ApTOLL: A new therapeutic aptamer for cytoprotection and (re)myelination after multiple sclerosis.

BACKGROUND AND PURPOSE: ApTOLL is an aptamer selected to antagonize toll-like receptor 4 (TLR4), a relevant actor for innate immunity involved in inflammatory responses in multiple sclerosis (MS) and other diseases. The currently available therapeutic arsenal to treat MS is composed of immunomodulators but, to date, there are no (re)myelinating drugs available in clinics. In our present study, we studied the effect of ApTOLL on different animal models of MS. EXPERIMENTAL APPROACH: The experimental autoimmune encephalomyelitis (EAE) model was used to evaluate the effect of ApTOLL on reducing the inflammatory component. A more direct effect on oligodendroglia was studied with the cuprizone model and purified primary cultures of murine and human oligodendrocyte precursor cells (OPCs) isolated through magnetic-activated cell sorting (MACS) from samples of brain cortex. Also, we tested these effects in an ex vivo model of organotypic cultures demyelinated with lysolecithin (LPC). KEY RESULTS: ApTOLL treatment positively impacted the clinical symptomatology of mice in the EAE and cuprizone models, which was associated with better preservation plus restoration of myelin and oligodendrocytes in the demyelinated lesions of animals. Restoration was corroborated on purified cultures of rodent and human OPCs. CONCLUSION AND IMPLICATIONS: Our findings reveal a new therapeutic approach for the treatment of inflammatory and demyelinating diseases such as MS. The molecular nature of the aptamer exerts not only an anti-inflammatory effect but also neuroprotective and remyelinating effects. The excellent safety profile demonstrated by ApTOLL in animals and humans opens the door to future clinical trials in MS patients.

Activation of Shh/Smo is sufficient to maintain oligodendrocyte precursor cells in an undifferentiated state and is not necessary for myelin formation and (re)myelination.

Myelination is the terminal step in a complex and precisely timed program that orchestrates the proliferation, migration and differentiation of oligodendroglial cells. It is thought that Sonic Hedgehog (Shh) acting on Smoothened (Smo) participates in regulating this process, but that these effects are highly context dependent. Here, we investigate oligodendroglial development and remyelination from three specific transgenic lines: NG2-CreERT2 (control), Smofl/fl/NG2-CreERT2 (loss of function), and SmoM2/NG2-CreERT2 (gain of function), as well as pharmacological manipulation that enhance or inhibit the Smo pathway (Smoothened Agonist (SAG) or cyclopamine treatment, respectively). To explore the effects of Shh/Smo on differentiation and myelination in vivo, we developed a highly quantifiable model by transplanting oligodendrocyte precursor cells (OPCs) in the retina. We find that myelination is greatly enhanced upon cyclopamine treatment and hypothesize that Shh/Smo could promote OPC proliferation to subsequently inhibit differentiation. Consistent with this hypothesis, we find that the genetic activation of Smo significantly increased numbers of OPCs and decreased oligodendrocyte differentiation when we examined the corpus callosum during development and after cuprizone demyelination and remyelination. However, upon loss of function with the conditional ablation of Smo, myelination in the same scenarios are unchanged. Taken together, our present findings suggest that the Shh pathway is sufficient to maintain OPCs in an undifferentiated state, but is not necessary for myelination and remyelination.

Utility of the Serum Protein Electrophoresis in the Opportunistic Screening for the Deficiency of Alpha-1 Antitrypsin.

