Ectodermal Invagination Research Articles

Formation of Coelomic Cavities during Abbreviated Development of the Brittle Star Ophioplocus esmarki.

AbstractIn brittle stars, the coelomic cavities that form during embryogenesis contribute to most of the internal organ systems of the juvenile. In the ancestral mode of development, the coelomic cavities begin with bilateral symmetry and play a minor role in the function of the ophiopluteus larva. However, the coelomic cavities undergo extensive changes during metamorphosis to set up the body systems of the juvenile brittle star. Many lineages of brittle stars have evolved life histories without the ophiopluteus larva. The non-feeding vitellaria larva has rapid development of juvenile structures. This work demonstrates the modifications to the origin and early development of the coelomic cavities in a vitellaria larva. Much of the archenteron forms an unpaired axocoel, hydrocoel, and somatocoel. The posterior-most portion of the archenteron forms the rudiment of the juvenile stomach. The right somatocoel and a portion of the left somatocoel form as invaginations of the lateral ectoderm. Later morphogenesis of the axocoel, the hydrocoel, and the two somatocoels is similar to what has been shown for brittle stars with an ophiopluteus larva. Confocal microscopy and three-dimensional modeling were used to show new details for the later morphogenesis of the coelomic cavities. The stone canal originates as an outgrowth of the hydrocoel between lobes 4 and 5. The hydrocoel lobes have minimal migration after they meet to complete the ring canal. The right somatocoel contributes to a component of the axial complex and perihemal system. A detailed description is given for how the left somatocoel contributes to multiple organ systems.

About the Cover

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreA defining feature of echinoderms is their five-fold symmetry, which arises during the metamorphosis of a bilaterally symmetrical larva. During echinoderm metamorphosis, the coelomic cavities undergo an elaborate transformation from early mesodermal pouches to a complex system of tubes and rings that make up the numerous internal components of the animal. In this issue (pp. 283–298), H. C. Sweet and several undergraduate research students (G. Azriel, N. Jaff, J. Moser, T. A. Riola, C. Ideman, M. Barton, J. Nelson, and M. M. Lenhart) demonstrate the origin of the coelomic structures and their morphogenesis in the vitellaria larva of the brittle star Ophioplocus esmarki. Many of the structures first form when the archenteron becomes subdivided into an unpaired axocoel, hydrocoel, somatocoel, and stomach rudiment. The right somatocoel and part of the left somatocoel originate as bilateral invaginations of the larval ectoderm. This supports the findings of others that ectodermal invagination of the somatocoels is an unusual feature of brittle star development. Confocal microscopy and 3D modeling were used to document the later morphogenesis of the coelomic cavities as they form juvenile structures with five-fold symmetry.The cover image demonstrates the complex structure of the vitellaria larva. The image shows the color-coded coelomic cavities superimposed with an image of the skeleton and an outline of body of the vitellaria larva. At this stage, the outer ectoderm has ciliary bands on raised ridges that are used for swimming (grayscale outline), but most of the internal structures are patterned in five-fold symmetry with the axial complex near the anterior end (top). Coelomic structures include the water vascular system derived from the hydrocoel (yellow), hypogastric coelom derived from the left somatocoel (purple), genital coelom (peach) derived from the left somatocoel, epigastric coelom derived from the right somatocoel (magenta), pericardial coelom (green), axial coelom (orange), and pore canal (red). The juvenile skeletal plates form adjacent to the coelomic structures and the overlying ectoderm. The image was generated with confocal microscopy, polarized light imaging, and image colorizing and processing in GIMP and Fiji.Credits: Photo, Hyla C. Sweet; cover design, Olivia Kinker. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 243, Number 3December 2022 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/724434 © 2022 The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.

