Abstract

During animal development, epithelial tissues undergo morphogenesis in order to build tissues, organs and body structure. A key driving force in epithelial morphogenesis is cell rearrangement, which results from the remodelling of cell-cell contacts. In epithelia, cell-cell contacts are connected via vertices, where 3 or more cells meet. I have used the Drosophila model to investigate the behaviour and role of vertices in epithelial morphogenesis, using as an entry point a newly discovered marker of epithelial vertices, the Immunoglobulin-superfamily domain protein Sidekick. Sidekick-YFP forms plaque-like structures at cell vertices at the level of adherens junctions, indicating that large multi-protein complexes containing Sidekick define a novel cortical domain in Drosophila epithelia. Sidekick is the first protein in any organism found to localise at vertices at the level of adherens junctions. Through characterisation of a null allele of sidekick, using both both manual and automated cell tracking based quantitative analysis, I have found that Sidekick at apical vertices is important for the regulation of adhesion, tissue geometry and junction remodelling during morphogenesis of the embryonic ectoderm.