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Molecular Systems Biology

Shiwei Zheng, Efthymia Papalexi, Andrew Butler, William Stephenson, Rahul Satija
Hematopoietic stem cells (HSCs) give rise to diverse cell types in the blood system, yet our molecular understanding of the early trajectories that generate this enormous diversity in humans remains incomplete. Here, we leverage Drop-seq, a massively parallel single-cell RNA sequencing (scRNA-seq) approach, to individually profile 20,000 progenitor cells from human cord blood, without prior enrichment or depletion for individual lineages based on surface markers. Our data reveal a transcriptional compendium of progenitor states in human cord blood, representing four committed lineages downstream from HSC, alongside the transcriptional dynamics underlying fate commitment...
March 15, 2018: Molecular Systems Biology
Antoine Vigouroux, Enno Oldewurtel, Lun Cui, David Bikard, Sven van Teeffelen
Over the past few years, tools that make use of the Cas9 nuclease have led to many breakthroughs, including in the control of gene expression. The catalytically dead variant of Cas9 known as dCas9 can be guided by small RNAs to block transcription of target genes, in a strategy also known as CRISPRi. Here, we reveal that the level of complementarity between the guide RNA and the target controls the rate at which RNA polymerase "kicks out" dCas9 from the target and completes transcription. We use this mechanism to precisely and robustly reduce gene expression by defined relative amounts...
March 8, 2018: Molecular Systems Biology
Alireza Azimi, Stefano Caramuta, Brinton Seashore-Ludlow, Johan Boström, Jonathan L Robinson, Fredrik Edfors, Rainer Tuominen, Kristel Kemper, Oscar Krijgsman, Daniel S Peeper, Jens Nielsen, Johan Hansson, Suzanne Egyhazi Brage, Mikael Altun, Mathias Uhlen, Gianluca Maddalo
Novel therapies are undergoing clinical trials, for example, the Hsp90 inhibitor, XL888, in combination with BRAF inhibitors for the treatment of therapy-resistant melanomas. Unfortunately, our data show that this combination elicits a heterogeneous response in a panel of melanoma cell lines including PDX-derived models. We sought to understand the mechanisms underlying the differential responses and suggest a patient stratification strategy. Thermal proteome profiling (TPP) identified the protein targets of XL888 in a pair of sensitive and unresponsive cell lines...
March 5, 2018: Molecular Systems Biology
Jérôme Salignon, Magali Richard, Etienne Fulcrand, Hélène Duplus-Bottin, Gaël Yvert
Living systems control cell growth dynamically by processing information from their environment. Although responses to a single environmental change have been intensively studied, little is known about how cells react to fluctuating conditions. Here, we address this question at the genomic scale by measuring the relative proliferation rate (fitness) of 3,568 yeast gene deletion mutants in out-of-equilibrium conditions: periodic oscillations between two environmental conditions. In periodic salt stress, fitness and its genetic variance largely depended on the oscillating period...
March 5, 2018: Molecular Systems Biology
Daniel D Seaton, Alexander Graf, Katja Baerenfaller, Mark Stitt, Andrew J Millar, Wilhelm Gruissem
Plants respond to seasonal cues such as the photoperiod, to adapt to current conditions and to prepare for environmental changes in the season to come. To assess photoperiodic responses at the protein level, we quantified the proteome of the model plant Arabidopsis thaliana by mass spectrometry across four photoperiods. This revealed coordinated changes of abundance in proteins of photosynthesis, primary and secondary metabolism, including pigment biosynthesis, consistent with higher metabolic activity in long photoperiods...
March 1, 2018: Molecular Systems Biology
Christoph Fritzsch, Stephan Baumgärtner, Monika Kuban, Daria Steinshorn, George Reid, Stefan Legewie
Cellular decision-making and environmental adaptation are dependent upon a heterogeneous response of gene expression to external cues. Heterogeneity arises in transcription from random switching between transcriptionally active and inactive states, resulting in bursts of RNA synthesis. Furthermore, the cellular state influences the competency of transcription, thereby globally affecting gene expression in a cell-specific manner. We determined how external stimuli interplay with cellular state to modulate the kinetics of bursting...
