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1
Hajeri, Vinita A., Brent A. Little, Mary L. Ladage und Pamela A. Padilla. „NPP-16/Nup50 Function and CDK-1 Inactivation Are Associated with Anoxia-induced Prophase Arrest in Caenorhabditis elegans“. Molecular Biology of the Cell 21, Nr. 5 (März 2010): 712–24. http://dx.doi.org/10.1091/mbc.e09-09-0787.
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Oxygen, an essential nutrient, is sensed by a multiple of cellular pathways that facilitate the responses to and survival of oxygen deprivation. The Caenorhabditis elegans embryo exposed to severe oxygen deprivation (anoxia) enters a state of suspended animation in which cell cycle progression reversibly arrests at specific stages. The mechanisms regulating interphase, prophase, or metaphase arrest in response to anoxia are not completely understood. Characteristics of arrested prophase blastomeres and oocytes are the alignment of condensed chromosomes at the nuclear periphery and an arrest of nuclear envelope breakdown. Notably, anoxia-induced prophase arrest is suppressed in mutant embryos lacking nucleoporin NPP-16/NUP50 function, indicating that this nucleoporin plays an important role in prophase arrest in wild-type embryos. Although the inactive form of cyclin-dependent kinase (CDK-1) is detected in wild-type–arrested prophase blastomeres, the inactive state is not detected in the anoxia exposed npp-16 mutant. Furthermore, we found that CDK-1 localizes near chromosomes in anoxia-exposed embryos. These data support the notion that NPP-16 and CDK-1 function to arrest prophase blastomeres in C. elegans embryos. The anoxia-induced shift of cells from an actively dividing state to an arrested state reveals a previously uncharacterized prophase checkpoint in the C. elegans embryo.
2
Watts, J. L., D. G. Morton, J. Bestman und K. J. Kemphues. „The C. elegans par-4 gene encodes a putative serine-threonine kinase required for establishing embryonic asymmetry“. Development 127, Nr. 7 (01.04.2000): 1467–75. http://dx.doi.org/10.1242/dev.127.7.1467.
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During the first cell cycle of Caenorhabditis elegans embryogenesis, asymmetries are established that are essential for determining the subsequent developmental fates of the daughter cells. The maternally expressed par genes are required for establishing this polarity. The products of several of the par genes have been found to be themselves asymmetrically distributed in the first cell cycle. We have identified the par-4 gene of C. elegans, and find that it encodes a putative serine-threonine kinase with similarity to a human kinase associated with Peutz-Jeghers Syndrome, LKB1 (STK11), and a Xenopus egg and embryo kinase, XEEK1. Several strong par-4 mutant alleles are missense mutations that alter conserved residues within the kinase domain, suggesting that kinase activity is essential for PAR-4 function. We find that the PAR-4 protein is present in the gonads, oocytes and early embryos of C. elegans, and is both cytoplasmically and cortically distributed. The cortical distribution begins at the late 1-cell stage, is more pronounced at the 2- and 4-cell stages and is reduced at late stages of embryonic development. We find no asymmetry in the distribution of PAR-4 protein in C. elegans embryos. The distribution of PAR-4 protein in early embryos is unaffected by mutations in the other par genes.
3
Keating, H. H., und J. G. White. „Centrosome dynamics in early embryos of Caenorhabditis elegans“. Journal of Cell Science 111, Nr. 20 (15.10.1998): 3027–33. http://dx.doi.org/10.1242/jcs.111.20.3027.
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The early Caenorhabditis elegans embryo divides with a stereotyped pattern of cleavages to produce cells that vary in developmental potential. Differences in cleavage plane orientation arise between the anterior and posterior cells of the 2-cell embryo as a result of asymmetries in centrosome positioning. Mechanisms that position centrosomes are thought to involve interactions between microtubules and the cortex, however, these mechanisms remain poorly defined. Interestingly, in the early embryo the shape of the centrosome predicts its subsequent movement. We have used rhodamine-tubulin and live imaging techniques to study the development of asymmetries in centrosome morphology and positioning. In contrast to studies using fixed embryos, our images provide a detailed characterization of the dynamics of centrosome flattening. In addition, our observations of centrosome behavior in vivo challenge previous assumptions regarding centrosome separation by illustrating that centrosome flattening and daughter centrosome separation are distinct processes, and by revealing that nascent daughter centrosomes may become separated from the nucleus. Finally, we provide evidence that the midbody specifies a region of the cortex that directs rotational alignment of the centrosome-nucleus complex and that the process is likely to involve multiple interactions between microtubules and the cortex; the process of alignment involves oscillations and overshoots, suggesting a multiplicity of cortical sites that interact with microtubules.
4
Browning, H., und S. Strome. „A sperm-supplied factor required for embryogenesis in C. elegans“. Development 122, Nr. 1 (01.01.1996): 391–404. http://dx.doi.org/10.1242/dev.122.1.391.
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The paternal-effect embryonic-lethal gene, spe-11, is required for normal development of early C. elegans embryos. Spe-11 embryos fail to complete meiosis, form a weak eggshell, fail to orient properly the first mitotic spindle, and fail to undergo cytokinesis. Here we report cloning and sequencing of the spe-11 gene, which encodes a novel protein. As predicted by the paternal-effect mutant phenotype, the gene is expressed during spermatogenesis but is not detectable in females undergoing oogenesis, and the protein is present in mature sperm. To investigate whether SPE-11's essential function is during spermatogenesis or whether sperm-delivered SPE-11 functions in the newly fertilized embryo, we engineered animals to supply SPE-11 to the embryo through the oocyte rather than through the sperm. We found that maternal expression is sufficient for embryonic viability. This result demonstrates that SPE-11 is not required during spermatogenesis, and suggests that SPE-11 is a sperm-supplied factor that participates directly in development of the early embryo. In contrast to the many known maternal factors required for embryogenesis, SPE-11 is the first paternally contributed factor to be genetically identified and molecularly characterized.
5
Edgar, L. G., N. Wolf und W. B. Wood. „Early transcription in Caenorhabditis elegans embryos“. Development 120, Nr. 2 (01.02.1994): 443–51. http://dx.doi.org/10.1242/dev.120.2.443.
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We have analysed early transcription in devitellinized, cultured embryos of the nematode Caenorhabditis elegans by two methods: measurement of [32P]UTP uptake into TCA-precipitable material and autoradiographic detection of [3H]UTP labelling both in the presence and absence of alpha-amanitin. RNA synthesis was first detected at the 8- to 12-cell stage, and alpha-amanitin sensitivity also appeared at this time, during the cleavages establishing the major founder cell lineages. The requirements for maternally supplied versus embryonically produced gene products in early embryogenesis were examined in the same culture system by observing the effects of alpha-amanitin on cell division and the early stereotyped lineage patterns. In the presence of high levels of alpha-amanitin added at varying times from two cells onward, cell division continued until approximately the 100-cell stage and then stopped during a single round of cell division. The characteristic unequal early cleavages, orientation of cleavage planes and lineage-specific timing of early divisions were unaffected by alpha-amanitin in embryos up to 87 cells. These results indicate that embryonic transcription starts well before gastrulation in C. elegans embryos, but that although embryonic transcripts may have important early functions, maternal products can support at least the mechanics of the first 6 to 7 cell cycles.
6
Zhang, Haining, Jayne M. Squirrell und John G. White. „RAB-11 Permissively Regulates Spindle Alignment by Modulating Metaphase Microtubule Dynamics in Caenorhabditis elegans Early Embryos“. Molecular Biology of the Cell 19, Nr. 6 (Juni 2008): 2553–65. http://dx.doi.org/10.1091/mbc.e07-09-0862.
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Alignment of the mitotic spindle along a preformed axis of polarity is crucial for generating cell diversity in many organisms, yet little is known about the role of the endomembrane system in this process. RAB-11 is a small GTPase enriched in recycling endosomes. When we depleted RAB-11 by RNAi in Caenorhabditis elegans, the spindle of the one-cell embryo failed to align along the axis of polarity in metaphase and underwent violent movements in anaphase. The distance between astral microtubules ends and the anterior cortex was significantly increased in rab-11(RNAi) embryos specifically during metaphase, possibly accounting for the observed spindle alignment defects. Additionally, we found that normal ER morphology requires functional RAB-11, particularly during metaphase. We hypothesize that RAB-11, in conjunction with the ER, acts to regulate cell cycle–specific changes in astral microtubule length to ensure proper spindle alignment in Caenorhabditis elegans early embryos.
