Zebrafish model unlocks new insights into hereditary brain disease

CADASIL, an inherited disease caused by mutations in the NOTCH3 gene, damages the brain’s small blood vessels, leading to strokes, cognitive decline, and early dementia. Despite decades of research, its underlying disease mechanisms remain poorly understood due to the lack of suitable disease models. To tackle this issue, researchers have developed the world’s first zebrafish model of CADASIL, which reproduces several key features of the disease. Their findings will help identify potential therapeutic targets. 

CADASIL, which stands for 'cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy,' is a hereditary disease that damages the brain's small blood vessels, causing recurrent strokes. Over time, CADASIL leads to a decline in cognitive functions and can progress to early-onset dementia, even in young patients. While scientists have known for decades that the disease is caused by mutations in a gene called NOTCH3, no effective treatment exists yet, as we still do not fully understand why and how the disease progresses at the biological level.

One reason for this knowledge gap is the lack of animal models that can accurately reproduce the disease in the laboratory. Existing mouse models can replicate some features of CADASIL, but they fail to show important symptoms seen in patients, such as significant memory decline, brain atrophy, and white matter lesions. Against this backdrop, scientists investigated whether zebrafish-a small freshwater fish increasingly used in biomedical research-could offer a better way to investigate this disorder.

Seeking to answer this question, a research team led by Professor Motoyuki Itoh from the Graduate School of Pharmaceutical Sciences at Chiba University, Japan, set out to develop the world's first zebrafish model of CADASIL. The paper was co-authored by Dr. Tohgo Kanoh from Chiba University, Dr. Ichio Aoki from the National Institutes for Quantum Science and Technology (QST), Japan, and Dr. Yoshinori Hasegawa and Dr. Osamu Ohara from Kazusa DNA Research Institute, Japan. Their latest study, published in Acta Neuropathologica Communications on June 3, 2026, describes how zebrafish carrying a specific NOTCH3 mutation was able to replicate the key features of the disease in ways that previous animal models could not.

The researchers worked with zebrafish carrying a mutation called p.C680S in the NOTCH3 gene, which mirrors a mutation associated with CADASIL in humans. They closely followed the animals as they aged, using live imaging to monitor blood flow in the brain and behavioral tests to assess learning and memory. They also performed magnetic resonance imaging to visualize brain structure and molecular analyses to examine changes in gene and protein activity.

From 11 months of age, the mutant zebrafish showed a progressive decline in cerebral blood flow. By 14 months, learning ability had dropped significantly, and working memory was impaired by 17 months. This followed a similar sequence of deterioration seen in actual patients. Brain scans confirmed tissue loss in a region of the brain equivalent to the human cerebrum, and electron microscopy revealed characteristic abnormal protein deposits known as granular osmiophilic material-a hallmark sign of CADASIL.

To understand what was driving these changes, the team performed detailed molecular analyses of gene and protein expression in the zebrafish brains. They found a consistent reduction in type IV collagen, which is a structural protein that forms a supportive mesh around blood vessels and helps keep them strong, intact, and flexible. Less type IV collagen was present around the cerebral blood vessels of the mutant zebrafish, and the vascular basement membrane that supports blood vessel walls appeared structurally disrupted.

"Our study provides new insights into the relationship between CADASIL-causing gene mutations and type IV collagen. The results may thus help identify new therapeutic targets for this disease," remarks Prof. Itoh.

Overall, this work showcases the untapped potential of zebrafish in the study of neurodegenerative diseases. "Over the next 5 to 10 years, we expect various new zebrafish models with different CADASIL mutations to be developed and used to discover new therapies and evaluate their effectiveness. This breakthrough is also leading to a wider recognition of zebrafish as a model for age-related dementia," concludes Prof. Itoh.

For patients and families affected by CADASIL worldwide, particularly in East Asia, where certain mutations are especially prevalent, this research marks a meaningful step toward treatments that have so far remained out of reach.