A spatial accommodation by neighboring cells is required for organ initiation in Arabidopsis.

Lateral root formation in plants can be studied as the process of interaction between chemical signals and physical forces during development. Lateral root primordia grow through overlying cell layers that must accommodate this incursion. Here, we analyze responses of the endodermis, the immediate neighbor to an initiating lateral root. Endodermal cells overlying lateral root primordia lose volume, change shape, and relinquish their tight junction-like diffusion barrier to make way for the emerging lateral root primordium. Endodermal feedback is absolutely required for initiation and growth of lateral roots, and we provide evidence that this is mediated by controlled volume loss in the endodermis. We propose that turgidity and rigid cell walls, typical of plants, impose constraints that are specifically modified for a given developmental process.

MHC class I expression dependent on bacterial infection and parental factors in whitefish embryos (Salmonidae).

Ecological conditions can influence not only the expression of a phenotype, but also the heritability of a trait. As such, heritable variation for a trait needs to be studied across environments. We have investigated how pathogen challenge affects the expression of MHC genes in embryos of the lake whitefish Coregonus palaea. In order to experimentally separate paternal (i.e. genetic) from maternal and environmental effects, and determine whether and how stress affects the heritable variation for MHC expression, embryos were produced in full-factorial in vitro fertilizations, reared singly, and exposed at 208 degree days (late-eyed stage) to either one of two strains of Pseudomonas fluorescens that differ in their virulence characteristics (one increased mortality, while both delayed hatching time). Gene expression was assessed 48 h postinoculation, and virulence effects of the bacterial infection were monitored until hatching. We found no evidence of MHC class II expression at this stage of development. MHC class I expression was markedly down-regulated in reaction to both pseudomonads. While MHC expression could not be linked to embryo survival, the less the gene was expressed, the earlier the embryos hatched within each treatment group, possibly due to trade-offs between immune function and developmental rate or further factors that affect both hatching timing and MHC expression. We found significant additive genetic variance for MHC class I expression in some treatments. That is, changes in pathogen pressures could induce rapid evolution in MHC class I expression. However, we found no additive genetic variance in reaction norms in our study population.

The handaxe and the microscope: individual and social learning in a multidimensional model of adaptation

When individuals learn by trial-and-error, they perform randomly chosen actions and then reinforce those actions that led to a high payoff. However, individuals do not always have to physically perform an action in order to evaluate its consequences. Rather, they may be able to mentally simulate actions and their consequences without actually performing them. Such fictitious learners can select actions with high payoffs without making long chains of trial-and-error learning. Here, we analyze the evolution of an n-dimensional cultural trait (or artifact) by learning, in a payoff landscape with a single optimum. We derive the stochastic learning dynamics of the distance to the optimum in trait space when choice between alternative artifacts follows the standard logit choice rule. We show that for both trial-and-error and fictitious learners, the learning dynamics stabilize at an approximate distance of root n/(2 lambda(e)) away from the optimum, where lambda(e) is an effective learning performance parameter depending on the learning rule under scrutiny. Individual learners are thus unlikely to reach the optimum when traits are complex (n large), and so face a barrier to further improvement of the artifact. We show, however, that this barrier can be significantly reduced in a large population of learners performing payoff-biased social learning, in which case lambda(e) becomes proportional to population size. Overall, our results illustrate the effects of errors in learning, levels of cognition, and population size for the evolution of complex cultural traits. (C) 2013 Elsevier Inc. All rights reserved.

Alps, genes, and chromosomes: their role in the formation of species in the Sorex araneus group (Mammalia, Insectivora), as inferred from two hybrid zones.