Sox21 Regulates Anpc10 Expression and Determines the Fate of Ectodermal Organ

Tooth and hair development initiates from ectodermal invaginations. However, the determination of organ-specific cell fates is poorly understood. The transcription factor Sox21 is expressed in the epithelium of developing teeth. The present study aimed to determine the role of Sox21 in tooth development. We found that disruption of Sox21 caused severe enamel hypoplasia, regional osteoporosis, and ectopic hair formation in the gingiva in Sox21 knockout incisors. Differentiation markers were lost in ameloblasts, which formed hair follicles expressing hair keratins. Molecular analysis and chromatin immunoprecipitation (ChIP) sequencing indicated that Sox21 regulated Anapc10, which recognizes substrates for ubiquitination-mediated degradation, and determined dental-epithelial versus hair-follicle cell fate. Disruption of either Sox21 or Anapc10 induced Smad3 expression, accelerated TGF-β1-induced promotion of epithelial-mesenchymal transition (EMT), and resulted in E-cadherin degradation via Skp2. We conclude that Sox21 disruption in the dental epithelium leads to the formation of a unique microenvironment promoting hair formation and that Sox21 controls dental epithelial differentiation and enamel formation by inhibiting EMT via Anapc10.

The uropygial gland of the monk parakeet Myiopsitta monachus: Histology, morphogenesis, and evolution within Psittaciformes (Aves).

We describe the morphology, histology, and histochemical characteristics of the uropygial gland (UG) of the monk parakeet Myiopsitta monachus. The UG has a heart-shape external appearance and adenomers extensively branched with a convoluted path, covered by a stratified epithelium formed by different cellular strata and divided into three zones (based on the epithelial height and lumen width), a cylindrical papilla with an internal structure of delicate type and two excretory pores surrounded by a feather tuft. Histochemical and lectin-histochemical techniques performed showed positivity against PAS, AB pH 2.5, AB-PAS, and some lectines, likely related to the granivorous feeding habits. Also, we describe the morphogenesis of the UG of the monk parakeet, which appears at embryological stage 34 as a pair of ectodermal invaginations. Heterochronic events in the onset development of the UG when compared with other birds could be recognized. Finally, to examine the phylogenetic occurrence of the UG within the Psittaciformes and infer its evolutionary history, we mapped its presence/absence over a molecular phylogeny. The reconstruction of the characters states at ancestral nodes revealed that the presence of the UG was the plesiomorphic feature for Psittaciformes and its loss evolved independently more than once.

Regeneration of the cell mass in larvae of temnopleurid sea urchins

Mechanisms of cell mass (CM) formation were analyzed by microsurgery in two temnopleurid sea urchins, Mespilia globulus and Temnopleurus toreumaticus. The CM in temnopleurids is formed at the early larval stage from the left ectodermal invagination, and with the hydrocoel derived from the mesoderm, forms an adult rudiment. After serial removal of the CM, it was strongly regenerated until its attachment to the hydrocoel, with the same timing as in control larvae. Embryos that had the tip of the archenteron or the coelomic pouches removed formed a CM in the normal manner. Removal of the CM plus the left somatocoel or the hydrocoel allowed CM regeneration with and without adult rudiment formation. A transplanted CM enlarged autonomously but did not contribute to adult rudiment formation, and larvae formed a new CM. Our observations suggest that the hydrocoel recognizes its distance from the CM to induce the growth of the CM and controls the normal timing of adult rudiment formation.

A clonal stem cell line established from a mouse mammary placode with ability to generate functional mammary glands.

The mammary gland develops from the placode at ectodermal invagination. The rudimentary parenchyma (mammary bud) develops mammary trees and alveolar structures, suggesting that the mammary bud consists of stem/progenitor cells. Here, we established a clonal stem cell line from a mammary bud of a p53 null female embryo at day 14.5. FP5-3-1 line was a homogeneous cell population with polygonal epithelial morphology and spontaneously became heterogeneous during passages. Recloning gave rise to four sublines; three sublines have basal epithelial property and one subline has luminal epithelial property. The former sublines generate functional mammary glands when injected into cleared fat pads and the latter subline does not. The cell lines also express many stemness-related genes. The clonal cell lines established in the present study are shown to be mammary stem cells and not tumorigenic. They provide useful models for normal and tumor biology of the mammary gland in vivo and in vitro.

