| Contributors: |
Johannesen, Katrine M; Liu, Yuanyuan; Koko, Mahmoud; Gjerulfsen, Cathrine E; Sonnenberg, Luka; Schubert, Julian; Fenger, Christina D; Eltokhi, Ahmed; Rannap, Maert; Koch, Nils A; Lauxmann, Stephan; Krüger, Johanna; Kegele, Josua; Canafoglia, Laura; Franceschetti, Silvana; Mayer, Thoma; Rebstock, Johanne; Zacher, Pia; Ruf, Susanne; Alber, Michael; Sterbova, Katalin; Lassuthová, Petra; Vlckova, Marketa; Lemke, Johannes R; Platzer, Konrad; Krey, Ilona; Heine, Constanze; Wieczorek, Dagmar; Kroell-Seger, Judith; Lund, Caroline; Klein, Karl Martin; Au, P Y Billie; Rho, Jong M; Ho, Alice W; Masnada, Silvia; Veggiotti, Pierangelo; Giordano, Lucio; Accorsi, Patrizia; Hoei-Hansen, Christina E; Striano, Pasquale; Zara, Federico; Verhelst, Helene; Verhoeven, Judith S; Braakman, Hilde M H; van der Zwaag, Bert; Harder, Aster V E; Brilstra, Eva; Pendziwiat, Manuela; Lebon, Sebastian; Vaccarezza, Maria; Le, Ngoc Minh; Christensen, Jakob; Grønborg, Sabine; Scherer, Stephen W; Howe, Jennifer; Fazeli, Walid; Howell, Katherine B; Leventer, Richard; Stutterd, Chloe; Walsh, Sonja; Gerard, Marion; Gerard, Bénédicte; Matricardi, Sara; Bonardi, Claudia M; Sartori, Stefano; Berger, Andrea; Hoffman-Zacharska, Dorota; Mastrangelo, Massimo; Darra, Francesca; Vøllo, Arve; Motazacker, M Mahdi; Lakeman, Philli; Nizon, Mathilde; Betzler, Cornelia; Altuzarra, Cecilia; Caume, Roseline; Roubertie, Agathe; Gélisse, Philippe; Marini, Carla; Guerrini, Renzo; Bilan, Frederic; Tibussek, Daniel; Koch-Hogrebe, Margarete; Perry, M Scott; Ichikawa, Shoji; Dadali, Elena; Sharkov, Artem; Mishina, Irina; Abramov, Mikhail; Kanivets, Ilya; Korostelev, Sergey; Kutsev, Sergey; Wain, Karen E; Eisenhauer, Nancy; Wagner, Monisa; Savatt, Juliann M; Müller-Schlüter, Karen; Bassan, Haim; Borovikov, Artem; Nassogne, Marie Cecile |
| Description: |
We report detailed functional analyses and genotype-phenotype correlations in 392 individuals carrying disease-causing variants in SCN8A, encoding the voltage-gated Na+ channel Na(v)1.6, 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 Na(v)1.6 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 ... |