ERC FUNDED PROJECTS

A central problem in developmental biology is to understand how tissues are patterned in time and space - how do identical cells differentiate to form the adult body plan? Patterns often arise from prior asymmetries in developing embryos, but there is also increasing evidence for self-organizing mechanisms that can break the symmetry of an initially homogeneous cell population. These patterning processes are mediated by a small number of signaling molecules, including the TGF-β superfamily members BMP and Nodal. While we have begun to analyze how biophysical properties such as signal diffusion and stability contribute to axis formation and tissue allocation during vertebrate embryogenesis, three key questions remain. First, how does signaling cross-talk control robust patterning in developing tissues? Opposing sources of Nodal and BMP are sufficient to produce secondary zebrafish axes, but it is unclear how the signals interact to orchestrate this mysterious process. Second, how do signaling systems self-organize to pattern tissues in the absence of prior asymmetries? Recent evidence indicates that axis formation in mammalian embryos is independent of maternal and extra-embryonic tissues, but the mechanism underlying this self-organized patterning is unknown. Third, what are the minimal requirements to engineer synthetic self-organizing systems? Our theoretical analyses suggest that self-organizing reaction-diffusion systems are more common and robust than previously thought, but this has so far not been experimentally demonstrated. We will address these questions in zebrafish embryos, mouse embryonic stem cells, and bacterial colonies using a combination of quantitative imaging, optogenetics, mathematical modeling, and synthetic biology. In addition to providing insights into signaling and development, this high-risk/high-gain approach opens exciting new strategies for tissue engineering by providing asymmetric or temporally regulated signaling in organ precursors.

1 997 750 €

Start date: 2020-07-01, End date: 2025-06-30

Today, our daily diet typically contains dozens of food additives (e.g. colours, emulsifiers, sweeteners: ~350 substances allowed on the EU market). Safety assessment is performed by health agencies to protect consumers against potential adverse effects of each additive, yet such an assessment is only based on current available evidence, i.e., for most additives, only in-vitro/in-vivo toxicological studies and exposure simulations. Meanwhile, the long-term health impact of additives intake and any potential ‘cocktail’ effects remain largely unknown and have become a source of serious concern. Growing evidence link the consumption of ultra-processed foods, containing numerous additives, to adverse health outcomes, in particular our recent results on cancer (Fiolet BMJ 2018). While most additives allowed in the EU are likely to be neutral for health and some may even be beneficial, recent animal and cell-based studies have suggested detrimental effects of several such compounds. In humans, data is lacking. No epidemiological study has ever assessed individual-level exposure to a wide range of food additives and its association with health, hampered by unsuited traditional dietary assessment tools facing the high additive content variability across commercial brands. Hence, a major breakthrough will come from the novel and unique tools I developed with my team, notably within the NutriNet-Santé cohort (n=164,000), collecting precise and repeated data on foods and beverages usually consumed, including names and brands of industrial products. With this unique resource, I propose a project at the forefront of international research to provide answers to a question of major importance for public health. Built as a combination of epidemiological studies and in-vitro/in-vivo experiments, this project will shed light on individual exposure to food additive 'cocktails' in relation to obesity, cancer, cardiovascular diseases and mortality, while depicting underlying mechanisms.

2 000 000 €

Start date: 2020-05-01, End date: 2025-04-30

The Type 6 secretion system (T6SS) allows Gram-negative bacteria to deliver toxins into both eukaryotic and bacterial target cells and thus cause disease or kill competitors. T6SS is composed of four main parts: a membrane complex, a baseplate and a long spring-like sheath wrapped around an inner tube. Sheath contraction generates a large amount of energy to push the tube with associated toxins through the baseplate and membrane complex out of the cell. However, the reach of the T6SS tube is limited and thus a direct contact with the target membrane and precise positioning of T6SS assembly is required for protein translocation. In this proposal, we will unravel principles of spatial and temporal coordination of T6SS assembly that we have recently observed in several bacterial species. We will study how cells sense attacks from neighboring bacteria to dynamically localize its T6SS. We will describe how bacteria initiate and position T6SS assembly in response to physical cell-cell interactions. We will identify the principles and the role of T6SS localization in intracellular pathogens. Using genetic and biochemical approaches, we will identify and characterize proteins interacting with the core components of T6SS and test their role in initiation and positioning of T6SS assembly. We will search for peptidoglycan remodeling enzymes required for T6SS assembly. We will use advanced microscopy techniques to describe dynamic localization of proteins upon T6SS activation to establish the order of their assembly. We will quantify how much T6SS aiming increases efficiency of protein delivery and T6SS function during bacterial competition and pathogenesis. Overall, we will unravel novel principles of spatial and temporal control of localization of protein complexes and show how this allows bacteria to quickly respond to external cues and interact with their environment.

2 493 650 €

Start date: 2021-01-01, End date: 2025-12-31

Action potentials are not all equal. Despite shared biophysical principles and even similar action-potential shape, neurons with different spike generators can encode vastly different aspects of a stimulus and result in radically different behaviors of the embedding network. Differences between spike generators may be hard to discern because the information content of a spike train is not obvious to the naked eye. This is where computational analysis comes into play: theoretical research has shown that spike generation can be classified into a few dynamical types with qualitatively distinct computational properties. Among these, so-called homoclinic spikes – unlike the other commonly considered types – have been largely ignored. Yet, homoclinic spike generators are special because only they react with high sensitivity to inputs during the refractory period. Indeed, it is directly after a spike when homoclinic spikers “listen” best. As we recently demonstrated, this unique property has computationally exciting consequences: it can provoke a dramatic increase in network synchronization in response to minimal changes in physiological parameters, without requiring alterations in synaptic strength or connectivity. Supported by in-vitro evidence for homoclinic spiking in the rodent brain, ANewSpike explores the intriguing hypothesis that this “forgotten“ spike generator provides a unifying framework for the induction of epileptic activity by a wide range of physiological trigger parameters, from temperature to energy deprivation. Using a theory-experiment approach, we explore (i) the prevalence of homoclinic spiking in the brain, (ii) its ability to promote the transmission of high frequencies, and (iii) its ability to boost network synchronization. Our multi-scale study aims to add a novel dimension to our understanding of neural dynamics at the cellular and network level by revealing homoclinic spiking as an integral part of brain dynamics in both health and pathology.

2 000 000 €

Start date: 2021-01-01, End date: 2025-12-31