GRIN2A mutations in acquired epileptic aphasia and related childhood focal epilepsies and encephalopathies with speech and language dysfunction.
Gaetan Lesca, Gabrielle Rudolf1, Nadine Bruneau, Natalia Lozovaya, Audrey Labalme2, Nadia Boutry-Kryza3, Manal Salmi, Timur Tsintsadze, Laura Addis4, Jacques Motte5, Sukhvir Wright6, Vera Tsintsadze7, Vera Tsintsadze8, Vera Tsintsadze3, Anne Michel, Diane Doummar, Karine Lascelles9, Lisa J. Strug10, Patrick Waters6, Julitta de Bellescize, Pascal Vrielynck11, Anne de Saint Martin1, Dorothée Ville, Philippe Ryvlin3, Alexis Arzimanoglou3, Edouard Hirsch1, Angela Vincent6, Deb K. Pal4, Nail Burnashev, Damien Sanlaville, Pierre Szepetowski •
TL;DR: It is demonstrated that about 20% of cases of LKS, CSWSS and electroclinically atypical rolandic epilepsy often associated with speech impairment can have a genetic origin sustained by de novo or inherited mutations in the GRIN2A gene (encoding the N-methyl-D-aspartate (NMDA) glutamate receptor α2 subunit, GluN2A).
Abstract: Pierre Szepetowski and colleagues report the identification of mutations in GRIN2A in individuals with acquired epileptic aphasia and related childhood focal epilepsies and encephalopathies with speech and language dysfunction.
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TL;DR: Gene discovery provides the basis for neurobiological insights, often showing convergence of mechanistic pathways that underpin the development of targeted therapies, which are essential to improve the outcome of these devastating disorders.
Abstract: Epileptic encephalopathies of infancy and childhood comprise a large, heterogeneous group of severe epilepsies characterised by several seizure types, frequent epileptiform activity on EEG, and developmental slowing or regression. The encephalopathies include many age-related electroclinical syndromes with specific seizure types and EEG features. With the molecular revolution, the number of known monogenic determinants underlying the epileptic encephalopathies has grown rapidly. De-novo dominant mutations are frequently identified; somatic mosaicism and recessive disorders are also seen. Several genes can cause one electroclinical syndrome, and, conversely, one gene might be associated with phenotypic pleiotropy. Diverse genetic causes and molecular pathways have been implicated, involving ion channels, and proteins needed for synaptic, regulatory, and developmental functions. Gene discovery provides the basis for neurobiological insights, often showing convergence of mechanistic pathways. These findings underpin the development of targeted therapies, which are essential to improve the outcome of these devastating disorders.
424 citations
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TL;DR: Exome-sequencing data is analyzed of 356 trios with the "classical" epileptic encephalopathies, infantile spasms and Lennox Gastaut syndrome, finding suggestive evidence for a role of three additional genes, and supporting a prominent role for de novo mutations in epilepsy.
Abstract: Emerging evidence indicates that epileptic encephalopathies are genetically highly heterogeneous, underscoring the need for large cohorts of well-characterized individuals to further define the genetic landscape. Through a collaboration between two consortia (EuroEPINOMICS and Epi4K/EPGP), we analyzed exome-sequencing data of 356 trios with the “classical” epileptic encephalopathies, infantile spasms and Lennox Gastaut syndrome, including 264 trios previously analyzed by the Epi4K/EPGP consortium. In this expanded cohort, we find 429 de novo mutations, including de novo mutations in DNM1 in five individuals and de novo mutations in GABBR2, FASN, and RYR3 in two individuals each. Unlike previous studies, this cohort is sufficiently large to show a significant excess of de novo mutations in epileptic encephalopathy probands compared to the general population using a likelihood analysis (p = 8.2 × 10−4), supporting a prominent role for de novo mutations in epileptic encephalopathies. We bring statistical evidence that mutations in DNM1 cause epileptic encephalopathy, find suggestive evidence for a role of three additional genes, and show that at least 12% of analyzed individuals have an identifiable causal de novo mutation. Strikingly, 75% of mutations in these probands are predicted to disrupt a protein involved in regulating synaptic transmission, and there is a significant enrichment of de novo mutations in genes in this pathway in the entire cohort as well. These findings emphasize an important role for synaptic dysregulation in epileptic encephalopathies, above and beyond that caused by ion channel dysfunction.
