients, even if without a clear clinical correlation. At the same time, increasing data on genotype–phenotype correlation have been found, but this is still not fully demonstrated. There are no specific therapies for the treatment of correlated NMDARs epilepsy, although some evidence with memantine, an antagonist of glutamate receptor, is reported in the literature in selected cases with mutation determining a gain of function.
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Affiliation(s)
- Annamaria Sapuppo
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Laura Portale
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Carmela R. Massimino
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Santiago Presti
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Lucia Tardino
- Unit of Pediatrics and Pediatric Emergency, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
| | - Simona Marino
- Unit of Pediatrics and Pediatric Emergency, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
| | - Agata Polizzi
- Chair of Pediatrics, Department of Educational Sciences, University of Catania, Catania, Italy
| | - Raffaele Falsaperla
- Unit of Pediatrics and Pediatric Emergency, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
- Unit of Neonatal Intensive Care and Neonatology, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
| | - Andrea D. Praticò
- Unit of Rare Diseases of the Nervous Systemin Childhood, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
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Siri L, Ragona F, Granata T, Moresco L, Cohen A. Immunotherapy in GRIN2A-negative Landau-Kleffner Syndrome. Minerva Pediatr 2020; 72:139-141. [PMID: 32441907 DOI: 10.23736/s0026-4946.19.05419-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Laura Siri
- Cesare Arrigo Children's Hospital, Alessandria, Italy -
| | - Francesca Ragona
- Department of Pediatric Neuroscience, C. Besta Institute of Neurology, IRCCS, and Foundation, Milan, Italy
| | - Tiziana Granata
- Department of Pediatric Neuroscience, C. Besta Institute of Neurology, IRCCS, and Foundation, Milan, Italy
| | - Luca Moresco
- Unit of Pediatrics, San Paolo Hospital, Savona, Italy
| | - Amnon Cohen
- Unit of Pediatrics, San Paolo Hospital, Savona, Italy
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Immunotherapy for GRIN2A and GRIN2D-related epileptic encephalopathy. Epilepsy Res 2020; 163:106325. [PMID: 32289570 DOI: 10.1016/j.eplepsyres.2020.106325] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 03/22/2020] [Accepted: 03/26/2020] [Indexed: 12/24/2022]
Abstract
BACKGROUND GRIN-related developmental-epileptic encephalopathies are associated with a spectrum of neurodevelopmental disorders, including intellectual disability, epilepsy including continuous spike-and-wave during sleep syndrome (CSWS), or epilepsy-aphasia spectrum phenotypes such as in Landau-Kleffner syndrome. Efficacy of IVIG treatment was recently reported in a patient with LKS related to GRIN2A mutation. AIM AND METHODS We describe the efficacy of Immunotherapy in 5 consecutive patients (4 males, age range 6 months-13 years) with molecularly confirmed GRIN-related epileptic encephalopathy (4 with GRIN2A- related epilepsy-aphasia spectrum/epileptic encephalopathy with CSWS, accompanied by verbal, communicative and behavioural regression, and one patient with GRIN2D - related infantile developmental-epileptic encephalopathy). All patients had global developmental delay/ intellectual disability in various degrees, and were resistant to anticonvulsants, but none of the patients had frequent clinical seizures. All patients received monthly infusion of IVIG 2 g/ kg for 6 months; 2 patients were also treated with high-dose corticosteroids. RESULTS Normalization or near normalization of the EEG was noted in 3 patients, from whom 2 had mild improvement in verbal abilities and communication skills. Perceptual/spatial abilities, as well as executive functions and attention span, remained significantly impaired. CONCLUSION according to this preliminary, open-label study, Immunotherapy may lead to a clinical and electrographic improvement in patients with GRIN-related developmental-epileptic encephalopathies. Further studies to validate the efficacy of immunotherapy and the potential role of autoimmunity in GRIN-related disorders are needed.
