Prechordal structures act cooperatively in early trabeculae development of gnathostome skull.

The vertebrate skull is formed by mesoderm and neural crest (NC) cells. The mesoderm contributes to the skull chordal domain, with the notochord playing an essential role in this process. The NC contributes to the skull prechordal domain, prompting investigation into the embryonic structures involved in prechordal neurocranium cartilage formation. The trabeculae cartilage, a structure of the prechordal neurocranium, arises at the convergence of prechordal plate (PCP), ventral midline (VM) cells of the diencephalon, and dorsal oral ectoderm. This study examines the molecular participation of these embryonic structures in gnathostome trabeculae development. PCP-secreted SHH induces its expression in VM cells of the diencephalon, initiating a positive feedback loop involving SIX3 and GLI1. SHH secreted by the VM cells of the diencephalon acts on the dorsal oral ectoderm, stimulating condensation of NC cells to form trabeculae. SHH from the prechordal region affects the expression of SOX9 in NC cells. BMP7 and SHH secreted by PCP induce NKX2.1 expression in VM cells of the diencephalon, but this does not impact trabeculae formation. Molecular cooperation between PCP, VM cells of the diencephalon, and dorsal oral ectoderm is crucial for craniofacial development by NC cells in the prechordal domain.

Oviductal fluid counterbalances the negative effect of high temperature on sperm in an ectotherm model.

Global warming is affecting biodiversity; however, the extent to which animal reproductive processes respond to predicted temperature increments remains largely unexplored. The thermal environment has a pronounced impact on metabolic rates of ectotherms; therefore, an interesting question to assess is whether temperature increase might affect specific reproductive mechanisms like sperm performance in ectotherms. Moreover, in many species, oviductal fluid (OF) is known to regulate and maintain sperm quality; however, the role of OF in relation to the effects of high temperature on sperm remains unclear. Our aim was to experimentally test the effect of increased temperature on sperm velocity, swimming path and percentage of motility in neutral conditions at ejaculation (without OF) and in female's reproductive tract fluid (with OF), in a social ectotherm lizard model, Tropidurus spinulosus, which has specific thermal requirements for reproduction. Our results suggest that a rising temperature associated with global warming (+4°C) affects negatively sperm dynamics and survival. However, OF ameliorated the harmful effects of high temperature. This is an important point, as this study is the first to have tested the role of OF in preserving sperm from a warmer pre-fertilization environment. These results contribute to our understanding of how thermal environment changes might affect post-copulatory reproductive mechanisms. This article has an associated First Person interview with the first author of the paper.

Establishing embryonic territories in the context of Wnt signaling.

This review highlights the work that my research group has been developing, together with international collaborators, during the last decade. Since we were able to establish the Xenopus laevis experimental model in Brazil, we have been focused on understanding early embryonic patterns regarding neural induction and axes establishment. In this context, the Wnt pathway appears as a major player and has been much explored by us and other research groups. Here, we chose to review three published works which we consider to be landmarks within the course of our research and also within the history of modern findings regarding neural induction and patterning. We intend to show how our series of discoveries, when painted together, tells a story that covers crucial developmental windows of early differentiation paths of anterior neural tissue: 1. establishing the head organizer in contrast to the trunk organizer in the early gastrula; 2. deciding between neural ectoderm and epidermis ectoderm at the blastula/gastrula stages, and 3. the gathering of prechordal unique properties in the late gastrula/early neurula.

Characterization of embryonic surface ectoderm cell protrusions.

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.

The number of biopsied trophectoderm cells may affect pregnancy outcomes.

OBJECTIVE: To study if the number of trophectoderm (TE) biopsied cells has an impact on implantation rates. DESIGN: A retrospective cohort study in a single-center study. SETTING: In vitro fertilization center. PATIENTS: Patients who underwent PGT-A from January 2013 to March 2016. In total, 482 vitrified/warmed single embryo transfers were included. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Clinical pregnancies rate, implantation rate. RESULTS: Overall, clinical pregnancies per embryo transfer were higher when a regular TE were biopsied compared to larger size biopsy cells (66% (175/267) vs 53% (115/215) (p < 0.005) respectively). Pregnancy rates were also analyzed according to embryo morphology at the moment of embryo biopsy, when a good-quality embryo was transferred the clinical outcome was 75% (81/108) in group 1 and 61% (60/99) in group 2 (p < 0.05). Data was also stratified by age in patients ≤ 35 years and > 35 years. The clinical pregnancy was 67% (51/76) in women ≤ 35 years and 65% (124/191) in women > 35 years when a regular size biopsy was performed. These results significantly reduced when a larger size biopsy was performed 54% (49/91) and 53% (66/124), respectively (p < 0.05). Further investigation indicated that miscarriage rate was similar between these groups (4% (7/182) in group 1 and 5% (6/121) in group 2). CONCLUSIONS: These findings underscore that when a large amount of TE cells are biopsied, it may negatively affect implantation rates, but once implanted, the embryos have the same chance to miscarry or reach term.

