Relationships between the central spindle and the contractile ring during cytokinesis in animal cells

During late anaphase and telophase, animal cells develop a bundle of antipa rallel, interdigitating microtubules between the two daughter nuclei. Recen t data indicate that this structure, called the central spindle, plays an e ssential role during cytokinesis. Studies in Drosophila and on vertebrate c ells strongly suggest that the molecular signals for cytokinesis specifical ly emanate from the central spindle midzone. Moreover, the analysis of Dros ophila mutants defective in cytokinesis has revealed a cooperative interact ion between the central spindle microtubules and the contractile ring: when either of these structures is perturbed, the proper assembly of the other is disrupted. Based on these results we propose a model for the role of the central spindle during cytokinesis. We suggest that the interaction betwee n central spindle microtubules and cortical actin filaments leads to two ea rly events crucial for cytokinesis: the positioning of the contractile ring , and the stabilization of the plus ends of the interdigitating microtubule s that comprise the central spindle. The latter event would provide the cel l with a specialized microtubule scaffold that could mediate the translocat ion of plus-end-directed molecular motors to the cell's equator. Among the cargoes transported by these motors could be proteins involved in the regul ation and execution of cytokinesis. Microsc. Res. Tech. 49:202-208, 2000. ( C) 2000 Wiley-Liss, Inc.