pinecone/core-2020-05-10-deduplication huggingface dataset:
Cadherin-6 Expression Transiently Delineates Specific Rhombomeres, Other Neural Tube Subdivisions, and Neural Crest Subpopulations in Mouse Embryos

AbstractMammalian cadherin-6 (K-cadherin, cad6) was originally identified by means of the polymerase chain reaction, but its biological functions have not yet been determined. We analyzed the expression pattern of the mouse homologue of this cadherin during development and found that it was transiently expressed in restricted rhombomeres and in other subdivisions of the neural plate and tube. In the midbrain and anterior hindbrain of E8.0-8.5 embryos, cad6 was expressed only in neural crest-generating regions. In contrast, in the posterior hindbrain and contiguous spinal cord of these embryos, cad6 occurred throughout the neural plate, forming a sharp anterior limit at the future rhombomere 4 and 5 boundary. Subsequently, this neural plate expression became confined to rhombomere 6, although most of the neural crest-generating areas remained positive throughout the body. Neural crest cells expressing cad6 migrated out of the neural tube, and subsequently accumulated mainly along peripheral nerves. We then studied the effect ofHoxa-1mutation on the expression of cad6, as their expressions spatiotemporally overlapped with each other in the early posterior hindbrain. In E8.0-8.5Hoxa-1mutants, cad6 expression was suppressed in the region of rhombomeres 4 to 6, although that in the other regions was not essentially affected. At later stages, however, cad6-positive crest cells appeared and migrated out of rhombomeres 4 to 6, indicating that the suppression of cad6 expression was transient and restricted to early stages. Importantly, this effect of theHoxa-1mutation concurred with the timing of the expression of this gene. We also studiedHoxa-3mutants, but found no effect of this mutation on the cad6 expression pattern. These findings suggest that cad6 may contribute to the formation of the segmental structure of the early brain through its ability to confer specific adhesiveness on cells and thatHoxa-1may be required for early cad6 expression in the posterior hindbrain
Contribution of Early-Emigrating Midbrain Crest Cells to the Dental Mesenchyme of Mandibular Molar Teeth in Rat Embryos

AbstractTeeth are formed by reciprocal interactions between the epithelium and mesenchyme in the first pharyngeal arch. Although the contribution of midbrain and hindbrain crest cells to the first pharyngeal arch has been previously examined in rodent embryos, no direct evidence exists that these cells are actually involved in the dental mesenchyme. In order to elucidate the contribution of the cranial neural crest cells in tooth formation, we first identified the emigration sites and stages providing the crest cells that migrate to the presumed tooth-forming region of the mandibular prominence. Focal labeling with DiI was performed at the midbrain and anterior hindbrain crests in rat embryos, and the labeled embryos were cultured for 30 or 60 hr. The resultant migration patterns indicated that posterior midbrain crest cells emigrating by the end of the 4-somite stage predominantly migrated to the region where tooth buds normally develop. Second, we established a new type of long-term culture system in which whole embryo culture is followed by a mandibular organ culture. Using this system, rat embryos were maintained from the early-somite stage and the molars in the explants were able to reach the bud stage within 8 days. Finally, to ascertain if posterior midbrain crest cells emigrating by the end of the 4-somite stage were involved in the dental mesenchyme, these cells were labeled with DiI and processed for the long-term culture. Labeled crest cells were clearly detectable in the dental mesenchyme. These findings indicate that the early-emigrating posterior midbrain crest cells contribute to mandibular molar tooth development in rat embryos
Wingless Signaling InducesnautilusExpression in the Ventral Mesoderm of theDrosophilaEmbryo

AbstractThe segregation of founder cells from the somatic mesoderm is a prerequisite for the formation of body wall muscles in theDrosophilaembryo. The myogenic basic helix-loop-helix protein, Nautilus (Nau), is expressed in a subset of these founder cells in medial and lateral positions in the somatic mesoderm. Mutations in thewingless(wg) gene, which encodes a secreted growth factor, lead to the complete loss of Nau-expressing medial muscle precursor cell clusters, but not lateral clusters. Using the GAL4/UAS system, we demonstrate that thewg-derived signal can originate from either ectoderm or mesoderm to influencenauexpression. By using a temperature-sensitivewgallele, we also show thatwgfunction is required during and after gastrulation for the formation of Nau-expressing medial muscle precursor cell clusters. Our results, combined with recent studies from chick, suggest a conserved role for Wg signaling pathways during muscle development
PDGF-A Is Required for Normal Murine Cardiovascular Development

