The microtubule organization in the zebrafish yolk adapts to transgene-mediated phenotypic variations

Abstract

The organization of microtubule networks in the cells is orchestrated by subcellular structures named microtubule organizing centers (MTOCs). In zebrafish embryos, the yolk is surrounded by a cytoplasmic layer containing a vast network of microtubules. In order to understand how this complex network is organized, we use dclk2-GFP zebrafish embryos, as a microtubule reporter line, and Light Sheet Fluorescence Microscopy. We find that this organization is mediated by a variable number of aster-like MTOCs during epiboly, and that it does not follow a rigid scheme, exemplifying developmental robustness. We characterize asters morphology, dynamics, and their uniform distribution in the yolk sphere. Consistent with their role as MTOCs we find that they contain key molecular machinery for MTs dynamics, amongst which centrin marks the assignation of MTOCs over time. Finally, we demonstrate that merely the overexpression of dclk2-GFP in wild type embryos can induce the formation of asters. We propose dclk2-GFP embryos as a model for the study of the collective behaviour of microtubules in complex systems.