Project description:The prevailing dogma that approximately 50% of our genome is “junk” DNA composed of transposable elements and retroviral insertions has recently been challenged. It has become evident that our genome has taken advantage of these transposable elements and uses them as a source of DNA to generate novel genes, which subsequently allow the organism to evolve. This process is termed “domestication of transposable elements” and the majority of these genes have been found to be essential for the existence of the organism. One of these developmentally essential domesticated genes: Peg10 (paternally expressed gene 10), was derived from a Ty3/gyspy LTR retrotransposon, yet lost its ability to transpose due to mutational events during its domestication. Remarkably, Peg10 has successfully maintained its Gag and Pol-like domains for millions of years. Peg10 orthologues are expressed in eutherian mammals and are essential for placentogenesis. To address the functional mechanisms of Peg10 we studied it in Trophoblast Stem Cells (TSCs). We find that the Gag of Peg10 is fully active: it promotes budding of vesicles, akin to the viral counterpart that catalyzes the budding of viruses. TSCs, deleted for Peg10, fail to differentiate into placental lineages, underscoring a critical role in lineage specification. This paper discusses our efforts to characterize the contents of Peg10 vesicles and whether such vesicles regulate lineage specification.
Project description:Peg10 (paternally expressed gene 10) is an imprinted gene that is essential for placental development (1). It is thought to derive from a Ty3-gyspy LTR (long terminal repeat) retrotransposon and retains Gag and Pol-like domains (2). Here we show that the Gag domain of PEG10 can promote vesicle budding similar to the HIV p24 Gag protein. Expressed in a subset of mouse endocrine organs in addition to the placenta, PEG10 was identified as a substrate of the deubiquitinating enzyme USP9X. Consistent with PEG10 having a critical role in placental development, PEG10-deficient trophoblast stem cells (TSCs) exhibited impaired differentiation into placental lineages. PEG10 expressed in wild-type, differentiating TSCs was bound to many cellular RNAs including Hbegf (Heparin-binding EGF-like growth factor), which is known to play an important role in placentation (3). Expression of Hbegf was reduced in PEG10-deficient TSCs suggesting that PEG10 might bind to and stabilize RNAs that are critical for normal placental development.
Project description:Human naive pluripotent stem cells have unrestricted lineage potential. Underpinning this property, naive cells are thought to lack chromatin-based lineage barriers. However, this assumption has not been tested. Here, we apply multi-omics to comprehensively define the chromatin-associated proteome, histone post-translational modifications and transcriptome of human naive and primed pluripotent stem cells. Integrating the chromatin-bound proteome and histone modification data sets reveals differences in the relative abundance and activities of distinct chromatin modules, identifying a strong enrichment of Polycomb Repressive Complex 2 (PRC2)-associated H3K27me3 in naive pluripotent stem cell chromatin. Single-cell approaches and human blastoid models reveal that PRC2 activity acts as a chromatin barrier restricting the differentiation of naive cells towards the trophoblast lineage, and inhibiting PRC2 promotes trophoblast fate induction and cavity formation. Our results establish that human naive pluripotent stem cells are not epigenetically unrestricted, but instead possess chromatin mechanisms that oppose the induction of alternative cell fates.
Project description:Porcine induced pluripotent stem cells (piPSCs) could serve as a great model system for human stem cell pre-clinical research. However, the pluripotency gene network of piPSCs, especially the function for the core transcription factor ESRRB, was poorly understood. Here, we constructed ESRRB-overexpressing piPSCs (ESRRB-piPSCs). Compared with the control piPSCs (CON-piPSCs), the ESRRB-piPSCs showed flat, monolayered colony morphology. Moreover, the ESRRB-piPSCs showed greater chimeric capacity into trophectoderm than CON-piPSCs. We found that ESRRB could directly regulate the expressions of trophoblast stem cell (TSC)-specific markers, including KRT8, KRT18 and CDX2, through binding to their promoter regions. Mutational analysis proved that the N-terminus zinc finger domain is indispensable for ESRRB to regulate the TSC markers. Furthermore, this regulation needs the participation of OCT4. Accordingly, the cooperation between ESRRB and OCT4 facilitates the conversion from pluripotent state to the trophoblast-like state.
