Different dynamical organization of Oct4 in pluripotent and terminally differentiated cells

CAMILA VAZQUEZ ECHEGARAY A, PAULA VERNERI A, CAMILA OSES A, MARCOS FRANCIA A, MARÍA VICTORIA PETRONE A, AYELÉN TORO A, VALERIA LEVI A, ALEJANDRA GUBERMAN

Congreso; Xth meeting of the Latin American Society for Developmental Biology (LASDB); 2019

Theachievement and maintenance of pluripotency requires specific transcriptionfactors (TFs) such as Oct4, Sox2 and Nanog, that induce genes required for pluripotencyand repress others involved in differentiation in pluripotent stem cells (PSC).Besides their levels, the distribution and interactions of these TFs withchromatin and their subnuclear localization impact on gene expression.  Therefore, it is essential to explore thedynamical organization of TFs to fully understand their role on transcriptionregulation. Here, we examine how Oct4 distributes in the nucleus of PSC andterminally differentiated cells and analyzed changes in its dynamicalorganization. For this aim, we constructed stable cell lines expressing Oct4fused to the fluorescent protein YPet. We found that, in undifferentiatedcells, Oct4 partitioned between the nucleoplasm and a few chromatin-dense foci,whereas the number of foci increased in differentiated cells. These focicolocalized with regions of condensed chromatin, and their formation does notinvolve liquid phase condensation. When comparing the dynamics of theinteraction of Oct4 and its chromatin targets, we found differences in residencetimes and bound fractions between the different cell lines. In conclusion, thedynamical reorganization of Oct4 may contribute to modulate its role atdifferentiation or during reprogramming. Overall, these evidences contribute tothe understanding of the molecular mechanisms involved in cell fate decisions.