pinecone/core-2020-05-10-deduplication huggingface dataset:
Commissure Formation in the Embryonic CNS ofDrosophila I. Identification of the Required Gene Functions

AbstractIn the ventral nerve cord ofDrosophilamost axons are organized in a simple, ladder-like pattern. Two segmental commissures connect the hemisegments along the mediolateral and two longitudinal connectives connect individual neuromeres along the anterior–posterior axis. Cells located at the midline of the developing CNS first guide commissural growth cones toward and across the midline. In later stages, midline glial cells are required to separate anterior and posterior commissures into distinct axon bundles. To unravel the genes underlying the formation of axon pattern in the embryonic ventral nerve cord, we conducted a saturating ethylmethane sulfonate mutagenesis, screening for mutations which disrupt this process. Subsequent genetic and phenotypic analyses support a sequential model of axon pattern formation in the embryonic ventral nerve cord. Specification of midline cell lineages is brought about by the action of segment polarity genes. Five genes are necessary for the establishment of the commissures. In addition tocommissureless,thenetringenes, and the netrin receptor encoded by thefrazzledgene, two gene functions are required for the initial formation of commissural tracts. Over 20 genes appear to be required for correct development of the midline glial cells which are necessary for the formation of distinct segmental commissures
Activation of the Proteasomes of Sand Dollar Eggs at Fertilization Depends on the Intracellular pH Rise

AbstractThe mechanism of the activation of intracellular proteasomes at fertilization was measured in living sand dollar eggs using the membrane-impermeant fluorogenic substrate, succinyl-Phe-Leu-Arg-coumarylamido-4-methanesulfonic acid. When the substrate was microinjected into unfertilized eggs, the initial velocity of hydrolysis of the substrate (V0) was low.V0measured 5 to 10 min after fertilization was five to nine times the prefertilization level and remained high throughout the first cell cycle. Hydrolysis of the substrate was inhibited byclasto-lactacystin β-lactone, a specific inhibitor of the proteasome. There has beenin vitroevidence that calcium may be involved in regulation of proteasome activity to either inhibit the increase in peptidase activity associated with PA 28 binding to the 20S proteasome or stimulate activity of the PA 700–proteasome complex. Since both intracellular free Ca2+concentration ([Ca2+]i) and intracellular pH (pHi) increase after fertilization, hydrolysis of the proteasome substrate was measured under conditions in which [Ca2+]iand pHiwere varied independently during activation. When the pHiof unfertilized eggs was elevated by exposure to 15 mM ammonium chloride in pH 9 seawater,V0increased to a level comparable to that measured after fertilization. In contrast, [Ca2+]ielevation without pHichange, induced by calcium ionophore in sodium-free seawater, had no effect onV0in the unfertilized egg. Moreover, when unfertilized eggs were microinjected with buffers modulating pHi,V0increased in a pH-dependent manner. These results indicate that the pHirise at fertilization is the necessary prerequisite for activation of the proteasome, an essential component in the regulation of the cell cycle
A Mouse Cerberus/Dan-Related Gene Family

AbstractTheXenopus cerberusgene is able to induce ectopic heads inXenopusembryos. At the time of its identification, cerberus shared significant homology with only one other protein, the putative rat tumor suppressor protein Dan. Sequence analysis has revealed that cerberus and Dan are members of a family of predicted secreted proteins, here called the can family. The identification of a can-family member in the nematodeCaenorhabditis elegans, CeCan1,suggests that this family is of ancient origin. In the mouse, there are at least five family members:Cer1, Drm, PRDC, Dan,andDte.These genes are expressed in patterns that suggest that they may play important roles in patterning the developing embryo.Cer1marks the anterior visceral endoderm at E6.5.Dteis expressed asymmetrically in the developing node.Danis first seen in the head mesoderm of early head fold stage embryos andDrmis expressed in the lateral paraxial mesoderm at E8.5. The region of homology shared by these genes, here called the can domain, closely resembles the cysteine knot motif found in a number of signaling molecules, such as members of the TGFβ superfamily. Epitope-tagged versions of Cer1 show that, unlike in TGFβ superfamily members, the cysteine knot motif is not processed away from a proprotein. Recent experiments inXenopushave suggested that cerberus may act as an inhibitor of BMP signaling. To examine this further, the ability of Dan, Cer1, and human DRM to attenuate Bmp4 signaling has been assessed in P19 cells using pTlx-Lux, a BMP-responsive reporter. All three genes are able to inhibit Bmp4 signaling. These data suggest that the different family members may act to modulate the action of TGFβ family members during development
GDF5 Coordinates Bone and Joint Formation during Digit Development

