Self-Coordination of Dyneins during Ciliary Beating

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The goal of this project is to elucidate the molecular mechanism of self-coordinated oscillations of motile cilia. Motile cilia are whip-like structures that protrude like bristles from the cell surface and generate a periodic beating waveform. Ciliary beating powers the swimming of sperm and many small organisms. Ciliary beating also generates fluid flow in the intestines and lungs, and mediates cell signaling. The core structural component of a cilium is the axoneme, which has a ring of nine outer microtubule doublets surrounding two central microtubules. A detailed investigation of the mechanism that powers self-coordinated ciliary beating will significantly contribute to our understanding of how ciliary malfunction is linked to a group of defects known as ciliopathies. The Broader Impacts of this Project will also help establish educational outreach programs for high school students from underrepresented groups in Oakland, CA. To attract a new generation to science, summer research opportunities, seminars and science fairs will be organized in local public schools. Undergraduate students will contribute to the Project by actively participating in the research. The results of the proposed research will be integrated into a new curriculum that will be developed for Physics undergraduates wishing to pursue a graduate career in the life sciences.The basic principle of ciliary beating relies on a sliding motion between microtubules and two different types of dynein motor proteins, the inner arm and the outer arm dyneins. To bend microtubules locally in cilia, dyneins on one side of an axoneme must be active while those on the opposite side are inactive. These states must switch periodically to propagate bending along the length of the axoneme. The negative feedback mechanisms that coordinate the activities of dynein motors across an axoneme remain to be determined. To elucidate the mechanisms that regulate ciliary beating, this project will test several predictions for the mechanical properties of Tetrahymena inner- and outer-arm dyneins in vitro. Using single-molecule fluorescence and manipulation methods, the project will complete three goals. It will determine the mechanism by which dynein monomers step relative to each other as the motor slides microtubule filaments. It will investigate the emergent properties of dynein motors when functioning in large teams. The project will also reconstitute a minimal system for ciliary oscillations and visualize the movement of individual microtubules. The successful completion of this project will reveal new molecular mechanisms of inner-arm and outer-arm dynein coordination and determine minimum requirements for self-coordinated oscillations of motile cilia.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.