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Shook DR, Wen JWH, Rolo A, O'Hanlon M, Francica B, Dobbins D, Skoglund P, DeSimone DW, Winklbauer R, Keller RE. Characterization of convergent thickening, a major convergence force producing morphogenic movement in amphibians. eLife 2022; 11:e57642. [PMID: 35404236 PMCID: PMC9064293 DOI: 10.7554/elife.57642] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 04/10/2022] [Indexed: 01/09/2023] Open
Abstract
The morphogenic process of convergent thickening (CT) was originally described as the mediolateral convergence and radial thickening of the explanted ventral involuting marginal zone (IMZ) of Xenopus gastrulae (Keller and Danilchik, 1988). Here, we show that CT is expressed in all sectors of the pre-involution IMZ, which transitions to expressing convergent extension (CE) after involution. CT occurs without CE and drives symmetric blastopore closure in ventralized embryos. Assays of tissue affinity and tissue surface tension measurements suggest CT is driven by increased interfacial tension between the deep IMZ and the overlying epithelium. The resulting minimization of deep IMZ surface area drives a tendency to shorten the mediolateral (circumblastoporal) aspect of the IMZ, thereby generating tensile force contributing to blastopore closure (Shook et al., 2018). These results establish CT as an independent force-generating process of evolutionary significance and provide the first clear example of an oriented, tensile force generated by an isotropic, Holtfreterian/Steinbergian tissue affinity change.
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Affiliation(s)
- David R Shook
- Department of Biology, University of VirginiaCharlottesvilleUnited States
- Department of Cell Biology, University of Virginia, School of MedicineCharlottesvilleUnited States
| | - Jason WH Wen
- Department of Cell and Systems Biology, University of TorontoTorontoCanada
| | - Ana Rolo
- Centre for Craniofacial and Regenerative Biology, King's College LondonLondonUnited Kingdom
| | - Michael O'Hanlon
- Department of Cell Biology, University of Virginia, School of MedicineCharlottesvilleUnited States
| | | | | | - Paul Skoglund
- Department of Biology, University of VirginiaCharlottesvilleUnited States
| | - Douglas W DeSimone
- Department of Cell Biology, University of Virginia, School of MedicineCharlottesvilleUnited States
| | - Rudolf Winklbauer
- Department of Cell and Systems Biology, University of TorontoTorontoCanada
| | - Ray E Keller
- Department of Biology, University of VirginiaCharlottesvilleUnited States
- Department of Cell Biology, University of Virginia, School of MedicineCharlottesvilleUnited States
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2
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Nagel M, Barua D, Damm EW, Kashef J, Hofmann R, Ershov A, Cecilia A, Moosmann J, Baumbach T, Winklbauer R. Capillarity and active cell movement at mesendoderm translocation in the Xenopus gastrula. Development 2021; 148:dev.198960. [PMID: 33674259 DOI: 10.1242/dev.198960] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Accepted: 02/24/2021] [Indexed: 12/19/2022]
Abstract
During Xenopus gastrulation, leading edge mesendoderm (LEM) advances animally as a wedge-shaped cell mass over the vegetally moving blastocoel roof (BCR). We show that close contact across the BCR-LEM interface correlates with attenuated net advance of the LEM, which is pulled forward by tip cells while the remaining LEM frequently separates from the BCR. Nevertheless, lamellipodia persist on the detached LEM surface. They attach to adjacent LEM cells and depend on PDGF-A, cell-surface fibronectin and cadherin. We argue that active cell motility on the LEM surface prevents adverse capillary effects in the liquid LEM tissue as it moves by being pulled. It counters tissue surface-tension effects with oriented cell movement and bulges the LEM surface out to keep it close to the curved BCR without attaching to it. Proximity to the BCR is necessary, in turn, for the maintenance and orientation of lamellipodia that permit mass cell movement with minimal substratum contact. Together with a similar process in epithelial invagination, vertical telescoping, the cell movement at the LEM surface defines a novel type of cell rearrangement: vertical shearing.
