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Cell Cycle (Georgetown, Tex.) Nov 2019Mouse primordial germ cells (PGCs), originate from the early post-implantation epiblast in response to BMP4 secreted by the extraembryonic ectoderm. However, how BMP4... (Review)
Review
Mouse primordial germ cells (PGCs), originate from the early post-implantation epiblast in response to BMP4 secreted by the extraembryonic ectoderm. However, how BMP4 acts here has remained unclear. Recent work has identified the transcription factor (TF), OTX2 as a key determinant of the segregation of the germline from the soma. OTX2 is expressed ubiquitously in the early post-implantation epiblast, decreasing rapidly in cells that initiate the PGC programme. mRNA is also rapidly repressed by BMP4 , in germline competent cells. Supporting a model in which BMP4 represses , enforcing sustained OTX2 expression in competent cells blocks germline entry. In contrast, -null epiblast cells enter the germline with increased efficiency and and can do so independently of BMP4. Also, -null cells can initiate germline entry even without the crucial PGC TF, BLIMP1. In this review, we survey recent advances and propose hypotheses concerning germline entry.
Topics: Animals; Bone Morphogenetic Protein 4; Cell Differentiation; Ectoderm; Gene Expression Regulation, Developmental; Germ Cells; Germ Layers; Mice; Nanog Homeobox Protein; Otx Transcription Factors; Positive Regulatory Domain I-Binding Factor 1
PubMed: 31583942
DOI: 10.1080/15384101.2019.1672466 -
Cell Reports Apr 2023Much progress has been made toward generating analogs of early embryos, such as gastruloids and embryoids, in vitro. However, methods for how to fully mimic the cell...
Much progress has been made toward generating analogs of early embryos, such as gastruloids and embryoids, in vitro. However, methods for how to fully mimic the cell movements of gastrulation and coordinate germ-layer patterning to induce head formation are still lacking. Here, we show that a regional Nodal gradient applied to zebrafish animal pole explant can generate a structure that recapitulates the key cell movements of gastrulation. Using single-cell transcriptome and in situ hybridization analysis, we assess the dynamics of the cell fates and patterning of this structure. The mesendoderm differentiates into the anterior endoderm, prechordal plate, notochord, and tailbud-like cells along an anterior-posterior axis, and an anterior-posterior-patterned head-like structure (HLS) progressively forms during late gastrulation. Among 105 immediate Nodal targets, 14 genes contain axis-induction ability, and 5 of them induce a complete or partial head structure when overexpressed in the ventral side of zebrafish embryos.
Topics: Animals; Zebrafish; Zebrafish Proteins; Transforming Growth Factor beta; Cell Differentiation; Mesoderm; Body Patterning; Gene Expression Regulation, Developmental
PubMed: 37018074
DOI: 10.1016/j.celrep.2023.112351 -
Protein & Cell Oct 2022Understanding the regulatory networks for germ cell fate specification is necessary to developing strategies for improving the efficiency of germ cell production in...
Understanding the regulatory networks for germ cell fate specification is necessary to developing strategies for improving the efficiency of germ cell production in vitro. In this study, we developed a coupled screening strategy that took advantage of an arrayed bi-molecular fluorescence complementation (BiFC) platform for protein-protein interaction screens and epiblast-like cell (EpiLC)-induction assays using reporter mouse embryonic stem cells (mESCs). Investigation of candidate interaction partners of core human pluripotent factors OCT4, NANOG, KLF4 and SOX2 in EpiLC differentiation assays identified novel primordial germ cell (PGC)-inducing factors including BEN-domain (BEND/Bend) family members. Through RNA-seq, ChIP-seq, and ATAC-seq analyses, we showed that Bend5 worked together with Bend4 and helped mark chromatin boundaries to promote EpiLC induction in vitro. Our findings suggest that BEND/Bend proteins represent a new family of transcriptional modulators and chromatin boundary factors that participate in gene expression regulation during early germline development.
