pinecone/core-2020-05-10-deduplication huggingface dataset:
TwocisElements Collaborate to Spatially Repress Transcription from a Sea Urchin Promoter

AbstractThe expression pattern of many territory-specific genes in metazoan embryos is maintained by an active process of negative spatial regulation. However, the mechanism of this strategy of gene regulation is not well understood in any system. Here we show that reporter constructs containing regulatory sequence for theSM30-α gene ofStronglyocentrotus purpuratusare expressed in a pattern congruent with that of the endogenousSM30gene(s), largely as a result of active transcriptional repression in cell lineages in which the gene is not normally expressed. Chloramphenicol acetyl transferase assays of deletion constructs from the 2600-bp upstream region showed that repressive elements were present in the region from −1628 to −300.In situhybridization analysis showed that the spatial fidelity of expression was severely compromised when the region from −1628 to −300 was deleted. Two highly repetitive sequence motifs, (G/A/C)CCCCT and (T/C)(T/A/C)CTTTT(T/A/C), are present in the −1628 to −300 region. Representatives of these elements were analyzed by gel mobility shift experiments and were found to interact specifically with proteins in crude nuclear extracts. When oligonucleotides containing either sequence element were co-injected with a correctly regulated reporter as potential competitors, the reporter was expressed in inappropriate cells. When composite oligonucleotides, containing both sequence elements, were fused to a misregulated reporter, the expression of the reporter in inappropriate cells was suppressed. Comparison of composite oligonucleotides with oligonucleotides containing single constituent elements show that both sequence elements are required for effective spatial regulation. Thus, both individual elements are required, but only a composite element containing both elements is sufficient to function as a tissue-specific repressive element
BMP-4 Regulates the Dorsal–Ventral Differences in FGF/MAPKK-Mediated Mesoderm Induction inXenopus

AbstractRecent studies onXenopusdevelopment have revealed an increasingly complex array of inductive, prepatterning, and competence signals that are necessary for proper mesoderm formation. In this study, we establish that fibroblast growth factor (FGF) signals through mitogen-activated protein kinase kinase (MAPKK) to induce mesodermal gene expression. We demonstrate that a partially activated form of MAPKK restores expression of the mesodermal genesXcad-3andXbra,eliminated by the dominant-negative FGF receptor (ΔFGFR). Similar to the results reported earlier with ΔFGFR, expression of a dominant-negative form of MAPKK (MAPKKD) preferentially eliminates the dorsal expression ofXcad-3andXbra.We tested whether the regional localization of bone morphogenetic protein-4 (BMP-4) could explain why both MAPKKD and ΔFGFR eliminate the dorsal and not the ventral expression ofXcad-3andXbra.We show that ectopic expression of BMP-4 is sufficient to maintain the dorsal expression ofXcad-3andXbrain embryos containing ΔFGFR and that expression of a dominant-negative BMP receptor reduces the dorsal–ventral differences in ΔFGFR embryos. These results indicate that regional localization of BMP-4 is responsible for the dorsal–ventral asymmetry in FGF/MAPKK-mediated mesoderm induction
Developmental Regulation of Genomic Imprinting during Gametogenesis

AbstractSuccessful mammalian development requires both the male and female genomes. This is due in part to genomic imprinting, which results in offspring inheriting only one functional copy of a gene from either the mother or the father. Evidence suggests that this specialization of the parental genomes is established during gametogenesis when the imprint pattern inherited from the parent is switched to reflect the sex of the progeny. We used reverse transcription–PCR to analyze the allele-specific expression ofIgf-2, Igf-2r,andH19in the testes and ovaries of mice derived from an interspecies cross betweenMus musculusandMus spretus.Because of genomic imprinting,Igf-2is expressed only from the paternal allele andIgf-2randH19only from the maternal allele, in most tissues. Although allele-specific expression was maintained in the neonatal testis and ovary, relaxation of imprinting was detected by 7 days after birth in the male and continued during testis development. In the female, relaxation of theIgf-2andIgf-2rparental imprints was observed in the adult ovary and oocyte. These results (1) indicate that imprinted expression is relaxed during gametogenesis, presumably as a consequence or prerequisite of the imprinting mechanism, and (2) predict a subsequent imprinting event after which the allele-specific expression ofIgf-2, Igf-2r,andH19reflects the parent of origin
Dermo-1: A Novel Twist-Related bHLH Protein Expressed in the Developing Dermis

