1. Stem Cell Project Group, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan
2. Department of Cell Biology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo 113-8549, Japan
3. Priority Organization for Innovation and Excellence, Kumamoto University, 2-39-1 Kurokami, Kumamoto-shi, Kumamoto 860-8555, Japan
4. Institute of Health Biosciences and Graduate School of Pharmaceutical Sciences, the University of Tokushima, 1-78-1 Shomachi, Tokushima-shi, Tokushima 770-8505, Japan