365 citations
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Gemma L. Carvill1, Brigid M. Regan2, Simone C. Yendle2, Brian J. O'Roak1, Natalia Lozovaya, Nadine Bruneau, Nail Burnashev, Adiba Khan1, Joseph Cook1, Eileen Geraghty1, Lynette G. Sadleir3, Samantha J. Turner2, Meng-Han Tsai2, Richard Webster4, Robert A. Ouvrier4, John A. Damiano2, Samuel F. Berkovic2, Jay Shendure1, Michael S. Hildebrand2, Pierre Szepetowski, Ingrid E. Scheffer5, Ingrid E. Scheffer2, Heather C Mefford1 •
TL;DR: The first monogenic cause, to the authors' knowledge, for EAS is reported and GRIN2A mutations are restricted to this group of cases, which has important ramifications for diagnostic testing and treatment and provides new insights into the pathogenesis of this debilitating group of conditions.
Abstract: Epilepsy-aphasia syndromes (EAS) are a group of rare, severe epileptic encephalopathies of unknown etiology with a characteristic electroencephalogram (EEG) pattern and developmental regression particularly affecting language. Rare pathogenic deletions that include GRIN2A have been implicated in neurodevelopmental disorders. We sought to delineate the pathogenic role of GRIN2A in 519 probands with epileptic encephalopathies with diverse epilepsy syndromes. We identified four probands with GRIN2A variants that segregated with the disorder in their families. Notably, all four families presented with EAS, accounting for 9% of epilepsy-aphasia cases. We did not detect pathogenic variants in GRIN2A in other epileptic encephalopathies (n = 475) nor in probands with benign childhood epilepsy with centrotemporal spikes (n = 81). We report the first monogenic cause, to our knowledge, for EAS. GRIN2A mutations are restricted to this group of cases, which has important ramifications for diagnostic testing and treatment and provides new insights into the pathogenesis of this debilitating group of conditions.
312 citations
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Tyler Mark Pierson1, Hongjie Yuan2, Eric D. Marsh3, Karin Fuentes-Fajardo, David R. Adams, Thomas C. Markello, Gretchen Golas, Dimitre R. Simeonov, Conisha Holloman, Anel Tankovic2, Manish M. Karamchandani2, John M. Schreiber, James C. Mullikin, Cynthia J. Tifft3, Camilo Toro3, Cornelius F. Boerkoel3, Stephen F. Traynelis2, William A Gahl3 •
TL;DR: Techniques of modern translational medicine are employed to identify a disease‐causing mutation, analyze its altered behavior, and screen for therapeutic compounds to treat the proband.
Abstract: Objective
Early-onset epileptic encephalopathies have been associated with de novo mutations of numerous ion channel genes. We employed techniques of modern translational medicine to identify a disease-causing mutation, analyze its altered behavior, and screen for therapeutic compounds to treat the proband.
Methods
Three modern translational medicine tools were utilized: (1) high-throughput sequencing technology to identify a novel de novo mutation; (2) in vitro expression and electrophysiology assays to confirm the variant protein's dysfunction; and (3) screening of existing drug libraries to identify potential therapeutic compounds.
Results
A de novo GRIN2A missense mutation (c.2434C>A; p.L812M) increased the charge transfer mediated by N-methyl-D-aspartate receptors (NMDAs) containing the mutant GluN2A-L812M subunit. In vitro analysis with NMDA receptor blockers indicated that GLuN2A-L812M-containing NMDARs retained their sensitivity to the use-dependent channel blocker memantine; while screening of a previously reported GRIN2A mutation (N615K) with these compounds produced contrasting results. Consistent with these data, adjunct memantine therapy reduced our proband's seizure burden.
