Topological Control of Life and Death in Non-Proliferative Epithelia

Programmed cell death is one of the most fascinating demonstrations of the plasticity of biological systems. It is classically described to act upstream of and govern major developmental patterning processes (e.g. inter-digitations in vertebrates, ommatidia in Drosophila). We show here the first evidence that massive apoptosis can also be controlled and coordinated by a pre-established pattern of a specific ‘master cell’ population. This new concept is supported by the development and validation of an original model of cell patterning. Ciona intestinalis eggs are surrounded by a three-layered follicular organization composed of 60 elongated floating extensions made of as many outer and inner cells, and indirectly spread through an extracellular matrix over 1200 test cells. Experimental and selective ablation of outer and inner cells results in the abrogation of apoptosis in respective remaining neighbouring test cells. In addition incubation of outer/inner follicular cell-depleted eggs with a soluble extract of apoptotic outer/inner cells partially restores apoptosis to apoptotic-defective test cells. The 60 inner follicular cells were thus identified as ‘apoptotic master’ cells which collectively are induction sites for programmed cell death of the underlying test cells. The position of apoptotic master cells is controlled by topological constraints exhibiting a tetrahedral symmetry, and each cell spreads over and can control the destiny of 20 smaller test cells, which leads to optimized apoptosis signalling

Innovations et gouvernance territoriale : une analyse par les dispositifs

Cette communication vise à présenter les outils méthodologiques d'analyse/évaluation de la gouvernance territoriale élaborés dans le cadre du projet de recherche PSDR Gouv.Innov sur les innovations organisationnelles relatives à la gouvernance territoriale. Il s'agit d'étudier les transformations introduites par les politiques de développement durable au niveau des dispositifs de gouvernance territoriale visant à favoriser une gestion intégrée des espaces ruraux. Dans un contexte de recomposition de l'action publique où les procédures d'aménagement sont plutôt normées par des représentations urbaines, l'accent est mis sur la question des modalités de représentation des activités rurales, pour lesquelles nous faisons l'hypothèse qu'elles sont sous représentées. Les premiers résultats méthodologiques permettent, dans une première partie, de proposer une définition générique et pragmatique de la gouvernance territoriale et de préciser la notion de dispositifs de gouvernance comme objet d'observation. A partir de cette définition une grille d'analyse permettant d'appréhender l'ensemble des dimensions en jeu dans les processus de gouvernance territoriale est élaboré. Dans la deuxième partie nous explorons l'intérêt de la notion de dispositif pour observer les processus de gouvernance et proposons une grille de collecte et de structuration des informations pour constituer des chroniques des dispositifs étudiés.(Résumé d'auteur

Oligonucleotide-based Strategies to Inhibit Human Hepatitis C Virus

International audienceHepatitis C virus (HCV) infection represents a worldwide problem, and current antiviral regimens are not satisfactory. The need to develop novel, specific, anti-HCV antiviral drugs is clear. Antisense oligonucleotides (AS-ON), ribozymes, and more recently, small interfering RNAs (siRNAs) have been widely used to control gene expression, and several clinical trials are in progress. The potential to use AS-ON as tools to control HCV infection, either by promoting an RNase H mediated cleavage of viral genomic RNA or by interfering with the assembly of a translation initiation complex on the internal ribosome entry site (IRES) is reviewed. Extensive knowledge of IRES structure and conservation among HCV genotypes have rendered the HCV IRES (and, in particular, its IIId loop) particularly attractive for antisense approaches. Encouraging data have been obtained with IRES-targeted RNase H-competent and incompetent ON analogs. We demonstrate here that very short steric blocking ONs can inhibit the formation of translation preinitiation complexes on the IRES and block IRES-mediated translation in a cell-free translation assay and in a transfected hepatoma cell line

Using Ciona to study developmental programmed cell death

ReviewInternational audienceCiona intestinalis, a member of Tunicates, the closest group to vertebrates, has emerged as an appropriate organism for the study of developmentally regulated programmed cell death. First, because massive phases of apoptosis occur all along embryogenesis. Second, because the lecithotrophic mode of development is associated with autophagic process occurring during juvenile formation. Third, because the biochemical cell death machinery is close to that found in mammals. Altogether, the Ciona system contributes to identify new specific regulatory pathways and to explain how molecular mechanisms of programmed cell death evolved from invertebrates to vertebrates. (c) 2006 Elsevier Ltd. All rights reserved

Localization of the Ribonuclease L Inhibitor Gene (RNS4I), a New Member of the Interferon-Regulated 2–5A Pathway, to 4q31 by Fluorescencein SituHybridization

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Inhibition of Replication of Reactivated Human Immunodeficiency Virus Type 1 (HIV-1) in Latently Infected U1 Cells Transduced with an HIV-1 Long Terminal Repeat-Driven PKR cDNA Construct

