Oct-3/4: not just a gatekeeper of pluripotency for embryonic stem cell, a cell fate instructor through a gene dosage effect.

Oct-3/4 encoded by Pou5f1 has been longwise recognised as a gatekeeper for embryonic stem (ES) cell pluripotency. Recently, it was suggested that Oct-3/4 one of the earliest transcription factor of the embryo might feature some functions in differentiation of cell lineages. We recently uncovered a key role of Oct-3/4 in both ES cell specification toward a cardiac lineage and in mesodermal commitment of the embryonic epiblast. Our findings demonstrated a gene dosage effect of Oct-3/4, a factor at the cross-road between cell self-renewal and cell lineage specification. What is the genetic and/or epigenetic mechanism underlying this process is still questionable. The extraview presents some hypotheses that might account for the pleiotropic dose-dependent functions of Oct-3/4.