During the Pleistocene glaciations, the Alps were an efficient barrier to gene flow between isolated populations, often leading to allopatric speciation. Afterwards, the Alps strongly influenced the post-glacial recolonization of Europe and represent a major suture zone between differentiated populations. Two hybrid zones in the Swiss and French Alps between genetically and chromosomally well-differentiated species-the Valais shrew, Sorex antinorii, and the common shrew, S. araneus-were studied karyotypically and by analyzing the distribution of seven microsatellite loci. In the center of the Haslital hybrid zone the two species coexist over a distance of 900 m. Hybrid karyotypes, among them the most complex known in Sorex, are rare. F-statistics based on microsatellite data revealed a strong heterozygote deficit only in the center of the zone, due to the sympatric distribution of the two species with little hybridization between them. Structuring within the species (both F(IS) and F(ST)) was low. An hierarchical analysis showed a high level of interspecific differentiation. Results were compared with those previously reported in another hybrid zone located at Les Houches in the French Alps. Genetic structuring within and between species was comparable in both hybrid zones, although chromosomal incompatibilities are more important in Haslital, where a linkage block of the race-specific chromosomes should additionally impede gene flow. Evidence for a more restricted gene flow in Haslital comes from the genetically intermediate hybrid karyotypes, whereas in Les Houches, hybrid karyotypes are genetically identical to individuals of the pure karyotypic races. Genic and chromosomal introgression was observed in Les Houches, but not in Haslital. The possible influence of a river, separating the two species at Les Houches, on gene flow is discussed.

Oligogalacturonide defense signals in plants: large fragments interact with the plasma membrane in vitro.

Oligogalacturonides are plant cell wall-derived regulatory molecules which stimulate defense gene expression during pathogenesis. In vitro, these compounds enhance the phosphorylation of an approximately 34-kDa protein (pp34) in purified plasma membranes from potato and tomato leaves. We now show that polygalacturonate-enhanced phosphorylation of pp34 occurs in plasma membranes purified from tomato roots, hypocotyls, and stems and from undifferentiated potato cells. Furthermore, a similar phosphorylation is detected in leaf plasma membranes from soybean, a plant distantly related to tomato. Purified oligogalacturonides 13 to at least 26 residues long stimulate pp34 thiophosphorylation in vitro. This stimulation pattern differs from the induction of many known defense responses in vivo, where a narrower range of smaller fragments, between approximately 10 and 15 residues long, are active. On the basis of these differences we suggest that observed effects of applied exogenous oligogalacturonides on defense responses may not necessarily reflect the situation during pathogenesis. The cell wall could act as a barrier to many exogenous oligo- and polygalacturonides as well as other large regulatory ligands.

Awareness of human immunodeficiency virus screening guidelines is low in emergency departments of western Switzerland.

Background: Human immunodeficiency virus (HIV) prevalence in Switzerland is 0.4% and 30% of HIV patients are diagnosed with CD4 counts <200 cells/microliter. In 2010, the Swiss Federal Office of Public Health (SFOP) published updated guidelines regarding Physician- Initiated Counseling and Testing (PICT) for HIV. In the new guidelines, when acute HIV infection is suspected or HIV is among the differential diagnoses, an HIV test is performed without risk assessment nor prior counseling, unless the patient specifically refuses it. Counseling and verbal consent are still required when the patient asks for an HIV test or belongs to a high risk group. Whist HIV testing in the emergency departments (ED) is recommended, only 1% of patients are currently screened. Lack of awareness among physicians has been cited in the literature as the first barrier to guideline implementation. Objectives: To test if physicians working in EDs of 5 large teaching hospitals in western Switzerland, admitting 175,000 patients / year, were aware of the updated SFOP guidelines. Methods: A survey was delivered to 167 ED physicians in the summer of 2011. The survey consisted of 26 vignettes designed to test whether physicians would request an HIV test according to the new guidelines and if they knew when the PICT strategy was allowed or counseling required. Finally, physicians were asked the number of HIV tests they had requested in the previous 4 weeks, and if they were aware of the new HIV guidelines. Results are presented as mean and standard deviation, median and interquartile range (IQR), or as proportions; Student's t test was used to compare continuous variables; Results: 143 physicians returned the survey (86%); mean age was 32 ± 8 years, and median postgraduate experience of 6 years (IQR 3-12); 52% were male and 17% were attendings. The percentage of correct responses was 60 ± 13% with no difference between attendings and residents (p = 0.31); 2 of the 3 questions with the lowest scores were failure to recognize situations in which HIV testing was indicated, and the third one a failure to recognize acute HIV infection. 82% of physicians were not aware of the new guidelines. The median number of test requests was 1 (IQR 0-2, range 1-10). Conclusion: ED physicians are not aware of current HIV screening guidelines published by the SFOP, and rarely perform HIV tests. An information campaign is required if ED physicians are expected to play a significant role in the reduction of undiagnosed HIV patients.

