Ciliary behaviour and mechano-transduction in the embryonic node: computational testing of hypotheses

Area of Science:

• Developmental Biology
• Biophysics
• Computational Biology

Background:

• Left-right symmetry breaking in mammalian embryos is crucial for organogenesis.
• The embryonic node's cilia are implicated in initiating this asymmetry.
• The 'two-cilia' hypothesis suggests motile and passive cilia cooperate.

Purpose of the Study:

• To computationally model the fluid dynamics and mechanics of embryonic node cilia.
• To investigate how active cilia generate flow and influence passive cilia.
• To explore protein motor activity underlying active cilia rotation.

Main Methods:

• Developed two computational models incorporating fluid dynamics and fluid-structure interaction.
• Solved three-dimensional unsteady transport equations with specific boundary conditions.
• Applied finite element analysis and grid deformation for ciliary motion simulation.

Main Results:

• Confirmed that active cilia whirling induces unidirectional leftward fluid flow.
• Demonstrated passive cilia are propelled leftward by the flow, deforming by 41.7%.
• Proposed a dynein activation pattern consistent with clockwise active cilia rotation.

Conclusions:

• The study supports the 'two-cilia' hypothesis for left-right symmetry breaking.
• Computational modeling provides insights into the physical mechanisms involved.
• Identified a plausible protein motor activation pattern driving embryonic cilia rotation.