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Cytoplasmic flows in starfish oocytes are fully determined by cortical contractions

Cytoplasmic flows are an ubiquitous feature of biological systems, in particular in large cells, such as oocytes and eggs in early animal development. Here we show that cytoplasmic flows in starfish oocytes, which can be imaged well with transmission light microscopy, are fully determined by the cor...

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Autores principales: Klughammer, Nils, Bischof, Johanna, Schnellbächer, Nikolas D., Callegari, Andrea, Lénárt, Péter, Schwarz, Ulrich S.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6264906/
https://www.ncbi.nlm.nih.gov/pubmed/30439934
http://dx.doi.org/10.1371/journal.pcbi.1006588
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author Klughammer, Nils
Bischof, Johanna
Schnellbächer, Nikolas D.
Callegari, Andrea
Lénárt, Péter
Schwarz, Ulrich S.
author_facet Klughammer, Nils
Bischof, Johanna
Schnellbächer, Nikolas D.
Callegari, Andrea
Lénárt, Péter
Schwarz, Ulrich S.
author_sort Klughammer, Nils
collection PubMed
description Cytoplasmic flows are an ubiquitous feature of biological systems, in particular in large cells, such as oocytes and eggs in early animal development. Here we show that cytoplasmic flows in starfish oocytes, which can be imaged well with transmission light microscopy, are fully determined by the cortical dynamics during surface contraction waves. We first show that the dynamics of the oocyte surface is highly symmetric around the animal-vegetal axis. We then mathematically solve the Stokes equation for flows inside a deforming sphere using the measured surface displacements as boundary conditions. Our theoretical predictions agree very well with the intracellular flows quantified by particle image velocimetry, proving that during this stage the starfish cytoplasm behaves as a simple Newtonian fluid on the micrometer scale. We calculate the pressure field inside the oocyte and find that its gradient is too small as to explain polar body extrusion, in contrast to earlier suggestions. Myosin II inhibition by blebbistatin confirms this conclusion, because it diminishes cell shape changes and hydrodynamic flow, but does not abolish polar body formation.
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spelling pubmed-62649062018-12-19 Cytoplasmic flows in starfish oocytes are fully determined by cortical contractions Klughammer, Nils Bischof, Johanna Schnellbächer, Nikolas D. Callegari, Andrea Lénárt, Péter Schwarz, Ulrich S. PLoS Comput Biol Research Article Cytoplasmic flows are an ubiquitous feature of biological systems, in particular in large cells, such as oocytes and eggs in early animal development. Here we show that cytoplasmic flows in starfish oocytes, which can be imaged well with transmission light microscopy, are fully determined by the cortical dynamics during surface contraction waves. We first show that the dynamics of the oocyte surface is highly symmetric around the animal-vegetal axis. We then mathematically solve the Stokes equation for flows inside a deforming sphere using the measured surface displacements as boundary conditions. Our theoretical predictions agree very well with the intracellular flows quantified by particle image velocimetry, proving that during this stage the starfish cytoplasm behaves as a simple Newtonian fluid on the micrometer scale. We calculate the pressure field inside the oocyte and find that its gradient is too small as to explain polar body extrusion, in contrast to earlier suggestions. Myosin II inhibition by blebbistatin confirms this conclusion, because it diminishes cell shape changes and hydrodynamic flow, but does not abolish polar body formation. Public Library of Science 2018-11-15 /pmc/articles/PMC6264906/ /pubmed/30439934 http://dx.doi.org/10.1371/journal.pcbi.1006588 Text en © 2018 Klughammer et al http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Klughammer, Nils
Bischof, Johanna
Schnellbächer, Nikolas D.
Callegari, Andrea
Lénárt, Péter
Schwarz, Ulrich S.
Cytoplasmic flows in starfish oocytes are fully determined by cortical contractions
title Cytoplasmic flows in starfish oocytes are fully determined by cortical contractions
title_full Cytoplasmic flows in starfish oocytes are fully determined by cortical contractions
title_fullStr Cytoplasmic flows in starfish oocytes are fully determined by cortical contractions
title_full_unstemmed Cytoplasmic flows in starfish oocytes are fully determined by cortical contractions
title_short Cytoplasmic flows in starfish oocytes are fully determined by cortical contractions
title_sort cytoplasmic flows in starfish oocytes are fully determined by cortical contractions
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6264906/
https://www.ncbi.nlm.nih.gov/pubmed/30439934
http://dx.doi.org/10.1371/journal.pcbi.1006588
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