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Nature Methods

Thomas Willems, Dina Zielinski, Jie Yuan, Assaf Gordon, Melissa Gymrek, Yaniv Erlich
Short tandem repeats (STRs) are highly variable elements that play a pivotal role in multiple genetic diseases, population genetics applications, and forensic casework. However, it has proven problematic to genotype STRs from high-throughput sequencing data. Here, we describe HipSTR, a novel haplotype-based method for robustly genotyping and phasing STRs from Illumina sequencing data, and we report a genome-wide analysis and validation of de novo STR mutations. HipSTR is freely available at https://hipstr-tool...
April 24, 2017: Nature Methods
Rhonda Bacher, Li-Fang Chu, Ning Leng, Audrey P Gasch, James A Thomson, Ron M Stewart, Michael Newton, Christina Kendziorski
The normalization of RNA-seq data is essential for accurate downstream inference, but the assumptions upon which most normalization methods are based are not applicable in the single-cell setting. Consequently, applying existing normalization methods to single-cell RNA-seq data introduces artifacts that bias downstream analyses. To address this, we introduce SCnorm for accurate and efficient normalization of single-cell RNA-seq data.
April 17, 2017: Nature Methods
Yarui Diao, Rongxin Fang, Bin Li, Zhipeng Meng, Juntao Yu, Yunjiang Qiu, Kimberly C Lin, Hui Huang, Tristin Liu, Ryan J Marina, Inkyung Jung, Yin Shen, Kun-Liang Guan, Bing Ren
Millions of cis-regulatory elements are predicted to be present in the human genome, but direct evidence for their biological function is scarce. Here we report a high-throughput method, cis-regulatory element scan by tiling-deletion and sequencing (CREST-seq), for the unbiased discovery and functional assessment of cis-regulatory sequences in the genome. We used it to interrogate the 2-Mb POU5F1 locus in human embryonic stem cells, and identified 45 cis-regulatory elements. A majority of these elements have active chromatin marks, DNase hypersensitivity, and occupancy by multiple transcription factors, which confirms the utility of chromatin signatures in cis-element mapping...
April 17, 2017: Nature Methods
Daniel Agudelo, Alexis Duringer, Lusiné Bozoyan, Caroline C Huard, Sophie Carter, Jeremy Loehr, Dafni Synodinou, Mathieu Drouin, Jayme Salsman, Graham Dellaire, Josée Laganière, Yannick Doyon
Targeted genome editing enables the creation of bona fide cellular models for biological research and may be applied to human cell-based therapies. Therefore, broadly applicable and versatile methods for increasing its efficacy in cell populations are highly desirable. We designed a simple and robust coselection strategy for enrichment of cells with either nuclease-driven nonhomologous end joining (NHEJ) or homology-directed repair (HDR) events by harnessing the multiplexing capabilities of CRISPR-Cas9 and Cpf1 systems...
April 17, 2017: Nature Methods
Jae-Byum Chang, Fei Chen, Young-Gyu Yoon, Erica E Jung, Hazen Babcock, Jeong Seuk Kang, Shoh Asano, Ho-Jun Suk, Nikita Pak, Paul W Tillberg, Asmamaw T Wassie, Dawen Cai, Edward S Boyden
We recently developed a method called expansion microscopy, in which preserved biological specimens are physically magnified by embedding them in a densely crosslinked polyelectrolyte gel, anchoring key labels or biomolecules to the gel, mechanically homogenizing the specimen, and then swelling the gel-specimen composite by ∼4.5× in linear dimension. Here we describe iterative expansion microscopy (iExM), in which a sample is expanded ∼20×. After preliminary expansion a second swellable polymer mesh is formed in the space newly opened up by the first expansion, and the sample is expanded again...
April 17, 2017: Nature Methods
John Paul Shen, Dongxin Zhao, Roman Sasik, Jens Luebeck, Amanda Birmingham, Ana Bojorquez-Gomez, Katherine Licon, Kristin Klepper, Daniel Pekin, Alex N Beckett, Kyle Salinas Sanchez, Alex Thomas, Chih-Chung Kuo, Dan Du, Assen Roguev, Nathan E Lewis, Aaron N Chang, Jason F Kreisberg, Nevan Krogan, Lei Qi, Trey Ideker, Prashant Mali
We developed a systematic approach to map human genetic networks by combinatorial CRISPR-Cas9 perturbations coupled to robust analysis of growth kinetics. We targeted all pairs of 73 cancer genes with dual guide RNAs in three cell lines, comprising 141,912 tests of interaction. Numerous therapeutically relevant interactions were identified, and these patterns replicated with combinatorial drugs at 75% precision. From these results, we anticipate that cellular context will be critical to synthetic-lethal therapies...
