1. Academic Validation
  2. Rac1 signalling coordinates epiboly movement by differential regulation of actin cytoskeleton in zebrafish

Rac1 signalling coordinates epiboly movement by differential regulation of actin cytoskeleton in zebrafish

  • Biochem Biophys Res Commun. 2017 Aug 26;490(3):1059-1065. doi: 10.1016/j.bbrc.2017.06.165.
Yu-Long Li 1 Ming Shao 1 De-Li Shi 2
Affiliations

Affiliations

  • 1 School of Life Sciences, Shandong University, 27, Shanda Nan Road, Jinan 250100, China.
  • 2 School of Life Sciences, Shandong University, 27, Shanda Nan Road, Jinan 250100, China; Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR7622, IBPS-Developmental Biology Laboratory, 75005 Paris, France. Electronic address: [email protected].
Abstract

Dynamic Cytoskeleton organization is essential for polarized cell behaviours in a wide variety of morphogenetic events. In zebrafish, epiboly involves coordinated cell shape changes and expansion of cell layers to close the blastopore, but many important regulatory aspects are still unclear. Especially, the spatio-temporal regulation and function of actin structures remain to be determined for a better understanding of the mechanisms that coordinate epiboly movement. Here we show that Rac1 signalling, likely functions downstream of phosphatiditylinositol-3 kinase, is required for F-actin organization during epiboly progression in zebtafish. Using a dominant negative mutant of Rac1 and specific inhibitors to block the activation of this pathway, we find that marginal contractile actin ring is sensitive to inhibition of Rac1 signalling. In particular, we identify a novel function for this actin structure in retaining the external yolk syncytial nuclei within the margin of enveloping layer for coordinated movement toward the vegetal pole. Furthermore, we find that F-actin bundles, progressively formed in the vegetal cortex of the yolk cell, act in concert with marginal actin ring and play an active role in pulling external yolk syncytial nuclei toward the vegetal pole direction. This study uncovers novel roles of different actin structures in orchestrating epiboly movement. It helps to provide insight into the mechanisms regulating cellular polarization during early development.

Keywords

Actin cytoskeleton; Epiboly; Gastrulation; Phosphatiditylinositol-3 kinase; Rac1; Zebrafish.

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