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9 Janelia Publications

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    01/03/21 | Direct detection of SARS-CoV-2 RNA using high-contrast pH-sensitive dyes.
    Timothy A. Brown , Katherine S. Schaefer , Arthur Tsang , Hyun Ah Yi , Jonathan B. Grimm , Andrew L. Lemire , Fadi M. Jradi , Charles Kim , Kevin McGowan , Kimberly Ritola , Derek T. Armstrong , Heba H. Mostafa , Wyatt Korff , Ronald D. Vale , Luke D. Lavis
    medRxiv. 2021 Jan 03:. doi:

    The worldwide COVID-19 pandemic has had devastating effects on health, healthcare infrastructure, social structure, and economics. One of the limiting factors in containing the spread of this virus has been the lack of widespread availability of fast, inexpensive, and reliable methods for testing of individuals. Frequent screening for infected and often asymptomatic people is a cornerstone of pandemic management plans. Here, we introduce two pH sensitive ‘LAMPshade’ dyes as novel readouts in an isothermal RT- LAMP amplification assay for SARS-CoV-2 RNA. The resulting JaneliaLAMP (jLAMP) assay is robust, simple, inexpensive, has low technical requirements and we describe its use and performance in direct testing of contrived and clinical samples without RNA extraction.

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    11/11/20 | Optimized Vivid-derived Magnets photodimerizers for subcellular optogenetics in mammalian cells.
    Benedetti L, Marvin JS, Falahati H, Guillén-Samander A, Looger LL, De Camilli P
    Elife. 2020 Nov 11;9:. doi: 10.7554/eLife.63230

    Light-inducible dimerization protein modules enable precise temporal and spatial control of biological processes in non-invasive fashion. Among them, Magnets are small modules engineered from the photoreceptor Vivid by orthogonalizing the homodimerization interface into complementary heterodimers. Both Magnets components, which are well-tolerated as protein fusion partners, are photoreceptors requiring simultaneous photoactivation to interact, enabling high spatiotemporal confinement of dimerization with a single-excitation wavelength. However, Magnets require concatemerization for efficient responses and cell preincubation at 28C to be functional. Here we overcome these limitations by engineering an optimized Magnets pair requiring neither concatemerization nor low temperature preincubation. We validated these 'enhanced' Magnets (eMags) by using them to rapidly and reversibly recruit proteins to subcellular organelles, to induce organelle contacts, and to reconstitute OSBP-VAP ER-Golgi tethering implicated in phosphatidylinositol-4-phosphate transport and metabolism. eMags represent a very effective tool to optogenetically manipulate physiological processes over whole cells or in small subcellular volumes.

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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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    11/01/18 | Stability, affinity and chromatic variants of the glutamate sensor iGluSnFR.
    Marvin JS, Scholl B, Wilson DE, Podgorski K, Kazemipour A, Mueller JA, Schoch-McGovern S, Wang SS, Quiroz FJ, Rebola N, Bao H, Little JP, Tkachuk AN, Hantman AW, Chapman ER, Dietrich D, DiGregorio DA, Fitzpatrick D, Looger LL
    Nature Methods. 2018 Nov;15(11):9386-9. doi: 10.1038/s41592-018-0171-3

    Single-wavelength fluorescent reporters allow visualization of specific neurotransmitters with high spatial and temporal resolution. We report variants of intensity-based glutamate-sensing fluorescent reporter (iGluSnFR) that are functionally brighter; detect submicromolar to millimolar amounts of glutamate; and have blue, cyan, green, or yellow emission profiles. These variants could be imaged in vivo in cases where original iGluSnFR was too dim, resolved glutamate transients in dendritic spines and axonal boutons, and allowed imaging at kilohertz rates.

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    10/25/18 | Improved methods for marking active neuron populations.
    Moeyaert B, Holt G, Madangopal R, Perez-Alvarez A, Fearey BC, Trojanowski NF, Ledderose J, Zolnik TA, Das A, Patel D, Brown TA, Sachdev RN, Eickholt BJ, Larkum ME, Turrigiano GG, Dana H, Gee CE, Oertner TG, Hope BT, Schreiter ER
    Nature Communications. 2018 Oct 25;9(1):4440. doi: 10.1038/s41467-018-06935-2

    Marking functionally distinct neuronal ensembles with high spatiotemporal resolution is a key challenge in systems neuroscience. We recently introduced CaMPARI, an engineered fluorescent protein whose green-to-red photoconversion depends on simultaneous light exposure and elevated calcium, which enabled marking active neuronal populations with single-cell and subsecond resolution. However, CaMPARI (CaMPARI1) has several drawbacks, including background photoconversion in low calcium, slow kinetics and reduced fluorescence after chemical fixation. In this work, we develop CaMPARI2, an improved sensor with brighter green and red fluorescence, faster calcium unbinding kinetics and decreased photoconversion in low calcium conditions. We demonstrate the improved performance of CaMPARI2 in mammalian neurons and in vivo in larval zebrafish brain and mouse visual cortex. Additionally, we herein develop an immunohistochemical detection method for specific labeling of the photoconverted red form of CaMPARI. The anti-CaMPARI-red antibody provides strong labeling that is selective for photoconverted CaMPARI in activated neurons in rodent brain tissue.