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Affiliation(s)
- Martina Nagel
- Department of Cell and Systems Biology, University of Toronto, Toronto M5S 3G5, Canada
| | - Debanjan Barua
- Department of Cell and Systems Biology, University of Toronto, Toronto M5S 3G5, Canada
| | - Erich W Damm
- Department of Cell and Systems Biology, University of Toronto, Toronto M5S 3G5, Canada
| | - Jubin Kashef
- Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Ralf Hofmann
- Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.,Institut für Theoretische Physik, Universität Heidelberg, 69120 Heidelberg, Germany
| | - Alexey Ershov
- Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | | | - Julian Moosmann
- Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung, 21502 Geesthacht, Germany
| | - Tilo Baumbach
- Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Rudolf Winklbauer
- Department of Cell and Systems Biology, University of Toronto, Toronto M5S 3G5, Canada
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3
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Fagotto F. Tissue segregation in the early vertebrate embryo. Semin Cell Dev Biol 2020; 107:130-146. [DOI: 10.1016/j.semcdb.2020.05.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 05/22/2020] [Accepted: 05/26/2020] [Indexed: 11/30/2022]
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Bruce AEE, Winklbauer R. Brachyury in the gastrula of basal vertebrates. Mech Dev 2020; 163:103625. [PMID: 32526279 DOI: 10.1016/j.mod.2020.103625] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 05/11/2020] [Accepted: 06/03/2020] [Indexed: 12/20/2022]
Abstract
The Brachyury gene encodes a transcription factor that is conserved across all animals. In non-chordate metazoans, brachyury is primarily expressed in ectoderm regions that are added to the endodermal gut during development, and often form a ring around the site of endoderm internalization in the gastrula, the blastopore. In chordates, this brachyury ring is conserved, but the gene has taken on a new role in the formation of the mesoderm. In this phylum, a novel type of mesoderm that develops into notochord and somites has been added to the ancestral lateral plate mesoderm. Brachyury contributes to a shift in cell fate from neural ectoderm to posterior notochord and somites during a major lineage segregation event that in Xenopus and in the zebrafish takes place in the early gastrula. In the absence of this brachyury function, impaired formation of posterior mesoderm indirectly affects the gastrulation movements of peak involution and convergent extension. These movements are confined to specific regions and stages, leaving open the question why brachyury expression in an extensive, coherent ring, before, during and after gastrulation, is conserved in the two species whose gastrulation modes differ considerably, and also in many other metazoan gastrulae of diverse structure.
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Affiliation(s)
- Ashley E E Bruce
- Department of Cell and Systems Biology, University of Toronto, Canada
| | - Rudolf Winklbauer
- Department of Cell and Systems Biology, University of Toronto, Canada.
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5
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Huang Y, Winklbauer R. Cell migration in the Xenopus gastrula. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2018; 7:e325. [PMID: 29944210 DOI: 10.1002/wdev.325] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 05/22/2018] [Accepted: 05/30/2018] [Indexed: 12/17/2022]
Abstract
Xenopus gastrulation movements are in large part based on the rearrangement of cells by differential cell-on-cell migration within multilayered tissues. Different patterns of migration-based cell intercalation drive endoderm and mesoderm internalization and their positioning along their prospective body axes. C-cadherin, fibronectin, integrins, and focal contact components are expressed in all gastrula cells and play putative roles in cell-on-cell migration, but their actual functions in this respect are not yet understood. The gastrula can be subdivided into two motility domains, and in the vegetal, migratory domain, two modes of cell migration are discerned. Vegetal endoderm cells show ingression-type migration, a variant of amoeboid migration characterized by the lack of locomotory protrusions and by macropinocytosis as a mechanism of trailing edge resorption. Mesendoderm and prechordal mesoderm cells use lamellipodia in a mesenchymal mode of migration. Gastrula cell motility can be dissected into traits, such as cell polarity, adhesion, mobility, or protrusive activity, which are controlled separately yet in complex, combinatorial ways. Cells can instantaneously switch between different combinations of traits, showing plasticity as they respond to substratum properties. This article is categorized under: Early Embryonic Development > Gastrulation and Neurulation.
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Affiliation(s)
- Yunyun Huang
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Rudolf Winklbauer
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
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Wen JWH, Winklbauer R. Ingression-type cell migration drives vegetal endoderm internalisation in the Xenopus gastrula. eLife 2017; 6:e27190. [PMID: 28826499 PMCID: PMC5589415 DOI: 10.7554/elife.27190] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 08/08/2017] [Indexed: 12/30/2022] Open
Abstract
During amphibian gastrulation, presumptive endoderm is internalised as part of vegetal rotation, a large-scale movement that encompasses the whole vegetal half of the embryo. It has been considered a gastrulation process unique to amphibians, but we show that at the cell level, endoderm internalisation exhibits characteristics reminiscent of bottle cell formation and ingression, known mechanisms of germ layer internalisation. During ingression proper, cells leave a single-layered epithelium. In vegetal rotation, the process occurs in a multilayered cell mass; we refer to it as ingression-type cell migration. Endoderm cells move by amoeboid shape changes, but in contrast to other instances of amoeboid migration, trailing edge retraction involves ephrinB1-dependent macropinocytosis and trans-endocytosis. Moreover, although cells are separated by wide gaps, they are connected by filiform protrusions, and their migration depends on C-cadherin and the matrix protein fibronectin. Cells move in the same direction but at different velocities, to rearrange by differential migration.
