A computational model for studying severing on a Microtubule lattice

The microtubule cytoskeleton is shaped by several proteins which regulate all aspects of microtubule growth and shrinkage. Severing proteins are one such microtubule regulator that plays a key role in many cellular processes including mitosis and meiosis, neurodevelopment, and cell migration. How severing proteins work with other microtubule regulating proteins in order to perform these functions is not well understood. Recent in-vitro experiments have shown that free tubulin can repair nanoscale damages of microtubules created by severing proteins. Based on this observation, we study a model that describes microtubule severing as a competition between the processes of damage spreading and tubulin-induced repair. We use a two-dimensional computational model that simulates the removal and reincorporation of tubulin dimers on a microtubule lattice, and quantitatively analyze the resulting severing events. We compute the probability of severing events and the time for severing events to complete as a function of tubulin concentration and compare our results to published results to extract information about severing events. Our preliminary results show similar qualitative behaviors to those seen in published experiments, such as mean severing time scaling with concentration of free tubulin. This model can be extended to examine the effect of tubulin-induced repair on rescues in dynamic microtubules and analyze the size of newly incorporated tubulin.