BACKGROUND: A deficiency in alpha-1 antitrypsin (AAT1) is a rare disorder that represents a significant health threat and early diagnostic priority issue. We investigated the usefulness of the serum protein electrophoresis (SPE) as an opportunistic screening tool for AAT1 deficiency. METHODS: For 6 months, all SPE carried out for any reasons were evaluated in our center. In those with less than 3% of alpha-1 globulins, AAT1 concentrations were studied. The SERPINA1 gene was subsequently sequenced in those patients displaying concentrations below 100 mg/dL. RESULTS: Out of the total, 14 patients (0.3%) were identified with low AAT1 concentrations, with 11 of them agreeing to enter the study. Of those, mutations in the SERPINA1 gene were discovered in 10 patients (91%). Heterozygous mutations were detected in seven patients; three had the c.1096G>A mutation (p.Glu366Lys; Pi*Z), two had the c.863A>T mutation (p.Glu288Val; Pi*S), one had the c.221_223delTCT mutation (p.Phe76del; Pi*Malton), and the last one had the c.1066G>A (p.Ala356Thr) mutation, which was not previously described. Finally, one patient had the c.863A>T mutation in homozygosis, whereas two double heterozygous patients c.863A>T/c.1096G>A were detected. CONCLUSIONS: An altered result in the concentration of AAT1 anticipates a mutation in the SERPINA1 gene in a manner close to 91%. The relationship between a decrease in the alpha-1 globulin band of the SPE and an alteration in the AAT1 concentration is direct in basal states of health. The SPE is presented as a highly sensitive test for opportunistic screening of AAT1 deficiency.

Dark Diazotrophy during the Late Summer in Surface Waters of Chile Bay, West Antarctic Peninsula.

Although crucial for the addition of new nitrogen in marine ecosystems, dinitrogen (N2) fixation remains an understudied process, especially under dark conditions and in polar coastal areas, such as the West Antarctic Peninsula (WAP). New measurements of light and dark N2 fixation rates in parallel with carbon (C) fixation rates, as well as analysis of the genetic marker nifH for diazotrophic organisms, were conducted during the late summer in the coastal waters of Chile Bay, South Shetland Islands, WAP. During six late summers (February 2013 to 2019), Chile Bay was characterized by high NO3− concentrations (~20 µM) and an NH4+ content that remained stable near 0.5 µM. The N:P ratio was approximately 14.1, thus close to that of the Redfield ratio (16:1). The presence of Cluster I and Cluster III nifH gene sequences closely related to Alpha-, Delta- and, to a lesser extent, Gammaproteobacteria, suggests that chemosynthetic and heterotrophic bacteria are primarily responsible for N2 fixation in the bay. Photosynthetic carbon assimilation ranged from 51.18 to 1471 nmol C L−1 d−1, while dark chemosynthesis ranged from 9.24 to 805 nmol C L−1 d−1. N2 fixation rates were higher under dark conditions (up to 45.40 nmol N L−1 d−1) than under light conditions (up to 7.70 nmol N L−1 d−1), possibly contributing more than 37% to new nitrogen-based production (≥2.5 g N m−2 y−1). Of all the environmental factors measured, only PO43- exhibited a significant correlation with C and N2 rates, being negatively correlated (p < 0.05) with dark chemosynthesis and N2 fixation under the light condition, revealing the importance of the N:P ratio for these processes in Chile Bay. This significant contribution of N2 fixation expands the ubiquity and biological potential of these marine chemosynthetic diazotrophs. As such, this process should be considered along with the entire N cycle when further reviewing highly productive Antarctic coastal waters and the diazotrophic potential of the global marine ecosystem.

Non-productive angiogenesis disassembles Aß plaque-associated blood vessels.

The human Alzheimer's disease (AD) brain accumulates angiogenic markers but paradoxically, the cerebral microvasculature is reduced around Aß plaques. Here we demonstrate that angiogenesis is started near Aß plaques in both AD mouse models and human AD samples. However, endothelial cells express the molecular signature of non-productive angiogenesis (NPA) and accumulate, around Aß plaques, a tip cell marker and IB4 reactive vascular anomalies with reduced NOTCH activity. Notably, NPA induction by endothelial loss of presenilin, whose mutations cause familial AD and which activity has been shown to decrease with age, produced a similar vascular phenotype in the absence of Aß pathology. We also show that Aß plaque-associated NPA locally disassembles blood vessels, leaving behind vascular scars, and that microglial phagocytosis contributes to the local loss of endothelial cells. These results define the role of NPA and microglia in local blood vessel disassembly and highlight the vascular component of presenilin loss of function in AD.

Myeloid-derived suppressor cells support remyelination in a murine model of multiple sclerosis by promoting oligodendrocyte precursor cell survival, proliferation, and differentiation.

