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Zeitschriftenartikel zum Thema „Ascidian embryo“

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Veröffentlicht am 25. Mai 2024

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1

Cone, Angela C., und Robert W. Zeller. „Using ascidian embryos to study the evolution of developmental gene regulatory networks“. Canadian Journal of Zoology 83, Nr. 1 (01.01.2005): 75–89. http://dx.doi.org/10.1139/z04-165.

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Ascidians are ideally positioned taxonomically at the base of the chordate tree to provide a point of comparison for developmental regulatory mechanisms that operate among protostomes, non-chordate deuterostomes, invertebrate chordates, and vertebrates. In this review, we propose a model for the gene regulatory network that gives rise to the ascidian notochord. The purpose of this model is not to clarify all of the interactions between molecules of this network, but to provide a working schematic of the regulatory architecture that leads to the specification of endoderm and the patterning of mesoderm in ascidian embryos. We describe a series of approaches, both computational and biological, that are currently being used, or are in development, for the study of ascidian embryo gene regulatory networks. It is our belief that the tools now available to ascidian biologists, in combination with a streamlined mode of development and small genome size, will allow for more rapid dissection of developmental gene regulatory networks than in more complex organisms such as vertebrates. It is our hope that the analysis of gene regulatory networks in ascidians can provide a basic template which will allow developmental biologists to superimpose the modifications and novelties that have arisen during deuterostome evolution.

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Wilding, Martin, Marcella Marino und Daniela Dale. „Nicotinamide alters the calcium release pattern and the degradation of MPF activity after fertilisation in ascidian oocytes“. Zygote 7, Nr. 3 (August 1999): 255–60. http://dx.doi.org/10.1017/s0967199499000647.

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Fertilisation in ascidian oocytes triggers a plasma membrane current, the release of intracellular calcium and the degradation of Maturation Promoting Factor (MPF) activity leading to the completion of meiosis and the initiation of embryo development. We have previously shown that the fertilisation current in ascidians is produced through the metabolism of nicotinamide nucleotide (NN) metabolites to ADP ribose. In this study we have used nicotinamide to test whether NN metabolism plays additional roles in fertilisation in ascidians. Nicotinamide treatment blocked calcium-induced calcium release (CICR) and arrested the cell cycle prior to the completion of meiosis I. Nicotinamide further prevented the abolition of MPF activity after fertilisation. Interestingly, nicotinamide treatment caused ascidian oocytes to form interphase-like pronuclei after fertilisation, despite the high MPF activity. The data demonstrate that NN metabolism is involved in calcium signalling through CICR and further suggest that a NN metabolite acts as a messenger connecting MPF activity to the formation of the meiotic apparatus.

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Yoshida, S., Y. Marikawa und N. Satoh. „Posterior end mark, a novel maternal gene encoding a localized factor in the ascidian embryo“. Development 122, Nr. 7 (01.07.1996): 2005–12. http://dx.doi.org/10.1242/dev.122.7.2005.

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Ascidian embryogenesis is regarded as a typical ‘mosaic’ type. Recent studies have provided convincing evidence that components of the posterior-vegetal cytoplasm of fertilized eggs are responsible for establishment of the anteroposterior axis of the embryo. We report here isolation and characterization of a novel maternal gene, posterior end mark (pem). After fertilization, the pem transcript is concentrated in the posterior-vegetal cytoplasm of the egg and later marks the posterior end of developing ascidian embryos. Despite its conspicuous localization pattern, the predicted PEM protein shows no significant homology to known proteins. Overexpression of this gene by microinjection of synthesized pem mRNA into fertilized eggs results in development of tadpole larvae with deficiency of the anteriormost adhesive organ, dorsal brain and sensory pigment-cells. Lineage tracing analysis revealed that the anterior epidermis and dorsal neuronal cells were translocated posteriorly into the tail region, suggesting that this gene plays a role in establishment of anterior and dorsal patterning of the embryo. The ascidian tadpole is regarded as a prototype of vertebrates, implying a similar function of pem in vertebrate embryogenesis.

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Bettoni, Rossana, Clare Hudson, Géraldine Williaume, Cathy Sirour, Hitoyoshi Yasuo, Sophie de Buyl und Geneviève Dupont. „Model of neural induction in the ascidian embryo“. PLOS Computational Biology 19, Nr. 2 (03.02.2023): e1010335. http://dx.doi.org/10.1371/journal.pcbi.1010335.

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How cell specification can be controlled in a reproducible manner is a fundamental question in developmental biology. In ascidians, a group of invertebrate chordates, geometry plays a key role in achieving this control. Here, we use mathematical modeling to demonstrate that geometry dictates the neural-epidermal cell fate choice in the 32-cell stage ascidian embryo by a two-step process involving first the modulation of ERK signaling and second, the expression of the neural marker gene, Otx. The model describes signal transduction by the ERK pathway that is stimulated by FGF and attenuated by ephrin, and ERK-mediated control of Otx gene expression, which involves both an activator and a repressor of ETS-family transcription factors. Considering the measured area of cell surface contacts with FGF- or ephrin-expressing cells as inputs, the solutions of the model reproduce the experimental observations about ERK activation and Otx expression in the different cells under normal and perturbed conditions. Sensitivity analyses and computations of Hill coefficients allow us to quantify the robustness of the specification mechanism controlled by cell surface area and to identify the respective role played by each signaling input. Simulations also predict in which conditions the dual control of gene expression by an activator and a repressor that are both under the control of ERK can induce a robust ON/OFF control of neural fate induction.

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5

Mita-Miyazawa, I., T. Nishikata und N. Satoh. „Cell- and tissue-specific monoclonal antibodies in eggs and embryos of the ascidian Halocynthia roretzi“. Development 99, Nr. 2 (01.02.1987): 155–62. http://dx.doi.org/10.1242/dev.99.2.155.

