1
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Spurrell M, Oulhen N, Foster S, Perillo M, Wessel G. Gene regulatory divergence amongst echinoderms underlies appearance of pigment cells in sea urchin development. Dev Biol 2023; 494:13-25. [PMID: 36519720 PMCID: PMC9870932 DOI: 10.1016/j.ydbio.2022.11.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 09/14/2022] [Accepted: 11/23/2022] [Indexed: 11/27/2022]
Abstract
Larvae of the sea urchin, Strongylocentrotus purpuratus, have pigmented migratory cells implicated in immune defense and gut patterning. The transcription factor SpGcm activates the expression of many pigment cell-specific genes, including those involved in pigment biosynthesis (SpPks1 and SpFmo3) and immune related genes (e.g. SpMif5). Despite the importance of this cell type in sea urchins, pigmented cells are absent in larvae of the sea star, Patiria miniata. In this study, we tested the premises that sea stars lack genes to synthesize echinochrome pigment, that the genes are present but are not expressed in the larvae, or rather that the homologous gene expression does not contribute to echinochrome synthesis. Our results show that orthologs of sea urchin pigment cell-specific genes (PmPks1, PmFmo3-1 and PmMifL1-2) are present in the sea star genome and expressed in the larvae. Although no cell lineage homologous to migratory sea urchin pigment cells is present, dynamic gene activation accomplishes a similar spatial and temporal expression profile. The mechanisms regulating the expression of these genes, though, is highly divergent. In sea stars, PmGcm lacks the central role in pigment gene expression since it is not expressed in PmPks1 and PmFmo3-1-positive cells, and knockdown of Gcm does not abrogate pigment gene expression. Pigment genes are instead expressed in the coelomic mesoderm early in development before later being expressed in the ectoderm. These findings were supported by in situ RNA hybridization and comparative scRNA-seq analyses. We conclude that simply the coexpression of Pks1 and Fmo3 orthologs in cells of the sea star is not sufficient to underlie the emergence of the larval pigment cell in the sea urchin.
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Affiliation(s)
- Maxwell Spurrell
- Brown University, Department of Molecular Biology, Cell Biology & Biochemistry, Providence, RI, USA
| | - Nathalie Oulhen
- Brown University, Department of Molecular Biology, Cell Biology & Biochemistry, Providence, RI, USA
| | - Stephany Foster
- Brown University, Department of Molecular Biology, Cell Biology & Biochemistry, Providence, RI, USA
| | - Margherita Perillo
- Brown University, Department of Molecular Biology, Cell Biology & Biochemistry, Providence, RI, USA
| | - Gary Wessel
- Brown University, Department of Molecular Biology, Cell Biology & Biochemistry, Providence, RI, USA.
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2
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Abstract
The micromeres of the sea urchin embryo are distinct from other blastomeres. After they arise through an asymmetric cell division at the 8- to 16-cell stage, micromeres immediately function as organizers. They also commit themselves to specific cell fates such as larval skeletogenic cells and primordial germ cells, while other blastomeres remain plastic and uncommitted at the 16-cell stage. In the phylum Echinodermata, only the sea urchin (class Echinoidea) embryo forms micromeres that serve as apparent organizers during early embryogenesis. Therefore, it is considered that micromeres are the derived features and that modification(s) of the developmental system allowed evolutionary introduction of this unique cell lineage. In this chapter, we summarize the both historic and recent observations that demonstrate unique properties of micromeres and discuss how this lineage of micromeres may have arisen during echinoderm evolution.
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Affiliation(s)
- Natsuko Emura
- Department of Molecular Biology Cell Biology Biochemistry, Brown University, Providence, RI, United States
| | - Mamiko Yajima
- Department of Molecular Biology Cell Biology Biochemistry, Brown University, Providence, RI, United States.
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3
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Andrikou C, Hejnol A. FGF signaling acts on different levels of mesoderm development within Spiralia. Development 2021; 148:264929. [PMID: 33999997 PMCID: PMC8180254 DOI: 10.1242/dev.196089] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 04/08/2021] [Indexed: 01/23/2023]
Abstract
FGF signaling is involved in mesoderm induction in members of deuterostomes (e.g. tunicates, hemichordates), but not in flies and nematodes, in which it has a role in mesoderm patterning and migration. However, we need comparable studies in other protostome taxa in order to decipher whether this mesoderm-inducing function of FGF extends beyond the lineage of deuterostomes. Here, we investigated the role of FGF signaling in mesoderm development in three species of lophophorates, a clade within the protostome group Spiralia. Our gene expression analyses show that the mesodermal molecular patterning is conserved between brachiopods and phoronids, but the spatial and temporal recruitment of transcription factors differs significantly. Moreover, the use of the inhibitor SU5402 demonstrates that FGF signaling is involved in different steps of mesoderm development, as well as in morphogenetic movements of gastrulation and axial elongation. Our findings suggest that the mesoderm-inducing role of FGF extends beyond the group of deuterostomes.
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Affiliation(s)
- Carmen Andrikou
- University of Bergen, Department of Biological Sciences, Thormøhlensgate 55, 5006 Bergen, Norway.,Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, 5006 Bergen, Norway
| | - Andreas Hejnol
- University of Bergen, Department of Biological Sciences, Thormøhlensgate 55, 5006 Bergen, Norway.,Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, 5006 Bergen, Norway
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4
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Molina MD, Gache C, Lepage T. Expression of exogenous mRNAs to study gene function in echinoderm embryos. Methods Cell Biol 2019; 151:239-282. [PMID: 30948011 DOI: 10.1016/bs.mcb.2018.10.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
With the completion of the genome sequencing projects, a new challenge for developmental biologists is to assign a function to the thousands of genes identified. Expression of exogenous mRNAs is a powerful, versatile and rapid technique that can be used to study gene function during development of the sea urchin. This chapter describes how this technique can be used to analyze gene function in echinoderm embryos, how it can be combined with cell transplantation to perform mosaic analysis and how it can be applied to identify downstream targets genes of transcription factors and signaling pathways. We describe specific examples of the use of overexpression of mRNA to analyze gene function, mention the benefits and current limitations of the technique and emphasize the importance of using different controls to assess the specificity of the effects observed. Finally, this chapter details the different steps, vectors and protocols for in vitro production of mRNA and phenotypic analysis.
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Affiliation(s)
| | - Christian Gache
- Université Pierre et Marie Curie, Observatoire Océanologique de Villefranche sur Mer, UMR7009 CNRS, Paris, France
| | - Thierry Lepage
- Université Côte d'Azur, CNRS, INSERM, iBV, Nice, France.
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5
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Calestani C, Wessel GM. These Colors Don't Run: Regulation of Pigment-Biosynthesis in Echinoderms. Results Probl Cell Differ 2018; 65:515-525. [PMID: 30083933 PMCID: PMC6550297 DOI: 10.1007/978-3-319-92486-1_22] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Pigment production is an important biological process throughout the tree of life. Some pigments function for collecting light energy, or for visual identification, while others have dramatic antimicrobial functions, or camouflage capabilities. The functions of these pigments and their biosynthesis are of great interest if only because of their diversity. The biochemistry of echinoderm pigmentation has been intensively studied for many years, and with more recent technologies, the origin and functions of these pigments are being exposed. Here we summarize the major pigment types in biology and emphasize the status of the field in echinoderms, taking full advantage of the new genomic and technologic resources for studying these important animals and their beautiful pigmentation.
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Affiliation(s)
| | - Gary M Wessel
- Department of Molecular and Cellular Biology and Biochemistry, Brown University, Providence, RI, USA.
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6
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Divergence of ectodermal and mesodermal gene regulatory network linkages in early development of sea urchins. Proc Natl Acad Sci U S A 2016; 113:E7202-E7211. [PMID: 27810959 DOI: 10.1073/pnas.1612820113] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Developmental gene regulatory networks (GRNs) are assemblages of gene regulatory interactions that direct ontogeny of animal body plans. Studies of GRNs operating in the early development of euechinoid sea urchins have revealed that little appreciable change has occurred since their divergence ∼90 million years ago (mya). These observations suggest that strong conservation of GRN architecture was maintained in early development of the sea urchin lineage. Testing whether this holds for all sea urchins necessitates comparative analyses of echinoid taxa that diverged deeper in geological time. Recent studies highlighted extensive divergence of skeletogenic mesoderm specification in the sister clade of euechinoids, the cidaroids, suggesting that comparative analyses of cidaroid GRN architecture may confer a greater understanding of the evolutionary dynamics of developmental GRNs. Here I report spatiotemporal patterning of 55 regulatory genes and perturbation analyses of key regulatory genes involved in euechinoid oral-aboral patterning of nonskeletogenic mesodermal and ectodermal domains in early development of the cidaroid Eucidaris tribuloides These results indicate that developmental GRNs directing mesodermal and ectodermal specification have undergone marked alterations since the divergence of cidaroids and euechinoids. Notably, statistical and clustering analyses of echinoid temporal gene expression datasets indicate that regulation of mesodermal genes has diverged more markedly than regulation of ectodermal genes. Although research on indirect-developing euechinoid sea urchins suggests strong conservation of GRN circuitry during early embryogenesis, this study indicates that since the divergence of cidaroids and euechinoids, developmental GRNs have undergone significant, cell type-biased alterations.
