-
Cell Differentiation Nov 1984This review considers the hypothesis that the limb bud ectoderm establishes the initial pattern of the various mesodermal components within the limb bud. The evidence... (Comparative Study)
Comparative Study Review
This review considers the hypothesis that the limb bud ectoderm establishes the initial pattern of the various mesodermal components within the limb bud. The evidence reviewed supports the hypothesis that the ectoderm establishes a peripheral, non-chondrogenic, avascular sleeve around the limb bud. The ectodermal influence is a diffusible factor that acts by altering the collagenous extracellular matrix so that cell flattening and fibrogenic differentiation are promoted. It is hypothesized that just within this sleeve is a vascular-rich zone where myogenic cells migrate in response to a chemotactic influence. In the center of the limb bud is the prechondrogenic core, whose size determines the number of skeletal elements which subsequently form. The dimensions of the developing limb bud are established during distal limb outgrowth by the reciprocal interaction between the apical ectodermal ridge, which has a mitogenic influence, and the underlying mesoderm.
Topics: Animals; Blood Vessels; Cartilage; Chick Embryo; Ectoderm; Extremities; Muscles; Vertebrates
PubMed: 6394145
DOI: 10.1016/0045-6039(84)90025-3 -
The International Journal of... Mar 1990As an immediate consequence of neural induction during gastrulation, some neuroectodermal cells acquire the ability to develop a number of specific neuronal and... (Review)
Review
As an immediate consequence of neural induction during gastrulation, some neuroectodermal cells acquire the ability to develop a number of specific neuronal and astroglial features, without requiring subsequent chordamesodermal cues. Thus, cholinergic, dopaminergic, noradrenergic, gabaergic, somatostatinergic, enkephalinergic, etc. traits are expressed in cultures of neural plate and neural fold isolated from amphibian late gastrulae immediately after induction and cultured in a defined medium. These results strongly suggest that at the late gastrula stage, the neural precursor population does not yet constitute a homogeneous set of cells. It was of interest to know the origin of this heterogeneity. Is it a direct result of the process of neural induction itself, stochastic phenomena being involved or not at the cellular level, or does it reflect a pre-existing heterogeneity in the presumptive ectoderm? At the early gastrula state, presumptive ectoderm can be neuralized consecutively to its dissociation into single cells. Using this experimental model, we have demonstrated by means of immunological probes that neuralized presumptive ectodermal cells, without any intervention of the chordamesoderm (natural inducing tissue), can develop autonomously into glial and neuronal lineages. These data suggest the existence of diverse predispositions of presumptive ectodermal cells. Competent ectoderm seems to be a heterogeneous structure with cells presenting distinct neural predispositions that can emerge as a consequence of a permissive inductive signal without real specificity (such as a target tissue dissociation). Moreover, such a differentiated neuronal population includes neurons of the GABAergic and enkephalinergic phenotypes but not of the cholinergic, catecholaminergic, somatostatinergic, etc. phenotypes. These data show that the developmental program of ectodermal cells induced without interaction with the chordamesoderm appears restricted compared to the naturally induced ectoderm. Experiments are now under way to analyze such sequential neural events.
Topics: Amphibians; Animals; Cell Aggregation; Cell Differentiation; Ectoderm; Embryo, Nonmammalian; Models, Biological; Nervous System
PubMed: 2203454
DOI: No ID Found -
Journal of Experimental Zoology. Part... Jul 2005In chordates, the ectoderm is divided into the neuroectoderm and the so-called non-neural ectoderm. In spite of its name, however, the non-neural ectoderm contains... (Review)
Review
In chordates, the ectoderm is divided into the neuroectoderm and the so-called non-neural ectoderm. In spite of its name, however, the non-neural ectoderm contains numerous sensory cells. Therefore, the term "non-neural" ectoderm should be replaced by "general ectoderm." At least in amphioxus and tunicates and possibly in vertebrates as well, both the neuroectoderm and the general ectoderm are patterned anterior/posteriorly by mechanisms involving retinoic acid and Hox genes. In amphioxus and tunicates the ectodermal sensory cells, which have a wide range of ciliary and microvillar configurations, are mostly primary neurons sending axons to the CNS, although a minority lack axons. In contrast, vertebrate mechanosensory cells, called hair cells, are all secondary neurons that lack axons and have a characteristic eccentric cilium adjacent to a group of microvilli of graded lengths. It has been highly controversial whether the ectodermal sensory cells in the oral siphons of adult tunicates are homologous to vertebrate hair cells. In some species of tunicates, these cells appear to be secondary neurons, and microvillar and ciliary configurations of some of these cells approach those of vertebrate hair cells. However, none of the tunicate cells has all the characteristics of a hair cell, and there is a high degree of variation among ectodermal sensory cells within and between different species. Thus, similarities between the ectodermal sensory cells of any one species of tunicate and craniate hair cells may well represent convergent evolution rather than homology.
