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Colette Kananura, MS; Karsten Haug, MD; Thomas Sander, MD; Uwe Runge, MD; Wenli Gu, MS; Kerstin Hallmann, MS; Johannes Rebstock, MD; Armin Heils, MD; Ortrud K. Steinlein, MD

Arch Neurol. 2002;59:1137-1141.

Context  Missense mutations in the GABRG2 gene, which encodes the 2 subunit of central nervous -aminobutyric acid (GABA)_A receptors, have recently been described in 2 families with idiopathic epilepsy. In one of these families, the affected individuals predominantly exhibited childhood absence epilepsy and febrile convulsions.

Objective  To assess the role of GABRG2 in the genetic predisposition to idiopathic absence epilepsies.

Design  The GABRG2 gene was screened by single-strand conformation analysis for mutations. Furthermore, a population-based association study assessing a common exon 5 polymorphism (C588T) was carried out.

Patients  The sample was composed of 135 patients with idiopathic absence epilepsy and 154 unrelated and ethnically matched controls.

Results  A point mutation (IVS6 + 2TG) leading to a splice–donor site mutation in intron 6 was found. The mutation, which is predicted to lead to a nonfunctional protein, cosegregates with the disease status in a family with childhood absence epilepsy and febrile convulsions. The association study did not find any significant differences in the allele and genotype frequencies of the common exon 5 polymorphism (C588T) between patients with idiopathic absence epilepsy and controls (P>.35).

Conclusions  Our study identified a splice–donor-site mutation that was probably causing a nonfunctional GABRG2 subunit. This mutation occurred in heterozygosity in the affected members of a single nuclear family, exhibiting a phenotypic spectrum of childhood absence epilepsy and febrile convulsions. The GABRG2 gene seems to confer a rare rather than a frequent major susceptibility effect to common idiopathic absence epilepsy syndromes.

From the Institute of Human Genetics (Mss Kananura, Gu, and Hallmann, and Drs Haug, Heils, and Steinlein), and Department of Epileptology (Drs Rebstock and Heils), University Hospital Bonn, Rheinische Friedrich Wilhelms-University Bonn, Bonn; Department of Neurology, University Hospital Charité, Humboldt University of Berlin, Berlin (Dr Sander); and Department of Neurology, University Hospital Greifswald, Ernst Moritz Arndt-University, Greifswald (Dr Runge), Germany.

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