Anomalies of the branchial arch apparatus in children: case series and review of literature

<p>Branchial apparatus develop between the 3rd and 7th weeks of embryonic life. There are five mesodermal arches separated by invaginations of ectoderm and endoderm. Branchial anomalies are result of aberrant embryonic development and are rarely seen in clinical practice. The objective of this article is to present few cases of branchial arch anomalies and to discuss the clinical presentation, diagnosis and surgical approach of such lesions in pediatric age group.</p>

Second branchial arch anomaly: case series of two

<p>Branchial apparatus develop between the 3<sup>rd</sup> and 7<sup>th</sup> weeks of embryonic life. There are 5 mesodermal arches separated by invaginations of ectoderm and endoderm. During development the second arch grows caudally to cover the third and fourth arches and the second, third, and fourth pharyngeal clefts eventually fusing with the lower neck. The enclosed II, III, and IV clefts are called as the cervical sinus. If this process does not occur for some reason then it gives rise to branchial cyst, sinus or fistula. We are presenting two cases of second branchial arch anomaly. In first case there was bilateral branchial fistula with right side fistula associated with branchial cyst. In second case there was unilateral right side branchial fistula. We operated both the cases by giving step ladder incision. In second case we find fistulous track opening in the tonsillar bed. Both the patients recovered well with no recurrence since 1 year. Brachial cleft cyst is a common cause of soft tissue swelling in the neck of a young adult. They generally occur unilaterally and are typically seen in the lateral aspect of the neck. It is clinically apparent in late childhood or early adulthood. In older adults with this presentation, it is important to exclude metastatic lymphadenopathy, lymphoma or tuberculosis.</p>

Structure, function and cell dynamics during chaetogenesis of abdominal uncini in Sabellaria alveolata (Sabellariidae, Annelida).

BackgroundDynamic apical microvilli of a single cell, called the chaetoblast, inside an ectodermal invagination form the template of annelid chaetae. Changes in the pattern of microvilli are frozen in time by release of chitin, such that the structure of the definitive chaeta reflects its formation. Cellular interactions during chaetogenesis also influence the structure of the chaeta. Analysing chaetogenesis allows for testing hypotheses on the homology of certain chaetal types. We used this approach to test whether the unusual uncini in Sabellaria alveolata are homologous to apparently similar uncini in other annelid taxa.ResultsOur study reveals unexpected details of sabellariid uncini, which mechanically reinforce the neuropodia enabling their use as paddles. The final structure of the chaeta is caused by pulses of microvilli formation and dynamic interaction between the chaetoblast and adjoining follicle cells. Cell dynamics during chaetogenesis of the uncini in Sabellaria alveolata exceeds by far that reported in previous studies on the formation of this type of chaetae.ConclusionDespite the superficial similarity of uncini in sabellariids and other annelids, differences in structure and details of formation do not support the homology of this type of chaetae. Chaetogenesis of sabellariid uncini involves unexpected microvilli and cell dynamics, and provides evidence that interactions between cells play a larger role in chaetogenesis than previously expected. In addition to their function as anchors, uncini in Sabellaridae stabilize the paddle-shaped notopodia, as each uncinus possesses a long, thin rod that extends deeply into the notopodium. The rods of all uncini in a single row form a bundle inside the notopodium that additionally serves as a muscle attachment site and thus have a similar function to the inner chaeta (acicula) of errant polychaetes (Aciculata).

The embryonic origin of the ampullate silk glands of the spider Cupiennius salei

Silk production in spiders is considered a key innovation, and to have been vital for the diversification of the clade. The evolutionary origin of the organs involved in spider silk production, however, and in particular of the silk glands, is poorly understood. Homologies have been proposed between these and other glands found in arachnids, but lacking knowledge of the embryonic development of spider silk glands hampers an evaluation of hypotheses. This study focuses on the embryonic origin of the largest silk glands of the spider Cupiennius salei, the major and minor ampullate glands. We show how the ampullate glands originate from ectodermal invaginations on the embryonic spinneret limb buds, in relation to morphogenesis of these buds. Moreover, we visualize the subsequent growth of the ampullate glands in sections of the early postembryonic stages. The invaginations are shown to correlate with expression of the proneural gene CsASH2, which is remarkable since it has been proposed that spider silk glands and their nozzles originate from sensory bristles. Hence, by confirming the ectodermal origin of spider silk glands, and by describing the (post-)embryonic morphogenesis of the ampullate glands, this work provides a starting point for further investigating into the genetic program that underlies their development.

