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Lin B, Shi W, Lu Q, Shito TT, Yu H, Dong B. Establishment of a developmental atlas and transgenetic tools in the ascidian Styela clava. MARINE LIFE SCIENCE & TECHNOLOGY 2023; 5:435-454. [PMID: 38045543 PMCID: PMC10689645 DOI: 10.1007/s42995-023-00200-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 09/28/2023] [Indexed: 12/05/2023]
Abstract
The ascidian Styela clava is an ecologically important species that is distributed along coastal regions worldwide. It has a long history as a model animal for evolutionary and developmental biology research owing to its phylogenetic position between vertebrates and invertebrates, and its classical mosaic expression patterns. However, the standard developmental atlas and protocols and tools for molecular manipulation of this organism are inadequate. In this study, we established a standard developmental table and provided a web-based digital image resource for S. clava embryogenesis at each developmental stage from fertilized eggs to hatching larvae by utilizing confocal laser microscopy and 3D reconstruction images. It takes around 10 h for fertilized eggs to develop into swimming larvae and 20-30 min to complete the tail regression processes at the metamorphic stage. We observed that the notochord cells in S. clava embryos did not produce an extracellular lumen like Ciona robusta, but showed polarized elongation behaviors, providing us an ideal comparative model to study tissue morphogenesis. In addition, we established a chemical-washing procedure to remove the chorion easily from the fertilized eggs. Based on the dechorionation technique, we further realized transgenic manipulation by electroporation and successfully applied tissue-specific fluorescent labeling in S. clava embryos. Our work provides a standard imaging atlas and powerful genetic tools for investigating embryogenesis and evolution using S. clava as a model organism. Supplementary Information The online version contains supplementary material available at 10.1007/s42995-023-00200-2.
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Affiliation(s)
- Boyan Lin
- Fang Zongxi Center, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003 China
| | - Wenjie Shi
- Fang Zongxi Center, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003 China
| | - Qiongxuan Lu
- Fang Zongxi Center, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003 China
| | - Takumi T. Shito
- Department of Bioscience and Informatics, Faculty of Science and Technology, Keio University, Yokohama, 223-8522 Japan
| | - Haiyan Yu
- Fang Zongxi Center, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003 China
| | - Bo Dong
- Fang Zongxi Center, College of Marine Life Sciences, Ocean University of China, Qingdao, 266003 China
- Laoshan Laboratory, Qingdao, 266237 China
- MoE Key Laboratory of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
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Actin Filament in the First Cell Cycle Contributes to the Determination of the Anteroposterior Axis in Ascidian Development. J Dev Biol 2022; 10:jdb10010010. [PMID: 35225963 PMCID: PMC8884010 DOI: 10.3390/jdb10010010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 01/28/2022] [Accepted: 02/02/2022] [Indexed: 02/01/2023] Open
Abstract
In many animal species, the body axis is determined by the relocalization of maternal determinants, organelles, or unique cell populations in a cytoskeleton-dependent manner. In the ascidian first cell cycle, the myoplasm, including mitochondria, endoplasmic reticulum (ER), and maternal mRNAs, move to the future posterior side concomitantly (called ooplasmic segregation or cytoplasmic and cortical reorganization). This translocation consists of first and second phases depending on the actin and microtubule, respectively. However, the transition from first to second phase, that is, translocation of myoplasmic components from microfilaments to microtubules, has been poorly investigated. In this study, we analyzed the relationship between these cytoskeletons and myoplasmic components during the first cell cycle and their role in morphogenesis by inhibitor experiments. Owing to our improved visualization techniques, there was unexpected F-actin accumulation at the vegetal pole during this transition period. When this F-actin was depolymerized, the microtubule structure was strongly affected, the myoplasmic components, including maternal mRNA, were mislocalized, and the anteroposterior axis formation was disordered. These results suggested the importance of F-actin during the first cell cycle and the existence of interactions between microfilaments and microtubules, implying the enigmatic mechanism of ooplasmic segregation. Solving this mystery leads us to an improved understanding of ascidian early development.
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Funakoshi HM, Shito TT, Oka K, Hotta K. Developmental Table and Three-Dimensional Embryological Image Resource of the Ascidian Ascidiella aspersa. Front Cell Dev Biol 2021; 9:789046. [PMID: 34977032 PMCID: PMC8718802 DOI: 10.3389/fcell.2021.789046] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 11/29/2021] [Indexed: 11/13/2022] Open
Abstract
Ascidiella aspersa is an ascidian in the class of chordates—the closest relatives of vertebrates. A. aspersa is a potential model organism for bio-imaging studies due to its extremely transparent embryos as well as is a globally distributed cosmopolitan species. However, there is no standard developmental table for this organism. Here, as a first step to establish A. aspersa as a model organism, we report a standard developmental table as a web-based digital image resource. This resource used confocal laser scanning microscopy to scan more than 3,000 cross-sectional images and 3D-reconstructed images of A. aspersa embryos during embryogenesis. With reference to the standardized developmental table of Ciona intestinalis type A, 26 different developmental stages (Stages 1–26) from fertilized eggs to hatched larvae were redefined for A. aspersa. Cell lineages up to the cleavage period were annotated: The cleavage patterns, the embryonic morphology, and the developmental time were then compared with Ciona. We found that the cleavage patterns and developmental time up to the neurula period in A. aspersa were extremely conserved versus. Ciona. The ratio of the trunk and tail length in the tailbud period were smaller than Ciona indicating a relatively short tail. In addition, the timing of the bending of the tail is earlier than Ciona. This A. aspersa standard 3D digital resource is essential for connecting different omics data to different spatiotemporal hierarchies and is useful for a system-level understanding of chordate development and evolution.
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Affiliation(s)
- Haruka M. Funakoshi
- Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Yokohama, Japan
| | - Takumi T. Shito
- Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Yokohama, Japan
| | - Kotaro Oka
- Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Yokohama, Japan
- Waseda Research Institute for Science and Engineering, Waseda University, Shinjuku, Japan
- Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung City, Taiwan
| | - Kohji Hotta
- Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Yokohama, Japan
- *Correspondence: Kohji Hotta,
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Godard BG, Dumollard R, Heisenberg CP, McDougall A. Combined effect of cell geometry and polarity domains determines the orientation of unequal division. eLife 2021; 10:75639. [PMID: 34889186 PMCID: PMC8691831 DOI: 10.7554/elife.75639] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 12/02/2021] [Indexed: 11/13/2022] Open
Abstract
Cell division orientation is thought to result from a competition between cell geometry and polarity domains controlling the position of the mitotic spindle during mitosis. Depending on the level of cell shape anisotropy or the strength of the polarity domain, one dominates the other and determines the orientation of the spindle. Whether and how such competition is also at work to determine unequal cell division (UCD), producing daughter cells of different size, remains unclear. Here, we show that cell geometry and polarity domains cooperate, rather than compete, in positioning the cleavage plane during UCDs in early ascidian embryos. We found that the UCDs and their orientation at the ascidian third cleavage rely on the spindle tilting in an anisotropic cell shape, and cortical polarity domains exerting different effects on spindle astral microtubules. By systematically varying mitotic cell shape, we could modulate the effect of attractive and repulsive polarity domains and consequently generate predicted daughter cell size asymmetries and position. We therefore propose that the spindle position during UCD is set by the combined activities of cell geometry and polarity domains, where cell geometry modulates the effect of cortical polarity domain(s).
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Affiliation(s)
- Benoit G Godard
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche sur Mer, France.,Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Remi Dumollard
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche sur Mer, France
| | | | - Alex McDougall
- Laboratoire de Biologie du Développement de Villefranche-sur-mer, Institut de la Mer de Villefranche-sur-mer, Sorbonne Université, CNRS, Villefranche sur Mer, France
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Nishida H, Matsuo M, Konishi S, Ohno N, Manni L, Onuma TA. Germline development during embryogenesis of the larvacean, Oikopleura dioica. Dev Biol 2021; 481:188-200. [PMID: 34755656 DOI: 10.1016/j.ydbio.2021.10.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 10/08/2021] [Accepted: 10/24/2021] [Indexed: 11/18/2022]
Abstract
Germ cells develop into eggs and sperms and represent a lineage that survives through multiple generations. Germ cell specification during embryogenesis proceeds through one of two basic modes: either the cell-autonomous mode or the inductive mode. In the cell-autonomous mode, specification of germ cell fate involves asymmetric partitioning of the specialized maternal cytoplasm, known as the germplasm. Oikopleura dioica is a larvacean (class Appendicularia) and a chordate. It is regarded as a promising animal model for studying chordate development because of its short life cycle (5 days) and small genome size (∼60 Mb). We show that their embryos possess germplasm, as observed in ascidians (class Ascidiacea). The vegetal cytoplasm shifted towards the future posterior pole before the first cleavage occurred. A bilateral pair of primordial germ cells (PGC, B11 cells) was formed at the posterior pole at the 32-cell stage through two rounds of unequal cleavage. These B11 cells did not undergo further division before hatching of the tadpole-shaped larvae. The centrosome-attracting body (CAB) is a subcellular structure that contains the germplasm and plays crucial roles in germ cell development in ascidians. The presence of CAB with germplasm was observed in the germline lineage cells of larvaceans via electron microscopy and using extracted embryos. The CAB appeared at the 8-cell stage and persisted until the middle stage of embryogenesis. The antigen for the phosphorylated histone 3 antibody was localized to the CAB and persisted in the PGC until hatching after the CAB disappeared. Maternal snail mRNA, which encodes a transcription factor, was co-localized with the antigen for the H3S28p antibody. Furthermore, we found a novel PGC-specific subcellular structure that we call the germ body (GB). This study thus highlights the conserved and non-conserved features of germline development between ascidians and larvaceans. The rapid development and short life cycle (five days) of O. dioica would open the way to genetically analyze germ cell development in the future.
