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Stochastic gene regulation

Matthew Z Anderson, Allison M Porman, Na Wang, Eugenio Mancera, Denis Huang, Christina A Cuomo, Richard J Bennett
Heritable epigenetic changes underlie the ability of cells to differentiate into distinct cell types. Here, we demonstrate that the fungal pathogen Candida tropicalis exhibits multipotency, undergoing stochastic and reversible switching between three cellular states. The three cell states exhibit unique cellular morphologies, growth rates, and global gene expression profiles. Genetic analysis identified six transcription factors that play key roles in regulating cell differentiation. In particular, we show that forced expression of Wor1 or Efg1 transcription factors can be used to manipulate transitions between all three cell states...
October 2016: PLoS Genetics
Kenn Gerdes
Bacteria form persisters, cells that are tolerant to multiple antibiotics and other types of environmental stress. Persister formation can be induced either stochastically in single cells of a growing bacterial ensemble, or by environmental stresses, such as nutrient starvation, in a subpopulation of cells. In many cases, the molecular mechanisms underlying persistence are still unknown. However, there is growing evidence that, in enterobacteria, both stochastically and environmentally induced persistence are controlled by the second messenger (p)ppGpp...
November 5, 2016: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Pavol Bokes, Abhyudai Singh
Inside individual cells, expression of genes is stochastic across organisms ranging from bacterial to human cells. A ubiquitous feature of stochastic expression is burst-like synthesis of gene products, which drives considerable intercellular variability in protein levels across an isogenic cell population. One common mechanism by which cells control such stochasticity is negative feedback regulation, where a protein inhibits its own synthesis. For a single gene that is expressed in bursts, negative feedback can affect the burst frequency or the burst size...
September 24, 2016: Journal of Mathematical Biology
Jin Chen, Junhong Choi, Seán E O'Leary, Arjun Prabhakar, Alexey Petrov, Rosslyn Grosely, Elisabetta Viani Puglisi, Joseph D Puglisi
Translation of proteins by the ribosome regulates gene expression, with recent results underscoring the importance of translational control. Misregulation of translation underlies many diseases, including cancer and many genetic diseases. Decades of biochemical and structural studies have delineated many of the mechanistic details in prokaryotic translation, and sketched the outlines of eukaryotic translation. However, translation may not proceed linearly through a single mechanistic pathway, but likely involves multiple pathways and branchpoints...
January 2016: Quarterly Reviews of Biophysics
Sayuri K Hahl, Andreas Kremling
In the mathematical modeling of biochemical reactions, a convenient standard approach is to use ordinary differential equations (ODEs) that follow the law of mass action. However, this deterministic ansatz is based on simplifications; in particular, it neglects noise, which is inherent to biological processes. In contrast, the stochasticity of reactions is captured in detail by the discrete chemical master equation (CME). Therefore, the CME is frequently applied to mesoscopic systems, where copy numbers of involved components are small and random fluctuations are thus significant...
2016: Frontiers in Genetics
Xavier Pichon, Amandine Bastide, Adham Safieddine, Racha Chouaib, Aubin Samacoits, Eugenia Basyuk, Marion Peter, Florian Mueller, Edouard Bertrand
Translation is an essential step in gene expression. In this study, we used an improved SunTag system to label nascent proteins and image translation of single messenger ribonucleoproteins (mRNPs) in human cells. Using a dedicated reporter RNA, we observe that translation of single mRNPs stochastically turns on and off while they diffuse through the cytoplasm. We further measure a ribosome density of 1.3 per kilobase and an elongation rate of 13-18 amino acids per second. Tagging the endogenous POLR2A gene revealed similar elongation rates and ribosomal densities and that nearly all messenger RNAs (mRNAs) are engaged in translation...
September 12, 2016: Journal of Cell Biology
Molly Starkovich, Seema R Lalani, Catherine L Mercer, Daryl A Scott
Congenital heart defects (CHD) are present in over 1% of all newborns and are the leading cause of birth-defect-related deaths in the United States. We describe two male subjects with CHD, one with an atrial septal defect, a ventricular septal defect, and pulmonary artery stenosis; and the other with tetralogy of Fallot and a right aortic arch, who carry partially overlapping, de novo deletions of chromosome 5q33. The maximum region of overlap between these deletions encompasses HAND1 and SAP30L, two genes that have previously been shown to play a role in cardiac development...
