101
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Gustafson EA, Yajima M, Juliano CE, Wessel GM. Post-translational regulation by gustavus contributes to selective Vasa protein accumulation in multipotent cells during embryogenesis. Dev Biol 2010; 349:440-50. [PMID: 21035437 DOI: 10.1016/j.ydbio.2010.10.031] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 10/17/2010] [Accepted: 10/20/2010] [Indexed: 01/15/2023]
Abstract
Vasa is a broadly conserved DEAD-box RNA helicase associated with germ line development and is expressed in multipotent cells in many animals. During embryonic development of the sea urchin Strongylocentrotus purpuratus, Vasa protein is enriched in the small micromeres despite a uniform distribution of vasa transcript. Here we show that the Vasa coding region is sufficient for its selective enrichment and find that gustavus, the B30.2/SPRY and SOCS box domain gene, contributes to this phenomenon. In vitro binding analyses show that Gustavus binds the N-terminal and DEAD-box portions of Vasa protein independently. A knockdown of Gustavus protein reduces both Vasa protein abundance and its propensity for accumulation in the small micromeres, whereas overexpression of the Vasa-interacting domain of Gustavus (GusΔSOCS) results in Vasa protein accumulation throughout the embryo. We propose that Gustavus has a conserved, positive regulatory role in Vasa protein accumulation during embryonic development.
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Affiliation(s)
- Eric A Gustafson
- Providence Institute of Molecular Oogenesis, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
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102
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Kranz AM, Tollenaere A, Norris BJ, Degnan BM, Degnan SM. Identifying the germline in an equally cleaving mollusc: Vasa and Nanos expression during embryonic and larval development of the vetigastropod Haliotis asinina. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2010; 314:267-79. [PMID: 20095031 DOI: 10.1002/jez.b.21336] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Members of the Vasa and Nanos gene families are important for the specification and development of the germline in diverse animals. Here, we determine spatial and temporal expression of Vasa and Nanos to investigate germline development in the vetigastropod Haliotis asinina. This is the first time these genes have been examined in an equally cleaving lophotrochozoan species. We find that HasVasa and HasNanos have largely overlapping, but not identical, expression patterns during embryonic and larval development, with both being maternally expressed and localized to the micromere cell lineages during cleavage. As embryonic development continues, HasVasa and HasNanos become progressively more enriched in the dorsal quadrant of the embryo. By the trochophore stage, both HasVasa and HasNanos are expressed in the putative mesodermal bands of the larva. This differs from the unequally cleaving gastropod Illyanasa obsoleta, in which IoVasa and IoNanos expression is detectable only in the early embryo and not during gastrulation and larval development. Our results suggest that the H. asinina germline arises from the 4d cell lineage and that primordial germ cells (PGCs) are not specified exclusively by maternally inherited determinants (preformation). As such, we infer that inductive signals (epigenesis) play an important role in specifying PGCs in H. asinina. We hypothesize that HasVasa is expressed in a population of undifferentiated multipotent cells, from which the PGCs are segregated later during development.
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Affiliation(s)
- Alexandrea M Kranz
- The University of Queensland, School of Biological Sciences, Brisbane, Queensland, Australia
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103
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Obata M, Sano N, Kimata S, Nagasawa K, Yoshizaki G, Komaru A. The proliferation and migration of immature germ cells in the mussel, Mytilus galloprovincialis: observation of the expression pattern in the M. galloprovincialis vasa-like gene (Myvlg) by in situ hybridization. Dev Genes Evol 2010; 220:139-49. [PMID: 20725841 DOI: 10.1007/s00427-010-0335-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 07/24/2010] [Indexed: 10/19/2022]
Abstract
In bivalve, the distribution of primordial germ cells can be traced from early embryogenesis to the veliger larva by the expression of the vasa ortholog. However, the distribution of germ cells from metamorphosis to maturation in bivalves has not been examined extensively. In this study, we used in situ hybridization to observe expression of the Mytilus galloprovincialis vasa-like gene (Myvlg). The distribution of germ cells was clarified in immature mussels. We observed germ cells in adult mussels during the non-reproductive and reproductive seasons. Myvlg was specifically expressed in germ cells. Gametogenesis occurs in acini surrounded by connective tissue. Myvlg expression was detected in spermatogonia, spermatocytes, oogonia, and oocytes. In the non-reproductive season, gametes were not observed in the acini, but Myvlg was expressed in germinal stem cells along the acini. The expression intensity in the non-reproductive season, however, was much weaker than that in the reproductive season. Myvlg-positive cells proliferated during the non-reproductive season. In immature mussels, a pair of germ cell clumps was distributed laterally in the connective tissue between the nephric tubules and posterior byssal retractor muscle. Germ cells were also observed along pericardium. When immature mussels grew, a pair of germ cell clumps migrated anteriorly in the connective tissue along the outer epithelium at the dorsal region of the mantle base between the mantle and gill. The number of germ cells increased significantly as the mussels grew. This is the first report to observe the proliferation and migration of germ cells in immature mussels.
