(A,B) E-cad:GFP image of cell and single pixel intensity line plot between arrowheads for 100 mM (A) and 25 mM (B) Y-27632 injection. (C,D) Heat map and plot of the normalized E-cad:GFP intensity at vertices with respect to the angle of the vertex and the area phase for 100 mM (c, n = 409 cells) and 25 mM (d, n = 363 cells) Y-27632 injection. (E) Quantification of vertex-to-junction intensity ratios measured for each vertex and each frame of 5 min during GBE (n = 86939 vertex time points). (F) Time sequence of images showing loss of E-cad:GFP dynamics at vertices in 25 mM Y-27832 injected embryos. (G) The averaged standard deviation over time for each vertex’s intensity ratio. Control, n = 3188 vertex trajectories; 25 mM, n = 1868 vertex trajectories. (H, I) Heat map of tangential vertex motion rates versus the phases of cell A and cell B (left) and cell A and cell C (right) for 25 mM (H) and 100 mM (I) Y-27632 injection. (H) n = 175 junctions. (I) n = 220 junctions. (J) Model for vertex-directed changes in cell topologies. As a cell adjacent to a vertex along the AP axis contracts (gray arrows), and the adjacent cell along the DV axis expands (blue arrows), the vertex experiences a cumulative asymmetric force, causing it to slide along the interface (middle row, cyan line). At the molecular level, medial Myosin II flows consolidate E-cadherin at cell vertices post-vertex sliding, resulting in a local increase in adhesive stability. This is coordinated with oscillations in apical cell area, which ensures progressive, non-reversible vertex displacements (bottom). Gray shading indicates a contractile phase; blue indicates expansion. Control data from three embryos, Y-27632 25 mM from three embryos, and Y-27632 100 mM from three embryos. Scale bars are 3 µm. *** denotes p<0.0001. (E, G) Mean ± s.e.m are shown. Data from first 20 min of cell intercalation.