1. Division of Neuronal Network; Institute of Medical Science; University of Tokyo; Tokyo 108-8639 Japan
2. Department of Anatomy; Hokkaido University Graduate School of Medicine; Sapporo Japan
3. Laboratory of Animal Resources; Center for Disease Biology and Integrative Medicine; Faculty of Medicine; University of Tokyo; Tokyo Japan
4. Division of Molecular Genetics; Kobe University Graduate School of Medicine; Kobe Japan
5. PRESTO JST; Kawaguchi Saitama Japan
6. Laboratory for Animal Resources and Genetic Engineering; Center for Developmental Biology; RIKEN; Kobe Japan