The most frequent variant of multiple sclerosis (MS) is the relapsing-remitting form, characterized by symptomatic phases followed by periods of total/partial recovery. Hence, it is possible that these patients can benefit from endogenous agents that control the inflammatory process and favor spontaneous remyelination. In this context, there is increasing interest in the role of myeloid-derived suppressor cells (MDSCs) during the clinical course of experimental autoimmune encephalomyelitis (EAE). MDSCs speed up infiltrated T-cell anergy and apoptosis. In different animal models of MS, a milder disease course is related to higher presence/density of MDSCs in the periphery, and smaller demyelinated lesions in the central nervous system (CNS). These observations lead us to wonder whether MDSCs might not only exert an anti-inflammatory effect but might also have direct influence on oligodendrocyte precursor cells (OPCs) and remyelination. In the present work, we reveal for the first time the relationship between OPCs and MDSCs in EAE, relationship that is guided by the distance from the inflammatory core. We describe the effects of MDSCs on survival, proliferation, as well as potent promoters of OPC differentiation toward mature phenotypes. We show for the first time that osteopontin is remarkably present in the analyzed secretome of MDSCs. The ablation of this cue from MDSCs-secretome demonstrates that osteopontin is the main MDSC effector on these oligodendroglial cells. These data highlight a crucial pathogenic interaction between innate immunity and the CNS, opening ways to develop MDSC- and/or osteopontin-based therapies to promote effective myelin preservation and repair in MS patients.

Inhibition of the Maillard Reaction by Phytochemicals Composing an Aqueous Coffee Silverskin Extract via a Mixed Mechanism of Action.

This work aimed to evaluate the contribution of isoflavones and melatonin to the aqueous extract obtained from the coffee silverskin (CSE) antiglycative properties, which has not been previously studied. To achieve this goal, two model systems constituted by bovine serum albumin (BSA) and reactive carbonyls (glucose or methylglyoxal) in the presence or absence of pure phytochemicals (chlorogenic acid (CGA), genistein, and melatonin) and CSE were employed. Glucose was used to evaluate the effect on the formation of glycation products formed mainly in the early stage of the reaction, while methylglyoxal was employed for looking at the formation of advanced products of the reaction, also called methylglyoxal-derivative advanced glycation end products (AGE) or glycoxidation products. CGA inhibited the formation of fructosamine, while genistein and melatonin inhibited the formation of advanced glycation end products and protein glycoxidation. It was also observed that phenolic compounds from CSE inhibited protein glycation and glycoxidation by forming BSA-phytochemical complexes. CSE showed a significant antiglycative effect (p < 0.05). Variations in the UV-Vis spectrum and the antioxidant capacity of protein fractions suggested the formation of protein-phytochemical complexes. Fluorescence quenching and in silico analysis supported the formation of antioxidant-protein complexes. For the first time, we illustrate that isoflavones and melatonin may contribute to the antiglycative/antiglycoxidative properties associated with CSE. CGA, isoflavones, and melatonin composing CSE seem to act simultaneously by different mechanisms of action.

Bioaccesibility, Metabolism, and Excretion of Lipids Composing Spent Coffee Grounds.

The bioaccessibility, metabolism, and excretion of lipids composing spent coffee grounds (SCGs) were investigated. An analysis of mycotoxins and an acute toxicity study in rats were performed for safety evaluation. Total fat, fatty acids, and diterpenes (cafestol and kahweol) were determined in SCGs and their digests obtained in vitro. A pilot repeated intake study was carried out in Wistar rats using a dose of 1 g SCGs/kg b.w. for 28 days. Fat metabolism was evaluated by analysis of total fat, cholesterol, and histology in liver. The dietary fiber effect of SCGs was measured radiographically. The absence of mycotoxins and toxicity was reported in SCGs. A total of 77% of unsaturated fatty acids and low amounts of kahweol (7.09 µg/g) and cafestol (414.39 µg/g) were bioaccessible after in vitro digestion. A significantly lower (p < 0.1) accumulation of lipids in the liver and a higher excretion of these in feces was found in rats treated with SCGs for 28 days. No lipid droplets or liver damage were observed by histology. SCGs acutely accelerated intestinal motility in rats. SCGs might be considered a sustainable, safe, and healthy food ingredient with potential for preventing hepatic steatosis due to their effect as dietary fiber with a high fat-holding capacity.

