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Developmental Biology Nov 2004The neural crest is a multipotent population of migratory cells unique to the vertebrate embryo. Neural crest arises at the lateral edge of the neural plate and migrates... (Review)
Review
The neural crest is a multipotent population of migratory cells unique to the vertebrate embryo. Neural crest arises at the lateral edge of the neural plate and migrates throughout the embryo to give rise to a wide variety of cell types including peripheral and enteric neurons and glia, craniofacial cartilage and bone, smooth muscle, and pigment cells. Here we review recent studies that have addressed the role of several signaling pathways in the induction of the neural crest. Work in the mouse, chick, Xenopus, and zebrafish have shown that a complex network of genes is activated at the neural plate border in response to neural crest-inducing signals. We also summarize some of these findings and discuss how the differential activation of these genes may contribute to the establishment of neural crest diversity.
Topics: Animals; Bone Morphogenetic Proteins; Chick Embryo; Embryonic Induction; Fibroblast Growth Factors; Gene Expression Regulation; Intracellular Signaling Peptides and Proteins; Membrane Proteins; Neural Crest; Proto-Oncogene Proteins; Receptors, Notch; Wnt Proteins
PubMed: 15464568
DOI: 10.1016/j.ydbio.2004.07.033 -
Journal of Anatomy Mar 2003The vertebrate tail is an extension of the main body axis caudal to the anus. The developmental origin of this structure has been a source of debate amongst... (Review)
Review
The vertebrate tail is an extension of the main body axis caudal to the anus. The developmental origin of this structure has been a source of debate amongst embryologists for the past century. Some view tail development as a continuation of the morphogenetic processes that shape the head and trunk (i.e. gastrulation). The alternative view, secondary development, holds that the tail forms in a manner similar to limb development, i.e. by secondary induction. Previous developmental studies have provided support for both views. Here I revisit these studies, describing caudal morphogenesis in select vertebrates, the associated genes and developmental defects, and, as a relevant aside, consider the developmental and evolutionary relationships of primary and secondary neurulation. I conclude that caudal development enlists both gastrulation and secondary induction, and that the application of recent high-resolution cell labelling technology may clarify how these discordant programmes interact in building the vertebrate tail.
Topics: Animals; Biological Evolution; Birds; Embryonic Induction; Gastrula; Gene Expression Regulation, Developmental; Mammals; Morphogenesis; Nervous System; Phylogeny; Tail; Vertebrates; Xenopus; Zebrafish
PubMed: 12713266
DOI: 10.1046/j.1469-7580.2003.00163.x -
Cell Feb 1995
Review
Topics: Animals; Cell Communication; Cyclic AMP-Dependent Protein Kinases; Drosophila; Drosophila Proteins; Embryonic Induction; Extremities; Feedback; Hedgehog Proteins; Proteins; Signal Transduction; Vertebrates
PubMed: 7867057
DOI: 10.1016/0092-8674(95)90503-0 -
Developmental Biology Aug 2009Whereas neural crest cells are the source of the peripheral nervous system in the trunk of vertebrates, the "ectodermal placodes," together with neural crest, form the... (Review)
Review
Whereas neural crest cells are the source of the peripheral nervous system in the trunk of vertebrates, the "ectodermal placodes," together with neural crest, form the peripheral nervous system of the head. Cranial ectodermal placodes are thickenings in the ectoderm that subsequently ingress or invaginate to make important contributions to cranial ganglia, including epibranchial and trigeminal ganglia, and sensory structures, the ear, nose, lens, and adenohypophysis. Recent studies have uncovered a number of molecular signals mediating induction and differentiation of placodal cells. Here, we described recent advances in understanding the tissue interactions and signals underlying induction and neurogenesis of placodes, with emphasis on the trigeminal and epibranchial. Important roles of Fibroblast Growth Factors, Platelet Derived Growth Factors, Sonic Hedgehog, TGFbeta superfamily members, and Wnts are discussed.
Topics: Animals; Ectoderm; Embryonic Induction; Head; Intercellular Signaling Peptides and Proteins; Morphogenesis; Neural Crest; Neurogenesis; Signal Transduction
PubMed: 19500565
DOI: 10.1016/j.ydbio.2009.05.572 -
The International Journal of... 2008The Apical Ectodermal Ridge (AER) is one of the main signaling centers during limb development. It controls outgrowth and patterning in the proximo-distal axis. In the... (Review)
Review
The Apical Ectodermal Ridge (AER) is one of the main signaling centers during limb development. It controls outgrowth and patterning in the proximo-distal axis. In the last few years a considerable amount of new data regarding the cellular and molecular mechanisms underlying AER function and structure has been obtained. In this review, we describe and discuss current knowledge of the regulatory networks which control the induction, maturation and regression of the AER, as well as the link between dorso-ventral patterning and the formation and position of the AER. Our aim is to integrate both recent and old knowledge to produce a wider picture of the AER which enhances our understanding of this relevant structure.
