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Current Opinion in Cell Biology Oct 2017It is during gastrulation that the primordial germ layers are specified, embryonic axes become morphologically manifest, and the embryonic body plan begins to take... (Review)
Review
It is during gastrulation that the primordial germ layers are specified, embryonic axes become morphologically manifest, and the embryonic body plan begins to take shape. As morphogenetic movements push and pull nascent tissues into position within the gastrula, new interactions are established between neighboring cells and tissues. These interactions represent an emergent property within gastrulating embryos, and serve to regulate and promote ensuing morphogenesis that establishes the next set of cell/tissue contacts, and so on. Several recent studies demonstrate the critical roles of such interactions during gastrulation, including those between germ layers, along embryonic axes, and at tissue boundaries. Emergent tissue interactions result from - and result in - morphogen signaling, cell contacts, and mechanical forces within the gastrula. Together, these comprise a dynamic and complex regulatory cascade that drives gastrulation morphogenesis.
Topics: Animals; Ectoderm; Embryo, Mammalian; Embryo, Nonmammalian; Gastrula; Gastrulation; Mesoderm; Morphogenesis; Signal Transduction
PubMed: 28586710
DOI: 10.1016/j.ceb.2017.04.006 -
Stem Cell Research Jul 2020We sought to elucidate how and when the ocular surface ectoderm commits to its differentiation into the corneal epithelium in eye development from human induced...
We sought to elucidate how and when the ocular surface ectoderm commits to its differentiation into the corneal epithelium in eye development from human induced pluripotent stem cells (hiPSCs) under the influence of WNT signaling and the actions of BMP4. These signals are key drivers ocular surface ectodermal cell fate determination. It was discovered that secreted frizzled related protein-2 (SFRP2) and Dickkopf1 (DKK1), which are expressed in neural ectoderm, are both influential in the differentiation of hiPSCs, where they act as canonical WNT antagonists. BMP4, moreover, was found to simultaneously initiate non-neural ectodermal differentiation into a corneal epithelial lineage. Combined treatment of hiPSCs with exogenous BMP4 aligned to WNT inhibition for the initial four days of differentiation increased the ocular surface ectodermal cell population and induced a corneal epithelial phenotype. Specification of a surface ectodermal lineage and its fate is thus determined by a fine balance of BMP4 exposure and WNT inhibition in the very earliest stages of human eye development.
Topics: Bone Morphogenetic Protein 4; Cell Differentiation; Ectoderm; Epithelium, Corneal; Humans; Induced Pluripotent Stem Cells; Wnt Signaling Pathway
PubMed: 32603880
DOI: 10.1016/j.scr.2020.101868 -
Developmental Biology May 2014For both the intricate morphogenetic layout of the sensory cells in the ear and the elegantly radial arrangement of the sensory neurons in the nose, numerous signaling... (Review)
Review
For both the intricate morphogenetic layout of the sensory cells in the ear and the elegantly radial arrangement of the sensory neurons in the nose, numerous signaling molecules and genetic determinants are required in concert to generate these specialized neuronal populations that help connect us to our environment. In this review, we outline many of the proteins and pathways that play essential roles in the differentiation of otic and olfactory neurons and their integration into their non-neuronal support structures. In both cases, well-known signaling pathways together with region-specific factors transform thickened ectodermal placodes into complex sense organs containing numerous, diverse neuronal subtypes. Olfactory and otic placodes, in combination with migratory neural crest stem cells, generate highly specialized subtypes of neuronal cells that sense sound, position and movement in space, odors and pheromones throughout our lives.
