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Cell Systems

Nil Ege, Anna M Dowbaj, Ming Jiang, Michael Howell, Steven Hooper, Charles Foster, Robert P Jenkins, Erik Sahai
The transcriptional regulator YAP1 is critical for the pathological activation of fibroblasts. In normal fibroblasts, YAP1 is located in the cytoplasm, while in activated cancer-associated fibroblasts, it is nuclear and promotes the expression of genes required for pro-tumorigenic functions. Here, we investigate the dynamics of YAP1 shuttling in normal and activated fibroblasts, using EYFP-YAP1, quantitative photobleaching methods, and mathematical modeling. Imaging of migrating fibroblasts reveals the tight temporal coupling of cell shape change and altered YAP1 localization...
June 8, 2018: Cell Systems
Pooja Jha, Molly T McDevitt, Rahul Gupta, Pedro M Quiros, Evan G Williams, Karim Gariani, Maroun B Sleiman, Leo Diserens, Adam Jochem, Arne Ulbrich, Joshua J Coon, Johan Auwerx, David J Pagliarini
The genetics of individual lipid species and their relevance in disease is largely unresolved. We profiled a subset of storage, signaling, membrane, and mitochondrial liver lipids across 385 mice from 47 strains of the BXD mouse population fed chow or high-fat diet and integrated these data with complementary multi-omics datasets. We identified several lipid species and lipid clusters with specific phenotypic and molecular signatures and, in particular, cardiolipin species with signatures of healthy and fatty liver...
June 7, 2018: Cell Systems
Leighton H Daigh, Chad Liu, Mingyu Chung, Karlene A Cimprich, Tobias Meyer
Faithful DNA replication is challenged by stalling of replication forks during S phase. Replication stress is further increased in cancer cells or in response to genotoxic insults. Using live single-cell image analysis, we found that CDK2 activity fluctuates throughout an unperturbed S phase. We show that CDK2 fluctuations result from transient ATR signals triggered by stochastic replication stress events. In turn, fluctuating endogenous CDK2 activity causes corresponding decreases and increases in DNA synthesis rates, linking changes in stochastic replication stress to fluctuating global DNA replication rates throughout S phase...
June 4, 2018: Cell Systems
Mantu Santra, Ken A Dill, Adam M R de Graff
The accumulation of protein damage in aging organisms is thought to contribute to many aging-related diseases. Yet the properties determining which proteins are most susceptible remain poorly understood. Are certain conformations more vulnerable? Which chaperones are the main guardians? We address these questions with a system-wide model of E. coli proteostasis. By predicting how proteins with different folding properties respond to each chaperone's concentration, the model computes "damage fingerprints" that identify unfolded conformations as the major damage target...
June 1, 2018: Cell Systems
Yael Steuerman, Merav Cohen, Naama Peshes-Yaloz, Liran Valadarsky, Ofir Cohn, Eyal David, Amit Frishberg, Lior Mayo, Eran Bacharach, Ido Amit, Irit Gat-Viks
The influenza virus is a major cause of morbidity and mortality worldwide. Yet, both the impact of intracellular viral replication and the variation in host response across different cell types remain uncharacterized. Here we used single-cell RNA sequencing to investigate the heterogeneity in the response of lung tissue cells to in vivo influenza infection. Analysis of viral and host transcriptomes in the same single cell enabled us to resolve the cellular heterogeneity of bystander (exposed but uninfected) as compared with infected cells...
June 1, 2018: Cell Systems
Chuan Xu, Jianzhi Zhang
Alternative polyadenylation (APA) produces from the same gene multiple mature RNAs with varying 3' ends. Although APA is commonly believed to generate beneficial functional diversity and be adaptive, we hypothesize that most genes have one optimal polyadenylation site and that APA is caused largely by deleterious polyadenylation errors. The error hypothesis, but not the adaptive hypothesis, predicts that, as the expression level of a gene increases, its polyadenylation diversity declines, relative use of the major (presumably optimal) polyadenylation site increases, and that of each minor (presumably nonoptimal) site decreases...
