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Jeong S, Kang HW, Kim SH, Hong GS, Nam MH, Seong J, Yoon ES, Cho IJ, Chung S, Bang S, Kim HN, Choi N. Integration of reconfigurable microchannels into aligned three-dimensional neural networks for spatially controllable neuromodulation. SCIENCE ADVANCES 2023; 9:eadf0925. [PMID: 36897938 PMCID: PMC10005277 DOI: 10.1126/sciadv.adf0925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 02/08/2023] [Indexed: 06/18/2023]
Abstract
Anisotropically organized neural networks are indispensable routes for functional connectivity in the brain, which remains largely unknown. While prevailing animal models require additional preparation and stimulation-applying devices and have exhibited limited capabilities regarding localized stimulation, no in vitro platform exists that permits spatiotemporal control of chemo-stimulation in anisotropic three-dimensional (3D) neural networks. We present the integration of microchannels seamlessly into a fibril-aligned 3D scaffold by adapting a single fabrication principle. We investigated the underlying physics of elastic microchannels' ridges and interfacial sol-gel transition of collagen under compression to determine a critical window of geometry and strain. We demonstrated the spatiotemporally resolved neuromodulation in an aligned 3D neural network by local deliveries of KCl and Ca2+ signal inhibitors, such as tetrodotoxin, nifedipine, and mibefradil, and also visualized Ca2+ signal propagation with a speed of ~3.7 μm/s. We anticipate that our technology will pave the way to elucidate functional connectivity and neurological diseases associated with transsynaptic propagation.
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Affiliation(s)
- Sohyeon Jeong
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
- Division of Bio-Medical Science and Technology, KIST School, University of Science and Technology (UST), Seoul 02792, Korea
- MEPSGEN Co. Ltd., Seoul 05836, Korea
| | - Hyun Wook Kang
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
- School of Mechanical Engineering, Korea University, Seoul 02841, Korea
| | - So Hyun Kim
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
- SK Biopharmaceuticals Co. Ltd., Seongnam 13494, Korea
| | - Gyu-Sang Hong
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Min-Ho Nam
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Jihye Seong
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
- Division of Bio-Medical Science and Technology, KIST School, University of Science and Technology (UST), Seoul 02792, Korea
- Department of Life Sciences, Korea University, Seoul 02841, Korea
- KHU-KIST Department of Converging Science and Technology, Kyung Hee University, Seoul 02453, Korea
| | - Eui-Sung Yoon
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
- Division of Nano and Information Technology, KIST School, University of Science and Technology (UST), Seoul 02792, Korea
| | - Il-Joo Cho
- Department of Biomedical Sciences, College of Medicine, Korea University, Seoul 02841, Korea
- Department of Anatomy, College of Medicine, Korea University, Seoul 02841, Korea
| | - Seok Chung
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
- School of Mechanical Engineering, Korea University, Seoul 02841, Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Korea
| | - Seokyoung Bang
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
- Department of Medical Biotechnology, Dongguk University, Goyang 10326, Korea
| | - Hong Nam Kim
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
- Division of Bio-Medical Science and Technology, KIST School, University of Science and Technology (UST), Seoul 02792, Korea
- School of Mechanical Engineering, Yonsei University, Seoul 03722, Korea
- Yonsei-KIST Convergence Research Institute, Yonsei University, Seoul 03722, Korea
| | - Nakwon Choi
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Korea
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Abstract
The voltage-gated sodium channel α-subunit genes comprise a highly conserved gene family. Mutations of three of these genes, SCN1A, SCN2A and SCN8A, are responsible for a significant burden of neurological disease. Recent progress in identification and functional characterization of patient variants is generating new insights and novel approaches to therapy for these devastating disorders. Here we review the basic elements of sodium channel function that are used to characterize patient variants. We summarize a large body of work using global and conditional mouse mutants to characterize the in vivo roles of these channels. We provide an overview of the neurological disorders associated with mutations of the human genes and examples of the effects of patient mutations on channel function. Finally, we highlight therapeutic interventions that are emerging from new insights into mechanisms of sodium channelopathies.
