An efficient and sensitive method for preparing cDNA libraries from scarce biological samples

The preparation and high-throughput sequencing of cDNA libraries from samples of small RNA is a pow-erful tool to quantify known small RNAs (such as microRNAs) and to discover novel RNA species. In-terest in identifying the small RNA repertoire present in tissues and in biofluids has grown substantially with the findings that small RNAs can serve as in-dicators of biological conditions and disease states. Here we describe a novel and straightforward method to clone cDNA libraries from small quantities of input RNA. This method permits the generation of cDNA libraries from sub-picogram quantities of RNA ro-bustly, efficiently and reproducibly. We demonstrate that the method provides a significant improvement in sensitivity compared to previous cloning methods while maintaining reproducible identification of di-verse small RNA species. This method should have widespread applications in a variety of contexts, in-cluding biomarker discovery from scarce samples of human tissue or body fluids