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Li X, Guo S, Sun Y, Ding J, Chen C, Wu Y, Li P, Sun T, Wang X. GABRG2 mutations in genetic epilepsy with febrile seizures plus: structure, roles, and molecular genetics. J Transl Med 2024; 22:767. [PMID: 39143639 PMCID: PMC11323400 DOI: 10.1186/s12967-024-05387-1] [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: 03/25/2024] [Accepted: 06/10/2024] [Indexed: 08/16/2024] Open
Abstract
Genetic epilepsy with febrile seizures plus (GEFS+) is a genetic epilepsy syndrome characterized by a marked hereditary tendency inherited as an autosomal dominant trait. Patients with GEFS+ may develop typical febrile seizures (FS), while generalized tonic-clonic seizures (GTCSs) with fever commonly occur between 3 months and 6 years of age, which is generally followed by febrile seizure plus (FS+), with or without absence seizures, focal seizures, or GTCSs. GEFS+ exhibits significant genetic heterogeneity, with polymerase chain reaction, exon sequencing, and single nucleotide polymorphism analyses all showing that the occurrence of GEFS+ is mainly related to mutations in the gamma-aminobutyric acid type A receptor gamma 2 subunit (GABRG2) gene. The most common mutations in GABRG2 are separated in large autosomal dominant families, but their pathogenesis remains unclear. The predominant types of GABRG2 mutations include missense (c.983A → T, c.245G → A, p.Met199Val), nonsense (R136*, Q390*, W429*), frameshift (c.1329delC, p.Val462fs*33, p.Pro59fs*12), point (P83S), and splice site (IVS6+2T → G) mutations. All of these mutations types can reduce the function of ion channels on the cell membrane; however, the degree and mechanism underlying these dysfunctions are different and could be linked to the main mechanism of epilepsy. The γ2 subunit plays a special role in receptor trafficking and is closely related to its structural specificity. This review focused on investigating the relationship between GEFS+ and GABRG2 mutation types in recent years, discussing novel aspects deemed to be great significance for clinically accurate diagnosis, anti-epileptic treatment strategies, and new drug development.
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Affiliation(s)
- Xinxiao Li
- Department of Neurosurgery, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, 450052, People's Republic of China.
| | - Shengnan Guo
- Department of Rehabilitative Medicine, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, 450052, People's Republic of China
| | - Yangyang Sun
- Ningxia Key Laboratory of Cerebrocranial Disease, The Incubation Base of National Key Laboratory, Ningxia Medical University, Yinchuan, Ningxia, 750001, People's Republic of China
| | - Jiangwei Ding
- Department of Neurosurgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, 450052, People's Republic of China
| | - Chao Chen
- Department of Neurosurgery, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, 450052, People's Republic of China
| | - Yuehui Wu
- Department of Neurosurgery, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, 450052, People's Republic of China
| | - Peidong Li
- Department of Neurosurgery, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, 450052, People's Republic of China
| | - Tao Sun
- Ningxia Key Laboratory of Cerebrocranial Disease, The Incubation Base of National Key Laboratory, Ningxia Medical University, Yinchuan, Ningxia, 750001, People's Republic of China.
| | - Xinjun Wang
- Department of Neurosurgery, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, 450052, People's Republic of China.
- Department of Neurosurgery, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, 450052, People's Republic of China.
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Poliquin S, Nwosu G, Randhave K, Shen W, Flamm C, Kang JQ. Modulating Endoplasmic Reticulum Chaperones and Mutant Protein Degradation in GABRG2(Q390X) Associated with Genetic Epilepsy with Febrile Seizures Plus and Dravet Syndrome. Int J Mol Sci 2024; 25:4601. [PMID: 38731820 PMCID: PMC11083348 DOI: 10.3390/ijms25094601] [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: 03/04/2024] [Revised: 04/10/2024] [Accepted: 04/17/2024] [Indexed: 05/13/2024] Open
Abstract
A significant number of patients with genetic epilepsy do not obtain seizure freedom, despite developments in new antiseizure drugs, suggesting a need for novel therapeutic approaches. Many genetic epilepsies are associated with misfolded mutant proteins, including GABRG2(Q390X)-associated Dravet syndrome, which we have previously shown to result in intracellular accumulation of mutant GABAA receptor γ2(Q390X) subunit protein. Thus, a potentially promising therapeutic approach is modulation of proteostasis, such as increasing endoplasmic reticulum (ER)-associated degradation (ERAD). To that end, we have here identified an ERAD-associated E3 ubiquitin ligase, HRD1, among other ubiquitin ligases, as a strong modulator of wildtype and mutant γ2 subunit expression. Overexpressing HRD1 or knockdown of HRD1 dose-dependently reduced the γ2(Q390X) subunit. Additionally, we show that zonisamide (ZNS)-an antiseizure drug reported to upregulate HRD1-reduces seizures in the Gabrg2+/Q390X mouse. We propose that a possible mechanism for this effect is a partial rescue of surface trafficking of GABAA receptors, which are otherwise sequestered in the ER due to the dominant-negative effect of the γ2(Q390X) subunit. Furthermore, this partial rescue was not due to changes in ER chaperones BiP and calnexin, as total expression of these chaperones was unchanged in γ2(Q390X) models. Our results here suggest that leveraging the endogenous ERAD pathway may present a potential method to degrade neurotoxic mutant proteins like the γ2(Q390X) subunit. We also demonstrate a pharmacological means of regulating proteostasis, as ZNS alters protein trafficking, providing further support for the use of proteostasis regulators for the treatment of genetic epilepsies.
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Affiliation(s)
- Sarah Poliquin
- Neuroscience Graduate Program, Vanderbilt University, Nashville, TN 37232, USA;
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37232, USA;
| | - Gerald Nwosu
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37232, USA;
- Department of Neuroscience and Pharmacology, Meharry Medical College, Nashville, TN 37208, USA
- Department of Neurology, Vanderbilt University Medical Center, 465 21st Ave South, Nashville, TN 37232, USA; (K.R.); (W.S.); (C.F.)
| | - Karishma Randhave
- Department of Neurology, Vanderbilt University Medical Center, 465 21st Ave South, Nashville, TN 37232, USA; (K.R.); (W.S.); (C.F.)
| | - Wangzhen Shen
- Department of Neurology, Vanderbilt University Medical Center, 465 21st Ave South, Nashville, TN 37232, USA; (K.R.); (W.S.); (C.F.)
| | - Carson Flamm
- Department of Neurology, Vanderbilt University Medical Center, 465 21st Ave South, Nashville, TN 37232, USA; (K.R.); (W.S.); (C.F.)
| | - Jing-Qiong Kang
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37232, USA;
- Department of Neurology, Vanderbilt University Medical Center, 465 21st Ave South, Nashville, TN 37232, USA; (K.R.); (W.S.); (C.F.)
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
- Vanderbilt Kennedy Center of Human Development, Vanderbilt University, Nashville, TN 37232, USA
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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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Liang W, Wang J, Sui J, Yun F, Shen Y, Zhou J, Wu Y, Shen D, Zhang Q. Inflammation as a target for the treatment of fever-associated epilepsy in zebrafish larvae. Int Immunopharmacol 2023; 116:109802. [PMID: 36738682 DOI: 10.1016/j.intimp.2023.109802] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 01/16/2023] [Accepted: 01/25/2023] [Indexed: 02/05/2023]
Abstract
Inflammation is considered to be involved in epileptogenesis. However, the relationship between fever and inflammation as well as the mechanisms of fever in the occurrence and development of childhood epilepsy need further investigation. Here, we described an in vivo model of hyperthermia-induced seizures in zebrafish larvae with pentylenetetrazole (PTZ) exposure. Hyperthermia increased the susceptibility to seizure and the production of pro-inflammatory factors in PTZ-induced zebrafish larvae. As mutations in GABRG2 have been associated with fever-associated epilepsy, we used a Tg(hGABRG2F343L) zebrafish model expressing mutant human GABRG2(F343L) to further investigate the involvement of inflammation in fever-induced seizures. Our data indicated that hyperthermia also increased the locomotor activity in Tg(hGABRG2F343L) zebrafish larvae. Although the production of pro-inflammatory factors was upregulated by GABRG2 mutation, hyperthermia did not change the production of pro-inflammatory factors significantly. Lipopolysaccharide (LPS) stimulation was sufficient to increase the locomotor activity in zebrafish larvae, suggesting that inflammation contributed to fever-associated epilepsy. The expression of GABRG2 was increased with PTZ induction, especially at a higher temperature. Moreover, inhibition of inflammation by dexamethasone (DEX) reduced the excitability of zebrafish larvae, especially at a higher temperature. Finally, in vitro experiments proved that LPS stimulation increased the production of IL-1β and IL-6 in GABRG2(F343L) transfected cells. Collectively, our study demonstrated that neuroinflammation was induced in febrile seizures, and the increased expression of IL-1β and IL-6 might be responsible for epileptogenesis. The vicious cycle between fever and inflammation might induce seizure onset, and anti-inflammatory strategies might be a potential treatment for fever-associated epilepsy.
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Affiliation(s)
- Wenpeng Liang
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Jie Wang
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Jiahui Sui
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Feng Yun
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Yuntian Shen
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Jing Zhou
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Youjia Wu
- Department of Pediatrics, Affiliated Hospital of Nantong University, Nantong, China
| | - Dingding Shen
- Department of Neurology & Collaborative Innovation Center for Brain Science, Ruijin Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai, China.
| | - Qi Zhang
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China.
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Yang Y, Niu X, Cheng M, Zeng Q, Deng J, Tian X, Wang Y, Yu J, Shi W, Wu W, Ma J, Li Y, Yang X, Zhang X, Jia T, Yang Z, Liao J, Sun Y, Zheng H, Sun S, Sun D, Jiang Y, Zhang Y. Phenotypic Spectrum and Prognosis of Epilepsy Patients With GABRG2 Variants. Front Mol Neurosci 2022; 15:809163. [PMID: 35359574 PMCID: PMC8964129 DOI: 10.3389/fnmol.2022.809163] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 01/28/2022] [Indexed: 02/05/2023] Open
Abstract
OBJECTIVE This study aimed to obtain a comprehensive understanding of the genetic and phenotypic aspects of GABRG2-related epilepsy and its prognosis and to explore the potential prospects for personalized medicine. METHODS Through a multicenter collaboration in China, we analyzed the genotype-phenotype correlation and antiseizure medication (ASM) of patients with GABRG2-related epilepsy. The three-dimensional protein structure of the GABRG2 variant was modeled to predict the effect of GABRG2 missense variants using PyMOL 2.3 software. RESULTS In 35 patients with GABRG2 variants, 22 variants were de novo, and 18 variants were novel. The seizure onset age was ranged from 2 days after birth to 34 months (median age: 9 months). The seizure onset age was less than 1 year old in 22 patients (22/35, 62.9%). Seizure types included focal seizures (68.6%), generalized tonic-clonic seizures (60%), myoclonic seizures (14.3%), and absence seizures (11.4%). Other clinical features included fever-sensitive seizures (91.4%), cluster seizures (57.1%), and developmental delay (45.7%). Neuroimaging was abnormal in 2 patients, including dysplasia of the frontotemporal cortex and delayed myelination of white matter. Twelve patients were diagnosed with febrile seizures plus, eleven with epilepsy and developmental delay, two with Dravet syndrome, two with developmental and epileptic encephalopathy, two with focal epilepsy, two with febrile seizures, and four with unclassified epilepsy. The proportions of patients with missense variants in the extracellular region and the transmembrane region exhibiting developmental delay were 40% and 63.2%, respectively. The last follow-up age ranged from 11 months to 17 years. Seizures were controlled in 71.4% of patients, and 92% of their seizures were controlled by valproate and/or levetiracetam. CONCLUSION The clinical features of GABRG2-related epilepsy included seizure onset, usually in infancy, and seizures were fever-sensitive. More than half of the patients had cluster seizures. Phenotypes of GABRG2-related epilepsy were ranged from mild febrile seizures to severe epileptic encephalopathies. Most patients with GABRG2 variants who experienced seizures had a good prognosis. Valproate and levetiracetam were effective treatments for most patients.
