The dynein-triggered ciliary motion in embryonic nodes: an exploratory study based on computational models

The cilia, presenting a rotational movement in the embryonic nodes, play a crucial role in the left-right specification during embryogenesis. The characteristic architecture of these cilia is based on a cylindrical arrangement of 9 doublet microtubules and the motion of the cilia is triggered by the dynein motors located between adjacent doublets by converting the chemical energy into mechanical work. Restricted by the inherent difficulties of experiments, the dynein activation patterns in moving cilia cannot be directly observed. Thus, the mechanism of nodal ciliary movement is still unclear. In this study, we present computational models of the nodal ciliary ultrastructure based on tomographic images of the ciliary body. By employing time accurate three-dimensional solid mechanics analysis, we investigate the dynein-triggered sliding between adjacent doublet microtubules and simulate the induced ciliary bending. As an exploratory study, two dynein activation patterns are proposed and their rationality is discussed. The mathematical model presented by this paper provides a platform to investigate various assumptions of dynein activity, facilitating us to propose the most possible dynein activation pattern and therefore improving our understandings regarding the protein-beating problems of cilia.