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Jiao D, Xu L, Gu Z, Yan H, Shen D, Gu X. Pathogenesis, diagnosis, and treatment of epilepsy: electromagnetic stimulation-mediated neuromodulation therapy and new technologies. Neural Regen Res 2025; 20:917-935. [PMID: 38989927 DOI: 10.4103/nrr.nrr-d-23-01444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 01/18/2024] [Indexed: 07/12/2024] Open
Abstract
Epilepsy is a severe, relapsing, and multifactorial neurological disorder. Studies regarding the accurate diagnosis, prognosis, and in-depth pathogenesis are crucial for the precise and effective treatment of epilepsy. The pathogenesis of epilepsy is complex and involves alterations in variables such as gene expression, protein expression, ion channel activity, energy metabolites, and gut microbiota composition. Satisfactory results are lacking for conventional treatments for epilepsy. Surgical resection of lesions, drug therapy, and non-drug interventions are mainly used in clinical practice to treat pain associated with epilepsy. Non-pharmacological treatments, such as a ketogenic diet, gene therapy for nerve regeneration, and neural regulation, are currently areas of research focus. This review provides a comprehensive overview of the pathogenesis, diagnostic methods, and treatments of epilepsy. It also elaborates on the theoretical basis, treatment modes, and effects of invasive nerve stimulation in neurotherapy, including percutaneous vagus nerve stimulation, deep brain electrical stimulation, repetitive nerve electrical stimulation, in addition to non-invasive transcranial magnetic stimulation and transcranial direct current stimulation. Numerous studies have shown that electromagnetic stimulation-mediated neuromodulation therapy can markedly improve neurological function and reduce the frequency of epileptic seizures. Additionally, many new technologies for the diagnosis and treatment of epilepsy are being explored. However, current research is mainly focused on analyzing patients' clinical manifestations and exploring relevant diagnostic and treatment methods to study the pathogenesis at a molecular level, which has led to a lack of consensus regarding the mechanisms related to the disease.
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Affiliation(s)
- Dian Jiao
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Lai Xu
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Zhen Gu
- Key Laboratory of Advanced Drug Delivery Systems of Zhejiang Province, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang Province, China
| | - Hua Yan
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Dingding Shen
- Affiliated Hospital of Nantong University, Nantong, Jiangsu Province, China
| | - Xiaosong Gu
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
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2
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Zhu X, Li P. GABA(A) Receptor Subunit (γ2, δ, β1-3) Variants in Genetic Epilepsy: A Comprehensive Summary of 206 Clinical Cases. J Child Neurol 2024:8830738241273437. [PMID: 39228214 DOI: 10.1177/08830738241273437] [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] [Indexed: 09/05/2024]
Abstract
Epilepsy is identified in individuals who experienced 2 or more unprovoked seizures occurring over 24 hours apart, which can have a profound impact on a person's neurobiological, cognitive, psychological, and social well-being. Epilepsy is considerably diverse, with classifications such as genetic epilepsy that result directly from a known or presumed genetic variant with the core symptoms of seizures. The GABAA receptor primarily functions as a heteropentamer, containing 3 of 8 subunit types: α, β, γ, δ, ε, π, θ, and ρ. In the adult brain, the GABAA receptor is the primary inhibitory component in neural networks. The involvement of GABAA receptors in the pathogenesis of epilepsy has been proposed. We extensively reviewed all relevant clinical data of previously published cases of GABAA receptor subunit γ2, δ, β1-3 variants included in PubMed up to February 2024, including the variant types, loci, postulated mechanisms, their relevant regions, first onset ages, and phenotypes. We summarized the postulated mechanisms of epileptic pathogenesis. We also divided the collected 206 cases of epilepsy into 4 epileptic phenotypes: genetic generalized epilepsies, focal epilepsy, developmental and epileptic encephalopathies, and epilepsy with fever sensibility. We showed that there were significant differences in the likelihood of the γ2, β2, and β3 subunit variants causing genetic generalized epilepsies, focal epilepsy, developmental and epileptic encephalopathies, and epilepsy with fever sensibility. Patients with the β3 subunit variant seemed related to an earlier first onset age. Our review supports that GABAA receptor subunit variants are a crucial area of epilepsy research and treatment exploration.
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Affiliation(s)
- Xinyi Zhu
- The Second School of Medicine, Wenzhou Medical University, Wenzhou, China
| | - Peijun Li
- Shandong Institute of Brain Science and Brain-inspired Research, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, China
- Department of Neurology, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China
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3
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Hernandez CC, Hu N, Shen W, Macdonald RL. Epileptic Encephalopathy GABRB Structural Variants Share Common Gating and Trafficking Defects. Biomolecules 2023; 13:1790. [PMID: 38136660 PMCID: PMC10741827 DOI: 10.3390/biom13121790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 12/08/2023] [Accepted: 12/12/2023] [Indexed: 12/24/2023] Open
Abstract
Variants in the GABRB gene, which encodes the β subunit of the GABAA receptor, have been implicated in various epileptic encephalopathies and related neurodevelopmental disorders such as Dravet syndrome and Angelman syndrome. These conditions are often associated with early-onset seizures, developmental regression, and cognitive impairments. The severity and specific features of these encephalopathies can differ based on the nature of the genetic variant and its impact on GABAA receptor function. These variants can lead to dysfunction in GABAA receptor-mediated inhibition, resulting in an imbalance between neuronal excitation and inhibition that contributes to the development of seizures. Here, 13 de novo EE-associated GABRB variants, occurring as missense mutations, were analyzed to determine their impact on protein stability and flexibility, channel function, and receptor biogenesis. Our results showed that all mutations studied significantly impact the protein structure, altering protein stability, flexibility, and function to varying degrees. Variants mapped to the GABA-binding domain, coupling zone, and pore domain significantly impact the protein structure, modifying the β+/α- interface of the receptor and altering channel activation and receptor trafficking. Our study proposes that the extent of loss or gain of GABAA receptor function can be elucidated by identifying the specific structural domain impacted by mutation and assessing the variability in receptor structural dynamics. This paves the way for future studies to explore and uncover links between the incidence of a variant in the receptor topology and the severity of the related disease.
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Affiliation(s)
- Ciria C. Hernandez
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Ningning Hu
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; (N.H.); (W.S.); (R.L.M.)
| | - Wangzhen Shen
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; (N.H.); (W.S.); (R.L.M.)
| | - Robert L. Macdonald
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; (N.H.); (W.S.); (R.L.M.)
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4
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Absalom NL, Lin SXN, Liao VWY, Chua HC, Møller RS, Chebib M, Ahring PK. GABA A receptors in epilepsy: Elucidating phenotypic divergence through functional analysis of genetic variants. J Neurochem 2023. [PMID: 37621067 DOI: 10.1111/jnc.15932] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Revised: 07/27/2023] [Accepted: 08/01/2023] [Indexed: 08/26/2023]
Abstract
Normal brain function requires a tightly regulated balance between excitatory and inhibitory neurotransmissions. γ-Aminobutyric acid type A (GABAA ) receptors represent the major class of inhibitory ion channels in the mammalian brain. Dysregulation of these receptors and/or their associated pathways is strongly implicated in the pathophysiology of epilepsy. To date, hundreds of different GABAA receptor subunit variants have been associated with epilepsy, making them a prominent cause of genetically linked epilepsy. While identifying these genetic variants is crucial for accurate diagnosis and effective genetic counselling, it does not necessarily lead to improved personalised treatment options. This is because the identification of a variant does not reveal how the function of GABAA receptors is affected. Genetic variants in GABAA receptor subunits can cause complex changes to receptor properties resulting in various degrees of gain-of-function, loss-of-function or a combination of both. Understanding how variants affect the function of GABAA receptors therefore represents an important first step in the ongoing development of precision therapies. Furthermore, it is important to ensure that functional data are produced using methodologies that allow genetic variants to be classified using clinical guidelines such as those developed by the American College of Medical Genetics and Genomics. This article will review the current knowledge in the field and provide recommendations for future functional analysis of genetic GABAA receptor variants.