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Affiliation(s)
- Ying Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Xueyang Niu
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Miaomiao Cheng
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Qi Zeng
- Department of Neurology, Shenzhen Children’s Hospital, Shenzhen, China
| | - Jie Deng
- Department of Neurology, Beijing Children’s Hospital, Capital Medical University, Beijing, China
| | - Xiaojuan Tian
- Department of Neurology, Beijing Children’s Hospital, Capital Medical University, Beijing, China
| | - Yi Wang
- Department of Neurology, National Children’s Medical Center, Children’s Hospital of Fudan University, Shanghai, China
| | - Jing Yu
- Department of Neurology, Children’s Hospital of Xinjiang Uygur Autonomous Region, Xinjiang Hospital of Beijing Children’s Hospital, Ürümqi, China
| | - Wenli Shi
- Department of Pediatrics, The First Affiliated Hospital of Henan University of Chinese Medicine, Zhengzhou, China
| | - Wenjuan Wu
- Department of Neurology, Hebei Children’s Hospital, Shijiazhuang, China
| | - Jiehui Ma
- Department of Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yufen Li
- Department of Pediatrics, Linyi People’s Hospital, Linyi, China
| | - Xiaoling Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Xiaoli Zhang
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Tianming Jia
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Zhixian Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Jianxiang Liao
- Department of Neurology, Shenzhen Children’s Hospital, Shenzhen, China
| | - Yan Sun
- Department of Neurology, Children’s Hospital of Xinjiang Uygur Autonomous Region, Xinjiang Hospital of Beijing Children’s Hospital, Ürümqi, China
| | - Hong Zheng
- Department of Pediatrics, The First Affiliated Hospital of Henan University of Chinese Medicine, Zhengzhou, China
| | - Suzhen Sun
- Department of Neurology, Hebei Children’s Hospital, Shijiazhuang, China
| | - Dan Sun
- Department of Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yuwu Jiang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
| | - Yuehua Zhang
- Department of Pediatrics, Peking University First Hospital, Beijing, China
- *Correspondence: Yuehua Zhang,
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Pavone P, Pappalardo XG, Parano E, Falsaperla R, Marino SD, Fink JK, Ruggieri M. Fever-Associated Seizures or Epilepsy: An Overview of Old and Recent Literature Acquisitions. Front Pediatr 2022; 10:858945. [PMID: 35529330 PMCID: PMC9070101 DOI: 10.3389/fped.2022.858945] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 03/17/2022] [Indexed: 02/06/2023] Open
Abstract
In addition to central nervous system infections, seizures and fever may occur together in several neurological disorders. Formerly, based on the clinical features and prognostic evolution, the co-association of seizure and fever included classical febrile seizures (FS) divided into simple, complex, and prolonged FS (also called febrile status epilepticus). Later, this group of disorders has been progressively indicated, with a more inclusive term, as "fever-associated seizures or epilepsy" (FASE) that encompasses: (a) FS divided into simple, complex, and prolonged FS; (b) FS plus; (c) severe myoclonic epilepsy in infancy (Dravet syndrome); (d) genetic epilepsy with FS plus; and (e) febrile infection-related epilepsy syndrome (FIRES). Among the FASE disorders, simple FS, the most common and benign condition, is rarely associated with subsequent epileptic seizures. The correlation of FS with epilepsy and other neurological disorders is highly variable. The pathogenesis of FASE is unclear but immunological and genetic factors play a relevant role and the disorders belonging to the FASE group show to have an underlying common clinical, immunological, and genetic pathway. In this study, we have reviewed and analyzed the clinical data of each of the heterogeneous group of disorders belonging to FASE.
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Affiliation(s)
- Piero Pavone
- Unit of Clinical Pediatrics, AOU "Policlinico", PO "G. Rodolico", University of Catania, Catania, Italy
| | - Xena Giada Pappalardo
- Unit of Catania, National Council of Research, Institute for Research and Biomedical Innovation (IRIB), Catania, Italy.,Department of Biomedical and Biotechnological Sciences (BIOMETEC), University of Catania, Catania, Italy
| | - Enrico Parano
- Unit of Catania, National Council of Research, Institute for Research and Biomedical Innovation (IRIB), Catania, Italy
| | - Raffaele Falsaperla
- Unit of Pediatrics, Neonatology and Neonatal Intensive Care, and Pediatric Emergency, AOU "Policlinico", PO "San Marco", University of Catania, Catania, Italy
| | - Simona Domenica Marino
- Unit of Pediatrics, Neonatology and Neonatal Intensive Care, and Pediatric Emergency, AOU "Policlinico", PO "San Marco", University of Catania, Catania, Italy
| | - John Kane Fink
- Department of Neurology and Ann Arbor Veterans Affairs Medical Center, University of Michigan, Ann Arbor, MI, United States
| | - Martino Ruggieri
- Unit of Rare Diseases of the Nervous System in Childhood, Department of Clinical and Experimental Medicine, Section of Pediatrics and Child Neuropsychiatry, University of Catania, AOU "Policlinico", PO "G. Rodolico", Catania, Italy
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GABRA1 and GABRA6 gene mutations in idiopathic generalized epilepsy patients. Seizure 2021; 93:88-94. [PMID: 34740144 DOI: 10.1016/j.seizure.2021.10.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Revised: 10/14/2021] [Accepted: 10/16/2021] [Indexed: 12/25/2022] Open
Abstract
The GABA receptor is an important epilepsy-associated candidate gene, and has always been a focus in etiology and in the treatment of epilepsy. This study explores the genetic association between GABA receptor gene polymorphisms and epilepsy in a cohort of the Pakistani population. A case-control study was conducted on 150 patients with idiopathic generalized epilepsy (IGE) and 150 controls. Blood samples were collected, and genomic DNA was extracted and amplified using polymerase chain reaction (PCR). The amplified products were subsequently genotyped by Sanger sequencing and the results were analyzed using the chi-square test. Among the five mutational sites observed, two GABRA1 (rs2279020 and novel c.1016_1017insT) and two GABRA6 (rs3219151 and novel c.1344C>G) were found to be significantly associated with IGE. Amino acid alignment showed that a novel insertion mutation, c.1016_1017insT, in GABRA1 disrupted the reading frame and was possibly damaging, whereas c.1344C>G in GABRA6 was responsible for a synonymous mutation. Therefore, both the GABA receptor genes may play critical roles in the development of epilepsy in Pakistani patients.
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Belelli D, Hales TG, Lambert JJ, Luscher B, Olsen R, Peters JA, Rudolph U, Sieghart W. GABA A receptors in GtoPdb v.2021.3. IUPHAR/BPS GUIDE TO PHARMACOLOGY CITE 2021; 2021. [PMID: 35005623 DOI: 10.2218/gtopdb/f72/2021.3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The GABAA receptor is a ligand-gated ion channel of the Cys-loop family that includes the nicotinic acetylcholine, 5-HT3 and strychnine-sensitive glycine receptors. GABAA receptor-mediated inhibition within the CNS occurs by fast synaptic transmission, sustained tonic inhibition and temporally intermediate events that have been termed 'GABAA, slow' [45]. GABAA receptors exist as pentamers of 4TM subunits that form an intrinsic anion selective channel. Sequences of six α, three β, three γ, one δ, three ρ, one ε, one π and one θ GABAA receptor subunits have been reported in mammals [278, 235, 236, 283]. The π-subunit is restricted to reproductive tissue. Alternatively spliced versions of many subunits exist (e.g. α4- and α6- (both not functional) α5-, β2-, β3- and γ2), along with RNA editing of the α3 subunit [71]. The three ρ-subunits, (ρ1-3) function as either homo- or hetero-oligomeric assemblies [359, 50]. Receptors formed from ρ-subunits, because of their distinctive pharmacology that includes insensitivity to bicuculline, benzodiazepines and barbiturates, have sometimes been termed GABAC receptors [359], but they are classified as GABA A receptors by NC-IUPHAR on the basis of structural and functional criteria [16, 235, 236]. Many GABAA receptor subtypes contain α-, β- and γ-subunits with the likely stoichiometry 2α.2β.1γ [168, 235]. It is thought that the majority of GABAA receptors harbour a single type of α- and β - subunit variant. The α1β2γ2 hetero-oligomer constitutes the largest population of GABAA receptors in the CNS, followed by the α2β3γ2 and α3β3γ2 isoforms. Receptors that incorporate the α4- α5-or α 6-subunit, or the β1-, γ1-, γ3-, δ-, ε- and θ-subunits, are less numerous, but they may nonetheless serve important functions. For example, extrasynaptically located receptors that contain α6- and δ-subunits in cerebellar granule cells, or an α4- and δ-subunit in dentate gyrus granule cells and thalamic neurones, mediate a tonic current that is important for neuronal excitability in response to ambient concentrations of GABA [209, 272, 83, 19, 288]. GABA binding occurs at the β+/α- subunit interface and the homologous γ+/α- subunits interface creates the benzodiazepine site. A second site for benzodiazepine binding has recently been postulated to occur at the α+/β- interface ([254]; reviewed by [282]). The particular α-and γ-subunit isoforms exhibit marked effects on recognition and/or efficacy at the benzodiazepine site. Thus, receptors incorporating either α4- or α6-subunits are not recognised by 'classical' benzodiazepines, such as flunitrazepam (but see [356]). The trafficking, cell surface expression, internalisation and function of GABAA receptors and their subunits are discussed in detail in several recent reviews [52, 140, 188, 316] but one point worthy of note is that receptors incorporating the γ2 subunit (except when associated with α5) cluster at the postsynaptic membrane (but may distribute dynamically between synaptic and extrasynaptic locations), whereas as those incorporating the δ subunit appear to be exclusively extrasynaptic. NC-IUPHAR [16, 235, 3, 2] class the GABAA receptors according to their subunit structure, pharmacology and receptor function. Currently, eleven native GABAA receptors are classed as conclusively identified (i.e., α1β2γ2, α1βγ2, α3βγ2, α4βγ2, α4β2δ, α4β3δ, α5βγ2, α6βγ2, α6β2δ, α6β3δ and ρ) with further receptor isoforms occurring with high probability, or only tentatively [235, 236]. It is beyond the scope of this Guide to discuss the pharmacology of individual GABAA receptor isoforms in detail; such information can be gleaned in the reviews [16, 95, 168, 173, 143, 278, 216, 235, 236] and [9, 10]. Agents that discriminate between α-subunit isoforms are noted in the table and additional agents that demonstrate selectivity between receptor isoforms, for example via β-subunit selectivity, are indicated in the text below. The distinctive agonist and antagonist pharmacology of ρ receptors is summarised in the table and additional aspects are reviewed in [359, 50, 145, 223]. Several high-resolution cryo-electron microscopy structures have been described in which the full-length human α1β3γ2L GABAA receptor in lipid nanodiscs is bound to the channel-blocker picrotoxin, the competitive antagonist bicuculline, the agonist GABA (γ-aminobutyric acid), and the classical benzodiazepines alprazolam and diazepam [198].
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9
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El Achkar CM, Harrer M, Smith L, Kelly M, Iqbal S, Maljevic S, Niturad CE, Vissers LELM, Poduri A, Yang E, Lal D, Lerche H, Møller RS, Olson HE. Characterization of the GABRB2-Associated Neurodevelopmental Disorders. Ann Neurol 2020; 89:573-586. [PMID: 33325057 DOI: 10.1002/ana.25985] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 11/30/2020] [Accepted: 12/01/2020] [Indexed: 11/09/2022]
Abstract
OBJECTIVE We aimed to characterize the phenotypic spectrum and functional consequences associated with variants in the gene GABRB2, coding for the γ-aminobutyric acid type A (GABAA ) receptor subunit β2. METHODS We recruited and systematically evaluated 25 individuals with variants in GABRB2, 17 of whom are newly described and 8 previously reported with additional clinical data. Functional analysis was performed using a Xenopus laevis oocyte model system. RESULTS Our cohort of 25 individuals from 22 families with variants in GABRB2 demonstrated a range of epilepsy phenotypes from genetic generalized epilepsy to developmental and epileptic encephalopathy. Fifty-eight percent of individuals had pharmacoresistant epilepsy; response to medications targeting the GABAergic pathway was inconsistent. Developmental disability (present in 84%) ranged from mild intellectual disability to severe global disability; movement disorders (present in 44%) included choreoathetosis, dystonia, and ataxia. Disease-associated variants cluster in the extracellular N-terminus and transmembrane domains 1-3, with more severe phenotypes seen in association with variants in transmembrane domains 1 and 2 and the allosteric binding site between transmembrane domains 2 and 3. Functional analysis of 4 variants in transmembrane domains 1 or 2 (p.Ile246Thr, p.Pro252Leu, p.Ile288Ser, p.Val282Ala) revealed strongly reduced amplitudes of GABA-evoked anionic currents. INTERPRETATION GABRB2-related epilepsy ranges broadly in severity from genetic generalized epilepsy to developmental and epileptic encephalopathies. Developmental disability and movement disorder are key features. The phenotypic spectrum is comparable to other GABAA receptor-encoding genes. Phenotypic severity varies by protein domain. Experimental evidence supports loss of GABAergic inhibition as the mechanism underlying GABRB2-associated neurodevelopmental disorders. ANN NEUROL 2021;89:573-586.
