Patients with SCN8A epileptic encephalopathy exhibit a range of clinical features, including multiple seizure types, movement disorders, and behavioral abnormalities, such as developmental delay, mild-to-severe intellectual disability, and autism. Recently, the de novo heterozygous SCN8A R1620L mutation was identified in an individual with autism, intellectual disability, and behavioral seizures without accompanying electrographic seizure activity. To date, the effects of SCN8A mutations that are primarily associated with behavioral abnormalities have not been studied in a mouse model. To better understand the phenotypic and functional consequences of the R1620L mutation, we used CRISPR/Cas9 technology to generate mice expressing the corresponding SCN8A amino acid substitution. Homozygous mutants exhibit tremors and a maximum lifespan of 22 days, while heterozygous mutants (RL/+) exhibit autistic-like behaviors, such as hyperactivity and learning and social deficits, increased seizure susceptibility, and spontaneous seizures. Current clamp analyses revealed a reduced threshold for firing action potentials in heterozygous CA3 pyramidal neurons and reduced firing frequency, suggesting that the R1620L mutation has both gain- and loss-of-function effects. In vivo calcium imaging using miniscopes in freely moving RL/+ mutants showed hyperexcitability of cortical excitatory neurons that is likely to increase seizure susceptibility. Finally, we found that oxcarbazepine and Huperzine A, a sodium channel blocker and reversible acetylcholinesterase inhibitor, respectively, were capable of conferring robust protection against induced seizures in RL/+ mutants. This mouse line will provide the opportunity to better understand the range of clinical phenotypes associated with SCN8A mutations and to develop new therapeutic approaches.
Subscribe to Journal
Get full journal access for 1 year
only $30.69 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Boiko T, Rasband MN, Levinson SR, Caldwell JH, Mandel G, Trimmer JS, et al. Compact myelin dictates the differential targeting of two sodium channel isoforms in the same axon. Neuron. 2001;30:91–104.
Boiko T, Van Wart A, Caldwell JH, Levinson SR, Trimmer JS, Matthews G. Functional specialization of the axon initial segment by isoform-specific sodium channel targeting. J Neurosci. 2003;23:2306–13.
Caldwell JH, Schaller KL, Lasher RS, Peles E, Levinson SR. Sodium channel Na(v)1.6 is localized at nodes of ranvier, dendrites, and synapses. Proc Natl Acad Sci USA. 2000;97:5616–20.
Hu W, Tian C, Li T, Yang M, Hou H, Shu Y. Distinct contributions of Na(v)1.6 and Na(v)1.2 in action potential initiation and backpropagation. Nat Neurosci. 2009;12:996–1002.
Raman IM, Sprunger LK, Meisler MH, Bean BP. Altered subthreshold sodium currents and disrupted firing patterns in Purkinje neurons of Scn8a mutant mice. Neuron. 1997;19:881–91.
Cummins TR, Dib-Hajj SD, Herzog RI, Waxman SG. Nav1.6 channels generate resurgent sodium currents in spinal sensory neurons. FEBS Lett. 2005;579:2166–70.
Hawkins NA, Martin MS, Frankel WN, Kearney JA, Escayg A. Neuronal voltage-gated ion channels are genetic modifiers of generalized epilepsy with febrile seizures plus. Neurobiol Dis. 2011;41:655–60.
Martin MS, Tang B, Papale LA, Yu FH, Catterall WA, Escayg A. The voltage-gated sodium channel Scn8a is a genetic modifier of severe myoclonic epilepsy of infancy. Hum Mol Genet. 2007;16:2892–9.
Makinson CD, Tanaka BS, Lamar T, Goldin AL, Escayg A. Role of the hippocampus in Nav1.6 (Scn8a) mediated seizure resistance. Neurobiol Dis. 2014;68:16–25.
Wong JC, Makinson CD, Lamar T, Cheng Q, Wingard JC, Terwilliger EF, et al. Selective targeting of Scn8a prevents seizure development in a mouse model of mesial temporal lobe epilepsy. Sci Rep. 2018;8:126.
Papale LA, Beyer B, Jones JM, Sharkey LM, Tufik S, Epstein M, et al. Heterozygous mutations of the voltage-gated sodium channel SCN8A are associated with spike-wave discharges and absence epilepsy in mice. Hum Mol Genet. 2009;18:1633–41.
Makinson CD, Tanaka BS, Sorokin JM, Wong JC, Christian CA, Goldin AL, et al. Regulation of thalamic and cortical network synchrony by Scn8a. Neuron. 2017;93:1165–79 e6.