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To obtain specific immunological probes for studying molecular mechanisms involved in the early embryonic development of ascidians, we have produced monoclonal antibodies directed against a homogenate of larvae of the ascidian Halocynthia roretzi. Among these, we have screened monoclonal antibodies that specifically recognize cells and/or tissues of the embryo. Characterization of six epidermis-specific monoclonal antibodies (including larval tunic-specific and larval fin-specific), three muscle-specific antibodies, two endoderm-specific antibodies, one notochord-specific antibody and two monoclonal antibodies that specifically recognize trunk-lateral cells suggests that these monoclonal antibodies may be useful as markers for analysing molecular mechanisms involved in specification of these cells. Seven monoclonal antibodies characteristically stain intercellular materials of the developing embryo and may therefore be valid for studying cellular construction of the embryo. Furthermore, monoclonal antibodies that recognize components of follicle cells, perivitelline space and sperm have also been established.

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6

Munro, Edwin M., und Garrett M. Odell. „Polarized basolateral cell motility underlies invagination and convergent extension of the ascidian notochord“. Development 129, Nr. 1 (01.01.2002): 13–24. http://dx.doi.org/10.1242/dev.129.1.13.

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We use 3D time-lapse analysis of living embryos and laser scanning confocal reconstructions of fixed, staged, whole-mounted embryos to describe three-dimensional patterns of cell motility, cell shape change, cell rearrangement and tissue deformation that accompany formation of the ascidian notochord. We show that notochord formation involves two simultaneous processes occurring within an initially monolayer epithelial plate: The first is invagination of the notochord plate about the axial midline to form a solid cylindrical rod. The second is mediolaterally directed intercalation of cells within the plane of the epithelial plate, and then later about the circumference of the cylindrical rod, that accompanies its extension along the anterior/posterior (AP) axis. We provide evidence that these shape changes and rearrangements are driven by active extension of interior basolateral notochord cell edges directly across the faces of their adjacent notochord neighbors in a manner analogous to leading edge extension of lamellapodia by motile cells in culture. We show further that local edge extension is polarized with respect to both the AP axis of the embryo and the apicobasal axis of the notochord plate. Our observations suggest a novel view of how active basolateral motility could drive both invagination and convergent extension of a monolayer epithelium. They further reveal deep similarities between modes of notochord morphogenesis exhibited by ascidians and other chordate embryos, suggesting that cellular mechanisms of ascidian notochord formation may operate across the chordate phylum.

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7

Dale, B., L. Santella und E. Tosti. „Gap-junctional permeability in early and cleavage-arrested ascidian embryos“. Development 112, Nr. 1 (01.05.1991): 153–60. http://dx.doi.org/10.1242/dev.112.1.153.

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Using the whole-cell voltage clamp technique, we have studied junctional conductance (Gj), and Lucifer Yellow (LY) coupling in 2-cell and 32-cell ascidian embryos. Gj ranges from 17.5 to 35.3 nS in the 2-cell embryo where there is no passage of LY, and from 3.5 to 12.2 nS in the later embryo where LY dye spread is extensive. In both cases, Gj is independent of the transjunctional potential (Vj). Manually apposed 2-cell or 32-cell embryos established a junctional conductance of up to 10 nS within 30 min of contact. Furthermore, since we did not observe any significant number of cytoplasmic bridges at the EM and Gj is sensitive to octanol, it is probable that blastomeres in the 2-cell and 32-cell embryos are in communication by gap junctions. In order to compare Gj in the two stages and to circumvent problems of cell size, movement and spatial location, we used cytochalasin B to arrest cleavage. Gj in cleavage-arrested 2-cell embryos ranged from 25.0 to 38.0 nS and remained constant over a period of 2.5 h. LY injected into a blastomere of these arrested embryos did not spread to the neighbour cell until they attained the developmental age of a 32- to 64-cell control embryo. Our experiments indicate a change in selectivity of gap junctions at the 32-cell stage that is not reflected by a macroscopic change in ionic permeability.

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8

Makabe, Kazuhiro W., Takeshi Kawashima, Shuichi Kawashima, Takuya Minokawa, Asako Adachi, Hiroshi Kawamura, Hisayoshi Ishikawa et al. „Large-scale cDNA analysis of the maternal genetic information in the egg of Halocynthia roretzi for a gene expression catalog of ascidian development“. Development 128, Nr. 13 (01.07.2001): 2555–67. http://dx.doi.org/10.1242/dev.128.13.2555.

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The ascidian egg is a well-known mosaic egg. In order to investigate the molecular nature of the maternal genetic information stored in the egg, we have prepared cDNAs from the mRNAs in the fertilized eggs of the ascidian, Halocynthia roretzi. The cDNAs of the ascidian embryo were sequenced, and the localization of individual mRNA was examined in staged embryos by whole-mount in situ hybridization. The data obtained were stored in the database MAGEST (http://www.genome.ad.jp/magest) and further analyzed. A total of 4240 cDNA clones were found to represent 2221 gene transcripts, including at least 934 different protein-coding sequences. The mRNA population of the egg consisted of a low prevalence, high complexity sequence set. The majority of the clones were of the rare sequence class, and of these, 42% of the clones showed significant matches with known peptides, mainly consisting of proteins with housekeeping functions such as metabolism and cell division. In addition, we found cDNAs encoding components involved in different signal transduction pathways and cDNAs encoding nucleotide-binding proteins. Large-scale analyses of the distribution of the RNA corresponding to each cDNA in the eight-cell, 110-cell and early tailbud embryos were simultaneously carried out. These analyses revealed that a small fraction of the maternal RNAs were localized in the eight-cell embryo, and that 7.9% of the clones were exclusively maternal, while 40.6% of the maternal clones showed expression in the later stages. This study provides global insights about the genes expressed during early development.

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Wada, S., Y. Katsuyama und H. Saiga. „Anteroposterior patterning of the epidermis by inductive influences from the vegetal hemisphere cells in the ascidian embryo“. Development 126, Nr. 22 (15.11.1999): 4955–63. http://dx.doi.org/10.1242/dev.126.22.4955.

