pinecone/core-2020-05-10-deduplication huggingface dataset:
SpRunt-1, a New Member of the Runt Domain Family of Transcription Factors, Is a Positive Regulator of the Aboral Ectoderm-SpecificCyIIIAGene in Sea Urchin Embryos

AbstractIn this paper we present a structural and functional characterization of a new sea urchin embryo transcription factor, SpRunt-1. This factor was isolated by means of its specific interaction with acis-regulatory target site of theCyIIIagene. Here we show that this target site, the P7I site, is required for normal embryonic activation ofCyIIIa·CATreporter gene constructs. An oligonucleotide affinity column bearing the P7I target site purifies a 21-kDa polypeptide from blastula-stage nuclear extracts, and the amino acid sequence obtained from this polypeptide was used to generate a nucleic acid probe with which the corresponding cDNA was cloned. The cDNA encodes an approximately 60-kDa protein, SpRunt-1, which includes a “runt domain” that is closely homologous to those ofDrosophilaand mammalian runt domain transcription factors. RNA and genomic blots show that SpRunt-1 is represented by a single embryonic transcript, encoded by one of possibly two runt-domain-containing genes. By RNA probe protection we found that transcripts of SpRunt-1 increase in concentration dramatically after the blastula stage of development, suggesting that the up-regulation ofCyIIIathat occurs after blastula stage is a function of zygotically transcribed SpRunt-1. These results are discussed with reference to known features of the runt domain family of transcription factors
inscuteable,A Neural Precursor Gene ofDrosophila,Encodes a Candidate for a Cytoskeleton Adaptor Protein

AbstractInDrosophila,neural precursor genes are expressed in neural progenitor cells as the neuroblasts and sense organ mother cells. These genes are thought to control the fate and/or behavior of neural progenitor cells once their fate decision has been made. We have isolated and characterized a novel neural precursor gene,inscuteable,whose expression is coincident with sites of cell shape changes or cell and tissue movement in the embryo, e.g., neuroblasts, trachea, Malphigian tubules, and in pupal wing epithelia. The Inscuteable protein is localized to the apical submembranous surface of neuroblasts and other cell types and shows certain features common to a family of putative cytoskeletal associated proteins. Theinscuteablemutant phenotype, together with these other observations, suggests a possible role for the protein in cytoskeleton organization
A Cell-Cycle Phase-Associated Cell-Type Choice Mechanism Monitors the Cell Cycle Rather Than Using an Independent Timer

AbstractUpon starvation, cells of the simple eukaryoteDictyostelium discoideumaggregate and differentiate into several cell types. Two main cell types are prestalk and prespore, which later usually become stalk and spore cells. The differentiation is plastic, and several factors can alter cell-type ratios. Two mechanisms have been proposed to regulate the initial differentiation. One hypothesis is that different levels of extracellular factors within the aggregate determine initial cell type. We and others have proposed that cell type is initially determined by cell-cycle phase at the time of starvation: prestalk cells are derived from cells which, at the time of starvation, happen to be in a roughly 2-hr-long sector of the cell cycle which overlaps S and early G2 and that certain extracellular factors are then used to maintain the proper prestalk: prespore ratio and to control later stages of development such as the prestalk-to-stalk conversion. To examine the relationship between initial cell-type choice and the cell cycle, and how this 2-hr-long sector is generated, we increased the length of S phase by mild treatments of cells with DNA-synthesis inhibitors. When the fraction of the cell cycle occupied by S phase is increased and the cells are then starved, the prestalk:prespore ratio increases. This increase was observed using two markers for prestalk cells, CP2 and ecmA::lacZ. In addition, there is a close correlation between the fraction of the cell cycle occupied by S phase and the prestalk:prespore ratio, irrespective of total cell-cycle length. These results validate the hypothesis that the initial choice of cell type is determined by cell-cycle phase at the time of starvation, and indicate that the cell-type choice mechanism monitors the cell cycle rather than using an independent 2-hr-long timer started at the beginning of S phase
Dorsal Mesoderm Has a Dual Origin and Forms by a Novel Mechanism inHymenochirus,a Relative ofXenopus

