scholarly journals Binary Expression Enhances Reliability of Messaging in Gene Networks

Entropy ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 479
Author(s):  
Leonardo R. Gama ◽  
Guilherme Giovanini ◽  
Gábor Balázsi ◽  
Alexandre F. Ramos

The promoter state of a gene and its expression levels are modulated by the amounts of transcription factors interacting with its regulatory regions. Hence, one may interpret a gene network as a communicating system in which the state of the promoter of a gene (the source) is communicated by the amounts of transcription factors that it expresses (the message) to modulate the state of the promoter and expression levels of another gene (the receptor). The reliability of the gene network dynamics can be quantified by Shannon’s entropy of the message and the mutual information between the message and the promoter state. Here we consider a stochastic model for a binary gene and use its exact steady state solutions to calculate the entropy and mutual information. We show that a slow switching promoter with long and equally standing ON and OFF states maximizes the mutual information and reduces entropy. That is a binary gene expression regime generating a high variance message governed by a bimodal probability distribution with peaks of the same height. Our results indicate that Shannon’s theory can be a powerful framework for understanding how bursty gene expression conciliates with the striking spatio-temporal precision exhibited in pattern formation of developing organisms.

2020 ◽  
Author(s):  
Leonardo R. Gama ◽  
Guilherme Giovanini ◽  
Gábor Balázsi ◽  
Alexandre F. Ramos

AbstractThe promoter state of a gene and its expression levels are modulated by the amounts of transcription factors interacting with its regulatory regions. Hence, one may interpret a gene network as a communicating system in which the state of the promoter of a gene (the source) is communicated by the amounts of transcription factors that it expresses (the message) to modulate the state of the promoter and expression levels of another gene (the receptor). The reliability of the gene network dynamics can be quantified by the Shannon’s entropy of the message and the mutual information between the message and the promoter state. Here we consider a stochastic model for a binary gene and use its exact steady state solutions to calculate the entropy and mutual information. We show that a slow switching promoter having long and equally standing ON and OFF states maximizes the mutual information and reduces entropy. That is a bursty regime generating a high variance message governed by a bimodal probability distribution with peaks of the same height. Our results indicate that Shannon’s theory can be a powerful framework for understanding how bursty gene expression conciliates with the striking spatio-temporal precision exhibited in pattern formation of developing organisms.


2012 ◽  
Vol 07 (01n02) ◽  
pp. 41-70 ◽  
Author(s):  
JASON SHULMAN ◽  
LARS SEEMANN ◽  
GREGG W. ROMAN ◽  
GEMUNU H. GUNARATNE

Networks are used to abstract large, highly-coupled sets of objects. Their analyses have included network classification into a few broad classes and selection of small substructures that perform simple yet common tasks. One issue that has received little attention is how the state of a network can be moved according to a pre-specified set of guidelines. In this paper, we address this question in the context of gene networks. In general, neither the full membership of the gene network associated with a biological process nor the precise form of interactions between nodes is known. What is available, through microarrays or sequencing, are gene expression profiles of an organism or its viable mutants. Our approach relies only on these expression profiles, and not on the availability of an accurate model for the network. The first step is to select a small set of core- or master- nodes, such as transcription factors or microRNAs, that can be used to alter the levels of many of the remaining genes in the network. We ask how the state — or solution — of the gene network changes as the levels of these master nodes are altered externally. The object of our study is, not the network, but the surface of these solutions. We argue that it can be approximated using gene expression profiles of the organism and single manipulation of master node activity. This is done through an "effective model." The effective model as well as error estimates for its predictions can be derived from experimental data. The method is validated using synthetic gene networks that have stationary solutions and those that are periodically driven, e.g., circadian networks. An effective model for the oxygen-deprivation network of E.coli is constructed using previously published gene expression profiles, and used to predict the expression levels in a double knockout mutant. Less that 30% of the predictions lie outside the 5% confidence level. We propose the use of the effective model methodology to compute how Drosophila melanogaster in the normal state can be genetically altered into a pre-defined sleep deprived-like state.


