Imaging Single mRNA Dynamics in Live Neurons and Brains.

RNA is a key player in the process of gene expression. Whereas fluorescence in situ hybridization allows single mRNA imaging in fixed cells, the MS2-GFP labeling technique enables the observation of mRNA dynamics in living cells. Recently, two genetically engineered mouse models have been developed for the application of the MS2-GFP system in live animals. First, the Actb-MBS mouse was generated by knocking in 24 repeats of the MS2 stem-loop sequence in the 3' untranslated region of the β-actin gene. Second, the MCP mouse was made to express the NLS-HA-MCP-GFP transgene in all cell types. By crossing Actb-MBS and MCP mice, a double homozygous mouse line, MCP×MBS, was established to visualize endogenous β-actin mRNA labeled with multiple green fluorescent proteins. By imaging hippocampal neurons or brain slices from MCP×MBS mice, the dynamics of mRNA, such as transcription, transport, and localization, can be studied at single mRNA resolution. In this chapter, we explain the basics of MCP×MBS mice and describe methods for utilizing these animals.