Primary cilia exert a profound impact on cell signalling and cell cycle progression. Recently, actin cytoskeleton destabilization has been recognized as a dominant inducer of ciliogenesis, but the exact mechanisms regulating ciliogenesis remain poorly understood. Here we show that the actin cytoskeleton remodelling controls ciliogenesis by regulating transcriptional coactivator YAP/TAZ as well as ciliary vesicle trafficking. Cytoplasmic retention of YAP/TAZ correlates with active ciliogenesis either in spatially confined cells or in cells treated with an actin filament destabilizer. Moreover, knockdown of YAP/TAZ is sufficient to induce ciliogenesis, whereas YAP/TAZ hyperactivation suppresses serum starvation-mediated ciliogenesis. We also identify actin remodelling factors LIMK2 and TESK1 as key players in the ciliogenesis control network in which YAP/TAZ and directional vesicle trafficking are integral components. Our work provides new insights for understanding the link between actin dynamics and ciliogenesis.

Primary cilia are evolutionarily conserved cellular organelles with a distinctive rod-like structure that protrudes from the cell surface. Primary cilia are non-motile and near-ubiquitous in animal body. Studies using model organisms have demonstrated that primary cilia are involved in signal transduction pathways that control embryonic development and adult homeostasis. Moreover, defects in the formation or function of primary cilia have been shown to underlie various genetic disorders in human. The biogenesis of cilia requires both the assembly of a microtubulebased core structure, called the axoneme, and the establishment of the ciliary membrane. Emerging evidence suggests that specialized vesicle trafficking is critical for the formation and maintenance of the ciliary membrane, whose composition is distinct from that of the surrounding plasma membrane. The signaling functions of primary cilia also depend on selective delivery of ciliary membrane proteins via vesicle trafficking routes to primary cilia. The list of genes that are thought to be required for ciliary membrane biogenesis increases at a steady pace. However, the sorting and trafficking mechanisms of cilium-bound transport vesicles remain elusive. Here, we review current findings on several key molecules that may regulate vesicle trafficking during and after ciliogenesis.