Abstracts

Rationale: Epilepsy is a neurologically complex and clinically diverse disorder, with seizure severity often varying widely among individuals carrying the disease-associated genetic variant. This phenotypic variability suggests that additional factors in the genetic background influence seizure expression, yet these genetic modifiers remain poorly defined. Drosophila models of epilepsy are a tractable tool for dissecting the genetic architecture of the disease.To explore potential roles of genetic background on variable seizure expression, we systematically manipulated the genetic background of Drosophila carrying hyperexcitable mutations in the sole voltage-gated sodium (Na_v) channel gene para. Fly para is orthologous to the mammalian SCN1A – 11A channel genes, and both loss- and gain-of-function variants cause spontaneous and/or heat-induced seizures.

Methods: To identify genetic modifiers of the para seizure expression, we crossed para females with males from the Drosophila Genetic Reference Panel (DGRP, a collection of 200+ fully sequenced inbred lines derived from a wild population). Thus far we have crossed para mutants with ~ 20 DGRP lines. Progeny were screened for motor impairment and spontaneous seizures at baseline (21 – 23 °C) and high temperature (36 – 39 °C), using the automated video tracking system IowaFLI Tracker. This software analysis allowed for high throughput and quantitative analysis of movement parameters, including time spent moving, average velocity, and path linearity.

Results: Thus far one line, DGRP 712, significantly suppressed the seizure-like phenotypes in para mutants. Compared to control backgrounds (n = 44), para mutants on the 712 genetic background (n = 16) demonstrated a marked improvement in locomotor activity at high temperatures. These flies maintained longer periods of movement (p < 0.001, Kruskal Wallis ANOVA, rank sum post hoc) and displayed greater path linearity (p < 0.001), indicating a substantial rescue of the seizure phenotypes.