ABSTRACT
Recent advances in single-molecule imaging of mRNAs in fixed and living cells have enabled the lives of mRNAs to be studied with unprecedented spatial and temporal detail. These approaches have moved beyond simply being able to observe specific events and have begun to allow an understanding of how regulation is coupled between steps in the mRNA life cycle. Additionally, these methodologies are now being applied in multicellular systems and animals to provide more nuanced insights into the physiological regulation of RNA metabolism.
Subject(s)
RNA, Messenger , Animals , RNA, Messenger/genetics , RNA, Messenger/metabolismABSTRACT
Visualization of single mRNA molecules in fixed cells can be achieved using single molecule fluorescent in situ hybridization (smFISH). This approach enables accurate quantification of mRNA numbers and localization at a single-cell level. To ensure reliable results using smFISH, it is critical to use fluorescent probes that are highly specific to their RNA target. To facilitate probe design, we have created anglerFISH, a user-friendly command-line based pipeline. In this chapter, we present how to perform a smFISH experiment using user-designed and labeled probes.
Subject(s)
Fluorescent Dyes , RNA , In Situ Hybridization, Fluorescence/methods , Nanotechnology , Oligonucleotide Probes/genetics , RNA/genetics , RNA, Messenger/geneticsABSTRACT
Detection of diffraction-limited spots in single-molecule microscopy images is traditionally performed with mathematical operators designed for idealized spots. This process requires manual tuning of parameters that is time-consuming and not always reliable. We have developed deepBlink, a neural network-based method to detect and localize spots automatically. We demonstrate that deepBlink outperforms other state-of-the-art methods across six publicly available datasets containing synthetic and experimental data.
Subject(s)
Image Processing, Computer-Assisted/methods , Neural Networks, Computer , Software , MicroscopyABSTRACT
Cellular stress leads to reprogramming of mRNA translation and formation of stress granules (SGs), membraneless organelles consisting of mRNA and RNA-binding proteins. Although the function of SGs remains largely unknown, it is widely assumed they contain exclusively non-translating mRNA. Here, we re-examine this hypothesis using single-molecule imaging of mRNA translation in living cells. Although we observe non-translating mRNAs are preferentially recruited to SGs, we find unequivocal evidence that mRNAs localized to SGs can undergo translation. Our data indicate that SG-associated translation is not rare, and the entire translation cycle (initiation, elongation, and termination) can occur on SG-localized transcripts. Furthermore, translating mRNAs can be observed transitioning between the cytosol and SGs without changing their translational status. Together, these results demonstrate that mRNA localization to SGs is compatible with translation and argue against a direct role for SGs in inhibition of protein synthesis.
