The dynamical organization of pluripotency transcription factors Oct4 and Sox2 changes at the onset of differentiation in Embryonic Stem Cells.

CAMILA OSES; PAULA VERNERI; MARTIN STORTZ; CAMILA VAZQUEZ ECHEGARAY

CABA

Congreso; Latin American Society for Developmental Biology (LASDB); 2019

Embryonic stem cells (ESCs) pluripotency depends on specific transcription factors (TFs) such as Oct4, Sox2 and Nanog, which induce genes necessary to preserve pluripotency and repress others involved in differentiation. Their dynamical interactions with DNA targets and nuclear distribution play a fundamental role in gene modulation that may impact on cell fate.We used a non-invasive microscopy method, namely fluorescence correlation spectroscopy to quantify the dynamical organization of TFs in ESCs with an inducible expression of Oct4 or Sox2 C-terminally fused to a fluorescent protein. We found that TFs partitioned between the nucleoplasm and heterochromatin-like foci in undifferentiated ESCs that restructure at early differentiation stages in which Oct4 and Sox2 levels remain constant. We also found differences on how the dynamics of these TFs respond to differentiation cues. Specifically, we detected an impairment of Oct4-chromatin interactions upon differentiation whereas Sox2 only showed a slight increase in the lifetime of short-lived and probably more unspecific interactions with chromatin. Taken together, our results reveal that early differentiation cues trigger changes of the organization of Oct4 and Sox2 within the nuclear space that also include modifications in TF-chromatin interactions. This dynamical reorganization precedes the downregulation of the TFs and may ultimately contribute to modulate the function of these pluripotency TFs at early differentiation stages.