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Destain H, Prahlad M, Kratsios P. Maintenance of neuronal identity in C. elegans and beyond: Lessons from transcription and chromatin factors. Semin Cell Dev Biol 2024; 154:35-47. [PMID: 37438210 PMCID: PMC10592372 DOI: 10.1016/j.semcdb.2023.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 06/30/2023] [Accepted: 07/01/2023] [Indexed: 07/14/2023]
Abstract
Neurons are remarkably long-lived, non-dividing cells that must maintain their functional features (e.g., electrical properties, chemical signaling) for extended periods of time - decades in humans. How neurons accomplish this incredible feat is poorly understood. Here, we review recent advances, primarily in the nematode C. elegans, that have enhanced our understanding of the molecular mechanisms that enable post-mitotic neurons to maintain their functionality across different life stages. We begin with "terminal selectors" - transcription factors necessary for the establishment and maintenance of neuronal identity. We highlight new findings on five terminal selectors (CHE-1 [Glass], UNC-3 [Collier/Ebf1-4], LIN-39 [Scr/Dfd/Hox4-5], UNC-86 [Acj6/Brn3a-c], AST-1 [Etv1/ER81]) from different transcription factor families (ZNF, COE, HOX, POU, ETS). We compare the functions of these factors in specific neuron types of C. elegans with the actions of their orthologs in other invertebrate (D. melanogaster) and vertebrate (M. musculus) systems, highlighting remarkable functional conservation. Finally, we reflect on recent findings implicating chromatin-modifying proteins, such as histone methyltransferases and Polycomb proteins, in the control of neuronal terminal identity. Altogether, these new studies on transcription factors and chromatin modifiers not only shed light on the fundamental problem of neuronal identity maintenance, but also outline mechanistic principles of gene regulation that may operate in other long-lived, post-mitotic cell types.
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Affiliation(s)
- Honorine Destain
- Department of Neurobiology, University of Chicago, Chicago, IL, USA; Committee on Development, Regeneration and Stem Cell Biology, University of Chicago, Chicago, IL, USA; University of Chicago Neuroscience Institute, Chicago, IL, USA
| | - Manasa Prahlad
- Department of Neurobiology, University of Chicago, Chicago, IL, USA; Committee on Genetics, Genomics, and Systems Biology, University of Chicago, Chicago, IL, USA; University of Chicago Neuroscience Institute, Chicago, IL, USA
| | - Paschalis Kratsios
- Department of Neurobiology, University of Chicago, Chicago, IL, USA; Committee on Development, Regeneration and Stem Cell Biology, University of Chicago, Chicago, IL, USA; Committee on Genetics, Genomics, and Systems Biology, University of Chicago, Chicago, IL, USA; University of Chicago Neuroscience Institute, Chicago, IL, USA.
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2
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Smith JJ, Kratsios P. Hox gene functions in the C. elegans nervous system: From early patterning to maintenance of neuronal identity. Semin Cell Dev Biol 2024; 152-153:58-69. [PMID: 36496326 PMCID: PMC10244487 DOI: 10.1016/j.semcdb.2022.11.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 11/14/2022] [Accepted: 11/30/2022] [Indexed: 12/12/2022]
Abstract
The nervous system emerges from a series of genetic programs that generate a remarkable array of neuronal cell types. Each cell type must acquire a distinct anatomical position, morphology, and function, enabling the generation of specialized circuits that drive animal behavior. How are these diverse cell types and circuits patterned along the anterior-posterior (A-P) axis of the animal body? Hox genes encode transcription factors that regulate cell fate and patterning events along the A-P axis of the nervous system. While most of our understanding of Hox-mediated control of neuronal development stems from studies in segmented animals like flies, mice, and zebrafish, important new themes are emerging from work in a non-segmented animal: the nematode Caenorhabditis elegans. Studies in C. elegans support the idea that Hox genes are needed continuously and across different life stages in the nervous system; they are not only required in dividing progenitor cells, but also in post-mitotic neurons during development and adult life. In C. elegans embryos and young larvae, Hox genes control progenitor cell specification, cell survival, and neuronal migration, consistent with their neural patterning roles in other animals. In late larvae and adults, C. elegans Hox genes control neuron type-specific identity features critical for neuronal function, thereby extending the Hox functional repertoire beyond early patterning. Here, we provide a comprehensive review of Hox studies in the C. elegans nervous system. To relate to readers outside the C. elegans community, we highlight conserved roles of Hox genes in patterning the nervous system of invertebrate and vertebrate animals. We end by calling attention to new functions in adult post-mitotic neurons for these paradigmatic regulators of cell fate.
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Affiliation(s)
- Jayson J Smith
- Department of Neurobiology, University of Chicago, 947 East 58th Street, Chicago, IL 60637, USA; University of Chicago Neuroscience Institute, 947 East 58th Street, Chicago, IL 60637, USA.
| | - Paschalis Kratsios
- Department of Neurobiology, University of Chicago, 947 East 58th Street, Chicago, IL 60637, USA; University of Chicago Neuroscience Institute, 947 East 58th Street, Chicago, IL 60637, USA.
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3
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Quesnelle DC, Bendena WG, Chin-Sang ID. A Compilation of the Diverse miRNA Functions in Caenorhabditis elegans and Drosophila melanogaster Development. Int J Mol Sci 2023; 24:ijms24086963. [PMID: 37108126 PMCID: PMC10139094 DOI: 10.3390/ijms24086963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 04/05/2023] [Accepted: 04/07/2023] [Indexed: 04/29/2023] Open
Abstract
MicroRNAs are critical regulators of post-transcriptional gene expression in a wide range of taxa, including invertebrates, mammals, and plants. Since their discovery in the nematode, Caenorhabditis elegans, miRNA research has exploded, and they are being identified in almost every facet of development. Invertebrate model organisms, particularly C. elegans, and Drosophila melanogaster, are ideal systems for studying miRNA function, and the roles of many miRNAs are known in these animals. In this review, we compiled the functions of many of the miRNAs that are involved in the development of these invertebrate model species. We examine how gene regulation by miRNAs shapes both embryonic and larval development and show that, although many different aspects of development are regulated, several trends are apparent in the nature of their regulation.
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Affiliation(s)
| | - William G Bendena
- Department of Biology, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Ian D Chin-Sang
- Department of Biology, Queen's University, Kingston, ON K7L 3N6, Canada
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4
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Gaunt SJ. Seeking Sense in the Hox Gene Cluster. J Dev Biol 2022; 10:jdb10040048. [PMID: 36412642 PMCID: PMC9680502 DOI: 10.3390/jdb10040048] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 10/31/2022] [Accepted: 11/09/2022] [Indexed: 11/18/2022] Open
Abstract
The Hox gene cluster, responsible for patterning of the head-tail axis, is an ancestral feature of all bilaterally symmetrical animals (the Bilateria) that remains intact in a wide range of species. We can say that the Hox cluster evolved successfully only once since it is commonly the same in all groups, with labial-like genes at one end of the cluster expressed in the anterior embryo, and Abd-B-like genes at the other end of the cluster expressed posteriorly. This review attempts to make sense of the Hox gene cluster and to address the following questions. How did the Hox cluster form in the protostome-deuterostome last common ancestor, and why was this with a particular head-tail polarity? Why is gene clustering usually maintained? Why is there collinearity between the order of genes along the cluster and the positions of their expressions along the embryo? Why do the Hox gene expression domains overlap along the embryo? Why have vertebrates duplicated the Hox cluster? Why do Hox gene knockouts typically result in anterior homeotic transformations? How do animals adapt their Hox clusters to evolve new structural patterns along the head-tail axis?
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Affiliation(s)
- Stephen J Gaunt
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
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5
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Murray JI, Preston E, Crawford JP, Rumley JD, Amom P, Anderson BD, Sivaramakrishnan P, Patel SD, Bennett BA, Lavon TD, Hsiao E, Peng F, Zacharias AL. The anterior Hox gene ceh-13 and elt-1/GATA activate the posterior Hox genes nob-1 and php-3 to specify posterior lineages in the C. elegans embryo. PLoS Genet 2022; 18:e1010187. [PMID: 35500030 PMCID: PMC9098060 DOI: 10.1371/journal.pgen.1010187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 05/12/2022] [Accepted: 04/04/2022] [Indexed: 12/18/2022] Open
Abstract
Hox transcription factors play a conserved role in specifying positional identity during animal development, with posterior Hox genes typically repressing the expression of more anterior Hox genes. Here, we dissect the regulation of the posterior Hox genes nob-1 and php-3 in the nematode C. elegans. We show that nob-1 and php-3 are co-expressed in gastrulation-stage embryos in cells that previously expressed the anterior Hox gene ceh-13. This expression is controlled by several partially redundant transcriptional enhancers. These enhancers act in a ceh-13-dependant manner, providing a striking example of an anterior Hox gene positively regulating a posterior Hox gene. Several other regulators also act positively through nob-1/php-3 enhancers, including elt-1/GATA, ceh-20/ceh-40/Pbx, unc-62/Meis, pop-1/TCF, ceh-36/Otx, and unc-30/Pitx. We identified defects in both cell position and cell division patterns in ceh-13 and nob-1;php-3 mutants, suggesting that these factors regulate lineage identity in addition to positional identity. Together, our results highlight the complexity and flexibility of Hox gene regulation and function and the ability of developmental transcription factors to regulate different targets in different stages of development.
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Affiliation(s)
- John Isaac Murray
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Elicia Preston
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Jeremy P. Crawford
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, United States of America
| | - Jonathan D. Rumley
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Prativa Amom
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, United States of America
| | - Breana D. Anderson
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, United States of America
| | - Priya Sivaramakrishnan
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Shaili D. Patel
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Barrington Alexander Bennett
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Teddy D. Lavon
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Erin Hsiao
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, United States of America
| | - Felicia Peng
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Amanda L. Zacharias
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, United States of America
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
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Bridoux L, Gofflot F, Rezsohazy R. HOX Protein Activity Regulation by Cellular Localization. J Dev Biol 2021; 9:jdb9040056. [PMID: 34940503 PMCID: PMC8707151 DOI: 10.3390/jdb9040056] [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: 10/31/2021] [Revised: 11/29/2021] [Accepted: 12/02/2021] [Indexed: 12/18/2022] Open
Abstract
While the functions of HOX genes have been and remain extensively studied in distinct model organisms from flies to mice, the molecular biology of HOX proteins remains poorly documented. In particular, the mechanisms involved in regulating the activity of HOX proteins have been poorly investigated. Nonetheless, based on data available from other well-characterized transcription factors, it can be assumed that HOX protein activity must be finely tuned in a cell-type-specific manner and in response to defined environmental cues. Indeed, records in protein–protein interaction databases or entries in post-translational modification registries clearly support that HOX proteins are the targets of multiple layers of regulation at the protein level. In this context, we review here what has been reported and what can be inferred about how the activities of HOX proteins are regulated by their intracellular distribution.
