TROPHININ AND TASTIN, A NOVEL CELL-ADHESION MOLECULE COMPLEX WITH POTENTIAL INVOLVEMENT IN EMBRYO IMPLANTATION

Two human epithelial cell lines, trophoblastic teratocarcinoma HT-H an d endometrial adenocarcinoma SNG-M cells, adhere to each other at thei r respective apical cell surfaces in a divalent cation-independent man ner. Two novel molecules responsible for the adhesion between these tw o cell types were identified by expression cDNA cloning. One, named tr ophinin, is an intrinsic membrane protein and mediates hemophilic self -binding. Another, named tastin, is a cytoplasmic protein and is neces sary for trophinin to function as a cell adhesion molecule. Trophinin and tastin appear to be associated with the cytoskeleton in HT-H and S NG-IM cells. These molecules are normally not expressed in various typ es of human cells in tissues, with the exception of macrophages. Stron g expression of these molecules was detected in the trophectoderm surf ace of monkey blastocyst. These molecules are also expressed in human endometrial surface epithelium on day 16/17 at the early secretary pha se of human endometrium, the time consistent with that expected for th e ''implantation window.''