Ectodermal Cells Research Articles

Eya1 protein distribution during embryonic development of Xenopus laevis

Eya1 and other Eya proteins are important regulators of progenitor proliferation, cell differentiation and morphogenesis in all three germ layers. At present, most of our knowledge of Eya1 distribution is based on in situ hybridization for Eya1 mRNA. However, to begin to dissect the mechanisms underlying Eya1 functions, we need a better understanding of the spatiotemporal distribution of Eya1 proteins during embryonic development, their subcellular localization and their levels of expression in various tissues. Here we report the localization of Eya1 protein throughout embryonic development from neural plate stages to tadpole stages of Xenopus laevis using a specific antibody for Xenopus Eya1. Our study confirms the expression of Eya1 protein in cranial placodes, placodally derived sensory primordia (olfactory epithelium, otic vesicle, lateral line primordia) and cranial ganglia, as well as in somites, secondary heart field and pharyngeal endoderm. In addition, we report here a novel expression of Eya1 proteins in scattered epidermal cells in Xenopus. Our findings also reveal that, while being predominantly expressed in nuclei in most expression domains, Eya1 protein is also localized to the cytoplasm, in particular in the early preplacodal ectoderm, some placode-derived ganglia and a subset of epidermal cells. While some cytoplasmic roles of Eya1 have been previously described in other contexts, the functions of cytoplasmic Eya1 in the preplacodal ectoderm, cranial ganglia and epidermal cells remain to be investigated.

SOX10 ablation severely impairs the generation of postmigratory neural crest from human pluripotent stem cells

Animal studies have indicated that SOX10 is one of the key transcription factors regulating the proliferation, migration and differentiation of multipotent neural crest (NC), and mutation of SOX10 in humans may lead to type 4 Waardenburg syndrome (WS). However, the exact role of SOX10 in human NC development and the underlying molecular mechanisms of SOX10-related human diseases remain poorly understood due to the lack of appropriate human model systems. In this study, we successfully generated SOX10-knockout human induced pluripotent stem cells (SOX10−/− hiPSCs) by the CRISPR-Cas9 gene editing tool. We found that loss of SOX10 significantly inhibited the generation of p75highHNK1+/CD49D+ postmigratory neural crest stem cells (NCSCs) and upregulated the cell apoptosis rate during NC commitment from hiPSCs. Moreover, we discovered that both the neuronal and glial differentiation capacities of SOX10−/− NCSCs were severely compromised. Intriguingly, we showed that SOX10−/− hiPSCs generated markedly more TFAP2C+nonneural ectoderm cells (NNE) than control hiPSCs during neural crest differentiation. Our results indicate that SOX10 is crucial for the transition of premigratory cells to migrating NC and is vital for NC survival. Taken together, these results provide new insights into the function of SOX10 in human NC development, and the SOX10-knockout hiPSC lines may serve as a valuable cell model to study the pathogenesis of SOX10-related human neurocristopathies.

Time-sequenced transcriptomes of developing distal mouse limb buds: A comparative tissue layer analysis.

The development of the amniote limb has been an important model system to study patterning mechanisms and morphogenesis. For proper growth and patterning, it requires the interaction between the distal sub-apical mesenchyme and the apical ectodermal ridge (AER) that involve the separate implementation of coordinated and tissue-specific genetic programs. Here, we produce and analyze the transcriptomes of both distal limb mesenchymal progenitors and the overlying ectodermal cells, following time-coursed dissections that cover from limb bud initiation to fully patterned limbs. The comparison of transcriptomes within each layer as well as between layers over time, allowed the identification of specific transcriptional signatures for each of the developmental stages. Special attention was given to the identification of genes whose transcription dynamics suggest a previously unnoticed role in the context of limb development and also to signaling pathways enriched between layers. We interpret the transcriptomic data in light of the known development pattern and we conclude that a major transcriptional transition occurs in distal limb buds between E9.5 and E10.5, coincident with the switch from an early phase continuation of the signature of trunk progenitors, related to the initial proximo distal specification, to a late intrinsic phase of development.

