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Henry JJ, Perry KJ, Fukui L, Alvi N. Differential localization of mRNAs during early development in the mollusc, Crepidula fornicata. Integr Comp Biol 2010; 50:720-33. [PMID: 21558235 DOI: 10.1093/icb/icq088] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Certain mRNAs have been shown to be segregated in different cells in various metazoan embryos. These events represent aspects of autonomous mechanisms that establish particular embryonic cell fates and axial properties associated with asymmetric cell divisions. The spiralian lophotrochozoans (which include molluscs, annelids, nemerteans, gnathostomulids, dicyemid mesozoans, entoprocts, and platyhelminthes) exhibit a highly conserved pattern of early development that involves stereotypical, asymmetric cell divisions (termed "spiral cleavage"). Recently, it was demonstrated that various mRNAs are dynamically localized to the centrosomes in specific cells during early development in the gastropod mollusc, Ilyanassa obsoleta. During subsequent cell divisions, these messages become segregated in particular daughter cells, and it has been proposed that these events distinguish the developmental potential of these cells within the early embryo of I. obsoleta. The molecular mechanisms underlying these events, however, are still unknown. Here we show for the first time in another spiralian lophotrochozoan (the gastropod Crepidula fornicata) that similar patterns of mRNA localization take place during early development. To characterize the transcriptome of early development, and identify candidate genes for the expression analyses, high-throughput sequencing was carried out, via GS FLX Titanium 454 pyrosequencing. The annotated sequences have been made available as a resource for the scientific community (www.life.illinoi.edu/henry/crepidula_databases.html). Presumably, specific proteins associated with centrosomes may be important for these mRNA localization events. In silico sequence comparisons with known centriolar/centrosomal, ciliary/basal body proteomes shows that a large number of those proteins are represented in the collection of expressed sequence tags of C. fornicata annotated in this study. These data should be useful for future studies of the role of specific mRNAs in controlling cell fate and axial specification in the spiralian Lophotrochozoa, and for dissecting the underlying molecular mechanisms that accomplish these events.
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Affiliation(s)
- Jonathan J Henry
- Department of Cell and Developmental Biology, University of Illinois, 601 S. Goodwin Ave., Urbana IL 61801, USA.
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103
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Gharbiah M, Cooley J, Leise EM, Nakamoto A, Rabinowitz JS, Lambert JD, Nagy LM. The snail Ilyanassa: a reemerging model for studies in development. Cold Spring Harb Protoc 2010; 2009:pdb.emo120. [PMID: 20147120 DOI: 10.1101/pdb.emo120] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Ilyanassa obsoleta is a marine gastropod that is a long-standing and very useful model for studies of embryonic development. It is especially important as a model for the spiralian development program, a distinctive mode of early development shared by a large group of animal phyla, but poorly understood. Ilyanassa adults are readily obtainable and easy to keep in the laboratory, and they produce large numbers of embryos throughout most of the year. The embryos are amenable to classic embryological manipulation techniques as well as a growing number of molecular approaches. In this article, we present an overview of aspects of its biology and use as a model organism.
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Affiliation(s)
- Maey Gharbiah
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721, USA
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104
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Abstract
At least five animal phyla exhibit spiralian development, which is characterized by striking similarities in the geometry of the early cleavage pattern and the fate map of the blastula, along with similarities in larval morphology. Recent advances in reconstructing the phylogeny of spiralians and their relatives suggest that the common ancestor of a large clade of protostome phyla known as the Lophotrochozoa had spiralian development. In this minireview, I describe characteristics of spiralian development and some recent insights into its mechanisms and evolution.
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Affiliation(s)
- J David Lambert
- Department of Biology, University of Rochester, Rochester, NY 14607, USA.
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105
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Tkemaladze J, Chichinadze K. Centriole, Differentiation, and Senescence. Rejuvenation Res 2010; 13:339-42. [DOI: 10.1089/rej.2009.0904] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- J. Tkemaladze
- A. Natishvili Institute of Morphology, Tbilisi, Georgia
| | - K. Chichinadze
- I. Beritashvili Institute of Physiology, Tbilisi, Georgia
- I. Javakhishvili Tbilisi State University, Tbilisi, Georgia
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Asymmetric centrosome inheritance maintains neural progenitors in the neocortex. Nature 2009; 461:947-55. [PMID: 19829375 PMCID: PMC2764320 DOI: 10.1038/nature08435] [Citation(s) in RCA: 355] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Accepted: 08/18/2009] [Indexed: 01/12/2023]
Abstract
Asymmetric divisions of radial glia progenitors produce self-renewing radial glia and differentiating cells simultaneously in the ventricular zone (VZ) of the developing neocortex. Whereas differentiating cells leave the VZ to constitute the future neocortex, renewing radial glia progenitors stay in the VZ for subsequent divisions. The differential behaviour of progenitors and their differentiating progeny is essential for neocortical development; however, the mechanisms that ensure these behavioural differences are unclear. Here we show that asymmetric centrosome inheritance regulates the differential behaviour of renewing progenitors and their differentiating progeny in the embryonic mouse neocortex. Centrosome duplication in dividing radial glia progenitors generates a pair of centrosomes with differently aged mother centrioles. During peak phases of neurogenesis, the centrosome retaining the old mother centriole stays in the VZ and is preferentially inherited by radial glia progenitors, whereas the centrosome containing the new mother centriole mostly leaves the VZ and is largely associated with differentiating cells. Removal of ninein, a mature centriole-specific protein, disrupts the asymmetric segregation and inheritance of the centrosome and causes premature depletion of progenitors from the VZ. These results indicate that preferential inheritance of the centrosome with the mature older mother centriole is required for maintaining radial glia progenitors in the developing mammalian neocortex.
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108
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Abstract
Subcellular localization of messenger RNAs (mRNAs) can give precise control over where protein products are synthesized and operate. However, just 10 years ago many in the broader cell biology community would have considered this a specialized mechanism restricted to a very small fraction of transcripts. Since then, it has become clear that subcellular targeting of mRNAs is prevalent, and there is mounting evidence for central roles for this process in many cellular events. Here, we review current knowledge of the mechanisms and functions of mRNA localization in animal cells.
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Affiliation(s)
- Christine E. Holt
- Department of Physiology, Development, and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Simon L. Bullock
- Cell Biology Division, Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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109
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A novel role for dpp in the shaping of bivalve shells revealed in a conserved molluscan developmental program. Dev Biol 2009; 329:152-66. [PMID: 19382296 DOI: 10.1016/j.ydbio.2009.01.021] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During the molluscan evolution leading to the bivalves, the single dorsal shell was doubled. To elucidate the molecular developmental basis underlying this prominent morphological transition, we described the cell cleavage and expression patterns of three genes, brachyury, engrailed, and dpp in the Japanese spiny oyster Saccostrea kegaki, and examined the function of dpp in this species. The cleavage pattern of the S. kegaki embryo was nearly the same as the previously described pattern of other bivalve species, suggesting that the pattern itself is highly important for the establishment or the maintenance of the bivalve body plan. The expression pattern of a brachyury homolog in S. kegaki (SkBra) was similar to the pattern in gastopods even at the single cell level despite the deep divergence of gastropods and bivalves. Engrailed and dpp were previously found to be expressed around the shell anlagen in gastropods. Like that of gastropods, an engrailed homolog in S. kegaki (SkEn) was found to be expressed around the shell anlagen. However, the dpp homologin S. kegaki (SkDpp) was expressed only in the cells along the dorsal midline. ZfBMP4 treatment experiments revealed the importance of dpp in establishing the characteristic shape of the bivalve shell anlagen.