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Affiliation(s)
- Jason WH Wen
- Department of Cell and Systems BiologyUniversity of TorontoTorontoCanada
| | - Rudolf Winklbauer
- Department of Cell and Systems BiologyUniversity of TorontoTorontoCanada
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Fagotto F. Regulation of Cell Adhesion and Cell Sorting at Embryonic Boundaries. Curr Top Dev Biol 2015; 112:19-64. [DOI: 10.1016/bs.ctdb.2014.11.026] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Evren S, Wen JWH, Luu O, Damm EW, Nagel M, Winklbauer R. EphA4-dependent Brachyury expression is required for dorsal mesoderm involution in the Xenopus gastrula. Development 2014; 141:3649-61. [PMID: 25209247 DOI: 10.1242/dev.111880] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Xenopus provides a well-studied model of vertebrate gastrulation, but a central feature, the movement of the mesoderm to the interior of the embryo, has received little attention. Here, we analyze mesoderm involution at the Xenopus dorsal blastopore lip. We show that a phase of rapid involution - peak involution - is intimately linked to an early stage of convergent extension, which involves differential cell migration in the prechordal mesoderm and a new movement of the chordamesoderm, radial convergence. The latter process depends on Xenopus Brachyury, the expression of which at the time of peak involution is controlled by signaling through the ephrin receptor, EphA4, its ligand ephrinB2 and its downstream effector p21-activated kinase. Our findings support a conserved role for Brachyury in blastopore morphogenesis.
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Affiliation(s)
- Sevan Evren
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
| | - Jason W H Wen
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
| | - Olivia Luu
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
| | - Erich W Damm
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
| | - Martina Nagel
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
| | - Rudolf Winklbauer
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
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10
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Abstract
Xenopus gastrulation consists of the orderly deformation of a single, multilayered cell sheet that resembles a multilayered epithelium, and flexible cell-cell adhesion has to provide tissue cohesion while allowing for cell rearrangements that drive gastrulation. A few classic cadherins are expressed in the Xenopus early embryo. The prominent C-cadherin is essential for the cohesion of the animal part of the gastrula including ectoderm and chordamesoderm, and it contributes to the adhesion of endoderm and anterior mesoderm in the vegetal moiety. The cadherin/catenin complex is expressed in a graded pattern which is stable during early development. Regional differences in cell adhesion conform to the graded cadherin/catenin expression pattern. However, although the cadherin/catenin pattern seems to be actively maintained, and cadherin function is modulated to reinforce differential adhesiveness, it is not clear how regional differences in tissue cohesion affect gastrulation. Manipulating cadherin expression or function does not induce cell sorting or boundary formation in the embryo. Moreover, known boundary formation mechanisms in the gastrula are based on active cell repulsion. Cell rearrangement is also compatible with variable tissue cohesion. Thus, identifying roles for differential adhesion in the Xenopus gastrula remains a challenge.
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Affiliation(s)
- Rudolf Winklbauer
- Department of Cell and Systems Biology, University of Toronto, Toronto, Canada,
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Winklbauer R, Damm EW. Internalizing the vegetal cell mass before and during amphibian gastrulation: vegetal rotation and related movements. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2011; 1:301-6. [PMID: 23801444 DOI: 10.1002/wdev.26] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The movement of the prospective mesoderm and endoderm to the interior of the amphibian embryo starts in the vegetal cell mass well before the onset of overt gastrulation. By an animally directed movement of cells, the vegetal mass constricts its outer part and expands its inner region including the blastocoel floor, in a process of pregastrulation emboly. Further internalization of the vegetal region has been studied in the Xenopus embryo. At the onset of gastrulation, vegetal rotation sets in at the periphery of the vegetal cell mass, first dorsally and then spreading laterally and ventrally. It consists of an intense inward surging of cells due to active cell rearrangements that can be observed in explants of the vegetal cell mass. In its course, the blastocoel floor expands further and becomes apposed to the blastocoel roof. The boundary between apposed floor and roof forms Brachet's cleft. Another effect of vegetal rotation is the downward and inward movement of the mesodermal marginal zone, constituting the first phase of involution. Together, the upward and outward movement of the peripheral vegetal mass and the downward and inward translocation of the marginal zone lead to an apparent rotation of the whole peripheral region of the gastrula. Vegetal rotation continues to contribute to endoderm internalization to near the end of gastrulation.
