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Shukla Y, Ghatpande V, Hu CF, Dickinson DJ, Cenik C. Landscape and regulation of mRNA translation in the early C. elegans embryo. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2025:2024.12.13.628416. [PMID: 39829802 PMCID: PMC11741243 DOI: 10.1101/2024.12.13.628416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/22/2025]
Abstract
Animal embryos rely on regulated translation of maternally deposited mRNAs to drive early development. Using low-input ribosome profiling combined with RNA sequencing on precisely staged embryos, we measured mRNA translation during the first four cell cycles of C. elegans development. We uncovered stage-specific patterns of developmentally coordinated translational regulation. We confirmed that mRNA localization correlates with translational eLiciency, though initial translational repression in germline precursors occurs before P-granule association. Our analysis suggests that the RNA-binding protein OMA-1 represses the translation of its target mRNAs in a stage-specific manner, while indirectly promoting the translational eLiciency of other transcripts. These findings illuminate how post-transcriptional mechanisms shape the embryonic proteome to direct cell diLerentiation, with implications for understanding similar regulation across species where maternal factors guide early development.
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Affiliation(s)
- Yash Shukla
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Vighnesh Ghatpande
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Cindy F. Hu
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Daniel J. Dickinson
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Can Cenik
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
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2
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Xu W, Liu J, Qi H, Si R, Zhao Z, Tao Z, Bai Y, Hu S, Sun X, Cong Y, Zhang H, Fan D, Xiao L, Wang Y, Li Y, Du Z. A lineage-resolved cartography of microRNA promoter activity in C. elegans empowers multidimensional developmental analysis. Nat Commun 2024; 15:2783. [PMID: 38555276 PMCID: PMC10981687 DOI: 10.1038/s41467-024-47055-4] [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: 01/08/2024] [Accepted: 03/13/2024] [Indexed: 04/02/2024] Open
Abstract
Elucidating the expression of microRNAs in developing single cells is critical for functional discovery. Here, we construct scCAMERA (single-cell cartography of microRNA expression based on reporter assay), utilizing promoter-driven fluorescent reporters in conjunction with imaging and lineage tracing. The cartography delineates the transcriptional activity of 54 conserved microRNAs in lineage-resolved single cells throughout C. elegans embryogenesis. The combinatorial expression of microRNAs partitions cells into fine clusters reflecting their function and anatomy. Notably, the expression of individual microRNAs exhibits high cell specificity and divergence among family members. Guided by cellular expression patterns, we identify developmental functions of specific microRNAs, including miR-1 in pharynx development and physiology, miR-232 in excretory canal morphogenesis by repressing NHR-25/NR5A, and a functional synergy between miR-232 and miR-234 in canal development, demonstrating the broad utility of scCAMERA. Furthermore, integrative analysis reveals that tissue-specific fate determinants activate microRNAs to repress protein production from leaky transcripts associated with alternative, especially neuronal, fates, thereby enhancing the fidelity of developmental fate differentiation. Collectively, our study offers rich opportunities for multidimensional expression-informed analysis of microRNA biology in metazoans.
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Affiliation(s)
- Weina Xu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jinyi Liu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Huan Qi
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Ruolin Si
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Zhiguang Zhao
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zhiju Tao
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Yuchuan Bai
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Shipeng Hu
- College of Life Sciences, Capital Normal University, Beijing, China
| | - Xiaohan Sun
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yulin Cong
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Haoye Zhang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Duchangjiang Fan
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Long Xiao
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Yangyang Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Yongbin Li
- College of Life Sciences, Capital Normal University, Beijing, China.
| | - Zhuo Du
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
- University of Chinese Academy of Sciences, Beijing, China.
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3
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Liu J, Murray JI. Mechanisms of lineage specification in Caenorhabditis elegans. Genetics 2023; 225:iyad174. [PMID: 37847877 PMCID: PMC11491538 DOI: 10.1093/genetics/iyad174] [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: 08/26/2023] [Accepted: 09/18/2023] [Indexed: 10/19/2023] Open
Abstract
The studies of cell fate and lineage specification are fundamental to our understanding of the development of multicellular organisms. Caenorhabditis elegans has been one of the premiere systems for studying cell fate specification mechanisms at single cell resolution, due to its transparent nature, the invariant cell lineage, and fixed number of somatic cells. We discuss the general themes and regulatory mechanisms that have emerged from these studies, with a focus on somatic lineages and cell fates. We next review the key factors and pathways that regulate the specification of discrete cells and lineages during embryogenesis and postembryonic development; we focus on transcription factors and include numerous lineage diagrams that depict the expression of key factors that specify embryonic founder cells and postembryonic blast cells, and the diverse somatic cell fates they generate. We end by discussing some future perspectives in cell and lineage specification.
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Affiliation(s)
- Jun Liu
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - John Isaac Murray
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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4
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Tabarraei H, Waddell BM, Wu CW. Investigation of PAL-1 requirement in C. elegans physiology using the auxin-inducible degradation system. MICROPUBLICATION BIOLOGY 2023; 2023:10.17912/micropub.biology.001057. [PMID: 38125784 PMCID: PMC10731474 DOI: 10.17912/micropub.biology.001057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 11/28/2023] [Accepted: 12/05/2023] [Indexed: 12/23/2023]
Abstract
The C. elegans PAL-1 protein encodes a caudal-like transcription factor that is required for posterior development and was recently implicated in stress response. We generated a transgenic strain of C. elegans with AID*::3xFLAG::wrmScarlet cassette knocked in at the C-terminal end of the pal-1 locus to enable an auxin-inducible degradation of PAL-1 . We found that auxin-induced degradation of PAL-1 starting from the L1 larval stage does not affect body length development but renders the animal sterile and shortens lifespan. This pal-1 ::AID*::3xFLAG::wrmScarlet strain will be a valuable resource for studying the requirement of PAL-1 in a temporal and tissue-specific manner.
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Affiliation(s)
- Hadi Tabarraei
- Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Brandon M. Waddell
- Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Cheng-Wei Wu
- Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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5
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Tabarraei H, Waddell BM, Raymond K, Murray SM, Wang Y, Choe KP, Wu CW. CCR4-NOT subunit CCF-1/CNOT7 promotes transcriptional activation to multiple stress responses in Caenorhabditis elegans. Aging Cell 2023; 22:e13795. [PMID: 36797658 PMCID: PMC10086529 DOI: 10.1111/acel.13795] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 01/13/2023] [Accepted: 02/01/2023] [Indexed: 02/18/2023] Open
Abstract
CCR4-NOT is a versatile eukaryotic protein complex that controls multiple steps in gene expression regulation from synthesis to decay. In yeast, CCR4-NOT has been implicated in stress response regulation, though this function in other organisms remains unclear. In a genome-wide RNAi screen, we identified a subunit of the CCR4-NOT complex, ccf-1, as a requirement for the C. elegans transcriptional response to cadmium and acrylamide stress. Using whole-transcriptome RNA sequencing, we show that the knockdown of ccf-1 attenuates the activation of a broad range of stress-protective genes in response to cadmium and acrylamide, including those encoding heat shock proteins and xenobiotic detoxification. Consistently, survival assays show that the knockdown of ccf-1 decreases C. elegans stress resistance and normal lifespan. A yeast 2-hybrid screen using a CCF-1 bait identified the homeobox transcription factor PAL-1 as a physical interactor. Knockdown of pal-1 inhibits the activation of ccf-1 dependent stress genes and reduces C. elegans stress resistance. Gene expression analysis reveals that knockdown of ccf-1 and pal-1 attenuates the activation of elt-2 and elt-3 under stress that encode master transcriptional co-regulators of stress response in the C. elegans, and that overexpression of ELT-2 can suppress ccf-1's requirement for gene transcription in a stress-dependent manner. Our findings reveal a new role for CCR4-NOT in the environmental stress response and define its role in stress resistance and longevity in C. elegans.
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Affiliation(s)
- Hadi Tabarraei
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Brandon M Waddell
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Kelly Raymond
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Sydney M Murray
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Ying Wang
- Department of Biology and Genetics Institute, University of Florida, Gainesville, Florida, USA
| | - Keith P Choe
- Department of Biology and Genetics Institute, University of Florida, Gainesville, Florida, USA
| | - Cheng-Wei Wu
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.,Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.,Department of Biochemistry, Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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6
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Albarqi MMY, Ryder SP. The role of RNA-binding proteins in orchestrating germline development in Caenorhabditis elegans. Front Cell Dev Biol 2023; 10:1094295. [PMID: 36684428 PMCID: PMC9846511 DOI: 10.3389/fcell.2022.1094295] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 12/19/2022] [Indexed: 01/06/2023] Open
Abstract
RNA passed from parents to progeny controls several aspects of early development. The germline of the free-living nematode Caenorhabditis elegans contains many families of evolutionarily conserved RNA-binding proteins (RBPs) that target the untranslated regions of mRNA transcripts to regulate their translation and stability. In this review, we summarize what is known about the binding specificity of C. elegans germline RNA-binding proteins and the mechanisms of mRNA regulation that contribute to their function. We examine the emerging role of miRNAs in translational regulation of germline and embryo development. We also provide an overview of current technology that can be used to address the gaps in our understanding of RBP regulation of mRNAs. Finally, we present a hypothetical model wherein multiple 3'UTR-mediated regulatory processes contribute to pattern formation in the germline to ensure the proper and timely localization of germline proteins and thus a functional reproductive system.
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7
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Peterson EJR, Abidi AA, Arrieta-Ortiz ML, Aguilar B, Yurkovich JT, Kaur A, Pan M, Srinivas V, Shmulevich I, Baliga NS. Intricate Genetic Programs Controlling Dormancy in Mycobacterium tuberculosis. Cell Rep 2021; 31:107577. [PMID: 32348771 PMCID: PMC7605849 DOI: 10.1016/j.celrep.2020.107577] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 12/18/2019] [Accepted: 04/06/2020] [Indexed: 11/24/2022] Open
Abstract
Mycobacterium tuberculosis (MTB) displays the remarkable ability to transition in and out of dormancy, a hallmark of the pathogen’s capacity to evade the immune system and exploit susceptible individuals. Uncovering the gene regulatory programs that underlie the phenotypic shifts in MTB during disease latency and reactivation has posed a challenge. We develop an experimental system to precisely control dissolved oxygen levels in MTB cultures in order to capture the transcriptional events that unfold as MTB transitions into and out of hypoxia-induced dormancy. Using a comprehensive genome-wide transcription factor binding map and insights from network topology analysis, we identify regulatory circuits that deterministically drive sequential transitions across six transcriptionally and functionally distinct states encompassing more than three-fifths of the MTB genome. The architecture of the genetic programs explains the transcriptional dynamics underlying synchronous entry of cells into a dormant state that is primed to infect the host upon encountering favorable conditions. Mycobacterium tuberculosis (MTB) persists within the host by counteracting disparate stressors including hypoxia. Peterson et al. report a transcriptional program that coordinates sequential state transitions to drive MTB in and out of hypoxia-induced dormancy. Among varied properties, this program encodes advanced preparedness to infect the host in favorable conditions.