The endodermis.

A Casparian strip-bearing endodermis is a feature that has been invariably present in the roots of ferns and angiosperms for approximately 400 million years. As the innermost cortical layer that surrounds the central vasculature of roots, the endodermis acts as a barrier to the free diffusion of solutes from the soil into the stele. Based on an enormous body of anatomical and physiological work, the protective endodermal diffusion barrier is thought to be of major importance for many aspects of root biology, reaching from efficient water and nutrient transport to defense against soil-borne pathogens. Until recently, however, we were ignorant about the genes and mechanisms that drive the differentiation of this intricately structured barrier. Recent work in Arabidopsis has now identified the first major players in Casparian strip formation. A mechanistic understanding of endodermal differentiation will finally allow us to specifically interfere with endodermal barrier function and study the effects on plant growth and survival under various stress conditions. Here, I critically review the major findings and models related to endodermal structure and function from other plant species and assess them in light of recent molecular data from Arabidopsis, pointing out where the older, descriptive work can provide a framework and inspiration for further molecular dissection.

Divergence with gene flow and fine-scale phylogeographical structure in the wedge-billed woodcreeper, Glyphorynchus spirurus, a Neotropical rainforest bird.

Determining the relative roles of vicariance and selection in restricting gene flow between populations is of central importance to the evolutionary process of population divergence and speciation. Here we use molecular and morphological data to contrast the effect of isolation (by mountains and geographical distance) with that of ecological factors (altitudinal gradients) in promoting differentiation in the wedge-billed woodcreeper, Glyphorynchus spirurus, a tropical forest bird, in Ecuador. Tarsus length and beak size increased relative to body size with altitude on both sides of the Andes, and were correlated with the amount of moss on tree trunks, suggesting the role of selection in driving adaptive divergence. In contrast, molecular data revealed a considerable degree of admixture along these altitudinal gradients, suggesting that adaptive divergence in morphological traits has occurred in the presence of gene flow. As suggested by mitochondrial DNA sequence data, the Andes act as a barrier to gene flow between ancient subspecific lineages. Genome-wide amplified fragment length polymorphism markers reflected more recent patterns of gene flow and revealed fine-scale patterns of population differentiation that were not detectable with mitochondrial DNA, including the differentiation of isolated coastal populations west of the Andes. Our results support the predominant role of geographical isolation in driving genetic differentiation in G. spirurus, yet suggest the role of selection in driving parallel morphological divergence along ecological gradients.