Blunt Force Trauma-Induced Total Bilateral Visual Impairment of 13 Years Duration Treated with Autologous Telomerase-Positive Stem Cells

Loss of visual acuity may result from genetics, cancer, metabolic disorders, trauma, or aging. Adult telomerase- positive totipotent stem cells have been identified in multiple species of animals, including humans. Characterization studies to identify differentiated cells utilized three clones of adult-derived totipotent stem cells (TSCs) and treated them with induction factors consisting of chemical mediators, human recombinant proteins and cell-specific exosomes. Results demonstrated that the TSC clones would form cells expressing phenotypic markers of the neural ectodermal lineage, e.g., ectodermal stem cells, ectodermal progenitor stem cells, neurons, ganglion cells, glial cells, and neural crest derivatives. Autologous TSCs were shown to partially restore function in clinical trial participants with Alzheimer’s disease, Parkinson’s disease, and Age-related Dry Macular Degeneration. It was hypothesized that following intranasal infusion, TSCs would migrate to areas associated with the visual pathway to repair and/or regenerate damaged and/or missing cells, thus restoring function. In this small cohort study (n=1), the presenting symptom for a 17-year-old female was total bilateral visual impairment (complete blindness) of 13-years duration, due to severe head trauma from an automobile accident at four years of age. Following her first TSC treatment, she could see indistinct black shapes on a background of a dark shade of gray. Following her second TSC treatment she could see background as a lighter shade of gray and a black square with slightly more distinct borders. No adverse effects were noted after either autologous TSC treatment. These results suggest that two treatments with TSCs were both safe and somewhat efficacious in helping to partially restore her ‘night’ vision.

Glyconectin Cell Adhesion Epitope, β-d-GlcpNAc3S-(1→3)-α-l-Fucp, Is Involved in Blastulation of Lytechinus pictus Sea Urchin Embryos

Glycans, as the most peripheral cell surface components, are the primary candidates to mediate the initial steps of cell recognition and adhesion via glycan–glycan binding. This molecular mechanism was quantitatively demonstrated by biochemical and biophysical measurements at the cellular and molecular level for the glyconectin 1 β-d-GlcpNAc3S-(1→3)-α-l-Fucp glycan structure (GN1). The use of adhesion blocking monoclonal antibody Block 2 that specifically recognize this epitope showed that, besides Porifera, human colon carcinoma also express this structure in the apical glycocalyx. Here we report that Block 2 selectively immune-precipitate a Mr 580 × 103 (g580) acidic non-glycosaminoglycan glycan from the total protein-free glycans of Lytechinus pictus sea urchin hatched blastula embryos. Immuno-fluorescence confocal light microscopy and immunogold electron microscopy localized the GN1 structure in the apical lamina glycocalyx attachments of ectodermal cells microvilli, and in the Golgi complex. Biochemical and immune-chemical analyses showed that the g580 glycan is carrying about 200 copies of the GN1 epitope. This highly polyvalent g580 glycan is one of the major components of the glycocalyx structure, maximally expressed at hatched blastula and gastrula. The involvement of g580 GN1 epitope in hatched blastula cell adhesion was demonstrated by: (1) enhancement of cell aggregation by g580 and sponge g200 glycans, (2) inhibition of cell reaggregation by Block 2, (3) dissociation of microvilli from the apical lamina matrix by the loss of its gel-like structure resulting in a change of the blastula embryonal form and consequent inhibition of gastrulation at saturating concentration of Block 2, and (4) aggregation of beads coated with the immune-purified g580 protein-free glycan. These results, together with the previous atomic force microscopy measurements of GN1 binding strength, indicated that this highly polyvalent and calcium ion dependent glycan–glycan binding can provide the force of 40 nanonewtons per single ectodermal cell association of microvilli with the apical lamina, and conservation of glycocalyx gel-like structure. This force can hold the weight of 160,000 cells in sea water, thus it is sufficient to establish, maintain and preserve blastula form after hatching, and prior to the complete formation of further stabilizing basal lamina.

