Serial Analysis of Gene Expression

Serial analysis of gene expression (SAGE™) is a patented, large-scale mRNA-profiling technology that produces comprehensive, quantitative, and reproducible gene expression profiles (originally described in refs. 1 and 2 ). Unlike the alternative technologies of differential display and subtractive hybridization, SAGE produces a full catalog of all transcripts, not only differentially expressed genes, and unlike smaller arrays, SAGE needs no assumptions about the genes that are likely to be expressed, thus allowing the identification of novel genes (are among many excellent reviews, see refs. 3 –5 ). SAGE is based on generating clones of concatenated (linked) short sequence tags derived from mRNA from the target cells or tissue (Fig. 1 ).