Knowledge Base

Introduction

Epilepsy encompasses a spectrum of neurological disorders characterized by epileptic seizures, arising from excessive neuronal activity in the brain. The development of accurate, high-throughput models for epilepsy research is crucial for the elucidation of the underlying genetic and molecular mechanisms and for the identification of potential therapeutic targets. Zebrafish (Danio rerio) have emerged as a premier model organism in neuroscience research, including epilepsy studies, due to their genetic manipulability, translational potential, and the feasibility of large-scale phenotypic screenings.

What Is Epilepsy?

Epilepsy is one of the most common neurological disorders, with over 70 million people diagnosed worldwide. This disorder is characterized by the appearance of seizures, a consequence of an imbalance between excitatory and inhibitory circuits, causing both cognitive and psychological impairment and increasing the risk of early death. The etiology underlying this disease is variable, genetic mutations being one of the most important causes. Many pediatric epilepsy patients present frequent seizures, events that damage and alter their quality of life. Seizures can be provoked by various sensory inputs. When they are produced in response to light, color, or patterns, it is considered photosensitive epilepsy. Photosensitivity occurs in several epileptic syndromes, being particularly prevalent in genetic generalized epilepsies. Moreover, several epilepsies are resistant to the treatments currently available, demonstrating the ongoing need to test novel anti-seizure medications (ASM).

Zebrafish Knock-Out Model

In this study, we aimed to establish a workflow allowing scientists to use somatic knock-out zebrafish larvae to analyze the function of genes involved in the pathogenesis of neurodevelopmental disorders. This was motivated by the advantages that the zebrafish model provides and the necessity of expanding the toolbox for modeling epilepsy in order to streamline the discovery of novel ASMs. Our objective is to develop a zebrafish-based comprehensive platform enabling the functional validation of common and de novo rare loss-of-function mutations in a high-throughput fashion.

As proof of principle, we knocked out a group of six genes associated with childhood epilepsy and characterized their loss-of-function phenotype through a multiparametric analysis using Noldus tools. Through our approach, we introduce a novel integrated method for high-throughput epilepsy mutant generation, behavioral characterization and ASM testing.

Epilepsy Research

Zebrafish offer several advantages for modeling human diseases, like epilepsy. Their transparent embryos and larvae provide a unique window into the brain's internal processes, allowing for direct observation of neuronal activity and drug effects in vivo. Additionally, the rapid development and high fecundity of zebrafish facilitate large-scale genetic screenings and drug discovery efforts. The genetic and physiological homologies between zebrafish and humans further underscore the relevance of this model to human epilepsy research.

Zebrafish larvae have been used to model various forms of epilepsy, including both genetic and chemically induced forms of the disorder. Researchers can use a variety of techniques to induce seizures in the larvae, such as administering convulsant drugs or exposing them to specific light stimuli, and then study the underlying neural mechanisms that drive the seizures.

Zebrafish Genetics

The advent of CRISPR/Cas9 gene-editing technology has revolutionized zebrafish research, enabling precise manipulation of the zebrafish genome to model human genetic diseases. By inducing targeted mutations in genes related with childhood epilepsy, we could generate zebrafish models in F0 that recapitulate the molecular and phenotypic characteristics of some human epileptic disorders, specifically light-induced seizures. The constant improvements in CRISPR/Cas9-induced gene disruption have allowed us to generate de-facto mutants of genes of interest in just a few days of development, enabling genetic target validation and compound treatment in a timely manner. This approach allows for the functional analysis of several epilepsy-associated genes and, importantly, the identification of novel potential pharmacological treatments.

Source: EthoVision XT 18 - THC - Trial and Hardware Control, Noldus Information Technology