AbstractA functional skeletal system requires the coordinated development of many different tissue types, including cartilage, bones, joints, and tendons. Members of the Bone morphogenetic protein (BMP) family of secreted signaling molecules have been implicated as endogenous regulators of skeletal development. This is based on their expression during bone and joint formation, their ability to induce ectopic bone and cartilage, and the skeletal abnormalities present in animals with mutations in BMP family members. One member of this family, Growth/differentiation factor 5 (GDF5), is encoded by the mousebrachypodismlocus. Mice with mutations in this gene show reductions in the length of bones in the limbs, altered formation of bones and joints in the sternum, and a reduction in the number of bones in the digits. The expression pattern ofGdf5during normal development and the phenotypes seen in mice with single or double mutations inGdf5andBmp5suggested thatGdf5has multiple functions in skeletogenesis, including roles in joint and cartilage development. To further understand the function of GDF5 in skeletal development, we assayed the response of developing chick and mouse limbs to recombinant GDF5 protein. The results from these assays, coupled with an analysis of the development ofbrachypodismdigits, indicate that GDF5 is necessary and sufficient for both cartilage development and the restriction of joint formation to the appropriate location. Thus, GDF5 function in the digits demonstrates a link between cartilage development and joint development and is an important determinant of the pattern of bones and articulations in the digits
TheCaenorhabditis elegans mel-11Myosin Phosphatase Regulatory Subunit Affects Tissue Contraction in the Somatic Gonad and the Embryonic Epidermis and Genetically Interacts with the Rac Signaling Pathway

AbstractCaenorhabditis elegansembryonic elongation is driven by cell shape changes that cause a contraction of the epidermal cell layer enclosing the embryo. We have previously shown that this process requires a Rho-associated kinase (LET-502) and is opposed by the activity of a myosin phosphatase regulatory subunit (MEL-11). We now extend our characterization and show thatmel-11activity is required both in the epidermis during embryonic elongation and in the spermatheca of the adult somatic gonad.let-502andmel-11reporter gene constructs show reciprocal expression patterns in the embryonic epidermis and the spermatheca, and mutations of the two genes have opposite effects in these two tissues. These results are consistent withlet-502andmel-11mediating tissue contraction and relaxation, respectively. We also find thatmel-11embryonic inviability is genetically enhanced by mutations in a Rac signaling pathway, suggesting that Rac potentiates or acts in parallel with the activity of the myosin phosphatase complex. Since Rho has been implicated in promoting cellular contraction, our results support a mechanism by which epithelial morphogenesis is regulated by the counteracting activities of Rho and Rac
Developmental Activation of the Capability to Undergo Checkpoint-Induced Apoptosis in the Early Zebrafish Embryo

AbstractIn this study, we demonstrate the developmental activation, in the zebrafish embryo, of a surveillance mechanism which triggers apoptosis to remove damaged cells. We determine the time course of activation of this mechanism by exposing embryos to camptothecin, an agent which specifically inhibits topoisomerase I within the DNA replication complex and which, as a consequence of this inhibition, also produces strand breaks in the genomic DNA. In response to an early (pre-gastrula) treatment with camptothecin, apoptosis is induced at a time corresponding approximately to mid-gastrula stage in controls. This apoptotic response to a block of DNA replication can also be induced by early (pre-MBT) treatment with the DNA synthesis inhibitors hydroxyurea and aphidicolin. After camptothecin treatment, a high proportion of cells in two of the embryo's three mitotic domains (the enveloping and deep cell layers), but not in the remaining domain (the yolk syncytial layer), undergoes apoptosis in a cell-autonomous fashion. The first step in this response is an arrest of the proliferation of all deep- and enveloping-layer cells. These cells continue to increase in nuclear volume and to synthesize DNA. Eventually they become apoptotic, by a stereotypic pathway which involves cell membrane blebbing, “margination” and fragmentation of nuclei, and cleavage of the genomic DNA to produce a nucleosomal ladder. Fragmentation of nuclei can be blocked by the caspase-1,4,5 inhibitor Ac-YVAD-CHO, but not by the caspase-2,3,7[,1] inhibitor Ac-DEVD-CHO. This suggests a functional requirement for caspase-4 or caspase-5 in the apoptotic response to camptothecin. Recently,Xenopushas been shown to display a developmental activation of the capability for stress- or damaged-induced apoptosis at early gastrula stage.En masse,our experiments suggest that the apoptotic responses in zebrafish andXenopusare fundamentally similar. Thus, as for mammals, embryos of the lower vertebrates exhibit the activation of surveillance mechanisms, early in development, to produce the selective apoptosis of damaged cells
The Centrosome-Attracting Body, Microtubule System, and Posterior Egg Cytoplasm Are Involved in Positioning of Cleavage Planes in the Ascidian Embryo

