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De-novo mutations and genetic variation in the SCN1A gene in Malaysian patients with generalized epilepsy with febrile seizures plus (GEFS+)

Tan EH, Razak SA, Abdullah JM, Mohamed Yusoff AA

Epilepsy Res, 2012 Dec;102(3):210-5.
PMID: 22944210 DOI: 10.1016/j.eplepsyres.2012.08.004

Generalized epilepsy with febrile seizures plus (GEFS+) comprises a group of clinically and genetically heterogeneous epilepsy syndrome. Here, we provide the first report of clinical presentation and mutational analysis of SCN1A gene in 36 Malaysian GEFS+ patients. Mutational analysis of SCN1A gene revealed twenty seven sequence variants (missense mutation and silent polymorphism also intronic polymorphism), as well as 2 novel de-novo mutations were found in our patients at coding regions, c.5197A>G (N1733D) and c.4748A>G (H1583R). Our findings provide potential genetic insights into the pathogenesis of GEFS+ in Malaysian populations concerning the SCN1A gene mutations.

Matched MeSH terms: Epilepsy, Generalized/genetics*
Whole exome sequencing identifies a novel SCN1A mutation in genetic (idiopathic) generalized epilepsy and juvenile myoclonic epilepsy subtypes

Chan CK, Low JS, Lim KS, Low SK, Tan CT, Ng CC

Neurol Sci, 2020 Mar;41(3):591-598.
PMID: 31720899 DOI: 10.1007/s10072-019-04122-9

INTRODUCTION: Genetic (idiopathic) generalized epilepsy (GGE) is a common form of epilepsy characterized by unknown aetiology and a presence of genetic component in its predisposition.
METHODS: To understand the genetic factor in a family with GGE, we performed whole exome sequencing (WES) on a trio of a juvenile myoclonic epilepsy/febrile seizure (JME/FS) proband with JME/FS mother and healthy father. Sanger sequencing was carried out for validation of WES results and variant detection in other family members.
RESULTS: Predictably damaging variant found in affected proband and mother but absent in healthy father in SCN1A gene was found to be associated with generalized epilepsy and febrile seizure. The novel non-synonymous substitution (c.5753C>T, p.S1918F) in SCN1A was found in all family members with GGE, of which 4/8 were JME subtypes, and/or febrile seizure, while 3 healthy family member controls did not have the mutation. This mutation was also absent in 41 GGE patients and 414 healthy Malaysian Chinese controls.
CONCLUSION: The mutation is likely to affect interaction between the sodium channel and calmodulin and subsequently interrupt calmodulin-dependent modulation of the channel.

Matched MeSH terms: Epilepsy, Generalized/genetics*
Novel biallelic SZT2 mutations in 3 cases of early-onset epileptic encephalopathy

Tsuchida N, Nakashima M, Miyauchi A, Yoshitomi S, Kimizu T, Ganesan V, et al.

Clin Genet, 2018 02;93(2):266-274.
PMID: 28556953 DOI: 10.1111/cge.13061

The seizure threshold 2 (SZT2) gene encodes a large, highly conserved protein that is associated with epileptogenesis. In mice, Szt2 is abundantly expressed in the central nervous system. Recently, biallelic SZT2 mutations were found in 7 patients (from 5 families) presenting with epileptic encephalopathy with dysmorphic features and/or non-syndromic intellectual disabilities. In this study, we identified by whole-exome sequencing compound heterozygous SZT2 mutations in 3 patients with early-onset epileptic encephalopathies. Six novel SZT2 mutations were found, including 3 truncating, 1 splice site and 2 missense mutations. The splice-site mutation resulted in skipping of exon 20 and was associated with a premature stop codon. All individuals presented with seizures, severe developmental delay and intellectual disabilities with high variability. Brain MRIs revealed a characteristic thick and short corpus callosum or a persistent cavum septum pellucidum in each of the 2 cases. Interestingly, in the third case, born to consanguineous parents, had unexpected compound heterozygous missense mutations. She showed microcephaly despite the other case and previous ones presenting with macrocephaly, suggesting that SZT2 mutations might affect head size.

Matched MeSH terms: Epilepsy, Generalized/genetics*
SCN1A IVS5N+5 polymorphism and response to sodium valproate: a multicenter study

Haerian BS, Baum L, Tan HJ, Kwan P, Raymond AA, Saruwatari J, et al.

Pharmacogenomics, 2012 Oct;13(13):1477-85.
PMID: 23057548 DOI: 10.2217/pgs.12.127

Approximately 30% of epilepsy patients do not response to antiepileptic drugs (AEDs). The functional SCN1A IVS5N+5 polymorphism may play a role in response to some AEDs. The purpose of this study was to examine this hypothesis in a cohort study of Malaysian and Hong Kong Chinese epilepsy patients on sodium valproate (VPA) monotherapy and in a meta-analysis.

Matched MeSH terms: Epilepsy, Generalized/genetics