Oct-4, a member of the family of POU-domain transcription factors, is expressed in pluripotent embryonic stem (ES) and germ cells [22] [23] . Oct-4 mRNA is normally found in totipotent and pluripotent stem cells of pregastrulation embryos [24] . Knocking out the Oct-4 gene in mice causes early lethality due to the lack of ICM formation, indicating that Oct-4 has a critical function for self-renewal of ES cells [25] . Oct-4 activates transcription via octamer motifs, and Oct-4 binding sites have been found in various genes, including fgf 4 (fibroblast growth factor 4) and pdgfar (platelet-derived growth factor a receptor) [26, 27] . This suggests that Oct-4 functions as a master switch during differentiation by regulating the pluripotent potentials of the stem cell, and Oct-4 plays a pivotal role in mammalian development [24, 25] .