Fine-tuned calcium homeostasis is crucial for murine erythropoiesis.

Intracellular calcium (Ca²⁺) is a crucial signaling molecule involved in multiple cellular processes. However, the functional role of Ca²⁺ in terminal erythropoiesis remains unclear. Here, we uncovered the dynamics of intracellular Ca²⁺ levels during mouse erythroid development. By using the calcium ionophore ionomycin, we found that low Ca²⁺ levels are required for the expansion of erythroid progenitors, whereas higher Ca²⁺ levels led to the differentiation and proliferation of early-stage erythroblasts. Intracellular Ca²⁺ levels were then gradually reduced, which is required for the nuclear condensation and polarisation at the late stage of erythroid differentiation. However, elevated Ca²⁺ levels in late-stage erythroblasts, achieved by using ionomycin, promoted erythroid enucleation via calmodulin (CaM)/calcium/calmodulin-dependent protein kinase kinase 1 (CaMKK1)/AMPK signaling. These data suggest that the reduction of intracellular Ca²⁺ plays a double-edged role at the late stage of erythroid differentiation, which is beneficial for nuclear condensation but compromises terminal enucleation. Our study highlighted the importance of the fine-tuned regulation of intracellular Ca²⁺ during terminal erythropoiesis, providing cues for the efficient generation of mature and enucleated erythrocytes in vitro.