Specification of germ cell fate is fundamental in development. With a highly representative single-cell microarray and rigorous quantitative-PCR analysis, we defined the genome-wide transcription dynamics that create primordial germ cells (PGCs) from the epiblast, a process that exclusively segregates them from their somatic neighbors. We also analyzed the effect of the loss of Blimp1, a key transcriptional regulator, on these dynamics. Our analysis revealed that PGC specification involves complex, yet highly ordered regulation of a large number of genes, proceeding under the strong influence of mesoderm induction with active repression of specific programs such as epithelial-mesenchymal transition, Hox gene activation, cell-cycle progression and DNA methyltransferase machinery. Remarkably, Blimp1 is essential for repressing nearly all the genes normally down-regulated in PGCs relative to their somatic neighbors, whereas it is dispensable for the activation of approximately half of the genes up-regulated in PGCs.
Complex genome-wide transcription dynamics orchestrated by Blimp1 for the specification of the germ cell lineage in mice.
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Induction of mouse germ-cell fate by transcription factors in vitro.
Sex, Specimen part
View SamplesThe germ cell lineage ensures the continuity of life through the generation of male and female gametes, which unite to form a totipotent zygote. We have established a culture system that recapitulates the mouse germ-cell specification pathway: Using cytokines, embryonic stem cells (ESCs)/induced pluripotent stem cells (iPSCs) are induced into epiblast-like cells (EpiLCs) and then into primordial germ cell-like cells (PGCLCs) with capacity both for spermatogenesis and oogenesis, creating an opportunity for understanding and regulating mammalian germ cell development in both sexes in vitro. Here we show that, without cytokines, simultaneous over-expression of three transcription factors (TFs), Blimp1 (also known as Prdm1), Prdm14 and Tfap2c (also known as AP2), directs EpiLCs, but not ESCs, swiftly and highly efficiently into a PGC state with endogenous transcription circuitry. The induction of the PGC state on EpiLCs minimally requires Prdm14 but not Blimp1 or Tfap2c. The TF-induced PGC state reconstitutes key transcriptome and epigenetic reprogramming in PGCs, but bypasses a mesodermal program that accompanies PGC specification in vivo and in vitro by cytokines including BMP4. Importantly, the TF-induced PGC-like cells robustly contribute to spermatogenesis and fertile offspring. Our findings provide not only a novel insight into the transcriptional logic that creates a germ cell state, but also a foundation for the TF-based reconstitution and regulation of mammalian gametogenesis.
Induction of mouse germ-cell fate by transcription factors in vitro.
Sex, Specimen part
View SamplesThe germ cell lineage ensures the continuity of life through the generation of male and female gametes, which unite to form a totipotent zygote. We have established a culture system that recapitulates the mouse germ-cell specification pathway: Using cytokines, embryonic stem cells (ESCs)/induced pluripotent stem cells (iPSCs) are induced into epiblast-like cells (EpiLCs) and then into primordial germ cell-like cells (PGCLCs) with capacity both for spermatogenesis and oogenesis, creating an opportunity for understanding and regulating mammalian germ cell development in both sexes in vitro. Here we show that, without cytokines, simultaneous over-expression of three transcription factors (TFs), Blimp1 (also known as Prdm1), Prdm14 and Tfap2c (also known as AP2), directs EpiLCs, but not ESCs, swiftly and highly efficiently into a PGC state with endogenous transcription circuitry. The induction of the PGC state on EpiLCs minimally requires Prdm14 but not Blimp1 or Tfap2c. The TF-induced PGC state reconstitutes key transcriptome and epigenetic reprogramming in PGCs, but bypasses a mesodermal program that accompanies PGC specification in vivo and in vitro by cytokines including BMP4. Importantly, the TF-induced PGC-like cells robustly contribute to spermatogenesis and fertile offspring. Our findings provide not only a novel insight into the transcriptional logic that creates a germ cell state, but also a foundation for the TF-based reconstitution and regulation of mammalian gametogenesis.
Induction of mouse germ-cell fate by transcription factors in vitro.
Sex
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An improved single-cell cDNA amplification method for efficient high-density oligonucleotide microarray analysis.
