Cell-cell adhesion in tissue mechanics and morphogenesis

During development, simple epithelia reorganize into tissues with complex form and structure. Tissue reorganization during morphogenesis can be rapid. In Drosophila, cell rearrangements in the embryonic epithelium double the length of the body axis in 30 minutes. Adhesion at cell-cell contacts, mediated by junctional proteins, and contractile tension, generated by actomyosin, are thought to be key machineries controlling epithelial tissues. However, it remains unclear how the balance between adhesion and tension determines epithelial structure and mechanics. To gain insight, we are systematically modulating the balance between adhesion and tension in vivo. E-cadherin is a primary component of cell-cell adhesions. Using multiple approaches, we increase or decrease E-cadherin levels relative to wild type and use confocal imaging to study the effects on cell shapes and movements. We find that modulating adhesion influences cell shapes prior to the onset of axis elongation as well as cell rearrangement rates during elongation. We will discuss how our results compare to vertex model predictions. These systematic, quantitative experimental studies of tissue mechanics in vivo are an essential step in building models of morphogenesis.