Microglia remodel synapses by presynaptic trogocytosis and spine head filopodia induction

By L. Weinhard, Giulia di Bartolomei, G. Bolasco, P. Machado, N. Schieber, Urte Neniskyte, Melanie Exiga, Auguste Vadisiute, A. Raggioli, A. Schertel and 2 more. Nature Communications, 2017

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Microglia are highly motile glial cells that are proposed to mediate synaptic pruning during neuronal circuit formation. Disruption of signaling between microglia and neurons leads to an excess of immature synaptic connections, thought to be the result of impaired phagocytosis of synapses by microglia. However, until now the direct phagocytosis of synapses by microglia has not been reported and fundamental questions remain about the precise synaptic structures and phagocytic mechanisms involved. Here we used light sheet fluorescence microscopy to follow microglia–synapse interactions in developing organotypic hippocampal cultures, complemented by a 3D ultrastructural characterization using correlative light and electron microscopy (CLEM). Our findings define a set of dynamic microglia–synapse interactions, including the selective partial phagocytosis, or trogocytosis (trogo-: nibble), of presynaptic structures and the induction of postsynaptic spine head filopodia by microglia. These findings allow us to propose a mechanism for the facilitatory role of microglia in synaptic circuit remodeling and maturation. Direct visualization of microglia-mediated synapse pruning has been lacking. This study shows direct evidence of microglia-synapse interaction where microglia do not necessarily ‘eat’ post-synaptic structure but ‘nibble’ on pre-synaptic terminals, much akin to trogocytosis by lymphocytes.

Subfields: Cellular and Molecular Neuroscience, Immunology, Neurology

View Paper: https://www.semanticscholar.org/paper/14e0cd52faee7bbd8a440cfa15fe4b893d601220