SCN1A mutational analysis in Korean patients with Dravet syndrome

OBJECTIVE The aim of this study was to characterize the SCN1A mutation spectrum in Korean patients with Dravet syndrome. METHODS Twenty-nine patients diagnosed with Dravet syndrome at the Seoul National University Children's Hospital were included in the study. Direct sequencing and multiplex ligation-dependent probe amplification (MLPA) were used to identify SCN1A mutations. Mutations were classified as either truncation (nonsense and frameshift) or missense mutations. RESULTS Nineteen pathogenic mutations (19/29; 66%) and three unclassified variants were identified. One large deletion mutation spanning exons 1-20 was detected using MLPA. Fifteen of these 19 SCN1A mutations were novel. Eleven mutations were classified as truncations (seven frameshift and four nonsense mutations) and seven were classified as missense mutations. Truncating mutations spanned the whole span of subunits of the SCN1A protein, whereas all missense mutations were localized at either the voltage sensor (S4) or the ion pore (S5-S6) regions. Analysis according to clinical phenotype revealed that SCN1A mutations were more frequent in the classic group than in the borderline group (78% vs. 45%). CONCLUSIONS SCN1A mutational analysis of Korean Dravet syndrome patients resulted in the identification of 15 novel mutations, which could expand the spectrum of SCN1A mutations and confirms the current understanding of genotype-phenotype correlations.