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Ghanegolmohammadi F, Eslami M, Ohya Y. Systematic data analysis pipeline for quantitative morphological cell phenotyping. Comput Struct Biotechnol J 2024; 23:2949-2962. [PMID: 39104709 PMCID: PMC11298594 DOI: 10.1016/j.csbj.2024.07.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2024] [Revised: 07/09/2024] [Accepted: 07/10/2024] [Indexed: 08/07/2024] Open
Abstract
Quantitative morphological phenotyping (QMP) is an image-based method used to capture morphological features at both the cellular and population level. Its interdisciplinary nature, spanning from data collection to result analysis and interpretation, can lead to uncertainties, particularly among those new to this actively growing field. High analytical specificity for a typical QMP is achieved through sophisticated approaches that can leverage subtle cellular morphological changes. Here, we outline a systematic workflow to refine the QMP methodology. For a practical review, we describe the main steps of a typical QMP; in each step, we discuss the available methods, their applications, advantages, and disadvantages, along with the R functions and packages for easy implementation. This review does not cover theoretical backgrounds, but provides several references for interested researchers. It aims to broaden the horizons for future phenome studies and demonstrate how to exploit years of endeavors to achieve more with less.
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Affiliation(s)
- Farzan Ghanegolmohammadi
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, Japan
| | - Mohammad Eslami
- Harvard Ophthalmology AI Lab, Schepen’s Eye Research Institute of Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, USA
| | - Yoshikazu Ohya
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, Japan
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2
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Powell-Rodgers G, Pirzada MUR, Richee J, Jungers CF, Colijn S, Stratman AN, Djuranovic S. Role of U11/U12 minor spliceosome gene ZCRB1 in Ciliogenesis and WNT Signaling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.09.607392. [PMID: 39149385 PMCID: PMC11326282 DOI: 10.1101/2024.08.09.607392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
Despite the fact that 0.5% of human introns are processed by the U11/U12 minor spliceosome, the latter influences gene expression across multiple cellular processes. The ZCRB1 protein is a recently described core component of the U12 mono-snRNP minor spliceosome, but its functional significance to minor splicing, gene regulation, and biological signaling cascades is poorly understood. Using CRISPR-Cas9 and siRNA targeted knockout and knockdown strategies, we show that human cell lines with a partial reduction in ZCRB1 expression exhibit significant dysregulation of the splicing and expression of U12-type genes, primarily due to dysregulation of U12 mono-snRNA. RNA-Seq and targeted analyses of minor intron-containing genes indicate a downregulation in the expression of genes involved in ciliogenesis, and consequentially an upregulation in WNT signaling. Additionally, zcrb1 CRISPR-Cas12a knockdown in zebrafish embryos led to gross developmental and body axis abnormalities, disrupted ciliogenesis, and upregulated WNT signaling, complementing our human cell studies. This work highlights a conserved and essential biological role of the minor spliceosome in general, and the ZCRB1 protein specifically in cellular and developmental processes across species, shedding light on the multifaceted relationship between splicing regulation, ciliogenesis, and WNT signaling.
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Affiliation(s)
- Geralle Powell-Rodgers
- Washington University in St. Louis, School of Medicine, Cell Biology and Physiology, St. Louis, MO
| | - Mujeeb Ur Rehman Pirzada
- Washington University in St. Louis, School of Medicine, Cell Biology and Physiology, St. Louis, MO
| | - Jahmiera Richee
- Washington University in St. Louis, School of Medicine, Cell Biology and Physiology, St. Louis, MO
| | - Courtney F. Jungers
- Washington University in St. Louis, School of Medicine, Cell Biology and Physiology, St. Louis, MO
| | - Sarah Colijn
- Washington University in St. Louis, School of Medicine, Cell Biology and Physiology, St. Louis, MO
| | - Amber N. Stratman
- Washington University in St. Louis, School of Medicine, Cell Biology and Physiology, St. Louis, MO
| | - Sergej Djuranovic
- Washington University in St. Louis, School of Medicine, Cell Biology and Physiology, St. Louis, MO
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3
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Condic N, Amiji H, Patel D, Shropshire WC, Lermi NO, Sabha Y, John B, Hanson B, Karras GI. Selection for robust metabolism in domesticated yeasts is driven by adaptation to Hsp90 stress. Science 2024; 385:eadi3048. [PMID: 39052788 DOI: 10.1126/science.adi3048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 12/31/2023] [Accepted: 05/24/2024] [Indexed: 07/27/2024]
Abstract
Protein folding both promotes and constrains adaptive evolution. We uncover this surprising duality in the role of the protein-folding chaperone heat shock protein 90 (Hsp90) in maintaining the integrity of yeast metabolism amid proteotoxic stressors within industrial domestication niches. Ethanol disrupts critical Hsp90-dependent metabolic pathways and exerts strong selective pressure for redundant duplications of key genes within these pathways, yielding the classical genomic signatures of beer and bread domestication. This work demonstrates a mechanism of adaptive canalization in an ecology of major economic importance and highlights Hsp90-dependent variation as an important source of phantom heritability in complex traits.
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Affiliation(s)
- Natalia Condic
- Department of Genetics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Hatim Amiji
- Department of Genetics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Dipak Patel
- Department of Genetics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - William Charles Shropshire
- Center for Infectious Diseases, Department of Epidemiology, Human Genetics and Environmental Sciences, UTHealth Houston School of Public Health, McGovern Medical School, University of Texas Health Science Center, Houston, TX, USA
- Center for Antimicrobial Resistance and Microbial Genomics, University of Texas Health Science Center McGovern Medical School, Houston, TX, USA
| | - Nejla Ozirmak Lermi
- Department of Genetics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Youssef Sabha
- Department of Genetics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Beryl John
- Department of Genetics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Blake Hanson
- Center for Infectious Diseases, Department of Epidemiology, Human Genetics and Environmental Sciences, UTHealth Houston School of Public Health, McGovern Medical School, University of Texas Health Science Center, Houston, TX, USA
- Center for Antimicrobial Resistance and Microbial Genomics, University of Texas Health Science Center McGovern Medical School, Houston, TX, USA
| | - Georgios Ioannis Karras
- Department of Genetics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Genetics and Epigenetics Graduate Program, The University of Texas MD Anderson Cancer Center, UTHealth Houston Graduate School of Biomedical Sciences, Houston, TX, USA
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4
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Spirov AV, Myasnikova EM, Holloway DM. Body plan evolvability: The role of variability in gene regulatory networks. J Bioinform Comput Biol 2024; 22:2450011. [PMID: 39036846 DOI: 10.1142/s0219720024500112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
Recent computational modeling of early fruit fly (Drosophila) development has characterized the degree to which gene regulation networks can be robust to natural variability. In the first few hours of development, broad spatial gradients of maternally derived transcription factors activate embryonic gap genes. These gap patterns determine the subsequent segmented insect body plan through pair-rule gene expression. Gap genes are expressed with greater spatial precision than the maternal patterns. Computational modeling of the gap-gap regulatory interactions provides a mechanistic understanding for this robustness to maternal variability in wild-type (WT) patterning. A long-standing question in evolutionary biology has been how a system which is robust, such as the developmental program creating any particular species' body plan, is also evolvable, i.e. how can a system evolve or speciate, if the WT form is strongly buffered and protected? In the present work, we use the WT model to explore the breakdown of such Waddington-type 'canalization'. What levels of variability will push the system out of the WT form; are there particular pathways in the gene regulatory mechanism which are more susceptible to losing the WT form; and when robustness is lost, what types of forms are most likely to occur (i.e. what forms lie near the WT)? Manipulating maternal effects in several different pathways, we find a common gap 'peak-to-step' pattern transition in the loss of WT. We discuss these results in terms of the evolvability of insect segmentation, and in terms of experimental perturbations and mutations which could test the model predictions. We conclude by discussing the prospects for using continuum models of pattern dynamics to investigate a wider range of evo-devo problems.
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Affiliation(s)
- Alexander V Spirov
- Lab Modeling of Evolution, I. M. Sechenov Institute of Evolutionary Physiology & Biochemistry, Russian Academy of Sciences, Thorez Pr. 44, St. Petersburg 2194223, Russia
| | - Ekaterina M Myasnikova
- Lab Modeling of Evolution, I. M. Sechenov Institute of Evolutionary Physiology & Biochemistry, Russian Academy of Sciences, Thorez Pr. 44, St. Petersburg 2194223, Russia
| | - David M Holloway
- Mathematics Department, British Columbia Institute of Technology, 3700 Willingdon Ave., Burnaby, B.C. V5G 3H2, Canada
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Otto RM, Turska-Nowak A, Brown PM, Reynolds KA. A continuous epistasis model for predicting growth rate given combinatorial variation in gene expression and environment. Cell Syst 2024; 15:134-148.e7. [PMID: 38340730 PMCID: PMC10885703 DOI: 10.1016/j.cels.2024.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 10/13/2023] [Accepted: 01/18/2024] [Indexed: 02/12/2024]
Abstract
Quantifying and predicting growth rate phenotype given variation in gene expression and environment is complicated by epistatic interactions and the vast combinatorial space of possible perturbations. We developed an approach for mapping expression-growth rate landscapes that integrates sparsely sampled experimental measurements with an interpretable machine learning model. We used mismatch CRISPRi across pairs and triples of genes to create over 8,000 titrated changes in E. coli gene expression under varied environmental contexts, exploring epistasis in up to 22 distinct environments. Our results show that a pairwise model previously used to describe drug interactions well-described these data. The model yielded interpretable parameters related to pathway architecture and generalized to predict the combined effect of up to four perturbations when trained solely on pairwise perturbation data. We anticipate this approach will be broadly applicable in optimizing bacterial growth conditions, generating pharmacogenomic models, and understanding the fundamental constraints on bacterial gene expression. A record of this paper's transparent peer review process is included in the supplemental information.
