1
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Leite DJ, Schönauer A, Blakeley G, Harper A, Garcia-Castro H, Baudouin-Gonzalez L, Wang R, Sarkis N, Nikola AG, Koka VSP, Kenny NJ, Turetzek N, Pechmann M, Solana J, McGregor AP. An atlas of spider development at single-cell resolution provides new insights into arthropod embryogenesis. EvoDevo 2024; 15:5. [PMID: 38730509 PMCID: PMC11083766 DOI: 10.1186/s13227-024-00224-4] [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: 07/10/2023] [Accepted: 04/15/2024] [Indexed: 05/13/2024] Open
Abstract
Spiders are a diverse order of chelicerates that diverged from other arthropods over 500 million years ago. Research on spider embryogenesis, particularly studies using the common house spider Parasteatoda tepidariorum, has made important contributions to understanding the evolution of animal development, including axis formation, segmentation, and patterning. However, we lack knowledge about the cells that build spider embryos, their gene expression profiles and fate. Single-cell transcriptomic analyses have been revolutionary in describing these complex landscapes of cellular genetics in a range of animals. Therefore, we carried out single-cell RNA sequencing of P. tepidariorum embryos at stages 7, 8 and 9, which encompass the establishment and patterning of the body plan, and initial differentiation of many tissues and organs. We identified 20 cell clusters, from 18.5 k cells, which were marked by many developmental toolkit genes, as well as a plethora of genes not previously investigated. We found differences in the cell cycle transcriptional signatures, suggestive of different proliferation dynamics, which related to distinctions between endodermal and some mesodermal clusters, compared with ectodermal clusters. We identified many Hox genes as markers of cell clusters, and Hox gene ohnologs were often present in different clusters. This provided additional evidence of sub- and/or neo-functionalisation of these important developmental genes after the whole genome duplication in an arachnopulmonate ancestor (spiders, scorpions, and related orders). We also examined the spatial expression of marker genes for each cluster to generate a comprehensive cell atlas of these embryonic stages. This revealed new insights into the cellular basis and genetic regulation of head patterning, hematopoiesis, limb development, gut development, and posterior segmentation. This atlas will serve as a platform for future analysis of spider cell specification and fate, and studying the evolution of these processes among animals at cellular resolution.
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Affiliation(s)
- Daniel J Leite
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK.
- Department of Biosciences, Durham University, Durham, DH1 3LE, UK.
| | - Anna Schönauer
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Grace Blakeley
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Amber Harper
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Helena Garcia-Castro
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | | | - Ruixun Wang
- Institute for Zoology, Biocenter, University of Cologne, Zuelpicher Str. 47B, 50674, Cologne, Germany
| | - Naïra Sarkis
- Institute for Zoology, Biocenter, University of Cologne, Zuelpicher Str. 47B, 50674, Cologne, Germany
| | - Alexander Günther Nikola
- Evolutionary Ecology, Faculty of Biology, Biocenter, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany
| | - Venkata Sai Poojitha Koka
- Evolutionary Ecology, Faculty of Biology, Biocenter, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany
| | - Nathan J Kenny
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
- Department of Biochemistry Te Tari Matū Koiora, University of Otago, Dunedin, New Zealand
| | - Natascha Turetzek
- Evolutionary Ecology, Faculty of Biology, Biocenter, Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany
| | - Matthias Pechmann
- Institute for Zoology, Biocenter, University of Cologne, Zuelpicher Str. 47B, 50674, Cologne, Germany
| | - Jordi Solana
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK.
| | - Alistair P McGregor
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK.
- Department of Biosciences, Durham University, Durham, DH1 3LE, UK.
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2
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Ramesh PS, Chu LF. Species-specific roles of the Notch ligands, receptors, and targets orchestrating the signaling landscape of the segmentation clock. Front Cell Dev Biol 2024; 11:1327227. [PMID: 38348091 PMCID: PMC10859470 DOI: 10.3389/fcell.2023.1327227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 12/20/2023] [Indexed: 02/15/2024] Open
Abstract
Somitogenesis is a hallmark feature of all vertebrates and some invertebrate species that involves the periodic formation of block-like structures called somites. Somites are transient embryonic segments that eventually establish the entire vertebral column. A highly conserved molecular oscillator called the segmentation clock underlies this periodic event and the pace of this clock regulates the pace of somite formation. Although conserved signaling pathways govern the clock in most vertebrates, the mechanisms underlying the species-specific divergence in various clock characteristics remain elusive. For example, the segmentation clock in classical model species such as zebrafish, chick, and mouse embryos tick with a periodicity of ∼30, ∼90, and ∼120 min respectively. This enables them to form the species-specific number of vertebrae during their overall timespan of somitogenesis. Here, we perform a systematic review of the species-specific features of the segmentation clock with a keen focus on mouse embryos. We perform this review using three different perspectives: Notch-responsive clock genes, ligand-receptor dynamics, and synchronization between neighboring oscillators. We further review reports that use non-classical model organisms and in vitro model systems that complement our current understanding of the segmentation clock. Our review highlights the importance of comparative developmental biology to further our understanding of this essential developmental process.
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Affiliation(s)
- Pranav S. Ramesh
- Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
- Reproductive Biology and Regenerative Medicine Research Group, University of Calgary, Calgary, AB, Canada
- Alberta Children’s Hospital Research Institute, Calgary, AB, Canada
| | - Li-Fang Chu
- Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
- Reproductive Biology and Regenerative Medicine Research Group, University of Calgary, Calgary, AB, Canada
- Alberta Children’s Hospital Research Institute, Calgary, AB, Canada
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3
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Clark E, Battistara M, Benton MA. A timer gene network is spatially regulated by the terminal system in the Drosophila embryo. eLife 2022; 11:e78902. [PMID: 36524728 PMCID: PMC10065802 DOI: 10.7554/elife.78902] [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: 03/23/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
In insect embryos, anteroposterior patterning is coordinated by the sequential expression of the 'timer' genes caudal, Dichaete, and odd-paired, whose expression dynamics correlate with the mode of segmentation. In Drosophila, the timer genes are expressed broadly across much of the blastoderm, which segments simultaneously, but their expression is delayed in a small 'tail' region, just anterior to the hindgut, which segments during germband extension. Specification of the tail and the hindgut depends on the terminal gap gene tailless, but beyond this the regulation of the timer genes is poorly understood. We used a combination of multiplexed imaging, mutant analysis, and gene network modelling to resolve the regulation of the timer genes, identifying 11 new regulatory interactions and clarifying the mechanism of posterior terminal patterning. We propose that a dynamic Tailless expression gradient modulates the intrinsic dynamics of a timer gene cross-regulatory module, delineating the tail region and delaying its developmental maturation.
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Affiliation(s)
- Erik Clark
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Department of Systems Biology, Harvard Medical SchoolBostonUnited States
- Department of Genetics, University of CambridgeCambridgeUnited Kingdom
| | - Margherita Battistara
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Department of Physiology, Development and Neuroscience, University of CambridgeCambridgeUnited Kingdom
| | - Matthew A Benton
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Developmental Biology Unit, EMBLHeidelbergGermany
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4
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Sanchez PGL, Mochulska V, Mauffette Denis C, Mönke G, Tomita T, Tsuchida-Straeten N, Petersen Y, Sonnen K, François P, Aulehla A. Arnold tongue entrainment reveals dynamical principles of the embryonic segmentation clock. eLife 2022; 11:79575. [PMID: 36223168 PMCID: PMC9560162 DOI: 10.7554/elife.79575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 08/23/2022] [Indexed: 11/13/2022] Open
Abstract
Living systems exhibit an unmatched complexity, due to countless, entangled interactions across scales. Here, we aim to understand a complex system, that is, segmentation timing in mouse embryos, without a reference to these detailed interactions. To this end, we develop a coarse-grained approach, in which theory guides the experimental identification of the segmentation clock entrainment responses. We demonstrate period- and phase-locking of the segmentation clock across a wide range of entrainment parameters, including higher-order coupling. These quantifications allow to derive the phase response curve (PRC) and Arnold tongues of the segmentation clock, revealing its essential dynamical properties. Our results indicate that the somite segmentation clock has characteristics reminiscent of a highly non-linear oscillator close to an infinite period bifurcation and suggests the presence of long-term feedbacks. Combined, this coarse-grained theoretical-experimental approach reveals how we can derive simple, essential features of a highly complex dynamical system, providing precise experimental control over the pace and rhythm of the somite segmentation clock.
