Showing results 1541 to 1560 on 1602 in total
Des chercheuses et chercheurs du LBBE ont suivit avec Claire Truche, metteuse en scène, les premiers pas de cette aventure théâtrale qui donnera lieu à trois représentations au théâtre Astrée cette fin de semaine.
Lisa Nicvert and Lucie Thel, doctoral students at the LBBE, participate in the 3rd edition of the "embarked conferences", on the lake of the Parc de la Tête d'Or.
Mitochondrial genomes (mtDNA) are normally maternally inherited and encode for subunits of respiratory chain complexes and ATP synthase among others. The integrity of mtDNA is crucial for cellular energetic and redox homeostasis, and mtDNA mutations are associated with modifications of individual fitness and longevity. Bivalves are the only zoological group in which Doubly Uniparental Inheritance (DUI), characterized by the presence of two divergent mitochondrial genomes within different tissues of male individuals, is frequently observed. The F-genome, maternally inherited, is found in somatic tissue and female gonads whereas the M-mtDNA is found in male gonadic tissue only. The clam Arctica islandica is widely distributed throughout the North Atlantic shelf regions. Due to different environmental regimes (salinity, temperature, oxygen), the maximum lifespan of its populations varies between >500 years around Iceland and 35 years in the Baltic Sea. I will present our recent investigations that describe for the first time the existence of the DUI system in Arctica islandica. Based on 16S and cytochrome b markers, we highlight the presence of an M-genome in male gonads in individuals belonging to Baltic and North Sea populations. The two genomes show a low level of sequence divergence compared to other DUI species, around 6-8% at the nucleotide level. Whilst the analysis of mitochondrial markers generally indicated genetically homogeneity of all North Atlantic populations, they further reveal few clam individuals that carry a "divergent" mtDNA haplotype, resembling the M-genome. These individuals occurred however exclusively in the Icelandic population. Unlike the M-genome, which is confined to male gonadic tissue in DUI species, this "divergent" mtDNA occurs in somatic tissues from 20% of individuals of both sexes. In association with transcriptomic and biochemical data, we will discuss the possible impacts of this uncommon mitochondrial genome on Arctica islandica biology and cellular physiology. This study will enhance the understanding of the role of DUI and mtDNA in general for fitness, aging and adaptation of bivalves.
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Le jeudi 13 Janvier à 20h30, Sylvain Charlat, chercheur au LBBE, participera à un débat à l'issue de la projection du film "Les Fils de l'homme", à l'aquarium ciné-café.
Biological networks of large dimensions, with their diagram of interactions, are often well represented by a Boolean model with a family of logical rules. An advantage of Boolean and discrete modelling is the possibility of fully characterizing all qualitative dynamical trajectories of a particular network, based simply on the structure of links and interactions between nodes. A biological network may have different qualitative behaviours in response to different conditions. For instance, in response to different inputs, the system may have a single steady state, or multiple steady states, or exhibit oscillatory behaviour. In this context, using the asynchronous transition graph of the Boolean network, we have developed a method for identifying the groups of active or operational interactions that are responsible for a given dynamic behaviour.As an example, a model of an apoptosis network will be analysed. Two core groups of elements and interactions are identified: they correspond to two different mechanisms that may be used by the cell for the decision between apoptosis or cell survival.
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The turn from the 20th to the 21st Century was marked by a drastic change in the scale at which biologists study regulatory networks. In the 1990, a PhD student could spend years analysing the regulation of one particular gene by one or a few transcription factors. Microarray technologies enabled monitoring the expression of all the genes of an organism in a single experiment (transcriptome arrays), and to lead genome-wide location analysis to report supposedly exhaustive lists of transcription factor binding sites. Next Generation Sequencing amplified the movement, and many labs are now combining ChIP-seq and RNA-seq experiments to get a wide view on transcription factor binding locations, histone modifications, and transcriptional responses to a multitude of conditions, cell types, developmental stages, etc. In the first part of the talk, I will present some of the bioinformatics approaches and tools that we developed to analyse regulatory motifs from various types of high-throughput data (e.g. co-expression clusters, ChIP-seq peaks, replication origins).At the light of the evolution of the domain, I would also like to address a more general question about the insights gained from high-throughput approaches on fundamental mechanisms of regulation. Indeed, it implicitly became standard to consider that a typical high-throughput experiments should return thousands of significant features (differentially expressed genes, TF binding sites, active enhancers). This however does not fit with our classical models, were transcription factors would turn on or off specific sets of target genes ("regulatory switches"), thereby forming regulatory networks whose behaviour was understandably determined by feedback loops. How can we conciliate the undeniable robustness of regulatory networks with the apparent noisiness of binding and transcription profiles?
Laure Ségurel, aujourd’hui chercheuse au LBBE (et précédemment au Musée de l’Homme) a contribué à éclairer l’histoire évolutive de la digestion du lait
Le mardi 29 septembre à 14h, sur France Inter, Marion Valeix était l’invitée de Mathieu Vidard et son émission la Terre au Carré, à l’occasion de la sortie sur Canal + du film d’Alexandre Soullier « Le Roi Bâtard » sur le lion d’Afrique. Les travaux de Marion Valeix portent plus généralement sur les communautés de grands mammifères africains et le rôle des interactions interspécifiques dans le fonctionnement de celles-ci.
Thèse Cecilia Coimbra Klein - mardi 12 novembre 2013 à 14 h 30, amphithéâtre CNRS