Spindle oscillations during asymmetric cell division require a threshold number of active cortical force generators.

@article{citeulike:1083026, abstract = {BACKGROUND: Asymmetric division of the C. elegans zygote is due to the posterior-directed movement of the mitotic spindle during metaphase and anaphase. During this movement along the anterior-posterior axis, the spindle oscillates transversely. These motions are thought to be driven by a force-generating complex-possibly containing the motor protein cytoplasmic dynein-that is located at the cell cortex and pulls on microtubules growing out from the spindle poles. A theoretical analysis indicates that the oscillations might arise from mechanical coordination of the force-generating motors, and this coordination is mediated by the load dependence of the motors' detachment from the microtubules. The model predicts that the motor activity must exceed a threshold for oscillations to occur. RESULTS: We have tested the existence of a threshold by using RNA interference to gradually reduce the levels of dynein light intermediate chain as well as GPR-1 and GPR-2 that are involved in the G protein-mediated regulation of the force generators. We found an abrupt cessation of oscillations as expected if the motor activity dropped below a threshold. Furthermore, we can account for the complex choreography of the mitotic spindle-the precise temporal coordination of the buildup and die-down of the transverse oscillations with the posterior displacement-by a gradual increase in the processivity of a single type of motor machinery during metaphase and anaphase. CONCLUSIONS: The agreement between our results and modeling suggests that the force generators themselves have the intrinsic capability of generating oscillations when opposing forces exceed a threshold.}, address = {Max-Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.}, author = {Pecreaux, J. and R\"{o}per, J. C. and Kruse, K. and J\"{u}licher, F. and Hyman, A. A. and Grill, S. W. and Howard, J. }, citeulike-article-id = {1083026}, doi = {http://dx.doi.org/10.1016/j.cub.2006.09.030}, issn = {0960-9822}, journal = {Curr Biol}, keywords = {c\_elegans, simulation, spindle}, month = {November}, number = {21}, pages = {2111--2122}, posted-at = {2007-02-02 09:13:53}, priority = {0}, title = {Spindle oscillations during asymmetric cell division require a threshold number of active cortical force generators.}, url = {http://dx.doi.org/10.1016/j.cub.2006.09.030}, volume = {16}, year = {2006} }

TY - JOUR ID - citeulike:1083026 L3 - citeulike-article-id:1083026 TI - Spindle oscillations during asymmetric cell division require a threshold number of active cortical force generators. JF - Curr Biol VL - 16 IS - 21 SP - 2111 EP - 2122 AD - Max-Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany. SN - 0960-9822 N2 - BACKGROUND: Asymmetric division of the C. elegans zygote is due to the posterior-directed movement of the mitotic spindle during metaphase and anaphase. During this movement along the anterior-posterior axis, the spindle oscillates transversely. These motions are thought to be driven by a force-generating complex-possibly containing the motor protein cytoplasmic dynein-that is located at the cell cortex and pulls on microtubules growing out from the spindle poles. A theoretical analysis indicates that the oscillations might arise from mechanical coordination of the force-generating motors, and this coordination is mediated by the load dependence of the motors' detachment from the microtubules. The model predicts that the motor activity must exceed a threshold for oscillations to occur. RESULTS: We have tested the existence of a threshold by using RNA interference to gradually reduce the levels of dynein light intermediate chain as well as GPR-1 and GPR-2 that are involved in the G protein-mediated regulation of the force generators. We found an abrupt cessation of oscillations as expected if the motor activity dropped below a threshold. Furthermore, we can account for the complex choreography of the mitotic spindle-the precise temporal coordination of the buildup and die-down of the transverse oscillations with the posterior displacement-by a gradual increase in the processivity of a single type of motor machinery during metaphase and anaphase. CONCLUSIONS: The agreement between our results and modeling suggests that the force generators themselves have the intrinsic capability of generating oscillations when opposing forces exceed a threshold. KW - c_elegans KW - simulation KW - spindle AU - Pecreaux, J AU - Röper, JC AU - Kruse, K AU - Jülicher, F AU - Hyman, AA AU - Grill, SW AU - Howard, J PY - 2006/11/07/ UR - http://dx.doi.org/10.1016/j.cub.2006.09.030 ER -