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Affiliation(s)
| | | | | | - Gregor Mönke
- European Molecular Biology Laboratory (EMBL), Developmental Biology Unit
| | - Takehito Tomita
- European Molecular Biology Laboratory (EMBL), Developmental Biology Unit
| | | | - Yvonne Petersen
- European Molecular Biology Laboratory (EMBL), Transgenic Service
| | - Katharina Sonnen
- European Molecular Biology Laboratory (EMBL), Developmental Biology Unit
| | | | - Alexander Aulehla
- European Molecular Biology Laboratory (EMBL), Developmental Biology Unit
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5
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Mundaca-Escobar M, Cepeda RE, Sarrazin AF. The organizing role of Wnt signaling pathway during arthropod posterior growth. Front Cell Dev Biol 2022; 10:944673. [PMID: 35990604 PMCID: PMC9389326 DOI: 10.3389/fcell.2022.944673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 07/11/2022] [Indexed: 11/28/2022] Open
Abstract
Wnt signaling pathways are recognized for having major roles in tissue patterning and cell proliferation. In the last years, remarkable progress has been made in elucidating the molecular and cellular mechanisms that underlie sequential segmentation and axial elongation in various arthropods, and the canonical Wnt pathway has emerged as an essential factor in these processes. Here we review, with a comparative perspective, the current evidence concerning the participation of this pathway during posterior growth, its degree of conservation among the different subphyla within Arthropoda and its relationship with the rest of the gene regulatory network involved. Furthermore, we discuss how this signaling pathway could regulate segmentation to establish this repetitive pattern and, at the same time, probably modulate different cellular processes precisely coupled to axial elongation. Based on the information collected, we suggest that this pathway plays an organizing role in the formation of the body segments through the regulation of the dynamic expression of segmentation genes, via controlling the caudal gene, at the posterior region of the embryo/larva, that is necessary for the correct sequential formation of body segments in most arthropods and possibly in their common segmented ancestor. On the other hand, there is insufficient evidence to link this pathway to axial elongation by controlling its main cellular processes, such as convergent extension and cell proliferation. However, conclusions are premature until more studies incorporating diverse arthropods are carried out.
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Affiliation(s)
| | | | - Andres F. Sarrazin
- CoDe-Lab, Instituto de Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
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6
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Diaz-Cuadros M, Pourquié O, El-Sherif E. Patterning with clocks and genetic cascades: Segmentation and regionalization of vertebrate versus insect body plans. PLoS Genet 2021; 17:e1009812. [PMID: 34648490 PMCID: PMC8516289 DOI: 10.1371/journal.pgen.1009812] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Oscillatory and sequential processes have been implicated in the spatial patterning of many embryonic tissues. For example, molecular clocks delimit segmental boundaries in vertebrates and insects and mediate lateral root formation in plants, whereas sequential gene activities are involved in the specification of regional identities of insect neuroblasts, vertebrate neural tube, vertebrate limb, and insect and vertebrate body axes. These processes take place in various tissues and organisms, and, hence, raise the question of what common themes and strategies they share. In this article, we review 2 processes that rely on the spatial regulation of periodic and sequential gene activities: segmentation and regionalization of the anterior-posterior (AP) axis of animal body plans. We study these processes in species that belong to 2 different phyla: vertebrates and insects. By contrasting 2 different processes (segmentation and regionalization) in species that belong to 2 distantly related phyla (arthropods and vertebrates), we elucidate the deep logic of patterning by oscillatory and sequential gene activities. Furthermore, in some of these organisms (e.g., the fruit fly Drosophila), a mode of AP patterning has evolved that seems not to overtly rely on oscillations or sequential gene activities, providing an opportunity to study the evolution of pattern formation mechanisms.
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Affiliation(s)
- Margarete Diaz-Cuadros
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Pathology, Brigham and Women’s Hospital, Boston, Massachusetts, United States of America
| | - Olivier Pourquié
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Pathology, Brigham and Women’s Hospital, Boston, Massachusetts, United States of America
- Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts, United States of America
| | - Ezzat El-Sherif
- Division of Developmental Biology, Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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7
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Fusco G, Minelli A. The Development of Arthropod Segmentation Across the Embryonic/Post-embryonic Divide – An Evolutionary Perspective. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.622482] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In many arthropods, the appearance of new segments and their differentiation are not completed by the end of embryogenesis but continue, in different form and degree, well after hatching, in some cases up to the last post-embryonic molt. Focusing on the segmentation process currently described as post-embryonic segment addition (or, anamorphosis), we revise here the current knowledge and discuss it in an evolutionary framework which involves data from fossils, comparative morphology of extant taxa and gene expression. We advise that for a better understanding of the developmental changes underlying the evolution of arthropod segmentation, some key concepts should be applied in a critical way. These include the notion of the segment as a body block and the idea that hatching represents a well-defined divide, shared by all arthropods, between two contrasting developmental phases, embryonic vs. post-embryonic. This eventually reveals the complexity of the developmental processes occurring across hatching, which can evolve in different directions and with a different pace, creating the observed vagueness of the embryonic/post-embryonic divide.
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8
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Spatiotemporal variation in cell proliferation patterns during arthropod axial elongation. Sci Rep 2021; 11:327. [PMID: 33431947 PMCID: PMC7801698 DOI: 10.1038/s41598-020-79373-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 12/04/2020] [Indexed: 01/29/2023] Open
Abstract
An elongated and segmented body plan is a common morphological characteristic of all arthropods and is probably responsible for their high adaptation ability to diverse environments. Most arthropods form their bodies by progressively adding segments, resembling vertebrate somitogenesis. This sequential segmentation relies on a molecular clock that operates in the posterior region of the elongating embryo that combines dynamically with cellular behaviors and tissue rearrangements, allowing the extension of the developing body along its main embryonic axis. Even though the molecular mechanisms involved in elongation and segment formation have been found to be conserved in a considerable degree, cellular processes such as cell division are quite variable between different arthropods. In this study, we show that cell proliferation in the beetle Tribolium castaneum has a nonuniform spatiotemporal patterning during axial elongation. We found that dividing cells are preferentially oriented along the anterior-posterior axis, more abundant and posteriorly localized during thoracic segments formation and that this cell proliferation peak was triggered at the onset of axis elongation. This raise in cell divisions, in turn, was correlated with an increase in the elongation rate, but not with changes in cell density. When DNA synthesis was inhibited over this period, both the area and length of thoracic segments were significantly reduced but not of the first abdominal segment. We discuss the variable participation that different cell division patterns and cell movements may have on arthropod posterior growth and their evolutionary contribution.
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9
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Liu Y, Ortega-Hernández J, Chen H, Mai H, Zhai D, Hou X. Computed tomography sheds new light on the affinities of the enigmatic euarthropod Jianshania furcatus from the early Cambrian Chengjiang biota. BMC Evol Biol 2020; 20:62. [PMID: 32487135 PMCID: PMC7268425 DOI: 10.1186/s12862-020-01625-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 05/11/2020] [Indexed: 11/16/2022] Open
Abstract
Background The Chengjiang biota is one of the most species-rich Cambrian Konservat-Lagerstätten, and preserves a community dominated by non-biomineralized euarthropods. However, several Chengjiang euarthropods have an unfamiliar morphology, are extremely rare, or incompletely preserved. Results We employed micro-computed tomography to restudy the enigmatic euarthropod Jianshania furcatus. We reveal new morphological details, and demonstrate that the specimens assigned to this species represent two different taxa. The holotype of J. furcatus features a head shield with paired anterolateral notches, stalked lateral eyes, and an articulated tailspine with a bifurcate termination. The other specimen is formally redescribed as Xiaocaris luoi gen. et sp. nov., and is characterized by stalked eyes connected to an anterior sclerite, a subtrapezoidal head shield covering three small segments with reduced tergites, a trunk with 15 overlapping tergites with a well-developed dorsal keel, and paired tail flukes. Conclusions The presence of antennae, biramous appendages with endopods composed of 15 articles, and multiple appendage pairs associated with the trunk tergites identify X. luoi nov. as a representative of Fuxianhuiida, an early branching group of stem-group euarthropods endemic to the early Cambrian of Southwest China. X. luoi nov. represents the fifth fuxianhuiid species described from the Chengjiang biota, and its functional morphology illuminates the ecological diversity of this important clade for understanding the early evolutionary history of euarthropods.
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Affiliation(s)
- Yu Liu
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, 650500, China. .,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650500, China.
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
| | - Hong Chen
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, 650500, China.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650500, China
| | - Huijuan Mai
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, 650500, China.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650500, China
| | - Dayou Zhai
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, 650500, China.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650500, China
| | - Xianguang Hou
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, 650500, China.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650500, China
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10
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Cabanillas D. Primera cita de <em>Strigamia maritima</em> (Leach, 1817) (Chilopoda, Geophilomorpha, Linotaeniidae) en España. GRAELLSIA 2020. [DOI: 10.3989/graellsia.2020.v76.254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
En este informe se describe la primera cita de Strigamia maritima (Leach, 1817) en la península ibérica, encontrándose la especie en la ría del Eo localizada en el noroeste de Asturias (norte de España). Se comentan características morfológicas y ecológicas de S. maritima y se proporcionan claves de identificación ilustradas de las especies de Strigamia Gray, 1843 presentes en la península ibérica.
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11
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Constantinou SJ, Duan N, Nagy LM, Chipman AD, Williams TA. Elongation during segmentation shows axial variability, low mitotic rates, and synchronized cell cycle domains in the crustacean, Thamnocephalus platyurus. EvoDevo 2020; 11:1. [PMID: 31988708 PMCID: PMC6969478 DOI: 10.1186/s13227-020-0147-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2019] [Accepted: 01/03/2020] [Indexed: 12/20/2022] Open
Abstract
Background Segmentation in arthropods typically occurs by sequential addition of segments from a posterior growth zone. However, the amount of tissue required for growth and the cell behaviors producing posterior elongation are sparsely documented. Results Using precisely staged larvae of the crustacean, Thamnocephalus platyurus, we systematically examine cell division patterns and morphometric changes associated with posterior elongation during segmentation. We show that cell division occurs during normal elongation but that cells in the growth zone need only divide ~ 1.5 times to meet growth estimates; correspondingly, direct measures of cell division in the growth zone are low. Morphometric measurements of the growth zone and of newly formed segments suggest tagma-specific features of segment generation. Using methods for detecting two different phases in the cell cycle, we show distinct domains of synchronized cells in the posterior trunk. Borders of cell cycle domains correlate with domains of segmental gene expression, suggesting an intimate link between segment generation and cell cycle regulation. Conclusions Emerging measures of cellular dynamics underlying posterior elongation already show a number of intriguing characteristics that may be widespread among sequentially segmenting arthropods and are likely a source of evolutionary variability. These characteristics include: the low rates of posterior mitosis, the apparently tight regulation of cell cycle at the growth zone/new segment border, and a correlation between changes in elongation and tagma boundaries.
