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Nature Methods

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https://www.readbyqxmd.com/read/28737741/rapidly-inducible-cas9-and-dsb-ddpcr-to-probe-editing-kinetics
#1
John C Rose, Jason J Stephany, William J Valente, Bridget M Trevillian, Ha V Dang, Jason H Bielas, Dustin J Maly, Douglas M Fowler
We developed a chemically inducible Cas9 (ciCas9) and a droplet digital PCR assay for double-strand breaks (DSB-ddPCR) to investigate the kinetics of Cas9-mediated generation and repair of DSBs in cells. ciCas9 is a rapidly activated, single-component Cas9 variant engineered by replacing the protein's REC2 domain with the BCL-xL protein and fusing an interacting BH3 peptide to the C terminus. ciCas9 can be tunably activated by a compound that disrupts the BCL-xL-BH3 interaction within minutes. DSB-ddPCR demonstrates time-resolved, highly quantitative, and targeted measurement of DSBs...
July 24, 2017: Nature Methods
https://www.readbyqxmd.com/read/28714987/comparison-of-algorithms-for-the-detection-of-cancer-drivers-at-subgene-resolution
#2
Eduard Porta-Pardo, Atanas Kamburov, David Tamborero, Tirso Pons, Daniela Grases, Alfonso Valencia, Nuria Lopez-Bigas, Gad Getz, Adam Godzik
Understanding genetic events that lead to cancer initiation and progression remains one of the biggest challenges in cancer biology. Traditionally, most algorithms for cancer-driver identification look for genes that have more mutations than expected from the average background mutation rate. However, there is now a wide variety of methods that look for nonrandom distribution of mutations within proteins as a signal for the driving role of mutations in cancer. Here we classify and review such subgene-resolution algorithms, compare their findings on four distinct cancer data sets from The Cancer Genome Atlas and discuss how predictions from these algorithms can be interpreted in the emerging paradigms that challenge the simple dichotomy between driver and passenger genes...
July 17, 2017: Nature Methods
https://www.readbyqxmd.com/read/28714986/genome-wide-reconstruction-of-complex-structural-variants-using-read-clouds
#3
Noah Spies, Ziming Weng, Alex Bishara, Jennifer McDaniel, David Catoe, Justin M Zook, Marc Salit, Robert B West, Serafim Batzoglou, Arend Sidow
In read cloud approaches, microfluidic partitioning of long genomic DNA fragments and barcoding of shorter fragments derived from these fragments retains long-range information in short sequencing reads. This combination of short reads with long-range information represents a powerful alternative to single-molecule long-read sequencing. We develop Genome-wide Reconstruction of Complex Structural Variants (GROC-SVs) for SV detection and assembly from read cloud data and apply this method to Illumina-sequenced 10x Genomics sarcoma and breast cancer data sets...
July 17, 2017: Nature Methods
https://www.readbyqxmd.com/read/28671674/addressing-preferred-specimen-orientation-in-single-particle-cryo-em-through-tilting
#4
Yong Zi Tan, Philip R Baldwin, Joseph H Davis, James R Williamson, Clinton S Potter, Bridget Carragher, Dmitry Lyumkis
We present a strategy for tackling preferred specimen orientation in single-particle cryogenic electron microscopy by employing tilts during data collection. We also describe a tool to quantify the resulting directional resolution using 3D Fourier shell correlation volumes. We applied these methods to determine the structures at near-atomic resolution of the influenza hemagglutinin trimer, which adopts a highly preferred specimen orientation, and of ribosomal biogenesis intermediates, which adopt moderately preferred orientations...
July 3, 2017: Nature Methods
https://www.readbyqxmd.com/read/28650478/a-dna-origami-platform-for-quantifying-protein-copy-number-in-super-resolution
#5
Francesca Cella Zanacchi, Carlo Manzo, Angel S Alvarez, Nathan D Derr, Maria F Garcia-Parajo, Melike Lakadamyali
Single-molecule-based super-resolution microscopy offers researchers a unique opportunity to quantify protein copy number with nanoscale resolution. However, while fluorescent proteins have been characterized for quantitative imaging using calibration standards, similar calibration tools for immunofluorescence with small organic fluorophores are lacking. Here we show that DNA origami, in combination with GFP antibodies, is a versatile platform for calibrating fluorophore and antibody labeling efficiency to quantify protein copy number in cellular contexts using super-resolution microscopy...
