pinecone/core-2020-05-10-deduplication huggingface dataset:
Precocious Expression of the Wilms' Tumor GenexWT1Inhibits Embryonic Kidney Development inXenopus laevis

AbstractThe tumor suppressor WT1 has been demonstrated to have a wide variety of activitiesin vitroand is required for metanephric developmentin vivo.In the experiments presented here, theXenopuspronephros was used as a simple model system to examine the activity ofXenopus WT1(xWT1) during kidney development.xWT1was ectopically expressed inXenopusembryos by mRNA injection and found to inhibit pronephric tubule development. Confocal microscopy confirmed this observation and revealed that the inhibition was the result of a failure to form a pronephric anlage of appropriate size rather than a defect in epithelialization. Examination ofXlim-1expression, an early molecular marker of pronephric specification, in tailbud embryos indicated that injectedxWT1mRNA inhibited pronephric specification prior to any overt sign of morphogenesis (Xenopusstage 21). These results suggest that xWT1 may act to repress tubule-specific gene expression in the portion of the pronephros fated to form its vascular structure, the glomus
Distinct Roles of Oncostatin M and Leukemia Inhibitory Factor in the Development of Primordial Germ Cells and Sertoli Cells in Mice

AbstractLeukemia inhibitory factor (LIF) stimulates the growth of primordial germ cells (PGCs) in mouse embryo. However, as neither mice lacking LIF nor mice lacking the LIF receptor show defects in PGC growth, an alternate cytokine for PGC growth has been postulated. We investigated the role of mouse oncostatin M (mOSM), which is structurally and functionally related to LIF, in germ cell development. While LIF enhanced the survival of migratory as well as postmigratory PGCs, mOSM acted only on the postmigratory PGCs. Consistent with its biological activity, mOSM was found to be expressed in developing gonads. In the male, Sertoli cells in neonatal testis express mOSM; however, its expression is downregulated in adult testes. Moreover, mOSM enhanced the proliferation of Sertoli cells derived from neonatal testesin vitromore than human OSM or LIF. In contrast, postnatal ovaries do not express mOSM. These results indicate that mOSM is a stage- and sex-specific autocrine growth factor for Sertoli cells
Partial Rescue of GATA-3 by Yeast Artificial Chromosome Transgenes

AbstractGATA-3 is essential for murine embryonic development, but elucidating the genetic controls over the complex temporal and tissue-specific transcriptional regulatory pattern of this transcription factor gene has been problematic. Here we report the isolation and characterization of two yeast artificial chromosomes (YACs) bearing the murine GATA-3 gene. Ordered deletions of both YACs show that they define a 1-megabase pair contig spanning the GATA-3 locus. We found that a 120-kb YAC transgene, including 35 kb of 5′ as well as 60 kb of 3′ flanking sequence, confers normal GATA-3 expression at sites not revealed previously through analysis of plasmid transgenic lines. However, even this 120-kb YAC does not contain sufficient information to recapitulate the complete GATA-3 expression program during embryogenesis. While not complete in its regulatory capacity, the YAC transgene is nonetheless able to complement several homozygous GATA-3 mutant phenotypes and thereby prolong embryonic life
Analysis of Epithelial–Mesenchymal Interactions in the Initial Morphogenesis of the Mammalian Tooth

AbstractEpithelial–mesenchymal interactions govern the development of epidermal organs such as teeth. During the early stages of tooth development, a local ectodermal thickening which expresses several signaling molecules appears. It is believed that these in turn signal to the underlying mesenchyme triggering mesenchymal condensation and tooth development. For example, epithelially expressed Bmp4 inducesMsx1andLef1as well as itself in the underlying mesenchyme. In this paper we have investigated the role of four epithelial signaling molecules, Bmp2, Shh, Wnt10a, and Wnt10b, in the early inductive cascades that govern tooth development. We show that all four genes are specifically expressed in the epithelium between E11.0 and E12.0 when tooth morphogenesis is first apparent. Although Shh, Bmp2, and Wnt10b have similar, if not identical, expression patterns, each signal has a distinct molecular action on the jaw mesenchyme. Whereas Shh and Wnt10b can induce general Hedgehog and Wnt targets,PtcandGlifor Shh andLef1for Wnt10b, only Bmp2 is able to induce tooth-specific expression ofMsx1. Thus, there are distinct targets for all three pathways. Interestingly, both Bmp and Wnt signaling activateLef1, making it a candidate for integrating the two distinct signaling pathways
Temporal Restriction of MyoD Induction and Autocatalysis duringXenopusMesoderm Formation

