Tau-ing and fro-ing: the tanycytic shuttle in neurodegeneration.

After more than a century since Alzheimer's disease (AD) was described and decades of research into β-amyloid and Tau proteins, mechanisms underlying pathogenic protein clearance from brain remain poorly understood. Recent research identifies tanycytes-specialized hypothalamic cells lining the third ventricle-as a previously unrecognized clearance system for brain Tau. These cells actively transport Tau from cerebrospinal fluid to blood via pituitary portal circulation but are dramatically fragmented in AD brains. Single-nucleus RNA sequencing reveals altered stress and transport gene expression in AD tanycytes, while functional studies show disrupted tanycytic transport reduces Tau efflux and exacerbates pathology. Beyond protein clearance, tanycytes maintain critical metabolic and neuroendocrine pathways influencing cognition. Their unique blood-brain interface position makes them attractive therapeutic targets. As transcriptomic evidence suggests tanycytes are hotspots for age-related changes, their dysfunction may herald "tanycytopathies" underlying multiple neurodegenerative disorders.