Figure 4 - Cadherin dynamics in MDCK cells.

(a) Distribution of VE-cadherin–EGFP introduced into MDCK cells. No directional movement of cadherin is observed in their confluent layers (see Supplementary Information, Movie 12). (b) Cadherin flow occurs at the junctions formed by locomotive MDCK cells. A cell located in the upper right is moving towards the lower left, as indicated by red arrow, keeping in contact with the left cell (see Supplementary Information, Movie 13). Kymographs were sampled at the magenta line in both a and b. (c) Schematic representations of the time-dependent distribution of cadherin clusters in the boxed area of b. The blue line indicates the front of the advancing cell protrusion and the green line indicates the apical-most portion of the junction. The distance between the cadherin clusters and the apical end of the junction is reduced as the cells move. (d) A projected image of the moving front lines (blue) and apical-most portions (green) of the junction, as well as cadherin clusters, in b. Cadherin clusters are maintained at relatively stable positions, instead the cell–cell contact area moves. The reduced colour intensities represent more advanced times. (e) A vertical-section schematic representation to explain the time-dependent shift of cadherin clusters relative to the contacting cell membranes. The grey and magenta rectangles represent cadherin trans-dimers. (f) Cadherin dynamics in MDCK cells at a wound margin. Cells are migrating in the direction indicated by red arrow and the front margin of the migrating cells is indicated by the blue dotted line. Cadherin flow occurs at the cell–cell contact sites, formed by the protrusions moving forward (green arrows). In cell junctions located at other sides of the cells (magenta arrowheads), cadherin flow is generally not observed (see Supplementary Information, Movie 14, as accurate kymograms could not be obtained, because of the extensive relocation of cell junctions during the observations). The scale bars represent 15 m in a and b, and 10 m in f.