Model of myosin node aggregation into a contractile ring: the effect of local alignment

Area of Science:

• Cell Biology
• Biophysics
• Computational Biology

Background:

• Actomyosin bundles, crucial for cell division, often form via myosin cluster aggregation.
• In fission yeast, contractile ring assembly involves the condensation of cortical nodes into a ring structure.
• Previous models like SCPR explain node transport but not transient linear or meshwork structures.

Purpose of the Study:

• To refine the search, capture, pull, and release (SCPR) model by incorporating local node alignment mechanisms.
• To investigate the impact of these alignment forces on contractile ring formation numerically.
• To reproduce experimentally observed transient structures during ring assembly.

Main Methods:

• Numerical simulation of a modified SCPR model including short-range aligning forces between nodes.
• Systematic variation of model parameters to identify conditions yielding viable ring formation.
• Comparison of simulated transient structures with experimental observations in wild-type and mutant fission yeast cells.

Main Results:

• The enhanced model, incorporating local alignment, successfully generates transient linear and meshwork structures.
• Viable contractile rings were formed within a realistic range of parameter values.
• Simulated structures closely resemble those observed in wild-type and cdc25-22 mutant cells during ring assembly.

Conclusions:

• Local node alignment is a critical, previously unmodeled, component in contractile ring formation.
• The study supports a hierarchical self-organization model for contractile rings, involving long-range transport followed by local stabilization.
• Unresolved mechanisms involving structural components, cross-linking, and bundling proteins likely contribute to node alignment.