May 3, 2019

Lewis Thomson

10.15-10.30 Lewis Thomson

‘Exploring the emergence of 3D cell movements driving zebrafish presomitic mesoderm elongation‘

During vertebrate development, axis elongation must be tightly coupled with the process of somitogenesis to ensure that the correct number of body segments (of the correct sizes) are formed. Although the clock and wavefront model explains this coupling at the genetic level, there is little known about the cell and tissue behaviours required for axis elongation – and how conserved these are throughout vertebrate evolution. Recent work has focused on emergent properties such as the random motility gradient in chick embryos, and the liquid-to-solid transition in the zebrafish. However, as drivers of presomitic mesoderm (PSM) elongation, both models rely on the occurrence of posterior growth – something that we have shown is not occurring in zebrafish. I will present my PhD work which uses morphometric analyses; photolabeling; and cell tracking to investigate the cell and tissue behaviours involved in the elongation of the zebrafish PSM. Our results indicate that this tissue undergoes convergent extension and that this is required for elongation. We are now working with an agent-based 3D model to mechanistically uncouple the contribution of the different cell behaviours towards this convergent extension. This model takes its initial conditions from confocal images of the tissue and implements simple contact-overlap rules between the cells to simulate their future positions. By altering parameters such as proliferation, cell motility and adhesion, we hope to simulate this process in other vertebrate species, in order to understand how the relative importance of different cell behaviours in axis elongation has changed throughout vertebrate evolution.