Peroxiredoxin stabilization of DE-cadherin promotes primordial germ cell adhesion

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Highlights? The peroxiredoxin, Jafrac1, controls primordial germ cell adhesion during gastrulation ? H₂O₂ treatment of Drosophila embryos reduces DE-cadherin and β-catenin levels ? Increasing DE-cadherin levels is sufficient to rescue the Jafrac1 phenotype ? Jafrac1 stabilizes the level of adherens junction components in Drosophila embryos     

An offspring signal of quality affects the timing of future parental reproduction

Solicitation signals by offspring are well known to influence parental behaviour, and it is commonly assumed that this behavioural effect translates into an effect on residual reproduction of parents. However, this equivalence assumption concerning behavioural and reproductive effects caused by offspring signals remains largely untested. Here, we tested the effect of a chemical offspring signal of quality on the relative timing and amount of future reproduction in the European earwig (Forficula auricularia). We manipulated the nutritional condition of earwig nymphs and exposed females to their extract, or to solvent as a control. There were no significant main effects of exposure treatment on 2nd clutch production, but exposure to extracts of well-fed nymphs induced predictable timing of the 2nd relative to the 1st clutch. This result demonstrates for the first time that an offspring signal per se, in the absence of any maternal behaviour, affects maternal reproductive timing, possibly through an effect on maternal reproductive physiology.     

A leachate a day keeps the seedlings away: mowing and the inhibitory effects of Festuca paniculata in subalpine grasslands

Background and Aims

Is the release of allelochemicals by the dominant tussock grass Festuca paniculata responsible for its dominance by inhibiting growth of neighbour grasses in subalpine grasslands? As such a community is also structured by mowing practices, what could be the impact of mowing on allelopathy?

Methods

A design was used that isolated allelopathy from resource competition by separating donor plants (Festuca paniculata) from target plants (F. paniculata, Dactylis glomerata and Bromus erectus). Leachates from donor pots containing bare soil, unmown F. paniculata or mown F. paniculata continuously irrigated target pots containing seedlings. Activated carbon was added in half of the target pots to adsorb potential allelochemicals. C and N analyses of target potting soil were used to test for any effect of treatments on resources. Total phenol concentration was measured in the solutions flowing from donor to target pots.

Results

Festuca paniculata leachates inhibited seedling growth of D. glomerata and B. erectus. Inhibition was correlated with polyphenol concentration, and was not due to resource competition for nitrogen. Mowing the leaves of the donor plants did not significantly increase this inhibition. The activated carbon treatment was not conclusive as it inhibited the seedling growing under control pots with only bare soil.

Conclusions

The results suggest that allelopathy may be at least partly responsible for F. paniculata dominance in subalpine meadows by inhibition of colonization by neighbouring species.Key words: Allelopathy, chemical interference, mowing, activated carbon, polyphenols, Festuca paniculata, Bromus erectus, Dactylis glomerata, subalpine, competition     

Retrovolution: HIV-Driven Evolution of Cellular Genes and Improvement of Anticancer Drug Activation

In evolution strategies aimed at isolating molecules with new functions, screening for the desired phenotype is generally performed in vitro or in bacteria. When the final goal of the strategy is the modification of the human cell, the mutants selected with these preliminary screenings may fail to confer the desired phenotype, due to the complex networks that regulate gene expression in higher eukaryotes. We developed a system where, by mimicking successive infection cycles with HIV-1 derived vectors containing the gene target of the evolution in their genome, libraries of gene mutants are generated in the human cell, where they can be directly screened. As a proof of concept we created a library of mutants of the human deoxycytidine kinase (dCK) gene, involved in the activation of nucleoside analogues used in cancer treatment, with the aim of isolating a variant sensitizing cancer cells to the chemotherapy compound Gemcitabine, to be used in gene therapy for anti-cancer approaches or as a poorly immunogenic negative selection marker for cell transplantation approaches. We describe the isolation of a dCK mutant, G12, inducing a 300-fold sensitization to Gemcitabine in cells originally resistant to the prodrug (Messa 10K), an effect 60 times stronger than the one induced by the wt enzyme. The phenotype is observed in different tumour cell lines irrespective of the insertion site of the transgene and is due to a change in specificity of the mutated kinase in favour of the nucleoside analogue. The mutations characterizing G12 are distant from the active site of the enzyme and are unpredictable on a rational basis, fully validating the pragmatic approach followed. Besides the potential interest of the G12 dCK variant for therapeutic purposes, the methodology developed is of interest for a large panel of applications in biotechnology and basic research.     