7
Lee, Kenneth K., Yosef Gruenbaum, Perah Spann, Jun Liu und Katherine L. Wilson. „C. elegans Nuclear Envelope Proteins Emerin, MAN1, Lamin, and Nucleoporins Reveal Unique Timing of Nuclear Envelope Breakdown during Mitosis“. Molecular Biology of the Cell 11, Nr. 9 (September 2000): 3089–99. http://dx.doi.org/10.1091/mbc.11.9.3089.
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Emerin, MAN1, and LAP2 are integral membrane proteins of the vertebrate nuclear envelope. They share a 43-residue N-terminal motif termed the LEM domain. We found three putative LEM domain genes inCaenorhabditis elegans, designated emr-1,lem-2, and lem-3. We analyzedemr-l, which encodes Ce-emerin, andlem-2, which encodes Ce-MAN1. Ce-emerin and Ce-MAN1 migrate on SDS-PAGE as 17- and 52-kDa proteins, respectively. Based on their biochemical extraction properties and immunolocalization, both Ce-emerin and Ce-MAN1 are integral membrane proteins localized at the nuclear envelope. We used antibodies against Ce-MAN1, Ce-emerin, nucleoporins, and Ce-lamin to determine the timing of nuclear envelope breakdown during mitosis in C. elegans. The C. elegans nuclear envelope disassembles very late compared with vertebrates and Drosophila. The nuclear membranes remained intact everywhere except near spindle poles during metaphase and early anaphase, fully disassembling only during mid-late anaphase. Disassembly of pore complexes, and to a lesser extent the lamina, depended on embryo age: pore complexes were absent during metaphase in >30-cell embryos but existed until anaphase in 2- to 24-cell embryos. Intranuclear mRNA splicing factors disassembled after prophase. The timing of nuclear disassembly in C. elegans is novel and may reflect its evolutionary position between unicellular and more complex eukaryotes.
8
Basham, Stephen E., und Lesilee S. Rose. „The Caenorhabditis elegans polarity gene ooc-5 encodes a Torsin-related protein of the AAA ATPase superfamily“. Development 128, Nr. 22 (15.11.2001): 4645–56. http://dx.doi.org/10.1242/dev.128.22.4645.
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The PAR proteins are required for polarity and asymmetric localization of cell fate determinants in C. elegans embryos. In addition, several of the PAR proteins are conserved and localized asymmetrically in polarized cells in Drosophila, Xenopus and mammals. We have previously shown that ooc-5 and ooc-3 mutations result in defects in spindle orientation and polarity in early C. elegans embryos. In particular, mutations in these genes affect the re-establishment of PAR protein asymmetry in the P1 cell of two-cell embryos. We now report that ooc-5 encodes a putative ATPase of the Clp/Hsp100 and AAA superfamilies of proteins, with highest sequence similarity to Torsin proteins; the gene for human Torsin A is mutated in individuals with early-onset torsion dystonia, a neuromuscular disease. Although Clp/Hsp100 and AAA family proteins have roles in diverse cellular activities, many are involved in the assembly or disassembly of proteins or protein complexes; thus, OOC-5 may function as a chaperone. OOC-5 protein co-localizes with a marker of the endoplasmic reticulum in all blastomeres of the early C. elegans embryo, in a pattern indistinguishable from that of OOC-3 protein. Furthermore, OOC-5 localization depends on the normal function of the ooc-3 gene. These results suggest that OOC-3 and OOC-5 function in the secretion of proteins required for the localization of PAR proteins in the P1 cell, and may have implications for the study of torsion dystonia.
9
Zilberman, Yuliya, Joshua Abrams, Dorian C. Anderson und Jeremy Nance. „Cdc42 regulates junctional actin but not cell polarization in the Caenorhabditis elegans epidermis“. Journal of Cell Biology 216, Nr. 11 (13.09.2017): 3729–44. http://dx.doi.org/10.1083/jcb.201611061.
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During morphogenesis, adherens junctions (AJs) remodel to allow changes in cell shape and position while preserving adhesion. Here, we examine the function of Rho guanosine triphosphatase CDC-42 in AJ formation and regulation during Caenorhabditis elegans embryo elongation, a process driven by asymmetric epidermal cell shape changes. cdc-42 mutant embryos arrest during elongation with epidermal ruptures. Unexpectedly, we find using time-lapse fluorescence imaging that cdc-42 is not required for epidermal cell polarization or junction assembly, but rather is needed for proper junctional actin regulation during elongation. We show that the RhoGAP PAC-1/ARHGAP21 inhibits CDC-42 activity at AJs, and loss of PAC-1 or the interacting linker protein PICC-1/CCDC85A-C blocks elongation in embryos with compromised AJ function. pac-1 embryos exhibit dynamic accumulations of junctional F-actin and an increase in AJ protein levels. Our findings identify a previously unrecognized molecular mechanism for inhibiting junctional CDC-42 to control actin organization and AJ protein levels during epithelial morphogenesis.
10
Rose, L. S., und K. Kemphues. „The let-99 gene is required for proper spindle orientation during cleavage of the C. elegans embryo“. Development 125, Nr. 7 (01.04.1998): 1337–46. http://dx.doi.org/10.1242/dev.125.7.1337.
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The orientation of cell division is a critical aspect of development. In 2-cell C. elegans embryos, the spindle in the posterior cell is aligned along the long axis of the embryo and contributes to the unequal partitioning of cytoplasm, while the spindle in the anterior cell is oriented transverse to the long axis. Differing spindle alignments arise from blastomere-specific rotations of the nuclear-centrosome complex at prophase. We have found that mutations in the maternally expressed gene let-99 affect spindle orientation in all cells during the first three cleavages. During these divisions, the nuclear-centrosome complex appears unstable in position. In addition, in almost half of the mutant embryos, there are reversals of the normal pattern of spindle orientations at second cleavage: the spindle of the anterior cell is aligned with the long axis of the embryo and nuclear rotation fails in the posterior cell causing the spindle to form transverse to the long axis. In most of the remaining embryos, spindles in both cells are transverse at second cleavage. The distributions of several asymmetrically localized proteins, including P granules and PAR-3, are normal in early let-99 embryos, but are perturbed by the abnormal cell division orientations at second cleavage. The accumulation of actin and actin capping protein, which marks the site involved in nuclear rotation in 2-cell wild-type embryos, is abnormal but is not reversed in let-99 mutant embryos. Based on these data, we conclude that let-99(+) is required for the proper orientation of spindles after the establishment of polarity, and we postulate that let-99(+) plays a role in interactions between the astral microtubules and the cortical cytoskeleton.
11
Schauer, I. E., und W. B. Wood. „Early C. elegans embryos are transcriptionally active“. Development 110, Nr. 4 (01.12.1990): 1303–17. http://dx.doi.org/10.1242/dev.110.4.1303.
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We have developed a nucleotide incorporation assay for run-on transcription in C. elegans embryonic extracts as an approach to characterizing early transcription. The incorporation is primarily polymerase II-catalyzed RNA synthesis, producing transcripts of the expected size range for mRNAs. Incorporation is insensitive to inhibitors of reinitiation, indicating that the activity represents primarily elongation of nascent chains initiated prior to extract preparation. The transcripts produced appear to be unprocessed pre-mRNAs. Hybridization of labeled transcripts from extracts of staged embryos to a set of cloned genes suggests that the specificity of the in vitro reaction accurately reflects developmentally regulated in vivo transcription. Comparative analyses of transcription in extracts from various stages indicate that pregastrulation embryos are active transcriptionally and that the level of transcription per nucleus is approximately constant throughout embryogenesis. Furthermore, most embryonically expressed genes are already being transcribed in pregastrulation embryos. We also demonstrate that the labeled embryonic run-on transcripts can be used as probes to screen for sequences transcribed preferentially in pregastrulation embryos. There appears to be only a small set of such sequences, which could represent a previously unsuspected class of embryonically transcribed genes important for early embryogenesis.
