Importantly, Tau was found to modulate Fyn mobility in dendritic shafts. Although the mutant Tau lacking its microtubule binding domains (ΔTau) did not affect Fyn mobility, the FTD-linked P301L mutant Tau largely increased Fyn trapping in nanodomains in the spines by increasing Fyn occupancy in the confined state and decreasing its occupancy in the free diffusive state. Here, MAPT is linked to frontotemporal dementia.