Genetic Causes of Pharmacoresistant Epilepsy Syndromes and Drug Repurposing Approaches Using Zebrafish as a Model Organism

Background: Many patients with neurodevelopmental disorders present with pharmacoresistant epileptic seizures that do not respond to available anti-seizure drugs (ASDs). Most of these diseases are caused by genetic mutations, such as SCN1A mutations in Dravet syndrome, CHD2 mutations in Lennox-Gasteaux syndrome, and HNRNPU and DHPS mutations in two of the growing number of ultra-rare epileptic encephalopathies. These syndromes are typically characterized by a combination of epileptic seizures, cognitive impairment, and behavioral abnormalities. In this study, we are generating and phenotypically characterizing new animal models for these syndromes, with the goal of using selected models for drug repurposing or drug discovery. Methods: Zebrafish loss-of-function models were generated using CRISPR mutagenesis, ENU mutagenesis (via the Zebrafish Mutation Project at the Sanger Centre), or by antisense knockdown using morpholino oligomers. Epileptic seizures were characterized in zebrafish larvae (1) by behavioral analysis, using an automated video tracking system to quantify locomotor activity and seizure-like behavior; (2) by electrophysiological analysis, using a single electrode placed in the midbrain to generated open-field recordings; (3) by whole-brain imaging of calcium dynamics using a transgenic line with pan-neuronal expression of gCaMP. Findings: Drug repurposing screening using our zebrafish epilepsy models identified constituents of the medicinal plant Curcuma longa as being able to significantly decrease seizure frequency. These results were obtained using behavioural analysis, and were confirmed by electrophysiological analysis. Ongoing studies into the mechanism of action of these constituents has revealed novel targets and signalling pathways, possibly identifying novel therapeutic entry points for pharmacoresistant epilepsies. Conclusion: Zebrafish, which are now well-accepted as a model organism for a wide range of human diseases, are an ideal platform for disease modelling and drug discovery, especially for neurodevelopmental syndromes with refractory seizures. We look forward to translating the findings from our zebrafish-based studies into the clinic in the near future.

کلیدواژه ها:

pharmacoresistant epilepsy syndromes ، drug repurposing ، Zebrafish ، genetic mutations