12
Keating, Heather H., und John G. White. „Centrosome dynamics in early embryos of Caenorhabditis elegans“. Journal of Cell Science 111, Nr. 20 (15.01.1998): 3027–33. http://dx.doi.org/10.1242/jcs.20.111.3027.
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ABSTRACT The early Caenorhabditis elegans embryo divides with a stereotyped pattern of cleavages to produce cells that vary in developmental potential. Differences in cleavage plane orientation arise between the anterior and posterior cells of the 2-cell embryo as a result of asymmetries in centrosome positioning. Mechanisms that position centrosomes are thought to involve interactions between microtubules and the cortex, however, these mechanisms remain poorly defined. Interestingly, in the early embryo the shape of the centrosome predicts its subsequent movement. We have used rhodamine-tubulin and live imaging techniques to study the development of asymmetries in centrosome morphology and positioning. In contrast to studies using fixed embryos, our images provide a detailed characterization of the dynamics of centrosome flattening. In addition, our observations of centrosome behavior in vivo challenge previous assumptions regarding centrosome separation by illustrating that centrosome flattening and daughter centrosome separation are distinct processes, and by revealing that nascent daughter centrosomes may become separated from the nucleus. Finally, we provide evidence that the midbody specifies a region of the cortex that directs rotational alignment of the centrosome-nucleus complex and that the process is likely to involve multiple interactions between microtubules and the cortex; the process of alignment involves oscillations and overshoots, suggesting a multiplicity of cortical sites that interact with microtubules.
13
Goutte, C., W. Hepler, K. M. Mickey und J. R. Priess. „aph-2 encodes a novel extracellular protein required for GLP-1-mediated signaling“. Development 127, Nr. 11 (01.06.2000): 2481–92. http://dx.doi.org/10.1242/dev.127.11.2481.
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In animal development, numerous cell-cell interactions are mediated by the GLP-1/LIN-12/NOTCH family of transmembrane receptors. These proteins function in a signaling pathway that appears to be conserved from nematodes to humans. We show here that the aph-2 gene is a new component of the GLP-1 signaling pathway in the early Caenorhabditis elegans embryo, and that proteins with sequence similarity to the APH-2 protein are found in Drosophila and vertebrates. During the GLP-1-mediated cell interactions in the C. elegans embryo, APH-2 is associated with the cell surfaces of both the signaling, and the responding, blastomeres. Analysis of chimeric embryos that are composed of aph-2(+) and aph-2(−) blastomeres suggests that aph-2(+) function may be provided by either the signaling or responding blastomere.
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DeBella, Leah R., Adam Hayashi und Lesilee S. Rose. „LET-711, the Caenorhabditis elegans NOT1 Ortholog, Is Required for Spindle Positioning and Regulation of Microtubule Length in Embryos“. Molecular Biology of the Cell 17, Nr. 11 (November 2006): 4911–24. http://dx.doi.org/10.1091/mbc.e06-02-0107.
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Spindle positioning is essential for the segregation of cell fate determinants during asymmetric division, as well as for proper cellular arrangements during development. In Caenorhabditis elegans embryos, spindle positioning depends on interactions between the astral microtubules and the cell cortex. Here we show that let-711 is required for spindle positioning in the early embryo. Strong loss of let-711 function leads to sterility, whereas partial loss of function results in embryos with defects in the centration and rotation movements that position the first mitotic spindle. let-711 mutant embryos have longer microtubules that are more cold-stable than in wild type, a phenotype opposite to the short microtubule phenotype caused by mutations in the C. elegans XMAP215 homolog ZYG-9. Simultaneous reduction of both ZYG-9 and LET-711 can rescue the centration and rotation defects of both single mutants. let-711 mutant embryos also have larger than wild-type centrosomes at which higher levels of ZYG-9 accumulate compared with wild type. Molecular identification of LET-711 shows it to be an ortholog of NOT1, the core component of the CCR4/NOT complex, which plays roles in the negative regulation of gene expression at transcriptional and post-transcriptional levels in yeast, flies, and mammals. We therefore propose that LET-711 inhibits the expression of ZYG-9 and potentially other centrosome-associated proteins, in order to maintain normal centrosome size and microtubule dynamics during early embryonic divisions.
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Jones, Clark A., und Phil S. Hartman. „Replication in UV-lrradiated Caenorhabditis elegans Embryos“. Photochemistry and Photobiology 63, Nr. 2 (Februar 1996): 187–92. http://dx.doi.org/10.1111/j.1751-1097.1996.tb03012.x.
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16
Goldstein, Bob. „Induction of gut in Caenorhabditis elegans embryos“. Nature 357, Nr. 6375 (Mai 1992): 255–57. http://dx.doi.org/10.1038/357255a0.
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17
Priess, James R., und J. Nichol Thomson. „Cellular interactions in early C. elegans embryos“. Cell 48, Nr. 2 (Januar 1987): 241–50. http://dx.doi.org/10.1016/0092-8674(87)90427-2.
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18
Goldstein, Bob, und Jeremy Nance. „Caenorhabditis elegans Gastrulation: A Model for Understanding How Cells Polarize, Change Shape, and Journey Toward the Center of an Embryo“. Genetics 214, Nr. 2 (Februar 2020): 265–77. http://dx.doi.org/10.1534/genetics.119.300240.
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Gastrulation is fundamental to the development of multicellular animals. Along with neurulation, gastrulation is one of the major processes of morphogenesis in which cells or whole tissues move from the surface of an embryo to its interior. Cell internalization mechanisms that have been discovered to date in Caenorhabditis elegans gastrulation bear some similarity to internalization mechanisms of other systems including Drosophila, Xenopus, and mouse, suggesting that ancient and conserved mechanisms internalize cells in diverse organisms. C. elegans gastrulation occurs at an early stage, beginning when the embryo is composed of just 26 cells, suggesting some promise for connecting the rich array of developmental mechanisms that establish polarity and pattern in embryos to the force-producing mechanisms that change cell shapes and move cells interiorly. Here, we review our current understanding of C. elegans gastrulation mechanisms. We address how cells determine which direction is the interior and polarize with respect to that direction, how cells change shape by apical constriction and internalize, and how the embryo specifies which cells will internalize and when. We summarize future prospects for using this system to discover some of the general principles by which animal cells change shape and internalize during development.
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Kapoor, Sukriti, und Sachin Kotak. „Centrosome Aurora A gradient ensures single polarity axis in C. elegans embryos“. Biochemical Society Transactions 48, Nr. 3 (29.06.2020): 1243–53. http://dx.doi.org/10.1042/bst20200298.
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Cellular asymmetries are vital for generating cell fate diversity during development and in stem cells. In the newly fertilized Caenorhabditis elegans embryo, centrosomes are responsible for polarity establishment, i.e. anterior–posterior body axis formation. The signal for polarity originates from the centrosomes and is transmitted to the cell cortex, where it disassembles the actomyosin network. This event leads to symmetry breaking and the establishment of distinct domains of evolutionarily conserved PAR proteins. However, the identity of an essential component that localizes to the centrosomes and promotes symmetry breaking was unknown. Recent work has uncovered that the loss of Aurora A kinase (AIR-1 in C. elegans and hereafter referred to as Aurora A) in the one-cell embryo disrupts stereotypical actomyosin-based cortical flows that occur at the time of polarity establishment. This misregulation of actomyosin flow dynamics results in the occurrence of two polarity axes. Notably, the role of Aurora A in ensuring a single polarity axis is independent of its well-established function in centrosome maturation. The mechanism by which Aurora A directs symmetry breaking is likely through direct regulation of Rho-dependent contractility. In this mini-review, we will discuss the unconventional role of Aurora A kinase in polarity establishment in C. elegans embryos and propose a refined model of centrosome-dependent symmetry breaking.
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Gönczy, Pierre, Silke Pichler, Matthew Kirkham und Anthony A. Hyman. „Cytoplasmic Dynein Is Required for Distinct Aspects of Mtoc Positioning, Including Centrosome Separation, in the One Cell Stage Caenorhabditis elegans Embryo“. Journal of Cell Biology 147, Nr. 1 (04.10.1999): 135–50. http://dx.doi.org/10.1083/jcb.147.1.135.
