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Journal of Molecular Medicine (Berlin,... Apr 2021Organoids derived from human pluripotent stem cells (hPSCs) have emerged as important models for investigating human-specific aspects of development and disease. Here we... (Review)
Review
Organoids derived from human pluripotent stem cells (hPSCs) have emerged as important models for investigating human-specific aspects of development and disease. Here we discuss hPSC-derived organoids through the lens of development-highlighting how stages of human development align with the development of hPSC-derived organoids in the tissue culture dish. Using hPSC-derived lung and intestinal organoids as examples, we discuss the value and application of such systems for understanding human biology, as well as strategies for enhancing organoid complexity and maturity.
Topics: Cell Differentiation; Cell Lineage; Forecasting; Germ Layers; Humans; Induced Pluripotent Stem Cells; Intestines; Lung; Organ Specificity; Organoids
PubMed: 32857169
DOI: 10.1007/s00109-020-01969-w -
Seminars in Cell & Developmental Biology Jun 2017Germ layer formation is among the earliest differentiation events in metazoan embryos. In triploblasts, three germ layers are formed, among which the endoderm gives rise... (Review)
Review
Germ layer formation is among the earliest differentiation events in metazoan embryos. In triploblasts, three germ layers are formed, among which the endoderm gives rise to the epithelial lining of the gut tube and associated organs including the liver, pancreas and lungs. In frogs (Xenopus), where early germ layer formation has been studied extensively, the process of endoderm specification involves the interplay of dozens of transcription factors. Here, we review the interactions between these factors, summarized in a transcriptional gene regulatory network (GRN). We highlight regulatory connections conserved between frog, fish, mouse, and human endodermal lineages. Especially prominent is the conserved role and regulatory targets of the Nodal signaling pathway and the T-box transcription factors, Vegt and Eomes. Additionally, we highlight network topologies and motifs, and speculate on their possible roles in development.
Topics: Animals; Cell Differentiation; Endoderm; Gene Regulatory Networks; Transcription Factors; Xenopus; Xenopus Proteins
PubMed: 28341363
DOI: 10.1016/j.semcdb.2017.03.003 -
Developmental Dynamics : An Official... Jul 2018T-box family proteins are DNA-binding transcriptional regulators that play crucial roles during germ layer formation in the early vertebrate embryo. Well-characterized...
BACKGROUND
T-box family proteins are DNA-binding transcriptional regulators that play crucial roles during germ layer formation in the early vertebrate embryo. Well-characterized members of this family, including the transcriptional activators Brachyury and VegT, are essential for the proper formation of mesoderm and endoderm, respectively. To date, T-box proteins have not been shown to play a role in the promotion of the third primary germ layer, ectoderm.
RESULTS
Here, we report that the T-box factor Tbx2 is both sufficient and necessary for ectodermal differentiation in the frog Xenopus laevis. Tbx2 is expressed zygotically in the presumptive ectoderm, during blastula and gastrula stages. Ectopic expression of Tbx2 represses mesoderm and endoderm, while loss of Tbx2 leads to inappropriate expression of mesoderm- and endoderm-specific genes in the region fated to give rise to ectoderm. Misexpression of Tbx2 also promotes neural tissue in animal cap explants, suggesting that Tbx2 plays a role in both the establishment of ectodermal fate and its dorsoventral patterning.
CONCLUSIONS
Our studies demonstrate that Tbx2 functions as a transcriptional repressor during germ layer formation, and suggest that this activity is mediated in part through repression of target genes that are stimulated, in the mesendoderm, by transactivating T-box proteins. Taken together, our results point to a critical role for Tbx2 in limiting the potency of blastula-stage progenitor cells during vertebrate germ layer differentiation. Developmental Dynamics 247:903-913, 2018. © 2018 Wiley Periodicals, Inc.
Topics: Animals; Cell Differentiation; Ectoderm; Embryo, Nonmammalian; Germ Layers; Mesoderm; Repressor Proteins; T-Box Domain Proteins; Xenopus laevis
PubMed: 29633424
DOI: 10.1002/dvdy.24633 -
Developmental Cell Mar 2022Human pluripotent stem cells (hPSCs) can self-renew indefinitely or can be induced to differentiate. We previously showed that exogenous glutamine (Gln) withdrawal...
Human pluripotent stem cells (hPSCs) can self-renew indefinitely or can be induced to differentiate. We previously showed that exogenous glutamine (Gln) withdrawal biased hPSC differentiation toward ectoderm and away from mesoderm. We revealed that, although all three germ lineages are capable of de novo Gln synthesis, only ectoderm generates sufficient Gln to sustain cell viability and differentiation, and this finding clarifies lineage fate restrictions under Gln withdrawal. Furthermore, we found that Gln acts as a signaling molecule for ectoderm that supersedes lineage-specifying cytokine induction. In contrast, Gln in mesoderm and endoderm is the preferred precursor of α-ketoglutarate without a direct signaling role. Our work raises a question about whether the nutrient environment functions directly in cell differentiation during development. Interestingly, transcriptome analysis of a gastrulation-stage human embryo shows that unique Gln enzyme-encoding gene expression patterns may also distinguish germ lineages in vivo. Together, our study suggests that intracellular Gln may help coordinate differentiation of the three germ layers.
