MAPT and early-onset autosomal dominant Alzheimer disease: The deposition of microtubule-associated protein tau (MAPT/tau) into insoluble fibrils is a major pathological hallmark of fatal and incurable neurodegenerative diseases—including Alzheimer’s disease (AD), frontotemporal dementia (FTD), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and others1–3.