Mobile E-cad is asymmetrically distributed in epidermal cells. (A–E) There are two junction types in the lateral epidermis of stage 15 embryos: short DV borders (DV, arrowhead in A and D) and long AP borders (AP; arrow in A and D). DV borders have higher junctional E-cad (A and B, anti–E-cad) and β-catenin levels (D and E, anti–β-catenin), and are shorter (C) than AP. Bars, 5 µm. (F and G) There is greater exchange of E-cad–GFP at DV borders than AP, shown by greater FRAP; single FRAP examples (F), with red circles on the prebleached frame (P) showing the bleach spots, and averaged recovery curves (mean ± SEM) plotted in G, with best fit curves as solid lines. (H) Combining the measurements of E-cad junctional levels and E-cad–GFP recovery provides estimates of mobile and immobile pools of E-cad at DV and AP borders (error bars indicate mean ± SEM), showing that DV borders have more mobile E-cad. Table S1 has detailed numbers for this and all other figures. *, P < 0.01; **, P < 0.001; ***, P < 0.0001.