PEC1/AtABCG32 transport function in cuticle biosynthesis

Most aerial parts of the plants are covered by a hydrophobic coating called cuticle. The cuticle is formed of cutin, a complex mixture of esterified fatty acids that are embedded and associated with waxes. The cuticle often appears as a superposition of layers of different composition: The cuticle proper formed of cutin and a mixture of waxes and underneath, the cuticle layer containing cutin, intracuticular waxes and polysaccharides of the cell wall. In addition to its involvement in plant development by preventing organ fusions, the cuticle acts as a barrier to prevent water loss and protect plants against environmental aggressions such as excessive radiation or pathogens attacks. PEC1/AtABCG32 is an ABC transporter from the PDR family involved in cutin biosynthesis. Characterization of the peci mutant in Arabidopsis thaliana showed that PEC1 plays a significant role in the diffusion barrier formation in leaves and petals. The cuticles of leaves and flowers of peci are permeable and the cuticular layer rather than the cuticular proper was altered in the petals, underlining the importance of this particular layer in the maintenance of the diffusion barrier. Chemical analysis on the flower cutin monomer composition of ped mutant revealed a decrease in hydroxylated cutin monomers, suggesting a function of PEC1 in the incorporation of these monomers in the polymer cutin. However, the exact nature of the substrates of PEC1 remained elusive. PEC1 homologues in barley and rice, respectively HvABCG31/EIBI1 and OsABCG31, are also implicated in cuticle biosynthesis. Interestingly, the rice mutant displays more severe phenotypes such as dwarfism and spreading necrosis conducting to the seedling death. In this work, we further characterized osabcg31 mutant and hairpin-RNAi downregulated OsABCG31 plant lines showing reduced growth and cuticle permeability. Our analysis showed a decrease in hydroxylated cutin monomers and severe disruptions in the cuticle, which explain the permeability. Further insights into the function of the cuticle in rice resistance/susceptibility to Pathogens were obtained after inoculation with Magnaporthe oryzae, the fungus responsible for the rice blast disease. Osabcg31 as well as the transgenic lines downregulating OsABCG31 showed increased resistance to the fungus. However, only later steps of infection are reduced . and no impact is obseived on the germination or penetration stages, suggesting that the cuticle disruption per se is not responsible for the resistance. We further investigated the cause of the resistance by analyzing the expression of defense related gene in osabcg31 prior to infection. We found that osabcg31 constitutively express defense related genes, which may explain the resistance, the dwarfism and the cell death. osabcg31 is thus a tool to study the connection between cuticle, plant development and defense signaling networks in rice. The transport function of PEC1 family members is still unknown. In order to link cutin biosynthesis and transport activity, we combined ped mutation with mutations in cutin synthesis related genes. Here, we show that PEC1 acts independently from GPAT4 and GPAT8 pathway and partially overlaps with GPAT6 biosynthesis pathway that leads to the production of hydroxylated C16 cutin precursor 2-Mono(10,16-dihydroxyhexadecanoylJglycerol (2-MHG). In addition, we noticed that despite a comparable cutin monomer composition, ped mutant leaves cuticle are permeable while that of gpat6 mutant are not. This finding raises the possibility of PEC1 being required for the incorporation of C16 hydroxylated monomers and their structural arrangement rather than their direct transport towards the cuticle. A careful investigation of the cuticle permeability, cutin composition and ultrastructure during leave development in Wt plants and ped mutants revealed a possible different regulation of several pathways of cutin biosynthesis and showed the importance of PEC1 function early during leave cuticle maturation. In order to elucidate the transport activity of PEC1, we successfully expressed PEC1 in Nicotiana benthamiana plant system for direct transport experiments. This system will be used to test the PEC 1-dependent transport of potential substrates such as sn-2-monoacylglycerol loaded with a hydroxylated C16 fatty acid. -- Toutes les parties aériennes des