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Patterning along the anteroposterior axis is a critical step during animal embryogenesis. Although mechanisms of anteroposterior patterning in the neural tube have been studied in various chordates, little is known about those of the epidermis. To approach this issue, we investigated patterning mechanisms of the epidermis in the ascidian embryo. First we examined expression of homeobox genes (Hrdll-1, Hroth, HrHox-1 and Hrcad) in the epidermis. Hrdll-1 is expressed in the anterior tip of the epidermis that later forms the adhesive papillae, while Hroth is expressed in the anterior part of the trunk epidermis. HrHox-1 and Hrcad are expressed in middle and posterior parts of the epidermis, respectively. These data suggested that the epidermis of the ascidian embryo is patterned anteroposteriorly. In ascidian embryogenesis, the epidermis is exclusively derived from animal hemisphere cells. To investigate regulation of expression of the four homeobox genes in the epidermis by vegetal hemisphere cells, we next performed hemisphere isolation and cell ablation experiments. We showed that removal of the vegetal cells before the late 16-cell stage results in loss of expression of these homeobox genes in the animal hemisphere cells. Expression of Hrdll-1 and Hroth depends on contact with the anterior-vegetal (the A-line) cells, while expression of HrHox-1 and Hrcad requires contact with the posterior-vegetal (the B-line) cells. We also demonstrated that contact with the vegetal cells until the late 32-cell stage is sufficient for animal cells to express Hrdll-1, Hroth and Hrcad, while longer contact is necessary for HrHox-1 expression. Contact with the A-line cells until the late 32-cell stage is also sufficient for formation of the adhesive papillae. Our data indicate that the epidermis of the ascidian embryo is patterned along the anteroposterior axis by multiple inductive influences from the vegetal hemisphere cells and provide the first insight into mechanisms of epidermis patterning in the chordate embryos.

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10

Tosti, E. „Gap junctional units are functionally expressed before first cleavage in the early ascidian embryo“. American Journal of Physiology-Cell Physiology 272, Nr. 5 (01.05.1997): C1445—C1449. http://dx.doi.org/10.1152/ajpcell.1997.272.5.c1445.

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Manually apposed ascidian zygotes established electrical communication within 50 min of fertilization and before cytokinesis. Junctional conductance between zygotes was 14.5 +/- 2.9 nS (n = 7), similar to that previously reported for ascidian two-cell-stage blastomeres, suggesting that zygotes and blastomeres express an equivalent number of gap junctional half-channels. Because puromycin at 400 microM does not inhibit the functional expression of these half-channels, they appear to be of maternal origin and their activation does not require protein synthesis. Loading zygotes with 500 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid or exposing zygotes to 10 microM of the calcium ionophore A-23187 shows that these half-channels are regulated by intracellular calcium, consistent with the behavior of these channels in adult tissues. The results show that gap junctional units are expressed in the ascidian at the zygote stage.

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Roegiers, F., A. McDougall und C. Sardet. „The sperm entry point defines the orientation of the calcium-induced contraction wave that directs the first phase of cytoplasmic reorganization in the ascidian egg“. Development 121, Nr. 10 (01.10.1995): 3457–66. http://dx.doi.org/10.1242/dev.121.10.3457.

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Ascidians eggs are spawned with their cytoskeleton and organelles organized along a preexisting animal-vegetal axis. Fertilization triggers a spectacular microfilament-dependant cortical contraction that causes the relocalization of preexisting cytoplasmic domains and the creation of new domains in the lower part of the vegetal hemisphere. We have investigated the relationship between fertilization, the cortical contraction and the localization of cytoplasmic domains in eggs of the ascidian Phallusia mammillata. We have also examined the link between this first phase of ooplasmic segregation and the site of gastrulation. The cortical contraction was found to be initiated on the side of the egg where intracellular calcium is first released either by the entering sperm or by photolysis of caged InsP3. The cortical contraction carries the sperm nucleus towards the vegetal hemisphere along with a subcortical mitochondria-rich domain (the myoplasm). If the sperm enters close to the animal or vegetal poles the cortical contraction is symmetrical, travelling along the animal-vegetal axis. If the sperm enters closer to the equator, the contraction is asymmetrical and its direction does not coincide with the animal-vegetal axis. The direction of contraction defines an axis along which preexisting (such as the myoplasm) or newly created cytoplasmic domains are relocalized. Two microfilament-rich surface constrictions, the ‘contraction pole’ and the ‘vegetal button’ (which forms 20 minutes later), appear along that axis approximately opposite the site where the contraction is initiated. The contraction pole can be situated as much as 55 degrees from the vegetal pole, and its location predicts the site of gastrulation. It thus appears that in ascidian eggs, the organization of the egg before fertilization defines a 110 degrees cone centered around the vegetal pole in which the future site of gastrulation of the embryo will lie. The calcium wave and cortical contraction triggered by the entering sperm adjust the location of cytoplasmic domains along an axis within that permissive zone. We discuss the relation between that axis and the establishment of the dorsoventral axis in the ascidian embryo.

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Gallo, Alessandra. „Toxicity of marine pollutants on the ascidian oocyte physiology: an electrophysiological approach“. Zygote 26, Nr. 1 (13.12.2017): 14–23. http://dx.doi.org/10.1017/s0967199417000612.

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SummaryIn marine animals with external fertilization, gametes are released into seawater where fertilization and embryo development occur. Consequently, pollutants introduced into the marine environment by human activities may affect gametes and embryos. These xenobiotics can alter cell physiology with consequent reduction of fertilization success. Here the adverse effects on the reproductive processes of the marine invertebrate Ciona intestinalis (ascidian) of different xenobiotics: lead, zinc, an organic tin compound and a phenylurea herbicide were evaluated. By using the electrophysiological technique of whole-cell voltage clamping, the effects of these compounds on the mature oocyte plasma membrane electrical properties and the electrical events of fertilization were tested by calculating the concentration that induced 50% normal larval formation (EC50). The results demonstrated that sodium currents in mature oocytes were reduced in a concentration-dependent manner by all tested xenobiotics, with the lowest EC50 value for lead. In contrast, fertilization current frequencies were differently affected by zinc and organic tin compound. Toxicity tests on gametes demonstrated that sperm fertilizing capability and fertilization oocyte competence were not altered by xenobiotics, whereas fertilization was inhibited in zinc solution and underwent a reduction in organic tin compound solution (EC50 value of 1.7 µM). Furthermore, fertilized oocytes resulted in a low percentage of normal larvae with an EC50 value of 0.90 µM. This study shows that reproductive processes of ascidians are highly sensitive to xenobiotics suggesting that they may be considered a reliable biomarker and that ascidians are suitable model organisms to assess marine environmental quality.

