Signals, forces, and cells: Decoding tissue morphogenesis

During development, cells move and reorganize in response to a wide range of signals to build the unique structures of different tissues in the animal. How these behaviors are systematically organized across hundreds of cells is a question that has long fascinated developmental biologists. We found that in the Drosophila embryo, the cell movements that elongate the head-to-tail body axis are regulated by a global positional code provided by an ancient family of Toll-related receptors that are widely used for pathogen recognition by the innate immune system. These receptors direct the localization of cellular force-generating proteins that drive cell intercalation and rosette formation, conserved cell behaviors that promote epithelial elongation in flies, chicks, frogs, worms, and mice. Recent work on how genes encode the forces that shape tissues, and how cells modulate their behavior in response to biochemical and mechanical changes in their environment, will be presented.