Study of the roles of autophagy in the differentiation of hematopoietic stem cells

Abstract

Hematopoietic stem cells (HSCs) in bone marrow are pluripotent cells that are capable to constitute the hematopoiesis system through self-renewal and differentiation into immune cells and red blood cells. To keep the hematopoiesis for a life time, the maintenance of HSCs is tightly regulated. Autophagy is a self-degradation pathway for cell homeostasis and Atg5 is essential molecule for autophagy. However, the role of Atg5 in hematopoietic stem cells is unknown. $Vav_Atg5^{-/-}$ mice that have defective autophagy function in HSCs due to Atg5 depletion showed survival defect and reduced number of HSCs. Furthermore, multi-lineage progenitor cells and differentiated immune cells and erythrocyte from Vav_Atg5 were not well differentiated compared to WT mice. Also, Atg5 defective HSCs had more accumulated mitochondria and higher ROS level and it leaded to increased apoptosis in late differentiation stage of HSCs. Although HSCs from $Vav_Atg5^{-/-}$ mice showed higher proliferation ratio than normal HSCs, their reconstitution ability were reduced. These data mean Atg5 dependent autophagy is crucial for maintenance of number and function in HSCs.