Cells have evolved multiple mechanisms to apprehend and adapt finely to their environment. Here we report a new cellular ability, which we term “curvotaxis” that enables the cells to respond to cell-scale curvature variations, a ubiquitous trait of cellular biotopes. We develop ultra-smooth sinusoidal surfaces presenting modulations of curvature in all directions, and monitor cell behavior on these topographic landscapes. We show that adherent cells avoid convex regions during their migration and position themselves in concave valleys. Live imaging combined with functional analysis shows that curvotaxis relies on a dynamic interplay between the nucleus and the cytoskeleton—the nucleus acting as a mechanical sensor that leads the migrating cell toward concave curvatures. Further analyses show that substratum curvature affects focal adhesions organization and dynamics, nuclear shape, and gene expression. Altogether, this work identifies curvotaxis as a new cellular guiding mechanism and promotes cell-scale curvature as an essential physical cue.

Moth sex pheromone communication is recognised as a long-standing model for insect olfaction studies, and a widespread knowledge has been accumulated on this subject thanks to numerous chemical, electrophysiological and behavioural studies. A key step has been the identification of candidate sex pheromone receptors, opening new routes to understanding the specificity and sensitivity of this communication system, but only few of these receptors have as yet been functionally characterised. In this context, we aim at unravelling the molecular bases of pheromone reception in the noctuid moth Spodoptera littoralis. Taking advantage of a collection of antennal-expressed sequence tags, we previously identified three fragments of candidate pheromone receptors in this species. Here, we report full-length cloning of one of these receptors, named SlitOR6. Both sequence and expression pattern analyses were consistent with its annotation as a pheromone receptor, which we further confirmed by functional characterization. Using Drosophila antennae as a heterologous expression system, we identified a single component of the pheromone blend of S. littoralis, (Z,E)-9,12-tetradecadienyl acetate, as the ligand of SlitOR6. Two strategies were employed: (i) expressing SlitOR6 in the majority of Drosophila olfactory neurons, in addition to endogenous receptors, and monitoring the responses to pheromone stimuli by electroantennography; (ii) replacing the Drosophila pheromone receptor OR67d with SlitOR6 and monitoring the response by single sensillum recordings. Results were fully congruent and responses to (Z,E)-9,12-tetradecadienyl acetate were highly specific in both heterologous systems. This approach appears to be efficient and reliable for studying moth pheromone receptors in an in vivo context.

Although the regulation of epithelial morphogenesis is essential for the formation of tissues and organs in multicellular organisms, little is known about how signalling pathways control cell shape changes in space and time. In the Drosophila ovarian epithelium, the transition from a cuboidal to a squamous shape is accompanied by a wave of cell flattening and by the ordered remodelling of E-cadherin-based adherens junctions. We show that activation of the TGFβ pathway is crucial to determine the timing, the degree and the dynamic of cell flattening. Within these cells, TGFβ signalling controls cell-autonomously the formation of Actin filament and the localisation of activated Myosin II, indicating that internal forces are generated and used to remodel AJ and to promote cytoskeleton rearrangement. Our results also reveal that TGFβ signalling controls Notch activity and that its functions are partly executed through Notch. Thus, we demonstrate that the cells that undergo the cuboidal-to-squamous transition produce active cell-shaping mechanisms, rather than passively flattening in response to a global force generated by the growth of the underlying cells. Thus, our work on TGFβ signalling provides new insights into the mechanisms through which signal transduction cascades orchestrate cell shape changes to generate proper organ structure.

