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Bringmann, Henrik Philipp. "Experiments concerning the mechanism of cytokinesis in Caenorhabditis elegans embryos." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1170257008922-66010.
Full textAbstract:
In my thesis I aimed to contribute to the understanding of the mechanism of cytokinesis in C. elegans embryos. I wanted to analyze the relative contributions of different spindle parts – microtubule asters and the midzone - to cytokinesis furrow positioning. I developed a UV laser-based severing assay that allows the spatial separation of the region midway between the asters and the spindle midzone. The spindle is severed asymmetrically between one aster and the midzone. I found that the spindle provides two consecutive signals that can each position a cytokinesis furrow: microtubule asters provide a first signal, and the spindle midzone provides a second signal. The use of mutants that do not form a midzone suggested that the aster-positioned furrow is able to divide the cell alone without a spindle midzone. Analysis of cytokinesis in hypercontracile mutants suggests that the aster-positioned cytokinesis furrow and the midzone positioned furrow inhibit each other by competing for cortical contractile elements. I then wanted to identify the molecular pathway responsible for cytokinesis furrow positioning in response to the microtubule asters. To this end, I performed an RNAi screen, which identified a role for LET-99 in cytokinesis: LET-99 appeared to be required for aster-positioned cytokinesis but not midzone-positioned cytokinesis. LET-99 localizes as a cortical band that overlaps with the cytokinesis furrow. Mechanical displacement of the spindle demonstrated that the spindle positions cortical LET-99 at the site of furrow formation. The furrow localization of LET-99 depended on G proteins, and consistent with this finding, G proteins are also required for aster-positioned cytokinesis. (Anlage: Quick time movies, 466, 67 MB)
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Bringmann, Henrik Philipp. "Experiments concerning the mechanism of cytokinesis in Caenorhabditis elegans embryos." Doctoral thesis, Technische Universität Dresden, 2006. https://tud.qucosa.de/id/qucosa%3A25039.
Full textAbstract:
In my thesis I aimed to contribute to the understanding of the mechanism of cytokinesis in C. elegans embryos. I wanted to analyze the relative contributions of different spindle parts – microtubule asters and the midzone - to cytokinesis furrow positioning. I developed a UV laser-based severing assay that allows the spatial separation of the region midway between the asters and the spindle midzone. The spindle is severed asymmetrically between one aster and the midzone. I found that the spindle provides two consecutive signals that can each position a cytokinesis furrow: microtubule asters provide a first signal, and the spindle midzone provides a second signal. The use of mutants that do not form a midzone suggested that the aster-positioned furrow is able to divide the cell alone without a spindle midzone. Analysis of cytokinesis in hypercontracile mutants suggests that the aster-positioned cytokinesis furrow and the midzone positioned furrow inhibit each other by competing for cortical contractile elements. I then wanted to identify the molecular pathway responsible for cytokinesis furrow positioning in response to the microtubule asters. To this end, I performed an RNAi screen, which identified a role for LET-99 in cytokinesis: LET-99 appeared to be required for aster-positioned cytokinesis but not midzone-positioned cytokinesis. LET-99 localizes as a cortical band that overlaps with the cytokinesis furrow. Mechanical displacement of the spindle demonstrated that the spindle positions cortical LET-99 at the site of furrow formation. The furrow localization of LET-99 depended on G proteins, and consistent with this finding, G proteins are also required for aster-positioned cytokinesis. (Anlage: Quick time movies, 466, 67 MB)
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Schlaitz, Anne-Lore. "Regulation of Mitotic Spindle Assembly in Caenorhabditis elegans Embryos." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1181247079528-57268.
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The mitotic spindle is a bipolar microtubule-based structure that mediates proper cell division by segregating the genetic material and by positioning the cytokinesis cleavage plane. Spindle assembly is a complex process, involving the modulation of microtubule dynamics, microtubule focusing at spindle poles and the formation of stable microtubule attachments to chromosomes. The cellular events leading to spindle formation are highly regulated, and mitotic kinases have been implicated in many aspects of this process. However, little is known about their counteracting phosphatases. A screen for genes required for early embryonic cell divisions in C. elegans identified rsa-1 (for regulator of spindle assembly 1), a putative Protein Phosphatase 2A (PP2A) regulatory subunit whose silencing causes defects in spindle formation. Upon rsa-1(RNAi), spindle poles collapse onto each other and microtubule amounts are strongly reduced. My thesis work demonstrates that RSA-1 indeed functions as a PP2A regulatory subunit. RSA-1 associates with the PP2A enzyme and recruits it to centrosomes. The centrosome binding of PP2A furthermore requires the new protein RSA-2 as well as the core centrosomal protein SPD-5 and is based on a hierarchical protein-protein interaction pathway. When PP2A is lacking at centrosomes after rsa-1(RNAi), the centrosomal amounts of two critical mitotic effectors, the microtubule destabilizer KLP-7 and the kinetochore microtubule stabilizer TPXL-1, are altered. KLP-7 is increased, which may account for the reduction of microtubule outgrowth from centrosomes in rsa-1(RNAi) embryos. TPXL-1 is lost from centrosomes, which may explain why spindle poles collapse in the absence of RSA-1. TPXL-1 physically associates with RSA-1 and RSA-2, suggesting that it is a direct target of PP2A. In summary, this work defines the role of a novel PP2A complex in mitotic spindle assembly and suggests a model for how different microtubule re-organization steps might be coordinated during spindle formation.
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Schonegg, Stephanie. "Rho GTPase family members in establishment of polarity in C. elegans embryos." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1139490285625-55732.
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Cell polarity is required for asymmetric division, a mechanism to generate cell diversity by distributing fate determinants unequally to daughter cells. The establishment of polarity requires the evolutionarily conserved partitioning-defective (PAR) proteins as well as the actin cytoskeleton. In Caenorhabditis elegans one-cell embryos, the PAR proteins are segregated into an anterior (PAR-3, PAR-6) and a posterior (PAR-1, PAR-2) corticaldomain. The formation of PAR polarity correlates with anterior-posterior differences in the contractile activity of the cortex, known as "contractile polarity". It is thought that regulation of contractile polarity controls the establishment of PAR polarity, but detailed evidence to support this idea is lacking. To investigate how modulation of the actomyosin cytoskeleton affects polarity establishment, the acto-myosin cytoskeleton was perturbed by RNA-mediated interference (RNAi) of two Rho GTPases, CDC-42 and RHO-1. To examine how Rho GTPases are implemented in actin remodeling, it is important to analyze how their activity is controlled and how different activities affect polarity formation. The role of two putative Rho GTPase regulators, the Rho GTPase exchange factor (GEF) ECT-2 and the Rho GTPase activating protein (GAP) K09H11.3 were analyzed with respect to polarity formation. The formation of polarity was analyzed by using GFP-labeled proteins, and several different tracking methods were used to investigate the establishment of contractile and PAR polarity in more detail.This study demonstrates that both RHO-1 and CDC-42 are involved in polarity establishment in C. elegans embryos. But importantly, both act by different mechanisms. RHO-1 organizes the acto-myosin cytoskeleton into a contractile network, and therefore is essential for the formation of contractile polarity. The organization of the acto-myosin cytoskeleton is critical to ensure proper PAR protein distribution. Furthermore, a balance of RHO-1 activity by the GEF ECT-2 and the GAP K09H11.3 appears to be important for cortical contractility, for PAR protein domain size and for mutual exclusion of the PAR proteins. Although CDC-42 was shown to be a universal regulator of the actin cytoskeleton, CDC-42 acts downstream of contractile polarity. CDC-42 is required for linking PAR-6 to the cortex. In the absence of RHO-1 and ECT-2, PAR-6 and CDC-42 are not localized to the anterior cortex. This suggests that RHO-1, by organizing the actomyosin cytoskeleton into a contractile network, regulates the segregation of CDC-42 to the anterior cortex, and concomitantly PAR-6 localization. This study shows that the distribution of PAR is related to cortical activity and supports the model that the actin cytoskeleton plays an important role in polarity establishment.
