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Inskeep TR, Groen SC. Network properties constrain natural selection on gene expression in Caenorhabditis elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2025:2025.02.19.639144. [PMID: 40060403 PMCID: PMC11888156 DOI: 10.1101/2025.02.19.639144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 03/17/2025]
Abstract
Gene regulatory networks (GRNs) integrate genetic and environmental signals to coordinate complex phenotypes and evolve through a balance of selection and drift. Using publicly available datasets from Caenorhabditis elegans, we investigated the extent of natural selection on transcript abundance by linking population-scale variation in gene expression to fecundity, a key fitness component. While the expression of most genes covaried only weakly with fitness, which is typical for polygenic traits, we identified seven transcripts under significant directional selection. These included nhr-114 and feh-1, implicating variation in nutrient-sensing and metabolic pathways as impacting fitness. Stronger directional selection on tissue-specific and older genes highlighted the germline and nervous system as focal points of adaptive change. Network position further constrained selection on gene expression; high-connectivity genes faced stronger stabilizing and directional selection, highlighting GRN architecture as a key factor in microevolutionary dynamics. The activity of transcription factors such as zip-3, which regulates mitochondrial stress responses, emerged as targets of selection, revealing potential links between energy homeostasis and fitness. Our findings demonstrate how GRNs mediate the interplay between selection and drift, shaping microevolutionary trajectories of gene expression and phenotypic diversity.
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Affiliation(s)
- Tyler R Inskeep
- Department of Botany and Plant Sciences, University of California, Riverside
- Institute for Integrative Genome Biology, University of California, Riverside
| | - Simon C Groen
- Department of Botany and Plant Sciences, University of California, Riverside
- Department of Nematology, University of California, Riverside
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2
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van Eijnatten AL, Sterken MG, Kammenga JE, Nijveen H, Snoek BL. The effect of developmental variation on expression QTLs in a multi parental Caenorhabditis elegans population. G3 (BETHESDA, MD.) 2024; 14:jkad273. [PMID: 38015660 PMCID: PMC10849341 DOI: 10.1093/g3journal/jkad273] [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: 09/21/2023] [Revised: 09/21/2023] [Accepted: 10/27/2023] [Indexed: 11/30/2023]
Abstract
Regulation of gene expression plays a crucial role in developmental processes and adaptation to changing environments. expression quantitative trait locus (eQTL) mapping is a technique used to study the genetic regulation of gene expression using the transcriptomes of recombinant inbred lines (RILs). Typically, the age of the inbred lines at the time of RNA sampling is carefully controlled. This is necessary because the developmental process causes changes in gene expression, complicating the interpretation of eQTL mapping experiments. However, due to genetics and variation in ambient micro-environments, organisms can differ in their "developmental age," even if they are of the same chronological age. As a result, eQTL patterns are affected by developmental variation in gene expression. The model organism Caenorhabditis elegans is particularly suited for studying the effect of developmental variation on eQTL mapping patterns. In a span of days, C. elegans transitions from embryo through 4 larval stages to adult while undergoing massive changes to its transcriptome. Here, we use C. elegans to investigate the effect of developmental age variation on eQTL patterns and present a normalization procedure. We used dynamical eQTL mapping, which includes the developmental age as a cofactor, to separate the variation in development from genotypic variation and explain variation in gene expression levels. We compare classical single marker eQTL mapping and dynamical eQTL mapping using RNA-seq data of ∼200 multi-parental RILs of C. elegans. The results show that (1) many eQTLs are caused by developmental variation, (2) most trans-bands are developmental QTLs, and (3) dynamical eQTL mapping detects additional eQTLs not found with classical eQTL mapping. We recommend that correction for variation in developmental age should be strongly considered in eQTL mapping studies given the large impact of processes like development on the transcriptome.
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Affiliation(s)
- Abraham L van Eijnatten
- Theoretical Biology and Bioinformatics, Utrecht University, Padualaan 8,3584 CH Utrecht, The Netherlands
| | - Mark G Sterken
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Jan E Kammenga
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Harm Nijveen
- Laboratory of Bioinformatics, Wageningen University, Droevendaalsesteeg 1, Radix West, Building 107, 6708 PB Wageningen, The Netherlands
| | - Basten L Snoek
- Theoretical Biology and Bioinformatics, Utrecht University, Padualaan 8,3584 CH Utrecht, The Netherlands
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3
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Ceron-Noriega A, Almeida MV, Levin M, Butter F. Nematode gene annotation by machine-learning-assisted proteotranscriptomics enables proteome-wide evolutionary analysis. Genome Res 2023; 33:112-128. [PMID: 36653121 PMCID: PMC9977148 DOI: 10.1101/gr.277070.122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 11/18/2022] [Indexed: 01/19/2023]
Abstract
Nematodes encompass more than 24,000 described species, which were discovered in almost every ecological habitat, and make up >80% of metazoan taxonomic diversity in soils. The last common ancestor of nematodes is believed to date back to ∼650-750 million years, generating a large and phylogenetically diverse group to be explored. However, for most species high-quality gene annotations are incomprehensive or missing. Combining short-read RNA sequencing with mass spectrometry-based proteomics and machine-learning quality control in an approach called proteotranscriptomics, we improve gene annotations for nine genome-sequenced nematode species and provide new gene annotations for three additional species without genome assemblies. Emphasizing the sensitivity of our methodology, we provide evidence for two hitherto undescribed genes in the model organism Caenorhabditis elegans Extensive phylogenetic systems analysis using this comprehensive proteome annotation provides new insights into evolutionary processes of this metazoan group.
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Affiliation(s)
| | | | - Michal Levin
- Institute of Molecular Biology (IMB), 55128 Mainz, Germany
| | - Falk Butter
- Institute of Molecular Biology (IMB), 55128 Mainz, Germany
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4
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Real age prediction from the transcriptome with RAPToR. Nat Methods 2022; 19:969-975. [PMID: 35817937 DOI: 10.1038/s41592-022-01540-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 05/25/2022] [Indexed: 11/08/2022]
Abstract
Transcriptomic data is often affected by uncontrolled variation among samples that can obscure and confound the effects of interest. This variation is frequently due to unintended differences in developmental stages between samples. The transcriptome itself can be used to estimate developmental progression, but existing methods require many samples and do not estimate a specimen's real age. Here we present real-age prediction from transcriptome staging on reference (RAPToR), a computational method that precisely estimates the real age of a sample from its transcriptome, exploiting existing time-series data as reference. RAPToR works with whole animal, dissected tissue and single-cell data for the most common animal models, humans and even for non-model organisms lacking reference data. We show that RAPToR can be used to remove age as a confounding factor and allow recovery of a signal of interest in differential expression analysis. RAPToR will be especially useful in large-scale single-organism profiling because it eliminates the need for accurate staging or synchronisation before profiling.