Histological and immunohistochemical effects of neuroectodermal cells transplantation after spinal cord injury in rats / Efectos histológicos e inmunohistoquímicos del trasplante de células neuroectodérmicas tras una lesión de la médula espinal en ratas

SUMMARY: In spinal cord injury, radical treatment is still a persistent hope for patients and clinicians. Our study aimed to determine the different histological changes in central, cranial and caudal sites of compressed spinal cord as a result of neuroectodermal stem cells (NESCs) transplantation in rats. For extraction of NESCs, future brains were extracted from mice embryos (10-days old) and cultured. Eighty, male rats were divided randomly into control, sham (20 rats each); while 40 rats were subjected to compressed spinal cord injury (CSCI). Seven days after spinal cord injury, rats were subdivided into 2 groups (20 rats each); an untreated and treated with NESCs injected cranial and caudal to the site of the spinal cord injury. Rats were sacrificed 4 weeks after transplantations of NESCs and specimens from the spinal cord at the central, cranial and caudal to site of spinal cord injury were proceeded to be stained with haematoxylin & eosin, osmic acid and Immunohistochemistry of glial fibrillary acidic protein (GFAP). Sections of CSCI revealed areas of hemorrhages, necrosis and cavitation limited by reactive astrocytosis, with upregulation of GFAP expression. Evidence of remyelination and mitigation of histopathological features, reactive astrocytosis in CSCI sections were more pronounced in cranial than in caudal region. NESCs transplantation ameliorated the pathological changes, promoted remyelination.

RESUMEN: En la lesión de la médula espinal, el tratamiento radical aún sigue siendo el tratamiento preferente para los pacientes y los médicos. El objetivo de este estudio fue determinar los diferentes cambios histológicos en los sitios centrales, craneales y caudales de la médula espinal comprimida, como resultado del trasplante de células madre neuroectodérmicas (NESCs) en ratas. Para la extracción de NESCs, se extrajeron y cultivaron los cerebros de embriones de ratones de 10 días de edad. Se dividieron 80 ratas macho aleatoriamente en grupos control, simulado (20 ratas cada una); mientras que 40 ratas fueron sometidas a lesión de la médula espinal comprimida (CSCI). Siete días después de la lesión de la médula espinal, las ratas se subdividieron en 2 grupos (20 ratas cada uno); un grupo no tratado y un grupo tratado con NESCs inyectado craneal y caudal en el sitio de la lesión. Las ratas fueron sacrificadas 4 semanas después de los trasplantes de NESCs y las muestras de la médula espinal en el centro, craneal y caudal del sitio de lesión fueron teñidas con hematoxilina y eosina, ácido ósmico e inmunohistoquímica de la proteína ácida fibrilar glial (GFAP). Las secciones de CSCI revelaron áreas de hemorragias, necrosis y cavitación limitadas por astrocitosis reactiva, con una regulación positiva de la expresión de GFAP. Evidencia de remielinización y mitigación de características histopatológicas, astrocitosis reactiva en secciones de CSCI fue más pronunciada en la región craneal que en la caudal. El trasplante de NESC mejoró los cambios patológicos, promoviendo la remielinización.

Methods to Study the Role of Progranulin in Preimplantation Mouse Embryo Development.

Progranulin is a 67-88 kDa glycoprotein, also known as acrogranin, PC-cell-derived growth factor, granulin-epithelin precursor, and proepithelin. This protein is present in a variety of mouse, rat, and human tissues. Progranulin, which is a growth factor, mediates cell cycle progression and cell migration in normal and pathological conditions. In several types of cancers, progranulin expression is upregulated, whereas function-interfering mutations in the granulin gene in humans have been linked to a subset of heritable cases of frontotemporal lobar degeneration. Also, progranulin has important effects on mouse preimplantation embryo development in vitro, including regulation of the appearance of the epithelium in the developing mouse blastocyst and growth of trophectoderm. Furthermore, progranulin promotes mouse blastocyst hatching, adhesion, and outgrowth in vitro. In this chapter, we describe some of the techniques that may be useful in the study of progranulin in embryo development.