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Schonegg, Stephanie. "Rho GTPase family members in establishment of polarity in C. elegans embryos." Doctoral thesis, Technische Universität Dresden, 2005. https://tud.qucosa.de/id/qucosa%3A24640.
Full textAbstract:
Cell polarity is required for asymmetric division, a mechanism to generate cell diversity by distributing fate determinants unequally to daughter cells. The establishment of polarity requires the evolutionarily conserved partitioning-defective (PAR) proteins as well as the actin cytoskeleton. In Caenorhabditis elegans one-cell embryos, the PAR proteins are segregated into an anterior (PAR-3, PAR-6) and a posterior (PAR-1, PAR-2) corticaldomain. The formation of PAR polarity correlates with anterior-posterior differences in the contractile activity of the cortex, known as "contractile polarity". It is thought that regulation of contractile polarity controls the establishment of PAR polarity, but detailed evidence to support this idea is lacking. To investigate how modulation of the actomyosin cytoskeleton affects polarity establishment, the acto-myosin cytoskeleton was perturbed by RNA-mediated interference (RNAi) of two Rho GTPases, CDC-42 and RHO-1. To examine how Rho GTPases are implemented in actin remodeling, it is important to analyze how their activity is controlled and how different activities affect polarity formation. The role of two putative Rho GTPase regulators, the Rho GTPase exchange factor (GEF) ECT-2 and the Rho GTPase activating protein (GAP) K09H11.3 were analyzed with respect to polarity formation. The formation of polarity was analyzed by using GFP-labeled proteins, and several different tracking methods were used to investigate the establishment of contractile and PAR polarity in more detail.This study demonstrates that both RHO-1 and CDC-42 are involved in polarity establishment in C. elegans embryos. But importantly, both act by different mechanisms. RHO-1 organizes the acto-myosin cytoskeleton into a contractile network, and therefore is essential for the formation of contractile polarity. The organization of the acto-myosin cytoskeleton is critical to ensure proper PAR protein distribution. Furthermore, a balance of RHO-1 activity by the GEF ECT-2 and the GAP K09H11.3 appears to be important for cortical contractility, for PAR protein domain size and for mutual exclusion of the PAR proteins. Although CDC-42 was shown to be a universal regulator of the actin cytoskeleton, CDC-42 acts downstream of contractile polarity. CDC-42 is required for linking PAR-6 to the cortex. In the absence of RHO-1 and ECT-2, PAR-6 and CDC-42 are not localized to the anterior cortex. This suggests that RHO-1, by organizing the actomyosin cytoskeleton into a contractile network, regulates the segregation of CDC-42 to the anterior cortex, and concomitantly PAR-6 localization. This study shows that the distribution of PAR is related to cortical activity and supports the model that the actin cytoskeleton plays an important role in polarity establishment.
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Tenlen, Jennifer R. "Linking PAR polarity proteins to cell fate regulation : analysis of MEX-5 localization in Caenorhabditis elegans embryos /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/5009.
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Wu, Edlyn. "MicroRNA-mediated deadenylation of natural UTRs in C. elegans embryos is prevalent and requires miRISC collaboration." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86859.
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MicroRNAs (miRNAs) are small RNAs that play a pivotal role in post-transcriptional gene regulation. These regulatory RNAs associate with the Argonaute proteins to form the miRNA-induced silencing complexes (miRISCs). In metazoans, miRISCs typically target mRNAs by imperfectly binding to complementary sites in 3' untranslated regions (3'UTRs), thereby affecting the translation of the targets, and/or reducing their stability. Despite the significant roles miRNAs play in various biological processes, the mechanistic details of how they regulate gene expression remain unclear. Using a C. elegans embryonic in vitro system, we focus on the mechanism for miRNA mode of action, and the significance of the poly(A) tail in miRNA-mediated silencing during development. We show that our miRNA luciferase reporters underwent deadenylation starting at 20 minutes of incubation of the RNA with C. elegans extract, and this process is dependent on the Argonautes involved in the miRNA pathway, ALG-1 and ALG-2. We also detect the presence of an RNA decay intermediate within two hours of target RNA-extract incubation. The appearance of this intermediate is independent of the m7GTP cap, indicating a 3'->5' decay pathway occurring in coordination or independently of miRNA-mediated deadenylation. Furthermore, we present here our screen for endogenous targets of the maternal miR-35-42 family, a miRNA family abundantly expressed in the embryo and essential for embryogenesis, via deadenylation assays. From our screen, we identified the tolloid/BMP-1 family member, toh-1, as a deadenylated target of miR-35-42. The pro-apoptotic egl-1 was also identified as a target of miR-35-42, as well as the zygotically expressed miR-58. Our findings demonstrate that more than half of the predicted natural UTRs were deadenylated in a miRNA-dependent manner. We also show that a minimum spacing is required for miRISCs to efficiently silence their targets, and we illustrate that at least two separate miRISC-binLes microARNs (miARNs) sont des petits ARNs qui jouent un rôle important dans la régulation post-transcriptionnelle des gènes. Ces ARNs régulateurs s'associent à des protéines, nommées les Argonautes, afin de former un complexe de répression induit par les miARNs (miRISCs). Chez les métazoaires, les miRISCs ciblent l'expression des gènes par une hybridation imparfaite avec la région non-codante en 3' (3'UTR) de l'ARN messager (ARNm) ciblé, ce qui a pour effet d'affecter la traduction des ARNm, et/ou de réduire leur stabilité. Malgré le fait que les miARNs jouent plusieurs rôles significatifs dans divers processus biologiques, leur mécanisme de contrôle de régulation génique demeure incompris. En utilisant un système in vitro chez les embryons de C. elegans, on se concentre sur le mécanisme d'action des miARNs et sur l'importance de la queue de poly(A) dans la répression des ARNm par le biais de miARNs pendant le développement. Nos résultats démontrent que suite à l'incubation de l'ARN avec l'extrait de C. elegans, nos gènes rapporteurs de luciférase-miARN ont commencé à être déadénylés après 20 minutes. Ce procédé est dépendant des Argonautes ALG-1 et ALG-2. On a aussi détecté la présence d'un deuxième ARN intermédiaire plus court après deux heures d'incubation de l'ARNm ciblé avec l'extrait. L'apparition de cet intermédiaire est indépendante du cap m7GTP, indiquant une voie de dégradation 3'->5'. On présente également un essai de déadénylation pour examiner les ARNm endogènes ciblés par la famille des miARNs maternelles, miR-35-42. Cette famille de miARNs est exprimée abondamment dans l'embryon et est essentielle pour l'embryogenèse. On a identifié un membre de la famille tolloid/BMP-1, toh-1, comme un ARNm ciblé et déadénylé. Le pro-apoptotique egl-1 a aussi été identifié comme un ARNm ciblé de la famille miR-35-42 ainsi que de miR-58, un miARN exprimé zygotiquement. Nos résultats démontrent$
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Redemann, Stefanie, Jacques Pecreaux, Nathan W. Goehring, Khaled Khairy, Ernst H. K. Stelzer, Anthony A. Hyman, and Jonathon Howard. "Membrane Invaginations Reveal Cortical Sites that Pull on Mitotic Spindles in One-Cell C. elegans Embryos." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-185631.
