Sexual differences in the behavioural response to a variation in predation risk

Predators may influence their prey populations not only through direct lethal effects, but also by causing behavioural changes. The natural expansion of the wolf (Canis lupus) into the Alps provided the rare opportunity to monitor the responses of a prey species to the return of a large predator. Density effects have rarely been considered in the study of antipredator strategies. We examined the effects of wolf recolonisation and density modifications on group size and use of safe areas by Alpine ibex (Capra ibex) in Gran Paradiso National Park (Italy), where no large terrestrial predator has been present for about a century. We documented that, in a few years, the variation in the factors affecting the landscape of fear caused significant modifications in ibex behavioural patterns that could not be accounted for by density changes only. Male groups decreased in size and moved closer to safer areas. The distance of female groups from refuge sites, instead, was not affected, and their propensity to live in groups was scarcely modified. Behavioural modifications likely caused a reduction in nutrient intake in adult male ibex, as they necessarily used lower‐quality feeding patches. Our results showed that male and female ibex, which are characterised by a strong dimorphism, adopted different strategies to solve the conflicting demands of foraging efficiently and avoiding predators.     

Targeting EDEM protects against ER stress and improves development and survival in C. elegans

EDEM-1, EDEM-2 and EDEM-3 are key players for the quality control of newly synthesized proteins in the endoplasmic reticulum (ER) by accelerating disposal and degradation of misfolded proteins through ER Associated Degradation (ERAD). Although many previous studies reported the role of individual ERAD components especially in cell-based systems, still little is known about the consequences of ERAD dysfunction under physiological and ER stress conditions in the context of a multicellular organism. Here we report the first individual and combined characterization and functional interplay of EDEM proteins in Caenorhabditis elegans using single, double, and triple mutant combinations. We found that EDEM-2 has a major role in the clearance of misfolded proteins from ER under physiological conditions, whereas EDEM-1 and EDEM-3 roles become prominent under acute ER stress. In contrast to SEL-1 loss, the loss of EDEMs in an intact organism induces only a modest ER stress under physiological conditions. In addition, chronic impairment of EDEM functioning attenuated both XBP-1 activation and up-regulation of the stress chaperone GRP78/BiP, in response to acute ER stress. We also show that pre-conditioning to EDEM loss in acute ER stress restores ER homeostasis and promotes survival by activating ER hormesis. We propose a novel role for EDEM in fine-tuning the ER stress responsiveness that affects ER homeostasis and survival.     

Stereotactic radiotherapy for brain oligometastases

Brain metastases, the most common metastases in adults, will develop in up to 40% of cancer patients, accounting for more than one-half of all intracranial tumors. They are most associated with breast and lung cancer, melanoma and, less frequently, colorectal and kidney carcinoma.Magnetic resonance imaging (MRI) is the gold standard for diagnosis. For the treatment plan, computed tomography (CT ) images are co-registered and fused with a gadolinium-enhanced T1-weighted MRI where tumor volume and organs at risk are contoured. Alternatively, plain and contrast-enhanced CT scans are co-registered. Single-fraction stereotactic radiotherapy (SRT ) is used to treat patients with good performance status and up to 4 lesions with a diameter of 30 mm or less that are distant from crucial brain function areas. Fractionated SRT (2–5 fractions) is used for larger lesions, in eloquent areas or in proximity to crucial or surgically inaccessible areas and to reduce treatment-related neurotoxicity. The single-fraction SRT dose, which depends on tumor diameter, impacts local control. Fractionated SRT may encompass different schedules. No randomized trial data compared the safety and efficacy of single and multiple fractions. Both single-fraction and fractionated SRT provide satisfactory local control rates, tolerance, a low risk of transient acute adverse events and of radiation necrosis the incidence of which correlated with the irradiated brain volume.     

Radiobiology of stereotactic radiotherapy

This paper focuses on the radiobiological mechanisms underlying the effects of stereotactic radiotherapy (SRT ) which, despite SRT expansion, have not yet been fully elucidated. Some authors postulated that radiobiology principles, as applied to conventional fractionations (5R: reoxygenation, repair, repopulation, redistribution, radioresistence), suffice in themselves to account for the excellent clinical results of SRT; others argued that the role of the 5R was limited. Recent preclinical data showed that hypofractionated ablative treatments altered the microenvironment, thus determining cell death either directly or indirectly. Furthermore, dead tumor cells released quantities of antigens, which stimulated antitumor immunity, thus reducing the risk of relapse and metastasis. Better understanding of the radiobiological mechanisms underlying response to high-dose radiation treatment is essential for predicting its short- and long-term effects on the tumor and surrounding healthy tissues and, consequently, for improving its related therapeutic index.     

