The goal of the GELIHPARBAL project is to create injectable hydrogels that can be used as an emergency solution for deep and jagged wounds, to decrease bleeding immediate threat while improving muscle repair and functional skin healing. A new avenue of research, based on the development of biomaterials, has appeared in recent years as an alternative to classical tissue reconstruction approaches, such as grafts. Their aim is to provide a scaffold that will activate or guide cellular responses to enhance or trigger tissue regeneration. Nevertheless, if these biomaterials are trying to reproduce specific properties of the extracellular matrix (notably rigidity) to influence cell fate, elasticity has seldom been considered so far. Concomitantly, the possibility to provide haemostatic competences to these biomaterials, through induction of the blood clotting cascade by prothrombotic molecules and through filling and compression of the wound, opens new possibilities to control haemorrhagic risks. The GELIHPARBAL project therefore aims to develop an innovative therapeutic approach for deep wounds based on the use of injectable porous elasto-mimetic hydrogels that, through their intrinsic properties, allow concomitantly (1) the haemostatic filling of deep wounds, while (2) providing a specific guidance of muscle and skin repair. A major innovation will be the injectable formulation of porous elastic hydrogels that can compressively fill and conform accurately to the wound shape; and allow wound healing cells colonization while reinforcing their regenerative properties through mechanic and structural properties. The elasto-mimetic porous hydrogels developed during a previous ANR project (DHERMIC, ANR-11-TECS-016) will serve as technological basis for the development of the injectable formulations. The coordinating laboratory (Laboratory of tissue biology and therapeutic engineering, LBTI) has indeed reached the "biological" proof of concept of these approaches by validating the efficacy of the hydrogels in forming reconstructed skin equivalents and enhancing skin wound healing in vivo. This project therefore falls within the design and creation of innovative, bioinspired biodegradable and bioactive materials. To reach this ambitious goal, the consortium formed by three institutional partners (CNRS and INSERM) possesses the required competences and expertise’s to develop the biomaterials (LBTI), to finely analyse their mechanical, rheological (RMeS) and biological properties (INMG), and to study and evaluate the improvement of tissue healing and the resulting functionality gain (LBTI) The scientific program is divided in 3 scientific work packages (chemistry/biomaterials, mechanobiology and in vivo) and an administrative WP. They have for goal to 1) design elasto-mimetic haemostatic injectable porous hydrogels of large mechanical versatility; 2) Determine the mechanical and structural properties of porous matrices most effective in guiding proliferation and differentiation of muscle stem cells and in inducing muscle regeneration; 3) develop injectable porous hydrogels that can simultaneously promote muscle and skin regeneration. The administrative task is dedicated to the project and intellectual property management.

Ageing is one of the most important challenges that modern societies have to struggle in order to prevent the burden of age-associated diseases and dependency. Longitudinal studies showed that physical performance is the most predictive criterion for mortality in the elderly. Thus, deciphering the limiting factors that cause muscle aging is a major public health issue. MUSAGE project aims to identify mechanisms responsible for muscle aging by novel approaches in C.elegans. Based on our recently published data we set-up an original non-targeted genetic screen that allowed us to identify unexpected regulators of muscle aging that are conserved through species. Based on those results, the main objectives of this proposal are: 1- Identify other regulators of muscle aging by extending the screen, 2- Define the molecular mechanisms by which one already identified (UNC-27/TNI) regulator is acting, 3- Evaluate the functional conservation of identified regulators in mammals.