Interpretation
This case exemplifies the potential for personalized genomics and therapeutics to be utilized for the early diagnosis and treatment of infantile-onset neurological disease.
244 citations
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TL;DR: These factors have been separately linked to schizophrenia pathogenesis, but evidence now suggests that they are mechanistically interdependent and contribute to a common schizophrenia-associated pathology.
Abstract: Molecular, genetic and pathological evidence suggests that deficits in GABAergic parvalbumin-positive interneurons contribute to schizophrenia pathophysiology through alterations in the brain's excitation-inhibition balance that result in impaired behaviour and cognition. Although the factors that trigger these deficits are diverse, there is increasing evidence that they converge on a common pathological hub that involves NMDA receptor hypofunction and oxidative stress. These factors have been separately linked to schizophrenia pathogenesis, but evidence now suggests that they are mechanistically interdependent and contribute to a common schizophrenia-associated pathology.
243 citations
References
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Anne T. Berg1, Anne T. Berg2, Samuel F. Berkovic3, Martin J. Brodie4, Jeffrey Buchhalter5, J. Helen Cross6, Walter van Emde Boas7, Jerome Engel8, Jacqueline A. French9, Tracy A. Glauser10, Gary W. Mathern8, Solomon L. Moshé11, Douglas R. Nordli2, Perrine Plouin12, Ingrid E. Scheffer3 •
Northern Illinois University1, Children's Memorial Hospital2, University of Melbourne3, Western Infirmary4, Boston Children's Hospital5, UCL Institute of Child Health6, Bosch7, University of California, Los Angeles8, New York University9, Cincinnati Children's Hospital Medical Center10, Albert Einstein College of Medicine11, University of Paris12
TL;DR: The International League Against Epilepsy (ILAE) Commission on Classification and Terminology has revised concepts, terminology, and approaches for classifying seizures and forms of epilepsy.
Abstract: The International League Against Epilepsy (ILAE) Commission on Classification and Terminology has revised concepts, terminology, and approaches for classifying seizures and forms of epilepsy. Generalized and focal are redefined for seizures as occurring in and rapidly engaging bilaterally distributed networks (generalized) and within networks limited to one hemisphere and either discretely localized or more widely distributed (focal). Classification of generalized seizures is simplified. No natural classification for focal seizures exists; focal seizures should be described according to their manifestations (e. g., dyscognitive, focal motor). The concepts of generalized and focal do not apply to electroclinical syndromes. Genetic, structural-metabolic, and unknown represent modified concepts to replace idiopathic, symptomatic, and cryptogenic. Not all epilepsies are recognized as electroclinical syndromes. Organization of forms of epilepsy is first by specificity: electroclinical syndromes, nonsyndromic epilepsies with structural-metabolic causes, and epilepsies of unknown cause. Further organization within these divisions can be accomplished in a flexible manner depending on purpose. Natural classes (e. g., specific underlying cause, age at onset, associated seizure type), or pragmatic groupings (e. g., epileptic encephalopathies, self-limited electroclinical syndromes) may serve as the basis for organizing knowledge about recognized forms of epilepsy and facilitate identification of new forms.
3,775 citations
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TL;DR: This review discusses International Union of Basic and Clinical Pharmacology glutamate receptor nomenclature, structure, assembly, accessory subunits, interacting proteins, gene expression and translation, post-translational modifications, agonist and antagonist pharmacology, allosteric modulation, mechanisms of gating and permeation, roles in normal physiological function, as well as the potential therapeutic use of pharmacological agents acting at glutamate receptors.