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3
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Yu W, Hill SF, Xenakis JG, Pardo-Manuel de Villena F, Wagnon JL, Meisler MH. Gabra2 is a genetic modifier of Scn8a encephalopathy in the mouse. Epilepsia 2020; 61:2847-2856. [PMID: 33140451 PMCID: PMC7756374 DOI: 10.1111/epi.16741] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 10/05/2020] [Accepted: 10/06/2020] [Indexed: 12/23/2022]
Abstract
Objective SCN8A encephalopathy is a developmental epileptic encephalopathy typically caused by de novo gain‐of‐function mutations in Nav1.6. Severely affected individuals exhibit refractory seizures, developmental delay, cognitive disabilities, movement disorders, and elevated risk of sudden death. Patients with the identical SCN8A variant can differ in clinical course, suggesting a role for modifier genes in determining disease severity. The identification of genetic modifiers contributes to understanding disease pathogenesis and suggesting therapeutic interventions. Methods We generated F1 and F2 crosses between inbred mouse strains and mice carrying the human pathogenic variants SCN8A‐R1872W and SCN8A‐N1768D. Quantitative trait locus (QTL) analysis of seizure‐related phenotypes was used for chromosomal mapping of modifier loci. Results In an F2 cross between strain SJL/J and C57BL/6J mice carrying the patient mutation R1872W, we identified a major QTL on chromosome 5 containing the Gabra2 gene. Strain C57BL/6J carries a splice site mutation that reduces expression of Gabra2, encoding the α2 subunit of the aminobutyric acid type A receptor. The protective wild‐type allele of Gabra2 from strain SJL/J delays the age at seizure onset and extends life span of the Scn8a mutant mice. Additional Scn8a modifiers were observed in the F2 cross and in an F1 cross with strain C3HeB/FeJ. Significance These studies demonstrate that the SJL/J strain carries multiple modifiers with protective effects against seizures induced by gain‐of‐function mutations in Scn8a. Homozygosity for the hypomorphic variant of Gabra2 in strain C57BL/6J is associated with early seizure onset and short life span. GABRA2 is a potential therapeutic target for SCN8A encephalopathy.
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Affiliation(s)
- Wenxi Yu
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Sophie F Hill
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - James G Xenakis
- Department of Genetics, University of North Carolina, Chapel Hill, NC, USA
| | | | - Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
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4
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Menezes LFS, Sabiá Júnior EF, Tibery DV, Carneiro LDA, Schwartz EF. Epilepsy-Related Voltage-Gated Sodium Channelopathies: A Review. Front Pharmacol 2020; 11:1276. [PMID: 33013363 PMCID: PMC7461817 DOI: 10.3389/fphar.2020.01276] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 07/31/2020] [Indexed: 12/29/2022] Open
Abstract
Epilepsy is a disease characterized by abnormal brain activity and a predisposition to generate epileptic seizures, leading to neurobiological, cognitive, psychological, social, and economic impacts for the patient. There are several known causes for epilepsy; one of them is the malfunction of ion channels, resulting from mutations. Voltage-gated sodium channels (NaV) play an essential role in the generation and propagation of action potential, and malfunction caused by mutations can induce irregular neuronal activity. That said, several genetic variations in NaV channels have been described and associated with epilepsy. These mutations can affect channel kinetics, modifying channel activation, inactivation, recovery from inactivation, and/or the current window. Among the NaV subtypes related to epilepsy, NaV1.1 is doubtless the most relevant, with more than 1500 mutations described. Truncation and missense mutations are the most observed alterations. In addition, several studies have already related mutated NaV channels with the electrophysiological functioning of the channel, aiming to correlate with the epilepsy phenotype. The present review provides an overview of studies on epilepsy-associated mutated human NaV1.1, NaV1.2, NaV1.3, NaV1.6, and NaV1.7.