Role of Apoptosis in Wound Healing and Apoptosis Alterations in Microgravity.

Functioning as the outermost self-renewing protective layer of the human organism, skin protects against a multitude of harmful biological and physical stimuli. Consisting of ectodermal, mesenchymal, and neural crest-derived cell lineages, tissue homeostasis, and signal transduction are finely tuned through the interplay of various pathways. A health problem of astronauts in space is skin deterioration. Until today, wound healing has not been considered as a severe health concern for crew members. This can change with deep space exploration missions and commercial spaceflights together with space tourism. Albeit the molecular process of wound healing is not fully elucidated yet, there have been established significant conceptual gains and new scientific methods. Apoptosis, e.g., programmed cell death, enables orchestrated development and cell removal in wounded or infected tissue. Experimental designs utilizing microgravity allow new insights into the role of apoptosis in wound healing. Furthermore, impaired wound healing in unloading conditions would depict a significant challenge in human-crewed exploration space missions. In this review, we provide an overview of alterations in the behavior of cutaneous cell lineages under microgravity in regard to the impact of apoptosis in wound healing. We discuss the current knowledge about wound healing in space and simulated microgravity with respect to apoptosis and available therapeutic strategies.

Co-development of central and peripheral neurons with trunk mesendoderm in human elongating multi-lineage organized gastruloids

Stem cell technologies including self-assembling 3D tissue models provide access to early human neurodevelopment and fundamental insights into neuropathologies. Gastruloid models have not been used to investigate co-developing central and peripheral neuronal systems with trunk mesendoderm which we achieve here in elongating multi-lineage organized (EMLO) gastruloids. We evaluate EMLOs over a forty-day period, applying immunofluorescence of multi-lineage and functional biomarkers, including day 16 single-cell RNA-Seq, and evaluation of ectodermal and non-ectodermal neural crest cells (NCCs). We identify NCCs that differentiate to form peripheral neurons integrated with an upstream spinal cord region after day 8. This follows initial EMLO polarization events that coordinate with endoderm differentiation and primitive gut tube formation during multicellular spatial reorganization. This combined human central-peripheral nervous system model of early organogenesis highlights developmental events of mesendoderm and neuromuscular trunk regions and enables systemic studies of tissue interactions and innervation of neuromuscular, enteric and cardiac relevance.

SARS-CoV-2 infects human adult donor eyes and hESC-derived ocular epithelium.

The SARS-CoV-2 pandemic has caused unparalleled disruption of global behavior and significant loss of life. To minimize SARS-CoV-2 spread, understanding the mechanisms of infection from all possible routes of entry is essential. While aerosol transmission is thought to be the primary route of spread, viral particles have been detected in ocular fluid, suggesting that the eye may be a vulnerable point of viral entry. To this end, we confirmed SARS-CoV-2 entry factor and antigen expression in post-mortem COVID-19 patient ocular surface tissue and observed productive viral replication in cadaver samples and eye organoid cultures, most notably in limbal regions. Transcriptional analysis of ex vivo infected ocular surface cells and hESC-derived eye cultures revealed robust induction of NF-κB in infected cells as well as diminished type I/III interferon signaling. Together these data suggest that the eye can be directly infected by SARS-CoV-2 and implicate limbus as a portal for viral entry.

FGF signalling plays similar roles in development and regeneration of the skeleton in the brittle star Amphiura filiformis.

