Zebrafish Models of Batten Disease: Replicating CLN3 Neurodegeneration and Epilepsy for Preclinical Drug Discovery

Batten Disease (CLN3): A High-Unmet-Need Rare Neurodegenerative Disorder Driving Early Drug Discovery Investment

CLN3, or Batten disease, is a rare childhood-onset neurodegenerative disorder caused by a ~1 kb deletion in the CLN3 gene, precisely on exons 7 and 8 on chromosome 16p11.2., predicted to result in a truncated protein. It is the most common subtype among the 13 known neuronal ceroid lipofuscinoses (NCLs), a group of lysosomal storage disorders. Clinically, the disease typically begins with vision loss around 6 years of age and progresses over 15–20 years through cognitive decline, seizures, and motor impairment, culminating in premature death, typically between 20 and 30 years of age. 

Despite this well-characterized clinical picture, the molecular function of the CLN3 protein remains poorly understood. CLN3 is a lysosomal transmembrane protein linked to processes such as pH homeostasis, protein trafficking, calcium signaling, phospholipid distribution, and lysosomal amino acid transport, but its actual function is unknown. Treatment focuses on symptom management and palliation, since there are no approved disease-modifying therapies. This mechanistic uncertainty, combined with the rarity of the disease, makes preclinical models that can rapidly recapitulate these hallmarks especially valuable for accelerating drug discovery.

From CLN2 to CLN7: Why Genetic Subtype Matters When Selecting a Preclinical Batten Disease Model

The NCLs are a genetically heterogeneous family: each subtype is named after the mutated gene (CLN1 through CLN14), and each protein plays a distinct biological role.  A comprehensive review of model organisms used in NCL research (Huber et al., 2020) shows that the choice of animal model needs to be matched carefully to the specific CLN gene under investigation, since not every model organism carries a clear homolog of every human NCL gene.

For example, CLN2 disease (caused by mutations in the soluble enzyme TPP1) has no clear homolog in Drosophila or C. elegans. Mouse and dog models were instrumental in developing the enzyme replacement therapy that led to the only approved NCL treatment to date (cerliponase alfa). The zebrafish CLN2 model has been used to screen anticonvulsant compounds and test nonsense-suppression therapies. CLN3, in contrast, encodes a transmembrane protein of largely unknown function, present as homologs across zebrafish, mouse, fruit fly, nematode, and even the social amoeba Dictyostelium discoideum. CLN6, CLN7, and CLN8 diseases have been modeled in sheep, dogs, and non-human primates, which are invaluable for late-stage gene therapy testing but are far too costly and slow for early screening.

The model organism must be selected based on gene conservation, expected phenotype, and the stage of the drug discovery pipeline. Invertebrate and cellular models offer speed and scale but may lack full pathway conservation; large animal models offer translational fidelity but at high cost and long timelines. Zebrafish sit in between, offering a vertebrate nervous system, genetic tractability, and the throughput required for early screening.

Batten Disease Gene Therapy Research: How Zebrafish Accelerate Target Validation and Candidate Screening

Beyond disease-specific findings, zebrafish offer several general advantages as a model organism for early-stage Batten disease research. Disease onset appears early: while CLN3 mouse models take 6–12 months to develop neurological hallmarks, zebrafish larvae can show retinal degeneration, neuronal loss, and epileptiform activity within just a few days, dramatically shortening the time needed to obtain a readout. The zebrafish retina is also cone-rich, unlike the rod-dominated mouse retina, making it a closer approximation of the human visual system, particularly valuable given that vision loss is typically the first symptom in CLN3 patients.

Zebrafish are also notably easier and faster to genetically manipulate than rodents, whether through the analysis of CRISPR/Cas9 F0-injected larvae for rapid initial screening or CRISPR/Cas9 for generating stable knockout lines within a couple of generations. Combined with their small size, which allows housing in 96-well plates and compatibility with automated behavioral tracking, EEG recording, and fluorescence-based imaging, this enables high-throughput screening of genes or compounds across large numbers of animals, at a fraction of the time and cost of equivalent rodent studies.

Together, these advantages position zebrafish as a practical bridge between cellular assays and mammalian models: fast enough for early target validation and compound screening, yet retaining the complexity of a whole vertebrate organism.