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Affiliation(s)
- Mayu Obata
- Faculty of Bioresources, Mie University, 1577 Kurimamachiya, Tsu, Mie, 514-8507, Japan.
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104
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Abstract
When do germ cells establish their separate, independent identity during animal development?
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Affiliation(s)
- Celina Juliano
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA. 02912
| | - Gary Wessel
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA. 02912
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105
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Smith JM, Cridge AG, Dearden PK. Germ cell specification and ovary structure in the rotifer Brachionus plicatilis. EvoDevo 2010; 1:5. [PMID: 20849649 PMCID: PMC2938724 DOI: 10.1186/2041-9139-1-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Accepted: 08/02/2010] [Indexed: 11/28/2022] Open
Abstract
Background The segregation of the germline from somatic tissues is an essential process in the development of all animals. Specification of the primordial germ cells (PGCs) takes place via different strategies across animal phyla; either specified early in embryogenesis by the inheritance of maternal determinants in the cytoplasm of the oocyte ('preformation') or selected later in embryonic development from undifferentiated precursors by a localized inductive signal ('epigenesis'). Here we investigate the specification and development of the germ cells in the rotifer Brachionus plicatilis, a member of the poorly-characterized superphyla Lophotrochozoa, by isolating the Brachionus homologues of the conserved germ cell markers vasa and nanos, and examining their expression using in situ hybridization. Results Bpvasa and Bpnos RNA expression have very similar distributions in the Brachionus ovary, showing ubiquitous expression in the vitellarium, with higher levels in the putative germ cell cluster. Bpvas RNA expression is present in freshly laid eggs, remaining ubiquitous in embryos until at least the 96 cell stage after which expression narrows to a small cluster of cells at the putative posterior of the embryo, consistent with the developing ovary. Bpnos RNA expression is also present in just-laid eggs but expression is much reduced by the four-cell stage and absent by the 16-cell stage. Shortly before hatching of the juvenile rotifer from the egg, Bpnos RNA expression is re-activated, located in a subset of posterior cells similar to those expressing Bpvas at the same stage. Conclusions The observed expression of vasa and nanos in the developing B. plicatilis embryo implies an epigenetic origin of primordial germ cells in Rotifer.
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Affiliation(s)
- James M Smith
- Laboratory for Evolution and Development, Genetics Otago and the National Research Centre for Growth and Development, Biochemistry Department, University of Otago, PO Box 56, Dunedin, Aotearoa-New Zealand.
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106
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Hasse C, Rebscher N, Reiher W, Sobjinski K, Moerschel E, Beck L, Tessmar-Raible K, Arendt D, Hassel M. Three consecutive generations of nephridia occur during development of Platynereis dumerilii (Annelida, Polychaeta). Dev Dyn 2010; 239:1967-76. [DOI: 10.1002/dvdy.22331] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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107
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Juliano CE, Yajima M, Wessel GM. Nanos functions to maintain the fate of the small micromere lineage in the sea urchin embryo. Dev Biol 2010; 337:220-32. [PMID: 19878662 PMCID: PMC2812692 DOI: 10.1016/j.ydbio.2009.10.030] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 10/09/2009] [Accepted: 10/21/2009] [Indexed: 11/16/2022]
Abstract
The translational regulator nanos is required for the survival and maintenance of primordial germ cells during embryogenesis. Three nanos homologs are present in the genome of the sea urchin Strongylocentrotus purpuratus, all of which are expressed with different timing in the small micromere lineage. This lineage is set-aside during embryogenesis and contributes to constructing the adult rudiment. Small micromeres lacking Sp-nanos1 and Sp-nanos2 undergo an extra division and are not incorporated into the coelomic pouches. Further, these cells do not accumulate Vasa protein even though they retain vasa mRNA. Larvae that develop from Sp-nanos1 and 2 knockdown embryos initially appear normal, but do not develop adult rudiments; although they are capable of eating, over time they fail to grow and eventually die. We conclude that the acquisition and maintenance of multipotency in the small micromere lineage requires nanos, which may function in part by repressing the cell cycle and regulating other multipotency factors such as vasa. This work, in combination with other recent results in Ilyanassa and Platynereis dumerilii, suggests the presence of a conserved molecular program underlying both primordial germ cell and multipotent cell specification and maintenance.