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Affiliation(s)
- Savvas J Constantinou
- 1Biology Department, Trinity College, Hartford, CT USA.,4Present Address: Department of Integrative Biology, Michigan State University, East Lansing, MI 48824 USA
| | - Nicole Duan
- 1Biology Department, Trinity College, Hartford, CT USA.,5Present Address: Bioinformatics and Quantitative Biosciences, Georgia Institute of Technology, North Avenue, Atlanta, GA 30332 USA
| | - Lisa M Nagy
- 2Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721 USA
| | - Ariel D Chipman
- 3The Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel
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12
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Grall E, Tschopp P. A sense of place, many times over ‐ pattern formation and evolution of repetitive morphological structures. Dev Dyn 2019; 249:313-327. [DOI: 10.1002/dvdy.131] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 10/30/2019] [Accepted: 11/04/2019] [Indexed: 12/14/2022] Open
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13
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Chipman AD, Edgecombe GD. Developing an integrated understanding of the evolution of arthropod segmentation using fossils and evo-devo. Proc Biol Sci 2019; 286:20191881. [PMID: 31575373 DOI: 10.1098/rspb.2019.1881] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Segmentation is fundamental to the arthropod body plan. Understanding the evolutionary steps by which arthropods became segmented is being transformed by the integration of data from evolutionary developmental biology (evo-devo), Cambrian fossils that allow the stepwise acquisition of segmental characters to be traced in the arthropod stem-group, and the incorporation of fossils into an increasingly well-supported phylogenetic framework for extant arthropods based on genomic-scale datasets. Both evo-devo and palaeontology make novel predictions about the evolution of segmentation that serve as testable hypotheses for the other, complementary data source. Fossils underpin such hypotheses as arthropodization originating in a frontal appendage and then being co-opted into other segments, and segmentation of the endodermal midgut in the arthropod stem-group. Insights from development, such as tagmatization being associated with different modes of segment generation in different body regions, and a distinct patterning of the anterior head segments, are complemented by palaeontological evidence for the pattern of tagmatization during ontogeny of exceptionally preserved fossils. Fossil and developmental data together provide evidence for a short head in stem-group arthropods and the mechanism of its formation and retention. Future breakthroughs are expected from identification of molecular signatures of developmental innovations within a phylogenetic framework, and from a focus on later developmental stages to identify the differentiation of repeated units of different systems within segmental precursors.
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Affiliation(s)
- Ariel D Chipman
- Department of Ecology, Evolution and Behavior, The Silberman Institute of Life Sciences, Edmond J. Safra Campus - Givat Ram, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Gregory D Edgecombe
- Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
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14
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Abstract
ABSTRACT
There is now compelling evidence that many arthropods pattern their segments using a clock-and-wavefront mechanism, analogous to that operating during vertebrate somitogenesis. In this Review, we discuss how the arthropod segmentation clock generates a repeating sequence of pair-rule gene expression, and how this is converted into a segment-polarity pattern by ‘timing factor’ wavefronts associated with axial extension. We argue that the gene regulatory network that patterns segments may be relatively conserved, although the timing of segmentation varies widely, and double-segment periodicity appears to have evolved at least twice. Finally, we describe how the repeated evolution of a simultaneous (Drosophila-like) mode of segmentation within holometabolan insects can be explained by heterochronic shifts in timing factor expression plus extensive pre-patterning of the pair-rule genes.
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Affiliation(s)
- Erik Clark
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
- Department of Zoology, University of Cambridge, Cambridge, CB2 3EJ, UK
| | - Andrew D. Peel
- School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Michael Akam
- Department of Zoology, University of Cambridge, Cambridge, CB2 3EJ, UK
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15
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Boos A, Distler J, Rudolf H, Klingler M, El-Sherif E. A re-inducible gap gene cascade patterns the anterior-posterior axis of insects in a threshold-free fashion. eLife 2018; 7:41208. [PMID: 30570485 PMCID: PMC6329609 DOI: 10.7554/elife.41208] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 12/19/2018] [Indexed: 12/05/2022] Open
Abstract
Gap genes mediate the division of the anterior-posterior axis of insects into different fates through regulating downstream hox genes. Decades of tinkering the segmentation gene network of Drosophila melanogaster led to the conclusion that gap genes are regulated (at least initially) through a threshold-based mechanism, guided by both anteriorly- and posteriorly-localized morphogen gradients. In this paper, we show that the response of the gap gene network in the beetle Tribolium castaneum upon perturbation is consistent with a threshold-free ‘Speed Regulation’ mechanism, in which the speed of a genetic cascade of gap genes is regulated by a posterior morphogen gradient. We show this by re-inducing the leading gap gene (namely, hunchback) resulting in the re-induction of the gap gene cascade at arbitrary points in time. This demonstrates that the gap gene network is self-regulatory and is primarily under the control of a posterior regulator in Tribolium and possibly other short/intermediate-germ insects.
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Affiliation(s)
- Alena Boos
- Division of Developmental Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Jutta Distler
- Division of Developmental Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Heike Rudolf
- Division of Developmental Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Martin Klingler
- Division of Developmental Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Ezzat El-Sherif
- Division of Developmental Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
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Vroomans RMA, Hogeweg P, ten Tusscher KHWJ. Around the clock: gradient shape and noise impact the evolution of oscillatory segmentation dynamics. EvoDevo 2018; 9:24. [PMID: 30555670 PMCID: PMC6288972 DOI: 10.1186/s13227-018-0113-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 11/22/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Segmentation, the subdivision of the major body axis into repeated elements, is considered one of the major evolutionary innovations in bilaterian animals. In all three segmented animal clades, the predominant segmentation mechanism is sequential segmentation, where segments are generated one by one in anterior-posterior order from a posterior undifferentiated zone. In vertebrates and arthropods, sequential segmentation is thought to arise from a clock-and-wavefront-type mechanism, where oscillations in the posterior growth zone are transformed into a segmental prepattern in the anterior by a receding wavefront. Previous evo-devo simulation studies have demonstrated that this segmentation type repeatedly arises, supporting the idea of parallel evolutionary origins in these animal clades. Sequential segmentation has been studied most extensively in vertebrates, where travelling waves have been observed that reflect the slowing down of oscillations prior to their cessation and where these oscillations involve a highly complex regulatory network. It is currently unclear under which conditions this oscillator complexity and slowing should be expected to evolve, how they are related and to what extent similar properties should be expected for sequential segmentation in other animal species. RESULTS To investigate these questions, we extend a previously developed computational model for the evolution of segmentation. We vary the slope of the posterior morphogen gradient and the strength of gene expression noise. We find that compared to a shallow gradient, a steep morphogen gradient allows for faster evolution and evolved oscillator networks are simpler. Furthermore, under steep gradients, damped oscillators often evolve, whereas shallow gradients appear to require persistent oscillators which are regularly accompanied by travelling waves, indicative of a frequency gradient. We show that gene expression noise increases the likelihood of evolving persistent oscillators under steep gradients and of evolving frequency gradients under shallow gradients. Surprisingly, we find that the evolutions of oscillator complexity and travelling waves are not correlated, suggesting that these properties may have evolved separately. CONCLUSIONS Based on our findings, we suggest that travelling waves may have evolved in response to shallow morphogen gradients and gene expression noise. These two factors may thus also be responsible for the observed differences between different species within both the arthropod and chordate phyla.
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Affiliation(s)
- Renske M. A. Vroomans
- Centre of Excellence in Experimental and Computational Developmental Biology, Institute of Biotechnology, University of Helsinki, Viikinkaari 5, 00790 Helsinki, Finland
- Theoretical Biology, Utrecht University, Padualaan 8, 3584CH Utrecht, Netherlands
| | - Paulien Hogeweg
- Theoretical Biology, Utrecht University, Padualaan 8, 3584CH Utrecht, Netherlands
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17
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Clark E, Peel AD. Evidence for the temporal regulation of insect segmentation by a conserved sequence of transcription factors. Development 2018; 145:dev.155580. [PMID: 29724758 PMCID: PMC6001374 DOI: 10.1242/dev.155580] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 04/25/2018] [Indexed: 01/20/2023]
Abstract
Long-germ insects, such as the fruit fly Drosophila melanogaster, pattern their segments simultaneously, whereas short-germ insects, such as the beetle Tribolium castaneum, pattern their segments sequentially, from anterior to posterior. While the two modes of segmentation at first appear quite distinct, much of this difference might simply reflect developmental heterochrony. We now show here that, in both Drosophila and Tribolium, segment patterning occurs within a common framework of sequential Caudal, Dichaete, and Odd-paired expression. In Drosophila these transcription factors are expressed like simple timers within the blastoderm, while in Tribolium they form wavefronts that sweep from anterior to posterior across the germband. In Drosophila, all three are known to regulate pair-rule gene expression and influence the temporal progression of segmentation. We propose that these regulatory roles are conserved in short-germ embryos, and that therefore the changing expression profiles of these genes across insects provide a mechanistic explanation for observed differences in the timing of segmentation. In support of this hypothesis we demonstrate that Odd-paired is essential for segmentation in Tribolium, contrary to previous reports.