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We have investigated the role of cytoplasmic dynein in microtubule organizing center (MTOC) positioning using RNA-mediated interference (RNAi) in Caenorhabditis elegans to deplete the product of the dynein heavy chain gene dhc-1. Analysis with time-lapse differential interference contrast microscopy and indirect immunofluorescence revealed that pronuclear migration and centrosome separation failed in one cell stage dhc-1 (RNAi) embryos. These phenotypes were also observed when the dynactin components p50/dynamitin or p150Glued were depleted with RNAi. Moreover, in 15% of dhc-1 (RNAi) embryos, centrosomes failed to remain in proximity of the male pronucleus. When dynein heavy chain function was diminished only partially with RNAi, centrosome separation took place, but orientation of the mitotic spindle was defective. Therefore, cytoplasmic dynein is required for multiple aspects of MTOC positioning in the one cell stage C. elegans embryo. In conjunction with our observation of cytoplasmic dynein distribution at the periphery of nuclei, these results lead us to propose a mechanism in which cytoplasmic dynein anchored on the nucleus drives centrosome separation.
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Cowing, D. W., und C. Kenyon. „Expression of the homeotic gene mab-5 during Caenorhabditis elegans embryogenesis“. Development 116, Nr. 2 (01.10.1992): 481–90. http://dx.doi.org/10.1242/dev.116.2.481.
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mab-5 is a member of a complex of homeobox-containing genes evolutionarily related to the Antennapedia and bithorax complexes of Drosophila melanogaster. Like the homeotic genes in Drosophila, mab-5 is required in a particular region along the anterior-posterior body axis, and acts during postembryonic development to give cells in this region their characteristic identities. We have used a mab-5-lacZ fusion integrated into the C. elegans genome to study the posterior-specific expression of mab-5 during embryogenesis. The mab-5-lacZ fusion was expressed in the posterior of the embryo by 180 minutes after the first cleavage, indicating that the mechanisms responsible for the position-specific expression of mab-5-lacZ act at a relatively early stage of embryogenesis. In embryos homozygous for mutations in the par genes, which disrupt segregation of factors during early cleavages, expression of mab-5-lacZ was no longer localized to the posterior. This suggests that posterior-specific expression of mab-5 depends on the appropriate segregation of developmental factors during early embryogenesis. After extrusion of any blastomere of the four-cell embryo, descendants of the remaining three cells could still express the mab-5-lacZ fusion. In these partial embryos, however, the fusion was often expressed in cells scattered throughout the embryo, suggesting that cell-cell interactions and/or proper positioning of early blastomeres are required for mab-5 expression to be localized to the posterior.
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Boyle, Thomas H. „PATHWAYS OF BACKCROSSING ZINNIA ANGUSTIFOLIA × Z. ELEGANS INTERSPECIFIC HYBRIDS TO THE PARENTAL SPECIES“. HortScience 25, Nr. 9 (September 1990): 1070a—1070. http://dx.doi.org/10.21273/hortsci.25.9.1070a.
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Allotetraploid Z. angustifolia × Z. elegans hybrids (2 n =46) were reciprocally backcrossed to Z. angustifolia (2 n = 22 or 44) and Z. elegans (2 n = 24 or 48). Pollen germination and pollen tube penetration of the stigmatic surface were observed for all 8 cross combinations. At 14 days after pollination, the percentage of florets with embryos ranged from 0 to 69%, and some hybrid embryos exhibited developmental abnormalities. Seed-propagated backcross (BC1) populations were generated with Z. angustifolia (2 n =44)as ♀ or ♂, and Z. elegans (2 n =48) as ♀ BC1 progeny from these 3 crosses demonstrated low to high levels of resistance to bacterial leaf and flower spot (incited by Xanthomonas campestris pv. zinniae) and high levels of resistance to powdery mildew (incited by Erysiphe cichoracearum). BC1 hybrids derived from crossing allotetraploid hybrids as ♀ and Z. elegans (2 n =48) lines have commercial potential as disease-resistant, flowering annuals.
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Schierenberg, Einhard. „Early development of nematode embryos: differences and similarities“. Nematology 2, Nr. 1 (2000): 57–64. http://dx.doi.org/10.1163/156854100508890.
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AbstractTo determine whether embryogenesis of Caenorhabditis elegans is typical for nematodes in general, we started to analyse in comparison several aspects of development in various nematode species. The differences we observed can be subdivided into two classes, those visible in the intact embryo and those requiring experimental interference. Particularly obvious differences of both types were revealed between C. elegans (Rhabditidae) and Acrobeloides nanus (Cephalobidae). Not only does the spatial and temporal pattern of early events differ but also that of intercellular communication and cell specification. Our data suggest that some developmental variations are characteristic for certain nematode groups and therefore may be useful as phylogenetic markers. In contrast, we detected little evidence so far for environmental influence on early developmental processes. Pour déterminer dans quelle mesure l’embryogenèse de Caenorhabditis elegans est une caractéristique générale des nématodes, nous avons commencé l’analyse de plusieurs aspects du développement chez différentes espèces de nématodes. Les différences observées peuvent être divisées en deux catégories: celles observables chez l’embryon intact et celles nécessitant une intervention expérimentale. En particulier, des différences nettes entre les deux catégories ont été mises en évidence chez C. elegans (Rhabditidae) et Acrobeloides nanus (Cephalobidae). Diffèrent non seulement le schéma spatio-temporel des évènements précoces, mais également la communication intercellulaire et la différenciation cellulaire. Nos données suggèrent que certaines variations du développement sont caractéristiques de certains groupes de nématodes et pourraient donc être utiles comme marqueurs phylogénétiques. A contrario, une influence de l’environnement sur les processus précoces du développement n’a pas, jusqu’à présent, été détectée.
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Hutter, H., und R. Schnabel. „glp-1 and inductions establishing embryonic axes in C. elegans“. Development 120, Nr. 7 (01.07.1994): 2051–64. http://dx.doi.org/10.1242/dev.120.7.2051.
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Two successive inductions specify blastomere identities, that is complex cell lineages and not specific tissues, in a major part of the early C. elegans embryo. The first induction acts along the anterior-posterior axis of the embryo and the second along the left-right axis. During the first induction a specific lineage program is induced in the posterior of the two AB blastomeres present in the four cell embryo. During the second induction, almost all of the left-right differences of the embryo are specified by interactions between a single signalling blastomere, MS, and the AB blastomeres that surround it. In both cases the inductions break the equivalence of pairs of blastomeres. The inductions correlate with the cell-cell contacts to the inducing blastomeres. The stereotype cleavage patterns of the early embryo results in invariant cell-cell contacts that guarantee the specificity of the inductions. Both inductions are affected in embryos mutant for glp-1 suggesting that in both cases glp-1 is involved in the reception of the signal.
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Hardin, Jeff. „Getting to the core of cadherin complex function in Caenorhabditis elegans“. F1000Research 4 (18.12.2015): 1473. http://dx.doi.org/10.12688/f1000research.6866.1.
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The classic cadherin-catenin complex (CCC) mediates cell-cell adhesion in metazoans. Although substantial insights have been gained by studying the CCC in vertebrate tissue culture, analyzing requirements for and regulation of the CCC in vertebrates remains challenging. Caenorhabditis elegans is a powerful system for connecting the molecular details of CCC function with functional requirements in a living organism. Recent data, using an “angstroms to embryos” approach, have elucidated functions for key residues, conserved across all metazoans, that mediate cadherin/β-catenin binding. Other recent work reveals a novel, potentially ancestral, role for the C. elegans p120ctn homologue in regulating polarization of blastomeres in the early embryo via Cdc42 and the partitioning-defective (PAR)/atypical protein kinase C (aPKC) complex. Finally, recent work suggests that the CCC is trafficked to the cell surface via the clathrin adaptor protein complex 1 (AP-1) in surprising ways. These studies continue to underscore the value of C. elegans as a model system for identifying conserved molecular mechanisms involving the CCC.
