For cells to divide properly, they must apply forces and move chromosomes to the correct positions. How do motor proteins in the mitotic spindle create proper chromosome movements? This sequence of images shows aberrant kinetochore pushing movement by microtubules in a cell lacking a kinesin-8 motor. Microtubules and mitotic spindle (red) and spindle-pole bodies and kinetochore (green) in fission-yeast cells in which lost chromosomes have been induced to study kinetochore capture and subsequent chromosome movements.
Motor proteins that walk on biological filaments perform important jobs in cells. How exactly do these motors distribute along the filaments? This image shows the phase plane of a model of motors that move on antiparallel microtubule overlaps and switch between filaments. At sufficiently high switching rate, new transition points (labeled TP) appear in the phase plane, which leads to a new phase with multiple domain walls. The phase-plane approach brings a new set of mathematical tools to the study of multi-lane motor problems.
Bipolar mitotic spindles form from a monopolar initial condition in a fundamental construction problem. Microtubules, motors, and cross-linkers are important for bipolarity, but the mechanisms necessary and sufficient for spindle assembly remain unknown. We developed a physical model that exhibits de novo bipolar spindle formation that agrees quantitatively with our experiments in fission yeast, thereby establishing a minimal system with which to interrogate collective self-assembly. This work was published in Science Advances.
In many biological systems, such as proteins in the nuclear pore complex, proteins in cells, and membrane proteins and lipids in the presence of lipid domains, particles diffuse in a crowded environment. Crowding can cause a particle's diffusion to be anomalous, leading to a mean squared displacement that is not linear in time. We studied a model of the dynamics of tracer particles which can bind to soft obstacles, and contrasted sticky (no bound motion) and slippery (motion while bound) obstacles.