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110
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Abstract
Asymmetric stem cell division is a mechanism widely employed by the cell to maintain tissue homeostasis, resulting in the production of one stem cell and one differentiating cell. However, asymmetric cell division is not limited to stem cells and is widely observed even in unicellular organisms as well as in cells that make up highly complex tissues. In asymmetric cell division, cells must organize their intracellular components along the axis of asymmetry (sometimes in the context of extracellular architecture). Recent studies have described cell asymmetry in many cell types and in many cases such asymmetry involves the centrosome (or spindle pole body in yeast) as the center of cytoskeleton organization. In this review, I summarize recent discoveries in cellular polarity that lead to an asymmetric outcome, with a focus on centrosome function.
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Affiliation(s)
- Yukiko M Yamashita
- Life Sciences Institute, Center for Stem Cell Biology, Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-2216, USA.
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111
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Gharbiah M, Cooley J, Leise EM, Nakamoto A, Rabinowitz JS, Lambert JD, Nagy LM. Fixation of Ilyanassa snail embryos and larvae. Cold Spring Harb Protoc 2009; 2009:pdb.prot5186. [PMID: 20147129 DOI: 10.1101/pdb.prot5186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The marine gastropod Ilyanassa obsoleta is a long-standing and very useful model for studies of embryonic development. It is an especially important model for spiralian development, and for studies of asymmetric cell division. The embryos are amenable to classic embryological manipulation techniques, as well as a growing number of molecular approaches. Ilyanassa is also an important model for studies of metamorphosis, the ecology of parasitism, the effects of environmental contaminants on morphology and sexual function, and comparative neurobiology. Ilyanassa embryos are particularly well suited for RNA and protein localization studies because of the relatively large cells and favorable properties for imaging. This protocol describes how to fix and store Ilyanassa embryos and larvae for use in whole-mount in situ hybridization and immunohistochemical studies.
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Affiliation(s)
- Maey Gharbiah
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721, USA
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112
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Graham AC, Kiss DL, Andrulis ED. Core exosome-independent roles for Rrp6 in cell cycle progression. Mol Biol Cell 2009; 20:2242-53. [PMID: 19225159 PMCID: PMC2669031 DOI: 10.1091/mbc.e08-08-0825] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Revised: 02/03/2009] [Accepted: 02/11/2009] [Indexed: 12/25/2022] Open
Abstract
Exosome complexes are 3' to 5' exoribonucleases composed of subunits that are critical for numerous distinct RNA metabolic (ribonucleometabolic) pathways. Several studies have implicated the exosome subunits Rrp6 and Dis3 in chromosome segregation and cell division but the functional relevance of these findings remains unclear. Here, we report that, in Drosophila melanogaster S2 tissue culture cells, dRrp6 is required for cell proliferation and error-free mitosis, but the core exosome subunit Rrp40 is not. Micorarray analysis of dRrp6-depleted cell reveals increased levels of cell cycle- and mitosis-related transcripts. Depletion of dRrp6 elicits a decrease in the frequency of mitotic cells and in the mitotic marker phospho-histone H3 (pH3), with a concomitant increase in defects in chromosome congression, separation, and segregation. Endogenous dRrp6 dynamically redistributes during mitosis, accumulating predominantly but not exclusively on the condensed chromosomes. In contrast, core subunits localize predominantly to MTs throughout cell division. Finally, dRrp6-depleted cells treated with microtubule poisons exhibit normal kinetochore recruitment of the spindle assembly checkpoint protein BubR1 without restoring pH3 levels, suggesting that these cells undergo premature chromosome condensation. Collectively, these data support the idea that dRrp6 has a core exosome-independent role in cell cycle and mitotic progression.
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Affiliation(s)
- Amy C Graham
- Department of Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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113
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Lederer CW, Santama N. Neural stem cells: mechanisms of fate specification and nuclear reprogramming in regenerative medicine. Biotechnol J 2009; 3:1521-38. [PMID: 19072908 DOI: 10.1002/biot.200800193] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Recently, intense interest in the potential use of neural stem cells (NSC) in the clinical therapy of brain disease and injury has resulted in rapid progress in research on the properties of NSC, their innate and directed differentiation potential and the induced reprogramming of differentiated somatic cells to revert to a pluripotent NSC-like state. The aim of this review is to give an overview of our current operational definitions of the NSC lineage, the growing understanding of extrinsic and intrinsic mechanisms, including heritable but reversible epigenetic chromatin modifications that regulate the maintenance and differentiation of NSC in vivo, and to emphasize ground-breaking efforts of cellular reprogramming with the view to generating patient-specific stem cells for cell replacement therapy. This is set against a summary of current practical procedures for the isolation, research and application of NSC, and of the state of the art in NSC-based regenerative medicine of the nervous system. Both provide the backdrop for the translation of recent findings into innovative clinical applications, with the hope of increasing the safety, efficiency and ethical acceptability of NSC-based therapies in the near future.
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114
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Song MH, Aravind L, Müller-Reichert T, O'Connell KF. The conserved protein SZY-20 opposes the Plk4-related kinase ZYG-1 to limit centrosome size. Dev Cell 2009; 15:901-12. [PMID: 19081077 DOI: 10.1016/j.devcel.2008.09.018] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Revised: 06/06/2008] [Accepted: 09/26/2008] [Indexed: 11/18/2022]
Abstract
Microtubules are organized by the centrosome, a dynamic organelle that exhibits changes in both size and number during the cell cycle. Here we show that SZY-20, a putative RNA-binding protein, plays a critical role in limiting centrosome size in C. elegans. SZY-20 localizes in part to centrosomes and in its absence centrosomes possess increased levels of centriolar and pericentriolar components including gamma-tubulin and the centriole duplication factors ZYG-1 and SPD-2. These enlarged centrosomes possess normal centrioles, nucleate more microtubules, and fail to properly direct a number of microtubule-dependent processes. Depletion of ZYG-1 restores normal centrosome size and function to szy-20 mutants, whereas loss of szy-20 suppresses the centrosome duplication defects in both zyg-1 and spd-2 mutants. Our results describe a pathway that determines centrosome size and implicate centriole duplication factors in this process.
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Affiliation(s)
- Mi Hye Song
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20894, USA.
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115
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116
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Yamashita YM. Regulation of asymmetric stem cell division: spindle orientation and the centrosome. Front Biosci (Landmark Ed) 2009; 14:3003-11. [PMID: 19273252 DOI: 10.2741/3430] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Asymmetric stem cell division, as a means of maintaining adequate numbers of stem cells, has attracted widespread attention from researchers in the stem cell biology field. Yet, the molecular and cellular mechanisms that govern asymmetric stem cell division remain poorly understood. Stem cells are not the only cell population that divides asymmetrically, and fortunately, great progress has been made in the understanding of asymmetric cell division during development, providing insight into strategies that stem cells may employ to divide asymmetrically. This review will summarize the importance of stem cell function and the role of asymmetric division in controlling stem cell behavior.