AbstractThe dorsal mesoderm in the frogHymenochirusforms by a mechanism not previously described in any other vertebrate. Unlike its close relative,Xenopus laevis,in which the mesoderm derives entirely from the deep mesenchymal cells of the marginal zone,Hymenochirushas “surface mesoderm” originating in the involuting marginal zone epithelium. Fluorescently labeled grafts show stage-specific invasion of deep axial tissue by cells originally located in the surface layer. These cells participate in normal mesoderm development. In video recordings, the labeled surface area shrinks as surface cells invade the deep layer. Furthermore, the mechanism of surface mesoderm morphogenesis differs from that described in other amphibians. Scanning electron microscopy at several neurula stages indicates that prospective somite cells do not individually detach from their epithelial neighbors to ingress into the deep layer, as seen in other amphibians; instead, their basal ends adhere to the somitic mesoderm as a coherent layer, taking on somitic morphology while still a part of the archenteron lining. This novel morphogenetic process we dub “relamination.” Prospective notochord cells individually spread on the ventral surface of the notochord, gradually ingressing from their epithelial neighbors, but by a mechanism involving active pulling and spreading by their invasive basal ends rather than depending on apical constriction as do the corresponding “bottle cells” in other amphibians. Lateral endoderm migrates dorsally, replacing the relaminating surface mesoderm and fusing at the dorsal midline of the archenteron. These processes demonstrate the diversity of morphogenesis at the cellular, and presumably the molecular, level and shed light on the evolution of morphogenetic mechanisms
AXenopusGene,Xbr-1,Defines a Novel Class of Homeobox Genes and Is Expressed in the Dorsal Ciliary Margin of the Eye

AbstractWe have isolatedXbr-1,a novelXenopushomeobox gene that defines a new class of homeobox genes, distantly related to theDrosophila BarH1andBarH2genes.Xbr-1is predominantly expressed in the developingXenopuseye, starting as early as the neural plate stage. At early stages of eye developmentXbr-1is expressed in the eye vesicle dorsally, in the tissue between the prospective neural retina and pigment epithelium. Later, in the optic cup, it is restricted to the prospective dorsal ciliary margin, an area containing progenitor cells at the edge of retina. Comparing the expression ofXbr-1in the eye to that ofX-Notch-1suggests thatXbr-1marks a unique population of pluripotent stem cells within the dorsal ciliary margin. The expression ofXbr-1andBMP-4in the dorsal ciliary margin is largely coincident, suggesting that the two molecules interact. We propose thatXbr-1andBMP-4may play a role in the development of progenitor cells on the dorsal half of the eye and that they may be involved in the establishment of polarity of the eye along the dorsoventral axis
Analysis of Regulatory Elements of the Developmentally Controlled Chorions15Promoter in TransgenicDrosophila

AbstractTheDrosophila s15chorion gene is expressed only in the follicular epithelium surrounding the developing oocyte, with tight quantitative control and a very narrow temporal specificity. We have used germ-line transformation analysis to conduct an extensive mutational dissection of its promoter between -189 and -39 bp relative to the transcriptional start site. Quantitative control and temporal specificity are disrupted by several of these mutations. The results suggest that this 150-bp DNA region encompasses many positive and negative, at least partially degenerate,cis-regulatory elements, which are involved in specifying the highly precise expression pattern of thes15gene during development
Synaptic Integrins in Developing, Adult, and Mutant Muscle: Selective Association of α1, α7A, and α7B Integrins with the Neuromuscular Junction

AbstractDifferentiation of both pre- and postsynaptic structures at the skeletal neuromuscular junction is organized by the basal lamina that occupies the synaptic cleft. As β1 integrins are a major class of receptors for basal lamina components, we stained muscles with antibodies to the 10 integrin α subunits known to form dimers with β1, to determine if any of these molecules were concentrated at synaptic sites on muscle fibers. In both developing and adult muscle, the integrin α1 chain was selectively associated with presynaptic cells (Schwann cells and/or nerve terminals), while α7 was present on both synaptic and extrasynaptic portions of the muscle fiber surface. Thus α1 and α7 integrins are present in synaptic membranes. Expression of the α7 chain was analyzed further by staining with antibodies specific for three alternatively spliced products of the α7 gene (A, B, and C), all of which were expressed in muscle. The α7A and α7B isoforms were confined to synaptic sites in adult muscle, while α7C was present both synaptically and extrasynaptically. In developing muscle, α7A appeared postnatally and specifically at the synapse; α7B was present throughout the muscle fiber perinatally, becoming confined to the synapse in the second postnatal week; and α7C was present extrasynaptically both perinatally and in adulthood. Thus, two of the α7 integrins are synapse-specific, and all three show distinct spatiotemporal patterns of expression within a single cell type. Finally, we asked whether perturbation of laminin expression affected the distribution of the α7 integrins. In normal mice, laminin β2 is concentrated in synaptic basal lamina. In β2-null mutant mice, α7A was still present at synaptic sites, but α7B was absent. This result provides genetic evidence that basal lamina composition is a determinant of integrin distribution
Myf-5m1/Myf-6m1Compound Heterozygous Mouse Mutants Down-regulate Myf-5 Expression and Exert Rib Defects: Evidence for Long-RangecisEffects on Myf-5 Transcription

