Comprendre les dommages causés à l’ADN par le développement des tissus et le vieillissement dans le temps – ChronoDamage

We combined advanced live imaging, mechanical perturbation, and genetic manipulation to dissect tissue‑level responses to compression. A custom micro‑device system enabled controlled mechanical stress on epithelia while monitoring DNA damage and repair markers.

Quantitative image analysis pipelines were developed to track nuclear deformation, replication stress, and apoptosis in real time. Complementary genetic tools—RNAi, CRISPR‑based reporters, and fluorescent biosensors—allowed targeted manipulation of candidate pathways involved in mechanotransduction and stress response.

Tissue physiology assays measured proliferation rates, cell extrusion, and repair dynamics. Together, these methods provided an integrated mechanical‑biological framework to assess how living tissues buffer or succumb to compressive stress.

The project combined the use of developing wing tissue and the adult intestine, to explore the mechanism by which cells respond to mechanical compression. To facilitate our studies, the two partners co-developed several devices to modify the pressur on tissues. First, the Stretch-Co device was built in collaboration by both partners in collaboration (Gracia, Lefevre et al., Star Protocols 2024). It is a user-friendly 3D printable device, allowing stretching of a tissue on a membrane. In addition, we developed the 3D- printable “Fly Press”, to allow pressing of small organisms. Using these devices, we found that compression does not induce a DNA damage stress response (Gracia, Lefevre et al., Star Protocols 2024). Instead, we identified that tissue compression is detected through a cell area–sensing mechanism. In particular, we demonstrated that compression reduces the activity of the oncogenic YAP signaling pathway, leading via Diap1 and Ban to increased cell apoptosis. We then explored the physiological role of this area-sensing process. We demonstrated that, within the tissue, cells with the smallest apical area tend to die during development, and that endogenous mechanical forces are necessary to ensure cell viability. Together, these findings demonstrate for the first time that endogenous mechanical forces in epithelial tissues play a critical role in controlling cell apoptosis (Cachoux, Balakeriva et al., Current Biology, 2023).

We next investigated the role of this regulation of apoptosis as a function of cell area. To this end, we modulated cell number within the tissue by inducing spindle misorientation. While this manipulation should theoretically lead to a decrease in cell number in the tissue, we observed that the total cell number remained similar to that in control tissues. We discovered that the compensation for spindle misorientation was driven by a drastic decrease in cell apoptosis. Connecting this observation with our previous work led us to propose that cell area sensing ensures the control of cell number within the tissue. To demonstrate this point, we inactivated the cell area-sensing mechanism and observed that the tissue could no longer regulate its total cell number (Bosveld et al., Developmental Cell, 2026).

Finally, we investigated the role of muscle mechanics on the intestinal epithelium. Consistent with our initial hypothesis, mechanical perturbation leads to dramatic changes to the underlying epithelium, compensatory proliferation, but also perturbation of mitotic spindle geometry and failing mitotic division (Lefèvre, in preparation).

Overall, our work in the frame of this grant illustrates that 1) tissue compression can be sensed by epithelial tissues through a reduction in apical cell area and cell number within the tissue, and 2) mechanical alteration of adjacent tissues, can alter the cell number of adjacent epithelia and cause mitotic defects.

One surprising finding for us was the extent to which the adjacent muscle mechanics could impact the underlying intestinal epithelium. We will further explore the nature of responses in the underlying epithelium.

Notre travail proposé vise à mieux comprendre comment les forces mécaniques exogènes et physiologiques peuvent être tamponnées, ou promouvoir les dommages à l'ADN et comment cela affecte les tissus en développement et les tissus adultes sur des échelles de temps courtes et longues. Nous combinerons les approches interdisciplinaires des équipes de Partner 1 (Allison Bardin) et Partner 2 (Yohanns Bellaïche), y compris l'imagerie en direct des dommages à l'ADN, de nouveaux dispositifs pour induire une compression mécanique des tissus, des outils génétiques ainsi que des tests physiologiques tissulaires. Nous explorerons les processus des points de contrôle permettant de détecter les dommages à l'ADN lors de la compression des tissus (objectif 1). Nous examinerons ensuite dans quelle mesure les dommages à l'ADN sont induits par les mouvements mécaniques des tissus physiologiques ou sont tamponnés (objectif 2). Enfin, nous examinerons l'impact à court et à long terme des forces mécaniques sur l'intégrité du génome au cours du vieillissement, et inversement, comment le vieillissement lui-même influe sur les propriétés mécaniques de l'intestin (objectif 3).