SCN1AIVS5-91G>A polymorphism is associated with susceptibility to epilepsy but not with drug responsiveness

Abstract

Sodium channel alpha subunit type 1 (SCN1A) is voltage gated ion channel which plays critical role in membrane excitability. A common SCN1A IVS5-91G>A (rs3812718) allele has been attributed to be a possible modifying factor for epilepsy susceptibility and therapeutic response. In the present study, we enrolled 485 epilepsy patients and 298 age-sex matched controls free of neurological deficits. Therapeutic response of carbamazepine/oxcarbamazepine (CBZ/OXC) and other antiepileptic drugs were observed in terms of drug responsiveness and drug resistance. Genotyping of SCN1A IVS5-91G>A is done by Taqman custom designed assay; in a real time7500HT System. We observe highly significant association [(P-values for GA (P = 6.58 × 10-5, OR = 2.13, 95% CI = 1.47-3.09) and AA (P = 4.11 × 10-9, OR = 3.59, 95% CI = 2.35-5.50)] at variant genotypes as well as A allele (P = 6.92 × 10-11), OR = 1.99, 95%, CI = 1.62-2.45) in epilepsy patients versus control subjects. The relative risk for epilepsy susceptibility due to variant containing genotypes (GA + AA) was also significant (P = 1.64 × 10 -5; OR = 2.56; 95% CI = 1.80-3.65) when compared with homozygous wild-type GG. The risk in recessive model (P = 1.34 × 10-5; OR = 2.12; 95% CI = 1.51-2.97) was also apparent when compared with GA + GG. In case-only analysis, we evaluated the effect of SCN1A IVS5-91G>A polymorphism with drug resistance of anti-epileptic drug therapies. However, we did not observe significant associations either with patients showing drug resistance to CBZ/OXC monotherapy or polytherapy. In conclusion, we report that SCN1AIVS5-91G>A polymorphism is associated with epilepsy susceptibility but not with drug responsiveness in epilepsy patients from North India. © 2013 Elsevier Masson SAS. All rights reserved.