Treatment of human immunodeficiency virus type 1 (HIV-1)-infected individuals with highly active antiretroviral therapy has effectively decreased viral load to undetectable levels. However, efforts to eliminate HIV-1 from these individuals have been unsuccessful, due to the presence of stable, latent viral reservoirs in resting and active CD4(+) T lymphocytes and macrophages. These latent populations have become critical targets in the effort to eradicate HIV-1 from infected individuals. The mechanisms of HIV-1 latency have been studied by using the HIV-1-infected promonocytic cell line U1. The interferon-inducible double-stranded RNA-dependent p68 protein kinase (PKR), a key enzyme in the host-mediated antiviral response, is known to be down-regulated during HIV-1 infection. Therefore, in order to evaluate the role of PKR in the inhibition of replication of reactivated HIV-1 in latently infected U1 cells, we have utilized cDNA constructs containing PKR under the transcriptional control of the HIV-1 long terminal repeat. One PKR-transduced clone, U1/106-4:27, inhibited the tumor necrosis factor alpha (TNF-α)-induced replication of HIV-1 by 99% compared to control U1 cells as measured by syncytium formation and HIV-1 p24 antigen enzyme-linked immunosorbent assay. Western blot analysis showed an increase in PKR expression through 96 h postinduction in the U1/106-4:27 clone, concomitant with maximal increases in phosphorylation of the α subunit of eukaryotic initiation factor 2 and NF-κB activity at 72 h postinduction. These results demonstrate that overexpression of PKR can inhibit the replication of reactivated HIV-1 in latently infected cells and confirm the involvement of PKR in the interferon-associated antiviral pathway against HIV-1 infection. Additionally, treatment of the PKR-transduced U1/106-4:27 clone with the protease inhibitor saquinavir (250 nM) completely inhibited TNF-α-induced HIV-1 replication

Cloning and Characterization of a RNase L Inhibitor.

International audienceThe 2-5A/RNase L system is considered as a central pathway of interferon (IFN) action and could possibly play a more general physiological role as for instance in the regulation of RNA stability in mammalian cells.We describe here the expression cloning and initial characterization of RLI (for RNase L inhibitor), a new type of endoribonuclease inhibitor.RLI cDNA codes for a 68-kDa polypeptide whose expression is not regulated by IFN. Its expression in reticulocyte extracts antagonizes the 2-5A binding ability and the nuclease activity of endogenous RNase L or the cloned 2DR polypeptide. The inhibition requires the association of RLI with the nuclease and is dependent on the ratio between the two proteins. Likewise RLI is co-immunoprecipitated with the RNase L complex by a nuclease-specific antibody. RLI does not lead to 2-5A degradation or to irreversible modification of RNase L. The overexpression of RLI in stably transfected HeLa cells inhibits the antiviral activity of IFN on encephalomyocarditis virus but not on vesicular stomatitis virus.RLI therefore appears as the first described and potentially important mediator of the 2-5A/RNase L pathway

Parallel Evolution of Ameloblastic scpp Genes in Bony and Cartilaginous Vertebrates

International audienceIn bony vertebrates, skeletal mineralization relies on the secretory calcium-binding phosphoproteins (Scpp) family whose members are acidic extracellular proteins posttranslationally regulated by the Fam20°C kinase. As scpp genes are absent from the elephant shark genome, they are currently thought to be specific to bony fishes (osteichthyans). Here, we report a scpp gene present in elasmobranchs (sharks and rays) that evolved from local tandem duplication of sparc-L 5 ′ exons and show that both genes experienced recent gene conversion in sharks. The elasmobranch scpp is remarkably similar to the osteichthyan scpp members as they share syntenic and gene structure features, code for a conserved signal peptide, tyrosine-rich and aspartate/glutamate-rich regions, and harbor putative Fam20°C phosphorylation sites. In addition, the catshark scpp is coexpressed with sparc-L and fam20°C in tooth and scale ameloblasts, similarly to some osteichthyan scpp genes. Despite these strong similarities, molecular clock and phylogenetic data demonstrate that the elasmobranch scpp gene originated independently from the osteichthyan scpp gene family. Our study reveals convergent events at the sparc-L locus in the two sister clades of jawed vertebrates, leading to parallel diversification of the skeletal biomineralization toolkit. The molecular evolution of sparc-L and its coexpression with fam20°C in catshark ameloblasts provides a unifying genetic basis that suggests that all convergent scpp duplicates inherited similar features from their sparc-L precursor. This conclusion supports a single origin for the hypermineralized outer odontode layer as produced by an ancestral developmental process performed by Sparc-L, implying the homology of the enamel and enameloid tissues in all vertebrates

Inhibition of human immunodeficiency virus (HIV-1) replication in SupT1 cells transduced with an HIV-1 LTR-driven PKR cDNA construct

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