From these results, we conclude that depletion of crb2 in Xenopus obstructs the communication between the lateral - 3rd and midbrain - 4th ventricles due to cerebral aqueduct stenosis, and this is associated, and likely due, to impairment of cilia-driven CSF flow in select populations of ependymal cells. The gene discussed is CRB2; the disease is Aqueductal stenosis.