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Affiliation(s)
| | - Abrar A Abidi
- Institute for Systems Biology, Seattle, WA 98109, USA
| | | | - Boris Aguilar
- Institute for Systems Biology, Seattle, WA 98109, USA
| | | | - Amardeep Kaur
- Institute for Systems Biology, Seattle, WA 98109, USA
| | - Min Pan
- Institute for Systems Biology, Seattle, WA 98109, USA
| | | | | | - Nitin S Baliga
- Institute for Systems Biology, Seattle, WA 98109, USA; Molecular and Cellular Biology Program, Departments of Microbiology and Biology, University of Washington, Seattle, WA; Lawrence Berkeley National Laboratories, Berkeley, CA.
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8
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Fan T, Huang Y. Accessible chromatin reveals regulatory mechanisms underlying cell fate decisions during early embryogenesis. Sci Rep 2021; 11:7896. [PMID: 33846424 PMCID: PMC8042068 DOI: 10.1038/s41598-021-86919-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 03/22/2021] [Indexed: 02/01/2023] Open
Abstract
This study was conducted to investigate epigenetic landscape across multiple species and identify transcription factors (TFs) and their roles in controlling cell fate decision events during early embryogenesis. We made a comprehensively joint-research of chromatin accessibility of five species during embryogenesis by integration of ATAC-seq and RNA-seq datasets. Regulatory roles of candidate early embryonic TFs were investigated. Widespread accessible chromatin in early embryos overlapped with putative cis-regulatory sequences. Sets of cell-fate-determining TFs were identified. YOX1, a key cell cycle regulator, were found to homologous to clusters of TFs that are involved in neuron and epidermal cell-fate determination. Our research provides an intriguing insight into evolution of cell-fate decision during early embryogenesis among organisms.
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Affiliation(s)
- Tongqiang Fan
- grid.443483.c0000 0000 9152 7385State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin’an, Hangzhou, 311300 People’s Republic of China
| | - Youjun Huang
- grid.443483.c0000 0000 9152 7385State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin’an, Hangzhou, 311300 People’s Republic of China
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9
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Haeussler S, Yeroslaviz A, Rolland SG, Luehr S, Lambie EJ, Conradt B. Genome-wide RNAi screen for regulators of UPRmt in Caenorhabditis elegans mutants with defects in mitochondrial fusion. G3-GENES GENOMES GENETICS 2021; 11:6204483. [PMID: 33784383 PMCID: PMC8495942 DOI: 10.1093/g3journal/jkab095] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 03/18/2021] [Indexed: 01/22/2023]
Abstract
Mitochondrial dynamics plays an important role in mitochondrial quality control and the adaptation of metabolic activity in response to environmental changes. The disruption of mitochondrial dynamics has detrimental consequences for mitochondrial and cellular homeostasis and leads to the activation of the mitochondrial unfolded protein response (UPRmt), a quality control mechanism that adjusts cellular metabolism and restores homeostasis. To identify genes involved in the induction of UPRmt in response to a block in mitochondrial fusion, we performed a genome-wide RNAi screen in Caenorhabditis elegans mutants lacking the gene fzo-1, which encodes the ortholog of mammalian Mitofusin, and identified 299 suppressors and 86 enhancers. Approximately 90% of these 385 genes are conserved in humans, and one third of the conserved genes have been implicated in human disease. Furthermore, many have roles in developmental processes, which suggests that mitochondrial function and the response to stress are defined during development and maintained throughout life. Our dataset primarily contains mitochondrial enhancers and non-mitochondrial suppressors of UPRmt, indicating that the maintenance of mitochondrial homeostasis has evolved as a critical cellular function, which, when disrupted, can be compensated for by many different cellular processes. Analysis of the subsets 'non-mitochondrial enhancers' and 'mitochondrial suppressors' suggests that organellar contact sites, especially between the ER and mitochondria, are of importance for mitochondrial homeostasis. In addition, we identified several genes involved in IP3 signaling that modulate UPRmt in fzo-1 mutants and found a potential link between pre-mRNA splicing and UPRmt activation.
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Affiliation(s)
- Simon Haeussler
- Faculty of Biology, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany
| | - Assa Yeroslaviz
- Computational Biology Group, Max Planck Institute of Biochemistry, 82152 Planegg-Martinsried, Germany
| | - Stéphane G Rolland
- Faculty of Biology, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany.,Center for Genomic Integrity, Institute for Basic Science (IBS), Ulsan 44919, South Korea
| | - Sebastian Luehr
- Faculty of Biology, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany
| | - Eric J Lambie
- Center for Integrated Protein Science, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany
| | - Barbara Conradt
- Faculty of Biology, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany.,Center for Integrated Protein Science, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany.,Research Department of Cell and Developmental Biology, Division of Biosciences, University College London, London WC1E 6AP, United Kingdom
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10
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Noh H, Hua Z, Chrysinas P, Shoemaker JE, Gunawan R. DeltaNeTS+: elucidating the mechanism of drugs and diseases using gene expression and transcriptional regulatory networks. BMC Bioinformatics 2021; 22:108. [PMID: 33663384 PMCID: PMC7934467 DOI: 10.1186/s12859-021-04046-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 02/23/2021] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Knowledge on the molecular targets of diseases and drugs is crucial for elucidating disease pathogenesis and mechanism of action of drugs, and for driving drug discovery and treatment formulation. In this regard, high-throughput gene transcriptional profiling has become a leading technology, generating whole-genome data on the transcriptional alterations caused by diseases or drug compounds. However, identifying direct gene targets, especially in the background of indirect (downstream) effects, based on differential gene expressions is difficult due to the complexity of gene regulatory network governing the gene transcriptional processes. RESULTS In this work, we developed a network analysis method, called DeltaNeTS+, for inferring direct gene targets of drugs and diseases from gene transcriptional profiles. DeltaNeTS+ uses a gene regulatory network model to identify direct perturbations to the transcription of genes using gene expression data. Importantly, DeltaNeTS+ is able to combine both steady-state and time-course expression profiles, as well as leverage information on the gene network structure. We demonstrated the power of DeltaNeTS+ in predicting gene targets using gene expression data in complex organisms, including Caenorhabditis elegans and human cell lines (T-cell and Calu-3). More specifically, in an application to time-course gene expression profiles of influenza A H1N1 (swine flu) and H5N1 (avian flu) infection, DeltaNeTS+ shed light on the key differences of dynamic cellular perturbations caused by the two influenza strains. CONCLUSION DeltaNeTS+ is a powerful network analysis tool for inferring gene targets from gene expression profiles. As demonstrated in the case studies, by incorporating available information on gene network structure, DeltaNeTS+ produces accurate predictions of direct gene targets from a small sample size (~ 10 s). Integrating static and dynamic expression data with transcriptional network structure extracted from genomic information, as enabled by DeltaNeTS+, is crucial toward personalized medicine, where treatments can be tailored to individual patients. DeltaNeTS+ can be freely downloaded from http://www.github.com/cabsel/deltanetsplus .
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Affiliation(s)
- Heeju Noh
- Institute for Chemical and Bioengineering, ETH Zurich, 8093 Zurich, Switzerland
- Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
- Present Address: Columbia University Medical Center, New York, NY 10032 USA
| | - Ziyi Hua
- Institute for Chemical and Bioengineering, ETH Zurich, 8093 Zurich, Switzerland
| | - Panagiotis Chrysinas
- Department of Chemical and Biological Engineering, University at Buffalo – SUNY, Buffalo, NY 14260 USA
| | - Jason E. Shoemaker
- Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261 USA
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA 15261 USA
| | - Rudiyanto Gunawan
- Department of Chemical and Biological Engineering, University at Buffalo – SUNY, Buffalo, NY 14260 USA
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11
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Chevignon G, Foray V, Pérez-Jiménez MM, Libro S, Chung M, Foster JM, Landmann F. Dual RNAseq analyses at soma and germline levels reveal evolutionary innovations in the elephantiasis-agent Brugia malayi, and adaptation of its Wolbachia endosymbionts. PLoS Negl Trop Dis 2021; 15:e0008935. [PMID: 33406151 PMCID: PMC7787461 DOI: 10.1371/journal.pntd.0008935] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 10/31/2020] [Indexed: 12/23/2022] Open
Abstract
Brugia malayi is a human filarial nematode responsible for elephantiasis, a debilitating condition that is part of a broader spectrum of diseases called filariasis, including lymphatic filariasis and river blindness. Almost all filarial nematode species infecting humans live in mutualism with Wolbachia endosymbionts, present in somatic hypodermal tissues but also in the female germline which ensures their vertical transmission to the nematode progeny. These α-proteobacteria potentially provision their host with essential metabolites and protect the parasite against the vertebrate immune response. In the absence of Wolbachia wBm, B. malayi females become sterile, and the filarial nematode lifespan is greatly reduced. In order to better comprehend this symbiosis, we investigated the adaptation of wBm to the host nematode soma and germline, and we characterized these cellular environments to highlight their specificities. Dual RNAseq experiments were performed at the tissue-specific and ovarian developmental stage levels, reaching the resolution of the germline mitotic proliferation and meiotic differentiation stages. We found that most wBm genes, including putative effectors, are not differentially regulated between infected tissues. However, two wBm genes involved in stress responses are upregulated in the hypodermal chords compared to the germline, indicating that this somatic tissue represents a harsh environment to which wBm have adapted. A comparison of the B. malayi and C. elegans germline transcriptomes reveals a poor conservation of genes involved in the production of oocytes, with the filarial germline proliferative zone relying on a majority of genes absent from C. elegans. The first orthology map of the B. malayi genome presented here, together with tissue-specific expression enrichment analyses, indicate that the early steps of oogenesis are a developmental process involving genes specific to filarial nematodes, that likely result from evolutionary innovations supporting the filarial parasitic lifestyle.
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Affiliation(s)
- Germain Chevignon
- CRBM, University of Montpellier, CNRS, Montpellier, France
- Laboratoire de Génétique et Pathologie des Mollusques Marins, Ifremer, La Tremblade, France
| | - Vincent Foray
- CRBM, University of Montpellier, CNRS, Montpellier, France
- Institut de Recherche sur la Biologie de l’Insecte, UMR 7261, CNRS, Université de Tours, Tours, France
| | - Mercedes Maria Pérez-Jiménez
- CRBM, University of Montpellier, CNRS, Montpellier, France
- Centro Andaluz de Biología del Desarrollo (CABD)–Universidad Pablo de Olavide (UPO), Departamento de Biología Molecular e Ingeniería Bioquímica, UPO/CSIC/JA, Sevilla, Spain
| | - Silvia Libro
- Division of Protein Expression & Modification, New England Biolabs, Ipswich, Massachusetts, United States of America
| | - Matthew Chung
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Jeremy M. Foster
- Division of Protein Expression & Modification, New England Biolabs, Ipswich, Massachusetts, United States of America
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12
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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: 11] [Impact Index Per Article: 2.2] [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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13
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Lausser L, Schäfer LM, Kühlwein SD, Kestler AMR, Kestler HA. Detecting Ordinal Subcascades. Neural Process Lett 2020. [DOI: 10.1007/s11063-020-10362-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
AbstractOrdinal classifier cascades are constrained by a hypothesised order of the semantic class labels of a dataset. This order determines the overall structure of the decision regions in feature space. Assuming the correct order on these class labels will allow a high generalisation performance, while an incorrect one will lead to diminished results. In this way ordinal classifier systems can facilitate explorative data analysis allowing to screen for potential candidate orders of the class labels. Previously, we have shown that screening is possible for total orders of all class labels. However, as datasets might comprise samples of ordinal as well as non-ordinal classes, the assumption of a total ordering might be not appropriate. An analysis of subsets of classes is required to detect such hidden ordinal substructures. In this work, we devise a novel screening procedure for exhaustive evaluations of all order permutations of all subsets of classes by bounding the number of enumerations we have to examine. Experiments with multi-class data from diverse applications revealed ordinal substructures that generate new and support known relations.