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Affiliation(s)
- Nathan L Absalom
- School of Science, University of Western Sydney, Sydney, New South Wales, Australia
- Brain and Mind Centre, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Susan X N Lin
- Brain and Mind Centre, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Vivian W Y Liao
- Brain and Mind Centre, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Han C Chua
- Brain and Mind Centre, Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Medicine, The Danish Epilepsy Centre, Filadelfia, Dianalund, Denmark
- Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
| | - Mary Chebib
- Brain and Mind Centre, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Philip K Ahring
- Brain and Mind Centre, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
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Brünger T, Pérez-Palma E, Montanucci L, Nothnagel M, Møller RS, Schorge S, Zuberi S, Symonds J, Lemke JR, Brunklaus A, Traynelis SF, May P, Lal D. Conserved patterns across ion channels correlate with variant pathogenicity and clinical phenotypes. Brain 2023; 146:923-934. [PMID: 36036558 PMCID: PMC9976975 DOI: 10.1093/brain/awac305] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 07/29/2022] [Accepted: 08/09/2022] [Indexed: 11/13/2022] Open
Abstract
Clinically identified genetic variants in ion channels can be benign or cause disease by increasing or decreasing the protein function. As a consequence, therapeutic decision-making is challenging without molecular testing of each variant. Our biophysical knowledge of ion-channel structures and function is just emerging, and it is currently not well understood which amino acid residues cause disease when mutated. We sought to systematically identify biological properties associated with variant pathogenicity across all major voltage and ligand-gated ion-channel families. We collected and curated 3049 pathogenic variants from hundreds of neurodevelopmental and other disorders and 12 546 population variants for 30 ion channel or channel subunits for which a high-quality protein structure was available. Using a wide range of bioinformatics approaches, we computed 163 structural features and tested them for pathogenic variant enrichment. We developed a novel 3D spatial distance scoring approach that enables comparisons of pathogenic and population variant distribution across protein structures. We discovered and independently replicated that several pore residue properties and proximity to the pore axis were most significantly enriched for pathogenic variants compared to population variants. Using our 3D scoring approach, we showed that the strongest pathogenic variant enrichment was observed for pore-lining residues and alpha-helix residues within 5Å distance from the pore axis centre and not involved in gating. Within the subset of residues located at the pore, the hydrophobicity of the pore was the feature most strongly associated with variant pathogenicity. We also found an association between the identified properties and both clinical phenotypes and functional in vitro assays for voltage-gated sodium channels (SCN1A, SCN2A, SCN8A) and N-methyl-D-aspartate receptor (GRIN1, GRIN2A, GRIN2B) encoding genes. In an independent expert-curated dataset of 1422 neurodevelopmental disorder pathogenic patient variants and 679 electrophysiological experiments, we show that pore axis distance is associated with seizure age of onset and cognitive performance as well as differential gain versus loss-of-channel function. In summary, we identified biological properties associated with ion-channel malfunction and show that these are correlated with in vitro functional readouts and clinical phenotypes in patients with neurodevelopmental disorders. Our results suggest that clinical decision support algorithms that predict variant pathogenicity and function are feasible in the future.
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Affiliation(s)
- Tobias Brünger
- Cologne Center for Genomics, University of Cologne, 50931 Cologne, Germany
| | - Eduardo Pérez-Palma
- Centro de Genética y Genómica, Facultad de Medicina Clínica Alemana, Universidad de Desarrollo, Santiago 7590943, Chile
| | - Ludovica Montanucci
- Lerner Research Institute Cleveland Clinic, Genomic Medicine Institute, Cleveland, OH 44195, USA
| | - Michael Nothnagel
- Cologne Center for Genomics, University of Cologne, 50931 Cologne, Germany
- University Hospital Cologne, 50937 Cologne, Germany
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Treatment, the Danish Epilepsy Center, DK 4293 Dianalund, Denmark
| | - Stephanie Schorge
- Department of Neuroscience, Physiology and Pharmacology, UCL, London WC1E 6BT, UK
| | - Sameer Zuberi
- The Paediatric Neurosciences Research Group, Royal Hospital for Children, Glasgow, UK
- Institute of Health and Wellbeing, University of Glasgow, UK
| | - Joseph Symonds
- The Paediatric Neurosciences Research Group, Royal Hospital for Children, Glasgow, UK
- Institute of Health and Wellbeing, University of Glasgow, UK
| | - Johannes R Lemke
- Institute of Human Genetics, University of Leipzig Medical Center, 04103 Leipzig, Germany
- Center for Rare Diseases, University of Leipzig Medical Center, 04103 Leipzig, Germany
| | - Andreas Brunklaus
- The Paediatric Neurosciences Research Group, Royal Hospital for Children, Glasgow, UK
- Institute of Health and Wellbeing, University of Glasgow, UK
| | - Stephen F Traynelis
- Department of Pharmacology, Emory University School of Medicine, Rollins Research Center, Atlanta, GA 30322-3090, USA
| | - Patrick May
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, L-4362 Esch-sur-Alzette, Luxembourg
| | - Dennis Lal
- Cologne Center for Genomics, University of Cologne, 50931 Cologne, Germany
- Lerner Research Institute Cleveland Clinic, Genomic Medicine Institute, Cleveland, OH 44195, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Epilepsy Center, Neurological Institute, Cleveland Clinic, Cleveland, OH 44195, USA
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6
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Gallagher MJ. No Gain, Less Pain: GABRB3 Mutations in Epileptic Encephalopathy. Epilepsy Curr 2023; 23:44-46. [PMID: 36923344 PMCID: PMC10009129 DOI: 10.1177/15357597221130199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Gain-of-Function and Loss-of-Function GABRB3 Variants Lead to Distinct Clinical Phenotypes in Patients With Developmental and Epileptic Encephalopathies Absalom NL, Liao VW, Johannesen KM, Gardella E, Jacobs J, Lesca G, Gokce-Samar Z, Arzimanoglou A, Zeidler S, Striano P, Meyer P, Benkel-Herrenbrueck I, Mero I-L, Rummel J, Chebib M, Møller RS, Ahring PK. Nat Commun. 2022;13(1):1822. doi:10.1038/s41467-022-29280-x Many patients with developmental and epileptic encephalopathies present with variants in genes coding for GABAA receptors. These variants are presumed to cause loss-of-function receptors leading to reduced neuronal GABAergic activity. Yet, patients with GABAA receptor variants have diverse clinical phenotypes and many are refractory to treatment despite the availability of drugs that enhance GABAergic activity. Here we show that 44 pathogenic GABRB3 missense variants segregate into gain-of-function and loss-of-function groups and respective patients display distinct clinical phenotypes. The gain-of-function cohort (n = 27 patients) presented with a younger age of seizure onset, higher risk of severe intellectual disability, focal seizures at onset, hypotonia, and lower likelihood of seizure freedom in response to treatment. Febrile seizures at onset are exclusive to the loss-of-function cohort (n = 47 patients). Overall, patients with GABRB3 variants that increase GABAergic activity have more severe developmental and epileptic encephalopathies. This paradoxical finding challenges our current understanding of the GABAergic system in epilepsy and how patients should be treated.
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7
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Castellano D, Wu K, Keramidas A, Lu W. Shisa7-Dependent Regulation of GABA A Receptor Single-Channel Gating Kinetics. J Neurosci 2022; 42:8758-8766. [PMID: 36216503 PMCID: PMC9698691 DOI: 10.1523/jneurosci.0510-22.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 08/19/2022] [Accepted: 09/27/2022] [Indexed: 12/29/2022] Open
Abstract
GABAA receptors (GABAARs) mediate the majority of fast inhibitory transmission throughout the brain. Although it is widely known that pore-forming subunits critically determine receptor function, it is unclear whether their single-channel properties are modulated by GABAAR-associated transmembrane proteins. We previously identified Shisa7 as a GABAAR auxiliary subunit that modulates the trafficking, pharmacology, and deactivation properties of these receptors. However, whether Shisa7 also regulates GABAAR single-channel properties has yet to be determined. Here, we performed single-channel recordings of α2β3γ2L GABAARs cotransfected with Shisa7 in HEK293T cells and found that while Shisa7 does not change channel slope conductance, it reduced the frequency of receptor openings. Importantly, Shisa7 modulates GABAAR gating by decreasing the duration and open probability within bursts. Through kinetic analysis of individual dwell time components, activation modeling, and macroscopic simulations, we demonstrate that Shisa7 accelerates GABAAR deactivation by governing the time spent between close and open states during gating. Together, our data provide a mechanistic basis for how Shisa7 controls GABAAR gating and reveal for the first time that GABAAR single-channel properties can be modulated by an auxiliary subunit. These findings shed light on processes that shape the temporal dynamics of GABAergic transmission.SIGNIFICANCE STATEMENT Although GABAA receptor (GABAAR) single-channel properties are largely determined by pore-forming subunits, it remains unknown whether they are also controlled by GABAAR-associated transmembrane proteins. Here, we show that Shisa7, a recently identified GABAAR auxiliary subunit, modulates GABAAR activation by altering single-channel burst kinetics. These results reveal that Shisa7 primarily decreases the duration and open probability of receptor burst activity during gating, leading to accelerated GABAAR deactivation. These experiments are the first to assess the gating properties of GABAARs in the presence of an auxiliary subunit and provides a kinetic basis for how Shisa7 modifies temporal attributes of GABAergic transmission at the single-channel level.
