Transcriptional shut-off of MAP kinase signaling enables pluripotency maintenance during diapause

Abstract

AbstractExposure of unicellular or multicellular organisms to adverse environmental conditions, including nutrient deprivation, may induce a state of suspended animation or diapause. The diapause minimizes the organism’s reliance on external energy sources and ensures survival. Among different forms of diapause, embryonic diapause, caused by a limited supply of nutrients to the growing embryos, is particularly challenging for the organism. Diapause embryos stop developing at the peak of pluripotent cell differentiation and maintain this undifferentiated yet entirely vital state despite the overall reduction in anabolic processes and genome-wide transcriptional repression. Using ES cells commonly employed to study the mechanism of embryonic diapause, we solve the paradox of the cell maintenance in an undifferentiated ES cell state during diapause. We find that broad transcriptional repression by long-term inhibition of the bromodomain and extra-terminal (BET) proteins causes diapause. These diapause ES cells upregulate a functionally linked group of genes encoding negative regulators of MAP kinase signaling (NRMKS), which play a crucial role in ES cell differentiation. We find that elevated NRMKS expression is a hallmark of the diapause cells and cells exposed to diapause-inducing conditions, including mTOR inhibition, and is required for the maintenance of ES cell pluripotency during diapause. Mechanistically, exposure of ES cells to diapause-inducing conditions leads to rapid decline of the Capicua transcriptional repressor (CIC) at the NRMKS gene promoters, followed by transcriptional upregulation of NRMKS genes. The mTOR and BET-dependent transcriptional switch supporting the undifferentiated state of the diapause ES cells suggests a broader usage of this mechanism in maintaining the undifferentiated state of metabolically dormant stem- or stem-like cells in different tissues.