AbstractSeveral lines of evidence suggest that platelet-derived growth factor A chain (PDGF-A) is required for normal embryonic cardiovascular development. To test this directly, we introduced anti-PDGF-A neutralizing antibodies into mouse deciduasin uteroat Embryonic Days (E) 8.5, 9.5, and 10.5. This resulted in the selective disruption of PDGF-A ligand–receptor interactionsin vivofor a period of 18–24 hr and allowed us to assess both if PDGF-A is required for cardiovascular development and when it is required. Embryos collected 48 hr after antibody treatment displayed severe cardiovascular abnormalities. These included both atrial and ventricular myocardial hypertrophy, epicardial and endocardial abnormalities, and aortic dilation, among others. Although heart abnormalities were observed in embryos treated at all three ages, they were more common in embryos treated at E8.5. In contrast, only embryos treated at E10.5 exhibited significant aortic dilation. This work (1) demonstrates directly for the first time that PDGF-A is required for normal cardiovascular development, (2) identifies several processes that require PDGF-A, and (3) defines discreet developmental periods during which these PDGF-A-dependent processes require the factor
A Novel Angiogenic Molecule Produced at the Time of Chondrocyte Hypertrophy during Endochondral Bone Formation

AbstractAngiogenesis is a pivotal event in endochondral ossification. Vessels grow into the hypertrophic cartilage and erode it to produce a scaffold on which osteoblasts settle to produce woven bone. A new culture system was used to determine whether growth-plate chondrocytes produce an angiogenic molecule. Chondrocytes from primary growth plates of bovine fetuses were separated into maturationally distinct subpopulations. When cultured these cells produce an extensive extracellular matrix and the prehypertrophic cells mature to express the hypertrophic phenotype defined by the synthesis of type X collagen and matrix calcification. The culture medium collected from the hypertrophic cells contains a chemoattractant, nonmitogenic molecule for bovine endothelial cells which can induce angiogenesisin vivoin the rabbit cornea model. This molecule has aMrof approximately 120 × 103. The production of this molecule by hypertrophic cells is enhanced by both 1,25-(OH)2vitamin D3and 24,25-(OH)2vitamin D3at 10−8–10−12M,but only in pre- and early hypertrophic cells. In contrast, these metabolites have either no effect or an inhibitory effect on the more mature hypertrophic cells. These results describe for the first time the production of an angiogenic molecule by hypertrophic chondrocytes. They demonstrate an important role for vitamin-D3metabolites in regulating hypertrophy and angiogenesis during normal skeletal growth and differentiation. Thus, a defective regulation of these processes, due to the lack of vitamin-D metabolites, may explain the observed enlargement of the hypertrophic zone and impairment of skeletal growth in rickets which is induced clinically and experimentally by a deficiency of vitamin D
Thyroid Hormone Controls the Onset of Androgen Sensitivity in the Developing Larynx ofXenopus laevis

AbstractGonadal differentiation, the onset of androgen-stimulated laryngeal growth and the genesis of a sex difference in laryngeal innervation, all temporally coincide with thyroid hormone (TH)-induced metamorphosis inXenopus laevis.To explore the role TH plays in the ontogeny of theXenopusandrogen-sensitive vocal neuromuscular system, we examined gonadal and laryngeal development in tadpoles in which metamorphosis had been blocked by treatment with the thyroxine synthesis inhibitor propylthiouracil (PTU). PTU treatment did not arrest gonadal differentiation. Testes from PTU-treated male tadpoles had seminiferous tubules and advanced stage male germ cells, while in females stage 1 oocytes were present. In contrast to the gonads, PTU did block morphological development of the larynx. Tadpoles treated with PTU for 50 or 100 days had larynges which structurally resembled those of stage 54 control tadpoles. PTU-treated animals did not exhibit the extensive development of the laryngeal cartilage seen in untreated animals. Laryngeal cartilages of hypothyroid tadpoles exhibited low density and minimal patterning of chondrocytes; the complex lumen and marked expansion of the dilator muscles characteristic of 50- and 100-day untreated animals were absent. Laryngeal growth evoked by exposure to exogenous androgen (dihydrotestosterone) was entirely prevented by PTU treatment. Hypothyroid tadpoles did not exhibit the decline in laryngeal nerve axon number characteristic of age-matched controls, nor were laryngeal nerve axon numbers sexually dimorphic. PTU treatment also interfered with the myelination of laryngeal axons. We conclude that while gonadal differentiation is independent of TH, androgen sensitive laryngeal development and sexually dimorphic laryngeal innervation require exposure to secreted TH
Characterization of aSpANPromoter Sufficient to Mediate Correct Spatial Regulation along the Animal–Vegetal Axis of the Sea Urchin Embryo

