Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China School of Life Science and Technology, Shanghai Jiaotong University, Shanghai 200240, China Shanghai Center for Bioinformation Technology, Shanghai Industrial Technology Institute, Shanghai 201203, China and Collaborative Innovation Center for Genetics and Development, Fudan University, Shanghai 200438, China.