Pluripotency transcription factors dynamics along the cell cycle in embryonic stem cells

CAMILA OSES, CAMILA VAZQUEZ ECHEGARAY, PAULA VERNERI, ALEJANDRA GUBERMAN, VALERIA LEVI

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

Embryonic stem cells (ESCs) are pluripotent and capable of self-renewal,so their study is highly relevant to understand embryo development. Duringdifferentiation, cells present different transcriptional profiles associatedwith changes in chromatin structure and nuclear architecture. Although it isknown that ESCs are only responsive to differentiation signals during the G1 phaseand inhibition of DNA synthesis impairs the exit from the naïve pluripotentground state, the mechanisms involved remain elusive. To fully understand gene regulation it is crucial to study the chromatin-transcription factors (TFs) interactions. In this work, we used advanced microcopy technics to study the dynamicalorganization of Sox2 and Oct4, key pluripotency TFs, and heterochromatinassociated protein 1 (HP1) along the cell cycle in ESCs. We transfected ESClines expressing the fusion proteins Sox2-YPet or Oct4-YPet with PCNA-RFP toidentify cells in early, middle or late S phase. We measured fluorescencefluctuations as a function of time by confocal microscopy and analyzed fluorescence correlation spectroscopy data with a model thatcontemplates fast and slow interactions with DNA. Our results evidence that HP1 diffusion fraction increases in late S respectto middle and early S phase, consistent with heterochromatin replication takingplace in late S.Deep comprehension of pluripotency TF dynamics along cell cycle isfundamental to understand molecular mechanisms involved in cell fate decisions.