AbstractIn order to investigate how the maternally specified animal–vegetal axis of the sea urchin embryo is established, we have examined the molecular basis of regulation of several genes transcribed differentially in nonvegetal and vegetal domains of the very early blastula. Here we present an initial characterization of the regulatory region of one of these,SpAN,which encodes a protease in the astacin family related toDrosophila tolloidand vertebrateBMP-1(Reynoldset al., Development114, 769–786). Tests ofSpANpromoter functionin vivoshow that high-level activity and correct not-vegetal expression are mediated by sequences within 300 bp upstream of the basal promoter.In vitrostudies have identified six protein binding sites serviced by at least five different proteins. Comparison of the structure of theSpANpromoter to that ofSpHE,whose expression pattern is identical, shows that both promoters contain multiple positively acting upstream elements close to the basal promoter. We show that two elements are critical for high-level transcription ofSpAN,since exact replacement of either results in 10- to 20-fold reduction in promoter strength. These shared elements are, however, not essential for spatially correctSpHEgene transcription. We conclude that the coordinate strong activities of theSpANandSpHEpromoters in the nonvegetal domain of the embryo rely primarily on different transcription factor activities
Exogenous Tau RNA Is Localized in Oocytes: Possible Evidence for Evolutionary Conservation of Localization Mechanisms

AbstractThe multistep pathway leading to intracellular RNA localization is known to involvecis-acting signals in targeted mRNAs, which are presumably recognized by specific RNA-binding proteins and interact with a functional cytoskeleton. Tau RNA is localized to the proximal hillock of rat axons, and this movement requires intact microtubules. BecauseXenopusoocytes demonstrate a clear polarity involving microtubule-mediated RNA localization, we have studied the distribution of tau RNA injected into oocytes. We find that a fragment from the 3′-untranslated region of tau RNA is localized to the vegetal cortex of stage III/IV oocytes in a distribution indistinguishable from Vg1 RNA, a vegetally localized oocyte mRNA. A fragment from the tau RNA coding region, however, is homogeneously distributed in oocytes. Tau RNA contains a functional binding site for Vg1 RBP, aXenopusmicrotubule-associated protein that binds vegetally localized oocyte RNAs with high affinity, and this binding correlates with vegetal localization ability. The present studies demonstrate, for the first time, localization of heterologous RNA in oocytes. Given the role of Vg1 RBP as a mediator of specific RNA–microtubule interactions, these results are strong evidence that Vg1 RBP is involved in the vegetal localization of RNAs in oocytes and raise the intriguing possibility of the existence of proteins with similar function in neurons
VEGF121Induces Proliferation of Vascular Endothelial Cells and Expression offlk-1without Affecting Lymphatic Vessels of the Chorioallantoic Membrane

