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Nature Feb 2024Recently, several studies using cultures of human embryos together with single-cell RNA-seq analyses have revealed differences between humans and mice, necessitating the...
Recently, several studies using cultures of human embryos together with single-cell RNA-seq analyses have revealed differences between humans and mice, necessitating the study of human embryos. Despite the importance of human embryology, ethical and legal restrictions have limited post-implantation-stage studies. Thus, recent efforts have focused on developing in vitro self-organizing models using human stem cells. Here, we report genetic and non-genetic approaches to generate authentic hypoblast cells (naive hPSC-derived hypoblast-like cells (nHyCs))-known to give rise to one of the two extraembryonic tissues essential for embryonic development-from naive human pluripotent stem cells (hPSCs). Our nHyCs spontaneously assemble with naive hPSCs to form a three-dimensional bilaminar structure (bilaminoids) with a pro-amniotic-like cavity. In the presence of additional naive hPSC-derived analogues of the second extraembryonic tissue, the trophectoderm, the efficiency of bilaminoid formation increases from 20% to 40%, and the epiblast within the bilaminoids continues to develop in response to trophectoderm-secreted IL-6. Furthermore, we show that bilaminoids robustly recapitulate the patterning of the anterior-posterior axis and the formation of cells reflecting the pregastrula stage, the emergence of which can be shaped by genetically manipulating the DKK1/OTX2 hypoblast-like domain. We have therefore successfully modelled and identified the mechanisms by which the two extraembryonic tissues efficiently guide the stage-specific growth and progression of the epiblast as it establishes the post-implantation landmarks of human embryogenesis.
Topics: Humans; Cell Differentiation; Embryo Implantation; Embryo, Mammalian; Embryonic Development; Germ Layers; Pluripotent Stem Cells; Interleukin-6; Gastrula; Amnion; Ectoderm; Intercellular Signaling Peptides and Proteins; Otx Transcription Factors
PubMed: 38052228
DOI: 10.1038/s41586-023-06871-2 -
Cells Aug 2021Fibroblast growth factors (FGFs) comprise a large family of growth factors, regulating diverse biological processes including cell proliferation, migration, and... (Review)
Review
Fibroblast growth factors (FGFs) comprise a large family of growth factors, regulating diverse biological processes including cell proliferation, migration, and differentiation. Each FGF binds to a set of FGF receptors to initiate certain intracellular signaling molecules. Accumulated evidence suggests that in early development and adult state of vertebrates, FGFs also play exclusive and context dependent roles. Although FGFs have been the focus of research for therapeutic approaches in cancer, cardiovascular disease, and metabolic syndrome, in this review, we mainly focused on their role in germ layer specification and axis patterning during early vertebrate embryogenesis. We discussed the functional roles of FGFs and their interacting partners as part of the gene regulatory network for germ layer specification, dorsal-ventral (DV), and anterior-posterior (AP) patterning. Finally, we briefly reviewed the regulatory molecules and pharmacological agents discovered that may allow modulation of FGF signaling in research.
Topics: Animals; Fibroblast Growth Factors; Gene Expression Regulation, Developmental; Germ Layers; Humans; Models, Biological; Protein Binding; Receptors, Fibroblast Growth Factor; Signal Transduction; Vertebrates
PubMed: 34440915
DOI: 10.3390/cells10082148 -
Seminars in Cell & Developmental Biology Dec 2015During embryonic development, tissues deform by a succession and combination of morphogenetic processes. Tissue compaction is the morphogenetic process by which a tissue... (Review)
Review
During embryonic development, tissues deform by a succession and combination of morphogenetic processes. Tissue compaction is the morphogenetic process by which a tissue adopts a tighter structure. Recent studies characterized the respective roles of cells' adhesive and contractile properties in tissue compaction. In this review, we formalize the mechanical and molecular principles of tissue compaction and we analyze through the prism of this framework several morphogenetic events: the compaction of the early mouse embryo, the formation of the fly retina, the segmentation of somites and the separation of germ layers during gastrulation.
