Project description:Dppa4 (Developmental pluripotency-associated 4) has been identified in several highprofile screens as a gene that is expressed exclusively in pluripotent cells. It encodes a nuclear protein with a SAP-like domain and appears to be associated preferentially with transcriptionally active chromatin. Its exquisite expression pattern and results of RNA interference experiments have led to speculation that Dppa4, as well as its nearby homolog Dppa2, might play essential roles in embryonic stem cell function and/or germ cell development. To rigorously assess suggested roles, we have generated Dppa4-deficient and Dppa4/Dppa2 double-deficient ES cells, as well as mice lacking Dppa4. Contrary to predictions, we find that Dppa4 is completely dispensable for ES cell identity and germ cell development. Instead, loss of Dppa4 in mice results in late embryonic/peri-natal death and striking skeletal defects with partial penetrance. Thus, surprisingly, Dppa4-deficiency affects tissues, which never transcribed the gene, and at least some loss-of-function defects manifest phenotypically at an embryonic stage long after physiologic Dppa4 expression has ceased. Concomitant with targeted gene inactivation, we have introduced into the Dppa4 locus a red fluorescent marker (tandem-dimer RFP), which is compatible with GFP-based proteins and allows non-invasive visualization of pluripotent cells and reprogramming events.
Project description:How maternal factors in oocytes initiate zygotic genome activation (ZGA) remains elusive. Recent studies indicate that DPPA2 and DPPA4 are required for establishing a 2-cell embryo-like (2C-like) state in mouse embryonic stem cells (ESCs) in a DUX-dependent manner. These results suggest that DPPA2 and DPPA4 are essential maternal factors that regulate Dux and ZGA in embryos. By analyzing maternal knockout and maternal-zygotic knockout embryos, we unexpectedly found that Dux activation, ZGA, and preimplantation development are normal in embryos without DPPA2 or DPPA4. Thus, unlike in ESCs/2C-like cells, DPPA2 and DPPA4 are dispensable for ZGA and preimplantation development.
Project description:The integration of cell metabolism with signalling pathways, transcription factor networks and epigenetic mediators is critical in coordinating molecular and cellular events during embryogenesis. Induced pluripotent stem cells (IPSCs) are an established model for embryogenesis, germ layer specification and cell lineage differentiation, advancing the study of human embryonic development and the translation of innovations in drug discovery, disease modelling and cell-based therapies. The metabolic regulation of IPSC pluripotency is mediated by balancing glycolysis and oxidative phosphorylation, but there is a paucity of data regarding the influence of individual metabolite changes during cell lineage differentiation. We used <sup>1</sup>H NMR metabolite fingerprinting and footprinting to monitor metabolite levels as IPSCs are directed in a three-stage protocol through primitive streak/mesendoderm, mesoderm and chondrogenic populations. Metabolite changes were associated with central metabolism, with aerobic glycolysis predominant in IPSC, elevated oxidative phosphorylation during differentiation and fatty acid oxidation and ketone body use in chondrogenic cells. Metabolites were also implicated in the epigenetic regulation of pluripotency, cell signalling and biosynthetic pathways. Our results show that <sup>1</sup>H NMR metabolomics is an effective tool for monitoring metabolite changes during the differentiation of pluripotent cells with implications on optimising media and environmental parameters for the study of embryogenesis and translational applications.
Project description:Enhancers control cell type-specific gene expression and direct cell fate transition. Enhancers are marked by H3K4me1/2. MLL4 (KMT2D) is a major enhancer H3K4me1/2 methyltransferase. Here we show in embryonic stem cells (ESCs), MLL4 associates with, but is dispensable for the maintenance of, active enhancers of ESC identity genes. As a result, MLL4 is dispensable for cell identity gene expression and self-renewal in ESCs. In contrast, MLL4 is essential for activation of de novo enhancers and induction of cell identity genes during ESC differentiation. Similarly, MLL4 is dispensable for maintaining fibroblast cell identity but is essential for reprogramming into induced pluripotent stem cells. These results indicate that while MLL4 is dispensable for maintaining cell identity, it controls cell fate transitions by orchestrating de novo enhancer activation.
Project description:The H3K4me2/3 histone demethylase Jarid1b (Kdm5b/Plu1) is dispensable for embryonic stem cell (ESC) self-renewal, but essential for ESC differentiation along the neural lineage. During neural differentiation, Jarid1b depleted ESCs fail to efficiently silence lineage-inappropriate genes, specifically stem and germ cell genes. Our results delineate an essential role for Jarid1b-mediated transcriptional control during ESC differentiation. Control (LKOScr) or Jarid1b knockdown (LKOJarid1b) mouse ES cells were used.Each experiment was performed in triplicates.