ABSTRACTRegeneration as an adult developmental process is in many aspects similar to embryonic development. Although many studies point out similarities and differences, no large-scale, direct and functional comparative analyses between development and regeneration of a specific cell type or structure in one animal exist. Here, we use the brittle star Amphiura filiformis to characterise the role of the FGF signalling pathway during skeletal development in embryos and arm regeneration. In both processes, we find ligands expressed in ectodermal cells that flank underlying skeletal mesenchymal cells, which express the receptors. Perturbation of FGF signalling showed inhibited skeleton formation in both embryogenesis and regeneration, without affecting other key developmental processes. Differential transcriptome analysis finds mostly differentiation genes rather than transcription factors to be downregulated in both contexts. Moreover, comparative gene analysis allowed us to discover brittle star-specific differentiation genes. In conclusion, our results show that the FGF pathway is crucial for skeletogenesis in the brittle star, as in other deuterostomes, and provide evidence for the re-deployment of a developmental gene regulatory module during regeneration.

Involvement of Huntingtin in Development and Ciliary Beating Regulation of Larvae of the Sea Urchin, Hemicentrotus pulcherrimus.

The multiple functions of the wild type Huntington’s disease protein of the sea urchin Hemicentrotus pulcherrimus (Hp-Htt) have been examined using the anti-Hp-Htt antibody (Ab) raised against synthetic oligopeptides. According to immunoblotting, Hp-Htt was detected as a single band at around the 350 kDa region at the swimming blastula stage to the prism larva stage. From the 2-arm pluteus stage (2aPL), however, an additional smaller band at the 165 kDa region appeared. Immunohistochemically, Hp-Htt was detected in the nuclei and the nearby cytoplasm of the ectodermal cells from the swimming blastula stage, and the blastocoelar cells from the mid-gastrula stage. The Ab-positive signal was converged to the ciliary band-associated strand (CBAS). There, it was accompanied by several CBAS-marker proteins in the cytoplasm, such as glutamate decarboxylase. Application of Hp-Htt morpholino (Hp-Htt-MO) has resulted in shortened larval arms, accompanied by decreased 5-bromo-2-deoxyuridin (BrdU) incorporation by the ectodermal cells of the larval arms. Hp-Htt-MO also resulted in lowered ciliary beating activity, accompanied by a disordered swirling pattern formation around the body. These Hp-Htt-MO-induced deficiencies took place after the onset of CBAS system formation at the larval arms. Thus, Hp-Htt is involved in cell proliferation and the ciliary beating pattern regulation signaling system in pluteus larvae.

Pinhead antagonizes Admp to promote notochord formation

SummaryDorsoventral patterning of a vertebrate embryo critically depends on the activity of Smad1 that mediates signaling by BMP proteins, anti-dorsalizing morphogenetic protein (Admp), and their antagonists. Pinhead (Pnhd), a cystine-knot-containing secreted protein, is expressed in the ventrolateral mesoderm during Xenopus gastrulation; however, its molecular targets and signaling mechanisms have not been fully elucidated. Our mass spectrometry-based screen of the gastrula secretome identified Admp as Pnhd-associated protein. We show that Pnhd binds Admp and inhibits its ventralizing activity by reducing Smad1 phosphorylation and its transcriptional targets. Importantly, Pnhd depletion further increased phospho-Smad1 levels in the presence of Admp. Furthermore, Pnhd synergized with Chordin and a truncated BMP4 receptor in the induction of notochord markers in ectoderm cells, and Pnhd-depleted embryos displayed notochord defects. Our findings suggest that Pnhd binds and inactivates Admp to promote notochord development. We propose that the interaction between Admp and Pnhd refines Smad1 activity gradients during vertebrate gastrulation.

