In situ hybridization detection of microRNAs

MicroRNAs (miRNAs) are endogenous approximately 22 nucleotide RNAs that play critical roles in many cellular processes including cell differentiation, proliferation, and apoptosis. The analysis of spatiotemporal expression of miRNAs is important for dissecting their roles in development and during physiological/pathophysiological processes. In situ hybridization is a powerful technology that allows cellular localization. However, the detection of miRNAs by in situ hybridization has been challenging because of the low affinity of conventional RNA or DNA probes due to the small sizes of miRNAs. Here, we describe a protocol for miRNA in situ hybridization on mouse tissue cryosections using locked nucleic acid (LNA) probes. LNA probes demonstrate a much higher affinity to their complimentary RNAs compared to conventional RNA and DNA oligo probes, which allow detection of miRNAs in tissue sections with excellent specificity.