Epileptic encephalopathies are a phenotypically and genetically heterogeneous group of severe epilepsies accompanied by intellectual disability and other neurodevelopmental features1,2,3,4,5,6. Using next-generation sequencing, we identified four different de novo mutations in KCNA2, encoding the potassium channel KV1.2, in six isolated patients with epileptic encephalopathy (one mutation recurred three times independently). Four individuals presented with febrile and multiple afebrile, often focal seizure types, multifocal epileptiform discharges strongly activated by sleep, mild to moderate intellectual disability, delayed speech development and sometimes ataxia. Functional studies of the two mutations associated with this phenotype showed almost complete loss of function with a dominant-negative effect. Two further individuals presented with a different and more severe epileptic encephalopathy phenotype. They carried mutations inducing a drastic gain-of-function effect leading to permanently open channels. These results establish KCNA2 as a new gene involved in human neurodevelopmental disorders through two different mechanisms, predicting either hyperexcitability or electrical silencing of KV1.2-expressing neurons.
This is a preview of subscription content, access via your institution
Open Access articles citing this article.
Acta Epileptologica Open Access 02 March 2022
De novo variants in CACNA1E found in patients with intellectual disability, developmental regression and social cognition deficit but no seizures
Molecular Autism Open Access 26 October 2021
Monatsschrift Kinderheilkunde Open Access 04 August 2021
Subscribe to Journal
Get full journal access for 1 year
only $6.58 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
NCBI Reference Sequence
Capovilla, G., Wolf, P., Beccaria, F. & Avanzini, G. The history of the concept of epileptic encephalopathy. Epilepsia 54 (suppl. 8), 2–5 (2013).
Guerrini, R. & Pellock, J.M. Age-related epileptic encephalopathies. Handb. Clin. Neurol. 107, 179–193 (2012).
Claes, L. et al. De novo mutations in the sodium-channel gene SCN1A cause severe myoclonic epilepsy of infancy. Am. J. Hum. Genet. 68, 1327–1332 (2001).
Nava, C. et al. De novo mutations in HCN1 cause early infantile epileptic encephalopathy. Nat. Genet. 46, 640–645 (2014).
Epi4K Consortium & Epilepsy Phenome/Genome Project. De novo mutations in epileptic encephalopathies. Nature 501, 217–221 (2013).
Lerche, H. et al. Ion channels in genetic and acquired forms of epilepsy. J. Physiol. (Lond.) 591, 753–764 (2013).
Lai, H.C. & Jan, L.Y. The distribution and targeting of neuronal voltage-gated ion channels. Nat. Rev. Neurosci. 7, 548–562 (2006).
Biervert, C. et al. A potassium channel mutation in neonatal human epilepsy. Science 279, 403–406 (1998).
Charlier, C. et al. A pore mutation in a novel KQT-like potassium channel gene in an idiopathic epilepsy family. Nat. Genet. 18, 53–55 (1998).
Singh, N.A. et al. A novel potassium channel gene, KCNQ2, is mutated in an inherited epilepsy of newborns. Nat. Genet. 18, 25–29 (1998).
Weckhuysen, S. et al. KCNQ2 encephalopathy: emerging phenotype of a neonatal epileptic encephalopathy. Ann. Neurol. 71, 15–25 (2012).
Orhan, G. et al. Dominant-negative effects of KCNQ2 mutations are associated with epileptic encephalopathy. Ann. Neurol. 75, 382–394 (2014).
Browne, D.L. et al. Episodic ataxia/myokymia syndrome is associated with point mutations in the human potassium channel gene, KCNA1. Nat. Genet. 8, 136–140 (1994).
Wuttke, T.V. et al. Peripheral nerve hyperexcitability due to dominant-negative KCNQ2 mutations. Neurology 69, 2045–2053 (2007).
Dedek, K. et al. Myokymia and neonatal epilepsy caused by a mutation in the voltage sensor of the KCNQ2 K+ channel. Proc. Natl. Acad. Sci. USA 98, 12272–12277 (2001).
