What you need is what you eat? Prey selection by the bat Myotis daubentonii

Optimal foraging theory predicts that predators are selective when faced with abundant prey, but become less picky when prey gets sparse. Insectivorous bats in temperate regions are faced with the challenge of building up fat reserves vital for hibernation during a period of decreasing arthropod abundances. According to optimal foraging theory, prehibernating bats should adopt a less selective feeding behaviour – yet empirical studies have revealed many apparently generalized species to be composed of specialist individuals. Targeting the diet of the bat Myotis daubentonii, we used a combination of molecular techniques to test for seasonal changes in prey selectivity and individual‐level variation in prey preferences. DNA metabarcoding was used to characterize both the prey contents of bat droppings and the insect community available as prey. To test for dietary differences among M. daubentonii individuals, we used ten microsatellite loci to assign droppings to individual bats. The comparison between consumed and available prey revealed a preference for certain prey items regardless of availability. Nonbiting midges (Chironomidae) remained the most highly consumed prey at all times, despite a significant increase in the availability of black flies (Simuliidae) towards the end of the season. The bats sampled showed no evidence of individual specialization in dietary preferences. Overall, our approach offers little support for optimal foraging theory. Thus, it shows how novel combinations of genetic markers can be used to test general theory, targeting patterns at both the level of prey communities and individual predators.     

The low spin - high spin equilibrium in the S2-state of the water oxidizing enzyme

In Photosystem II (PSII), the Mn₄CaO₅-cluster of the active site advances through five sequential oxidation states (S₀ to S₄) before water is oxidized and O₂ is generated. Here, we have studied the transition between the low spin (LS) and high spin (HS) configurations of S₂ using EPR spectroscopy, quantum chemical calculations using Density Functional Theory (DFT), and time-resolved UV-visible absorption spectroscopy. The EPR experiments show that the equilibrium between S₂^LS and S₂^HS is pH dependent, with a pK_a?≈?8.3 (n?≈?4) for the native Mn₄CaO₅ and pK_a?≈?7.5 (n?≈?1) for Mn₄SrO₅. The DFT results suggest that exchanging Ca with Sr modifies the electronic structure of several titratable groups within the active site, including groups that are not direct ligands to Ca/Sr, e.g., W1/W2, Asp61, His332 and His337. This is consistent with the complex modification of the pK_a upon the Ca/Sr exchange. EPR also showed that NH₃ addition reversed the effect of high pH, NH₃-S₂^LS being present at all pH values studied. Absorption spectroscopy indicates that NH₃ is no longer bound in the S₃Tyr_Z state, consistent with EPR data showing minor or no NH₃-induced modification of S₃ and S₀. In both Ca-PSII and Sr-PSII, S₂^HS was capable of advancing to S₃ at low temperature (198?K). This is an experimental demonstration that the S₂^LS is formed first and advances to S₃via the S₂^HS state without detectable intermediates. We discuss the nature of the changes occurring in the S₂^LS to S₂^HS transition which allow the S₂^HS to S₃ transition to occur below 200?K. This work also provides a protocol for generating S₃ in concentrated samples without the need for saturating flashes.     

Ultrastructural immunolocalization of elastic fibers in rat blood vessels using the protein A-gold technique

Identification of elastic fibers at the ultrastructural level is accomplished by a post-embedding immunohistochemical technique using the protein A-colloidal gold method. Antisera against elastins from human dermis and rat aorta have been characterized by radioimmunoassay and then applied to thin sections of rat blood vessels. Two fixative solutions and two embedding media have been tested. Both antibodies bind to elastic fibers of normal arteries and veins, indicating crossreactions among organs and species. The high sensitivity of this method is demonstrated by its application to the detection of neo-elastogenesis in the intimal thickening of aortic grafts.     

Identification of Non-HLA Genes Associated with Celiac Disease and Country-Specific Differences in a Large,International Pediatric Cohort

Objectives

There are significant geographical differences in the prevalence and incidence of celiac disease that cannot be explained by HLA alone. More than 40 loci outside of the HLA region have been associated with celiac disease. We investigated the roles of these non-HLA genes in the development of tissue transglutaminase autoantibodies (tTGA) and celiac disease in a large international prospective cohort study.

Methods

A total of 424,788 newborns from the US and European general populations and first-degree relatives with type 1 diabetes were screened for specific HLA genotypes. Of these, 21,589 carried 1 of the 9 HLA genotypes associated with increased risk for type 1 diabetes and celiac disease; we followed 8676 of the children in a 15 y prospective follow-up study. Genotype analyses were performed on 6010 children using the Illumina ImmunoChip. Levels of tTGA were measured in serum samples using radio-ligand binding assays; diagnoses of celiac disease were made based on persistent detection of tTGA and biopsy analysis. Data were analyzed using Cox proportional hazards analyses.