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Affiliation(s)
- David Castellano
- Synapse and Neural Circuit Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
| | - Kunwei Wu
- Synapse and Neural Circuit Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
| | - Angelo Keramidas
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Wei Lu
- Synapse and Neural Circuit Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
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GABA A receptor proline 273 at the interdomain interface of the β 2 subunit regulates entry into desensitization and opening/closing transitions. Life Sci 2022; 308:120943. [PMID: 36096246 DOI: 10.1016/j.lfs.2022.120943] [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: 05/31/2022] [Revised: 08/29/2022] [Accepted: 09/06/2022] [Indexed: 11/23/2022]
Abstract
AIMS GABAA receptors belong to Cys-loop ion channel family and mediate inhibition in the brain. Despite the abundance of structural data on receptor structure, the molecular scenarios of activation are unknown. In this study we investigated the role of a β2P273 residue in channel gating transitions. This residue is located in a central position of the M2-M3 linker of the interdomain interface, expected to be predisposed to interact with another interfacial element, the β1-β2 loop of the extracellular side. The interactions occurring on this interface have been reported to couple agonist binding to channel gating. MAIN METHODS We recorded micro- and macroscopic current responses of recombinant GABAA receptors mutated at the β2P273 residue (to A, K, E) to saturating GABA. Electrophysiological data served as basis to kinetic modeling, used to decipher which gating transition were affected by mutations. KEY FINDINGS Mutations of this residue impaired macroscopic desensitization and accelerated current deactivation with P273E mutant showing greatest deviation from wild-type. Single-channel analysis revealed alterations mainly in short-lived shut times and shortening of openings, resulting in dramatic changes in intraburst open probability. Kinetic modeling indicated that β2P273 mutants show diminished entry into desensitized and open states as well as faster channel closing transitions. SIGNIFICANCE In conclusion, we demonstrate that β2P273 of the M2-M3 linker is a crucial element of the ECD-TMD interface regulating the receptor's ability to undergo late gating transitions. Henceforth, this region could be an important target for new pharmacological tools affecting GABAAR-mediated inhibition.
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Yang Y, Zeng Q, Cheng M, Niu X, Xiangwei W, Gong P, Li W, Ma J, Zhang X, Yang X, Yang Z, Sun D, Zhou S, Liao J, Jiang Y, Zhang Y. GABRB3-related epilepsy: novel variants, clinical features and therapeutic implications. J Neurol 2022; 269:2649-2665. [PMID: 34698933 DOI: 10.1007/s00415-021-10834-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 09/28/2021] [Accepted: 09/29/2021] [Indexed: 02/08/2023]
Abstract
OBJECTIVE This study aimed to comprehensively examine the genetic and phenotypic aspects of GABRB3-related epilepsy and to explore the potential prospects of personalized medicine. METHODS Genetic testing was conducted in all epilepsy patients without acquired factors for epilepsy. Through the collaboration of multicenter in China, we analyzed the genotype-phenotype correlation and antiepileptic therapy of 26 patients with GABRB3-related epilepsy. RESULTS Thirteen GABRB3 variants were novel, and 25 were de novo. The seizure onset age ranged from 1 to 21 months (median age 3.75 months). Seizure types predominated including focal seizures (92.3%), generalized tonic-clonic seizures (23.1%), and epileptic spasms (15.4%). Clinical features included cluster seizures (80.8%), fever sensitivity (53.8%), and developmental delay (96.2%). Neuroimaging was abnormal in 10 patients, including dysplasia of the cerebral cortex, dysplasia of the frontal and temporal cortex, delayed myelination, and corpus callosum dysplasia. Eleven patients were diagnosed with developmental and epileptic encephalopathy (DEE), four with West syndrome, three with epilepsy of infancy with migrating focal seizures (EIMFS), one with epilepsy with myoclonic-atonic seizures (EMAS), one with Dravet syndrome, and one with febrile seizures plus (FS+). Seizures were controlled in 57.7% of patients by valproate, levetiracetam, or perampanel in the majority. CONCLUSIONS The clinical features of GABRB3-related epilepsy included seizure onset in early infancy, cluster seizures and fever sensitivity. Most patients manifest severe epilepsy phenotypes. Valproate, levetiracetam and perampanel seem to have positive effects on seizure control for patients with GABRB3 variants.
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Affiliation(s)
- Ying Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Qi Zeng
- Department of Neurology, Shenzhen Children's Hospital, Shenzhen, 518038, China
| | - Miaomiao Cheng
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Xueyang Niu
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Wenshu Xiangwei
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Pan Gong
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Wenhui Li
- Department of Neurology, Children's Hospital of Fudan University, National Children's Medical Center, Shanghai, 201102, China
| | - Jiehui Ma
- Department of Neurology, Wuhan Children's Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430015, China
| | - Xiaoli Zhang
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China
| | - Xiaoling Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Zhixian Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Dan Sun
- Department of Neurology, Wuhan Children's Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430015, China
| | - Shuizhen Zhou
- Department of Neurology, Children's Hospital of Fudan University, National Children's Medical Center, Shanghai, 201102, China
| | - Jianxiang Liao
- Department of Neurology, Shenzhen Children's Hospital, Shenzhen, 518038, China
| | - Yuwu Jiang
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China
| | - Yuehua Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China.
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10
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Absalom NL, Liao VWY, Johannesen KMH, Gardella E, Jacobs J, Lesca G, Gokce-Samar Z, Arzimanoglou A, Zeidler S, Striano P, Meyer P, Benkel-Herrenbrueck I, Mero IL, Rummel J, Chebib M, Møller RS, Ahring PK. Gain-of-function and loss-of-function GABRB3 variants lead to distinct clinical phenotypes in patients with developmental and epileptic encephalopathies. Nat Commun 2022; 13:1822. [PMID: 35383156 PMCID: PMC8983652 DOI: 10.1038/s41467-022-29280-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 03/08/2022] [Indexed: 12/23/2022] Open
Abstract
Many patients with developmental and epileptic encephalopathies present with variants in genes coding for GABAA receptors. These variants are presumed to cause loss-of-function receptors leading to reduced neuronal GABAergic activity. Yet, patients with GABAA receptor variants have diverse clinical phenotypes and many are refractory to treatment despite the availability of drugs that enhance GABAergic activity. Here we show that 44 pathogenic GABRB3 missense variants segregate into gain-of-function and loss-of-function groups and respective patients display distinct clinical phenotypes. The gain-of-function cohort (n = 27 patients) presented with a younger age of seizure onset, higher risk of severe intellectual disability, focal seizures at onset, hypotonia, and lower likelihood of seizure freedom in response to treatment. Febrile seizures at onset are exclusive to the loss-of-function cohort (n = 47 patients). Overall, patients with GABRB3 variants that increase GABAergic activity have more severe developmental and epileptic encephalopathies. This paradoxical finding challenges our current understanding of the GABAergic system in epilepsy and how patients should be treated.
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Affiliation(s)
- Nathan L Absalom
- Brain and Mind Centre, School of Pharmacy, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia.,School of Science, Western Sydney University, Sydney, NSW, Australia
| | - Vivian W Y Liao
- Brain and Mind Centre, School of Pharmacy, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Katrine M H Johannesen
- Department of Epilepsy Genetics and Personalized Treatment, Member of the ERN EpiCARE, The Danish Epilepsy Centre, Dianalund, Denmark.,Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
| | - Elena Gardella
- Department of Epilepsy Genetics and Personalized Treatment, Member of the ERN EpiCARE, The Danish Epilepsy Centre, Dianalund, Denmark.,Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
| | - Julia Jacobs
- Department of Neuropediatrics and Muscle Disorders, Medical Center-University of Freiburg, Freiburg, Germany.,Department of Paediatrics and Department of Neuroscience, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.,Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada
| | - Gaetan Lesca
- Department of Medical Genetics, Member of the ERN EpiCARE, University Hospitals of Lyon (HCL), Lyon, France.,Institut Neuromyogène, CNRS UMR 5310 - INSERM U1217, Université de Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Zeynep Gokce-Samar
- Department of Paediatric Clinical Epileptology, Sleep Disorders and Functional Neurology, Member of the ERN EpiCARE, University Hospitals of Lyon (HCL), Lyon, France
| | - Alexis Arzimanoglou
- Department of Paediatric Clinical Epileptology, Sleep Disorders and Functional Neurology, Member of the ERN EpiCARE, University Hospitals of Lyon (HCL), Lyon, France
| | - Shimriet Zeidler
- Department of Clinical Genetics, Erasmus MC, Rotterdam, The Netherlands
| | - Pasquale Striano
- IRCCS Institute "Giannina Gaslini", Genova, Italy.,Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova, Genova, Italy
| | - Pierre Meyer
- Pediatric Neurology Department, Phymedexp, Montpellier University, Inserm, CRNS, Montpellier University Hospital, Montpellier, France
| | - Ira Benkel-Herrenbrueck
- Sana-Krankenhaus Düsseldorf-Gerresheim, Academic Teaching Hospital der Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Inger-Lise Mero
- Department of Medical Genetics, Oslo University Hospital, Oslo, Norway
| | - Jutta Rummel
- Department of Neurohabilitation, Oslo University Hospital, Oslo, Norway
| | - Mary Chebib
- Brain and Mind Centre, School of Pharmacy, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Treatment, Member of the ERN EpiCARE, The Danish Epilepsy Centre, Dianalund, Denmark. .,Department of Regional Health Research, University of Southern Denmark, Odense, Denmark.
| | - Philip K Ahring
- Brain and Mind Centre, School of Pharmacy, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia.