June 26, 2017: Nature Methods
https://www.readbyqxmd.com/read/28650477/video-rate-volumetric-ca-2-imaging-across-cortex-using-seeded-iterative-demixing-sid-microscopy
#6
Tobias Nöbauer, Oliver Skocek, Alejandro J Pernía-Andrade, Lukas Weilguny, Francisca Martínez Traub, Maxim I Molodtsov, Alipasha Vaziri
Light-field microscopy (LFM) is a scalable approach for volumetric Ca(2+) imaging with high volumetric acquisition rates (up to 100 Hz). Although the technology has enabled whole-brain Ca(2+) imaging in semi-transparent specimens, tissue scattering has limited its application in the rodent brain. We introduce seeded iterative demixing (SID), a computational source-extraction technique that extends LFM to the mammalian cortex. SID can capture neuronal dynamics in vivo within a volume of 900 × 900 × 260 μm located as deep as 380 μm in the mouse cortex or hippocampus at a 30-Hz volume rate while discriminating signals from neurons as close as 20 μm apart, at a computational cost three orders of magnitude less than that of frame-by-frame image reconstruction...
June 26, 2017: Nature Methods
https://www.readbyqxmd.com/read/28650476/cry2h-seq-a-massively-multiplexed-assay-for-deep-coverage-interactome-mapping
#7
Shelly A Trigg, Renee M Garza, Andrew MacWilliams, Joseph R Nery, Anna Bartlett, Rosa Castanon, Adeline Goubil, Joseph Feeney, Ronan O'Malley, Shao-Shan C Huang, Zhuzhu Z Zhang, Mary Galli, Joseph R Ecker
Broad-scale protein-protein interaction mapping is a major challenge given the cost, time, and sensitivity constraints of existing technologies. Here, we present a massively multiplexed yeast two-hybrid method, CrY2H-seq, which uses a Cre recombinase interaction reporter to intracellularly fuse the coding sequences of two interacting proteins and next-generation DNA sequencing to identify these interactions en masse. We applied CrY2H-seq to investigate sparsely annotated Arabidopsis thaliana transcription factors interactions...
June 26, 2017: Nature Methods
https://www.readbyqxmd.com/read/28628129/high-speed-fixed-target-serial-virus-crystallography
#8
Philip Roedig, Helen M Ginn, Tim Pakendorf, Geoff Sutton, Karl Harlos, Thomas S Walter, Jan Meyer, Pontus Fischer, Ramona Duman, Ismo Vartiainen, Bernd Reime, Martin Warmer, Aaron S Brewster, Iris D Young, Tara Michels-Clark, Nicholas K Sauter, Abhay Kotecha, James Kelly, David J Rowlands, Marcin Sikorsky, Silke Nelson, Daniel S Damiani, Roberto Alonso-Mori, Jingshan Ren, Elizabeth E Fry, Christian David, David I Stuart, Armin Wagner, Alke Meents
We report a method for serial X-ray crystallography at X-ray free-electron lasers (XFELs), which allows for full use of the current 120-Hz repetition rate of the Linear Coherent Light Source (LCLS). Using a micropatterned silicon chip in combination with the high-speed Roadrunner goniometer for sample delivery, we were able to determine the crystal structures of the picornavirus bovine enterovirus 2 (BEV2) and the cytoplasmic polyhedrosis virus type 18 polyhedrin, with total data collection times of less than 14 and 10 min, respectively...
June 19, 2017: Nature Methods
https://www.readbyqxmd.com/read/28628128/adaptive-optics-improves-multiphoton-super-resolution-imaging
#9
Wei Zheng, Yicong Wu, Peter Winter, Robert Fischer, Damian Dalle Nogare, Amy Hong, Chad McCormick, Ryan Christensen, William P Dempsey, Don B Arnold, Joshua Zimmerberg, Ajay Chitnis, James Sellers, Clare Waterman, Hari Shroff
We improve multiphoton structured illumination microscopy using a nonlinear guide star to determine optical aberrations and a deformable mirror to correct them. We demonstrate our method on bead phantoms, cells in collagen gels, nematode larvae and embryos, Drosophila brain, and zebrafish embryos. Peak intensity is increased (up to 40-fold) and resolution recovered (up to 176 ± 10 nm laterally, 729 ± 39 nm axially) at depths ∼250 μm from the coverslip surface.
