Trophinin is a membrane protein that mediates apical cell adhesion between trophoblastic cells and luminal epithelial cells of the endometrium and is implicated in the initial attachment during the process of embryo implantation. This gene is related to the MAGED gene family by sequence similarity and chromosome location. Multiple alternatively spliced transcript variants have been found for this gene; however, the full-length nature of some variants has not been defined.Strong expression at implantation sites. Found in the placenta from the sixth week of pregnancy. Was localized in the cytoplasm of the syncytiotrophoblast in the chorionic villi and in endometrial decidual cells at the uteroplacental interface. After week 10, the level decreased and then disappeared from placental villi. Also found in macrophages.