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Fan K, Pfister E, Weng Z. Toward a comprehensive catalog of regulatory elements. Hum Genet 2023; 142:1091-1111. [PMID: 36935423 DOI: 10.1007/s00439-023-02519-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Accepted: 01/03/2023] [Indexed: 03/21/2023]
Abstract
Regulatory elements are the genomic regions that interact with transcription factors to control cell-type-specific gene expression in different cellular environments. A precise and complete catalog of functional elements encoded by the human genome is key to understanding mammalian gene regulation. Here, we review the current state of regulatory element annotation. We first provide an overview of assays for characterizing functional elements, including genome, epigenome, transcriptome, three-dimensional chromatin interaction, and functional validation assays. We then discuss computational methods for defining regulatory elements, including peak-calling and other statistical modeling methods. Finally, we introduce several high-quality lists of regulatory element annotations and suggest potential future directions.
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Affiliation(s)
- Kaili Fan
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Chan Medical School, 368 Plantation Street, ASC5-1069, Worcester, MA, 01605, USA
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Edith Pfister
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Chan Medical School, 368 Plantation Street, ASC5-1069, Worcester, MA, 01605, USA
| | - Zhiping Weng
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Chan Medical School, 368 Plantation Street, ASC5-1069, Worcester, MA, 01605, USA.
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2
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Yuan X, Scott IC, Wilson MD. Heart Enhancers: Development and Disease Control at a Distance. Front Genet 2021; 12:642975. [PMID: 33777110 PMCID: PMC7987942 DOI: 10.3389/fgene.2021.642975] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 01/29/2021] [Indexed: 12/14/2022] Open
Abstract
Bound by lineage-determining transcription factors and signaling effectors, enhancers play essential roles in controlling spatiotemporal gene expression profiles during development, homeostasis and disease. Recent synergistic advances in functional genomic technologies, combined with the developmental biology toolbox, have resulted in unprecedented genome-wide annotation of heart enhancers and their target genes. Starting with early studies of vertebrate heart enhancers and ending with state-of-the-art genome-wide enhancer discovery and testing, we will review how studying heart enhancers in metazoan species has helped inform our understanding of cardiac development and disease.
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Affiliation(s)
- Xuefei Yuan
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON, Canada
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON, Canada
| | - Ian C. Scott
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Michael D. Wilson
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
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3
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Coulcher JF, Roure A, Chowdhury R, Robert M, Lescat L, Bouin A, Carvajal Cadavid J, Nishida H, Darras S. Conservation of peripheral nervous system formation mechanisms in divergent ascidian embryos. eLife 2020; 9:e59157. [PMID: 33191918 PMCID: PMC7710358 DOI: 10.7554/elife.59157] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 11/13/2020] [Indexed: 01/23/2023] Open
Abstract
Ascidians with very similar embryos but highly divergent genomes are thought to have undergone extensive developmental system drift. We compared, in four species (Ciona and Phallusia for Phlebobranchia, Molgula and Halocynthia for Stolidobranchia), gene expression and gene regulation for a network of six transcription factors regulating peripheral nervous system (PNS) formation in Ciona. All genes, but one in Molgula, were expressed in the PNS with some differences correlating with phylogenetic distance. Cross-species transgenesis indicated strong levels of conservation, except in Molgula, in gene regulation despite lack of sequence conservation of the enhancers. Developmental system drift in ascidians is thus higher for gene regulation than for gene expression and is impacted not only by phylogenetic distance, but also in a clade-specific manner and unevenly within a network. Finally, considering that Molgula is divergent in our analyses, this suggests deep conservation of developmental mechanisms in ascidians after 390 My of separate evolution.
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Affiliation(s)
- Joshua F Coulcher
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Agnès Roure
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Rafath Chowdhury
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Méryl Robert
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Laury Lescat
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Aurélie Bouin
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Juliana Carvajal Cadavid
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
| | - Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka UniversityToyonakaJapan
| | - Sébastien Darras
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM)Banyuls-sur-MerFrance
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4
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Colgan W, Leanza A, Hwang A, DeBiasse MB, Llosa I, Rodrigues D, Adhikari H, Barreto Corona G, Bock S, Carillo-Perez A, Currie M, Darkoa-Larbi S, Dellal D, Gutow H, Hokama P, Kibby E, Linhart N, Moody S, Naganuma A, Nguyen D, Stanton R, Stark S, Tumey C, Velleca A, Ryan JF, Davidson B. Variable levels of drift in tunicate cardiopharyngeal gene regulatory elements. EvoDevo 2019; 10:24. [PMID: 31632631 PMCID: PMC6790052 DOI: 10.1186/s13227-019-0137-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 09/13/2019] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Mutations in gene regulatory networks often lead to genetic divergence without impacting gene expression or developmental patterning. The rules governing this process of developmental systems drift, including the variable impact of selective constraints on different nodes in a gene regulatory network, remain poorly delineated. RESULTS Here we examine developmental systems drift within the cardiopharyngeal gene regulatory networks of two tunicate species, Corella inflata and Ciona robusta. Cross-species analysis of regulatory elements suggests that trans-regulatory architecture is largely conserved between these highly divergent species. In contrast, cis-regulatory elements within this network exhibit distinct levels of conservation. In particular, while most of the regulatory elements we analyzed showed extensive rearrangements of functional binding sites, the enhancer for the cardiopharyngeal transcription factor FoxF is remarkably well-conserved. Even minor alterations in spacing between binding sites lead to loss of FoxF enhancer function, suggesting that bound trans-factors form position-dependent complexes. CONCLUSIONS Our findings reveal heterogeneous levels of divergence across cardiopharyngeal cis-regulatory elements. These distinct levels of divergence presumably reflect constraints that are not clearly associated with gene function or position within the regulatory network. Thus, levels of cis-regulatory divergence or drift appear to be governed by distinct structural constraints that will be difficult to predict based on network architecture.
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Affiliation(s)
| | - Alexis Leanza
- Thomas Jefferson University Sidney Kimmel Medical College, Philadelphia, USA
| | - Ariel Hwang
- University of North Carolina, Chapel Hill, USA
| | | | | | | | | | | | | | | | | | | | - Daniel Dellal
- Icahn School of Medicine at Mount Sinai, New York, USA
| | | | | | - Emily Kibby
- University of Colorado Boulder, Boulder, USA
| | | | | | | | | | | | - Sierra Stark
- University of California San Francisco, San Francisco, USA
| | | | | | - Joseph F. Ryan
- Whitney Laboratory for Marine Bioscience, St. Augustine, USA
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5
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Aliaga B, Bulla I, Mouahid G, Duval D, Grunau C. Universality of the DNA methylation codes in Eucaryotes. Sci Rep 2019; 9:173. [PMID: 30655579 PMCID: PMC6336885 DOI: 10.1038/s41598-018-37407-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 10/24/2018] [Indexed: 12/26/2022] Open
Abstract
Genetics and epigenetics are tightly linked heritable information classes. Question arises if epigenetics provides just a set of environment dependent instructions, or whether it is integral part of an inheritance system. We argued that in the latter case the epigenetic code should share the universality quality of the genetic code. We focused on DNA methylation. Since availability of DNA methylation data is biased towards model organisms we developed a method that uses kernel density estimations of CpG observed/expected ratios to infer DNA methylation types in any genome. We show here that our method allows for robust prediction of mosaic and full gene body methylation with a PPV of 1 and 0.87, respectively. We used this prediction to complement experimental data, and applied hierarchical clustering to identify methylation types in ~150 eucaryotic species covering different body plans, reproduction types and living conditions. Our analysis indicates that there are only four gene body methylation types. These types do not follow phylogeny (i.e. phylogenetically distant clades can have identical methylation types) but they are consistent within clades. We conclude that the gene body DNA methylation codes have universality similar to the universality of the genetic code and should consequently be considered as part of the inheritance system.
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Affiliation(s)
- Benoît Aliaga
- University Perpignan Via Domitia, IHPE UMR 5244, CNRS, IFREMER, University Montpellier, F-66860, Perpignan, France
| | - Ingo Bulla
- University Perpignan Via Domitia, IHPE UMR 5244, CNRS, IFREMER, University Montpellier, F-66860, Perpignan, France
- Institute for Mathematics and Informatics, University of Greifswald, Greifswald, Germany
- Department of Computer Science, ETH Zürich, Zürich, Switzerland
| | - Gabriel Mouahid
- University Perpignan Via Domitia, IHPE UMR 5244, CNRS, IFREMER, University Montpellier, F-66860, Perpignan, France
| | - David Duval
- University Perpignan Via Domitia, IHPE UMR 5244, CNRS, IFREMER, University Montpellier, F-66860, Perpignan, France
| | - Christoph Grunau
- University Perpignan Via Domitia, IHPE UMR 5244, CNRS, IFREMER, University Montpellier, F-66860, Perpignan, France.
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6
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Shimai K, Kusakabe TG. The Use of cis-Regulatory DNAs as Molecular Tools. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018. [DOI: 10.1007/978-981-10-7545-2_6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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7
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Zeller RW. Electroporation in Ascidians: History, Theory and Protocols. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018. [PMID: 29542079 DOI: 10.1007/978-981-10-7545-2_5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Embryonic development depends on the orchestration of hundreds of regulatory and structural genes to initiate expression at the proper time, in the correct spatial domain(s), and in the amounts required for cells and tissues to become specified, determined, and ultimately to differentiate into a multicellular embryo. One of the key approaches to studying embryonic development is the generation of transgenic animals in which recombinant DNA molecules are transiently or stably introduced into embryos to alter gene expression, to manipulate gene function or to serve as reporters for specific cell types or subcellular compartments. In some model systems, such as the mouse, well-defined approaches for generating transgenic animals have been developed. In other systems, particularly non-model systems, a key challenge is to find a way of introducing molecules or other reagents into cells that produces large numbers of embryos with a minimal effect on normal development. A variety of methods have been developed, including the use of viral vectors, microinjection, and electroporation. Here, I describe how electroporation was adapted to generate transgenic embryos in the ascidian, a nontraditional invertebrate chordate model that is particularly well-suited for studying gene regulatory activity during development. I present a review of the electroporation process, describe how electroporation was first implemented in the ascidian, and provide a series of protocols describing the electroporation process, as implemented in our laboratory.
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Affiliation(s)
- Robert W Zeller
- Center for Applied and Experimental Genomics, Department of Biology, San Diego State University, San Diego, CA, USA.
