PLoS ONE (Aug 2010)

Membrane invaginations reveal cortical sites that pull on mitotic spindles in one-cell C. elegans embryos.

  • Stefanie Redemann,
  • Jacques Pecreaux,
  • Nathan W Goehring,
  • Khaled Khairy,
  • Ernst H K Stelzer,
  • Anthony A Hyman,
  • Jonathon Howard

DOI
https://doi.org/10.1371/journal.pone.0012301
Journal volume & issue
Vol. 5, no. 8
p. e12301

Abstract

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Asymmetric positioning of the mitotic spindle in C. elegans embryos is mediated by force-generating complexes that are anchored at the plasma membrane and that pull on microtubules growing out from the spindle poles. Although asymmetric distribution of the force generators is thought to underlie asymmetric positioning of the spindle, the number and location of the force generators has not been well defined. In particular, it has not been possible to visualize individual force generating events at the cortex. We discovered that perturbation of the acto-myosin cortex leads to the formation of long membrane invaginations that are pulled from the plasma membrane toward the spindle poles. Several lines of evidence show that the invaginations, which also occur in unperturbed embryos though at lower frequency, are pulled by the same force generators responsible for spindle positioning. Thus, the invaginations serve as a tool to localize the sites of force generation at the cortex and allow us to estimate a lower limit on the number of cortical force generators within the cell.