A tau homeostasis signature is linked with the cellular and regional vulnerability of excitatory neurons to tau pathology

Excitatory neurons are preferentially impaired in early Alzheimer’s disease but the pathways contributing to their relative vulnerability remain largely unknown. Here we report that pathological tau accumulation takes place predominantly in excitatory neurons compared to inhibitory neurons, not only in the entorhinal cortex, a brain region affected in early Alzheimer’s disease, but also in areas affected later by the disease. By analyzing RNA transcripts from single-nucleus RNA datasets, we identified a specific tau homeostasis signature of genes differentially expressed in excitatory compared to inhibitory neurons. One of the genes, BCL2 associated athanogene 3BAG3, a facilitator of autophagy, was identified as a hub or master regulator, gene. We verified that reducing BAG3 levels in primary neurons exacerbated pathological tau accumulation whereas overexpression attenuated it. These results support the conclusion that tau homeostasis underlies the cellular and regional vulnerability of excitatory neurons to tau pathology.