The Expressions And The Effect Of The Transcription Factor Tbx18in Mice Embryonic Hearts Development

The T-box gene family members are essential for the vertebratenormal hearts development, they have great importance for the earlycardiac lineage determination, and they have been involved in the chamberspecification and diversification of the specialized conduction system inembryos. Transcription Factor Tbx18is a member of the T-box gene familyand it is a new signs factor of progenitor cells, it has the potentiality to inducethe progenitor cells differentiation to different cells and it in charge of theelongation of the simple cardiac tube at the posterior pole， The heartprogenitor cells marked by Tbx18are called as the third heart developmentzone heart progenitor cells, they played an important role in the heartdevelopment. Therefore, it is important to assure the spatiotemporalexpressions and the effect to the hearts of transcription factors Tbx18inmouse embryonic development for the further research on the function of theheart development.Objective: To detect the spatiotemporal expressions of thetranscription factor Tbx18mRNA in mice embryonic hearts development and reveal the effect of Tbx18in the mice hearts development.Method: We synthesized Tbx18RNA probes using Dig RNA labelingkits, we detect whole embryos and whole hearts Tbx18mRNA expressionsin the process of mice embryonic hearts development using whole mount insitu hybridization technology, and analysis the results of hybrided section.We detect the quantity of whole mouse embryonic hearts mRNA usingfluorescence quantitative PCR. We also detect the reporter LacZ proteinexpression of Tbx18-Cre/Rosa26R/LacZ genetic lineage tracer model miceembryos using X-gal strain technology. We observed the whole miceembryos appearance change of Tbx18Cre/Creknock out model, and detectedthe histological appearance change of Tbx18Cre/Creknock out model usingHE stain technology.Result:1. The in situ hybridization results: at E9.5d The Tbx18hybridization signal mainly expressed in the proepicardium; at E10.5dmainly expressed in the proepicardium and epicardium; at E11.5d no signalsexpressed in the proepicardium, but the signals expressed in the epicardiumincreased; Form E12.5d and older than that days the signals aredifferentiated to myocardial cells gradually. Tbx18mRNA in the heartswas increased gradually in E12.5d to E16.5d embryonic hearts, and thenreduced gradually in older than E16.5d embryonic hearts, was significantlyreduced in the new born mice hearts.2.Fluorescence quantitative PCR results shows that the quantity of Tbx18mRNA in the hearts was increased gradually in E12.5d to E16.5dembryonic hearts, and then reduced gradually in older than E16.5dembryonic hearts, was significantly reduced in the new born mice hearts.3. X-gal strain results： The expressions of the LacZ protein ofTbx18-Cre/Rosa26R/LacZ genetic lineage tracer model mice embryonichearts are as follow: at E9.5d mainly express in the proepicardium; atE10.5d mainly expressed in the proepicardium and epicardium; at E11.5dexpressed in the epicardium; Form E12.5d and older than that days, thesecells marked by Tbx18are gradually differentiated to atrial, ventricular andsinus horn myocardial tissue.4. The Tbx18Cre/Creknockout mice study shows that the length of theTbx18Cre/Creknockout mice embryonic bodies are shorter than the normalmice bodies, and the whole bodies are edematous. The hearts of theTbx18Cre/Creknockout mice are also unnormal, the sinus angle areamyocardial cells differentiation are delayed、lack of the heads of sinus nodeand so on.Conclusion: Transcription factors Tbx18is a sign of proepicardiumprogenitor cells and it has specificity spatiotemporal expression in miceembryonic development. At first, it mainly expressed in the proepicardiumin mice embryos, then emigrated to the epicardium gradually, finallydifferentiated to myocardial cells. Tbx18-Cre/Rosa26R/LacZ geneticlineage tracer model mice revealed that in the early stage of the mice embryonic Tbx18mainly emigrated from proepicardium to epicardiumgradually, in the middle and late stage these cells marked by Tbx18aregradually differentiated to atrial, ventricular and sinus horn myocardialtissue, so Tbx18plays an important role in the hearts development; TheTbx18Cre/Creknockout mice study shows that the development of wholemice embryonic bodies and hearts are abnormal, especially the sinusangle area myocardial cells differentiation are delayed, that is to say lackof the Tbx18will lead to abnormal heart development. This study assuredthe spatiotemporal expressions and the effect to the hearts of transcriptionfactors Tbx18, it can provide evidence for the further function andmechanism research.