Novel regulatory mechanisms in adipogenesis: role of the ES-cell transcription f

East Carolina University, Greenville NC

Investigators

Abstract

DESCRIPTION (provided by applicant): The differentiation program leading to the adipocyte phenotype is controlled by a cascade of transcription factors, the CCAAT/enhancer binding proteins (C/EBPs) and a nuclear hormone receptor, peroxisome proliferator activated receptor ??? (PPAR?). C/EBP? and C/EBPa are rapidly induced in the early stage of adipogenesis and subsequently drive C/EBP? and PPAR? expression. C/EBP? and PPAR? can induce each other in a positive feedback loop and directly activate many of the genes for terminal adipocyte differentiation. PPARg is considered the master regulator of adipogenesis as it alone can induce differentiation in C/EBP? deficient murine embryonic fibroblasts (MEFs), while C/EBP? is incapable of driving differentiation in the absence of PPAR. Superimposed on this framework of C/EBPs and PPAR?, we have recently identified the transient expression of the embryonic stem cell transcription factor Zfp206 and its splice variant ZScan10/201. Zfp206 expression occurs at confluency and is attenuated by day 3 as expression switches to the splice variant. The splice variant lacks the entire zinc-finger DNA binding domain and we propose functions as a dominant negative. Our hypothesis is that expression of Zfp206 is essential for maintenance of the differentiation potential and as terminal differentiation is established with the expression of PPARg, Zfp206 expression is diminished. The transient expression of the splice variant ZScan insures Zfp206 effects are negated. To test our hypothesis we will define the role of Zfp206 in the differentiation program through the use of knock out and over expression studies as well as the identification of genes activated by this embryonic stem cell transcription factor. Additionally we will determine the mechanism by which Zfp206 expression is controlled through analysis of the 5'flanking region and first intron. The studies will yield information on a novel regulatory system in the adipogenic differentiation program previously thought to be localized to embryonic stem cells. PUBLIC HEALTH RELEVANCE: Adipose tissue plays a critical role with respect to the pathology of both diabetes and obesity and has become recognized as a dynamic endocrine-like tissue, synthesizing and secreting proteins responsible for regulation of the balance between energy storage and energy expenditure. If we are to identify new diagnostic biomarkers and discover new treatment options, we need to understand the regulation of the differentiation process as well as the maintenance of the differentiated phenotype in this complex tissue. Control of the differentiation process has been demonstrated to rest largely with two families of transcription factors, the C/EBPs and PPAR?. We have recently identified the transient expression of the embryonic stem cell transcription factor Zfp206 and its splice variant ZScan10/201, that we propose bring an additional level of regulation to the differentiation process. Our hypothesis is that expression of Zfp206 is essential for maintenance of the differentiation potential and as terminal differentiation is established with the expression of PPAR?, Zfp206 expression is diminished. Thus, the proposed studies examining the mechanism of action of Zfp206 and Zscan 10/201 are expected to yield information on a novel target for control of adipocyte differentiation and thus fundamental insights into obesity and diabetes.