AbstractMyf-6 and Myf-5, two members of the family of muscle-specific regulatory genes, are located less than 10 kb apart in the mouse and human genomes. We have shown recently that homozygous mutant mice carrying a pgk-neo-cassette in the first exon of the Myf-6 gene display minor alterations of skeletal musculature but develop a severe rib defect, most likely due to a drastic down-regulation of Myf-5 expression. The mechanism by which the Myf-6 mutation affects the Myf-5 gene is unknown. In order to determine whether Myf-5 transcription is inhibited by the Myf-6 mutation incisor intrans,we generated compound heterozygous mice carrying inactivated Myf-5 and Myf-6 alleles on different chromosomes. Here, we demonstrate that double-heterozygous mutants exhibit truncated ribs and severe depression of Myf-5 transcription, a phenotype similar to the previously described homozygous Myf-6 mutant mice. These results indicate that the Myf-6 mutation inhibits Myf-5 gene expression by a long-rangeciseffect
Purification of AV-1, a Position-Specific Molecule, and the Effects of Its Antiserum on Chick Limb Pattern Formation

AbstractAV-1 protein is a membrane-localized glycoprotein which is expressed in a stage- and position-specific manner during limb development and is a candidate pattern formation molecule. In this study, we have purified the AV-1 protein using an affinity column coupled with the anti-AV-1 monoclonal antibody. Using the purified protein, we produced a rat anti-AV-1 antiserum. Characterization of the antiserum by immunoblotting and immunostaining showed highly specific reactivity which was identical to that of the anti-AV-1 monoclonal antibody. The rat anti-AV-1 antiserum was injected into the vitelline vein of stage 20 chick embryos and these embryos were allowed to develop further to examine the effect of the antibody on limb pattern. The injected embryos developed deformed limbs. Many of the abnormalities in limb cartilage pattern were related to the normal pattern of the AV-1 expression, suggesting an involvement of the AV-1 protein in the process of limb pattern formation
Tip-Localized Calcium Entry Fluctuates during Pollen Tube Growth

AbstractStudies have been conducted on the dynamics of Ca2+entry in pollen tubes using ratiometric ion imaging to measure the intracellular gradient and an ion selective vibrating electrode to detect the extracellular influx. A steep tip-focused gradient occurs in all species examined, includingLilium longiflorum, Nicotiana sylvestris,andTradescantia virginiana.Analysis ofLiliumpollen tubes loaded with dextran conjugated fura-2 reveals that the gradient derives from Ca2+entry that is restricted to a small area of plasma membrane at the extreme apex of the tube dome. Since the apical membrane is continually swept to the flanks during tube elongation, either Ca2+channels are specifically retained at the extreme apex or, as seems more likely, the Ca2+channels which were active at the tip rapidly inactivate, as new ones are inserted during vesicle fusion. Ratiometric imaging further indicates that the high point of the gradient fluctuates in magnitude from 0.75 to above 3 μM,during measuring intervals of 60 sec, with the elevated points being correlated with an increased rate of tube growth. Independent analysis of the growth at 2- to 3-sec intervals reveals that the rates can fluctuate more than threefold; tubes longer than 700 μm exhibit oscillations with a period of 23 sec, while tubes shorter than 700 μm display erratic fluctuations. Inhibition of pollen tube growth caused by mild temperature shock or caffeine (1.5 to 3.0 mM) is correlated with the dissipation of the tip-focused gradient and the Ca2+influx. Recovery from both treatments is denoted by a global swelling of the pollen tube tip, concomitant with a high transient entry of Ca2+in the tip. The location of the highest Ca2+domain within the tip region defines the point from which normal cylindrical elongation will proceed
Overexpression of the Homeobox GeneXnot-2Leads to Notochord Formation inXenopus

