Memory-relevant neuronal plasticity is believed to require local translation of new proteins at synapses. Understanding this process has necessitated the development of tools to visualize mRNA within relevant neuronal compartments. In this review, we summarize the technical developments that now enable mRNA transcripts and their translation to be visualized at single-molecule resolution in both fixed and live cells. These tools include single-molecule fluorescence in situ hybridization (smFISH) to visualize mRNA in fixed cells, MS2/PP7 labelling for live mRNA imaging and SunTag labelling to observe the emergence of nascent polypeptides from a single translating mRNA. The application of these tools in cultured neurons and more recently in whole brains promises to revolutionize our understanding of local translation in the neuronal plasticity that underlies behavioural change.
Long Terminal Repeat (LTR) retrotransposons replicate through “copy and paste” mechanisms mediated by reverse transcription in virus-like particles (VLPs) and integration in the nucleus (see article from Lee and Martienssen, pp. 2241–2251). VLP DNA-sequencing reveals complementary DNA (cDNA) replication intermediates from active retrotransposons. Instead of functional linear intermediates that integrate in the nucleus, the Arabidopsis retroelement SISYPHUS lacks features important for nuclear import, and instead accumulates circular cDNA from futile autointegration within the VLP. In Greek mythology, Sisyphus was condemned to the futile task of rolling a huge boulder uphill eternally. Image created and provided Seung Cho Lee, Evan Ernst, and Robert A. Martienssen.
Single-molecule mRNA and translation imaging in neurons
Jessica Mitchell, Jeffrey A. Chao; Single-molecule mRNA and translation imaging in neurons. Biochem Soc Trans 1 November 2021; 49 (5): 2221–2227. doi: https://doi.org/10.1042/BST20210313
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