Intracellular Ca²⁺ Homeostasis and Nuclear Export Mediate Exit from Naive Pluripotency

Progression through states of pluripotency is required for cells in early mammalian embryos to transition away from heightened self-renewal and toward competency for lineage specification. Here, we use a CRISPR mutagenesis screen in mouse embryonic stem cells (ESCs) to identify unexpected roles for nuclear export and intracellular Ca²⁺ homeostasis during the exit out of the naive state of pluripotency. Mutation of a plasma membrane Ca²⁺ pump encoded by Atp2b1 increased intracellular Ca²⁺ such that it overcame effects of intracellular Ca²⁺ reduction, which is required for naive exit. Persistent self-renewal of ESCs was supported both in Atp2b1^-/-Tcf7l1^-/- double-knockout ESCs passaged in defined media alone (no LIF or inhibitors) and in wild-type cells passaged in media containing only calcitonin and a GSK3 inhibitor. These new findings suggest a central role for intracellular Ca²⁺ in safeguarding naive pluripotency.