The strong association with both dementia status and P-tau pathology in a large cohort of human subjects indicates that perivascular astrocytic endfoot function, and specifically the 15 gene products (AQP4, the DAC genes, and the 11 candidate endfoot genes) may represent novel regulators of tau aggregation and the propagation of tau pathology in the setting of AD. The gene discussed is AQP4; the disease is Alzheimer disease.