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Affiliation(s)
- Erik Clark
- Laboratory for Development and Evolution, Department of Zoology, University of Cambridge, UK
| | - Andrew D Peel
- Faculty of Biological Sciences, University of Leeds, UK
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18
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Hemmi N, Akiyama-Oda Y, Fujimoto K, Oda H. A quantitative study of the diversity of stripe-forming processes in an arthropod cell-based field undergoing axis formation and growth. Dev Biol 2018; 437:84-104. [DOI: 10.1016/j.ydbio.2018.03.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2017] [Revised: 03/01/2018] [Accepted: 03/01/2018] [Indexed: 12/25/2022]
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Auman T, Chipman AD. The Evolution of Gene Regulatory Networks that Define Arthropod Body Plans. Integr Comp Biol 2018; 57:523-532. [PMID: 28957519 DOI: 10.1093/icb/icx035] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Our understanding of the genetics of arthropod body plan development originally stems from work on Drosophila melanogaster from the late 1970s and onward. In Drosophila, there is a relatively detailed model for the network of gene interactions that proceeds in a sequential-hierarchical fashion to define the main features of the body plan. Over the years, we have a growing understanding of the networks involved in defining the body plan in an increasing number of arthropod species. It is now becoming possible to tease out the conserved aspects of these networks and to try to reconstruct their evolution. In this contribution, we focus on several key nodes of these networks, starting from early patterning in which the main axes are determined and the broad morphological domains of the embryo are defined, and on to later stage wherein the growth zone network is active in sequential addition of posterior segments. The pattern of conservation of networks is very patchy, with some key aspects being highly conserved in all arthropods and others being very labile. Many aspects of early axis patterning are highly conserved, as are some aspects of sequential segment generation. In contrast, regional patterning varies among different taxa, and some networks, such as the terminal patterning network, are only found in a limited range of taxa. The growth zone segmentation network is ancient and is probably plesiomorphic to all arthropods. In some insects, it has undergone significant modification to give rise to a more hardwired network that generates individual segments separately. In other insects and in most arthropods, the sequential segmentation network has undergone a significant amount of systems drift, wherein many of the genes have changed. However, it maintains a conserved underlying logic and function.
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Affiliation(s)
- Tzach Auman
- The Department of Ecology, Evolution & Behavior, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904, Jerusalem, Israel
| | - Ariel D Chipman
- The Department of Ecology, Evolution & Behavior, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904, Jerusalem, Israel
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20
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A damped oscillator imposes temporal order on posterior gap gene expression in Drosophila. PLoS Biol 2018; 16:e2003174. [PMID: 29451884 PMCID: PMC5832388 DOI: 10.1371/journal.pbio.2003174] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 03/01/2018] [Accepted: 01/31/2018] [Indexed: 12/21/2022] Open
Abstract
Insects determine their body segments in two different ways. Short-germband insects, such as the flour beetle Tribolium castaneum, use a molecular clock to establish segments sequentially. In contrast, long-germband insects, such as the vinegar fly Drosophila melanogaster, determine all segments simultaneously through a hierarchical cascade of gene regulation. Gap genes constitute the first layer of the Drosophila segmentation gene hierarchy, downstream of maternal gradients such as that of Caudal (Cad). We use data-driven mathematical modelling and phase space analysis to show that shifting gap domains in the posterior half of the Drosophila embryo are an emergent property of a robust damped oscillator mechanism, suggesting that the regulatory dynamics underlying long- and short-germband segmentation are much more similar than previously thought. In Tribolium, Cad has been proposed to modulate the frequency of the segmentation oscillator. Surprisingly, our simulations and experiments show that the shift rate of posterior gap domains is independent of maternal Cad levels in Drosophila. Our results suggest a novel evolutionary scenario for the short- to long-germband transition and help explain why this transition occurred convergently multiple times during the radiation of the holometabolan insects. Different insect species exhibit one of two distinct modes of determining their body segments (known as segmentation) during development: they either use a molecular oscillator to position segments sequentially, or they generate segments simultaneously through a hierarchical gene-regulatory cascade. The sequential mode is ancestral, while the simultaneous mode has been derived from it independently several times during evolution. In this paper, we present evidence suggesting that simultaneous segmentation also involves an oscillator in the posterior end of the embryo of the vinegar fly, Drosophila melanogaster. This surprising result indicates that both modes of segment determination are much more similar than previously thought. Such similarity provides an important step towards our understanding of the frequent evolutionary transitions observed between sequential and simultaneous segmentation.
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21
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Newman SA, Glimm T, Bhat R. The vertebrate limb: An evolving complex of self-organizing systems. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2018; 137:12-24. [PMID: 29325895 DOI: 10.1016/j.pbiomolbio.2018.01.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 01/03/2018] [Accepted: 01/04/2018] [Indexed: 11/28/2022]
Abstract
The paired appendages (fins or limbs) of jawed vertebrates contain an endoskeleton consisting of nodules, bars and, in some groups, plates of cartilage, or bone arising from replacement of cartilaginous templates. The generation of the endoskeletal elements occurs by processes involving production and diffusion of morphogens, with, variously, positive and negative feedback circuits, adhesion, and receptor dynamics with similarities to the mechanism for chemical pattern formation proposed by Alan Turing. This review presents a unified interpretation of the evolution and functioning of these mechanisms. Studies are described indicating that protocondensations, compacted mesenchymal cell aggregates that prefigure the appendicular skeleton, arise through the adhesive activity of galectin-1, a matricellular protein with skeletogenic homologs in all jawed vertebrates. In the cartilaginous and lobe-finned fishes (and to a variable extent in ray-finned fishes) it additionally cooperates with an isoform of galectin-8 to constitute a self-organizing network capable of generating arrays of preskeletal nodules, bars and plates. Further, in the tetrapods, a putative galectin-8 control module was acquired that may have enabled proximodistal increase in the number of protocondensations. In parallel to this, other self-organizing networks emerged that acted, via Bmp, Wnt, Sox9 and Runx2, as well as transforming factor-β and fibronectin, to convert protocondensations into skeletal tissues. The progressive appearance and integration of these skeletogenic networks over evolution occurred in the context of an independently evolved system of Hox protein and Shh gradients that interfaced with them to tune the spatial wavelengths and refine the identities of the resulting arrays of elements.
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Affiliation(s)
- Stuart A Newman
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY, 10595, USA.
| | - Tilmann Glimm
- Department of Mathematics, Western Washington University, Bellingham, WA, 98229, USA
| | - Ramray Bhat
- Department of Molecular Reproduction, Development and Genetics, Biological Sciences Division, Indian Institute of Science, Bangalore, 560012, India
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22
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Hunnekuhl VS, Akam M. Formation and subdivision of the head field in the centipede Strigamia maritima, as revealed by the expression of head gap gene orthologues and hedgehog dynamics. EvoDevo 2017; 8:18. [PMID: 29075435 PMCID: PMC5654096 DOI: 10.1186/s13227-017-0082-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 10/11/2017] [Indexed: 11/22/2022] Open
Abstract
Background There have been few studies of head patterning in non-insect arthropods, and even in the insects, much is not yet understood. In the fly Drosophila three head gap genes, orthodenticle (otd), buttonhead (btd) and empty spiracles (ems) are essential for patterning the head. However, they do not act through the same pair-rule genes that pattern the trunk from the mandibular segment backwards. Instead they act through the downstream factors collier (col) and cap‘n’collar (cnc), and presumably other unknown factors. In the beetle Tribolium, these same gap and downstream genes are also expressed during early head development, but in more restricted domains, and some of them have been shown to be of minor functional importance. In the spider Parasteatoda tepidariorum, hedgehog (hh) and otd have been shown to play an important role in head segmentation. Results We have investigated the expression dynamics of otx (otd), SP5/btd, ems, and the downstream factors col, cnc and hh during early head development of the centipede Strigamia maritima. Our results reveal the process of head condensation and show that the anteroposterior sequence of specific gene expression is conserved with that in insects. SP5/btd and otx genes are expressed prior to and during head field formation, whereas ems is not expressed until after the initial formation of the head field, in an emerging gap between SP5/btd and otx expression. Furthermore, we observe an early domain of Strigamia hh expression in the head field that splits to produce segmental stripes in the ocular, antennal and intercalary segments. Conclusions The dynamics of early gene expression in the centipede show considerable similarity with that in the beetle, both showing more localised expression of head gap genes than occurs in the fly. This suggests that the broad overlapping domains of head gap genes observed in Drosophila are derived in this lineage. We also suggest that the splitting of the early hh segmental stripes may reflect an ancestral and conserved process in arthropod head patterning. A remarkably similar stripe splitting process has been described in a spider, and in the Drosophila head hh expression starts from a broad domain that transforms into three stripes. Electronic supplementary material The online version of this article (doi:10.1186/s13227-017-0082-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Vera S Hunnekuhl
- Laboratory for Development and Evolution, Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB23EJ UK.,Department of Evolutionary Developmental Genetics, Georg-August-Universität Göttingen, Caspari Haus, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
| | - Michael Akam
- Laboratory for Development and Evolution, Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB23EJ UK
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23
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Cepeda RE, Pardo RV, Macaya CC, Sarrazin AF. Contribution of cell proliferation to axial elongation in the red flour beetle Tribolium castaneum. PLoS One 2017; 12:e0186159. [PMID: 29016664 PMCID: PMC5633189 DOI: 10.1371/journal.pone.0186159] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 09/26/2017] [Indexed: 11/18/2022] Open
Abstract
Most arthropods generate their posterior bodies by adding segments periodically, as the embryo grows, from a posteriorly located region called the segment addition zone. This mode of segmentation is shared with vertebrates and relies on oscillatory mechanisms, where the temporal periodicity of a clock is translated into repetitive spatial patterns. This ordered anterior-to-posterior pattern is achieved at the same time as the tissue elongates, opening the question of the functional coordination between the mechanisms of segmental patterning and posterior growth. The study of these processes in different arthropods has played an important role in unravelling some of the molecular mechanisms of segment formation. However, the behavior of cells during elongation and how cellular processes affect this segmental patterning has been poorly studied. Cell proliferation together with cell rearrangements are presumed to be the major forces driving axis elongation in the red flour beetle Tribolium castaneum. However, there still no strong evidence about the role and distribution of cell proliferation within the embryo. In this study, we propose to address these questions by using whole embryo cultures and pharmacological manipulation. We show that considerable cell proliferation occurs during germband elongation, measured by incorporation of the nucleoside analog of thymidine 5-Ethynyl-2’-deoxyuridine, EdU. Moreover, proliferating cells appeared to be spread along the elongating embryo with a posterior bias at early segmentation. In addition, when we blocked cell division, treated germbands were always shorter than controls and in some cases not able to fully elongate, even when control embryos already started to retract and leg buds are evident. Finally, we found that the absence of cell proliferation has no apparent effect on segmental patterning, as evidenced by Tc-engrailed (Tc-en) gene expression.
