1. Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology 1 , Yokohama 226-8503 , Japan
2. Graduate School of Pharmaceutical Sciences, The University of Tokyo 2 , Tokyo 113-0033 , Japan
3. Max Planck Institute of Molecular Cell Biology and Genetics 3 , Dresden - 01307 , Germany
4. University of Lausanne, Center for Integrative Genomics 4 , Lausanne 1015 , Switzerland