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Eric H. Davidson - One of the best experts on this subject based on the ideXlab platform.

  • A provisional regulatory gene network for specification of endomesoderm in the Sea Urchin Embryo.
    2018
    Co-Authors: Eric H. Davidson, Andrew Ransick, Takuya Minokawa, Paola Oliveri, Gabriele Amore, Jonathan P Rast, Cristina Calestani, Chiou-hwa Yuh, Veronica F. Hinman, César Arenas-mena
    Abstract:

    We 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 beta-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 veg(2) endomesodermal domain; the blastula-stage separation of the central veg(2) mesodermal domain (i.e., the secondary mesenchyme progenitor field) from the peripheral veg(2) 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.

  • encoding regulatory state boundaries in the pregastrular oral ectoderm of the Sea Urchin Embryo
    Proceedings of the National Academy of Sciences of the United States of America, 2014
    Co-Authors: Enhu Li, Isabelle S Peter, Eric H. Davidson
    Abstract:

    By gastrulation the ectodermal territories of the Sea Urchin Embryo have developed an unexpectedly complex spatial pattern of sharply bounded regulatory states, organized orthogonally with respect to the animal/vegetal and oral/aboral axes of the Embryo. Although much is known of the gene regulatory network (GRN) linkages that generate these regulatory states, the principles by which the boundaries between them are positioned and maintained have remained undiscovered. Here we determine the encoded genomic logic responsible for the boundaries of the oral aspect of the Embryo that separate endoderm from ectoderm and ectoderm from neurogenic apical plate and that delineate the several further subdivisions into which the oral ectoderm per se is partitioned. Comprehensive regulatory state maps, including all spatially expressed oral ectoderm regulatory genes, were established. The circuitry at each boundary deploys specific repressors of regulatory states across the boundary, identified in this work, plus activation by broadly expressed positive regulators. These network linkages are integrated with previously established interactions on the oral/aboral axis to generate a GRN model encompassing the 2D organization of the regulatory state pattern in the pregastrular oral ectoderm of the Embryo.

  • Direct and indirect control of oral ectoderm regulatory gene expression by Nodal signaling in the Sea Urchin Embryo.
    Developmental biology, 2012
    Co-Authors: Stefan C. Materna, Eric H. Davidson
    Abstract:

    The Nodal signaling pathway is known from earlier work to be an essential mediator of oral ectoderm specification in the Sea Urchin Embryo, and indirectly, of aboral ectoderm specification as well. Following expression of the Nodal ligand in the future oral ectoderm during cleavage, a sequence of regulatory gene activations occur within this territory which depend directly or indirectly on nodal gene expression. Here we describe additional regulatory genes that contribute to the oral ectoderm regulatory state during specification in Strongylocentrotus purpuratus, and show how their spatial expression changes dynamically during development. By means of system wide perturbation analyses we have significantly improved current knowledge of the epistatic relations among the regulatory genes of the oral ectoderm. From these studies there emerge diverse circuitries relating downstream regulatory genes directly and indirectly to Nodal signaling. A key intermediary regulator, the role of which had not previously been discerned, is the not gene. In addition to activating several genes earlier described as targets of Nodal signaling, the not gene product acts to repress other oral ectoderm genes, contributing crucially to the bilateral spatial organization of the Embryonic oral ectoderm.

  • the gene regulatory network basis of the community effect and analysis of a Sea Urchin Embryo example
    Developmental Biology, 2010
    Co-Authors: Hamid Bolouri, Eric H. Davidson
    Abstract:

    The "Community Effect" denotes intra-territorial signaling amongst cells which constitute a particular tissue or Embryonic progenitor field. The cells of the territory express the same transcriptional regulatory state, and the intra-territorial signaling is essential to maintenance of this specific regulatory state. The structure of the underlying gene regulatory network (GRN) subcircuitry explains the genomically wired mechanism by which community effect signaling is linked to the continuing transcriptional generation of the territorial regulatory state. A clear example is afforded by the oral ectoderm GRN of the Sea Urchin Embryo where cis-regulatory evidence, experimental Embryology, and network analysis combine to provide a complete picture. We review this example and consider less well known but similar cases in other developing systems where the same subcircuit GRN topology is present. To resolve mechanistic issues that arise in considering how community effect signaling could operate to produce its observed effects, we construct and analyze the behavior of a quantitative model of community effect signaling in the Sea Urchin Embryo oral ectoderm. Community effect network topology could constitute part of the genomic regulatory code that defines transcriptional function in multicellular tissues composed of cells in contact, and hence may have arisen as a metazoan developmental strategy.