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7
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Schrankel CS, Solek CM, Buckley KM, Anderson MK, Rast JP. A conserved alternative form of the purple sea urchin HEB/E2-2/E2A transcription factor mediates a switch in E-protein regulatory state in differentiating immune cells. Dev Biol 2016; 416:149-161. [PMID: 27265865 DOI: 10.1016/j.ydbio.2016.05.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 05/26/2016] [Accepted: 05/27/2016] [Indexed: 12/11/2022]
Abstract
E-proteins are basic helix-loop-helix (bHLH) transcription factors with essential roles in animal development. In mammals, these are encoded by three loci: E2-2 (ITF-2/ME2/SEF2/TCF4), E2A (TCF3), and HEB (ME1/REB/TCF12). The HEB and E2-2 paralogs are expressed as alternative (Alt) isoforms with distinct N-terminal sequences encoded by unique exons under separate regulatory control. Expression of these alternative transcripts is restricted relative to the longer (Can) forms, suggesting distinct regulatory roles, although the functions of the Alt proteins remain poorly understood. Here, we characterize the single sea urchin E-protein ortholog (SpE-protein). The organization of the SpE-protein gene closely resembles that of the extended HEB/E2-2 vertebrate loci, including a transcript that initiates at a homologous alternative transcription start site (SpE-Alt). The existence of an Alt form in the sea urchin indicates that this feature predates the emergence of the vertebrates. We present additional evidence indicating that this transcript was present in the common bilaterian ancestor. In contrast to the widely expressed canonical form (SpE-Can), SpE-Alt expression is tightly restricted. SpE-Alt is expressed in two phases: first in aboral non-skeletogenic mesenchyme (NSM) cells and then in oral NSM cells preceding their differentiation and ingression into the blastocoel. Derivatives of these cells mediate immune response in the larval stage. Inhibition of SpE-Alt activity interferes with these events. Notably, although the two isoforms are initially co-expressed, as these cells differentiate, SpE-Can is excluded from the SpE-Alt(+) cell population. This mutually exclusive expression is dependent on SpE-Alt function, which reveals a previously undescribed negative regulatory linkage between the two E-protein forms. Collectively, these findings reorient our understanding of the evolution of this transcription factor family and highlight fundamental properties of E-protein biology.
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Affiliation(s)
- Catherine S Schrankel
- Biological Sciences, Sunnybrook Research Institute, Toronto, ON, Canada; Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Cynthia M Solek
- Biological Sciences, Sunnybrook Research Institute, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - Katherine M Buckley
- Biological Sciences, Sunnybrook Research Institute, Toronto, ON, Canada; Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Michele K Anderson
- Biological Sciences, Sunnybrook Research Institute, Toronto, ON, Canada; Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Jonathan P Rast
- Biological Sciences, Sunnybrook Research Institute, Toronto, ON, Canada; Department of Immunology, University of Toronto, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.
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8
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Katow H. Mechanisms of the epithelial-to-mesenchymal transition in sea urchin embryos. Tissue Barriers 2015; 3:e1059004. [PMID: 26716069 PMCID: PMC4681286 DOI: 10.1080/21688370.2015.1059004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 05/25/2015] [Accepted: 05/29/2015] [Indexed: 12/30/2022] Open
Abstract
Sea urchin mesenchyme is composed of the large micromere-derived spiculogenetic primary mesenchyme cells (PMC), veg2-tier macromere-derived non-spiculogenetic mesenchyme cells, the small micromere-derived germ cells, and the macro- and mesomere-derived neuronal mesenchyme cells. They are formed through the epithelial-to-mesenchymal transition (EMT) and possess multipotency, except PMCs that solely differentiate larval spicules. The process of EMT is associated with modification of epithelial cell surface property that includes loss of affinity to the apical and basal extracellular matrices, inter-epithelial cell adherens junctions and epithelial cell surface-specific proteins. These cell surface structures and molecules are endocytosed during EMT and utilized as initiators of cytoplasmic signaling pathways that often initiate protein phosphorylation to activate the gene regulatory networks. Acquisition of cell motility after EMT in these mesenchyme cells is associated with the expression of proteins such as Lefty, Snail and Seawi. Structural simplicity and genomic database of this model will further promote detailed EMT research.
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Affiliation(s)
- Hideki Katow
- Research Center for Marine Biology; Tohoku University; Asamushi, Aomori, Japan
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9
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Stepicheva N, Nigam PA, Siddam AD, Peng CF, Song JL. microRNAs regulate β-catenin of the Wnt signaling pathway in early sea urchin development. Dev Biol 2015; 402:127-41. [PMID: 25614238 DOI: 10.1016/j.ydbio.2015.01.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 12/18/2014] [Accepted: 01/09/2015] [Indexed: 12/19/2022]
Abstract
Development of complex multicellular organisms requires careful regulation at both transcriptional and post-transcriptional levels. Post-transcriptional gene regulation is in part mediated by a class of non-coding RNAs of 21-25 nucleotides in length known as microRNAs (miRNAs). β-catenin, regulated by the canonical Wnt signaling pathway, has a highly evolutionarily conserved function in patterning early metazoan embryos, in forming the Anterior-Posterior axis, and in establishing the endomesoderm. Using reporter constructs and site-directed mutagenesis, we identified at least three miRNA binding sites within the 3' untranslated region (3'UTR) of the sea urchin β-catenin. Further, blocking these three miRNA binding sites within the β-catenin 3'UTR to prevent regulation of endogenous β-catenin by miRNAs resulted in a minor increase in β-catenin protein accumulation that is sufficient to induce aberrant gut morphology and circumesophageal musculature. These phenotypes are likely the result of increased transcript levels of Wnt responsive endomesodermal regulatory genes. This study demonstrates the importance of miRNA regulation of β-catenin in early development.
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Affiliation(s)
- Nadezda Stepicheva
- Department of Biological Sciences, University of Delaware, 323 Wolf Hall, Newark, DE 19716, USA
| | - Priya A Nigam
- Department of Biological Sciences, University of Delaware, 323 Wolf Hall, Newark, DE 19716, USA
| | - Archana D Siddam
- Department of Biological Sciences, University of Delaware, 323 Wolf Hall, Newark, DE 19716, USA
| | - Chieh Fu Peng
- Department of Biology, University of Miami, Coral Gables, FL 33124, USA
| | - Jia L Song
- Department of Biological Sciences, University of Delaware, 323 Wolf Hall, Newark, DE 19716, USA.
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10
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Cheng X, Lyons DC, Socolar JES, McClay DR. Delayed transition to new cell fates during cellular reprogramming. Dev Biol 2014; 391:147-57. [PMID: 24780626 PMCID: PMC4064802 DOI: 10.1016/j.ydbio.2014.04.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 04/19/2014] [Accepted: 04/21/2014] [Indexed: 01/08/2023]
Abstract
In many embryos specification toward one cell fate can be diverted to a different cell fate through a reprogramming process. Understanding how that process works will reveal insights into the developmental regulatory logic that emerged from evolution. In the sea urchin embryo, cells at gastrulation were found to reprogram and replace missing cell types after surgical dissections of the embryo. Non-skeletogenic mesoderm (NSM) cells reprogrammed to replace missing skeletogenic mesoderm cells and animal caps reprogrammed to replace all endomesoderm. In both cases evidence of reprogramming onset was first observed at the early gastrula stage, even if the cells to be replaced were removed earlier in development. Once started however, the reprogramming occurred with compressed gene expression dynamics. The NSM did not require early contact with the skeletogenic cells to reprogram, but the animal cap cells gained the ability to reprogram early in gastrulation only after extended contact with the vegetal halves prior to that time. If the entire vegetal half was removed at early gastrula, the animal caps reprogrammed and replaced the vegetal half endomesoderm. If the animal caps carried morpholinos to either hox11/13b or foxA (endomesoderm specification genes), the isolated animal caps failed to reprogram. Together these data reveal that the emergence of a reprogramming capability occurs at early gastrulation in the sea urchin embryo and requires activation of early specification components of the target tissues.
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Affiliation(s)
- Xianrui Cheng
- Program in Computational Biology and Bioinformatics, Duke University, Durham, NC 27708, USA; Duke Center for Systems Biology, Duke University, Durham, NC 27708, USA; Department of Biology, Duke University, Durham, NC 27708, USA.
| | - Deirdre C Lyons
- Department of Biology, Duke University, Durham, NC 27708, USA.
| | - Joshua E S Socolar
- Program in Computational Biology and Bioinformatics, Duke University, Durham, NC 27708, USA; Duke Center for Systems Biology, Duke University, Durham, NC 27708, USA; Department of Physics, Duke University, Durham, NC 27708, USA.
| | - David R McClay
- Program in Computational Biology and Bioinformatics, Duke University, Durham, NC 27708, USA; Duke Center for Systems Biology, Duke University, Durham, NC 27708, USA; Department of Biology, Duke University, Durham, NC 27708, USA.
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11
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Sethi AJ, Angerer RC, Angerer LM. Multicolor labeling in developmental gene regulatory network analysis. Methods Mol Biol 2014; 1128:249-62. [PMID: 24567220 DOI: 10.1007/978-1-62703-974-1_17] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
The sea urchin embryo is an important model system for developmental gene regulatory network (GRN) analysis. This chapter describes the use of multicolor fluorescent in situ hybridization (FISH) as well as a combination of FISH and immunohistochemistry in sea urchin embryonic GRN studies. The methods presented here can be applied to a variety of experimental settings where accurate spatial resolution of multiple gene products is required for constructing a developmental GRN.
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Affiliation(s)
- Aditya J Sethi
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
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12
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Röttinger E, Dahlin P, Martindale MQ. A framework for the establishment of a cnidarian gene regulatory network for "endomesoderm" specification: the inputs of ß-catenin/TCF signaling. PLoS Genet 2012; 8:e1003164. [PMID: 23300467 PMCID: PMC3531958 DOI: 10.1371/journal.pgen.1003164] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Accepted: 10/27/2012] [Indexed: 12/03/2022] Open
Abstract
Understanding the functional relationship between intracellular factors and
extracellular signals is required for reconstructing gene regulatory networks
(GRN) involved in complex biological processes. One of the best-studied
bilaterian GRNs describes endomesoderm specification and predicts that both
mesoderm and endoderm arose from a common GRN early in animal evolution.