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5
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Inferring biological age from the transcriptome with RAPToR. Nat Methods 2022; 19:936-937. [PMID: 35817939 DOI: 10.1038/s41592-022-01542-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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6
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van Sluijs L, Bosman KJ, Pankok F, Blokhina T, Wilten JIHA, te Molder DM, Riksen JAG, Snoek BL, Pijlman GP, Kammenga JE, Sterken MG. Balancing Selection of the Intracellular Pathogen Response in Natural Caenorhabditis elegans Populations. Front Cell Infect Microbiol 2022; 11:758331. [PMID: 35174100 PMCID: PMC8841876 DOI: 10.3389/fcimb.2021.758331] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 12/21/2021] [Indexed: 12/17/2022] Open
Abstract
Genetic variation in host populations may lead to differential viral susceptibilities. Here, we investigate the role of natural genetic variation in the Intracellular Pathogen Response (IPR), an important antiviral pathway in the model organism Caenorhabditis elegans against Orsay virus (OrV). The IPR involves transcriptional activity of 80 genes including the pals-genes. We examine the genetic variation in the pals-family for traces of selection and explore the molecular and phenotypic effects of having distinct pals-gene alleles. Genetic analysis of 330 global C. elegans strains reveals that genetic diversity within the IPR-related pals-genes can be categorized in a few haplotypes worldwide. Importantly, two key IPR regulators, pals-22 and pals-25, are in a genomic region carrying signatures of balancing selection, suggesting that different evolutionary strategies exist in IPR regulation. We infected eleven C. elegans strains that represent three distinct pals-22 pals-25 haplotypes with Orsay virus to determine their susceptibility. For two of these strains, N2 and CB4856, the transcriptional response to infection was also measured. The results indicate that pals-22 pals-25 haplotype shapes the defense against OrV and host genetic variation can result in constitutive activation of IPR genes. Our work presents evidence for balancing genetic selection of immunity genes in C. elegans and provides a novel perspective on the functional diversity that can develop within a main antiviral response in natural host populations.
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Affiliation(s)
- Lisa van Sluijs
- Laboratory of Nematology, Wageningen University and Research, Wageningen, Netherlands
- Laboratory of Virology, Wageningen University and Research, Wageningen, Netherlands
| | - Kobus J. Bosman
- Laboratory of Nematology, Wageningen University and Research, Wageningen, Netherlands
| | - Frederik Pankok
- Laboratory of Nematology, Wageningen University and Research, Wageningen, Netherlands
| | - Tatiana Blokhina
- Laboratory of Nematology, Wageningen University and Research, Wageningen, Netherlands
| | - Jop I. H. A. Wilten
- Laboratory of Nematology, Wageningen University and Research, Wageningen, Netherlands
| | - Dennie M. te Molder
- Laboratory of Nematology, Wageningen University and Research, Wageningen, Netherlands
| | - Joost A. G. Riksen
- Laboratory of Nematology, Wageningen University and Research, Wageningen, Netherlands
| | - Basten L. Snoek
- Laboratory of Nematology, Wageningen University and Research, Wageningen, Netherlands
| | - Gorben P. Pijlman
- Laboratory of Virology, Wageningen University and Research, Wageningen, Netherlands
| | - Jan E. Kammenga
- Laboratory of Nematology, Wageningen University and Research, Wageningen, Netherlands
| | - Mark G. Sterken
- Laboratory of Nematology, Wageningen University and Research, Wageningen, Netherlands
- Laboratory of Virology, Wageningen University and Research, Wageningen, Netherlands
- *Correspondence: Mark G. Sterken,
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7
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Snoek BL, Sterken MG, Nijveen H, Volkers RJM, Riksen J, Rosenstiel PC, Schulenburg H, Kammenga JE. The genetics of gene expression in a Caenorhabditis elegans multiparental recombinant inbred line population. G3 (BETHESDA, MD.) 2021; 11:jkab258. [PMID: 34568931 PMCID: PMC8496280 DOI: 10.1093/g3journal/jkab258] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 07/17/2021] [Indexed: 11/29/2022]
Abstract
Studying genetic variation of gene expression provides a powerful way to unravel the molecular components underlying complex traits. Expression quantitative trait locus (eQTL) studies have been performed in several different model species, yet most of these linkage studies have been based on the genetic segregation of two parental alleles. Recently, we developed a multiparental segregating population of 200 recombinant inbred lines (mpRILs) derived from four wild isolates (JU1511, JU1926, JU1931, and JU1941) in the nematode Caenorhabditis elegans. We used RNA-seq to investigate how multiple alleles affect gene expression in these mpRILs. We found 1789 genes differentially expressed between the parental lines. Transgression, expression beyond any of the parental lines in the mpRILs, was found for 7896 genes. For expression QTL mapping almost 9000 SNPs were available. By combining these SNPs and the RNA-seq profiles of the mpRILs, we detected almost 6800 eQTLs. Most trans-eQTLs (63%) co-locate in six newly identified trans-bands. The trans-eQTLs found in previous two-parental allele eQTL experiments and this study showed some overlap (17.5-46.8%), highlighting on the one hand that a large group of genes is affected by polymorphic regulators across populations and conditions, on the other hand, it shows that the mpRIL population allows identification of novel gene expression regulatory loci. Taken together, the analysis of our mpRIL population provides a more refined insight into C. elegans complex trait genetics and eQTLs in general, as well as a starting point to further test and develop advanced statistical models for detection of multiallelic eQTLs and systems genetics studying the genotype-phenotype relationship.
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Affiliation(s)
- Basten L Snoek
- Laboratory of Nematology, Wageningen University, NL-6708 PB Wageningen, The Netherlands
- Theoretical Biology and Bioinformatics, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Mark G Sterken
- Laboratory of Nematology, Wageningen University, NL-6708 PB Wageningen, The Netherlands
| | - Harm Nijveen
- Bioinformatics Group, Wageningen University, NL-6708 PB Wageningen, The Netherlands
| | - Rita J M Volkers
- Laboratory of Nematology, Wageningen University, NL-6708 PB Wageningen, The Netherlands
| | - Joost Riksen
- Laboratory of Nematology, Wageningen University, NL-6708 PB Wageningen, The Netherlands
| | - Philip C Rosenstiel
- Institute for Clinical Molecular Biology, University of Kiel, 24098 Kiel, Germany
- Competence Centre for Genomic Analysis (CCGA) Kiel, University of Kiel, 24098 Kiel, Germany
| | - Hinrich Schulenburg
- Zoological Institute, University of Kiel, 24098 Kiel, Germany
- Max Planck Institute for Evolutionary Biology, 24306 Ploen, Germany
| | - Jan E Kammenga
- Laboratory of Nematology, Wageningen University, NL-6708 PB Wageningen, The Netherlands
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8
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Faerberg DF, Gurarie V, Ruvinsky I. Inferring temporal organization of postembryonic development from high-content behavioral tracking. Dev Biol 2021; 475:54-64. [PMID: 33636188 PMCID: PMC8107144 DOI: 10.1016/j.ydbio.2021.02.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 02/16/2021] [Accepted: 02/17/2021] [Indexed: 11/22/2022]
Abstract
Understanding temporal regulation of development remains an important challenge. Whereas average, species-typical timing of many developmental processes has been established, less is known about inter-individual variability and correlations in timing of specific events. We addressed these questions in the context of postembryonic development in Caenorhabditis elegans. Based on patterns of locomotor activity of freely moving animals, we inferred durations of four larval stages (L1-L4) in over 100 individuals. Analysis of these data supports several conclusions. Individuals have consistently faster or slower rates of development because durations of L1 through L3 stages are positively correlated. The last larval stage, the L4, is less variable than the earlier stages and its duration is largely independent of the rate of early larval development, implying existence of two distinct larval epochs. We describe characteristic patterns of variation and correlation, as well as the fact that stage durations tend to scale relative to total developmental time. This scaling relationship suggests that each larval stage is not limited by an absolute duration, but is instead terminated when a subset of events that must occur prior to adulthood have been completed. The approach described here offers a scalable platform that will facilitate the study of temporal regulation of postembryonic development.
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Affiliation(s)
- Denis F Faerberg
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, 60208, USA
| | - Victor Gurarie
- Department of Physics, University of Colorado, Boulder, CO, 80309, USA
| | - Ilya Ruvinsky
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, 60208, USA.
