ABSTRACT: Comparative principles of DNA methylation reprogramming during human and mouse in vitro primordial germ cell specification [Mouse smallRNA-Seq]
Project description:Comparative principles of DNA methylation reprogramming during human and mouse in vitro primordial germ cell specification [Mouse and Human RNA-seq and BS-seq]
Project description:The molecular mechanisms of human primordial germ cell (PGC) specification are poorly understood due to the inaccessibility of cell materials and the lack of an alternative in vitro model that enables tracking of the earliest stages of germ cell development. Here, we introduce a defined and efficient differentiation system for the induction of pre-migratory PGC-like cells from human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). By step-wise differentiation, we generated an OCT4+/ T+/BLIMP1+ cell population that transitioned into STELLA expressing PGC-like cells that exhibited a similar key gene expression as mouse PGCs as well as global epigenetic reprogramming. Even though, these PGC-like cells expressed PRDM14 at very low levels, they underwent activation of pluripotency/PGC genes, suppression of neural induction and suppression of de novo DNA methylation, events that are regulated by Prdm14 during mouse PGC specification. This study demonstrates that human PGC commitment shares many key features with mouse PGC specification, but harbors unique and so far unknown mechanisms that, point to a novel human transcriptional regulation. 7 samples were analyzed. ESC: Human Embryonic Stem Cells, 1 biological rep iPSC: Human induced Pluripotent Stem Cells, 1 biological rep d2: Human induced Pluripotent Stem Cells, 2 days differentiation treatment , 2 biological rep d4PGCLC: Human induced Pluripotent Stem Cells, 4 days differentiation treatment towards Primordial Germ Cells Like Cells, 1 biological rep d6PGCLC: Human induced Pluripotent Stem Cells, 6 days differentiation treatment towards Primordial Germ Cells Like Cells, 2 biological rep
Project description:PRMT5 is a type II protein arginine methyltransferase with roles in stem cell biology, reprogramming, cancer and neurogenesis. During embryogenesis in the mouse it was hypothesized that PRMT5 functions with the master germline determinant BLIMP1 to promote primordial germ cell (PGC) specification. Using a Blimp1-Cre germline conditional knockout, we discovered that Prmt5 has no major role in murine germline specification, or the first global epigenetic reprogramming event involving depletion of cytosine methylation from DNA and histone H3 lysine 9 dimethylation from chromatin. Instead, we discovered that PRMT5 functions at the conclusion of PGC reprogramming I to promote proliferation, survival and expression of the gonadal germline program as marked by MVH. We show that PRMT5 regulates gene expression by promoting methylation of the Sm spliceosomal proteins, and significantly altering the spliced repertoire of RNAs in mammalian embryonic cells and primordial cells. Examination of transcriptional profile of iPHet (Control) vs. iPKO (Prmt5 knock out) 2i Embryonic Stem Cells
Project description:Germ cell specification is an elusive biological event, as it occurs in a small group of cells in the very early embryo (E6.5). In vitro differentiation of naive mouse Embryonic Stem Cells (mESCs) to mouse Primordial Germ Cell like cells (mPGCLCs) allows the mechanistic investigation of germ cell specification. The goal of this study is to profile of gene expression via single cell RNA sequencing throughout the differentiation protocol. In particular, this project aims at examining the transcriptional activation of the molecular networks that direct the epigenetic reprogramming of mPGCLCs.
Project description:PRMT5 is a type II protein arginine methyltransferase with roles in stem cell biology, reprogramming, cancer and neurogenesis. During embryogenesis in the mouse it was hypothesized that PRMT5 functions with the master germline determinant BLIMP1 to promote primordial germ cell (PGC) specification. Using a Blimp1-Cre germline conditional knockout, we discovered that Prmt5 has no major role in murine germline specification, or the first global epigenetic reprogramming event involving depletion of cytosine methylation from DNA and histone H3 lysine 9 dimethylation from chromatin. Instead, we discovered that PRMT5 functions at the conclusion of PGC reprogramming I to promote proliferation, survival and expression of the gonadal germline program as marked by MVH. We show that PRMT5 regulates gene expression by promoting methylation of the Sm spliceosomal proteins, and significantly altering the spliced repertoire of RNAs in mammalian embryonic cells and primordial cells.