Veeramah KR, O’Brien JE, Meisler MH, Cheng X, Dib-Hajj SD, Waxman SG, et al. De novo pathogenic SCN8A mutation identified by whole-genome sequencing of a family quartet affected by infantile epileptic encephalopathy and SUDEP. Am J Hum Genet. 2012;90:502–10.
Wagnon JL, Meisler MH. Recurrent and non-recurrent mutations of SCN8A in epileptic encephalopathy. Front Neurol. 2015;6:104.
Butler KM, da Silva C, Shafir Y, Weisfeld-Adams JD, Alexander JJ, Hegde M, et al. De novo and inherited SCN8A epilepsy mutations detected by gene panel analysis. Epilepsy Res. 2017;129:17–25.
Hammer MF, Wagnon JL, Mefford HC, Meisler MH, SCN8A-related epilepsy with encephalopathy, In: Adam MP, et al., editors. GeneReviews, Seattle, WA; 1993.
Wagnon JL, Korn MJ, Parent R, Tarpey TA, Jones JM, Hammer MF, et al. Convulsive seizures and SUDEP in a mouse model of SCN8A epileptic encephalopathy. Hum Mol Genet. 2015;24:506–15.
Bunton-Stasyshyn RKA, Wagnon JL, Wengert ER, Barker BS, Faulkner A, Wagley PK, et al., Prominent role of forebrain excitatory neurons in SCN8A encephalopathy. Brain. 2019;142:362–75.
Larsen J, Carvill GL, Gardella E, Kluger G, Schmiedel G, Barisic N, et al. The phenotypic spectrum of SCN8A encephalopathy. Neurology. 2015;84:480–9.
Rossi M, El-Khechen D, Black MH, Farwell Hagman KD, Tang S, Powis Z. Outcomes of diagnostic exome sequencing in patients with diagnosed or suspected autism spectrum disorders. Pediatr Neurol. 2017;70:34–43 e2.
Liu Y, Schubert J, Sonnenberg L, Helbig KL, Hoei-Hansen CE, Koko M, et al., Neuronal mechanisms of mutations in SCN8A causing epilepsy or intellectual disability. Brain. 2019.
Ma Y, Yu L, Pan S, Gao S, Chen W, Zhang X, et al. CRISPR/Cas9-mediated targeting of the Rosa26 locus produces Cre reporter rat strains for monitoring Cre-loxP-mediated lineage tracing. FEBS J. 2017;284:3262–77.
Yen ST, Zhang M, Deng JM, Usman SJ, Smith CN, Parker-Thornburg J, et al. Somatic mosaicism and allele complexity induced by CRISPR/Cas9 RNA injections in mouse zygotes. Dev Biol. 2014;393:3–9.
Lamar T, Vanoye CG, Calhoun J, Wong JC, Dutton SBB, Jorge BS, et al. SCN3A deficiency associated with increased seizure susceptibility. Neurobiol Dis. 2017;102:38–48.
Rha J, Jones SK, Fidler J, Banerjee A, Leung SW, Morris KJ, et al. The RNA-binding protein, ZC3H14, is required for proper poly(A) tail length control, expression of synaptic proteins, and brain function in mice. Hum Mol Genet. 2017;26:3663–81.
Wong JC, Shapiro L, Thelin JT, Heaton EC, Zaman RU, D’Souza MJ, et al. Nanoparticle encapsulated oxytocin increases resistance to induced seizures and restores social behavior in Scn1a-derived epilepsy. Neurobiol Dis. 2021;147:105147.
Inglis GAS, Wong JC, Butler KM, Thelin JT, Mistretta OC, Wu X, et al., Mutations in the Scn8a DIIS4 voltage sensor reveal new distinctions among hypomorphic and null Nav 1.6 sodium channels. Genes Brain Behav. 2019;19:e12612.
Shapiro L, Wong JC, Escayg A. Reduced cannabinoid 2 receptor activity increases susceptibility to induced seizures in mice. Epilepsia. 2019;60:2359–69.
Wong JC, Dutton SB, Collins SD, Schachter S, Escayg A. Huperzine A provides robust and sustained protection against induced seizures in Scn1a mutant mice. Front Pharmacol. 2016;7:357.
Wong JC, Thelin JT, Escayg A. Donepezil increases resistance to induced seizures in a mouse model of Dravet syndrome. Ann Clin Transl Neurol. 2019;6:1566–71.
Kearney JA, Buchner DA, De Haan G, Adamska M, Levin SI, Furay AR, et al. Molecular and pathological effects of a modifier gene on deficiency of the sodium channel Scn8a (Na(v)1.6). Hum Mol Genet. 2002;11:2765–75.
