Novel function of TRIP6, in brain ciliogenesis

TRIP6, a member of the zyxin-family of LIM domain proteins, is a focal adhesion component. trip6 deletion in the mouse revealed, unexpectedly, in view of its ubiquitous expression, a function in the brain: ependymal and choroid plexus epithelial cells were poorly developed, carrying fewer and shorter cilia, and the mice developed hydrocephalus. TRIP6 disruption, via RNAi or inhibition of its homodimerization, in a choroid plexus epithelial cell line, confirmed its function in ciliogenesis. Zyxin-family members carry numerous protein interaction domains. In common with assembly of other multiprotein complexes, ciliogenesis may be facilitated by molecular assembly factors. Super-resolution microscopy demonstrated TRIP6 localization at the pericentriolar material and along the ciliary axoneme. The requirement for homodimerization which doubles its interaction sites, its punctate localization along the axoneme, and its co-localization with other cilia components suggest a scaffold/co-transporter function for TRIP6 in cilia. This is the first discovery of a protein assembly factor essential for mammalian ciliogenesis.