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Affiliation(s)
- Celina E Juliano
- Department of Molecular and Cell Biology and Biochemistry, Brown University, 185 Meeting St., Providence, RI 02912, USA
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108
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Yoshida-Noro C, Tochinai S. Stem cell system in asexual and sexual reproduction of Enchytraeus japonensis (Oligochaeta, Annelida). Dev Growth Differ 2009; 52:43-55. [PMID: 20039928 DOI: 10.1111/j.1440-169x.2009.01149.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Enchytraeus japonensis is a small oligochaete species that proliferates asexually via fragmentation and regeneration. As sexual reproduction can also be induced, it is a good model system for the study of both regenerative and germline stem cells. It has been shown by histological study that putative mesodermal stem cells called neoblasts, and dedifferentiated epidermal and endodermal cells are involved in blastema formation. Recently, we isolated three region-specific marker genes expressed in the digestive tract and showed by in situ hybridization that morphallactic as well as epimorphic regulation of the body patterning occurs during regeneration. We also cloned two vasa-related genes and analyzed their expression during development and in mature worms that undergo sexual reproduction. The results arising form these studies suggest that the origin and development of germline stem cells and neoblasts may be independent. Furthermore, we carried out functional analysis using RNA interference (RNAi) and showed that a novel gene termed grimp is required for mesodermal cell proliferation at the initial stages of regeneration. These findings indicate that the stem cell system in E. japonensis is regulated by both internal and external environmental factors.
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Affiliation(s)
- Chikako Yoshida-Noro
- Department of Applied Molecular Chemistry, College of Industrial Technology, Advanced Research Institute for the Sciences and Humanities, Nihon University, Chiba 275-8575.
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109
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Latent regeneration abilities persist following recent evolutionary loss in asexual annelids. Proc Natl Acad Sci U S A 2009; 107:1464-9. [PMID: 19966282 DOI: 10.1073/pnas.0907931107] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Regeneration abilities have been repeatedly lost in many animal phyla. However, because regeneration research has focused almost exclusively on highly regenerative taxa or on comparisons between regenerating and nonregenerating taxa that are deeply diverged, virtually nothing is known about how regeneration loss occurs. Here, we show that, following a recent evolutionary loss of regeneration, regenerative abilities can remain latent and still be elicited. Using comparative regeneration experiments and a molecular phylogeny, we show that ancestral head regeneration abilities have been lost three times among naidine annelids, a group of small aquatic worms that typically reproduce asexually by fission. In all three lineages incapable of head regeneration, worms consistently seal the wound but fail to progress to the first stage of tissue replacement. However, despite this coarse-level convergence in regeneration loss, further investigation of two of these lineages reveals marked differences in how much of the regeneration machinery has been abolished. Most notably, in a species representing one of these two lineages, but not in a representative of the other, amputation within a narrow proliferative region that forms during fission can still elicit regeneration of an essentially normal head. Thus, the presence at the wound site of elements characteristic of actively growing tissues, such as activated stem cells or growth factors, may permit blocks to regeneration to be circumvented, allowing latent regeneration abilities to be manifested.
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110
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Kawamura K, Sunanaga T. Hemoblasts in colonial tunicates: Are they stem cells or tissue-restricted progenitor cells? Dev Growth Differ 2009; 52:69-76. [DOI: 10.1111/j.1440-169x.2009.01142.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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111
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Brown FD, Tiozzo S, Roux MM, Ishizuka K, Swalla BJ, De Tomaso AW. Early lineage specification of long-lived germline precursors in the colonial ascidian Botryllus schlosseri. Development 2009; 136:3485-94. [PMID: 19783737 PMCID: PMC2752397 DOI: 10.1242/dev.037754] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2009] [Indexed: 11/20/2022]
Abstract
In many taxa, germline precursors segregate from somatic lineages during embryonic development and are irreversibly committed to gametogenesis. However, in animals that can propagate asexually, germline precursors can originate in adults. Botryllus schlosseri is a colonial ascidian that grows by asexual reproduction, and on a weekly basis regenerates all somatic and germline tissues. Embryonic development in solitary ascidians is the classic example of determinative specification, and we are interested in both the origins and the persistence of stem cells responsible for asexual development in colonial ascidians. In this study, we characterized vasa as a putative marker of germline precursors. We found that maternally deposited vasa mRNA segregates early in development to a posterior lineage of cells, suggesting that germline formation is determinative in colonial ascidians. In adults, vasa expression was observed in the gonads, as well as in a population of mobile cells scattered throughout the open circulatory system, consistent with previous transplantation/reconstitution results. vasa expression was dynamic during asexual development in both fertile and infertile adults, and was also enriched in a population of stem cells. Germline precursors in juveniles could contribute to gamete formation immediately upon transplantation into fertile adults, thus vasa expression is correlated with the potential for gamete formation, which suggests that it is a marker for embryonically specified, long-lived germline progenitors. Transient vasa knockdown did not have obvious effects on germline or somatic development in adult colonies, although it did result in a profound heterochrony, suggesting that vasa might play a homeostatic role in asexual development.
