Single mRNA Imaging with Fluorogenic RNA Aptamers and Small‐molecule Fluorophores

Messenger RNA (mRNA) is the fundamental information transfer system in the cell. Tracking single mRNA from transcription to degradation with fluorescent probes provides spatiotemporal information in cells about how the genetic information is transferred from DNA to proteins. The traditional single mRNA imaging approach utilizes RNA hairpins (e.g. MS2) and tethered fluorescent protein as probes. As an exciting alternative, RNA aptamers: small-molecule fluorophores (SFs) systems have emerged as novel single mRNA imaging probes since 2019, exhibiting several advantages including fluorogenic ability and minimal perturbation. This review summarizes all five reported RNA aptamers: SFs systems for single mRNA imaging in living cells so far. It also discusses the challenges and provides prospects for single mRNA imaging applications. This review is expected to inspire researchers to develop RNA aptamers: SFs systems for studying gene expression at single-molecule resolution in cells.