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Affiliation(s)
- Rudolf Winklbauer
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada.
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12
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Damm EW, Winklbauer R. PDGF-A controls mesoderm cell orientation and radial intercalation during Xenopus gastrulation. Development 2011; 138:565-75. [PMID: 21205800 DOI: 10.1242/dev.056903] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Radial intercalation is a common, yet poorly understood, morphogenetic process in the developing embryo. By analyzing cell rearrangement in the prechordal mesoderm during Xenopus gastrulation, we have identified a mechanism for radial intercalation. It involves cell orientation in response to a long-range signal mediated by platelet-derived growth factor (PDGF-A) and directional intercellular migration. When PDGF-A signaling is inhibited, prechordal mesoderm cells fail to orient towards the ectoderm, the endogenous source of PDGF-A, and no longer migrate towards it. Consequently, the prechordal mesoderm fails to spread during gastrulation. Orientation and directional migration can be rescued specifically by the expression of a short splicing isoform of PDGF-A, but not by a long matrix-binding isoform, consistent with a requirement for long-range signaling.
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Affiliation(s)
- Erich W Damm
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario, Canada
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Nagel M, Luu O, Bisson N, Macanovic B, Moss T, Winklbauer R. Role of p21-activated kinase in cell polarity and directional mesendoderm migration in the Xenopus gastrula. Dev Dyn 2009; 238:1709-26. [PMID: 19504461 DOI: 10.1002/dvdy.21985] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The p21 activated kinases (Paks) are prominently involved in the regulation of cell motility. Using a kinase-dead mutant of xPak1, we show that during Xenopus gastrulation, the kinase activity of Pak1 is required upstream of Cdc42 for the establishment of cell polarity in the migrating mesendoderm. Overactivation of Pak1 function by the expression of constitutively active xPak1 compromises the maintenance of cell polarity, by indirectly inhibiting RhoA function. Inhibition of cell polarization does not affect the migration of single mesendoderm cells. However, Pak1 inhibition interferes with the guidance of mesendoderm migration by directional cues residing in the extracellular matrix of the blastocoel roof, and with mesendoderm translocation in the embryo.
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Affiliation(s)
- Martina Nagel
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
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14
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Abstract
Formation of tissue boundaries can be studied in a simple, inexpensive system, the Xenopus gastrula. Here, the internalized mesoderm and endoderm are separated from the ectodermal blastocoel roof by Brachet's cleft. Non-canonical Wnt signaling mediated by the Wnt receptor, Xfz-7, is essential for this tissue separation event. The function of Wnt pathway components and other factors in tissue separation at Brachet's cleft can be tested in a blastocoel roof assay. Small pieces of mesoderm or endoderm are placed on large blastocoel roof explants, and it is observed whether these test explants remain on the surface of their in vivo substratum, or sink into it.
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Affiliation(s)
- Rudolf Winklbauer
- Dept of Cell & Systems Biology, University of Toronto, Toronto, ON, Canada
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Winklbauer R. Cell adhesion in amphibian gastrulation. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 278:215-75. [PMID: 19815180 DOI: 10.1016/s1937-6448(09)78005-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The amphibian gastrula can be regarded as a single coherent tissue which folds and distorts itself in a reproducible pattern to establish the embryonic germ layers. It is held together by cadherins which provide the flexible adhesion required for the massive cell rearrangements that accompany gastrulation. Cadherin expression and adhesiveness increase as one goes from the vegetal cell mass through the anterior mesendoderm to the chordamesoderm, and then decrease again slightly in the ectoderm. Together with a basic random component of cell motility, this flexible, differentially expressed adhesiveness generates surface and interfacial tension effects which, in principle, can exert strong forces. However, conclusive evidence for an in vivo role of differential adhesion-related effects in gastrula morphogenesis is still lacking. The most important morphogenetic process in the amphibian gastrula seems to be intercellular migration, where cells crawl actively across each other's surface. The crucial aspect of this process is that cell motility is globally oriented, leading for example to mediolateral intercalation of bipolar cells during convergent extension of the chordamesoderm or to the directional migration of unipolar cells during translocation of the anterior mesendoderm on the ectodermal blastocoel roof. During these movements, the boundary between ectoderm and mesoderm is maintained by a tissue separation process.
