Biology subjects

Ronsin, B.

Publications and source records attributed to Ronsin, B..

3 recordsLinked to original sources

bioRxiv2024

Compressive stress drives morphogenetic apoptosis

Tissues and organs are constantly submitted to physical stress, including compression, stretching, shear stress. The impact of compression due to overcrowding on cell extrusion has been the focus of recent studies. However, how tissue compression impact cell death in the context of morphogenesis is mostly unexplored. Here, we showed that a natural compression is exerted on the Drosophila developing leg by the surrounding tissue (or envelope) that is required for correct leg morphogenesis. In this tissue, apoptosis, preferentially localized in the future fold region, contributes to drive tissue folding through the generation of a pulling force on the apical surface. However, only a subset of these cells are dying within the expression domain of proapoptotic genes and how this precise pattern of cell death is established is totally unknown. We found that the natural compression exerted by the envelope contributes to the regulation of apoptosis, revealing that compression constitutes an integral part of apoptosis regulation during leg morphogenesis. We further reveal that compression drives a significant increase in lateral tension and favors apoptosis through the mechanosensor Piezo. Finally, perturbing cell cortex anchoring or membrane stiffness prove sufficient to block this process. Altogether, these results open new perspectives in term of mechanotransduction during morphogenesis.

developmental biology↗

bioRxiv2023

Smell and Aftersmell: Fast Calcium Imaging Dynamics of Honey Bee Olfactory Coding

Odour processing exhibits multiple parallels between vertebrate and invertebrate olfactory systems. Insects, in particular, have emerged as relevant models for olfactory studies because of the tractability of their olfactory circuits. Here, we used fast calcium imaging to track the activity of projection neurons in the honey bee antennal lobe (AL) during olfactory stimulation at high temporal resolution. We observed a heterogeneity of response profiles and an abundance of inhibitory activities, resulting in various response latencies and stimulus- specific post-odour neural signatures. Recorded calcium signals were fed to a mushroom body (MB) model constructed implementing the fundamental features of connectivity between olfactory projection neurons, Kenyon cells (KC), and MB output neurons (MBON). The model accounts for the increase of odorant discrimination in the MB compared to the AL and reveals the recruitment of two distinct KC populations that represent odorants and their aftersmell as two separate but temporally coherent neural objects. Finally, we showed that the learning- induced modulation of KC-to-MBON synapses can explain both the variations in associative learning scores across different conditioning protocols used in bees and the bees response latency. Thus, it provides a simple explanation of how the time contingency between the stimulus and the reward can be encoded without the need for time tracking. This study broadens our understanding of olfactory coding and learning in honey bees. It demonstrates that a model based on simple MB connectivity rules and fed with real physiological data can explain fundamental aspects of odour processing and associative learning.

neuroscience↗

bioRxiv2019

Shavenbaby protein isoforms orchestrate the self-renewal versus differentiation of Drosophila intestinal stem cells

Signaling pathways are key regulators of adult stem cell homeostasis and underlying mechanisms are often deregulated in cancers. Recent studies of epithelial tumors have involved OvoL/Svb transcription factors, which produce isoforms with antagonistic activities. Here we show that Svb, the unique OvoL factor in Drosophila, directly integrates multiple signaling inputs to coordinate the behavior of adult intestinal stem cell lineage. Under steady state, Svb mediates Wnt and EGFR signaling to ensure stem cell renewal and progenitor survival. This requires the post-translational processing of Svb into a transcriptional activator by Polished rice (Pri) regulatory peptides, under the regulation of ecdysone signaling. In response to PDM1, Svb expression is specifically maintained in enterocytes where it acts as a transcriptional repressor sufficient to override mitogenic signals and impose differentiation. Altogether, these results demonstrate that the OvoL/Svb transcriptional switch controls the balance between stem cell survival, self-renewal and differentiation.

developmental biology↗