AbstractInXenopus,the activation of the myogenic determination factors MyoD and Myf-5 in the muscle-forming region of the embryo occurs in response to mesoderm-inducing factors (MIFs). Different members of the FGF, TGF-β, and Wnt protein families have been implicated in this process, but how MIFs induce the myogenic regulators is not known. For MyoD, the induction process may serve to locally stabilize a transient burst of ubiquitous transcription at the midblastula transition, possibly by triggering MyoD's autocatalytic loop. Here we have sought to distinguish separate activating functions during MyoD induction by analyzing when MyoD responds to different MIF signaling or to MyoD autoactivation. We show that MyoD induction depends on the developmental age of the induced cells, rather than on the type or time point of inducer application. At the permissive time,de novoMyoD induction by Activin requires less than 90 min, arguing for an immediate response, rather than a series of inductive events. MyoD autoactivation is direct, but subject to the same temporal restriction as MyoD induction by MIF signaling. Further evidence implicating MyoD autocatalysis as an essential component of the induction process comes from the observation that both autocatalysis and induction of MyoD are selectively repressed by a dominant-negative MyoD mutant. In summary, our observations let us conclude that MyoD's expression domain in the embryo results from an interplay of timed changes in cellular competence, pleiotropic signaling pathways, and autocatalysis
Expression of DjY1, a Protein Containing a Cold Shock Domain and RG Repeat Motifs, Is Targeted to Sites of Regeneration in Planarians

AbstractPlanarians are well-known for their exceptional regenerative abilities. This investigation focuses on the involvement of a Y-box protein, defined by the presence of a cold-shock domain, in regeneration-specific processes. Previous studies have shown that developmentally expressed Y-box proteins bind to mRNA molecules and regulate the timing of their translation. We have isolated and characterized a planarian Y-box gene, DjY1, which is specifically expressed at the site of regeneration, the blastema. DjY1 transcripts appear rapidly at the site of cutting and increase in number as the blastema grows. The timing and level of expression is similar irrespective of the orientation of the cut: in anterior, posterior, and lateral regenerative tissue. As regeneration nears completion, there is a general decrease in transcript level except in structures which are still differentiating, specifically in the auricles where new DjY1 transcripts are produced. A similarly modulated temporal pattern of expression throughout regeneration is seen in assaying the DjY1 protein. Within the population of blastemal cells, a subset of differentiating cells is specifically immunostained using antibodies to DjY1. The DjY1 protein contains a cold-shock domain and RG-repeat motifs, both of which are associated with RNA-binding properties:in vitrobinding studies using recombinant DjY1 show that the preferred template is single-stranded RNA of heterogeneous sequence. These data provide the first direct evidence that a Y-box protein is involved in the regeneration process in planarians and implicate DjY1 in the translational regulation of differentiation-specific mRNAs
A Novel Alternative Spliced Variant of the Transcription Factor AP2α Is Expressed in the Murine Ocular Lens

AbstractThe AP2α gene encodes a transcription factor containing a basic, helix–span–helix DNA-binding/dimerization domain, which is developmentally regulated and retinoic acid inducible. Recent reports about AP2α null mice indicate that AP2α plays an important role in embryogenesis, especially in craniofacial development and midline fusion. Ocular development is also affected in these null mice. As AP2α may be involved in transcriptional regulation in the lens, it was important to examine the expression of the AP2α gene in the lens. Four AP2α mRNA variants have been previously isolated from whole mouse embryos. Variants 1, 3, and 4 are transcriptional activators that are transcribed from different promoters and variant 2 is a repressor lacking the activation domain encoded by exon 2. Usingin situ-PCR, we found that AP2α is expressed in the lens epithelia but not in the lens fibers. RT-PCR analysis of lens mRNA with amplimers specific for each variant revealed that AP2α variants 1, 2, and 3 are expressed in newborn mouse lenses. However, variant 4 is not expressed in the lens. In this report we characterized a novel isoform, which we named variant 5, expressed in the lens and kidney. Variant 5, which is generated by alternative splicing, may function as a repressor due to the partial deletion of the proline-rich transactivation domain encoded by exon 2. This is the first molecular characterization of AP2α gene expression in the lens. Our results indicate that two activator and two repressor AP2α isoforms may play a role in regulating gene expression in the lens
Dredd,a Novel Effector of the Apoptosis ActivatorsReaper, Grim,andHidinDrosophila

