Expression of tau exon 8 in different species

A synthetic peptide corresponding to a region encoded by tau gene exon 8 was used to raise an antibody. The antibody, E8, was used to probe normal tau from different species and abnormal tau proteins from subjects with Alzheimer's disease. Immunoblotting and enzyme-linked immunosorbent assays demonstrated that only bovine tau reacted with the E8 antibody. The E8 immunoreactive tau isoform was estimated to represent less than 2% of the bovine tau. Our results indicate that bovine tau is unique in containing isoforms positive with E8, and that PHF formation does not require the presence of PHF-tau with exon 8.