Topics: Animals; Body Patterning; Ectoderm; Embryonic Induction; Extremities; Fibroblast Growth Factors; Hedgehog Proteins; Limb Buds; Models, Biological; Signal Transduction; Wnt Proteins
PubMed: 18956316
DOI: 10.1387/ijdb.072416mf -
The International Journal of... 2020The forebrain roof plate undergoes dramatic morphogenetic changes to invaginate, and this leads to formation of the two cerebral hemispheres. While many genetic factors... (Review)
Review
The forebrain roof plate undergoes dramatic morphogenetic changes to invaginate, and this leads to formation of the two cerebral hemispheres. While many genetic factors are known to regulate this process, the mechanism of forebrain roof plate invagination remains unknown. In a recent study we have identified retinoic acid as a signal from the dorsal mesenchyme that regulates the invagination of the roof plate. This has brought into focus the importance of the interaction between the dorsal mesenchyme and the underlying roof plate. One of the structures derived from the dorso-medial forebrain after roof plate invagination is the hippocampus. While the functions of the hippocampus are conserved between birds and mammals, there are distinct structural differences. We have studied hippocampus development in the chick embryo and uncovered several similarities and differences between the process in mammals and birds. This study has also lent support to one of the prevalent models of structural homology between the avian and mammalian hippocampus. In this review, we have underscored the importance of the chick embryo as a model for studying forebrain roof plate morphogenesis and hippocampus development.
Topics: Animals; Chick Embryo; Embryonic Induction; Hippocampus; Morphogenesis; Prosencephalon
PubMed: 32659013
DOI: 10.1387/ijdb.190143js -
The International Journal of... 2011The role of somites and notochords in neuroectoderm differentiation from the embryonic ectoderm and its subsequent patterning into regional compartments along...
The role of somites and notochords in neuroectoderm differentiation from the embryonic ectoderm and its subsequent patterning into regional compartments along rostro-caudal and dorso-ventral axes, especially in humans, remains elusive. Here, we demonstrate the co-culture effect of somites and notochords isolated from chicken embryos on the neuronal differentiation and regional identity of an adherent culture of human embryonic stem cells (hESCs). Notochord increased the efficiency and speed of neuronal induction, whereas somites had a weak neuronal inducing effect on hESCs. However, a synergistic effect was not observed when notochords and somites were used together. Moreover, in somite and notochord co-culture groups, hESCs-derived neuronal cells expressed HOXB4, OTX2, IRX3 and PAX6, indicative of dorsal hindbrain and ventral anterior identities, respectively. Our results reveal the influence of embryonic notochord and somite co-culture in providing neuronal induction as well as rostro-caudal and dorso-ventral regional identity of hESCs-derived neuronal cells. This study provides a model through which in vivo neuronal induction events may be imitated.
Topics: Animals; Cell Differentiation; Chick Embryo; Chickens; Coculture Techniques; Embryonic Induction; Embryonic Stem Cells; Eye Proteins; Gene Expression Regulation, Developmental; Homeodomain Proteins; Humans; Neural Plate; Notochord; Otx Transcription Factors; PAX6 Transcription Factor; Paired Box Transcription Factors; Repressor Proteins; Signal Transduction; Somites; Transcription Factors
PubMed: 21710438
DOI: 10.1387/ijdb.103185hs -
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 -
Molecular Reproduction and Development Aug 2014The formation of the germ line in an embryo marks a fresh round of reproductive potential. The developmental stage and location within the embryo where the primordial... (Review)
Review
The formation of the germ line in an embryo marks a fresh round of reproductive potential. The developmental stage and location within the embryo where the primordial germ cells (PGCs) form, however, differs markedly among species. In many animals, the germ line is formed by an inherited mechanism, in which molecules made and selectively partitioned within the oocyte drive the early development of cells that acquire this material to a germ-line fate. In contrast, the germ line of other animals is fated by an inductive mechanism that involves signaling between cells that directs this specialized fate. In this review, we explore the mechanisms of germ-line determination in echinoderms, an early-branching sister group to the chordates. One member of the phylum, sea urchins, appears to use an inherited mechanism of germ-line formation, whereas their relatives, the sea stars, appear to use an inductive mechanism. We first integrate the experimental results currently available for germ-line determination in the sea urchin, for which considerable new information is available, and then broaden the investigation to the lesser-known mechanisms in sea stars and other echinoderms. Even with this limited insight, it appears that sea stars, and perhaps the majority of the echinoderm taxon, rely on inductive mechanisms for germ-line fate determination. This enables a strongly contrasted picture for germ-line determination in this phylum, but one for which transitions between different modes of germ-line determination might now be experimentally addressed.