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9
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Sterken MG, van Wijk MH, Quamme EC, Riksen JAG, Carnell L, Mathies LD, Davies AG, Kammenga JE, Bettinger JC. Transcriptional analysis of the response of C. elegans to ethanol exposure. Sci Rep 2021; 11:10993. [PMID: 34040055 PMCID: PMC8155136 DOI: 10.1038/s41598-021-90282-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 05/07/2021] [Indexed: 11/30/2022] Open
Abstract
Ethanol-induced transcriptional changes underlie important physiological responses to ethanol that are likely to contribute to the addictive properties of the drug. We examined the transcriptional responses of Caenorhabditis elegans across a timecourse of ethanol exposure, between 30 min and 8 h, to determine what genes and genetic pathways are regulated in response to ethanol in this model. We found that short exposures to ethanol (up to 2 h) induced expression of metabolic enzymes involved in metabolizing ethanol and retinol, while longer exposure (8 h) had much more profound effects on the transcriptome. Several genes that are known to be involved in the physiological response to ethanol, including direct ethanol targets, were regulated at 8 h of exposure. This longer exposure to ethanol also resulted in the regulation of genes involved in cilia function, which is consistent with an important role for the effects of ethanol on cilia in the deleterious effects of chronic ethanol consumption in humans. Finally, we found that food deprivation for an 8-h period induced gene expression changes that were somewhat ameliorated by the presence of ethanol, supporting previous observations that worms can use ethanol as a calorie source.
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Affiliation(s)
- Mark G Sterken
- Laboratory of Nematology, Wageningen University and Research, 6708 PB, Wageningen, The Netherlands
| | - Marijke H van Wijk
- Laboratory of Nematology, Wageningen University and Research, 6708 PB, Wageningen, The Netherlands
| | - Elizabeth C Quamme
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Box 980613, Richmond, VA, 23298, USA
| | - Joost A G Riksen
- Laboratory of Nematology, Wageningen University and Research, 6708 PB, Wageningen, The Netherlands
| | - Lucinda Carnell
- Department of Biological Sciences, Central Washington University, Ellensburg, WA, 98926, USA
| | - Laura D Mathies
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Box 980613, Richmond, VA, 23298, USA
- Virginia Commonwealth University Alcohol Research Center, Richmond, VA, USA
| | - Andrew G Davies
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Box 980613, Richmond, VA, 23298, USA
- Virginia Commonwealth University Alcohol Research Center, Richmond, VA, USA
| | - Jan E Kammenga
- Laboratory of Nematology, Wageningen University and Research, 6708 PB, Wageningen, The Netherlands
| | - Jill C Bettinger
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Box 980613, Richmond, VA, 23298, USA.
- Virginia Commonwealth University Alcohol Research Center, Richmond, VA, USA.
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10
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Sterken MG, Bevers RPJ, Volkers RJM, Riksen JAG, Kammenga JE, Snoek BL. Dissecting the eQTL Micro-Architecture in Caenorhabditis elegans. Front Genet 2020; 11:501376. [PMID: 33240309 PMCID: PMC7670075 DOI: 10.3389/fgene.2020.501376] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Accepted: 10/13/2020] [Indexed: 01/11/2023] Open
Abstract
The study of expression quantitative trait loci (eQTL) using natural variation in inbred populations has yielded detailed information about the transcriptional regulation of complex traits. Studies on eQTL using recombinant inbred lines (RILs) led to insights on cis and trans regulatory loci of transcript abundance. However, determining the underlying causal polymorphic genes or variants is difficult, but ultimately essential for the understanding of regulatory networks of complex traits. This requires insight into whether associated loci are single eQTL or a combination of closely linked eQTL, and how this QTL micro-architecture depends on the environment. We addressed these questions by testing for independent replication of previously mapped eQTL in Caenorhabditis elegans using new data from introgression lines (ILs). Both populations indicate that the overall heritability of gene expression, number, and position of eQTL differed among environments. Across environments we were able to replicate 70% of the cis- and 40% of the trans-eQTL using the ILs. Testing eight different simulation models, we suggest that additive effects explain up to 60-93% of RIL/IL heritability for all three environments. Closely linked eQTL explained up to 40% of RIL/IL heritability in the control environment whereas only 7% in the heat-stress and recovery environments. In conclusion, we show that reproducibility of eQTL was higher for cis vs. trans eQTL and that the environment affects the eQTL micro-architecture.
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Affiliation(s)
- Mark G. Sterken
- Laboratory of Nematology, Wageningen University & Research, Wageningen, Netherlands
| | - Roel P. J. Bevers
- Laboratory of Nematology, Wageningen University & Research, Wageningen, Netherlands
| | - Rita J. M. Volkers
- Laboratory of Nematology, Wageningen University & Research, Wageningen, Netherlands
| | - Joost A. G. Riksen
- Laboratory of Nematology, Wageningen University & Research, Wageningen, Netherlands
| | - Jan E. Kammenga
- Laboratory of Nematology, Wageningen University & Research, Wageningen, Netherlands
| | - Basten L. Snoek
- Laboratory of Nematology, Wageningen University & Research, Wageningen, Netherlands
- Theoretical Biology & Bioinformatics, Utrecht University, Utrecht, Netherlands
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11
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Snoek BL, Sterken MG, Hartanto M, van Zuilichem AJ, Kammenga JE, de Ridder D, Nijveen H. WormQTL2: an interactive platform for systems genetics in Caenorhabditis elegans. Database (Oxford) 2020; 2020:baz149. [PMID: 31960906 PMCID: PMC6971878 DOI: 10.1093/database/baz149] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 11/30/2019] [Accepted: 12/13/2019] [Indexed: 12/19/2022]
Abstract
Quantitative genetics provides the tools for linking polymorphic loci to trait variation. Linkage analysis of gene expression is an established and widely applied method, leading to the identification of expression quantitative trait loci (eQTLs). (e)QTL detection facilitates the identification and understanding of the underlying molecular components and pathways, yet (e)QTL data access and mining often is a bottleneck. Here, we present WormQTL2, a database and platform for comparative investigations and meta-analyses of published (e)QTL data sets in the model nematode worm C. elegans. WormQTL2 integrates six eQTL studies spanning 11 conditions as well as over 1000 traits from 32 studies and allows experimental results to be compared, reused and extended upon to guide further experiments and conduct systems-genetic analyses. For example, one can easily screen a locus for specific cis-eQTLs that could be linked to variation in other traits, detect gene-by-environment interactions by comparing eQTLs under different conditions, or find correlations between QTL profiles of classical traits and gene expression. WormQTL2 makes data on natural variation in C. elegans and the identified QTLs interactively accessible, allowing studies beyond the original publications. Database URL: www.bioinformatics.nl/WormQTL2/.
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Affiliation(s)
- Basten L Snoek
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB Wageningen, The Netherlands
- Theoretical Biology and Bioinformatics, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Mark G Sterken
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB Wageningen, The Netherlands
| | - Margi Hartanto
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB Wageningen, The Netherlands
- Bioinformatics Group, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB Wageningen, The Netherlands
| | - Albert-Jan van Zuilichem
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB Wageningen, The Netherlands
| | - Jan E Kammenga
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB Wageningen, The Netherlands
| | - Dick de Ridder
- Bioinformatics Group, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB Wageningen, The Netherlands
| | - Harm Nijveen
- Bioinformatics Group, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB Wageningen, The Netherlands
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12
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Jovic K, Grilli J, Sterken MG, Snoek BL, Riksen JAG, Allesina S, Kammenga JE. Transcriptome resilience predicts thermotolerance in Caenorhabditis elegans. BMC Biol 2019; 17:102. [PMID: 31822273 PMCID: PMC6905072 DOI: 10.1186/s12915-019-0725-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 11/18/2019] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND The detrimental effects of a short bout of stress can persist and potentially turn lethal, long after the return to normal conditions. Thermotolerance, which is the capacity of an organism to withstand relatively extreme temperatures, is influenced by the response during stress exposure, as well as the recovery process afterwards. While heat-shock response mechanisms have been studied intensively, predicting thermal tolerance remains a challenge. RESULTS Here, we use the nematode Caenorhabditis elegans to measure transcriptional resilience to heat stress and predict thermotolerance. Using principal component analysis in combination with genome-wide gene expression profiles collected in three high-resolution time series during control, heat stress, and recovery conditions, we infer a quantitative scale capturing the extent of stress-induced transcriptome dynamics in a single value. This scale provides a basis for evaluating transcriptome resilience, defined here as the ability to depart from stress-expression dynamics during recovery. Independent replication across multiple highly divergent genotypes reveals that the transcriptional resilience parameter measured after a spike in temperature is quantitatively linked to long-term survival after heat stress. CONCLUSION Our findings imply that thermotolerance is an intrinsic property that pre-determines long-term outcome of stress and can be predicted by the transcriptional resilience parameter. Inferring the transcriptional resilience parameters of higher organisms could aid in evaluating rehabilitation strategies after stresses such as disease and trauma.