Irani, S.R. et al. Antibodies to KV1 potassium channel-complex proteins leucine-rich, glioma inactivated 1 protein and contactin-associated protein-2 in limbic encephalitis, Morvan's syndrome and acquired neuromyotonia. Brain 133, 2734–2748 (2010).
Lemke, J.R. et al. Targeted next generation sequencing as a diagnostic tool in epileptic disorders. Epilepsia 53, 1387–1398 (2012).
Lubbers, W.J. et al. Hereditary myokymia and paroxysmal ataxia linked to chromosome 12 is responsive to acetazolamide. J. Neurol. Neurosurg. Psychiatry 59, 400–405 (1995).
Pena, S.D. & Coimbra, R.L. Ataxia and myoclonic epilepsy due to a heterozygous new mutation in KCNA2: proposal for a new channelopathy. Clin. Genet. 87, e1–e3 (2015).
Xie, G. et al. A new KV1.2 channelopathy underlying cerebellar ataxia. J. Biol. Chem. 285, 32160–32173 (2010).
Brew, H.M. et al. Seizures and reduced life span in mice lacking the potassium channel subunit KV1.2, but hypoexcitability and enlarged KV1 currents in auditory neurons. J. Neurophysiol. 98, 1501–1525 (2007).
Jan, L.Y. & Jan, Y.N. Voltage-gated potassium channels and the diversity of electrical signalling. J. Physiol. (Lond.) 590, 2591–2599 (2012).
Holmgren, M., Shin, K.S. & Yellen, G. The activation gate of a voltage-gated K+ channel can be trapped in the open state by an intersubunit metal bridge. Neuron 21, 617–621 (1998).
Long, S.B., Campbell, E.B. & Mackinnon, R. Voltage sensor of KV1.2: structural basis of electromechanical coupling. Science 309, 903–908 (2005).
Labro, A.J., Raes, A.L., Bellens, I., Ottschytsch, N. & Snyders, D.J. Gating of Shaker-type channels requires the flexibility of S6 caused by prolines. J. Biol. Chem. 278, 50724–50731 (2003).
Chen, X., Wang, Q., Ni, F. & Ma, J. Structure of the full-length Shaker potassium channel KV1.2 by normal-mode-based X-ray crystallographic refinement. Proc. Natl. Acad. Sci. USA 107, 11352–11357 (2010).
Klein, A., Boltshauser, E., Jen, J. & Baloh, R.W. Episodic ataxia type 1 with distal weakness: a novel manifestation of a potassium channelopathy. Neuropediatrics 35, 147–149 (2004).
Nybo, K. Molecular biology techniques Q&A. Western blot: protein migration. Biotechniques 53, 23–24 (2012).
Lorincz, A. & Nusser, Z. Cell-type-dependent molecular composition of the axon initial segment. J. Neurosci. 28, 14329–14340 (2008).
Wang, H., Kunkel, D.D., Schwartzkroin, P.A. & Tempel, B.L. Localization of Kv1.1 and Kv1.2, two K channel proteins, to synaptic terminals, somata, and dendrites in the mouse brain. J. Neurosci. 14, 4588–4599 (1994).
Suls, A. et al. De novo loss-of-function mutations in CHD2 cause a fever-sensitive myoclonic epileptic encephalopathy sharing features with Dravet syndrome. Am. J. Hum. Genet. 93, 967–975 (2013).
Suls, A. et al. Microdeletions involving the SCN1A gene may be common in SCN1A-mutation-negative SMEI patients. Hum. Mutat. 27, 914–920 (2006).
Wang, H., Kunkel, D.D., Martin, T.M., Schwartzkroin, P.A. & Tempel, B.L. Heteromultimeric K+ channels in terminal and juxtaparanodal regions of neurons. Nature 365, 75–79 (1993).
Liu, X., Jian, X. & Boerwinkle, E. dbNSFP v2.0: a database of human non-synonymous SNVs and their functional predictions and annotations. Hum. Mutat. 34, E2393–E2402 (2013).