June 1, 2018: Cell Systems
Pooja Jha, Molly T McDevitt, Emina Halilbasic, Evan G Williams, Pedro M Quiros, Karim Gariani, Maroun B Sleiman, Rahul Gupta, Arne Ulbrich, Adam Jochem, Joshua J Coon, Michael Trauner, David J Pagliarini, Johan Auwerx
The genetic regulation and physiological impact of most lipid species are unexplored. Here, we profiled 129 plasma lipid species across 49 strains of the BXD mouse genetic reference population fed either chow or a high-fat diet. By integrating these data with genomics and phenomics datasets, we elucidated genes by environment (diet) interactions that regulate systemic metabolism. We found quantitative trait loci (QTLs) for ∼94% of the lipids measured. Several QTLs harbored genes associated with blood lipid levels and abnormal lipid metabolism in human genome-wide association studies...
May 31, 2018: Cell Systems
Somponnat Sampattavanich, Bernhard Steiert, Bernhard A Kramer, Benjamin M Gyori, John G Albeck, Peter K Sorger
Extracellular growth factors signal to transcription factors via a limited number of cytoplasmic kinase cascades. It remains unclear how such cascades encode ligand identities and concentrations. In this paper, we use live-cell imaging and statistical modeling to study FOXO3, a transcription factor regulating diverse aspects of cellular physiology that is under combinatorial control. We show that FOXO3 nuclear-to-cytosolic translocation has two temporally distinct phases varying in magnitude with growth factor identity and cell type...
May 31, 2018: Cell Systems
Elliot Dine, Agnieszka A Gil, Giselle Uribe, Clifford P Brangwynne, Jared E Toettcher
Protein/RNA clusters arise frequently in spatially regulated biological processes, from the asymmetric distribution of P granules and PAR proteins in developing embryos to localized receptor oligomers in migratory cells. This co-occurrence suggests that protein clusters might possess intrinsic properties that make them a useful substrate for spatial regulation. Here, we demonstrate that protein droplets show a robust form of spatial memory, maintaining the spatial pattern of an inhibitor of droplet formation long after it has been removed...
May 24, 2018: Cell Systems
Joshua Pan, Robin M Meyers, Brittany C Michel, Nazar Mashtalir, Ann E Sizemore, Jonathan N Wells, Seth H Cassel, Francisca Vazquez, Barbara A Weir, William C Hahn, Joseph A Marsh, Aviad Tsherniak, Cigall Kadoch
Protein complexes are assemblies of subunits that have co-evolved to execute one or many coordinated functions in the cellular environment. Functional annotation of mammalian protein complexes is critical to understanding biological processes, as well as disease mechanisms. Here, we used genetic co-essentiality derived from genome-scale RNAi- and CRISPR-Cas9-based fitness screens performed across hundreds of human cancer cell lines to assign measures of functional similarity. From these measures, we systematically built and characterized functional similarity networks that recapitulate known structural and functional features of well-studied protein complexes and resolve novel functional modules within complexes lacking structural resolution, such as the mammalian SWI/SNF complex...
May 14, 2018: Cell Systems
Dimitris Christodoulou, Hannes Link, Tobias Fuhrer, Karl Kochanowski, Luca Gerosa, Uwe Sauer
To counteract oxidative stress and reactive oxygen species (ROS), bacteria evolved various mechanisms, primarily reducing ROS through antioxidant systems that utilize cofactor NADPH. Cells must stabilize NADPH levels by increasing flux through replenishing metabolic pathways like pentose phosphate (PP) pathway. Here, we investigate the mechanism enabling the rapid increase in NADPH supply by exposing Escherichia coli to hydrogen peroxide and quantifying the immediate metabolite dynamics. To systematically infer active regulatory interactions governing this response, we evaluated ensembles of kinetic models of glycolysis and PP pathway, each with different regulation mechanisms...
May 2, 2018: Cell Systems
Carolin Loos, Katharina Moeller, Fabian Fröhlich, Tim Hucho, Jan Hasenauer
All biological systems exhibit cell-to-cell variability. Frameworks exist for understanding how stochastic fluctuations and transient differences in cell state contribute to experimentally observable variations in cellular responses. However, current methods do not allow identification of the sources of variability between and within stable subpopulations of cells. We present a data-driven modeling framework for the analysis of populations comprising heterogeneous subpopulations. Our approach combines mixture modeling with frameworks for distribution approximation, facilitating the integration of multiple single-cell datasets and the detection of causal differences between and within subpopulations...
