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      Network inference performance complexity: a consequence of topological, experimental and algorithmic determinants

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          Abstract

          Motivation

          Network inference algorithms aim to uncover key regulatory interactions governing cellular decision-making, disease progression and therapeutic interventions. Having an accurate blueprint of this regulation is essential for understanding and controlling cell behavior. However, the utility and impact of these approaches are limited because the ways in which various factors shape inference outcomes remain largely unknown.

          Results

          We identify and systematically evaluate determinants of performance—including network properties, experimental design choices and data processing—by developing new metrics that quantify confidence across algorithms in comparable terms. We conducted a multifactorial analysis that demonstrates how stimulus target, regulatory kinetics, induction and resolution dynamics, and noise differentially impact widely used algorithms in significant and previously unrecognized ways. The results show how even if high-quality data are paired with high-performing algorithms, inferred models are sometimes susceptible to giving misleading conclusions. Lastly, we validate these findings and the utility of the confidence metrics using realistic in silico gene regulatory networks. This new characterization approach provides a way to more rigorously interpret how algorithms infer regulation from biological datasets.

          Availability and implementation

          Code is available at http://github.com/bagherilab/networkinference/.

          Supplementary information

          Supplementary data are available at Bioinformatics online.

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          Most cited references50

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          Structure and function of the feed-forward loop network motif.

          Engineered systems are often built of recurring circuit modules that carry out key functions. Transcription networks that regulate the responses of living cells were recently found to obey similar principles: they contain several biochemical wiring patterns, termed network motifs, which recur throughout the network. One of these motifs is the feed-forward loop (FFL). The FFL, a three-gene pattern, is composed of two input transcription factors, one of which regulates the other, both jointly regulating a target gene. The FFL has eight possible structural types, because each of the three interactions in the FFL can be activating or repressing. Here, we theoretically analyze the functions of these eight structural types. We find that four of the FFL types, termed incoherent FFLs, act as sign-sensitive accelerators: they speed up the response time of the target gene expression following stimulus steps in one direction (e.g., off to on) but not in the other direction (on to off). The other four types, coherent FFLs, act as sign-sensitive delays. We find that some FFL types appear in transcription network databases much more frequently than others. In some cases, the rare FFL types have reduced functionality (responding to only one of their two input stimuli), which may partially explain why they are selected against. Additional features, such as pulse generation and cooperativity, are discussed. This study defines the function of one of the most significant recurring circuit elements in transcription networks.
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            Inferring genetic networks and identifying compound mode of action via expression profiling.

            The complexity of cellular gene, protein, and metabolite networks can hinder attempts to elucidate their structure and function. To address this problem, we used systematic transcriptional perturbations to construct a first-order model of regulatory interactions in a nine-gene subnetwork of the SOS pathway in Escherichia coli. The model correctly identified the major regulatory genes and the transcriptional targets of mitomycin C activity in the subnetwork. This approach, which is experimentally and computationally scalable, provides a framework for elucidating the functional properties of genetic networks and identifying molecular targets of pharmacological compounds.
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              Transcriptional regulation by the numbers: models.

              The expression of genes is regularly characterized with respect to how much, how fast, when and where. Such quantitative data demands quantitative models. Thermodynamic models are based on the assumption that the level of gene expression is proportional to the equilibrium probability that RNA polymerase (RNAP) is bound to the promoter of interest. Statistical mechanics provides a framework for computing these probabilities. Within this framework, interactions of activators, repressors, helper molecules and RNAP are described by a single function, the "regulation factor". This analysis culminates in an expression for the probability of RNA polymerase binding at the promoter of interest as a function of the number of regulatory proteins in the cell.
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                Author and article information

                Contributors
                Role: Associate Editor
                Journal
                Bioinformatics
                Bioinformatics
                bioinformatics
                Bioinformatics
                Oxford University Press
                1367-4803
                1367-4811
                15 September 2019
                14 February 2019
                14 February 2019
                : 35
                : 18
                : 3421-3432
                Affiliations
                [1 ] Department of Chemical and Biological Engineering, Northwestern University , Evanston, IL, USA
                [2 ] Interdisciplinary Biological Sciences Program, Northwestern University , Evanston, IL, USA
                [3 ] Department of Biomedical Engineering, Northwestern University , Evanston, IL, USA
                [4 ] Center for Synthetic Biology, Northwestern University , Evanston, IL, USA
                [5 ] Chemistry of Life Processes Institute, Northwestern University , Evanston, IL, USA
                [6 ] Northwestern Institute on Complex Systems, Northwestern University , Evanston, IL, USA
                Author notes
                To whom correspondence should be addressed E-mail: n-bagheri@ 123456northwestern.edu

                The authors wish it to be known that, in their opinion, Joseph J. Muldoon and Jessica S. Yu authors should be regarded as Joint First authors.

                Article
                btz105
                10.1093/bioinformatics/btz105
                6748731
                30932143
                16b81e1f-60e4-4a64-8868-1e68332739bc
                © The Author(s) 2019. Published by Oxford University Press.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

                History
                : 12 September 2018
                : 24 January 2019
                : 11 February 2019
                Page count
                Pages: 12
                Funding
                Funded by: Northwestern University Biotechnology Training Program
                Funded by: National Science Foundation GRFP
                Funded by: National Science Foundation CAREER
                Award ID: CBET-1653315
                Funded by: Northwestern University McCormick School of Engineering
                Funded by: Northwestern University 10.13039/100007059
                Funded by: Office of the Provost
                Funded by: Office for Research
                Funded by: Northwestern University Information Technology
                Categories
                Original Papers
                Systems Biology

                Bioinformatics & Computational biology
                Bioinformatics & Computational biology

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