Topics: Animals; Cell Differentiation; Chromatin; Embryonic Stem Cells; Germ Cells; Germ Layers; Mice
PubMed: 34731408
DOI: 10.1007/s13238-021-00884-1 -
Development (Cambridge, England) Feb 2017The regulative capability of single cells to give rise to all primary embryonic lineages is termed pluripotency. Observations of fluctuating gene expression and... (Review)
Review
The regulative capability of single cells to give rise to all primary embryonic lineages is termed pluripotency. Observations of fluctuating gene expression and phenotypic heterogeneity in vitro have fostered a conception of pluripotency as an intrinsically metastable and precarious state. However, in the embryo and in defined culture environments the properties of pluripotent cells change in an orderly sequence. Two phases of pluripotency, called naïve and primed, have previously been described. In this Hypothesis article, a third phase, called formative pluripotency, is proposed to exist as part of a developmental continuum between the naïve and primed phases. The formative phase is hypothesised to be enabling for the execution of pluripotency, entailing remodelling of transcriptional, epigenetic, signalling and metabolic networks to constitute multi-lineage competence and responsiveness to specification cues.
Topics: Animals; Cell Differentiation; Cell Lineage; Embryonic Development; Embryonic Stem Cells; Gene Expression Regulation, Developmental; Germ Layers; Humans; Mice; Models, Biological; Pluripotent Stem Cells
PubMed: 28143843
DOI: 10.1242/dev.142679 -
Nature Communications Sep 2023Understanding of the molecular drivers of lineage diversification and tissue patterning during primary germ layer development requires in-depth knowledge of the dynamic...
Understanding of the molecular drivers of lineage diversification and tissue patterning during primary germ layer development requires in-depth knowledge of the dynamic molecular trajectories of cell lineages across a series of developmental stages of gastrulation. Through computational modeling, we constructed at single-cell resolution, a spatio-temporal transcriptome of cell populations in the germ-layers of gastrula-stage mouse embryos. This molecular atlas enables the inference of molecular network activity underpinning the specification and differentiation of the germ-layer tissue lineages. Heterogeneity analysis of cellular composition at defined positions in the epiblast revealed progressive diversification of cell types. The single-cell transcriptome revealed an enhanced BMP signaling activity in the right-side mesoderm of late-gastrulation embryo. Perturbation of asymmetric BMP signaling activity at late gastrulation led to randomization of left-right molecular asymmetry in the lateral mesoderm of early-somite-stage embryo. These findings indicate the asymmetric BMP activity during gastrulation may be critical for the symmetry breaking process.
Topics: Animals; Mice; Gastrulation; Functional Laterality; Gastrula; Germ Layers; Mesoderm
PubMed: 37709743
DOI: 10.1038/s41467-023-41482-5 -
Journal of Anatomy Dec 2010Relative to recent advances in understanding molecular requirements for endoderm differentiation, the dynamics of germ layer morphology and the topographical...
Relative to recent advances in understanding molecular requirements for endoderm differentiation, the dynamics of germ layer morphology and the topographical distribution of molecular factors involved in endoderm formation at the caudal pole of the embryonic disc are still poorly defined. To discover common principles of mammalian germ layer development, pig and rabbit embryos at late gastrulation and early neurulation stages were analysed as species with a human-like embryonic disc morphology, using correlative light and electron microscopy. Close intercellular contact but no direct structural evidence of endoderm formation such as mesenchymal-epithelial transition between posterior primitive streak mesoderm and the emerging posterior endoderm were found. However, a two-step process closely related to posterior germ layer differentiation emerged for the formation of the cloacal membrane: (i) a continuous mesoderm layer and numerous patches of electron-dense flocculent extracellular matrix mark the prospective region of cloacal membrane formation; and (ii) mesoderm cells and all extracellular matrix including the basement membrane are lost locally and close intercellular contact between the endoderm and ectoderm is established. The latter process involves single cells at first and then gradually spreads to form a longitudinally oriented seam-like cloacal membrane. These gradual changes were found from gastrulation to early somite stages in the pig, whereas they were found from early somite to mid-somite stages in the rabbit; in both species cloacal membrane formation is complete prior to secondary neurulation. The results highlight the structural requirements for endoderm formation during development of the hindgut and suggest new mechanisms for the pathogenesis of common urogenital and anorectal malformations.
