To investigate whether alterations in RNA editing (an enzymatic base-specific change to the RNA sequence during primary transcript formation from
DNA) of
neurotransmitter receptor genes and of transmembrane
ion channel genes play a role in human
temporal lobe epilepsy (TLE), this exploratory study analyzed 14 known cerebral editing sites in
RNA extracted from the brain tissue of 41 patients who underwent surgery for mesial TLE, 23 with
hippocampal sclerosis (MTLE+HS). Because intraoperatively sampled
RNA cannot be obtained from healthy controls and the best feasible control is identically sampled
RNA from patients with a clinically shorter history of
epilepsy, the primary aim of the study was to assess the correlation between
epilepsy duration and RNA editing in the homogenous group of MTLE+HS. At the functionally relevant I/V site of the
voltage-gated potassium channel Kv1.1, an inverse correlation of RNA editing was found with
epilepsy duration (r=-0.52, p=0.01) but not with patient age at surgery, suggesting a specific association with either the epileptic process itself or its
antiepileptic medication history. No significant correlations were found between RNA editing and clinical parameters at other sites within
glutamate receptor or
serotonin 2C receptor gene transcripts. An "all-or-none" (≥95% or ≤5%) editing pattern at most or all sites was discovered in 2 patients. As a secondary part of the study, RNA editing was also analyzed as in the previous literature where up to now, few single editing sites were compared with differently obtained
RNA from inhomogenous patient groups and autopsies, and by measuring editing changes in our mouse model. The present screening study is first to identify an editing site correlating with a clinical parameter, and to also provide an estimate of the possible effect size at other sites, which is a prerequisite for power analysis needed in planning future studies.