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Affiliation(s)
- Katharina Jovic
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, Wageningen, 6708 PB, The Netherlands
| | - Jacopo Grilli
- Department of Ecology and Evolution, University of Chicago, 1101 E 57th St, Chicago, IL, 60637, USA
- Santa Fe Institute, 1399 Hyde Park Rd, Santa Fe, NM, 87501, USA
- The Abdus Salam International Center for Theoretical Physics (ICTP), Strada Costiera 11, I-34014, Trieste, Italy
| | - Mark G Sterken
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, Wageningen, 6708 PB, The Netherlands
| | - Basten L Snoek
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, Wageningen, 6708 PB, The Netherlands
- Theoretical Biology and Bioinformatics, Utrecht University, Padualaan 8, Utrecht, 3584 CH, The Netherlands
| | - Joost A G Riksen
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, Wageningen, 6708 PB, The Netherlands
| | - Stefano Allesina
- Department of Ecology and Evolution, University of Chicago, 1101 E 57th St, Chicago, IL, 60637, USA.
| | - Jan E Kammenga
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, Wageningen, 6708 PB, The Netherlands.
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13
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Hart MP. Stress-Induced Neuron Remodeling Reveals Differential Interplay Between Neurexin and Environmental Factors in Caenorhabditis elegans. Genetics 2019; 213:1415-1430. [PMID: 31558583 PMCID: PMC6893388 DOI: 10.1534/genetics.119.302415] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 09/24/2019] [Indexed: 01/30/2023] Open
Abstract
Neurexins are neuronal adhesion molecules important for synapse maturation, function, and plasticity. Neurexins have been genetically associated with neurodevelopmental disorders, including autism spectrum disorders (ASDs) and schizophrenia, but can have variable penetrance and phenotypic severity. Heritability studies indicate that a significant percentage of risk for ASD and schizophrenia includes environmental factors, highlighting a poorly understood interplay between genetic and environmental factors. The singular Caenorhabditis elegans ortholog of human neurexins, nrx-1, controls experience-dependent morphologic remodeling of a GABAergic neuron in adult males. Here, I show remodeling of this neuron's morphology in response to each of three environmental stressors (nutritional, heat, or genotoxic stress) when applied specifically during sexual maturation. Increased outgrowth of axon-like neurites following adolescent stress is the result of an altered morphologic plasticity in adulthood. Despite remodeling being induced by each of the three stressors, only nutritional stress affects downstream behavior and is dependent on neurexin/nrx-1 Heat or genotoxic stress in adolescence does not alter behavior despite inducing GABAergic neuron remodeling, in a neurexin/nrx-1 independent fashion. Starvation-induced remodeling is also dependent on neuroligin/nlg-1, the canonical binding partner for neurexin/nrx-1, and the transcription factors FOXO/daf-16 and HSF1/hsf-1hsf-1 and daf-16, in addition, each have unique roles in remodeling induced by heat and UV stress. The differential molecular mechanisms underlying GABAergic neuron remodeling in response to different stressors, and the disparate effects of stressors on downstream behavior, are a paradigm for understanding how genetics, environmental exposures, and plasticity may contribute to brain dysfunction in ASDs and schizophrenia.
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Affiliation(s)
- Michael P Hart
- Department of Genetics, University of Pennsylvania, Philadelphia, Pennsylvania 19104
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14
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Wang YA, Snoek BL, Sterken MG, Riksen JAG, Stastna JJ, Kammenga JE, Harvey SC. Genetic background modifies phenotypic and transcriptional responses in a C. elegans model of α-synuclein toxicity. BMC Genomics 2019; 20:232. [PMID: 30894116 PMCID: PMC6427842 DOI: 10.1186/s12864-019-5597-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 03/11/2019] [Indexed: 11/13/2022] Open
Abstract
Background Accumulation of protein aggregates are a major hallmark of progressive neurodegenerative disorders such as Parkinson’s disease and Alzheimer’s disease. Transgenic Caenorhabditis elegans nematodes expressing the human synaptic protein α-synuclein in body wall muscle show inclusions of aggregated protein, which affects similar genetic pathways as in humans. It is not however known how the effects of α-synuclein expression in C. elegans differs among genetic backgrounds. Here, we compared gene expression patterns and investigated the phenotypic consequences of transgenic α-synuclein expression in five different C. elegans genetic backgrounds. Results Transcriptome analysis indicates that α-synuclein expression effects pathways associated with nutrient storage, lipid transportation and ion exchange and that effects vary depending on the genetic background. These gene expression changes predict that a range of phenotypes will be affected by α-synuclein expression. We confirm this, showing that α-synuclein expression delayed development, reduced lifespan, increased rate of matricidal hatching, and slows pharyngeal pumping. Critically, these phenotypic effects depend on the genetic background and coincide with the core changes in gene expression. Conclusions Together, our results show genotype-specific effects and core alterations in both gene expression and in phenotype in response to α-synuclein expression. We conclude that the effects of α-synuclein expression are substantially modified by the genetic background, illustrating that genetic background needs to be considered in C. elegans models of neurodegenerative disease. Electronic supplementary material The online version of this article (10.1186/s12864-019-5597-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yiru A Wang
- Biomolecular Research Group, School of Human and Life Sciences, Canterbury Christ Church University, North Holmes Road, Canterbury, CT1 1QU, UK.,Laboratory of Nematology, Wageningen University, 6708, PB, Wageningen, The Netherlands
| | - Basten L Snoek
- Laboratory of Nematology, Wageningen University, 6708, PB, Wageningen, The Netherlands.,Theoretical Biology and Bioinformatics, Utrecht University, Utrecht, The Netherlands
| | - Mark G Sterken
- Laboratory of Nematology, Wageningen University, 6708, PB, Wageningen, The Netherlands
| | - Joost A G Riksen
- Laboratory of Nematology, Wageningen University, 6708, PB, Wageningen, The Netherlands
| | - Jana J Stastna
- Biomolecular Research Group, School of Human and Life Sciences, Canterbury Christ Church University, North Holmes Road, Canterbury, CT1 1QU, UK
| | - Jan E Kammenga
- Laboratory of Nematology, Wageningen University, 6708, PB, Wageningen, The Netherlands
| | - Simon C Harvey
- Biomolecular Research Group, School of Human and Life Sciences, Canterbury Christ Church University, North Holmes Road, Canterbury, CT1 1QU, UK.