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Affiliation(s)
- Rodrigo E. Cepeda
- Instituto de Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Renato V. Pardo
- Instituto de Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Constanza C. Macaya
- Instituto de Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Andres F. Sarrazin
- Instituto de Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
- * E-mail:
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24
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Speed regulation of genetic cascades allows for evolvability in the body plan specification of insects. Proc Natl Acad Sci U S A 2017; 114:E8646-E8655. [PMID: 28973882 DOI: 10.1073/pnas.1702478114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
During the anterior-posterior fate specification of insects, anterior fates arise in a nonelongating tissue (called the "blastoderm"), and posterior fates arise in an elongating tissue (called the "germband"). However, insects differ widely in the extent to which anterior-posterior fates are specified in the blastoderm versus the germband. Here we present a model in which patterning in both the blastoderm and germband of the beetle Tribolium castaneum is based on the same flexible mechanism: a gradient that modulates the speed of a genetic cascade of gap genes, resulting in the induction of sequential kinematic waves of gap gene expression. The mechanism is flexible and capable of patterning both elongating and nonelongating tissues, and hence converting blastodermal to germband fates and vice versa. Using RNAi perturbations, we found that blastodermal fates could be shifted to the germband, and germband fates could be generated in a blastoderm-like morphology. We also suggest a molecular mechanism underlying our model, in which gradient levels regulate the switch between two enhancers: One enhancer is responsible for sequential gene activation, and the other is responsible for freezing temporal rhythms into spatial patterns. This model is consistent with findings in Drosophila melanogaster, where gap genes were found to be regulated by two nonredundant "shadow" enhancers.
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25
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Clark E. Dynamic patterning by the Drosophila pair-rule network reconciles long-germ and short-germ segmentation. PLoS Biol 2017; 15:e2002439. [PMID: 28953896 PMCID: PMC5633203 DOI: 10.1371/journal.pbio.2002439] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 10/09/2017] [Accepted: 09/07/2017] [Indexed: 02/07/2023] Open
Abstract
Drosophila segmentation is a well-established paradigm for developmental pattern formation. However, the later stages of segment patterning, regulated by the "pair-rule" genes, are still not well understood at the system level. Building on established genetic interactions, I construct a logical model of the Drosophila pair-rule system that takes into account the demonstrated stage-specific architecture of the pair-rule gene network. Simulation of this model can accurately recapitulate the observed spatiotemporal expression of the pair-rule genes, but only when the system is provided with dynamic "gap" inputs. This result suggests that dynamic shifts of pair-rule stripes are essential for segment patterning in the trunk and provides a functional role for observed posterior-to-anterior gap domain shifts that occur during cellularisation. The model also suggests revised patterning mechanisms for the parasegment boundaries and explains the aetiology of the even-skipped null mutant phenotype. Strikingly, a slightly modified version of the model is able to pattern segments in either simultaneous or sequential modes, depending only on initial conditions. This suggests that fundamentally similar mechanisms may underlie segmentation in short-germ and long-germ arthropods.
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Affiliation(s)
- Erik Clark
- Laboratory for Development and Evolution, Department of Zoology, University of Cambridge, Cambridge, United Kingdom
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26
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Liao BK, Oates AC. Delta-Notch signalling in segmentation. ARTHROPOD STRUCTURE & DEVELOPMENT 2017; 46:429-447. [PMID: 27888167 PMCID: PMC5446262 DOI: 10.1016/j.asd.2016.11.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 11/20/2016] [Accepted: 11/21/2016] [Indexed: 06/06/2023]
Abstract
Modular body organization is found widely across multicellular organisms, and some of them form repetitive modular structures via the process of segmentation. It's vastly interesting to understand how these regularly repeated structures are robustly generated from the underlying noise in biomolecular interactions. Recent studies from arthropods reveal similarities in segmentation mechanisms with vertebrates, and raise the possibility that the three phylogenetic clades, annelids, arthropods and chordates, might share homology in this process from a bilaterian ancestor. Here, we discuss vertebrate segmentation with particular emphasis on the role of the Notch intercellular signalling pathway. We introduce vertebrate segmentation and Notch signalling, pointing out historical milestones, then describe existing models for the Notch pathway in the synchronization of noisy neighbouring oscillators, and a new role in the modulation of gene expression wave patterns. We ask what functions Notch signalling may have in arthropod segmentation and explore the relationship between Notch-mediated lateral inhibition and synchronization. Finally, we propose open questions and technical challenges to guide future investigations into Notch signalling in segmentation.
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Affiliation(s)
- Bo-Kai Liao
- Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, London NW7 1AA, UK
| | - Andrew C Oates
- Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, London NW7 1AA, UK; Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
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27
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Savriama Y, Gerber S, Baiocco M, Debat V, Fusco G. Development and evolution of segmentation assessed by geometric morphometrics: The centipede Strigamia maritima as a case study. ARTHROPOD STRUCTURE & DEVELOPMENT 2017; 46:419-428. [PMID: 28302585 DOI: 10.1016/j.asd.2017.03.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 02/22/2017] [Accepted: 03/11/2017] [Indexed: 05/14/2023]
Abstract
Using the centipede model species Strigamia maritima as a subject of study, we illustrate the potential of geometric morphometrics for investigating the development and evolution of segmentation, with a specific focus on post-embryonic segmental patterning. We show how these techniques can contribute detailed descriptive data for comparative purposes, but also precious information on some features of the developmental system that are considered relevant for the evolvability of a segmented body architecture, such as developmental stability and canalization. Morphometric analyses allow to separately investigate several sources of phenotypic variation along a segmented body axis, like constitutive and random segment heteronomy, both within and among individuals. Specifically, in S. maritima, the segmental pattern of ventral sclerite shapes mirrors that of their bilateral fluctuating asymmetry and among-individual variation in associating the most anterior and most posterior segments in diverging from the central ones. Also, among segments, there seems to be a correlation between fluctuating asymmetry and shape variation among individuals, suggesting that canalization and developmental stability are somehow associated. Overall, these associations might stem from a joint influence of the segmental position on the two processes of developmental buffering.
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Affiliation(s)
- Yoland Savriama
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Sylvain Gerber
- Institut de Systématique, Évolution, Biodiversité ISYEB - UMR 7205 - MNHN CNRS UPMC EPHE, Muséum national d'Histoire naturelle, Sorbonne Universités, 57 rue Cuvier, CP 50, 75005 Paris, France
| | - Matteo Baiocco
- Department of Biology, University of Padova, Via U. Bassi 58/B, I-35131 Padova, Italy
| | - Vincent Debat
- Institut de Systématique, Évolution, Biodiversité ISYEB - UMR 7205 - MNHN CNRS UPMC EPHE, Muséum national d'Histoire naturelle, Sorbonne Universités, 57 rue Cuvier, CP 50, 75005 Paris, France
| | - Giuseppe Fusco
- Department of Biology, University of Padova, Via U. Bassi 58/B, I-35131 Padova, Italy.
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28
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Williams TA, Nagy LM. Linking gene regulation to cell behaviors in the posterior growth zone of sequentially segmenting arthropods. ARTHROPOD STRUCTURE & DEVELOPMENT 2017; 46:380-394. [PMID: 27720841 DOI: 10.1016/j.asd.2016.10.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Accepted: 10/03/2016] [Indexed: 06/06/2023]
Abstract
Virtually all arthropods all arthropods add their body segments sequentially, one by one in an anterior to posterior progression. That process requires not only segment specification but typically growth and elongation. Here we review the functions of some of the key genes that regulate segmentation: Wnt, caudal, Notch pathway, and pair-rule genes, and discuss what can be inferred about their evolution. We focus on how these regulatory factors are integrated with growth and elongation and discuss the importance and challenges of baseline measures of growth and elongation. We emphasize a perspective that integrates the genetic regulation of segment patterning with the cellular mechanisms of growth and elongation.
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Affiliation(s)
| | - Lisa M Nagy
- Department of Molecular and Cellular Biology, The University of Arizona, Tucson, AZ 85721, USA.
