High autophagic flux guards ESC identity through coordinating autophagy machinery gene program by FOXO1.

Although much is known about transcriptional networks that control embryonic stem cell (ESC) self-renewal and differentiation, the metabolic regulation of ESC is less clear. Autophagy is a catabolic process that is activated under both stress and normal conditions to degrade damaged organelles and aggregated proteins, and thus plays pivotal roles in somatic and adult stem cell function. However, if and how ESCs harness autophagy to regulate stemness remains largely unknown. Recently, we have defined that autophagy is essential for mitochondrial homeostasis regulation in pluripotency acquirement and maintenance. Here we identified high autophagic flux as an essential mechanism to maintain ESC identity. We show that mouse ESCs exhibit a high autophagic flux that is maintained by coordinating expression of autophagy core molecular machinery genes through FOXO1, a forkhead family transcription factor. Tapering autophagic flux by manipulating either Atg3 or Foxo1 expression compromised ESC self-renewal, pluripotency, and differentiation that could be restored by gain of wild-type but not function-deficient Atg3 or Foxo1 mutants, respectively. Our results define a newly recognized role of autophagic flux in mouse ESC identity maintenance that links cellular catabolism to ESC fate regulation.