The origin of the lakes in the Nicaraguan fault and of the Middle American isthmus in the light of studies of the fish fauna

The geological hypothesis of a marine origin of the Nicaraguan depression and its lakes was until the fifties of the present century exclusively based upon the occurrence of marine species (shark, sawfish and tarpon) in Lake Nicaragua. A recent view, however, is that the fault was never connected with the sea and that the lakes were filled by rain only. In view of the fact that there seems to be no agreement among geologists about the geological history of the Nicaraguan depression, an attempt is made to contribute to the discussion by evaluating the fish faunal elements of the fault. The nature, composition and evolution of Central American inlandwater fish are discussed in relation to the various geohistorical views about the formation of the Isthmian link of Southern Middle America

Single-cell analysis uncovers a novel influenza A virus-derived defective interfering particle for antiviral therapy

Single-cell analysis of virus-infected cells (Heldt and Kupke et al., 2015) enables the characterization of individual highly productive cells, which may support strategies to improve cell culture-based vaccine production. However, the definition of poor producer single cells can also yield valuable information. Here we show that low-productive single Madin-Darby canine kidney (MDCK) cells, infected with influenza A virus (IAV) of strain A/PR/8/34 (PR8), were affected by a yet unrecognized form of defective-interfering particle (DIP). Conventional DIPs (cDIPs) typically contain a deleted form of the viral genome and are therefore unable to reproduce in an infection. However, upon complementation by the co-infection with fully infectious standard virus (STV), interference with the normal viral life cycle can be observed. Interestingly, considering their ability to suppress STV replication, cDIPs are of growing interest for clinical application, i.e. for their use as antivirals (Dimmock and Easton, 2014). Single-cell infection experiments revealed a surprisingly high variability in IAV replication with progeny virus yields that ranged from 0 to roughly 1000 plaque-forming units (PFU) per cell. Intriguingly, low-productive cells (0-10 PFU) displayed an abnormal phenotype, which was caused by the co-infection of a subpopulation of virus, in the following termed OP7 virus. Sequences of the genomic viral RNA (vRNA) of OP7 virions showed a significant amount of nucleotide substitutions in one of the eight vRNA segments, affecting its promotor, encoded proteins and virus packaging signals. We showed that these alterations were all directed towards the predominant genomic replication and packaging of the mutated vRNA over other genome segments. Concurrently, OP7 virions lacked a large fraction of other vRNAs, which constitute its defect in virus replication. Finally, co-infection experiments showed strong interference of OP7 virus with IAV replication, as indicated by a dramatic reduction in the infectivity of released virions. This interference was directed against relevant homologous and heterologous IAV strains, including strains of the current influenza season. Furthermore, we demonstrated interference in human cell lines. Therefore, OP7 virions are a novel form of IAV-derived DIPs with a non-deleted but mutated genomic RNA segment. First, it seems reasonable to investigate the presence of OP7 virions in seed virus preparations, as they can reduce virus titers in a production process, similar to cDIPs (Frensing et al., 2014). Second, OP7 virus may be used for antiviral therapy. As they are not able to reproduce on their own, they may be administered to organisms with no harm. The presence of OP7 virions can then inhibit the propagation of IAV of a natural infection. In addition, the induction of the innate immune response, observed upon infection with OP7 virus, can even further promote the antiviral effect. In the future, the design of efficient production systems for OP7 virions and the execution of animal trials may facilitate its utilization as a novel antiviral agent. References Heldt and Kupke et al. (2015) Nature Commun 6, 8938 Dimmock and Easton (2014) J Virol 88(10), 5217-5227 Frensing et al. (2014) Appl Microbiol Biotechnol 98, 8999-9008 Patent Patent pending for usage of OP7 virions as an antiviral agen

Specification of primordial germ cells in medaka (Oryzias latipes)

BACKGROUND: Primordial germ cells (PGCs) give rise to gametes that are responsible for the development of a new organism in the next generation. Two modes of germ line specification have been described: the inheritance of asymmetrically-localized maternally provided cytoplasmic determinants and the induction of the PGC fate by other cell types. PGCs specification in zebrafish appears to depend on inheritance of germ plasm in which several RNA molecules such as vasa and nanos reside. Whether the specification mode of PGCs found in zebrafish is general for other fish species was brought into question upon analysis of olvas expression – the vasa homologue in another teleost, medaka (Oryzias latipes). Here, in contrast to the findings in zebrafish, the PGCs are found in a predictable position relative to a somatic structure, the embryonic shield. This finding, coupled with the fact that vasa mRNA, which is localized to the germ plasm of zebrafish but does not label a similar structure in medaka opened the possibility of fundamentally different mechanisms governing PGC specification in these two fish species. RESULTS: In this study we addressed the question concerning the mode of PGC specification in medaka using embryological experiments, analysis of RNA stability in the PGCs and electron microscopy observations. Dramatic alterations in the somatic environment, i.e. induction of a secondary axis or mesoderm formation alteration, did not affect the PGC number. Furthermore, the PGCs of medaka are capable of protecting specific RNA molecules from degradation and could therefore exhibit a specific mRNA expression pattern controlled by posttrancriptional mechanisms. Subsequent analysis of 4-cell stage medaka embryos using electron microscopy revealed germ plasm-like structures located at a region corresponding to that of zebrafish germ plasm. CONCLUSION: Taken together, these results are consistent with the idea that in medaka the inheritance of maternally provided asymmetrically-localized cytoplasmic determinants directs cells to assume the germ line fate similar to zebrafish PGCs