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Myers SJ, Yuan H, Kang JQ, Tan FCK, Traynelis SF, Low CM. Distinct roles of GRIN2A and GRIN2B variants in neurological conditions. F1000Res 2019; 8:F1000 Faculty Rev-1940. [PMID: 31807283 PMCID: PMC6871362 DOI: 10.12688/f1000research.18949.1] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/08/2019] [Indexed: 12/12/2022] Open
Abstract
Rapid advances in sequencing technology have led to an explosive increase in the number of genetic variants identified in patients with neurological disease and have also enabled the assembly of a robust database of variants in healthy individuals. A surprising number of variants in the GRIN genes that encode N-methyl-D-aspartate (NMDA) glutamatergic receptor subunits have been found in patients with various neuropsychiatric disorders, including autism spectrum disorders, epilepsy, intellectual disability, attention-deficit/hyperactivity disorder, and schizophrenia. This review compares and contrasts the available information describing the clinical and functional consequences of genetic variations in GRIN2A and GRIN2B. Comparison of clinical phenotypes shows that GRIN2A variants are commonly associated with an epileptic phenotype but that GRIN2B variants are commonly found in patients with neurodevelopmental disorders. These observations emphasize the distinct roles that the gene products serve in circuit function and suggest that functional analysis of GRIN2A and GRIN2B variation may provide insight into the molecular mechanisms, which will allow more accurate subclassification of clinical phenotypes. Furthermore, characterization of the pharmacological properties of variant receptors could provide the first opportunity for translational therapeutic strategies for these GRIN-related neurological and psychiatric disorders.
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Affiliation(s)
- Scott J Myers
- Center for Functional Evaluation of Rare Variants (CFERV), Emory University, Atlanta, GA, USA
- Department of Pharmacology and Chemical Biology, Emory University, Atlanta, GA, USA
| | - Hongjie Yuan
- Center for Functional Evaluation of Rare Variants (CFERV), Emory University, Atlanta, GA, USA
- Department of Pharmacology and Chemical Biology, Emory University, Atlanta, GA, USA
| | - Jing-Qiong Kang
- Department of Neurology, Vanderbilt Brain Institute, Vanderbilt Kennedy Center of Human Development, Vanderbilt University, Nashville, TN, USA
| | - Francis Chee Kuan Tan
- Department of Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Stephen F Traynelis
- Center for Functional Evaluation of Rare Variants (CFERV), Emory University, Atlanta, GA, USA
- Department of Pharmacology and Chemical Biology, Emory University, Atlanta, GA, USA
| | - Chian-Ming Low
- Department of Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
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Abstract
The clinical presentation of patients with epileptic encephalopathies can be heterogenous. When attempting to classify a patient's epilepsy syndrome, challenges can arise due to the phenotypic overlap of various epilepsies as well as the different presentations of mutations within the same gene. Genetic testing can be most helpful in evaluation of children with features spanning several epilepsy phenotypes. In this case, we report on a boy with an epileptic encephalopathy found to have a previously unreported mutation in a recently described gene.
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Yang X, Qian P, Xu X, Liu X, Wu X, Zhang Y, Yang Z. GRIN2A mutations in epilepsy-aphasia spectrum disorders. Brain Dev 2018; 40:205-210. [PMID: 29056244 DOI: 10.1016/j.braindev.2017.09.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Revised: 07/16/2017] [Accepted: 09/26/2017] [Indexed: 12/30/2022]
Abstract
OBJECTIVE Epilepsy-aphasia spectrum (EAS) are a group of epilepsy syndromes denoting an association between epilepsy, speech disorders and the EEG signature of centrotemporal spikes. Mutations in the GRIN2A gene, encoding the NMDA glutamate receptor α2 subunit were reported in focal epilepsy with speech disorder. We aimed to explore the role of GRIN2A mutations in patients with centrotemporal spikes related epileptic syndromes in a Chinese cohort. METHODS Patients with Landau-Kleffner syndrome (LKS), epileptic encephalopathy with continuous spike-and-wave during sleep (ECSWS), atypical benign partial epilepsy (ABPE), and benign epilepsy with centrotemporal spikes (BECTS) were recruited. GRIN2A mutation screening was performed using PCR and Sanger sequencing. RESULTS 122 patients, including 9 LKS, 26 ECSWS, 42 ABPE and 45 BECTS were enrolled. The mean age of seizure or aphasia onset was 5 years, ranging from 10 months to 11 years. Heterozygous GRIN2A mutations were detected in four patients (G760S, D1385Y, C455Y and C231R) GRIN2A mutation was found in 11.1% (1 out of 9 cases) of LKS, and in 7.1% (3 out of 42 cases) of ABPE, but in none with ECSWS and BECTS. No GRIN2A mutation was found in patients with a family history of febrile seizures or epilepsy. CONCLUSION GRIN2A mutation is a genetic cause in less than 11% patients with LKS or ABPE. GRIN2A gene is a rare causative gene in Chinese patients with EAS, suggesting the possibility of other gene involved in the pathogenesis.
