An example of molecular co-evolution: reactive oxygen species (ROS) and ROS scavenger levels in Schistosoma mansoni/Biomphalaria glabrata interactions

The co-evolution between hosts and parasites involves huge reciprocal selective pressures on both protagonists. However, relatively few reports have evaluated the impact of these reciprocal pressures on the molecular determinants at the core of the relevant interaction, such as the factors influencing parasitic virulence and host resistance. Here, we address this question in a host-parasite model that allows co-evolution to be monitored in the field: the interaction between the mollusc, Biomphalaria glabrata, and its trematode parasite, Schistosoma mansoni. Reactive oxygen species (ROS) produced by the haemocytes of B. glabrata are known to play a crucial role in killing S. mansoni. Therefore, the parasite must defend itself against oxidative damage caused by ROS using ROS scavengers in order to survive. In this context, ROS and ROS scavengers are involved in a co-evolutionary arms race, and their respective production levels by sympatric host and parasite could be expected to be closely related. Here, we test this hypothesis by comparing host oxidant and parasite antioxidant capabilities between two S. mansoni/B. glabrata populations that have co-evolved independently. As expected, our findings show a clear link between the oxidant and antioxidant levels, presumably resulting from sympatric co-evolution. We believe this work provides the first supporting evidence of the Red Queen Hypothesis of reciprocal evolution for functional traits at the field-level in a model involving a host and a eukaryotic parasite.     

Impaired integrin‐mediated adhesion contributes to reduced barrier properties in VASP‐deficient microvascular endothelium

Recent studies point to a significant role of vasodilator‐stimulated phosphoprotein (VASP) in the maintenance of endothelial barrier functions in vivo and in vitro. Moreover, it has been reported that VASP is required for activation of the small GTPase Rac 1. However, little is known whether VASP is involved in the regulation of cell adhesion molecules that are critical for maintenance of the endothelial barrier. Here we demonstrate that impaired barrier properties in VASP‐deficient (VASP?/?) microvascular myocardial endothelial cells (MyEnd) correlated with both impaired integrin‐mediated adhesion as revealed by laser tweezer trapping and reduced integrin‐dependent cell migration. This was paralleled by reduction of focal adhesions at the cell periphery as well as of β₁‐integrin and VE‐cadherin cytoskeletal anchorage. Incubation of MyEnd VASP wt with RGD peptide to block interaction of integrins with extracellular matrix (ECM) reduced barrier properties and Rac 1 activity in wt endothelial monolayers mimicking the situation in VASP (?/?) cells under resting conditions. Moreover, cAMP‐mediated Rac 1 activation was reduced under conditions of impaired integrin‐mediated adhesion in wt cells and cAMP‐induced increase in VE‐cadherin cytoskeletal anchorage was abolished in VASP (?/?) endothelium. In summary, these data indicate that VASP is required for integrin‐mediated adhesion which stabilizes endothelial barrier properties at least in part by facilitating Rac 1 activation. J. Cell. Physiol. 220: 357–366, 2009. © 2009 Wiley‐Liss, Inc.     

P53 protein in proliferation,repair and apoptosis of cells

The p53 protein is an important factor of many intra- and extracellular processes. This protein regulates the repair of cellular DNA and induces apoptosis. It is also responsible for the regulation of the senescence and the cell entering the subsequent stages of the cellular cycle. The protein p53 is also involved in inhibiting angiogenesis and the induction of oxidative shock. In our study, we examined the activity of p53 protein in the uterine epithelial cells in rats treated with cladribine. Its action is mainly based on apoptosis induction. We compared the activity of p53 protein in cells with a high apoptosis index and in cells with active repair mechanisms and high proliferation index. We observed stronger p53 protein expression in the epithelial cells of the materials taken 24 h after the last dose of 2-CdA associated with the active process of apoptosis and inhibition of proliferation. After 4 weeks from the last dose of cladribine, the stronger expression of p53 protein was associated with both the existing changes in the cell's genome, the effects of the ongoing repair mechanisms, as well as the high proliferation activity.     

