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81 Janelia Publications

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    09/14/20 | Novel fluorescent ligands enable single-molecule localization microscopy of the dopamine transporter.
    Guthrie D, Klein Herenbrink C, Lycas M, Ku T, Bonifazi A, DeVree B, Mathiasen S, Javitch J, Grimm JB, Lavis LD, Gether U, Newman AH
    ACS Chemical Neuroscience. 2020 Sep 14:. doi: 10.1021/acschemneuro.0c00397

    The dopamine transporter (DAT) is critical for spatiotemporal control of dopaminergic neurotransmission and the target for therapeutic agents, including ADHD medications, and abused substances, such as cocaine. Here, we develop new fluorescently labeled ligands that bind DAT with high affinity and enable single-molecule detection of the transporter. The cocaine analogue MFZ2-12 (1) was conjugated to novel rhodamine-based Janelia Fluorophores (JF549 and JF646). High affinity binding of the resulting ligands to DAT was demonstrated by potent inhibition of [3H]dopamine uptake in DAT transfected CAD cells and by competition radioligand binding experiments on rat striatal membranes. Visualization of binding was substantiated by confocal or TIRF microscopy revealing selective binding of the analogues to DAT transfected CAD cells. Single particle tracking experiments were performed with JF549-conjugated DG3-80 (3) and JF646-conjugated DG4-91 (4) on DAT transfected CAD cells enabling quantification and categorization of the dynamic behavior of DAT into four distinct motion classes (immobile, confined, Brownian, and directed). Finally, we show that the ligands can be used in direct stochastic optical reconstruction microscopy (dSTORM) experiments permitting further analyses of DAT distribution on the nanoscale. In summary, these novel fluorescent ligands are promising new tools for studying DAT localization and regulation with single-molecule resolution.

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    08/20/20 | Rational design of bioavailable photosensitizers for manipulation and imaging of biological systems.
    Binns TC, Ayala AX, Grimm JB, Tkachuk AN, Castillon GA, Phan S, Zhang L, Brown TA, Liu Z, Adams SR, Ellisman MH, Koyama M, Lavis LD
    Cell Chemical Biology. 2020 Aug 20;27(8):1063-72. doi: 10.1016/j.chembiol.2020.07.001

    Light-mediated chemical reactions are powerful methods for manipulating and interrogating biological systems. Photosensitizers, compounds that generate reactive oxygen species upon excitation with light, can be utilized for numerous biological experiments, but the repertoire of bioavailable photosensitizers is limited. Here, we describe the synthesis, characterization, and utility of two photosensitizers based upon the widely used rhodamine scaffold and demonstrate their efficacy for chromophore-assisted light inactivation, cell ablation in culture and in vivo, and photopolymerization of diaminobenzidine for electron microscopy. These chemical tools will facilitate a broad range of applications spanning from targeted destruction of proteins to high-resolution imaging.

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    07/27/20 | A general method to optimize and functionalize red-shifted rhodamine dyes.
    Grimm JB, Tkachuk AN, Xie L, Choi H, Mohar B, Falco N, Schaefer K, Patel R, Zheng Q, Liu Z, Lippincott-Schwartz J, Brown TA, Lavis LD
    Nature Methods. 2020 Jul 27:. doi: 10.1038/s41592-020-0909-6

    Expanding the palette of fluorescent dyes is vital to push the frontier of biological imaging. Although rhodamine dyes remain the premier type of small-molecule fluorophore owing to their bioavailability and brightness, variants excited with far-red or near-infrared light suffer from poor performance due to their propensity to adopt a lipophilic, nonfluorescent form. We report a framework for rationalizing rhodamine behavior in biological environments and a general chemical modification for rhodamines that optimizes long-wavelength variants and enables facile functionalization with different chemical groups. This strategy yields red-shifted 'Janelia Fluor' (JF) dyes useful for biological imaging experiments in cells and in vivo.

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    04/27/20 | Live-cell single particle imaging reveals the role of RNA polymerase II in histone H2A.Z eviction.
    Ranjan A, Nguyen VQ, Liu S, Wisniewski J, Kim JM, Tang X, Mizuguchi G, Elalaoui E, Nickels TJ, Jou V, English BP, Zheng Q, Luk E, Lavis LD, Lionnet T, Wu C
    eLife. 2020 Apr 27;9:. doi: 10.7554/eLife.55667

    The H2A.Z histone variant, a genome-wide hallmark of permissive chromatin, is enriched near transcription start sites in all eukaryotes. H2A.Z is deposited by the SWR1 chromatin remodeler and evicted by unclear mechanisms. We tracked H2A.Z in living yeast at single-molecule resolution, and found that H2A.Z eviction is dependent on RNA Polymerase II (Pol II) and the Kin28/Cdk7 kinase, which phosphorylates Serine 5 of heptapeptide repeats on the carboxy-terminal domain of the largest Pol II subunit Rpb1. These findings link H2A.Z eviction to transcription initiation, promoter escape and early elongation activities of Pol II. Because passage of Pol II through +1 nucleosomes genome-wide would obligate H2A.Z turnover, we propose that global transcription at yeast promoters is responsible for eviction of H2A.Z. Such usage of yeast Pol II suggests a general mechanism coupling eukaryotic transcription to erasure of the H2A.Z epigenetic signal.