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Serras, F., C. Baud, M. Moreau, P. Guerrier und J. A. M. Van den Biggelaar. „Intercellular communication in the early embryo of the ascidian Ciona intestinalis“. Development 102, Nr. 1 (01.01.1988): 55–63. http://dx.doi.org/10.1242/dev.102.1.55.

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We have studied the intercellular communication pathways in early embryos of the ascidian Ciona intestinalis. In two different series of experiments, we injected iontophoretically the dyes Lucifer Yellow and Fluorescein Complexon, and we analysed the spread of fluorescence to the neighbouring cells. We found that before the 32-cell stage no dye spread occurs between nonsister cells, whereas sister cells are dye-coupled, possibly via cytoplasmic bridges. After the 32-cell stage, dye spread occurs throughout the embryo. However, electrophysiological experiments showed that nonsister cells are ionically coupled before the 32-cell stage. We also found that at the 4-cell stage junctional conductance between nonsister cells is voltage dependent, which suggests that conductance is mediated by gap junctions in a way similar to that observed in other embryos.

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Takahashi, H., K. Hotta, A. Erives, A. Di Gregorio, R. W. Zeller, M. Levine und N. Satoh. „Brachyury downstream notochord differentiation in the ascidian embryo“. Genes & Development 13, Nr. 12 (15.06.1999): 1519–23. http://dx.doi.org/10.1101/gad.13.12.1519.

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15

Satou, Yutaka, Nori Satoh und Kaoru S. Imai. „Gene regulatory networks in the early ascidian embryo“. Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms 1789, Nr. 4 (April 2009): 268–73. http://dx.doi.org/10.1016/j.bbagrm.2008.03.005.

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16

Tanaka-Kunishima, Motoko, Kunitaro Takahashi und Fumiyuki Watanabe. „Cell contact induces multiple types of electrical excitability from ascidian two-cell embryos that are cleavage arrested and contain all cell fate determinants“. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 293, Nr. 5 (November 2007): R1976—R1996. http://dx.doi.org/10.1152/ajpregu.00835.2006.

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Ascidian early embryonic cells undergo cell differentiation without cell cleavage, thus enabling mixture of cell fate determinants in single cells, which will not be possible in mammalian systems. Either cell in a two-cell embryo (2C cell) has multiple fates and develops into any cell types in a tadpole. To find the condition for controlled induction of a specific cell type, cleavage-arrested cell triplets were prepared in various combinations. They were 2C cells in contact with a pair of anterior neuroectoderm cells from eight-cell embryos (2C-aa triplet), with a pair of presumptive notochordal neural cells (2C-AA triplet), with a pair of presumptive posterior epidermal cells (2C-bb triplet), and with a pair of presumptive muscle cells (2C-BB triplet). The fate of the 2C cell was electrophysiologically identified. When two-cell embryos had been fertilized 3 h later than eight-cell embryos and triplets were formed, the 2C cells became either anterior-neuronal, posterior-neuronal or muscle cells, depending on the cell type of the contacting cell pair. When two-cell embryos had been fertilized earlier than eight-cell embryos, most 2C cells became epidermal. When two- and eight-cell embryos had been simultaneously fertilized, the 2C cells became any one of three cell types described above or the epidermal cell type. Differentiation of the ascidian 2C cell into major cell types was reproducibly induced by selecting the type of contacting cell pair and the developmental time difference between the contacting cell pair and 2C cell. We discuss similarities between cleavage-arrested 2C cells and vertebrate embryonic stem cells and propose the ascidian 2C cell as a simple model for toti-potent stem cells.

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Ohtsuki, Hisashi. „Statocyte and Ocellar Pigment Cell in Embryos and Larvae of the Ascidian, Styela plicata (Lesueur). (statocyte/ocellus/ascidian/embryo/larva)“. Development, Growth and Differentiation 32, Nr. 1 (Februar 1990): 85–90. http://dx.doi.org/10.1111/j.1440-169x.1990.00085.x.

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YOSHIDA, Shoko, und Noriyuki SATOH. „Mechanisms of muscle cell differentiation in the ascidian embryo.“ Seibutsu Butsuri 36, Nr. 3 (1996): 129–33. http://dx.doi.org/10.2142/biophys.36.129.

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19

Okamura, Yasushi, Haruo Okado und Kunitaro Takahashi. „The ascidian embryo as a prototype of vertebrate neurogenesis“. BioEssays 15, Nr. 11 (November 1993): 723–30. http://dx.doi.org/10.1002/bies.950151105.

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Ueki, Tatsuya, Kazuhiro W. Makabe und Noriyuki Satoh. „Isolation of cDNA Clones for Epidermis-Specific Genes of the Ascidian Embryo. (ascidian embryos/epidermal cells/specific gene expression/cDNA probes)“. Development, Growth and Differentiation 33, Nr. 6 (Dezember 1991): 579–86. http://dx.doi.org/10.1111/j.1440-169x.1991.00579.x.

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21

Meedel, T. H., R. J. Crowther und J. R. Whittaker. „Determinative properties of muscle lineages in ascidian embryos“. Development 100, Nr. 2 (01.06.1987): 245–60. http://dx.doi.org/10.1242/dev.100.2.245.