Zebrafish CLN3 Models: Replicating Neurodegeneration, Retinopathy, and Seizures for Batten Disease Drug Discovery

Two independent studies illustrate how these advantages translate into practice for CLN3 disease specifically. Wager et al. (2016) knocked down cln3 in zebrafish and reproduced several core hallmarks of the human disease within just a few days of larval development: retinal degeneration, neuronal loss, axonal disorganization, reduced motor function, and lysosomal accumulation of subunit c, the same storage material found in CLN3 patients. Using surface EEG recordings, they also detected epileptiform activity in the mutant larvae, directly reproducing the seizures that characterize the human condition.

More recently, Heins-Marroquin et al. (2024) generated stable cln3 CRISPR knockout zebrafish lines and combined behavioral testing with metabolomics and lipidomics. While the mutants developed did not show any obvious developmental or morphological defects, behavioral phenotyping of the mutant larvae revealed hyposensitivity to abrupt light changes and hypersensitivity to pro-convulsive drugs. Most notably, the study identified a build-up of glycerophosphodiesters and a depletion of BMP lipids in the mutant larvae, metabolic changes also found in CLN3 mouse tissue and human patient samples, highlighting these molecules as promising early biomarker candidates detectable in zebrafish within just 5 days of development.

Building a Preclinical Pipeline for Rare Neurodegenerative Diseases: Lessons from Batten Disease Modeling

CLN3 disease exemplifies a recurring challenge in rare, monogenic neurodegenerative disorders: the biology is well described clinically, but functional validation of the underlying gene and screening of candidate therapies often need to start with an in vivo model that is fast, scalable, and translatable. As the NCL model-organism literature makes clear, no single species covers every CLN gene equally well, so building a preclinical pipeline for a rare neurodegenerative disease means selecting the right organism for the target gene, then layering in the correct phenotypic readouts—behavioral, electrophysiological, or metabolomic-to capture disease-relevant biology.

As officially licensed CRISPR/Cas9 genome editing experts (via the Broad Institute of MIT/Harvard), we can engineer stable knockout or knock-in zebrafish lines targeting specific CLN genes, or generate rapid F0 Crispant models for early functional screening of candidate targets. These models can then be coupled with our high-throughput phenotyping platforms to quantify disease-relevant endpoints at scale. For studies requiring deeper mechanistic insight, molecular profiling can be integrated as an additional layer of analysis. Our omics capabilities include transcriptomics (RNA-seq, differential expression, pathway enrichment), targeted gene expression via qPCR, proteomics, and lipidomics.

Pipeline for the generation of stable F1 and F2 KO using the CRISPR/Cas9 technique.

If you are working in the neurodegenerative disorder space and need a custom zebrafish model to validate targets or screen compounds, ZeClinics can help you. 

References

Heins-Marroquin U, et al. CLN3 deficiency leads to neurological and metabolic perturbations during early development. Life Sci Alliance. 2024 Jan 9;7(3):e202302057. doi: 10.26508/lsa.202302057. 

Huber RJ, et al. The contribution of multicellular model organisms to neuronal ceroid lipofuscinosis research. Biochim Biophys Acta Mol Basis Dis. 2020 Sep 1;1866(9):165614. doi: 10.1016/j.bbadis.2019.165614.

Wager K, et al. Neurodegeneration and Epilepsy in a Zebrafish Model of CLN3 Disease (Batten Disease). PLoS One. 2016 Jun 21;11(6):e0157365. doi: 10.1371/journal.pone.0157365. 

Whiteman IT, et al. A timeline of symptom onset and disease progression in CLN3 disease. Orphanet J Rare Dis. 2026 Jan 7;21(1):38. doi: 10.1186/s13023-025-04174-5.

By Javier Terriente

Javier is the co-founder of ZeClinics and ZeCardio Therapeutics, two biotech firms specializing in zebrafish-based preclinical drug discovery for cardiovascular, neural, and toxicology applications. He combines scientific leadership with business acumen, having successfully driven fundraising efforts and strategic partnerships.

Currently leading scientific efforts at ZeCardioTx (and formerly CSO at ZeClinics), Javier also serves on the Board of Directors of AseBio, where he advocates for industry collaboration. His academic background includes a PhD in Molecular Biology and a Marie Curie Fellowship. Recognized as an expert in zebrafish models, he has published extensively and has supervised five industrial PhD theses.