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Developing new tools to investigate microglia behavior in the zebrafish embryo

par Montanari, Alice
Président du jury Lybaert, Pascale
Promoteur Wittamer, Valérie
Publication Non publié, 2025-05-20

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Résumé :

Microglia, the resident macrophages of the central nervous system (CNS), play an essential role in brain development and the maintenance of homeostasis throughout life. As the primary immune cells of the brain, they are key mediators of neuroinflammation and significantly contribute to the pathogenesis of various neurological and neurodegenerative diseases. Their multifaceted roles in both physiological and pathological contexts have driven a growing interest in understanding the complexities of this cell population.Zebrafish have emerged as a valuable model for microglia research due to the conserved ontogeny of embryonic microglia and the shared molecular regulators governing their differentiation and function. Despite these advantages, the development of advanced tools specifically optimized for zebrafish is crucial to further characterize microglia and solidify zebrafish as a widely established model in this field.In the first part of this study, our objective was to develop novel protocols for characterizing embryonic microglia behavior and morphology in vivo. By establishing an analysis pipeline, we systematically examined steady-state microglia density, motility, distribution, and morphology throughout the first week of embryonic development, thereby establishing a baseline for these parameters under normal conditions. Applying the same analysis after disrupting key microglia development pathways, such as Colony-stimulating factor 1 receptor (Csf1r) and Transforming growth factor Beta (Tgfβ), enabled us to assess changes in these parameters and gain insights into how these pathways influence microglia morphology and functionality during embryonic development.In the second part of this study, we tested several CSF1R inhibitors commonly used in mouse studies to induce microglia depletion, aiming to determine their efficacy in zebrafish, while characterizing their specificity for the two csf1r paralogs present in this model. Among the inhibitors tested, we identified Ki20227 as the only compound capable of targeting Csf1ra. Depending on the dose, duration of treatment, and age of the treated embryos, Ki20227 effectively induces either complete or partial depletion of the embryonic microglia population. Together, this work introduces new tools and methodologies that advance the characterization of microglia in the zebrafish model, paving the way for deeper insights into their development and function.