Wnt5b integrates Fak1a to mediate gastrulation cell movements via Rac1 and Cdc42.

I-Chen Hung,Jing-Ping Lin,Shyh-Jye Lee,Tang-Long Shen,Tsung-Ming Chen,Yu-Ling Tai

doi:10.1098/rsob.190273

Abstract

Focal adhesion kinase (FAK) mediates vital cellular pathways during development. Despite its necessity, how FAK regulates and integrates with other signals during early embryogenesis remains poorly understood. We found that the loss of Fak1a impaired epiboly, convergent extension and hypoblast cell migration in zebrafish embryos. We also observed a clear disturbance in cortical actin at the blastoderm margin and distribution of yolk syncytial nuclei. In addition, we investigated a possible link between Fak1a and a well-known gastrulation regulator, Wnt5b, and revealed that the overexpression of fak1a or wnt5b could cross-rescue convergence defects induced by a wnt5b or fak1a antisense morpholino (MO), respectively. Wnt5b and Fak1a were shown to converge in regulating Rac1 and Cdc42, which could synergistically rescue wnt5b and fak1a morphant phenotypes. Furthermore, we generated several alleles of fak1a mutants using CRISPR/Cas9, but those mutants only revealed mild gastrulation defects. However, injection of a subthreshold level of the wnt5b MO induced severe gastrulation defects in fak1a mutants, which suggested that the upregulated expression of wnt5b might complement the loss of Fak1a. Collectively, we demonstrated that a functional interaction between Wnt and FAK signalling mediates gastrulation cell movements via the possible regulation of Rac1 and Cdc42 and subsequent actin dynamics.

Highlights

Vertebrate gastrulation is vital to establish germ layers and body axes by coordinated cell movements in zebrafish [1,2]
We show that the loss of Fak1a impairs gastrulation cell movements via regulation of actin dynamics in zebrafish
We demonstrate that zebrafish Fak1a is chemically conserved with mammalian Focal adhesion kinase (FAK) and functions cooperatively with Wnt5b to regulate Rac1 and Cdc42 activities for the modulation of actin dynamics during gastrulation cell movements

Summary

Introduction

Vertebrate gastrulation is vital to establish germ layers and body axes by coordinated cell movements in zebrafish [1,2]. Hypoblast cells migrate on the dorsal epiblast via tightly regulated cell–cell and cell–extracellular matrix (ECM) adhesions and move anteriorly to become mesendodermal layers. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase and is central to the regulation of cell movements and cell–ECM adhesions [6,7]. It is autophosphorylated upon activation by integrin, growth factor stimuli and/or G-protein-coupled signalling [8]. The phosphorylated FAK binds to activated Src to phosphorylate additional tyrosine residues on FAK and recruits other proteins to modulate distinct signal transduction pathways involved in regulating multiple cellular functions such as cell adhesion, spreading and migration via cytoskeletal reorganization [9,10,11]

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Results

Conclusion