AbstractXnot-2is a homeobox gene expressed in Spemann's organizer. Here we present evidence that microinjection of syntheticXnot-2mRNA leads to the formation of notochord. Microinjection into the dorsal side of theXenopusembryo results in greatly expanded notochords. Nearby somitic and prechordal mesoderm becomes recruited into these enlarged notochords, which also affect CNS patterning. Two early genes expressed in the developing notochord,chdandXFKH-1,are activated byXnot-2.We conclude that gain-of-function ofXnot-2promotes notochord formation
Apical Membrane Turnover Is Accelerated Near Cell–Cell Contacts in an Embryonic Epithelium

AbstractDuring embryogenesis, the killifishFundulus heteroclitusforms a monolayered tight epithelium called the enveloping layer (EVL). These epithelial cells have been shown to rearrange during epiboly, as they spread to cover the large yolk cell. Membrane remodeling by exocytosis and endocytosis is important in establishing and maintaining the apical–basolateral polarity of many epithelial cells and is a necessary component of epithelial rearrangements, as cells constantly break contacts and reform tight junctions. To study these phenomena inFundulus heteroclitusembryos, we labeled the apical membranes of EVL cells with fluorescent lectins and lipids and followed membrane dynamics. Apical membrane components were found to be highly immobilized, allowing us to observe localized sites of apical membrane turnoverin situ,over the period of several days. We found that apical membrane turnover in the EVL cells of post-epiboly killifish embryos is accelerated at cell–cell contacts, in a peripheral band of apical membrane which closely borders circumferential tight junctions. Moreover, this turnover rate is increased during epiboly, when the cells are actively rearranging. To investigate whether this increased membrane turnover may be related to the mechanical forces experienced by the rearranging EVL cells, post-epiboly embryos, whose EVL cells no longer rearrange, were subjected to mechanical deformation. In these manipulated embryos, apical membrane turnover was accelerated at cell–cell contacts in EVL cells which experienced externally applied mechanical tension. These results suggest that local mechanical tension may modulate regional apical membrane turnover within EVL cells during the process of epiboly
Transient Expression of Translation Initiation Factor eIF-4C during the 2-Cell Stage of the Preimplantation Mouse Embryo: Identification by mRNA Differential Display and the Role of DNA Replication in Zygotic Gene Activation

AbstractZygotic gene activation (ZGA) definitely occurs by the 2-cell stage in the mouse embryo. Analysis of protein synthesis by two-dimensional gel electrophoresis reveals a class of genes whose expression transiently increases in the 2-cell embryo. Although the paucity of biological material has prevented a systematic identification of these genes, the mRNA differential display method circumvents this problem. Using this approach we find a transient increase in the mRNA abundance of the translation initiation factor eIF-4C that is inhibited by α-amanitin and correlated with a transient increase in the relative rate of protein synthesis for eIF-4C. We confirm the transient increase in eIF-4C mRNA abundance by a reverse transcription–PCR-based assay using eIF-4C-specific primers. The first round of DNA replication seems critical for eIF-4C expression, since addition of aphidicolin prior to S phase in the 1-cell embryo inhibits the magnitude of the increase in eIF-4C expression. Aphidicolin treatment also inhibits the synthesis of an accepted marker for ZGA, the transcription-requiring complex (TRC), which is also transiently expressed during the 2-cell stage. Incubating late 1-cell/early 2-cell embryos in medium containing aphidicolin reveals that the second round of DNA replication is not required for the increase in eIF-4C expression but DNA replication is required for the decrease in both eIF-4C expression and TRC synthesis. The decrease in eIF-4C expression, however, does not require cytokinesis or mitosis, since it occurs when 2-cell embryos are cultured in the presence of cytochalasin D or nocodazole, respectively. Changes in chromatin structure may be involved in the decrease in both eIF-4C and TRC expression, since neither decrease occurs when 2-cell embryos are cultured in trapoxin, which is a specific and irreversible inhibitor of histone deacetylase. Results of these experiments suggest that the first round of DNA replication is permissive with respect to ZGA and that the second round is repressive
Initial Cell Type Divergence inDictyosteliumIs Independent of DIF-1

