Inhibition of the Beta-catenin Signaling Pathway in Blastocyst and Uterus During the Window of Implantation in Mice 1 Running Title:

ABSTRACT 20 Beta-catenin，the mammalian homolog of Drosophila armadillo protein, was first identified as a cadherin-associated protein at cell-cell junctions. Another function of beta-catenin is the transduction of cytosolic signals to the nucleus in a variety of cellular contexts, which are usually elicited by the active form of beta-catenin. The aim of this study was to examine the potential role of active beta-catenin in the mouse embryo and 25 uterus during embryo implantation. As shown by these results, active beta-catenin was detected differentially in mouse embryos and uteri during the periimplantation period. Aberrant activation of beta-catenin by LiCl, a well-known GSK3 (glycogen synthase kinase3) inhibitor, significantly inhibited blastocyst hatching and subsequent adhesion and outgrowth on FN (fibronectin). Results obtained from pseudopregnant and 30 implantation-delayed mice imply an important role for implanting blastocysts on the temporal and spatial changes of active beta-catenin in the uterus during the window of implantation. Collectively, these results suggest that the beta-catenin signaling pathway is inhibited in both blastocyst and uterus during the window of implantation, which ma