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Affiliation(s)
- Ryan M Otto
- Green Center for Systems Biology - Lyda Hill Department of Bioinformatics, The University of Texas Southwestern Medical Center, Dallas, TX 75230, USA
| | - Agata Turska-Nowak
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75230, USA
| | - Philip M Brown
- Green Center for Systems Biology - Lyda Hill Department of Bioinformatics, The University of Texas Southwestern Medical Center, Dallas, TX 75230, USA
| | - Kimberly A Reynolds
- Green Center for Systems Biology - Lyda Hill Department of Bioinformatics, The University of Texas Southwestern Medical Center, Dallas, TX 75230, USA; Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75230, USA.
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Ohya Y, Ghanegolmohammadi F, Itto-Nakama K. Application of unimodal probability distribution models for morphological phenotyping of budding yeast. FEMS Yeast Res 2024; 24:foad056. [PMID: 38169030 PMCID: PMC10804223 DOI: 10.1093/femsyr/foad056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 09/28/2023] [Accepted: 12/30/2023] [Indexed: 01/05/2024] Open
Abstract
Morphological phenotyping of the budding yeast Saccharomyces cerevisiae has helped to greatly clarify the functions of genes and increase our understanding of cellular functional networks. It is necessary to understand cell morphology and perform quantitative morphological analysis (QMA) but assigning precise values to morphological phenotypes has been challenging. We recently developed the Unimodal Morphological Data image analysis pipeline for this purpose. All true values can be estimated theoretically by applying an appropriate probability distribution if the distribution of experimental values follows a unimodal pattern. This reliable pipeline allows several downstream analyses, including detection of subtle morphological differences, selection of mutant strains with similar morphology, clustering based on morphology, and study of morphological diversity. In addition to basic research, morphological analyses of yeast cells can also be used in applied research to monitor breeding and fermentation processes and control the fermentation activity of yeast cells.
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Affiliation(s)
- Yoshikazu Ohya
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8562, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo 113-8657, Japan
| | - Farzan Ghanegolmohammadi
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8562, Japan
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
| | - Kaori Itto-Nakama
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba 277-8562, Japan
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Alexandre CM, Bubb KL, Schultz KM, Lempe J, Cuperus JT, Queitsch C. LTP2 hypomorphs show genotype-by-environment interaction in early seedling traits in Arabidopsis thaliana. THE NEW PHYTOLOGIST 2024; 241:253-266. [PMID: 37865885 PMCID: PMC10843042 DOI: 10.1111/nph.19334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 09/26/2023] [Indexed: 10/23/2023]
Abstract
Isogenic individuals can display seemingly stochastic phenotypic differences, limiting the accuracy of genotype-to-phenotype predictions. The extent of this phenotypic variation depends in part on genetic background, raising questions about the genes involved in controlling stochastic phenotypic variation. Focusing on early seedling traits in Arabidopsis thaliana, we found that hypomorphs of the cuticle-related gene LIPID TRANSFER PROTEIN 2 (LTP2) greatly increased variation in seedling phenotypes, including hypocotyl length, gravitropism and cuticle permeability. Many ltp2 hypocotyls were significantly shorter than wild-type hypocotyls while others resembled the wild-type. Differences in epidermal properties and gene expression between ltp2 seedlings with long and short hypocotyls suggest a loss of cuticle integrity as the primary determinant of the observed phenotypic variation. We identified environmental conditions that reveal or mask the increased variation in ltp2 hypomorphs and found that increased expression of its closest paralog LTP1 is necessary for ltp2 phenotypes. Our results illustrate how decreased expression of a single gene can generate starkly increased phenotypic variation in isogenic individuals in response to an environmental challenge.
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Affiliation(s)
| | - Kerry L Bubb
- Department of Genome Sciences, University of Washington, Seattle WA 98195, USA
| | - Karla M Schultz
- Department of Genome Sciences, University of Washington, Seattle WA 98195, USA
| | - Janne Lempe
- Julius Kühn Institute (JKI) - Federal Research Centre for Cultivated Plants, Institute for Breeding Research on Fruit Crops, Dresden, Germany 1099
| | - Josh T Cuperus
- Department of Genome Sciences, University of Washington, Seattle WA 98195, USA
| | - Christine Queitsch
- Department of Genome Sciences, University of Washington, Seattle WA 98195, USA
- Brotman Baty Institute for Precision Medicine, Seattle, WA 98195, USA
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8
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Powell G, Simon MM, Pulit S, Mallon AM, Lindgren CM. Genic constraint against nonsynonymous variation across the mouse genome. BMC Genomics 2023; 24:562. [PMID: 37736706 PMCID: PMC10514939 DOI: 10.1186/s12864-023-09637-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 08/30/2023] [Indexed: 09/23/2023] Open
Abstract
BACKGROUND Selective constraint, the depletion of variation due to negative selection, provides insights into the functional impact of variants and disease mechanisms. However, its characterization in mice, the most commonly used mammalian model, remains limited. This study aims to quantify mouse gene constraint using a new metric called the nonsynonymous observed expected ratio (NOER) and investigate its relationship with gene function. RESULTS NOER was calculated using whole-genome sequencing data from wild mouse populations (Mus musculus sp and Mus spretus). Positive correlations were observed between mouse gene constraint and the number of associated knockout phenotypes, indicating stronger constraint on pleiotropic genes. Furthermore, mouse gene constraint showed a positive correlation with the number of pathogenic variant sites in their human orthologues, supporting the relevance of mouse models in studying human disease variants. CONCLUSIONS NOER provides a resource for assessing the fitness consequences of genetic variants in mouse genes and understanding the relationship between gene constraint and function. The study's findings highlight the importance of pleiotropy in selective constraint and support the utility of mouse models in investigating human disease variants. Further research with larger sample sizes can refine constraint estimates in mice and enable more comprehensive comparisons of constraint between mouse and human orthologues.
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Affiliation(s)
- George Powell
- Li Ka Shing Centre for Health Information and Discovery, Big Data Institute, University of Oxford, Oxford, UK.
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, OX11 0RD, UK.
| | - Michelle M Simon
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, OX11 0RD, UK
| | - Sara Pulit
- Li Ka Shing Centre for Health Information and Discovery, Big Data Institute, University of Oxford, Oxford, UK
| | - Ann-Marie Mallon
- Mammalian Genetics Unit, MRC Harwell Institute, Oxfordshire, OX11 0RD, UK
| | - Cecilia M Lindgren
- Li Ka Shing Centre for Health Information and Discovery, Big Data Institute, University of Oxford, Oxford, UK
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
- Medical and Population Genetics Program, Broad Institute of MIT and Harvard, Cambridge, MA, USA
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Alexandre CM, Bubb KL, Schultz KM, Lempe J, Cuperus JT, Queitsch C. LTP2 hypomorphs show genotype-by-environment interaction in early seedling traits in Arabidopsis thaliana. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.11.540469. [PMID: 37214854 PMCID: PMC10197655 DOI: 10.1101/2023.05.11.540469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Isogenic individuals can display seemingly stochastic phenotypic differences, limiting the accuracy of genotype-to-phenotype predictions. The extent of this phenotypic variation depends in part on genetic background, raising questions about the genes involved in controlling stochastic phenotypic variation. Focusing on early seedling traits in Arabidopsis thaliana, we found that hypomorphs of the cuticle-related gene LTP2 greatly increased variation in seedling phenotypes, including hypocotyl length, gravitropism and cuticle permeability. Many ltp2 hypocotyls were significantly shorter than wild-type hypocotyls while others resembled the wild type. Differences in epidermal properties and gene expression between ltp2 seedlings with long and short hypocotyls suggest a loss of cuticle integrity as the primary determinant of the observed phenotypic variation. We identified environmental conditions that reveal or mask the increased variation in ltp2 hypomorphs, and found that increased expression of its closest paralog LTP1 is necessary for ltp2 phenotypes. Our results illustrate how decreased expression of a single gene can generate starkly increased phenotypic variation in isogenic individuals in response to an environmental challenge.
