Fig. 9. Model of how misexpression of cadherins in the heart may interfere with normal intercalated disc function. Schematic diagrams representing adherens junctions comprised of different cadherin subtypes through which the contractile force is transduced across the plasma membrane (A-C). In wild-type heart muscle (A), N-cadherin dimers (black bars) interact to form a zipper structure critical for strong cell-cell adhesion. In MHC/Ncad mice (B), the mouse (black) and chicken (gray) N-cadherin are very homologous and interact, at least in trans, to generate a chimeric zipper structure. Mouse and chicken N-cadherin are nearly identical in the cytoplasmic and transmembrane domains; therefore we predict normal interaction(s) with the submembranous myofibril connection. However, the excess cadherin/catenin complexes compared with myofibrils alters the contractile dynamics leading to less efficient force transduction across the plasma membrane. In MHC/Ecad mice (C), in addition to excess cadherin/catenin complexes the contractile dynamics may be further perturbed due to the presence of E-cadherin (stipple), since it cannot interact with N-cadherin and differences in the cytoplasmic domain may alter myofibril connections. In both models (B,C), the dissipation of the contractile force across the plasma membrane leads to a compensatory response (i.e. hypertrophy) with the greater effect caused by introduction of the epithelial cadherin.