A hinge between Dendra and αABD changes properties of the clusters. (a) The models of cadherin clusters made from EcDnΔ-αABD (EcDnΔ-αABD), from hinge-containing EcDnΔ-HαABD (EcDnΔ-HαABD), and from a combination of EcDnΔ-HαABD and the tailless mutant EcChΔ (EcDnΔ-HαABD + EcChΔ). Note that the hinge (blue) connecting the Dendra2 tag (Dn) and αABD (yellow) allows connection of each cadherin molecule in the cluster with F-actin. Such clusters could be very stable. In contrast, the lack of the hinge hampers interactions of the majority of cluster molecules with F-actin, resulting in cluster instability. ABD, actin-binding domain; TM, transmembrane domain; mCh, mCherry. (b and b′) Immunostaining of EcDnΔ-HαABD–expressing cells for the chimera (b, HαABD) and for actin filaments (b′, actin). Note that the apical cell–cell contact areas exhibit no filopodia-like protrusions, and the lateral areas (arrowhead) have no lateral clusters. (c) Dendra photoconversion assay of the clusters in cells expressing EcDnΔ-αABD (Δ-αABD) and EcDnΔ-HαABD (Δ-HαABD). See Fig. 7 c for other details. Note that the hinge significantly stabilized the clusters. The error bars represent SD (n = 30). (d–d′′) A431D cells coexpressing EcDnΔ-HαABD (d, green, HαABD) and EcChΔ (d′, red, Δ). Both images are merged in d′′. Note that, upon coexpression with the tailless cadherin mutant, the hinge-containing EcDnΔ-HαABD produced many lateral clusters (arrowhead) and resulted in formation of numerous filopodia on the subapical area of cell–cell contact regions. Bars: (main images) 10 µm; (insets) 3 µm.