Identification of microRNA Targets using microRNA Modulation Techniques and Gene Expression Arrays

MicroRNAs (miRNAs) have been shown to regulate gene expression through both translational attenuation and degradation of messenger RNAs (mRNAs). Though these small noncoding RNAs are predicted to play a signicant role in development, differentiation, and disease etiology, validation of miRNA targets remains a challenge. miRNA mimics and inhibitors are valuable tools for elucidating the roles of miRNAs. Here we have transfected a human liver cell line alternately with a miRNA mimic and inhibitor to miR-122 and analyzed mRNA expression changes by whole genome microarray. By examining the overlap of messages down-regulated by miRNA mimics and up-regulated by miRNA inhibitors, we robustly identify miRNA-regulated messages, many of which have canonical seed matches and some which are not identied by standard target prediction programs.