Topics: Animals; Body Patterning; Chordata; Ectoderm; Gene Expression Regulation, Developmental; Neurons, Afferent
PubMed: 15834938
DOI: 10.1002/jez.b.21038 -
Biochimica Et Biophysica Acta Apr 2009The current gene regulatory network (GRN) of the sea urchin Strongylocentrotus purpuratus embryo describes the specification of the endomesodermal territories. However,... (Review)
Review
The current gene regulatory network (GRN) of the sea urchin Strongylocentrotus purpuratus embryo describes the specification of the endomesodermal territories. However, the specification of the adjacent ectodermal territories of the embryo has been far less explored. Several recent studies on the cis-regulatory analysis of nodal and the early oral ectoderm determinants have provided clues on how the specification of this territory is initiated. Recently, a large-scale of gene regulatory network analysis was carried out in an effort to build the ectoderm specification GRN. The deduced ectodermal GRN model provides the first peek at the overall picture of ectoderm specification in the sea urchin embryo. This review integrates the current knowledge on the specification of the ectoderm by linking recent discoveries to the GRN model to understand the process of ectoderm specification in sea urchin embryos.
Topics: Animals; Cell Lineage; Ectoderm; Embryo, Nonmammalian; Gene Regulatory Networks; Sea Urchins
PubMed: 19429544
DOI: 10.1016/j.bbagrm.2009.02.002 -
Developmental Dynamics : An Official... Sep 2022Deciphering how ectodermal tissues form, and how they maintain their integrity, is crucial for understanding epidermal development and pathogenesis. However, lack of...
BACKGROUND
Deciphering how ectodermal tissues form, and how they maintain their integrity, is crucial for understanding epidermal development and pathogenesis. However, lack of simple and rapid gene manipulation techniques limits genetic studies to elucidate mechanisms underlying these events.
RESULTS
Here we describe an easy method for electroporation of chick limb bud ectoderm enabling gene manipulation during ectoderm development and wound healing. Taking advantage of a small parafilm well that constrains DNA plasmids locally and the fact that the limb ectoderm arises from a defined site, we target the limb ectoderm forming region by in ovo electroporation. This approach results in focal and efficient transgenesis of the limb ectodermal cells. Further, using a previously described Msx2 promoter, gene manipulation can be specifically targeted to the apical ectodermal ridge (AER), a signaling center regulating limb development. Using the electroporation technique to deliver a fluorescent marker into the embryonic limb ectoderm, we show its utility in performing time-lapse imaging during wound healing. This analysis revealed previously unrecognized dynamic remodeling of the actin cytoskeleton and lamellipodia formation at the edges of the wound. We find that the lamellipodia formation requires activity of Rac1 GTPase, suggesting its necessity for wound closure.
CONCLUSION
Our method is simple and easy. Thus, it would permit high throughput tests for gene function during limb ectodermal development and wound healing.
Topics: Animals; Chickens; Ectoderm; Electroporation; Extremities; Limb Buds
PubMed: 33899315
DOI: 10.1002/dvdy.352 -
Journal of Neurobiology Aug 1998During gastrulation in vertebrates the cells of the embryonic ectoderm give rise to epidermal progenitors in the ventral side and neural progenitors in the dorsal side.... (Review)
Review
During gastrulation in vertebrates the cells of the embryonic ectoderm give rise to epidermal progenitors in the ventral side and neural progenitors in the dorsal side. Despite many years of scrutiny, the molecular basis of these important embryonic cell fate decisions have not been solved. Only recently have we witnessed swift progress in the quest for factors involved in neural and epidermal induction. Several of what seem to be bona fide in vivo neural and epidermal inducers have been cloned, and the mechanism of their functions in embryos is also beginning to be understood. These new molecular results have revolutionized our view on the patterning of embryonic ectoderm and suggest that while the induction of epidermis requires instructive inductive signals, the establishment of neural fate occurs by default when epidermal inducers are inhibited. In this review, we discuss recent advances of our knowledge on epidermal and neural induction in the context of the "default model". We will then address the process of neurogenesis as well as recent findings on neural patterning. Emphasis is placed on, but not limited to, discoveries made in Xenopus, as most of our progress in understanding the ectodermal patterning is obtained from studies using this organism.
