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Pourtavakoli A, Ghafouri-Fard S. Calcium signaling in neurodevelopment and pathophysiology of autism spectrum disorders. Mol Biol Rep 2022; 49:10811-10823. [PMID: 35857176 DOI: 10.1007/s11033-022-07775-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 07/05/2022] [Indexed: 11/24/2022]
Abstract
BACKGROUND Autism spectrum disorder (ASD) covers a group of neurodevelopmental disorders with complex genetic background. Several genetic mutations, epigenetic alterations, copy number variations and single nucleotide polymorphisms have been reported that cause ASD or modify its phenotype. Among signaling pathways that influence pathogenesis of ASD, calcium signaling has a prominent effect. METHODS We searched PubMed and Google Scholar databases with key words "Calcium signaling" and "Autism spectrum disorder". CONCLUSION This type of signaling has essential roles in the cell physiology. Endoplasmic reticulum and mitochondria are the key organelles involved in this signaling. It is vastly accepted that organellar disorders intensely influence the central nervous system (CNS). Several lines of evidence indicate alterations in the function of calcium channels in polygenic disorders affecting CNS. In the current review, we describe the role of calcium signaling in normal function of CNS and pathophysiology of ASD.
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Affiliation(s)
- Ashkan Pourtavakoli
- Department of Medical Genetics, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Soudeh Ghafouri-Fard
- Department of Medical Genetics, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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2
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Weiss N, Zamponi GW. Genetic T-type calcium channelopathies. J Med Genet 2019; 57:1-10. [PMID: 31217264 PMCID: PMC6929700 DOI: 10.1136/jmedgenet-2019-106163] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 05/02/2019] [Accepted: 05/18/2019] [Indexed: 12/13/2022]
Abstract
T-type channels are low-voltage-activated calcium channels that contribute to a variety of cellular and physiological functions, including neuronal excitability, hormone and neurotransmitter release as well as developmental aspects. Several human conditions including epilepsy, autism spectrum disorders, schizophrenia, motor neuron disorders and aldosteronism have been traced to variations in genes encoding T-type channels. In this short review, we present the genetics of T-type channels with an emphasis on structure-function relationships and associated channelopathies.
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Affiliation(s)
- Norbert Weiss
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Praha, Czech Republic
| | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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Becker F, Reid CA, Hallmann K, Tae HS, Phillips AM, Teodorescu G, Weber YG, Kleefuss-Lie A, Elger C, Perez-Reyes E, Petrou S, Kunz WS, Lerche H, Maljevic S. Functional variants in HCN4 and CACNA1H may contribute to genetic generalized epilepsy. Epilepsia Open 2017; 2:334-342. [PMID: 29588962 PMCID: PMC5862120 DOI: 10.1002/epi4.12068] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/23/2017] [Indexed: 01/11/2023] Open
Abstract
Objective Genetic generalized epilepsy (GGE) encompasses seizure disorders characterized by spike‐and‐wave discharges (SWD) originating within thalamo‐cortical circuits. Hyperpolarization‐activated (HCN) and T‐type Ca2+ channels are key modulators of rhythmic activity in these brain regions. Here, we screened HCN4 and CACNA1H genes for potentially contributory variants and provide their functional analysis. Methods Targeted gene sequencing was performed in 20 unrelated familial cases with different subtypes of GGE, and the results confirmed in 230 ethnically matching controls. Selected variants in CACNA1H and HCN4 were functionally assessed in tsA201 cells and Xenopus laevis oocytes, respectively. Results We discovered a novel CACNA1H (p.G1158S) variant in two affected members of a single family. One of them also carried an HCN4 (p.P1117L) variant inherited from the unaffected mother. In a separate family, an HCN4 variant (p.E153G) was identified in one of several affected members. Voltage‐clamp analysis of CACNA1H (p.G1158S) revealed a small but significant gain‐of‐function, including increased current density and a depolarizing shift of steady‐state inactivation. HCN4 p.P1117L and p.G153E both caused a hyperpolarizing shift in activation and reduced current amplitudes, resulting in a loss‐of‐function. Significance Our results are consistent with a model suggesting cumulative contributions of subtle functional variations in ion channels to seizure susceptibility and GGE.
