Dresden 2014 – scientific programme
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BP: Fachverband Biologische Physik
BP 7: Posters: Cell adhesion, mechanics and migration
BP 7.2: Poster
Monday, March 31, 2014, 17:30–19:30, P3
Xenopus spindle size is set by the microtubule mass balance in an active liquid crystal — •Johannes Baumgart1, Simone B. Reber2, Anthony A. Hyman2, and Frank Julicher1 — 1Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden, Germany — 2Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauer Str. 108, 01307 Dresden, Germany
The spindle apparatus consists mainly of microtubules and associated proteins. Correct spindle length is essential to reliably segregate chromosomes. Although we have extensive knowledge of microtubule dynamics, we still lack an understanding of how their collective properties give rise to a spindle with a defined size. We describe the spindle as an active liquid crystal because the individual rod-like microtubules turnover fast and are short compared to the overall spindle length. Furthermore, they slide and align by the activity of specific motors and crosslinkers. This allows us to determine spindle size by using mass balance of dynamic microtubules considering a constant spindle mass density. Spindle size then results from the balance of localized nucleation mediated by chromatin and global disassembly of microtubules.
This model implies a linear relationship between spindle length and microtubule growth velocity. This is indeed observed experimentally (Reber et al., Nat Cell Biol, 2013, 15, 1116–1122). In experiments, Xenopus laevis egg extract was used, which rules out size control due to external constrains and component limitations.