Neurocristopathies: New insights 150 years after the neural crest discovery.

The neural crest (NC) is a transient, multipotent and migratory cell population that generates an astonishingly diverse array of cell types during vertebrate development. These cells, which originate from the ectoderm in a region lateral to the neural plate in the neural fold, give rise to neurons, glia, melanocytes, chondrocytes, smooth muscle cells, odontoblasts and neuroendocrine cells, among others. Neurocristopathies (NCP) are a class of pathologies occurring in vertebrates, especially in humans that result from the abnormal specification, migration, differentiation or death of neural crest cells during embryonic development. Various pigment, skin, thyroid and hearing disorders, craniofacial and heart abnormalities, malfunctions of the digestive tract and tumors can also be considered as neurocristopathies. In this review we revisit the current classification and propose a new way to classify NCP based on the embryonic origin of the affected tissues, on recent findings regarding the molecular mechanisms that drive NC formation, and on the increased complexity of current molecular embryology techniques.

Par3 in chick lens placode development.

The lens originates from a simple cuboidal epithelium, which, on its basal side, contacts the optic vesicle, whilst facing the extraembryonic environment on its apical side. As this epithelium changes into the pseudostratified lens placode, its cells elongate and become narrower at their apical ends. This is due to the formation of an apical actin network, whose appearance is restricted to cells of the placodal region, as a result of region-specific signaling mechanisms that remain largely unknown. Here, we investigated the role of the polarity protein PAR3 and the phosphorylation state of its Threonine 833 (T833) aPKC-binding site in the recruitment of aPKC and in the establishment of actin network in the chick lens placode. Overexpression of wild type PAR3 recruited aPKC and punctate actin clusters to the basolateral membranes of the placodal cells. Recruitment of aPKC depended on the charge of the residue that replaced the T833 residue. In contrast, induction of the ectopic actin spots was independent on the charge of this residue.

Displasia ectodérmica hipohidrótica: reporte de casos / Hypohydrotic ectodermal dysplasia: Report of case

La Displasia Ectodérmica Hipohidrótica (DEH) es una genodermatosis que se caracteriza por presentar alteraciones en las estructuras deri-vadas del ectodermo, frecuentemente se da la triada: hipohidrosis, hipotricosis e hipodoncia. El síndrome puede manifestarse como heren-cia autosómica dominante o recesiva y tam-bién como herencia ligada al sexo, la forma más frecuente es la de herencia recesiva relacionada al cromosoma X con sujetos de sexo masculino afectados y de sexo femenino portadores. Puede ocurrir a través de mutacio-nes autosómicas, de las cuales las del gen EDA1 son responsables del 58% de los casos. La DEH presenta tasa de mortalidad infantil entre 2% y 20%, dependiendo de la precocidad del diag-nóstico y de los protocolos de tratamiento. Este artículo presenta un paciente de 23 meses de edad quien había sido hospitalizado por otra-patología y se re rió al Instituto Hondureño de Seguridad Social (IHSS), por observar cabello hipopigmentado, escaso, no, ausencia de pestañas y cejas, dientes cónicos e hipohidro-sis: por lo que se diagnostica displasia ectodér-mica hipohidrótica, quedando pendiente la realización de biopsia de piel y exámenes genéticos debido a que no se cuenta con el equipo médico necesario. Por tal motivo, no se conoció el patrón de segregación...(AU)

La reactividad constitucional del sujeto: una piedra de rosetta interdisciplinaria / A reatividade constitucional do sujeito. Uma pedra de roseta interdisciplinar / Subject’s constitutional reactivitya: interdisciplinary rosetta stone

Aprender a identificar de manera integral, mixta y dinámica la constitución de un sujeto significa, por un lado, ayudarlo a autoconocerse en su manera de reaccionar (por eso se habla de reactividad constitucional y no más de biotipos o rasgos), de desarrollarse (madurar o destruirse), de relacionarse y aceptar a los demás tal como son; por otro lado, sirve para personalizar diagnóstico, terapia y pronóstico. La historia del constitucionalismo y un esquema sinóptico interdisciplinario (filosofía griega, teología, medicina hipocrática, galénica, homeopática, china, ayurvédica y holística, biología, embriología, bioquímica, fisiopatología, neurología, endocrinología, psicología y espiritualidad) muestra una precisa correspondencia y un denominador común sobre la base de la teoría constitucional embriológica que habla de endoblasto, mesoblasto y ectoblasto. Una coherencia que dura por más de 24 siglos en occidente y pasa también las barreras culturales (oriente y occidente) y paradigmáticas (biomedicina y homeopatía), no puede ser casual.