4th Branchial Cleft Cyst Anomaly: Case Presentation

4th Branchial Cleft Cyst Anomaly: Case Presentation The human branchial apparatus is composed of six paired mesodermal arches, separated by endodermal and ectodermal invaginations known as pouches and clefts, respectively. Error in obliteration of a pouch or groove may create a sinus, fistula or a cyst. Approximately 95% of congenital anomalies of the branchial apparatus involve the second arch, pouch or cleft, while the remaining mostly arise from the first and third arches. Fourth branchial involvement is extremely rare with only few cases published in the English literature. In this report we will emphasize the working dilemma in establishing the correct diagnosis of fourth branchial cleft cyst. Diagnostic tools and appropriate treatment will be addressed as well.

Chaetal arrangement and chaetogenesis of hooded hooks in Lumbrineris (Scoletoma) fragilis and Lumbrineris tetraura (Eunicida, Annelida)

AbstractAs the structure and arrangement of chaetae are highly specific for annelid species and higher taxonomic entities, we assume that rather conservative information guarantees formation of specific chaetae. Each chaeta of an annelid is formed within an ectodermal invagination, and the modulation of the apical microvilli pattern of the basalmost cell of this invagination determines the structure of the chaeta. Any hypothesis of the homology of chaetae could thus be tested by examining the process of chaetal formation. Investigations into the ultrastructure and formation of hooded hooks in different capitellids and spionids revealed that these chaetae can be homologized. The hood of each of their hooded hooks is formed by elongation of two rings of microvilli peripheral to the chaetal anlage, which give rise to the inner and outer layers of the hood. The hood layers are well separated and surround an empty space. Superficially similar hooded hooks are described for certain Eunicida. Presently available cladistic analyses suggest that the hooded hooks of eunicidans evolved independently of those in Capitellidae and Spionidae. Compared with the latter two families, we therefore expected to find differences in chaetogenesis of the hooded hooks in the eunicids Lumbrineris (Scoletoma) fragilis and Lumbrineris tetraura (Lumbrineridae). This was the case. In these eunicidans, the hood was formed by the bisected apical wall of the chaetoblast right after the mid‐apical section of the chaeta had been sunk deeply into the chaetoblast during its formation. The apical wall generated a brush of microvilli that preformed the hood. Because the microvilli of the hood showed some accelerated differentiation, they soon merged with those of the slowly growing setal shaft to form the broad manubrium of the hooded hook in lumbrinerids. Our study confirms the predicted differences in chaetogenesis of the superficially similar hooded hooks of capitellids and spionids compared with those of eunicids.

4th Branchial Cleft Cyst Anomaly: Case Presentation

4th Branchial Cleft Cyst Anomaly: Case Presentation The human branchial apparatus is composed of six paired mesodermal arches, separated by endodermal and ectodermal invaginations known as pouches and clefts, respectively. Error in obliteration of a pouch or groove may create a sinus, fistula or a cyst. Approximately 95% of congenital anomalies of the branchial apparatus involve the second arch, pouch or cleft, while the remaining mostly arise from the first and third arches. Fourth branchial involvement is extremely rare with only few cases published in the English literature. In this report we will emphasize the working dilemma in establishing the correct diagnosis of fourth branchial cleft cyst. Diagnostic tools and appropriate treatment will be addressed as well.

Dual epithelial origin of vertebrate oral teeth

The oral cavity of vertebrates is generally thought to arise as an ectodermal invagination. Consistent with this, oral teeth are proposed to arise exclusively from ectoderm, contributing to tooth enamel epithelium, and from neural crest derived mesenchyme, contributing to dentin and pulp. Yet in many vertebrate groups, teeth are not restricted only to the oral cavity, but extend posteriorly as pharyngeal teeth that could be derived either directly from the endodermal epithelium, or from the ectodermal epithelium that reached this location through the mouth or through the pharyngeal slits. However, when the oropharyngeal membrane, which forms a sharp ecto/endodermal border, is broken, the fate of these cells is poorly known. Here, using transgenic axolotls with a combination of fate-mapping approaches, we present reliable evidence of oral teeth derived from both the ectoderm and endoderm and, moreover, demonstrate teeth with a mixed ecto/endodermal origin. Despite the enamel epithelia having a different embryonic source, oral teeth in the axolotl display striking developmental uniformities and are otherwise identical. This suggests a dominant role for the neural crest mesenchyme over epithelia in tooth initiation and, from an evolutionary point of view, that an essential factor in teeth evolution was the odontogenic capacity of neural crest cells, regardless of possible 'outside-in' or 'inside-out' influx of the epithelium.

