PROJECT SUMMARY / ABSTRACT The overarching goal in my lab is to identify mechanisms that promote maintenance, reinforcement, and remodeling of cell-cell adhesion and barrier function in response to cell-scale and tissue-scale forces. Epithelial cell-cell junctions including adherens junctions, tight junctions, and tricellular junctions adhere epithelial cells to one another, transmit forces between cells, and generate barrier function that selectively regulates what can pass in the paracellular space between cells. Each of these cell-cell junctions is connected to a contractile apical actomyosin array, and the connections between junctional proteins and the cytoskeleton are highly dynamic. Cells sense their mechanical environment as mechanical forces challenge cell-cell junctions – from cell-scale forces like a dividing cell pulling on its neighbors, to tissue-scale forces like morphogenesis sculpting the organism. Epithelial cells modulate their cell-cell junctions and connections to the actin cytoskeleton to ensure a stable yet adaptable architecture. My group seeks to understand how signaling proteins like Rho GTPases, RhoGEFs & RhoGAPs, scaffolding proteins, mechanosensitive proteins, calcium, and the cytoskeleton work together to create a strong but flexible epithelial barrier. We use developing Xenopus laevis embryos as a model for the vertebrate epithelium, an array of innovative molecular tools for live microscopy of key molecular players, a live imaging barrier assay developed in our lab, and several approaches to mechanically challenge the epithelium either globally or locally. The major research themes of this R35 MIRA are: 1) “Rho flare-mediated tight junction remodeling” where we will address the question: What are the signaling pathways that promote tight junction repair when tight junctions are damaged as cells change shape? 2) “Mechanics of epithelial cytokinesis” where we will address the question: How do cells neighboring the dividing cell contribute to maintenance of adhesion and barrier function during epithelial cytokinesis? 3) “Tension transmission & signaling at tricellular junctions” where we will address the question: How are tricellular junctions reinforced and remodeled when mechanically challenged? By pursuing these research goals over the next five years, my group will discover novel mechanisms that promote maintenance, reinforcement, and remodeling of cell-cell junctions and their cytoskeletal connections in response to physiological mechanical forces.