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Affiliation(s)
- Rudolf Winklbauer
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario M5S 3G5, Canada
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Luu O, Nagel M, Wacker S, Lemaire P, Winklbauer R. Control of gastrula cell motility by the Goosecoid/Mix.1/ Siamois network: basic patterns and paradoxical effects. Dev Dyn 2008; 237:1307-20. [PMID: 18407556 DOI: 10.1002/dvdy.21522] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
In the vegetal half of the Xenopus gastrula, cell populations differ with respect to migration on fibronectin substratum. We show that the paired-class homeodomain transcription factors Goosecoid (Gsc), Mix.1, and Siamois (Sia) are involved in the modulation of migration velocity and cell polarity. Mix.1 is expressed in the whole vegetal half and serves as a competence factor that is necessary, but not sufficient, for rapid cell migration and polarization. In the head mesoderm, Gsc and Sia are coexpressed with Mix.1, promoting rapid cell migration and polarization. Ectopic expression of Gsc and Sia in both vegetal and ventral regions often generates paradoxical effects; if a factor activates a certain motility trait in one region, it inhibits it in the other. Migration velocity and cell polarity are regulated independently. Fast and efficiently migrating multipolar cells and slow-moving polarized cells can be obtained by ectopic expression of these transcription factors in different combinations.
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Affiliation(s)
- Olivia Luu
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
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Molecular characterization of the gastrula in the turtle Emys orbicularis: an evolutionary perspective on gastrulation. PLoS One 2008; 3:e2676. [PMID: 18628985 PMCID: PMC2442194 DOI: 10.1371/journal.pone.0002676] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Accepted: 05/23/2008] [Indexed: 11/19/2022] Open
Abstract
Due to the presence of a blastopore as in amphibians, the turtle has been suggested to exemplify a transition form from an amphibian- to an avian-type gastrulation pattern. In order to test this hypothesis and gain insight into the emergence of the unique characteristics of amniotes during gastrulation, we have performed the first molecular characterization of the gastrula in a reptile, the turtle Emys orbicularis. The study of Brachyury, Lim1, Otx2 and Otx5 expression patterns points to a highly conserved dynamic of expression with amniote model organisms and makes it possible to identify the site of mesoderm internalization, which is a long-standing issue in reptiles. Analysis of Brachyury expression also highlights the presence of two distinct phases, less easily recognizable in model organisms and respectively characterized by an early ring-shaped and a later bilateral symmetrical territory. Systematic comparisons with tetrapod model organisms lead to new insights into the relationships of the blastopore/blastoporal plate system shared by all reptiles, with the blastopore of amphibians and the primitive streak of birds and mammals. The biphasic Brachyury expression pattern is also consistent with recent models of emergence of bilateral symmetry, which raises the question of its evolutionary significance.
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Shook DR, Keller R. Morphogenic machines evolve more rapidly than the signals that pattern them: lessons from amphibians. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2008; 310:111-35. [PMID: 18041048 DOI: 10.1002/jez.b.21204] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The induction of mesoderm and the patterning of its dorsal-ventral and anterior-posterior axes seems to be relatively conserved throughout the chordates, as do the morphogenic movements that produce a phylotypic stage embryo. What is not conserved is the initial embryonic architecture of the fertilized egg, and the specific cell behaviors used to drive mesoderm morphogenesis. How then do conserved patterning pathways adapt to diverse architectures and where do they diverge to direct the different cell behaviors used to shape the phylotypic body plan? Amphibians in particular, probably because of their broad range of reproductive strategies, show diverse embryonic architectures across their class and use diverse cell behaviors during their early morphogenesis, making them an interesting comparative group. We examine three examples from our work on amphibians that show variations in the use of cell behaviors to drive the morphogenesis of the same tissues. We also consider possible points where the conserved patterning pathways might diverge to produce different cell behaviors.
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Affiliation(s)
- David R Shook
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904-4328, USA.
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Abstract
Morphogenesis integrates a wide range of cellular processes into a self-organizing, self-deforming tissue. No single molecular "magic bullet" controls morphogenesis. Wide ranging cellular processes, often without parallels in conventional cell culture systems, work together to generate the architecture and modulate forces that produce and guide shape changes in the embryo. In this review we summarize the early development of the frog Xenopus laevis from a biomechanical perspective. We describe processes operating in the embryo from whole embryo scale, the tissue-scale, to the cellular and extracellular matrix scale. We focus on describing cells, their behaviors and the unique microenvironments they traverse during gastrulation and discuss the role of tissue mechanics in these processes.
