pinecone/core-2020-05-10-deduplication huggingface dataset:
Rescue of Sensory Ganglia That Are Programmed to Degenerate in Normal Development: Evidence That NGF Modulates Proliferation of DRG Cellsin Vivo

AbstractThe dorsal root ganglia (DRG, spinal ganglia) are a metameric series of structures that develop from neural crest cells within the dorsal somitic mesoderm. A striking element of patterning within this meristic series is the disappearance of the five or six most rostral DRG early in the embryonic development of birds and mammals. The transient DRG have been named “Froriep's ganglia” after their 19th century discoverer (reviewed in Limet al.,1987). The ontogeny of the longest surviving Froriep's ganglion of the chick embryo, DRG C2, has recently been examined in detail (Rosenet al.,1996). At St. 18 (Embryonic Day (E)2.5+), the C2 DRG had the same shape and volume as permanent ganglia C5 and C6. C2’s development first diverged from that of normal DRG at St. 19 (E3−), when C2 was observed to be half the size and shaped differently from its neighbors, and its peripheral nerve root began to degenerate. Both lower proliferation and higher apoptosis rates contribute to the reduced size of C2 compared to normal DRG at St. 19–20. One-third fewer C2 cells were found to be in S-phase when compared to neighboring ganglia, and apoptotic cells were more than three times more abundant in C2 than in conventional DRG at this stage. Since growth factors modulate both proliferation and apoptosis, we postulated that these molecules and/or their receptors might be responsible for the difference in fate between C2 and C5. In order to begin to evaluate this hypothesis, we have now treated embryos with nerve growth factor (NGF)in ovo.NGF treatments partially rescued C2, producing a 50% reduction in the normal difference in size between C2 and C5 at St. 23. At least part of this rescue could be accounted for by increased levels of proliferation in the NGF-treated C2 compared to those in control embryos. Proliferation in normal DRG C5 was unaffected by NGF application. NGF treatment rescued DRG cells in both C2 and C5 from cell death. Staining of pycnotic nuclei revealed that NGF dramatically reduced the death in the C2 ganglia. In addition to providing insight into the early patterning of the DRG, our results shed new light on the best-studied neurotrophic factor, NGF. Our finding is the first direct evidence for a role for NGF in control of DRG cell proliferationin vivo
TheDrosophila kekkonGenes: Novel Members of both the Leucine-Rich Repeat and Immunoglobulin Superfamilies Expressed in the CNS

AbstractWe have identified two members of a novel class of genes inDrosophilathat encode putative transmembrane proteins with six leucine-rich repeats and a single immunoglobulin loop. These two molecules, Kek1 and Kek2, show striking conservation in their extracellular domains and have large and more divergent intracellular regions. Both genes are expressed in neurons as they differentiate in the embryonic central nervous system (CNS).kek1is also expressed in other patterned epithelia, such as the follicle cells of the developing egg chamber, where it is found in a dorsal–ventral gradient around the oocyte. The homology of thekekgenes to other known adhesion and signaling molecules, together with their expression patterns, suggests that both genes are involved in interactions at the cell surface. Genetic analysis reveals that deletion of thekek1gene causes no obvious developmental defects. The coexpression ofkek2in the CNS leads us to suggest that Kek1 is part of a family of cell surface proteins with redundant function
Role of HB-GAM (Heparin-Binding Growth-Associated Molecule) in Proliferation Arrest in Cells of the Developing Rat Limb and Its Expression in the Differentiating Neuromuscular System