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7
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Baker EA, Woollard A. How Weird is The Worm? Evolution of the Developmental Gene Toolkit in Caenorhabditis elegans. J Dev Biol 2019; 7:E19. [PMID: 31569401 PMCID: PMC6956190 DOI: 10.3390/jdb7040019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 09/20/2019] [Accepted: 09/25/2019] [Indexed: 01/14/2023] Open
Abstract
Comparative developmental biology and comparative genomics are the cornerstones of evolutionary developmental biology. Decades of fruitful research using nematodes have produced detailed accounts of the developmental and genomic variation in the nematode phylum. Evolutionary developmental biologists are now utilising these data as a tool with which to interrogate the evolutionary basis for the similarities and differences observed in Nematoda. Nematodes have often seemed atypical compared to the rest of the animal kingdom-from their totally lineage-dependent mode of embryogenesis to their abandonment of key toolkit genes usually deployed by bilaterians for proper development-worms are notorious rule breakers of the bilaterian handbook. However, exploring the nature of these deviations is providing answers to some of the biggest questions about the evolution of animal development. For example, why is the evolvability of each embryonic stage not the same? Why can evolution sometimes tolerate the loss of genes involved in key developmental events? Lastly, why does natural selection act to radically diverge toolkit genes in number and sequence in certain taxa? In answering these questions, insight is not only being provided about the evolution of nematodes, but of all metazoans.
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Affiliation(s)
- Emily A Baker
- Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK.
| | - Alison Woollard
- Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK.
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8
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Baldwin-Brown JG, Weeks SC, Long AD. A New Standard for Crustacean Genomes: The Highly Contiguous, Annotated Genome Assembly of the Clam Shrimp Eulimnadia texana Reveals HOX Gene Order and Identifies the Sex Chromosome. Genome Biol Evol 2018; 10:143-156. [PMID: 29294012 PMCID: PMC5765565 DOI: 10.1093/gbe/evx280] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/23/2017] [Indexed: 02/06/2023] Open
Abstract
Vernal pool clam shrimp (Eulimnadia texana) are a promising model system due to their ease of lab culture, short generation time, modest sized genome, a somewhat rare stable androdioecious sex determination system, and a requirement to reproduce via desiccated diapaused eggs. We generated a highly contiguous genome assembly using 46× of PacBio long read data and 216× of Illumina short reads, and annotated using Illumina RNAseq obtained from adult males or hermaphrodites. Of the 120 Mb genome 85% is contained in the largest eight contigs, the smallest of which is 4.6 Mb. The assembly contains 98% of transcripts predicted via RNAseq. This assembly is qualitatively different from scaffolded Illumina assemblies: It is produced from long reads that contain sequence data along their entire length, and is thus gap free. The contiguity of the assembly allows us to order the HOX genes within the genome, identifying two loci that contain HOX gene orthologs, and which approximately maintain the order observed in other arthropods. We identified a partial duplication of the Antennapedia complex adjacent to the few genes homologous to the Bithorax locus. Because the sex chromosome of an androdioecious species is of special interest, we used existing allozyme and microsatellite markers to identify the E. texana sex chromosome, and find that it comprises nearly half of the genome of this species. Linkage patterns indicate that recombination is extremely rare and perhaps absent in hermaphrodites, and as a result the location of the sex determining locus will be difficult to refine using recombination mapping.
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Affiliation(s)
| | | | - Anthony D Long
- Department of Ecology and Evolutionary Biology, University of California Irvine
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9
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Darbellay F, Duboule D. Topological Domains, Metagenes, and the Emergence of Pleiotropic Regulations at Hox Loci. Curr Top Dev Biol 2017; 116:299-314. [PMID: 26970625 DOI: 10.1016/bs.ctdb.2015.11.022] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Hox gene clusters of jaw vertebrates display a tight genomic organization, which has no equivalent in any other bilateria genomes sequenced thus far. It was previously argued that such a topological consolidation toward a condensed, metagenic structure was due to the accumulation of long-range regulations flanking Hox loci, a phenomenon made possible by the successive genome duplications that occurred at the root of the vertebrate lineage, similar to gene neofunctionalization but applied to a coordinated multigenic system. Here, we propose that the emergence of such large vertebrate regulatory landscapes containing a range of global enhancers was greatly facilitated by the presence of topologically associating domains (TADs). These chromatin domains, mostly constitutive, may have been used as genomic niches where novel regulations could evolve due to both the preexistence of a structural backbone poised to integrate novel regulatory inputs, and a highly adaptive transcriptional readout. We propose a scenario for the coevolution of such TADs and the emergence of pleiotropy at ancestral vertebrate Hox loci.
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Affiliation(s)
- Fabrice Darbellay
- School of Life Sciences, Federal Institute of Technology, Lausanne, Switzerland
| | - Denis Duboule
- School of Life Sciences, Federal Institute of Technology, Lausanne, Switzerland; Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland.
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10
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Yoshida Y, Koutsovoulos G, Laetsch DR, Stevens L, Kumar S, Horikawa DD, Ishino K, Komine S, Kunieda T, Tomita M, Blaxter M, Arakawa K. Comparative genomics of the tardigrades Hypsibius dujardini and Ramazzottius varieornatus. PLoS Biol 2017; 15:e2002266. [PMID: 28749982 PMCID: PMC5531438 DOI: 10.1371/journal.pbio.2002266] [Citation(s) in RCA: 128] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 06/23/2017] [Indexed: 01/27/2023] Open
Abstract
Tardigrada, a phylum of meiofaunal organisms, have been at the center of discussions of the evolution of Metazoa, the biology of survival in extreme environments, and the role of horizontal gene transfer in animal evolution. Tardigrada are placed as sisters to Arthropoda and Onychophora (velvet worms) in the superphylum Panarthropoda by morphological analyses, but many molecular phylogenies fail to recover this relationship. This tension between molecular and morphological understanding may be very revealing of the mode and patterns of evolution of major groups. Limnoterrestrial tardigrades display extreme cryptobiotic abilities, including anhydrobiosis and cryobiosis, as do bdelloid rotifers, nematodes, and other animals of the water film. These extremophile behaviors challenge understanding of normal, aqueous physiology: how does a multicellular organism avoid lethal cellular collapse in the absence of liquid water? Meiofaunal species have been reported to have elevated levels of horizontal gene transfer (HGT) events, but how important this is in evolution, and particularly in the evolution of extremophile physiology, is unclear. To address these questions, we resequenced and reassembled the genome of H. dujardini, a limnoterrestrial tardigrade that can undergo anhydrobiosis only after extensive pre-exposure to drying conditions, and compared it to the genome of R. varieornatus, a related species with tolerance to rapid desiccation. The 2 species had contrasting gene expression responses to anhydrobiosis, with major transcriptional change in H. dujardini but limited regulation in R. varieornatus. We identified few horizontally transferred genes, but some of these were shown to be involved in entry into anhydrobiosis. Whole-genome molecular phylogenies supported a Tardigrada+Nematoda relationship over Tardigrada+Arthropoda, but rare genomic changes tended to support Tardigrada+Arthropoda.
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Affiliation(s)
- Yuki Yoshida
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Kanagawa, Japan
| | - Georgios Koutsovoulos
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Dominik R. Laetsch
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
- The James Hutton Institute, Dundee, United Kingdom
| | - Lewis Stevens
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Sujai Kumar
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Daiki D. Horikawa
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Kanagawa, Japan
| | - Kyoko Ishino
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
| | - Shiori Komine
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
| | - Takekazu Kunieda
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Masaru Tomita
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Kanagawa, Japan
| | - Mark Blaxter
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Kazuharu Arakawa
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan
- Systems Biology Program, Graduate School of Media and Governance, Keio University, Kanagawa, Japan
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11
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Clustered brachiopod Hox genes are not expressed collinearly and are associated with lophotrochozoan novelties. Proc Natl Acad Sci U S A 2017; 114:E1913-E1922. [PMID: 28228521 DOI: 10.1073/pnas.1614501114] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Temporal collinearity is often considered the main force preserving Hox gene clusters in animal genomes. Studies that combine genomic and gene expression data are scarce, however, particularly in invertebrates like the Lophotrochozoa. As a result, the temporal collinearity hypothesis is currently built on poorly supported foundations. Here we characterize the complement, cluster, and expression of Hox genes in two brachiopod species, Terebratalia transversa and Novocrania anomalaT. transversa has a split cluster with 10 genes (lab, pb, Hox3, Dfd, Scr, Lox5, Antp, Lox4, Post2, and Post1), whereas N. anomala has 9 genes (apparently missing Post1). Our in situ hybridization, real-time quantitative PCR, and stage-specific transcriptomic analyses show that brachiopod Hox genes are neither strictly temporally nor spatially collinear; only pb (in T. transversa), Hox3 (in both brachiopods), and Dfd (in both brachiopods) show staggered mesodermal expression. Thus, our findings support the idea that temporal collinearity might contribute to keeping Hox genes clustered. Remarkably, expression of the Hox genes in both brachiopod species demonstrates cooption of Hox genes in the chaetae and shell fields, two major lophotrochozoan morphological novelties. The shared and specific expression of Hox genes, together with Arx, Zic, and Notch pathway components in chaetae and shell fields in brachiopods, mollusks, and annelids provide molecular evidence supporting the conservation of the molecular basis for these lophotrochozoan hallmarks.
