Fig. 2.

Pretreatment with Aβ oligomers but not Aβ freshly prepared or Aβ fibrils promotes tau seeding. a Fluorescence microscopy images of tau-biosensor cells treated with 500 nM of freshly prepared, oligomeric, or fibrillar Aβ followed 24-h later by 200 nM tau seeds. Tau aggregates are indicated by white arrows. The scale bar denotes 50 μm. b–d Flow-cytometry-based FRET quantification of intracellular tau aggregation seeded by recombinant tau RD fibrils (b), tau 40 fibrils (c), or PS19 mouse brain extracts (d). The enhancement by Aβ pretreatment is much stronger for Aβ oligomers (red), compared to Aβ fresh (green) and fibrils (blue), and occurs in a dose-dependent manner. c Aβ promotes intracellular tau aggregation seeded by full-length tau. d Aβ promotes seeding with brain extract from mice expressing human full-length P301S tau. ELISA was used to quantify human tau expressed in mouse brain extracts. The data are presented as mean ± SD (n = 6–9)