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Affiliation(s)
- Federico D Brown
- Biology Department, Center for Developmental Biology, and Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98195, USA
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112
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Watanabe H, Hoang VT, Mättner R, Holstein TW. Immortality and the base of multicellular life: Lessons from cnidarian stem cells. Semin Cell Dev Biol 2009; 20:1114-25. [PMID: 19761866 DOI: 10.1016/j.semcdb.2009.09.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Revised: 09/08/2009] [Accepted: 09/09/2009] [Indexed: 02/01/2023]
Abstract
Cnidarians are phylogenetically basal members of the animal kingdom (>600 million years old). Together with plants they share some remarkable features that cannot be found in higher animals. Cnidarians and plants exhibit an almost unlimited regeneration capacity and immortality. Immortality can be ascribed to the asexual mode of reproduction that requires cells with an unlimited self-renewal capacity. We propose that the basic properties of animal stem cells are tightly linked to this archaic mode of reproduction. The cnidarian stem cells can give rise to a number of differentiated cell types including neuronal and germ cells. The genomes of Hydra and Nematostella, representatives of two major cnidarian classes indicate a surprising complexity of both genomes, which is in the range of vertebrates. Recent work indicates that highly conserved signalling pathways control Hydra stem cell differentiation. Furthermore, the availability of genomic resources and novel technologies provide approaches to analyse these cells in vivo. Studies of stem cells in cnidarians will therefore open important insights into the basic mechanisms of stem cell biology. Their critical phylogenetic position at the base of the metazoan branch in the tree of life makes them an important link in unravelling the common mechanisms of stem cell biology between animals and plants.
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Affiliation(s)
- Hiroshi Watanabe
- Heidelberg University, Institute of Zoology, Department of Molecular Evolution and Genomics, Im Neuenheimer Feld 230, 69120 Heidelberg, Germany
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113
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Abstract
Vasa, a DEAD box helicase, is a germline marker that may also function in multipotent cells. In the embryo of the sea urchin Strongylocentrotus purpuratus, Vasa protein is posttranscriptionally enriched in the small micromere lineage, which results from two asymmetric cleavage divisions early in development. The cells of this lineage are subsequently set aside during embryogenesis for use in constructing the adult rudiment. Although this mode of indirect development is prevalent among echinoderms, early asymmetric cleavage divisions are a derived feature in this phylum. The goal of this study is to explore how vasa is regulated in key members of the phylum with respect to the evolution of the micromere and small micromere lineages. We find that although striking similarities exist between the vasa mRNA expression patterns of several sea urchins and sea stars, the time frame of enriched protein expression differs significantly. These results suggest that a conserved mechanism of vasa regulation was shifted earlier in sea urchin embryogenesis with the derivation of micromeres. These data also shed light on the phenotype of a sea urchin embryo upon removal of the Vasa-positive micromeres, which appears to revert to a basal mechanism used by extant sea stars and pencil urchins to regulate Vasa protein accumulation. Furthermore, in all echinoderms tested here, Vasa protein and/or message is enriched in the larval coelomic pouches, the site of adult rudiment formation, thus suggesting a conserved role for vasa in undifferentiated multipotent cells set aside during embryogenesis for use in juvenile development.
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Affiliation(s)
- Celina E. Juliano
- Department of Molecular and Cell Biology and Biochemistry, Brown University, 185 Meeting Street, Providence, RI 02912, USA
| | - Gary M. Wessel
- Department of Molecular and Cell Biology and Biochemistry, Brown University, 185 Meeting Street, Providence, RI 02912, USA
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114
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Tanaka ED, Hartfelder K. Sequence and expression pattern of the germ line marker vasa in honey bees and stingless bees. Genet Mol Biol 2009; 32:582-93. [PMID: 21637523 PMCID: PMC3036037 DOI: 10.1590/s1415-47572009005000043] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Accepted: 04/24/2009] [Indexed: 12/20/2022] Open
Abstract
Queens and workers of social insects differ in the rates of egg laying. Using genomic information we determined the sequence of vasa, a highly conserved gene specific to the germ line of metazoans, for the honey bee and four stingless bees. The vasa sequence of social bees differed from that of other insects in two motifs. By RT-PCR we confirmed the germ line specificity of Amvasa expression in honey bees. In situ hybridization on ovarioles showed that Amvasa is expressed throughout the germarium, except for the transition zone beneath the terminal filament. A diffuse vasa signal was also seen in terminal filaments suggesting the presence of germ line cells. Oocytes showed elevated levels of Amvasa transcripts in the lower germarium and after follicles became segregated. In previtellogenic follicles, Amvasa transcription was detected in the trophocytes, which appear to supply its mRNA to the growing oocyte. A similar picture was obtained for ovarioles of the stingless bee Melipona quadrifasciata, except that Amvasa expression was higher in the oocytes of previtellogenic follicles. The social bees differ in this respect from Drosophila, the model system for insect oogenesis, suggesting that changes in the sequence and expression pattern of vasa may have occurred during social evolution.