AbstractHB-GAM (heparin-binding growth-associated molecule) is a secretory, extracellular matrix-associated protein that was isolated by screening for proteins that enhance neurite outgrowth in perinatal rat brain neurons. In the present study we have investigated the possible role of HB-GAM in cell proliferation in the developing rat limb. Exogenously added recombinant HB-GAM was found to inhibit the proliferation of mesenchymal and epithelial cells in cultured limb buds, as demonstrated by bromodeoxyuridine incorporation and by staining for PCNA (proliferating cell nuclear antigen). The inhibitory effect of HB-GAM on cell proliferation was reversed by heparin, suggesting that HB-GAM may bind to a heparin-type carbohydrate epitope that is required for cell proliferation in the developing limb. Endogenous HB-GAM of the developing limb was found to be expressed in a proximal-to-distal pattern, in agreement with the putative role in proliferation arrest and cell differentiation. In addition, double immunostaining of HB-GAM with PCNA showed that in early (Embryonic Day 12) limb mesenchyme HB-GAM was associated mainly with the surface of growth-arrested cells. Furthermore, HB-GAM was associated with the muscle surface, as demonstrated in double immunostaining of HB-GAM with desmin and myosin heavy chain proteins. Coinciding with the onset of synapse formation (Embryonic Day 16), HB-GAM was found in patches on the muscle cell surface in close proximity to nicotinic acetylcholine receptor clusters. This finding is in agreement with a previous study that has suggested a role for HB-GAM in the differentiation of the neuromuscular junction in Xenopus muscle
Tosca:ADrosophilaGene Encoding a Nuclease Specifically Expressed in the Female Germline

AbstractWe describe here aDrosophilagene,tosca(tos), that is specifically expressed in the female germline.tosmRNA accumulates selectively within the pro-oocyte in germarial region 2 and persists throughout oogenesis. In the early embryo, the maternally suppliedtosmRNA is evenly distributed at the syncytial blastoderm stage, but is excluded from the forming cells when cellularization begins.tosproduct is the firstDrosophilamember of the RAD2 protein family, a group of related DNA repair nucleases conserved from yeast to humans. Within the family, Tos is more closely related to ExoI, aSchizosaccharomyces pombe5′ → 3′ double-stranded DNA exonuclease specifically induced in meiotic prophase I. The definite oocyte localization oftostranscript during meiosis and its ubiquitous distribution in early embryos suggest thattosmay play a role in mismatch repair during genetic recombination and early cleavage divisions
Differential Expression of Cell Adhesion Molecules on Trigeminal Cutaneous and Muscle Afferents

AbstractPrevious work from our laboratory (Woodbury and Scott, 1995) suggested that embryonic cutaneous and muscle afferents might express different surface cell adhesion molecules (CAMs) on their growth cones. To examine this possibility directly we measured the relative levels of expression of various adhesion molecules on growth cones of neurons from the dorsomedial portion of the trigeminal ganglion (DM-TG), which are largely cutaneous, and from the trigeminal mesencephalic nucleus (TMN), which are exclusively muscle afferents. Axonin-1, L1, BEN, and N-cadherin were expressed more abundantly on DM-TG growth cones, whereas N-CAM was more abundant on TMN neurons. Expression of polysialated N-CAM was similar on the two populations; addition of NGF and NT-3 appeared to increase expression of polysialated N-CAM on TMN neurons. Although the levels of L1 and axonin-1, both of which bind L1, were markedly different on TMN and DM-TG neurons, these differences were not sufficient to cause dramatic differences in the growth rates of TMN and DM-TG neurons on L1
Androgen-Induced Proliferation in the Developing Larynx ofXenopus laevisIs Regulated by Thyroid Hormone

AbstractExposure to exogenous androgen regulates cell number in the developing larynx ofXenopus laevisand hormone-regulated laryngeal development requires secretion of thyroid hormone (TH). We sought to determine whether exposure to TH is both sufficient and necessary for androgen-evoked cell proliferation (androgen competency) in developing larynx. Androgen competency was not observed in the premetamorphic larynx (tadpole stage 53, before TH secretion) but was present just prior to metamorphic climax (stage 58, during TH secretion). However, when TH is administered precociously (between stages 48 and 50), androgen competency can be observed at stage 53. The stage 52 larynx expresses high levels of the mRNA for TH receptor α. The duration of TH exposure required at tadpole stage 48 is greater than 2 days; studies in juveniles indicate that TH exposure need not be maintained in order for androgen competency to persist. The effects of exposure to TH on androgen competency are long lasting and perhaps permanent. While organotypic cultures obtained from tadpoles during premetamorphosis (stage 52) can proliferatein vitroand proliferation is augmented by TH exposure as it isin vivo,precocious exposure to TH does not induce androgen competency. In contrast, androgen does evoke cell proliferation in cultures obtained from metamorphosing (stage 58) tadpoles; proliferation is confined to the cartilage component. Thus, unlike laryngesin vivo,muscle will not proliferate in response to androgen, indicating the necessity for an additional factor not presentin vitro.Androgen receptor mRNA expression, believed required for androgen competency, was assessedin vivoandin vitro.The tadpole larynx strongly expresses AR mRNA; expression does not require exposure to TH nor is expression diminished in culture
The Allocation of Epiblast Cells to Ectodermal and Germ-Line Lineages Is Influenced by the Position of the Cells in the Gastrulating Mouse Embryo