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Affiliation(s)
- Christelle M El Achkar
- Division of Epilepsy and Clinical Neurophysiology and Epilepsy Genetics Program, Department of Neurology, Boston Children's Hospital, Boston, MA.,Department of Neurology, Harvard Medical School, Boston, MA
| | - Merle Harrer
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Lacey Smith
- Division of Epilepsy and Clinical Neurophysiology and Epilepsy Genetics Program, Department of Neurology, Boston Children's Hospital, Boston, MA
| | - McKenna Kelly
- Division of Epilepsy and Clinical Neurophysiology and Epilepsy Genetics Program, Department of Neurology, Boston Children's Hospital, Boston, MA.,Dartmouth Geisel School of Medicine, Hanover, NH
| | - Sumaiya Iqbal
- Center for Development of Therapeutics and Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA
| | - Snezana Maljevic
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.,Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Cristina E Niturad
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Lisenka E L M Vissers
- Department of Human Genetics, Donders Institute for Brain, Cognition, and Behavior, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Annapurna Poduri
- Division of Epilepsy and Clinical Neurophysiology and Epilepsy Genetics Program, Department of Neurology, Boston Children's Hospital, Boston, MA.,Department of Neurology, Harvard Medical School, Boston, MA
| | - Edward Yang
- Department of Radiology, Boston Children's Hospital, Boston, MA
| | - Dennis Lal
- Cleveland Clinic Genomic Medicine Institute and Neurological Institute, Cleveland, OH
| | - Holger Lerche
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Treatment, Danish Epilepsy Center Filadelfia, Dianalund, Denmark.,Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
| | - Heather E Olson
- Division of Epilepsy and Clinical Neurophysiology and Epilepsy Genetics Program, Department of Neurology, Boston Children's Hospital, Boston, MA.,Department of Neurology, Harvard Medical School, Boston, MA
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10
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Fortin O, Vincelette C, Chénier S, Ghais A, Shevell MI, Simard-Tremblay E, Myers KA. Copy number variation in genetic epilepsy with febrile seizures plus. Eur J Paediatr Neurol 2020; 27:111-115. [PMID: 32595013 DOI: 10.1016/j.ejpn.2020.05.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 05/10/2020] [Accepted: 05/14/2020] [Indexed: 11/17/2022]
Abstract
AIM Genetic epilepsy with febrile seizures plus (GEFS+) is a familial epilepsy syndrome in which affected individuals may have a variety of epilepsy phenotypes, the most common being febrile seizures (FS) and febrile seizures plus (FS+). We investigated the possible contribution of copy number variation to GEFS+. METHOD We searched our epilepsy research database for patients in GEFS + families who underwent chromosomal microarray analysis. We reviewed the clinical features and results of genetic testing in these families. RESULTS Of twelve families with available microarray data, four had at least one copy number variant (CNV) identified. In Family 1, the proband had a maternally-inherited 15q11.2 deletion. In Family 5, four different CNVs were identified, variably present in the affected individuals; this included a 19p13.3 deletion affecting CACNA1A. Finally, in both Families 9 and 10, the proband had Dravet syndrome with pathogenic SCN1A variant, as well as a CNV (10q11.22 duplication in Family 9 and 22q11.2 deletion in Family 10). INTERPRETATION The significance of these specific variants is difficult to precisely determine; however, there appeared to be an overrepresentation of CNVs in this small cohort. These findings suggest chromosomal microarray analysis could have clinical utility as part of the workup in GEFS + families.
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Affiliation(s)
- Olivier Fortin
- Department of Pediatrics, Montreal Children's Hospital, McGill University, Montreal, Quebec, Canada
| | - Christian Vincelette
- School of Nursing, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, Quebec, Canada
| | - Sébastien Chénier
- Department of Pediatrics, University of Sherbrooke, Sherbrooke, Quebec, Canada
| | - Ahmad Ghais
- Department of Pediatrics, University of Montreal, Montreal, Quebec, Canada
| | - Michael I Shevell
- Department of Pediatrics, Montreal Children's Hospital, McGill University, Montreal, Quebec, Canada; Department of Neurology & Neurosurgery, Montreal Children's Hospital, McGill University, Montreal, Quebec, Canada; Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - Elisabeth Simard-Tremblay
- Department of Pediatrics, Montreal Children's Hospital, McGill University, Montreal, Quebec, Canada; Department of Neurology & Neurosurgery, Montreal Children's Hospital, McGill University, Montreal, Quebec, Canada
| | - Kenneth A Myers
- Department of Pediatrics, Montreal Children's Hospital, McGill University, Montreal, Quebec, Canada; Department of Neurology & Neurosurgery, Montreal Children's Hospital, McGill University, Montreal, Quebec, Canada; Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada.
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11
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GABRG2 Deletion Linked to Genetic Epilepsy with Febrile Seizures Plus Affects the Expression of GABA A Receptor Subunits and Other Genes at Different Temperatures. Neuroscience 2020; 438:116-136. [PMID: 32418750 DOI: 10.1016/j.neuroscience.2020.04.049] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 04/29/2020] [Accepted: 04/30/2020] [Indexed: 12/11/2022]
Abstract
Mutations in γ-aminobutyric acid A receptor (GABAA) subunits and sodium channel genes, especially GABRG2 and SCN1A, have been reported to be associated with febrile seizures (FS) and genetic epilepsy with febrile seizures plus (GEFS+). GEFS+ is a well-known family of epileptic syndrome with autosomal dominant inheritance in children. Its most common phenotypes are febrile seizures often with accessory afebrile generalized tonic-clonic seizures, febrile seizures plus (FS+), severe epileptic encephalopathy, as well as other types of generalized or localization-related seizures. However, the pathogenesis of febrile seizures remains largely unknown. Here, we generated a GABRG2 gene knockout cell line (HT22GABRG2KO) by applying the CRISPR/Cas9-mediated genomic deletion in HT-22 mouse hippocampal neuronal cell line to explore the function of GABRG2 in vitro. With mRNA-seq, we found significant changes in the expression profiles of several epilepsy-related genes when GABRG2 was knockout, some of them showing temperature-induced changes as well. Kyoto Encyclopedia Gene and Genomic (KEGG) analysis revealed a significant alteration in the MAPK and PI3K-Akt signaling pathways. We also observed an up-regulation of the matrix metalloproteinases (MMPs) family after GABRG2 knockout. Furthermore, the significant decrease in expression of GABRA1 and CACNA1A (but not others) with an increase in temperature is a novel finding. In summary, mutations in the GABAA receptor can lead to a decrease in numbers of receptors, which may cause the impairment of GABAergic pathway signaling. This data has been the first time to reveal that GABRG2 mutations would affect the function of other genes, and based on this finding we hope this work would also provide a new direction for the research of GABRG2 in GEFS+. It also may provide a molecular basis for the severity of epilepsy, and guide the clinical medication for the treatment of the epilepsy focused on the function on GABAA receptors, which, might be a new strategy for genetic diagnosis and targeted treatment of epilepsy.
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12
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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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13
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Angione K, Eschbach K, Smith G, Joshi C, Demarest S. Genetic testing in a cohort of patients with potential epilepsy with myoclonic-atonic seizures. Epilepsy Res 2019; 150:70-77. [PMID: 30660939 DOI: 10.1016/j.eplepsyres.2019.01.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 01/10/2019] [Accepted: 01/13/2019] [Indexed: 10/27/2022]
Abstract
Epilepsy with myoclonic-atonic seizures (EMAS) accounts for 1-2% of all childhood-onset epilepsies. EMAS has been shown to have an underlying genetic component, however the genetics of this disorder is not yet well understood. The purpose of this study was to review genetic testing results for a cohort of EMAS patients. A retrospective chart review was conducted for 77 patients evaluated at Children's Hospital Colorado with a potential diagnosis of EMAS. Genetic testing and biochemical testing was reviewed. Family history data was also collected. Seventy-seven percent of the cohort had at least one genetic test performed, and a molecular diagnosis was reached for six patients. Thirty-seven patients had a microarray, six of which identified a copy number variant. Only one was felt to contribute to the phenotype (2p16.3 deletion including NRXN1). Fifty-one patients had an epilepsy panel, two of which were positive (likely pathogenic variant in SCN1A, pathogenic variant in GABRG2). Of the six patients who had whole exome sequencing, two were negative, three were positive or likely positive, and one had multiple variants not felt to explain the phenotype. While EMAS is widely accepted to have a strong genetic component, the diagnostic yield of genetic testing remains low. This may be because several genes now thought to be associated with EMAS are not included on the more commonly ordered epilepsy panels, or have only recently been added to them.
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Affiliation(s)
- Katie Angione
- University of Colorado Denver, Department of Pediatrics, Section of Neurology, United States.
| | - Krista Eschbach
- University of Colorado Denver, Department of Pediatrics, Section of Neurology, United States
| | - Garnett Smith
- University of Colorado Denver, Department of Pediatrics, Section of Neurology, United States
| | - Charuta Joshi
- University of Colorado Denver, Department of Pediatrics, Section of Neurology, United States
| | - Scott Demarest
- University of Colorado Denver, Department of Pediatrics, Section of Neurology, United States
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14
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Wong SQ, Jones A, Dodd S, Grimes D, Barclay JW, Marson AG, Cunliffe VT, Burgoyne RD, Sills GJ, Morgan A. A Caenorhabditis elegans assay of seizure-like activity optimised for identifying antiepileptic drugs and their mechanisms of action. J Neurosci Methods 2018; 309:132-142. [PMID: 30189284 PMCID: PMC6200019 DOI: 10.1016/j.jneumeth.2018.09.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 08/14/2018] [Accepted: 09/02/2018] [Indexed: 11/28/2022]
Abstract
Worms with mutant GABAA receptors exhibit convulsions upon exposure to pentylenetetrazol. Convulsions are prevented by the approved anti-epileptic drug, ethosuximide. C. elegans model is a higher throughput, ethical alternative to rodent seizure models.
Background Epilepsy affects around 1% of people, but existing antiepileptic drugs (AEDs) only offer symptomatic relief and are ineffective in approximately 30% of patients. Hence, new AEDs are sorely needed. However, a major bottleneck is the low-throughput nature of early-stage AED screens in conventional rodent models. This process could potentially be expedited by using simpler invertebrate systems, such as the nematode Caenorhabditis elegans. New method Head-bobbing convulsions were previously reported to be inducible by pentylenetetrazol (PTZ) in C. elegans with loss-of-function mutations in unc-49, which encodes a GABAA receptor. Given that epilepsy-linked mutations in human GABAA receptors are well documented, this could represent a clinically-relevant system for early-stage AED screens. However, the original agar plate-based assay is unsuited to large-scale screening and has not been validated for identifying AEDs. Therefore, we established an alternative streamlined, higher-throughput approach whereby mutants were treated with PTZ and AEDs via liquid-based incubation. Results Convulsions induced within minutes of PTZ exposure in unc-49 mutants were strongly inhibited by the established AED ethosuximide. This protective activity was independent of ethosuximide’s suggested target, the T-type calcium channel, as a null mutation in the worm cca-1 ortholog did not affect ethosuximide’s anticonvulsant action. Comparison with existing method Our streamlined assay is AED-validated, feasible for higher throughput compound screens, and can facilitate insights into AED mechanisms of action. Conclusions Based on an epilepsy-associated genetic background, this C. elegans unc-49 model of seizure-like activity presents an ethical, higher throughput alternative to conventional rodent seizure models for initial AED screens.
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Affiliation(s)
- Shi Quan Wong
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Alistair Jones
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Steven Dodd
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Douglas Grimes
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Jeff W Barclay
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Anthony G Marson
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Vincent T Cunliffe
- Department of Biomedical Science, University of Sheffield, Sheffield, UK.
| | - Robert D Burgoyne
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Graeme J Sills
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
| | - Alan Morgan
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
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15
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Lorenz-Guertin JM, Bambino MJ, Jacob TC. γ2 GABA AR Trafficking and the Consequences of Human Genetic Variation. Front Cell Neurosci 2018; 12:265. [PMID: 30190672 PMCID: PMC6116786 DOI: 10.3389/fncel.2018.00265] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 08/02/2018] [Indexed: 11/13/2022] Open
Abstract
GABA type A receptors (GABAARs) mediate the majority of fast inhibitory neurotransmission in the central nervous system (CNS). Most prevalent as heteropentamers composed of two α, two β, and a γ2 subunit, these ligand-gated ionotropic chloride channels are capable of extensive genetic diversity (α1-6, β1-3, γ1-3, δ, 𝜀, 𝜃, π, ρ1-3). Part of this selective GABAAR assembly arises from the critical role for γ2 in maintaining synaptic receptor localization and function. Accordingly, mutations in this subunit account for over half of the known epilepsy-associated genetic anomalies identified in GABAARs. Fundamental structure-function studies and cellular pathology investigations have revealed dynamic GABAAR trafficking and synaptic scaffolding as critical regulators of GABAergic inhibition. Here, we introduce in vitro and in vivo findings regarding the specific role of the γ2 subunit in receptor trafficking. We then examine γ2 subunit human genetic variation and assess disease related phenotypes and the potential role of altered GABAAR trafficking. Finally, we discuss new-age imaging techniques and their potential to provide novel insight into critical regulatory mechanisms of GABAAR function.
