Injection of Pseudomonas aeruginosa Exo toxins into host cells can be modulated by host factors at the level of translocon assembly and/or activity

Pseudomonas aeruginosa type III secretion apparatus exports and translocates four exotoxins into the cytoplasm of the host cell. The translocation requires two hydrophobic bacterial proteins, PopB and PopD, that are found associated with host cell membranes following infection. In this work we examined the influence of host cell elements on exotoxin translocation efficiency. We developed a quantitative flow cytometry based assay of translocation that used protein fusions between either ExoS or ExoY and the ?-lactamase reporter enzyme. In parallel, association of translocon proteins with host plasma membranes was evaluated by immunodetection of PopB/D following sucrose gradient fractionation of membranes. A pro-myelocytic cell line (HL-60) and a pro-monocytic cell line (U937) were found resistant to toxin injection even though PopB/D associated with host cell plasma membranes. Differentiation of these cells to either macrophage- or neutrophil-like cell lines resulted in injection-sensitive phenotype without significantly changing the level of membrane-inserted translocon proteins. As previous in vitro studies have indicated that the lysis of liposomes by PopB and PopD requires both cholesterol and phosphatidyl-serine, we first examined the role of cholesterol in translocation efficiency. Treatment of sensitive HL-60 cells with methyl-?-cyclodextrine, a cholesterol-depleting agent, resulted in a diminished injection of ExoS-Bla. Moreover, the PopB translocator was found in the membrane fraction, obtained from sucrose-gradient purifications, containing the lipid-raft marker flotillin. Examination of components of signalling pathways influencing the toxin injection was further assayed through a pharmacological approach. A systematic detection of translocon proteins within host membranes showed that, in addition to membrane composition, some general signalling pathways involved in actin polymerization may be critical for the formation of a functional pore. In conclusion, we provide new insights in regulation of translocation process and suggest possible cross-talks between eukaryotic cell and the pathogen at the level of exotoxin translocation.     

miR-125 potentiates early neural specification of human embryonic stem cells

The role of microRNAs (miRNAs) as coordinators of stem cell fate has emerged over the last decade. We have used human embryonic stem cells to identify miRNAs involved in neural lineage commitment induced by the inhibition of TGFβ-like molecule-mediated pathways. Among several candidate miRNAs expressed in the fetal brain, the two isoforms of miR-125 alone were detected in a time window compatible with a role in neural commitment in vitro. Functional analysis indicated that miR-125 isoforms were actively involved in the promotion of pluripotent cell conversion into SOX1-positive neural precursors. miR-125 promotes neural conversion by avoiding the persistence of non-differentiated stem cells and repressing alternative fate choices. This was associated with the regulation by miR-125 of SMAD4, a key regulator of pluripotent stem cell lineage commitment. Activation of miR-125 was directly responsive to the levels of TGFβ-like molecules, placing miR-125 at the core of mechanisms that lead to the irreversible neural lineage commitment of pluripotent stem cells in response to external stimuli.     

Lanthanide(III) complexes of pyridine-tetraacetic acid-glycoconjugates: synthesis and luminescence studies of mono and divalent derivatives

A potent lanthanide chelate, fulfilling the requirements for the development of MRI contrast agents or luminescent probes, was armed with alkyne groups. We then implemented a click methodology to graft the bifunctional ligand to azide-containing glucoside and maltoside scaffolds. The resulting hydrophilic glycoconjugates retained the ligand binding capacity for Eu(3+) or Tb(3+) ion as evidenced by the number of bound water molecules to the lanthanide ion. Divalent Eu(3+) and Tb(3+) complexes were shown to double the brightness of the emitted fluorescent signal compared to its monovalent derivatives. Designing multivalent lanthanide luminescent probes would enable the fluorescent signal of labeled biomolecules to be enhanced.     