  • modularity and design principles in the Sea Urchin Embryo gene regulatory network
    FEBS Letters, 2009
    Co-Authors: Isabelle S Peter, Eric H. Davidson
    Abstract:

    The gene regulatory network (GRN) established experimentally for the pre-gastrular Sea Urchin Embryo provides causal explanations of the biological functions required for spatial specification of Embryonic regulatory states. Here we focus on the structure of the GRN which controls the progressive increase in complexity of territorial regulatory states during Embryogenesis; and on the types of modular subcircuits of which the GRN is composed. Each of these subcircuit topologies executes a particular operation of spatial information processing. The GRN architecture reflects the particular mode of Embryogenesis represented by Sea Urchin development. Network structure not only specifies the linkages constituting the genomic regulatory code for development, but also indicates the various regulatory requirements of regional developmental processes.

Robert C. Angerer - One of the best experts on this subject based on the ideXlab platform.

  • neurogenic gene regulatory pathways in the Sea Urchin Embryo
    Development, 2015
    Co-Authors: Zheng Wei, Lynne M. Angerer, Robert C. Angerer
    Abstract:

    During Embryogenesis the Sea Urchin early pluteus larva differentiates 40-50 neurons marked by expression of the pan-neural marker synaptotagmin B (SynB) that are distributed along the ciliary band, in the apical plate and pharyngeal endoderm, and 4-6 serotonergic neurons that are confined to the apical plate. Development of all neurons has been shown to depend on the function of Six3. Using a combination of molecular screens and tests of gene function by morpholino-mediated knockdown, we identified SoxC and Brn1/2/4, which function sequentially in the neurogenic regulatory pathway and are also required for the differentiation of all neurons. Misexpression of Brn1/2/4 at low dose caused an increase in the number of serotonin-expressing cells and at higher dose converted most of the Embryo to a neurogenic epithelial sphere expressing the Hnf6 ciliary band marker. A third factor, Z167, was shown to work downstream of the Six3 and SoxC core factors and to define a branch specific for the differentiation of serotonergic neurons. These results provide a framework for building a gene regulatory network for neurogenesis in the Sea Urchin Embryo.

  • patterning the Sea Urchin Embryo gene regulatory networks signaling pathways and cellular interactions
    Current Topics in Developmental Biology, 2003
    Co-Authors: Lynne M. Angerer, Robert C. Angerer
    Abstract:

    We discuss steps in the specification of major tissue territories of the Sea Urchin Embryo that occur between fertilization and hatching blastula stage and the cellular interactions required to coordinate morphogenetic processes that begin after hatching. We review evidence that has led to new ideas about how this Embryo is initially patterned: (1) Specification of most of the tissue territories is not direct, but proceeds gradually by progressive subdivision of broad, maternally specified domains that depend on opposing gradients in the ratios of animalizing transcription factors (ATFs) and vegetalizing (beta-catenin) transcription factors; (2) the range of maternal nuclear beta-catenin extends further than previously proposed, that is, into the animal hemisphere, where it programs many cells to adopt early aboral ectoderm characteristics; (3) cells at the extreme animal pole constitute a unique ectoderm region, lacking nuclear beta-catenin; (4) the pluripotential mesendoderm is created by the combined outputs of ATFs and nuclear beta-catenin, which initially overlap in the macromeres, and by an undefined early micromere signal; (5) later micromere signals, which activate Notch and Wnt pathways, subdivide mesendoderm into secondary mesenchyme and endoderm; and (6) oral ectoderm specification requires reprogramming early aboral ectoderm at about the hatching blastula stage. Morphogenetic processes that follow initial fate specification depend critically on continued interactions among cells in different territories. As illustrations, we discuss the regulation of (1) the ectoderm/endoderm boundary, (2) mesenchyme positioning and skeletal growth, (3) ciliated band formation, and (4) several suppressive interactions operating late in Embryogenesis to limit the fates of multipotent cells.