Compelling molecular, genomic, developmental, and evolutionary evidence supports
the hypothesis that the bifunctional gastrodermis of the cnidarian-bilaterian
ancestor is derived from the same evolutionary precursor of both endodermal and
mesodermal germ layers in all other triploblastic bilaterian animals. We have
begun to establish the framework of a provisional cnidarian
“endomesodermal” gene regulatory network in the sea anemone,
Nematostella vectensis, by using a genome-wide microarray
analysis on embryos in which the canonical Wnt/ß-catenin pathway was
ectopically targeted for activation by two distinct pharmaceutical agents
(lithium chloride and 1-azakenpaullone) to identify potential targets of
endomesoderm specification. We characterized 51 endomesodermally expressed
transcription factors and signaling molecule genes (including 18 newly
identified) with fine-scale temporal (qPCR) and spatial (in
situ) analysis to define distinct co-expression domains within the
animal plate of the embryo and clustered genes based on their earliest zygotic
expression. Finally, we determined the input of the canonical
Wnt/ß-catenin pathway into the cnidarian endomesodermal GRN using
morpholino and mRNA overexpression experiments to show that NvTcf/canonical Wnt
signaling is required to pattern both the future endomesodermal and ectodermal
domains prior to gastrulation, and that both BMP and FGF (but not Notch)
pathways play important roles in germ layer specification in this animal. We
show both evolutionary conserved as well as profound differences in
endomesodermal GRN structure compared to bilaterians that may provide
fundamental insight into how GRN subcircuits have been adopted, rewired, or
co-opted in various animal lineages that give rise to specialized endomesodermal
cell types. Cnidarians (anemones, corals, and “jellyfish”) are an animal group
whose adults possess derivatives of only two germ layers: ectoderm and a
bifunctional (absorptive and contractile) gastrodermal (gut) layer. Cnidarians
are the closest living relatives to bilaterally symmetrical animals that possess
all three germ layers (ecto, meso, and endoderm); and compelling molecular,
genomic, developmental, and evolutionary evidence exists to demonstrate that the
cnidarian gastrodermis is evolutionarily related to both endodermal and
mesodermal germ layers in all other triploblastic bilaterian animals. Little is
known about endomesoderm specification in cnidarians. In this study, we
constructed the framework of a cnidarian endomesodermal gene regulatory network
in the sea anemone, Nematostella vectensis, using a combination
of experimental approaches. We identified and characterized by both qPCR and
in situ hybridization 51 genes expressed in defined domains
within the presumptive endomesoderm. In addition, we functionally demonstrate
that Wnt/Tcf signaling is crucial for regionalized expression of a defined
subset of these genes prior to gut formation and endomesoderm maintenance. Our
results support the idea of an ancient gene regulatory network underlying
endomesoderm specification that involves inputs from multiple signaling pathways
(Wnt, FGF, BMP, but not Notch) early in development, that are temporarily
uncoupled in bilaterian animals.
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Affiliation(s)
- Eric Röttinger
- Kewalo Marine Laboratory, Pacific Biosciences Research Center,
University of Hawai'i, Honolulu, Hawai'i, United States of
America
| | - Paul Dahlin
- Kewalo Marine Laboratory, Pacific Biosciences Research Center,
University of Hawai'i, Honolulu, Hawai'i, United States of
America
| | - Mark Q. Martindale
- Kewalo Marine Laboratory, Pacific Biosciences Research Center,
University of Hawai'i, Honolulu, Hawai'i, United States of
America
- * E-mail:
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13
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Bessodes N, Haillot E, Duboc V, Röttinger E, Lahaye F, Lepage T. Reciprocal signaling between the ectoderm and a mesendodermal left-right organizer directs left-right determination in the sea urchin embryo. PLoS Genet 2012; 8:e1003121. [PMID: 23271979 PMCID: PMC3521660 DOI: 10.1371/journal.pgen.1003121] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 10/12/2012] [Indexed: 02/01/2023] Open
Abstract
During echinoderm development, expression of nodal on the right side plays a crucial role in positioning of the rudiment on the left side, but the mechanisms that restrict nodal expression to the right side are not known. Here we show that establishment of left-right asymmetry in the sea urchin embryo relies on reciprocal signaling between the ectoderm and a left-right organizer located in the endomesoderm. FGF/ERK and BMP2/4 signaling are required to initiate nodal expression in this organizer, while Delta/Notch signaling is required to suppress formation of this organizer on the left side of the archenteron. Furthermore, we report that the H(+)/K(+)-ATPase is critically required in the Notch signaling pathway upstream of the S3 cleavage of Notch. Our results identify several novel players and key early steps responsible for initiation, restriction, and propagation of left-right asymmetry during embryogenesis of a non-chordate deuterostome and uncover a functional link between the H(+)/K(+)-ATPase and the Notch signaling pathway.
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Affiliation(s)
- Nathalie Bessodes
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
| | - Emmanuel Haillot
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
| | - Véronique Duboc
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
| | - Eric Röttinger
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
| | - François Lahaye
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
| | - Thierry Lepage
- UMR 7009 CNRS, Université de Pierre et Marie Curie (Paris 6), Observatoire Océanologique de Villefranche-sur-Mer, Villefranche-sur-Mer, France
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14
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Sethi AJ, Wikramanayake RM, Angerer RC, Range RC, Angerer LM. Sequential signaling crosstalk regulates endomesoderm segregation in sea urchin embryos. Science 2012; 335:590-3. [PMID: 22301319 PMCID: PMC4827163 DOI: 10.1126/science.1212867] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The segregation of embryonic endomesoderm into separate endoderm and mesoderm fates is not well understood in deuterostomes. Using sea urchin embryos, we showed that Notch signaling initiates segregation of the endomesoderm precursor field by inhibiting expression of a key endoderm transcription factor in presumptive mesoderm. The regulatory circuit activated by this transcription factor subsequently maintains transcription of a canonical Wnt (cWnt) ligand only in endoderm precursors. This cWnt ligand reinforces the endoderm state, amplifying the distinction between emerging endoderm and mesoderm. Before gastrulation, Notch-dependent nuclear export of an essential β-catenin transcriptional coactivator from mesoderm renders it refractory to cWnt signals, insulating it against an endoderm fate. Thus, we report that endomesoderm segregation is a progressive process, requiring a succession of regulatory interactions between cWnt and Notch signaling.
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Affiliation(s)
- Aditya J. Sethi
- National Institute of Dental and Craniofacial Research,
National Institutes of Health, Bethesda, Maryland, USA
| | | | - Robert C. Angerer
- National Institute of Dental and Craniofacial Research,
National Institutes of Health, Bethesda, Maryland, USA
| | - Ryan C. Range
- National Institute of Dental and Craniofacial Research,
National Institutes of Health, Bethesda, Maryland, USA
| | - Lynne M. Angerer
- National Institute of Dental and Craniofacial Research,
National Institutes of Health, Bethesda, Maryland, USA
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15
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Abstract
Embryonic development is controlled by networks of interacting regulatory genes. The individual linkages of gene regulatory networks (GRNs) are customarily validated by functional cis-regulatory analysis, but an additional approach to validation is to rewire GRN circuitry to test experimentally predictions derived from network structure. Here we use this synthetic method to challenge specific predictions of the sea urchin embryo endomesoderm GRN. Expression vectors generated by in vitro recombination of exogenous sequences into BACs were used to cause elements of a nonskeletogenic mesoderm GRN to be deployed in skeletogenic cells and to detect their effects. The result of reengineering the regulatory circuitry in this way was to divert the developmental program of these cells from skeletogenesis to pigment cell formation, confirming a direct prediction of the GRN. In addition, the experiment revealed previously undetected cryptic repression functions.
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16
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Select microRNAs are essential for early development in the sea urchin. Dev Biol 2011; 362:104-13. [PMID: 22155525 DOI: 10.1016/j.ydbio.2011.11.015] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Revised: 10/22/2011] [Accepted: 11/22/2011] [Indexed: 11/22/2022]
Abstract
microRNAs (miRNAs) are small noncoding RNAs that mediate post-transcriptional gene regulation and have emerged as essential regulators of many developmental events. The transcriptional network during early embryogenesis of the purple sea urchin, Strongylocentrotus purpuratus, is well described and can serve as an excellent model to test functional contributions of miRNAs in embryogenesis. We examined the loss of function phenotypes of major components of the miRNA biogenesis pathway. Inhibition of de novo synthesis of Drosha and Dicer in the embryo led to consistent developmental defects, a failure to gastrulate, and embryonic lethality, including changes in the steady state levels of transcription factors and signaling molecules involved in germ layer specification. We annotated and profiled small RNA expression from the ovary and several early embryonic stages by deep sequencing followed by computational analysis. miRNAs as well as a large population of putative piRNAs (piwi-interacting RNAs) had dynamic accumulation profiles through early development. Defects in morphogenesis caused by loss of Drosha could be rescued with four miRNAs. Taken together our results indicate that post-transcriptional gene regulation directed by miRNAs is functionally important for early embryogenesis and is an integral part of the early embryonic gene regulatory network in S. purpuratus.
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17
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Takata H, Kominami T. Novel population of embryonic secondary mesenchyme cells in the keyhole sand dollar Astriclypeus manni. Dev Growth Differ 2011; 53:625-38. [DOI: 10.1111/j.1440-169x.2011.01278.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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18
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Peter IS, Davidson EH. A gene regulatory network controlling the embryonic specification of endoderm. Nature 2011; 474:635-9. [PMID: 21623371 DOI: 10.1038/nature10100] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 04/01/2011] [Indexed: 12/26/2022]
Abstract
Specification of endoderm is the prerequisite for gut formation in the embryogenesis of bilaterian organisms. Modern lineage labelling studies have shown that in the sea urchin embryo model system, descendants of the veg1 and veg2 cell lineages produce the endoderm, and that the veg2 lineage also gives rise to mesodermal cell types. It is known that Wnt/β-catenin signalling is required for endoderm specification and Delta/Notch signalling is required for mesoderm specification. Some direct cis-regulatory targets of these signals have been found and various phenomenological patterns of gene expression have been observed in the pre-gastrular endomesoderm. However, no comprehensive, causal explanation of endoderm specification has been conceived for sea urchins, nor for any other deuterostome. Here we propose a model, on the basis of the underlying genomic control system, that provides such an explanation, built at several levels of biological organization. The hardwired core of the control system consists of the cis-regulatory apparatus of endodermal regulatory genes, which determine the relationship between the inputs to which these genes are exposed and their outputs. The architecture of the network circuitry controlling the dynamic process of endoderm specification then explains, at the system level, a sequence of developmental logic operations, which generate the biological process. The control system initiates non-interacting endodermal and mesodermal gene regulatory networks in veg2-derived cells and extinguishes the endodermal gene regulatory network in mesodermal precursors. It also generates a cross-regulatory network that specifies future anterior endoderm in veg2 descendants and institutes a distinct network specifying posterior endoderm in veg1-derived cells. The network model provides an explanatory framework that relates endoderm specification to the genomic regulatory code.