Project description:DPPA4 is a DNA-associated factor that is highly and selectively expressed in embryonic stem cells. DPPA4 expression is strikingly downregulated upon loss of pluripotency, but is reactivated in a number of cancer cell types. It has recently been identified as an oncogene and shown to promote cell proliferation and anchorage independent growth; Dppa4-transformed cells can form tumors in vivo in mice. DPPA4 has been shown to associate with active chromatin and histone H3, but the global binding dynamics of DPPA4 are unknown. Additionally, only several DPPA4 gene targets are known. To better understand the role of DPPA4 in embryonic stem cell pluripotency and oncogenesis, we performed ChIP-Seq in E14 mouse embryonic stem cells (mESC), 3T3 cells ectopically expressing DPPA4, and P19 embryonic carcinoma cells.
Project description:The H3K4me2/3 histone demethylase Jarid1b (Kdm5b/Plu1) is dispensable for embryonic stem cell (ESC) self-renewal, but essential for ESC differentiation along the neural lineage. During neural differentiation, Jarid1b depleted ESCs fail to efficiently silence lineage-inappropriate genes, specifically stem and germ cell genes. Our results delineate an essential role for Jarid1b-mediated transcriptional control during ESC differentiation.
Project description:Post-translational modification by SUMO is a key regulator of cell identity. In mouse embryonic fibroblasts (MEFs), SUMO impedes reprogramming to pluripotency, while in embryonic stem cells (ESCs), it represses the emergence of totipotent-like cells, suggesting that SUMO targets distinct substrates to preserve somatic and pluripotent states. Using MS-based proteomics, we show that the composition of endogenous SUMOylomes differs dramatically between MEFs and ESCs. In MEFs, SUMO2/3 targets proteins associated with canonical SUMO functions, such as splicing, and transcriptional regulators driving somatic enhancer selection. In contrast, in ESCs, SUMO2/3 primarily modifies highly interconnected repressive chromatin complexes, thereby preventing chromatin opening and transitioning to totipotent-like states. We also characterize several SUMO-modified pluripotency factors and show that SUMOylation of Dppa2 and Dppa4 impedes the conversion to 2-cell-embryo-like states. Altogether, we propose that rewiring the repertoire of SUMO target networks is a major driver of cell fate decision during embryonic development.
Project description:Post-translational modification by SUMO is a key regulator of cell identity. In mouse embryonic fibroblasts (MEFs), SUMO impedes reprogramming to pluripotency, while in embryonic stem cells (ESCs), it represses the emergence of totipotent-like cells, suggesting that SUMO targets distinct substrates to preserve somatic and pluripotent states. Using MS-based proteomics, we show that the composition of endogenous SUMOylomes differs dramatically between MEFs and ESCs. In MEFs, SUMO2/3 targets proteins associated with canonical SUMO functions, such as splicing, and transcriptional regulators driving somatic enhancer selection. In contrast, in ESCs, SUMO2/3 primarily modifies highly interconnected repressive chromatin complexes, thereby preventing chromatin opening and transitioning to totipotent-like states. We also characterize several SUMO-modified pluripotency factors and show that SUMOylation of Dppa2 and Dppa4 impedes the conversion to 2-cell-embryo-like states. Altogether, we propose that rewiring the repertoire of SUMO target networks is a major driver of cell fate decision during embryonic development.
Project description:In mouse development, long-term silencing by CpG island DNA methylation is specifically targeted to germline genes, however the molecular mechanisms of this specificity remain unclear. Here we demonstrate that the transcription factor E2F6, a member of the polycomb repressive complex 1.6 (PRC1.6), is critical to target and initiate epigenetic silencing at germline genes in early embryogenesis. Genome-wide, E2F6 binds preferentially to CpG islands in embryonic cells. E2F6 cooperates with MGA to silence a subgroup of germline genes in mouse embryonic stem cells and in vivo, a function that critically depends on the E2F6 marked box domain. Inactivation of E2f6 leads to a failure to deposit CpG island DNA methylation at these genes during implantation. Furthermore, E2F6 is required to initiate epigenetic silencing in early embryonic cells but becomes dispensable for the maintenance in differentiated cells. Our findings elucidate the mechanisms of epigenetic targeting of germline genes and provide a paradigm for how transient repression signals by DNA-binding factors in early embryonic cells are translated into long term epigenetic silencing during mammalian development.