The interferon-inducible protein viperin inhibits influenza virus release by perturbing lipid rafts

Interferons initiate the host antiviral response by inducing a number of genes, most with no defined antiviral function. Here we show that the interferon-induced protein viperin inhibits influenza A virus release from the plasma membrane of infected cells. Viperin expression altered plasma membrane fluidity by affecting the formation of lipid rafts, which are detergent-resistant membrane microdomains known to be the sites of influenza virus budding. Intracellular interaction of viperin with farnesyl diphosphate synthase (FPPS), an enzyme essential for isoprenoid biosynthesis, decreased the activity of the enzyme. Overexpression of FPPS reversed viperin-mediated inhibition of virus production and restored normal membrane fluidity, and reduction of FPPS levels by siRNA inhibited virus release and replication, indicating that the FPPS interaction underlies viperin's effects. These findings suggest that targeting the release stage of the life cycle may affect the replication of many enveloped viruses. Furthermore, FPPS may be an attractive target for antiviral therapy.     

Overexpression of manganese superoxide dismutase ameliorates high-fat diet-induced insulin resistance in rat skeletal muscle

Elevated mitochondrial reactive oxygen species have been suggested to play a causative role in some forms of muscle insulin resistance. However, the extent of their involvement in the development of diet-induced insulin resistance remains unclear. To investigate, manganese superoxide dismutase (MnSOD), a key mitochondrial-specific enzyme with antioxidant modality, was overexpressed, and the effect on in vivo muscle insulin resistance induced by a high-fat (HF) diet in rats was evaluated. Male Wistar rats were maintained on chow or HF diet. After 3 wk, in vivo electroporation (IVE) of MnSOD expression and empty vectors was undertaken in right and left tibialis cranialis (TC) muscles, respectively. After one more week, insulin action was evaluated using hyperinsulinemic euglycemic clamp, and tissues were subsequently analyzed for antioxidant enzyme capacity and markers of oxidative stress. MnSOD mRNA was overexpressed 4.5-fold, and protein levels were increased by 70%, with protein detected primarily in the mitochondrial fraction of muscle fibers. This was associated with elevated MnSOD and glutathione peroxidase activity, indicating that the overexpressed MnSOD was functionally active. The HF diet significantly reduced whole body and TC muscle insulin action, whereas overexpression of MnSOD in HF diet animals ameliorated this reduction in TC muscle glucose uptake by 50% (P < 0.05). Decreased protein carbonylation was seen in MnSOD overexpressing TC muscle in HF-treated animals (20% vs. contralateral control leg, P < 0.05), suggesting that this effect was mediated through an altered redox state. Thus interventions causing elevation of mitochondrial antioxidant activity may offer protection against diet-induced insulin resistance in skeletal muscle.     

Personality and problem-solving performance explain competitive ability in the wild

Competitive ability is a major determinant of fitness, but why individuals vary so much in their competitiveness remains only partially understood. One increasingly prevalent view is that realized competitive ability varies because it represents alternative strategies that arise because of the costs associated with competitiveness. Here we use a population of great tits (Parus major) to explore whether individual differences in competitive ability when foraging can be explained by two traits that have previously been linked to alternative behavioural strategies: the personality trait 'exploration behaviour' and a simple cognitive trait, 'innovative problem-solving performance'. We assayed these traits under standardized conditions in captivity and then measured competitive ability at feeders with restricted access in the wild. Competitive ability was repeatable within individual males across days and correlated positively with exploration behaviour, representing the first such demonstration of a link between a personality trait and both competitive ability and food intake in the wild. Competitive ability was also simultaneously negatively correlated with problem-solving performance; individuals who were poor competitors were good at problem-solving. Rather than being the result of variation in 'individual quality', our results support the hypothesis that individual variation in competitive ability can be explained by alternative behavioural strategies.     

Late ontogeny growth acceleration and size form transformations in Transbaikalian Arctic charr, <Emphasis Type="Italic">Salvelinus alpinus</Emphasis> complex: evidence from fin ray cross section growth layers

In some polymorphic populations of Arctic charr in Transbaikalia, an individual can transform from a smaller to larger size form during their lifetime as a result of accelerated growth that follows a period of slow growth and reproduction as a small size form. Alternating periods of slow and fast growth are reflected in growth layer patterns visible in fin ray cross sections. Stained microtome fin ray cross sections were used to reveal the incidence of transformations from one form to another. Data were collected from 14 northern Transbaikalian lakes containing two or three sympatric Arctic charr forms (‘dwarf’, ‘small’, and ‘large’) exhibiting varying levels of morphological separation. Individuals recruited from the dwarf or small form were found in varying proportions among the small and/or large form in 12 lakes. Small or large form charr that grew without noticeable acceleration to the adult size typical of the form or experienced accelerated growth as juveniles prior to maturation were also observed. There were no transformations between sympatric forms that differed in the length and number of gill rakers and in some other meristic characters. Results indicate that in the region under study, transformations of sympatric Arctic charr size forms are a widespread, but not a ubiquitous, phenomenon. Such transformations reflect the plasticity of the developmental channels of the forms. In the course of intra-lacustrine form divergence and genetic differentiation, the frequency of the observed transformations decreases to zero.     

