Project description:Dexamethasone (DEX), a synthetic ligand for glucocorticoid receptor (GR), is routinely used to stimulate adipogenesis in culture. GR-depleted preadipocytes show adipogenesis defects one week after induction of differentiation. However, it has remained unclear whether GR is required for adipogenesis in vivo. By deleting GR in precursors of brown adipocytes, we found unexpectedly that GR is dispensable for brown adipose tissue development in mice. In culture, GR-deficient primary or immortalized white and brown preadipocytes showed severely delayed adipogenesis one week after induction of differentiation. However, when differentiation was extended to 3 weeks, GR-deficient preadipocytes showed similar levels of adipogenesis marker expression and lipid accumulation as the wild type cells, indicating that DEX-bound GR accelerates, but is dispensable for, adipogenesis. Consistently, DEX accelerates, but is dispensable for, adipogenesis in culture. We show that DEX-bound GR accelerates adipogenesis by directly promoting the expression of adipogenic transcription factors C/EBPb, C/EBPd, C/EBPa, KLF5, KLF9 and PPARg in the early phase of differentiation. Mechanistically, DEX-bound GR recruits histone H3K27 acetyltransferase CBP to promote activation of C/EBPb-primed enhancers of adipogenic genes. These results clarify the role of GR in adipogenesis in vivo and demonstrate that DEX-mediated activation of GR accelerates, but is dispensable for, adipogenesis.
