1. Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea.
2. KAIST Institute for the BioCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea.
3. Bio Core Center, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea.
4. Department of Neuroscience, Cell Biology, and Anatomy, The University of Texas Medical Branch, Galveston, TX 77555, USA.