Ontogeny of apelin and its receptor in the rodent gastrointestinal tract

Apelin is the endogenous ligand for the APJ receptor and both apelin and APJ are expressed in the gastrointestinal (GI) tract. The aim of this study was to define ontogeny of apelin and APJ in the developing rodent GI tract by measuring expression levels and characterizing abundance and cellular localization at an embryonic stage (E18.5 or E21), two postnatal stages (P4, P16) and in the adult. Apelin and APJ mRNA levels were measured by real time RT-PCR, apelin and APJ-containing cells were identified by immunohistochemical (IHC) staining. Gastric, duodenal and colonic apelin and APJ mRNA levels were highest at birth and declined postnatally. In the postnatal rat stomach, few apelin peptide-containing cells were identified, the density of gastric apelin-containing cells increased progressively after weaning and into adulthood. A robust APJ immunostaining was observed postnatally in the epithelium, intestinal goblet cells and in smooth muscle cells. In the adult rat, APJ immunostaining in the surface epithelium and goblet cells decreased markedly. During the early postnatal period, in an apelin-deficient mouse, APJ expression and immunostaining in the gut were reduced suggesting that apelin regulates APJ. Together, our data support a role for the apelin–APJ system in the regulation of smooth muscle, epithelial and goblet cell function in the GI tract.     

Rapid differentiation of <Emphasis Type="Italic">Francisella</Emphasis> species and subspecies by fluorescent in situ hybridization targeting the 23S rRNA

Background  

Francisella (F.) tularensis is the causative agent of tularemia. Due to its low infectious dose, ease of dissemination and high case fatality rate, F. tularensis was the subject in diverse biological weapons programs and is among the top six agents with high potential if misused in bioterrorism. Microbiological diagnosis is cumbersome and time-consuming. Methods for the direct detection of the pathogen (immunofluorescence, PCR) have been developed but are restricted to reference laboratories.     

A novel approach to investigate tissue-specific trinucleotide repeat instability

Background

In Huntington's disease (HD), an expanded CAG repeat produces characteristic striatal neurodegeneration. Interestingly, the HD CAG repeat, whose length determines age at onset, undergoes tissue-specific somatic instability, predominant in the striatum, suggesting that tissue-specific CAG length changes could modify the disease process. Therefore, understanding the mechanisms underlying the tissue specificity of somatic instability may provide novel routes to therapies. However progress in this area has been hampered by the lack of sensitive high-throughput instability quantification methods and global approaches to identify the underlying factors.

Results

Here we describe a novel approach to gain insight into the factors responsible for the tissue specificity of somatic instability. Using accurate genetic knock-in mouse models of HD, we developed a reliable, high-throughput method to quantify tissue HD CAG repeat instability and integrated this with genome-wide bioinformatic approaches. Using tissue instability quantified in 16 tissues as a phenotype and tissue microarray gene expression as a predictor, we built a mathematical model and identified a gene expression signature that accurately predicted tissue instability. Using the predictive ability of this signature we found that somatic instability was not a consequence of pathogenesis. In support of this, genetic crosses with models of accelerated neuropathology failed to induce somatic instability. In addition, we searched for genes and pathways that correlated with tissue instability. We found that expression levels of DNA repair genes did not explain the tissue specificity of somatic instability. Instead, our data implicate other pathways, particularly cell cycle, metabolism and neurotransmitter pathways, acting in combination to generate tissue-specific patterns of instability.

Conclusion

Our study clearly demonstrates that multiple tissue factors reflect the level of somatic instability in different tissues. In addition, our quantitative, genome-wide approach is readily applicable to high-throughput assays and opens the door to widespread applications with the potential to accelerate the discovery of drugs that alter tissue instability.     

Skeletal muscle NADPH oxidase is increased and triggers stretch-induced damage in the mdx mouse

Recent studies have shown that oxidative stress contributes to the pathogenesis of muscle damage in dystrophic (mdx) mice. In this study we have investigated the role of NADPH oxidase as a source of the oxidative stress in these mice. The NADPH oxidase subunits gp91(phox), p67(phox) and rac 1 were increased 2-3 fold in tibilais anterior muscles from mdx mice compared to wild type. Importantly, this increase occurred in 19 day old mice, before the onset of muscle necrosis and inflammation, suggesting that NADPH oxidase is an important source of oxidative stress in mdx muscle. In muscles from 9 week old mdx mice, gp91(phox) and p67(phox) were increased 3-4 fold and NADPH oxidase superoxide production was 2 times greater than wild type. In single fibers from mdx muscle NADPH oxidase subunits were all located on or near the sarcolemma, except for p67(phox),which was expressed in the cytosol. Pharmacological inhibition of NADPH oxidase significantly reduced the intracellular Ca(2+) rise following stretched contractions in mdx single fibers, and also attenuated the loss of muscle force. These results suggest that NADPH oxidase is a major source of reactive oxygen species in dystrophic muscle and its enhanced activity has a stimulatory effect on stretch-induced Ca(2+) entry, a key mechanism for muscle damage and functional impairment.