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Affiliation(s)
- Felicitas Becker
- Department of Neurology and Epileptology Hertie-Institute for Clinical Brain-Research University of Tübingen Tübingen Germany.,RKU-University Neurology Clinic of Ulm Ulm Germany
| | - Christopher A Reid
- The Florey Institute of Neuroscience and Mental Health Melbourne Victoria Australia
| | - Kerstin Hallmann
- Department of Neurology and Epileptology University of Bonn Medical Center Bonn Germany
| | - Han-Shen Tae
- The Florey Institute of Neuroscience and Mental Health Melbourne Victoria Australia.,Present address: Illawarra Health and Medical Research Institute (IHMRI) University of Wollongong Wollongong New South Wales Australia
| | - A Marie Phillips
- The Florey Institute of Neuroscience and Mental Health Melbourne Victoria Australia.,School of Biosciences The University of Melbourne Melbourne Victoria Australia
| | - Georgeta Teodorescu
- Department of Neurology and Epileptology Hertie-Institute for Clinical Brain-Research University of Tübingen Tübingen Germany
| | - Yvonne G Weber
- Department of Neurology and Epileptology Hertie-Institute for Clinical Brain-Research University of Tübingen Tübingen Germany
| | - Ailing Kleefuss-Lie
- Department of Neurology and Epileptology University of Bonn Medical Center Bonn Germany
| | - Christian Elger
- Department of Neurology and Epileptology University of Bonn Medical Center Bonn Germany
| | - Edward Perez-Reyes
- Department of Pharmacology University of Virginia Charlottesville Virginia U.S.A
| | - Steven Petrou
- The Florey Institute of Neuroscience and Mental Health Melbourne Victoria Australia
| | - Wolfram S Kunz
- Department of Neurology and Epileptology University of Bonn Medical Center Bonn Germany
| | - Holger Lerche
- Department of Neurology and Epileptology Hertie-Institute for Clinical Brain-Research University of Tübingen Tübingen Germany
| | - Snezana Maljevic
- Department of Neurology and Epileptology Hertie-Institute for Clinical Brain-Research University of Tübingen Tübingen Germany.,The Florey Institute of Neuroscience and Mental Health Melbourne Victoria Australia
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Glauser TA, Holland K, O’Brien VP, Keddache M, Martin LJ, Clark PO, Cnaan A, Dlugos D, Hirtz DG, Shinnar S, Grabowski G. Pharmacogenetics of antiepileptic drug efficacy in childhood absence epilepsy. Ann Neurol 2017; 81:444-453. [PMID: 28165634 PMCID: PMC6171340 DOI: 10.1002/ana.24886] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Revised: 01/30/2017] [Accepted: 01/31/2017] [Indexed: 01/09/2023]
Abstract
OBJECTIVE To determine whether common polymorphisms in CACNA1G, CACNA1H, CACNA1I, and ABCB1 are associated with differential short-term seizure outcome in childhood absence epilepsy (CAE). METHODS Four hundred forty-six CAE children in a randomized double-blind trial of ethosuximide, lamotrigine, and valproate had short-term seizure outcome determined. Associations between polymorphisms (minor allele frequency ≥ 15%) in 4 genes and seizure outcomes were assessed. In vitro electrophysiology on transfected CACNA1H channels determined impact of 1 variant on T-type calcium channel responsiveness to ethosuximide. RESULTS Eighty percent (357 of 446) of subjects had informative short-term seizure status (242 seizure free, 115 not seizure free). In ethosuximide subjects, 2 polymorphisms (CACNA1H rs61734410/P640L, CACNA1I rs3747178) appeared more commonly among not-seizure-free participants (p = 0.011, odds ratio [OR] = 2.63, 95% confidence limits [CL] = 1.25-5.56; p = 0.026, OR = 2.38, 95% CL = 1.11-5.00). In lamotrigine subjects, 1 ABCB1 missense polymorphism (rs2032582/S893A; p = 0.015, OR = 2.22, 95% CL = 1.16-4.17) was more common in not-seizure-free participants, and 2 CACNA1H polymorphisms (rs2753326, rs2753325) were more common in seizure-free participants (p = 0.038, OR = 0.52, 95% CL = 0.28-0.96). In valproate subjects, no common polymorphisms were associated with seizure status. In vitro electrophysiological studies showed no effect of the P640L polymorphism on channel physiology in the absence of ethosuximide. Ethosuximide's effect on rate of decay of CaV 3.2 was significantly less for P640L channel compared to wild-type channel. INTERPRETATION Four T-type calcium channel variants and 1 ABCB1 transporter variant were associated with differential drug response in CAE. The in vivo P640L variant's ethosuximide effect was confirmed by in vitro electrophysiological studies. This suggests that genetic variation plays a role in differential CAE drug response. Ann Neurol 2017;81:444-453.