Topics: Animals; Body Patterning; Cell Adhesion; Cell Communication; Embryonic Development; Gastrulation; Germ Layers; Humans; Mechanical Phenomena; Models, Biological
PubMed: 26256955
DOI: 10.1016/j.semcdb.2015.08.001 -
Mechanisms of Development Sep 2020Among the basally branching metazoans, cnidarians display well-defined gastrulation processes leading to a diploblastic body plan, consisting of an endodermal and an... (Review)
Review
Among the basally branching metazoans, cnidarians display well-defined gastrulation processes leading to a diploblastic body plan, consisting of an endodermal and an ectodermal cell layer. As the outgroup to all Bilateria, cnidarians are an interesting group to investigate ancestral developmental mechanisms. Interestingly, all known gastrulation mechanisms known in Bilateria are already found in different species of Cnidaria. Here I review the morphogenetic processes found in different Cnidaria and focus on the investigation of the cellular and molecular mechanisms in the sea anemone Nematostella vectensis, which has been a major model organism among cnidarians for evolutionary developmental biology. Many of the genes involved in germ layer specification and morphogenetic processes in Bilateria are also found active during gastrulation of Nematostella and other cnidarians, suggesting an ancestral role of this process. The molecular analyses indicate a tight link between gastrulation and axis patterning processes by Wnt and FGF signaling. Interestingly, the endodermal layer displays many features of the mesodermal layer in Bilateria, while the pharyngeal ectoderm has an endodermal expression profile. Comparative analyses as well as experimental studies using embryonic aggregates suggest that minor differences in the gene regulatory networks allow the embryo to transition relatively easily from one mode of gastrulation to another.
Topics: Animals; Body Patterning; Cnidaria; Ectoderm; Embryo, Nonmammalian; Endoderm; Gastrulation; Gene Expression Regulation, Developmental; Gene Regulatory Networks; Germ Layers; Mesoderm; Sea Anemones; Signal Transduction
PubMed: 32603823
DOI: 10.1016/j.mod.2020.103628 -
Cells & Development Dec 2021Early in animal development many cells are conditionally specified based on observations that those cells can be directed toward alternate fates. The endomesoderm is so... (Review)
Review
Early in animal development many cells are conditionally specified based on observations that those cells can be directed toward alternate fates. The endomesoderm is so named because early specification produces cells that often have been observed to simultaneously express both early endoderm and mesoderm transcription factors. Experiments with these cells demonstrate that their progeny can directed entirely toward endoderm or mesoderm, whereas normally they establish both germ layers. This review examines the mechanisms that initiate the conditional endomesoderm state, its metastability, and the mechanisms that resolve that state into definitive endoderm and mesoderm.
Topics: Animals; Embryo, Nonmammalian; Endoderm; Mesoderm; Sea Urchins; Signal Transduction
PubMed: 34610899
DOI: 10.1016/j.cdev.2021.203731 -
Cellular and Molecular Life Sciences :... Mar 2016In order to generate the tissues and organs of a multicellular organism, different cell types have to be generated during embryonic development. The first step in this... (Review)
Review
In order to generate the tissues and organs of a multicellular organism, different cell types have to be generated during embryonic development. The first step in this process of cellular diversification is the formation of the three germ layers: ectoderm, endoderm and mesoderm. The ectoderm gives rise to the nervous system, epidermis and various neural crest-derived tissues, the endoderm goes on to form the gastrointestinal, respiratory and urinary systems as well as many endocrine glands, and the mesoderm will form the notochord, axial skeleton, cartilage, connective tissue, trunk muscles, kidneys and blood. Classic experiments in amphibian embryos revealed the tissue interactions involved in germ layer formation and provided the groundwork for the identification of secreted and intracellular factors involved in this process. We will begin this review by summarising the key findings of those studies. We will then evaluate them in the light of more recent genetic studies that helped clarify which of the previously identified factors are required for germ layer formation in vivo, and to what extent the mechanisms identified in amphibians are conserved across other vertebrate species. Collectively, these studies have started to reveal the gene regulatory network (GRN) underlying vertebrate germ layer specification and we will conclude our review by providing examples how our understanding of this GRN can be employed to differentiate stem cells in a targeted fashion for therapeutic purposes.
Topics: Animals; Gene Expression Regulation, Developmental; Gene Regulatory Networks; Germ Layers; Humans; Signal Transduction; Stem Cells
PubMed: 26667903
DOI: 10.1007/s00018-015-2092-y -
Development (Cambridge, England) Dec 2021Despite four decades of effort, robust propagation of pluripotent stem cells from livestock animals remains challenging. The requirements for self-renewal are unclear...
