pinecone/core-2020-05-10-deduplication huggingface dataset:
Regional Specification during Embryogenesis in the Inarticulate BrachiopodGlottidia

AbstractA fate map has been constructed for the lingulid brachiopodGlottidia pyramidata.The animal half of the egg forms part of the apical lobe and the dorsal valve of the larva. The vegetal half of the egg forms mesoderm and endoderm and is the site of gastrulation; it also forms part of the apical lobe and the ventral valve 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 or vegetal, anterior or posterior, or lateral regions at different times from prior to fertilization through gastrulation. Animal halves isolated at all stages formed an epithelial vesicle and did not gastrulate. When these halves were isolated from unfertilized eggs or early cleavage stage embryos, they usually did not form an apical lobe or valve; however, when the halves were isolated at later developmental stages, these structures differentiated in a high frequency of cases. Vegetal halves isolated at all stages gastrulated and formed a larva; however, when these halves were isolated at gastrulation they frequently lacked a dorsal valve. When lateral cuts were made along the animal–vegetal axis at all developmental stages, both halves gastrulated. When the cut was made perpendicular to the plane of the first cleavage from the four-cell stage on, one-half formed the anterior end and the other half formed the posterior end of the larva. These results suggest that there are localized determinants in the egg that specify the different regions of the larva, but there is also an inductive signal(s) from the vegetal region of the embryo that is necessary in order for cells that inherit a given determinant to differentiate. Embryogenesis inGlottidiais compared with articulate brachiopods and phoronids
Myogenin's Functions Do Not Overlap with Those of MyoD or Myf-5 during Mouse Embryogenesis

AbstractThe four myogenic basic helix-loop-helix proteins, MyoD, myogenin, Myf-5, and MRF4, can each activate skeletal muscle differentiation when introduced into nonmuscle cells. During embryogenesis, each of these genes is expressed in a unique but overlapping pattern in skeletal muscle precursors and their descendants. Gene knockout experiments have shown that MyoD and Myf-5 play seemingly redundant roles in the generation of myoblasts. However, the role of either of these genes during differentiationin vivohas not been determined. In contrast, a myogenin-null mutation blocks differentiation and results in a dramatic decrease in muscle fiber formation, yet the role of myogenin in the generation or maintenance of myoblast populations is not known. Because myogenin possesses the same myogenic activity as MyoD and Myf-5in vitroand the expression patterns of these three genes overlapin vivo,we sought to determine if myogenin shares certain functions with either MyoD or Myf-5in vivo.We therefore generated mice with double homozygous null mutations in the genes encoding MyoD and myogenin or Myf-5 and myogenin. These mice showed embryonic and perinatal phenotypes characteristic of the combined defects observed in mice mutant for each gene alone. As shown by histological analysis and expression of muscle-specific genes, the numbers of undifferentiated myoblasts and residual myofibers were comparable between myogenin-mutant homozygotes and the double-mutant homozygotes. Myoblasts isolated from neonates of the combined mutant genotypes underwent myogenesis in tissue culture, indicating that no more than two of the four myogenic factors are required to support muscle differentiation. These results demonstrate that the functions of myogenin do not overlap with those of MyoD or Myf-5 and support the view that myogenin acts in a genetic pathway downstream of MyoD and Myf-5
Differential Regulation of Oocyte Maturation and Cumulus Expansion in the Mouse Oocyte– Cumulus Cell Complex by Site-Selective Analogs of Cyclic Adenosine Monophosphate

