Gretchen J. Darlington, Ph.D.
Departments of Pathology, Molecular & Human Genetics, Molecular and Cellular Biology, and the Huffington Center on Aging
B.A., University of Colorado
Ph.D., University of Michigan
My laboratory is currently investigating the role of the C/EBP family of transcription factors in the acute phase or inflammatory response of the liver, in the differentiation of adipose tissue in vivo, and the gene expression patterns that correlate with longevity. Our laboratory has studied the molecular mechanisms that regulate the acute phase or inflammatory response and we have identified a number of factors that are important in the transcriptional regulation of the acute phase genes, including C/EBP family of transcription factors. In order to investigate the role of the C/EBP genes in vivo, we carried out experiments in which the C/EBPa gene was mutated in mice. The C/EBPa knockout mice have numerous interesting phenotypes, among them is the observation that in the newborn animals, the acute phase response is totally lacking. We have begun to dissect the molecular changes that occur in the knockout animals in order to establish the molecular basis for the dependence of the inflammatory response on C/EBP C/EBPa.
A second area of interest is the role of C/EBPa in adipocyte differentiation. The knockout animals have demonstrated that brown adipose tissue development is delayed but ultimately reaches full differentiation in the absence of C/EBPa. In contrast, white adipose tissue is completely lacking in animals that fail to express C/EBPa protein. The knockout animal model provides a unique opportunity to identify the genes that are governed by C/EBPa which are responsible for failure to form white adipose tissue. Our future directions in this area are to clone the differentially expressed genes in the adipose tissues of the knockout mice, compared to their normal littermates, in order to identify genes whose activities are required for differentiation of the white adipose tissue lineage. In addition, we will define the critical promoter regions of the C/EBPa that dictate gene expression in white adipose tissue. A definition of this target may permit modulation of C/EBPa expression, which in turn may alter the amount or activity of target genes in white adipose tissue. This area of investigation will be important in understanding potential therapeutic measures that may be taken to alter fat composition. The association of obesity with adult onset diabetes suggests that modulation of the degree of obesity may provide a therapeutic approach to this common disorder.
A third area of interest is the definition of the molecular basis for longevity in three different long-lived mouse strains. A single gene mutation in a pituitary-specific transcription factor (Pit-1) leads to increased longevity in mice. Two other mutations (P66shc and growth hormone receptor releasing hormone) also result in increased longevity. By comparing the gene expression profiles of these strains with their wild type counterparts and with each of the other mutant strains, we will identify candidate genes for longevity. These studies will be done using microarray technology.
Amador-Noguez D, Yagi K, Darlington, G. (2004) Gene expression profile of long-lived Ames dwarf mice and Little mice. Aging Cel. In Press.
Mackey S, Singh P, Darlington GJ. (2003) Making the Liver Young again. Hepatology, 38:1349-52, 2003.
Welm AL, Timchenko NA, Darlington GJ. (1999) C/EBP regulates generation of C/EBP, isoforms through activation of specific proteolytic cleavage. Mol. Cell Biol. 19:1695-1704.
Burgess-Beusse BL, Darlington GJ. (1998) C/EBP is critical for the neonatal acute phase response to inflammation. Mol. Cell Biol. 18:7269-7277.
Darlington GJ, Ross S, MacDougald OA. (1998) The role of C/EBP genes in adipocyte differentiation. J. Biol. Chem. 273:30057-30060.
Timchenko NA, Wilde M, Nakanishi M, Smith JR, Darlington GJ. (1996) CCAAT/enhancer binding protein a(C/EBP ) inhibits cell proliferation through the p21 (WAF-1/CIP-1/SDI-1) protein. Genes Dev. 10:804-815.
Wang ND, et al. (1995) Impaired energy homeostasis in C/EBP knockout mice. Science 269:1108-1112.