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Pimentel-Acosta CA, Ramírez-Salcedo J, Morales-Serna FN, Fajer-Ávila EJ, Chávez-Sánchez C, Lara HH, García-Gasca A. Molecular Effects of Silver Nanoparticles on Monogenean Parasites: Lessons from Caenorhabditis elegans. Int J Mol Sci 2020; 21:ijms21165889. [PMID: 32824343 PMCID: PMC7460582 DOI: 10.3390/ijms21165889] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 08/12/2020] [Accepted: 08/14/2020] [Indexed: 12/15/2022] Open
Abstract
The mechanisms of action of silver nanoparticles (AgNPs) in monogenean parasites of the genus Cichlidogyrus were investigated through a microarray hybridization approach using genomic information from the nematode Caenorhabditis elegans. The effects of two concentrations of AgNPs were explored, low (6 µg/L Ag) and high (36 µg/L Ag). Microarray analysis revealed that both concentrations of AgNPs activated similar biological processes, although by different mechanisms. Expression profiles included genes involved in detoxification, neurotoxicity, modulation of cell signaling, reproduction, embryonic development, and tegument organization as the main biological processes dysregulated by AgNPs. Two important processes (DNA damage and cell death) were mostly activated in parasites exposed to the lower concentration of AgNPs. To our knowledge, this is the first study providing information on the sub-cellular and molecular effects of exposure to AgNPs in metazoan parasites of fish.
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Affiliation(s)
- Citlalic A. Pimentel-Acosta
- Centro de Investigación en Alimentación y Desarrollo, Unidad Mazatlán en Acuicultura y Manejo Ambiental, Mazatlán, Sinaloa 82112, Mexico; (C.A.P.-A.); (F.N.M.-S.); (E.J.F.-Á.); (C.C.-S.)
| | - Jorge Ramírez-Salcedo
- Unidad de Microarreglos, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Avenida Universidad 3000, Mexico City 04510, Mexico;
| | - Francisco Neptalí Morales-Serna
- Centro de Investigación en Alimentación y Desarrollo, Unidad Mazatlán en Acuicultura y Manejo Ambiental, Mazatlán, Sinaloa 82112, Mexico; (C.A.P.-A.); (F.N.M.-S.); (E.J.F.-Á.); (C.C.-S.)
- CONACYT, Centro de Investigación en Alimentación y Desarrollo, Unidad Mazatlán en Acuicultura y Manejo Ambiental, Mazatlán, Sinaloa 82112, Mexico
| | - Emma J. Fajer-Ávila
- Centro de Investigación en Alimentación y Desarrollo, Unidad Mazatlán en Acuicultura y Manejo Ambiental, Mazatlán, Sinaloa 82112, Mexico; (C.A.P.-A.); (F.N.M.-S.); (E.J.F.-Á.); (C.C.-S.)
| | - Cristina Chávez-Sánchez
- Centro de Investigación en Alimentación y Desarrollo, Unidad Mazatlán en Acuicultura y Manejo Ambiental, Mazatlán, Sinaloa 82112, Mexico; (C.A.P.-A.); (F.N.M.-S.); (E.J.F.-Á.); (C.C.-S.)
| | - Humberto H. Lara
- Department of Biology and South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, TX 78249, USA;
| | - Alejandra García-Gasca
- Centro de Investigación en Alimentación y Desarrollo, Unidad Mazatlán en Acuicultura y Manejo Ambiental, Mazatlán, Sinaloa 82112, Mexico; (C.A.P.-A.); (F.N.M.-S.); (E.J.F.-Á.); (C.C.-S.)
- Correspondence: ; Tel.: +52-66-9989-8700
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15
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Guan G, Fang M, Wong MK, Ho VWS, An X, Tang C, Huang X, Zhao Z. Multilevel regulation of muscle-specific transcription factor hlh-1 during Caenorhabditis elegans embryogenesis. Dev Genes Evol 2020; 230:265-278. [PMID: 32556563 PMCID: PMC7371654 DOI: 10.1007/s00427-020-00662-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Accepted: 05/31/2020] [Indexed: 11/29/2022]
Abstract
hlh-1 is a myogenic transcription factor required for body-wall muscle specification during embryogenesis in Caenorhabditis elegans. Despite its well-known role in muscle specification, comprehensive regulatory control upstream of hlh-1 remains poorly defined. Here, we first established a statistical reference for the spatiotemporal expression of hlh-1 at single-cell resolution up to the second last round of divisions for most of the cell lineages (from 4- to 350-cell stage) using 13 wild-type embryos. We next generated lineal expression of hlh-1 after RNA interference (RNAi) perturbation of 65 genes, which were selected based on their degree of conservation, mutant phenotypes, and known roles in development. We then compared the expression profiles between wild-type and RNAi embryos by clustering according to their lineal expression patterns using mean-shift and density-based clustering algorithms, which not only confirmed the roles of existing genes but also uncovered the potential functions of novel genes in muscle specification at multiple levels, including cellular, lineal, and embryonic levels. By combining the public data on protein-protein interactions, protein-DNA interactions, and genetic interactions with our RNAi data, we inferred regulatory pathways upstream of hlh-1 that function globally or locally. This work not only revealed diverse and multilevel regulatory mechanisms coordinating muscle differentiation during C. elegans embryogenesis but also laid a foundation for further characterizing the regulatory pathways controlling muscle specification at the cellular, lineal (local), or embryonic (global) level.
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Affiliation(s)
- Guoye Guan
- Center for Quantitative Biology, Peking University, Beijing, 100871, China
| | - Meichen Fang
- School of Life Sciences, Peking University, Beijing, 100871, China
| | - Ming-Kin Wong
- Department of Biology, Hong Kong Baptist University, Hong Kong, 999077, China
| | - Vincy Wing Sze Ho
- Department of Biology, Hong Kong Baptist University, Hong Kong, 999077, China
| | - Xiaomeng An
- Department of Biology, Hong Kong Baptist University, Hong Kong, 999077, China
| | - Chao Tang
- Center for Quantitative Biology, Peking University, Beijing, 100871, China
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China
- School of Physics, Peking University, Beijing, 100871, China
| | - Xiaotai Huang
- School of Computer Science and Technology, Xidian University, Xi'an, 710126, Shaanxi, China.
| | - Zhongying Zhao
- Department of Biology, Hong Kong Baptist University, Hong Kong, 999077, China.
- State Key Laboratory of Environmental and Biological Analysis, Hong Kong Baptist University, Hong Kong, 999077, China.
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16
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Caudal-dependent cell positioning directs morphogenesis of the C. elegans ventral epidermis. Dev Biol 2020; 461:31-42. [PMID: 31923384 PMCID: PMC7181193 DOI: 10.1016/j.ydbio.2020.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 12/20/2019] [Accepted: 01/02/2020] [Indexed: 01/21/2023]
Abstract
Strikingly, epithelial morphogenesis remains incomplete at the end of C. elegans embryonic development; newly hatched larvae undergo extensive remodelling of their ventral epidermis during the first larval stage (L1), when newly-born epidermal cells move ventrally to complete the epidermal syncytium. Prior to this remodelling, undivided lateral seam cells produce anterior adherens junction processes that are inherited by the anterior daughter cells following an asymmetric division during L1. These adherens junction processes provide the ventral migratory route for these anterior daughters. Here, we show that these processes are perturbed in pal-1/caudal mutant animals, resulting in their inheritance by posterior, seam-fated daughters. This causes aberrant migration of seam daughter cells, disrupting the ventral epidermis. Using 4D-lineaging, we demonstrate that this larval epidermal morphogenesis defect in pal-1 mutants can be traced directly back to an initial cell positioning defect in the embryo. pal-1 expression, driven by a single intronic enhancer, is required to correctly position the seam cells in embryos such that the appropriate cell junctions support the correct migratory paths of seam daughters later in development, irrespective of their fate. Thus, during ventral epithelial remodelling in C. elegans, we show that the position of migrating cells, specified by pal-1/caudal, appears to be more important than their fate in driving morphogenesis. caudal/pal-1 is required to form the correct cell junctions during embryogenesis. Correctly placed cell junctions direct larval ventral epithelial cell migration. larval epithelial cell migration occurs independently of cell fate. Embryonic epidermal expression of pal-1 is dependent on a single intronic enhancer.
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Abstract
Biological entities are key elements of biomedical research. Their definition and their relationships are important in areas such as phylogenetic reconstruction, developmental processes or tumor evolution. Hypotheses about relationships like phenotype order are often postulated based on prior knowledge or belief. Evidence on a molecular level is typically unknown and whether total orders are reflected in the molecular measurements is unclear or not assessed. In this work we propose a method that allows a fast and exhaustive screening for total orders in large datasets. We utilise ordinal classifier cascades to identify discriminable molecular representations of the phenotypes. These classifiers are constrained by an order hypothesis and are highly sensitive to incorrect assumptions. Two new error bounds, which are introduced and theoretically proven, lead to a substantial speed-up and allow the application to large collections of many phenotypes. In our experiments we show that by exhaustively evaluating all possible candidate orders, we are able to identify phenotype orders that best coincide with the high-dimensional molecular profiles.
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18
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Tarkhov AE, Alla R, Ayyadevara S, Pyatnitskiy M, Menshikov LI, Shmookler Reis RJ, Fedichev PO. A universal transcriptomic signature of age reveals the temporal scaling of Caenorhabditis elegans aging trajectories. Sci Rep 2019; 9:7368. [PMID: 31089188 PMCID: PMC6517414 DOI: 10.1038/s41598-019-43075-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 04/15/2019] [Indexed: 12/13/2022] Open
Abstract
We collected 60 age-dependent transcriptomes for C. elegans strains including four exceptionally long-lived mutants (mean adult lifespan extended 2.2- to 9.4-fold) and three examples of lifespan-increasing RNAi treatments. Principal Component Analysis (PCA) reveals aging as a transcriptomic drift along a single direction, consistent across the vastly diverse biological conditions and coinciding with the first principal component, a hallmark of the criticality of the underlying gene regulatory network. We therefore expected that the organism's aging state could be characterized by a single number closely related to vitality deficit or biological age. The "aging trajectory", i.e. the dependence of the biological age on chronological age, is then a universal stochastic function modulated by the network stiffness; a macroscopic parameter reflecting the network topology and associated with the rate of aging. To corroborate this view, we used publicly available datasets to define a transcriptomic biomarker of age and observed that the rescaling of age by lifespan simultaneously brings together aging trajectories of transcription and survival curves. In accordance with the theoretical prediction, the limiting mortality value at the plateau agrees closely with the mortality rate doubling exponent estimated at the cross-over age near the average lifespan. Finally, we used the transcriptomic signature of age to identify possible life-extending drug compounds and successfully tested a handful of the top-ranking molecules in C. elegans survival assays and achieved up to a +30% extension of mean lifespan.