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12
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Schierwater B, Holland PWH, Miller DJ, Stadler PF, Wiegmann BM, Wörheide G, Wray GA, DeSalle R. Never Ending Analysis of a Century Old Evolutionary Debate: “Unringing” the Urmetazoon Bell. Front Ecol Evol 2016. [DOI: 10.3389/fevo.2016.00005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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13
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Kuraku S, Feiner N, Keeley SD, Hara Y. Incorporating tree-thinking and evolutionary time scale into developmental biology. Dev Growth Differ 2016; 58:131-42. [PMID: 26818824 DOI: 10.1111/dgd.12258] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 11/04/2015] [Accepted: 11/04/2015] [Indexed: 01/11/2023]
Abstract
Phylogenetic approaches are indispensable in any comparative molecular study involving multiple species. These approaches are in increasing demand as the amount and availability of DNA sequence information continues to increase exponentially, even for organisms that were previously not extensively studied. Without the sound application of phylogenetic concepts and knowledge, one can be misled when attempting to infer ancestral character states as well as the timing and order of evolutionary events, both of which are frequently exerted in evolutionary developmental biology. The ignorance of phylogenetic approaches can also impact non-evolutionary studies and cause misidentification of the target gene or protein to be examined in functional characterization. This review aims to promote tree-thinking in evolutionary conjecture and stress the importance of a sense of time scale in cross-species comparisons, in order to enhance the understanding of phylogenetics in all biological fields including developmental biology. To this end, molecular phylogenies of several developmental regulatory genes, including those denoted as "cryptic pan-vertebrate genes", are introduced as examples.
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Affiliation(s)
- Shigehiro Kuraku
- Phyloinformatics Unit, RIKEN Center for Life Science Technologies, 2-2-3 Minatojima-minami, Chuo-ku, Kobe, 650-0047, Japan
| | | | - Sean D Keeley
- Phyloinformatics Unit, RIKEN Center for Life Science Technologies, 2-2-3 Minatojima-minami, Chuo-ku, Kobe, 650-0047, Japan
| | - Yuichiro Hara
- Phyloinformatics Unit, RIKEN Center for Life Science Technologies, 2-2-3 Minatojima-minami, Chuo-ku, Kobe, 650-0047, Japan
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14
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Bürglin TR, Affolter M. Homeodomain proteins: an update. Chromosoma 2015; 125:497-521. [PMID: 26464018 PMCID: PMC4901127 DOI: 10.1007/s00412-015-0543-8] [Citation(s) in RCA: 256] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2015] [Revised: 09/20/2015] [Accepted: 09/21/2015] [Indexed: 12/17/2022]
Abstract
Here, we provide an update of our review on homeobox genes that we wrote together with Walter Gehring in 1994. Since then, comprehensive surveys of homeobox genes have become possible due to genome sequencing projects. Using the 103 Drosophila homeobox genes as example, we present an updated classification. In animals, there are 16 major classes, ANTP, PRD, PRD-LIKE, POU, HNF, CUT (with four subclasses: ONECUT, CUX, SATB, and CMP), LIM, ZF, CERS, PROS, SIX/SO, plus the TALE superclass with the classes IRO, MKX, TGIF, PBC, and MEIS. In plants, there are 11 major classes, i.e., HD-ZIP (with four subclasses: I to IV), WOX, NDX, PHD, PLINC, LD, DDT, SAWADEE, PINTOX, and the two TALE classes KNOX and BEL. Most of these classes encode additional domains apart from the homeodomain. Numerous insights have been obtained in the last two decades into how homeodomain proteins bind to DNA and increase their specificity by interacting with other proteins to regulate cell- and tissue-specific gene expression. Not only protein-DNA base pair contacts are important for proper target selection; recent experiments also reveal that the shape of the DNA plays a role in specificity. Using selected examples, we highlight different mechanisms of homeodomain protein-DNA interaction. The PRD class of homeobox genes was of special interest to Walter Gehring in the last two decades. The PRD class comprises six families in Bilateria, and tinkers with four different motifs, i.e., the PAIRED domain, the Groucho-interacting motif EH1 (aka Octapeptide or TN), the homeodomain, and the OAR motif. Homologs of the co-repressor protein Groucho are also present in plants (TOPLESS), where they have been shown to interact with small amphipathic motives (EAR), and in yeast (TUP1), where we find an EH1-like motif in MATα2.
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Affiliation(s)
- Thomas R. Bürglin
- />Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
- />Department of Biomedicine, University of Basel, Mattenstrasse 28, 4058 Basel, Switzerland
| | - Markus Affolter
- />Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
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15
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Dillman AR, Macchietto M, Porter CF, Rogers A, Williams B, Antoshechkin I, Lee MM, Goodwin Z, Lu X, Lewis EE, Goodrich-Blair H, Stock SP, Adams BJ, Sternberg PW, Mortazavi A. Comparative genomics of Steinernema reveals deeply conserved gene regulatory networks. Genome Biol 2015; 16:200. [PMID: 26392177 PMCID: PMC4578762 DOI: 10.1186/s13059-015-0746-6] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 08/10/2015] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Parasitism is a major ecological niche for a variety of nematodes. Multiple nematode lineages have specialized as pathogens, including deadly parasites of insects that are used in biological control. We have sequenced and analyzed the draft genomes and transcriptomes of the entomopathogenic nematode Steinernema carpocapsae and four congeners (S. scapterisci, S. monticolum, S. feltiae, and S. glaseri). RESULTS We used these genomes to establish phylogenetic relationships, explore gene conservation across species, and identify genes uniquely expanded in insect parasites. Protein domain analysis in Steinernema revealed a striking expansion of numerous putative parasitism genes, including certain protease and protease inhibitor families, as well as fatty acid- and retinol-binding proteins. Stage-specific gene expression of some of these expanded families further supports the notion that they are involved in insect parasitism by Steinernema. We show that sets of novel conserved non-coding regulatory motifs are associated with orthologous genes in Steinernema and Caenorhabditis. CONCLUSIONS We have identified a set of expanded gene families that are likely to be involved in parasitism. We have also identified a set of non-coding motifs associated with groups of orthologous genes in Steinernema and Caenorhabditis involved in neurogenesis and embryonic development that are likely part of conserved protein-DNA relationships shared between these two genera.
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Affiliation(s)
- Adler R Dillman
- Department of Nematology, University of California, Riverside, CA, 92521, USA.
| | - Marissa Macchietto
- Department of Developmental and Cell Biology, University of California, Irvine, CA, 92697, USA.
| | - Camille F Porter
- Department of Biology and Evolutionary Ecology Laboratories, Brigham Young University, Provo, UT, 84602, USA.
| | - Alicia Rogers
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA.
| | - Brian Williams
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA.
| | - Igor Antoshechkin
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA.
| | - Ming-Min Lee
- Department of Entomology, University of Arizona, Tucson, AZ, 85721, USA.
| | - Zane Goodwin
- Division of Biology and Biomedical Sciences, Washington University, St Louis, MO, 63110, USA.
| | - Xiaojun Lu
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
| | - Edwin E Lewis
- Department of Entomology and Nematology, University of California, Davis, CA, 95616, USA.
| | - Heidi Goodrich-Blair
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
| | - S Patricia Stock
- Department of Entomology, University of Arizona, Tucson, AZ, 85721, USA.
| | - Byron J Adams
- Department of Biology and Evolutionary Ecology Laboratories, Brigham Young University, Provo, UT, 84602, USA.
| | - Paul W Sternberg
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA.
- Howard Hughes Medical Institute, Pasadena, CA, 91125, USA.
| | - Ali Mortazavi
- Department of Developmental and Cell Biology, University of California, Irvine, CA, 92697, USA.
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Abstract
Apoptosis is a cellular suicide program, which is on the one hand used to remove superfluous cells thereby promoting tissue or organ morphogenesis. On the other hand, the programmed killing of cells is also critical when potentially harmful cells emerge in a developing or adult organism thereby endangering survival. Due to its critical role apoptosis is tightly controlled, however so far, its regulation on the transcriptional level is less studied and understood. Hox genes, a highly conserved gene family encoding homeodomain transcription factors, have crucial roles in development. One of their prominent functions is to shape animal body plans by eliciting different developmental programs along the anterior-posterior axis. To this end, Hox proteins transcriptionally regulate numerous processes in a coordinated manner, including cell-type specification, differentiation, motility, proliferation as well as apoptosis. In this review, we will focus on how Hox proteins control organismal morphology and function by regulating the apoptotic machinery. We will first focus on well-established paradigms of Hox-apoptosis interactions and summarize how Hox transcription factors control morphological outputs and differentially shape tissues along the anterior-posterior axis by fine-tuning apoptosis in a healthy organism. We will then discuss the consequences when this interaction is disturbed and will conclude with some ideas and concepts emerging from these studies.
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17
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Biscotti MA, Canapa A, Forconi M, Barucca M. HoxandParaHoxgenes: A review on molluscs. Genesis 2014; 52:935-45. [DOI: 10.1002/dvg.22839] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 11/10/2014] [Accepted: 11/11/2014] [Indexed: 01/28/2023]
Affiliation(s)
- Maria Assunta Biscotti
- Dipartimento di Scienze della Vita e dell'Ambiente; Università Politecnica delle Marche; Ancona Italy
| | - Adriana Canapa
- Dipartimento di Scienze della Vita e dell'Ambiente; Università Politecnica delle Marche; Ancona Italy
| | - Mariko Forconi
- Dipartimento di Scienze della Vita e dell'Ambiente; Università Politecnica delle Marche; Ancona Italy
| | - Marco Barucca
- Dipartimento di Scienze della Vita e dell'Ambiente; Università Politecnica delle Marche; Ancona Italy
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Sakamaki K, Shimizu K, Iwata H, Imai K, Satou Y, Funayama N, Nozaki M, Yajima M, Nishimura O, Higuchi M, Chiba K, Yoshimoto M, Kimura H, Gracey AY, Shimizu T, Tomii K, Gotoh O, Akasaka K, Sawasaki T, Miller DJ. The apoptotic initiator caspase-8: its functional ubiquity and genetic diversity during animal evolution. Mol Biol Evol 2014; 31:3282-301. [PMID: 25205508 DOI: 10.1093/molbev/msu260] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The caspases, a family of cysteine proteases, play multiple roles in apoptosis, inflammation, and cellular differentiation. Caspase-8 (Casp8), which was first identified in humans, functions as an initiator caspase in the apoptotic signaling mediated by cell-surface death receptors. To understand the evolution of function in the Casp8 protein family, casp8 orthologs were identified from a comprehensive range of vertebrates and invertebrates, including sponges and cnidarians, and characterized at both the gene and protein levels. Some introns have been conserved from cnidarians to mammals, but both losses and gains have also occurred; a new intron arose during teleost evolution, whereas in the ascidian Ciona intestinalis, the casp8 gene is intronless and is organized in an operon with a neighboring gene. Casp8 activities are near ubiquitous throughout the animal kingdom. Exogenous expression of a representative range of nonmammalian Casp8 proteins in cultured mammalian cells induced cell death, implying that these proteins possess proapoptotic activity. The cnidarian Casp8 proteins differ considerably from their bilaterian counterparts in terms of amino acid residues in the catalytic pocket, but display the same substrate specificity as human CASP8, highlighting the complexity of spatial structural interactions involved in enzymatic activity. Finally, it was confirmed that the interaction with an adaptor molecule, Fas-associated death domain protein, is also evolutionarily ancient. Thus, despite structural diversity and cooption to a variety of new functions, the ancient origins and near ubiquitous distribution of this activity across the animal kingdom emphasize the importance and utility of Casp8 as a central component of the metazoan molecular toolkit.
