REST–miR-21–SOX2 axis maintains pluripotency in E14Tg2a.4 embryonic stem cells

• How cellular context maintain pluripotency in mouse embryonic stem cells (mESCs) is beginning to be understood.
• REST represses miR-21 expression in E14Tg2a.4 mouse ESCs cultured in the absence of feeder cells.
• MiR-21 directly suppresses Sox2, one of the core pluripotency regulators.
• REST–miR-21–Sox2 axis regulates pluripotency.
• A working model describing, “maintenance factors” versus “core factors” of mESC pluripotency

Our previous studies have shown that the regulatory network that maintains pluripotency in mouse embryonic stem cells (mESCs) is regulated in a context-dependent manner and can be modulated, at least in part, by re-calibration of an intracellular network of pluripotency factors as well as cues arising from the extracellular matrix. The transcriptional repressor REST represses miR-21 and, thus, regulates self-renewal in E14Tg2a.4 mESCs cultured in the absence of mouse embryonic fibroblast feeder cell effects. However, how miR-21 connects to the nuclear regulatory network has not been clear. Here, we show that miR-21, a direct target of REST-mediated repression, directly targets Sox2. Exogenously added miR-21 to mESCs decreases the expression of Sox2, decreasing mESC self-renewal, and this effect of miR-21 on mESC self-renewal can be blocked by expression of exogenous Sox2. Conversely, destabilization of Sox2 by miR-21 can be blocked by anti-miR-21. Thus, the REST–miR-21–Sox2 axis connects REST to the core nuclear pluripotency regulators in E14Tg2a.4 mESCs cultured in the absence of feeder cells.