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Asymmetric positioning of the mitotic spindle in C. elegans embryos is mediated by force-generating complexes that are anchored at the plasma membrane and that pull on microtubules growing out from the spindle poles. Although asymmetric distribution of the force generators is thought to underlie asymmetric positioning of the spindle, the number and location of the force generators has not been well defined. In particular, it has not been possible to visualize individual force generating events at the cortex. We discovered that perturbation of the acto-myosin cortex leads to the formation of long membrane invaginations that are pulled from the plasma membrane toward the spindle poles. Several lines of evidence show that the invaginations, which also occur in unperturbed embryos though at lower frequency, are pulled by the same force generators responsible for spindle positioning. Thus, the invaginations serve as a tool to localize the sites of force generation at the cortex and allow us to estimate a lower limit on the number of cortical force generators within the cell.
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Redemann, Stefanie, Jacques Pecreaux, Nathan W. Goehring, Khaled Khairy, Ernst H. K. Stelzer, Anthony A. Hyman, and Jonathon Howard. "Membrane Invaginations Reveal Cortical Sites that Pull on Mitotic Spindles in One-Cell C. elegans Embryos." PloS, 2010. https://tud.qucosa.de/id/qucosa%3A29013.
Full textAbstract:
Asymmetric positioning of the mitotic spindle in C. elegans embryos is mediated by force-generating complexes that are anchored at the plasma membrane and that pull on microtubules growing out from the spindle poles. Although asymmetric distribution of the force generators is thought to underlie asymmetric positioning of the spindle, the number and location of the force generators has not been well defined. In particular, it has not been possible to visualize individual force generating events at the cortex. We discovered that perturbation of the acto-myosin cortex leads to the formation of long membrane invaginations that are pulled from the plasma membrane toward the spindle poles. Several lines of evidence show that the invaginations, which also occur in unperturbed embryos though at lower frequency, are pulled by the same force generators responsible for spindle positioning. Thus, the invaginations serve as a tool to localize the sites of force generation at the cortex and allow us to estimate a lower limit on the number of cortical force generators within the cell.
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Samandar, eweis Dureen. "Asymmetric division in single cell nematode embryos outside the Caenorhabditis genus." Electronic Thesis or Diss., Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLS063.
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La division cellulaire asymétrique est un processus essentiel du développement. Ce processus ainsi que sa régulation ont fait l’objet de nombreuses études chez l’embryon de Caenorhabditis elegans. La division asymétrique de l'embryon unicellulaire est un processus conservé à travers les espèces de nématodes, cependant les caractéristiques cellulaires menant à la division sont étonnamment variables. Au cours de mon doctorat, j'ai voulu étudier ces différences en utilisant deux embryons non-C. elegans : Diploscapter pachys et Pristionchus pacificus. D. pachys est le parent parthénogénétique le plus proche de C. elegans. La polarité étant induite par le sperme chez C. elegans, on ne peut expliquer ce qui brise la symétrie chez D. pachys. Mes résultats montrent que le noyau occupe le plus souvent l’hémisphère de D. pachys qui deviendra le pole postérieur. Dans les embryons où il est astreint à un pôle par centrifugation, le noyau fini par revenir à son pôle préférentiel. Même si l’embryon est polarisé, l’agitation corticale et le cytosquelette d’actine semblent identiques aux deux pôles. D’autre part, la position du fuseau méiotique est corrélée avec la future cellule postérieure. Dans certains ovocytes, on observe des structures de microtubules émanant du fuseau méiotique combiné à un faible enrichissement en actine au future pôle postérieur. Finalement, mon principal projet de thèse montre que la polarité de D. pachys est atteinte durant la méiose, au cours de laquelle le fuseau méiotique pourrait jouer un rôle par un mécanisme présent mais inhibé chez C. elegans. Chez P. pacificus, la transgénèse biolistique a été récemment utilisée avec succès. Toutefois, par manque d’un marqueur de sélection fiable, il était illusoire de poursuivre cette approche. En conclusion, les résultats de ma thèse contribuent à une meilleure compréhension de l’embryogénèse hors C. elegans. Ils soulignent l’importance de ces espèces dans l’optique d’études comparativesAsymmetric cell division is an essential process of development. The process and its regulation have been studied extensively in the Caenorhabditis elegans embryo. Asymmetric division of the single-cell embryo is a conserved process in nematode species, however, the cellular features leading up to division are surprisingly variable. During my PhD, I aimed to study these differences by using two non-C. elegans embryos: Diploscapter pachys and Pristionchus pacificus. D. pachys is the closest parthenogenetic relative to C. elegans. Since the polarity cue in C. elegans is brought by the sperm, how polarity is triggered in D. pachys remains unknown. My results show that the nucleus inhabits principally the hemisphere of the D. pachys embryo that will become the posterior pole. Moreover, in embryos where the nucleus is forced to one pole by centrifugation, it returns to its preferred pole. Although the embryo is polarized, cortical ruffling and actin cytoskeleton at both poles appear identical. Interestingly, the location of the meiotic spindle also correlates with the future posterior cell. In some oocytes, a slight actin enrichment along with unusual microtubule structures emanating from the meiotic spindle are observed at the future posterior pole. Overall, my main PhD project shows that polarity of the D. pachys embryo is attained during meiosis wherein the meiotic spindle could potentially be playing a role by a mechanism that may be present but suppressed in C. elegans. For P. pacificus, biolistic transgenesis has been shown recently successful. However, due to a lack of a stringent selection marker, the continuation of this project was unfeasible during my PhD. Altogether, the results of my PhD add to the understanding of non-C. elegans early embryogenesis and emphasizes on the importance of using these species for comparative studies
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Jaensch, Steffen. "Time-Resolved Quantification of Centrosomes by Automated Image Analysis Suggests Limiting Component to Set Centrosome Size in C. Elegans Embryos." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-63034.
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The centrosome is a dynamic organelle found in all animal cells that serves as a microtubule organizing center during cell division. Most of the centrosome components have been identified by genetic screens over the last decade, but little is known about how these components interact with each other to form a functional centrosome. Towards a better understanding of the molecular organization of the centrosome, we investigated the mechanism that regulates the size of the centrosome in the early C. elegans embryo. For this, we monitored fluorescently labeled centrosomes in living embryos and developed a suite of image analysis algorithms to quantify the centrosomes in the resulting 3D time-lapse images. In particular, we developed a novel algorithm involving a two-stage linking process for tracking entrosomes,
which is a multi-object tracking task. This fully automated analysis pipeline enabled us to acquire time-resolved data of centrosome growth in a large number of embryos and could detect subtle phenotypes that were missed by previous assays based on manual image analysis. In a first set of experiments, we quantified centrosome size over development in wild-type embryos and made three essential observations. First, centrosome volume scales proportionately with cell volume. Second, beginning at the 4-cell stage, when cells are small, centrosome size plateaus during the cell cycle. Third, the total centrosome volume the embryo gives rise to in any one cell stage is approximately constant. Based on our observations, we propose a ‘limiting component’ model in which centrosome size is limited by the
amounts of maternally derived centrosome components. In a second set of experiments, we tested our hypothesis by varying cell size, centrosome number and microtubule-mediated pulling forces. We then
manipulated the amounts of several centrosomal proteins and found that the conserved centriolar and pericentriolar material protein SPD-2 is one such component that determines centrosome size.