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Affiliation(s)
- Xiaoling Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Ping Qian
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Xiaojing Xu
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Xiaoyan Liu
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Xiru Wu
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Yuehua Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, China.
| | - Zhixian Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, China.
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XiangWei W, Jiang Y, Yuan H. De Novo Mutations and Rare Variants Occurring in NMDA Receptors. CURRENT OPINION IN PHYSIOLOGY 2017; 2:27-35. [PMID: 29756080 DOI: 10.1016/j.cophys.2017.12.013] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A significant number of variants/mutations in the N-methyl-D-aspartate glutamatergic receptor (NMDAR) gene family (GRIN) have been identified along with stunning advances in the technologies of next generation of whole-exome sequencing. Mutations in human GRIN genes are distributed throughout the entire gene, from amino terminal domain to C-terminal domain, in patients with various neuropsychiatric disorders, including autism spectrum disorders, epilepsy, intellectual disability, attention deficit hyperactivity disorder, and schizophrenia. Analyzing the currently available human genetic variations illustrates the genetic variation intolerance to missense mutations differs significantly among domains within the GRIN genes. Functional analyses of these mutations and their pharmacological profiles provide the first opportunity to understand the molecular mechanism and targeted therapeutic strategies for these neurological and psychiatric disorders, as well as unfold novel clues to channel function.
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Affiliation(s)
- Wenshu XiangWei
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
| | - Yuwu Jiang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China.,Center of Epilepsy, Beijing Institute for Brain Disorders, Beijing 100069, China
| | - Hongjie Yuan
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA.,Center for Functional Evaluation of Rare Variants (CFERV), Emory University School of Medicine, Atlanta, GA 30322, USA
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Mutations of N-Methyl-D-Aspartate Receptor Subunits in Epilepsy. Neurosci Bull 2017; 34:549-565. [PMID: 29124671 DOI: 10.1007/s12264-017-0191-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 09/19/2017] [Indexed: 01/31/2023] Open
Abstract
Epilepsy is one of the most common neurological diseases. Of all cases, 70%-80% are considered to be due to genetic factors. In recent years, a large number of genes have been identified as being involved in epilepsy. Among them, N-methyl-D-aspartate receptor (NMDAR) subunit-encoding genes represent a large proportion, suggesting an important role for NMDARs in epilepsy. In this review, we summarize and analyze the genotypes, functional alterations, and clinical aspects of NMDAR subunit mutations/variants identified from patients with epilepsy. These data will help to throw light upon the pathogenicity of these NMDAR mutations and advance our understanding of the subtle and complicated role of NMDARs in epilepsy. It will also offer new insights into precision therapy for this disorder.
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Mullier B, Wolff C, Sands ZA, Ghisdal P, Muglia P, Kaminski RM, André VM. GRIN2B gain of function mutations are sensitive to radiprodil, a negative allosteric modulator of GluN2B-containing NMDA receptors. Neuropharmacology 2017; 123:322-331. [DOI: 10.1016/j.neuropharm.2017.05.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 05/12/2017] [Accepted: 05/16/2017] [Indexed: 12/18/2022]
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Xiong W, Zhou D. Progress in unraveling the genetic etiology of rolandic epilepsy. Seizure 2017; 47:99-104. [PMID: 28351718 DOI: 10.1016/j.seizure.2017.02.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 02/22/2017] [Accepted: 02/24/2017] [Indexed: 02/05/2023] Open
Abstract
Rolandic epilepsy (RE), or benign epilepsy of childhood with centrotemporal spikes (BECT), is the most frequent idiopathic partial epilepsy syndrome of childhood, where the "idiopathic" implies a genetic predisposition. Although RE has long been presumed to have a genetic component, clinical and genetic studies have shown a complex inheritance pattern. Furthermore, the underlying major genetic influence in RE has been challenged by recent reports of twin studies. Meanwhile, many genes or loci have been shown to be associated the RE/atypical RE (ARE) spectrum, with a higher frequency of causative variants in ARE. However, a full understanding of the genetic basis in the more common forms of the RE spectrum remains elusive.