In vitro formation of Maillard reaction products during simulated digestion of meal-resembling systems.

The aim of the present research was to study the formation of Maillard reaction products (MRPs) during digestive process of meal-resembling systems. An average meal (protein, starch and oil) and sugar-containing meals (protein and glucose or fructose or high fructose corn syrup (HCFS)) were tested. Intestinal simple amino acid systems were also analyzed to gain insight into their contribution to the Maillard reaction (MR). Decrease of lysine (11.7-34%), arginine (24-35%) and other amino acids occurred after digestion of the meals. Fructosamine (42.6±4.7 and 332.9±10.4µg/ml) and fluorescent adducts (22,270±119.6 and 9283±188.3 RFU) were detected in digests of those meals containing HCFS and starch, respectively. Carboxymethyllysine (CML) (5.03±1.09µg/ml) and MGO-derivative AGEs (12.2±1.5µg/ml) were found in the meals composed of fructose and only MGO-derivative AGEs (12.2±1.6µg/ml) in presence of glucose. Physiological intestinal concentrations (43mM) of sugars in simplified systems composed by single amino acids caused formation of MRPs under digestive conditions. Arginine and fructose (314mM) showed formation of fructosamine and different AGEs. Fructose (43mM) gave rise to CML by interaction with lysine, which was observed within 1h of incubation at intestinal conditions. These conditions are possible in the intestine during fructose malabsorption. The results suggest the importance of using meal systems for better understanding of complex chemical events taking place during digestion such as MR. This is the first study proposing the formation of non-fluorescent AGEs associated to the pathogenesis of diabetes during digestion of sugar containing and average meals. This formation may be possible in conditions where sugar absorption is delayed such as fructose malabsorption or intake of a fatty meal. The occurrence of the MR during the digestion process may reduce the bioavailability of essential amino acids and increase the production of MRPs causing health disorders.

Bacterial communities associated to Chilean altiplanic native plants from the Andean grasslands soils.

The rhizosphere is considered the primary place for soil microbiome differentiation and plays a key role in plant survival, especially for those subjected to environmental stress. Using high-throughput sequencing of the 16S rRNA gene, we analyzed and compared soil bacterial communities associated to four of the most abundant high altitude native plant species of the Chilean Andean grasslands. We examined three soil compartments: the rhizosphere (bacteria firmly attached to the roots), the rhizosphere-surrounding soil (bacteria loosely attached to the roots) and the bulk soil (plant-free soil). The rhizosphere microbiome was in all cases the least diverse, exposing that the bulk soil was a more complex environment. Taxonomic analysis revealed an abrupt change between the rhizosphere and the rest of the non-rhizospheric soils. Thus, while rhizobacterial communities were enriched in Proteobacteria (mainly Alphaproteobacteria), Actinobacteria (mostly Blastocatellia) dominated in bulk soils. Finally, we detected certain taxonomic rhizosphere signatures, which could be attributed to a particular genotype. Overall, our results indicate that the thin layer of soil surrounding the roots constitute a distinctive soil environment. This study contributes to expand the knowledge about soil bacterial communities in the Chilean highlands and takes the first step to understand the processes that might lead to the rhizosphere differentiation in that area.

Bacterial community structure in a sympagic habitat expanding with global warming: brackish ice brine at 85-90 °N.

