Global surveys, inaugurated by almost complete compendiums of the genes of various organisms, have been expanded to cover proteins and, more recently, microRNAs (miRNAs), which are roughly 25-nucleotide-long RNA molecules that function to block the production of proteins from mRNAs. Cummins et al. describe a protocol—the miRNA serial analysis of gene expression (miRAGE)—and its application to assessing the miRNA composition of human colorectal cancer cells. Their approach meets the technical challenge of recovering short RNA pieces, present in vanishingly small quantities; analyzing an enormous number of parallel amplification reactions resulted in the identification of 200 miRNAs known within these cells (with one-quarter differentially expressed in comparison to normal colonic epithelial cells) and of 168 candidate miRNAs, of which one-fifth were independently identified and deposited by other groups during the course of their study. — GJC
Proc. Natl. Acad. Sci. U.S.A. 103, 3687 (2006).