AbstractMany kinds of animal embryos exhibit stereotyped cleavage patterns during early embryogenesis. In the ascidianHalocynthia roretzi,cleavage patterns are invariant but they are complicated by successive unequal cleavages that occur in the posterior region. Here we report the essential roles of a novel structure, called the centrosome-attracting body (CAB), which exists in the posterior pole cortex of cleaving embryos, in generating unequal cleavages. By removing and transplanting posterior egg cytoplasm and by treatment with sodium dodecyl sulfate, we demonstrated that loss of the CAB resulted in abolishment of unequal cleavage, while ectopic formation of the CAB caused ectopic unequal cleavages to occur. Experiments with a microtubule inhibitor demonstrated that the centrosome and nucleus were attracted toward the posterior cortex, where the CAB is located, by shortening of microtubule bundles formed between the centrosome and the CAB. Consequently, the mitotic apparatus was positioned asymmetrically, resulting in unequal cleavage. Immunohistochemistry provided evidence that a microtubule motor protein, a kinesin or kinesin-like molecule, may be associated with the CAB. Formation of the CAB during the early cleavage stage was resistant to treatment with the microtubule inhibitor. In contrast, the integrity of the CAB was lost upon treatment with a microfilament inhibitor. We propose that the CAB plays key roles in the orientation and positioning of cleavage planes during unequal cell division
Elucidating the Origins of the Vascular System: A Fate Map of the Vascular Endothelial and Red Blood Cell Lineages inXenopus laevis

AbstractRequired to supply nutrients and oxygen to the growing embryo, the vascular system is the first functional organ system to develop during vertebrate embryogenesis. Although there has been substantial progress in identifying the genetic cascade regulating vascular development, the initial stages of vasculogenesis, namely, the origin of vascular endothelial cells within the early embryo, remain unclear. To address this issue we constructed a fate map for specific vascular structures, including the aortic arches, endocardium, dorsal aorta, cardinal veins, and lateral abdominal veins, as well as for the red blood cells at the 16-cell stage and the 32-cell stage ofXenopus laevis.Using genetic markers to identify these cell types, our results suggest that vascular endothelial cells can arise from virtually every blastomere of the 16-cell-stage and the 32-cell-stage embryo, with different blastomeres preferentially, though not exclusively, giving rise to specific vascular structures. Similarly, but more surprisingly, every blastomere in the 16-cell-stage embryo and all but those in the most animal tier of the 32-cell-stage embryo serve as progenitors for red blood cells. Taken together, our results suggest that during normal development, both dorsal and ventral blastomeres contribute significantly to the vascular endothelial and red blood cell lineages
bves:A Novel Gene Expressed during Coronary Blood Vessel Development

AbstractWe have used a subtractive method to clone novel messages enriched in the heart. Here we show that one such message,bves(blood vessel/epicardial substance) is a novel protein that is highly conserved between chicken and mouse. Thebvesmessage is detected at high levels in early chick hearts. Using anti-Bves antibodies, we show expression in cells of the proepicardial organ, migrating epicardium, epicardial-derived mesenchyme, and smooth muscle of the developing intracardiac arterial system, including the coronary arteries. Our data suggest that Bves is an early marker of developing vascular smooth muscle cells. In addition, the expression pattern of Bves protein reveals the patterning of intracardiac vascular smooth muscle and possible insights into the cellular regulation of smooth muscle differentiation during vasculogenesis
Ca2+Is Required for Phosphorylation of Clam p82/CPEBin Vitro:Implications for Dual and Independent Roles of MAP and Cdc2 Kinases

