| Mouse uterus is important for mouse embryo implantation and early embryo development.Ovarian steroid hormones and various factors secreted by luminal epithelium,uterine gland and decidual cells play an important role in the regulation of mouse blastocyst implantation,gastrulation,and germ layer differentiation.The early development of mouse embryos is complex process of multi-gene regulation stages,including blastocyst implantation,gastrulation,and germ layer differentiation,etc.YY1,a transcription foctor,can regulate gene expression as a transcriptional repressor,activator or initiation factor.YY1 protein is involved in a variety of important physiological processes during growth and development.YY1 also plays an important role in mouse embryo development,Yy1 knockout mouse embryos cannot form egg cylinder and embryo lethal before the gastrulation.Previous studies in our laboratory have found that YY1 can binds to the Rtcb promoter response element in vitro cultured cell and regulates RTCB expression.RTCB is an RNA ligase that plays a role in t RNA maturation and splicing of Xbp1 m RNA.It is involved in physiological processes such as antibody secretion and neuroprotection.The role and mechanism of Yy1 and Rtcb in the early pregnancy of uterus and embryo development in mice is still unclear.Our previous study demonstrated that Yy1 m RNA is highly expressed in uterine luminal epithelium,glandular epithelium and decidual cells in early pregnancy,but whether YY1 protein expression pattern and downstream Rtcb gene play a role in early pregnancy remains to be further studied.This experiment used a variety of experimental animal models,such as early pregnancy,pseudopregnancy,delayed implantation,hormone regulation,artificial induced decidualization,etc,to study the expression patterns of YY1 in early pregnancy uterus and embryo in mice by immunohistochemistry and RT-q PCR.In the D1-D4 of early pregnancy,pseudopregnancy and delayed implantation,YY1 was strongly expressed in the uterine luminal,glandular epithelium,stroma surrounding implanting blastocyst and embryo.Yy1 m RNA was strongly expressed at the implantation site of D8 and the difference was significant.The results indicated that YY1 may play a role in embryo implantation.In the D5-D8 of early pregnancy and artificial induced decidualization,YY1 and Yy1 m RNA were strongly expressed in the decidual cells and the difference was significant.The results indicated that YY1 may also play a role in decidualization.YY1 was highly expression in the uterine of ovariectomized mice by estrogen or a combination of estrogen and progesterone.Yy1 m RNA was strongly expressed in the estrogen-treated uterus and the difference was significant.The results indicated that YY1 expression was significantly stimulated by estrogen.And then,a variety of experimental animal models,such as early pregnancy,pseudopregnancy,delayed implantation,hormone regulation,artificial induced decidualization,etc,were used to study the expression patterns of RTCB in early pregnancy uterus and embryo in mice.RTCB was highly expression in the uterine by estrogen or a combination of estrogen and progesterone.Rtcb m RNA was also strongly expressed in the estrogen-treated uterus and the difference was significant.The results indicated that RTCB expression was significantly stimulated by estrogen.The expression of RTCB protein is similar to the YY1,they were dynamic expression pattern in early pregnancy uterus and embryos,and the expression of YY1 and RTCB is up-regulated by estrogen.In order to study YY1 whether regulates Rtcb gene expression during mouse early embryo development,this study used mouse early pregnancy D8 uterine decidua and embryo tissue through chromatin immunoprecipitation,and the results showed that YY1 protein can bind to the response element of the Rtcb gene promoter region in vivo and is involved in the regulation of early embryo development in miceThe Yy1 knockout mouse embryo can develop into the blastocyst,embryo implantation and decidualization,but the embryo rapidly degenerates to lethal shortly after implantation.The lethal of Yy1 knockout mouse embryo was caused by the decrease of proliferating cells,which leads the number of epiblast cells could not to differentiation,so that embryo development stops before the gastrulation.Immunohistochemistry of RTCB showed that Rtcb gene was expressed in normal embryos.However,RTCB signal was not detected in abnormal embryos.The abnormal embryos were small,hypogenesis and the germ layers were disordered.The phenotype of the Rtcb knockout mouse is similar to that of the Yy1 knockout mouse.Mouse development abnormalities occurred during the differentiation of the germ layer;and embryo development was arrested before the gastrulation.In order to determine whether the lethal of Rtcb knockout mouse embryos is also due to decreased cell proliferation or increased apoptosis,we examined cell proliferation(Brd U,Ki67)and apoptosis(Cleaved-Caspase-3)by immunohistochemistry and found that the number of proliferation cells was significantly reduced,b and there was no significant difference in the number of apoptotic cells in abnormal embryos compared with the normal embryos.Therefore,we hypothesized that the number of proliferation cells was significantly reduced may be one of the causes of lethal in Rtcb knockout mice during early pregnancy.These results suggested that YY1 may play a role in early embryo development by regulates expression of the Rtcb gene.In conclusion,this study suggests that Yy1 and Rtcb are important genes in early pregnancy uterus and embryo in mouse,and YY1 and RTCB were dynamic express in the uterus and embryo.YY1 may play a role in embryo implantation and decidualization,YY1 and RTCB expression were up-regulated by estrogen.The YY1 protein binds to the Rtcb gene promoter and regulates mouse early embryo development of mice.The decrease in cell proliferation may be one of the causes of lethal in Rtcb knockout mouse embryo.These results will help to further understand the complex gene regulation process in embryo development,and have a great significance for early embryo disease prevention and treatment. |
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