Ines Hristovska (équipe Honnorat) soutiendra sa thèse le 12 décembre à 14h, à la Mediathèque Paul Zech (site Rockefeller).
Title : « Microglial dynamics in physiological conditions: A vigilance state and neuronal activity-driven mechanism ».
Microglia, the resident immune cells of the central nervous system (CNS), were traditionally believed to be set into action only by injury or diseases. Strikingly, in the healthy brain, microglia actively carry out parenchyma patrolling by extending and retracting their ramified processes. These movements are referred to as microglial motility and may be to some extent directed toward synapses. However, motility regulation and the purpose of microglia-spine contacts remain elusive. We thus examined the influence of neuronal activity on microglial motility, morphology and microglia-spine interactions during sleep and wakefulness. We found that microglial motility and morphology are modulated by vigilance states. Microglial processes were found to be attracted by active synapses particularly during wake, whereas sleep downregulates microglial proximity and activity-dependent contact with spines. Microglial contact resulted in increased spine activity which was mainly observed during sleep. Understanding the mechanisms regulating microglial dynamics and microglia-spine interactions across the vigilance states will provide further insights into how microglial cells may be involved in sleep- associated functions such as synaptic homeostasis, learning and memory. Grasping these cellular interactions in physiological conditions is crucial to understand synaptic functioning and alterations when microglia are engaged into their immune functions, a hallmark of most brain pathologies.