September 2, 2016: American Journal of Medical Genetics. Part A
Thomas R Pisanic, Pornpat Athamanolap, Tza-Huei Wang
DNA methylation is a fundamental means of epigenetic gene regulation that occurs in virtually all cell types. In many higher organisms, including humans, it plays vital roles in cell differentiation and homeostatic maintenance of cell phenotype. The control of DNA methylation has traditionally been attributed to a highly coordinated, linear process, whose dysregulation has been associated with numerous pathologies including cancer, where it occurs early in, and even prior to, the development of neoplastic tissues...
August 28, 2016: Seminars in Cell & Developmental Biology
Daryl A Scott, Andres Hernandez-Garcia, Mahshid S Azamian, Valerie K Jordan, Bum Jun Kim, Molly Starkovich, Jinglan Zhang, Lee-Jun Wong, Sandra A Darilek, Amy M Breman, Yaping Yang, James R Lupski, Amyn K Jiwani, Bibhuti Das, Seema R Lalani, Alejandro D Iglesias, Jill A Rosenfeld, Fan Xia
BACKGROUND: The non-POU domain containing octamer-binding gene (NONO) is located on chromosome Xq13.1 and encodes a member of a small family of RNA-binding and DNA-binding proteins that perform a variety of tasks involved in RNA synthesis, transcriptional regulation and DNA repair. Loss-of-function variants in NONO have been described as a cause of intellectual disability in males but have not been described in association with congenital heart defects or cardiomyopathy. In this article, we seek to further define the phenotypic consequences of NONO depletion in human subjects...
August 22, 2016: Journal of Medical Genetics
Robin Tecon, Johan H J Leveau
Microorganisms are capable of remarkable social behaviours, such as forming transient multicellular assemblages with properties and adaptive abilities exceeding those of individual cells. Here, we report on the formation and structure of genets known as symplasmata produced by Pantoea eucalypti bacteria. Each symplasmatum develops clonally and stochastically from a single bacterium into a membrane-delimited, capsule-embedded cluster of progeny cells and with a frequency that depends on temperature, pH, and nutrient availability...
2016: Scientific Reports
Jakub Jędrak, Anna Ochab-Marcinek
Using an analytically solvable stochastic model, we study the properties of a simple genetic circuit consisting of multiple copies of a self-regulating gene. We analyse how the variation in gene copy number and the mutations changing the auto-regulation strength affect the steady-state distribution of protein concentration. We predict that one-reporter assay, an experimental method where the extrinsic noise level is inferred from the comparison of expression variance of a single and duplicated reporter gene, may give an incorrect estimation of the extrinsic noise contribution when applied to self-regulating genes...
November 7, 2016: Journal of Theoretical Biology
Young-Hee Jeong, Hanlin Lu, Chi-Hun Park, Meiyan Li, Huijuan Luo, Joung Joo Kim, Siyang Liu, Kyeong Hee Ko, Shujia Huang, In Sung Hwang, Mi Na Kang, Desheng Gong, Kang Bae Park, Eun Ji Choi, Jung Hyun Park, Yeon Woo Jeong, Changjong Moon, Sang-Hwan Hyun, Nam Hyung Kim, Eui-Bae Jeung, Huanming Yang, Woo Suk Hwang, Fei Gao
Somatic cell nuclear transfer (SCNT) provides an excellent model for studying epigenomic reprogramming during mammalian development. We mapped the whole genome and whole methylome for potential anomalies of mutations or epimutations in SCNT-generated dogs with XY chromosomal sex but complete gonadal dysgenesis, which is classified as 78, XY disorder of sex development (DSD). Whole genome sequencing revealed no potential genomic variations that could explain the pathogenesis of DSD. However, extensive but stochastic anomalies of genome-wide DNA methylation were discovered in these SCNT DSD dogs...
2016: Scientific Reports
K G Petrosyan, Chin-Kun Hu
We extend a previously introduced model of stochastic gene regulation of cancer to a nonlinear case having both gene and pseudogene messenger RNAs (mRNAs) self-regulated. The model consists of stochastic Boolean genetic elements and possesses noise-induced multistability (multimodality). We obtain analytical expressions for probabilities for the case of constant but finite number of microRNA molecules which act as a noise source for the competing gene and pseudogene mRNAs. The probability distribution functions display both the global bistability regime as well as even-odd number oscillations for a certain range of model parameters...