Spatial Transcriptomics for the Analysis of Human Pituitary Development

The pituitary develops from oral ectoderm in contact with the adjacent hypothalamus. However, the precise mechanisms underlying pituitary development in concert with plural tissues are not fully understood, especially in human. A protocol to induce pituitary cells from human induced pluripotent stem cells (hiPSCs) has been established and applied to study pituitary development and disorders. In the method, oral ectoderm and hypothalamus are induced in one organoid, which enables recapitulation of the interactions between these tissues during embryonic development. It leads to self-organization of pituitary cells. Recently, spatial transcriptome technology has been developed and is suitable for the analysis of tissue interactions. Here, we utilized spatial transcriptomics to analyze pituitary organoids, especially focusing on the mechanisms regulating pituitary progenitor cell differentiation. Spatial transcriptomics revealed that the organoids consisted of several cell populations including hypothalamus, oral ectoderm, neural retina, and cortex neuron cells. Pituitary progenitor cells, characterized by the upregulation of LHX3, were included as part of the oral ectoderm population. Further analysis of the population identified human pituitary progenitor-specific genes including many causal genes for congenital hypopituitarism (CPH). Finally, using spatially resolved gene expression data, we examined the hypothalamic population that was in contact with pituitary progenitor cells and identified hypothalamic factors that might regulate progenitor cell differentiation in a paracrine manner. The genes upregulated in the pituitary progenitor and neighboring hypothalamus cell populations are potential causal gene candidates for CPH. In conclusion, spatial transcriptomics provides a novel platform to analyze tissue interaction networks during human pituitary development.

In ovo electroporation of chicken limb bud ectoderm: Electroporation to chick limb ectoderm: Electroporation to chick limb ectoderm.

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. 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. Our method is simple and easy. Thus, it would permit high throughput tests for gene function during limb ectodermal development and wound healing.

Disrupted Trigeminal Ganglion Development in a Mouse Model of Familial Dysautonomia

Neurons in the trigeminal ganglion (TG) relay somatosensory information from the face and oral cavity to the central nervous system. Arising from the differentiation of both neural crest cell and ectodermal placode cell precursors during embryogenesis, neurons in the TG ultimately encode one sensory modality (i.e., touch, pain, temperature). TG neuron identity is discernable by particular molecular markers, including the mutually exclusive expression of the neurotrophin receptors TrkA, TrkB, or TrkC, which are required for long-term neuronal function and survival. While little is known about the mechanisms that establish and maintain distinct neuronal subpopulations in the TG, disease studies offer some insight. Familial Dysautonomia (FD) is a hereditary neuropathy caused by a mutation in Elongator complex protein 1 (ELP1), which leads to reduced ELP1 protein levels in sensory and autonomic neurons. FD patients have clinical deficits that point to abnormal TG function, including impaired sensation of facial pain and temperature. Moreover, FD patients have smaller trigeminal nerves compared to healthy controls, in the absence of overt degeneration. Given these findings, we hypothesize that ELP1 is necessary for the development and survival of TG sensory neurons. Our initial results uncovered cytoplasmic Elp1 expression in both placode cell- and neural crest cell-derived neurons of the developing mouse TG starting from embryonic day (E)10.5. Using a conditional knockout mouse model in which Elp1 is deleted from Wnt1-positive neural crest cells and derivatives, including sensory neurons, we next examined the effect of Elp1 loss on TG development. Our preliminary data reveal Elp1 depletion from neural crest cells leads to abnormal TG morphology and fewer trigeminal nerve branches as early as embryonic day (E)11, a phenotype that persists throughout development and suggests defects in both neural crest- and placode cell-derived neurons in the TG. TrkA-expressing neurons, which typically function in pain perception, are especially vulnerable to Elp1 loss during this period of TG formation. By E12.5, we observe decreased TrkA expression in distal trigeminal nerve endings and fewer TrkA-positive neuron cell bodies in the TG. Analyses from TUNEL staining reveal increased cell death in the TG at E12.5, suggesting TrkA-expressing neurons, progenitor cells, and/or supporting cells may undergo aberrant apoptosis in Elp1 conditional knockout TG. Together, our results confirm a role for Elp1 in the development and survival of TG sensory neurons. These findings help explain the loss of facial sensation in FD and may guide future therapeutic interventions to increase quality of life for FD patients.

