Research

Gene expression profiling of potential peroxisome proliferator-activated receptor (PPAR) target genes in human hepatoblastoma cell lines inducibly expressing different PPAR isoforms

Keisuke Tachibana¹, Yumi Kobayashi¹, Toshiya Tanaka², Masayuki Tagami¹, Akira Sugiyama^2,3, Tatsuya Katayama¹, Chihiro Ueda¹, Daisuke Yamasaki¹, Kenji Ishimoto¹, Mikako Sumitomo¹, Yasutoshi Uchiyama^2,3, Takahide Kohro², Juro Sakai², Takao Hamakubo², Tatsuhiko Kodama² and Takefumi Doi^1,4

¹  Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan

²  Laboratory for System Biology and Medicine, The Research Center for Advanced Science and Technology, the University of Tokyo, Tokyo, Japan

³  Perseus Proteomics Inc, Tokyo, Japan

⁴  Graduate School of Medicine, Osaka University, Osaka, Japan

Nuclear Receptor 2005, 3:3doi:10.1186/1478-1336-3-3

Published:	3 October 2005

Abstract

Background

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors and commonly play an important role in the regulation of lipid homeostasis. To identify human PPARs-responsive genes, we established tetracycline-regulated human hepatoblastoma cell lines that can be induced to express each human PPAR and investigated the gene expression profiles of these cells.

Results

The expression of each introduced PPAR gene was investigated using the various concentrations of doxycycline in the culture media. We found that the expression of each PPAR subtype was tightly controlled by the concentration of doxycycline in these established cell lines. DNA microarray analyses using these cell lines were performed with or without adding each subtype ligand and provided much important information on the PPAR target genes involved in lipid metabolism, transport, storage and other activities. Interestingly, it was noted that while ligand-activated PPARδ induced target gene expression, unliganded PPARδ repressed these genes. The real-time RT-PCR was used to verify the altered expression of selected genes by PPARs and we found that these genes were induced to express in the same pattern as detected in the microarray analyses. Furthermore, we analysed the 5'-flanking region of the human adipose differentiation-related protein (adrp) gene that responded to all subtypes of PPARs. From the detailed analyses by reporter assays, the EMSAs, and ChIP assays, we determined the functional PPRE of the human adrp gene.

Conclusion

The results suggest that these cell lines are important tools used to identify the human PPARs-responsive genes.