Competition for Space in Development and Diseases

Project Information

CoSpaDD

Grant agreement ID: 758457

DOI

10.3030/758457

Project closed

EC signature date 4 October 2017

Start date 1 January 2018

End date 30 June 2023

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 489 147,00

EU contribution

€ 1 489 147,00

Coordinated by

INSTITUT PASTEUR
France

Periodic Reporting for period 4 - CoSpaDD (Competition for Space in Development and Diseases)

Reporting period: 2022-07-01 to 2023-06-30

Summary of the context and overall objectives of the project

The tissues composing our body are incredibly dynamics. For instance, all the cells in the gut can be entirely renewed within 10 days. This suggests that cell proliferation has to be perfectly adjusted to the rate of cell elimination and cell death. While we know quite well the mechanisms that regulate cell proliferation or programmed cell death (also called apoptosis), how those two mechanisms are adjusted to tissue-wide information is not clear. While this adjustment is important in physiological conditions during embryogenesis and during tissue homeostasis, it may also be co-opted to kill preferentially one cell type. This mechanism of cell competition was characterised more than 40 years ago in the fruit fly Drosophila and is now becoming an intensive field of interest both in mammals and human cell culture. This context-dependent cell elimination can fine tune the composition of a tissue by eliminating suboptimal cells. However, it can also be exploited by tumoural cells to kill and replace their neighbours, hence accelerating tumour expansion.

In this project, we aim to characterise a specific mode of competition called "mechanical cell competition", where the mechanical stress can trigger preferential elimination of one cell population. We would like to better understand how cell deformation can trigger apoptosis in epithelial tissue and characterise signaling molecules that relay mechanical information in chemical signaling. We would like to understand how much the adjustment of cell death by mechanical input participate to the normal development of tissue, tissue size and tissue shape regulation as well as tissue homeostasis. Eventually, we would like to know how the same signals can be exploited by tumoural cells to induce neighbouring cell elimination and expand in the host tissue. The characterisation of compaction sensing and cell death induced by compaction will not only help to understand how cells coordinate in a tissue, but also may lead to the characterisation of cancer relevant targets that may help to slow down tumour expansion.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

We managed to characterise a new function of the EGFR/ERK pathway in cell deformation sensing and cell death induction which is also essential for cell elimination near oncogenic clones. This is one of the first characterisation of a pathway invovlved in mechanical cell competition in vivo (Current Biology, 2019).
We also started to dissect the mechanism of mechanosensing by screening for EGFR interactors and test their impact on deformation sensing in the notum. We developed several tools, including KI lines of EGFR and sensors of the pathway combined with optogenetics tool to modulate local tissue mechanics (activation or inhibition of Rho). This confirmed that ERK can be downregulated by tension release which seems to be associated with a transient relocalisation of EGFR. Importantly, the sensitivity to cell compaction/tension release is abolished upon depletion of the E3 ubiquitin ligase Cbl. This points to a potential mechanism based on EGFR trafficking modulation by cell mechanics.

We also found that every dying cell activates transiently ERK in the direct neighbours through their stretching. This modulates the spatiotemporal distribution of cell elimination and helps to maintain tissue integrity. This conserved mechanism is essential to maintain tissue sealing in context of high rates of cell elimination (Dev Cell 2021).
We also characterised the pattern of cell death in the wing imaginal disc and its contribution to clone dynamics and shape of the adult wing. This works shows that subtle spatial bias of apoptosis can significantly alter local growth and tissue shape even in fast growing tissues (bioRxiv 2022).
We are also characterising the conditions in which fast growing clones can deform and kill neighbouring cells. Using quantitative live imaging in the pupal notum combined with vertex simuatios, we found that different modes of compaction can coexist and have distinctive signatures : compaction driven by growth or compaction driven by increased line tension at clone boundaries. This project is close to completion and should be submited by the end of 2023.
Lastly, we also studied how cells engage in apoptosis and how caspases ochestrate cell extrusion. Doing so, we found an unexpected contributions of microtubules which through their depletion by caspases increase cell deformability and initiates cell extrusion without modulations of actomyosin dynamics (Nat. Comm 2022).
Along the way, we have also developed several pipelines for image analysis which have shared through accessible plugins and python procedures, including tools for local projection and tissue reconstruction (Herbert &Valon L et al., BMC Biol 2021) and more recently machine learning tools to automatically recognize cellular events in movies, including extrusion and cell division (Villars & Letort et al., Development 2023).

Overall, this project have led to several publications (Moreno et al. Curr. Biol. 2019, Valon et al., Dev Cell. 2021, Villars et al., Nat. Comm 2022, Matamoro-Vidal et al., BiorXiv 2021, in revision in Curr. Biol., Herbert et al., BMC Biol 2021, Villars et al. Development 2023) and reviews (Valon et al., Bio Cell 1019, Matamoro-Vidal A & Levayer R, Curr. Biol. 2019, Levayer R, Semin. Cancer Biol 2020, Villars & Levayer Curr. Opin Genet Dev 2023, Staneva and Levayer R, Curr Top Dev Biol 2023, Cumming & Levayer, Semin Cell Dev Biol 2023). The results of these projects were also disseminated through many conferences and symposium and discussed every year in front of high school students in Paris area throught the Declics intiative. We have also made several press releases related to the articles which for some were then also disclosed in general public scientific journals (Pour la science, Science et avenir, The scientist). We also describe part of the project in the radio show CQFD on "France Culture". The project also heped to mentor and train many students for long and short internships that were all instrumental for their training (many of them are now pursuing a PhD or following a science master program).

We have now a better understanding of epithelial cell death orchestration and the role of mechanics on cell elimination during competition and in physiologial contexts. It opens many avenues of research related to the self-organisation of tissues and the emerging properties that module the distribution and number of dying cell in a tissue and point to new players of mechanosensing. As mentioned above, this project have also led to the creation of many new tools (new fly lines and sensors, new optogenetic tools, image analysis pipelines) that were all shared widely thus promoting many other aspect of basic research.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

We now better understand how mechanics orchestrate cell elimination in physiological conditions but also during competition. We have a better understanding of the mechanisms of mechanosensing (mostly through EGFR/ERK) and a better understanding of how tissue can cope with local perturbations and adjust locally cell elimination. This project also characterised new mechanisms at play allowing the elimination of aberrant cells or promoting the expansion of tumoural cells. Altogether, we have a better understanding of how tissue can self organise and how cells communicate within the tissue to adjust the local rate of cell death.

Ras clones (purple) deforming the neighbouring cells (green: E-cad marking the cell contour)