Expression Of Egr1,Egr2and Egr3in Mouse Uterus

Early growth response (EGR) factor are cellular immediate early genes that become rapidlyinduced in response to stimulation of cells, e.g. by growth factors. They play a key role in avariety of cell biological processes, including proliferation, apoptosis, and diferentiation. The EGRfamily is composed of Egr1, Egr2, Egr3and Egr4. They encode closely related transcription factors thatcontain three Cys2Hys2zinc fingers shared by the four members and that can bind to the same cognateGCrich consensus DNA binding motif, the Egr response element (ERE). However, outside their commonDNA binding domain, the sequences of the different Egr members have less homology, suggesting theycan be differentially therefore serve different functions.The aim of this study was to investigate the expression of the Egr1, Egr2and Egr3in themouse uterus during early pregnancy and pseudopregnancy, delayed implantation and artificialdecidualization, and its regulation by steroid hormones using in situ hybridization. There was alow level Egr1mRNA signal in luminal epithelium and glandular epithelium on day1ofpregnancy. Egr1mRNA expressed in glandular epithelium on days3and4. Egr1mRNA signalwas found in both implantation site and nonimplantation site on day5. Egr1mRNA wasdistinctly expressed in the stroma cells surrounding the embryo on day5, and lowly expressed inthe stroma cell of nonimplantation site. On day6, Egr1mRNA was lowly expressed in theprimary deciduas surrounding the embryo. On day7, Egr1mRNA was widely expressed indeciduas. The pattern of Egr1mRNA expression on day8was similar to that observed on day7but at much higher levels. Egr1mRNA expression of days1-4of pseudopregnancy was similarto that observed on days1-4of pregnancy. Egr1mRNA was highly expressed in the stroma cellssurrounding the embryo on activated implantation sites. The level of Egr1mRNA in thedecidualized cells, under artificial decidualization, was much higher than that in Stromas ofcontrol. After ovariectomized mouse were injected estrogenion, the levels of Egr1mRNAshowed a sudden increase at3h, then the expression gradually declined. Progesterone injectionresulted in an increase in uterine Egr1mRNA levels, that reached the peak at6h then decreasedto control levels at24h. Corresponding to estrogen and progesterone treatmented group, Egr1 mRNA reached the highest level at6h.Egr2mRNA was expressed in Uterine glandular epithelium and muscularis on days1-4ofpregnancy. Egr2mRNA lowly expressed in uterine luminal epithelium on days1-3of pregnancy,suggesting that Egr2was Associated with proliferation of uterine luminal epithelium. On day5of pregnancy, Egr2mRNA signal was detected in both implantation site and nonimplantation site. Egr2mRNA was highly expressed in the stroma cell surrounding the embryo on days5and6. Egr2expressioncould be detected in myometrium on days5and6, that Egr1could not be detected. There was Egr2mRNAsignal in the primary and secondary decidualized zone. Experession of Egr2mRNA was detected inembryos on days6-8of pregnancy. Expression of Egr2mRNA during pseudopregnant was similar to thesame periods of early pregnancy. The expression of Egr2mRNA in activated implantation sites was sameto in implantation sites on day5of pregnancy. The level of Egr2mRNA in the decidualized cells, underartificial decidualization, was much higher than that in Stroma cells of control. The levels of Egr2mRNAexpression reached the highest level at3h after ovariectomized mouse estrogen injection, then graduallydeclined. Egr2mRNA expression rised from1h to12h, reached the highest level at12h after progesteroneinjection. The level of Egr2expression reached its peak at3h after estrogen and progesterone treatmented.Egr3mRNA was expressed in luminal epithelium cells on days1and2of pregnancy, andexpressed in glandular epithelium cells on days3and4of pregnancy. Egr1mRNA wasexpressed in muscularis, and distinctly expressed in stroma cells surrounding the embryo on day5. Egr3mRNA was highly expressed in decidualized zone on days6and7of pregnancy. Egr3was mainly detected in deciduas of mesometrial side on day6, but on day7Egr3primarilyexpressed in deciduas of the opposite mesometrial side. Egr3mRNA expression on day8waslower than expression on day7. Egr3mRNA was extensively detected in the decidualized cellsunder artificial decidualization. Egr3mRNA was highly expressed at12h and24h after estrogeninjection. The level of Egr3expression reached its peak at12h after progesterone treatmented. Inestrogen and progesterone treatmented group, the levels of Egr3mRNA expression showed a riseand reached the highest level at6h then declined.In summary, Egr1, Egr2and Egr3are closely related to mouse embryo implantation anddecidualization. Estrogen and progesterone can induce the expression of Egr1,Egr2and Egr3.