1Department of Pediatrics, Jichi Medical School, 3,311-1 Yakushiji, Minamikawachi, Kawachi-gun, Tochigi 329-0498 Japan,
2Department of Pediatrics, Dokkyo University School of Medicine, Mibu, Japan,
3Department of Pathology, The Hospital for Sick Children, Toronto, Ontario, Canada
4Department of Mental Retardation and Birth Defect Research, National Institute of Neuroscience, NCNP, Kodaira, Japan,