Target Discovery and Validation Reviews and Protocols

6
Discovery of Differentially Expressed Genes
Technical Considerations
Øystein Røsok and Mouldy Sioud
Summary
Identification and characterization of differentially expressed genes may be an important
first step toward the understanding of both normal physiology and disease. A multitude of techniques
belonging to two main categories have been developed to identify the differences in
gene expression between samples from different biological origin: selection techniques and
global techniques. Whereas the selection techniques strive to identify specific differentially
expressed genes, the global techniques analyze the total transcriptome or a major part of the
RNA population in a defined biological material. By exploiting the known sequences of
the adaptors used in suppressive subtraction hybridization technique, a strategy named novel
rescue–suppression-subtractive hybridization was developed. It should facilitate the discovery
of differentially expressed genes.
Key Words: Differential display; microarray; representational difference analysis (RDA);
serial analysis of gene expression (SAGE); target discovery; target identification.
1. Introduction
There are two eras of selection techniques: before and after the development
of PCR (1). Traditionally, selection was achieved by subtractive hybridization
and differential screening of cDNA libraries. However, the introduction of PCR
made it possible to design several new techniques that sped up gene discovery.
The new techniques also allowed for analysis of small amounts of biological
material (2,3).
From: Methods in Molecular Biology, vol. 360, Target Discovery and Validation Reviews and Protocols
Volume I, Emerging Strategies for Targets and Biomarker Discovery
Edited by: M. Sioud © Humana Press Inc., Totowa, NJ
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