NCOA2 promotes the return of hematopoietic stem cells to quiescence after irradiation stress by regulating FOXO3a-dependent mitophagy.

Hematopoietic stem cells (HSCs) are responsible for replenishing blood cells under stress conditions through increasing proliferation and differentiation. After the hematopoietic function has reconstructed, HSCs must re-enter a quiescent state to avoid their depletion, whereas the underlying mechanisms remain to be elucidated. Here, we show that the translocation of nuclear receptor coactivator 2 (NCOA2) into the nucleus is gradually increased in HSCs during the hematopoietic recovery phase after sub-lethal dose irradiation (IR). Although deletion of NCOA2 only slightly affects the steady state hematopoiesis, its deficiency leads to HSC pool exhaustion and delayed hematopoietic recovery after exposure to IR. Further investigations reveal that loss of NCOA2 decreases the quiescence, survival, and long-term reconstituting ability of HSCs following IR due to increased mitochondria-derived oxidative stress. Mechanistically, NCOA2 promotes the clearance of activated or damaged mitochondria by coactivating FOXO3a-dependent transcription of PINK1, which drives HSCs to return to quiescence after being activated by IR stress. Collectively, our findings demonstrate a critical role of NCOA2 in facilitating the restoration of HSC homeostasis after IR via the FOXO3a-PINK1-mediated mitophagy axis and thus provide an additional strategy to prevent hematopoietic failure induced by IR.