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Blastomeres removed from early cleavage stage ascidian embryos and reared to ‘maturity’ as partial embryos often elaborate tissue-specific features typical of their constituent cell lineages. We used this property to study recent corrections of the ascidian larval muscle lineage and to compare the ways in which different lineages give rise to muscle. Our evaluation of muscle differentiation was based on histochemical localization and quantitative radiometric measurement of a muscle-specific acetylcholinesterase activity, and the development of myofilaments and myofibrils as observed by electron microscopy. Although the posterior-vegetal blastomeres (B4.1 pair) of the 8-cell embryo have long been believed to be the sole precursors of larval muscle, recent studies using horseradish peroxidase to mark cell lineages have shown that small numbers of muscle cells originate from the anterior-vegetal (A4.1) and posterior-animal (b4.2) blastomeres of this stage. Fully differentiated muscle expression in isolated partial embryos of A4.1-derived cells requires an association with cells from other lineages whereas muscle from B4.1 blastomeres develops autonomously. Clear differences also occurred in the time acetylcholinesterase activity was first detected in partial embryos from these two sources. Isolated b4.2 cells failed to show any muscle development even in combination with anterior-animal cells (a4.2) and are presumably even more dependent on normal cell interactions and associations. Others have noted an additional distinction between the different sources of muscle: muscle cells from non-B4.1 lineages occur exclusively in the distal part of the tail, while the B4.1 descendants contribute those cells in the proximal and middle regions. During the course of ascidian larval evolution tail muscle probably had two origins: the primary lineage (B4.1) whose fate was set rigidly at early cleavage stages and secondarily evolved lineages which arose later by recruitment of cells from other tissues resulting in increased tail length. In contrast to the B4.1 lineage, muscle development in the secondary lineages is controlled less rigidly by processes that depend on cell interactions.

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NISHIKATA, TAKAHITO, IZUMI MITA-MIYAZAWA und NORIYUKI SATOH. „Differentiation Expression in Blastomeres of Cleavage-Arrested Embryos of the Ascidian Halocynthia roretzi. (differentiation without cleavage/monoclonal antibodies/exclusive differentiation/ascidian embryo)“. Development, Growth and Differentiation 30, Nr. 4 (August 1988): 371–81. http://dx.doi.org/10.1111/j.1440-169x.1988.00371.x.

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23

Stewart-Savage, J., Aimee Phillippi und Philip O. Yund. „Delayed Insemination Results in Embryo Mortality in a Brooding Ascidian“. Biological Bulletin 201, Nr. 1 (August 2001): 52–58. http://dx.doi.org/10.2307/1543525.

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24

Oda-Ishii, Izumi, und Yutaka Satou. „Initiation of the zygotic genetic program in the ascidian embryo“. Seminars in Cell & Developmental Biology 84 (Dezember 2018): 111–17. http://dx.doi.org/10.1016/j.semcdb.2018.02.012.

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25

NISHIDA, HIROKI. „Cell Division Pattern during Gastrulation of the Ascidian, Halocynthia roretzi. (cell division pattern/gastrulation/neurulation/ascidian embryo)“. Development, Growth and Differentiation 28, Nr. 2 (April 1986): 191–201. http://dx.doi.org/10.1111/j.1440-169x.1986.00191.x.

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26

Darras, Sébastien, und Hiroki Nishida. „The BMP signaling pathway is required together with the FGF pathway for notochord induction in the ascidian embryo“. Development 128, Nr. 14 (15.07.2001): 2629–38. http://dx.doi.org/10.1242/dev.128.14.2629.

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The 40 notochord cells of the ascidian tadpole invariably arise from two different lineages: the primary (A-line) and the secondary (B-line) lineages. It has been shown that the primary notochord cells are induced by presumptive endoderm blastomeres between the 24-cell and the 64-cell stage. Signaling through the fibroblast growth factor (FGF) pathway is required for this induction. We have investigated the role of the bone morphogenetic protein (BMP) pathway in ascidian notochord formation. HrBMPb (the ascidian BMP2/4 homologue) is expressed in the anterior endoderm at the 44-cell stage before the completion of notochord induction. The BMP antagonist Hrchordin is expressed in a complementary manner in all surrounding blastomeres and appears to be a positive target of the BMP pathway. Unexpectedly, chordin overexpression reduced formation of both primary and secondary notochord. Conversely, primary notochord precursors isolated prior to induction formed notochord in presence of BMP-4 protein. While bFGF protein had a similar activity, notochord precursors showed a different time window of competence to respond to BMP-4 and bFGF. Our data are consistent with bFGF acting from the 24-cell stage, while BMP-4 acts during the 44-cell stage. However, active FGF signaling was also required for induction by BMP-4. In the secondary lineage, notochord specification also required two inducing signals: an FGF signal from anterior and posterior endoderm from the 24-cell stage and a BMP signal from anterior endoderm during the 44-cell stage.

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Nishida, H. „Regionality of egg cytoplasm that promotes muscle differentiation in embryo of the ascidian, Halocynthia roretzi“. Development 116, Nr. 3 (01.11.1992): 521–29. http://dx.doi.org/10.1242/dev.116.3.521.

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Development of ascidians occurs in typical mosaic fashion: blastomeres isolated from early embryos differentiate into tissues according to their normal fates, an indication that cytoplasmic determinants exist in early blastomeres. To provide direct evidence for such cytoplasmic determinants, we have devised methods for fusing blastomeres and cytoplasmic fragments from various regions. (1) Presumptive-epidermis blastomeres were fused to cytoplasmic fragments from various regions of blastomeres of 8-cell embryos of Halocynthia roretzi and development of muscle cells was monitored by an antibody to ascidian myosin. Muscle differentiation was observed only when presumptive-epidermis blastomeres were fused with fragments from the posterior region of B4.1 (posterior-vegetal) blastomeres, the normal progenitor of muscle cells. The results indicate that muscle determinants are present and localized in the cytoplasm that enters muscle-lineage cells. (2) To investigate the presence and localization of muscle determinants in the egg, cytoplasmic fragments from various regions of unfertilized and fertilized eggs were fused with the presumptive- epidermis blastomeres, and formation of muscle cells was assessed by monitoring myosin, actin and acetylcholinesterase expression. These proteins were expressed only when cytoplasm from a restricted region of the eggs, i.e. the vegetal region, after the first phase of ooplasmic segregation, and posterior region, after the second phase of segregation, were fused. Based on these experiments, it is suggested that muscle determinants are segregated by ooplasmic movements after fertilization. They move initially to the vegetal pole of the egg and, prior to first cleavage, to the posterior region from whence future muscle-lineage blastomeres are formed. The inferred movements of muscle determinants correspond to those of the myoplasm, a microscopically visible portion of the egg cytoplasm.