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Affiliation(s)
- Yukiko M Yamashita
- Life Sciences Institute, Center for Stem Cell Biology, University of Michigan, Ann Arbor, MI, USA.
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117
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Barral Y, Liakopoulos D. Role of spindle asymmetry in cellular dynamics. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 278:149-213. [PMID: 19815179 DOI: 10.1016/s1937-6448(09)78004-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The mitotic spindle is mostly perceived as a symmetric structure. However, in many cell divisions, the two poles of the spindle organize asters with different dynamics, associate with different biomolecules or subcellular domains, and perform different functions. In this chapter, we describe some of the most prominent examples of spindle asymmetry. These are encountered during cell-cycle progression in budding and fission yeast and during asymmetric cell divisions of stem cells and embryos. We analyze the molecular mechanisms that lead to generation of spindle asymmetry and discuss the importance of spindle-pole differentiation for the correct outcome of cell division.
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Affiliation(s)
- Yves Barral
- Institute of Biochemistry, ETH Hönggerberg, HPM, CH-8093 Zurich, Switzerland
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118
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Diverse RNA-binding proteins interact with functionally related sets of RNAs, suggesting an extensive regulatory system. PLoS Biol 2008; 6:e255. [PMID: 18959479 PMCID: PMC2573929 DOI: 10.1371/journal.pbio.0060255] [Citation(s) in RCA: 456] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Accepted: 09/11/2008] [Indexed: 11/19/2022] Open
Abstract
RNA-binding proteins (RBPs) have roles in the regulation of many post-transcriptional steps in gene expression, but relatively few RBPs have been systematically studied. We searched for the RNA targets of 40 proteins in the yeast Saccharomyces cerevisiae: a selective sample of the approximately 600 annotated and predicted RBPs, as well as several proteins not annotated as RBPs. At least 33 of these 40 proteins, including three of the four proteins that were not previously known or predicted to be RBPs, were reproducibly associated with specific sets of a few to several hundred RNAs. Remarkably, many of the RBPs we studied bound mRNAs whose protein products share identifiable functional or cytotopic features. We identified specific sequences or predicted structures significantly enriched in target mRNAs of 16 RBPs. These potential RNA-recognition elements were diverse in sequence, structure, and location: some were found predominantly in 3′-untranslated regions, others in 5′-untranslated regions, some in coding sequences, and many in two or more of these features. Although this study only examined a small fraction of the universe of yeast RBPs, 70% of the mRNA transcriptome had significant associations with at least one of these RBPs, and on average, each distinct yeast mRNA interacted with three of the RBPs, suggesting the potential for a rich, multidimensional network of regulation. These results strongly suggest that combinatorial binding of RBPs to specific recognition elements in mRNAs is a pervasive mechanism for multi-dimensional regulation of their post-transcriptional fate. Regulation of gene transcription has been extensively studied, but much less is known about how the fates of the resulting mRNA transcripts are regulated. We were intrigued by the fact that while most eukaryotic genomes encode hundreds of RNA-binding proteins (RBPs), the targets and regulatory roles of only a small fraction of these proteins have been characterized. In this study, we systematically identified the RNAs associated with a select sample of 40 of the approximately 600 predicted RBPs in the budding yeast, Saccharomyces cerevisiae. We found that most of these RBPs bound specific sets of mRNAs whose protein products share physiological themes or similar locations within the cell. For 16 of the 40 RBPs, we identified sequence motifs significantly enriched in their RNA targets that presumably mediate recognition of the target by the RBP. The intricate, overlapping patterns of mRNAs associated with RBPs suggest an extensive combinatorial system for post-transcriptional regulation, involving dozens or even hundreds of RBPs. The organization and molecular mechanisms involved in this regulatory system, including how RBP–mRNA interactions are integrated with signal transduction systems and how they affect the fates of their RNA targets, provide abundant opportunities for investigation and discovery. A systematic study of the RNA targets of 40 known or predicted RNA-binding proteins in yeast suggests that an extensive system of dozens or hundreds of specific RNA-binding proteins may act to regulate the post-transcriptional fate of most or all RNAs in the yeast cell.
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119
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Abstract
When and why did cell polarization arise? Recent work in bacteria and yeast suggests that polarization may have evolved to restrict senescence to one daughter during division by enabling the differential segregation of damaged material. In more complex organisms, polarity functions have diversified to permit the differential inheritance of centrosomes, RNAs, proteins, and membranes, which is essential for the generation of diverse cell types from stem cells and for morphogenesis.
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120
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Besse F, Ephrussi A. Translational control of localized mRNAs: restricting protein synthesis in space and time. Nat Rev Mol Cell Biol 2008; 9:971-80. [PMID: 19023284 DOI: 10.1038/nrm2548] [Citation(s) in RCA: 256] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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121
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Simonova OB, Vorontsova JE. Source of asymmetry in ontogeny: Early polarization of the germline cyst and oocyte in Drosophila. RUSS J GENET+ 2008. [DOI: 10.1134/s1022795408090019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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122
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Eliscovich C, Peset I, Vernos I, Méndez R. Spindle-localized CPE-mediated translation controls meiotic chromosome segregation. Nat Cell Biol 2008; 10:858-65. [PMID: 18536713 DOI: 10.1038/ncb1746] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Accepted: 04/22/2008] [Indexed: 12/31/2022]
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123
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Asymmetric mitosis: Unequal segregation of proteins destined for degradation. Proc Natl Acad Sci U S A 2008; 105:7732-7. [PMID: 18511557 DOI: 10.1073/pnas.0803027105] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Mitotic cell division ensures that two daughter somatic cells inherit identical genetic material. Previous work has shown that signaling by the Smad1 transcription factor is terminated by polyubiquitinylation and proteasomal degradation after essential phosphorylations by MAPK and glycogen synthase kinase 3 (GSK3). Here, we show that, unexpectedly, proteins specifically targeted for proteasomal degradation are inherited preferentially by one mitotic daughter during somatic cell division. Experiments with dividing human embryonic stem cells and other mammalian cultured cell lines demonstrated that in many supposedly equal mitoses the segregation of proteins destined for degradation (Smad1 phosphorylated by MAPK and GSK3, phospho-beta-catenin, and total polyubiquitinylated proteins) was asymmetric. Transport of pSmad1 targeted for degradation to the centrosome required functional microtubules. In vivo, an antibody specific for Mad phosphorylated by MAPK showed that this antigen was associated preferentially with one of the two centrosomes in Drosophila embryos at cellular blastoderm stage. We propose that this remarkable cellular property may be explained by the asymmetric inheritance of peripheral centrosomal proteins when centrioles separate and migrate to opposite poles of the cell, so that one mitotic daughter remains pristine. We conclude that many mitotic divisions are unequal, unlike what was previously thought.