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Affiliation(s)
- Andrei E Tarkhov
- Gero LLC, Nizhny Susalny per. 5/4, Moscow, 105064, Russia.
- Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, Bolshoy Boulevard 30, bld. 1, Moscow, 121205, Russia.
| | - Ramani Alla
- Central Arkansas Veterans Healthcare System, Research Service, Little Rock, Arkansas, USA
- Department of Geriatrics, Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Srinivas Ayyadevara
- Central Arkansas Veterans Healthcare System, Research Service, Little Rock, Arkansas, USA
- Department of Geriatrics, Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Mikhail Pyatnitskiy
- Gero LLC, Nizhny Susalny per. 5/4, Moscow, 105064, Russia
- Institute of Biomedical Chemistry, 119121, Moscow, Russia
| | - Leonid I Menshikov
- Gero LLC, Nizhny Susalny per. 5/4, Moscow, 105064, Russia
- National Research Center "Kurchatov Institute", 1, Akademika Kurchatova pl., Moscow, 123182, Russia
| | - Robert J Shmookler Reis
- Central Arkansas Veterans Healthcare System, Research Service, Little Rock, Arkansas, USA
- Department of Geriatrics, Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
- Bioinformatics Program, University of Arkansas for Medical Sciences, and University of Arkansas at Little Rock, Little Rock, Arkansas, USA
| | - Peter O Fedichev
- Gero LLC, Nizhny Susalny per. 5/4, Moscow, 105064, Russia.
- Moscow Institute of Physics and Technology, 141700, Institutskii per. 9, Dolgoprudny, Moscow Region, Russia.
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19
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Murray JI. Systems biology of embryonic development: Prospects for a complete understanding of the Caenorhabditis elegans embryo. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2018; 7:e314. [PMID: 29369536 DOI: 10.1002/wdev.314] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 12/01/2017] [Accepted: 12/12/2017] [Indexed: 01/07/2023]
Abstract
The convergence of developmental biology and modern genomics tools brings the potential for a comprehensive understanding of developmental systems. This is especially true for the Caenorhabditis elegans embryo because its small size, invariant developmental lineage, and powerful genetic and genomic tools provide the prospect of a cellular resolution understanding of messenger RNA (mRNA) expression and regulation across the organism. We describe here how a systems biology framework might allow large-scale determination of the embryonic regulatory relationships encoded in the C. elegans genome. This framework consists of two broad steps: (a) defining the "parts list"-all genes expressed in all cells at each time during development and (b) iterative steps of computational modeling and refinement of these models by experimental perturbation. Substantial progress has been made towards defining the parts list through imaging methods such as large-scale green fluorescent protein (GFP) reporter analysis. Imaging results are now being augmented by high-resolution transcriptome methods such as single-cell RNA sequencing, and it is likely the complete expression patterns of all genes across the embryo will be known within the next few years. In contrast, the modeling and perturbation experiments performed so far have focused largely on individual cell types or genes, and improved methods will be needed to expand them to the full genome and organism. This emerging comprehensive map of embryonic expression and regulatory function will provide a powerful resource for developmental biologists, and would also allow scientists to ask questions not accessible without a comprehensive picture. This article is categorized under: Invertebrate Organogenesis > Worms Technologies > Analysis of the Transcriptome Gene Expression and Transcriptional Hierarchies > Gene Networks and Genomics.
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Affiliation(s)
- John Isaac Murray
- Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
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20
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Cell Fate Maintenance and Reprogramming During the Oocyte-to-Embryo Transition. Results Probl Cell Differ 2017; 59:269-286. [PMID: 28247053 DOI: 10.1007/978-3-319-44820-6_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
This chapter reviews our current understanding of the mechanisms that regulate reprogramming during the oocyte-to-embryo transition (OET). There are two major events reshaping the transcriptome during OET. One is the clearance of maternal transcripts in the early embryo, extensively reviewed by others. The other event, which is the focus of this chapter, is the embryonic (or zygotic) genome activation (EGA). The mechanisms controlling EGA can be broadly divided into transcriptional and posttranscriptional. The former includes the regulation of the basal transcription machinery, the regulation by specific transcription factors and chromatin modifications. The latter is performed mostly via specific RNA-binding proteins (RBPs). Different animal models have been used to decipher the regulation of EGA. These models are often biased for the specific type of regulation, which is why we discuss the models ranging from invertebrates to mammals. Whether these biases stem from incomplete understanding of EGA in these models, or reflect evolutionarily distinct solutions to EGA regulation, is a key unresolved problem in developmental biology. As the mechanisms controlling developmental reprogramming can, and in some cases have been shown to, function in differentiated cells subjected to induced reprogramming, our understanding of EGA regulation may have implications for the efficiency of induced reprogramming and, thus, for regenerative medicine.
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21
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Tintori SC, Osborne Nishimura E, Golden P, Lieb JD, Goldstein B. A Transcriptional Lineage of the Early C. elegans Embryo. Dev Cell 2016; 38:430-44. [PMID: 27554860 PMCID: PMC4999266 DOI: 10.1016/j.devcel.2016.07.025] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 05/19/2016] [Accepted: 07/27/2016] [Indexed: 12/30/2022]
Abstract
During embryonic development, cells must establish fates, morphologies, and behaviors in coordination with one another to form a functional body. A prevalent hypothesis for how this coordination is achieved is that each cell's fate and behavior is determined by a defined mixture of RNAs. Only recently has it become possible to measure the full suite of transcripts in a single cell. Here we quantify genome-wide mRNA abundance in each cell of the Caenorhabditis elegans embryo up to the 16-cell stage. We describe spatially dynamic expression, quantify cell-specific differential activation of the zygotic genome, and identify genes that were previously unappreciated as being critical for development. We present an interactive data visualization tool that allows broad access to our dataset. This genome-wide single-cell map of mRNA abundance, alongside the well-studied life history and fate of each cell, describes at a cellular resolution the mRNA landscape that guides development.
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Affiliation(s)
- Sophia C Tintori
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Erin Osborne Nishimura
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Patrick Golden
- School of Information and Library Science, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jason D Lieb
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Bob Goldstein
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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22
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Wiesenfahrt T, Osborne Nishimura E, Berg JY, McGhee JD. Probing and rearranging the transcription factor network controlling the C. elegans endoderm. WORM 2016; 5:e1198869. [PMID: 27695655 DOI: 10.1080/21624054.2016.1198869] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 06/02/2016] [Indexed: 10/21/2022]
Abstract
The ELT-2 GATA factor is the predominant transcription factor regulating gene expression in the C. elegans intestine, following endoderm specification. We comment on our previous study (Wiesenfahrt et al., 2016) that investigated how the elt-2 gene is controlled by END-1, END-3 and ELT-7, the 3 endoderm specific GATA factors that lie upstream in the regulatory hierarchy. We also discuss the unexpected result that ELT-2, if expressed sufficiently early and at sufficiently high levels, can specify the C. elegans endoderm, replacing the normal functions of END-1 and END-3.
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Affiliation(s)
- Tobias Wiesenfahrt
- Department of Biochemistry and Molecular Biology, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary , Calgary, AB, Canada
| | - Erin Osborne Nishimura
- Department of Biochemistry and Molecular Biology, Colorado State University , Fort Collins, CO, USA
| | - Janette Y Berg
- Department of Biochemistry and Molecular Biology, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary , Calgary, AB, Canada
| | - James D McGhee
- Department of Biochemistry and Molecular Biology, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary , Calgary, AB, Canada
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23
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Zacharias AL, Murray JI. Combinatorial decoding of the invariant C. elegans embryonic lineage in space and time. Genesis 2016; 54:182-97. [PMID: 26915329 PMCID: PMC4840027 DOI: 10.1002/dvg.22928] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 02/18/2016] [Accepted: 02/22/2016] [Indexed: 12/19/2022]
Abstract
Understanding how a single cell, the zygote, can divide and differentiate to produce the diverse animal cell types is a central goal of developmental biology research. The model organism Caenorhabditis elegans provides a system that enables a truly comprehensive understanding of this process across all cells. Its invariant cell lineage makes it possible to identify all of the cells in each individual and compare them across organisms. Recently developed methods automate the process of cell identification, allowing high-throughput gene expression characterization and phenotyping at single cell resolution. In this Review, we summarize the sequences of events that pattern the lineage including establishment of founder cell identity, the signaling pathways that diversify embryonic fate, and the regulators involved in patterning within these founder lineages before cells adopt their terminal fates. We focus on insights that have emerged from automated approaches to lineage tracking, including insights into mechanisms of robustness, context-specific regulation of gene expression, and temporal coordination of differentiation. We suggest a model by which lineage history produces a combinatorial code of transcription factors that act, often redundantly, to ensure terminal fate.
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Affiliation(s)
- Amanda L. Zacharias
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104 USA
| | - John Isaac Murray
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104 USA
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24
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Zacharias AL, Walton T, Preston E, Murray JI. Quantitative Differences in Nuclear β-catenin and TCF Pattern Embryonic Cells in C. elegans. PLoS Genet 2015; 11:e1005585. [PMID: 26488501 PMCID: PMC4619327 DOI: 10.1371/journal.pgen.1005585] [Citation(s) in RCA: 30] [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: 02/23/2015] [Accepted: 09/16/2015] [Indexed: 12/22/2022] Open
Abstract
The Wnt signaling pathway plays a conserved role during animal development in transcriptional regulation of distinct targets in different developmental contexts but it remains unclear whether quantitative differences in the nuclear localization of effector proteins TCF and β-catenin contribute to context-specific regulation. We investigated this question in Caenorhabditis elegans embryos by quantifying nuclear localization of fluorescently tagged SYS-1/β-catenin and POP-1/TCF and expression of Wnt ligands at cellular resolution by time-lapse microscopy and automated lineage tracing. We identified reproducible, quantitative differences that generate a subset of Wnt-signaled cells with a significantly higher nuclear concentration of the TCF/β-catenin activating complex. Specifically, β-catenin and TCF are preferentially enriched in nuclei of daughter cells whose parents also had high nuclear levels of that protein, a pattern that could influence developmental gene expression. Consistent with this, we found that expression of synthetic reporters of POP-1-dependent activation is biased towards cells that had high nuclear SYS-1 in consecutive divisions. We identified new genes whose embryonic expression patterns depend on pop-1. Most of these require POP-1 for either transcriptional activation or repression, and targets requiring POP-1 for activation are more likely to be expressed in the cells with high nuclear SYS-1 in consecutive divisions than those requiring POP-1 for repression. Taken together, these results indicate that SYS-1 and POP-1 levels are influenced by the parent cell’s SYS-1/POP-1 levels and this may provide an additional mechanism by which POP-1 regulates distinct targets in different developmental contexts. The Wnt signaling pathway is active during the development of all multi-cellular animals and also improperly re-activated in many cancers. Here, we use time-lapse microscopy to quantify the nuclear localization of several proteins in response to Wnt signaling throughout early embryonic development in the nematode worm, C. elegans. We find that cells that received a Wnt signal in the previous division respond more strongly to a Wnt signal in the next division, in part by localizing more of the regulator β-catenin to the nucleus. This causes the relative enrichment of Wnt pathway proteins in the nuclei of repeatedly signaled cells, which we show likely impacts the activation of Wnt target genes. This represents a novel mechanism for the regulation of Wnt pathway targets in development and disease.