AbstractDuring early development gene expression is controlled principally at the translational level. Oocytes of the surf clamSpisula solidissimacontain large stockpiles of maternal mRNAs which are translationally dormant or masked until meiotic maturation. Fertilisation of the oocyte leads to rapid polysomal recruitment of the abundant cyclin and ribonucleotide reductase mRNAs at about the time they undergo cytoplasmic polyadenylation. Clam p82, a 3′ UTR RNA-binding protein, and a member of the CPEB (cytoplasmic polyadenylation element binding protein) family, functions as a translational masking factor in oocytes and as a polyadenylation factor in fertilised eggs. In meiotically maturing clam oocytes, p82/CPEB is rapidly phosphorylated on multiple residues to a 92-kDa apparent size, prior to its degradation during the first cell cleavage. Here we examine the protein kinase(s) that phosphorylates clam p82/CPEB using a clam oocyte activation cell-free system that responds to elevated pH, mirroring the pH rise that accompanies fertilisation. We show that p82/CPEB phosphorylation requires Ca2+(<100 μM) in addition to raised pH. Examination of the calcium dependency combined with the use of specific inhibitors implicates the combined and independent actions of cdc2 and MAP kinases in p82/CPEB phosphorylation. Calcium is necessary for both the activation and the maintenance of MAP kinase, whose activity is transientin vitro,asin vivo.While cdc2 kinase plays a role in the maintenance of MAP kinase activity, it is not required for the activation of MAP kinase. We propose a model of clam p82/CPEB phosphorylation in which MAP kinase initially phosphorylates clam p82/CPEB, at a minor subset of sites that does not alter its migration, and cdc2 kinase is necessary for the second wave of phosphorylation that results in the large mobility size shift of clam p82/CPEB. The possible roles of phosphorylation for the function and regulation of p82/CPEB are discussed
G-Protein βγ Subunit-Dependent Phosphorylation of 62-kDa Protein in the Early Signaling Pathway of Starfish Oocyte Maturation Induced by 1-Methyladenine

AbstractIn starfish oocytes, maturation is induced by a hormone, 1-methyladenine (1-MA), that binds to the receptors exposed to the outer surface of the plasma membrane. The signal of 1-MA stimulates the heterotrimeric G protein, resulting in dissociation of the βγ subunit of G protein (Gβγ) from a pertussis toxin-sensitive Gi-type α subunit. To investigate the targets for Gβγ, we analyzed 1-MA- or Gβγ-dependent phosphorylation usingin vivoandin vitrosystems. A 62-kDa protein was phosphorylated immediately after 1-MA treatment in intact oocytes. In the cell-free preparations, the 62-kDa protein was also phosphorylated on serine residue(s) immediately after addition of 1-MA or Gβγ. The Gβγ-dependent phosphorylation of the 62-kDa protein was inhibited by wortmannin or LY294002, which are mechanistically different inhibitors of phosphatidylinositol 3-kinase (PI3K). LY294002 also inhibited Gβγ- as well as 1-MA-induced maturation of oocytes. Taken together, these results indicate that the 62-kDa protein functions downstream of Gβγ and PI3K in the early signaling pathway of 1-MA-induced starfish oocyte maturation. The phosphorylation of the 62-kDa protein may be required for the activation of maturation-promoting factor
Measurements of Mechanical Properties of the Blastula Wall Reveal Which Hypothesized Mechanisms of Primary Invagination Are Physically Plausible in the Sea UrchinStrongylocentrotus purpuratus

AbstractComputer simulations showed that the elastic modulus of the cell layer relative to the elastic modulus of the extracellular layers predicted the effectiveness of different force-generating mechanisms for sea urchin primary invagination [L. A. Davidson, M. A. R. Koehl, R. Keller, and G. F. Oster (1995)Development121, 2005–2018]. Here, we measured the composite elastic modulus of the cellular and extracellular matrix layers in the blastula wall ofStrongylocentrotus purpuratusembryos at the mesenchyme blastula stage. Combined, these two layers exhibit a viscoelastic response with an initial stiffness ranging from 600 to 2300 Pa. To identify the cellular structures responsible for this stiffness we disrupted these structures and correlated the resulting lesions to changes in the elastic modulus. We treated embryos with cytochalasin D to disrupt the actin-based cytoskeleton, nocodazole to disrupt the microtubule-based cytoskeleton, and a gentle glycine extraction to disrupt the apical extracellular matrix (ECM). Embryos treated less than 60 min in cytochalasin D showed no change in their time-dependent elastic modulus even though F-actin was severely disrupted. Similarly, nocodazole had no effect on the elastic modulus even as the microtubules were severely disrupted. However, glycine extraction resulted in a 40 to 50% decrease in the elastic modulus along with a dramatic reduction in the hyalin protein at the apical ECM, thus implicating the apical ECM as a major mechanical component of the blastula wall. This finding bears on the mechanical plausibility of several models for primary invagination
Nr-CAM Promotes Neurite Outgrowth from Peripheral Ganglia by a Mechanism Involving Axonin-1 as a Neuronal Receptor

