Endothelial TDP-43 depletion disrupts core blood-brain barrier pathways in neurodegeneration.

Endothelial cells (ECs) help maintain the blood-brain barrier but deteriorate in many neurodegenerative disorders. Here we show, using a specialized method to isolate EC and microglial nuclei from postmortem human cortex (92 donors, 50 male and 42 female, aged 20-98 years), that intranuclear cellular indexing of transcriptomes and epitopes enables simultaneous profiling of nuclear proteins and RNA transcripts at a single-nucleus resolution. We identify a disease-associated subset of capillary ECs in Alzheimer's disease, amyotrophic lateral sclerosis and frontotemporal degeneration. These capillaries exhibit reduced nuclear β-catenin and β-catenin-downstream genes, along with elevated TNF/NF-κB markers. Notably, these transcriptional changes correlate with the loss of nuclear TDP-43, an RNA-binding protein also depleted in neuronal nuclei. TDP-43 disruption in human and mouse ECs replicates these alterations, suggesting that TDP-43 deficiency in ECs is an important factor contributing to blood-brain barrier breakdown in neurodegenerative diseases.