A Cell-Free System for Regulated Exocytosis in Pc12 Cells

We have developed a cell-free system for regulated exocytosis in the PC12 neuroendocrine cell line. Secretory vesicles were preloaded with acridine orange in intact cells, and the cells were sonicated to produce flat, carrier-supported plasma membrane patches with attached vesicles. Exocytosis resulted in the release of acridine orange which was visible as a disappearance of labeled vesicles and, under optimal conditions, produced light flashes by fluorescence dequenching. Exocytosis in vitro requires cytosol and Ca2+ at concentrations in the micromolar range, and is sensitive to Tetanus toxin. Imaging of membrane patches at diffraction- limited resolution revealed that 42% of docked granules were released in a Ca2+-dependent manner dur- ing 1 min of stimulation. Electron microscopy of membrane patches confirmed the presence of dense-core vesicles. Imaging of membrane patches by atomic force microscopy revealed the presence of numerous particles attached to the membrane patches which decreased in number upon stimula- tion. Thus, exocytotic membrane fusion of single vesicles can be monitored with high temporal and spatial resolution, while providing access to the site of exocytosis for biochemical and molecular tools

beta-Amyloid Clustering around ASC Fibrils Boosts Its Toxicity in Microglia

Alzheimer\u27s disease is the world\u27s most common neurodegenerative disorder. It is associated with neuroinflammation involving activation of microglia by beta-amyloid (Abeta) deposits. Based on previous studies showing apoptosis-associated speck-like protein containing a CARD (ASC) binding and cross-seeding extracellular Abeta, we investigate the propagation of ASC between primary microglia and the effects of ASC-Abeta composites on microglial inflammasomes and function. Indeed, ASC released by a pyroptotic cell can be functionally built into the neighboring microglia NOD-like receptor protein (NLRP3) inflammasome. Compared with protein-only application, exposure to ASC-Abeta composites amplifies the proinflammatory response, resulting in pyroptotic cell death, setting free functional ASC and inducing a feedforward stimulating vicious cycle. Clustering around ASC fibrils also compromises clearance of Abeta by microglia. Together, these data enable a closer look at the turning point from acute to chronic Abeta-related neuroinflammation through formation of ASC-Abeta composites

An Innovative Protocol for Metaproteomic Analyses of Microbial Pathogens in Cystic Fibrosis Sputum

Hallmarks of cystic fibrosis (CF) are increased viscosity of mucus and impaired mucociliary clearance within the airways due to mutations of the cystic fibrosis conductance regulator gene. This facilitates the colonization of the lung by microbial pathogens and the concomitant establishment of chronic infections leading to tissue damage, reduced lung function, and decreased life expectancy. Although the interplay between key CF pathogens plays a major role during disease progression, the pathophysiology of the microbial community in CF lungs remains poorly understood. Particular challenges in the analysis of the microbial population present in CF sputum is (I) the inhomogeneous, viscous, and slimy consistence of CF sputum, and (II) the high number of human proteins masking comparably low abundant microbial proteins. To address these challenges, we used 21 CF sputum samples to develop a reliable, reproducible and widely applicable protocol for sputum processing, microbial enrichment, cell disruption, protein extraction and subsequent metaproteomic analyses. As a proof of concept, we selected three sputum samples for detailed metaproteome analyses and complemented and validated metaproteome data by 16S sequencing, metabolomic as well as microscopic analyses. Applying our protocol, the number of bacterial proteins/protein groups increased from 199-425 to 392-868 in enriched samples compared to nonenriched controls. These early microbial metaproteome data suggest that the arginine deiminase pathway and multiple proteases and peptidases identified from various bacterial genera could so far be underappreciated in their contribution to the CF pathophysiology. By providing a standardized and effective protocol for sputum processing and microbial enrichment, our study represents an important basis for future studies investigating the physiology of microbial pathogens in CF in vivo – an important prerequisite for the development of novel antimicrobial therapies to combat chronic recurrent airway infection in CF

