C/EBP homologous protein deficiency enhances hematopoietic stem cell function via reducing ATF3/ROS-induced cell apoptosis

Hematopoietic stem cells (HSCs) reside in a quiescent niche to reserve their capacity of self-renewal. Upon hematopoietic injuries, HSCs enter the cell cycle and encounter protein homeostasis problems caused by accumulation of misfolded proteins. However, the mechanism by which protein homeostasis influences HSC function and maintenance remains poorly understood. Here, we show that C/EBP homologous protein (CHOP), demonstrated previously to induces cell death upon unfolded protein response (UPR), plays an important role in HSCs regeneration. CHOP^-/- mice showed normal hematopoietic stem and progenitor cell frequencies in steady state. However, when treated with 5-FU, CHOP deficiency resulted in higher survival rates, associated with an increased number of HSCs and reduced level of Apoptosis. In serial competitive transplantation experiments, CHOP^-/- HSCs showed a dramatic enhancement of repopulation ability and a reduction of protein aggresomes. Mechanistically, CHOP deletion causes reduced ATF3 expression and further leads to decreased protein aggregation and ROS. In addition, CHOP^-/- HSCs exhibited an increased resistance to IR-induced DNA damage and improved HSCs homeostasis and function in telomere dysfunctional (G3Terc^-/- ) mice. In summary, these findings disclose a new role of CHOP in the regulation of the HSCs function and homeostasis through reducing ATF3 and ROS signaling.