Zebrafish Neurological Disease Models: Bridging In Vitro Studies and Mammalian Systems

In the late 1960s, George Streisinger laid the groundwork for the first laboratory zebrafish strains. He developed methods for inducting genetic lesions in zebrafish and isolated the earliest mutants affecting brain development.

60 years later, zebrafish are an established vertebrate model for neurological disease modeling. It enables research teams and CROs to bridge the gap between in vitro studies and mammalian systems, unraveling disease mechanisms, discovering new targets, and accelerating the drug discovery process. 

Modeling Neurological Disorders: Functional and Molecular Readouts

Zebrafish are highly valuable in modeling neurological diseases due to their considerable genetic homology with humans. Over 80% of human disease-associated genes have zebrafish orthologs. The core brain structures (telencephalon, diencephalon, midbrain, cerebellum, and spinal cord) are evolutionarily conserved, and neurotransmitters such as GABA, glutamate, dopamine, serotonin, and acetylcholine show high functional similarity between zebrafish and human brains.​​

These conserved regions and markers are registered in neuroanatomical atlases. These comprehensive resources provide three-dimensional references for the larval and adult zebrafish brain, integrating anatomical region definitions, gene expression patterns, and neuronal connectivity data. They have propelled zebrafish translation, allowing precise comparison of experimental results with cutting-edge brain annotations.  

Figure 1. Max Planck Zebrafish Brain Atlas. This atlas resource combines diverse, spatially resolvable data from the 6 dpf larval zebrafish brain and offers a range of online visualization and analysis tools. In its current version, the web portal at https://fishatlas.neuro.mpg.de exhibits three data modalities. (a) shows 3D views of 112 anatomical regions (b) allows the user to inspect over 4000 stochastically labeled neuronal morphologies (c) lets the user interrogate over 400 transgenic reporter lines and a rapidly growing number (>100) of gene expression and antibody staining patterns. Source: Baier H, Wullimann MF. Anatomy and function of retinorecipient arborization fields in zebrafish. J Comp Neurol. 2021 Oct;529(15):3454-3476. 

Recent advances in genetic engineering, especially CRISPR/Cas9, provide the tools to introduce precise mutations found in humans into zebrafish. This enables rapid analysis of how specific gene variants impact neural development, synaptic transmission, and overall brain function. The optical clarity of larval zebrafish and the availability of transgenic lines expressing fluorescent reporters further allow direct visualization of cell behavior and molecular dynamics in real time. These technologies reveal changes in mitochondrial state, redox balance, and cellular organization at a resolution often unattainable in rodent systems.​

High-Throughput Neurobehavioral Screening with Zebrafish Platforms

Automated zebrafish platforms have revolutionized high-throughput neurobehavioral screening for neurological disorders. Phenotypic analyses, including spontaneous movement, light-induced sensitivity, and motor abnormalities, are conducted in 96-well plates using automated video tracking systems such as Noldus Daniovision. These approaches enable validating drug candidates and functional genetic variants related to specific pathologies, such as epileptic syndromes, channelopathies, and neurodevelopmental disorders.​​

A notable example is the use of the convulsant agent pentylenetetrazole (PTZ), which induces a stereotyped, concentration-dependent sequence of behavioral changes that lead to convulsions in zebrafish. Thanks to the large zebrafish progenies and the automated video tracking systems, we can test a high number of compounds in this model. Automated locomotion monitoring rapidly highlights epilepsy phenotype rescue, identifying promising therapeutic compounds.

We can measure (Figure 2): 

• Total spontaneous locomotion activity.
• Convulsive response in response to visual stimuli: maximum velocity and angle turn (change in direction).
• Anomalies in the stereotyped dark/light larval locomotion pattern.

Figure 2. Spontaneous locomotion and response to visual stimuli. From left to right: Total distance moved in the initial 15-minute light phase, Maximum velocity, and Angle turn (change in direction) in response to flashes of light (seizure characterization). PTZ-treated larvae show a general hyperactive phenotype (increased total distance moved). In this group, the flash of light produces a fast-darting type of movement (increased maximum velocity), and an increased number of turns (change in direction) compared to the negative control. The observed phenotype is rescued by the anti-convulsive compound. Means and SEM are plotted. **p<0,01; ***p<0,001.

