Effect of knockdown of Zbtb9 on gene expression during adipogenic differentiation of 3T3-L1 preadipocytes

Adipocytes play a critical role in metabolic homeostasis. Here we report that Zbtb9 acts as a positive regulator of PPARγ transcriptional activity in 3T3-L1 mature adipocytes, and PPARγ target gene expression was decreased when Zbtb9 deficiency was induced by shRNA-mediated knockdown (KD), establishing Zbtb9 as a newly identified PPARγ cofactor. Given the central role of PPARγ in adipogenesis, we also sought to investigate the role of Zbtb9 in adipogenesis in 3T3-L1 cells. Surprisingly, lipid droplet formation was significantly increased in Zbtb9 KD cells compared with the control, as was the expression of adipogenic genes including Pparg, Adipoq, Fabp4, and Cd36. The transcriptome of Zbtb9-KD fibroblasts, prior to the initiation of differentiation showed that the E2F targets pathway was significantly upregulated compared to the control cells. In addition, E2F activity was increased in Zbtb9-KD fibroblasts using luciferase reporter assay. Accordingly, RB phosphorylation was enhanced in Zbtb9-KD cells. Collectively, these results demonstrate that Zbtb9 inhibits adipogenesis as a negative regulator of Pparg expression via altered pRB-E2F1 signaling. Together, our findings revealed complex cell-state dependent roles of Zbtb9 in adipocytes, identifying a new molecule that may be important in the pathogenesis and treatment of obesity and T2D.