VGLL1-TEAD4 Complex Regulates Human Trophectoderm Induction And Self-renewal

Placenta,originating from blastocyst trophectoderm,is the bridge between the mother and the fetus,through which the mother provides the fetus with nutrients,delivers blood(oxygen)and removes metabolites(carbon dioxide,urea,etc.)to maintain the healthy development of the fetus.Researches on TE and placental development is very limited due to the scarcity of human embryonic resources,immature embryo isolation technology and ethical restrictions.Data analysis of embryos developed to day 5 showed that VGLL1 was highly expressed in TE,and VGLL1 was rapidly upregulated in the induction of TE and continued to be highly expressed in the later stage.Therefore,VGLL1 was suspected to be a specific factor for human TE induction,and it was necessary to verify VGLL1 in the induction system of TE in vitro.In this thesis,by establishing an in-vitro model of TE and TSC induction from human primitive pluripotent stem cells,using small hairpin RNA(sh RNA)mediated knockdown assay and next generation sequencing technology,we found that knockdown of VGLL1(Vestigial Loke family Member 1)resulted in severe impairment of TE self-renewal,loss of TE typical cell morphology,and down-regulation of the expression of cell cycle genes and TE marker genes,which further verified that VGLL1 was a key specific factor in TE development and is necessary for the induction and self-renewal of human TE.Through CUT&Tag assay and co-immunoprecipitation assay,we found VGLL1 interacts with TEAD4(a transcription factor of TEAD family)to form a complex,which affects the induction of TE by regulating histone acetylation modification.In addition,ATACseq experiments demonstrated that VGLL1 and TEAD4 combined to form a complex,which changed chromatin openness by regulating histone acetylation modification to affect the expression levels of cell cycle genes and TE/TSC related genes.The results show the VGLL1-TEAD4 complex regulates TE induction and self-renewal by regulating histone acetylation modifications.TSC is a differentiated and expansible cell formed by further development of TE.To expand our understanding of Trophoblast stem cell and extra-embryonic lineage development,this thesis further explored whether the same TE-induced regulatory mechanism is also applicable in TSC maintenance.Results showed the regulatory mechanism induced by TE was the same as that in TSC maintenance culture in vitro.VGLL1-TEAD4,complex,regulates the cell cycle and the transcriptional activity of TSC related genes through the regulation of histone acetylation modification,and then affected the self-renewal of TSC.Overall,VGLL1-TEAD4 binding to complex in human TE is different from YAP-TEAD4 complex in mouse TE.The results of this paper show that in human TE/TSC,VGLL1 interacts with TEAD4 to form a complex by regulating the acetylation of histones,the cell cycle genes and TE/TSC genes are regulated to affect the induction of TE/TSC self-renewal.This study is a further understanding of the extra-embryonic lineage of human beings,which is helpful for the study and treatment of placenta-related diseases.