pinecone/core-2020-05-10-deduplication huggingface dataset:
Programmed Cell Death Is Required for Palate Shelf Fusion and Is Regulated by Retinoic Acid

AbstractThe actual role of programmed cell death (PCD) in embryonic processes and the extrinsic signals that define the death fate in developing cells are still poorly understood. Here, we show that during secondary palate shelf fusion in the mouse, PCD appeared in the medial edge epithelia (MEE) of the anterior region only after shelf contact. Contact was necessary for efficient cell death activation in the MEE. However, exogenous all-trans-retinoic acid (RA) increased cell death independently of contact. Competence to induce cell death by contact or by RA exposure was obtained when the MEE were close to touch. Endogenous RA is a relevant regulator of the secondary palate PCD since this was reduced by a retinol dehydrogenase inhibitor and an RAR specific antagonist. Bmp-7 expression was positively regulated by RA. However, BMP-7 was unable to activate cell death within the palate tissue and NOGGIN, a natural BMP antagonist, did not block PCD. Reduction of PCD at the MEE directly with a caspase inhibitor or by inhibiting retinol dehydrogenase resulted in unfused palate shelves, but adhesion was not affected. In contrast, exogenous RA also blocked fusion, but in this situation the increased cell death within the MEE appeared to affect adhesion, thereby causing cleft palate in vivo
Transcription Factor AP-2 Is an Essential and Direct Regulator of Epidermal Development in Xenopus

AbstractExpression of the Xenopus homolog of the mammalian transcription factor AP-2α (XAP-2) is activated throughout the animal hemisphere shortly after the midblastula transition, and becomes restricted to prospective epidermis by the end of gastrulation, under the control of BMP signal modulation. Elevated expression in the future neural crest region begins at this time. Ectopic expression of XAP-2 can restore transcription of epidermal genes in neuralized ectoderm, both in ectodermal explants and in the intact embryo. Likewise, loss of XAP-2 function, accomplished by injection of antisense oligonucleotides or by overexpression of antimorphic XAP-2 derivatives, leads to loss of epidermal and gain of neural gene expression. These treatments also result in gastrulation failure. Thus, AP-2 is a critical regulator of ectodermal determination that is required for normal epidermal development and morphogenesis in the frog embryo
Posttranscriptional Regulation of p18 and p27 Cdk Inhibitor Proteins and the Timing of Oligodendrocyte Differentiation

AbstractA cell-intrinsic timer helps control when rodent oligodendrocyte precursor cells (OPCs) exit the cell cycle and terminally differentiate when cultured in platelet-derived growth factor (PDGF) and thyroid hormone (TH). There is evidence that the cyclin-dependent kinase inhibitor (CKI) p27/Kip1 (p27) is a component of this TH-regulated timer, as it increases as OPCs proliferate and is required for the timer to operate accurately. Here, we provide evidence that another CKI, p18/INK (p18), may also be a component of the timer: it increases as OPCs proliferate, and its overexpression in OPCs accelerates the timer, causing the cells to differentiate prematurely. We also show that the overexpression of p27 accelerates the timer and that the increases in both p27 and p18 that occur in proliferating OPCs are controlled posttranscriptionally. By contrast, we show that the overexpression of either p18 or p27 in OPCs proliferating in PDGF and the absence of TH greatly slows the cell cycle but fails to accelerate the spontaneous differentiation that normally occurs independently of TH
A Regulatory Gene Network That Directs Micromere Specification in the Sea Urchin Embryo

