No evidence for association between the KCNQ3 gene and susceptibility to idiopathic generalized epilepsy

Idiopathic generalized epilepsy (IGE) comprises a heterogeneous group of disorders, in which a high genetic predisposition and a complex mode of inheritance have been suggested. Recent identification of ion channel gene mutations in Mendelian epileptic disorders suggests genetically driven neuronal hyperexcitability as one important factor in epileptogenesis. Mutations in two neuronal voltage-gated potassium channel genes (KCNQ2 and KCNQ3) have already been shown to cause epilepsy (BFNC), and we now tested the hypothesis that genetic variation in the KCNQ3 gene confers liability to common IGE subtypes. Length variation of two intragenic polymorphic markers (D8S558 and D8S1835) were therefore assessed in 71 nuclear families ascertained for an affected child. However, the transmission-disequilibrium-test did not show significant differences between the transmitted and non-transmitted parental alleles. Thus, our findings do not provide evidence that genetic variation in the KCNQ3 gene exerts a relevant effect in the etiology of common IGE subtypes.