Model-based trajectory classification of anchored molecular motor-biopolymer interactions

Area of Science:

• Cell Biology
• Biophysics
• Molecular Motors

Background:

• Cellular forces at the cortex drive key events in zygotic mitosis, including chromosome segregation and asymmetric cell division.
• Microtubule-cortex interactions position the mitotic spindle, essential for asymmetric cell division, but the individual force-generating units remain unidentified.
• Existing methods lack the spatiotemporal resolution to pinpoint these individual cortical force generators in vivo.

Purpose of the Study:

• To develop a novel method for identifying and quantifying microtubule-dependent cortical force-generating units in vivo.
• To elucidate the mechanical and molecular mechanisms underlying force generation at the cell cortex during mitosis.
• To provide a tool for understanding dynein motor function and regulation in cellular processes.

Main Methods:

• Utilized single-molecule imaging of fluorescently labeled dynein motors.
• Developed a computational model to classify dynein trajectories based on microtubule interaction.
• Applied RNA interference (RNAi) to deplete tubulin (TBA-2) to validate the method's robustness.

Main Results:

• Successfully determined the location and relative number of microtubule-dependent cortical force-generating units.
• The dynein trajectory classification method accurately reflected known force asymmetries in C. elegans zygote mitosis.
• Depletion of tubulin (TBA-2) led to a predicted decrease in microtubule-engaged dynein trajectories.

Conclusions:

• The developed technique enables high spatiotemporal resolution identification of individual cortical force-generating units.
• This method is valuable for defining the molecular mechanisms of dynein-mediated cortical force generation.
• The approach is applicable to studying other systems involving anchored motor proteins interacting with biopolymers.