Project description:The prevailing dogma that approximately 50% of our genome is “junk” DNA composed of transposable elements and retroviral insertions has recently been challenged. It has become evident that our genome has taken advantage of these transposable elements and uses them as a source of DNA to generate novel genes, which subsequently allow the organism to evolve. This process is termed “domestication of transposable elements” and the majority of these genes have been found to be essential for the existence of the organism. One of these developmentally essential domesticated genes: Peg10 (paternally expressed gene 10), was derived from a Ty3/gyspy LTR retrotransposon, yet lost its ability to transpose due to mutational events during its domestication. Remarkably, Peg10 has successfully maintained its Gag and Pol-like domains for millions of years. Peg10 orthologues are expressed in eutherian mammals and are essential for placentogenesis. To address the functional mechanisms of Peg10 we studied it in Trophoblast Stem Cells (TSCs). We find that the Gag of Peg10 is fully active: it promotes budding of vesicles, akin to the viral counterpart that catalyzes the budding of viruses. TSCs, deleted for Peg10, fail to differentiate into placental lineages, underscoring a critical role in lineage specification. This paper discusses our efforts to characterize the contents of Peg10 vesicles and whether such vesicles regulate lineage specification.
Project description:Extraembryonic trophoblast stem cells (TSC) can be converted to induced pluripotent stem cells (TSC-iPSCs) by overexpressing Oct4, Sox2, Klf4 and cMyc.
Project description:Embryonic stem (ES) cells and trophoblast stem (TS) cells are both derived from early embryos, yet these cells have distinct differentiation properties. ES cells can differentiate into all three germ layer cell types, whereas TS cells can only differentiate into placental cells. It has not been determined whether TS cells can be converted into ES-like pluripotent stem (PS) cells. Here we report that overexpression of a single transcription factor, Oct4, in TS cells is sufficient to convert TS cells into a pluripotent state. These Oct4 induced pluripotent stem (OiPS) cells have the epigenetic characteristics of ES cells, including X chromosome reactivation and elevated H3K27 me3 modifications. The gene expression profile of OiPS cells and ES cells was very similar. Moreover, OiPS cells can differentiate into the three germ layer cell types in vitro and in vivo. More importantly, chimeric mice with germline transmission could be efficiently produced from OiPS cells. To our knowledge, this is the first evidence showing that only one single transcription factor could convert the non-embryonic TS cells into pluripotent stem cells with pluripotency. Gene expression profile of iPS cells and trophoblast stem cells were generated by Affymetrix Mouse Gene 1.0 ST Array. The Gene expression profile of ES cell R1 in GSE17004 was used as control. Three biological repeats were included for each line.
Project description:Human pluripotent stem cells (hPSCs) require precise control of post-transcriptional RNA networks to maintain proliferation and survival. Using a recently developed enhanced UV crosslinking and immunoprecipitation (eCLIP) approach, we identify RNA targets of the IMP/IGF2BP family of RNA-binding proteins in hPSCs. At the broad region- and binding site-level IMP1 and IMP2 show reproducible binding to a large and overlapping set of 3'UTR-enriched targets. RNA Bind-N-Seq applied to recombinant full-length IMP1 and IMP2 reveals CA-rich motifs that are enriched in eCLIP-defined binding sites. We observe that IMP1 loss in hPSCs recapitulates IMP1 phenotypes, including a reduction in cell adhesion and an increase in cell death. For cell adhesion, in hPSCs we find IMP1 maintains levels of integrin mRNA, specifically regulating RNA stability of ITGB5. Additionally, we show IMP1 can be linked to hPSC survival via direct target BCL2. Thus, transcriptome-wide binding profiles identify hPSC targets modulating well-characterized IMP1 roles. eCLIP-seq was performed in biological replicate for IGF2BP1/IMP1 and IGF2BP2/IMP2, as well as one replicate each for IGF2BP3/IMP3, RBFOX2, and an IgG control. Each sample has a size-matched input control for analysis
Project description:Extraembryonic trophoblast stem cells (TSC) can be converted to induced pluripotent stem cells (TSC-iPSCs) by overexpressing Oct4, Sox2, Klf4 and cMyc. TSC lines were derived from mice harboring a doxycycline inducible Oct4 allele and an Oct4-GFP reporter that has been demonstrated to be activated in cells upon acquisition of pluripotency. Oct4-GFP-positive blastocysts were collected at 3.5 dpc and transduced with lentiviruses encoding doxycycline inducible Sox2, Klf4 and cMyc transgenes (4FTSC). 4FTSC lines were passaged 10 times to establish a population of constantly growing, self-renewing TSCs in the presence of FGF4 and fibroblast conditioned media. To induce lineage conversion, 4FTSCs were cultured under ESC/Lif conditions and doxycycline. After 28 days, several colonies displaying ESC-characteristic dome-shaped colony morphology and bright Oct4-GFP fluorescence could be detected. The 4FTSC-derived colonies were isolated mechanically, dissociated by trypsinization, and plated onto MEFs in ESC medium without doxycycline demonstrating the independence of exogenous factors. They will be called TSC-iPSCs (Trophoblast stem cell derived induced pluripotent stem cells). To examine if the extraembryonic lineage-specific mRNA profile was overcome, the gene-expression profiles of TSC-iPSCs and their parental 4FTSCs were analyzed by microarray analyses and compared to control ESCs.