Topics: Cell Differentiation; Cell Lineage; Endoderm; Germ Layers; Glutamine; Humans; Mesoderm; Pluripotent Stem Cells
PubMed: 35216682
DOI: 10.1016/j.devcel.2022.02.003 -
Proceedings of the National Academy of... Jul 2020The polar trophoblast overlays the epiblast in eutherian mammals and, depending on the species, has one of two different fates. It either remains a single-layered,...
The polar trophoblast overlays the epiblast in eutherian mammals and, depending on the species, has one of two different fates. It either remains a single-layered, thinning epithelium called "Rauber's layer," which soon disintegrates, or, alternatively, it keeps proliferating, contributing heavily to the population of differentiating, invasive trophoblast cells and, at least in mice, to the induction of gastrulation. While loss of the persistent polar trophoblast in mice leads to reduced induction of gastrulation, we show here that prevention of the loss of the polar trophoblast in cattle results in ectopic domains of the gastrulation marker, This phenotype, and increased epiblast proliferation, arose when Rauber's layer was maintained for a day longer by countering apoptosis through BCL2 overexpression. This suggests that the disappearance of Rauber's layer is a necessity, presumably to avoid excessive signaling interactions between this layer and the subjacent epiblast. We note that, in all species in which the polar trophoblast persists, including humans and mice, ectopic polar trophoblast signaling is prevented via epiblast cavitation which leads to the (pro)amniotic cavity, whose function is to distance the central epiblast from such signaling interactions.
Topics: Animals; Apoptosis; Cattle; Cell Differentiation; Cell Proliferation; Female; Fetal Proteins; Gastrulation; Germ Layers; Mice; Proto-Oncogene Proteins c-bcl-2; T-Box Domain Proteins; Trophoblasts
PubMed: 32601185
DOI: 10.1073/pnas.2002008117 -
Biomaterials Advances Mar 2023Induced pluripotent stem cells (iPSCs) form aggregates that recapitulate aspects of the self-organization in early embryogenesis. Within few days, cells undergo a...
Induced pluripotent stem cells (iPSCs) form aggregates that recapitulate aspects of the self-organization in early embryogenesis. Within few days, cells undergo a transition from epithelial-like structures to organized three-dimensional embryoid bodies (EBs) with upregulation of germ layer-specific genes. However, it is largely unclear, which signaling cascades regulate self-organized differentiation. The Yes-associated protein 1 (YAP1) is a downstream effector of the Hippo pathway and essential mechanotransducer. YAP1 has been suggested to play a crucial role for early embryo development, but the relevance for early germ layer commitment of human iPSCs remains to be elucidated. To gain insights into the function of YAP1 in early cell-fate decisions, we generated YAP1 knockout (YAP) iPSC lines with CRISPR/Cas9 technology and analyzed transcriptomic and epigenetic modifications. YAP iPSCs showed increased expression of several YAP1 targets and of NODAL, an important regulator of cell differentiation. Furthermore, YAP1 deficiency evoked global DNA methylation changes. Directed differentiation of adherent iPSC colonies towards endoderm, mesoderm, and ectoderm could be induced, albeit endodermal and ectodermal differentiation showed transcriptomic and epigenetic changes in YAP lines. Notably, in undirected self-organized YAP EBs germ layer specification was clearly impaired. This phenotype was rescued via lentiviral overexpression of YAP1 and also by NODAL inhibitors. Our results demonstrate that YAP1 plays an important role during early germ layer specification of iPSCs, particularly for the undirected self-organization of EBs, and this is at least partly attributed to activation of the NODAL signaling.
Topics: Humans; Cell Differentiation; Germ Layers; Pluripotent Stem Cells; Endoderm; Transcription Factors; Transforming Growth Factor beta
PubMed: 36774716
DOI: 10.1016/j.bioadv.2023.213308 -
Developmental Biology Jan 2021Among animals, diploblasts contain two germ layers, endoderm and ectoderm, while triploblasts have a distinct third germ layer called the mesoderm. Spiralians are a...
Among animals, diploblasts contain two germ layers, endoderm and ectoderm, while triploblasts have a distinct third germ layer called the mesoderm. Spiralians are a group of triploblast animals that have highly conserved development: they share the distinctive spiralian cleavage pattern as well as a unique source of mesoderm, the ectomesoderm. This population of mesoderm is distinct from endomesoderm and is considered a hallmark of spiralian development, but the regulatory network that drives its development is unknown. Here we identified ectomesoderm-specific genes in the mollusc Tritia (aka Ilyanassa) obsoleta through differential gene expression analyses comparing control and ectomesoderm-ablated embryos, followed by in situ hybridization of identified transcripts. We identified a Tritia serpin gene (ToSerpin1) that appears to be specifically expressed in the ectomesoderm of the posterior and head. Ablation of the 3a and 3b cells, which make most of the ectomesoderm, abolishes ToSerpin1 expression, consistent with its expression in these cells. Morpholino knockdown of ToSerpin1 causes ectomesoderm defects, most prominently in the muscle system of the larval head. This is the first gene identified that is specifically implicated in spiralian ectomesoderm development.
