Reconstruction of gene association network reveals a transmembrane protein required for adipogenesis and targeted by PPARγ
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We have developed a method for reconstructing gene association networks and have applied this method to gene profiles from 3T3-L1 cells. Priorization of the candidate genes pinpointed a transcript annotated as APMAP (adipocyte plasma membrane-associated protein). Functional studies showed that APMAP is upregulated in murine and human adipogenic cell models as well as in a genetic mouse model of obesity. Silencing APMAP in 3T3-L1 cells strongly impaired the differentiation into adipocytes. Moreover, APMAP expression was strongly induced by the PPARγ ligand rosiglitazone in adipocytes in vitro and in vivo in adipose tissue. Using ChIP-qPCR and luciferase reporter assays, we show a functional PPARγ binding site. In addition, we provide evidence that the extracellular C-terminal domain of APMAP is required for the function of APMAP in adipocyte differentiation. Finally, we demonstrate that APMAP translocates from the endoplasmatic reticulum to the plasma membrane during adipocyte differentiation.
KeywordsAdipogenesis APMAP PPARγ Transcriptional regulation Gene expression Gene networks
This work was supported by the Austrian Ministry for Science and Research (GEN-AU projects GOLD and BIN) and the Austrian Science Fund SFB (Project Lipotoxicity). PPARγ-MEFs were a gift from Dr. E. Rosen. OP9 cells were kindly provided by B. Pickel and SGBS cells by Novo Department of Pediatrics and Adolescent Medicine, University of Ulm. We thank David J. Steger and Mitch A. Lazar for providing ChIP material. The authors acknowledge the technical assistance provided by Stephan Seifriedsberger, Florian Stoeger, Martina Schweiger and Marie Loh.
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