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Affiliation(s)
- Isabelle S Peter
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
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19
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McCauley BS, Weideman EP, Hinman VF. A conserved gene regulatory network subcircuit drives different developmental fates in the vegetal pole of highly divergent echinoderm embryos. Dev Biol 2010; 340:200-8. [DOI: 10.1016/j.ydbio.2009.11.020] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Revised: 11/13/2009] [Accepted: 11/17/2009] [Indexed: 11/16/2022]
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20
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Calestani C, Rogers DJ. Cis-regulatory analysis of the sea urchin pigment cell gene polyketide synthase. Dev Biol 2010; 340:249-55. [PMID: 20122918 DOI: 10.1016/j.ydbio.2010.01.026] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 01/21/2010] [Accepted: 01/22/2010] [Indexed: 11/19/2022]
Abstract
The Strongylocentrotus purpuratus polyketide synthase gene (SpPks) encodes an enzyme required for the biosynthesis of the larval pigment echinochrome. SpPks is expressed exclusively in pigment cells and their precursors starting at blastula stage. The 7th-9th cleavage Delta-Notch signaling, required for pigment cell development, positively regulates SpPks. In previous studies, the transcription factors glial cell missing (SpGcm), SpGatae and kruppel-like (SpKrl/z13) have been shown to positively regulate SpPks. To uncover the structure of the Gene Regulatory Network (GRN) regulating the specification and differentiation processes of pigment cells, we experimentally analyzed the putative SpPks cis-regulatory region. We established that the -1.5kb region is sufficient to recapitulate the correct spatial and temporal expression of SpPks. Predicted DNA-binding sites for SpGcm, SpGataE and SpKrl are located within this region. The mutagenesis of these DNA-binding sites indicated that SpGcm, SpGataE and SpKrl are direct positive regulators of SpPks. These results demonstrate that the sea urchin GRN for pigment cell development is quite shallow, which is typical of type I embryo development.
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Affiliation(s)
- Cristina Calestani
- Department of Biology, University of Central Florida, Orlando, FL 32816, USA.
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21
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Duboc V, Lapraz F, Saudemont A, Bessodes N, Mekpoh F, Haillot E, Quirin M, Lepage T. Nodal and BMP2/4 pattern the mesoderm and endoderm during development of the sea urchin embryo. Development 2010; 137:223-35. [PMID: 20040489 DOI: 10.1242/dev.042531] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Nodal factors play fundamental roles in induction and patterning of the mesoderm and endoderm in vertebrates, but whether this reflects an ancient role or one that evolved recently in vertebrates is not known. Here, we report that in addition to its primary role in patterning the ectoderm, sea urchin Nodal is crucial for patterning of the endoderm and skeletogenic mesoderm through the regulation of the expression of key transcription factors and signalling molecules, including BMP2/4 and FGFA. In addition, we uncovered an essential role for Nodal and BMP2/4 in the formation and patterning of the non-skeletogenic mesoderm. By comparing the effects of misexpressing Nodal or an activated Nodal receptor in clones of cells, we provide evidence that Nodal acts over a long range in the endomesoderm and that its effects on the blastocoelar cell precursors are likely to be direct. The activity of Nodal and BMP2/4 are antagonistic, and although bmp2/4 is transcribed in the ventral ectoderm downstream of Nodal, the BMP2/4 ligand is translocated to the dorsal side, where it activates signalling in the dorsal primary mesenchyme cells, the dorsal endoderm and in pigment cell precursors. Therefore, correct patterning of the endomesoderm depends on a balance between ventralising Nodal signals and dorsalising BMP2/4 signals. These experiments confirm that Nodal is a key regulator of dorsal-ventral polarity in the sea urchin and support the idea that the ventral ectoderm, like the Spemann organiser in vertebrates, is an organising centre that is required for patterning all three germ layers of the embryo.
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Affiliation(s)
- Véronique Duboc
- UPMC Univ Paris 06-CNRS, UMR 7009 Biologie du Développement Observatoire Océanologique, 06230 Villefranche-sur-mer, France
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22
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Peter IS, Davidson EH. The endoderm gene regulatory network in sea urchin embryos up to mid-blastula stage. Dev Biol 2009; 340:188-99. [PMID: 19895806 DOI: 10.1016/j.ydbio.2009.10.037] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2009] [Revised: 10/27/2009] [Accepted: 10/27/2009] [Indexed: 12/20/2022]
Abstract
As the result of early specification processes, sea urchin embryos eventually form various mesodermal cell lineages and a gut consisting of fore-, mid- and hindgut. The progression of specification as well as the overall spatial organization of the organism is encoded in its gene regulatory networks (GRNs). We have analyzed the GRN driving endoderm specification up to the onset of gastrulation and present in this paper the mechanisms which determine this process up to mid-blastula stage. At this stage, the embryo consists of two separate lineages of endoderm precursor cells with distinct regulatory states. One of these lineages, the veg2 cell lineage, gives rise to endoderm and mesoderm cell types. The separation of these cell fates is initiated by the spatially confined activation of the mesoderm GRN superimposed on a generally activated endoderm GRN within veg2 descendants. Here we integrate the architecture of regulatory interactions with the spatial restriction of regulatory gene expression to model the logic control of endoderm development.
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Affiliation(s)
- Isabelle S Peter
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
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23
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Karasawa K, Sakamoto N, Fujita K, Ochiai H, Fujii T, Akasaka K, Yamamoto T. Suppressor of Hairless (Su(H)) is required for foregut development in the sea urchin embryo. Zoolog Sci 2009; 26:686-90. [PMID: 19832680 DOI: 10.2108/zsj.26.686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In sea urchin embryos, Notch signaling is required to segregate non-skeletogenic mesoderm from early endomesoderm, and is involved in endoderm development. To further investigate the role of Notch signaling in the endoderm cell lineage, we cloned a cDNA for the Hemicentrotus pulcherrimus ortholog of Suppressor of Hairless (HpSu(H)), which is a major mediator of the Notch signaling pathway, examined the expression during development and performed a functional analysis. HpSu(H) mRNA was ubiquitously expressed up to the unhatched blastula stage, and expression was exclusively detected in the vegetal plate region from the hatched blastula stage and then in the archenteron at the gastrula stage. Perturbation of HpSu(H) by injection of the dominant negative form of HpSu(H) (dn-HpSu(H)) mRNA into fertilized eggs led to the disappearance of secondary mesenchyme cells at the tip of the archenteron in the gastrula and pigment cells in the pluteus larva, confirming that Notch signaling is required for non-skeletogenic me soderm specification. In addition, injection of relatively high amounts of dn-HpSu(H) mRNA caused a defect or atrophy of the foregut in the archenteron at the pluteus stage. This result strongly suggests that Notch signaling is involved in foregut development during sea urchin development.
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Affiliation(s)
- Koji Karasawa
- Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
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24
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Walton KD, Warner J, Hertzler PH, McClay DR. Hedgehog signaling patterns mesoderm in the sea urchin. Dev Biol 2009; 331:26-37. [PMID: 19393640 PMCID: PMC2702090 DOI: 10.1016/j.ydbio.2009.04.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Revised: 03/30/2009] [Accepted: 04/17/2009] [Indexed: 10/20/2022]
Abstract
The Hedgehog (Hh) signaling pathway is essential for patterning many structures in vertebrates including the nervous system, chordamesoderm, limb and endodermal organs. In the sea urchin, a basal deuterostome, Hh signaling is shown to participate in organizing the mesoderm. At gastrulation the Hh ligand is expressed by the endoderm downstream of the Brachyury and FoxA transcription factors in the endomesoderm gene regulatory network. The co-receptors Patched (Ptc) and Smoothened (Smo) are expressed by the neighboring skeletogenic and non-skeletogenic mesoderm. Perturbations of Hh, Ptc and Smo cause embryos to develop with skeletal defects and inappropriate non-skeletogenic mesoderm patterning, although initial specification of mesoderm occurs without detectable abnormalities. Perturbations of the pathway caused late defects in skeletogenesis and in the non-skeletogenic mesoderm, including altered numbers of pigment and blastocoelar cells, randomized left-right asymmetry of coelomic pouches, and disorganized circumesophageal muscle causing an inability to swallow. Together the data support the requirement of Hh signaling in patterning each of the mesoderm subtypes in the sea urchin embryo.
