Visualizing mRNA in live mammalian cells.

mRNAs play essential role in gene expression and regulation. Direct visualization of specific intracellular mRNAs can provide key information about mRNA distribution and dynamics that accelerating study of their functionality. This highlights the necessity of characterizing mRNA in mammalian cells with good spatial and temporal resolution. Live cell imaging and tracking of mRNA remains a challenge due to their relatively short half-life and lack of versatile imaging probes. This review provides an overview of current methods of live-cell mRNA imaging, including exogenous hybridization probes and genetically encoded strategies. It then focuses on the development and application of aptamer initiated fluorescence complementation (AiFC) method for real-time imaging of mammalian mRNAs and includes a detailed protocol for observing β-actin mRNA in HeLa cells.