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Affiliation(s)
- Luis Felipe Santos Menezes
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
| | - Elias Ferreira Sabiá Júnior
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
| | - Diogo Vieira Tibery
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
| | - Lilian Dos Anjos Carneiro
- Faculdade de Medicina, Centro Universitário Euro Americano, Brasília, Brazil.,Faculdade de Medicina, Centro Universitário do Planalto Central, Brasília, Brazil
| | - Elisabeth Ferroni Schwartz
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
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Pan Y, Cummins TR. Distinct functional alterations in SCN8A epilepsy mutant channels. J Physiol 2020; 598:381-401. [PMID: 31715021 PMCID: PMC7216308 DOI: 10.1113/jp278952] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 11/12/2019] [Indexed: 01/12/2023] Open
Abstract
KEY POINTS Mutations in the SCN8A gene cause early infantile epileptic encephalopathy. We characterize a new epilepsy-related SCN8A mutation, R850Q, in the human SCN8A channel and present gain-of-function properties of the mutant channel. Systematic comparison of R850Q with three other SCN8A epilepsy mutations, T761I, R1617Q and R1872Q, identifies one common dysfunction in resurgent current, although these mutations alter distinct properties of the channel. Computational simulations in two different neuron models predict an increased excitability of neurons carrying these mutations, which explains the over-excitation that underlies seizure activities in patients. These data provide further insight into the mechanism of SCN8A-related epilepsy and reveal subtle but potentially important distinction of functional characterization performed in the human vs. rodent channels. ABSTRACT SCN8A is a novel causal gene for early infantile epileptic encephalopathy. It is well accepted that gain-of-function mutations in SCN8A underlie the disorder, although the remarkable heterogeneity of its clinical presentation and poor treatment response demand a better understanding of the disease mechanisms. Here, we characterize a new epilepsy-related SCN8A mutation, R850Q, in human Nav1.6. We show that it is a gain-of-function mutation, with a hyperpolarizing shift in voltage dependence of activation, a two-fold increase of persistent current and a slowed decay of resurgent current. We systematically compare its biophysics with three other SCN8A epilepsy mutations, T767I, R1617Q and R1872Q, in the human Nav1.6 channel. Although all of these mutations are gain-of-function, the mutations affect different aspects of channel properties. One commonality that we discovered is an alteration of resurgent current kinetics, although the mechanisms by which resurgent currents are augmented remain unclear for all of the mutations. Computational simulations predict an increased excitability of neurons carrying these mutations with differential enhancement by open channel blockade.
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Affiliation(s)
- Yanling Pan
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, IN, USA
| | - Theodore R Cummins
- Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, IN, USA
- Department of Biology, School of Science, IUPUI, IN, USA
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6
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Mason ER, Wu F, Patel RR, Xiao Y, Cannon SC, Cummins TR. Resurgent and Gating Pore Currents Induced by De Novo SCN2A Epilepsy Mutations. eNeuro 2019; 6:ENEURO.0141-19.2019. [PMID: 31558572 PMCID: PMC6795554 DOI: 10.1523/eneuro.0141-19.2019] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 09/12/2019] [Accepted: 09/16/2019] [Indexed: 12/31/2022] Open
Abstract
Over 150 mutations in the SCN2A gene, which encodes the neuronal Nav1.2 protein, have been implicated in human epilepsy cases. Of these, R1882Q and R853Q are two of the most commonly reported mutations. This study utilized voltage-clamp electrophysiology to characterize the biophysical effects of the R1882Q and R853Q mutations on the hNav1.2 channel, including their effects on resurgent current and gating pore current, which are not typically investigated in the study of Nav1.2 channel mutations. HEK cells transiently transfected with DNA encoding either wild-type (WT) or mutant hNav1.2 revealed that the R1882Q mutation induced a gain-of-function phenotype, including slowed fast inactivation, depolarization of the voltage dependence of inactivation, and increased persistent current. In this model system, the R853Q mutation primarily produced loss-of-function effects, including reduced transient current amplitude and density, hyperpolarization of the voltage dependence of inactivation, and decreased persistent current. The presence of a Navβ4 peptide (KKLITFILKKTREK-OH) in the pipette solution induced resurgent currents, which were increased by the R1882Q mutation and decreased by the R853Q mutation. Further study of the R853Q mutation in Xenopus oocytes indicated a reduced surface expression and revealed a robust gating pore current at negative membrane potentials, a function absent in the WT channel. This not only shows that different epileptogenic point mutations in hNav1.2 have distinct biophysical effects on the channel, but also illustrates that individual mutations can have complex consequences that are difficult to identify using conventional analyses. Distinct mutations may, therefore, require tailored pharmacotherapies in order to eliminate seizures.