June 19, 2017: Nature Methods
https://www.readbyqxmd.com/read/28628127/rosettaes-a-sampling-strategy-enabling-automated-interpretation-of-difficult-cryo-em-maps
#10
Brandon Frenz, Alexandra C Walls, Edward H Egelman, David Veesler, Frank DiMaio
Accurate atomic modeling of macromolecular structures into cryo-electron microscopy (cryo-EM) maps is a major challenge, as the moderate resolution makes accurate placement of atoms difficult. We present Rosetta enumerative sampling (RosettaES), an automated tool that uses a fragment-based sampling strategy for de novo model completion of macromolecular structures from cryo-EM density maps at 3-5-Å resolution. On a benchmark set of nine proteins, RosettaES was able to identify near-native conformations in 85% of segments...
June 19, 2017: Nature Methods
https://www.readbyqxmd.com/read/28604724/visualizing-adenosine-to-inosine-rna-editing-in-single-mammalian-cells
#11
Ian A Mellis, Rohit Gupte, Arjun Raj, Sara H Rouhanifard
Conversion of adenosine to inosine is a frequent type of RNA editing, but important details about the biology of this conversion remain unknown because of a lack of imaging tools. We developed inoFISH to directly visualize and quantify adenosine-to-inosine-edited transcripts in situ. We found that editing of the GRIA2, EIF2AK2, and NUP43 transcripts is uncorrelated with nuclear localization and paraspeckle association. Further, NUP43 exhibits constant editing levels between single cells, while GRIA2 editing levels vary...
June 12, 2017: Nature Methods
https://www.readbyqxmd.com/read/28604722/webknossos-efficient-online-3d-data-annotation-for-connectomics
#12
Kevin M Boergens, Manuel Berning, Tom Bocklisch, Dominic Bräunlein, Florian Drawitsch, Johannes Frohnhofen, Tom Herold, Philipp Otto, Norman Rzepka, Thomas Werkmeister, Daniel Werner, Georg Wiese, Heiko Wissler, Moritz Helmstaedter
We report webKnossos, an in-browser annotation tool for 3D electron microscopic data. webKnossos provides flight mode, a single-view egocentric reconstruction method enabling trained annotator crowds to reconstruct at a speed of 1.5 ± 0.6 mm/h for axons and 2.1 ± 0.9 mm/h for dendrites in 3D electron microscopic data from mammalian cortex. webKnossos accelerates neurite reconstruction for connectomics by 4- to 13-fold compared with current state-of-the-art tools, thus extending the range of connectomes that can realistically be mapped in the future...
June 12, 2017: Nature Methods
https://www.readbyqxmd.com/read/28581495/quantitative-mrna-imaging-throughout-the-entire-drosophila-brain
#13
Xi Long, Jennifer Colonell, Allan M Wong, Robert H Singer, Timothée Lionnet
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)...
June 5, 2017: Nature Methods
https://www.readbyqxmd.com/read/28581493/crispr-stop-gene-silencing-through-base-editing-induced-nonsense-mutations
#14
Cem Kuscu, Mahmut Parlak, Turan Tufan, Jiekun Yang, Karol Szlachta, Xiaolong Wei, Rashad Mammadov, Mazhar Adli
CRISPR-Cas9-induced DNA damage may have deleterious effects at high-copy-number genomic regions. Here, we use CRISPR base editors to knock out genes by changing single nucleotides to create stop codons. We show that the CRISPR-STOP method is an efficient and less deleterious alternative to wild-type Cas9 for gene-knockout studies. Early stop codons can be introduced in ∼17,000 human genes. CRISPR-STOP-mediated targeted screening demonstrates comparable efficiency to WT Cas9, which indicates the suitability of our approach for genome-wide functional screenings...
