Project description:DNA and Histone-3 Lysine 27 methylation typically function as repressive modifications and operate within distinct genomic compartments. In mammals, the majority of the genome is kept in a DNA methylated state, whereas the Polycomb Repressive Complexes regulate the unmethylated CpG-rich promoters of developmental genes. In contrast to this general framework, the extraembryonic lineages display non-canonical, globally intermediate DNA methylation levels that includes disruption of local Polycomb domains. To better understand this unusual landscape’s molecular properties, we genetically and chemically perturbed major epigenetic pathways in mouse Trophoblast Stem Cells (TSCs). We find that the extraembryonic epigenome reflects ongoing and dynamic de novo methyltransferase recruitment, which is continuously antagonized by Polycomb to maintain intermediate, locally disordered methylation. Despite its disorganized molecular appearance, our data point to a highly controlled equilibrium between counteracting repressors within extraembryonic cells, one that can seemingly persist indefinitely without bistable features typically seen for embryonic forms of epigenetic regulation.
Project description:DNA and Histone-3 Lysine 27 methylation typically function as repressive modifications and operate within distinct genomic compartments. In mammals, the majority of the genome is kept in a DNA methylated state, whereas the Polycomb Repressive Complexes regulate the unmethylated CpG-rich promoters of developmental genes. In contrast to this general framework, the extraembryonic lineages display non-canonical, globally intermediate DNA methylation levels that includes disruption of local Polycomb domains. To better understand this unusual landscape’s molecular properties, we genetically and chemically perturbed major epigenetic pathways in mouse Trophoblast Stem Cells (TSCs). We find that the extraembryonic epigenome reflects ongoing and dynamic de novo methyltransferase recruitment, which is continuously antagonized by Polycomb to maintain intermediate, locally disordered methylation. Despite its disorganized molecular appearance, our data point to a highly controlled equilibrium between counteracting repressors within extraembryonic cells, one that can seemingly persist indefinitely without bistable features typically seen for embryonic forms of epigenetic regulation. Dataset 1: EED co-immunoprecipitation of wild type mouse trophoblast stem cells (TSCs) and Eed knockout TSCs as control, with 3 biological replicates per condition.
Project description:One of the most important topic in mammalian embryogenesis is cell lineage segregation. Briefly, one totipotent zygote will develop into inner cell mass (ICM) and trophectoderm (TE) at blastocyst stage, then the ICM will finally develop into multiple somatic cell lineages and TE will majorly become the placenta tissue which supports and protects the development of the embryo proper. Multiple extrinsic and intrinsic regulatory pathways are involved in facilitating the appropriate development of the embryo. Epigenetic reprogramming is one of the most pervasive events during mouse embryo development(Li, 2002). Recent studies had implied that distinct features for the establishment of DNA methylation(Monk et al., 1987) and histone modifications especially H3K27me3(Liu et al., 2016) during mouse early embryo development. The re-establishment of DNA methylation in early mouse embryos starts at blastocyst stage (about embryonic day 3.5, E3.5) and peaks around the gastrulation stage, while the re-establishment of H3K27me3 exhibits a great level of dynamics and gradually increased CpG preference during pre-implantation embryo development(Liu et al., 2016). However, the underlying epigenetic mechanism concerning the lineage segregation and developmental competence restriction between the pluripotent embryo proper and the supporting extraembryonic tissues especially extraembryonic ectoderm (ExE) remains largely unknown. Surprisingly, no significant difference exists for the distribution of H3K27me3 and DNA methylation between ICM and TE in the preimplantation embryos. Therefore, it is of great importance for unveiling the interplays between H3K27me3 and DNA methylation involving in the restriction of developmental competence between embryonic cells and extraembryonic cells in post-implantation embryos.
Project description:Induction of the Arf tumor suppressor in response to hyperproliferative stress following oncogene activation activates a p53-dependent transcriptional program that limits the expansion of incipient cancer cells. Although Arf is not expressed in most tissues of fetal or young adult mice, it is physiologically expressed in the fetal yolk sac, a tissue derived from the extraembryonic endoderm. We demonstrate that expression of the mouse p19Arf protein marks late stages of extraembryonic endoderm differentiation in cultured embryoid bodies derived from either embryonic stem cells or induced pluripotent stem cells, and that Arf inactivation specifically delays the differentiation of the extraembryonic endoderm lineage, but not the formation of other germ cell lineages from pluripotent progenitors. Arf is required for the timely induction of extraembryonic endodermal cells in response to Ras/Erk signaling and, in turn, acts through p53 to ensure extraembryonic endoderm lineage development, but not maintenance. Remarkably, a significant temporal delay in extraembryonic endoderm differentiation detected during the maturation of Arf-null embryoid bodies is rescued by enforced expression of miR-205, a micro-RNA up-regulated by p19Arf and p53. Introduction of miR-205 into Arf-null embryonic stem cells rescues defective ExEn formation and elicits a program of gene expression that controls the migration and adhesion of embryonic endodermal cells. This occurs, at least in part, through atypical regulation of genes that control the epithelial-to-mesenchymal transition in cancer cells. Our findings suggest that noncanonical and canonical roles of Arf in extraembryonic endoderm development and tumor suppression, respectively, may be conceptually linked through mechanisms that govern cell-to-cell attachment and migration. 4 samples total two each at two time points in ESC development At each time point one sample was treted with miR-205 and the other with a GFP control vector