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Developmental Biology Oct 2022In the primitive vertebrate gastrula, the boundary between ectoderm and mesoderm is formed by Brachet's cleft. Here we examine Brachet's cleft and its control by...
In the primitive vertebrate gastrula, the boundary between ectoderm and mesoderm is formed by Brachet's cleft. Here we examine Brachet's cleft and its control by Eph/ephrin signaling in Xenopus at the ultrastructural level and by visualizing cortical F-actin. We infer cortical tension ratios at tissue surfaces and their interface in normal gastrulae and after depletion of receptors EphB4 and EphA4 and ligands ephrinB2 and ephrinB3. We find that cortical tension downregulation at cell contacts, a normal process in adhesion, is asymmetrically blocked in the ectoderm by Eph/ephrin signals from the mesoderm. This generates high interfacial tension that can prevent cell mixing across the boundary. Moreover, it determines an asymmetric boundary structure that is suited for the respective roles of ectoderm and mesoderm, as substratum and as migratory layers. The Eph and ephrin isoforms also control different cell-cell contact types in ectoderm and mesoderm. Respective changes of adhesion upon isoform depletion affect adhesion at the boundary to different degrees but usually do not prohibit cleft formation. In an extreme case, a new type of cleft-like boundary is even generated where cortical tension is symmetrically increased on both sides of the boundary.
Topics: Animals; Ectoderm; Ephrins; Gastrula; Mesoderm; Xenopus laevis
PubMed: 35868403
DOI: 10.1016/j.ydbio.2022.07.007 -
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 -
International Journal of Experimental... Jun 2016Heparan sulphate (HS) is ubiquitously expressed and is formed of repeating glucosamine and glucuronic/iduronic acid units which are generally highly sulphated. HS is... (Review)
Review
Heparan sulphate (HS) is ubiquitously expressed and is formed of repeating glucosamine and glucuronic/iduronic acid units which are generally highly sulphated. HS is found in tissues bound to proteins forming HS proteoglycans (HSPGs) which are present on the cell membrane or in the extracellular matrix. HSPGs influence a variety of biological processes by interacting with physiologically important proteins, such as morphogens, creating storage pools, generating morphogen gradients and directly mediating signalling pathways, thereby playing vital roles during development. This review discusses the vital role HS plays in the development of tissues from the ectodermal lineage. The ectodermal layer differentiates to form the nervous system (including the spine, peripheral nerves and brain), eye, epidermis, skin appendages and tooth enamel.
Topics: Animals; Ectoderm; Extracellular Matrix; Extracellular Matrix Proteins; Heparan Sulfate Proteoglycans; Heparitin Sulfate; Humans; Skin
PubMed: 27385054
DOI: 10.1111/iep.12180 -
Development (Cambridge, England) Jul 2018Upon gastrulation, the mammalian conceptus transforms rapidly from a simple bilayer into a multilayered embryo enveloped by its extra-embryonic membranes. Impaired...
Upon gastrulation, the mammalian conceptus transforms rapidly from a simple bilayer into a multilayered embryo enveloped by its extra-embryonic membranes. Impaired development of the amnion, the innermost membrane, causes major malformations. To clarify the origin of the mouse amnion, we used single-cell labelling and clonal analysis. We identified four clone types with distinct clonal growth patterns in amniotic ectoderm. Two main types have progenitors in extreme proximal-anterior epiblast. Early descendants initiate and expand amniotic ectoderm posteriorly, while descendants of cells remaining anteriorly later expand amniotic ectoderm from its anterior side. Amniogenesis is abnormal in embryos deficient in the bone morphogenetic protein (BMP) signalling effector SMAD5, with delayed closure of the proamniotic canal, and aberrant amnion and folding morphogenesis. Transcriptomics of individual mutant amnions isolated before visible malformations and tetraploid chimera analysis revealed two amnion defect sets. We attribute them to impairment of progenitors of the two main cell populations in amniotic ectoderm and to compromised cuboidal-to-squamous transition of anterior amniotic ectoderm. In both cases, SMAD5 is crucial for expanding amniotic ectoderm rapidly into a stretchable squamous sheet to accommodate exocoelom expansion, axial growth and folding morphogenesis.
Topics: Amnion; Animals; Ectoderm; Mice; Morphogenesis; Signal Transduction; Smad5 Protein; Stem Cells
PubMed: 29884675
DOI: 10.1242/dev.157222 -
Developmental Dynamics : An Official... Dec 1997Previous studies suggest that bending of the neural plate requires the juxtaposition of neural plate and non-neuroepithelial tissues. The current study examines the role...