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McKeown, C., V. Praitis und J. Austin. „sma-1 encodes a betaH-spectrin homolog required for Caenorhabditis elegans morphogenesis“. Development 125, Nr. 11 (01.06.1998): 2087–98. http://dx.doi.org/10.1242/dev.125.11.2087.
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Morphogenesis transforms the C. elegans embryo from a ball of cells into a vermiform larva. During this transformation, the embryo increases fourfold in length; present data indicates this elongation results from contraction of the epidermal actin cytoskeleton. In sma-1 mutants, the extent of embryonic elongation is decreased and the resulting sma-1 larvae, although viable, are shorter than normal. We find that sma-1 mutants elongate for the same length of time as wild-type embryos, but at a decreased rate. The sma-1 mutants we have isolated vary in phenotypic severity, with the most severe alleles showing the greatest decrease in elongation rate. The sma-1 gene encodes a homolog of betaH-spectrin, a novel beta-spectrin isoform first identified in Drosophila. sma-1 RNA is expressed in epithelial tissues in the C. elegans embryo: in the embryonic epidermis at the start of morphogenesis and subsequently in the developing pharynx, intestine and excretory cell. In Drosophila, betaH-spectrin associates with the apical plasma membrane of epithelial cells; beta-spectrin is found at the lateral membrane. We propose that SMA-1 is a component of an apical membrane skeleton in the C. elegans embryonic epidermis that determines the rate of elongation during morphogenesis.
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Fang, Chao, Xi Wei, Xueying Shao und Yuan Lin. „Force-mediated cellular anisotropy and plasticity dictate the elongation dynamics of embryos“. Science Advances 7, Nr. 27 (Juni 2021): eabg3264. http://dx.doi.org/10.1126/sciadv.abg3264.
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We developed a unified dynamic model to explain how cellular anisotropy and plasticity, induced by alignment and severing/rebundling of actin filaments, dictate the elongation dynamics of Caenorhabditis elegans embryos. It was found that the gradual alignment of F-actins must be synchronized with the development of intracellular forces for the embryo to elongate, which is then further sustained by muscle contraction–triggered plastic deformation of cells. In addition, we showed that preestablished anisotropy is essential for the proper onset of the process while defects in the integrity or bundling kinetics of actin bundles result in abnormal embryo elongation, all in good agreement with experimental observations.
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Strome, Susan, James Powers, Melanie Dunn, Kimberly Reese, Christian J. Malone, John White, Geraldine Seydoux und William Saxton. „Spindle Dynamics and the Role of γ-Tubulin in EarlyCaenorhabditis elegans Embryos“. Molecular Biology of the Cell 12, Nr. 6 (Juni 2001): 1751–64. http://dx.doi.org/10.1091/mbc.12.6.1751.
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γ-Tubulin is a ubiquitous and highly conserved component of centrosomes in eukaryotic cells. Genetic and biochemical studies have demonstrated that γ-tubulin functions as part of a complex to nucleate microtubule polymerization from centrosomes. We show that, as in other organisms, Caenorhabditis elegans γ-tubulin is concentrated in centrosomes. To study centrosome dynamics in embryos, we generated transgenic worms that express GFP::γ-tubulin or GFP::β-tubulin in the maternal germ line and early embryos. Multiphoton microscopy of embryos produced by these worms revealed the time course of daughter centrosome appearance and growth and the differential behavior of centrosomes destined for germ line and somatic blastomeres. To study the role of γ-tubulin in nucleation and organization of spindle microtubules, we used RNA interference (RNAi) to deplete C. elegansembryos of γ-tubulin. γ-Tubulin (RNAi) embryos failed in chromosome segregation, but surprisingly, they contained extensive microtubule arrays. Moderately affected embryos contained bipolar spindles with dense and long astral microtubule arrays but with poorly organized kinetochore and interpolar microtubules. Severely affected embryos contained collapsed spindles with numerous long astral microtubules. Our results suggest that γ-tubulin is not absolutely required for microtubule nucleation in C. elegans but is required for the normal organization and function of kinetochore and interpolar microtubules.
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Strome, Susan. „Asymmetric movements of cytoplasmic components in Caenorhabditis elegans zygotes“. Development 97, Supplement (01.10.1986): 15–29. http://dx.doi.org/10.1242/dev.97.supplement.15.
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One of the central problems facing developmental biologists is understanding how the unicellular zygote develops into a multicellular embryo composed of different tissue types. It is now clear that differentiated cell types differ because they express different sets of genes. However, how cells become instructed to express different sets of genes remains a mystery. One popular model for how cell fates are determined invokes the existence and asymmetric distribution of cytoplasmic ‘determinants’ of cell fates (for reviews see Wilson, 1925; Davidson, 1976). According to this model, the developmental programmes of embryonic blastomeres are specified by internal factors that are differentially segregated to different blastomeres during the early cleavages of the zygote. Alternatively, cells may be instructed by extrinsic signals, in which case the positions of cells in the embryo and cell-cell interactions would be important. Observation and manipulation of embryos that show ‘mosaic’ development provide indirect support for the cell determinant theory.
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Adames, K. A., Jocelyn Gawne, Chantal Wicky, Fritz Müller und Ann M. Rose. „Mapping a Telomere Using the Translocation eT1(III;V) in Caenorhabditis elegans“. Genetics 150, Nr. 3 (01.11.1998): 1059–66. http://dx.doi.org/10.1093/genetics/150.3.1059.
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Abstract In Caenorhabditis elegans, individuals heterozygous for a reciprocal translocation produce reduced numbers of viable progeny. The proposed explanation is that the segregational pattern generates aneuploid progeny. In this article, we have examined the genotype of arrested embryonic classes. Using appropriate primers in PCR amplifications, we identified one class of arrested embryo, which could be readily recognized by its distinctive spot phenotype. The corresponding aneuploid genotype was expected to be lacking the left portion of chromosome V, from the eT1 breakpoint to the left (unc-60) end. The phenotype of the homozygotes lacking this DNA was a stage 2 embryonic arrest with a dark spot coinciding with the location in wild-type embryos of birefringent gut granules. Unlike induced events, this deletion results from meiotic segregation patterns, eliminating complexity associated with unknown material that may have been added to the end of a broken chromosome. We have used the arrested embryos, lacking chromosome V left sequences, to map a telomere probe. Unique sequences adjacent to the telomeric repeats in the clone cTel3 were missing in the arrested spot embryo. The result was confirmed by examining aneuploid segregants from a second translocation, hT1(I;V). Thus, we concluded that the telomere represented by clone cTel3 maps to the left end of chromosome V. In this analysis, we have shown that reciprocal translocations can be used to generate segregational aneuploids. These aneuploids are deleted for terminal sequences at the noncrossover ends of the C. elegans autosomes.
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Bishop, John D., Zhenbo Han und Jill M. Schumacher. „The Caenorhabditis elegans Aurora B Kinase AIR-2 Phosphorylates and Is Required for the Localization of a BimC Kinesin to Meiotic and Mitotic Spindles“. Molecular Biology of the Cell 16, Nr. 2 (Februar 2005): 742–56. http://dx.doi.org/10.1091/mbc.e04-08-0682.
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BimC kinesins are required for mitotic spindle assembly in a variety of organisms. These proteins are localized to centrosomes, spindle microtubules, and the spindle midzone. We have previously shown that the Caenorhabditis elegans Aurora B kinase AIR-2 is required for the localization of the ZEN-4 kinesin protein to midzone microtubules. To determine whether the association of BimC kinesins with spindle microtubules is also dependent on AIR-2, we examined the expression pattern of BMK-1, a C. elegans BimC kinesin, in wild-type and AIR-2–deficient embryos. BMK-1 is highly expressed in the hermaphrodite gonad and is localized to meiotic spindle microtubules in the newly fertilized embryo. In mitotic embryos, BMK-1 is associated with spindle microtubules from prophase through anaphase and is concentrated at the spindle midzone during anaphase and telophase. In the absence of AIR-2, BMK-1 localization to meiotic and mitotic spindles is greatly reduced. This is not a consequence of loss of ZEN-4 localization because BMK-1 is appropriately localized in ZEN-4–deficient embryos. Furthermore, AIR-2 and BMK-1 directly interact with one another and the C-terminal tail domain of BMK-1 is specifically phosphorylated by AIR-2 in vitro. Together with our previous data, these results suggest that at least one function of the Aurora B kinases is to recruit spindle-associated motor proteins to their sites of action.