Social hybridogenesis in the clonal ant Cataglyphis hispanica

With a few rare exceptions, the vast majority of animals reproduce sexually. Some species have, however, evolved alternative modes of reproduction by shifting from classical bisexuality to unorthodox reproductive systems, like parthenogenesis, gynogenesis, or hybridogenesis. Under hybridogenesis, both the maternal and paternal genomes are expressed in somatic tissues, whereas the germline is purely maternal. Recently, a form of hybridogenesis at the level of the society has been reported in some ants, where purebred females develop into reproductive queens and interlineage hybrids into sterile workers. Here, we report a unique case of social hybridogenesis in the desert ant Cataglyphis hispanica. Workers are produced exclusively from interbreeding between two distinct genetic lineages, whereas male and female sexuals are produced by asexual reproduction through parthenogenesis. As a consequence, all workers are pure hybridogens, and only maternal genes are perpetuated from one generation to the next. Thus, queens of C. hispanica use sexual reproduction for colony growth, whereas they reproduce asexually through parthenogenesis for germline production.     

Design of a bovine low-density SNP array optimized for imputation

The Illumina BovineLD BeadChip was designed to support imputation to higher density genotypes in dairy and beef breeds by including single-nucleotide polymorphisms (SNPs) that had a high minor allele frequency as well as uniform spacing across the genome except at the ends of the chromosome where densities were increased. The chip also includes SNPs on the Y chromosome and mitochondrial DNA loci that are useful for determining subspecies classification and certain paternal and maternal breed lineages. The total number of SNPs was 6,909. Accuracy of imputation to Illumina BovineSNP50 genotypes using the BovineLD chip was over 97% for most dairy and beef populations. The BovineLD imputations were about 3 percentage points more accurate than those from the Illumina GoldenGate Bovine3K BeadChip across multiple populations. The improvement was greatest when neither parent was genotyped. The minor allele frequencies were similar across taurine beef and dairy breeds as was the proportion of SNPs that were polymorphic. The new BovineLD chip should facilitate low-cost genomic selection in taurine beef and dairy cattle.     

Protecting persistent dynamic oceanographic features: transboundary conservation efforts are needed for the critically endangered Balearic shearwater

The protection of key areas for biodiversity at sea is not as widespread as on land and research investment is necessary to identify biodiversity hotspots in the open ocean. Spatially explicit conservation measures such as the creation of representative networks of marine protected areas (MPAs) is a critical step towards the conservation and management of marine ecosystems, as well as to improve public awareness. Conservation efforts in ecologically rich and threatened ecosystems are specially needed. This is particularly urgent for the Mediterranean marine biodiversity, which includes highly mobile marine vertebrates. Here, we studied the at sea distribution of one of the most endangered Mediterranean seabird, the critically endangered Balearic shearwater Puffinus mauretanicus. Present knowledge, from vessel-based surveys, suggests that this species has a coastal distribution over the productive Iberian shelf in relation to the distribution of their main prey, small pelagic fish. We used miniaturised satellite transmitters to determine the key marine areas of the southern population of Balearic shearwaters breeding on Eivissa and spot the spatial connections between breeding and key marine areas. Our tracking study indicates that Balearic shearwaters do not only forage along the Iberian continental shelf but also in more distant marine areas along the North African coast, in particular W of Algeria, but also NE coast of Morocco. Birds recurrently visit these shelf areas at the end of the breeding season. Species distribution modelling identified chlorophyll a as the most important environmental variable in defining those oceanographic features characterizing their key habitats in the western Mediterranean. We identified persistent oceanographic features across time series available in the study area and discuss our results within the current conservation scenario in relation to the ecology of the species.     