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Affiliation(s)
- Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan.
| | - Masaki Matsuo
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
| | - Shohei Konishi
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
| | - Nobuhiko Ohno
- Division of Ultrastructural Research, National Institute for Physiological Sciences, Okazaki, 444-8787, Japan; Division of Histology and Cell Biology, Department of Anatomy, Jichi Medical University, Shimotsuke, Tochigi, 329-0498, Japan
| | - Lucia Manni
- Dipartimento di Biologia, Università degli Studi di Padova, via U. Bassi 58/B, I-35121, Padova, Italy
| | - Takeshi A Onuma
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043, Japan
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Winkley KM, Reeves WM, Veeman MT. Single-cell analysis of cell fate bifurcation in the chordate Ciona. BMC Biol 2021; 19:180. [PMID: 34465302 PMCID: PMC8408944 DOI: 10.1186/s12915-021-01122-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 08/12/2021] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Inductive signaling interactions between different cell types are a major mechanism for the further diversification of embryonic cell fates. Most blastomeres in the model chordate Ciona robusta become restricted to a single predominant fate between the 64-cell and mid-gastrula stages. The deeply stereotyped and well-characterized Ciona embryonic cell lineages allow the transcriptomic analysis of newly established cell types very early in their divergence from sibling cell states without the pseudotime inference needed in the analysis of less synchronized cell populations. This is the first ascidian study to use droplet scRNAseq with large numbers of analyzed cells as early as the 64-cell stage when major lineages such as primary notochord first become fate restricted. RESULTS AND CONCLUSIONS We identify 59 distinct cell states, including new subregions of the b-line neural lineage and the early induction of the tail tip epidermis. We find that 34 of these cell states are directly or indirectly dependent on MAPK-mediated signaling critical to early Ciona patterning. Most of the MAPK-dependent bifurcations are canalized with the signal-induced cell fate lost upon MAPK inhibition, but the posterior endoderm is unique in being transformed into a novel state expressing some but not all markers of both endoderm and muscle. Divergent gene expression between newly bifurcated sibling cell types is dominated by upregulation in the induced cell type. The Ets family transcription factor Elk1/3/4 is uniquely upregulated in nearly all the putatively direct inductions. Elk1/3/4 upregulation together with Ets transcription factor binding site enrichment analysis enables inferences about which bifurcations are directly versus indirectly controlled by MAPK signaling. We examine notochord induction in detail and find that the transition between a Zic/Ets-mediated regulatory state and a Brachyury/FoxA-mediated regulatory state is unexpectedly late. This supports a "broad-hourglass" model of cell fate specification in which many early tissue-specific genes are induced in parallel to key tissue-specific transcriptional regulators via the same set of transcriptional inputs.
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Affiliation(s)
- Konner M Winkley
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
| | - Wendy M Reeves
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA
| | - Michael T Veeman
- Division of Biology, Kansas State University, Manhattan, KS, 66506, USA.
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Zheng T, Nakamoto A, Kumano G. H3K27me3 suppresses sister-lineage somatic gene expression in late embryonic germline cells of the ascidian, Halocynthia roretzi. Dev Biol 2020; 460:200-214. [PMID: 31904374 DOI: 10.1016/j.ydbio.2019.12.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 11/21/2019] [Accepted: 12/29/2019] [Indexed: 10/25/2022]
Abstract
Protection of the germline from somatic differentiation programs is crucial for germ cell development. In many animals, whose germline development relies on the maternally inherited germ plasm, such protection in particular at early stages of embryogenesis is achieved by maternally localized global transcriptional repressors, such as PIE-1 of Caenorhabditis elegans, Pgc of Drosophila melanogaster and Pem of ascidians. However, zygotic gene expression starts in later germline cells eventually and mechanisms by which somatic gene expression is selectively kept under repression in the transcriptionally active cells are poorly understood. By using the ascidian species Halocynthia roretzi, we found that H3K27me3, a repressive transcription-related chromatin mark, became enriched in germline cells starting at the 64-cell stage when Pem protein level and its contribution to transcriptional repression decrease. Interestingly, inhibition of H3K27me3 together with Pem knockdown resulted in ectopic expression in germline cells of muscle developmental genes Muscle actin (MA4) and Snail, and of Clone 22 (which is expressed in all somatic but not germline cells), but not of other tissue-specific genes such as the notochord gene Brachyury, the nerve cord marker ETR-1 and a heart precursor gene Mesp, at the 110-cell stage. Importantly, these ectopically expressed genes are normally expressed in the germline sister cells (B7.5), the last somatic lineage separated from the germline. Also, the ectopic expression of MA4 was dependent on a maternally localized muscle determinant Macho-1. Taken together, we propose that H3K27me3 may be responsible for selective transcriptional repression for somatic genes in later germline cells in Halocynthia embryos and that the preferential repression of germline sister-lineage genes may be related to the mechanism of germline segregation in ascidian embryos, where the germline is segregated progressively by successive asymmetric cell divisions during cell cleavage stages. Together with findings from C. elegans and D. melanogaster, our data for this urochordate animal support the proposal for a mechanism, conserved widely throughout the animal kingdom, where germline transcriptional repression is mediated initially by maternally localized factors and subsequently by a chromatin-based mechanism.
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Affiliation(s)
- Tao Zheng
- Asamushi Research Center for Marine Biology, Graduate School of Life Sciences, Tohoku University, Japan.
| | - Ayaki Nakamoto
- Asamushi Research Center for Marine Biology, Graduate School of Life Sciences, Tohoku University, Japan
| | - Gaku Kumano
- Asamushi Research Center for Marine Biology, Graduate School of Life Sciences, Tohoku University, Japan
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Abstract
Tunicates are a diverse group of invertebrate marine chordates that includes the larvaceans, thaliaceans, and ascidians. Because of their unique evolutionary position as the sister group of the vertebrates, tunicates are invaluable as a comparative model and hold the promise of revealing both conserved and derived features of chordate gastrulation. Descriptive studies in a broad range of tunicates have revealed several important unifying traits that make them unique among the chordates, including invariant cell lineages through gastrula stages and an overall morphological simplicity. Gastrulation has only been studied in detail in ascidians such as Ciona and Phallusia, where it involves a simple cup-shaped gastrula driven primarily by endoderm invagination. This appears to differ significantly from vertebrate models, such as Xenopus, in which mesoderm convergent extension and epidermal epiboly are major contributors to involution. These differences may reflect the cellular simplicity of the ascidian embryo.
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Affiliation(s)
- Konner M Winkley
- Division of Biology, Kansas State University, Manhattan, KS, United States
| | - Matthew J Kourakis
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, United States
| | - Anthony W DeTomaso
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, United States
| | - Michael T Veeman
- Division of Biology, Kansas State University, Manhattan, KS, United States
| | - William C Smith
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, United States.
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Massive cytoplasmic transport and microtubule organization in fertilized chordate eggs. Dev Biol 2018; 448:154-160. [PMID: 30521810 DOI: 10.1016/j.ydbio.2018.11.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 11/24/2018] [Accepted: 11/30/2018] [Indexed: 01/13/2023]
Abstract
Eggs have developed their own strategies for early development. Amphibian, teleost fish, and ascidian eggs show cortical rotation and an accompanying structure, a cortical parallel microtubule (MT) array, during the one-cell embryonic stage. Cortical rotation is thought to relocate maternal deposits to a certain compartment of the egg and to polarize the embryo. The common features and differences among chordate eggs as well as localized maternal proteins and mRNAs that are related to the organization of MT structures are described in this review. Furthermore, recent studies report progress in elucidating the molecular nature and functions of the noncentrosomal MT organizing center (ncMTOC). The parallel array of MT bundles is presumably organized by ncMTOCs; therefore, the mechanism of ncMTOC control is likely inevitable for these species. Thus, the molecules related to the ncMTOC provide clues for understanding the mechanisms of early developmental systems, which ultimately determine the embryonic axis.
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Hashimoto H, Munro E. Dynamic interplay of cell fate, polarity and force generation in ascidian embryos. Curr Opin Genet Dev 2018; 51:67-77. [PMID: 30007244 DOI: 10.1016/j.gde.2018.06.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 06/11/2018] [Accepted: 06/22/2018] [Indexed: 10/28/2022]
Abstract
A fundamental challenge in developmental biology is to understand how forces produced by individual cells are patterned in space and time and then integrated to produce stereotyped changes in tissue-level or embryo-level morphology. Ascidians offer a unique opportunity to address this challenge by studying how small groups of cells collectively execute complex, but highly stereotyped morphogenetic movements. Here we highlight recent progress and open questions in the study of ascidian morphogenesis, emphasizing the dynamic interplay of cell fate determination, cellular force generation and tissue-level mechanics.
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Affiliation(s)
- Hidehiko Hashimoto
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, United States.
| | - Edwin Munro
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, United States; Committee on Development, Regeneration and Stem Cell Biology, University of Chicago, Chicago, IL 60637, United States.
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Tokuoka M, Kobayashi K, Satou Y. Distinct regulation of Snail in two muscle lineages of the ascidian embryo achieves temporal coordination of muscle development. Development 2018; 145:dev.163915. [PMID: 29764858 DOI: 10.1242/dev.163915] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Accepted: 05/03/2018] [Indexed: 01/29/2023]
Abstract
The transcriptional repressor Snail is required for proper differentiation of the tail muscle of ascidian tadpole larvae. Two muscle lineages (B5.1 and B6.4) contribute to the anterior tail muscle cells, and are consecutively separated from a transcriptionally quiescent germ cell lineage at the 16- and 32-cell stages. Concomitantly, cells of these lineages begin to express Tbx6.b (Tbx6-r.b) at the 16- and 32-cell stages, respectively. Meanwhile, Snail expression begins in these two lineages simultaneously at the 32-cell stage. Here, we show that Snail expression is regulated differently between these two lineages. In the B5.1 lineage, Snail was activated through Tbx6.b, which is activated by maternal factors, including Zic-r.a. In the B6.4 lineage, the MAPK pathway was cell-autonomously activated by a constitutively active form of Raf, enabling Zic-r.a to activate Snail independently of Tbx6.b As a result, Snail begins to be expressed at the 32-cell stage simultaneously in these two lineages. Such shortcuts might be required for coordinating developmental programs in embryos in which cells become separated progressively from stem cells, including germline cells.
