The syncytial Drosophila embryo as a mechanically excitable medium

TL;DR

This study models the mitotic wavefronts in early Drosophila embryos as nonlinear waves propagating through a mechanically excitable medium, combining microscopy analysis and theoretical models to understand their dynamics.

Contribution

It introduces a novel mechanical signaling model to explain mitotic wavefront propagation, integrating experimental observations with theoretical analysis.

Findings

Mitotic wavefronts travel at a decreasing speed across cycles.

Wavefronts correspond to metaphase and anaphase onsets.

Mechanical signaling best explains the wavefront speed dependence.

Abstract

Mitosis in the early syncytial Drosophila embryo is highly correlated in space and time, as manifested in mitotic wavefronts that propagate across the embryo. In this paper we investigate the idea that the embryo can be considered a mechanically-excitable medium, and that mitotic wavefronts can be understood as nonlinear wavefronts that propagate through this medium. We study the wavefronts via both image analysis of confocal microscopy videos and theoretical models. We find that the mitotic waves travel across the embryo at a well-defined speed that decreases with replication cycle. We find two markers of the wavefront in each cycle, corresponding to the onsets of metaphase and anaphase. Each of these onsets is followed by displacements of the nuclei that obey the same wavefront pattern. To understand the mitotic wavefronts theoretically we analyze wavefront propagation in excitable media. We study two classes of models, one with biochemical signaling and one with mechanical signaling. We find that the dependence of wavefront speed on cycle number is most naturally explained by mechanical signaling, and that the entire process suggests a scenario in which biochemical and mechanical signaling are coupled.