Trophinin and tastin, a novel cell adhesion molecule complex with potential involvement in embryo implantation.

Abstract

Two human epithelial cell lines, trophoblastic teratocarcinoma HT-H and endometrial adenocarcinoma SNG-M cells, adhere to each other at their respective apical cell surfaces in a divalent cation-independent manner. Two novel molecules responsible for the adhesion between these two cell types were identified by expression eDNA cloning. One, named trophinin, is an intrinsic membrane protein and mediates homophilic self-binding. Another, named tastin, is a cytoplasmic protein and is necessary for trophinin to function as a cell adhesion molecule. Trophinin and tastin appear to be associated with the cytoskeleton in HT-H and SNG-M cells. These molecules are normally not expressed in various types of human cells in tissues, with the exception of macrophages. Strong expression of these molecules was detected in the trophectoderm surface of monkey blastocyst. These molecules are also expressed in human endometrial surface epithelium on day 16/17 at the early secretory phase of human endometrium, the time consistent with that expected for the "implantation window."

Transcriptional analysis of the B cell germinal center reaction

“…These genes include trophinin and tastin (both 19-fold o.b.) that are involved in embryo implantation (26), as well as OIP5 and GARP (8-and 10-fold, respectively), two molecules whose structure suggest functions in cellular adhesion.…”

Oviductal and endometrial mRNA expression of implantation candidate biomarkers during early pregnancy in rabbit

“…Several key maternal factors that may contribute to maximal 53" uterine receptivity have been identified: ultrastructural components such as pinopodes 54" (Psychoyos & Nikas, 1994); steroids or cytokines and growth factors (Pollard et al, 55" 1991;Stewart et al, 1992;Fukuda et al, 1995, Zhu et al, 1998Hoffman et al, 1998).…”

Induction of trophinin in human endometrial surface epithelia by CGβ and IL‐1β

“…When we examined frozen sections of human endometrium, we detected weak and widely distributed signals for trophinin protein in surface and glandular epithelia and stroma that varied over the hormonal cycle (Lessey and Fukuda, unpublished data). However, in rare cases the endometrial surface epithelia strongly expressed trophinin [6]. Such rare but distinct observations prompted us to test the hypothesis that endometrial epithelial cells were responding to CGb derived from a blastocyst.…”

“…Using HT-H cells, we identified an apical cell adhesion molecule, trophinin [6], the gene product of TRO [7,8], that mediates cell adhesion between human trophoblastic and endometrial epithelial cells at their respective apical cell surfaces through homophilic trophinin-trophinin binding. The in vivo expression pattern of trophinin supports this function: trophinin is expressed in chorionic villi trophoblasts and in maternal endometrial epithelium in the first trimester [6,9]. Subsequent studies of signals triggered by trophinin-mediated cell adhesion in monkey blastocysts further validate HT-H cells as a model for human embryo implantation [10].…”

“…We have previously established an in vitro model using human embryonal carcinoma HT-H cells, which represent some, if not all, aspects of trophectoderm cells at the initial step of human embryo implantation, specifically, at adhesion of trophectoderm cells to endometrial epithelial cells [6]. Using HT-H cells, we identified an apical cell adhesion molecule, trophinin [6], the gene product of TRO [7,8], that mediates cell adhesion between human trophoblastic and endometrial epithelial cells at their respective apical cell surfaces through homophilic trophinin-trophinin binding.…”