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Affiliation(s)
- Miki Tokuoka
- Department of Zoology, Graduate School of Science, Kyoto University Sakyo, Kyoto, 606-8502, Japan
| | - Kenji Kobayashi
- Department of Zoology, Graduate School of Science, Kyoto University Sakyo, Kyoto, 606-8502, Japan
| | - Yutaka Satou
- Department of Zoology, Graduate School of Science, Kyoto University Sakyo, Kyoto, 606-8502, Japan
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Control of Pem protein level by localized maternal factors for transcriptional regulation in the germline of the ascidian, Halocynthia roretzi. PLoS One 2018; 13:e0196500. [PMID: 29709000 PMCID: PMC5927453 DOI: 10.1371/journal.pone.0196500] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 04/13/2018] [Indexed: 12/04/2022] Open
Abstract
Localized maternal mRNAs play important roles in embryogenesis, e.g. the establishment of embryonic axes and the developmental cell fate specification, in various animal species. In ascidians, a group of maternal mRNAs, called postplasmic/PEM RNAs, is localized to a subcellular structure, called the Centrosome-Attracting Body (CAB), which contains the ascidian germ plasm, and is inherited by the germline cells during embryogenesis. Posterior end mark (Pem), a postplasmic/PEM RNAs member, represses somatic gene expression in the germline during cleavage stages by inhibition of RNA polymerase II activity. However, the functions of other postplasmic/ PEM RNAs members in germline formation are largely unknown. In this study, we analyzed the functions of two postplasmic/PEM RNAs, Popk-1 and Zf-1, in transcriptional regulation in the germline cells. We show that Popk-1 contributes to transcriptional quiescence by controlling the size of the CAB and amount of Pem protein translated at the CAB. Our studies also indicated that zygotic expression of a germline gene starts around the onset of gastrulation and that the decrease of Pem protein is necessary and sufficient for the zygotic germline gene expression. Finally, further studies showed that the decrease of the Pem protein level is facilitated by Zf-1. Taken together, we propose that postplasmic/PEM RNAs such as Popk-1 and Zf-1 control the protein level of the transcriptional repressor Pem and regulate its transcriptional state in the ascidian germline.
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13
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Olsen LC, Kourtesis I, Busengdal H, Jensen MF, Hausen H, Chourrout D. Evidence for a centrosome-attracting body like structure in germ-soma segregation during early development, in the urochordate Oikopleura dioica. BMC DEVELOPMENTAL BIOLOGY 2018; 18:4. [PMID: 29486709 PMCID: PMC5830320 DOI: 10.1186/s12861-018-0165-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 02/16/2018] [Indexed: 11/27/2022]
Abstract
Background Germ cell formation has been investigated in sessile forms of tunicates. This process involves the release of a subset of maternal transcripts from the centrosome-attracting body (CAB) in the progenitor cells of the germ line. When germ-soma segregation is completed, CAB structures are missing from the newly formed primordial germ cells (PGCs). In free-swimming tunicates, knowledge about germ cell formation is lacking. In this investigation, comparative gene expression and electron microscopy studies were used to address germ cell formation in Oikopleura dioica (O. dioica). Results We found that the RNA localization pattern of pumilio (pum1) is similar to the pattern described for a subset of maternal transcripts marking the posterior end of ascidian embryos. Transcripts marking the posterior end are called postplasmic or posterior-end mark (PEM) transcripts. We found no localization of vasa (vas) transcripts to any sub-region within the germ-line precursor cells. Expression of vas4 was detected in the newly formed PGCs. Electron microscopy studies confirmed the presence of structures with similar morphology to CAB. In the same cytoplasmic compartment, we also identified pum1 transcripts and an epitope recognized by an antibody to histone H3 phosphorylated on serine 28. Conclusions Our findings support that a CAB-like structure participates in the segregation of maternal pum1 transcripts during germ-soma separation in O. dioica. Electronic supplementary material The online version of this article (10.1186/s12861-018-0165-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lisbeth Charlotte Olsen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway. .,Department of Molecular Biology, University of Bergen, Thormöhlensgt 55, 5008, Bergen, Norway. .,Department of Biological Sciences, University of Bergen, Thormöhlensgt 55, 5008, Bergen, Norway.
| | - Ioannis Kourtesis
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Henriette Busengdal
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Marit Flo Jensen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Harald Hausen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Daniel Chourrout
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
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14
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Transgenic Techniques for Investigating Cell Biology During Development. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018. [PMID: 29542088 DOI: 10.1007/978-981-10-7545-2_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Ascidians are increasingly being used as a system for investigating cell biology during development. The extreme genetic and cellular simplicity of ascidian embryos in combination with superior experimental tractability make this an ideal system for in vivo analysis of dynamic cellular processes. Transgenic approaches to cellular and sub-cellular analysis of ascidian development have begun to yield new insights into the mechanisms regulating developmental signaling and morphogenesis. This chapter focuses on the targeted expression of fusion proteins in ascidian embryos and how this technique is being deployed to garner new insights into the cell biology of development.
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Costache V, Hebras C, Pruliere G, Besnardeau L, Failla M, Copley RR, Burgess D, Chenevert J, McDougall A. Kif2 localizes to a subdomain of cortical endoplasmic reticulum that drives asymmetric spindle position. Nat Commun 2017; 8:917. [PMID: 29030551 PMCID: PMC5640700 DOI: 10.1038/s41467-017-01048-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 08/16/2017] [Indexed: 12/22/2022] Open
Abstract
Asymmetric positioning of the mitotic spindle is a fundamental process responsible for creating sibling cell size asymmetry; however, how the cortex causes the depolymerization of astral microtubules during asymmetric spindle positioning has remained elusive. Early ascidian embryos possess a large cortical subdomain of endoplasmic reticulum (ER) that causes asymmetric spindle positioning driving unequal cell division. Here we show that the microtubule depolymerase Kif2 localizes to this subdomain of cortical ER. Rapid live-cell imaging reveals that microtubules are less abundant in the subdomain of cortical ER. Inhibition of Kif2 function prevents the development of mitotic aster asymmetry and spindle pole movement towards the subdomain of cortical ER, whereas locally increasing microtubule depolymerization causes exaggerated asymmetric spindle positioning. This study shows that the microtubule depolymerase Kif2 is localized to a cortical subdomain of endoplasmic reticulum that is involved in asymmetric spindle positioning during unequal cell division. Early ascidian embryos have a cortical subdomain of endoplasmic reticulum (ER) that controls asymmetric spindle positioning driving unequal cell division. Here the authors show that the microtubule depolymerase Kif2 is localized to a cortical subdomain of the ER that is involved in asymmetric spindle positioning.
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Affiliation(s)
- Vlad Costache
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), Observatoire Océanologique, Villefranche sur-mer, 06230, France
| | - Celine Hebras
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), Observatoire Océanologique, Villefranche sur-mer, 06230, France
| | - Gerard Pruliere
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), Observatoire Océanologique, Villefranche sur-mer, 06230, France
| | - Lydia Besnardeau
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), Observatoire Océanologique, Villefranche sur-mer, 06230, France
| | - Margaux Failla
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), Observatoire Océanologique, Villefranche sur-mer, 06230, France
| | - Richard R Copley
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), Observatoire Océanologique, Villefranche sur-mer, 06230, France
| | - David Burgess
- Boston College, Biology Department, 528 Higgins Hall, 140 Commonwealth Ave, Chestnut Hill, MA, 0246, USA
| | - Janet Chenevert
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), Observatoire Océanologique, Villefranche sur-mer, 06230, France.
| | - Alex McDougall
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), Observatoire Océanologique, Villefranche sur-mer, 06230, France.
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Ogura Y, Sasakura Y. Emerging mechanisms regulating mitotic synchrony during animal embryogenesis. Dev Growth Differ 2017; 59:565-579. [DOI: 10.1111/dgd.12391] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2017] [Revised: 07/20/2017] [Accepted: 07/23/2017] [Indexed: 01/21/2023]
Affiliation(s)
- Yosuke Ogura
- Laboratory for Morphogenetic Signaling; RIKEN Center for Developmental Biology; Kobe Japan
| | - Yasunori Sasakura
- Shimoda Marine Research Center; University of Tsukuba; Shizuoka Japan
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Hasley A, Chavez S, Danilchik M, Wühr M, Pelegri F. Vertebrate Embryonic Cleavage Pattern Determination. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 953:117-171. [PMID: 27975272 PMCID: PMC6500441 DOI: 10.1007/978-3-319-46095-6_4] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The pattern of the earliest cell divisions in a vertebrate embryo lays the groundwork for later developmental events such as gastrulation, organogenesis, and overall body plan establishment. Understanding these early cleavage patterns and the mechanisms that create them is thus crucial for the study of vertebrate development. This chapter describes the early cleavage stages for species representing ray-finned fish, amphibians, birds, reptiles, mammals, and proto-vertebrate ascidians and summarizes current understanding of the mechanisms that govern these patterns. The nearly universal influence of cell shape on orientation and positioning of spindles and cleavage furrows and the mechanisms that mediate this influence are discussed. We discuss in particular models of aster and spindle centering and orientation in large embryonic blastomeres that rely on asymmetric internal pulling forces generated by the cleavage furrow for the previous cell cycle. Also explored are mechanisms that integrate cell division given the limited supply of cellular building blocks in the egg and several-fold changes of cell size during early development, as well as cytoskeletal specializations specific to early blastomeres including processes leading to blastomere cohesion. Finally, we discuss evolutionary conclusions beginning to emerge from the contemporary analysis of the phylogenetic distributions of cleavage patterns. In sum, this chapter seeks to summarize our current understanding of vertebrate early embryonic cleavage patterns and their control and evolution.
