@article {69457, title = {Deep-tissue transcriptomics and subcellular imaging at high spatial resolution}, journal = {Science}, year = {2025}, month = {2025 Feb 20}, abstract = {

Limited color channels in fluorescence microscopy have long constrained spatial analysis in biological specimens. Here, we introduce cycle Hybridization Chain Reaction (HCR), a method that integrates multicycle DNA barcoding with HCR to overcome this limitation. cycleHCR enables highly multiplexed imaging of RNA and proteins using a unified barcode system. Whole-embryo transcriptomics imaging achieved precise three-dimensional gene expression and cell fate mapping across a specimen depth of ~310 μm. When combined with expansion microscopy, cycleHCR revealed an intricate network of 10 subcellular structures in mouse embryonic fibroblasts. In mouse hippocampal slices, multiplex RNA and protein imaging uncovered complex gene expression gradients and cell-type-specific nuclear structural variations. cycleHCR provides a quantitative framework for elucidating spatial regulation in deep tissue contexts for research and potentially diagnostic applications.

bioRxiv preprint:\ 10.1101/2024.05.17.594641

}, doi = { 10.1126/science.adq2084}, url = {https://www.science.org/doi/10.1126/science.adq2084}, author = {Gandin, Valentina and Kim, Jun and Yang, Liang-Zhong and Lian, Yumin and Kawase, Takashi and Hu, Amy and Rokicki, Konrad and Fleishman, Greg and Tillberg, Paul and Aguilera Castrejon, Alejandro and Stringer, Carsen and Preibisch, Stephan and Liu, Zhe J.} } @article {69548, title = {Cohesin prevents cross-domain gene coactivation.}, journal = {Nat Genet}, year = {2024}, month = {2024 Jul 24}, abstract = {

The contrast between the disruption of genome topology after cohesin loss and the lack of downstream gene expression changes instigates intense debates regarding the structure-function relationship between genome and gene regulation. Here, by analyzing transcriptome and chromatin accessibility at the single-cell level, we discover that, instead of dictating population-wide gene expression levels, cohesin supplies a general function to neutralize stochastic coexpression tendencies of cis-linked genes in single cells. Notably, cohesin loss induces widespread gene coactivation and chromatin co-opening tens of million bases apart in cis. Spatial genome and protein imaging reveals that cohesin prevents gene co-bursting along the chromosome and blocks spatial mixing of transcriptional hubs. Single-molecule imaging shows that cohesin confines the exploration of diverse enhancer and core promoter binding transcriptional regulators. Together, these results support that cohesin arranges nuclear topology to control gene coexpression in single cells.

}, issn = {1546-1718}, doi = {10.1038/s41588-024-01852-1}, url = {https://doi.org/10.1038/s41588-024-01852-1}, author = {Dong, Peng and Zhang, Shu and Gandin, Valentina and Xie, Liangqi and Wang, Lihua and Lemire, Andrew L and Li, Wenhong and Otsuna, Hideo and Kawase, Takashi and Lander, Arthur D and Chang, Howard Y and Liu, Zhe J} } @article {69042, title = {Optimized Red-Absorbing Dyes for Imaging and Sensing}, journal = {Journal of the American Chemical Society}, year = {2023}, month = {2023 Oct 16}, abstract = {

Rhodamine dyes are excellent scaffolds for developing a broad range of fluorescent probes. A key property of rhodamines is their equilibrium between a colorless lactone and fluorescent zwitterion. Tuning the lactone{\textendash}zwitterion equilibrium constant (KL{\textendash}Z) can optimize dye properties for specific biological applications. Here, we use known and novel organic chemistry to prepare a comprehensive collection of rhodamine dyes to elucidate the structure{\textendash}activity relationships that govern\ KL{\textendash}Z. We discovered that the auxochrome substituent strongly affects the lactone{\textendash}zwitterion equilibrium, providing a roadmap for the rational design of improved rhodamine dyes. Electron-donating auxochromes, such as julolidine, work in tandem with fluorinated pendant phenyl rings to yield bright, red-shifted fluorophores for live-cell single-particle tracking (SPT) and multicolor imaging. The\ N-aryl auxochrome combined with fluorination yields red-shifted F{\"o}rster resonance energy transfer (FRET) quencher dyes useful for creating a new semisynthetic indicator to sense cAMP using fluorescence lifetime imaging microscopy (FLIM). Together, this work expands the synthetic methods available for rhodamine synthesis, generates new reagents for advanced fluorescence imaging experiments, and describes structure{\textendash}activity relationships that will guide the design of future probes.