Kong, A. et al. Rate of de novo mutations and the importance of father's age to disease risk. Nature 488, 471–475 (2012).
We thank all patients and family members for their participation in this study, S. Grissmer (Ulm University) for providing the human cDNA clone of KCNA2, and F. Lang and his colleagues (University of Tübingen) for providing Xenopus oocytes. J.R.L. (32EP30_136042/1), J.M.S. (EUI-EURC2011-4325), H. Lerche (DFG Le1030/11-1), P.D.J. (G.A.136.11.N, FWO/ESF-ECRP), H.S.C. (TUBITAK 110S518) and I.H. (DFG HE 5415 3-1) received financial support within the EuroEPINOMICS RES and EuroEPINOMICS CoGIE networks (http://www.euroepinomics.org/), a Eurocores project of the European Science Foundation. R.S. received funding from the European Union (E-Rare JTC grants 01GM1408B and PIOF-GA-2012-326681). J.M.S. received further support from the Ministerio de Economía y Competitividad (SAF2010-18586). H. Lerche, S.B. and S. Maljevic received further support from the Federal Ministry for Education and Research (BMBF, program on rare diseases, IonNeurONet: 01GM1105A). S.Z. received support from the US National Institutes of Health (R01NS072248). S.M.S. received support from the Wellcome Trust (084730), National Institute for Health Research (NIHR) University College London Hospital Biomedical Research Centre and Epilepsy Society, UK. M. Synofzik received support from the Interdisciplinary Center for Clinical Research (IZKF) Tübingen (2191-0-0). A.S. received funding for a postdoctoral fellowship from the Fonds Wetenschappelijk Onderzoek. T. Djémié is a PhD fellow of the Institute of Science and Technology (IWT).
The authors declare no competing financial interests.
Integrated supplementary information
Screening of patients with different epilepsy phenotypes by panel sequencing (dark gray) or parent-offspring trio WES (light gray) revealed several KCNA2 de novo mutations resulting in loss of function (red) or gain of function (blue) as well as one variant of unknown inheritance with no detectable effect on channel function (white). Sanger sequencing of two follow-up cohorts revealed no additional mutations in KCNA2. MAQ screening in most WES cohorts as well as the two follow-up cohorts did not reveal CNVs affecting KCNA2.
Electropherograms of patients 1, 2 and 4–7 (top) and their parents (father in the middle, mother at bottom) with patients 1, 4 and 5 showing the same de novo mutation.
(a) Structure of the voltage-gated potassium channel KV1.2 with transmembrane segments S1–S4 forming the voltage sensor domain (light gray) and the pore region S5–S6 (dark gray) with its pore-forming loop. Mutation R147K is in the N terminus. (b) R147 and the respective surrounding amino acids show evolutionary conservation. (c) Pedigree of patients 3 and electropherogram of the mutation. (d) Representative current traces derived from KV1.2 wild-type (WT, top) and mutant KV1.2 R147K (bottom) channels recorded in a Xenopus oocyte 2 d after cRNA injection during voltage steps ranging from –80 mV to +70 mV. (e) Mean current amplitudes of KV1.2-WT (1.0; n = 20), R147K (1.0; n = 20) and coexpressed WT + R147K (0.5:0.5) (n = 24) did not show significant differences between each other. All currents were normalized to the mean current amplitude of 1.0 WT with H2O recorded on the same day. (f) Western blot analysis from lysates of Xenopus oocytes injected with equal amounts of KV1.2-WT or mutant (R147K) cRNA were performed using a mouse anti-KV1.2 antibody. KV1.2-WT and R147K mutant (n = 4) channels showed similar bands (57 kDa) in total cell lysates. Water-injected oocytes were used as controls.