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124
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Centrosomal RNA correlates with intron-poor nuclear genes in Spisula oocytes. Proc Natl Acad Sci U S A 2008; 105:6993-7. [PMID: 18458332 DOI: 10.1073/pnas.0802293105] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The evolutionary origin of centriole/kinetosomes, centrosomes, and other microtubule organizing centers (MTOCs), whether by direct filiation or symbiogenesis, has been controversial for >50 years. Centrioles, like mitochondria and chloroplasts, duplicate independently of the nucleus and constitute a heritable system independent of chromosomal DNA. Nucleic acids endogenous to the MTOC would support evolutionary origin by symbiogenesis. To date, most reports of centrosome-associated nucleic acids have used generalized reagents such as RNases and nucleic acid dyes. Here, from a library of RNAs extracted from isolated surf clam (Spisula solidissima) centrosomes, we describe a group of centrosome-associated transcripts representing a structurally unique intron-poor collection of nuclear genes skewed toward nucleic acid metabolism. Thus, we resolve the debate over the existence of centrosome-associated RNA (cnRNA). A subset of cnRNAs contain functional domains that are highly conserved across distant taxa, such as nucleotide polymerase motifs. In situ localization of cnRNA65, a molecule with an RNA polymerase domain, showed it is present in the intact oocyte nucleus (germinal vesicle). Its expression, therefore, precedes the appearance of gamma-tubulin-containing centrosomes. At this stage, the in situ signal resembles the nucleolinus, a poorly understood organelle proposed to play a role in spindle formation. After oocyte activation and germinal vesicle breakdown, cnRNA65 persists as a cytoplasmic patch within which gamma-tubulin-stained centrosomes can be seen. These observations provoke the question of whether cnRNAs and the nucleolinus serve as cytological progenitors of the centrosome and may support a symbiogenetic model for its evolution.
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125
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Lambert JD. Mesoderm in spiralians: the organizer and the 4d cell. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2008; 310:15-23. [PMID: 17577229 DOI: 10.1002/jez.b.21176] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The Spiralia is a clade of protostome invertebrate phyla that share a highly conserved mode of early development. Spiralian development is characterized by regularities in the arrangement of early cleavages, the fates of the cells that are produced by these divisions, and the development of the distinctive trochophore larva. Because of the strong conservation in early development, homologies can be identified between cells in divergent taxa. Some of the most striking examples of conservation in the spiralian embryo are in the cells that generate the mesoderm. The specification of the mesodermal precursors has been well characterized by embryological approaches, and recently the molecular mechanisms of mesoderm specification are starting to be elucidated. This review examines the development of mesoderm in spiralians in a comparative context, with particular focus on the relationship between the mesendodermal cell 4d and the embryonic organizer.
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Affiliation(s)
- J David Lambert
- Department of Biology, University of Rochester, Rochester, New York 14627, USA.
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126
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Blower MD, Feric E, Weis K, Heald R. Genome-wide analysis demonstrates conserved localization of messenger RNAs to mitotic microtubules. ACTA ACUST UNITED AC 2008; 179:1365-73. [PMID: 18166649 PMCID: PMC2373496 DOI: 10.1083/jcb.200705163] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
RNA localization is of critical importance in many fundamental cell biological and developmental processes by regulating the spatial control of gene expression. To investigate how spindle-localized RNAs might influence mitosis, we comprehensively surveyed all messenger RNAs (mRNAs) that bound to microtubules during metaphase in both Xenopus laevis egg extracts and mitotic human cell extracts. We identify conserved classes of mRNAs that are enriched on microtubules in both human and X. laevis. Active mitotic translation occurs on X. laevis meiotic spindles, and a subset of microtubule-bound mRNAs (MT-mRNAs) associate with polyribosomes. Although many MT-mRNAs associate with polyribosomes, we find that active translation is not required for mRNA localization to mitotic microtubules. Our results represent the first genome-wide survey of mRNAs localized to a specific cytoskeletal component and suggest that microtubule localization of specific mRNAs is likely to function in mitotic regulation and mRNA segregation during cell division.
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Affiliation(s)
- Michael D Blower
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
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127
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Lécuyer E, Yoshida H, Parthasarathy N, Alm C, Babak T, Cerovina T, Hughes TR, Tomancak P, Krause HM. Global analysis of mRNA localization reveals a prominent role in organizing cellular architecture and function. Cell 2008; 131:174-87. [PMID: 17923096 DOI: 10.1016/j.cell.2007.08.003] [Citation(s) in RCA: 708] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 07/30/2007] [Accepted: 08/02/2007] [Indexed: 01/01/2023]
Abstract
Although subcellular mRNA trafficking has been demonstrated as a mechanism to control protein distribution, it is generally believed that most protein localization occurs subsequent to translation. To address this point, we developed and employed a high-resolution fluorescent in situ hybridization procedure to comprehensively evaluate mRNA localization dynamics during early Drosophila embryogenesis. Surprisingly, of the 3370 genes analyzed, 71% of those expressed encode subcellularly localized mRNAs. Dozens of new and striking localization patterns were observed, implying an equivalent variety of localization mechanisms. Tight correlations between mRNA distribution and subsequent protein localization and function, indicate major roles for mRNA localization in nucleating localized cellular machineries. A searchable web resource documenting mRNA expression and localization dynamics has been established and will serve as an invaluable tool for dissecting localization mechanisms and for predicting gene functions and interactions.
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Affiliation(s)
- Eric Lécuyer
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Canada
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128
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Abstract
Asymmetric cell divisions are a crucial mode of cell fate specification in multicellular organisms, but their relative contribution to early embryonic patterning varies among taxa. In the embryo of the mollusc Ilyanassa, most of the early cell divisions are overtly asymmetric. During Ilyanassa early cleavage, mRNAs for several conserved developmental patterning genes localize to interphase centrosomes, and then during division they move to a portion of the cortex that will be inherited by one daughter cell. Here we report an unbiased survey of RNA localization in the Ilyanassa embryo, and examine the overall patterns of centrosomal localization during early development. We find that 3-4% of RNAs are specifically localized to centrosomes during early development, and the remainder are either ubiquitously distributed throughout the cytoplasm or weakly enriched on centrosomes compared with levels in the cytoplasm. We observe centrosomal localization of RNAs in all cells from zygote through the fifth cleavage cycle, and asymmetric RNA segregation in all divisions after the four-cell stage. Remarkably, each specifically localized message is found on centrosomes in a unique subset of cells during early cleavages, and most are found in unique sets of cells at the 24-cell stage. Several specifically localized RNAs are homologous to developmental regulatory proteins in other embryos. These results demonstrate that the mechanisms of localization and segregation are extraordinarily intricate in this system, and suggest that these events are involved in cell fate specification across all lineages in the early Ilyanassa embryo. We propose that greater reliance on segregation of determinants in early cleavage increases constraint on cleavage patterns in molluscs and other spiralian groups.
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Affiliation(s)
- Evan P Kingsley
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
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129
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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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130
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Yamashita YM, Fuller MT. Asymmetric centrosome behavior and the mechanisms of stem cell division. ACTA ACUST UNITED AC 2008; 180:261-6. [PMID: 18209101 PMCID: PMC2213579 DOI: 10.1083/jcb.200707083] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The ability of dividing cells to produce daughters with different fates is an important developmental mechanism conserved from bacteria to fungi, plants, and metazoan animals. Asymmetric outcomes of a cell division can be specified by two general mechanisms: asymmetric segregation of intrinsic fate determinants or asymmetric placement of daughter cells into microenvironments that provide extrinsic signals that direct cells to different states. For both, spindle orientation must be coordinated with the localization of intrinsic determinants or source of extrinsic signals to achieve the proper asymmetric outcome. Recent work on spindle orientation in Drosophila melanogaster male germline stem cells and neuroblasts has brought into sharp focus the key role of differential centrosome behavior in developmentally programmed asymmetric division (for reviews see Cabernard, C., and C.Q. Doe. 2007. Curr. Biol. 17:R465-R467; Gonzalez, C. 2007. Nat. Rev. Genet. 8:462-472). These findings provide new insights and suggest intriguing new models for how cells coordinate spindle orientation with their cellular microenvironment to regulate and direct cell fate decisions within tissues.
