Differential phosphorylation of tau proteins during kitten brain development and Alzheimer's disease

Differential distribution and phosphorylation of tau proteins were studied in developing kitten brain by using several antibodies, and was compared to phosphorylation in Alzheimer's disease. Several antibodies demonstrated th e presence of phosphorylated tau proteins during kitten brain development a nd identified pathological structures in human brain tissue. Antibody AD2, recognized tau in kittens and adult cats, but reacted in Alzheimer's tissue only with a pathological tau form. Antibody AT8 was prominent in developin g kitten neurons and was found in axons and dendrites. After the first post natal month this phosphorylation type disappeared from axons. Furthermore, dephosphorylation of kitten tau with alkaline phosphatase abolished immunor eactivity of AT8, but not that of AD2, pointing to a protection of the AD2 epitope in cats. Tau proteins during early cat brain development are phosph orylated at several sites that are also phosphorylated in paired helical fi laments during Alzheimer's disease. In either event, phosphorylation of tau may play a crucial role to modulate microtubule dynamics, contributing to increased microtubule instability and promoting growth of processes during neuronal development or changing dynamic properties of the cytoskeleton and contributing to the formation of pathological structures in neurodegenerat ive diseases.