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8
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José-Edwards DS, Oda-Ishii I, Kugler JE, Passamaneck YJ, Katikala L, Nibu Y, Di Gregorio A. Brachyury, Foxa2 and the cis-Regulatory Origins of the Notochord. PLoS Genet 2015; 11:e1005730. [PMID: 26684323 PMCID: PMC4684326 DOI: 10.1371/journal.pgen.1005730] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 11/16/2015] [Indexed: 11/18/2022] Open
Abstract
A main challenge of modern biology is to understand how specific constellations of genes are activated to differentiate cells and give rise to distinct tissues. This study focuses on elucidating how gene expression is initiated in the notochord, an axial structure that provides support and patterning signals to embryos of humans and all other chordates. Although numerous notochord genes have been identified, the regulatory DNAs that orchestrate development and propel evolution of this structure by eliciting notochord gene expression remain mostly uncharted, and the information on their configuration and recurrence is still quite fragmentary. Here we used the simple chordate Ciona for a systematic analysis of notochord cis-regulatory modules (CRMs), and investigated their composition, architectural constraints, predictive ability and evolutionary conservation. We found that most Ciona notochord CRMs relied upon variable combinations of binding sites for the transcription factors Brachyury and/or Foxa2, which can act either synergistically or independently from one another. Notably, one of these CRMs contains a Brachyury binding site juxtaposed to an (AC) microsatellite, an unusual arrangement also found in Brachyury-bound regulatory regions in mouse. In contrast, different subsets of CRMs relied upon binding sites for transcription factors of widely diverse families. Surprisingly, we found that neither intra-genomic nor interspecific conservation of binding sites were reliably predictive hallmarks of notochord CRMs. We propose that rather than obeying a rigid sequence-based cis-regulatory code, most notochord CRMs are rather unique. Yet, this study uncovered essential elements recurrently used by divergent chordates as basic building blocks for notochord CRMs.
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Affiliation(s)
- Diana S. José-Edwards
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Izumi Oda-Ishii
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Jamie E. Kugler
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Yale J. Passamaneck
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Lavanya Katikala
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Yutaka Nibu
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Anna Di Gregorio
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
- * E-mail:
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9
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Yokomori R, Shimai K, Nishitsuji K, Suzuki Y, Kusakabe TG, Nakai K. Genome-wide identification and characterization of transcription start sites and promoters in the tunicate Ciona intestinalis. Genome Res 2015; 26:140-50. [PMID: 26668163 PMCID: PMC4691747 DOI: 10.1101/gr.184648.114] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2014] [Accepted: 10/13/2015] [Indexed: 02/05/2023]
Abstract
The tunicate Ciona intestinalis, an invertebrate chordate, has recently emerged as a powerful model organism for gene regulation analysis. However, few studies have been conducted to identify and characterize its transcription start sites (TSSs) and promoters at the genome-wide level. Here, using TSS-seq, we identified TSSs at the genome-wide scale and characterized promoters in C. intestinalis. Specifically, we identified TSS clusters (TSCs), high-density regions of TSS-seq tags, each of which appears to originate from an identical promoter. TSCs were found not only at known TSSs but also in other regions, suggesting the existence of many unknown transcription units in the genome. We also identified candidate promoters of 79 ribosomal protein (RP) genes, each of which had the major TSS in a polypyrimidine tract and showed a sharp TSS distribution like human RP gene promoters. Ciona RP gene promoters, however, did not appear to have typical TATA boxes, unlike human RP gene promoters. In Ciona non-RP promoters, two pyrimidine-purine dinucleotides, CA and TA, were frequently used as TSSs. Despite the absence of CpG islands, Ciona TATA-less promoters showed low expression specificity like CpG-associated human TATA-less promoters. By using TSS-seq, we also predicted trans-spliced gene TSSs and found that their downstream regions had higher G+T content than those of non-trans-spliced gene TSSs. Furthermore, we identified many putative alternative promoters, some of which were regulated in a tissue-specific manner. Our results provide valuable information about TSSs and promoter characteristics in C. intestinalis and will be helpful in future analysis of transcriptional regulation in chordates.
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Affiliation(s)
- Rui Yokomori
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8568, Japan
| | - Kotaro Shimai
- Institute for Integrative Neurobiology, Graduate School of Natural Science, Konan University, Kobe 658-8501, Japan
| | - Koki Nishitsuji
- Graduate School of Life Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan
| | - Yutaka Suzuki
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8568, Japan
| | - Takehiro G Kusakabe
- Institute for Integrative Neurobiology, Graduate School of Natural Science, Konan University, Kobe 658-8501, Japan; Department of Biology, Faculty of Science and Engineering, Konan University, Kobe 658-8501, Japan
| | - Kenta Nakai
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8568, Japan; Institute for Integrative Neurobiology, Graduate School of Natural Science, Konan University, Kobe 658-8501, Japan; Human Genome Center, Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
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10
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Ramlee MK, Zhang Q, Idris M, Peng X, Sim CK, Han W, Xu F. Histone H3 K27 acetylation marks a potent enhancer element on the adipogenic master regulator gene Pparg2. Cell Cycle 2015; 13:3414-22. [PMID: 25485585 DOI: 10.4161/15384101.2014.953424] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
PPARγ2 is expressed almost exclusively in adipose tissue and plays a central role in adipogenesis. Despite intensive studies over the last 2 decades, the mechanism regulating the expression of the Pparg2 gene, especially the role of cis-regulatory elements, is still not completely understood. Here, we report a comprehensive investigation of the enhancer elements within the murine Pparg2 gene. Utilizing the combined techniques of sequence conservation analysis and chromatin marker examination, we identified a potent enhancer element that augmented the expression of a reporter gene under the control of the Pparg2 promoter by 20-fold. This enhancer element was first identified as highly conserved non-coding sequence 10 (CNS10) and was later shown to be enriched with the enhancer marker H3 K27 acetylation. Further studies identified a binding site for p300 as the essential enhancer element in CNS10. Moreover, p300 physically binds to CNS10 and is required for the enhancer activity of CNS10. The depletion of p300 by siRNA resulted in significantly impaired activation of Pparg2 at the early stages of 3T3-L1 adipogenesis. In summary, our study identified a novel enhancer element on the murine Pparg2 gene and suggested a novel mechanism for the regulation of Pparg2 expression by p300 in 3T3-L1 adipogenesis.
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Affiliation(s)
- Muhammad Khairul Ramlee
- a Singapore Institute for Clinical Sciences ; Agency for Science ; Technology and Research (A*STAR ); Singapore
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11
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Suryamohan K, Halfon MS. Identifying transcriptional cis-regulatory modules in animal genomes. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2015; 4:59-84. [PMID: 25704908 PMCID: PMC4339228 DOI: 10.1002/wdev.168] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 11/04/2014] [Accepted: 11/16/2014] [Indexed: 11/08/2022]
Abstract
UNLABELLED Gene expression is regulated through the activity of transcription factors (TFs) and chromatin-modifying proteins acting on specific DNA sequences, referred to as cis-regulatory elements. These include promoters, located at the transcription initiation sites of genes, and a variety of distal cis-regulatory modules (CRMs), the most common of which are transcriptional enhancers. Because regulated gene expression is fundamental to cell differentiation and acquisition of new cell fates, identifying, characterizing, and understanding the mechanisms of action of CRMs is critical for understanding development. CRM discovery has historically been challenging, as CRMs can be located far from the genes they regulate, have few readily identifiable sequence characteristics, and for many years were not amenable to high-throughput discovery methods. However, the recent availability of complete genome sequences and the development of next-generation sequencing methods have led to an explosion of both computational and empirical methods for CRM discovery in model and nonmodel organisms alike. Experimentally, CRMs can be identified through chromatin immunoprecipitation directed against TFs or histone post-translational modifications, identification of nucleosome-depleted 'open' chromatin regions, or sequencing-based high-throughput functional screening. Computational methods include comparative genomics, clustering of known or predicted TF-binding sites, and supervised machine-learning approaches trained on known CRMs. All of these methods have proven effective for CRM discovery, but each has its own considerations and limitations, and each is subject to a greater or lesser number of false-positive identifications. Experimental confirmation of predictions is essential, although shortcomings in current methods suggest that additional means of validation need to be developed. For further resources related to this article, please visit the WIREs website. CONFLICT OF INTEREST The authors have declared no conflicts of interest for this article.
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Affiliation(s)
- Kushal Suryamohan
- Department of Biochemistry, University at Buffalo-State University of New York, Buffalo, NY 14203, USA
- NY State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY 14203, USA
| | - Marc S. Halfon
- Department of Biochemistry, University at Buffalo-State University of New York, Buffalo, NY 14203, USA
- Department of Biological Sciences, University at Buffalo-State University of New York, Buffalo, NY 14203, USA
- Department of Biomedical Informatics, University at Buffalo-State University of New York, Buffalo, NY 14203, USA
- NY State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY 14203, USA
- Molecular and Cellular Biology Department and Program in Cancer Genetics, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
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12
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Stolfi A, Lowe EK, Racioppi C, Ristoratore F, Brown CT, Swalla BJ, Christiaen L. Divergent mechanisms regulate conserved cardiopharyngeal development and gene expression in distantly related ascidians. eLife 2014; 3:e03728. [PMID: 25209999 PMCID: PMC4356046 DOI: 10.7554/elife.03728] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 09/05/2014] [Indexed: 12/13/2022] Open
Abstract
Ascidians present a striking dichotomy between conserved phenotypes and divergent genomes: embryonic cell lineages and gene expression patterns are conserved between distantly related species. Much research has focused on Ciona or Halocynthia spp. but development in other ascidians remains poorly characterized. In this study, we surveyed the multipotent myogenic B7.5 lineage in Molgula spp. Comparisons to the homologous lineage in Ciona revealed identical cell division and fate specification events that result in segregation of larval, cardiac, and pharyngeal muscle progenitors. Moreover, the expression patterns of key regulators are conserved, but cross-species transgenic assays uncovered incompatibility, or ‘unintelligibility’, of orthologous cis-regulatory sequences between Molgula and Ciona. These sequences drive identical expression patterns that are not recapitulated in cross-species assays. We show that this unintelligibility is likely due to changes in both cis- and trans-acting elements, hinting at widespread and frequent turnover of regulatory mechanisms underlying otherwise conserved aspects of ascidian embryogenesis. DOI:http://dx.doi.org/10.7554/eLife.03728.001 When two species have features that look similar, this may be because the features arise by the same processes during development. Other features may look similar yet develop by different mechanisms. ‘Developmental system drift’ refers to the process where a physical feature remains unaltered during evolution, but the underlying pathway that controls its development is changed. However, to date, there have been only a few experimental studies that support this idea. Ascidians—also commonly known as sea squirts—are vase-like marine creatures, which start off as tadpole-like larvae that swim around until they find a place to settle down and attach themselves. Once attached, the sea squirts lose the ability to swim and start feeding, typically by filtering material out of the seawater. Sea squirts and their close relatives are the invertebrates (animals without backbones) that are most closely related to all vertebrates (animals with backbones), including humans. Furthermore, although different species of sea squirt have almost identical embryos, their genomes are very different. Stolfi et al. have now studied whether developmental system drift may have occurred during the evolution of ascidians, by analyzing different species of sea squirt named Molgula and Ciona. Stolfi et al. compared the genomes of Molgula and Ciona and studied the expression of genes in the cells that give rise to the heart and the muscles of the head. As an embryo develops, specific genes are switched on or off, and these patterns of gene activation were broadly identical in the two species of sea squirt examined. Enhancers are sequences of DNA that control when and how a gene is switched on. Given the similarities between the development of heart and head muscle cells in the different sea squirts, Stolfi et al. looked to see if the mechanisms of gene expression, and therefore the enhancers, were also conserved. Unexpectedly, this was not the case. When enhancers from Molgula were introduced into Ciona (and vice versa), these sequences were unable to switch on gene expression—thus enhancers from one sea squirt species could not function in the other. Stolfi et al. conclude that the developmental systems may have drifted considerably during evolution of the sea squirts, in spite of their nearly identical embryos. This reinforces the view that different paths can lead to the formation of similar physical features. DOI:http://dx.doi.org/10.7554/eLife.03728.002
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Affiliation(s)
- Alberto Stolfi
- Center for Developmental Genetics, Department of Biology, New York University, New York, United States
| | - Elijah K Lowe
- Department of Computer Science and Engineering, Michigan State University, East Lansing, United States
| | - Claudia Racioppi
- Cellular and Developmental Biology Laboratory, Stazione Zoologica Anton Dohrn, Napoli, Italy
| | - Filomena Ristoratore
- Cellular and Developmental Biology Laboratory, Stazione Zoologica Anton Dohrn, Napoli, Italy
| | - C Titus Brown
- Department of Computer Science and Engineering, Michigan State University, East Lansing, United States
| | - Billie J Swalla
- Department of Biology, University of Washington, Seattle, United States
| | - Lionel Christiaen
- Center for Developmental Genetics, Department of Biology, New York University, New York, United States
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Abstract
Tunicates have been extensively studied because of their crucial phylogenetic location (the closest living relatives of vertebrates) and particular developmental plan. Recent genome efforts have disclosed that tunicates are also remarkable in their genome organization and molecular evolutionary patterns. Here, we review these latter aspects, comparing the similarities and specificities of two model species of the group: Oikopleura dioica and Ciona intestinalis. These species exhibit great genome plasticity and Oikopleura in particular has undergone a process of extreme genome reduction and compaction that can be explained in part by gene loss, but is mostly due to other mechanisms such as shortening of intergenic distances and introns, and scarcity of mobile elements. In Ciona, genome reorganization was less severe being more similar to the other chordates in several aspects. Rates and patterns of molecular evolution are also peculiar in tunicates, being Ciona about 50% faster than vertebrates and Oikopleura three times faster. In fact, the latter species is considered as the fastest evolving metazoan recorded so far. Two processes of increase in evolutionary rates have taken place in tunicates. One of them is more extreme, and basically restricted to genes encoding regulatory proteins (transcription regulators, chromatin remodeling proteins, and metabolic regulators), and the other one is less pronounced but affects the whole genome. Very likely adaptive evolution has played a very significant role in the first, whereas the functional and/or evolutionary causes of the second are less clear and the evidence is not conclusive. The evidences supporting the incidence of increased mutation and less efficient negative selection are presented and discussed.
