Abstracts

Epilepsies due to a single gene mutation could provide a useful experimental condition in which to study the therapeutic efficacy of replacing a lost and/or non-functional gene. Mice lacking the Kv1.1[alpha] subunit (delayed rectifier potassium channel) develop recurrent behavioral seizures early in life associated with pathologies similar to temporal lobe epilepsy in humans. We examined the effects of injecting a viral vector carrying the deleted Kv1.1 gene into hippocampal neurons of Kv1.1 knockout (-/-) mice. We hypothesized that Kv1.1 channel protein would be expressed in transfected hippocampal neurons, and that spontaneous seizures (thresholds and/or frequencies) would be appropriately [ldquo]normalized.[rdquo] Wild-type and Kv1.1 -/- mice were prepared for a long-term video/EEG recording using a video/EEG telemetry system (Data Sciences International and Stellate). Animals were monitored two days prior to vector injections and then for 4-6 days after injections. The HSV1 amplicon vector (provided by Dr. Robert Sapolsky, Stanford University) contained the rat Kv1.1 gene and the E.coli lacZ gene (to express a reporter molecule, beta-galactosidase ([beta]-gal)). Control vectors contained only the [beta]-gal gene. Mice were stereotaxically injected with the viral vectors into the hippocampus. Injections (two sites per hemisphere) were placed bilaterally within the CA3 region of the middle hippocampus; injection volume was 1.2[micro]l/site. At the predetermined survival time, brains were fixed (4% paraformaldehyde) and processed for histochemistry of [beta]-galactosidase (x-gal staining). Initial results of long-term video/EEG monitoring failed to demonstrate changes in seizure frequency, type or severity following the Kv1.1 gene transfer. General histological findings of brains from the Kv1.1-/- mice were consistent with previous results (hippocampal neuronal cell loss, reactive gliosis and mossy fiber reorganization). Hippocampi of animals injected with [beta]-gal and/or [beta]-gal + Kv1.1 vectors showed vector-mediated transfection (based on x-gal staining) limited to a few hundred hippocampal neurons. Peak expression was observed [sim]4 days post injection. The majority of x-gal stained cells were neuronal, primarily granule cells. Viral vector-mediated gene transfection ([beta]-gal and Kv1.1 genes) in the hippocampus of Kv1.1 -/- mice results in infection of a limited population of granule cells and CA3 pyramidal cells. Thus far, this level of transfection has not been found to affect the seizure pattern in Kv1.1 knockout mice. (Supported by a grant from Citizens United for Research in Epilepsy (CURE))