Cell lineage analysis demonstrates an endodermal origin of the distal urethra and perineum

Congenital malformations of anorectal and genitourinary (collectively, anogenital) organs occur at a high frequency in humans, however the lineage of cells that gives rise to anogenital organs remains poorly understood. The penile urethra has been reported to develop from two cell populations, with the proximal urethra developing from endoderm and the distal urethra forming from an apical ectodermal invagination, however this has never been tested by direct analysis of cell lineage. During gut development, endodermal cells express Sonic hedgehog ( Shh), which is required for normal patterning of digestive and genitourinary organs. We have taken advantage of the properties of Shh expression to genetically label and follow the fate of posterior gut endoderm during anogenital development. We report that the entire urethra, including the distal (glandar) region, is derived from endoderm. Cloacal endoderm also gives rise to the epithelial linings of the bladder, rectum and anterior region of the anus. Surprisingly, the lineage map also revealed an endodermal origin of the perineum, which is the first demonstration that endoderm differentiates into skin. In addition, we fate mapped genital tubercle ectoderm and show that it makes no detectable contribution to the urethra. In males, formation of the urethral tube involves septation of the urethral plate by continued growth of the urorectal septum. Analysis of cell lineage following disruption of androgen signaling revealed that the urethral plate of flutamide-treated males does not undergo this septation event. Instead, urethral plate cells persist to the ventral margin of the tubercle, mimicking the pattern seen in females. Based on these spatial and temporal fate maps, we present a new model for anogenital development and suggest that disruptions at specific developmental time points can account for the association between anorectal and genitourinary defects.

Spalt4mediates invagination and otic placode gene expression in cranial ectoderm

Vertebrate placodes are regions of thickened head ectoderm that contribute to paired sensory organs and cranial ganglia. We demonstrate that the transcription factor Spalt4 (also known as Sall4) is broadly expressed in chick preplacodal epiblast and later resolves to otic, lens and olfactory placodes. Ectopic expression of Spalt4 by electroporation is sufficient to induce invagination of non-placodal head ectoderm and prevent neurogenic placodes from contributing to cranial ganglia. Conversely, loss of Spalt4 function in the otic placode results in abnormal otic vesicle development. Intriguingly, Spalt4 appears to initiate a placode program appropriate for the axial level but is not involved in later development of specific placode fates. Fgfs can regulate Spalt4, since implantation of Fgf2 beads into the area opaca induces its expression. The results suggest that Spalt4 is involved in early stages of placode development, initiating cranial ectodermal invagination and region-specific gene regulatory networks.

Noggin regulates Bmp4 activity during pituitary induction

Bone morphogenetic protein (Bmp) signaling is critical for the development and patterning of the mouse pituitary from the initial induction of Rathke’s pouch to cell specification in the anterior lobe. We examined the regulation of Bmp signaling during pituitary development by analyzing null embryos for noggin, a Bmp 2 and 4 antagonist. Noggin is expressed in the ventral diencephalon during Rathke’s pouch induction, in the underlying cartilage plate during cell specification and in the adult anterior pituitary gland. Noggin null embryos have a variable pituitary phenotype, which ranges from a rostrally displaced Rathke’s pouch to induction of secondary pituitary tissue. While cell specification in the anterior pituitary appears normal, patterning in the ventral diencephalon is disrupted; Bmp4 activity is expanded resulting in Fibroblast growth factor 10 repression and in a rostral shift in the boundary between the Bmp4 and Sonic hedgehog expression domains. The expanded domain of Bmp4 activity also results in additional invaginations of oral ectoderm and can shift the position of Rathke’s pouch or create secondary pituitary tissue. This work demonstrates the importance of attenuating the activity of Bmp signaling during pituitary induction in order to maintain the proper balance of signaling factors necessary for pituitary organogenesis.