  • Animal-vegetal axis patterning mechanisms in the early Sea Urchin Embryo
    Developmental Biology, 2000
    Co-Authors: Lynne M. Angerer, Robert C. Angerer
    Abstract:

    We discuss recent progress in understanding how cell fates are specified along the animal-vegetal axis of the Sea Urchin Embryo. This process is initiated by cell-autonomous, maternally directed, mechanisms that establish three unique gene-regulatory domains. These domains are defined by distinct sets of vegetalizing (β-catenin) and animalizing transcription factor (ATF) activities and their region of overlap in the macromeres, which specifies these cells as early mesendoderm. Subsequent signaling among cleavage-stage blastomeres further subdivides fates of macromere progeny to yield major Embryonic tissues. Zygotically produced Wnt8 reinforces maternally regulated levels of nuclear β-catenin in vegetal derivatives to down regulate ATF activity and further promote mesendoderm fates. Signaling through the Notch receptor from the vegetal micromere lineages diverts adjacent mesendoderm to secondary mesenchyme fates. Continued Wnt signaling expands the vegetal domain of β-catenin's transcriptional regulatory activity and competes with animal signaling factors, including BMP2/4, to specify the endoderm-ectoderm border within veg, progeny. This model places new emphasis on the importance of the ratio of maternally regulated vegetal and animal transcription factor activities in initial specification events along the animal-vegetal axis. (C) 2000 Academic Press.

  • spatially regulated spets4 transcription factor activity along the Sea Urchin Embryo animal vegetal axis
    Development, 1999
    Co-Authors: Lynne M. Angerer, Robert C. Angerer
    Abstract:

    Because the transcription of the SpHE gene is regulated cell-autonomously and asymmetrically along the maternally determined animal-vegetal axis of the very early Sea Urchin Embryo, its regulators provide an excellent entry point for investigating the mechanism(s) that establishes this initial polarity. Previous studies support a model in which spatial regulation of SpHE transcription relies on multiple nonvegetal positive transcription factor activities (Wei, Z., Angerer, L. M. and Angerer, R. C. (1997) Dev. Biol. 187, 71–78) and a yeast one-hybrid screen has identified one, SpEts4, which binds with high specificity to a cis element in the SpHE regulatory region and confers positive activation of SpHE promoter transgenes (Wei, Z., Angerer, R. C. and Angerer, L. M. (1999) Mol. Cell. Biol. 19, 1271–1278). Here we demonstrate that SpEts4 can bind to the regulatory region of the endogenous SpHE gene because a dominant repressor, created by fusing SpEts4 DNA binding and Drosophila engrailed repression domains, suppresses its transcription. The pattern of expression of the SpEts4 gene is consistent with a role in regulating SpHE transcription in the nonvegetal region of the Embryo during late cleavage/early blastula stages. Although maternal transcripts are uniformly distributed in the egg and early cleaving Embryo, they rapidly turn over and are replaced by zygotic transcripts that accumulate in a pattern congruent with SpHE transcription. In addition, in vivo functional tests show that the SpEts4 cis element confers nonvegetal transcription of a beta-galactosidase reporter gene containing the SpHE basal promoter, and provide strong evidence that the activity of this transcription factor is an integral component of the nonvegetal transcriptional regulatory apparatus, which is proximal to, or part of, the mechanism that establishes the animal-vegetal axis of the Sea Urchin Embryo.

  • characterization of a span promoter sufficient to mediate correct spatial regulation along the animal vegetal axis of the Sea Urchin Embryo
    Developmental Biology, 1996
    Co-Authors: David J Kozlowski, Lynne M. Angerer, Michael L Gagnon, Jeffrey K Marchant, Susan D Reynolds, Robert C. Angerer
    Abstract:

    Abstract In order to investigate how the maternally specified animal–vegetal axis of the Sea Urchin Embryo is established, we have examined the molecular basis of regulation of several genes transcribed differentially in nonvegetal and vegetal domains of the very early blastula. Here we present an initial characterization of the regulatory region of one of these,SpAN,which encodes a protease in the astacin family related toDrosophila tolloidand vertebrateBMP-1(Reynoldset al., Development114, 769–786). Tests ofSpANpromoter functionin vivoshow that high-level activity and correct not-vegetal expression are mediated by sequences within 300 bp upstream of the basal promoter.In vitrostudies have identified six protein binding sites serviced by at least five different proteins. Comparison of the structure of theSpANpromoter to that ofSpHE,whose expression pattern is identical, shows that both promoters contain multiple positively acting upstream elements close to the basal promoter. We show that two elements are critical for high-level transcription ofSpAN,since exact replacement of either results in 10- to 20-fold reduction in promoter strength. These shared elements are, however, not essential for spatially correctSpHEgene transcription. We conclude that the coordinate strong activities of theSpANandSpHEpromoters in the nonvegetal domain of the Embryo rely primarily on different transcription factor activities.

L D Konyushkin - One of the best experts on this subject based on the ideXlab platform.