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Affiliation(s)
- Joshua M Lorenz-Guertin
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
| | - Matthew J Bambino
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
| | - Tija C Jacob
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
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16
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Abstract
Fever-associated seizures or epilepsy (FASE) is primarily characterised by the occurrence of a seizure or epilepsy usually accompanied by a fever. It is common in infants and children, and generally includes febrile seizures (FS), febrile seizures plus (FS+), Dravet syndrome (DS) and genetic epilepsy with febrile seizures plus (GEFSP). The aetiology of FASE is unclear. Genetic factors may play crucial roles in FASE. Mutations in certain genes may cause a wide spectrum of phenotypical overlap ranging from isolated FS, FS+ and GEFSP to DS. Synapse-associated proteins, postsynaptic GABAA receptor, and sodium channels play important roles in synaptic transmission. Mutations in these genes may involve in the pathogenesis of FASE. Elevated temperature promotes synaptic vesicle (SV) recycling and enlarges SV size, which may enhance synaptic transmission and contribute to FASE occurring. This review provides an overview of the loci, genes, underlying pathogenesis and the fever-inducing effect of FASE. It may provide a more comprehensive understanding of pathogenesis and contribute to the clinical diagnosis of FASE.
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17
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Chuang SH, Reddy DS. Genetic and Molecular Regulation of Extrasynaptic GABA-A Receptors in the Brain: Therapeutic Insights for Epilepsy. J Pharmacol Exp Ther 2017; 364:180-197. [PMID: 29142081 DOI: 10.1124/jpet.117.244673] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 11/13/2017] [Indexed: 12/18/2022] Open
Abstract
GABA-A receptors play a pivotal role in many brain diseases. Epilepsy is caused by acquired conditions and genetic defects in GABA receptor channels regulating neuronal excitability in the brain. The latter is referred to as GABA channelopathies. In the last two decades, major advances have been made in the genetics of epilepsy. The presence of specific GABAergic genetic abnormalities leading to some of the classic epileptic syndromes has been identified. Advances in molecular cloning and recombinant systems have helped characterize mutations in GABA-A receptor subunit genes in clinical neurology. GABA-A receptors are the prime targets for neurosteroids (NSs). However, GABA-A receptors are not static but undergo rapid changes in their number or composition in response to the neuroendocrine milieu. This review describes the recent advances in the genetic and neuroendocrine control of extrasynaptic and synaptic GABA-A receptors in epilepsy and its impact on neurologic conditions. It highlights the current knowledge of GABA genetics in epilepsy, with an emphasis on the neuroendocrine regulation of extrasynaptic GABA-A receptors in network excitability and seizure susceptibility. Recent advances in molecular regulation of extrasynaptic GABA-A receptor-mediated tonic inhibition are providing unique new therapeutic approaches for epilepsy, status epilepticus, and certain brain disorders. The discovery of an extrasynaptic molecular mechanism represents a milestone for developing novel therapies such as NS replacement therapy for catamenial epilepsy.
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Affiliation(s)
- Shu-Hui Chuang
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
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18
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Steel D, Symonds JD, Zuberi SM, Brunklaus A. Dravet syndrome and its mimics: Beyond SCN1A. Epilepsia 2017; 58:1807-1816. [DOI: 10.1111/epi.13889] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/10/2017] [Indexed: 12/11/2022]
Affiliation(s)
- Dora Steel
- The Paediatric Neurosciences Research Group; Royal Hospital for Children; Glasgow United Kingdom
| | - Joseph D. Symonds
- The Paediatric Neurosciences Research Group; Royal Hospital for Children; Glasgow United Kingdom
- School of Medicine; University of Glasgow; Glasgow United Kingdom
| | - Sameer M. Zuberi
- The Paediatric Neurosciences Research Group; Royal Hospital for Children; Glasgow United Kingdom
- School of Medicine; University of Glasgow; Glasgow United Kingdom
| | - Andreas Brunklaus
- The Paediatric Neurosciences Research Group; Royal Hospital for Children; Glasgow United Kingdom
- School of Medicine; University of Glasgow; Glasgow United Kingdom
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19
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Kang JQ. Defects at the crossroads of GABAergic signaling in generalized genetic epilepsies. Epilepsy Res 2017; 137:9-18. [PMID: 28865303 DOI: 10.1016/j.eplepsyres.2017.08.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 08/14/2017] [Accepted: 08/22/2017] [Indexed: 12/16/2022]
Abstract
Seizure disorders are very common and affect 3% of the general population. The recurrent unprovoked seizures that are also called epilepsies are highly diverse as to both underlying genetic basis and clinic presentations. Recent genetic advances and sequencing technologies indicate that many epilepsies previously thought to be without known causes, or idiopathic generalized epilepsies (IGEs), are virtually genetic epilepsy as they are caused by genetic variations. IGEs are estimated to account for ∼15-20% of all epilepsies. Initially IGEs were primarily considered channelopathies, because the first genetic defects identified in IGEs involved ion channel genes. However, new findings indicate that mutations in many non ion channel genes are also involved in addition to those in ion channel genes. Interestingly, mutations in many genes associated with epilepsy affect GABAergic signaling, a major biological pathway in epilepsy. Additionally, many antiepileptic drugs work via enhancing GABAergic signaling. Hence, the review will focus on the mutations that impair GABAergic signaling and selectively discuss the newly identified STXBP1, PRRT2, and DNM1 in addition to those long-established epilepsy ion channel genes that also impair GABAergic signaling like SCN1A and GABAA receptor subunit genes. GABAergic signaling includes the pre- and post- synaptic mechanisms. Some mutations, such as STXBP1, PRRT2, DNM1, and SCN1A, impair GABAergic signaling mainly via pre-synaptic mechanisms while those mutations in GABAA receptor subunit genes impair GABAergic signaling via post-synaptic mechanisms. Nevertheless, these findings suggest impaired GABAergic signaling is a converging pathway of defects for many ion channel or non ion channel mutations associated with genetic epilepsies.
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Affiliation(s)
- Jing-Qiong Kang
- Departments of Neurology, Vanderbilt University Medical Center, Nashville, TN, 37232-8552, USA; Affiliated Hospital of Nantong University, Jiangsu, 226001, China; Vanderbilt Brain Institute, Vanderbilt Kennedy Center of Human Development, Vanderbilt University, Nashville, TN, 37232-8522, USA.
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20
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Kang JQ, Macdonald RL. Molecular Pathogenic Basis for GABRG2 Mutations Associated With a Spectrum of Epilepsy Syndromes, From Generalized Absence Epilepsy to Dravet Syndrome. JAMA Neurol 2017; 73:1009-16. [PMID: 27367160 DOI: 10.1001/jamaneurol.2016.0449] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
OBJECTIVE In this review article, we focus on the molecular pathogenic basis for genetic generalized epilepsies associated with mutations in the inhibitory γ-aminobutyric acid (GABAA) receptor γ2 subunit gene, GABRG2 (OMIM 137164), an established epilepsy gene. OBSERVATIONS The γ-aminobutyric acid (GABAA) receptor γ2 subunit gene, GABRG2, is abundantly expressed in the mammalian brain, and its encoded γ2 subunit is assembled into αβγ2 receptors, which are the major GABAA receptor isoforms in the brain. The γ2 subunits have a critical role in GABAA receptor trafficking and clustering at synapses. They reside inside the endoplasmic reticulum after synthesis, where they oligomerize with other binding partners, such as α and β subunits, and further assemble into pentameric receptors. Only correctly assembled receptors can traffic beyond the endoplasmic reticulum and reach the cell surface and synapses, where they conduct chloride ion current when activated by GABA. Mutations in GABRG2 have been associated with simple febrile seizures and with genetic epilepsy syndromes, including childhood absence epilepsy, generalized epilepsy with febrile seizures plus, and Dravet syndrome or severe myoclonic epilepsy in infancy. The mutations include missense, nonsense, and frameshift mutations, as well as splice-site and deletion mutations. The mutations have been identified in both coding and noncoding sequences like splice sites. In the coding sequence, these mutations are found in multiple locations, including the extracellular N-terminus, transmembrane domains, and transmembrane 3-transmembrane 4 intracellular loop. All of these mutations reduced channel function but to different extents and by diverse mechanisms, including nonsense-mediated messenger RNA decay, endoplasmic reticulum-associated protein degradation, dominant negative suppression of partnering subunits, mutant subunit aggregation causing cell stress and cell death, and gating defects. CONCLUSIONS AND RELEVANCE We conclude that the epilepsy phenotypic heterogeneity associated with GABRG2 mutations may be related to the extent of the reduction of GABAA receptor channel function and the differential dominant negative suppression, as well to toxicity related to the metabolism of mutant subunit proteins resulting from each mutant γ2 subunit, in addition to different genetic backgrounds.
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Affiliation(s)
- Jing-Qiong Kang
- Department of Neurology, Vanderbilt University, Nashville, Tennessee
| | - Robert L Macdonald
- Department of Neurology, Vanderbilt University, Nashville, Tennessee2Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee3Department of Pharmacology, Vanderbilt University, Nashville, Tennessee
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21
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Ion Channel Genes and Epilepsy: Functional Alteration, Pathogenic Potential, and Mechanism of Epilepsy. Neurosci Bull 2017; 33:455-477. [PMID: 28488083 DOI: 10.1007/s12264-017-0134-1] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 02/20/2017] [Indexed: 01/29/2023] Open
Abstract
Ion channels are crucial in the generation and modulation of excitability in the nervous system and have been implicated in human epilepsy. Forty-one epilepsy-associated ion channel genes and their mutations are systematically reviewed. In this paper, we analyzed the genotypes, functional alterations (funotypes), and phenotypes of these mutations. Eleven genes featured loss-of-function mutations and six had gain-of-function mutations. Nine genes displayed diversified funotypes, among which a distinct funotype-phenotype correlation was found in SCN1A. These data suggest that the funotype is an essential consideration in evaluating the pathogenicity of mutations and a distinct funotype or funotype-phenotype correlation helps to define the pathogenic potential of a gene.
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22
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Zou F, McWalter K, Schmidt L, Decker A, Picker JD, Lincoln S, Sweetser DA, Briere LC, Harini C, Marsh E, Medne L, Wang RY, Leydiker K, Mower A, Visser G, Cuppen I, van Gassen KL, van der Smagt J, Yousaf A, Tennison M, Shanmugham A, Butler E, Richard G, McKnight D. Expanding the phenotypic spectrum of GABRG2 variants: a recurrent GABRG2 missense variant associated with a severe phenotype. J Neurogenet 2017; 31:30-36. [PMID: 28460589 DOI: 10.1080/01677063.2017.1315417] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Pathogenic missense and truncating variants in the GABRG2 gene cause a spectrum of epilepsies, from Dravet syndrome to milder simple febrile seizures. In most cases, pathogenic missense variants in the GABRG2 gene segregate with a febrile seizure phenotype. In this case series, we report a recurrent, de novo missense variant (c0.316 G > A; p.A106T) in the GABRG2 gene that was identified in five unrelated individuals. These patients were described to have a more severe phenotype than previously reported for GABRG2 missense variants. Common features include variable early-onset seizures, significant motor and speech delays, intellectual disability, hypotonia, movement disorder, dysmorphic features and vision/ocular issues. Our report further explores a recurrent pathogenic missense variant within the GABRG2 variant family and broadens the spectrum of associated phenotypes for GABRG2-associated disorders.