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Affiliation(s)
- Amanda L. Zacharias
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Travis Walton
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Elicia Preston
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - John Isaac Murray
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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25
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Jamil M, Wang W, Xu M, Tu J. Exploring the roles of basal transcription factor 3 in eukaryotic growth and development. Biotechnol Genet Eng Rev 2015; 31:21-45. [PMID: 26428578 DOI: 10.1080/02648725.2015.1080064] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Basal transcription factor 3 (BTF3) has been reported to play a significant part in the transcriptional regulation linking with eukaryotes growth and development. Alteration in the BTF3 gene expression patterns or variation in their activities adds to the explanation of different signaling pathways and regulatory networks. Moreover, BTF3s often respond to numerous stresses, and subsequently they are involved in regulation of various mechanisms. BTF3 proteins also function through protein-protein contact, which can assist us to identify the multifaceted processes of signaling and transcriptional regulation controlled by BTF3 proteins. In this review, we discuss current advances made in starting to explore the roles of BTF3 transcription factors in eukaryotes especially in plant growth and development.
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Affiliation(s)
- Muhammad Jamil
- a College of Agriculture and Biotechnology, Institute of Crop Science , Zhejiang University , Yu-Hang-Tang Rd. 866, Hangzhou 310058 , China.,b Department of Biotechnology and Genetic Engineering , Kohat University of Science and Technology , Kohat 26000 , Pakistan
| | - Wenyi Wang
- a College of Agriculture and Biotechnology, Institute of Crop Science , Zhejiang University , Yu-Hang-Tang Rd. 866, Hangzhou 310058 , China
| | - Mengyun Xu
- a College of Agriculture and Biotechnology, Institute of Crop Science , Zhejiang University , Yu-Hang-Tang Rd. 866, Hangzhou 310058 , China
| | - Jumin Tu
- a College of Agriculture and Biotechnology, Institute of Crop Science , Zhejiang University , Yu-Hang-Tang Rd. 866, Hangzhou 310058 , China
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26
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Robert VJ, Garvis S, Palladino F. Repression of somatic cell fate in the germline. Cell Mol Life Sci 2015; 72:3599-620. [PMID: 26043973 PMCID: PMC11113910 DOI: 10.1007/s00018-015-1942-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 05/26/2015] [Accepted: 05/27/2015] [Indexed: 01/13/2023]
Abstract
Germ cells must transmit genetic information across generations, and produce gametes while also maintaining the potential to form all cell types after fertilization. Preventing the activation of somatic programs is, therefore, crucial to the maintenance of germ cell identity. Studies in Caenorhabditis elegans, Drosophila melanogaster, and mouse have revealed both similarities and differences in how somatic gene expression is repressed in germ cells, thereby preventing their conversion into somatic tissues. This review will focus on recent developments in our understanding of how global or gene-specific transcriptional repression, chromatin regulation, and translational repression operate in the germline to maintain germ cell identity and repress somatic differentiation programs.
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Affiliation(s)
- Valérie J Robert
- Ecole Normale Supérieure de Lyon, Université de Lyon, 46 allée d'Italie, 69007, Lyon, France
| | - Steve Garvis
- Ecole Normale Supérieure de Lyon, Université de Lyon, 46 allée d'Italie, 69007, Lyon, France
| | - Francesca Palladino
- Ecole Normale Supérieure de Lyon, Université de Lyon, 46 allée d'Italie, 69007, Lyon, France.
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27
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Du Z, He F, Yu Z, Bowerman B, Bao Z. E3 ubiquitin ligases promote progression of differentiation during C. elegans embryogenesis. Dev Biol 2014; 398:267-79. [PMID: 25523393 DOI: 10.1016/j.ydbio.2014.12.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 12/02/2014] [Accepted: 12/04/2014] [Indexed: 01/22/2023]
Abstract
Regulated choice between cell fate maintenance and differentiation provides decision points in development to progress toward more restricted cell fates or to maintain the current one. Caenorhabditis elegans embryogenesis follows an invariant cell lineage where cell fate is generally more restricted upon each cell division. EMS is a progenitor cell in the four-cell embryo that gives rise to the endomesoderm. We recently found that when ubiquitin-mediated protein degradation is compromised, the anterior daughter of EMS, namely MS, reiterates the EMS fate. This observation demonstrates an essential function of ubiquitin-mediated protein degradation in driving the progression of EMS-to-MS differentiation. Here we report a genome-wide screen of the ubiquitin pathway and extensive lineage analyses. The results suggest a broad role of E3 ligases in driving differentiation progression. First, we identified three substrate-binding proteins for two Cullin-RING ubiquitin ligase (CRL) E3 complexes that promote the progression from the EMS fate to MS, namely LIN-23/β-TrCP and FBXB-3 for the CRL1/SCF complex and ZYG-11/ZYG-11B for the CRL2 complex. Genetic analyses suggest these E3 ligases function through a multifunctional protein OMA-1 and the endomesoderm lineage specifier SKN-1 to drive differentiation. Second, we found that depletion of components of the CRL1/SCF complex induces fate reiteration in all major founder cell lineages. These data suggest that regulated choice between self-renewal and differentiation is widespread during C. elegans embryogenesis as in organisms with regulative development, and ubiquitin-mediated protein degradation drives the choice towards differentiation. Finally, bioinformatic analysis of time series gene expression data showed that expression of E3 genes is transiently enriched during time windows of developmental stage transitions. Transcription factors show similar enrichment, but not other classes of regulatory genes. Based on these findings we propose that ubiquitin-mediated protein degradation, like many transcription factors, function broadly as regulators driving developmental progression during embryogenesis in C. elegans.
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Affiliation(s)
- Zhuo Du
- Developmental Biology Program, Sloan Kettering Institute, 1275 York Ave. New York, NY 10065, United States
| | - Fei He
- Developmental Biology Program, Sloan Kettering Institute, 1275 York Ave. New York, NY 10065, United States
| | - Zidong Yu
- Developmental Biology Program, Sloan Kettering Institute, 1275 York Ave. New York, NY 10065, United States; School of Energy and Power Engineering, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu 212003, China
| | - Bruce Bowerman
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, United States
| | - Zhirong Bao
- Developmental Biology Program, Sloan Kettering Institute, 1275 York Ave. New York, NY 10065, United States.
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28
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Statistical stage transition detection method for small sample gene expression time series data. Math Biosci 2014; 254:58-63. [PMID: 24960588 DOI: 10.1016/j.mbs.2014.06.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 06/03/2014] [Accepted: 06/04/2014] [Indexed: 11/20/2022]
Abstract
In terms of their internal (genetic) and external (phenotypic) states, living cells are always changing at varying rates. Periods of stable or low rate of change are often called States, Stages, or Phases, whereas high-rate periods are called Transitions or Transients. While states and transitions are observed phenotypically, such as cell differentiation, cancer progression, for example, are related with gene expression levels. On the other hand, stages of gene expression are definable based on changes of expression levels. Analyzing relations between state changes of phenotypes and stage transitions of gene expression levels is a general approach to elucidate mechanisms of life phenomena. Herein, we propose an algorithm to detect stage transitions in a time series of expression levels of a gene by defining statistically optimal division points. The algorithm shows detecting ability for simulated datasets. An annotation based analysis on detecting results for a dataset of initial development of Caenorhabditis elegans agrees with that are presented in the literature.
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29
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Lezzerini M, Budovskaya Y. A dual role of the Wnt signaling pathway during aging in Caenorhabditis elegans. Aging Cell 2014; 13:8-18. [PMID: 23879250 PMCID: PMC4326866 DOI: 10.1111/acel.12141] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/16/2013] [Indexed: 11/30/2022] Open
Abstract
Wnt signaling is a major and highly conserved developmental pathway that guides many important events during embryonic and larval development. In adulthood, misregulation of Wnt signaling has been implicated in tumorigenesis and various age-related diseases. These effects occur through highly complicated cell-to-cell interactions mediated by multiple Wnt-secreted proteins. While they share a high degree of sequence similarity, their function is highly diversified. Although the role of Wnt ligands during development is well studied, very little is known about the possible actions of Wnt signaling in natural aging. In this study, Caenorhabditis elegans serves, for the first time, as a model system to determine the role of Wnt ligands in aging. Caenorhabditis elegans has five Wnt proteins, mom-2, egl-20, lin-44, cwn-1, and cwn-2. We show that all five Wnt ligands are expressed and active past the development stages. The ligand mom-2/Wnt plays a major detrimental role in longevity, whereas the function of lin-44/Wnt is beneficial for long life. Interestingly, no evidence was found for Wnt signaling being involved in cellular or oxidative stress responses during aging. Our results suggest that Wnt signaling regulates aging-intrinsic genetic pathways, opening a new research direction on the role of Wnt signaling in aging and age-related diseases.
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Affiliation(s)
- Marco Lezzerini
- Swammerdam Institute for Life Sciences; University of Amsterdam; Amsterdam The Netherlands
| | - Yelena Budovskaya
- Swammerdam Institute for Life Sciences; University of Amsterdam; Amsterdam The Netherlands
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30
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Shao J, He K, Wang H, Ho WS, Ren X, An X, Wong MK, Yan B, Xie D, Stamatoyannopoulos J, Zhao Z. Collaborative regulation of development but independent control of metabolism by two epidermis-specific transcription factors in Caenorhabditis elegans. J Biol Chem 2013; 288:33411-26. [PMID: 24097988 DOI: 10.1074/jbc.m113.487975] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cell fate specification is typically initiated by a master regulator, which is relayed by tissue-specific regulatory proteins (usually transcription factors) for further enforcement of cell identities, but how the factors are coordinated among each other to "finish up" the specification remains poorly understood. Caenorhabditis elegans epidermis specification is initiated by a master regulator, ELT-1, that activates its targets, NHR-25 and ELT-3, two epidermis-specific transcription factors that are important for development but not for initial specification of epidermis, thus providing a unique paradigm for illustrating how the tissue-specific regulatory proteins work together to enforce cell fate specification. Here we addressed the question through contrasting genome-wide in vivo binding targets between NHR-25 and ELT-3. We demonstrate that the two factors bind discrete but conserved DNA motifs, most of which remain in proximity, suggesting formation of a complex between the two. In agreement with this, gene ontology analysis of putative target genes suggested differential regulation of metabolism but coordinated control of epidermal development between the two factors, which is supported by quantitative analysis of expression of their specific or common targets in the presence or absence of either protein. Functional validation of a subset of the target genes showed both activating and inhibitory roles of NHR-25 and ELT-3 in regulating their targets. We further demonstrated differential control of specification of AB and C lineage-derived epidermis. The results allow us to assemble a comprehensive gene network underlying C. elegans epidermis development that is likely to be widely used across species and provides insights into how tissue-specific transcription factors coordinate with one another to enforce cell fate specification initiated by its master regulator.
