Éditeur(s) : Public Library Science
Résumé : Background: Resolving threats to widely distributed marine megafauna requires definition of the geographic distributions of both the threats as well as the population unit(s) of interest. In turn, because individual threats can operate on varying spatial scales, their impacts can affect different segments of a population of the same species. Therefore, integration of multiple tools and techniques - including site-based monitoring, genetic analyses, mark-recapture studies and telemetry - can facilitate robust definitions of population segments at multiple biological and spatial scales to address different management and research challenges. Methodology/Principal Findings: To address these issues for marine turtles, we collated all available studies on marine turtle biogeography, including nesting sites, population abundances and trends, population genetics, and satellite telemetry. We georeferenced this information to generate separate layers for nesting sites, genetic stocks, and core distributions of population segments of all marine turtle species. We then spatially integrated this information from fine-to coarse-spatial scales to develop nested envelope models, or Regional Management Units (RMUs), for marine turtles globally. Conclusions/Significance: The RMU framework is a solution to the challenge of how to organize marine turtles into units of protection above the level of nesting populations, but below the level of species, within regional entities that might be on independent evolutionary trajectories. Among many potential applications, RMUs provide a framework for identifying data gaps, assessing high diversity areas for multiple species and genetic stocks, and evaluating conservation status of marine turtles. Furthermore, RMUs allow for identification of geographic barriers to gene flow, and can provide valuable guidance to marine spatial planning initiatives that integrate spatial distributions of protected species and human activities. In addition, the RMU framework - including maps and supporting metadata - will be an iterative, user-driven tool made publicly available in an online application for comments, improvements, download and analysis.
Plos One (1932-6203) (Public Library Science), 2010-12 , Vol. 5 , N. 12 , P. -

Droits : 2010 Plos One
http://archimer.ifremer.fr/doc/00028/13926/11308.pdf
DOI:10.1371/journal.pone.0015465
http://archimer.ifremer.fr/doc/00028/13926/

Éditeur(s) : HAL CCSD
Résumé : Due to their phylogenetic position outside from Bilateria, cnidarians and ctenophores are key phyla to understanding the origin and early evolution of molecular mechanisms, cell types, or body plan features at the level of Metazoa. Unlike other non-bilaterian phyla (sponges and placozoans), they possess neurons and muscle cells. The first part of my work relates to the problem of the origin of the metazoan nervous system. Recent studies have suggested a dual origin for nerve cells, with ctenophore neurons having emerged independently from those of cnidarians and bilaterians. This hypothesis relies on phylogenomic analyses supporting ctenophores as sister-group to all other metazoans, and on the purported absence in ctenophores of almost all well-known neuro-transmission systems, including the cholinergic system. Refuting this claim, I present substantial evidence in favour of acetylcholine (Ach) being used in the ctenophore Pleurobrachia pileus as an extra-cellular messenger, including within the nervous system. This conclusion arises from the conjunction of multiple approaches at the molecular scale (orthology analyses, Ach immuno-localisation, gene in situ hybridisation), at the cellular scale (calcium imaging on muscle cells exposed to Ach) and at the organism scale (pharmacological treatments with an Ach analogue and Ach antagonists). In the second part of my thesis, I address the conservation of molecular mechanisms involved in the control of cellular proliferation. Notably, the Hippo pathway is known for its role in bilaterians in the negative control of cellular proliferation. I show that components of this pathway are conserved in Pleurobrachia pileus and in Clytia hemisphaerica and that the nuclear vs. cytoplasmic localisation of the transcriptional co-factor Yorkie is correlated to the extent of proliferation within C. hemisphaerica tissues. Finally, RNAseq differential gene expression analyses along a cellular conveyor belt of the C. hemisphaerica medusa suggests a tendency for conservation of function among a set of genes whose mammalian orthologues have documented roles in the arrest of cellular proliferation.
Les Cnidaires et les Cténaires sont deux embranchements extérieurs aux Bilatériens qui, de par leur position phylogénétique, constituent des modèles d'étude cruciaux pour comprendre l'origine et l'évolution de mécanismes moléculaires ou encore de types cellulaires à grande échelle chez les Métazoaires. Ils sont les deux seuls embranchements non-Bilatériens à posséder des cellules nerveuses ainsi que des cellules musculaires. La première partie de mon travail de thèse s'inscrit dans le contexte de la compréhension de l'origine du système nerveux des Métazoaires. Des études récentes suggèrent une origine double du système nerveux ; ainsi celui des Cténaires aurait été acquis de manière convergente par rapport à celui des Cnidaires et des Bilatériens. Cela repose sur des données récentes de phylogénomique proposant les Cténaires en tant que groupe-frère de tous les autres Métazoaires et sur l'absence supposée chez les Cténaires de quasiment tous les systèmes de neurotransmission connus y compris le système cholinergique. A l'encontre de ces hypothèses, j'ai pu mettre en évidence l'existence d'un système cholinergique chez le Cténaire Pleurobrachia pileus ainsi que son étroite association avec le système nerveux. Cette conclusion repose sur une multiplicité d'approches à l'échelle moléculaire (analyses d'orthologie, immunolocalisation, hybridations in situ), cellulaire (imagerie calcique) et de l'organisme (approche pharmacologique). Dans la seconde partie de ma thèse, j'aborde la question de la conservation des mécanismes moléculaires impliqués dans le contrôle de la prolifération cellulaire à l'échelle des Métazoaires. J'ai pu mettre en évidence la conservation des acteurs.
https://tel.archives-ouvertes.fr/tel-01633223