AbstractThe developmental potency of cells in the proximal and distal regions of the epiblast of pre- and early-primitive-streak-stage mouse embryos was assessed by their differentiation in the host embryo following orthotopic and heterotopic cell transplantation. Normally, cells in the distal epiblast differentiate predominantly into neuroectoderm and surface ectoderm. However, when they were transplanted to proximal regions of the epiblast, distal epiblast cells behaved like proximal epiblast cells: they colonised the extraembryonic mesoderm and other mesodermal tissues in the posterior region of the host embryo. In addition, about 3.7% of the transplanted distal epiblast cells differentiated into primordial germ cells. This proportion is comparable to the 3.9% of orthotopically transplanted proximal epiblast cells that became primordial germ cells. When proximal epiblast cells were transplanted heterotopically to distal sites, their descendants were generally absent from the extraembryonic mesoderm and the germ cell population of the host embryo. Like cells in the distal epiblast, they mostly colonised the neural plate and surface ectoderm. This plasticity of cell fate suggests that the epiblast cells are not irreversibly allocated to any specific lineages, including the germ line. The adoption of developmental fate that is typical of the cell population at the site of transplantation suggests that the specification of cell lineages is subject to certain site-specific influences in the epiblast. Allocation of cells to the ectodermal and germ cell lineages may be subject to local tissue interactions and the restriction of morphogenetic tissue movement of different epiblast cell populations during gastrulation
Functional Analysis ofDrosophilaand Mammalian Cut Proteins in Flies

AbstractThecutlocus acts as a bimodal switch controlling cell fate in the peripheral nervous system ofDrosophilaand is also required for the development of the wing margin. It encodes a protein, Cut, that contains an atypical homeodomain and three copies of a new motif which can bind DNAin vitro.The human protein CDP and the murine protein Cux have recently been isolated as DNA-binding activities and they are structurally related to Cut. We show that ectopic expression of Cut, CDP, or Cux similarly affects embryonic sensory organ development and can rescue a wing scalloping mutant phenotype associated with loss ofcutexpression along the prospective wing margins. This suggests that the function of Cut is evolutionarily conserved
Early Embryonic Lethality Caused by Targeted Disruption of the Mouse Thioredoxin Gene

AbstractThioredoxins belong to a widely distributed group of small proteins with strong reducing activities mediated by a consensus redox-active dithiol (Cys-Gly-Pro-Cys). Thioredoxin was first isolated as a hydrogen donor for enzymatic synthesis of deoxyribonucleotides by ribonucleotide reductase inEscherichia coli.Recent studies have revealed a variety of roles that thioredoxin plays in transcription, growth control, and immune function. In this report, we describe the phenotype of mice carrying a targeted disruption of the thioredoxin gene (Txn). Heterozygotes are viable, fertile, and appear normal. In contrast, homozygous mutants die shortly after implantation, and the concepti were resorbed prior to gastrulation. When preimplantation embryos were placed in culture, the inner cell mass cells of the homozygous embryos failed to proliferate. These results indicate thatTxnexpression is essential for early differentiation and morphogenesis of the mouse embryo
Inhibition of Protein Kinase A Phenocopies Ectopic Expression ofhedgehogin the CNS of Wild-Type andcyclopsMutant Embryos

AbstractThe zebrafishhedgehog(hh) family memberstiggy-winkle hedgehog(twhh) andsonic hedgehog(shh) are involved in patterning the ventral CNS and proximal eye. Using a dominant negative protein kinase A regulatory subunit mutant, we show that these hh activities are mediated by protein kinase A. The effects of dominant negative protein kinase A onpax2expression appear to be cell nonautonomous, suggesting that cells can respond to regulation of hh signaling by modulating an additional cell–cell signaling pathway. We also investigate the potential involvement ofcyclopsin the hh signaling pathway and conclude that althoughcyclopsmutant cells can respond to hh signaling, neither hh nor dominant negative protein kinase A rescues the phenotypes associated withcyclops
Virally Mediated Misexpression of Hoxc-6 in the Cervical Mesoderm Results in Spinal Nerve Truncations