Topics: Animals; Asymmetric Cell Division; Calcium; Calcium Channels, L-Type; DEAD-box RNA Helicases; Echinodermata; Embryonic Induction; Endoplasmic Reticulum; Gametogenesis; Gene Expression Regulation, Developmental; Germ Cells; Models, Biological; Signal Transduction; Species Specificity
PubMed: 23900765
DOI: 10.1002/mrd.22223 -
Progress in Biophysics and Molecular... Sep 2005The central problem in biological development is the understanding of epigenesis. The dominant theory of development in the last 80 years that also purports to explain... (Review)
Review
The central problem in biological development is the understanding of epigenesis. The dominant theory of development in the last 80 years that also purports to explain epigenesis is induction theory. It suggests that development is driven by sequential inductions where each "induction" (in one sense of the word induction) is effected by the action of an inducing part of the embryo on a responding part of the embryo. The theory stems from Spemann and Mangold (W.Roux' Arch.f.Entw.d.Organis.u.mikrosk.Anat.100 (1924) 599) who transplanted a tissue from the dorsal blastopore lip of Triturus into the ventral ectoderm of another gastrula and thus initiated and "induced" (in another sense of the word induction) gastrulation and embryogenesis in the ventral side of the host that became a double embryo (siamese twins). We explain this induction, i.e. the formation of the double embryo, according to the Child theory and the Turing-Gierer-Meinhardt theory when it is also assumed that cAMP and ATP are the Turing activator and inhibitor, respectively. Spemann and Mangold (W.Roux' Arch.f.Entw.d.Organis.u.mikrosk.Anat.100 (1924) 599) also suggested that the ingressing mesoderm induces the overlying ectoderm to form the neural plate and neural tube. This 'neural induction', the 'primary embryonic induction', became the cornerstone of induction theory, i.e. of the sequential induction concept referred to above. But we argue that the metabolic gradients that precede and accompany neurulation, as obtained by Child, also for Triturus, arise through a Turing self-organization if it is assumed that cAMP and ATP are the Turing morphogens, and these gradients are the cause and primary event of neurulation. Thus there is no need to invoke the 'neural induction'. It is argued that fundamental events such as gastrulation and also organ formation are caused by the Turing-Child field and not by sequential induction. Similar principles, such as bud formation caused by a radial metabolic pattern that transforms to a longitudinal pattern, govern the formation, for example, of the mouth and the gut. The formation and localization of bottle cells is explained according to the Child-Turing field and modern biochemistry. The chemical metabolic pre-pattern precedes, and causes, morphogenesis and differentiation as envisaged by Turing. The Spemann and Mangold (W.Roux' Arch.f.Entw.d.Organis.u.mikrosk.Anat.100 (1924) 599) transplantation experiment when performed on a sea urchin duplicates not only the phenotype but also the metabolic (reduction) pattern. These experimental results, by Horstadius, predicted by Child, follow from the Turing-Gierer-Meinhardt theory if it is assumed that cAMP and ATP are the Turing morphogens. If the transplantation is performed not onto the whole sea urchin but onto only a part of it, that manifests only a part of the metabolic pattern, then from the part a phenotypic whole underlain by a normal and a whole metabolic pattern can be rescued. These experimental results of Horstadius follow from Turing theory if cAMP and ATP are the Turing morphogens. Understanding how to transform a part into a whole can be valuable in regenerative medicine. Unspecific induction of a secondary amphibian embryo is similar to the induction of posterior structures at the anterior pole of an insect, and the "double abdomen" (and Kalthoff's experimental results) of the midge Smittia resulting from UV irradiation of the anterior pole, can be explained by Meinhardt theory of unspecific induction if ATP is the Turing morphogen. When not working on regeneration, Child investigated intact living organisms and his observation method was not disruptive to normal development, whereas workers in induction theory work with pieces and in general disrupt normal development. We conclude that the Turing-Child field causes all development and explains epigenesis. Sequential induction does not explain epigenesis and does not exist in normal development. But induction in the sense of a transplantation leading to double embryo or rescuing a whole phenotype from a part is of interest.
Topics: Adenosine Triphosphate; Animals; Cell Differentiation; Echinodermata; Embryonic Induction; Epigenesis, Genetic; Feedback; Humans; Models, Biological; Morphogenesis; Organogenesis
PubMed: 15826672
DOI: 10.1016/j.pbiomolbio.2004.08.018