To learn to identify in an integral, mixed and dynamic way the subject’s constitution means, on one hand, to help him to a self-knowledgement of his reactive way (for this, we speak of constitutional reactivity and no more of biotipe or trait), to develop himself (to mature or to destroy), to join and accept the others like they are; on the other way, it serve to personalize diagnosis, therapy and prognosis. The constitution history and a synoptic interdisciplinary diagram (Greek philosophy, theology, hippocratic, galenic, homeopatic, chinese, ayurvedic and holistic medicines, biology, embriology, biochemistry, physiopathology, neurology, endocrinology, psychology and spirituality) shows a precise link and a common denominator according to an embriologic constitutional theory, that speaks about endoblast, mesoblast and ectoblast. A coherence thas lasts for more than 24 centuries in occident and goes through even the cultural borders (eastern and western world) and paradigmatic logics (biomedicine and homeopaty) cannot be casual.

Aprender a identificar de maneira integral, mista e dinâmica a constituição de um sujeito significa, por um lado, ajudá-lo a se autoconhecer na sua maneira de reagir (por isso se fala de reatividade constitucional e não mais de biotipos ou traços), de desenvolver-se (amadurecer ou destruir-se), de relacionar-se e aceitar os demais taisl como são; por outro lado, serve para personalizar diagnóstico, terapia e prognóstico. A história do constitucionalismo e um esquema sinóptico interdisciplinar (filosofia grega, teologia, medicina hipocrática, galênica, homeopática, chinesa, ayurvédica e holística, biologia, embriologia, bioquímica, fisiopatologia, neurologia, endocrinologia, psicologia e espiritualidade) mostra uma precisa correspondência e um denominador comum sobre a base da teoria constitucional embriológica que fala de endoblasto, mesoblasto e ectoblasto. Uma coerência que dura por mais de 24 séculos no ocidente e ultrapassa também as barreiras culturais (oriente e ocidente) e paradigmáticas (biomedicina e homeopatia), não pode ser casual.

c-Myc regulates cell proliferation during lens development.

Myc protooncogenes play important roles in the regulation of cell proliferation, growth, differentiation and survival during development. In various developing organs, c-myc has been shown to control the expression of cell cycle regulators and its misregulated expression is detected in many human tumors. Here, we show that c-myc gene (Myc) is highly expressed in developing mouse lens. Targeted deletion of c-myc gene from head surface ectoderm dramatically impaired ocular organogenesis, resulting in severe microphtalmia, defective anterior segment development, formation of a lens stalk and/or aphakia. In particular, lenses lacking c-myc presented thinner epithelial cell layer and growth impairment that was detectable soon after its inactivation. Defective development of c-myc-null lens was not caused by increased cell death of lens progenitor cells. Instead, c-myc loss reduced cell proliferation, what was associated with an ectopic expression of Prox1 and p27(Kip1) proteins within epithelial cells. Interestingly, a sharp decrease in the expression of the forkhead box transcription factor Foxe3 was also observed following c-myc inactivation. These data represent the first description of the physiological roles played by a Myc family member in mouse lens development. Our findings support the conclusion that c-myc regulates the proliferation of lens epithelial cells in vivo and may, directly or indirectly, modulate the expression of classical cell cycle regulators in developing mouse lens.

Sipuncula: an emerging model of spiralian development and evolution.