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Affiliation(s)
- Weixi Xiong
- Department of Neurology, West China Hospital of Sichuan University, Chengdu, 610041, Sichuan, People's Republic of China
| | - Dong Zhou
- Department of Neurology, West China Hospital of Sichuan University, Chengdu, 610041, Sichuan, People's Republic of China.
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Gao K, Tankovic A, Zhang Y, Kusumoto H, Zhang J, Chen W, XiangWei W, Shaulsky GH, Hu C, Traynelis SF, Yuan H, Jiang Y. A de novo loss-of-function GRIN2A mutation associated with childhood focal epilepsy and acquired epileptic aphasia. PLoS One 2017; 12:e0170818. [PMID: 28182669 PMCID: PMC5300259 DOI: 10.1371/journal.pone.0170818] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Accepted: 01/11/2017] [Indexed: 12/22/2022] Open
Abstract
OBJECTIVE N-methyl-D-aspartate receptors (NMDAR) subunit GRIN2A/GluN2A mutations have been identified in patients with various neurological diseases, such as epilepsy and intellectual disability / developmental delay (ID/DD). In this study, we investigated the phenotype and underlying molecular mechanism of a GRIN2A missense mutation identified by next generation sequencing on idiopathic focal epilepsy using in vitro electrophysiology. METHODS Genomic DNA of patients with epilepsy and ID/DD were sequenced by targeted next-generation sequencing within 300 genes related to epilepsy and ID/DD. The effects of one missense GRIN2A mutation on NMDAR function were evaluated by two-electrode voltage clamp current recordings and whole cell voltage clamp current recordings. RESULTS We identified one de novo missense GRIN2A mutation (Asp731Asn, GluN2A(D731N)) in a child with unexplained epilepsy and DD. The D731N mutation is located in a portion of the agonist-binding domain (ABD) in the GluN2A subunit, which is the binding pocket for agonist glutamate. This residue in the ABD is conserved among vertebrate species and all other NMDAR subunits, suggesting an important role in receptor function. The proband shows developmental delay as well as EEG-confirmed seizure activity. Functional analyses reveal that the GluN2A(D731N) mutation decreases glutamate potency by over 3,000-fold, reduces amplitude of current response, shortens synaptic-like response time course, and decreases channel open probability, while enhancing sensitivity to negative allosteric modulators, including extracellular proton and zinc inhibition. The combined effects reduce NMDAR function. SIGNIFICANCE We identified a de novo missense mutation in the GRIN2A gene in a patient with childhood focal epilepsy and acquired epileptic aphasia. The mutant decreases NMDAR activation suggesting NMDAR hypofunction may contribute to the epilepsy pathogenesis.
