Extended Data Fig. 4Figure 9
Primary microglia engulf synaptosomes through extrinsic SPP1. (a) Schematic illustrating in vitro engulfment assay whereby primary microglia isolated from WT or Spp1 KO/KO mice phagocytose S26C oAβ-treated synaptosomes that are tagged with pHrodo upon PBS or recombinant SPP1 treatment. (b) Representative images showing engulfment of pHrodo-synaptosomes by primary microglia isolated from WT mice (upper panel) or Spp1 KO/KO mice (lower panel), treated with vehicle (left) or 100 nM recombinant SPP1 (right). Data are representative of primary microglial cultures prepared from n = 6−8 neonates per genotype, examined over 2 independent experiments. Scale bar represents 100 µm. (c) Representative FACS plot showing pHrodo signal in CD11b + cells collected from primary microglial culture (upper). No pHrodo signal was observed after Bafilomycin treatment, confirming lysosomal acidification as the source of pHrodo signal (lower). Data are representative of 2 independent experiments.