plantes sont recouvertes d'une couche hydrophobe appelée «cuticule». Cette cuticule est composée de cutine, un polymère d'acides gras estérifiés, et de cires. La cuticule apparaît souvent sous forme de couches superposées: une première couche extérieure appelée «cuticle proper» formée de cutine et d'un mélange de cires, et une deuxième couche, la «cuticle layer», formée de cutine associée à des cires intracuticulaires et des polysaccharides pariétaux. La cuticule joue le rôle de barrière prévenant contre la perte d'eau et les agressions environnementales. AtABCG32/PEC1 est un transporteur ABC de la famille des PDR impliqué dans la synthèse de la cutine. L'étude du mutant peci d'Arabidopsis thaliana a révélé une fonction de PEC1 dans la formation de la barrière de diffusion. La cuticule des feuilles et fleurs de peci est perméable. Des altérations de la «cuticle layer» ont été démontrées, soulignant son importance dans le maintien de la barrière. L'analyse de la composition de la cutine de peci a montré une réduction spécifique en monomères hydroxylés, suggérant un rôle de PEC1 dans leur incorporation dans la cuticule. Cependant, la nature exacte des substrats de PEC1 n'a pas été identifiée. PEC1 possède deux homologues chez l'orge et le riz, respectivement HvABCG31 et OsABCG31, et qui sont impliqués dans la biosynthèse de la cuticule. Chez le riz, des phénotypes plus sévères ont été observés tels que nanisme et nécroses conduisant à la mort des jeunes plants. Dans cette étude, nous avons continué la caractérisation de osabcg31 ainsi que des lignées de riz sous exprimant le gène OsABCG31 et présentant une cuticule perméable tout en ayant une meilleure croissance. Notre étude a démontré une réduction des monomères hydroxylés de cutine et une désorganisation de la structure de la cuticule, aggravée dans le mutant osabcg31. Ce résultat explique la perméabilité observée. Des mformations P|us approfondies sur l'implication de la cuticule dans la résistance aux pathogènes ont été obtenues après inoculation du mutant osabcg31 et les lignées sous- exprimant OsABCG31 avec une souche virulente de Magnaporthe Oryzae, le champignon responsable de la pyriculariose du riz. Les différentes lignées testées ont démontré une résistance au pathogène. Cependant, seules les étapes tardives de l'infection sont réduites et aucun impact n'est observé sur la germination des spores ou la pénétration du champignon, suggérant que les modifications de la cuticule ne sont pas directement à l'origine de la résistance. L'analyse de l'expression de gènes impliqués dans la résistance à Magnaporthe.oryzae a mis en évidence l'expression constitutive de ces gènes en l'absence de tout contact avec le pathogène. Ceci explique la résistance, le nanisme et la mort cellulaire observés. Ainsi, osabcg31 représente un outil efficace pour l'étude intégrée des systèmes de régulation de la défense, de développement des plantes et la cuticule. La nature des substrats transportés par PEC1/AtABCG32 reste inconnue. Dans le but d'établir une liaison entre biosynthèse de cutine et transport des précurseurs par PEC1, la mutation peci a été combinée avec des mutants impliqués dans différentes voies de biosynthèse. Cette étude a démontré une fonction indépendante de PEC1 de la voie de biosynthèse impliquant les enzymes GPAT4 et GPAT8, et une fonction partiellement indépendante de la voie impliquant GPAT6 qui mène à la production de précurseurs sn-2- monoacylglycerol chargés en acides gras en C16 (2-MHG). De plus, malgré un profil similaire en monomères de cutine, gpat6 conserve une cuticule imperméable alors que celle de PEC1 est perméable. Ceci suggère que PEC1 est nécessaire à l'incorporation des monomères en C16 et leur arrangement structurel plutôt que simplement à leur transport direct. L'étude approfondie de la perméabilité cuticulaire, de la structure ainsi que de la composition en cutine pendant le développement des feuilles de peci et la plante sauvage a révélé l'existence de différentes régulations des voies de biosynthèses des monomères et a démontré l'importance de PEC1 dans les premières étapes de la mise en place de la cuticule. Pour identifier les substrats transportés, l'expression de PEC1 chez le système hétérologue Nicotiana benthamiana a été conduite avec succès. Ce système sera utilisé pour tester le transport de substrats potentiels tels que le sn-2-monoacylglycerol chargé en acide gras en C16.