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Affiliation(s)
- Kai Gao
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
| | - Anel Tankovic
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, United States of America
| | - Yujia Zhang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
| | - Hirofumi Kusumoto
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, United States of America
| | - Jin Zhang
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, United States of America
| | - Wenjuan Chen
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, United States of America
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Wenshu XiangWei
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
| | - Gil H. Shaulsky
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, United States of America
| | - Chun Hu
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, United States of America
| | - Stephen F. Traynelis
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, United States of America
- Center for Functional Evaluation of Rare Variant (CFERV), Emory University School of Medicine, Atlanta, GA, United States of America
| | - Hongjie Yuan
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, United States of America
- Center for Functional Evaluation of Rare Variant (CFERV), Emory University School of Medicine, Atlanta, GA, United States of America
| | - Yuwu Jiang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
- Center of Epilepsy, Beijing Institute for Brain Disorders, Beijing, China
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Swanger SA, Chen W, Wells G, Burger PB, Tankovic A, Bhattacharya S, Strong KL, Hu C, Kusumoto H, Zhang J, Adams DR, Millichap JJ, Petrovski S, Traynelis SF, Yuan H. Mechanistic Insight into NMDA Receptor Dysregulation by Rare Variants in the GluN2A and GluN2B Agonist Binding Domains. Am J Hum Genet 2016; 99:1261-1280. [PMID: 27839871 PMCID: PMC5142120 DOI: 10.1016/j.ajhg.2016.10.002] [Citation(s) in RCA: 132] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2016] [Accepted: 10/03/2016] [Indexed: 12/30/2022] Open
Abstract
Epilepsy and intellectual disability are associated with rare variants in the GluN2A and GluN2B (encoded by GRIN2A and GRIN2B) subunits of the N-methyl-D-aspartate receptor (NMDAR), a ligand-gated ion channel with essential roles in brain development and function. By assessing genetic variation across GluN2 domains, we determined that the agonist binding domain, transmembrane domain, and the linker regions between these domains were particularly intolerant to functional variation. Notably, the agonist binding domain of GluN2B exhibited significantly more variation intolerance than that of GluN2A. To understand the ramifications of missense variation in the agonist binding domain, we investigated the mechanisms by which 25 rare variants in the GluN2A and GluN2B agonist binding domains dysregulated NMDAR activity. When introduced into recombinant human NMDARs, these rare variants identified in individuals with neurologic disease had complex, and sometimes opposing, consequences on agonist binding, channel gating, receptor biogenesis, and forward trafficking. Our approach combined quantitative assessments of these effects to estimate the overall impact on synaptic and non-synaptic NMDAR function. Interestingly, similar neurologic diseases were associated with both gain- and loss-of-function variants in the same gene. Most rare variants in GluN2A were associated with epilepsy, whereas GluN2B variants were associated with intellectual disability with or without seizures. Finally, discerning the mechanisms underlying NMDAR dysregulation by these rare variants allowed investigations of pharmacologic strategies to correct NMDAR function.
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Affiliation(s)
- Sharon A Swanger
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Wenjuan Chen
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Gordon Wells
- Department of Chemistry, Emory University, Atlanta, GA 30322, USA
| | - Pieter B Burger
- Department of Chemistry, Emory University, Atlanta, GA 30322, USA
| | - Anel Tankovic
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | | | - Katie L Strong
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA; Department of Chemistry, Emory University, Atlanta, GA 30322, USA
| | - Chun Hu
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Hirofumi Kusumoto
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Jing Zhang
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - David R Adams
- Undiagnosed Diseases Network, National Human Genome Research Institute, NIH, Bethesda, MD 20892, USA
| | - John J Millichap
- Departments of Pediatrics and Neurology, Northwestern University Feinberg School of Medicine and Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL 60611, USA
| | - Slavé Petrovski
- Department of Medicine, The University of Melbourne, Austin Health and Royal Melbourne Hospital, Melbourne, VIC 3050, Australia
| | - Stephen F Traynelis
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA; Center for Functional Evaluation of Rare Variants (CFERV), Emory University School of Medicine, Atlanta, GA 30322, USA.
| | - Hongjie Yuan
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA; Center for Functional Evaluation of Rare Variants (CFERV), Emory University School of Medicine, Atlanta, GA 30322, USA.