AbstractIn the present study, we have examined how differential distribution of cyclic adenosine 5′-monophosphate (cAMP)-dependent protein kinase isozymes within the mouse oocyte–cumulus cell complex might influence the physiological response of the complex to cAMP, by determining the actions of site-selective cAMP analogs on oocyte maturation and cumulus expansion. Five different analogs of cAMP were utilized: 8-thiomethyl-cAMP and 8-bromo-cAMP, which bind to site 1 on the type II regulatory subunit (RII) of cAMP-dependent protein kinase A (PKA); 8-aminohexylamino-cAMP, which binds to site 1 on the type I regulatory subunit (RI) of PKA; N6-monobutyryl cAMP, which binds to site 2 on either RI or RII; and 8-piperidino-cAMP, which binds to either site 1 on RII or site 2 on RI. These analogs were tested alone or in paired combinations that synergistically activate either the type I or type II PKA isozyme. When tested alone, analogs that can bind to, and presumably activate, type I PKA were the most potent inhibitors of germinal vesicle breakdown (GVB) in both cumulus cell-enclosed and denuded oocytes. Consistent with this result was the finding that paired combinations of analogs that selectively activate type I PKA were also most effective in preventing GVB. On the other hand, pulsing meiotically arrested cumulus cell-enclosed oocytes with high concentrations of analogs that bind to PKA II, or with paired combinations of analogs that selectively activate type II PKA, led to induction of GVB; stimulation with analogs or combinations thereof that presumably stimulate type I PKA was less effective. Cumulus expansion in response to PKA stimulation showed similar selectivity in that type II PKA-stimulating treatments were considerably more effective in provoking expansion than type I PKA-stimulating treatments. 8-N3-[32P]cAMP photoaffinity labeling of PKA regulatory subunits revealed that only RI was present in oocyte extracts, while extracts from oocyte–cumulus cell complexes contained both RI and RII. These results support the hypothesis that type II PKA mediates cAMP-stimulated cumulus expansion and resumption of meiotic maturation, while direct elevation of type I PKA within the oocyte is instrumental in maintaining meiotic arrest
Expression ofsnail2,a Second Member of the Zebrafish Snail Family, in Cephalic Mesendoderm and Presumptive Neural Crest of Wild-Type andspadetailMutant Embryos

AbstractTranscripts of a newly discovered gene calledsnail2,encoding a zinc finger protein of the Snail family, first appear in rows of cephalic mesendodermal cells in gastrulating zebrafish embryos. At the end of gastrulation,snail2RNA accumulates in a domain of ectodermal cells that mark the border between the epidermal epithelium and the neural plate and includes precursors of the neural crest. During somitogenesis,snail2expression becomes restricted to neural crest.snail2is thus one of the earliest genes yet known to be specifically expressed in neural crest in zebrafish embryos. Sincesnail2is expressed in mesendoderm, a tissue layer whose convergence in the trunk is known to be altered in embryos homozygous for thespadetailmutation, we examinedsnail2expression inspadetailembryos. In these mutants, the number of cephalic mesendodermal cells expressingsnail2is strongly reduced and the distribution of cells containingsnail2andno tailtranscripts in the axial mesoderm is much broader than normal. Moreover, the embryos are shorter than normal at the end of gastrulation. This shows that, in addition to the failure of paraxial mesoderm to converge normally in the trunk during gastrulation,spadetailalso affects the elongation of the embryo and the convergence of axial and lateral mesendoderm in both trunk and head
Thein VivoExpression of the FGF Receptor FREK mRNA in Avian Myoblasts Suggests a Role in Muscle Growth and Differentiation

AbstractMuscle growth during embryogenesis is the result of a balance between the proliferation of myoblasts and their differentiation into mature, contractile fibers. Fibroblast growth factors (FGFs) are potent stimulators of myoblast proliferation and inhibitors of myoblast differentiationin vitro.However, it is not clear at present if FGFs and their receptors regulate this processin vivo,partially because no FGF receptor was known to be expressed by myoblasts during embryogenesis. In this study, we have used quail/chick grafting and BrdU labeling techniques to demonstrate that a recently cloned avian FGF receptor, FREK, is expressed by replicating skeletal muscle myoblasts, while differentiated muscle cells no longer express this receptor. In the limb, muscle progenitors originating from the somite start expressing FREK at 3 days of development (E3). FREK expression in the limb myoblasts follows that of Pax-3 and Pax-7, but precedes that of MyoD. Since MyoD expression signals the onset of terminal differentiation, this demonstrates that FREK is expressed in muscle progenitors prior to overt muscle differentiation. A more complex situation is observed in the trunk region, where a first wave of MyoD-positive myocytes, which are postmitotic and never express FREK, appear in the early myotomal compartment of the somite. Slightly later, at E2.5, FREK-positive myoblasts migrate into the myotome as a second wave of muscle progenitors, 15 hr after the first MyoD-positive cells. FREK's expression by myoblasts arising at all stages of myogenesis indicates that this growth factor receptor represents one of the earliest molecular markers for this cell population. FREK's prominent expression during muscle differentiation sets it apart from other FGF receptors and suggests that this molecule plays an important role during muscle growth and differentiation
β-Catenin Has Wnt-like Activity and Mimics the Nieuwkoop Signaling Center inXenopusDorsal–Ventral Patterning