Larger volumes of sea ice have been thawing in the Central Arctic Ocean (CAO) during the last decades than during the past 800,000 years. Brackish brine (fed by meltwater inside the ice) is an expanding sympagic habitat in summer all over the CAO. We report for the first time the structure of bacterial communities in this brine. They are composed of psychrophilic extremophiles, many of them related to phylotypes known from Arctic and Antarctic regions. Community structure displayed strong habitat segregation between brackish ice brine (IB; salinity 2.4-9.6) and immediate sub-ice seawater (SW; salinity 33.3-34.9), expressed at all taxonomic levels (class to genus), by dominant phylotypes as well as by the rare biosphere, and with specialists dominating IB and generalists SW. The dominant phylotypes in IB were related to Candidatus Aquiluna and Flavobacterium, those in SW to Balneatrix and ZD0405, and those shared between the habitats to Halomonas, Polaribacter and Shewanella. A meta-analysis for the oligotrophic CAO showed a pattern with Flavobacteriia dominating in melt ponds, Flavobacteriia and Gammaproteobacteria in solid ice cores, Flavobacteriia, Gamma- and Betaproteobacteria, and Actinobacteria in brine, and Alphaproteobacteria in SW. Based on our results, we expect that the roles of Actinobacteria and Betaproteobacteria in the CAO will increase with global warming owing to the increased production of meltwater in summer. IB contained three times more phylotypes than SW and may act as an insurance reservoir for bacterial diversity that can act as a recruitment base when environmental conditions change.

Structure and co-occurrence patterns in microbial communities under acute environmental stress reveal ecological factors fostering resilience.

Understanding the factors that modulate bacterial community assembly in natural soils is a longstanding challenge in microbial community ecology. In this work, we compared two microbial co-occurrence networks representing bacterial soil communities from two different sections of a pH, temperature and humidity gradient occurring along a western slope of the Andes in the Atacama Desert. In doing so, a topological graph alignment of co-occurrence networks was used to determine the impact of a shift in environmental variables on OTUs taxonomic composition and their relationships. We observed that a fraction of association patterns identified in the co-occurrence networks are persistent despite large environmental variation. This apparent resilience seems to be due to: (1) a proportion of OTUs that persist across the gradient and maintain similar association patterns within the community and (2) bacterial community ecological rearrangements, where an important fraction of the OTUs come to fill the ecological roles of other OTUs in the other network. Actually, potential functional features suggest a fundamental role of persistent OTUs along the soil gradient involving nitrogen fixation. Our results allow identifying factors that induce changes in microbial assemblage configuration, altering specific bacterial soil functions and interactions within the microbial communities in natural environments.

Viral to metazoan marine plankton nucleotide sequences from the Tara Oceans expedition.

A unique collection of oceanic samples was gathered by the Tara Oceans expeditions (2009-2013), targeting plankton organisms ranging from viruses to metazoans, and providing rich environmental context measurements. Thanks to recent advances in the field of genomics, extensive sequencing has been performed for a deep genomic analysis of this huge collection of samples. A strategy based on different approaches, such as metabarcoding, metagenomics, single-cell genomics and metatranscriptomics, has been chosen for analysis of size-fractionated plankton communities. Here, we provide detailed procedures applied for genomic data generation, from nucleic acids extraction to sequence production, and we describe registries of genomics datasets available at the European Nucleotide Archive (ENA, www.ebi.ac.uk/ena). The association of these metadata to the experimental procedures applied for their generation will help the scientific community to access these data and facilitate their analysis. This paper complements other efforts to provide a full description of experiments and open science resources generated from the Tara Oceans project, further extending their value for the study of the world's planktonic ecosystems.

Effect of theanine and polyphenols enriched fractions from decaffeinated tea dust on the formation of Maillard reaction products and sensory attributes of breads.

The antiglycoxidative properties of theanine (TEF) and polyphenols enriched fractions (PEF) prepared from tea dust were tested in a model system composed of bovine serum albumin (BSA) and methylglyoxal (MGO). PEF caused a decrease in available free amino groups of BSA in presence and absence of MGO, suggesting the simultaneous occurrence of glycoxidation reaction and phenols-protein interaction. The presence of PEF and TEF inhibited formation of fluorescent advanced glycation end-products (AGEs). Moreover, theanine (TB) and polyphenol-enriched bread (PB) were formulated. A significant increase in free amino groups was observed in TBs with a dose-response effect, while addition of PEF in bread produced a significant decrease (p<0.05). PEF efficiently reduced fluorescent AGE formation in breads compared with TEF. The results are in line with the simplified model systems. PEF used as food ingredient allows obtaining a tasty food possessing health promoting properties and lower content of potential harmful compounds (AGEs).

Correction: New knowledge on the antiglycoxidative mechanism of chlorogenic acid.