Previous studies suggest that bending of the neural plate requires the juxtaposition of neural plate and non-neuroepithelial tissues. The current study examines the role of one of these tissues, the epidermal ectoderm, in bending. Chick blastoderms were harvested from fertile eggs incubated for 24 hr and cultured dorsal-side-up on agar-albumen substrates. In one experiment, a rectangular flap of epidermal ectoderm on one side of each blastoderm was separated from underlying layers and gently reflected onto the area opaca; a fragment of tungsten wire was placed on top of the flap to hold it down and to prevent healing. Embryos were then allowed to develop in a humidified incubator for 2-18 hr. Asymmetric neurulation was observed between the operated and control sides as early as 2 hr after surgery. The amount of asymmetry was quantified in serial transverse sections from embryos collected 8 hr after surgery. Elevation of the lateral edge of the neural plate on the operated side averaged one half to two thirds of that on the control side, and convergence of the operated side around the dorsolateral hinge point toward the dorsal midline did not occur. These results demonstrate that epidermal ectoderm is required for full elevation and for convergence during bending. In another experiment, lateral epidermal ectoderm was removed, leaving only a medial strip consisting of both the epidermal component of the future neural fold and flanking future epidermis. This experiment revealed that although epidermal ectoderm is necessary for full elevation and for convergence of the neural folds, a medial strip of epidermal ectoderm is sufficient to drive bending. Collectively, these results further support the idea that neurulation is a multifactorial process driven by both intrinsic and extrinsic factors acting in concert.
Topics: Animals; Brain; Chick Embryo; Chickens; Ectoderm; Epidermis
PubMed: 9415425
DOI: 10.1002/(SICI)1097-0177(199712)210:4<397::AID-AJA4>3.0.CO;2-B -
Journal of Zhejiang University....Understanding limb development not only gives insights into the outgrowth and differentiation of the limb, but also has clinical relevance. Limb development begins with... (Review)
Review
Understanding limb development not only gives insights into the outgrowth and differentiation of the limb, but also has clinical relevance. Limb development begins with two paired limb buds (forelimb and hindlimb buds), which are initially undifferentiated mesenchymal cells tipped with a thickening of the ectoderm, termed the apical ectodermal ridge (AER). As a transitional embryonic structure, the AER undergoes four stages and contributes to multiple axes of limb development through the coordination of signalling centres, feedback loops, and other cell activities by secretory signalling and the activation of gene expression. Within the scope of proximodistal patterning, it is understood that while fibroblast growth factors (FGFs) function sequentially over time as primary components of the AER signalling process, there is still no consensus on models that would explain proximodistal patterning itself. In anteroposterior patterning, the AER has a dual-direction regulation by which it promotes the sonic hedgehog (Shh) gene expression in the zone of polarizing activity (ZPA) for proliferation, and inhibits Shh expression in the anterior mesenchyme. In dorsoventral patterning, the AER activates Engrailed-1 (En1) expression, and thus represses Wnt family member 7a (Wnt7a) expression in the ventral ectoderm by the expression of Fgfs, Sp6/8, and bone morphogenetic protein (Bmp) genes. The AER also plays a vital role in shaping the individual digits, since levels of Fgf4/8 and Bmps expressed in the AER affect digit patterning by controlling apoptosis. In summary, the knowledge of crosstalk within AER among the three main axes is essential to understand limb growth and pattern formation, as the development of its areas proceeds simultaneously.
Topics: Animals; Apoptosis; Body Patterning; Bone Morphogenetic Proteins; Developmental Biology; Ectoderm; Extremities; Fibroblast Growth Factor 10; Fibroblast Growth Factors; Gene Expression Regulation; Hedgehog Proteins; Homeodomain Proteins; Mesoderm; Mice; Signal Transduction; Wnt Proteins
PubMed: 33043642
DOI: 10.1631/jzus.B2000285 -
The International Journal of... 2017Cranial placodes are an evolutionary novelty of vertebrates that give rise to many cranial sense organs and ganglia, as well as to the neurosecretory anterior pituitary.... (Review)
Review
Cranial placodes are an evolutionary novelty of vertebrates that give rise to many cranial sense organs and ganglia, as well as to the neurosecretory anterior pituitary. Although amphioxus does not have placodes, it shares with vertebrates several of the ectodermal patterning mechanisms and cell types that are important in placode development. Comparisons between amphioxus, vertebrates and other groups provide us with important insights into what the last common chordate ancestor probably looked like and allow us to propose a scenario for how placodes evolved by rewiring of gene regulatory networks. After reviewing ectodermal patterning and the cytodifferentiation of neurosecretory and sensory cells in amphioxus, this review will argue that the evolutionary origin of cranial placodes involved 1) the concentration of sensory and neurosecretory cell types in the head by linking their development to ancient cranial ectodermal patterning mechanisms; and 2) the formation of high density arrays of sensorineural precursors by intercalating a progenitor expansion module into the gene regulatory network driving differentiation of sensory or neurosecretory cells.
Topics: Animals; Body Patterning; Cell Differentiation; Ectoderm; Evolution, Molecular; Gene Expression Regulation, Developmental; Gene Regulatory Networks; Lancelets; Phylogeny; Vertebrates
PubMed: 29319112
DOI: 10.1387/ijdb.170127gs -
Journal of Visualized Experiments : JoVE Apr 2013Orofacial clefts are the most frequent craniofacial defects, which affect 1.5 in 1,000 newborns worldwide. Orofacial clefting is caused by abnormal facial development....