Topics: Animals; Anorectal Malformations; Anus, Imperforate; Cell Differentiation; Cloaca; Embryo, Mammalian; Endoderm; Germ Layers; Morphogenesis; Rabbits; Swine; Urogenital Abnormalities
PubMed: 20874819
DOI: 10.1111/j.1469-7580.2010.01303.x -
Biological Reviews of the Cambridge... Feb 2022There are several competing hypotheses on tooth origins, with discussions eventually settling in favour of an 'outside-in' scenario, in which internal odontodes (teeth)... (Review)
Review
There are several competing hypotheses on tooth origins, with discussions eventually settling in favour of an 'outside-in' scenario, in which internal odontodes (teeth) derived from external odontodes (skin denticles) in jawless vertebrates. The evolution of oral teeth from skin denticles can be intuitively understood from their location at the mouth entrance. However, the basal condition for jawed vertebrates is arguably to possess teeth distributed throughout the oropharynx (i.e. oral and pharyngeal teeth). As skin denticle development requires the presence of ectoderm-derived epithelium and of mesenchyme, it remains to be answered how odontode-forming skin epithelium, or its competence, were 'transferred' deep into the endoderm-covered oropharynx. The 'modified outside-in' hypothesis for tooth origins proposed that this transfer was accomplished through displacement of odontogenic epithelium, that is ectoderm, not only through the mouth, but also via any opening (e.g. gill slits) that connects the ectoderm to the epithelial lining of the pharynx (endoderm). This review explores from an evolutionary and from a developmental perspective whether ectoderm plays a role in (pharyngeal) tooth and denticle formation. Historic and recent studies on tooth development show that the odontogenic epithelium (enamel organ) of oral or pharyngeal teeth can be of ectodermal, endodermal, or of mixed ecto-endodermal origin. Comprehensive data are, however, only available for a few taxa. Interestingly, in these taxa, the enamel organ always develops from the basal layer of a stratified epithelium that is at least bilayered. In zebrafish, a miniaturised teleost that only retains pharyngeal teeth, an epithelial surface layer with ectoderm-like characters is required to initiate the formation of an enamel organ from the basal, endodermal epithelium. In urodele amphibians, the bilayered epithelium is endodermal, but the surface layer acquires ectodermal characters, here termed 'epidermalised endoderm'. Furthermore, ectoderm-endoderm contacts at pouch-cleft boundaries (i.e. the prospective gill slits) are important for pharyngeal tooth initiation, even if the influx of ectoderm via these routes is limited. A balance between sonic hedgehog and retinoic acid signalling could operate to assign tooth-initiating competence to the endoderm at the level of any particular pouch. In summary, three characters are identified as being required for pharyngeal tooth formation: (i) pouch-cleft contact, (ii) a stratified epithelium, of which (iii) the apical layer adopts ectodermal features. These characters delimit the area in which teeth can form, yet cannot alone explain the distribution of teeth over the different pharyngeal arches. The review concludes with a hypothetical evolutionary scenario regarding the persisting influence of ectoderm on pharyngeal tooth formation. Studies on basal osteichthyans with less-specialised types of early embryonic development will provide a crucial test for the potential role of ectoderm in pharyngeal tooth formation and for the 'modified outside-in' hypothesis of tooth origins.
Topics: Animals; Biological Evolution; Germ Layers; Gills; Pharynx; Zebrafish
PubMed: 34647411
DOI: 10.1111/brv.12805 -
Current Opinion in Genetics &... Jun 2012Pluripotency manifests during mammalian development through formation of the epiblast, founder tissue of the embryo proper. Rodent pluripotent stem cells can be... (Review)
Review
Pluripotency manifests during mammalian development through formation of the epiblast, founder tissue of the embryo proper. Rodent pluripotent stem cells can be considered as two distinct states: naïve and primed. Naïve pluripotent stem cell lines are distinguished from primed cells by self-renewal in response to LIF signaling and MEK/GSK3 inhibition (LIF/2i conditions) and two active X chromosomes in female cells. In rodent cells, the naïve pluripotent state may be accessed through at least three routes: explantation of the inner cell mass, somatic cell reprogramming by ectopic Oct4, Sox2, Klf4, and C-myc, and direct reversion of primed post-implantation-associated epiblast stem cells (EpiSCs). In contrast to their rodent counterparts, human embryonic stem cells and induced pluripotent stem cells more closely resemble rodent primed EpiSCs. A critical question is whether naïve human pluripotent stem cells with bona fide features of both a pluripotent state and naïve-specific features can be obtained. In this review, we outline current understanding of the differences between these pluripotent states in mice, new perspectives on the origins of naïve pluripotency in rodents, and recent attempts to apply the rodent paradigm to capture naïve pluripotency in human cells. Unraveling how to stably induce naïve pluripotency in human cells will influence the full realization of human pluripotent stem cell biology and medicine.