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Hannak, Eva, Karen Oegema, Matthew Kirkham, Pierre Gönczy, Bianca Habermann und Anthony A. Hyman. „The kinetically dominant assembly pathway for centrosomal asters in Caenorhabditis elegans is γ-tubulin dependent“. Journal of Cell Biology 157, Nr. 4 (13.05.2002): 591–602. http://dx.doi.org/10.1083/jcb.200202047.
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γ-Tubulin–containing complexes are thought to nucleate and anchor centrosomal microtubules (MTs). Surprisingly, a recent study (Strome, S., J. Powers, M. Dunn, K. Reese, C.J. Malone, J. White, G. Seydoux, and W. Saxton. Mol. Biol. Cell. 12:1751–1764) showed that centrosomal asters form in Caenorhabditis elegans embryos depleted of γ-tubulin by RNA-mediated interference (RNAi). Here, we investigate the nucleation and organization of centrosomal MT asters in C. elegans embryos severely compromised for γ-tubulin function. We characterize embryos depleted of ∼98% centrosomal γ-tubulin by RNAi, embryos expressing a mutant form of γ-tubulin, and embryos depleted of a γ-tubulin–associated protein, CeGrip-1. In all cases, centrosomal asters fail to form during interphase but assemble as embryos enter mitosis. The formation of these mitotic asters does not require ZYG-9, a centrosomal MT-associated protein, or cytoplasmic dynein, a minus end–directed motor that contributes to self-organization of mitotic asters in other organisms. By kinetically monitoring MT regrowth from cold-treated mitotic centrosomes in vivo, we show that centrosomal nucleating activity is severely compromised by γ-tubulin depletion. Thus, although unknown mechanisms can support partial assembly of mitotic centrosomal asters, γ-tubulin is the kinetically dominant centrosomal MT nucleator.
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Riche, Soizic, Melissa Zouak, Françoise Argoul, Alain Arneodo, Jacques Pecreaux und Marie Delattre. „Evolutionary comparisons reveal a positional switch for spindle pole oscillations in Caenorhabditis embryos“. Journal of Cell Biology 201, Nr. 5 (20.05.2013): 653–62. http://dx.doi.org/10.1083/jcb.201210110.
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During the first embryonic division in Caenorhabditis elegans, the mitotic spindle is pulled toward the posterior pole of the cell and undergoes vigorous transverse oscillations. We identified variations in spindle trajectories by analyzing the outwardly similar one-cell stage embryo of its close relative Caenorhabditis briggsae. Compared with C. elegans, C. briggsae embryos exhibit an anterior shifting of nuclei in prophase and reduced anaphase spindle oscillations. By combining physical perturbations and mutant analysis in both species, we show that differences can be explained by interspecies changes in the regulation of the cortical Gα–GPR–LIN-5 complex. However, we found that in both species (1) a conserved positional switch controls the onset of spindle oscillations, (2) GPR posterior localization may set this positional switch, and (3) the maximum amplitude of spindle oscillations is determined by the time spent in the oscillating phase. By investigating microevolution of a subcellular process, we identify new mechanisms that are instrumental to decipher spindle positioning.
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Natesan, Gunalan, Timothy Hamilton, Eric J. Deeds und Pavak K. Shah. „Novel metrics reveal new structure and unappreciated heterogeneity in Caenorhabditis elegans development“. PLOS Computational Biology 19, Nr. 12 (19.12.2023): e1011733. http://dx.doi.org/10.1371/journal.pcbi.1011733.
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High throughput experimental approaches are increasingly allowing for the quantitative description of cellular and organismal phenotypes. Distilling these large volumes of complex data into meaningful measures that can drive biological insight remains a central challenge. In the quantitative study of development, for instance, one can resolve phenotypic measures for single cells onto their lineage history, enabling joint consideration of heritable signals and cell fate decisions. Most attempts to analyze this type of data, however, discard much of the information content contained within lineage trees. In this work we introduce a generalized metric, which we term the branch edit distance, that allows us to compare any two embryos based on phenotypic measurements in individual cells. This approach aligns those phenotypic measurements to the underlying lineage tree, providing a flexible and intuitive framework for quantitative comparisons between, for instance, Wild-Type (WT) and mutant developmental programs. We apply this novel metric to data on cell-cycle timing from over 1300 WT and RNAi-treated Caenorhabditis elegans embryos. Our new metric revealed surprising heterogeneity within this data set, including subtle batch effects in WT embryos and dramatic variability in RNAi-induced developmental phenotypes, all of which had been missed in previous analyses. Further investigation of these results suggests a novel, quantitative link between pathways that govern cell fate decisions and pathways that pattern cell cycle timing in the early embryo. Our work demonstrates that the branch edit distance we propose, and similar metrics like it, have the potential to revolutionize our quantitative understanding of organismal phenotype.
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Hoege, Carsten, und Anthony A. Hyman. „Principles of PAR polarity in Caenorhabditis elegans embryos“. Nature Reviews Molecular Cell Biology 14, Nr. 5 (18.04.2013): 315–22. http://dx.doi.org/10.1038/nrm3558.
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Sawh, Ahilya N., und Susan E. Mango. „Multiplexed Sequential DNA FISH in Caenorhabditis elegans Embryos“. STAR Protocols 1, Nr. 3 (Dezember 2020): 100107. http://dx.doi.org/10.1016/j.xpro.2020.100107.
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Ma, Tian-Hsiang, Po-Hsiang Chen, Bertrand Chin-Ming Tan und Szecheng J. Lo. „Size scaling of nucleolus in Caenorhabditis elegans embryos“. Biomedical Journal 41, Nr. 5 (Oktober 2018): 333–36. http://dx.doi.org/10.1016/j.bj.2018.07.003.
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Lee, Zuo Yen, Manoël Prouteau, Monica Gotta und Yves Barral. „Compartmentalization of the endoplasmic reticulum in the early C. elegans embryos“. Journal of Cell Biology 214, Nr. 6 (05.09.2016): 665–76. http://dx.doi.org/10.1083/jcb.201601047.
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The one-cell Caenorhabditis elegans embryo is polarized to partition fate determinants between the cell lineages generated during its first division. Using fluorescence loss in photobleaching, we find that the endoplasmic reticulum (ER) of the C. elegans embryo is physically continuous throughout the cell, but its membrane is compartmentalized shortly before nuclear envelope breakdown into an anterior and a posterior domain, indicating that a diffusion barrier forms in the ER membrane between these two domains. Using mutants with disorganized ER, we show that ER compartmentalization is independent of the morphological transition that the ER undergoes in mitosis. In contrast, compartmentalization takes place at the position of the future cleavage plane in a par-3–dependent manner. Together, our data indicate that the ER membrane is compartmentalized in cells as diverse as budding yeast, mouse neural stem cells, and the early C. elegans embryo.
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Kaitna, Susanne, Heinke Schnabel, Ralf Schnabel, Anthony A. Hyman und Michael Glotzer. „A ubiquitin C-terminal hydrolase is required to maintain osmotic balance and execute actin-dependent processes in the early C. elegansembryo“. Journal of Cell Science 115, Nr. 11 (01.06.2002): 2293–302. http://dx.doi.org/10.1242/jcs.115.11.2293.
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In the early Caenorhabditis elegans embryo, establishment of cell polarity and cytokinesis are both dependent upon reorganization of the actin cytoskeleton. Mutations in the cyk-3 gene cause maternal effect embryonic lethality. Embryos produced by homozygous cyk-3 mutant animals become multinucleate. We have further analyzed the cyk-3mutant phenotype and have found that cyk-3 mutant embryos fail to properly polarize the actin cytoskeleton and fail to segregate germline determinants. In addition, they fail to assemble an intact cleavage furrow. However, we have found that cyk-3 mutant embryos are intrinsically defective in osmotic regulation and that the cytokinesis defects can be partially rescued by providing osmotic support. The cyk-3 gene has been identified and found to encode a ubiquitin C-terminal hydrolase that is active against model substrates. These data indicate that the deubiquitination of certain substrates by CYK-3 is crucial for cellular osmoregulation. Defects in osmoregulation appear to indirectly affect actin-dependent processes.