February 23, 2018: Molecular Systems Biology
H Tomas Rube, Chaitanya Rastogi, Judith F Kribelbauer, Harmen J Bussemaker
Transcription factors (TFs) interpret DNA sequence by probing the chemical and structural properties of the nucleotide polymer. DNA shape is thought to enable a parsimonious representation of dependencies between nucleotide positions. Here, we propose a unified mathematical representation of the DNA sequence dependence of shape and TF binding, respectively, which simplifies and enhances analysis of shape readout. First, we demonstrate that linear models based on mononucleotide features alone account for 60-70% of the variance in minor groove width, roll, helix twist, and propeller twist...
February 22, 2018: Molecular Systems Biology
Benedikt Rauscher, Florian Heigwer, Luisa Henkel, Thomas Hielscher, Oksana Voloshanenko, Michael Boutros
Cancer genomes often harbor hundreds of molecular aberrations. Such genetic variants can be drivers or passengers of tumorigenesis and create vulnerabilities for potential therapeutic exploitation. To identify genotype-dependent vulnerabilities, forward genetic screens in different genetic backgrounds have been conducted. We devised MINGLE, a computational framework to integrate CRISPR/Cas9 screens originating from different libraries building on approaches pioneered for genetic network discovery in model organisms...
February 21, 2018: Molecular Systems Biology
Thomas Brown, Françoise S Howe, Struan C Murray, Meredith Wouters, Philipp Lorenz, Emily Seward, Scott Rata, Andrew Angel, Jane Mellor
Antisense transcription is widespread in genomes. Despite large differences in gene size and architecture, we find that yeast and human genes share a unique, antisense transcription-associated chromatin signature. We asked whether this signature is related to a biological function for antisense transcription. Using quantitative RNA-FISH, we observed changes in sense transcript distributions in nuclei and cytoplasm as antisense transcript levels were altered. To determine the mechanistic differences underlying these distributions, we developed a mathematical framework describing transcription from initiation to transcript degradation...
February 12, 2018: Molecular Systems Biology
Ayako Yachie-Kinoshita, Kento Onishi, Joel Ostblom, Matthew A Langley, Eszter Posfai, Janet Rossant, Peter W Zandstra
Pluripotent stem cells (PSCs) exist in multiple stable states, each with specific cellular properties and molecular signatures. The mechanisms that maintain pluripotency, or that cause its destabilization to initiate development, are complex and incompletely understood. We have developed a model to predict stabilized PSC gene regulatory network (GRN) states in response to input signals. Our strategy used random asynchronous Boolean simulations (R-ABS) to simulate single-cell fate transitions and strongly connected components (SCCs) strategy to represent population heterogeneity...
January 29, 2018: Molecular Systems Biology
Jette Strasen, Uddipan Sarma, Marcel Jentsch, Stefan Bohn, Caibin Sheng, Daniel Horbelt, Petra Knaus, Stefan Legewie, Alexander Loewer
The cytokine TGFβ provides important information during embryonic development, adult tissue homeostasis, and regeneration. Alterations in the cellular response to TGFβ are involved in severe human diseases. To understand how cells encode the extracellular input and transmit its information to elicit appropriate responses, we acquired quantitative time-resolved measurements of pathway activation at the single-cell level. We established dynamic time warping to quantitatively compare signaling dynamics of thousands of individual cells and described heterogeneous single-cell responses by mathematical modeling...
January 25, 2018: Molecular Systems Biology
Reinoud de Groot, Joel Lüthi, Helen Lindsay, René Holtackers, Lucas Pelkmans
High-content imaging using automated microscopy and computer vision allows multivariate profiling of single-cell phenotypes. Here, we present methods for the application of the CISPR-Cas9 system in large-scale, image-based, gene perturbation experiments. We show that CRISPR-Cas9-mediated gene perturbation can be achieved in human tissue culture cells in a timeframe that is compatible with image-based phenotyping. We developed a pipeline to construct a large-scale arrayed library of 2,281 sequence-verified CRISPR-Cas9 targeting plasmids and profiled this library for genes affecting cellular morphology and the subcellular localization of components of the nuclear pore complex (NPC)...
January 23, 2018: Molecular Systems Biology
Magali Richard, Florent Chuffart, Hélène Duplus-Bottin, Fanny Pouyet, Martin Spichty, Etienne Fulcrand, Marianne Entrevan, Audrey Barthelaix, Michael Springer, Daniel Jost, Gaël Yvert
More and more natural DNA variants are being linked to physiological traits. Yet, understanding what differences they make on molecular regulations remains challenging. Important properties of gene regulatory networks can be captured by computational models. If model parameters can be "personalized" according to the genotype, their variation may then reveal how DNA variants operate in the network. Here, we combined experiments and computations to visualize natural alleles of the yeast GAL3 gene in a space of model parameters describing the galactose response network...