Topics: Animals; Cell Differentiation; Ear, Inner; Ectoderm; Gene Expression Regulation, Developmental; Humans; Neurogenesis; Olfactory Pathways; Sense Organs; Sensory Receptor Cells
PubMed: 24508480
DOI: 10.1016/j.ydbio.2014.01.023 -
Developmental Biology May 2014The neurogenic cranial placodes are a unique transient epithelial niche of neural progenitor cells that give rise to multiple derivatives of the peripheral nervous... (Review)
Review
The neurogenic cranial placodes are a unique transient epithelial niche of neural progenitor cells that give rise to multiple derivatives of the peripheral nervous system, particularly, the sensory neurons. Placode neurogenesis occurs throughout an extended period of time with epithelial cells continually recruited as neural progenitor cells. Sensory neuron development in the trigeminal, epibranchial, otic, and olfactory placodes coincides with detachment of these neuroblasts from the encompassing epithelial sheet, leading to delamination and ingression into the mesenchyme where they continue to differentiate as neurons. Multiple signaling pathways are known to direct placodal development. This review defines the signaling pathways working at the finite spatiotemporal period when neuronal selection within the placodes occurs, and neuroblasts concomitantly delaminate from the epithelium. Examining neurogenesis and delamination after initial placodal patterning and specification has revealed a common trend throughout the neurogenic placodes, which suggests that both activated FGF and attenuated Notch signaling activities are required for neurogenesis and changes in epithelial cell adhesion leading to delamination. We also address the varying roles of other pathways such as the Wnt and BMP signaling families during sensory neurogenesis and neuroblast delamination in the differing placodes.
Topics: Animals; Bone Morphogenetic Proteins; Ectoderm; Epidermal Growth Factor; Humans; Models, Neurological; Nervous System; Neurogenesis; Receptors, Notch; Signal Transduction
PubMed: 24315854
DOI: 10.1016/j.ydbio.2013.11.025 -
Developmental Biology May 2014Vertebrate cranial placodes are crucial contributors to the vertebrate cranial sensory apparatus. Their evolutionary origin has attracted much attention from... (Review)
Review
Vertebrate cranial placodes are crucial contributors to the vertebrate cranial sensory apparatus. Their evolutionary origin has attracted much attention from evolutionary and developmental biologists, yielding speculation and hypotheses concerning their putative homologues in other lineages and the developmental and genetic innovations that might have underlain their origin and diversification. In this article we first briefly review our current understanding of placode development and the cell types and structures they form. We next summarise previous hypotheses of placode evolution, discussing their strengths and caveats, before considering the evolutionary history of the various cell types that develop from placodes. In an accompanying review, we also further consider the evolution of ectodermal patterning. Drawing on data from vertebrates, tunicates, amphioxus, other bilaterians and cnidarians, we build these strands into a scenario of placode evolutionary history and of the genes, cells and developmental processes that underlie placode evolution and development.
Topics: Animals; Biological Evolution; Body Patterning; Cell Differentiation; Cell Movement; Ectoderm; Models, Biological; Sense Organs; Vertebrates
PubMed: 24495912
DOI: 10.1016/j.ydbio.2014.01.017 -
Journal of Anatomy Jan 2013Many of the features that distinguish the vertebrates from other chordates are found in the head. Prominent amongst these differences are the paired sense organs and... (Review)
Review
Many of the features that distinguish the vertebrates from other chordates are found in the head. Prominent amongst these differences are the paired sense organs and associated cranial ganglia. Significantly, these structures are derived developmentally from the ectodermal placodes. It has therefore been proposed that the emergence of the ectodermal placodes was concomitant with and central to the evolution of the vertebrates. More recent studies, however, indicate forerunners of the ectodermal placodes can be readily identified outside the vertebrates, particularly in urochordates. Thus the evolutionary history of the ectodermal placodes is deeper and more complex than was previously appreciated with the full repertoire of vertebrate ectodermal placodes, and their derivatives, being assembled over a protracted period rather than arising collectively with the vertebrates.
Topics: Animals; Biological Evolution; Chordata; Ectoderm; Evolution, Molecular; Phylogeny; Vertebrates
PubMed: 22512454
DOI: 10.1111/j.1469-7580.2012.01506.x -
Seminars in Cell & Developmental Biology Mar 2023During development of the vertebrate sensory system, many important components like the sense organs and cranial sensory ganglia arise within the head and neck. Two... (Review)
Review
During development of the vertebrate sensory system, many important components like the sense organs and cranial sensory ganglia arise within the head and neck. Two progenitor populations, the neural crest, and cranial ectodermal placodes, contribute to these developing vertebrate peripheral sensory structures. The interactions and contributions of these cell populations to the development of the lens, olfactory, otic, pituitary gland, and cranial ganglia are vital for appropriate peripheral nervous system development. Here, we review the origins of both neural crest and placode cells at the neural plate border of the early vertebrate embryo and investigate the molecular and environmental signals that influence specification of different sensory regions. Finally, we discuss the underlying molecular pathways contributing to the complex vertebrate sensory system from an evolutionary perspective, from basal vertebrates to amniotes.
