Serial analysis of gene expression and its applications

Serial analysis of gene expression or SAGE is a powerful technique that can be used for global analysis of gene expression. The result of a SAGE experiment is reported as a SAGE library, which contains the counts of various short segments (tags) of the cDNA clones. Unlike many other techniques SAGE does not require prior knowledge of the genes of interest and provides qualitative and quantitative data of every transcribed sequence in a particular cell or tissue type. The SAGE method is based on the isolation of unique sequence tags from individual mRNAs and serial concatenation of tags into long DNA molecules for lump-sum sequencing. SAGE has been widely applied to analyzing gene expression in many biological and medical studies. Some variations of the original SAGE were derived to improve the utility of SAGE in certain conditions for example microSAGE, miniSAGE, longSAGE, superSAGE, etc. In this review, we present an outline of the original method, the basic principle of SAGE, compare SAGE with microarray, some of the modified SAGE, discusses the advantages and limitations of SAGE as well as examples of applications.