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Olfaction is primarily mediated by the large family of olfactory receptors. Although all insect olfactory receptors share the same structure with seven transmembrane domains, they present poor sequence homologies within and between species. As the only exception, Drosophila melanogaster OR83b and its orthologues define a receptor subtype singularly conserved between insect species. In this article, we report the identification of a new subtype of putative olfactory receptors exceptionally conserved within noctuids, a taxonomic group that includes crop pest insects. Through homology‐based molecular cloning, homologues of the previously identified OR18 from Heliothis virescens were identified in the antennae of six noctuid species from various genera, presenting an average of 88% sequence identity. No orthologues were found in genomes available from diverse insect orders and selection pressure analysis revealed that the noctuid OR18s are under purifying selection. The OR18 gene was studied in details in the cotton leafworm, Spodoptera littoralis, where it presented all the characteristic features of an olfactory receptor encoding gene: its expression was restricted to the antennae, with expression in both sexes; its developmental expression pattern was reminiscent of that from other olfactory genes; and in situ hybridization experiments within the antennae revealed that the receptor‐expressing cells were closely associated with the olfactory structures, including pheromone‐ and non‐pheromone‐sensitive structures. Taken together, our data suggest that we have identified a new original subtype of olfactory receptors that are extremely conserved within noctuids and that might fulfil a critical function in male and female noctuid chemosensory neurones.

Cell deformation occurs in many critical biological processes, including cell extravasation during immune response and cancer metastasis. These cells deform the nucleus, its largest and stiffest organelle, while passing through narrow constrictions in vivo and the underlying mechanisms still remain elusive. It is unclear which biochemical actors are responsible and whether the nucleus is pushed or pulled (or both) during deformation. Herein we use an easily-tunable poly-L-lactic acid micropillar topography, mimicking in vivo constrictions to determine the mechanisms responsible for nucleus deformation. Using biochemical tools, we determine that actomyosin contractility, vimentin and nucleo-cytoskeletal connections play essential roles in nuclear deformation, but not A-type lamins. We chemically tune the adhesiveness of the micropillars to show that pulling forces are predominantly responsible for the deformation of the nucleus. We confirm these results using an in silico cell model and propose a comprehensive mechanism for cellular and nuclear deformation during confinement. These results indicate that microstructured biomaterials are extremely versatile tools to understand how forces are exerted in biological systems and can be useful to dissect and mimic complex in vivo behaviour.

In insects, biogenic amines have been shown to play an important role in olfactory plasticity. In a first attempt to decipher the underlying molecular mechanisms, we report the molecular cloning and precise expression pattern of a newly identified octopamine/tyramine-receptor-encoding gene in the antennae of the noctuid moth Mamestra brassicae (MbraOAR/TAR). A full-length cDNA has been obtained through homology cloning in combination with rapid amplification of cDNA ends/polymerase chain reaction; the deduced protein exhibits high identities with previously identified octopamine/tyramine receptors in other moths. In situ hybridization within the antennae has revealed that MbraOAR/TAR is expressed at the bases of both pheromone-sensitive and non-sensitive olfactory sensilla and in cells with a neurone-like shape. In accordance with previous physiological studies that have revealed a role of biogenic amines in the electrical activity of the receptor neurones, our results suggest that biogenic amines (either octopamine or tyramine) target olfactory receptor neurones to modulate olfactory coding as early as the antennal level.

Background: Texturing processes have been designed to improve biocompatibility and mechanical anchoring of breast implants. However, high texturing degree has been associated with severe pathologies. Here, we aimed to determine whether implant surface topography could also affect physiology of asymptomatic capsules. Methods: We collected topographical measurements from 17 different breast implant devices by interferometry and X-ray microtomography. Morphological structures were statistically analyzed to obtain a robust breast implant surface classification. We obtained 3 topographical categories of textured implants ("peak and valleys", "open cavities", and "semi-opened cavities") based on the cross-sectional aspects. We simultaneously collected 31 Baker I capsules, sorted them according to the new classification, established their molecular profile, and examined the tissue organization. Results: Each of the categories showed distinct expression patterns of genes associated with the extracellular matrix (Timp and Mmp members) and inflammatory response (Saa1, Tnsf11, Il8), despite originating from healthy capsules. Besides, slight variations were observed in the organization of capsular tissues at the histological level. Conclusions: We combined a novel surface implant classification system and gene profiling analysis to show that implant surface topography is a bioactive cue that can trigger gene expression changes in surrounding tissue, even in Baker I capsules. Our new classification system avoids confusions around the word "texture", and could be transposed to implant ranges of every manufacturer. This new classification could prove useful in studies on potential links between specific texturations and the incidence of certain breast-implant associated complications.