Tau proteins are microtubule-associated proteins transcribed from the MAPT gene. They promote microtubule assembly and stability, and might be involved in the establishment and maintenance of neuronal polarity. In Alzheimer’s disease, the neuronal cytoskeleton in the brain is progressively disrupted and replaced by tangles of paired helical filaments (PHF) and straight filaments, mainly composed of hyperphosphorylated forms of TAU. Abnormal quantities of Tau protein in neurons and sometimes astrocytes are also seen in progressive supranuclear palsy. In immunohistochemistry of normal tissue, Tau has positive cytoplasmic staining in the central nervous system, renal tubules and in peripheral nerves, with some expression in other tissues including skeletal muscle, kidney and breast. References: J Mol Biol. 2016 May 8;428(9 Pt A):1742-59, PMID: 26996940; PNAS. 2015 June. 112 (24) 7501-7506, DOI: 10.1073/pnas.1504081112; Acta Neuropathol. 1991;81(6):591-6, PMID: 1831952