Microglia remodel synapses by presynaptic trogocytosis and spine head filopodia induction

• DOI: 10.1038/s41467-018-03566-5
• Publication Date: 2018-04-04T02:47:28Z
• Authors: Laetitia Weinhard; Giulia di Bartolomei; Giulia Bolasco; Pedro Machado; Nicole L. Schieber; Urte Neniskyte; Melanie Exiga; Auguste Vadisiute; Angelo Raggioli; Andreas Schertel; Yannick Schwab; Cornelius T. Gross
• Keywords: 0301 basic medicine; Neuronal Plasticity; Science; Q; Presynaptic Terminals; Macrophage-1 Antigen; Mice, Transgenic; Hippocampus; Models, Biological; Article; hippocampal slice cultures ; 3D electron-microscopy ; in-vivo ; dendritic spines ; fluorescent protein ; rat hippocampus ; visual-cortex ; complement ; cells ; mice; Mice, Inbred C57BL; 03 medical and health sciences; Phagocytosis; Synapses; Animals; Microglia; Pseudopodia; Signal Transduction

AbstractMicroglia 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.