Toward the use of novel alternative methods in epilepsy modeling and drug discovery

The fruit fly Drosophila melanogaster as a screening model for antiseizure medications

Objective

Resistance to antiseizure medications (ASMs) is a major challenge in the treatment of patients with epilepsy. Despite numerous newly marketed ASMs, the proportion of drug-resistant people with epilepsy has not significantly decreased over the years. Therefore, novel and innovative seizure models for preclinical drug screening are highly desirable. Here, we explore the efficacy of a broad spectrum of ASMs in suppressing seizure activity in two established Drosophila melanogaster bang-sensitive mutants. These mutants respond with seizures to mechanical stimulation, providing a promising platform for screening novel ASMs.

Methods

Seven frequently used ASMs (brivaracetam, cenobamate, lacosamide, lamotrigine, levetiracetam, phenytoin, and valproate) were administered to the bang-sensitive mutants easily shocked 2F (eas 2F ) and paralytic bss1 (para bss1 ). After 48 h of treatment, the flies were vortexed to induce mechanical stimulation. The seizure probability (i.e., ratio of seizing and non-seizing flies) as well as the seizure duration were analyzed.

Results

In case of eas 2F mutants, treatment with the sodium channel blockers phenytoin and lamotrigine resulted in a robust reduction of seizure probability, whereas flies treated with lacosamide showed a decrease in seizure duration. Treatment with valproate resulted in both a reduction in seizure probability and in seizure duration. In contrast, levetiracetam, brivaracetam and cenobamate had no effect on the bang-sensitive phenotype of eas 2F flies. In case of para bss1 flies, none of the tested medications significantly reduced seizure activity, supporting its role as a model of intractable epilepsy.

Significance

Our results show that particularly sodium channel blockers as well as valproate are effective in suppressing seizure activity in the bang-sensitive mutant eas 2F . These findings demonstrate the usability of Drosophila for screening drugs with antiseizure properties. Due to fewer ethical concerns, the short life cycle, and low maintenance costs, Drosophila might provide an attractive and innovative high-throughput model for the discovery of novel antiseizure compounds.

Next-generation sequencing in pediatric-onset epilepsies: Analysis with target panels and personalized therapeutic approach

OBJECTIVE

The objective of this study is to report the results of the genetic analysis in a large and well-characterized population with pediatric-onset epilepsies and to identify those who could benefit from precision medicine treatments.

METHODS

In this retrospective observational study, we consecutively recruited patients with pediatric-onset epilepsy observed at a tertiary neurological center over a time span of 7 years, collecting clinical and laboratory findings. Following in-depth diagnostic process to exclude possible structural and metabolic causes of the disease, patients with a suspected genetically determined etiology underwent next-generation sequencing (NGS) screening with panels for the analysis of target genes causative of epilepsy.

RESULTS

We detected likely pathogenic or pathogenic variants (classes IV and V) in 24% of the 562 patients who underwent genetic investigations. By the evaluation of patients' data, we observed that some features (onset of epilepsy before one year old, presence of neurological deficits, psychomotor delay/cognitive disability, and malformative aspects at brain MRI) were significantly associated with class IV or V variants. Moreover, statistical analysis showed that the diagnostic yield resulted higher for patients affected by Progressive Myoclonic Epilepsy (PME) and with early onset developmental and epileptic encephalopathies (DEE), compared with focal epilepsies, genetic generalized epilepsies, DEE with onset at/after 1 y.o., and unclassified epileptic syndromes. According to the results of the genetic screening, up to 33% of patients carrying class IV or V variants resulted potentially eligible for precision medicine treatments.

SIGNIFICANCE

The large-scale application of NGS multigene panels of analysis is a useful tool for the molecular diagnosis of patients with pediatric-onset epilepsies, allowing the identification of those who could benefit from a personalized therapeutic approach.

PLAIN LANGUAGE SUMMARY

The analysis of patients with pediatric-onset epilepsy using advanced technologies for the screening of all the implicated genes allows the identification of the cause of diseases in an ever-increasing number of cases. Understanding the pathogenic mechanisms could, in some cases, guide the selection and optimization of appropriate treatment approaches for patients.

In Search of a Target Gene for a Desirable Phenotype in Aquaculture: Genome Editing of Cyprinidae and Salmonidae Species

Aquaculture supplies the world food market with a significant amount of valuable protein. Highly productive aquaculture fishes can be derived by utilizing genome-editing methods, and the main problem is to choose a target gene to obtain the desirable phenotype. This paper presents a review of the studies of genome editing for genes controlling body development, growth, pigmentation and sex determination in five key aquaculture Salmonidae and Cyprinidae species, such as rainbow trout (Onchorhynchus mykiss), Atlantic salmon (Salmo salar), common carp (Cyprinus carpio), goldfish (Carassius auratus), Gibel carp (Carassius gibelio) and the model fish zebrafish (Danio rerio). Among the genes studied, the most applicable for aquaculture are mstnba, pomc, and acvr2, the knockout of which leads to enhanced muscle growth; runx2b, mutants of which do not form bones in myoseptae; lepr, whose lack of function makes fish fast-growing; fads2, Δ6abc/5Mt, and Δ6bcMt, affecting the composition of fatty acids in fish meat; dnd mettl3, and wnt4a, mutants of which are sterile; and disease-susceptibility genes prmt7, gab3, gcJAM-A, and cxcr3.2. Schemes for obtaining common carp populations consisting of only large females are promising for use in aquaculture. The immobilized and uncolored zebrafish line is of interest for laboratory use.

A Zebrafish-Based Platform for High-Throughput Epilepsy Modeling and Drug Screening in F0

The zebrafish model has emerged as a reference tool for phenotypic drug screening. An increasing number of molecules have been brought from bench to bedside thanks to zebrafish-based assays over the last decade. The high homology between the zebrafish and the human genomes facilitates the generation of zebrafish lines carrying loss-of-function mutations in disease-relevant genes; nonetheless, even using this alternative model, the establishment of isogenic mutant lines requires a long generation time and an elevated number of animals. In this study, we developed a zebrafish-based high-throughput platform for the generation of F0 knock-out (KO) models and the screening of neuroactive compounds. We show that the simultaneous inactivation of a reporter gene (tyrosinase) and a second gene of interest allows the phenotypic selection of F0 somatic mutants (crispants) carrying the highest rates of mutations in both loci. As a proof of principle, we targeted genes associated with neurodevelopmental disorders and we efficiently generated de facto F0 mutants in seven genes involved in childhood epilepsy. We employed a high-throughput multiparametric behavioral analysis to characterize the response of these KO models to an epileptogenic stimulus, making it possible to employ kinematic parameters to identify seizure-like events. The combination of these co-injection, screening and phenotyping methods allowed us to generate crispants recapitulating epilepsy features and to test the efficacy of compounds already during the first days post fertilization. Since the strategy can be applied to a wide range of indications, this study paves the ground for high-throughput drug discovery and promotes the use of zebrafish in personalized medicine and neurotoxicity assessment.