Understanding the molecular mechanisms of cilia formation

Project Summary: The Primary cilium is an organelle that majority of human cells possess with only one per a cell. This immotile cellular structure senses extracellular signaling via receptors that specifically accumulate on the ciliary portion of the cellular membrane. Dysfunction in the structure or the function of the organelle results in pleiotropic disorders called ciliopathies, which include obesity and retinal degeneration. The cilium needs to be disassembled prior to mitosis, as cells use centrosome, from which the cilium extends, as spindle poles. Cells reassemble the cilium in G0/G1 phase of the cell cycle. My lab at University of Oklahoma Health Science Center interrogates the molecular mechanisms of the formation of the cilium. The initial step of the cilium formation is recruitment of a ciliary vesicle, to the distal end of the mother centriole. The small vesicles fuse to form a larger vesicle, which finally merges with plasma membrane to form the primary cilium. While the attachment of the ciliary vesicle to the centriole is the first step, many important questions remain to be elucidated. One potential problem that has hampered our understanding of the ciliary vesicle is the lack of markers of the ciliary vesicle. To overcome this challenge, I previously characterized a small GTPase, RAB34, a more specific marker for the ciliary vesicle, and determined that Neuronal Calcium Sensor-1 (NCS1) captures the ciliary vesicle using its myristoylation motif at the ciliary base. Using these proteins as powerful biochemical tools, we will focus on answering key unsolved questions including the composition and origin of the ciliary vesicle. We will isolate the ciliary vesicle to uncover the lipid and protein composition of the vesicle, monitor the movement of the ciliary vesicle from its emergence to reveal the origin of the vesicle, and screen for the regulators that determine how the vesicle is generated and transported to the centriole. If successful, our research projects will uncover the largely unexplored molecular mechanisms of the early step of the cilium formation, which will pave the way to get to the root of the pathogenesis of the syndrome caused by ciliary dysfunction.