Abstracts

Despite extensive research into the molecular basis of epilepsy, genetic pathways which initiate and propagate epileptogenesis are not well understood. Broad spectrum gene expression profiling provides one strategy to enhance our understanding of the global gene transcription patterns which may contribute to functional gene expression alterations that underlie epileptogenesis. In this preliminary study we have analyzed RNA message abundance for 12633 DNA transcripts in the human adult superior temporal lobe of patients with temporal lobe epilepsy (TLE).
Total RNA was extracted and purified from control and age-matched TLE cases using phenol-guanidine isothiocyanate reagents. Potential RNA samples were screened for spectal 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 HG U95A Genechips (Affymetrix, Santa Clara, CA) and elevated gene abundances were confirmed independently by using RT-PCR. Gene expression data were analyzed using GeneSpring (Silicon Genetics, Redwood City, CA) and Microarray Data Mining Tool (Affymetrix) software.
We have observed 36 genes increased in expression in TLE, at least 3-fold or greater over controls. Several of these enhanced gene expression levels have been confirmed independently by RT-PCR. About two thirds of the products of the up-regulated genes were found to encode neural-specific elements involved in calcium signaling and neurotransmitter release, nuclear, cytoskeletal and extracellular matrix attachment, and related vesicle trafficking, plasticity and cytoarchitectural functions. About one third of all up-regulated genes, and amongst the most significant changes observed, encoded early response genes (ERG), transcription factors (TF) and associated molecules involved in genetic signal transduction. Up-regulated ERG and TF gene expression of many genes, including the zinc finger ERGs encoding NGFI-A, NGFI-B, NGFI-C, Nurr1 and their receptors were highly significant.
The most significant changes, observed in RNA messages that regulate gene signaling, indicates that in TLE there occurs (a) a prolonged messenger RNA turnover for specific ERGs, (b) a robust synaptic activity dependent mediation of ERG and/or TF genetic output, (c) an ERG-mediated stress response by which neural cells are eliciting neuroprotection, (d) an initiation of apoptotic signaling pathways that lead to programmed cell dysfunction or (e) any combination of (a)-(d). These data expand considerably our understanding of the molecular genetic basis of epileptogenesis and provide novel targets for the rational development of anti-epileptogenic pharmaceuticals.
[Supported by: NIH AG18031, NS22002 and COBRE NIH P29RR16816-02]