Tau seeds induce neurofibrillary tangle formation across brain regions via individual-specific connectivity.

The spread of tau pathology across the cerebral cortex is closely tied to cognitive decline in Alzheimer's disease (AD). To investigate mechanisms underlying tau spread, we measured bioactivity of tau seeds from inferior temporal gyrus (ITG) and superior frontal gyrus (SFG) synaptosomes in 128 individuals and demonstrated that tau seed bioactivity associates with tau phosphorylation, neurofibrillary tangles (NFTs), and cognitive impairment. Incorporating genotype data from the same individuals within a Mendelian randomization framework showed that tau seeds in ITG induce NFTs locally as well as drive tau seeds and NFTs in SFG. Integrating antemortem functional magnetic resonance imaging data from the same individuals showed that person-specific connectivity modulates the tau seed-NFT relationships. These findings indicate that tau seeds underlie the spread of NFTs both locally and across distal brain regions via individual-specific connectivity.