Febrile Seizures and GABAA receptor trafficking

Febrile Seizures and temperature-dependent GABAA receptor trafficking deficiencies in the R43Q mutant

Febrile seizures affect as many as one in fifteen children. Epilepsy has long been thought to be related to alterations in GABAergic transmission in the thalamocortical circuitry of the brain. Our lab has generated a knock-in mutant mouse with an arginine replaced by a glutamine residue (R43Q) in the gamma2 subunit of the GABAA receptor. This mouse model exhibits a phenotype similar to that seen in a large Australian family demonstrating a high incidence of febrile seizures carrying the same gene mutation. The gamma2 GABAA receptor subunit is critical for normal receptor trafficking. Furthermore, febrile seizures have been correlated with a temperature dependent reduction of cell-surface expression of GABAA receptors containing impaired gamma2 subunit function.  This project aims to assess the temperature dependence of R43Q GABAA receptor trafficking in cortical slices by examining GABAA receptor-mediated synaptic events using the patch clamp electrophysiological technique. It is hypothesised that at elevated temperatures, GABAA receptor-mediated signal detection will be reduced, resulting in increased excitability in the thalamocortical circuitry. In the presence of glutamatergic receptor antagonists, synaptic GABAA currents will be recorded from cortical pyramidal cells in preheated or room temperature acute slices from mutant and wild type animals. In addition, the expression of the gamma2 subunit in preheated versus control cortical slices will be assessed by quantitative image analysis of immunocytochemical distribution patterns of cell-surface expressed receptor. The identification and analysis of a temperature-sensitive reduction in receptor expression in acute cortical slices may lead to important advances in drug targets and possible therapies in the field of febrile epilepsy.