Subgroups of Paediatric Acute Lymphoblastic Leukaemia Might Differ Significantly in Genetic Predisposition to Asparaginase Hypersensitivity

L-asparaginase (ASP) is a key element in the treatment of paediatric acute lymphoblastic leukaemia (ALL). However, hypersensitivity reactions (HSRs) to ASP are major challenges in paediatric patients. Our aim was to investigate genetic variants that may influence the risk to Escherichia coli-derived ASP hypersensitivity. Sample and clinical data collection was carried out from 576 paediatric ALL patients who were treated according to protocols from the Berlin—Frankfurt—Münster Study Group. A total of 20 single nucleotide polymorphisms (SNPs) in GRIA1 and GALNT10 genes were genotyped. Patients with GRIA1 rs4958351 AA/AG genotype showed significantly reduced risk to ASP hypersensitivity compared to patients with GG genotype in the T-cell ALL subgroup (OR = 0.05 (0.01–0.26); p = 4.70E-04), while no such association was found in pre-B-cell ALL. In the medium risk group two SNPs of GRIA1 (rs2055083 and rs707176) were associated significantly with the occurrence of ASP hypersensitivity (OR = 0.21 (0.09–0.53); p = 8.48E-04 and OR = 3.02 (1.36–6.73); p = 6.76E-03, respectively). Evaluating the genders separately, however, the association of rs707176 with ASP HSRs was confined only to females. Our results suggest that genetic variants of GRIA1 might influence the risk to ASP hypersensitivity, but subgroups of patients can differ significantly in this respect.     

Conjugative transposition of the vancomycin resistance carrying Tn1549: enzymatic requirements and target site preferences

Rapid spread of resistance to vancomycin has generated difficult to treat bacterial pathogens worldwide. Though vancomycin resistance is often conferred by the conjugative transposon Tn1549, it is yet unclear whether Tn1549 moves actively between bacteria. Here we demonstrate, through development of an in vivo assay system, that a mini‐Tn1549 can transpose in E. coli away from its natural Gram‐positive host. We find the transposon‐encoded INT enzyme and its catalytic tyrosine Y380 to be essential for transposition. A second Tn1549 protein, XIS is important for efficient and accurate transposition. We further show that DNA flanking the left transposon end is critical for excision, with changes to nucleotides 7 and 9 impairing movement. These mutations could be partially compensated for by changing the final nucleotide of the right transposon end, implying concerted excision of the two ends. With changes in these essential DNA sequences, or without XIS, a large amount of flanking DNA transposes with Tn1549. This rescues mobility and allows the transposon to capture and transfer flanking genomic DNA. We further identify the transposon integration target sites as TTTT‐N6‐AAAA. Overall, our results provide molecular insights into conjugative transposition and the adaptability of Tn1549 for efficient antibiotic resistance transfer.     

Photosensitizers and antioxidants: a way to new drugs?

Photodynamic therapy (PDT) is a relatively new modality of treatment of diseases involving uncontrolled cell proliferation. It is based on the production of reactive species upon illumination of a photosensitizer in the presence of oxygen. Antioxidants are primarily reducing agents prone to scavenge reactive species in one way or another. Their presence in photodynamic reactions usually reduces the efficacy of PDT. Some antioxidants like ascorbic acid, alpha-tocopherol or butyl-4-hydroxyanisole, however, when added to cells at adequate concentrations may enhance the photodamaging activity of PDT. The presence of transition metals and precise timing of antioxidant administration may also be important factors in increasing the efficacy of PDT. Antioxidant carrier sensitizers have been designed, synthesised and tested for their antibacterial PDT activity. The promising results raise the question whether the introduction of antioxidant moieties into sensitizer molecules would lead to the synthesis of highly effective new drugs.     

Light enough to travel or wise enough to stay? Brain size evolution and migratory behavior in birds

Brain size relative to body size is smaller in migratory than in nonmigratory birds. Two mutually nonexclusive hypotheses had been proposed to explain this association. On the one hand, the “energetic trade‐off hypothesis” claims that migratory species were selected to have smaller brains because of the interplay between neural tissue volume and migratory flight. On the other hand, the “behavioral flexibility hypothesis” argues that resident species are selected to have higher cognitive capacities, and therefore larger brains, to enable survival in harsh winters, or to deal with environmental seasonality. Here, I test the validity and setting of these two hypotheses using 1466 globally distributed bird species. First, I show that the negative association between migration distance and relative brain size is very robust across species and phylogeny. Second, I provide strong support for the energetic trade‐off hypothesis, by showing the validity of the trade‐off among long‐distance migratory species alone. Third, using resident and short‐distance migratory species, I demonstrate that environmental harshness is associated with enlarged relative brain size, therefore arguably better cognition. My study provides the strongest comparative support to date for both the energetic trade‐off and the behavioral flexibility hypotheses, and highlights that both mechanisms contribute to brain size evolution, but on different ends of the migratory spectrum.     

