Global analysis of differential luminal epithelial gene expression at mouse implantation sites

Although implantation types differ between species, the interaction between blastocyst trophectoderm and apical surface of the uterine epithelium is a common event during the implantation process. In this study, uterine luminal epithelium at implantation and inter-implantation sites was isolated by enzymatic digestion and used for microarray analysis. In a mouse microarray containing 12 345 unigenes, we found 136 genes upregulated more than twofold at the implantation site, while 223 genes were downregulated by at least twofold. Reverse transcription-PCR was used to verify the differential expression of seven upregulated and six downregulated genes chosen randomly from our microarray analysis, and the expression trends were similar. The differential expression patterns of eight upregulated genes were verified by in situ hybridization. Compared with the inter-implantation site on day 5 of pregnancy and the uterus on day 5 of pseudopregnancy, protease, serine, 12 neurotrypsin, endothelin-1, gamma-glutamyl hydrolase, Ras homolog gene family, member U, T-cell immunoglobulin, and mucin domain containing 2, proline-serine-threonine phosphatase-interacting protein 2, 3-monooxgenase/tryptophan 5-monooxgenase activation protein, gamma-polypeptide, and cysteine-rich protein 61 (Cyr61) were upregulated in the luminal epithelium at implantation site on day 5 of pregnancy. These genes may be related to embryo apposition and adhesion during embryo implantation. Cyr61, a gene upregulated at the implantation site, was chosen to examine its expression and regulation during the periimplantation period by in situ hybridization. Cyr61 mRNA was specifically localized in the luminal epithelium surrounding the implanting blastocyst at day 4 midnight and on day 5 of pregnancy, and in the activated uterus, but not expressed in inter-implantation sites and under delayed implantation, suggesting a role for Cyr61 in mediating embryonic-uterine dialog during embryo attachment. Our data could be a valuable source for future study on embryo implantation.