Fig. 1: SPP1 upregulation at onset of microglia–synapse phagocytosis.
a, Representative 3D reconstructed images showing Homer1 engulfment within CD68+ lysosomes of P2Y12+ microglia in 6-month AppWT (WT) versus AppNL-F CA1 hippocampal SLM. Scale bar represents 5 µm. b, Quantification of Homer1 engulfment in 6-month WT and AppNL-F P2Y12+ microglia. One datapoint represents average of 1 mouse from n = 4 animals per genotype examined over two independent experiments. P values from two-tailed unpaired Student’s t-test with Welch’s correction. c, Representative confocal images of C1q protein expression in 6-month WT versus AppNL-F mice. Insert represents C1qa mRNA within Tmem119+ microglia. Scale bar represents 20 µm. Data are representative of two mice per genotype examined over at least five independent experiments. d, Quantification of C1q puncta in 6-month WT and AppNL-F CA1 hippocampus. One datapoint represents one ROI per mouse from n = 9 WT mice and n = 7 AppNL-F mice examined over two independent experiments. Average amount of cells per datapoint is 30–40. P values from two-tailed unpaired Student’s t-test. e,f, 3D-τ-STED imaging of secreted SPP1 in 6-month WT and AppNL-F SLM (e) and quantification of SPP1 total fluorescence particles (f). One datapoint represents one ROI per mouse, with total of n = 3 mice examined over one independent experiment. P values from two-tailed unpaired Student’s t-test. Scale bar represents 2 µm. g,h, Quantification of Spp1 expression within hippocampus of 6-month WT versus AppNL-F as measured by smFISH in hippocampus (g) or via qPCR on hippocampal homogenates (h). One datapoint represents one individual value per mouse, with total of n = 5–6 mice (per genotype) (g) or 4–5 mice (per genotype) (h) examined over two independent experiments. P values from two-tailed unpaired Student’s t-test. i, Representative 3D reconstruction of SPP1 adjacent to GLUT1+ vasculature in SLM of 6-month AppNL-F. Scale bar represents 10 µm. Image representative of two AppNL-F mice examined over four independent experiments. j, Representative images of SPP1 expression along vasculature in postmortem hippocampal brain slices of three AD patients. Images are representative of six AD patients (see also Supplementary Table 1). Scale bar represents 20 µm. Data are shown as mean ± s.e.m.