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Brunschwig, K., C. Wittmann, R. Schnabel, T. R. Burglin, H. Tobler und F. Muller. „Anterior organization of the Caenorhabditis elegans embryo by the labial-like Hox gene ceh-13“. Development 126, Nr. 7 (01.04.1999): 1537–46. http://dx.doi.org/10.1242/dev.126.7.1537.
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The Caenorhabditis elegans lin-39, mab-5 and egl-5 Hox genes specify cell fates along the anterior-posterior body axis of the nematode during postembryonic development, but little is known about Hox gene functions during embryogenesis. Here, we show that the C. elegans labial-like gene ceh-13 is expressed in cells of many different tissues and lineages and that the rostral boundary of its expression domain is anterior to those of the other Hox genes. By transposon-mediated mutagenesis, we isolated a zygotic recessive ceh-13 loss-of-function allele, sw1, that exhibits an embryonic sublethal phenotype. Lineage analyses and immunostainings revealed defects in the organization of the anterior lateral epidermis and anterior body wall muscle cells. The epidermal and mesodermal identity of these cells, however, is correctly specified. ceh-13(sw1) mutant embryos also show fusion and adhesion defects in ectodermal cells. This suggests that ceh-13 plays a role in the anterior organization of the C. elegans embryo and is involved in the regulation of cell affinities.
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Xie, Chao, Yuxiang Jiang, Zhiwen Zhu, Shanjin Huang, Wei Li und Guangshuo Ou. „Actin filament debranching regulates cell polarity during cell migration and asymmetric cell division“. Proceedings of the National Academy of Sciences 118, Nr. 37 (10.09.2021): e2100805118. http://dx.doi.org/10.1073/pnas.2100805118.
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The formation of the branched actin networks is essential for cell polarity, but it remains unclear how the debranching activity of actin filaments contributes to this process. Here, we showed that an evolutionarily conserved coronin family protein, the Caenorhabditis elegans POD-1, debranched the Arp2/3-nucleated actin filaments in vitro. By fluorescence live imaging analysis of the endogenous POD-1 protein, we found that POD-1 colocalized with Arp2/3 at the leading edge of the migrating C. elegans neuroblasts. Conditional mutations of POD-1 in neuroblasts caused aberrant actin assembly, disrupted cell polarity, and impaired cell migration. In C. elegans one-cell−stage embryos, POD-1 and Arp2/3, moved together during cell polarity establishment, and inhibition of POD-1 blocked Arp2/3 motility and affected the polarized cortical flow, leading to symmetric segregation of cell fate determinants. Together, these results indicate that F-actin debranching organizes actin network and cell polarity in migrating neuroblasts and asymmetrically dividing embryos.
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Broitman-Maduro, Gina, und Morris F. Maduro. „Evolutionary Change in Gut Specification in Caenorhabditis Centers on the GATA Factor ELT-3 in an Example of Developmental System Drift“. Journal of Developmental Biology 11, Nr. 3 (08.07.2023): 32. http://dx.doi.org/10.3390/jdb11030032.
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Cells in a developing animal embryo become specified by the activation of cell-type-specific gene regulatory networks. The network that specifies the gut in the nematode Caenorhabditis elegans has been the subject of study for more than two decades. In this network, the maternal factors SKN-1/Nrf and POP-1/TCF activate a zygotic GATA factor cascade consisting of the regulators MED-1,2 → END-1,3 → ELT-2,7, leading to the specification of the gut in early embryos. Paradoxically, the MED, END, and ELT-7 regulators are present only in species closely related to C. elegans, raising the question of how the gut can be specified without them. Recent work found that ELT-3, a GATA factor without an endodermal role in C. elegans, acts in a simpler ELT-3 → ELT-2 network to specify gut in more distant species. The simpler ELT-3 → ELT-2 network may thus represent an ancestral pathway. In this review, we describe the elucidation of the gut specification network in C. elegans and related species and propose a model by which the more complex network might have formed. Because the evolution of this network occurred without a change in phenotype, it is an example of the phenomenon of Developmental System Drift.
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Hermann, Greg J., Lena K. Schroeder, Caroline A. Hieb, Aaron M. Kershner, Beverley M. Rabbitts, Paul Fonarev, Barth D. Grant und James R. Priess. „Genetic Analysis of Lysosomal Trafficking inCaenorhabditis elegans“. Molecular Biology of the Cell 16, Nr. 7 (Juli 2005): 3273–88. http://dx.doi.org/10.1091/mbc.e05-01-0060.
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The intestinal cells of Caenorhabditis elegans embryos contain prominent, birefringent gut granules that we show are lysosome-related organelles. Gut granules are labeled by lysosomal markers, and their formation is disrupted in embryos depleted of AP-3 subunits, VPS-16, and VPS-41. We define a class of gut granule loss (glo) mutants that are defective in gut granule biogenesis. We show that the glo-1 gene encodes a predicted Rab GTPase that localizes to lysosome-related gut granules in the intestine and that glo-4 encodes a possible GLO-1 guanine nucleotide exchange factor. These and other glo genes are homologous to genes implicated in the biogenesis of specialized, lysosome-related organelles such as melanosomes in mammals and pigment granules in Drosophila. The glo mutants thus provide a simple model system for the analysis of lysosome-related organelle biogenesis in animal cells.
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Ciarletta, P., M. Ben Amar und M. Labouesse. „Continuum model of epithelial morphogenesis during Caenorhabditis elegans embryonic elongation“. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, Nr. 1902 (13.09.2009): 3379–400. http://dx.doi.org/10.1098/rsta.2009.0088.
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The purpose of this work is to provide a biomechanical model to investigate the interplay between cellular structures and the mechanical force distribution during the elongation process of Caenorhabditis elegans embryos. Epithelial morphogenesis drives the elongation process of an ovoid embryo to become a worm-shaped embryo about four times longer and three times thinner. The overall anatomy of the embryo is modelled in the continuum mechanics framework from the structural organization of the subcellular filaments within epithelial cells. The constitutive relationships consider embryonic cells as homogeneous materials with an active behaviour, determined by the non-muscle myosin II molecular motor, and a passive viscoelastic response, related to the directional properties of the filament network inside cells. The axisymmetric elastic solution at equilibrium is derived by means of the incompressibility conditions, the continuity conditions for the overall embryo deformation and the balance principles for the embryonic cells. A particular analytical solution is proposed from a simplified geometry, demonstrating the mechanical role of the microtubule network within epithelial cells in redistributing the stress from a differential contraction of circumferentially oriented actin filaments. The theoretical predictions of the biomechanical model are discussed within the biological scenario proposed through genetic analysis and pharmacological experiments.
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Wang, Huan, Anne Spang, Mark A. Sullivan, Jennifer Hryhorenko und Fred K. Hagen. „The Terminal Phase of Cytokinesis in the Caenorhabditis elegans Early Embryo Requires Protein Glycosylation“. Molecular Biology of the Cell 16, Nr. 9 (September 2005): 4202–13. http://dx.doi.org/10.1091/mbc.e05-05-0472.
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RNA interference (RNAi) was used to characterize the requirement of protein glycosylation for cell membrane stability during cytokinesis in the early embryo. This screen targeted 13 enzymes or components of polypeptide sugar transferases that initiate either N-glycosylation or three different pathways of O-glycosylation. RNAi of genes in the mucin-type and epidermal growth factor-fringe glycosylation pathways did not affect cytokinesis. However, embryos deficient in N-glycosylation exhibited a variable inability to complete cytokinesis. The most potent block in early embryonic cell division was obtained by RNAi of the polypeptide xylose transferase (ppXyl-T), which is required to initiate the proteoglycan modification pathway. Two generations of ppXyl-T RNAi-feeding treatment reduced the body size, mobility, brood size, and life span of adult animals. Embryos escaping ppXyl-T and Gal-T2 RNAi lethality develop to adulthood but have cytokinesis-deficient offspring, suggesting that glycosyltransferases in the proteoglycan pathway are maternal proteins in the early embryo. Gal-T2::GFP fusions and anti-Gal-T2 antibodies revealed a perinuclear staining pattern, consistent with the localization of the Golgi apparatus. RNAi in green fluorescent protein (GFP)-tagged strains to follow tubulin, PIE-1, and chromatin showed that deficient proteoglycan biosynthesis uncouples the stability of newly formed cell membranes from cytokinesis, whereas cleavage furrow initiation, mitotic spindle function, karyokinesis, and partitioning of intrinsic components are intact.