Project description:Primordial germ cell (PGC) development is characterized by global epigenetic remodeling, which resets genomic potential and establishes an epigenetic ground state. Here we recapitulate PGC specification in vitro from naive embryonic stem cells and characterize the early events of epigenetic reprogramming during the formation of the human and mouse germline. Following rapid de novo DNA methylation during priming to epiblast-like cells, methylation is globally erased in PGC-like cells (PGCLCs). Repressive chromatin marks (H3K9me2/3) and transposable elements are enriched at demethylation resistant regions, while active chromatin marks (H3K4me3 or H3K27ac) are more prominent at regions that demethylate faster. The dynamics of specification and epigenetic reprogramming show species-specific differences, in particular markedly slower reprogramming kinetics in the human germline. Differences in developmental kinetics between species may be explained by differential regulation of epigenetic modifiers. Our work establishes a robust and faithful experimental system of the early events of epigenetic reprogramming and its regulation in the germline.
Project description:Primordial germ cell (PGC) development is characterized by global epigenetic remodeling, which resets genomic potential and establishes an epigenetic ground state. Here we recapitulate PGC specification in vitro from naive embryonic stem cells and characterize the early events of epigenetic reprogramming during the formation of the human and mouse germline. Following rapid de novo DNA methylation during priming to epiblast-like cells, methylation is globally erased in PGC-like cells (PGCLCs). Repressive chromatin marks (H3K9me2/3) and transposable elements are enriched at demethylation resistant regions, while active chromatin marks (H3K4me3 or H3K27ac) are more prominent at regions that demethylate faster. The dynamics of specification and epigenetic reprogramming show species-specific differences, in particular markedly slower reprogramming kinetics in the human germline. Differences in developmental kinetics between species may be explained by differential regulation of epigenetic modifiers. Our work establishes a robust and faithful experimental system of the early events of epigenetic reprogramming and its regulation in the germline.
Project description:Mechanisms underlying human germ cell development are unclear, partly due to difficulties in studying human embryos and lack of suitable experimental systems. Here, we show that human induced pluripotent stem cells (hiPSCs) differentiate into incipient mesoderm-like cells (iMeLCs), which robustly generate human primordial germ cell-like cells (hPGCLCs) that can be purified using the surface markers EpCAM and INTEGRINα6. The transcriptomes of hPGCLCs and primordial germ cells (PGCs) isolated from non-human primates are similar, and although specification of hPGCLCs and mouse PGCs rely on similar signaling pathways, hPGCLC specification transcriptionally activates germline fate without transiently inducing eminent somatic programs. This includes genes important for naive pluripotency and repression of key epigenetic modifiers, concomitant with epigenetic reprogramming. Accordingly, BLIMP1, which represses somatic programs in mice, activates and stabilizes a germline transcriptional circuit and represses a default neuronal differentiation program. Together, these findings provide a foundation for understanding and reconstituting human germ cell development in vitro.
Project description:The molecular mechanisms of human primordial germ cell (PGC) specification are poorly understood due to the inaccessibility of cell materials and the lack of an alternative in vitro model that enables tracking of the earliest stages of germ cell development. Here, we introduce a defined and efficient differentiation system for the induction of pre-migratory PGC-like cells from human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). By step-wise differentiation, we generated an OCT4+/ T+/BLIMP1+ cell population that transitioned into STELLA expressing PGC-like cells that exhibited a similar key gene expression as mouse PGCs as well as global epigenetic reprogramming. Even though, these PGC-like cells expressed PRDM14 at very low levels, they underwent activation of pluripotency/PGC genes, suppression of neural induction and suppression of de novo DNA methylation, events that are regulated by Prdm14 during mouse PGC specification. This study demonstrates that human PGC commitment shares many key features with mouse PGC specification, but harbors unique and so far unknown mechanisms that, point to a novel human transcriptional regulation.