Despite four decades of effort, robust propagation of pluripotent stem cells from livestock animals remains challenging. The requirements for self-renewal are unclear and the relationship of cultured stem cells to pluripotent cells resident in the embryo uncertain. Here, we avoided using feeder cells or serum factors to provide a defined culture microenvironment. We show that the combination of activin A, fibroblast growth factor and the Wnt inhibitor XAV939 (AFX) supports establishment and continuous expansion of pluripotent stem cell lines from porcine, ovine and bovine embryos. Germ layer differentiation was evident in teratomas and readily induced in vitro. Global transcriptome analyses highlighted commonality in transcription factor expression across the three species, while global comparison with porcine embryo stages showed proximity to bilaminar disc epiblast. Clonal genetic manipulation and gene targeting were exemplified in porcine stem cells. We further demonstrated that genetically modified AFX stem cells gave rise to cloned porcine foetuses by nuclear transfer. In summary, for major livestock mammals, pluripotent stem cells related to the formative embryonic disc are reliably established using a common and defined signalling environment. This article has an associated 'The people behind the papers' interview.
Topics: Animals; Cattle; Cell Differentiation; Embryo, Mammalian; Germ Layers; Livestock; Pluripotent Stem Cells; Sheep; Species Specificity; Swine
PubMed: 34874452
DOI: 10.1242/dev.199901 -
Developmental Biology Mar 2019The secreted TGF-β superfamily signals Nodal and BMP coordinate the patterning of vertebrate embryos. Nodal specifies endoderm and mesoderm during germ layer formation,... (Review)
Review
The secreted TGF-β superfamily signals Nodal and BMP coordinate the patterning of vertebrate embryos. Nodal specifies endoderm and mesoderm during germ layer formation, and BMP specifies ventral fates and patterns the dorsal/ventral axis. Five major models have been proposed to explain how the correct distributions of Nodal and BMP are achieved within tissues to orchestrate embryogenesis: source/sink, transcriptional determination, relay, self-regulation, and shuttling. Here, we discuss recent experiments probing these signal dispersal models, focusing on early zebrafish development.
Topics: Animals; Bone Morphogenetic Proteins; Embryonic Development; Endoderm; Mesoderm; Models, Biological; Nodal Signaling Ligands; Zebrafish; Zebrafish Proteins
PubMed: 29653088
DOI: 10.1016/j.ydbio.2018.04.002 -
Philosophical Transactions of the Royal... Dec 2014Formation of a eutherian mammal requires concurrent establishment of embryonic and extraembryonic lineages. The functions of the trophectoderm and primitive endoderm are... (Review)
Review
Formation of a eutherian mammal requires concurrent establishment of embryonic and extraembryonic lineages. The functions of the trophectoderm and primitive endoderm are to enable implantation in the maternal uterus, axis specification and delivery of nutrients. The pluripotent epiblast represents the founding cell population of the embryo proper, which is protected from ectopic and premature differentiation until it is required to respond to inductive cues to form the fetus. While positional information plays a major role in specifying the trophoblast lineage, segregation of primitive endoderm from epiblast depends upon gradual acquisition of transcriptional identity, directed but not initiated by fibroblast growth factor (FGF) signalling. Following early cleavage divisions and formation of the blastocyst, cells of the inner cell mass lose totipotency. Developing epiblast cells transiently attain the state of naive pluripotency and competence to self-renew in vitro as embryonic stem cells and in vivo by means of diapause. This property is lost after implantation as the epiblast epithelializes and becomes primed in preparation for gastrulation and subsequent organogenesis.
Topics: Animals; Cell Differentiation; Cell Lineage; Embryo, Mammalian; Embryonic Development; Germ Layers; Hippo Signaling Pathway; Mice; Models, Biological; Protein Serine-Threonine Kinases; Signal Transduction; Totipotent Stem Cells
PubMed: 25349450
DOI: 10.1098/rstb.2013.0541 -
Trends in Cell Biology Feb 2022The endoderm, one of the three primary germ layers, gives rise to lung, liver, stomach, intestine, colon, pancreas, bladder, and thyroid. These endoderm-originated... (Review)
Review
The endoderm, one of the three primary germ layers, gives rise to lung, liver, stomach, intestine, colon, pancreas, bladder, and thyroid. These endoderm-originated organs are subject to many life-threatening diseases. However, primary cells/tissues from endodermal organs are often difficult to grow in vitro. Human pluripotent stem cells (hPSCs), therefore, hold great promise for generating endodermal cells and their derivatives for the development of new therapeutics against these human diseases. Although a wealth of research has provided crucial information on the mechanisms underlying endoderm differentiation from hPSCs, increasing evidence has shown that metabolism, in connection with epigenetics, actively regulates endoderm differentiation in addition to the conventional endoderm inducing signals. Here we review recent advances in metabolic and epigenetic regulation of endoderm differentiation.
Topics: Cell Differentiation; Endoderm; Epigenesis, Genetic; Humans; Pluripotent Stem Cells
PubMed: 34607773
DOI: 10.1016/j.tcb.2021.09.002