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Affiliation(s)
| | | | | | | | - Jonathan D Picker
- b Division of Genetics and Genomics , Boston Children's Hospital , Boston , MA , USA
| | - Sharyn Lincoln
- b Division of Genetics and Genomics , Boston Children's Hospital , Boston , MA , USA.,c NIH Common Fund , Undiagnosed Diseases Network , Bethesda , MD , USA
| | - David A Sweetser
- c NIH Common Fund , Undiagnosed Diseases Network , Bethesda , MD , USA.,d Department of Medical Genetics , Massachusetts General Hospital for Children , Boston , MA , USA
| | - Lauren C Briere
- c NIH Common Fund , Undiagnosed Diseases Network , Bethesda , MD , USA.,d Department of Medical Genetics , Massachusetts General Hospital for Children , Boston , MA , USA
| | - Chellamani Harini
- e Division of Neurophysiology , Boston Children's Hospital , Boston , MA , USA
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- c NIH Common Fund , Undiagnosed Diseases Network , Bethesda , MD , USA
| | - Eric Marsh
- f Division of Child Neurology, Departments of Neurology and Pediatrics , Children's Hospital of Philadelphia , Philadelphia , PA , USA
| | - Livija Medne
- g Individualized Medical Genetics Center, Division of Human Genetics, Division of Neurology , The Children's Hospital of Philadelphia , Philadelphia , PA , USA
| | - Raymond Y Wang
- h Division of Metabolic Disorders , CHOC Children's Hospital , Orange , CA , USA
| | - Karen Leydiker
- h Division of Metabolic Disorders , CHOC Children's Hospital , Orange , CA , USA
| | - Andrew Mower
- i Neurology , CHOC Children's Hospital , Orange , CA , USA
| | - Gepke Visser
- j Wilhelmina Children's Hospital/University Medical Center , Utrecht , the Netherlands
| | - Inge Cuppen
- j Wilhelmina Children's Hospital/University Medical Center , Utrecht , the Netherlands
| | - Koen L van Gassen
- k Department of Genetics , University Medical Center Utrecht , Utrecht , the Netherlands
| | - Jasper van der Smagt
- k Department of Genetics , University Medical Center Utrecht , Utrecht , the Netherlands
| | - Adeel Yousaf
- l University of North Carolina at Chapel Hill , Chapel Hill , NC , USA
| | - Michael Tennison
- m University of North Carolina at Chapel Hill , Chapel Hill , NC , USA
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23
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Lim KS, Ng CC, Chan CK, Foo WS, Low JSY, Tan CT. Ethnic variation of genetic (idiopathic) generalized epilepsy in Malaysia. Seizure 2017; 45:24-27. [DOI: 10.1016/j.seizure.2016.11.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 10/19/2016] [Accepted: 11/17/2016] [Indexed: 10/20/2022] Open
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24
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Differential protein structural disturbances and suppression of assembly partners produced by nonsense GABRG2 epilepsy mutations: implications for disease phenotypic heterogeneity. Sci Rep 2016; 6:35294. [PMID: 27762395 PMCID: PMC5071880 DOI: 10.1038/srep35294] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 09/14/2016] [Indexed: 12/01/2022] Open
Abstract
Mutations in GABAA receptor subunit genes are frequently associated with epilepsy, and nonsense mutations in GABRG2 are associated with several epilepsy syndromes including childhood absence epilepsy, generalized tonic clonic seizures and the epileptic encephalopathy, Dravet syndrome. The molecular basis for the phenotypic heterogeneity of mutations is unclear. Here we focused on three nonsense mutations in GABRG2 (GABRG2(R136*), GABRG2(Q390*) and GABRG2(W429*)) associated with epilepsies of different severities. Structural modeling and structure-based analysis indicated that the surface of the wild-type γ2 subunit was naturally hydrophobic, which is suitable to be buried in the cell membrane. Different mutant γ2 subunits had different stabilities and different interactions with their wild-type subunit binding partners because they adopted different conformations and had different surface hydrophobicities and different tendency to dimerize. We utilized flow cytometry and biochemical approaches in combination with lifted whole cell patch-clamp recordings. We demonstrated that the truncated subunits had no to minimal surface expression and unchanged or reduced surface expression of wild-type partnering subunits. The amplitudes of GABA-evoked currents from the mutant α1β2γ2(R136*), α1β2γ2(Q390*) and α1β2γ2(W429*) receptors were reduced compared to the currents from α1β2γ2 receptors but with differentially reduced levels. This thus suggests differential protein structure disturbances are correlated with disease severity.
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25
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Warner TA, Shen W, Huang X, Liu Z, Macdonald RL, Kang JQ. Differential molecular and behavioural alterations in mouse models of GABRG2 haploinsufficiency versus dominant negative mutations associated with human epilepsy. Hum Mol Genet 2016; 25:3192-3207. [PMID: 27340224 PMCID: PMC5179921 DOI: 10.1093/hmg/ddw168] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 05/19/2016] [Accepted: 05/23/2016] [Indexed: 11/12/2022] Open
Abstract
Genetic epilepsy is a common disorder with phenotypic variation, but the basis for the variation is unknown. Comparing the molecular pathophysiology of mutations in the same epilepsy gene may provide mechanistic insights into the phenotypic heterogeneity. GABRG2 is an established epilepsy gene, and mutations in it produce epilepsy syndromes with varying severities. The disease phenotype in some cases may be caused by simple loss of subunit function (functional haploinsufficiency), while others may be caused by loss-of-function plus dominant negative suppression and other cellular toxicity. Detailed molecular defects and the corresponding seizures and related comorbidities resulting from haploinsufficiency and dominant negative mutations, however, have not been compared. Here we compared two mouse models of GABRG2 loss-of-function mutations associated with epilepsy with different severities, Gabrg2+/Q390X knockin (KI) and Gabrg2+/- knockout (KO) mice. Heterozygous Gabrg2+/Q390X KI mice are associated with a severe epileptic encephalopathy due to a dominant negative effect of the mutation, while heterozygous Gabrg2+/- KO mice are associated with mild absence epilepsy due to simple haploinsufficiency. Unchanged at the transcriptional level, KI mice with severe epilepsy had neuronal accumulation of mutant γ2 subunits, reduced remaining functional wild-type subunits in dendrites and synapses, while KO mice with mild epilepsy had no intracellular accumulation of the mutant subunits and unaffected biogenesis of the remaining wild-type subunits. Consequently, KI mice with dominant negative mutations had much less wild-type receptor expression, more severe seizures and behavioural comorbidities than KO mice. This work provides insights into the pathophysiology of epilepsy syndrome heterogeneity and designing mechanism-based therapies.
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Affiliation(s)
| | | | | | | | - Robert L Macdonald
- Departments of Neurology
- Molecular Physiology and Biophysics
- Pharmacology
- The Vanderbilt Brain Institute, Vanderbilt University Medical Center Nashville, TN 37212, USA
| | - Jing-Qiong Kang
- Departments of Neurology
- The Vanderbilt Brain Institute, Vanderbilt University Medical Center Nashville, TN 37212, USA
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26
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Dixit AB, Banerjee J, Ansari A, Tripathi M, Chandra SP. Mutations in GABRG2 receptor gene are not a major factor in the pathogenesis of mesial temporal lobe epilepsy in Indian population. Ann Indian Acad Neurol 2016; 19:236-41. [PMID: 27293336 PMCID: PMC4888688 DOI: 10.4103/0972-2327.182304] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
AIM This study is focused on GABRG2 gene sequence variations in patients with mesial temporal lobe epilepsy (mTLE). The GABAAreceptor is a heteropentameric receptor and alpha-1 beta-2 gamma-2 subunits combination is most abundant and present in almost all regions of the brain. The gamma-2 subunit (GABRG2) gene mutations have been reported in different epilepsy pathologies. In the present study we have looked for GABRG2 gene sequence variations in patients with mTLE. MATERIALS AND METHODS Twenty patients (12 females and eight males, age 4.6-38 years) with MTLE were recruited for this investigation. Patients were recommended for epilepsy surgery after all clinical investigations as per the epilepsy protocol. Ethnically matched glioma or meningioma patients were considered as nonepileptic controls. During temporal lobectomy of amygdalohippocampectomy, hippocampal brain tissue samples were resected guided by intraoperative electrocorticography (ECoG) activity. All 11 exons of GABRG2 gene with their flanking intronic regions were amplified by polymerase chain reaction (PCR) and screened by DNA sequencing analysis for sequence variations. STATISTICAL ANALYSIS USED Comparison of allele frequencies between patient and control groups was determined using a c(2) test. RESULTS AND CONCLUSIONS Total five DNA sequence variations were identified, three in exonic regions (c.643A > G, rs211035), (c.T > A, rs424740), and (c.C > T, rs418210) and two in intronic regions (c.751 + 41A > G, rs211034) and (c.751 + 52G > A, rs 34281163). Allele frequencies of variants identified in this study did not differ between patients and normal controls. Thus, we conclude that GABRG2 gene may not be playing significant role in the development of epilepsy or as a susceptibility gene in patients with MTLE in Indian population.
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Affiliation(s)
- Aparna Banerjee Dixit
- Center for Excellence in Epilepsy, A joint National Brain Research Centre-All Institute of Medical Sciences Collaboration, National Brain Research Centre, Manesar, Haryana, India
| | - Jyotirmoy Banerjee
- Center for Excellence in Epilepsy, A joint National Brain Research Centre-All Institute of Medical Sciences Collaboration, National Brain Research Centre, Manesar, Haryana, India
| | - Abuzar Ansari
- Department of Neurosurgery, All Institute of Medical Sciences, New Delhi, India
| | - Manjari Tripathi
- Department of Neurology, All Institute of Medical Sciences, New Delhi, India
| | - Sarat P Chandra
- Department of Neurosurgery, All Institute of Medical Sciences, New Delhi, India
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27
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Kodera H, Ohba C, Kato M, Maeda T, Araki K, Tajima D, Matsuo M, Hino-Fukuyo N, Kohashi K, Ishiyama A, Takeshita S, Motoi H, Kitamura T, Kikuchi A, Tsurusaki Y, Nakashima M, Miyake N, Sasaki M, Kure S, Haginoya K, Saitsu H, Matsumoto N. De novo GABRA1 mutations in Ohtahara and West syndromes. Epilepsia 2016; 57:566-73. [PMID: 26918889 DOI: 10.1111/epi.13344] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/28/2016] [Indexed: 12/01/2022]
Abstract
OBJECTIVE GABRA1 mutations have been identified in patients with familial juvenile myoclonic epilepsy, sporadic childhood absence epilepsy, and idiopathic familial generalized epilepsy. In addition, de novo GABRA1 mutations were recently reported in a patient with infantile spasms and four patients with Dravet syndrome. Those reports suggest that GABRA1 mutations are associated with infantile epilepsy including early onset epileptic encephalopathies. In this study, we searched for GABRA1 mutations in patients with infantile epilepsy to investigate the phenotypic spectrum of GABRA1 mutations. METHODS In total, 526 and 145 patients with infantile epilepsy were analyzed by whole-exome sequencing and GABRA1-targeted resequencing, respectively. RESULTS We identified five de novo missense GABRA1 mutations in six unrelated patients. A p.R112Q mutation in the long extracellular N-terminus was identified in a patient with infantile epilepsy; p.P260L, p.M263T, and p.M263I in transmembrane spanning domain 1 (TM1) were identified in three unrelated patients with West syndrome and a patient with Ohtahara syndrome, respectively; and p.V287L in TM2 was identified in a patient with unclassified early onset epileptic encephalopathy. Four of these mutations have not been observed previously. SIGNIFICANCE Our study suggests that de novo GABRA1 mutations can cause early onset epileptic encephalopathies, including Ohtahara syndrome and West syndrome.
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Affiliation(s)
- Hirofumi Kodera
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Chihiro Ohba
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Mitsuhiro Kato
- Department of Pediatrics, Yamagata University Faculty of Medicine, Yamagata, Japan.,Department of Pediatrics, Showa University School of Medicine, Tokyo, Japan
| | - Toshiyuki Maeda
- Department of Pediatrics, Faculty of Medicine, Saga University, Saga, Japan
| | - Kaoru Araki
- Department of Pediatrics, Faculty of Medicine, Saga University, Saga, Japan
| | - Daisuke Tajima
- Department of Pediatrics, Faculty of Medicine, Saga University, Saga, Japan
| | - Muneaki Matsuo
- Department of Pediatrics, Faculty of Medicine, Saga University, Saga, Japan
| | - Naomi Hino-Fukuyo
- Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan
| | - Kosuke Kohashi
- Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Akihiko Ishiyama
- Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Saoko Takeshita
- Department of Pediatrics, Yokohama City University Medical Center, Yokohama, Japan
| | - Hirotaka Motoi
- Department of Pediatrics, Yokohama City University Medical Center, Yokohama, Japan
| | - Taro Kitamura
- Division of Pediatrics, Sendai City Hospital, Sendai, Japan
| | - Atsuo Kikuchi
- Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan
| | - Yoshinori Tsurusaki
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Mitsuko Nakashima
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Noriko Miyake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Masayuki Sasaki
- Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Shigeo Kure
- Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan
| | - Kazuhiro Haginoya
- Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan.,Department of Pediatric Neurology, Takuto Rehabilitation Center for Children, Sendai, Japan
| | - Hirotomo Saitsu
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
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28
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Boillot M, Morin-Brureau M, Picard F, Weckhuysen S, Lambrecq V, Minetti C, Striano P, Zara F, Iacomino M, Ishida S, An-Gourfinkel I, Daniau M, Hardies K, Baulac M, Dulac O, Leguern E, Nabbout R, Baulac S. Novel GABRG2 mutations cause familial febrile seizures. NEUROLOGY-GENETICS 2015; 1:e35. [PMID: 27066572 PMCID: PMC4811385 DOI: 10.1212/nxg.0000000000000035] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 09/30/2015] [Indexed: 12/14/2022]
Abstract
Objective: To identify the genetic cause in a large family with febrile seizures (FS) and temporal lobe epilepsy (TLE) and subsequently search for additional mutations in a cohort of 107 families with FS, with or without epilepsy. Methods: The cohort consisted of 1 large family with FS and TLE, 64 smaller French families recruited through a national French campaign, and 43 Italian families. Molecular analyses consisted of whole-exome sequencing and mutational screening. Results: Exome sequencing revealed a p.Glu402fs*3 mutation in the γ2 subunit of the GABAA receptor gene (GABRG2) in the large family with FS and TLE. Three additional nonsense and frameshift GABRG2 mutations (p.Arg136*, p.Val462fs*33, and p.Pro59fs*12), 1 missense mutation (p.Met199Val), and 1 exonic deletion were subsequently identified in 5 families of the follow-up cohort. Conclusions: We report GABRG2 mutations in 5.6% (6/108) of families with FS, with or without associated epilepsy. This study provides evidence that GABRG2 mutations are linked to the FS phenotype, rather than epilepsy, and that loss-of-function of GABAA receptor γ2 subunit is the probable underlying pathogenic mechanism.