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Affiliation(s)
- Erica Donato Tanaka
- Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP Brazil
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115
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De Mulder K, Pfister D, Kuales G, Egger B, Salvenmoser W, Willems M, Steger J, Fauster K, Micura R, Borgonie G, Ladurner P. Stem cells are differentially regulated during development, regeneration and homeostasis in flatworms. Dev Biol 2009; 334:198-212. [PMID: 19631639 DOI: 10.1016/j.ydbio.2009.07.019] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2009] [Revised: 07/15/2009] [Accepted: 07/15/2009] [Indexed: 01/18/2023]
Abstract
The flatworm stem cell system is exceptional within the animal kingdom, as totipotent stem cells (neoblasts) are the only dividing cells within the organism. In contrast to most organisms, piwi-like gene expression in flatworms is extended from germ cells to somatic stem cells. We describe the isolation and characterization of the piwi homologue macpiwi in the flatworm Macrostomum lignano. We use in situ hybridization, antibody staining and RNA interference to study macpiwi expression and function in adults, during postembryonic development, regeneration and upon starvation. We found novelties regarding piwi function and observed differences to current piwi functions in flatworms. First, macpiwi was essential for the maintenance of somatic stem cells in adult animals. A knock-down of macpiwi led to a complete elimination of stem cells and death of the animals. Second, the regulation of stem cells was different in adults and regenerates compared to postembryonic development. Third, sexual reproduction of M. lignano allowed to follow germline formation during postembryonic development, regeneration, and starvation. Fourth, piwi expression in hatchlings further supports an embryonic formation of the germline in M. lignano. Our findings address new questions in flatworm stem cell research and provide a basis for comparison with higher organisms.
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Affiliation(s)
- Katrien De Mulder
- University of Innsbruck, Institute of Zoology and CMBI, Technikerstrasse 25, A-6020 Innsbruck, Austria
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116
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Abstract
Hydra are remarkable because they are immortal. Much of immortality can be ascribed to the asexual mode of reproduction by budding, which requires a tissue consisting of stem cells with continuous self-renewal capacity. Emerging novel technologies and the availability of genomic resources enable for the first time to analyse these cells in vivo. Stem cell differentiation in Hydra is governed through the coordinated actions of conserved signaling pathways. Studies of stem cells in Hydra, therefore, promise critical insights of general relevance into stem cell biology including cellular senescence, lineage programming and reprogramming, the role of extrinsic signals in fate determination and tissue homeostasis, and the evolutionary origin of these cells. With these new facts as a backdrop, this review traces the history of studying stem cells in Hydra and offers a view of what the future may hold.
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Affiliation(s)
- Thomas C G Bosch
- Zoological Institute, Christian-Albrechts-University Kiel, Kiel, Germany.
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117
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Rosner A, Moiseeva E, Rinkevich Y, Lapidot Z, Rinkevich B. Vasa and the germ line lineage in a colonial urochordate. Dev Biol 2009; 331:113-28. [PMID: 19406116 DOI: 10.1016/j.ydbio.2009.04.025] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Revised: 03/22/2009] [Accepted: 04/22/2009] [Indexed: 01/13/2023]
Abstract
Germ cell sequestering in Animalia is enlightened by either, launching true germ line along epigenetic or preformistic modes of development, or by somatic embryogenesis, where no true germ line is set aside. The research on germ line-somatic tissue segregation is of special relevancy to colonial organisms like botryllid ascidians that reconstruct, on a weekly basis, completely new sets of male and female gonads in newly formed somatic tissues. By sequencing and evaluating expression patterns of BS-Vasa, the Botryllus schlosseri orthologue of Vasa, in sexually mature and asexual colonies during blastogenesis, we have demonstrated that the BS-Vasa mRNA and protein are not expressed exclusively in germ cell lineages, but appeared in cells repeatedly emerging de novo in the colony, independently of its sexual state. In addition, we recorded an immediate Vasa response to cellular stress (UV irradiation) indicating additional functions to its germ line assignments. To confirm germ lineage exclusivity, we examined the expression of three more stem cell markers (BS-Pl10, Bl-piwi and Oct4). Vasa co-expression with Pl10 and Oct4 was detected in germ line derivatives and with Bl-piwi in somatic tissues. Presumptive primordial germ cells (PGC-like cells), that are Vasa(+)/Pl10(+)/Oct4(+) and 6-12 microm in diameter, were first detected in wrapped-tail embryos, in oozooids, in sexual/asexual colonies, within a newly identified PGC niche termed as 'budlet niche', and in circulating blood borne cells, indicating epigenetic embryogenesis. Alternatively, BS-Vasa co-expression with piwi orthologue, an omnipresent bona fide stemness flag, in non germ line cell populations, may indicate germ cell neogenesis (somatic embryogenesis) in B. schlosseri. Both alternatives are not necessarily mutually exclusive.
