Dottorato in SCIENZE DELLA VITA

Titolo della tesi: Microglia reactivity entails microtubule remodeling from acentrosomal to centrosomal arrays

Microglia reactivity entails a large-scale remodeling of cellular geometry, but while the role of the actin cytoskeleton in driving these morphological changes and the specialized functions of activated microglia has been extensively studied, the behavior of the microtubule cytoskeleton during these changes remains unexplored. We hypothesize that rearrangement of the microtubule cytoskeleton would play a major role in the morphological changes guiding microglia transition from homeostatic to activated states providing a novel target to modulate microglia activation. Through a detailed in vitro phenotyping approach and validation in mouse retinal tissue we report that: 1) in homeostatic conditions, ramified microglia possess stable microtubule arrays, while microglia activation increases microtubule dynamic behavior. 2) A non-centrosomal microtubule organization in arrays with mixed polarity is a hallmark of homeostatic microglia, similar to the architecture typical of highly specialized cells such as neurons and oligodendrocytes, while activation induces recruitment of the majority of microtubule minus end at the centrosome. 3) Homeostatic microglia nucleate non-centrosomal microtubules at Golgi outposts, similar to what occurs in neurons, while activating signaling induces recruitment of nucleating material nearby the centrosome, a process inhibited by microtubule stabilization. Our results unveil the remodeling of the microtubule cytoskeleton as a striking hallmark of microglia reactivity and suggest that while pericentrosomal microtubule nucleation may serve as a distinct marker of activated microglia, inhibition of microtubule dynamics may provide a novel strategy to reduce microglia reactivity in inflammatory disease.