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Affiliation(s)
- Kazuhiro Sakamaki
- Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Kouhei Shimizu
- Proteo-Science Center, Ehime University, Matsuyama, Japan
| | - Hiroaki Iwata
- Multi-Scale Research Center for Medical Science, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
| | - Kenichiro Imai
- Computational Biology Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tokyo, Japan
| | - Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Noriko Funayama
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Masami Nozaki
- Department of Cell Biology, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
| | - Mamiko Yajima
- Bio Med Molecular, Cellular Biology Biochemistry Department, Brown University, Providence, RI
| | - Osamu Nishimura
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Mayura Higuchi
- Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Kumiko Chiba
- Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Michi Yoshimoto
- Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Haruna Kimura
- Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Andrew Y Gracey
- Marine Environmental Biology, University of Southern California, Los Angeles, CA
| | - Takashi Shimizu
- Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Kentaro Tomii
- Computational Biology Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tokyo, Japan
| | - Osamu Gotoh
- Computational Biology Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tokyo, Japan
| | - Koji Akasaka
- Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | | | - David J Miller
- Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
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19
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Liu WJ, Reece-Hoyes JS, Walhout AJM, Eisenmann DM. Multiple transcription factors directly regulate Hox gene lin-39 expression in ventral hypodermal cells of the C. elegans embryo and larva, including the hypodermal fate regulators LIN-26 and ELT-6. BMC DEVELOPMENTAL BIOLOGY 2014; 14:17. [PMID: 24885717 PMCID: PMC4051164 DOI: 10.1186/1471-213x-14-17] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 02/27/2014] [Indexed: 01/05/2023]
Abstract
Background Hox genes encode master regulators of regional fate specification during early metazoan development. Much is known about the initiation and regulation of Hox gene expression in Drosophila and vertebrates, but less is known in the non-arthropod invertebrate model system, C. elegans. The C. elegans Hox gene lin-39 is required for correct fate specification in the midbody region, including the Vulval Precursor Cells (VPCs). To better understand lin-39 regulation and function, we aimed to identify transcription factors necessary for lin-39 expression in the VPCs, and in particular sought factors that initiate lin-39 expression in the embryo. Results We used the yeast one-hybrid (Y1H) method to screen for factors that bound to 13 fragments from the lin-39 region: twelve fragments contained sequences conserved between C. elegans and two other nematode species, while one fragment was known to drive reporter gene expression in the early embryo in cells that generate the VPCs. Sixteen transcription factors that bind to eight lin-39 genomic fragments were identified in yeast, and we characterized several factors by verifying their physical interactions in vitro, and showing that reduction of their function leads to alterations in lin-39 levels and lin-39::GFP reporter expression in vivo. Three factors, the orphan nuclear hormone receptor NHR-43, the hypodermal fate regulator LIN-26, and the GATA factor ELT-6 positively regulate lin-39 expression in the embryonic precursors to the VPCs. In particular, ELT-6 interacts with an enhancer that drives GFP expression in the early embryo, and the ELT-6 site we identified is necessary for proper embryonic expression. These three factors, along with the factors ZTF-17, BED-3 and TBX-9, also positively regulate lin-39 expression in the larval VPCs. Conclusions These results significantly expand the number of factors known to directly bind and regulate lin-39 expression, identify the first factors required for lin-39 expression in the embryo, and hint at a positive feedback mechanism involving GATA factors that maintains lin-39 expression in the vulval lineage. This work indicates that, as in other organisms, the regulation of Hox gene expression in C. elegans is complicated, redundant and robust.
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Affiliation(s)
| | | | | | - David M Eisenmann
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21250, USA.
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20
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Janssen R, Eriksson BJ, Tait NN, Budd GE. Onychophoran Hox genes and the evolution of arthropod Hox gene expression. Front Zool 2014; 11:22. [PMID: 24594097 PMCID: PMC4015684 DOI: 10.1186/1742-9994-11-22] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Accepted: 02/21/2014] [Indexed: 11/24/2022] Open
Abstract
Introduction Onychophora is a relatively small phylum within Ecdysozoa, and is considered to be the sister group to Arthropoda. Compared to the arthropods, that have radiated into countless divergent forms, the onychophoran body plan is overall comparably simple and does not display much in-phylum variation. An important component of arthropod morphological diversity consists of variation of tagmosis, i.e. the grouping of segments into functional units (tagmata), and this in turn is correlated with differences in expression patterns of the Hox genes. How these genes are expressed in the simpler onychophorans, the subject of this paper, would therefore be of interest in understanding their subsequent evolution in the arthropods, especially if an argument can be made for the onychophoran system broadly reflecting the ancestral state in the arthropods. Results The sequences and embryonic expression patterns of the complete set of ten Hox genes of an onychophoran (Euperipatoides kanangrensis) are described for the first time. We find that they are all expressed in characteristic patterns that suggest a function as classical Hox genes. The onychophoran Hox genes obey spatial colinearity, and with the exception of Ultrabithorax (Ubx), they all have different and distinct anterior expression borders. Notably, Ubx transcripts form a posterior to anterior gradient in the onychophoran trunk. Expression of all onychophoran Hox genes extends continuously from their anterior border to the rear end of the embryo. Conclusions The spatial expression pattern of the onychophoran Hox genes may contribute to a combinatorial Hox code that is involved in giving each segment its identity. This patterning of segments in the uniform trunk, however, apparently predates the evolution of distinct segmental differences in external morphology seen in arthropods. The gradient-like expression of Ubx may give posterior segments their specific identity, even though they otherwise express the same set of Hox genes. We suggest that the confined domains of Hox gene expression seen in arthropods evolved from an ancestral onychophoran-like Hox gene pattern. Reconstruction of the ancestral arthropod Hox pattern and comparison with the patterns in the different arthropod classes reveals phylogenetic support for Mandibulata and Tetraconata, but not Myriochelata and Atelocerata.
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Affiliation(s)
- Ralf Janssen
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, 75236 Uppsala, Sweden.
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21
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Schiffer PH, Kroiher M, Kraus C, Koutsovoulos GD, Kumar S, R Camps JI, Nsah NA, Stappert D, Morris K, Heger P, Altmüller J, Frommolt P, Nürnberg P, Thomas WK, Blaxter ML, Schierenberg E. The genome of Romanomermis culicivorax: revealing fundamental changes in the core developmental genetic toolkit in Nematoda. BMC Genomics 2013; 14:923. [PMID: 24373391 PMCID: PMC3890508 DOI: 10.1186/1471-2164-14-923] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 12/17/2013] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND The genetics of development in the nematode Caenorhabditis elegans has been described in exquisite detail. The phylum Nematoda has two classes: Chromadorea (which includes C. elegans) and the Enoplea. While the development of many chromadorean species resembles closely that of C. elegans, enoplean nematodes show markedly different patterns of early cell division and cell fate assignment. Embryogenesis of the enoplean Romanomermis culicivorax has been studied in detail, but the genetic circuitry underpinning development in this species has not been explored. RESULTS We generated a draft genome for R. culicivorax and compared its gene content with that of C. elegans, a second enoplean, the vertebrate parasite Trichinella spiralis, and a representative arthropod, Tribolium castaneum. This comparison revealed that R. culicivorax has retained components of the conserved ecdysozoan developmental gene toolkit lost in C. elegans. T. spiralis has independently lost even more of this toolkit than has C. elegans. However, the C. elegans toolkit is not simply depauperate, as many novel genes essential for embryogenesis in C. elegans are not found in, or have only extremely divergent homologues in R. culicivorax and T. spiralis. Our data imply fundamental differences in the genetic programmes not only for early cell specification but also others such as vulva formation and sex determination. CONCLUSIONS Despite the apparent morphological conservatism, major differences in the molecular logic of development have evolved within the phylum Nematoda. R. culicivorax serves as a tractable system to contrast C. elegans and understand how divergent genomic and thus regulatory backgrounds nevertheless generate a conserved phenotype. The R. culicivorax draft genome will promote use of this species as a research model.
