Extended Data Fig. 4: Bassoon overexpression increases tau accumulation in vitro and in a Drosophila model of tauopathy.

a–c, hTau levels by ELISA (a), Western blot of total tau (b), seeding activity (c) from HEK cells overexpressing hTau^WT or hTau^P301S. Western blot membrane was overexposed in the upper level for better visualization of oligomeric tau (denoted by the asterisk*). d, Location of BSN peptides detected by IP⁻mass spec. e, Representative images, and quantification of 6X-His immunofluorescences from HEK cells overexpressing hTau^P301S and 6X-His-BSN N- or C- terminal fragments (BSN-N or BSN-C, respectively). f, Disordered residues of human and mouse bassoon. 85.1% of residues in human BSN and 85.8% of residues in mouse BSN were predicted to be disordered. g, Hydrophobicity profile of bassoon using method of Kyte & Doolittle. Average hydrophobicity is −0.81 for human BSN, and −0.85 for mouse BSN, h, Western blot confirming the overexpression of the UAS-BSN under the GMR-Gal4 driver in different fly lines. i, Western blot for BSN of co-immunoprecipitation (Co-IP) of human tau (HT7) from hTau^P301L/BSN^WT and hTau^P301L/BSN^mut fly head lysates. Experiments were repeated three times with similar results (h, i). j, k, Western blot (j), of the level of HMW and 117 kDa MC1 detected and quantified (k), in hTau^P301L, hTau^P301L/BSN^WT and hTau^P301L/BSN^mut fly head lysates. Each sample is a pool of 20 fly brains from 3 different eclosion events. l, m Western blot (l), and quantification of misfolded tau (MC1) (m), in fly lysates denatured by increasing concentrations of guanidine HCl, in hTau^P301L, hTau^P301L/BSN^WT, and hTau^P301L/BSN^mut head lysates. Data are the mean ± s.e.m. Experiments were performed with n = 3 (a–c, e, j–m). Significance was determined by unpaired two-tailed Student’s t-test (a, c, e) and one-way ANOVA (k, m).

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