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Affiliation(s)
- Luisa Berná
- Sección Biomatemática, Facultad de Ciencias, Universidad de la República, Montevideo, UruguayUnidad de Biología Molecular, Institut Pasteur Montevideo, Montevideo, Uruguay
| | - Fernando Alvarez-Valin
- Sección Biomatemática, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
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14
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Treen N, Yoshida K, Sakuma T, Sasaki H, Kawai N, Yamamoto T, Sasakura Y. Tissue-specific and ubiquitous gene knockouts by TALEN electroporation provide new approaches to investigating gene function in Ciona. Development 2013; 141:481-7. [PMID: 24353063 DOI: 10.1242/dev.099572] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Custom designed nucleases can simplify gene targeting experiments and have the potential to allow these techniques to be performed in a wide range of organisms. Transcriptional activator-like effector nucleases (TALENs) are starting to fulfill this potential with the advantages of low cost and fast construction times. Here, we report that TALENs are highly effective at inducing mutations in specific genomic loci in the ascidian chordate Ciona intestinalis. In Ciona there are well-established methods to introduce exogenous DNA by electroporation, and we show that this method can be used to introduce constructs that can express TALENs ubiquitously or in specific tissues. Our current protocols enable the rapid analysis of hundreds of TALEN-induced mutants. TALEN electroporations result in a high rate of mutations. These mutations can result in gene knockouts that recapitulate previously described functions of Fgf3 and Hox12. We show that TALENs can work efficiently to cause tissue-specific knockouts and demonstrate this by knocking out Hox12 in the epidermis and Fgf3 in neural tissues. We also use tissue-specific knockouts to reveal a new function of Fgf3 during ascidian larval metamorphosis.
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Affiliation(s)
- Nicholas Treen
- Shimoda Marine Research Center, University of Tsukuba, Shimoda, Shizuoka, 415-0025, Japan
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15
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Parallel evolution of chordate cis-regulatory code for development. PLoS Genet 2013; 9:e1003904. [PMID: 24282393 PMCID: PMC3836708 DOI: 10.1371/journal.pgen.1003904] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 09/09/2013] [Indexed: 12/17/2022] Open
Abstract
Urochordates are the closest relatives of vertebrates and at the larval stage, possess a characteristic bilateral chordate body plan. In vertebrates, the genes that orchestrate embryonic patterning are in part regulated by highly conserved non-coding elements (CNEs), yet these elements have not been identified in urochordate genomes. Consequently the evolution of the cis-regulatory code for urochordate development remains largely uncharacterised. Here, we use genome-wide comparisons between C. intestinalis and C. savignyi to identify putative urochordate cis-regulatory sequences. Ciona conserved non-coding elements (ciCNEs) are associated with largely the same key regulatory genes as vertebrate CNEs. Furthermore, some of the tested ciCNEs are able to activate reporter gene expression in both zebrafish and Ciona embryos, in a pattern that at least partially overlaps that of the gene they associate with, despite the absence of sequence identity. We also show that the ability of a ciCNE to up-regulate gene expression in vertebrate embryos can in some cases be localised to short sub-sequences, suggesting that functional cross-talk may be defined by small regions of ancestral regulatory logic, although functional sub-sequences may also be dispersed across the whole element. We conclude that the structure and organisation of cis-regulatory modules is very different between vertebrates and urochordates, reflecting their separate evolutionary histories. However, functional cross-talk still exists because the same repertoire of transcription factors has likely guided their parallel evolution, exploiting similar sets of binding sites but in different combinations. Vertebrates share many aspects of early development with our closest chordate ancestors, the tunicates. However, whilst the repertoire of genes that orchestrate development is essentially the same in the two lineages, the genomic code that regulates these genes appears to be very different, even though it is highly conserved within vertebrates themselves. Using comparative genomics, we have identified a parallel developmental code in tunicates and confirmed that this code, despite a lack of sequence conservation, associates with a similar repertoire of genes. However, the organisation of the code spatially is very different in the two lineages, strongly suggesting that most of it arose independently in vertebrates and tunicates, and in most cases lacking any direct sequence ancestry. We have assayed elements of the tunicate code, and found that at least some of them can regulate gene expression in zebrafish embryos. Our results suggest that regulatory code has arisen independently in different animal lineages but possesses some common functionality because its evolution has been driven by a similar cohort of developmental transcription factors. Our work helps illuminate how complex, stable gene regulatory networks evolve and become fixed within lineages.
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16
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Katikala L, Aihara H, Passamaneck YJ, Gazdoiu S, José-Edwards DS, Kugler JE, Oda-Ishii I, Imai JH, Nibu Y, Di Gregorio A. Functional Brachyury binding sites establish a temporal read-out of gene expression in the Ciona notochord. PLoS Biol 2013; 11:e1001697. [PMID: 24204212 PMCID: PMC3812116 DOI: 10.1371/journal.pbio.1001697] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2013] [Accepted: 09/19/2013] [Indexed: 11/18/2022] Open
Abstract
During notochord formation in chordate embryos, the transcription factor Brachyury employs different regulatory strategies to ensure the sequential activation of downstream genes and thereby the deployment of a specific developmental program at the right time and place. The appearance of the notochord represented a milestone in Deuterostome evolution. The notochord is necessary for the development of the chordate body plan and for the formation of the vertebral column and numerous organs. It is known that the transcription factor Brachyury is required for notochord formation in all chordates, and that it controls transcription of a large number of target genes. However, studies of the structure of the cis-regulatory modules (CRMs) through which this control is exerted are complicated in vertebrates by the genomic complexity and the pan-mesodermal expression territory of Brachyury. We used the ascidian Ciona, in which the single-copy Brachyury is notochord-specific and CRMs are easily identifiable, to carry out a systematic characterization of Brachyury-downstream notochord CRMs. We found that Ciona Brachyury (Ci-Bra) controls most of its targets directly, through non-palindromic binding sites that function either synergistically or individually to activate early- and middle-onset genes, respectively, while late-onset target CRMs are controlled indirectly, via transcriptional intermediaries. These results illustrate how a transcriptional regulator can efficiently shape a shallow gene regulatory network into a multi-tiered transcriptional output, and provide insights into the mechanisms that establish temporal read-outs of gene expression in a fast-developing chordate embryo. Transcription factors control where and when gene expression is switched on by binding to specific stretches of DNA known as cis-regulatory modules (CRMs). In this study, we investigated the architecture and composition of CRMs that direct gene expression in the notochord—a transient rod-like structure found in all embryos that belong to the phylum chordata, which includes humans. Here we used the sea squirt Ciona, a simple chordate, and analyzed how the transcription factor Brachyury ensures the appropriate deployment of its target genes at specific times during the sequential steps of notochord formation. We compared CRMs found in different notochord genes downstream of Brachyury, expecting to find genes associated with greater numbers of Brachyury binding sites to be expressed at higher levels. To our surprise, we found instead that a higher number of functional Brachyury binding sites is typical of CRMs associated with genes that are expressed early in notochord development, while single-site CRMs are characteristic of genes that are turned on during the intermediate stages of this process. Finally, CRMs associated with genes expressed late in notochord development do not contain functional Brachyury binding sites but are controlled by Brachyury indirectly, through the action of intermediary transcription factors. These differences explain how a transcription factor that is present at all stages in a certain cell type can generate a sequential transcriptional output of gene expression.
