Pectin- Derived Acidic Oligosaccharides Improve the Outcome of Pseudomonas aeruginosa Lung Infection in C57BL/6 Mice

The administration of prebiotics as oligosaccharides (OS), by acting on intestinal microbiota, could modulate the immune and inflammatory response and represent a new strategy to improve the outcome of bacterial infection. The aim of this study was to determine whether pectin-derived acidic oligosaccharides (pAOS) could modulate the outcome of pulmonary P. aeruginosa (PA) infection in C57BL/6 mice, which develop a Th1 response to PA lung infection. Mice were randomized for 5 weeks to consume a control or a 5% pAOS diet and chronically infected by PA. Resistance to a second PA infection was also analyzed by reinfecting the surviving mice 2 weeks after the first infection. Compared with control mice, mice fed pAOS had reduced mortality (P<0.05). This improvement correlated with a better control of the inflammatory response with a lower neutrophil count on day 1 (P<0.05), a sustained neutrophil and macrophage recruitment on days 2 and 3 (P<0.01) a greater and sustained IL-10 release in lung (P<0.05) and a reduction of the Th1 response and M1 activation with a lower IFN-γ/IL-4 (P<0.01) and nos2/arg1 (P<0.05) ratios. These results coincided with a modulation of the intestinal microbiota as shown by an increased butyric acid concentration in feces (P<0.05). Moreover, pAOS decreased the bacterial load (P<0.01) in mice reinfected 2 weeks after the first infection, suggesting that pAOS could reduce pulmonary exacerbations. In conclusion, pAOS improved the outcome of PA infection in C57BL/6 mice by modulating the intestinal microbiota and the inflammatory and immune responses.     

Distinct polymer physics principles govern chromatin dynamics in mouse and Drosophila topological domains

Background

In higher eukaryotes, the genome is partitioned into large "Topologically Associating Domains" (TADs) in which the chromatin displays favoured long-range contacts. While a crumpled/fractal globule organization has received experimental supports at higher-order levels, the organization principles that govern chromatin dynamics within these TADs remain unclear. Using simple polymer models, we previously showed that, in mouse liver cells, gene-rich domains tend to adopt a statistical helix shape when no significant locus-specific interaction takes place.

Results

Here, we use data from diverse 3C-derived methods to explore chromatin dynamics within mouse and Drosophila TADs. In mouse Embryonic Stem Cells (mESC), that possess large TADs (median size of 840 kb), we show that the statistical helix model, but not globule models, is relevant not only in gene-rich TADs, but also in gene-poor and gene-desert TADs. Interestingly, this statistical helix organization is considerably relaxed in mESC compared to liver cells, indicating that the impact of the constraints responsible for this organization is weaker in pluripotent cells. Finally, depletion of histone H1 in mESC alters local chromatin flexibility but not the statistical helix organization. In Drosophila, which possesses TADs of smaller sizes (median size of 70 kb), we show that, while chromatin compaction and flexibility are finely tuned according to the epigenetic landscape, chromatin dynamics within TADs is generally compatible with an unconstrained polymer configuration.

Conclusions

Models issued from polymer physics can accurately describe the organization principles governing chromatin dynamics in both mouse and Drosophila TADs. However, constraints applied on this dynamics within mammalian TADs have a peculiar impact resulting in a statistical helix organization.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1786-8) contains supplementary material, which is available to authorized users.     