March 20, 2017: Nature Methods
Alexander Song, Adam S Charles, Sue Ann Koay, Jeff L Gauthier, Stephan Y Thiberge, Jonathan W Pillow, David W Tank
Two-photon laser scanning microscopy of calcium dynamics using fluorescent indicators is a widely used imaging method for large-scale recording of neural activity in vivo. Here, we introduce volumetric two-photon imaging of neurons using stereoscopy (vTwINS), a volumetric calcium imaging method that uses an elongated, V-shaped point spread function to image a 3D brain volume. Single neurons project to spatially displaced 'image pairs' in the resulting 2D image, and the separation distance between projections is proportional to depth in the volume...
March 20, 2017: Nature Methods
Wei Zhang, Alexander W Lohman, Yevgeniya Zhuravlova, Xiaocen Lu, Matthew D Wiens, Hiofan Hoi, Sine Yaganoglu, Manuel A Mohr, Elena N Kitova, John S Klassen, Periklis Pantazis, Roger J Thompson, Robert E Campbell
To expand the range of experiments that are accessible with optogenetics, we developed a photocleavable protein (PhoCl) that spontaneously dissociates into two fragments after violet-light-induced cleavage of a specific bond in the protein backbone. We demonstrated that PhoCl can be used to engineer light-activatable Cre recombinase, Gal4 transcription factor, and a viral protease that in turn was used to activate opening of the large-pore ion channel Pannexin-1.
March 13, 2017: Nature Methods
Jakob Birnbaum, Sven Flemming, Nick Reichard, Alexandra Blancke Soares, Paolo Mesén-Ramírez, Ernst Jonscher, Bärbel Bergmann, Tobias Spielmann
Current systems to study essential genes in the human malaria parasite Plasmodium falciparum are often inefficient and time intensive, and they depend on the genetic modification of the target locus, a process hindered by the low frequency of integration of episomal DNA into the genome. Here, we introduce a method, termed selection-linked integration (SLI), to rapidly select for genomic integration. SLI allowed us to functionally analyze targets at the gene and protein levels, thus permitting mislocalization of native proteins, a strategy known as knock sideways, floxing to induce diCre-based excision of genes and knocking in altered gene copies...
March 13, 2017: Nature Methods
Bo Wang, Junjie Zhu, Emma Pierson, Daniele Ramazzotti, Serafim Batzoglou
We present single-cell interpretation via multikernel learning (SIMLR), an analytic framework and software which learns a similarity measure from single-cell RNA-seq data in order to perform dimension reduction, clustering and visualization. On seven published data sets, we benchmark SIMLR against state-of-the-art methods. We show that SIMLR is scalable and greatly enhances clustering performance while improving the visualization and interpretability of single-cell sequencing data.
March 6, 2017: Nature Methods
Sven Dorkenwald, Philipp J Schubert, Marius F Killinger, Gregor Urban, Shawn Mikula, Fabian Svara, Joergen Kornfeld
Teravoxel volume electron microscopy data sets from neural tissue can now be acquired in weeks, but data analysis requires years of manual labor. We developed the SyConn framework, which uses deep convolutional neural networks and random forest classifiers to infer a richly annotated synaptic connectivity matrix from manual neurite skeleton reconstructions by automatically identifying mitochondria, synapses and their types, axons, dendrites, spines, myelin, somata and cell types. We tested our approach on serial block-face electron microscopy data sets from zebrafish, mouse and zebra finch, and computed the synaptic wiring of songbird basal ganglia...
February 27, 2017: Nature Methods
Dimitre G Ouzounov, Tianyu Wang, Mengran Wang, Danielle D Feng, Nicholas G Horton, Jean C Cruz-Hernández, Yu-Ting Cheng, Jacob Reimer, Andreas S Tolias, Nozomi Nishimura, Chris Xu
High-resolution optical imaging is critical to understanding brain function. We demonstrate that three-photon microscopy at 1,300-nm excitation enables functional imaging of GCaMP6s-labeled neurons beyond the depth limit of two-photon microscopy. We record spontaneous activity from up to 150 neurons in the hippocampal stratum pyramidale at ∼1-mm depth within an intact mouse brain. Our method creates opportunities for noninvasive recording of neuronal activity with high spatial and temporal resolution deep within scattering brain tissues...
February 20, 2017: Nature Methods
Jared T Simpson, Rachael E Workman, P C Zuzarte, Matei David, L J Dursi, Winston Timp
In nanopore sequencing devices, electrolytic current signals are sensitive to base modifications, such as 5-methylcytosine (5-mC). Here we quantified the strength of this effect for the Oxford Nanopore Technologies MinION sequencer. By using synthetically methylated DNA, we were able to train a hidden Markov model to distinguish 5-mC from unmethylated cytosine. We applied our method to sequence the methylome of human DNA, without requiring special steps for library preparation.
