Dr. Christian Tischer, Damian Brunner, and Marileen Dogterom
Institute for Atomic and Molecular Physics, NL

Microtubules are protein polymers that form an integral part of functional cytoskeletal networks inside eukaryotic cells. Specific microtubule networks are central to the organization of the intracellular space and they are involved in the control of  cell morphology. To understand how microtubules fulfill these functions it is important to understand how the lengths of microtubules are adapted to cell size and shape. In fact, individual microtubules typically have no fixed length but constantly switch between a growing and a shrinking state in a process termed dynamic instability. One of the keys to better understand microtubule function is to investigate how the rates that govern microtubule dynamics are regulated inside cells.
In interphase fission yeast (S. Pombe) cells, microtubule catastrophes occur preferentially at the distal ends of elongating cells, but the mechanism by which this spatial selectivity is obtained is not yet understood. We developed automated image analysis procedures to measure microtubule catastrophe rates with unprecedented statistics and at high spatial resolution. We find that: (i) pushing forces generated by growing microtubules induce catastrophes specifically at the cell poles; and (ii) long microtubules undergo catastrophes more often than short ones. Moreover, we show that the microtubule destabilizing motor protein klp5p enhances the catastrophe rate in a spatially selective way.