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Affiliation(s)
| | - Kerry L Bubb
- Department of Genome Sciences, University of Washington, Seattle WA 98195, USA
| | - Karla M Schultz
- Department of Genome Sciences, University of Washington, Seattle WA 98195, USA
| | - Janne Lempe
- Julius Kühn Institute (JKI) - Federal Research Centre for Cultivated Plants, Institute for Breeding Research on Fruit Crops, Dresden, Germany
| | - Josh T Cuperus
- Department of Genome Sciences, University of Washington, Seattle WA 98195, USA
| | - Christine Queitsch
- Department of Genome Sciences, University of Washington, Seattle WA 98195, USA
- Brotman Baty Institute for Precision Medicine, Seattle, WA 98195, USA
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10
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Patel D, Amiji H, Shropshire W, Condic N, Lermi NO, Sabha Y, John B, Hanson B, Karras GI. Ethanol Drives Evolution of Hsp90-Dependent Robustness by Redundancy in Yeast Domestication. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.21.547572. [PMID: 37745611 PMCID: PMC10516021 DOI: 10.1101/2023.07.21.547572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
Protein folding promotes and constrains adaptive evolution. We uncover this surprising duality in the role the protein-folding chaperone Hsp90 plays in mediating the interplay between proteome and the genome which acts to maintain the integrity of yeast metabolism in the face of proteotoxic stressors in anthropic niches. Of great industrial relevance, ethanol concentrations generated by fermentation in the making of beer and bread disrupt critical Hsp90-dependent nodes of metabolism and exert strong selective pressure for increased copy number of key genes encoding components of these nodes, yielding the classical genetic signatures of beer and bread domestication. This work establishes a mechanism of adaptive canalization in an ecology of major economic significance and highlights Hsp90-contingent variation as an important source of phantom heritability in complex traits.
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11
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Gene loss and compensatory evolution promotes the emergence of morphological novelties in budding yeast. Nat Ecol Evol 2022; 6:763-773. [PMID: 35484218 DOI: 10.1038/s41559-022-01730-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 03/10/2022] [Indexed: 01/05/2023]
Abstract
Deleterious mutations are generally considered to be irrelevant for morphological evolution. However, they could be compensated by conditionally beneficial mutations, thereby providing access to new adaptive paths. Here we use high-dimensional phenotyping of laboratory-evolved budding yeast lineages to demonstrate that new cellular morphologies emerge exceptionally rapidly as a by-product of gene loss and subsequent compensatory evolution. Unexpectedly, the capacities for invasive growth, multicellular aggregation and biofilm formation also spontaneously evolve in response to gene loss. These multicellular phenotypes can be achieved by diverse mutational routes and without reactivating the canonical regulatory pathways. These ecologically and clinically relevant traits originate as pleiotropic side effects of compensatory evolution and have no obvious utility in the laboratory environment. The extent of morphological diversity in the evolved lineages is comparable to that of natural yeast isolates with diverse genetic backgrounds and lifestyles. Finally, we show that both the initial gene loss and subsequent compensatory mutations contribute to new morphologies, with their synergistic effects underlying specific morphological changes. We conclude that compensatory evolution is a previously unrecognized source of morphological diversity and phenotypic novelties.
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Bheemireddy S, Srinivasan N. Computational Study on the Dynamics of Mycobacterium Tuberculosis RNA Polymerase Assembly. Methods Mol Biol 2022; 2516:61-79. [PMID: 35922622 DOI: 10.1007/978-1-0716-2413-5_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Gene regulation is an intricate phenomenon involving precise function of many macromolecular complexes. Molecular basis of this phenomenon is highly complex and cannot be fully understood using a single technique. Computational approaches can play a crucial role in overall understanding of functional and mechanistic features of a protein or an assembly. Large amounts of structural data pertaining to these complexes are publicly available. In this project, we took advantage of the availability of the structural information to unravel functional intricacies of Mycobacterium tuberculosis RNA polymerase upon interaction with RbpA. In this article, we discuss how the knowledge on protein structure and dynamics can be exploited to study function using various computational tools and resources. Overall, this article provides an overview of various computational methods which can be efficiently used to understand the role of any protein. We hope especially the nonexperts in the field could benefit from our article.
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Affiliation(s)
- Sneha Bheemireddy
- Molecular Biophysics Unit, Indian Institute of Science, Bengaluru, Karnataka, India.
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Virulence Factors and in-Host Selection on Phenotypes in Infectious Probiotic Yeast Isolates ( Saccharomyces 'boulardii'). J Fungi (Basel) 2021; 7:jof7090746. [PMID: 34575784 PMCID: PMC8472476 DOI: 10.3390/jof7090746] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/07/2021] [Accepted: 09/09/2021] [Indexed: 12/27/2022] Open
Abstract
Saccharomyces yeast probiotics (S. ‘boulardii’) have long been applied in the treatment of several gastrointestinal conditions. Despite their widespread use, they are rare opportunistic pathogens responsible for a high proportion of Saccharomyces mycosis cases. The potential virulence attributes of S. ‘boulardii’ as well as its interactions with the human immune system have been studied, however, no information is available on how these yeasts may change due to in-host evolution. To fill this gap, we compared the general phenotypic characteristics, cell morphology, virulence factors, epithelial and immunological interactions, and pathogenicity of four probiotic product samples, two mycosis, and eight non-mycosis samples of S. ‘boulardii’. We assessed the characteristics related to major steps of yeast infections. Mycosis and non-mycosis isolates both displayed novel characters when compared to the product isolates, but in the case of most virulence factors and in pathogenicity, differences were negligible or, surprisingly, the yeasts from products showed elevated levels. No isolates inflicted considerable damage to the epithelial model or bore the hallmarks of immune evasion. Our results show that strains in probiotic products possess characteristics that enable them to act as pathogens upon permissive conditions, and their entry into the bloodstream is not due to active mechanisms but depends on the host. Survival in the host is dependent on yeast phenotypic characteristics which may change in many ways once they start evolving in the host. These facts call attention to the shortcomings of virulence phenotyping in yeast research, and the need for a more thorough assessment of probiotic use.
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Hintze M, Katsanos D, Shahrezaei V, Barkoulas M. Phenotypic Robustness of Epidermal Stem Cell Number in C. elegans Is Modulated by the Activity of the Conserved N-acetyltransferase nath-10/NAT10. Front Cell Dev Biol 2021; 9:640856. [PMID: 34084768 PMCID: PMC8168469 DOI: 10.3389/fcell.2021.640856] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 04/19/2021] [Indexed: 12/14/2022] Open
Abstract
Individual cells and organisms experience perturbations from internal and external sources, yet manage to buffer these to produce consistent phenotypes, a property known as robustness. While phenotypic robustness has often been examined in unicellular organisms, it has not been sufficiently studied in multicellular animals. Here, we investigate phenotypic robustness in Caenorhabditis elegans seam cells. Seam cells are stem cell-like epithelial cells along the lateral edges of the animal, which go through asymmetric and symmetric divisions contributing cells to the hypodermis and neurons, while replenishing the stem cell reservoir. The terminal number of seam cells is almost invariant in the wild-type population, allowing the investigation of how developmental precision is achieved. We report here that a loss-of-function mutation in the highly conserved N-acetyltransferase nath-10/NAT10 increases seam cell number variance in the isogenic population. RNA-seq analysis revealed increased levels of mRNA transcript variability in nath-10 mutant populations, which may have an impact on the phenotypic variability observed. Furthermore, we found disruption of Wnt signaling upon perturbing nath-10 function, as evidenced by changes in POP-1/TCF nuclear distribution and ectopic activation of its GATA transcription factor target egl-18. These results highlight that NATH-10/NAT-10 can influence phenotypic variability partly through modulation of the Wnt signaling pathway.
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Affiliation(s)
- Mark Hintze
- Department of Life Sciences, Imperial College, London, United Kingdom
| | - Dimitris Katsanos
- Department of Life Sciences, Imperial College, London, United Kingdom
| | - Vahid Shahrezaei
- Department of Mathematics, Imperial College, London, United Kingdom
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15
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Mathis AD, Otto RM, Reynolds KA. A simplified strategy for titrating gene expression reveals new relationships between genotype, environment, and bacterial growth. Nucleic Acids Res 2021; 49:e6. [PMID: 33221881 PMCID: PMC7797047 DOI: 10.1093/nar/gkaa1073] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 10/02/2020] [Accepted: 10/22/2020] [Indexed: 11/13/2022] Open
Abstract
A lack of high-throughput techniques for making titrated, gene-specific changes in expression limits our understanding of the relationship between gene expression and cell phenotype. Here, we present a generalizable approach for quantifying growth rate as a function of titrated changes in gene expression level. The approach works by performing CRISPRi with a series of mutated single guide RNAs (sgRNAs) that modulate gene expression. To evaluate sgRNA mutation strategies, we constructed a library of 5927 sgRNAs targeting 88 genes in Escherichia coli MG1655 and measured the effects on growth rate. We found that a compounding mutational strategy, through which mutations are incrementally added to the sgRNA, presented a straightforward way to generate a monotonic and gradated relationship between mutation number and growth rate effect. We also implemented molecular barcoding to detect and correct for mutations that 'escape' the CRISPRi targeting machinery; this strategy unmasked deleterious growth rate effects obscured by the standard approach of ignoring escapers. Finally, we performed controlled environmental variations and observed that many gene-by-environment interactions go completely undetected at the limit of maximum knockdown, but instead manifest at intermediate expression perturbation strengths. Overall, our work provides an experimental platform for quantifying the phenotypic response to gene expression variation.