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Kim, Soyoung. "A Study of Cell Polarity and Fate Specification in Early C. Elegans Embryos: A Dissertation." eScholarship@UMMS, 2008. https://escholarship.umassmed.edu/gsbs_diss/385.
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Asymmetric cell divisions constitute a basic foundation of animal development, providing a mechanism for placing specific cell types at defined positions in a developing organism. In a 4-cell stage embryo in Caenorhabditis elegansthe EMS cell divides asymmetrically to specify intestinal cells, which requires a polarizing signal from the neighboring P2 cell. Here we describe how the extracellular signal from P2 is transmitted from the membrane to the nucleus during asymmetric EMS cell division, and present the identification of additional components in the pathways that accomplish this signaling.
P2/EMS signaling involves multiple inputs, which impinge on the Wnt, MAPK-like, and Src pathways. Transcriptional outputs downstream of these pathways depend on a homolog of β-catenin, WRM-1. Here we analyze the regulation of WRM-1, and show that the MAPK-like pathway maintains WRM-1 at the membrane, while its release and nuclear translocation depend on Wnt/Src signaling and sequential phosphorylation events by the major cell-cycle regulator CDK-1 and by the membrane-bound GSK-3 during EMS cell division. Our results provide novel mechanistic insights into how the signaling events at the cortex are coupled to the asymmetric EMS cell division through WRM-1.
To identify additional regulators in the pathways governing gut specification, we performed suppressor genetic screens using temperature-sensitive alleles of the gutless mutant mom-2/Wnt, and extra-gut mutant cks-1. Five intragenic suppressors and three semi-dominant suppressors were isolated in mom-2 suppressor screens. One extragenic suppressor was mapped to the locus ifg-1, eukaryotic translation initiation factor eIF4G. From the suppressor screen using cks-1(ne549), an allele of the self-cleaving nucleopore protein npp-10 was identified as a suppressor of cks-1(ne549)and other extra-gut mutants.
Taken together, these results help us better understand how the fate of intestinal cells are specified and regulated in early C. elegans embryos and broaden our knowledge of cell polarity and fate specification.
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Panbianco, Costanza. "Control of spindle pulling forces in Caenorhabditis elegans embryos by a Casein Kinase 1 and PI(4)P5-kinase." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612809.
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Irmisch, Linda [Verfasser], Antje [Gutachter] Gohla, Klaus [Gutachter] Brehm, and Ann [Gutachter] Wehman. "The role of septins and other regulatory proteins in abscission and midbody fate in C. elegans embryos / Linda Irmisch ; Gutachter: Antje Gohla, Klaus Brehm, Ann Wehman." Würzburg : Universität Würzburg, 2019. http://d-nb.info/119003784X/34.
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Chauca, Espinoza Karen Lorena. "Study of the dynamics of cortical myosin in the early embryo of the nematode C. elegans." Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS411.pdf.
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La myosine II non musculaire est un acteur clé dans la morphogenèse cellulaire et tissulaire. La dynamique corticale de la myosine sous forme de minifilaments in vivo reste cependant mal comprise. Ici, nous utilisons la microscopie SIM-TIRF dans un embryon en développement pour mieux comprendre les mécanismes et la structure de l’assemblage des minifilaments bipolaires. En combinant la microscopie SIM-TIRF et TIRF à molécule unique, nous avons d'abord caractérisé la structure des minifilaments, en particulier leur taille et leur stœchiométrie, à plusieurs stades du début de l'embryon. À l'aide de films SIM-TIRF à haute résolution temporelle, nous avons ensuite caractérisé une gamme diversifiée de comportements des minifilaments de myosine, des événements de division de minifilaments, des alignements de plusieurs minifilaments sur de longues distances (que nous avons appelés fibres de protostress), des événements de déliaison partielle et, de manière surprenante, des événements de déliaison et rereliure séquentielles au cortex. En utilisant des mutants du domaine moteur de la myosine, nous avons testé comment ces comportements reposaient sur l'activité motrice de la myosine. Nos données suggèrent que l'unité fonctionnelle de l'assemblage de la myosine peut être composée d'un ou de plusieurs minifilaments bipolaires de myosine, mais également que les minifilaments ne se désassemblent pas complètement lors de leur déliaison et de leur diffusion dans le cytoplasme. Pour tester la stabilité globale des assemblages bipolaires, nous avons ainsi utilisé des expériences de photoconversion et montré que les minifilaments de myosine sont bien recyclés sur de longues distances et temps de diffusion dans le cytoplasme sous forme d'unités minifilamentaires, qui ne se dissolvent pas lors de leur déliaison. Nos travaux mettent ainsi en lumière la manière dont les minifilaments de myosine interagissent avec le cortex, mais offrent une nouvelle perspective sur la manière dont ils s'assemblent, se désassemblent et sont recyclés au cours de la morphogenèse cellulaireNon-muscle myosin II is a key player in cell and tissue morphogenesis. The cortical dynamics Myosin as minifilaments in vivo however remain poorly understood. Here, we use SIM-TIRF microscopy in a developing embryo to gain further insights into the mechanisms and structure of bipolar minifilaments assembly. Combining SIM-TIRF and TIRF single-molecule microscopy, we first characterized the structure of minifilaments, specifically size and stoichiometry, at multiple stages in the early embryo. Using high temporal-resolution SIM- TIRF movies, we then characterized a diverse range of behaviors of myosin minifilaments, minifilament split events, alignments of multiple minifilaments over long distances (which we called protostress fibers), partial unbinding events and, surprisingly, events of sequential unbinding and rebinding to the cortex. Using mutants of the myosin motor domain, we tested how these behaviors relied on the myosin motor activity. Our data suggest that the functional unit of myosin assembly may be composed of one or multiple myosin bipolar minifilaments, but also that minifilaments do not fully disassemble upon unbinding and diffusing in the cytoplasm. To test the overall stability of bipolar assemblies, we thus used photoconversion experiments and show that the myosin minifilaments are indeed recycled over long distances and diffusion times in the cytoplasm as minifilamentous units, that do not dissolve upon unbinding. Our work thus sheds light on how myosin minifilaments interact with the cortex, but offers a new perspective on how they assemble, disassemble and are recycled during cell morphogenesis
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Leung, Benjamin Hong Nien. "Intestinal morphogenesis in the Caenorhabditis elegans embryo /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/5073.
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Willis, John Henry. "Regulation of the cytoskeleton in the early Caenorhabditis elegans embryo /." view abstract or download file of text, 2004. http://wwwlib.umi.com/cr/uoregon/fullcit?p3136453.