AbstractTranscription factors belonging to the basic helix–loop–helix (bHLH) family have been shown to control differentiation of a variety of cell types. Tissue-specific bHLH proteins dimerize preferentially with ubiquitous bHLH proteins to form heterodimers that bind the E-box consensus sequence (CANNTG) in the control regions of target genes. Using the yeast two-hybrid system to screen for tissue-specific bHLH proteins, which dimerize with the ubiquitous bHLH protein E12, we cloned a novel bHLH protein, named Dermo-1. Within its bHLH region, Dermo-1 shares extensive homology with members of the twist family of bHLH proteins, which are expressed in embryonic mesoderm. During mouse embryogenesis, Dermo-1 showed an expression pattern similar to, but distinct from, that of mouse twist. Dermo-1 was expressed at a low level in the sclerotome and dermatome of the somites, and in the limb buds at Day 10.5 post coitum (p.c.), and accumulated predominantly in the dermatome, prevertebrae, and the derivatives of the branchial arches by Day 13.5 p.c. As differentiation of prechondrial cells proceeded, Dermo-1 expression became restricted to the perichondrium. Expression of Dermo-1 increased continuously in the dermis through Day 17.5 p.c. and was also detected in the dermis of neonates, but became downregulated in adult tissues. The Dermo-1 protein bound the E-box consensus sequence in the presence of E12, but transcriptional activity was not detectable. Instead, Dermo-1 repressed transcriptional activity of myogenic bHLH proteins. The expression pattern of Dermo-1 suggests that it functions as a regulator of gene expression in a subset of mesenchymal cell lineages including developing dermis
Progression and Recapitulation of the Chondrocyte Differentiation Program: Cartilage Matrix Protein Is a Marker for Cartilage Maturation

AbstractDuring endochondral bone formation, chondrocytes in the cartilaginous anlage of long bones progress through a spatially and temporally regulated differentiation program before being replaced by bone. To understand this process, we have characterized the differentiation program and analyzed the relationship between chondrocytes and their extracellular environment in the regulation of the program. Our results indicate that, within an epiphyseal growth plate, the zone of proliferating chondrocytes is not contiguous with the zone of hypertrophic chondrocytes identified by the transcription of the type X collagen gene. We find that the postproliferative chondrocytes which make up the zone between the zones of proliferation and hypertrophy specifically transcribe the gene for cartilage matrix protein (CMP). This zone has been termed the zone of maturation. The identification of this unique population of chondrocytes demonstrates that the chondrocyte differentiation program consists of at least three stages. CMP translation products are present in the matrix surrounding the nonproliferative chondrocytes of both the zones of maturation and hypertrophy. Thus, CMP is a marker for postmitotic chondrocytes. As a result of the changes in gene expression during the differentiation program, chondrocytes in each zone reside in an extracellular matrix with a unique macromolecular composition. Chondrocytes in primary cell culture can proceed through the same differentiation program as they do in the cartilaginous rudiments. In culture, a wave of differentiation begins in the center of a colony and spreads to its periphery. The cessation of proliferation coincides with the appearance of CMP and eventually the cells undergo hypertrophy and synthesize type X collagen. These results reveal distinct switches at the proliferative–maturation transition and at the maturation–hypertrophy transition during chondrocyte differentiation and indicate that chondrocytes synthesize new matrix molecules and thus modify their preexisting microenvironment as differentiation progresses. However, when “terminally” differentiated hypertrophic chondrocytes are released from their surrounding environment and incubated in pellet culture, they stop type X collagen synthesis, resume proliferation, and reinitiate aggrecan synthesis. Eventually they cease proliferation and reinitiate CMP synthesis and finally type X collagen. Thus they are capable of recapitulating all three stages of the differentiation programin vitro.The data suggest a high degree of plasticity in the chondrocyte differentiation program and demonstrate that the progression and maintenance of this program is regulated, at least in part, by the extracellular environment which surrounds a differentiating chondrocyte during endochondral bone formation
Apoptosis in the Neuronal Lineage of the Mouse Olfactory Epithelium: Regulationin Vivoandin Vitro