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Affiliation(s)
- Morgane Boillot
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Mélanie Morin-Brureau
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Fabienne Picard
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Sarah Weckhuysen
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Virginie Lambrecq
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Carlo Minetti
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Pasquale Striano
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Federico Zara
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Michele Iacomino
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Saeko Ishida
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Isabelle An-Gourfinkel
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Mailys Daniau
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Katia Hardies
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Michel Baulac
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Olivier Dulac
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Eric Leguern
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Rima Nabbout
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
| | - Stéphanie Baulac
- Sorbonne Universités (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UPMC Univ Paris 06, UM 75, ICM; INSERM, U1127 (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), ICM; CNRS (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), UMR 7225, ICM; ICM (M.B., S.I., M.D., S.B., M.M.-B., E.L., S.W., M.B., V.L., I.A.-G.), Paris, France; Department of Neurology (F.P.), University Hospitals of Geneva (HUG), Switzerland; Centre de Reference Épilepsies Rares, Epilepsy Unit (S.W., M.B., V.L., I.A.-G.), and Département de Génétique et de Cytogénétique (E.L.), AP-HP Groupe Hospitalier Pitié-Salpêtrière, Paris, France; Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova (C.M., P.S.), and Laboratory of Neurogenetics, Department of Neurosciences (F.Z., M.I.), "G. Gaslini" Institute, Genova, Italy; Neurogenetics Group, VIB-Department of Molecular Genetics (K.H.), and Laboratory of Neurogenetics, Institute Born-Bunge (K.H.), University of Antwerp, Belgium; Centre de Reference Épilepsies Rares (O.D., R.N.), Department of Pediatric Neurology, Necker Enfants Malades Hospital, AP-HP, Paris; INSERM (O.D., R.N.), U1129, Necker, Paris, France; and University Paris Descartes (O.D., R.N.), Paris, France
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Copy number variants associated with epilepsy from gene expression microarrays. J Clin Neurosci 2015; 22:1907-10. [PMID: 26275332 DOI: 10.1016/j.jocn.2015.05.033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 03/20/2015] [Accepted: 05/09/2015] [Indexed: 11/21/2022]
Abstract
We aimed to identify novel copy number variations (CNV) that might contribute to the pathogenesis of epilepsy. Epilepsy is a common brain disorder characterized by recurring seizures and various serious comorbidities, including respiratory, cardiovascular, and neurologic dysfunction. CNV have recently been considered as important risk factors for epilepsy. With public gene expression data from brain tissue of 23 epilepsy patients and 23 healthy controls, we detected CNV using the R language package CAFÉ. Real-time quantitative polymerase chain reaction validation was performed in a further nine patients and 10 controls. Functional analyses of the genes in the validated CNV were also carried out, using Ingenuity pathway analysis. Three copy number abnormalities (19q13.33, 19q13.11 and 4q35.1) were detected with the gene expression data. The duplication in 19q13.33 (approximately 1.22 million bases) was further validated in three additional epilepsy patients, and the deletion in 19q13.11 (approximately 855 kilobases) was further validated in another two epilepsy patients. The functional analyses of the genes in these two CNV suggested that they may be involved in the pathogenesis of epilepsy. The CNV that we detected may be common genetic etiological factors of epilepsy, and there is potential for the identification of a novel biomarker for treatment from these CNV regions.
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Yuan H, Low CM, Moody OA, Jenkins A, Traynelis SF. Ionotropic GABA and Glutamate Receptor Mutations and Human Neurologic Diseases. Mol Pharmacol 2015; 88:203-17. [PMID: 25904555 PMCID: PMC4468639 DOI: 10.1124/mol.115.097998] [Citation(s) in RCA: 153] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 04/22/2015] [Indexed: 01/03/2023] Open
Abstract
The advent of whole exome/genome sequencing and the technology-driven reduction in the cost of next-generation sequencing as well as the introduction of diagnostic-targeted sequencing chips have resulted in an unprecedented volume of data directly linking patient genomic variability to disorders of the brain. This information has the potential to transform our understanding of neurologic disorders by improving diagnoses, illuminating the molecular heterogeneity underlying diseases, and identifying new targets for therapeutic treatment. There is a strong history of mutations in GABA receptor genes being involved in neurologic diseases, particularly the epilepsies. In addition, a substantial number of variants and mutations have been found in GABA receptor genes in patients with autism, schizophrenia, and addiction, suggesting potential links between the GABA receptors and these conditions. A new and unexpected outcome from sequencing efforts has been the surprising number of mutations found in glutamate receptor subunits, with the GRIN2A gene encoding the GluN2A N-methyl-d-aspartate receptor subunit being most often affected. These mutations are associated with multiple neurologic conditions, for which seizure disorders comprise the largest group. The GluN2A subunit appears to be a locus for epilepsy, which holds important therapeutic implications. Virtually all α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor mutations, most of which occur within GRIA3, are from patients with intellectual disabilities, suggesting a link to this condition. Similarly, the most common phenotype for kainate receptor variants is intellectual disability. Herein, we summarize the current understanding of disease-associated mutations in ionotropic GABA and glutamate receptor families, and discuss implications regarding the identification of human mutations and treatment of neurologic diseases.
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Affiliation(s)
- Hongjie Yuan
- Departments of Pharmacology (H.Y., A.J., S.F.T.) and Anesthesiology (O.A.M., A.J.), Emory University School of Medicine, Rollins Research Center, Atlanta, Georgia; and Departments of Pharmacology and Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore Graduate School for Integrative Sciences and Engineering, and Neurobiology/Ageing Programme, National University of Singapore, Singapore (C.-M.L.)
| | - Chian-Ming Low
- Departments of Pharmacology (H.Y., A.J., S.F.T.) and Anesthesiology (O.A.M., A.J.), Emory University School of Medicine, Rollins Research Center, Atlanta, Georgia; and Departments of Pharmacology and Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore Graduate School for Integrative Sciences and Engineering, and Neurobiology/Ageing Programme, National University of Singapore, Singapore (C.-M.L.)
| | - Olivia A Moody
- Departments of Pharmacology (H.Y., A.J., S.F.T.) and Anesthesiology (O.A.M., A.J.), Emory University School of Medicine, Rollins Research Center, Atlanta, Georgia; and Departments of Pharmacology and Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore Graduate School for Integrative Sciences and Engineering, and Neurobiology/Ageing Programme, National University of Singapore, Singapore (C.-M.L.)
| | - Andrew Jenkins
- Departments of Pharmacology (H.Y., A.J., S.F.T.) and Anesthesiology (O.A.M., A.J.), Emory University School of Medicine, Rollins Research Center, Atlanta, Georgia; and Departments of Pharmacology and Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore Graduate School for Integrative Sciences and Engineering, and Neurobiology/Ageing Programme, National University of Singapore, Singapore (C.-M.L.)
| | - Stephen F Traynelis
- Departments of Pharmacology (H.Y., A.J., S.F.T.) and Anesthesiology (O.A.M., A.J.), Emory University School of Medicine, Rollins Research Center, Atlanta, Georgia; and Departments of Pharmacology and Anaesthesia, Yong Loo Lin School of Medicine, National University of Singapore Graduate School for Integrative Sciences and Engineering, and Neurobiology/Ageing Programme, National University of Singapore, Singapore (C.-M.L.)
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Lachance-Touchette P, Choudhury M, Stoica A, Di Cristo G, Cossette P. Single-cell genetic expression of mutant GABAA receptors causing Human genetic epilepsy alters dendritic spine and GABAergic bouton formation in a mutation-specific manner. Front Cell Neurosci 2014; 8:317. [PMID: 25352779 PMCID: PMC4196543 DOI: 10.3389/fncel.2014.00317] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 09/21/2014] [Indexed: 11/13/2022] Open
Abstract
Mutations in genes encoding for GABAA receptor subunits is a well-established cause of genetic generalized epilepsy. GABA neurotransmission is implicated in several developmental processes including neurite outgrowth and synapse formation. Alteration in excitatory/inhibitory synaptic activities plays a critical role in epilepsy, thus here we investigated whether mutations in α1 subunit of GABAA receptor may affect dendritic spine and GABAergic bouton formation. In particular, we examined the effects of three mutations of the GABRA1 gene (D219N, A322D and K353delins18X) that were found in a cohort of French Canadian families with genetic generalized epilepsy. We used a novel single-cell genetic approach, by preparing cortical organotypic cultures from GABRA1flox/flox mice and simultaneously inactivating endogenous GABRA1 and transfecting mutant α1 subunits in single glutamatergic pyramidal cells and basket GABAergic interneurons by biolistic transfection. We found that GABRA1−/− GABAergic cells showed reduced innervation field, which was rescued by co-expressing α1-A322D and α1-WT but not α1-D219N. We further found that the expression of the most severe GABRA1 missense mutation (α1-A322D) induced a striking increase of spine density in pyramidal cells along with an increase in the number of mushroom-like spines. In addition, α1-A322D expression in GABAergic cells slightly increased perisomatic bouton density, whereas other mutations did not alter bouton formation. All together, these results suggest that the effects of different GABAAR mutations on GABAergic bouton and dendritic spine formation are specific to the mutation and cannot be always explained by a simple loss-of-function gene model. The use of single cell genetic manipulation in organotypic cultures may provide a better understanding of the specific and distinct neural circuit alterations caused by different GABAA receptor subunit mutations and will help define the pathophysiology of genetic generalized epilepsy syndromes.
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Affiliation(s)
- Pamela Lachance-Touchette
- Centre d'Excellence en Neuromique de l'Université de Montréal, Centre de Recherche, Centre Hospitalier de l'Université de Montréal, Université de Montréal Montréal, QC, Canada
| | - Mayukh Choudhury
- Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal Montréal, QC, Canada
| | - Ana Stoica
- Centre d'Excellence en Neuromique de l'Université de Montréal, Centre de Recherche, Centre Hospitalier de l'Université de Montréal, Université de Montréal Montréal, QC, Canada
| | - Graziella Di Cristo
- Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal Montréal, QC, Canada
| | - Patrick Cossette
- Centre d'Excellence en Neuromique de l'Université de Montréal, Centre de Recherche, Centre Hospitalier de l'Université de Montréal, Université de Montréal Montréal, QC, Canada
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Srivastava S, Cohen J, Pevsner J, Aradhya S, McKnight D, Butler E, Johnston M, Fatemi A. A novel variant in GABRB2 associated with intellectual disability and epilepsy. Am J Med Genet A 2014; 164A:2914-21. [PMID: 25124326 DOI: 10.1002/ajmg.a.36714] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2014] [Accepted: 07/07/2014] [Indexed: 01/26/2023]
Abstract
The γ-aminobutyric acid type A (GABAA ) receptor is one of the three main classes of receptors activated by GABA, the principal inhibitory neurotransmitter in the central nervous system. Mutations in genes encoding various subunits of this receptor (GABRA1, GABRA2, GABRA4, GABRA5, GABRA6, GABRB1, GABRB3, GABRG1, GABRG2, GABRG3, and GABRD) are implicated in a number of neurological and developmental disorders, including epilepsy and autism. To date, no human genetics studies have implicated mutations in GABRB2, encoding the β2 subunit of the GABAA receptor, with neurodevelopmental disorders. Here we present a 12-year-old girl with intellectual disability and epilepsy, who was discovered by whole exome sequencing to have a de novo heterozygous missense variant in exon 4 of GABRB2 (c.236T>C; p.M79T). This variant is likely pathogenic, based on in silico analyses, as well as the fact that it results in the non-conservative substitution of a non-polar amino acid with a polar amino acid at a position that is evolutionarily conserved across multiple species. Our findings underscore the need for further investigation into the mechanisms by which mutations in GABRB2 contribute to neurological and developmental dysfunction.