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Nishikata, T., I. Mita-Miyazawa, T. Deno und N. Satoh. „Muscle cell differentiation in ascidian embryos analysed with a tissue-specific monoclonal antibody“. Development 99, Nr. 2 (01.02.1987): 163–71. http://dx.doi.org/10.1242/dev.99.2.163.

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Utilizing a muscle-specific monoclonal antibody (Mu-2) as a probe, we analysed developmental mechanisms involved in muscle cell differentiation in ascidian embryos. The antigen recognized by Mu-2 was a single polypeptide with a relative molecular mass of about 220 X 10(3). It first appeared at the early tailbud stage and continued to be expressed until the swimming larva stage. There were distinct and separate puromycin and actinomycin D sensitivity periods during the occurrence of the antigen, suggesting the new synthesis of the polypeptide by developing muscle cells. Embryos that had been permanently arrested with aphidicolin in the early cleavage stages up to the 32-cell stage did not express the antigen. DNA replications may be required for the antigen expression. Embryos that had been arrested with cytochalasin B in the 8-cell and later stages developed the antigen, and the number and position of the arrested blastomeres exhibiting the differentiation marker almost corresponded to those of the B4.1-line muscle lineage. Furthermore, in quarter embryos developed from each blastomere pair isolated from the 8-cell embryo, all the B4.1 as well as a part of b4.2 partial embryos expressed the antigen, while the a4.2 and A4.1 partial embryos did not show the antigen expression. These results may provide further support for the existence of cytoplasmic determinants for muscle cell differentiation in this mosaic egg.

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Jeffery, William R. „A model for ascidian development and developmental modifications during evolution“. Journal of the Marine Biological Association of the United Kingdom 74, Nr. 1 (Februar 1994): 35–48. http://dx.doi.org/10.1017/s0025315400035645.

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Ascidian development is reviewed and a model is presented for specification of the larval body plan and cell fate during embryogenesis. The model involves the combined activity of determinants inherited from the egg and inductive cell interactions in the embryo. It is suggested that there are four determinant systems in the egg which are segregated to different blastomeres during cleavage. The ectodermal, endodermal, and muscle determinants specify cell fate autonomously, while the axial determinants initiate cell-shape changes at gastrulation and generate a cascade of inductive activities establishing the larval body plan. In the proposed signalling cascade, the endoderm induces notochord by generating a planar inductive signal late during the cleavage phase, and the notochord cells in turn induce the nervous system by generating a vertical inductive signal in the overlying ectoderm during gastrulation. Ultraviolet (UV) irradiation experiments are described which suggest that axial and muscle determinants exhibit UV-sensitive components resembling nucleic acids and proteins, respectively. The model is evaluated in terms of developmental changes during the evolutionary transition from indirect to direct development. This transition can be explained according to the model by loss or inactivation of the muscle determinants and modification of the inductive activities generated by the axial determinants. These changes are supported by recent studies of embryogenesis in direct-developing ascidians.

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Ueno, Naoto, und Takefumi Negishi. „A novel membrane invagination controls oriented cell division in ascidian embryo“. Mechanisms of Development 145 (Juli 2017): S4—S5. http://dx.doi.org/10.1016/j.mod.2017.04.527.

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31

Ueki, Tatsuya, Shoko Yoshida, Yusuke Marikawa und Noriyuki Satoh. „Autonomy of Expression of Epidermis-Specific Genes in the Ascidian Embryo“. Developmental Biology 164, Nr. 1 (Juli 1994): 207–18. http://dx.doi.org/10.1006/dbio.1994.1192.

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32

Ichbiah, Sacha, Fabrice Delbary, Alex McDougall, Rémi Dumollard und Hervé Turlier. „Embryo mechanics cartography: inference of 3D force atlases from fluorescence microscopy“. Nature Methods 20, Nr. 12 (Dezember 2023): 1989–99. http://dx.doi.org/10.1038/s41592-023-02084-7.

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AbstractTissue morphogenesis results from a tight interplay between gene expression, biochemical signaling and mechanics. Although sequencing methods allow the generation of cell-resolved spatiotemporal maps of gene expression, creating similar maps of cell mechanics in three-dimensional (3D) developing tissues has remained a real challenge. Exploiting the foam-like arrangement of cells, we propose a robust end-to-end computational method called ‘foambryo’ to infer spatiotemporal atlases of cellular forces from fluorescence microscopy images of cell membranes. Our method generates precise 3D meshes of cells’ geometry and successively predicts relative cell surface tensions and pressures. We validate it with 3D foam simulations, study its noise sensitivity and prove its biological relevance in mouse, ascidian and worm embryos. 3D force inference allows us to recover mechanical features identified previously, but also predicts new ones, unveiling potential new insights on the spatiotemporal regulation of cell mechanics in developing embryos. Our code is freely available and paves the way for unraveling the unknown mechanochemical feedbacks that control embryo and tissue morphogenesis.

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Jeffery, William R. „A gastrulation center in the ascidian egg“. Development 116, Supplement (01.04.1992): 53–63. http://dx.doi.org/10.1242/dev.116.supplement.53.

