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Takemoto A, Miyamoto T, Simono F, Kurogi N, Shirae-Kurabayashi M, Awazu A, Suzuki KIT, Yamamoto T, Sakamoto N. Cilia play a role in breaking left-right symmetry of the sea urchin embryo. Genes Cells 2016; 21:568-78. [DOI: 10.1111/gtc.12362] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/25/2016] [Indexed: 11/29/2022]
Affiliation(s)
- Ayumi Takemoto
- Department of Mathematical and Life Sciences; Graduate School of Science; Hiroshima University; Higashi-Hiroshima 739-8526 Japan
| | - Tatsuo Miyamoto
- Department of Genetics and Cell Biology; Research Institute for Radiation Biology and Medicine; Hiroshima University; Hiroshima 734-8553 Japan
| | - Fumie Simono
- Hiroshima Prefectural Hiroshima Kokutaiji High School; Hiroshima 730-0042 Japan
- An Educational Project for Exciting Science Learning for Pupils; Hiroshima University; Higashi-Hiroshima 739-8524 Japan
| | - Nao Kurogi
- Department of Mathematical and Life Sciences; Graduate School of Science; Hiroshima University; Higashi-Hiroshima 739-8526 Japan
| | - Maki Shirae-Kurabayashi
- Sugashima Marine Biological Laboratory; Graduate School of Science; Nagoya University; Mie 517-0004 Japan
| | - Akinori Awazu
- Department of Mathematical and Life Sciences; Graduate School of Science; Hiroshima University; Higashi-Hiroshima 739-8526 Japan
- Research Center for the Mathematics on Chromatin Live Dynamics; Hiroshima University; Higashi-Hiroshima 739-8526 Japan
| | - Ken-ichi T. Suzuki
- Department of Mathematical and Life Sciences; Graduate School of Science; Hiroshima University; Higashi-Hiroshima 739-8526 Japan
| | - Takashi Yamamoto
- Department of Mathematical and Life Sciences; Graduate School of Science; Hiroshima University; Higashi-Hiroshima 739-8526 Japan
- Research Center for the Mathematics on Chromatin Live Dynamics; Hiroshima University; Higashi-Hiroshima 739-8526 Japan
| | - Naoaki Sakamoto
- Department of Mathematical and Life Sciences; Graduate School of Science; Hiroshima University; Higashi-Hiroshima 739-8526 Japan
- Research Center for the Mathematics on Chromatin Live Dynamics; Hiroshima University; Higashi-Hiroshima 739-8526 Japan
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Abstract
With few exceptions, all animals acquire the ability to produce eggs or sperm at some point in their life cycle. Despite this near-universal requirement for sexual reproduction, there exists an incredible diversity in germ line development. For example, animals exhibit a vast range of differences in the timing at which the germ line, which retains reproductive potential, separates from the soma, or terminally differentiated, nonreproductive cells. This separation may occur during embryonic development, after gastrulation, or even in adults, depending on the organism. The molecular mechanisms of germ line segregation are also highly diverse, and intimately intertwined with the overall transition from a fertilized egg to an embryo. The earliest embryonic stages of many species are largely controlled by maternally supplied factors. Later in development, patterning control shifts to the embryonic genome and, concomitantly with this transition, the maternally supplied factors are broadly degraded. This chapter attempts to integrate these processes--germ line segregation, and how the divergence of germ line and soma may utilize the egg to embryo transitions differently. In some embryos, this difference is subtle or maybe lacking altogether, whereas in other embryos, this difference in utilization may be a key step in the divergence of the two lineages. Here, we will focus our discussion on the echinoderms, and in particular the sea urchins, in which recent studies have provided mechanistic understanding in germ line determination. We propose that the germ line in sea urchins requires an acquisition of maternal factors from the egg and, when compared to other members of the taxon, this appears to be a derived mechanism. The acquisition is early--at the 32-cell stage--and involves active protection of maternal mRNAs, which are instead degraded in somatic cells with the maternal-to-embryonic transition. We collectively refer to this model as the Time Capsule method for germ line determination.
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Affiliation(s)
- S Zachary Swartz
- Department of Molecular and Cellular Biology, Brown University, Providence, Rhode Island, USA
| | - Gary M Wessel
- Department of Molecular and Cellular Biology, Brown University, Providence, Rhode Island, USA.