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Affiliation(s)
- Emily R Mason
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Fenfen Wu
- Department of Physiology, David Geffen School of Medicine at the University of California at Los Angeles, Los Angeles, CA 90095-1751
| | - Reesha R Patel
- Program in Medical Neuroscience, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Yucheng Xiao
- School of Science, Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202
| | - Stephen C Cannon
- Department of Physiology, David Geffen School of Medicine at the University of California at Los Angeles, Los Angeles, CA 90095-1751
| | - Theodore R Cummins
- School of Science, Biology Department Chair, Indiana University-Purdue University of Indianapolis, Indianapolis, IN 46202
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7
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Bunton-Stasyshyn RKA, Wagnon JL, Wengert ER, Barker BS, Faulkner A, Wagley PK, Bhatia K, Jones JM, Maniaci MR, Parent JM, Goodkin HP, Patel MK, Meisler MH. Prominent role of forebrain excitatory neurons in SCN8A encephalopathy. Brain 2019; 142:362-375. [PMID: 30601941 DOI: 10.1093/brain/awy324] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 10/29/2018] [Indexed: 12/25/2022] Open
Abstract
De novo mutations of the sodium channel gene SCN8A result in an epileptic encephalopathy with refractory seizures, developmental delay, and elevated risk of sudden death. p.Arg1872Trp is a recurrent de novo SCN8A mutation reported in 14 unrelated individuals with epileptic encephalopathy that included seizure onset in the prenatal or infantile period and severe verbal and ambulatory comorbidities. The major biophysical effect of the mutation was previously shown to be impaired channel inactivation accompanied by increased current density. We have generated a conditional mouse mutation in which expression of this severe gain-of-function mutation is dependent upon Cre recombinase. Global activation of p.Arg1872Trp by EIIa-Cre resulted in convulsive seizures and lethality at 2 weeks of age. Neural activation of the p.Arg1872Trp mutation by Nestin-Cre also resulted in early onset seizures and death. Restriction of p.Arg1872Trp expression to excitatory neurons using Emx1-Cre recapitulated seizures and juvenile lethality between 1 and 2 months of age. In contrast, activation of p.Arg1872Trp in inhibitory neurons by Gad2-Cre or Dlx5/6-Cre did not induce seizures or overt neurological dysfunction. The sodium channel modulator GS967/Prax330 prolonged survival of mice with global expression of R1872W and also modulated the activity of the mutant channel in transfected cells. Activation of the p.Arg1872Trp mutation in adult mice was sufficient to generate seizures and death, indicating that successful therapy will require lifelong treatment. These findings provide insight into the pathogenic mechanism of this gain-of-function mutation of SCN8A and identify excitatory neurons as critical targets for therapeutic intervention.
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Affiliation(s)
| | - Jacy L Wagnon
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Eric R Wengert
- Department of Anesthesiology, University of Virginia, Charlottesville VA, USA.,Neuroscience Graduate Program, University of Virginia, Charlottesville VA, USA
| | - Bryan S Barker
- Department of Anesthesiology, University of Virginia, Charlottesville VA, USA.,Neuroscience Graduate Program, University of Virginia, Charlottesville VA, USA
| | - Alexa Faulkner
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Pravin K Wagley
- Department of Neurology, University of Virginia, Charlottesville VA, USA
| | - Kritika Bhatia
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Julie M Jones
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Marissa R Maniaci
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Jack M Parent
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA.,Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Howard P Goodkin
- Neuroscience Graduate Program, University of Virginia, Charlottesville VA, USA.,Department of Neurology, University of Virginia, Charlottesville VA, USA
| | - Manoj K Patel
- Department of Anesthesiology, University of Virginia, Charlottesville VA, USA.,Neuroscience Graduate Program, University of Virginia, Charlottesville VA, USA
| | - Miriam H Meisler
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA.,Department of Neurology, University of Michigan, Ann Arbor, MI, USA
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9
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Atanasoska M, Vazharova R, Ivanov I, Balabanski L, Andonova S, Ivanov S, Pacheva I, Malinov M, Toncheva D. SCN8A p.Arg1872Gln mutation in early infantile epileptic encephalopathy type 13: Review and case report. BIOTECHNOL BIOTEC EQ 2018. [DOI: 10.1080/13102818.2018.1532815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Affiliation(s)
- Maya Atanasoska
