Control of programmed cell death during zebrafish embryonic development

Programmed cell death (PCD) is a conserved cellular process, which is essential during embryonic development, morphogenesis and tissue homeostasis. PCD participates in the elimination of unwanted or potentially harmful cells, and contributes in this way to the precise shaping of the developing embryo. In this review the current knowledge related to the role of PCD during zebrafish development was described and an overview was provided about the main actors that induce, control and execute the apoptosis pathways during zebrafish development. Finally, we point out some important issues regarding the regulation of apoptosis during the early stages of zebrafish development

Cytoskeleton dynamics in early zebrafish development: A matter of phosphorylation?

Early morphogenic movements are an important feature of embryonic development in vertebrates. During zebrafish gastrulation, epiboly progression is driven by the coordinated remodeling of the YSL microtubule network and F-actin cables. We recently described the implication of Nrz, an anti-apoptotic Bcl-2 homolog, in the control of the YSL cytoskeleton dynamics. Nrz knock-down induces premature actin-myosin ring formation leading to margin constriction, epiboly arrest and embryo lethality. At the molecular level, the Nrz protein controls the actin-myosin dynamics through IP3R-dependent calcium levels variation. Here, we discuss these novel findings and propose a model in which reversible phosphorylation of the Nrz/IP3R complex modulates the permeability of the IP3R calcium channel and thus may explain the Nrz-dependent control of IP3R opening required for proper epiboly completion

The Apoptotic Regulator Nrz Controls Cytoskeletal Dynamics via the Regulation of Ca2+ Trafficking in the Zebrafish Blastula

SummaryBcl-2 family members are key regulators of apoptosis. Their involvement in other cellular processes has been so far overlooked. We have studied the role of the Bcl-2 homolog Nrz in the developing zebrafish. Nrz was found to be localized to the yolk syncytial layer, a region containing numerous mitochondria and ER membranes. Nrz knockdown resulted in developmental arrest before gastrulation, due to free Ca2+ increase in the yolk cell, activating myosin light chain kinase, which led to premature contraction of actin-myosin cables in the margin and separation of the blastomeres from the yolk cell. In the yolk syncytial layer, Nrz appears to prevent the release of Ca2+ from the endoplasmic reticulum by directly interacting with the IP3R1 Ca2+ channel. Thus, the Bcl-2 family may participate in early development, not only by controlling apoptosis but also by acting on cytoskeletal dynamics and cell movements via Ca2+ fluxes inside the embryo

Collision-Free Intersection Crossing of Mobile Robots Using Decentralized Navigation Functions on Predefined Paths

This paper deals with the coordination of a group of mobile robots at an intersection. It focusses on decentralized navigation functions (DNFs) to achieve efficient traffic control. The main challenge is to define virtual potentials, which are used by decentralized navigation functions, such that traffic is both fluent and safe, while taking into account real-world limitations like acceleration, braking and speed limits. Our method consists in defining the navigation function with respect to the desired acceleration profile and is accompanied by a set of visibility conditions that increase the capacity of the intersection in terms of vehicle throughput. Priority conditions have been used to both avoid blockades of robots and to save energy by assigning higher priorities to robots with higher inertias

Modern pollen rain and fungal spore assemblages from pasture woodlands around Lake Saint-Point (France)

Modern analogs are commonly used to investigate the relationships between modern pollen rain and the surrounding present vegetation and to improve our interpretation of fossil data. We collected modern pollen and spore rain in 18 more or less grazed and/or forested sites around Lake Saint-Point (Jura Mountains, France). Multivariate numerical techniques were applied to understand how modern pollen and non-pollen palynomorphs (NPP) taxa, collected in moss and dung samples, record local vegetation in the surroundings, and to identify indicators of tree cover or grazing. We show a strong relationship between current local herbaceous vegetation and pollen but underline the limits of past vegetation reconstructions based on AP/NAP ratio. In moss samples, we identified Picea, Abies, Fagus and Coollus pollen as well as Trichocladium, Kretschmaria deusta and Cirrenalia as indicators of tree cover. Spores of Sporormiella and some undetermined palynomorphs such as new NPP LCE-13 were positively correlated with openness while LCE-23 and LCE-32 could represent grazing indicators and/or coprophilous types. As compared to moss samples, dung samples contained much more pollen grains from Trifolium repens-type, Trifolium pratense-type, Plantago lanceolata-type and Plantago major/media-type taxa (grassland species eaten by cattle) and spores from coprophilous fungi. (C) 2012 Elsevier B.V. All rights reserved

