Fig 1: Astrocytes with MAPT S305 mutations are in an inflammatory state and rapidly internalize exogenous tauA. Representative trace of integrated fluorescence intensity of pHrodo Red signal in S305 mutation astrocytes and isogenic controls treated with labelled 0N3R and 0N4R tau isoforms over 48 hours. Error bars = SEM. N = 4, each point is an average of 3 fields of view per well. Linear regression.B. Representative Incucyte images of S305 mutation astrocytes and controls at 48 hours following treatment with pHrodo-labelled 0N tau, quantified in A. Scale bar = 200μm.C. Representative trace of integrated fluorescence intensity of pHrodo Red signal in S305 mutation astrocytes and isogenic controls treated with labelled 1N3R and 1N4R tau isoforms over 48 hours. Error bars = SEM. N = 4, each point is an average of 3 fields of view per well. Linear regression.D. Representative Incucyte images of S305 mutation astrocytes and controls at 48 hours following treatment with pHrodo-labelled 1N tau, quantified in C. Scale bar = 200μm.E. Representative trace of integrated fluorescence intensity of pHrodo Red signal in S305 mutation astrocytes and isogenic controls treated with labelled 2N3R and 2N4R tau isoforms over 48 hours. Error bars = SEM. N = 4, each point is an average of 3 fields of view per well. Linear regression.F. Representative Incucyte images of S305 mutation astrocytes and controls at 48 hours following treatment with pHrodo-labelled 2N tau, quantified in E. Scale bar = 200μm.G. Log2 CXCL5 concentration (pg/ml) in iPSC-astrocyte culture media, corrected for cellular density, either untreated or following treatment with exogenous tau isoforms. Error bars = SEM. N = 3–12, each point represents an independent experiment averaging 3 technical replicates. Two-way ANOVA with Dunnett’s multiple comparison tests.H. Log2 CXCL5 concentration (pg/ml) in iPSC-astrocyte culture media, corrected for cellular density, pooled across all tau isoform treatment conditions for each genotype. Error bars = SEM. N = 21–70. One-way ANOVA with Dunnett’s multiple comparison tests.