1. Genotype-phenotype correlations in SCN8A-related disorders reveal prognostic and therapeutic implications
- Author
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Roseline Caume, M Scott Perry, Massimo Mastrangelo, Margarete Koch-Hogrebe, Pasquale Striano, Karen Müller-Schlüter, Petra Laššuthová, Monisa D. Wagner, Ingo Helbig, Stephan Lauxmann, Emmanuel Scalais, Marie-Cécile Nassogne, Silvia Masnada, Henrike O. Heyne, Konrad Platzer, Frederic Bilan, Chloe A Stutterd, Sonja Walsh, Katrine M Johannesen, Damien Lederer, Ngoc Minh Le, Christina Fenger, Daniel Tibussek, Lukas Sonnenberg, Andrea Berger, Yuanyuan Liu, Mikhail Abramov, Karen E. Wain, Sergey Korostelev, P Y Billie Au, Elena L. Dadali, An-Sofie Schoonjans, Cornelia Betzler, Artem Borovikov, Johanna Krüger, Maert Rannap, Sebastian Lebon, Nils A Koch, Nancy Eisenhauer, Judith Kroell-Seger, Julian Schubert, Marije Meuwissen, Caroline Lund, Mark Fitzgerald, Federico Zara, Siddharth Srivastava, Claudia M Bonardi, Pia Zacher, Haim Bassan, Arve Vøllo, Katherine B. Howell, Francesca Darra, Guido Rubboli, Stephen W. Scherer, Bénédicte Gérard, Stefano Sartori, Annapurna Poduri, Helene Verhelst, Katalin Sterbova, Mathilde Nizon, Marketa Vlckova, Christina E. Hoei-Hansen, Renzo Guerrini, Ilya V. Kanivets, Juliann M. Savatt, Johannes Rebstock, Jakob Christensen, Cecilia Altuzarra, Dennis Lal, Judith S. Verhoeven, Agathe Roubertie, Constanze Heine, Dagmar Wieczorek, Ingo Borggraefe, Aster V. E. Harder, Anne Destrée, Wen-Hann Tan, Tobias Brünger, Shoji Ichikawa, Laura Canafoglia, Mahmoud Koko, Sergey Kutsev, Sabine Grønborg, Patrizia Accorsi, Heather E. Olson, Bert van der Zwaag, Cathrine E Gjerulfsen, Patrick May, A. A. Sharkov, M. Mahdi Motazacker, Manuela Pendziwiat, Richard J. Leventer, Anna Jansen, Lucio Giordano, Holger Lerche, Carla Marini, Karl Martin Klein, Eva H. Brilstra, Ahmed Eltokhi, Ethan M. Goldberg, Walid Fazeli, Rikke S. Møller, Dorota Hoffman-Zacharska, Michael Alber, Susanne Ruf, Jennifer L. Howe, Phillis Lakeman, Josua Kegele, Katherine L. Helbig, Marga Buzatu, Alice W Ho, Jan Benda, Ilona Krey, Marion Gérard, Sara Matricardi, Thomas U. Mayer, Philippe Gelisse, Jong M. Rho, Johannes R. Lemke, Pierangelo Veggiotti, Tobias Loddenkemper, Gaetan Lesca, Ulrike B. S. Hedrich, Silvana Franceschetti, Elena Gardella, Irina Mishina, María Vaccarezza, Timo Roser, Public Health Sciences, Mental Health and Wellbeing research group, Neurogenetics, Neuroprotection & Neuromodulation, Pediatrics, Human Genetics, ANS - Complex Trait Genetics, ARD - Amsterdam Reproduction and Development, Human genetics, and Amsterdam Reproduction & Development (AR&D)
- Subjects
medicine.medical_specialty ,SCN8A ,Gastroenterology ,Epilepsy ,Sodium channel blocker ,Neurodevelopmental disorder ,Seizures ,Intellectual Disability ,Internal medicine ,medicine ,Humans ,Missense mutation ,genetics ,Generalized epilepsy ,Genetic Association Studies ,Benign familial infantile epilepsy ,Generalized ,business.industry ,Infant ,personalized medicine ,Prognosis ,medicine.disease ,Phenotype ,Settore MED/39 - Neuropsichiatria Infantile ,NAV1.6 Voltage-Gated Sodium Channel ,Mutation ,epilepsy ,Original Article ,Epilepsy, Generalized ,Human medicine ,Neurology (clinical) ,Age of onset ,business ,Epileptic Syndromes ,Sodium Channel Blockers - Abstract
We report detailed functional analyses and genotype-phenotype correlations in 392 individuals carrying disease-causing variants in SCN8A, encoding the voltage-gated Na+ channel Nav1.6, with the aim of describing clinical phenotypes related to functional effects. Six different clinical subgroups were identified: Group 1, benign familial infantile epilepsy (n = 15, normal cognition, treatable seizures); Group 2, intermediate epilepsy (n = 33, mild intellectual disability, partially pharmaco-responsive); Group 3, developmental and epileptic encephalopathy (n = 177, severe intellectual disability, majority pharmaco-resistant); Group 4, generalized epilepsy (n = 20, mild to moderate intellectual disability, frequently with absence seizures); Group 5, unclassifiable epilepsy (n = 127); and Group 6, neurodevelopmental disorder without epilepsy (n = 20, mild to moderate intellectual disability). Those in Groups 1–3 presented with focal or multifocal seizures (median age of onset: 4 months) and focal epileptiform discharges, whereas the onset of seizures in patients with generalized epilepsy was later (median: 42 months) with generalized epileptiform discharges. We performed functional studies expressing missense variants in ND7/23 neuroblastoma cells and primary neuronal cultures using recombinant tetrodotoxin-insensitive human Nav1.6 channels and whole-cell patch-clamping. Two variants causing developmental and epileptic encephalopathy showed a strong gain-of-function (hyperpolarizing shift of steady-state activation, strongly increased neuronal firing rate) and one variant causing benign familial infantile epilepsy or intermediate epilepsy showed a mild gain-of-function (defective fast inactivation, less increased firing). In contrast, all three variants causing generalized epilepsy induced a loss-of-function (reduced current amplitudes, depolarizing shift of steady-state activation, reduced neuronal firing). Functional effects were known for 170 individuals. All 136 individuals carrying a functionally tested gain-of-function variant had either focal (n = 97, Groups 1–3) or unclassifiable (n = 39) epilepsy, whereas 34 individuals with a loss-of-function variant had either generalized (n = 14), no (n = 11) or unclassifiable (n = 6) epilepsy; only three had developmental and epileptic encephalopathy. Computational modelling in the gain-of-function group revealed a significant correlation between the severity of the electrophysiological and clinical phenotypes. Gain-of-function variant carriers responded significantly better to sodium channel blockers than to other anti-seizure medications, and the same applied for all individuals in Groups 1–3. In conclusion, our data reveal clear genotype-phenotype correlations between age at seizure onset, type of epilepsy and gain- or loss-of-function effects of SCN8A variants. Generalized epilepsy with absence seizures is the main epilepsy phenotype of loss-of-function variant carriers and the extent of the electrophysiological dysfunction of the gain-of-function variants is a main determinant of the severity of the clinical phenotype in focal epilepsies. Our pharmacological data indicate that sodium channel blockers present a treatment option in SCN8A-related focal epilepsy with onset in the first year of life.
- Published
- 2022