- Genetic Laboratory, Gynecology and Assisted Reproduction Hospital “Dr Malinov D.M.”, Sofia, Bulgaria
| | - Radoslava Vazharova
- Genetic Laboratory, Gynecology and Assisted Reproduction Hospital “Dr Malinov D.M.”, Sofia, Bulgaria
- Department of Biology, Medical Genetics and Microbiology, Faculty of Medicine, Sofia University “St. Kliment Ohridski”, Sofia, Bulgaria
| | - Ivan Ivanov
- Department of Paediatrics and Medical Genetics, St. George University Hospital, Medical University - Plovdiv, Plovdiv, Bulgaria
| | - Lubomir Balabanski
- Genetic Laboratory, Gynecology and Assisted Reproduction Hospital “Dr Malinov D.M.”, Sofia, Bulgaria
| | - Silvia Andonova
- National Genetic Laboratory, University Hospital of Obstetrics and Gynecology “Maichin dom”, Medical University of Sofia, Sofia, Bulgaria
| | - Samuil Ivanov
- Genetic Laboratory, Gynecology and Assisted Reproduction Hospital “Dr Malinov D.M.”, Sofia, Bulgaria
| | - Iliana Pacheva
- Department of Paediatrics and Medical Genetics, St. George University Hospital, Medical University - Plovdiv, Plovdiv, Bulgaria
| | - Maxim Malinov
- Genetic Laboratory, Gynecology and Assisted Reproduction Hospital “Dr Malinov D.M.”, Sofia, Bulgaria
| | - Draga Toncheva
- Genetic Laboratory, Gynecology and Assisted Reproduction Hospital “Dr Malinov D.M.”, Sofia, Bulgaria
- Department of Medical Genetics, Faculty of Medicine, Medical University of Sofia, Sofia, Bulgaria
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10
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Gamal El-Din TM, Lenaeus MJ, Catterall WA. Structural and Functional Analysis of Sodium Channels Viewed from an Evolutionary Perspective. Handb Exp Pharmacol 2018; 246:53-72. [PMID: 29043505 DOI: 10.1007/164_2017_61] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Voltage-gated sodium channels initiate and propagate action potentials in excitable cells. They respond to membrane depolarization through opening, followed by fast inactivation that terminates the sodium current. This ON-OFF behavior of voltage-gated sodium channels underlays the coding of information and its transmission from one location in the nervous system to another. In this review, we explore and compare structural and functional data from prokaryotic and eukaryotic channels to infer the effects of evolution on sodium channel structure and function.
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Affiliation(s)
- Tamer M Gamal El-Din
- Department of Pharmacology, University of Washington, Seattle, WA, 98195-7280, USA.
| | - Michael J Lenaeus
- Department of Pharmacology, University of Washington, Seattle, WA, 98195-7280, USA
| | - William A Catterall
- Department of Pharmacology, University of Washington, Seattle, WA, 98195-7280, USA
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11
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Zhou X, Zhang Y, Tang D, Liang S, Chen P, Tang C, Liu Z. A Chimeric NaV1.8 Channel Expression System Based on HEK293T Cell Line. Front Pharmacol 2018; 9:337. [PMID: 29686617 PMCID: PMC5900924 DOI: 10.3389/fphar.2018.00337] [Citation(s) in RCA: 6] [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: 11/22/2017] [Accepted: 03/22/2018] [Indexed: 11/13/2022] Open
Abstract
Among the nine voltage-gated sodium channel (NaV) subtypes, NaV1.8 is an attractive therapeutic target for pain. The heterologous expression of recombinant NaV1.8 currents is of particular importance for its electrophysiological and pharmacological studies. However, NaV1.8 expresses no or low-level functional currents when transiently transfected into non-neuronal cell lines. The present study aims to explore the molecular determinants limiting its functional expression and accordingly establish a functional NaV1.8 expression system. We conducted screening analysis of the NaV1.8 intracellular loops by constructing NaV chimeric channels and confirmed that the NaV1.8 C-terminus was the only limiting factor. Replacing this sequence with that of NaV1.4, NaV1.5, or NaV1.7 constructed functional channels (NaV1.8/1.4L5, NaV1.8/1.5L5, and NaV1.8/1.7L5, respectively), which expressed high-level NaV1.8-like currents in HEK293T cells. The chimeric channel NaV1.8/1.7L5 displayed much faster inactivation of its macroscopic currents than NaV1.8/1.4L5 and NaV1.8/1.5L5, and it was the most similar to wild-type NaV1.8 expressed in ND7/23 cells. Its currents were very stable during repetitive depolarizations, while its repriming kinetic was different from wild-type NaV1.8. Most importantly, NaV1.8/1.7L5 pharmacologically resembled wild-type NaV1.8 as revealed by testing their susceptibility to two NaV1.8 selective antagonists, APETx-2 and MrVIB. NaV chimeras study showed that at least the domain 2 and domain 4 of NaV1.8 were involved in binding with APETx-2. Our study provided new insights into the function of NaV1.8 intracellular loops, as well as a reliable and convenient expression system which could be useful in NaV1.8 studies.