AbstractWe have studied the effect of VEGF121homodimer and VEGF121/165heterodimer on the chorioallantoic membrane (CAM) of 13-day-old chick embryos. The factors were applied in doses of 2–4 μg and the effects were evaluated macroscopically after 2 and 3 days. Histological studies were performed on semi- and ultrathin sections. Proliferation was studied according to the BrdU–anti-BrdU method on whole mounts and sections. The labeling density was quantified in whole mounts. The fractal dimension,D,of the vascular tree was assessed as a value for vascular bifurcation density. Both forms of VEGF induce brush-like vessel formation in the precapillary region. New capillaries are found in the stroma of the CAM, which normally does not contain capillaries. Our results show that VEGF121is a specific endothelial cell mitogen. A fourfold increase of BrdU-labeled endothelial cells is found after VEGF121application. The fractal dimension of the vascular tree increases from 1.26 in the controls to 1.44 (VEGF121) and 1.41 (VEGF121/165). The endothelial cells of the newly formed capillaries possess many mitochondria and micropinocytotic vesicles, but no fenestrations. These capillaries are obviously formed by intussusceptive microvascular growth. Signs of sprouting are almost absent. An effect on the lymphatic vessels of the CAM is not detectable. Compared to VEGF165and VEGF121/165, VEGF121diffuses over a slightly greater distance. Usingin situhybridization, VEGF receptor-2 (flk-1/Quek1) and the homologousflt-4(Quek2) receptor were studied in the CAM of normal quail embryos and after VEGF121application on the CAM of 11-day-old quail embryos. During normal development,flk-1expression becomes restricted to vascular endothelial cells of large vessels in the stroma of the CAM. VEGF121application induces expression offlk-1in capillaries that normally do not express the receptor. In the normal development of the CAM,flt-4becomes restricted to endothelial cells of vessels that appear to be lymphatic vessels. Application of VEGF121does not alterflt-4expression
Immortalized Hensen's Node Cells Secrete a Factor That Regulates Avian Neural Crest Cell Fatesin Vitro

AbstractThe derivatives of the neural crest are regionally specified with respect to the anterior–posterior axis of the avian embryo. We have shown previously that young Hensen's node can actin vitroto regulate the expression of certain region-specific phenotypes in trunk neural crest cells. To study potential factors acting on the neural crest, we have generated an immortalized cell line from young Hensen's node. Here we show that a factor produced by these cells stimulates the expression of two cranial-specific phenotypes (fibronectin and smooth muscle actin) in trunk neural crest cells and decreases their expression of a trunk-specific phenotype (melanin). The active factor is a secreted protein with a molecular weight >30 kDa. Clonal studies suggest that the factor acts by changing the phenotypic fates of individual neural crest cells, rather than by selective effects on cell proliferation or survival. Previous work has shown that TGF-βs can mimic the effects of Hensen's node cells on neural crest differentiation. Results from the present study suggest that the factor in the conditioned medium of the immortalized node cell line is not a TGF-β isoform. However, the cranial phenotype-inducing activity of the conditioned medium factor requires the presence of neural crest cell-derived TGF-βs
Nuclear Localization of Type II cAMP-Dependent Protein Kinase during Limb Cartilage Differentiation Is Associated with a Novel Developmentally Regulated A-Kinase Anchoring Protein

AbstractDifferentiation of chicken limb cartilage is accompanied by a rise in intracellular cyclic AMP, an inducer of cartilage-specific gene expression. A basic ∼35-kDa protein, designated p35, is the major nuclear substrate for cAMP-dependent protein kinase (PKA) during this process. Here we show that whereas both precartilage and cartilage nuclei contain p35, only precartilage nuclei contain PKA. The phosphorylation of p35 in isolated cell fractions was used as an index of changes in the cellular comparmentalization of components of PKA during chondrogenesis. Both the catalytic subunit and type II regulatory subunit (RII) of PKA were present in the precartilage nuclear fraction, but were undetectable or present in only trace amounts in the cartilage nuclear fraction. Furthermore, a novel ∼150-kDa A-kinase anchoring protein (AKAP), which binds to RII, was detected in the nuclear matrix of precartilage nuclei but, like RII, was virtually absent in the nuclei of fully differentiated cartilage cells. In limb mesenchymal cells undergoing chondrogenesis in culture a corresponding set of changes occurred: cartilage differentiation was accompanied by a marked reduction in the amounts of both nuclear RII and nAKAP150. These observations indicate that type II PKA holoenzyme is imported into the mesenchymal cell nucleus prior to chondrogenesis, an event that appears to depend on the the activity of the developmentally regulated nAKAP150
Identification ofcis-Acting Sequences That ControlnanosRNA Localization

