Association between variation in the human KCNJ10 potassium ion channel gene and seizure susceptibility

Purpose: Our research program uses genetic linkage and association analysis to identify human seizure sensitivity and resistance alleles. Quantitative trait loci mapping in mice led to identification of genetic variation in the potassium ion channel gene Kcnj10, implicating it as a putative seizure susceptibility gene. The purpose of this work was to translate these animal model data to a human genetic association study. Methods: We used single stranded conformation polymorphism (SSCP) electrophoresis, DNA sequencing and database searching (NCBI) to identify variation in the human KCNJ10 gene. Restriction fragment length polymorphism (RFLP) analysis, SSCP and Pyrosequencing™ were used to genotype a single nucleotide polymorphism (SNP, dbSNP rs#1130183) in KCNJ10 in epilepsy patients (n=407) and unrelated controls (n=284). The epilepsy group was comprised of patients with refractory mesial temporal lobe epilepsy (n=153), childhood absence (n=84), juvenile myoclonic (n=111) and idiopathic generalized epilepsy not otherwise specified (IGE-NOS, n=59) and all were of European ancestry. Results: SNP rs#1130183 (C>T) alters amino acid 271 (of 379) from an arginine to a cysteine (R271C). The C allele (Arg) is common with conversion to the T allele (Cys) occurring twice as often in controls compared to epilepsy patients. Contingency analysis documented a statistically significant association between seizure resistance and allele frequency, Mantel-Haenszel chi square=5.65, d.f.=1, P=0.017, odds ratio 0.52, 95% CI 0.33-0.82. Conclusion: The T allele of SNP rs#1130183 is associated with seizure resistance when common forms of focal and generalized epilepsy are analyzed as a group. These data suggest that this missense variation in KCNJ10 (or a nearby variation) is related to general seizure susceptibility in humans