The phosphatase activity null PTEN leads to formation of visible tau aggregates in cells. COS-7 cells stably expressing the FTDP-17 mutant tau were transfected with pIRES-EGFP (A-D), pIRES-EGFP-PTENwt (E-H) or pIRES-EGFP-PTENcg (I-L). Expression of EGFP control (A), PTEN-WT (E) or PTEN-CG (I) was visualized based on the EGFP fluorescence. Cells were further immunostained to detect tau (B,F,J) and α-tubulin (C,G,K). Fluorescence micrographs were visualized and recorded by fluorescence microscope. D, H, and L are merged images of tau and α-tubulin immunostaining.