July 28, 2016: Journal of Chemical Physics
Katjana Tantale, Florian Mueller, Alja Kozulic-Pirher, Annick Lesne, Jean-Marc Victor, Marie-Cécile Robert, Serena Capozi, Racha Chouaib, Volker Bäcker, Julio Mateos-Langerak, Xavier Darzacq, Christophe Zimmer, Eugenia Basyuk, Edouard Bertrand
Live-cell imaging has revealed unexpected features of gene expression. Here using improved single-molecule RNA microscopy, we show that synthesis of HIV-1 RNA is achieved by groups of closely spaced polymerases, termed convoys, as opposed to single isolated enzymes. Convoys arise by a Mediator-dependent reinitiation mechanism, which generates a transient but rapid succession of polymerases initiating and escaping the promoter. During elongation, polymerases are spaced by few hundred nucleotides, and physical modelling suggests that DNA torsional stress may maintain polymerase spacing...
2016: Nature Communications
A J Genot, A Baccouche, R Sieskind, N Aubert-Kato, N Bredeche, J F Bartolo, V Taly, T Fujii, Y Rondelez
Analog molecular circuits can exploit the nonlinear nature of biochemical reaction networks to compute low-precision outputs with fewer resources than digital circuits. This analog computation is similar to that employed by gene-regulation networks. Although digital systems have a tractable link between structure and function, the nonlinear and continuous nature of analog circuits yields an intricate functional landscape, which makes their design counter-intuitive, their characterization laborious and their analysis delicate...
August 2016: Nature Chemistry
Silvia Grigolon, Francesca Di Patti, Andrea De Martino, Enzo Marinari
The intrinsic stochasticity of gene expression is usually mitigated in higher eukaryotes by post-transcriptional regulation channels that stabilise the output layer, most notably protein levels. The discovery of small non-coding RNAs (miRNAs) in specific motifs of the genetic regulatory network has led to identifying noise buffering as the possible key function they exert in regulation. Recent in vitro and in silico studies have corroborated this hypothesis. It is however also known that miRNA-mediated noise reduction is hampered by transcriptional bursting in simple topologies...
April 2016: Heliyon
C A Brackley, J Johnson, A Bentivoglio, S Corless, N Gilbert, G Gonnella, D Marenduzzo
We propose a stochastic model for gene transcription coupled to DNA supercoiling, where we incorporate the experimental observation that polymerases create supercoiling as they unwind the DNA helix and that these enzymes bind more favorably to regions where the genome is unwound. Within this model, we show that when the transcriptionally induced flux of supercoiling increases, there is a sharp crossover from a regime where torsional stresses relax quickly and gene transcription is random, to one where gene expression is highly correlated and tightly regulated by supercoiling...
July 1, 2016: Physical Review Letters
Aashish Ranjan, Jessica M Budke, Steven D Rowland, Daniel H Chitwood, Ravi Kumar, Leonela Carriedo, Yasunori Ichihashi, Kristina Zumstein, Julin N Maloof, Neelima R Sinha
Variation in gene expression, in addition to sequence polymorphisms, is known to influence developmental, physiological, and metabolic traits in plants. Genetic mapping populations have facilitated identification of expression quantitative trait loci (eQTL), the genetic determinants of variation in gene expression patterns. We used an introgression population developed from the wild desert-adapted Solanum pennellii and domesticated tomato (Solanum lycopersicum) to identify the genetic basis of transcript level variation...
September 2016: Plant Physiology
Hao Yuan Kueh, Mary A Yui, Kenneth K H Ng, Shirley S Pease, Jingli A Zhang, Sagar S Damle, George Freedman, Sharmayne Siu, Irwin D Bernstein, Michael B Elowitz, Ellen V Rothenberg
During T cell development, multipotent progenitors relinquish competence for other fates and commit to the T cell lineage by turning on Bcl11b, which encodes a transcription factor. To clarify lineage commitment mechanisms, we followed developing T cells at the single-cell level using Bcl11b knock-in fluorescent reporter mice. Notch signaling and Notch-activated transcription factors collaborate to activate Bcl11b expression irrespectively of Notch-dependent proliferation. These inputs work via three distinct, asynchronous mechanisms: an early locus 'poising' function dependent on TCF-1 and GATA-3, a stochastic-permissivity function dependent on Notch signaling, and a separate amplitude-control function dependent on Runx1, a factor already present in multipotent progenitors...
August 2016: Nature Immunology
Gaurav Kaushik, Yu Xia, Luobin Yang, Michael A Thomas
BACKGROUND: A number of researchers have speculated that neurological disorders are mostly due to the interaction of common susceptibility genes with environmental, epigenetic and stochastic factors. Genetic factors such as mutations, insertions, deletions and copy number variations (CNVs) are responsible for only a small subset of cases, suggesting unknown environmental contaminants play a role in triggering neurological disorders like idiopathic autism. Psychoactive pharmaceuticals have been considered as potential environmental contaminants as they are detected in the drinking water at very low concentrations...
2016: BMC Genomics
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