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Affiliation(s)
- Andrew Hasley
- Laboratory of Genetics, University of Wisconsin-Madison, Genetics/Biotech Addition, Room 2424, 425-G Henry Mall, Madison, WI, 53706, USA
| | - Shawn Chavez
- Division of Reproductive & Developmental Sciences, Oregon National Primate Research Center, Department of Physiology & Pharmacology, Oregon Heath & Science University, 505 NW 185th Avenue, Beaverton, OR, 97006, USA
- Division of Reproductive & Developmental Sciences, Oregon National Primate Research Center, Department of Obstetrics & Gynecology, Oregon Heath & Science University, 505 NW 185th Avenue, Beaverton, OR, 97006, USA
| | - Michael Danilchik
- Department of Integrative Biosciences, L499, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA
| | - Martin Wühr
- Department of Molecular Biology & The Lewis-Sigler Institute for Integrative Genomics, Princeton University, Icahn Laboratory, Washington Road, Princeton, NJ, 08544, USA
| | - Francisco Pelegri
- Laboratory of Genetics, University of Wisconsin-Madison, Genetics/Biotech Addition, Room 2424, 425-G Henry Mall, Madison, WI, 53706, USA.
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Abstract
Asymmetric cell division during embryogenesis contributes to cell diversity by generating daughter cells that adopt distinct developmental fates. In this chapter, we summarize current knowledge of three examples of asymmetric cell division occurring in ascidian early embryos: (1) Three successive cell divisions that are asymmetric in terms of cell fate and unequal in cell size in the germline lineage at the embryo posterior pole. A subcellular structure, the centrosome-attracting body (CAB), and maternal PEM mRNAs localized within it control both the positioning of the cell division planes and segregation of the germ cell fates. (2) Asymmetric cell divisions involving endoderm and mesoderm germ layer separation. Asymmetric partitioning of zygotically expressed mRNA for Not, a homeodomain transcription factor, promotes the mesoderm fate and suppresses the endoderm fate. This asymmetric partitioning is mediated by transient nuclear migration toward the mesodermal pole of the mother cell, where the mRNA is delivered. In this case, there is no special regulation of cleavage plane orientation. (3) Asymmetric cell divisions in the marginal region of the vegetal hemisphere. The directed extracellular FGF and ephrin signals polarize the mother cells, inducing distinct fates in a pair of daughter cells (nerve versus notochord and mesenchyme versus muscle). The directions of cell division are regulated and oriented but independently of FGF and ephrin signaling. In these examples, polarization of the mother cells is facilitated by localized maternal factors, by delivery of transcripts from the nucleus to one pole of each cell, and by directed extracellular signals. Two cellular processes-asymmetric fate allocation and orientation of the cell division plane-are coupled by a single factor in the first example, but these processes are regulated independently in the third example. Thus, various modes of asymmetric cell division operate even at the early developmental stages in this single type of organism.
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Affiliation(s)
- Takefumi Negishi
- Division of Morphogenesis, National Institute for Basic Biology, Nishigonaka 38, Myodaiji, Okazaki, Aichi, 444-8585, Japan
| | - Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-Cho, Toyonaka, Osaka, 560-0043, Japan.
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Yaguchi S, Yaguchi J, Inaba K. bicaudal-C is required for the formation of anterior neurogenic ectoderm in the sea urchin embryo. Sci Rep 2014; 4:6852. [PMID: 25358387 PMCID: PMC4215294 DOI: 10.1038/srep06852] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 10/10/2014] [Indexed: 02/07/2023] Open
Abstract
bicaudal-C (bicC) mRNA encodes a protein containing RNA-binding domains that is reported to be maternally present with deflection in the oocytes/eggs of some species. The translated protein plays a critical role in the regulation of cell fate specification along the body axis during early embryogenesis in flies and frogs. However, it is unclear how it functions in eggs in which bicC mRNA is uniformly distributed, for instance, sea urchin eggs. Here, we show the function of BicC in the formation of neurogenic ectoderm of the sea urchin embryo. Loss-of-function experiments reveal that BicC is required for serotonergic neurogenesis and for expression of ankAT-1 gene, which is essential for the formation of apical tuft cilia in the neurogenic ectoderm of the sea urchin embryo. In contrast, the expression of FoxQ2, the neurogenic ectoderm specification transcription factor, is invariant in BicC morphants. Because FoxQ2 is an upstream factor of serotonergic neurogenesis and ankAT-1 expression, these data indicate that BicC functions in regulating the events that are coordinated by FoxQ2 during sea urchin embryogenesis.
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Affiliation(s)
- Shunsuke Yaguchi
- Shimoda Marine Research Center, University of Tsukuba, 5-10-1 Shimoda, Shizuoka 415-0025, Japan
- Japanese Association for Marine Biology (JAMBIO)
| | - Junko Yaguchi
- Shimoda Marine Research Center, University of Tsukuba, 5-10-1 Shimoda, Shizuoka 415-0025, Japan
- JSPS
| | - Kazuo Inaba
- Shimoda Marine Research Center, University of Tsukuba, 5-10-1 Shimoda, Shizuoka 415-0025, Japan
- Japanese Association for Marine Biology (JAMBIO)
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20
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Nishida H, Stach T. Cell Lineages and Fate Maps in Tunicates: Conservation and Modification. Zoolog Sci 2014; 31:645-52. [DOI: 10.2108/zs140117] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Thomas Stach
- lnstitute of Biology, Comparative Zoology, Humboldt-Unlversity Berlin, 10115 Berlin, Germany
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21
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Moorhouse KS, Burgess DR. How to be at the right place at the right time: the importance of spindle positioning in embryos. Mol Reprod Dev 2014; 81:884-95. [PMID: 25258000 DOI: 10.1002/mrd.22418] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 08/26/2014] [Indexed: 01/03/2023]
Abstract
Spindle positioning is an imperative cellular process that regulates a number of different developmental events throughout embryogenesis. The spindle must be properly positioned in embryos not only for the segregation of chromosomes, but also to segregate developmental determinants into different daughter blastomeres. In this review, the role of spindle positioning is explored in several different developmental model systems, which have revealed the diversity of factors that regulate spindle positioning. The C. elegans embryo, the Drosophila neuroblast, and ascidian embryos have all been utilized for the study of polarity-dependent spindle positioning, and exploration of the proteins that are required for asymmetric cell division. Work in the sea urchin embryo has examined the influence of cell shape and factors that affect secondary furrow formation. The issue of size scaling in extremely large cells, as well as the requirement for spindle positioning in developmental fate decisions in vertebrates, has been addressed by work in the Xenopus embryo. Further work in mouse oocytes has examined the roles of actin and myosin in spindle positioning. The data generated from these model organisms have made unique contributions to our knowledge of spindle positioning. Future work will address how all of these different factors work together to regulate the position of the spindle.
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Hashimoto N, Kurita Y, Murakami K, Wada H. Cleavage pattern and development of isolated D blastomeres in bivalves. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2014; 324:13-21. [PMID: 25059484 DOI: 10.1002/jez.b.22585] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 04/21/2014] [Accepted: 06/03/2014] [Indexed: 12/30/2022]
Abstract
Although bivalves develop through spiral cleavage patterns, similar to other lophotrochozoans, the cleavage pattern of D lineage blastomeres is unique, since 2d shows four rounds of stereotypic unequal cleavage before bilateral cleavage of the largest derivative of 2d: 2d(1121) . This unique modification of spiral cleavage is directly associated with the characteristic morphology of bivalves, namely, bilaterally separated shell plates, because the bilateral shell plates are thought to be derived from the bilateral derivatives of 2d(1121) . In this report, to determine whether the unique cleavage pattern of bivalves is regulated depending on the interaction with other cells or by cell autonomous mechanisms, we performed cell isolation experiments and observed subsequent cleavage patterns of isolated blastomeres. When focusing on the largest derivatives of D blastomeres, 8% of isolated D blastomeres followed the cleavage pattern of normal development up to bilateral cleavage. Importantly, the remainder of the partial embryos ended cleavage before that stage, and none of the isolated blastomeres showed abnormal cleavage patterns. We also examined the development of isolated blastomeres and found that isolated D blastomeres could develop shell plates, whereas larvae developed from AB blastomeres never had shell plates. Based on these observations, we concluded that D blastomeres control their unique cleavage pattern through intrinsic mechanisms and develop shell glands autonomously without any cell-cell interaction with other lineages.
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Affiliation(s)
- Naoki Hashimoto
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
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Ishii H, Shirai T, Makino C, Nishikata T. Mitochondrial inhibitor sodium azide inhibits the reorganization of mitochondria-rich cytoplasm and the establishment of the anteroposterior axis in ascidian embryo. Dev Growth Differ 2014; 56:175-88. [DOI: 10.1111/dgd.12117] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 12/04/2013] [Accepted: 12/04/2013] [Indexed: 11/30/2022]
Affiliation(s)
- Hirokazu Ishii
- Frontiers of Innovative Research in Science and Technology (FIRST); Konan University; Kobe Hyogo 650-0047 Japan
| | - Takuma Shirai
- Frontiers of Innovative Research in Science and Technology (FIRST); Konan University; Kobe Hyogo 650-0047 Japan
| | - Chisato Makino
- Frontiers of Innovative Research in Science and Technology (FIRST); Konan University; Kobe Hyogo 650-0047 Japan
| | - Takahito Nishikata
- Frontiers of Innovative Research in Science and Technology (FIRST); Konan University; Kobe Hyogo 650-0047 Japan
- Frontier Institute for Biomolecular Engineering Research (FIBER); Konan University; Kobe Hyogo 650-0047 Japan
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Ogura Y, Sasakura Y. Ascidians as excellent models for studying cellular events in the chordate body plan. THE BIOLOGICAL BULLETIN 2013; 224:227-236. [PMID: 23995746 DOI: 10.1086/bblv224n3p227] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The larvae of non-vertebrate chordate ascidians consist of countable numbers of cells. With this feature, ascidians provide us with excellent models for studying cellular events in the construction of the chordate body. This review discusses the recent observations of morphogenetic movements and cell cycles and divisions along with tissue specifications during ascidian embryogenesis. Unequal cleavages take place at the posterior blastomeres during the early cleavage stages of ascidians, and the structure named the centrosome-attracting body restricts the position of the nuclei near the posterior pole to achieve the unequal cleavages. The most-posterior cells differentiate into the primordial germ cells. The gastrulation of ascidians starts as early as the 110-cell stage. During gastrulation, the endodermal cells show two-step changes in cell shape that are crucial for gastrulation. The ascidian notochord is composed of only 40 cells. The 40 cells align to form a single row by an event named the convergent extension, and then the notochord cells undergo vacuolation to transform the notochord into a single hollowed tube. The strictly restricted number of notochord cells is achieved by the regulated number of cell divisions coupled with the differentiation of the cells conducted by a key transcription factor, Brachyury. The dorsally located neural tube is a characteristic of chordates. During the closure of the ascidian neural tube, the epidermis surrounding the neural plate moves toward the midline to close the neural fold. This morphogenetic movement is allowed by an elongation of interphase in the epidermal cell cycles.
