Project Summary/Abstract Embryonic development requires the dynamic remodeling of epithelial sheets as the embryo transforms itself during morphogenesis. Embryonic epithelia are hybrid tissues: they must maintain their integrity as mechanically integrated cell sheets, connected by cell-cell junctions, yet their cells must also retain the ability to dynamically change shape and position. The actin cytoskeleton is central to these activities; cells must link actomyosin networks dynamically to the cell surface via junctional complexes, and they must dynamically polymerize actin networks during cell shape changes and cell migratory events. Our goal is to understand the dynamics of actin networks during rapid cell shape change and during directed cell rearrangement in embryos. Our goal is a multidisciplinary, integrated analysis of morphogenetic movements in embryos that unites detailed structural analysis, single-molecule biophysics, genetics, and dynamic in vivo analysis, in an "Angstroms to embryos" approach to morphogenesis. Upgrading our ability to image nucleic and protein gels using modern USB3-based and more sensitive cameras controlled by computers that adhere to modern security standards will allow us to generate more sensitive and reproducible molecular analyses relevant to all aims of the parent award, including quantitative assessment of protein-protein interactions between proteins that are part of a network of mechanosensitive proteins that acts to stabilize junctional actin networks during rapid morphogenetic changes in embryos.