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Thesis (Ph. D.)--University of Oregon, 2004.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 68-73). Also available for download via the World Wide Web; free to University of Oregon users.
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Severson, Aaron Frederick. "An investigation into the mechanism of cytokinesis in the Caenorhabditis elegans embryo /." view abstract or download file of text, 2001. http://wwwlib.umi.com/cr/uoregon/fullcit?p3018394.
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Thesis (Ph. D.)--University of Oregon, 2001.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 118-127). Also available for download via the World Wide Web; free to University of Oregon users.
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Grill, Stephan W. "The mechanics of asymmetric spindle positioning in the Caenorhabditis elegans embryo." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964461773.
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Prigent, Serena. "Biochemical regulation of cell mechanics in C. elegans Embryo." Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS395.
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L’architecture et la dynamique du cortex d’Actine joue un rôle central dans la contractilité cellulaire et la morphogénèse des tissus. La modulation locale de la dynamique du réseau d’Actomyosine dépend majoritairement de la cascade d’activation de RhoA. Dans ma thèse, j’ai combiné des approches de microscopie quantitative en TIRFM, de l’imagerie en molécule unique, des simulations numériques et de la modélisation mathématique simple pour explorer l’architecture dynamique du réseau sous-jacent aux contractions pulsées dans un modèle simple : le jeune embryon de C. elegans. En se concentrant sur la Formine, élongateurs de l’Actine, nous avons observé que l’élongation de la F-Actine était catalysée par une population spécifique de Formines corticales – appelées Formines élongatrices – qui montrent une mobilité de type balistique. Nous avons ensuite montré que les Formines saturent les extrémités barbées disponibles et convertissent un gradient biochimique local de l’activité de RhoA en un réseau d’architecture polaire. Dans une seconde étude, en se concentrant sur la cinétique de la cascade d’activation de RhoA, nous avons développé un modèle numérique simple. Celui-ci tire profit des mesures des paramètres dynamiques de la Myosine, un effecteur terminal de la cascade d’activation de RhoA, pour prédire l’évolution temporelle de cette cascade. Je propose ici que ce modèle simple et générique – qui peut par essence s’adapter à n’importe quelle cascade – offre un cadre mathématique simple pour comprendre la dynamique temporelle des cascades d’activation, et le délai et changement dans la forme de la réponse qui peuvent être observés entre l’entrée et la sortieActin network architecture and dynamics play a central role in cell contractility and tissue morphogenesis. Local modulations of Actomyosin network dynamics depend largely on the activation of the RhoA activation cascade. In my thesis, I combined quantitative microscopy using TIRFM, single-molecule imaging, numerical simulations and simple mathematical modeling, to explore the dynamic network architecture underlying pulsed contractions in a simple model, the C. elegans early embryo. Focusing on the Actin elongator Formin, we observed that F-Actin elongation was catalyzed by a specific subpopulation of cortical Formins – termed elongating Formins – that displayed a characteristic ballistic mobility. My results also showed that Formin-mediated F-Actin elongation rate was dependent on the phase of the cell cycle and embryonic stage. We subsequently showed that elongating Formins saturate available barbed ends of Actin filaments, converting a local biochemical gradient of RhoA activity into a polar network architecture. In second study, focusing on the kinetics of the RhoA activation cascade, we developed and functionally challenged a simple numerical model. This model takes advantage of the measurements of the dynamical parameters of the Myosin, downstream effector of the RhoA activation cascade, to predict the temporal evolution of this cascade. I propose that this simple and generic model – which can in essence fit any activation cascade – offers a simple mathematical framework to understand the temporal dynamics of signaling cascades, and the delay and change in the shape of the response which can be observed between the input and the output of a cascade
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Encalada, Sandra Elizabeth. "Regulation of cell cycle timing in the early Caenorhabditis elegans embryo /." view abstract or download file of text, 2003. http://wwwlib.umi.com/cr/uoregon/fullcit?p3102163.
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Thesis (Ph. D.)--University of Oregon, 2003.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 159-180). Also available for download via the World Wide Web; free to University of Oregon users.
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McCarthy, Erin Kate Goldstein Robert P. "Regulation of asymmetric spindle positioning in the early C. elegans embryo." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1690.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Sep. 16, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Biology." Discipline: Biology; Department/School: Biology.
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Li, Jialing Ph D. Massachusetts Institute of Technology. "Dynamic patterning of maternal mRNAs in the Early C. elegans embryo." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77072.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 97-[108]).
Asymmetric segregation of maternally-encoded proteins is essential to cell fate determination during early cell divisions of the Caenorhabditis elegans (C. elegans) embryo, but little is known about the patterning of maternal transcripts inside somatic lineages. In the first Chapter of this thesis, by detecting individual mRNA molecules in situ, we measured the densities of the two maternal mRNAs pie-1 and nos-2 in non-germline cells. We find that nos-2 mRNA degrades at a constant rate in all somatic lineages, starting approximately 1 cell-cycle after each lineage separated from the germline, consistent with a model in which the germline protects maternal mRNAs from degradation. In contrast, the degradation of pie-1 mRNAs in one somatic lineage, AB, takes place at a rate slower than that of the other lineages, leading to an accumulation of that transcript. We further show that the 3' untranslated (UTR) region of the pie-1 transcript at least partly encodes the AB-specific degradation delay. Our results indicate that embryos actively control maternal mRNA distributions in somatic lineages via regulated degradation, providing another potential mechanism for lineage specification. The evolutionary fate of an allele ordinarily depends on its contribution to host fitness. Occasionally, however, genetic elements arise that are able to gain a transmission advantage while simultaneously imposing a fitness cost on their hosts. Seidel et al. previously discovered one such element in C. elegans that gains a transmission advantage through a combination of paternal-effect killing and zygotic self-rescue. In the second Chapter of this thesis we demonstrate that this element is composed of a sperm-delivered toxin, peel-1, and an embryo-expressed antidote, zeel-1. peel-1 and zeel-1 are located adjacent to one another in the genome and co-occur in an insertion/ deletion polymorphism. peel-1 encodes a novel four-pass transmembrane protein that is expressed in sperm and delivered to the embryo via specialized, sperm-specific vesicles. In the absence of zeel-1, sperm-delivered PEEL-1 causes lethal defects in muscle and epidermal tissue at the two-fold stage of embryogenesis. zeel-1 is expressed transiently in the embryo and encodes a novel six-pass transmembrane domain fused to a domain with sequence similarity to zyg-11, a substrate-recognition subunit of an E3 ubiquitin ligase. zeel-1 appears to have arisen recently, during an expansion of the zyg-11 family, and the transmembrane domain of zeel-1 is required and partially sufficient for antidote activity. Although PEEL-1 and ZEEL-1 normally function in embryos, these proteins can act at other stages as well. When expressed ectopically in adults, PEEL-1 kills a variety of cell types, and ectopic expression of ZEEL-1 rescues these effects. Our results demonstrate that the tight physical linkage between two novel transmembrane proteins has facilitated their co-evolution into an element capable of promoting its own transmission to the detriment of the rest of the genome. The Apical Epidermal Ridge (AER) in vertebrates is essential to the outgrowth of a growing limb bud. Induction and maintenance of the AER reply heavily on the coordination and signaling between two surrounding cell types: ectodermal and mesenchymal cells. In morphogenesis during embryonic development, a process called the epithelial-mesenchymal transition (EMT) occurs to transform epithelial cells into mesenchymal cells for increased cell mobility and decreased cell adhesion. To check whether the AER, which originated from the ectodermal layer, undergoes EMT for enhanced cell motility and invasiveness at an early stage of the limb outgrowth, we examined expression of biomarkers of the epithelial and mesenchymal cell types in the AER of a mouse forelimb at embryonic day 10.5 in Chapter three of this thesis. We also customized correlation-based image registration algorithm to perform image stitching for more direct visualization of a big field of tissue sample. We found that the AER surprisingly expresses both the epithelial marker and the mesenchymal marker, unlike a normal non-transitioning epithelial cell or a cell undergoing EMT. Our finding serves as a basis for potential future cell isolation experiments to further look into cell type switching of the AER and its interaction with the surrounding ectodermal and mesenchymal cells.
by Jialing Li.
