Expression, Regulation And Function Of Junctional Adhesion Molecule 2 In Mouse Uterus During Early Pregnancy

The establishment of molecular crosstalk between active blastocyst and receptive endometrium is necessary for successful implantation in mammalian reproduction. The process of implantation includes three phases, apposition, attachment and penetration. The implantation of blastocyst is regulated by estrogen and progesterone, steroid hormone secreted by ovary. These hormones orchestrate the changes of the epithelium cell and stroma compartment that make it competent to attach to the blastocyst during this"implantation window". By microarray analysis, we found that junctional adhesion molecule 2 was high expression on day 3 and day 4 of early pregnancy, suggesting this molecule might play a role during the open of implantation window. Junctional adhesion molecules(JAMs) family belongs to immunoglobulin superfamily, a member of CAMs. Here we examed the expression, regulation and function of JAMs, especially Jam2 in the mouse uterus during early pregnancy by in situ hybridization, immunohistochemistry, Real-time PCR, Western blot, embryo adhesion analysis and injection of uterine horn.In mouse uterus during early pregnancy, there were no Jam2 mRNA signals on days 1 and 2. Strong signals were detected in luminal epithelium on days 3 and 4. On day 5 of pregnancy, Jam2 mRNA signals were weak. Jam2 protein was weakly detected in luminal epithelium of day 3 and strongly on day 4, and the detailed analysis of Jam2 protein expression in different times of day 4 showed that Jam2 protein level were the strongest at 12:00-16:00. There was a low level of Jam2 protein in luminal epithelium of implantation site on day 5. Further results from Real-time PCR and Western blot also confirmed this pattern.Jam2 in mouse uterus during early pregnancy was up-regulated by progesterone, and mifepristone (RU486), a progesterone receptor antagonist, could inhibit this up-regulation. A further exam found that transcription factor Msx1 had mediated the up-regulation of Jam2 by progesterone, overexpression of Msx1 by electroporation could up-regulate Jam2 expression in luminal epithelium tissues cultured in vitro.On the other hand, we found that estrogen and its downstream gene LIF could also up-regulate Jam2 expression by inducing the phosphorylation of Signal transducer and activator of transcription 3(Stat3). Both LIF and the inhibitor of phosphorylation of Stat3 could up-regulate or down-regulate the expression of Jam2 in luminal epithelium tissues cultured in vitro. A sustained activation Stat3 transfected by electroporation could induce Jam2 expression in luminal epithelium tissues cultured in vitro.Adhesional analysis showed that immobilized r-mJam2 promoted the adhesion of hatched blastocyst at the bottom of coated wells, and soluble r-mJam2 and r-mJam3 could inhibit this process. In vivo, the number of implantation sites was much lower in horns which were injected with Jam2 antibody than goat IgG as negative control. These results showed that Jam2 could induce the interaction between blastocyst and endometrium luminal epithelium.Our data showed that progesterone could induce Jam2 expression in endometrium luminal epithelium during receptive phase via transcription factor Msx1, while estrogen and its downstream pathway LIF- Stat3 could also promote Jam2 expression. Jam2 interactes with its ligands expressed by trophoblast cells to promote the apposition and attachment of blastocyst.