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Affiliation(s)
- Yukiko M Yamashita
- Center for Stem Cell Biology, Life Sciences Institute, Ann Arbor, MI 48109, USA.
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131
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Gonzales EE, van der Zee M, Dictus WJAG, van den Biggelaar J. Brefeldin A and monensin inhibit the D quadrant organizer in the polychaete annelids Arctonoe vittata and Serpula columbiana. Evol Dev 2007; 9:416-31. [PMID: 17845514 DOI: 10.1111/j.1525-142x.2007.00172.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The D quadrant organizer is a developmental signaling center that is localized to the vegetal D quadrant in different spiral-cleaving lophotrochozoan embryos and may be homologous to axial organizing regions in other metazoans. Patterning by this organizing center creates a secondary developmental axis and is required for the transition from spiral to bilateral cleavage and later establishment of the adult body plan. Organizer specification in equal-cleaving embryos is thought to involve inductive interactions between opposing animal and vegetal blastomeres. To date, experimental demonstration of this interaction has been limited to molluscs and nemerteans. Here, we examine three families of equal-cleaving polychaete annelids for evidence of animal-vegetal contact. We find that contact is present in the polynoid, Arctonoe vittata, but is absent in the serpulid, Serpula columbiana, and in the oweniid, Oweniia fusiformis. To interfere with cell signaling during the period predicted for organizer specification and patterning in A. vittata and S. columbiana, we use two general inhibitors of protein processing and secretion: Brefeldin A (BFA) and monensin. In A. vittata, we detail subsequent embryonic and larval adult development and show that treatment with either chemical results in radialization of the embryo and subsequent body plan. Radialized larvae differentiate many larval and adult structures despite the loss of bilateral symmetry but do so in either a radially symmetric or four-fold radially symmetric fashion. Our results suggest that the D quadrant organizer is functionally conserved in equal-cleaving polychaetes, but that details of its specification, induction, and patterning have diverged relative to other spiral-cleaving phyla.
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Affiliation(s)
- Eric E Gonzales
- Department of Developmental Biology, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
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132
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K’ergaard AV, Mamon LA. Hyperthermia of male Drosophila melanogaster meiocytes induces abnormalities in both paternal and maternal sex chromosome sets of the offspring. RUSS J GENET+ 2007. [DOI: 10.1134/s1022795407100092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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133
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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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134
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Schneider SQ, Bowerman B. beta-Catenin asymmetries after all animal/vegetal- oriented cell divisions in Platynereis dumerilii embryos mediate binary cell-fate specification. Dev Cell 2007; 13:73-86. [PMID: 17609111 DOI: 10.1016/j.devcel.2007.05.002] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2007] [Revised: 04/30/2007] [Accepted: 05/02/2007] [Indexed: 10/23/2022]
Abstract
In response to Wnt signaling during animal development, beta-catenin accumulates in nuclei to mediate the transcriptional activation of target genes. Here, we show that a highly conserved beta-catenin in the annelid Platynereis dumerilii exhibits a reiterative, nearly universal embryonic pattern of nuclear accumulation remarkably similar to that observed in the nematode Caenorhabditis elegans. Platynereis exhibits beta-catenin sister-cell asymmetries after all cell divisions that occur along the animal/vegetal axis beginning early in embryogenesis, but not after two transverse divisions that establish bilateral symmetry in the trunk. Moreover, ectopic activation of nuclear beta-catenin accumulation in Platynereis causes animal-pole sister cells, which normally have low nuclear beta-catenin levels, to adopt the fate of their vegetal-pole sisters, which normally have high nuclear beta-catenin levels. The presence of reiterative and functionally important beta-catenin asymmetries in two distantly related animal phyla suggests an ancient metazoan origin of a beta-catenin-mediated binary cell-fate specification module.
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135
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Herpin A, Lelong C, Becker T, Favrel P, Cunningham C. A tolloid homologue from the Pacific oyster Crassostrea gigas. Gene Expr Patterns 2007; 7:700-8. [PMID: 17433792 DOI: 10.1016/j.modgep.2007.03.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 02/23/2007] [Accepted: 03/01/2007] [Indexed: 10/23/2022]
Abstract
The genes governing mesoderm specification have been extensively studied in vertebrates, arthropods and nematodes. The latter two phyla belong to the Ecdysozoan clade but little is understood of the role that these genes might play in the development of the other major protostomal clade, the Lophotrochozoa. As part of a wider project to analyze the functions associated with transforming growth factor beta superfamily members in Lophotrochozoa, we have cloned a gene encoding a tolloid homologue from the bivalve mollusc Crassostrea gigas. Tolloid is a key developmental protein that regulates the activity of bone morphogenetic proteins (BMPs). We have determined the intron-exon structure of the gene encoding C. gigas tolloid and have compared it with those of homologous genes from both protostomes and deuterostomes. In order to analyze the functionality of oyster tolloid the zebrafish embryo has been employed as a reporter organism and we show that over-expression of this protein results in the ventralization of zebrafish embryos at 24h post fertilization. The expression of the C. gigas tolloid gene during embryonic and larval development as well as in adult tissues is also explored.
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Affiliation(s)
- Amaury Herpin
- Sars International Centre for Marine Molecular Biology, High Technology Centre, Bergen, Norway
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136
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Rujano MA, Bosveld F, Salomons FA, Dijk F, van Waarde MA, van der Want JJ, de Vos RA, Brunt ER, Sibon OC, Kampinga HH. Polarised asymmetric inheritance of accumulated protein damage in higher eukaryotes. PLoS Biol 2007; 4:e417. [PMID: 17147470 PMCID: PMC1750924 DOI: 10.1371/journal.pbio.0040417] [Citation(s) in RCA: 195] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2005] [Accepted: 10/02/2006] [Indexed: 12/29/2022] Open
Abstract
Disease-associated misfolded proteins or proteins damaged due to cellular stress are generally disposed via the cellular protein quality-control system. However, under saturating conditions, misfolded proteins will aggregate. In higher eukaryotes, these aggregates can be transported to accumulate in aggresomes at the microtubule organizing center. The fate of cells that contain aggresomes is currently unknown. Here we report that cells that have formed aggresomes can undergo normal mitosis. As a result, the aggregated proteins are asymmetrically distributed to one of the daughter cells, leaving the other daughter free of accumulated protein damage. Using both epithelial crypts of the small intestine of patients with a protein folding disease and Drosophila melanogaster neural precursor cells as models, we found that the inheritance of protein aggregates during mitosis occurs with a fixed polarity indicative of a mechanism to preserve the long-lived progeny. Human cells containing polyglutamine damage enter mitosis and complete cytokinesis. The association of aggresomes with one centrosome means that accumulated damage is asymmetrically inherited in only one daughter cell.
