EXPRESSION OF BETACELLULIN AND EPIREGULIN GENES IN THE MOUSE UTERUS TEMPORALLY BY THE BLASTOCYST SOLELY AT THE SITE OF ITS APPOSITION IS COINCIDENT WITH THE WINDOW OF IMPLANTATION

In the mouse, the process of implantation is initiated by the attachme nt reaction between the blastocyst trophectoderm and uterine luminal e pithelium that occurs at 2200-2300 h on day 4 (day 1 = vaginal plug) o f pregnancy. Several members of the EGF family are considered importan t in embryo-uterine interactions during implantation. This investigati on demonstrates that the expression of two additions to the family, be tacellulin and epiregulin, are exquisitely restricted to the mouse ute rine luminal epithelium and underlying stroma adjacent to the implanti ng blastocyst. These genes are not expressed during progesterone-maint ained delayed implantation, but are rapidly switched on in the uterus surrounding the implanting blastocyst following termination of the del ay by estrogen. These results provide evidence that expression of beta cellulin and epiregulin in the uterus requires the presence of an acti ve blastocyst and suggest an involvement of these growth factors in th e process of implantation. (C) 1997 Academic Press.