Sensing photosynthetic herbicides in an electrochemical flow cell

Specific inhibitory reactions of herbicides with photosynthetic reaction centers bound to working electrodes were monitored in a conventional electrochemical cell and a newly designed microfluidic electrochemical flow cell. In both cases, the bacterial reaction centers were bound to a transparent conductive metal oxide, indium-tin-oxide, electrode through carbon nanotubes. In the conventional cell, photocurrent densities of up to a few μA/cm² could be measured routinely. The photocurrent could be blocked by the photosynthetic inhibitor terbutryn (I ₅₀ = 0.38 ± 0.14 μM) and o-phenanthroline (I ₅₀ = 63.9 ± 12.2 μM). The microfluidic flow cell device enabled us to reduce the sample volume and to simplify the electrode arrangement. The useful area of the electrodes remained the same (ca. 2 cm²), similar to the classical electrochemical cell; however, the size of the cell was reduced considerably. The microfluidic flow control enabled us monitoring in real time the binding/unbinding of the inhibitor and cofactor molecules at the secondary quinone site.     

New aspects of grassland recovery in old‐fields revealed by trait‐based analyses of perennial‐crop‐mediated succession

Classical old‐field succession studies focused on vegetation changes after the abandonment of annual croplands or on succession after the elimination of cultivated crops. Perennial‐crop‐mediated succession, where fields are initially covered by perennial crops, reveals alternative aspects of old‐field succession theories. We tested the validity of classical theories of old‐field succession for perennial‐crop‐mediated succession. We formulated the following hypotheses: (1) functional diversity increases with increasing field age; (2) resource acquisition versus conservation trade‐off shifts toward conservation at community level during the succession; (3) the importance of spatial and temporal seed dispersal decreases during the succession; and (4) competitiveness and stress‐tolerance increases and ruderality decreases at community level during the succession. We studied functional diversity, trait distributions and plant strategies in differently aged old‐fields using chronosequence method. We found increasing functional richness and functional divergence, but also unchanged or decreasing functional evenness. We detected a shift from resource acquisition to resource conservation strategy of communities during the succession. The role of spatial and temporal seed dispersal was found to be important not only at the initial but also at latter successional stages. We found an increasing stress‐tolerance and a decreasing ruderality during succession, while the competitiveness remained unchanged at the community level. Despite the markedly different starting conditions, we found that classical and perennial‐crop‐mediated old‐field successions have some similarities regarding the changes of functional diversity, resource acquisition versus conservation trade‐off, and seed dispersal strategies. However, we revealed also the subsequent differences. The competitive character of communities remained stable during the succession; hence, the initial stages of perennial‐crop‐mediated succession can be similar to the middle stages of classical old‐field succession. Moreover, the occupied functional niche space and differentiation were larger in the older stages, but resources were not effectively utilized within this space, suggesting that the stabilization of the vegetation requires more time.     

Do large‐seeded herbs have a small range size? The seed mass–distribution range trade‐off hypothesis

We aimed to introduce and test the “seed mass–distribution range trade‐off” hypothesis, that is, that range size is negatively related to seed mass due to the generally better dispersal ability of smaller seeds. Studying the effects of environmental factors on the seed mass and range size of species, we also aimed to identify habitats where species may be at risk and need extra conservation effort to avoid local extinctions. We collected data for seed mass, global range size, and indicators for environmental factors of the habitat for 1,600 species of the Pannonian Ecoregion (Central Europe) from the literature. We tested the relationship between species’ seed mass, range size, and indicator values for soil moisture, light intensity, and nutrient supply. We found that seed mass is negatively correlated with range size; thus, a seed mass–distribution range trade‐off was validated based on the studied large species pool. We found increasing seed mass with decreasing light intensity and increasing nutrient availability, but decreasing seed mass with increasing soil moisture. Range size increased with increasing soil moisture and nutrient supply, but decreased with increasing light intensity. Our results supported the hypothesis that there is a trade‐off between seed mass and distribution range. We found that species of habitats characterized by low soil moisture and nutrient values but high light intensity values have small range size. This emphasizes that species of dry, infertile habitats, such as dry grasslands, could be more vulnerable to habitat fragmentation or degradation than species of wet and fertile habitats. The remarkably high number of species and the use of global distribution range in our study support our understanding of global biogeographic processes and patterns that are essential in defining conservation priorities.     

