Abstracts

The molecular mechanisms involved in the development and maintenance of human epileptic cortex in children are not well understood. We are investigating what makes certain areas of neocortex epileptic by measuring gene expression changes in human epileptic tissue identified by subdural grid electrical recordings compared to nearby tissue from the same patient without spontaneous interictal epileptiform activity. Using cDNA microarray analysis, followed by confirmatory in situ hybridization studies, we have identified differentially expressed genes in common to many patients with neocortical epilepsy that may either be the cause of or result from the heightened electrical activity found in focal regions of human epileptic neocortex.
Epileptiform cortex was identified using subdural grid recording electrodes in 8 patients with intractable neocortical epilepsy undergoing a 2 stage surgical resection for intractable epilepsy. Since these were large resections, relatively non-spiking areas of neocortex were also present. Differentially expressed genes between areas of seizure onset and non-spiking cortex were identified for each patient using quadruplicate cDNA microarrays containing over 3300 genes derived from a human embryonic brain cDNA library. An ANOVA model using a dye-swap design was used to measure gene expression changes and assign statistical significance. Genes that were differentially expressed in multiple patients were studied further by in situ hybridization to confirm the change and localize the cell type expressing the gene.
We have identified a group of differentially expressed genes at regions of seizure onset relative to nearby non-spiking cortex in 8 patients with neocortical epilepsy. These include immediate early genes, transcription factors, second messenger signaling factors, and ion channels. In situ hybridization studies are currently underway to confirm these changes and determine the cellular localization of these genes. We have further identified [ldquo]activity-dependent[rdquo] genes whose expression correlates to interictal gradients of epileptiform activity.
We have used a functional genomic approach to demonstrate that focal, epileptic regions of neocortex have distinct patterns of gene expression that may underlie what makes epileptic tissue epileptic. Our results show specific genes expression patterns in common to many patients that include immediate early genes, transcription factors, signaling factors and ion channels that may be involved in molecular pathways responsible for the production and maintenance of epileptic foci and that may lead to novel diagnostic and therapeutic options in epilepsy.
[Supported by: NIH grant RO1NS45207, Ralph Wilson Foundation
S.N.R. supported by a pre-doctoral training fellowship from Epilepsy Foundation of America]