A rapid mini-prep method for isolation of ectomycorrhizal DNA from Tuber species

A rapid procedure has been developed to isolate DNA from the ectomycorrhizae of Tuber spp. for use in PCR experiments. The method described is fast and sensitive and can overcome the amplification problems that can arise in the presence of inhibitors. For this reason it can be used to type ectomycorrhizae even starting from a single root tip and make mycorrhizae identification much more rapid.     

Fanconi DNA repair pathway is required for survival and long-term maintenance of neural progenitors

Although brain development abnormalities and brain cancer predisposition have been reported in some Fanconi patients, the possible role of Fanconi DNA repair pathway during neurogenesis is unclear. We thus addressed the role of fanca and fancg, which are involved in the activation of Fanconi pathway, in neural stem and progenitor cells during brain development and adult neurogenesis. Fanca(-/-) and fancg(-/-) mice presented with microcephalies and a decreased neuronal production in developing cortex and adult brain. Apoptosis of embryonic neural progenitors, but not that of postmitotic neurons, was increased in the neocortex of fanca(-/-) and fancg(-/-) mice and was correlated with chromosomal instability. In adult Fanconi mice, we showed a reduced proliferation of neural progenitor cells related to apoptosis and accentuated neural stem cells exhaustion with ageing. In addition, embryonic and adult Fanconi neural stem cells showed a reduced capacity to self-renew in vitro. Our study demonstrates a critical role for Fanconi pathway in neural stem and progenitor cells during developmental and adult neurogenesis.     

Topoisomerase IIIalpha is required for normal proliferation and telomere stability in alternative lengthening of telomeres

Topoisomerase (Topo) IIIalpha associates with BLM helicase, which is proposed to be important in the alternative lengthening of telomeres (ALT) pathway that allows telomere recombination in the absence of telomerase. Here, we show that human Topo IIIalpha colocalizes with telomeric proteins at ALT-associated promyelocytic bodies from ALT cells. In these cells, Topo IIIalpha immunoprecipitated with telomere binding protein (TRF) 2 and BLM and was shown to be associated with telomeric DNA by chromatin immunoprecipitation, suggesting that these proteins form a complex at telomere sequences. Topo IIIalpha depletion by small interfering RNA reduced ALT cell survival, but did not affect telomerase-positive cell lines. Moreover, repression of Topo IIIalpha expression in ALT cells reduced the levels of TRF2 and BLM proteins, provoked a strong increase in the formation of anaphase bridges, induced the degradation of the G-overhang signal, and resulted in the appearance of DNA damage at telomeres. In contrast, telomere maintenance and TRF2 levels were unaffected in telomerase-positive cells. We conclude that Topo IIIalpha is an important telomere-associated factor, essential for telomere maintenance and chromosome stability in ALT cells, and speculate on its potential mechanistic function.     

Maximizing the Power of Principal-Component Analysis of Correlated Phenotypes in Genome-wide Association Studies

Many human traits are highly correlated. This correlation can be leveraged to improve the power of genetic association tests to identify markers associated with one or more of the traits. Principal component analysis (PCA) is a useful tool that has been widely used for the multivariate analysis of correlated variables. PCA is usually applied as a dimension reduction method: the few top principal components (PCs) explaining most of total trait variance are tested for association with a predictor of interest, and the remaining components are not analyzed. In this study we review the theoretical basis of PCA and describe the behavior of PCA when testing for association between a SNP and correlated traits. We then use simulation to compare the power of various PCA-based strategies when analyzing up to 100 correlated traits. We show that contrary to widespread practice, testing only the top PCs often has low power, whereas combining signal across all PCs can have greater power. This power gain is primarily due to increased power to detect genetic variants with opposite effects on positively correlated traits and variants that are exclusively associated with a single trait. Relative to other methods, the combined-PC approach has close to optimal power in all scenarios considered while offering more flexibility and more robustness to potential confounders. Finally, we apply the proposed PCA strategy to the genome-wide association study of five correlated coagulation traits where we identify two candidate SNPs that were not found by the standard approach.