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Affiliation(s)
- Lance A Davidson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pensylvania 15260, USA
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Jansen HJ, Wacker SA, Bardine N, Durston AJ. The role of the Spemann organizer in anterior-posterior patterning of the trunk. Mech Dev 2007; 124:668-81. [PMID: 17703924 DOI: 10.1016/j.mod.2007.07.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Revised: 06/06/2007] [Accepted: 07/10/2007] [Indexed: 02/03/2023]
Abstract
The formation of the vertebrate body axis during gastrulation strongly depends on a dorsal signaling centre, the Spemann organizer as it is called in amphibians. This organizer affects embryonic development by self-differentiation, regulation of morphogenesis and secretion of inducing signals. Whereas many molecular signals and mechanisms of the organizer have been clarified, its function in anterior-posterior pattern formation remains unclear. We dissected the organizer functions by generally blocking organizer formation and then restoring a single function. In experiments using a dominant inhibitory BMP receptor construct (tBr) we find evidence that neural activation by antagonism of the BMP pathway is the organizer function that enables the establishment of a detailed anterior-posterior pattern along the trunk. Conversely, the exclusive inhibition of neural activation by expressing a constitutive active BMP receptor (hAlk-6) in the ectoderm prohibits the establishment of an anterior-posterior pattern, even though the organizer itself is still intact. Thus, apart from the formerly described separation into a head and a trunk/tail organizer, the organizer does not deliver positional information for anterior-posterior patterning. Rather, by inducing neurectoderm, it makes ectodermal cells competent to receive patterning signals from the non-organizer mesoderm and thereby enable the formation of a complete and stable AP pattern along the trunk.
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Affiliation(s)
- Hans J Jansen
- Leiden University, Institute of Biology, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands
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21
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Evolution of the mechanisms and molecular control of endoderm formation. Mech Dev 2007; 124:253-78. [PMID: 17307341 DOI: 10.1016/j.mod.2007.01.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2006] [Revised: 12/24/2006] [Accepted: 01/03/2007] [Indexed: 01/13/2023]
Abstract
Endoderm differentiation and movements are of fundamental importance not only for subsequent morphogenesis of the digestive tract but also to enable normal patterning and differentiation of mesoderm- and ectoderm-derived organs. This review defines the tissues that have been called endoderm in different species, their cellular origin and their movements. We take a comparative approach to ask how signaling pathways leading to embryonic and extraembryonic endoderm differentiation have emerged in different organisms, how they became integrated and point to specific gaps in our knowledge that would be worth filling. Lastly, we address whether the gastrulation movements that lead to endoderm internalization are coupled with its differentiation.
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Buchholz DR, Singamsetty S, Karadge U, Williamson S, Langer CE, Elinson RP. Nutritional endoderm in a direct developing frog: A potential parallel to the evolution of the amniote egg. Dev Dyn 2007; 236:1259-72. [PMID: 17436277 DOI: 10.1002/dvdy.21153] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The egg of the direct-developing frog, Eleutherodactylus coqui, has 20 x the volume as that of the model amphibian, Xenopus laevis. Increased egg size led to the origin of nutritional endoderm, a novel cell type that provides nutrition but does not differentiate into digestive tract tissues. As the E. coqui endoderm develops, a distinct boundary exists between differentiating intestinal cells and large yolky cells, which persists even when yolk platelets are depleted. The yolky cells do not become tissues of the digestive tract and are lost, as shown by histology and lineage tracing. EcSox17, an endodermal transcriptional factor, did not distinguish these two cell types, however. When cleavage of the yolky cells was inhibited, embryogenesis continued, indicating that some degree of incomplete cleavage can be tolerated. The presence of cellularized nutritional endoderm in E. coqui may parallel changes that occurred in the evolution of the amniote egg 360 million years ago.