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15
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Singh D, Lau M, Ayers T, Singh Y, Akingbola O, Barbiero L, Nelson S. De Novo Heterogeneous Mutations in SCN2A and GRIN2A Genes and Seizures With Ictal Vocalizations. Clin Pediatr (Phila) 2016; 55:867-70. [PMID: 26283219 DOI: 10.1177/0009922815601060] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Dinesh Singh
- Tulane University School of Medicine, New Orleans, LA, USA
| | - Monica Lau
- Tulane University School of Medicine, New Orleans, LA, USA
| | - Travis Ayers
- Tulane University School of Medicine, New Orleans, LA, USA
| | - Yashna Singh
- Tulane University School of Medicine, New Orleans, LA, USA
| | | | - Lisa Barbiero
- Tulane University School of Medicine, New Orleans, LA, USA
| | - Stephen Nelson
- Tulane University School of Medicine, New Orleans, LA, USA
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16
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Myers C, Mefford H. Genetic investigations of the epileptic encephalopathies. PROGRESS IN BRAIN RESEARCH 2016; 226:35-60. [DOI: 10.1016/bs.pbr.2016.04.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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18
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Abstract
Epilepsy is a group of disorders characterized by recurrent seizures, and is one of the most common neurological conditions. The genetic basis of epilepsy is clear from epidemiological studies and from rare gene discoveries in large families. The three major classes of epilepsy disorders are genetic generalized, focal and encephalopathic epilepsies, with several specific disorders within each class. Advances in genomic technologies that facilitate genome-wide discovery of both common and rare variants have led to a rapid increase in our understanding of epilepsy genetics. Copy number variant and genome-wide association studies have contributed to our understanding of the complex genetic architecture of generalized epilepsy, while genetic insights into the focal epilepsies and epileptic encephalopathies have come primarily from exome sequencing. It is increasingly clear that epilepsy is genetically heterogeneous, and novel gene discoveries have moved the field beyond the known contribution of ion channels to implicate chromatin remodeling, transcriptional regulation and regulation of the mammalian target of rapamycin (mTOR) protein in the etiology of epilepsy. Such discoveries pave the way for new therapeutics, some of which are already being studied. In this review, we discuss the rapid pace of gene discovery in epilepsy, as facilitated by genomic technologies, and highlight several novel genes and potential therapies.
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Affiliation(s)
- Candace T Myers
- Department of Pediatrics, Division of Genetic Medicine, University of Washington, Seattle, WA, 98195, USA
| | - Heather C Mefford
- Department of Pediatrics, Division of Genetic Medicine, University of Washington, Seattle, WA, 98195, USA.
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19
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Yuan H, Low CM, Moody OA, Jenkins A, Traynelis SF. Ionotropic GABA and Glutamate Receptor Mutations and Human Neurologic Diseases. Mol Pharmacol 2015; 88:203-17. [PMID: 25904555 PMCID: PMC4468639 DOI: 10.1124/mol.115.097998] [Citation(s) in RCA: 153] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 04/22/2015] [Indexed: 01/03/2023] Open
Abstract
The advent of whole exome/genome sequencing and the technology-driven reduction in the cost of next-generation sequencing as well as the introduction of diagnostic-targeted sequencing chips have resulted in an unprecedented volume of data directly linking patient genomic variability to disorders of the brain. This information has the potential to transform our understanding of neurologic disorders by improving diagnoses, illuminating the molecular heterogeneity underlying diseases, and identifying new targets for therapeutic treatment. There is a strong history of mutations in GABA receptor genes being involved in neurologic diseases, particularly the epilepsies. In addition, a substantial number of variants and mutations have been found in GABA receptor genes in patients with autism, schizophrenia, and addiction, suggesting potential links between the GABA receptors and these conditions. A new and unexpected outcome from sequencing efforts has been the surprising number of mutations found in glutamate receptor subunits, with the GRIN2A gene encoding the GluN2A N-methyl-d-aspartate receptor subunit being most often affected. These mutations are associated with multiple neurologic conditions, for which seizure disorders comprise the largest group. The GluN2A subunit appears to be a locus for epilepsy, which holds important therapeutic implications. Virtually all α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor mutations, most of which occur within GRIA3, are from patients with intellectual disabilities, suggesting a link to this condition. Similarly, the most common phenotype for kainate receptor variants is intellectual disability. Herein, we summarize the current understanding of disease-associated mutations in ionotropic GABA and glutamate receptor families, and discuss implications regarding the identification of human mutations and treatment of neurologic diseases.
