Exploring the nuclear distribution of the pluripotency transcription factor SOX2 in embryonic stem cells

DIAZ MC; VERNERI P; FRANCIA M; OSES C; STORTZ M; DE ROSSI MC; GUBERMAN A; LEVI V

Congreso; L Reunión Anual de la Sociedad Argentina de Biofísica; 2022

Pluripotent stem cells present two key features: unlimited self-renewal capability and pluripotency. The preservation of these fundamental properties depends on specific transcription factors (TFs), particularly, OCT4, SOX2 and NANOG, that induce genes necessary to maintain the undifferentiated state and repress others that promote differentiation. We have previously observed that these TFs distribute heterogeneously in the nucleus of mouse embryonic stem cells (mESCs) concentrating in domains referred to as foci. It has been proposed that many membrane-less, nuclear compartments form through a liquid-liquid phase separation process. Particularly, it has been suggested that some components of the transcriptional machinery, including TFs such as OCT4 form liquid condensates that seem to play a relevant role in chromatin remodeling and cell fate transitions. It is still unknown if SOX2 and NANOG are also incorporated into these nuclear condensates and their functional relevance. Here, we studied the nuclear distribution of SOX2 using quantitative confocal microscopy in living mESCs. We analyzed the biophysical behavior of foci formed by SOX2 fused to the fluorescent YPet in mESCs and observed that they present properties compatible with those expected for liquid condensates. Furthermore, we show that OCT4 also concentrate in SOX2 foci. Finally, we perturbed the chromatin structure with chemical inhibitors of histone deacetylases or DNA methyltransferases and analyzed the subnuclear distribution of SOX2-YPet; our results suggest that SOX2-YPet foci formation require a specific chromatin environment.