Topics: Animals; Neural Crest; Gene Expression Regulation, Developmental; Ectoderm; Vertebrates; Organogenesis
PubMed: 35760729
DOI: 10.1016/j.semcdb.2022.06.009 -
Developmental Dynamics : An Official... Feb 2021During embryonic development, complex changes in cell behavior generate the final form of the tissues. Extension of cell protrusions have been described as an important...
BACKGROUND
During embryonic development, complex changes in cell behavior generate the final form of the tissues. Extension of cell protrusions have been described as an important component in this process. Cellular protrusions have been associated with generation of traction, intercellular communication or establishment of signaling gradients. Here, we describe and compare in detail from live imaging data the dynamics of protrusions in the surface ectoderm of chick and mouse embryos. In particular, we explore the differences between cells surrounding the lens placode and other regions of the head.
RESULTS
Our results showed that protrusions from the eye region in mouse embryos are longer than those in chick embryos. In addition, protrusions from regions where there are no significant changes in tissue shape are longer and more stable than protrusions that surround the invaginating lens placode. We did not find a clear directionality to the protrusions in any region. Finally, we observed intercellular trafficking of membrane puncta in the protrusions of both embryos in all the regions analyzed.
CONCLUSIONS
In summary, the results presented here suggest that the dynamics of these protrusions adapt to their surroundings and possibly contribute to intercellular communication in embryonic cephalic epithelia.
Topics: Animals; Cell Surface Extensions; Chick Embryo; Ectoderm; Mice; Morphogenesis
PubMed: 32562595
DOI: 10.1002/dvdy.219 -
Developmental Biology May 2014The neural crest and craniofacial placodes are two distinct progenitor populations that arise at the border of the vertebrate neural plate. This border region develops... (Review)
Review
The neural crest and craniofacial placodes are two distinct progenitor populations that arise at the border of the vertebrate neural plate. This border region develops through a series of inductive interactions that begins before gastrulation and progressively divide embryonic ectoderm into neural and non-neural regions, followed by the emergence of neural crest and placodal progenitors. In this review, we describe how a limited repertoire of inductive signals-principally FGFs, Wnts and BMPs-set up domains of transcription factors in the border region which establish these progenitor territories by both cross-inhibitory and cross-autoregulatory interactions. The gradual assembly of different cohorts of transcription factors that results from these interactions is one mechanism to provide the competence to respond to inductive signals in different ways, ultimately generating the neural crest and cranial placodes.
Topics: Animals; Body Patterning; Bone Morphogenetic Proteins; Ectoderm; Epidermal Growth Factor; Gene Expression Regulation, Developmental; Humans; Neural Crest; Neural Plate; Wnt Proteins
PubMed: 24321819
DOI: 10.1016/j.ydbio.2013.11.027 -
Developmental Biology Feb 1997Recent molecular insights on how the ectodermal layer is patterned in vertebrates are reviewed. Studies on the induction of the central nervous system (CNS) by Spemann's... (Review)
Review
Recent molecular insights on how the ectodermal layer is patterned in vertebrates are reviewed. Studies on the induction of the central nervous system (CNS) by Spemann's Organizer led to the isolation of noggin and chordin. These secretory proteins function by binding to, and inhibiting, ventral BMPs, in particular BMP-4. Neural induction can be considered as the dorsalization of ectoderm, in which low levels of BMP-signaling result in CNS formation. At high levels of BMP signaling the ectoderm adopts a ventral fate and skin is formed. In Xenopus the forming neural plate already has extensive dorsal-ventral (D-V) patterning, and neural induction and D-V patterning may share common molecular mechanisms. At later stages sonic hedgehog (shh) plays a principal role in D-V patterning, particularly in the neural tube of the amniote embryo. A great many transcription factor markers are available and mouse knockouts provide evidence of their involvement in the regional specification of the neural tube. Recent evidence indicating that differentiation of posterior CNS is promoted by FGF, Wnt-3a, and retinoic acid is reviewed from the point of view of the classical experiments of Nieuwkoop that defined an activation and a transformation step during neural induction.
Topics: Animals; Bone Morphogenetic Proteins; Brain; Ectoderm; Embryonic Induction; Mice; Mice, Knockout; Nervous System; Skin; Spinal Cord; Transcription Factors; Vertebrates; Xenopus
PubMed: 9073437
DOI: 10.1006/dbio.1996.8445