Shown is the effect of an increasing amount of injected WT-KV1.2 cRNA on the absolute, i.e., non-normalized current amplitudes (in contrast to Fig. 2b showing the relative amplitudes normalized to the amount of 1.0 WT-KV1.2 cRNA). The differences with Figure 2b are small, reflecting the relative stability of our experiments on different experimental days and different batches of oocytes: 0.25, n = 13; 0.5, n = 18; 1, n = 22; 2, n = 17; 4, n = 20; 8, n = 19. There was an overall difference between the groups (one-way ANOVA, P < 0.001); pairwise multiple comparisons between the single groups (Dunn’s method) showed a statistically significant difference between all tested groups of mutants (*P < 0.05).
(a) Mean voltage dependence of KV1.2 channel activation for P405L (left, dark blue), I263T (middle, light blue) and R147K (right, green) mutant and WT channels. Shown are means ± s.e.m. with lines showing Boltzmann functions fit to data points. For P405L (left): V1/2 = –12.5 ± 1.5 mV for WT (n = 16) versus V1/2 = –13.5 ± 2.0 mV for P405L (n = 7); P < 0.05, Student’s t test. kV = –6.9 ± 0.2 for WT versus kV = –6.9 ± 0.3 for P405L; n.s., Student’s t test. For I263T (middle): V1/2 = –14.8 ± 1.0 mV for WT (n = 16) versus V1/2 = –5.8 ± 1.5 mV for I263T (n = 22); P < 0.001, Mann-Whitney rank-sum test; kV = –6.8 ± 1.8 for WT versus kV = –11.5 ± 1.3 for I263T; P < 0.001, Mann-Whitney rank-sum test. For R147K (right): V1/2 = –12.1 ± 1.1 mV for WT (n = 20) versus V1/2 = –12.5 ± 0.8 mV for R147K (n = 12); n.s., Student’s t test. kV = –6.8 ± 0.3 for WT versus kV = –6.7 ± 0.2 for WT; n.s., Student’s t test. (b) Mean voltage dependence of KV1.2 channel inactivation for P405L (left, dark blue), I263T (middle, light blue) and R147K (right, green) mutants. Shown are means ± s.e.m. fitted to a standard Boltzmann function. For P405L (left): V1/2 = –24.4 ± 0.5 mV for WT (n = 11) versus V1/2 = –28.9 ± 0.9 mV for P405L (n = 7); P < 0.05, Student’s t test. kV = 3.8 ± 0.8 for WT versus kV = 3.6 ± 0.6 for P405L; n.s., Student’s t test. For I263T (middle): V1/2 = –23.3 ± 1.1 mV for WT (n = 13) versus V1/2 = –23.5 ± 1.1 mV for I263T (n = 7); n.s., Student’s t test. kV = 3.9 ± 0.4 for WT versus kV = 5.2 ± 0.6 for I263T; n.s., Student’s t test. For R147K (right): V1/2 = –24.8 ± 0.1 mV for WT (n = 18) versus V1/2 = –23.4 ± 0.5 mV for R147K (n = 16); n.s., Student’s t test. kV = 3.4 ± 0.1 for WT versus kV = 3.6 ± 0.1 for WT; n.s., Student’s t test.
Supplementary Figures 1–5 and Supplementary Note. (PDF 674 kb)
List of all variants detected in patients 1, 3 and 5 by panel analysis. (XLS 41 kb)
Prediction of the pathogenicity of all KCNA2 variants detected within this study as well as of all nonsynonymous KCNA2 variants reported in the ExAC database. (XLS 95 kb)
About this article
Cite this article
Syrbe, S., Hedrich, U., Riesch, E. et al. De novo loss- or gain-of-function mutations in KCNA2 cause epileptic encephalopathy. Nat Genet 47, 393–399 (2015). https://doi.org/10.1038/ng.3239
This article is cited by
Acta Epileptologica (2022)
Re-engineering the adenine deaminase TadA-8e for efficient and specific CRISPR-based cytosine base editing
Nature Biotechnology (2022)
Zeitschrift für Epileptologie (2021)
Monatsschrift Kinderheilkunde (2021)
Bee venom acupuncture therapy ameliorates neuroinflammatory alterations in a pilocarpine-induced epilepticus model
Metabolic Brain Disease (2021)