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15
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Snoek BL, Volkers RJM, Nijveen H, Petersen C, Dirksen P, Sterken MG, Nakad R, Riksen JAG, Rosenstiel P, Stastna JJ, Braeckman BP, Harvey SC, Schulenburg H, Kammenga JE. A multi-parent recombinant inbred line population of C. elegans allows identification of novel QTLs for complex life history traits. BMC Biol 2019; 17:24. [PMID: 30866929 PMCID: PMC6417139 DOI: 10.1186/s12915-019-0642-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 02/26/2019] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND The nematode Caenorhabditis elegans has been extensively used to explore the relationships between complex traits, genotypes, and environments. Complex traits can vary across different genotypes of a species, and the genetic regulators of trait variation can be mapped on the genome using quantitative trait locus (QTL) analysis of recombinant inbred lines (RILs) derived from genetically and phenotypically divergent parents. Most RILs have been derived from crossing two parents from globally distant locations. However, the genetic diversity between local C. elegans populations can be as diverse as between global populations and could thus provide means of identifying genetic variation associated with complex traits relevant on a broader scale. RESULTS To investigate the effect of local genetic variation on heritable traits, we developed a new RIL population derived from 4 parental wild isolates collected from 2 closely located sites in France: Orsay and Santeuil. We crossed these 4 genetically diverse parental isolates to generate a population of 200 multi-parental RILs and used RNA-seq to obtain sequence polymorphisms identifying almost 9000 SNPs variable between the 4 genotypes with an average spacing of 11 kb, doubling the mapping resolution relative to currently available RIL panels for many loci. The SNPs were used to construct a genetic map to facilitate QTL analysis. We measured life history traits such as lifespan, stress resistance, developmental speed, and population growth in different environments, and found substantial variation for most traits. We detected multiple QTLs for most traits, including novel QTLs not found in previous QTL analysis, including those for lifespan and pathogen responses. This shows that recombining genetic variation across C. elegans populations that are in geographical close proximity provides ample variation for QTL mapping. CONCLUSION Taken together, we show that using more parents than the classical two parental genotypes to construct a RIL population facilitates the detection of QTLs and that the use of wild isolates facilitates the detection of QTLs. The use of multi-parent RIL populations can further enhance our understanding of local adaptation and life history trade-offs.
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Affiliation(s)
- Basten L Snoek
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB, Wageningen, The Netherlands. .,Theoretical Biology and Bioinformatics, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
| | - Rita J M Volkers
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB, Wageningen, The Netherlands
| | - Harm Nijveen
- Bioinformatics Group, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB, Wageningen, The Netherlands
| | - Carola Petersen
- Zoological Institute, University of Kiel, 24098, Kiel, Germany
| | - Philipp Dirksen
- Zoological Institute, University of Kiel, 24098, Kiel, Germany
| | - Mark G Sterken
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB, Wageningen, The Netherlands
| | - Rania Nakad
- Zoological Institute, University of Kiel, 24098, Kiel, Germany
| | - Joost A G Riksen
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB, Wageningen, The Netherlands
| | - Philip Rosenstiel
- Institute for Clinical Molecular Biology, University of Kiel, 24098, Kiel, Germany
| | - Jana J Stastna
- Biomolecular Research Group, School of Human and Life Sciences, Canterbury Christ Church University, North Holmes Road, Canterbury, CT1 1QU, UK
| | - Bart P Braeckman
- Department of Biology, Ghent University, K. L. Ledeganckstraat 35, B-9000, Ghent, Belgium
| | - Simon C Harvey
- Biomolecular Research Group, School of Human and Life Sciences, Canterbury Christ Church University, North Holmes Road, Canterbury, CT1 1QU, UK
| | - Hinrich Schulenburg
- Zoological Institute, University of Kiel, 24098, Kiel, Germany. .,Max Planck Institute for Evolutionary Biology, August-Thienemann-Str. 2, 24306, Plön, Germany.
| | - Jan E Kammenga
- Laboratory of Nematology, Wageningen University, Droevendaalsesteeg 1, NL-6708 PB, Wageningen, The Netherlands.
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16
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Jovic K, Sterken MG, Grilli J, Bevers RPJ, Rodriguez M, Riksen JAG, Allesina S, Kammenga JE, Snoek LB. Temporal dynamics of gene expression in heat-stressed Caenorhabditis elegans. PLoS One 2017; 12:e0189445. [PMID: 29228038 PMCID: PMC5724892 DOI: 10.1371/journal.pone.0189445] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 11/25/2017] [Indexed: 12/21/2022] Open
Abstract
There is considerable insight into pathways and genes associated with heat-stress conditions. Most genes involved in stress response have been identified using mutant screens or gene knockdowns. Yet, there is limited understanding of the temporal dynamics of global gene expression in stressful environments. Here, we studied global gene expression profiles during 12 hours of heat stress in the nematode C. elegans. Using a high-resolution time series of increasing stress exposures, we found a distinct shift in gene expression patterns between 3–4 hours into the stress response, separating an initially highly dynamic phase from a later relatively stagnant phase. This turning point in expression dynamics coincided with a phenotypic turning point, as shown by a strong decrease in movement, survival and, progeny count in the days following the stress. Both detectable at transcriptional and phenotypic level, this study pin-points a relatively small time frame during heat stress at which enough damage is accumulated, making it impossible to recover the next few days.
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Affiliation(s)
- Katharina Jovic
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Mark G. Sterken
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Jacopo Grilli
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois, United States of America
| | - Roel P. J. Bevers
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Miriam Rodriguez
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Joost A. G. Riksen
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Stefano Allesina
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois, United States of America
| | - Jan E. Kammenga
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
- * E-mail:
| | - L. Basten Snoek
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
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17
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Kim B, Suo B, Emmons SW. Gene Function Prediction Based on Developmental Transcriptomes of the Two Sexes in C. elegans. Cell Rep 2017; 17:917-928. [PMID: 27732864 PMCID: PMC5656000 DOI: 10.1016/j.celrep.2016.09.051] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 08/03/2016] [Accepted: 09/16/2016] [Indexed: 11/29/2022] Open
Abstract
We compare whole-animal RNA-seq transcriptomes for C. elegans males and hermaphrodites from the late L3 larval stage to young adulthood. During this interval, male sexual structures develop, including extensive neurogenesis and synaptogenesis that nearly doubles the size of the nervous system. Previous genome-wide expression studies in C. elegans have usually focused on only one sex—the hermaphrodite—and there are a relatively large number of genes that remain without meaningful annotation. In the present study, differential expression analysis of the RNA-seq data revealed 1,751 genes expressed at a higher level in the male. By differential expression and co-expression analyses, we identified transcription factors required for differentiation of male genital structures, semen proteins, and candidates for components of synapse function. Comparison with other prediction tools suggests that our dataset can expand gene predictions. The results validate the dataset as a rich resource for future gene discovery in C. elegans.