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Affiliation(s)
- Siddharth Srivastava
- Hugo W. Moser Research Institute at Kennedy Krieger Institute, Baltimore, Maryland; Departments of Neurology and Pediatrics, The Johns Hopkins Hospital, Baltimore, Maryland
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A novel GABRG2 mutation, p.R136*, in a family with GEFS+ and extended phenotypes. Neurobiol Dis 2014; 64:131-141. [PMID: 24407264 DOI: 10.1016/j.nbd.2013.12.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 12/19/2013] [Accepted: 12/26/2013] [Indexed: 01/06/2023] Open
Abstract
Genetic mutations in voltage-gated and ligand-gated ion channel genes have been identified in a small number of Mendelian families with genetic generalised epilepsies (GGEs). They are commonly associated with febrile seizures (FS), childhood absence epilepsy (CAE) and particularly with generalised or genetic epilepsy with febrile seizures plus (GEFS+). In clinical practice, despite efforts to categorise epilepsy and epilepsy families into syndromic diagnoses, many generalised epilepsies remain unclassified with a presumed genetic basis. During the systematic collection of epilepsy families, we assembled a cohort of families with evidence of GEFS+ and screened for variations in the γ2 subunit of the γ-aminobutyric acid (GABA) type A receptor gene (GABRG2). We detected a novel GABRG2(p.R136*) premature translation termination codon in one index-case from a two-generation nuclear family, presenting with an unclassified GGE, a borderline GEFS+ phenotype with learning difficulties and extended behavioural presentation. The GABRG2(p.R136*) mutation segregates with the febrile seizure component of this family's GGE and is absent in 190 healthy control samples. In vitro expression assays demonstrated that γ2(p.R136*) subunits were produced, but had reduced cell-surface and total expression. When γ2(p.R136*) subunits were co-expressed with α1 and β2 subunits in HEK 293T cells, GABA-evoked currents were reduced. Furthermore, γ2(p.R136*) subunits were highly-expressed in intracellular aggregations surrounding the nucleus and endoplasmic reticulum (ER), suggesting compromised receptor trafficking. A novel GABRG2(p.R136*) mutation extends the spectrum of GABRG2 mutations identified in GEFS+ and GGE phenotypes, causes GABAA receptor dysfunction, and represents a putative epilepsy mechanism.
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Abstract
The γ-aminobutyric acid receptor type A (GABAA receptor) is a ligand-gated chloride channel that mediates major inhibitory functions in the central nervous system. GABAA receptors function mainly as pentamers containing α, β, and either γ or δ subunits. A number of antiepileptic drugs have agonistic effects on GABAA receptors. Hence, dysfunctions of GABAA receptors have been postulated to play important roles in the etiology of epilepsy. In fact, mutations or genetic variations of the genes encoding the α1, α6, β2, β3, γ2, or δ subunits (GABRA1, GABRA6, GABRB2, GABRB3, GABRG2, and GABRD, respectively) have been associated with human epilepsy, both with and without febrile seizures. Epilepsy resulting from mutations is commonly one of following, genetic (idiopathic) generalized epilepsy (e.g., juvenile myoclonic epilepsy), childhood absence epilepsy, genetic epilepsy with febrile seizures, or Dravet syndrome. Recently, mutations of GABRA1, GABRB2, and GABRB3 were associated with infantile spasms and Lennox-Gastaut syndrome. These mutations compromise hyperpolarization through GABAA receptors, which is believed to cause seizures. Interestingly, most of the insufficiencies are not caused by receptor gating abnormalities, but by complex mechanisms, including endoplasmic reticulum (ER)-associated degradation, nonsense-mediated mRNA decay, intracellular trafficking defects, and ER stress. Thus, GABAA receptor subunit mutations are now thought to participate in the pathomechanisms of epilepsy, and an improved understanding of these mutations should facilitate our understanding of epilepsy and the development of new therapies.
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Kang JQ, Shen W, Macdonald RL. Trafficking-deficient mutant GABRG2 subunit amount may modify epilepsy phenotype. Ann Neurol 2013; 74:547-59. [PMID: 23720301 DOI: 10.1002/ana.23947] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 03/27/2013] [Accepted: 05/17/2013] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Genetic epilepsies and many other human genetic diseases display phenotypic heterogeneity, often for unknown reasons. Disease severity associated with nonsense mutations is dependent partially on mutation gene location and resulting efficiency of nonsense-mediated mRNA decay (NMD) to eliminate potentially toxic proteins. Nonsense mutations in the last exon do not activate NMD, thus producing truncated proteins. We compared the protein metabolism and the impact on channel biogenesis, function, and cellular homeostasis of truncated γ2 subunits produced by GABRG2 nonsense mutations associated with epilepsy of different severities and by a nonsense mutation in the last exon unassociated with epilepsy. METHODS γ-Aminobutyric acid type A receptor subunits were coexpressed in non-neuronal cells and neurons. NMD was studied using minigenes that support NMD. Protein degradation rates were determined using (35) S radiolabeling pulse chase. Channel function was determined by whole cell recordings, and subunits trafficking and cellular toxicity were determined using flow cytometry, immunoblotting, and immunohistochemistry. RESULTS Although all GABRG2 nonsense mutations resulted in loss of γ2 subunit surface expression, the truncated subunits had different degradation rates and stabilities, suppression of wild-type subunit biogenesis and function, amounts of conjugation with polyubiquitin, and endoplasmic reticulum stress levels. INTERPRETATION We compared molecular phenotypes of GABRG2 nonsense mutations. The findings suggest that despite the common loss of mutant allele function, each mutation produced different intracellular levels of trafficking-deficient subunits. The concentration-dependent suppression of wild-type channel function and cellular disturbance resulting from differences in mutant subunit metabolism may contribute to associated epilepsy severities and by implication to phenotypic heterogeneity in many inherited human diseases.
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Affiliation(s)
- Jing-Qiong Kang
- Departments of Neurology, Vanderbilt University Medical Center, Nashville, TN
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Macdonald RL, Kang JQ. mRNA surveillance and endoplasmic reticulum quality control processes alter biogenesis of mutant GABAA receptor subunits associated with genetic epilepsies. Epilepsia 2013; 53 Suppl 9:59-70. [PMID: 23216579 DOI: 10.1111/epi.12035] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Previous studies from our and other groups have demonstrated that the majority of γ-aminobutyric acid (GABA)(A) receptor subunit mutations produce mutant subunits with impaired biogenesis and trafficking. These GABA(A) receptor mutations include missense, nonsense, deletion, or insertion mutations that result in a frameshift with premature translation-termination codons (PTCs) and splice-site mutations. Frameshift or splice-site mutations produce mutant proteins with PTCs, thus generating nonfunctional truncated proteins. All of these mutant GABA(A) receptor subunits are subject to cellular quality control at the messenger RNA (mRNA) or protein level. These quality-control checkpoints shape the cell's response to the presence of the mutant subunits and attempt to reduce the impact of the mutant subunit on GABA(A) receptor expression and function. The check points prevent nonfunctioning or malfunctioning GABA(A) receptor subunits from trafficking to the cell surface or to synapses, and help to ensure that the receptor channels trafficked to the membrane and synapses are indeed functional. However, if and how these quality control or check points impact the posttranslational modifications of functional GABA(A) receptor channels such as receptor phosphorylation and ubiquitination and their involvement in mediating GABAergic inhibitory synaptic strength needs to be investigated in the near future.
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Affiliation(s)
- Robert L Macdonald
- Department of Neurology Molecular Physiology and Biophysics Pharmacology, Vanderbilt University, Nashville, Tennessee 37232-8552, USA.
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Lemoine D, Jiang R, Taly A, Chataigneau T, Specht A, Grutter T. Ligand-gated ion channels: new insights into neurological disorders and ligand recognition. Chem Rev 2012; 112:6285-318. [PMID: 22988962 DOI: 10.1021/cr3000829] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Damien Lemoine
- Laboratoire de Biophysicochimie des Récepteurs Canaux, UMR 7199 CNRS, Conception et Application de Molécules Bioactives, Faculté de Pharmacie, Université de Strasbourg , 67400 Illkirch, France
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Shi YW, Yu MJ, Long YS, Qin B, He N, Meng H, Liu XR, Deng WY, Gao MM, Yi YH, Li BM, Liao WP. Mosaic SCN1A mutations in familial partial epilepsy with antecedent febrile seizures. GENES BRAIN AND BEHAVIOR 2011; 11:170-6. [PMID: 22151702 DOI: 10.1111/j.1601-183x.2011.00756.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
SCN1A is the most relevant epilepsy gene. Mutations of SCN1A generate phenotypes ranging from the extremely severe form of Dravet syndrome (DS) to a mild form of generalized epilepsy with febrile seizures plus (GEFS+). Mosaic SCN1A mutations have been identified in rare familial DS. It is suspected that mosaic mutations of SCN1A may cause other types of familial epilepsies with febrile seizures (FS), which are more common clinically. Thus, we screened SCN1A mutations in 13 families with partial epilepsy with antecedent febrile seizures (PEFS+) using denaturing high-performance liquid chromatography and sequencing. The level of mosaicism was further quantified by pyrosequencing. Two missense SCN1A mutations with mosaic origin were identified in two unrelated families, accounting for 15.4% (2/13) of the PEFS+ families tested. One of the mosaic carriers with ~25.0% mutation of c.5768A>G/p.Q1923R had experienced simple FS; another with ~12.5% mutation of c.4847T>C/p.I1616T was asymptomatic. Their heterozygous children had PEFS+. Recurrent transmission occurred in both families, as noted in most of the families with germline mosaicism reported previously. The two mosaic mutations identified in this study are less destructive missense, compared with the more destructive truncating and splice-site mutations identified in the majority of previous studies. This is the first report of mosaic SCN1A mutations in families with probands that do not exhibit DS, but manifest only a milder phenotype. Therefore, such families with mild cases should be approached with caution in genetic counseling and the possibility of mosaicism origin associated with high recurrence risk should be excluded.
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Affiliation(s)
- Y-W Shi
- Institute of Neuroscience, The Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangdong, China
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Bouthour W, Leroy F, Emmanuelli C, Carnaud M, Dahan M, Poncer JC, Lévi S. A human mutation in Gabrg2 associated with generalized epilepsy alters the membrane dynamics of GABAA receptors. Cereb Cortex 2011; 22:1542-53. [PMID: 21908847 DOI: 10.1093/cercor/bhr225] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Neuronal activity modulates the membrane diffusion of postsynaptic γ-aminobutyric acid (GABA)(A) receptors (GABA(A)Rs), thereby regulating the efficacy of GABAergic synapses. The K289M mutation in GABA(A)Rs subunit γ2 has been associated with the generalized epilepsy with febrile seizures plus (GEFS+) syndrome. This mutation accelerates receptor deactivation and therefore reduces inhibitory synaptic transmission. Yet, it is not clear why this mutation specifically promotes febrile seizures. We show that upon raising temperature both the number of GABA(A)Rs clusters and the frequency of miniature inhibitory postsynaptic currents decreased in neurons expressing the K289M mutant but not wild-type (WT) recombinant γ2. Single-particle tracking experiments revealed that raising temperature increases the membrane diffusion of synaptic GABA(A)Rs containing the K289M mutant but not WT recombinant γ2. This effect was mediated by enhanced neuronal activity as it was blocked by glutamate receptor antagonists and was mimicked by the convulsant 4-aminopyridine. Our data suggest the K289M mutation in γ2 confers GABA(A)Rs with enhanced sensitivity of their membrane diffusion to neuronal activity. Enhanced activity during hyperthermia may then trigger the escape of receptors from synapses and thereby further reduce the efficacy of GABAergic inhibition. Alteration of the membrane diffusion of neurotransmitter receptors therefore represents a new mechanism in human epilepsy.
