Microtubule Sliding within the Bridging Fiber Pushes Kinetochore Fibers Apart to Segregate Chromosomes

Publication date: 9 October 2017
Source:Developmental Cell, Volume 43, Issue 1
Author(s): Kruno Vukušić, Renata Buđa, Agneza Bosilj, Ana Milas, Nenad Pavin, Iva M. Tolić
During cell division, mitotic spindle microtubules segregate chromosomes by exerting forces on kinetochores. What forces drive chromosome segregation in anaphase remains a central question. The current model for anaphase in human cells includes shortening of kinetochore fibers and separation of spindle poles. Both processes require kinetochores to be linked with the poles. Here we show, by combining laser ablation, photoactivation, and theoretical modeling, that kinetochores can separate without any attachment to one spindle pole. This separation requires the bridging fiber, a microtubule bundle that connects sister kinetochore fibers. Bridging fiber microtubules in intact spindles slide apart with kinetochore fibers, indicating strong crosslinks between them. We conclude that sliding of microtubules within the bridging fibers drives pole separation and pushes kinetochore fibers poleward by the friction of passive crosslinks between these fibers. Thus, sliding within the bridging fiber works together with the shortening of kinetochore fibers to segregate chromosomes.

Graphical abstract

Teaser

The forces that drive chromosome segregation in mitosis in human cells remain poorly understood. Vukušić, Buđa et al. combine laser ablation, photoactivation, and theory to uncover a key role for bridging fibers, non-kinetochore microtubule bundles, in spindle pole separation. Forces from kinetochore and bridging fiber crosslinking contribute to chromosome segregation.


http://ift.tt/2gqkz7X