Epithelial cells form adhesive connections through cell-cell junctions, maintaining a selective barrier despite significant shape changes during development and tissue homeostasis. This is accomplished through the active remodeling of cell-cell junctions, a process largely driven by actomyosin contractility. Using live microscopy of the Xenopus laevis embryonic epithelium, my lab has characterized “tricellular zipping”, a vertex remodeling process that contributes to the transition from irregular epithelial geometries at the blastula stage to the more regular hexagonal packing that emerges at the gastrula stage of development. Tricellular zipping involves the resolution of a long, thin cellular extension that stretches toward a vertex where four or more cells meet. As two cells 'zip' together to lengthen a new bicellular interface, the other cell recedes, thus forming a new tricellular vertex at the end of zipping. Tricellular zipping is accompanied by transient flashes of cytoplasmic calcium within the long cell extension. My research had focused on investigating these calcium flashes, whether the calcium flashes are correlated with actomyosin accumulation, and how pulsatile calcium and actin accumulations drive the elongation of the new bicellular interface between two zipping cells. My data reveals that each zipping event is accompanied by multiple calcium flashes within the long cellular extension and an increase in the length of the new bicellular interface between the zipping cells. Following calcium flashes, there is an increase in the rate of elongation of the new bicellular interface. Actin also accumulates in a pulsatile fashion within the long cellular extension during tricellular zipping. Cross correlation analysis shows that * We hypothesize that the long cellular extensions experience increased membrane tension, which might activate mechanosensitive calcium channels, leading to the observed pulsatile mechanosensitive calcium signaling. To test this idea, we are using FLIPPER-TR to measure membrane tension at the site of zipping and at tricellular and multicellular vertices more generally. Together, these findings suggest that calcium-associated actomyosin pulses drive tricellular zipping.