We measured aggregate seeding with TauRD-YT cells, a HEK293T cell line stably co-expressing the repeat domain of Tau (TauRD; residues 244-372 with FTD mutations P301L/V337M) fused to YFP or mTurquoise2, whose co-aggregation during fibril formation results in fluorescence resonance energy transfer (FRET)41 (Fig. 1a). The gene discussed is MAPT; the disease is frontotemporal dementia.