HIF-2α regulates Oct-4: effects of hypoxia on stem cell function, embryonic development, and tumor growth

TLDR

Stem cell division, differentiation, and function are regulated by microenvironmental signals, notably oxygen levels. A genetic knock‑in replacing HIF‑1α with HIF‑2α expands HIF‑2α‑specific targets such as Oct‑4, key for stem cell pluripotency. HIF‑2α binds the Oct‑4 promoter, upregulates Oct‑4, and its loss impairs primordial germ cells, while its overexpression causes developmental defects, defective hematopoietic differentiation, and tumor growth, underscoring Oct‑4 as a HIF‑2α‑specific target that drives tumor promotion.

Abstract

The division, differentiation, and function of stem cells and multipotent progenitors are influenced by complex signals in the microenvironment, including oxygen availability. Using a genetic “knock-in” strategy, we demonstrate that targeted replacement of the oxygen-regulated transcription factor HIF-1α with HIF-2α results in expanded expression of HIF-2α-specific target genes including Oct-4, a transcription factor essential for maintaining stem cell pluripotency. We show that HIF-2α, but not HIF-1α, binds to the Oct-4 promoter and induces Oct-4 expression and transcriptional activity, thereby contributing to impaired development in homozygous Hif-2 α KI/KI embryos, defective hematopoietic stem cell differentiation in embryoid bodies, and large embryonic stem cell (ES)-derived tumors characterized by altered cellular differentiation. Furthermore, loss of HIF-2α severely reduces the number of embryonic primordial germ cells, which require Oct-4 expression for survival and/or maintenance. These results identify Oct-4 as a HIF-2α-specific target gene and indicate that HIF-2α can regulate stem cell function and/or differentiation through activation of Oct-4 , which in turn contributes to HIF-2α's tumor promoting activity.