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Affiliation(s)
- Lavanya Katikala
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Hitoshi Aihara
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Yale J. Passamaneck
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Stefan Gazdoiu
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Diana S. José-Edwards
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Jamie E. Kugler
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Izumi Oda-Ishii
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Janice H. Imai
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Yutaka Nibu
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
- * E-mail: (YN); (ADG)
| | - Anna Di Gregorio
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, New York, United States of America
- * E-mail: (YN); (ADG)
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17
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Irvine SQ. Study of Cis-regulatory Elements in the Ascidian Ciona intestinalis. Curr Genomics 2013; 14:56-67. [PMID: 23997651 PMCID: PMC3580780 DOI: 10.2174/138920213804999192] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Revised: 12/30/2012] [Accepted: 01/01/2013] [Indexed: 01/31/2023] Open
Abstract
The ascidian (sea squirt) C. intestinalis has become an important model organism for the study of cis-regulation. This is largely due to the technology that has been developed for assessing cis-regulatory activity through the use of transient reporter transgenes introduced into fertilized eggs. This technique allows the rapid and inexpensive testing of endogenous or altered DNA for regulatory activity in vivo. This review examines evidence that C. intestinaliscis-regulatory elements are located more closely to coding regions than in other model organisms. I go on to compare the organization of cis-regulatory elements and conserved non-coding sequences in Ciona, mammals, and other deuterostomes for three representative C.intestinalis genes, Pax6, FoxAa, and the DlxA-B cluster, along with homologs in the other species. These comparisons point out some of the similarities and differences between cis-regulatory elements and their study in the various model organisms. Finally, I provide illustrations of how C. intestinalis lends itself to detailed study of the structure of cis-regulatory elements, which have led, and promise to continue to lead, to important insights into the fundamentals of transcriptional regulation.
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Affiliation(s)
- Steven Q Irvine
- Department of Biological Sciences, University of Rhode Island, Kingston, RI 02881, USA
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18
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Nelson AC, Wardle FC. Conserved non-coding elements and cis regulation: actions speak louder than words. Development 2013; 140:1385-95. [PMID: 23482485 DOI: 10.1242/dev.084459] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
It is a truth (almost) universally acknowledged that conserved non-coding genomic sequences function in the cis regulation of neighbouring genes. But is this a misconception? The literature is strewn with examples of conserved non-coding sequences being able to drive reporter expression, but the extent to which such sequences are actually used endogenously in vivo is only now being rigorously explored using unbiased genome-scale approaches. Here, we review the emerging picture, examining the extent to which conserved non-coding sequences equivalently regulate gene expression in different species, or at different developmental stages, and how genomics approaches are revealing the relationship between sequence conservation and functional use of cis-regulatory elements.
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Affiliation(s)
- Andrew C Nelson
- Randall Division of Cell and Molecular Biophysics, New Hunt's House, King's College London, Guy's Campus, London SE1 1UL, UK.
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19
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Vascular Endothelial Growth Factor Receptor Family in Ascidians, Halocynthia roretzi (Sea Squirt). Its High Expression in Circulatory System-Containing Tissues. Int J Mol Sci 2013; 14:4841-53. [PMID: 23455462 PMCID: PMC3634500 DOI: 10.3390/ijms14034841] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 02/07/2013] [Accepted: 02/15/2013] [Indexed: 11/19/2022] Open
Abstract
The vascular endothelial growth factor (VEGF)-VEGF Receptor (VEGFR) system is an important pathway for regulation of angiogenesis. However, its evolutionary development, particularly the step from invertebrates to vertebrates, is still largely unknown. Here, we molecularly cloned the VEGFR-like gene from Halocynthia roretzi, a species belonging to the Tunicata, the chordate subphylum recently considered the sister group of vertebrates. The cDNA encoded a homolog of human VEGFR, including the transmembrane domain, and the tyrosine kinase domain with a kinase-insert region, which was designated S. sq VEGFR (GenBank AB374180). Similar to Tunicates including ascidians in the phylogenetic tree, the Amphioxus, another chordate, is located close to vertebrates. However, S. sq VEGFR has a higher homology than the Amphioxus VEGFR-like molecule (GenBank AB025557) to human VEGFR in the kinase domain-2 region. The S. sq VEGFR mRNA was expressed at highest levels in circulatory system-containing tissues, suggesting that S. sq VEGFR plays an important role in the formation or maintenance of circulatory system in Tunicates, Halocynthia roretzi.
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20
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Izzi SA, Colantuono BJ, Sullivan K, Khare P, Meedel TH. Functional studies of the Ciona intestinalis myogenic regulatory factor reveal conserved features of chordate myogenesis. Dev Biol 2013; 376:213-23. [PMID: 23391688 DOI: 10.1016/j.ydbio.2013.01.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Revised: 01/08/2013] [Accepted: 01/24/2013] [Indexed: 10/27/2022]
Abstract
Ci-MRF is the sole myogenic regulatory factor (MRF) of the ascidian Ciona intestinalis, an invertebrate chordate. In order to investigate its properties we developed a simple in vivo assay based on misexpressing Ci-MRF in the notochord of Ciona embryos. We used this assay to examine the roles of three structural motifs that are conserved among MRFs: an alanine-threonine (Ala-Thr) dipeptide of the basic domain that is known in vertebrates as the myogenic code, a cysteine/histidine-rich (C/H) domain found just N-terminal to the basic domain, and a carboxy-terminal amphipathic α-helix referred to as Helix III. We show that the Ala-Thr dipeptide is necessary for normal Ci-MRF function, and that while eliminating the C/H domain or Helix III individually has no demonstrable effect on Ci-MRF, simultaneous loss of both motifs significantly reduces its activity. Our studies also indicate that direct interaction between CiMRF and an essential E-box of Ciona Troponin I is required for the expression of this muscle-specific gene and that multiple classes of MRF-regulated genes exist in Ciona. These findings are consistent with substantial conservation of MRF-directed myogenesis in chordates and demonstrate for the first time that the Ala/Thr dipeptide of the basic domain of an invertebrate MRF behaves as a myogenic code.
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Affiliation(s)
- Stephanie A Izzi
- Department of Biology, Rhode Island College, Providence, RI 02908, USA
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21
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Abstract
Differential gene expression is the fundamental mechanism underlying animal development and cell differentiation. However, it is a challenge to identify comprehensively and accurately the DNA sequences that are required to regulate gene expression: namely, cis-regulatory modules (CRMs). Three major features, either singly or in combination, are used to predict CRMs: clusters of transcription factor binding site motifs, non-coding DNA that is under evolutionary constraint and biochemical marks associated with CRMs, such as histone modifications and protein occupancy. The validation rates for predictions indicate that identifying diagnostic biochemical marks is the most reliable method, and understanding is enhanced by the analysis of motifs and conservation patterns within those predicted CRMs.
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22
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Woznica A, Haeussler M, Starobinska E, Jemmett J, Li Y, Mount D, Davidson B. Initial deployment of the cardiogenic gene regulatory network in the basal chordate, Ciona intestinalis. Dev Biol 2012; 368:127-39. [PMID: 22595514 DOI: 10.1016/j.ydbio.2012.05.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 04/26/2012] [Accepted: 05/04/2012] [Indexed: 12/31/2022]
Abstract
The complex, partially redundant gene regulatory architecture underlying vertebrate heart formation has been difficult to characterize. Here, we dissect the primary cardiac gene regulatory network in the invertebrate chordate, Ciona intestinalis. The Ciona heart progenitor lineage is first specified by Fibroblast Growth Factor/Map Kinase (FGF/MapK) activation of the transcription factor Ets1/2 (Ets). Through microarray analysis of sorted heart progenitor cells, we identified the complete set of primary genes upregulated by FGF/Ets shortly after heart progenitor emergence. Combinatorial sequence analysis of these co-regulated genes generated a hypothetical regulatory code consisting of Ets binding sites associated with a specific co-motif, ATTA. Through extensive reporter analysis, we confirmed the functional importance of the ATTA co-motif in primary heart progenitor gene regulation. We then used the Ets/ATTA combination motif to successfully predict a number of additional heart progenitor gene regulatory elements, including an intronic element driving expression of the core conserved cardiac transcription factor, GATAa. This work significantly advances our understanding of the Ciona heart gene network. Furthermore, this work has begun to elucidate the precise regulatory architecture underlying the conserved, primary role of FGF/Ets in chordate heart lineage specification.
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Affiliation(s)
- Arielle Woznica
- Department of Molecular and Cellular Biology, Molecular Cardiovascular Research Program, University of Arizona, Arizona 85724, USA
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23
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Esposito R, D'Aniello S, Squarzoni P, Pezzotti MR, Ristoratore F, Spagnuolo A. New insights into the evolution of metazoan tyrosinase gene family. PLoS One 2012; 7:e35731. [PMID: 22536431 PMCID: PMC3334994 DOI: 10.1371/journal.pone.0035731] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Accepted: 03/24/2012] [Indexed: 11/19/2022] Open
Abstract
Tyrosinases, widely distributed among animals, plants and fungi, are involved in the biosynthesis of melanin, a pigment that has been exploited, in the course of evolution, to serve different functions. We conducted a deep evolutionary analysis of tyrosinase family amongst metazoa, thanks to the availability of new sequenced genomes, assessing that tyrosinases (tyr) represent a distinctive feature of all the organisms included in our study and, interestingly, they show an independent expansion in most of the analyzed phyla. Tyrosinase-related proteins (tyrp), which derive from tyr but show distinct key residues in the catalytic domain, constitute an invention of chordate lineage. In addition we here reported a detailed study of the expression territories of the ascidian Ciona intestinalis tyr and tyrps. Furthermore, we put efforts in the identification of the regulatory sequences responsible for their expression in pigment cell lineage. Collectively, the results reported here enlarge our knowledge about the tyrosinase gene family as valuable resource for understanding the genetic components involved in pigment cells evolution and development.
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Affiliation(s)
| | | | | | | | | | - Antonietta Spagnuolo
- Cellular and Developmental Biology Department, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy
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24
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Berná L, D’Onofrio G, Alvarez-Valin F. Peculiar patterns of amino acid substitution and conservation in the fast evolving tunicate Oikopleura dioica. Mol Phylogenet Evol 2012; 62:708-17. [DOI: 10.1016/j.ympev.2011.11.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 09/08/2011] [Accepted: 11/16/2011] [Indexed: 01/28/2023]
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25
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Abstract
The study of cis-regulatory DNAs that control developmental gene expression is integral to the modeling of comprehensive genomic regulatory networks for embryogenesis. Ascidian embryos provide a unique opportunity for the analysis of cis-regulatory DNAs with cellular resolution in the context of a simple but typical chordate body plan. Here, we review landmark studies that have laid the foundations for the study of transcriptional enhancers, among other cis-regulatory DNAs, and their roles in ascidian development. The studies using ascidians of the Ciona genus have capitalized on a unique electroporation technique that permits the simultaneous transfection of hundreds of fertilized eggs, which develop rapidly and express transgenes with little mosaicism. Current studies using the ascidian embryo benefit from extensively annotated genomic resources to characterize transcript models in silico. The search for functional noncoding sequences can be guided by bioinformatic analyses combining evolutionary conservation, gene coexpression, and combinations of overrepresented short-sequence motifs. The power of the transient transfection assays has allowed thorough dissection of numerous cis-regulatory modules, which provided insights into the functional constraints that shape enhancer architecture and diversification. Future studies will benefit from pioneering stable transgenic lines and the analysis of chromatin states. Whole genome expression, functional and DNA binding data are being integrated into comprehensive genomic regulatory network models of early ascidian cell specification with a single-cell resolution that is unique among chordate model systems.