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Costa, Michael, William Raich, Cristina Agbunag, Ben Leung, Jeff Hardin und James R. Priess. „A Putative Catenin–Cadherin System Mediates Morphogenesis of the Caenorhabditis elegans Embryo“. Journal of Cell Biology 141, Nr. 1 (06.04.1998): 297–308. http://dx.doi.org/10.1083/jcb.141.1.297.
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During morphogenesis of the Caenorhabditis elegans embryo, hypodermal (or epidermal) cells migrate to enclose the embryo in an epithelium and, subsequently, change shape coordinately to elongate the body (Priess, J.R., and D.I. Hirsh. 1986. Dev. Biol. 117:156– 173; Williams-Masson, E.M., A.N. Malik, and J. Hardin. 1997. Development [Camb.]. 124:2889–2901). We have isolated mutants defective in morphogenesis that identify three genes required for both cell migration during body enclosure and cell shape change during body elongation. Analyses of hmp-1, hmp-2, and hmr-1 mutants suggest that products of these genes anchor contractile actin filament bundles at the adherens junctions between hypodermal cells and, thereby, transmit the force of bundle contraction into cell shape change. The protein products of all three genes localize to hypodermal adherens junctions in embryos. The sequences of the predicted HMP-1, HMP-2, and HMR-1 proteins are related to the cell adhesion proteins α-catenin, β-catenin/Armadillo, and classical cadherin, respectively. This putative catenin–cadherin system is not essential for general cell adhesion in the C. elegans embryo, but rather mediates specific aspects of morphogenetic cell shape change and cytoskeletal organization.
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Gattegno, Tamar, Aditya Mittal, Clari Valansi, Ken C. Q. Nguyen, David H. Hall, Leonid V. Chernomordik und Benjamin Podbilewicz. „Genetic Control of Fusion Pore Expansion in the Epidermis ofCaenorhabditis elegans“. Molecular Biology of the Cell 18, Nr. 4 (April 2007): 1153–66. http://dx.doi.org/10.1091/mbc.e06-09-0855.
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Developmental cell fusion is found in germlines, muscles, bones, placentae, and stem cells. In Caenorhabditis elegans 300 somatic cells fuse during development. Although there is extensive information on the early intermediates of viral-induced and intracellular membrane fusion, little is known about late stages in membrane fusion. To dissect the pathway of cell fusion in C. elegans embryos, we use genetic and kinetic analyses using live-confocal and electron microscopy. We simultaneously monitor the rates of multiple cell fusions in developing embryos and find kinetically distinct stages of initiation and completion of membrane fusion in the epidermis. The stages of cell fusion are differentially blocked or retarded in eff-1 and idf-1 mutants. We generate kinetic cell fusion maps for embryos grown at different temperatures. Different sides of the same cell differ in their fusogenicity: the left and right membrane domains are fusion-incompetent, whereas the anterior and posterior membrane domains fuse with autonomous kinetics in embryos. All but one cell pair can initiate the formation of the largest syncytium. The first cell fusion does not trigger a wave of orderly fusions in either direction. Ultrastructural studies show that epidermal syncytiogenesis require eff-1 activities to initiate and expand membrane merger.
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Encalada, Sandra E., John Willis, Rebecca Lyczak und Bruce Bowerman. „A Spindle Checkpoint Functions during Mitosis in the Early Caenorhabditis elegans Embryo“. Molecular Biology of the Cell 16, Nr. 3 (März 2005): 1056–70. http://dx.doi.org/10.1091/mbc.e04-08-0712.
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During mitosis, chromosome segregation is regulated by a spindle checkpoint mechanism. This checkpoint delays anaphase until all kinetochores are captured by microtubules from both spindle poles, chromosomes congress to the metaphase plate, and the tension between kinetochores and their attached microtubules is properly sensed. Although the spindle checkpoint can be activated in many different cell types, the role of this regulatory mechanism in rapidly dividing embryonic animal cells has remained controversial. Here, using time-lapse imaging of live embryonic cells, we show that chemical or mutational disruption of the mitotic spindle in early Caenorhabditis elegans embryos delays progression through mitosis. By reducing the function of conserved checkpoint genes in mutant embryos with defective mitotic spindles, we show that these delays require the spindle checkpoint. In the absence of a functional checkpoint, more severe defects in chromosome segregation are observed in mutants with abnormal mitotic spindles. We also show that the conserved kinesin CeMCAK, the CENP-F-related proteins HCP-1 and HCP-2, and the core kinetochore protein CeCENP-C all are required for this checkpoint. Our analysis indicates that spindle checkpoint mechanisms are functional in the rapidly dividing cells of an early animal embryo and that this checkpoint can prevent chromosome segregation defects during mitosis.
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Raich, William B., Adrienne N. Moran, Joel H. Rothman und Jeff Hardin. „Cytokinesis and Midzone Microtubule Organization inCaenorhabditis elegans Require the Kinesin-like Protein ZEN-4“. Molecular Biology of the Cell 9, Nr. 8 (August 1998): 2037–49. http://dx.doi.org/10.1091/mbc.9.8.2037.
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Members of the MKLP1 subfamily of kinesin motor proteins localize to the equatorial region of the spindle midzone and are capable of bundling antiparallel microtubules in vitro. Despite these intriguing characteristics, it is unclear what role these kinesins play in dividing cells, particularly within the context of a developing embryo. Here, we report the identification of a null allele ofzen-4, an MKLP1 homologue in the nematodeCaenorhabditis elegans, and demonstrate that ZEN-4 is essential for cytokinesis. Embryos deprived of ZEN-4 form multinucleate single-celled embryos as they continue to cycle through mitosis but fail to complete cell division. Initiation of the cytokinetic furrow occurs at the normal time and place, but furrow propagation halts prematurely. Time-lapse recordings and microtubule staining reveal that the cytokinesis defect is preceded by the dissociation of the midzone microtubules. We show that ZEN-4 protein localizes to the spindle midzone during anaphase and persists at the midbody region throughout cytokinesis. We propose that ZEN-4 directly cross-links the midzone microtubules and suggest that these microtubules are required for the completion of cytokinesis.
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Golden, Andy, Penny L. Sadler, Matthew R. Wallenfang, Jill M. Schumacher, Danielle R. Hamill, Gayle Bates, Bruce Bowerman, Geraldine Seydoux und Diane C. Shakes. „Metaphase to Anaphase (mat) Transition–Defective Mutants inCaenorhabditis elegans“. Journal of Cell Biology 151, Nr. 7 (25.12.2000): 1469–82. http://dx.doi.org/10.1083/jcb.151.7.1469.
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The metaphase to anaphase transition is a critical stage of the eukaryotic cell cycle, and, thus, it is highly regulated. Errors during this transition can lead to chromosome segregation defects and death of the organism. In genetic screens for temperature-sensitive maternal effect embryonic lethal (Mel) mutants, we have identified 32 mutants in the nematode Caenorhabditis elegans in which fertilized embryos arrest as one-cell embryos. In these mutant embryos, the oocyte chromosomes arrest in metaphase of meiosis I without transitioning to anaphase or producing polar bodies. An additional block in M phase exit is evidenced by the failure to form pronuclei and the persistence of phosphohistone H3 and MPM-2 antibody staining. Spermatocyte meiosis is also perturbed; primary spermatocytes arrest in metaphase of meiosis I and fail to produce secondary spermatocytes. Analogous mitotic defects cause M phase delays in mitotic germline proliferation. We have named this class of mutants “mat” for metaphase to anaphase transition defective. These mutants, representing six different complementation groups, all map near genes that encode subunits of the anaphase promoting complex or cyclosome, and, here, we show that one of the genes, emb-27, encodes the C. elegans CDC16 ortholog.