Identification of zinc finger protein Bcl6 as a novel regulator of early adipose commitment

Adipose tissue is a key determinant of whole-body metabolism and energy homeostasis. Unravelling the transcriptional regulatory process during adipogenesis is therefore highly relevant from a biomedical perspective. In these studies, zinc finger protein B-cell lymphoma 6 (Bcl6) was demonstrated to have a role in early adipogenesis of mesenchymal stem cells. Bcl6 is enriched in preadipose versus non-preadipose fibroblasts and shows upregulated expression in the early stage of adipogenesis. Gain- and loss-of-function studies revealed that Bcl6 acts as a key regulator of adipose commitment and differentiation both in vitro and ex vivo RNAi-mediated knockdown of Bcl6 in C3H10T1/2 cells greatly inhibited adipogenic potential, whereas Bcl6 overexpression enhanced adipogenic differentiation. This transcription factor also directly or indirectly targets and controls the expression of some early and late adipogenic regulators (i.e. Zfp423, Zfp467, KLF15, C/EBPδ, C/EBPα and PPARγ). We further identified that Bcl6 transactivated the signal transducers and activators of transcription 1 (STAT1), which was determined as a required factor for adipogenesis. Moreover, overexpression of STAT1 rescued the impairment of adipogenic commitment and differentiation induced by Bcl6 knockdown in C3H10T1/2 cells, thereby confirming that STAT1 is a downstream direct target of Bcl6. This study identifies Bcl6 as a positive transcriptional regulator of early adipose commitment.