NOTCH3 Mutations in CADASIL: a multicellular perspective on neurodegeneration.

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) is a hereditary cerebral small-vessel disease caused by NOTCH3 cysteine-altering mutations. Clinical evidence, including early-onset migraines, psychiatric symptoms, and diffuse white-matter hyperintensities preceding strokes, suggests a nonvascular pathology. NOTCH3 is broadly expressed in neural progenitors, neurons, astrocytes, oligodendrocytes, and brain microvascular endothelial cells (BMECs), and is responsible for neurodevelopment, blood-brain barrier (BBB) homeostasis, glymphatic function, and myelination. In vitro studies suggest that mutant NOTCH3 disrupts hippocampal neurogenesis via impaired neural stem cell self-renewal, causes astrocytic aquaporin-4 (AQP4) mislocalisation leading to glymphatic failure, compromises endothelial integrity, and derails oligodendrocyte maturation. These dysfunctions can collectively perturb neurovascular unit (NVU) integrity, accelerating neurodegeneration independent of infarcts. This review puts together evidence for nonvascular NOTCH3 pathology, emphasizing its role in neuroglial development and NVU crosstalk. We aim to reframe CADASIL as a multicellular interface disorder that stems from neurodevelopmental pathways, suggesting that advanced 3D in vitro NVU models to unravel disease mechanisms leading to the new therapeutic strategies that target glial and neuronal NOTCH3 signalling to mitigate early symptoms and slow progression.