January 15, 2018: Molecular Systems Biology
Adam James Waite, Nicholas W Frankel, Yann S Dufour, Jessica F Johnston, Junjiajia Long, Thierry Emonet
No abstract text is available yet for this article.
January 10, 2018: Molecular Systems Biology
Irina Pavelescu, Josep Vilarrasa-Blasi, Ainoa Planas-Riverola, Mary-Paz González-García, Ana I Caño-Delgado, Marta Ibañes
Plant roots grow due to cell division in the meristem and subsequent cell elongation and differentiation, a tightly coordinated process that ensures growth and adaptation to the changing environment. How the newly formed cells decide to stop elongating becoming fully differentiated is not yet understood. To address this question, we established a novel approach that combines the quantitative phenotypic variability of wild-type Arabidopsis roots with computational data from mathematical models. Our analyses reveal that primary root growth is consistent with a Sizer mechanism, in which cells sense their length and stop elongating when reaching a threshold value...
January 10, 2018: Molecular Systems Biology
Anisha M Perez, Marcella M Gomez, Prashant Kalvapalle, Erin O'Brien-Gilbert, Matthew R Bennett, Yousif Shamoo
The major facilitator superfamily (MFS) effluxers are prominent mediators of antimicrobial resistance. The biochemical characterization of MFS proteins is hindered by their complex membrane environment that makes in vitro biochemical analysis challenging. Since the physicochemical properties of proteins drive the fitness of an organism, we posed the question of whether we could reverse that relationship and derive meaningful biochemical parameters for a single protein simply from fitness changes it confers under varying strengths of selection...
December 22, 2017: Molecular Systems Biology
Maria Polychronidou, Thomas Lemberger
No abstract text is available yet for this article.
December 21, 2017: Molecular Systems Biology
Lisa Van den Broeck, Marieke Dubois, Mattias Vermeersch, Veronique Storme, Minami Matsui, Dirk Inzé
Plants have established different mechanisms to cope with environmental fluctuations and accordingly fine-tune their growth and development through the regulation of complex molecular networks. It is largely unknown how the network architectures change and what the key regulators in stress responses and plant growth are. Here, we investigated a complex, highly interconnected network of 20 Arabidopsis transcription factors (TFs) at the basis of leaf growth inhibition upon mild osmotic stress. We tracked the dynamic behavior of the stress-responsive TFs over time, showing the rapid induction following stress treatment, specifically in growing leaves...
December 21, 2017: Molecular Systems Biology
Jochen Weile, Song Sun, Atina G Cote, Jennifer Knapp, Marta Verby, Joseph C Mellor, Yingzhou Wu, Carles Pons, Cassandra Wong, Natascha van Lieshout, Fan Yang, Murat Tasan, Guihong Tan, Shan Yang, Douglas M Fowler, Robert Nussbaum, Jesse D Bloom, Marc Vidal, David E Hill, Patrick Aloy, Frederick P Roth
Although we now routinely sequence human genomes, we can confidently identify only a fraction of the sequence variants that have a functional impact. Here, we developed a deep mutational scanning framework that produces exhaustive maps for human missense variants by combining random codon mutagenesis and multiplexed functional variation assays with computational imputation and refinement. We applied this framework to four proteins corresponding to six human genes: UBE2I (encoding SUMO E2 conjugase), SUMO1 (small ubiquitin-like modifier), TPK1 (thiamin pyrophosphokinase), and CALM1/2/3 (three genes encoding the protein calmodulin)...
December 21, 2017: Molecular Systems Biology
Jian Wang, Keke Huo, Lixin Ma, Liujun Tang, Dong Li, Xiaobi Huang, Yanzhi Yuan, Chunhua Li, Wei Wang, Wei Guan, Hui Chen, Chaozhi Jin, Juncheng Wei, Wanqiao Zhang, Yongsheng Yang, Qiongming Liu, Ying Zhou, Cuili Zhang, Zhihao Wu, Wangxiang Xu, Ying Zhang, Tao Liu, Donghui Yu, Yaping Zhang, Liang Chen, Dewu Zhu, Xing Zhong, Lixin Kang, Xiang Gan, Xiaolan Yu, Qi Ma, Jing Yan, Li Zhou, Zhongyang Liu, Yunping Zhu, Tao Zhou, Fuchu He, Xiaoming Yang
No abstract text is available yet for this article.
December 18, 2017: Molecular Systems Biology
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