AbstractThe generation of anterior–posterior polarity during development inDrosophilarequires the localization of determinant molecules to the anterior and posterior poles of the embryo. Localization of the maternally synthesizednanosRNA to the posterior pole of the embryo is essential to provide a source for a gradient of Nanos protein that directs abdomen formation.nanosRNA localization occurs during oogenesis and requires the function of at least nine genes.cis-acting sequences that directnanosRNA localization lie within thenanos3′UTR. In this analysis, we have usednanos3′UTR deletion mutants to define the localization signal more precisely. Our results indicate that thenanosRNA localization signal is large and complex and that targeting ofnanosRNA may be achieved by the combined effects of multiple, partially independent sequences. This idea is supported by evolutionary conservation, both in sequence and in function, of thenanos3′UTRs ofDrosophila melanogasterandDrosophila virilis
Cellular Interactions That Guide Sensory and Motor Neurites Identified in an Embryo Slice Preparation

AbstractWe used cultured cross sections (“slices”) of avian embryos to identify interactions that guide neurites during their encounters with seven tissues that impose a stereotyped gross anatomical nerve pattern. We show that cultured slices retain tissue morphology, molecular distribution patterns, and guidance cues. They also allow us to directly visualize responses of labeled sensory and motor neurons deposited on the slice's surface. This assay has high predictive power. Contact-mediated avoidance or stimulation and long-range attraction or repulsion are each distinguishable because each predicts different neurite lengths and trajectories. The analysis shows that all but one of these mechanisms contributes to guidance. Three tissues similarly stimulated neurite elongation, suggesting common responses to a contact-mediated stimulation. Four tissues similarly elicited avoidance on contact, suggesting a common contact-mediated inhibition. Neurite orientations implicate a previously unsuspected long-distance attraction to one tissue, dorsal anterior sclerotome. Long-range repulsion plays no detectable role. Each tissue elicits the same response in two different neural populations, sensory and motor neurons. These results suggest that a small set of repeated mechanisms mediates responses to tissues that axons contact serially during pathfinding
Early Embryonic Induction inC. elegansCan Be Inhibited with Polysulfated Hydrocarbon Dyes

AbstractDuring embryogenesis ofCaenorhabditis eleganscellular interactions are necessary to determine the fate of blastomeres. In one of these interactions, taking place in the 4-cell stage, the germline cell P2 induces longitudinal orientation of the cleavage spindle in the neighboring EMS cell, its asymmetric division, and the establishment of a gut lineage. Application of several polysulfated hydrocarbon dyes (e.g., trypan blue, TB) in the 1- to 4-cell stages inhibits induction of the gut precursor cell. However, dye application from the late 4-cell stage onward does not interfere with gut induction, supporting the earlier finding of a short time window for this interaction. We also tested the effect of TB on the induction of pharyngeal muscle cells by the MS blastomere, which appears to involve a surface receptor–ligand interaction. We found that this process is inhibited as well. These and additional data indicate that polysulfated hydrocarbon dyes are suitable tools to generally interfere with cell–cell interactions in the nematode embryo
A Novel Chloride Channel Localizes toCaenorhabditis elegansSpermatids and Chloride Channel Blockers Induce Spermatid Differentiation

AbstractCaenorhabditis elegansspermatogenesis is especially suited for studies of nonrandom cytoplasmic segregation during cellular differentiation. Spermatocytes separate from an anuclear cytoplasmic core and undergo two sequential divisions. During the second division, intracellular organelles segregate specifically to spermatids as they bud from an anuclear residual body. We have applied patch-clamp techniques in order to investigate membrane protein distribution during these asymmetric divisions. We show that membrane components, as assayed by voltage-dependent ion channel activity, follow a specific distribution pattern during sperm development. Several voltage-sensitive ion channel activities are observed in spermatocytes and residual bodies, but only a single-channel type can be detected in spermatids, indicating that other channel activities are excluded from or inactivated within these cells as they form. The channel that is observed in spermatids is an inward-rectifying chloride channel (Clir), as indicated by its sensitivity to chloride channel inhibitors and Cl-dependent shifts in its conductance. Treatment of spermatids with Cl channel blockers induce their differentiation into spermatozoa, suggesting that Clir plays a role during this developmental step. These studies are the first application of patch-clamp electrophysiology toC. elegansdevelopment