Modern drug discovery increasingly demands new approaches for the screening, identification, validation and toxicity testing of new compounds prior to their entry into clinical trials. Cell based assays can be advantageous to researchers by providing a means to test compound libraries of interest directly in systems yielding information of physiological relevance. Regulation of mRNA transcription is an important cellular readout and is a primary biological control point of gene expression that is dependent on multiple factors. Increases or decreases in mRNA expression from target genes may result after treatment of cells with various compounds such as cytokines, GPCR ligands and second-messenger agonists or antagonists. Thus, the need for easy-to-perform, highly sensitive and reproducible mRNA quantitation is of paramount importance to the discovery and validation of new therapeutic compounds. To address this need and accelerate the drug discovery process, Bayer Corporation offers the QuantiGene assay system, providing direct quantitation of cellular transcription from a user-specified target gene. In these microplate-based assays, mRNA is released directly from lysed cells, captured via hybridization to a user-specified target probe set and measured by chemiluminescence. Branched DNA technology is utilized in the QuantiGene kit to directly measure mRNA levels from selected target genes. With the QuantiGene assay, specific mRNA expression can be measured from both suspension and adherent tissue culture cells, as well as from solid tissue. QuantiGene technology has proven to be a highly sensitive, reproducible and accurate means of quantifying mRNA from any cell line or tissue.