THE CADHERIN-BINDING SPECIFICITIES OF B-CADHERIN AND LCAM

The cadherin family of calcium-dependent cell adhesion molecules plays an important part in the organization of cell adhesion and tissue seg regation during development. The expression pattern and the binding sp ecificity of each cadherin are of principal importance for its role in morphogenesis. B-Cadherin and LCAM, two chicken cadherins, have simil ar, but not identical, spatial and temporal patterns of expression. To examine the possibility that they might bind to one another in a hete rophilic manner, we generated, by cDNA transfection, L-cell lines that express LCAM or B-cadherin. We then examined the abilities of these c ells to coaggregate with each other and with other cadherin-expressing cells in short-term aggregation assays. The B-cadherin- and the LCAM- expressing cell lines segregate from P-, N-, or R-cadherin-expressing cells. B-cadherin- and LCAM-expressing cell lines, however, appear to be completely miscible, forming large mixed aggregates. Chick B-cadher in and murine E-cadherin also form mixed aggregates, indistinguishable from homophilic aggregates. Murine E-cadherin and chick LCAM coaggreg ate less completely, suggesting that the heterophilic interactions of these two cell lines are weak relative to homophilic interactions. The se data suggest that heterophilic interactions between B-cadherin and LCAM are important during avian morphogenesis and help identify the am ino acids in the binding domain that determine cadherin specificity.