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Affiliation(s)
- Tracy A. Glauser
- Comprehensive Epilepsy Center, Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA and the University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Katherine Holland
- Comprehensive Epilepsy Center, Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA and the University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Valerie P. O’Brien
- Comprehensive Epilepsy Center, Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA and the University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Mehdi Keddache
- Division of Human Genetics, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA and the University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Lisa J. Martin
- Division of Human Genetics, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA and the University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Peggy O. Clark
- Comprehensive Epilepsy Center, Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA and the University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Avital Cnaan
- Division of Biostatistics and Study Methodology, Children’s National Health System, Washington, D.C
| | - Dennis Dlugos
- Division of Neurology, The Children’s Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania
| | - Deborah G Hirtz
- National Institute of Neurological Disorders and Stroke, Bethesda, Maryland
| | - Shlomo Shinnar
- Division of Neurology, Montefiore Medical Center, Albert Einstein College of Medicine, New York, New York
| | - Gregory Grabowski
- Division of Human Genetics, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA and the University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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Powell KL, Cain SM, Snutch TP, O'Brien TJ. Low threshold T-type calcium channels as targets for novel epilepsy treatments. Br J Clin Pharmacol 2015; 77:729-39. [PMID: 23834404 DOI: 10.1111/bcp.12205] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 07/02/2013] [Indexed: 12/21/2022] Open
Abstract
Low voltage-activated T-type calcium channels were originally cloned in the 1990s and much research has since focused on identifying the physiological roles of these channels in health and disease states. T-type calcium channels are expressed widely throughout the brain and peripheral tissues, and thus have been proposed as therapeutic targets for a variety of diseases such as epilepsy, insomnia, pain, cancer and hypertension. This review discusses the literature concerning the role of T-type calcium channels in physiological and pathological processes related to epilepsy. T-type calcium channels have been implicated in pathology of both the genetic and acquired epilepsies and several anti-epileptic drugs (AEDs) in clinical use are known to suppress seizures via inhibition of T-type calcium channels. Despite the fact that more than 15 new AEDs have become clinically available over the past 20 years at least 30% of epilepsy patients still fail to achieve seizure control, and many patients experience unwanted side effects. Furthermore there are no treatments that prevent the development of epilepsy or mitigate the epileptic state once established. Therefore there is an urgent need for the development of new AEDs that are effective in patients with drug resistant epilepsy, are anti-epileptogenic and are better tolerated. We also review the mechanisms of action of the current AEDs with known effects on T-type calcium channels and discuss novel compounds that are being investigated as new treatments for epilepsy.
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Affiliation(s)
- Kim L Powell
- Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Melbourne, Victoria, Australia
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Chen Y, Parker WD, Wang K. The role of T-type calcium channel genes in absence seizures. Front Neurol 2014; 5:45. [PMID: 24847307 PMCID: PMC4023043 DOI: 10.3389/fneur.2014.00045] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 03/24/2014] [Indexed: 12/05/2022] Open
Abstract
The thalamic relay neurons, reticular thalamic nucleus, and neocortical pyramidal cells form a circuit that sustains oscillatory burst firing, and is regarded as the underlying mechanism of absence seizures. T-type calcium channels play a key role in this circuit. Here, we review the role of T-type calcium channel genes in the development of absence seizures, and emphasize gain or loss of function mutations, and other variations that alter both quantity and quality of transcripts, and methylation status of isoforms of T-type calcium channel proteins might be of equal importance in understanding the pathological mechanism of absence seizures.
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Affiliation(s)
- Yucai Chen
- University of Illinois at Chicago , Peoria, IL , USA
| | | | - Keling Wang
- Hebei Children Hospital , Shijiazhuang , China
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T-type Ca2+ channels in absence epilepsy. Pflugers Arch 2014; 466:719-34. [DOI: 10.1007/s00424-014-1461-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Accepted: 01/22/2014] [Indexed: 11/25/2022]
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Abstract
Low-voltage-activated T-type Ca(2+) channels are widely expressed in various types of neurons. Once deinactivated by hyperpolarization, T-type channels are ready to be activated by a small depolarization near the resting membrane potential and, therefore, are optimal for regulating the excitability and electroresponsiveness of neurons under physiological conditions near resting states. Ca(2+) influx through T-type channels engenders low-threshold Ca(2+) spikes, which in turn trigger a burst of action potentials. Low-threshold burst firing has been implicated in the synchronization of the thalamocortical circuit during sleep and in absence seizures. It also has been suggested that T-type channels play an important role in pain signal transmission, based on their abundant expression in pain-processing pathways in peripheral and central neurons. In this review, we will describe studies on the role of T-type Ca(2+) channels in the physiological as well as pathological generation of brain rhythms in sleep, absence epilepsy, and pain signal transmission. Recent advances in studies of T-type channels in the control of cognition will also be briefly discussed.