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Affiliation(s)
| | - Michael Kroiher
- Zoologisches Institut, Universität zu Köln, Cologne, NRW, Germany
| | | | - Georgios D Koutsovoulos
- Institute of Evolutionary Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, Scotland, UK
| | - Sujai Kumar
- Institute of Evolutionary Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, Scotland, UK
| | - Julia I R Camps
- Zoologisches Institut, Universität zu Köln, Cologne, NRW, Germany
| | - Ndifon A Nsah
- Zoologisches Institut, Universität zu Köln, Cologne, NRW, Germany
| | - Dominik Stappert
- Institute für Entwicklungsbiologie, Universität zu Köln, Cologne, NRW, Germany
| | - Krystalynne Morris
- Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH, USA
| | - Peter Heger
- Zoologisches Institut, Universität zu Köln, Cologne, NRW, Germany
| | - Janine Altmüller
- Cologne Center for Genomics, Universität zu Köln, Cologne, NRW, Germany
| | - Peter Frommolt
- Cologne Center for Genomics, Universität zu Köln, Cologne, NRW, Germany
| | - Peter Nürnberg
- Cologne Center for Genomics, Universität zu Köln, Cologne, NRW, Germany
| | - W Kelley Thomas
- Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH, USA
| | - Mark L Blaxter
- Institute of Evolutionary Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, Scotland, UK
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Abstract
Receptor Tyrosine Kinase (RTK)-Ras-Extracellular signal-regulated kinase (ERK) signaling pathways control many aspects of C. elegans development and behavior. Studies in C. elegans helped elucidate the basic framework of the RTK-Ras-ERK pathway and continue to provide insights into its complex regulation, its biological roles, how it elicits cell-type appropriate responses, and how it interacts with other signaling pathways to do so. C. elegans studies have also revealed biological contexts in which alternative RTK- or Ras-dependent pathways are used instead of the canonical pathway.
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Affiliation(s)
- Meera V Sundaram
- Dept. of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6145, USA.
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Chisholm AD, Hsiao TI. The Caenorhabditis elegans epidermis as a model skin. I: development, patterning, and growth. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 1:861-78. [PMID: 23539299 DOI: 10.1002/wdev.79] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The skin of the nematode Caenorhabditis elegans is composed of a simple epidermal epithelium and overlying cuticle. The skin encloses the animal and plays central roles in body morphology and physiology; its simplicity and accessibility make it a tractable genetic model for several aspects of skin biology. Epidermal precursors are specified by a hierarchy of transcriptional regulators. Epidermal cells form on the dorsal surface of the embryo and differentiate to form the epidermal primordium, which then spreads out in a process of epiboly to enclose internal tissues. Subsequent elongation of the embryo into a vermiform larva is driven by cell shape changes and cell fusions in the epidermis. Most epidermal cells fuse in mid-embryogenesis to form a small number of multinucleate syncytia. During mid-embryogenesis the epidermis also becomes intimately associated with underlying muscles, performing a tendon-like role in transmitting muscle force. Post-embryonic development of the epidermis involves growth by addition of new cells to the syncytia from stem cell-like epidermal seam cells and by an increase in cell size driven by endoreplication of the chromosomes in epidermal nuclei.
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Affiliation(s)
- Andrew D Chisholm
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA, USA.
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Ezziane Z. Analysis of the Hox epigenetic code. World J Clin Oncol 2012; 3:48-56. [PMID: 22553504 PMCID: PMC3341740 DOI: 10.5306/wjco.v3.i4.48] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Revised: 11/21/2011] [Accepted: 04/01/2012] [Indexed: 02/06/2023] Open
Abstract
Archetypes of histone modifications associated with diverse chromosomal states that regulate access to DNA are leading the hypothesis of the histone code (or epigenetic code). However, it is still not evident how these post-translational modifications of histone tails lead to changes in chromatin structure. Histone modifications are able to activate and/or inactivate several genes and can be transmitted to next generation cells due to an epigenetic memory. The challenging issue is to identify or “decrypt” the code used to transmit these modifications to descent cells. Here, an attempt is made to describe how histone modifications operate as part of histone code that stipulates patterns of gene expression. This papers emphasizes particularly on the correlation between histone modifications and patterns of Hox gene expression in Caenorhabditis elegans. This work serves as an example to illustrate the power of the epigenetic machinery and its use in drug design and discovery.
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Affiliation(s)
- Zoheir Ezziane
- Zoheir Ezziane, Welcome Trust Centre For Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, United Kingdom
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25
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Abstract
MicroRNAs (miRNAs) are small non-coding RNAs that negatively regulate gene expression and thus control diverse biological processes. The high interest in miRNAs as an important mediator of post-transcriptional gene regulation has led to the discovery of miRNAs in several organisms. The present article outlines and discusses the current status of miRNAs information on the basal chordate amphioxus and the evolution of miRNAs in metazoans.
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Affiliation(s)
- Simona Candiani
- Laboratorio di Neurobiologia dello Sviluppo, Università di Genova, Italia.
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26
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Rapid evolution and copy number variation of primate RHOXF2, an X-linked homeobox gene involved in male reproduction and possibly brain function. BMC Evol Biol 2011; 11:298. [PMID: 21988730 PMCID: PMC3214919 DOI: 10.1186/1471-2148-11-298] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 10/12/2011] [Indexed: 11/30/2022] Open
Abstract
Background Homeobox genes are the key regulators during development, and they are in general highly conserved with only a few reported cases of rapid evolution. RHOXF2 is an X-linked homeobox gene in primates. It is highly expressed in the testicle and may play an important role in spermatogenesis. As male reproductive system is often the target of natural and/or sexual selection during evolution, in this study, we aim to dissect the pattern of molecular evolution of RHOXF2 in primates and its potential functional consequence. Results We studied sequences and copy number variation of RHOXF2 in humans and 16 nonhuman primate species as well as the expression patterns in human, chimpanzee, white-browed gibbon and rhesus macaque. The gene copy number analysis showed that there had been parallel gene duplications/losses in multiple primate lineages. Our evidence suggests that 11 nonhuman primate species have one RHOXF2 copy, and two copies are present in humans and four Old World monkey species, and at least 6 copies in chimpanzees. Further analysis indicated that the gene duplications in primates had likely been mediated by endogenous retrovirus (ERV) sequences flanking the gene regions. In striking contrast to non-human primates, humans appear to have homogenized their two RHOXF2 copies by the ERV-mediated non-allelic recombination mechanism. Coding sequence and phylogenetic analysis suggested multi-lineage strong positive selection on RHOXF2 during primate evolution, especially during the origins of humans and chimpanzees. All the 8 coding region polymorphic sites in human populations are non-synonymous, implying on-going selection. Gene expression analysis demonstrated that besides the preferential expression in the reproductive system, RHOXF2 is also expressed in the brain. The quantitative data suggests expression pattern divergence among primate species. Conclusions RHOXF2 is a fast-evolving homeobox gene in primates. The rapid evolution and copy number changes of RHOXF2 had been driven by Darwinian positive selection acting on the male reproductive system and possibly also on the central nervous system, which sheds light on understanding the role of homeobox genes in adaptive evolution.
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28
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Abstract
Cancer is a complex disease in which cells have circumvented normal restraints on tissue growth and have acquired complex abnormalities in their genomes, posing a considerable challenge to identifying the pathways and mechanisms that drive fundamental aspects of the malignant phenotype. Genetic analyses of the normal development of the nematode Caenorhabditis elegans have revealed evolutionarily conserved mechanisms through which individual cells establish their fates, and how they make and execute the decision to survive or undergo programmed cell death. The pathways identified through these studies have mammalian counterparts that are co-opted by malignant cells. Effective cancer drugs now target some of these pathways, and more are likely to be discovered.
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Affiliation(s)
- Malia B Potts
- Departments of Pediatrics and Molecular Biology, University of Texas Southwestern Medical Center at Dallas, 75390-9148, USA
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Choo SW, Russell S. Genomic approaches to understanding Hox gene function. ADVANCES IN GENETICS 2011; 76:55-91. [PMID: 22099692 DOI: 10.1016/b978-0-12-386481-9.00003-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
For many years, biologists have sought to understand how the homeodomain-containing transcriptional regulators encoded by Hox genes are able to control the development of animal morphology. Almost a century of genetics and several decades of molecular biology have defined the conserved organization of homeotic gene clusters in animals and the basic molecular properties of Hox transcription factors. In contrast to these successes, we remain relatively ignorant of how Hox proteins find their target genes in the genome or what sets of genes a Hox protein regulates to direct morphogenesis. The recent deployment of genomic methods, such as whole transcriptome mRNA expression profiling and genome-wide analysis of protein-DNA interactions, begins to shed light on these issues. Results from such studies, principally in the fruit fly, indicate that Hox proteins control the expression of hundreds, if not thousands, of genes throughout the gene regulatory network and that, in many cases, the effects on the expression of individual genes may be quite subtle. Hox proteins regulate both high-level effectors, including other transcription factors and signaling molecules, as well as the cytodifferentiation genes or Realizators at the bottom of regulatory hierarchies. Insights emerging from mapping Hox binding sites in the genome begin to suggest that Hox binding may be strongly influenced by chromatin accessibility rather than binding site affinity. If this is the case, it indicates we need to refocus our efforts at understanding Hox function toward the dynamics of gene regulatory networks and chromatin epigenetics.
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Affiliation(s)
- Siew Woh Choo
- Department of Genetics and Cambridge Systems Biology Centre, University of Cambridge, Cambridge, United Kingdom
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Abstract
The homeodomain is a protein domain of about 60 amino acids that is encoded by homeobox genes. The homeodomain is a DNA binding domain, and hence homeodomain proteins are essentially transcription factors (TFs). They have been shown to play major roles in many developmental processes of animals, as well as fungi and plants. A primary function of homeodomain proteins is to regulate the expression of other genes in development and differentiation. Thousands of homeobox genes have been identified, and they can be grouped into many different classes. Often other conserved protein domains are found linked to a homeodomain. Several particular types of homeobox genes are organized into chromosomal clusters. The best-known cluster, the HOX cluster, is found in all bilaterian animals. Tetrapods contain four HOX clusters that arose through duplication in early vertebrate evolution. The genes in these clusters are called Hox genes. Lower chordates, insects and nematodes tend to have only one HOX cluster. Of particular interest is that many of the HOX cluster genes function in the process of pattern formation along the anterior-posterior body axis. Many other types of homeodomain proteins play roles in the determination of cell fates and cell differentiation. Homeobox genes thus perform key roles for all aspects of the development of an organism.