Abstractβ-Catenin is a protein known to associate with the cytoplasmic domains of members of the cadherin family of cell adhesion molecules. Recently, Funayamaet al.(Funayamaet al.(1995).J. Cell Biol.128, 959–968.) demonstrated that overexpression of β-catenin causes the formation of a secondary axis inXenopus laevisembryos. In order to understand the role of β-catenin in axis formation, we examined its biological activity in further detail. β-Catenin is effective at inducing a secondary axis when overexpressed in the vegetal ventral region of early cleavage stage (4–32 cell) embryos. β-Catenin may act as part of the Nieuwkoop center because cells overexpressing β-catenin do not contribute directly to axial structures. Overexpression of β-catenin can specifyde novoaxis formation, as shown by its ability to rescue UV-ventralized embryos. Overexpression of β-catenin alone is not sufficient to cause elongation of animal caps or to induce mesodermal markers in animal caps. In these assays, overexpression of β-catenin behaves like ectopic expression of certain members of theWntgene family. Like Wnts, overexpression of β-catenin was also found to increase gap junctional communication in cells of the ventral animal cap. Overexpression of β-catenin causes a small increase in the rate of aggregation ofXenopusblastomeres. Overexpression of C-cadherin causes a more dramatic increase in the rate of aggregation ofXenopusblastomeres, but does not enhance gap junction communication or induce axis duplication; hence, we argue that increased adhesion is not sufficient to account for β-catenin's ability to regulate patterning or gap junction communication. We propose a signaling role for β-catenin during axis formation inXenopus
HedgehogandBmpGenes Are Coexpressed at Many Diverse Sites of Cell–Cell Interaction in the Mouse Embryo

AbstractThe mouseHedgehoggene family consists of three members,Sonic, Desert,andIndian hedgehog(Shh, Dhh,andIhh,respectively), relatives of the Drosophila segment polarity gene,hedgehog(hh). All encode secreted proteins implicated in cell–cell interactions. One of these,Shh,is expressed in and mediates the signaling activities of several key organizing centers which regulate central nervous system, limb, and somite polarity. However, nothing is known of the roles ofDhhorIhh,nor of the possible function ofShhduring later embryogenesis. We have used serial-sectionin situhybridization to obtain a detailed profile of mouseHhgene expression from 11.5 to 16.5 days post coitum. Apart from the gut, which expresses bothShhandIhh,there is no overlap in the variousHhexpression domains.Shhis predominantly expressed in epithelia at numerous sites of epithelial–mesenchymal interactions, including the tooth, hair, whisker, rugae, gut, bladder, urethra, vas deferens, and lung,Dhhin Schwann and Sertoli cell precursors, andIhhin gut and cartilage. Thus, it is likely that Hh signaling plays a central role in a diverse array of morphogenetic processes. Furthermore, we have comparedHhexpression with that of a second family of signaling molecules, theBone morphogenetic proteins(Bmps), vertebrate relatives ofdecapentaplegic,a target of the Drosophila Hh signaling pathway. The frequent expression of Bmp-2, -4, and -6 in similar or adjacent cell populations suggests a conserved role for Hh/Bmp interactions in vertebrate development
Effect on Sperm-Induced Activation Current and Increase of Cytosolic Ca2+by Agents That Modify the Mobilization of [Ca2+]i I. Heparin and Pentosan Polysulfate