NNT : 2015PA066629
tel-01633223
https://tel.archives-ouvertes.fr/tel-01633223
https://tel.archives-ouvertes.fr/tel-01633223v2/document
https://tel.archives-ouvertes.fr/tel-01633223/file/2015PA066629.pdf

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
Background: The Hippo pathway regulates growth rate and organ size in fly and mouse, notably through control of cell proliferation. Molecular interactions at the heart of this pathway are known to have originated in the unicellular ancestry of metazoans. They notably involve a cascade of phosphorylations triggered by the kinase Hippo, with sub‑ sequent nuclear to cytoplasmic shift of Yorkie localisation, preventing its binding to the transcription factor Scalloped, thereby silencing proliferation genes. There are few comparative expression data of Hippo pathway genes in non‑ model animal species and notably none in non‑bilaterian phyla.Results: All core Hippo pathway genes could be retrieved from the ctenophore Pleurobrachia pileus and the hydro‑ zoan cnidarian Clytia hemisphaerica, with the important exception of Yorkie in ctenophore. Expression study of the Hippo, Salvador and Scalloped genes in tentacle " cellular conveyor belts " of these two organisms revealed striking differences. In P. pileus, their transcripts were detected in areas where undifferentiated progenitors intensely prolifer‑ ate and where expression of cyclins B and D was also seen. In C. hemisphaerica, these three genes and Yorkie are expressed not only in the proliferating but also in the differentiation zone of the tentacle bulb and in mature tentacle cells. However, using an antibody designed against the C. hemiphaerica Yorkie protein, we show in two distinct cell lineages of the medusa that Yorkie localisation is predominantly nuclear in areas of active cell proliferation and mainly cytoplasmic elsewhere.Conclusions: This is the first evidence of nucleocytoplasmic Yorkie shift in association with the arrest of cell prolifera‑ tion in a cnidarian, strongly evoking the cell division‑promoting role of this protein and its inhibition by the activated Hippo pathway in bilaterian models. Our results furthermore highlight important differences in terms of deployment and regulation of Hippo pathway genes between cnidarians and ctenophores.
ISSN: 2041-9139

Droits : http://creativecommons.org/licenses/by/
hal-01286578
http://hal.upmc.fr/hal-01286578
http://hal.upmc.fr/hal-01286578/document
http://hal.upmc.fr/hal-01286578/file/comparative.pdf
DOI : 10.1186/s13227-016-0041-y

Éditeur(s) : Public Library Science
Résumé : Where conservation resources are limited and conservation targets are diverse, robust yet flexible priority-setting frameworks are vital. Priority-setting is especially important for geographically widespread species with distinct populations subject to multiple threats that operate on different spatial and temporal scales. Marine turtles are widely distributed and exhibit intra-specific variations in population sizes and trends, as well as reproduction and morphology. However, current global extinction risk assessment frameworks do not assess conservation status of spatially and biologically distinct marine turtle Regional Management Units (RMUs), and thus do not capture variations in population trends, impacts of threats, or necessary conservation actions across individual populations. To address this issue, we developed a new assessment framework that allowed us to evaluate, compare and organize marine turtle RMUs according to status and threats criteria. Because conservation priorities can vary widely (i.e. from avoiding imminent extinction to maintaining long-term monitoring efforts) we developed a "conservation priorities portfolio" system using categories of paired risk and threats scores for all RMUs (n = 58). We performed these assessments and rankings globally, by species, by ocean basin, and by recognized geopolitical bodies to identify patterns in risk, threats, and data gaps at different scales. This process resulted in characterization of risk and threats to all marine turtle RMUs, including identification of the world's 11 most endangered marine turtle RMUs based on highest risk and threats scores. This system also highlighted important gaps in available information that is crucial for accurate conservation assessments. Overall, this priority-setting framework can provide guidance for research and conservation priorities at multiple relevant scales, and should serve as a model for conservation status assessments and priority-setting for widespread, long-lived taxa.
Plos One (1932-6203) (Public Library Science), 2011-09 , Vol. 6 , N. 9 , P. 1-14

Droits : 2011 Wallace et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License
http://archimer.ifremer.fr/doc/00050/16097/13573.pdf
DOI:10.1371/journal.pone.0024510
http://archimer.ifremer.fr/doc/00050/16097/

Éditeur(s) : HAL CCSD Landes Bioscience
Résumé : International audience
In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
Autophagy

hal-00735751
https://hal.archives-ouvertes.fr/hal-00735751
PUBMED : 22966490