Gut physiology mediates a trade-off between adaptation to malnutrition and susceptibility to food-borne pathogens.

The animal gut plays a central role in tackling two common ecological challenges, nutrient shortage and food-borne parasites, the former by efficient digestion and nutrient absorption, the latter by acting as an immune organ and a barrier. It remains unknown whether these functions can be independently optimised by evolution, or whether they interfere with each other. We report that Drosophila melanogaster populations adapted during 160 generations of experimental evolution to chronic larval malnutrition became more susceptible to intestinal infection with the opportunistic bacterial pathogen Pseudomonas entomophila. However, they do not show suppressed immune response or higher bacterial loads. Rather, their increased susceptibility to P. entomophila is largely mediated by an elevated predisposition to loss of intestinal barrier integrity upon infection. These results may reflect a trade-off between the efficiency of nutrient extraction from poor food and the protective function of the gut, in particular its tolerance to pathogen-induced damage.

Early antibiotic administration affects the gut barrier function and the immune response to oral antigen in suckling rats

Abstract: The increasingly high hygienic standards characterizing westernized societies correlate with an increasingly high prevalence of allergic disease. Initially based on these observations, the hygiene hypothesis postulates that reduced microbial stimulation during infancy impairs the immune system development and increases the risk of allergy. Moreover, there is increasing evidence that the crosstalk existing between the intestine and the resident microbiota is crucial for gut homeostasis. In particular, bacterial colonization of the gut affects the integrity of the gut barrier and stimulates the development of the gut associated immune tissue, both phenomena being essential for the immune system to mount a controlled response to food antigens. Therefore, alterations in the microbial colonization process, by compromising the barrier homeostasis, may increase the risk of food allergy. In this context, antibiotic treatment, frequently prescribed during infancy, affects gut colonization by bacteria. However, little is known about the impact of alterations in the colonization process on the maturation of the gut barrier and on the immunological response to oral antigens. The objective of this work was to determine the impact of a commercial antibiotic preparation employed in pediatric settings on the gut barrier status at the critical period of the suckling/weaning transition and to evaluate the physiological consequences of this treatment in terms of immune response to food antigens. We established an antibiotic-treated suckling rat model relevant to the pediatric population in terms of type, dose and route of administration of the antibiotic and of changes in the patterns of microbial colonization. Oral tolerance to a novel luminal antigen (ovalbumin) was impaired when the antigen was introduced during antibiotic treatment. These results paralleled to alterations in the intestinal permeability to macromolecules and reduced intestinal expression of genes coding for the major histocomptatibility complex II molecules, which suggest a reduced capacity of antigen handling and presentation in the intestine of the antibiotic-treated animals. In addition, low luminal IgA levels and reduced intestinal expression of genes coding for antimicrobial proteins suggest that protection against pathogens was reduced under antibiotic treatment. In conclusion, we observed in suckling rats that treatment with abroad-spectrum antibiotic commonly used in pediatric practices reduced the capacity of the immune system to develop tolerance. The impact of the antibiotic treatment on the immune response to the antigen-was likely mediated by the alterations of the gut microbiota, through impairment in the mechanisms of antigen handling and presentation. This work reinforces the body of data supporting a key role of the intestinal microbiota modulating the risk of allergy development and leads us to propose that the introduction of new food antigens should be avoided during antibiotic treatment in infants. Résumé: L'augmentation du niveau d'hygiène caractérisant les sociétés occidentales semble être fortement corrélée avec l'augmentation des cas d'allergie dans ces pays. De cette observation est née l'hypothèse qu'une diminution des stimuli microbiens pendant l'enfance modifie le développement du système immunitaire augmentant ainsi le risque d'allergie. En ce sens, un nombre croissant de données indiquent que les interactions existant entre l'intestin et les bactéries résidantes sont cruciales pour l'équilibre du système. En effet, la présence de bactéries dans l'intestin affecte l'intégrité de sa fonction de barrière et stimule le développement du système immunitaire intestinal. Ces deux paramètres étant essentiels à la mise en place d'une réponse contrôlée vis à vis d'un antigène reçu oralement, toute modification du processus naturel de colonisation compromettant l'équilibre intestinal pourrait augmenter le risque d'allergie. Les traitements aux antibiotiques, fréquemment prescrits en pédiatrie, modifient de façon conséquente le processus de colonisation bactérienne. Cependant peu de données existent concernant l'impact d'une altération du processus de colonisation sur la maturation de la barrière intestinale et de la réponse immunitaire dirigée contre un antigène. L'objectif de ce travail était de déterminer l'impact d'un antibiotique commercial et employé en pédiatrie sur l'état de la barrière intestinale au moment critique du sevrage et d'évaluer les conséquences physiologiques d'un tel traitement sur la réponse immune à un antigène alimentaire. Nous avons mis en place un modèle de rats allaités, traités à l'antibiotique, le plus proche possible des pratiques pédiatriques, en terme de nature, dose et voie d'administration de l'antibiotique. Nous avons constaté que l'établissement de la tolérance orale à un nouvel antigène (l'ovalbumine) est altéré quand celui-ci est donné pour la première fois au cours du traitement antibiotique. Ces résultats coïncident avec une diminution de la perméabilité intestinale aux macromolécules, ainsi qu'avec une diminution de l'expression des gènes codant pour les molécules du complexe majeur d'histocomptatibilité de classe II, suggérant une modification de l'apprêtement et de la présentation de l'antigène au niveau intestinal chez les rats traités à l'antibiotique. De plus, un faible taux d'IgA et une diminution de l'expression des gènes codant pour des protéines antimicrobiennes, observés après l'administration d'antibiotique, laissent à penser que la protection contre un pathogène est diminuée lors d'un traitement antibiotique. En conclusion, nous avons observé qu'un traitement antibiotique à large spectre d'activité, couramment utilisé en pédiatrie, réduit la capacité d'induction de la tolérance orale chez le rat allaité. L'impact du traitement antibiotique sur la réponse immune semble induite par l'altération de la flore intestinale via son effet sur les mécanismes d'apprêtement et de présentation de l'antigène. Ce travail renforce l'ensemble des données existantes qui accorde à la flore intestinale un rôle clef dans la modulation du risque de développement d'allergie et nous amène à recommander d'éviter l'introduction d'un nouvel aliment lorsqu'un enfant est traité aux antibiotiques.