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Affiliation(s)
- Walid Bouthour
- Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 839, 75005 Paris, France
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Altered GABA signaling in early life epilepsies. Neural Plast 2011; 2011:527605. [PMID: 21826277 PMCID: PMC3150203 DOI: 10.1155/2011/527605] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 05/04/2011] [Accepted: 05/27/2011] [Indexed: 01/13/2023] Open
Abstract
The incidence of seizures is particularly high in the early ages of life. The immaturity of inhibitory systems, such as GABA, during normal brain development and its further dysregulation under pathological conditions that predispose to seizures have been speculated to play a major role in facilitating seizures. Seizures can further impair or disrupt GABAA signaling by reshuffling the subunit composition of its receptors or causing aberrant reappearance of depolarizing or hyperpolarizing GABAA receptor currents. Such effects may not result in epileptogenesis as frequently as they do in adults. Given the central role of GABAA signaling in brain function and development, perturbation of its physiological role may interfere with neuronal morphology, differentiation, and connectivity, manifesting as cognitive or neurodevelopmental deficits. The current GABAergic antiepileptic drugs, while often effective for adults, are not always capable of stopping seizures and preventing their sequelae in neonates. Recent studies have explored the therapeutic potential of chloride cotransporter inhibitors, such as bumetanide, as adjunctive therapies of neonatal seizures. However, more needs to be known so as to develop therapies capable of stopping seizures while preserving the age- and sex-appropriate development of the brain.
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Fine architecture and mutation mapping of human brain inhibitory system ligand gated ion channels by high-throughput homology modeling. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2011; 80:117-52. [PMID: 21109219 DOI: 10.1016/b978-0-12-381264-3.00004-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The common architecture of the brain inhibitory system ligand-gated ion-channels was examined at the level of each of the subunits and in their assembled pentameric arrangements. Structural modeling of the GABAA receptor, GlyR1, and the serotonin receptor, 5HTR3A, was carried out on a multi-homolog basis employing a high-throughput homology modeling pipeline. The locations of all the known mutations of each of the subunits of the receptor subfamily were mapped upon their computed structures and structural relationships between patterns of mutations in different subunits were identified, resulting in the zoning of mutations to four specific regions of the common subunit structure. These classifications may be of value in discerning probable molecular mechanisms and functional manifestations of emerging mutations and polymorphisms, providing the foundation for a family-specific predictive algorithm that may allow researchers to focus experimental effort on the most probable molecular indicators of compromised receptor function and disease mechanism.
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Grover S, Gourie-Devi M, Baghel R, Sharma S, Bala K, Gupta M, Narayanasamy K, Varma B, Gupta M, Kaur K, Talwar P, Kaur H, Giddaluru S, Sharma A, Brahmachari SK, Consortium IGV, Kukreti R. Genetic profile of patients with epilepsy on first-line antiepileptic drugs and potential directions for personalized treatment. Pharmacogenomics 2010; 11:927-41. [DOI: 10.2217/pgs.10.62] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Background: The first-line antiepileptic drugs, although affordable and effective in the control of seizures, are associated with adverse drug effects, and there is large interindividual variability in the appropriate dose at which patients respond favorably. This variability may partly be explained by functional consequences of genetic polymorphisms in the drug-metabolizing enzymes, such as the CYP450 family, microsomal epoxide hydrolase and UDP-glucuronosyltransferases, drug transporters, mainly ATP-binding cassette transporters, and drug targets, including sodium channels. The purpose of this study was to determine the allele and genotype frequencies of such genetic variants in patients with epilepsy from North India administered first-line antiepileptic drugs, such as phenobarbitone, phenytoin, carbamazepine and valproic acid, and compare them with worldwide epilepsy populations. Materials & methods: SNP screening of 19 functional variants from 12 genes in 392 patients with epilepsy was carried out, and the patients were classified with respect to the metabolizing rate of their drug-metabolizing enzymes, efflux rate of drug transporters and sensitivity of drug targets. Results: A total of 16 SNPs were found to be polymorphic, and the allelic frequencies for these SNPs were in conformance with Hardy–Weinberg equilibrium. Among all the polymorphisms studied, functional variants from genes encoding CYP2C19, EPHX1, ABCB1 and SCN1A were highly polymorphic in North Indian epilepsy patients, and might account for differential drug response to first-line antiepileptic drugs. Conclusion: Interethnic differences were elucidated for several polymorphisms that might be responsible for differential serum drug levels and optimal dose requirement for efficacious treatment.
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Affiliation(s)
- Sandeep Grover
- Institute of Genomics & Integrative Biology (IGIB), Council of Scientific & Industrial Research (CSIR), India
| | | | - Ruchi Baghel
- Institute of Genomics & Integrative Biology (IGIB), Council of Scientific & Industrial Research (CSIR), India
| | - Sangeeta Sharma
- Institute of Human Behavior & Allied Sciences (IHBAS), Delhi, India
| | - Kiran Bala
- Institute of Human Behavior & Allied Sciences (IHBAS), Delhi, India
| | - Meena Gupta
- Institute of Human Behavior & Allied Sciences (IHBAS), Delhi, India
| | | | - Binuja Varma
- The Centre for Genomic Application (TCGA), New Delhi, India
| | - Meenal Gupta
- Institute of Genomics & Integrative Biology (IGIB), Council of Scientific & Industrial Research (CSIR), India
| | - Kavita Kaur
- Institute of Genomics & Integrative Biology (IGIB), Council of Scientific & Industrial Research (CSIR), India
| | - Puneet Talwar
- Institute of Genomics & Integrative Biology (IGIB), Council of Scientific & Industrial Research (CSIR), India
| | - Harpreet Kaur
- Institute of Genomics & Integrative Biology (IGIB), Council of Scientific & Industrial Research (CSIR), India
| | - Sudheer Giddaluru
- Institute of Genomics & Integrative Biology (IGIB), Council of Scientific & Industrial Research (CSIR), India
| | - Abhay Sharma
- Institute of Genomics & Integrative Biology (IGIB), Council of Scientific & Industrial Research (CSIR), India
| | - Samir K Brahmachari
- Institute of Genomics & Integrative Biology (IGIB), Council of Scientific & Industrial Research (CSIR), India
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Macdonald RL, Kang JQ. Molecular pathology of genetic epilepsies associated with GABAA receptor subunit mutations. Epilepsy Curr 2010; 9:18-23. [PMID: 19396344 DOI: 10.1111/j.1535-7511.2008.01278.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Mutations in ligand-gated ion channel genes associated with idiopathic generalized epilepsies have been reported in excitatory acetylcholine receptor alpha4 and beta2 subunit genes linked to autosomal dominant nocturnal frontal lobe epilepsy and in inhibitory GABA(A) receptor alpha1, beta3, gamma2, and delta subunit genes associated with childhood absence epilepsy, juvenile myoclonic epilepsy, pure febrile seizures, generalized epilepsy with febrile seizures plus, and generalized epilepsy with tonic-clonic seizures. Recent studies suggest that these mutations alter receptor function or biogenesis, including impaired receptor subunit messenger RNA stability, receptor subunit protein folding and stability, receptor assembly, and receptor trafficking.
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Affiliation(s)
- Robert L Macdonald
- Departments of Neurology, Vanderbilt University, Nashville, Tennessee, USA.
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Galanopoulou AS. Mutations affecting GABAergic signaling in seizures and epilepsy. Pflugers Arch 2010; 460:505-23. [PMID: 20352446 DOI: 10.1007/s00424-010-0816-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2009] [Revised: 02/18/2010] [Accepted: 02/23/2010] [Indexed: 02/02/2023]
Abstract
The causes of epilepsies and epileptic seizures are multifactorial. Genetic predisposition may contribute in certain types of epilepsies and seizures, whether idiopathic or symptomatic of genetic origin. Although these are not very common, they have offered a unique opportunity to investigate the molecular mechanisms underlying epileptogenesis and ictogenesis. Among the implicated gene mutations, a number of GABAA receptor subunit mutations have been recently identified that contribute to several idiopathic epilepsies, febrile seizures, and rarely to certain types of symptomatic epilepsies, like the severe myoclonic epilepsy of infancy. Deletion of GABAA receptor genes has also been linked to Angelman syndrome. Furthermore, mutations of proteins controlling chloride homeostasis, which indirectly defines the functional consequences of GABAA signaling, have been identified. These include the chloride channel 2 (CLCN2) and the potassium chloride cotransporter KCC3. The pathogenic role of CLCN2 mutations has not been clearly demonstrated and may represent either susceptibility genes or, in certain cases, innocuous polymorphisms. KCC3 mutations have been associated with hereditary motor and sensory polyneuropathy with corpus callosum agenesis (Andermann syndrome) that often manifests with epileptic seizures. This review summarizes the recent progress in the genetic linkages of epilepsies and seizures to the above genes and discusses potential pathogenic mechanisms that contribute to the age, sex, and conditional expression of these seizures in carriers of these mutations.
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Affiliation(s)
- Aristea S Galanopoulou
- Saul R. Korey Department of Neurology and Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1410 Pelham Parkway South, Kennedy Center Room 306, Bronx, NY 10461, USA.
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Macdonald RL, Kang JQ, Gallagher MJ. Mutations in GABAA receptor subunits associated with genetic epilepsies. J Physiol 2010; 588:1861-9. [PMID: 20308251 DOI: 10.1113/jphysiol.2010.186999] [Citation(s) in RCA: 186] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mutations in inhibitory GABAA receptor subunit genes (GABRA1, GABRB3, GABRG2 and GABRD) have been associated with genetic epilepsy syndromes including childhood absence epilepsy (CAE), juvenile myoclonic epilepsy (JME), pure febrile seizures (FS), generalized epilepsy with febrile seizures plus (GEFS+), and Dravet syndrome (DS)/severe myoclonic epilepsy in infancy (SMEI). These mutations are found in both translated and untranslated gene regions and have been shown to affect the GABAA receptors by altering receptor function and/or by impairing receptor biogenesis by multiple mechanisms including reducing subunit mRNA transcription or stability, impairing subunit folding, stability, or oligomerization and by inhibiting receptor trafficking.
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Affiliation(s)
- Robert L Macdonald
- Department of Neurology, Vanderbilt University, 6140 Medical Research Building III, 465 21st Avenue, Nashville, TN 37232-8552, USA.
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Kang JQ, Macdonald RL. Making sense of nonsense GABA(A) receptor mutations associated with genetic epilepsies. Trends Mol Med 2009; 15:430-8. [PMID: 19717338 DOI: 10.1016/j.molmed.2009.07.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Revised: 07/07/2009] [Accepted: 07/08/2009] [Indexed: 11/29/2022]
Abstract
Nonsense mutations that generate premature translation-termination codons (PTCs) are responsible for approximately one- third of human genetic diseases. PTCs in both voltage- and ligand-gated ion channel genes, including those for sodium, potassium, nicotinic cholinergic receptor and GABA(A) receptor channels, have been associated with genetic epilepsies but the epilepsy syndromes they cause are variable. It was recently proposed that two well-established molecular pathways, nonsense-mediated decay (NMD) and endoplasmic reticulum-associated degradation (ERAD), determine the effects of PTCs in GABA(A) receptor subunit genes associated with genetic epilepsies on the cellular fates of mutant subunit mRNAs and proteins. Activation of these different molecular mechanisms might contribute in part to different clinical phenotypes in patients with GABA(A) receptor subunit gene PTCs and thus different approaches for treatment of their genetic epilepsies might be required.
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Affiliation(s)
- Jing-Qiong Kang
- Department of Neurology, Vanderbilt University, Nashville, TN 37232-8552, USA.
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Two molecular pathways (NMD and ERAD) contribute to a genetic epilepsy associated with the GABA(A) receptor GABRA1 PTC mutation, 975delC, S326fs328X. J Neurosci 2009; 29:2833-44. [PMID: 19261879 DOI: 10.1523/jneurosci.4512-08.2009] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Approximately one-third of human genetic diseases are caused by premature translation-termination codon (PTC)-generating mutations. These mutations in sodium channel and GABA(A) receptor genes have been associated with idiopathic generalized epilepsies, but the cellular consequences of the PTCs on the mutant channel subunit biogenesis and function are unknown. The PTCs could result in translation of a truncated subunit, or more likely, trigger mRNA degradation through nonsense-mediated mRNA decay (NMD), thus preventing or reducing production of mutant subunit at the transcriptional level. The GABA(A) receptor alpha1 subunit mutation, 975delC, S326fs328X, is an autosomal dominant mutation associated with childhood absence epilepsy that generates a PTC in exon 8 of the 9 exon GABRA1 gene that is 74 bp upstream of intron 8. Using an intron 8-inclusion minigene that supports NMD, we demonstrated that mutant mRNA was substantially reduced, but not absent. Loss of mutant transcripts was blocked by ribosome inhibition or by silencing the NMD-essential gene hUPF-1. In both neurons and non-neuronal cells, the PTC caused substantial loss of mutant alpha1(S326fs328X) subunit mRNA through NMD with a minor portion of the mRNA escaping NMD and producing a mutant protein. The translated mutant protein had reduced stability due to endoplasmic reticulum associated degradation (ERAD) and had enhanced association with molecular chaperones. This study suggests that loss of mRNA due to activation of NMD and activation of ERAD by the mutant protein may contribute to epileptogenesis. The molecular mechanisms outlined here delineate a model for the pathogenesis of many PTC-generating mutations.
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