AbstractThe olfactory epithelium (OE) of the mouse provides a unique system for understanding how cell birth and cell death interact to regulate neuron number during development and regeneration. We have examined cell death in the OE in normal adult mice; in adult mice subjected to unilateral olfactory bulbectomy (surgical removal of one olfactory bulb, the synaptic target of olfactory receptor neurons (ORNs) of the OE); and in primary cell cultures derived from embryonic mouse OE.In vivo,cells at all stages in the neuronal lineage—proliferating neuronal precursors, immature ORNs, and mature ORNs—displayed signs of apoptotic cell death; nonneuronal cells did not. Bulbectomy dramatically increased the number of apoptotic cells in the OE on the bulbectomized side. Shortly following bulbectomy, increased cell death involved neuronal cells of all stages. Later, cell death remained persistently elevated, but this was due to increased apoptosis by mature ORNs alone.In vitro,apoptotic death of both ORNs and their precursors could be inhibited by agents that prevent apoptosis in other cells: aurintricarboxylic acid (ATA), a membrane-permeant analog of cyclic AMP (CPT-cAMP), and certain members of the neurotrophin family of growth factors (brain-derived neurotrophic factor, neurotrophin 3, and neurotrophin 5), although no neurotrophin was as effective at promoting survival as ATA or CPT-cAMP. Consistent with observed effects of neurotrophins, immunohistochemistry localized the neurotrophin receptors trkB and trkC to fractions of ORNs scattered throughout neonatal OE. These results suggest that apoptosis may regulate neuronal number in the OE at multiple stages in the neuronal lineage and that multiple factors—potentially including certain neurotrophins—may be involved in this process
Genetic Analysis of Developmental Mechanisms in Hydra. XXII. Two Types of Female Germ Stem Cells Are Present in a Male Strain ofHydra magnipapillata

AbstractThree types of interstitial stem cell subpopulation were isolated fromHydra magnipapillata,and their roles in sex determination were examined. A subpopulation of interstitial stem cells restricted to the sperm differentiation pathway was isolated previously from strain nem-1 (male). Another subpopulation restricted to the egg differentiation pathway was also isolated from the same strain. Hydroxyurea treatment was used for isolation in both cases. “Pseudoepithelial hydra” containing only sperm- or egg-restricted stem cell but no other interstitial stem cell types were maintained by force-feeding for 2 years. Sex reversal from egg- to sperm-restricted stem cells occurred three times during this period. Both of these two stem cell types are numerous in the central gastric region of the pseudoepithelial hydra, but absent in the foot region below the budding zone. Foot tissue was cut out from normal nem-1 polyps (male) and allowed to regenerate. The regenerates produced eggs but no sperm upon sex induction. These and other results suggest that the foot tissue contains multipotent stem cells capable of differentiating into eggs during sexual differentiation. These observations suggest that strain nem-1 (male) contains three types of interstitial stem cell subpopulations: (1) sperm-restricted stem cells, (2) egg-restricted stem cells, and (3) multipotent stem cells capable of differentiating into nerve cells, nematocytes, and eggs. Upon sex induction, however, differentiation of eggs by the latter two types is suppressed, and only sperm are produced by the sperm-restricted stem cells. Evidence is presented which suggests that similar “phenotypic males,” which normally only produce sperm but contain the stem cell types capable of differentiating into eggs, occur widely inHydra magnipapillata.A possible relationship between phenotypic male hydra and hermaphroditic hydra is discussed
Specification of the Anteroposterior Neural Axis through Synergistic Interaction of the Wnt Signaling Cascade withnogginandfollistatin