Orofacial clefts are the most frequent craniofacial defects, which affect 1.5 in 1,000 newborns worldwide. Orofacial clefting is caused by abnormal facial development. In human and mouse, initial growth and patterning of the face relies on several small buds of tissue, the facial prominences. The face is derived from six main prominences: paired frontal nasal processes (FNP), maxillary prominences (MxP) and mandibular prominences (MdP). These prominences consist of swellings of mesenchyme that are encased in an overlying epithelium. Studies in multiple species have shown that signaling crosstalk between facial ectoderm and mesenchyme is critical for shaping the face. Yet, mechanistic details concerning the genes involved in these signaling relays are lacking. One way to gain a comprehensive understanding of gene expression, transcription factor binding, and chromatin marks associated with the developing facial ectoderm and mesenchyme is to isolate and characterize the separated tissue compartments. Here we present a method for separating facial ectoderm and mesenchyme at embryonic day (E) 10.5, a critical developmental stage in mouse facial formation that precedes fusion of the prominences. Our method is adapted from the approach we have previously used for dissecting facial prominences. In this earlier study we had employed inbred C57BL/6 mice as this strain has become a standard for genetics, genomics and facial morphology. Here, though, due to the more limited quantities of tissue available, we have utilized the outbred CD-1 strain that is cheaper to purchase, more robust for husbandry, and tending to produce more embryos (12-18) per litter than any inbred mouse strain. Following embryo isolation, neutral protease Dispase II was used to treat the whole embryo. Then, the facial prominences were dissected out, and the facial ectoderm was separated from the mesenchyme. This method keeps both the facial ectoderm and mesenchyme intact. The samples obtained using this methodology can be used for techniques including protein detection, chromatin immunoprecipitation (ChIP) assay, microarray studies, and RNA-seq.
Topics: Animals; Dissection; Ectoderm; Embryo, Mammalian; Face; Female; Mesoderm; Mice; Mice, Inbred C57BL; Pregnancy
PubMed: 23603693
DOI: 10.3791/50248 -
PLoS Genetics Feb 2014The cranial bones and dermis differentiate from mesenchyme beneath the surface ectoderm. Fate selection in cranial mesenchyme requires the canonical Wnt effector...
The cranial bones and dermis differentiate from mesenchyme beneath the surface ectoderm. Fate selection in cranial mesenchyme requires the canonical Wnt effector molecule β-catenin, but the relative contribution of Wnt ligand sources in this process remains unknown. Here we show Wnt ligands are expressed in cranial surface ectoderm and underlying supraorbital mesenchyme during dermal and osteoblast fate selection. Using conditional genetics, we eliminate secretion of all Wnt ligands from cranial surface ectoderm or undifferentiated mesenchyme, to uncover distinct roles for ectoderm- and mesenchyme-derived Wnts. Ectoderm Wnt ligands induce osteoblast and dermal fibroblast progenitor specification while initiating expression of a subset of mesenchymal Wnts. Mesenchyme Wnt ligands are subsequently essential during differentiation of dermal and osteoblast progenitors. Finally, ectoderm-derived Wnt ligands provide an inductive cue to the cranial mesenchyme for the fate selection of dermal fibroblast and osteoblast lineages. Thus two sources of Wnt ligands perform distinct functions during osteoblast and dermal fibroblast formation.
Topics: Animals; Cell Differentiation; Ectoderm; Gene Expression Regulation, Developmental; Ligands; Mesoderm; Mice; Osteoblasts; Signal Transduction; Skull; Stem Cells; Wnt Proteins; beta Catenin
PubMed: 24586192
DOI: 10.1371/journal.pgen.1004152 -
Open Biology Mar 2019In this decade, substantial progress in the fields of developmental biology and stem cell biology has ushered in a new era for three-dimensional organ regenerative... (Review)
Review
In this decade, substantial progress in the fields of developmental biology and stem cell biology has ushered in a new era for three-dimensional organ regenerative therapy. The emergence of novel three-dimensional cell manipulation technologies enables the effective mimicking of embryonic organ germ formation using the fate-determined organ-inductive potential of epithelial and mesenchymal stem cells. This advance shows great potential for the regeneration of functional organs with substitution of complete original function in situ. Organoids generated from multipotent stem cells or tissue stem cells via establishment of an organ-forming field can only partially recover original organ function owing to the size limitation; they are considered 'mini-organs'. Nevertheless, they hold great promise to realize regenerative medicine. In particular, regeneration of a functional salivary gland and an integumentary organ system by orthotopic and heterotopic implantation of organoids clearly points to the future direction of organ regeneration research. In this review, we describe multiple strategies and recent progress in regenerating functional three-dimensional organs, focusing on ectodermal organs, and discuss their potential and future directions to achieve organ replacement therapy as a next-generation regenerative medicine.
Topics: Animals; Artificial Organs; Ectoderm; Epithelial Cells; Humans; Mesenchymal Stem Cells; Organoids; Regeneration; Regenerative Medicine; Salivary Glands; Tissue Engineering
PubMed: 30836846
DOI: 10.1098/rsob.190010