AbstractCaspases are widely conserved proteases considered to be essential effectors of apoptosis. We identified a novelDrosophilagene,dredd,which shares extensive homology to all members of the caspase gene family. Cells specified for programmed death in development exhibit a striking accumulation ofdreddRNA that requires signaling by the death activators REAPER, GRIM, and HID. Furthermore, directed misexpression of each activator was sufficient to drive ectopic accumulation ofdreddRNA. Heterozygosity at thedreddlocus suppressed apoptosis in transgenic models ofreaper- andgrim-induced cell killing, demonstrating that levels ofdreddproduct can modulate signaling triggered by these death activators. Finally, expression of REAPER, GRIM, and HID was found to trigger processing of DREDD protein precursor through a mechanism that is insensitive to, and upstream of, known caspase inhibitors. Taken together, these observations establish mechanistic connections between activators of apoptosis and a new downstream death effector inDrosophila
Loss of β1Integrin Function Results in a Retardation of Myogenic, but an Acceleration of Neuronal, Differentiation of Embryonic Stem Cellsin Vitro

AbstractIntegrin cell surface receptors play an important role for cell adhesion, migration, and differentiation during embryonic development by mediating cell–cell and cell–matrix interactions. Less is known about the function of integrins during commitment and lineage determination of early embryogenesis. Homozygous inactivation of the β1integrin gene results in embryonal death in mice around the time of implantation.In vitro,differentiation of embryonic stem (ES) cells which lack β1integrin (β1−/−) into the cardiogenic lineage is delayed and results in a disordered cellular specification (Fässleret al., J. Cell Sci.109, 2989–2999, 1996). To analyze β1integrin function during myogenesis and neurogenesis we studied differentiation of β1−/−ES cells via embryoid bodies into skeletal muscle and neuronal cellsin vitro.β1−/−cells showed delayed and reduced myogenic differentiation compared to wildtype and heterozygous (β1+/−) ES cells. RT–PCR analysis demonstrated delayed expression of skeletal muscle-specific genes in the absence of β1integrin. Immunofluorescence studies with antibodies against the sarcomeric proteins myosin heavy chain, titin, nebulin, and slow C-protein showed that myotubes formed, but their number was reduced and the assembly of sarcomeric structures was retarded. In contrast, neuronal cells differentiating from β1−/−ES cells appeared earlier than wildtype and heterozygous (β1+/−) ES cells. This was shown by the accelerated expression of neuron-specific genes and an increased number of neuronal cells in β1−/−embryoid bodies. However, neuronal outgrowth was retarded in the absence of β1integrin. No functional difference between wildtype and β1−/−cells was found with respect to secretion of γ-aminobutyric acid, the main neurotransmitter of ES cell-derived neuronal cells. The lineage-specific effects of loss of β1integrin function, that is the inhibition of mesodermal and acceleration of neuroectodermal differentiation, were supported by differential expression of genes encoding lineage-specific transcription factors (Brachyury, Pax-6, Mash1) and signaling molecules (BMP-4 and Wnt-1). Because of the reduced and delayed expression of the BMP-4 encoding gene in β1−/−cells, we analyzed in wildtype and β1−/−cells the regulatory role of exogenously added BMP-4 on the expression of the mesodermal and neuronal marker genes,Brachyuryandwnt-1,respectively. The data suggest that BMP-4 plays a regulatory role during differentiation of wildtype and β1−/−cells by modifying mesodermal and neuronal pathways. The reduced expression of BMP-4 in β1−/−cells may account for the accelerated neuronal differentiation in β1−/−ES cells
Follistatin and Noggin Are Excluded from the Zebrafish Organizer