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Affiliation(s)
- Andrew D Mathis
- The Green Center for Systems Biology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Ryan M Otto
- The Green Center for Systems Biology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Kimberly A Reynolds
- The Green Center for Systems Biology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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16
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Ewe CK, Alok G, Rothman JH. Stressful development: integrating endoderm development, stress, and longevity. Dev Biol 2020; 471:34-48. [PMID: 33307045 DOI: 10.1016/j.ydbio.2020.12.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 12/02/2020] [Accepted: 12/03/2020] [Indexed: 10/22/2022]
Abstract
In addition to performing digestion and nutrient absorption, the intestine serves as one of the first barriers to the external environment, crucial for protecting the host from environmental toxins, pathogenic invaders, and other stress inducers. The gene regulatory network (GRN) governing embryonic development of the endoderm and subsequent differentiation and maintenance of the intestine has been well-documented in C. elegans. A key regulatory input that initiates activation of the embryonic GRN for endoderm and mesoderm in this animal is the maternally provided SKN-1 transcription factor, an ortholog of the vertebrate Nrf1 and 2, which, like C. elegans SKN-1, perform conserved regulatory roles in mediating a variety of stress responses across metazoan phylogeny. Other key regulatory factors in early gut development also participate in stress response as well as in innate immunity and aging and longevity. In this review, we discuss the intersection between genetic nodes that mediate endoderm/intestine differentiation and regulation of stress and homeostasis. We also consider how direct signaling from the intestine to the germline, in some cases involving SKN-1, facilitates heritable epigenetic changes, allowing transmission of adaptive stress responses across multiple generations. These connections between regulation of endoderm/intestine development and stress response mechanisms suggest that varying selective pressure exerted on the stress response pathways may influence the architecture of the endoderm GRN, thereby leading to genetic and epigenetic variation in early embryonic GRN regulatory events.
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Affiliation(s)
- Chee Kiang Ewe
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA.
| | - Geneva Alok
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA.
| | - Joel H Rothman
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA.
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17
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Hawkins JS, Silvis MR, Koo BM, Peters JM, Osadnik H, Jost M, Hearne CC, Weissman JS, Todor H, Gross CA. Mismatch-CRISPRi Reveals the Co-varying Expression-Fitness Relationships of Essential Genes in Escherichia coli and Bacillus subtilis. Cell Syst 2020; 11:523-535.e9. [PMID: 33080209 PMCID: PMC7704046 DOI: 10.1016/j.cels.2020.09.009] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 08/26/2020] [Accepted: 09/25/2020] [Indexed: 11/24/2022]
Abstract
Essential genes are the hubs of cellular networks, but lack of high-throughput methods for titrating gene expression has limited our understanding of the fitness landscapes against which their expression levels are optimized. We developed a modified CRISPRi system leveraging the predictable reduction in efficacy of imperfectly matched sgRNAs to generate defined levels of CRISPRi activity and demonstrated its broad applicability. Using libraries of mismatched sgRNAs predicted to span the full range of knockdown levels, we characterized the expression-fitness relationships of most essential genes in Escherichia coli and Bacillus subtilis. We find that these relationships vary widely from linear to bimodal but are similar within pathways. Notably, despite ∼2 billion years of evolutionary separation between E. coli and B. subtilis, most essential homologs have similar expression-fitness relationships with rare but informative differences. Thus, the expression levels of essential genes may reflect homeostatic or evolutionary constraints shared between the two organisms.
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Affiliation(s)
- John S Hawkins
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Melanie R Silvis
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Byoung-Mo Koo
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jason M Peters
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Hendrik Osadnik
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Marco Jost
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA; California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Cameron C Hearne
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jonathan S Weissman
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA; California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Horia Todor
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA.
| | - Carol A Gross
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94158, USA; California Institute of Quantitative Biology, University of California, San Francisco, San Francisco, CA 94158, USA.
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18
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Poyatos JF. Genetic buffering and potentiation in metabolism. PLoS Comput Biol 2020; 16:e1008185. [PMID: 32925942 PMCID: PMC7514045 DOI: 10.1371/journal.pcbi.1008185] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 09/24/2020] [Accepted: 07/23/2020] [Indexed: 01/12/2023] Open
Abstract
Cells adjust their metabolism in response to mutations, but how this reprogramming depends on the genetic context is not well known. Specifically, the absence of individual enzymes can affect reprogramming, and thus the impact of mutations in cell growth. Here, we examine this issue with an in silico model of Saccharomyces cerevisiae's metabolism. By quantifying the variability in the growth rate of 10000 different mutant metabolisms that accumulated changes in their reaction fluxes, in the presence, or absence, of a specific enzyme, we distinguish a subset of modifier genes serving as buffers or potentiators of variability. We notice that the most potent modifiers refer to the glycolysis pathway and that, more broadly, they show strong pleiotropy and epistasis. Moreover, the evidence that this subset depends on the specific growing condition strengthens its systemic underpinning, a feature only observed before in a toy model of a gene-regulatory network. Some of these enzymes also modulate the effect that biochemical noise and environmental fluctuations produce in growth. Thus, the reorganization of metabolism induced by mutations has not only direct physiological implications but also transforms the influence that other mutations have on growth. This is a general result with implications in the development of cancer therapies based on metabolic inhibitors.
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Affiliation(s)
- Juan F. Poyatos
- Logic of Genomic Systems Lab (CNB-CSIC), Madrid, Spain
- Center for Genomics and Systems Biology (NYU), New York, United States of America
- * E-mail:
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19
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Geiler-Samerotte KA, Li S, Lazaris C, Taylor A, Ziv N, Ramjeawan C, Paaby AB, Siegal ML. Extent and context dependence of pleiotropy revealed by high-throughput single-cell phenotyping. PLoS Biol 2020; 18:e3000836. [PMID: 32804946 PMCID: PMC7451985 DOI: 10.1371/journal.pbio.3000836] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 08/27/2020] [Accepted: 07/31/2020] [Indexed: 01/08/2023] Open
Abstract
Pleiotropy-when a single mutation affects multiple traits-is a controversial topic with far-reaching implications. Pleiotropy plays a central role in debates about how complex traits evolve and whether biological systems are modular or are organized such that every gene has the potential to affect many traits. Pleiotropy is also critical to initiatives in evolutionary medicine that seek to trap infectious microbes or tumors by selecting for mutations that encourage growth in some conditions at the expense of others. Research in these fields, and others, would benefit from understanding the extent to which pleiotropy reflects inherent relationships among phenotypes that correlate no matter the perturbation (vertical pleiotropy). Alternatively, pleiotropy may result from genetic changes that impose correlations between otherwise independent traits (horizontal pleiotropy). We distinguish these possibilities by using clonal populations of yeast cells to quantify the inherent relationships between single-cell morphological features. Then, we demonstrate how often these relationships underlie vertical pleiotropy and how often these relationships are modified by genetic variants (quantitative trait loci [QTL]) acting via horizontal pleiotropy. Our comprehensive screen measures thousands of pairwise trait correlations across hundreds of thousands of yeast cells and reveals ample evidence of both vertical and horizontal pleiotropy. Additionally, we observe that the correlations between traits can change with the environment, genetic background, and cell-cycle position. These changing dependencies suggest a nuanced view of pleiotropy: biological systems demonstrate limited pleiotropy in any given context, but across contexts (e.g., across diverse environments and genetic backgrounds) each genetic change has the potential to influence a larger number of traits. Our method suggests that exploiting pleiotropy for applications in evolutionary medicine would benefit from focusing on traits with correlations that are less dependent on context.