}, issn = {0002-7863}, doi = {10.1021/jacs.3c0527310.1021/jacs.3c05273}, url = {https://pubs.acs.org/doi/10.1021/jacs.3c05273}, author = {Grimm, Jonathan B. and Tkachuk, Ariana N. and Patel, Ronak and Hennigan, S. Thomas and Gutu, Alina and Dong, Peng and Gandin, Valentina and Osowski, Anastasia M. and Holland, Katie L. and Liu, Zhe J. and Brown, Timothy A. and Lavis, Luke D.} } @article {68462, title = {Cap-dependent translation initiation monitored in living cells.}, journal = {Nature Communications}, volume = {13}, year = {2022}, month = {2022 Nov 02}, pages = {6558}, abstract = {

mRNA translation is tightly regulated to preserve cellular homeostasis. Despite extensive biochemical, genetic, and structural studies, a detailed understanding of mRNA translation regulation is lacking. Imaging methodologies able to resolve the binding dynamics of translation factors at single-cell and single-mRNA resolution were necessary to fully elucidate regulation of this paramount process. Here live-cell spectroscopy and single-particle tracking were combined to interrogate the binding dynamics of endogenous initiation factors to the 5{\textquoteright}cap. The diffusion of initiation factors (IFs) changed markedly upon their association with mRNA. Quantifying their diffusion characteristics revealed the sequence of IFs assembly and disassembly in cell lines and the clustering of translation in neurons. This approach revealed translation regulation at high spatial and temporal resolution that can be applied to the formation of any endogenous complex that results in a measurable shift in diffusion.

}, keywords = {Peptide Chain Initiation, Translational, Peptide Initiation Factors, Protein Biosynthesis, RNA Caps, RNA, Messenger}, issn = {2041-1723}, doi = {10.1038/s41467-022-34052-8}, author = {Gandin, Valentina and English, Brian P and Freeman, Melanie and Leroux, Louis-Philippe and Preibisch, Stephan and Walpita, Deepika and Jaramillo, Maritza and Singer, Robert H} } @article {68556, title = {Inhibition of coronavirus HCoV-OC43 by targeting the eIF4F complex.}, journal = {Frontiers in Pharmacology}, volume = {13}, year = {2022}, month = {2022 Dec 01}, pages = {1029093}, abstract = {

The translation initiation complex 4F (eIF4F) is a rate-limiting factor in protein synthesis. Alterations in eIF4F activity are linked to several diseases, including cancer and infectious diseases. To this end, coronaviruses require eIF4F complex activity to produce proteins essential for their life cycle. Efforts to target coronaviruses by abrogating translation have been largely limited to repurposing existing eIF4F complex inhibitors. Here, we report the results of a high throughput screen to identify small molecules that disrupt eIF4F complex formation and inhibit coronavirus RNA and protein levels. Of 338,000 small molecules screened for inhibition of the eIF4F-driven, CAP-dependent translation, we identified SBI-1232 and two structurally related analogs, SBI-5844 and SBI-0498, that inhibit human coronavirus OC43 (HCoV-OC43; OC43) with minimal cell toxicity. Notably, gene expression changes after OC43 infection of Vero E6 or A549 cells were effectively reverted upon treatment with SBI-5844 or SBI-0498. Moreover, SBI-5844 or SBI-0498 treatment effectively impeded the eIF4F complex assembly, with concomitant inhibition of newly synthesized OC43 nucleocapsid protein and OC43 RNA and protein levels. Overall, we identify SBI-5844 and SBI-0498 as small molecules targeting the eIF4F complex that may limit coronavirus transcripts and proteins, thereby representing a basis for developing novel therapeutic modalities against coronaviruses.