Angaut-Petit D, McArdle JJ, Mallart A, Bournaud R, Pincon-Raymond M, Rieger F. Electrophysiological and morphological studies of a motor nerve in ‘motor endplate disease’ of the mouse. Proc R Soc Lond B Biol Sci. 1982;215:117–25.
Hammad M, Schmidt SL, Zhang X, Bray R, Frohlich F, Ghashghaei HT. Transplantation of GABAergic interneurons into the neonatal primary visual cortex reduces absence seizures in stargazer mice. Cereb Cortex. 2015;25:2970–9.
Powell EM, Campbell DB, Stanwood GD, Davis C, Noebels JL, Levitt P. Genetic disruption of cortical interneuron development causes region- and GABA cell type-specific deficits, epilepsy, and behavioral dysfunction. J Neurosci. 2003;23:622–31.
Mainardi M, Pietrasanta M, Vannini E, Rossetto O, Caleo M. Tetanus neurotoxin-induced epilepsy in mouse visual cortex. Epilepsia. 2012;53:e132–6.
Sun Y, Jin S, Lin X, Chen L, Qiao X, Jiang L, et al. CA1-projecting subiculum neurons facilitate object-place learning. Nat Neurosci. 2019;22:1857–70.
Gardella E, Marini C, Trivisano M, Fitzgerald MP, Alber M, Howell KB, et al. The phenotype of SCN8A developmental and epileptic encephalopathy. Neurology. 2018;91:e1112–24.
Silverman JL, Yang M, Lord C, Crawley JN. Behavioural phenotyping assays for mouse models of autism. Nat Rev Neurosci. 2010;11:490–502.
Hammond RS, Tull LE, Stackman RW. On the delay-dependent involvement of the hippocampus in object recognition memory. Neurobiol Learn Mem. 2004;82:26–34.
Phillips RG, LeDoux JE. Differential contribution of amygdala and hippocampus to cued and contextual fear conditioning. Behav Neurosci. 1992;106:274–85.
Kim JJ, Rison RA, Fanselow MS. Effects of amygdala, hippocampus, and periaqueductal gray lesions on short- and long-term contextual fear. Behav Neurosci. 1993;107:1093–8.
Han S, Tai C, Westenbroek RE, Yu FH, Cheah CS, Potter GB, et al. Autistic-like behaviour in Scn1a+/- mice and rescue by enhanced GABA-mediated neurotransmission. Nature. 2012;489:385–90.
Xie W, Strong JA, Zhang JM. Local knockdown of the NaV1.6 sodium channel reduces pain behaviors, sensory neuron excitability, and sympathetic sprouting in rat models of neuropathic pain. Neuroscience. 2015;291:317–30.
Escayg A, Goldin AL. Sodium channel SCN1A and epilepsy: mutations and mechanisms. Epilepsia. 2010;51:1650–8.
Dutton SBB, Dutt K, Papale LA, Helmers S, Goldin AL, Escayg A. Early-life febrile seizures worsen adult phenotypes in Scn1a mutants. Exp Neurol. 2017;293:159–71.
Martin MS, Dutt K, Papale LA, Dube CM, Dutton SB, de Haan G, et al. Altered function of the SCN1A voltage-gated sodium channel leads to gamma-aminobutyric acid-ergic (GABAergic) interneuron abnormalities. J Biol Chem. 2010;285:9823–34.
Epifanio R, Zanotta N, Giorda R, Bardoni A, Zucca C. Novel epilepsy phenotype associated to a known SCN8A mutation. Seizure. 2019;67:15–17.
Encinas AC, Moore IKM, Watkins JC, Hammer MF. Influence of age at seizure onset on the acquisition of neurodevelopmental skills in an SCN8A cohort. Epilepsia. 2019;60:1711–20.
Zaman T, Abou Tayoun A, Goldberg EM. A single-center SCN8A-related epilepsy cohort: clinical, genetic, and physiologic characterization. Ann Clin Transl Neurol. 2019;6:1445–55.
Cellot G, Maggi L, Di Castro MA, Catalano M, Migliore R, Migliore M, et al. Premature changes in neuronal excitability account for hippocampal network impairment and autistic-like behavior in neonatal BTBR T+tf/J mice. Sci Rep. 2016;6:31696.
The authors would like to acknowledge Dr. Mike Epstein for guidance on statistical analyses and Cheryl Strauss for editorial assistance.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Wong, J.C., Grieco, S.F., Dutt, K. et al. Autistic-like behavior, spontaneous seizures, and increased neuronal excitability in a Scn8a mouse model. Neuropsychopharmacol. (2021). https://doi.org/10.1038/s41386-021-00985-9