Rab8-, Rab11-, and Rab35-dependent mechanisms coordinating lumen and cilia formation during Left-Right Organizer development

An essential process for cilia formation during epithelialization is the movement of the centrosome to dock with the cell’s nascent apical membrane. Our study examined centrosome positioning during the development of Danio rerio’s left-right organizer (Kupffer’s Vesicle, KV). We found that when KV mesenchymal-like cells transition into epithelial cells that are organizing into a rosette-like structure, KV cells move their centrosomes from random intracellular positions to the forming apical membrane in a Rab11 and Rab35 dependent manner. During this process, centrosomes construct cilia intracellularly that associated with Myo-Va while the centrosomes repositioned towards the rosette center. Once the centrosomes with associated cilia reach the rosette center, the intracellular cilia recruit Arl13b until they extend into the forming lumen. This process begins when the lumen reaches an area of approximately 300 μm2. Using optogenetic and depletion strategies, we identified that the small GTPases, Rab11 and Rab35, regulate not only cilia formation, but lumenogenesis, whereas Rab8 was primarily involved in regulating cilia length. These studies substantiate both conserved and unique roles for Rab11, Rab35, and Rab8 function in cilia formation during lumenogenesis.