Sipuncula is an ancient clade of unsegmented marine worms that develop through a conserved pattern of unequal quartet spiral cleavage. They exhibit putative character modifications, including conspicuously large first-quartet micromeres and prototroch cells, postoral metatroch with exclusive locomotory function, paired retractor muscles and terminal organ system, and a U-shaped digestive architecture with left-right asymmetric development. Four developmental life history patterns are recognized, and they have evolved a unique metazoan larval type, the pelagosphera. When compared with other quartet spiral-cleaving models, sipunculan development is understudied, challenging and typically absent from evolutionary interpretations of spiralian larval and adult body plan diversity. If spiral cleavage is appropriately viewed as a flexible character complex, then understudied clades and characters should be investigated. We are pursuing sipunculan models for modern molecular, genetic and cellular research on evolution of spiralian development. Protocols for whole mount gene expression studies are established in four species. Molecular labeling and confocal imaging techniques are operative from embryogenesis through larval development. Next-generation sequencing of developmental transcriptomes has been completed for two species with highly contrasting life history patterns, Phascolion cryptum (direct development) and Nephasoma pellucidum (indirect planktotrophy). Looking forward, we will attempt intracellular lineage tracing and fate-mapping studies in a proposed model sipunculan, Themiste lageniformis. Importantly, with the unsegmented Sipuncula now repositioned within the segmented Annelida, sipunculan worms have become timely and appropriate models for investigating the potential for flexibility in spiralian development, including segmentation. We briefly review previous studies, and discuss new observations on the spiralian character complex within Sipuncula.

Embryonic development of chicken (Gallus Gallus Domesticus) from 1st to 19th day-ectodermal structures.

Birds occupy a prominent place in the Brazilian economy not only in the poultry industry but also as an animal model in many areas of scientific research. Thus the aim of this study was to provide a description of macro and microscopic aspects of the ectoderm-derived structures in chicken embryos / fetuses poultry (Gallus gallus domesticus) from 1st to 19th day of incubation. 40 fertilized eggs, from a strain of domestic chickens, with an incubation period of 2-19 days were subjected to macroscopic description, biometrics, light, and scanning microscopy. All changes observed during the development were described. The nervous system, skin and appendages and organs related to vision and hearing began to be identified, both macro and microscopically, from the second day of incubation. The vesicles from the primitive central nervous system-forebrain, midbrain, and hindbrain-were identified on the third day of incubation. On the sixth day of incubation, there was a clear vascularization of the skin. The optic vesicle was first observed fourth day of development and on the fifth day there was the beginning of the lens formation. Although embryonic development is influenced by animal line as well as external factors such as incubation temperature, this paper provides a chronological description for chicken (Gallus gallus domesticus) during its embryonic development.

Insights into the transcriptome of oenocytes from Aedes aegypti pupae.

Oenocytes are ectodermic cells present in the fat body of several insect species and these cells are considered to be analogous to the mammalian liver, based on their role in lipid storage, metabolism and secretion. Although oenocytes were identified over a century ago, little is known about their messenger RNA expression profiles. In this study, we investigated the transcriptome of Aedes aegypti oenocytes. We constructed a cDNA library from Ae. aegypti MOYO-R strain oenocytes collected from pupae and randomly sequenced 687 clones. After sequences editing and assembly, 326 high-quality contigs were generated. The most abundant transcripts identified corresponded to the cytochrome P450 superfamily, whose members have roles primarily related to detoxification and lipid metabolism. In addition, we identified 18 other transcripts with putative functions associated with lipid metabolism. One such transcript, a fatty acid synthase, is highly represented in the cDNA library of oenocytes. Moreover, oenocytes expressed several immunity-related genes and the majority of these genes were lysozymes. The transcriptional profile suggests that oenocytes play diverse roles, such as detoxification and lipid metabolism, and increase our understanding of the importance of oenocytes in Ae. aegypti homeostasis and immune competence.

Insights into the transcriptome of oenocytes from Aedes aegypti pupae

Oenocytes are ectodermic cells present in the fat body of several insect species and these cells are considered to be analogous to the mammalian liver, based on their role in lipid storage, metabolism and secretion. Although oenocytes were identified over a century ago, little is known about their messenger RNA expression profiles. In this study, we investigated the transcriptome of Aedes aegypti oenocytes. We constructed a cDNA library from Ae. aegypti MOYO-R strain oenocytes collected from pupae and randomly sequenced 687 clones. After sequences editing and assembly, 326 high-quality contigs were generated. The most abundant transcripts identified corresponded to the cytochrome P450 superfamily, whose members have roles primarily related to detoxification and lipid metabolism. In addition, we identified 18 other transcripts with putative functions associated with lipid metabolism. One such transcript, a fatty acid synthase, is highly represented in the cDNA library of oenocytes. Moreover, oenocytes expressed several immunity-related genes and the majority of these genes were lysozymes. The transcriptional profile suggests that oenocytes play diverse roles, such as detoxification and lipid metabolism, and increase our understanding of the importance of oenocytes in Ae. aegypti homeostasis and immune competence.