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Affiliation(s)
- Eunji Cheong
- Department of Biotechnology, Translational Research Center for Protein Function Control, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea.
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Cheong E, Shin HS. T-type Ca²⁺ channels in absence epilepsy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1560-71. [PMID: 23416255 DOI: 10.1016/j.bbamem.2013.02.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 01/15/2013] [Accepted: 02/01/2013] [Indexed: 11/28/2022]
Abstract
Low-voltage-activated T-type Ca²⁺ channels are highly expressed in the thalamocortical circuit, suggesting that they play a role in this brain circuit. Indeed, low-threshold burst firing mediated by T-type Ca²⁺ channels has long been implicated in the synchronization of the thalamocortical circuit. Over the past few decades, the conventional view has been that rhythmic burst firing mediated by T-type channels in both thalamic reticular nuclie (TRN) and thalamocortical (TC) neurons are equally critical in the generation of thalamocortical oscillations during sleep rhythms and spike-wave-discharges (SWDs). This review broadly investigates recent studies indicating that even though both TRN and TC nuclei are required for thalamocortical oscillations, the contributions of T-type channels to TRN and TC neurons are not equal in the genesis of sleep spindles and SWDs. T-type channels in TC neurons are an essential component of SWD generation, whereas the requirement for TRN T-type channels in SWD generation remains controversial at least in the GBL model of absence seizures. Therefore, a deeper understanding of the functional consequences of modulating each T-type channel subtype could guide the development of therapeutic tools for absence seizures while minimizing side effects on physiological thalamocortical oscillations. This article is part of a Special Issue entitled: Calcium channels.
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Affiliation(s)
- Eunji Cheong
- Department of Biotechnology, Translational Research Center for Protein Function Control, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea.
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Kim YO, Kim MK, Nam TS, Jang SY, Park KW, Kim EY, Rho YI, Woo YJ. Mutation Screening of the γ-Aminobutyric Acid Type-A Receptor Subunit γ2 Gene in Korean Patients with Childhood Absence Epilepsy. J Clin Neurol 2012; 8:271-5. [PMID: 23323135 PMCID: PMC3540286 DOI: 10.3988/jcn.2012.8.4.271] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Revised: 04/16/2012] [Accepted: 04/16/2012] [Indexed: 11/25/2022] Open
Abstract
Background and Purpose Since the γ-aminobutyric acid type-A receptor subunit γ2 gene (GABRG2) mutation was discovered in an Australian family with childhood absence epilepsy (CAE) and febrile convulsions, a few screening studies for the GABRG2 mutation have been conducted in sporadic individuals with CAE from other ethnic groups. The aim of this study was to determine whether or not the previously reported genetic mutations and single-nucleotide polymorphisms (SNPs) of GABRG2 can be reproduced in sporadic Korean individuals with CAE, compared to healthy Korean individuals. Methods Thirty-five children with CAE in Chonnam National University Hospital and healthy controls (n=207) were enrolled, and the medical records of patients with CAE were reviewed. CAE was diagnosed according to the Classification and Terminology of the International League Against Epilepsy. All nine exons of GABRG2 were directly sequenced. In addition, the two SNPs found in our CAE patients were analyzed: C315T in exon 3 (E3) and C588T in exon 5 (E5). The frequencies of the two SNPs in the CAE patients were compared with data from healthy controls (for E3 and E5) and from previously reported Korean population data (only for E3). Results No mutation of GABRG2 was found in our CAE patients. In addition, the allele and genotype frequencies of the two polymorphisms did not differ significantly between CAE patients, healthy controls, and the Korean general population (p>0.05). Conclusions Our study of sporadic Korean individuals with CAE found no evidence that GABRG2 contributes to the genetic basis of CAE.
