UCSF

The identification of beige fat within the last decade, its ability to burn energy in adult humans, and its great potential for therapeutic applications has motivated many to work towards understanding how beige fat is made. Although several proteins have been identified as important for beige fat differentiation, it is clear that the differences that distinguish beige fat from other types of fat cannot be explained by the presence of these proteins alone. Additional regulatory proteins, including transcription factors and their co-factor proteins, must be involved.

I took advantage of two important developments in the field of fat differentiation to develop two high throughput approaches that identified new transcription factors involved in beige fat: (1) our ability to culture beige fat cells by differentiating white fat pre-adipocytes in the presence of Rosiglitazone and (2) the established role for PRDM16 as required for beige fat differentiation. In brief, I combined RNA-seq data from beige fat cells and proteomics data from Rosiglitazone-dependent PRDM16 protein complexes to identify a set of candidate transcription factors involved in beige fat differentiation. The most promising candidate among this pool of putative beige fat regulatory transcription factors was GTF2IRD1.

I determined that GTF2IRD1 is a PRDM16-interacting transcription factor that is enriched in beige and brown fat cells. In vivo, GTF2IRD1 is enriched in brown adipose tissue and is increased in beige and brown fat in response to beta-3-adrenergic stimulus. In the presence of the potent PPARgamma agonist Rosiglitazone, GTF2IRD1 overexpression enhances and shRNA-mediated knockdown reduces beige fat differentiation. GTF2IRD1 represses TGF-beta-mediated inhibition of beige fat differentiation. In summary, my data strongly supports that GTF2IRD1 is an essential regulator of beige fat differentiation through interaction with PRDM16 and inhibition of TGF-beta-mediated repression of differentiation.