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A gastrulation center is described in ascidian eggs. Extensive cytoplasmic rearrangements occur in ascidian eggs between fertilization and first cleavage. During ooplasmic segregation, a specific cytoskeletal domain (the myoplasm) is translocated first to the vegetal pole (VP) and then to the posterior region of the zygote. A few hours later, gastrulation is initiated by invagination of endoderm cells in the VP region of the 110-cell embryo. After the completion of gastrulation, the embryonic axis is formed, which includes induction of the nervous system, morphogenesis of the larval tail and differentiation of tail muscle cells. Microsurgical deletion or ultraviolet (UV) irradiation of the VP region during the first phase of myoplasmic segregation prevents gastrulation, nervous system induction and tail formation, without affecting muscle cell differentiation. Similar manipulations of unfertilized eggs or uncleaved zygotes after the second phase of segregation have no effect on development, suggesting that a gastrulation center is established by transient localization of myoplasm in the VP region. The function of the gastrulation center was investigated by comparing protein synthesis in normal and UV-irradiated embryos. About 5% of 433 labelled polypeptides detected in 2D gels were affected by UV irradiation. The most prominent protein is a 30 kDa cytoskeletal component (p30), whose synthesis is abolished by UV irradiation. p30 synthesis peaks during gastrulation, is affected by the same UV dose and has the same UV-sensitivity period as gastrulation. However, p30 is not a UV-sensitive target because it is absent during ooplasmic segregation, the UV-sensitivity period. Moreover, the UV target has the absorption maximum of a nucleic acid rather than a protein. Cell-free translation studies indicate that p30 is encoded by a maternal mRNA. UV irradiation inhibits the ability of this transcript to direct p30 synthesis, indicating that p30 mRNA is a UV-sensitive target The gastrulation center may function by sequestration or activation of maternal mRNAs encoding proteins that function during embryogenesis.

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Nishida, H. „Determinative mechanisms in secondary muscle lineages of ascidian embryos: development of muscle-specific features in isolated muscle progenitor cells“. Development 108, Nr. 4 (01.04.1990): 559–68. http://dx.doi.org/10.1242/dev.108.4.559.

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Muscle cells of the ascidian larva originate from three different lines of progenitor cells, the B-line, A-line and b-line. Experiments with 8-cell embryos have indicated that isolated blastomeres of the B-line (primary) muscle lineage show autonomous development of a muscle-specific enzyme, whereas blastomeres of the A-line and b-line (secondary) muscle lineage rarely develop the enzyme in isolation. In order to study the mechanisms by which different lines of progenitors are determined to give rise to muscle, blastomeres were isolated from embryos of Halocynthia roretzi at the later cleavage stages when conspicuous restriction of the developmental fate of blastomeres had already occurred. Partial embryos derived from B-line muscle-lineage cells of the 64-cell embryo (B7.4, B7.5 and B7.8) showed autonomous expression of specific features of muscle cells (acetylcholinesterase, filamentous actin and muscle-specific antigen). In contrast, b-line muscle-lineage cells, even those isolated from the 110-cell embryo (b8.17 and b8.19), did not express any muscle-specific features, even though their developmental fate was mainly restricted to generation of muscle. Isolated A-line cells from the 64-cell embryos (A7.8) did not show any features of muscle differentiation, whereas some isolated A-line cells from the 110-cell embryos (A8.16) developed all three above-mentioned features of muscle cells. This transition was shown to occur during the eighth cell cycle. These results suggest that the mechanism involved in the process of determination of the secondary-lineage muscle cells differs from that of the primary-lineage muscle cells. Interaction with cells of other lineages may be required for the determination of secondary precursors to muscle cells. The presumptive b-line and A-line muscle cells that failed to express muscle-specific features in isolation did not develop into epidermal cells. Thus, although interactions between cells may be required for muscle determination in secondary lineages, the process may represent a permissive type of induction and may differ from the processes of induction of mesoderm in amphibian embryos.

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Kim, Gil Jung, und Hiroki Nishida. „Role of the FGF and MEK signaling pathway in the ascidian embryo“. Development, Growth and Differentiation 43, Nr. 5 (Oktober 2001): 521–33. http://dx.doi.org/10.1046/j.1440-169x.2001.00594.x.

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WHITTAKER, J. R. „Chordate Evolution and Autonomous Specification of Cell Fate: The Ascidian Embryo Model“. American Zoologist 37, Nr. 3 (Juni 1997): 237–49. http://dx.doi.org/10.1093/icb/37.3.237.

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37

Nishida, Hiroki, und Noriyuki Satoh. „Determination and regulation in the pigment cell lineage of the ascidian embryo“. Developmental Biology 132, Nr. 2 (April 1989): 355–67. http://dx.doi.org/10.1016/0012-1606(89)90232-7.

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38

Jeffery, William R., und Billie J. Swalla. „Factors necessary for restoring an evolutionary change in an anural ascidian embryo“. Developmental Biology 153, Nr. 2 (Oktober 1992): 194–205. http://dx.doi.org/10.1016/0012-1606(92)90105-p.

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39

Jeffery, William R., und Billie J. Swalla. „An evolutionary change in the muscle lineage of an anural ascidian embryo is restored by interspecific hybridization with a urodele ascidian“. Developmental Biology 145, Nr. 2 (Juni 1991): 328–37. http://dx.doi.org/10.1016/0012-1606(91)90131-l.

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40

Minokawa, Takuya, Kasumi Yagi, Kazuhiro W. Makabe und Hiroki Nishida. „Binary specification of nerve cord and notochord cell fates in ascidian embryos“. Development 128, Nr. 11 (01.06.2001): 2007–17. http://dx.doi.org/10.1242/dev.128.11.2007.

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In the ascidian embryo, the nerve cord and notochord of the tail of tadpole larvae originate from the precursor blastomeres for both tissues in the 32-cell-stage embryo. Each fate is separated into two daughter blastomeres at the next cleavage. We have examined mechanisms that are responsible for nerve cord and notochord specification through experiments involving blastomere isolation, cell dissociation, and treatment with basic fibroblast growth factor (bFGF) and inhibitors for the mitogen-activated protein kinase (MAPK) cascade. It has been shown that inductive cell interaction at the 32-cell stage is required for notochord formation. Our results show that the nerve cord fate is determined autonomously without any cell interaction. Presumptive notochord blastomeres also assume a nerve cord fate when they are isolated before induction is completed. By contrast, not only presumptive notochord blastomeres but also presumptive nerve cord blastomeres forsake their default nerve cord fate and choose the notochord fate when they are treated with bFGF. When the FGF-Ras-MAPK signaling cascade is inhibited, both blastomeres choose the default nerve cord pathway, supporting the results of blastomere isolation. Thus, binary choice of alternative fates and asymmetric division are involved in this nerve cord/notochord fate determination system, mediated by FGF signaling.

