Defining the role of oxygen tension in human neural progenitor fate

Hypoxia augments human embryonic stem cell self-renewal via hypoxia-inducible factor 2α (HIF2α) activated OCT4 (POU5F1) transcription. Hypoxia also increases the efficiency of reprogramming differentiated cells to a pluripotent-like state. Combined, these findings suggest that low oxygen (O2) tension would impair the purposeful differentiation of pluripotent stem cells. Here, we show that low O2 tension and HIF activity instead promotes appropriate hESC differentiation. Through gain and loss of function studies, we implicate O2 tension as a modifier of a key cell fate decision, namely whether neural progenitors differentiate towards neurons or glia. Furthermore, our data show that even transient changes in O2 concentration can affect cell fate through HIF by regulating the activity of MYC, a regulator of LIN28/let-7 that is critical for fate decisions in the neural lineage. We also identify key small molecules that can take advantage of this pathway to quickly and efficiently promote the development of mature cell types. We used microarrays to detail the global gene expression of human neural progenitor cells (NPC) cultured in physiological (2%) oxygen tension. By comparing NPCs with activated Hypoxia inducible factor (HIF) activity (DFX treatment) and NPCs with diminished HIF activity (HIF1β knockdown), we identified genes that are important for NPC fate decision under physiological oxygen concentration. We also used microarrays to obtain a global gene expression profiling during embryoid bodies formation using ES cells with diminished HIF activity. In HIF activation experiments, two ES lines and one iPS line-derived NPC were used, with or without DFX treatment for 5 days. In HIF1β knockdown experiments, NPCs were derived from either shHIF1β or control ES lines. In embryoid body formation experiments, day0 (ES stage) and day6 EBs were generated from either shHIF1β or control ES lines in 2% oxygen.