2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Saivageethi Nuthikattu ◽  
Dragan Milenkovic ◽  
John Rutledge ◽  
Amparo Villablanca

AbstractHyperlipidemia is a risk factor for dementia, and chronic consumption of a Western Diet (WD) is associated with cognitive impairment. However, the molecular mechanisms underlying the development of microvascular disease in the memory centers of the brain are poorly understood. This pilot study investigated the nutrigenomic pathways by which the WD regulates gene expression in hippocampal brain microvessels of female mice. Five-week-old female low-density lipoprotein receptor deficient (LDL-R−/−) and C57BL/6J wild type (WT) mice were fed a chow or WD for 8 weeks. Metabolics for lipids, glucose and insulin were determined. Differential gene expression, gene networks and pathways, transcription factors, and non-protein coding RNAs were evaluated by genome-wide microarray and bioinformatics analysis of laser captured hippocampal microvessels. The WD resulted in differential expression of 2,412 genes. The majority of differential gene expression was attributable to differential regulation of cell signaling proteins and their transcription factors, approximately 7% was attributable to differential expression of miRNAs, and a lesser proportion was due to other non-protein coding RNAs, primarily long non-coding RNAs (lncRNAs) and small nucleolar RNAs (snoRNAs) not previously described to be modified by the WD in females. Our findings revealed that chronic consumption of the WD resulted in integrated multilevel molecular regulation of the hippocampal microvasculature of female mice and may provide one of the mechanisms underlying vascular dementia.


Author(s):  
Daniele Mercatelli ◽  
Gonzalo Lopez-Garcia ◽  
Federico M. Giorgi

AbstractMotivationGene Network Inference and Master Regulator Analysis (MRA) have been widely adopted to define specific transcriptional perturbations from gene expression signatures. Several tools exist to perform such analyses, but most require a computer cluster or large amounts of RAM to be executed.ResultsWe developed corto, a fast and lightweight R package to infer gene networks and perform MRA from gene expression data, with optional corrections for Copy Number Variations (CNVs) and able to run on signatures generated from RNA-Seq or ATAC-Seq data. We extensively benchmarked it to infer context-specific gene networks in 39 human tumor and 27 normal tissue datasets.AvailabilityCross-platform and multi-threaded R package on CRAN (stable version) https://cran.rproject.org/package=corto and Github (development release) https://github.com/federicogiorgi/[email protected]


2019 ◽  
Vol 53 (3) ◽  
pp. 323-330 ◽  
Author(s):  
Tanja Kosak Soklic ◽  
Matija Rijavec ◽  
Mira Silar ◽  
Ana Koren ◽  
Izidor Kern ◽  
...  

Abstract Background Chronic rhinosinusitis (CRS) current therapeutic approaches still fail in some patients with severe persistent symptoms and recurrences after surgery. We aimed to evaluate the master transcription factors gene expression levels of T cell subtypes in chronic rhinosinusitis with nasal polyps (CRSwNP) and chronic rhinosinusitis without nasal polyps (CRSsNP) that could represent new, up-stream targets for topical DNAzyme treatment. Patients and methods Twenty-two newly diagnosed CRS patients (14 CRSwNP and 8 CRSsNP) were prospectively biopsied and examined histopathologically. Gene expression levels of T-box transcription factor (T-bet, TBX21), GATA binding protein 3 (GATA3), Retinoic acid-related orphan receptor C (RORC) and Forkhead box P3 (FOXP3) were analyzed by real-time quantitative polymerase chain reaction (RT-qPCR). Results Eosinophilic CRSwNP was characterized by higher level of GATA3 gene expression compared to noneosinophilic CRSwNP, whereas there was no difference in T-bet, RORC and FOXP3 between eosinophilic and noneosinophilic CRSwNP. In CRSsNP, we found simultaneous upregulation of T-bet, GATA3 and RORC gene expression levels in comparison to CRSwNP; meanwhile, there was no difference in FOXP3 gene expression between CRSwNP and CRSsNP. Conclusions In eosinophilic CRSwNP, we confirmed the type 2 inflammation by elevated GATA3 gene expression level. In CRSsNP, we unexpectedly found simultaneous upregulation of T-bet and GATA3 that is currently unexplained; however, it might originate from activated CD8+ cells, abundant in nasal mucosa of CRSsNP patients. The elevated RORC in CRSsNP could be part of homeostatic nasal immune response that might be better preserved in CRSsNP patients compared to CRSwNP patients. Further data on transcription factors expression rates in CRS phenotypes are needed.