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Affiliation(s)
| | | | | | | | | | - Cheng Tang
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Zhonghua Liu
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
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12
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Early-onset epileptic encephalopathy with de novo SCN8A mutation. Epilepsy Res 2018; 139:9-13. [DOI: 10.1016/j.eplepsyres.2017.10.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Revised: 09/09/2017] [Accepted: 10/24/2017] [Indexed: 01/09/2023]
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13
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Butler KM, da Silva C, Shafir Y, Weisfeld-Adams JD, Alexander JJ, Hegde M, Escayg A. De novo and inherited SCN8A epilepsy mutations detected by gene panel analysis. Epilepsy Res 2017; 129:17-25. [PMID: 27875746 PMCID: PMC5321682 DOI: 10.1016/j.eplepsyres.2016.11.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 10/31/2016] [Accepted: 11/05/2016] [Indexed: 12/19/2022]
Abstract
OBJECTIVES To determine the incidence of pathogenic SCN8A variants in a cohort of epilepsy patients referred for clinical genetic testing. We also investigated the contribution of SCN8A to autism spectrum disorder, intellectual disability, and neuromuscular disorders in individuals referred for clinical genetic testing at the same testing laboratory. METHODS Sequence data from 275 epilepsy panels screened by Emory Genetics Laboratory were reviewed for variants in SCN8A. Two additional cases with variants in SCN8A were ascertained from other testing laboratories. Parental samples were tested for variant segregation and clinical histories were examined. SCN8A variants detected from gene panel analyses for autism spectrum disorder, intellectual disability, and neuromuscular disorders were also examined. RESULTS Five variants in SCN8A were identified in five individuals with epilepsy. Three variants were de novo, one was inherited from an affected parent, and one was inherited from an unaffected parent. Four of the individuals have epilepsy and developmental delay/intellectual disability. The remaining individual has a milder epilepsy presentation without cognitive impairment. We also identified an amino acid substitution at an evolutionarily conserved SCN8A residue in a patient who was screened on the autism spectrum disorder panel. Additionally, we examined the distribution of pathogenic SCN8A variants across the Nav1.6 channel and identified four distinct clusters of variants. These clusters are primarily located in regions of the channel that are important for the kinetics of channel inactivation. CONCLUSIONS Variants in SCN8A may be responsible for a spectrum of epilepsies as well as other neurodevelopmental disorders without seizures. The predominant pathogenic mechanism appears to involve disruption of channel inactivation, leading to gain-of-function effects.
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Affiliation(s)
- Kameryn M Butler
- Department of Human Genetics, Emory University, Atlanta, GA 30322, United States
| | - Cristina da Silva
- Department of Human Genetics, Emory University, Atlanta, GA 30322, United States; EGL Genetic Diagnostics, Decatur, GA 30033, United States
| | - Yuval Shafir
- The Herman and Walter Samuelson Children's Hospital at Sinai, Division of Pediatric Neurology, Baltimore, MD 21209, United States
| | - James D Weisfeld-Adams
- Division of Clinical Genetics and Metabolism, Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, United States
| | - John J Alexander
- Department of Human Genetics, Emory University, Atlanta, GA 30322, United States; EGL Genetic Diagnostics, Decatur, GA 30033, United States
| | - Madhuri Hegde
- Department of Human Genetics, Emory University, Atlanta, GA 30322, United States
| | - Andrew Escayg
- Department of Human Genetics, Emory University, Atlanta, GA 30322, United States.