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Johannesen KM, Iqbal S, Guazzi M, Mohammadi NA, Pérez-Palma E, Schaefer E, De Saint Martin A, Abiwarde MT, McTague A, Pons R, Piton A, Kurian MA, Ambegaonkar G, Firth H, Sanchis-Juan A, Deprez M, Jansen K, De Waele L, Briltra EH, Verbeek NE, van Kempen M, Fazeli W, Striano P, Zara F, Visser G, Braakman HMH, Haeusler M, Elbracht M, Vaher U, Smol T, Lemke JR, Platzer K, Kennedy J, Klein KM, Au PYB, Smyth K, Kaplan J, Thomas M, Dewenter MK, Dinopoulos A, Campbell AJ, Lal D, Lederer D, Liao VWY, Ahring PK, Møller RS, Gardella E. Structural mapping of GABRB3 variants reveals genotype-phenotype correlations. Genet Med 2022; 24:681-693. [PMID: 34906499 DOI: 10.1016/j.gim.2021.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 09/30/2021] [Accepted: 11/05/2021] [Indexed: 12/27/2022] Open
Abstract
PURPOSE Pathogenic variants in GABRB3 have been associated with a spectrum of phenotypes from severe developmental disorders and epileptic encephalopathies to milder epilepsy syndromes and mild intellectual disability (ID). In this study, we analyzed a large cohort of individuals with GABRB3 variants to deepen the phenotypic understanding and investigate genotype-phenotype correlations. METHODS Through an international collaboration, we analyzed electro-clinical data of unpublished individuals with variants in GABRB3, and we reviewed previously published cases. All missense variants were mapped onto the 3-dimensional structure of the GABRB3 subunit, and clinical phenotypes associated with the different key structural domains were investigated. RESULTS We characterized 71 individuals with GABRB3 variants, including 22 novel subjects, expressing a wide spectrum of phenotypes. Interestingly, phenotypes correlated with structural locations of the variants. Generalized epilepsy, with a median age at onset of 12 months, and mild-to-moderate ID were associated with variants in the extracellular domain. Focal epilepsy with earlier onset (median: age 4 months) and severe ID were associated with variants in both the pore-lining helical transmembrane domain and the extracellular domain. CONCLUSION These genotype-phenotype correlations will aid the genetic counseling and treatment of individuals affected by GABRB3-related disorders. Future studies may reveal whether functional differences underlie the phenotypic differences.
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Affiliation(s)
- Katrine M Johannesen
- Department of Epilepsy Genetics and Personalized Treatment, The Danish Epilepsy Centre "Filadelfia", Dianalund, Denmark; Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
| | - Sumaiya Iqbal
- The Center for the Development of Therapeutics (CDOT), Broad Institute of MIT and Harvard, Cambridge, MA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA; Analytic & Translational Genetics Unit (ATGU), Department of Medicine, Massachusetts General Hospital, Boston, MA
| | - Milena Guazzi
- Department of Medicine, University of Genoa, Genoa, Italy; Department of Clinical Neurophysiology, The Danish Epilepsy Centre "Filadelfia", Dianalund, Denmark
| | - Nazanin A Mohammadi
- Department of Epilepsy Genetics and Personalized Treatment, The Danish Epilepsy Centre "Filadelfia", Dianalund, Denmark; Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
| | - Eduardo Pérez-Palma
- Centro de Genética y Genómica, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago, Chile
| | - Elise Schaefer
- Service de Génétique Médicale, Institut de Génétique Médicale d'Alsace, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | - Anne De Saint Martin
- Department of Pediatric Neurology, Strasbourg University Hospital, Strasbourg, France
| | | | - Amy McTague
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, London, United Kingdom; Department of Neurology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - Roser Pons
- First Department of Pediatrics, "I Agia Sofia" Children Hospital, National & Kapodistrian University of Athens, Athens, Greece
| | - Amelie Piton
- Laboratoire de diagnostic génétique, Hôpital Civil, CHRU de Strasburg, Strasbourg, France
| | - Manju A Kurian
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, London, United Kingdom; Department of Neurology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - Gautam Ambegaonkar
- Department of Paediatric Neurology, Child Development Centre, Addenbrookes Hospital, Cambridge, United Kingdom
| | - Helen Firth
- Department of Clinical Genetics, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom
| | - Alba Sanchis-Juan
- NIHR BioResource, Department of Haematology, University of Cambridge, United Kingdom
| | - Marie Deprez
- CNRS, IPMC, Université Côte d'Azur, Sophia-Antipolis, France
| | - Katrien Jansen
- Department of Pediatric Neurology, University Hospitals KU Leuven, Leuven, Belgium
| | - Liesbeth De Waele
- Department of Pediatric Neurology, University Hospitals KU Leuven, Leuven, Belgium; Department of Development and Regeneration, Kulak Kortrijk Campus, Kortrijk, Belgium
| | - Eva H Briltra
- Department of Genetics, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Nienke E Verbeek
- Department of Genetics, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Marjan van Kempen
- Department of Genetics, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Walid Fazeli
- Department of Pediatric Neurology, University Hospital Bonn, Bonn, Germany
| | - Pasquale Striano
- IRCCS Giannina Gaslini Institute, Genova, Italy; Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova, Genova, Italy
| | - Federico Zara
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova, Genova, Italy; Laboratory of Neurogenetics and Neuroscience, IRCCS Giannina Gaslini Institute, Genova, Italy
| | - Gerhard Visser
- Stichting Epilepsie Instellingen Nederland (SEIN), Hoofddorp, The Netherlands
| | - Hilde M H Braakman
- Department of Pediatric Neurology, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Neurology, Academic Center for Epileptology Kempenhaeghe & Maastricht University Medical Center, Heeze, The Netherlands
| | - Martin Haeusler
- Division of Neuropediatrics and Social Pediatrics, Department of Pediatrics, University Hospital RWTH Aachen, Aachen, Germany
| | - Miriam Elbracht
- Institute of Human Genetics, Faculty of Medicine, RWTH Aachen University, Aachen, Germany
| | - Ulvi Vaher
- Children's Clinic of Tartu University Hospital, Tartu, Estonia; ERN EpiCARE, Tartu, Estonia
| | - Thomas Smol
- Institut de Genetique Medicale, CHU Lille, Universite de Lille, Lille, France
| | - Johannes R Lemke
- Institute of Human Genetics, University of Leipzig Medical Center, Leipzig, Germany
| | - Konrad Platzer
- Institute of Human Genetics, University of Leipzig Medical Center, Leipzig, Germany
| | - Joanna Kennedy
- Clinical Genetics Service, University Hospitals Bristol NHS Foundation Trust, St Michael's Hospital, Bristol, United Kingdom
| | - Karl Martin Klein
- Department of Clinical Neurosciences, Hotchkiss Brain Institute & Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Department of Medical Genetics, Hotchkiss Brain Institute & Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Department of Community Health Sciences, Hotchkiss Brain Institute & Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada; Epilepsy Center Frankfurt Rhine-Main, Department of Neurology, Center of Neurology and Neurosurgery, University Hospital, Goethe-University Frankfurt, Frankfurt, Germany; Center for Personalized Translational Epilepsy Research (CePTER), Goethe University Frankfurt, Frankfurt, Germany
| | - Ping Yee Billie Au
- Department of Medical Genetics, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Kimberly Smyth
- Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Julie Kaplan
- Division of Medical Genetics, Nemours A.I. duPont Hospital for Children, Wilmington, DE
| | - Morgan Thomas
- Precision Medicine/Genetic Testing Stewardship Program, Nemours A.I. duPont Hospital for Children, Wilmington, DE
| | - Malin K Dewenter
- Institute of Human Genetics, Universitätsmedizin, Johannes Gutenberg-University, Mainz Institut für Humangenetik, Mainz, Germany
| | - Argirios Dinopoulos
- Third Department of Pediatrics, Attiko University Hospital, University of Athens, Haidari, Greece
| | - Arthur J Campbell
- The Center for the Development of Therapeutics (CDOT), Broad Institute of MIT and Harvard, Cambridge, MA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA
| | - Dennis Lal
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA; Genomic Medicine Institute, Cleveland Clinic Lerner Research Institute, Cleveland, OH; Epilepsy Center, Neurological Institute, Cleveland Clinic, Cleveland, OH; Cologne Center for Genomics (CCG), University of Cologne, Cologne, Germany
| | - Damien Lederer
- Centre de Génétique Humaine, Institut de Pathologie et de Génétique, Charleroi, Belgium
| | - Vivian W Y Liao
- Brain and Mind Centre, Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Philip K Ahring
- Brain and Mind Centre, Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, Sydney, New South Wales, Australia
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Treatment, The Danish Epilepsy Centre "Filadelfia", Dianalund, Denmark; Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
| | - Elena Gardella
- Department of Epilepsy Genetics and Personalized Treatment, The Danish Epilepsy Centre "Filadelfia", Dianalund, Denmark; Department of Regional Health Research, University of Southern Denmark, Odense, Denmark; Department of Medicine, University of Genoa, Genoa, Italy; Department of Clinical Neurophysiology, The Danish Epilepsy Centre "Filadelfia", Dianalund, Denmark.