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Affiliation(s)
- Thomas R Bürglin
- Department of Biosciences and Nutrition, and Center for Biosciences, Karolinska Institutet, Hälsovägen 7, Novum, SE 141 83, Huddinge, Sweden,
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Lanfear R. Are the deuterostome posterior Hox genes a fast-evolving class? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 689:111-22. [PMID: 20795326 DOI: 10.1007/978-1-4419-6673-5_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
There has been a great deal of interest in analysing the molecular evolution of the Hox cluster using both bioinformatic and experimental approaches. The posterior Hox genes have been of particular interest to both groups of biologists for a number of reasons: they appear to be associated with the evolution of a number of morphological novelties; the protostomes appear to be have lost a highly-conserved and functionally important amino acid motif (the hexapeptide motif) from their posterior Hox genes; and deuterostome posterior Hox genes seem to be evolving more quickly than all other Hox genes. In this chapter I will discuss the last of these points. The idea that Deuterostome posterior Hox genes were evolving more quickly than other Hox genes was first suggested by David Ferrier and colleagues. In this chapter, I start by introducing the posterior Hox genes--their distribution among the animal phyla and the likely sequence of duplications that led to this distribution. I then introduce the idea of 'deuterostome posterior flexibility' and examine this hypothesis in light of more recent phylogenetic and genomic work on the Hox cluster. Finally, I discuss some new approaches that could be used to test directly for differential rates of evolution among Hox genes and to assess what might underlie these differences.
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Affiliation(s)
- Robert Lanfear
- Centre for Macroevolution and Macroecology, School of Botany and Zoology, Building 116 Daley Road, Australian National University, ACT 0200, Australia.
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A negative regulatory loop between microRNA and Hox gene controls posterior identities in Caenorhabditis elegans. PLoS Genet 2010; 6:e1001089. [PMID: 20824072 PMCID: PMC2932687 DOI: 10.1371/journal.pgen.1001089] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Accepted: 07/23/2010] [Indexed: 12/05/2022] Open
Abstract
MicroRNAs (miRNAs) have been found to regulate gene expression across eukaryotic species, but the function of most miRNA genes remains unknown. Here we describe how the analysis of the expression patterns of a well-conserved miRNA gene, mir-57, at cellular resolution for every minute during early development of Caenorhabditis elegans provided key insights in understanding its function. Remarkably, mir-57 expression shows strong positional bias but little tissue specificity, a pattern reminiscent of Hox gene function. Despite the minor defects produced by a loss of function mutation, overexpression of mir-57 causes dramatic posterior defects, which also mimic the phenotypes of mutant alleles of a posterior Hox gene, nob-1, an Abd homolog. More importantly, nob-1 expression is found in the same two posterior AB sublineages as those expressing mir-57 but with an earlier onset. Intriguingly, nob-1 functions as an activator for mir-57 expression; it is also a direct target of mir-57. In agreement with this, loss of mir-57 function partially rescues the nob-1 allele defects, indicating a negative feedback regulatory loop between the miRNA and Hox gene to provide positional cues. Given the conservation of the miRNA and Hox gene, the regulatory mechanism might be broadly used across species. The strategy used here to explore mir-57 function provides a path to dissect the regulatory relationship between genes. miRNAs are small RNAs found in many multi-cellular species that inhibit gene expression. Many of them play important roles in cancer and cell fate determination, but the function of most miRNAs is uncertain. Using live cell imaging and automated expression analysis, we found a miRNA gene, mir-57, is expressed in a position rather than tissue dependent way. Hox genes also regulate cell fate patterning along anterior-posterior (a-p) axis across different tissues. By investigating interactions between genes of these classes expressed in mir-57 expressing cells, we demonstrated by both genetic analysis and gene expression assays that a negative feedback loop between a posterior Hox gene, nob-1, and mir-57 regulates posterior cell fate determination in C. elegans. On the one hand, the Hox gene is required for normal activation of mir-57 expression, and on the other, the Hox gene functions as a direct target of and is repressed by the miRNA. Given the conservation of the two genes, a negative feedback loop between Hox and miRNA genes might be broadly used across species to regulate cell fate along the a-p axis. Detailed expression analysis may provide a general way to dissect the regulatory role of miRNAs.
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Alvarez-Venegas R. Regulation by polycomb and trithorax group proteins in Arabidopsis. THE ARABIDOPSIS BOOK 2010; 8:e0128. [PMID: 22303254 PMCID: PMC3244960 DOI: 10.1199/tab.0128] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Polycomb group (PcG) and trithorax group (trxG) proteins are key regulators of homeotic genes and have crucial roles in cell proliferation, growth and development. PcG and trxG proteins form higher order protein complexes that contain SET domain proteins, with a histone methyltransferase (HMTase) activity, responsible for the different types of lysine methylation at the N-terminal tails of the core histone proteins. In recent years, genetic studies along with biochemical and cell biological analyses in Arabidopsis have enabled researchers to begin to understand how PcG and trxG proteins are recruited to chromatin and how they regulate their target genes and to elucidate their functions. This review focuses on the advances in our understanding of the biological roles of PcG and trxG proteins, their molecular mechanisms of action and further examines the role of histone marks in PcG and trxG regulation in Arabidopsis.
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Affiliation(s)
- Raúl Alvarez-Venegas
- Department of Genetic Engineering, Center for Research and Advanced Studies, CINVESTAV-IPN Unidad lrapuato, C.P. 36821 lrapuato, Guanajuato, México
- Address correspondence to
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Aboobaker A, Blaxter M. The nematode story: Hox gene loss and rapid evolution. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 689:101-10. [PMID: 20795325 DOI: 10.1007/978-1-4419-6673-5_7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The loss in some taxa of conserved developmental control genes that are present in the vast majority of animal lineages is an understudied phenomenon. It is likely that in those lineages in which loss has occurred it may be a strong signal of the mode, tempo and direction of developmental evolution and thus identify ways of generating morphological novelties. Intuitively we might expect these novelties to be particularly those associated with morphological simplifications. One striking example of this has occurred within the nematodes. It appears that over half the ancestral bilaterian Hox cluster has been lost from the model organism Caenorhabditis elegans and its closest related species. Studying the Hox gene complement of nematodes across the phylum has shown that many, if not all these losses occurred within the phylum. Other nematode clades only distantly related to C. elegans have additional Hox genes orthologous to those present in the ancestral bilaterian but absent from the model nematode. In some of these cases rapid sequence evolution of the homeodomain itself obscures orthology assignment until comparison is made with sequences from multiple nematode clades with slower evolving Hox genes. Across the phylum the homeodomains of the Hox genes that are present are evolving very rapidly. In one particular case the genomic arrangement of two homeodomains suggests a mechanism for gene loss. Studying the function in nematodes of the Hox genes absent from C. elegans awaits further research and the establishment of new nematode models. However, what we do know about Hox gene functions suggests that the genetic circuits within which Hox genes act have changed significantly within C. elegans and its close relatives.
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Affiliation(s)
- Aziz Aboobaker
- Institute of Genetics, The University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK.
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Schulze J, Schierenberg E. Embryogenesis of Romanomermis culicivorax: an alternative way to construct a nematode. Dev Biol 2009; 334:10-21. [PMID: 19523940 DOI: 10.1016/j.ydbio.2009.06.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 06/03/2009] [Accepted: 06/06/2009] [Indexed: 11/17/2022]
Abstract
The current picture of embryonic development in nematodes is essentially shaped by Caenorhabditis elegans and its close relatives. As their pattern of embryogenesis is rather similar, it is often considered to be representative for the taxon Nematoda as a whole. Here we give for the first time a comprehensive description of embryonic development in an ancestrally diverged nematode. Romanomermis culicivorax differs strikingly from C. elegans with respect to cell division pattern, spatial arrangement of blastomeres and tissue formation. Our study reveals a number of unexpected phenomena. These include (i) unique polar interphase microtubule caps forming in early blastomeres destined to undergo asymmetric cleavages, suggesting the presence of a so far undescribed MTOC; (ii) embryonic cell lineages of reduced complexity with predominantly monoclonal sublineages, generating just a single tissue type; (iii) construction of major parts of the body from duplicating building blocks consisting of rings of cells, a pattern showing some resemblance to segmentation; (iv) prominent differences in cell fate assignment which can be best explained with a global shift affecting all somatic founder cells. In summary, our data indicate that during nematode evolution massive alterations in the developmental program took place of how to generate a juvenile.
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Affiliation(s)
- Jens Schulze
- Zoological Institute, University of Cologne, 50923 Köln, Germany
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Li X, Kulkarni RP, Hill RJ, Chamberlin HM. HOM-C genes, Wnt signaling and axial patterning in the C. elegans posterior ventral epidermis. Dev Biol 2009; 332:156-65. [PMID: 19481074 DOI: 10.1016/j.ydbio.2009.05.567] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2008] [Revised: 05/14/2009] [Accepted: 05/19/2009] [Indexed: 12/27/2022]
Abstract
Wnt signaling and HOM-C/Hox genes pattern cell fate along the anterior/posterior axis in many animals. In general, Wnt signaling participates in establishing the anterior/posterior axis, whereas HOM-C genes confer regional identities to cells along the axis. However, recent work in non-bilaterial metazoans suggests that the ancestral patterning system relied on Wnts, with a later co-option of HOM-C genes to replace Wnts in regional patterning. Here we provide direct experimental support for this model from C. elegans, where a regional Wnt patterning system is uncovered in HOM-C gene mutants. Anterior/posterior patterning of P11/P12 cell fate in the C. elegans tail is normally dependent on the HOM-C gene egl-5/Abdominal-B. If the HOM-C gene mab-5/fushi tarazu is also mutant, however, a Wnt signal can promote P12 fate in the absence of egl-5. Furthermore, transcription of egl-5 in the P12.pa cell is influenced by an autoregulatory element that is essential in wild type, but not in mab-5 egl-5 double mutants, identifying regulatory parallels between P12 cell fate specification and egl-5 transcriptional regulation in the P12 lineage. Together, our results identify complex regulatory relationships among signaling pathways and HOM-C genes, and uncover a layering of patterning systems that may reflect their evolutionary history.