AbstractMicromeres and their immediate descendants have three known developmental functions in regularly developing sea urchins: immediately after their initial segregation, they are the source of an unidentified signal to the adjacent veg2 cells that is required for normal endomesodermal specification; a few cleavages later, they express Delta, a Notch ligand which triggers the conditional specification of the central mesodermal domain of the vegetal plate; and they exclusively give rise to the skeletogenic mesenchyme of the postgastrular embryo. We demonstrate the key components of the zygotic regulatory gene network that accounts for micromere specificity. This network is a subelement of the overall endomesoderm specification network of the Strongylocentrotus purpuratus embryo. A central role is played by a newly discovered gene encoding a paired class homeodomain transcription factor which in micromeres acts as a repressor of a repressor: the gene is named pmar1 (paired-class micromere anti-repressor). pmar1 is expressed only during cleavage and early blastula stages, and exclusively in micromeres. It is initially activated as soon as the micromeres are formed, in response to Otx and β-Catenin/Tcf inputs. The repressive nature of the interactions mediated by the pmar1 gene product was shown by the identical effect of introducing mRNA encoding the Pmar1 factor, and mRNA encoding an Engrailed-Pmar1 (En-Pmar1) repressor domain fusion. In both cases, the effects are derepression: of the delta gene; and of skeletogenic genes, including several transcription factors normally expressed only in micromere descendants, and also a set of downstream skeletogenic differentiation genes. The spatial phenotype of embryos bearing exogenous mRNA encoding Pmar1 factor or En-Pmar1 is expansion of the domains of expression of the downstream genes over most or all of the embryo. This results in transformation of much of the embryo into skeletogenic mesenchyme cells that express skeletogenic markers. The normal role of pmarl is to prevent, exclusively in the micromeres, the expression of a repressor that is otherwise operative throughout the embryo. This function accounts for the localization of delta transcription in micromeres, and thereby for the conditional specification of the vegetal plate mesoderm. It also explains why skeletogenic differentiation gene batteries normally function only in micromere descendants. More generally, the regulatory network subelement emerging from this work shows how the specificity of micromere function depends on continuing global regulatory interactions, as well as on early localized inputs
Dynamics of Dnmt1 Methyltransferase Expression and Intracellular Localization during Oogenesis and Preimplantation Development

AbstractThe imprinting of mammalian genes depends on the maintenance of DNA methylation patterns during pre- and postimplantation development. Dnmt1o is a variant form of the somatically expressed Dnmt1 cytosine methyltransferase that is synthesized and stored in the oocyte cytoplasm and trafficks to the eight-cell nucleus during preimplantation development, where it maintains DNA methylation patterns on alleles of imprinted genes. Transcripts encoding Dnmt1 are present in preimplantation embryos, suggesting that Dnmt1 protein is also expressed in the preimplantation embryo, and may account for maintenance methylation at preimplantation stages other than the eight-cell embryo. However, using an antibody that detects Dnmt1, but not Dnmt1o, no Dnmt1 protein was detected on immunoblots or by immunocytochemical staining in wildtype preimplantation embryos. Moreover, Dnmt1 protein produced in the oocyte from a modified Dnmt1 allele, Dnmt11s/1o, trafficked to nuclei of eight-cell embryos, but not to nuclei of other stages. The highly restricted nuclear localization patterns of oocyte-derived Dnmt1o and Dnmt1 during preimplantation development add further support to the notion that DNA methyltransferases other than Dnmt1 are required for maintaining imprints during preimplantation development
Noggin and Chordin Have Distinct Activities in Promoting Lineage Commitment of Mouse Embryonic Stem (ES) Cells

AbstractTo examine the role of secreted signaling molecules and neurogenic genes in early development, we have developed a culture system for the controlled differentiation of mouse embryonic stem (ES) cells. In the current investigation, two of the earliest identified BMP antagonists/neural-inducing factors, noggin and chordin, were expressed in pluripotent mouse ES cells. Neurons were present as early as 24 h following transfection of ES cells with a pCS2/noggin expression plasmid, with differentiation peaking at 72 h. With neuronal differentiation, stem cell marker genes were down-regulated and neural determination genes expressed. Coculture experiments and exposure to noggin-conditioned medium produced similar neuronal differentiation of control ES cells, while addition of BMP-4 to noggin expressants strikingly inhibited neuronal differentiation. Transfection of ES cells with a pCS2/chordin expression vector or exposure to chordin-conditioned medium produced a more complex pattern of differentiation; ES cells formed neurons, mesenchymal cells as well as N-CAM-positive, nestin-positive neuroepithelial progenitors. These data suggest that, consistent with their different expression fields, noggin and chordin may play distinct roles in patterning the early mouse embryo
Follicle-Stimulating Hormone Induces a Gap Junction-Dependent Dynamic Change in [cAMP] and Protein Kinase A in Mammalian Oocytes

