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

Curr Biol. 2006 Nov 7;16(21):2111-22. doi: 10.1016/j.cub.2006.09.030.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaphase / physiology
  • Animals
  • Caenorhabditis elegans / cytology*
  • Caenorhabditis elegans / physiology
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism
  • Cell Division / physiology*
  • Dyneins / genetics
  • Dyneins / metabolism
  • Metaphase / physiology
  • Models, Biological
  • RNA Interference
  • Spindle Apparatus / physiology*


  • Caenorhabditis elegans Proteins
  • G protein regulator 1, C elegans
  • G protein regulator 2, C elegans
  • Dli-1 protein, C elegans
  • Dyneins