Ph.D.
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Benenati, Gaspare. "Osmotic balance and establishment of polarity in C. elegans embryo require cytochrome P450 CYP31A." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1162562262718-44203.
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Lipids carry out important structural as well as signaling functions in the cell. In recent years, enzymes that metabolize lipids have been emerging as key regulators of basic cellular functions and developmental processes. In order to study metabolism of lipids, we have focused our research on a class of proteins: the cytochrome P450s (CYPs), which are involved in lipid production in many organisms. We have used C. elegans, a classical genetic model system, to investigate lipid metabolism because this nematode offers several technical advantages that render it suitable for our investigations. The aim of our project was to identify and characterize essential lipids for the development of worms. We have performed RNAi (RNA interference) against C. elegans CYP31A, and found that silencing of this enzyme leads to the arrest of embryonic development. Further characterization of this embryonic lethal phenotype revealed that it is caused by problems in establishment of polarity and failure in the extrusion of a polar body. Moreover, we found that embryos depleted of CYP31A are osmotic sensitive and their eggs are permeable to dyes (hoechst, FM 4-64 etc.). The defects described above are common to a class of mutants that received the denomination of POD (for Polarity and Osmotic Defects). Analysis by electron microscopy demonstrated that cyp31A(RNAi) embryos exhibit an improperly constructed eggshell. Further functional studies have demonstrated that the defects observed in cyp31A(RNAi) embryos can be ascribed to the malfunctioning of one of the three layers of the eggshell: the lipid-rich layer, but additional problems in the assembling of the other two layers are also present. In order to identify the product of CYP31A, we set up a bioassay in which we tested the capability of lipidic extract from wild type embryos to rescue the embryonic lethality. The bioassay provided a method to track the activity and allowed us to enrich the metabolic product of CYP31A by the fractionation of the total lipid extract. Another POD gene, emb-8, codes for an NADPH CYP reductase. This 4 protein supplies electrons to the CYPs for their metabolic reactions. A mutant of emb-8 (emb-8(hc69)), gives a similar phenotype as the knockdown CYP31A. With the aim to test if EMB-8 and CYP31A act in the same pathway we extracted lipids from emb-8TS mutants. We tested in the bioassay if extracts from emb-8(hc69) mutants, containing the metabolic product of CYP31A, can rescue cyp31A(RNAi) phenotype. The results obtained suggest that EMB-8 and CYP31A work in the same metabolic pathway. Conclusively, CYP31A and EMB-8 cooperate to produce a class of lipids that are required for the construction of a functional eggshell. A defective eggshell causes failure in polarity establishment, extrusion of the polar bodies, osmotic sensitivity and permeability and eventually it leads to the arrest of the development of C. elegans embryos.
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Garzon-Coral, Carlos. "The forces that center the mitotic spindle in the C. elegans embryo." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-163529.
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The precise positioning of the mitotic spindle to the cell center during mitosis is a fundamental process for chromosome segregation and the division plane definition. Despite its importance, the mechanism for spindle centering remains elusive. To study this mechanism, the dynamic of the microtubules was characterized at the bulk and at the cortex in the C. elegans embryo. Then, this dynamic was correlated to the centering forces of the spindle that were studied by applying calibrated magnetic forces via super-paramagnetic beads inserted into the cytoplasm of one- and two-cell C. elegans embryos. Finally, these results were confronted with the different centering models: cortical pushing model, cortical pulling model and the cytoplasmic pulling model.
This thesis shows that: (i) The microtubules dynamic of the spindle aster is controlled spatially in the C. elegans embryo, with not rescues and catastrophes in the cytoplasm but in the centrosome and the cortex, respectively. (ii) The centering mechanism of the spindle behaved roughly as a damped spring with a spring constant of 18 12 pN/ m and a drag coefficient of 127 65 pN s/ m (mean SD). This viscoelastic behavior is evidence of a centering force that recovers and/or maintains the position of the spindle in the cell center. (iii) It seems to be two mechanisms that recover/maintain the spindle position. A fast one that may work for transient displacements of the spindle and a slow one that work over large and long perturbations. (iv) The centering forces scale with the cell size. The centering forces are higher in the two-cell embryo. This result argues against a centering mechanism mediated by cytoplasmic factors. It seems to be a limit for the relation of centering force to size, as the forces found in the four-cell embryo are comparable to the single-cell ones. (v) The centering forces scale with the amount of microtubules in the cell. This strengthens the belief that the microtubules are the force transmission entities of the centering mechanism. (vi) The boundary conditions are important to maintain the centering forces. A transient residency time of microtubules at the cortex, which is controlled by cortical catastrophe factors, is indispensable for a proper force transmission by the microtubules. (vii) The elimination of cortical catastrophe factors provides evidence for microtubules buckling, which is taken as a proof of polymerization forces. (viii) The cortical pulling forces mediated by the gpr-1/2 pathway do not seem to be involved in centering and it is proposed they are present in the cell for off-center positioning purposes. (ix) The forces generated by vesicle transport are enough to displace the spindle and they are suggested to be auxiliary forces to centering. (x) The forces associated with the spindle change dramatically during cell division. From metaphase to anaphase the forces associated with the spindle scale up to five times. This behavior was consistent during the development of the embryo as the same pattern was observed in the one-, two- and four-cell embryo. (xi) The higher forces found during anaphase are not cortical pulling (via pgr-1/2 pathway) depended, and it is proposed the spindle is `immobilised' by tethering or by an unknown cortical pulling pathway.
To this date, this thesis presents the most complete in-vivo measurements of the centering forces in association with the microtubules dynamics. Taken together the results constrain molecular models of centering. This thesis concludes that most probably the predominant forces of the spindle centering mechanism during mitosis are generated by astral microtubules pushing against the cortex.
Additionally, this thesis presents the most complete map of forces during cell division during development, which will prove to be indispensable to understand the changes the spindle undergoes when it changes its function.
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Kravtsova, Natalia. "Theoretical Investigation of Cell Polarity Initiation in the Early C. Elegans Embryo." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397254117.
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DeBella, Leah Rae. "Analysis of genes required for spindle positioning in the early C. elegans embryo /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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Kaur, Shilpa. "Role of Wnt signaling in the polarization of neuronal precursors in the C. elegans embryo." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0068.