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    04/01/20 | 3D ATAC-PALM: super-resolution imaging of the accessible genome.
    Xie L, Dong P, Chen X, Hsieh TS, Banala S, De Marzio M, English BP, Qi Y, Jung SK, Kieffer-Kwon K, Legant WR, Hansen AS, Schulmann A, Casellas R, Zhang B, Betzig E, Lavis LD, Chang HY, Tjian R, Liu Z
    Nature Methods. 2020 Apr 01;17(4):430-6. doi: 10.1038/s41592-020-0775-2

    To image the accessible genome at nanometer scale in situ, we developed three-dimensional assay for transposase-accessible chromatin-photoactivated localization microscopy (3D ATAC-PALM) that integrates an assay for transposase-accessible chromatin with visualization, PALM super-resolution imaging and lattice light-sheet microscopy. Multiplexed with oligopaint DNA–fluorescence in situ hybridization (FISH), RNA–FISH and protein fluorescence, 3D ATAC-PALM connected microscopy and genomic data, revealing spatially segregated accessible chromatin domains (ACDs) that enclose active chromatin and transcribed genes. Using these methods to analyze genetically perturbed cells, we demonstrated that genome architectural protein CTCF prevents excessive clustering of accessible chromatin and decompacts ACDs. These results highlight 3D ATAC-PALM as a useful tool to probe the structure and organizing mechanism of the genome.

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    01/22/20 | Accurate measurement of fast endocytic recycling kinetics in real time.
    Jonker CT, Deo C, Zager PJ, Tkachuk AN, Weinstein AM, Rodriguez-Boulan E, Lavis LD, Schreiner R
    Journal of Cell Science. 2020 Jan 22;133(2):. doi: 10.1242/jcs.231225

    The fast turnover of membrane components through endocytosis and recycling allows precise control of the composition of the plasma membrane. Endocytic recycling can be rapid with some molecules returning to the plasma membrane with a <5 minutes. Existing methods to study these trafficking pathways utilize chemical, radioactive, or fluorescent labeling of cell surface receptors in pulse-chase experiments, which require tedious washing steps and manual collection of samples. Here, we introduce a live-cell endocytic recycling assay, based on a newly designed cell-impermeable, fluorogenic ligand for HaloTag: 'Janelia Fluor 635i' (JFi; i=impermeant) which allows real-time detection of membrane receptor recycling at steady state. We used this method to study the effect of iron depletion on transferrin receptor (TfR) recycling using the chelator desferrioxamine. We found this perturbation significantly increases the TfR recycling rate. The high temporal resolution and simplicity of this assay provides a clear advantage over extant methods and makes it ideal for large scale cellular imaging studies. This assay can be adapted to examine other cellular kinetic parameters such as protein turnover and biosynthetic trafficking.

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    01/14/20 | Improved HaloTag Ligand Enables BRET Imaging With NanoLuc
    Thirukkumaran OM, Wang C, Asouzu NJ, Fron E, Rocha S, Hofkens J, Lavis LD, Mizuno H
    Frontiers in Chemistry. 2020 Jan 14;7:. doi: 10.3389/fchem.2019.0093810.3389/fchem.2019.00938.s001
    01/09/20 | Bright and tunable far-red chemigenetic indicators.
    Deo C, Abdelfattah AS, Bhargava HK, Berro AJ, Falco N, Moeyaert B, Chupanova M, Lavis LD, Schreiter ER
    bioRxiv. 2020 Jan 9:
    01/06/20 | Nanoscale subcellular architecture revealed by multicolor three-dimensional salvaged fluorescence imaging.
    Zhang Y, Schroeder LK, Lessard MD, Kidd P, Chung J, Song Y, Benedetti L, Li Y, Ries J, Grimm JB, Lavis LD, De Camilli P, Rothman JE, Baddeley D, Bewersdorf J
    Nature Methods. 2020 Jan 06;17(2):225-231. doi: 10.1038/s41592-019-0676-4

    Combining the molecular specificity of fluorescent probes with three-dimensional imaging at nanoscale resolution is critical for investigating the spatial organization and interactions of cellular organelles and protein complexes. We present a 4Pi single-molecule switching super-resolution microscope that enables ratiometric multicolor imaging of mammalian cells at 5-10-nm localization precision in three dimensions using 'salvaged fluorescence'. Imaging two or three fluorophores simultaneously, we show fluorescence images that resolve the highly convoluted Golgi apparatus and the close contacts between the endoplasmic reticulum and the plasma membrane, structures that have traditionally been the imaging realm of electron microscopy. The salvaged fluorescence approach is equally applicable in most single-objective microscopes.

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    09/25/19 | Rational design of fluorogenic and spontaneously blinking labels for super-resolution imaging.
    Zheng Q, Ayala AX, Chung I, Weigel AV, Ranjan A, Falco N, Grimm JB, Tkachuk AN, Wu C, Lippincott-Schwartz J, Singer RH, Lavis LD
    ACS Central Science. 2019 Sep 25;5(9):1602-1613. doi: 10.1021/acscentsci.9b00676

    Rhodamine dyes exist in equilibrium between a fluorescent zwitterion and a nonfluorescent lactone. Tuning this equilibrium toward the nonfluorescent lactone form can improve cell-permeability and allow creation of "fluorogenic" compounds-ligands that shift to the fluorescent zwitterion upon binding a biomolecular target. An archetype fluorogenic dye is the far-red tetramethyl-Si-rhodamine (SiR), which has been used to create exceptionally useful labels for advanced microscopy. Here, we develop a quantitative framework for the development of new fluorogenic dyes, determining that the lactone-zwitterion equilibrium constant () is sufficient to predict fluorogenicity. This rubric emerged from our analysis of known fluorophores and yielded new fluorescent and fluorogenic labels with improved performance in cellular imaging experiments. We then designed a novel fluorophore-Janelia Fluor 526 (JF)-with SiR-like properties but shorter fluorescence excitation and emission wavelengths. JF is a versatile scaffold for fluorogenic probes including ligands for self-labeling tags, stains for endogenous structures, and spontaneously blinking labels for super-resolution immunofluorescence. JF constitutes a new label for advanced microscopy experiments, and our quantitative framework will enable the rational design of other fluorogenic probes for bioimaging.

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