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Affiliation(s)
- Byunghyuk Kim
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Bangxia Suo
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Scott W Emmons
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA; Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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18
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Snoek BL, Sterken MG, Bevers RPJ, Volkers RJM, Van't Hof A, Brenchley R, Riksen JAG, Cossins A, Kammenga JE. Contribution of trans regulatory eQTL to cryptic genetic variation in C. elegans. BMC Genomics 2017; 18:500. [PMID: 28662696 PMCID: PMC5492678 DOI: 10.1186/s12864-017-3899-8] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 06/22/2017] [Indexed: 11/10/2022] Open
Abstract
Background Cryptic genetic variation (CGV) is the hidden genetic variation that can be unlocked by perturbing normal conditions. CGV can drive the emergence of novel complex phenotypes through changes in gene expression. Although our theoretical understanding of CGV has thoroughly increased over the past decade, insight into polymorphic gene expression regulation underlying CGV is scarce. Here we investigated the transcriptional architecture of CGV in response to rapid temperature changes in the nematode Caenorhabditis elegans. We analyzed regulatory variation in gene expression (and mapped eQTL) across the course of a heat stress and recovery response in a recombinant inbred population. Results We measured gene expression over three temperature treatments: i) control, ii) heat stress, and iii) recovery from heat stress. Compared to control, exposure to heat stress affected the transcription of 3305 genes, whereas 942 were affected in recovering animals. These affected genes were mainly involved in metabolism and reproduction. The gene expression pattern in recovering animals resembled both the control and the heat-stress treatment. We mapped eQTL using the genetic variation of the recombinant inbred population and detected 2626 genes with an eQTL in the heat-stress treatment, 1797 in the control, and 1880 in the recovery. The cis-eQTL were highly shared across treatments. A considerable fraction of the trans-eQTL (40–57%) mapped to 19 treatment specific trans-bands. In contrast to cis-eQTL, trans-eQTL were highly environment specific and thus cryptic. Approximately 67% of the trans-eQTL were only induced in a single treatment, with heat-stress showing the most unique trans-eQTL. Conclusions These results illustrate the highly dynamic pattern of CGV across three different environmental conditions that can be evoked by a stress response over a relatively short time-span (2 h) and that CGV is mainly determined by response related trans regulatory eQTL. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3899-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Basten L Snoek
- Laboratory of Nematology, Wageningen University and Research, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands
| | - Mark G Sterken
- Laboratory of Nematology, Wageningen University and Research, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands
| | - Roel P J Bevers
- Laboratory of Nematology, Wageningen University and Research, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands
| | - Rita J M Volkers
- Laboratory of Nematology, Wageningen University and Research, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands
| | - Arjen Van't Hof
- Centre for Genome research, Institute of Integrative Biology, Biosciences Building, University of Liverpool, L69 7ZB, Liverpool, UK
| | - Rachel Brenchley
- Centre for Genome research, Institute of Integrative Biology, Biosciences Building, University of Liverpool, L69 7ZB, Liverpool, UK
| | - Joost A G Riksen
- Laboratory of Nematology, Wageningen University and Research, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands
| | - Andrew Cossins
- Centre for Genome research, Institute of Integrative Biology, Biosciences Building, University of Liverpool, L69 7ZB, Liverpool, UK
| | - Jan E Kammenga
- Laboratory of Nematology, Wageningen University and Research, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands.
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19
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Variation in gene expression within clones of the earthworm Dendrobaena octaedra. PLoS One 2017; 12:e0174960. [PMID: 28384196 PMCID: PMC5383104 DOI: 10.1371/journal.pone.0174960] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 03/19/2017] [Indexed: 12/23/2022] Open
Abstract
Gene expression is highly plastic, which can help organisms to both acclimate and adapt to changing environments. Possible variation in gene expression among individuals with the same genotype (among clones) is not widely considered, even though it could impact the results of studies that focus on gene expression phenotypes, for example studies using clonal lines. We examined the extent of within and between clone variation in gene expression in the earthworm Dendrobaena octaedra, which reproduces through apomictic parthenogenesis. Five microsatellite markers were developed and used to confirm that offspring are genetic clones of their parent. After that, expression of 12 genes was measured from five individuals each from six clonal lines after exposure to copper contaminated soil. Variation in gene expression was higher over all genotypes than within genotypes, as initially assumed. A subset of the genes was also examined in the offspring of exposed individuals in two of the clonal lines. In this case, variation in gene expression within genotypes was as high as that observed over all genotypes. One gene in particular (chymotrypsin inhibitor) also showed significant differences in the expression levels among genetically identical individuals. Gene expression can vary considerably, and the extent of variation may depend on the genotypes and genes studied. Ensuring a large sample, with many different genotypes, is critical in studies comparing gene expression phenotypes. Researchers should be especially cautious inferring gene expression phenotypes when using only a single clonal or inbred line, since the results might be specific to only certain genotypes.
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20
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Singh KD, Roschitzki B, Snoek LB, Grossmann J, Zheng X, Elvin M, Kamkina P, Schrimpf SP, Poulin GB, Kammenga JE, Hengartner MO. Natural Genetic Variation Influences Protein Abundances in C. elegans Developmental Signalling Pathways. PLoS One 2016; 11:e0149418. [PMID: 26985669 PMCID: PMC4795773 DOI: 10.1371/journal.pone.0149418] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 01/30/2016] [Indexed: 12/11/2022] Open
Abstract
Complex traits, including common disease-related traits, are affected by many different genes that function in multiple pathways and networks. The apoptosis, MAPK, Notch, and Wnt signalling pathways play important roles in development and disease progression. At the moment we have a poor understanding of how allelic variation affects gene expression in these pathways at the level of translation. Here we report the effect of natural genetic variation on transcript and protein abundance involved in developmental signalling pathways in Caenorhabditis elegans. We used selected reaction monitoring to analyse proteins from the abovementioned four pathways in a set of recombinant inbred lines (RILs) generated from the wild-type strains N2 (Bristol) and CB4856 (Hawaii) to enable quantitative trait locus (QTL) mapping. About half of the cases from the 44 genes tested showed a statistically significant change in protein abundance between various strains, most of these were however very weak (below 1.3-fold change). We detected a distant QTL on the left arm of chromosome II that affected protein abundance of the phosphatidylserine receptor protein PSR-1, and two separate QTLs that influenced embryonic and ionizing radiation-induced apoptosis on chromosome IV. Our results demonstrate that natural variation in C. elegans is sufficient to cause significant changes in signalling pathways both at the gene expression (transcript and protein abundance) and phenotypic levels.
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Affiliation(s)
- Kapil Dev Singh
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Bernd Roschitzki
- Functional Genomics Center Zurich, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - L. Basten Snoek
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Jonas Grossmann
- Functional Genomics Center Zurich, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Xue Zheng
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Mark Elvin
- Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom
| | - Polina Kamkina
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Sabine P. Schrimpf
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Gino B. Poulin
- Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom
| | - Jan E. Kammenga
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Michael O. Hengartner
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
- * E-mail:
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21
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Kamkina P, Snoek LB, Grossmann J, Volkers RJM, Sterken MG, Daube M, Roschitzki B, Fortes C, Schlapbach R, Roth A, von Mering C, Hengartner MO, Schrimpf SP, Kammenga JE. Natural Genetic Variation Differentially Affects the Proteome and Transcriptome in Caenorhabditis elegans. Mol Cell Proteomics 2016; 15:1670-80. [PMID: 26944343 DOI: 10.1074/mcp.m115.052548] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Indexed: 11/06/2022] Open
Abstract
Natural genetic variation is the raw material of evolution and influences disease development and progression. An important question is how this genetic variation translates into variation in protein abundance. To analyze the effects of the genetic background on gene and protein expression in the nematode Caenorhabditis elegans, we quantitatively compared the two genetically highly divergent wild-type strains N2 and CB4856. Gene expression was analyzed by microarray assays, and proteins were quantified using stable isotope labeling by amino acids in cell culture. Among all transcribed genes, we found 1,532 genes to be differentially transcribed between the two wild types. Of the total 3,238 quantified proteins, 129 proteins were significantly differentially expressed between N2 and CB4856. The differentially expressed proteins were enriched for genes that function in insulin-signaling and stress-response pathways, underlining strong divergence of these pathways in nematodes. The protein abundance of the two wild-type strains correlates more strongly than protein abundance versus transcript abundance within each wild type. Our findings indicate that in C. elegans only a fraction of the changes in protein abundance can be explained by the changes in mRNA abundance. These findings corroborate with the observations made across species.