AbstractThe mechanism of the elevation of intracellular free Ca2+([Ca2+]i) induced by a single sperm in eggs of the sea urchinLytechinus variegatuswas investigated. Simultaneous measurements of [Ca2+]i, and of the activation current, were carried out on eggs microinjected with Ca Green-1 or Ca Green dextran, and voltage clamped at −20 mV. The microinjection of 0.5 to 1.0 mg/ml heparin (MW 6000) or pentosan polysulfate (MW 3000), final intracellular concentration, causes a concentration-dependent inhibition in all parameters of the sperm-induced elevation of [Ca2+]iand the phase 2 calcium-activated cation current (Ip). For each: (1) the onset is delayed; (2) the rate of change is slowed; and (3) the peak amplitude attained is diminished. In some experiments at the higher concentrations, the microinjected polysulfates cause the complete suppression of the sperm-induced elevation of [Ca2+]iandIp. The entry of multiple sperm overcomes the inhibitory effects of the polysulfates. Our data suggest that inositol 1,4,5-trisphosphate is the primary mechanism responsible for the sperm-induced release of Ca2+from intracellular stores
Synapse-Associated Expression of an Acetylcholine Receptor-Inducing Protein, ARIA/Heregulin, and Its Putative Receptors, ErbB2 and ErbB3, in Developing Mammalian Muscle

AbstractDeveloping motor axons induce synaptic specializations in muscle fibers, including preferential transcription of acetylcholine receptor (AChR) subunit genes by subsynaptic nuclei. One candidate nerve-derived signaling molecule is AChR-inducing activity (ARIA)/heregulin, a ligand of the erbB family of receptor tyrosine kinases. Here, we asked whether ARIA and erbB kinases are expressed in patterns compatible with their proposed signaling roles. In developing muscle, ARIA was present not only at synaptic sites, but also in extrasynaptic regions of the muscle fiber. ARIA was synthesized, rather than merely taken up, by muscle cells, as indicated by the presence of ARIA mRNA in muscle and of ARIA protein in a clonal muscle cell line. ARIA-responsive myotubes expressed both erbB2 and erbB3, but little EGFR/erbB1 or erbB4. In adults, erbB2 and erbB3 were localized to the postsynaptic membrane. ErbB3 was restricted to the postsynaptic membrane perinatally, at a time when ARIA was still broadly distributed. Thus, our data are consistent with a model in which ARIA interacts with erbB kinases on the muscle cell surface to provide a local signal that induces synaptic expression of AChR genes. However, much of the ARIA is produced by muscle, not nerve, and the spatially restricted response may result from the localization of erbB kinases as well as of ARIA. Finally, we show that erbB3 is not concentrated at synaptic sites in mutant mice that lack rapsyn, a cytoskeletal protein required for AChR clustering, suggesting that pathways for synaptic AChR expression and clustering interact
Nerve Cell Differentiation in Nerve-Free Tissue of Epithelial Hydra from Precursor Cells Introduced by Grafting I. Tentacles and Hypostome

AbstractThe differentiation of hydra nerve cells in the nerve-free tissue of epithelial hydra was examined inHydra magnipapillata.Nerve cell precursors, the interstitial cells, were introduced into the upper half of epithelial hydra by grafting it onto the lower half of normal hydra. In the tentacles of grafted epithelial hydra, a small number of RF+ganglion cells first appeared in the proximal area at 1.5 days after grafting, followed by the appearance of NV1+sensory cells in the same area about a day later. In the following days, both neuron types appeared more numerously in more distal positions. The front boundary for each type moved gradually from the base to the tip of the tentacles in about 7 days. In the hypostome, a small number of RF+ganglion cells first appeared in the apex at 1.5 days. More nerve cells appeared in the following days, eventually forming a cluster of RF+sensory cells at the apex surrounded by numerous RF+ganglion cells in the adjacent tissue. These results show that nerve cells do not differentiate randomly in the epithelial hydra host. Instead, differentiation occurs in a strongly region-specific manner in the same way as in normal hydra, suggesting that epithelial cells in each region provide different cues or signals to produce region-specific nerve cell distribution in normal hydra tissue
Involvement of Cyanide-Resistant Respiration in Cell-Type Proportioning duringDictyosteliumDevelopment

AbstractInvolvement of cyanide (CN)-resistant respiration in cell-type proportioning was analyzed using the developmental system ofDictyostelium discoideum.When migrating slugs were vitally stained with rhodamine 123, which is known to stain actively respirating mitochondria coupled with an elevated electronic potential of the inner membrane, the posterior prespore region was stained more strongly than the anterior prestalk region. Application of benzohydroxamic acid (BHAM) and propyl gallate, specific inhibitors of CN-resistant respiration, to starvedDictyosteliumcells induced formation of unique cell masses, in which almost all of the cells differentiated into stalk-like cells with a large vacuole and thick cell wall. BHAM was also found to enhance the expressions of prestalk-specific genes such asecmAandecmBin the unique cell mass in a position-dependent manner. In contrast, the expression of a prespore-specific gene,Dp87,was almost completely inhibited by BHAM. Taken together these results strongly suggest the involvement of CN-resistant respiration in the proportion regulation of cell types differentiating during theDictyosteliumdevelopment
Activin and Its Receptors during Gastrulation and the Later Phases of Mesoderm Development in the Chick Embryo