Loss of Kindlin-1 Causes Skin Atrophy and Lethal Neonatal Intestinal Epithelial Dysfunction

Kindler Syndrome (KS), characterized by transient skin blistering followed by abnormal pigmentation, skin atrophy, and skin cancer, is caused by mutations in the FERMT1 gene. Although a few KS patients have been reported to also develop ulcerative colitis (UC), a causal link to the FERMT1 gene mutation is unknown. The FERMT1 gene product belongs to a family of focal adhesion proteins (Kindlin-1, -2, -3) that bind several β integrin cytoplasmic domains. Here, we show that deleting Kindlin-1 in mice gives rise to skin atrophy and an intestinal epithelial dysfunction with similarities to human UC. This intestinal dysfunction results in perinatal lethality and is triggered by defective intestinal epithelial cell integrin activation, leading to detachment of this barrier followed by a destructive inflammatory response.     

Optimal moult strategies in migratory birds

Avian migration, which involves billions of birds flying vast distances, is known to influence all aspects of avian life. Here we investigate how birds fit moult into an annual cycle determined by the need to migrate. Large variation exists in moulting patterns in relation to migration: for instance, moult can occur after breeding in the summer or after arrival in the wintering quarters. Here we use an optimal annual routine model to investigate why this variation exists. The modelled bird's decisions depend on the time of year, its energy reserves, breeding status, experience, flight feather quality and location. Our results suggest that the temporal and spatial variations in food are an important influence on a migratory bird's annual cycle. Summer moult occurs when food has a high peak on the breeding site in the summer, but it is less seasonal elsewhere. Winter moult occurs if there is a short period of high food availability in summer and a strong winter peak at different locations (i.e. the food is very seasonal but in opposite phase on these areas). This finding might explain why only long-distance migrants have a winter moult.     

Methylene substitution at the alpha-beta bridging position within the phosphate chain of dUDP profoundly perturbs ligand accommodation into the dUTPase active site

dUTP pyrophosphatase, a preventive DNA repair enzyme, contributes to maintain the appropriate cellular dUTP/dTTP ratio by catalyzing dUTP hydrolysis. dUTPase is essential for viability in bacteria and eukaryotes alike. Identification of species-specific antagonists of bacterial dUTPases is expected to contribute to the development of novel antimicrobial agents. As a first general step, design of dUTPase inhibitors should be based on modifications of the substrate dUTP phosphate chain, as modifications in either base or sugar moieties strongly impair ligand binding. Based on structural differences between bacterial and human dUTPases, derivatization of dUTP-analogous compounds will be required as a second step to invoke species-specific character. Studies performed with dUTP analogues also offer insights into substrate binding characteristics of this important and structurally peculiar enzyme. In this study, alpha,beta-methylene-dUDP was synthesized and its complex with dUTPase was characterized. Enzymatic phosphorylation of this substrate analogue by pyruvate kinase was not possible in contrast to the successful enzymatic phosphorylation of alpha,beta-imino-dUDP. One explanation for this finding is that the different bond angles and the presence of the methylene group may preclude formation of a catalytically competent complex with the kinase. Crystal structure of E. coli dUTPase:alpha,beta-methylene-dUDP and E. coli dUTPase:dUDP:Mn complexes were determined and analyzed in comparison with previous data. Results show that the "trans" alpha-phosphate conformation of alpha,beta-methylene-dUDP differs from the catalytically competent "gauche" alpha-phosphate conformation of the imino analogue and the oxo substrate, manifested in the shifted position of the alpha-phosphorus by more than 3 A. The three-dimensional structures determined in this work show that the binding of the methylene analogue with the alpha-phosphorus in the "gauche" conformation would result in steric clash of the methylene group with the protein atoms. In addition, the metal ion cofactor was not bound in the crystal of the complex with the methylene analogue while it was clearly visible as coordinated to dUDP, arguing that the altered phosphate chain conformation also perturbs metal ion complexation. Isothermal calorimetry titrations indicate that the binding affinity of alpha,beta-methylene-dUDP toward dUTPase is drastically decreased when compared with that of dUDP. In conclusion, the present data suggest that while alpha,beta-methylene-dUDP seems to be practically nonhydrolyzable, it is not a strong binding inhibitor of dUTPase probably due to the altered binding mode of the phosphate chain. Results indicate that in some cases methylene analogues may not faithfully reflect the competent substrate ligand properties, especially if the methylene hydrogens are in steric conflict with the protein.