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Affiliation(s)
- Yosuke Ogura
- Shimoda Marine Research Center, University of Tsukuba, Shizuoka, Japan
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Ishii H, Kunihiro S, Tanaka M, Hatano K, Nishikata T. Cytosolic subunits of ATP synthase are localized to the cortical endoplasmic reticulum-rich domain of the ascidian egg myoplasm. Dev Growth Differ 2013; 54:753-66. [PMID: 23067137 DOI: 10.1111/dgd.12003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Previously, we revealed that p58, one of the ascidian maternal factors, is identical to the alpha-subunit of F1-ATP synthase (ATPα), a protein complex of the inner mitochondrial membrane. In the current study, we used immunological probes for ascidian mitochondria components to show that the ascidian ATPα is ectopically localized to the cytosol. Virtually all mitochondrial components were localized to the mitochondria-rich myoplasm. However, in detail, ATP synthase subunits and the matrix proteins showed different localization patterns. At least at the crescent stage, transmission electron microscopy (TEM) distinguished the mitochondria-less, endoplasmic reticulum (ER)-rich cortical region and the mitochondria-rich internal region. ATPα was enriched in the cortical region and MnSOD was limited to the internal region. Using subcellular fractionation, although all of the mitochondria components were highly enriched in the mitochondria-enriched fraction, a considerable amount of ATPα and F1-ATP synthase beta-subunit (ATPβ) were recovered in the insoluble cytoplasmic fraction. Even under these conditions, F1-ATP synthase gamma-subunit (ATPγ) and F0-ATP synthase subunit b (ATPb) were not recovered in the insoluble cytoplasmic fraction. This result strongly supports the exomitochondrial localization of both ATPα and ATPβ. In addition, the detergent extraction of eggs supports the idea that these cytosolic ATP synthase subunits are associated with the egg cytoskeleton. These results suggest that the subunits of ATP synthase might play dual roles at different subcellular compartments during early development.
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Affiliation(s)
- Hirokazu Ishii
- Frontiers of Innovative Research in Science and Technology (FIRST), Konan University, Kobe, Hyogo, 650-0047, Japan.
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Makabe KW, Nishida H. Cytoplasmic localization and reorganization in ascidian eggs: role of postplasmic/PEM RNAs in axis formation and fate determination. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 1:501-18. [PMID: 23801532 DOI: 10.1002/wdev.54] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Localization of maternal molecules in eggs and embryos and cytoplasmic movements to relocalize them are fundamental for the orderly cellular and genetic processes during early embryogenesis. Ascidian embryos have been known as 'mosaic eggs' because of their autonomous differentiation abilities based on localized cell fate determinants. This review gives a historical overview of the concept of cytoplasmic localization, and then explains the key features such as ooplasmic movements and cell lineages that are essential to grasp the process of ascidian development mediated by localized determinant activities. These activities are partly executed by localized molecules named postplasmic/PEM RNAs, originating from approximately 50 genes, of which the muscle determinant, macho-1, is an example. The cortical domain containing these RNAs is relocalized to the posterior-vegetal region of the egg by cytoskeletal movements after fertilization, and plays crucial roles in axis formation and cell fate determination. The cortical domain contains endoplasmic reticulum and characteristic granules, and gives rise to a subcellular structure called the centrosome-attracting body (CAB), in which postplasmic/PEM RNAs are highly concentrated. The CAB is responsible for a series of unequal partitionings of the posterior-vegetal cytoplasmic domain and the postplasmic/PEM RNAs at the posterior pole during cleavage. Some components of this domain, which is rich in granules, are eventually inherited by prospective germline cells with particular postplasmic/PEM RNAs such as vasa. The postplasmic/PEM RNAs are classified into two groups according to their final cellular destinations and localization pathways. Localization of these RNAs is regulated by specific nucleotide sequences in the 3' untranslated regions (3'UTRs).
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Affiliation(s)
- Kazuhiro W Makabe
- Institute of Socio-Arts and Sciences, University of Tokushima, Tokushima, Japan
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Cell-Cycle Control in Oocytes and During Early Embryonic Cleavage Cycles in Ascidians. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 297:235-64. [DOI: 10.1016/b978-0-12-394308-8.00006-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Abstract
The localization of mRNAs in developing animal cells is essential for establishing cellular polarity and setting up the body plan for subsequent development. Cellular and molecular mechanisms by which maternal mRNAs are localized during oogenesis have been extensively studied in Drosophila and Xenopus. In contrast, evidence for mechanisms used in the localization of mRNAs encoded by developmentally important genes has also been accumulating in several other organisms. This offers the opportunity to unravel the fundamental mechanisms of mRNA localization shared among many species, as well as unique mechanisms specifically acquired or retained by animals based on their developmental needs. In addition to maternal mRNAs, the localization of zygotically expressed mRNAs in the cells of cleaving embryos is also important for early development. In this review, mRNA localization dynamics in the oocytes/eggs of Drosophila and Xenopus are first summarized, and evidence for localized mRNAs in the oocytes/eggs and cleaving embryos of other organisms is then presented.
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Affiliation(s)
- Gaku Kumano
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
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Schulze J, Schierenberg E. Evolution of embryonic development in nematodes. EvoDevo 2011; 2:18. [PMID: 21929824 PMCID: PMC3195109 DOI: 10.1186/2041-9139-2-18] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 09/20/2011] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Nematodes can be subdivided into basal Enoplea (clades 1 and 2) and more derived Chromadorea (clades 3 to 12). Embryogenesis of Caenorhabditis elegans (clade 9) has been analyzed in most detail. Their establishment of polarity and asymmetric cleavage requires the differential localization of PAR proteins. Earlier studies on selected other nematodes revealed that embryonic development of nematodes is more diverse than the essentially invariant development of C. elegans and the classic study object Ascaris had suggested. To obtain a more detailed picture of variations and evolutionary trends we compared embryonic cell lineages and pattern formation in embryos of all 12 nematode clades. METHODS The study was conducted using 4-D microscopy and 3-D modeling of developing embryos. RESULTS We found dramatic differences compared to C. elegans in Enoplea but also considerable variations among Chromadorea. We discovered 'Polarity Organizing Centers' (POCs) that orient cleavage spindles along the anterior-posterior axis in distinct cells over consecutive cell generations. The resulting lineally arranged blastomeres represent a starting point for the establishment of bilateral symmetry within individual lineages. We can discern six different early cleavage types and suggest that these variations are due to modifications in the activity of the POCs in conjunction with changes in the distribution of PAR proteins. In addition, our studies indicate that lineage complexity advanced considerably during evolution, that is we observe trends towards an increase of somatic founder cells, from monoclonal to polyclonal lineages and from a variable (position-dependent) to an invariable (lineage-dependent) way of cell fate specification. In contrast to the early phase of embryogenesis, the second half ('morphogenesis') appears similar in all studied nematodes. Comparison of early cleavage between the basal nematode Tobrilus stefanskii and the tardigrade Hypsibius dujardini revealed surprising similarities indicating that the presence of POCs is not restricted to nematode embryos. CONCLUSIONS The pattern of cleavage, spatial arrangement and differentiation of cells diverged dramatically during the history of the phylum Nematoda without corresponding changes in the phenotype. While in all studied representatives the same distinctive developmental steps need to be taken, cell behavior leading to these is not conserved.
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Affiliation(s)
- Jens Schulze
- University of Cologne, Biocenter, Zuelpicher Str. 47b 50967 Köln, Germany
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Shirae-Kurabayashi M, Matsuda K, Nakamura A. Ci-Pem-1 localizes to the nucleus and represses somatic gene transcription in the germline of Ciona intestinalis embryos. Development 2011; 138:2871-81. [PMID: 21693510 DOI: 10.1242/dev.058131] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
In many animal embryos, germ-cell formation depends on maternal factors located in the germ plasm. To ensure the development of germ cells, germline progenitors must be prevented from differentiating inappropriately into somatic cells. A common mechanism for this appears to be the active repression of somatic gene transcription. Species-specific germ-plasm components, such as Pgc in Drosophila and PIE-1 in C. elegans, establish germline transcriptional quiescence by inhibiting general transcriptional machineries. In the ascidian Ciona intestinalis, although transcriptional repression in the germline has been proposed, the factors and mechanisms involved have been unknown. We found that the protein products of Ci-pem-1 RNA, which is an ascidian-specific component of the postplasm (the germ plasm equivalent in ascidians), localized to the nucleus of germline blastomeres, as well as to the postplasm. Morpholino oligonucleotide-mediated Ci-pem-1 knockdown resulted in the ectopic expression of several somatic genes that are usually silent in the germline. In the Ci-pem-1 knockdown embryos, the expression of both β-catenin- and GATAa-dependent genes was derepressed in the germline blastomeres, suggesting that Ci-Pem-1 broadly represses germline mRNA transcription. Immunoprecipitation assays showed that Ci-Pem-1 could interact with two C. intestinalis homologs of Groucho, which is a general co-repressor of mRNA transcription. These results suggest that Ci-pem-1 is the C. intestinalis version of a germ-plasm RNA whose protein product represses the transcription of somatic genes during specification of the germ-cell fate, and that this repression may be operated through interactions between Ci-Pem-1 and Groucho co-repressors.
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Affiliation(s)
- Maki Shirae-Kurabayashi
- Laboratory for Germline Development, RIKEN Center for Developmental Biology, Kobe, Hyogo, Japan.