AbstractEmbryological data and the activities of the neural-inducing factorsnogginandfollistatinare consistent with the hypothesis that the nervous system is initially induced with an anterior character, with subsequent signals imparting posterior pattern. We report thatXwnt3ais a candidate for involvement in anteroposterior neural patterning, as it synergizes with the neural-inducing factorsnogginandfollistatinto increase the expression of posterior neural genes. Furthermore we show that β-catenin, an intracellular protein implicated in the Wnt signal transduction cascade, mimics the activity ofXwnt3a.These data suggest that the generation of pattern within the vertebrate nervous system may rely on synergism between a Wnt signaling pathway and multiple neural-inducing factors
Fetal Brain Subdivisions Defined by R- and E-Cadherin Expressions: Evidence for the Role of Cadherin Activity in Region-Specific, Cell–Cell Adhesion

AbstractWe found that R-cadherin, a Ca2+-dependent cell–cell adhesion molecule, is expressed in restricted regions of the mouse fetal brain, as was found for E-cadherin previously. R-cadherin delineated a subset of alar domains within forebrain neuromeres and certain future nuclei, while E-cadherin was expressed in another distinctive pattern. When cells were collected from various local regions of the fetal brain, dissociated, and reaggregated under the conditions in which only cadherins are active for cell aggregation, R-cadherin-positive and -negative cells segregated from one another. Similar results were obtained for E-cadherin. Such segregation of cells was, however, suppressed when the cadherins were inactivated either by Ca2+depletion or with blocking antibodies. These results suggest that cadherins confer region-specific adhesiveness on fetal brain cells and that this process may take part in brain segmentation
Sequence and Expression of Grasshopper Antennapedia: Comparison toDrosophila

AbstractWe have cloned and characterized theAntennapedia(Antp) gene from the grasshopperSchistocerca americana.The Antennapedia protein contains seven blocks of sequence, including the homeodomain, that are conserved in the homologous proteins of other insects, interspersed with (usually repetitive) sequences unique to each species. There is no similarity between 1.8 kb of 3′ untranslated sequence in grasshopper andDrosophila.We examined Antennapedia protein expression in grasshopper using an antibody raised against a grasshopper fusion protein and reexamined its expression inDrosophilausing several different antibodies. Early patterns of expression in the two insects are quite different, reflecting differing modes of early development. However, by the germband stage, expression patterns are quite similar, with relatively uniform epithelial expression throughout the thoracic and abdominal segments which later retracts to the thorax. Expression is observed in muscle pioneers, the peripheral nervous system, and the central nervous system (CNS). In the CNS expression is initially limited to a few neurons, but eventually becomes widespread. Both insects show strong expression in certain homologous identified neurons and similar temporal modulation of expression
HairlessPromotes Stable Commitment to the Sensory Organ Precursor Cell Fate by Negatively Regulating the Activity of theNotchSignaling Pathway

AbstractInDrosophilaimaginal discs, the function of theHairless(H) gene is required at multiple steps during the development of adult sensory organs. Here we report the results of a series of experiments designed to investigate thein vivorole ofHin sensory organ precursor (SOP) cell specification. We show that the proneural cluster pattern of proneural gene expression and of transcriptional activation by proneural proteins is established normally in the absence ofHactivity. By contrast, single cells with the high levels ofachaete, scabrous,andneuralizedexpression characteristic of SOPs almost always fail to appear inHmutant proneural clusters. These results indicate thatHis required for a relatively late step in the development of the proneural cluster, namely, the stable commitment of a single cell to the SOP cell fate. We also show that expression of an activated form of the Notch receptor leads to bristle loss with the same cellular basis—failure of SOP determination—as loss ofHfunction and that simultaneous overexpression ofHsuppresses this effect. Finally, we demonstrate by epistasis experiments that the failure of stable commitment to the SOP fate inHnull mutants requires the activity of the genes of theEnhancer of splitcomplex, includinggroucho.Our results indicate thatHpromotes SOP determination by antagonizing the activity of theNotchpathway in this cell, thereby protecting it from inhibitory signaling by its neighbors in the proneural cluster. We propose a simple threshold model in which the principal role ofHin SOP specification is to translate a quantitative difference in the activity of theNotchpathway (in the SOP versus the non-SOP cells) into a stable binary cell fate decision
Neuronal Production of Fibronectin in the Cerebral Cortex during Migration and Layer Formation Is Unique to Specific Cortical Domains

