State Key Laboratory of Bio-membrane and Membrane Bio-engineering; Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing 100871, China. State Key Laboratory of Bio-membrane and Membrane Bio-engineering; Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing 100871, China; Center for Quantitative Biology, Peking University, Beijing 100871, China. Electronic address: chenjg@pku.edu.cn.