Identification of the het-r vegetative incompatibility gene of Podospora anserina as a member of the fast evolving HNWD gene family

In fungi, vegetative incompatibility is a conspecific non-self recognition mechanism that restricts formation of viable heterokaryons when incompatible alleles of specific het loci interact. In Podospora anserina, three non-allelic incompatibility systems have been genetically defined involving interactions between het-c and het-d, het-c and het-e, het-r and het-v. het-d and het-e are paralogues belonging to the HNWD gene family that encode proteins of the STAND class. HET-D and HET-E proteins comprise an N-terminal HET effector domain, a central GTP binding site and a C-terminal WD repeat domain constituted of tandem repeats of highly conserved WD40 repeat units that define the specificity of alleles during incompatibility. The WD40 repeat units of the members of this HNWD family are undergoing concerted evolution. By combining genetic analysis and gain of function experiments, we demonstrate that an additional member of this family, HNWD2, corresponds to the het-r non-allelic incompatibility gene. As for het-d and het-e, allele specificity at the het-r locus is determined by the WD repeat domain. Natural isolates show allelic variation for het-

Validation of suitable internal control genes for expression studies in aging.

Quantitative data from experiments of gene expression are often normalized through levels of housekeeping genes transcription by assuming that expression of these genes is highly uniform. This practice is being questioned as it becomes increasingly clear that the level of housekeeping genes expression may vary considerably in certain biological samples. To date, the validation of reference genes in aging has received little attention and suitable reference genes have not yet been defined. Our aim was to evaluate the expression stability of frequently used reference genes in human peripheral blood mononuclear cells with respect to aging. Using quantitative RT-PCR, we carried out an extensive evaluation of five housekeeping genes, i.e. 18s rRNA, ACTB, GAPDH, HPRT1 and GUSB, for stability of expression in samples from donors in the age range 35-74 years. The consistency in the expression stability was quantified on the basis of the coefficient of variation and two algorithms termed geNorm and NormFinder. Our results indicated GUSB be the most suitable transcript and 18s the least for accurate normalization in PBMCs. We also demonstrated that aging is a confounding factor with respect to stability of 18s, HPRT1 and ACTB expression, which were particularly prone to variability in aged donors

A role for lipid rafts in the protection afforded by docosahexaenoic acid against ethanol toxicity in primary rat hepatocytes.

International audience: Previously, we demonstrated that eicosapentaenoic acid enhanced ethanol-induced oxidative stress and cell death in primary rat hepatocytes via an increase in membrane fluidity and lipid raft clustering. In this context, another n-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA), was tested with a special emphasis on physical and chemical alteration of lipid rafts. Pretreatment of hepatocytes with DHA reduced significantly ethanol-induced oxidative stress and cell death. DHA protection could be related to an alteration of lipid rafts. Indeed, rafts exhibited a marked increase in membrane fluidity and packing defects leading to the exclusion of a raft protein marker, flotillin. Furthermore, DHA strongly inhibited disulfide bridge formation, even in control cells, thus suggesting a disruption of protein-protein interactions inside lipid rafts. This particular spatial organization of lipid rafts due to DHA subsequently prevented the ethanol-induced lipid raft clustering. Such a prevention was then responsible for the inhibition of phospholipase C-γ translocation into rafts, and consequently of both lysosome accumulation and elevation in cellular low-molecular-weight iron content, a prooxidant factor. In total, the present study suggests that DHA supplementation could represent a new preventive approach for patients with alcoholic liver disease based upon modulation of the membrane structures

Son, image, imaginaire

La subjectivité de la représentation descriptive ou picturale de l’autre résulte de relations multiples entre signifiant et signifié, image et chose, réel et virtuel, champ et hors-champ... Mais elle résulte également de l’interaction du transfert et du contre-transfert induits par la médiatisation de l’image. Comment dans ces conditions est-il possible de rendre compte d’une réalité non subjectivisée par l’observateur, afin de restituer son objectivité scientifique au film ethnographique ? Nous tenterons ici de cerner la problématique des relations de l’homme à son image et à l’imaginaire.The subjectivity of the descriptive or pictorial representation of the other is the result of multiple relationships between signifiant and signified, image and thing, real and virtual, in shot and off-screen... But subjectivity also results from the interaction of the transfer and counter-transfer induced by the mediation of images. How, in these conditions, is it possible to give an account of a reality non-subjectivized by the observer in order to restitute scientific objectivity to the ethnographic film? In this article we shall attempt to define the problem of Man’s relations with his image and his imagination