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Chez les vertébrés et les invertébrés les neurones sont souvent produits par division cellulaire asymétrique. Ce processus est notamment régulé par certains composants de la voie de signalisation Wnt. Cependant, comment les ligands Wnt, des molécules sécrétées activatrices de la voie Wnt, régulent ces divisions n’est pas compris. Le but de ma thèse est d’analyser le rôle des ligands Wnt et de leurs récepteurs dans les divisions asymétriques des précurseurs neuronaux en utilisant C. elegans comme organisme modèle. Chez C. elegans, les précurseurs neuronaux se divisent asymétriquement le long de l’axe antéro-posterieur. Le laboratoire d’accueil a montré que ces divisions sont régulées par un composant nucléaire de la voie Wnt, la beta-caténine, qui s’accumule spécifiquement dans le noyau de la cellule fille postérieure suite à la division asymétrique. Durant ma thèse, j’ai analysé le rôle de composants extracellulaires et corticaux dans ces divisions en utilisant le lignage cholinergique AIY comme lignage test. J’ai tout d’abord observé que les précurseurs neuronaux sont allongés le long de l’axe antéro-postérieur avant leur division. Trois ligands Wnt (CWN-1, CWN-2 et MOM-2) sont transcrits de façon plus importante dans la région postérieure de l’embryon. Via des expériences de perte et gain de fonction j’ai montré que les ligands Wnt régulent l’orientation des divisions ainsi que l’asymétrie d’identité des cellules filles. J’ai également identifié un rôle pour le récepteur de Wnt MOM-5 et la protéine corticale APC au cours des divisions asymétriques. MOM-5 est enrichi au pôle postérieur et APC au pôle antérieur des précurseurs neuronaux avant leur divisionIn both vertebrates and invertebrates neurons are often produced by asymmetric cell divisions. Some components of the Wnt pathway have been implicated in this process. However, how Wnt ligands, secreted activators of the Wnt pathway, regulate these divisions is not understood. The aim of my PhD is to analyze the role of Wnt ligands and of their receptors in neuronal precursor asymmetric divisions using C. elegans as a model organism. In the C. elegans embryo, neuronal precursors divide asymmetrically along the antero-posterior axis. The host laboratory has shown that these asymmetric divisions are regulated by a nuclear component of the Wnt pathway, beta-catenin, which accumulates specifically in the nucleus of the posterior daughter cell following asymmetric cell division. During my PhD, I analyzed the role of extracellular and cortical components in the asymmetric divisions of neuronal precursors using the AIY cholinergic lineage as a test lineage. I first observed that neuronal precursors are elongated along the antero-posterior axis before their division. Three Wnt ligands (CWN-1, CWN-2 and MOM-2) are transcribed at a higher level in the posterior region of the embryo. Using loss and gain of function experiments, I have observed that the Wnt ligands regulate the orientation of the divisions as well as the asymmetry in the identity of the daughter cells. I also identified a role for the Wnt receptor MOM-5 and the cortical protein APC during these asymmetric divisions. MOM-5 is enriched at the posterior pole and APC at the anterior pole of the neuronal precursors before their divisions
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Struntz, Philipp [Verfasser], and Matthias [Akademischer Betreuer] Weiss. "Quantitative Beobachtung dynamischer Prozesse im frühen C. elegans Embryo / Philipp Struntz ; Betreuer: Matthias Weiss." Bayreuth : Universität Bayreuth, 2018. http://d-nb.info/1169210805/34.
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Guedes, Maria Susana Ramos Ferreira. "The mex-1 gene and specification of germ cell identity in the Caenorhabditis elegans Embryo." Doctoral thesis, Porto : Edição do Autor, 1998. http://hdl.handle.net/10216/64557.
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Tsou, Meng-Fu Bryan. "The mechanisms of spindle positioning in asymmetric cell divisions of the early C. elegans embryo /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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Guedes, Maria Susana Ramos Ferreira. "The mex-1 gene and specification of germ cell identity in the Caenorhabditis elegans Embryo." Tese, Porto : Edição do Autor, 1998. http://catalogo.up.pt/F?func=find-b&local_base=UPB01&find_code=SYS&request=000086736.
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Pasti, Gabriella. "Etude du rôle des propriétés mécaniques des cellules de l'épiderme au cours de l'allongement des embryons de C. elegans." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAJ068.
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Mon travail se concentre sur la morphogenèse épithéliale pendant l’élongation embryonnaire de C. elegans. Ce processus s’appuie sur la transmission de signaux mécaniques, jouent un rôle essentiel également au cours de l’homéostasie tissulaire. Le gène pak-1 joue un rôle essentiel au cours des tels processus à la fois chez l’homme et dans l’élongation chez C. elegans. Nous avons montré que α-spectrine (SPC-1) est un nouveau partenaire de la kinase PAK-1. Pendant mon doctorat, j’ai confirmé que la perte simultanée de PAK-1 et de SPC-1 induit des défauts sévères d’élongation, impliquant une rétractation et un collapse général de l’embryon et suggèrent la présence de défauts biomécaniques. Mon travail était destiné à déterminer comment la perte de PAK-1 et SPC-1 influence le comportement mécanique des cellules épidermales. Cette étude permettra de mieux d’établir le rôle de SPC-1 et de PAK-1 dans la morphogenèse épithéliale et de mieux comprendre la régulation des propriétés mécaniques des cellules dans un contexte vivantI study epithelial morphogenesis during C. elegans embryonic elongation. This process depends on mechanical cues that also influence tissue homeostasis. The pak-1 gene plays an essential role equally during such processes in human and during C. elegans elongation. Our work identified α-spectrin (SPC-1) as a new interactor of the kinase PAK-1. During my PhD I confirmed that the simultaneous lack of PAK-1 and SPC-1 induces serious elongation defects, including a retraction and general collapse of the embryo and suggests that the mechanical properties of the epidermis are modified. My work aimed to determine how the simultaneous lack of PAK-1 and SPC-1 could influence these processes. Such studies would allow to better establish the role of SPC-1 and PAK-1 during epithelial morphogenesis and to better understand the regulation of cellular mechanical properties in the living organisms
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Lewellyn, Lindsay Kyle. "Signaling from the asters and spindle midzone is required to promote cytokinesis in the early C. elegans embryo." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3397053.
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Thesis (Ph. D.)--University of California, San Diego, 2010.Title from first page of PDF file (viewed March 16, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 143-156).
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Garzon-Coral, Carlos [Verfasser], and Jonathon [Akademischer Betreuer] Howard. "The forces that center the mitotic spindle in the C. elegans embryo / Carlos Garzon-Coral. Gutachter: Jonathon Howard. Betreuer: Jonathon Howard." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://d-nb.info/1069518239/34.
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Tak, Saurabh. "Les voies de mécanotransduction entre muscles et épiderme impliquées dans l'élongation embryonnaire de C. elegans." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAJ054/document.