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12
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Hernandez CC, Tian X, Hu N, Shen W, Catron MA, Yang Y, Chen J, Jiang Y, Zhang Y, Macdonald RL. Dravet syndrome-associated mutations in GABRA1, GABRB2 and GABRG2 define the genetic landscape of defects of GABA A receptors. Brain Commun 2021; 3:fcab033. [PMID: 34095830 PMCID: PMC8176149 DOI: 10.1093/braincomms/fcab033] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 01/07/2021] [Accepted: 01/14/2021] [Indexed: 12/29/2022] Open
Abstract
Dravet syndrome is a rare, catastrophic epileptic encephalopathy that begins in the first year of life, usually with febrile or afebrile hemiclonic or generalized tonic-clonic seizures followed by status epilepticus. De novo variants in genes that mediate synaptic transmission such as SCN1A and PCDH19 are often associated with Dravet syndrome. Recently, GABAA receptor subunit genes (GABRs) encoding α1 (GABRA1), β3 (GABRB3) and γ2 (GABRG2), but not β2 (GABRB2) or β1 (GABRB1), subunits are frequently associated with Dravet syndrome or Dravet syndrome-like phenotype. We performed next generation sequencing on 870 patients with Dravet syndrome and identified nine variants in three different GABRs. Interestingly, the variants were all in genes encoding the most common GABAA receptor, the α1β2γ2 receptor. Mutations in GABRA1 (c.644T>C, p. L215P; c.640C>T, p. R214C; c.859G>A; V287I; c.641G>A, p. R214H) and GABRG2 (c.269C>G, p. T90R; c.1025C>T, p. P342L) presented as de novo cases, while in GABRB2 two variants were de novo (c.992T>C, p. F331S; c.542A>T, p. Y181F) and one was autosomal dominant and inherited from the maternal side (c.990_992del, p.330_331del). We characterized the effects of these GABR variants on GABAA receptor biogenesis and channel function. We found that defects in receptor gating were the common deficiency of GABRA1 and GABRB2 Dravet syndrome variants, while mainly trafficking defects were found with the GABRG2 (c.269C>G, p. T90R) variant. It seems that variants in α1 and β2 subunits are less tolerated than in γ2 subunits, since variant α1 and β2 subunits express well but were functionally deficient. This suggests that all of these GABR variants are all targeting GABR genes that encode the assembled α1β2γ2 receptor, and regardless of which of the three subunits are mutated, variants in genes coding for α1, β2 and γ2 receptor subunits make them candidate causative genes in the pathogenesis of Dravet syndrome.
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Affiliation(s)
- Ciria C Hernandez
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48198, USA
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - XiaoJuan Tian
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
- Department of Neurology, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing 100045, China
| | - Ningning Hu
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - Wangzhen Shen
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - Mackenzie A Catron
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
- Neuroscience Graduate Program, Vanderbilt University, Nashville, TN 37240, USA
| | - Ying Yang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
| | - Jiaoyang Chen
- 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
| | - Yuehua Zhang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
| | - Robert L Macdonald
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
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13
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Intricacies of GABA A Receptor Function: The Critical Role of the β3 Subunit in Norm and Pathology. Int J Mol Sci 2021; 22:ijms22031457. [PMID: 33535681 PMCID: PMC7867123 DOI: 10.3390/ijms22031457] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 01/27/2021] [Accepted: 01/28/2021] [Indexed: 12/23/2022] Open
Abstract
Neuronal intracellular chloride ([Cl−]i) is a key determinant in γ-aminobutyric acid type A (GABA)ergic signaling. γ-Aminobutyric acid type A receptors (GABAARs) mediate both inhibitory and excitatory neurotransmission, as the passive fluxes of Cl− and HCO3− via pores can be reversed by changes in the transmembrane concentration gradient of Cl−. The cation–chloride co-transporters (CCCs) are the primary systems for maintaining [Cl−]i homeostasis. However, despite extensive electrophysiological data obtained in vitro that are supported by a wide range of molecular biological studies on the expression patterns and properties of CCCs, the presence of ontogenetic changes in [Cl−]i—along with the consequent shift in GABA reversal potential—remain a subject of debate. Recent studies showed that the β3 subunit possesses properties of the P-type ATPase that participates in the ATP-consuming movement of Cl− via the receptor. Moreover, row studies have demonstrated that the β3 subunit is a key player in GABAAR performance and in the appearance of serious neurological disorders. In this review, we discuss the properties and driving forces of CCCs and Cl−, HCO3−ATPase in the maintenance of [Cl−]i homeostasis after changes in upcoming GABAAR function. Moreover, we discuss the contribution of the β3 subunit in the manifestation of epilepsy, autism, and other syndromes.
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14
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Juvale IIA, Che Has AT. Possible interplay between the theories of pharmacoresistant epilepsy. Eur J Neurosci 2020; 53:1998-2026. [PMID: 33306252 DOI: 10.1111/ejn.15079] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Revised: 11/22/2020] [Accepted: 12/04/2020] [Indexed: 02/06/2023]
Abstract
Epilepsy is one of the oldest known neurological disorders and is characterized by recurrent seizure activity. It has a high incidence rate, affecting a broad demographic in both developed and developing countries. Comorbid conditions are frequent in patients with epilepsy and have detrimental effects on their quality of life. Current management options for epilepsy include the use of anti-epileptic drugs, surgery, or a ketogenic diet. However, more than 30% of patients diagnosed with epilepsy exhibit drug resistance to anti-epileptic drugs. Further, surgery and ketogenic diets do little to alleviate the symptoms of patients with pharmacoresistant epilepsy. Thus, there is an urgent need to understand the underlying mechanisms of pharmacoresistant epilepsy to design newer and more effective anti-epileptic drugs. Several theories of pharmacoresistant epilepsy have been suggested over the years, the most common being the gene variant hypothesis, network hypothesis, multidrug transporter hypothesis, and target hypothesis. In our review, we discuss the main theories of pharmacoresistant epilepsy and highlight a possible interconnection between their mechanisms that could lead to the development of novel therapies for pharmacoresistant epilepsy.
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Affiliation(s)
- Iman Imtiyaz Ahmed Juvale
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Malaysia
| | - Ahmad Tarmizi Che Has
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Malaysia
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15
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Absalom NL, Liao VWY, Kothur K, Indurthi DC, Bennetts B, Troedson C, Mohammad SS, Gupta S, McGregor IS, Bowen MT, Lederer D, Mary S, De Waele L, Jansen K, Gill D, Kurian MA, McTague A, Møller RS, Ahring PK, Dale RC, Chebib M. Gain-of-function GABRB3 variants identified in vigabatrin-hypersensitive epileptic encephalopathies. Brain Commun 2020; 2:fcaa162. [PMID: 33585817 PMCID: PMC7869430 DOI: 10.1093/braincomms/fcaa162] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 07/31/2020] [Accepted: 08/28/2020] [Indexed: 01/06/2023] Open
Abstract
Variants in the GABRB3 gene encoding the β3-subunit of the γ-aminobutyric acid type A ( receptor are associated with various developmental and epileptic encephalopathies. Typically, these variants cause a loss-of-function molecular phenotype whereby γ-aminobutyric acid has reduced inhibitory effectiveness leading to seizures. Drugs that potentiate inhibitory GABAergic activity, such as nitrazepam, phenobarbital or vigabatrin, are expected to compensate for this and thereby reduce seizure frequency. However, vigabatrin, a drug that inhibits γ-aminobutyric acid transaminase to increase tonic γ-aminobutyric acid currents, has mixed success in treating seizures in patients with GABRB3 variants: some patients experience seizure cessation, but there is hypersensitivity in some patients associated with hypotonia, sedation and respiratory suppression. A GABRB3 variant that responds well to vigabatrin involves a truncation variant (p.Arg194*) resulting in a clear loss-of-function. We hypothesized that patients with a hypersensitive response to vigabatrin may exhibit a different γ-aminobutyric acid A receptor phenotype. To test this hypothesis, we evaluated the phenotype of de novo variants in GABRB3 (p.Glu77Lys and p.Thr287Ile) associated with patients who are clinically hypersensitive to vigabatrin. We introduced the GABRB3 p.Glu77Lys and p.Thr287Ile variants into a concatenated synaptic and extrasynaptic γ-aminobutyric acid A receptor construct, to resemble the γ-aminobutyric acid A receptor expression by a patient heterozygous for the GABRB3 variant. The mRNA of these constructs was injected into Xenopus oocytes and activation properties of each receptor measured by two-electrode voltage clamp electrophysiology. Results showed an atypical gain-of-function molecular phenotype in the GABRB3 p.Glu77Lys and p.Thr287Ile variants characterized by increased potency of γ-aminobutyric acid A without change to the estimated maximum open channel probability, deactivation kinetics or absolute currents. Modelling of the activation properties of the receptors indicated that either variant caused increased chloride flux in response to low concentrations of γ-aminobutyric acid that mediate tonic currents. We therefore propose that the hypersensitivity reaction to vigabatrin is a result of GABRB3 variants that exacerbate GABAergic tonic currents and caution is required when prescribing vigabatrin. In contrast, drug strategies increasing tonic currents in loss-of-function variants are likely to be a safe and effective therapy. This study demonstrates that functional genomics can explain beneficial and adverse anti-epileptic drug effects, and propose that vigabatrin should be considered in patients with clear loss-of-function GABRB3 variants.