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Wessel GM, Brayboy L, Fresques T, Gustafson EA, Oulhen N, Ramos I, Reich A, Swartz SZ, Yajima M, Zazueta V. The biology of the germ line in echinoderms. Mol Reprod Dev 2014; 81:679-711. [PMID: 23900765 PMCID: PMC4102677 DOI: 10.1002/mrd.22223] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Accepted: 07/23/2013] [Indexed: 12/16/2022]
Abstract
The formation of the germ line in an embryo marks a fresh round of reproductive potential. The developmental stage and location within the embryo where the primordial germ cells (PGCs) form, however, differs markedly among species. In many animals, the germ line is formed by an inherited mechanism, in which molecules made and selectively partitioned within the oocyte drive the early development of cells that acquire this material to a germ-line fate. In contrast, the germ line of other animals is fated by an inductive mechanism that involves signaling between cells that directs this specialized fate. In this review, we explore the mechanisms of germ-line determination in echinoderms, an early-branching sister group to the chordates. One member of the phylum, sea urchins, appears to use an inherited mechanism of germ-line formation, whereas their relatives, the sea stars, appear to use an inductive mechanism. We first integrate the experimental results currently available for germ-line determination in the sea urchin, for which considerable new information is available, and then broaden the investigation to the lesser-known mechanisms in sea stars and other echinoderms. Even with this limited insight, it appears that sea stars, and perhaps the majority of the echinoderm taxon, rely on inductive mechanisms for germ-line fate determination. This enables a strongly contrasted picture for germ-line determination in this phylum, but one for which transitions between different modes of germ-line determination might now be experimentally addressed.
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Affiliation(s)
- Gary M. Wessel
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Lynae Brayboy
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Tara Fresques
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Eric A. Gustafson
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Nathalie Oulhen
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Isabela Ramos
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Adrian Reich
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - S. Zachary Swartz
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Mamiko Yajima
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Vanessa Zazueta
- Department of Molecular Biology, Cellular Biology, and Biochemistry, Brown University, Providence, Rhode Island
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Yajima M, Wessel GM. Small micromeres contribute to the germline in the sea urchin. Development 2011; 138:237-43. [PMID: 21177341 PMCID: PMC3005600 DOI: 10.1242/dev.054940] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/27/2010] [Indexed: 11/20/2022]
Abstract
Many indirect developing animals create specialized multipotent cells in early development to construct the adult body and perhaps to hold the fate of the primordial germ cells. In sea urchin embryos, small micromeres formed at the fifth division appear to be such multipotent cells: they are relatively quiescent in embryos, but contribute significantly to the coelomic sacs of the larvae, from which the major tissues of the adult rudiment are derived. These cells appear to be regulated by a conserved gene set that includes the classic germline lineage genes vasa, nanos and piwi. In vivo lineage mapping of the cells awaits genetic manipulation of the lineage, but previous research has demonstrated that the germline is not specified at the fourth division because animals are fertile even when micromeres, the parent blastomeres of small micromeres, are deleted. Here, we have deleted small micromeres at the fifth division and have raised the resultant larvae to maturity. These embryos developed normally and did not overexpress Vasa, as did embryos from a micromere deletion, implying the compensatory gene regulatory network was not activated in small micromere-deleted embryos. Adults from control and micromere-deleted embryos developed gonads and visible gametes, whereas small micromere-deleted animals formed small gonads that lacked gametes. Quantitative PCR results indicate that small micromere-deleted animals produce background levels of germ cell products, but not specifically eggs or sperm. These results suggest that germline specification depends on the small micromeres, either directly as lineage products, or indirectly by signaling mechanisms emanating from the small micromeres or their descendants.
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Affiliation(s)
- Mamiko Yajima
- MCB Department, Brown University, 185 Meeting Street, BOX-GL173, Providence, RI 02912, USA
| | - Gary M. Wessel
- MCB Department, Brown University, 185 Meeting Street, BOX-GL173, Providence, RI 02912, USA
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Yamazaki A, Furuzawa Y, Yamaguchi M. Conserved early expression patterns of micromere specification genes in two echinoid species belonging to the orders clypeasteroida and echinoida. Dev Dyn 2010; 239:3391-403. [DOI: 10.1002/dvdy.22476] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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Fujii T, Sakamoto N, Ochiai H, Fujita K, Okamitsu Y, Sumiyoshi N, Minokawa T, Yamamoto T. Role of the nanos homolog during sea urchin development. Dev Dyn 2010; 238:2511-21. [PMID: 19705446 DOI: 10.1002/dvdy.22074] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The nanos genes play important roles in the development of primordial germ cells in animal species. In the sea urchin, Hemicentrotus pulcherrimus, small micromere descendants specifically express HpNanos mRNA and this expression continues in the left coelomic pouch, which produces the major component of the adult rudiment. In this study, we showed that morpholino knockdown of HpNanos resulted in a delay of primary mesenchyme cell ingression and a decrease in the number of cells comprising the left coelomic pouch. Knockdown analysis in chimeras and whole embryos revealed the disappearance of small micromere descendants from the archenteron tip. Furthermore, the expression of HpNanos mRNA was induced in other cell lineages in the HpNanos-knockdown and micromere-deleted embryos. Taken together, our results suggest that HpNanos is involved in the inductive interaction of small micromere descendants with other cell lineages, and that HpNanos is required for the survival of small micromere descendants.
