Co-movement of astral microtubules, organelles and F-actin by dynein and actomyosin forces in frog egg cytoplasm
- Harvard Medical School, United States
- Flatiron Institute, United States
Abstract
How bulk cytoplasm generates forces to separate post-anaphase microtubule (MT) asters in Xenopus laevis and other large eggs remains unclear. Previous models proposed that dynein-based, inward organelle transport generates length-dependent pulling forces that move centrosomes and MTs outwards while other components of cytoplasm are static. We imaged aster movement by dynein and actomyosin forces in Xenopus egg extracts and observed outward co-movement of MTs, endoplasmic reticulum (ER), mitochondria, acidic organelles, F-actin, keratin and soluble fluorescein. Organelles exhibited a burst of dynein-dependent inward movement at the growing aster periphery, then mostly halted inside the aster, while dynein-coated beads moved to the aster center at a constant rate, suggesting organelle movement is limited by brake proteins or other sources of drag. These observations call for new models in which all components of the cytoplasm comprise a mechanically integrated aster gel that moves collectively in response to dynein and actomyosin forces.
Data availability
All data generated or analyzed during this study are included in the manuscript and supporting files. We are in the process of uploading the source data and code to GitHub https://github.com/jamespelletier/Co-movement
Article and author information
Author details
Timothy J Mitchison
Funding
National Institute of General Medical Sciences (R35GM131753)
- Timothy J Mitchison
Hertz Foundation
- James F Pelletier
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All of the animals were handled according to approved institutional animal care and use committee (IACUC) protocols (#IS00000519-3) of Harvard Medical School. The institution has an approved Animal Welfare Assurance on file with the Office of Laboratory Animal Welfare. The Assurance number on file is #D16-00270.
Copyright
© 2020, Pelletier et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Co-movement of astral microtubules, organelles and F-actin by dynein and actomyosin forces in frog egg cytoplasm
eLife 9:e60047.
https://doi.org/10.7554/eLife.60047
