Title: De novo loss- or gain-of-function mutations in KCNA2 cause epileptic encephalopathy.

Authors: Steffen Syrbe, Ulrike B S Hedrich, Erik Riesch, Tania Djémié, Stephan Müller, Rikke S Møller, Bridget Maher, Laura Hernandez-Hernandez, Matthis Synofzik, Hande S Caglayan, Mutluay Arslan, José M Serratosa, Michael Nothnagel, Patrick May, Roland Krause, Heidrun Löffler, Katja Detert, Thomas Dorn, Heinrich Vogt, Günter Krämer, Ludger Schols, Primus E Mullis, Tarja Linnankivi, Anna-Elina Lehesjoki, Katalin Sterbova, Dana C Craiu, Dorota Hoffman-Zacharska, Christian M Korff, Yvonne G Weber, Maja Steinlin, Sabina Gallati, Astrid Bertsche, Matthias K Bernhard, Andreas Merkenschlager, Wieland Kiess, , Michael Gonzalez, Stephan Züchner, Aarno Palotie, Arvid Suls, Peter De Jonghe, Ingo Helbig, Saskia Biskup, Markus Wolff, Snezana Maljevic, Rebecca Schüle, Sanjay M Sisodiya, Sarah Weckhuysen, Holger Lerche, Johannes R Lemke

Journal, date & volume: Nat. Genet., 2015 Apr , 47, 393-9

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/25751627

Abstract
Epileptic encephalopathies are a phenotypically and genetically heterogeneous group of severe epilepsies accompanied by intellectual disability and other neurodevelopmental features. 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.