title: Association study of TRPC4 as a candidate gene for generalized epilepsy with photosensitivity.
abstract: Photoparoxysmal response (PPR) is characterized by abnormal visual sensitivity of the brain to photic stimulation. Frequently associated with idiopathic generalized epilepsies (IGEs), it might be an endophenotype for cortical excitability. Transient receptor potential cation (TRPC) channels are involved in the generation of epileptiform discharges, and TRPC4 constitutes the main TRPC channel in the central nervous system. The present study investigated an association of PPR with sequence variations of the TRPC4 gene. Thirty-five single nucleotide polymorphisms (SNP) within TRPC4 were genotyped in 273 PPR probands and 599 population controls. Association analyses were performed for the broad PPR endophenotype (PPR types I-IV; n = 273), a narrow model of affectedness (PPR types III and IV; n = 214) and PPR associated with IGE (PPR/IGE; n = 106) for each SNP and for corresponding haplotypes. Association was found between the intron 5 SNP rs10507456 and PPR/IGE both for single markers (P = 0.005) and haplotype level (P = 0.01). Three additional SNPs (rs1535775, rs10161932 and rs7338118) within the same haplotype block were associated with PPR/IGE at P < 0.05 (uncorrected) as well as two more markers (rs10507457, rs7329459) located in intron 3. Again, the corresponding haplotype also showed association with PPR/IGE. Results were not significant following correction for multiple comparisons by permutation analysis for single markers and Bonferroni-Holm for haplotypes. No association was found between variants in TRPC4 and other phenotypes. Our results showed a trend toward association of TRPC4 variants and PPR/IGE. Further studies including larger samples of photosensitive probands are required to clarify the relevance of TRPC4 for PPR and IGE.
authors.affiliation: Department of Neuropediatrics, University Hospital Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str.3, Building 9, Kiel, Germany. s.vonspiczak@pedneuro.uni-kiel.de
authors.forename: Sarah
authors.initials: S
authors.lastname: von Spiczak
authors.forename: Hiltrud
authors.initials: H
authors.lastname: Muhle
authors.forename: Ingo
authors.initials: I
authors.lastname: Helbig
authors.forename: Carolien G F
authors.initials: CG
authors.lastname: de Kovel
authors.forename: Jochen
authors.initials: J
authors.lastname: Hampe
authors.forename: Verena
authors.initials: V
authors.lastname: Gaus
authors.forename: Bobby P C
authors.initials: BP
authors.lastname: Koeleman
authors.forename: Dick
authors.initials: D
authors.lastname: Lindhout
authors.forename: Stefan
authors.initials: S
authors.lastname: Schreiber
authors.forename: Thomas
authors.initials: T
authors.lastname: Sander
authors.forename: Ulrich
authors.initials: U
authors.lastname: Stephani
mesh_terms: D001483:Base Sequence; D004829:Epilepsy, Generalized / Q000235:genetics*; D020195:Epilepsy, Reflex / Q000235:genetics*; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006239:Haplotypes; D010775:Photic Stimulation; D020641:Polymorphism, Single Nucleotide; D050052:TRPC Cation Channels / Q000235:genetics*
chemical_list: D050052:TRPC Cation Channels; C489571:TRPC4 ion channel