Knockout of Insulin-Like Growth Factor-1 Receptor Impairs Distal Lung Morphogenesis

Background

Insulin-like growth factors (IGF-I and -II) are pleiotropic regulators of somatic growth and development in vertebrate species. Endocrine and paracrine effects of both hormones are mediated by a common IGF type 1 receptor (IGF-1R). Lethal respiratory failure in neonatal IGF-1R knockout mice suggested a particular role for this receptor in pulmonary development, and we therefore investigated the consequences of IGF-1R inactivation in lung tissue.

Methods and Findings

We first generated compound heterozygous mutant mice harboring a hypomorphic (Igf1r^neo) and a null (Igf1r⁻) allele. These IGF-1R^neo/− mice express only 22% of normal IGF-1R levels and are viable. In adult IGF-1R^neo/− mice, we assessed lung morphology and respiratory physiology and found normal histomorphometric characteristics and normal breathing response to hypercapnia. We then generated homozygous IGF-1R knockout mutants (IGF-1R^−/−) and analyzed their lung development during late gestation using histomorphometric and immunohistochemical methods. IGF-1R^−/− embryos displayed severe lung hypoplasia and markedly underdeveloped diaphragms, leading to lethal neonatal respiratory distress. Importantly, IGF-1R^−/− lungs from late gestation embryos were four times smaller than control lungs and showed markedly thickened intersaccular mesenchyme, indicating strongly delayed lung maturation. Cell proliferation and apoptosis were significantly increased in IGF-1R^−/− lung tissue as compared with IGF-1R^+/+ controls. Immunohistochemistry using pro-SP-C, NKX2-1, CD31 and vWF as markers revealed a delay in cell differentiation and arrest in the canalicular stage of prenatal respiratory organ development in IGF-1R^−/− mutant mice.

Conclusions/Significance

We found that low levels of IGF-1R were sufficient to ensure normal lung development in mice. In contrast, complete absence of IGF-1R significantly delayed end-gestational lung maturation. Results indicate that IGF-1R plays essential roles in cell proliferation and timing of cell differentiation during fetal lung development.     

Intramyocardial Delivery of Mesenchymal Stem Cell-Seeded Hydrogel Preserves Cardiac Function and Attenuates Ventricular Remodeling after Myocardial Infarction

Background

To improve the efficacy of bone marrow-derived mesenchymal stem cell (MSC) therapy targeted to infarcted myocardium, we investigated whether a self-setting silanized hydroxypropyl methylcellulose (Si-HPMC) hydrogel seeded with MSC (MSC+hydrogel) could preserve cardiac function and attenuate left ventricular (LV) remodeling during an 8-week follow-up study in a rat model of myocardial infarction (MI).

Methodology/Principal Finding

Si-HPMC hydrogel alone, MSC alone or MSC+hydrogel were injected into the myocardium immediately after coronary artery ligation in female Lewis rats. Animals in the MSC+hydrogel group showed an increase in cardiac function up to 28 days after MI and a mid-term prevention of cardiac function alteration at day 56. Histological analyses indicated that the injection of MSC+hydrogel induced a decrease in MI size and an increase in scar thickness and ultimately limited the transmural extent of MI. These findings show that intramyocardial injection of MSC+hydrogel induced short-term recovery of ventricular function and mid-term attenuation of remodeling after MI.

Conclusion/Significance

These beneficial effects may be related to the specific scaffolding properties of the Si-HPMC hydrogel that may provide the ability to support MSC injection and engraftment within myocardium.     

Real-time fluorescence detection of exoribonucleases

The identification of RNases or RNase effectors is a continuous challenge, particularly given the current importance of RNAs in the control of genome expression. Here, we show that a fluorogenic RNA–DNA hybrid is a powerful tool for a real-time fluorescence detection and assay of exoribonucleases (RT-FeDEx). This RT-FeDEx assay provides a new strategy for the isolation, purification, and assay of known and unknown exoribonucleases.     

Murine Models for Trypanosoma brucei gambiense Disease Progression��From Silent to Chronic Infections and Early Brain Tropism

BackgroundHuman African trypanosomiasis (HAT) caused by Trypanosoma brucei gambiense remains highly prevalent in west and central Africa and is lethal if left untreated. The major problem is that the disease often evolves toward chronic or asymptomatic forms with low and fluctuating parasitaemia producing apparently aparasitaemic serological suspects who remain untreated because of the toxicity of the chemotherapy. Whether the different types of infections are due to host or parasite factors has been difficult to address, since T. b. gambiense isolated from patients is often not infectious in rodents thus limiting the variety of isolates.Conclusions/SignificanceWhereas trypanosome characterisation assigned all these isolates to the homogeneous Group I of T. b. gambiense, they clearly induce very different infections in mice thus mimicking the broad clinical diversity observed in HAT due to T. b. gambiense. Therefore, these murine models will be very useful for the understanding of different aspects of the physiopathology of HAT and for the development of new diagnostic tools and drugs.