Expression pattern of the epithelial V‐like antigen (Eva) transcript suggests a possible role in placental morphogenesis

Adhesive mechanisms are considered to be of crucial importance for blastocyst adherence to the uterine wall, as well as for the interactions between embryonal and decidual tissues during hemochorial placenta formation. Epithelial V-like Antigen (Eva) is a novel homophilic adhesion molecule of the immunoglobulin superfamily, which during mouse embryonic development is expressed by various differentiating epithelia. In the present paper we describe Eva expression during mouse trophoblast invasion and placental morphogenesis, analysing day 5.5 to 18.5 postcoitum (p.c.) placentas and deciduomas by in situ hybridization. Eva transcripts were detected in spongiotrophoblast cells from 7.5 to 18.5 days p.c. Expression was uniform at early stages, but after day 11.5, p.c. became limited to the invasive subpopulation of spongiotrophoblasts (known as glycogen cells). Trophoblast giant cells did not express Eva in any of the stages analysed. Besides trophoblasts, also early postimplantation decidua was positive for Eva transcripts. In decidual tissue, Eva expression was present at day 5.5 p.c., peaked at day 7.5 p.c., and declined on successive days. The expression pattern of Eva transcripts suggests that during mouse placenta formation, its protein product may play a role in the processes of trophoblast invasion, decidual response, and trophoblast-decidual interaction.