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Gawali V, Todt H. Mechanism of Inactivation in Voltage-Gated Na+ Channels. CURRENT TOPICS IN MEMBRANES 2016; 78:409-50. [DOI: 10.1016/bs.ctm.2016.07.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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15
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Wagnon JL, Barker BS, Hounshell JA, Haaxma CA, Shealy A, Moss T, Parikh S, Messer RD, Patel MK, Meisler MH. Pathogenic mechanism of recurrent mutations of SCN8A in epileptic encephalopathy. Ann Clin Transl Neurol 2015; 3:114-23. [PMID: 26900580 PMCID: PMC4748308 DOI: 10.1002/acn3.276] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 11/20/2015] [Indexed: 12/03/2022] Open
Abstract
Objective The early infantile epileptic encephalopathy type 13 (EIEE13, OMIM #614558) results from de novo missense mutations of SCN8A encoding the voltage‐gated sodium channel Nav1.6. More than 20% of patients have recurrent mutations in residues Arg1617 or Arg1872. Our goal was to determine the functional effects of these mutations on channel properties. Methods Clinical exome sequencing was carried out on patients with early‐onset seizures, developmental delay, and cognitive impairment. Two mutations identified here, p.Arg1872Leu and p.Arg1872Gln, and two previously identified mutations, p.Arg1872Trp and p.Arg1617Gln, were introduced into Nav1.6 cDNA, and effects on electrophysiological properties were characterized in transfected ND7/23 cells. Interactions with FGF14, G‐protein subunit Gβγ, and sodium channel subunit β1 were assessed by coimmunoprecipitation. Results We identified two patients with the novel mutation p.Arg1872Leu and one patient with the recurrent mutation p.Arg1872Gln. The three mutations of Arg1872 and the mutation of Arg1617 all impaired the sodium channel transition from open state to inactivated state, resulting in channel hyperactivity. Other observed abnormalities contributing to elevated channel activity were increased persistent current, increased peak current density, hyperpolarizing shift in voltage dependence of activation, and depolarizing shift in steady‐state inactivation. Protein interactions were not affected. Interpretation Recurrent mutations at Arg1617 and Arg1872 lead to elevated Nav1.6 channel activity by impairing channel inactivation. Channel hyperactivity is the major pathogenic mechanism for gain‐of‐function mutations of SCN8A. EIEE13 differs mechanistically from Dravet syndrome, which is caused by loss‐of‐function mutations of SCN1A. This distinction has important consequences for selection of antiepileptic drugs and the development of gene‐ and mutation‐specific treatments.
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Affiliation(s)
- Jacy L Wagnon
- Department of Human Genetics University of Michigan Ann Arbor Michigan
| | - Bryan S Barker
- Department of Anesthesiology and Neuroscience Graduate Program University of Virginia Health System Charlottesville Virginia
| | - James A Hounshell
- Department of Anesthesiology and Neuroscience Graduate Program University of Virginia Health System Charlottesville Virginia
| | - Charlotte A Haaxma
- Department of Pediatric Neurology Radboud University Nijmegen The Netherlands
| | - Amy Shealy
- Cleveland Clinic Genomic Medicine Institute Cleveland Ohio
| | - Timothy Moss
- Cleveland Clinic Genomic Medicine Institute Cleveland Ohio
| | - Sumit Parikh
- Department of Pediatric Neurology Cleveland Clinic Cleveland Ohio
| | - Ricka D Messer
- Department of Pediatric Neurology Johns Hopkins Medical Institute Baltimore Maryland
| | - Manoj K Patel
- Department of Anesthesiology and Neuroscience Graduate Program University of Virginia Health System Charlottesville Virginia
| | - Miriam H Meisler
- Department of Human Genetics University of Michigan Ann Arbor Michigan
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Heterologous expression of NaV1.9 chimeras in various cell systems. Pflugers Arch 2015; 467:2423-35. [PMID: 25916202 DOI: 10.1007/s00424-015-1709-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 03/31/2015] [Accepted: 04/16/2015] [Indexed: 01/27/2023]
Abstract
SCN11A encodes the voltage-gated sodium channel NaV1.9, which deviates most strongly from the other eight NaV channels expressed in mammals. It is characterized by resistance to the prototypic NaV channel blocker tetrodotoxin and exhibits slow activation and inactivation gating. Its expression in dorsal root ganglia neurons suggests a role in motor or pain signaling functions as also recently demonstrated by the occurrence of various mutations in human SCN11A leading to altered pain sensation syndromes. The systematic investigation of human NaV1.9, however, is severely hampered because of very poor heterologous expression in host cells. Using patch-clamp and two-electrode voltage-clamp methods, we show that this limitation is caused by the C-terminal structure of NaV1.9. A chimera of NaV1.9 harboring the C terminus of NaV1.4 yields functional expression not only in neuronal cells but also in non-excitable cells, such as HEK 293T or Xenopus oocytes. The major functional difference of the chimeric channel with respect to NaV1.9 is an accelerated activation and inactivation. Since the entire transmembrane domain is preserved, it is suited for studying pharmacological properties of the channel and the functional impact of disease-causing mutations. Moreover, we demonstrate how mutation S360Y makes NaV1.9 channels sensitive to tetrodotoxin and saxitoxin and that the unusual slow open-state inactivation of NaV1.9 is also mediated by the IFM (isoleucine-phenylalanine-methionine) inactivation motif located in the linker connecting domains III and IV.
