Comptes Rendus Biologies最新文献

Proton minibeam radiation therapy (pMBRT) is a novel cancer therapy approach based on a high spatial dose modulation. pMBRT activates distinct radiobiological mechanisms and it has been shown to lead in small animal experiments to a significant increase in normal tissue dose tolerances while maintaining or enhancing tumor control effectiveness as compared with conventional radiotherapy. Although recently proposed, the biological observations collected thus far challenge the classical paradigm in RT and encourage the preparation of phase I clinical trials.

The plasma membrane is a physical boundary made of amphiphilic lipid molecules, proteins and carbohydrates extensions. Its role in mechanotransduction generates increasing attention in animal systems, where membrane tension is mainly induced by cortical actomyosin. In plant cells, cortical tension is of osmotic origin. Yet, because the plasma membrane in plant cells has comparable physical properties, findings from animal systems likely apply to plant cells too. Recent results suggest that this is indeed the case, with a role of membrane tension in vesicle trafficking, mechanosensitive channel opening or cytoskeleton organization in plant cells. Prospects for the plant science community are at least three fold: (i) to develop and use probes to monitor membrane tension in tissues, in parallel with other biochemical probes, with implications for protein activity and nanodomain clustering, (ii) to develop single cell approaches to decipher the mechanisms operating at the plant cell cortex at high spatio-temporal resolution, and (iii) to revisit the role of membrane composition at cell and tissue scale, by considering the physical implications of phospholipid properties and interactions in mechanotransduction.

The colon is primarily responsible for absorbing fluids. It contains a large number of microorganisms including fungi, which are enriched in its distal segment. The colonic mucosa must therefore tightly regulate fluid influx to control absorption of fungal metabolites, which can be toxic to epithelial cells and lead to barrier dysfunction. How this is achieved remains unknown. Here, we describe a mechanism by which the innate immune system allows rapid quality-check of absorbed fluids to avoid intoxication of colonocytes. This mechanism relies on a population of distal colon macrophages that are equipped with "balloon-like" protrusions (BLPs) inserted in the epithelium, which sample absorbed fluids. In the absence of macrophages or BLPs, epithelial cells keep absorbing fluids containing fungal products, leading to their death and subsequent loss of epithelial barrier integrity. These results reveal an unexpected and essential role of macrophages in the maintenance of colon-microbiota interactions in homeostasis.

On the occasion of the 200th anniversary of the birth of Henri de Lacaze-Duthiers, one of the most curious and active scientific minds among 19th century naturalists, this article retraces his scientific career and recalls the long-term changes he made in the practice of science: promotion of experimental zoology, foundation of a modern scientific journal and establishment of the marine stations of Roscoff and Banyuls.

Transvection, the functional interaction between homologous alleles, was first described in Drosophila in the 1950's. While transvection has been documented in a growing list of genes, using mutant alleles or synthetic constructs, in Drosophila and other organisms, the extent of its relevance to gene expression in physiological conditions has remained questionable. The molecular mechanisms underlying transvection are still largely unexplored, although hints suggest a link with the general machinery that controls the genome organization in the nucleus. In this review, we discuss recent results establishing the relevance of transvection for proper gene regulation, and in particular for the sexually dimorphic regulation of the Drosophila X-linked gene yellow. We also discuss the role that DNA insulator sequences and chromatin architectural proteins play in bringing in proximity homologous alleles, and how they may contribute to interallelic gene regulation.

Biological tissues are composed of various cell types working cooperatively to perform their respective function within organs and the whole body. During development, embryogenesis followed by histogenesis relies on orchestrated division, death, differentiation and collective movements of cellular constituents. These cells are anchored to each other and/or the underlying substrate through adhesion complexes and they regulate force generation by active cytoskeleton remodeling. The resulting changes in contractility at the level of each single cell impact tissue architecture and remodeling by triggering changes in cell shape, cell movement and remodeling of the surrounding environment. These out of equilibrium processes occur through cellular energy consumption, allowing biological systems to be described by active matter physics. Cytoskeleton filaments, bacterial and eukaryotic cells can be considered as a sub-class of active matter termed "active nematics". These biological objects can be modelled as rod-like elements to which nematic liquid crystal theories can be applied. In this work, using an analogy from liquid crystal physics, we show that cell sorting and boundary formation can be explained using differences in nematic activity. This difference in nematic activity arises from a balance of inter- and intra-cellular activity.

Most bacterial ribonucleases (RNases) known to date have been identified in either Escherichia coli or Bacillus subtilis. These two organisms lie on opposite poles of the phylogenetic spectrum, separated by 1-3 billion years of evolution. As a result, the RNA maturation and degradation machineries of these two organisms have little overlap, with each having a distinct set of RNases in addition to a core set of enzymes that is highly conserved across the bacterial spectrum. In this paper, we describe what the functions performed by major RNases in these two bacteria, and how the evolutionary space between them can be described by two opposing gradients of enzymes that fade out and fade in, respectively, as one walks across the phylogenetic tree from E. coli to B. subtilis.

The intestinal epithelium is one of our main interfaces with the outside world, including the intestinal microbiota. This epithelium thus combines the two essential functions of nutrient absorption and barrier. In order to fulfill its different roles, the intestinal epithelium is made up of several specialized cell types. Among these, tuft cells have long remained in the shadows, but the understanding of their function has accelerated dramatically in recent years. The purpose of this review is to outline the characterization of tuft cells and the discovery of their sentinel function in the intestinal mucosa.