Murid herpesvirus 4 infection protects mice from the development of an anti-pneumovirus vaccine-induced TH2 immunopathology

Gammaherpesvirus imprintin

Anchoring tick salivary anti-complement proteins IRAC I and IRAC II to membrane increases their immunogenicity

Tick salivary proteins are promising targets for the development of anti-tick vaccines. Recently, we described two paralogous anti-complement proteins, called Ixodes ricinus anti-complement (IRAC) proteins I and II, that are co-expressed in tick I. ricinus salivary glands. However, our previous attempts to immunize rabbits against IRAC via infection with recombinant Bovine herpesvirus 4 (BoHV-4) vectors invariably failed although both recombinants expressed high levels of functional IRAC proteins in vitro. As IRAC are soluble monovalent antigens, one of the possible explanations is that monovalent ligation of the B-cell receptor induces receptor activation but fails to promote antigen presentation, a phenomenon that is thought to induce a state of B-cell tolerance. In the present study, we tried to increase IRAC immunogenicity by expressing them as oligovalent antigens. To this end, IRAC were fused to membrane anchors and BoHV-4 vectors expressing these recombinant forms were produced. The immunization potentials of recombinant viruses expressing either secreted or transmembrane IRAC proteins were then compared. While the former did not induce a detectable immune response against IRAC, the latter led to high titres of anti-IRAC antibodies that only marginally affected tick blood feeding. All together, the data presented in this study demonstrate that the immunogenicity of a soluble antigen can be greatly improved by anchoring it in membrane

High-pressure investigations of CaTiO3 up to 60 GPa using X-ray diffraction and Raman spectroscopy

In this work, we investigate calcium titanate (CaTiO3 - CTO) using X-ray diffraction and Raman spectroscopy up to 60 and 55 GPa respectively. Both experiments show that the orthorhombic Pnma structure remains stable up to the highest pressures measured, in contradiction to ab-initio predictions. A fit of the compression data with a second-order Birch-Murnaghan equation of state yields a bulk modulus K0 of 181.0(6) GPa. The orthorhombic distortion is found to increase slightly with pressure, in agreement with previous experiments at lower pressures and the general rules for the evolution of perovskites under pressure. High-pressure polarized Raman spectra also enable us to clarify the Raman mode assignment of CTO and identify the modes corresponding to rigid rotation of the octahedra, A-cation shifts and Ti-O bond stretching. The Raman signature is then discussed in terms of compression mechanisms.Comment: 11 pages, 6 figures, 4 table

Bacterial Adaptation to the Host's Diet Is a Key Evolutionary Force Shaping Drosophila-Lactobacillus Symbiosis

Animal-microbe facultative symbioses play a fundamental role in ecosystem and organismal health. Yet, due to the flexible nature of their association, the selection pressures that act on animals and their facultative symbionts remain elusive. Here we apply experimental evolution to Drosophila melanogaster associated with its growth-promoting symbiont Lactobacillus plantarum, representing a well-established model of facultative symbiosis. We find that the diet of the host, rather than the host itself, is a predominant driving force in the evolution of this symbiosis. Furthermore, we identify a mechanism resulting from the bacterium's adaptation to the diet, which confers growth benefits to the colonized host. Our study reveals that bacterial adaptation to the host's diet may be the foremost step in determining the evolutionary course of a facultative animal-microbe symbiosis

Evidence of coat color variation sheds new light on ancient canids.

International audienceWe have used a paleogenetics approach to investigate the genetic landscape of coat color variation in ancient Eurasian dog and wolf populations. We amplified DNA fragments of two genes controlling coat color, Mc1r (Melanocortin 1 Receptor) and CBD103 (canine-β-defensin), in respectively 15 and 19 ancient canids (dogs and wolf morphotypes) from 14 different archeological sites, throughout Asia and Europe spanning from ca. 12 000 B.P. (end of Upper Palaeolithic) to ca. 4000 B.P. (Bronze Age). We provide evidence of a new variant (R301C) of the Melanocortin 1 receptor (Mc1r) and highlight the presence of the beta-defensin melanistic mutation (CDB103-K locus) on ancient DNA from dog-and wolf-morphotype specimens. We show that the dominant K(B) allele (CBD103), which causes melanism, and R301C (Mc1r), the variant that may cause light hair color, are present as early as the beginning of the Holocene, over 10 000 years ago. These results underline the genetic diversity of prehistoric dogs. This diversity may have partly stemmed not only from the wolf gene pool captured by domestication but also from mutations very likely linked to the relaxation of natural selection pressure occurring in-line with this process