Mapping the Requirement of Local Cortical Integrity for Cytokinesis by Local Drug Release

O'Connell et al., Curr. Biol. 11:702-707 (2001)

The conventional purse string model predicts that the integrity of equatorial cortex is critical for cytokinesis, while the cortex elsewhere plays only a passive role. To assess the requirement of cortical integrity in different regions, actin disrupting agents were released in a highly localized manner near either the equator or the pole. Drug distribution was confined by using a release needle in conjunction with a suction pipette placed a few microns away.

Local Disruption of Equatorial Cortex Facilitates Cytokinesis

Contrary to the prediction, local release of cytochalasin D near the equator not only allows cytokinesis to proceed but appears to facilitate the process, suggesting that the integrity of equatorial cortex may not be essential for the ingression of these adherent epithelial cells. Instead, the rate-limiting step may be disassembly of the equatorial cortex to allow ingression to proceed. Recording time, 19 min.

Local Disruption of Polar Cortex Inhibits Cytokinesis

Equally surprising is that local release of cytochalasin D near the spindle pole inhibits cytokinesis, suggesting that the integrity of polar cortex is essential. Together, these observations suggest that cytokinesis in these cells may be effected by global cortical contraction and equatorial cortical disintegration. This conclusion differs substantially from the conventional purse string model. Recording time, 37 min.

Local Stabilization of Equatorial Cortex Inhibits Cytokinesis

Local release of jasplakinolide, a drug that stabilizes actin filaments, near the equator of dividing NRK cells inhibits cytokinesis, consistent with the idea that disintegration of the equatorial cortex is essential. Recording time, 39 min.