Three-dimensional motion and torque generation of mitotic motors

• Applicant: Professor Dr. Stefan Diez
• Subject Area: Biophysics ; Cell Biology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 525453498

In mitosis, the cell is using the spindle apparatus to segregate the chromosomes. Correct segregation is essential because errors can lead to aneuploidy and ultimately cancer. During segregation, spindle fibers (i.e., bundles of microtubules that move chromosomes during cell division) need to be organized, determining the spindle shape. Molecular motors, such as kinesin-5, kinesin-14 and cytoplasmic dynein, are present in the spindle and were shown to bend microtubule bundles, which twists the spindle. Although the motors are well studied in two dimension (2D) and were shown to step in forward and sideward direction, their functioning in spindle fibers remains elusive due to the three-dimensional (3D) shape of the structure. In this project, we aim to determine the individual 3D motility parameters of human kinesin-5 (KIF11), kinesin-14 (HSET) and cytoplasmic dynein ensembles, as well as, their collective, counteracting behavior. Moreover, we plan to elucidate the role of motor extension during microtubule sliding. With regard to force generation, we will investigate the 3D torques generated by the motors with novel in vitro reconstitution assays, optical tweezers and mathematical modeling. This will clarify how forward and sideward motion as well as force production are coupled to each other. Taken together, the results of this project shall provide a detailed picture of the functioning of mitotic motors and will clarify how they contribute to spindle architecture and chromosome segregation. We expect that our findings will help to address the observed phenomenon of twist in the mitotic spindle, whose purpose could be mechanical robustness, efficient force transmission in late anaphase through release of stored bending energy or providing physical separation of adjacent bundles.

• DFG Programme: Research Grants