June 5, 2017: Nature Methods
https://www.readbyqxmd.com/read/28553965/fast-high-resolution-miniature-two-photon-microscopy-for-brain-imaging-in-freely-behaving-mice
#15
Weijian Zong, Runlong Wu, Mingli Li, Yanhui Hu, Yijun Li, Jinghang Li, Hao Rong, Haitao Wu, Yangyang Xu, Yang Lu, Hongbo Jia, Ming Fan, Zhuan Zhou, Yunfeng Zhang, Aimin Wang, Liangyi Chen, Heping Cheng
Developments in miniaturized microscopes have enabled visualization of brain activities and structural dynamics in animals engaging in self-determined behaviors. However, it remains a challenge to resolve activity at single dendritic spines in freely behaving animals. Here, we report the design and application of a fast high-resolution, miniaturized two-photon microscope (FHIRM-TPM) that accomplishes this goal. With a headpiece weighing 2.15 g and a hollow-core photonic crystal fiber delivering 920-nm femtosecond laser pulses, the FHIRM-TPM is capable of imaging commonly used biosensors (GFP and GCaMP6) at high spatiotemporal resolution (0...
May 29, 2017: Nature Methods
https://www.readbyqxmd.com/read/28504682/testing-for-differential-abundance-in-mass-cytometry-data
#16
Aaron T L Lun, Arianne C Richard, John C Marioni
When comparing biological conditions using mass cytometry data, a key challenge is to identify cellular populations that change in abundance. Here, we present a computational strategy for detecting 'differentially abundant' populations by assigning cells to hyperspheres, testing for significant differences between conditions and controlling the spatial false discovery rate. Our method (http://bioconductor.org/packages/cydar) outperforms other approaches in simulations and finds novel patterns of differential abundance in real data...
May 15, 2017: Nature Methods
https://www.readbyqxmd.com/read/28504680/nm-seq-maps-2-o-methylation-sites-in-human-mrna-with-base-precision
#17
Qing Dai, Sharon Moshitch-Moshkovitz, Dali Han, Nitzan Kol, Ninette Amariglio, Gideon Rechavi, Dan Dominissini, Chuan He
The ribose of RNA nucleotides can be 2'-O-methylated (Nm). Despite advances in high-throughput detection, the inert chemical nature of Nm still limits sensitivity and precludes mapping in mRNA. We leveraged the differential reactivity of 2'-O-methylated and 2'-hydroxylated nucleosides to periodate oxidation to develop Nm-seq, a sensitive method for transcriptome-wide mapping of Nm with base precision. Nm-seq uncovered thousands of Nm sites in human mRNA with features suggesting functional roles.
May 15, 2017: Nature Methods
https://www.readbyqxmd.com/read/28504681/fused-cerebral-organoids-model-interactions-between-brain-regions
#18
Joshua A Bagley, Daniel Reumann, Shan Bian, Julie Lévi-Strauss, Juergen A Knoblich
Human brain development involves complex interactions between different regions, including long-distance neuronal migration or formation of major axonal tracts. Different brain regions can be cultured in vitro within 3D cerebral organoids, but the random arrangement of regional identities limits the reliable analysis of complex phenotypes. Here, we describe a coculture method combining brain regions of choice within one organoid tissue. By fusing organoids of dorsal and ventral forebrain identities, we generate a dorsal-ventral axis...
May 10, 2017: Nature Methods
https://www.readbyqxmd.com/read/28604723/fish-ing-for-captured-contacts-towards-reconciling-fish-and-3c
#19
Geoffrey Fudenberg, Maxim Imakaev
Chromosome conformation capture (3C) and fluorescence in situ hybridization (FISH) are two widely used technologies that provide distinct readouts of 3D chromosome organization. While both technologies can assay locus-specific organization, how to integrate views from 3C, or genome-wide Hi-C, and FISH is far from solved. Contact frequency, measured by Hi-C, and spatial distance, measured by FISH, are often assumed to quantify the same phenomena and used interchangeably. Here, however, we demonstrate that contact frequency is distinct from average spatial distance, both in polymer simulations and in experimental data...
July 2017: Nature Methods
https://www.readbyqxmd.com/read/28604721/comparison-of-computational-methods-for-hi-c-data-analysis
#20
Mattia Forcato, Chiara Nicoletti, Koustav Pal, Carmen Maria Livi, Francesco Ferrari, Silvio Bicciato
Hi-C is a genome-wide sequencing technique used to investigate 3D chromatin conformation inside the nucleus. Computational methods are required to analyze Hi-C data and identify chromatin interactions and topologically associating domains (TADs) from genome-wide contact probability maps. We quantitatively compared the performance of 13 algorithms in their analyses of Hi-C data from six landmark studies and simulations. This comparison revealed differences in the performance of methods for chromatin interaction identification, but more comparable results for TAD detection between algorithms...
July 2017: Nature Methods
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