Project description:The successful segregation of germ cells from somatic lineages is vital for sexual reproduction and species survival. In the mouse, primordial germ cells (PGCs), precursors of all germ cells, are induced from the post-implantation epiblast. Induction requires BMP4 signalling to prospective PGCs and the intrinsic action of PGC transcription factors (TFs). However, the molecular mechanisms connecting BMP4 action to induction of PGC TFs that are responsible for segregation of PGCs from somatic lineages are unknown. Here we show that the transcription factor OTX2 is a key regulator of these processes. Down-regulation of Otx2 precedes the initiation of the PGC programme both in vitro and in vivo. Deletion of Otx2 in vitro dramatically increases PGCLC differentiation efficiency and prolongs the period of PGC competence. In the absence of Otx2 activity, PGCLC differentiation becomes independent of the otherwise essential cytokine signals, with germline entry initiating even in the absence of the PGC TF Blimp1. Deletion of Otx2 in vivo increases PGC numbers. These data demonstrate that Otx2 acts repressively upstream of PGC TFs and functions as a roadblock to prevent the untimely entry of pluripotent stem cells into the PGC lineage, thereby ensuring correct spatio-temporal segregation of the germline and soma.
Project description:The choice between somatic and germline fates is essential for species survival. This choice occurs in embryonic epiblast cells, as these cells are competent for both somatic and germline differentiation. Transcription factors (TFs) play a central role in this process by binding to specific chromatin loci to modulate gene expression and determine cell identity. The TF OTX2 regulates the choice between somatic and germline fates, as Otx2-null epiblast-like cells (EpiLCs) form primordial germ cell-like cells (PGCLCs) with enhanced efficiency. However, the mechanisms by which OTX2 achieves this function are not fully characterized. Here we show that OTX2 controls chromatin accessibility to enable somatic differentiation. By performing CUT&RUN for OTX2 and ATAC-seq in wild-type and Otx2-null embryonic stem cells and EpiLCs, we identified regions where OTX2 binding opens chromatin. Enforced OTX2 expression maintains accessibility at these regions and induces opening of 4,000 additional somatic-associated regions in the presence of PGC-inducing cytokines. Once cells have acquired germline identity, the 4,000 additional somatic associated regions do not respond to OTX2 and remain closed. Our results indicate that OTX2 works in cells with dual competence for both somatic and germline differentiation to increase accessibility of somatic regulatory regions and induce the somatic fate at the expense of the germline.
Project description:The choice between somatic and germline fates is essential for species survival. This choice occurs in embryonic epiblast cells, as these cells are competent for both somatic and germline differentiation. Transcription factors (TFs) play a central role in this process by binding to specific chromatin loci to modulate gene expression and determine cell identity. The TF OTX2 regulates the choice between somatic and germline fates, as Otx2-null epiblast-like cells (EpiLCs) form primordial germ cell-like cells (PGCLCs) with enhanced efficiency. However, the mechanisms by which OTX2 achieves this function are not fully characterized. Here we show that OTX2 controls chromatin accessibility to enable somatic differentiation. By performing CUT&RUN for OTX2 and ATAC-seq in wild-type and Otx2-null embryonic stem cells and EpiLCs, we identified regions where OTX2 binding opens chromatin. Enforced OTX2 expression maintains accessibility at these regions and induces opening of 4,000 additional somatic-associated regions in the presence of PGC-inducing cytokines. Once cells have acquired germline identity, the 4,000 additional somatic associated regions do not respond to OTX2 and remain closed. Our results indicate that OTX2 works in cells with dual competence for both somatic and germline differentiation to increase accessibility of somatic regulatory regions and induce the somatic fate at the expense of the germline.
Project description:Germline-soma segregation is a fundamental event during mammalian embryonic development. Here we establish the epigenetic principles of human primordial germ cell (hPGC) development using in vivo hPGCs and stem cell models recapitulating gastrulation. We show that morphogen-induced remodelling of mesendoderm enhancers transiently confers the competence for hPGC fate, but further activation favours mesoderm and endoderm fates. Consistently, reducing the expression of the mesendodermal transcription factor OTX2 promotes the PGC fate. In hPGCs, SOX17 and TFAP2C initiate activation of enhancers to establish a core germline programme, including the transcriptional repressor PRDM1 and pluripotency factors POU5F1 and NANOG. We demonstrate that SOX17 enhancers are the critical components in the regulatory circuitry of germline competence. Furthermore, activation of upstream cis-regulatory elements by an optimized CRISPR activation system is sufficient for hPGC specification. We reveal an enhancer-linked germline transcription factor network that provides the basis for the evolutionary divergence of mammalian germlines.
