1. Department of Hematopoietic Stem Cells, SSP Stem Cell Unit, Kyushu University Faculty of Medical Sciences, Fukuoka 812-8582, Japan.
2. Laboratory for Animal Resources and Genetic Engineering Animal Resource Unit, Center for Developmental Biology, RIKEN, Kobe 650-0047, Japan.
3. Department of Medicine and Biosystemic Science, Kyushu University Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.