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Affiliation(s)
- María A Rujano
- Department of Cell Biology, Section of Radiation and Stress Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Floris Bosveld
- Department of Cell Biology, Section of Radiation and Stress Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Florian A Salomons
- Department of Cell Biology, Section of Radiation and Stress Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Freark Dijk
- Department of Cell Biology, Section of Electron Microscopy, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Maria A.W.H van Waarde
- Department of Cell Biology, Section of Radiation and Stress Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Johannes J.L van der Want
- Department of Cell Biology, Section of Electron Microscopy, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Rob A.I de Vos
- Pathology Laboratory Oost Nederland, Enschede, The Netherlands
| | - Ewout R Brunt
- Department of Neurology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Ody C.M Sibon
- Department of Cell Biology, Section of Radiation and Stress Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Harm H Kampinga
- Department of Cell Biology, Section of Radiation and Stress Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
- * To whom correspondence should be addressed. E-mail:
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137
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Davidson B. Movers and shakers: evolution and development of the mesoderm. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2007; 310:1-4. [DOI: 10.1002/jez.b.21199] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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138
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Fichelson P, Huynh JR. Asymmetric divisions of germline cells. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2007; 45:97-120. [PMID: 17585498 DOI: 10.1007/978-3-540-69161-7_5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
In most vertebrates and invertebrates, germ cells produce female and male gametes after one or several rounds of asymmetric cell division. Germline-specific features are used for the asymmetric segregation of fates, chromosomes and size during gametogenesis. In Drosophila females, for example, a germline-specific organelle called the fusome is used repeatedly to polarize the divisions of germline stem cells for their self-renewal, and during the divisions of cyst cells for the specification of the oocyte among a group of sister cells sharing a common cytoplasm. Later during oogenesis of most species, meiotic divisions produce a striking size asymmetry between a large oocyte and small polar bodies. The strategy used to create this asymmetry may involve the microtubules or the actin microfilaments or both, depending on the considered species. Despite this diversity and species-particularities, recent molecular data suggest that the PAR proteins, which control asymmetric cell division in a wide range of organisms and somatic cell types, could also play an important role at different steps of gametogenesis in many species. Here, we review the asymmetric features of germline cell division, from mitosis of germline stem cells to the extrusion of polar bodies after meiotic divisions.
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Affiliation(s)
- Pierre Fichelson
- Medical Research Council, LMCB, Cell biology unit, University College London, Gower street, WC1E 6BT London, UK
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139
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Arenas-Mena C. Sinistral equal-size spiral cleavage of the indirectly developing polychaeteHydroides elegans. Dev Dyn 2007; 236:1611-22. [PMID: 17471539 DOI: 10.1002/dvdy.21164] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Two major variants of the stereotypic spiral cleavage correlate with distinct developmental modes in polychaetes. Indirect development through a feeding trochophore larva correlates with development from four equal-sized blastomeres, whereas direct development correlates with unequal cleavage characterized by a large dorsal blastomere precursor maternally predetermined. The equal-size spiral cleavage of the indirectly developing serpulid Hydroides elegans has been reconstructed from serial sections of nuclei-stained embryos. The order of cell divisions has been determined from the 2-cell stage to the 80-cell stage, when gastrulation cell movements start to overlap with late spiral-cleavage divisions. In contrast to related species, the third cleavage in Hydroides elegans is invariably sinistral. The four quadrants remain indistinct until the 60-cell stage, when the small 2d22 and large 2d21 cells are generated. The developmental significance of the invariant spiral cleavage relates to the spatial distribution of gene functions that it partitions and their relation to blastomere fate commitments. The conservation and divergence of the cleavage pattern among spiralians is well suited to study the developmental control of the cell-cleavage machinery and its evolution.
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Affiliation(s)
- Cesar Arenas-Mena
- Department of Biology, San Diego State University, San Diego, California 92182-4614, USA.
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140
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Gonzales EE, van der Zee M, Dictus WJAG, van den Biggelaar J. Brefeldin A or monensin inhibits the 3D organizer in gastropod, polyplacophoran, and scaphopod molluscs. Dev Genes Evol 2006; 217:105-18. [PMID: 17120024 DOI: 10.1007/s00427-006-0118-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Accepted: 10/17/2006] [Indexed: 10/23/2022]
Abstract
In molluscs, the 3D vegetal blastomere acts as a developmental signaling center, or organizer, and is required to establish bilateral symmetry in the embryo. 3D is similar to organizing centers in other metazoans, but detailed comparisons are difficult, in part because its organizing function is poorly understood. To elucidate 3D function in a standardized fashion, we used monensin and brefeldin A (BFA) to rapidly and reversibly interfere with protein processing and secretion, thereby inhibiting the signaling interactions that underlie its specification and patterning. In the gastropods, Patella vulgata and Lymnaea stagnalis, the polyplacophoran, Mopalia muscosa, and the scaphopod, Antalis entalis, treatments initiated before the organizer-dependent onset of bilateral cleavage resulted in radialization of subsequent development. In radialized P. vulgata, L. stagnalis, and M. muscosa, organizer specification was blocked, and embryos failed to make the transition to bilateral cleavage. In all four species, the subsequent body plan was radially symmetric and was similarly organized about a novel aboral-oral axis. Our results demonstrate that brefeldin A (BFA) and monensin can be used to inhibit 3D's organizing function in a comparative fashion and that, at least in M. muscosa, the organizer-dependent developmental architecture of the embryo predicts subsequent patterns of morphogenetic movements in gastrulation and, ultimately, the layout of the adult body plan.
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Affiliation(s)
- Eric E Gonzales
- Department of Developmental Biology, University of Utrecht, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
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141
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Miller D, Ostermeier GC. Towards a better understanding of RNA carriage by ejaculate spermatozoa. Hum Reprod Update 2006; 12:757-67. [PMID: 16882702 DOI: 10.1093/humupd/dml037] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Research on spermatozoal RNA has made considerable progress since the original reports on its presence appeared in the late 1950s and early 1960s. Through the use of stringent procedures aimed at eliminating contamination artefacts, we now appreciate that a complex cohort of mRNAs persists in the ejaculate cell but that 80S (cytoplasmic) ribosomal complexes are not present in sufficient quantities to support cytoplasmic mRNA translation. Despite this, under certain conditions, at least some cytoplasmic mRNAs can apparently be translated de novo, possibly on mitochondrial polysomes. The detection of mRNA translation by mature spermatozoa essentially supports the earliest research reports on spermatozoal gene expression although the suggested relationship with protein turnover and capacitation is wholly unexpected. We also examine some alternative explanations and roles for RNA carriage, including the RNAs passive retention as a consequence of nuclear shutdown and a more active role in chromatin repackaging, genomic imprinting, gene silencing and post-fertilization requirements of essential paternal RNAs. The recent report of an RNA-mediated epigenetic alteration to phenotype that is likely to be sperm derived is of particular interest in this regard. We finally show that regardless of the biological role(s) of spermatozoal RNA, its utility in infertility studies, particularly when coupled with modern techniques in gene-expression analysis (e.g. microarrays), is obvious. As a wholly non-invasive proxy for the testis, this RNA offers considerable potential as a marker for fertility status and the genetic and environmental influences that could make all the difference between a fertile and an infertile phenotype.
