OCT3/4 (encoded by Pou5f1, also known as OCT3, OCT4) was first identified in mice as an ESC-specific and germline-specific transcription factor. In humans, OCT4 is the product of the OTF3 gene, and has been reported to have three isoforms, OCT4A, OCT4B and OCT4B1. Among these isoforms, only OCT4A-which shares 87% amino acid sequence identity with mouse OCT4-has been demonstrated to maintain the pluripotency of stem cells; it is referred to as OCT4 in the vast majority of reports.
