Tissue tectonics
An embryo changes shape because thousands of cells move, change shape and swap neighbours at the same time. Together with Guy Blanchard, Richard Adams, Benedicte Sanson and L. Mahadevan, we developed a framework, tissue tectonics, that measures the deformation of groups of cells and splits it into cell shape change and cell rearrangement (Blanchard et al., Nature Methods 2009). Applied to the fruit fly embryo, it showed that cell shape change, and not only intercalation, drives the first fast phase of germ-band extension, which points to a role for forces from outside the cells involved (Butler et al., Nature Cell Biology 2009). The same strain-map approach now describes the large-scale movements of the zebrafish embryo during gastrulation (Bhattacharya et al., Scientific Reports 2021, with Paul Matsudaira).