Extraction and Characterization of Dental Pulp Stem Cells from Rat Mandibles to Develop a Multi‐potential Cell Bank for Tissue Graft Technologies

Establishment of well-characterized cell banks for use in both experimental and clinical settings has long been a challenge with primary multi-potent cells. Vital to this process is the initial selection of tissue for harvesting, as tissue types display varying differentiation capacity profiles. Additionally, the quantity of a tissue available and the required method for extraction will dictate the quality of the downstream cell populations. To examine the practicality of developing a primary cell bank that could be utilized for regenerative therapies, both as standalone and in combination with biomaterials, in multiple tissues, we determined dental pulp-derived stem cells (DPSCs) to be a promising candidate. As neural crest lineage cells, DPSCs should be capable of differentiating to mesoderm and ectodermal cell types, thereby offering a robust therapeutic reservoir. Mandibles were collected from euthanized rats at the completion of an IACUC approved study, soft tissue was removed from the bone structure, and samples were placed in 70% ethanol to prevent contamination during sample transfer to cell culture cabinet. The dental pulp canal was exposed using a scalpel blade on both ends, allowing for the pulp tissue to be extruded by placing pressure on one end of the canal. Whole tissue was then dissected and placed directly into T25 culture flasks. Cells were expanded in both α-MEM and DMEM/F12-based mediums to assess the impact of media on differentiation potential. Additionally, media was supplemented with 20% FBS to encourage population growth initially, which was reduced to 10% for subsequent passages. Characterization of α-MEM cultured cells using flow cytometry demonstrated expression of the key stem cell markers CD90 and CD73. CD29, an integrin associated with angiogenesis, was also positively expressed indicating that these cell populations may have undergone some degree of differentiation. This was supported by cell morphology that revealed rounded cell shapes distributed through-out that appeared to resemble endothelial-like cells as opposed to the spindled shape of stem cells. Comparative morphological observations of cultures grown in DMEM/F12 revealed that these population maintained spindled morphology exclusively and exhibited enhanced growth rates based on passaging intervals. Cryopreservation and subsequent thawing further showed that banked cells are viable and can be expanded. Given these data, DPSCs offer a means for developing stem cell aliquot banks that are multi-potent and readily expanded. Furthermore, the expansion of these cells should be carried out using DMEM/F12-based media in order to preserve stem characteristics. The methods employed avoid enzymatic degradation of cells during collection and allow for the generation of large culture population from relatively small quantities of tissue, thereby presenting a promising biological therapeutic agent for application in a wide variety of tissue injuries.

Establishing Sustainable Cell Lines of a Coral, Acropora tenuis

Planula larvae of the scleractinian coral, Acropora tenuis, consist of elongated ectodermal cells and developing inner endodermal cells. To establish in vitro cell lines for future studies of cellular and developmental potential of coral cells, larvae were successfully dissociated into single cells by treating them with a tissue dissociation solution consisting of trypsin, EDTA, and collagenase. Brown-colored cells, translucent cells, and pale blue cells were the major components of dissociated larvae. Brown-colored cells began to proliferate transiently in the culture medium that was devised for the coral, while translucent cells and pale blue cells decreased in number about 1 week after cell dissociation. In addition, when a modular protease, plasmin, was added to the cell culture medium, brown-colored cells extended pseudopodia and assumed amorphous shapes. They then continued to proliferate in clumps for more than 6 months with a doubling time of approximately 4–5 days. From 3 weeks of cell culture onward, brown-colored cells often aggregated and exhibited morphogenesis-like behavior to form flat sheets, and blastula-like clusters or gastrula-like spheres. Single cells or cell-clusters of the cell lines were analyzed by RNA-seq. This analysis showed that genes expressed in these cells in vitro were A. tenuis genes. Furthermore, each cell line expressed a specific set of genes, suggesting that their properties include gastroderm, secretory cells, undifferentiated cells, neuronal cells, and epidermis. All cell properties were maintained stably throughout successive cell cultures. These results confirm the successful establishment of a coral in vitro cell line.

A Rare Case Report of Unilateral Maxillary Mass from Adrenal Neuroblastoma.

