Microtubule depolymerization and severing during mitosis

Abstract

Cell division involves the separation of chromosomes (mitosis) and the cytoplasm (cytokinesis) of a mother cell into two daughter cells. Many of the physical event during mitosis rely on the dynamics of the microtubules within the mitotic bipolar spindle and their constant remodelling. In the last phases of mitosis, the spindle needs to be highly dynamic to segregate the chromosomes and needs to quickly disassemble to allow for abscission of the membrane to complete cytokinesis. Here, we first discuss the microtubule severing enzymes and depolymerizing kinesins involved in spindle microtubule regulation. Second, we discuss their function and regulation over the course of metaphase to abscission. Microtubule severing enzymes of the meiotic clade of AAA ATPases function through removing tubulin dimers from the lattice and can be either positive or negative regulators of total cellular microtubule mass. They play important functions at spindle poles and in disassembling the spindle during cytokinesis. Depolymerizing kinesins of the kinesin-13 family function at both spindle poles and kinetochores to facilitate microtubule depolymerization. Kinesin-8 family members destabilize microtubules in a length dependent manner and have both a stabilizing and a destabilizing effect on microtubules in different contexts. They have diverse roles over the course of mitosis, but in general regulate the spatial dynamics of microtubules by keeping their length within a specific range.