Single-molecule direct RNA sequencing without cDNA synthesis.

Methods for in-depth genome-wide characterization of transcriptomes and quantification of transcript levels using various microarray and next-generation sequencing technologies have emerged as valuable tools for understanding cellular physiology and human disease biology and have begun to be utilized in various clinical diagnostic applications. Current methods, however, typically require RNA to be converted to complementary DNA prior to measurements. This step has been shown to introduce many biases and artifacts. In order to best characterize the 'true' transcriptome, the single-molecule direct RNA sequencing (DRS) technology was developed. This review focuses on the underlying principles behind the DRS, sample preparation steps, and the current and novel avenues of research and applications DRS offers.