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Affiliation(s)
| | - Jacob Warner
- Department of Biology, Duke University, Box 90338, Durham, NC 27708
| | - Philip H. Hertzler
- Department of Biology, Central Michigan University, Mount Pleasant, MI 48859
| | - David R. McClay
- Department of Biology, Duke University, Box 90338, Durham, NC 27708
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25
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Iijima M, Ishizuka Y, Nakajima Y, Amemiya S, Minokawa T. Evolutionary modification of specification for the endomesoderm in the direct developing echinoid Peronella japonica: loss of the endomesoderm-inducing signal originating from micromeres. Dev Genes Evol 2009; 219:235-47. [PMID: 19437036 DOI: 10.1007/s00427-009-0286-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Accepted: 04/23/2009] [Indexed: 10/20/2022]
Abstract
We investigated the inductive signals originating from the vegetal blastomeres of embryos of the sand dollar Peronella japonica, which is the only direct developing echinoid species that forms micromeres. To investigate the inductive signals, three different kinds of experimental embryos were produced: micromere-less embryos, in which all micromeres were removed at the 16-cell stage; chimeric embryos produced by an animal cap (eight mesomeres) recombined with a micromere quartet isolated from a 16-cell stage embryo; and chimeric embryos produced by an animal cap recombined with a macromere-derived layer, the veg1 or veg2 layer, isolated from a 64-cell stage embryo. Novel findings obtained from this study of the development of these embryos are as follows. Micromeres lack signals for endomesoderm specification, but are the origin of a signal establishing the oral-aboral (O-Ab) axis. Some non-micromere blastomeres, as well as micromeres, have the potential to form larval skeletons. Macromere descendants have endomesoderm-inducing potential. Based on these results, we propose the following scenario for the first step in the evolution of direct development in echinoids: micromeres lost the ability to send a signal endomesoderm induction so that the archenteron was formed autonomously by macromere descendants. The micromeres retained the ability to form larval spicules and to establish the O-Ab axis.
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Affiliation(s)
- Minoru Iijima
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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26
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Abstract
Mesenchymal cells of the sea urchin embryo provide a valuable experimental model for the analysis of cell-cell fusion in vivo. The unsurpassed optical transparency of the sea urchin embryo facilitates analysis of cell fusion in vivo using fluorescent markers and time-lapse three-dimensional imaging. Two populations of mesodermal cells engage in homotypic cell-cell fusion during gastrulation: primary mesenchyme cells and blastocoelar cells. In this chapter, we describe methods for studying the dynamics of cell fusion in living embryos. These methods have been used to analyze the fusion of primary mesenchyme cells and are also applicable to blastocoelar cell fusion. Although the molecular basis of cell fusion in the sea urchin has not been investigated, tools have recently become available that highlight the potential of this experimental model for integrating dynamic morphogenetic behaviors with underlying molecular mechanisms.
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Affiliation(s)
- Paul G Hodor
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, USA
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27
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Yamazaki A, Kawabata R, Shiomi K, Tsuchimoto J, Kiyomoto M, Amemiya S, Yamaguchi M. Krüppel-like is required for nonskeletogenic mesoderm specification in the sea urchin embryo. Dev Biol 2007; 314:433-42. [PMID: 18166171 DOI: 10.1016/j.ydbio.2007.11.035] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Revised: 11/06/2007] [Accepted: 11/20/2007] [Indexed: 11/16/2022]
Abstract
The canonical Wnt pathway plays a central role in specifying vegetal cell fate in sea urchin embryos. SpKrl has been cloned as a direct target of nuclear beta-catenin. Using Hemicentrotus pulcherrimus embryos, here we show that HpKrl controls the specification of secondary mesenchyme cells (SMCs) through both cell-autonomous and non-autonomous means. Like SpKrl, HpKrl was activated in both micromere and macromere progenies. To examine the functions of HpKrl in each blastomere, we constructed chimeric embryos composed of blastomeres from control and morpholino-mediated HpKrl-knockdown embryos and analyzed the phenotypes of the chimeras. Micromere-swapping experiments showed that HpKrl is not involved in micromere specification, while micromere-deprivation assays indicated that macromeres require HpKrl for cell-autonomous specification. Transplantation of normal micromeres into a micromere-less host with morpholino revealed that macromeres are able to receive at least some micromere signals regardless of HpKrl function. From these observations, we propose that two distinct pathways of endomesoderm formation exist in macromeres, a Krl-dependent pathway and a Krl-independent pathway. The Krl-independent pathway may correspond to the Delta/Notch signaling pathway via GataE and Gcm. We suggest that Krl may be a downstream component of nuclear beta-catenin required by macromeres for formation of more vegetal tissues, not as a member of the Delta/Notch pathway, but as a parallel effector of the signaling (Krl-dependent pathway).
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Affiliation(s)
- Atsuko Yamazaki
- Division of Life Science, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan
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28
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Abstract
Controlling the differential expression of many thousands of genes is the most fundamental task of a developing organism. It requires an enormous computational device that has the capacity to process in parallel a vast number of regulatory inputs in the various cells of the embryo and come out with regulatory outputs that are tissue specific. The regulatory genome constitutes this computational device, comprising many thousands of processing units in the form of cis-regulatory modules. The interconnected cis-regulatory modules that control regulatory gene expression create a network that is the underlying mechanism of specification. In this review we use the gene regulatory network that governs endomesoderm specification in the sea urchin embryo to demonstrate the salient features of developmental gene regulatory networks and illustrate the information processing that is done by the regulatory sequences.
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29
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Revilla-i-Domingo R, Oliveri P, Davidson EH. A missing link in the sea urchin embryo gene regulatory network: hesC and the double-negative specification of micromeres. Proc Natl Acad Sci U S A 2007; 104:12383-8. [PMID: 17636127 PMCID: PMC1941478 DOI: 10.1073/pnas.0705324104] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Specification of sea urchin embryo micromeres occurs early in cleavage, with the establishment of a well defined regulatory state. The architecture of the gene regulatory network controlling the specification process indicates that transcription of the initial tier of control genes depends on a double-negative gate. A gene encoding a transcriptional repressor, pmar1, is activated specifically in micromeres, where it represses transcription of a second repressor that is otherwise active globally. Thus, the micromere-specific control genes, which are the target of the second repressor, are expressed exclusively in this lineage. The double-negative specification gate was logically required from the results of numerous prior experiments, but the identity of the gene encoding the second repressor remained elusive. Here we show that hesC is this gene, and we demonstrate experimentally all of its predicted functions, including global repression of micromere-specific regulatory genes. As logically required, blockade of hesC mRNA translation and global overexpression of pmar1 mRNA have the same effect, which is to cause all of the cells of the embryo to express micromere-specific genes.
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Affiliation(s)
| | - Paola Oliveri
- Division of Biology 156–29, California Institute of Technology, Pasadena, CA 91125
| | - Eric H. Davidson
- Division of Biology 156–29, California Institute of Technology, Pasadena, CA 91125
- *To whom correspondence should be addressed. E-mail:
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30
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Hardin J, Illingworth CA. A homologue of snail is expressed transiently in subsets of mesenchyme cells in the sea urchin embryo and is down-regulated in axis-deficient embryos. Dev Dyn 2007; 235:3121-31. [PMID: 16958110 DOI: 10.1002/dvdy.20941] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Vertebrate members of the zinc finger transcription factor family related to Drosophila snail are expressed in neural crest and paraxial mesoderm along the left-right axis of the embryo. As simple deuterostomes, echinoderms are an important sister phylum for the chordates. We have identified populations of patterned, nonskeletogenic mesenchyme in the sea urchin Lytechinus variegatus by their expression of a sea urchin member of the snail family (Lv-snail). Lv-snail mRNA and protein are detectable at the midgastrula stage within the archenteron. At the late gastrula stage, a contiguous cluster of cells on the left side of the tip of the archenteron is Lv-snail-positive. At the early prism stage, two small clusters of mesenchyme cells near the presumptive arm buds are also Lv-snail-positive. At the pluteus stage, staining is detectable in isolated mesenchyme cells and the ciliated band. Based on fate mapping of secondary mesenchyme cells (SMCs) and double-label immunostaining, these patterns are consistent with expression of SNAIL by novel subsets of SMCs that are largely distinct from skeletogenic mesenchyme. In radialized embryos lacking normal bilateral symmetry, mesenchymal expression of Lv-SNAIL is abolished. These results suggest that transient expression of Lv-snail may be important for the differentiation of a subset of axially patterned nonskeletogenic mesenchyme cells and suggest conserved functions for snail family members in deuterostome development.
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Affiliation(s)
- Jeff Hardin
- Department of Zoology, University of Wisconsin-Madison, Madison, Wisconsin, USA.
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31
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Duboc V, Lepage T. A conserved role for the nodal signaling pathway in the establishment of dorso-ventral and left–right axes in deuterostomes. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2007; 310:41-53. [PMID: 16838294 DOI: 10.1002/jez.b.21121] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Nodal factors play crucial roles during embryogenesis of chordates. They have been implicated in a number of developmental processes, including mesoderm and endoderm formation and patterning of the embryo along the anterior-posterior and left-right axes. We have analyzed the function of the Nodal signaling pathway during the embryogenesis of the sea urchin, a non-chordate organism. We found that Nodal signaling plays a central role in axis specification in the sea urchin, but surprisingly, its first main role appears to be in ectoderm patterning and not in specification of the endoderm and mesoderm germ layers as in vertebrates. Starting at the early blastula stage, sea urchin nodal is expressed in the presumptive oral ectoderm where it controls the formation of the oral-aboral axis. A second conserved role for nodal signaling during vertebrate evolution is its involvement in the establishment of left-right asymmetries. Sea urchin larvae exhibit profound left-right asymmetry with the formation of the adult rudiment occurring only on the left side. We found that a nodal/lefty/pitx2 gene cassette regulates left-right asymmetry in the sea urchin but that intriguingly, the expression of these genes is reversed compared to vertebrates. We have shown that Nodal signals emitted from the right ectoderm of the larva regulate the asymmetrical morphogenesis of the coelomic pouches by inhibiting rudiment formation on the right side of the larva. This result shows that the mechanisms responsible for patterning the left-right axis are conserved in echinoderms and that this role for nodal is conserved among the deuterostomes. We will discuss the implications regarding the reference axes of the sea urchin and the ancestral function of the nodal gene in the last section of this review.
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Affiliation(s)
- Véronique Duboc
- UMR 7009 CNRS, Université de Paris VI, Biologie du Développement, Observatoire Oceanologique, 06230 Villefranche-sur-Mer, France.