Topics: Animals; Bone Morphogenetic Proteins; Cell Line; Ectoderm; Embryo, Mammalian; Embryo, Nonmammalian; Epidermal Cells; Epidermis; Nervous System; Stem Cells
PubMed: 9712300
DOI: No ID Found -
Developmental Dynamics : An Official... Dec 2018Echinoderms and hemichordates are sister taxa that both have larvae with tripartite coeloms. Hemichordates inherit the coelom plan and ectoderm from larvae, whereas...
BACKGROUND
Echinoderms and hemichordates are sister taxa that both have larvae with tripartite coeloms. Hemichordates inherit the coelom plan and ectoderm from larvae, whereas echinoderms form the adult rudiment comprising rearranged coeloms and a vestibule that then develops into adult oral ectoderm. Molecular networks that control patterns of the ectoderm and the central nervous system along the anteroposterior (AP) axis are highly conserved between hemichordates and chordates, respectively. In echinoderms, however, little is known about the AP registry in the ectoderm.
RESULTS
We isolated ectodermal AP map genes from the sand dollar Peronella japonica and examined their expression. Comparative expression analyses showed that (1) P. japonica orthologs of hemichordate anterior markers are expressed in the larval apical plate, which degenerates during metamorphosis; (2) P. japonica orthologs of the medial markers are expressed in the ambulacral ectoderm of the rudiment; and (3) few P. japonica orthologs of the posterior markers are expressed in ectoderm.
CONCLUSIONS
We suggest that echinoids only inherit the ambulacral ectoderm from a common ambulacrarian ancestor, which largely corresponds to the collar ectoderm in hemichordates. The ectodermal AP registry provides insights into the AP axis and evolutionary processes of echinoderms from a common ambulacrarian ancestor. Developmental Dynamics 247:1297-1307, 2018. © 2018 Wiley Periodicals, Inc.
Topics: Animals; Biological Evolution; Body Patterning; Chordata; Ectoderm; Embryo, Nonmammalian; Embryonic Development; Larva; Metamorphosis, Biological; Sea Urchins
PubMed: 30394653
DOI: 10.1002/dvdy.24686 -
Current Opinion in Genetics &... Apr 2017The surface ectoderm is the source of ectodermal appendages including hair, teeth, and many glands. The development and function of ectodermal appendages has been... (Review)
Review
The surface ectoderm is the source of ectodermal appendages including hair, teeth, and many glands. The development and function of ectodermal appendages has been researched extensively, but many of the molecular mechanisms that govern the developmental programs of ectodermal appendages remain elusive. While several protein-coding genes are established as key regulators of ectodermal appendage development, the role of noncoding RNAs is an emerging area of investigation. This review highlights recent advances in studies of microRNA-mediated control of ectodermal appendage development using mouse models. We will also discuss future directions and technological advances that will drive the microRNA field forward and expand our understanding of how individual microRNAs control ectodermal appendage development.
Topics: Animals; Ectoderm; Hair; Humans; Mice; MicroRNAs; Tooth
PubMed: 28103525
DOI: 10.1016/j.gde.2016.12.006 -
Science Advances Mar 2024Mechanisms specifying amniotic ectoderm and surface ectoderm are unresolved in humans due to their close similarities in expression patterns and signal requirements....
Mechanisms specifying amniotic ectoderm and surface ectoderm are unresolved in humans due to their close similarities in expression patterns and signal requirements. This lack of knowledge hinders the development of protocols to accurately model human embryogenesis. Here, we developed a human pluripotent stem cell model to investigate the divergence between amniotic and surface ectoderms. In the established culture system, cells differentiated into functional amnioblast-like cells. Single-cell RNA sequencing analyses of amnioblast differentiation revealed an intermediate cell state with enhanced surface ectoderm gene expression. Furthermore, when the differentiation started at the confluent condition, cells retained the expression profile of surface ectoderm. Collectively, we propose that human amniotic ectoderm and surface ectoderm are specified along a common nonneural ectoderm trajectory based on cell density. Our culture system also generated extraembryonic mesoderm-like cells from the primed pluripotent state. Together, this study provides an integrative understanding of the human nonneural ectoderm development and a model for embryonic and extraembryonic human development around gastrulation.
Topics: Humans; Ectoderm; Cell Differentiation; Mesoderm; Pluripotent Stem Cells
PubMed: 38427729
DOI: 10.1126/sciadv.adh7748 -
Developmental Biology May 2014
Topics: Animals; Biological Evolution; Body Patterning; Ectoderm; Gene Expression Regulation, Developmental; Humans; Neural Crest; Vertebrates
PubMed: 24684751
DOI: 10.1016/j.ydbio.2014.02.009