Wnt-controlled sphingolipids modulate Anthrax Toxin Receptor palmitoylation to regulate oriented mitosis in zebrafish

I Castanon,J T Hannich,M Dubois,L Abrami,M Gonzalez-Gaitan,F Huber,M Müller,F G Van Der Goot

doi:10.1038/s41467-020-17196-3

Abstract

Oriented cell division is a fundamental mechanism to control asymmetric stem cell division, neural tube elongation and body axis extension, among other processes. During zebrafish gastrulation, when the body axis extends, dorsal epiblast cells display divisions that are robustly oriented along the animal-vegetal embryonic axis. Here, we use a combination of lipidomics, metabolic tracer analysis and quantitative image analysis to show that sphingolipids mediate spindle positioning during oriented division of epiblast cells. We identify the Wnt signaling as a regulator of sphingolipid synthesis that mediates the activity of serine palmitoyltransferase (SPT), the first and rate-limiting enzyme in sphingolipid production. Sphingolipids determine the palmitoylation state of the Anthrax receptor, which then positions the mitotic spindle of dividing epiblast cells. Our data show how Wnt signaling mediates sphingolipid-dependent oriented division and how sphingolipids determine Anthrax receptor palmitoylation, which ultimately controls the activation of Diaphanous to mediate spindle rotation and oriented mitosis.

Highlights

Oriented cell division is a fundamental mechanism to control asymmetric stem cell division, neural tube elongation and body axis extension, among other processes
We find that sphingolipids mediate mitotic spindle positioning by regulating the palmitoylation state of the Anthrax toxin receptor, which in turn is critical for the activation of Diaphanous to mediate the rotation of the spindle during oriented mitosis of epiblast cells
We have previously shown that the actin cytoskeleton plays three distinct roles during oriented division of epiblast cells[5]: (i) in metaphase, the actin cytoskeleton is organized in a RhoA-dependent polarized cortical F-actin cap, which aligns with the embryonic axis, (ii) F-actin binds to Anthrax toxin receptor 2a (Antxr2a), recruiting the receptor to the cap and, (iii) actin torques the mitotic spindle until it becomes aligned with the cap in a Diaphanous-dependent manner (Fig. 5a)

Summary

Introduction

Oriented cell division is a fundamental mechanism to control asymmetric stem cell division, neural tube elongation and body axis extension, among other processes. We have previously shown that these cells form a polarized F-actin cap in metaphase that is aligned with respect to the embryonic axis, a process mediated by the Wnt/Planar Cell Polarity (PCP) pathway[5] This cortical F-actin cap triggers the spatial redistribution of the transmembrane protein Anthrax toxin receptor 2a (Antxr2a), which becomes enriched at the Factin cap and is required to position the mitotic spindle along the embryonic axis[5]. We find that sphingolipids mediate mitotic spindle positioning by regulating the palmitoylation state of the Anthrax toxin receptor, which in turn is critical for the activation of Diaphanous to mediate the rotation of the spindle during oriented mitosis of epiblast cells

Methods

Results

Conclusion