  • Sea Urchin Embryo model as a reliable in vivo phenotypic screen to characterize selective antimitotic molecules comparative evaluation of combretapyrazoles isoxazoles 1 2 3 triazoles and pyrroles as tubulin binding agents
    ACS Combinatorial Science, 2018
    Co-Authors: Marina N Semenova, Dmitry V Tsyganov, Dmitry V Demchuk, N B Chernysheva, Alexander V Samet, Eugenia A Silyanova, V P Kislyi, Anna S Maksimenko, Alexander E Varakutin, L D Konyushkin
    Abstract:

    A series of both novel and reported combretastatin analogues, including diarylpyrazoles, -isoxazoles, -1,2,3-triazoles, and -pyrroles, were synthesized via improved protocols to evaluate their antimitotic antitubulin activity using in vivo Sea Urchin Embryo assay and a panel of human cancer cells. A systematic comparative structure–activity relationship studies of these compounds were conducted. Pyrazoles 1i and 1p, isoxazole 3a, and triazole 7b were found to be the most potent antimitotics across all tested compounds causing cleavage alteration of the Sea Urchin Embryo at 1, 0.25, 1, and 0.5 nM, respectively. These agents exhibited comparable cytotoxicity against human cancer cells. Structure–activity relationship studies revealed that compounds substituted with 3,4,5-trimethoxyphenyl ring A and 4-methoxyphenyl ring B displayed the highest activity. 3-Hydroxy group in the ring B was essential for the antiproliferative activity in the diarylisoxazole series, whereas it was not required for potency of diar...

  • 3 amino thieno 2 3 b pyridines as microtubule destabilising agents molecular modelling and biological evaluation in the Sea Urchin Embryo and human cancer cells
    Bioorganic & Medicinal Chemistry, 2017
    Co-Authors: Chatchakorn Eurtivong, Marina N Semenova, L D Konyushkin, V V Semenov, Olga P Atamanenko, Johannes Reynisson, Alex S Kiselyov
    Abstract:

    Abstract A series of 3-amino-thieno[2,3-b]pyridines was prepared and tested in a phenotypic Sea Urchin Embryo assay to identify potent and specific molecules that affect tubulin dynamics. The most active compounds featured a tricyclic core ring system with a fused cycloheptyl or cyclohexyl substituent and unsubstituted or alkyl-substituted phenyl moiety tethered via a carboxamide. Low nano-molar potency was observed in the Sea Urchin Embryos for the most active compounds (1–5) suggestive of a microtubule-destabilising effect. The molecular modelling studies indicated that the tubulin colchicine site is inhibited, which often leads to microtubule-destabilisation in line with the Sea Urchin Embryo results. Finally, the identified hits displayed a robust growth inhibition (GI50 of 50–250 nM) of multidrug-resistant melanoma MDA-MB-435 and breast MDA-MB-468 human cancer cell lines. This work demonstrates that for the thieno[2,3-b]pyridines the most effective mechanism of action is microtubule-destabilisation initiated by binding to the colchicine pocket.

  • synthesis and antiproliferative activity of conformationally restricted 1 2 3 triazole analogues of combretastatins in the Sea Urchin Embryo model and against human cancer cell lines
    Bioorganic & Medicinal Chemistry, 2014
    Co-Authors: Dmitry V Demchuk, Mikhail M Raihstat, L D Konyushkin, S I Firgang, N B Chernysheva, Alexander V Samet, Vladimir I Ushkarov, Galina A Stashina, Alex Philchenkov, M P Zavelevich
    Abstract:

    A series of 1,5-diaryl- and 4,5-diaryl-1,2,3-triazole derivatives of combretastatin A4 were synthesized and evaluated as antimitotic microtubule destabilizing agents using the Sea Urchin Embryo model. Structure–activity relationship studies identified compounds substituted with 3,4,5-trimethoxyphenyl and 3,4-methylenedioxy-5-methoxyphenyl ring A and 4-methoxyphenyl ring B as potent antiproliferative agents with high cytotoxicity against a panel of human cancer cell lines including multi-drug resistant cells. 4,5-Diaryl-1,2,3-triazoles (C–C geometry) were found to be considerably more active than the

  • synthesis and antiproliferative activity of conformationally restricted 1 2 3 triazole analogues of combretastatins in the Sea Urchin Embryo model and against human cancer cell lines
    Bioorganic & Medicinal Chemistry, 2014
    Co-Authors: Dmitry V Demchuk, Mikhail M Raihstat, L D Konyushkin, S I Firgang, N B Chernysheva, Alexander V Samet, Vladimir I Ushkarov, Galina A Stashina, Alex Philchenkov, M P Zavelevich
    Abstract:

    Abstract A series of 1,5-diaryl- and 4,5-diaryl-1,2,3-triazole derivatives of combretastatin A4 were synthesized and evaluated as antimitotic microtubule destabilizing agents using the Sea Urchin Embryo model. Structure–activity relationship studies identified compounds substituted with 3,4,5-trimethoxyphenyl and 3,4-methylenedioxy-5-methoxyphenyl ring A and 4-methoxyphenyl ring B as potent antiproliferative agents with high cytotoxicity against a panel of human cancer cell lines including multi-drug resistant cells. 4,5-Diaryl-1,2,3-triazoles (C–C geometry) were found to be considerably more active than the respective 1,5-diaryl-1,2,3-triazoles (N–C geometry). Compound 10ad′ induced G2/M cell cycle arrest and apoptosis in human T-leukemia Jurkat cells via caspase 2/3/9 activation and downregulation of the antiapoptotic protein XIAP. A mitotic catastrophe has been evaluated as another possible cell death mode.

  • cis restricted 3 aminopyrazole analogues of combretastatins synthesis from plant polyalkoxybenzenes and biological evaluation in the cytotoxicity and phenotypic Sea Urchin Embryo assays
    Journal of Natural Products, 2013
    Co-Authors: Dmitry V Tsyganov, Alex S Kiselyov, Marina N Semenova, L D Konyushkin, S I Firgang, Irina B Karmanova, Yuri A Strelenko, Victor V Semenov
    Abstract:

    We have synthesized a series of novel cis-restricted 4,5-polyalkoxydiaryl-3-aminopyrazole analogues of combretastatins via short synthetic sequences using building blocks isolated from dill and parsley seed extracts. The resulting compounds were tested in vivo in the phenotypic Sea Urchin Embryo assay to reveal their antimitotic and antitubulin effects. The most potent aminopyrazole, 14a, altered Embryonic cell division at 10 nM concentration, exhibiting microtubule-destabilizing properties. Compounds 12a and 14a displayed pronounced cytotoxicity in the NCI60 anticancer drug screen, with the ability to inhibit growth of multi-drug-resistant cancer cells.

Thierry Lepage - One of the best experts on this subject based on the ideXlab platform.

  • the maternal maverick gdf15 like tgf β ligand panda directs dorsal ventral axis formation by restricting nodal expression in the Sea Urchin Embryo
    PLOS Biology, 2015
    Co-Authors: Emmanuel Haillot, Maria Dolores Molina, Francois Lapraz, Thierry Lepage
    Abstract:

    Specification of the dorsal-ventral axis in the highly regulative Sea Urchin Embryo critically relies on the zygotic expression of nodal, but whether maternal factors provide the initial spatial cue to orient this axis is not known. Although redox gradients have been proposed to entrain the dorsal-ventral axis by acting upstream of nodal, manipulating the activity of redox gradients only has modest consequences, suggesting that other factors are responsible for orienting nodal expression and defining the dorsal-ventral axis. Here we uncover the function of Panda, a maternally provided transforming growth factor beta (TGF-β) ligand that requires the activin receptor-like kinases (Alk) Alk3/6 and Alk1/2 receptors to break the radial symmetry of the Embryo and orient the dorsal-ventral axis by restricting nodal expression. We found that the double inhibition of the bone morphogenetic protein (BMP) type I receptors Alk3/6 and Alk1/2 causes a phenotype dramatically more severe than the BMP2/4 loss-of-function phenotype, leading to extreme ventralization of the Embryo through massive ectopic expression of nodal, suggesting that an unidentified signal acting through BMP type I receptors cooperates with BMP2/4 to restrict nodal expression. We identified this ligand as the product of maternal Panda mRNA. Double inactivation of panda and bmp2/4 led to extreme ventralization, mimicking the phenotype caused by inactivation of the two BMP receptors. Inhibition of maternal panda mRNA translation disrupted the early spatial restriction of nodal, leading to persistent massive ectopic expression of nodal on the dorsal side despite the presence of Lefty. Phylogenetic analysis indicates that Panda is not a prototypical BMP ligand but a member of a subfamily of TGF-β distantly related to Inhibins, Lefty, and TGF-β that includes Maverick from Drosophila and GDF15 from vertebrates. Indeed, overexpression of Panda does not appear to directly or strongly activate phosphoSmad1/5/8 signaling, suggesting that although this TGF-β may require Alk1/2 and/or Alk3/6 to antagonize nodal expression, it may do so by sequestering a factor essential for Nodal signaling, by activating a non-Smad pathway downstream of the type I receptors, or by activating extremely low levels of pSmad1/5/8. We provide evidence that, although panda mRNA is broadly distributed in the early Embryo, local expression of panda mRNA efficiently orients the dorsal-ventral axis and that Panda activity is required locally in the early Embryo to specify this axis. Taken together, these findings demonstrate that maternal panda mRNA is both necessary and sufficient to orient the dorsal-ventral axis. These results therefore provide evidence that in the highly regulative Sea Urchin Embryo, the activity of spatially restricted maternal factors regulates patterning along the dorsal-ventral axis.