LUBAC assembles a ubiquitin signaling platform at mitochondria for signal amplification and transport of NF-κB to the nucleus

Mitochondria are increasingly recognized as cellular hubs to orchestrate signaling pathways that regulate metabolism, redox homeostasis, and cell fate decisions. Recent research revealed a role of mitochondria also in innate immune signaling; however, the mechanisms of how mitochondria affect signal transduction are poorly understood. Here, we show that the NF-κB pathway activated by TNF employs mitochondria as a platform for signal amplification and shuttling of activated NF-κB to the nucleus. TNF treatment induces the recruitment of HOIP, the catalytic component of the linear ubiquitin chain assembly complex (LUBAC), and its substrate NEMO to the outer mitochondrial membrane, where M1- and K63-linked ubiquitin chains are generated. NF-κB is locally activated and transported to the nucleus by mitochondria, leading to an increase in mitochondria-nucleus contact sites in a HOIP-dependent manner. Notably, TNF-induced stabilization of the mitochondrial kinase PINK1 furthermore contributes to signal amplification by antagonizing the M1-ubiquitin-specific deubiquitinase OTULIN. Overall, our study reveals a role for mitochondria in amplifying TNF-mediated NF-κB activation, both serving as a signaling platform, as well as a transport mode for activated NF-κB to the nuclear

miR449 Protects Airway Regeneration by Controlling AURKA/HDAC6-Mediated Ciliary Disassembly

Airway mucociliary regeneration and function are key players for airway defense and are impaired in chronic obstructive pulmonary disease (COPD). Using transcriptome analysis in COPD-derived bronchial biopsies, we observed a positive correlation between cilia-related genes and microRNA-449 (miR449). In vitro, miR449 was strongly increased during airway epithelial mucociliary differentiation. In vivo, miR449 was upregulated during recovery from chemical or infective insults. miR0449-/- mice (both alleles are deleted) showed impaired ciliated epithelial regeneration after naphthalene and Haemophilus influenzae exposure, accompanied by more intense inflammation and emphysematous manifestations of COPD. The latter occurred spontaneously in aged miR449-/- mice. We identified Aurora kinase A and its effector target HDAC6 as key mediators in miR449-regulated ciliary homeostasis and epithelial regeneration. Aurora kinase A is downregulated upon miR449 overexpression in vitro and upregulated in miR449-/- mouse lungs. Accordingly, imaging studies showed profoundly altered cilia length and morphology accompanied by reduced mucociliary clearance. Pharmacological inhibition of HDAC6 rescued cilia length and coverage in miR449-/- cells, consistent with its tubulin-deacetylating function. Altogether, our study establishes a link between miR449, ciliary dysfunction, and COPD pathogenesis

miR449 Protects Airway Regeneration by Controlling AURKA/HDAC6-Mediated Ciliary Disassembly

Airway mucociliary regeneration and function are key players for airway defense and are impaired in chronic obstructive pulmonary disease (COPD). Using transcriptome analysis in COPD-derived bronchial biopsies, we observed a positive correlation between cilia-related genes and microRNA-449 (miR449). In vitro, miR449 was strongly increased during airway epithelial mucociliary differentiation. In vivo, miR449 was upregulated during recovery from chemical or infective insults. miR0449−/− mice (both alleles are deleted) showed impaired ciliated epithelial regeneration after naphthalene and Haemophilus influenzae exposure, accompanied by more intense inflammation and emphysematous manifestations of COPD. The latter occurred spontaneously in aged miR449−/− mice. We identified Aurora kinase A and its effector target HDAC6 as key mediators in miR449-regulated ciliary homeostasis and epithelial regeneration. Aurora kinase A is downregulated upon miR449 overexpression in vitro and upregulated in miR449−/− mouse lungs. Accordingly, imaging studies showed profoundly altered cilia length and morphology accompanied by reduced mucociliary clearance. Pharmacological inhibition of HDAC6 rescued cilia length and coverage in miR449−/− cells, consistent with its tubulin-deacetylating function. Altogether, our study establishes a link between miR449, ciliary dysfunction, and COPD pathogenesis

Amyloid Precursor Protein Is Trafficked and Secreted via Synaptic Vesicles

A large body of evidence has implicated amyloid precursor protein (APP) and its proteolytic derivatives as key players in the physiological context of neuronal synaptogenesis and synapse maintenance, as well as in the pathology of Alzheimer's Disease (AD). Although APP processing and release are known to occur in response to neuronal stimulation, the exact mechanism by which APP reaches the neuronal surface is unclear. We now demonstrate that a small but relevant number of synaptic vesicles contain APP, which can be released during neuronal activity, and most likely represent the major exocytic pathway of APP. This novel finding leads us to propose a revised model of presynaptic APP trafficking that reconciles existing knowledge on APP with our present understanding of vesicular release and recycling