Behavioral Comorbidities and Drug Treatments in a Zebrafishscn1labModel of Dravet Syndrome

Abstract

Loss-of-function mutations in SCN1A cause Dravet syndrome (DS), a catastrophic childhood epilepsy in which patients experience comorbid behavioral conditions, including movement disorders, sleep abnormalities, anxiety, and intellectual disability. To study the functional consequences of voltage-gated sodium channel mutations, we use zebrafish with a loss-of-function mutation in scn1lab, a zebrafish homolog of human SCN1A. Homozygous scn1labs552/s552 mutants exhibit early-life seizures, metabolic deficits, and early death. Here, we developed in vivo assays using scn1labs552 mutants between 3 and 6 d postfertilization (dpf). To evaluate sleep disturbances, we monitored larvae for 24 h with locomotion tracking software. Locomotor activity during dark (night phase) was significantly higher in mutants than in controls. Among anticonvulsant drugs, clemizole and diazepam, but not trazodone or valproic acid, decreased distance moved at night for scn1lab s552 mutant larvae. To monitor exploratory behavior in an open field, we tracked larvae in a novel arena. Mutant larvae exhibited impaired exploratory behavior, with increased time spent near the edge of the arena and decreased mobility, suggesting greater anxiety. Both clemizole and diazepam, but not trazodone or valproic acid, decreased distance moved and increased time spent in the center of the arena. Counting inhibitory neurons in vivo revealed no differences between scn1lab s552 mutants and siblings. Taken together, our results demonstrate conserved features of sleep, anxiety, and movement disorders in scn1lab mutant zebrafish, and provide evidence that a zebrafish model allows effective tests of treatments for behavioral comorbidities associated with DS.

A simple and effective F0 knockout method for rapid screening of behaviour and other complex phenotypes

“…In humans, loss-of-function mutations of its ortholog SCN1A are associated with Dravet syndrome, a rare and intractable childhood epilepsy (Anwar et al, 2019). In zebrafish, scn1lab homozygous null mutants display hyperpigmentation, seizures, and complex day-night differences in free-swimming behaviour (Baraban et al, 2013;Grone et al, 2017). As expected, all (91/91) scn1lab F0 knockouts were hyperpigmented ( Figure 6A insert).…”

Imaging epilepsy in larval zebrafish

“…Interestingly, scn1lab 552À/larvae exhibit spontaneous abnormal electrographic activity, motor hyperactivity and convulsive activities starting at 3 dpf and persisting until early fatality around 10e12 dpf. This model of Dravet Syndrome has been characterised at behavioural, electrophysiological, transcriptomic and metabolic levels [9,52,53] and has been used extensively for drug-screening purposes [17,18,54]. More recently, the emergence of novel targeted mutagenesis techniques such as CRISPR/Cas9 opens the door to the generation of stable genetic models targeting all possible human epilepsy single gene mutations.…”

Phenotype-Based Screening of Synthetic Cannabinoids in a Dravet Syndrome Zebrafish Model

“…The scn1lab mutant zebrafish line exhibits spontaneous seizures that can be easily monitored using acute behavioral and electrophysiological assays (Baraban et al, 2013;Hong et al, 2016;Griffin et al, 2017;Hunyadi et al, 2017). These mutants exhibit metabolic deficit, early fatality, sleep disturbances, and a pharmacological profile similar to Dravet syndrome patients (Schoonheim et al, 2010;Kumar et al, 2016;Grone et al, 2017). In addition to replicating key aspects of Dravet syndrome, scn1lab mutants were shown to be a useful model system for large-scale phenotype-based drug screening and experimental drugs identified in this model have shown efficacy in the clinic (Baraban et al, 2013;Dinday and Baraban, 2015;Griffin et al, 2017;Sourbron et al, 2017;Griffin et al, 2018).…”