Correction for 'New knowledge on the antiglycoxidative mechanism of chlorogenic acid' by Beatriz Fernandez-Gomez et al., Food Funct., 2015, DOI: 10.1039/c5fo00194c.

New knowledge on the antiglycoxidative mechanism of chlorogenic acid.

The role of chlorogenic acid (CGA) in the formation of advanced glycation end-products (AGEs) (glycoxidation reaction) was studied. Model systems composed of bovine serum albumin (BSA) (1 mg mL(-1)) and methylglyoxal (5 mM) under mimicked physiological conditions (pH 7.4, 37 °C) were used to evaluate the antiglycoxidative effect of CGA (10 mM). The stability of CGA under reaction conditions was assayed by HPLC and MALDI-TOF MS. The glycoxidation reaction was estimated by analysis of free amino groups by the OPA assay, spectral analysis of fluorescent AGEs and total AGEs by ELISA, and colour formation by absorbance at 420 nm. Structural changes in protein were evaluated by analysis of phenol bound to the protein backbone using the Folin reaction, UV-Vis spectral analysis and MALDI-TOF-MS, while changes in protein function were measured by determining the antioxidant capacity using the ABTS radical cation decolourisation assay. CGA was isomerised and oxidised under our experimental conditions. Evidence of binding between BSA and multiple CGA and/or its derivative molecules (isomers and oxidation products) was found. CGA inhibited (p < 0.05) the formation of fluorescent and total AGEs at 72 h of reaction by 91.2 and 69.7%, respectively. The binding of phenols to BSA significantly increased (p < 0.001) its antioxidant capacity. Correlations between free amino group content, phenol bound to protein and antioxidant capacity were found. Results indicate that CGA simultaneously inhibits the formation of potentially harmful compounds (AGEs) and promotes the generation of neoantioxidant structures.

Taxonomic composition of the particle-attached and free-living bacterial assemblages in the Northwest Mediterranean Sea analyzed by pyrosequencing of the 16S rRNA.

Free-living (FL) and particle-attached (PA) bacterial assemblages in the Northwest Mediterranean Sea were studied using pyrosequencing data of the 16S rRNA. We have described and compared the richness, the distribution of Operational Taxonomic Units (OTUs) within the two fractions, the spatial distribution, and the taxonomic composition of FL and PA bacterial assemblages. The number of OTUs in the present work was two orders of magnitude higher than in previous studies. Only 25% of the total OTUs were common to both fractions, whereas 49% OTUs were exclusive to the PA fraction and 26% to the FL fraction. The OTUs exclusively present in PA or FL assemblages were very low in abundance (6% of total abundance). Detection of the rare OTUs revealed the larger richness of PA bacteria that was hidden in previous studies. Alpha-Proteobacteria dominated the FL bacterial assemblage and gamma-Proteobacteria dominated the PA fraction. Bacteroidetes were important in the PA fraction mainly at the coast. The high number of sequences in this study detected additional phyla from the PA fraction, such as Actinobacteria, Firmicutes, and Verrucomicrobia.

Ecology of marine Bacteroidetes: a comparative genomics approach.

Bacteroidetes are commonly assumed to be specialized in degrading high molecular weight (HMW) compounds and to have a preference for growth attached to particles, surfaces or algal cells. The first sequenced genomes of marine Bacteroidetes seemed to confirm this assumption. Many more genomes have been sequenced recently. Here, a comparative analysis of marine Bacteroidetes genomes revealed a life strategy different from those of other important phyla of marine bacterioplankton such as Cyanobacteria and Proteobacteria. Bacteroidetes have many adaptations to grow attached to particles, have the capacity to degrade polymers, including a large number of peptidases, glycoside hydrolases (GHs), glycosyl transferases, adhesion proteins, as well as the genes for gliding motility. Several of the polymer degradation genes are located in close association with genes for TonB-dependent receptors and transducers, suggesting an integrated regulation of adhesion and degradation of polymers. This confirmed the role of this abundant group of marine bacteria as degraders of particulate matter. Marine Bacteroidetes had a significantly larger number of proteases than GHs, while non-marine Bacteroidetes had equal numbers of both. Proteorhodopsin containing Bacteroidetes shared two characteristics: small genome size and a higher number of genes involved in CO2 fixation per Mb. The latter may be important in order to survive when floating freely in the illuminated, but nutrient-poor, ocean surface.