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Affiliation(s)
- Kerry A. Geiler-Samerotte
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- Center for Mechanisms of Evolution, Biodesign Institutes, School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - Shuang Li
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Charalampos Lazaris
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
| | - Austin Taylor
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
| | - Naomi Ziv
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- Department of Microbiology and Immunology, University of California, San Francisco, California, United States of America
| | - Chelsea Ramjeawan
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
| | - Annalise B. Paaby
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | - Mark L. Siegal
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
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20
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Sarkar D, Maranas CD. SNPeffect: identifying functional roles of SNPs using metabolic networks. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 103:512-531. [PMID: 32167625 PMCID: PMC9328443 DOI: 10.1111/tpj.14746] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 02/20/2020] [Indexed: 05/04/2023]
Abstract
Genetic sources of phenotypic variation have been a focus of plant studies aimed at improving agricultural yield and understanding adaptive processes. Genome-wide association studies identify the genetic background behind a trait by examining associations between phenotypes and single-nucleotide polymorphisms (SNPs). Although such studies are common, biological interpretation of the results remains a challenge; especially due to the confounding nature of population structure and the systematic biases thus introduced. Here, we propose a complementary analysis (SNPeffect) that offers putative genotype-to-phenotype mechanistic interpretations by integrating biochemical knowledge encoded in metabolic models. SNPeffect is used to explain differential growth rate and metabolite accumulation in A. thaliana and P. trichocarpa accessions as the outcome of SNPs in enzyme-coding genes. To this end, we also constructed a genome-scale metabolic model for Populus trichocarpa, the first for a perennial woody tree. As expected, our results indicate that growth is a complex polygenic trait governed by carbon and energy partitioning. The predicted set of functional SNPs in both species are associated with experimentally characterized growth-determining genes and also suggest putative ones. Functional SNPs were found in pathways such as amino acid metabolism, nucleotide biosynthesis, and cellulose and lignin biosynthesis, in line with breeding strategies that target pathways governing carbon and energy partition.
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Affiliation(s)
- Debolina Sarkar
- Department of Chemical EngineeringPennsylvania State UniversityUniversity ParkPAUSA
| | - Costas D. Maranas
- Department of Chemical EngineeringPennsylvania State UniversityUniversity ParkPAUSA
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21
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Jost M, Santos DA, Saunders RA, Horlbeck MA, Hawkins JS, Scaria SM, Norman TM, Hussmann JA, Liem CR, Gross CA, Weissman JS. Titrating gene expression using libraries of systematically attenuated CRISPR guide RNAs. Nat Biotechnol 2020; 38:355-364. [PMID: 31932729 PMCID: PMC7065968 DOI: 10.1038/s41587-019-0387-5] [Citation(s) in RCA: 101] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 12/05/2019] [Indexed: 02/07/2023]
Abstract
A lack of tools to precisely control gene expression has limited our ability to evaluate relationships between expression levels and phenotypes. Here, we describe an approach to titrate expression of human genes using CRISPR interference and series of single-guide RNAs (sgRNAs) with systematically modulated activities. We used large-scale measurements across multiple cell models to characterize activities of sgRNAs containing mismatches to their target sites and derived rules governing mismatched sgRNA activity using deep learning. These rules enabled us to synthesize a compact sgRNA library to titrate expression of ~2,400 genes essential for robust cell growth and to construct an in silico sgRNA library spanning the human genome. Staging cells along a continuum of gene expression levels combined with single-cell RNA-seq readout revealed sharp transitions in cellular behaviors at gene-specific expression thresholds. Our work provides a general tool to control gene expression, with applications ranging from tuning biochemical pathways to identifying suppressors for diseases of dysregulated gene expression.
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Affiliation(s)
- Marco Jost
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
- California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA, USA
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA
| | - Daniel A Santos
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
- California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA, USA
| | - Reuben A Saunders
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
- California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA, USA
| | - Max A Horlbeck
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
- California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA, USA
| | - John S Hawkins
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA
| | - Sonia M Scaria
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
- California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA, USA
| | - Thomas M Norman
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
- California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA, USA
- Computational & Systems Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Jeffrey A Hussmann
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
- California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA, USA
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA
| | - Christina R Liem
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
- California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA, USA
| | - Carol A Gross
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA, USA
| | - Jonathan S Weissman
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, USA.
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA.
- California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA, USA.
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22
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Large-effect flowering time mutations reveal conditionally adaptive paths through fitness landscapes in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2019; 116:17890-17899. [PMID: 31420516 PMCID: PMC6731683 DOI: 10.1073/pnas.1902731116] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Mutations are often assumed to be largely detrimental to fitness, but they may also be beneficial, and mutations with large phenotypic effects can persist in nature. One explanation for these observations is that mutations may be beneficial in specific environments because these conditions shift trait expression toward higher fitness. This hypothesis is rarely tested due to the difficulty of replicating mutants in multiple natural environments and measuring their phenotypes. We did so by planting Arabidopsis thaliana genotypes with large-effect flowering time mutations in field sites across the species’ European climate range. We quantified the adaptive value of mutant traits, finding that certain mutations increased fitness in some environments but not in others. Contrary to previous assumptions that most mutations are deleterious, there is increasing evidence for persistence of large-effect mutations in natural populations. A possible explanation for these observations is that mutant phenotypes and fitness may depend upon the specific environmental conditions to which a mutant is exposed. Here, we tested this hypothesis by growing large-effect flowering time mutants of Arabidopsis thaliana in multiple field sites and seasons to quantify their fitness effects in realistic natural conditions. By constructing environment-specific fitness landscapes based on flowering time and branching architecture, we observed that a subset of mutations increased fitness, but only in specific environments. These mutations increased fitness via different paths: through shifting flowering time, branching, or both. Branching was under stronger selection, but flowering time was more genetically variable, pointing to the importance of indirect selection on mutations through their pleiotropic effects on multiple phenotypes. Finally, mutations in hub genes with greater connectedness in their regulatory networks had greater effects on both phenotypes and fitness. Together, these findings indicate that large-effect mutations may persist in populations because they influence traits that are adaptive only under specific environmental conditions. Understanding their evolutionary dynamics therefore requires measuring their effects in multiple natural environments.
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23
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Adames NR, Gallegos JE, Peccoud J. Yeast genetic interaction screens in the age of CRISPR/Cas. Curr Genet 2019; 65:307-327. [PMID: 30255296 PMCID: PMC6420903 DOI: 10.1007/s00294-018-0887-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 09/14/2018] [Accepted: 09/18/2018] [Indexed: 12/21/2022]
Abstract
The ease of performing both forward and reverse genetics in Saccharomyces cerevisiae, along with its stable haploid state and short generation times, has made this budding yeast the consummate model eukaryote for genetics. The major advantage of using budding yeast for reverse genetics is this organism's highly efficient homology-directed repair, allowing for precise genome editing simply by introducing DNA with homology to the chromosomal target. Although plasmid- and PCR-based genome editing tools are quite efficient, they depend on rare spontaneous DNA breaks near the target sequence. Consequently, they can generate only one genomic edit at a time, and the edit must be associated with a selectable marker. However, CRISPR/Cas technology is efficient enough to permit markerless and multiplexed edits in a single step. These features have made CRISPR/Cas popular for yeast strain engineering in synthetic biology and metabolic engineering applications, but it has not been widely employed for genetic screens. In this review, we critically examine different methods to generate multi-mutant strains in systematic genetic interaction screens and discuss the potential of CRISPR/Cas to supplement or improve on these methods.
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Affiliation(s)
- Neil R Adames
- Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO, 80523, USA
| | - Jenna E Gallegos
- Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO, 80523, USA
| | - Jean Peccoud
- Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO, 80523, USA.