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Affiliation(s)
- Daniel R Buchholz
- Section on Molecular Morphogenesis, LGRD, NICHD, NIH, Bethesda, Maryland, USA
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23
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Webb SE, Miller AL. Ca2+ signaling and early embryonic patterning during the Blastula and Gastrula Periods of Zebrafish and Xenopus development. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:1192-208. [PMID: 16962186 DOI: 10.1016/j.bbamcr.2006.08.004] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2006] [Accepted: 08/02/2006] [Indexed: 11/23/2022]
Abstract
It has been proposed that Ca(2+) signaling, in the form of pulses, waves and steady gradients, may play a crucial role in key pattern forming events during early vertebrate development [L.F. Jaffe, Organization of early development by calcium patterns, BioEssays 21 (1999) 657-667; M.J. Berridge, P. Lipp, M.D. Bootman, The versatility and universality of calcium signaling, Nat. Rev. Mol. Cell Biol. 1 (2000) 11-21; S.E. Webb, A.L. Miller, Calcium signalling during embryonic development, Nat. Rev. Mol. Cell Biol. 4 (2003) 539-551]. With reference to the embryos of zebrafish (Danio rerio) and the frog, Xenopus laevis, we review the Ca(2+) signals reported during the Blastula and Gastrula Periods. This developmental window encompasses the major pattern forming events of epiboly, involution, and convergent extension, which result in the establishment of the basic germ layers and body axes [C.B. Kimmel, W.W. Ballard, S.R. Kimmel, B. Ullmann, T.F. Schilling, Stages of embryonic development of the zebrafish, Dev. Dyn. 203 (1995) 253-310]. Data will be presented to support the suggestion that propagating waves (both long and short range) of Ca(2+) release, followed by sequestration, may play a crucial role in: (1) Coordinating cell movements during these pattern forming events and (2) Contributing to the establishment of the basic embryonic axes, as well as (3) Helping to define the morphological boundaries of specific tissue domains and embryonic structures, including future organ anlagen [E. Gilland, A.L. Miller, E. Karplus, R. Baker, S.E. Webb, Imaging of multicellular large-scale rhythmic calcium waves during zebrafish gastrulation, Proc. Natl. Acad. Sci. USA 96 (1999) 157-161; J.B. Wallingford, A.J. Ewald, R.M. Harland, S.E. Fraser, Calcium signaling during convergent extension in Xenopus, Curr. Biol. 11 (2001) 652-661]. The various potential targets of these Ca(2+) transients will also be discussed, as well as how they might integrate with other known pattern forming pathways known to modulate early developmental events (such as the Wnt/Ca(2+)pathway; [T.A. Westfall, B. Hjertos, D.C. Slusarski, Requirement for intracellular calcium modulation in zebrafish dorsal-ventral patterning, Dev. Biol. 259 (2003) 380-391]).
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Affiliation(s)
- Sarah E Webb
- Department of Biology, the Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China
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24
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Kumano G, Ezal C, Smith WC. ADMP2 is essential for primitive blood and heart development in Xenopus. Dev Biol 2006; 299:411-23. [PMID: 16959239 DOI: 10.1016/j.ydbio.2006.08.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Revised: 06/29/2006] [Accepted: 08/02/2006] [Indexed: 10/24/2022]
Abstract
We describe here the cloning of a new member of the TGF-beta family with similarity to the anti-dorsalizing morphogenetic proteins (ADMPs). This new gene, ADMP2, is expressed in a broad band of mesendoderm cells that appear to include the progenitors of the endoderm and the ventral mesoderm. Antisense morpholino oligonucleotide knockdown of ADMP2 results in near-complete disruption of primitive blood and heart development, while the development of other mesoderm derivatives, including pronephros, muscle and lateral plate is not disrupted. Moreover, the development of the primitive blood in ADMP2 knockdown embryos cannot be rescued by BMP. These results suggests that ADMP2 plays an early role in specifying presumptive ventral mesoderm in the leading edge mesoderm, and that ADMP2 activity may be necessary to respond to BMP signaling in the context of ventral mesoderm induction.
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Affiliation(s)
- Gaku Kumano
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA 93106, USA
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25
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Ewald AJ, Peyrot SM, Tyszka JM, Fraser SE, Wallingford JB. Regional requirements for Dishevelled signaling duringXenopusgastrulation: separable effects on blastopore closure, mesendoderm internalization and archenteron formation. Development 2004; 131:6195-209. [PMID: 15548584 DOI: 10.1242/dev.01542] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During amphibian gastrulation, the embryo is transformed by the combined actions of several different tissues. Paradoxically, many of these morphogenetic processes can occur autonomously in tissue explants, yet the tissues in intact embryos must interact and be coordinated with one another in order to accomplish the major goals of gastrulation: closure of the blastopore to bring the endoderm and mesoderm fully inside the ectoderm, and generation of the archenteron. Here, we present high-resolution 3D digital datasets of frog gastrulae, and morphometrics that allow simultaneous assessment of the progress of convergent extension, blastopore closure and archenteron formation in a single embryo. To examine how the diverse morphogenetic engines work together to accomplish gastrulation, we combined these tools with time-lapse analysis of gastrulation, and examined both wild-type embryos and embryos in which gastrulation was disrupted by the manipulation of Dishevelled (Xdsh)signaling. Remarkably, although inhibition of Xdsh signaling disrupted both convergent extension and blastopore closure, mesendoderm internalization proceeded very effectively in these embryos. In addition, much of archenteron elongation was found to be independent of Xdsh signaling, especially during the second half of gastrulation. Finally, even in normal embryos, we found a surprising degree of dissociability between the various morphogenetic processes that occur during gastrulation. Together, these data highlight the central role of PCP signaling in governing distinct events of Xenopusgastrulation, and suggest that the loose relationship between morphogenetic processes may have facilitated the evolution of the wide variety of gastrulation mechanisms seen in different amphibian species.
