Affiliation:
1. Instituto Gulbenkian de Ciência, Fundação Calouste Gulbenkian
2. Mechanobiology Institute and Department of Biological Sciences, National University of Singapore
3. Institute of Molecular and Cellular Biology
4. Centre for Mechanochemical Cell Biology, Warwick Medical School, University of Warwick
Abstract
Microtubule asters are essential in localizing the action of microtubules in processes including mitosis and organelle positioning. In large cells, such as the one-cell sea urchin embryo, aster dynamics are dominated by hydrodynamic pulling forces. However, in systems with more densely positioned nuclei such as the early
Drosophila
embryo, which packs around 6000 nuclei within the syncytium in a crystalline-like order, it is unclear what processes dominate aster dynamics. Here, we take advantage of a cell cycle regulation
Drosophila
mutant to generate embryos with multiple asters, independent from nuclei. We use an
ex vivo
assay to further simplify this biological system to explore the forces generated by and between asters. Through live imaging, drug and optical perturbations, and theoretical modelling, we demonstrate that these asters likely generate an effective pushing force over short distances.Using cytosolic explants from
Drosophila
syncytial embryos combined with quantitative microscopy and perturbations, de-Carvalho
et al
., reveal the mechanical forces separating
Drosophila
microtubule asters. Aster separation drives precise nuclear positioning in multinucleated embryo cells, a vital process for tissue formation and gene expression during subsequent embryo development.
Publisher
eLife Sciences Publications, Ltd