Abstracts

Gene-expression changes and genetic mechanisms underlying kindling epileptogenesis are not well understood. The use of DNA arrays and gene-expression profiling provides one strategy to enhance our understanding of global transcription patterns that accompany kindling. In this study we have analyzed RNA message abundance for 12000 gene transcripts in the mouse hippocampus using kindling as a model for epileptogenesis. Eight-week-old, C57BL/6 mice were implanted with Tripolar electrode units (Plastic One Inc., Roanoke, VA) in the right dorsal hippocampus; a ground electrode was attached to the occipital bone. Ten days post surgery, kindling was achieved by stimulating 6 times daily for 4 days with a subconvulsive electrical stimulation (a 10-s train containing 50-Hz biphasic pulses of 300-[mu]A amplitude) at 30-min intervals. Seizures were graded according to Racine[rsquo]s Scale. Total RNA was extracted and purified using phenol-guanidine isothiocyanate reagents. RNA samples were screened for spectral purity and integrity using RNA LabChips (Caliper Technologies, Mountain View, CA) and a 2100 Bioanalyzer (Agilent Technologies, Palo Alto, CA). DNA-array analysis was performed using murine U74v2 GeneChip probe arrays (Affymetrix, Santa Clara, CA). Gene-expression data were mined and analyzed for significance using GeneSpring (Silicon Genetics, Redwood City, CA) and Microarray Data Mining Tool (Affymetrix) software. Surprisingly, only a relatively small number of genes (N=8) reached a high significance of 2-fold or greater in up- or down-regulation with ANOVA ([italic]p[/italic][lt]0.05) under the experimental conditions used. Using the following format: gene name (abbreviated form)* [fold-change] * (ANOVA); the most significantly up- and down-regulated genes included: glial fibrillary acidic protein (GFAP) * [+2.1] * (0.001); neuronal pentraxin 2 (NP2)* [+2.88] * (0.022); mouse-specific tolloid-like protein (MSTLP)* [+2.80] * (0.03); mouse-specific homer 1A (MSH1A)* [+2.72] * (0.167); transcription factor for growth inhibitory factor (TF-GIF) * [+2.1] * (0.006); neurotrophin 3 (NT3)* [-2.84] * (0.167); aquaporin 1 (AQ1)* [-2.7] * (0.167); vascular endothelial factor (VEGF) * [-2.11] * 0.167. GFAP up-regulation suggests induction of gliosis or glial-mediated events; up-regulation of NP2 and MSTLP suggests triggering of inflammatory signaling, and up-regulation of MSH1A and TG-GIF suggests modulation of long-term potentiation and inhibition of neural growth and/or differentiation. Down-regulation of NT3, AQ1, and VEGF suggests repression of neurotrophic support, water transport at the blood-brain barrier, and angiogenesis-related signaling, respectively. These profiling data provide new insights into the cellular and molecular basis of epileptogenesis and may provide novel genetic targets for the development of anti-epileptogenic drugs. (Supported by NIH AG18031, NS22002 and COBRE NIH P29RR16816-02)