When exposed to healthy brain environments such as Alzheimer’s disease or other tauopathies such as multiple myeloma or parkinsonism, the levels of tau phosphorylation vary; in healthy brain tissue there are around two or three residues, while neurodegenerative conditions such as Alzheimer’s or tauopathies involve much higher phosphorylation, with nine or ten phosphates per molecule being created by imbalanced activity between tau kinases and phosphatases. Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.