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    09/19/17 | Synthesis of Janelia Fluor HaloTag and SNAP-Tag Ligands and Their Use in Cellular Imaging Experiments.
    Grimm JB, Brown TA, English BP, Lionnet T, Lavis LD
    Methods in Molecular Biology (Clifton, N.J.). 2017;1663:179-188. doi: 10.1007/978-1-4939-7265-4_15

    The development of genetically encoded self-labeling protein tags such as the HaloTag and SNAP-tag has expanded the utility of chemical dyes in microscopy. Intracellular labeling using these systems requires small, cell-permeable dyes with high brightness and photostability. We recently discovered a general method to improve the properties of classic fluorophores by replacing N,N-dimethylamino groups with four-membered azetidine rings to create the "Janelia Fluor" dyes. Here, we describe the synthesis of the HaloTag and SNAP-tag ligands of Janelia Fluor 549 and Janelia Fluor 646 as well as standard labeling protocols for use in ensemble and single-molecule cellular imaging.

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    09/05/17 | A general method to fine-tune fluorophores for live-cell and in vivo imaging.
    Grimm JB, Muthusamy AK, Liang Y, Brown TA, Lemon WC, Patel R, Lu R, Macklin JJ, Keller PJ, Ji N, Lavis LD
    Nature Methods. 2017 Oct;14(10):987-994. doi: 10.1038/nmeth.4403

    Pushing the frontier of fluorescence microscopy requires the design of enhanced fluorophores with finely tuned properties. We recently discovered that incorporation of four-membered azetidine rings into classic fluorophore structures elicits substantial increases in brightness and photostability, resulting in the Janelia Fluor (JF) series of dyes. We refined and extended this strategy, finding that incorporation of 3-substituted azetidine groups allows rational tuning of the spectral and chemical properties of rhodamine dyes with unprecedented precision. This strategy allowed us to establish principles for fine-tuning the properties of fluorophores and to develop a palette of new fluorescent and fluorogenic labels with excitation ranging from blue to the far-red. Our results demonstrate the versatility of these new dyes in cells, tissues and animals.

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    08/09/17 | General synthetic method for Si-Fluoresceins and Si-Rhodamines.
    Grimm JB, Brown TA, Tkachuk AN, Lavis LD
    ACS Central Science. 2017 Aug 09;3(9):975-85. doi: 10.1021/acscentsci.7b00247

    The century-old fluoresceins and rhodamines persist as flexible scaffolds for fluorescent and fluorogenic compounds. Extensive exploration of these xanthene dyes has yielded general structure–activity relationships where the development of new probes is limited only by imagination and organic chemistry. In particular, replacement of the xanthene oxygen with silicon has resulted in new red-shifted Si-fluoresceins and Si-rhodamines, whose high brightness and photostability enable advanced imaging experiments. Nevertheless, efforts to tune the chemical and spectral properties of these dyes have been hindered by difficult synthetic routes. Here, we report a general strategy for the efficient preparation of Si-fluoresceins and Si-rhodamines from readily synthesized bis(2-bromophenyl)silane intermediates. These dibromides undergo metal/bromide exchange to give bis-aryllithium or bis(aryl Grignard) intermediates, which can then add to anhydride or ester electrophiles to afford a variety of Si-xanthenes. This strategy enabled efficient (3–5 step) syntheses of known and novel Si-fluoresceins, Si-rhodamines, and related dye structures. In particular, we discovered that previously inaccessible tetrafluorination of the bottom aryl ring of the Si-rhodamines resulted in dyes with improved visible absorbance in solution, and a convenient derivatization through fluoride-thiol substitution. This modular, divergent synthetic method will expand the palette of accessible xanthenoid dyes across the visible spectrum, thereby pushing further the frontiers of biological imaging.

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    10/24/16 | Bright photoactivatable fluorophores for single-molecule imaging.
    Lavis LD, Grimm JB, English BP, Choi H, Muthusamy AK, Mehl BP, Dong P, Brown TA, Lippincott-Schwartz J, Liu Z, Lionnet T
    Nature Methods. 2016 Oct 24;13(12):985-8. doi: 10.1038/nmeth.4034

    Small molecule fluorophores are important tools for advanced imaging experiments. The development of self-labeling protein tags such as the HaloTag and SNAP-tag has expanded the utility of chemical dyes in live-cell microscopy. We recently described a general method for improving the brightness and photostability of small, cell-permeable fluorophores, resulting in the novel azetidine-containing "Janelia Fluor" (JF) dyes. Here, we refine and extend the utility of the JF dyes by synthesizing photoactivatable derivatives that are compatible with live cell labeling strategies. These compounds retain the superior brightness of the JF dyes once activated, but their facile photoactivation also enables improved single-particle tracking and localization microscopy experiments.

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