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Constriction kinetics of the cytokinetic ring are expected to depend on dynamic adjustment of contractile ring composition, but the impact of ring component abundance dynamics on ring constriction is understudied. Computational models generally assume that contractile networks maintain constant total amounts of components, which is not always true. To test how compositional dynamics affect constriction kinetics, we first measured F-actin, non-muscle myosin II, septin, and anillin during Caenorhabditis elegans zygotic mitosis. A custom microfluidic device that positioned the cell with the division plane parallel to a light sheet allowed even illumination of the cytokinetic ring. Measured component abundances were implemented in a three-dimensional agent-based model of a membrane-associated contractile ring. With constant network component amounts, constriction completed with biologically unrealistic kinetics. However, imposing the measured changes in component quantities allowed this model to elicit realistic constriction kinetics. Simulated networks were more sensitive to changes in motor and filament amounts than those of crosslinkers and tethers. Our findings highlight the importance of network composition for actomyosin contraction kinetics.

Constriction kinetics of the cytokinetic ring are expected to depend on dynamic adjustment of ring composition, but the impact of component abundance dynamics on ring constriction is understudied. Computational models generally assume that contractile networks maintain constant composition. To test how compositional dynamics affect constriction kinetics, we first measured F-actin, non-muscle myosin II, septin, and anillin during C. elegans zygotic mitosis. A custom microfluidic device that positioned the cell with the division plane parallel to a light sheet allowed even illumination of the cytokinetic ring. Measured component abundances were implemented in an agent-based 3D model of a membrane-associated contractile ring. With constant network composition, constriction occurred with biologically unrealistic kinetics. Measured changes in component quantities elicited realistic constriction kinetics. Simulated networks were more sensitive to changes in motor and filament amounts, than that of crosslinkers and tethers. Our findings highlight the importance of network composition for actomyosin contraction kinetics.SummaryWe created a microfluidic device compatible with high numerical aperture light sheet microscopy to measure cytokinetic ring component abundance in the C. elegans zygote. Implementing measured dynamics into our three-dimensional agent-based model of a contractile ring elicited biologically realistic kinetics.