Visualization of Single mRNAs in Live Neurons

Transcription and post-transcriptional regulations are critical in gene expression. To study the spatiotemporal regulation of RNA inside a cell, techniques for high-resolution imaging of RNA have been developed. In this chapter, we describe RNA fluorescent labeling methods using MS2 and PP7 systems to detect single RNA molecules in live neurons. We use hippocampal neurons cultured from knock-in mouse models in which β-actin or Arc mRNAs are tagged with MS2 or PP7 stem-loops. Adeno-associated virus (AAV) or lentiviral vectors are used to express MS2 or PP7 capsid proteins fused with GFP in those neurons. Then, GFP-labeled RNAs in live neurons can be detected by epifluorescence microscopy, and their moving pathways can be analyzed using single-particle tracking software. For these processes, we introduce protocols for neuron culture, transfection, imaging, and particle tracking methods.