Theoretical relationships between axoneme distortion and internal forces and torques in ciliary beating

Area of Science:

• Biophysics
• Cell Biology
• Structural Biology

Background:

• The axoneme powers cilia and flagella movement through complex mechanical processes.
• High-resolution imaging reveals axoneme structure, but its mechanical function remains unclear.
• Current models often assume signal-based dynein regulation for oscillations.

Purpose of the Study:

• To investigate the mechanical roles of axoneme components in generating oscillatory motion.
• To explore the potential for dynamic mechanical instability to drive axonemal beating.
• To develop a multifilament model incorporating structural distortions during bending.

Main Methods:

• Utilizing cryoelectron-tomography (cryo-ET) and subtomogram averaging for structural analysis.
• Developing a theoretical multifilament model of the axoneme.
• Analyzing the mechanical responses of axonemal components to bending-induced loads.

Main Results:

• Radial spokes may confer torsional stiffness by maintaining alignment between central pair and outer doublets.
• Dynein arm kinematics influence the relationship between active forces and bending moments on doublets.
• These factors enhance the capacity of models to produce oscillatory waveforms via instability.

Conclusions:

• Axonemal components actively resist and respond to mechanical loads during bending.
• Dynamic mechanical instability, rather than solely signal-based regulation, may drive axonemal oscillations.
• A deeper understanding of these mechanics is crucial for explaining cilia and flagella motility.