Brain plasticity that underlies memory function likely results from a balance between synapse formation, potentiation and removal. The synapse formation and potentiation occur mostly during wakefulness, while synaptic downscaling and removal take place mostly during sleep. Immune signaling molecules present in the healthy brain can interact with neurochemical systems including serotonin to contribute to the regulation of normal sleep. While it has been widely shown that sleep alterations impair learning, there remains much debate over the mechanisms involved. Recent studies revealed key tasks for microglia, the main immune cells in the brain, interactions with neurons during normal physiological conditions, especially in regulating the maturation of neural circuits and shaping their connectivity in an activity- and experience-dependent manner. However, their role in learning and memory remains elusive. Specifying the role of microglia in synaptic consolidation according to the sleep/wake cycle is undoubtedly a particular challenge to research. Consortium members have shown (i) that microglia motility can be modulated by serotonin, whose levels vary with arousal/sleep states, and (ii) that microglia dynamics is different in arousal vs. sleep states and (iii) that mice lacking 5-HT2B receptors, which is the main serotonin receptor expressed by microglia, display sleep and memory deficits. Together, these observations support the hypothesis that microglia and serotonin actively participate to memory consolidation by regulating synaptic plasticity, that microglia interact with synapses in different modes and potentially with different outcome during sleep and wakefulness, and that serotonin could be implicated in this switch. The role of microglia in learning and/or cognitive flexibility could therefore be more prominent during either the wakefulness or the sleep period. Exploring this hypothesis, the consortium will delineate the signaling pathways induced in microglia by serotonin, and show how serotonin participates to microglia dynamics and to synaptic plasticity. By multidisciplinary approaches combining the analysis of EEG (electroencephalogram) and in-vivo imaging, field potential in acute slices, behavior, conditional mutants, optogenetic and chemogenetic (DREADD) approaches, we propose to elucidate how a control of microglia by serotonin is implicated in synaptic and brain plasticity and if this occurs mainly during awake-learning phases, or asleep-consolidation phases and by which intracellular pathway. This proposed preclinical approach includes a totally new pathophysiological axis since no one has ever established a link between immune cells microglia, memory consolidation and sleep. Thus it may open new perspectives for pharmacological treatment of neuropsychiatric disorders, which are associated with microglia activation, and/or sleep alterations such as schizophrenia, autism and depressive disorders.

The structure of a complete nucleosome (including linker DNA and linker histone H1), the three-dimensional organization of the 30-nm chromatin fiber, and the structure of centromeric chromatin represent key problems in the chromatin and epigenetics field. Moreover, how centromeric chromatin, which is characterized by nucleosomes bearing the H3 histone variant CENP-A, recruits the centromere protein CENP-C to mediate assembly of an active kinetochore is poorly understood. Research into these questions will advance our understanding of fundamental chromatin biology and shed light on the molecular mechanisms underlying specific genetic and epigenetic disorders. Objectives: The aims of this project are to obtain three-dimensional structural data for the H1-containing nucleosome, the 30-nm chromatin fiber and CENP-A chromatin, and to decipher how CENP-C specifically recognizes CENP-A chromatin. Methodology: We will reconstitute mono-nucleosomes using recombinant core histones, different isoforms of the H1 linker histone and DNA bearing a strong nucleosome positioning sequence. We will determine structures by X-ray crystallography and electron cryo-microscopy (cryo-EM) exploiting the latest technological developments. We will validate these structures using DNA-footprinting and a novel cross-linking/qPCR technology developed by the consortium called Identification of Closest Neighbouring Nucleosomes (ICNN). Consortium: The project is an interdisciplinary collaboration involving five research teams located in Grenoble, Lyon and Strasbourg. The work envisaged is a comprehensive effort that combines expertise in the structural biology, biochemistry, biophysics and cell biology of chromatin. Expected results and impact: This project is expected to generate new knowledge regarding the structure of chromatin, the roles of linker histone H1 and of CENP-A in determining chromatin structure, and the interactions of CENP-A chromatin with CENP-C. This foundational knowledge is indispensable for understanding the organization of the genome as well as the genetic and epigenetic mechanisms that underlie major nuclear processes such as gene expression, DNA replication, DNA repair and mitosis. Biomedical relevance: Understanding the higher-order structure of chromatin and the regulatory role played by linker histones and CENP-A is critical for understanding how several severe diseases arise at the molecular level. Alterations in CENP-A chromatin are associated with severe chromosome and segregation defects as well as perturbed cytokinesis. These lead to meiotic aneuploidy, a major cause of spontaneous abortions, infertility and birth defects, including Down, Edwards and Patau syndromes that affect a significant proportion of newborns every year. This project is expected to advance our understanding of the detailed molecular mechanisms that give rise to the above disorders.