AbstractMembers of theHoxgene family appear to regulate anterior–posterior (A–P) regionalization in embryos. Genetic manipulation of numerousHoxgenes in the developing trunk region of vertebrates results in changes in the morphology of individual vertebrae. We have used virally mediated, targeted misexpression to ectopically express the Hoxc-6 protein in chick embryos.Hoxc-6has an anterior border of expression at the cervical–thoracic transition in tetrapods. Misexpression of this gene in the cervical mesoderm of chick embryos results in dramatic truncations of the ventral rami of cervical spinal nerves in the infected region. These data point to a role forHoxc-6in axon guidance, and suggest that in addition to regulating proliferative rates,Hoxgene expression provides positional information utilized in producing domain-specific extracellular signals
Combined BMP-2 and FGF-4, but Neither Factor Alone, Induces Cardiogenesis in Non-Precardiac Embryonic Mesoderm

AbstractPrevious work in this laboratory has shown that endoderm cells in the heart forming region (HFR endoderm) of the chicken embryo induce terminal cardiac differentiation in explanted precardiac mesoderm cells. Immunostaining patterns indicating that HFR endoderm cells expressDrosophiladecapentaplegic (dpp)-like antigens prompted a degenerate polymerase chain reaction (PCR) screen to identify cDNAs in the dpp subgroup of the transforming growth factor-β (TGF-β) family. Among 50 clones of PCR products that have been sequenced, over half have identity with bone morphogenetic protein-2 (BMP-2). No other TGF-β cDNAs have been detected, suggesting that BMP-2 is the major dpp subgroup protein synthesized by HFR endoderm cells. However, BMP-2 protein did not promote survival of either precardiac or non-precardiac mesoderm cells in culture. Whereas FGF-4 supports cardiogenesis in precardiac mesoderm, it did not induce cardiogenesis in non-precardiac mesoderm, although explant viability was maintained. In contrast to the isolated effects of these growth factors, treatment of non-precardiac mesoderm with combined BMP-2 and FGF-4 induced cardiogenesis in the majority of explants, as revealed by the formation of a rhythmically contractile multicellular vesicle that expresses sarcomeric α-actin. These findings suggest that BMP-2 and FGF-4 possess respective differentiative and proliferative activities, the combination of which specifies cells to the cardiac lineage
NK-2Homeobox Genes and Heart Development

AbstractAnalysis of the phylogenetically ancientNK-2class of homeobox genes has opened up an entirely new approach to molecular, genetic, and biochemical analysis of early heart development. TheDrosophila NK-2homeobox genetinmanplays an essential role in segregating cardiac and visceral muscle potentiality, as well as that of some somatic muscles, in nascent mesoderm of the fly embryo. In its absence, precursor cells for these muscles do not form.tinmanhomologues have now been isolated from vertebrate genomes and at least one of them,Nkx2-5,is expressed in heart progenitor cells and is essential for myogenic and morphogenetic differentiation of the mammalian heart. Signaling pathways that establish thetinexpression domain also appear to be conserved in vertebrates. These findings suggest that heart development in flies and vertebrates utilize similar genetic pathways and engender optimism that the dissection of mammalian heart development will profoundly profit from the rich genetics ofDrosophila.The findings also prompt the questions: are the hearts of vertebrates and invertebrates actually homologous, and how much can we learn from the comparative approach? In the sections below, the structure, regulation, function, and evolution ofNKclass homeobox genes will be reviewed, emphasizing and contrasting the roles oftinmanandNkx2-5in heart development
A Comparison of Sperm- and IP3-Induced Ca2+Release in Activated and Aging Mouse Oocytes