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Affiliation(s)
- Andrew J Ewald
- Department of Biology and Biological Imaging Center, California Institute of Technology, Pasadena, CA 91125, USA
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26
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Abstract
In vertebrates, EGF-CFC factors are essential for Nodal signaling. Here, we show that the zygotic function of one-eyed pinhead, the zebrafish EGF-CFC factor, is necessary for cell movement throughout the blastoderm of the early embryo. During the blastula and gastrula stages, mutant cells are more cohesive and migrate slower than wild-type cells. Chimeric analysis reveals that these early motility defects are cell-autonomous; later, one-eyed pinhead mutant cells have a cell-autonomous tendency to acquire ectodermal rather than mesendodermal fates. Moreover, wild-type cells transplanted into the axial region of mutant hosts tend to form isolated aggregates of notochord tissue adjacent to the mutant notochord. Upon misexpressing the Nodal-like ligand Activin in whole embryos, which rescues aspects of the mutant phenotype, cell behavior retains the one-eyed pinhead motility phenotype. However, in squint;cyclops double mutants, which lack Nodal function and possess a more severe phenotype than zygotic one-eyed pinhead mutants, cells of the dorsal margin exhibit a marked tendency to widely disperse rather than cohere together. Elsewhere in the double mutants, for cells of the blastoderm and for rare cells of the gastrula that involute into the hypoblast, motility appears wild-type. Notably, cells at the animal pole, which are not under direct regulation by the Nodal pathway, behave normal in squint;cyclops mutants but exhibit defective motility in one-eyed pinhead mutants. We conclude that, in addition to a role in Nodal signaling, One-eyed pinhead is required for aspects of cell movement, possibly by regulating cell adhesion.
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Affiliation(s)
- Rachel M Warga
- Department of Biology, University of Rochester, Rochester, NY 14627, USA.
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27
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Roël G, van den Broek O, Spieker N, Peterson-Maduro J, Destrée O. Tcf-1 expression during Xenopus development. Gene Expr Patterns 2003; 3:123-6. [PMID: 12711535 DOI: 10.1016/s1567-133x(03)00039-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report the cloning and expression of Xenopus Tcf-1. The amino acid sequence of Tcf-1 of Xenopus laevis and Xenopus tropicalis is closely related to that of chicken, mouse and man. Thus, the family of Tcf/Lef proteins in the amphibian Xenopus comprises four members as in higher vertebrates. RT-PCR analysis revealed that Tcf-1 RNA encoding a beta-catenin binding isoform is maternally present as well as throughout early development. Different transcripts are expressed by alternative splicing. In cleavage and blastula stage embryos, Tcf-1 RNA is present at high levels in the animal hemisphere. During gastrulation Tcf-1 is differentially expressed with high levels in the animal cap and most of the marginal zone except for a narrow domain around the blastopore. At neurula stages expression is predominant in the neural plate. At tailbud stages expression is localized in specific areas of the brain, in the eyes, the otic vesicle, branchial arches and head mesenchyme, somites, tailbud, pronephros and pronephric duct.
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Affiliation(s)
- Giulietta Roël
- Netherlands Institute for Developmental Biology (NIOB), Hubrecht Laboratory, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands
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28
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Elinson RP, Beckham Y. Development in frogs with large eggs and the origin of amniotes. ZOOLOGY 2002; 105:105-17. [PMID: 16351861 DOI: 10.1078/0944-2006-00060] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2002] [Revised: 06/04/2002] [Accepted: 06/10/2002] [Indexed: 11/18/2022]
Abstract
The origin of the amniote egg is one of the most significant events in the evolution of terrestrial vertebrates. This innovation was probably driven by increased egg size, and to find potential parallels, we can examine the derived development of extant amphibians with large eggs. The embryo of the Puerto Rican tree frog, Eleutherodactylus coqui, exhibits an alteration of its fate map and a secondary coverage of its yolky cells, reflecting the large 3.5 mm egg. Comparable changes may have occurred with the derivation of an amniote pattern of development. Future investigations should focus on the molecular organization of the egg. In the model amphibian for development, Xenopus laevis, information for embryonic germ layers, the dorsal axis, and germ cells is stored mainly as localized RNAs at the vegetal pole of the egg. These localizations would likely be changed with increased egg size. A review of the orthologues of the key X. laevis genes raises the possibility that their activities are not conserved in other vertebrates.
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Affiliation(s)
- Richard P Elinson
- Department of Biological Sciences, Duquesne University, Pittsburgh, PA 15282, USA.
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