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24
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Li S, Giardina DM, Siegal ML. Control of nongenetic heterogeneity in growth rate and stress tolerance of Saccharomyces cerevisiae by cyclic AMP-regulated transcription factors. PLoS Genet 2018; 14:e1007744. [PMID: 30388117 PMCID: PMC6241136 DOI: 10.1371/journal.pgen.1007744] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 11/14/2018] [Accepted: 10/05/2018] [Indexed: 01/01/2023] Open
Abstract
Genetically identical cells exhibit extensive phenotypic variation even under constant and benign conditions. This so-called nongenetic heterogeneity has important clinical implications: within tumors and microbial infections, cells show nongenetic heterogeneity in growth rate and in susceptibility to drugs or stress. The budding yeast, Saccharomyces cerevisiae, shows a similar form of nongenetic heterogeneity in which growth rate correlates positively with susceptibility to acute heat stress at the single-cell level. Using genetic and chemical perturbations, combined with high-throughput single-cell assays of yeast growth and gene expression, we show here that heterogeneity in intracellular cyclic AMP (cAMP) levels acting through the conserved Ras/cAMP/protein kinase A (PKA) pathway and its target transcription factors, Msn2 and Msn4, underlies this nongenetic heterogeneity. Lower levels of cAMP correspond to slower growth, as shown by direct comparison of cAMP concentration in subpopulations enriched for slower vs. faster growing cells. Concordantly, an endogenous reporter of this pathway’s activity correlates with growth in individual cells. The paralogs Msn2 and Msn4 differ in their roles in nongenetic heterogeneity in a way that demonstrates slow growth and stress tolerance are not inevitably linked. Heterogeneity in growth rate requires each, whereas only Msn2 is required for heterogeneity in expression of Tsl1, a subunit of trehalose synthase that contributes to acute-stress tolerance. Perturbing nongenetic heterogeneity by mutating genes in this pathway, or by culturing wild-type cells with the cell-permeable cAMP analog 8-bromo-cAMP or the PKA inhibitor H89, significantly impacts survival of acute heat stress. Perturbations that increase intracellular cAMP levels reduce the slower-growing subpopulation and increase susceptibility to acute heat stress, whereas PKA inhibition slows growth and decreases susceptibility to acute heat stress. Loss of Msn2 reduces, but does not completely eliminate, the correlation in individual cells between growth rate and acute-stress survival, suggesting a major role for the Msn2 pathway in nongenetic heterogeneity but also a residual benefit of slow growth. Our results shed light on the genetic control of nongenetic heterogeneity and suggest a possible means of defeating bet-hedging pathogens or tumor cells by making them more uniformly susceptible to treatment. Nongenetic heterogeneity exists when a trait differs among individuals that have identical genotypes and environments. A clonal population can maximize its long-term success in an uncertain environment by diversifying its phenotypes via nongenetic heterogeneity: the currently unfavored ones may become the favored ones when conditions change. Nongenetic heterogeneity has clinical relevance. For example, populations of tumor cells or infectious microbes show cell-to-cell differences in growth and in drug or stress tolerance. This heterogeneity hampers efficient treatment and can potentiate harmful evolution of a tumor or pathogen. We show that in budding yeast, heterogeneity in intracellular cyclic AMP levels acting through the conserved Ras/cAMP/protein kinase A (PKA) pathway and its target transcription factors, Msn2 and Msn4, underlies the nongenetic heterogeneity of both single-cell growth rate and acute heat-stress tolerance. Perturbations of this pathway significantly affect population survival upon acute heat stress. These results illuminate a mechanism of nongenetic heterogeneity and suggest the potential value of antitumor or antifungal treatment strategies that target nongenetic heterogeneity to render the tumor or pathogen population more uniformly susceptible to a second drug that aims to kill.
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Affiliation(s)
- Shuang Li
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
| | - Daniella M. Giardina
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
| | - Mark L. Siegal
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- * E-mail:
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25
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Sieriebriennikov B, Sommer RJ. Developmental Plasticity and Robustness of a Nematode Mouth-Form Polyphenism. Front Genet 2018; 9:382. [PMID: 30254664 PMCID: PMC6141628 DOI: 10.3389/fgene.2018.00382] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 08/27/2018] [Indexed: 11/23/2022] Open
Abstract
In the last decade, case studies in plants and animals provided increasing insight into the molecular mechanisms of developmental plasticity. When complemented with evolutionary and ecological analyses, these studies suggest that plasticity represents a mechanism facilitating adaptive change, increasing diversity and fostering the evolution of novelty. Here, we summarize genetic, molecular and evolutionary studies on developmental plasticity of feeding structures in nematodes, focusing on the model organism Pristionchus pacificus and its relatives. Like its famous cousin Caenorhabditis elegans, P. pacificus reproduces as a self-fertilizing hermaphrodite and can be cultured in the laboratory on E. coli indefinitely with a four-day generation time. However, in contrast to C. elegans, Pristionchus worms show more complex feeding structures in adaptation to their life history. Pristionchus nematodes live in the soil and are reliably found in association with scarab beetles, but only reproduce after the insects’ death. Insect carcasses usually exist only for a short time period and their turnover is partially unpredictable. Strikingly, Pristionchus worms can have two alternative mouth-forms; animals are either stenostomatous (St) with a single tooth resulting in strict bacterial feeding, or alternatively, they are eurystomatous (Eu) with two teeth allowing facultative predation. Laboratory-based studies revealed a regulatory network that controls the irreversible decision of individual worms to adopt the St or Eu form. These studies revealed that a developmental switch controls the mouth-form decision, confirming long-standing theory about the role of switch genes in developmental plasticity. Here, we describe the current understanding of P. pacificus mouth-form regulation. In contrast to plasticity, robustness describes the property of organisms to produce unchanged phenotypes despite environmental perturbations. While largely opposite in principle, the relationship between developmental plasticity and robustness has only rarely been tested in particular study systems. Based on a study of the Hsp90 chaperones in nematodes, we suggest that robustness and plasticity are indeed complementary concepts. Genetic switch networks regulating plasticity require robustness to produce reproducible responses to the multitude of environmental inputs and the phenotypic output requires robustness because the range of possible phenotypic outcomes is constrained. Thus, plasticity and robustness are actually not mutually exclusive, but rather complementary concepts.
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Affiliation(s)
- Bogdan Sieriebriennikov
- Max Planck Institute for Developmental Biology, Department of Integrative Evolutionary Biology, Tübingen, Germany
| | - Ralf J Sommer
- Max Planck Institute for Developmental Biology, Department of Integrative Evolutionary Biology, Tübingen, Germany
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Ohnuki S, Ohya Y. High-dimensional single-cell phenotyping reveals extensive haploinsufficiency. PLoS Biol 2018; 16:e2005130. [PMID: 29768403 PMCID: PMC5955526 DOI: 10.1371/journal.pbio.2005130] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 04/06/2018] [Indexed: 12/17/2022] Open
Abstract
Haploinsufficiency, a dominant phenotype caused by a heterozygous loss-of-function mutation, has been rarely observed. However, high-dimensional single-cell phenotyping of yeast morphological characteristics revealed haploinsufficiency phenotypes for more than half of 1,112 essential genes under optimal growth conditions. Additionally, 40% of the essential genes with no obvious phenotype under optimal growth conditions displayed haploinsufficiency under severe growth conditions. Haploinsufficiency was detected more frequently in essential genes than in nonessential genes. Similar haploinsufficiency phenotypes were observed mostly in mutants with heterozygous deletion of functionally related genes, suggesting that haploinsufficiency phenotypes were caused by functional defects of the genes. A global view of the gene network was presented based on the similarities of the haploinsufficiency phenotypes. Our dataset contains rich information regarding essential gene functions, providing evidence that single-cell phenotyping is a powerful approach, even in the heterozygous condition, for analyzing complex biological systems. Diploid organisms harboring a wild-type gene and a loss-of-function mutation are called heterozygotes. They are expected to have weak or no individual phenotypes because the mutation is compensated for by the intact allele. The dominant inheritance of phenotypes in heterozygotes is an exceptional phenomenon called haploinsufficiency. Haploinsufficiency was thought to be a rare occurrence; however, a sensitive technique called high-dimensional single-cell phenotyping challenges this perspective. Investigations of single-cell phenotypes revealed that a large extent of the essential genes in yeast exhibit haploinsufficiency. Our analyses also provided crucial information on gene functional networks based on haploinsufficiency phenotypes. This work shows that high-dimensional single-cell phenotyping is a useful tool that can be used to better understand complex biological systems.
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Affiliation(s)
- Shinsuke Ohnuki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
| | - Yoshikazu Ohya
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
- AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory (OPERANDO-OIL), National Institute of Advanced Industrial Science and Technology (AIST), Kashiwa, Chiba, Japan
- * E-mail:
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Conley D, Johnson R, Domingue B, Dawes C, Boardman J, Siegal M. A sibling method for identifying vQTLs. PLoS One 2018; 13:e0194541. [PMID: 29617452 PMCID: PMC5884517 DOI: 10.1371/journal.pone.0194541] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 03/05/2018] [Indexed: 12/11/2022] Open
Abstract
The propensity of a trait to vary within a population may have evolutionary, ecological, or clinical significance. In the present study we deploy sibling models to offer a novel and unbiased way to ascertain loci associated with the extent to which phenotypes vary (variance-controlling quantitative trait loci, or vQTLs). Previous methods for vQTL-mapping either exclude genetically related individuals or treat genetic relatedness among individuals as a complicating factor addressed by adjusting estimates for non-independence in phenotypes. The present method uses genetic relatedness as a tool to obtain unbiased estimates of variance effects rather than as a nuisance. The family-based approach, which utilizes random variation between siblings in minor allele counts at a locus, also allows controls for parental genotype, mean effects, and non-linear (dominance) effects that may spuriously appear to generate variation. Simulations show that the approach performs equally well as two existing methods (squared Z-score and DGLM) in controlling type I error rates when there is no unobserved confounding, and performs significantly better than these methods in the presence of small degrees of confounding. Using height and BMI as empirical applications, we investigate SNPs that alter within-family variation in height and BMI, as well as pathways that appear to be enriched. One significant SNP for BMI variability, in the MAST4 gene, replicated. Pathway analysis revealed one gene set, encoding members of several signaling pathways related to gap junction function, which appears significantly enriched for associations with within-family height variation in both datasets (while not enriched in analysis of mean levels). We recommend approximating laboratory random assignment of genotype using family data and more careful attention to the possible conflation of mean and variance effects.