AbstractThe second messenger cyclic adenosine 5′monophosphate (cAMP) has been implicated in controlling meiotic maturation. To date, there have been no direct measurements of cAMP in living mammalian oocytes. Here, we have used the fluorescently labelled cAMP-dependent protein kinase A (PKA), FlCRhR, to monitor cAMP in mouse oocytes. In cumulus-enclosed oocytes, follicle-stimulating hormone (FSH) stimulated an increase in the oocyte [cAMP] that was prevented by using the gap junction inhibitor, carbenoxolone. The FSH-induced increase in oocyte [cAMP] was suppressed in a time-dependent manner by prior exposure to ATP, while epidermal growth factor had no effect on basal or stimulated levels of cAMP. Finally, using confocal microscopy, we show that the regulatory and catalytic subunits of the microinjected PKA are distributed in a punctate manner with a stronger accumulation in the perinuclear region. On an increase in [cAMP], in response to phosphodiesterase inhibition or FSH, the catalytic subunit diffused throughout the cytoplasm and germinal vesicle, while the regulatory subunit remained anchored. These experiments show that increases in cAMP in ovarian somatic cells are communicated via gap junctions to the oocyte, where it can lead to a redistribution of the catalytic subunit of PKA
3D-DIASemb: A Computer-Assisted System for Reconstructing and Motion Analyzing in 4D Every Cell and Nucleus in a Developing Embryo

AbstractA computer-assisted three-dimensional (3D) system, 3D-DIASemb, has been developed that allows reconstruction and motion analysis of cells and nuclei in a developing embryo. In the system, 75 optical sections through a live embryo are collected in the z axis by using differential interference contrast microscopy. Optical sections for one reconstruction are collected in a 2.5-s period, and this process is repeated every 5 s. The outer perimeter and nuclear perimeter of each cell in the embryo are outlined in each optical section, converted into β-spline models, and then used to construct 3D faceted images of the surface and nucleus of every cell in the developing embryo. Because all individual components of the embryo (i.e., each cell surface and each nuclear surface) are individually reconstructed, 3D-DIASemb allows isolation and analysis of (1) all or select nuclei in the absence of cell surfaces, (2) any single cell lineage, and (3) any single nuclear lineage through embryogenesis. Because all reconstructions represent mathematical models, 3D-DIASemb computes over 100 motility and dynamic morphology parameters for every cell, nucleus, or group of cells in the developing embryo at time intervals as short as 5 s. Finally, 3D-DIASemb reconstructs and motion analyzes cytoplasmic flow through the generation and analysis of “vector flow plots.” To demonstrate the unique capabilities of this new technology, a Caenorhabditis elegans embryo is reconstructed and motion analyzed through the 28-cell stage. Although 3D-DIASemb was developed by using the C. elegans embryo as the experimental model, it can be applied to other embryonic systems. 3D-DIASemb therefore provides a new method for reconstructing and motion analyzing in 4D every cell and nucleus in a live, developing embryo, and should provide a powerful tool for assessing the effects of drugs, environmental perturbations, and mutations on the cellular and nuclear dynamics accompanying embryogenesis
Ecdysone Triggers the Expression of Golgi Genes in Drosophila Imaginal Discs via Broad-Complex