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Paix A, Le Nguyen PN, Sardet C. Bi-polarized translation of ascidian maternal mRNA determinant pem-1 associated with regulators of the translation machinery on cortical Endoplasmic Reticulum (cER). Dev Biol 2011; 357:211-26. [PMID: 21723275 DOI: 10.1016/j.ydbio.2011.06.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 06/10/2011] [Accepted: 06/16/2011] [Indexed: 01/07/2023]
Abstract
Polarized cortical mRNA determinants such as maternal macho-1 and pem-1 in ascidians, like budding yeast mating factor ASH1 reside on the cER-mRNA domain a subdomain of cortical Endoplasmic Reticulum(ER) and are translated in its vicinity. Using high resolution imaging and isolated cortical fragments prepared from eggs and embryos we now find that macho-1 and pem-1 RNAs co-localize with phospho-protein regulators of translation initiation (MnK/4EBP/S6K). Translation of cortical pem-1 RNA follows its bi-polarized relocalization. About 10 min after fertilization or artificial activation with a calcium ionophore, PEM1 protein is detected in the vegetal cortex in the vicinity of pem-1 RNA. About 40 min after fertilization-when pem-1 RNA and P-MnK move to the posterior pole-PEM1 protein remains in place forming a network of cortical patches anchored at the level of the zygote plasma membrane before disappearing. Cortical PEM1 protein is detected again at the 4 cell stage in the posterior centrosome attracting body (CAB) region where the cER-mRNA domain harboring pem-1/P-MnK/P-4EBP/P-S6K is concentrated. Bi-polarized PEM1 protein signals are not detected when pem-1 morpholinos are injected into eggs or zygotes or when MnK is inhibited. We propose that localized translation of the pem-1 RNA determinant is triggered by the fertilization/calcium wave and that the process is controlled by phospho-protein regulators of translation initiation co-localized with the RNA determinant on a sub-domain of the cortical Endoplasmic Reticulum.
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Affiliation(s)
- Alexandre Paix
- Université Pierre et Marie Curie and Centre National de la Recherche Scientifique, BioMarCell, UMR BioDev, Observatoire Océanologique, Villefranche-sur-mer, France
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Negishi T, Kumano G, Nishida H. Polo-like kinase 1 is required for localization of Posterior End Mark protein to the centrosome-attracting body and unequal cleavages in ascidian embryos. Dev Growth Differ 2011; 53:76-87. [PMID: 21261613 DOI: 10.1111/j.1440-169x.2010.01231.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In ascidian embryos, the posterior-localized maternal factor Posterior End Mark (PEM) is responsible for patterning embryos along the anterior-posterior axis with regard to both cleavage pattern involving unequal cell divisions and gene expression. Although PEM plays important roles in embryogenesis, its mechanism of action is still unclear because PEM has no known functional domain. In the present study, we explored the candidate of PEM partner proteins in Halocynthia roretzi using yeast two-hybrid screening. We isolated a homologue of Polo-like kinase 1 (Plk1), a key regulator of cell division and highly conserved in eukaryotes, as the first potential binding partner of PEM. We biochemically confirmed that interaction occurred between the Plk1 and PEM proteins. Immunostaining showed that Plk1 protein concentrates in the centrosome-attracting body (CAB) at the posterior pole, where PEM protein is also localized. The CAB is a subcellular structure that plays an important role in generating the posterior cleavage pattern. Plk1 localization to the CAB was dependent on the cell cycle phases during unequal cleavage. Inhibition of Plk1 with specific drugs resulted in failure of the nucleus to migrate towards the posterior pole and formation of a microtubule bundle between the CAB and a centrosome, similarly to inhibition of PEM function, suggesting that both proteins are involved in the same process of unequal cleavages. This interrupted nuclear migration was rescued by overexpression of PEM. In Plk1-inhibited embryos, the localization of PEM protein to the CAB was impaired, indicating that Plk1 is required for appropriate localization of PEM.
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Affiliation(s)
- Takefumi Negishi
- Department of Biological Sciences, Osaka University, Toyonaka, Japan.
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McDougall A, Chenevert J, Lee KW, Hebras C, Dumollard R. Cell cycle in ascidian eggs and embryos. Results Probl Cell Differ 2011; 53:153-169. [PMID: 21630145 DOI: 10.1007/978-3-642-19065-0_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In ascidians the cell cycle machinery has been studied mainly in oocytes while ascidian embryos have been used to dissect the mechanism that controls asymmetric cell division (ACD). Here we overview the most specific and often exceptional points and events in cell cycle control in ascidian oocytes and early embryos. Mature stage IV eggs are arrested at metaphase I due to cytostatic factor (CSF). In vertebrates, unfertilized eggs are arrested at metaphase II by CSF. Meta II-CSF is mediated by the Mos/MEK/MAPK/Erp1 pathway, which inhibits the ubiquitin ligase APC/C(cdc20) preventing cyclin B destruction thus stabilizing MPF activity. CSF is inactivated by the fertilization Ca(2+) transient that stimulates the destruction of Erp1 thus releasing APC/C(cdc20) from inhibition. Although many of the components of CSF are conserved between the ascidian and the vertebrates, the lack of Erp1 in the ascidians (and indeed other invertebrates) is notable since the Mos/MAPK pathway nonetheless mediates Meta I-CSF. Moreover, since the fertilization Ca(2+) transient targets Erp1, it is not clear how the sperm-triggered Ca(2+) transient in ascidians (and again other invertebrates) stimulates cyclin B destruction in the absence of Erp1. Nonetheless, like mammalian eggs, sperm trigger a series of Ca(2+) oscillations that increases the rate of cyclin B destruction and the subsequent loss of MAPK activity leading to meiotic exit in ascidians. Positive feedback from MPF maintains the Ca(2+) oscillations in fertilized ascidian eggs ensuring the eventual loss of MPF stimulating the egg-to-embryo transition. Embryonic cell cycles in the ascidian are highly stereotyped where both the rate of cell division and the orientation of cell division planes are precisely controlled. Three successive rounds of ACD generate two small posterior germ cell precursors at the 64 cell stage. The centrosome-attracting body (CAB) is a macroscopic cortical structure visible by light microscopy that causes these three rounds of ACD. Entry into mitosis activates the CAB causing the whole mitotic spindle to rotate and migrate toward the cortical CAB leading to a highly ACD whereby one small cell is formed that inherits the CAB and approximately 40 maternal postplasmic/PEM RNAs including the germ cell marker vasa.
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Affiliation(s)
- Alex McDougall
- Developmental Biology Unit UMR 7009, UMPC Univ. Paris 06 and Center National de la Recherche (CNRS), Observatoire Océanologique, 06230 Villefranche-sur-Mer, France.
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Parton RM, Davis I. How the sea squirt nucleus tells mesoderm not to be endoderm. Dev Cell 2010; 19:487-8. [PMID: 20951340 PMCID: PMC3232446 DOI: 10.1016/j.devcel.2010.10.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Sea squirts are simple invertebrate chordates. In this issue of Developmental Cell, Takatori et al. show nuclear migration within ascidian mesendodermal cells enables polarized localization of Not mRNA, which encodes a homeobox protein that distinguishes mesoderm from endoderm fates. The link between nuclear migration and mRNA localization suggests exciting parallels with protostomes.
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Affiliation(s)
- Richard M. Parton
- Department of Biochemistry The University Oxford South Parks Road Oxford OX1 3QU United Kingdom
| | - Ilan Davis
- Department of Biochemistry The University Oxford South Parks Road Oxford OX1 3QU United Kingdom
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Prodon F, Chenevert J, Hébras C, Dumollard R, Faure E, Gonzalez-Garcia J, Nishida H, Sardet C, McDougall A. Dual mechanism controls asymmetric spindle position in ascidian germ cell precursors. Development 2010; 137:2011-21. [DOI: 10.1242/dev.047845] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Mitotic spindle orientation with respect to cortical polarity cues generates molecularly distinct daughter cells during asymmetric cell division (ACD). However, during ACD it remains unknown how the orientation of the mitotic spindle is regulated by cortical polarity cues until furrowing begins. In ascidians, the cortical centrosome-attracting body (CAB) generates three successive unequal cleavages and the asymmetric segregation of 40 localized postplasmic/PEM RNAs in germ cell precursors from the 8-64 cell stage. By combining fast 4D confocal fluorescence imaging with gene-silencing and classical blastomere isolation experiments, we show that spindle repositioning mechanisms are active from prometaphase until anaphase, when furrowing is initiated in B5.2 cells. We show that the vegetal-most spindle pole/centrosome is attracted towards the CAB during prometaphase, causing the spindle to position asymmetrically near the cortex. Next, during anaphase, the opposite spindle pole/centrosome is attracted towards the border with neighbouring B5.1 blastomeres, causing the spindle to rotate (10°/minute) and migrate (3 μm/minute). Dynamic 4D fluorescence imaging of filamentous actin and plasma membrane shows that precise orientation of the cleavage furrow is determined by this second phase of rotational spindle displacement. Furthermore, in pairs of isolated B5.2 blastomeres, the second phase of rotational spindle displacement was lost. Finally, knockdown of PEM1, a protein localized in the CAB and required for unequal cleavage in B5.2 cells, completely randomizes spindle orientation. Together these data show that two separate mechanisms active during mitosis are responsible for spindle positioning, leading to precise orientation of the cleavage furrow during ACD in the cells that give rise to the germ lineage in ascidians.