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Affiliation(s)
- Amalia Rosner
- National Institute of Oceanography, Tel Shikmona, Haifa, Israel.
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118
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Özhan-Kizil G, Havemann J, Gerberding M. Germ cells in the crustacean Parhyale hawaiensis depend on Vasa protein for their maintenance but not for their formation. Dev Biol 2009; 327:230-9. [DOI: 10.1016/j.ydbio.2008.10.028] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Revised: 10/20/2008] [Accepted: 10/22/2008] [Indexed: 12/21/2022]
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119
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Dill KK, Seaver EC. Vasa and nanos are coexpressed in somatic and germ line tissue from early embryonic cleavage stages through adulthood in the polychaete Capitella sp. I. Dev Genes Evol 2008; 218:453-63. [DOI: 10.1007/s00427-008-0236-x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2008] [Accepted: 06/16/2008] [Indexed: 11/28/2022]
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120
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Simionato E, Kerner P, Dray N, Le Gouar M, Ledent V, Arendt D, Vervoort M. atonal- and achaete-scute-related genes in the annelid Platynereis dumerilii: insights into the evolution of neural basic-Helix-Loop-Helix genes. BMC Evol Biol 2008; 8:170. [PMID: 18541016 PMCID: PMC2435551 DOI: 10.1186/1471-2148-8-170] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Accepted: 06/09/2008] [Indexed: 11/21/2022] Open
Abstract
Background Functional studies in model organisms, such as vertebrates and Drosophila, have shown that basic Helix-loop-Helix (bHLH) proteins have important roles in different steps of neurogenesis, from the acquisition of neural fate to the differentiation into specific neural cell types. However, these studies highlighted many differences in the expression and function of orthologous bHLH proteins during neural development between vertebrates and Drosophila. To understand how the functions of neural bHLH genes have evolved among bilaterians, we have performed a detailed study of bHLH genes during nervous system development in the polychaete annelid, Platynereis dumerilii, an organism which is evolutionary distant from both Drosophila and vertebrates. Results We have studied Platynereis orthologs of the most important vertebrate neural bHLH genes, i.e. achaete-scute, neurogenin, atonal, olig, and NeuroD genes, the latter two being genes absent of the Drosophila genome. We observed that all these genes have specific expression patterns during nervous system formation in Platynereis. Our data suggest that in Platynereis, like in vertebrates but unlike Drosophila, (i) neurogenin is the main proneural gene for the formation of the trunk central nervous system, (ii) achaete-scute and olig genes are involved in neural subtype specification in the central nervous system, in particular in the specification of the serotonergic phenotype. In addition, we found that the Platynereis NeuroD gene has a broad and early neuroectodermal expression, which is completely different from the neuronal expression of vertebrate NeuroD genes. Conclusion Our analysis suggests that the Platynereis bHLH genes have both proneural and neuronal specification functions, in a way more akin to the vertebrate situation than to that of Drosophila. We conclude that these features are ancestral to bilaterians and have been conserved in the vertebrates and annelids lineages, but have diverged in the evolutionary lineage leading to Drosophila.
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Affiliation(s)
- Elena Simionato
- Evolution et Développement des métazoaires, Centre de Génétique Moléculaire-UPR 2167 CNRS, 1, av. de terrasse, 91198 Gif-sur-Yvette, France.