Abstract: The mammalian ionotropic glutamate receptor family encodes 18 gene products that coassemble to form ligand-gated ion channels containing an agonist recognition site, a transmembrane ion permeation pathway, and gating elements that couple agonist-induced conformational changes to the opening or closing of the permeation pore. Glutamate receptors mediate fast excitatory synaptic transmission in the central nervous system and are localized on neuronal and non-neuronal cells. These receptors regulate a broad spectrum of processes in the brain, spinal cord, retina, and peripheral nervous system. Glutamate receptors are postulated to play important roles in numerous neurological diseases and have attracted intense scrutiny. The description of glutamate receptor structure, including its transmembrane elements, reveals a complex assembly of multiple semiautonomous extracellular domains linked to a pore-forming element with striking resemblance to an inverted potassium channel. In this review we discuss International Union of Basic and Clinical Pharmacology glutamate receptor nomenclature, structure, assembly, accessory subunits, interacting proteins, gene expression and translation, post-translational modifications, agonist and antagonist pharmacology, allosteric modulation, mechanisms of gating and permeation, roles in normal physiological function, as well as the potential therapeutic use of pharmacological agents acting at glutamate receptors.
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TL;DR: A well-defined set of clinical characteristics are associated with anti-NMDA-receptor encephalitis and the pathogenesis of the disorder seems to be mediated by antibodies.
Abstract: Summary Background A severe form of encephalitis associated with antibodies against NR1–NR2 heteromers of the NMDA receptor was recently identified. We aimed to analyse the clinical and immunological features of patients with the disorder and examine the effects of antibodies against NMDA receptors in neuronal cultures. Methods We describe the clinical characteristics of 100 patients with encephalitis and NR1–NR2 antibodies. HEK293 cells ectopically expressing single or assembled NR1–NR2 subunits were used to determine the epitope targeted by the antibodies. Antibody titres were measured with ELISA. The effect of antibodies on neuronal cultures was determined by quantitative analysis of NMDA-receptor clusters. Findings Median age of patients was 23 years (range 5–76 years); 91 were women. All patients presented with psychiatric symptoms or memory problems; 76 had seizures, 88 unresponsiveness (decreased conciousness), 86 dyskinesias, 69 autonomic instability, and 66 hypoventilation. 58 (59%) of 98 patients for whom results of oncological assessments were available had tumours, most commonly ovarian teratoma. Patients who received early tumour treatment (usually with immunotherapy) had better outcome (p=0·004) and fewer neurological relapses (p=0·009) than the rest of the patients. 75 patients recovered or had mild deficits and 25 had severe deficits or died. Improvement was associated with a decrease of serum antibody titres. The main epitope targeted by the antibodies is in the extracellular N-terminal domain of the NR1 subunit. Patients' antibodies decreased the numbers of cell-surface NMDA receptors and NMDA-receptor clusters in postsynaptic dendrites, an effect that could be reversed by antibody removal. Interpretation A well-defined set of clinical characteristics are associated with anti-NMDA-receptor encephalitis. The pathogenesis of the disorder seems to be mediated by antibodies. Funding National Institutes for Health, University of Pennsylvania Institute for Translational Medicine, Lankenau Institute for Medical Research, Foederer Foundation of the Children's Hospital of Philadelphia.
2,604 citations
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Joep de Ligt1, Marjolein H. Willemsen, Bregje W.M. van Bon, Tjitske Kleefstra, Helger G. Yntema, Thessa Kroes, Anneke T. Vulto-van Silfhout, David A. Koolen, Petra de Vries, Christian Gilissen, Marisol del Rosario, Alexander Hoischen, Hans Scheffer, Bert B.A. de Vries, Han G. Brunner, Joris A. Veltman, Lisenka E.L.M. Vissers •
TL;DR: De novo mutations represent an important cause of intellectual disability; exome sequencing was used as an effective diagnostic strategy for their detection.
