SIMILARITIES IN STRUCTURE AND EXPRESSION BETWEEN MOUSE P-CADHERIN, CHICKEN B-CADHERIN AND FROG XB U-CADHERIN/

By immunological methods, we show that the monoclonal antibody 6D5 whi ch reacts specifically with Xenopus laevis XB/U-cadherin, also binds t o mouse P-cadherin and to chicken B-cadherin but not to the respective E-cadherins (L-CAM) or other ''classical'' cadherins in these species . In the first extracellular domain, three amino acid residues are ide ntified that are shared by frog XB/U-cadherin, chicken B-cadherin and mammalian P-cadherins but not by the other ''classical'' cadherins. Wi th few exceptions, the other cadherins possess residues at these posit ions that are also characteristic of each type of cadherin. Moreover, the expression patterns of P-, B-, and XB/U-cadherin in mouse, chicken and frog are more similar to each other than they are to those of the E-cadherins, L-CAM or other classical cadherins. Taken together, our results suggest that mammalian P-cadherins, chicken B-cadherin and fro g XB/U-cadherin are closely related, if not homologous, molecules. A n umber of differences in the expression patterns between P-, B-, and XB /U-cadherin indicate that these molecules assume differential morphoge netic roles in different species.