Expression of human and human tau-Δ18–28 in COS-7 cells.

A) Alignment of human and mouse tau sequences at the N-terminal domain. Mouse tau lacks the motif spanning residues 18–28 that is present in human tau. B) Expression of human and htau-Δ18–28 in COS-7 cells. Tau expression was analyzed by Western blot using tau antibody 7.51. GADPH was used as loading control for cell lysates. C) Secreted tau levels from experiment 1B were analyzed by Western blot of cell culture medium. D) Densitometric quantitation of the extracellular tau from panel C. *P < 0.05.