Protective action of n-3 fatty acids on benzo[a]pyrene-induced apoptosis through the plasma membrane remodeling-dependent NHE1 pathway

International audiencePlasma membrane is an early target of polycyclic aromatic hydrocarbons (PAH). We previously showed that the PAH prototype, benzo[a]pyrene (B[a]P), triggers apoptosis via DNA damage-induced p53 activation (genotoxic pathway) and via remodeling of the membrane cholesterol-rich microdomains called lipid rafts, leading to changes in pH homeostasis (non-genotoxic pathway). As omega-3 (n-3) fatty acids can affect membrane composition and function or hamper in vivo PAH genotoxicity, we hypothesized that addition of physiologically relevant levels of polyunsaturated n-3 fatty acids (PUFAs) might interfere with B[a]P-induced toxicity. The effects of two major PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), were tested on B[a]P cytotoxicity in the liver epithelial cell line F258. Both PUFAs reduced B[a]P-induced apoptosis. Surprisingly, pre-treatment with DHA increased the formation of reactive B[a]P metabolites, resulting in higher levels of B[a]P-DNA adducts. EPA had no apparent effect on B[a]P metabolism or related DNA damage. EPA and DHA prevented B[a]P-induced apoptotic alkalinization by affecting Na(+)/H(+) exchanger 1 activity. Thus, the inhibitory effects of omega-3 fatty acids on B[a]P-induced apoptosis involve a non-genotoxic pathway associated with plasma membrane remodeling. Our results suggest that dietary omega-3 fatty acids may have marked effects on the biological consequences of PAH exposure

Ethnologie et préhistoire au quotidien

Le IXe Championnat européen de tir aux armes préhistoriques du Mas d’Azil (Ariège) a réuni plus de soixante-dix participants représentant l’Italie, l’Allemagne, l’Angleterre, la Belgique, les Pays‑Bas, l’Espagne et la France, devant la grotte du Mas d’Azil, mondialement connue des préhistoriens pour la spécificité des vestiges exhumés par  Edouard Piette au début du XXe siècle. Malgré certains aspects folkloriques, cette manifestation mérite qu’on s’y arrête car elle met clairement en éviden..

WD-repeat instability and diversification of the Podospora anserina hnwd non-self recognition gene family

<p>Abstract</p> <p>Background</p> <p>Genes involved in non-self recognition and host defence are typically capable of rapid diversification and exploit specialized genetic mechanism to that end. Fungi display a non-self recognition phenomenon termed heterokaryon incompatibility that operates when cells of unlike genotype fuse and leads to the cell death of the fusion cell. In the fungus <it>Podospora anserina</it>, three genes controlling this allorecognition process <it>het-d, het-e </it>and <it>het-r </it>are paralogs belonging to the same <it>hnwd </it>gene family. HNWD proteins are STAND proteins (signal transduction NTPase with multiple domains) that display a WD-repeat domain controlling recognition specificity. Based on genomic sequence analysis of different <it>P. anserina </it>isolates, it was established that repeat regions of all members of the gene family are extremely polymorphic and undergoing concerted evolution arguing for frequent recombination within and between family members.</p> <p>Results</p> <p>Herein, we directly analyzed the genetic instability and diversification of this allorecognition gene family. We have constituted a collection of 143 spontaneous mutants of the <it>het-R </it>(<it>HNWD2</it>) and <it>het-E </it>(<it>hnwd5</it>) genes with altered recognition specificities. The vast majority of the mutants present rearrangements in the repeat arrays with deletions, duplications and other modifications as well as creation of novel repeat unit variants.</p> <p>Conclusions</p> <p>We investigate the extreme genetic instability of these genes and provide a direct illustration of the diversification strategy of this eukaryotic allorecognition gene family.</p