  • Nodal: master and commander of the dorsal-ventral and left-right axes in the Sea Urchin Embryo.
    Current Opinion in Genetics and Development, 2013
    Co-Authors: M Dolores Molina, Noémie De Crozé, Emmanuel Haillot, Thierry Lepage
    Abstract:

    Recent studies suggest that specification of the dorsal-ventral and left-right axes of the Sea Urchin Embryo relies on Nodal-expressing signalling centres located in the ventral ectoderm and in the archenteron that share striking similarities with vertebrate organising centres. Nodal and its downstream target BMP2/4 pattern all three germ layers along the dorsal-ventral axis, repress neural fates and control morphogenesis of the larva. Moreover, Nodal establishes left-right asymmetry by repressing formation of the adult rudiment and inhibiting germline cells differentiation on the right side, while BMP2/4 promotes expression of mesodermal genes on the left side. These findings provide a framework for future studies and raise new questions regarding the events upstream and downstream of Nodal and BMP signalling during axis formation.

  • Reciprocal Signaling between the Ectoderm and a Mesendodermal Left-Right Organizer Directs Left-Right Determination in the Sea Urchin Embryo
    PLoS Genetics, 2012
    Co-Authors: Nathalie Bessodes, Eric Rottinger, Veronique Duboc, Emmanuel Haillot, François Lahaye, Thierry Lepage
    Abstract:

    During echinoderm development, expression of nodal on the right side plays a crucial role in positioning of the rudiment on the left side, but the mechanisms that restrict nodal expression to the right side are not known. Here we show that establishment of left-right asymmetry in the Sea Urchin Embryo relies on reciprocal signaling between the ectoderm and a left-right organizer located in the endomesoderm. FGF/ERK and BMP2/4 signaling are required to initiate nodal expression in this organizer, while Delta/Notch signaling is required to suppress formation of this organizer on the left side of the archenteron. Furthermore, we report that the H(+)/K(+)-ATPase is critically required in the Notch signaling pathway upstream of the S3 cleavage of Notch. Our results identify several novel players and key early steps responsible for initiation, restriction, and propagation of left-right asymmetry during Embryogenesis of a non-chordate deuterostome and uncover a functional link between the H(+)/K(+)-ATPase and the Notch signaling pathway.

  • maternal oct1 2 is required for nodal and vg1 univin expression during dorsal ventral axis specification in the Sea Urchin Embryo
    Developmental Biology, 2011
    Co-Authors: Ryan Range, Thierry Lepage
    Abstract:

    The TGFβ family member Nodal is expressed early in the presumptive ventral ectoderm of the early Sea Urchin Embryo and its activity is crucial for dorsal–ventral (D/V) axis specification. Analysis of the nodal promoter identified a number of critical binding sites for transcription factors of different families including Sox, Oct, TCF and bZIP, but in most cases the specific factors that regulate nodal expression are not known. In this study, we report that the maternal factor Oct1/2 functions as a positive regulator of nodal and that its activity is essential for the initiation of nodal expression. Inhibition of Oct1/2 mRNA translation produced Embryos with severe axial defects similar to those observed following inhibition of Nodal function. We show that perturbing Oct1/2 function specifically disrupted specification of the ventral and dorsal ectodermal regions and that these effects were caused by the failure of nodal to be expressed early in development. Furthermore, we identified the key gene vg1/univin, which is also necessary for nodal expression, as an additional factor that was completely dependent on Oct1/2 for its zygotic expression. These data demonstrate that the maternal Oct1/2 protein plays an early and essential role in D/V axis specification by initiating the expression of nodal and vg1/univin, two genes that act at the top of the D/V ectoderm gene regulatory network.