2021 ◽  
Vol 28 ◽  
Author(s):  
Ruifen Zhang ◽  
Jing Gao ◽  
Hui Xie ◽  
Yan Sun ◽  
Yuan Zhang ◽  
...  

Background: Palustrin-2CE2 and brevinin-2CE3 are antimicrobial peptides from Rana chensinensis. In R. chensinensis tadpoles, the expression of prepropalustrin-2CE2 and preprobrevinin-2CE3 increased with the developmental stage. In addition, the expression of the two genes was dramatically upregulated with stimulation by Escherichia coli, Staphylococcus aureus, and the chemical lipopolysaccharide (LPS). The genomic organization of the two antimicrobial peptide genes was confirmed. Both prepropalustrin-2CE2 and preprobrevinin-2CE3 contain three exons separated by two large introns. Additionally, several presumed transcription factor binding sites were identified in the promoter sequence. Functional analysis of the promoter was performed using a luciferase reporter system, and further confirmed by yeast one-hybrid experiment and EMSA assay. The results indicated that the transcription factors NF-κB and RelA are involved in regulating the expression of prepropalustrin-2CE2 and preprobrevinin-2CE3. As amphibian populations decline globally, this study provides new data demonstrating how frogs defend against pathogens from the environment by regulating AMP expression. For amphibians, antimicrobial peptides are innate immune molecules that resist adverse external environmental stimuli. However, the regulation mechanism of antimicrobial peptide gene expression in frogs is still unclear. Objective: The two antimicrobial peptides, palustrin-2CE2 and brevinin-2CE3, are produced under external stimulation in Rana chensinensis. Using this model, we analyzed the gene structure and regulatory elements of the two antimicrobial peptide genes and explored the regulatory effects of related transcription factors on the two genes. Method: Different stimuli such as E. coli, S. aureus, and chemical substance lipopolysaccharide (LPS) were applied to Rana chensinensis tadpoles at different developmental stages, and antimicrobial peptide expression levels were detected by RT-PCR. Bioinformatics analysis and 5'-RACE and genome walking technologies were employed to analyze the genome structure and promoter region of the antimicrobial peptide genes. With dual-luciferase reporter gene assays, yeast one-hybrid experiment and EMSA assays, we assessed the regulatory effect of the endogenous regulators of the cell on the antimicrobial peptide promoter. Results: The transcription levels of prepropalustrin-2CE2 and preprobrevinin-2CE3 were significantly upregulated after different stimulations. Genomic structure analysis showed that both genes contained three exons and two introns. Promoter analysis indicated that there are binding sites for regulatory factors of the NF-κB family in the promoter region, and experiments showed that endogenous NF-κB family regulatory factors in frog cells activate the promoters of the antimicrobial peptide genes. Yeast one-hybrid experiment and EMSA assay demonstrated that RelA and NF-κB1 might interact with specific motifs in the prepropalustrin-2CE2 promoter. Conclusion: In this paper, we found that the gene expression levels of the antimicrobial peptides, palustrin-2CE2 and brevinin-2CE3, in R. chensinensis will increase under environmental stimuli, and we verified that the changes in gene expression levels are affected by the transcription factors RelA and NF-κB1. The yeast one-hybrid experiment and EMSA assay confirmed that RelA and NF-κB1 could directly interact with the frog antimicrobial peptide gene promoter, providing new data for the regulatory mechanism of antimicrobial peptides in response to environmental stimuli.


Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1600-1600 ◽  
Author(s):  
Verena I. Gaidzik ◽  
Cailian Wang ◽  
Richard F. Schlenk ◽  
Lars Bullinger ◽  
Peter Paschka ◽  
...  