Age-Related Changes in the Functional Network Underlying Specific and General Autobiographical Memory Retrieval: A Pivotal Role for the Anterior Cingulate Cortex

Age-related changes in autobiographical memory (AM) recall are characterized by a decline in episodic details, while semantic aspects are spared. This deleterious effect is supposed to be mediated by an inefficient recruitment of executive processes during AM retrieval. To date, contrasting evidence has been reported on the neural underpinning of this decline, and none of the previous studies has directly compared the episodic and semantic aspects of AM in elderly. We asked 20 young and 17 older participants to recall specific and general autobiographical events (i.e., episodic and semantic AM) elicited by personalized cues while recording their brain activity by means of fMRI. At the behavioral level, we confirmed that the richness of episodic AM retrieval is specifically impoverished in aging and that this decline is related to the reduction of executive functions. At the neural level, in both age groups, we showed the recruitment of a large network during episodic AM retrieval encompassing prefrontal, cortical midline and posterior regions, and medial temporal structures, including the hippocampus. This network was very similar, but less extended, during semantic AM retrieval. Nevertheless, a greater activity was evidenced in the dorsal anterior cingulate cortex (dACC) during episodic, compared to semantic AM retrieval in young participants, and a reversed pattern in the elderly. Moreover, activity in dACC during episodic AM retrieval was correlated with inhibition and richness of memories in both groups. Our findings shed light on the direct link between episodic AM retrieval, executive control, and their decline in aging, proposing a possible neuronal signature. They also suggest that increased activity in dACC during semantic AM retrieval in the elderly could be seen as a compensatory mechanism underpinning successful AM performance observed in aging. These results are discussed in the framework of recently proposed models of neural reorganization in aging.     

Truncating mutations in NRXN2 and NRXN1 in autism spectrum disorders and schizophrenia

Growing genetic evidence is converging in favor of common pathogenic mechanisms for autism spectrum disorders (ASD), intellectual disability (ID or mental retardation) and schizophrenia (SCZ), three neurodevelopmental disorders affecting cognition and behavior. Copy number variations and deleterious mutations in synaptic organizing proteins including NRXN1 have been associated with these neurodevelopmental disorders, but no such associations have been reported for NRXN2 or NRXN3. From resequencing the three neurexin genes in individuals affected by ASD (n = 142), SCZ (n = 143) or non-syndromic ID (n = 94), we identified a truncating mutation in NRXN2 in a patient with ASD inherited from a father with severe language delay and family history of SCZ. We also identified a de novo truncating mutation in NRXN1 in a patient with SCZ, and other potential pathogenic ASD mutations. These truncating mutations result in proteins that fail to promote synaptic differentiation in neuron coculture and fail to bind either of the established postsynaptic binding partners LRRTM2 or NLGN2 in cell binding assays. Our findings link NRXN2 disruption to the pathogenesis of ASD for the first time and further strengthen the involvement of NRXN1 in SCZ, supporting the notion of a common genetic mechanism in these disorders.     

Non-stimulated, agonist-stimulated and store-operated Ca2+ influx in MDA-MB-468 breast cancer cells and the effect of EGF-induced EMT on calcium entry

In addition to their well-defined roles in replenishing depleted endoplasmic reticulum (ER) Ca(2+) reserves, molecular components of the store-operated Ca(2+) entry pathway regulate breast cancer metastasis. A process implicated in cancer metastasis that describes the conversion to a more invasive phenotype is epithelial-mesenchymal transition (EMT). In this study we show that EGF-induced EMT in MDA-MB-468 breast cancer cells is associated with a reduction in agonist-stimulated and store-operated Ca(2+) influx, and that MDA-MB-468 cells prior to EMT induction have a high level of non-stimulated Ca(2+) influx. The potential roles for specific Ca(2+) channels in these pathways were assessed by siRNA-mediated silencing of ORAI1 and transient receptor potential canonical type 1 (TRPC1) channels in MDA-MB-468 breast cancer cells. Non-stimulated, agonist-stimulated and store-operated Ca(2+) influx were significantly inhibited with ORAI1 silencing. TRPC1 knockdown attenuated non-stimulated Ca(2+) influx in a manner dependent on Ca(2+) influx via ORAI1. TRPC1 silencing was also associated with reduced ERK1/2 phosphorylation and changes in the rate of Ca(2+) release from the ER associated with the inhibition of the sarco/endoplasmic reticulum Ca(2+)-ATPase (time to peak [Ca(2+)](CYT) = 188.7 ± 34.6 s (TRPC1 siRNA) versus 124.0 ± 9.5 s (non-targeting siRNA); P<0.05). These studies indicate that EMT in MDA-MB-468 breast cancer cells is associated with a pronounced remodeling of Ca(2+) influx, which may be due to altered ORAI1 and/or TRPC1 channel function. Our findings also suggest that TRPC1 channels in MDA-MB-468 cells contribute to ORAI1-mediated Ca(2+) influx in non-stimulated cells.     

