Retinoic acid responsive genes in the murine hepatocyte cell line AML 12

Retinoic acid (RA) exerts profound effects on multiple aspects of vertebrate development, homeostasis and cellular differentiation. Although the liver is a major target organ for RA, no data exist on global expression of RA-responsive genes in hepatocytes. Therefore, the aim of this study was to characterize RA-responsive genes in a simple system, by using a non-transformed hepatic cell line that is able to express sufficient amounts of endogenous retinoic acid receptors (RARs). For this purpose we used the murine non-transformed hepatocyte cell line AML12. We performed analyses using a cDNA microarray containing 39,000 murine genes. We identified 15 genes that were up-regulated > or =2 fold while 3 were down-regulated > or =2 fold after 3 h treatment with all-trans RA. Following 24 h all-trans RA treatment, 26 genes were up-regulated > or =2 fold, whereas 48 genes were down-regulated > or =2 fold. For some of the genes not previously known to be regulated by RA, we confirmed the regulation by RA using real time PCR. Our data in AML12 cells provide a simple and physiologically relevant system to study RA action, without the influence of neoplastic transformation or artificial RAR over-expression. Furthermore, our data describe novel RA responsive genes and provide insight into the role of RA in important processes such as cholesterol metabolism, bile acid secretion, and oncogenesis, among others, that can be tested in future experiments in vivo.