Results

We found 54 single-nucleotide polymorphisms (SNPs) in 5 genes associated with celiac disease (TAGAP, IL18R1, RGS21, PLEK, and CCR9) in time to celiac disease analyses (10⁻⁴>P>5.8x10⁻⁶). The hazard ratios (HR) for the SNPs with the smallest P values in each region were 1.59, 1.45, 2.23, 2.64, and 1.40, respectively. Outside of regions previously associated with celiac disease, we identified 10 SNPs in 8 regions that could also be associated with the disease (P<10⁻⁴). A SNP near PKIA (rs117128341, P = 6.5x10⁻⁸, HR = 2.8) and a SNP near PFKFB3 (rs117139146, P<2.8x10⁻⁷, HR = 4.9) reached the genome-wide association threshold in subjects from Sweden. Analyses of time to detection of tTGA identified 29 SNPs in 2 regions previously associated with celiac disease (CTLA4, P = 1.3x10⁻⁶, HR = 0.76 and LPP, P = 2.8x10⁻⁵, HR = .80) and 6 SNPs in 5 regions not previously associated with celiac disease (P<10⁻⁴); non-HLA genes are therefore involved in development of tTGA.

Conclusions

In conclusion, using a genetic analysis of a large international cohort of children, we associated celiac disease development with 5 non-HLA regions previously associated with the disease and 8 regions not previously associated with celiac disease. We identified 5 regions associated with development of tTGA. Two loci associated with celiac disease progression reached a genome-wide association threshold in subjects from Sweden.     

Cloning and characterization of a novel acidic cutinase from Sirococcus conigenus

A cutinase gene (ScCut1) was amplified by PCR from the genomic DNA of the ascomycetous plant pathogen Sirococcous conigenus VTT D-04989 using degenerate primers designed on the basis of conserved segments of known cutinases and cutinase-like enzymes. No introns or N- or O-glycosylation sites could be detected by analysis of the ScCut1 gene sequence. The alignment of ScCut1 with other fungal cutinases indicated that ScCut1 contained the conserved motif G-Y-S-Q-G surrounding the active site serine as well as the aspartic acid and histidine residues of the cutinase active site. The gene was expressed in Pichia pastoris, and the recombinantly produced ScCut1 enzyme was purified to homogeneity by immobilized metal affinity chromatography exploiting a C-terminal His-tag translationally fused to the protein. The purified ScCut1 exhibited activity at acidic pH. The K _m and V _max values determined for pNP-butyrate esterase activity at pH 4.5 were 1.7 mM and 740 nkat mg^?1, respectively. Maximal activities were determined at between pH 4.7 and 5.2 and at between pH 4.1 and 4.6 with pNP-butyrate and tritiated cutin as the substrates, respectively. With both substrates, the enzyme was active over a broad pH range (between pH 3.0 and 7.5). Activity could still be detected at pH 3.0 both with tritiated cutin and with p-nitrophenyl butyrate (relative activity of 25 %) as the substrates. ScCut1 showed activity towards shorter (C2 to C3) fatty acid esters of p-nitrophenol than towards longer ones. Circular dichroism analysis suggested that the denaturation of ScCut1 by heating the protein sample to 80 °C was to a great extent reversible.     

SUMOylation regulates the chromatin occupancy and anti-proliferative gene programs of glucocorticoid receptor

In addition to the glucocorticoids, the glucocorticoid receptor (GR) is regulated by post-translational modifications, including SUMOylation. We have analyzed how SUMOylation influences the activity of endogenous GR target genes and the receptor chromatin binding by using isogenic HEK293 cells expressing wild-type GR (wtGR) or SUMOylation-defective GR (GR3KR). Gene expression profiling revealed that both dexamethasone up- and downregulated genes are affected by the GR SUMOylation and that the affected genes are significantly associated with pathways of cellular proliferation and survival. The GR3KR-expressing cells proliferated more rapidly, and their anti-proliferative response to dexamethasone was less pronounced than in the wtGR-expressing cells. ChIP-seq analyses indicated that the SUMOylation modulates the chromatin occupancy of GR on several loci associated with cellular growth in a fashion that parallels with their differential dexamethasone-regulated expression between the two cell lines. Moreover, chromatin SUMO-2/3 marks, which were associated with active GR-binding sites, showed markedly higher overlap with the wtGR cistrome than with the GR3KR cistrome. In sum, our results indicate that the SUMOylation does not simply repress the GR activity, but regulates the activity of the receptor in a target locus selective fashion, playing an important role in controlling the GR activity on genes influencing cell growth.