Central Nervous System Immediate Early Gene Expression Patterns in Zebrafish Models of Epilepsy

Abstract

Zebrafish are a powerful model for studying neurodevelopmental disease, and more recently epilepsy. The characteristics of seizures in zebrafish have until now included largely descriptive abnormalities in swim patterns and electrophysiology in larval zebrafish. A quantitative method of characterization that capitalizes on the high-throughput potential of zebrafish is analysis of immediate early gene (IEG) transcription. IEGs are transiently and rapidly activated in response to stimuli such as calcium influx in neurons. In order to better understand the abnormal expression patterns of IEGs due to seizure in a zebrafish model, we investigated transcriptional activity of the six IEGs, cfos, npas4, nr4a1, bdnf, cebpβ, and homer1a, in both a chemical and genetic model of epilepsy. This study found that a number of commonly used qPCR loading control are unsuitable for pentylentyterazole (PTZ) models of zebrafish epilepsy because they are altered with exposure to PTZ. However, mglobulin remained static across all tested drug exposures, making it an appropriate control. Abnormal IEG expression from PTZ exposure generally recapitulated the data found in the mouse models, but expression was also greatly induced by conventional chemicals controls. These data suggest that IEGs tested can reveal a transcriptional PTZ effect in zebrafish, but that the effect cannot be attributed solely to an increase in neuronal activity. Finally, differential IEG expression in a genetic model of zebrafish epilepsy was explored by generating an osgep KO zebrafish. IEGs tested in this study however did not show a statistically significant difference between osgep +/- osgep-/-, and control.