  • nemo like kinase nlk acts downstream of notch delta signalling to downregulate tcf during mesoderm induction in the Sea Urchin Embryo
    Development, 2006
    Co-Authors: Eric Rottinger, Lydia Besnardeau, Guy Lhomond, Christian Gache, Jenifer C Croce, Thierry Lepage
    Abstract:

    Studies in Caenorhabditis elegans and vertebrates have established that the MAP kinase-related protein NLK counteracts Wnt signalling by downregulating the transcription factor TCF. Here, we present evidence that during early development of the Sea Urchin Embryo, NLK is expressed in the mesodermal precursors in response to Notch signalling and directs their fate by downregulating TCF. The expression pattern of nlk is strikingly similar to that of Delta and the two genes regulate the expression of each other. nlk overexpression, like ectopic activation of Notch signalling, provoked massive formation of mesoderm and associated epithelial mesenchymal transition. NLK function was found to be redundant with that of the MAP kinase ERK during mesoderm formation and to require the activity of the activating kinase TAK1. In addition, the Sea Urchin NLK, like its vertebrate counterpart, antagonizes the activity of the transcription factor TCF. Finally, activating the expression of a TCF-VP16 construct at blastula stages strongly inhibits endoderm and mesoderm formation, indicating that while TCF activity is required early for launching the endomesoderm gene regulatory network, it has to be downregulated at blastula stage in the mesodermal lineage. Taken together, our results indicate that the evolutionarily conserved TAK/NLK regulatory pathway has been recruited downstream of the Notch/Delta pathway in the Sea Urchin to switch off TCF-beta-catenin signalling in the mesodermal territory, allowing precursors of this germ layer to segregate from the endomesoderm.

Marina N Semenova - One of the best experts on this subject based on the ideXlab platform.

  • Sea Urchin Embryo model as a reliable in vivo phenotypic screen to characterize selective antimitotic molecules comparative evaluation of combretapyrazoles isoxazoles 1 2 3 triazoles and pyrroles as tubulin binding agents
    ACS Combinatorial Science, 2018
    Co-Authors: Marina N Semenova, Dmitry V Tsyganov, Dmitry V Demchuk, N B Chernysheva, Alexander V Samet, Eugenia A Silyanova, V P Kislyi, Anna S Maksimenko, Alexander E Varakutin, L D Konyushkin
    Abstract:

    A series of both novel and reported combretastatin analogues, including diarylpyrazoles, -isoxazoles, -1,2,3-triazoles, and -pyrroles, were synthesized via improved protocols to evaluate their antimitotic antitubulin activity using in vivo Sea Urchin Embryo assay and a panel of human cancer cells. A systematic comparative structure–activity relationship studies of these compounds were conducted. Pyrazoles 1i and 1p, isoxazole 3a, and triazole 7b were found to be the most potent antimitotics across all tested compounds causing cleavage alteration of the Sea Urchin Embryo at 1, 0.25, 1, and 0.5 nM, respectively. These agents exhibited comparable cytotoxicity against human cancer cells. Structure–activity relationship studies revealed that compounds substituted with 3,4,5-trimethoxyphenyl ring A and 4-methoxyphenyl ring B displayed the highest activity. 3-Hydroxy group in the ring B was essential for the antiproliferative activity in the diarylisoxazole series, whereas it was not required for potency of diar...

  • 3 amino thieno 2 3 b pyridines as microtubule destabilising agents molecular modelling and biological evaluation in the Sea Urchin Embryo and human cancer cells
    Bioorganic & Medicinal Chemistry, 2017
    Co-Authors: Chatchakorn Eurtivong, Marina N Semenova, L D Konyushkin, V V Semenov, Olga P Atamanenko, Johannes Reynisson, Alex S Kiselyov
    Abstract:

    Abstract A series of 3-amino-thieno[2,3-b]pyridines was prepared and tested in a phenotypic Sea Urchin Embryo assay to identify potent and specific molecules that affect tubulin dynamics. The most active compounds featured a tricyclic core ring system with a fused cycloheptyl or cyclohexyl substituent and unsubstituted or alkyl-substituted phenyl moiety tethered via a carboxamide. Low nano-molar potency was observed in the Sea Urchin Embryos for the most active compounds (1–5) suggestive of a microtubule-destabilising effect. The molecular modelling studies indicated that the tubulin colchicine site is inhibited, which often leads to microtubule-destabilisation in line with the Sea Urchin Embryo results. Finally, the identified hits displayed a robust growth inhibition (GI50 of 50–250 nM) of multidrug-resistant melanoma MDA-MB-435 and breast MDA-MB-468 human cancer cell lines. This work demonstrates that for the thieno[2,3-b]pyridines the most effective mechanism of action is microtubule-destabilisation initiated by binding to the colchicine pocket.