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32
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Abstract
The Endo16 gene encodes a large extracellular protein with several functional domains that provide some insight into the role of this protein during embryonic development. We isolated the full-length cDNA sequence from Lytechinus variegatus and utilized morpholinos to further investigate the role of Endo16 during embryonic development in this species. Endo16-deficient embryos failed to undergo gastrulation and the blastocoele became filled with dissociated cells after 24 h of incubation. Moreover, there was a delay in endoderm differentiation as assayed by staining with an antibody that recognizes Endo1. The differentiation of other cell types including oral ectoderm, primary mesenchymal cells (PMC) and secondary mesenchymal cells (SMC) appeared to be normal, although the patterns of protein expression did not resemble control embryos due to the gross morphological abnormalities elicited by the LvEndo16 morpholino. Microinjection of full-length EGFP mRNA with the LvEndo16 morpholino-targeted sequence confirmed that this phenotype can be attributed specifically to the loss of Endo16 protein. Taken together, our data suggest that Endo16 may be required for the cell-extracellular matrix (ECM) interactions that are required for endoderm differentiation in the sea urchin embryo.
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Affiliation(s)
- Laura A Romano
- Department of Biology, Duke University, Durham, North Carolina 27708, USA.
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33
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Angerer L, Hussain S, Wei Z, Livingston BT. Sea urchin metalloproteases: a genomic survey of the BMP-1/tolloid-like, MMP and ADAM families. Dev Biol 2006; 300:267-81. [PMID: 17059814 DOI: 10.1016/j.ydbio.2006.07.046] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Revised: 07/25/2006] [Accepted: 07/26/2006] [Indexed: 10/24/2022]
Abstract
Analysis of the Strongylocentrotus purpuratus genome has revealed approximately 240 metalloprotease genes, and they represent all 23 families expressed in vertebrates. EST/cDNA sequencing and microarray analysis show that nearly 70% are represented in embryo RNA. Among them are many metalloproteases with demonstrated developmental roles in other systems-BMP-1/TLD (tolloid) (astacins), MMPs (matrix metalloproteases) and the ADAMs (disintegrin/metalloproteases). The developmental functions of these kinds of metalloproteases include modifying the extracellular matrix, regulating signaling pathways or modulating cellular adhesive properties. The unexpectedly large number of BMP-1/TLD-like protease genes (23) results primarily from expansion of a set encoding an unusual domain conserved in structure and primary sequence only in nematode astacins. Such proteases may have interesting developmental functions because the expression patterns of several are highly regulated along the primary axis at times when cell differentiation and morphogenesis begin. The size of the sea urchin MMP family and the clustered arrangement of many of its members are similar to vertebrates, but phylogenetic analyses suggest that different ancestral genes were independently amplified in sea urchins and vertebrates. One expansion appears to be genes encoding MMPs that have putative transmembrane domains and may be membrane-tethered (MT). Interestingly, the genes encoding TIMPs, inhibitors of MMPs, have also been amplified and the 10 genes are tandemly arranged in a single cluster. In contrast, there are fewer ADAM and ADAMTS genes in sea urchins, but they represent all but one of the chordate-specific groups. The genome sequence now opens the door to experimental manipulations designed to understand how modulation of the extracellular environment affects development.
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Affiliation(s)
- Lynne Angerer
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20815, USA.
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Ransick A, Davidson EH. cis-regulatory processing of Notch signaling input to the sea urchin glial cells missing gene during mesoderm specification. Dev Biol 2006; 297:587-602. [PMID: 16925988 DOI: 10.1016/j.ydbio.2006.05.037] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Accepted: 05/25/2006] [Indexed: 10/24/2022]
Abstract
The glial cells missing regulatory gene of Strongylocentrotus purpuratus (spgcm) was proposed earlier to be the genomic target of Delta/Notch (D/N) signaling required for specification of the mesodermal precursors of pigment cells. Here, we show that microinjection of a spgcm antisense morpholino oligonucleotide results in larvae without pigment cells. Microinjection of an mRNA encoding a dominant negative form of Suppressor of Hairless (dn-Su(H)) results in reduced levels of spgcm mRNA, disruption of mesodermal founder cell specification and failure to produce pigment cells. These results confirm that this gene is required for pigment cell specification. Three cis-regulatory modules of the spgcm gene were identified, which when incorporated in a GFP expression construct recapitulate the early expression pattern of this gene. Spatial expression of this GFP expression construct is severely disrupted by co-expression of dn-Su(H) mRNA, confirming that spgcm is a direct target of canonical N signaling mediated through Su(H) inputs. cis-perturbation analysis by mutation of consensus Su(H) sites identified a conserved motif paired-site and a lone site in the middle module that function both to drive expression in SMC precursors which receive the Delta signal and to repress expression in ectopic locations which lack this signal. While these Su(H) target sites provide the cis-regulatory architecture with the core of an N signaling transcriptional response switch, both the on and off outputs from this module require additional inputs.
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Affiliation(s)
- Andrew Ransick
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
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35
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Holland LZ, Panfilio KA, Chastain R, Schubert M, Holland ND. Nuclear beta-catenin promotes non-neural ectoderm and posterior cell fates in amphioxus embryos. Dev Dyn 2005; 233:1430-43. [PMID: 15973712 DOI: 10.1002/dvdy.20473] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
In vertebrate development, Wnt/beta-catenin signaling has an early role in specification of dorsal/anterior identity and a late one in posterior specification. To understand the evolution of these roles, we cloned beta-catenin from the invertebrate chordate amphioxus. The exon/intron organization of beta-catenin is highly conserved between amphioxus and other animals including a cnidarian, but not Drosophila. In development, amphioxus beta-catenin is concentrated in all nuclei from the 16-cell stage until the onset of gastrulation when it becomes undetectable in presumptive mesendoderm. Li(+), which up-regulates Wnt/beta-catenin signaling, had no detectable effect on axial patterning when applied before the late blastula stage, suggesting that a role for beta-catenin in specification of dorsal/anterior identity may be a vertebrate innovation. From the mid-gastrula through the neurula stage, the highest levels of nuclear beta-catenin are around the blastopore. In the early neurula, beta-catenin is down-regulated in the neural plate, but remains high in adjacent non-neural ectoderm. Embryos treated with Li(+) at the late blastula stage are markedly posteriorized and lack a neural plate. These results suggest that in amphioxus, as in vertebrates, down-regulation of Wnt/beta-catenin signaling in the neural plate is necessary for maintenance of the neuroectoderm and that a major evolutionarily conserved role of Wnt/beta-catenin signaling is to specify posterior identity and pattern the anterior/posterior axis.
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Affiliation(s)
- Linda Z Holland
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0202, USA.
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36
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Primus AE. Regional specification in the early embryo of the brittle star Ophiopholis aculeata. Dev Biol 2005; 283:294-309. [PMID: 15922322 DOI: 10.1016/j.ydbio.2005.04.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2004] [Revised: 03/16/2005] [Accepted: 04/19/2005] [Indexed: 11/26/2022]
Abstract
Early embryogenesis has been examined experimentally in several echinoderm and hemichordate classes. Although these studies suggest that the mechanisms which underlie regional specification have been highly conserved within the echinoderm + hemichordate clade, nothing is known about these mechanisms in several other echinoderm classes, including the Ophiuroidea. In this study, early embryogenesis was examined in a very little studied animal, the ophiuroid Ophiopholis aculeata. In O. aculeata, the first two cleavage planes do not coincide with the animal-vegetal axis but rather form approximately 45 degrees off this axis. A fate map of the early embryo was constructed using microinjected lineage tracers. Most significantly, this fate map indicates that there is a major segregation of ectodermal from endomesodermal fates at first cleavage. The distribution of developmental potential in the early embryo was also examined by isolating different regions of the early embryo and following these isolates though larval development. These analyses indicate that endomesodermal developmental potential segregates unequally at first, second, and third cleavage in O. aculeata. These results provide insight into the mechanisms of regional specification in O. aculeata and yield new material for the study of the evolution of echinoderm development.
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Affiliation(s)
- Alexander E Primus
- Section of Integrative Biology, University of Texas, 1 University Station CO939, Austin, 78712, USA.
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Yamazaki A, Kawabata R, Shiomi K, Amemiya S, Sawaguchi M, Mitsunaga-Nakatsubo K, Yamaguchi M. The micro1 gene is necessary and sufficient for micromere differentiation and mid/hindgut-inducing activity in the sea urchin embryo. Dev Genes Evol 2005; 215:450-59. [PMID: 16078091 DOI: 10.1007/s00427-005-0006-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Accepted: 05/18/2005] [Indexed: 10/25/2022]
Abstract
In the sea urchin embryo, micromeres have two distinct functions: they differentiate cell autonomously into the skeletogenic mesenchyme cells and act as an organizing center that induces endomesoderm formation. We demonstrated that micro1 controls micromere specification as a transcriptional repressor. Because micro1 is a multicopy gene with at least six polymorphic loci, it has been difficult to consistently block micro1 function by morpholino-mediated knockdown. Here, to block micro1 function, we used an active activator of micro1 consisting of a fusion protein of the VP16 activation domain and the micro1 homeodomain. Embryos injected with mRNA encoding the fusion protein exhibited a phenotype similar to that of micromere-less embryos. To evaluate micro1 function in the micromere, we constructed chimeric embryos composed of animal cap mesomeres and a micromere quartet from embryos injected with the fusion protein mRNA. The chimeras developed into dauerblastulae with no vegetal structures, in which the micromere progeny constituted the blastula wall. We also analyzed the phenotype of chimeras composed of an animal cap and a mesomere expressing micro1. These chimeras developed into pluteus larvae, in which the mesomere descendants ingressed as primary mesenchyme cells and formed a complete set of skeletal rods. The hindgut and a part of the midgut were also generated from host mesomeres. However, the foregut and nonskeletogenic mesoderm were not formed in the larvae. From these observations, we conclude that micro1 is necessary and sufficient for both micromere differentiation and mid/hindgut-inducing activity, and we also suggest that micro1 may not fulfill all micromere functions.