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Affiliation(s)
- Jiaofang Shao
- From the Department of Biology, Hong Kong Baptist University, Hong Kong, China and
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31
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Lin X, Chen XW. Heterogeneous data integration by tree-augmented naïve Bayes for protein-protein interactions prediction. Proteomics 2012; 13:261-8. [DOI: 10.1002/pmic.201200326] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 09/23/2012] [Accepted: 10/11/2012] [Indexed: 11/08/2022]
Affiliation(s)
- Xiaotong Lin
- Department of Electrical Engineering and Computer Science; The University of Kansas; Lawrence; KS; USA
| | - Xue-wen Chen
- Department of Computer Science; Wayne State University; Detroit; MI; USA
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32
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McGhee JD. TheCaenorhabditis elegansintestine. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 2:347-67. [DOI: 10.1002/wdev.93] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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33
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Schulz MH, Devanny WE, Gitter A, Zhong S, Ernst J, Bar-Joseph Z. DREM 2.0: Improved reconstruction of dynamic regulatory networks from time-series expression data. BMC SYSTEMS BIOLOGY 2012; 6:104. [PMID: 22897824 PMCID: PMC3464930 DOI: 10.1186/1752-0509-6-104] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 07/18/2012] [Indexed: 12/28/2022]
Abstract
Background Modeling dynamic regulatory networks is a major challenge since much of the protein-DNA interaction data available is static. The Dynamic Regulatory Events Miner (DREM) uses a Hidden Markov Model-based approach to integrate this static interaction data with time series gene expression leading to models that can determine when transcription factors (TFs) activate genes and what genes they regulate. DREM has been used successfully in diverse areas of biological research. However, several issues were not addressed by the original version. Results DREM 2.0 is a comprehensive software for reconstructing dynamic regulatory networks that supports interactive graphical or batch mode. With version 2.0 a set of new features that are unique in comparison with other softwares are introduced. First, we provide static interaction data for additional species. Second, DREM 2.0 now accepts continuous binding values and we added a new method to utilize TF expression levels when searching for dynamic models. Third, we added support for discriminative motif discovery, which is particularly powerful for species with limited experimental interaction data. Finally, we improved the visualization to support the new features. Combined, these changes improve the ability of DREM 2.0 to accurately recover dynamic regulatory networks and make it much easier to use it for analyzing such networks in several species with varying degrees of interaction information. Conclusions DREM 2.0 provides a unique framework for constructing and visualizing dynamic regulatory networks. DREM 2.0 can be downloaded from: www.sb.cs.cmu.edu/drem.
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Affiliation(s)
- Marcel H Schulz
- Ray and Stephanie Lane Center for Computational Biology, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA.
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34
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McEwan DL, Weisman AS, Hunter CP. Uptake of extracellular double-stranded RNA by SID-2. Mol Cell 2012; 47:746-54. [PMID: 22902558 DOI: 10.1016/j.molcel.2012.07.014] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 05/10/2012] [Accepted: 07/10/2012] [Indexed: 01/25/2023]
Abstract
Ingested dsRNAs trigger RNA interference (RNAi) in many invertebrates, including the nematode Caenorhabditis elegans. Here we show that the C. elegans apical intestinal membrane protein SID-2 is required in C. elegans for the import of ingested dsRNA and that, when expressed in Drosophila S2 cells, SID-2 enables the uptake of dsRNAs. SID-2-dependent dsRNA transport requires an acidic extracellular environment and is selective for dsRNAs with at least 50 base pairs. Through structure-function analysis, we identify several SID-2 regions required for this activity, including three extracellular, positively charged histidines. Finally, we find that SID-2-dependent transport is inhibited by drugs that interfere with vesicle transport. Therefore, we propose that environmental dsRNAs are imported from the acidic intestinal lumen by SID-2 via endocytosis and are released from internalized vesicles in a secondary step mediated by the dsRNA channel SID-1. Similar multistep mechanisms may underlie the widespread observations of environmental RNAi.
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Affiliation(s)
- Deborah L McEwan
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
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35
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Aburatani S. Network inference of pal-1 lineage-specific regulation in the C. elegans embryo by structural equation modeling. Bioinformation 2012; 8:652-7. [PMID: 23055605 PMCID: PMC3449367 DOI: 10.6026/97320630008652] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 07/07/2012] [Indexed: 01/06/2023] Open
Abstract
The elucidation of spatial and temporal control during developmental stages is one of the central tasks for systems biology, and a variety of intracellular factors are known as regulators for specific gene expression. The activity information of those various factors is not directly reflected in their gene expression profiles. Hence, a method based on Structural Equation Modeling (SEM) is described. SEM can include the latent variables within the constructed model and infer the relationships among latent and observed variables, as a network model. An improved SEM approach for the construction of an optimal model is applied to infer the regulatory network for the determination of C lineage fate in C. elegans development. The inferred network model shows that the 13 analysed transcription factor genes were regulated by several other factors in addition to pal-1 expression. The other regulatory factors are those involved in protein accumulation and localization as important regulatory factors for normal development. Those regulatory factors were regulated sequentially in the network model. The regulation of the known pal-1 regulated genes was dependent on this sequential control of the regulatory factors. The interpretation of the network model shows insights to the complex regulation occurring during the C lineage determination by pal-1.
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Affiliation(s)
- Sachiyo Aburatani
- Computational Biology Research Center, National Institute of Advanced Industrial Science and Technology, 2-4-7 Aomi, Koto-ku, Tokyo, Japan
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36
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Stigler B, Chamberlin HM. A regulatory network modeled from wild-type gene expression data guides functional predictions in Caenorhabditis elegans development. BMC SYSTEMS BIOLOGY 2012; 6:77. [PMID: 22734688 PMCID: PMC3463499 DOI: 10.1186/1752-0509-6-77] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 06/04/2012] [Indexed: 12/18/2022]
Abstract
BACKGROUND Complex gene regulatory networks underlie many cellular and developmental processes. While a variety of experimental approaches can be used to discover how genes interact, few biological systems have been systematically evaluated to the extent required for an experimental definition of the underlying network. Therefore, the development of computational methods that can use limited experimental data to define and model a gene regulatory network would provide a useful tool to evaluate many important but incompletely understood biological processes. Such methods can assist in extracting all relevant information from data that are available, identify unexpected regulatory relationships and prioritize future experiments. RESULTS To facilitate the analysis of gene regulatory networks, we have developed a computational modeling pipeline method that complements traditional evaluation of experimental data. For a proof-of-concept example, we have focused on the gene regulatory network in the nematode C. elegans that mediates the developmental choice between mesodermal (muscle) and ectodermal (skin) cell fates in the embryonic C lineage. We have used gene expression data to build two models: a knowledge-driven model based on gene expression changes following gene perturbation experiments, and a data-driven mathematical model derived from time-course gene expression data recovered from wild-type animals. We show that both models can identify a rich set of network gene interactions. Importantly, the mathematical model built only from wild-type data can predict interactions demonstrated by the perturbation experiments better than chance, and better than an existing knowledge-driven model built from the same data set. The mathematical model also provides new biological insight, including a dissection of zygotic from maternal functions of a key transcriptional regulator, PAL-1, and identification of non-redundant activities of the T-box genes tbx-8 and tbx-9. CONCLUSIONS This work provides a strong example for a mathematical modeling approach that solely uses wild-type data to predict an underlying gene regulatory network. The modeling approach complements traditional methods of data analysis, suggesting non-intuitive network relationships and guiding future experiments.
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Affiliation(s)
- Brandilyn Stigler
- Department of Mathematics, Southern Methodist University, Dallas, TX 75275, USA.
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37
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Kuntz SG, Williams BA, Sternberg PW, Wold BJ. Transcription factor redundancy and tissue-specific regulation: evidence from functional and physical network connectivity. Genome Res 2012; 22:1907-19. [PMID: 22730465 PMCID: PMC3460186 DOI: 10.1101/gr.133306.111] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Two major transcriptional regulators of Caenorhabditis elegans bodywall muscle (BWM) differentiation, hlh-1 and unc-120, are expressed in muscle where they are known to bind and regulate several well-studied muscle-specific genes. Simultaneously mutating both factors profoundly inhibits formation of contractile BWM. These observations were consistent with a simple network model in which the muscle regulatory factors drive tissue-specific transcription by binding selectively near muscle-specific targets to activate them. We tested this model by measuring the number, identity, and tissue-specificity of functional regulatory targets for each factor. Some joint regulatory targets (218) are BWM-specific and enriched for nearby HLH-1 binding. However, contrary to the simple model, the majority of genes regulated by one or both muscle factors are also expressed significantly in non-BWM tissues. We also mapped global factor occupancy by HLH-1, and created a genetic interaction map that identifies hlh-1 collaborating transcription factors. HLH-1 binding did not predict proximate regulatory action overall, despite enrichment for binding among BWM-specific positive regulatory targets of hlh-1. We conclude that these tissue-specific factors contribute much more broadly to the transcriptional output of muscle tissue than previously thought, offering a partial explanation for widespread HLH-1 occupancy. We also identify a novel regulatory connection between the BWM-specific hlh-1 network and the hlh-8/twist nonstriated muscle network. Finally, our results suggest a molecular basis for synthetic lethality in which hlh-1 and unc-120 mutant phenotypes are mutually buffered by joint additive regulation of essential target genes, with additional buffering suggested via newly identified hlh-1 interacting factors.
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Affiliation(s)
- Steven G Kuntz
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA
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38
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Chisholm AD, Hsiao TI. The Caenorhabditis elegans epidermis as a model skin. I: development, patterning, and growth. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 1:861-78. [PMID: 23539299 DOI: 10.1002/wdev.79] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The skin of the nematode Caenorhabditis elegans is composed of a simple epidermal epithelium and overlying cuticle. The skin encloses the animal and plays central roles in body morphology and physiology; its simplicity and accessibility make it a tractable genetic model for several aspects of skin biology. Epidermal precursors are specified by a hierarchy of transcriptional regulators. Epidermal cells form on the dorsal surface of the embryo and differentiate to form the epidermal primordium, which then spreads out in a process of epiboly to enclose internal tissues. Subsequent elongation of the embryo into a vermiform larva is driven by cell shape changes and cell fusions in the epidermis. Most epidermal cells fuse in mid-embryogenesis to form a small number of multinucleate syncytia. During mid-embryogenesis the epidermis also becomes intimately associated with underlying muscles, performing a tendon-like role in transmitting muscle force. Post-embryonic development of the epidermis involves growth by addition of new cells to the syncytia from stem cell-like epidermal seam cells and by an increase in cell size driven by endoreplication of the chromosomes in epidermal nuclei.
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Affiliation(s)
- Andrew D Chisholm
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA, USA.
