Transcriptional Basis of Adipogenesis

Our lab is interested in virtually all aspects of fat cell development, but none more so than the transcriptional cascade that promotes differentiation of the adipogenic lineage.

We are using genetic, biochemical, and physiological approaches to understanding this complex process. Some specific areas of focus include:

a. Identification of novel transcription factors and pathways acting downstream or in parallel to PPAR g .
Studies include the screening of a retroviral adipocyte cDNA library in target cells that have been engineered to lack PPAR g . Fluorescently "tagging" the expression of fat cell genes in these cells allows us to use flow cytometry to select for clones that promote transcription in the absence of PPAR g .

b. Computational prediction of adipose-selective cis-regulatory elements.
In collaboration with Eric Lander's group at the Whitehead Institute Center for Genome Research, we are using in silico methodology to identify important conserved regulatory elements in the flanking regions of adipose-selective genes.

c. Functional studies of the role of O/E proteins in adipogenesis.

The bHLH protein O/E-1 has been shown to promote adipogenesis in NIH-3T3 fibroblasts. We are performing both gain-of-function and loss-of-function experiments designed to place O/E-1 and other O/E isoforms in the transcriptional cascade leading to adipogenesis. In collaboration with Peter Akerblad and Mikael Sigvardsson, we are also using transgenic and knockout mice to study other functions of O/E proteins in adipose tissue biology.

d. Transcriptional regulation of specific adipose-selective genes.
Projects are underway designed to analyze the tissue-specific expression of the leptin, adiponectin, adipsin, and UCP1 genes. These studies utilize powerful "recombineering" techniques to modify bacterial artificial chromosomes that can then be used to perform critical loss-of-function tests on putative regulatory elements in transgenic mice. Data from other studies, such as DNAse hypersensitivity mapping, in silico cross-species homology, and in vitro trans-activation studies are integrated to provide a comprehensive picture of how these genes are regulated in a tissue-specific manner and in response to various metabolic challenges.