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Rebscher N, Volk C, Teo R, Plickert G. The germ plasm component vasa allows tracing of the interstitial stem cells in the cnidarianHydractinia echinata. Dev Dyn 2008; 237:1736-45. [DOI: 10.1002/dvdy.21562] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Hejnol A, Martindale MQ. Acoel development supports a simple planula-like urbilaterian. Philos Trans R Soc Lond B Biol Sci 2008; 363:1493-501. [PMID: 18192185 PMCID: PMC2614228 DOI: 10.1098/rstb.2007.2239] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Molecular approaches to the study of development and evolution have had profound effects on our understanding of the nature of the evolutionary process. Developmental biologists became intoxicated with fanciful notions of reconstructing genetic pathways of morphogenesis while evolutionary biologists were sobered by the fallacy of reconstructing organismal relationships along increasing grades of morphological complexity. Increased taxon sampling and improvements in analytical techniques are providing a new approach and are forcing biologists to move past historical biases to allow more accurate mapping of morphological and developmental characters through evolutionary time. Here, we discuss the possible developmental and morphological features of the 'urbilaterian', the triploblastic animal with anterior-posterior and dorsoventral axes and predecessor of the protostome-deuterostome ancestor. We argue that this animal, with features resembling acoelomorph flatworms, was far simpler morphologically than the protostome-deuterostome ancestor despite possessing a nearly complete eubilaterian genome. We show that the deployment of some genes expected to pattern the protostome-deuterostome ancestor is not deployed in acoels in the predicted manner and thus might have been co-opted after the evolution of the urbilaterian. We also identify the developmental changes related to gastrulation that gave rise to the urbilaterian from a simpler cnidarian-like ancestor.
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Affiliation(s)
| | - Mark Q Martindale
- Kewalo Marine Laboratory, Pacific Bioscience Research Center, University of Hawaii41 Ahui Street, Honolulu, HI 96813, USA
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Flatworm stem cells and the germ line: developmental and evolutionary implications of macvasa expression in Macrostomum lignano. Dev Biol 2008; 319:146-59. [PMID: 18405892 DOI: 10.1016/j.ydbio.2008.02.045] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2007] [Revised: 02/19/2008] [Accepted: 02/20/2008] [Indexed: 11/22/2022]
Abstract
We have isolated and identified the vasa homologue macvasa, expressed in testes, ovaries, eggs and somatic stem cells of the flatworm Macrostomum lignano. Molecular tools such as in situ hybridization and RNA interference were developed for M. lignano to study gene expression and function. Macvasa expression was followed during postembryonic development, regeneration and in starvation experiments. We were able to follow gonad formation in juveniles and the reformation of gonads from stem cells after amputation by in situ hybridization and a specific Macvasa antibody. Expression of macvasa in the germ cells was highly affected by feeding conditions and correlated with the decrease and regrowth of the gonads. RNA interference showed specific down-regulation of macvasa mRNA and protein. The absence of Macvasa did not influence gonad formation and stem cell proliferation. Our results corroborate the exclusive nature of the flatworm stem cell system but challenge the concept of a solely postembryonic specification of the germ line in Platyhelminthes. We address the transition of somatic stem cells to germ cells and speculate on Macrostomum as a system to unravel the mechanisms of preformation or epigenesis in the evolution of germ line specification from somatic stem cells.
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Nanos Is Required in Somatic Blast Cell Lineages in the Posterior of a Mollusk Embryo. Curr Biol 2008; 18:331-6. [DOI: 10.1016/j.cub.2008.01.055] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 01/17/2008] [Accepted: 01/21/2008] [Indexed: 11/20/2022]
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125
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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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Swartz SZ, Chan XY, Lambert JD. Localization of Vasa mRNA during early cleavage of the snail Ilyanassa. Dev Genes Evol 2008; 218:107-13. [DOI: 10.1007/s00427-008-0203-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2007] [Accepted: 12/28/2007] [Indexed: 10/22/2022]
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127
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Exploration of embryonic origins of germline stem cells and neoblasts in Enchytraeus japonensis (Oligochaeta, Annelida). Gene Expr Patterns 2008; 8:227-36. [PMID: 18272431 DOI: 10.1016/j.gep.2007.12.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2007] [Revised: 12/19/2007] [Accepted: 12/21/2007] [Indexed: 11/21/2022]
Abstract
An oligochaete annelid species, Enchytraeus japonensis, reproduces not only asexually but also sexually. It has been reported that putative mesodermal stem cells called neoblasts contribute to blastema formation and that Ej-piwi(+) germline stem cells participate in gonadal regeneration. To delineate the origin and formation of both of these stem cells, we isolated two vasa-related genes (Ej-vlg1 and Ej-vlg2) and analyzed the expression of each along with that of germline marker gene Ej-piwi. In adults, Ej-vlg1 and Ej-vlg2 were expressed in Ej-piwi(+) germline stem cells and germ cells in gonads, while only Ej-vlg2 mRNAs were detected in neoblasts. Expression analysis during embryogenesis indicated that clusters of Ej-vlg1(+)/Ej-vlg2(+) cells, located at the posterior ventral region in late embryos, became Ej-vlg1(+)/Ej-vlg2(+)/Ej-piwi(+) germline stem cells just after embryogenesis. On the other hand, Ej-vlg2 single positive cells with morphological characteristics of neoblasts became detectable much later after embryogenesis at the ventral position on each septum where adult neoblasts exist, although these early detected cells were much smaller in size than adult neoblasts. The present results suggest that (1) germline stem cells specified just after embryogenesis are derived from Ej-vlg1(+)/Ej-vlg2(+) cells which appear at the posterior ventral region in late embryos, and that (2) neoblasts appear much later in development.