AbstractThe patterning activity of the Spemann organizer in early amphibian embryos has been characterized by a number of organizer-specific secreted proteins including Chordin, Noggin, and Follistatin, which all share the same inductive properties. They can neuralize ectoderm and dorsalize ventral mesoderm by blocking the ventralizing signals Bmp2 and Bmp4. In the zebrafish, null mutations in thechordingene, namedchordino, lead to a severe reduction of organizer activity, indicating that Chordino is an essential, but not the only, inductive signal generated by the zebrafish organizer. A second gene required for zebrafish organizer function ismercedes, but the molecular nature of its product is not known as yet. To investigate whether and how Follistatin and Noggin are involved in dorsoventral (D-V) patterning of the zebrafish embryo, we have now isolated and characterized their zebrafish homologues. Overexpression studies demonstrate that both proteins have the same dorsalizing properties as theirXenopushomologues. However, unlike theXenopusgenes, zebrafishfollistatinandnogginare not expressed in the organizer region, nor are they linked to themercedesmutation. Expression of both genes starts at midgastrula stages. While no patternednogginexpression was detectable byin situhybridization during gastrulation stages, later expression is confined to presumptive cartilage cells in the branchial arches and the neurocranium and to proximal regions of the pectoral fin buds.follistatintranscripts in gastrulating embryos are confined to anterior paraxial regions, which give rise to head mesoderm and the first five somites. The dorsolateral extent of this expression domain is regulated by Bmp2b, Chordino, and Follistatin itself. In addition, transient expression was observed in a subset of cells in the posterior notochord anlage. Later,follistatinis expressed in brain, eyes, and somites. Comparison of the spatiotemporal expression pattern offollistatinandnogginwith those ofbmp2bandbmp4and overexpression studies suggest that Noggin and Follistatin may function as Bmp antagonists in later processes of zebrafish development, including late phases of D-V patterning, to refine the early pattern set up by the interaction of Chordino and Bmp2/4. It thus appears that many, but not all, aspects of early dorsoventral patterning are shared among different vertebrate species
The MouseTsxGene Is Expressed in Sertoli Cells of the Adult Testis and Transiently in Premeiotic Germ Cells during Puberty

AbstractTsxis a gene of unknown function that was previously shown to be expressed specifically in the testis. In order to gain insight into the function ofTsxits pattern of expression was characterized with regard to both timing and cell type in the testis. Northern blot analysis of early postnatal testes showed not only thatTsxmessage was detectable shortly after birth, but that it increased substantially between 7 and 12 days postpartum (dpp), roughly coincident with the onset of meiosis in the mouse. AlternativeTsxtranscripts, detected by RT-PCR, included a spliced form that first appeared at around 12 dpp.In situhybridization revealedTsxsignal in the somatic Sertoli cells of the adult testis. Consistent with the data from Northern blots,in situhybridization signal was first detectable in normal pubertal testes at 12 dpp. An anti-Tsx polyclonal antiserum specifically stained premeiotic germ cells in addition to Sertoli cells of pubertal testes at 16, 19, and 27 dpp. Tsx immunostaining in germ cells was nuclear, while Sertoli cells displayed signal throughout the cytoplasm and nucleus. In the adult, Tsx was detected exclusively in Sertoli cells. In contrast, in the adult testis of the oligotriche (olt) mutant, where spermatogenesis is blocked after meiosis, Tsx protein was still present in the spermatogonial nuclei of a subset of tubules. Taken together, these results demonstrate thatTsxexpression is induced in both premeiotic germ cells and Sertoli cells during the first wave of spermatogenesis, but that expression is maintained at a detectable level only in Sertoli cells of the normal adult. The persistence ofTsxexpression seen in spermatogonia of the adultoltmutant supports the hypothesis that during the first wave of normal spermatogenesis, the advent of a late-stage cell type, either elongating spermatid or spermatozoan, is responsible for extinguishing expression in spermatogonia in normal adult testis. To our knowledge,Tsxis the first gene to show a pattern of germ cell expression that is apparently specific to the pubertal testis
Centromeric Protein B Null Mice Are Viable with No Apparent Abnormalities

AbstractThe centromere protein B (CENP-B) is a centromeric DNA/binding protein. It recognizes a 17-bp sequence motif called the CENP-B box, which is found in the centromeric region of most chromosomes. It binds DNA through its amino terminus and dimerizes through its carboxy terminus. CENP-B protein has been proposed to perform a vital role in organizing chromatin structures at centromeres. However, other evidence does not agree with this view. For example, CENP-B is found at inactive centromeres on stable dicentric chromosomes, and also mitotically stable chromosomes lacking α-satellite DNA have been reported. To address the biological function of CENP-B, we generated mouse null mutants of CENP-B by homologous recombination. Mice lacking CENP-B were viable and fertile, indicating that mice without CENP-B undergo normal somatic and germline development. Thus, both mitosis and meiosis are able to proceed normally in the absence of CENP-B
Chondroitin Sulfates Modulate Axon Guidance in EmbryonicXenopusBrain