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Affiliation(s)
- Hongjie Yuan
- Departments of Pharmacology (H.Y., A.J., S.F.T.) and Anesthesiology (O.A.M., A.J.), Emory University School of Medicine, Rollins Research Center, Atlanta, Georgia; and Departments of Pharmacology and Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore Graduate School for Integrative Sciences and Engineering, and Neurobiology/Ageing Programme, National University of Singapore, Singapore (C.-M.L.)
| | - Chian-Ming Low
- Departments of Pharmacology (H.Y., A.J., S.F.T.) and Anesthesiology (O.A.M., A.J.), Emory University School of Medicine, Rollins Research Center, Atlanta, Georgia; and Departments of Pharmacology and Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore Graduate School for Integrative Sciences and Engineering, and Neurobiology/Ageing Programme, National University of Singapore, Singapore (C.-M.L.)
| | - Olivia A Moody
- Departments of Pharmacology (H.Y., A.J., S.F.T.) and Anesthesiology (O.A.M., A.J.), Emory University School of Medicine, Rollins Research Center, Atlanta, Georgia; and Departments of Pharmacology and Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore Graduate School for Integrative Sciences and Engineering, and Neurobiology/Ageing Programme, National University of Singapore, Singapore (C.-M.L.)
| | - Andrew Jenkins
- Departments of Pharmacology (H.Y., A.J., S.F.T.) and Anesthesiology (O.A.M., A.J.), Emory University School of Medicine, Rollins Research Center, Atlanta, Georgia; and Departments of Pharmacology and Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore Graduate School for Integrative Sciences and Engineering, and Neurobiology/Ageing Programme, National University of Singapore, Singapore (C.-M.L.)
| | - Stephen F Traynelis
- Departments of Pharmacology (H.Y., A.J., S.F.T.) and Anesthesiology (O.A.M., A.J.), Emory University School of Medicine, Rollins Research Center, Atlanta, Georgia; and Departments of Pharmacology and Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore Graduate School for Integrative Sciences and Engineering, and Neurobiology/Ageing Programme, National University of Singapore, Singapore (C.-M.L.)
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20
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Lesca G, Depienne C. Epilepsy genetics: the ongoing revolution. Rev Neurol (Paris) 2015; 171:539-57. [PMID: 26003806 DOI: 10.1016/j.neurol.2015.01.569] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 12/24/2014] [Accepted: 01/20/2015] [Indexed: 01/04/2023]
Abstract
Epilepsies have long remained refractory to gene identification due to several obstacles, including a highly variable inter- and intrafamilial expressivity of the phenotypes, a high frequency of phenocopies, and a huge genetic heterogeneity. Recent technological breakthroughs, such as array comparative genomic hybridization and next generation sequencing, have been leading, in the past few years, to the identification of an increasing number of genomic regions and genes in which mutations or copy-number variations cause various epileptic disorders, revealing an enormous diversity of pathophysiological mechanisms. The field that has undergone the most striking revolution is that of epileptic encephalopathies, for which most of causing genes have been discovered since the year 2012. Some examples are the continuous spike-and-waves during slow-wave sleep and Landau-Kleffner syndromes for which the recent discovery of the role of GRIN2A mutations has finally confirmed the genetic bases. These new technologies begin to be used for diagnostic applications, and the main challenge now resides in the interpretation of the huge mass of variants detected by these methods. The identification of causative mutations in epilepsies provides definitive confirmation of the clinical diagnosis, allows accurate genetic counselling, and sometimes permits the development of new appropriate and specific antiepileptic therapies. Future challenges include the identification of the genetic or environmental factors that modify the epileptic phenotypes caused by mutations in a given gene and the understanding of the role of somatic mutations in sporadic epilepsies.
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Affiliation(s)
- G Lesca
- Service de génétique, groupement hospitalier Est, hospices civils de Lyon, 59, boulevard Pinel, 69677 Bron, France; Université Claude-Bernard Lyon 1, 43, boulevard du 11-Novembre-1918, 69100 Villeurbanne, France; CRNL, CNRS UMR 5292, Inserm U1028, bâtiment IMBL, 11, avenue Jean-Capelle, 69621 Villeurbanne cedex, France.
