Rapid <i>in situ</i> RNA imaging based on Cas12a thrusting strand displacement reaction

Abstract

RNA In situ imaging through DNA self-assembly is advantaged in illustrating its structures and functions with high-resolution, while the limited reaction efficiency and time-consuming operation hinder its clinical application. Here, we first proposed a new strand displacement reaction (SDR) model (Cas12a thrusting SDR, CtSDR), in which Cas12a could overcome the inherent reaction limitation and dramatically enhance efficiency through energy replenishment and by-product consumption. The target-initiated CtSDR amplification was established for RNA analysis, with order of magnitude lower limit of detection (LOD) than the Cas13a system. The CtSDR-based RNA in situ imaging strategy was developed to monitor intra-cellular microRNA expression change and delineate the landscape of oncogenic RNA in 66 clinic tissue samples, possessing a clear advantage over classic in situ hybridization (ISH) in terms of operation time (1 h versus 14 h) while showing comparable sensitivity and specificity. This work presents a promising approach to developing advanced molecular diagnostic tools.