DEVELOPMENTAL-CHANGES IN TAU-PHOSPHORYLATION - FETAL-TAU IS TRANSIENTLY PHOSPHORYLATED IN A MANNER SIMILAR TO PAIRED HELICAL FILAMENT-TAU CHARACTERISTIC OF ALZHEIMERS-DISEASE

Rat and human fetal brain tau were probed with a panel of monoclonal a ntibodies (tau-1, AT8, 8D8, RT97, SM131, SM134) that distinguish betwe en paired helical filament (PHF)-tau of Alzheimer's disease and normal adult brain tau. These antibodies discriminate between normal and PHF -tau because their epitopes are phosphorylated in PHF-tau. Although on ly one molecular isoform of tau was shown to be expressed in fetal bra in, two fetal tau species could be distinguished on sodium dodecyl sul fate-polyacrylamide gel electrophoresis and the slower migrating speci es was recognized by all of the PHF-tau-specific antibodies. Moreover, this immunoreactivity was shown to be phosphorylation dependent. Our observations suggest that the abnormal phosphorylation of tau in Alzhe imer's disease may be the result of reactivation of pathways governing the phosphorylation of tau in the developing brain.