Placental growth factor contributes to micro-vascular abnormalization and blood-retinal barrier breakdown in diabetic retinopathy.

OBJECTIVE: There are controversies regarding the pro-angiogenic activity of placental growth factor (PGF) in diabetic retinopathy (DR). For a better understanding of its role on the retina, we have evaluated the effect of a sustained PGF over-expression in rat ocular media, using ciliary muscle electrotransfer (ET) of a plasmid encoding rat PGF-1 (pVAX2-rPGF-1). MATERIALS AND METHODS: pVAX2-rPGF-1 ET in the ciliary muscle (200 V/cm) was achieved in non diabetic and diabetic rat eyes. Control eyes received saline or naked plasmid ET. Clinical follow up was carried out over three months using slit lamp examination and fluorescein angiography. After the control of rPGF-1 expression, PGF-induced effects on retinal vasculature and on the blood-external barrier were evaluated respectively by lectin and occludin staining on flat-mounts. Ocular structures were visualized through histological analysis. RESULTS: After fifteen days of rPGF-1 over-expression in normal eyes, tortuous and dilated capillaries were observed. At one month, microaneurysms and moderate vascular sprouts were detected in mid retinal periphery in vivo and on retinal flat-mounts. At later stages, retinal pigmented epithelial cells demonstrated morphological abnormalities and junction ruptures. In diabetic retinas, PGF expression rose between 2 and 5 months, and, one month after ET, rPGF-1 over-expression induced glial activation and proliferation. CONCLUSION: This is the first demonstration that sustained intraocular PGF production induces vascular and retinal changes similar to those observed in the early stages of diabetic retinopathy. PGF and its receptor Flt-1 may therefore be looked upon as a potential regulatory target at this stage of the disease.

Toll-Interacting Protein Modulates Gut Flora Composition, Epithelial Barrier Integrity and Susceptibility to Colitis

Toll-like receptor ( TLR) s ignals are key to maintaining hostmicrobial i nteractions. T he T oll-interacting-protein (Tollip) is a ubiquitously-expressed inhibitor of inflammasome a nd TLR signaling. W e hypothesized that T ollip might control g ut homeostasis. G enetic ablation of T ollip d id not lead to spontaneous colitis b ut h ad d ramatic c onsequences on t he intestinal expression of the α-defensin cryptidin 4 and the C-type lectin R EGIIIβ. These c hanges were associated with intestinal dysbiosis a nd e nhanced colonization b y segmented filamentous bacteria - a k ey p ro-inflammatory component of the microbiota. Tollip deficiency increased susceptibility to dextran sulfate sodium (DSS) colitis and aggravated chronic Th17-driven colitis in IL-10-/- mice. Flora d epletion w ith a ntibiotics in T ollip-/- mice w as not sufficient to restore DSS colitis susceptibility and deletion of Tollip in n on-hematopoietic c ells using bone-marrow chimeras w as sufficient to increase s usceptibility t o DSS colitis. After D SS administration, we o bserved several e pithelial defects i n Tollip-/- mice including early tight junctions disruption, increased epithelial apoptosis, and increased intestinal permeability. Overall, our data show that T ollip significantly impacts intestinal h omeostasis by controlling b acterial ecology and intestinal r esponse to chemical and immunological stresses.