| Method |
P.217 right column 2nd paragraph: "After the discovery of the first few hundred miRNAs by cloning, sufficient miRNA sequences were available to begin applying bioinformatic analyses to scan genomes for additional miRNA genes. Although numerous methods exist (refs 11, 12, 84, 95, 137), they generally rely on three main principles for miRNA recognition. First, miRNAs are contained within regions that fold into characteristic hairpin structures. Second, miRNAs tend to be highly conserved in related species. Third, the specific pattern of conservation displayed by miRNAs is very distinctive, with extreme conservation of the hairpin stems and less conservation of the loop of the hairpin and flanking sequences. Applying these methods to scans of the human genome has revealed ∼800–1000 potential human miRNAs, including those previously identified by cloning. Both direct sequencing and bioinformatics efforts to comprehensively identify miRNAs are ongoing at a rapid pace and, undoubtedly, the existence of many more miRNAs will be confirmed by the time this review is published." |