Oct-3/4, a member of POU transcription factors, was identified as a DNA-binding protein that activates gene transcription via a cis-element containing an octamer motif. It is expressed in totipotent embryonic stem and germ cells. When embryonic stem cells are induced to differentiate, Oct-3/4 is downregulated and this downregulation of Oct-3/4 has proven to be essential for proper and divergent developmental program. The Oct-3/4 molecule is not only a master regulator of pluripotency that controls the lineage commitment but also is the most recognized marker used for the identification of totipotent embryonic stem cells.