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29
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Minelli A. Introduction: The evolution of segmentation. ARTHROPOD STRUCTURE & DEVELOPMENT 2017; 46:323-327. [PMID: 28235577 DOI: 10.1016/j.asd.2017.02.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 02/20/2017] [Accepted: 02/20/2017] [Indexed: 06/06/2023]
Affiliation(s)
- Alessandro Minelli
- Department of Biology, University of Padova, Via Ugo Bassi, 58 B, I 35131 Padova, Italy.
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Auman T, Vreede BMI, Weiss A, Hester SD, Williams TA, Nagy LM, Chipman AD. Dynamics of growth zone patterning in the milkweed bug Oncopeltus fasciatus. Development 2017; 144:1896-1905. [PMID: 28432218 PMCID: PMC5450833 DOI: 10.1242/dev.142091] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 04/10/2017] [Indexed: 01/19/2023]
Abstract
We describe the dynamic process of abdominal segment generation in the milkweed bug Oncopeltus fasciatus. We present detailed morphological measurements of the growing germband throughout segmentation. Our data are complemented by cell division profiles and expression patterns of key genes, including invected and even-skipped as markers for different stages of segment formation. We describe morphological and mechanistic changes in the growth zone and in nascent segments during the generation of individual segments and throughout segmentation, and examine the relative contribution of newly formed versus existing tissue to segment formation. Although abdominal segment addition is primarily generated through the rearrangement of a pool of undifferentiated cells, there is nonetheless proliferation in the posterior. By correlating proliferation with gene expression in the growth zone, we propose a model for growth zone dynamics during segmentation in which the growth zone is functionally subdivided into two distinct regions: a posterior region devoted to a slow rate of growth among undifferentiated cells, and an anterior region in which segmental differentiation is initiated and proliferation inhibited. Summary: A detailed analysis of posterior segment addition in an insect reveals that the growth zone is divided into two functional domains responsible for growth and differentiation.
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Affiliation(s)
- Tzach Auman
- Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram 91904, Jerusalem, Israel
| | - Barbara M I Vreede
- Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram 91904, Jerusalem, Israel
| | - Aryeh Weiss
- Faculty of Engineering and The Bar-Ilan Institute of Nanotechnology & Advanced Materials, Bar Ilan University, Ramat Gan 52900, Israel.,Bio-Imaging Unit, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram 91904, Jerusalem, Israel
| | - Susan D Hester
- Molecular and Cellular Biology Department, University of Arizona, Tucson, AZ 85721, USA
| | | | - Lisa M Nagy
- Molecular and Cellular Biology Department, University of Arizona, Tucson, AZ 85721, USA
| | - Ariel D Chipman
- Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram 91904, Jerusalem, Israel
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Clark E, Akam M. Odd-paired controls frequency doubling in Drosophila segmentation by altering the pair-rule gene regulatory network. eLife 2016; 5:e18215. [PMID: 27525481 PMCID: PMC5035143 DOI: 10.7554/elife.18215] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 08/14/2016] [Indexed: 01/08/2023] Open
Abstract
The Drosophila embryo transiently exhibits a double-segment periodicity, defined by the expression of seven 'pair-rule' genes, each in a pattern of seven stripes. At gastrulation, interactions between the pair-rule genes lead to frequency doubling and the patterning of 14 parasegment boundaries. In contrast to earlier stages of Drosophila anteroposterior patterning, this transition is not well understood. By carefully analysing the spatiotemporal dynamics of pair-rule gene expression, we demonstrate that frequency-doubling is precipitated by multiple coordinated changes to the network of regulatory interactions between the pair-rule genes. We identify the broadly expressed but temporally patterned transcription factor, Odd-paired (Opa/Zic), as the cause of these changes, and show that the patterning of the even-numbered parasegment boundaries relies on Opa-dependent regulatory interactions. Our findings indicate that the pair-rule gene regulatory network has a temporally modulated topology, permitting the pair-rule genes to play stage-specific patterning roles.
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Affiliation(s)
- Erik Clark
- Laboratory for Development and Evolution, Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - Michael Akam
- Laboratory for Development and Evolution, Department of Zoology, University of Cambridge, Cambridge, United Kingdom
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Leite DJ, McGregor AP. Arthropod evolution and development: recent insights from chelicerates and myriapods. Curr Opin Genet Dev 2016; 39:93-100. [DOI: 10.1016/j.gde.2016.06.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 06/06/2016] [Accepted: 06/07/2016] [Indexed: 01/30/2023]
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Toll Genes Have an Ancestral Role in Axis Elongation. Curr Biol 2016; 26:1609-1615. [DOI: 10.1016/j.cub.2016.04.055] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 04/06/2016] [Accepted: 04/20/2016] [Indexed: 12/17/2022]
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Rothschild JB, Tsimiklis P, Siggia ED, François P. Predicting Ancestral Segmentation Phenotypes from Drosophila to Anopheles Using In Silico Evolution. PLoS Genet 2016; 12:e1006052. [PMID: 27227405 PMCID: PMC4882032 DOI: 10.1371/journal.pgen.1006052] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 04/23/2016] [Indexed: 12/23/2022] Open
Abstract
Molecular evolution is an established technique for inferring gene homology but regulatory DNA turns over so rapidly that inference of ancestral networks is often impossible. In silico evolution is used to compute the most parsimonious path in regulatory space for anterior-posterior patterning linking two Dipterian species. The expression pattern of gap genes has evolved between Drosophila (fly) and Anopheles (mosquito), yet one of their targets, eve, has remained invariant. Our model predicts that stripe 5 in fly disappears and a new posterior stripe is created in mosquito, thus eve stripe modules 3+7 and 4+6 in fly are homologous to 3+6 and 4+5 in mosquito. We can place Clogmia on this evolutionary pathway and it shares the mosquito homologies. To account for the evolution of the other pair-rule genes in the posterior we have to assume that the ancestral Dipterian utilized a dynamic method to phase those genes in relation to eve. The last common ancestor of the fruit fly (Drosophila) and mosquito (Anopheles) lived more than 200 Million years ago. Can we use available data on insects alive today to infer what their ancestor looked like? In this manuscript, we focus on early embryonic development, when stripes of genetic expression appear and define the location of insect segments (“segmentation”). We use an evolutionary algorithm to reconstruct and predict dynamics of genes controlling stripes in the last common ancestor of fly and mosquito. We predict a new and different combinatorial logic of stripe formation in mosquito compared to fly, which is fully consistent with development of intermediate species such as moth-fly (Clogmia). Our simulations further suggest that the dynamics of gene expression in this last common ancestor were similar to other insects, such as wasps (Nasonia). Our method illustrates how computational methods inspired by machine learning and non-linear physics can be used to infer gene dynamics in species that disappeared millions of years ago.
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Affiliation(s)
- Jeremy B. Rothschild
- Physics Department, McGill University, Ernest Rutherford Physics Building, Montreal, Quebec, Canada
| | - Panagiotis Tsimiklis
- Physics Department, McGill University, Ernest Rutherford Physics Building, Montreal, Quebec, Canada
| | - Eric D. Siggia
- Center for Studies in Physics and Biology, The Rockefeller University, New York, New York, United States of America
| | - Paul François
- Physics Department, McGill University, Ernest Rutherford Physics Building, Montreal, Quebec, Canada
- * E-mail:
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XX/XY System of Sex Determination in the Geophilomorph Centipede Strigamia maritima. PLoS One 2016; 11:e0150292. [PMID: 26919730 PMCID: PMC4769173 DOI: 10.1371/journal.pone.0150292] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 02/11/2016] [Indexed: 11/19/2022] Open
Abstract
We show that the geophilomorph centipede Strigamia maritima possesses an XX/XY system of sex chromosomes, with males being the heterogametic sex. This is, to our knowledge, the first report of sex chromosomes in any geophilomorph centipede. Using the recently assembled Strigamia genome sequence, we identified a set of scaffolds differentially represented in male and female DNA sequence. Using quantitative real-time PCR, we confirmed that three candidate X chromosome-derived scaffolds are present at approximately twice the copy number in females as in males. Furthermore, we confirmed that six candidate Y chromosome-derived scaffolds contain male-specific sequences. Finally, using this molecular information, we designed an X chromosome-specific DNA probe and performed fluorescent in situ hybridization against mitotic and meiotic chromosome spreads to identify the Strigamia XY sex-chromosome pair cytologically. We found that the X and Y chromosomes are recognizably different in size during the early pachytene stage of meiosis, and exhibit incomplete and delayed pairing.