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Knapp O, Nevin ST, Yasuda T, Lawrence N, Lewis RJ, Adams DJ. Biophysical properties of Na(v) 1.8/Na(v) 1.2 chimeras and inhibition by µO-conotoxin MrVIB. Br J Pharmacol 2012; 166:2148-60. [PMID: 22452751 DOI: 10.1111/j.1476-5381.2012.01955.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE Voltage-gated sodium channels are expressed primarily in excitable cells and play a pivotal role in the initiation and propagation of action potentials. Nine subtypes of the pore-forming α-subunit have been identified, each with a distinct tissue distribution, biophysical properties and sensitivity to tetrodotoxin (TTX). Na(v) 1.8, a TTX-resistant (TTX-R) subtype, is selectively expressed in sensory neurons and plays a pathophysiological role in neuropathic pain. In comparison with TTX-sensitive (TTX-S) Na(v) α-subtypes in neurons, Na(v) 1.8 is most strongly inhibited by the µO-conotoxin MrVIB from Conus marmoreus. To determine which domain confers Na(v) 1.8 α-subunit its biophysical properties and MrVIB binding, we constructed various chimeric channels incorporating sequence from Na(v) 1.8 and the TTX-S Na(v) 1.2 using a domain exchange strategy. EXPERIMENTAL APPROACH Wild-type and chimeric Na(v) channels were expressed in Xenopus oocytes, and depolarization-activated Na⁺ currents were recorded using the two-electrode voltage clamp technique. KEY RESULTS MrVIB (1 µM) reduced Na(v) 1.2 current amplitude to 69 ± 12%, whereas Na(v) 1.8 current was reduced to 31 ± 3%, confirming that MrVIB has a binding preference for Na(v) 1.8. A similar reduction in Na⁺ current amplitude was observed when MrVIB was applied to chimeras containing the region extending from S6 segment of domain I through the S5-S6 linker of domain II of Na(v) 1.8. In contrast, MrVIB had only a small effect on Na⁺ current for chimeras containing the corresponding region of Na(v) 1.2. CONCLUSIONS AND IMPLICATIONS Taken together, these results suggest that domain II of Na(v) 1.8 is an important determinant of MrVIB affinity, highlighting a region of the α-subunit that may allow further nociceptor-specific ligand targeting.
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Affiliation(s)
- O Knapp
- Health Innovations Research Institute, RMIT University, Melbourne, Vic, Australia
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Aguirre J, Del Moral A, Cobo I, Borgeat A, Blumenthal S. The role of continuous peripheral nerve blocks. Anesthesiol Res Pract 2012; 2012:560879. [PMID: 22761615 PMCID: PMC3385590 DOI: 10.1155/2012/560879] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 04/10/2012] [Accepted: 04/17/2012] [Indexed: 12/29/2022] Open
Abstract
A continuous peripheral nerve block (cPNB) is provided in the hospital and ambulatory setting. The most common use of CPNBs is in the peri- and postoperative period but different indications have been described like the treatment of chronic pain such as cancer-induced pain, complex regional pain syndrome or phantom limb pain. The documented benefits strongly depend on the analgesia quality and include decreasing baseline/dynamic pain, reducing additional analgesic requirements, decrease of postoperative joint inflammation and inflammatory markers, sleep disturbances and opioid-related side effects, increase of patient satisfaction and ambulation/functioning improvement, an accelerated resumption of passive joint range-of-motion, reducing time until discharge readiness, decrease in blood loss/blood transfusions, potential reduction of the incidence of postsurgical chronic pain and reduction of costs. Evidence deriving from randomized controlled trials suggests that in some situations there are also prolonged benefits of regional anesthesia after catheter removal in addition to the immediate postoperative effects. Unfortunately, there are only few data demonstrating benefits after catheter removal and the evidence of medium- or long-term improvements in health-related quality of life measures is still lacking. This review will give an overview of the advantages and adverse effects of cPNBs.
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Affiliation(s)
- José Aguirre
- Division of Anesthesiology, Balgrist University Hospital, 8008 Zurich, Switzerland
| | - Alicia Del Moral
- Department of Anesthesiology, General University Hospital of Valencia, 46014 Valencia, Spain
| | - Irina Cobo
- Department of Anesthesiology, General University Hospital of Valencia, 46014 Valencia, Spain
| | - Alain Borgeat
- Division of Anesthesiology, Balgrist University Hospital, 8008 Zurich, Switzerland
| | - Stephan Blumenthal
- Department of Anesthesiology, Triemli Hospital, 8063 Zurich, Switzerland
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