RT Journal Article SR Electronic T1 Endogenous fluctuations of OCT4 and SOX2 bias pluripotent cell fate decisions JF bioRxiv FD Cold Spring Harbor Laboratory SP 299073 DO 10.1101/299073 A1 Strebinger, Daniel A1 Deluz, Cédric A1 Friman, Elias T. A1 Govindan, Subashika A1 Alber, Andrea B. A1 Suter, David M. YR 2019 UL http://biorxiv.org/content/early/2019/05/13/299073.abstract AB SOX2 and OCT4 are pioneer transcription factors playing a key role in embryonic stem (ES) cell self-renewal and differentiation. However, how temporal fluctuations in their expression levels bias lineage commitment is unknown. Here we generated knock-in reporter fusion ES cell lines allowing to monitor endogenous SOX2 and OCT4 protein fluctuations in living cells and to determine their impact on mesendodermal and neuroectodermal commitment. We found that small differences in SOX2 and OCT4 levels impact cell fate commitment in G1 but not in S phase. Elevated SOX2 levels modestly increased neuroectodermal commitment and decreased mesendodermal commitment upon directed differentiation. In contrast, elevated OCT4 levels strongly biased ES cell towards both neuroectodermal and mesendodermal fates. Using ATAC-seq on ES cells gated for different endogenous SOX2 and OCT4 levels, we found that high OCT4 levels increased chromatin accessibility at differentiation-associated enhancers. This suggests that small endogenous fluctuations of pioneer transcription factors can bias cell fate decisions by concentration-dependent priming of differentiation-associated enhancers.