AbstractOne of the most significant morphogenic events in the development of Drosophila melanogaster is the elongation of imaginal discs during puparium formation. We have shown that this macroscopic event is accompanied by the formation of Golgi stacks from small Golgi larval clusters of vesicles and tubules that are present prior to the onset of disc elongation. We have shown that the fly steroid hormone 20-hydroxyecdysone triggers both the elongation itself and the formation of Golgi stacks (V. Kondylis, S. E. Goulding, J. C. Dunne, and C. Rabouille, 2001, Mol. Biol. Cell, 12, 2308). Using mRNA in situ hybridisation, we show here that ecdysone triggers the upregulation of a subset of genes encoding Golgi-related proteins (such as dnsf1, dsec23, dsed5, and drab1) and downregulates the expression of others (such as dergic53, dβ'COP, anddrab6). We show that the transcription factor Broad-complex, itself an “early” ecdysone target, mediates this regulation. And we show that the ecdysone-independent upregulation of dnsf1 and dsnap prior to the ecdysone peak leads to a precocious formation of large Golgi stacks. The ecdysone-triggered biogenesis of Golgi stacks at the onset of imaginal disc elongation offers the exciting possibility of advancing our understanding of the relationship between gene expression and organelle biogenesis
Zygotic Wnt/β-Catenin Signaling Preferentially Regulates the Expression of Myf5 Gene in the Mesoderm of Xenopus

AbstractZygotic Wnt signaling has been shown to be involved in dorsoventral mesodermal patterning in Xenopus embryos, but how it regulates different myogenic gene expression in the lateral mesodermal domains is not clear. Here, we use transient exposure of embryos or explants to lithium, which mimics Wnt/β-catenin signaling, as a tool to regulate the activation of this pathway at different times and places during early development. We show that activation of Wnt/β-catenin signaling at the early gastrula stage rapidly induces ectopic expression of XMyf5 in both the dorsal and ventral mesoderm. In situ hybridization analysis reveals that the induction of ectopic XMyf5 expression in the dorsal mesoderm occurs within 45 min and is not blocked by the protein synthesis inhibitor cycloheximide. By contrast, the induction of XMyoD is observed after 2 h of lithium treatment and the normal expression pattern of XMyoD is blocked by cycloheximide. Analysis by RT-PCR of ectodermal explants isolated soon after midblastula transition indicates that lithium also specifically induces XMyf5 expression, which takes place 30 min following lithium treatment and is not blocked by cycloheximide, arguing strongly for an immediate-early response. In the early gastrula, inhibition of Wnt/β-catenin signaling blocks the expression of XMyf5 and XMyoD, but not of Xbra. We further show that zygotic Wnt/β-catenin signaling interacts specifically with bFGF and eFGF to promote XMyf5 expression in ectodermal cells. These results suggest that Wnt/β-catenin pathway is required for regulating myogenic gene expression in the presumptive mesoderm. In particular, it may directly activate the expression of the XMyf5 gene in the muscle precursor cells
Germline X Chromosomes Exhibit Contrasting Patterns of Histone H3 Methylation in Caenorhabditis elegans

AbstractIn mammals, one of the two somatic X chromosomes in the female is inactivated, thereby equalizing X chromosome-derived transcription in the two sexes, a process known as dosage compensation. In the germline, however, the situation is quite different. Both X chromosomes are transcriptionally active during female oogenesis, whereas the X and Y chromosomes are transcriptionally silent during male spermatogenesis. Previous studies suggest that Caenorhabditis elegans germline X chromosomes might have different transcriptional activity in the two sexes in a manner similar to that in mammals. Using antibodies specific to H3 methylated at either lysine 4 or lysine 9, we show that the pattern of site-specific H3 methylation is different between X chromosomes and autosomes as well as between germline X chromosomes from the two sexes in C. elegans. We show that the pachytene germline X chromosomes in both sexes lack Me(K4)H3 when compared with autosomes, consistent with their being transcriptionally inactive. This transcriptional inactivity of germline X chromosomes is apparently transient in hermaphrodites because both X chromosomes stain brightly for Me(K4)H3 after germ nuclei exit pachytene. The male single X chromosome, on the other hand, remains devoid of Me(K4)H3 staining throughout the germline. Instead, the male germline X chromosome exhibits a high level of Me(K9)H3 that is not detected on any other chromosomes in either sex, consistent with stable silencing of this chromosome. Using mutants defective in the sex determination pathway, we show that X-chromosomal Me(K9)H3 staining is determined by the sexual phenotype, and not karyotype, of the animal. We detect a similar high level of Me(K9)H3 in male mouse XY bodies, suggesting an evolutionarily conserved mechanism for silencing the X chromosome specifically in the male germline
A Provisional Regulatory Gene Network for Specification of Endomesoderm in the Sea Urchin Embryo