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Whittaker, J. R. „Determination of Alkaline Phosphatase Expression in Endodermal Cell Lineages of an Ascidian Embryo“. Biological Bulletin 178, Nr. 3 (Juni 1990): 222–30. http://dx.doi.org/10.2307/1541823.

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42

Ishida, Kouichi, Tatsuya Ueki und Noriyuki Satoh. „Spatio-Temporal Expression Patterns of Eight Epidermis-Specific Genes in the Ascidian Embryo“. Zoological Science 13, Nr. 5 (Oktober 1996): 699–709. http://dx.doi.org/10.2108/zsj.13.699.

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Iwasa, Tatsuo, Sachiko Mishima, Ayako Watari, Mahito Ohkuma, Takahiro Azuma, Kazue Kanehara und Motoyuki Tsuda. „A Novel G Protein α Subunit in Embryo of the Ascidian, Halocynthia roretzi“. Zoological Science 20, Nr. 2 (Februar 2003): 141–51. http://dx.doi.org/10.2108/zsj.20.141.

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Katsuyama, You, und Hidetoshi Saiga. „Retinoic acid affects patterning along the anterior-posterior axis of the ascidian embryo“. Development, Growth and Differentiation 40, Nr. 4 (August 1998): 413–22. http://dx.doi.org/10.1046/j.1440-169x.1998.t01-2-00006.x.

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45

Imai, Kaoru S., Nori Satoh und Yutaka Satou. „Region specific gene expressions in the central nervous system of the ascidian embryo“. Mechanisms of Development 119 (Dezember 2002): S275—S277. http://dx.doi.org/10.1016/s0925-4773(03)00128-x.

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46

Ikeda, Tatsuro, und Yutaka Satou. „Differential temporal control ofFoxa.aandZic-r.bspecifies brain versus notochord fate in the ascidian embryo“. Development 144, Nr. 1 (25.11.2016): 38–43. http://dx.doi.org/10.1242/dev.142174.

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47

Nishida, Hiroki. „Developmental potential for tissue differentiation of fully dissociated cells of the ascidian embryo“. Roux's Archives of Developmental Biology 201, Nr. 2 (April 1992): 81–87. http://dx.doi.org/10.1007/bf00420418.

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48

Zaniolo, Giovanna, Paolo Burighel und Gianbruno Martinucci. „Ovulation and placentation in Botryllus schlosseri (Ascidiacea): an ultrastructural study“. Canadian Journal of Zoology 65, Nr. 5 (01.05.1987): 1181–90. http://dx.doi.org/10.1139/z87-183.

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The mode of ovulation and placentation was studied by light and electron microscopy in the ovoviviparous ascidian Botryllus schlosseri using colonies from the laboratory. The full-grown oocyte is surrounded by the outer and inner follicle cell layers, the acellular vitelline coat (chorion), and the test cells, and it is furnished with its own vesicular oviduct which is interposed between the egg and the atrial epithelium. In contrast to most ascidians, the outer follicle is thick and has an ultrastructure consistent with intense protein synthesis. At ovulation the outer follicle shows signs of involution where it contacts the oviduct. When the oviducal wall breaks and the egg moves through the oviduct, the outer follicle cells are discharged in the mantle to form a sort of corpus luteum. The egg remains hanging in the atrial chamber by means of a cuplike "placenta." The placental tissues are all of maternal origin, being derived from both the atrial and oviducal epithelia together with some of the inner follicle cells. These latter anchor to the oviducal epithelium by means of junctional spots and a filamentous cementing secretion. Our results suggest that the main role of the "placenta" is to attach the embryo to the parent, thus exposing it to the flow of seawater.

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Meedel, T. H., S. C. Farmer und J. J. Lee. „The single MyoD family gene of Ciona intestinalis encodes two differentially expressed proteins: implications for the evolution of chordate muscle gene regulation“. Development 124, Nr. 9 (01.05.1997): 1711–21. http://dx.doi.org/10.1242/dev.124.9.1711.

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A MyoD family gene was identified in the ascidian Ciona intestinalis and designated CiMDF (Ciona intestinalis Muscle Determination Factor). Expression of CiMDF was restricted to the muscle cells of the developing embryo and the body-wall muscle of adults. Northern blots showed that two differentially regulated CiMDF transcripts were expressed during development. A 1.8 kb transcript (CiMDFa) appeared first and was gradually replaced by a 2.7 kb transcript (CiMDFb). These transcripts encoded essentially identical MyoD family proteins with the exception of a 68 amino acid C-terminal sequence present in CiMDFb that was absent from CiMDFa. Although both CiMDFa and CiMDFb contained the cysteine-rich/basic-helix loop helix domain (Cys-rich/bHLH) present in all MyoD family proteins, only CiMDFb contained the region near the C terminus (Domain III) characteristic of this gene family. Genomic Southern blots showed that C. intestinalis has only one MyoD family gene, suggesting that CiMDFa and CiMDFb result from differential processing of primary transcripts. The existence of two MyoD family proteins that are differentially expressed during ascidian embryogenesis has novel parallels to vertebrate muscle development and may reflect conserved myogenic regulatory mechanisms among chordates.

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Oka, Takuya, Reiko Amikura, Satoru Kobayashi, Hiroki Yamamoto und Hiroki Nishida. „Localization of mitochondrial large ribosomal RNA in the myoplasm of the early ascidian embryo“. Development, Growth and Differentiation 41, Nr. 1 (Februar 1999): 1–8. http://dx.doi.org/10.1046/j.1440-169x.1999.00409.x.

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