The splicing regulator Sam68 binds to a novel exonic splicing silencer and functions in SMN2 alternative splicing in spinal muscular atrophy

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by loss of motor neurons in patients with null mutations in the SMN1 gene. An almost identical SMN2 gene is unable to compensate for this deficiency because a single C‐to‐T transition at position +6 in exon‐7 causes skipping of the exon by a mechanism not yet fully elucidated. We observed that the C‐to‐T transition in SMN2 creates a putative binding site for the RNA‐binding protein Sam68. RNA pull‐down assays and UV‐crosslink experiments showed that Sam68 binds to this sequence. In vivo splicing assays showed that Sam68 triggers SMN2 exon‐7 skipping. Moreover, mutations in the Sam68‐binding site of SMN2 or in the RNA‐binding domain of Sam68 completely abrogated its effect on exon‐7 skipping. Retroviral infection of dominant‐negative mutants of Sam68 that interfere with its RNA‐binding activity, or with its binding to the splicing repressor hnRNP A1, enhanced exon‐7 inclusion in endogenous SMN2 and rescued SMN protein expression in fibroblasts of SMA patients. Our results thus indicate that Sam68 is a novel crucial regulator of SMN2 splicing.     

Protein titration in the crystal state.

Proteins are complex structures whose overall stability critically depends on a delicate balance of numerous interactions of similar strength, which are markedly influenced by their environment. Here, we present an analysis of the effect of pH on a protein structure in the crystalline state using RNase A as a model system. By altering only one physico-chemical parameter in a controlled manner, we are able to quantify the structural changes induced in the protein. Atomic resolution X-ray diffraction data were collected for crystals at six pH* values ranging from 5.2 to 8.8, and the six independently refined structures reveal subtle, albeit well-defined variations directly related to the pH titration of the protein. The deprotonation of the catalytic His12 residue is clearly evident in the electron density maps, confirming the reaction mechanism proposed by earlier enzymatic and structural studies. The concerted structural changes observed in the regions remote from the active-site point to an adaptation of the protein structure to the changes in the physico-chemical environment. Analysis of the stereochemistry of the six structures provided accurate estimates of p Kavalues of most of the histidine residues. This study gives further evidence for the advantage of atomic resolution X-ray crystallographic analyses for revealing small but significant structural changes which provide clues to the function of a biological macromolecule.     

Filamentous Alphaproteobacteria associated with bulking in industrial wastewater treatment plants

The phylogeny and distribution of filamentous Alphaproteobacteria, morphologically similar to “Nostocoida limicola” and Eikelboom Type 021N that cause the solids separation problem of bulking in industrial activated sludge plants is described here. A combination of culture-dependent and culture-independent molecular methods has characterized 5 novel species. 16S rRNA targeted oligonucleotide probes were designed for their in situ identification by fluorescence in situ hybridisation (FISH) and used to monitor their presence in 86 WWTPs treating different industrial effluents in four European countries. The involvement of these bacteria in bulking in these plants was confirmed. Filaments hybridising with the ALF-968 probe for the Alphaproteobacteria were present in 65% of the WWTPs examined. They were dominant and therefore probably responsible for bulking in 25.5% of them. The heterogeneous filamentous alphaproteobacterial populations in these communities could be completely identified after application of the oligonucleotide probes used in this study in 91% of the plants containing them. The only filamentous Alphaproteobacteria retrieved in pure culture was isolated from three different industrial WWTPs plants. None of these isolates could grow anaerobically on glucose or denitrify, but all grew aerobically and heterotrophically on a range of carbon sources. Although morphologically similar to the Eikelboom Type 021N morphotype, they were not involved in sulphur metabolism. These bacteria accumulated lipidic storage granules that were associated with their presence under the unbalanced growth conditions existing in these plants.     

Development of ectopic roots from abortive nodule primordia

The symbiotic phenotype of five Tn5-induced mutants of Rhizobium etli affected in different anabolic pathways (namely, gluconeogenesis and biosynthesis of lysine, purine, or pyrimidine) was analyzed. These mutants induced, on the root of Phaseolus vulgaris, a normal early sequence of morphogenetics events, including root hair deformation and development of nodule primordia. Later on, however, from the resulting root outgrowths, instead of nodules, one or more ectopic roots (spaced closely related and agravitropic) emerged. Therefore, this group of mutant was collectively called "root inducer" (RIND). It was observed that the RIND-induced infection threads aborted early inside the invaded root hair, and that the resulting abortive nodules lack induction of late nodulin genes. Moreover, experiments performed using a conditional mutant (a methionine-requiring invader) revealed that bacterial invasion plays a key role in the maintenance of the program of nodule development and, in particular, in the differentiation of the most specific symbiotic tissue of globose nodules, the central tissue. These data indicate that, in P. vulgaris, the nodule primordium is a root-specified pro-meristematic tissue.     

Endocytosis and cancer

Eukaryotic cells use endocytosis to internalise plasma membrane, surface receptors and their ligands, viruses and various extracellular soluble molecules. Endocytosis has been regarded as a long-term mechanism of signal attenuation via receptor clearance from the cell surface. However, additional, and quite unexpected, functions for endocytosis have emerged, which, together with its attenuation function, project a central role for this process in cellular homeostasis and control of proliferation. Subversion of endocytic control is thus predicted to play a causative role in hyperproliferative conditions, first and foremost cancer.