We thank Drs. Iqbal K. and Grundke-Iqbal I. from NYS Institute for Basic Research for antibody R134d. We also thank Dr. Davies P. from Albert Einstein College of Medicine, Bronx, NY, USA for antibody PHF-1. This work was supported in part by grants from National Major Grant for Basic Research (2006CB500703) and the National Natural Science Foundation of China (32328007 and 30430270).