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Schönauer A, Paese CLB, Hilbrant M, Leite DJ, Schwager EE, Feitosa NM, Eibner C, Damen WGM, McGregor AP. The Wnt and Delta-Notch signalling pathways interact to direct pair-rule gene expression via caudal during segment addition in the spider Parasteatoda tepidariorum. Development 2016; 143:2455-63. [DOI: 10.1242/dev.131656] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 05/19/2016] [Indexed: 12/16/2022]
Abstract
In short germ arthropods, posterior segments are added sequentially from a growth zone or segment addition zone (SAZ) during embryogenesis. Studies in spiders such as the common house spider, Parasteatoda tepidariorum, have provided insights into the gene regulatory network (GRN) that underlies the development of the SAZ, and revealed the involvement of two important signalling pathways. It was shown that Wnt8 maintains a pool of undifferentiated cells in the SAZ, but this ligand is also required for dynamic Delta (Dl) expression associated with the formation of new segments. However, it remains unclear how these pathways interact during SAZ formation and subsequently regulate segment addition. Here we show that Delta-Notch signalling is required for Wnt8 expression in posterior SAZ cells, but represses the expression of this Wnt gene in anterior SAZ cells. We also found that these two signalling pathways are required for the expression of the spider orthologues of the segmentation genes even-skipped (eve) and runt-1 (run-1), at least in part via the transcription factor encoded by caudal (cad). Moreover, it appears that dynamic expression of eve in this spider does not require a feedback loop with run-1, as is found in the pair-rule circuit of the beetle Tribolium. Taken together, our results suggest that the development of posterior segments in Parasteatoda is directed by dynamic interactions between Wnt8 and Delta-Notch signalling that are read out by cad, which is necessary but not sufficient to regulate the expression of the pair-rule genes eve and run-1. Our study therefore provides new insights towards better understanding the evolution and developmental regulation of segmentation in other arthropods including insects.
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Affiliation(s)
- Anna Schönauer
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Christian L. B. Paese
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Maarten Hilbrant
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
- Present address: Institute for Developmental Biology, University of Cologne, Zülpicher Str. 47b, 50674 Cologne, Germany
| | - Daniel J. Leite
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Evelyn E. Schwager
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
- Present address: Department of Biological Sciences, University of Massachusetts Lowell, 198 Riverside St., Lowell, MA 01854, USA
| | - Natália Martins Feitosa
- Laboratório Integrado de Ciências Morfofuncionais, Universidade Federal do Rio de Janeiro- UFRJ/NUPEM-Campus Macaé
| | - Cornelius Eibner
- Department of Genetics, Friedrich-Schiller-University Jena, Philosophenweg 12, 07743 Jena, Germany
| | - Wim G. M. Damen
- Department of Genetics, Friedrich-Schiller-University Jena, Philosophenweg 12, 07743 Jena, Germany
| | - Alistair P. McGregor
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
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Fusco G, Leśniewska M, Congiu L, Bertorelle G. Population genetic structure of a centipede species with high levels of developmental instability. PLoS One 2015; 10:e0126245. [PMID: 26029915 PMCID: PMC4452494 DOI: 10.1371/journal.pone.0126245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 03/30/2015] [Indexed: 11/26/2022] Open
Abstract
European populations of the geophilomorph centipede Haplophilus subterraneus show a high proportion of individuals with morphological anomalies, suggesting high levels of developmental instability. The broad geographic distribution of this phenomenon seems to exclude local environmental causes, but the source of instability is still to be identified. The goal of the present study was to collect quantitative data on the occurrence of phenodeviants in different populations, along with data on the patterns of genetic variation within and between populations, in order to investigate possible association between developmental instability and genetic features. In a sample of 11 populations of H. subterraneus, distributed in western and central Europe, we looked for phenodeviants, in particular with respect to trunk morphology, and studied genetic variation through the genotyping of microsatellite loci. Overall, no support was found to the idea that developmental instability in H. subterraneus is related to a specific patterns of genetic variation, including inbreeding estimates. We identified a major genetic partition that subdivides French populations from the others, and a low divergence among northwestern areas, which are possibly related to the post-glacial recolonization from southern refugia and/or to recent anthropogenic soil displacements. A weak correlation between individual number of leg bearing segments and the occurrence of trunk anomalies seems to support a trade-off between these two developmental traits. These results, complemented by preliminary data on developmental stability in two related species, suggest that the phenomenon has not a simple taxonomic distribution, while it exhibits an apparent localization in central and eastern Europe.
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Affiliation(s)
- Giuseppe Fusco
- Department of Biology, University of Padova, Padova, Italy
| | | | | | - Giorgio Bertorelle
- Department of Life Sciences and Biotechnologies, University of Ferrara, Ferrara, Italy
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38
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Robertson HE, Lapraz F, Rhodes AC, Telford MJ. The complete mitochondrial genome of the geophilomorph centipede Strigamia maritima. PLoS One 2015; 10:e0121369. [PMID: 25794168 PMCID: PMC4368715 DOI: 10.1371/journal.pone.0121369] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Accepted: 01/31/2015] [Indexed: 12/05/2022] Open
Abstract
Strigamia maritima (Myriapoda; Chilopoda) is a species from the soil-living order of geophilomorph centipedes. The Geophilomorpha is the most speciose order of centipedes with over a 1000 species described. They are notable for their large number of appendage bearing segments and are being used as a laboratory model to study the embryological process of segmentation within the myriapods. Using a scaffold derived from the recently published genome of Strigamia maritima that contained multiple mitochondrial protein-coding genes, here we report the complete mitochondrial genome of Strigamia, the first from any geophilomorph centipede. The mitochondrial genome of S. maritima is a circular molecule of 14,938 base pairs, within which we could identify the typical mitochondrial genome complement of 13 protein-coding genes and 2 ribosomal RNA genes. Sequences resembling 16 of the 22 transfer RNA genes typical of metazoan mitochondrial genomes could be identified, many of which have clear deviations from the standard ‘cloverleaf’ secondary structures of tRNA. Phylogenetic trees derived from the concatenated alignment of protein-coding genes of S. maritima and >50 other metazoans were unable to resolve the Myriapoda as monophyletic, but did support a monophyletic group of chilopods: Strigamia was resolved as the sister group of the scolopendromorph Scolopocryptos sp. and these two (Geophilomorpha and Scolopendromorpha), along with the Lithobiomorpha, formed a monophyletic group the Pleurostigmomorpha. Gene order within the S. maritima mitochondrial genome is unique compared to any other arthropod or metazoan mitochondrial genome to which it has been compared. The highly unusual organisation of the mitochondrial genome of Strigamia maritima is in striking contrast with the conservatively evolving nuclear genome: sampling of more members of this order of centipedes will be required to see whether this unusual organization is typical of the Geophilomorpha or results from a more recent reorganisation in the lineage leading to Strigamia.
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Affiliation(s)
- Helen E. Robertson
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London, United Kingdom
| | - François Lapraz
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London, United Kingdom
| | - Adelaide C. Rhodes
- Center for Genome Research and Biocomputing, 2750 SW Campus Way, Oregon State University, Corvallis, Oregon, United States of America
| | - Maximilian J. Telford
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London, United Kingdom
- * E-mail:
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39
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Abstract
Centipedes are a very old lineage of terrestrial animals. The first completely sequenced myriapod genome reveals that the blind centipede Strigamia maritima has no gene for light-sensory proteins, lacks the canonical circadian clock and possesses unusual features related to chemosensory perception.
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40
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Chipman AD, Ferrier DEK, Brena C, Qu J, Hughes DST, Schröder R, Torres-Oliva M, Znassi N, Jiang H, Almeida FC, Alonso CR, Apostolou Z, Aqrawi P, Arthur W, Barna JCJ, Blankenburg KP, Brites D, Capella-Gutiérrez S, Coyle M, Dearden PK, Du Pasquier L, Duncan EJ, Ebert D, Eibner C, Erikson G, Evans PD, Extavour CG, Francisco L, Gabaldón T, Gillis WJ, Goodwin-Horn EA, Green JE, Griffiths-Jones S, Grimmelikhuijzen CJP, Gubbala S, Guigó R, Han Y, Hauser F, Havlak P, Hayden L, Helbing S, Holder M, Hui JHL, Hunn JP, Hunnekuhl VS, Jackson L, Javaid M, Jhangiani SN, Jiggins FM, Jones TE, Kaiser TS, Kalra D, Kenny NJ, Korchina V, Kovar CL, Kraus FB, Lapraz F, Lee SL, Lv J, Mandapat C, Manning G, Mariotti M, Mata R, Mathew T, Neumann T, Newsham I, Ngo DN, Ninova M, Okwuonu G, Ongeri F, Palmer WJ, Patil S, Patraquim P, Pham C, Pu LL, Putman NH, Rabouille C, Ramos OM, Rhodes AC, Robertson HE, Robertson HM, Ronshaugen M, Rozas J, Saada N, Sánchez-Gracia A, Scherer SE, Schurko AM, Siggens KW, Simmons D, Stief A, Stolle E, Telford MJ, Tessmar-Raible K, Thornton R, van der Zee M, von Haeseler A, Williams JM, Willis JH, Wu Y, Zou X, Lawson D, Muzny DM, Worley KC, Gibbs RA, Akam M, Richards S. The first myriapod genome sequence reveals conservative arthropod gene content and genome organisation in the centipede Strigamia maritima. PLoS Biol 2014; 12:e1002005. [PMID: 25423365 PMCID: PMC4244043 DOI: 10.1371/journal.pbio.1002005] [Citation(s) in RCA: 176] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 10/15/2014] [Indexed: 12/14/2022] Open
Abstract
Myriapods (e.g., centipedes and millipedes) display a simple homonomous body plan relative to other arthropods. All members of the class are terrestrial, but they attained terrestriality independently of insects. Myriapoda is the only arthropod class not represented by a sequenced genome. We present an analysis of the genome of the centipede Strigamia maritima. It retains a compact genome that has undergone less gene loss and shuffling than previously sequenced arthropods, and many orthologues of genes conserved from the bilaterian ancestor that have been lost in insects. Our analysis locates many genes in conserved macro-synteny contexts, and many small-scale examples of gene clustering. We describe several examples where S. maritima shows different solutions from insects to similar problems. The insect olfactory receptor gene family is absent from S. maritima, and olfaction in air is likely effected by expansion of other receptor gene families. For some genes S. maritima has evolved paralogues to generate coding sequence diversity, where insects use alternate splicing. This is most striking for the Dscam gene, which in Drosophila generates more than 100,000 alternate splice forms, but in S. maritima is encoded by over 100 paralogues. We see an intriguing linkage between the absence of any known photosensory proteins in a blind organism and the additional absence of canonical circadian clock genes. The phylogenetic position of myriapods allows us to identify where in arthropod phylogeny several particular molecular mechanisms and traits emerged. For example, we conclude that juvenile hormone signalling evolved with the emergence of the exoskeleton in the arthropods and that RR-1 containing cuticle proteins evolved in the lineage leading to Mandibulata. We also identify when various gene expansions and losses occurred. The genome of S. maritima offers us a unique glimpse into the ancestral arthropod genome, while also displaying many adaptations to its specific life history. Arthropods are the most abundant animals on earth. Among them, insects clearly dominate on land, whereas crustaceans hold the title for the most diverse invertebrates in the oceans. Much is known about the biology of these groups, not least because of genomic studies of the fruit fly Drosophila, the water flea Daphnia, and other species used in research. Here we report the first genome sequence from a species belonging to a lineage that has previously received very little attention—the myriapods. Myriapods were among the first arthropods to invade the land over 400 million years ago, and survive today as the herbivorous millipedes and venomous centipedes, one of which—Strigamia maritima—we have sequenced here. We find that the genome of this centipede retains more characteristics of the presumed arthropod ancestor than other sequenced insect genomes. The genome provides access to many aspects of myriapod biology that have not been studied before, suggesting, for example, that they have diversified receptors for smell that are quite different from those used by insects. In addition, it shows specific consequences of the largely subterranean life of this particular species, which seems to have lost the genes for all known light-sensing molecules, even though it still avoids light.