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Affiliation(s)
- David Miller
- Reproduction and Early Development Research Group, Department of Obstetrics and Gynaecology, University of Leeds, Leeds General Infirmary, Belmont Grove, Leeds, UK.
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142
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Freeman G. Oocyte and egg organization in the patellogastropod Lottia and its bearing on axial specification during early embryogenesis. Dev Biol 2006; 295:141-55. [PMID: 16630607 DOI: 10.1016/j.ydbio.2006.03.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2005] [Revised: 02/28/2006] [Accepted: 03/13/2006] [Indexed: 10/24/2022]
Abstract
In the basal gastropod Lottia, the apical region of the oocyte is normally the site where the meiotic apparatus attaches and polar body formation occurs following fertilization. This site marks the animal-vegetal axis of the egg. A stereotypical cleavage pattern is organized, and the segregation of developmental potential occurs along this axis during early development. The segregation of developmental potential is a relatively late event and probably does not start until after cleavage begins. By compressing oocytes during the process of germinal vesicle breakdown, the position where the meiotic apparatus attaches to the cell membrane can be altered so that it no longer corresponds to the apical end of the oocyte. This new site of polar body formation sets up a new animal-vegetal axis that organizes cleavage and the segregation of developmental potential. The timing of animal-vegetal axis specification in Lottia is much later than it is in derived gastropods with a precocious specification of the D quadrant.
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Affiliation(s)
- Gary Freeman
- Friday Harbor Laboratories, University of Washington and Section of Integrative Biology, University of Texas, Austin, TX 78712, USA.
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143
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Alliegro MC, Alliegro MA, Palazzo RE. Centrosome-associated RNA in surf clam oocytes. Proc Natl Acad Sci U S A 2006; 103:9034-8. [PMID: 16754862 PMCID: PMC1482561 DOI: 10.1073/pnas.0602859103] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2005] [Indexed: 12/23/2022] Open
Abstract
Centrosomes are the major microtubule-organizing center in animal cells. They are composed of a pair of [9(3) + 0] centrioles surrounded by a relatively ill-defined pericentriolar matrix, provide the ciliary centriole-kinetosome (basal body) progenitor, and organize the assembly of microtubules into the mitotic spindle during cell division. Despite >100 years of microscopic observation and their obvious significance, our understanding of centrosome composition, dynamic organization, and mechanism of action is limited when compared with that of other cellular organelles. Centrosomes duplicate only once per cell cycle to ensure development of a normal bipolar spindle. The initial event in centrosome duplication is centriole replication, which is generative, semiconservative, and independent of the nucleus. Such observations led to the proposal that centrosomes contain their own complement of nucleic acids, possibly representative of an organellar genome comparable with those described for mitochondria and chloroplasts. The consensus in the field is that centrosomes lack DNA but may contain RNA. We isolated centrosomes from oocytes of the surf clam, Spisula solidissima, and purified from them a unique set of RNAs. We show here by biochemical means and subcellular in situ hybridization that the first transcript we analyzed is intimately associated with centrosomes. Sequence analysis reveals that this centrosome-associated RNA encodes a conserved RNA-directed polymerase domain. The hypothesis that centrosomes contain an intrinsic complement of specific RNAs suggests new opportunities to address the century-old problem of centrosome function, heredity, and evolution.
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Affiliation(s)
- Mark C. Alliegro
- *Department of Cell Biology, Louisiana State University Health Sciences Center, New Orleans, LA 70112
- Marine Biological Laboratory, Woods Hole, MA 02543
| | - Mary Anne Alliegro
- *Department of Cell Biology, Louisiana State University Health Sciences Center, New Orleans, LA 70112
- Marine Biological Laboratory, Woods Hole, MA 02543
| | - Robert E. Palazzo
- Department of Biology, Rensselear Polytechnic Institute, Troy, NY 12180
- Wadsworth Center, New York State Department of Health, Albany, NY 12237; and
- Marine Biological Laboratory, Woods Hole, MA 02543
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144
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Ren X, Weisblat DA. Asymmetrization of first cleavage by transient disassembly of one spindle pole aster in the leech Helobdella robusta. Dev Biol 2006; 292:103-15. [PMID: 16458880 DOI: 10.1016/j.ydbio.2005.12.049] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Revised: 11/15/2005] [Accepted: 12/21/2005] [Indexed: 01/10/2023]
Abstract
Unequal first cleavage is characteristic of a diverse group of protostome animals. In the nematode Caenorhabditis elegans, unequal first cleavage is achieved through the interaction of an apparently symmetric mitotic spindle apparatus with a clearly polarized cell cortex. In the clitellate annelid Tubifex tubifex, by contrast, the spindle is monastral and contains only one gamma-tubulin-reactive centrosome; this monastral spindle is inherently asymmetric throughout mitosis. Here, we have used immunostaining for beta- and gamma-tubulin to follow spindle dynamics during the unequal first cleavage in another clitellate annelid, the leech Helobdella robusta. We find that the mitotic spindle is diastral and symmetric through early metaphase, then becomes asymmetric following the transient down-regulation of one centrosome, as judged by gamma-tubulin immunofluorescence. Low levels of drugs that affect microtubule dynamics can symmetrize the first cleavage without affecting the gamma-tubulin dynamics. Our results provide a striking example of the evolvability of cellular mechanisms underlying an unambiguously homologous developmental process.
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Affiliation(s)
- Xiaoyun Ren
- Department of Molecular and Cell Biology, 385 LSA, University of California, Berkeley, CA 94720-3200, USA
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145
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Siegrist SE, Doe CQ. Microtubule-induced Pins/Galphai cortical polarity in Drosophila neuroblasts. Cell 2006; 123:1323-35. [PMID: 16377571 DOI: 10.1016/j.cell.2005.09.043] [Citation(s) in RCA: 205] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2005] [Revised: 08/26/2005] [Accepted: 09/22/2005] [Indexed: 12/23/2022]
Abstract
Cortical polarity regulates cell division, migration, and differentiation. Microtubules induce cortical polarity in yeast, but few examples are known in metazoans. We show that astral microtubules, kinesin Khc-73, and Discs large (Dlg) induce cortical polarization of Pins/Galphai in Drosophila neuroblasts; this cortical domain is functional for generating spindle asymmetry, daughter-cell-size asymmetry, and distinct sibling fates. Khc-73 localizes to astral microtubule plus ends, and Dlg/Khc-73 and Dlg/Pins coimmunoprecipitate, suggesting that microtubules induce Pins/Galphai cortical polarity through Dlg/Khc-73 interactions. The microtubule/Khc-73/Dlg pathway acts in parallel to the well-characterized Inscuteable/Par pathway, but each provides unique spatial and temporal information: The Inscuteable/Par pathway initiates at prophase to coordinate neuroblast cortical polarity with CNS tissue polarity, whereas the microtubule/Khc-73/Dlg pathway functions at metaphase to coordinate neuroblast cortical polarity with the mitotic spindle axis. These results identify a role for microtubules in polarizing the neuroblast cortex, a fundamental step for generating cell diversity through asymmetric cell division.
