High-yield purification of fetal tau preserving its structure and phosphorylation pattern.

The fetal type of tau phosphorylation always re-appears during pathogenesis of Alzheimer's disease and related tauopathies. The major obstacle in the study of the fetal tau phosphorylation has been the lack of a simple and reproducible purification method yielding fetal tau with high purity and unmodified phosphorylation pattern. We have developed a two-step, highly efficient purification procedure of perchloric acid-extracted fetal tau by immunoaffinity chromatography and trichloroacetic acid (TCA) precipitation. The method yielded tau with more than 90% purity. Most importantly, purified fetal tau exhibited unmodified phosphorylation pattern as confirmed by phosphorylation-dependent antibodies. In summary, this purification process preserves and protects unstable phosphoresidues from dephosphorylation and allows their detailed molecular analysis especially in the pathogenesis of Alzheimer's disease and related tauopathies.