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26
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Abstract
We tested whether functionally important sites in bacterial, yeast, and animal promoters are more conserved than their neighbors. We found that substitutions are predominantly seen in less important sites and that those that occurred tended to have less impact on gene expression than possible alternatives. These results suggest that purifying selection operates on promoter sequences.
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27
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Barrière A, Gordon KL, Ruvinsky I. Distinct functional constraints partition sequence conservation in a cis-regulatory element. PLoS Genet 2011; 7:e1002095. [PMID: 21655084 PMCID: PMC3107193 DOI: 10.1371/journal.pgen.1002095] [Citation(s) in RCA: 21] [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: 10/25/2010] [Accepted: 04/07/2011] [Indexed: 11/25/2022] Open
Abstract
Different functional constraints contribute to different evolutionary rates across genomes. To understand why some sequences evolve faster than others in a single cis-regulatory locus, we investigated function and evolutionary dynamics of the promoter of the Caenorhabditis elegans unc-47 gene. We found that this promoter consists of two distinct domains. The proximal promoter is conserved and is largely sufficient to direct appropriate spatial expression. The distal promoter displays little if any conservation between several closely related nematodes. Despite this divergence, sequences from all species confer robustness of expression, arguing that this function does not require substantial sequence conservation. We showed that even unrelated sequences have the ability to promote robust expression. A prominent feature shared by all of these robustness-promoting sequences is an AT-enriched nucleotide composition consistent with nucleosome depletion. Because general sequence composition can be maintained despite sequence turnover, our results explain how different functional constraints can lead to vastly disparate rates of sequence divergence within a promoter. Comparison between genome sequences of different species is a powerful tool in modern biology because important features are maintained by natural selection and are therefore conserved. However, some important sequences within genomes evolve considerably faster than others. One possible explanation is that they encode little or no function. Alternatively, they may evolve under different constraints that permit sequence turnover while maintaining function. Here we report that the promoter of the unc-47 gene of C. elegans contains two discrete elements. One has a highly conserved sequence that determines the spatial expression pattern. Another shows no sequence conservation, but it makes expression of the gene robust, that is, consistent between individuals and resilient to environmental challenges. Remarkably, multiple unrelated sequences are capable of promoting robust expression. Nucleotide composition of these sequences suggests that open chromatin may play a role in conferring robustness of gene expression. Because general sequence composition and therefore expression robustness can be maintained despite sequence turnover, our results offer an explanation of how rapidly diverging promoter elements can nevertheless remain functionally conserved.
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Affiliation(s)
- Antoine Barrière
- Department of Ecology and Evolution and Institute for Genomics and Systems Biology, Chicago, Illinois, United States of America
| | - Kacy L. Gordon
- Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, Illinois, United States of America
| | - Ilya Ruvinsky
- Department of Ecology and Evolution and Institute for Genomics and Systems Biology, Chicago, Illinois, United States of America
- Department of Organismal Biology and Anatomy, The University of Chicago, Chicago, Illinois, United States of America
- * E-mail:
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28
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Khare P, Mortimer SI, Cleto CL, Okamura K, Suzuki Y, Kusakabe T, Nakai K, Meedel TH, Hastings KEM. Cross-validated methods for promoter/transcription start site mapping in SL trans-spliced genes, established using the Ciona intestinalis troponin I gene. Nucleic Acids Res 2011; 39:2638-48. [PMID: 21109525 PMCID: PMC3074122 DOI: 10.1093/nar/gkq1151] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2010] [Revised: 10/22/2010] [Accepted: 10/25/2010] [Indexed: 11/12/2022] Open
Abstract
In conventionally-expressed eukaryotic genes, transcription start sites (TSSs) can be identified by mapping the mature mRNA 5'-terminal sequence onto the genome. However, this approach is not applicable to genes that undergo pre-mRNA 5'-leader trans-splicing (SL trans-splicing) because the original 5'-segment of the primary transcript is replaced by the spliced leader sequence during the trans-splicing reaction and is discarded. Thus TSS mapping for trans-spliced genes requires different approaches. We describe two such approaches and show that they generate precisely agreeing results for an SL trans-spliced gene encoding the muscle protein troponin I in the ascidian tunicate chordate Ciona intestinalis. One method is based on experimental deletion of trans-splice acceptor sites and the other is based on high-throughput mRNA 5'-RACE sequence analysis of natural RNA populations in order to detect minor transcripts containing the pre-mRNA's original 5'-end. Both methods identified a single major troponin I TSS located ∼460 nt upstream of the trans-splice acceptor site. Further experimental analysis identified a functionally important TATA element 31 nt upstream of the start site. The two methods employed have complementary strengths and are broadly applicable to mapping promoters/TSSs for trans-spliced genes in tunicates and in trans-splicing organisms from other phyla.
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Affiliation(s)
- Parul Khare
- Montreal Neurological Institute and Department of Biology, McGill University, 3801 University St., Montreal, Quebec, Canada H3A 2B4, Biology Department, Rhode Island College, Providence, RI 02908, USA, Human Genome Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo, 108-8639 and Department of Biology, Faculty of Science and Engineering, Konan Univeristy, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
| | - Sandra I. Mortimer
- Montreal Neurological Institute and Department of Biology, McGill University, 3801 University St., Montreal, Quebec, Canada H3A 2B4, Biology Department, Rhode Island College, Providence, RI 02908, USA, Human Genome Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo, 108-8639 and Department of Biology, Faculty of Science and Engineering, Konan Univeristy, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
| | - Cynthia L. Cleto
- Montreal Neurological Institute and Department of Biology, McGill University, 3801 University St., Montreal, Quebec, Canada H3A 2B4, Biology Department, Rhode Island College, Providence, RI 02908, USA, Human Genome Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo, 108-8639 and Department of Biology, Faculty of Science and Engineering, Konan Univeristy, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
| | - Kohji Okamura
- Montreal Neurological Institute and Department of Biology, McGill University, 3801 University St., Montreal, Quebec, Canada H3A 2B4, Biology Department, Rhode Island College, Providence, RI 02908, USA, Human Genome Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo, 108-8639 and Department of Biology, Faculty of Science and Engineering, Konan Univeristy, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
| | - Yutaka Suzuki
- Montreal Neurological Institute and Department of Biology, McGill University, 3801 University St., Montreal, Quebec, Canada H3A 2B4, Biology Department, Rhode Island College, Providence, RI 02908, USA, Human Genome Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo, 108-8639 and Department of Biology, Faculty of Science and Engineering, Konan Univeristy, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
| | - Takehiro Kusakabe
- Montreal Neurological Institute and Department of Biology, McGill University, 3801 University St., Montreal, Quebec, Canada H3A 2B4, Biology Department, Rhode Island College, Providence, RI 02908, USA, Human Genome Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo, 108-8639 and Department of Biology, Faculty of Science and Engineering, Konan Univeristy, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
| | - Kenta Nakai
- Montreal Neurological Institute and Department of Biology, McGill University, 3801 University St., Montreal, Quebec, Canada H3A 2B4, Biology Department, Rhode Island College, Providence, RI 02908, USA, Human Genome Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo, 108-8639 and Department of Biology, Faculty of Science and Engineering, Konan Univeristy, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
| | - Thomas H. Meedel
- Montreal Neurological Institute and Department of Biology, McGill University, 3801 University St., Montreal, Quebec, Canada H3A 2B4, Biology Department, Rhode Island College, Providence, RI 02908, USA, Human Genome Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo, 108-8639 and Department of Biology, Faculty of Science and Engineering, Konan Univeristy, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
| | - Kenneth E. M. Hastings
- Montreal Neurological Institute and Department of Biology, McGill University, 3801 University St., Montreal, Quebec, Canada H3A 2B4, Biology Department, Rhode Island College, Providence, RI 02908, USA, Human Genome Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokane-dai, Minato-ku, Tokyo, 108-8639 and Department of Biology, Faculty of Science and Engineering, Konan Univeristy, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
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Sardet C, McDougall A, Yasuo H, Chenevert J, Pruliere G, Dumollard R, Hudson C, Hebras C, Le Nguyen N, Paix A. Embryological methods in ascidians: the Villefranche-sur-Mer protocols. Methods Mol Biol 2011; 770:365-400. [PMID: 21805272 DOI: 10.1007/978-1-61779-210-6_14] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Ascidians (marine invertebrates: urochordates) are thought to be the closest sister groups of vertebrates. They are particularly attractive models because of their non-duplicated genome and the fast and synchronous development of large populations of eggs into simple tadpoles made of about 3,000 cells. As a result of stereotyped asymmetric cleavage patterns all blastomeres become fate restricted between the 16- and 110 cell stage through inheritance of maternal determinants and/or cellular interactions. These advantageous features have allowed advances in our understanding of the nature and role of maternal determinants, inductive interactions, and gene networks that are involved in cell lineage specification and differentiation of embryonic tissues. Ascidians have also contributed to our understanding of fertilization, cell cycle control, self-recognition, metamorphosis, and regeneration. In this chapter we provide basic protocols routinely used at the marine station in Villefranche-sur-Mer using the cosmopolitan species of reference Ciona intestinalis and the European species Phallusia mammillata. These two models present complementary advantages with regard to molecular, functional, and imaging approaches. We describe techniques for basic culture of embryos, micro-injection, in vivo labelling, micro-manipulations, fixation, and immuno-labelling. These methods allow analysis of calcium signals, reorganizations of cytoplasmic and cortical domains, meiotic and mitotic cell cycle and cleavages as well as the roles of specific genes and cellular interactions. Ascidians eggs and embryos are also an ideal material to isolate cortical fragments and to isolate and re-associate individual blastomeres. We detail the experimental manipulations which we have used to understand the structure and role of the egg cortex and of specific blastomeres during development.
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Affiliation(s)
- Christian Sardet
- Biologie du Développement, UMR 7009 CNRS/UPMC, Observatoire Océanologique, Villefranche sur Mer 06230, France.
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30
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Hendrix D, Levine M, Shi W. miRTRAP, a computational method for the systematic identification of miRNAs from high throughput sequencing data. Genome Biol 2010; 11:R39. [PMID: 20370911 PMCID: PMC2884542 DOI: 10.1186/gb-2010-11-4-r39] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Revised: 01/19/2010] [Accepted: 04/06/2010] [Indexed: 12/14/2022] Open
Abstract
A novel method for prediction of miRs from deep sequencing data. Its utility is demonstrated when applied to Ciona data. MicroRNAs (miRs) have been broadly implicated in animal development and disease. We developed a novel computational strategy for the systematic, whole-genome identification of miRs from high throughput sequencing information. This method, miRTRAP, incorporates the mechanisms of miR biogenesis and includes additional criteria regarding the prevalence and quality of small RNAs arising from the antisense strand and neighboring loci. This program was applied to the simple chordate Ciona intestinalis and identified nearly 400 putative miR loci.
