Tau

Abstract

Tau protein binds to microtubules and can induce tubulin polymerization in vitro. It has been proposed that Tau makes crossbridges between the microtubules in axons and plays a role in axon extension. This chapter presents a study in which no gross abnormalities were observed in Tau–/– mice and no developmental deficits were revealed by histological examination. The relative levels of various microtubule-associated proteins, neurofilament proteins, synapsin 1, and various tubulin isoforms were similar to those in control littermates. The microtubule (MT) number and density of parallel fiber axons in the cerebellar tissue was reduced in Tau–/– mice but the MT density in Purkinje cell dendrites was not significantly affected. MT density also did not differ significantly in axons with larger diameters, suggesting that Tau affects the stability of MTs in small-caliber axons. The frequency of crossbridges between MTs was greatly reduced in Tau–/– axons but filamentous crossbridges between MT and axonal plasma membrane occur in both Tau–/– and Tau+/+axons. The results demonstrate that Tau is important for the stabilization of microtubules in small-caliber axons, rather than dendrites.