Embryogenesis and larval development of Phoronopsis harmeri Pixell, 1912 (Phoronida): dual origin of the coelomic mesoderm

Summary Phoronids are marine invertebrates which great significance from the perspective of comparative anatomy. Phoronids have traditionally been described as deuterostomes because they exhibit developmental and larval traits similar to those traits found in echinoderms and hemichordates. However, molecular phylogenetic evidence has consistently identified the phoronids and brachiopods as a monophyletic group within the lophotrochozoan protostomes. The nature of egg cleavage, gastrulation and the origin of coelomic mesoderm can help to resolve this contradiction. These questions were investigated with Phoronopsis harmeri. Embryos and actinotroch larvae were cultivated in the laboratory, and embryonic and larval development was followed with SEM, light and video microscopy. Egg cleavage is radial, although the furrows of the 4th and succeeding divisions are oblique, which allows for blastula formation by the 16-cell stage. The ciliated blastula hatches 10 h after the onset of cleavage and acquires the apical tuft. Gastrulation proceeds by invagination. Coelomic mesoderm derives from two, the anterior and posterior, precursors. The anterior precursor forms by cell migration from the anterior wall of the archenteron, the posterior one by enterocoelic outpouching of the midgut. The lining of preoral coelom and tentacle coelom is derived from the anterior precursor, whilst the lining of trunk coelom originates from the posterior one. The intestine forms as an ectodermal invagination of the posterior part of larval body. Protonephridial canals form as ectodermal dorso-lateral furrows on both sides of the anus. A typical actinotroch is formed 100 h after the onset of cleavage. Larvae are described at the stages of 8, 12,20 and 24 tentacles.

Tissue-specific laminin expression facilitates integrin-dependent association of the embryonic wing disc with the trachea in Drosophila

The interaction of heterologous tissues involves cell adhesion mediated by the extracellular matrix and its receptor integrins. The Drosophila wing disc is an ectodermal invagination that contacts specific tracheal branches at the basolateral cell surface. We show that an α subunit of laminin, encoded by wing blister ( wb), is essential for the establishment of the interaction between the wing and trachea. During embryogenesis, wing disc cells present Wb at their basolateral surface and extend posteriorly, expanding their association to more posteriorly located tracheal branches. These migratory processes are impaired in the absence of the trachea, Wb, or integrins. Time-lapse and transmission electron microscopy analyses suggest that Wb facilitates integrin-dependent contact over a large surface and controls the cellular behavior of the wing cells, including their exploratory filopodial activity. Our data identify Wb laminin as an extracellular matrix ligand that is essential for integrin-dependent cellular migration in Drosophila.

Morphology of the prosomal endoskeleton of Scorpiones (Arachnida) and a new hypothesis for the evolution of cuticular cephalic endoskeletons in arthropods

Skeletomuscular anatomy of the scorpion prosoma is examined in an attempt to explain the evolution of two endoskeletal features, a muscular diaphragm dividing the prosoma and opisthosoma and cuticular epistomal entapophyses with a uniquely complex arrangement of muscles, tendons and ligaments. Both structures appear to be derived from modifications of the mesodermal intersegmental endoskeleton that is primitive for all major arthropod groups. The scorpion diaphragm is a compound structure comprising axial muscles and pericardial ligaments of segments VI to VIII and extrinsic muscles of leg 4 brought into contact by longitudinal reduction of segment VII and integrated into a continuous subvertical sheet. This finding reconciles a long-standing conflict between one interpretation of opisthosomal segmentation based on scorpion embryology and another derived from comparative skeletomuscular anatomy. A new evolutionary-developmental mechanism is proposed to account for the complex morphology of the epistomal entapophyses. Each entapophysis receives 14 muscles and tendons that in other taxa would attach to the anterior connective endoskeleton in the same relative positions. This observation suggests that the embryological precursor to the connective endoskeleton can initiate and guide ectodermal invagination and thereby serve as a spatial template for the development of cuticular apodemes. This mesoderm-template model of ectodermal invagination is potentially applicable to all arthropods and may explain structural diversity and convergence in cephalic apodemes throughout the group. The model is used to interpret the cephalic endoskeletons of two non-chelicerate arthropods, Archaeognatha (Hexapoda) and Symphyla (Myriapoda), to demonstrate the generality of the model.