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Affiliation(s)
- David Hendrix
- Department of Molecular and Cell Biology, Division of Genetics, Genomics and Development, Center for Integrative Genomics, University of California, Berkeley, 142 LSA#3200, Berkeley, CA 94720-3200, USA.
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31
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Abstract
Genomewide analyses of distances between orthologous gene pairs from the ascidian species Ciona intestinalis and Ciona savignyi were compared with those of vertebrates. Combining this data with a detailed and careful use of vertebrate fossil records, we estimated the time of divergence between the two ascidians nearly 180 My. This estimation was obtained after correcting for the different substitution rates found comparing several groups of chordates; indeed we determine here that on average Ciona species evolve 50% faster than vertebrates.
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32
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Drosophila P transposons of the urochordata Ciona intestinalis. Mol Genet Genomics 2009; 282:165-72. [PMID: 19424726 DOI: 10.1007/s00438-009-0453-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Accepted: 04/21/2009] [Indexed: 10/20/2022]
Abstract
P transposons belong to the eukaryotic DNA transposons, which are transposed by a cut and paste mechanism using a P-element-coded transposase. They have been detected in Drosophila, and reside as single copies and stable homologous sequences in many vertebrate species. We present the P elements Pcin1, Pcin2 and Pcin3 from Ciona intestinalis, a species of the most primitive chordates, and compare them with those from Ciona savignyi. They showed typical DNA transposon structures, namely terminal inverted repeats and target site duplications. The coding region of Pcin1 consisted of 13 small exons that could be translated into a P-transposon-homologous protein. C. intestinalis and C. savignyi displayed nearly the same phenotype. However, their P elements were highly divergent and the assumed P transposase from C. intestinalis was more closely related to the transposase from Drosophila melanogaster than to the transposase of C. savignyi. The present study showed that P elements with typical features of transposable DNA elements may be found already at the base of the chordate lineage.
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33
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Eisermann K, Tandon S, Bazarov A, Brett A, Fraizer G, Piontkivska H. Evolutionary conservation of zinc finger transcription factor binding sites in promoters of genes co-expressed with WT1 in prostate cancer. BMC Genomics 2008; 9:337. [PMID: 18631392 PMCID: PMC2515153 DOI: 10.1186/1471-2164-9-337] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Accepted: 07/16/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Gene expression analyses have led to a better understanding of growth control of prostate cancer cells. We and others have identified the presence of several zinc finger transcription factors in the neoplastic prostate, suggesting a potential role for these genes in the regulation of the prostate cancer transcriptome. One of the transcription factors (TFs) identified in the prostate cancer epithelial cells was the Wilms tumor gene (WT1). To rapidly identify coordinately expressed prostate cancer growth control genes that may be regulated by WT1, we used an in silico approach. RESULTS Evolutionary conserved transcription factor binding sites (TFBS) recognized by WT1, EGR1, SP1, SP2, AP2 and GATA1 were identified in the promoters of 24 differentially expressed prostate cancer genes from eight mammalian species. To test the relationship between sequence conservation and function, chromatin of LNCaP prostate cancer and kidney 293 cells were tested for TF binding using chromatin immunoprecipitation (ChIP). Multiple putative TFBS in gene promoters of placental mammals were found to be shared with those in human gene promoters and some were conserved between genomes that diverged about 170 million years ago (i.e., primates and marsupials), therefore implicating these sites as candidate binding sites. Among those genes coordinately expressed with WT1 was the kallikrein-related peptidase 3 (KLK3) gene commonly known as the prostate specific antigen (PSA) gene. This analysis located several potential WT1 TFBS in the PSA gene promoter and led to the rapid identification of a novel putative binding site confirmed in vivo by ChIP. Conversely for two prostate growth control genes, androgen receptor (AR) and vascular endothelial growth factor (VEGF), known to be transcriptionally regulated by WT1, regulatory sequence conservation was observed and TF binding in vivo was confirmed by ChIP. CONCLUSION Overall, this targeted approach rapidly identified important candidate WT1-binding elements in genes coordinately expressed with WT1 in prostate cancer cells, thus enabling a more focused functional analysis of the most likely target genes in prostate cancer progression. Identifying these genes will help to better understand how gene regulation is altered in these tumor cells.
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Affiliation(s)
- Kurtis Eisermann
- School of Biomedical Sciences, Kent State University, Kent, Ohio, USA.
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34
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Hill MM, Broman KW, Stupka E, Smith WC, Jiang D, Sidow A. The C. savignyi genetic map and its integration with the reference sequence facilitates insights into chordate genome evolution. Genome Res 2008; 18:1369-79. [PMID: 18519652 DOI: 10.1101/gr.078576.108] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The urochordate Ciona savignyi is an emerging model organism for the study of chordate evolution, development, and gene regulation. The extreme level of polymorphism in its population has inspired novel approaches in genome assembly, which we here continue to develop. Specifically, we present the reconstruction of all of C. savignyi's chromosomes via the development of a comprehensive genetic map, without a physical map intermediate. The resulting genetic map is complete, having one linkage group for each one of the 14 chromosomes. Eighty-three percent of the reference genome sequence is covered. The chromosomal reconstruction allowed us to investigate the evolution of genome structure in highly polymorphic species, by comparing the genome of C. savignyi to its divergent sister species, Ciona intestinalis. Both genomes have been extensively reshaped by intrachromosomal rearrangements. Interchromosomal changes have been extremely rare. This is in striking contrast to what has been observed in vertebrates, where interchromosomal events are commonplace. These results, when considered in light of the neutral theory, suggest fundamentally different modes of evolution of animal species with large versus small population sizes.
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Affiliation(s)
- Matthew M Hill
- Department of Pathology, SUMC, Stanford, CA 94305-5324, USA
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35
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Irvine SQ, Fonseca VC, Zompa MA, Antony R. Cis-regulatory organization of the Pax6 gene in the ascidian Ciona intestinalis. Dev Biol 2008; 317:649-59. [PMID: 18342846 DOI: 10.1016/j.ydbio.2008.01.036] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Revised: 01/17/2008] [Accepted: 01/19/2008] [Indexed: 10/22/2022]
Abstract
The Pax6 gene has attracted intense research interest due to its apparently important role in the development of eyes and the central nervous system (CNS) in many animal groups. Pax6 is also of interest for comparative genomics since it has not been duplicated in tetrapods, making for a direct orthology between the Ciona intestinalis gene CiPax6 and Pax6 in mammals. CiPax6 has been shown to be expressed in the anterior brain, caudal nerve cord, and in parts of the brain associated with the photoreceptive ocellus. This information was extended here using in-situ hybridization, and shows that CiPax6 transcripts mark the lateral regions of the nerve cord, remarkably similar to Pax6 expression in the mouse. As a means of dissecting the cis-regulation of CiPax6 we tested 8 kb of sequence using transient reporter transgene assays. Three separate regions were found that work together to drive the overall CiPax6 expression pattern. A 211 bp sequence 2 kb upstream of the first exon was found to be a major enhancer driving expression in the sensory vesicle (the anterior portion of the ascidian brain). Other upstream sequences were shown to work with the sensory vesicle enhancer to drive expression in the remainder of the CNS. An "eye enhancer" was localized to the first intron, which controls specific expression in the central portion of the sensory vesicle, including photoreceptor cells. The fourth intron was found to repress ectopic expression of the reporter gene in middle portions of the embryonic brain. Aspects of this overall regulatory organization are similar to the organization of the Pax6 homologs in mice and Drosophila, particularly the presence of intronic elements driving expression in the eye, brain and nerve cord.
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Affiliation(s)
- Steven Q Irvine
- Department of Biological Sciences, University of Rhode Island, 100 Flagg Road, Kingston, RI 02840, USA.
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36
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Norden-Krichmar TM, Holtz J, Pasquinelli AE, Gaasterland T. Computational prediction and experimental validation of Ciona intestinalis microRNA genes. BMC Genomics 2007; 8:445. [PMID: 18047675 PMCID: PMC2243180 DOI: 10.1186/1471-2164-8-445] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Accepted: 11/29/2007] [Indexed: 12/26/2022] Open
Abstract
Background This study reports the first collection of validated microRNA genes in the sea squirt, Ciona intestinalis. MicroRNAs are processed from hairpin precursors to ~22 nucleotide RNAs that base pair to target mRNAs and inhibit expression. As a member of the subphylum Urochordata (Tunicata) whose larval form has a notochord, the sea squirt is situated at the emergence of vertebrates, and therefore may provide information about the evolution of molecular regulators of early development. Results In this study, computational methods were used to predict 14 microRNA gene families in Ciona intestinalis. The microRNA prediction algorithm utilizes configurable microRNA sequence conservation and stem-loop specificity parameters, grouping by miRNA family, and phylogenetic conservation to the related species, Ciona savignyi. The expression for 8, out of 9 attempted, of the putative microRNAs in the adult tissue of Ciona intestinalis was validated by Northern blot analyses. Additionally, a target prediction algorithm was implemented, which identified a high confidence list of 240 potential target genes. Over half of the predicted targets can be grouped into the gene ontology categories of metabolism, transport, regulation of transcription, and cell signaling. Conclusion The computational techniques implemented in this study can be applied to other organisms and serve to increase the understanding of the origins of non-coding RNAs, embryological and cellular developmental pathways, and the mechanisms for microRNA-controlled gene regulatory networks.
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Affiliation(s)
- Trina M Norden-Krichmar
- Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, MSC 0202, La Jolla, CA 92093 USA.
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37
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Brown CD, Johnson DS, Sidow A. Functional architecture and evolution of transcriptional elements that drive gene coexpression. Science 2007; 317:1557-60. [PMID: 17872446 DOI: 10.1126/science.1145893] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Transcriptional coexpression of interacting gene products is required for complex molecular processes; however, the function and evolution of cis-regulatory elements that orchestrate coexpression remain largely unexplored. We mutagenized 19 regulatory elements that drive coexpression of Ciona muscle genes and obtained quantitative estimates of the cis-regulatory activity of the 77 motifs that comprise these elements. We found that individual motif activity ranges broadly within and among elements, and among different instantiations of the same motif type. The activity of orthologous motifs is strongly constrained, although motif arrangement, type, and activity vary greatly among the elements of different co-regulated genes. Thus, the syntactical rules governing this regulatory function are flexible but become highly constrained evolutionarily once they are established in a particular element.