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Affiliation(s)
- François Prodon
- Developmental Biology Unit UMR 7009, UPMC (University of Paris 06) and Centre National de la Recherche (CNRS), Observatoire Océanologique, 06230 Villefranche-sur-Mer, France
| | - Janet Chenevert
- Developmental Biology Unit UMR 7009, UPMC (University of Paris 06) and Centre National de la Recherche (CNRS), Observatoire Océanologique, 06230 Villefranche-sur-Mer, France
| | - Céline Hébras
- Developmental Biology Unit UMR 7009, UPMC (University of Paris 06) and Centre National de la Recherche (CNRS), Observatoire Océanologique, 06230 Villefranche-sur-Mer, France
| | - Rémi Dumollard
- Developmental Biology Unit UMR 7009, UPMC (University of Paris 06) and Centre National de la Recherche (CNRS), Observatoire Océanologique, 06230 Villefranche-sur-Mer, France
| | - Emmanuel Faure
- ISCPIF-CREA, Ecole Polytechnique–CNRS, 75015 Paris, France
| | - Jose Gonzalez-Garcia
- Department of Obstetrics and Gynaecology, School of Medicine, Cardiff University, Heath Park, Cardiff CF14 4XN, UK
| | - Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Christian Sardet
- Developmental Biology Unit UMR 7009, UPMC (University of Paris 06) and Centre National de la Recherche (CNRS), Observatoire Océanologique, 06230 Villefranche-sur-Mer, France
| | - Alex McDougall
- Developmental Biology Unit UMR 7009, UPMC (University of Paris 06) and Centre National de la Recherche (CNRS), Observatoire Océanologique, 06230 Villefranche-sur-Mer, France
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Kumano G, Kawai N, Nishida H. Macho-1 regulates unequal cell divisions independently of its function as a muscle determinant. Dev Biol 2010; 344:284-92. [PMID: 20478299 DOI: 10.1016/j.ydbio.2010.05.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 03/30/2010] [Accepted: 05/08/2010] [Indexed: 02/05/2023]
Abstract
The anterior-posterior (A-P) axis in ascidian embryos is established through the posteriorizing activities of a localized egg region known as the posterior vegetal cortex/cytoplasm (PVC). Here we describe a novel function of macho-1, a maternally-localized muscle determinant, in establishment of the A-P axis in the Halocynthia roretzi embryo. Macho-1, in addition to its known function in the formation of posterior tissue such as muscle and mesenchyme, and suppression of the anterior-derived notochord fate, acts independently of its transcriptional activity as a regulator of posterior-specific unequal cell divisions, in cooperation with beta-catenin. Our results suggest that macho-1 and beta-catenin regulate the formation of a microtubule bundle that shortens and pulls the centrosome toward a sub-cellular cortical structure known as centrosome-attracting body (CAB), which is located at the posterior pole of the embryo during unequal cell divisions, and act upstream of PEM, a recently-identified regulator of unequal cell divisions. We also present data that suggest that PEM localization to the CAB may not be required for unequal cleavage regulation. The present study provides an important and novel insight into the role of the zinc-finger-containing transcription factor and indicates that it constitutes a major part of the PVC activity.
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Affiliation(s)
- Gaku Kumano
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
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37
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Świątek P, Kubrakiewicz J, Klag J. Formation of germ-line cysts with a central cytoplasmic core is accompanied by specific orientation of mitotic spindles and partitioning of existing intercellular bridges. Cell Tissue Res 2009; 337:137-48. [DOI: 10.1007/s00441-009-0788-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 02/23/2009] [Indexed: 01/04/2023]
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Actin microfilaments guide the polarized transport of nuclear pore complexes and the cytoplasmic dispersal of Vasa mRNA during GVBD in the ascidian Halocynthia roretzi. Dev Biol 2009; 330:377-88. [PMID: 19362546 DOI: 10.1016/j.ydbio.2009.04.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Revised: 03/30/2009] [Accepted: 04/03/2009] [Indexed: 12/16/2022]
Abstract
Meiosis reinitiation starts with the germinal vesicle breakdown (GVBD) within the gonad before spawning. Here, we have extended our previous observations and identified the formation of conspicuous actin bundles emanating from the germinal vesicle (GV) during its breakdown in the ascidian Halocynthia roretzi. Time-lapse video recordings and fluorescent labelling of microfilaments (MFs) indicate that these microfilamentous structures invariantly elongate towards the vegetal hemisphere at the estimated speed of 20 mum/min. Interestingly, the nuclear pore complex protein Nup153 accumulates at the vegetal tip of actin bundles. To determine if these structures play a role in the formation of the germ plasm, we have analyzed the localization pattern of Vasa transcript in maturing oocytes and early embryos. We found that Hr-Vasa mRNA, one of Type II postplasmic/PEM mRNAs, changes from a granular and perinuclear localization to an apparent uniform cytoplasmic distribution during oocyte maturation, and then concentrate in the centrosome-attracting body (CAB) by the eight-cell stage. In addition, treatments with Latrunculin B, but not with Nocodazole, blocked the redistribution of Nup153 and Hr-Vasa mRNA, suggesting that these mechanisms are both actin-dependant. We discuss the pleiotropic role played by MFs, and the relationship between nuclear pores, maternal Vasa mRNA and germ plasm in maturing ascidian oocytes.
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Sunanaga T, Saito Y, Kawamura K. Postembryonic epigenesis of Vasa-positive germ cells from aggregated hemoblasts in the colonial ascidian, Botryllus primigenus. Dev Growth Differ 2009; 48:87-100. [PMID: 16512853 DOI: 10.1111/j.1440-169x.2006.00849.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We investigated whether Vasa was a germline-specific marker in the colonial ascidian Botryllus primigenus, and whether it was inducible epigenetically in the adult life span. We cloned a Botryllus Vasa homologue (BpVas). The deduced open reading frame encoded 687 amino acid residues. It was expressed specifically by germline cells such as the loose cell mass, oogonia and juvenile oocytes in the ovary, and the primordial testis (compact cell mass), spermatogonia and juvenile spermatocytes in the testis. The loose cell mass, the most primitive germline cells, showed an ultrastructure of undifferentiated cells known as hemoblasts. The hemoblasts did not contain electron-dense materials or a mitochondrial assembly in the cytoplasm. These organelles appeared later in the oogonia and oocytes. When the loose cell mass and developing germ cells were eliminated by extirpating all zooids and buds from the colonies, BpVas transcripts disappeared completely from the vascularized colonies. After 14 days, when the colonies regenerated by vascular budding, BpVas-positive cells reappeared in some cases, and in 30 day colonies, BpVas-positive germ cells were observed in all the regenerated colonies. These results show that in B. primigenus, germ cells are inducible de novo from the Vasa-negative cells even at postembryonic stages.
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Affiliation(s)
- Takeshi Sunanaga
- Laboratory of Cellular and Molecular Biotechnology, Faculty of Science, Kochi University, Kochi 780-8520, Japan.
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Nomura M, Nakajima A, Inaba K. Proteomic profiles of embryonic development in the ascidian Ciona intestinalis. Dev Biol 2009; 325:468-81. [DOI: 10.1016/j.ydbio.2008.10.038] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2008] [Revised: 10/24/2008] [Accepted: 10/28/2008] [Indexed: 12/24/2022]
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Nishida H. Development of the appendicularian Oikopleura dioica: Culture, genome, and cell lineages. Dev Growth Differ 2008; 50 Suppl 1:S239-56. [PMID: 18494706 DOI: 10.1111/j.1440-169x.2008.01035.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Hiroki Nishida
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
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42
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Fujii S, Nishio T, Nishida H. Cleavage pattern, gastrulation, and neurulation in the appendicularian, Oikopleura dioica. Dev Genes Evol 2008; 218:69-79. [PMID: 18236068 DOI: 10.1007/s00427-008-0205-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Accepted: 01/08/2008] [Indexed: 10/22/2022]
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Schulze J, Schierenberg E. Cellular pattern formation, establishment of polarity and segregation of colored cytoplasm in embryos of the nematode Romanomermis culicivorax. Dev Biol 2008; 315:426-36. [PMID: 18275948 DOI: 10.1016/j.ydbio.2007.12.043] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2007] [Revised: 12/17/2007] [Accepted: 12/31/2007] [Indexed: 01/04/2023]
Abstract
We have begun to analyze the early embryogenesis of Romanomermis culicivorax, an insect-parasitic nematode phylogenetically distant to Caenorhabditis elegans. Development of R. culicivorax differs from C. elegans in many aspects including establishment of polarity, formation of embryonic axes and the pattern of asymmetric cleavages. Here, a polarity reversal in the germline takes place already in P(1) rather than P(2), the dorsal-ventral axis appears to be inverted and gut fate is derived from the AB rather than from the EMS blastomere. So far unique for nematodes is the presence of colored cytoplasm and its segregation into one specific founder cell. Normal development observed after experimentally induced abnormal partitioning of pigment indicates that it is not involved in cell specification. Another typical feature is prominent midbodies (MB). We investigated the role of the MB region in the establishment of asymmetry. After its irradiation the potential for unequal cleavage in somatic and germline cells as well as differential distribution of pigment are lost. This indicates a crucial involvement of this region for spindle orientation, positioning, and cytoplasmic segregation. A scenario is sketched suggesting why and how during evolution the observed differences between R. culicivorax and C. elegans may have evolved.
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Affiliation(s)
- Jens Schulze
- Zoological Institute, University of Cologne, Germany
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Prodon F, Yamada L, Shirae-Kurabayashi M, Nakamura Y, Sasakura Y. Postplasmic/PEM RNAs: a class of localized maternal mRNAs with multiple roles in cell polarity and development in ascidian embryos. Dev Dyn 2007; 236:1698-715. [PMID: 17366574 DOI: 10.1002/dvdy.21109] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Ascidian is a good model to understand the cellular and molecular mechanisms responsible for mRNA localization with the discovery of a large family of localized maternal mRNAs, called postplasmic/PEM RNAs, which includes more than 40 members in three different ascidian species (Halocynthia roretzi, Ciona intestinalis, and C. savignyi). Among these mRNAs, two types (Type I and Type II) have been identified and show two different localization patterns from fertilization to the eight-cell stage. At the eight-cell stage, both types concentrate to a macromolecular cortical structure called CAB (for Centrosome Attracting Body) in the posterior-vegetal B4.1 blastomeres. The CAB is responsible for unequal cleavages and the partitioning of postplasmic/PEM RNAs at the posterior pole of embryos during cleavage stages. It has also been suggested that the CAB region could contain putative germ granules. In this review, we discuss recent data obtained on the distribution of Type I postplasmic/PEM RNAs from oogenesis to late development, in relation to their localization and translational control. We have first regrouped localization patterns for Type I and Type II into a comparative diagram and included all important definitions in the field. We also have made an exhaustive classification of their embryonic expression profiles (Type I or Type II), and analyzed their functions after knockdown and/or overexpression experiments and the role of the 3'-untranslated region (3'UTR) controlling both their localization and translation. Finally, we propose a speculative model integrating recent data, and we also discuss the relationship between postplasmic/PEM RNAs, posterior specification, and germ cell formation in ascidians.