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Affiliation(s)
- Dalton Conley
- Department of Sociology, Princeton University, Princeton, NJ, United States of America
| | - Rebecca Johnson
- Department of Sociology, Princeton University, Princeton, NJ, United States of America
| | - Ben Domingue
- Graduate School of Education, Stanford University, Stanford, CA, United States of America
| | - Christopher Dawes
- Wilff Family Department of Politics, New York University, New York City, NY, United States of America
| | - Jason Boardman
- Institute for Behavioral Sciences, University of Colorado, Boulder, Boulder, CO, United States of America
| | - Mark Siegal
- Center for Genomics and Systems Biology, New York University, New York University, New York City, NY, United States of America
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28
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Katsanos D, Koneru SL, Mestek Boukhibar L, Gritti N, Ghose R, Appleford PJ, Doitsidou M, Woollard A, van Zon JS, Poole RJ, Barkoulas M. Stochastic loss and gain of symmetric divisions in the C. elegans epidermis perturbs robustness of stem cell number. PLoS Biol 2017; 15:e2002429. [PMID: 29108019 PMCID: PMC5690688 DOI: 10.1371/journal.pbio.2002429] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 11/16/2017] [Accepted: 10/20/2017] [Indexed: 11/19/2022] Open
Abstract
Biological systems are subject to inherent stochasticity. Nevertheless, development is remarkably robust, ensuring the consistency of key phenotypic traits such as correct cell numbers in a certain tissue. It is currently unclear which genes modulate phenotypic variability, what their relationship is to core components of developmental gene networks, and what is the developmental basis of variable phenotypes. Here, we start addressing these questions using the robust number of Caenorhabditis elegans epidermal stem cells, known as seam cells, as a readout. We employ genetics, cell lineage tracing, and single molecule imaging to show that mutations in lin-22, a Hes-related basic helix-loop-helix (bHLH) transcription factor, increase seam cell number variability. We show that the increase in phenotypic variability is due to stochastic conversion of normally symmetric cell divisions to asymmetric and vice versa during development, which affect the terminal seam cell number in opposing directions. We demonstrate that LIN-22 acts within the epidermal gene network to antagonise the Wnt signalling pathway. However, lin-22 mutants exhibit cell-to-cell variability in Wnt pathway activation, which correlates with and may drive phenotypic variability. Our study demonstrates the feasibility to study phenotypic trait variance in tractable model organisms using unbiased mutagenesis screens.
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Affiliation(s)
- Dimitris Katsanos
- Department of Life Sciences, Imperial College, London, United Kingdom
| | - Sneha L. Koneru
- Department of Life Sciences, Imperial College, London, United Kingdom
| | | | - Nicola Gritti
- Institute for Atomic and Molecular Physics (AMOLF), Amsterdam, The Netherlands
| | - Ritobrata Ghose
- Department of Life Sciences, Imperial College, London, United Kingdom
| | - Peter J. Appleford
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Maria Doitsidou
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, United Kingdom
| | - Alison Woollard
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Jeroen S. van Zon
- Institute for Atomic and Molecular Physics (AMOLF), Amsterdam, The Netherlands
| | - Richard J. Poole
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
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29
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Variable Cell Growth Yields Reproducible OrganDevelopment through Spatiotemporal Averaging. Dev Cell 2017; 38:15-32. [PMID: 27404356 DOI: 10.1016/j.devcel.2016.06.016] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 05/04/2016] [Accepted: 06/09/2016] [Indexed: 11/22/2022]
Abstract
Organ sizes and shapes are strikingly reproducible, despite the variable growth and division of individual cells within them. To reveal which mechanisms enable this precision, we designed a screen for disrupted sepal size and shape uniformity in Arabidopsis and identified mutations in the mitochondrial i-AAA protease FtsH4. Counterintuitively, through live imaging we observed that variability of neighboring cell growth was reduced in ftsh4 sepals. We found that regular organ shape results from spatiotemporal averaging of the cellular variability in wild-type sepals, which is disrupted in the less-variable cells of ftsh4 mutants. We also found that abnormal, increased accumulation of reactive oxygen species (ROS) in ftsh4 mutants disrupts organ size consistency. In wild-type sepals, ROS accumulate in maturing cells and limit organ growth, suggesting that ROS are endogenous signals promoting termination of growth. Our results demonstrate that spatiotemporal averaging of cellular variability is required for precision in organ size.
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30
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Resolving the Complex Genetic Basis of Phenotypic Variation and Variability of Cellular Growth. Genetics 2017; 206:1645-1657. [PMID: 28495957 DOI: 10.1534/genetics.116.195180] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 05/02/2017] [Indexed: 01/10/2023] Open
Abstract
In all organisms, the majority of traits vary continuously between individuals. Explaining the genetic basis of quantitative trait variation requires comprehensively accounting for genetic and nongenetic factors as well as their interactions. The growth of microbial cells can be characterized by a lag duration, an exponential growth phase, and a stationary phase. Parameters that characterize these growth phases can vary among genotypes (phenotypic variation), environmental conditions (phenotypic plasticity), and among isogenic cells in a given environment (phenotypic variability). We used a high-throughput microscopy assay to map genetic loci determining variation in lag duration and exponential growth rate in growth rate-limiting and nonlimiting glucose concentrations, using segregants from a cross of two natural isolates of the budding yeast, Saccharomyces cerevisiae We find that some quantitative trait loci (QTL) are common between traits and environments whereas some are unique, exhibiting gene-by-environment interactions. Furthermore, whereas variation in the central tendency of growth rate or lag duration is explained by many additive loci, differences in phenotypic variability are primarily the result of genetic interactions. We used bulk segregant mapping to increase QTL resolution by performing whole-genome sequencing of complex mixtures of an advanced intercross mapping population grown in selective conditions using glucose-limited chemostats. We find that sequence variation in the high-affinity glucose transporter HXT7 contributes to variation in growth rate and lag duration. Allele replacements of the entire locus, as well as of a single polymorphic amino acid, reveal that the effect of variation in HXT7 depends on genetic, and allelic, background. Amplifications of HXT7 are frequently selected in experimental evolution in glucose-limited environments, but we find that HXT7 amplifications result in antagonistic pleiotropy that is absent in naturally occurring variants of HXT7 Our study highlights the complex nature of the genotype-to-phenotype map within and between environments.
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Geiler-Samerotte KA, Zhu YO, Goulet BE, Hall DW, Siegal ML. Selection Transforms the Landscape of Genetic Variation Interacting with Hsp90. PLoS Biol 2016; 14:e2000465. [PMID: 27768682 PMCID: PMC5074785 DOI: 10.1371/journal.pbio.2000465] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 09/26/2016] [Indexed: 11/18/2022] Open
Abstract
The protein-folding chaperone Hsp90 has been proposed to buffer the phenotypic effects of mutations. The potential for Hsp90 and other putative buffers to increase robustness to mutation has had major impact on disease models, quantitative genetics, and evolutionary theory. But Hsp90 sometimes contradicts expectations for a buffer by potentiating rapid phenotypic changes that would otherwise not occur. Here, we quantify Hsp90’s ability to buffer or potentiate (i.e., diminish or enhance) the effects of genetic variation on single-cell morphological features in budding yeast. We corroborate reports that Hsp90 tends to buffer the effects of standing genetic variation in natural populations. However, we demonstrate that Hsp90 tends to have the opposite effect on genetic variation that has experienced reduced selection pressure. Specifically, Hsp90 tends to enhance, rather than diminish, the effects of spontaneous mutations and recombinations. This result implies that Hsp90 does not make phenotypes more robust to the effects of genetic perturbation. Instead, natural selection preferentially allows buffered alleles to persist and thereby creates the false impression that Hsp90 confers greater robustness. Most biologists appreciate that natural selection filters new mutations (e.g., by eliminating deleterious ones), such that genetic variation in nature is biased. The idea that selection also skews the types of genetic interactions that exist in nature is less appreciated. For example, studies spanning diverse species have shown that the protein Hsp90, which helps other proteins to fold properly, tends to diminish the observable effects of genetic variation. This observation has led to the assumption that Hsp90 also buffers the effects of new mutations. This untested assumption has served as a rationale for cancer-treatment strategies and shaped our understanding of variation in complex traits. We measured the effects of new mutations on the shapes and sizes of individual yeast cells and found that Hsp90 does not tend to buffer these effects. Instead, Hsp90 interacts with new mutations in diverse ways, sometimes buffering, but more often enhancing mutational effects on cell shape and size. We conclude that selection preferentially allows buffered mutations to persist in natural populations. This result alters common perceptions about why cryptic (i.e., buffered) genetic variation exists and casts doubt on cancer-treatment strategies aiming to target presumed buffers of mutational effects.
