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6 Janelia Publications

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    09/21/17 | Genomic probes.
    Singer RH, Deng W, Lionnet T
    USPTO. 2017 Sep 21;A1:

    Labeled probes, and methods of use thereof, comprise a Cas polypeptide conjugated to gRNA that is specific for target nucleic acid sequences, including genomic DNA sequences. The probes and methods can be used to label nucleic acid sequences without global DNA denaturation. The presently-disclosed subject matter meets some or all of the above identified needs, as will become evident to those of ordinary skill in the art after a study of information provided in this document.

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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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    07/28/17 | Myc Regulates Chromatin Decompaction and Nuclear Architecture during B Cell Activation.
    Kieffer-Kwon K, Nimura K, Rao SS, Xu J, Jung S, Pekowska A, Dose M, Stevens E, Mathe E, Dong P, Huang S, Ricci MA, Baranello L, Zheng Y, Ardori FT, Resch W, Stavreva D, Nelson S, McAndrew M, Casellas A, Finn E, Gregory C, St Hilaire BG, Johnson SM, Dubois W, Cosma MP, Batchelor E, Levens D, Phair RD, Misteli T, Tessarollo L, Hager G, Lakadamyali M, Liu Z, Floer M, Shroff H, Aiden EL, Casellas R
    Molecular Cell. 2017 Jul 28;67(4):566-78. doi: 10.1016/j.molcel.2017.07.013

    50 years ago, Vincent Allfrey and colleagues discovered that lymphocyte activation triggers massive acetylation of chromatin. However, the molecular mechanisms driving epigenetic accessibility are still unknown. We here show that stimulated lymphocytes decondense chromatin by three differentially regulated steps. First, chromatin is repositioned away from the nuclear periphery in response to global acetylation. Second, histone nanodomain clusters decompact into mononucleosome fibers through a mechanism that requires Myc and continual energy input. Single-molecule imaging shows that this step lowers transcription factor residence time and non-specific collisions during sampling for DNA targets. Third, chromatin interactions shift from long range to predominantly short range, and CTCF-mediated loops and contact domains double in numbers. This architectural change facilitates cognate promoter-enhancer contacts and also requires Myc and continual ATP production. Our results thus define the nature and transcriptional impact of chromatin decondensation and reveal an unexpected role for Myc in the establishment of nuclear topology in mammalian cells.

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    07/01/17 | mRNA quantification using single-molecule FISH in Drosophila embryos.
    Trcek T, Lionnet T, Shroff H, Lehmann R
    Nature Protocols. 2017 Jul;12(7):1326-1348. doi: 10.1038/nprot.2017.030

    Spatial information is critical to the interrogation of developmental and tissue-level regulation of gene expression. However, this information is usually lost when global mRNA levels from tissues are measured using reverse transcriptase PCR, microarray analysis or high-throughput sequencing. By contrast, single-molecule fluorescence in situ hybridization (smFISH) preserves the spatial information of the cellular mRNA content with subcellular resolution within tissues. Here we describe an smFISH protocol that allows for the quantification of single mRNAs in Drosophila embryos, using commercially available smFISH probes (e.g., short fluorescently labeled DNA oligonucleotides) in combination with wide-field epifluorescence, confocal or instant structured illumination microscopy (iSIM, a super-resolution imaging approach) and a spot-detection algorithm. Fixed Drosophila embryos are hybridized in solution with a mixture of smFISH probes, mounted onto coverslips and imaged in 3D. Individual fluorescently labeled mRNAs are then localized within tissues and counted using spot-detection software to generate quantitative, spatially resolved gene expression data sets. With minimum guidance, a graduate student can successfully implement this protocol. The smFISH procedure described here can be completed in 4-5 d.

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    Harris LabSinger LabTranscription ImagingFly Functional Connectome
    06/05/17 | Quantitative mRNA imaging throughout the entire Drosophila brain.
    Long X, Colonell J, Wong AM, Singer RH, Lionnet T
    Nature Methods. 2017 Jun 05;14(7):703-6. doi: 10.1038/nmeth.4309

    We describe a fluorescence in situ hybridization method that permits detection of the localization and abundance of single mRNAs (smFISH) in cleared whole-mount adult Drosophila brains. The approach is rapid and multiplexable and does not require molecular amplification; it allows facile quantification of mRNA expression with subcellular resolution on a standard confocal microscope. We further demonstrate single-mRNA detection across the entire brain using a custom Bessel beam structured illumination microscope (BB-SIM).

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    02/27/17 | A variant Sp1 (R218Q) transcription factor might enhance HbF expression in β(0) -thalassaemia homozygotes.
    Jiang Z, Luo H, Farrell JJ, Zhang Z, Schulz VP, Albarawi D, Steinberg MH, Al-Allawi NA, Gallagher PG, Forget BG, Chui DH
    British Journal of Haematology. 2017 Feb 27;180(5):755-7. doi: 10.1111/bjh.14445