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View SamplesThe inner cell mass (ICM) of the early blastocyst at E3.5, a source of ES cell derivation, is a morphologically homogeneous population of undifferentiated pluripotent cells that give rise to all embryonic lineages. The immediate application of the newly developed V1V3 method to single cells in this stage of mouse embryos revealed the presence of two populations of cells, one with primitive endoderm expression and the other with pluripotent epiblast-like gene expression. The genes expressed differentially between these two populations were well preserved in morphologically differentiated primitive endoderm and epiblast in the embryos one day later (E4.5), demonstrating that the method successfully detects subtle but essential differences in gene expression at the single-cell level among seemingly homogeneous cell populations. This study provides a strategy to analyze biophysical events in medicine as well as in neural, stem cell, and developmental biology, where small numbers of distinctive or diseased cells play critical roles.
An improved single-cell cDNA amplification method for efficient high-density oligonucleotide microarray analysis.
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View SamplesA systems-level understanding of a small but essential population of cells in development or adulthood (e.g., somatic stem cells) requires accurate quantitative monitoring of genome-wide gene expression, ideally from single cells. We report here a strategy to globally amplify mRNAs from single cells for highly quantitative high-density oligonucleotide microarray analysis that combines a small number of directional PCR cycles with subsequent linear amplification. Using this strategy, both the representation of gene expression profiles and reproducibility between individual experiments are unambiguously improved from the original method, along with high coverage and accuracy.
An improved single-cell cDNA amplification method for efficient high-density oligonucleotide microarray analysis.
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View SamplesMouse embryonic stem cells (mESCs) fluctuate between a nave inner cell mass (ICM)-like state and a primed epiblast-like state of pluripotency in serum, but are harnessed exclusively in a distinctive, apparently more nave state of pluripotency (the ground state) with inhibitors for mitogen-activated protein kinase (MAPK) and glycogen synthase kinase 3 pathways (2i). Understanding the mechanism ensuring a nave state of pluripotency would be critical in realizing a full potential of ESCs. We show here that PRDM14, a PR domain-containing transcriptional regulator, ensures a nave pluripotency by a dual mechanism: Antagonizing fibroblast growth factor receptor (FGFR) signaling that is activated paradoxically by the core transcriptional circuitry for pluripotency and directs a primed state and repressing de novo DNA methyltransferases that create a primed epiblast-like epigenome. PRDM14 exerts these functions by recruiting polycomb repressive complex 2 (PRC2) specifically to key targets and repressing their expression.
PRDM14 ensures naive pluripotency through dual regulation of signaling and epigenetic pathways in mouse embryonic stem cells.
Sex, Specimen part
View SamplesSingle-base resolution DNA methylation maps of mouse embryonic stem cells (ESCs), epiblast-like cells (EpiLCs), and primordial germ cell-like cells (PGCLCs) of wild-type and Prdm14-depleted using the post-bisulfite adaptor tagging (PBAT) method.
Global Landscape and Regulatory Principles of DNA Methylation Reprogramming for Germ Cell Specification by Mouse Pluripotent Stem Cells.
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View SamplesThe germ cell lineage ensures reproduction and heredity in metazoans. Primordial germ cells (PGCs) in mice are induced in pluripotent epiblast cells by BMP4 and WNT3, yet their mechanism of action remains elusive. Here, using in vitro PGC specification system, we show that WNT3, but not BMP4, induces many transcription factors associated with mesoderm in epiblast-like cells (EpiLCs) through beta-CATENIN. Among these, T (BRACHYURY), a classical and conserved mesodermal factor, was essential for robust activation of Blimp1 and Prdm14, two of the germline determinants. T, but not SMAD1 or beta-CATENIN/TCF1, binds distinct regulatory elements of both Blimp1 and Prdm14, and directly up-regulates these genes without BMP4 and WNT3. Without BMP4, a program induced by WNT3 prevents T from activating Blimp1 and Prdm14, demonstrating that BMP4 is permissive for PGC specification. These findings establish a fundamental role of a mesodermal gene in PGC specification, a potentially evolutionarily conserved mechanism across metazoans.
A mesodermal factor, T, specifies mouse germ cell fate by directly activating germline determinants.
Sex, Specimen part
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