AbstractWe present the current form of a provisional DNA sequence-based regulatory gene network that explains in outline how endomesodermal specification in the sea urchin embryo is controlled. The model of the network is in a continuous process of revision and growth as new genes are added and new experimental results become available; see http://www.its.caltech.edu/~mirsky/endomeso.htm (End-mes Gene Network Update) for the latest version. The network contains over 40 genes at present, many newly uncovered in the course of this work, and most encoding DNA-binding transcriptional regulatory factors. The architecture of the network was approached initially by construction of a logic model that integrated the extensive experimental evidence now available on endomesoderm specification. The internal linkages between genes in the network have been determined functionally, by measurement of the effects of regulatory perturbations on the expression of all relevant genes in the network. Five kinds of perturbation have been applied: (1) use of morpholino antisense oligonucleotides targeted to many of the key regulatory genes in the network; (2) transformation of other regulatory factors into dominant repressors by construction of Engrailed repressor domain fusions; (3) ectopic expression of given regulatory factors, from genetic expression constructs and from injected mRNAs; (4) blockade of the β-catenin/Tcf pathway by introduction of mRNA encoding the intracellular domain of cadherin; and (5) blockade of the Notch signaling pathway by introduction of mRNA encoding the extracellular domain of the Notch receptor. The network model predicts the cis-regulatory inputs that link each gene into the network. Therefore, its architecture is testable by cis-regulatory analysis. Strongylocentrotus purpuratus and Lytechinus variegatus genomic BAC recombinants that include a large number of the genes in the network have been sequenced and annotated. Tests of the cis-regulatory predictions of the model are greatly facilitated by interspecific computational sequence comparison, which affords a rapid identification of likely cis-regulatory elements in advance of experimental analysis. The network specifies genomically encoded regulatory processes between early cleavage and gastrula stages. These control the specification of the micromere lineage and of the initial veg2 endomesodermal domain; the blastula-stage separation of the central veg2 mesodermal domain (i.e., the secondary mesenchyme progenitor field) from the peripheral veg2 endodermal domain; the stabilization of specification state within these domains; and activation of some downstream differentiation genes. Each of the temporal–spatial phases of specification is represented in a subelement of the network model, that treats regulatory events within the relevant embryonic nuclei at particular stages
Deregulated Expression of the Homeobox Gene Cux-1 in Transgenic Mice Results in Downregulation of p27kip1 Expression during Nephrogenesis, Glomerular Abnormalities, and Multiorgan Hyperplasia

AbstractCux-1 is a murine homeobox gene that is highly expressed in the developing kidney with expression restricted to the nephrogenic zone. Cux-1 is highly expressed in cyst epithelium of polycystic kidneys from C57BL/6J-cpk/cpk mice, but not in kidneys isolated from age-matched phenotypically normal littermates. To further elucidate the role of Cux-1 in renal development, we generated transgenic mice expressing Cux-1 under the control of the CMV immediate early gene promoter. Mice constitutively expressing Cux-1 developed multiorgan hyperplasia and organomegaly, but not an overall increase in body size. Transgenic kidneys were enlarged 50% by 6 weeks of age, with the increased growth primarily restricted to the cortex. Proliferating cells were found in proximal and distal tubule epithelium throughout the cortex, and the squamous epithelium that normally lines Bowman's capsule was replaced with proximal tubule epithelium. However, the total number of nephrons was not increased. In the developing kidneys of transgenic mice, Cux-1 was ectopically expressed in more highly differentiated tubules and glomeruli, and this was associated with reduced expression of the cyclin kinase inhibitor, p27. Transient transfection experiments revealed that Cux-1 is an inhibitor of p27 promoter activity. These results suggest that Cux-1 regulates cell proliferation during early nephrogenesis by inhibiting expression of p27