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Affiliation(s)
- Nathan L Absalom
- Faculty of Medicine and Health, School of Pharmacy, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Vivian W Y Liao
- Faculty of Medicine and Health, School of Pharmacy, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Kavitha Kothur
- Kids Neuroscience Centre at The Children’s Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Dinesh C Indurthi
- Faculty of Medicine and Health, School of Pharmacy, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Bruce Bennetts
- Department of Molecular Genetics, The Children’s Hospital at Westmead, Westmead, New South Wales 2145, Australia
- Discipline of Paediatrics and Adolescent Health, The Children's Hospital at Westmead Clinical School, The University of Sydney, 2145, Australia
| | - Christopher Troedson
- T.Y. Nelson Department of Neurology and Neurosurgery, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Shekeeb S Mohammad
- Kids Neuroscience Centre at The Children’s Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Sachin Gupta
- T.Y. Nelson Department of Neurology and Neurosurgery, The Children's Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Iain S McGregor
- Faculty of Science, Lambert Initiative for Cannabinoid Therapeutics, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Michael T Bowen
- Faculty of Science, Lambert Initiative for Cannabinoid Therapeutics, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Damien Lederer
- Institute of Pathology and Genetics, Center for Human Genetics, Gosselies 6041, Belgium
| | - Sandrine Mary
- Institute of Pathology and Genetics, Center for Human Genetics, Gosselies 6041, Belgium
| | - Liesbeth De Waele
- Department of Development and Regeneration, KULeuven, Leuven 3000, Belgium
| | - Katrien Jansen
- Department of Development and Regeneration, KULeuven, Leuven 3000, Belgium
| | - Deepak Gill
- Kids Neuroscience Centre at The Children’s Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Manju A Kurian
- Molecular Neurosciences, UCL Great Ormond Street Institute of Child Health, London WC1E 6BT, UK
- Department of Neurology, Great Ormond Street Hospital for Children, London WC1N 3JH, UK
| | - Amy McTague
- Molecular Neurosciences, UCL Great Ormond Street Institute of Child Health, London WC1E 6BT, UK
- Department of Neurology, Great Ormond Street Hospital for Children, London WC1N 3JH, UK
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Centre, Dianalund 4293, Denmark
- Department of Regional Health Research, University of Southern Denmark, Odense 5230, Denmark
| | - Philip K Ahring
- Faculty of Medicine and Health, School of Pharmacy, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Russell C Dale
- Kids Neuroscience Centre at The Children’s Hospital at Westmead, Westmead, New South Wales 2145, Australia
| | - Mary Chebib
- Faculty of Medicine and Health, School of Pharmacy, Brain and Mind Centre, The University of Sydney, Sydney, New South Wales 2006, Australia
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16
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Menzikov SA, Zaichenko DM, Moskovtsev AA, Morozov SG, Kubatiev AA. Ectopic GABA A receptor β3 subunit determines Cl - / HCO 3 - -ATPase and chloride transport in HEK 293FT cells. FEBS J 2020; 288:699-712. [PMID: 32383536 DOI: 10.1111/febs.15359] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 04/09/2020] [Accepted: 05/04/2020] [Indexed: 01/20/2023]
Abstract
Neuronal intracellular chloride concentration ([Cl- ]i ) is a crucial determinant of transmission mediated by the γ-aminobutyric acid type A receptor (GABAA R), which subserves synaptic and extrasynaptic inhibition as well as excitation. The Cl- ion is the main carrier of charge through the GABAA R; however, bicarbonate ions ( HCO 3 - ) flowing in the opposite direction can also contribute to the net current. The direction of Cl- and HCO 3 - fluxes is determined by the underlying electrochemical gradient, which is controlled by Cl- transporters and channels. Accumulating evidence suggests that active mechanisms of chloride transport across the GABAA R pore can underlie the regulation of [Cl- ]i . Measurement of Cl- / HCO 3 - -ATPase activity and Cl- transport in HEK 293FT cells expressing homomeric or heteromeric GABAA R ensembles (α2, β3, or γ2) with fluorescent dye for chloride demonstrated that receptor subtypes containing the β3 subunit show enzymatic activity and participate in GABA-mediated or ATP-dependent Cl- transport. GABA-mediated flow of Cl- ions into and out of the cells occurred for a short time period but then rapidly declined. However, Cl- ion flux was stabilized for a long time period in the presence of HCO 3 - ions. The reconstituted β3 subunit isoform, purified as a fusion protein, confirmed that β3 is critical for ATPase; however, only the triplet variant showed the full receptor function. The high sensitivity of the enzyme to γ-phosphate inhibitors led us to postulate that the β3 subunit is catalytic. Our discovery of a GABAA R type that requires ATP consumption for chloride movement provides new insight into the molecular mechanisms of inhibitory signaling.
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Affiliation(s)
| | | | - Aleksey A Moskovtsev
- Institute of General Pathology and Pathophysiology, Moscow, Russia.,Russian Medical Academy of Postdoctoral Education, Moscow, Russia
| | - Sergey G Morozov
- Institute of General Pathology and Pathophysiology, Moscow, Russia
| | - Aslan A Kubatiev
- Institute of General Pathology and Pathophysiology, Moscow, Russia.,Russian Medical Academy of Postdoctoral Education, Moscow, Russia
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17
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Cárdenas-Rodríguez N, Carmona-Aparicio L, Pérez-Lozano DL, Ortega-Cuellar D, Gómez-Manzo S, Ignacio-Mejía I. Genetic variations associated with pharmacoresistant epilepsy (Review). Mol Med Rep 2020; 21:1685-1701. [PMID: 32319641 PMCID: PMC7057824 DOI: 10.3892/mmr.2020.10999] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 01/16/2020] [Indexed: 12/13/2022] Open
Abstract
Epilepsy is a common, serious neurological disorder worldwide. Although this disease can be successfully treated in most cases, not all patients respond favorably to medical treatments, which can lead to pharmacoresistant epilepsy. Drug-resistant epilepsy can be caused by a number of mechanisms that may involve environmental and genetic factors, as well as disease- and drug-related factors. In recent years, numerous studies have demonstrated that genetic variation is involved in the drug resistance of epilepsy, especially genetic variations found in drug resistance-related genes, including the voltage-dependent sodium and potassium channels genes, and the metabolizer of endogenous and xenobiotic substances genes. The present review aimed to highlight the genetic variants that are involved in the regulation of drug resistance in epilepsy; a comprehensive understanding of the role of genetic variation in drug resistance will help us develop improved strategies to regulate drug resistance efficiently and determine the pathophysiological processes that underlie this common human neurological disease.
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Affiliation(s)
- Noemí Cárdenas-Rodríguez
- Laboratory of Neuroscience, National Institute of Pediatrics, Ministry of Health, Coyoacán, Mexico City 04530, Mexico
| | - Liliana Carmona-Aparicio
- Laboratory of Neuroscience, National Institute of Pediatrics, Ministry of Health, Coyoacán, Mexico City 04530, Mexico
| | - Diana L Pérez-Lozano
- Laboratory of Neuroscience, National Institute of Pediatrics, Ministry of Health, Coyoacán, Mexico City 04530, Mexico
| | - Daniel Ortega-Cuellar
- Laboratory of Experimental Nutrition, National Institute of Pediatrics, Ministry of Health, Coyoacán, Mexico City 04530, Mexico
| | - Saúl Gómez-Manzo
- Laboratory of Genetic Biochemistry, National Institute of Pediatrics, Ministry of Health, Coyoacán, Mexico City 04530, Mexico
| | - Iván Ignacio-Mejía
- Laboratory of Translational Medicine, Military School of Health Graduates, Lomas de Sotelo, Militar, Mexico City 11200, Mexico
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18
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Pathophysiology of and therapeutic options for a GABRA1 variant linked to epileptic encephalopathy. Mol Brain 2019; 12:92. [PMID: 31707987 PMCID: PMC6842544 DOI: 10.1186/s13041-019-0513-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 10/14/2019] [Indexed: 01/07/2023] Open
Abstract
We report the identification of a de novo GABRA1 (R214C) variant in a child with epileptic encephalopathy (EE), describe its functional characterization and pathophysiology, and evaluate its potential therapeutic options. The GABRA1 (R214C) variant was identified using whole exome sequencing, and the pathogenic effect of this mutation was investigated by comparing wild-type (WT) α1 and R214C α1 GABAA receptor-expressing HEK cells. GABA-evoked currents in these cells were recorded using whole-cell, outside-out macro-patch and cell-attached single-channel patch-clamp recordings. Changes to surface and total protein expression levels of WT α1 and R214C α1 were quantified using surface biotinylation assay and western blotting, respectively. Finally, potential therapeutic options were explored by determining the effects of modulators, including diazepam, insulin, and verapamil, on channel gating and receptor trafficking of WT and R214C GABAA receptors. We found that the GABRA1 (R214C) variant decreased whole-cell GABA-evoked currents by reducing single channel open time and both surface and total GABAA receptor expression levels. The GABA-evoked currents in R214C GABAA receptors could only be partially restored with benzodiazepine (diazepam) and insulin. However, verapamil treatment for 24 h fully restored the function of R214C mutant receptors, primarily by increasing channel open time. We conclude that the GABRA1 (R214C) variant reduces channel activity and surface expression of mutant receptors, thereby contributing to the pathogenesis of genetic EE. The functional restoration by verapamil suggests that it is a potentially new therapeutic option for patients with the R214C variant and highlights the value of precision medicine in the treatment of genetic EEs.