Zebrafish as a Translational Bridge in Neurological Disease Research

A principal advantage of zebrafish as a vertebrate model for neurological disorders lies in their ability to integrate findings from basic molecular studies and translate them into disease mechanisms relevant to humans. Their conserved neuroanatomy and neurotransmitter systems permit correlating genetic and molecular changes with observable behavioral outputs. 

Zebrafish has been instrumental in advancing drug candidates from preclinical to clinical phases. The most striking example is the repurposing of the antihistamine Clemizole as an adjunctive therapy for Dravet Syndrome. The scn1lab mutant line mimics SCN1A-driven Dravet Syndrome, exhibiting spontaneous seizures and pharmacological responses comparable to human patients. Clemizole was first identified in zebrafish to reduce seizure activity by Baraban et al. in 2013. Their research has progressed to reach a phase 3 randomized, double-blind, placebo-controlled clinical trial designed to evaluate the efficacy and safety of clemizole hydrochloride (EPX-100). 

→ Discover the role of zebrafish in other marketed compounds for neurological disorders.

Combining the ease of zebrafish genetic manipulation, their physiological and genetic homology, and the use of automated videotracking systems leads to a personalized, quick target validation and drug screening. Zebrafish offers the possibility to create patients' avatars to assess specific mutations in diseases such as epilepsy in just 7 weeks using crispants. 

At ZeClinics, we have developed a zebrafish-based high-throughput platform for generating F0 knock-out (KO) models, using CRISPR/Cas9, and screening neuroactive compounds. Crispants allow for the immediate assessment of gene function, with a shorter generation time than homozygous mutants in the F2 generation. We identify fish with a high level of somatic mutations without the need for genotyping, thanks to our screening system.

These crispants show epilepsy features and allow for identifying targets and testing compounds during the first days post-fertilization, efficiently and quickly. We use automated technology for whole zebrafish organ-level imaging or behavior monitoring that allows high-throughput phenotypic evaluation of single individuals.

→ If you want more information about our epilepsy models or have any other questions, please contact our experts.

By enabling fast in vivo assessment of candidate drugs and genetic mutations, zebrafish models dramatically accelerate the preclinical development pipeline. High-throughput screening in zebrafish helps prioritize the most promising compounds based on robust functional readouts before proceeding to costly and time-consuming mammalian studies. This strategic use of zebrafish not only reduces overall development timelines and expenses but also minimizes the number of mammals needed in research, supporting the 3Rs principle (Replacement, Reduction, Refinement) in animal experimentation. 

References

Baier H, Wullimann MF. Anatomy and function of retinorecipient arborization fields in zebrafish. J Comp Neurol. 2021 Oct;529(15):3454-3476. doi: 10.1002/cne.25204. 

Baraban SC, Dinday MT, Hortopan GA. Drug screening in Scn1a zebrafish mutant identifies clemizole as a potential Dravet syndrome treatment. Nat Commun. 2013;4:2410. doi: 10.1038/ncomms3410.

Baraban SC, Taylor MR, Castro PA, Baier H. Pentylenetetrazole induced changes in zebrafish behavior, neural activity and c-fos expression. Neuroscience. 2005;131(3):759-68. doi: 10.1016/j.neuroscience.2004.11.031.

Burgess HA, Burton EA. A Critical Review of Zebrafish Neurological Disease Models-1. The Premise: Neuroanatomical, Cellular and Genetic Homology and Experimental Tractability. Oxf Open Neurosci. 2023 Jan 6;2:kvac018. doi: 10.1093/oons/kvac018.

By Miriam Martínez

Miriam is a Human Biologist with a strong background in neuropharmacology and a passion for bridging science and innovation. After earning a master’s degree in the Pharmaceutical and Biotech Industry, she completed her PhD in Biomedicine at Pompeu Fabra University (Barcelona), where her research focused on the behavioral analysis of animal models for neurophenotypical characterization. Following her doctoral studies, Miriam transitioned into the healthcare marketing and communication sector, where she played a key role in developing impactful marketing strategies and educational campaigns for leading pharmaceutical brands. She now leverages her scientific expertise, strategic thinking, and creative communication skills in her current role at ZeClinics.