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Denker E, Manuel M, Leclère L, Le Guyader H, Rabet N. Ordered progression of nematogenesis from stem cells through differentiation stages in the tentacle bulb of Clytia hemisphaerica (Hydrozoa, Cnidaria). Dev Biol 2007; 315:99-113. [PMID: 18234172 DOI: 10.1016/j.ydbio.2007.12.023] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Revised: 12/11/2007] [Accepted: 12/11/2007] [Indexed: 12/01/2022]
Abstract
Nematogenesis, the production of stinging cells (nematocytes) in Cnidaria, can be considered as a model neurogenic process. Most molecular data concern the freshwater polyp Hydra, in which nematocyte production is scattered throughout the body column ectoderm, the mature cells then migrating to the tentacles. We have characterized tentacular nematogenesis in the Clytia hemisphaerica hydromedusa and found it to be confined to the ectoderm of the tentacle bulb, a specialized swelling at the tentacle base. Analysis by a variety of light and electron microscope techniques revealed that while cellular aspects of nematogenesis are similar to Hydra, the spatio-temporal characteristics are markedly more ordered. The tentacle bulb nematogenic ectoderm (TBE) was found to be polarized, with a clear progression of successive nematoblast stages from a proximal zone (comprising a majority of undifferentiated cells) to the distal end where the tentacle starts. Pulse-chase labelling experiments demonstrated a continuous displacement of differentiating nematoblasts towards the tentacle tip, and that nematogenesis proceeds more rapidly in Clytia than in Hydra. Compact expression domains of orthologues of known nematogenesis-associated genes (Piwi, dickkopf-3, minicollagens and NOWA) were correspondingly staggered along the TBE. These distinct characteristics make the Clytia TBE a promising experimental system for understanding the mechanisms regulating nematogenesis.
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Affiliation(s)
- Elsa Denker
- Université Pierre et Marie Curie-Paris 6, UMR 7138 CNRS UPMC MNHN IRD, Case 05, 7 quai St. Bernard, 75005 Paris, France.
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Lankenau DH. The Legacy of the Germ Line – Maintaining Sex and Life in Metazoans: Cognitive Roots of the Concept of Hierarchical Selection. RECOMBINATION AND MEIOSIS 2007. [DOI: 10.1007/7050_2007_030] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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131
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Oyama A, Shimizu T. Transient occurrence of vasa-expressing cells in nongenital segments during embryonic development in the oligochaete annelid Tubifex tubifex. Dev Genes Evol 2007; 217:675-90. [PMID: 17851685 DOI: 10.1007/s00427-007-0180-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Accepted: 08/22/2007] [Indexed: 11/30/2022]
Abstract
The primordial germ cells (PGCs) in the oligochaete annelid Tubifex tubifex are mesodermal in origin and are located in the two midbody segments X and XI in which the testis and the ovary are formed, respectively. To identify a molecular marker for the Tubifex PGCs, we isolated the Tubifex homologue (Ttu-vas) of the Drosophila vasa gene. Using whole-mount in situ hybridization, we examined the spatial expression patterns of Ttu-vas from one-cell stage through juvenile stage. Ttu-vas messenger ribonucleic acid (RNA) is present as a maternal transcript distributed broadly throughout the early stages. Ttu-vas is expressed in all of the early cleavage blastomeres, in which Ttu-vas RNA associates with mitotic spindles and pole plasms. Expression of Ttu-vas gradually becomes restricted, first to teloblasts, then to their blast cell progeny comprising the germ bands (GBs), and finally to a set of large ventral cells (termed VE cells) in a variable set of midbody segments including the genital segments (X and XI). At the end of embryogenesis, VE cells are confined to genital segments where they are presumably germline precursors in the juvenile. Staining with a cross-reacting anti-Vasa antibody suggested that VE cells express Ttu-vas protein to the same extent irrespective of their positions along the anteroposterior axis. A set of cell ablation experiments suggested that VE cells are derived from the mesodermal teloblast lineage and that the emergence of VE cells takes place independently of the presence of the ectodermal GBs that normally overlay the mesoderm. These results suggest that T. tubifex generates supernumerary presumptive PGCs during embryogenesis whose number is variable among embryos.
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Affiliation(s)
- Atsuko Oyama
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, 060-0810, Japan
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