}, issn = {1663-9812}, doi = {10.3389/fphar.2022.1029093}, author = {Feng, Yongmei and Grotegut, Stefan and Jovanovic, Predrag and Gandin, Valentina and Olson, Steven H and Murad, Rabi and Beall, Anne and Colayco, Sharon and De-Jesus, Paul and Chanda, Sumit and English, Brian P and Singer, Robert H and Jackson, Michael and Topisirovic, Ivan and Ronai, Ze{\textquoteright}ev A} } @article {67210, title = {Intracellular mRNA transport and localized translation.}, journal = {Nature Reviews Molecular Cell Biology}, volume = {22}, year = {2021}, month = {2021 Jul 1}, pages = {483-504}, abstract = {

Fine-tuning cellular physiology in response to intracellular and environmental cues requires precise temporal and spatial control of gene expression. High-resolution imaging technologies to detect mRNAs and their translation state have revealed that all living organisms localize mRNAs in subcellular compartments and create translation hotspots, enabling cells to tune gene expression locally. Therefore, mRNA localization is a conserved and integral part of gene expression regulation from prokaryotic to eukaryotic cells. In this Review, we discuss the mechanisms of mRNA transport and local mRNA translation across the kingdoms of life and at organellar, subcellular and multicellular resolution. We also discuss the properties of messenger ribonucleoprotein and higher order RNA granules and how they may influence mRNA transport and local protein synthesis. Finally, we summarize the technological developments that allow us to study mRNA localization and local translation through the simultaneous detection of mRNAs and proteins in single cells, mRNA and nascent protein single-molecule imaging, and bulk RNA and protein detection methods.

}, issn = {1471-0080}, doi = {10.1038/s41580-021-00356-8}, author = {Das, Sulagna and Vera, Maria and Gandin, Valentina and Singer, Robert H and Tutucci, Evelina} } @article {65791, title = {The mTORC1/S6K/PDCD4/eIF4A axis determines outcome of mitotic arrest.}, journal = {Cell Reports}, volume = {33}, year = {2020}, month = {2020 Oct 06}, pages = {108230}, abstract = {

mTOR is a serine/threonine kinase and a master regulator of cell growth and proliferation. Raptor, a scaffolding protein that recruits substrates to mTOR complex 1 (mTORC1), is known to be phosphorylated during mitosis, but the significance of this phosphorylation remains largely unknown. Here we show that raptor expression and mTORC1 activity are dramatically reduced in cells arrested in mitosis. Expression of a non-phosphorylatable raptor mutant reactivates mTORC1 and significantly reduces cytotoxicity of the mitotic poison Taxol. This effect is mediated via degradation of PDCD4, a tumor suppressor protein that inhibits eIF4A activity and is negatively regulated by the mTORC1/S6K pathway. Moreover, pharmacological inhibition of eIF4A is able to enhance the effects of Taxol and restore sensitivity in Taxol-resistant cancer cells. These findings indicate that the mTORC1/S6K/PDCD4/eIF4A axis has a pivotal role in the death versus slippage decision during mitotic arrest and may be exploited clinically to treat tumors resistant to anti-mitotic agents.

}, issn = {2211-1247}, doi = {10.1016/j.celrep.2020.108230}, author = {Moustafa-Kamal, Mohamed and Kucharski, Thomas J and El-Assaad, Wissal and Abbas, Yazan M and Gandin, Valentina and Nagar, Bhushan and Pelletier, Jerry and Topisirovic, Ivan and Teodoro, Jose G} }