Modelling the role of catastrophe, crossover and Katanin in the self organisation of cortical microtubules

Cortical microtubules can form ordered arrays through interactions among themselves. When an incident microtubule collides with a barrier microtubule it may entrain if below a certain angle of collision. Else it undergoes collision induced catastrophe (CIC) or crosses over the barrier microtubule. It has been proposed that katanin, a microtubule severing protein, contributes to ordering by severing the overlying microtubule at these crossover sites.

We present a 3-state computational model to show how the probability of CIC against crossover affects microtubule ordering and how katanin interacts with this. We observe the highest order at 0.8 CIC and a rapid drop in order as CIC decreases past 0.5. Enabling katanin at 0.4 CIC increases the order towards 0.8 CIC levels, however, as the CIC drops further towards 0.1 CIC the time needed for katanin to localise and sever the microtubule and form an ordered array greatly decreases and does not appear biologically feasible. Therefore we propose that in cells that exhibit a very low level of CIC but have a clear ordered microtubule array, that katanin and microtubule-to-microtubule interactions are not sufficient and other factors are needed to develop an ordered microtubule array.