AbstractWe have cloned chick homologues of the type-II activin receptor, which we have designated cActR-IIA and -IIB. Binding assays show that the two receptors are indistinguishable in their ability to bind activin-A, with comparablekds. Injection of mRNAs encoding these receptors intoXenopusembryos causes axial duplications. Expression of both receptors can first be detected in the primitive streak byin situhybridization. This suggests that these genes may be activated in response to mesoderm induction. In agreement with this, we find that treatment of preprimitive streak chick embryos with activin-A leads to rapid induction of the expression of cActR-IIB. At later stages, cActR-IIA transcripts become localized mainly in the notochord and myotome and cActR-IIB in the dorsal neural tube, proximal-anterior part of the limb bud, sensory placodes, and specific regions of the fore- and midbrain. To test the response of early chick embryonic tissues to activin, we designed a newin vitroassay for differentiation. We find that explants of area opaca epiblast or posterior primitive streak from various stages can respond to activin treatment by differentiating into a variety of mesodermal cell types in a dose-dependent manner. These results suggest that the importance of activin-related signaling pathways is not confined to pregastrulation stages and that these receptors may be involved in mediating the effects of inducing signals during later stages of development of the mesoderm, limbs, and nervous system
Is There aBrachyury the Second?Analysis of a Transgenic Mutation Involved in Notochord Maintenance in Mice

AbstractA new phenotype mapping to thet-complex, which is designatedBrachyury the Second(T2), is characterized by a slightly shortened tail in heterozygotes and homozygous failure to form an organized notochord with subsequent abnormal development of posterior somites and neural tube. The phenotype ofT2superficially resembles that ofBrachyury;however, there are several important differences.Brachyuryhomozygotes fail to make posterior somites, notochord, floor plate, and a placental connection, resulting in death by 10.5 days of development. In contrast,T2homozygotes make posterior somites, scattered notochord cells, and floorplate and achieve an allantoic connection. However, despite making a maternal connection,T2homozygotes cease development at E11.5 and die soon after. We have cloned and analyzed the transgene insertion site, which maps within 100 kb of theBrachyurygene, but does not seem to physically interrupt nor affect transcription from that locus. The existence of a second gene mapping nearBrachyuryand affecting the same developmental processes was alluded to over 50 years ago and has been debated ever since. An embryological description ofT2is presented, as is a discussion of the implications of a single, largerBrachyurylocus versus two closely linked genes coordinately regulating axial development
Neoplastic Transformation and Aberrant Cell–Cell Interactions in Genetic Mosaics oflethal(2)giant larvae (lgl),a Tumor Suppressor Gene ofDrosophila

AbstractHomozygosity forlethal(2)giant larvae (lgl),a mutation in a tumor suppressor gene ofDrosophila,induces neoplasia of the imaginal discs. To explore the developmental capacities oflglmutant cells, we have investigated their growth and differentiation in genetic mosaics. Adult wings mosaic forlgldisplayed abnormal growth and differentiation of thelglmutant and neighboring wild-type cells, suggesting aberrant cell–cell interactions during development.lglmutant clones also straddled the anteroposterior boundary of the wing imaginal disc, apparently due to failure of the cells of the anterior and the posterior compartment to segregate at the boundary. To further test if anteroposterior compartmentalization takes place in the neoplastic imaginal discs oflglmutant larvae, we studied the expression of anengrailed (en)-specificlacZreporter gene during progressive stages of their tumorous growth. Our results show thatenis activated in the posterior compartments of the neoplastic imaginal discs. However, during later stages of tumorous overgrowth, theen-expressing and nonexpressing cells appear to show extensive intermixing. These observations suggest that neoplastic transformation of imaginal discs involves loss of their normal cell–cell interactions and signaling