AbstractCa2+release mechanisms in oocytes are highly sensitive and a number of agents including sperm and inositol trisphosphate (IP3) generate Ca2+transients. Recently it was shown that this sensitivity decreases after fertilization and subsequent entry into the first mitotic cell cycle (Joneset al., Development121, 3259–3266, 1995). In this study a similar decrease in the ability of IP3to cause repetitive Ca2+transients was observed in parthenogenetic embryos following activation with Sr2+, ethanol, or cycloheximide. This indicates that the decline in sensitivity of the Ca2+releasing mechanism after oocyte activation is not associated with the fertilizing sperm. A similar decline in IP3-induced Ca2+release was observed in metaphase II oocytes at 24 hr post hCG or later, although repetitive Ca2+transients were induced in the aged oocytes afterin vitrofertilization. Sperm-induced Ca2+transients in aged oocytes were similar in duration and peak amplitude to younger oocytes, 15–18 hr post hCG. However, they showed a much reduced rate of rise which was also observed in younger oocytes after the intracellular stores had been depleted by thapsigargin. The results suggest that factors within the oocyte, such as store size, are important in enabling sperm to generate repetitive Ca2+transients. Also, the Ca2+release processes decline as the oocyte ages as well as after activation
Micromere Formation at Third Cleavage Is Decisive for Trochoblast Specification in the Embryogenesis ofPatella vulgata

AbstractTrochoblasts of the molluscPatella vulgatadifferentiate early in development into ciliated cells due to a cell intrinsic developmental capacity. The third cleavage appears to be decisive for their specification. Permanent inhibition of cleavage after the third cleavage, as induced by a continuous incubation with the drug Cytochalasin B, had no effect on trochoblast-specific gene expression later in development. However, permanent inhibition of cleavage before third cleavage abolished trochoblast differentiation including trochoblast-specific gene expression. Inhibition of just the third cleavage itself was sufficient to repress trochoblast-specific gene expression. In contrast, inhibiting the second or fourth cleavage did not effect trochoblast-specific gene expression. Correct formation of micromeres at the third cleavage is required to obtain trochoblast-specific gene expression as was shown in experiments in which the formation of micromeres during third cleavage was suppressed by pressure. In addition, centrifugation before or during the third cleavage disturbs trochoblast-specific gene expression, whereas centrifugation after the third cleavage does not affect trochoblast-specific gene expression. Thus, during the third cleavage a decisive step in the determination of developmental fate of trochoblasts takes place, likely resulting in a segregation of activating and inhibitory determinants. Trochoblast-specific markers inPatellawere only expressed in embryos that were division arrested after third cleavage. This suggests that a segregation of differentiation potentials has to take place before trochoblast differentiation markers are expressed. The restriction of differentiation potentials in the cleaving stage embryo is thus required to enable trochoblast-specific gene expression
Reduction of the Current of Injury Leaving the Amputation Inhibits Limb Regeneration in the Red Spotted Newt

AbstractImmediately following amputation of the limb in salamanders, a strong, steady, and polarized flow of ionic current is produced by the injury. Current flows in a proximodistal direction within the limb stump and is associated with a fall in electrical potential of about 50 mV/mm near the stump's end. This current is electrogenically driven by the Na+-dependent, internally positive transcutaneous voltage of the intact skin of the limb stump. Reduction of this EMF, the skin's battery, by topical application of Na+blocking agents leads to inhibition or disruption of normal limb regeneration. This suggests electrical factors are a critical control of limb regeneration. Here we test another means to reduce the injury current and its associated electrical field within the forelimb stump of red spotted newts. A fine (40 gauge), insulated, multistrand wire was inserted beneath the skin of the animal's back, with the uninsulated portion terminating either at the shoulder region or at the base of the tail. When this cathodal (negative) electrode is connected to a regulated current source, sufficient current was pulled into the stump end from an external anode (placed in the water the animal was immersed in) to markedly reduce or null the endogenous current for the first 8 days following amputation. The extent of limb regeneration in sham-treated and experimentally treated animals was determined 1 month following amputation at the elbow. Sham-treated animals regenerated normally, with most producing digits within this time. Limb regeneration was completely arrested, or caused to be strikingly hypomorphic, in half of the experimentally treated animals. This effect was independent of where the subcutaneous electrode was placed and suggests that electrical (physiological) factors are indeed a critical control of limb regeneration in urodeles