Abstract Abstract 1600 Poster Board I-626 Background The V-ets erythroblastosis virus E26 (ETS) oncogene family is one of the largest families of transcription factors. ETS transcription factors are characterized by two major functional domains, a transcription domain and an evolutionarily highly conserved DNA-binding domain, also known as ETS domain that mediates binding to purine-rich DNA sequences. Most ETS family proteins are nuclear targets for activation of the Ras-MAP kinase signalling pathway. Therefore, they play a significant role in regulating cellular functions such as cell growth, apoptosis, development and differentiation. ETS transcription factors have been implicated in leukemia by chromosomal rearrangement, and more commonly by gene amplification and/or overexpression. Moreover, overexpression of ERG was shown to be an adverse predictor for clinical outcome in AML with normal cytogenetics (CN). In our recent study on complex karyotype AML, array-CGH (comparative genomic hybridization) analysis identified small genomic amplifications affecting ERG/ETS2 in 21q22 and ETS1/FLI1 in 11q23 in about 10% of the cases. Correlation with global gene expression profiling showed that ERG and ETS2 as well as ETS1 and FLI1 were overexpressed in these cases. Aims: To evaluate expression levels of ERG, ETS2, ETS1 and FLI1 in a large cohort of younger (16 to 60 years of age) adult CN-AML patients (pts) and their impact on clinical outcome. Methods The expression of ERG, ETS2, ETS1 and FLI1 was determined by quantitative real-time reverse transcriptase polymerase chain reaction (qPCR) assay in 343 CN-AML pts who were entered on 3 AMLSG treatment protocols (AMLHD93, AML HD98-A, AMLSG 07-04). ERG, ETS2, ETS1, and FLI1 were dichotomized into two major groups according to their expression levels. The upper quartile was chosen as the cut point and the set of patients with gene expression above were defined as Q4 group. Univariable as well as multivariable regression models were used to evaluate the influence of ERG, ETS2, ETS1 and FLI1 on induction success, event-free, relapse-free and overall survival. Multivariable analyses were stratified for AMLSG treatment protocols. Results Partial correlation analysis revealed positive correlations of expression levels between ETS2 and ERG (ρ=0.45) being the strongest, followed by ERG and FLI1 (ρ=0.4), as well as ETS1 and FLI1 (ρ=0.31). Correlation of ERG, ETS2, ETS1 and FLI1 with white blood count (WBC) revealed a significant association between high gene expression (Q4) and elevated WBC (ERG, p=0.004; ETS2, p=0.002, FLI1 p<0.001), whereas high expression of ETS1 was associated with a significantly lower WBC (p<0.001). Univariable as well as multivariable analyses on induction success revealed high ETS2 as an unfavourable marker (OR, 0.29, p=0.01). In univariable analysis, there was a significantly inferior relapse-free survival (RFS) and overall survival (OS) for high ERG (p=.01; p=.06, respectively) and high ETS2 (p=.002; p=.03, respectively) that was even more pronounced when both ERG Q4 and ETS2 Q4 (ERG Q4 ∩ ETS2 Q4) (p<0.001; p=.001, respectively) were included as one variable and compared with the rest. In multivariable analysis for the endpoints event-free survival (EFS), RFS and OS, a significant effect was found for RFS for ERG Q4 ∩ ETS2 Q4 (p=.002); the only significant variables that consistently appeared in the model were NPM1mut, FLT3-ITDpos and WBC. In subgroup analysis for the genotypes CEBPAmut, NPM1mut/FLT3-ITDneg, and all others (NPM1mut/FLT3-ITDpos, NPM1wt/FLT3-ITDpos, NPM1wt/FLT3-ITDneg) according to the hierarchical model, ERG Q4 was associated with an inferior EFS (p=.04) and OS (p=.03) in the favorable CEBPAmut genotype and became even more significant for the variable ERG Q4 ∩ ETS2 Q4 (EFS, p=.007, RFS, p=.002; OS, p=.06, respectively). For the NPM1mut/FLT3-ITDneg subgroup, again ERG Q4 ∩ ETS2 Q4 was associated with an adverse RFS (p=.04), but not with OS (p=0.07). Conclusions In our study on a large cohort of homogenously treated CN-AML patients, ERG and ETS2 expression were highly correlated. Overexpression of both genes had a significant impact on clinical outcome of CN-AML patients. Moreover, adverse effects of high ERG and high ETS2 expression on prognosis were also shown for the genetic AML subgroups CEBPAmut and NPM1mut/FLT3-ITDneg. Disclosures No relevant conflicts of interest to declare.


2002 ◽  
Vol 76 (13) ◽  
pp. 6800-6814 ◽  
Author(s):  
Bing Tian ◽  
Yuhong Zhang ◽  
Bruce A. Luxon ◽  
Roberto P. Garofalo ◽  
Antonella Casola ◽  
...  

