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Updated: Dec 6, 2025

Reconstitution of Basic Mitotic Spindles in Spherical Emulsion Droplets
Published on: August 13, 2016
A Pushing Mechanism for Microtubule Aster Positioning in a Large Cell Type
Johnathan L Meaders1, Salvador N de Matos2, David R Burgess1
1Department of Biology, Boston College, Chestnut Hill, MA 02467, USA; Marine Biological Laboratory, Woods Hole, MA 02543, USA.
Abstract:
After fertilization, microtubule (MT) sperm asters undergo long-range migration to accurately position pronuclei. Due to the large sizes of zygotes, the forces driving aster migration are considered to be from pulling on the astral MTs by dynein, with no significant contribution from pushing forces. Here, we re-investigate the forces responsible for sperm aster centration in sea urchin zygotes. Our quantifications of aster geometry and MT density preclude a pulling mechanism. Manipulation of aster radial lengths and growth rates, combined with quantitative tracking of aster migration dynamics, indicates that aster migration is equal to the length of rear aster radii, supporting a pushing model for centration. We find that dynein inhibition causes an increase in aster migration rates. Finally, ablation of rear astral MTs halts migration, whereas front and side ablations do not. Collectively, our data indicate that a pushing mechanism can drive the migration of asters in a large cell type.
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