Topics: Animals; Cell Differentiation; Chimera; Embryo Culture Techniques; Embryo, Mammalian; Embryonic Development; Embryonic Stem Cells; Germ Layers; Homeodomain Proteins; Humans; Induced Pluripotent Stem Cells; Kruppel-Like Factor 4; MAP Kinase Signaling System; Mice; Nanog Homeobox Protein; Rats; Species Specificity; Teratoma
PubMed: 22463982
DOI: 10.1016/j.gde.2012.03.001 -
PloS One 2013Huntington's disease (HD) is a neurodegenerative disease caused by abnormal polyglutamine expansion in the huntingtin protein (Htt). Although both Htt and the HD...
Huntington's disease (HD) is a neurodegenerative disease caused by abnormal polyglutamine expansion in the huntingtin protein (Htt). Although both Htt and the HD pathogenic mutation (mHtt) are implicated in early developmental events, their individual involvement has not been adequately explored. In order to better define the developmental functions and pathological consequences of the normal and mutant proteins, respectively, we employed embryonic stem cell (ESC) expansion, differentiation and induction experiments using huntingtin knock-out (KO) and mutant huntingtin knock-in (Q111) mouse ESC lines. In KO ESCs, we observed impairments in the spontaneous specification and survival of ectodermal and mesodermal lineages during embryoid body formation and under inductive conditions using retinoic acid and Wnt3A, respectively. Ablation of BAX improves cell survival, but failed to correct defects in germ layer specification. In addition, we observed ensuing impairments in the specification and maturation of neural, hepatic, pancreatic and cardiomyocyte lineages. These developmental deficits occurred in concert with alterations in Notch, Hes1 and STAT3 signaling pathways. Moreover, in Q111 ESCs, we observed differential developmental stage-specific alterations in lineage specification and maturation. We also observed changes in Notch/STAT3 expression and activation. Our observations underscore essential roles of Htt in the specification of ectoderm, endoderm and mesoderm, in the specification of neural and non-neural organ-specific lineages, as well as cell survival during early embryogenesis. Remarkably, these developmental events are differentially deregulated by mHtt, raising the possibility that HD-associated early developmental impairments may contribute not only to region-specific neurodegeneration, but also to non-neural co-morbidities.
Topics: Animals; Cell Differentiation; Ectoderm; Embryoid Bodies; Embryonic Stem Cells; Endoderm; Gene Knockout Techniques; Germ Layers; Huntingtin Protein; Mesoderm; Mice; Mutation; Nerve Tissue Proteins; Neurogenesis; Neurons; Nuclear Proteins; Oligodendroglia; Organogenesis; Receptors, Notch; Signal Transduction
PubMed: 23967334
DOI: 10.1371/journal.pone.0072698 -
Cytometry. Part a : the Journal of the... Aug 2022Mouse embryonic stem cells (ESCs) and epiblast stem cells (EpiSCs) are both pluripotent stem cells from early embryos. Another type of pluripotent stem cells, which are...
Mouse embryonic stem cells (ESCs) and epiblast stem cells (EpiSCs) are both pluripotent stem cells from early embryos. Another type of pluripotent stem cells, which are similar with EpiSCs and derive from pre-implantation embryos in feeder-free and chemically defined medium containing Activin A and basic fibroblast growth factors (bFGF), is termed as AFSCs. The pluripotency and self-renewal maintenance of ESCs rely on Leukemia inhibitory factor (LIF)/STAT/BMP4/SMAD signaling, while the pluripotency and self-renewal maintenance of EpiSCs and AFSCs rely on bFGF and Activin/Nodal signaling. However, the establishment efficiency of AFSCs lines is low. In this study, we stimulated early embryos by 2i/LIF (CHIR99021 + PD0325901 + LIF) and Activin A + bFGF respectively, to change the cell fate in inner cell mass (ICM). The "fate changed embryos" by 2i/LIF can efficiently produce AFSCs in feeder-free and chemically defined medium, but the efficiency of embryos treated with Activin A + bFGF were poor. The AFSCs from fate-changed embryos share similar molecular characteristics with conventional AFSCs and EpiSCs. Our results suggest that the advanced stimulation of 2i/LIF and the premature stimulation of Activin A + bFGF contribute to capturing the pluripotent stem cells in early embryos, and the FGF/MAPK signaling dominate early embryo development. Our study provides a new approach to capturing pluripotency from pre-implantation embryos.
Topics: Animals; Cell Differentiation; Embryonic Stem Cells; Germ Layers; Mice; Pluripotent Stem Cells; Signal Transduction
PubMed: 35332996
DOI: 10.1002/cyto.a.24551