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19
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XiangWei W, Kannan V, Xu Y, Kosobucki GJ, Schulien AJ, Kusumoto H, Moufawad El Achkar C, Bhattacharya S, Lesca G, Nguyen S, Helbig KL, Cuisset JM, Fenger CD, Marjanovic D, Schuler E, Wu Y, Bao X, Zhang Y, Dirkx N, Schoonjans AS, Syrbe S, Myers SJ, Poduri A, Aizenman E, Traynelis SF, Lemke JR, Yuan H, Jiang Y. Heterogeneous clinical and functional features of GRIN2D-related developmental and epileptic encephalopathy. Brain 2019; 142:3009-3027. [PMID: 31504254 PMCID: PMC6763743 DOI: 10.1093/brain/awz232] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 04/30/2019] [Accepted: 05/31/2019] [Indexed: 01/08/2023] Open
Abstract
N-methyl d-aspartate receptors are ligand-gated ionotropic receptors mediating a slow, calcium-permeable component of excitatory synaptic transmission in the CNS. Variants in genes encoding NMDAR subunits have been associated with a spectrum of neurodevelopmental disorders. Here we report six novel GRIN2D variants and one previously-described disease-associated GRIN2D variant in two patients with developmental and epileptic encephalopathy. GRIN2D encodes for the GluN2D subunit protein; the GluN2D amino acids affected by the variants in this report are located in the pre-M1 helix, transmembrane domain M3, and the intracellular carboxyl terminal domain. Functional analysis in vitro reveals that all six variants decreased receptor surface expression, which may underline some shared clinical symptoms. In addition the GluN2D(Leu670Phe), (Ala675Thr) and (Ala678Asp) substitutions confer significantly enhanced agonist potency, and/or increased channel open probability, while the GluN2D(Ser573Phe), (Ser1271Phe) and (Arg1313Trp) substitutions result in a mild increase of agonist potency, reduced sensitivity to endogenous protons, and decreased channel open probability. The GluN2D(Ser573Phe), (Ala675Thr), and (Ala678Asp) substitutions significantly decrease current amplitude, consistent with reduced surface expression. The GluN2D(Leu670Phe) variant slows current response deactivation time course and increased charge transfer. GluN2D(Ala678Asp) transfection significantly decreased cell viability of rat cultured cortical neurons. In addition, we evaluated a set of FDA-approved NMDAR channel blockers to rescue functional changes of mutant receptors. This work suggests the complexity of the pathological mechanisms of GRIN2D-mediated developmental and epileptic encephalopathy, as well as the potential benefit of precision medicine.
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Affiliation(s)
- Wenshu XiangWei
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Varun Kannan
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Yuchen Xu
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, USA
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Gabrielle J Kosobucki
- Department of Neurobiology, University of Pittsburgh School of Medicine and Pittsburgh Institute for Neurodegenerative Diseases, Pittsburgh PA, USA
| | - Anthony J Schulien
- Department of Neurobiology, University of Pittsburgh School of Medicine and Pittsburgh Institute for Neurodegenerative Diseases, Pittsburgh PA, USA
| | - Hirofumi Kusumoto
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Christelle Moufawad El Achkar
- Division of Epilepsy, Department of Neurology, Boston Children’s Hospital, Boston, MA, USA
- Department of Neurology, Harvard Medical School, Boston, MA, USA
| | - Subhrajit Bhattacharya
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Gaetan Lesca
- Service de Genetique, Centre de Reference Anomalies du Developpement, Hospices Civils de Lyon, Bron, France; INSERM U1028, CNRS UMR5292, Paris, France
- Centre de Recherche en Neurosciences de Lyon, GENDEV Team, Universite Claude Bernard Lyon 1, Bron, France; Claude Bernard Lyon I University, Lyon, France
| | - Sylvie Nguyen
- Department of Pediatric Neurology, University Hospital of Lille, and Lille Reference Centre for Rare Epileptic Disorders, Lille, France
| | - Katherine L Helbig
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, USA
| | - Jean-Marie Cuisset
- Department of Pediatric Neurology, University Hospital of Lille, and Lille Reference Centre for Rare Epileptic Disorders, Lille, France
| | | | | | - Elisabeth Schuler
- Division of Child Neurology and Inherited Metabolic Diseases, Centre for Paediatrics and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany
| | - Ye Wu
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
| | - Xinhua Bao
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
| | - Yuehua Zhang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
| | - Nina Dirkx
- Neurogenetics Group, University of Antwerp, Belgium
- Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium
| | - An-Sofie Schoonjans
- Department of Child Neurology, Antwerp University Hospital, Antwerp, Belgium
| | - Steffen Syrbe
- Division of Child Neurology and Inherited Metabolic Diseases, Centre for Paediatrics and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany
| | - Scott J Myers
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, USA
- Center for Functional Evaluation of Rare Variants (CFERV), Emory University School of Medicine, Atlanta, GA, USA
| | - Annapurna Poduri
- Division of Epilepsy, Department of Neurology, Boston Children’s Hospital, Boston, MA, USA
- Department of Neurology, Harvard Medical School, Boston, MA, USA
| | - Elias Aizenman
- Department of Neurobiology, University of Pittsburgh School of Medicine and Pittsburgh Institute for Neurodegenerative Diseases, Pittsburgh PA, USA
| | - Stephen F Traynelis
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, USA
- Center for Functional Evaluation of Rare Variants (CFERV), Emory University School of Medicine, Atlanta, GA, USA
| | - Johannes R Lemke
- Institute of Human Genetics, University of Leipzig Hospitals and Clinics, Leipzig, Germany
| | - Hongjie Yuan
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, USA
- Center for Functional Evaluation of Rare Variants (CFERV), Emory University School of Medicine, Atlanta, GA, USA
| | - Yuwu Jiang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
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20
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Shi YW, Zhang Q, Cai K, Poliquin S, Shen W, Winters N, Yi YH, Wang J, Hu N, Macdonald RL, Liao WP, Kang JQ. Synaptic clustering differences due to different GABRB3 mutations cause variable epilepsy syndromes. Brain 2019; 142:3028-3044. [PMID: 31435640 PMCID: PMC6776116 DOI: 10.1093/brain/awz250] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 06/19/2019] [Accepted: 06/25/2019] [Indexed: 11/13/2022] Open
Abstract
GABRB3 is highly expressed early in the developing brain, and its encoded β3 subunit is critical for GABAA receptor assembly and trafficking as well as stem cell differentiation in embryonic brain. To date, over 400 mutations or variants have been identified in GABRB3. Mutations in GABRB3 have been increasingly recognized as a major cause for severe paediatric epilepsy syndromes such as Lennox-Gastaut syndrome, Dravet syndrome and infantile spasms with intellectual disability as well as relatively mild epilepsy syndromes such as childhood absence epilepsy. There is no plausible molecular pathology for disease phenotypic heterogeneity. Here we used a very high-throughput flow cytometry assay to evaluate the impact of multiple human mutations in GABRB3 on receptor trafficking. In this study we found that surface expression of mutant β3 subunits is variable. However, it was consistent that surface expression of partnering γ2 subunits was lower when co-expressed with mutant than with wild-type subunits. Because γ2 subunits are critical for synaptic GABAA receptor clustering, this provides an important clue for understanding the pathophysiology of GABRB3 mutations. To validate our findings further, we obtained an in-depth comparison of two novel mutations [GABRB3 (N328D) and GABRB3 (E357K)] associated with epilepsy with different severities of epilepsy phenotype. GABRB3 (N328D) is associated with the relatively severe Lennox-Gastaut syndrome, and GABRB3 (E357K) is associated with the relatively mild juvenile absence epilepsy syndrome. With functional characterizations in both heterologous cells and rodent cortical neurons by patch-clamp recordings, confocal microscopy and immunoblotting, we found that both the GABRB3 (N328D) and GABRB3 (E357K) mutations reduced total subunit expression in neurons but not in HEK293T cells. Both mutant subunits, however, were reduced on the cell surface and in synapses, but the Lennox-Gastaut syndrome mutant β3 (N328D) subunit was more reduced than the juvenile absence epilepsy mutant β3 (E357K) subunit. Interestingly, both mutant β3 subunits impaired postsynaptic clustering of wild-type GABAA receptor γ2 subunits and prevented γ2 subunits from incorporating into GABAA receptors at synapses, although by different cellular mechanisms. Importantly, wild-type γ2 subunits were reduced and less clustered at inhibitory synapses in Gabrb3+/- knockout mice. This suggests that impaired receptor localization to synapses is a common pathophysiological mechanism for GABRB3 mutations, although the extent of impairment may be different among mutant subunits. The study thus identifies the novel mechanism of impaired targeting of receptors containing mutant β3 subunits and provides critical insights into understanding how GABRB3 mutations produce severe epilepsy syndromes and epilepsy phenotypic heterogeneity.
