How does a fly make itself? Dissecting morphogenesis with
laser-microsurgery.
Shane Hutson, Vanderbilt University
During the development of an organism, sheets of epithelial cells dynamically expand, contract and bend. In so doing, they generate organismal form in a process known as morphogenesis - a process driven by cell-generated forces. Mathematical and computational models for the generation, distribution and regulation of these forces abound, but very few attempts have been made to test the validity of these models in vivo. We present a method for probing morphogenetic forces in vivo through laser hole-drilling - a method borrowed from the analysis of residual stress in manufactured widgets - in which laser-microsurgery is used to ablate a single cell edge or surface. The adjacent cells move away from this wound (i.e. recoil) in accord with their mechanical properties and the post-ablation stress imbalance. We have applied this method to the embryonic epithelia of GFP-labeled fruit fly (Drosophila) embryos. We ablate a single cell edge or surface and measure the subsequent plasma, cavitation and tissue recoil dynamics. With an appropriate inversion, these dynamics are a reporter of the both the mechanical properties and stresses inside a living fly embryo.