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Affiliation(s)
- Atsuko Yamazaki
- Division of Life Science, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, 920-1192, Japan
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Peterson RE, McClay DR. A Fringe-modified Notch signal affects specification of mesoderm and endoderm in the sea urchin embryo. Dev Biol 2005; 282:126-37. [PMID: 15936334 DOI: 10.1016/j.ydbio.2005.02.033] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2004] [Revised: 10/12/2004] [Accepted: 02/24/2005] [Indexed: 11/19/2022]
Abstract
Fringe proteins are O-fucose-specific beta-1,3 N-acetylglucosaminyltransferases that glycosylate the extracellular EGF repeats of Notch and enable Notch to be activated by the ligand Delta. In the sea urchin, signaling between Delta and Notch is known to be necessary for specification of secondary mesenchyme cells (SMCs). The Lytechinus variegatus Fringe homologue is expressed in both the signaling and receiving cells during this first Delta-Notch signal. Perturbation of Fringe expression through morpholino antisense oligonucleotide (MO) injection results in fewer SMCs but also causes decreased and delayed archenteron invagination. Partial endoderm specification occurs but expression of some endoderm genes is compromised. The data are consistent with a Fringe-requiring Notch signal as one upstream component of archenteron morphogenesis. Finally, Fringe perturbations result in more severe phenotypes than those previously reported for Notch dominant-negative (LvN(neg)) injections or reported here for Notch MO (NMO) injections. Injecting a combination of LvN(neg) and NMO results in a more severe phenotype than either treatment alone, and this combination phenocopies the fringe MO embryos. Taken together, the results show that Fringe is necessary both for maternal and zygotic Notch signals, and these Notch signals affect specification of mesoderm and endoderm.
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Affiliation(s)
- Robert E Peterson
- Department of Biology and Developmental, Cell, and Molecular Biology Group, Duke University, Box 91000, Durham, NC 27708, USA.
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Wikramanayake AH, Peterson R, Chen J, Huang L, Bince JM, McClay DR, Klein WH. Nuclear beta-catenin-dependent Wnt8 signaling in vegetal cells of the early sea urchin embryo regulates gastrulation and differentiation of endoderm and mesodermal cell lineages. Genesis 2005; 39:194-205. [PMID: 15282746 DOI: 10.1002/gene.20045] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The entry of beta-catenin into vegetal cell nuclei beginning at the 16-cell stage is one of the earliest known molecular asymmetries seen along the animal-vegetal axis in the sea urchin embryo. Nuclear beta-catenin activates a vegetal signaling cascade that mediates micromere specification and specification of the endomesoderm in the remaining cells of the vegetal half of the embryo. Only a few potential target genes of nuclear beta-catenin have been functionally analyzed in the sea urchin embryo. Here, we show that SpWnt8, a Wnt8 homolog from Strongylocentrotus purpuratus, is zygotically activated specifically in 16-cell-stage micromeres in a nuclear beta-catenin-dependent manner, and its expression remains restricted to the micromeres until the 60-cell stage. At the late 60-cell stage nuclear beta-catenin-dependent SpWnt8 expression expands to the veg2 cell tier. SpWnt8 is the only signaling molecule thus far identified with expression localized to the 16-60-cell stage micromeres and the veg2 tier. Overexpression of SpWnt8 by mRNA microinjection produced embryos with multiple invagination sites and showed that, consistent with its localization, SpWnt8 is a strong inducer of endoderm. Blocking SpWnt8 function using SpWnt8 morpholino antisense oligonucleotides produced embryos that formed micromeres that could transmit the early endomesoderm-inducing signal, but these cells failed to differentiate as primary mesenchyme cells. SpWnt8-morpholino embryos also did not form endoderm, or secondary mesenchyme-derived pigment and muscle cells, indicating a role for SpWnt8 in gastrulation and in the differentiation of endomesodermal lineages. These results establish SpWnt8 as a critical component of the endomesoderm regulatory network in the sea urchin embryo.
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Revilla-i-Domingo R, Minokawa T, Davidson EH. R11: a cis-regulatory node of the sea urchin embryo gene network that controls early expression of SpDelta in micromeres. Dev Biol 2004; 274:438-51. [PMID: 15385170 DOI: 10.1016/j.ydbio.2004.07.008] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2004] [Accepted: 07/09/2004] [Indexed: 11/19/2022]
Abstract
A gene regulatory network (GRN) controls the process by which the endomesoderm of the sea urchin embryo is specified. In this GRN, the program of gene expression unique to the skeletogenic micromere lineage is set in train by activation of the pmar1 gene. Through a double repression system, this gene is responsible for localization of expression of downstream regulatory and signaling genes to cells of this lineage. One of these genes, delta, encodes a Notch ligand, and its expression in the right place and time is crucial to the specification of the endomesoderm. Here we report a cis-regulatory element R11 that is responsible for localizing the expression of delta by means of its response to the pmar1 repression system. R11 was identified as an evolutionarily conserved genomic sequence located about 13 kb downstream of the last exon of the delta gene. We demonstrate here that this cis-regulatory element is able to drive the expression of a reporter gene in the same cells and at the same time that the endogenous delta gene is expressed, and that temporally, spatially, and quantitatively it responds to the pmar1 repression system just as predicted for the delta gene in the endomesoderm GRN. This work illustrates the application of cis-regulatory analysis to the validation of predictions of the GRN model. In addition, we introduce new methodological tools for quantitative measurement of the output of expression constructs that promise to be of general value for cis-regulatory analysis in sea urchin embryos.
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41
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Prodon F, Prulière G, Chenevert J, Sardet C. [Establishment and expression of embryonic axes: comparisons between different model organisms]. Med Sci (Paris) 2004; 20:526-38. [PMID: 15190470 DOI: 10.1051/medsci/2004205526] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In an accompanying article (C. Sardet et al. m/s 2004; 20 : 414-423) we reviewed determinants of polarity in early development and the mechanisms which regulate their localization and expression. Such determinants have for the moment been identified in only a few species: the insect Drosophila melanogaster, the worm Caenorhabditis elegans, the frog Xenopus laevis and the ascidians Ciona intestinalis and Holocynthia roretzi. Although oogenesis, fertilization, and cell divisions in these embryos differ considerably, with respect to early polarities certain common themes emerge, such as the importance of cortical mRNAs, the PAR polarity proteins, and reorganizations mediated by the cytoskeleton. Here we highlight similarities and differences in axis establishment between these species, describing them in a chronological order from oocyte to gastrula, and add two more classical model organisms, sea urchin and mouse, to complete the comparisons depicted in the form of a Poster which can be downloaded from the site http://biodev.obs-vlfr.fr/biomarcell.
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Affiliation(s)
- François Prodon
- BioMarCell, Laboratoire de biologie du développement, UMR 7009 CNRS-UPMC, Observatoire, Station zoologique, 06230 Villefranche-sur-Mer, France
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Fernandez-Serra M, Consales C, Livigni A, Arnone MI. Role of the ERK-mediated signaling pathway in mesenchyme formation and differentiation in the sea urchin embryo. Dev Biol 2004; 268:384-402. [PMID: 15063175 DOI: 10.1016/j.ydbio.2003.12.029] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2003] [Revised: 12/12/2003] [Accepted: 12/22/2003] [Indexed: 12/25/2022]
Abstract
Mesoderm and mesodermal structures in the sea urchin embryo are entirely generated by two embryologically distinct populations of mesenchyme cells: the primary (PMC) and the secondary (SMC) mesenchyme cells. We have identified the extracellular signal-regulated kinase (ERK) as a key component of the regulatory machinery that controls the formation of both these cell types. ERK is activated in a spatial-temporal manner, which coincides with the epithelial-mesenchyme transition (EMT) of the prospective PMCs and SMCs. Here, we show that ERK controls EMT of both primary and secondary mesenchyme cells. Loss and gain of function experiments demonstrate that ERK signaling is not required for the early specification of either PMCs or SMCs, but controls the maintenance and/or the enhancement of expression levels of regulatory genes which participate in the process of specification of these cell types. In addition, ERK-mediated signaling is essential for the transcription of terminal differentiation genes encoding proteins that define the final structures generated by PMCs and SMCs. Our findings suggest that ERK has a central pan-mesodermal role in coupling EMT and terminal differentiation of all mesenchymal cell types in the sea urchin embryo.
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Takata H, Kominami T. Pigment cells trigger the onset of gastrulation in tropical sea urchin Echinometra mathaei. Dev Growth Differ 2004; 46:23-35. [PMID: 15008852 DOI: 10.1111/j.1440-169x.2004.00726.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the tropical sea urchin Echinometra mathaei, pigment cells are just detectable before the onset of gastrulation, owing to an early accumulation of red pigment granules. Taking advantage of this feature, behavior of pigment cells was studied in relation to the processes of gastrulation. Before the initiation of primary invagination, pigment cells were arranged in a hemi-circle in the dorsal half of the vegetal plate. Inward bending of the vegetal plate first occurred at the position occupied by pigment cells, while the bending was not conspicuous in the ventral half of the blastopore. Rhodamine-phalloidin staining showed that actin filaments were abundant at the apical corticies of pigment cells. It was also found that the onset of gastrulation was considerably delayed in the NiCl2-treated embryos, in which pigment cells were drastically reduced in number. It is notable that the NiCl2-treated embryos began to gastrulate on schedule if they contained a number of pigment cells in spite of treatment. This shows that pigment cells are the bottle cells that trigger the onset of gastrulation. In the embryos devoid of pigment cells, a short stub-like gut rudiment formed in a delayed fashion, and several secondary mesenchyme cells (SMC) appeared at the tip of the rudiment and elongated gradually until its tip reached the apical plate. This observation suggests that the SMC that pull the gut rudiment upward are not pigment cells but blastocoelar cells, because pigment cells change their fate to blastocoelar cells upon NiCl2-treatment.