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Affiliation(s)
- François Prodon
- Department of Biology, Graduate School of Science, Osaka University, Osaka, Japan.
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Hotta K, Mitsuhara K, Takahashi H, Inaba K, Oka K, Gojobori T, Ikeo K. A web-based interactive developmental table for the ascidian Ciona intestinalis, including 3D real-image embryo reconstructions: I. From fertilized egg to hatching larva. Dev Dyn 2007; 236:1790-805. [PMID: 17557317 DOI: 10.1002/dvdy.21188] [Citation(s) in RCA: 174] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The ascidian chordate Ciona intestinalis is an established model organism frequently exploited to examine cellular development and a rapidly emerging model organism with a strong potential for developmental systems biology studies. However, there is no standardized developmental table for this organism. In this study, we made the standard web-based image resource called FABA: Four-dimensional Ascidian Body Atlas including ascidian's three-dimensional (3D) and cross-sectional images through the developmental time course. These images were reconstructed from more than 3,000 high-resolution real images collected by confocal laser scanning microscopy (CLSM) at newly defined 26 distinct developmental stages (stages 1-26) from fertilized egg to hatching larva, which were grouped into six periods named the zygote, cleavage, gastrula, neurula, tailbud, and larva periods. Our data set will be helpful in standardizing developmental stages for morphology comparison as well as for providing the guideline for several functional studies of a body plan in chordate.
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Affiliation(s)
- Kohji Hotta
- Department of Bioscience and Informatics, Faculty of Science and Technology, Keio University, Yokohama, Japan.
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Negishi T, Takada T, Kawai N, Nishida H. Localized PEM mRNA and protein are involved in cleavage-plane orientation and unequal cell divisions in ascidians. Curr Biol 2007; 17:1014-25. [PMID: 17570671 DOI: 10.1016/j.cub.2007.05.047] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2007] [Revised: 05/17/2007] [Accepted: 05/17/2007] [Indexed: 01/01/2023]
Abstract
BACKGROUND Orientation and positioning of the cell division plane are essential for generation of invariant cleavage patterns and for unequal cell divisions during development. Precise control of the division plane is important for appropriate partitioning of localized factors, spatial arrangement of cells for proper intercellular interactions, and size control of daughter cells. Ascidian embryos show complex but invariant cleavage patterns mainly due to three rounds of unequal cleavage at the posterior pole. RESULTS The ascidian embryo is an emerging model for studies of developmental and cellular processes. The maternal Posterior End Mark (PEM) mRNA is localized within the egg and embryo to the posterior region. PEM is a novel protein that has no known domain. Immunostaining showed that the protein is also present in the posterior cortex and the in centrosome-attracting body (CAB) and that the localization is extraction-resistant. Here we show that PEM of Halocynthia roretzi is required for correct orientation of early-cleavage planes and subsequent unequal cell divisions because it repeatedly pulls a centrosome toward the posterior cortex and the CAB, respectively, where PEM mRNA and protein are localized. When PEM activity is suppressed, formation of the microtubule bundle linking the centrosome and the posterior cortex did not occur. PEM possibly plays a role in anchoring microtubule ends to the cortex. In our model of orientation of the early-cleavage planes, we also amend the allocation of the conventional animal-vegetal axis in ascidian embryos, and discuss how the newly proposed A-V axis provides the rationale for various developmental events and the fate map of this animal. CONCLUSIONS The complex cleavage pattern in ascidian embryos can be explained by a simple rule of centrosome attraction mediated by localized PEM activity. PEM is the first gene identified in ascidians that is required for multiple spindle-positioning events.
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Affiliation(s)
- Takefumi Negishi
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
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47
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Abstract
To divide asymmetrically, a cell must position the mitotic spindle relative to localized cell fate determinants. Recent work in the early ascidian embryo reveals the function of a single factor that coordinates this act to control cleavage pattern and cell fate determination.
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Affiliation(s)
- Edwin Munro
- Center for Cell Dynamics, Friday Harbor Laboratories, University of Washington, 620 University Road, Friday Harbor, Washington 98250, USA.
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48
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Kawai N, Iida Y, Kumano G, Nishida H. Nuclear accumulation of β-catenin and transcription of downstream genes are regulated by zygotic Wnt5α and maternal Dsh in ascidian embryos. Dev Dyn 2007; 236:1570-82. [PMID: 17474118 DOI: 10.1002/dvdy.21169] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Nuclear beta-catenin plays crucial roles in the establishment of the embryonic axis and formation of mesendoderm tissues in ascidians and other animals. However, the cue responsible for nuclear accumulation of beta-catenin in the vegetal hemisphere is still unknown in ascidians. Here, we investigated the roles of Wnt5alpha and Dsh in the nuclear accumulation of beta-catenin and activation of its downstream genes in the ascidian Halocynthia roretzi. Wnt5alpha knockdown embryos lost nuclear accumulation of beta-catenin at the 64-cell stage but not at the 32-cell stage, and expression of Hr-lim, one of the targets of beta-catenin, was impaired in the anterior region of the embryo. Zygotic Wnt5alpha expression in the anterior-vegetal blastomeres was primarily responsible for these defects. Dsh knockdown showed no effect on nuclear localization of beta-catenin, but inhibited Hr-lim expression in the posterior region. These results suggest that maintenance of nuclear Hr-beta-catenin after the 64-cell stage is regulated by zygotic Hr-Wnt5alpha, and that expression of its target genes is modulated by both Hr-Wnt5alpha and Hr-Dsh. Our results also highlight the importance of nuclear accumulation of beta-catenin up to the 32-cell stage through a still unclarified mechanism.
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Affiliation(s)
- Narudo Kawai
- Department of Biological Sciences, Graduate School of Sciences, Osaka University, Osaka, Japan.
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Sardet C, Paix A, Prodon F, Dru P, Chenevert J. From oocyte to 16-cell stage: Cytoplasmic and cortical reorganizations that pattern the ascidian embryo. Dev Dyn 2007; 236:1716-31. [PMID: 17420986 DOI: 10.1002/dvdy.21136] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The dorsoventral and anteroposterior axes of the ascidian embryo are defined before first cleavage by means of a series of reorganizations that reposition cytoplasmic and cortical domains established during oogenesis. These domains situated in the periphery of the oocyte contain developmental determinants and a population of maternal postplasmic/PEM RNAs. One of these RNAs (macho-1) is a determinant for the muscle cells of the tadpole embryo. Oocytes acquire a primary animal-vegetal (a-v) axis during meiotic maturation, when a subcortical mitochondria-rich domain (myoplasm) and a domain rich in cortical endoplasmic reticulum (cER) and maternal postplasmic/PEM RNAs (cER-mRNA domain) become polarized and asymmetrically enriched in the vegetal hemisphere. Fertilization at metaphase of meiosis I initiates a series of dramatic cytoplasmic and cortical reorganizations of the zygote, which occur in two major phases. The first major phase depends on sperm entry which triggers a calcium wave leading in turn to an actomyosin-driven contraction wave. The contraction concentrates the cER-mRNA domain and myoplasm in and around a vegetal/contraction pole. The precise localization of the vegetal/contraction pole depends on both the a-v axis and the location of sperm entry and prefigures the future site of gastrulation and dorsal side of the embryo. The second major phase of reorganization occurs between meiosis completion and first cleavage. Sperm aster microtubules and then cortical microfilaments cause the cER-mRNA domain and myoplasm to reposition toward the posterior of the zygote. The location of the posterior pole depends on the localization of the sperm centrosome/aster attained during the first major phase of reorganization. Both cER-mRNA and myoplasm domains localized in the posterior region are partitioned equally between the first two blastomeres and then asymmetrically over the next two cleavages. At the eight-cell stage the cER-mRNA domain compacts and gives rise to a macroscopic cortical structure called the Centrosome Attracting Body (CAB). The CAB is responsible for a series of unequal divisions in posterior-vegetal blastomeres, and the postplasmic/PEM RNAs it contains are involved in patterning the posterior region of the embryo. In this review, we discuss these multiple events and phases of reorganizations in detail and their relationship to physiological, cell cycle, and cytoskeletal events. We also examine the role of the reorganizations in localizing determinants, postplasmic/PEM RNAs, and PAR polarity proteins in the cortex. Finally, we summarize some of the remaining questions concerning polarization of the ascidian embryo and provide comparisons to a few other species. A large collection of films illustrating the reorganizations can be consulted by clicking on "Film archive: ascidian eggs and embryos" at http://biodev.obs-vlfr.fr/recherche/biomarcell/.
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Affiliation(s)
- Christian Sardet
- BioMarCell group, UMR 7009 Biodev CNRS/ Université Pierre et Marie Curie (Paris VI), Observatoire Océanologique, Villefranche-sur-Mer, France.
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Inaba K, Nomura M, Nakajima A, Hozumi A. Functional proteomics inCiona intestinalis: A breakthrough in the exploration of the molecular and cellular mechanism of ascidian development. Dev Dyn 2007; 236:1782-9. [PMID: 17373714 DOI: 10.1002/dvdy.21121] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Ascidians have been providing a unique experimental system for a variety of fields, including reproductive biology, developmental biology, neurobiology, immunology, and evolutional biology. Recent progress in the genome sequencing of Ciona intestinalis has led to the development of a great tool for investigating the gene functions and expressions involved in several biological events in ascidians. The disclosure of genomic information has ushered in the postgenomic era, spearheaded by extensive protein analysis. The characterization of the function, localization, and molecular interaction of cellular proteins results in a more direct description of the molecular mechanism underlying several biological processes. Proteomics in ascidians, however, has just recently appeared and is not well established yet. In this study, we give an outline of the technical processes used in proteomics and review the recent status of ascidian proteomics.
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Affiliation(s)
- Kazuo Inaba
- Shimoda Marine Research Center, University of Tsukuba, Shizuoka, Japan.
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