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Affiliation(s)
- Polina Kamkina
- From the ‡Institute of Molecular Life Sciences, University of Zurich, 8057 Zurich, Switzerland; §Ph.D. Program in Molecular Life Sciences Zurich, 8057 Zurich, Switzerland
| | - L Basten Snoek
- ‖Laboratory of Nematology, Wageningen University, Wageningen 6708 PB, The Netherlands
| | - Jonas Grossmann
- **Functional Genomics Center Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, 8057 Zurich, Switzerland
| | - Rita J M Volkers
- ‖Laboratory of Nematology, Wageningen University, Wageningen 6708 PB, The Netherlands
| | - Mark G Sterken
- ‖Laboratory of Nematology, Wageningen University, Wageningen 6708 PB, The Netherlands
| | - Michael Daube
- From the ‡Institute of Molecular Life Sciences, University of Zurich, 8057 Zurich, Switzerland
| | - Bernd Roschitzki
- **Functional Genomics Center Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, 8057 Zurich, Switzerland
| | - Claudia Fortes
- **Functional Genomics Center Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, 8057 Zurich, Switzerland
| | - Ralph Schlapbach
- **Functional Genomics Center Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, 8057 Zurich, Switzerland
| | - Alexander Roth
- From the ‡Institute of Molecular Life Sciences, University of Zurich, 8057 Zurich, Switzerland
| | - Christian von Mering
- From the ‡Institute of Molecular Life Sciences, University of Zurich, 8057 Zurich, Switzerland
| | - Michael O Hengartner
- From the ‡Institute of Molecular Life Sciences, University of Zurich, 8057 Zurich, Switzerland
| | - Sabine P Schrimpf
- From the ‡Institute of Molecular Life Sciences, University of Zurich, 8057 Zurich, Switzerland;
| | - Jan E Kammenga
- ‖Laboratory of Nematology, Wageningen University, Wageningen 6708 PB, The Netherlands;
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22
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Roux J, Rosikiewicz M, Robinson-Rechavi M. What to compare and how: Comparative transcriptomics for Evo-Devo. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2015; 324:372-82. [PMID: 25864439 PMCID: PMC4949521 DOI: 10.1002/jez.b.22618] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 02/19/2015] [Indexed: 12/30/2022]
Abstract
Evolutionary developmental biology has grown historically from the capacity to relate patterns of evolution in anatomy to patterns of evolution of expression of specific genes, whether between very distantly related species, or very closely related species or populations. Scaling up such studies by taking advantage of modern transcriptomics brings promising improvements, allowing us to estimate the overall impact and molecular mechanisms of convergence, constraint or innovation in anatomy and development. But it also presents major challenges, including the computational definitions of anatomical homology and of organ function, the criteria for the comparison of developmental stages, the annotation of transcriptomics data to proper anatomical and developmental terms, and the statistical methods to compare transcriptomic data between species to highlight significant conservation or changes. In this article, we review these challenges, and the ongoing efforts to address them, which are emerging from bioinformatics work on ontologies, evolutionary statistics, and data curation, with a focus on their implementation in the context of the development of our database Bgee (http://bgee.org). J. Exp. Zool. (Mol. Dev. Evol.) 324B: 372–382, 2015. © 2015 The Authors. J. Exp. Zool. (Mol. Dev. Evol.) published by Wiley Periodicals, Inc.
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Affiliation(s)
- Julien Roux
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.,Swiss Institute of Bioinformatics, Lausanne, Switzerland.,Department of Human Genetics, University of Chicago, Chicago, Illinois
| | - Marta Rosikiewicz
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.,Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Marc Robinson-Rechavi
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.,Swiss Institute of Bioinformatics, Lausanne, Switzerland
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23
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The laboratory domestication of Caenorhabditis elegans. Trends Genet 2015; 31:224-31. [PMID: 25804345 DOI: 10.1016/j.tig.2015.02.009] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Revised: 02/19/2015] [Accepted: 02/20/2015] [Indexed: 12/17/2022]
Abstract
Model organisms are of great importance to our understanding of basic biology and to making advances in biomedical research. However, the influence of laboratory cultivation on these organisms is underappreciated, and especially how that environment can affect research outcomes. Recent experiments led to insights into how the widely used laboratory reference strain of the nematode Caenorhabditis elegans compares with natural strains. Here we describe potential selective pressures that led to the fixation of laboratory-derived alleles for the genes npr-1, glb-5, and nath-10. These alleles influence a large number of traits, resulting in behaviors that affect experimental interpretations. Furthermore, strong phenotypic effects caused by these laboratory-derived alleles hinder the discovery of natural alleles. We highlight strategies to reduce the influence of laboratory-derived alleles and to harness the full power of C. elegans.
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Francesconi M, Lehner B. Reconstructing and analysing cellular states, space and time from gene expression profiles of many cells and single cells. MOLECULAR BIOSYSTEMS 2015; 11:2690-8. [DOI: 10.1039/c5mb00339c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Gene expression profiling is a fast, cheap and standardised analysis that provides a high dimensional measurement of the state of a biological sample, including of single cells. Computational methods to reconstruct the composition of samples and spatial and temporal information from expression profiles are described, as well as how they can be used to describe the effects of genetic variation.
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Affiliation(s)
- Mirko Francesconi
- EMBL-CRG Systems Biology Unit
- Centre for Genomic Regulation (CRG)
- 08003 Barcelona
- Spain
- Universitat Pompeu Fabra (UPF)
| | - Ben Lehner
- EMBL-CRG Systems Biology Unit
- Centre for Genomic Regulation (CRG)
- 08003 Barcelona
- Spain
- Universitat Pompeu Fabra (UPF)
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George-Raizen JB, Shockley KR, Trojanowski NF, Lamb AL, Raizen DM. Dynamically-expressed prion-like proteins form a cuticle in the pharynx of Caenorhabditis elegans. Biol Open 2014; 3:1139-49. [PMID: 25361578 PMCID: PMC4232772 DOI: 10.1242/bio.20147500] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
In molting animals, a cuticular extracellular matrix forms the first barrier to infection and other environmental insults. In the nematode Caenorhabditis elegans there are two types of cuticle: a well-studied collagenous cuticle lines the body, and a poorly-understood chitinous cuticle lines the pharynx. In the posterior end of the pharynx is the grinder, a tooth-like cuticular specialization that crushes food prior to transport to the intestine for digestion. We here show that the grinder increases in size only during the molt. To gain molecular insight into the structure of the grinder and pharyngeal cuticle, we performed a microarray analysis to identify mRNAs increased during the molt. We found strong transcriptional induction during the molt of 12 of 15 previously identified abu genes encoding Prion-like (P) glutamine (Q) and asparagine (N) rich PQN proteins, as well as 15 additional genes encoding closely related PQN proteins. abu/pqn genes, which we name the abu/pqn paralog group (APPG) genes, were expressed in pharyngeal cells and the proteins encoded by two APPG genes we tested localized to the pharyngeal cuticle. Deleting the APPG gene abu-14 caused abnormal pharyngeal cuticular structures and knocking down other APPG genes resulted in abnormal cuticular function. We propose that APPG proteins promote the assembly and function of a unique cuticular structure. The strong developmental regulation of the APPG genes raises the possibility that such genes would be identified in transcriptional profiling experiments in which the animals' developmental stage is not precisely staged.
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Affiliation(s)
- Julia B George-Raizen
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Keith R Shockley
- Biostatistics Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, USA
| | - Nicholas F Trojanowski
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Annesia L Lamb
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA Present address: Department of Earth and Environmental Sciences, The Graduate Center, The City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
| | - David M Raizen
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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Snoek LB, Orbidans HE, Stastna JJ, Aartse A, Rodriguez M, Riksen JAG, Kammenga JE, Harvey SC. Widespread genomic incompatibilities in Caenorhabditis elegans. G3 (BETHESDA, MD.) 2014; 4:1813-23. [PMID: 25128438 PMCID: PMC4199689 DOI: 10.1534/g3.114.013151] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 07/17/2014] [Indexed: 01/18/2023]
Abstract
In the Bateson-Dobzhansky-Muller (BDM) model of speciation, incompatibilities emerge from the deleterious interactions between alleles that are neutral or advantageous in the original genetic backgrounds, i.e., negative epistatic effects. Within species such interactions are responsible for outbreeding depression and F2 (hybrid) breakdown. We sought to identify BDM incompatibilities in the nematode Caenorhabditis elegans by looking for genomic regions that disrupt egg laying; a complex, highly regulated, and coordinated phenotype. Investigation of introgression lines and recombinant inbred lines derived from the isolates CB4856 and N2 uncovered multiple incompatibility quantitative trait loci (QTL). These QTL produce a synthetic egg-laying defective phenotype not seen in CB4856 and N2 nor in other wild isolates. For two of the QTL regions, results are inconsistent with a model of pairwise interaction between two loci, suggesting that the incompatibilities are a consequence of complex interactions between multiple loci. Analysis of additional life history traits indicates that the QTL regions identified in these screens are associated with effects on other traits such as lifespan and reproduction, suggesting that the incompatibilities are likely to be deleterious. Taken together, these results indicate that numerous BDM incompatibilities that could contribute to reproductive isolation can be detected and mapped within C. elegans.
