IDENTIFYING INHIBITORY NETWORK OF TOTIPOTENCY IN MOUSE EMBRYONIC STEM CELL

Abstract

Expanded-pluripotent 2-cell-like state is known to be regulated via retroviral MERVL in the mouse embryonic stem cell genome. Using a CRISPR-dCas9 CAPTURE system, our study revealed the compendium of regulators associated with the MERVL loci. Among the regulators was SSRP1, which served as a key inhibitor, governing the expression of the MERVL and 2-Cell genes through direct binding. Knockdown of SSRP1 triggered chromatin accessibility at the MERVL loci and 2-Cell genes, ensuing their expression. Mechanistically, KD of SSRP1 led to nucleosome disassembly at the TSS of 2C genes, thus activating their expression. Overall, we provided an encyclopaedic network of MERVL regulators and delineated the transitional roadmap towards the 2C-like-state, on which the SSRP1 is the forbidding gatekeeper. Also, we reported that a panel of ribosomal proteins ( e.g. RPL14, RPL18 and RPL23), besides their fundamental roles in translation, safeguarded the identity of mESC and modulated the 2C-like-state transition.