Peptidoglycan Sensing by the Receptor PGRP-LE in the Drosophila Gut Induces Immune Responses to Infectious Bacteria and Tolerance to Microbiota

Gut epithelial cells contact both commensal and pathogenic bacteria, and proper responses to these bacteria require a balance of positive and negative regulatory signals. In the Drosophila intestine, peptidoglycan-recognition proteins (PGRPs), including PGRP-LE, play central roles in bacterial recognition and activation of immune responses, including induction of the IMD-NF-κB pathway. We show that bacteria recognition is regionalized in the Drosophila gut with various functional regions requiring different PGRPs. Specifically, peptidoglycan recognition by PGRP-LE in the gut induces NF-κB-dependent responses to infectious bacteria but also immune tolerance to microbiota through upregulation of pirk and PGRP-LB, which negatively regulate IMD pathway activation. Loss of PGRP-LE-mediated detection of bacteria in the gut results in systemic immune activation, which can be rescued by overexpressing PGRP-LB in the gut. Together these data indicate that PGRP-LE functions as a master gut bacterial sensor that induces balanced responses to infectious bacteria and tolerance to microbiota.     

Multiple Kisspeptin Receptors in Early Osteichthyans Provide New Insights into the Evolution of This Receptor Family

Deorphanization of GPR54 receptor a decade ago led to the characterization of the kisspeptin receptor (Kissr) in mammals and the discovery of its major role in the brain control of reproduction. While a single gene encodes for Kissr in eutherian mammals including human, other vertebrates present a variable number of Kissr genes, from none in birds, one or two in teleosts, to three in an amphibian, xenopus. In order to get more insight into the evolution of Kissr gene family, we investigated the presence of Kissr in osteichthyans of key-phylogenetical positions: the coelacanth, a representative of early sarcopterygians, the spotted gar, a non-teleost actinopterygian, and the European eel, a member of an early group of teleosts (elopomorphs). We report the occurrence of three Kissr for the first time in a teleost, the eel. As measured by quantitative RT-PCR, the three eel Kissr were differentially expressed in the brain-pituitary-gonadal axis, and differentially regulated in experimentally matured eels, as compared to prepubertal controls. Subfunctionalisation, as shown by these differences in tissue distribution and regulation, may have represented significant evolutionary constraints for the conservation of multiple Kissr paralogs in this species. Furthermore, we identified four Kissr in both coelacanth and spotted gar genomes, providing the first evidence for the presence of four Kissr in vertebrates. Phylogenetic and syntenic analyses supported the existence of four Kissr paralogs in osteichthyans and allowed to propose a clarified nomenclature of Kissr (Kissr-1 to -4) based on these paralogs. Syntenic analysis suggested that the four Kissr paralogs arose through the two rounds of whole genome duplication (1R and 2R) in early vertebrates, followed by multiple gene loss events in the actinopterygian and sarcopterygian lineages. Due to gene loss there was no impact of the teleost-specific whole genome duplication (3R) on the number of Kissr paralogs in current teleosts.     

Determination of vertical dimension of occlusion in dentate patients by cephalometric analysis--pilot study

doi: 10.1111/j.1741‐2358.2011.00469.x
Determination of vertical dimension of occlusion in dentate patients by cephalometric analysis – pilot study Objectives: The concept of vertical dimension of occlusion (VDO) refers to a measure in the vertical plane that establishes the relation between the maxilla and the mandible when the posterior teeth, both from the maxillary and from the mandibular arches, are occluded, regardless of whether they are natural or prosthetic, healthy or restored. This measure is subject to change, and when this occurs, it can compromise both the function and the facial aesthetics. This study proposed to develop a methodology based on cephalometric analysis by studying the 31 lateral teleradiographs of adult, dentate individuals to determine the VDO, based on bone structures that are not dependent on the presence or absence of posterior teeth. The final goal was to make this application accessible to individuals who have undergone alterations of the lower portion of the face. Materials and methods: The cephalometric analysis of this study, called Seraidarian‐Tavano, was verified through facial angles (upper and middle angles) that, when correlated, determine the lower position of the face. Results: The analysis of results showed that no statistically significant difference between the angles studied could be observed (superior angle 50.29 ± 3.35 e median angle 49.95 ± 3.37). In the same manner, no variation in the results regarding gender in the measure of these angles could be observed. Conclusion: This cephalometric analysis can be applied to determine the VDO, regardless of the presence or absence of posterior teeth.