1. Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan.
2. Department of Neurosurgery, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan.
3. Department of Physiological Sciences, School of Life Science, The Graduate University for Advanced Studies, SOKENDAI, Hayama 240-0193, Japan.
4. Department of Neurosurgery, Sapporo Medical University, Sapporo 060-8543, Japan.
5. Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies, Kobe 650-0047, Japan.
6. Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Tokyo 102-0076, Japan.