Transcription factor Snail is a novel regulator of adipocyte differentiation via inhibiting the expression of peroxisome proliferator-activated receptor γ

Abstract

Snail belongs to the superfamily of zinc-finger transcription factors and plays a crucial role in processes regulating cell fate, such as the formation of mesoderm and initiation of epithelial-mesenchymal transition. We have previously discovered that Snail modulates adiponectin expression in 3T3-L1 cells during adipogenesis. In the present study, we elucidated the functional role of Snail in adipocyte differentiation and its underlying molecular mechanism. Snail expression was dramatically decreased during adipogenesis in 3T3-L1 cells. Overexpression of Snail blocked adipocyte differentiation by suppressing the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT-enhancer-binding protein alpha, while knockdown of Snail expression stimulated adipogenesis in 3T3-L1 cells. Chromatin immunoprecipitation assay and luciferase assay showed that Snail inhibits the transcriptional activity of the PPARγ gene by directly binding to the E-box motifs in the PPARγ promoter. Wnt10b induced phosphorylation of glycogen synthase kinase 3 beta (GSK3β), leading to inhibition of adipogenesis in 3T3-L1 cells in accordance with increased expression of Snail, whereas adipogenic capacity was restored in Snail siRNA-transfected preadipocytes. LiCl (a GSK3β inhibitor)-treated cells also showed increased expression of Snail, with a reduced adipogenic potential. Snail-overexpressing 3T3-F442A cells did not differentiate into mature adipocytes in immunodeficient nude mice. Taken together, Snail is a novel regulator of adipocyte differentiation, which acts by direct suppression of PPARγ expression. Our data also indicate that the expression of Snail is mediated by the Wnt-GSK3β signaling pathway.

A Proteomic Analysis Reveals That Snail Regulates the Expression of the Nuclear Orphan Receptor Nuclear Receptor Subfamily 2 Group F Member 6 (Nr2f6) and Interleukin 17 (IL-17) to Inhibit Adipocyte Differentiation *

“…Another report suggested a direct repression of PPAR␥ by Snail based on a luciferase assay (12). However, to the light of our results and the capacity of Snail to bind multiple promoters, it is difficult to know if PPAR␥ inhibition by Snail is functionally relevant in 3T3-L1 cells or is another unspecific repressor capacity of Snail.…”

“…Snail1 ectopic expression inhibits the adipocyte differentiation program (6,12). Snail effect on adipogenesis was proposed to be mediated, among others, by activation of AKT (6) and was associated to an apparent inhibition of PPAR␥ and C/EBP␣ expression (12). Similar results were obtained in preventing the differentiation of bone marrowderived mMSCs to osteoblasts or adipocytes (6).…”

“…Alike mMSCs, confluent 3T3-L1 preadipocytes differentiate to adipocytes upon exposure to a mixture of adipogenic inducers (10). Upon adipogenic differentiation, Snail expression is almost negligible in 3T3-L1 cells (12). Snail1 ectopic expression inhibits the adipocyte differentiation program (6,12).…”

“…Upon adipogenic differentiation, Snail expression is almost negligible in 3T3-L1 cells (12). Snail1 ectopic expression inhibits the adipocyte differentiation program (6,12). Snail effect on adipogenesis was proposed to be mediated, among others, by activation of AKT (6) and was associated to an apparent inhibition of PPAR␥ and C/EBP␣ expression (12).…”

Systematic dissection of genomic features determining transcription factor binding and enhancer function

“…Third, the TFs that recognize several of the positively correlated motifs are known to promote adipocyte differentiation (64,65) or regulate gene expression in various stages of adipogenesis (54,(66)(67)(68)(69). Conversely, the TFs that recognize several of the negatively correlated motifs are transcriptional repressors involved in inhibiting adipocyte-specific genes (68,70) or promoting an alternate cell fate (71) (SI Appendix, Supplemental Note).…”