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Affiliation(s)
- Yi-Wu Shi
- Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou, China
| | - Qi Zhang
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
- Key laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, Department of Neurology, Nantong University, 19 Qixiu Road, Nantong, JS, China
| | - Kefu Cai
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Neurology, Nantong University, 19 QiXiu Road, Nantong, JS, China
| | - Sarah Poliquin
- Neuroscience Graduate Program, Vanderbilt Brain Institute, Nashville, TN, USA
| | - Wangzhen Shen
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Nathan Winters
- Neuroscience Graduate Program, Vanderbilt Brain Institute, Nashville, TN, USA
| | - Yong-Hong Yi
- Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou, China
| | - Jie Wang
- Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou, China
| | - Ningning Hu
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Robert L Macdonald
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Wei-Ping Liao
- Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou, China
| | - Jing-Qiong Kang
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
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21
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Hernandez CC, XiangWei W, Hu N, Shen D, Shen W, Lagrange AH, Zhang Y, Dai L, Ding C, Sun Z, Hu J, Zhu H, Jiang Y, Macdonald RL. Altered inhibitory synapses in de novo GABRA5 and GABRA1 mutations associated with early onset epileptic encephalopathies. Brain 2019; 142:1938-1954. [PMID: 31056671 PMCID: PMC6598634 DOI: 10.1093/brain/awz123] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 02/20/2019] [Accepted: 03/07/2019] [Indexed: 12/22/2022] Open
Abstract
We performed next generation sequencing on 1696 patients with epilepsy and intellectual disability using a gene panel with 480 epilepsy-related genes including all GABAA receptor subunit genes (GABRs), and we identified six de novo GABR mutations, two novel GABRA5 mutations (c.880G>T, p.V294F and c.1238C>T, p.S413F), two novel GABRA1 mutations (c.778C>T, p.P260S and c.887T>C, p.L296S/c.944G>T, p.W315L) and two known GABRA1 mutations (c.335G>A, p.R112Q and c.343A>G, p.N115D) in six patients with intractable early onset epileptic encephalopathy. The α5(V294F and S413F) and α1(P260S and L296S/W315L) subunit residue substitutions were all in transmembrane domains, while the α1(R112Q and N115R) subunit residue substitutions were in the N-terminal GABA binding domain. Using multidisciplinary approaches, we compared effects of mutant GABAA receptor α5 and α1 subunits on the properties of recombinant α5β3γ2 and α1β3γ2 GABAA receptors in both neuronal and non-neuronal cells and characterized their effects on receptor clustering, biogenesis and channel function. GABAA receptors containing mutant α5 and α1 subunits all had reduced cell surface and total cell expression with altered endoplasmic reticulum processing, impaired synaptic clustering, reduced GABAA receptor function and decreased GABA binding potency. Our study identified GABRA5 as a causative gene for early onset epileptic encephalopathy and expands the mutant GABRA1 phenotypic spectrum, supporting growing evidence that defects in GABAergic neurotransmission contribute to early onset epileptic encephalopathy phenotypes.
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Affiliation(s)
- Ciria C Hernandez
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Wenshu XiangWei
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
- Center of Epilepsy, Beijing Institute for Brain Disorders, Beijing, China
| | - Ningning Hu
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Dingding Shen
- The Graduate Program of Neuroscience, Vanderbilt University, Nashville, TN, USA
- Department of Neurology, Rui Jin Hospital, Shanghai Jiao Tong University, School of Medicine. Shanghai, China
| | - Wangzhen Shen
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Andre H Lagrange
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Pharmacology and Molecular Physiology and Biophysics, Vanderbilt University, and the Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN, USA
| | - Yujia Zhang
- Department of Neurology, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing, China
| | - Lifang Dai
- Department of Neurology, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing, China
| | - Changhong Ding
- Department of Neurology, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing, China
| | - Zhaohui Sun
- Epilepsy center of Yuquan Hospital, Tsinghua University, Beijing, China
| | - Jiasheng Hu
- Department of Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hongmin Zhu
- Department of Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - 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
| | - Robert L Macdonald
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
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22
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Hernandez CC, Macdonald RL. A structural look at GABA A receptor mutations linked to epilepsy syndromes. Brain Res 2019; 1714:234-247. [PMID: 30851244 DOI: 10.1016/j.brainres.2019.03.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 02/25/2019] [Accepted: 03/06/2019] [Indexed: 12/12/2022]
Abstract
Understanding the genetic variation in GABAA receptor subunit genes (GABRs), GABRA1-6, GABRB1-3, GABRG1-3 and GABRD, in individuals affected by epilepsy may improve the diagnosis and treatment of epilepsy syndromes through identification of disease-associated variants. However, the lack of functional analysis and validation of many novel and previously reported familial and de novo mutations have made it challenging to address meaningful gene associations with epilepsy syndromes. GABAA receptors belong to the Cys-loop receptor family. Even though GABAA receptor mutant residues are widespread among different GABRs, their frequent occurrence in important structural domains that share common functional features suggests associations between structure and function.
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Affiliation(s)
- Ciria C Hernandez
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA.
| | - Robert L Macdonald
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
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23
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Laverty D, Desai R, Uchański T, Masiulis S, Stec WJ, Malinauskas T, Zivanov J, Pardon E, Steyaert J, Miller KW, Aricescu AR. Cryo-EM structure of the human α1β3γ2 GABA A receptor in a lipid bilayer. Nature 2019; 565:516-520. [PMID: 30602789 PMCID: PMC6364807 DOI: 10.1038/s41586-018-0833-4] [Citation(s) in RCA: 212] [Impact Index Per Article: 42.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 12/03/2018] [Indexed: 02/04/2023]
Abstract
Type A γ-aminobutyric acid (GABAA) receptors are pentameric ligand-gated ion channels and the main drivers of fast inhibitory neurotransmission in the vertebrate nervous system1,2. Their dysfunction is implicated in a range of neurological disorders, including depression, epilepsy and schizophrenia3,4. Among the numerous assemblies that are theoretically possible, the most prevalent in the brain are the α1β2/3γ2 GABAA receptors5. The β3 subunit has an important role in maintaining inhibitory tone, and the expression of this subunit alone is sufficient to rescue inhibitory synaptic transmission in β1-β3 triple knockout neurons6. So far, efforts to generate accurate structural models for heteromeric GABAA receptors have been hampered by the use of engineered receptors and the presence of detergents7-9. Notably, some recent cryo-electron microscopy reconstructions have reported 'collapsed' conformations8,9; however, these disagree with the structure of the prototypical pentameric ligand-gated ion channel the Torpedo nicotinic acetylcholine receptor10,11, the large body of structural work on homologous homopentameric receptor variants12 and the logic of an ion-channel architecture. Here we present a high-resolution cryo-electron microscopy structure of the full-length human α1β3γ2L-a major synaptic GABAA receptor isoform-that is functionally reconstituted in lipid nanodiscs. The receptor is bound to a positive allosteric modulator 'megabody' and is in a desensitized conformation. Each GABAA receptor pentamer contains two phosphatidylinositol-4,5-bisphosphate molecules, the head groups of which occupy positively charged pockets in the intracellular juxtamembrane regions of α1 subunits. Beyond this level, the intracellular M3-M4 loops are largely disordered, possibly because interacting post-synaptic proteins are not present. This structure illustrates the molecular principles of heteromeric GABAA receptor organization and provides a reference framework for future mechanistic investigations of GABAergic signalling and pharmacology.
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Affiliation(s)
- Duncan Laverty
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK.
| | - Rooma Desai
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Tomasz Uchański
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Simonas Masiulis
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
| | - Wojciech J Stec
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Tomas Malinauskas
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Jasenko Zivanov
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
| | - Els Pardon
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Jan Steyaert
- Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
- VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Keith W Miller
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
| | - A Radu Aricescu
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK.
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.
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24
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Enhanced GABAergic actions resulting from the coapplication of the steroid 3α-hydroxy-5α-pregnane-11,20-dione (alfaxalone) with propofol or diazepam. Sci Rep 2018; 8:10341. [PMID: 29985445 PMCID: PMC6037692 DOI: 10.1038/s41598-018-28754-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 06/29/2018] [Indexed: 11/09/2022] Open
Abstract
Many GABAergic drugs are in clinical use as anesthetics, sedatives, or anxiolytics. We have investigated the actions of the combinations of the neuroactive steroid 3α-hydroxy-5α-pregnane-11,20-dione (alfaxalone) with the intravenous anesthetic propofol or the benzodiazepine diazepam. The goal of the study was to determine whether coapplication of alfaxalone reduces the effective doses and concentrations of propofol and diazepam. Behavioral effects of alfaxalone, propofol, diazepam, and the combinations of the drugs were evaluated during a 30-min activity test in mice. Functional effects of the individual drugs and drug combinations were tested by measuring the decay times of spontaneous inhibitory postsynaptic currents in rat hippocampal neurons, and peak current responses from heterologously expressed concatemeric α1β2γ2L GABAA receptors. Co-administration of alfaxalone increased the sedative actions of propofol and diazepam in mice. The combination of alfaxalone with propofol or diazepam increased the decay times of sIPSCs and shifted the concentration-response relationships for GABA-activated receptors to lower transmitter concentrations. We infer that alfaxalone acts as a co-agonist to enhance the GABAergic effects of propofol and diazepam. We propose that co-administration of alfaxalone, and possibly other neuroactive steroids, can be employed to reduce dosage requirements for propofol and diazepam.
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