AbstractChondroitin sulfate proteoglycans display both inhibitory and stimulatory effects on cell adhesion and neurite outgrowthin vitro.The functional activity of these proteoglycans appears to be context specific and dependent on the presence of different chondroitin sulfate-binding molecules. Little is known about the role of chondroitin sulfate proteoglycans in the growth and guidance of axonsin vivo.To address this question, we examined the effects of exogenous soluble chondroitin sulfates on the growth and guidance of axons arising from a subpopulation of neurons in the vertebrate brain which express NOC-2, a novel glycoform of the neural cell adhesion molecule N-CAM. Intact brains of stage 28Xenopusembryos were unilaterally exposed to medium containing soluble exogenous chondroitin sulfates. When exposed to chondroitin sulfate, NOC-2+axons within the tract of the postoptic commissure failed to follow their normal trajectory across the ventral midline via the ventral commissure in the midbrain. Instead, these axons either stalled or grew into the dorsal midbrain or continued growing longitudinally within the ventral longitudinal tract. These findings suggest that chondroitin sulfate proteoglycans indirectly modulate the growth and guidance of a subpopulation of forebrain axons by regulating either matrix-bound or cell surface cues at specific choice points within the developing vertebrate brain
The Classical Mouse Mutant Postaxial Hemimelia Results from a Mutation in theWnt7a Gene

AbstractThe study of spontaneous mutations has aided the understanding of developmental processes. A large collection of spontaneous or “classical” mouse mutations has been accumulated over many decades. One of the mutations causes the postaxial hemimelia (px) phenotype, which consists of limb patterning defects accompanied by Müllerian duct-associated sterility in both sexes. We were intrigued that both the limb and the Müllerian ductpxphenotypes are similar to those caused by mutations in the gene encoding the Wnt 7a signaling molecule. In this paper, we investigate the nature of thepxmutation. Morphological analysis and breeding experiments demonstrate that thepxphenotype indeed results from a mutation in theWnt7a gene. Molecular analysis demonstrates thatpxresults from a 515-bp deletion in theWnt7a gene. This generates an abnormal splicing event, which ultimately produces a truncated Wnt 7a protein of half the normal size. Thus, thepxmutation is predicted to be a likely null allele of theWnt7a gene. Our results provide another interesting example of a classical mutation that disrupts an important patterning gene in development
Regulation of the Trunk–Tail Patterning in the Ascidian Embryo: A Possible Interaction of Cascades between Lithium/β-Catenin and Localized Maternal Factor pem

AbstractEmbryonic cell specification and pattern formation in the ascidian embryo are controlled by prelocalized egg cytoplasmic determinants. In previous studies, we showed that overexpression of a maternal gene,posterior end mark(pem), whose transcript localizes to posterior–vegetal cytoplasm of the fertilized egg, causes a loss of the anterior and dorsal structures of the larva (Yoshidaet al., Development122, 2005–2012, 1996). In the present study, first we observed that lithium treatment resulted in reduction of the larval tail. Lineage tracing analyses revealed that descendants of the A4.1 blastomere of the 8-cell-stage embryo (which forms the greater part of notochord and nerve cord) were missing from the tail region, that they were translocated anteriorly into the trunk region, and that the fate of the A4.1-line notochord cells had changed to endoderm. These results suggest that lithium treatment affects the trunk–tail patterning during embryogenesis by changing the cell fate of specific cell lineages. Second, we showed that lithium treatment could rescue the anterior and dorsal structures inpem-overexpressed larvae. This result suggests thatpemplays a role in the patterning of the ascidian embryo via a signaling cascade that is affected by lithium. Third, we isolated an ascidian β-catenin gene and found that overexpression of β-catenin in the A4.1 blastomere had effects very similar to lithium treatment, such as reduction of the tail and anterior translocation of A4.1 descendants. These results suggest that the target of lithium is, at least in part, the Wnt-signaling cascade and thatpemmay also function via this cascade