Genotype–phenotype associations in 1018 individuals with <i>SCN1A</i>‐related epilepsies
Journal
Epilepsia
ISSN
0013-9580
1528-1167
Date Issued
2024
Author(s)
Declan Gallagher
Eduardo Pérez‐Palma
Tobias Bruenger
Ismael Ghanty
Eva Brilstra
Berten Ceulemans
Nicole Chemaly
Iris de Lange
Christel Depienne
Renzo Guerrini
Davide Mei
Rikke S. Møller
Rima Nabbout
Brigid M. Regan
Amy L. Schneider
Ingrid E. Scheffer
An‐Sofie Schoonjans
Joseph D. Symonds
Sarah Weckhuysen
Sameer M. Zuberi
Dennis Lal
Andreas Brunklaus
Type
journal-article
Abstract
<jats:title>Abstract</jats:title><jats:sec><jats:title>Objective</jats:title><jats:p><jats:italic>SCN1A</jats:italic> variants are associated with epilepsy syndromes ranging from mild genetic epilepsy with febrile seizures plus (GEFS+) to severe Dravet syndrome (DS). Many variants are de novo, making early phenotype prediction difficult, and genotype–phenotype associations remain poorly understood.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We assessed data from a retrospective cohort of 1018 individuals with <jats:italic>SCN1A‐</jats:italic>related epilepsies. We explored relationships between variant characteristics (position, in silico prediction scores: Combined Annotation Dependent Depletion (CADD), Rare Exome Variant Ensemble Learner (REVEL), <jats:italic>SCN1A</jats:italic> genetic score), seizure characteristics, and epilepsy phenotype.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>DS had earlier seizure onset than other GEFS+ phenotypes (5.3 vs. 12.0 months, <jats:italic>p</jats:italic> < .001). In silico variant scores were higher in DS versus GEFS+ (<jats:italic>p</jats:italic> < .001). Patients with missense variants in functionally important regions (conserved N‐terminus, S4–S6) exhibited earlier seizure onset (6.0 vs. 7.0 months, <jats:italic>p</jats:italic> = .003) and were more likely to have DS (280/340); those with missense variants in nonconserved regions had later onset (10.0 vs. 7.0 months, <jats:italic>p</jats:italic> = .036) and were more likely to have GEFS+ (15/29, χ<jats:sup>2</jats:sup> = 19.16, <jats:italic>p</jats:italic> < .001). A minority of protein‐truncating variants were associated with GEFS+ (10/393) and more likely to be located in the proximal first and last exon coding regions than elsewhere in the gene (9.7% vs. 1.0%, <jats:italic>p</jats:italic> < .001). Carriers of the same missense variant exhibited less variability in age at seizure onset compared with carriers of different missense variants for both DS (1.9 vs. 2.9 months, <jats:italic>p</jats:italic> = .001) and GEFS+ (8.0 vs. 11.0 months, <jats:italic>p</jats:italic> = .043). Status epilepticus as presenting seizure type is a highly specific (95.2%) but nonsensitive (32.7%) feature of DS.</jats:p></jats:sec><jats:sec><jats:title>Significance</jats:title><jats:p>Understanding genotype–phenotype associations in <jats:italic>SCN1A</jats:italic>‐related epilepsies is critical for early diagnosis and management. We demonstrate an earlier disease onset in patients with missense variants in important functional regions, the occurrence of GEFS+ truncating variants, and the value of in silico prediction scores. Status epilepticus as initial seizure type is a highly specific, but not sensitive, early feature of DS.</jats:p></jats:sec>
Cite this document
Gallagher, D., Pérez‐Palma, E., Bruenger, T., Ghanty, I., Brilstra, E., Ceulemans, B., Chemaly, N., De Lange, I., Depienne, C., Guerrini, R., Mei, D., Møller, R. S., Nabbout, R., Regan, B. M., Schneider, A. L., Scheffer, I. E., Schoonjans, A., Symonds, J. D., Weckhuysen, S., … Brunklaus, A. (2024). Genotype–phenotype associations in 1018 individuals with SCN1A ‐related epilepsies. Epilepsia, 65(4), 1046-1059. https://doi.org/10.1111/epi.17882