ABSTRACT
Voltage-dependent sodium channels consist of a pore-forming alpha-subunit and regulatory beta-subunits. Alterations in these channels have been implicated in temporal lobe epilepsy (TLE) and several genetic epilepsy syndromes. Recently we identified Na(v)beta3 as a TLE-regulated gene. Here we performed a detailed analysis of the hippocampal expression of Na(v)beta3 in TLE patients with hippocampal sclerosis (HS) and without HS (non-HS) and compared expression with autopsy controls (ACs). Immunoblot analysis showed that Na(v)beta3 levels were dramatically reduced in the hippocampus, but not in the cortex of non-HS patients when compared to HS patients. This was confirmed by immunohistochemistry showing reduced Na(v)beta3 expression in all principal neurons of the hippocampus proper. Sequence analysis revealed no Na(v)beta3 mutations. The functional consequences of the reduced Na(v)beta3 expression in non-HS patients are unknown. Altered Na(v)beta3 expression might influence microcircuitry in the hippocampus, affecting excitability and contributing to epileptogenesis in non-HS patients. Further experiments are required to elucidate these functional possibilities.
Subject(s)
Epilepsy, Temporal Lobe/pathology , Hippocampus/metabolism , Hippocampus/pathology , Sodium Channels/metabolism , Adolescent , Adult , Aged , Analysis of Variance , Child , DNA Mutational Analysis/methods , Female , Gene Expression , Genotype , Humans , Infant , Male , Middle Aged , Mutation/genetics , Sclerosis/genetics , Sclerosis/pathology , Sodium Channels/genetics , Voltage-Gated Sodium Channel beta-3 Subunit , Young AdultABSTRACT
PURPOSE: The interaction of genetic predisposition and the environment in the development of epilepsy is often discussed, but, aside from some animal reflex epilepsies, little evidence supports such interaction in the development of reflex epilepsy in humans. METHODS: We describe the history of a 16-year-old boy in whom photosensitive epilepsy developed after a period of weekly exposures to high-intensity light flashes. RESULTS: Both he and his clinically unaffected monozygotic twin were found to be photosensitive. CONCLUSIONS: This case report suggests that some genetic forms of human reflex epilepsy may be elicited by repeated environmental exposure to the appropriate stimulus, similar to some of the stimulus-induced epilepsies seen in animals.