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Affiliation(s)
- Takayoshi Fujii
- Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Japan
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Voronina E, Lopez M, Juliano CE, Gustafson E, Song JL, Extavour C, George S, Oliveri P, McClay D, Wessel G. Vasa protein expression is restricted to the small micromeres of the sea urchin, but is inducible in other lineages early in development. Dev Biol 2008; 314:276-86. [PMID: 18191830 PMCID: PMC2692673 DOI: 10.1016/j.ydbio.2007.11.039] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Revised: 11/06/2007] [Accepted: 11/20/2007] [Indexed: 11/18/2022]
Abstract
Vasa is a DEAD-box RNA helicase that functions in translational regulation of specific mRNAs. In many animals it is essential for germ line development and may have a more general stem cell role. Here we identify vasa in two sea urchin species and analyze the regulation of its expression. We find that vasa protein accumulates in only a subset of cells containing vasa mRNA. In contrast to vasa mRNA, which is present uniformly throughout all cells of the early embryo, vasa protein accumulates selectively in the 16-cell stage micromeres, and then is restricted to the small micromeres through gastrulation to larval development. Manipulating early embryonic fate specification by blastomere separations, exposure to lithium, and dominant-negative cadherin each suggest that, although vasa protein accumulation in the small micromeres is fixed, accumulation in other cells of the embryo is inducible. Indeed, we find that embryos in which micromeres are removed respond by significant up-regulation of vasa protein translation, followed by spatial restriction of the protein late in gastrulation. Overall, these results support the contention that sea urchins do not have obligate primordial germ cells determined in early development, that vasa may function in an early stem cell population of the embryo, and that vasa expression in this embryo is restricted early by translational regulation to the small micromere lineage.
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Affiliation(s)
- Ekaterina Voronina
- Providence Institute of Molecular Oogenesis, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence RI 02912
| | - Manuel Lopez
- Department of Biology, LSRC Building, Duke University, Durham, NC 27708
| | - Celina E. Juliano
- Providence Institute of Molecular Oogenesis, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence RI 02912
| | - Eric Gustafson
- Providence Institute of Molecular Oogenesis, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence RI 02912
| | - Jia L. Song
- Providence Institute of Molecular Oogenesis, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence RI 02912
| | - Cassandra Extavour
- Laboratory for Development and Evolution, University Museum of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, England
| | - Sophie George
- Department of Biology, Georgia Southern University, Statesboro, Georgia 30460
| | - Paola Oliveri
- Division of Biology 156-29, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125
| | - David McClay
- Department of Biology, LSRC Building, Duke University, Durham, NC 27708
| | - Gary Wessel
- Providence Institute of Molecular Oogenesis, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence RI 02912
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MORICI GIOVANNI, AGNELLO MARIA, SPAGNOLO FILIPPO, ROCCHERI MARIACARMELA, LIEGRO CARLOMARIADI, RINALDI ANNAMARIA. Confocal microscopy study of the distribution, content and activity of mitochondria during Paracentrotus lividus development. J Microsc 2007; 228:165-73. [DOI: 10.1111/j.1365-2818.2007.01860.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Kominami T, Akagawa M, Takata H. Subequatorial cytoplasm plays an important role in ectoderm patterning in the sea urchin embryo. Dev Growth Differ 2006; 48:101-15. [PMID: 16512854 DOI: 10.1111/j.1440-169x.2006.00850.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
To gain information on the process of ectoderm patterning, the animal halves of sea urchin embryos were isolated at various stages, and their morphology was examined when control embryos developed into pluteus larvae. The animal halves separated at the 8-cell stage developed into 'dauerblastula', without showing any conspicuous ectoderm differentiation. In contrast, some of the animal halves isolated at the 60-cell stage (after the sixth cleavage) formed a ciliated band and oral opening, suggesting that some patterning signal was transmitted from the vegetal to animal hemisphere during early cleavage. Further patterning of the animal hemisphere did not seem to occur until hatching, since both the animal halves isolated at the 60-cell stage and hatching stage showed the same degree of ectoderm patterning. After hatching, the later animal halves were isolated, the more patterned ectoderm they formed. The animal halves isolated just prior to gastrulation differentiated well-patterned ectoderm. It is of note, however, that the level of separation was a more crucial factor than the timing of separation; even the animal fragments of newly hatched embryos differentiated well-patterned ectoderm if they had been separated at a subequatorial level. This suggests that the signal for ectoderm patterning is transmitted over the equator after hatching, and once the cells in the supra-equatorial region receive the signal, they, in turn, can transmit the signal upwardly. Interestingly, if the third cleavage plane was shifted toward the vegetal pole, the isolated animal pole-side fragments developed into 'embryoids' with fully patterned ectoderm. These results indicate that not the micromere descendants but the subequatorial cytoplasm plays an important role in ectoderm patterning.
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Affiliation(s)
- Tetsuya Kominami
- Department of Biology, Faculty of Science, Ehime University, 2-5, Bunkyo-Cho, Matsuyama 790-8577, Japan.
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