Alternative splicing and adhesion properties of a mouse carcinoembryonic antigen gene family member

Carcinoembryonic antigen (CEA) is a tumor marker used clinically to assess post-operative recurrences of breast, lung and colon cancers. The CEA gene family, which is part of the immunoglobulin superfamily, is composed of several proteins crossreactive with anti-CEA antibodies. Carcinoembryonic antigen appears to function in the development of the gastro-intestinal tract as well in tumor formation; it is capable of mediating cell-cell adhesion in vitro which is consistent with its putative role of maintaining tissue architecture in vivo. CEA gene family members have also been identified in various tissues of the mouse. Two of the mouse proteins, mmCGMla and mmCGMlb, have been characterized. By sequence homology, mmCGMla and mmCGMlb are the mouse homologues of human biliary glycoprotein and of rat hepatocyte ecto-ATPase. Both of the mouse CEA related proteins function as adhesion molecules when expressed on the cell surface of transfectant cells; however, mmCGMla, unlike mmCGMlb, mediates cellular aggregation irrespective of calcium concentration or temperature. Sequence comparison of mmCGMla, mmCGMlb, and other cDNAs isolated by polymerase chain reaction techniques, demonstrates that there are at least eight possible transcripts encoding CEA-related proteins and that these transcripts are all produced by alternative splicing of one precursor messenger RNA