| | - C Depienne
- Département de génétique et cytogénétique, hôpital Pitié-Salpêtrière, AP-HP, 47-83, boulevard de l'Hôpital, 75651 Paris cedex 13, France; Sorbonne universités, UPMC université Paris 06, 4, place Jussieu, 75005 Paris, France; ICM, CNRS UMR 7225, Inserm U1127, 47, boulevard de l'Hôpital, 75651 Paris cedex 13, France
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21
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Insights into the genetic foundations of human communication. Neuropsychol Rev 2015; 25:3-26. [PMID: 25597031 DOI: 10.1007/s11065-014-9277-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 12/22/2014] [Indexed: 12/19/2022]
Abstract
The human capacity to acquire sophisticated language is unmatched in the animal kingdom. Despite the discontinuity in communicative abilities between humans and other primates, language is built on ancient genetic foundations, which are being illuminated by comparative genomics. The genetic architecture of the language faculty is also being uncovered by research into neurodevelopmental disorders that disrupt the normally effortless process of language acquisition. In this article, we discuss the strategies that researchers are using to reveal genetic factors contributing to communicative abilities, and review progress in identifying the relevant genes and genetic variants. The first gene directly implicated in a speech and language disorder was FOXP2. Using this gene as a case study, we illustrate how evidence from genetics, molecular cell biology, animal models and human neuroimaging has converged to build a picture of the role of FOXP2 in neurodevelopment, providing a framework for future endeavors to bridge the gaps between genes, brains and behavior.
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22
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Burnashev N, Szepetowski P. NMDA receptor subunit mutations in neurodevelopmental disorders. Curr Opin Pharmacol 2014; 20:73-82. [PMID: 25498981 DOI: 10.1016/j.coph.2014.11.008] [Citation(s) in RCA: 140] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 11/24/2014] [Accepted: 11/25/2014] [Indexed: 12/21/2022]
Abstract
N-Methyl-D-aspartate receptors (NMDARs) are glutamate-gated cation channels that are expressed throughout the brain and play essential role in brain functioning. Diversity of the subunits and of their spatio-temporal expression imparts distinct functional properties for the particular NMDAR in a particular brain region and developmental stage. Mutations in NMDARs may have pathological consequences and actually lead to various neurological disorders. Recent human genetic studies as highlighted here show the existence of multiple alterations in NMDARs subunits genes in several usual and common brain diseases, such as intellectual disability, autism spectrum disorders (ASD), or epilepsy. Relation of a particular mutation to the corresponding alteration of NMDARs function may provide an avenue to the targeted therapy for the pharmacological treatment of the disorders.
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Affiliation(s)
- Nail Burnashev
- INSERM UMR_S901, Marseille, France; Mediterranean Institute of Neurobiology (INMED), Marseille, France; Aix-Marseille University, Marseille, France.
| | - Pierre Szepetowski
- INSERM UMR_S901, Marseille, France; Mediterranean Institute of Neurobiology (INMED), Marseille, France; Aix-Marseille University, Marseille, France; French Epilepsy, Language and Development (EPILAND) Network, France.
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23
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Venkateswaran S, Myers KA, Smith AC, Beaulieu CL, Schwartzentruber JA, Majewski J, Bulman D, Boycott KM, Dyment DA. Whole-exome sequencing in an individual with severe global developmental delay and intractable epilepsy identifies a novel, de novoGRIN2Amutation. Epilepsia 2014; 55:e75-9. [DOI: 10.1111/epi.12663] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/18/2014] [Indexed: 01/06/2023]
Affiliation(s)
- Sunita Venkateswaran
- Division of Neurology; Children's Hospital of Eastern Ontario; Ottawa Ontario Canada
| | - Ken A. Myers
- Department of Pediatric Neurology; Alberta Children's Hospital; Calgary Alberta Canada
| | - Amanda C. Smith
- Children's Hospital of Eastern Ontario Research Institute; Ottawa Ontario Canada
| | - Chandree L. Beaulieu
- Children's Hospital of Eastern Ontario Research Institute; Ottawa Ontario Canada
| | | | - Jacek Majewski
- McGill University and Genome Quebec Innovation Centre; Montréal Québec Canada
| | - Dennis Bulman
- Children's Hospital of Eastern Ontario Research Institute; Ottawa Ontario Canada
| | - Kym M. Boycott
- Children's Hospital of Eastern Ontario Research Institute; Ottawa Ontario Canada
- Department of Genetics; Children's Hospital of Eastern Ontario; Ottawa Ontario Canada
| | - David A. Dyment
- Children's Hospital of Eastern Ontario Research Institute; Ottawa Ontario Canada
- Department of Genetics; Children's Hospital of Eastern Ontario; Ottawa Ontario Canada
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