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39
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Murray JI, Boyle TJ, Preston E, Vafeados D, Mericle B, Weisdepp P, Zhao Z, Bao Z, Boeck M, Waterston RH. Multidimensional regulation of gene expression in the C. elegans embryo. Genome Res 2012; 22:1282-94. [PMID: 22508763 PMCID: PMC3396369 DOI: 10.1101/gr.131920.111] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
How cells adopt different expression patterns is a fundamental question of developmental biology. We quantitatively measured reporter expression of 127 genes, primarily transcription factors, in every cell and with high temporal resolution in C. elegans embryos. Embryonic cells are highly distinct in their gene expression; expression of the 127 genes studied here can distinguish nearly all pairs of cells, even between cells of the same tissue type. We observed recurrent lineage-regulated expression patterns for many genes in diverse contexts. These patterns are regulated in part by the TCF-LEF transcription factor POP-1. Other genes' reporters exhibited patterns correlated with tissue, position, and left–right asymmetry. Sequential patterns both within tissues and series of sublineages suggest regulatory pathways. Expression patterns often differ between embryonic and larval stages for the same genes, emphasizing the importance of profiling expression in different stages. This work greatly expands the number of genes in each of these categories and provides the first large-scale, digitally based, cellular resolution compendium of gene expression dynamics in live animals. The resulting data sets will be a useful resource for future research.
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Affiliation(s)
- John Isaac Murray
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA 98195, USA
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40
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Yang D, Zhong F, Li D, Liu Z, Wei H, Jiang Y, He F. General trends in the utilization of structural factors contributing to biological complexity. Mol Biol Evol 2012; 29:1957-68. [PMID: 22328715 DOI: 10.1093/molbev/mss064] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
During evolution, proteins containing newly emerged domains and the increasing proportion of multidomain proteins in the full genome-encoded proteome (GEP) have substantially contributed to increasing biological complexity. However, it is not known how these two potential structural factors are preferentially utilized at given physiological states. Here, we classified proteins according to domain number and domain age and explored the general trends across species for the utilization of proteins from GEP to various certain-state proteomes (CSPs, i.e., all the proteins expressed at certain physiological states). We found that multidomain proteins or only older domain-containing proteins are significantly overrepresented in CSPs compared with GEP, which is a trend that is stronger in multicellular organisms than in unicellular organisms. Interestingly, the strengths of overrepresentation decreased during evolution of multicellular eukaryotes. When comparing across CSPs, we found that multidomain proteins are more overrepresented in complex tissues than in simpler ones, whereas no difference among proteins with domains of different ages is evident between complex and simple tissues. Thus, biological complexity under certain conditions is more significantly realized by diverse domain organization than by the emergence of new types of domain. In addition, we found that multidomain or only older domain-containing proteins tend to evolve slowly and generally are under stronger purifying selection, which may partly result from their general overrepresentation trends in CSPs.
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Affiliation(s)
- Dong Yang
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing, P R China
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41
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Gunsalus KC, Rhrissorrakrai K. Networks in Caenorhabditis elegans. Curr Opin Genet Dev 2011; 21:787-98. [PMID: 22054717 DOI: 10.1016/j.gde.2011.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 10/11/2011] [Indexed: 10/15/2022]
Abstract
The network paradigm has become a pervasive theme in biology over the last decade, as increasingly large functional genomic datasets are being collected to interrogate regulatory influences, physical interactions, and genetic dependencies between genes, transcripts, and proteins. These 'molecular interaction' networks can be analyzed collectively and individually to define their global architecture and local patterns of connectivity. These structural features ultimately underlie functional properties such as robustness, modularity, component circuitry (e.g. feedback loops), dynamics, and responses to perturbations. This review focuses on recent progress in elucidating molecular interaction networks using different kinds of functional assays in the classical genetic model for animal development, the roundworm Caenorhabditis elegans, with representative examples to illustrate current directions in different areas of network biology.
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Affiliation(s)
- Kristin C Gunsalus
- Center for Genomics and Systems Biology and Department of Biology, New York University, 12 Waverly Place, 8th floor, New York, NY 10012, USA.
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42
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Myogenic conversion and transcriptional profiling of embryonic blastomeres in Caenorhabditis elegans. Methods 2011; 56:50-4. [PMID: 22019720 DOI: 10.1016/j.ymeth.2011.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 10/03/2011] [Accepted: 10/04/2011] [Indexed: 11/22/2022] Open
Abstract
Myogenesis has proven to be a powerful paradigm for understanding cell fate specification and differentiation in many model organisms. This includes the nematode Caenorhabditis elegans for which the genetic, cellular, and molecular tools have allowed an in-depth understanding of muscle development. One tool not yet available in C. elegans is a robust, pure and prolific cell culture system to study myogenesis. As an alternative, this chapter describes a method by which the cell fates of early, uncommitted blastomeres in the embryo are converted to a myogenic lineage. This technique permits the nearly synchronous induction of myogenesis in vivo with the potential to generate a nearly homogeneous population of cells. Coupled with the RNA isolation and cDNA amplification methods that are also described, one can now profile gene expression throughout myogenesis using any platform of choice (e.g. expression arrays, next generation sequencing). Although limited by the artificial nature of this developing mass of muscle inside the eggshell, blastomere conversion and transcriptional profiling is a very powerful tool to investigate changes in gene expression associated with myogenesis in C. elegans that is applicable to many different cell types. When coupled with next generation sequencing, the method has the potential to yield a very high-resolution map of changes in gene expression throughout myogenesis.
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The branched actin nucleator Arp2/3 promotes nuclear migrations and cell polarity in the C. elegans zygote. Dev Biol 2011; 357:356-69. [PMID: 21798253 DOI: 10.1016/j.ydbio.2011.07.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 06/17/2011] [Accepted: 07/06/2011] [Indexed: 01/08/2023]
Abstract
Regulated movements of the nucleus are essential during zygote formation, cell migrations, and differentiation of neurons. The nucleus moves along microtubules (MTs) and is repositioned on F-actin at the cellular cortex. Two families of nuclear envelope proteins, SUN and KASH, link the nucleus to the actin and MT cytoskeletons during nuclear movements. However, the role of actin nucleators in nuclear migration and positioning is poorly understood. We show that the branched actin nucleator, Arp2/3, affects nuclear movements throughout embryonic and larval development in C. elegans, including nuclear migrations in epidermal cells and neuronal precursors. In one-cell embryos the migration of the male pronucleus to meet the female pronucleus after fertilization requires Arp2/3. Loss of Arp2/3 or its activators changes the dynamics of non-muscle myosin, NMY-2, and alters the cortical accumulation of posterior PAR proteins. Reduced establishment of the posterior microtubule cytoskeleton in Arp2/3 mutants correlates with reduced male pronuclear migration. The UNC-84/SUN nuclear envelope protein that links the nucleus to the MT and actin cytoskeleton is known to regulate later nuclear migrations. We show here it also positions the male pronucleus. These studies demonstrate a global role for Arp2/3 in nuclear migrations. In the C. elegans one-cell embryo Arp2/3 promotes the establishment of anterior/posterior polarity and promotes MT growth that propels the anterior migration of the male pronucleus. In contrast with previous studies emphasizing pulling forces on the male pronucleus, we propose that robust MT nucleation pushes the male pronucleus anteriorly to join the female pronucleus.
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Sawyer JM, Glass S, Li T, Shemer G, White ND, Starostina NG, Kipreos ET, Jones CD, Goldstein B. Overcoming redundancy: an RNAi enhancer screen for morphogenesis genes in Caenorhabditis elegans. Genetics 2011; 188:549-64. [PMID: 21527776 PMCID: PMC3176534 DOI: 10.1534/genetics.111.129486] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2010] [Accepted: 04/23/2011] [Indexed: 01/02/2023] Open
Abstract
Morphogenesis is an important component of animal development. Genetic redundancy has been proposed to be common among morphogenesis genes, posing a challenge to the genetic dissection of morphogenesis mechanisms. Genetic redundancy is more generally a challenge in biology, as large proportions of the genes in diverse organisms have no apparent loss of function phenotypes. Here, we present a screen designed to uncover redundant and partially redundant genes that function in an example of morphogenesis, gastrulation in Caenorhabditis elegans. We performed an RNA interference (RNAi) enhancer screen in a gastrulation-sensitized double-mutant background, targeting genes likely to be expressed in gastrulating cells or their neighbors. Secondary screening identified 16 new genes whose functions contribute to normal gastrulation in a nonsensitized background. We observed that for most new genes found, the closest known homologs were multiple other C. elegans genes, suggesting that some may have derived from rounds of recent gene duplication events. We predict that such genes are more likely than single copy genes to comprise redundant or partially redundant gene families. We explored this prediction for one gene that we identified and confirmed that this gene and five close relatives, which encode predicted substrate recognition subunits (SRSs) for a CUL-2 ubiquitin ligase, do indeed function partially redundantly with each other in gastrulation. Our results implicate new genes in C. elegans gastrulation, and they show that an RNAi-based enhancer screen in C. elegans can be used as an efficient means to identify important but redundant or partially redundant developmental genes.
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Affiliation(s)
- Jacob M. Sawyer
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Stephanie Glass
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Trudy Li
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Gidi Shemer
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Noor D. White
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599
| | | | - Edward T. Kipreos
- Department of Cellular Biology, University of Georgia, Athens, Georgia 30602
| | - Corbin D. Jones
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Bob Goldstein
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599
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Arda HE, Taubert S, MacNeil LT, Conine CC, Tsuda B, Van Gilst M, Sequerra R, Doucette-Stamm L, Yamamoto KR, Walhout AJM. Functional modularity of nuclear hormone receptors in a Caenorhabditis elegans metabolic gene regulatory network. Mol Syst Biol 2010; 6:367. [PMID: 20461074 PMCID: PMC2890327 DOI: 10.1038/msb.2010.23] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 03/26/2010] [Indexed: 12/15/2022] Open
Abstract
We present the first gene regulatory network (GRN) that pertains to post-developmental gene expression. Specifically, we mapped a transcription regulatory network of Caenorhabditis elegans metabolic gene promoters using gene-centered yeast one-hybrid assays. We found that the metabolic GRN is enriched for nuclear hormone receptors (NHRs) compared with other gene-centered regulatory networks, and that these NHRs organize into functional network modules. The NHR family has greatly expanded in nematodes; C. elegans has 284 NHRs, whereas humans have only 48. We show that the NHRs in the metabolic GRN have metabolic phenotypes, suggesting that they do not simply function redundantly. The mediator subunit MDT-15 preferentially interacts with NHRs that occur in the metabolic GRN. We describe an NHR circuit that responds to nutrient availability and propose a model for the evolution and organization of NHRs in C. elegans metabolic regulatory networks.
