Functions of calcineurin-NFAT signaling pathway in human embryonic stem cells

Calcineurin-NFAT signaling is associated with a wide range of biological processes and diseases. Our previous study showed that this pathway plays a critical role in mouse embryonic stem cell (mESC) differentiation. However, its function in human ESCs (hESCs) remains unclear. Here, we report that expression of PPP3CC, the gene encoding the catalytic subunit of calcineurin, increases along with the process of hESC differentiation, and its knockdown (KD) enhances the self-renewal ability of hESCs with a simultaneous reduction in the expression of differentiation-associated markers regardless of culture conditions. Moreover, we observed that NFATC3 translocates from the cytoplasm to the nucleus when hESCs exit from a self-renewal state. These results indicate that calcineurin-NFAT signaling is activated and required during hESC differentiation. Mechanistically, we also found that in hESCs NFATC3 interacts with JUN， one of AP-1 complex subunit, and co-expression of exogenous NFATC3 and JUN upregulates lineage markers remarkably even under a self-renewal culture condition. Additionally, inhibition of this cascade represses MAPK signaling rapidly, including ERK1/2, JNK and P38. Taken together, this study delineates the importance of the calcineurin-NFATC3/JUN signaling cascade for the pluripotency maintenance of hESCs.