Crb2-dependent progenitor adhesion safeguards ventricular lining integrity and prevents hydrocephalus.

Congenital hydrocephalus is a heterogeneous neurodevelopmental disorder in which ventricular enlargement can arise from impaired cerebrospinal fluid (CSF) flow, aqueductal obstruction, or altered ventricular wall integrity. Although human CRB2 mutations are associated with hydrocephalus, aqueductal abnormalities, and periventricular heterotopia, the relevant cell types and pathogenic sequence remain poorly defined. Here, using lineage-specific Crb1/2 conditional mouse models, we show that Crb2-dependent polarity and adhesion in neural progenitors are required to preserve ventricular system integrity. Pan-neural Crb1/2 deletion recapitulated major features of CRB2-associated disease, whereas deletion in ependymal lineage-specified progenitors did not disrupt ependymal maintenance or cause ventriculomegaly. Cortical progenitor-specific deletion caused progressive ventriculomegaly and impaired CSF transit despite a patent, ciliated aqueduct and largely intact neurogenesis. Mechanistically, Crb2 loss disrupted apical polarity, adherens junction continuity, actomyosin organization, and ventricular barrier integrity, leading to ventricular lining detachment and increased permeability to ventricular contents. Furthermore, intracerebroventricular administration of bumetanide attenuated ventricular enlargement without restoring ependymal organization, indicating that CSF load contributes to ventricular expansion when the ventricular wall is mechanically weakened. Importantly, detached rostral progenitor/ependymal precursor can be preserved at the blocked caudal aqueduct, providing evidence of unaffected ependymal cell generation without Crb1/2. These findings define CRB2-associated hydrocephalus as a progenitor-stage adhesion and ventricular wall integrity disorder.