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Affiliation(s)
- L Basten Snoek
- Laboratory of Nematology, Wageningen University, 6708 PB Wageningen, The Netherlands
| | - Helen E Orbidans
- Biomolecular Research Group, School of Human and Life Sciences, Canterbury Christ Church University, North Holmes Road, Canterbury, CT1 1QU, UK
| | - Jana J Stastna
- Biomolecular Research Group, School of Human and Life Sciences, Canterbury Christ Church University, North Holmes Road, Canterbury, CT1 1QU, UK
| | - Aafke Aartse
- Laboratory of Nematology, Wageningen University, 6708 PB Wageningen, The Netherlands
| | - Miriam Rodriguez
- Laboratory of Nematology, Wageningen University, 6708 PB Wageningen, The Netherlands
| | - Joost A G Riksen
- Laboratory of Nematology, Wageningen University, 6708 PB Wageningen, The Netherlands
| | - Jan E Kammenga
- Laboratory of Nematology, Wageningen University, 6708 PB Wageningen, The Netherlands
| | - Simon C Harvey
- Biomolecular Research Group, School of Human and Life Sciences, Canterbury Christ Church University, North Holmes Road, Canterbury, CT1 1QU, UK
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Loss-of-function of β-catenin bar-1 slows development and activates the Wnt pathway in Caenorhabditis elegans. Sci Rep 2014; 4:4926. [PMID: 24819947 PMCID: PMC4019968 DOI: 10.1038/srep04926] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 04/23/2014] [Indexed: 02/07/2023] Open
Abstract
C. elegans is extensively used to study the Wnt-pathway and most of the core-signalling components are known. Four β-catenins are important gene expression regulators in Wnt-signalling. One of these, bar-1, is part of the canonical Wnt-pathway. Together with Wnt effector pop-1, bar-1 forms a transcription activation complex which regulates the transcription of downstream genes. The effects of bar-1 loss-of-function mutations on many phenotypes have been studied well. However, the effects on global gene expression are unknown. Here we report the effects of a loss-of-function mutation bar-1(ga80). By analysing the transcriptome and developmental phenotyping we show that bar-1(ga80) impairs developmental timing. This developmental difference confounds the comparison of the gene expression profile between the mutant and the reference strain. When corrected for this difference it was possible to identify genes that were directly affected by the bar-1 mutation. We show that the Wnt-pathway itself is activated, as well as transcription factors elt-3, pqm-1, mdl-1 and pha-4 and their associated genes. The outcomes imply that this response compensates for the loss of functional bar-1. Altogether we show that bar-1 loss-of function leads to delayed development possibly caused by an induction of a stress response, reflected by daf-16 activated genes.
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Snoek LB, Joeri van der Velde K, Li Y, Jansen RC, Swertz MA, Kammenga JE. Worm variation made accessible: Take your shopping cart to store, link, and investigate! WORM 2014; 3:e28357. [PMID: 24843834 PMCID: PMC4024057 DOI: 10.4161/worm.28357] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 02/17/2014] [Accepted: 02/25/2014] [Indexed: 11/20/2022]
Abstract
In Caenorhabditis elegans, the recent advances in high-throughput quantitative analyses of natural genetic and phenotypic variation have led to a wealth of data on genotype phenotype relations. This data has resulted in the discovery of genes with major allelic effects and insights in the effect of natural genetic variation on a whole range of complex traits as well as how this variation is distributed across the genome. Regardless of the advances presented in specific studies, the majority of the data generated in these studies had yet to be made easily accessible, allowing for meta-analysis. Not only data in figures or tables but meta-data should be accessible for further investigation and comparison between studies. A platform was created where all the data, phenotypic measurements, genotypes, and mappings can be stored, compared, and new linkages within and between published studies can be discovered. WormQTL focuses on quantitative genetics in Caenorhabditis and other nematode species, whereas WormQTLHD quantitatively links gene expression quantitative trait loci (eQTL) in C. elegans to gene–disease associations in humans.
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Affiliation(s)
- L Basten Snoek
- Laboratory of Nematology; Wageningen University; The Netherlands
| | - K Joeri van der Velde
- Genomics Coordination Center; University of Groningen; University Medical Center Groningen; The Netherlands ; Groningen Bioinformatics Center; University of Groningen; The Netherlands ; Department of Genetics; University of Groningen; University Medical Center Groningen; The Netherlands
| | - Yang Li
- Genomics Coordination Center; University of Groningen; University Medical Center Groningen; The Netherlands ; Groningen Bioinformatics Center; University of Groningen; The Netherlands
| | - Ritsert C Jansen
- Groningen Bioinformatics Center; University of Groningen; The Netherlands
| | - Morris A Swertz
- Genomics Coordination Center; University of Groningen; University Medical Center Groningen; The Netherlands ; Groningen Bioinformatics Center; University of Groningen; The Netherlands ; Department of Genetics; University of Groningen; University Medical Center Groningen; The Netherlands
| | - Jan E Kammenga
- Laboratory of Nematology; Wageningen University; The Netherlands
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Sterken MG, Snoek LB, Bosman KJ, Daamen J, Riksen JAG, Bakker J, Pijlman GP, Kammenga JE. A heritable antiviral RNAi response limits Orsay virus infection in Caenorhabditis elegans N2. PLoS One 2014; 9:e89760. [PMID: 24587016 PMCID: PMC3933659 DOI: 10.1371/journal.pone.0089760] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 01/23/2014] [Indexed: 11/21/2022] Open
Abstract
Orsay virus (OrV) is the first virus known to be able to complete a full infection cycle in the model nematode species Caenorhabditis elegans. OrV is transmitted horizontally and its infection is limited by antiviral RNA interference (RNAi). However, we have no insight into the kinetics of OrV replication in C. elegans. We developed an assay that infects worms in liquid, allowing precise monitoring of the infection. The assay revealed a dual role for the RNAi response in limiting Orsay virus infection in C. elegans. Firstly, it limits the progression of the initial infection at the step of recognition of dsRNA. Secondly, it provides an inherited protection against infection in the offspring. This establishes the heritable RNAi response as anti-viral mechanism during OrV infections in C. elegans. Our results further illustrate that the inheritance of the anti-viral response is important in controlling the infection in the canonical wild type Bristol N2. The OrV replication kinetics were established throughout the worm life-cycle, setting a standard for further quantitative assays with the OrV-C. elegans infection model.
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Affiliation(s)
- Mark G. Sterken
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
- Laboratory of Virology, Wageningen University, Wageningen, The Netherlands
| | - L. Basten Snoek
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Kobus J. Bosman
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Jikke Daamen
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Joost A. G. Riksen
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Jaap Bakker
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Gorben P. Pijlman
- Laboratory of Virology, Wageningen University, Wageningen, The Netherlands
| | - Jan E. Kammenga
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
- * E-mail:
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