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Affiliation(s)
- Christopher D Brown
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA
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38
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Yoshida R, Horie T, Tsuda M, Kusakabe TG. Comparative genomics identifies a cis-regulatory module that activates transcription in specific subsets of neurons in Ciona intestinalis larvae. Dev Growth Differ 2007; 49:657-67. [PMID: 17711474 DOI: 10.1111/j.1440-169x.2007.00960.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The larval nervous system of the ascidian Ciona intestinalis exhibits an abstract form of the vertebrate nervous system. The Ci-Galphai1 gene, which encodes a G-protein alpha subunit, is specifically expressed in distinct sets of neurons in C. intestinalis larvae, including papillar neurons of the adhesive organ, ocellus photoreceptor cells, and cholinergic and GABAergic neurons in the central nervous system (CNS). A GFP reporter gene driven by the 4.2-kb 5' flanking region of Ci-Galphai1 recapitulated the endogenous gene expression patterns. Comparative genomic analysis of the Galphai1 gene between C. intestinalis and Ciona savignyi identified an 87-bp highly conserved non-coding sequence located between -3176 and -3090 bp upstream of the gene. Deletion of this conserved upstream sequence resulted in the complete loss of reporter expression in the central nervous system, while reporter expression in the adhesive organ and mesenchyme cells remained unaffected. The conserved upstream sequence can activate gene expression from basal promoters in the brain vesicle, although it requires additional cis-regulatory sequences to fully activate the CNS-specific gene expression. These results suggest that different types of central neurons share a common transcriptional activation mechanism that is different from that of papillar neurons.
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Affiliation(s)
- Reiko Yoshida
- Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako-gun, Hyogo 678-1297, Japan
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39
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Alfano C, Teresa Russo M, Spagnuolo A. Developmental expression and transcriptional regulation of Ci-Pans, a novel neural marker gene of the ascidian, Ciona intestinalis. Gene 2007; 406:36-41. [PMID: 17616447 DOI: 10.1016/j.gene.2007.05.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Revised: 05/11/2007] [Accepted: 05/18/2007] [Indexed: 11/23/2022]
Abstract
A novel gene, named Ci-Pans, was isolated and characterized from the ascidian Ciona intestinalis. It is an 885-bp cDNA, is thought to encode a protein with no sequence similarities to known proteins and shows a spatial and temporal specific expression pattern. In fact, besides a transient early localization in the muscle precursors, it is expressed in a dynamic fashion in the nervous system, during C. intestinalis embryogenesis, reaching very high level of expression as the development proceeds. To study Ci-Pans transcriptional control, we isolated the predicted promoter region of C. intestinalis Ci-Pans using databases for this species. Analysis of transgenic embryos, with a green fluorescence protein (GFP) reporter, showed that approximately 1 kb of the 5'-flanking sequence of the Ci-Pans gene was implicated in its specific expression in the CNS. The data on the expression pattern of Ci-Pans together with the strong activity exhibited by the 1 kb promoter region we have identified, indicate that a more deeply investigation on Ci-Pans could provide clues for exploring the complex network of nervous system-specific genes.
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Affiliation(s)
- Christian Alfano
- Laboratory of Biochemistry and Molecular Biology, Stazione Zoologica A. Dohrn, Villa Comunale, 80121, Naples, Italy
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40
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Kim JH, Waterman MS, Li LM. Diploid genome reconstruction of Ciona intestinalis and comparative analysis with Ciona savignyi. Genome Res 2007; 17:1101-10. [PMID: 17567986 PMCID: PMC1899121 DOI: 10.1101/gr.5894107] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
One of the main goals in genome sequencing projects is to determine a haploid consensus sequence even when clone libraries are constructed from homologous chromosomes. However, it has been noticed that haplotypes can be inferred from genome assemblies by investigating phase conservation in sequenced reads. In this study, we seek to infer haplotypes, a diploid consensus sequence, from the genome assembly of an organism, Ciona intestinalis. The Ciona intestinalis genome is an ideal resource from which haplotypes can be inferred because of the high polymorphism rate (1.2%). The haplotype estimation scheme consists of polymorphism detection and phase estimation. The core step of our method is a Gibbs sampling procedure. The mate-pair information from two-end sequenced clone inserts is exploited to provide long-range continuity. We estimate the polymorphism rate of Ciona intestinalis to be 1.2% and 1.5%, according to two different polymorphism counting schemes. The distribution of heterozygosity number is well fit by a compound Poisson distribution. The N50 length of haplotype segments is 37.9 kb in our assembly, while the N50 scaffold length of the Ciona intestinalis assembly is 190 kb. We also infer diploid gene sequences from haplotype segments. According to our reconstruction, 85.4% of predicted gene sequences are continuously covered by single haplotype segments. Our results indicate 97% accuracy in haplotype estimation, based on a simulated data set. We conduct a comparative analysis with Ciona savignyi, and discover interesting patterns of conserved DNA elements in chordates.
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Affiliation(s)
- Jong Hyun Kim
- Department of Computer Science, Yonsei University, Seoul, Republic of Korea.
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41
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Small KS, Brudno M, Hill MM, Sidow A. A haplome alignment and reference sequence of the highly polymorphic Ciona savignyi genome. Genome Biol 2007; 8:R41. [PMID: 17374142 PMCID: PMC1868934 DOI: 10.1186/gb-2007-8-3-r41] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Revised: 02/15/2007] [Accepted: 03/20/2007] [Indexed: 01/11/2023] Open
Abstract
The high degree of polymorphism in the genome of the sea squirt Ciona savignyi complicated the assembly of sequence contigs, but a new alignment method results in a much improved sequence. The sequence of Ciona savignyi was determined using a whole-genome shotgun strategy, but a high degree of polymorphism resulted in a fractured assembly wherein allelic sequences from the same genomic region assembled separately. We designed a multistep strategy to generate a nonredundant reference sequence from the original assembly by reconstructing and aligning the two 'haplomes' (haploid genomes). In the resultant 174 megabase reference sequence, each locus is represented once, misassemblies are corrected, and contiguity and continuity are dramatically improved.
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Affiliation(s)
- Kerrin S Small
- Departments of Pathology and of Genetics, Stanford University Medical Center, 300 Pasteur Drive, Stanford, California 94305-5324, USA
| | - Michael Brudno
- Department of Computer Science, Banting and Best Department of Medical Research, University of Toronto, Toronto, 6 King's College Rd, Ontario, M5S 3G4, Canada
| | - Matthew M Hill
- Departments of Pathology and of Genetics, Stanford University Medical Center, 300 Pasteur Drive, Stanford, California 94305-5324, USA
| | - Arend Sidow
- Departments of Pathology and of Genetics, Stanford University Medical Center, 300 Pasteur Drive, Stanford, California 94305-5324, USA
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42
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Kuraku S, Kuratani S. Time scale for cyclostome evolution inferred with a phylogenetic diagnosis of hagfish and lamprey cDNA sequences. Zoolog Sci 2007; 23:1053-64. [PMID: 17261918 DOI: 10.2108/zsj.23.1053] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Cyclostomata consists of the two orders Myxiniformes (hagfishes) and Petromyzoniformes (lampreys), and its monophyly has been unequivocally supported by recent molecular phylogenetic studies. Under this updated vertebrate phylogeny, we performed in silico evolutionary analyses using currently available cDNA sequences of cyclostomes. We first calculated the GC-content at four-fold degenerate sites (GC(4)), which revealed that an extremely high GC-content is shared by all the lamprey species we surveyed, whereas no striking pattern in GC-content was observed in any of the hagfish species surveyed. We then estimated the timing of diversification in cyclostome evolution using nucleotide and amino acid sequences. We obtained divergence times of 470-390 million years ago (Mya) in the Ordovician-Silurian-Devonian Periods for the interordinal split between Myxiniformes and Petromyzoniformes; 90-60 Mya in the Cretaceous-Tertiary Periods for the split between the two hagfish subfamilies, Myxininae and Eptatretinae; 280-220 Mya in the Permian-Triassic Periods for the split between the two lamprey subfamilies, Geotriinae and Petromyzoninae; and 30-10 Mya in the Tertiary Period for the split between the two lamprey genera, Petromyzon and Lethenteron. This evolutionary configuration indicates that Myxiniformes and Petromyzoniformes diverged shortly after the common ancestor of cyclostomes split from the future gnathostome lineage. Our results also suggest that intra-subfamilial diversification in hagfish and lamprey lineages (especially those distributed in the northern hemisphere) occurred in the Cretaceous or Tertiary Periods.
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Affiliation(s)
- Shigehiro Kuraku
- Laboratory for Evolutionary Morphology, RIKEN Center for Developmental Biology, Kobe 650-0047, Japan.
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43
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Meedel TH, Chang P, Yasuo H. Muscle development in Ciona intestinalis requires the b-HLH myogenic regulatory factor gene Ci-MRF. Dev Biol 2007; 302:333-44. [PMID: 17055476 PMCID: PMC1797879 DOI: 10.1016/j.ydbio.2006.09.043] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2006] [Revised: 09/22/2006] [Accepted: 09/22/2006] [Indexed: 11/21/2022]
Abstract
The activity of myogenic regulatory factor (MRF) genes is essential for vertebrate muscle development, whereas invertebrate muscle development is largely independent of MRF function. This difference indicates that myogenesis is controlled by distinct regulatory mechanisms in these two groups of animals. Here we used overexpression and gene knockdown to investigate the role in embryonic myogenesis of the single MRF gene of the invertebrate chordate Ciona intestinalis (Ci-MRF). Injection of Ci-MRF mRNA into eggs resulted in increased embryonic muscle-specific gene activity and revealed the myogenic activity of Ci-MRF by inducing the expression of four muscle marker genes, Acetylcholinesterase, Actin, Troponin I, and Myosin Light Chain in non-muscle lineages. Conversely, inhibiting Ci-MRF activity with antisense morpholinos down-regulated the expression of these genes. Consistent with the effects of morpholinos on muscle gene activity, larvae resulting from morpholino injection were paralyzed and their "muscle" cells lacked myofibrils. We conclude that Ci-MRF is required for larval tail muscle development and thus that an MRF-dependent myogenic regulatory network probably existed in the ancestor of tunicates and vertebrates. This possibility raises the question of whether the earliest myogenic regulatory networks were MRF-dependent or MRF-independent.
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Affiliation(s)
- Thomas H Meedel
- Department of Biology, Rhode Island College, Providence, RI, USA.
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Abstract
The primitive chordate Ciona intestinalis has emerged as a significant model system for the study of heart development. The Ciona embryo employs a conserved heart gene network in the context of extremely low cell numbers and reduced genetic redundancy. Here, I review recent studies on the molecular genetics of Ciona cardiogenesis as well as classic work on heart anatomy and physiology. I also discuss the potential of employing Ciona to decipher a comprehensive chordate gene network and to determine how this network controls heart morphogenesis.
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Affiliation(s)
- Brad Davidson
- Department of Molecular and Cellular Biology, Division of Genetics & Development, University of California, Berkeley, CA 94720, United States.
