ABSTRACT
Genome mapping projects have provided a wealth of information concerning the genomic sequence of higher organisms. This information can be used to investigate the underlying genetic changes giving rise to a variety of normal, developmental, and disease states. It is important, however, to study how genes work in concert rather than in isolation. Several methods are capable of determining global gene expression changes, including subtractive hybridization,1 differential display,2 and cDNA microarray hybridization.3 However, the numbers of different transcripts that can be analyzed with subtractive hybridization and differential display are limited. Microarray technology has the potential to examine expression of a larger number of genes but requires some a priori decision on what sequences should be examined. The SAGE method, originally described in 1995 by Velculescu et al.,4 has all the advantages of an “open system” (see overview Chapter 25 by Timothy Lohret and Karen Kelly); it allows quantitative and qualitative analysis of a large number of transcripts without prior knowledge concerning about which might be affected.5
