-
Proceedings of the National Academy of... Jun 2021Markers for the endoderm and mesoderm germ layers are commonly expressed together in the early embryo, potentially reflecting cells' ability to explore potential fates...
Markers for the endoderm and mesoderm germ layers are commonly expressed together in the early embryo, potentially reflecting cells' ability to explore potential fates before fully committing. It remains unclear when commitment to a single-germ layer is reached and how it is impacted by external signals. Here, we address this important question in , a convenient model system in which mesodermal and endodermal fates are associated with distinct cellular movements during gastrulation. Systematically applying endoderm-inducing extracellular signal-regulated kinase (ERK) signals to the ventral medial embryo-which normally only receives a mesoderm-inducing cue-reveals a critical time window during which mesodermal cell movements and gene expression are suppressed by proendoderm signaling. We identify the ERK target gene () as the main cause of the ventral furrow suppression and use computational modeling to show that Hkb repression of the mesoderm-associated gene is sufficient to account for a broad range of transcriptional and morphogenetic effects. Our approach, pairing precise signaling perturbations with observation of transcriptional dynamics and cell movements, provides a general framework for dissecting the complexities of combinatorial tissue patterning.
Topics: Animals; DNA-Binding Proteins; Drosophila Proteins; Drosophila melanogaster; Endoderm; Gastrula; Gastrulation; MAP Kinase Signaling System; Mesoderm; Models, Biological
PubMed: 34083443
DOI: 10.1073/pnas.2102691118 -
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 -
Proceedings of the National Academy of... May 2008ATP-dependent chromatin remodeling complexes are a notable group of epigenetic modifiers that use the energy of ATP hydrolysis to change the structure of chromatin,...
ATP-dependent chromatin remodeling complexes are a notable group of epigenetic modifiers that use the energy of ATP hydrolysis to change the structure of chromatin, thereby altering its accessibility to nuclear factors. BAF250a (ARID1a) is a unique and defining subunit of the BAF chromatin remodeling complex with the potential to facilitate chromosome alterations critical during development. Our studies show that ablation of BAF250a in early mouse embryos results in developmental arrest (about embryonic day 6.5) and absence of the mesodermal layer, indicating its critical role in early germ-layer formation. Moreover, BAF250a deficiency compromises ES cell pluripotency, severely inhibits self-renewal, and promotes differentiation into primitive endoderm-like cells under normal feeder-free culture conditions. Interestingly, this phenotype can be partially rescued by the presence of embryonic fibroblast cells. DNA microarray, immunostaining, and RNA analyses revealed that BAF250a-mediated chromatin remodeling contributes to the proper expression of numerous genes involved in ES cell self-renewal, including Sox2, Utf1, and Oct4. Furthermore, the pluripotency defects in BAF250a mutant ES cells appear to be cell lineage-specific. For example, embryoid body-based analyses demonstrated that BAF250a-ablated stem cells are defective in differentiating into fully functional mesoderm-derived cardiomyocytes and adipocytes but are capable of differentiating into ectoderm-derived neurons. Our results suggest that BAF250a is a key component of the gene regulatory machinery in ES cells controlling self-renewal, differentiation, and cell lineage decisions.
Topics: Adipocytes; Animals; Cell Differentiation; Cell Line; Cell Lineage; Cell Proliferation; Chromatin Assembly and Disassembly; Chromosomal Proteins, Non-Histone; DNA-Binding Proteins; Embryo, Mammalian; Embryonic Development; Embryonic Stem Cells; Female; Genes, Developmental; Germ Layers; Male; Mice; Mice, Knockout; Muscle, Skeletal; Myocytes, Cardiac; Nuclear Proteins; Pluripotent Stem Cells; Transcription Factors
PubMed: 18448678
DOI: 10.1073/pnas.0801802105 -
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 -
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 -
Current Biology : CB Mar 2005Vertebrate embryogenesis entails an exquisitely coordinated combination of cell proliferation, fate specification and movement. After induction of the germ layers, the... (Review)
Review
Vertebrate embryogenesis entails an exquisitely coordinated combination of cell proliferation, fate specification and movement. After induction of the germ layers, the blastula is transformed by gastrulation movements into a multilayered embryo with head, trunk and tail rudiments. Gastrulation is heralded by formation of a blastopore, an opening in the blastula. The axial side of the blastopore is marked by the organizer, a signaling center that patterns the germ layers and regulates gastrulation movements. During internalization, endoderm and mesoderm cells move via the blastopore beneath the ectoderm. Epiboly movements expand and thin the nascent germ layers. Convergence movements narrow the germ layers from lateral to medial while extension movements elongate them from head to tail. Despite different morphology, parallels emerge with respect to the cellular and genetic mechanisms of gastrulation in different vertebrate groups. Patterns of gastrulation cell movements relative to the blastopore and the organizer are similar from fish to mammals, and conserved molecular pathways mediate gastrulation movements.
Topics: Animals; Cell Differentiation; Cell Movement; Embryonic Induction; Endoderm; Gastrula; Gene Expression Regulation, Developmental; Mesoderm; Models, Biological; Organizers, Embryonic; Signal Transduction; Vertebrates
PubMed: 15797016
DOI: 10.1016/j.cub.2005.03.016