Local externalization of phosphatidylserine mediates developmental synaptic pruning by microglia

Nicole Scott-Hewitt, Fabio Perrucci, Raffaella Morini, Marco Erreni, Matthew Mahoney, Agata Witkowska, Alanna Carey, Elisa Faggiani, Lisa Theresia Schuetz, Sydney Mason, Matteo Tamborini, Matteo Bizzotto, Lorena Passoni, Fabia Filipello, Reinhard Jahn, Beth Stevens, Michela Matteoli

Research output: Contribution to journalArticlepeer-review

Abstract

Neuronal circuit assembly requires the fine balance between synapse formation and elimination. Microglia, through the elimination of supernumerary synapses, have an established role in this process. While the microglial receptor TREM2 and the soluble complement proteins C1q and C3 are recognized as key players, the neuronal molecular components that specify synapses to be eliminated are still undefined. Here, we show that exposed phosphatidylserine (PS) represents a neuronal "eat-me" signal involved in microglial-mediated pruning. In hippocampal neuron and microglia co-cultures, synapse elimination can be partially prevented by blocking accessibility of exposed PS using Annexin V or through microglial loss of TREM2. In vivo, PS exposure at both hippocampal and retinogeniculate synapses and engulfment of PS-labeled material by microglia occurs during established developmental periods of microglial-mediated synapse elimination. Mice deficient in C1q, which fail to properly refine retinogeniculate connections, have elevated presynaptic PS exposure and reduced PS engulfment by microglia. These data provide mechanistic insight into microglial-mediated synapse pruning and identify a novel role of developmentally regulated neuronal PS exposure that is common among developing brain structures.

Original languageEnglish
Pages (from-to)e105380
JournalEMBO Journal
Volume39
Issue number16
DOIs
Publication statusPublished - Aug 17 2020

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