Chapter Twenty-Three - Detection and quantification of microRNAs (miRNAs) and high-throughput miRNA profiling

Abstract

MicroRNAs (miRNAs) are short, non-coding RNAs that regulate gene expression through epigenetic mechanisms such as stimulating controlled messenger RNA degradation or inhibiting translation initiation. Since their discovery in 1993, thousands of miRNAs have been identified in various species. To date, more than 2,600 mature miRNAs from Homo sapiens have been deposited in the miRNA repository, miRbase 22.1. As one miRNA can silence hundreds of target genes, and vice versa, one gene can be regulated by multiple miRNAs, miRNAs are regarded as fine tuners of various physiological processes, including cell development, differentiation, homeostasis, and apoptosis. Furthermore, increasing evidence suggests that miRNAs have clinical potential as diagnostic biomarkers and therapeutic targets in several diseases. Accurate detection and quantification of miRNAs are crucial in miRNA functional research. To date, there is a wide choice of technologies for this purpose with the advantages and limitations of each technology. qPCR has the highest sensitivity and specificity and is the least costly, but is not suitable for high-throughput miRNA profiling. Microarrays offer comprehensive coverage of known miRNAs, but accuracy is limited. miRNA-seq is ideal for the discovery of novel miRNAs and to distinguish isoforms of miRNAs, but the cost is high and data analysis is complex. In this chapter, therefore, we will review these major technologies for the detection and quantification of miRNAs, especially in blood plasma/serum samples.