May 1, 2018: Cell Systems
John D Lapek, Robert H Mills, Jacob M Wozniak, Anaamika Campeau, Ronnie H Fang, Xiaoli Wei, Kirsten van de Groep, Araceli Perez-Lopez, Nina M van Sorge, Manuela Raffatellu, Rob Knight, Liangfang Zhang, David J Gonzalez
Group A Streptococcus (GAS) remains one of the top 10 deadliest human pathogens worldwide despite its sensitivity to penicillin. Although the most common GAS infection is pharyngitis (strep throat), it also causes life-threatening systemic infections. A series of complex networks between host and pathogen drive invasive infections, which have not been comprehensively mapped. Attempting to map these interactions, we examined organ-level protein dynamics using a mouse model of systemic GAS infection. We quantified over 11,000 proteins, defining organ-specific markers for all analyzed tissues...
April 28, 2018: Cell Systems
John Salamon, Xiaoyan Qian, Mats Nilsson, David John Lynn
In situ sequencing methods generate spatially resolved RNA localization and expression data at an almost single-cell resolution. Few methods, however, currently exist to analyze and visualize the complex data that is produced, which can encode the localization and expression of a million or more individual transcripts in a tissue section. Here, we present InsituNet, an application that converts in situ sequencing data into interactive network-based visualizations, where each unique transcript is a node in the network and edges represent the spatial co-expression relationships between transcripts...
April 27, 2018: Cell Systems
Paul D Hutchins, Jason D Russell, Joshua J Coon
State-of-the-art proteomics software routinely quantifies thousands of peptides per experiment with minimal need for manual validation or processing of data. For the emerging field of discovery lipidomics via liquid chromatography-tandem mass spectrometry (LC-MS/MS), comparably mature informatics tools do not exist. Here, we introduce LipiDex, a freely available software suite that unifies and automates all stages of lipid identification, reducing hands-on processing time from hours to minutes for even the most expansive datasets...
April 17, 2018: Cell Systems
Han Chen, Chunyan Li, Zhicheng Zhou, Han Liang
The antagonistic pleiotropy theory hypothesizes that evolutionary adaptations maximizing the fitness in early age increase disease burden after reproduction. This theory remains largely untested at the molecular level. Here, we analyzed enhancer evolution in primates to investigate the relationships between aging-related diseases and enhancers acquired after the human-chimpanzee divergence. We report a 5-fold increased evolutionary rate of enhancers that are activated in neural tissues, leading to fixation of ∼100 human-specific enhancers potentially under adaptation...
May 23, 2018: Cell Systems
Savanna Dorsey, Sylvain Tollis, Jing Cheng, Labe Black, Stephen Notley, Mike Tyers, Catherine A Royer
To understand how commitment to cell division in late G1 phase (Start) is controlled by growth and nutrients in budding yeast, we determined the absolute concentrations of the G1/S transcription factors SBF (composed of Swi4 and Swi6) and MBF (composed of Mbp1 and Swi6), the transcriptional repressor Whi5, and the G1 cyclins, Cln1 and Cln2, in single live yeast cells using scanning number and brightness (sN&B) microscopy. In rich medium, Whi5, Mbp1, and Swi6 concentrations were independent of cell size, whereas Swi4 concentration doubled in G1 phase, leading to a size-dependent decrease in the Whi5/Swi4 ratio...
May 23, 2018: Cell Systems
Amelia T Soderholm, Mark J Walker
Multiplex quantitative proteomics analysis of mice infected with Group A Streptococcus reveals organ-specific biomarkers of infection.
May 23, 2018: Cell Systems
(no author information available yet)
This month: in silico labeling of microscopy images (Christiansen/Finkbeiner), single-cell lineage trees and data integration (Rajewsky, Satija), gene expression (Weinberger/Simpson, Tavazoie, Ameres/Zuber), and signalling networks (Mercer/Wollscheid, Fussenegger).
May 23, 2018: Cell Systems
Stéphane Chevrier, Helena L Crowell, Vito R T Zanotelli, Stefanie Engler, Mark D Robinson, Bernd Bodenmiller
The advent of mass cytometry increased the number of parameters measured at the single-cell level while decreasing the extent of crosstalk between channels relative to dye-based flow cytometry. Although reduced, spillover still exists in mass cytometry data, and minimizing its effect requires considerable expert knowledge and substantial experimental effort. Here, we describe a novel bead-based compensation workflow and R-based software that estimates and corrects for interference between channels. We performed an in-depth characterization of the spillover properties in mass cytometry, including limitations defined by the linear range of the mass cytometer and the reproducibility of the spillover over time and across machines...
May 23, 2018: Cell Systems
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