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Affiliation(s)
- Ariel D. Chipman
- The Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat Ram, Jerusalem, Israel
| | - David E. K. Ferrier
- The Scottish Oceans Institute, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife, United Kingdom
| | - Carlo Brena
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - Jiaxin Qu
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Daniel S. T. Hughes
- EMBL - European Bioinformatics Institute, Hinxton, Cambridgeshire, United Kingdom
| | - Reinhard Schröder
- Institut für Biowissenschaften, Universität Rostock, Abt. Genetik, Rostock, Germany
| | | | - Nadia Znassi
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - Huaiyang Jiang
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Francisca C. Almeida
- Departament de Genètica and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain
- Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Universidad Nacional de Tucumán, Facultad de Ciencias Naturales e Instituto Miguel Lillo, San Miguel de Tucumán, Argentina
| | - Claudio R. Alonso
- School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Zivkos Apostolou
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
- Institute of Molecular Biology & Biotechnology, Foundation for Research & Technology - Hellas, Heraklion, Crete, Greece
| | - Peshtewani Aqrawi
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Wallace Arthur
- Department of Zoology, National University of Ireland, Galway, Ireland
| | | | - Kerstin P. Blankenburg
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Daniela Brites
- Evolutionsbiologie, Zoologisches Institut, Universität Basel, Basel, Switzerland
- Swiss Tropical and Public Health Institute, Basel, Switzerland
| | | | - Marcus Coyle
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Peter K. Dearden
- Gravida and Genetics Otago, Biochemistry Department, University of Otago, Dunedin, New Zealand
| | - Louis Du Pasquier
- Evolutionsbiologie, Zoologisches Institut, Universität Basel, Basel, Switzerland
| | - Elizabeth J. Duncan
- Gravida and Genetics Otago, Biochemistry Department, University of Otago, Dunedin, New Zealand
| | - Dieter Ebert
- Evolutionsbiologie, Zoologisches Institut, Universität Basel, Basel, Switzerland
| | - Cornelius Eibner
- Department of Zoology, National University of Ireland, Galway, Ireland
| | - Galina Erikson
- Razavi Newman Center for Bioinformatics, Salk Institute, La Jolla, California, United States of America
- Scripps Translational Science Institute, La Jolla, California, United States of America
| | | | - Cassandra G. Extavour
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Liezl Francisco
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Toni Gabaldón
- Centre for Genomic Regulation, Barcelona, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
| | - William J. Gillis
- Department of Biochemistry and Cell Biology, Center for Developmental Genetics, Stony Brook University, Stony Brook, New York, United States of America
| | | | - Jack E. Green
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - Sam Griffiths-Jones
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | | | - Sai Gubbala
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Roderic Guigó
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Center for Genomic Regulation, Barcelona, Spain
| | - Yi Han
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Frank Hauser
- Center for Functional and Comparative Insect Genomics, University of Copenhagen, Copenhagen, Denmark
| | - Paul Havlak
- Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas, United States of America
| | - Luke Hayden
- Department of Zoology, National University of Ireland, Galway, Ireland
| | - Sophie Helbing
- Institut für Biologie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
| | - Michael Holder
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Jerome H. L. Hui
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China
| | - Julia P. Hunn
- Department of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Vera S. Hunnekuhl
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - LaRonda Jackson
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Mehwish Javaid
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Shalini N. Jhangiani
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Francis M. Jiggins
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Tamsin E. Jones
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Tobias S. Kaiser
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
| | - Divya Kalra
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Nathan J. Kenny
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China
| | - Viktoriya Korchina
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Christie L. Kovar
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - F. Bernhard Kraus
- Institut für Biologie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
- Department of Laboratory Medicine, University Hospital Halle (Saale), Halle (Saale), Germany
| | - François Lapraz
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Sandra L. Lee
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Jie Lv
- Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas, United States of America
| | - Christigale Mandapat
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Gerard Manning
- Razavi Newman Center for Bioinformatics, Salk Institute, La Jolla, California, United States of America
| | - Marco Mariotti
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- Center for Genomic Regulation, Barcelona, Spain
| | - Robert Mata
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Tittu Mathew
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Tobias Neumann
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
- Center for Integrative Bioinformatics Vienna, Max F. Perutz Laboratories, University of Vienna, Medical University of Vienna, Vienna, Austria
| | - Irene Newsham
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Dinh N. Ngo
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Maria Ninova
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Geoffrey Okwuonu
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Fiona Ongeri
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - William J. Palmer
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Shobha Patil
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Pedro Patraquim
- School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Christopher Pham
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Ling-Ling Pu
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Nicholas H. Putman
- Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas, United States of America
| | - Catherine Rabouille
- Hubrecht Institute for Developmental Biology and Stem Cell Research, Utrecht, The Netherlands
| | - Olivia Mendivil Ramos
- The Scottish Oceans Institute, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife, United Kingdom
| | - Adelaide C. Rhodes
- Harte Research Institute, Texas A&M University Corpus Christi, Corpus Christi, Texas, United States of America
| | - Helen E. Robertson
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Hugh M. Robertson
- Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Matthew Ronshaugen
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Julio Rozas
- Departament de Genètica and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain
| | - Nehad Saada
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Alejandro Sánchez-Gracia
- Departament de Genètica and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain
| | - Steven E. Scherer
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Andrew M. Schurko
- Department of Biology, Hendrix College, Conway, Arkansas, United States of America
| | - Kenneth W. Siggens
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - DeNard Simmons
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Anna Stief
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
- Institute for Biochemistry and Biology, University Potsdam, Potsdam-Golm, Germany
| | - Eckart Stolle
- Institut für Biologie, Martin-Luther-Universität Halle-Wittenberg, Halle, Germany
| | - Maximilian J. Telford
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Kristin Tessmar-Raible
- Max F. Perutz Laboratories, University of Vienna, Vienna, Austria
- Research Platform “Marine Rhythms of Life”, Vienna, Austria
| | - Rebecca Thornton
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | | | - Arndt von Haeseler
- Center for Integrative Bioinformatics Vienna, Max F. Perutz Laboratories, University of Vienna, Medical University of Vienna, Vienna, Austria
- Bioinformatics and Computational Biology, Faculty of Computer Science, University of Vienna, Vienna, Austria
| | - James M. Williams
- Department of Biology, Hendrix College, Conway, Arkansas, United States of America
| | - Judith H. Willis
- Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Yuanqing Wu
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Xiaoyan Zou
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Daniel Lawson
- EMBL - European Bioinformatics Institute, Hinxton, Cambridgeshire, United Kingdom
| | - Donna M. Muzny
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Kim C. Worley
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Richard A. Gibbs
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Michael Akam
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
| | - Stephen Richards
- Human Genome Sequencing Center, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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Brena C. The embryoid development of Strigamia maritimaand its bearing on post-embryonic segmentation of geophilomorph centipedes. Front Zool 2014. [DOI: 10.1186/s12983-014-0058-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Valentin G, Oates AC. Opening a can of centipedes: new insights into mechanisms of body segmentation. BMC Biol 2013; 11:116. [PMID: 24289333 PMCID: PMC4220798 DOI: 10.1186/1741-7007-11-116] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Indexed: 11/10/2022] Open
Abstract
The search for a common developmental genetic mechanism of body segmentation appears to become more difficult, and more interesting, as new segmented organisms are added to the roster. Recent work in this journal by Brena and Akam on segmentation of the geophilomorph centipede Strigamia maritima, an arthropod distantly related to the standard insect models, contains developmental and evolutionary surprises that highlight the importance of a wider sampling of phyla.See research article: http://www.biomedcentral.com/1741-7007/11/112.
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Affiliation(s)
- Guillaume Valentin
- MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK.
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