AbstractNr-CAM is a neuronal cell adhesion molecule (CAM) belonging to the immunoglobulin superfamily that has been implicated as a ligand for another CAM, axonin-1, in guidance of commissural axons across the floor plate in the spinal cord. Nr-CAM also serves as a neuronal receptor for several other cell surface molecules, but its role as a ligand in neurite outgrowth is poorly understood. We studied this problem using a chimeric Fc-fusion protein of the extracellular region of Nr-CAM (Nr-Fc) and investigated potential neuronal receptors in the developing peripheral nervous system. A recombinant Nr-CAM-Fc fusion protein, containing all six Ig domains and the first two fibronectin type III repeats of the extracellular region of Nr-CAM, retains cellular and molecular binding activities of the native protein. Injection of Nr-Fc into the central canal of the developing chick spinal cordin ovoresulted in guidance errors for commissural axons in the vicinity of the floor plate. This effect is similar to that resulting from treatment with antibodies against axonin-1, confirming that axonin-1/Nr-CAM interactions are important for guidance of commissural axons through a spatially and temporally restricted Nr-CAM positive domain in the ventral spinal cord. When tested as a substrate, Nr-Fc induced robust neurite outgrowth from dorsal root ganglion and sympathetic ganglion neurons, but it was not effective for tectal and forebrain neurons. The peripheral but not the central neurons expressed high levels of axonin-1 bothin vitroandin vivo.Moreover, antibodies against axonin-1 inhibited Nr-Fc-induced neurite outgrowth, indicating that axonin-1 is a neuronal receptor for Nr-CAM on these peripheral ganglion neurons. The results demonstrate a role for Nr-CAM as a ligand in axon growth by a mechanism involving axonin-1 as a neuronal receptor and suggest that dynamic changes in Nr-CAM expression can modulate axonal growth and guidance during development
Regional Specification during Embryogenesis in the Inarticulate BrachiopodDiscinisca

AbstractThe process of embryogenesis is described for the inarticulate brachiopodDiscinisca strigataof the family Discinidae. A fate map has been constructed for the early embryo. The animal half of the egg forms the dorsal ectoderm of the apical and mantle lobes. The vegetal half forms mesoderm and endoderm and is the site of gastrulation; it also forms the ectoderm of the ventral regions of the apical and mantle lobes of the larva. The plane of the first cleavage goes through the animal–vegetal axis of the egg along the future plane of bilateral symmetry of the larva. The timing of regional specification in these embryos was examined by isolating animal, vegetal, or lateral regions at different times from the 2-cell stage through gastrulation. Animal halves isolated at the 8-cell and blastula stages formed an epithelial vesicle and did not gastrulate. When these halves were isolated from blastulae they formed the cell types typical of apical and mantle lobes. Vegetal halves isolated at all stages gastrulated and formed a more or less normal larva; the only defect these larvae had was the lack of an apical tuft, which normally forms from cells at the animal pole of the embryo. When lateral isolates were created at all developmental stages, these halves gastrulated. Cuts which separated presumptive anterior and posterior regions generated isolates at the 4-cell and blastula stages that formed essentially normal larvae; however, at the midgastrula stage these halves formed primarily anterior or posterior structures indicating that regional specification had taken place along the anterior–posterior axis. The plane of the first cleavage, which predicts the plane of bilateral symmetry, can be shifted by either changing the cleavage pattern that generates the bilateral 16-cell blastomere configuration or by isolating embryo halves prior to, or during, the 16-cell stage. These results indicate that while the plane of the first cleavage predicts the axis of bilateral symmetry, the axis is not established until the fourth cleavage. The development ofDisciniscais compared to development in the inarticulate brachiopodGlottidiaof the family Lingulidae and toPhoronisin the phylum Phoronida