The dynamical organization of the core pluripotency transcription factors responds to differentiation cues in early S-phase

CAMILA OSES; MARCOS FRANCIA; PAULA VERNERI; CAMILA VAZQUEZ ECHEGARAY; ALEJANDRA GUBERMAN; VALERIA LEVI

Rosario

Congreso; Sociedad Argentina de Biofísica (SAB) anual meeting 2022; 2022

Pluripotent stem cells (PSCs) are a promise for regenerative medicine and disease modeling due to their capabilities to self-renew indefinitely and differentiate into all somatic cell types. The cell cycle plays a central role on pluripotency maintenance and cell fate decisions. Relevantly, the cell cycle of PSCs presents unique properties since it is faster than that of somatic cells and has a very short G1 phase. This phase was suggested as the “window of opportunity” when PSCs can switch its gene expression program to differentiation. Pluripotency is controlled by a large regulatory network directed by the transcription factors (TFs) OCT4, SOX2 and NANOG which induce genes that promote pluripotency and repress those involved in differentiation. The dynamical distribution of TFs defines their interactions with chromatin targets and modulate gene expression. In this context, we asked whether the nuclear organization of the pluripotency TFs changes during the cell cycle. We hypothesized that the S phase could be a window of opportunity to execute changes that impact in the chromatin landscape and in the dynamical distribution of the TFs. We used quantitative advanced microscopy methods to explore the dynamical organization of the pluripotency TFs in embryonic stem cell (ESC) lines expressing OCT4, SOX2 or NANOG fused to fluorescent proteins and identified cells in G1/G2 or S phases through the distribution of PCNA-RFP. We found that TFs distribution and dynamics change during DNA replication of undifferentiated ESCs. Moreover, differentiation cues trigger the dissolution of OCT4 and SOX2 foci in early S phase and favor their interactions with chromatin, contrary to NANOG that detaches from chromatin. Our results show pluripotency TFs-chromatin landscape of interactions is highly dynamic during the cell cycle providing new insights into the fine tune regulation of pluripotency maintenance and cell fate transitions.