AbstractPrespore and prestalk cells can be distinguished within aggregates ofDictyosteliumby the expression of well-characterized cell type-specific genes. Fusion of thetagBregulatory region toEscherichia coliβ-galactosidase revealed that this prestalk-specific gene marks the differentiation of the initial prestalk cell population, PST-1. The reporter gene was expressed normally intagB−mutant cells despite the fact that they do not accumulate measurable levels of DIF-1, a morphogen that was previously implicated in prestalk differentiation. In an independent experimental system, wild-type cells respond to the addition of DIF-1 by induction of the prestalk markerecmAand repression of the prespore markercotB.We found that DIF-1 did not affect the expression of thetagBorcarBgenes, both of which are prestalk specific and essential for PST-A cell differentiation. We conclude that the initiation of prestalk development is not dependent on DIF-1 and suggest that the morphogen participates mainly at later stages
Pericardial Mesoderm Generates a Population of Coronary Smooth Muscle Cells Migrating into the Heart along with Ingrowth of the Epicardial Organ

AbstractThe vascular smooth muscle cells of coronary arteries are distinguished from those of the proximal aorta by a number of structural and functional criteria which may include an increased propensity for atherosclerotic transformation. At present, the source of this variation between smooth muscle subpopulations is uncertain. Whilst smooth muscle of the proximal aorta is thought to be derived from neural crest, the origin of coronary vascular smooth muscle remains uncharacterized. We have previously shown that precursors of the coronary vasculature enter the tubular heart on the same day as the epicardial mantle starts to envelop the myocardium and that coronary vessels form by ingrowth of these migratory precursors and not by outgrowth from the aorta (Mikawa and Fischman, 1992). To study the origin of coronary smooth muscle cells, the proepicardial organ, from which epicardial cells arise, was tagged with either a vital dye (DiI) or replication-defective retroviruses encoding β-galactosidase. Cellular lineage marking was achieved by either direct targeting of putative vasculogenic cells in the proepicardiumin ovoor tagging dissected proepicardial cellsin vitrofollowed by transplantation to stage-matched host embryos. Monitoring of tagged cells during coronary vasculogenesis indicate incorporation of proepicardial-derived cells into three vessel-associated populations; coronary mooth muscle, perivascular connective tissue, and endothelial cells. Immunoconfocal microscopy identified both endothelial and smooth muscle cell populations within the proepicardial organ. The results demonstrate that: (1) the proepicardium contains a progenitor population of coronary smooth muscle cells that migrates into the heart along with ingrowth of the epicardium and (2) prior to the migration, the coronary smooth muscle lineage is established
A Chick Homologue ofSerrateand Its Relationship withNotchandDeltaHomologues during Central Neurogenesis

AbstractIn theDrosophilanervous system, lateral inhibition regulates commitment to a neural fate by preventing neighbouring cells from developing alike. This signalling process is mediated by two transmembrane proteins—Notch as receptor and Delta as its ligand. The Delta-related protein Serrate also acts as a Notch ligand inDrosophila,but in a different developmental process that organises patterning of the wing. We have previously shown that lateral inhibition operates at early stages of neurogenesis in vertebrates, via genes homologous toDrosophila DeltaandNotch.We report here the cloning of a chickSerratehomologue,C-Serrate-1.This gene is expressed in the central nervous system, as well as in the cranial placodes, nephric epithelium, vascular system, and distal limb-bud mesenchyme. In most of these sites, its expression is associated with expression ofC-Notch-1andC-Delta-1.All three genes are expressed in the ventricular zone of the hindbrain and spinal cord, throughout the period when neurons are being born. Within this zone,C-Delta-1andC-Serrate-1are expressed in complementary subsets of nondividing cells that appear to be nascent neurons:C-Serrate-1expression is restricted to specific locations along the dorsoventral axis, forming narrow bands extending from the anterior hindbrain to the tail. Our observations strongly suggest that Delta–Notch signalling delivers lateral inhibition not only early but throughout vertebrate neurogenesis to regulate neuronal commitment, and that Serrate–Notch signalling may act similarly in this process. By analogy with its role inDrosophilawing patterning,C-Serrate-1may also have a role in organising the dorso-ventral pattern of the neural tube. We argue that signalling via Notch maintains neurogenesis, both in vertebrates and in flies, by keeping a proportion of the neuroepithelial cells in an uncommitted stem-cell-like state