Zebrafish model for high throughput drug screening in Dravet Syndrome

Abstract

Dravet syndrome (DS) is a rare and severe form of epilepsy that typically manifests in children, which occur due to loss-of-function mutations in SCN1A gene. Despite advances in understanding the genetic basis and pathophysiology of DS, current treatments, including standard antiepileptic drugs (AEDs), provide limited efficacy in reducing seizure frequency and severity. Zebrafish with a mutation in scn1lab mimic phenotype characteristic of DS like seizures. In order to optimize the zebrafish model for potential therapeutic candidates for DS treatment, three different scn1lab zebrafish lines and wildtype zebrafish were utilized. Homozygous scn1lab mutants exhibit seizures. Here, an in vivo assay was developed using scn1lab mutants and siblings between 5 and 7 days post-fertilization (dpf), where sensitizers such as light pulses, glucose metabolism modifiers (3-MPA), and seizure promoting compound (PTZ) are employed to enhance the model’s predictive validity. To evaluate seizure activity, larvae were monitored between 40 minutes and 3 hours with an automated tracking system. Bouts higher than 20 mm/s served as indirect indicator of seizure activity and can be applied for efficient in vivo assessment of drug treatments. The A15 scn1lab mutant line was shown to have a sufficient seizure-like locomotion, which was not detected in the other mutant lines. No discernible differences were found in seizure-like locomotion between mutants and siblings when utilizing PTZ, 3-MPA, and light pulses, with A21 mutants. A15 mutants, on the other hand, yielded distinguishable results with light pulses. Additionally, CBD has been found to decrease seizure-like locomotion in A15 mutants and to a lesser extent in siblings. By employing zebrafish as a preclinical model for DS, researchers can bridge the gap between basic research and clinical applications, paving the way for the development of novel treatment strategies. However, further research is needed to improve understanding discrepancies and refine the zebrafish model to enhance its effectiveness in studying DS-related seizures and evaluating potential therapeutic interventions.