HYDIN and Hydrocephalus: Furthermore, Hydin, a gene that encodes a central pair protein within the axon of motile cilia and expresses ependymal cell layer lining the ventricles, also may induce hydrocephalus when mutated [39, 40, 44]. Mdnah5 is specifically expressed in ependymal cells, and is essential for ultra-structural and functional integrity of ependymal cilia [41].