Abstract: Background The causes of intellectual disability remain largely unknown because of extensive clinical and genetic heterogeneity. Methods We evaluated patients with intellectual disability to exclude known causes of the disorder. We then sequenced the coding regions of more than 21,000 genes obtained from 100 patients with an IQ below 50 and their unaffected parents. A data-analysis procedure was developed to identify and classify de novo, autosomal recessive, and X-linked mutations. In addition, we used high-throughput resequencing to confirm new candidate genes in 765 persons with intellectual disability (a confirmation series). All mutations were evaluated by molecular geneticists and clinicians in the context of the patients' clinical presentation. Results We identified 79 de novo mutations in 53 of 100 patients. A total of 10 de novo mutations and 3 X-linked (maternally inherited) mutations that had been previously predicted to compromise the function of known intellectual-disability genes were found in 13 patients. Potentially causative de novo mutations in novel candidate genes were detected in 22 patients. Additional de novo mutations in 3 of these candidate genes were identified in patients with similar phenotypes in the confirmation series, providing support for mutations in these genes as the cause of intellectual disability. We detected no causative autosomal recessive inherited mutations in the discovery series. Thus, the total diagnostic yield was 16%, mostly involving de novo mutations. Conclusions De novo mutations represent an important cause of intellectual disability; exome sequencing was used as an effective diagnostic strategy for their detection. (Funded by the European Union and others.).
1,239 citations
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TL;DR: Overall, the data support a model in which the early features of N-methyl-d-aspartate receptor encephalopathy are associated with cerebrospinal fluid lymphocytosis, and the later features with appearance of oligoclonal bands, which is associated with restriction to the first stage.
Abstract: Antibodies to the N-methyl-d-aspartate subtype of glutamate receptor have been associated with a newly-described encephalopathy that has been mainly identified in young females with ovarian tumours. However, the full clinical spectrum and treatment responses are not yet clear. We established a sensitive cell-based assay for detection of N-methyl-d-aspartate receptor antibodies in serum or cerebrospinal fluid, and a quantitative fluorescent immunoprecipitation assay for serial studies. Although there was marked intrathecal synthesis of N-methyl-d-aspartate receptor antibodies, the absolute levels of N-methyl-d-aspartate receptor antibodies were higher in serum than in cerebrospinal fluid. N-methyl-d-aspartate receptor antibodies were of the immunoglobulin G1 subclass and were able to activate complement on N-methyl d-aspartate receptor-expressing human embryonic kidney cells. From questionnaires returned on 44 N-methyl-d-aspartate receptor antibody-positive patients, we identified a high proportion without a detected tumour (35/44, 80%: follow-up 3.6–121 months, median 16 months). Among the latter were 15 adult females (43%), 10 adult males (29%) and 10 children (29%), with four in the first decade of life. Overall, there was a high proportion (29%) of non-Caucasians. Good clinical outcomes, as defined by reductions in modified Rankin scores, correlated with decreased N-methyl-d-aspartate receptor antibody levels and were associated with early (<40 days) administration of immunotherapies in non-paraneoplastic patients (P < 0.0001) and earlier tumour removal in paraneoplastic patients (P = 0.02). Ten patients (23%) who were first diagnosed during relapses had no evidence of tumours but had received minimal or no immunotherapy during earlier episodes. Temporal analysis of the onset of the neurological features suggested progression through two main stages. The time of onset of the early features, characterized by neuropsychiatric symptoms and seizures preceded by a median of 10–20 days, the onset of movement disorders, reduction in consciousness and dysautonomia. This temporal dichotomy was also seen in the timing of cerebrospinal fluid, electroencephalographic and in the rather infrequent cerebral imaging changes. Overall, our data support a model in which the early features are associated with cerebrospinal fluid lymphocytosis, and the later features with appearance of oligoclonal bands. The immunological events and neuronal mechanisms underlying these observations need to be explored further, but one possibility is that the early stage represents diffusion of serum antibodies into the cortical grey matter, whereas the later stage results from secondary expansion of the immunological repertoire within the intrathecal compartment acting on subcortical neurons. Four patients, who only had temporal lobe epilepsy without oligoclonal bands, may represent restriction to the first stage.
889 citations
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