The respiratory ciliary motion produced by dynein activity alone: A computational model of ciliary ultrastructure.

BACKGROUND Respiratory ciliary motion is enabled by dynein/microtubule activity. Current observation techniques can hardly capture the dynein activation pattern in moving cilia. Here we introduce a computational model to mimic the ciliary ultrastructure and simulate the dynein-driven ciliary motion. METHODS A three-dimensional model is established to mimic the ``9 + 2'' ciliary ultrastructure. The dynein force is simulated as point loads embedded along the microtubules. The dynein-triggered ciliary motion is solved by using the Finite Element Method along with grid deformation techniques. RESULTS By comparing the simulated ciliary movement to the observation results, the rationality of different dynein activity hypotheses are evaluated and the dynein activation pattern that can produce the planar beating of lung cilia is proposed. The results also reveal that the dynein force alone can only generate longitudinal microtubule sliding and ciliary bending; to produce the ciliary `curl-up' movement, transverse forces (possibly induced by radial spokes) need to be considered. CONCLUSION This model provides a platform to investigate various assumptions of dynein activity, facilitating us to evaluate their rationality and propose possible dynein activation patterns.