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Affiliation(s)
- Xin Li
- Molecular, Cellular and Developmental Biology Program, The Ohio State University, Columbus, OH 43210, USA
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Trithorax, Hox, and TALE-class homeodomain proteins ensure cell survival through repression of the BH3-only gene egl-1. Dev Biol 2009; 329:374-85. [PMID: 19254707 DOI: 10.1016/j.ydbio.2009.02.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Revised: 02/05/2009] [Accepted: 02/18/2009] [Indexed: 12/21/2022]
Abstract
Mutations that aberrantly activate trithorax-group proteins, Hox transcription factors and TALE-class Hox cofactors promote leukemogenesis, but their target genes critical for leukemogenesis remain largely unknown. Through genetic analyses in C. elegans, we find that the trithorax-group gene lin-59 and the TALE-class Hox cofactor unc-62 are required for survival of the VC motor neurons. With the goal of providing a model for how aberrantly active Hox complexes might promote leukemia, we elucidate the mechanism through which these new inhibitors of programmed cell death act: lin-59 maintains transcription of the Hox gene lin-39, while unc-62 promotes nuclear localization of the TALE-class Hox cofactor ceh-20. A LIN-39/CEH-20 complex binds the promoter of the pro-apoptotic BH3-only gene egl-1, repressing its transcription and ensuring survival of the VC neurons. In the absence of this regulatory mechanism, egl-1 is transcribed and the VC neurons die. Furthermore, ectopic expression of the Hox gene lin-39, as occurs for human Hox genes in leukemia, is sufficient to block death of some cells. This work identifies BH3-only pro-apoptotic genes as targets of Hox-mediated repression and suggests that aberrant activation of Hox networks may promote leukemia in part by inhibiting apoptosis.
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Sugiyama S, Prochiantz A, Hensch TK. From brain formation to plasticity: insights on Otx2 homeoprotein. Dev Growth Differ 2009; 51:369-77. [PMID: 19298552 DOI: 10.1111/j.1440-169x.2009.01093.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The shaping of neuronal circuits is essential during postnatal brain development. A window of neuronal remodeling by sensory experience typically occurs during a unique time in early life. The many types of behavior and perception, like human language, birdsong, hearing and vision are refined by experience during these distinct 'critical periods'. The onset of critical periods for vision is delayed in animals that remain in complete darkness from birth. It is then predicted that a 'messenger' within the visual pathway signals the amount of sensory experience that has occurred. Our recent results indicate that Otx2 homeoprotein, an essential morphogen for embryonic head formation, is reused later in life as this 'messenger' for critical period plasticity. The homeoprotein is stimulated by visual experience to propagate into the visual cortex, where it is internalized by GABAergic interneurons, especially Parvalbumin-positive cells (PV-cells). Otx2 promotes the maturation of PV-cells, consequently activating critical period onset in the visual cortex. Here, we discuss recent data that are beginning to illuminate the physiological function of non-cell autonomous homeoproteins, as well as the restriction of their transfer to PV-cells in vivo.
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Affiliation(s)
- Sayaka Sugiyama
- Department of Neurology, FM Kirby Neurobiology Center, Children's Hospital Boston, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA.
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Nicholas HR, Hodgkin J. The C. elegans Hox gene egl-5 is required for correct development of the hermaphrodite hindgut and for the response to rectal infection by Microbacterium nematophilum. Dev Biol 2009; 329:16-24. [PMID: 19232338 DOI: 10.1016/j.ydbio.2009.01.044] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 12/29/2008] [Accepted: 01/09/2009] [Indexed: 10/21/2022]
Abstract
Members of the Hox gene family encode transcription factors that specify positional identity along the anterior-posterior axis of nearly all metazoans. One among the Caenorhabditis elegans Hox genes is egl-5. A deletion allele of egl-5 was isolated in a screen for animals which fail to develop swollen tails when exposed to the bacterial pathogen Microbacterium nematophilum. We show that compromised rectal development, which occurs as a result of loss of egl-5 function, results in a failure of rectal epithelial cells to express the ERK MAP kinase mpk-1, which was previously shown to mediate tail-swelling in response to bacterial infection. Tissue-specific rescue experiments demonstrated that egl-5 and mpk-1 act autonomously in rectal cells in the morphological response. The weak egl-5 allele (n1439), which does not compromise rectal development, fails to affect tail-swelling. We find that this allele carries an inserted repeat element approximately 13.8 kb upstream of the egl-5 open reading frame, which specifically disrupts the cell-specific expression of this gene in HSN egg-laying neurons. Together these findings extend the complexity of regulation and function of Hox genes in C. elegans and demonstrate the importance of their tissue-specific expression for correct development and response to infection.
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Affiliation(s)
- Hannah R Nicholas
- School of Molecular and Microbial Biosciences, University of Sydney, NSW, Australia
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40
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Kuntz SG, Schwarz EM, DeModena JA, De Buysscher T, Trout D, Shizuya H, Sternberg PW, Wold BJ. Multigenome DNA sequence conservation identifies Hox cis-regulatory elements. Genome Res 2008; 18:1955-68. [PMID: 18981268 DOI: 10.1101/gr.085472.108] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
To learn how well ungapped sequence comparisons of multiple species can predict cis-regulatory elements in Caenorhabditis elegans, we made such predictions across the large, complex ceh-13/lin-39 locus and tested them transgenically. We also examined how prediction quality varied with different genomes and parameters in our comparisons. Specifically, we sequenced approximately 0.5% of the C. brenneri and C. sp. 3 PS1010 genomes, and compared five Caenorhabditis genomes (C. elegans, C. briggsae, C. brenneri, C. remanei, and C. sp. 3 PS1010) to find regulatory elements in 22.8 kb of noncoding sequence from the ceh-13/lin-39 Hox subcluster. We developed the MUSSA program to find ungapped DNA sequences with N-way transitive conservation, applied it to the ceh-13/lin-39 locus, and transgenically assayed 21 regions with both high and low degrees of conservation. This identified 10 functional regulatory elements whose activities matched known ceh-13/lin-39 expression, with 100% specificity and a 77% recovery rate. One element was so well conserved that a similar mouse Hox cluster sequence recapitulated the native nematode expression pattern when tested in worms. Our findings suggest that ungapped sequence comparisons can predict regulatory elements genome-wide.
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Affiliation(s)
- Steven G Kuntz
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA
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Abstract
There is increasing interest in the use of the free-living nematode Caenorhabditis elegans as a tool for parasitic nematode research and there are now a number of compelling examples of its successful application. C. elegans has the potential to become a standard tool for molecular helminthology researchers, just as yeast is routinely used by molecular biologists to study vertebrate biology. However, in order to exploit C. elegans in a meaningful manner, we need a detailed understanding of the extent to which different aspects of C. elegans biology have been conserved with particular groups of parasitic nematodes. This review first considers the current state of knowledge regarding the conservation of genome organisation across the nematode phylum and then discusses some recent evolutionary development studies in free-living nematodes. The aim is to provide some important concepts that are relevant to the extrapolation of information from C. elegans to parasitic nematodes and also to the interpretation of experiments that use C. elegans as a surrogate expression system. In general, examples have been specifically chosen because they highlight the importance of careful experimentation and interpretation of data. Consequently, the focus is on the differences that have been found between nematode species rather than the similarities. Finally, there is a detailed discussion of the current status of C. elegans as a heterologous expression system to study parasite gene function and regulation using successful examples from the literature.
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Affiliation(s)
- J S Gilleard
- Department of Veterinary Parasitology, Institute of Comparative Medicine, Faculty of Veterinary Medicine, University of Glasgow, Glasgow, UK.
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Shippy TD, Ronshaugen M, Cande J, He J, Beeman RW, Levine M, Brown SJ, Denell RE. Analysis of the Tribolium homeotic complex: insights into mechanisms constraining insect Hox clusters. Dev Genes Evol 2008; 218:127-39. [PMID: 18392875 PMCID: PMC2292473 DOI: 10.1007/s00427-008-0213-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2007] [Accepted: 02/12/2008] [Indexed: 01/28/2023]
Abstract
The remarkable conservation of Hox clusters is an accepted but little understood principle of biology. Some organizational constraints have been identified for vertebrate Hox clusters, but most of these are thought to be recent innovations that may not apply to other organisms. Ironically, many model organisms have disrupted Hox clusters and may not be well-suited for studies of structural constraints. In contrast, the red flour beetle, Tribolium castaneum, which has a long history in Hox gene research, is thought to have a more ancestral-type Hox cluster organization. Here, we demonstrate that the Tribolium homeotic complex (HOMC) is indeed intact, with the individual Hox genes in the expected colinear arrangement and transcribed from the same strand. There is no evidence that the cluster has been invaded by non-Hox protein-coding genes, although expressed sequence tag and genome tiling data suggest that noncoding transcripts are prevalent. Finally, our analysis of several mutations affecting the Tribolium HOMC suggests that intermingling of enhancer elements with neighboring transcription units may constrain the structure of at least one region of the Tribolium cluster. This work lays a foundation for future studies of the Tribolium HOMC that may provide insights into the reasons for Hox cluster conservation.
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Affiliation(s)
- Teresa D Shippy
- Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506, USA.
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Hoegg S, Boore JL, Kuehl JV, Meyer A. Comparative phylogenomic analyses of teleost fish Hox gene clusters: lessons from the cichlid fish Astatotilapia burtoni. BMC Genomics 2007; 8:317. [PMID: 17845724 PMCID: PMC2080641 DOI: 10.1186/1471-2164-8-317] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Accepted: 09/10/2007] [Indexed: 11/10/2022] Open
Abstract
Background Teleost fish have seven paralogous clusters of Hox genes stemming from two complete genome duplications early in vertebrate evolution, and an additional genome duplication during the evolution of ray-finned fish, followed by the secondary loss of one cluster. Gene duplications on the one hand, and the evolution of regulatory sequences on the other, are thought to be among the most important mechanisms for the evolution of new gene functions. Cichlid fish, the largest family of vertebrates with about 2500 species, are famous examples of speciation and morphological diversity. Since this diversity could be based on regulatory changes, we chose to study the coding as well as putative regulatory regions of their Hox clusters within a comparative genomic framework. Results We sequenced and characterized all seven Hox clusters of Astatotilapia burtoni, a haplochromine cichlid fish. Comparative analyses with data from other teleost fish such as zebrafish, two species of pufferfish, stickleback and medaka were performed. We traced losses of genes and microRNAs of Hox clusters, the medaka lineage seems to have lost more microRNAs than the other fish lineages. We found that each teleost genome studied so far has a unique set of Hox genes. The hoxb7a gene was lost independently several times during teleost evolution, the most recent event being within the radiation of East African cichlid fish. The conserved non-coding sequences (CNS) encompass a surprisingly large part of the clusters, especially in the HoxAa, HoxCa, and HoxDa clusters. Across all clusters, we observe a trend towards an increased content of CNS towards the anterior end. Conclusion The gene content of Hox clusters in teleost fishes is more variable than expected, with each species studied so far having a different set. Although the highest loss rate of Hox genes occurred immediately after whole genome duplications, our analyses showed that gene loss continued and is still ongoing in all teleost lineages. Along with the gene content, the CNS content also varies across clusters. The excess of CNS at the anterior end of clusters could imply a stronger conservation of anterior expression patters than those towards more posterior areas of the embryo.