  • Triphenylphosphonium Cations of the Diterpenoid Isosteviol: Synthesis and Antimitotic Activity in a Sea Urchin Embryo Model
    2015
    Co-Authors: Irina Yu. Strobykina, Marina N Semenova, Victor V Semenov, Mayya G. Belenok, Vasiliy M. Babaev, Ildar Kh. Rizvanov, Vladimir F. Mironov, Vladimir E. Kataev
    Abstract:

    A series of novel triphenylphosphonium (TPP) cations of the diterpenoid isosteviol (1, 16-oxo-ent-beyeran-19-oic acid) have been synthesized and evaluated in an in vivo phenotypic Sea Urchin Embryo assay for antimitotic activity. The TPP moiety was applied as a carrier to provide selective accumulation of a connected compound into mitochondria. When applied to fertilized eggs, the targeted isosteviol TPP conjugates induced mitotic arrest with the formation of aberrant multipolar mitotic spindles, whereas both isosteviol and the methyltriphenylphosphonium cation were inactive. The structure–activity relationship study revealed the essential role of the TPP group for the realization of the isosteviol effect, while the chemical structure and the length of the linker only slightly influenced the antimitotic potency. The results obtained using the Sea Urchin Embryo model suggested that TPP conjugates of isosteviol induced mitotic spindle defects and mitotic arrest presumably by affecting mitochondrial DNA. Since targeting mitochondria is considered as an encouraging strategy for cancer therapy, TPP-isosteviol conjugates may represent promising candidates for further design as anticancer agents

  • cis restricted 3 aminopyrazole analogues of combretastatins synthesis from plant polyalkoxybenzenes and biological evaluation in the cytotoxicity and phenotypic Sea Urchin Embryo assays
    Journal of Natural Products, 2013
    Co-Authors: Dmitry V Tsyganov, Alex S Kiselyov, Marina N Semenova, L D Konyushkin, S I Firgang, Irina B Karmanova, Yuri A Strelenko, Victor V Semenov
    Abstract:

    We have synthesized a series of novel cis-restricted 4,5-polyalkoxydiaryl-3-aminopyrazole analogues of combretastatins via short synthetic sequences using building blocks isolated from dill and parsley seed extracts. The resulting compounds were tested in vivo in the phenotypic Sea Urchin Embryo assay to reveal their antimitotic and antitubulin effects. The most potent aminopyrazole, 14a, altered Embryonic cell division at 10 nM concentration, exhibiting microtubule-destabilizing properties. Compounds 12a and 14a displayed pronounced cytotoxicity in the NCI60 anticancer drug screen, with the ability to inhibit growth of multi-drug-resistant cancer cells.

  • polyalkoxybenzenes from plants 5 parsley seed extract in synthesis of azapodophyllotoxins featuring strong tubulin destabilizing activity in the Sea Urchin Embryo and cell culture assays
    Journal of Medicinal Chemistry, 2011
    Co-Authors: Marina N Semenova, Mikhail M Raihstat, Alex S Kiselyov, Dmitry V Tsyganov, L D Konyushkin, S I Firgang, Roman V Semenov, Oleg R Malyshev, Fabian Fuchs, Anne Stielow
    Abstract:

    A series of 4-azapodophyllotoxin derivatives with modified rings B and E have been synthesized using allylpolyalkoxybenzenes from parsley seed oil. The targeted molecules were evaluated in vivo in a phenotypic Sea Urchin Embryo assay for antimitotic and tubulin destabilizing activity. The most active compounds identified by the in vivo Sea Urchin Embryo assay featured myristicin-derived ring E (4e, 6e, and 8e). These molecules were determined to be more potent than podophyllotoxin. Cytotoxic effects of selected molecules were further confirmed and evaluated by conventional assays with A549 and Jurkat human leukemic T-cell lines including cell growth inhibition, cell cycle arrest, cellular microtubule disruption, and induction of apoptosis. The ring B modification yielded 6-OMe substituted molecule 8e as the most active compound. Finally, in Jurkat cells, compound 8e induced caspase-dependent apoptosis mediated by the apical caspases-2 and -9 and not caspase-8, implying the involvement of the intrinsic cas...