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Wang H, Zhang Y, Cheng Y, Zhou Y, King DC, Taylor J, Chiaromonte F, Kasturi J, Petrykowska H, Gibb B, Dorman C, Miller W, Dore LC, Welch J, Weiss MJ, Hardison RC. Experimental validation of predicted mammalian erythroid cis-regulatory modules. Genes Dev 2006; 16:1480-92. [PMID: 17038566 PMCID: PMC1665632 DOI: 10.1101/gr.5353806] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2006] [Accepted: 06/07/2006] [Indexed: 11/25/2022]
Abstract
Multiple alignments of genome sequences are helpful guides to functional analysis, but predicting cis-regulatory modules (CRMs) accurately from such alignments remains an elusive goal. We predict CRMs for mammalian genes expressed in red blood cells by combining two properties gleaned from aligned, noncoding genome sequences: a positive regulatory potential (RP) score, which detects similarity to patterns in alignments distinctive for regulatory regions, and conservation of a binding site motif for the essential erythroid transcription factor GATA-1. Within eight target loci, we tested 75 noncoding segments by reporter gene assays in transiently transfected human K562 cells and/or after site-directed integration into murine erythroleukemia cells. Segments with a high RP score and a conserved exact match to the binding site consensus are validated at a good rate (50%-100%, with rates increasing at higher RP), whereas segments with lower RP scores or nonconsensus binding motifs tend to be inactive. Active DNA segments were shown to be occupied by GATA-1 protein by chromatin immunoprecipitation, whereas sites predicted to be inactive were not occupied. We verify four previously known erythroid CRMs and identify 28 novel ones. Thus, high RP in combination with another feature of a CRM, such as a conserved transcription factor binding site, is a good predictor of functional CRMs. Genome-wide predictions based on RP and a large set of well-defined transcription factor binding sites are available through servers at http://www.bx.psu.edu/.
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Affiliation(s)
- Hao Wang
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Department of Biochemistry and Molecular Biology
| | - Ying Zhang
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Intercollege Graduate Degree Program in Genetics
| | - Yong Cheng
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Department of Biochemistry and Molecular Biology
| | - Yuepin Zhou
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Department of Biochemistry and Molecular Biology
| | - David C. King
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Intercollege Graduate Degree Program in Integrative Biosciences
| | - James Taylor
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Department of Computer Science and Engineering
| | - Francesca Chiaromonte
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Department of Statistics, and
| | - Jyotsna Kasturi
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Department of Computer Science and Engineering
| | - Hanna Petrykowska
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Department of Biochemistry and Molecular Biology
| | - Brian Gibb
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Department of Biochemistry and Molecular Biology
| | - Christine Dorman
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Department of Biochemistry and Molecular Biology
| | - Webb Miller
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Department of Computer Science and Engineering
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Louis C. Dore
- Department of Pediatrics, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
| | - John Welch
- Department of Pediatrics, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
| | - Mitchell J. Weiss
- Department of Pediatrics, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
| | - Ross C. Hardison
- Center for Comparative Genomics and Bioinformatics of the Huck Institutes of Life Sciences
- Department of Biochemistry and Molecular Biology
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Huntingtin gene evolution in Chordata and its peculiar features in the ascidian Ciona genus. BMC Genomics 2006; 7:288. [PMID: 17092333 PMCID: PMC1636649 DOI: 10.1186/1471-2164-7-288] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Accepted: 11/08/2006] [Indexed: 01/20/2023] Open
Abstract
Background To gain insight into the evolutionary features of the huntingtin (htt) gene in Chordata, we have sequenced and characterized the full-length htt mRNA in the ascidian Ciona intestinalis, a basal chordate emerging as new invertebrate model organism. Moreover, taking advantage of the availability of genomic and EST sequences, the htt gene structure of a number of chordate species, including the cogeneric ascidian Ciona savignyi, and the vertebrates Xenopus and Gallus was reconstructed. Results The C. intestinalis htt transcript exhibits some peculiar features, such as spliced leader trans-splicing in the 98 nt-long 5' untranslated region (UTR), an alternative splicing in the coding region, eight alternative polyadenylation sites, and no similarities of both 5' and 3'UTRs compared to homologs of the cogeneric C. savignyi. The predicted protein is 2946 amino acids long, shorter than its vertebrate homologs, and lacks the polyQ and the polyP stretches found in the the N-terminal regions of mammalian homologs. The exon-intron organization of the htt gene is almost identical among vertebrates, and significantly conserved between Ciona and vertebrates, allowing us to hypothesize an ancestral chordate gene consisting of at least 40 coding exons. Conclusion During chordate diversification, events of gain/loss, sliding, phase changes, and expansion of introns occurred in both vertebrate and ascidian lineages predominantly in the 5'-half of the htt gene, where there is also evidence of lineage-specific evolutionary dynamics in vertebrates. On the contrary, the 3'-half of the gene is highly conserved in all chordates at the level of both gene structure and protein sequence. Between the two Ciona species, a fast evolutionary rate and/or an early divergence time is suggested by the absence of significant similarity between UTRs, protein divergence comparable to that observed between mammals and fishes, and different distribution of repetitive elements.
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Sherwood NM, Tello JA, Roch GJ. Neuroendocrinology of protochordates: Insights from Ciona genomics. Comp Biochem Physiol A Mol Integr Physiol 2006; 144:254-71. [PMID: 16413805 DOI: 10.1016/j.cbpa.2005.11.013] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 11/07/2005] [Accepted: 11/10/2005] [Indexed: 11/17/2022]
Abstract
The genome for two species of Ciona is available making these tunicates excellent models for studies on the evolution of the chordates. In this review most of the data is from Ciona intestinalis, as the annotation of the C. savignyi genome is not yet available. The phylogenetic position of tunicates at the origin of the chordates and the nature of the genome before expansion in vertebrates allows tunicates to be used as a touchstone for understanding genes that either preceded or arose in vertebrates. A comparison of Ciona, a sea squirt, to other model organisms such as a nematode, fruit fly, zebrafish, frog, chicken and mouse shows that Ciona has many useful traits including accessibility for embryological, lineage tracing, forward genetics, and loss- or gain-of-function experiments. For neuroendocrine studies, these traits are important for determining gene function, whereas the availability of the genome is critical for identification of ligands, receptors, transcription factors and signaling pathways. Four major neurohormones and their receptors have been identified by cloning and to some extent by function in Ciona: gonadotropin-releasing hormone, insulin, insulin-like growth factor, and cionin, a member of the CCK/gastrin family. The simplicity of tunicates should be an advantage in searching for novel functions for these hormones. Other neuroendocrine components that have been annotated in the genome are a multitude of receptors, which are available for cloning, expression and functional studies.
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Affiliation(s)
- Nancy M Sherwood
- Department of Biology, University of Victoria, Victoria, B.C., Canada V8W 3N5.
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Shoguchi E, Kawashima T, Satou Y, Hamaguchi M, Sin-I T, Kohara Y, Putnam N, Rokhsar DS, Satoh N. Chromosomal mapping of 170 BAC clones in the ascidian Ciona intestinalis. Genes Dev 2006; 16:297-303. [PMID: 16354750 PMCID: PMC1361726 DOI: 10.1101/gr.4156606] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2005] [Accepted: 10/23/2005] [Indexed: 11/25/2022]
Abstract
The draft genome ( approximately 160 Mb) of the urochordate ascidian Ciona intestinalis has been sequenced by the whole-genome shotgun method and should provide important insights into the origin and evolution of chordates as well as vertebrates. However, because this genomic data has not yet been mapped onto chromosomes, important biological questions including regulation of gene expression at the genome-wide level cannot yet be addressed. Here, we report the molecular cytogenetic characterization of all 14 pairs of C. intestinalis chromosomes, as well as initial large-scale mapping of genomic sequences onto chromosomes by fluorescent in situ hybridization (FISH). Two-color FISH using 170 bacterial artificial chromosome (BAC) clones and construction of joined scaffolds using paired BAC end sequences allowed for mapping of up to 65% of the deduced 117-Mb nonrepetitive sequence onto chromosomes. This map lays the foundation for future studies of the protochordate C. intestinalis genome at the chromosomal level.
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Affiliation(s)
- Eiichi Shoguchi
- Department of Zoology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
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Zeller RW, Weldon DS, Pellatiro MA, Cone AC. Optimized green fluorescent protein variants provide improved single cell resolution of transgene expression in ascidian embryos. Dev Dyn 2006; 235:456-67. [PMID: 16287050 DOI: 10.1002/dvdy.20644] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The green fluorescent protein (GFP) is used extensively to monitor gene expression and protein localization in living cells, particularly in developing embryos from a variety of species. Several GFP mutations have been characterized that improve protein expression and alter the emission spectra to produce proteins that emit green, blue, cyan, and yellow wavelengths. DsRed and its variants encode proteins that emit in the orange to red wavelengths. Many of these commercially available fluorescent proteins have been "codon optimized" for maximal levels of expression in mammalian cells. We have generated several fluorescent protein color variants that have been codon optimized for maximal expression in the ascidian Ciona intestinalis. By analyzing quantitative time-lapse recordings of transgenic embryos, we demonstrate that, in general, our Ciona optimized variants are detected and expressed at higher levels than commercially available fluorescent proteins. We show that three of these proteins, expressed simultaneously in different spatial domains within the same transgenic embryo are easily detectable using optimized fluorescent filter sets for epifluorescent microscopy. Coupled with recently developed quantitative imaging techniques, our GFP variants should provide useful reagents for monitoring the simultaneous expression of multiple genes in transgenic ascidian embryos.
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Affiliation(s)
- Robert W Zeller
- Molecular Biology Institute and Coastal and Marine Institute, San Diego State University, San Diego, California 92182-4614, USA.
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50
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Abstract
Setting up future body axes is the first important event before and at the beginning of embryogenesis. The ascidian embryo is a classic model that has been used to gain insight into developmental processes for over a century. This review summarizes advances made in this decade in our understanding of the developmental processes involved in the specification of the embryonic axes and cell fates during early ascidian embryogenesis. Maternal factors, including mRNAs, are translocated to specific regions of the egg by cytoplasmic and cortical reorganization, so-called ooplasmic segregation, and specify the animal-vegetal axis and the one perpendicular to it, which is defined as the anteroposterior axis in ascidians. Some postplasmic/PEM RNAs that are anchored to cortical endoplasmic reticulum are brought to the future posterior pole of fertilized eggs, and play crucial roles in posterior development. Following specification of the animal-vegetal axis, nuclear localization of beta-catenin takes place in the vegetal blastomeres; this occurrence is important for the acquisition of the vegetal character of the blastomeres in later development. Positioning of these maternal factors lead to subsequent cell interactions and zygotic gene expression responsible for axis establishment and for cell fate specification. We describe how endoderm blastomeres in the vegetal pole region emanate inductive signals mainly attributable to fibroblast growth factor. Marginal blastomeres next to endoderm blastomeres respond differently in ways that are determined by intrinsic competence factors. Expression patterns of developmentally important genes, including key transcription factors of each tissue type, are also summarized.
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Affiliation(s)
- Hiroki Nishida
- Department of Biology, Graduate School of Science, Osaka University, Osaka, Japan.
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