Asymmetric Division in a Two-Cell-Like State Rejuvenates Embryonic Stem Cells

An intriguing question in biology is whether all cells age. Embryonic stem cells (ESCs) stand out as rare normal cells capable of indefinite in vitro passage. However, it remains unclear how ESC lineage immortality is achieved and whether individual ESCs are immortal. Using long term live-cell imaging to follow fates of single ESCs, we show here that lineage renewal of ESCs can be attributed to a sporadic state characterized by the expression of markers found in two-cell embryos. During this state, cells undergo asymmetric divisions, giving rise to one dying branch, and one that reverts to the pluripotent state. Importantly, the latter lineage exhibits signs of rejuvenation, including reduced DNA damage and enhanced chimeric efficiency. These findings underscore the crucial role of asymmetric cell division in maintaining the long-term health of the ESC lineage against mounting damage within individual cells. Overall design: To trace the fate of 2C-like cells, we established a mouse embryonic stem (mES) cell line expressing a MERVL promoter driven GFP reporter (MERVL::GFP) to mark the 2C-like state, and H2B-mIFP to track cells. The MERVL::GFP signal strongly correlates with endogenous MERVL-Gag protein staining.