Extended Data Fig. 1. MFG-E8 is expressed primarily by astrocytes in APP transgenic mice.

a, Immunofluorescent co-staining of MFG-E8 (green) with astrocytic (Aldh1l1, cyan) and microglial (Iba1, red) markers demonstrates co-localisation only with astrocytes. Note that in Mfge8 C2 KO mice, the truncated MFG-E8/β-galactosidase fusion protein (cf. Fig. 1a) is still expressed but is retained inside the cell due to an artificial transmembrane domain, causing a punctate staining pattern. b, Astrocytic (‘A’) staining is also evident by immuno-electron microscopy in 4-month-old APPPS1 x Mfge8 wild-type (WT) animals (arrowheads indicate positively stained structures, which are magnified in inset b₁). The arrow (top left) indicates bundles of intermediate filaments in the astrocytic cytoplasm, which are shown at higher magnification in b₂. c, Astrocytes in Mfge8 C2 KO animals also contain heavily labelled punctate structures, indicating intracellular accumulation of the truncated MFG-E8 protein (arrowheads indicate positively stained structures, which are magnified in c₁ inserts; n = 1f/1m Mfge8 WT and n = 1f/1m Mfge8 C2 KO animals analysed). Scale bar; 15 µm in a, 500 nm in b.