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Affiliation(s)
- Young Ok Kim
- Department of Pediatrics, Chonnam National University Medical School, Gwangju, Korea
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Yalçın O. Genes and molecular mechanisms involved in the epileptogenesis of idiopathic absence epilepsies. Seizure 2011; 21:79-86. [PMID: 22206818 DOI: 10.1016/j.seizure.2011.12.002] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Revised: 12/02/2011] [Accepted: 12/04/2011] [Indexed: 11/16/2022] Open
Abstract
Idiopathic absence epilepsies (IAE), that have high prevalence particularly among children and adolescents, are complex disorders mainly caused by genetic factors. Childhood absence epilepsy and juvenile absence epilepsy are among the most common subtypes of IAEs. While the role of ion channels has been the primary focus of epilepsy research, the analysis of mutation and association in both patients with absence epilepsies and animal models revealed the involvement of GABA receptors and calcium channels, but also of novel non-ion channel proteins in inducing spike wave discharges (SWD). Functional studies on a mutated variant of these proteins also support their role in the epileptogenesis of absence seizures. Studies in animal models point to both the thalamus and cortex as the origin of SWDs: the abnormalities in the components of these circuits leading to seizure activity. This review examines the current research on mutations and susceptibility alleles determined in the genes that code for the subunits of GABA receptors (GABRG2, GABRA1, GABRB3, GABRA5, GABA(B1) and GABA(B2)), calcium channels (CACNA1A, CACNA1G, CACNA1H, CACNA1I, CACNAB4, CACNAG2 and CACNG3), and novel non-ion channel proteins, taking into account the results of functional studies on these variants.
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Affiliation(s)
- Ozlem Yalçın
- Department of Molecular Biology and Genetics, T.C. Istanbul Arel University, Tepekent-Buyukcekmece, Istanbul, Turkey.
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Bazyan AS, Segal OL. Hyperpolarization-activated I h pacemaker channel in the mammalian brain. NEUROCHEM J+ 2010. [DOI: 10.1134/s181971241004001x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Midzyanovskaya IS, Folomkina AA, Koshtoyants OK, Kuznetsova GD, Bazyan AS. The concentration of serotonin and its metabolite 5-hydroxyindolacetic acid in brain structures of Wistar and WAG/Rij rats and the influence of imipramine on spike-wave discharges. NEUROCHEM J+ 2010. [DOI: 10.1134/s1819712410030086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Hughes JR. Absence seizures: a review of recent reports with new concepts. Epilepsy Behav 2009; 15:404-12. [PMID: 19632158 DOI: 10.1016/j.yebeh.2009.06.007] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 06/02/2009] [Accepted: 06/07/2009] [Indexed: 02/01/2023]
Abstract
Absence seizures with bilateral spike-wave (SW) complexes at 3Hz are divided into the childhood form, with onset at around 6 years of age, and the juvenile form, with onset usually at 12 years of age. These seizures typically last 9-12s and, at times, are activated by hyperventilation and occasionally by photic stimulation. Generalized tonic-clonic (GTC) seizures may also occur, especially in the juvenile form. There may be cognitive changes, in addition to linguistic and behavioral problems. Possible mechanisms for epileptogenesis may involve GABAergic systems, but especially T-calcium channels. The thalamus, especially the reticular nucleus, plays a major role, as does the frontal cortex, mainly the dorsolateral and orbital frontal areas, to the extent that some investigators have concluded that absence seizures are not truly generalized, but rather have selective cortical networks, mainly ventromesial frontal areas and the somatosensory cortex. The latter network is a departure from the more popular concept of a generalized epilepsy. Between the "centrencephalic" and "corticoreticular" theories, a "unified" theory is presented. Proposed genes include T-calcium channel gene CACNA1H, likely a susceptible gene in the Chinese Han population and a contributory gene in Caucasians. Electroencephalography has revealed an interictal increase in prefrontal activity, essential for the buildup of the ictal SW complexes maximal in that region. Infraslow activity can also be seen during ictal SW complexes. For treatment, counter to common belief, ethosuximide may not increase GTC seizures, as it reduces low-threshold T-calcium currents in thalamic neurons. Valproic acid and lamotrigine are also first-line medications. In addition, zonisamide and levetiracetam can be very helpful in absence epilepsy.
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Affiliation(s)
- John R Hughes
- Department of Neurology, University of Illinois Medical Center (M/C 796), 912 South Wood Street, Chicago, IL 60612, USA.
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Voltage-gated calcium channels, calcium signaling, and channelopathies. CALCIUM - A MATTER OF LIFE OR DEATH 2007. [DOI: 10.1016/s0167-7306(06)41005-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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