Neuroblastoma is the most common extracranial neoplasm among paediatric patients, which arises from ectodermal neural crest cells. The most frequent primary site of neuroblastoma arises from retroperitoneum, specifically in the adrenal medulla. We present a rare case of adrenal neuroblastoma metastasis to maxillary sinus in a 20month-old boy presenting with right maxillary swelling for the past 2months. Computed tomography (CT) scan of paranasal sinus demonstrated right maxillary mass. A biopsy performed via a sublabial approach, surprisingly revealed neuroblastoma. Subsequent further workup depicted a huge right adrenal tumour. He was diagnosed with adrenal neuroblastoma stage 4 and treated with chemotherapy and surgical resection.

Neuromesodermal Lineage Contribution to CNS Development in Invertebrate and Vertebrate Chordates.

Ascidians are invertebrate chordates and the closest living relative to vertebrates. In ascidian embryos a large part of the central nervous system arises from cells associated with mesoderm rather than ectoderm lineages. This seems at odds with the traditional view of vertebrate nervous system development which was thought to be induced from ectoderm cells, initially with anterior character and later transformed by posteriorizing signals, to generate the entire anterior-posterior axis of the central nervous system. Recent advances in vertebrate developmental biology, however, show that much of the posterior central nervous system, or spinal cord, in fact arises from cells that share a common origin with mesoderm. This indicates a conserved role for bi-potential neuromesoderm precursors in chordate CNS formation. However, the boundary between neural tissue arising from these distinct neural lineages does not appear to be fixed, which leads to the notion that anterior-posterior patterning and neural fate formation can evolve independently.

Structure of the paraplacenta and the yolk sac placenta of the viviparous Australian sharpnose shark, Rhizoprionodon taylori

IntroductionViviparity (live-birth) has evolved from oviparity (egg-laying) multiple times in sharks. While most transitions from oviparity to viviparity have resulted in non-placental forms of viviparity, some sharks develop a yolk sac placenta during pregnancy. The Australian sharpnose shark (Rhizoprionodon taylori) is a placental species that suspends embryonic development in a diapause for most of pregnancy. MethodsTo identify structures involved in supporting rapid embryonic growth in late pregnancy, we examined uterine and placental morphology by light and electron microscopy. ResultsParaplacental uterine regions have morphological specialisations consistent with secretion and fluid transport between uterine tissues and the lumen. Uterine secretions in the lumen may be absorbed by the outgrowths on the embryonic umbilical cord (‘appendiculae’), which are densely covered by microvilli. The placenta consists of uterine villi that interdigitate with the yolk sac and enhance the surface area available for fetomaternal exchange. The yolk sac does not invade the uterine epithelium, and the egg capsule remains intact at the placental interface, separating maternal and fetal tissues. Some placental uterine epithelial cells are secretory, and endocytic vesicles in the opposing yolk sac ectodermal cells suggest that nutrient transport is by histotrophic uterine secretion followed by fetal absorption. Respiratory gases, water and possibly small nutrients likely diffuse across the placenta, where maternal and fetal blood vessels are ~2 μm apart. DiscussionPlacental structure in R. taylori is similar to most other sharks, but there are differences in cellular structures between species that may indicate species-specific placental transport mechanisms.

Cav1 channels is also a story of non excitable cells: Application to calcium signalling in two different non related models

Calcium is a second messenger essential, in all cells, for most cell functions. The spatio-temporal control of changes in intracellular calcium concentration is partly due to the activation of calcium channels. Voltage-operated calcium channels are present in excitable and non-excitable cells. If the mechanism of voltage-operated calcium channels is well known in excitable cells the Ca2+ toolkit used in non-excitable cells to activate the calcium channels is less described. Herein we discuss about very similar pathways involving voltage activated Cav1 channels in two unrelated non-excitable cells; ectoderm cells undergoing neural development and effector Th2 lymphocytes responsible for parasite elimination and also allergic diseases. We will examine the way by which these channels operate and are regulated, as well as the consequences in terms of gene transcription. Finally, we will consider the questions that remain unsolved and how they might be a challenge for the future.