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Affiliation(s)
- Simone Hoegg
- Lehrstuhl für Evolutionsbiologie und Zoologie, Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Jeffrey L Boore
- Program in Evolutionary Genomics, DOE Joint Genome Institute and Lawrence Berkeley National Laboratory, and University of California, Berkeley, California 94720, USA
- SymBio Corporation, 1455 Adams Drive, Menlo Park, CA 94025, and University of California, Berkeley, California 94720, USA
| | - Jennifer V Kuehl
- Program in Evolutionary Genomics, DOE Joint Genome Institute and Lawrence Berkeley National Laboratory, and University of California, Berkeley, California 94720, USA
| | - Axel Meyer
- Lehrstuhl für Evolutionsbiologie und Zoologie, Department of Biology, University of Konstanz, 78457 Konstanz, Germany
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Abstract
Although all bilaterian animals have a related set of Hox genes, the genomic organization of this gene complement comes in different flavors. In some unrelated species, Hox genes are clustered; in others, they are not. This indicates that the bilaterian ancestor had a clustered Hox gene family and that, subsequently, this genomic organization was either maintained or lost. Remarkably, the tightest organization is found in vertebrates, raising the embarrassingly finalistic possibility that vertebrates have maintained best this ancestral configuration. Alternatively, could they have co-evolved with an increased ;organization' of the Hox clusters, possibly linked to their genomic amplification, which would be at odds with our current perception of evolutionary mechanisms? When discussing the why's and how's of Hox gene clustering, we need to account for three points: the mechanisms of cluster evolution; the underlying biological constraints; and the developmental modes of the animals under consideration. By integrating these parameters, general conclusions emerge that can help solve the aforementioned dilemma.
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Affiliation(s)
- Denis Duboule
- National Research Centre Frontiers in Genetics, Department of Zoology and Animal Biology, University of Geneva, Sciences III, Switzerland.
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Schuettengruber B, Chourrout D, Vervoort M, Leblanc B, Cavalli G. Genome regulation by polycomb and trithorax proteins. Cell 2007; 128:735-45. [PMID: 17320510 DOI: 10.1016/j.cell.2007.02.009] [Citation(s) in RCA: 1035] [Impact Index Per Article: 60.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Polycomb group (PcG) and trithorax group (trxG) proteins are critical regulators of numerous developmental genes. To silence or activate gene expression, respectively, PcG and trxG proteins bind to specific regions of DNA and direct the posttranslational modification of histones. Recent work suggests that PcG proteins regulate the nuclear organization of their target genes and that PcG-mediated gene silencing involves noncoding RNAs and the RNAi machinery.
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Affiliation(s)
- Bernd Schuettengruber
- Institute of Human Genetics, CNRS, 141, rue de la Cardonille, 34396 Montpellier Cedex 5, France
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46
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Portman DS. Genetic control of sex differences in C. elegans neurobiology and behavior. ADVANCES IN GENETICS 2007; 59:1-37. [PMID: 17888793 DOI: 10.1016/s0065-2660(07)59001-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
As a well-characterized, genetically tractable animal, the nematode Caenorhabditis elegans is an ideal model to explore the connections between genes and the sexual regulation of the nervous system and behavior. The two sexes of C. elegans, males and hermaphrodites, have precisely defined differences in neuroanatomy: superimposed onto a "core" nervous system of exactly 294 neurons, hermaphrodites and males have 8 and 89 sex-specific neurons, respectively. These sex-specific neurons are essential for cognate sex-specific behaviors, including hermaphrodite egg-laying and male mating. In addition, regulated sex differences in the core nervous system itself may provide additional, though poorly understood, controls on behavior. These differences in the nervous system and behavior, like all known sex differences in the C. elegans soma, are controlled by the master regulator of C. elegans sex determination, tra-1. Downstream of tra-1 lie specific effectors of sex determination, including genes controlling sex-specific cell death and a family of regulators, the DM-domain genes, related to Drosophila doublesex and the vertebrate DMRT genes. There is no central (i.e., gonadal) regulator of sexual phenotype in the C. elegans nervous system; instead, tra-1 acts cell-autonomously in nearly all sexually dimorphic somatic cells. However, recent results suggest that the status of the gonad can be communicated to the nervous system to modulate sex-specific behaviors. Continuing research into the genetic control of neural sex differences in C. elegans is likely to yield insight into conserved mechanisms of cell-autonomous cross talk between cell fate patterning and sexual differentiation pathways.
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Affiliation(s)
- Douglas S Portman
- Department of Biomedical Genetics and Center for Aging and Developmental Biology, University of Rochester, Rochester, New York 14642, USA
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47
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Bondos S. Variations on a theme: Hox and Wnt combinatorial regulation during animal development. ACTA ACUST UNITED AC 2006; 2006:pe38. [PMID: 17018850 DOI: 10.1126/stke.3552006pe38] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Shockingly few transcription factors and cell signaling pathways are utilized to pattern organs and to specify the fate of a seemingly endless variety of unique cell types during animal development. This dichotomy led to the hypothesis that each factor is used in multiple tissues and that a combinatorial code of factors determines cell fate or tissue identity in a unique fashion. Two recent papers describe temporal changes in the interplay between Hox transcription factors, which specify positional identity, and Wnt signaling, which provides spatial information and promotes asymmetric cell division. These changes guide cells through a series of discrete steps, leading to unique fates. Variations between these two studies highlight the diversifying potential of combinatorial regulation, in short, that the pathways through which these molecules interact can vary even between adjacent cells. Shared features include cross-regulatory interactions to redeploy patterning genes in a tissue-specific manner for organogenesis and coregulation of common downstream targets. Identification of additional combinatorial gene targets and elucidation of their underlying molecular mechanisms are important future tasks in developmental biology and the study of evolution.
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Affiliation(s)
- Sarah Bondos
- Department of Biochemistry and Cell Biology, Rice University, 6100 South Main Street, Houston, TX 77005, USA.
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48
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Abstract
The family of Hox genes, which number 4 to 48 per genome depending on the animal, control morphologies on the main body axis of nearly all metazoans. The conventional wisdom is that Hox genes are arranged in chromosomal clusters in colinear order with their expression patterns on the body axis. However, recent evidence has shown that Hox gene clusters are fragmented, reduced, or expanded in many animals-findings that correlate with interesting morphological changes in evolution. Hox gene clusters also contain many noncoding RNAs, such as intergenic regulatory transcripts and evolutionarily conserved microRNAs, some of whose developmental functions have recently been explored.
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Affiliation(s)
- Derek Lemons
- Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093, USA
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49
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Wagmaister JA, Miley GR, Morris CA, Gleason JE, Miller LM, Kornfeld K, Eisenmann DM. Identification of cis-regulatory elements from the C. elegans Hox gene lin-39 required for embryonic expression and for regulation by the transcription factors LIN-1, LIN-31 and LIN-39. Dev Biol 2006; 297:550-65. [PMID: 16782085 DOI: 10.1016/j.ydbio.2006.05.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Revised: 05/03/2006] [Accepted: 05/04/2006] [Indexed: 12/01/2022]
Abstract
Expression of the Caenorhabditis elegans Hox gene lin-39 begins in the embryo and continues in multiple larval cells, including the P cell lineages that generate ventral cord neurons (VCNs) and vulval precursor cells (VPCs). lin-39 is regulated by several factors and by Wnt and Ras signaling pathways; however, no cis-acting sites mediating lin-39 regulation have been identified. Here, we describe three elements controlling lin-39 expression: a 338-bp upstream fragment that directs embryonic expression in P5-P8 and their descendants in the larva, a 247-bp intronic region sufficient for VCN expression, and a 1.3-kb upstream cis-regulatory module that drives expression in the VPC P6.p in a Ras-dependent manner. Three trans-acting factors regulate expression via the 1.3-kb element. A single binding site for the ETS factor LIN-1 mediates repression in VPCs other than P6.p; however, loss of LIN-1 decreases expression in P6.p. Therefore, LIN-1 acts both negatively and positively on lin-39 in different VPCs. The Forkhead domain protein LIN-31 also acts positively on lin-39 in P6.p via this module. Finally, LIN-39 itself binds to this element, suggesting that LIN-39 autoregulates its expression in P6.p. Therefore, we have begun to unravel the cis-acting sites regulating lin-39 Hox gene expression and have shown that lin-39 is a direct target of the Ras pathway acting via LIN-1 and LIN-31.
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Affiliation(s)
- Javier A Wagmaister
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250, USA
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50
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Liu H, Strauss TJ, Potts MB, Cameron S. Direct regulation of egl-1 and of programmed cell death by the Hox protein MAB-5 and by CEH-20, a C. elegans homolog of Pbx1. Development 2006; 133:641-50. [PMID: 16421192 DOI: 10.1242/dev.02234] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Hox genes are crucial determinants of cell fates and of body morphology of animals; mutations affecting these genes result in abnormal patterns of programmed cell death. How Hox genes regulate programmed cell death is an important and poorly understood aspect of normal development. In the nematode C. elegans, the Hox gene mab-5 is required for the programmed cell deaths of two lineally related cells generated in the P11 and P12 lineages. We show here that in the P11 lineage, a complex between MAB-5 and the Pbx homolog CEH-20 directly regulates transcription of the BH3 domain gene egl-1 to initiate programmed cell death; in the P12 lineage, mab-5 and ceh-20 apparently act indirectly to initiate programmed cell death. Direct regulation of programmed cell death may be an evolutionarily ancient and conserved function of Hox genes.
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Affiliation(s)
- Huarui Liu
- Department of Pediatrics, Division of Pediatric Hematology-Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75039-9148, USA
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