AbstractThe distribution of fibronectin (FN) changes rapidly during early development of the cerebral cortex, but its cellular source is not known. Within situhybridization we find two spatially and temporally distinct periods of FN mRNA expression in the embryonic and early postnatal cortex of the mouse. Before and during formation of the preplate by the first postmitotic neurons, FN mRNA levels are high throughout the telencephalic vesicle, deep in the neuroepithelial proliferative zone that contains dividing cells and the cell bodies of radial glia; expression in the cortical proliferative zone is limited to the period of neurogenesis. Just after the cortical plate is formed within the preplate, FN mRNA is expressed in the intermediate zone, which contains migrating neurons, and in the cortical plate, where neurons migrate past their predecessors to form layers. Brefeldin A treatment of an organotypic slice preparation demonstrates FN production in the intermediate zone and cortical plate, in locations that correspond exactly to the distribution of FN mRNA byin situhybridization. FN-producing cells immunolabel with neuron-specific markers; in the intermediate zone and lower cortical plate they have morphological features characteristic of migrating neurons and are closely apposed to radial glia. FN mRNA expression and protein production continue in neurons of the cortical plate through the period of layer formation and then are down-regulated. Examination of dissociated cortical cells by laser confocal microscopy confirms that FN accumulation after brefeldin A treatment is intracellular in neurons as well as in glia. Neuroepithelial expression of FN mRNA takes place throughout the telencephalon; FN produced by neurons is restricted to cells migrating toward and into specific cortical domains that include neocortex, insular and perirhinal cortex, and subiculum. Thus FN may be involved initially in supporting the cell division and fate determination that takes place in the neuroepithelium; later production by migrating neurons may play a role in the selection of radial glial pathways that lead to specific cortical regions, and in interactions between neurons as they form cortical layers within these regions
Dorsal and Ventral Cell Types Can Arise from Common Neural Tube Progenitors

AbstractTo challenge the developmental potential of dorsal neural tube cells and test whether single neuroepithelial cells can give rise to the full range of neural tube derivatives, we grafted a notochord lateral to the closing neural folds. This results in juxtaposition of dorsal and ventral cell types, by inducing floor plate cells and motor neurons dorsally. Clonal analysis with the vital dye lysinated rhodamine dextran showed that both “dorsal” and “ventral” neural tube derivatives can arise from a single precursor. Cells as diverse as sensory ganglion cells, presumptive pigment cells, roof plate cells, motor neurons, and floor plate cells were observed in the same clone. The presence of such diversity within single clones indicates that the responses to dorsal and ventral signals are not mutually exclusive; even in the early neural tube, neuroepithelial cells are not restricted to form only dorsal or ventral neural tube derivatives
Polarized Expression of the Receptor Protein Tyrosine Kinase Cek5 in the Developing Avian Visual System

AbstractReceptor protein tyrosine kinases of the Eph subfamily have been proposed to play roles in pattern formation based on their distribution during embryonic development. Cek5 (chicken embryo kinase 5) and Cek8 (chicken embryo kinase 8) are Eph-related kinases highly expressed in the chicken embryonic retina. To assess their potential roles in the development of the visual pathway, we examined their distribution by immunoperoxidase labeling. Cek8 is expressed throughout the pathway of the retinal ganglion cell axons, including the nerve fiber layer of the retina, optic nerve, optic chiasm, and stratum opticum of the tectum. Cek5 immunoreactivity is highly concentrated in only a portion of the optic nerve and optic chiasm, and in retinal cultures, Cek5 is detected in neurons. This prompted us to examine the regional distribution of Cek5 in the developing retina and led to the observation that Cek5 is most concentrated in the ventral aspect. RT-PCR established that the differential regulation of Cek5 expression in different portions of the retina occurs at the transcriptional level. Immunoblotting analysis revealed that this unusual expression pattern is distinctive for Cek5, as three other mem- bers of the Eph subfamily, Cek4, Cek8, and Cek9, are evenly expressed across the dorsal–ventral axis of the retina. Both Cek5 and Cek8 are distributed in manners which are consistent with their regulating the outgrowth of retinal gan- glion cell axons to the tectum. Furthermore, Cek5 represents the first signal transduction molecule found to exhibit the polarized pattern of expression predicted for proteins that control the specificity of the retinotectal projections