TG-interacting factor 1 regulates mitotic clonal expansion during adipocyte differentiation.

Obesity is one of the significant health challenges in the world and is highly associated with abnormal adipogenesis. TG-interacting factor 1 (TGIF1) is essential for differentiating murine adipocytes and human adipose tissue-derived stem cells. However, the mode of action needs to be better elucidated. To investigate the roles of TGIF1 in differentiation in-depth, CRISPR/Cas9 knockout technology was performed to generate TGIF1-silenced preadipocytes. The absence of TGIF1 in 3 T3-F442A preadipocytes abolished lipid accumulation throughout the differentiation using Oil Red O staining. Conversely, we established 3 T3-F442A preadipocytes stably expressing TGIF1 and doxycycline-inducible TGIF1 in TGIF1-silenced 3 T3-F442A preadipocytes. Remarkably, the induction of TGIF1 by doxycycline during the initial differentiation phase successfully promoted lipid accumulation in TGIF1-silenced 3 T3-F442A cells. We further explored the mechanisms of TGIF1 in early differentiation. We demonstrated that TGIF1 promoted the mitotic clonal expansion via upregulation of CCAAT/enhancer-binding proteins β expression, interruption with peroxisome proliferators activated receptor γ downstream regulation, and inhibition of p27kip1 expression. In conclusion, we strengthen the pivotal roles of TGIF1 in early differentiation, which might contribute to resolving obesity-associated metabolic syndromes. • We demonstrated that TGIF1 was essential for early differentiation by using several advanced techniques in preadipocytes, including enforced overexpression, CRISPR/Cas9 knockout, and Tet-inducible gene expression. • TGIF1 contributes to the early differentiation through novel mechanisms, including upregulation of C/EBP β expression, interference in PPAR γ downstream regulation, and inhibition of p27kip1 expression, thereby promoting mitotic clonal expansion in the early differentiation. • We conclude that p27kip1, a PPAR γ -regulated gene, is suppressed by TGIF1 in early differentiation until the endogenous PPAR γ ligands production which is tightly linked to mitotic clonal expansion to strengthen the binding ability of PPAR γ to the promoter of p27kip1 and stop the cell cycle to proceed to differentiation. [ABSTRACT FROM AUTHOR]