Med12 cooperates with multiple differentiation signals to enhance embryonic stem cell plasticity

Abstract

AbstractCell differentiation results from coordinated changes in gene transcription in response to combinations of signals. FGF, Wnt, and mTOR signals regulate the differentiation of pluripotent mammalian cells towards embryonic and extraembryonic lineages, but how these signals cooperate with general transcriptional regulators is not fully resolved. Here, we report a genome-wide CRISPR screen that reveals both signaling components and general transcriptional regulators for differentiation-associated gene expression in mESCs. Focusing on the Mediator subunitMed12as one of the strongest hits in the screen, we show that it regulates gene expression in parallel to FGF and mTOR signals. Loss ofMed12is compatible with differentiation along both the embryonic epiblast and the extraembryonic primitive endoderm lineage, but pluripotency transitions are slowed down, and the transcriptional separation between epiblast and primitive endoderm identities is enhanced inMed12-mutant cells. These cellular phenotypes correlate with reduced biological noise upon loss ofMed12. These findings suggest thatMed12regulates cellular plasticity through the priming of transcriptional changes during differentiation, thereby modulating the effects of a broad range of signals.