Rho signaling pathway and apical constriction in the early lens placode.

Epithelial invagination in many model systems is driven by apical cell constriction, mediated by actin and myosin II contraction regulated by GTPase activity. Here we investigate apical constriction during chick lens placode invagination. Inhibition of actin polymerization and myosin II activity by cytochalasin D or blebbistatin prevents lens invagination. To further verify if lens placode invaginate through apical constriction, we analyzed the role of Rho-ROCK pathway. Rho GTPases expression at the apical portion of the lens placode occurs with the same dynamics as that of the cytoskeleton. Overexpression of the pan-Rho inhibitor C3 exotoxin abolished invagination and had a strong effect on apical myosin II enrichment and a mild effect on apical actin localization. In contrast, pharmacological inhibition of ROCK activity interfered significantly with apical enrichment of both actin and myosin. These results suggest that apical constriction in lens invagination involves ROCK but apical concentration of actin and myosin are regulated through different pathways upstream of ROCK. genesis 49:368-379, 2011.

Embryonic, larval, and juvenile development of the sea biscuit Clypeaster subdepressus (Echinodermata: Clypeasteroida).

Sea biscuits and sand dollars diverged from other irregular echinoids approximately 55 million years ago and rapidly dispersed to oceans worldwide. A series of morphological changes were associated with the occupation of sand beds such as flattening of the body, shortening of primary spines, multiplication of podia, and retention of the lantern of Aristotle into adulthood. To investigate the developmental basis of such morphological changes we documented the ontogeny of Clypeaster subdepressus. We obtained gametes from adult specimens by KCl injection and raised the embryos at 26 degrees C. Ciliated blastulae hatched 7.5 h after sperm entry. During gastrulation the archenteron elongated continuously while ectodermal red-pigmented cells migrated synchronously to the apical plate. Pluteus larvae began to feed in 3 d and were 20 d old at metamorphosis; starved larvae died 17 d after fertilization. Postlarval juveniles had neither mouth nor anus nor plates on the aboral side, except for the remnants of larval spicules, but their bilateral symmetry became evident after the resorption of larval tissues. Ossicles of the lantern were present and organized in 5 groups. Each group had 1 tooth, 2 demipyramids, and 2 epiphyses with a rotula in between. Early appendages consisted of 15 spines, 15 podia (2 types), and 5 sphaeridia. Podial types were distributed in accordance to Lovén's rule and the first podium of each ambulacrum was not encircled by the skeleton. Seven days after metamorphosis juveniles began to feed by rasping sand grains with the lantern. Juveniles survived in laboratory cultures for 9 months and died with wide, a single open sphaeridium per ambulacrum, aboral anus, and no differentiated food grooves or petaloids. Tracking the morphogenesis of early juveniles is a necessary step to elucidate the developmental mechanisms of echinoid growth and important groundwork to clarify homologies between irregular urchins.

Delta-Notch signaling is involved in the segregation of the three germ layers in Xenopus laevis.

In vertebrates, the induction of the three germ layers (ectoderm, mesoderm and endoderm) has been extensively studied, but less is known about how they segregate. Here, we investigated whether Delta-Notch signaling is involved in this process. Activating the pathway in the marginal zone with Notch(ICD) resulted in an expansion of endodermal and neural ectoderm precursors, leaving a thinner mesodermal ring around the blastopore at gastrula stage, when germ layers are segregated. On the other hand, when the pathway was blocked with Delta-1(STU) or with an antisense morpholino oligonucleotide against Notch, the pan-mesodermal brachyury (bra) domain was expanded and the neural border was moved animalwards. Strikingly, the suprablastoporal endoderm was either expanded when Delta-1 signaling was blocked, or reduced after the general knock-down of Notch. In addition, either activating or blocking the pathway delays the blastopore closure. We conclude that the process of delimiting the three germ layers requires Notch signaling, which may be finely regulated by ligands and/or involve non-canonical components of the pathway. Moreover, Notch activity must be modulated at appropriate levels during this process in order to keep normal morphogenetic movements during gastrulation.