Project Summary MicroRNAs (miRNAs) are a family of small non-coding RNA molecules that downregulate the expression of their gene targets. Both computational and experimental studies have shown that thousands of human protein-coding genes are regulated by miRNAs, and miRNAs are master regulators of many important biological processes. Changes in miRNA expression can have profound biological impacts, leading to a variety of human diseases. Due to their critical roles in gene expression regulation, functional characterization of miRNAs has become one of the most active research fields in biology in recent years. Despite rapid progress in miRNA research, one major obstacle in this field is the lack of robust computational and experimental methods for functional miRNA analysis. Funded by this NIGMS R01 grant over the past ten years, we have made significant progress and published many methods on miRNA and gene expression studies. The methods we established have been widely adopted by the scientific community. In particular, we have developed a miRNA target prediction tool, miRDB, which has quickly become a major bioinformatics resource and has been cited by thousands of publications. Moreover, we have developed innovative experimental methods to manipulate the expression levels of miRNAs. Built on our recent progress, we propose to perform combined computational and experimental analyses to continue to develop cutting-edge technologies for miRNA studies. Our work is expected to exert a significant impact in the miRNA field by providing valuable resources for functional miRNA analysis.