Alternative splicing of the nuclear progestin receptor in a perciform teleost generates novel mechanisms of dominant-negative transcriptional regulation.

In mammals, downstream function of the nuclear progestin receptor (PGR) can be differentially regulated in each target tissue by altering the expression levels of PGR mRNA variants. Such PGR isoforms have also been identified in birds and reptiles, but not in non-amniote vertebrates. Based upon extensive phylogenetic, syntenic and functional analyses, here we show that higher orders of Teleostei retain a single pgr gene, and that four different pgr transcript variants of the extant gene are expressed in the ovary of an evolutionary advanced perciform teleost, the gilthead seabream (Sparus aurata). Three of the isoforms (pgr_tv2, pgr_tv3 and pgr_tv4) arise from alternative pre-mRNA splicing resulting in different N-terminally truncated receptors, whereas one isoform (pgr_tv1) is a deletion variant. Seabream wild-type Pgr shows the highest transactivational response to native euteleostean progestins, 17α,20ß-dihydroxy-4-pregnen-3-one and 17α,20ß,21-trihydroxy-4-pregnen-3-one, whereas the Pgr_tv3 and Pgr_tv4 isoforms independently regulate novel nuclear and cytosolic mechanisms of dominant-negative repression of Pgr-mediated transcription. In the seabream ovary, the wild-type Pgr protein is localized in oogonia, in the nuclei of primary (previtellogenic) oocytes, as well as in follicular (granulosa) cells and the oocyte cytoplasm of early and late vitellogenic ovarian follicles. Expression of wild-type pgr, pgr_tv3 and pgr_tv4 was the highest in seabream primary ovaries, while expression of both inhibitory receptor isoforms, but not of pgr, decreased during vitellogenesis. Stimulation of primary ovarian explants in vitro with recombinant piscine follicle-stimulating hormone and estrogen differentially regulated the temporal expression of pgr, pgr_tv3 and pgr_tv4. These findings suggest that, as in mammals, ovarian progestin responsiveness in the seabream, particularly during early oogenesis, may be regulated through alternative splicing of the nuclear pgr mRNA. Thus, the dominant-negative mechanism of PGR transcriptional regulation likely evolved prior to the separation of Actinopterygii (ray-finned fishes) from Sarcopterygii (lobe-finned fishes).

Patterns and architecture of genomic islands in marine bacteria.

BACKGROUND: Genomic Islands (GIs) have key roles since they modulate the structure and size of bacterial genomes displaying a diverse set of laterally transferred genes. Despite their importance, GIs in marine bacterial genomes have not been explored systematically to uncover possible trends and to analyze their putative ecological significance. RESULTS: We carried out a comprehensive analysis of GIs in 70 selected marine bacterial genomes detected with IslandViewer to explore the distribution, patterns and functional gene content in these genomic regions. We detected 438 GIs containing a total of 8152 genes. GI number per genome was strongly and positively correlated with the total GI size. In 50% of the genomes analyzed the GIs accounted for approximately 3% of the genome length, with a maximum of 12%. Interestingly, we found transposases particularly enriched within Alphaproteobacteria GIs, and site-specific recombinases in Gammaproteobacteria GIs. We described specific Homologous Recombination GIs (HR-GIs) in several genera of marine Bacteroidetes and in Shewanella strains among others. In these HR-GIs, we recurrently found conserved genes such as the ß-subunit of DNA-directed RNA polymerase, regulatory sigma factors, the elongation factor Tu and ribosomal protein genes typically associated with the core genome. CONCLUSIONS: Our results indicate that horizontal gene transfer mediated by phages, plasmids and other mobile genetic elements, and HR by site-specific recombinases play important roles in the mobility of clusters of genes between taxa and within closely related genomes, modulating the flexible pool of the genome. Our findings suggest that GIs may increase bacterial fitness under environmental changing conditions by acquiring novel foreign genes and/or modifying gene transcription and/or transduction.