February 20, 2017: Nature Methods
Martin Harterink, Marta Esteves da Silva, Lena Will, Julia Turan, Adiljan Ibrahim, Alexander E Lang, Eljo Y van Battum, R Jeroen Pasterkamp, Lukas C Kapitein, Dmitri Kudryashov, Ben A Barres, Casper C Hoogenraad, J Bradley Zuchero
The actin cytoskeleton is essential for many fundamental biological processes, but tools for directly manipulating actin dynamics are limited to cell-permeable drugs that preclude single-cell perturbations. Here we describe DeActs, genetically encoded actin-modifying polypeptides, which effectively induce actin disassembly in eukaryotic cells. We demonstrate that DeActs are universal tools for studying the actin cytoskeleton in single cells in culture, tissues, and multicellular organisms including various neurodevelopmental model systems...
May 2017: Nature Methods
Andy T Kong, Felipe V Leprevost, Dmitry M Avtonomov, Dattatreya Mellacheruvu, Alexey I Nesvizhskii
There is a need to better understand and handle the 'dark matter' of proteomics-the vast diversity of post-translational and chemical modifications that are unaccounted in a typical mass spectrometry-based analysis and thus remain unidentified. We present a fragment-ion indexing method, and its implementation in peptide identification tool MSFragger, that enables a more than 100-fold improvement in speed over most existing proteome database search tools. Using several large proteomic data sets, we demonstrate how MSFragger empowers the open database search concept for comprehensive identification of peptides and all their modified forms, uncovering dramatic differences in modification rates across experimental samples and conditions...
May 2017: Nature Methods
Shreya Shukla, Matthew A Langley, Jastaranpreet Singh, John M Edgar, Mahmood Mohtashami, Juan Carlos Zúñiga-Pflücker, Peter W Zandstra
The molecular and cellular signals that guide T-cell development from hematopoietic stem and progenitor cells (HSPCs) remain poorly understood. The thymic microenvironment integrates multiple niche molecules to potentiate T-cell development in vivo. Recapitulating these signals in vitro in a stromal cell-free system has been challenging and limits T-cell generation technologies. Here, we describe a fully defined engineered in vitro niche capable of guiding T-lineage development from HSPCs. Synergistic interactions between Notch ligand Delta-like 4 and vascular cell adhesion molecule 1 (VCAM-1) were leveraged to enhance Notch signaling and progenitor T-cell differentiation rates...
May 2017: Nature Methods
Christopher S Seet, Chongbin He, Michael T Bethune, Suwen Li, Brent Chick, Eric H Gschweng, Yuhua Zhu, Kenneth Kim, Donald B Kohn, David Baltimore, Gay M Crooks, Amélie Montel-Hagen
Studies of human T cell development require robust model systems that recapitulate the full span of thymopoiesis, from hematopoietic stem and progenitor cells (HSPCs) through to mature T cells. Existing in vitro models induce T cell commitment from human HSPCs; however, differentiation into mature CD3(+)TCR-αβ(+) single-positive CD8(+) or CD4(+) cells is limited. We describe here a serum-free, artificial thymic organoid (ATO) system that supports efficient and reproducible in vitro differentiation and positive selection of conventional human T cells from all sources of HSPCs...
May 2017: Nature Methods
Dongmin Lee, Meaghan Creed, Kanghoon Jung, Thomas Stefanelli, Daniel J Wendler, Won Chan Oh, Neymi Layne Mignocchi, Christian Lüscher, Hyung-Bae Kwon
Few tools exist to visualize and manipulate neurons that are targets of neuromodulators. We present iTango, a light- and ligand-gated gene expression system based on a light-inducible split tobacco etch virus protease. Cells expressing the iTango system exhibit increased expression of a marker gene in the presence of dopamine and blue-light exposure, both in vitro and in vivo. We demonstrated the iTango system in a behaviorally relevant context, by inducing expression of optogenetic tools in neurons under dopaminergic control during a behavior of interest...
May 2017: Nature Methods
Vladimir Yu Kiselev, Kristina Kirschner, Michael T Schaub, Tallulah Andrews, Andrew Yiu, Tamir Chandra, Kedar N Natarajan, Wolf Reik, Mauricio Barahona, Anthony R Green, Martin Hemberg
Single-cell RNA-seq enables the quantitative characterization of cell types based on global transcriptome profiles. We present single-cell consensus clustering (SC3), a user-friendly tool for unsupervised clustering, which achieves high accuracy and robustness by combining multiple clustering solutions through a consensus approach ( We demonstrate that SC3 is capable of identifying subclones from the transcriptomes of neoplastic cells collected from patients.
May 2017: Nature Methods
Georg Dorn, Alexander Leitner, Julien Boudet, Sébastien Campagne, Christine von Schroetter, Ahmed Moursy, Ruedi Aebersold, Frédéric H-T Allain
Ribonucleoproteins (RNPs) are key regulators of cellular function. We established an efficient approach, crosslinking of segmentally isotope-labeled RNA and tandem mass spectrometry (CLIR-MS/MS), to localize protein-RNA interactions simultaneously at amino acid and nucleotide resolution. The approach was tested on polypyrimidine tract binding protein 1 and U1 small nuclear RNP. Our method provides distance restraints to support integrative atomic-scale structural modeling and to gain mechanistic insights into RNP-regulated processes...
May 2017: Nature Methods
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