Topics: Animals; Gastropoda; Gene Knockdown Techniques; Mesoderm; Mice; Muscles; Serpins; Transcriptome
PubMed: 33148394
DOI: 10.1016/j.ydbio.2020.10.011 -
Cold Spring Harbor Perspectives in... Aug 2012Specific cells within the early mammalian embryo have the capacity to generate all somatic lineages plus the germline. This property of pluripotency is confined to the... (Review)
Review
Specific cells within the early mammalian embryo have the capacity to generate all somatic lineages plus the germline. This property of pluripotency is confined to the epiblast, a transient tissue that persists for only a few days. In vitro, however, pluripotency can be maintained indefinitely through derivation of stem cell lines. Pluripotent stem cells established from the newly formed epiblast are known as embryonic stem cells (ESCs), whereas those generated from later stages are called postimplantation epiblast stem cells (EpiSCs). These different classes of pluripotent stem cell have distinct culture requirements and gene expression programs, likely reflecting the dynamic development of the epiblast in the embryo. In this chapter we review current understanding of how the epiblast forms and relate this to the properties of derivative stem cells. We discuss whether ESCs and EpiSCs are true counterparts of different phases of epiblast development or are culture-generated phenomena. We also consider the proposition that early epiblast cells and ESCs may represent a naïve ground state without any prespecification of lineage choice, whereas later epiblasts and EpiSCs may be primed in favor of particular fates.
Topics: Animals; Blastocyst; Cell Differentiation; Embryonic Development; Gene Expression Regulation, Developmental; Germ Layers; Humans; Mice; Models, Biological; Pluripotent Stem Cells; Transcription Factors
PubMed: 22855723
DOI: 10.1101/cshperspect.a008128 -
Developmental Biology Dec 1997The morphogenetic properties causing germ-layer spreading and stratification in amphibian gastrulation were called "tissue affinities" by Holtfreter. The differential...
The morphogenetic properties causing germ-layer spreading and stratification in amphibian gastrulation were called "tissue affinities" by Holtfreter. The differential adhesion hypothesis (DAH) attributes such liquid-like tissue rearrangements to forces generated by intercellular adhesions within and between the migrating cell populations. This theory predicts that, among the primary germ layers, the cohesiveness of deep ectoderm should be the greatest, that of deep mesoderm should be intermediate, and that of deep endoderm should be the least. Also, the cohesiveness of differentiating neural ectoderm should increase after induction, causing it to internalize and segregate from epidermis. The DAH also explains why the cohesiveness of "liquid" tissues, whose cells are free to rearrange, should be measurable as tissue surface tensions. Using a specially designed tissue surface tensiometer, we demonstrate that (i) aggregates of Rana pipiens deep germ layers do possess liquid-like surface tensions, (ii) their surface tension values lie in precisely the sequence necessary to account for germ-layer stratification in vitro and in vivo, and (iii) the surface tension of deep ectoderm just underlain by the archenteron roof is twice that of not-yet-underlain deep ectoderm. These measurements provide direct, quantitative evidence that the "tissue affinities" governing germ-layer flow during early stages of vertebrate morphogenesis are reflected in tissue surface tensions.
Topics: Animals; Cell Adhesion; Cell Aggregation; Ectoderm; Embryo, Nonmammalian; Endoderm; Gastrula; Morphogenesis; Rana pipiens; Surface Tension
PubMed: 9441694
DOI: 10.1006/dbio.1997.8741 -
Nature Cell Biology Dec 2014Gastrulation leads to three germ layers--ectoderm, mesoderm and endoderm--that are separated by two basement membranes. In the mouse embryo, the emergent gut endoderm...
Gastrulation leads to three germ layers--ectoderm, mesoderm and endoderm--that are separated by two basement membranes. In the mouse embryo, the emergent gut endoderm results from the widespread intercalation of cells of two distinct origins: pluripotent epiblast-derived definitive endoderm (DE) and extra-embryonic visceral endoderm (VE). Here we image the trajectory of prospective DE cells before intercalating into the VE epithelium. We show that the transcription factor SOX17, which is activated in prospective DE cells before intercalation, is necessary for gut endoderm morphogenesis and the assembly of the basement membrane that separates gut endoderm from mesoderm. Our results mechanistically link gut endoderm morphogenesis and germ layer segregation, two central and conserved features of gastrulation.
Topics: Animals; Basement Membrane; Cadherins; Cell Differentiation; Embryo, Mammalian; Endoderm; Epithelium; Extracellular Matrix; Extracellular Matrix Proteins; Fibronectins; Gastrulation; Germ Layers; Green Fluorescent Proteins; HMGB Proteins; Hepatocyte Nuclear Factor 3-beta; Mesoderm; Mice; Mice, Transgenic; Morphogenesis; Optical Imaging; SOXF Transcription Factors
PubMed: 25419850
DOI: 10.1038/ncb3070