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Affiliation(s)
- Sarah E Siegrist
- Institutes of Neuroscience and Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, Oregon 97403, USA
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146
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Matsuo K, Shimizu T. Embryonic expression of a decapentaplegic gene in the oligochaete annelid Tubifex tubifex. Gene Expr Patterns 2006; 6:800-6. [PMID: 16517217 DOI: 10.1016/j.modgep.2006.01.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Revised: 01/21/2006] [Accepted: 01/26/2006] [Indexed: 11/24/2022]
Abstract
We have cloned and characterized the expression of a decapentaplegic homologue (designated Ttu-dpp) from the oligochaete annelid Tubifex tubifex. RT-PCR analysis and in situ hybridization revealed that Ttu-dpp begins to be expressed around the time of the onset of ectodermal germ band (GB) elongation (i.e., the onset of gastrulation). At this time, Ttu-dpp expression is detected in the anteriormost part of the GBs. As development proceeds and the GBs elongate, the domain of Ttu-dpp-expressing cells extends posteriorly. Then Ttu-dpp-expressing cells within the GB are divided into two groups: one group occurs along the ventral midline and coincides with the domain of ventral ganglia; the other is located more dorsally. The latter group of Ttu-dpp-expressing cells subsequently undergoes dorsalward expansion, which results in the formation of a lateral stripe of cells in every segment except the first (i.e., segment I). In embryos that undergo body elongation (that is one of the last morphogenetic movements occurring prior to hatchout), Ttu-dpp expression in the lateral region is confined to setal sacs, which are arranged in the same transverse plane around the periphery of each segment (except segment I).
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Affiliation(s)
- Kei Matsuo
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan
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147
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Rivera AS, Gonsalves FC, Song MH, Norris BJ, Weisblat DA. Characterization of Notch-class gene expression in segmentation stem cells and segment founder cells in Helobdella robusta (Lophotrochozoa; Annelida; Clitellata; Hirudinida; Glossiphoniidae). Evol Dev 2006; 7:588-99. [PMID: 16336412 DOI: 10.1111/j.1525-142x.2005.05062.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To understand the evolution of segmentation, we must compare segmentation in all three major groups of eusegmented animals: vertebrates, arthropods, and annelids. The leech Helobdella robusta is an experimentally tractable annelid representative, which makes segments in anteroposterior progression from a posterior growth zone consisting of 10 identified stem cells. In vertebrates and some arthropods, Notch signaling is required for normal segmentation and functions via regulation of hes-class genes. We have previously characterized the expression of an hes-class gene (Hro-hes) during segmentation in Helobdella, and here, we characterize the expression of an H. robusta notch homolog (Hro-notch) during this process. We find that Hro-notch is transcribed in the segmental founder cells (blast cells) and their stem-cell precursors (teloblasts), as well as in other nonsegmental tissues. The mesodermal and ectodermal lineages show clear differences in the levels of Hro-notch expression. Finally, Hro-notch is shown to be inherited by newly born segmental founder cells as well as transcribed by them before their first cell division.
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Affiliation(s)
- Ajna S Rivera
- Department of Molecular and Cell Biology, 385 LSA University of California, Berkeley, CA 94720-3200, USA
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148
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Gore AV, Maegawa S, Cheong A, Gilligan PC, Weinberg ES, Sampath K. The zebrafish dorsal axis is apparent at the four-cell stage. Nature 2005; 438:1030-5. [PMID: 16355228 DOI: 10.1038/nature04184] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2005] [Accepted: 08/30/2005] [Indexed: 11/08/2022]
Abstract
A central question in the development of multicellular organisms pertains to the timing and mechanisms of specification of the embryonic axes. In many organisms, specification of the dorsoventral axis requires signalling by proteins of the Transforming growth factor-beta and Wnt families. Here we show that maternal transcripts of the zebrafish Nodal-related morphogen, Squint (Sqt), can localize to two blastomeres at the four-cell stage and predict the dorsal axis. Removal of cells containing sqt transcripts from four-to-eight-cell embryos or injection of antisense morpholino oligonucleotides targeting sqt into oocytes can cause a loss of dorsal structures. Localization of sqt transcripts is independent of maternal Wnt pathway function and requires a highly conserved sequence in the 3' untranslated region. Thus, the dorsoventral axis is apparent by early cleavage stages and may require the maternally encoded morphogen Sqt and its associated factors. Because the 3' untranslated region of the human nodal gene can also localize exogenous sequences to dorsal cells, this mechanism may be evolutionarily conserved.
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Affiliation(s)
- Aniket V Gore
- Vertebrate Development Group, Temasek Life Sciences Laboratory, 1 Research Link, 117604 Singapore
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149
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Tkemaladze JV, Chichinadze KN. Centriolar Mechanisms of Differentiation and Replicative Aging of Higher Animal Cells. BIOCHEMISTRY (MOSCOW) 2005; 70:1288-303. [PMID: 16336191 DOI: 10.1007/s10541-005-0261-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The centrosome (centriole) and the cytoskeleton produced by it are structures, which probably determine differentiation, morphogenesis, and switching on the mechanism of replicative aging in all somatic cells of multicellular animals. The mechanism of such programming of the events seems to include cytoskeleton influences and small RNAs related to the centrosome. 1) If these functions are really related with centrioles, the multicellular organism's cells which: a) initially lack centrioles (e.g., higher plant cells and also zygote and early blastomeres of some animals) or cytoskeleton (e.g., embryonic stem cells); or b) generate centrioles de novo (e.g., zygote and early blastomeres of some animals), will be totipotent and lack replicative aging. Consequently, the absence (constant or temporary) of the structure determining the counting of divisions also means the absence of counting of differentiation processes. 2) Although a particular damage to centrioles or cytoskeleton (e.g., in tumor cells) fails to make the cells totipotent (because the morphogenetic status of these cells, as differentiated from that of totipotent ones, is not zero), but such a transformation can suppress the initiation of the aging mechanism induced by these structures and, thus, make such cells replicatively "immortal".
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Affiliation(s)
- J V Tkemaladze
- Georgian Systemic Research Center, Tbilisi, 0160, Georgia
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150
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Delanoue R, Davis I. Dynein anchors its mRNA cargo after apical transport in the Drosophila blastoderm embryo. Cell 2005; 122:97-106. [PMID: 16009136 DOI: 10.1016/j.cell.2005.04.033] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2004] [Revised: 03/04/2005] [Accepted: 04/28/2005] [Indexed: 11/28/2022]
Abstract
Molecular motors actively transport many types of cargo along the cytoskeleton in a wide range of organisms. One class of cargo is localized mRNAs, which are transported by myosin on actin filaments or by kinesin and dynein on microtubules. How the cargo is kept at its final intracellular destination and whether the motors are recycled after completion of transport are poorly understood. Here, we use a new RNA anchoring assay in living Drosophila blastoderm embryos to show that apical anchoring of mRNA after completion of dynein transport does not depend on actin or on continuous active transport by the motor. Instead, apical anchoring of RNA requires microtubules and involves dynein as a static anchor that remains with the cargo at its final destination. We propose a general principle that could also apply to other dynein cargo and to some other molecular motors, whereby cargo transport and anchoring reside in the same molecule.
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Affiliation(s)
- Renald Delanoue
- Wellcome Trust Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, EH9 3JR, United Kingdom
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