Physical and/or regulatory interactions between transcription factors (TFs) and their target genes are essential to establish body plans of multicellular organisms during development, and these interactions have been studied extensively in the context of GRNs. The precise control of differential gene expression is also of critical importance to maintain physiological homeostasis, and many metabolic disorders such as obesity and diabetes coincide with substantial changes in gene expression. Much work has focused on the GRNs that control metazoan development; however, the design principles and organization of the GRNs that control systems physiology remain largely unexplored. In this study, we present the first gene-centered GRN that includes ∼70 genes involved in C. elegans metabolism and physiology, 100 TFs and more than 500 protein–DNA interactions between them. The resulting metabolic GRN is enriched for NHRs, compared with other gene-centered regulatory networks. NHRs are well-known regulators of lipid meta-qj;bolism in mammals. The transcriptional activity of NHRs can be modified by diffusible ligands, which allows these TFs to function as molecular sensors and rapidly alter the expression of their target genes. Interestingly, NHRs comprise the largest family of TFs in nematodes; the C. elegans genome encodes 284 NHRs, most of which are uncharacterized. Furthermore, their organization in GRNs has not yet been investigated. In our study, we show that the C. elegans NHRs that we retrieved in the metabolic GRN organize into network modules, and that most of these NHRs function to maintain lipid homeostasis in the nematode. Interestingly, network modularity has been proposed to facilitate rapid and robust changes in gene expression. Our results suggest that the C. elegans metabolic GRN may have evolved by combining NHR family expansion with the specific modular wiring of NHRs to enable the rapid adaptation of the animal to different environmental cues. NHRs can interact with transcriptional cofactors such as chromatin remodeling complexes and Mediator components. For instance, the C. elegans Mediator subunit, MDT-15, can interact with NHR-49 to regulate the expression of its target genes. To find all the TFs that MDT-15 can interact with, we performed systematic yeast two-hybrid assays with MDT-15 versus 755 full-length TFs. We found that MDT-15 preferentially associates with NHRs, and specifically with those NHRs that confer a metabolic phenotype and that occur in the metabolic GRN. This illustrates the central role of MDT-15 in the regulation of metabolic gene expression. Using a variety of genetic and biochemical approaches, we characterized NHR-86 in more detail. NHR-86 participates in one of the two NHR modules, and has a high-flux capacity; that is it has both a high incoming and a high outgoing degree. We obtained an nhr-86 mutant and generated an NHR-86 antibody, and showed that NHR-86 functions as an auto-repressor in vivo and that nhr-86 mutant animals store abnormally high levels of body fat. Finally, we discovered a novel NHR circuit that responds to nutrient availability. In this circuit NHR-45 regulates the activity of nhr-178 promoter in two distinct physiologically important tissues: the intestine and the hypodermis. Both of these NHRs are required to maintain lipid homeostasis in C. elegans. The expression of nhr-178 is responsive to the nutritional status of the animal, which switches between ON and OFF states in the hypodermis. We found that NHR-45 activity is necessary to control this switch in the hypodermis. Interestingly, NHR-45 has opposite effects on the activity of the nhr-178 promoter in these tissues: NHR-45 activates this promoter in the intestine, but represses it in the hypodermis. Altogether our study leads to a model in which the expansion of the NHR family, TFs that have the capacity to act as fast molecular sensors, is combined with a modular network organization to enable rapid and robust responses to various environmental cues. Gene regulatory networks (GRNs) provide insights into the mechanisms of differential gene expression at a systems level. GRNs that relate to metazoan development have been studied extensively. However, little is still known about the design principles, organization and functionality of GRNs that control physiological processes such as metabolism, homeostasis and responses to environmental cues. In this study, we report the first experimentally mapped metazoan GRN of Caenorhabditis elegans metabolic genes. This network is enriched for nuclear hormone receptors (NHRs). The NHR family has greatly expanded in nematodes: humans have 48 NHRs, but C. elegans has 284, most of which are uncharacterized. We find that the C. elegans metabolic GRN is highly modular and that two GRN modules predominantly consist of NHRs. Network modularity has been proposed to facilitate a rapid response to different cues. As NHRs are metabolic sensors that are poised to respond to ligands, this suggests that C. elegans GRNs evolved to enable rapid and adaptive responses to different cues by a concurrence of NHR family expansion and modular GRN wiring.
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Affiliation(s)
- H Efsun Arda
- Program in Gene Function and Expression and Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
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Abstract
Cell specification requires that particular subsets of cells adopt unique expression patterns that ultimately define the fates of their descendants. In C. elegans, cell fate specification involves the combinatorial action of multiple signals that produce activation of a small number of "blastomere specification" factors. These initiate expression of gene regulatory networks that drive development forward, leading to activation of "tissue specification" factors. In this review, the C. elegans embryo is considered as a model system for studies of cell specification. The techniques used to study cell fate in this species, and the themes that have emerged, are described.
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Affiliation(s)
- Morris F Maduro
- Department of Biology, University of California, Riverside, Riverside, California 92521, USA.
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Hashimshony T, Yanai I. Revealing developmental networks by comparative transcriptomics. Transcription 2010; 1:154-158. [PMID: 21326891 DOI: 10.4161/trns.1.3.13190] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Revised: 07/25/2010] [Accepted: 07/27/2010] [Indexed: 11/19/2022] Open
Abstract
Metazoan development relies upon the precise control of the genome's expression. This enables different cells in the animal to have different properties, despite having the same genetic material, and different animals to have different morphologies despite sharing developmental genes. However, near-identical organisms may have different overall genomic content, suggesting that the mechanisms by which evolution of the phenotype proceeds on a global level are not well understood. We review here recent works that have discovered a tremendous amount of variation between the developmental transcriptomes of both closely and distantly related organisms. It is evident that the evolution of regulatory programs occurs at a rapid rate comparable to that of other genomic processes. Distinguishing the selective pressures on each regulatory element will thus be crucial towards understanding its functional relevance. We propose that such a comparative approach is most suited to the identification of unifying principles in cell fate specification and differentiation in the animal embryo.
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Affiliation(s)
- Tamar Hashimshony
- Department of Biology; Technion-Israel Institute of Technology; Haifa, Israel
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Landmann F, Foster JM, Slatko B, Sullivan W. Asymmetric Wolbachia segregation during early Brugia malayi embryogenesis determines its distribution in adult host tissues. PLoS Negl Trop Dis 2010; 4:e758. [PMID: 20689574 PMCID: PMC2910707 DOI: 10.1371/journal.pntd.0000758] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Accepted: 06/07/2010] [Indexed: 11/25/2022] Open
Abstract
Wolbachia are required for filarial nematode survival and
fertility and contribute to the immune responses associated with human filarial
diseases. Here we developed whole-mount immunofluorescence techniques to
characterize Wolbachia somatic and germline transmission
patterns and tissue distribution in Brugia malayi, a nematode
responsible for lymphatic filariasis. In the initial embryonic divisions,
Wolbachia segregate asymmetrically such that they occupy
only a small subset of cells in the developing embryo, facilitating their
concentration in the adult hypodermal chords and female germline.
Wolbachia are not found in male reproductive tissues and
the absence of Wolbachia from embryonic germline precursors in
half of the embryos indicates Wolbachia loss from the male
germline may occur in early embryogenesis. Wolbachia rely on
fusion of hypodermal cells to populate adult chords. Finally, we detect
Wolbachia in the secretory canal lumen suggesting living
worms may release bacteria and/or their products into their host. Filarial diseases affect over 150 million people in tropical countries. They are
caused by parasitic nematodes like Brugia malayi that rely on
their endosymbiont Wolbachia for their survival and fertility.
These bacteria are a recognized drug target in the search for treatments killing
adult worms. To understand the transmission of Wolbachia from
the embryonic to adult stages, we developed new techniques to track these
bacteria at the cellular and tissue levels. These techniques include
immunofluorescence in whole mount adult tissues and embryos. We found that
Wolbachia segregate asymetrically in specific cells, in a
lineage-specific manner during early Brugia embryogenesis, and
rely on cell fusion to subsequently populate the adult hypodermal chords. From
the chords, the Wolbachia can be secreted in the
secretory-excretory canal, suggesting that in addition to dead worms releasing
the bacteria in the human body, living worms may also secrete
Wolbachia, whose role in stimulating the immune system in
filarial pathologies is now well established.
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Affiliation(s)
- Frédéric Landmann
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, California, United States of America.
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Gurevich V, Kassir Y. A switch from a gradient to a threshold mode in the regulation of a transcriptional cascade promotes robust execution of meiosis in budding yeast. PLoS One 2010; 5:e11005. [PMID: 20543984 PMCID: PMC2882377 DOI: 10.1371/journal.pone.0011005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 05/18/2010] [Indexed: 01/26/2023] Open
Abstract
Tight regulation of developmental pathways is of critical importance to all organisms, and is achieved by a transcriptional cascade ensuring the coordinated expression of sets of genes. We aimed to explore whether a strong signal is required to enter and complete a developmental pathway, by using meiosis in budding yeast as a model. We demonstrate that meiosis in budding yeast is insensitive to drastic changes in the levels of its consecutive positive regulators (Ime1, Ime2, and Ndt80). Entry into DNA replication is not correlated with the time of transcription of the early genes that regulate this event. Entry into nuclear division is directly regulated by the time of transcription of the middle genes, as premature transcription of their activator NDT80, leads to a premature entry into the first meiotic division, and loss of coordination between DNA replication and nuclear division. We demonstrate that Cdk1/Cln3 functions as a negative regulator of Ime2, and that ectopic expression of Cln3 delays entry into nuclear division as well as NDT80 transcription. Because Ime2 functions as a positive regulator for premeiotic DNA replication and NDT80 transcription, as well as a negative regulator of Cdk/Cln, we suggest that a double negative feedback loop between Ime2 and Cdk1/Cln3 promotes a bistable switch from the cell cycle to meiosis. Moreover, our results suggest a regulatory mode switch that ensures robust meiosis as the transcription of the early meiosis-specific genes responds in a graded mode to Ime1 levels, whereas that of the middle and late genes as well as initiation of DNA replication, are regulated in a threshold mode.
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Affiliation(s)
- Vyacheslav Gurevich
- Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Yona Kassir
- Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel
- * E-mail:
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Meister P, Towbin BD, Pike BL, Ponti A, Gasser SM. The spatial dynamics of tissue-specific promoters during C. elegans development. Genes Dev 2010; 24:766-82. [PMID: 20395364 PMCID: PMC2854392 DOI: 10.1101/gad.559610] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Accepted: 02/25/2010] [Indexed: 12/23/2022]
Abstract
To understand whether the spatial organization of the genome reflects the cell's differentiated state, we examined whether genes assume specific subnuclear positions during Caenorhabditis elegans development. Monitoring the radial position of developmentally controlled promoters in embryos and larval tissues, we found that small integrated arrays bearing three different tissue-specific promoters have no preferential position in nuclei of undifferentiated embryos. However, in differentiated cells, they shifted stably toward the nuclear lumen when activated, or to the nuclear envelope when silent. In contrast, large integrated arrays bearing the same promoters became heterochromatic and nuclear envelope-bound in embryos. Tissue-specific activation of promoters in these large arrays in larvae overrode the perinuclear anchorage. For transgenes that carry both active and inactive promoters, the inward shift of the active promoter was dominant. Finally, induction of master regulator HLH-1 prematurely induced internalization of a muscle-specific promoter array in embryos. Fluorescence in situ hybridization confirmed analogous results for the endogenous endoderm-determining gene pha-4. We propose that, in differentiated cells, subnuclear organization arises from the selective positioning of active and inactive developmentally regulated promoters. We characterize two forces that lead to tissue-specific subnuclear organization of the worm genome: large repeat-induced heterochromatin, which associates with the nuclear envelope like repressed genes in differentiated cells, and tissue-specific promoters that shift inward in a dominant fashion over silent promoters, when they are activated.
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Affiliation(s)
- Peter Meister
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland
| | - Benjamin D. Towbin
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland
| | - Brietta L. Pike
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland
| | - Aaron Ponti
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland
| | - Susan M. Gasser
- Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland
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