Oligomerization of tau was performed as described (Ward et al. 2013 (link)). Briefly, the 2N4R isoform of human recombinant tau (rPeptide) was incubated at 4 µM with 75 µM of arachidonic acid in aggregation buffer (10 mM HEPES, pH 7.6, 100 mM NaCl, 0.1 mM EGTA, 5 mM DTT) for 6 h at room temperature with no agitation. To stop the reaction, the buffer was exchanged to PBS via 3 rounds of buffer exchange in a 10 kDa MWCO centrifugal filter (Millipore Ultrafree-MC). The sample was stored at −80 °C until analysis. Successful oligomerization was confirmed by Western immunoblotting (Supp. Fig. 1). For this, samples were diluted in Laemmli sample buffer without addition of a reducing agent or sample boiling. 10 ng of tau was loaded per well of a 4–20% Tris-Glycine SDS-polyacrylamide gel (Novex, ThermoFisher Scientific). After transfer, tau was detected using the DA31 total tau antibody (Acker et al. 2013 (link)) diluted to 1.5 µg/mL.