Modelling fungal sink competitiveness with grains for assimilates in wheat infected by a biotrophic pathogen

Background and Aims

Experiments have shown that biotrophic fungi divert assimilates for their growth. However, no attempt has been made either to account for this additional sink or to predict to what extent it competes with both grain filling and plant reserve metabolism for carbon. Fungal sink competitiveness with grains was quantified by a mixed experimental–modelling approach based on winter wheat infected by Puccinia triticina.

Methods

One week after anthesis, plants grown under controlled conditions were inoculated with varying loads. Sporulation was recorded while plants underwent varying degrees of shading, ensuring a range of both fungal sink and host source levels. Inoculation load significantly increased both sporulating area and rate. Shading significantly affected net assimilation, reserve mobilization and sporulating area, but not grain filling or sporulation rates. An existing carbon partitioning (source–sink) model for wheat during the grain filling period was then enhanced, in which two parameters characterize every sink: carriage capacity and substrate affinity. Fungal sink competitiveness with host sources and sinks was modelled by representing spore production as another sink in diseased wheat during grain filling.

Key Results

Data from the experiment were fitted to the model to provide the fungal sink parameters. Fungal carriage capacity was 0·56 ± 0·01 µg dry matter °Cd⁻¹ per lesion, much less than grain filling capacity, even in highly infected plants; however, fungal sporulation had a competitive priority for assimilates over grain filling. Simulation with virtual crops accounted for the importance of the relative contribution of photosynthesis loss, anticipated reserve depletion and spore production when light level and disease severity vary. The grain filling rate was less reduced than photosynthesis; however, over the long term, yield loss could double because the earlier reserve depletion observed here would shorten the duration of grain filling.

Conclusions

Source–sink modelling holds the promise of accounting for plant–pathogen interactions over time under fluctuating climatic/lighting conditions in a robust way.     

TM9 and cannibalism: how to learn more about cancer by studying amoebae and invertebrates

Phagocytosis is used not only for immune defense but may also be used to obtain nutrients, as observed when tumor cells feed upon neighboring cells during "tumor cell cannibalism". The TM9 protein TM9SF4, important in canonical phagocytosis, is involved in this cannibalism by metastatic cells and may represent a novel therapeutic target.     

Cloned ovarian cells from sheep: Cholesterol dependency in progesterone synthesis

The TV4 cell line is derived from sheep ovarian tissues trypsinized for 60 min and developed from a clone after serial dilutions. The TV4 cells had a doubling time of 24 h in B2 medium with 10% fetal calf serum and 10% BSA. TV4 cells synthesized progesterone (P4) in the presence of cholesterol. As the concentration of cholesterol increased (0, 92.5 and 125 mg/l), synthesis of P4 increased (P<0.01) from 1.05 +/- 0.20 to 30.6 +/- 3.03 ng/ml. Kinetics of P4 production were determined; a linear production response (y = 5.816 + 1.05 x, y = ng/ml, x = hour of incubation; R(2) = 0.97) was observed with up to 35 ng/ml of P4 obtained by 30 h of incubation. Follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone, or FSH and testosterone did not have any effect on estradiol-17beta (E2) or P4 production. Aromatase activity measured by RIA and HPLC following incubation with either nonradiolabeled or labeled testosterone was undetectable. In conclusion, this study established a cell line from the sheep ovary which has a high ability of divide and produce progesterone.