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Affiliation(s)
- Kerry A Geiler-Samerotte
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America.,Department of Biology, Stanford University, Stanford, California, United States of America
| | - Yuan O Zhu
- Department of Biology, Stanford University, Stanford, California, United States of America.,Department of Genetics, Stanford University, Stanford, California, United States of America
| | - Benjamin E Goulet
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
| | - David W Hall
- Department of Genetics, University of Georgia, Athens, Georgia, United States of America
| | - Mark L Siegal
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
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32
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Hewitt SK, Foster DS, Dyer PS, Avery SV. Phenotypic heterogeneity in fungi: Importance and methodology. FUNGAL BIOL REV 2016. [DOI: 10.1016/j.fbr.2016.09.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Abstract
The demand for phenomics, a high-dimensional and high-throughput phenotyping method, has been increasing in many fields of biology. The budding yeast Saccharomyces cerevisiae, a unicellular model organism, provides an invaluable system for dissecting complex cellular processes using high-resolution phenotyping. Moreover, the addition of spatial and temporal attributes to subcellular structures based on microscopic images has rendered this cell phenotyping system more reliable and amenable to analysis. A well-designed experiment followed by appropriate multivariate analysis can yield a wealth of biological knowledge. Here we review recent advances in cell imaging and illustrate their broad applicability to eukaryotic cells by showing how these techniques have advanced our understanding of budding yeast.
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Affiliation(s)
- Yoshikazu Ohya
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa 277-8562, Japan
| | - Yoshitaka Kimori
- Department of Imaging Science, Center for Novel Science Initiatives, National Institutes of Natural Sciences, Okazaki 444-8787, Japan
| | - Hiroki Okada
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa 277-8562, Japan
| | - Shinsuke Ohnuki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa 277-8562, Japan
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34
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Keren L, Hausser J, Lotan-Pompan M, Vainberg Slutskin I, Alisar H, Kaminski S, Weinberger A, Alon U, Milo R, Segal E. Massively Parallel Interrogation of the Effects of Gene Expression Levels on Fitness. Cell 2016; 166:1282-1294.e18. [PMID: 27545349 DOI: 10.1016/j.cell.2016.07.024] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Revised: 07/05/2016] [Accepted: 07/18/2016] [Indexed: 02/02/2023]
Abstract
Data of gene expression levels across individuals, cell types, and disease states is expanding, yet our understanding of how expression levels impact phenotype is limited. Here, we present a massively parallel system for assaying the effect of gene expression levels on fitness in Saccharomyces cerevisiae by systematically altering the expression level of ∼100 genes at ∼100 distinct levels spanning a 500-fold range at high resolution. We show that the relationship between expression levels and growth is gene and environment specific and provides information on the function, stoichiometry, and interactions of genes. Wild-type expression levels in some conditions are not optimal for growth, and genes whose fitness is greatly affected by small changes in expression level tend to exhibit lower cell-to-cell variability in expression. Our study addresses a fundamental gap in understanding the functional significance of gene expression regulation and offers a framework for evaluating the phenotypic effects of expression variation.
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Affiliation(s)
- Leeat Keren
- Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot 76100, Israel; Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel; Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Jean Hausser
- Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Maya Lotan-Pompan
- Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot 76100, Israel; Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ilya Vainberg Slutskin
- Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot 76100, Israel; Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Hadas Alisar
- Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot 76100, Israel; Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sivan Kaminski
- Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Adina Weinberger
- Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot 76100, Israel; Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Uri Alon
- Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ron Milo
- Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Eran Segal
- Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot 76100, Israel; Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
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35
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Lachowiec J, Queitsch C, Kliebenstein DJ. Molecular mechanisms governing differential robustness of development and environmental responses in plants. ANNALS OF BOTANY 2016; 117:795-809. [PMID: 26473020 PMCID: PMC4845800 DOI: 10.1093/aob/mcv151] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 07/08/2015] [Accepted: 08/25/2015] [Indexed: 05/04/2023]
Abstract
BACKGROUND Robustness to genetic and environmental perturbation is a salient feature of multicellular organisms. Loss of developmental robustness can lead to severe phenotypic defects and fitness loss. However, perfect robustness, i.e. no variation at all, is evolutionarily unfit as organisms must be able to change phenotype to properly respond to changing environments and biotic challenges. Plasticity is the ability to adjust phenotypes predictably in response to specific environmental stimuli, which can be considered a transient shift allowing an organism to move from one robust phenotypic state to another. Plants, as sessile organisms that undergo continuous development, are particularly dependent on an exquisite fine-tuning of the processes that balance robustness and plasticity to maximize fitness. SCOPE AND CONCLUSIONS This paper reviews recently identified mechanisms, both systems-level and molecular, that modulate robustness, and discusses their implications for the optimization of plant fitness. Robustness in living systems arises from the structure of genetic networks, the specific molecular functions of the underlying genes, and their interactions. This very same network responsible for the robustness of specific developmental states also has to be built such that it enables plastic yet robust shifts in response to environmental changes. In plants, the interactions and functions of signal transduction pathways activated by phytohormones and the tendency for plants to tolerate whole-genome duplications, tandem gene duplication and hybridization are emerging as major regulators of robustness in development. Despite their obvious implications for plant evolution and plant breeding, the mechanistic underpinnings by which plants modulate precise levels of robustness, plasticity and evolvability in networks controlling different phenotypes are under-studied.
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Affiliation(s)
- Jennifer Lachowiec
- Department of Ecology and Evolutionary Biology, University of Michigan, 830 North University Avenue, Ann Arbor, MI 48197, USA
| | - Christine Queitsch
- Department of Genome Sciences, University of Washington, 3720 15th Avenue NE, Seattle, WA 98155, USA
| | - Daniel J Kliebenstein
- Department of Plant Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA and DynaMo Center of Excellence, University of Copenhagen, Thorvaldsensvej 40, DK-1871, Frederiksberg C, Denmark
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36
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Mestek Boukhibar L, Barkoulas M. The developmental genetics of biological robustness. ANNALS OF BOTANY 2016; 117:699-707. [PMID: 26292993 PMCID: PMC4845795 DOI: 10.1093/aob/mcv128] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 05/07/2015] [Accepted: 06/29/2015] [Indexed: 05/10/2023]
Abstract
BACKGROUND Living organisms are continuously confronted with perturbations, such as environmental changes that include fluctuations in temperature and nutrient availability, or genetic changes such as mutations. While some developmental systems are affected by such challenges and display variation in phenotypic traits, others continue consistently to produce invariable phenotypes despite perturbation. This ability of a living system to maintain an invariable phenotype in the face of perturbations is termed developmental robustness. Biological robustness is a phenomenon observed across phyla, and studying its mechanisms is central to deciphering the genotype-phenotype relationship. Recent work in yeast, animals and plants has shown that robustness is genetically controlled and has started to reveal the underlying mechinisms behind it. SCOPE AND CONCLUSIONS Studying biological robustness involves focusing on an important property of developmental traits, which is the phenotypic distribution within a population. This is often neglected because the vast majority of developmental biology studies instead focus on population aggregates, such as trait averages. By drawing on findings in animals and yeast, this Viewpoint considers how studies on plant developmental robustness may benefit from strict definitions of what is the developmental system of choice and what is the relevant perturbation, and also from clear distinctions between gene effects on the trait mean and the trait variance. Recent advances in quantitative developmental biology and high-throughput phenotyping now allow the design of targeted genetic screens to identify genes that amplify or restrict developmental trait variance and to study how variation propagates across different phenotypic levels in biological systems. The molecular characterization of more quantitative trait loci affecting trait variance will provide further insights into the evolution of genes modulating developmental robustness. The study of robustness mechanisms in closely related species will address whether mechanisms of robustness are evolutionarily conserved.
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Affiliation(s)
- Lamia Mestek Boukhibar
- Imperial College London, Department of Life Sciences, Sir Alexander Fleming Building, South Kensington Campus, London SW7 2AZ, UK
| | - Michalis Barkoulas
- Imperial College London, Department of Life Sciences, Sir Alexander Fleming Building, South Kensington Campus, London SW7 2AZ, UK
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37
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Norman KL, Kumar A. Mutant power: using mutant allele collections for yeast functional genomics. Brief Funct Genomics 2016; 15:75-84. [PMID: 26453908 PMCID: PMC5065357 DOI: 10.1093/bfgp/elv042] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The budding yeast has long served as a model eukaryote for the functional genomic analysis of highly conserved signaling pathways, cellular processes and mechanisms underlying human disease. The collection of reagents available for genomics in yeast is extensive, encompassing a growing diversity of mutant collections beyond gene deletion sets in the standard wild-type S288C genetic background. We review here three main types of mutant allele collections: transposon mutagen collections, essential gene collections and overexpression libraries. Each collection provides unique and identifiable alleles that can be utilized in genome-wide, high-throughput studies. These genomic reagents are particularly informative in identifying synthetic phenotypes and functions associated with essential genes, including those modeled most effectively in complex genetic backgrounds. Several examples of genomic studies in filamentous/pseudohyphal backgrounds are provided here to illustrate this point. Additionally, the limitations of each approach are examined. Collectively, these mutant allele collections in Saccharomyces cerevisiae and the related pathogenic yeast Candida albicans promise insights toward an advanced understanding of eukaryotic molecular and cellular biology.
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