The Pou5f1 distal enhancer is sufficient to drive Pou5f1 promoter-EGFP expression in embryonic stem cells.

The POU5F1 transcription factor is the gatekeeper of the pluripotent state in mammals. It is essential for epigenetic reprogramming events and also for germ cell viability. Pou5f1 gene expression is tightly controlled during embryogenesis, but its regulatory regions are not fully deciphered. The GOF18ΔPE-EGFP transgene, harboring the enhanced green fluorescence protein reporter gene inserted into a 17- kilobase long mouse Pou5f1 genomic sequence, has been widely used to visualize pluripotent embryonic cells and primordial germ cells in the mouse and other mammalian species. This construct includes the Pou5f1 promoter under the control of the distal enhancer and also includes the Pou5f1 gene body and flanking sequences. In search of the essential regulatory regions of Pou5f1, we generated four shorter forms of this construct. We found that the shortest form, containing the Pou5f1 promoter and distal enhancer but lacking the gene body and upstream flanking sequences, correctly expressed EGFP in transiently transformed undifferentiated ES cells, correctly switched it off upon ES cell differentiation, and correctly kept it silenced in differentiated Hep3B cells. Similarly to the original GOF18ΔPE-EGFP, this shortest form was expressed in the fetal mouse gonad. Our data suggest that the Pou5f1 distal enhancer and proximal promoter may be sufficient to specify transgene expression in pluripotent cells.