Ependymal Cells and Hydrocephalus: Recent Advances in Molecular Mechanisms.

Ependymal cells are specialized multiciliated epithelial cells that line the brain ventricles. Their coordinated ciliary beating contributes to cerebrospinal fluid circulation and neural homeostasis. Hydrocephalus, a severe neurological condition affecting ∼1-3 per 1000 births worldwide, can arise from defects in ciliary motility, ependymal cell differentiation, planar cell polarity (PCP), and cytoskeletal organization. Mutations in genes that regulate these processes have been identified in patients with congenital hydrocephalus and related ciliopathies, establishing the clinical relevance of these pathways. This review summarizes the recent advances in the molecular mechanisms underlying ependymal cell biology. We describe the structural and functional organization of the ependymal cilia and discuss how ciliary defects range from severe developmental disruptions causing neonatal hydrocephalus to subtle maintenance defects underlying late-onset forms of the disease. We then examine the hierarchical transcriptional programs controlling ependymal differentiation, from master regulators such as GemC1 and Multicilin to downstream effectors, including FoxJ1 and Regulatory Factor X proteins. The core PCP pathway, comprising Vangl, Celsr, Frizzled, and Dishevelled proteins, coordinates tissue-wide ciliary orientation. Recent cryo-electron microscopy studies have provided structural insights into core components. Finally, we discuss the role of cytoskeletal networks in ependymal maintenance. Actin networks support structural integrity through mechanosensitive feedback loops and transduce mechanical forces into transcriptional activation of multiciliogenesis. In parallel, microtubule-based systems coordinate the planar polarized ciliary orientation via the Daple-dynein axis. Taken together, these molecular insights advance our understanding of the pathogenesis of hydrocephalus and may inform future diagnostic and therapeutic strategies.