1. Department of Pediatrics, Hokkaido University Graduate School of Medicine , North 15 West 7, Kita-ku, Sapporo 060-8638 , Japan
2. Department of Pediatrics, Japanese Red Cross Kitami Hospital , North 6 East 2, Kitami 090-8666 , Japan
3. Department of Neuromuscular Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry , 4-1-1 Ogawahigashi-cho, Kodaira, Tokyo 187-8502 , Japan
4. Department of Genome Medicine Development, Medical Genome Center, National Center of Neurology and Psychiatry , 4-1-1 Ogawahigashi-cho, Kodaira, Tokyo 187-8551 , Japan