Reverse engineering of gene regulatory relationships from genomics datais a crucial task to dissect the complex underlying regulatory mechanismoccurring in a cell. From a computational point of view thereconstruction of gene regulatory networks is an undetermined problem asthe large number of possible solutions is typically high in contrast tothe number of available independent data points. Many possible solutionscan fit the available data, explaining the data equally well, but onlyone of them can be the biologically true solution. Several strategieshave been proposed in literature to reduce the search space and/orextend the amount of independent information. Moreover, several methodshave been developed to infer gene networks from steady-state data, muchless literature is produced about time-course data, so the developmentof algorithms to infer gene networks from time-series measurements is acurrent challenge into bioinformatics research area. Here I will present two recently proposed algorithms, the first termedTimeDelay-ARACNE tries to extract dependencies between pairs of genesat different time…

DNA microarrays have been intensively used in the past years for gene expression studies and for the analysis of full genomes. These devices are high throughput and rely on the hybridization between target sequences in solution and sequences covalently linked at a solid surface. During this talk I will review some results of the analysis of dedicated experiments to characterize the thermodynamics of the hybridization process in microarrays. I will show that accurate nearest-neighbor model parameters can be obtained from the analysis of hybridizations with sequences carrying one or more mismatches. These inputs can be used to design accurate diagnostic tools for the analysis of samples containing mutations. As an example the case of HIV will be discussed. References: J. Hooyberghs, M. Baiesi, A. Ferrantini and E. Carlon "Breakdown of thermodynamic equilibrium for DNA hybridization in microarrays" Phys. Rev. E 81, 012901 (2010) W. Hadiwikarta, J.-C.Walter, J. Hooyberghs and E. Carlon ,…

Polarisation in yeast cells consists of an aggregation of proteins (here CdC42) on the membrane which becomes asymmetric. The two main mechanisms involved in the breaking of symmetry in this process seem to be : -reaction-diffusion mechanism -actin mediated transport Experiments have shown that the polar cap size depends on the local curvature of the affected cell and more precisely that it is the actin mediated transport which is crucial to obtain this correlation. The aim of this talk is to give some hypotheses which may explain the mechanisms underlying this correlation. To this, we in particular use a mathematical model in order to test different components in reaction diffusions and actin transport mechanisms which may influence the cap size of cDc42. This work is made in collaboration with D. Bonazzi and N. Minc from the Institut Jacques Monod, part of Université Paris Diderot.

For marine photoautotrophs, light is a key environmental signal controlling a range of physiological and adaptive processes. In this talk, I will present two projects in our lab that focus on the role of light and photosynthesis on the physiology of marine phytoplankton. In the coastal diatom, Thalassiosira pseudonana, we have identified a protein that mediates photosynthetic responses under iron (Fe) limitation and high light. TpDSP1 is a Ca2+-binding, plastid-localized protein that, when over-expressed in T. pseudonana, significantly increases fitness under Fe limitation by increasing growth rates, photosynthetic efficiency, and cyclic electron flow around photosystem I. However, TpDSP1 also conferred a physiological disadvantage whereby over-expression led to increased sensitivity to high light, forcing cells to walk an ecological ‘tightrope’ through the regulation of this protein. In the second part of my talk, I will discuss the role of light in mediating host-virus interactions. Microalgal viruses are inherently dependent on light and host…

Growth is a highly optimized process in bacteria since the battle for the conquest of ecological niches is though. Understanding the key elements governing the growth rate management is then crucial to further understand and predict the bacterium behavior with respect to various environmental conditions. In this context, we have proposed in [Goelzer et al, Automatica 2011], a promising theoretical framework, so-called Resource Balance Analysis (RBA) formalizing the problem of resource repartition at the cell scale as a convex optimization problem. In this talk, we present the biological validation of this theoretical framework by applying it on the Gram-positive model bacterium Bacillus subtilis. To this end, through the European Project BasynTech, we have generated a dedicated and large fluxomic and proteomic datasets for grown in various conditions. We have used these data to calibrate/validate our RBA method leading to successful identification of over 600 parameters, including estimated activities of individual enzymes under…

In the last decade there has been an increasing amount of experimental and computational evidence pointing out that the proteome of eukaryotes and viruses is enriched in intrinsically disordered protein (IDPs) and/or intrinsically disordered regions (IDRs). IDPs/IDRs are ubiquitous functional proteins that lack stable II and III structures under physiological conditions in the absence of a partner and that rather exist as highly dynamic conformational ensembles. IDPs are often involved in biological processes implying manifold protein-protein interactions, such as cellular regulation, transcription and signal transduction.In the course of the structural and functional characterization of the measles virus replicative complex, we discovered that the nucleoprotein (N) and the phosphoprotein (P) contain long (up to 230 residues) disordered regions possessing sequence and biochemical features that typify IDPs. More recently, by combining computational and experimental approaches, we extended these results to the N and P proteins from the newly emerged Nipah and Hendra viruses. My…

Combining genomic analyses with evolution experiments provides a dynamic view of virtually all cellular processes. Indeed, the full revivable fossil record produced in such experiments can be investigated for phenotypic, genomic and global expression changes. During the longest-running evolution experiment with Escherichia coli, adaptive changes have been shown to strongly affect the sequence, structure and expression of evolved genomes, with sometimes unexpected phenotypic outcomes.