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Affiliation(s)
- Hiromi Takata
- Department of Biology and Earth Sciences, Faculty of Science, Ehime University, Matsuyama, 790-8577, Japan.
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Sweet H, Amemiya S, Ransick A, Minokawa T, McClay DR, Wikramanayake A, Kuraishi R, Kiyomoto M, Nishida H, Henry J. Blastomere Isolation and Transplantation. Methods Cell Biol 2004; 74:243-71. [PMID: 15575610 DOI: 10.1016/s0091-679x(04)74011-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2023]
Affiliation(s)
- Hyla Sweet
- Department of Biological Sciences, College of Science, Rochester Institute of Technology, Rochester, New York 14623, USA
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45
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Venuti JM, Pepicelli C, Flowers VL. Analysis of Sea Urchin Embryo Gene Expression by Immunocytochemistry. Methods Cell Biol 2004; 74:333-69. [PMID: 15575614 DOI: 10.1016/s0091-679x(04)74015-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Affiliation(s)
- Judith M Venuti
- Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA
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Cavalieri V, Spinelli G, Di Bernardo M. Impairing Otp homeodomain function in oral ectoderm cells affects skeletogenesis in sea urchin embryos. Dev Biol 2003; 262:107-18. [PMID: 14512022 DOI: 10.1016/s0012-1606(03)00317-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In the sea urchin embryo skeletogenesis is the result of a complex series of molecular and cellular events that coordinate the morphogenetic process. Past and recent evidence strongly indicate that skeletal initiation and growth are strictly dependent on signals emanating from the oral ectodermal wall. As previously suggested, Orthopedia (Otp), a homeodomain-containing transcription factor specifically expressed in a small subset of oral ectoderm cells, might be implicated in this signalling pathway. In this study, we utilize three different strategies to address the issue of whether Otp is an upstream regulator of sketelogenesis. We describe the effects of microinjection of Otp morpholino-substituted antisense oligonucleotides and dominant-negative Otp-engrailed mRNA in Paracentrotus lividus embryos. We demonstrate that inhibition of Otp expression completely abolishes skeletal synthesis. By contrast, coinjection of Otp mRNA and the morpholino antisense oligonucleotide specifically rescues the skeletogenic program. In addition, localized ectodermal expression of the Otp-GFP fusion gene construct driven by the hatching enzyme promoter, induces ectopic and abnormal spiculogenesis. We further show that an indirect target of this homeoprotein is the skeletogenic specific gene SM30, whose expression is known to be under the strict control of the oral ectoderm territory. Based on these results, we conclude that Otp triggers the ectoderm-specific signal that promotes skeletogenesis.
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Affiliation(s)
- Vincenzo Cavalieri
- Dipartimento di Biologia Cellulare e dello Sviluppo A. Monroy, Università di Palermo, Viale delle Scienze Parco d'Orleans II, 90128 Palermo, Italy
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Abstract
BACKGROUND Morphogenetic movements are closely regulated by the expression of developmental genes. Here I examine whether developmental gene expression can in turn be mechanically regulated by morphogenetic movements. I have analyzed the effects of mechanical stress on the expression of Twist, which is normally expressed only in the most ventral cells of the cellular blastoderm embryo under the control of the Dorsal morphogen gradient. At embryogenesis gastrulation (stage 7), Twist is also expressed in the anterior foregut and stomodeal primordia. RESULTS Submitting the early Drosophila embryo to a transient 10% uniaxial lateral deformation induces the ectopic expression of Twist around the entire dorsal-ventral axis and results in the ventralization of the embryo. This induction is independent of the Dorsal gradient and is triggered by mechanically induced Armadillo nuclear translocation. I also show that Twist is not expressed in the anterior foregut and stomodeal primordia at stage 7 in mutants that block the morphogenetic movement of germ-band extension. Because I can rescue the mutants with gentle compression of these cells, my interpretation is that the stomodeal-cell compression normally caused by the germ-band extension induces the expression of Twist. Correspondingly, laser ablation of dorsal cells in wild-type embryos relaxes stomodeal cell compression and reduces Twist expression in the stomodeal primordium. I also demonstrate that the induction of Twist in these cells depends on the nuclear translocation of Armadillo. CONCLUSIONS I propose that anterior-gut formation is mechanically induced by the movement of germ-band extension through the induction of Twist expression in stomodeal cells.
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Affiliation(s)
- Emmanuel Farge
- Mechanics and Genetics of Developmental Embryogenesis Group, Unité Mixte de Recherche 168 Physico-Chimie Curie, Curie Institute, 11 rue Pierre et Marie Curie, 75005 Paris, France.
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Hamada M, Kiyomoto M. Signals from primary mesenchyme cells regulate endoderm differentiation in the sea urchin embryo. Dev Growth Differ 2003; 45:339-50. [PMID: 12950275 DOI: 10.1046/j.1440-169x.2003.00702.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Primary mesenchyme cells (PMC), the skeletogenic cells derived from the micromeres of the sea urchin embryo, are involved in the differentiation of the gut. When PMC were deleted from the mesenchyme blastula, both formation of the constrictions in the gut and expression of endoderm-specific alkaline phosphatase were significantly delayed. Therefore, the correct timing of gut differentiation depends on the existence of PMC, probably via a type of promotive signal. To date, the only role of PMC in other tissue differentiation has been a suppressive signal for the conversion of secondary mesenchyme cells (SMC) into skeletogenic cells. The present experiments using PMC ablation and transplantation showed that both signaling processes occurred in the same short period during gastrulation, but the embryos kept their competence for gut differentiation until a later stage. Further investigations indicated that conversion of SMC did not cause delay in gut differentiation and that SMC did not mediate the PMC signal to the endoderm. Therefore, the effect of PMC on gut differentiation could be a new role that is independent of the suppressive effect for SMC conversion.
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Affiliation(s)
- Mayuko Hamada
- Tateyama Marine Laboratory, Ochanomizu University, Kou-yatsu 11, Tateyama, Chiba 294-0301, Japan
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49
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Angerer LM, Angerer RC. Patterning the sea urchin embryo: gene regulatory networks, signaling pathways, and cellular interactions. Curr Top Dev Biol 2003; 53:159-98. [PMID: 12509127 DOI: 10.1016/s0070-2153(03)53005-8] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We discuss steps in the specification of major tissue territories of the sea urchin embryo that occur between fertilization and hatching blastula stage and the cellular interactions required to coordinate morphogenetic processes that begin after hatching. We review evidence that has led to new ideas about how this embryo is initially patterned: (1) Specification of most of the tissue territories is not direct, but proceeds gradually by progressive subdivision of broad, maternally specified domains that depend on opposing gradients in the ratios of animalizing transcription factors (ATFs) and vegetalizing (beta-catenin) transcription factors; (2) the range of maternal nuclear beta-catenin extends further than previously proposed, that is, into the animal hemisphere, where it programs many cells to adopt early aboral ectoderm characteristics; (3) cells at the extreme animal pole constitute a unique ectoderm region, lacking nuclear beta-catenin; (4) the pluripotential mesendoderm is created by the combined outputs of ATFs and nuclear beta-catenin, which initially overlap in the macromeres, and by an undefined early micromere signal; (5) later micromere signals, which activate Notch and Wnt pathways, subdivide mesendoderm into secondary mesenchyme and endoderm; and (6) oral ectoderm specification requires reprogramming early aboral ectoderm at about the hatching blastula stage. Morphogenetic processes that follow initial fate specification depend critically on continued interactions among cells in different territories. As illustrations, we discuss the regulation of (1) the ectoderm/endoderm boundary, (2) mesenchyme positioning and skeletal growth, (3) ciliated band formation, and (4) several suppressive interactions operating late in embryogenesis to limit the fates of multipotent cells.
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Affiliation(s)
- Lynne M Angerer
- Department of Biology, University of Rochester, Rochester, New York 14627, USA
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Oliveri P, Davidson EH, McClay DR. Activation of pmar1 controls specification of micromeres in the sea urchin embryo. Dev Biol 2003; 258:32-43. [PMID: 12781680 DOI: 10.1016/s0012-1606(03)00108-8] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
pmar1 is a transcription factor in the paired class homeodomain family that was identified and found to be transcribed in micromeres beginning at the fourth cleavage of sea urchin development [Dev. Biol. 246 (2002), 209]. Based on in situ data, molecular perturbation studies, and QPCR data, the recently published gene regulatory network (GRN) model for endomesoderm specification [Science 295 (2002) 1669; Dev. Biol. 246 (2002), 162] places pmar1 early in the micromere specification pathway, and upstream of two important micromere induction signals. The goal of this study was to test these three predictions of the network model. A series of embryo chimeras were produced in which pmar1 activity was perturbed in one cell that was transplanted to control hosts. At the fourth cleavage, micromeres bearing altered pmar1 activity were combined with a normal micromereless host embryo. If beta-catenin signaling is blocked, the micromeres remain unspecified and are unable to signal to the host cells. When such beta-catenin-blocked micromeres also express Pmar1, all observed micromere functions are rescued. The rescue includes expression of the primary mesenchyme cell (PMC) differentiation program, expression and execution of the Delta signal to induce secondary mesoderm cell (SMC) specification in macromere progeny, and expression of the early endomesoderm induction signal necessary for full specification of the endoderm. Additionally, Pmar1 expressed mosaically from inserted DNA constructs causes induction of ectopic Endo 16 in adjacent cells, demonstrating further that Pmar1 controls expression of the early endomesoderm induction signal. Based on these experiments, Pmar1 is an important transcription factor necessary for initiating the micromere specification program and for the expression of two inductive signals produced by micromeres. Each of the tests we describe supports the placement and function of Pmar1 in the endomesoderm GRN model.
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Affiliation(s)
- Paola Oliveri
- Division of Biology, 156-29, California Institute of Technology, Pasadena, CA 91125, USA
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