Growing Microtubules Push the Oocyte Nucleus to Polarize the Drosophila Dorsal-Ventral Axis

Abstract

Pull Me-No!-Push You The Drosophila dorsal-ventral (DV) axis is polarized by the movement of the nucleus from the posterior end of the oocyte to its anterior margin. It has long been assumed that the nucleus is pulled to the anterior end by the molecular motor dynein along the polarized microtubule cytoskeleton that defines the anterior-posterior (AP) axis. Using live imaging, Zhao et al. (p. 999, published online 12 April; see the Perspective by Bowerman and O'Rourke ) now demonstrate that the nucleus is pushed toward the anterior by the force exerted by growing microtubules hitting its posterior side. DV polarity thus depends on the posterior positioning of the microtubule organizing center rather than on AP axis formation.