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L'élongation embryonnaire de C. elegans a lieu en deux étapes. La première phase est permise par les contractions d’actomyosine et régulée par les kinases let-502 et pak-1. La seconde dépend des contractions musculaires (après le stade 1,7-fold). La tension fournie par ces contractions permet le recrutement de GIT-1 aux hémidesmosomes, facilitant la poursuite de l’élongation via l’activation de PAK-1 (Nature, 2011). Étonnamment, en l'absence de git-1 ou pak-1, l'élongation se poursuit, nous conduisant à émettre l'hypothèse de voies de régulation parallèles. Un crible ARNi a été réalisé pour rechercher les candidats impliqués. La majorité des candidats interagissant fortement avec git-1 appartenait au complexe dynéine-dynactine. En utilisant des allèles sensibles à la température et des protéines affectant les microtubules, nous avons décrit un rôle de la dynactine indépendant des microtubules dans l'épiderme ainsi que son interaction avec la spectraplakine vab-10 et la spectrine spc-1C. elegans embryonic elongation is driven by 2 forces: Actomyosin contractility and Muscle contraction (after 1.7-fold). Actomyosin contraction is regulated by the Rho kinase and the serine/threonine p21 activated kinase pak-1. Tension provided by muscle contraction recruits GIT-1 to hemidesmosomes (HD), which in turn facilitates further elongation by activating proteins such as PAK-1 (Nature 2011). Surprisingly in absence of git-1/pak-1, elongation still continues, which led us to hypothesize parallel pathways. An RNAi screen was performed to get the candidates in the parallel pathway/s. Candidates interacting strongly with git-1 belonged to the Dynein Dynactin complex. By use of temperature sensitive alleles and microtubule severing proteins, we found a microtubule independent role of Dynactin in epidermis and that dynactin functionally interacts with spectraplakin vab-10 and spectrin spc-1, which allows us to portray the role of Dynein Dynactin complex during embryonic elongation
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Bei, Yanxia. "Analysis of Polarity Signaling in Both Early Embryogenesis and Germline Development in C. Elegans: A Dissertation." eScholarship@UMMS, 2005. https://escholarship.umassmed.edu/gsbs_diss/147.
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In a 4-cell C. elegans embryo the ventral blastomere EMS requires polarity signaling from its posterior sister cell, P2. This signaling event enables EMS to orient its division spindle along the anterior-posterior (A/P) axis and to specify the endoderm fate of its posterior daughter cell, E.
Wnt pathway components have been implicated in mediating P2/EMS signaling. However, no single mutants or various mutant combinations of the Wnt pathway components disrupt EMS polarity completely. Here we describe the identification of a pathway that is defined by two tyrosine kinase related proteins, SRC-1 and MES-1, which function in parallel with Wnt signaling to specify endoderm and to orient the division axis of EMS. We show that SRC-1, a C. elegans homolog of c-Src, functions downstream of MES-1 to specifically enhance phosphotyrosine accumulation at the P2/EMS junction in order to control cell fate and mitotic spindle orientation in both the P2 and EMS cells.
In the canonical Wnt pathway, GSK-3 is conserved across species and acts as a negative regulator. However, in C. elegans we find that GSK-3 functions in a positive manner and in parallel with other components in the Wnt pathway to specify endoderm during embryogenesis. In addition, we also show that GSK-3 regulates C. elegans germline development, a function of GSK-3 that is not associated with Wnt signaling. It is required for the differentiation of somatic gonadal cells as well as the regulation of meiotic cell cycle in germ cells. Our results indicate that GSK-3 modulates multiple signaling pathways to regulate both embryogenesis and germline development in C. elegans.
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Schlaitz, Anne-Lore [Verfasser]. "Regulation of mitotic spindle assembly in Caenorhabditis elegans embryos / von Anne-Lore Schlaitz." 2007. http://d-nb.info/98474536X/34.
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Bringmann, Henrik [Verfasser]. "Experiments concerning the mechanism of cytokinesis in Caenorhabditis elegans embryos / von Henrik Bringmann." 2007. http://d-nb.info/983644500/34.
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Saramago, Joana Filipa Silva. "Phospho-regulation of Myosin Regulatory Light Chain in Caenorhabditis elegans embryos during cytokinesis." Master's thesis, 2014. https://repositorio-aberto.up.pt/handle/10216/80077.
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Saramago, Joana Filipa Silva. "Phospho-regulation of Myosin Regulatory Light Chain in Caenorhabditis elegans embryos during cytokinesis." Dissertação, 2014. https://repositorio-aberto.up.pt/handle/10216/80077.
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Lo, Miao-Chia. "The study of WNT signaling effector POP-1/TCF in c. elegans early embryos." 2005. http://edissertations.library.swmed.edu/pdf/LoM042905/LoMiaoChia.pdf.
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Schonegg, Stephanie [Verfasser]. "Rho GTPase family members in establishment of polarity in C. elegans embryos / von Stephanie Schonegg." 2005. http://d-nb.info/97874702X/34.
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Irmisch, Linda. "The role of septins and other regulatory proteins in abscission and midbody fate in C. elegans embryos." Doctoral thesis, 2019. https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-183244.
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Abscission marks the last step of cytokinesis and gives rise to two physically separated daughter cells and a midbody remnant. This work studies abscission by examining the extent of the abscission failure in C. elegans septin and ESCRT mutants with the help of the ZF1-degradation technique. The ZF1 technique is also applied to discern a possible role for PI3K during abscission. Lastly, we test the role of proteins required for macroautophagy but not for LC3-associated phagocytosis (LAP) and show that after release into the extracellular space, the midbody is resolved via LAPDurch Abszission, den letzten Schritt der Zytokinese, entstehen zwei physisch voneinander getrennte Tochterzellen und ein Mittelkörper, auch Flemming-Körper oder Midbody genannt. In dieser Arbeit wird mittels ZF1-vermittelter Abbautechnik in C. elegans Septin- und ESCRT-Mutanten das Ausmaß eines Abszissionsdefekts untersucht. Die ZF1-Technik wird ebenso eingesetzt, um eine mögliche Rolle von PI3K in Abszission festzustellen. Schließlich wird die Rolle von Proteinen erforderlich für Makroautophagie aber nicht für LC3-assoziierte Phagozytose (LAP) getestet und gezeigt, dass der Midbody nach Freilassung in den extrazellulären Raum mittels LAP verarbeitet wird
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Dinklemann, Maria Irena Vidal. "A study of sprindle orientation in C. elegans early embryos : the characterization of SPD-3 and STU-10 /." 2006. http://www.library.wisc.edu/databases/connect/dissertations.html.
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Jaensch, Steffen [Verfasser]. "Time-resolved quantifikation of centrosomes by automated image analysis suggests limiting component to set centrosome size in C. elegans embryos / eingereicht von Steffen Jaensch." 2010. http://d-nb.info/101166089X/34.
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"Inference of gene spatio-temporal expression in C. elegans embryo." 2015. http://repository.lib.cuhk.edu.hk/en/item/cuhk-1291749.
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Hu, Jie.Thesis Ph.D. Chinese University of Hong Kong 2015.
Includes bibliographical references (leaves 60-68).
Abstracts also in Chinese.
Title from PDF title page (viewed on 09, November, 2016).
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Saramago, Joana Filipa Silva. "Myosin Function During Cytokinesis in the C. elegans One-cell Embryo." Doctoral thesis, 2021. https://hdl.handle.net/10216/133814.
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Saramago, Joana Filipa Silva. "Myosin Function During Cytokinesis in the C. elegans One-cell Embryo." Tese, 2021. https://hdl.handle.net/10216/133814.
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Simões, Patrícia Alexandra Carvalho. "Functional Characterization of Dynein Cofactors in the One-Cell C. elegans Embryo." Master's thesis, 2014. https://repositorio-aberto.up.pt/handle/10216/83205.
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