Project description:Germline-soma segregation is a fundamental event during mammalian embryonic development. Here we establish the epigenetic principles of human primordial germ cell (hPGC) development using in vivo hPGCs and stem cell models recapitulating gastrulation. We show that morphogen-induced remodelling of mesendoderm enhancers transiently confers the competence for hPGC fate, but further activation favours mesoderm and endoderm fates. Consistently, reducing the expression of the mesendodermal transcription factor OTX2 promotes the PGC fate. In hPGCs, SOX17 and TFAP2C initiate activation of enhancers to establish a core germline programme, including the transcriptional repressor PRDM1 and pluripotency factors POU5F1 and NANOG. We demonstrate that SOX17 enhancers are the critical components in the regulatory circuitry of germline competence. Furthermore, activation of upstream cis-regulatory elements by an optimized CRISPR activation system is sufficient for hPGC specification. We reveal an enhancer-linked germline transcription factor network that provides the basis for the evolutionary divergence of mammalian germlines.
Project description:Germline-soma segregation is a fundamental event during mammalian embryonic development. Here we establish the epigenetic principles of human primordial germ cell (hPGC) development using in vivo hPGCs and stem cell models recapitulating gastrulation. We show that morphogen-induced remodelling of mesendoderm enhancers transiently confers the competence for hPGC fate, but further activation favours mesoderm and endoderm fates. Consistently, reducing the expression of the mesendodermal transcription factor OTX2 promotes the PGC fate. In hPGCs, SOX17 and TFAP2C initiate activation of enhancers to establish a core germline programme, including the transcriptional repressor PRDM1 and pluripotency factors POU5F1 and NANOG. We demonstrate that SOX17 enhancers are the critical components in the regulatory circuitry of germline competence. Furthermore, activation of upstream cis-regulatory elements by an optimized CRISPR activation system is sufficient for hPGC specification. We reveal an enhancer-linked germline transcription factor network that provides the basis for the evolutionary divergence of mammalian germlines.
Project description:Germline-soma segregation is a fundamental event during mammalian embryonic development. Here we establish the epigenetic principles of human primordial germ cell (hPGC) development using in vivo hPGCs and stem cell models recapitulating gastrulation. We show that morphogen-induced remodelling of mesendoderm enhancers transiently confers the competence for hPGC fate, but further activation favours mesoderm and endoderm fates. Consistently, reducing the expression of the mesendodermal transcription factor OTX2 promotes the PGC fate. In hPGCs, SOX17 and TFAP2C initiate activation of enhancers to establish a core germline programme, including the transcriptional repressor PRDM1 and pluripotency factors POU5F1 and NANOG. We demonstrate that SOX17 enhancers are the critical components in the regulatory circuitry of germline competence. Furthermore, activation of upstream cis-regulatory elements by an optimized CRISPR activation system is sufficient for hPGC specification. We reveal an enhancer-linked germline transcription factor network that provides the basis for the evolutionary divergence of mammalian germlines.
Project description:Germline-soma segregation is a fundamental event during mammalian embryonic development. Here we establish the epigenetic principles of human primordial germ cell (hPGC) development using in vivo hPGCs and stem cell models recapitulating gastrulation. We show that morphogen-induced remodelling of mesendoderm enhancers transiently confers the competence for hPGC fate, but further activation favours mesoderm and endoderm fates. Consistently, reducing the expression of the mesendodermal transcription factor OTX2 promotes the PGC fate. In hPGCs, SOX17 and TFAP2C initiate activation of enhancers to establish a core germline programme, including the transcriptional repressor PRDM1 and pluripotency factors POU5F1 and NANOG. We demonstrate that SOX17 enhancers are the critical components in the regulatory circuitry of germline competence. Furthermore, activation of upstream cis-regulatory elements by an optimized CRISPR activation system is sufficient for hPGC specification. We reveal an enhancer-linked germline transcription factor network that provides the basis for the evolutionary divergence of mammalian germlines.
Project description:To define what genes are predominantly or specifically expressed in either soma or germline in C. elegans adults, total RNA was extracted from germline-less glp-4 mutant animals or from dissected gonads, respectively. Total RNA sequencing was peformed in duplicates. Four samples in total.