ABSTRACT Respiratory syncytial virus (RSV) is a mucosa-restricted virus that is a leading cause of epidemic respiratory tract infections in children. In epithelial cells, RSV replication activates nuclear translocation of the inducible transcription factor nuclear factor κB (NF-κB) through proteolysis of its cytoplasmic inhibitor, IκB. In spite of a putative role in mediating virus-inducible gene expression, the spectrum of NF-κB-dependent genes induced by RSV infection has not yet been determined. To address this, we developed a tightly regulated cell system expressing a nondegradable, epitope-tagged IκBα isoform (Flag-IκBα Mut) whose expression could be controlled by exogenous addition of nontoxic concentrations of doxycycline. Flag-IκBα Mut expression potently inhibited IκBα proteolysis, NF-κB binding, and NF-κB-dependent gene transcription in cells stimulated with the prototypical NF-κB-activating cytokine tumor necrosis factor alpha (TNF-α) and in response to RSV infection. High-density oligonucleotide microarrays were then used to profile constitutive and RSV-induced gene expression in the absence or presence of Flag-IκBα Mut. Comparison of these profiles revealed 380 genes whose expression was significantly changed by the dominant-negative NF-κB. Of these, 236 genes were constitutive (not RSV regulated), and surprisingly, only 144 genes were RSV regulated, representing numerically ∼10% of the total population of RSV-inducible genes at this time point. Hierarchical clustering of the 144 RSV- and Flag-IκBα Mut-regulated genes identified two discrete gene clusters. The first group had high constitutive expression, and its expression levels fell in response to RSV infection. In this group, constitutive mRNA expression was increased by Flag-IκBα Mut expression, and the RSV-induced decrease in expression was partly inhibited. In the second group, constitutive expression was very low (or undetectable) and, after RSV infection, expression levels strongly increased. In this group, NF-κB was required for RSV-inducible expression because Flag-IκBα Mut expression blocked their induction by RSV. This latter cluster includes chemokines, transcriptional regulators, intracellular proteins regulating translation and proteolysis, and secreted proteins (complement components and growth factor regulators). These data suggest that NF-κB action induces global cellular responses after viral infection.


2014 ◽  
Vol 111 (10) ◽  
pp. 3683-3688 ◽  
Author(s):  
Dmitry Krotov ◽  
Julien O. Dubuis ◽  
Thomas Gregor ◽  
William Bialek

Spatial patterns in the early fruit fly embryo emerge from a network of interactions among transcription factors, the gap genes, driven by maternal inputs. Such networks can exhibit many qualitatively different behaviors, separated by critical surfaces. At criticality, we should observe strong correlations in the fluctuations of different genes around their mean expression levels, a slowing of the dynamics along some but not all directions in the space of possible expression levels, correlations of expression fluctuations over long distances in the embryo, and departures from a Gaussian distribution of these fluctuations. Analysis of recent experiments on the gap gene network shows that all these signatures are observed, and that the different signatures are related in ways predicted by theory. Although there might be other explanations for these individual phenomena, the confluence of evidence suggests that this genetic network is tuned to criticality.


2020 ◽  
Author(s):  
Johanna Hörberg ◽  
Kevin Moreau ◽  
Anna Reymer

AbstractActivator proteins 1 (AP-1) comprise one of the largest families of eukaryotic basic leucine zipper transcription factors. Despite advances in the characterization of AP-1 DNA-binding sites, our ability to predict new binding sites and explain how the proteins achieve different gene expression levels remains limited. Here we address the role of sequence-specific DNA dynamics for stability and specific binding of AP-1 factors, using microseconds long molecular dynamics simulations. As a model system, we employ yeast AP-1 factor Yap1 binding to three different response elements from two genetic environments. Our data show that Yap1 actively exploits the sequence-specific plasticity of DNA within the response element to form stable protein-DNA complexes. The stability also depends on the four to six flanking nucleotides, adjacent to the response elements. The flanking sequences modulate the conformational adaptability of the response element, making it more shape-efficient to form specific contacts with the protein. Bioinformatics analysis of differential expression of the studied genes supports our conclusions: the stability of Yap1-DNA complexes, modulated by the flanking environment, influences the gene expression levels. Our results provide new insights into mechanisms of protein-DNA recognition and the biological regulation of gene expression levels in eukaryotes.


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