In order to assess the chloride channel gene
CLCN2 as a candidate susceptibility gene for
childhood absence epilepsy, parametric and non-parametric linkage analysis was performed in 65 nuclear pedigrees. This provided suggestive evidence for linkage with heterogeneity: NPL score = 2.3,
p < 0.009; HLOD = 1.5,
α = 0.44. Mutational analysis of the entire genomic sequence of
CLCN2 was performed in 24 unrelated patients from pedigrees consistent with linkage, identifying 45 sequence variants including the known non-synonymous polymorphism rs2228292 (G2154C, Glu718Asp) and a novel variant IVS4 + 12G > A. Intra-familial association analysis using the pedigrees and a further 308 parent–child trios showed suggestive evidence for transmission disequilibrium of the G2154C minor allele: AVE-PDT
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p < 0.03. Case–control analysis provided evidence for a protective effect of the IVS4 + 12G > A minor allele:
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p < 0.008. The 65 nuclear pedigrees were screened for three previously identified mutations shown to segregate with a variety of idiopathic generalised
epilepsy phenotypes (597insG, IVS2-14del11 and G2144A) but none were found. We conclude that
CLCN2 may be a susceptibility locus in a subset of cases of
childhood absence epilepsy.