The role of Wnt/β-catenin-lin28a/let-7 axis in embryo implantation competency and epithelial-mesenchymal transition (EMT).

BACKGROUND The pre-implantation embryo in a competent status and post-implantation fully differentiation of the inner cell mass (ICM) and trophectoderm (TE) are prerequisites of successful implantation. Type I embryonic epithelial-mesenchymal transition (EMT) involves in these processes. A high level of the mir-let-7 family was found in the dormant mouse embryo of implantation failure in our previous study. Besides, its natural inhibitor lin28a was found to function in maintained stem cell pluripotency and involved in early embryo nucleolus construction. Until now, few studies got involved in the exact molecular mechanism that affects embryo implantation potential. In this study, the possible function of Wnt/β-catenin-lin28a/let-7 pathway in mouse embryo implantation was studied. METHODS ICR mouse, Lin28a/Let-7 g transgenic mice (Lin28a-TG/Let-7 g-TG), and implanting dormant mice models were used for the study. RESULTS Wnt/β-catenin signaling is essential in embryo implantation, which promotes embryo implantation through directly trigger lin28a expression, thus represses the mir-let-7 family. Lin28a and mir-let-7 both participate in implantation via an inverse function. Lin28a and mir-let-7 participate in embryo implantation through embryonic EMT. CONCLUSIONS Wnt/β-catenin signaling promotes embryo implantation and accompanying embryonic EMT, which is mediated by directly activate lin28a/let-7 axis. Video abstract.